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Oldham, Mark

Overview:

Dr Oldham is Professor in the Department of Radiation Oncology (primary) and Biomedical Engineering (Secondary). He is the Director of the Optical Biophysics and 3D Dosimetry Lab. The lab has received NIH R01 funding to develop optical imaging techniques for 3D dosimetry. We are also developing a new optical imaging technique for high-resolution 3D imaging of vascular networks and gene expression in unsectioned tissue samples. A range of applications are being explored through collaborations with the Dept of Radiobiology (Prof Mark Dewhirst).  In addition to these efforts, the Lab is heavily involved in several research projects aimed at modifying radiation treatments in order to stimulate a long term anti-cancer immune response: radiation and immunotherapy. 

Dr Oldham is the Director of the Radiation Therapy Track of the Duke Medical Physics MS/PhD program.

Positions:

Professor of Radiation Oncology

Radiation Oncology
School of Medicine

Member of the Duke Cancer Institute

Duke Cancer Institute
School of Medicine

Education:

Ph.D. 1991

Ph.D. — Newcastle University

Grants:

Image-guided Dosimetry for Injectable Brachytherapy based on Elastin-like Polypeptide Nanoparticles

Administered By
Radiation Oncology
AwardedBy
National Institutes of Health
Role
Co Investigator
Start Date
August 01, 2017
End Date
July 31, 2019

An investigation of the dosimetry of the ViewRay radiation therapy system

Administered By
Radiation Oncology
AwardedBy
Washington University in St. Louis
Role
Principal Investigator
Start Date
September 23, 2014
End Date
September 22, 2016

Accurate, High Resolution 3D Dosimetry

Administered By
Radiation Oncology
AwardedBy
National Institutes of Health
Role
Principal Investigator
Start Date
April 09, 2004
End Date
December 31, 2013

Cross-disciplinary Training in Medical Physics

Administered By
Radiology
AwardedBy
National Institutes of Health
Role
Associate Director
Start Date
July 01, 2007
End Date
June 30, 2013

Digital tomosynthesis: a new paradigm for radiation treatment verification

Administered By
Radiation Oncology
AwardedBy
National Institutes of Health
Role
Collaborator
Start Date
August 11, 2007
End Date
July 31, 2009
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Awards:

Farrington Daniel Award. American Association of Medical Physicists..

Type
International
Awarded By
American Association of Medical Physicists
Date
April 04, 2016

Excellence in Teaching. Duke Medical Physics Graduate Program.

Type
Department
Awarded By
Duke Medical Physics Graduate Program
Date
January 01, 2014

Director’s Award for Exemplary Service . Duke Medical Physics Graduate Program.

Type
Department
Awarded By
Duke Medical Physics Graduate Program
Date
January 01, 2011

Excellence in Mentoring. Duke Medical Physics Graduate Program.

Type
Department
Awarded By
Duke Medical Physics Graduate Program
Date
January 01, 2011

Fellow of the AAPM. American Association of Medical Physicists.

Type
National
Awarded By
American Association of Medical Physicists
Date
January 01, 2010

Director’s Award for Exemplary Service . Duke Medical Physics Graduate Program.

Type
Department
Awarded By
Duke Medical Physics Graduate Program
Date
January 01, 2009

AAPM/IPEM Travel Award. AAPM/IPEM.

Type
International
Awarded By
AAPM/IPEM
Date
January 01, 2006

Farrington Daniel Award. American Association of Medical Physicists.

Type
International
Awarded By
American Association of Medical Physicists
Date
January 01, 2002

Publications:

A precision 3D conformal treatment technique in rats: Application to whole-brain radiotherapy with hippocampal avoidance.

To develop and validate three-dimensional (3D) conformal hippocampal sparing whole-brain radiation therapy (HA-WBRT) for Wistar rats utilizing precision 3D-printed immobilization and micro-blocks. This technique paves the way for future preclinical studies investigating brain treatments that reduce neurotoxicity.A novel preclinical treatment planning and delivery process was developed to enable precision 3D conformal treatment and hippocampal avoidance capability for the Xrad 225cx small animal irradiator. A range of conformal avoidance plans were evaluated consisting of equiangularly spaced coplanar axial beams, with plans containing 2, 4, 7, and 8 fields. The hippocampal sparing and coverage of these plans were investigated through Monte Carlo dose calculation (SmART-Plan Xrad 225cx planning system). Treatment delivery was implemented through a novel process where hippocampal block shapes were computer generated from an MRI rat atlas which was registered to on-board cone beam CT of the rat in treatment position. The blocks were 3D printed with a tungsten-doped filament at lateral resolution of 80 μm. Precision immobilization was achieved utilizing a 3D-printed support system which enabled angled positioning of the rat head in supine position and bite block to improve coverage of the central diencephalon. Treatment delivery was verified on rodent-morphic Presage® 3D dosimeters optically scanned at 0.2-mm isotropic resolution. Biological verification of hippocampal avoidance was performed with immunohistologic staining.All simulated plans spared the hippocampus while delivering high dose to the brain (22.5-26.2 Gy mean dose to brain at mean hippocampal dose of 7 Gy). No significant improvement in hippocampal sparing was observed by adding beams beyond four fields. Dosimetric sparing of hippocampal region of the four-field plan was verified with the Presage® dosimeter (mean dose = 9.6 Gy, D100% = 7.1 Gy). Simulation and dosimeter match at distance-to-agreement of 2 mm and dose difference of ±3% at 91.7% gamma passing rate (passing criteria of γ < 1). Agreement is less at 1 mm and ±5% at 69.0% gamma passing rate. The four-field plan was further validated with immunohistochemistry and showed a significant reduction in DNA double-strand breaks within the spared region compared with whole-brain irradiated groups (P = 0.021). However, coverage of the whole brain was low at 48.5-57.8% of the volume receiving 30Gy at 7Gy mean hippocampal dose in simulation and 46.7-52.5% in dosimetric measurements. This can be attributed to the shape of the rat hippocampus and the inability of treatment platform to employ non-coplanar beams.A novel approach for conformal microradiation therapy using 3D-printing technology was developed, implemented, and validated. A workflow was developed to generate accurate 3D-printed blocks from registered high-resolution rat MRI atlas structures. Although hippocampus was spared with this technique, whole-brain target coverage was suboptimal, indicating that non-coplanar beams and IMRT capability may be required to meet stringent dose criteria associated with current human RTOG trials.

Authors
Yoon, SW; Cramer, CK; Miles, DA; Reinsvold, MH; Joo, KM; Kirsch, DG; Oldham, M
MLA Citation
Yoon, SW, Cramer, CK, Miles, DA, Reinsvold, MH, Joo, KM, Kirsch, DG, and Oldham, M. "A precision 3D conformal treatment technique in rats: Application to whole-brain radiotherapy with hippocampal avoidance." Medical physics (August 24, 2017).
PMID
28837234
Source
epmc
Published In
Medical physics
Publish Date
2017
DOI
10.1002/mp.12533

Noninvasive measurement of tissue blood oxygenation with Cerenkov imaging during therapeutic radiation delivery.

Tumor tissue oxygenation significantly affects the outcome of radiotherapy. Real-time monitoring of tumor hypoxia is highly desirable for effective radiotherapy, and is the basis for improved treatment because hypoxic tumor cells are more resistant to radiation damage than fully oxygenated cells. We propose to use Cerenkov imaging to monitor tumor hypoxia by means of tissue blood oxygenation without the need for any exogenous contrast agent. Using a rodent hypoxia model, we demonstrate that Cerenkov imaging can be used as a noninvasive and noncontact method to measure tissue blood oxygenation level during radiation delivery. The data from Cerenkov imaging were validated using near infrared spectrometry methods. The results demonstrate the feasibility of using Cerenkov imaging to monitor tumor hypoxia during therapeutic radiation delivery.

Authors
Zhang, X; Lam, SK; Palmer, G; Das, S; Oldham, M; Dewhirst, M
MLA Citation
Zhang, X, Lam, SK, Palmer, G, Das, S, Oldham, M, and Dewhirst, M. "Noninvasive measurement of tissue blood oxygenation with Cerenkov imaging during therapeutic radiation delivery." Optics letters 42.16 (August 2017): 3101-3104.
Website
http://hdl.handle.net/10161/15411
PMID
28809883
Source
epmc
Published In
Optics Letters
Volume
42
Issue
16
Publish Date
2017
Start Page
3101
End Page
3104
DOI
10.1364/ol.42.003101

A prototype optical-CT system for PRESAGE 3D dosimeter readout

Authors
Miles, D; Yoon, P; Kodra, J; Adamovics, J; Oldham, M
MLA Citation
Miles, D, Yoon, P, Kodra, J, Adamovics, J, and Oldham, M. "A prototype optical-CT system for PRESAGE 3D dosimeter readout." May 2017.
Source
crossref
Published In
Journal of Physics
Volume
847
Publish Date
2017
Start Page
012026
End Page
012026
DOI
10.1088/1742-6596/847/1/012026

Characterization of novel preclinical dose distributions for micro irradiator

Authors
Kodra, J; Miles, D; Yoon, SW; Kirsch, DG; Oldham, M
MLA Citation
Kodra, J, Miles, D, Yoon, SW, Kirsch, DG, and Oldham, M. "Characterization of novel preclinical dose distributions for micro irradiator." May 2017.
Source
crossref
Published In
Journal of Physics
Volume
847
Publish Date
2017
Start Page
012054
End Page
012054
DOI
10.1088/1742-6596/847/1/012054

Treatment planning and 3D dose verification of whole brain radiation therapy with hippocampal avoidance in rats

Authors
Yoon, SW; Miles, D; Cramer, C; Reinsvold, M; Kirsch, D; Oldham, M
MLA Citation
Yoon, SW, Miles, D, Cramer, C, Reinsvold, M, Kirsch, D, and Oldham, M. "Treatment planning and 3D dose verification of whole brain radiation therapy with hippocampal avoidance in rats." May 2017.
Source
crossref
Published In
Journal of Physics
Volume
847
Publish Date
2017
Start Page
012004
End Page
012004
DOI
10.1088/1742-6596/847/1/012004

How feasible is remote 3D dosimetry for MR guided Radiation Therapy (MRgRT)?

Authors
Mein, S; Rankine, L; Miles, D; Juang, T; Cai, B; Curcuru, A; Mutic, S; Fenoli, J; Adamovics, J; Li, H; Oldham, M
MLA Citation
Mein, S, Rankine, L, Miles, D, Juang, T, Cai, B, Curcuru, A, Mutic, S, Fenoli, J, Adamovics, J, Li, H, and Oldham, M. "How feasible is remote 3D dosimetry for MR guided Radiation Therapy (MRgRT)?." May 2017.
Source
crossref
Published In
Journal of Physics
Volume
847
Publish Date
2017
Start Page
012056
End Page
012056
DOI
10.1088/1742-6596/847/1/012056

Innovation and the future of advanced dosimetry: 2D to 5D

Authors
Oldham, M
MLA Citation
Oldham, M. "Innovation and the future of advanced dosimetry: 2D to 5D." May 2017.
Source
crossref
Published In
Journal of Physics
Volume
847
Publish Date
2017
Start Page
012006
End Page
012006
DOI
10.1088/1742-6596/847/1/012006

Three-Dimensional Dosimetric Validation of a Magnetic Resonance Guided Intensity Modulated Radiation Therapy System.

To validate the dosimetric accuracy of a commercially available magnetic resonance guided intensity modulated radiation therapy (MRgIMRT) system using a hybrid approach: 3-dimensional (3D) measurements and Monte Carlo calculations.We used PRESAGE radiochromic plastic dosimeters with remote optical computed tomography readout to perform 3D high-resolution measurements, following a novel remote dosimetry protocol. We followed the intensity modulated radiation therapy commissioning recommendations of American Association of Physicists in Medicine Task Group 119, adapted to incorporate 3D data. Preliminary tests ("AP" and "3D-Bands") were delivered to 9.5-cm usable diameter cylindrical PRESAGE dosimeters to validate the treatment planning system (TPS) for nonmodulated deliveries; assess the sensitivity, uniformity, and rotational symmetry of the PRESAGE dosimeters; and test the robustness of the remote dosimetry protocol. Following this, 4 clinical MRgIMRT plans ("MultiTarget," "Prostate," "Head/Neck," and "C-Shape") were measured using 13-cm usable diameter PRESAGE dosimeters. For all plans, 3D-γ (3% or 3 mm global, 10% threshold) passing rates were calculated and 3D-γ maps were examined. Point doses were measured with an IBA-CC01 ionization chamber for validation of absolute dose. Finally, by use of an in-house-developed, GPU-accelerated Monte Carlo algorithm (gPENELOPE), we independently calculated dose for all 6 Task Group 119 plans and compared against the TPS.For PRESAGE measurements, 3D-γ analysis yielded passing rates of 98.7%, 99.2%, 98.5%, 98.0%, 99.2%, and 90.7% for AP, 3D-Bands, MultiTarget, Prostate, Head/Neck, and C-Shape, respectively. Ion chamber measurements were within an average of 0.5% (±1.1%) from the TPS dose. Monte Carlo calculations demonstrated good agreement with the TPS, with a mean 3D-γ passing rate of 98.5% ± 1.9% using a stricter 2%/2-mm criterion.We have validated the dosimetric accuracy of a commercial MRgIMRT system using high-resolution 3D techniques. We have demonstrated for the first time that hybrid 3D remote dosimetry is a comprehensive and feasible approach to commissioning MRgIMRT. This may provide better sensitivity in error detection compared with standard 2-dimensional measurements and could be used when implementing complex new magnetic resonance guided radiation therapy technologies.

Authors
Rankine, LJ; Mein, S; Cai, B; Curcuru, A; Juang, T; Miles, D; Mutic, S; Wang, Y; Oldham, M; Li, HH
MLA Citation
Rankine, LJ, Mein, S, Cai, B, Curcuru, A, Juang, T, Miles, D, Mutic, S, Wang, Y, Oldham, M, and Li, HH. "Three-Dimensional Dosimetric Validation of a Magnetic Resonance Guided Intensity Modulated Radiation Therapy System." International journal of radiation oncology, biology, physics 97.5 (April 2017): 1095-1104.
PMID
28332995
Source
epmc
Published In
International Journal of Radiation Oncology, Biology, Physics
Volume
97
Issue
5
Publish Date
2017
Start Page
1095
End Page
1104
DOI
10.1016/j.ijrobp.2017.01.223

Optical-CT 3D Dosimetry Using Fresnel Lenses with Minimal Refractive-Index Matching Fluid.

Telecentric optical computed tomography (optical-CT) is a state-of-the-art method for visualizing and quantifying 3-dimensional dose distributions in radiochromic dosimeters. In this work a prototype telecentric system (DFOS-Duke Fresnel Optical-CT Scanner) is evaluated which incorporates two substantial design changes: the use of Fresnel lenses (reducing lens costs from $10-30K t0 $1-3K) and the use of a 'solid tank' (which reduces noise, and the volume of refractively matched fluid from 1 ltr to 10 cc). The efficacy of DFOS was evaluated by direct comparison against commissioned scanners in our lab. Measured dose distributions from all systems were compared against the predicted dose distributions from a commissioned treatment planning system (TPS). Three treatment plans were investigated including a simple four-field box treatment, a multiple small field delivery, and a complex IMRT treatment. Dosimeters were imaged within 2 h post irradiation, using consistent scanning techniques (360 projections acquired at 1 degree intervals, reconstruction at 2mm). DFOS efficacy was evaluated through inspection of dose line-profiles, and 2D and 3D dose and gamma maps. DFOS/TPS gamma pass rates with 3%/3mm dose difference/distance-to-agreement criteria ranged from 89.3% to 92.2%, compared to from 95.6% to 99.0% obtained with the commissioned system. The 3D gamma pass rate between the commissioned system and DFOS was 98.2%. The typical noise rates in DFOS reconstructions were up to 3%, compared to under 2% for the commissioned system. In conclusion, while the introduction of a solid tank proved advantageous with regards to cost and convenience, further work is required to improve the image quality and dose reconstruction accuracy of the new DFOS optical-CT system.

Authors
Bache, S; Malcolm, J; Adamovics, J; Oldham, M
MLA Citation
Bache, S, Malcolm, J, Adamovics, J, and Oldham, M. "Optical-CT 3D Dosimetry Using Fresnel Lenses with Minimal Refractive-Index Matching Fluid." PloS one 11.3 (January 2016): e0152606-.
Website
http://hdl.handle.net/10161/12017
PMID
27019460
Source
epmc
Published In
PloS one
Volume
11
Issue
3
Publish Date
2016
Start Page
e0152606
DOI
10.1371/journal.pone.0152606

X-Ray Psoralen Activated Cancer Therapy (X-PACT).

This work investigates X-PACT (X-ray Psoralen Activated Cancer Therapy): a new approach for the treatment of solid cancer. X-PACT utilizes psoralen, a potent anti-cancer therapeutic with current application to proliferative disease and extracorporeal photopheresis (ECP) of cutaneous T Cell Lymphoma. An immunogenic role for light-activated psoralen has been reported, contributing to long-term clinical responses. Psoralen therapies have to-date been limited to superficial or extracorporeal scenarios due to the requirement for psoralen activation by UVA light, which has limited penetration in tissue. X-PACT solves this challenge by activating psoralen with UV light emitted from novel non-tethered phosphors (co-incubated with psoralen) that absorb x-rays and re-radiate (phosphoresce) at UV wavelengths. The efficacy of X-PACT was evaluated in both in-vitro and in-vivo settings. In-vitro studies utilized breast (4T1), glioma (CT2A) and sarcoma (KP-B) cell lines. Cells were exposed to X-PACT treatments where the concentrations of drug (psoralen and phosphor) and radiation parameters (energy, dose, and dose rate) were varied. Efficacy was evaluated primarily using flow cell cytometry in combination with complimentary assays, and the in-vivo mouse study. In an in-vitro study, we show that X-PACT induces significant tumor cell apoptosis and cytotoxicity, unlike psoralen or phosphor alone (p<0.0001). We also show that apoptosis increases as doses of phosphor, psoralen, or radiation increase. Finally, in an in-vivo pilot study of BALBc mice with syngeneic 4T1 tumors, we show that the rate of tumor growth is slower with X-PACT than with saline or AMT + X-ray (p<0.0001). Overall these studies demonstrate a potential therapeutic effect for X-PACT, and provide a foundation and rationale for future studies. In summary, X-PACT represents a novel treatment approach in which well-tolerated low doses of x-ray radiation are delivered to a specific tumor site to generate UVA light which in-turn unleashes both short- and potentially long-term antitumor activity of photo-active therapeutics like psoralen.

Authors
Oldham, M; Yoon, P; Fathi, Z; Beyer, WF; Adamson, J; Liu, L; Alcorta, D; Xia, W; Osada, T; Liu, C; Yang, XY; Dodd, RD; Herndon, JE; Meng, B; Kirsch, DG; Lyerly, HK; Dewhirst, MW; Fecci, P; Walder, H; Spector, NL
MLA Citation
Oldham, M, Yoon, P, Fathi, Z, Beyer, WF, Adamson, J, Liu, L, Alcorta, D, Xia, W, Osada, T, Liu, C, Yang, XY, Dodd, RD, Herndon, JE, Meng, B, Kirsch, DG, Lyerly, HK, Dewhirst, MW, Fecci, P, Walder, H, and Spector, NL. "X-Ray Psoralen Activated Cancer Therapy (X-PACT)." PloS one 11.9 (January 2016): e0162078-.
Website
http://hdl.handle.net/10161/13034
PMID
27583569
Source
epmc
Published In
PloS one
Volume
11
Issue
9
Publish Date
2016
Start Page
e0162078
DOI
10.1371/journal.pone.0162078

Utility and validation of biomechanical deformable image registration in low-contrast images.

The application of a biomechanical deformable image registration algorithm has been demonstrated to overcome the potential limitations in the use of intensity-based algorithms on low-contrast images that lack prominent features. Because validation of deformable registration is particularly challenging on such images, the dose distribution predicted via a biomechanical algorithm was evaluated using the measured dose from a deformable dosimeter.A biomechanical model-based image registration algorithm registered computed tomographic (CT) images of an elastic radiochromic dosimeter between its undeformed and deformed positions. The algorithm aligns the external boundaries of the dosimeter, created from CT contours, and the internal displacements are solved by modeling the physical material properties of the dosimeter. The dosimeter was planned and irradiated in its deformed position, and subsequently, the delivered dose was measured with optical CT in the undeformed position. The predicted dose distribution, created by applying the deformable registration displacement map to the planned distribution, was then compared with the measured optical CT distribution.Compared with the optical CT distribution, biomechanical image registration predicted the position and size of the deformed dose fields with mean errors of ≤1 mm (maximum, 3 mm). The accuracy did not differ between cross sections with a greater or lesser deformation magnitude despite the homogenous CT intensities throughout the dosimeter. The overall 3-dimensional voxel passing rate of the predicted distribution was γ3%/3mm = 91% compared with optical CT.Biomechanical registration accurately predicted the deformed dose distribution measured in a deformable dosimeter, whereas previously, evaluations of a commercial intensity-based algorithm demonstrated substantial errors. The addition of biomechanical algorithms to the collection of adaptive radiation therapy tools would be valuable for dose accumulation, particularly in feature-poor images such as cone beam CT and organs such as the liver.

Authors
Velec, M; Juang, T; Moseley, JL; Oldham, M; Brock, KK
MLA Citation
Velec, M, Juang, T, Moseley, JL, Oldham, M, and Brock, KK. "Utility and validation of biomechanical deformable image registration in low-contrast images." Practical radiation oncology 5.4 (July 2015): e401-e408.
PMID
25823381
Source
epmc
Published In
Practical Radiation Oncology
Volume
5
Issue
4
Publish Date
2015
Start Page
e401
End Page
e408
DOI
10.1016/j.prro.2015.01.011

WE-EF-BRA-11: Precision Partial-Tumor Irradiation of Dorsal Rodent Mammary Tumors.

PURPOSE: To introduce a pre-clinical treatment technique on a micro-irradiator to treat specific volumes of dorsal mammary tumors in BALB/c mice while sparing lungs and spine. This technique facilitates pre-clinical investigation of tumor response to sub-optimal radiation treatments in which a portion of the tumor is unirradiated, known as a "marginal miss". In-vitro data suggests that partial tumor radiations trigger a more aggressive phenotype in non-irradiated, regional tumor cells via bystander effects. As the lung tissue is spared, the impact of marginal miss on the development of pulmonary metastasis may be assessed. METHODS: End to end test was performed on three BALB/c mice as proof of concept for larger studies. 1Gy was delivered on the micro-irradiator employing previously unexplored lateral parallel-opposed diamond and/or triangle-shaped beams. The margins of the treatment beam were defined using a combination of tumor palpation, barium fiducial markers, and real-time fluoroscopic images. The dose distribution was independently verified with kilovoltage beam Monte Carlo dose calculations with 7% statistical uncertainty and double exposure images. As a final step, the technique was used in a larger pre-clinical study (15Gy, 36 BALB/c mice) and lung metastasis in response to tumor irradiation of 100%, 50% and 0% was quantified. RESULTS: For the Monte-Carlo dose calculations, the dose volume histograms established a maximum dose within the un-irradiated and radiated portions of the mammary tumor of 0.3Gy and 1.5Gy respectively, with a sharp gradient at the boundary. 100% of the lung volume received less than 0.5Gy. This technique proved suitable for a pre-clinical marginal miss study with 50% more lung metastases in partially-radiated mouse models compared to completely. CONCLUSION: We have developed a novel treatment technique for partial or full irradiation of dorsal mammary tumors incorporating lung sparing.The technique will be useful for exploring the phenomena of aggressive tumor phenotype that may arise from miss-irradiation.

Authors
Malcolm, J; Boss, K; Dewhirst, M; Oldham, M
MLA Citation
Malcolm, J, Boss, K, Dewhirst, M, and Oldham, M. "WE-EF-BRA-11: Precision Partial-Tumor Irradiation of Dorsal Rodent Mammary Tumors." Medical physics 42.6 (June 2015): 3677-.
PMID
26129291
Source
epmc
Published In
Medical physics
Volume
42
Issue
6
Publish Date
2015
Start Page
3677
DOI
10.1118/1.4925990

TH-AB-204-02: Preliminary Study of Up-Converting Nanocrystal (UCNC) Imaging in Optical-ECT.

PURPOSE: Optical-emission computed tomography (optical- ECT) enables high-resolution 3D imaging of emission in optically cleared tissues on the order of 1 cm(3). This work demonstrates capabilities of optical-ECT to quantify the red fluorescent protein (RFP) tdTomato in rat lung, and presents preliminary data on the feasibility of imaging near-IR absorptive up-converting nanocrystals (UCNCs) with optical-ECT. METHODS: The nanocrystal NaYF4:Yb/Er studied in this work up-converts 980nm light to visible light peaking sharply at ∼530nm. Collimation of light using telecentric lenses coupled with a CCD array allows for inverse radon 3D reconstruction of fluorescent molecules in optically cleared tissue or whole-organ samples in emission mode. As demonstration of the typical capability of the system, tdTomato RFP emission in the lung of a Cre mouse model is reconstructed in 3D. Compatibility of UCNC with optical clearing is assessed with agarose phantom, to which 1mg/mL of 100-nm diameter NaYF4:Yb/Er coated with polyethyleneimine was injected at two different locations before the agarose was fixed with ethanol and cleared with methyl salicylate. RESULTS: Emission mode imaging of the tdTomato-expressing mouse lung reveals in high-resolution (25.8µm(3)/voxel) information unseen in transmission imaging. UCNCs are shown to emit in ethanol and methyl salicylate, detected by fluorimetry. Projection images of injected UCNC crystals in agarose confirm that the crystal is unaffected by optical clearing. One-second exposure images of the excited nanocrystals yield maximum CCD counts of ∼3800 with a 530nm filter, a significant increase compared to three-second exposure image of tdTomato yielding ∼1200 counts. CONCLUSION: Optical-ECT imaging enables 3D emission mapping of un-sectioned tissue or whole organ on the order of 1cm(3). UCNCs are not only confirmed to be unaffected by optical clearing but also yield high intensity fluorescence. Since UCNC is biocompatible, 3D imaging of the behavior of cancer cells in small animal models with UCNCs is currently under exploration.

Authors
Yoon, P; Langloss, B; Stecher, J; Oldham, M; Therien, M
MLA Citation
Yoon, P, Langloss, B, Stecher, J, Oldham, M, and Therien, M. "TH-AB-204-02: Preliminary Study of Up-Converting Nanocrystal (UCNC) Imaging in Optical-ECT." Medical physics 42.6 (June 2015): 3714-.
PMID
26129469
Source
epmc
Published In
Medical physics
Volume
42
Issue
6
Publish Date
2015
Start Page
3714
DOI
10.1118/1.4926169

SU-E-T-353: Effects of Time and Temperature On a Potential Reusable 3D Dosimeter.

PURPOSE: Preliminary studies of a novel, optically-clearing PRESAGE 3D dosimeter formulation (Presage-RU) demonstrated potential reusability. This study investigates the effects of time and temperature on the accuracy and reusability of Presage-RU, and reports on progress toward developing a reusable 3D dosimeter. METHODS: Presage-RU was cast as small volume samples (1×1×4.5cm). The effect of dose response sensitivity with reirradiation and time was evaluated by irradiating samples from 0-10Gy, measuring change in optical density (ΔOD), clearing at room temperature (RT) (5-7 days to fully clear), and then repeating for a total of 5 irradiations. Effects of heating on clearing rate were investigated by irradiating samples to 8Gy, then tracking measurements with samples held at RT, 35°C, and 45°C. Two cylindrical dosimeters (11cm diameter, 9.5cm length) were evaluated for dosimetric accuracy when stored at RT and -3°C prior to irradiation. Plans delivered were 2 overlapping AP fields (RT) and VMAT (-3°C). RESULTS: Heating the dosimeters reduced the clearing half-life from 16.3h at RT to 5.8h (35°C) and 5.1h (45°C), but also increased background ΔOD by 1.7x (35°C) and 2.3x (45°C). Reductions in dose response were more closely linked to age than reirradiation, and storage at RT showed pronounced desensitization from dosimeter edges. These results suggest desensitization from oxygen diffusion. It should be noted that atmospheric diffusion into the dosimeter is not seen in standard, single-use PRESAGE, and is likely caused by differences in the Presage-RU polyurethane matrix. The dosimeter kept in cold storage, however, showed no evidence of desensitization and exhibited accuracy on par with standard PRESAGE with a 3%/3mm 3D gamma passing rate of 98.1%. CONCLUSIONS: Presage-RU is sensitive to storage temperatures and time, both of which affect oxygen diffusion and subsequent desensitization. Development shows promising progress with further formulation optimization as the next step toward achieving a successful reusable 3D dosimeter. This work was supported by NIH R01CA100835. John Adamovics is the president of Heuris Inc., which commercializes PRESAGE.

Authors
Juang, T; Miles, D; Crockett, E; Adamovics, J; Oldham, M
MLA Citation
Juang, T, Miles, D, Crockett, E, Adamovics, J, and Oldham, M. "SU-E-T-353: Effects of Time and Temperature On a Potential Reusable 3D Dosimeter." Medical physics 42.6 (June 2015): 3414-.
PMID
26128016
Source
epmc
Published In
Medical physics
Volume
42
Issue
6
Publish Date
2015
Start Page
3414
DOI
10.1118/1.4924714

SU-E-T-675: Remote Dosimetry with a Novel PRESAGE Formulation.

PURPOSE: 3D-gel dosimetry provides high-resolution treatment validation; however, scanners aren't widely available. In remote dosimetry, dosimeters are shipped out from a central base institution to a remote site for irradiation, then shipped back for scanning and analysis, affording a convenient service for treatment validation to institutions lacking the necessary equipment and resources. Previous works demonstrated the high-resolution performance and temporal stability of PRESAGE. Here the newest formulation is investigated for remote dosimetry use. METHODS: A new formulation of PRESAGE was created with the aim of improved color stability post irradiation. Dose sensitivity was determined by irradiating cuvettes on a Varian Linac (6MV) from 0-15Gy and measuring change in optical density at 633nm. Sensitivity readings were tracked over time in a temperature control study to determine long-term stability. A large volume study was performed to evaluate the accuracy for remote dosimetry. A 1kg dosimeter was pre-scanned, irradiated on-site with an 8Gy 4field box treatment, post-scanned and shipped to Princess Margaret Hospital for remote reading on an identical scanner. RESULTS: Dose sensitivities ranged from 0.0194-0.0295 ΔOD/(Gy*cm)-similar to previous formulations. Post-irradiated cuvettes stored at 10°C retained 100% initial sensitivity over 5 days and 98.6% over 10 weeks while cuvettes stored at room temperature fell to 95.8% after 5 days and 37.4% after 10 weeks. The immediate and 5-day scans of the 4field box dosimeter data was reconstructed, registered to the corresponding eclipse dose-distribution, and compared with analytical tools in CERR. Immediate and 5-day scans looked visually similar. Line profiles revealed close agreement aside from a slight elevation in dose at the edge in the 5-day readout. CONCLUSION: The remote dosimetry formulation exhibits excellent temporal stability in small volumes. While immediate and 5-day readout scans of large volume dosimeters show promising agreement, further development is required to reduce an apparent time dependent edge elevation.

Authors
Mein, S; Juang, T; Malcolm, J; Adamovics, J; Oldham, M
MLA Citation
Mein, S, Juang, T, Malcolm, J, Adamovics, J, and Oldham, M. "SU-E-T-675: Remote Dosimetry with a Novel PRESAGE Formulation." Medical physics 42.6 (June 2015): 3492-.
PMID
26128342
Source
epmc
Published In
Medical physics
Volume
42
Issue
6
Publish Date
2015
Start Page
3492
DOI
10.1118/1.4925038

SU-E-T-341: DVH-Based Comparison of True 3D Measurements to a Delta4 System.

PURPOSE: Delta4 dosimetric software can be used to calculate DVH-based metrics for patient-specific quality assurance from measurements made by a Delta4 QA device. This study investigates the effectiveness of a novel transform method that transposes measurements made with a full-density 3D dosimeter onto patient anatomy, enabling the calculation of DVHs. This allows for DVH comparisons from the transformed dose distribution, which are based on true 3D measurements, to those from the Delta4 system, which are based on semi-3D measurements and interpolation. METHODS: A double-arc VMAT treatment for a head-and-neck case was delivered to a 1kg PRESAGE 3D dosimeter inserted into a polyurethane head phantom. The dosimeter was readout using an in-house optical-CT scanner to gather full-density 3D dosimetric data. The transform method is achieved by multiplication of the measured doses with a "transformation matrix" which accounts for heterogeneities and differences in geometry between the patient and the phantom. The transformation matrix is a voxel-by-voxel division of the patient planned dose by the phantom planned dose, both calculated in the treatment planning system (Eclipse). The transformed distribution was then overlaid on the patient CT data, enabling the calculation of DVHs. The same VMAT treatment was delivered to the Delta4 phantom and DVH data was calculated using its associated software. RESULTS: The transformed dose distribution showed good agreement with calculated patient values, determined by similarity in dose profiles between the two distributions and a 3D gamma index passing rate of 94.87% for 3%/3mm criteria. For every structure contained within the dosimeter volume, the transformed DVHs demonstrated better agreement than the Delta4 DVHs, when compared to the values calculated in the treatment planning system. CONCLUSION: The coupled technique of full-density 3D dose measurements and the presented transform method enables clinical patient-specific quality assurance data that is more accurate than the semi-3D Delta4 system. This work was supported by NIH R01CA100835.

Authors
Crockett, E; Oldham, M; Ren, L
MLA Citation
Crockett, E, Oldham, M, and Ren, L. "SU-E-T-341: DVH-Based Comparison of True 3D Measurements to a Delta4 System." Medical physics 42.6 (June 2015): 3411-.
PMID
26128004
Source
epmc
Published In
Medical physics
Volume
42
Issue
6
Publish Date
2015
Start Page
3411
DOI
10.1118/1.4924702

SU-D-213-05: Design, Evaluation and First Applications of a Off-Site State-Of-The-Art 3D Dosimetry System.

PURPOSE: To design, construct and commission a prototype in-house three dimensional (3D) dose verification system for stereotatic body radiotherapy (SBRT) verification at an off-site partner institution. To investigate the potential of this system to achieve sufficient performance (1mm resolution, 3% noise, within 3% of true dose reading) for SBRT verification. METHODS: The system was designed utilizing a parallel ray geometry instigated by precision telecentric lenses and an LED 630nm light source. Using a radiochromic dosimeter, a 3D dosimetric comparison with our gold-standard system and treatment planning software (Eclipse) was done for a four-field box treatment, under gamma passing criteria of 3%/3mm/10% dose threshold. Post off-site installation, deviations in the system's dose readout performance was assessed by rescanning the four-field box irradiated dosimeter and using line-profiles to compare on-site and off-site mean and noise levels in four distinct dose regions. As a final step, an end-to-end test of the system was completed at the off-site location, including CT-simulation, irradiation of the dosimeter and a 3D dosimetric comparison of the planned (Pinnacle(3)) to delivered dose for a spinal SBRT treatment(12 Gy per fraction). RESULTS: The noise level in the high and medium dose regions of the four field box treatment was relatively 5% pre and post installation. This reflects the reduction in positional uncertainty through the new design. This At 1mm dose voxels, the gamma pass rates(3%,3mm) for our in-house gold standard system and the off-site system were comparable at 95.8% and 93.2% respectively. CONCLUSION: This work will describe the end-to-end process and results of designing, installing, and commissioning a state-of-the-art 3D dosimetry system created for verification of advanced radiation treatments including spinal radiosurgery.

Authors
Malcolm, J; Mein, S; McNiven, A; Letourneau, D; Oldham, M
MLA Citation
Malcolm, J, Mein, S, McNiven, A, Letourneau, D, and Oldham, M. "SU-D-213-05: Design, Evaluation and First Applications of a Off-Site State-Of-The-Art 3D Dosimetry System." Medical physics 42.6 (June 2015): 3207-.
PMID
26127163
Source
epmc
Published In
Medical physics
Volume
42
Issue
6
Publish Date
2015
Start Page
3207
DOI
10.1118/1.4923857

SU-E-T-93: Activation of Psoralen at Depth Using Kilovoltage X-Rays: Physics Considerations in Implementing a New Teletherapy Paradigm.

PURPOSE: Psoralen is a UV-light activated anti-cancer biotherapeutic used for treating skin lesions (PUVA) and advanced cutaneous T-cell lymphoma (ECP). To date psoralen has not been used to treat deep seated tumors due to difficulty in generating UV-light at depth. We recently demonstrated psoralen activation at depth by introducing energy converting particles that absorb kV x-ray radiation and re-emit UV-light. Our in-vitro work found that 0.2-1Gy using 40-100kVp x-rays combined with psoralen and particles can induce a substantial apoptotic response beyond that expected from the sum of individual components. In preparation for a phase I clinical trial of canine companion animals, we address the physics and dosimetry considerations for applying this new teletherapy paradigm to an in-vivo setting. METHODS: The kV on-board imaging (OBI) system mounted on a medical linear accelerator (Varian) was commissioned to deliver the prescribed dose (0.6Gy) using 80 and 100kVp. Dosimetric measurements included kVp, HVL, depth dose, backscatter factors, collimator and phantom scatter factors, field size factors, and blade leakage. Absolute dosimetry was performed following AAPM TG61 recommendations and verified with an independent kV dose meter. We also investigated collimated rotational delivery to minimize skin dose using simple dose calculations on homogeneous cylindrical phantoms. RESULTS: Single beam delivery is feasible for shallow targets (<5cm) without exceeding skin tolerance, while a rotational delivery may be utilized for deeper targets; skin dose is ∼75% of target dose for 80kVp collimated rotational delivery to a 3cm target within a 20cm phantom. Heat loading was tolerable; 0.6Gy to 5cm can be delivered before the anode reaches 75% capacity. CONCLUSION: KV teletherapy for Psoralen activation in deep seated tissue was successfully commissioned for a Varian OBI machine for use in a phase I clinical trial in canines. Future work will use Monte Carlo dosimetry to investigate dose in presence of bone. Research funded by Immunolight LLC. H. Walder, Z. Fathi, & W. Beyer are employees of Immunolight LLC which holds a patent on the technology. Drs. Adamson and Oldham are consultants to Immunolight LLC.

Authors
Adamson, J; Nolan, M; Gieger, T; Walder, H; Yoon, P; Fathi, Z; Beyer, W; Liu, L; Alcorta, D; Spector, N; Oldham, M
MLA Citation
Adamson, J, Nolan, M, Gieger, T, Walder, H, Yoon, P, Fathi, Z, Beyer, W, Liu, L, Alcorta, D, Spector, N, and Oldham, M. "SU-E-T-93: Activation of Psoralen at Depth Using Kilovoltage X-Rays: Physics Considerations in Implementing a New Teletherapy Paradigm." Medical physics 42.6 (June 2015): 3352-.
PMID
26127757
Source
epmc
Published In
Medical physics
Volume
42
Issue
6
Publish Date
2015
Start Page
3352
DOI
10.1118/1.4924454

Effects of Time and Temperature On a Potential Reusable 3D Dosimeter

Authors
Juang, T; Miles, D; Crockett, E; Adamovics, J; Oldham, M
MLA Citation
Juang, T, Miles, D, Crockett, E, Adamovics, J, and Oldham, M. "Effects of Time and Temperature On a Potential Reusable 3D Dosimeter." June 2015.
Source
wos-lite
Published In
Medical physics
Volume
42
Issue
6
Publish Date
2015
Start Page
3414
End Page
3414

DVH-Based Comparison of True 3D Measurements to a Delta4 System

Authors
Crockett, E; Oldham, M; Ren, L
MLA Citation
Crockett, E, Oldham, M, and Ren, L. "DVH-Based Comparison of True 3D Measurements to a Delta4 System." June 2015.
Source
wos-lite
Published In
Medical physics
Volume
42
Issue
6
Publish Date
2015
Start Page
3411
End Page
3412

Design, Evaluation and First Applications of a Off-Site State-Of-The-Art 3D Dosimetry System

Authors
Malcolm, I; Mein, S; McNiven, A; Letourneau, D; Oldham, M
MLA Citation
Malcolm, I, Mein, S, McNiven, A, Letourneau, D, and Oldham, M. "Design, Evaluation and First Applications of a Off-Site State-Of-The-Art 3D Dosimetry System." June 2015.
Source
wos-lite
Published In
Medical physics
Volume
42
Issue
6
Publish Date
2015
Start Page
3207
End Page
3207

Activation of Psoralen at Depth Using Kilovoltage X-Rays: Physics Considerations in Implementing a New Teletherapy Paradigm

Authors
Adamson, J; Nolan, M; Gieger, T; Walder, H; Yoon, P; Fathi, Z; Beyer, W; Liu, L; Alcorta, D; Spector, N; Oldham, M
MLA Citation
Adamson, J, Nolan, M, Gieger, T, Walder, H, Yoon, P, Fathi, Z, Beyer, W, Liu, L, Alcorta, D, Spector, N, and Oldham, M. "Activation of Psoralen at Depth Using Kilovoltage X-Rays: Physics Considerations in Implementing a New Teletherapy Paradigm." June 2015.
Source
wos-lite
Published In
Medical physics
Volume
42
Issue
6
Publish Date
2015
Start Page
3352
End Page
3352

Preliminary Study of Up-Converting Nanocrystal (UCNC) Imaging in Optical-ECT

Authors
Yoon, P; Langloss, B; Stecher, J; Oldham, M; Therien, M
MLA Citation
Yoon, P, Langloss, B, Stecher, J, Oldham, M, and Therien, M. "Preliminary Study of Up-Converting Nanocrystal (UCNC) Imaging in Optical-ECT." June 2015.
Source
wos-lite
Published In
Medical physics
Volume
42
Issue
6
Publish Date
2015
Start Page
3714
End Page
3714

Precision Partial-Tumor Irradiation of Dorsal Rodent Mammary Tumors

Authors
Malcolm, J; Boss, K; Dewhirst, M; Oldham, M
MLA Citation
Malcolm, J, Boss, K, Dewhirst, M, and Oldham, M. "Precision Partial-Tumor Irradiation of Dorsal Rodent Mammary Tumors." June 2015.
Source
wos-lite
Published In
Medical physics
Volume
42
Issue
6
Publish Date
2015
Start Page
3677
End Page
3677

Remote Dosimetry with a Novel PRESAGE Formulation

Authors
Mein, S; Juang, T; Malcolm, J; Adamovics, J; Oldham, M
MLA Citation
Mein, S, Juang, T, Malcolm, J, Adamovics, J, and Oldham, M. "Remote Dosimetry with a Novel PRESAGE Formulation." June 2015.
Source
wos-lite
Published In
Medical physics
Volume
42
Issue
6
Publish Date
2015
Start Page
3492
End Page
3492

Investigations into the feasibility of optical-CT 3D dosimetry with minimal use of refractively matched fluids.

In optical-CT, the use of a refractively matched polyurethane solid-tank in place of a fluid bath has the potential to greatly increase practical convenience, reduce cost, and possibly improve the efficacy of flood corrections. This work investigates the feasibility of solid-tank optical-CT imaging for 3D dosimetry through computer simulation.A matlab ray-tracing simulation platform, ScanSim, was used to model a parallel-source telecentric optical-CT imaging system through a polyurethane solid-tank containing a central cylindrical hollow into which PRESAGE radiochromic dosimeters can be placed. A small amount of fluid fills the 1-5 mm gap between the dosimeter and the walls of the tank. The use of the solid-tank reduces the required amount of fluid by approximately 97%. To characterize the efficacy of solid-tank, optical-CT scanning simulations investigated sensitivity to refractive index (RI) mismatches between dosimeter, solid-tank, and fluid, for a variety of dosimeter (RI = 1.5-1.47) and fluid (RI = 1.55-1.0) combinations. Efficacy was evaluated through the usable radius (ru) metric, defined as the fraction of the radius of the dosimeter where measured dose is predicted to be within 2% of the ground truth entered into the simulation. Additional simulations examined the effect of increasing gap size (1-5 mm) between the dosimeter and solid-tank well. The effects of changing the lens tolerance (0.5°-5.0°) were also investigated.As the RI mismatch between the dosimeter and solid-tank increased from 0 to 0.02, the usable radius decreased from 97.6% to 50.2%. The optimal fluid RI decreased nonlinearly from 1.5 to 1.34 as the mismatch increased and was up to 9% lower than the tank. Media mismatches between the dosimeter and solid-tank also exacerbate the effects of changing the gap size, with no easily quantifiable relationship with usable radius. Generally, the optimal fluid RI value increases as gap size increases and is closely matched to the dosimeter at large gap sizes (> 3 mm). Increasing the telecentric lens tolerance increases the usable radius for all refractive media combinations and improves the maximum usable radius of mismatched media to that of perfectly matched media for tolerances > 5.0°. The maximum usable radius can be improved up to a factor of 2 when lens tolerances are small (< 1.0°).Dry solid-tank optical-CT imaging in a telecentric system is feasible if the dosimeter RI is a close match with the solid-tank (< 0.01 difference), providing accurate dose measurements within ± 2% of true dose to over 80% of the dosimeter volume. In order to achieve accurate measurements over 96% of the dosimeter volume (representing out to 2 mm from the dosimeter edge), the dosimeter-tank RI mismatch must be less than 0.005. Optimal results occur when the RI of the dosimeter and tank is the same, in which case the fluid will have the same RI. If mismatches between the tank and dosimeter RI occur, the RI of the matching fluid needs to be fine tuned to achieve the highest usable radius.

Authors
Chisholm, K; Miles, D; Rankine, L; Oldham, M
MLA Citation
Chisholm, K, Miles, D, Rankine, L, and Oldham, M. "Investigations into the feasibility of optical-CT 3D dosimetry with minimal use of refractively matched fluids." Medical physics 42.5 (May 2015): 2607-2614.
PMID
25979052
Source
epmc
Published In
Medical physics
Volume
42
Issue
5
Publish Date
2015
Start Page
2607
End Page
2614
DOI
10.1118/1.4915530

An investigation of PRESAGE® 3D dosimetry for IMRT and VMAT radiation therapy treatment verification.

The purpose of this work was to characterize three formulations of PRESAGE(®) dosimeters (DEA-1, DEA-2, and DX) and to identify optimal readout timing and procedures for accurate in-house 3D dosimetry. The optimal formulation and procedure was then applied for the verification of an intensity modulated radiation therapy (IMRT) and a volumetric modulated arc therapy (VMAT) treatment technique. PRESAGE(®) formulations were studied for their temporal stability post-irradiation, sensitivity, and linearity of dose response. Dosimeters were read out using a high-resolution optical-CT scanner. Small volumes of PRESAGE(®) were irradiated to investigate possible differences in sensitivity for large and small volumes ('volume effect'). The optimal formulation and read-out technique was applied to the verification of two patient treatments: an IMRT plan and a VMAT plan. A gradual decrease in post-irradiation optical-density was observed in all formulations with DEA-1 exhibiting the best temporal stability with less than 4% variation between 2-22 h post-irradiation. A linear dose response at the 4 h time point was observed for all formulations with an R(2) value >0.99. A large volume effect was observed for DEA-1 with sensitivity of the large dosimeter being ~63% less than the sensitivity of the cuvettes. For the IMRT and VMAT treatments, the 3D gamma passing rates for 3%/3 mm criteria using absolute measured dose were 99.6 and 94.5% for the IMRT and VMAT treatments, respectively. In summary, this work shows that accurate 3D dosimetry is possible with all three PRESAGE(®) formulations. The optimal imaging windows post-irradiation were 3-24 h, 2-6 h, and immediately for the DEA-1, DEA-2, and DX formulations, respectively. Because of the large volume effect, small volume cuvettes are not yet a reliable method for calibration of larger dosimeters to absolute dose. Finally, PRESAGE(®) is observed to be a useful method of 3D verification when careful consideration is given to the temporal stability and imaging protocols for the specific formulation used.

Authors
Jackson, J; Juang, T; Adamovics, J; Oldham, M
MLA Citation
Jackson, J, Juang, T, Adamovics, J, and Oldham, M. "An investigation of PRESAGE® 3D dosimetry for IMRT and VMAT radiation therapy treatment verification." Physics in medicine and biology 60.6 (March 2015): 2217-2230.
PMID
25683902
Source
epmc
Published In
Physics in Medicine and Biology
Volume
60
Issue
6
Publish Date
2015
Start Page
2217
End Page
2230
DOI
10.1088/0031-9155/60/6/2217

Investigating the accuracy of microstereotactic-body-radiotherapy utilizing anatomically accurate 3D printed rodent-morphic dosimeters.

Sophisticated small animal irradiators, incorporating cone-beam-CT image-guidance, have recently been developed which enable exploration of the efficacy of advanced radiation treatments in the preclinical setting. Microstereotactic-body-radiation-therapy (microSBRT) is one technique of interest, utilizing field sizes in the range of 1-15 mm. Verification of the accuracy of microSBRT treatment delivery is challenging due to the lack of available methods to comprehensively measure dose distributions in representative phantoms with sufficiently high spatial resolution and in 3 dimensions (3D). This work introduces a potential solution in the form of anatomically accurate rodent-morphic 3D dosimeters compatible with ultrahigh resolution (0.3 mm(3)) optical computed tomography (optical-CT) dose read-out.Rodent-morphic dosimeters were produced by 3D-printing molds of rodent anatomy directly from contours defined on x-ray CT data sets of rats and mice, and using these molds to create tissue-equivalent radiochromic 3D dosimeters from Presage. Anatomically accurate spines were incorporated into some dosimeters, by first 3D printing the spine mold, then forming a high-Z bone equivalent spine insert. This spine insert was then set inside the tissue equivalent body mold. The high-Z spinal insert enabled representative cone-beam CT IGRT targeting. On irradiation, a linear radiochromic change in optical-density occurs in the dosimeter, which is proportional to absorbed dose, and was read out using optical-CT in high-resolution (0.5 mm isotropic voxels). Optical-CT data were converted to absolute dose in two ways: (i) using a calibration curve derived from other Presage dosimeters from the same batch, and (ii) by independent measurement of calibrated dose at a point using a novel detector comprised of a yttrium oxide based nanocrystalline scintillator, with a submillimeter active length. A microSBRT spinal treatment was delivered consisting of a 180° continuous arc at 225 kVp with a 20 × 10 mm field size. Dose response was evaluated using both the Presage/optical-CT 3D dosimetry system described above, and independent verification in select planes using EBT2 radiochromic film placed inside rodent-morphic dosimeters that had been sectioned in half.Rodent-morphic 3D dosimeters were successfully produced from Presage radiochromic material by utilizing 3D printed molds of rat CT contours. The dosimeters were found to be compatible with optical-CT dose readout in high-resolution 3D (0.5 mm isotropic voxels) with minimal artifacts or noise. Cone-beam CT image guidance was possible with these dosimeters due to sufficient contrast between high-Z spinal inserts and tissue equivalent Presage material (CNR ∼10 on CBCT images). Dose at isocenter measured with optical-CT was found to agree with nanoscintillator measurement to within 2.8%. Maximum dose in line profiles taken through Presage and film dose slices agreed within 3%, with FWHM measurements through each profile found to agree within 2%.This work demonstrates the feasibility of using 3D printing technology to make anatomically accurate Presage rodent-morphic dosimeters incorporating spinal-mimicking inserts. High quality optical-CT 3D dosimetry is feasible on these dosimeters, despite the irregular surfaces and implanted inserts. The ability to measure dose distributions in anatomically accurate phantoms represents a powerful useful additional verification tool for preclinical microSBRT.

Authors
Bache, ST; Juang, T; Belley, MD; Koontz, BF; Adamovics, J; Yoshizumi, TT; Kirsch, DG; Oldham, M
MLA Citation
Bache, ST, Juang, T, Belley, MD, Koontz, BF, Adamovics, J, Yoshizumi, TT, Kirsch, DG, and Oldham, M. "Investigating the accuracy of microstereotactic-body-radiotherapy utilizing anatomically accurate 3D printed rodent-morphic dosimeters." Medical physics 42.2 (February 2015): 846-855.
PMID
25652497
Source
epmc
Published In
Medical physics
Volume
42
Issue
2
Publish Date
2015
Start Page
846
End Page
855
DOI
10.1118/1.4905489

Verification of micro-beam irradiation

Authors
Li, Q; Juang, T; Beth, R; Chang, S; Oldham, M
MLA Citation
Li, Q, Juang, T, Beth, R, Chang, S, and Oldham, M. "Verification of micro-beam irradiation." January 12, 2015.
Source
crossref
Published In
Journal of Physics
Volume
573
Publish Date
2015
Start Page
012047
End Page
012047
DOI
10.1088/1742-6596/573/1/012047

Radiochromic 3D Detectors

Authors
Oldham, M
MLA Citation
Oldham, M. "Radiochromic 3D Detectors." January 12, 2015.
Source
crossref
Published In
Journal of Physics
Volume
573
Publish Date
2015
Start Page
012006
End Page
012006
DOI
10.1088/1742-6596/573/1/012006

Characterization of a reusable PRESAGE® 3D dosimeter

Authors
Juang, T; Adamovics, J; Oldham, M
MLA Citation
Juang, T, Adamovics, J, and Oldham, M. "Characterization of a reusable PRESAGE® 3D dosimeter." January 12, 2015.
Source
crossref
Published In
Journal of Physics
Volume
573
Publish Date
2015
Start Page
012039
End Page
012039
DOI
10.1088/1742-6596/573/1/012039

Investigation of a low-cost optical-CT system with minimal refractive index-matching fluid

Authors
Bache, S; Malcolm, J; Adamovics, J; Oldham, M
MLA Citation
Bache, S, Malcolm, J, Adamovics, J, and Oldham, M. "Investigation of a low-cost optical-CT system with minimal refractive index-matching fluid." January 12, 2015.
Source
crossref
Published In
Journal of Physics
Volume
573
Publish Date
2015
Start Page
012052
End Page
012052
DOI
10.1088/1742-6596/573/1/012052

Treatment Planning and Delivery of Whole Brain Irradiation with Hippocampal Avoidance in Rats.

Despite the clinical benefit of whole brain radiotherapy (WBRT), patients and physicians are concerned by the long-term impact on cognitive functioning. Many studies investigating the molecular and cellular impact of WBRT have used rodent models. However, there has not been a rodent protocol comparable to the recently reported Radiation Therapy Oncology Group (RTOG) protocol for WBRT with hippocampal avoidance (HA) which is intended to spare cognitive function. The aim of this study was to develop a hippocampal-sparing WBRT protocol in Wistar rats.The technical and clinical challenges encountered in hippocampal sparing during rat WBRT are substantial. Three key challenges were identified: hippocampal localization, treatment planning, and treatment localization. Hippocampal localization was achieved with sophisticated imaging techniques requiring deformable registration of a rat MRI atlas with a high resolution MRI followed by fusion via rigid registration to a CBCT. Treatment planning employed a Monte Carlo dose calculation in SmART-Plan and creation of 0.5 cm thick lead blocks custom-shaped to match DRR projections. Treatment localization necessitated the on-board image-guidance capability of the XRAD C225Cx micro-CT/micro-irradiator (Precision X-Ray). Treatment was accomplished with opposed lateral fields with 225 KVp X-rays at a current of 13 mA filtered through 0.3 mm of copper using a 40x40 mm square collimator and the lead blocks. A single fraction of 4 Gy was delivered (2 Gy per lateral field) with a 41 second beam on time per field at a dose rate of 304.5 cGy/min. Dosimetric verification of hippocampal sparing was performed using radiochromic film. In vivo verification of HA was performed after delivery of a single 4 Gy fraction either with or without HA using γ-H2Ax staining of tissue sections from the brain to quantify the amount of DNA damage in rats treated with HA, WBRT, or sham-irradiated (negative controls).The mean dose delivered to radiochromic film beneath the hippocampal block was 0.52 Gy compared to 3.93 Gy without the block, indicating an 87% reduction in the dose delivered to the hippocampus. This difference was consistent with doses predicted by Monte Carlo dose calculation. The Dose Volume Histogram (DVH) generated via Monte Carlo simulation showed an underdose of the target volume (brain minus hippocampus) with 50% of the target volume receiving 100% of the prescription isodose as a result of the lateral blocking techniques sparing some midline thalamic and subcortical tissue. Staining of brain sections with anti-phospho-Histone H2A.X (reflecting double-strand DNA breaks) demonstrated that this treatment protocol limited radiation dose to the hippocampus in vivo. The mean signal intensity from γ-H2Ax staining in the cortex was not significantly different from the signal intensity in the cortex of rats treated with WBRT (5.40 v. 5.75, P = 0.32). In contrast, the signal intensity in the hippocampus of rats treated with HA was significantly lower than rats treated with WBRT (4.55 v. 6.93, P = 0.012).Despite the challenges of planning conformal treatments for small volumes in rodents, our dosimetric and in vivo data show that WBRT with HA is feasible in rats. This study provides a useful platform for further application and refinement of the technique.

Authors
Cramer, CK; Yoon, SW; Reinsvold, M; Joo, KM; Norris, H; Hood, RC; Adamson, JD; Klein, RC; Kirsch, DG; Oldham, M
MLA Citation
Cramer, CK, Yoon, SW, Reinsvold, M, Joo, KM, Norris, H, Hood, RC, Adamson, JD, Klein, RC, Kirsch, DG, and Oldham, M. "Treatment Planning and Delivery of Whole Brain Irradiation with Hippocampal Avoidance in Rats." PloS one 10.12 (January 2015): e0143208-.
PMID
26636762
Source
epmc
Published In
PloS one
Volume
10
Issue
12
Publish Date
2015
Start Page
e0143208
DOI
10.1371/journal.pone.0143208

Deformable Dose Reconstruction With Biomechanical Registration: Validation in Low-Contrast Images

Authors
Velec, M; Juang, T; Moseley, JL; Oldham, M; Brock, KK
MLA Citation
Velec, M, Juang, T, Moseley, JL, Oldham, M, and Brock, KK. "Deformable Dose Reconstruction With Biomechanical Registration: Validation in Low-Contrast Images." September 1, 2014.
Source
wos-lite
Published In
International Journal of Radiation Oncology, Biology, Physics
Volume
90
Publish Date
2014
Start Page
S73
End Page
S73

An investigation of a PRESAGE® in vivo dosimeter for brachytherapy.

Determining accurate in vivo dosimetry in brachytherapy treatment with high dose gradients is challenging. Here we introduce, investigate, and characterize a novel in vivo dosimeter and readout technique with the potential to address this problem. A cylindrical (4 mm × 20 mm) tissue equivalent radiochromic dosimeter PRESAGE® in vivo (PRESAGE®-IV) is investigated. Two readout methods of the radiation induced change in optical density (OD) were investigated: (i) volume-averaged readout by spectrophotometer, and (ii) a line profile readout by 2D projection imaging utilizing a high-resolution (50 micron) telecentric optical system. Method (i) is considered the gold standard when applied to PRESAGE® in optical cuvettes. The feasibility of both methods was evaluated by comparison to standard measurements on PRESAGE® in optical cuvettes via spectrophotometer. An end-to-end feasibility study was performed by a side-by-side comparison with TLDs in an (192)Ir HDR delivery. 7 and 8 Gy was delivered to PRESAGE®-IV and TLDs attached to the surface of a vaginal cylinder. Known geometry enabled direct comparison of measured dose with a commissioned treatment planning system. A high-resolution readout study under a steep dose gradient region showed 98.9% (5%/1 mm) agreement between PRESAGE®-IV and Gafchromic® EBT2 Film. Spectrometer measurements exhibited a linear dose response between 0-15 Gy with sensitivity of 0.0133 ± 0.0007 ΔOD/(Gy ⋅ cm) at the 95% confidence interval. Method (ii) yielded a linear response with sensitivity of 0.0132 ± 0.0006 (ΔOD/Gy), within 2% of method (i). Method (i) has poor spatial resolution due to volume averaging. Method (ii) has higher resolution (∼1 mm) without loss of sensitivity or increased noise. Both readout methods are shown to be feasible. The end-to-end comparison revealed a 2.5% agreement between PRESAGE®-IV and treatment plan in regions of uniform high dose. PRESAGE®-IV shows promise for in vivo dose verification, although improved sensitivity would be desirable. Advantages include high-resolution, convenience and fast, low-cost readout.

Authors
Vidovic, AK; Juang, T; Meltsner, S; Adamovics, J; Chino, J; Steffey, B; Craciunescu, O; Oldham, M
MLA Citation
Vidovic, AK, Juang, T, Meltsner, S, Adamovics, J, Chino, J, Steffey, B, Craciunescu, O, and Oldham, M. "An investigation of a PRESAGE® in vivo dosimeter for brachytherapy." Physics in medicine and biology 59.14 (July 2014): 3893-3905.
PMID
24957850
Source
epmc
Published In
Physics in Medicine and Biology
Volume
59
Issue
14
Publish Date
2014
Start Page
3893
End Page
3905
DOI
10.1088/0031-9155/59/14/3893

On the feasibility of comprehensive high-resolution 3D remote dosimetry.

This study investigates the feasibility of remote high-resolution 3D dosimetry with the PRESAGE®/Optical-CT system. In remote dosimetry, dosimeters are shipped out from a central base institution to a remote institution for irradiation, then shipped back to the base institution for subsequent readout and analysis.Two nominally identical optical-CT scanners for 3D dosimetry were constructed and placed at the base (Duke University) and remote (Radiological Physics Center) institutions. Two formulations of PRESAGE® (SS1, SS2) radiochromic dosimeters were investigated. Higher sensitivity was expected in SS1, which had higher initiator content (0.25% bromotrichloromethane), while greater temporal stability was expected in SS2. Four unirradiated PRESAGE® dosimeters (two per formulation, cylindrical dimensions 11 cm diameter, 8.5-9.5 cm length) were imaged at the base institution, then shipped to the remote institution for planning and irradiation. Each dosimeter was irradiated with the same simple treatment plan: an isocentric 3-field "cross" arrangement of 4 × 4 cm open 6 MV beams configured as parallel opposed laterals with an anterior beam. This simple plan was amenable to accurate and repeatable setup, as well as accurate dose modeling by a commissioned treatment planning system (Pinnacle). After irradiation and subsequent (within 1 h) optical-CT readout at the remote institution, the dosimeters were shipped back to the base institution for remote dosimetry readout 3 days postirradiation. Measured on-site and remote relative 3D dose distributions were registered to the Pinnacle dose calculation, which served as the reference distribution for 3D gamma calculations with passing criteria of 5%/2 mm, 3%/3 mm, and 3%/2 mm with a 10% dose threshold. Gamma passing rates, dose profiles, and color-maps were all used to assess and compare the performance of both PRESAGE® formulations for remote dosimetry.The best agreements between the Pinnacle plan and dosimeter readout were observed in PRESAGE® formulation SS2. Under 3%/3 mm 3D gamma passing criteria, passing rates were 91.5% ± 3.6% (SS1) and 97.4% ± 2.2% (SS2) for immediate on-site dosimetry, 96.7% ± 2.4% (SS1) and 97.6% ± 0.6% (SS2) for remote dosimetry. These passing rates are well within TG119 recommendations (88%-90% passing). Under the more stringent criteria of 3%/2 mm, there is a pronounced difference [8.0 percentage points (pp)] between SS1 formulation passing rates for immediate and remote dosimetry while the SS2 formulation maintains both higher passing rates and consistency between immediate and remote results (differences ≤ 1.2 pp) at all metrics. Both PRESAGE® formulations under study maintained high linearity of dose response (R(2) > 0.996) for 1-8 Gy over 14 days with response slope consistency within 4.9% (SS1) and 6.6% (SS2), and a relative dose distribution that remained stable over time was demonstrated in the SS2 dosimeters.Remote 3D dosimetry was shown to be feasible with a PRESAGE® dosimeter formulation (SS2) that exhibited relative temporal stability and high accuracy when read off-site 3 days postirradiation. Characterization of the SS2 dose response demonstrated linearity (R(2) > 0.998) over 14 days and suggests accurate readout over longer periods of time would be possible. This result provides a foundation for future investigations using remote dosimetry to study the accuracy of advanced radiation treatments. Further work is planned to characterize dosimeter reproducibility and dose response over longer periods of time.

Authors
Juang, T; Grant, R; Adamovics, J; Ibbott, G; Oldham, M
MLA Citation
Juang, T, Grant, R, Adamovics, J, Ibbott, G, and Oldham, M. "On the feasibility of comprehensive high-resolution 3D remote dosimetry." Medical physics 41.7 (July 2014): 071706-.
PMID
24989375
Source
epmc
Published In
Medical physics
Volume
41
Issue
7
Publish Date
2014
Start Page
071706
DOI
10.1118/1.4884018

On the feasibility of polyurethane based 3D dosimeters with optical CT for dosimetric verification of low energy photon brachytherapy seeds.

To investigate the feasibility of and challenges yet to be addressed to measure dose from low energy (effective energy <50 keV) brachytherapy sources (Pd-103, Cs-131, and I-125) using polyurethane based 3D dosimeters with optical CT.The authors' evaluation used the following sources: models 200 (Pd-103), CS-1 Rev2 (Cs-131), and 6711 (I-125). The authors used the Monte Carlo radiation transport code MCNP5, simulations with the ScanSim optical tomography simulation software, and experimental measurements with PRESAGE(®) dosimeters/optical CT to investigate the following: (1) the water equivalency of conventional (density = 1.065 g/cm(3)) and deformable (density = 1.02 g/cm(3)) formulations of polyurethane dosimeters, (2) the scatter conditions necessary to achieve accurate dosimetry for low energy photon seeds, (3) the change in photon energy spectrum within the dosimeter as a function of distance from the source in order to determine potential energy sensitivity effects, (4) the optimal delivered dose to balance optical transmission (per projection) with signal to noise ratio in the reconstructed dose distribution, and (5) the magnitude and characteristics of artifacts due to the presence of a channel in the dosimeter. Monte Carlo simulations were performed using both conventional and deformable dosimeter formulations. For verification, 2.8 Gy at 1 cm was delivered in 92 h using an I-125 source to a PRESAGE(®) dosimeter with conventional formulation and a central channel with 0.0425 cm radius for source placement. The dose distribution was reconstructed with 0.02 and 0.04 cm(3) voxel size using the Duke midsized optical CT scanner (DMOS).While the conventional formulation overattenuates dose from all three sources compared to water, the current deformable formulation has nearly water equivalent attenuation properties for Cs-131 and I-125, while underattenuating for Pd-103. The energy spectrum of each source is relatively stable within the first 5 cm especially for I-125. The inherent assumption of radial symmetry in the TG43 geometry leads to a linear increase in sample points within the 3D dosimeter as a function of distance away from the source, which partially offsets the decreasing signal. Simulations of dose reconstruction using optical CT showed the feasibility of reconstructing dose out to a radius of 10 cm without saturating projection images using an optimal dose and high dynamic range scanning; the simulations also predicted that reconstruction artifacts at the channel surface due to a small discrepancy in refractive index should be negligible. Agreement of the measured with calculated radial dose function for I-125 was within 5% between 0.3 and 2.5 cm from the source, and the median difference of measured from calculated anisotropy function was within 5% between 0.3 and 2.0 cm from the source.3D dosimetry using polyurethane dosimeters with optical CT looks to be a promising application to verify dosimetric distributions surrounding low energy brachytherapy sources.

Authors
Adamson, J; Yang, Y; Juang, T; Chisholm, K; Rankine, L; Adamovics, J; Yin, FF; Oldham, M
MLA Citation
Adamson, J, Yang, Y, Juang, T, Chisholm, K, Rankine, L, Adamovics, J, Yin, FF, and Oldham, M. "On the feasibility of polyurethane based 3D dosimeters with optical CT for dosimetric verification of low energy photon brachytherapy seeds." Medical physics 41.7 (July 2014): 071705-.
PMID
24989374
Source
epmc
Published In
Medical physics
Volume
41
Issue
7
Publish Date
2014
Start Page
071705
DOI
10.1118/1.4883779

A comprehensive investigation of the accuracy and reproducibility of a multitarget single isocenter VMAT radiosurgery technique.

PURPOSE: Recent trends in stereotactic radiosurgery use multifocal volumetric modulated arc therapy (VMAT) plans to simultaneously treat several distinct targets. Conventional verification often involves low resolution measurements in a single plane, a cylinder, or intersecting planes of diodes or ion chambers. This work presents an investigation into the consistency and reproducibility of this new treatment technique using a comprehensive commissioned high-resolution 3D dosimetry system (PRESAGE(®)∕Optical-CT). METHODS: A complex VMAT plan consisting of a single isocenter but five separate targets was created in Eclipse for a head phantom containing a cylindrical PRESAGE(®) dosimetry insert of 11 cm diameter and height. The plan contained five VMAT arcs delivering target doses from 12 to 20 Gy. The treatment was delivered to four dosimeters positioned in the head phantom and repeated four times, yielding four separate 3D dosimetry verifications. Each delivery was completely independent and was given after image guided radiation therapy (IGRT) positioning using Brainlab ExacTrac and cone beam computed tomography. A final delivery was given to a modified insert containing a pin-point ion chamber enabling calibration of PRESAGE(®) 3D data to dose. Dosimetric data were read out in an optical-CT scanner. Consistency and reproducibility of the treatment technique (including IGRT setup) was investigated by comparing the dose distributions in the four inserts, and with the predicted treatment planning system distribution. RESULTS: Dose distributions from the four dosimeters were registered and analyzed to determine the mean and standard deviation at all points throughout the dosimeters. A dose standard deviation of <3% was found from dosimeter to dosimeter. Global 3D gamma maps show that the predicted and measured dose matched well [3D gamma passing rate was 98.0% (3%, 2 mm)]. CONCLUSIONS: The deliveries of the irradiation were found to be consistent and matched the treatment plan, demonstrating high accuracy and reproducibility of both the treatment machine and the IGRT procedure. The complexity of the treatment (multiple arcs) and dosimetry (multiple strong gradients) pose a substantial challenge for comprehensive verification. 3D dosimetry can be uniquely effective in this scenario.

Authors
Thomas, A; Niebanck, M; Juang, T; Wang, Z; Oldham, M
MLA Citation
Thomas, A, Niebanck, M, Juang, T, Wang, Z, and Oldham, M. "A comprehensive investigation of the accuracy and reproducibility of a multitarget single isocenter VMAT radiosurgery technique." Med Phys 40.12 (December 2013): 121725-.
PMID
24320511
Source
pubmed
Volume
40
Issue
12
Publish Date
2013
Start Page
121725
DOI
10.1118/1.4829518

Investigating end-to-end accuracy of image guided radiation treatment delivery using a micro-irradiator.

There is significant interest in delivering precisely targeted small-volume radiation treatments, in the pre-clinical setting, to study dose-volume relationships with tumour control and normal tissue damage. For these studies it is vital that image guidance systems and target positioning are accurately aligned (IGRT), in order to deliver dose precisely and accurately according to the treatment plan. In this work we investigate the IGRT targeting accuracy of the X-RAD 225 Cx system from Precision X-Ray using high-resolution 3D dosimetry techniques. Small cylindrical PRESAGE® dosimeters were used with optical-CT readout (DMOS) to verify the accuracy of 2.5, 1.0, and 5.0 mm X-RAD cone attachments. The dosimeters were equipped with four target points, visible on both CBCT and optical-CT, at which a 7-field coplanar treatment plan was delivered with the respective cone. Targeting accuracy (distance to agreement between the target point and delivery isocenter) and cone alignment (isocenter precision under gantry rotation) were measured using the optical-CT images. Optical-CT readout of the first 2.5 mm cone dosimeter revealed a significant targeting error of 2.1 ± 0.6 mm and a cone misalignment of 1.3 ± 0.1 mm. After the IGRT hardware and software had been recalibrated, these errors were reduced to 0.5 ± 0.1 and 0.18 ± 0.04 mm respectively, within the manufacturer specified 0.5 mm. Results from the 1.0 mm cone were 0.5 ± 0.3 mm targeting accuracy and 0.4 ± 0.1 mm cone misalignment, within the 0.5 mm specification. The results from the 5.0 mm cone were 1.0 ± 0.2 mm targeting accuracy and 0.18 ± 0.06 mm cone misalignment, outside of accuracy specifications. Quality assurance of small field IGRT targeting and delivery accuracy is a challenging task. The use of a 3D dosimetry technique, where targets are visible on both CBCT and optical-CT, enabled identification and quantification of a targeting error in 3D. After correction, the targeting accuracy of the irradiator was verified to be within 0.5 mm (or 1.0 mm for the 5.0 mm cone) and the cone alignment was verified to be within 0.2 mm (or 0.4 mm for the 1.0 mm cone). The PRESAGE®/DMOS system proved valuable for end-to-end verification of small field IGRT capabilities.

Authors
Rankine, LJ; Newton, J; Bache, ST; Das, SK; Adamovics, J; Kirsch, DG; Oldham, M
MLA Citation
Rankine, LJ, Newton, J, Bache, ST, Das, SK, Adamovics, J, Kirsch, DG, and Oldham, M. "Investigating end-to-end accuracy of image guided radiation treatment delivery using a micro-irradiator." Phys Med Biol 58.21 (November 7, 2013): 7791-7801.
PMID
24140983
Source
pubmed
Published In
Physics in Medicine and Biology
Volume
58
Issue
21
Publish Date
2013
Start Page
7791
End Page
7801
DOI
10.1088/0031-9155/58/21/7791

On the need for comprehensive validation of deformable image registration, investigated with a novel 3-dimensional deformable dosimeter.

PURPOSE: To introduce and evaluate a novel deformable 3-dimensional (3D) dosimetry system (Presage-Def/Optical-CT) and its application toward investigating the accuracy of dose deformation in a commercial deformable image registration (DIR) package. METHODS AND MATERIALS: Presage-Def is a new dosimetry material consisting of an elastic polyurethane matrix doped with radiochromic leuco dye. Radiologic and mechanical properties were characterized using standard techniques. Dose-tracking feasibility was evaluated by comparing dose distributions between dosimeters irradiated with and without 27% lateral compression. A checkerboard plan of 5-mm square fields enabled precise measurement of true deformation using 3D dosimetry. Predicted deformation was determined from a commercial DIR algorithm. RESULTS: Presage-Def exhibited a linear dose response with sensitivity of 0.0032 ΔOD/(Gy∙cm). Mass density is 1.02 g/cm(3), and effective atomic number is within 1.5% of water over a broad (0.03-10 MeV) energy range, indicating good water-equivalence. Elastic characteristics were close to that of liver tissue, with Young's modulus of 13.5-887 kPa over a stress range of 0.233-303 kPa, and Poisson's ratio of 0.475 (SE, 0.036). The Presage-Def/Optical-CT system successfully imaged the nondeformed and deformed dose distributions, with isotropic resolution of 1 mm. Comparison with the predicted deformed 3D dose distribution identified inaccuracies in the commercial DIR algorithm. Although external contours were accurately deformed (submillimeter accuracy), volumetric dose deformation was poor. Checkerboard field positioning and dimension errors of up to 9 and 14 mm, respectively, were identified, and the 3D DIR-deformed dose γ passing rate was only γ(3%/3 mm) = 60.0%. CONCLUSIONS: The Presage-Def/Optical-CT system shows strong potential for comprehensive investigation of DIR algorithm accuracy. Substantial errors in a commercial DIR were found in the conditions evaluated. This work highlights the critical importance of careful validation of DIR algorithms before clinical implementation.

Authors
Juang, T; Das, S; Adamovics, J; Benning, R; Oldham, M
MLA Citation
Juang, T, Das, S, Adamovics, J, Benning, R, and Oldham, M. "On the need for comprehensive validation of deformable image registration, investigated with a novel 3-dimensional deformable dosimeter." Int J Radiat Oncol Biol Phys 87.2 (October 1, 2013): 414-421.
PMID
23886417
Source
pubmed
Published In
International Journal of Radiation: Oncology - Biology - Physics
Volume
87
Issue
2
Publish Date
2013
Start Page
414
End Page
421
DOI
10.1016/j.ijrobp.2013.05.045

SU-D-108-03: Evaluation of the Feasibility of a Novel Radiochromic Dosimetry System for In-Vivo Dose Verification in Organs at Risk in HDR Intracavitary Gynecological Brachytherapy.

To evaluate the feasibility of a novel radiochromic dosimetry system for in-vivo dose verification in organs at risk in HDR intracavitary gynecological brachytherapy.Novel, small cylindrical PRESAGE dosimeters (4mm in diameter by 20mm in height) were attached to intracavitary HDR brachytherapy applicators near the rectum and bladder of three patients undergoing Ir-192 HDR brachytherapy treatments. Two methods of dose-readout were investigated (i) a volume averaged readout by spectrophotometer, and (ii) 2D projection imaging in a high-resolution (50 micron) telecentric optical system. Both readout techniques were benchmarked against a gold standard. The gold standard consisted of spectrophotometer readout of precision 1×1×4cm optical cuvettes filled with PRESAGE, and irradiated to known doses in a 6 MV photon beam. Temperature corrections were required to account for increased PRESAGE sensitivity at body temperature. Estimated doses were compared with measured dose distributions in Eclipse.Examination of the change in optical density between dosimeters and cuvettes shows a linear relationship in sensitivity between 1-15 Gy with a 95% confidence interval in the slope (0.8703 +/- 0.0192). Patient data showed a 0 % and 2.8% difference in estimated doses vs. Eclipse measurements in the bladder and rectum, respectively.This work presents the spectrophotometer/optical scanning system as a viable dosimetry system, which can provide in-vivo dose verification in intracavitary HDR brachytherapy. Further work needs to be done in regard to dosimeter positioning in patient treatments. NIH Grant RO1CA100835.

Authors
Vidovic, A; Juang, ; Steffey, B; Meltsner, S; Adamovics, J; Chino, J; Craciunescu, O; Oldham, M
MLA Citation
Vidovic, A, Juang, , Steffey, B, Meltsner, S, Adamovics, J, Chino, J, Craciunescu, O, and Oldham, M. "SU-D-108-03: Evaluation of the Feasibility of a Novel Radiochromic Dosimetry System for In-Vivo Dose Verification in Organs at Risk in HDR Intracavitary Gynecological Brachytherapy." Medical physics 40.6Part3 (June 2013): 104-.
PMID
28519546
Source
epmc
Published In
Medical physics
Volume
40
Issue
6Part3
Publish Date
2013
Start Page
104
DOI
10.1118/1.4814013

SU-E-T-353: Feasibility of 3D Dosimetry for Prostate LDR: Monte Carlo Simulations of Pd-103,I-125, and Cs-131 Seeds in Deformable PRESAGE.

Recent innovations in 3D dosimetry include deformable polyurethane dosimeters (PRESAGE) and high resolution optical CT (∼50 microns). These developments enable 3D dosimetry in deformation conditions present during prostate LDR brachytherapy. However, water equivalence for the deformable dosimeter formulations has not been quantified. The purpose of this study was to characterize the dose distributions of Pd-103, I-125, and Cs-131 in different PRESAGE using Monte Carlo (MC) simulations.Dose distributions from models 200(Pd-103), 6711(I-125), and CS-1 Rev2(Cs-131) seeds were simulated using the MCNP5 radiation transport. Geometric function g(r) and anisotropy function Φ(r) from TG43 were calculated from MC results in water and compared to published results to verify the MC technique. Dose distributions were then simulated in 5×5×10 cm^ 3 cylindrical PRESAGE with (0.1cm)^ 3 resolution. Current formulations of both conventional (rigid, 1.065 g/cm^ 3) and deformable (1.02 g/cm^ 3) PRESAGE with effective Z of 7.61 and 7.48 were simulated and g(r) and Φ(r) were calculated in X-Y and X-Z planes respectively. The 2×10^ 9 histories gave a typical statistical uncertainty (k=1) of ∼3% at 6 cm on the transverse plane.Conventional PRESAGE over-attenuated all three sources. Relative to water, g(r) in conventional PRESAGE decreased linearly ∼2.5%/cm within a radius of 1-6 cm for Pd-103, and 1-10 cm for I-125 and Cs-131. Deformable PRESAGE under-attenuated Pd-103 but was water equivalent for I-125 and Cs-131, with g(r) within 5% and 1% of water within a radius of 0-10 cm, respectively. Differences for Φ(r) were <1% for Pd-103 and Cs-131, and <5% for I-125 for both conventional and deformable PRESAGE. MC results indicated underdose >10% at dosimeter surface, while <2% with 2 cm backscatter.Dose distributions for Pd-103, I-125, and Cs-131 have been characterized in PRESAGE and show great potential for water equivalent 3D dosimetry and further deformable formulations optimization. Research efforts at Duke University and Rider University were partially supported by National Institutes of Health (NIH) Grant No. R01 CA100835-01. Dr. John Adamovics is the owner of Heuris Inc.

Authors
Yang, Y; Oldham, M; Adamovics, J; Adamson, J
MLA Citation
Yang, Y, Oldham, M, Adamovics, J, and Adamson, J. "SU-E-T-353: Feasibility of 3D Dosimetry for Prostate LDR: Monte Carlo Simulations of Pd-103,I-125, and Cs-131 Seeds in Deformable PRESAGE." Medical physics 40.6Part16 (June 2013): 285-.
PMID
28517761
Source
epmc
Published In
Medical physics
Volume
40
Issue
6Part16
Publish Date
2013
Start Page
285
DOI
10.1118/1.4814787

WE-E-108-09: An Investigation of the Feasibility of Rodentmorphic 3D Dosimeters for Verification of Precision Micro-Irradiator Treatment.

To evaluate the feasibility of novel rodentmorphic 3D dosimeters for comprehensive high-resolution verification of the treatment accuracy of a state-of-the-art micro-irradiator equipped with on-line cone-beam-CT guidance.Anatomically accurate 3D dosimeter molds were created in a two step procedure. First, rodents were CT scanned and the structures of interest contoured (e.g. body and spine). These contours were then exported for input to a 3D printer, to generate positive dosimeter molds. The rat body dosimeter was made of regular water-equivalent PRESAGE, while the spine was made from high-Z PRESAGE with an effective atomic-number close to bone. Evaluation of the dosimeters involved (i) establishing the feasibility of manufacture and accurate positioning of heterogenous inserts, (ii) verification of accurate dose-readout by optical-CT, and (iii) verification of sufficient bony/soft-tissue contrast for representative CBCT IGRT positioning. Simulated rat prostate treatments were delivered with dose of 16Gy given by 4 2.5cm diameter circular fields.High resolution (0.5mm isotropic) 3D dosimetry data was acquired in rodentmorphic dosimeters both with and without the high-Z spinal insert. The spinal insert was visible under kV radiographs and CBCT, demonstrating the feasibility of IGRT positioning. Pronounced edge artifacts were observed near the flat undersurface of the rat, and near regions of sharp curvature. Further artifacts were observed in some regions near the spinal insert caused by bubbles trapped during manufacture. New manufacturing procedures utilizing the flexibility of 3D printing to precisely customize contours in non-critical regions have improved on both of these limitations.This work demonstrates promising feasibility for anatomically accurate 3D rodentmorphic dosimeters compatible with very high resolution 3D dosimetry. The ability to create such dosimeters is an important step forward in enabling accurate verification of complex micro-irradiator treatments in the pre-clinical setting. NIH Grant No. R01 CA 100835.

Authors
Bache, S; Juang, T; Adamovics, J; Benning, R; Koontz, B; Predmore, K; Dewhirst, M; Oldham, M
MLA Citation
Bache, S, Juang, T, Adamovics, J, Benning, R, Koontz, B, Predmore, K, Dewhirst, M, and Oldham, M. "WE-E-108-09: An Investigation of the Feasibility of Rodentmorphic 3D Dosimeters for Verification of Precision Micro-Irradiator Treatment." Medical physics 40.6Part29 (June 2013): 490-.
PMID
28518639
Source
epmc
Published In
Medical physics
Volume
40
Issue
6Part29
Publish Date
2013
Start Page
490
DOI
10.1118/1.4815587

SU-E-T-53: An Investigation of the Dosimetric Characteristics of a Novel Radiochromic 3D Dosimeter.

A new formulation of PRESAGE has been developed with potential for increased dose sensitivity and post irradiation temporal stability. DEA-PRESAGE differs from conventional PRESAGE by incorporating a methoxy group adjacent to the methine and N,N diethyl groups vs the N,N dimethyl groups of LMG. This work presents an evaluation of the temporal and spatial variation of dose response.All measurements were made on cylindrical DEA-PRESAGE dosimeters of 11cm diameter and 11cm height. Dosimeters were irradiated with five small 6MV radiation beams incident on the upper flat surface. The maximum doses were 3, 6 and 9.5 Gy, with the 3 and 9.5 Gy beams being delivered at two separate locations, and the 6 Gy beam irradiating along the central axis of the dosimeter. Post irradiation, the dose distribution was imaged by optical-CT (1mm isotropic spatial resolution) at half hour intervals for the first 4 hours, then hourly for the next two hours, hourly from 20 to 24 hours, and again at 26 hours. Temporal and spatial variations in dose sensitivity were determined by tracking the radiochromic response in different regions of interest within the dosimeter at different times.Between 6 and 26 hours, the radiochromic response at all dose levels and spatial locations was found to be very stable, with <1% variation. In peripheral regions, an initial drop followed by a gradual rise in OD was observed. Centrally in the dosimeter, a gradual reduction in OD was observed. The dose response throughout was found initially to be ∼3.30±0.12×10-2 /cm/Gy. However larger differences were observed (up to tilde;8%) after stabilizationConclusion: The DEA-PRESAGE formulation is found to be extremely stable between 6 and 26 hours post irradiation at room temperature. However the variation in stabilized dose response will need to be accounted for in situations of delayed readout. NIH Grant No. RO1 CA 100835.

Authors
Jackson, J; Juang, T; Adamovics, J; Oldham, M
MLA Citation
Jackson, J, Juang, T, Adamovics, J, and Oldham, M. "SU-E-T-53: An Investigation of the Dosimetric Characteristics of a Novel Radiochromic 3D Dosimeter." Medical physics 40.6Part11 (June 2013): 215-.
PMID
28520039
Source
epmc
Published In
Medical physics
Volume
40
Issue
6Part11
Publish Date
2013
Start Page
215
DOI
10.1118/1.4814488

SU-E-T-40: Is Accurate 3D Dosimetry Possible When Using Optical-CT Readout with Low (or Without) Refractive Index Matching Fluids?

Achieving accurate optical-CT 3D dosimetry without the use of viscous refractive index (RI) matching fluids would greatly increase convenience. This work evaluates various potential 'dry-scan' optical-CT configurations (including parallel, point, and converging light-ray geometries) through computer simulations.Three surrounding refractive media were investigated: air, water, and a fluid closely matched to PRESAGE™ (n=1.00,1.33,1.49). Reconstructions performed using both filtered-back-projection (FBP) and algebraic-reconstruction-technique (ART). For each media, the efficacy of the three configurations and the two algorithms was evaluated by calculating usable radius (i.e. the outermost radius where data was accurate to within 2%), and gamma analysis. This definition recognizes that, for optical-CT imaging, errors are greatest near the edge of the dosimeter where refraction can be most pronounced. Simulations were performed on three types of dose distribution: uniform, volumetric modulated arc therapy (VMAT), and brachytherapy (Cs-137).Uniformly irradiated dosimeter useable radius recovered using FBP was 68% for water-matching, and 31% for air-matching (dry-scanning). ART gave useable radii of 99% for both water and dry-scanning, indicating greater recovery of useful data for the uniform distribution. FBP and ART performed equally well for a VMAT dose distribution where less dose is delivered near the edge of the dosimeter (useable radius of 86% and 53% for water and dry-scanning respectively). Brachytherapy useable radius recovered using FBP was 99% and 98% for water and dry-scanning respectively, and a major decrease was seen with ART. Point-source geometry provided 1-2% larger usable radii than parallel. Converging geometry recovered up to 10% reduced useable radii than point and parallel.For applications where dose information is not required in the periphery of the dosimeter, some dry and low-viscous matching configurations may be feasible. When dosimetry is required on the periphery, best results were obtained using close refractive matching and ART.

Authors
Rankine, L; Oldham, M
MLA Citation
Rankine, L, and Oldham, M. "SU-E-T-40: Is Accurate 3D Dosimetry Possible When Using Optical-CT Readout with Low (or Without) Refractive Index Matching Fluids?." Medical physics 40.6Part11 (June 2013): 212-.
PMID
28520065
Source
epmc
Published In
Medical physics
Volume
40
Issue
6Part11
Publish Date
2013
Start Page
212
DOI
10.1118/1.4814475

MO-F-108-11: 3D Verification for Multifocal Single Isocenter SRS.

Recent trends in SRS use multifocal VMAT plans to simultaneously treat several, distinct targets. Conventional verification often involves low resolution measurements in a single plane, cylinder, or intersecting planes of diodes or ion chambers. This work presents an investigation into the accuracy, consistency and reproducibility of this treatment technique using a high-resolution 3D dosimetry system (PRESAGE/Optical-CT).A complex VMAT plan consisting of a single isocenter but 5 separate targets was created in Eclipse for a head phantom containing a cylindrical PRESAGE dosimetry insert of 10cm diameter and height. The plan contained 5 arcs delivering doses from 12-20 Gy. The treatment was delivered to four separate dosimeters positioned in the head-phantom. Each delivery was performed after IGRT positioning using 2D and 3D kilovoltage images. A final delivery was given to a modified insert containing a pin-point ion chamber enabling calibration of Presage data to dose. Dosimetric data was read out in an optical-CT scanner. Consistency and reproducibility of the treatment technique (including IGRT set-up) was investigated by comparing the dose distributions in the 4 inserts, and with the predicted TPS distribution.Dose distributions from the 4 dosimeters were registered to find the mean and standard deviation at all points throughout the dosimeters. They showed less than 3% standard deviation within voxels of similar dose regions. 3D gamma maps show the calculated delivered dose matched output to within expected tolerances and errors - passing rate was 98.0% (3%, 2mm).The deliveries of the irradiation were found to be consistent and matched the treatment plan, demonstrating high accuracy and reproducibility of the treatment machine, the IGRT procedure, and the 3D measurement. The complexity of the treatment (multiple arcs) and dosimetry (multiple strong gradients) pose a substantial challenge for comprehensive verification. 3D dosimetry can be uniquely effective in this scenario.

Authors
Thomas, A; Niebanck, M; Wang, Z; Kirkpatrick, J; Oldham, M
MLA Citation
Thomas, A, Niebanck, M, Wang, Z, Kirkpatrick, J, and Oldham, M. "MO-F-108-11: 3D Verification for Multifocal Single Isocenter SRS." Medical physics 40.6Part24 (June 2013): 409-.
PMID
28518457
Source
epmc
Published In
Medical physics
Volume
40
Issue
6Part24
Publish Date
2013
Start Page
409
DOI
10.1118/1.4815287

MO-D-141-09: An Investigation of the Feasibility of Volumetric Imaging of Fluorescent Bio-Markers Using Optical-ECT.

Toptical-ECT is a technique with potential for high resolution 3D imaging of the distribution of fluoresent biomarkers (including reporter proteins like GFP) in un-sectioned tissue samples. Accurate optical-ECT data is only feasible if the biomarkers survive an optical clearing procedure. This work presents investigates this question, and the feasibility of extracting volume metrics from optical-ECT data.4T1 tumors were grown in window chambers on nude mice, following an approved protocol. Tumor cells constitutively expressed RFP, and endogenously expressed GFP labeling HIF-1 transcription. Microvasculature was labeled by colloidal carbon. When the tumors were ∼5-7mm, they were imaged in-vivo (in the chamber) using conventional epi-fluorescent microspcopy. Tumors were then immediately removed, optically-cleared, and imaged ex-vivo by optical-CT/ECT. Comparison of the in-vivo and ex-vivo images enabled investigation of the stability of the biomarkers through optical clearing. Volume measurements of regions expressing different markers (GFP and RFP) were generated though automatic thresholding.Biomarker expressing regions (GFP and RFP) were generally consistent between comparable optical-ECT projections and in-vivo microscopy. In some tumors, GFP and RFP expression was observed to be partially obscured in in-vivo images, due to absorption in overlying tissue. In optical-ECT views, these regions became visible, due to optical clearing. In one tumor, 31% of the gross tumor was deemed viable, as determined from RFP expression. 13% of the tumor was hypoxic as inferred from HIF-1 expression. Almost all the GFP hypoxic volume was within the viable RFP tumor volume.Our preliminary data supports several key concepts: fluorescent biomarkers can survive the optical clearing process representative of in-vivo condition; the cleared tumor revealed new regions of signal that were partially obscured in in-vivo images; and 3D quantitative metrics can be determined from optical-CT/ECT that correspond to their 2D counterparts in standard microscopy (e.g. sub-volume of HIF-1 expression).

Authors
Oldham, M; Thomas, A; Dewhirst, M
MLA Citation
Oldham, M, Thomas, A, and Dewhirst, M. "MO-D-141-09: An Investigation of the Feasibility of Volumetric Imaging of Fluorescent Bio-Markers Using Optical-ECT." Medical physics 40.6Part24 (June 2013): 401-.
PMID
28518425
Source
epmc
Published In
Medical physics
Volume
40
Issue
6Part24
Publish Date
2013
Start Page
401
DOI
10.1118/1.4815256

SU-C-105-03: Progress Toward the Development of a Deformable Anthropomorphic 3D Dosimetric Phantom.

Previous work has demonstrated that Presage-Def, a deformable, polyurethane-based radiochromic 3D dosimeter, has strong potential for validating deformable image registration algorithms by tracking optically measured radiation patterns from the deformed shape to the non-deformed shape. Here we present recent investigations into the efficacy of variant Presage-Def formulations with a range of elastic properties in terms of increased dose sensitivity and post-irradiation stability.Eleven formulations of Presage-Def were created from combinations of 3 elastic polyurethane matrices (Shore Hardness 10-20A and 30A) and 7 leuco dyes. Dose sensitivity for each formulation was determined by irradiating cuvettes from 0-8Gy and measuring change in optical density at 633nm. Sensitivity readings were tracked over time to determine stability. Complementary to the small volume studies, a 15.7cm diameter cylindrical Presage-Def deformable dosimeter was created incorporating two air cavities (4.0cm diameter) and a rigid high-Z spine-mimic insert (2.8cm diameter). The dosimeter was subjected to bilateral compression to demonstrate complex, non-uniform deformation, and also irradiated with an 8.6cm×7.4cm field and imaged with optical-CT to investigate feasibility of optical-CT dose readout in a heterogeneous phantom.Dose sensitivities ranged from 0.0004-0.0071ΔOD/(Gy*cm) versus 0.0032ΔOD/(Gy*cm) in the original formulation. Highest sensitivity and stability were both seen in formulation PD1 (#2 polyurethane, leuco dye 1-napthal-N,N-diethylamine LMG), which retained 98.6% initial sensitivity over 4 hours whereas the original dropped to 90.6% after 1 hour. X-ray CT images of the prototype phantom with and without compression demonstrated non-uniform deformation of Presage-Def and air cavity geometry while the rigid region remained constant. The irradiated field was clearly visible in 3D dose distributions obtained by optical-CT.A Presage-Def formulation was identified from 10 variants with improved dosimetric characteristics. Optical-CT dose readout was achieved in the prototype phantom, demonstrating feasibility of 3D dosimetry in a large deformable dosimeter containing air and rigid bone-mimic inserts. NIH R01CA100835.

Authors
Juang, T; Das, S; Adamovics, J; Oldham, M
MLA Citation
Juang, T, Das, S, Adamovics, J, and Oldham, M. "SU-C-105-03: Progress Toward the Development of a Deformable Anthropomorphic 3D Dosimetric Phantom." Medical physics 40.6Part2 (June 2013): 83-.
PMID
28518310
Source
epmc
Published In
Medical physics
Volume
40
Issue
6Part2
Publish Date
2013
Start Page
83
DOI
10.1118/1.4813927

On the feasibility of optical-CT imaging in media of different refractive index.

PURPOSE: Achieving accurate optical-CT 3D dosimetry without the use of viscous refractive index (RI) matching fluids would greatly increase convenience. METHODS: Software has been developed to simulate optical-CT 3D dosimetry for a range of scanning configurations including parallel-beam, point, and converging light sources. For each configuration the efficacy of three refractive media was investigated: air, water, a fluid closely matched to PRESAGE(®), and perfect matching (RI = 1.00, 1.33, 1.49, and 1.501 respectively). Reconstructions were performed using both filtered backprojection (FBP) and algebraic reconstruction technique (ART). The efficacy of the three configurations and the two algorithms was evaluated by calculating the usable radius (i.e., the outermost radius where data were accurate to within 2%), and gamma (Γ) analysis. This definition recognizes that for optical-CT imaging, errors are greatest near the edge of the dosimeter, where refraction can be most pronounced. Simulations were performed on three types of dose distribution: uniform, volumetric modulated arc therapy (VMAT), and brachytherapy (Cs-137). RESULTS: For a uniformly irradiated dosimeter the usable radius achieved with filtered backprojection was 68% for water-matching and 31% for dry-scanning in air. Algebraic reconstruction gave usable radii of 99% for both water and air (dry-scanning), indicating greater recovery of useful data for the uniform distribution. FBP and ART performed equally well for a VMAT dose distribution where less dose is delivered near the edge of the dosimeter. In this case, the usable radius was 86% and 53% for scanning in water and air, respectively. For brachytherapy, the usable radius was 99% and 98% for scanning in water and air, respectively using FBP, and a major decrease was seen with ART. Point source geometry provided 1%-2% larger usable radii than parallel geometry. Converging geometry recovered less usable dosimetry data (up to 10% reduced usable radii) than point and parallel geometries. A further disadvantage of converging geometry was an increased requirement on detector size by up to 18°. CONCLUSIONS: For applications where dose information is not required in the periphery of the dosimeter, some dry and low-viscous matching configurations may be feasible. For all three dose distributions (uniform, VMAT, brachytherapy) the point source geometry produced slightly more favorable results (an extra 1%-2% usable radii) than parallel and converging. When dosimetry is required on the periphery, best results were obtained using close refractive matching and ART. A concern for water or dry-scanning is the increase in required detector size, introducing potential cost penalties for manufacturing.

Authors
Rankine, L; Oldham, M
MLA Citation
Rankine, L, and Oldham, M. "On the feasibility of optical-CT imaging in media of different refractive index." Med Phys 40.5 (May 2013): 051701-.
PMID
23635249
Source
pubmed
Volume
40
Issue
5
Publish Date
2013
Start Page
051701
DOI
10.1118/1.4798980

Preliminary investigation and application of a novel deformable PRESAGE(®) dosimeter.

Deformable 3D dosimeters have potential applications in validating deformable dose mapping algorithms. This study evaluates a novel deformable PRESAGE(®) dosimeter and its application toward validating the deformable algorithm employed by VelocityAI. The deformable PRESAGE(®) dosimeter exhibited a linear dose response with a sensitivity of 0.0032 ΔOD/(Gy/cm). Comparison of an experimental dosimeter irradiated with an MLC pencilbeam checkerboard pattern under lateral compression up to 27% to a non-deformed control dosimeter irradiated with the same pattern verified dose tracking under deformation. CTs of the experimental dosimeter prior to and during compression were exported into VelocityAI and used to map an Eclipse dose distribution calculated on the compressed dosimeter to its original shape. A comparison between the VelocityAI dose distribution and the distribution from the dosimeter showed field displacements up to 7.3 mm and up to a 175% difference in field dimensions. These results highlight the need for validating deformable dose mapping algorithms to ensure patient safety and quality of care.

Authors
Juang, T; Newton, J; Das, S; Adamovics, J; Oldham, M
MLA Citation
Juang, T, Newton, J, Das, S, Adamovics, J, and Oldham, M. "Preliminary investigation and application of a novel deformable PRESAGE(®) dosimeter." January 2013.
PMID
24454522
Source
epmc
Published In
Journal of Physics
Volume
444
Publish Date
2013
Start Page
12080
DOI
10.1088/1742-6596/444/1/012080

How accurate is image guided radiation therapy (IGRT) delivered with a micro-irradiator?

There is significant interest in delivering precisely targeted small-volume radiation treatments, in the pre-clinical setting, to study dose-volume relationships with tumor control and normal tissue damage. In this work we investigate the IGRT targeting accuracy of the XRad225Cx system from Precision x-Ray using high resolution 3D dosimetry techniques. Initial results revealed a significant targeting error of about 2.4mm. This error was reduced to within 0.5mm after the IGRT hardware and software had been recalibrated. The facility for 3D dosimetry was essential to gain a comprehensive understanding of the targeting error in 3D.

Authors
Oldham, M; Newton, J; Rankine, L; Adamovics, J; Kirsch, D; Das, S
MLA Citation
Oldham, M, Newton, J, Rankine, L, Adamovics, J, Kirsch, D, and Das, S. "How accurate is image guided radiation therapy (IGRT) delivered with a micro-irradiator?." January 2013.
PMID
24454521
Source
epmc
Published In
Journal of Physics
Volume
444
Publish Date
2013
Start Page
12070
DOI
10.1088/1742-6596/444/1/012070

Towards comprehensive characterization of Cs-137 Seeds using PRESAGE (R) dosimetry with optical tomography

Authors
Adamson, J; Yang, Y; Rankine, L; Newton, J; Adamovics, J; Craciunescu, O; Oldham, M; IOP,
MLA Citation
Adamson, J, Yang, Y, Rankine, L, Newton, J, Adamovics, J, Craciunescu, O, Oldham, M, and IOP, . "Towards comprehensive characterization of Cs-137 Seeds using PRESAGE (R) dosimetry with optical tomography." 2013.
PMID
24454523
Source
wos-lite
Published In
Journal of Physics
Volume
444
Publish Date
2013
DOI
10.1088/1742-6596/444/1/012100

Comprehensive quality assurance for base of skull IMRT

Authors
Thomas, A; O'Daniel, J; Adamovics, J; Ibbott, G; Oldham, M; IOP,
MLA Citation
Thomas, A, O'Daniel, J, Adamovics, J, Ibbott, G, Oldham, M, and IOP, . "Comprehensive quality assurance for base of skull IMRT." 2013.
PMID
24567740
Source
wos-lite
Published In
Journal of Physics
Volume
444
Publish Date
2013
DOI
10.1088/1742-6596/444/1/012050

Customising PRESAGE (R) for diverse applications

Authors
Juang, T; Newton, J; Niebanck, M; Benning, R; Adamovics, J; Oldham, M; IOP,
MLA Citation
Juang, T, Newton, J, Niebanck, M, Benning, R, Adamovics, J, Oldham, M, and IOP, . "Customising PRESAGE (R) for diverse applications." 2013.
PMID
24567739
Source
wos-lite
Published In
Journal of Physics
Volume
444
Publish Date
2013
DOI
10.1088/1742-6596/444/1/012029

Evaluation of a clinically intuitive quality assurance method

Authors
Norris, H; Thomas, A; Oldham, M; IOP,
MLA Citation
Norris, H, Thomas, A, Oldham, M, and IOP, . "Evaluation of a clinically intuitive quality assurance method." 2013.
PMID
24454519
Source
wos-lite
Published In
Journal of Physics
Volume
444
Publish Date
2013
DOI
10.1088/1742-6596/444/1/012022

The effect of motion on IMRT - looking at interplay with 3D measurements

Authors
Thomas, A; Yan, H; Oldham, M; Juang, T; Adamovics, J; Yin, FF; IOP,
MLA Citation
Thomas, A, Yan, H, Oldham, M, Juang, T, Adamovics, J, Yin, FF, and IOP, . "The effect of motion on IMRT - looking at interplay with 3D measurements." 2013.
PMID
26877756
Source
wos-lite
Published In
Journal of Physics
Volume
444
Publish Date
2013
DOI
10.1088/1742-6596/444/1/012049

Investigating the reproducibility of a complex multifocal radiosurgery treatment

Authors
Niebanck, M; Juang, T; Newton, J; Adamovics, J; Wang, Z; Oldham, M; IOP,
MLA Citation
Niebanck, M, Juang, T, Newton, J, Adamovics, J, Wang, Z, Oldham, M, and IOP, . "Investigating the reproducibility of a complex multifocal radiosurgery treatment." 2013.
PMID
27081397
Source
wos-lite
Published In
Journal of Physics
Volume
444
Publish Date
2013
DOI
10.1088/1742-6596/444/1/012072

On the need for comprehensive validation of deformable image registration, investigated with a novel 3-dimensional deformable dosimeter

Purpose To introduce and evaluate a novel deformable 3-dimensional (3D) dosimetry system (Presage-Def/Optical-CT) and its application toward investigating the accuracy of dose deformation in a commercial deformable image registration (DIR) package. Methods and Materials Presage-Def is a new dosimetry material consisting of an elastic polyurethane matrix doped with radiochromic leuco dye. Radiologic and mechanical properties were characterized using standard techniques. Dose-tracking feasibility was evaluated by comparing dose distributions between dosimeters irradiated with and without 27% lateral compression. A checkerboard plan of 5-mm square fields enabled precise measurement of true deformation using 3D dosimetry. Predicted deformation was determined from a commercial DIR algorithm. Results Presage-Def exhibited a linear dose response with sensitivity of 0.0032 ΔOD/(Gy*cm). Mass density is 1.02 g/cm3, and effective atomic number is within 1.5% of water over a broad (0.03-10 MeV) energy range, indicating good water-equivalence. Elastic characteristics were close to that of liver tissue, with Young's modulus of 13.5-887 kPa over a stress range of 0.233-303 kPa, and Poisson's ratio of 0.475 (SE, 0.036). The Presage-Def/Optical-CT system successfully imaged the nondeformed and deformed dose distributions, with isotropic resolution of 1 mm. Comparison with the predicted deformed 3D dose distribution identified inaccuracies in the commercial DIR algorithm. Although external contours were accurately deformed (submillimeter accuracy), volumetric dose deformation was poor. Checkerboard field positioning and dimension errors of up to 9 and 14 mm, respectively, were identified, and the 3D DIR-deformed dose γ passing rate was only γ3%/3 mm = 60.0%. Conclusions The Presage-Def/Optical-CT system shows strong potential for comprehensive investigation of DIR algorithm accuracy. Substantial errors in a commercial DIR were found in the conditions evaluated. This work highlights the critical importance of careful validation of DIR algorithms before clinical implementation. © 2013 Elsevier Inc.

Authors
Juang, T; Das, S; Adamovics, J; Benning, R; Oldham, M
MLA Citation
Juang, T, Das, S, Adamovics, J, Benning, R, and Oldham, M. "On the need for comprehensive validation of deformable image registration, investigated with a novel 3-dimensional deformable dosimeter." International Journal of Radiation Oncology Biology Physics 87.2 (2013): 414-421.
Source
scival
Published In
International Journal of Radiation Oncology, Biology, Physics
Volume
87
Issue
2
Publish Date
2013
Start Page
414
End Page
421
DOI
10.1016/j.ijrobp.2013.05.045

Journal of Physics: Conference Series - Preface

Authors
Thwaites, D; Baldock, C; Price, L; Starkey, E; Whitaker, M; Greer, P; Holloway, L; Vial, P; Hill, R; Back, S; Wuu, C-S; Deene, YD; Doran, S; Ibbott, G; Jiraseka, A; Jordan, K; Lepage, M; Oldham, M; Pappas, E; Schreiner, J
MLA Citation
Thwaites, D, Baldock, C, Price, L, Starkey, E, Whitaker, M, Greer, P, Holloway, L, Vial, P, Hill, R, Back, S, Wuu, C-S, Deene, YD, Doran, S, Ibbott, G, Jiraseka, A, Jordan, K, Lepage, M, Oldham, M, Pappas, E, and Schreiner, J. "Journal of Physics: Conference Series - Preface." Journal of Physics: Conference Series 444.1 (2013).
Source
scival
Published In
Journal of Physics
Volume
444
Issue
1
Publish Date
2013
DOI
10.1088/1742-6596/444/1/011001

A quality assurance method that utilizes 3D dosimetry and facilitates clinical interpretation.

PURPOSE: To demonstrate a new three-dimensional (3D) quality assurance (QA) method that provides comprehensive dosimetry verification and facilitates evaluation of the clinical significance of QA data acquired in a phantom. Also to apply the method to investigate the dosimetric efficacy of base-of-skull (BOS) intensity-modulated radiotherapy (IMRT) treatment. METHODS AND MATERIALS: Two types of IMRT QA verification plans were created for 6 patients who received BOS IMRT. The first plan enabled conventional 2D planar IMRT QA using the Varian portal dosimetry system. The second plan enabled 3D verification using an anthropomorphic head phantom. In the latter, the 3D dose distribution was measured using the DLOS/Presage dosimetry system (DLOS = Duke Large-field-of-view Optical-CT System, Presage Heuris Pharma, Skillman, NJ), which yielded isotropic 2-mm data throughout the treated volume. In a novel step, measured 3D dose distributions were transformed back to the patient's CT to enable calculation of dose-volume histograms (DVH) and dose overlays. Measured and planned patient DVHs were compared to investigate clinical significance. RESULTS: Close agreement between measured and calculated dose distributions was observed for all 6 cases. For gamma criteria of 3%, 2 mm, the mean passing rate for portal dosimetry was 96.8% (range, 92.0%-98.9%), compared to 94.9% (range, 90.1%-98.9%) for 3D. There was no clear correlation between 2D and 3D passing rates. Planned and measured dose distributions were evaluated on the patient's anatomy, using DVH and dose overlays. Minor deviations were detected, and the clinical significance of these are presented and discussed. CONCLUSIONS: Two advantages accrue to the methods presented here. First, treatment accuracy is evaluated throughout the whole treated volume, yielding comprehensive verification. Second, the clinical significance of any deviations can be assessed through the generation of DVH curves and dose overlays on the patient's anatomy. The latter step represents an important development that advances the clinical relevance of complex treatment QA.

Authors
Oldham, M; Thomas, A; O'Daniel, J; Juang, T; Ibbott, G; Adamovics, J; Kirkpatrick, JP
MLA Citation
Oldham, M, Thomas, A, O'Daniel, J, Juang, T, Ibbott, G, Adamovics, J, and Kirkpatrick, JP. "A quality assurance method that utilizes 3D dosimetry and facilitates clinical interpretation." Int J Radiat Oncol Biol Phys 84.2 (October 1, 2012): 540-546.
PMID
22361085
Source
pubmed
Published In
International Journal of Radiation: Oncology - Biology - Physics
Volume
84
Issue
2
Publish Date
2012
Start Page
540
End Page
546
DOI
10.1016/j.ijrobp.2011.12.015

Submerged RadBall® deployments in Hanford Site hot cells containing 137CsCl capsules.

The overall objective of this study was to demonstrate that a new technology, known as RadBall®, could locate submerged radiological hazards. RadBall® is a novel, passive, radiation detection device that provides a 3-D visualization of radiation from areas where measurements have not been previously possible due to lack of access or extremely high radiation doses. This technology has been under development during recent years, and all of its previous tests have included dry deployments. This study involved, for the first time, underwater RadBall® deployments in hot cells containing 137CsCl capsules at the U.S. Department of Energy's Hanford Site. RadBall® can be used to characterize a contaminated room, hot cell, or glovebox by providing the locations of the radiation sources and hazards, identifying the radionuclides present within the cell, and determining the radiation sources' strength (e.g., intensities or dose rates). These parameters have been previously determined for dry deployments; however, only the location of radiation sources and hazards can be determined for an underwater RadBall® deployment. The results from this study include 3-D images representing the location of the radiation sources within the Hanford Site cells. Due to RadBall®'s unique deployability and non-electrical nature, this technology shows significant promise for future characterization of radiation hazards prior to and during the decommissioning of contaminated nuclear facilities.

Authors
Farfán, EB; Coleman, JR; Stanley, S; Adamovics, J; Oldham, M; Thomas, A
MLA Citation
Farfán, EB, Coleman, JR, Stanley, S, Adamovics, J, Oldham, M, and Thomas, A. "Submerged RadBall® deployments in Hanford Site hot cells containing 137CsCl capsules." Health Phys 103.1 (July 2012): 100-106.
PMID
22647921
Source
pubmed
Published In
Health Physics
Volume
103
Issue
1
Publish Date
2012
Start Page
100
End Page
106
DOI
10.1097/HP.0b013e31824dada5

Commissioning a CT-compatible LDR tandem and ovoid applicator using Monte Carlo calculation and 3D dosimetry.

PURPOSE: To determine the geometric and dose attenuation characteristics of a new commercially available CT-compatible LDR tandem and ovoid (T&O) applicator using Monte Carlo calculation and 3D dosimetry. METHODS: For geometric characterization, we quantified physical dimensions and investigated a systematic difference found to exist between nominal ovoid angle and the angle at which the afterloading buckets fall within the ovoid. For dosimetric characterization, we determined source attenuation through asymmetric gold shielding in the buckets using Monte Carlo simulations and 3D dosimetry. Monte Carlo code MCNP5 was used to simulate 1.5 × 10(9) photon histories from a (137)Cs source placed in the bucket to achieve statistical uncertainty of 1% at a 6 cm distance. For 3D dosimetry, the distribution about an unshielded source was first measured to evaluate the system for (137)Cs, after which the distribution was measured about sources placed in each bucket. Cylindrical PRESAGE(®) dosimeters (9.5 cm diameter, 9.2 cm height) with a central channel bored for source placement were supplied by Heuris Inc. The dosimeters were scanned with the Duke Large field of view Optical CT-Scanner before and after delivering a nominal dose at 1 cm of 5-8 Gy. During irradiation the dosimeter was placed in a water phantom to provide backscatter. Optical CT scan time lasted 15 min during which 720 projections were acquired at 0.5° increments, and a 3D distribution was reconstructed with a (0.05 cm)(3) isotropic voxel size. The distributions about the buckets were used to calculate a 3D distribution of transmission rate through the bucket, which was applied to a clinical CT-based T&O implant plan. RESULTS: The systematic difference in bucket angle relative to the nominal ovoid angle (105°) was 3.1°-4.7°. A systematic difference in bucket angle of 1°, 5°, and 10° caused a 1% ± 0.1%, 1.7% ± 0.4%, and 2.6% ± 0.7% increase in rectal dose, respectively, with smaller effect to dose to Point A, bladder, sigmoid, and bowel. For 3D dosimetry, 90.6% of voxels had a 3D γ-index (criteria = 0.1 cm, 3% local signal) below 1.0 when comparing measured and expected dose about the unshielded source. Dose transmission through the gold shielding at a radial distance of 1 cm was 85.9% ± 0.2%, 83.4% ± 0.7%, and 82.5% ± 2.2% for Monte Carlo, and measurement for left and right buckets, respectively. Dose transmission was lowest at oblique angles from the bucket with a minimum of 56.7% ± 0.8%, 65.6% ± 1.7%, and 57.5% ± 1.6%, respectively. For a clinical T&O plan, attenuation from the buckets leads to a decrease in average Point A dose of ∼3.2% and decrease in D(2cc) to bladder, rectum, bowel, and sigmoid of 5%, 18%, 6%, and 12%, respectively. CONCLUSIONS: Differences between dummy and afterloading bucket position in the ovoids is minor compared to effects from asymmetric ovoid shielding, for which rectal dose is most affected. 3D dosimetry can fulfill a novel role in verifying Monte Carlo calculations of complex dose distributions as are common about brachytherapy sources and applicators.

Authors
Adamson, J; Newton, J; Yang, Y; Steffey, B; Cai, J; Adamovics, J; Oldham, M; Chino, J; Craciunescu, O
MLA Citation
Adamson, J, Newton, J, Yang, Y, Steffey, B, Cai, J, Adamovics, J, Oldham, M, Chino, J, and Craciunescu, O. "Commissioning a CT-compatible LDR tandem and ovoid applicator using Monte Carlo calculation and 3D dosimetry." Med Phys 39.7 (July 2012): 4515-4523.
PMID
22830783
Source
pubmed
Published In
Medical physics
Volume
39
Issue
7
Publish Date
2012
Start Page
4515
End Page
4523
DOI
10.1118/1.4730501

SU-D-213AB-05: Commissioning a CT Compatible LDR T&O Applicator Using Analytical Calculation with ID and 3D Dosimetry.

To determine the characteristics of a new commercially available CT-compatible LDR Tandem and Ovoid (T&O) applicator using 3D dosimetry.We characterized source attenuation through the asymmetric gold shielding in the buckets by measuring dose with diode and 3D dosimetry and compared to an analytical line integral calculation. For 3D dosimetry, a cylindrical PRESAGE dosimeter (9.5cm diameter, 9.2cm height) with a central 6mm channel bored for source placement was scanned with the Duke Large field of view Optical CT-Scanner (DLOS) before and after delivering a nominal 7.7Gy at a distance of 1 cm using a Cs-137 source loaded in the bucket. The optical CT scan time lasted approximately 15 minutes during which 720 projections were acquired at 0.5° increments, anda 3D dose distribution was reconstructed with a 0.5mm3 isotropic voxel size. The 3D dose distribution was applied to a CT-based T&O implant to determine effect of ovoid shielding on the dose delivered to ICRU 38 Point A as well as D2cc of the bladder, rectum, bowel, and sigmoid.Dose transmission through the gold shielding at a radial distance of 1-3cm from midplane of the source was 86.6%, 86.1, and 87.0% for analytical calculation, diode, and 3D dosimetry, respectively. For the gold shielding of the bucket, dose transmission calculated using the 3D dosimetrymeasurement was found to be lowest at oblique angles from the bucket witha minimum of ∼51%. For the patient case, attenuation from the buckets leadto a decrease in average Point A dose of ∼4% and decrease in D2cc to bladder, rectum, sigmoid, and bowel of 2%, 15%, 2%, and 7%, respectively.The measured 3D dose distribution provided unique insight to the dosimetry and shielding characteristics of the investigated applicator, the technique for which can be applied to commissioning of other brachytherapy applicators. John Adamovics is the owner of Heuris Pharma LLC. Partially supported by NIH Grant R01 CA100835-01.

Authors
Adamson, J; Newton, J; Steffey, B; Cai, J; Adamovics, J; Oldham, M; Chino, J; Craciunescu, O
MLA Citation
Adamson, J, Newton, J, Steffey, B, Cai, J, Adamovics, J, Oldham, M, Chino, J, and Craciunescu, O. "SU-D-213AB-05: Commissioning a CT Compatible LDR T&O Applicator Using Analytical Calculation with ID and 3D Dosimetry." Medical physics 39.6Part3 (June 2012): 3612-.
PMID
28517412
Source
epmc
Published In
Medical physics
Volume
39
Issue
6Part3
Publish Date
2012
Start Page
3612
DOI
10.1118/1.4734665

TU-E-BRB-09: Validation of Multi-Focal Stereotactic Radiosurgery with Volumetric Modulated Arc Therapy with High-Resolution 3D Dosimetry.

Volumetric modulated arc therapy (VMAT) enables stereotactic radiosurgery (SRS) treatment for multiple lesions with a single isocenter setup. Dosimetry verification is highly challenging however, and the purpose of this study is to validate this new treatment using novel 3D dosimetry techniques, with potential for dramatically more comprehensive verification than possible with conventional approaches.A cylindrical PRESAGE dosimeter was inserted into an RPC type head phantom for treatment validation. The phantom was immobilized with an SRS U-frame system and a set of simulation CT images was acquired with a SRS localizer. A 5-arc VMAT multi-focal SRS plan was created to treat 5 intracranial lesions simultaneously. A set of cone-beam CT (CBCT) images was then acquired to localize the isocenter, and the VMAT plan delivered to the combined phantom. The PRESAGE dosimeter was then removed and scanned by optical-computed-tomography (optical-CT). The 3D PRESAGE dose measurement was reconstructed with 1 mm resolution. Another PRESAGE insert with a pre-drilled ion chamber channel was placed in the phantom and an SRS ion chamber was mounted for an absolute dose measurement. The phantom was again localized with CBCT and the VMAT plan was delivered. The dose measured with the ion chamber was compared with calculated dose.The mean planned and PRESAGE measured doses to target 1 were 12.1Gy and 12.2 Gy, 18.7 Gy and 18.5 Gy for target 2, 18.6 Gy and 18.4 Gy for target 3, 15.5 Gy and 15.4 Gy for target 4, 18.7 Gy and 19.0 Gy for target 5. The 3D gamma passing rate was 95.6% for 3% and 1mm. The ion chamber measured dose was within 1% of the planned dose.Our 3D PRESAGE dose measurement shows that multi-focal VMAT is a valid technique for single isocenter SRS treatment of multiple lesions. This research is partially supported by NCI R01CA100835. This research is partially supported by NCI R01CA100835.

Authors
Wang, Z; Newton, J; Niebanck, M; Juang, T; Kirkpatrick, J; Oldham, M
MLA Citation
Wang, Z, Newton, J, Niebanck, M, Juang, T, Kirkpatrick, J, and Oldham, M. "TU-E-BRB-09: Validation of Multi-Focal Stereotactic Radiosurgery with Volumetric Modulated Arc Therapy with High-Resolution 3D Dosimetry." Medical physics 39.6Part24 (June 2012): 3910-.
PMID
28518712
Source
epmc
Published In
Medical physics
Volume
39
Issue
6Part24
Publish Date
2012
Start Page
3910
DOI
10.1118/1.4735958

WE-E-BRB-04: Quantitative Dose Tracking Enabled Through a Novel Deformable 3D Dosimeter.

To evaluate and investigate the feasibility of a new method for validating dose tracking algorithms in deforming tissues using a novel deformable 3D dosimeter.A novel deformable 3D Presage dosimeter is reported consisting of a stretchy polyurethane matrix doped with radiochromic leuco-dye. Two deformable cylindrical dosimeters (6 cm diameter, 5 cm long) were manufactured and irradiated with a checkerboard arrangement of 5 mm square pencil beams created by MLC fields. One dosimeter was irradiated under lateral compression by 33% (6 cm down to 4 cm diameter) to simulate a deformed organ. A second control dosimeter was irradiated with the same checkerboard pattern but without deformation applied. High-resolution 3D dose distributions (isotropic 1 mm resolution) were obtained by optical-CT imaging. Physical dose deformation was quantified by comparing checkerboard pencil beam shapes and positions in the deformed and control dosimeters.Deformation of dose in the deformed dosimeter was clearly visible in all 3 dimensions. The deformed checkerboard dose pattern showed expansion of 16% - 46% along the axis of compression, with higher expansion observed in the central regions of the dosimeter. Perpendicular to the compression axis, the dose pattern contracted by 7% - 13%. Peak dose changes of -6% and +30% were observed parallel and perpendicular to the compression axis respectively. Dose response was linear from 0-8 Gy.Dose tracking was successfully quantified in a novel deforming 3D dosimeter. This capability has potential as a powerful new method for validating deformable dose tracking and registration algorithms. NCI R01CA100835.

Authors
Juang, T; Newton, J; Das, S; Adamovics, J; Oldham, M
MLA Citation
Juang, T, Newton, J, Das, S, Adamovics, J, and Oldham, M. "WE-E-BRB-04: Quantitative Dose Tracking Enabled Through a Novel Deformable 3D Dosimeter." Medical physics 39.6Part27 (June 2012): 3956-.
PMID
28519995
Source
epmc
Published In
Medical physics
Volume
39
Issue
6Part27
Publish Date
2012
Start Page
3956
DOI
10.1118/1.4736146

SU-E-T-108: 3D Measurement of Neutron Dose from a Novel Neutron Imaging Technique.

We have been developing a fast-neutron spectroscopic technique to quantitatively image the distribution of elements in the body using quasi-monochromatic neutron beams. Previously, we demonstrated the ability of the technique to quantify specific elements in the liver and breast while limiting radiation dose to clinically acceptable levels. Here we present the results of a physical dose measurement performed through neutron irradiation of 3D PRESAGE dosimetry phantoms.Two PRESAGE optical-CT dosimeters were placed inside a physical phantom of the human torso and irradiated with 8 MeV neutrons produced via the 2H(d,n) reaction using a tandem Van-de-Graaff accelerator. The dosimeters, measuring 10 cm and 4 cm in diameter, were located in regions corresponding to the liver (10 cm), and the kidney (4 cm). Irradiation was performed with the neutron beam incident directly on the larger dosimeter. Cumulative neutron fluence incident upon each dosimeter was determined using an aluminum-foil activation technique. Following irradiation, the change in optical density in both dosimeters was measured to determine the relative irradiation and dose distribution in each volume.Both PRESAGE dosimeters exhibited detectable changes in optical density corresponding to the dose deposited in the volume. The two dosimeters registered doses of 8.5 Gy (direct incidence, 4.5 hour irradiation) and 0.25 Gy (off-axis, 20 hour irradiation), respectively. The larger dosimeter showed highest intensity at the entry point of the beam with exponential drop-off along the beam direction. The smaller dosimeter registered a more uniform change in intensity, consistent with the higher incidence of scattered neutrons at this location.The results demonstrate the utility of PRESAGE dosimeters in measuring dose from neutron irradiation and highlight the difference in relative doses between primary and proximal organs when exposed to neutron beams. This work was supported by the United States Department of Energy, Office of Nuclear Physics under Grant No. DE-FG02-97ER41033, the National Cancer Institute under grant R01CA100835, and by the Department of Defense under award W81XWH-09-1-0066.

Authors
Kapadia, A; Crowell, A; Fallin, B; Howell, C; Agasthya, G; Lakshmanan, M; Newton, J; Juang, T; Oldham, M
MLA Citation
Kapadia, A, Crowell, A, Fallin, B, Howell, C, Agasthya, G, Lakshmanan, M, Newton, J, Juang, T, and Oldham, M. "SU-E-T-108: 3D Measurement of Neutron Dose from a Novel Neutron Imaging Technique." Medical physics 39.6Part11 (June 2012): 3727-.
PMID
28517114
Source
epmc
Published In
Medical physics
Volume
39
Issue
6Part11
Publish Date
2012
Start Page
3727
DOI
10.1118/1.4735166

SU-E-T-93: High Dynamic Range Scanning for Optical-CT in 3D Dosimetry.

The recent emergence of powerful, fast and high-resolution 3D dosimetry techniques brings exciting potential to radically strengthen the foundations of quality-assurance in radiation therapy, and hence treatment efficacy. This work presents a new acquisition method for 3D dosimetry by optical-computed-tomography (optical-CT), which can improve accuracy when imaging strongly attenuating dosimeters (e.g. large or heavily dosed).The method involves acquiring optical-CT projection images where the intensity of the light source is increased as much as possible without causing detector saturation within the dosimeter. This improves signal-to-noise in dark regions of the dosimeter, but flood-field and regions outside the dosimeter are unuseable due to saturation. The problem of acquiring a useable flood is solved by acquisition at a reduced shutter opening time. The non-saturated flood is then scaled up for use with projections, by the ratio of shutter times. The method relies on linearity of signal with shutter time, which is investigated here. The method is evaluated by application to a range of dosimeters with varying degrees of strong attenuation.The relationship between signal and shutter time in the flood was found to be highly linear, a key enabling result for this method. When applied to moderately attenuating dosimeters, the new method agrees with the standard method to a high degree (<1% deviation on average). For very dark dosimeters, the new method was found to have greatly improved signal-to-noise (a factor of 2-3 times better) in the darkest regions and eliminated streak artifacts present in reconstructions using the standard acquisition method.A new optical-CT acquisition method is presented which yields improved signal-to-noise for dosimetry measurements in strongly attenuating dosimeters. A further important advantage is the method does not require any tinting of the refractively-matched fluid in the optical-CT water-bath, which greatly increases convenience and practicability. Grant - R01CA100835.

Authors
Niebanck, M; Newton, J; Juang, T; Oldham, M
MLA Citation
Niebanck, M, Newton, J, Juang, T, and Oldham, M. "SU-E-T-93: High Dynamic Range Scanning for Optical-CT in 3D Dosimetry." Medical physics 39.6Part11 (June 2012): 3724-.
PMID
28517121
Source
epmc
Published In
Medical physics
Volume
39
Issue
6Part11
Publish Date
2012
Start Page
3724
DOI
10.1118/1.4735150

TU-C-BRB-02: Identification of a Targeting Error in a Small Field Biological Irradiator Using 3D Dosimetry Techniques

Authors
Newton, J; Li, Y; Adamovics, J; Kirsch, D; Das, S; Oldham, M
MLA Citation
Newton, J, Li, Y, Adamovics, J, Kirsch, D, Das, S, and Oldham, M. "TU-C-BRB-02: Identification of a Targeting Error in a Small Field Biological Irradiator Using 3D Dosimetry Techniques." June 2012.
Source
crossref
Published In
Medical physics
Volume
39
Issue
6Part23
Publish Date
2012
Start Page
3898
End Page
3898
DOI
10.1118/1.4735914

SU-E-T-381: Experimental Measurements of 3D Dose Distribution for a Moving Target Treated with IMRT and VMAT

Authors
Yan, H; Thomas, A; Oldham, M; Yin, F
MLA Citation
Yan, H, Thomas, A, Oldham, M, and Yin, F. "SU-E-T-381: Experimental Measurements of 3D Dose Distribution for a Moving Target Treated with IMRT and VMAT." June 2012.
Source
crossref
Published In
Medical physics
Volume
39
Issue
6Part15
Publish Date
2012
Start Page
3792
End Page
3792
DOI
10.1118/1.4735468

SU-C-213AB-06: Validation Study of the Accuracy of the Transform Method for Clinically Intuitive Quality Assurance

Authors
Norris, H; Thomas, A; Oldham, M
MLA Citation
Norris, H, Thomas, A, and Oldham, M. "SU-C-213AB-06: Validation Study of the Accuracy of the Transform Method for Clinically Intuitive Quality Assurance." June 2012.
Source
crossref
Published In
Medical physics
Volume
39
Issue
6Part2
Publish Date
2012
Start Page
3599
End Page
3599
DOI
10.1118/1.4734611

Locating, quantifying and characterising radiation hazards in contaminated nuclear facilities using a novel passive non-electrical polymer based radiation imaging device.

This paper provides a summary of recent trials which took place at the US Department of Energy Oak Ridge National Laboratory (ORNL) during December 2010. The overall objective for the trials was to demonstrate that a newly developed technology could be used to locate, quantify and characterise the radiological hazards within two separate ORNL hot cells (B and C). The technology used, known as RadBall(®), is a novel, passive, non-electrical polymer based radiation detection device which provides a 3D visualisation of radiation from areas where effective measurements have not been previously possible due to lack of access. This is particularly useful in the nuclear industry prior to the decommissioning of facilities where the quantity, location and type of contamination are often unknown. For hot cell B, the primary objective of demonstrating that the technology could be used to locate, quantify and characterise three radiological sources was met with 100% success. Despite more challenging conditions in hot cell C, two sources were detected and accurately located. To summarise, the technology performed extremely well with regards to detecting and locating radiation sources and, despite the challenging conditions, moderately well when assessing the relative energy and intensity of those sources. Due to the technology's unique deployability, non-electrical nature and its directional awareness the technology shows significant promise for the future characterisation of radiation hazards prior to and during the decommissioning of contaminated nuclear facilities.

Authors
Stanley, SJ; Lennox, K; Farfán, EB; Coleman, JR; Adamovics, J; Thomas, A; Oldham, M
MLA Citation
Stanley, SJ, Lennox, K, Farfán, EB, Coleman, JR, Adamovics, J, Thomas, A, and Oldham, M. "Locating, quantifying and characterising radiation hazards in contaminated nuclear facilities using a novel passive non-electrical polymer based radiation imaging device." J Radiol Prot 32.2 (June 2012): 131-145.
PMID
22555190
Source
pubmed
Published In
Journal of Radiological Protection
Volume
32
Issue
2
Publish Date
2012
Start Page
131
End Page
145
DOI
10.1088/0952-4746/32/2/131

Commissioning a CT Compatible LDR T&O Applicator Using Analytical Calculation with 1D and 3D Dosimetry

Authors
Adamson, J; Newton, J; Steffey, B; Cai, J; Adamovics, J; Oldham, M; Chino, J; Craciunescu, O
MLA Citation
Adamson, J, Newton, J, Steffey, B, Cai, J, Adamovics, J, Oldham, M, Chino, J, and Craciunescu, O. "Commissioning a CT Compatible LDR T&O Applicator Using Analytical Calculation with 1D and 3D Dosimetry." June 2012.
Source
wos-lite
Published In
Medical physics
Volume
39
Issue
6
Publish Date
2012
Start Page
3612
End Page
3612

Identification of a Targeting Error in a Small Field Biological Irradiator Using 3D Dosimetry Techniques

Authors
Newton, J; Li, Y; Adamovics, J; Kirsch, D; Das, S; Oldham, M
MLA Citation
Newton, J, Li, Y, Adamovics, J, Kirsch, D, Das, S, and Oldham, M. "Identification of a Targeting Error in a Small Field Biological Irradiator Using 3D Dosimetry Techniques." June 2012.
Source
wos-lite
Published In
Medical physics
Volume
39
Issue
6
Publish Date
2012
Start Page
3898
End Page
3898

Experimental Measurements of 3D Dose Distribution for a Moving Target Treated with IMRT and VMAT

Authors
Yan, H; Thomas, A; Oldham, M; Yin, F
MLA Citation
Yan, H, Thomas, A, Oldham, M, and Yin, F. "Experimental Measurements of 3D Dose Distribution for a Moving Target Treated with IMRT and VMAT." June 2012.
Source
wos-lite
Published In
Medical physics
Volume
39
Issue
6
Publish Date
2012
Start Page
3792
End Page
3792

High Dynamic Range Scanning for Optical-CT in 3D Dosimetry

Authors
Niebanck, M; Newton, J; Juang, T; Oldham, M
MLA Citation
Niebanck, M, Newton, J, Juang, T, and Oldham, M. "High Dynamic Range Scanning for Optical-CT in 3D Dosimetry." June 2012.
Source
wos-lite
Published In
Medical physics
Volume
39
Issue
6
Publish Date
2012
Start Page
3724
End Page
3724

3D Measurement of Neutron Dose From a Novel Neutron Imaging Technique

Authors
Kapadia, A; Crowell, A; Fallin, B; Howell, C; Agasthya, G; Lakshmanan, M; Newton, J; Juang, T; Oldham, M
MLA Citation
Kapadia, A, Crowell, A, Fallin, B, Howell, C, Agasthya, G, Lakshmanan, M, Newton, J, Juang, T, and Oldham, M. "3D Measurement of Neutron Dose From a Novel Neutron Imaging Technique." June 2012.
Source
wos-lite
Published In
Medical physics
Volume
39
Issue
6
Publish Date
2012
Start Page
3727
End Page
3727

Validation of Multi-Focal Stereotactic Radiosurgery with Volumetric Modulated Arc Therapy with High-Resolution 3D Dosimetry

Authors
Wang, Z; Newton, J; Niebanck, M; Juang, T; Kirkpatrick, J; Oldham, M
MLA Citation
Wang, Z, Newton, J, Niebanck, M, Juang, T, Kirkpatrick, J, and Oldham, M. "Validation of Multi-Focal Stereotactic Radiosurgery with Volumetric Modulated Arc Therapy with High-Resolution 3D Dosimetry." June 2012.
Source
wos-lite
Published In
Medical physics
Volume
39
Issue
6
Publish Date
2012
Start Page
3910
End Page
3910

Quantitative Dose Tracking Enabled Through a Novel Deformable 3D Dosimeter

Authors
Juang, T; Newton, J; Das, S; Adamovics, J; Oldham, M
MLA Citation
Juang, T, Newton, J, Das, S, Adamovics, J, and Oldham, M. "Quantitative Dose Tracking Enabled Through a Novel Deformable 3D Dosimeter." June 2012.
Source
wos-lite
Published In
Medical physics
Volume
39
Issue
6
Publish Date
2012
Start Page
3956
End Page
3956

Validation Study of the Accuracy of the Transform Method for Clinically Intuitive Quality Assurance

Authors
Norris, H; Thomas, A; Oldham, M
MLA Citation
Norris, H, Thomas, A, and Oldham, M. "Validation Study of the Accuracy of the Transform Method for Clinically Intuitive Quality Assurance." June 2012.
Source
wos-lite
Published In
Medical physics
Volume
39
Issue
6
Publish Date
2012
Start Page
3599
End Page
3599

Locating radiation hazards and sources within contaminated areas by implementing a reverse ray tracing technique in the RadBall™ technology.

RadBall™ is a novel technology that can locate unknown radioactive hazards within contaminated areas, hot cells, and gloveboxes. The device consists of a colander-like outer tungsten collimator that houses a radiation-sensitive polymer semisphere. The collimator has a number of small holes; as a result, specific areas of the polymer are exposed to radiation, becoming increasingly more opaque in proportion to the absorbed dose. The polymer semisphere is imaged in an optical computed tomography scanner that produces a high resolution three-dimensional map of optical attenuation coefficients. A subsequent analysis of the optical attenuation data, using a reverse ray tracing technique, provides information on the spatial distribution of gamma-ray sources in a given area, forming a three-dimensional characterization of the area of interest. The RadBall™ technology and its reverse ray tracing technique were investigated using known radiation sources at the Savannah River Site's Health Physics Instrument Calibration Laboratory and unknown sources at the Savannah River National Laboratory's Shielded Cells facility.

Authors
Farfán, EB; Stanley, S; Holmes, C; Lennox, K; Oldham, M; Clift, C; Thomas, A; Adamovics, J
MLA Citation
Farfán, EB, Stanley, S, Holmes, C, Lennox, K, Oldham, M, Clift, C, Thomas, A, and Adamovics, J. "Locating radiation hazards and sources within contaminated areas by implementing a reverse ray tracing technique in the RadBall™ technology." Health Phys 102.2 (February 2012): 196-207.
PMID
22217592
Source
pubmed
Published In
Health Physics
Volume
102
Issue
2
Publish Date
2012
Start Page
196
End Page
207
DOI
10.1097/HP.0b013e3182348c0a

Feasibility of using PRESAGE®for relative 3D dosimetry of small proton fields

Small field dosimetry is challenging due to the finite size of the conventional detectors that underestimate the dose distribution. With the fast development of the dynamic proton beam delivery system, it is essential to find a dosimeter which can be used for 3D dosimetry of small proton fields. We investigated the feasibility of using a proton formula PRESAGE®for 3D dosimetry of small fields in a uniform scanning proton beam delivery system with dose layer stacking technology. The relationship between optical density and the absorbed dose was found to be linear through small volume cuvette studies for both photon and proton irradiation. Two circular fields and three patient-specific fields were used for proton treatment planning calculation and beam delivery. The measured results were compared with the calculated results in the form of lateral dose profiles, depth dose, isodose plots and gamma index analysis. For the circular field study, lateral dose profile comparison showed that the relative PRESAGE®profile falls within ± 5% from the calculated profile for most of the spatial range. For unmodulated depth dose comparison, the agreement between the measured and calculated results was within 3% in the beam entrance region before the Bragg peak. However, at the Bragg peak, there was about 20% underestimation of the absorbed dose from PRESAGE®. For patient-specific field 3D dosimetry, most of the data points within the target volume passed gamma analysis for 3% relative dose difference and 3mm distance to agreement criteria. Our results suggest that this proton formula PRESAGE®dosimeter has the potential for 3D dosimetry of small fields in proton therapy, but further investigation is needed to improve the dose under-response of the PRESAGE®in the Bragg peak region. © 2012 Institute of Physics and Engineering in Medicine.

Authors
Zhao, L; Newton, J; Oldham, M; Das, IJ; Cheng, C-W; Adamovics, J
MLA Citation
Zhao, L, Newton, J, Oldham, M, Das, IJ, Cheng, C-W, and Adamovics, J. "Feasibility of using PRESAGE®for relative 3D dosimetry of small proton fields." Physics in Medicine and Biology 57.22 (2012): N431-N443.
PMID
23103526
Source
scival
Published In
Physics in Medicine and Biology
Volume
57
Issue
22
Publish Date
2012
Start Page
N431
End Page
N443
DOI
10.1088/0031-9155/57/22/N431

Commissioning a small-field biological irradiator using point, 2D, and 3D dosimetry techniques.

PURPOSE: To commission a small-field biological irradiator, the XRad225Cx from Precision x-Ray, Inc., for research use. The system produces a 225 kVp x-ray beam and is equipped with collimating cones that produce both square and circular radiation fields ranging in size from 1 to 40 mm. This work incorporates point, 2D, and 3D measurements to determine output factors (OF), percent-depth-dose (PDD) and dose profiles at multiple depths. METHODS: Three independent dosimetry systems were used: ion-chambers (a farmer chamber and a micro-ionisation chamber), 2D EBT2 radiochromic film, and a novel 3D dosimetry system (DLOS∕PRESAGE®). Reference point dose rates and output factors were determined from in-air ionization chamber measurements for fields down to ∼13 mm using the formalism of TG61. PDD, profiles, and output factors at three separate depths (0, 0.5, and 2 cm), were determined for all field sizes from EBT2 film measurements in solid water. Several film PDD curves required a scaling correction, reflecting the challenge of accurate film alignment in very small fields. PDDs, profiles, and output factors were also determined with the 3D DLOS∕PRESAGE® system which generated isotropic 0.2 mm data, in scan times of 20 min. RESULTS: Surface output factors determined by ion-chamber were observed to gradually drop by ∼9% when the field size was reduced from 40 to 13 mm. More dramatic drops were observed for the smallest fields as determined by EBT∼18% and ∼42% for the 2.5 mm and 1 mm fields, respectively. PRESAGE® and film output factors agreed well for fields <20 mm (where 3D data were available) with mean deviation of 2.2% (range 1%-4%). PDD values at 2 cm depth varied from ∼72% for the 40 mm field, down to ∼55% for the 1 mm field. EBT and PRESAGE® PDDs agreed within ∼3% in the typical therapy region (1-4 cm). At deeper depths the EBT curves were slightly steeper (2.5% at 5 cm). These results indicate good overall consistency between ion-chamber, EBT2 and PRESAGE® measured OFs, PDDs, and profiles. CONCLUSIONS: The combination of independent 2D and 3D measurements was found to be valuable to ensure accurate and comprehensive commissioning. Film measurements were time consuming and challenging due to the difficulty of film alignment in small fields. PRESAGE® 3D measurements were comprehensive and efficient, because alignment errors are negligible, and all parameters for multiple fields could be obtained from a single dosimeter and scan. However, achieving accurate superficial data (within 4 mm) is not yet feasible due to optical surface artifacts.

Authors
Newton, J; Oldham, M; Thomas, A; Li, Y; Adamovics, J; Kirsch, DG; Das, S
MLA Citation
Newton, J, Oldham, M, Thomas, A, Li, Y, Adamovics, J, Kirsch, DG, and Das, S. "Commissioning a small-field biological irradiator using point, 2D, and 3D dosimetry techniques." Med Phys 38.12 (December 2011): 6754-6762.
PMID
22149857
Source
pubmed
Published In
Medical physics
Volume
38
Issue
12
Publish Date
2011
Start Page
6754
End Page
6762
DOI
10.1118/1.3663675

Commissioning and benchmarking a 3D dosimetry system for clinical use.

PURPOSE: A 3D dosimetry system is described which consists of two parts: a radiochromic plastic dosimeter PRESAGE (which responds to absorbed dose with a linear change in optical-density) and the Duke large-field-of-view optical-CT scanner (DLOS). The DLOS/PRESAGE system has recently been commissioned and benchmarked for clinical use and, in particular, for verification and commissioning of complex radiation treatments. METHODS: DLOS commissioning involved determining the dynamic range, spatial resolution, noise, temporal, and other characteristics of the light source and imaging components. Benchmarking tests were performed on the combined DLOS/PRESAGE system to establish baseline dosimetric performance. The tests consisted of delivering simple radiation treatments to PRESAGE dosimeters, and comparing the measured 3D relative dose distributions with the known gold standard. The gold standard distribution was obtained from machine beam-data or the treatment planning system (TPS). All studies used standardized procedures to ensure consistency. RESULTS: For commissioning, isotropic spatial resolution was submillimeter (MTF > 0.5 for frequencies of 1.5 lp/mm) and the dynamic range was -60 dB. Flood field uniformity was within 10% and stable after 45 min of warm-up. Stray-light is small, due to telecentricity, but even the residual can be removed through deconvolution by a point-spread-function. For benchmarking, the mean 3D passing NDD (normalized dose distribution) rate (3%, 3mm, 5% dose threshold) over the benchmark data sets was 97.3% +/- 0.6% (range 96%-98%), which is on par with other planar dosimeters used in external beam radiation therapy indicating excellent agreement. Noise was low at < 2% of maximum dose (4-12 Gy) for 2 mm reconstructions. The telecentric design was critical to enabling fast imaging with minimal stray-light artifacts. CONCLUSIONS: This work presents the first comprehensive benchmarking of a 3D dosimetry system for clinical use. The DLOS/PRESAGE benchmark tests show consistently good agreement to simple known distributions. The system produces accurate isotropic 2 mm dose data over clinical volumes (e.g., 16 cm diameter phantoms, 12 cm height), in under 15 min. It represents a uniquely useful and versatile new tool for commissioning and verification of complex therapy treatments.

Authors
Thomas, A; Newton, J; Adamovics, J; Oldham, M
MLA Citation
Thomas, A, Newton, J, Adamovics, J, and Oldham, M. "Commissioning and benchmarking a 3D dosimetry system for clinical use." Med Phys 38.8 (August 2011): 4846-4857.
PMID
21928656
Source
pubmed
Published In
Medical physics
Volume
38
Issue
8
Publish Date
2011
Start Page
4846
End Page
4857
DOI
10.1118/1.3611042

A method to correct for stray light in telecentric optical-CT imaging of radiochromic dosimeters.

Radiochromic plastic and gel materials have recently emerged which can yield 3D dose information over clinical volumes in high resolution. These dosimeters can provide a much more comprehensive verification of complex radiation therapy treatments than can be achieved by conventional planar and point dosimeters. To achieve full clinical potential, these dosimeters require a fast and accurate read-out technology. Broad-beam optical-computed tomography (optical-CT) systems have shown promise, but can be sensitive to stray light artifacts originating in the imaging chain. In this work we present and evaluate a method to correct for stray light artifacts by deconvolving a measured, spatially invariant, point spread function (PSF). The correction was developed for the DLOS (Duke large field-of-view optical-CT scanner) in conjunction with radiochromic PRESAGE® dosimeters. The PSF was constructed from a series of acquisitions of projection images of various sized apertures placed in the optical imaging chain. Images were acquired with a range of exposure times, and for a range of aperture sizes (0.2-11 mm). The PSF is investigated under a variety of conditions, and found to be robust and spatially invariant, key factors enabling the viability of the deconvolution approach. The spatial invariance and robustness of the PSF are facilitated by telecentric imaging, which produces a collimated light beam and removes stray light originating upstream of the imaging lens. The telecentric capability of the DLOS therefore represents a significant advantage, both in keeping stray light levels to a minimum and enabling viability of an accurate PSF deconvolution method to correct for the residual. The performance of the correction method was evaluated on projection images containing known optical-density variations, and also on known 3D dose distributions. The method is shown to accurately account for stray light on small field dosimetry with corrections up to 3% in magnitude shown here although corrections of >10% have been observed in extreme cases. The dominant source of stray light was found to be within the imaging lens. Correcting for stray light extended the dynamic range of the system from ∼30 to ∼60 dB. The correction should be used when measurements need to be accurate within 3%.

Authors
Thomas, A; Newton, J; Oldham, M
MLA Citation
Thomas, A, Newton, J, and Oldham, M. "A method to correct for stray light in telecentric optical-CT imaging of radiochromic dosimeters." Phys Med Biol 56.14 (July 21, 2011): 4433-4451.
PMID
21719946
Source
pubmed
Published In
Physics in Medicine and Biology
Volume
56
Issue
14
Publish Date
2011
Start Page
4433
End Page
4451
DOI
10.1088/0031-9155/56/14/013

A method to correct for spectral artifacts in optical-CT dosimetry.

The recent emergence of radiochromic dosimeters with low inherent light-scattering presents the possibility of fast 3D dosimetry using broad-beam optical computed tomography (optical-CT). Current broad beam scanners typically employ either a single or a planar array of light-emitting diodes (LED) for the light source. The spectrum of light from LED sources is polychromatic and this, in combination with the non-uniform spectral absorption of the dosimeter, can introduce spectral artifacts arising from preferential absorption of photons at the peak absorption wavelengths in the dosimeter. Spectral artifacts can lead to large errors in the reconstructed attenuation coefficients, and hence dose measurement. This work presents an analytic method for correcting for spectral artifacts which can be applied if the spectral characteristics of the light source, absorbing dosimeter, and imaging detector are known or can be measured. The method is implemented here for a PRESAGE® dosimeter scanned with the DLOS telecentric scanner (Duke Large field-of-view Optical-CT Scanner). Emission and absorption profiles were measured with a commercial spectrometer and spectrophotometer, respectively. Simulations are presented that show spectral changes can introduce errors of 8% for moderately attenuating samples where spectral artifacts are less pronounced. The correction is evaluated by application to a 16 cm diameter PRESAGE® cylindrical dosimeter irradiated along the axis with two partially overlapping 6 × 6 cm fields of different doses. The resulting stepped dose distribution facilitates evaluation of the correction as each step had different spectral contributions. The spectral artifact correction was found to accurately correct the reconstructed coefficients to within ∼1.5%, improved from ∼7.5%, for normalized dose distributions. In conclusion, for situations where spectral artifacts cannot be removed by physical filters, the method shown here is an effective correction. Physical filters may be less viable if they introduce strong sensitivity to Schlieren bands in the dosimeters.

Authors
Thomas, A; Pierquet, M; Jordan, K; Oldham, M
MLA Citation
Thomas, A, Pierquet, M, Jordan, K, and Oldham, M. "A method to correct for spectral artifacts in optical-CT dosimetry." Phys Med Biol 56.11 (June 7, 2011): 3403-3416.
PMID
21572184
Source
pubmed
Published In
Physics in Medicine and Biology
Volume
56
Issue
11
Publish Date
2011
Start Page
3403
End Page
3416
DOI
10.1088/0031-9155/56/11/014

MO-G-BRB-02: Commissioning a Small Animal Irradiator Using 2D and 3D Dosimetry Techniques

Authors
Newton, J; Oldham, M; Li, Y; Adamovics, J; Das, S
MLA Citation
Newton, J, Oldham, M, Li, Y, Adamovics, J, and Das, S. "MO-G-BRB-02: Commissioning a Small Animal Irradiator Using 2D and 3D Dosimetry Techniques." June 2011.
Source
crossref
Published In
Medical physics
Volume
38
Issue
6Part27
Publish Date
2011
Start Page
3734
End Page
3734
DOI
10.1118/1.3613053

SU-E-T-133: A Method to Improve the Accuracy of Optical-CT 3D Dosimetry by Correcting for Stray Light

Authors
Thomas, A; Newton, J; Oldham, M
MLA Citation
Thomas, A, Newton, J, and Oldham, M. "SU-E-T-133: A Method to Improve the Accuracy of Optical-CT 3D Dosimetry by Correcting for Stray Light." June 2011.
Source
crossref
Published In
Medical physics
Volume
38
Issue
6Part12
Publish Date
2011
Start Page
3517
End Page
3517
DOI
10.1118/1.3612084

TU-E-BRA-02: How Should We Verify Complex Radiation Therapy Treatments ?

Authors
Ibbott, G; Oldham, M; Mijnheer, B; Zhu, T
MLA Citation
Ibbott, G, Oldham, M, Mijnheer, B, and Zhu, T. "TU-E-BRA-02: How Should We Verify Complex Radiation Therapy Treatments ?." June 2011.
Source
crossref
Published In
Medical physics
Volume
38
Issue
6Part29
Publish Date
2011
Start Page
3766
End Page
3766
DOI
10.1118/1.3613176

WE-E-BRB-08: Commissioning and Benchmarking a 3D Dosimetry System for Clinical Use

Authors
Thomas, A; Newton, J; Adamovics, J; Oldham, M
MLA Citation
Thomas, A, Newton, J, Adamovics, J, and Oldham, M. "WE-E-BRB-08: Commissioning and Benchmarking a 3D Dosimetry System for Clinical Use." June 2011.
Source
crossref
Published In
Medical physics
Volume
38
Issue
6Part32
Publish Date
2011
Start Page
3817
End Page
3817
DOI
10.1118/1.3613375

TU-C-BRB-01: A Method to Determine Measured Dose-Volume-Histograms (DVH) in Patient from 3D Dose Measurement in Phantom

Authors
Oldham, M; Thomas, A
MLA Citation
Oldham, M, and Thomas, A. "TU-C-BRB-01: A Method to Determine Measured Dose-Volume-Histograms (DVH) in Patient from 3D Dose Measurement in Phantom." June 2011.
Source
crossref
Published In
Medical physics
Volume
38
Issue
6Part28
Publish Date
2011
Start Page
3753
End Page
3753
DOI
10.1118/1.3613121

SU-E-T-88: 3D Dosimetry for Small Irregular Proton Fields Using a New PRESAGE® Dosimeter

Authors
Zhao, L; Newton, J; Adamovics, J; Oldham, M; Cheng, C; Das, I
MLA Citation
Zhao, L, Newton, J, Adamovics, J, Oldham, M, Cheng, C, and Das, I. "SU-E-T-88: 3D Dosimetry for Small Irregular Proton Fields Using a New PRESAGE® Dosimeter." June 2011.
Source
crossref
Published In
Medical physics
Volume
38
Issue
6Part11
Publish Date
2011
Start Page
3506
End Page
3506
DOI
10.1118/1.3612039

SU-E-T-363: Investigation of PRESAGE® Dosimeters for Proton Therapy

Authors
Grant, R; Ibbott, G; Zhu, X; Carroll, M; Adamovics, J; Oldham, M; Followill, D
MLA Citation
Grant, R, Ibbott, G, Zhu, X, Carroll, M, Adamovics, J, Oldham, M, and Followill, D. "SU-E-T-363: Investigation of PRESAGE® Dosimeters for Proton Therapy." June 2011.
Source
crossref
Published In
Medical physics
Volume
38
Issue
6Part16
Publish Date
2011
Start Page
3571
End Page
3571
DOI
10.1118/1.3612317

SU-E-T-99: A Patient Specific QA Protocol for Verification of 4D Dosimetry

Authors
Yin, F; Thomas, A; Yan, H; Vergalasova, I; Adamovics, J; Wu, Q; Oldham, M
MLA Citation
Yin, F, Thomas, A, Yan, H, Vergalasova, I, Adamovics, J, Wu, Q, and Oldham, M. "SU-E-T-99: A Patient Specific QA Protocol for Verification of 4D Dosimetry." June 2011.
Source
crossref
Published In
Medical physics
Volume
38
Issue
6Part11
Publish Date
2011
Start Page
3508
End Page
3508
DOI
10.1118/1.3612050

Dosimetry tools and techniques for IMRT.

Intensity modulated radiation therapy (IMRT) poses a number of challenges for properly measuring commissioning data and quality assurance (QA) radiation dose distributions. This report provides a comprehensive overview of how dosimeters, phantoms, and dose distribution analysis techniques should be used to support the commissioning and quality assurance requirements of an IMRT program. The proper applications of each dosimeter are described along with the limitations of each system. Point detectors, arrays, film, and electronic portal imagers are discussed with respect to their proper use, along with potential applications of 3D dosimetry. Regardless of the IMRT technique utilized, some situations require the use of multiple detectors for the acquisition of accurate commissioning data. The overall goal of this task group report is to provide a document that aids the physicist in the proper selection and use of the dosimetry tools available for IMRT QA and to provide a resource for physicists that describes dosimetry measurement techniques for purposes of IMRT commissioning and measurement-based characterization or verification of IMRT treatment plans. This report is not intended to provide a comprehensive review of commissioning and QA procedures for IMRT. Instead, this report focuses on the aspects of metrology, particularly the practical aspects of measurements that are unique to IMRT. The metrology of IMRT concerns the application of measurement instruments and their suitability, calibration, and quality control of measurements. Each of the dosimetry measurement tools has limitations that need to be considered when incorporating them into a commissioning process or a comprehensive QA program. For example, routine quality assurance procedures require the use of robust field dosimetry systems. These often exhibit limitations with respect to spatial resolution or energy response and need to themselves be commissioned against more established dosimeters. A chain of dosimeters, from secondary standards to field instruments, is established to assure the quantitative nature of the tests. This report is intended to describe the characteristics of the components of these systems; dosimeters, phantoms, and dose evaluation algorithms. This work is the report of AAPM Task Group 120.

Authors
Low, DA; Moran, JM; Dempsey, JF; Dong, L; Oldham, M
MLA Citation
Low, DA, Moran, JM, Dempsey, JF, Dong, L, and Oldham, M. "Dosimetry tools and techniques for IMRT." Med Phys 38.3 (March 2011): 1313-1338. (Review)
PMID
21520843
Source
pubmed
Published In
Medical physics
Volume
38
Issue
3
Publish Date
2011
Start Page
1313
End Page
1338
DOI
10.1118/1.3514120

Preliminary Investigation of the Dosimetric Properties of 'RadGel'

A preliminary investigation into the efficacy of a new 3D dosimetry material, RadGel™, for verification of radiation therapy dose distributions is presented. Small volumes of RadGel™ were found to exhibit a linear, reproducible response to dose. A gradual increase in optical-density (OD) with time was observed, suggesting scanning should be completed within 18 hours to keep a linear correlation of R(2) > 0.99. A larger 10 cm diameter volume of RadGel™ was irradiated with a rotationally symmetric "spoke" plan designed to rigorously evaluate scanner/dosimeter combined performance. The dosimeter was imaged with the Duke Mid-sized Optical-CT Scanner (DMOS). Promising OD and corresponding dose maps were obtained. Edge artefacts were observed and are suspected to be exacerbated by the particular container used in this early study. Further studies will evaluate new containers and methods for refractive matching at the gel-container-fluid interface.

Authors
Newton, JR; Thomas, A; Appleby, A; Marsden, C; Christman, EA; Wolodzko, JG; Oldham, M
MLA Citation
Newton, JR, Thomas, A, Appleby, A, Marsden, C, Christman, EA, Wolodzko, JG, and Oldham, M. "Preliminary Investigation of the Dosimetric Properties of 'RadGel'." J Phys Conf Ser 250.1 (2011): 49-53.
PMID
21617743
Source
pubmed
Published In
Journal of Physics
Volume
250
Issue
1
Publish Date
2011
Start Page
49
End Page
53
DOI
10.1088/1742-6596/250/1/012011

Investigation of Proton Beam Dose Distributions with 3D Dosimetry

Authors
Grant, R; Ibbott, G; Zhu, X; Adamovics, J; Oldham, M; Followill, D
MLA Citation
Grant, R, Ibbott, G, Zhu, X, Adamovics, J, Oldham, M, and Followill, D. "Investigation of Proton Beam Dose Distributions with 3D Dosimetry." INTERNATIONAL JOURNAL OF RADIATION ONCOLOGY BIOLOGY PHYSICS 81.2 (2011): S885-S886.
Source
wos-lite
Published In
International Journal of Radiation Oncology, Biology, Physics
Volume
81
Issue
2
Publish Date
2011
Start Page
S885
End Page
S886

Initial experience with optical-CT scanning of RadBall Dosimeters.

The RadBall dosimeter is a novel device for providing 3-D information on the magnitude and distribution of contaminant sources of unknown radiation in a given hot cell, glovebox, or contaminated room. The device is presently under evaluation by the National Nuclear Lab (NNL, UK) and the Savannah River National Laboratory (SRNL, US), for application as a diagnostic device for such unknown contaminants in the nuclear industry. A critical component of the technique is imaging the dose distribution recorded in the RadBall using optical-CT scanning. Here we present our initial investigations using the Duke Mid-sized Optical-CT Scanner (DMOS) to image dose distributions deposited in RadBalls exposed to a variety of radiation treatments.

Authors
Oldham, M; Clift, C; Thomas, A; Farfan, E; Foley, T; Jannik, T; Adamovics, J; Holmes, C; Stanley, S
MLA Citation
Oldham, M, Clift, C, Thomas, A, Farfan, E, Foley, T, Jannik, T, Adamovics, J, Holmes, C, and Stanley, S. "Initial experience with optical-CT scanning of RadBall Dosimeters." J Phys Conf Ser 250.1 (December 7, 2010).
PMID
21218190
Source
pubmed
Published In
Journal of Physics
Volume
250
Issue
1
Publish Date
2010
DOI
10.1088/1742-6596/250/1/012079

Dose Verification of Stereotactic Radiosurgery Treatment for Trigeminal Neuralgia with Presage 3D Dosimetry System.

Achieving adequate verification and quality-assurance (QA) for radiosurgery treatment of trigeminal-neuralgia (TGN) is particularly challenging because of the combination of very small fields, very high doses, and complex irradiation geometries (multiple gantry and couch combinations). TGN treatments have extreme requirements for dosimetry tools and QA techniques, to ensure adequate verification. In this work we evaluate the potential of Presage/Optical-CT dosimetry system as a tool for the verification of TGN distributions in high-resolution and in 3D. A TGN treatment was planned and delivered to a Presage 3D dosimeter positioned inside the Radiological-Physics-Center (RPC) head and neck IMRT credentialing phantom. A 6-arc treatment plan was created using the iPlan system, and a maximum dose of 80Gy was delivered with a Varian Trilogy machine. The delivered dose to Presage was determined by optical-CT scanning using the Duke Large field-of-view Optical-CT Scanner (DLOS) in 3D, with isotropic resolution of 0.7mm(3). DLOS scanning and reconstruction took about 20minutes. 3D dose comparisons were made with the planning system. Good agreement was observed between the planned and measured 3D dose distributions, and this work provides strong support for the viability of Presage/Optical-CT as a highly useful new approach for verification of this complex technique.

Authors
Wang, Z; Thomas, A; Newton, J; Ibbott, G; Deasy, J; Oldham, M
MLA Citation
Wang, Z, Thomas, A, Newton, J, Ibbott, G, Deasy, J, and Oldham, M. "Dose Verification of Stereotactic Radiosurgery Treatment for Trigeminal Neuralgia with Presage 3D Dosimetry System." J Phys Conf Ser 250.1 (December 7, 2010).
PMID
21218143
Source
pubmed
Published In
Journal of Physics
Volume
250
Issue
1
Publish Date
2010
DOI
10.1088/1742-6596/250/1/012058

Three-Dimensional Dosimetry of a Beta-Emitting Radionuclide Using PRESAGE Dosimeters.

Three-dimensional dose distributions from liquid brachytherapy were measured using PRESAGE(®) dosimeters. The dosimeters were exposed to Y-90 for 5.75 days and read by optical tomography. The distributions are consistent with estimates from beta dose kernels.

Authors
Grant, RL; Crowder, ML; Ibbott, GS; Simon, J; Frank, RK; Rogers, J; Loy, HM; Adamovics, J; Newton, J; Oldham, M; Stearns, S; Wendt, RE
MLA Citation
Grant, RL, Crowder, ML, Ibbott, GS, Simon, J, Frank, RK, Rogers, J, Loy, HM, Adamovics, J, Newton, J, Oldham, M, Stearns, S, and Wendt, RE. "Three-Dimensional Dosimetry of a Beta-Emitting Radionuclide Using PRESAGE Dosimeters." J Phys Conf Ser 250.1 (December 7, 2010).
PMID
21218189
Source
pubmed
Published In
Journal of Physics
Volume
250
Issue
1
Publish Date
2010
DOI
10.1088/1742-6596/250/1/012095

On the Feasibility of Verification of 3D Dosimetry Near Brachytherapy Sources Using PRESAGE/Optical-CT.

PURPOSE: The feasibility of using the PRESAGE/Optical-CT system for 3D dosimetry verification around a brachytherapy source is investigated. METHOD AND MATERIALS: Brachytherapy dose distributions were obtained by irradiation of cylindrical PRESAGE volumes 6cm in diameter by 8cm height with a GammaMed 12i Ir-192 HDR unit (Varian Medical Systems). A narrow channel on the central axis was created by setting a steel catheter in the Presage during manufacture, enabling measurements close to the source (~3mm). RESULTS: Comparison of dose line profiles shows good agreement between PRESAGE and verified calculated dose calculation, in both high and low dose regions. CONCLUSION: The PRESAGE/Optical-CT shows good potential in verification of 3D dose distributions around brachytherapy sources.

Authors
Pierquet, M; Craciunescu, O; Steffey, B; Song, H; Oldham, M
MLA Citation
Pierquet, M, Craciunescu, O, Steffey, B, Song, H, and Oldham, M. "On the Feasibility of Verification of 3D Dosimetry Near Brachytherapy Sources Using PRESAGE/Optical-CT." J Phys Conf Ser 250.1 (December 7, 2010): 120911-120915.
PMID
22235233
Source
pubmed
Published In
Journal of Physics
Volume
250
Issue
1
Publish Date
2010
Start Page
120911
End Page
120915
DOI
10.1088/1742-6596/250/1/012091

A comprehensive method for optical-emission computed tomography.

Optical-computed tomography (CT) and optical-emission computed tomography (ECT) are recent techniques with potential for high-resolution multi-faceted 3D imaging of the structure and function in unsectioned tissue samples up to 1-4 cc. Quantitative imaging of 3D fluorophore distribution (e.g. GFP) using optical-ECT is challenging due to attenuation present within the sample. Uncorrected reconstructed images appear hotter near the edges than at the center. A similar effect is seen in SPECT/PET imaging, although an important difference is attenuation occurs for both emission and excitation photons. This work presents a way to implement not only the emission attenuation correction utilized in SPECT, but also excitation attenuation correction and source strength modeling which are unique to optical-ECT. The performance of the correction methods was investigated by the use of a cylindrical gelatin phantom whose central region was filled with a known distribution of attenuation and fluorophores. Uncorrected and corrected reconstructions were compared to a sectioned slice of the phantom imaged using a fluorescent dissecting microscope. Significant attenuation artifacts were observed in uncorrected images and appeared up to 80% less intense in the central regions due to attenuation and an assumed uniform light source. The corrected reconstruction showed agreement throughout the verification image with only slight variations ( approximately 5%). Final experiments demonstrate the correction in tissue as applied to a tumor with constitutive RFP.

Authors
Thomas, A; Bowsher, J; Roper, J; Oliver, T; Dewhirst, M; Oldham, M
MLA Citation
Thomas, A, Bowsher, J, Roper, J, Oliver, T, Dewhirst, M, and Oldham, M. "A comprehensive method for optical-emission computed tomography." Phys Med Biol 55.14 (July 21, 2010): 3947-3957.
PMID
20577042
Source
pubmed
Published In
Physics in Medicine and Biology
Volume
55
Issue
14
Publish Date
2010
Start Page
3947
End Page
3957
DOI
10.1088/0031-9155/55/14/001

TU-E-201C-08: A Comprehensive Method for Optical - Emission Computed Tomography

Authors
Thomas, A; Bowsher, J; Roper, J; Oldham, M
MLA Citation
Thomas, A, Bowsher, J, Roper, J, and Oldham, M. "TU-E-201C-08: A Comprehensive Method for Optical - Emission Computed Tomography." June 2010.
Source
crossref
Published In
Medical physics
Volume
37
Issue
6Part7
Publish Date
2010
Start Page
3406
End Page
3406
DOI
10.1118/1.3469310

TU-E-201C-06: Imaging the Biological Structure and Characteristics of Model Tumors Using Optical Computed Transmission and Emission Tomography

Authors
Oldham, M; Thomas, A; Schroeder, T; Fontanella, A; Dewhirst, M
MLA Citation
Oldham, M, Thomas, A, Schroeder, T, Fontanella, A, and Dewhirst, M. "TU-E-201C-06: Imaging the Biological Structure and Characteristics of Model Tumors Using Optical Computed Transmission and Emission Tomography." June 2010.
Source
crossref
Published In
Medical physics
Volume
37
Issue
6Part7
Publish Date
2010
Start Page
3405
End Page
3405
DOI
10.1118/1.3469308

SU-GG-T-363: 3D Dosimetric Verification of Ir-192 HDR Brachytherapy Source Irradiation

Authors
Pierquet, M; Oldham, M
MLA Citation
Pierquet, M, and Oldham, M. "SU-GG-T-363: 3D Dosimetric Verification of Ir-192 HDR Brachytherapy Source Irradiation." June 2010.
Source
crossref
Published In
Medical physics
Volume
37
Issue
6Part21
Publish Date
2010
Start Page
3269
End Page
3269
DOI
10.1118/1.3468760

TU-C-BRA-01: Memorial to Lester Skaggs

Authors
Oldham, M
MLA Citation
Oldham, M. "TU-C-BRA-01: Memorial to Lester Skaggs." June 2010.
Source
crossref
Published In
Medical physics
Volume
37
Issue
6Part26
Publish Date
2010
Start Page
3381
End Page
3381
DOI
10.1118/1.3469213

SU-GG-T-371: Measurement of Dose to Pacemakers and Other Implantable Medical Devices

Authors
Pursley, J; Oldham, M
MLA Citation
Pursley, J, and Oldham, M. "SU-GG-T-371: Measurement of Dose to Pacemakers and Other Implantable Medical Devices." June 2010.
Source
crossref
Published In
Medical physics
Volume
37
Issue
6Part21
Publish Date
2010
Start Page
3271
End Page
3271
DOI
10.1118/1.3468768

SU-GG-T-362: Is Distance-Dependent Energy Correction Needed for Dosimetric Measurements Surrounding Brachytherapy Sources?

Authors
Song, H; Oldham, M; Yin, F
MLA Citation
Song, H, Oldham, M, and Yin, F. "SU-GG-T-362: Is Distance-Dependent Energy Correction Needed for Dosimetric Measurements Surrounding Brachytherapy Sources?." June 2010.
Source
crossref
Published In
Medical physics
Volume
37
Issue
6Part21
Publish Date
2010
Start Page
3269
End Page
3269
DOI
10.1118/1.3468759

Investigation into the feasibility of using PRESAGE/optical-CT dosimetry for the verification of gating treatments.

This work presents an investigation into the use of PRESAGE dosimeters with an optical-CT scanner as a 3D dosimetry system for quantitative verification of respiratory-gated treatments. The CIRS dynamic thorax phantom was modified to incorporate a moving PRESAGE dosimeter-simulating respiration motion in the lungs. A simple AP/PA lung treatment plan was delivered three times to the phantom containing a different but geometrically identical PRESAGE insert each time. Each delivery represented a treatment scenario: static, motion (free-breathing) and gated. The dose distributions, in the three dosimeters, were digitized by the optical-CT scanner. Improved optical-CT readout yielded an increased signal-to-noise ratio by a factor of 3 and decreased reconstruction artifacts compared with prior work. Independent measurements of dose distributions were obtained in the central plane using EBT film. Dose distributions were normalized to a point corresponding to the 100% isodose region prior to the measurement of dose profiles and gamma maps. These measurements were used to quantify the agreement between measured and ECLIPSE(R) dose distributions. Average gamma pass rates between PRESAGE and EBT were >99% (criteria 3% dose difference and 1.2 mm distance-to-agreement) for all three treatments. Gamma pass rates between PRESAGE and ECLIPSE(R) 3D dose distributions showed excellent agreement for the gated treatment (100% pass rate), but poor for the motion scenario (85% pass rate). This work demonstrates the feasibility of using PRESAGE/optical-CT 3D dosimetry to verify gating-enabled radiation treatments. The capability of the Varian gating system to compensate for motion in this treatment scenario was demonstrated.

Authors
Brady, SL; Brown, WE; Clift, CG; Yoo, S; Oldham, M
MLA Citation
Brady, SL, Brown, WE, Clift, CG, Yoo, S, and Oldham, M. "Investigation into the feasibility of using PRESAGE/optical-CT dosimetry for the verification of gating treatments." Phys Med Biol 55.8 (April 21, 2010): 2187-2201.
PMID
20348606
Source
pubmed
Published In
Physics in Medicine and Biology
Volume
55
Issue
8
Publish Date
2010
Start Page
2187
End Page
2201
DOI
10.1088/0031-9155/55/8/005

Polymer gel dosimetry.

Polymer gel dosimeters are fabricated from radiation sensitive chemicals which, upon irradiation, polymerize as a function of the absorbed radiation dose. These gel dosimeters, with the capacity to uniquely record the radiation dose distribution in three-dimensions (3D), have specific advantages when compared to one-dimensional dosimeters, such as ion chambers, and two-dimensional dosimeters, such as film. These advantages are particularly significant in dosimetry situations where steep dose gradients exist such as in intensity-modulated radiation therapy (IMRT) and stereotactic radiosurgery. Polymer gel dosimeters also have specific advantages for brachytherapy dosimetry. Potential dosimetry applications include those for low-energy x-rays, high-linear energy transfer (LET) and proton therapy, radionuclide and boron capture neutron therapy dosimetries. These 3D dosimeters are radiologically soft-tissue equivalent with properties that may be modified depending on the application. The 3D radiation dose distribution in polymer gel dosimeters may be imaged using magnetic resonance imaging (MRI), optical-computerized tomography (optical-CT), x-ray CT or ultrasound. The fundamental science underpinning polymer gel dosimetry is reviewed along with the various evaluation techniques. Clinical dosimetry applications of polymer gel dosimetry are also presented.

Authors
Baldock, C; De Deene, Y; Doran, S; Ibbott, G; Jirasek, A; Lepage, M; McAuley, KB; Oldham, M; Schreiner, LJ
MLA Citation
Baldock, C, De Deene, Y, Doran, S, Ibbott, G, Jirasek, A, Lepage, M, McAuley, KB, Oldham, M, and Schreiner, LJ. "Polymer gel dosimetry." Phys Med Biol 55.5 (March 7, 2010): R1-63. (Review)
PMID
20150687
Source
pubmed
Published In
Physics in Medicine and Biology
Volume
55
Issue
5
Publish Date
2010
Start Page
R1
End Page
63
DOI
10.1088/0031-9155/55/5/R01

Toward acquiring comprehensive radiosurgery field commissioning data using the PRESAGE/optical-CT 3D dosimetry system.

Achieving accurate small field dosimetry is challenging. This study investigates the utility of a radiochromic plastic PRESAGE read with optical-CT for the acquisition of radiosurgery field commissioning data from a Novalis Tx system with a high-definition multileaf collimator (HDMLC). Total scatter factors (Sc, p), beam profiles, and penumbrae were measured for five different radiosurgery fields (5, 10, 20, 30 and 40 mm) using a commercially available optical-CT scanner (OCTOPUS, MGS Research). The percent depth dose (PDD), beam profile and penumbra of the 10 mm field were also measured using a higher resolution in-house prototype CCD-based scanner. Gafchromic EBT film was used for independent verification. Measurements of Sc, p made with PRESAGE and film agreed with mini-ion chamber commissioning data to within 4% for every field (range 0.2-3.6% for PRESAGE, and 1.6-3.6% for EBT). PDD, beam profile and penumbra measurements made with the two PRESAGE/optical-CT systems and film showed good agreement with the high-resolution diode commissioning measurements with a competitive resolution (0.5 mm pixels). The in-house prototype optical-CT scanner allowed much finer resolution compared with previous applications of PRESAGE. The advantages of the PRESAGE system for small field dosimetry include 3D measurements, negligible volume averaging, directional insensitivity, an absence of beam perturbations, energy and dose rate independence.

Authors
Clift, C; Thomas, A; Adamovics, J; Chang, Z; Das, I; Oldham, M
MLA Citation
Clift, C, Thomas, A, Adamovics, J, Chang, Z, Das, I, and Oldham, M. "Toward acquiring comprehensive radiosurgery field commissioning data using the PRESAGE/optical-CT 3D dosimetry system." Phys Med Biol 55.5 (March 7, 2010): 1279-1293.
PMID
20134082
Source
pubmed
Published In
Physics in Medicine and Biology
Volume
55
Issue
5
Publish Date
2010
Start Page
1279
End Page
1293
DOI
10.1088/0031-9155/55/5/002

An investigation into a new re-useable 3D radiochromic dosimetry material, Presage.

PURPOSE: To investigate the dosimetric properties of a new Presage formulation which exhibits a reversible color change on exposure to radiation. Presage(REU) offers the intriguing possibility of the first re-useable 3D dosimetry material. METHOD AND MATERIALS: Small volumes of Presage(REU) in 1×1×5cm optical cuvettes were irradiated and re-irradiated under a variety of conditions and times to investigate a range of properties including re-usability, dose-rate dependence, dose sensitivity, temporal response, energy sensitivity, and temperature dependence. RESULTS: The radiation induced change in optical density (OD) was found to be linear with dose after initial and subsequent irradiations. After the first irradiation OD was observed to clear in ~2 weeks when stored at room temperature. 3 subsequent irradiations of the same cuvettes showed a very similar strong OD response, although there was a significant increase between this response and that achieve at initial irradiation. CONCLUSION: The Presage(REU) formulation shows strong potential as the first re-useable 3D dosimetry material. When dosimeters are stored at room temperature (~22°C) clearing can occur in 2-3 weeks.

Authors
Pierquet, M; Thomas, A; Adamovics, J; Oldham, M
MLA Citation
Pierquet, M, Thomas, A, Adamovics, J, and Oldham, M. "An investigation into a new re-useable 3D radiochromic dosimetry material, Presage." J Phys Conf Ser 250.1 (January 1, 2010): 1-4.
PMID
21218168
Source
pubmed
Published In
Journal of Physics
Volume
250
Issue
1
Publish Date
2010
Start Page
1
End Page
4
DOI
10.1088/1742-6596/250/1/012047

Fast, large field-of-view, telecentric optical-CT scanning system for 3D radiochromic dosimetry.

We describe initial experiences with an in-house, fast, large field-of-view optical-CT telecentric scanner (the Duke Large field of view Optical-CT Scanner (DLOS)). The DLOS system is designed to enable telecentric optical-CT imaging of dosimeters up to 24 cm in diameter with a spatial resolution of 1 mm(3), in approximately 10 minutes. These capabilities render the DLOS system a unique device at present. The system is a scaled up version of early prototypes in our lab. This scaling introduces several challenges, including the accurate measurement of a greatly increased range of light attenuation within the dosimeter, and the need to reduce even minor reflections and scattered light within the imaging chain. We present several corrections and techniques that enable accurate, low noise, 3D dosimetery with the DLOS system.

Authors
Thomas, A; Oldham, M
MLA Citation
Thomas, A, and Oldham, M. "Fast, large field-of-view, telecentric optical-CT scanning system for 3D radiochromic dosimetry." J Phys Conf Ser 250.1 (January 1, 2010): 1-5.
PMID
21218169
Source
pubmed
Published In
Journal of Physics
Volume
250
Issue
1
Publish Date
2010
Start Page
1
End Page
5
DOI
10.1088/1742-6596/250/1/012007

Preliminary commissioning investigations with the DMOS-RPC optical-CT Scanner.

A midsized broad beam Optical-CT scanner is being developed for collaborative research between Duke and the Radiological Physics Center (RPC). The Duke Midsized Optical-CT Scanner (DMOS-RPC) is designed to be compatible with several of the RPC phantoms, including the head and neck, stereotactic SRS, and lung phantoms. Preliminary data investigating the basic performance of the scanner is described. Two 10 cm PRESAGE cylinders were irradiated with simple test plans. Projections of ~80 μm resolution of each dosimeter were collected at 1 degree intervals over a full 360 degrees both before and after irradiation. 3 dimensional reconstructions of attenuation coefficients throughout the dosimeter were computed with 1 mm(3) resolution. Scans were normalized to the calculated dose distribution and a 3D comparison was made with a commissioned treatment planning system. Initial results indicate DMOS-RPC can produce accurate relative dose distributions with high spatial resolution (up to 1 mm(3) in 3D) in less than 30 minutes (acquisition and reconstruction). A maximum dose of ~3.6Gy was delivered in these tests, and observed noise was ~2% for 1 mm(3) reconstructions. Good agreement is observed with the planning system in these simple distributions, indicating promising potential for this scanner.

Authors
Newton, J; Thomas, A; Ibbott, G; Oldham, M
MLA Citation
Newton, J, Thomas, A, Ibbott, G, and Oldham, M. "Preliminary commissioning investigations with the DMOS-RPC optical-CT Scanner." J Phys Conf Ser 250.1 (2010): 12078-.
PMID
21218171
Source
pubmed
Published In
Journal of Physics
Volume
250
Issue
1
Publish Date
2010
Start Page
12078
DOI
10.1088/1742-6596/250/1/012078

Achieving accurate radiochromic optical-CT imaging when using a polychromatic light source.

Optical-CT performed with a broad spectrum light source can lead to inaccurate reconstructed attenuation coefficients (and hence dose) due to 'spectral warping' as the beam passes through the dosimeter. Some wavelengths will be attenuated more strongly than others depending on the absorption spectrum of the radiochromic dosimeter. A simulation was run to characterize the error introduced by the spectrum warping phenomena. Simulations of a typical dosimeter and delivered dose (6cm diameter, 2 Gy irradiation) showed reconstructed attenuation coefficients can be in error by >12% when compared to those obtained from a monochromatic scan. A method to correct for these errors is presented and preliminary data suggests that with the correction, polychromatic imaging can yield imaging results equal in accuracy to those of monochromatic imaging. The advantage is that polychromatic imaging may be less sensitive to prominent schlerring artefacts that are often observed in telecentric optical-CT scanning systems with tight bandwidth filters applied.

Authors
Thomas, A; Pierquet, M; Oldham, M
MLA Citation
Thomas, A, Pierquet, M, and Oldham, M. "Achieving accurate radiochromic optical-CT imaging when using a polychromatic light source." J Phys Conf Ser 250.12045 (2010): 210-214.
PMID
21289868
Source
pubmed
Published In
Journal of Physics
Volume
250
Issue
12045
Publish Date
2010
Start Page
210
End Page
214
DOI
10.1088/1742-6596/250/1/012045

A 'quad-phantom' film dosimeter for use as a multi-planar verification tool for PRESAGE/optical-CT.

INTRODUCTION: To develop and characterize the accuracy and reproducibility of a quad-phantom dosimeter which will serve as an independent verification tool during commissioning of a PRESAGE/optical-CT 3D dosimetry system. METHODS: A 16cm × 12cm cylindrical quad-phantom was constructed from four pieces of solid polyurethane mimicking the PRESAGE material. Films were placed and anchored in orthogonal planes and the quad-phantom was fastened tightly together and placed in a water-filled Styrofoam container for irradiation. A simple, two-field plan consisting of 6×6cm anterior-posterior and right-lateral 6MV photon beams (400cGy) was delivered three times (fresh films inserted for each) with a Varian Clinac 600C. Image registration was performed in the Computational Environment for Radiological Research (CERR) and dose profiles and gamma analysis was performed in CERR and MATLAB. RESULTS #ENTITYSTARTX00026; DISCUSSION: Excellent reproducibility was observed during the irradiations, with ~2.3% standard deviation between all pixels. Using a 3%, 3mm gamma criteria, excellent dosimetric accuracy was observed, with 98.8% and 96.3% passing rates in the sagittal and axial planes, respectively. CONCLUSION: The preliminary results indicate that the quad-phantom can serve as a reproducible and accurate system for high resolution dosimetry in orthogonal planes and should serve as an effective verification tool for PRESAGE/optical-CT in more challenging clinical scenarios.

Authors
Stunja, L; Thomas, A; Adamovics, J; Deasy, J; Oldham, M
MLA Citation
Stunja, L, Thomas, A, Adamovics, J, Deasy, J, and Oldham, M. "A 'quad-phantom' film dosimeter for use as a multi-planar verification tool for PRESAGE/optical-CT." J Phys Conf Ser 250.1 (2010): 12097-.
PMID
21218141
Source
pubmed
Published In
Journal of Physics
Volume
250
Issue
1
Publish Date
2010
Start Page
12097
DOI
10.1088/1742-6596/250/1/012097

RadBall Technology Testing and MCNP Modeling of the Tungsten Collimator.

The United Kingdom's National Nuclear Laboratory (NNL) has developed a remote, non-electrical, radiation-mapping device known as RadBall(™), which can locate and quantify radioactive hazards within contaminated areas of the nuclear industry. RadBall(™) consists of a colander-like outer shell that houses a radiation-sensitive polymer sphere. The outer shell works to collimate radiation sources and those areas of the polymer sphere that are exposed react, becoming increasingly more opaque, in proportion to the absorbed dose. The polymer sphere is imaged in an optical-CT scanner, which produces a high resolution 3D map of optical attenuation coefficients. Subsequent analysis of the optical attenuation matrix provides information on the spatial distribution of sources in a given area forming a 3D characterization of the area of interest. RadBall(™) has no power requirements and can be positioned in tight or hard-to reach locations. The RadBall(™) technology has been deployed in a number of technology trials in nuclear waste reprocessing plants at Sellafield in the United Kingdom and facilities of the Savannah River National Laboratory (SRNL). This study focuses on the RadBall(™) testing and modeling accomplished at SRNL.

Authors
Farfán, EB; Foley, TQ; Coleman, JR; Jannik, GT; Holmes, CJ; Oldham, M; Adamovics, J; Stanley, SJ
MLA Citation
Farfán, EB, Foley, TQ, Coleman, JR, Jannik, GT, Holmes, CJ, Oldham, M, Adamovics, J, and Stanley, SJ. "RadBall Technology Testing and MCNP Modeling of the Tungsten Collimator." J Phys Conf Ser 250.1 (2010): 403-407.
PMID
21617740
Source
pubmed
Published In
Journal of Physics
Volume
250
Issue
1
Publish Date
2010
Start Page
403
End Page
407
DOI
10.1088/1742-6596/250/1/012081

ScanSim: A tool for simulating optical-CT imaging.

A software tool has been developed that can simulate image formation in a variety of optical-CT scanning configurations. The formalism of the simulation is introduced, including two main modes: a diverging point source mode, and a converging broad beam mode. Preliminary results are presented for scanning Presage dosimeters in both modes and immersed in refractive media of widely varying refractive index (RI), including air, water, and a fully matched medium. Pronounced differences in the edge artifacts and accuracy of reconstructed coefficients is observed. The ScanSim software is shown to be a useful tool to investigate and quantify many aspects of optical-CT image formation, including reducing dependence on matching fluids.

Authors
Oldham, M
MLA Citation
Oldham, M. "ScanSim: A tool for simulating optical-CT imaging." J Phys Conf Ser 250.1 (2010): 311-315.
PMID
21617744
Source
pubmed
Published In
Journal of Physics
Volume
250
Issue
1
Publish Date
2010
Start Page
311
End Page
315
DOI
10.1088/1742-6596/250/1/012064

Dosimetry challenges for implementing emerging technologies.

During the last 10 years, radiation therapy technologies have gone through major changes, mainly related introduction of sophisticated delivery and imaging techniques to improve the target localization accuracy and dose conformity. While implementation of these emerging technologies such as image-guided SRS/SBRT, IMRT/IMAT, IGRT, 4D motion management, and special delivery technologies showed substantial clinical gains for patient care, many other factors, such as training/quality, efficiency/efficacy, and cost/effectiveness etc. remain to be challenging. This talk will address technical challenges for dosimetry verification of implementing these emerging technologies in radiation therapy.

Authors
Yin, F-F; Oldham, M; Cai, J; Wu, Q
MLA Citation
Yin, F-F, Oldham, M, Cai, J, and Wu, Q. "Dosimetry challenges for implementing emerging technologies." J Phys Conf Ser 250.1 (2010): 8-11.
PMID
21617745
Source
pubmed
Published In
Journal of Physics
Volume
250
Issue
1
Publish Date
2010
Start Page
8
End Page
11
DOI
10.1088/1742-6596/250/1/012002

RadBall Technology Testing in the Savannah River Site's Health Physics Instrument Calibration Laboratory.

The United Kingdom's National Nuclear Laboratory (NNL) has developed a radiation-mapping device that can locate and quantify radioactive hazards within contaminated areas of the nuclear industry. The device, known as RadBall(™), consists of a colander-like outer collimator that houses a radiation-sensitive polymer sphere. The collimator has over two hundred small holes; thus, specific areas of the polymer sphere are exposed to radiation becoming increasingly more opaque in proportion to the absorbed dose. The polymer sphere is imaged in an optical-CT scanner that produces a high resolution 3D map of optical attenuation coefficients. Subsequent analysis of the optical attenuation data provides information on the spatial distribution of sources in a given area forming a 3D characterization of the area of interest. The RadBall(™) technology has been deployed in a number of technology trials in nuclear waste reprocessing plants at Sellafield in the United Kingdom and facilities of the Savannah River National Laboratory (SRNL). This paper summarizes the tests completed at SRNL Health Physics Instrument Calibration Laboratory (HPICL).

Authors
Farfán, EB; Foley, TQ; Jannik, GT; Harpring, LJ; Gordon, JR; Blessing, R; Coleman, JR; Holmes, CJ; Oldham, M; Adamovics, J; Stanley, SJ
MLA Citation
Farfán, EB, Foley, TQ, Jannik, GT, Harpring, LJ, Gordon, JR, Blessing, R, Coleman, JR, Holmes, CJ, Oldham, M, Adamovics, J, and Stanley, SJ. "RadBall Technology Testing in the Savannah River Site's Health Physics Instrument Calibration Laboratory." J Phys Conf Ser 250.1 (2010): 398-402.
PMID
21617738
Source
pubmed
Published In
Journal of Physics
Volume
250
Issue
1
Publish Date
2010
Start Page
398
End Page
402
DOI
10.1088/1742-6596/250/1/012080

RadBall technology testing for hot cell characterization

Authors
Farfán, EB; Foley, TQ; Jannik, GT; Gladden, JB; Mackenzie, D; Stanley, SJ; Holmes, CJ; Oldham, M; Adamovics, J; Gordon, JR; Harpring, LJ
MLA Citation
Farfán, EB, Foley, TQ, Jannik, GT, Gladden, JB, Mackenzie, D, Stanley, SJ, Holmes, CJ, Oldham, M, Adamovics, J, Gordon, JR, and Harpring, LJ. "RadBall technology testing for hot cell characterization." Decommissioning, Decontamination, and Reutilization Topical Meeting 2010, DD and R 2010 (2010): 199-200.
Source
scival
Published In
Decommissioning, Decontamination, and Reutilization Topical Meeting 2010, DD and R 2010
Publish Date
2010
Start Page
199
End Page
200

Chairman's introduction and welcome message

Authors
Oldham, M
MLA Citation
Oldham, M. "Chairman's introduction and welcome message." Journal of Physics: Conference Series 250 (2010).
Source
scival
Published In
Journal of Physics
Volume
250
Publish Date
2010
DOI
10.1088/1742-6596/250/1/011001

Investigation of the feasibility of relative 3D dosimetry in the Radiologic Physics Center Head and Neck IMRT phantom using presage/optical-CT.

This study presents the application of the Presage/optical-CT 3D dosimetry system for relative dosimetry in the Radiologic Physics Center (RPC) Head and Neck (H&N) IMRT phantom. Performance of the system was evaluated by comparison with the "gold-standard" RPC credentialing test. A modified Presage cylindrical insert was created that extended the capability of the RPC H&N phantom to 3D dosimetry. The RPC phantom was taken through the entire treatment planning procedure with both the standard RPC insert and the modified Presage insert. An IMRT plan was created to match the desired dose constraints of the credentialing test. This plan was delivered twice to the RPC phantom: first containing the standard insert, and then again containing the Presage insert. After irradiation, the standard insert was sent for routine credentialing analysis; including point dose measurements (TLD) and planar Gafchromic EBT film measurement. The 3D dose distribution from Presage was read out at Duke using the OCTOPUS 5X optical-CT scanner. The Presage distribution was compared with gold-standard EBT measurement (determined by the RPC) and the calculated Eclipse distribution. The agreement between the normalized EBT, Presage, and Eclipse distributions, in the central axial plane was evaluated using profiles and gamma-map comparisons (4% dose difference and 3 mm distance to agreement). Profiles showed good agreement between EBT, Presage, and Eclipse distributions. 2D gamma-map comparisons between all three modalities showed at least 98% pass rate. The excellent agreement between Presage and EBT in the central plane established Presage as a standard against which to evaluate the accuracy of the 3D calculated Eclipse distribution. A gamma comparison between normalized Presage and Eclipse 3D distributions gave an overall pass rate of approximately 94%. In conclusion, the Presage/optical-CT system was found to be feasible for relative 3D dosimetry in the RPC IMRT H&N phantom. The potential to extend the RPC IMRT credentialing procedure to 3D may be feasible provided accurate calibration to dose (Gy) and robustness to shipping stress are demonstrated.

Authors
Sakhalkar, H; Sterling, D; Adamovics, J; Ibbott, G; Oldham, M
MLA Citation
Sakhalkar, H, Sterling, D, Adamovics, J, Ibbott, G, and Oldham, M. "Investigation of the feasibility of relative 3D dosimetry in the Radiologic Physics Center Head and Neck IMRT phantom using presage/optical-CT." Med Phys 36.7 (July 2009): 3371-3377.
PMID
19673232
Source
pubmed
Published In
Medical physics
Volume
36
Issue
7
Publish Date
2009
Start Page
3371
End Page
3377
DOI
10.1118/1.3148534

SU-FF-J-103: Concepts for Normal Tissue Sparing with Patient-Specific Margins in IMRT Boost Treatments for Cervix

Authors
Mader, B; Cabrera, A; Jones, E; Oldham, M
MLA Citation
Mader, B, Cabrera, A, Jones, E, and Oldham, M. "SU-FF-J-103: Concepts for Normal Tissue Sparing with Patient-Specific Margins in IMRT Boost Treatments for Cervix." June 2009.
Source
crossref
Published In
Medical physics
Volume
36
Issue
6Part7
Publish Date
2009
Start Page
2500
End Page
2500
DOI
10.1118/1.3181395

TU-E-304A-06: A 3D Solution for Advanced Photon Arc Therapy Quality Assurance

Authors
Thomas, A; Clift, C; O'Daniel, J; McMahon, R; Sakhalkar, H; Brown, W; Adamovics, J; Washington, A; Oldham, M
MLA Citation
Thomas, A, Clift, C, O'Daniel, J, McMahon, R, Sakhalkar, H, Brown, W, Adamovics, J, Washington, A, and Oldham, M. "TU-E-304A-06: A 3D Solution for Advanced Photon Arc Therapy Quality Assurance." June 2009.
Source
crossref
Published In
Medical physics
Volume
36
Issue
6Part24
Publish Date
2009
Start Page
2748
End Page
2748
DOI
10.1118/1.3182430

TH-D-BRB-03: The Application of a Novel Three Dimensional Dosimetry System to the Acquisition of Commissioning Data of Small Photon Fields

Authors
Clift, C; Thomas, A; Washington, A; Adamovics, J; Das, I; Oldham, M
MLA Citation
Clift, C, Thomas, A, Washington, A, Adamovics, J, Das, I, and Oldham, M. "TH-D-BRB-03: The Application of a Novel Three Dimensional Dosimetry System to the Acquisition of Commissioning Data of Small Photon Fields." June 2009.
Source
crossref
Published In
Medical physics
Volume
36
Issue
6Part28
Publish Date
2009
Start Page
2810
End Page
2810
DOI
10.1118/1.3182666

SU-FF-I-153: First Experience of High Resolution 3D Optical-CT Scanning of An Anthropomorphic, Leuco-Dye Doped, Radiochromic Plastic Dosimeter

Authors
Sakhalkar, H; Thomas, A; McMahon, R; Washington, A; Adamovics, J; Oldham, M
MLA Citation
Sakhalkar, H, Thomas, A, McMahon, R, Washington, A, Adamovics, J, and Oldham, M. "SU-FF-I-153: First Experience of High Resolution 3D Optical-CT Scanning of An Anthropomorphic, Leuco-Dye Doped, Radiochromic Plastic Dosimeter." June 2009.
Source
crossref
Published In
Medical physics
Volume
36
Issue
6Part5
Publish Date
2009
Start Page
2470
End Page
2470
DOI
10.1118/1.3181274

SU-FF-T-482: Extension of An Informatics Architecture to Compare and Analyze 3D Dosimetric Data

Authors
Brown, W; Deasy, J; Khullar, D; Apte, A; Thomas, A; Oldham, M
MLA Citation
Brown, W, Deasy, J, Khullar, D, Apte, A, Thomas, A, and Oldham, M. "SU-FF-T-482: Extension of An Informatics Architecture to Compare and Analyze 3D Dosimetric Data." June 2009.
Source
crossref
Published In
Medical physics
Volume
36
Issue
6Part16
Publish Date
2009
Start Page
2634
End Page
2634
DOI
10.1118/1.3181980

An Investigation into the Robustness of Optical-CT Dosimetry of a Radiochromic Dosimeter Compatible with the RPC Head-and-Neck Phantom.

The potential of the PRESAGE™/Optical-CT system as a comprehensive 3D dosimetry tool has been demonstrated. The current study focused on detailed characterization of robustness (intra-dosimeter uniformity and temporal stability) and reproducibility (inter-dosimeter reproducibility) of PRESAGE™ inserts compatible with the RPC H&N phantom. In addition, the accuracy and precision of PRESAGE dose measurement was also evaluated. Four identical PRESAGE™ dosimeters (10cm diameter and 7cm height cylinders) were irradiated with the same rotationally symmetric treatment plan using a Varian accelerator. The treatment plan was designed to rigorously evaluate robustness and reproducibility for multiple dose levels and in 3D. All dosimeters were scanned by optical-CT at daily intervals to study temporal stability. Dose comparisons were made between PRESAGE, ECLIPSE, and independent measurement with EBT film at a select depth. The use of improved optics and acquisition technique yielded substantially higher quality 3D dosimetry data from PRESAGE than has been achieved previously (noise reduced to ~1%, accuracy to within 3%). Data analysis showed excellent intra-dosimeter uniformity, temporal stability and inter-dosimeter reproducibility of relative radiochromic response. In general, the PRESAGE™ dose-distribution was found to agree better with EBT (~99% pass rate) than with ECLIPSE calculations (~92% pass rate) especially in penumbral regions for a 3% dose-difference and 3 mm distance-to-agreement evaluation criteria. The results demonstrate excellent robustness and reproducibility of the PRESAGE™ for relative 3D-dosimetry and represent a significant step towards incorporation in the RadOnc-clinic (e.g. integration with RPC phantom).

Authors
Sakhalkar, HS; Adamovics, J; Ibbott, G; Oldham, M
MLA Citation
Sakhalkar, HS, Adamovics, J, Ibbott, G, and Oldham, M. "An Investigation into the Robustness of Optical-CT Dosimetry of a Radiochromic Dosimeter Compatible with the RPC Head-and-Neck Phantom." J Phys Conf Ser 164.1 (January 1, 2009): 12059-.
PMID
20407594
Source
pubmed
Published In
Journal of Physics
Volume
164
Issue
1
Publish Date
2009
Start Page
12059
DOI
10.1088/1742-6596/164/1/012059

A comprehensive evaluation of the PRESAGE/optical-CT 3D dosimetry system.

This work presents extensive investigations to evaluate the robustness (intradosimeter consistency and temporal stability of response), reproducibility, precision, and accuracy of a relatively new 3D dosimetry system comprising a leuco-dye doped plastic 3D dosimeter (PRESAGE) and a commercial optical-CT scanner (OCTOPUS 5x scanner from MGS Research, Inc). Four identical PRESAGE 3D dosimeters were created such that they were compatible with the Radiologic Physics Center (RPC) head-and-neck (H&N) IMRT credentialing phantom. Each dosimeter was irradiated with a rotationally symmetric arrangement of nine identical small fields (1 x 3 cm2) impinging on the flat circular face of the dosimeter. A repetitious sequence of three dose levels (4, 2.88, and 1.28 Gy) was delivered. The rotationally symmetric treatment resulted in a dose distribution with high spatial variation in axial planes but only gradual variation with depth along the long axis of the dosimeter. The significance of this treatment was that it facilitated accurate film dosimetry in the axial plane, for independent verification. Also, it enabled rigorous evaluation of robustness, reproducibility and accuracy of response, at the three dose levels. The OCTOPUS 5x commercial scanner was used for dose readout from the dosimeters at daily time intervals. The use of improved optics and acquisition technique yielded substantially improved noise characteristics (reduced to approximately 2%) than has been achieved previously. Intradosimeter uniformity of radiochromic response was evaluated by calculating a 3D gamma comparison between each dosimeter and axially rotated copies of the same dosimeter. This convenient technique exploits the rotational symmetry of the distribution. All points in the gamma comparison passed a 2% difference, 1 mm distance-to-agreement criteria indicating excellent intradosimeter uniformity even at low dose levels. Postirradiation, the dosimeters were all found to exhibit a slight increase in opaqueness with time. However, the relative dose distribution was found to be extremely stable up to 90 h postirradiation indicating excellent temporal stability. Excellent interdosimeter reproducibility was also observed between the four dosimeters. Gamma comparison maps between each dosimeter and the average distribution of all four dosimeters showed full agreement at the 2% difference, 2 mm distance-to-agreement level. Dose readout from the 3D dosimetry system was found to agree better with independent film measurement than with treatment planning system calculations in penumbral regions and was generally accurate to within 2% dose difference and 2 mm distance-to-agreement. In conclusion, these studies demonstrate excellent precision, accuracy, robustness, and reproducibility of the PRESAGE/optical-CT system for relative 3D dosimetry and support its potential integration with the RPC H&N credentialing phantom for IMRT verification.

Authors
Sakhalkar, HS; Adamovics, J; Ibbott, G; Oldham, M
MLA Citation
Sakhalkar, HS, Adamovics, J, Ibbott, G, and Oldham, M. "A comprehensive evaluation of the PRESAGE/optical-CT 3D dosimetry system." Med Phys 36.1 (January 2009): 71-82.
PMID
19235375
Source
pubmed
Published In
Medical physics
Volume
36
Issue
1
Publish Date
2009
Start Page
71
End Page
82
DOI
10.1118/1.3005609

Investigating the Feasibility of 3D Dosimetry in the RPC IMRT H&N Phantom.

An urgent requirement for 3D dosimetry has been recognized because of high failure rate (~25%) in RPC credentialing, which relies on point and 2D dose measurements. Comprehensive 3D dosimetry is likely to resolve more errors and improve IMRT quality assurance. This work presents an investigation of the feasibility of PRESAGE/optical-CT 3D dosimetry in the Radiologic Physics Center (RPC) IMRT H&N phantom. The RPC H&N phantom (with standard and PRESAGE dosimetry inserts alternately) was irradiated with the same IMRT plan. The TLD and EBT film measurement data from standard insert irradiation was provided by RPC. The 3D dose measurement data from PRESAGE insert irradiation was readout using the OCTOPUS™ 5X optical-CT scanner at Duke. TLD, EBT and PRESAGE dose measurements were inter-compared with Eclipse calculations to evaluate consistency of planning and delivery. Results showed that the TLD point dose measurements agreed with Eclipse calculations to within 5% dose-difference. Relative dose comparison between Eclipse dose, EBT dose and PRESAGE dose was conducted using profiles and gamma comparisons (4% dose-difference and 4 mm distance-to-agreement). Profiles showed good agreement between measurement and calculation except along steep dose gradient regions where Eclipse modelling might be inaccurate. Gamma comparisons showed that the measurement and calculation showed good agreement (>96%) if edge artefacts in measurements are ignored. In conclusion, the PRESAGE/optical-CT dosimetry system was found to be feasible as an independent dosimetry tool in the RPC IMRT H&N phantom.

Authors
Sakhalkar, H; Sterling, D; Adamovics, J; Ibbott, G; Oldham, M
MLA Citation
Sakhalkar, H, Sterling, D, Adamovics, J, Ibbott, G, and Oldham, M. "Investigating the Feasibility of 3D Dosimetry in the RPC IMRT H&N Phantom." J Phys Conf Ser 164.2009 (2009): 12058-.
PMID
20333319
Source
pubmed
Published In
Journal of Physics
Volume
164
Issue
2009
Publish Date
2009
Start Page
12058
DOI
10.1088/1742-6596/164/1/012058

Normal Tissue Sparing with Patient-specific Margins in IMRT Boost Plans for Cervical Cancer

Authors
Cabrera, AR; Mader, BC; Oldham, M; Taylor, BN; Boyd, JA; Jones, EL
MLA Citation
Cabrera, AR, Mader, BC, Oldham, M, Taylor, BN, Boyd, JA, and Jones, EL. "Normal Tissue Sparing with Patient-specific Margins in IMRT Boost Plans for Cervical Cancer." 2009.
Source
wos-lite
Published In
International Journal of Radiation Oncology, Biology, Physics
Volume
75
Issue
3
Publish Date
2009
Start Page
S373
End Page
S373

Improving the quantitative accuracy of optical-emission computed tomography by incorporating an attenuation correction: application to HIF1 imaging.

Optical computed tomography (optical-CT) and optical-emission computed tomography (optical-ECT) are new techniques for imaging the 3D structure and function (including gene expression) of whole unsectioned tissue samples. This work presents a method of improving the quantitative accuracy of optical-ECT by correcting for the 'self'-attenuation of photons emitted within the sample. The correction is analogous to a method commonly applied in single-photon-emission computed tomography reconstruction. The performance of the correction method was investigated by application to a transparent cylindrical gelatin phantom, containing a known distribution of attenuation (a central ink-doped gelatine core) and a known distribution of fluorescing fibres. Attenuation corrected and uncorrected optical-ECT images were reconstructed on the phantom to enable an evaluation of the effectiveness of the correction. Significant attenuation artefacts were observed in the uncorrected images where the central fibre appeared approximately 24% less intense due to greater attenuation from the surrounding ink-doped gelatin. This artefact was almost completely removed in the attenuation-corrected image, where the central fibre was within approximately 4% of the others. The successful phantom test enabled application of attenuation correction to optical-ECT images of an unsectioned human breast xenograft tumour grown subcutaneously on the hind leg of a nude mouse. This tumour cell line had been genetically labelled (pre-implantation) with fluorescent reporter genes such that all viable tumour cells expressed constitutive red fluorescent protein and hypoxia-inducible factor 1 transcription-produced green fluorescent protein. In addition to the fluorescent reporter labelling of gene expression, the tumour microvasculature was labelled by a light-absorbing vasculature contrast agent delivered in vivo by tail-vein injection. Optical-CT transmission images yielded high-resolution 3D images of the absorbing contrast agent, and revealed highly inhomogeneous vasculature perfusion within the tumour. Optical-ECT emission images yielded high-resolution 3D images of the fluorescent protein distribution in the tumour. Attenuation-uncorrected optical-ECT images showed clear loss of signal in regions of high attenuation, including regions of high perfusion, where attenuation is increased by increased vascular ink stain. Application of attenuation correction showed significant changes in an apparent expression of fluorescent proteins, confirming the importance of the attenuation correction. In conclusion, this work presents the first development and application of an attenuation correction for optical-ECT imaging. The results suggest that successful attenuation correction for optical-ECT is feasible and is essential for quantitatively accurate optical-ECT imaging.

Authors
Kim, E; Bowsher, J; Thomas, AS; Sakhalkar, H; Dewhirst, M; Oldham, M
MLA Citation
Kim, E, Bowsher, J, Thomas, AS, Sakhalkar, H, Dewhirst, M, and Oldham, M. "Improving the quantitative accuracy of optical-emission computed tomography by incorporating an attenuation correction: application to HIF1 imaging." Phys Med Biol 53.19 (October 7, 2008): 5371-5383.
PMID
18765891
Source
pubmed
Published In
Physics in Medicine and Biology
Volume
53
Issue
19
Publish Date
2008
Start Page
5371
End Page
5383
DOI
10.1088/0031-9155/53/19/007

TU-FF-A4-03: Improving the Accuracy of Optical-Emission-CT Imaging Through Application of a Non-Uniform Attenuation Correction

Authors
Kim, E; Bowsher, J; Sakhalkar, H; Dewhirst, M; Oldham, M
MLA Citation
Kim, E, Bowsher, J, Sakhalkar, H, Dewhirst, M, and Oldham, M. "TU-FF-A4-03: Improving the Accuracy of Optical-Emission-CT Imaging Through Application of a Non-Uniform Attenuation Correction." June 2008.
Source
crossref
Published In
Medical physics
Volume
35
Issue
6Part22
Publish Date
2008
Start Page
2923
End Page
2923
DOI
10.1118/1.2962658

SU-GG-T-438: Rind Radiosurgery: Investigation of a Novel Radiation Therapy Technique for the Treatment of Intracranial Lesions

Authors
Hosfeld, V; Kirkpatrick, J; Oldham, M
MLA Citation
Hosfeld, V, Kirkpatrick, J, and Oldham, M. "SU-GG-T-438: Rind Radiosurgery: Investigation of a Novel Radiation Therapy Technique for the Treatment of Intracranial Lesions." June 2008.
Source
crossref
Published In
Medical physics
Volume
35
Issue
6Part16
Publish Date
2008
Start Page
2825
End Page
2825
DOI
10.1118/1.2962186

TU-D-AUD C-02: An Investigation of the Consistency and Robustness of the PRESAGE/optical-CT 3D Dosimetry System

Authors
Sakhalkar, H; Adamovics, J; Gluckman, G; Oldham, M
MLA Citation
Sakhalkar, H, Adamovics, J, Gluckman, G, and Oldham, M. "TU-D-AUD C-02: An Investigation of the Consistency and Robustness of the PRESAGE/optical-CT 3D Dosimetry System." June 2008.
Source
crossref
Published In
Medical physics
Volume
35
Issue
6Part21
Publish Date
2008
Start Page
2903
End Page
2904
DOI
10.1118/1.2962583

SU-GG-J-28: An Investigation of Intra and Inter-Fraction Motion in Cervical Cancer Patients

Authors
Taylor, B; Boyd, J; Kasibhatla, M; Oldham, M
MLA Citation
Taylor, B, Boyd, J, Kasibhatla, M, and Oldham, M. "SU-GG-J-28: An Investigation of Intra and Inter-Fraction Motion in Cervical Cancer Patients." June 2008.
Source
crossref
Published In
Medical physics
Volume
35
Issue
6Part5
Publish Date
2008
Start Page
2685
End Page
2685
DOI
10.1118/1.2961585

TU-FF-A2-06: The Verification of Respiratory-Gated Radiation Treatments Using 3D Dosimetry Techniques

Authors
Brady, S; Sakhalkar, H; Maurer, J; Yoo, S; Adamovics, J; Gluckman, G; Oldham, M
MLA Citation
Brady, S, Sakhalkar, H, Maurer, J, Yoo, S, Adamovics, J, Gluckman, G, and Oldham, M. "TU-FF-A2-06: The Verification of Respiratory-Gated Radiation Treatments Using 3D Dosimetry Techniques." June 2008.
Source
crossref
Published In
Medical physics
Volume
35
Issue
6Part22
Publish Date
2008
Start Page
2921
End Page
2921
DOI
10.1118/1.2962649

SU-GG-T-153: Scaling the Prescription Dose: How Accurate Is the Varian Delivery System?

Authors
Sterling, D; Sakhalkar, H; Oldham, M
MLA Citation
Sterling, D, Sakhalkar, H, and Oldham, M. "SU-GG-T-153: Scaling the Prescription Dose: How Accurate Is the Varian Delivery System?." June 2008.
Source
crossref
Published In
Medical physics
Volume
35
Issue
6Part11
Publish Date
2008
Start Page
2761
End Page
2761
DOI
10.1118/1.2961904

SU-GG-T-135: Evaluation of PRESAGE/optical-CT 3D Dosimetry for Commissioning a Linac for IMRT

Authors
Oldham, M; Sterling, D; Sakhalkar, H; Molineu, A; Adamovics, J; Ibbott, G
MLA Citation
Oldham, M, Sterling, D, Sakhalkar, H, Molineu, A, Adamovics, J, and Ibbott, G. "SU-GG-T-135: Evaluation of PRESAGE/optical-CT 3D Dosimetry for Commissioning a Linac for IMRT." June 2008.
Source
crossref
Published In
Medical physics
Volume
35
Issue
6Part11
Publish Date
2008
Start Page
2757
End Page
2757
DOI
10.1118/1.2961887

An investigation of the accuracy of an IMRT dose distribution using two- and three-dimensional dosimetry techniques.

Complex dose delivery techniques like intensity-modulated radiation therapy (IMRT) require dose measurement in three dimensions for comprehensive validation. Previously, we demonstrated the feasibility of the "PRESAGE/optical-computed tomography (CT)" system for the three-dimensional verification of simple open beam dose distributions where the planning system was known to be accurate. The present work extends this effort and presents the first application of the PRESAGE/optical-CT system for the verification of a complex IMRT distribution. A highly modulated 11 field IMRT plan was delivered to a cylindrical PRESAGE dosimeter (16 cm in diameter and 11 cm in height), and the dose distribution was readout using a commercial scanning-laser optical-CT scanner. Comparisons were made with independent GAFCHROMIC EBT film measurements, and the calculated dose distribution from a commissioned treatment planning system (ECLIPSE). Isodose plots, dose profiles, gamma maps, and dose-volume histograms were used to evaluate the agreement. The isodose plots and dose profiles from the PRESAGE/optical-CT system were in excellent agreement with both the EBT measurements and the ECLIPSE calculation at all points except within 3 mm of the outer edge of the dosimeter where an edge artifact occurred. Excluding this 3 mm rim, gamma map comparisons show that all three distributions mutually agreed to within a 3% (dose difference) and 3 mm (distance-to-agreement) criteria. A 96% gamma pass ratio was obtained between the PRESAGE and ECLIPSE distributions over the entire volume excluding this rim. In conclusion, for the complex IMRT plan studied, and in the absence of inhomogeneities, the ECLIPSE dose calculation was found to agree with both independent measurements, to within 3%, 3 mm gamma criteria.

Authors
Oldham, M; Sakhalkar, H; Guo, P; Adamovics, J
MLA Citation
Oldham, M, Sakhalkar, H, Guo, P, and Adamovics, J. "An investigation of the accuracy of an IMRT dose distribution using two- and three-dimensional dosimetry techniques." Med Phys 35.5 (May 2008): 2072-2080.
PMID
18561683
Source
pubmed
Published In
Medical physics
Volume
35
Issue
5
Publish Date
2008
Start Page
2072
End Page
2080
DOI
10.1118/1.2899995

Optical clearing of unsectioned specimens for three-dimensional imaging via optical transmission and emission tomography.

Optical computed tomography (optical-CT) and optical emission computed tomography (optical-ECT) are new techniques that enable unprecedented high-resolution 3-D multimodal imaging of tissue structure and function. Applications include imaging macroscopic gene expression and microvasculature structure in unsectioned biological specimens up to 8 cm(3). A key requisite for these imaging techniques is effective sample preparation including optical clearing, which enables light transport through the sample while preserving the signal (either light absorbing stain or fluorescent proteins) in representative form. We review recent developments in optical-CT and optical-ECT, and compatible "fluorescence-friendly" optical clearing protocols.

Authors
Oldham, M; Sakhalkar, H; Oliver, T; Allan Johnson, G; Dewhirst, M
MLA Citation
Oldham, M, Sakhalkar, H, Oliver, T, Allan Johnson, G, and Dewhirst, M. "Optical clearing of unsectioned specimens for three-dimensional imaging via optical transmission and emission tomography." J Biomed Opt 13.2 (March 2008): 021113-. (Review)
PMID
18465962
Source
pubmed
Published In
Journal of Biomedical Optics
Volume
13
Issue
2
Publish Date
2008
Start Page
021113
DOI
10.1117/1.2907968

Fast, high-resolution 3D dosimetry utilizing a novel optical-CT scanner incorporating tertiary telecentric collimation.

This study introduces a charge coupled device (CCD) area detector based optical-computed tomography (optical-CT) scanner for comprehensive verification of radiation dose distributions recorded in nonscattering radiochromic dosimeters. Defining characteristics include: (i) a very fast scanning time of approximately 5 min to acquire a complete three-dimensional (3D) dataset, (ii) improved image formation through the use of custom telecentric optics, which ensures accurate projection images and minimizes artifacts from scattered and stray-light sources, and (iii) high resolution (potentially 50 microm) isotropic 3D dose readout. The performance of the CCD scanner for 3D dose readout was evaluated by comparison with independent 3D readout from the single laser beam OCTOPUS-scanner for the same PRESAGE dosimeters. The OCTOPUS scanner was considered the "gold standard" technique in light of prior studies demonstrating its accuracy. Additional comparisons were made against calculated dose distributions from the ECLIPSE treatment-planning system. Dose readout for the following treatments were investigated: (i) a single rectangular beam irradiation to investigate small field and very steep dose gradient dosimetry away from edge effects, (ii) a 2-field open beam parallel-opposed irradiation to investigate dosimetry along steep dose gradients, and (iii) a 7-field intensity modulated radiation therapy (IMRT) irradiation to investigate dosimetry for complex treatment delivery involving modulation of fluence and for dosimetry along moderate dose gradients. Dose profiles, dose-difference plots, and gamma maps were employed to evaluate quantitative estimates of agreement between independently measured and calculated dose distributions. Results indicated that dose readout from the CCD scanner was in agreement with independent gold-standard readout from the OCTOPUS-scanner as well as the calculated ECLIPSE dose distribution for all treatments, except in regions within a few millimeters of the edge of the dosimeter, where edge artifact is predominant. Agreement of line profiles was observed, even along steep dose gradients. Dose difference plots indicated that the CCD scanner dose readout differed from the OCTOPUS scanner readout and ECLIPSE calculations by approximately 10% along steep dose gradients and by approximately 5% along moderate dose gradients. Gamma maps (3% dose-difference and 3 mm distance-to-agreement acceptance criteria) revealed agreement, except for regions within 5 mm of the edge of the dosimeter where the edge artifact occurs. In summary, the data demonstrate feasibility of using the fast, high-resolution CCD scanner for comprehensive 3D dosimetry in all applications, except where dose readout is required close to the edges of the dosimeter. Further work is ongoing to reduce this artifact.

Authors
Sakhalkar, HS; Oldham, M
MLA Citation
Sakhalkar, HS, and Oldham, M. "Fast, high-resolution 3D dosimetry utilizing a novel optical-CT scanner incorporating tertiary telecentric collimation." Med Phys 35.1 (January 2008): 101-111.
PMID
18293567
Source
pubmed
Published In
Medical physics
Volume
35
Issue
1
Publish Date
2008
Start Page
101
End Page
111
DOI
10.1118/1.2804616

An implantable MOSFET dosimeter for the measurement of radiation dose in tissue during cancer therapy

This paper describes the functionality, radiation characteristics, and clinical implementation of an implantable MOSFET radiation detector (dosimeter). The dosimeter is powered by radio frequency telemetry eliminating the need for a power source inside the dosimeter. The data can be accessed telemetrically for each treatment day during the course of therapy. The detector has been validated in vitro to confirm its accuracy. Variance between predicted and measured dose in patients is discussed. Factors such as patient setup, treatment plan error, and physiologic motion can affect the accuracy of dose delivery in moving from in vitro to in vivo dose measurements. The initial data suggests that the dosimeters can play a useful role in tracking dose discrepancies, both random and systematic, in patients treated with external beam radiation therapy. The implantable dosimeter can be used, together with the current radiation delivery and planning techniques, to optimize radiation treatment on an individual basis. © 2007 IEEE.

Authors
Beyer, GP; Mann, GG; Pursley, JA; Espenhahn, ET; Fraisse, C; Godfrey, DJ; Oldham, M; Carrea, TB; Bolick, N; Scarantino, CW
MLA Citation
Beyer, GP, Mann, GG, Pursley, JA, Espenhahn, ET, Fraisse, C, Godfrey, DJ, Oldham, M, Carrea, TB, Bolick, N, and Scarantino, CW. "An implantable MOSFET dosimeter for the measurement of radiation dose in tissue during cancer therapy." IEEE Sensors Journal 8.1 (2008): 38-51.
Source
scival
Published In
IEEE Sensors Journal
Volume
8
Issue
1
Publish Date
2008
Start Page
38
End Page
51
DOI
10.1109/JSEN.2007.912542

The feasibility of comprehensive IMRT verification using novel 3D dosimetry techniques compatible with the RPC head and neck phantom

Authors
Oldham, M; Sakhalkar, H; Adamovics, J; Molineu, A; Ibbott, G
MLA Citation
Oldham, M, Sakhalkar, H, Adamovics, J, Molineu, A, and Ibbott, G. "The feasibility of comprehensive IMRT verification using novel 3D dosimetry techniques compatible with the RPC head and neck phantom." 2008.
Source
wos-lite
Published In
International Journal of Radiation Oncology, Biology, Physics
Volume
72
Issue
1
Publish Date
2008
Start Page
S145
End Page
S145
DOI
10.1016/j.ijrobp.2008.06.469

Evaluation of three types of reference image data for external beam radiotherapy target localization using digital tomosynthesis (DTS).

Digital tomosynthesis (DTS) is a fast, low-dose three-dimensional (3D) imaging approach which yields slice images with excellent in-plane resolution, though low plane-to-plane resolution. A stack of DTS slices can be reconstructed from a single limited-angle scan, with typical scan angles ranging from 10 degrees to 40 degrees and acquisition times of less than 10 s. The resulting DTS slices show soft tissue contrast approaching that of full cone-beam CT. External beam radiotherapy target localization using DTS requires the registration of on-board DTS images with corresponding reference image data. This study evaluates three types of reference volume: original reference CT, exact reference DTS (RDTS), and a more computationally efficient approximate reference DTS (RDTSapprox), as well as three different DTS scan angles (22 degrees, 44 degrees, and 65 degrees) for the DTS target localization task. Three-dimensional mutual information (MI) shared between reference and onboard DTS volumes was computed in a region surrounding the spine of a chest phantom, as translations spanning +/-5 mm and rotations spanning +/-5 degrees were simulated along each dimension in the reference volumes. The locations of the MI maxima were used as surrogates for registration accuracy, and the width of the MI peaks were used to characterize the registration robustness. The results show that conventional treatment planning CT volumes are inadequate reference volumes for direct registration with on-board DTS data. The efficient RDTSapprox method also appears insufficient for MI-based registration without further refinement of the technique, though it may be suitable for manual registration performed by a human observer. The exact RDTS volumes, on the other hand, delivered a 3D DTS localization accuracy of 0.5 mm and 0.50 along each axis, using only a single 44 degrees coronal on-board DTS scan of the chest phantom.

Authors
Godfrey, DJ; Ren, L; Yan, H; Wu, Q; Yoo, S; Oldham, M; Yin, FF
MLA Citation
Godfrey, DJ, Ren, L, Yan, H, Wu, Q, Yoo, S, Oldham, M, and Yin, FF. "Evaluation of three types of reference image data for external beam radiotherapy target localization using digital tomosynthesis (DTS)." Med Phys 34.8 (August 2007): 3374-3384.
PMID
17879800
Source
pubmed
Published In
Medical physics
Volume
34
Issue
8
Publish Date
2007
Start Page
3374
End Page
3384
DOI
10.1118/1.2756941

Characterization of buildup effects in OneDosePlus MOSFET-based dosimeters

Authors
Pursley, J; Beyer, GP; Craciunescu, O; Fraisse, C; Carroll, J; Oldham, M
MLA Citation
Pursley, J, Beyer, GP, Craciunescu, O, Fraisse, C, Carroll, J, and Oldham, M. "Characterization of buildup effects in OneDosePlus MOSFET-based dosimeters." June 2007.
Source
wos-lite
Published In
Medical physics
Volume
34
Issue
6
Publish Date
2007
Start Page
2423
End Page
2423
DOI
10.1118/1.2760752

Characterization of a novel, fast, in-house, CCD-based optical-CT scanner for 3D dosimetry in radiochromic dosimeters

Authors
Sakhalkar, H; Guo, P; Adamovics, J; Oldham, M
MLA Citation
Sakhalkar, H, Guo, P, Adamovics, J, and Oldham, M. "Characterization of a novel, fast, in-house, CCD-based optical-CT scanner for 3D dosimetry in radiochromic dosimeters." June 2007.
Source
wos-lite
Published In
Medical physics
Volume
34
Issue
6
Publish Date
2007
Start Page
2610
End Page
2610
DOI
10.1118/1.2761595

Evaluation of a new ractiochromic Film/Flatbed scanner system for planar clinical dosimetry

Authors
Goss, M; Oldham, M
MLA Citation
Goss, M, and Oldham, M. "Evaluation of a new ractiochromic Film/Flatbed scanner system for planar clinical dosimetry." June 2007.
Source
wos-lite
Published In
Medical physics
Volume
34
Issue
6
Publish Date
2007
Start Page
2449
End Page
2449
DOI
10.1118/1.2760869

Radiation characteristics and hypo-fractionation dose response for the DVS implantable MOSFET dosimeter

Authors
Beyer, GP; Pursley, J; Mann, G; Espenhahn, E; Fraisse, C; Godfrey, D; Oldham, M
MLA Citation
Beyer, GP, Pursley, J, Mann, G, Espenhahn, E, Fraisse, C, Godfrey, D, and Oldham, M. "Radiation characteristics and hypo-fractionation dose response for the DVS implantable MOSFET dosimeter." June 2007.
Source
wos-lite
Published In
Medical physics
Volume
34
Issue
6
Publish Date
2007
Start Page
2610
End Page
2610
DOI
10.1118/1.2761596

Functional imaging in bulk tissue specimens using optical emission tomography: fluorescence preservation during optical clearing.

Optical emission computed tomography (optical-ECT) is a technique for imaging the three-dimensional (3D) distribution of fluorescent probes in biological tissue specimens with high contrast and spatial resolution. In optical-ECT, functional information can be imaged by (i) systemic application of functional labels (e.g. fluorophore labelled proteins) and/or (ii) endogenous expression of fluorescent reporter proteins (e.g. red fluorescent protein (RFP), green fluorescent protein (GFP)) in vivo. An essential prerequisite for optical-ECT is optical clearing, a procedure where tissue specimens are made transparent to light by sequential perfusion with fixing, dehydrating and clearing agents. In this study, we investigate clearing protocols involving a selection of common fixing (4% buffered paraformaldehyde (PFA), methanol and ethanol), dehydrating (methanol and ethanol) and clearing agents (methyl salicylate and benzyl-alcohol-benzyl-benzoate (BABB)) in order to determine a 'fluorescence friendly' clearing procedure. Cell culture experiments were employed to optimize the sequence of chemical treatments that best preserve fluorescence. Texas red (TxRed), fluorescein isothiocyanate (FITC), RFP and GFP were tested as fluorophores and fluorescent reporter proteins of interest. Fluorescent and control cells were imaged on a microscope using a DSred2 and FITC filter set. The most promising clearing protocols of cell culture experiments were applied to whole xenograft tumour specimens, to test their effectiveness in large unsectioned samples. Fluorescence of TxRed/FITC fluorophores was not found to be significantly affected by any of the test clearing protocols. RFP and GFP fluorescence, however, was found to be significantly greater when cell fixation was in ethanol. Fixation in either PFA or methanol resulted in diminished fluorescence. After ethanol fixation, the RFP and GFP fluorescence proved remarkably robust to subsequent exposure to either methyl salicylate or BABB. The optimized optical clearing procedure of ethanol fixation followed by methyl salicylate clearing preserved the fluorescence of constitutive RFP in whole xenograft tumour specimens, about 1 cc in dimension, indicating successful extension from cell plating experiments to whole tissue samples. Finally, the feasibility of imaging the 3D distribution of viable tumour cells (as indicated by the RFP emission) is demonstrated by optical-ECT imaging of cleared xenograft tumours using an in-house system.

Authors
Sakhalkar, HS; Dewhirst, M; Oliver, T; Cao, Y; Oldham, M
MLA Citation
Sakhalkar, HS, Dewhirst, M, Oliver, T, Cao, Y, and Oldham, M. "Functional imaging in bulk tissue specimens using optical emission tomography: fluorescence preservation during optical clearing." Phys Med Biol 52.8 (April 21, 2007): 2035-2054.
PMID
17404454
Source
pubmed
Published In
Physics in Medicine and Biology
Volume
52
Issue
8
Publish Date
2007
Start Page
2035
End Page
2054
DOI
10.1088/0031-9155/52/8/001

Three-dimensional imaging of whole rodent organs using optical computed and emission tomography.

We explore the potential of optical computed tomography (optical-CT) and optical emission computed tomography (optical-ECT) in a new area-whole organ imaging. The techniques are implemented on an in-house prototype benchtop system with improved image quality and the capacity to image larger samples (up to 3 cm) than previous systems based on stereo microscopes. Imaging performance tests confirm high geometrical accuracy, accurate relative measurement of linear attenuation coefficients, and the ability to image features at the 50-microm level. Optical labeling of organ microvasculature was achieved using two stains deposited via natural in vivo circulatory processes: a passive absorbing ink-based stain and an active fluorescin FITC-lectin conjugate. The lectin protein binds to the endothelial lining, and FITC fluorescense enables optical-ECT imaging. Three-dimensional (3-D) optical-CT images have been acquired of a normal rat heart and left lung and a mouse right lung showing exquisite detail of the functional vasculature and relative perfusion distribution. Coregistered optical-ECT images were also acquired of the mouse lung and kidney. Histological sections confirmed effective labeling of microvasculature throughout the organs. The advantages of optical-CT and optical-ECT include the potential for a unique combination of high resolution and high contrast and compatibility with a wide variety of optical probes, including gene expression labeling fluorescent reporter proteins.

Authors
Oldham, M; Sakhalkar, H; Wang, YM; Guo, P; Oliver, T; Bentley, R; Vujaskovic, Z; Dewhirst, M
MLA Citation
Oldham, M, Sakhalkar, H, Wang, YM, Guo, P, Oliver, T, Bentley, R, Vujaskovic, Z, and Dewhirst, M. "Three-dimensional imaging of whole rodent organs using optical computed and emission tomography." J Biomed Opt 12.1 (January 2007): 014009-.
PMID
17343484
Source
pubmed
Published In
Journal of Biomedical Optics
Volume
12
Issue
1
Publish Date
2007
Start Page
014009
DOI
10.1117/1.2709858

Quality assurance in 3D dosimetry by optical-CT.

Authors
Guo, P; Adamovics, J; Oldham, M
MLA Citation
Guo, P, Adamovics, J, and Oldham, M. "Quality assurance in 3D dosimetry by optical-CT." J Phys Conf Ser 56.1 (December 1, 2006): 191-194.
PMID
17464369
Source
pubmed
Published In
Journal of Physics
Volume
56
Issue
1
Publish Date
2006
Start Page
191
End Page
194
DOI
10.1088/1742-6596/56/1/025

A dual-purpose CCD based micro-optical-CT scanning system.

Authors
Oldham, M; Sakhalkar, H; Guo, P
MLA Citation
Oldham, M, Sakhalkar, H, and Guo, P. "A dual-purpose CCD based micro-optical-CT scanning system." J Phys Conf Ser 56.1 (December 1, 2006): 199-202.
PMID
17464370
Source
pubmed
Published In
Journal of Physics
Volume
56
Issue
1
Publish Date
2006
Start Page
199
End Page
202
DOI
10.1088/1742-6596/56/1/027

A practical three-dimensional dosimetry system for radiation therapy.

There is a pressing need for a practical three-dimensional (3D) dosimetry system, convenient for clinical use, and with the accuracy and resolution to enable comprehensive verification of the complex dose distributions typical of modern radiation therapy. Here we introduce a dosimetry system that can achieve this challenge, consisting of a radiochromic dosimeter (PRESAGE) and a commercial optical computed tomography (CT) scanning system (OCTOPUS). PRESAGE is a transparent material with compelling properties for dosimetry, including insensitivity of the dose response to atmospheric exposure, a solid texture negating the need for an external container (reducing edge effects), and amenability to accurate optical CT scanning due to radiochromic optical contrast as opposed to light-scattering contrast. An evaluation of the performance and viability of the PRESAGE/OCTOPUS, combination for routine clinical 3D dosimetry is presented. The performance of the two components (scanner and dosimeter) was investigated separately prior to full system test. The optical CT scanner has a spatial resolution of < or = 1 mm, geometric accuracy within 1 mm, and high reconstruction linearity (with a R2 value of 0.9979 and a standard error of estimation of approximately 1%) relative to independent measurement. The overall performance of the PRESAGE/OCTOPUS system was evaluated with respect to a simple known 3D dose distribution, by comparison with GAFCHROMIC EBT film and the calculated dose from a commissioned planning system. The "measured" dose distribution in a cylindrical PRESAGE dosimeter (16 cm diameter and 11 cm height) was determined by optical-CT, using a filtered backprojection reconstruction algorithm. A three-way Gamma map comparison (4% dose difference and 4 mm distance to agreement), between the PRESAGE, EBT and calculated dose distributions, showed full agreement in measurable region of PRESAGE dosimeter (approximately 90% of radius). The EBT and PRESAGE distributions agreed more closely with each other than with the calculated plan, consistent with penumbral blurring in the planning data which was acquired with an ion chamber. In summary, our results support the conclusion that the PRESAGE optical-CT combination represents a significant step forward in 3D dosimetry, and provides a robust, clinically effective and viable high-resolution relative 3D dosimetry system for radiation therapy.

Authors
Guo, P; Adamovics, J; Oldham, M
MLA Citation
Guo, P, Adamovics, J, and Oldham, M. "A practical three-dimensional dosimetry system for radiation therapy." Med Phys 33.10 (October 2006): 3962-3972.
PMID
17089858
Source
pubmed
Published In
Medical physics
Volume
33
Issue
10
Publish Date
2006
Start Page
3962
End Page
3972
DOI
10.1118/1.2349686

Three-dimensional imaging of xenograft tumors using optical computed and emission tomography.

The physical basis and preliminary applications of optical computed tomography (optical-CT) and optical emission computed tomography (optical-ECT) are introduced, as new techniques with potential to provide unique 3D information on a variety of aspects of tumor structure and function. A particular focus here is imaging tumor micro-vasculature, and the spatial distribution of viable tumor cells, although the techniques have the potential for much wider application. The principle attractiveness of optical-CT and optical-ECT are that high resolution (<20 microm) and high contrast co-registered 3D images of structure and function can be acquired for relatively large intact samples. The unique combination of high contrast and resolution offers advantages over micro-CT and micro-MRI, and the lack of requirement for sectioning offers advantages over confocal microscopy, conventional microscopy, and histological sectioning techniques. Optical-CT/ECT are implemented using in-house custom apparatus and a commercial dissecting microscope capable of both transmission and fluorescence imaging. Basic studies to characterize imaging performance are presented. Negligible geometrical distortion and accurate reconstruction of relative attenuation coefficients was observed. Optical-CT and optical-ECT are investigated here by application to high resolution imaging of HCT116 xenograft tumors, about 1 cc in dimension, which were transfected with constitutive red fluorescent protein (RFP). Tumor microvasculature was stained in vivo by tail vein injection of either passive absorbing dyes or active fluorescent markers (FITC conjugated lectin). Prior to imaging, the tumors were removed (ex vivo) and optically cleared in a key process to make the samples amenable to light transmission. The cleared tumors were imaged in three modes (i) optical-CT to image the 3D distribution of microvasculature as indicated by absorbing dye, (ii) optical-ECT using the FITC excitation and emission filter set, to determine microvasculature as indicated by lectin-endothelial binding, and (iii) optical-ECT using the DSRed2 filter set to determine the 3D distribution of viable tumor as indicated by RFP emission. A clear correlation was observed between the independent vasculature imaging modes (i) and (ii) and postimaging histological sections, providing substantial validation of the optical-CT and optical-ECT techniques. Strong correlation was also observed between the RFP imaging of mode iii, and modes i and ii, supporting the intuitive conclusion that well-perfused regions contain significant viable tumor. In summary, optical-CT and optical-ECT, when combined with new optical clearing techniques, represent powerful new imaging modalities with potential for providing unique information on the structure and function of tumors.

Authors
Oldham, M; Sakhalkar, H; Oliver, T; Wang, YM; Kirpatrick, J; Cao, Y; Badea, C; Johnson, GA; Dewhirst, M
MLA Citation
Oldham, M, Sakhalkar, H, Oliver, T, Wang, YM, Kirpatrick, J, Cao, Y, Badea, C, Johnson, GA, and Dewhirst, M. "Three-dimensional imaging of xenograft tumors using optical computed and emission tomography." Medical physics 33.9 (September 2006): 3193-3202.
PMID
17022212
Source
epmc
Published In
Medical physics
Volume
33
Issue
9
Publish Date
2006
Start Page
3193
End Page
3202
DOI
10.1118/1.2217109

TH-C-ValB-04: Evaluation of the Quality of 3D-3D Mutual Information (MI) Shared Between Reference and On-Board DTS Images

Authors
Godfrey, D; Ren, L; Yan, H; Oldham, M; Yin, F
MLA Citation
Godfrey, D, Ren, L, Yan, H, Oldham, M, and Yin, F. "TH-C-ValB-04: Evaluation of the Quality of 3D-3D Mutual Information (MI) Shared Between Reference and On-Board DTS Images." June 2006.
Source
crossref
Published In
Medical physics
Volume
33
Issue
6Part21
Publish Date
2006
Start Page
2268
End Page
2268
DOI
10.1118/1.2241855

Evaluation of the performance of an optical CT scanner

Authors
Guo, P; Oldham, M
MLA Citation
Guo, P, and Oldham, M. "Evaluation of the performance of an optical CT scanner." June 2006.
Source
wos-lite
Published In
Medical physics
Volume
33
Issue
6
Publish Date
2006
Start Page
2101
End Page
2101
DOI
10.1118/1.2241153

Rapid low-dose 3D image-guided treatment verification of sites prone to respiratory motion using breath-hold on-board digital tomosynthesis (DTS)

Authors
Godfrey, D; Yin, F; Wang, Z; Yoo, S; Oldham, M; Willett, C
MLA Citation
Godfrey, D, Yin, F, Wang, Z, Yoo, S, Oldham, M, and Willett, C. "Rapid low-dose 3D image-guided treatment verification of sites prone to respiratory motion using breath-hold on-board digital tomosynthesis (DTS)." June 2006.
Source
wos-lite
Published In
Medical physics
Volume
33
Issue
6
Publish Date
2006
Start Page
2268
End Page
2269
DOI
10.1118/1.2241856

Optical-computed-and emmission tomography: Applications in cancer research

Authors
Oldham, M; Sakhalkar, H; Oliver, T; Dewhirst, M
MLA Citation
Oldham, M, Sakhalkar, H, Oliver, T, and Dewhirst, M. "Optical-computed-and emmission tomography: Applications in cancer research." June 2006.
Source
wos-lite
Published In
Medical physics
Volume
33
Issue
6
Publish Date
2006
Start Page
2239
End Page
2240
DOI
10.1118/1.2241740

An exploration of new formulations for PRESAGETM 3D dosimetry

Authors
Manzoor, A; Guo, P; Adamovics, J; Oldham, M
MLA Citation
Manzoor, A, Guo, P, Adamovics, J, and Oldham, M. "An exploration of new formulations for PRESAGETM 3D dosimetry." June 2006.
Source
wos-lite
Published In
Medical physics
Volume
33
Issue
6
Publish Date
2006
Start Page
2069
End Page
2069
DOI
10.1118/1.2241014

Evaluation of the quality of 3D-3D mutual information (MI) shared between reference and on-board DTS images

Authors
Godfrey, D; Ren, L; Yan, H; Oldham, M; Yin, F
MLA Citation
Godfrey, D, Ren, L, Yan, H, Oldham, M, and Yin, F. "Evaluation of the quality of 3D-3D mutual information (MI) shared between reference and on-board DTS images." June 2006.
Source
wos-lite
Published In
Medical physics
Volume
33
Issue
6
Publish Date
2006
Start Page
2268
End Page
2268
DOI
10.1118/1.2241856

Evaluation of a practical and low cost Gafchromic film/flat-bed scanner combination for planar dosimetry

Authors
Goss, M; Guo, P; Yin, F; Oldham, M
MLA Citation
Goss, M, Guo, P, Yin, F, and Oldham, M. "Evaluation of a practical and low cost Gafchromic film/flat-bed scanner combination for planar dosimetry." June 2006.
Source
wos-lite
Published In
Medical physics
Volume
33
Issue
6
Publish Date
2006
Start Page
2098
End Page
2098
DOI
10.1118/1.2241139

3D optical imaging of tumor microvasculature and viable cell distribution

Authors
Sakhalkar, H; Wang, Y; Oliver, T; Dewhirst, M; Oldham, M
MLA Citation
Sakhalkar, H, Wang, Y, Oliver, T, Dewhirst, M, and Oldham, M. "3D optical imaging of tumor microvasculature and viable cell distribution." June 2006.
Source
wos-lite
Published In
Medical physics
Volume
33
Issue
6
Publish Date
2006
Start Page
2239
End Page
2239
DOI
10.1118/1.2241739

A practical and accurate 3D dosimetry system for radiation therapy

Authors
Guo, P; Adamovics, J; Oldham, M
MLA Citation
Guo, P, Adamovics, J, and Oldham, M. "A practical and accurate 3D dosimetry system for radiation therapy." June 2006.
Source
wos-lite
Published In
Medical physics
Volume
33
Issue
6
Publish Date
2006
Start Page
2193
End Page
2193
DOI
10.1118/1.2241537

Digital tomosynthesis with an on-board kilovoltage imaging device.

PURPOSE: To generate on-board digital tomosynthesis (DTS) and reference DTS images for three-dimensional image-guided radiation therapy (IGRT) as an alternative to conventional portal imaging or on-board cone-beam computed tomography (CBCT). METHODS AND MATERIALS: Three clinical cases (prostate, head-and-neck, and liver) were selected to illustrate the capabilities of on-board DTS for IGRT. Corresponding reference DTS images were reconstructed from digitally reconstructed radiographs computed from planning CT image sets. The effect of scan angle on DTS slice thickness was examined by computing the mutual information between coincident CBCT and DTS images, as the DTS scan angle was varied from 0 degrees to 165 degrees . A breath-hold DTS acquisition strategy was implemented to remove respiratory motion artifacts. RESULTS: Digital tomosynthesis slices appeared similar to coincident CBCT planes and yielded substantially more anatomic information than either kilovoltage or megavoltage radiographs. Breath-hold DTS acquisition improved soft-tissue visibility by suppressing respiratory motion. CONCLUSIONS: Improved bony and soft-tissue visibility in DTS images is likely to improve target localization compared with radiographic verification techniques and might allow for daily localization of a soft-tissue target. Breath-hold DTS is a potential alternative to on-board CBCT for sites prone to respiratory motion.

Authors
Godfrey, DJ; Yin, F-F; Oldham, M; Yoo, S; Willett, C
MLA Citation
Godfrey, DJ, Yin, F-F, Oldham, M, Yoo, S, and Willett, C. "Digital tomosynthesis with an on-board kilovoltage imaging device." Int J Radiat Oncol Biol Phys 65.1 (May 1, 2006): 8-15.
PMID
16618573
Source
pubmed
Published In
International Journal of Radiation Oncology, Biology, Physics
Volume
65
Issue
1
Publish Date
2006
Start Page
8
End Page
15
DOI
10.1016/j.ijrobp.2006.01.025

Characterization of a new radiochromic three-dimensional dosimeter.

The development of intensity-modulated radiotherapy (IMRT) has created a clear need for a dosimeter that can accurately and conveniently measure dose distributions in three dimensions to assure treatment quality. PRESAGE is a new three dimensional (3D) dosimetry material consisting of an optically clear polyurethane matrix, containing a leuco dye that exhibits a radiochromic response when exposed to ionizing radiation. A number of potential advantages accrue over other gel dosimeters, including insensitivity to oxygen, radiation induced light absorption contrast rather than scattering contrast, and a solid texture amenable to machining to a variety of shapes and sizes without the requirement of an external container. In this paper, we introduce an efficient method to investigate the basic properties of a 3D dosimetry material that exhibits an optical dose response. The method is applied here to study the key aspects of the optical dose response of PRESAGE: linearity, dose rate dependency, reproducibility, stability, spectral changes in absorption, and temperature effects. PRESAGE was prepared in 1 x 1 x 4.5 cm3 optical cuvettes for convenience and was irradiated by both photon and electron beams to different doses, dose rates, and energies. Longer PRESAGE columns (2 x 2 x 13 cm3) were formed without an external container, for measurements of photon and high energy electron depth-dose curves. A linear optical scanning technique was used to detect the depth distribution of radiation induced optical density (OD) change along the PRESAGE columns and cuvettes. Measured depth-OD curves were compared with percent depth dose (PDD). Results indicate that PRESAGE has a linear optical response to radiation dose (with a root mean square error of -1%), little dependency on dose rate (-2%), high intrabatch reproducibility (< 2%), and can be stable (-2%) during 2 hours to 2 days post irradiation. Accurate PRESAGE dosimetry requires temperature control within 1 degrees C. Variations in the PRESAGE formulation yield corresponding variations in sensitivity, stability, and density. CT numbers in the range 100-470 were observed. In conclusion, the small volume studies presented here indicate PRESAGE to be a promising, versatile, and practical new dosimetry material with applicability for radiation therapy.

Authors
Guo, PY; Adamovics, JA; Oldham, M
MLA Citation
Guo, PY, Adamovics, JA, and Oldham, M. "Characterization of a new radiochromic three-dimensional dosimeter." Med Phys 33.5 (May 2006): 1338-1345.
PMID
16752569
Source
pubmed
Published In
Medical physics
Volume
33
Issue
5
Publish Date
2006
Start Page
1338
End Page
1345
DOI
10.1118/1.2192888

Physics and imaging for targeting of oligometastases.

Oligometastases refer to metastases that are limited in number and location and are amenable to regional treatment. The majority of these metastases appear in the brain, lung, liver, and bone. Although the focus of interest in the past within radiation oncology has been on the treatment of intracranial metastases, there has been growing interest in extracranial sites such as the liver and lung. This is largely because of the rapid development of targeting techniques for oligometastases such as intensity-modulated and image-guided radiation therapy, which has made it possible to deliver single or a few fractions of high-dose radiation treatments, highly conformal to the target. The clinical decision to use radiation to treat oligometastases is based on both radiobiological and physics considerations. The radiobiological considerations involve improvement of treatment schema for time, dose, and volume. Areas of interests are hypofractionation, tumor and normal tissue tolerance, and hypoxia. The physics considerations for oligometastases treatment are focused mainly on ensuring treatment accuracy and precision. This article discusses the physics and imaging aspects involved in each step of the radiation treatment process for oligometastases, including target definition, treatment simulation, treatment planning, pretreatment target localization, radiation delivery, treatment verification, and treatment evaluation.

Authors
Yin, F-F; Das, S; Kirkpatrick, J; Oldham, M; Wang, Z; Zhou, S-M
MLA Citation
Yin, F-F, Das, S, Kirkpatrick, J, Oldham, M, Wang, Z, and Zhou, S-M. "Physics and imaging for targeting of oligometastases." Semin Radiat Oncol 16.2 (April 2006): 85-101. (Review)
PMID
16564444
Source
pubmed
Published In
Seminars in Radiation Oncology
Volume
16
Issue
2
Publish Date
2006
Start Page
85
End Page
101
DOI
10.1016/j.semradonc.2005.12.004

Optical-computed-and emission tomography: A new imaging modality for cancer research

Authors
Oldham, M; Wang, Y; Vujaskovic, Z; Dewhirst, M
MLA Citation
Oldham, M, Wang, Y, Vujaskovic, Z, and Dewhirst, M. "Optical-computed-and emission tomography: A new imaging modality for cancer research." March 2006.
Source
wos-lite
Published In
Radiotherapy & Oncology
Volume
78
Publish Date
2006
Start Page
S55
End Page
S56
DOI
10.1016/S0167-8140(06)80643-2

3D dosimetry by optical-CT scanning.

The need for an accurate, practical, low-cost 3D dosimetry system is becoming ever more critical as modern dose delivery techniques increase in complexity and sophistication. A recent report from the Radiological Physics Center (RPC) (1), revealed that 38% of institutions failed the head-and-neck IMRT phantom credentialing test at the first attempt. This was despite generous passing criteria (within 7% dose-difference or 4mm distance-to-agreement) evaluated at a half-dozen points and a single axial plane. The question that arises from this disturbing finding is - what percentage of institutions would have failed if a comprehensive 3D measurement had been feasible, rather than measurements restricted to the central film-plane and TLD points? This question can only be adequately answered by a comprehensive 3D-dosimetry system, which presents a compelling argument for its development as a clinically viable low cost dosimetry solution. Optical-CT dosimetry is perhaps the closest system to providing such a comprehensive solution. In this article, we review the origins and recent developments of optical-CT dosimetry systems. The principle focus is on first generation systems known to have highest accuracy but longer scan times.

Authors
Oldham, M
MLA Citation
Oldham, M. "3D dosimetry by optical-CT scanning." J Phys Conf Ser 56 (2006): 58-71.
PMID
17460781
Source
pubmed
Published In
Journal of Physics
Volume
56
Publish Date
2006
Start Page
58
End Page
71
DOI
10.1088/1742-6596/56/1/006

IMRT verification using a radiochromic/optical-CT dosimetry system.

Authors
Oldham, M; Guo, P; Gluckman, G; Adamovics, J
MLA Citation
Oldham, M, Guo, P, Gluckman, G, and Adamovics, J. "IMRT verification using a radiochromic/optical-CT dosimetry system." J Phys Conf Ser 56 (2006): 221-224.
PMID
17460782
Source
pubmed
Published In
Journal of Physics
Volume
56
Publish Date
2006
Start Page
221
End Page
224
DOI
10.1088/1742-6596/56/1/033

Towards four dimensional (4D) dosimetry for radiation-therapy.

Authors
Oldham, M; Guo, P; Adamovics, J; Sakhalkar, H; Wang, Z; Yin, F
MLA Citation
Oldham, M, Guo, P, Adamovics, J, Sakhalkar, H, Wang, Z, and Yin, F. "Towards four dimensional (4D) dosimetry for radiation-therapy." J Phys Conf Ser 56 (2006): 225-227.
PMID
17460783
Source
pubmed
Published In
Journal of Physics
Volume
56
Publish Date
2006
Start Page
225
End Page
227
DOI
10.1088/1742-6596/56/1/034

PRESAGETM - Development and optimization studies of a 3D radiochromic plastic dosimeter-Part 2

In a previous paper we described the evaluation of seven different transparent plastics as dosimeter matrices along with six different leuco dyes as the radiochromic agent. Here we present the evaluation of the dosimeter sensitivity and post irradiation stability of an additional plastic matrix and five different leuco dyes. © 2006 IOP Publishing Ltd.

Authors
Adamovics, J; Guo, P; Burgess, D; Manzoor, A; Oldham, M
MLA Citation
Adamovics, J, Guo, P, Burgess, D, Manzoor, A, and Oldham, M. "PRESAGETM - Development and optimization studies of a 3D radiochromic plastic dosimeter-Part 2." Journal of Physics: Conference Series 56.1 (2006): 176-178.
Source
scival
Published In
Journal of Physics
Volume
56
Issue
1
Publish Date
2006
Start Page
176
End Page
178
DOI
10.1088/1742-6596/56/1/021

Investigation of the dosimetric characteristics of PRESAGETM

In this work we perform a detailed investigation of the fundamental dosimetric characteristics of PRESAGETM, to determine its potential for dosimetry. A common problem encountered when attempting to evaluate a new material, is how to efficiently evaluate the large multitude of potential mechanisms and response-characteristics that may affect the practicality and accuracy of that material for dosimetry. We introduce a new method designed to enable rapid, accurate and convenient evaluation of any material which has an optical dose-response, and can be formed into columns of precise dimension (e.g. spectro-photometric cuvettes). The method is also optimised to enable evaluation of dosimetric characteristics with the minimum volume of material, to minimise cost, and problems associated to storage, transportation etc. © 2006 IOP Publishing Ltd.

Authors
Guo, P; Adamovics, J; Oldham, M
MLA Citation
Guo, P, Adamovics, J, and Oldham, M. "Investigation of the dosimetric characteristics of PRESAGETM." Journal of Physics: Conference Series 56.1 (2006): 207-210.
Source
scival
Published In
Journal of Physics
Volume
56
Issue
1
Publish Date
2006
Start Page
207
End Page
210
DOI
10.1088/1742-6596/56/1/029

Simple 3D validation experiments for PRESAGETM/optical-CT dosimetry

Detailed studies of the basic dosimetric properties of small volumes of PRESAGETM have confirmed its promise as a new material with enhanced properties for 3D dosimetry. PRESAGETM is a transparent polyurethane material containing a radiochromic leucodye. Principle advantages include a relative insensitivity of the dose response to atmospheric exposure, and a radiochromic optical contrast which is light absorbing rather than light-scattering (peak optical density change is at ∼633 nm). The absorptive nature of the contrast is more amenable to accurate dose read-out by optical-computed-tomography. This work represents our first feasibility tests of large volumes of PRESAGETM for dosimetric validation of radiation treatments. © 2006 IOP Publishing Ltd.

Authors
Guo, P; Adamovics, J; Oldham, M
MLA Citation
Guo, P, Adamovics, J, and Oldham, M. "Simple 3D validation experiments for PRESAGETM/optical-CT dosimetry." Journal of Physics: Conference Series 56.1 (2006): 187-190.
Source
scival
Published In
Journal of Physics
Volume
56
Issue
1
Publish Date
2006
Start Page
187
End Page
190
DOI
10.1088/1742-6596/56/1/024

On-board breath-hold digital tomosynthesis (DTS) for target localization prior to breath-hold treatment

Authors
Godfrey, DJ; Wang, Z; Yoo, S; Wu, J; Oldham, M; Willett, C; Yin, F
MLA Citation
Godfrey, DJ, Wang, Z, Yoo, S, Wu, J, Oldham, M, Willett, C, and Yin, F. "On-board breath-hold digital tomosynthesis (DTS) for target localization prior to breath-hold treatment." 2006.
Source
wos-lite
Published In
International Journal of Radiation Oncology, Biology, Physics
Volume
66
Issue
3
Publish Date
2006
Start Page
S613
End Page
S614
DOI
10.1016/j.ijrobp.2006.07.1142

A novel water-clear, low-modulus bolus material

Authors
Kirkpatrick, JP; Irani, FR; Johnston, SE; Stalnecker, AM; Cooney, TM; Georgas, DL; Oldham, M
MLA Citation
Kirkpatrick, JP, Irani, FR, Johnston, SE, Stalnecker, AM, Cooney, TM, Georgas, DL, and Oldham, M. "A novel water-clear, low-modulus bolus material." 2006.
Source
wos-lite
Published In
International Journal of Radiation Oncology, Biology, Physics
Volume
66
Issue
3
Publish Date
2006
Start Page
S704
End Page
S705
DOI
10.1016/j.ijrobp.2006.07.1294

Three-dimensional dose verification for radiation therapy

Authors
Guo, P; Adamovics, J; Oldham, M
MLA Citation
Guo, P, Adamovics, J, and Oldham, M. "Three-dimensional dose verification for radiation therapy." 2006.
Source
wos-lite
Published In
International Journal of Radiation Oncology, Biology, Physics
Volume
66
Issue
3
Publish Date
2006
Start Page
S710
End Page
S711
DOI
10.1016/j.ijrobp.2006.07.1304

Optical computed and emission tomography for high-resolution 3D imaging of xenograft tumors

Authors
Sakhalkar, HS; Oliver, T; Dewhirst, M; Oldham, M
MLA Citation
Sakhalkar, HS, Oliver, T, Dewhirst, M, and Oldham, M. "Optical computed and emission tomography for high-resolution 3D imaging of xenograft tumors." 2006.
Source
wos-lite
Published In
International Journal of Radiation Oncology, Biology, Physics
Volume
66
Issue
3
Publish Date
2006
Start Page
S18
End Page
S19
DOI
10.1016/j.ijrobp.2006.07.1326

Cone-beam-CT guided radiation therapy: technical implementation.

BACKGROUND AND PURPOSE: X-ray volumetric imaging system (XVI) mounted on a linear accelerator is available for image guidance applications. In preparation for clinical implementation, phantom and patient imaging studies were conducted to determine the irradiation parameters that would trade-off image quality, patient dose and scanning time. PATIENTS AND METHODS: The XVI image quality and imaging dose were benchmarked against those obtained with a helical CT scanner for a head and body phantom. The irradiation parameters were varied including the total imaging dose, number of projections, field of view, reconstruction resolution and use of a scatter rejection grid. We characterized the image quality based on relative contrast, noise, contrast to noise ratio (CNR) and point spread function (PSF). XVI scans of pelvis, head and neck and lung patients were acquired and submitted to a range of observers to identify the favorable reconstruction parameters. RESULTS: Phantom studies have demonstrated that a scatter rejection grid reduces photon scattering and improves the image uniformity. For the body phantom, the helical CT and the wide field XVI technique produce similar image quality, with surface doses of 0.025 and 0.044 Gy respectively. We have demonstrated that the local tomography technique improves the image contrast and the CNR while reducing the skin dose by 40-50% compared to the wide field technique. Clinical scans of head and neck, lung and prostate patients present good soft tissue contrast and excellent bone definition. CONCLUSIONS: With adjustment of irradiation parameters and an imaging surface dose of less than 0.05 Gy, high quality XVI images can be obtained for a phantom simulating the body thickness. XVI is currently feasible for image-guided treatments of head and neck, torso and pelvic areas using soft tissue and bony structures.

Authors
Létourneau, D; Wong, JW; Oldham, M; Gulam, M; Watt, L; Jaffray, DA; Siewerdsen, JH; Martinez, AA
MLA Citation
Létourneau, D, Wong, JW, Oldham, M, Gulam, M, Watt, L, Jaffray, DA, Siewerdsen, JH, and Martinez, AA. "Cone-beam-CT guided radiation therapy: technical implementation." Radiother Oncol 75.3 (June 2005): 279-286.
PMID
15890424
Source
pubmed
Published In
Radiotherapy & Oncology
Volume
75
Issue
3
Publish Date
2005
Start Page
279
End Page
286
DOI
10.1016/j.radonc.2005.03.001

Cone-beam-CT guided radiation therapy: A model for on-line application.

BACKGROUND AND PURPOSE: This paper presents efficient and generalized processes for the clinical application of on-line X-ray volumetric cone-beam CT imaging (XVI) to improve the accuracy of patient set-up in radiation therapy. XVI image-guided therapy is illustrated by application to two contrasting sites, intra-cranial radiosurgery and prostate radiation therapy, with very different characteristics regarding organ motion, treatment precision, and imaging conditions. PATIENTS AND METHODS: On-line set-up errors are determined in a two-step process. First the XVI data is registered to the planning data by matching the machine-isocenter with the planning-isocenter, respectively. The machine isocenter is defined in the XVI data during the reconstruction. The planning-isocenter is defined during the planning process in the planning CT data. Set-up errors are then determined from a second registration to remove residual displacements. The accuracy of the entire procedure for on-line set-up error correction was investigated in precision radiosurgery phantom studies. RESULTS: The phantom studies showed that sub-pixel size set-up errors (down to 0.5mm) can be correctly determined and implemented in the radiosurgery environment. XVI is demonstrated to provide quality skull detail enabling precise skull based on-line alignment in radiosurgery. A 'local XVI' technique was found to give encouraging soft-tissue detail in the high-scatter pelvic environment, enabling on-line soft-tissue based set-up for prostate treatment. The two-step process for determination of set-up errors was found to be efficient and effective when implemented with a dedicated six panel interface enabling simultaneous visualization on the XVI and planning CT data sets. CONCLUSIONS: XVI has potential to significantly improve the accuracy of radiation treatments. Present image quality is highly encouraging and can enable bony and soft-tissue patient set-up error determination and correction. As with all image guided treatment techniques the development of efficient procedures to utilize on-line data are of paramount importance.

Authors
Oldham, M; Létourneau, D; Watt, L; Hugo, G; Yan, D; Lockman, D; Kim, LH; Chen, PY; Martinez, A; Wong, JW
MLA Citation
Oldham, M, Létourneau, D, Watt, L, Hugo, G, Yan, D, Lockman, D, Kim, LH, Chen, PY, Martinez, A, and Wong, JW. "Cone-beam-CT guided radiation therapy: A model for on-line application." Radiother Oncol 75.3 (June 2005): 271-278.
PMID
15890419
Source
pubmed
Published In
Radiotherapy & Oncology
Volume
75
Issue
3
Publish Date
2005
Start Page
271
End Page
278
DOI
10.1016/j.radonc.2005.03.026

Characterization of a new 3D dosimetric material "PRESAGE" (TM)

Authors
Guo, P; Adamovics, J; Oldham, M
MLA Citation
Guo, P, Adamovics, J, and Oldham, M. "Characterization of a new 3D dosimetric material "PRESAGE" (TM)." June 2005.
Source
wos-lite
Published In
Medical physics
Volume
32
Issue
6
Publish Date
2005
Start Page
2136
End Page
2136
DOI
10.1118/1.1998561

The study of the dosimetric properties of 'RadGell, a new dosimeter for three-dimensional gel dosimetry

Authors
Guo, P; Appleby, A; Oldham, M
MLA Citation
Guo, P, Appleby, A, and Oldham, M. "The study of the dosimetric properties of 'RadGell, a new dosimeter for three-dimensional gel dosimetry." June 2005.
Source
wos-lite
Published In
Medical physics
Volume
32
Issue
6
Publish Date
2005
Start Page
2009
End Page
2009
DOI
10.1118/1.1997986

SU-FF-J-30: Quantification of Normal Organ Motion Due to the Respiratory and Cardiac Cycles

Authors
Wang, Z; Yin, F; Raidy, T; Kelly, K; Oldham, M; Das, S; Zhou, S; Marks, L; Kasibhatla, M; Willett, C
MLA Citation
Wang, Z, Yin, F, Raidy, T, Kelly, K, Oldham, M, Das, S, Zhou, S, Marks, L, Kasibhatla, M, and Willett, C. "SU-FF-J-30: Quantification of Normal Organ Motion Due to the Respiratory and Cardiac Cycles." June 2005.
Source
crossref
Published In
Medical physics
Volume
32
Issue
6Part4
Publish Date
2005
Start Page
1926
End Page
1926
DOI
10.1118/1.1997576

Multidimensional dosimetry without film processors

Authors
Low, D; Dempsey, J; Jursinic, P; Oldham, M
MLA Citation
Low, D, Dempsey, J, Jursinic, P, and Oldham, M. "Multidimensional dosimetry without film processors." June 2005.
Source
wos-lite
Published In
Medical physics
Volume
32
Issue
6
Publish Date
2005
Start Page
2148
End Page
2148
DOI
10.1118/1.1998609

TOMAS, a tool for organ motion AnalysiS

Authors
Raj, K; Guo, P; Raidy, T; Oldham, M
MLA Citation
Raj, K, Guo, P, Raidy, T, and Oldham, M. "TOMAS, a tool for organ motion AnalysiS." June 2005.
Source
wos-lite
Published In
Medical physics
Volume
32
Issue
6
Publish Date
2005
Start Page
2142
End Page
2143
DOI
10.1118/1.1998589

SU-FF-J-57: Digital Tomosynthesis for Verification of Radiation Therapy Positioning: Preliminary Results From a Kilovoltage On-Board Imaging System

Authors
Godfrey, D; Oldham, M; Dobbins, J; Yin, F
MLA Citation
Godfrey, D, Oldham, M, Dobbins, J, and Yin, F. "SU-FF-J-57: Digital Tomosynthesis for Verification of Radiation Therapy Positioning: Preliminary Results From a Kilovoltage On-Board Imaging System." June 2005.
Source
crossref
Published In
Medical physics
Volume
32
Issue
6Part5
Publish Date
2005
Start Page
1932
End Page
1932
DOI
10.1118/1.1997603

Optical imaging of tumor microvasculature in 3D

Authors
Oldham, M; Oliver, T; Dewhirst, M
MLA Citation
Oldham, M, Oliver, T, and Dewhirst, M. "Optical imaging of tumor microvasculature in 3D." June 2005.
Source
wos-lite
Published In
Medical physics
Volume
32
Issue
6
Publish Date
2005
Start Page
2134
End Page
2134
DOI
10.1118/1.1998550

Optical-CT imaging of complex 3D dose distributions.

The limitations of conventional dosimeters restrict the comprehensiveness of verification that can be performed for advanced radiation treatments presenting an immediate and substantial problem for clinics attempting to implement these techniques. In essence, the rapid advances in the technology of radiation delivery have not been paralleled by corresponding advances in the ability to verify these treatments. Optical-CT gel-dosimetry is a relatively new technique with potential to address this imbalance by providing high resolution 3D dose maps in polymer and radiochromic gel dosimeters. We have constructed a 1(st) generation optical-CT scanner capable of high resolution 3D dosimetry and applied it to a number of simple and increasingly complex dose distributions including intensity-modulated-radiation-therapy (IMRT). Prior to application to IMRT, the robustness of optical-CT gel dosimetry was investigated on geometry and variable attenuation phantoms. Physical techniques and image processing methods were developed to minimize deleterious effects of refraction, reflection, and scattered laser light. Here we present results of investigations into achieving accurate high-resolution 3D dosimetry with optical-CT, and show clinical examples of 3D IMRT dosimetry verification. In conclusion, optical-CT gel dosimetry can provide high resolution 3D dose maps that greatly facilitate comprehensive verification of complex 3D radiation treatments. Good agreement was observed at high dose levels (>50%) between planned and measured dose distributions. Some systematic discrepancies were observed however (rms discrepancy 3% at high dose levels) indicating further work is required to eliminate confounding factors presently compromising the accuracy of optical-CT 3D gel-dosimetry.

Authors
Oldham, M; Kim, L; Hugo, G
MLA Citation
Oldham, M, Kim, L, and Hugo, G. "Optical-CT imaging of complex 3D dose distributions." J Phys Conf Ser 5745 (April 2005): 138-146.
PMID
17235366
Source
pubmed
Published In
Journal of Physics
Volume
5745
Publish Date
2005
Start Page
138
End Page
146
DOI
10.1117/12.595525

Predicting radiotherapy-induced cardiac perfusion defects.

The purpose of this work is to compare the efficacy of mathematical models in predicting the occurrence of radiotherapy-induced left ventricular perfusion defects assessed using single-photon emission computed tomography (SPECT). The basis of this study is data from 73 left-sided breast/ chestwall patients treated with tangential photon fields. The mathematical models compared were three commonly used parametric models [Lyman normal tissue complication probability (LNTCP), relative serialty (RS), generalized equivalent uniform dose (gEUD)] and a nonparametric model (Linear discriminant analysis--LDA). Data used by the models were the left ventricular dose--volume histograms, or SPECT-based dose-function histograms, and the presence/absence of SPECT perfusion defects 6 months postradiation therapy (21 patients developed defects). For the parametric models, maximum likelihood estimation and F-tests were used to fit the model parameters. The nonparametric LDA model step-wise selected features (volumes/function above dose levels) using a method based on receiver operating characteristics (ROC) analysis to best separate the groups with and without defects. Optimistic (upper bound) and pessimistic (lower bound) estimates of each model's predictive capability were generated using ROC curves. A higher area under the ROC curve indicates a more accurate model (a model that is always accurate has area = 1). The areas under these curves for different models were used to statistically test for differences between them. Pessimistic estimates of areas under the ROC curve using dose-volume histogram/ dose-function histogram inputs, in order of increasing prediction accuracy, were LNTCP (0.79/0.75), RS (0.80/0.77), gEUD (0.81/0.78), and LDA (0.84/0.86). Only the LDA model benefited from SPECT-based regional functional information. In general, the LDA model was statistically superior to the parametric models. The LDA model selected as features the left ventricular volumes above approximately 23 Gy (V23), essentially volume in field, and 33 Gy (V33), as best separating the groups with and without defects. In conclusion, the nonparametric LDA model appears to be a more accurate predictor of radiotherapy-induced left ventricular perfusion defects than commonly used parametric models.

Authors
Das, SK; Baydush, AH; Zhou, S; Miften, M; Yu, X; Craciunescu, O; Oldham, M; Light, K; Wong, T; Blazing, M; Borges-Neto, S; Dewhirst, MW; Marks, LB
MLA Citation
Das, SK, Baydush, AH, Zhou, S, Miften, M, Yu, X, Craciunescu, O, Oldham, M, Light, K, Wong, T, Blazing, M, Borges-Neto, S, Dewhirst, MW, and Marks, LB. "Predicting radiotherapy-induced cardiac perfusion defects." Med Phys 32.1 (January 2005): 19-27.
PMID
15719950
Source
pubmed
Published In
Medical physics
Volume
32
Issue
1
Publish Date
2005
Start Page
19
End Page
27
DOI
10.1118/1.1823571

Initial application of digital tomosynthesis with on-board imaging in radiation oncology

We present preliminary investigations that examine the feasibility of incorporating digital tomosynthesis into radiation oncology practice with the use of kilovoltage on-board imagers (OBI). Modern radiation oncology linear accelerators now include hardware options for the addition of OBI for on-line patient setup verification. These systems include an x-ray tube and detector mounted directly on the accelerator gantry that rotate with the same isocenter. Applications include cone beam computed tomography (CBCT), fluoroscopy, and radiographs to examine daily patient positioning to determine if the patient is in the same location as the treatment plan. While CBCT provides the greatest anatomical detail, this approach is limited by long acquisition and reconstruction times and higher patient dose. We propose to examine the use of tomosynthesis reconstructed volumetric data from limited angle projection images for short imaging time and reduced patient dose. Initial data uses 61 projection images acquired over an isocentric arc of twenty degrees with the detector approximately fifty-four centimeters from isocenter. A modified filtered back projection technique, which included a mathematical correction for isocentric motion, was used to reconstruct volume images. These images will be visually and mathematically compared to volumetric computed tomography images to determine efficacy of this system for daily patient positioning verification. Initial images using the tomosynthesis reconstruction technique show much promise and bode well for effective daily patient positioning verification with reduced patient dose and imaging time. Additionally, the fast image acquisition may allow for a single breath hold imaging sequence, which will have no breath motion.

Authors
Baydush, AH; Godfrey, DJ; Oldham, M; III, JTD
MLA Citation
Baydush, AH, Godfrey, DJ, Oldham, M, and III, JTD. "Initial application of digital tomosynthesis with on-board imaging in radiation oncology." Progress in Biomedical Optics and Imaging - Proceedings of SPIE 5745.II (2005): 1300-1305.
Source
scival
Published In
Proceedings of SPIE
Volume
5745
Issue
II
Publish Date
2005
Start Page
1300
End Page
1305
DOI
10.1117/12.596245

Assessment of setup accuracy for prostate radiotherapy using on-board imaging and cone beam computed tomography

Authors
Kasibhalta, M; Yoo, S; Yin, F; Godfrey, D; Oldham, M; Das, SK
MLA Citation
Kasibhalta, M, Yoo, S, Yin, F, Godfrey, D, Oldham, M, and Das, SK. "Assessment of setup accuracy for prostate radiotherapy using on-board imaging and cone beam computed tomography." 2005.
Source
wos-lite
Published In
International Journal of Radiation Oncology, Biology, Physics
Volume
63
Issue
2
Publish Date
2005
Start Page
S535
End Page
S535
DOI
10.1016/j.ijrobp.2005.07.903

Online digital tomosynthesis (DTS): A novel technique for improving target localization in radiation therapy

Authors
Godfrey, DJ; Oldham, M; Dobbins, J; Yin, F
MLA Citation
Godfrey, DJ, Oldham, M, Dobbins, J, and Yin, F. "Online digital tomosynthesis (DTS): A novel technique for improving target localization in radiation therapy." 2005.
Source
wos-lite
Published In
International Journal of Radiation Oncology, Biology, Physics
Volume
63
Issue
2
Publish Date
2005
Start Page
S556
End Page
S556
DOI
10.1016/j.ijrobp.2005.07.937

Intrafraction organ motion of the normal cervix

Authors
Raj, KA; Guo, P; Jones, E; Marks, L; Raidy, T; Oldham, M
MLA Citation
Raj, KA, Guo, P, Jones, E, Marks, L, Raidy, T, and Oldham, M. "Intrafraction organ motion of the normal cervix." 2005.
Source
wos-lite
Published In
International Journal of Radiation Oncology, Biology, Physics
Volume
63
Issue
2
Publish Date
2005
Start Page
S220
End Page
S220
DOI
10.1016/j.ijrobp.2005.07.378

A novel method of imaging unperturbed tumor vasculature in 3D

Authors
Oldham, M; Oliver, T; Dewhirst, M
MLA Citation
Oldham, M, Oliver, T, and Dewhirst, M. "A novel method of imaging unperturbed tumor vasculature in 3D." 2005.
Source
wos-lite
Published In
International Journal of Radiation Oncology, Biology, Physics
Volume
63
Issue
2
Publish Date
2005
Start Page
S134
End Page
S134
DOI
10.1016/j.ijrobp.2005.07.228

PRESAGE - A promising new material for 3D dosimetry

Authors
Guo, P; Adamovics, J; Oldham, M
MLA Citation
Guo, P, Adamovics, J, and Oldham, M. "PRESAGE - A promising new material for 3D dosimetry." 2005.
Source
wos-lite
Published In
International Journal of Radiation Oncology, Biology, Physics
Volume
63
Issue
2
Publish Date
2005
Start Page
S206
End Page
S206
DOI
10.1016/j.ijrobp.2005.07.355

Combining cardiac/respiratory gating to minimize the organ motion effect

Authors
Willett, C; Wang, Z; Marks, L; Raidy, T; Kelly, K; Oldham, M; Das, S; Zhou, S; Kasibhalta, M; Yin, F
MLA Citation
Willett, C, Wang, Z, Marks, L, Raidy, T, Kelly, K, Oldham, M, Das, S, Zhou, S, Kasibhalta, M, and Yin, F. "Combining cardiac/respiratory gating to minimize the organ motion effect." 2005.
Source
wos-lite
Published In
International Journal of Radiation Oncology, Biology, Physics
Volume
63
Issue
2
Publish Date
2005
Start Page
S558
End Page
S559
DOI
10.1016/j.ijrobp.2005.07.940

Novel dosimetry systems for IMRT and complex radiation treatments

Authors
Oldham, M; Letourneau, D
MLA Citation
Oldham, M, and Letourneau, D. "Novel dosimetry systems for IMRT and complex radiation treatments." June 2004.
Source
wos-lite
Published In
Medical physics
Volume
31
Issue
6
Publish Date
2004
Start Page
1761
End Page
1761

Radiation dose and temperature dependence of metabolite signals in proton magnetic resonance imaging and spectroscopy

Authors
Gultekin, D; Raidy, T; Oldham, M
MLA Citation
Gultekin, D, Raidy, T, and Oldham, M. "Radiation dose and temperature dependence of metabolite signals in proton magnetic resonance imaging and spectroscopy." June 2004.
Source
wos-lite
Published In
Medical physics
Volume
31
Issue
6
Publish Date
2004
Start Page
1773
End Page
1773

Initial application of 3D gel-dosimetry for the clinical verification of complex dose distributions

Authors
Kim, L; Gluckman, G; Oldham, M
MLA Citation
Kim, L, Gluckman, G, and Oldham, M. "Initial application of 3D gel-dosimetry for the clinical verification of complex dose distributions." June 2004.
Source
wos-lite
Published In
Medical physics
Volume
31
Issue
6
Publish Date
2004
Start Page
1823
End Page
1823

Optical-CT gel-dosimetry. II: Optical artifacts and geometrical distortion.

There is a clear need for technology that enables accurate, high-resolution, three-dimensional (3D) measurement of intricate dose distributions associated with modern radiation treatments. A potential candidate has emerged in the form of water-equivalent "3D gel dosimetry" utilizing optical-computed-tomography (optical-CT). In a previous paper we presented basic physical characterization of an in-house prototype optical-CT scanning system. The present paper builds on that work by investigating sources of optical artifacts and geometric distortion in optical-CT scanning. Improvements in scanner design are described. Correction strategies were developed to compensate for reflection and refraction, imperfections in the water-bath, signal drift, and other effects. Refraction and reflection were identified as the principal factors causing inaccurate reconstruction of absolute attenuation coefficients. A correction specific to a given flask was developed utilizing prescans of the flask when filled with water-bath fluid, thereby isolating the refractive and reflective components for that flask. Residual artifacts were corrected by fitting a theoretical model to the well-behaved portion of these prescans and extrapolating to regions of lost data, enabling reconstruction of absolute optical-CT attenuation coefficients to within 4% of corresponding spectrophotometer values. Needle phantoms are introduced to quantify geometric distortion under a range of conditions. Radial distortion of reconstructed needle positions was reduced to < 0.3 mm (0.27% of the field of view) through adjustment of the water-bath refractive index. Geometric distortion in polymer gel due to radiation-induced refractive index changes was found to be negligible under the conditions examined. The influence of scattered light on reconstructed attenuation coefficients was investigated by repeat optical-CT scans while varying the aperture of a scatter-rejecting collimator. Significant depression of reconstructed attenuation coefficients was observed, particularly under conditions of poor scatter rejection collimation. The general conclusion is that the first-generation optical-CT technique can be made insensitive to geometrical distortion, but can be susceptible to scatter effects. For accurate reconstruction of absolute attenuation coefficients, correction strategies are essential.

Authors
Oldham, M; Kim, L
MLA Citation
Oldham, M, and Kim, L. "Optical-CT gel-dosimetry. II: Optical artifacts and geometrical distortion." Med Phys 31.5 (May 2004): 1093-1104.
PMID
15191297
Source
pubmed
Published In
Medical physics
Volume
31
Issue
5
Publish Date
2004
Start Page
1093
End Page
1104
DOI
10.1118/1.1655710

Evaluation of a 2D diode array for IMRT quality assurance.

BACKGROUND AND PURPOSE: The QA of intensity modulated radiotherapy (IMRT) dosimetry is a laborious task. The goal of this work is to evaluate the dosimetric characteristics of a new 2D diode array (MapCheck from Sun Nuclear Corporation, Melbourne, Florida) and assess the role it can play in routine IMRT QA. MATERIAL AND METHODS: Fundamental properties of the MapCheck such as reproducibility, linearity and temperature dependence are studied for high-energy photon beams. The accuracy of the correction for difference of diode sensitivity is also assessed. The diode array is benchmarked against film and ion chambers for conventional and IMRT treatments. The MapCheck sensitivity to multileaf collimator position errors is determined. RESULTS: The diode array response is linear with dose up to 295 cGy. All diodes are calibrated to within +/-1% of each other, and mostly within +/-0.5%. The MapCheck readings are reproducible to within a maximum SD of +/-0.15%. A temperature dependence of 0.57%/ degrees C was noted and should be taken into account for absolute dosimetric measurement. Clinical performance of the MapCheck for relative and absolute dosimetry is demonstrated with seven beam (6 MV) head and neck IMRT plans, and compares well with film and ion chamber measurements. Comparison to calculated dose maps demonstrates that the planning system model underestimates the dose gradients in the penumbra region. CONCLUSIONS: The MapCheck offers the dosimetric characteristics required for performing both relative and absolute dose measurements. Its use in the clinic can simplify and reduce the IMRT QA workload.

Authors
Létourneau, D; Gulam, M; Yan, D; Oldham, M; Wong, JW
MLA Citation
Létourneau, D, Gulam, M, Yan, D, Oldham, M, and Wong, JW. "Evaluation of a 2D diode array for IMRT quality assurance." Radiother Oncol 70.2 (February 2004): 199-206.
PMID
15028408
Source
pubmed
Published In
Radiotherapy & Oncology
Volume
70
Issue
2
Publish Date
2004
Start Page
199
End Page
206
DOI
10.1016/j.radonc.2003.10.014

Optical-CT scanning of polymer gels.

The application of optical-CT scanning to achieve accurate high-resolution 3D dosimetry is a subject of current interest. The purpose of this paper is to provide a brief overview of past research and achievements in optical-CT polymer gel dosimetry, and to review current issues and challenges. The origins of optical-CT imaging of light-scattering polymer gels are reviewed. Techniques to characterize and optimize optical-CT performance are presented. Particular attention is given to studies of artifacts in optical-CT imaging, an important area that has not been well studied to date. The technique of optical-CT simulation by Monte-Carlo modeling is introduced as a tool to explore such artifacts. New simulation studies are presented and compared with experimental data.

Authors
Oldham, M
MLA Citation
Oldham, M. "Optical-CT scanning of polymer gels." J Phys Conf Ser 3 (2004): 122-135.
PMID
17082823
Source
pubmed
Published In
Journal of Physics
Volume
3
Publish Date
2004
Start Page
122
End Page
135
DOI
10.1088/1742-6596/3/1/011

Optical-CT gel-dosimetry I: basic investigations.

Comprehensive verification of the intricate dose distributions associated with advanced radiation treatments is now an immediate and substantial problem. The task is challenging using traditional dosimeters because of restrictions to point measurements (ion chambers, diodes, TLD, etc.) or planar measurements (film). In essence, rapid advances in the technology to deliver radiation treatments have not been paralleled by corresponding advances in the ability to verify these treatments. A potential solution has emerged in the form of water equivalent three dimensional (3D) gel-dosimetry. In this paper we present basic characterization and performance studies of a prototype optical-CT scanning system developed in our laboratory. An analysis of the potential role or scope of gel dosimetry, in relation to other dosimeters, and to verification across the spectrum of therapeutic techniques is also given. The characterization studies enabled the determination of nominal operating conditions for optical-CT scanning. "Finger" phantoms are introduced as a powerful and flexible tool for the investigation of optical-CT performance. The modulation-transfer function (MTF) of the system is determined to be better than 10% out to 1 mm(-1), confirming sub-mm imaging ability. System performance is demonstrated by the acquisition of a 1 x 1 x 1 mm3 dataset through the dose distribution delivered by an x-ray lens that focuses x rays in the energy range 40-80 KeV. This 3D measurement would be extremely difficult to achieve with other dosimetry techniques and highlights some of the strengths of gel dosimetry. Finally, an optical Monte Carlo model is introduced and shown to have potential to model light transport through gel-dosimetry systems, and to provide a tool for the study and optimization of optical-CT gel dosimetry. The model utilizes Mie scattering theory and requires knowledge of the variation of the particle size distribution with dose. The latter was determined here using the technique of dynamic-light-scattering.

Authors
Oldham, M; Siewerdsen, JH; Kumar, S; Wong, J; Jaffray, DA
MLA Citation
Oldham, M, Siewerdsen, JH, Kumar, S, Wong, J, and Jaffray, DA. "Optical-CT gel-dosimetry I: basic investigations." Med Phys 30.4 (April 2003): 623-634.
PMID
12722814
Source
pubmed
Published In
Medical physics
Volume
30
Issue
4
Publish Date
2003
Start Page
623
End Page
634
DOI
10.1118/1.1559835

Practical aspects of in situ 16O (gamma,n) 15O activation using a conventional medical accelerator for the purpose of perfusion imaging.

We report investigations into the feasibility of generating radioactive oxygen (15O, a positron emitter, with half-life 2.05 min) using a tuned Elekta SL25 accelerator, for the end purpose of imaging tumor perfusion. 15O is produced by the "gamma, neutron," (gamma,n) reaction between high-energy photons and normal oxygen (16O) in the body. As most in vivo 16O is bound in water molecules the 15O radio-marker is produced in proportion to water content in tissue. Imaging the washout of the 15O distribution using sensitive positron-emission-tomography (PET) technology can yield spatial information about blood perfusion in the tissue. The aim of this article was to determine the amount of 15O activity that could be produced by the tuned medical accelerator. A further aim was to model the activation process using Monte Carlo and to investigate ways to optimize the amount of 15O that could be generated. Increased activation was achieved by (i) tuning the beam to give higher-energy electrons incident on the target of the accelerator, (ii) increasing dose rate by removing the conventional filtration in the beam and reducing the source to object distance, and (iii) reducing low-energy photons by means of a carbon block absorber. The activity per-unit-dose produced by the tuned beam was measured by irradiating spheres of water to known doses and placing the spheres in a calibrated coincidence-counting apparatus. Peak energy of the tuned bremsstrahlung beam was estimated at 29 MeV, and generated activity up to 0.24/microCi/cc/3Gy in water. The measured amount of 15O agreed to within 10% of the prediction from the Monte-Carlo-computed spectrum, indicating reasonable ability to model the activation process. The optimal thickness of the carbon absorber was found to be about 25 cm. The insertion of a carbon absorber improved spectral quality for activation purposes but at the cost of reduced dose rate. In conclusion, the viability of generating 15O with an Elekta SL25 has been demonstrated. In conjunction with recent advances in high-sensitivity portable PET imaging devices, real potential exists for imaging in situ activated 15O washout as a surrogate measurement of macroscopic tumor perfusion.

Authors
Oldham, M; Sapareto, SA; Li, XA; Allen, J; Sutlief, S; Wong, OC; Wong, JW
MLA Citation
Oldham, M, Sapareto, SA, Li, XA, Allen, J, Sutlief, S, Wong, OC, and Wong, JW. "Practical aspects of in situ 16O (gamma,n) 15O activation using a conventional medical accelerator for the purpose of perfusion imaging." Med Phys 28.8 (August 2001): 1669-1678.
PMID
11548936
Source
pubmed
Published In
Medical physics
Volume
28
Issue
8
Publish Date
2001
Start Page
1669
End Page
1678
DOI
10.1118/1.1386777

High resolution gel-dosimetry by optical-CT and MR scanning.

The increased intricacy of Intensity-Modulated-Radiation-Therapy (IMRT) delivery has created the need for a high-resolution 3D-dosimetry (three-dimensional) system capable of measuring and verifying the complex delivery. Present clinical methods are inadequate being restricted to single points (e.g., ion-chambers) or to 2D planes (e.g., film), and are labor intensive. In this paper we show that gel-dosimetry in conjunction with optical-CT scanning can yield maps of dose that are of sufficient accuracy, resolution and precision to allow verification of complex radiosurgery deliveries, and by extension IMRT deliveries. The radiosurgery dose-distribution represents the most challenging case encountered in external beam therapy by virtue of the steep dose-gradients and high resolution of delivery. We characterize the stringent radiosurgery requirements by the RTAP (Resolution-Time-Accuracy-Precision) criteria defined as < or = 1 mm3 spatial resolution, < or = 1 hour imaging time, accurate to within 3%, and within -1% precision. The RTAP criteria is applied to an in-house laser-based optical-CT scanning system presented here, and evaluated using gel-flasks containing BANG3 gel. The same gel flasks were subsequently imaged using the MR imaging protocol recommended by the gel manufacturer, but modified to match as closely as possible the RTAP. The resulting dose-maps demonstrate the high precision (< 1.3% noise at high dose) achievable with optical CT scanning while preserving high spatial resolution (<1 mm3). Using the sequence above, the MR gel-dose maps were found to have poorer precision by a factor of 5, under the strict conditions of the RTAP. The optical CT gel-dosimetry system was further evaluated for the verification of a complex 3-isocenter radiosurgery delivery. In conclusion, this work demonstrates that gel-dosimetry and optical-CT scanning approach an important long-term goal of radiation dosimetry, as specified by the RTAP criteria, and have potential to impact the clinic by improving and facilitating clinical dose verification for the most complex external beam radiation treatments.

Authors
Oldham, M; Siewerdsen, JH; Shetty, A; Jaffray, DA
MLA Citation
Oldham, M, Siewerdsen, JH, Shetty, A, and Jaffray, DA. "High resolution gel-dosimetry by optical-CT and MR scanning." Med Phys 28.7 (July 2001): 1436-1445.
PMID
11488576
Source
pubmed
Published In
Medical physics
Volume
28
Issue
7
Publish Date
2001
Start Page
1436
End Page
1445
DOI
10.1118/1.1380430

Radiation dosimetry using polymer gels: methods and applications.

New, complex radiotherapy delivery techniques require dosimeters that are able to measure complex three-dimensional dose distributions accurately and with good spatial resolution. Polymer gel is an emerging new dosimeter being applied to these challenges. The aim of this review is to present a practical overview of polymer gel dosimetry, including gel manufacture, imaging, calibration and application to radiotherapy verification. The dosimeters consist of a gel matrix within which is suspended a solution of acrylic molecules. These molecules polymerize upon exposure to radiation, with the degree of polymerization being proportional to absorbed dose. The polymer distribution can be measured in two or three dimensions using MRI or optical tomography and, after calibration, the images can be converted into radiation dose distributions. Manufacture of the gel is reported to be reproducible, and measured dose in the range 0-10 Gy is accurate to within 3-5%. In-plane image resolution of 1 mm x 1 mm, with image slice thicknesses of between 2-5 mm, is typically achievable using clinical 1.5 T MR scanners and standard T2 weighted imaging sequences. The gels have been used to verify a number of conventional and novel radiotherapy modalities, including brachytherapy, intensity modulated radiotherapy and stereotactic radiosurgery. All the studies have confirmed the value and versatility of the dosimetry technique.

Authors
McJury, M; Oldham, M; Cosgrove, VP; Murphy, PS; Doran, S; Leach, MO; Webb, S
MLA Citation
McJury, M, Oldham, M, Cosgrove, VP, Murphy, PS, Doran, S, Leach, MO, and Webb, S. "Radiation dosimetry using polymer gels: methods and applications." Br J Radiol 73.873 (September 2000): 919-929. (Review)
PMID
11064643
Source
pubmed
Published In
British Journal of Radiology
Volume
73
Issue
873
Publish Date
2000
Start Page
919
End Page
929
DOI
10.1259/bjr.73.873.11064643

Noise in polymer gel measurements using MRI.

With the development of conformal radiotherapy, particularly intensity modulated radiation therapy (IMRT), there is a clear need for multidimensional dosimeters. A commercial polymerizing gel, BANG-2 gel (MGS Research, Inc., Guilford, CT), has recently been developed that shows potential as a multi-dimensional dosimeter. This study investigates and characterizes the noise and magnetic resonance (MR) artifacts from imaging BANG-2 gels. Seven cylindrical vials (4 cm diam, 20 cm length) were irradiated end on in a water bath and read using MRI (B0=1.5 T, TE=20 ms/100 ms, TR=3000 ms). The gel calibration compared the measured depth-dose distributions in water against the change in solvent-proton R2 relaxivity of the gel. A larger vial (13 cm diam, 14 cm length) was also irradiated to test the calibration accuracy in a vial of sufficient volume for dose distribution measurements. The calibration curve proved accurate to within 1.3% in determining the depth dose measured by the larger vial. An investigation of the voxel-to-voxel (IXIX 3 mm3) noise and sensitivity response curve showed that the voxel-to-voxel variation dominated the dose measurement uncertainty. The voxel-to-voxel standard deviation ranged from 0.2 Gy for the unirradiated gel to 0.7 Gy at 20 Gy. Slice-to-slice R2 magnitude deviations were also observed corresponding to 0.2 Gy. These variations limited the overall accuracy of the gel dose measurements and warrant an investigation of more accurate MR readout sequences.

Authors
Low, DA; Markman, J; Dempsey, JF; Mutic, S; Oldham, M; Venkatesan, R; Haacke, EM; Purdy, JA
MLA Citation
Low, DA, Markman, J, Dempsey, JF, Mutic, S, Oldham, M, Venkatesan, R, Haacke, EM, and Purdy, JA. "Noise in polymer gel measurements using MRI." Med Phys 27.8 (August 2000): 1814-1817.
PMID
10984228
Source
pubmed
Published In
Medical physics
Volume
27
Issue
8
Publish Date
2000
Start Page
1814
End Page
1817
DOI
10.1118/1.1287284

Optimized MR imaging for polyacrylamide gel dosimetry.

Polyacrylamide gels are a powerful tool to measure radiation dose by quantifying the NMR T2 relaxation times of the irradiated gel. The exploitation of these radiation sensitive gels in clinical radiotherapy requires accurate mapping of T2 values. This paper describes the optimization strategy used to identify accurate and practical methods of measuring the range of T2 values typical of gel dosimeters (140-700 ms). The MR imaging techniques used to measure T2 values and the choice of image acquisition parameters are described. Four sequences are compared and the results are analysed in terms of accuracy, signal-to-noise ratio and acquisition time. A multiple spin echo sequence was found to yield the most accurate results (98.9%). Single spin echo sequences, such as Hahn spin echo and EPI spin echo, were found to measure gel T2 values with an accuracy of 90.1%. This paper reports the importance of careful selection and optimization of the MR imaging sequences for accurate and reliable polyacrylamide gel dosimetry.

Authors
Baustert, IC; Oldham, M; Smith, TA; Hayes, C; Webb, S; Leach, MO
MLA Citation
Baustert, IC, Oldham, M, Smith, TA, Hayes, C, Webb, S, and Leach, MO. "Optimized MR imaging for polyacrylamide gel dosimetry." Phys Med Biol 45.4 (April 2000): 847-858.
PMID
10795976
Source
pubmed
Published In
Physics in Medicine and Biology
Volume
45
Issue
4
Publish Date
2000
Start Page
847
End Page
858

An investigation comparing optical CT with MR scanning for polymer gel dosimetry

An overview is given of an optical scanning system and a preliminary study that compares, for the same gel samples, MR with optical scanning. The comparison has two parts: calibration methods and accuracy; and noise and resolution in dosimetric images. A novel optical calibration method with primary advantages is described in terms of speed and robustness.

Authors
Oldham, M; Siewerdsen, JH; Shetty, A; Jaffray, DA
MLA Citation
Oldham, M, Siewerdsen, JH, Shetty, A, and Jaffray, DA. "An investigation comparing optical CT with MR scanning for polymer gel dosimetry." Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings 2 (2000): 1165-1171.
Source
scival
Published In
Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings
Volume
2
Publish Date
2000
Start Page
1165
End Page
1171

Rind-therapy: A new approach to treatment and management of larger brain lesions

A new technique for the treatment and management of larger brain lesions is presented. The technique, so called rind-therapy, achieves boosting the dose to rapidly proliferating tumour tissue at the periphery of the lesion. This technique boosts the peripheral dose to effectivel levels whilst maintaining the dose to normal brain within tolerance, and maintaining low volume receiving high dose.

Authors
Oldham, M; Jaffray, DA; Zakalik, K; Chen, P; Wong, J
MLA Citation
Oldham, M, Jaffray, DA, Zakalik, K, Chen, P, and Wong, J. "Rind-therapy: A new approach to treatment and management of larger brain lesions." Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings 3 (2000): 2136-2140.
Source
scival
Published In
Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings
Volume
3
Publish Date
2000
Start Page
2136
End Page
2140

Experimental 3D dosimetry around a high-dose-rate clinical 192Ir source using a polyacrylamide gel (PAG) dosimeter.

It is well known that the experimental dosimetry of brachytherapy sources presents a challenge. Depending on the particular-dosimeter used, measurements can suffer from poor spatial resolution (ion chambers), lack of 3D information (film) or errors due to the presence of the dosimeter itself distorting the radiation flux. To avoid these problems, we have investigated the dosimetry of a clinical 192Ir source using a polyacrylamide gel (PAG) dosimeter. Experimental measurements of dose versus radial distance from the centre of the source (cross-line plots) were compared with calculations produced with a Nucletron NPS planning system. Good agreement was found between the planning system and gel measurements in planes selected for analysis. Gel dosimeter measurements in a coronal plane through the phantom showed a mean difference between measured absorbed dose and calculated dose of 0.17 Gy with SD = 0.13 Gy. Spatially, the errors at the reference point remain within one image pixel (1.0 mm). The use of polymer gel dosimetry shows promise for brachytherapy applications, offering complete, three-dimensional dose information, good spatial resolution and small measurement errors. Measurements close to the source, however, are difficult, due to some of the limiting properties of the polyacrylamide gel.

Authors
McJury, M; Tapper, PD; Cosgrove, VP; Murphy, PS; Griffin, S; Leach, MO; Webb, S; Oldham, M
MLA Citation
McJury, M, Tapper, PD, Cosgrove, VP, Murphy, PS, Griffin, S, Leach, MO, Webb, S, and Oldham, M. "Experimental 3D dosimetry around a high-dose-rate clinical 192Ir source using a polyacrylamide gel (PAG) dosimeter." Phys Med Biol 44.10 (October 1999): 2431-2444.
PMID
10533920
Source
pubmed
Published In
Physics in Medicine and Biology
Volume
44
Issue
10
Publish Date
1999
Start Page
2431
End Page
2444

Comparison of intensity-modulated tomotherapy with stereotactically guided conformal radiotherapy for brain tumors.

PURPOSE: Intensity-modulated radiotherapy (IMRT) offers the potential to more closely conform dose distributions to the target, and spare organs at risk (OAR). Its clinical value is still being defined. The present study aims to compare IMRT with stereotactically guided conformal radiotherapy (SCRT) for patients with medium size convex-shaped brain tumors. METHODS AND MATERIALS: Five patients planned with SCRT were replanned with the IMRT-tomotherapy method using the Peacock system (Nomos Corporation). The planning target volume (PTV) and relevant OAR were assessed, and compared relative to SCRT plans using dose statistics, dose-volume histograms (DVH), and the Radiation Therapy Oncology Group (RTOG) stereotactic radiosurgery criteria. RESULTS: The median and mean PTV were 78 cm3 and 85 cm3 respectively (range 62-119 cm3). The differences in PTV doses for the whole group (Peacock-SCRT +/-1 SD) were 2%+/-1.8 (minimum PTV), and 0.1%+/-1.9 (maximum PTV). The PTV homogeneity achieved by Peacock was 12.1%+/-1.7 compared to 13.9%+/-1.3 with SCRT. Using RTOG guidelines, Peacock plans provided acceptable PTV coverage for all 5/5 plans compared to minor coverage deviations in 4/5 SCRT plans; acceptable homogeneity index for both plans (Peacock = 1.1 vs. SCRT = 1.2); and comparable conformity index (1.4 each). As a consequence of the transaxial method of arc delivery, the optic nerves received mean and maximum doses that were 11.1 to 11.6%, and 10.3 to 15.2% higher respectively with Peacock plan. The maximum optic lens, and brainstem dose were 3.1 to 4.8% higher, and 0.6% lower respectively with Peacock plan. However, all doses remained below the tolerance threshold (5 Gy for lens, and 50 Gy for optic nerves) and were clinically acceptable. CONCLUSIONS: The Peacock method provided improved PTV coverage, albeit small, in this group of convex tumors. Although the OAR doses were higher using the Peacock plans, all doses remained within the clinically defined threshold and were clinically acceptable. Further improvements may be expected using other methods of IMRT planning that do not limit the treatment delivery to transaxial arcs. Each IMRT system needs to be individually assessed as the paradigm utilized may provide different outcomes.

Authors
Khoo, VS; Oldham, M; Adams, EJ; Bedford, JL; Webb, S; Brada, M
MLA Citation
Khoo, VS, Oldham, M, Adams, EJ, Bedford, JL, Webb, S, and Brada, M. "Comparison of intensity-modulated tomotherapy with stereotactically guided conformal radiotherapy for brain tumors." Int J Radiat Oncol Biol Phys 45.2 (September 1, 1999): 415-425.
PMID
10487565
Source
pubmed
Published In
International Journal of Radiation Oncology, Biology, Physics
Volume
45
Issue
2
Publish Date
1999
Start Page
415
End Page
425

Beam-orientation customization using an artificial neural network.

A methodology for the constrained customization of coplanar beam orientations in radiotherapy treatment planning using an artificial neural network (ANN) has been developed. The geometry of the patients, with cancer of the prostate, was modelled by reducing the external contour, planning target volume (PTV) and organs at risk (OARs) to a set of cuboids. The coordinates and size of the cuboids were given to the ANN as inputs. A previously developed beam-orientation constrained-customization (BOCC) scheme employing a conventional computer algorithm was used to determine the customized beam orientations in a training set containing 45 patient datasets. Twelve patient datasets not involved in the training of the artificial neural network were used to test whether the ANN was able to map the inputs to customized beam orientations. Improvements from the customized beam orientations were compared with standard treatment plans with fixed gantry angles and plans produced from the BOCC scheme. The ANN produced customized beam orientations within 5 degrees of the BOCC scheme in 62.5% of cases. The average difference in the beam orientations produced by the ANN and the BOCC scheme was 7.7 degrees (+/-1.7, 1 SD). Compared with the standard treatment plans, the BOCC scheme produced plans with an increase in the average tumour control probability (TCP) of 5.7% (+/-1.4, 1 SD) whilst the ANN generated plans increased the average TCP by 3.9% (+/-1.3, 1 SD). Both figures refer to the TCP at a fixed rectal normal tissue complication probability (NTCP) of 1%. In conclusion, even using a very simple model for the geometry of the patient, an ANN was able to produce beam orientations that were similar to those produced by a conventional computer algorithm.

Authors
Rowbottom, CG; Webb, S; Oldham, M
MLA Citation
Rowbottom, CG, Webb, S, and Oldham, M. "Beam-orientation customization using an artificial neural network." Phys Med Biol 44.9 (September 1999): 2251-2262.
PMID
10495119
Source
pubmed
Published In
Physics in Medicine and Biology
Volume
44
Issue
9
Publish Date
1999
Start Page
2251
End Page
2262

Dynamics of polymerization in polyacrylamide gel (PAG) dosimeters: (I) ageing and long-term stability.

Few quantitative data are available on the kinetics of polymerization reactions in polymer gel (PAG) dosimeters and their long-term stability. Post-irradiation polymerization reactions have been found to continue for several weeks, posing questions regarding dosimeter stability and its achievement. In this paper we report an investigation of polymerization kinetics in PAG dosimeters and the effect of diffusing oxygen into the dosimeter, post irradiation, as a potential method of inhibiting further polymerization and stabilizing the dose distribution. Results show continuous post-irradiation changes in transverse relaxation rate R2 with time over the five week study period and that a steady-state may not be reached for a period of months. An assessment is made of the appropriate time to image the dosimeter which shows that after three to four days the polymerization change is slow compared with imaging time. The implications of the time delay between irradiation and imaging are discussed in terms of the resultant sensitivity of the dosimeter and accuracy of the dose measured. In pairs of dosimeters, one sealed the other open to air, oxygen diffusing into the dosimeter arrests polymerization. However, the diffusion rate is too slow to make this method practicable. The slow diffusion means that while in regions near the air/gel interface polymerization is quickly arrested, in deeper regions it may continue for many hours, causing artefacts in the dose distribution. In the companion paper to this from a collaborating team, a study focusing on modelling oxygen diffusion in dosimeter gel will be presented.

Authors
McJury, M; Oldham, M; Leach, MO; Webb, S
MLA Citation
McJury, M, Oldham, M, Leach, MO, and Webb, S. "Dynamics of polymerization in polyacrylamide gel (PAG) dosimeters: (I) ageing and long-term stability." Phys Med Biol 44.8 (August 1999): 1863-1873.
PMID
10473200
Source
pubmed
Published In
Physics in Medicine and Biology
Volume
44
Issue
8
Publish Date
1999
Start Page
1863
End Page
1873

A comparison of coplanar four-field techniques for conformal radiotherapy of the prostate.

BACKGROUND AND PURPOSE: Conformal radiotherapy of the prostate is an increasingly common technique, but the optimal choice of beam configuration remains unclear. This study systematically compares a number of coplanar treatment plans for four-field irradiation of two different clinical treatment volumes: prostate only (PO) and the prostate plus seminal vesicles (PSV). MATERIALS AND METHODS: A variety of four-field coplanar treatment plans were created for PO and PSV volumes in each of ten patients. Plans included a four-field 'box' plan, a symmetric plan having bilateral anterior and posterior oblique fields, a plan with anterior oblique and lateral fields, a series of asymmetric plans, and a three-field plan having anterior and bilateral fields for comparison. Doses of 64 and 74 Gy were prescribed to the isocentre. Plans were compared using the volume of rectum irradiated to greater than 50% (V50), 80% (V80) and 90% (V90) of the prescribed dose. Tumour control probabilities (TCP) and normal tissue complication probabilities (NTCP) for the rectum, bladder and femoral heads were also evaluated. Femoral head dose was limited such that less than 10% of each femoral head received 70% of the prescribed dose. RESULTS: For the PO group, the optimal plan consisted of anterior oblique and lateral fields (Rectal V80 = 23.8+/-5.0% (1 SD)), while the box technique (V80 = 26.0+/-5.8%) was less advantageous in terms of rectal sparing (P = 0.001). Similar results were obtained for the PSV group (Rectal V80 = 43.9+/-5.0% and 47.3+/-5.5% for the two plan types, respectively, P = 0.001). The three-field plan was comparable to the optimal four-field plan but gave higher superficial body dose. With dose escalation from 64 to 74 Gy, the mean TCP for the optimal plan rose from 52.0+/-2.8% to 74.1+/-2.0%. Meanwhile, rectal NTCP for the optimal plan rose by 3.5% (PO) or 8.4% (PSV), compared to 4.7% (PO) or 10.1% (PSV) for the box plan. CONCLUSIONS: For PO volumes, a plan with gantry angles of 35 degrees, 90 degrees, 270 degrees and 325 degrees offers a high level of rectal sparing and acceptable dose to the femoral heads for all patients, while for PSV volumes, the corresponding plan has gantry angles of 20 degrees, 90 degrees , 270 degrees and 340 degrees. Using these plans, the gain in TCP resulting from dose escalation can be achieved with a smaller increase in anticipated rectal NTCP.

Authors
Bedford, JL; Khoo, VS; Oldham, M; Dearnaley, DP; Webb, S
MLA Citation
Bedford, JL, Khoo, VS, Oldham, M, Dearnaley, DP, and Webb, S. "A comparison of coplanar four-field techniques for conformal radiotherapy of the prostate." Radiother Oncol 51.3 (June 1999): 225-235.
PMID
10435818
Source
pubmed
Published In
Radiotherapy & Oncology
Volume
51
Issue
3
Publish Date
1999
Start Page
225
End Page
235

Is it possible to optimize a radiotherapy treatment plan?

Authors
Rowbottom, CG; Webb, S; Oldham, M
MLA Citation
Rowbottom, CG, Webb, S, and Oldham, M. "Is it possible to optimize a radiotherapy treatment plan?." Int J Radiat Oncol Biol Phys 43.3 (February 1, 1999): 698-699. (Letter)
PMID
10078659
Source
pubmed
Published In
International Journal of Radiation Oncology, Biology, Physics
Volume
43
Issue
3
Publish Date
1999
Start Page
698
End Page
699

Constrained customization of non-coplanar beam orientations in radiotherapy of brain tumours.

A methodology for the constrained customization of non-coplanar beam orientations in radiotherapy treatment planning has been developed and tested on a cohort of five patients with tumours of the brain. The methodology employed a combination of single and multibeam cost functions to produce customized beam orientations. The single-beam cost function was used to reduce the search space for the multibeam cost function, which was minimized using a fast simulated annealing algorithm. The scheme aims to produce well-spaced, customized beam orientations for each patient that produce low dose to organs at risk (OARs). The customized plans were compared with standard plans containing the number and orientation of beams chosen by a human planner. The beam orientation constraint-customized plans employed the same number of treatment beams as the standard plan but with beam orientations chosen by the constrained-customization scheme. Improvements from beam orientation constraint-customization were studied in isolation by customizing the beam weights of both plans using a dose-based downhill simplex algorithm. The results show that beam orientation constraint-customization reduced the maximum dose to the orbits by an average of 18.8 (+/-3.8, ISD)% and to the optic nerves by 11.4 (+/-4.8, ISD)% with no degradation of the planning target volume (PTV) dose distribution. The mean doses, averaged over the patient cohort, were reduced by 4.2 (+/-1.1, ISD)% and 12.4 (+/-3.1, ISD)% for the orbits and optic nerves respectively. In conclusion, the beam orientation constraint-customization can reduce the dose to OARs, for few-beam treatment plans, when compared with standard treatment plans developed by a human planner.

Authors
Rowbottom, CG; Oldham, M; Webb, S
MLA Citation
Rowbottom, CG, Oldham, M, and Webb, S. "Constrained customization of non-coplanar beam orientations in radiotherapy of brain tumours." Phys Med Biol 44.2 (February 1999): 383-399.
PMID
10070789
Source
pubmed
Published In
Physics in Medicine and Biology
Volume
44
Issue
2
Publish Date
1999
Start Page
383
End Page
399

Dose mapping of inhomogeneities positioned in radiosensitive polymer gels

A gel matrix (gelatin), infused with acrylamide monomer and a crosslinking agent has been used as a three-dimensional dosimeter of X- and γ-rays as used in radiotherapy. Magnetic resonance imaging is used to create a parameter map of transverse relaxation time (T2) from which a map of absorbed dose is calculated. We are using the technique to investigate the interfacial radiation patterns resulting from the presence of implanted inhomogeneities in the gel phantom being irradiated, a concept which is as yet underdeveloped. The inhomogeneities, which may be either low or high density with respect to the surrounding medium, are designed to simulate the effects of air cavities or bone in the body and their effects on the absorbed dose during radiotherapy. This paper explores ways of introducing inhomogeneities into the gel and presents results of dose maps obtained post irradiation. An inherent problem of the dosimeter is the inhibition of polymerisation due to dissolved oxygen. Free radicals produced by the incident radiation are key to the polymerisation and crosslinking effects but are consumed by the dissolved oxygen. This paper describes the observed effects of oxygen contamination within a gel and suggests steps to be taken to minimise the problem. © 1999 Elsevier Science B.V. All rights reserved.

Authors
Hepworth, SJ; McJury, M; Oldham, M; Morton, EJ; Doran, SJ
MLA Citation
Hepworth, SJ, McJury, M, Oldham, M, Morton, EJ, and Doran, SJ. "Dose mapping of inhomogeneities positioned in radiosensitive polymer gels." Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 422.1-3 (1999): 756-760.
Source
scival
Published In
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
Volume
422
Issue
1-3
Publish Date
1999
Start Page
756
End Page
760
DOI
10.1016/S0168-9002(98)01031-6

A comparison of conventional and conformal radiotherapy of the oesophagus: Work in progress

A retrospective treatment planning study was carried out in five patients to assess the effectiveness of conformal radiotherapy of the oesophagus. A two-phase conventional treatment plan was created for each patient, with a prescribed dose of 55 Gy. This plan was compared with a single-phase conformal plan consisting of the same field arrangement as the second phase of the conventional treatment, but with conformal blocks shaped to the beam's eye view of the planning target volume. A further comparison was made between the conventional plan and a two-phase plan using the same beam angles and weights as the conventional plan, but with conformal field shapes. The effectiveness of each treatment plan was assessed using dose-volume histograms and normal tissue complication probabilities for the lungs. On average, the single-phase conformal technique increased the mean lung dose from 22.5% (± 6.2 SD) of the prescribed dose to 29.5% (± 5.2 SD) compared with the conventional technique (p = 0.0001). This indicates that this technique did not offer any benefit in terms of reducing the risk of pneumonitis. However, the two-phase conformal technique reduced the mean lung dose from 22.5% (± 6.2 SD) of the prescribed dose to 19.8% (± 4.6 SD) (p = 0.03), showing that this technique should reduce the risk of pneumonitis. Further work is underway to study more patients and to investigate tumour control probability and dose escalation.

Authors
Guzel, Z; Bedford, JL; Childs, PJ; Nahum, AE; Webb, S; Oldham, M; Tait, D
MLA Citation
Guzel, Z, Bedford, JL, Childs, PJ, Nahum, AE, Webb, S, Oldham, M, and Tait, D. "A comparison of conventional and conformal radiotherapy of the oesophagus: Work in progress." British Journal of Radiology 71.OCT. (October 27, 1998): 1076-1082.
Source
scopus
Published In
British Journal of Radiology
Volume
71
Issue
OCT.
Publish Date
1998
Start Page
1076
End Page
1082

A comparison of conventional and conformal radiotherapy of the oesophagus: work in progress.

A retrospective treatment planning study was carried out in five patients to assess the effectiveness of conformal radiotherapy of the oesophagus. A two-phase conventional treatment plan was created for each patient, with a prescribed dose of 55 Gy. This plan was compared with a single-phase conformal plan consisting of the same field arrangement as the second phase of the conventional treatment, but with conformal blocks shaped to the beam's eye view of the planning target volume. A further comparison was made between the conventional plan and a two-phase plan using the same beam angles and weights as the conventional plan, but with conformal field shapes. The effectiveness of each treatment plan was assessed using dose--volume histograms and normal tissue complication probabilities for the lungs. On average, the single-phase conformal technique increased the mean lung dose from 22.5% (+/- 6.2 SD) of the prescribed dose to 29.5% (+/- 5.2 SD) compared with the conventional technique (p = 0.0001). This indicates that this technique did not offer any benefit in terms of reducing the risk of pneumonitis. However, the two-phase conformal technique reduced the mean lung dose from 22.5% (+/- 6.2 SD) of the prescribed dose to 19.8% (+/- 4.6 SD)(p = 0.03), showing that this technique should reduce the risk of pneumonitis. Further work is underway to study more patients and to investigate tumour control probability and dose escalation.

Authors
Guzel, Z; Bedford, JL; Childs, PJ; Nahum, AE; Webb, S; Oldham, M; Tait, D
MLA Citation
Guzel, Z, Bedford, JL, Childs, PJ, Nahum, AE, Webb, S, Oldham, M, and Tait, D. "A comparison of conventional and conformal radiotherapy of the oesophagus: work in progress." Br J Radiol 71.850 (October 1998): 1076-1082.
PMID
10211069
Source
pubmed
Published In
British Journal of Radiology
Volume
71
Issue
850
Publish Date
1998
Start Page
1076
End Page
1082
DOI
10.1259/bjr.71.850.10211069

Improving calibration accuracy in gel dosimetry.

A new method of calibrating gel dosimeters (applicable to both Fricke and polyacrylamide gels) is presented which has intrinsically higher accuracy than current methods, and requires less gel. Two test-tubes of gel (inner diameter 2.5 cm, length 20 cm) are irradiated separately with a 10 x 10 cm2 field end-on in a water bath, such that the characteristic depth-dose curve is recorded in the gel. The calibration is then determined by fitting the depth-dose measured in water, against the measured change in relaxivity with depth in the gel. Increased accuracy is achieved in this simple depth-dose geometry by averaging the relaxivity at each depth. A large number of calibration data points, each with relatively high accuracy, are obtained. Calibration data over the full range of dose (1.6-10 Gy) is obtained by irradiating one test-tube to 10 Gy at dose maximum (Dmax), and the other to 4.5 Gy at Dmax. The new calibration method is compared with a 'standard method' where five identical test-tubes of gel were irradiated to different known doses between 2 and 10 Gy. The percentage uncertainties in the slope and intercept of the calibration fit are found to be lower with the new method by a factor of about 4 and 10 respectively, when compared with the standard method and with published values. The gel was found to respond linearly within the error bars up to doses of 7 Gy, with a slope of 0.233 +/- 0.001 s(-1) Gy(-1) and an intercept of 1.106 +/- 0.005 Gy. For higher doses, nonlinear behaviour was observed.

Authors
Oldham, M; McJury, M; Baustert, IB; Webb, S; Leach, MO
MLA Citation
Oldham, M, McJury, M, Baustert, IB, Webb, S, and Leach, MO. "Improving calibration accuracy in gel dosimetry." Phys Med Biol 43.10 (October 1998): 2709-2720.
PMID
9814511
Source
pubmed
Published In
Physics in Medicine and Biology
Volume
43
Issue
10
Publish Date
1998
Start Page
2709
End Page
2720

A case study comparing the relative benefit of optimizing beam weights, wedge angles, beam orientations and tomotherapy in stereotactic radiotherapy of the brain.

A treatment-planning case study has been performed on a patient with a medium-sized, convex brain tumour. The study involved the application of advanced treatment-plan optimization techniques to improve on the dose distribution of the 'standard plan' used to treat the patient. The standard plan was created according to conventional protocol at the Royal Marsden NHS Trust, and consisted of a three-field (one open and two wedged) non-coplanar arrangement, with field shaping to the beam's-eye view of the planning target volume (PTV). Three optimized treatment plans were created corresponding to (i) the optimization of the beam weights and wedge angles of the standard plan, (ii) the optimization of the beam orientations, beam weights and wedge angles of the standard plan, and (iii) a full fluence tomotherapy optimization of 1 cm wide (at isocentre), 270 degree arcs. (i) and (ii) were created on the VOXELPLAN research 3D treatment-planning system, using in-house developed optimization algorithms, and (iii) was created on the PEACOCK tomotherapy planning system. The downhill-simplex optimization algorithm is used, in conjunction with 'threshold-dose' cost-function terms enabling the algorithm to optimize specific regions of the dose-volume histogram (DVH) curve. The 'beam-cost plot' tool is presented as a visual aid to the selection of beneficial beam directions. The methods and pitfalls in the transfer of plans and patient data between the two planning systems are discussed. Each optimization approach was evaluated, relative to the standard plan, on the basis of DVH and dose statistics in the PTV and organs at risk (OARs). All three optimization approaches were able to improve on the dose distribution of the standard plan. The magnitude of the improvement was greater for the optimized beam-orientation and tomotherapy plans (up to 15% and 30% for the maximum and mean OAR doses). A smaller improvement was observed in the beam-weight and wedge-angle optimized plan (up to 5% and 10% in the maximum and mean OAR doses). In the tomotherapy plan, difficulty was encountered achieving an acceptable homogeneity of dose in the PTV. This was improved by treating the gross tumour volume (GTV) and (PTV - GTV) regions as separate targets in the inverse planning, with the latter region prescribed a slightly higher dose to reduce edge under-dosing. In conclusion, for the medium-sized convex tumour studied, the tomotherapy dose distribution showed a significant improvement on the standard plan, but no significant improvement over a conventional three-field plan where the beam orientations, beam weights and wedge angles had been optimized.

Authors
Oldham, M; Khoo, VS; Rowbottom, CG; Bedford, JL; Webb, S
MLA Citation
Oldham, M, Khoo, VS, Rowbottom, CG, Bedford, JL, and Webb, S. "A case study comparing the relative benefit of optimizing beam weights, wedge angles, beam orientations and tomotherapy in stereotactic radiotherapy of the brain." Phys Med Biol 43.8 (August 1998): 2123-2146.
PMID
9725594
Source
pubmed
Published In
Physics in Medicine and Biology
Volume
43
Issue
8
Publish Date
1998
Start Page
2123
End Page
2146

Improvements in prostate radiotherapy from the customization of beam directions.

A methodology for optimizing the beam directions in radiotherapy treatment planning has been developed and tested on a cohort of twelve prostate patients. An optimization algorithm employing a an objective cost function was used, based on beam's-eye-view volumetrics but also employing a simple dose model and biological considerations for organs-at-risk (OARs). The cost function embodies information about the volume of OARs in a single field and their position relative to the planning target volume (PTV). The proximity of the PTV to the surface of the patient is also included. Within the algorithm "importance factor" were used to model the clinical importance of different organs-at-risk so that all organs-at-risk were included in a single objective score. "Gantry-angle-windows" were introduced to restrict the available beam directions. The methodology was applied to twelve prostate patients to determine the optimum beam directions for three-field direction plans. Orientation-optimized and standard treatment plans were compared via measures of tumor control probability (TCP) and normal tissue complication probability (NTCP). Standard plans had fixed beam directions whereas orientation-optimized plans contained beam directions chosen by the algorithm. The beam-weights of both the orientation-optimized and standard plans were optimized using a dose-based simulated annealing algorithm to allow the improvements by optimizing the beam directions to be studied in isolation. The results of the comparison show that optimization of the beam directions yielded better plans, in terms of TCP and NTCP, than the standard plans. When the dose to the isocenter was scaled to produce a rectal NTCP of 1%, the average TCP of the orientation-optimized plans was (5.7 +/- 1.4)% greater than that for the standard plans. In conclusion, the customization of beam directions in the treatment planning of prostate patients using and objective cost function and allowed gantry-angle-windows produces superior three-field direction plans compared to standard treatment plans.

Authors
Rowbottom, CG; Webb, S; Oldham, M
MLA Citation
Rowbottom, CG, Webb, S, and Oldham, M. "Improvements in prostate radiotherapy from the customization of beam directions." Med Phys 25.7 Pt 1 (July 1998): 1171-1179.
PMID
9682202
Source
pubmed
Published In
Medical physics
Volume
25
Issue
7 Pt 1
Publish Date
1998
Start Page
1171
End Page
1179
DOI
10.1118/1.598308

An investigation into the dosimetry of a nine-field tomotherapy irradiation using BANG-gel dosimetry.

BANG-gel dosimetry offers the potential for measuring the dose delivered by a radiotherapy treatment technique, in three dimensions, with high spatial resolution and good accuracy. The ability to measure comprehensively a 3D dose distribution is a major advantage of the gel dosimeter over conventional planar and point-based dosimeter devices, particularly when applied to the verification of complex dose distributions characteristic of intensity-modulated radiotherapy (IMRT). In this paper an in-house manufactured BANG-gel dosimeter was applied to study the dose distributions of two irradiation experiments for which the distributions were known: (i) a dosimetrically simple parallel-opposed irradiation, and (ii) a more complex nine-field 'static tomotherapy' intensity-modulated irradiation delivered with the Nomos MIMiC. The uniform distribution in (i) allowed a study of the magnetic resonance (MR) imaging parameters to achieve an optimal trade-off between noise and image resolution (optimum image resolution for the Siemens 1.5T Vision system was determined to be approximately 0.8 mm2 with a slice thickness of 2 mm). The spatial uniformity of gel sensitivity to radiation was found to depend strongly on the presence of oxygen, which must be eliminated for the gel dosimeter to be of use. The gel dosimeter was found to agree well with predicted dose distributions and accurately measured the steep penumbral fall-off of dose, even after many days, proving its potential for the verification of IMRT distributions. In the nine-field IMRT delivery (ii) the predicted dose was computed by both an in-house 'component-delivery' dose algorithm and the Peacock planning-system dose algorithm. Good agreement was found between the two algorithms despite the latter's omission of the change in penumbral characteristics with aperture-size during delivery, lack of inhomogeneity correction and approximate modelling of leaf leakage. These effects were found to be small for the problem studied. The predicted distribution agreed well with the gel-measured distribution at medium and high doses (50-90% isodose lines) although differences of up to 10% were observed at lower doses (30% isodose line). The gel dosimeter was found to have the potential to verify IMRT distributions but required considerable care to achieve accurate results. Attention was required to achieve uniformity of gel sensitivity (to prevent oxygen contamination), and in the calibration process.

Authors
Oldham, M; Baustert, I; Lord, C; Smith, TA; McJury, M; Warrington, AP; Leach, MO; Webb, S
MLA Citation
Oldham, M, Baustert, I, Lord, C, Smith, TA, McJury, M, Warrington, AP, Leach, MO, and Webb, S. "An investigation into the dosimetry of a nine-field tomotherapy irradiation using BANG-gel dosimetry." Phys Med Biol 43.5 (May 1998): 1113-1132.
PMID
9623644
Source
pubmed
Published In
Physics in Medicine and Biology
Volume
43
Issue
5
Publish Date
1998
Start Page
1113
End Page
1132

Improvements in prostate radiotherapy from the customization of beam directions

A methodology for optimizing the beam directions in radiotherapy treatment planning has been developed and tested on a cohort of twelve prostate patients. An optimization algorithm employing an objective cost function was used, based on beam's-eye-view volumetrics but also employing a simple dose model and biological considerations for organs-at-risk (OARs). The cost function embodies information about the volume of OARs in a single field and their position relative to the planning target volume (PTV). The proximity of the PTV to the surface of the patient is also included. Within the algorithm 'importance factors' were used to model the clinical importance of different organs-at-risk so that all organs-at-risk were included in a single objective score. 'Gantryangle-windows' were introduced to restrict the available beam directions. The methodology was applied to twelve prostate patients to determine the optimum beam directions for three-field direction plans. Orientation-optimized and standard treatment plans were compared via measures of tumor control probability (TCP) and normal tissue complication probability (NTCP). Standard plans had fixed beam directions whereas orientation-optimized plans contained beam directions chosen by the algorithm. The beam-weights of both the orientation-optimized and standard plans were optimized using a dose-based simulated annealing algorithm to allow the improvements by optimizing the beam directions to be studied in isolation. The results of the Comparison show that optimization of the beam directions yielded better plans, in terms of TCP and NTCP, than the standard plans. When the dose to the isocenter was scaled to produce a rectal NTCP of 1%, the average TCP of the orientation-optimized plans was (5.7±1.4)% greater than that for the standard plans. In conclusion, the customization of beam directions in the treatment planning of prostate patients using an objective cost function and allowed gantry-angle-windows produces superior three-field direction plans compared to standard treatment plans.

Authors
Rowbottom, CG; Webb, S; Oldham, M
MLA Citation
Rowbottom, CG, Webb, S, and Oldham, M. "Improvements in prostate radiotherapy from the customization of beam directions." Medical Physics 25.7 I (1998): 1171-1179.
Source
scival
Published In
Medical physics
Volume
25
Issue
7 I
Publish Date
1998
Start Page
1171
End Page
1179
DOI
10.1118/1.598308

Methods for transferring patient and plan data between radiotherapy treatment planning systems

The effectiveness of conformai radiotherapy can ultimately only be assessed by the use of clinical trials. As large multicentre clinical trials become more widespread, methods of transferring patient and plan data between radiotherapy treatment planning systems become increasingly important. In this paper, the general strategy for the transfer of data is discussed, and also illustrated with reference to two specific systems: TARGET 2 (GE Medical Systems) and VOXELPLAN (DKFZ-Heidelberg). The transfer method involves using a computer program to translate the data formats used by each of the two systems for CT scans, patient outlines, plan information and block descriptions. This paper does not address the question of transferring beam data between systems: beam data must first be entered separately into both machines. The physical concepts encountered when transferring plans are described, with specific reference to the two planning systems used. Differences in the strategies used by the two planning systems for definition of irregular field shapes are compared. The dose calculations used by the two systems are also briefly evaluated. Isodoses produced by VOXELPLAN around a circular target volume are found to be up to 3 mm different in location to those produced by TARGET 2, owing to the use of a smooth field shape contour as opposed to a stepped field shape which closely models the leaves of a multileaf collimator. In general, dose distributions generated by both systems are comparable, but some differences are found in the presence of large tissue inhomogeneities. It is concluded that the transfer of patient and plan data between two different treatment planning systems is feasible, provided that any differences in field shape definition methods or dose calculation methods between the two systems are understood. © 1997 The British Institute of Radiology.

Authors
Bedford, JL; Oldham, M; Hoess, A; Evans, PM; Shentall, GS; Webb, S
MLA Citation
Bedford, JL, Oldham, M, Hoess, A, Evans, PM, Shentall, GS, and Webb, S. "Methods for transferring patient and plan data between radiotherapy treatment planning systems." British Journal of Radiology 70.JULY (December 1, 1997): 740-749.
Source
scopus
Published In
British Journal of Radiology
Volume
70
Issue
JULY
Publish Date
1997
Start Page
740
End Page
749

Methods for transferring patient and plan data between radiotherapy treatment planning systems.

The effectiveness of conformal radiotherapy can ultimately only be assessed by the use of clinical trials. As large multicentre clinical trials become more widespread, methods of transferring patient and plan data between radiotherapy treatment planning systems become increasingly important. In this paper, the general strategy for the transfer of data is discussed, and also illustrated with reference to two specific systems: TARGET 2 (GE Medical Systems) and VOXELPLAN (DKFZ-Heidelberg). The transfer method involves using a computer program to translate the data formats used by each of the two systems for CT scans, patient outlines, plan information and block descriptions. This paper does not address the question of transferring beam data between systems: beam data must first be entered separately into both machines. The physical concepts encountered when transferring plans are described, with specific reference to the two planning systems used. Differences in the strategies used by the two planning systems for definition of irregular field shapes are compared. The dose calculations used by the two systems are also briefly evaluated. Isodoses produced by VOXELPLAN around a circular target volume are found to be up to 3 mm different in location to those produced by TARGET 2, owing to the use of a smooth field shape contour as opposed to a stepped field shape which closely models the leaves of a multileaf collimator. In general, dose distributions generated by both systems are comparable, but some differences are found in the presence of large tissue inhomogeneities. It is concluded that the transfer of patient and plan data between two different treatment planning systems is feasible, provided that any differences in field shape definition methods or dose calculation methods between the two systems are understood.

Authors
Bedford, JL; Oldham, M; Hoess, A; Evans, PM; Shentall, GS; Webb, S
MLA Citation
Bedford, JL, Oldham, M, Hoess, A, Evans, PM, Shentall, GS, and Webb, S. "Methods for transferring patient and plan data between radiotherapy treatment planning systems." Br J Radiol 70.835 (July 1997): 740-749.
PMID
9245886
Source
pubmed
Published In
British Journal of Radiology
Volume
70
Issue
835
Publish Date
1997
Start Page
740
End Page
749
DOI
10.1259/bjr.70.835.9245886

Intensity-modulated radiotherapy by means of static tomotherapy: a planning and verification study.

There is currently much research interest in developing, evaluating, and verifying intensity-modulation techniques. Of particular interest is how well the delivery of intensity-modulated profiles can be simulated by planning algorithms, and how accurately these profiles can be delivered given the specification constraints of linear accelerators. In this paper we present a planning and verification study based on delivering radiation in "static-tomotherapy" mode via the NOMOS MIMiC (Multileaf intensity-modulation collimator), which sheds some light on these issues. An inverse-planning algorithm was used to compute intensity-modulated profiles for a 9-coplanar-field plan for a body phantom. The algorithm makes several approximations about the form of the elementary fluence profile through bixels during delivery. Specifically, it is independent of the state of adjacent bixels (i.e., open or closed) and obeys the superposition principle. From the standpoint of comparing the predicted versus the delivered dose, these assumptions were made irrelevant by a final one-step forward dose calculation performed using the optimized intensity profiles. This forward dose calculation took into account the penumbral characteristics of the delivery system by decomposing the intensity profiles into the set of delivery components. Each component was assigned the appropriate penumbral functions thereby ensuring that the calculated dose distribution closely predicted the delivered dose distribution. The nine intensity modulated fields were delivered to a perspex phantom with the same geometry, containing a verification film. In general good agreement was found between the predicted and the measured delivered dose distributions. All the main features of the predicted dose distribution are seen in the delivered. The 90% isodoses were consistently in spatial agreement to within 3 mm. At the 50% isodose level consistent spatial agreement was again found to within 3 mm, the largest deviation being about 5 mm. The close correspondence between the predicted and measured dose distribution demonstrates the potential of the MIMiC delivery system. Our results indicate the level of dose conformation that is achievable in practice and the accuracy of the dose computation algorithm. However, this study only concerned delivery of radiation to a 2 cm thick slice, and the dose distribution was only verified in the central plane of the phantom where the film was placed. We therefore cannot comment as yet on what happens to the dose distribution away from the central film-plane.

Authors
Oldham, M; Webb, S
MLA Citation
Oldham, M, and Webb, S. "Intensity-modulated radiotherapy by means of static tomotherapy: a planning and verification study." Med Phys 24.6 (June 1997): 827-836.
PMID
9198015
Source
pubmed
Published In
Medical physics
Volume
24
Issue
6
Publish Date
1997
Start Page
827
End Page
836
DOI
10.1118/1.598003

Advanced methods for delivering conformal therapy and dose planning techniques

Highly-conformal dose-distributions can be created by the superposition of many radiation fields from different directions, each with its intensity spatially modulated. One class of treatment technique, sometimes referred to as tomotherapy, involves creating a narrow slit of radiation and modulating the intensity of the radiation along the slit with a series of small stubby vanes moving at right angles to the long axis of the slit aperture. At the planning stage, the intensity of radiation of each beam-element (or bixel) is determined by working out the effect of superposing the radiation through all bixels using an elemental dose-distribution specified as that for a single bixel with all its neighbours closed. However, at the treatment delivery stage neighbouring bixels may not necessarily be closed. Instead the slit beam is delivered with the vanes closed for different periods of time to create the intensity-modulation. As a result, the three-dimensional dose- distribution actually delivered will be different from that determined at the planning stage. This paper explores these differences. At the planning stage an elemental dose contribution was assumed that corresponded to that for a single open bixel of a NOMOS MIMIC prototype collimator either: i) as directly measured or ii) as fitted to a 'stretched function' with the property that combinations of adjacent open bixels create a flat field. Delivery was simulated in two modes. The 3D dose-distribution has been computed in 'independent vane (IV)' mode, corresponding to delivery of each bixel component independently in time and in 'component delivery (CD)' mode which models the actual treatment geometry in which the 'walls' of a bixel have different configurations for different fractions of the total irradiation time per bixel. CD-mode delivery has been coded and the resulting 3D dose distributions compared with the planned (IV) dose-distributions. The CD-mode dose-distributions are better matched to the IV-mode dose distributions when the latter are calculated using the stretched fit to the elemental dose-distribution. However there are still differences which the inverse-planning calculation does not take into account. The CD-mode dose distributions compared favourably with experimental delivery with a prototype NOMOS MIMIC collimator attached to a Philips SL75/5 accelerator.

Authors
Webb, S; Oldham, M
MLA Citation
Webb, S, and Oldham, M. "Advanced methods for delivering conformal therapy and dose planning techniques." Physica Medica 13.SUPPL. 1 (1997): 39-44.
Source
scival
Published In
Physica Medica
Volume
13
Issue
SUPPL. 1
Publish Date
1997
Start Page
39
End Page
44

Methods for transferring patient and plan data between radiotherapy treatment planning systems

The effectiveness of conformai radiotherapy can ultimately only be assessed by the use of clinical trials. As large multicentre clinical trials become more widespread, methods of transferring patient and plan data between radiotherapy treatment planning systems become increasingly important. In this paper, the general strategy for the transfer of data is discussed, and also illustrated with reference to two specific systems: TARGET 2 (GE Medical Systems) and VOXELPLAN (DKFZ-Heidelberg). The transfer method involves using a computer program to translate the data formats used by each of the two systems for CT scans, patient outlines, plan information and block descriptions. This paper does not address the question of transferring beam data between systems: beam data must first be entered separately into both machines. The physical concepts encountered when transferring plans are described, with specific reference to the two planning systems used. Differences in the strategies used by the two planning systems for definition of irregular field shapes are compared. The dose calculations used by the two systems are also briefly evaluated. Isodoses produced by VOXELPLAN around a circular target volume are found to be up to 3 mm different in location to those produced by TARGET 2, owing to the use of a smooth field shape contour as opposed to a stepped field shape which closely models the leaves of a multileaf collimator. In general, dose distributions generated by both systems are comparable, but some differences are found in the presence of large tissue inhomogeneities. It is concluded that the transfer of patient and plan data between two different treatment planning systems is feasible, provided that any differences in field shape definition methods or dose calculation methods between the two systems are understood. © 1997 The British Institute of Radiology.

Authors
Bedford, JL; Oldham, M; Hoess, A; Evans, PM; Shentall, GS; Webb, S
MLA Citation
Bedford, JL, Oldham, M, Hoess, A, Evans, PM, Shentall, GS, and Webb, S. "Methods for transferring patient and plan data between radiotherapy treatment planning systems." British Journal of Radiology 70.JULY (1997): 740-749.
Source
scival
Published In
British Journal of Radiology
Volume
70
Issue
JULY
Publish Date
1997
Start Page
740
End Page
749

A method to study the characteristics of 3D dose distributions created by superposition of many intensity-modulated beams delivered via a slit aperture with multiple absorbing vanes.

Highly conformal dose distributions can be created by the superposition of many radiation fields from different directions, each with its intensity spatially modulated by the method known as tomotherapy. At the planning stage, the intensity of radiation of each beam element (or bixel) is determined by working out the effect of superposing the radiation through all bixels with the elemental dose distribution specified as that from a single bixel with all its neighbours closed (the 'independent-vane' (IV) model). However, at treatment-delivery stage, neighbouring bixels may not be closed. Instead the slit beam is delivered with parts of the beam closed for different periods of time to create the intensity modulation. As a result, the 3D dose distribution actually delivered will differ from that determined at the planning stage if the elemental beams do not obey the superposition principle. The purpose of this paper is to present a method to investigate and quantify the relation between planned and delivered 3D dose distributions. Two modes of inverse planning have been performed: (i) with a fit to the measured elemental dose distribution and (ii) with a 'stretched fit' obeying the superposition principle as in the PEACOCK 3D planning system. The actual delivery has been modelled as a series of component deliveries (CDs). The algorithm for determining the component intensities and the appropriate collimation conditions is specified. The elemental beam from the NOMOS MIMiC collimator is too narrow to obey the superposition principle although it can be 'stretched' and fitted to a superposition function. Hence there are differences between the IV plans made using modes (i) and (ii) and the raw and the stretched elemental beam, and also differences with CD delivery. This study shows that the differences between IV and CD dose distributions are smaller for mode (ii) inverse planning than for mode (i), somewhat justifying the way planning is done within PEACOCK. Using a stretched elemental beam is a useful adjustment to improve the accuracy of inverse planning but the 3D dose distribution actually delivered will display characteristics of the collimation.

Authors
Webb, S; Oldham, M
MLA Citation
Webb, S, and Oldham, M. "A method to study the characteristics of 3D dose distributions created by superposition of many intensity-modulated beams delivered via a slit aperture with multiple absorbing vanes." Phys Med Biol 41.10 (October 1996): 2135-2153.
PMID
8912386
Source
pubmed
Published In
Physics in Medicine and Biology
Volume
41
Issue
10
Publish Date
1996
Start Page
2135
End Page
2153

The optimisation of wedge filters in radiotherapy of the prostate.

A treatment plan optimisation algorithm has been applied to 12 patients with early prostate cancer in order to determine the optimum beam-weights and wedge angles for a standard conformal three-field treatment technique. The optimisation algorithm was based on fast-stimulated-annealing using a cost function designed to achieve a uniform dose in the planning-target-volume (PTV) and to minimise the integral doses to the organs-at-risk. The algorithm has been applied to standard conformal three-field plans created by an experienced human planner, and run in three PLAN MODES: (1) where the wedge angles were fixed by the human planner and only the beam-weights were optimised; (2) where both the wedge angles and beam-weights were optimised; and (3) where both the wedge angles and beam-weights were optimised and a non-uniform dose was prescribed to the PTV. In the latter PLAN MODE, a uniform 100% dose was prescribed to all of the PTV except for that region that overlaps with the rectum where a lower (e.g., 90%) dose was prescribed. The resulting optimised plans have been compared with those of the human planner who found beam-weights by conventional forward planning techniques. Plans were compared on the basis of dose statistics, normal-tissue-complication-probability (NTCP) and tumour-control-probability (TCP). The results of the comparison showed that all three PLAN MODES produced plans with slightly higher TCP for the same rectal NTCP, than the human planner. The best results were observed for PLAN MODE 3, where an average increase in TCP of 0.73% (+/- 0.20, 95% confidence interval) was predicted by the biological models. This increase arises from a beneficial dose gradient which is produced across the tumour. Although the TCP gain is small it comes with no increase in treatment complexity, and could translate into increased cures given the large numbers of patients being referred. A study of the beam-weights and wedge angles chosen by the optimisation algorithm revealed significant inter-patient variability the implications of which are examined. Probably the most significant benefit of the algorithm is the time saved (about a factor of 10) in computing optimised beam-weights and wedge angles for this simple plan.

Authors
Oldham, M; Neal, AJ; Webb, S
MLA Citation
Oldham, M, Neal, AJ, and Webb, S. "The optimisation of wedge filters in radiotherapy of the prostate." Radiother Oncol 37.3 (December 1995): 209-220.
PMID
8746589
Source
pubmed
Published In
Radiotherapy & Oncology
Volume
37
Issue
3
Publish Date
1995
Start Page
209
End Page
220

Corrigendum to "a comparison of conventional 'forward planning' with inverse planning for 3D conformal radiotherapy of the prostate". Radiotherapy and Oncology 35 (1995) 248-262 (PII:0167-8140(94)01556-V)

Authors
Oldham, M; Neal, A; Webb, S
MLA Citation
Oldham, M, Neal, A, and Webb, S. "Corrigendum to "a comparison of conventional 'forward planning' with inverse planning for 3D conformal radiotherapy of the prostate". Radiotherapy and Oncology 35 (1995) 248-262 (PII:0167-8140(94)01556-V)." Radiotherapy and Oncology 37.2 (November 1, 1995): 171-172.
Source
scopus
Published In
Radiotherapy & Oncology
Volume
37
Issue
2
Publish Date
1995
Start Page
171
End Page
172

Comparison of treatment techniques for conformal radiotherapy of the prostate using dose-volume histograms and normal tissue complication probabilities.

The aim of this study was to evaluate the relative merits of the coplanar field arrangements most frequently used for conformal radiotherapy of the prostate using dose-volume histograms and normal tissue complication probabilities (NTCPs). Twelve patients with early prostate cancer underwent a planning CT scan of the pelvis. Isocentric plans for each patient were devised using three, four, six and eight conformal fields and beam-weights optimised using fast simulated annealing to give a dose homogeneity across the planning target volume of +/- 5% or better while minimising irradiation of the relevant organs at risk. The plans were then evaluated using dose-volume histograms of the organs at risk (bladder, rectum and both femoral heads) and the Lyman model of normal tissue complication probability for the rectum. Analysis of dose-volume histogram data averaged over the 12 patients indicates an advantage for six (p = 0.002) and eight (p = 0.0001) fields with respect to the percentage volume of the femoral heads receiving > 50% of the prescribed dose compared with three fields. There was a similar advantage for six (p = 0.0007) and eight (p = 0.0001) fields compared with four fields. Ranking of the treatment techniques indicates that the four-field technique is the worst with respect to femoral head irradiation but the best with respect to reducing rectal irradiation. A higher dose can be prescribed to the isocentre with the four-field technique for a 5% rectal NTCP. The six-field technique led to sparing of the bladder when the different treatment techniques were ranked using bladder dose-volume histogram data. We conclude that none of the techniques studied consistently proved to be superior when applied to this sample of patients with prostate cancer with respect to sparing all the organs at risk. The absolute differences between techniques are small and would be very difficult to detect with respect to clinically relevant endpoints.

Authors
Neal, AJ; Oldham, M; Dearnaley, DP
MLA Citation
Neal, AJ, Oldham, M, and Dearnaley, DP. "Comparison of treatment techniques for conformal radiotherapy of the prostate using dose-volume histograms and normal tissue complication probabilities." Radiother Oncol 37.1 (October 1995): 29-34.
PMID
8539454
Source
pubmed
Published In
Radiotherapy & Oncology
Volume
37
Issue
1
Publish Date
1995
Start Page
29
End Page
34

The optimization and inherent limitations of 3D conformal radiotherapy treatment plans of the prostate.

This paper describes the applications of an inverse planning optimization algorithm to the real clinical problem of prostate cancer. The algorithm has been designed to compute optimized beam-weights taking full account of three-dimensional spatial information of dose inside the patient. The algorithm is based on fast simulated annealing, utilizing a cost-function containing both linear and quadratic terms. The linear part of the cost function allows for the implementation of "short-cuts" in the cost-function computation, which reduces the calculation time by a factor of about 30. It has been applied to compute optimized beam-weights for a three-field and a seven-field prostate treatment plan. It is shown for the three-field plan that the optimization algorithm can reproduce, and even slightly improve on, the results of an experienced human planner. For the seven-field plan, the human planner experienced difficulty finding beam-weights that gave an acceptable dose distribution. It is shown that the optimization algorithm can achieve good results in this case. The outcome of the optimization of the seven-field plan prompted an investigation into the best results that could be achieved by an "ideal" conformal radiotherapy technique. The results of this investigation are presented and it is shown that the limiting factor for conformal therapy of the prostate is the size of the overlap volume between the planning target volume (PTV) and the rectum. Finally, the efficiency and accuracy of fast simulated annealing is compared with that of classical simulated annealing. The former was found to be at least 10 times faster for the problem studied.

Authors
Oldham, M; Webb, S
MLA Citation
Oldham, M, and Webb, S. "The optimization and inherent limitations of 3D conformal radiotherapy treatment plans of the prostate." Br J Radiol 68.812 (August 1995): 882-893.
PMID
7551787
Source
pubmed
Published In
British Journal of Radiology
Volume
68
Issue
812
Publish Date
1995
Start Page
882
End Page
893
DOI
10.1259/0007-1285-68-812-882

A comparison of conventional 'forward planning' with inverse planning for 3D conformal radiotherapy of the prostate.

A radiotherapy treatment plan optimisation algorithm has been applied to 48 prostate plans and the results compared with those of an experienced human planner. Twelve patients were used in the study, and 3-, 4-, 6- and 8-field plans (with standard coplanar beam angles for each plan type) were optimised by both the human planner and the optimisation algorithm. The human planner 'optimised' the plan by conventional forward planning techniques. The optimisation algorithm was based on fast simulated annealing using a cost-function designed to achieve a homogenous dose in the 'planning-target-volume' and to minimise the integral dose to the organs at risk. 'Importance factors' assigned to different regions of the patient provide a method for controlling the algorithm, and it was found that the same values gave good results for almost all plans. A study of the convergence of the algorithm is presented and optimal convergence parameters are determined. The plans were compared on the basis of both dose statistics and 'normal-tissue-complication-probability' (NTCP) and 'tumour-control-probability' (TCP). The results of the comparison study show that the optimisation algorithm yielded results that were at least as good as the human planner for all plan types, and on the whole slightly better. A study of the beam-weights chosen by the optimisation algorithm and the planner revealed differences that increased with the number of beams in the plan. The planner was found to make small perturbations about a conceived optimal beam-weight set. The optimisation algorithm showed much greater showed much greater variation, in response to individual patient geometry, frequently deselecting certain beams altogether from the plan. The algorithm is shown to be a useful tool for radiotherapy treatment planning. For simple (e.g., three-field) plans it was found to consistently achieve slightly higher TCP and lower NTCP values. For more complicated (e.g., eight-field) plans the optimisation also achieved slightly better results with generally less numbers of beams, unfavourable beams being deselected from the plan. Probably the greatest benefit is the reduced time taken by the optimisation to compute optimised beam-weights. This time always < or = 5 min; a factor of up to 20-times faster than the human planner.

Authors
Oldham, M; Neal, A; Webb, S
MLA Citation
Oldham, M, Neal, A, and Webb, S. "A comparison of conventional 'forward planning' with inverse planning for 3D conformal radiotherapy of the prostate." Radiother Oncol 35.3 (June 1995): 248-262.
PMID
7480829
Source
pubmed
Published In
Radiotherapy & Oncology
Volume
35
Issue
3
Publish Date
1995
Start Page
248
End Page
262

Erratum: A comparison of conventional 'forward planning' with inverse planning for 3D conformal radiotherapy of the prostate (Radiotherapy and Oncology 35 (1995) (248-262))

Authors
Oldham, M; Neal, A; Webb, S
MLA Citation
Oldham, M, Neal, A, and Webb, S. "Erratum: A comparison of conventional 'forward planning' with inverse planning for 3D conformal radiotherapy of the prostate (Radiotherapy and Oncology 35 (1995) (248-262))." Radiotherapy and Oncology 37.2 (1995): 171-172.
Source
scival
Published In
Radiotherapy and Oncology
Volume
37
Issue
2
Publish Date
1995
Start Page
171
End Page
172
DOI
10.1016/0167-8140(95)01652-W
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