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Adamson, Justus D

Overview:

Radiosurgery and SBRT
Image Guided Radiation Therapy (IGRT)
Quality Assurance (QA) in Radiation Therapy
3D Dosimetry

Positions:

Associate Professor of Radiation Oncology

Radiation Oncology
School of Medicine

Member of the Duke Cancer Institute

Duke Cancer Institute
School of Medicine

Education:

Ph.D. 2009

Ph.D. — Wayne State University

Research Assistant

William Beaumont Hospital Royal Oak

Postdoctoral Associate/Medical Physicist Residency Program, Radiation Oncology Physics Division

Duke University School of Medicine

Publications:

Single fraction stereotactic radiosurgery for multiple brain metastases

Authors
Limon, D; McSherry, F; Herndon, J; Sampson, J; Fecci, P; Adamson, J; Wang, Z; Yin, F-F; Floyd, S; Kirkpatrick, J; Kim, GJ
MLA Citation
Limon, D, McSherry, F, Herndon, J, Sampson, J, Fecci, P, Adamson, J, Wang, Z, Yin, F-F, Floyd, S, Kirkpatrick, J, and Kim, GJ. "Single fraction stereotactic radiosurgery for multiple brain metastases." Advances in Radiation Oncology (September 2017).
Source
crossref
Published In
Advances in Radiation Oncology
Publish Date
2017
DOI
10.1016/j.adro.2017.09.002

Hippocampal dose from stereotactic radiosurgery for 4 to 10 brain metastases: Risk factors, feasibility of dose reduction via re-optimization, and patient outcomes.

This study aimed to report hippocampal dose from single-fraction stereotactic radiosurgery (SRS) for 4 to 10 brain metastases and determine feasibility of hippocampal-sparing SRS. Patients with 4 to 10 brain metastases receiving single-isocenter, multi-target single-fraction SRS were identified. Hippocampi were contoured using the Radiation Therapy Oncology Group (RTOG) 0933 atlas. RTOG 0933 dose constraints were converted to a biologically effective dose using an alpha/beta of 2 (D100 421 cGy, Dmax 665 cGy). Number of metastases, total target volume, prescribed dose, and distance of nearest metastasis (dmin) were analyzed as risk factors for exceeding hippocampal constraints. If hippocampi exceeded constraints, the SRS plan was re-optimized. Key dosimetric parameters were compared between original and re-optimized plans. To determine if a single target can exceed constraints, all targets but the closest metastasis were removed from the plan, and dosimetry was compared. Forty plans were identified. Fifteen hippocampi (19%) exceeded constraints in 12 SRS plans. Hippocampal sparing was achieved in 10 of 12 replanned cases (83%). Risk factors associated with exceeding hippocampal constraints were decreasing dmin (24.0 vs 8.0 mm, p = 0.002; odds ratio [OR] 1.14, 95% confidence interval [CI] 1.04 to 1.26) and total target volume (5.46 cm(3)vs 1.98 cm(3), p = 0.03; OR 1.14, 95% CI 1.00 to 1.32). There was no difference in exceeding constraints for 4 to 5 vs 6 to 10 metastases (27% vs 21%, p = 0.409) or prescribed dose (18 Gy, p = 0.58). For re-optimized plans, there were no significant differences in planning target volume (PTV) coverage (99.6% vs 99.0%, p = 0.17) or conformality index (1.47 vs 1.4, p = 0.78). Six (50%) plans exceeded constraints with a single target. A substantial minority of hippocampi receive high radiation dose from SRS for 4 to 10 brain metastases. Decreasing distance of the closest metastasis and total target volume are associated with exceeding hippocampal constraints. Re-optimizing these plans yielded hippocampal-sparing SRS plans with acceptable dosimetry. Prospective evaluation of the impact of hippocampal dose from SRS on neurocognition merits consideration.

Authors
Birer, SR; Olson, AC; Adamson, J; Hood, R; Susen, M; Kim, G; Salama, JK; Kirkpatrick, JP
MLA Citation
Birer, SR, Olson, AC, Adamson, J, Hood, R, Susen, M, Kim, G, Salama, JK, and Kirkpatrick, JP. "Hippocampal dose from stereotactic radiosurgery for 4 to 10 brain metastases: Risk factors, feasibility of dose reduction via re-optimization, and patient outcomes." July 28, 2017.
PMID
28760560
Source
epmc
Published In
Medical Dosimetry
Publish Date
2017
DOI
10.1016/j.meddos.2017.06.007

Triphasic contrast enhanced CT simulation with bolus tracking for pancreas SBRT target delineation.

Bolus-tracked multiphasic contrast computed tomography (CT) is often used in diagnostic radiology to enhance the visibility of pancreas tumors, but is uncommon in radiation therapy pancreas CT simulation, and its impact on gross tumor volume (GTV) delineation is unknown. This study evaluates the lesion conspicuity and consistency of pancreas stereotactic body radiation therapy (SBRT) GTVs contoured in the different contrast phases of triphasic CT simulation scans.Triphasic, bolus-tracked planning CT simulation scans of 10 consecutive pancreas SBRT patients were acquired, yielding images of the pancreas during the late arterial (LA), portal venous (PV), and either the early arterial or delayed phase. GTVs were contoured on each phase by a gastrointestinal-specialized radiation oncologist and reviewed by a fellowship-trained abdominal radiologist who specializes in pancreatic imaging. The volumes of the registered GTVs, their overlap ratio, and the 3-dimensional margin expansions necessary for each GTV to fully encompass GTVs from the other phases were calculated. The contrast difference between tumor and normal pancreas was measured, and 2 radiation oncologists rank-ordered the phases according to their value for the lesion-contouring task.Tumor-to-pancreas enhancement was on average much larger for the LA and PV than the delayed phase or early arterial phases; the LA and PV phases were also consistently preferred by the radiation oncologists. Enhancement differences among the phases resulted in highly variable GTV volumes with no observed trends. Overlap ratios ranged from 18% to 75% across all 3 phases, improving to 43% to 91% when considering only the preferred LA and PV phases. GTV expansions necessary to encompass all GTVs ranged from 0.3 to 1.8 cm for all 3 phases, improving slightly to 0.1 to 1.4 cm when considering just the LA and PV phases.For pancreas SBRT, we recommend combining the GTVs from a multiphasic CT simulation with bolus-tracking, including, at a minimum, a Boolean "OR" of the LA and PV phases.

Authors
Godfrey, DJ; Patel, BN; Adamson, JD; Subashi, E; Salama, JK; Palta, M
MLA Citation
Godfrey, DJ, Patel, BN, Adamson, JD, Subashi, E, Salama, JK, and Palta, M. "Triphasic contrast enhanced CT simulation with bolus tracking for pancreas SBRT target delineation." Practical radiation oncology (April 13, 2017).
PMID
28666905
Source
epmc
Published In
Practical Radiation Oncology
Publish Date
2017
DOI
10.1016/j.prro.2017.04.008

An in-house protocol for improved flood field calibration of TrueBeam FFF cine imaging.

TrueBeams equipped with the 40 × 30 cm2 Electronic Portal Imaging Devices (EPIDs) are prone to image saturation at the image center when used with flattening filter free (FFF) photon energies. While cine imaging during treatment may not saturate because the beam is attenuated by the patient, the flood field calibration is affected when the standard calibration procedure is followed. Here, we describe the hardware and protocol to achieve improved image quality for this model of TrueBeam EPID.A stainless steel filter of uniform thickness was designed to have sufficient attenuation to avoid panel saturation. The cine imaging flood field calibration was acquired with the filter in place for the FFF energies under the standard calibration geometry (SID = 150 cm). Image quality during MV cine was assessed with & without the modified flood field calibration using a low contrast resolution phantom and an anthropomorphic phantom.When the flood field is acquired without the filter in place, a pixel gain artifact is clearly present in the image center which may be mis-attributed to panel saturation in the subject image. At the image center, the artifact obscured all low contrast inserts and was also visible on the anthropomorphic phantom. Using the filter for flood field calibration eliminates the artifact.TrueBeams equipped with the 40 × 30 cm2 IDU can utilize a modified flood field calibration procedure for FFF photon energies that improves image quality for cine MV imaging.

Authors
Faught, AM; Yin, F-F; Adamson, J
MLA Citation
Faught, AM, Yin, F-F, and Adamson, J. "An in-house protocol for improved flood field calibration of TrueBeam FFF cine imaging." Journal of applied clinical medical physics 18.1 (January 2017): 265-268.
PMID
28291919
Source
epmc
Published In
Journal of applied clinical medical physics / American College of Medical Physics
Volume
18
Issue
1
Publish Date
2017
Start Page
265
End Page
268
DOI
10.1002/acm2.12023

Characterization of Water-Clear Polymeric Gels for Use as Radiotherapy Bolus.

Our purpose was to investigate polymeric gels for use as a highly transparent radiotherapy bolus and determine the relevant physical and dosimetric properties. We first quantified tensile properties (maximum stress, strain, and Young modulus) for various polymeric gels, along with a commercial bolus product in order to illustrate the wide variety of potential materials. For a select polymeric gel with tensile properties similar to currently used radiotherapy bolus, we also evaluated mass and electron density, effective atomic number, optical transparency, and percent depth dose in clinical megavoltage photon and electron beams. For this polymeric gel, mass density was 872 ± 12 and 896 ± 13 g/cm(3) when measured via weight/volume and computed tomography Hounsfield units, respectively. Electron density was 2.95 ± 0.04 ×10(23) electrons/cm(3). Adding fused silica (9% by weight) increases density to that of water. The ratio of the effective atomic number to that of water without and with added silica was 0.780 and 0.835 at 1 MeV, 0.767 and 0.826 at 6 MeV, and 0.746 and 0.809 at 20 MeV. Percent depth dose for 6 MV photons was within 2% of water within the first 2.5 cm and after scaling by the density coincided within 1% out to >7 cm. For 6 and 20 MeV electrons, after scaling for density D80% was within 1.3 and 1.5 mm of water, respectively. The high transparency and mechanical flexibility of polymeric gels indicate potential for use as a radiotherapy bolus; differences in density from water may be managed via either using "water equivalent thickness" or by incorporating fused silica into the material.

Authors
Adamson, JD; Cooney, T; Demehri, F; Stalnecker, A; Georgas, D; Yin, F-F; Kirkpatrick, J
MLA Citation
Adamson, JD, Cooney, T, Demehri, F, Stalnecker, A, Georgas, D, Yin, F-F, and Kirkpatrick, J. "Characterization of Water-Clear Polymeric Gels for Use as Radiotherapy Bolus." Technology in cancer research & treatment (January 2017): 1533034617710579-.
PMID
28554255
Source
epmc
Published In
Technology in cancer research & treatment
Publish Date
2017
Start Page
1533034617710579
DOI
10.1177/1533034617710579

Is a single isocenter sufficient for volumetric modulated arc therapy radiosurgery when multiple itracranial metastases are spatially dispersed?

Previous work demonstrated improved dosimetry of single isocenter volumetric modulated arc therapy (VMAT) of multiple intracranial targets when they are located ≤ 4cm from isocenter because of narrower multileaf collimators (MLCs). In follow-up, we sought to determine if decreasing isocenter-target distance (diso) by using 2 to 3 isocenters would improve dosimetry for spatially dispersed targets. We also investigated the effect of a maximum dose constraint during VMAT optimization, and the dosimetric effect of the number of VMAT arcs used for a larger number of targets (i.e., 7 to 9). We identified radiosurgery cases that had multiple intracranial targets with diso of at least 1 target > 5cm. A single isocenter VMAT plan was created using a standardized 4-arc technique with 18Gy per target. Each case was then replanned (1) using 2 to 3 isocenters, (2) including a maximum dose constraint per target, and in the case of 7 to 9 targets, (3) using 3 to 6 arcs. Dose evaluation included brain V6Gy and V12Gy, and conformity index (CI), gradient index (GI), and heterogeneity index (HI) per target. Two isocenters were sufficient to limit diso to ≤ 4cm and ≤ 5cm for 11/15 and 13/15 cases, respectively; after replanning with 2 to 3 isocenters, diso decreased from 5.8 ± 2.8cm (2.3 14.9) to 2.5 ± 1.4cm (0 5.2). All dose statistics improved on average, albeit modestly: V6Gy = 6.9 ± 7.1%, V12Gy = 0.9% ± 4.4%, CI = 2.6% ± 4.6%, GI = 0.9% ± 12.7%, and HI = 2.6% ± 5.2%; however, the number of arcs doubled and monitor units increase by nearly 2-fold. A maximum dose constraint had a negative effect on all dose indices, increasing V12Gy by 9.7 ± 6.9%. For ≥ 7 targets, increasing number of arcs to > 3 improved CI, V12Gy, and V6Gy. A single isocenter is likely sufficient for VMAT radiosurgery of multiple intracranial metastases. Optimal treatment plan quality is achieved when no constraint is placed on the maximum target dose; for cases with many targets at least 4 arcs are needed for optimal plan quality.

Authors
Morrison, J; Hood, R; Yin, F-F; Salama, JK; Kirkpatrick, J; Adamson, J
MLA Citation
Morrison, J, Hood, R, Yin, F-F, Salama, JK, Kirkpatrick, J, and Adamson, J. "Is a single isocenter sufficient for volumetric modulated arc therapy radiosurgery when multiple itracranial metastases are spatially dispersed?." Medical dosimetry : official journal of the American Association of Medical Dosimetrists 41.4 (December 2016): 285-289.
PMID
27614790
Source
epmc
Published In
Medical Dosimetry
Volume
41
Issue
4
Publish Date
2016
Start Page
285
End Page
289
DOI
10.1016/j.meddos.2016.06.007

Re-examining TG-142 recommendations in light of modern techniques for linear accelerator based radiosurgery.

The recent development of multifocal stereotactic radiosurgery (SRS) using a single isocenter volumetric modulated arc theory (VMAT) technique warrants a re-examination of the quality assurance (QA) tolerances for routine mechanical QA recommended by the American Association of Physicists in Medicine Task Group Report Number 142. Multifocal SRS can result in targets with small volumes being at a large off-axis distance from the treatment isocenter. Consequently, angular errors in the collimator, patient support assembly (PSA), or gantry could have an increased impact on target coverage.The authors performed a retrospective analysis of dose deviations caused by systematic errors in PSA, collimator, and gantry angle at the tolerance level for routine linear accelerator QA as recommended by TG-142. Dosimetric deviations from multifocal SRS plans (N = 10) were compared to traditional single target SRS using dynamic conformal arcs (N = 10). The chief dosimetric quantities used in determining clinical impact were V100% and D99% of the individual planning target volumes and V12Gy of the healthy brain.Induced errors at tolerance levels showed the greatest change in multifocal SRS target coverage for collimator rotations (±1.0°) with the average changes to V100% and D99% being 5% and 6%, respectively, with maximum changes of 33% and 20%. A reduction in the induced error to half the TG-142 tolerance (±0.5°) demonstrated similar changes in coverage loss to traditional single target SRS assessed at the recommended tolerance level. The observed change in coverage for multifocal SRS was reduced for gantry errors (±1.0°) at 2% and 4.5% for V100% and D99%, respectively, with maximum changes of 18% and 12%. Minimal change in coverage was noted for errors in PSA rotation.This study indicates that institutions utilizing a single isocenter VMAT technique for multifocal disease should pay careful attention to the angular mechanical tolerances in designing a robust and complete QA program.

Authors
Faught, AM; Trager, M; Yin, F-F; Kirkpatrick, J; Adamson, J
MLA Citation
Faught, AM, Trager, M, Yin, F-F, Kirkpatrick, J, and Adamson, J. "Re-examining TG-142 recommendations in light of modern techniques for linear accelerator based radiosurgery." Medical physics 43.10 (October 2016): 5437-.
PMID
27782700
Source
epmc
Published In
Medical physics
Volume
43
Issue
10
Publish Date
2016
Start Page
5437
DOI
10.1118/1.4962471

Physics considerations for single-isocenter, volumetric modulated arc radiosurgery for treatment of multiple intracranial targets.

Our purpose was to address challenges associated with single-isocenter radiosurgery for multiple intracranial targets (SIRMIT) including increased sensitivity to rotational uncertainties (resulting from distance of the targets from isocenter) as well as potential for decreased plan quality from larger multileaf collimator width >4 cm from isocenter.We evaluated the effect that a 6 degrees-of-freedom couch correction had on localization uncertainty for SIRMIT using thermoplastic mask immobilization. Required setup margin was determined from rotation of the skull and mask (setup kV cone beam computed tomography relative to planning computed tomography). Intraoperational margin was determined from skull rotation within the mask (difference between pre- and posttreatment cone beam computed tomography). We also investigated 4 isocenter placement strategies: volume centroid, centroid of equally weighted points (1 per target), centroid of points weighted by inverse of volume, and Eclipse's built-in method.When no 6 degrees-of-freedom couch correction is performed after initial setup, a 0.35-mm margin is required per centimeter of target-isocenter separation to account for 95% of rotational uncertainties at initial setup. This margin is reduced to 0.10 mm/cm of target-isocenter separation to account for intraoperative rotational uncertainties when the initial setup uncertainty is eliminated via image guided 6 degrees-of-freedom couch correction. Analysis of 11 multitarget plans (37 targets) showed that conformity index and gradient index improved with decreasing distance from isocenter, this trend being more pronounced for targets <1 mL. Alternative isocenters aimed at decreasing distance of small targets improved their gradient index, but resulted in poorer dose indices for large targets. Mean distance from isocenter was smallest for the centroid of equally weighted points (4.1 ± 1.6cm vs 4.2-4.5cm).Rotational corrections via image guidance are necessary for SIRMIT with a thermoplastic mask for immobilization. There is a clear tradeoff between dosimetric quality of small and large targets that should be considered carefully when placing the isocenter.

Authors
Stanhope, C; Chang, Z; Wang, Z; Yin, F-F; Kim, G; Salama, JK; Kirkpatrick, J; Adamson, J
MLA Citation
Stanhope, C, Chang, Z, Wang, Z, Yin, F-F, Kim, G, Salama, JK, Kirkpatrick, J, and Adamson, J. "Physics considerations for single-isocenter, volumetric modulated arc radiosurgery for treatment of multiple intracranial targets." May 2016.
PMID
26723551
Source
epmc
Published In
Practical Radiation Oncology
Volume
6
Issue
3
Publish Date
2016
Start Page
207
End Page
213
DOI
10.1016/j.prro.2015.10.010

Adaptive planning using positron emission tomography for locally advanced lung cancer: A feasibility study.

To evaluate the feasibility of adaptive planning using positron emission tomography-computed tomography (PET-CT) in locally advanced non-small cell lung cancer.Patients with locally advanced non-small cell lung cancer receiving definitive radiation therapy (RT) were eligible. Initial planning PET-CT was performed and a conventional RT plan (2 Gy/fraction to 60 Gy) was designed. A second planning PET-CT was obtained at ~50 Gy. Dose escalation to ~70 Gy for residual fludeoxyglucose-avid disease was pursued at the discretion of the treating oncologists. The primary endpoint was feasibility of adaptive planning using interim PET-CT. Normal tissue dose-volume parameters were calculated for both adaptive and simulated nonadaptive plans.From 2012 to 2014, 33 eligible patients were enrolled and underwent planning PET-CT, 3 of which were found to have new distant metastases. Of 30 patients who initiated RT, interim PET-CT was obtained in 29. This showed complete response in 2 patients, partial response/stable disease in 24, and new distant metastases in 3. Selective dose escalation was performed in 17 patients. For those receiving a boost, the median gross tumor volumes pre-RT and at ~50 Gy were 78 mL and 29 mL, respectively (P = .01). Reasons for no dose escalation were normal tissue constraints (n = 3), poorly defined residual disease (n = 2), acute toxicity (n = 1), and refusal of further therapy (n = 1). Adaptive planning compared with a simulated nonadaptive approach allowed for significant dose reductions to the lungs, heart, and esophagus (all P < .01).Adaptive planning using PET-CT was feasible and allows for significant dose reductions to normal tissues compared with traditional planning techniques.

Authors
Kelsey, CR; Christensen, JD; Chino, JP; Adamson, J; Ready, NE; Perez, BA
MLA Citation
Kelsey, CR, Christensen, JD, Chino, JP, Adamson, J, Ready, NE, and Perez, BA. "Adaptive planning using positron emission tomography for locally advanced lung cancer: A feasibility study." Practical radiation oncology 6.2 (March 2016): 96-104.
PMID
26723555
Source
epmc
Published In
Practical Radiation Oncology
Volume
6
Issue
2
Publish Date
2016
Start Page
96
End Page
104
DOI
10.1016/j.prro.2015.10.009

On the sensitivity of TG-119 and IROC credentialing to TPS commissioning errors.

We investigate the sensitivity of IMRT commissioning using the TG-119 C-shape phantom and credentialing with the IROC head and neck phantom to treatment planning system commissioning errors. We introduced errors into the various aspects of the commissioning process for a 6X photon energy modeled using the analytical anisotropic algorithm within a commercial treatment planning system. Errors were implemented into the various components of the dose calculation algorithm including primary photons, secondary photons, electron contamination, and MLC parameters. For each error we evaluated the probability that it could be committed unknowingly during the dose algorithm commissioning stage, and the probability of it being identified during the verification stage. The clinical impact of each commissioning error was evaluated using representative IMRT plans including low and intermediate risk prostate, head and neck, mesothelioma, and scalp; the sensitivity of the TG-119 and IROC phantoms was evaluated by comparing dosimetric changes to the dose planes where film measurements occur and change in point doses where dosimeter measurements occur. No commissioning errors were found to have both a low probability of detection and high clinical severity. When errors do occur, the IROC credentialing and TG 119 commissioning criteria are generally effective at detecting them; however, for the IROC phantom, OAR point-dose measurements are the most sensitive despite being currently excluded from IROC analysis. Point-dose measurements with an absolute dose constraint were the most effective at detecting errors, while film analysis using a gamma comparison and the IROC film distance to agreement criteria were less effective at detecting the specific commissioning errors implemented here. PACS number: 87.55.Qr.

Authors
McVicker, D; Yin, F-F; Adamson, JD
MLA Citation
McVicker, D, Yin, F-F, and Adamson, JD. "On the sensitivity of TG-119 and IROC credentialing to TPS commissioning errors." Journal of applied clinical medical physics 17.1 (January 2016): 34-48.
PMID
28297489
Source
epmc
Published In
Journal of applied clinical medical physics / American College of Medical Physics
Volume
17
Issue
1
Publish Date
2016
Start Page
34
End Page
48
DOI
10.1120/jacmp.v17i1.5452

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

Utilizing knowledge from prior plans in the evaluation of quality assurance.

Increased interest regarding sensitivity of pre-treatment intensity modulated radiotherapy and volumetric modulated arc radiotherapy (VMAT) quality assurance (QA) to delivery errors has led to the development of dose-volume histogram (DVH) based analysis. This paradigm shift necessitates a change in the acceptance criteria and action tolerance for QA. Here we present a knowledge based technique to objectively quantify degradations in DVH for prostate radiotherapy. Using machine learning, organ-at-risk (OAR) DVHs from a population of 198 prior patients' plans were adapted to a test patient's anatomy to establish patient-specific DVH ranges. This technique was applied to single arc prostate VMAT plans to evaluate various simulated delivery errors: systematic single leaf offsets, systematic leaf bank offsets, random normally distributed leaf fluctuations, systematic lag in gantry angle of the mutli-leaf collimators (MLCs), fluctuations in dose rate, and delivery of each VMAT arc with a constant rather than variable dose rate.Quantitative Analyses of Normal Tissue Effects in the Clinic suggests V75Gy dose limits of 15% for the rectum and 25% for the bladder, however the knowledge based constraints were more stringent: 8.48 ± 2.65% for the rectum and 4.90 ± 1.98% for the bladder. 19 ± 10 mm single leaf and 1.9 ± 0.7 mm single bank offsets resulted in rectum DVHs worse than 97.7% (2σ) of clinically accepted plans. PTV degradations fell outside of the acceptable range for 0.6 ± 0.3 mm leaf offsets, 0.11 ± 0.06 mm bank offsets, 0.6 ± 1.3 mm of random noise, and 1.0 ± 0.7° of gantry-MLC lag.Utilizing a training set comprised of prior treatment plans, machine learning is used to predict a range of achievable DVHs for the test patient's anatomy. Consequently, degradations leading to statistical outliers may be identified. A knowledge based QA evaluation enables customized QA criteria per treatment site, institution and/or physician and can often be more sensitive to errors than criteria based on organ complication rates.

Authors
Stanhope, C; Wu, QJ; Yuan, L; Liu, J; Hood, R; Yin, F-F; Adamson, J
MLA Citation
Stanhope, C, Wu, QJ, Yuan, L, Liu, J, Hood, R, Yin, F-F, and Adamson, J. "Utilizing knowledge from prior plans in the evaluation of quality assurance." Physics in medicine and biology 60.12 (June 9, 2015): 4873-4891.
PMID
26056801
Source
epmc
Published In
Physics in Medicine and Biology
Volume
60
Issue
12
Publish Date
2015
Start Page
4873
End Page
4891
DOI
10.1088/0031-9155/60/12/4873

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

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

Evaluating radiation-induced white matter changes in patients treated with stereotactic radiosurgery using diffusion tensor imaging: a pilot study.

Stereotactic radiosurgery (SRS) has been an effective treatment method for brain tumors; however, few data are available regarding radiation-induced white matter (WM) damage by SRS. In this work, diffusion tensor imaging (DTI) was used to investigate WM changes following SRS. Fifteen patients with gliomas were enrolled, with prescription doses ranging 18-25 Gy. Patients were scanned with magnetic resonance imaging (MRI) including DTI before and after SRS. Diffusion tensors were calculated and fiber tracking was performed. Non-irradiated WM volumes and irradiated WM volumes receiving ≥ 12 Gy and ≥ Gy were contoured as volumes of interest (VOI). Apparent diffusion coefficient (〈D〉), fractional anisotropy (FA) and number of fibers (NF) were calculated and assessed using the Wilcoxon signed-rank test. Compared with those of non-irradiated VOIs, FA and NF decreased considerably after two months of SRS in the irradiated WM VOIs. The variation in (〈D〉 was however small and was not statistically significant. The preliminary results suggested that FA and NF might potentially be more sensitive indicators than (〈D〉 in measuring radiation-induced WM changes and DTI could be a valuable tool to assess radiation-induced WM changes in SRS. Although it is still preliminary, this pilot study may be useful to provide insights for future studies.

Authors
Chang, Z; Kirkpatrick, JP; Wang, Z; Cai, J; Adamson, J; Yin, F-F
MLA Citation
Chang, Z, Kirkpatrick, JP, Wang, Z, Cai, J, Adamson, J, and Yin, F-F. "Evaluating radiation-induced white matter changes in patients treated with stereotactic radiosurgery using diffusion tensor imaging: a pilot study." Technol Cancer Res Treat 13.1 (February 2014): 21-28.
PMID
23862743
Source
pubmed
Published In
Technology in cancer research & treatment
Volume
13
Issue
1
Publish Date
2014
Start Page
21
End Page
28
DOI
10.7785/tcrt.2012.500358

A novel technique for VMAT QA with EPID in cine mode on a Varian TrueBeam linac.

Volumetric modulated arc therapy (VMAT) is a relatively new treatment modality for dynamic photon radiation therapy. Pre-treatment quality assurance (QA) is necessary and many efforts have been made to apply electronic portal imaging device (EPID)-based IMRT QA methods to VMAT. It is important to verify the gantry rotation speed during delivery as this is a new variable that is also modulated in VMAT. In this paper, we present a new technique to perform VMAT QA using an EPID. The method utilizes EPID cine mode and was tested on Varian TrueBeam in research mode. The cine images were acquired during delivery and converted to dose matrices after profile correction and dose calibration. A sub-arc corresponding to each cine image was extracted from the original plan and its portal image prediction was calculated. Several analyses were performed including 3D γ analysis (2D images + gantry angle axis), 2D γ analysis, and other statistical analyses. The method was applied to 21 VMAT photon plans of 3 photon energies. The accuracy of the cine image information was investigated. Furthermore, this method's sensitivity to machine delivery errors was studied. The pass rate (92.8 ± 1.4%) for 3D γ analysis was comparable to those from Delta(4) system (99.9 ± 0.1%) under similar criteria (3%, 3 mm, 5% threshold and 2° angle to agreement) at 6 MV. The recorded gantry angle and start/stop MUs were found to have sufficient accuracy for clinical QA. Machine delivery errors can be detected through combined analyses of 3D γ, gantry angle, and percentage dose difference. In summary, we have developed and validated a QA technique that can simultaneously verify the gantry angle and delivered MLC fluence for VMAT treatment.This technique is efficient and its accuracy is comparable to other QA methods.

Authors
Liu, B; Adamson, J; Rodrigues, A; Zhou, F; Yin, F-F; Wu, Q
MLA Citation
Liu, B, Adamson, J, Rodrigues, A, Zhou, F, Yin, F-F, and Wu, Q. "A novel technique for VMAT QA with EPID in cine mode on a Varian TrueBeam linac." Phys Med Biol 58.19 (October 7, 2013): 6683-6700.
PMID
24018655
Source
pubmed
Published In
Physics in Medicine and Biology
Volume
58
Issue
19
Publish Date
2013
Start Page
6683
End Page
6700
DOI
10.1088/0031-9155/58/19/6683

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

SU-E-T-196: Pretreatment Patient Clinical Objective IMRT Quality Assurance Using a 3D Diode Array.

To evaluate the accuracy and sensitivity of a patient clinical objective IMRT QA tool using a 3D diode array.A 3D QA device (Delta4, Scandidos Inc.) with 2 orthogonal diode array planes was used for IMRT QA. The diode spacing is 5mm in central 6cmx6cm region and 1cm in the peripheral 20cmx20cm region. 3D volumetric dose is interpolated from the measured planar dose. The Delta4 Anatomy software (Anatomy) calculates the entrance energy fluence for each beam, which is then applied to the patient anatomy to calculate dose to the patient using a pencil-beam dose calculation algorithm. The accuracy of Anatomy was evaluated in both solid water phantom using open fields and in patient anatomy using a prostate IMRT plan. The dose calculated by Eclipse was used as the gold standard. The sensitivity of the Anatomy was also evaluated by introducing leaf positioning errors in the delivery of a spine SBRT plan.Excellent agreement between Anatomy and Eclipse was achieved for the solid water phantom with open fields. Discrepancy was observed for the PTV DVH calculated in patient anatomy using the prostate IMRT plan. This is mainly due to sharp dose fall-off outside PTV and phantom setup errors during QA. Good agreement between Anatomy and Eclipse was achieved for bladder and rectum DVH. For spine case with introduced 1cm single leaf positioning error, the traditional gamma analysis using Delta4 still showed 95% pass rate using 3%, 3mm criteria. However, Anatomy showed 40% increase of cord max dose due to this error, which was consistent with Eclipse.Patient clinical objective QA using Delta4 Anatomy can potentially provide valuable information about the clinical significance of the QA results. It can potentially catch clinically significant delivery errors that would otherwise be missed in the traditional QA process using gamma analysis. Funding from Scandidos Inc.

Authors
Ren, L; Zhang, Y; Yang, Y; Adamson, J; Yin, F
MLA Citation
Ren, L, Zhang, Y, Yang, Y, Adamson, J, and Yin, F. "SU-E-T-196: Pretreatment Patient Clinical Objective IMRT Quality Assurance Using a 3D Diode Array." Medical physics 40.6Part13 (June 2013): 249-.
PMID
28519276
Source
epmc
Published In
Medical physics
Volume
40
Issue
6Part13
Publish Date
2013
Start Page
249
DOI
10.1118/1.4814631

WE-G-108-08: A Novel Technique for VMAT QA with EPID in Cine Mode On Varian TrueBeam.

Volumetric modulated arc therapy (VMAT) is a relatively new treatment modality for dynamic photon radiation therapy. Pre-treatment quality assurance (QA) is necessary and many efforts have been taken to apply electronic portal imaging device (EPID) based IMRT QA methods to VMAT. It is important to verify the gantry angles during delivery as this is new variable that is also modulated in VMAT. The purpose of this study is to develop and validate a new technique that is accurate and efficient to perform VMAT QA using EPID.The method utilized EPID cine mode and was tested on Varian TrueBeam in research mode. The cine images were acquired during delivery and converted to dose matrices after profile correction and dose calibration. Sub-arc corresponding to each cine image was extracted from the original plan and its portal image prediction was calculated. Several analyses were performed including 3D γ analysis (2D images plus gantry angle axis), 2D γ analysis, and other statistical analyses. The method was applied to 21 VMAT beams of 6MV photons and the accuracy of cine image information was investigated. Furthermore, this method's sensitivity to machine delivery errors was studied.The pass rate (97.8±1.1%) for 3D γ analysis was comparable to that from Delta4 (99.9±0.1%) under similar criteria (3%, 3mm, 5% threshold and 3°angle to agreement). The recorded gantry angle and start/stop MUs were found to have sufficient accuracy for clinical QA. Machine delivery errors can be detected through combined analyses of 3D γ index, gantry angle, and percentage dose difference.We have developed and validated a QA technique that can simultaneously verify the gantry angle and delivered MLC fluence for VMAT treatment. The method is efficient and its accuracy is comparable to other methods. B Liu's work was supported by the Chinese Scholarship Council.

Authors
Liu, B; Adamson, J; Rodrigues, A; Zhou, F; Yin, F; Wu, Q
MLA Citation
Liu, B, Adamson, J, Rodrigues, A, Zhou, F, Yin, F, and Wu, Q. "WE-G-108-08: A Novel Technique for VMAT QA with EPID in Cine Mode On Varian TrueBeam." Medical physics 40.6Part30 (June 2013): 502-.
PMID
28519131
Source
epmc
Published In
Medical physics
Volume
40
Issue
6Part30
Publish Date
2013
Start Page
502
DOI
10.1118/1.4815632

WE-G-108-06: Evaluating Pre-Treatment IMRT & VMAT QA Techniques Quantitatively Using Receiver Operating Characteristic (ROC) Analysis.

Pre-treatment IMRT and VMAT QA techniques are often commissioned without knowledge of their sensitivity to clinically relevant delivery errors. The purpose of this work is to develop a method to quantify the sensitivity and specificity of pre-treatment IMRT and VMAT QA techniques to treatment delivery errors.To evaluate a QA technique, a population of treatment plans and a population of clinically relevant delivery errors are defined. For each delivery error, a threshold magnitude is determined that induces a substantial change in clinically relevant dosimetric indices. Errors at the threshold magnitude are introduced into the plans and QA is performed with and without intentionally introduced errors. The QA technique is treated as a binary classifier to predict error plans using Receiver Operator Characteristic (ROC) analysis. We applied this technique to evaluate portal imager and 2D ion chamber array based QA for VMAT treatment of brain lesions. Delivery errors included discrepancies in MLC positioning (single leaf and leaf bank); lag of MLC trajectory; and discrepancy in dose rate per control point or gantry angle. The threshold magnitude was determined by achieving a 5% change in target conformity index.The area under the curve (AUC) for the ROC analysis was 0.592 and 0.509 for the ion chamber array and portal imager, respectively, using a gamma index of 3%, 3mm. The AUC increased to 0.632 and 0.777 when 2%, 2mm was used for the ion chamber array and portal imager, respectively. Comparison based on 3% dose agreement resulted in an AUC of 0.557 and 0.693, respectively.For both portal imager and ion chamber array based QA, stricter tolerance than 3%, 3mm is needed to detect clinically relevant delivery errors. This method can be used to quantitatively compare the sensitivity of various QA techniques to clinically relevant dosimetric errors.

Authors
Mitchell, A; Adamson, J
MLA Citation
Mitchell, A, and Adamson, J. "WE-G-108-06: Evaluating Pre-Treatment IMRT & VMAT QA Techniques Quantitatively Using Receiver Operating Characteristic (ROC) Analysis." Medical physics 40.6Part30 (June 2013): 502-.
PMID
28519157
Source
epmc
Published In
Medical physics
Volume
40
Issue
6Part30
Publish Date
2013
Start Page
502
DOI
10.1118/1.4815630

SU-E-T-560: A Method to Determine Optimal Dynamic MLC Parameters for Varian Truebeam with Millennium MLC and HDMLC.

Correct MLC modeling is essential to the accurate IMRT delivery. Most TPSs use simplified models with parameters of leaf transmission (LT) and dynamic leaf gap (DLG). The common way to determine them is through extrapolation from measurements. In this study, we propose a new technique to determine these parameters with EPID and ion chambers using specially designed fluence pattern.The fluence has symmetric twin peaks separated by 10cm and each has a width of 2cm. The DMLC files were generated based on initial values of LT and DLG from measurements. Plans were delivered to EPID and analyzed in portal dosimetry software. The FWHM of each peak was evaluated. The optimal DLG value was determined by iteratively adjusting its value and repeating calculation to match the FWHM between calculation and measurement. To determine LT, an ion chamber was placed at the central axis where dose is primarily from MLC leakage. Both Millennium MLC (MMLC) and HDMLC in Varian Truebeam were investigated for photon energies of 6X, 10X, 15X. QAs of realistic IMRT plans were performed and compared.The MMLC has measured LT values from 1.3%-1.5%, and corresponding optimal values 1.6-1.9%, an increase of 20% on average. The DLGs extrapolated from measurement are 0.8-0.9 mm, and optimal at 1.2-1.6 mm, a 60% increase. For HDMLC, the LTs are similar. However, the DLGs are much smaller, with extrapolations at 0.15-0.21 mm, and optimal at 0.4-0.7 mm. The portal dosimetry QA for 6X plan with MMLC reduces pixels failing γ (criteria: 3%/1mm) from 9% to 3% with optimal parameters. Similarly, QA for 15X plan with HDMLC reduces from 21% to 6%.We have developed a method to determine optimal MLC parameters that minimize TPS modeling errors. This ensures that patient specific QA reflects the true discrepancies in treatment plan or machine delivery.

Authors
Wu, Q; Chang, Z; Adamson, J; Ren, L; Yin, F
MLA Citation
Wu, Q, Chang, Z, Adamson, J, Ren, L, and Yin, F. "SU-E-T-560: A Method to Determine Optimal Dynamic MLC Parameters for Varian Truebeam with Millennium MLC and HDMLC." Medical physics 40.6Part19 (June 2013): 334-.
PMID
28524505
Source
epmc
Published In
Medical physics
Volume
40
Issue
6Part19
Publish Date
2013
Start Page
334
DOI
10.1118/1.4814989

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

Can Standard Radiation Therapy Quality Assurance (QA) Detect Potential Delivery Errors?

Authors
Ren, L; O'Daniel, J; Adamson, J; Yan, H; Yin, F
MLA Citation
Ren, L, O'Daniel, J, Adamson, J, Yan, H, and Yin, F. "Can Standard Radiation Therapy Quality Assurance (QA) Detect Potential Delivery Errors?." November 1, 2012.
Source
wos-lite
Published In
International Journal of Radiation Oncology, Biology, Physics
Volume
84
Issue
3
Publish Date
2012
Start Page
S779
End Page
S779

Commissioning and dosimetric characteristics of TrueBeam system: composite data of three TrueBeam machines.

PURPOSE: A TrueBeam linear accelerator (TB-LINAC) is designed to deliver traditionally flattened and flattening-filter-free (FFF) beams. Although it has been widely adopted in many clinics for patient treatment, limited information is available related to commissioning of this type of machine. In this work, commissioning data of three units were measured, and multiunit comparison was presented to provide valuable insights and reliable evaluations on the characteristics of the new treatment system. METHODS: The TB-LINAC is equipped with newly designed waveguide, carousel assembly, monitoring control, and integrated imaging systems. Each machine in this study has 4, 6, 8, 10, 15 MV flattened photon beams, and 6 MV and 10 MV FFF photon beams as well as 6, 9, 12, 16, 20, and 22 MeV electron beams. Dosimetric characteristics of the three new TB-LINAC treatment units are systematically measured for commissioning. High-resolution diode detectors and ion chambers were used to measure dosimetric data for a range of field sizes from 10 × 10 to 400 × 400 mm(2). The composite dosimetric data of the three units are presented in this work. The commissioning of intensity modulated radiotherapy (IMRT), volumetric modulated arc therapy (VMAT), image-guided radiation therapy, and gating systems are also illustrated. Critical considerations of P(ion) of FFF photon beams and small field dosimetric measurements were investigated. RESULTS: The authors found all PDDs and profiles matched well among the three machines. Beam data were quantitatively compared and combined through average to yield composite beam data. The discrepancies among the machines were quantified using standard deviation (SD). The mean SD of the PDDs among the three units is 0.12%, and the mean SD of the profiles is 0.40% for 10 MV FFF open fields. The variations of P(ion) of the chamber CC13 is 1.2 ± 0.1% under 6 MV FFF and 2.0 ± 0.5% under 10 MV FFF from dmax to the 18 cm-off-axis point at 35 cm depth under 40 × 40 cm(2). The mean penumbra of crossplane flattened photon beams at collimator angle of 0° is measured from 5.88 ± 0.09 to 5.99 ± 0.13 mm from 4 to 15 MV at 10 cm depth of 100 × 100 mm(2). The mean penumbra of crossplane beams at collimator angle of 0° is measured as 3.70 ± 0.21 and 4.83 ± 0.04 mm for 6 MV FFF and 10 MV FFF, respectively, at 10 cm depth with a field size of 5 × 5 cm(2). The end-to-end test procedures of both IMRT and VMAT were performed for various energy modes. The mean ion chamber measurements of three units showed less than 2% between measurement and calculation; the mean MultiCube ICA measurements demonstrated over 90% pixels passing gamma analysis (3%, 3 mm, 5% threshold). The imaging dosimetric data of KV planar imaging and CBCT demonstrated improved consistency with vendor specifications and dose reduction for certain imaging protocols. The gated output verification showed a discrepancy of 0.05% or less between gating radiation delivery and nongating radiation delivery. CONCLUSIONS: The commissioning data indicated good consistency among the three TB-LINAC units. The commissioning data provided us valuable insights and reliable evaluations on the characteristics of the new treatment system. The systematically measured data might be useful for future reference.

Authors
Chang, Z; Wu, Q; Adamson, J; Ren, L; Bowsher, J; Yan, H; Thomas, A; Yin, F-F
MLA Citation
Chang, Z, Wu, Q, Adamson, J, Ren, L, Bowsher, J, Yan, H, Thomas, A, and Yin, F-F. "Commissioning and dosimetric characteristics of TrueBeam system: composite data of three TrueBeam machines." Med Phys 39.11 (November 2012): 6981-7018.
PMID
23127092
Source
pubmed
Published In
Medical physics
Volume
39
Issue
11
Publish Date
2012
Start Page
6981
End Page
7018
DOI
10.1118/1.4762682

Independent verification of gantry angle for pre-treatment VMAT QA using EPID.

We propose a method to incorporate independent verification of gantry angle for electronic portal imaging device (EPID)-based pre-treatment quality assurance (QA) of clinical volumetric modulated arc therapy (VMAT) plans. Gantry angle is measured using projections in the EPID of a custom phantom placed on the couch and the treatment plan is modified so as to be incident on the phantom with a portion of the beam that is collimated in the clinical plan. For our implementation, collimator and couch angles were set to zero and the inferior jaw and two most inferior multi-leaf collimator pairs were opened for the entire QA delivery. A phantom containing five gold coils was used to measure the gantry rotation through which each portal image was acquired. We performed the EPID QA for ten clinical plans and evaluated accuracy of gantry angle measurement, scatter incident on the imager due to the phantom, inter-image pixel linearity and inter- and intra-image noise. The gantry angle could be measured to within 0.0 ± 0.3° for static gantry and 0.2 ± 0.2° for arc acquisitions. Scatter due to the presence of the phantom was negligible. The procedure was shown to be feasible and adds gantry angle to the treatment planning parameters that can be verified by EPID-based pre-treatment VMAT QA.

Authors
Adamson, J; Wu, Q
MLA Citation
Adamson, J, and Wu, Q. "Independent verification of gantry angle for pre-treatment VMAT QA using EPID." Phys Med Biol 57.20 (October 21, 2012): 6587-6600.
PMID
23010739
Source
pubmed
Published In
Physics in Medicine and Biology
Volume
57
Issue
20
Publish Date
2012
Start Page
6587
End Page
6600
DOI
10.1088/0031-9155/57/20/6587

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

SU-E-T-104: Commissioning and Dosimetric Characteristics of TrueBeam System: Composite Data of Three TrueBeam Machines.

A TrueBeam linear accelerator (TB-LINAC) is designed to deliver standard flattened and flattening-filter-free (FFF) beams. In our institute, three TB-LINAC units are installed. In this work, composite data of the three units and multi-unit comparison are presented.Each TB-LINAC can deliver photon beams from 4MV to 15MV, electron beams from 6MeV to 22MeV, and 6MV-FFF and 10MV-FFF. Dosimetric characteristics are systematically measured for commissioning including percent depth dose (PDD), beam profile, relative scatter factor, dynamic leaf shift, output factor and MLC leakage. Critic considerations of Pion of FFF photon beams and dosimetric penumbra are investigated.All measured PDDs and profiles of photon and electron matched well across the three machines. Beam data were quantitatively compared and combined through average to yield composite beam data. The discrepancies among the machines were quantified using standard deviation (SD). For example, the mean SD of the PDDs among the three units is 0.12%, and the mean SD of the profiles is 0.40% for 10MV-FFF open fields. The variations of Pion of the chamber CC13 is 1.2±0.1% under 6MV-FFF and 2.0±0.5% from dmax to the 18cm-off-axis point at 35cm depth under 40×40cm2 . The measured relative output factors range from 0.866 to 1.141 with the mean discrepancy of 0.06±0.04% among the three units. The measured wedge factors range from 0.863 to 1.254 with the mean overall discrepancy of 0.04±0.04%. The mean MLC transmission and dynamic leaf shift were measured from 1.0% to 1.5% and from 0.77mm to 0.96 mm from 4MV to 15MV. The mean penumbra of various photon beams are measured from 5.88±0.09mm to 5.99±0.13mm from 4MV to 15MV at 10cm depth of 10×10 cm2 .Dosimetric data demonstrated that the three units could and had been matched well. The systematically measured data might be useful for future reference.

Authors
Chang, Z; Wu, Q; Adamson, J; Ren, L; Bowsher, J; Yan, H; Thomas, A; Yin, F
MLA Citation
Chang, Z, Wu, Q, Adamson, J, Ren, L, Bowsher, J, Yan, H, Thomas, A, and Yin, F. "SU-E-T-104: Commissioning and Dosimetric Characteristics of TrueBeam System: Composite Data of Three TrueBeam Machines." Medical physics 39.6Part11 (June 2012): 3726-.
PMID
28517167
Source
epmc
Published In
Medical physics
Volume
39
Issue
6Part11
Publish Date
2012
Start Page
3726
DOI
10.1118/1.4735162

SU-E-T-74: Assessing Effects of Ion Collection Efficiency in Flattening Filter-Free (FFF) Beams on Three TrueBeam Machines

Authors
Chang, Z; Wu, Q; Adamson, J; Ren, L; Bowsher, J; Yan, H; Thomas, A; Yin, F
MLA Citation
Chang, Z, Wu, Q, Adamson, J, Ren, L, Bowsher, J, Yan, H, Thomas, A, and Yin, F. "SU-E-T-74: Assessing Effects of Ion Collection Efficiency in Flattening Filter-Free (FFF) Beams on Three TrueBeam Machines." June 2012.
Source
crossref
Published In
Medical physics
Volume
39
Issue
6Part10
Publish Date
2012
Start Page
3719
End Page
3719
DOI
10.1118/1.4735130

Preoperative single fraction partial breast radiotherapy for early-stage breast cancer.

PURPOSE: Several recent series evaluating external beam accelerated partial breast irradiation (PBI) have reported adverse cosmetic outcomes, possibly related to large volumes of normal tissue receiving near-prescription doses. We hypothesized that delivery of external beam PBI in a single fraction to the preoperative tumor volume would be feasible and result in a decreased dose to the uninvolved breast compared with institutional postoperative PBI historical controls. METHODS AND MATERIALS: A total of 17 patients with unifocal Stage T1 breast cancer were identified. Contrast-enhanced subtraction magnetic resonance images were loaded into an Eclipse treatment planning system and used to define the target volumes. A "virtual plan" was created using four photon beams in a noncoplanar beam arrangement and optimized to deliver 15 Gy to the planning target volume. RESULTS: The median breast volume was 1,713 cm(3) (range: 1,014-2,140), and the median clinical target volume was 44 cm(3) (range: 26-73). In all cases, 100% of the prescription dose covered 95% of the clinical target volume. The median conformity index was 0.86 (range: 0.70-1.12). The median percentage of the ipsilateral breast volume receiving 100% and 50% of the prescribed dose was 3.8% (range: 2.2-6.9) and 13.3% (range: 7.5-20.8) compared with 18% (range: 3-42) and 53% (range: 24-65) in the institutional historical controls treated with postoperative external beam PBI (p = .002). The median maximum skin dose was 9 Gy. The median dose to 1 and 10 cm(3) of skin was 6.7 and 4.9 Gy. The doses to the heart and ipsilateral lung were negligible. CONCLUSION: Preoperative PBI resulted in a substantial reduction in ipsilateral breast tissue dose compared with postoperative PBI. The skin dose appeared reasonable, given the small volumes. A prospective Phase I trial evaluating this technique is ongoing.

Authors
Palta, M; Yoo, S; Adamson, JD; Prosnitz, LR; Horton, JK
MLA Citation
Palta, M, Yoo, S, Adamson, JD, Prosnitz, LR, and Horton, JK. "Preoperative single fraction partial breast radiotherapy for early-stage breast cancer." Int J Radiat Oncol Biol Phys 82.1 (January 1, 2012): 37-42.
PMID
21093166
Source
pubmed
Published In
International Journal of Radiation: Oncology - Biology - Physics
Volume
82
Issue
1
Publish Date
2012
Start Page
37
End Page
42
DOI
10.1016/j.ijrobp.2010.09.041

Imaging system QA of a medical accelerator, Novalis Tx, for IGRT per TG 142: our 1 year experience.

American Association of Physicists in Medicine (AAPM) task group (TG) 142 has recently published a report to update recommendations of the AAPM TG 40 report and add new recommendations concerning medical accelerators in the era of image-guided radiation therapy (IGRT). The recommendations of AAPM TG 142 on IGRT are timely. In our institute, we established a comprehensive imaging QA program on a medical accelerator based on AAPM TG 142 and implemented it successfully. In this paper, we share our one-year experience and performance evaluation of an OBI capable linear accelerator, Novalis Tx, per TG 142 guidelines.

Authors
Chang, Z; Bowsher, J; Cai, J; Yoo, S; Wang, Z; Adamson, J; Ren, L; Yin, FF
MLA Citation
Chang, Z, Bowsher, J, Cai, J, Yoo, S, Wang, Z, Adamson, J, Ren, L, and Yin, FF. "Imaging system QA of a medical accelerator, Novalis Tx, for IGRT per TG 142: our 1 year experience." Journal of applied clinical medical physics / American College of Medical Physics 13.4 (2012): 3754-. (Academic Article)
PMID
22766946
Source
manual
Published In
Journal of applied clinical medical physics / American College of Medical Physics
Volume
13
Issue
4
Publish Date
2012
Start Page
3754

Imaging system QA of a medical accelerator, Novalis Tx, for IGRT per TG 142: Our 1 year experience

American Association of Physicists in Medicine (AAPM) task group (TG) 142 has recently published a report to update recommendations of the AAPM TG 40 report and add new recommendations concerning medical accelerators in the era of image-guided radiation therapy (IGRT). The recommendations of AAPM TG 142 on IGRT are timely. In our institute, we established a comprehensive imaging QA program on a medical accelerator based on AAPM TG 142 and implemented it successfully. In this paper, we share our one-year experience and performance evaluation of an OBI capable linear accelerator, Novalis Tx, per TG 142 guidelines.

Authors
Chang, Z; Bowsher, J; Cai, J; Yoo, S; Wang, Z; Adamson, J; Ren, L; Yin, F-F
MLA Citation
Chang, Z, Bowsher, J, Cai, J, Yoo, S, Wang, Z, Adamson, J, Ren, L, and Yin, F-F. "Imaging system QA of a medical accelerator, Novalis Tx, for IGRT per TG 142: Our 1 year experience." Journal of Applied Clinical Medical Physics 13.4 (2012): 113-140.
Source
scival
Published In
Journal of applied clinical medical physics / American College of Medical Physics
Volume
13
Issue
4
Publish Date
2012
Start Page
113
End Page
140

Contour based respiratory motion analysis for free breathing CT.

We propose a method to quantify superior-inferior (SI) motion of a rigid target using the 3D contour from free-breathing CT (FBCT). The technique utilizes similarity between 2D contours (Jaccard Index) and a population based density function for probability of motion amplitude, and is applicable both when the static target shape is and is not known beforehand. Simulations and phantom measurements showed that motion reconstruction is often feasible, with decreasing accuracy as discrepancy is introduced between assumed and actual static shape. When no static shape is used the analysis is most robust for slow scanning speeds relative to the motion period.

Authors
Adamson, J; Zhuang, T; Yin, F-F
MLA Citation
Adamson, J, Zhuang, T, and Yin, F-F. "Contour based respiratory motion analysis for free breathing CT." Comput Biol Med 41.10 (October 2011): 908-915.
PMID
21839991
Source
pubmed
Published In
Computers in Biology and Medicine
Volume
41
Issue
10
Publish Date
2011
Start Page
908
End Page
915
DOI
10.1016/j.compbiomed.2011.08.002

Dosimetric effect of intrafraction motion and residual setup error for hypofractionated prostate intensity-modulated radiotherapy with online cone beam computed tomography image guidance.

PURPOSE: To quantify the dosimetric effect and margins required to account for prostate intrafractional translation and residual setup error in a cone beam computed tomography (CBCT)-guided hypofractionated radiotherapy protocol. METHODS AND MATERIALS: Prostate position after online correction was measured during dose delivery using simultaneous kV fluoroscopy and posttreatment CBCT in 572 fractions to 30 patients. We reconstructed the dose distribution to the clinical tumor volume (CTV) using a convolution of the static dose with a probability density function (PDF) based on the kV fluoroscopy, and we calculated the minimum dose received by 99% of the CTV (D(99)). We compared reconstructed doses when the convolution was performed per beam, per patient, and when the PDF was created using posttreatment CBCT. We determined the minimum axis-specific margins to limit CTV D(99) reduction to 1%. RESULTS: For 3-mm margins, D(99) reduction was ≤5% for 29/30 patients. Using post-CBCT rather than localizations at treatment delivery exaggerated dosimetric effects by ~47%, while there was no such bias between the dose convolved with a beam-specific and patient-specific PDF. After eight fractions, final cumulative D(99) could be predicted with a root mean square error of <1%. For 90% of patients, the required margins were ≤2, 4, and 3 mm, with 70%, 40%, and 33% of patients requiring no right-left (RL), anteroposterior (AP), and superoinferior margins, respectively. CONCLUSIONS: For protocols with CBCT guidance, RL, AP, and SI margins of 2, 4, and 3 mm are sufficient to account for translational errors; however, the large variation in patient-specific margins suggests that adaptive management may be beneficial.

Authors
Adamson, J; Wu, Q; Yan, D
MLA Citation
Adamson, J, Wu, Q, and Yan, D. "Dosimetric effect of intrafraction motion and residual setup error for hypofractionated prostate intensity-modulated radiotherapy with online cone beam computed tomography image guidance." Int J Radiat Oncol Biol Phys 80.2 (June 1, 2011): 453-461.
PMID
20646842
Source
pubmed
Published In
International Journal of Radiation: Oncology - Biology - Physics
Volume
80
Issue
2
Publish Date
2011
Start Page
453
End Page
461
DOI
10.1016/j.ijrobp.2010.02.033

WE-E-BRB-07: EPID Based Verification of Delivered Fluence for VMAT with High Angular Resolution

Authors
Adamson, J; Wu, Q
MLA Citation
Adamson, J, and Wu, Q. "WE-E-BRB-07: EPID Based Verification of Delivered Fluence for VMAT with High Angular Resolution." June 2011.
Source
crossref
Published In
Medical physics
Volume
38
Issue
6Part32
Publish Date
2011
Start Page
3817
End Page
3817
DOI
10.1118/1.3613374

Prostate intrafraction motion assessed by simultaneous kilovoltage fluoroscopy at megavoltage delivery I: clinical observations and pattern analysis.

PURPOSE: To describe prostate intrafraction motion using kilovoltage fluoroscopy at treatment delivery for a hypofractionated radiotherapy protocol. METHODS AND MATERIALS: Kilovoltage images were acquired during treatment delivery, as well as pre- and posttreatment cone-beam computed tomography (CBCT) for each fraction of 30 patients, totaling 571 fractions for analysis. We calculated population statistics, evaluated correlation between interfraction and intrafraction motion, evaluated effect of treatment duration, classified whether motion resolved by posttreatment CBCT, and compared motion magnitude on a per-patient basis. RESULTS: The elapsed time between pre- and post-CBCTs was (18.6 ± 4.5) min. The population mean of motion measured by kilovoltage fluoroscopy was (-0.1, 0.5, -0.6) mm, the systematic was (0.5, 1.3, 1.2) mm, and random was (0.9, 1.9, 2.0) mm in the right-left, anterior-posterior, and superior-inferior axes, respectively. The probability of motion increased with treatment duration, with the mean increasing to (0.0, 1.0, -0.9) mm and the systematic to (0.6, 1.7, 1.5) mm when measured using posttreatment CBCT. For any motion ≥2 mm, approximately 75% did not resolve by posttreatment CBCT. Motion magnitude varied considerably among patients, with the probability of a 5-mm displacement ranging from 0.0% to 58.8%. CONCLUSIONS: Time dependency of intrafraction motion should be considered to avoid bias in margin assessment, with posttreatment CBCT slightly exaggerating the true motion. The patient-specific nature of the intrafraction motion suggests that a patient-specific management approach may be beneficial.

Authors
Adamson, J; Wu, Q
MLA Citation
Adamson, J, and Wu, Q. "Prostate intrafraction motion assessed by simultaneous kilovoltage fluoroscopy at megavoltage delivery I: clinical observations and pattern analysis." Int J Radiat Oncol Biol Phys 78.5 (December 1, 2010): 1563-1570.
PMID
20579817
Source
pubmed
Published In
International Journal of Radiation: Oncology - Biology - Physics
Volume
78
Issue
5
Publish Date
2010
Start Page
1563
End Page
1570
DOI
10.1016/j.ijrobp.2009.09.027

Prostate intrafraction motion assessed by simultaneous kV fluoroscopy at MV delivery II: adaptive strategies.

PURPOSE: To investigate potential benefits of adaptive strategies for managing prostate intrafractional uncertainties when interfraction motion is corrected online. METHODS AND MATERIALS: Prostate intrafraction motion was measured using kV fluoroscopy during MV delivery for 571 fractions from 30 hypofractionated radiotherapy patients. We evaluated trending over treatment course using analysis of variance statistics, and we evaluated the ability to correct patient-specific systematic error and apply patient-specific statistical margins after 2 to 15 fractions to compensate 90% of motion. We also evaluated the ability to classify patients into small- and large-motion subgroups based on the first 2 to 20 fractions using discriminant analysis. RESULTS: No time trend was observed over treatment course, and intrafraction motion was patient specific (p < 0.0001). Systematic error in the first week correlated well with that in subsequent weeks, with correlation coefficients of 0.53, 0.50, and 0.41 in right-left (RL), anterior-posterior (AP), and superior-inferior (SI), respectively. After 5 fractions, the adaptive strategy resulted in average margin reductions of 0.3, 0.7, and 0.7 mm in RL, AP, and SI, respectively, with margins ranging from 1 to 3.2 mm in RL, 2 to 7.0 mm in AP, and 2 to 6.6 mm in SI. By contrast, population margins to include the same percentage of motion were 1.7, 4.0, and 4.1 mm. After 2 and 5 fractions, patients were classified into small- and large-motion groups with ~77% and ~83% accuracy. CONCLUSIONS: Adaptive strategies are feasible and beneficial for intrafraction motion management in prostate cancer online image guidance. Patients may be classified into large- and small-motion groups in early fractions using discriminant analysis.

Authors
Adamson, J; Wu, Q
MLA Citation
Adamson, J, and Wu, Q. "Prostate intrafraction motion assessed by simultaneous kV fluoroscopy at MV delivery II: adaptive strategies." Int J Radiat Oncol Biol Phys 78.5 (December 1, 2010): 1323-1330.
PMID
20584578
Source
pubmed
Published In
International Journal of Radiation: Oncology - Biology - Physics
Volume
78
Issue
5
Publish Date
2010
Start Page
1323
End Page
1330
DOI
10.1016/j.ijrobp.2009.09.079

Maximum intensity projection (MIP) imaging using slice-stacking MRI.

PURPOSE: To evaluate the feasibility of acquiring maximum intensity projection (MIP) images using a novel slice-stacking MRI (SS-MRI) technique. METHODS: The proposed technique employed a steady state acquisition sequence to image multiple axial slices. At each axial slice, the scan is repeated throughout one respiratory cycle. Four objects (small, medium, and large triangles, and a cylinder) moving with a patient breathing trajectory were imaged repeatedly for six times using the slice-stacking MRI and 4D-CT. MIP(SS-MRI) and MIP(4D-CT) were reconstructed. The internal target volume (ITV) was segmented for each object on the six scans and compared between MIP(SS-MRI) and MIP(4D-CT). The medium triangle was also imaged with various motion patterns using slice-stacking MRI, 4D-CT, and sagittal cine-MRI. The corresponding MIP images were reconstructed and volume/area measurements were performed and compared between different imaging methods. Three healthy volunteers underwent the slice-stacking MRI and sagittal cine-MRI scans. A region of interest (ROI) was selected and contoured for each subject in both MIP(SS-MRI) and MIP(cine-MRI). The area of the selected ROI was computed and compared. RESULTS: Volume comparison between MIP(SS-MRI) and MIP(4D-CT) showed statistically insignificant (p > 0.05 in all cases) difference in the mean ITVs for all four objects. For the study of the medium triangle with multiple motion patterns, there was a good agreement in the measured ITVs between MIP(SS-MRI) and MIP(4D-CT) (p = 0.46, correlation coefficient = 0.91), with a mean difference of 1.4% +/- 4.4%. The area measurements between MIP(SS-MRI) and MIP(cine-MRI) also showed good agreement (p=0.47, correlation coefficient = 0.97), with a mean difference of 0.2% +/- 2.9%. For the healthy volunteer study, the average difference in the area of selected ROI was -2.5% +/- 2.5% between MIP(SS-MRI) and MIP(cine-MRI). CONCLUSIONS: These preliminary results showed good agreement in volume/area measurements between the slice-stacking MRI technique and 4D-CT/cine-MRI, indicating that it is feasible to use this technique for MIP imaging.

Authors
Adamson, J; Chang, Z; Wang, Z; Yin, F-F; Cai, J
MLA Citation
Adamson, J, Chang, Z, Wang, Z, Yin, F-F, and Cai, J. "Maximum intensity projection (MIP) imaging using slice-stacking MRI." Med Phys 37.11 (November 2010): 5914-5920.
PMID
21158304
Source
pubmed
Published In
Medical physics
Volume
37
Issue
11
Publish Date
2010
Start Page
5914
End Page
5920
DOI
10.1118/1.3503850

SU-GG-I-140: Maximum Intensity Projection (MIP) Imaging Using Multi-Slice Cine MRI

Authors
Adamson, J; Chang, Z; Wang, Z; Yin, F; Cai, J
MLA Citation
Adamson, J, Chang, Z, Wang, Z, Yin, F, and Cai, J. "SU-GG-I-140: Maximum Intensity Projection (MIP) Imaging Using Multi-Slice Cine MRI." June 2010.
Source
crossref
Published In
Medical physics
Volume
37
Issue
6Part5
Publish Date
2010
Start Page
3133
End Page
3133
DOI
10.1118/1.3468174

SU-GG-T-483: Does Breath-Hold Immobilization Affect Tumor Radioresistance in Breast?

Authors
Adamson, J; Kirkpatrick, J; Yin, F
MLA Citation
Adamson, J, Kirkpatrick, J, and Yin, F. "SU-GG-T-483: Does Breath-Hold Immobilization Affect Tumor Radioresistance in Breast?." June 2010.
Source
crossref
Published In
Medical physics
Volume
37
Issue
6Part23
Publish Date
2010
Start Page
3298
End Page
3298
DOI
10.1118/1.3468881

Variation of Clinically Relevant Dose Indices for 3DCRT of Lung with Respect to Dose Calculation Algorithm

Authors
Adamson, JD; Yoo, S; Wu, Q; Yin, F
MLA Citation
Adamson, JD, Yoo, S, Wu, Q, and Yin, F. "Variation of Clinically Relevant Dose Indices for 3DCRT of Lung with Respect to Dose Calculation Algorithm." 2010.
Source
wos-lite
Published In
International Journal of Radiation Oncology, Biology, Physics
Volume
78
Issue
3
Publish Date
2010
Start Page
S712
End Page
S713

Inferences about prostate intrafraction motion from pre- and posttreatment volumetric imaging.

PURPOSE: To evaluate the ability of rectal filling, bladder filling, and prostate localization from pre- and posttreatment volumetric imaging to predict prostate intrafraction motion. METHODS AND MATERIALS: Pre- and posttreatment cone beam computed tomography images (CBCTs) and intrafractional kV fluoroscopy were acquired at each fraction for 20 prostate patients in supine position, totaling 374 fractions available for analysis. Rectal and bladder filling status were evaluated for each CBCT, and correlation with prostate intrafraction motion measured from kV fluoroscopy was performed. The accuracy of pre and posttreatment prostate localization to predict intrafraction motion was evaluated. RESULTS: Rectal filling status was a significant predictor of prostate intrafraction motion (p <0.001), and gas volume was correlated with the maximum vector displacement at MV delivery with a correlation coefficient (cc) of 0.37 and p <0.001. Prostate motion was greater for patients who consistently had gas volume >0.5 cm(3) within the imaged region (cc = 0.52, p = 0.028). A weak relationship was found between bladder filling and posterior prostate drift for fractions with gas volume

Authors
Adamson, J; Wu, Q
MLA Citation
Adamson, J, and Wu, Q. "Inferences about prostate intrafraction motion from pre- and posttreatment volumetric imaging." Int J Radiat Oncol Biol Phys 75.1 (September 1, 2009): 260-267.
PMID
19515507
Source
pubmed
Published In
International Journal of Radiation: Oncology - Biology - Physics
Volume
75
Issue
1
Publish Date
2009
Start Page
260
End Page
267
DOI
10.1016/j.ijrobp.2009.03.007

SU-FF-T-620: Assessment of Dose Reconstruction Methods for Prostate Image Guided Radiotherapy Protocols

Authors
Wu, Q; Adamson, J
MLA Citation
Wu, Q, and Adamson, J. "SU-FF-T-620: Assessment of Dose Reconstruction Methods for Prostate Image Guided Radiotherapy Protocols." June 2009.
Source
crossref
Published In
Medical physics
Volume
36
Issue
6Part18
Publish Date
2009
Start Page
2667
End Page
2667
DOI
10.1118/1.3182118

TU-C-303A-08: A Hybrid Strategy Using Discriminant Analysis for Prostate Intrafraction Motion Management

Authors
Adamson, J; Wu, Q; Yan, D
MLA Citation
Adamson, J, Wu, Q, and Yan, D. "TU-C-303A-08: A Hybrid Strategy Using Discriminant Analysis for Prostate Intrafraction Motion Management." June 2009.
Source
crossref
Published In
Medical physics
Volume
36
Issue
6Part22
Publish Date
2009
Start Page
2726
End Page
2726
DOI
10.1118/1.3182345

Optimizing monoscopic kV fluoro acquisition for prostate intrafraction motion evaluation.

Monoscopic kV imaging during radiotherapy has been recently implemented for prostate intrafraction motion evaluation. However, the accuracy of 3D localization techniques from monoscopic imaging of prostate and the effect of acquisition parameters on the 3D accuracy have not been studied in detail, with imaging dose remaining a concern. In this paper, we investigate methods to optimize the kV acquisition parameters and imaging protocol to achieve improved 3D localization and 2D image registration accuracy for minimal imaging dose. Prostate motion during radiotherapy was simulated using existing cine-MRI measurements, and was used to investigate the accuracy of various 3D localization techniques and the effect of the kV acquisition protocol. We also investigated the relationship between mAs and the accuracy of the 2D image registration for localization of fiducial markers and we measured imaging dose for a 30 cm diameter phantom to evaluate the necessary dose to achieve acceptable image registration accuracy. Simulations showed that the error in assuming the shortest path to localize the prostate in 3D using monoscopic imaging during a typical IMRT fraction will be less than approximately 1.5 mm for 95% of localizations, and will also depend on prostate motion distribution, treatment duration and image acquisition and treatment protocol. Most uncertainty cannot be reduced from higher imaging frequency or acquiring during gantry rotation between beams. Measured maximum surface dose to the cylindrical phantom from monoscopic kV intrafraction acquisitions varied between 0.4 and 5.5 mGy, depending on the acquisition protocol, and was lower than the required dose for CBCT (21.1 mGy). Imaging dose can be lowered by approximately 15-40% when mAs is optimized with acquisition angle. Images acquired during MV beam delivery require increased mAs to obtain the same level of registration accuracy, with mAs/registration increasing roughly linearly with field size and dose rate.

Authors
Adamson, J; Wu, Q
MLA Citation
Adamson, J, and Wu, Q. "Optimizing monoscopic kV fluoro acquisition for prostate intrafraction motion evaluation." Phys Med Biol 54.1 (January 7, 2009): 117-133.
PMID
19075358
Source
pubmed
Published In
Physics in Medicine and Biology
Volume
54
Issue
1
Publish Date
2009
Start Page
117
End Page
133
DOI
10.1088/0031-9155/54/1/008

Adaptive Management of Intrafraction Motion in Online Image Guided Prostate Cancer Radiotherapy

Authors
Adamson, JD; Wu, Q; Yan, D
MLA Citation
Adamson, JD, Wu, Q, and Yan, D. "Adaptive Management of Intrafraction Motion in Online Image Guided Prostate Cancer Radiotherapy." 2009.
Source
wos-lite
Published In
International Journal of Radiation Oncology, Biology, Physics
Volume
75
Issue
3
Publish Date
2009
Start Page
S628
End Page
S629

TU-C-351-03: Can Pre- and Post-Imaging Determine Prostate Intrafraction Motion?

Authors
Adamson, J; Wu, Q
MLA Citation
Adamson, J, and Wu, Q. "TU-C-351-03: Can Pre- and Post-Imaging Determine Prostate Intrafraction Motion?." June 2008.
Source
crossref
Published In
Medical physics
Volume
35
Issue
6Part20
Publish Date
2008
Start Page
2891
End Page
2891
DOI
10.1118/1.2962462

TU-FF-A3-05: Optimizing KV Fluoro Acquisition for Prostate Intrafraction Motion Evaluation

Authors
Adamson, J; Wu, Q
MLA Citation
Adamson, J, and Wu, Q. "TU-FF-A3-05: Optimizing KV Fluoro Acquisition for Prostate Intrafraction Motion Evaluation." June 2008.
Source
crossref
Published In
Medical physics
Volume
35
Issue
6Part22
Publish Date
2008
Start Page
2922
End Page
2922
DOI
10.1118/1.2962654

Prostate intrafraction motion evaluation using kV fluoroscopy during treatment delivery: a feasibility and accuracy study.

Margin reduction for prostate radiotherapy is limited by uncertainty in prostate localization during treatment. We investigated the feasibility and accuracy of measuring prostate intrafraction motion using kV fluoroscopy performed simultaneously with radiotherapy. Three gold coils used for target localization were implanted into the patient's prostate gland before undergoing hypofractionated online image-guided step-and-shoot intensity modulated radiation therapy (IMRT) on an Elekta Synergy linear accelerator. At each fraction, the patient was aligned using a cone-beam computed tomography (CBCT), after which the IMRT treatment delivery and fluoroscopy were performed simultaneously. In addition, a post-treatment CBCT was acquired with the patient still on the table. To measure the intrafraction motion, we developed an algorithm to register the fluoroscopy images to a reference image derived from the post-treatment CBCT, and we estimated coil motion in three-dimensional (3D) space by combining information from registrations at different gantry angles. We also detected the MV beam turning on and off using MV scatter incident in the same fluoroscopy images, and used this information to synchronize our intrafraction evaluation with the treatment delivery. In addition, we assessed the following: the method to synchronize with treatment delivery, the dose from kV imaging, the accuracy of the localization, and the error propagated into the 3D localization from motion between fluoroscopy acquisitions. With 0.16 mAs/frame and a bowtie filter implemented, the coils could be localized with the gantry at both 0 degrees and 270 degrees with the MV beam off, and at 270 degrees with the MV beam on when multiple fluoroscopy frames were averaged. The localization in two-dimensions for phantom and patient measurements was performed with submillimeter accuracy. After backprojection into 3D the patient localization error was (-0.04 +/- 0.30) mm, (0.09 +/- 0.36)mm, and (0.03 +/- 0.68)mm in the right-left (RL), anterior-posterior (AP), and superior-inferior (SI) axes, respectively. Simulations showed that while oscillating (stationary) motion cannot be effectively represented in 3D, linearly drifting (nonstationary) motion is detectable with good accuracy. These results show that measuring prostate intrafraction motion using a single kV imager during radiotherapy is feasible and can be performed with acceptable accuracy.

Authors
Adamson, J; Wu, Q
MLA Citation
Adamson, J, and Wu, Q. "Prostate intrafraction motion evaluation using kV fluoroscopy during treatment delivery: a feasibility and accuracy study." Med Phys 35.5 (May 2008): 1793-1806.
PMID
18561654
Source
pubmed
Published In
Medical physics
Volume
35
Issue
5
Publish Date
2008
Start Page
1793
End Page
1806
DOI
10.1118/1.2899998

WE-E-M100F-07: Prostate Intrafraction Motion Measurement Using KV Fluoroscopy During Treatment Delivery

Authors
Adamson, J; Wu, Q
MLA Citation
Adamson, J, and Wu, Q. "WE-E-M100F-07: Prostate Intrafraction Motion Measurement Using KV Fluoroscopy During Treatment Delivery." Medical Physics 34.6Part21 (June 2007): 2608-2609.
Source
crossref
Published In
Medical physics
Volume
34
Issue
6Part21
Publish Date
2007
Start Page
2608
End Page
2609
DOI
10.1118/1.2761589

Long-path measurements of ultrasonic attenuation and velocity for very dilute slurries and liquids and detection of contaminates.

The objective was to use multiple paths through the slurry to determine the lowest concentration that provided accurate attenuation measurements and to measure the velocity of sound through an effective long path. Ultrasonic attenuation measurements were obtained for slurries of silica (10 microm diameter) in water for concentrations of 0.1%, 0.25%, 0.5%, 0.75% and 1% silica by weight. Attenuation measurements for concentrations less than 0.1% may prove useful for process control to detect contaminants. A long path is obtained due to multiple reflections occurring within the stainless steel (SS) vessel used; broad-band transducers are affixed on the outside of the thick-walled vessel. The signal in the receive transducer permits the measurement of the attenuation and also the velocity by measuring the time-of-flight. The FFT of the appropriate signal for each echo was obtained and compared with that for water to yield the attenuation as a function of frequency. The attenuation measurements are self-calibrating because they are not affected by changes in the pulser voltage. The data show the feasibility for measuring a concentration of 0.025 wt% silica, which is equivalent to 0.25 g of silica in 1 l of water. Therefore, such measurements can prove useful for detecting contaminants in liquid. The velocity of sound measurements for solutions of hydrogen peroxide in water were obtained and accurate to about 0.3m/s, or 0.02% uncertainty.

Authors
Greenwood, MS; Adamson, JD; Bamberger, JA
MLA Citation
Greenwood, MS, Adamson, JD, and Bamberger, JA. "Long-path measurements of ultrasonic attenuation and velocity for very dilute slurries and liquids and detection of contaminates." Ultrasonics 44 Suppl 1 (December 22, 2006): e461-e466.
PMID
16781750
Source
pubmed
Published In
Ultrasonics
Volume
44 Suppl 1
Publish Date
2006
Start Page
e461
End Page
e466
DOI
10.1016/j.ultras.2006.05.024

Measurement of the viscosity-density product using multiple reflections of ultrasonic shear horizontal waves.

We have developed an on-line computer-controlled sensor, based on ultrasound reflection measurements, to determine the product of the viscosity and density of a liquid or slurry for Newtonian fluids and the shear impedance of the liquid for non-Newtonian fluids. A 14 MHz shear wave transducer is bonded to one side of a 45-90 degrees fused silica wedge and the base is in contract with the liquid. Twenty-eight echoes were observed due to the multiple reflections of an ultrasonic shear horizontal (SH) wave within the wedge. The fast Fourier transform of each echo was obtained for a liquid and for water, which serves as the calibration fluid, and the reflection coefficient at the solid-liquid interface was obtained. Data were obtained for 11 sugar water solutions ranging in concentration from 10% to 66% by weight. The viscosity values are shown to be in good agreement with those obtained independently using a laboratory viscometer. The data acquisition time is 14s and this can be reduced by judicious selection of the echoes for determining the reflection coefficient. The measurement of the density results in a determination of the viscosity for Newtonian fluids or the shear wave velocity for non-Newtonian fluids. The sensor can be deployed for process control in a pipeline, with the base of the wedge as part of the pipeline wall, or immersed in a tank.

Authors
Greenwood, MS; Adamson, JD; Bond, LJ
MLA Citation
Greenwood, MS, Adamson, JD, and Bond, LJ. "Measurement of the viscosity-density product using multiple reflections of ultrasonic shear horizontal waves." Ultrasonics 44 Suppl 1 (December 22, 2006): e1031-e1036.
PMID
16793108
Source
pubmed
Published In
Ultrasonics
Volume
44 Suppl 1
Publish Date
2006
Start Page
e1031
End Page
e1036
DOI
10.1016/j.ultras.2006.05.093

Measurement of the viscosity-density product using a quartz wedge

The on-line measurement of the viscosity-density product is accomplished by analyzing the multiple reflections of an ultrasonic shear horizontal (SH) wave within a quartz wedge. Many echoes are observed as the ultrasound is reflected from the two sides (inclined at a 70° angle) and the quartz-liquid interface at the base of the wedge. The analysis yields a very accurate measurement of the reflection coefficient. The measurement is self-calibrating because it is not affected by changes in the pulser voltage. © 2005 American Institute of Physics.

Authors
Greenwood, MS; Adamson, JD; Bond, LJ
MLA Citation
Greenwood, MS, Adamson, JD, and Bond, LJ. "Measurement of the viscosity-density product using a quartz wedge." AIP Conference Proceedings 760 (2005): 1690-1697.
Source
scival
Published In
AIP Conference Proceedings
Volume
760
Publish Date
2005
Start Page
1690
End Page
1697
DOI
10.1063/1.1916874

Development of enhanced ultrasonic imaging for in situ inspection of a tension-stressed, threaded fastener

A laboratory system was developed that utilized an ultrasonic pulse-echo technique to detect very small cracks emanating from the thread root of a tensile-stressed fastener. Primary benefits were 1) the ability to inspect the fastener without its removal from the structure, 2) much improved detection sensitivity to small cracks, and 3) easy interpretation of data. The fastener of interest had threads with nominal inner and outer diameters of 1.8 cm (0.73 in.) and 2.2 cm (0.86 in.), respectively, and a thread pitch of 3.1 threads per centimeter (8.0 threads per in.). A plastic washer was placed over the fastener nut to shield the nut from ultrasound and thereby eliminate spurious signals. B-scan images provided feedback to align the ultrasonic scanner and fastener for optimal detection sensitivity. A tone-burst pulser-receiver controlled excitation frequency and bandwidth to maintain focal properties, minimize backscatter noise from the base material, and increase penetration into the coarse-grained Inconel. A custom ultrasonic transducer was used to optimize the focal properties over the inspection zone of 2.3 cm to 3.3 cm (0.9 in. to 1.3 in.) from the threaded end of the fastener. A calibration part with four 1.0-mm (0.040-in.) deep notches spanning the length of the inspection zone was used to calibrate distance-amplitude correction and system sensitivity. Custom B-scan and C-scan views were used to present data to the inspector and optimize the signal-to-noise ratio. A direct comparison was made between ultrasonic and destructive test images. Details of system hardware, data-acquisition procedure, analysis, and plans for a portable hand-held system for field inspection are provided.

Authors
Good, MS; Jr, RVH; Skorpik, JR; Pardini, AF; Smith, CM; Bowey, RE; Diaz, AA; Burghard, BJ; Judd, KM; Adamson, JD
MLA Citation
Good, MS, Jr, RVH, Skorpik, JR, Pardini, AF, Smith, CM, Bowey, RE, Diaz, AA, Burghard, BJ, Judd, KM, and Adamson, JD. "Development of enhanced ultrasonic imaging for in situ inspection of a tension-stressed, threaded fastener." Proceedings of SPIE - The International Society for Optical Engineering 3995 (2000): 590-599.
Source
scival
Published In
Proceedings of SPIE - The International Society for Optical Engineering
Volume
3995
Publish Date
2000
Start Page
590
End Page
599
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