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Tornai, Martin Paul

Overview:

The major research focus of my laboratory concerns high resolution and sensitivity molecular imaging of normalcy and/or disease in the breast using dedicated molecular 3D imaging techniques. Particular attention is paid to improved patient comfort such that no breast compression is necessary, which then dictates novel physics and engineering approaches to obtaining the highest quality data. The term "molecular imaging" means determining the spatial distribution of biological materials based on their molecular characteristics. Two examples include: the in vivo detection and spatial localization of tracer quantities of discretely emitted nuclear radiation which can be used to quantitatively measure aspects of the biological system (e.g. reaction kinetics, hyper/hypo-metabolism, etc.), and the in vivo spatial localization of objects based on their intrinsic physical properties, e.g. differentiation of skin, fat and connective tissue based on differences in their intrinsic electron densities.

Two classes of devices have been developed, are in refinement and are undergoing patient studies: (1) a dedicated, fully 3D, volumetric imaging Single Photon Emission Computed Tomograph (SPECT) device which produces functional molecular images with high resolution and sensitivity; and (2) a dedicated, fully 3D, volumetric x-ray CT device which incorporates a novel quasi-monochromatic x-ray source allowing more optimal imaging with lower radiation doses which produces molecular anatomical images. Along with geometric calibration objects, small animals and cadaveric breast tissue samples have been scanned, yielding high resolution and high quality in vivo images. Patient imaging has successfully begun on these novel developed systems. We have integrated a flexible patient bed to help comfortably position patients in each systems' field of view. Further, the individual systems have been integrated to form a hybrid SPECT/CT mammotomograph providing inherently coregistered, fully 3D, complementary molecular/anatomical information for the same patient and in a common field of view. These technologies could be used for diagnostic purposes, monitoring therapy and/or treatment planning, screening difficult or otherwise inconclusive breasts or scanning women at high risk for breast cancer. Due to the very low x-ray radiation doses possible to obtain the 3D images, the CT system could potentially be used to screen the population at large.

Positions:

Associate Professor of Radiology

Radiology
School of Medicine

Member of the Duke Cancer Institute

Duke Cancer Institute
School of Medicine

Education:

B.S. 1989

B.S. — Cornell University

Ph.D. 1997

Ph.D. — University of California at Los Angeles

Grants:

Training in Medical Imaging

Administered By
Biomedical Engineering
AwardedBy
National Institutes of Health
Role
Mentor
Start Date
July 15, 2003
End Date
August 31, 2019

X-Ray Scatter and Phase Imaging for Explosive Detection

Administered By
Electrical and Computer Engineering
AwardedBy
US Department of Homeland Security
Role
Co-Principal Investigator
Start Date
September 23, 2011
End Date
September 25, 2015

Simultaneous Emission and Transmission Mammotomography

Administered By
Radiology
AwardedBy
National Institutes of Health
Role
Principal Investigator
Start Date
September 19, 2002
End Date
July 31, 2014

Cross-disciplinary Training in Medical Physics

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

Design, Implementation, and Characterization of a Dedicated Breast Computed MamoTomography (CmT) System for Enhanced

Administered By
Radiology
AwardedBy
Department of Defense
Role
Principal Investigator
Start Date
March 01, 2005
End Date
March 31, 2008

Two Day Workshop on the Nuclear Radiology of Breast Cancer

Administered By
Radiology
AwardedBy
National Institutes of Health
Role
Principal Investigator
Start Date
November 20, 2002
End Date
October 31, 2003
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Publications:

Implementation and first results of the fully suspended cone beam CT and SPECT system for dedicated breast imaging

© 2015 IEEE.Stand-alone cone beam CT and SPECT systems capable of complex sinusoidal acquisition trajectories have previously been developed for dedicated breast imaging and used in early clinical studies. The fully-3D motions of the SPECT system can view into the chest wall and throughout the breast volume. The polar tilting capability of the CT system has shown a marked improvement in sampling into the chest wall, with comparable <6 mGy total dose delivered to the volume as with a circular orbit, while eliminating cone beam artifacts because of the fully-3D acquisitions. A hybrid SPECT-CT system, with each individual modality capable of independently traversing complex trajectories around a pendant breast, was recently designed and the practical implementation of this design is presented here. The CT system consists of a 40×30 cm2 CsI(Tl) flat panel imager and an x-ray tube with a 16° W-anode angle, placed on opposing ends of the completely suspended gantry. A linear stage mechanism utilizing a pulley and cabling was implemented to tilt the suspended gantry within 0.02° positioning error about the 3D center of rotation; the fully-3D SPECT system with 16×20 cm2 CZT detector is nested inside the suspended CT gantry, oriented perpendicular to the CT source-detector pair. Both sub-systems are positioned on an azimuthal rotation stage enabling spherical trajectories. Initial imaging results demonstrate that additional off-axis projection views of various phantoms, allowed by the ±15° polar tilting of the CT system, facilitate more complete sampling and markedly improved reconstructions. To date, this is the first implementation of a fully-3D positioning hybrid SPECT-CT system that we are aware of, and could have various applications in diagnostic or therapeutic breast imaging.

Authors
Shah, JP; Mann, SD; McKinley, RL; Tornai, MP
MLA Citation
Shah, JP, Mann, SD, McKinley, RL, and Tornai, MP. "Implementation and first results of the fully suspended cone beam CT and SPECT system for dedicated breast imaging." October 3, 2016.
Source
scopus
Published In
2015 IEEE Nuclear Science Symposium and Medical Imaging Conference, NSS/MIC 2015
Publish Date
2016
DOI
10.1109/NSSMIC.2015.7582132

Development of fully-3D CT in a hybrid SPECT-CT breast imaging system

© Springer International Publishing Switzerland 2016.This work describes initial measurements with the CT subsystem of the assembled, fully-3D, hybrid SPECT-CT system for dedicated breast imaging. The hybrid system, designed for clinical breast imaging, consists of fully-flexible SPECT and CT subsystems, with each capable of 3D acquisition motions. The SPECT subsystem employs a 16 × 20 cm2 CZT detector with 2.5 mm pixellation, is capable of viewing into the chest wall in addition to imaging the complete breast volume, and has been extensively reported elsewhere. The polar tilting capability of the CT subsystem has marked improvement in volumetric sampling while eliminating cone beam artifacts due to the fully-3D acquisitions. The CT subsystem can also view into the chest wall, while delivering <5 mGy total dose, compared with a simple circular orbit breast CT. The CT subsystem consists of a 0.4 mm focal spot x-ray tube with a rotating 14° W-anode angle, and a 40 × 30 cm2 CsI(Tl) flat panel imager having 127 micron pixellation and 8.0 mm bezel edge, placed on opposing ends of the completely suspended gantry. A linear stage mechanism is used to tilt the suspended CT gantry up to ±15° in the polar directions about the 3D center of rotation; the SPECT system is nestled inside the suspended CT gantry, oriented perpendicular to the CT source-detector pair. Both subsystems rest on an azimuthal rotation stage enabling truncated spherical trajectories independently for each. Several simple and more complex 3D trajectories were implemented and characterized for the CT subsystem. Imaging results demonstrate that additional off-axis projection views of various geometric phantoms and intact cadaveric breast, facilitated by the polar tilting yield more complete breast-volume sampling and markedly improved iteratively reconstructed images, especially compared to simple circular orbit data. This is the first implementation of a hybrid SPECT-CT system with fully-3D positioning for the two subsystems, and could have various applications in diagnostic breast imaging.

Authors
Tornai, MP; Shah, JP; Mann, SD; McKinley, RL
MLA Citation
Tornai, MP, Shah, JP, Mann, SD, and McKinley, RL. "Development of fully-3D CT in a hybrid SPECT-CT breast imaging system." January 1, 2016.
Source
scopus
Published In
Lecture notes in computer science
Volume
9699
Publish Date
2016
Start Page
567
End Page
575
DOI
10.1007/978-3-319-41546-8_71

Three dimensional dose distribution comparison of simple and complex acquisition trajectories in dedicated breast CT.

A novel breast CT system capable of arbitrary 3D trajectories has been developed to address cone beam sampling insufficiency as well as to image further into the patient's chest wall. The purpose of this study was to characterize any trajectory-related differences in 3D x-ray dose distribution in a pendant target when imaged with different orbits.Two acquisition trajectories were evaluated: circular azimuthal (no-tilt) and sinusoidal (saddle) orbit with ±15° tilts around a pendant breast, using Monte Carlo simulations as well as physical measurements. Simulations were performed with tungsten (W) filtration of a W-anode source; the simulated source flux was normalized to the measured exposure of a W-anode source. A water-filled cylindrical phantom was divided into 1 cm(3) voxels, and the cumulative energy deposited was tracked in each voxel. Energy deposited per voxel was converted to dose, yielding the 3D distributed dose volumes. Additionally, three cylindrical phantoms of different diameters (10, 12.5, and 15 cm) and an anthropomorphic breast phantom, initially filled with water (mimicking pure fibroglandular tissue) and then with a 75% methanol-25% water mixture (mimicking 50-50 fibroglandular-adipose tissues), were used to simulate the pendant breast geometry and scanned on the physical system. Ionization chamber calibrated radiochromic film was used to determine the dose delivered in a 2D plane through the center of the volume for a fully 3D CT scan using the different orbits.Measured experimental results for the same exposure indicated that the mean dose measured throughout the central slice for different diameters ranged from 3.93 to 5.28 mGy, with the lowest average dose measured on the largest cylinder with water mimicking a homogeneously fibroglandular breast. These results align well with the cylinder phantom Monte Carlo studies which also showed a marginal difference in dose delivered by a saddle trajectory in the central slice. Regardless of phantom material or filled fluid density, dose delivered by the saddle scan was negligibly different than the simple circular, no-tilt scans. The average dose measured in the breast phantom was marginally higher for saddle than the circular no tilt scan at 3.82 and 3.87 mGy, respectively.Not only does nontraditional 3D-trajectory CT scanning yield more complete sampling of the breast volume but also has comparable dose deposition throughout the breast and anterior chest volume, as verified by Monte Carlo simulation and physical measurements.

Authors
Shah, JP; Mann, SD; McKinley, RL; Tornai, MP
MLA Citation
Shah, JP, Mann, SD, McKinley, RL, and Tornai, MP. "Three dimensional dose distribution comparison of simple and complex acquisition trajectories in dedicated breast CT." Medical physics 42.8 (August 2015): 4497-4510.
PMID
26233179
Source
epmc
Published In
Medical physics
Volume
42
Issue
8
Publish Date
2015
Start Page
4497
End Page
4510
DOI
10.1118/1.4923169

Characterization of simulated incident scatter and the impact on quantification in dedicated breast single-photon emission computed tomography.

The objective was to characterize the changes seen from incident Monte Carlo-based scatter distributions in dedicated three-dimensional (3-D) breast single-photon emission computed tomography, with emphasis on the impact of scatter correction using the dual-energy window (DEW) method. Changes in scatter distributions with 3-D detector position were investigated for prone breast imaging with an ideal detector. Energy spectra within a high-energy scatter window measured from simulations were linearly fit, and the slope was used to characterize scatter distributions. The impact of detector position on the measured scatter fraction within various photopeak windows and the [Formula: see text] value (ratio of scatter within the photopeak and scatter energy windows) useful for scatter correction was determined. Results indicate that application of a single [Formula: see text] value with the DEW method in the presence of anisotropic object scatter distribution is not appropriate for trajectories including the heart and liver. The scatter spectra's slope demonstrates a strong correlation to measured [Formula: see text] values. Reconstructions of fixed-tilt 3-D acquisition trajectories with a single [Formula: see text] value show quantification errors up to 5% compared to primary-only reconstructions. However, a variable-tilt trajectory provides improved sampling and minimizes quantification errors, and thus allows for a single [Formula: see text] value to be used with the DEW method leading to more accurate quantification.

Authors
Mann, SD; Tornai, MP
MLA Citation
Mann, SD, and Tornai, MP. "Characterization of simulated incident scatter and the impact on quantification in dedicated breast single-photon emission computed tomography." Journal of medical imaging (Bellingham, Wash.) 2.3 (July 2015): 033504-.
PMID
26839906
Source
epmc
Published In
Journal of medical imaging (Bellingham, Wash.)
Volume
2
Issue
3
Publish Date
2015
Start Page
033504
DOI
10.1117/1.jmi.2.3.033504

The Spectrum of Medical Imaging in the 2015 International Year of Light.

Authors
Giger, ML; Tornai, MP
MLA Citation
Giger, ML, and Tornai, MP. "The Spectrum of Medical Imaging in the 2015 International Year of Light." Journal of medical imaging (Bellingham, Wash.) 2.3 (July 2015): 030101-.
PMID
26839902
Source
epmc
Published In
Journal of medical imaging (Bellingham, Wash.)
Volume
2
Issue
3
Publish Date
2015
Start Page
030101
DOI
10.1117/1.jmi.2.3.030101

Initial evaluation of a modified dual-energy window scatter correction method for CZT-based gamma cameras for breast SPECT

© 2015 SPIE.Solid state Cadmium Zinc Telluride (CZT) gamma cameras for SPECT imaging offer significantly improved energy resolution compared to traditional scintillation detectors. However, the photopeak resolution is often asymmetric due to incomplete charge collection within the detector, resulting in many photopeak events incorrectly sorted into lower energy bins ("tailing"). These misplaced events contaminate the true scatter signal, which may negatively impact scatter correction methods that rely on estimates of scatter from the spectra. Additionally, because CZT detectors are organized into arrays, each individual detector element may exhibit different degrees of tailing. Here, we present a modified dualenergy window scatter correction method for emission detection and imaging that attempts to account for positiondependent effects of incomplete charge collection in the CZT gamma camera of our dedicated breast SPECT-CT system. Point source measurements and geometric phantoms were used to estimate the impact of tailing on the scatter signal and extract a better estimate of the ratio of scatter within two energy windows. To evaluate the method, cylindrical phantoms with and without a separate fillable chamber were scanned to determine the impact on quantification in hot, cold, and uniform background regions. Projections were reconstructed using OSEM, and the results for the traditional and modified scatter correction methods were compared. Results show that while modest reduced quantification accuracy was observed in hot and cold regions of the multi-chamber phantoms, the modified scatter correction method yields up to 8% improved quantification accuracy with 4% less added noise than the traditional DEW method within uniform background regions.

Authors
Mann, SD; Tornai, MP
MLA Citation
Mann, SD, and Tornai, MP. "Initial evaluation of a modified dual-energy window scatter correction method for CZT-based gamma cameras for breast SPECT." January 1, 2015.
Source
scopus
Published In
Proceedings of SPIE
Volume
9413
Publish Date
2015
DOI
10.1117/12.2082195

Three dimensional dose distribution comparison of simple and complex acquisition trajectories in dedicated breast CT using radiochromic film

© 2015 SPIE.A novel breast CT system capable of traversing non-traditional 3D trajectories was developed to address cone beam sampling insufficiency for pendant breast imaging. The purpose of this study was to characterize differences in three dimensional x-ray dose distributions in a target volume due to the acquisition trajectory. Three cylindrical phantoms of different diameters and an anthropomorphic breast phantom were scanned in a pendant geometry with two orbits- azimuthal orbit with no polar tilt, and a saddle orbit with ±15° contiguous polar tilts. The phantoms were initially filled with water and then with a 75:25% water: methanol mixture, to simulate different density breast tissues. Fully-3D CT scans were performed using a tungsten anode x-ray source. Ionization chamber calibrated radiochromic film was used to determine average dose delivered to the central sagittal slice of a volume, as well as to visualize the 2D dose distribution across the slice. Results indicated that the mean glandular dose for normal imaging exposures, measured at the central slice across different diameters ranged from 3.93-5.28 mGy, with the lowest average dose measured on the largest diameter cylinder. In all cases, the dose delivered by the saddle was consistently 1-3% lower than the no-tilt scans. These results corroborate previous cylinder Monte Carlo studies which showed a 1% reduction in saddle dose. The average dose measured in the breast phantom filled with 75:25 mixture was slightly higher for saddle. Non-traditional 3D breast CT scans have slightly better dose performance for equal image noise compared with simple, under sampled circular orbits.

Authors
Shah, JP; Mann, SD; McKinley, RL; Tornai, MP
MLA Citation
Shah, JP, Mann, SD, McKinley, RL, and Tornai, MP. "Three dimensional dose distribution comparison of simple and complex acquisition trajectories in dedicated breast CT using radiochromic film." January 1, 2015.
Source
scopus
Published In
Proceedings of SPIE
Volume
9412
Publish Date
2015
DOI
10.1117/12.2082081

Coded aperture x-ray scatter tomography

We present a system for X-ray tomography using a coded aperture. A fan beam illuminates a 2D cross-section of an object and our coded aperture system produces a tomographic image from each static snapshot; as such, we can reconstruct either a static object scanned in 3D or an x-ray video of a non-static object. © 2014 SPIE-IS&T.

Authors
Holmgren, AD; Maccabe, KP; Tornai, MP; Brady, DJ
MLA Citation
Holmgren, AD, Maccabe, KP, Tornai, MP, and Brady, DJ. "Coded aperture x-ray scatter tomography." Proceedings of SPIE - The International Society for Optical Engineering 9020 (January 1, 2014).
Source
scopus
Published In
Proceedings of SPIE - The International Society for Optical Engineering
Volume
9020
Publish Date
2014
DOI
10.1117/12.2048267

MTF characterization in 2D and 3D for a high resolution, large field of view flat panel imager for cone beam CT

The 2D and 3D modulation transfer functions (MTFs) of a custom made, large 40x30cm2 area, 600- micron CsI-TFT based flat panel imager having 127-micron pixellation, along with the micro-fiber scintillator structure, were characterized in detail using various techniques. The larger area detector yields a reconstructed FOV of 25cm diameter with an 80cm SID in CT mode. The MTFs were determined with 1x1 (intrinsic) binning. The 2D MTFs were determined using a 50.8 micron tungsten wire and a solid lead edge, and the 3D MTF was measured using a custom made phantom consisting of three nearly orthogonal 50.8 micron tungsten wires suspended in an acrylic cubic frame. The 2D projection data was reconstructed using an iterative OSC algorithm using 16 subsets and 5 iterations. As additional verification of the resolution, along with scatter, the Catphan® phantom was also imaged and reconstructed with identical parameters. The measured 2D MTF was 4% using the wire technique and 1% using the edge technique at the 3.94 lp/mm Nyquist cut-off frequency. The average 3D MTF measured along the wires was 8% at the Nyquist. At 50% MTF, the resolutions were 1.2 and 2.1 lp/mm in 2D and 3D, respectively. In the Catphan® phantom, the 1.7 lp/mm bars were easily observed. Lastly, the 3D MTF measured on the three wires has an observed 5.9% RMSD, indicating that the resolution of the imaging system is uniform and spatially independent. This high performance detector is integrated into a dedicated breast SPECT-CT imaging system. © 2014 SPIE.

Authors
Shah, J; Mann, SD; Tornai, MP; Richmond, M; Zentai, G
MLA Citation
Shah, J, Mann, SD, Tornai, MP, Richmond, M, and Zentai, G. "MTF characterization in 2D and 3D for a high resolution, large field of view flat panel imager for cone beam CT." Progress in Biomedical Optics and Imaging - Proceedings of SPIE 9033 (January 1, 2014).
Source
scopus
Published In
Proceedings of SPIE
Volume
9033
Publish Date
2014
DOI
10.1117/12.2043727

Comparison of the effect of simple and complex acquisition trajectories on the 2D SPR and 3D voxelized differences for dedicated breast CT imaging

The 2D scatter-to-primary (SPR) ratios and 3D voxelized difference volumes were characterized for a cone beam breast CT scanner capable of arbitrary (non-traditional) 3D trajectories. The CT system uses a 30x30cm2 flat panel imager with 197 micron pixellation and a rotating tungsten anode x-ray source with 0.3mm focal spot, with an SID of 70cm. Data were acquired for two cylindrical phantoms (12.5cm and 15cm diameter) filled with three different combinations of water and methanol yielding a range of uniform densities. Projections were acquired with two acquisition trajectories: 1) simple-circular azimuthal orbit with fixed tilt; and 2) saddle orbit following a ±15° sinusoidal trajectory around the object. Projection data were acquired in 2x2 binned mode. Projections were scatter corrected using a beam stop array method, and the 2D SPR was measured on the projections. The scatter corrected and uncorrected data were then reconstructed individually using an iterative ordered subsets convex algorithm, and the 3D difference volumes were calculated as the absolute difference between the two. Results indicate that the 2D SPR is 7-15% higher on projections with greatest tilt for the saddle orbit, due to the longer x-ray path length through the volume, compared to the 0° tilt projections. Additionally, the 2D SPR increases with object diameter as well as density. The 3D voxelized difference volumes are an estimate of the scatter contribution to the reconstructed attenuation coefficients on a voxel level. They help visualize minor deficiencies and artifacts in the volumes due to correction methods. © 2014 SPIE.

Authors
Shah, JP; Mann, SD; McKinley, RL; Tornai, MP
MLA Citation
Shah, JP, Mann, SD, McKinley, RL, and Tornai, MP. "Comparison of the effect of simple and complex acquisition trajectories on the 2D SPR and 3D voxelized differences for dedicated breast CT imaging." Progress in Biomedical Optics and Imaging - Proceedings of SPIE 9033 (January 1, 2014).
Source
scopus
Published In
Proceedings of SPIE
Volume
9033
Publish Date
2014
DOI
10.1117/12.2043764

Design of a nested SPECT-CT system with fully suspended CT sub-system for dedicated breast imaging

A fully suspended, stand-Alone cone beam CT system capable of complex trajectories, in addition to a simple circular trajectory, has previously been developed and shown to minimize cone beam sampling insufficiencies and have better sampling close to the chest wall for pendant breast CT imaging. A hybrid SPECT-CT system with SPECT capable of complex 3D trajectories has already been implemented and is currently in use. Here, the individual systems are redesigned into one hybrid system where each individual component is capable of traversing independent, arbitrary trajectories around a pendant breast and anterior chest wall in a common field of view. The integration also involves key hardware upgrades: a new high resolution 40x30cm2 flat panel CT imager with an 8mm bezel on two sides for closer chest wall access, a new x-ray source, and a unique tilting mechanism to enable the spherical trajectories for CT. A novel method to tilt the CT gantry about a 3D center of rotation is developed and included in the new gantry, while preserving the fully-3D SPECT system nested within the larger CT gantry. The flexibility of the integrated system is illustrated. © 2014 SPIE.

Authors
Shah, JP; Mann, SD; McKinley, RL; Tornai, MP
MLA Citation
Shah, JP, Mann, SD, McKinley, RL, and Tornai, MP. "Design of a nested SPECT-CT system with fully suspended CT sub-system for dedicated breast imaging." Progress in Biomedical Optics and Imaging - Proceedings of SPIE 9033 (January 1, 2014).
Source
scopus
Published In
Proceedings of SPIE
Volume
9033
Publish Date
2014
DOI
10.1117/12.2043739

Analysis of dependence of detector position on detected scatter distribution in dedicated breast SPECT

In SPECT, scattered photons contribute to the detected signal, reducing contrast and quantification accuracy. Several methods exist to correct scatter, including the dual-energy window technique, but have not been fully evaluated on non-traditional SPECT trajectories. Using MCNP5, a Monte Carlo study was performed to analyze how incident scatter is affected by detector position for breast SPECT. An ideal detector was positioned at various azimuthal and polar angles relative to a pendant breast geometry. Detected scatter from the breast, heart, liver, torso, and lesion was linearly fit; the slope was used to characterize the distribution. Typical photopeak and scatter energy window ratios were calculated. Results indicate detected scatter depends upon detector position and its vantage of major uptake organs; however, the effect is minimal for non-direct views, with a ratio of 0.37. A single coefficient for dual-energy window scatter correction should suffice for breast imaging trajectories ignoring direct views of the heart/liver. © 2014 Springer International Publishing.

Authors
Mann, SD; Shah, JP; Tornai, MP
MLA Citation
Mann, SD, Shah, JP, and Tornai, MP. "Analysis of dependence of detector position on detected scatter distribution in dedicated breast SPECT." Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) 8539 LNCS (January 1, 2014): 501-507.
Source
scopus
Published In
Lecture notes in computer science
Volume
8539 LNCS
Publish Date
2014
Start Page
501
End Page
507
DOI
10.1007/978-3-319-07887-8_70

Three dimensional dose distribution comparison of simple and complex acquisition trajectories in dedicated breast CT - A Monte Carlo study

The purpose of this study was to characterize the three dimensional (3D) x-ray dose distributions in a target scanned with different acquisition trajectories for dedicated breast CT imaging. Monte Carlo simulations were used to evaluate two acquisition trajectories: circular azimuthal (no tilt) and complex sinusoidal (saddle) orbit with ±15° tilts around a pendant breast. Simulations were performed with tungsten (W) and cerium (Ce) filtration of a W-anode source; the simulated source flux was normalized to the measured exposure of a clinically used W-anode source. A water filled cylindrical phantom, was divided into 1cc voxels, and each voxel was set to track the cumulative energy deposited. Energy deposited per voxel was converted to dose, yielding the 3D distributed dose volumes. Results indicate that the mean absorbed dose at the isocenter of a volume for the un-tilted acquisition is ∼10% higher than that from a saddle scan, regardless of filtration used. © 2014 Springer International Publishing.

Authors
Shah, JP; Mann, SD; McKinley, RL; Tornai, MP
MLA Citation
Shah, JP, Mann, SD, McKinley, RL, and Tornai, MP. "Three dimensional dose distribution comparison of simple and complex acquisition trajectories in dedicated breast CT - A Monte Carlo study." Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) 8539 LNCS (January 1, 2014): 187-194.
Source
scopus
Published In
Lecture notes in computer science
Volume
8539 LNCS
Publish Date
2014
Start Page
187
End Page
194
DOI
10.1007/978-3-319-07887-8_27

Snapshot 2D tomography via coded aperture x-ray scatter imaging.

This paper describes a fan beam coded aperture x-ray scatter imaging system that acquires a tomographic image from each snapshot. This technique exploits the cylindrical symmetry of the scattering cross section to avoid the scanning motion typically required by projection tomography. We use a coded aperture with a harmonic dependence to determine range and a shift code to determine cross range. Here we use a forward-scatter configuration to image 2D objects and use serial exposures to acquire tomographic video of motion within a plane. Our reconstruction algorithm also estimates the angular dependence of the scattered radiance, a step toward materials imaging and identification.

Authors
MacCabe, KP; Holmgren, AD; Tornai, MP; Brady, DJ
MLA Citation
MacCabe, KP, Holmgren, AD, Tornai, MP, and Brady, DJ. "Snapshot 2D tomography via coded aperture x-ray scatter imaging." Appl Opt 52.19 (July 1, 2013): 4582-4589.
PMID
23842254
Source
pubmed
Published In
Applied Optics
Volume
52
Issue
19
Publish Date
2013
Start Page
4582
End Page
4589

Size-Dependent Computed Tomography Histogram Analysis: Towards Breast Tissue Segmentation

Authors
Mann, SD; Shah, JP; Tornai, MP
MLA Citation
Mann, SD, Shah, JP, and Tornai, MP. "Size-Dependent Computed Tomography Histogram Analysis: Towards Breast Tissue Segmentation." June 2012.
Source
wos-lite
Published In
Medical physics
Volume
39
Issue
6
Publish Date
2012
Start Page
3625
End Page
3625

Quantification of Tc-99m sestamibi distribution in normal breast tissue using dedicated breast SPECT-CT

The use of Tc-99m-Sestamibi in molecular breast imaging is common due to its preferential uptake in malignant tissue. However, quantification of the baseline uptake in normal, healthy breast tissue is not possible using planar-imaging devices. Using our dedicated breast SPECT-CT system, an IRB approved pilot study is underway to quantify mean activity in normal breast tissue, and to differentiate uptake between adipose and glandular tissues. A cohort of patients at normal breast cancer risk undergoing another diagnostic Sestamibi study was imaged using the breast SPECT-CT system. SPECT images were corrected and quantitatively reconstructed using previously developed methods, and registered with the CT images. The CT images were segmented, and the average activity concentration was measured for glandular, adipose, and total breast tissue. Results indicate no preferential uptake between tissues and low average uptake, which may be used to determine a universal threshold for cancer detection. © 2012 Springer-Verlag Berlin Heidelberg.

Authors
Mann, SD; Perez, KL; McCracken, EKE; Shah, JP; Choudhury, KR; Wong, TZ; Tornai, MP
MLA Citation
Mann, SD, Perez, KL, McCracken, EKE, Shah, JP, Choudhury, KR, Wong, TZ, and Tornai, MP. "Quantification of Tc-99m sestamibi distribution in normal breast tissue using dedicated breast SPECT-CT." Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) 7361 LNCS (2012): 402-409.
Source
scival
Published In
Lecture notes in computer science
Volume
7361 LNCS
Publish Date
2012
Start Page
402
End Page
409
DOI
10.1007/978-3-642-31271-7_52

Initial In Vivo Quantification of Tc-99m Sestamibi Uptake as a Function of Tissue Type in Healthy Breasts Using Dedicated Breast SPECT-CT.

A pilot study is underway to quantify in vivo the uptake and distribution of Tc-99m Sestamibi in subjects without previous history of breast cancer using a dedicated SPECT-CT breast imaging system. Subjects undergoing diagnostic parathyroid imaging studies were consented and imaged as part of this IRB-approved breast imaging study. For each of the seven subjects, one randomly selected breast was imaged prone-pendant using the dedicated, compact breast SPECT-CT system underneath the shielded patient support. Iteratively reconstructed and attenuation and/or scatter corrected images were coregistered; CT images were segmented into glandular and fatty tissue by three different methods; the average concentration of Sestamibi was determined from the SPECT data using the CT-based segmentation and previously established quantification techniques. Very minor differences between the segmentation methods were observed, and the results indicate an average image-based in vivo Sestamibi concentration of 0.10 ± 0.16 μCi/mL with no preferential uptake by glandular or fatty tissues.

Authors
Mann, SD; Perez, KL; McCracken, EK; Shah, JP; Wong, TZ; Tornai, MP
MLA Citation
Mann, SD, Perez, KL, McCracken, EK, Shah, JP, Wong, TZ, and Tornai, MP. "Initial In Vivo Quantification of Tc-99m Sestamibi Uptake as a Function of Tissue Type in Healthy Breasts Using Dedicated Breast SPECT-CT." J Oncol 2012 (2012): 146943-.
Website
http://hdl.handle.net/10161/12981
PMID
22956950
Source
pubmed
Published In
Journal of Oncology
Volume
2012
Publish Date
2012
Start Page
146943
DOI
10.1155/2012/146943

Development and initial demonstration of a low-dose dedicated fully 3D breast CT system

Based on earlier work demonstrating more complete, 3D cone beam sampling acquisition approaches that additionally facilitate chest wall imaging posterior to an uncompressed breast, a new, clinic-ready, low-dose breast CT system was developed and is undergoing initial clinical validation. The system includes a small focal spot pulsed x-ray source and 30x30cm 2 flat panel detector having 3 degrees of freedom of motion, and a radiopaque patient support that facilitates whole-breast and universal anterior chest-wall imaging. Data is acquired with fully-3D trajectories and iteratively reconstructed within minutes of acquisition. Performance characteristics include: sub-200 micron isotropic reconstructed resolution, low-dose (<4.5 mGy) fully-3D scans acquired in ∼1.5 min, clinic throughput of 1patient/11min, and DICOM compatible images. To date, 25 subjects have been successfully scanned. Characterization results and volumetric clinical images are presented including demonstration of routine anterior chest wall imaging and comparison with digital mammography. © 2012 Springer-Verlag Berlin Heidelberg.

Authors
McKinley, RL; Tornai, MP; Tuttle, LA; Steed, D; Kuzmiak, CM
MLA Citation
McKinley, RL, Tornai, MP, Tuttle, LA, Steed, D, and Kuzmiak, CM. "Development and initial demonstration of a low-dose dedicated fully 3D breast CT system." Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) 7361 LNCS (2012): 442-449.
Source
scival
Published In
Lecture notes in computer science
Volume
7361 LNCS
Publish Date
2012
Start Page
442
End Page
449
DOI
10.1007/978-3-642-31271-7_57

Initial evaluation of a newly developed high resolution CT imager for dedicated breast CT

A new, high resolution 40x30cm 2 area CsI-TFT based CT imager having 127μm pixel pitch was developed for fully-3D breast CT imaging as part of a SPECT-CT system. The imager has two narrow edges suited for pendant breast CT imaging close to the chest wall. The scintillator thickness of 600 microns provides >90% absorption for the 36keV mean x-ray energy of the cone beam source. The 2D MTF is ∼7.5% at the 3.9 lp/mm Nyquist frequency. The imager has excellent linearity over the full dynamic range. The imager is mounted on the CT device and initial tomographic imaging of geometric and breast phantoms demonstrate the reliable and robust imaging capabilities of this device for breast CT. © 2012 Springer-Verlag Berlin Heidelberg.

Authors
Shah, JP; Mann, SD; Polemi, AM; Tornai, MP; McKinley, RL; Zentai, G; Richmond, M; Partain, L
MLA Citation
Shah, JP, Mann, SD, Polemi, AM, Tornai, MP, McKinley, RL, Zentai, G, Richmond, M, and Partain, L. "Initial evaluation of a newly developed high resolution CT imager for dedicated breast CT." Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) 7361 LNCS (2012): 426-433.
Source
scival
Published In
Lecture notes in computer science
Volume
7361 LNCS
Publish Date
2012
Start Page
426
End Page
433
DOI
10.1007/978-3-642-31271-7_55

Comparison of dual-window scatter correction and effective attenuation coefficients for quantification in dedicated breast SPECT

Correction for scattered and attenuated photons is necessary for accurate quantification in dedicated breast SPECT. An implemented dual energy window (DEW) scatter correction method along with attenuation correction has been shown to be accurate to within 10% of true values; however, the DEW method requires multiple processing steps, and thus more time, than an effective attenuation coefficient (EAC) method. This study aims to determine an EAC for quantification accuracy comparable to the DEW method. Our dedicated, high performance CZT-based breast SPECT system is capable of novel 3D, non-traditional trajectories. A breast phantom containing lesions ranging from 0.1 to 1.6mL was filled with Tc-99m to 8:1 and 4:1 lesion-to-background activity concentrations. Multiple acquisitions were collected using vertical axis of rotation (VAOR) and projected sine wave (PROJSINE) orbits and an 8% energy window. The PROJSINE trajectory incompletely samples the volume, but offers potential clinical benefits by contouring the breast and acquiring chest wall projections. Images were reconstructed with OSEM to 20 iterations using both uniform EAC masks with values of 0.12 to 0.165cm -1 and the DEW method with measured 0.16 scatter coefficient and the NIST attenuation value of 0.1545cm -1 for water at 140keV. ROIs were seeded and automatically drawn within each lesion, and measured values were compared to known truth. Results indicate that the DEW method is superior for VAOR trajectories and a single EAC value may not adequately compensate non-uniformly shaped objects that have a spatially varying scatter distribution. However, for PROJSINE trajectories, an EAC of approximately 0.13cm -1 yields comparable quantification accuracy for background and large lesions without the need for additional image processing, indicating this may have clinical utility in image quantification. © 2011 IEEE.

Authors
Mann, S; Perez, K; Tornai, M
MLA Citation
Mann, S, Perez, K, and Tornai, M. "Comparison of dual-window scatter correction and effective attenuation coefficients for quantification in dedicated breast SPECT." IEEE Nuclear Science Symposium Conference Record (2012): 3760-3763.
Source
scival
Published In
IEEE Nuclear Science Symposium Conference Record
Publish Date
2012
Start Page
3760
End Page
3763
DOI
10.1109/NSSMIC.2011.6153711

Bienvenidos!

Authors
Tornai, M; Majewski, S; Williams, M; Duval, M-A; Hofmann, M; Levin, C
MLA Citation
Tornai, M, Majewski, S, Williams, M, Duval, M-A, Hofmann, M, and Levin, C. "Bienvenidos!." IEEE Nuclear Science Symposium Conference Record (2012): 2--.
Source
scival
Published In
IEEE Nuclear Science Symposium Conference Record
Publish Date
2012
Start Page
2-
DOI
10.1109/NSSMIC.2011.6152965

Towards Quantification of Functional Breast Images Using Dedicated SPECT With Non-Traditional Acquisition Trajectories.

Quantification of radiotracer uptake in breast lesions can provide valuable information to physicians in deciding patient care or determining treatment efficacy. Physical processes (e.g., scatter, attenuation), detector/collimator characteristics, sampling and acquisition trajectories, and reconstruction artifacts contribute to an incorrect measurement of absolute tracer activity and distribution. For these experiments, a cylinder with three syringes of varying radioactivity concentration, and a fillable 800 mL breast with two lesion phantoms containing aqueous (99m)Tc pertechnetate were imaged using the SPECT sub-system of the dual-modality SPECT-CT dedicated breast scanner. SPECT images were collected using a compact CZT camera with various 3D acquisitions including vertical axis of rotation, 30° tilted, and complex sinusoidal trajectories. Different energy windows around the photopeak were quantitatively compared, along with appropriate scatter energy windows, to determine the best quantification accuracy after attenuation and dual-window scatter correction. Measured activity concentrations in the reconstructed images for syringes with greater than 10 µCi /mL corresponded to within 10% of the actual dose calibrator measured activity concentration for ±4% and ±8% photopeak energy windows. The same energy windows yielded lesion quantification results within 10% in the breast phantom as well. Results for the more complete complex sinsusoidal trajectory are similar to the simple vertical axis acquisition, and additionally allows both anterior chest wall sampling, no image distortion, and reasonably accurate quantification.

Authors
Perez, KL; Cutler, SJ; Madhav, P; Tornai, MP
MLA Citation
Perez, KL, Cutler, SJ, Madhav, P, and Tornai, MP. "Towards Quantification of Functional Breast Images Using Dedicated SPECT With Non-Traditional Acquisition Trajectories." IEEE Trans Nucl Sci 58.5 (October 2011): 2219-2225.
PMID
22262925
Source
pubmed
Published In
IEEE Transactions on Nuclear Science
Volume
58
Issue
5
Publish Date
2011
Start Page
2219
End Page
2225
DOI
10.1109/TNS.2011.2165223

Evaluation of the absorbed dose to the breast using radiochromic film in a dedicated CT mammotomography system employing a quasi-monochromatic x-ray beam.

PURPOSE: A dual modality SPECT-CT prototype system dedicated to uncompressed breast imaging (mammotomography) has been developed. The computed tomography subsystem incorporates an ultrathick K-edge filtration technique producing a quasi-monochromatic x-ray cone beam that optimizes the dose efficiency of the system for lesion imaging in an uncompressed breast. Here, the absorbed dose in various geometric phantoms and in an uncompressed and pendant cadaveric breast using a normal tomographic cone beam imaging protocol is characterized using both thermoluminescent dosimeter (TLD) measurements and ionization chamber-calibrated radiochromic film. METHODS: Initially, two geometric phantoms and an anthropomorphic breast phantom are filled in turn with oil and water to simulate the dose to objects that mimic various breast shapes having effective density bounds of 100% fatty and glandular breast compositions, respectively. Ultimately, an excised human cadaver breast is tomographically scanned using the normal tomographic imaging protocol, and the dose to the breast tissue is evaluated and compared to the earlier phantom-based measurements. RESULTS: Measured trends in dose distribution across all breast geometric and anthropomorphic phantom volumes indicate lower doses in the medial breast and more proximal to the chest wall, with consequently higher doses near the lateral peripheries and nipple regions. Measured doses to the oil-filled phantoms are consistently lower across all volume shapes due to the reduced mass energy-absorption coefficient of oil relative to water. The mean measured dose to the breast cadaver, composed of adipose and glandular tissues, was measured to be 4.2 mGy compared to a mean whole-breast dose of 3.8 and 4.5 mGy for the oil- and water-filled anthropomorphic breast phantoms, respectively. CONCLUSIONS: Assuming rotational symmetry due to the tomographic acquisition exposures, these results characterize the 3D dose distributions in an uncompressed human breast tissue volume for this dedicated breast imaging device and illustrate advantages of using the novel ultrathick K-edge filtered beam to minimize the dose to the breast during fully-3D imaging.

Authors
Crotty, DJ; Brady, SL; Jackson, DC; Toncheva, GI; Anderson, CE; Yoshizumi, TT; Tornai, MP
MLA Citation
Crotty, DJ, Brady, SL, Jackson, DC, Toncheva, GI, Anderson, CE, Yoshizumi, TT, and Tornai, MP. "Evaluation of the absorbed dose to the breast using radiochromic film in a dedicated CT mammotomography system employing a quasi-monochromatic x-ray beam." Med Phys 38.6 (June 2011): 3232-3245.
PMID
21815398
Source
pubmed
Published In
Medical physics
Volume
38
Issue
6
Publish Date
2011
Start Page
3232
End Page
3245
DOI
10.1118/1.3574875

A high-performance SPECT-CT system for dedicated molecular breast imaging

Authors
Tornai, MP; McKinley, RL
MLA Citation
Tornai, MP, and McKinley, RL. "A high-performance SPECT-CT system for dedicated molecular breast imaging." JOURNAL OF NUCLEAR MEDICINE 52.4 (April 1, 2011): 673-674.
Source
wos-lite
Published In
Journal of nuclear medicine : official publication, Society of Nuclear Medicine
Volume
52
Issue
4
Publish Date
2011
Start Page
673
End Page
674

Detailed Characterization of 2D and 3D Scatter-to-Primary Ratios of Various Breast Geometries Using a Dedicated CT Mammotomography System.

With a dedicated breast CT system using a quasi-monochromatic x-ray source and flat-panel digital detector, the 2D and 3D scatter to primary ratios (SPR) of various geometric phantoms having different densities were characterized in detail. Projections were acquired using geometric and anthropomorphic breast phantoms. Each phantom was filled with 700ml of 5 different water-methanol concentrations to simulate effective boundary densities of breast compositions from 100% glandular (1.0g/cm(3)) to 100% fat (0.79g/cm(3)). Projections were acquired with and without a beam stop array. For each projection, 2D scatter was determined by cubic spline interpolating the values behind the shadow of each beam stop through the object. Scatter-corrected projections were obtained by subtracting the scatter, and the 2D SPRs were obtained as a ratio of the scatter to scatter-corrected projections. Additionally the (un)corrected data were individually iteratively reconstructed. The (un)corrected 3D volumes were subsequently subtracted, and the 3D SPRs obtained from the ratio of the scatter volume-to-scatter-corrected (or primary) volume. Results show that the 2D SPR values peak in the center of the volumes, and were overall highest for the simulated 100% glandular composition. Consequently, scatter corrected reconstructions have visibly reduced cupping regardless of the phantom geometry, as well as more accurate linear attenuation coefficients. The corresponding 3D SPRs have increased central density, which reduces radially. Not surprisingly, for both 2D and 3D SPRs there was a dependency on both phantom geometry and object density on the measured SPR values, with geometry dominating for 3D SPRs. Overall, these results indicate the need for scatter correction given different geometries and breast densities that will be encountered with 3D cone beam breast CT.

Authors
Shah, J; Pachon, JH; Madhav, P; Tornai, MP
MLA Citation
Shah, J, Pachon, JH, Madhav, P, and Tornai, MP. "Detailed Characterization of 2D and 3D Scatter-to-Primary Ratios of Various Breast Geometries Using a Dedicated CT Mammotomography System." Proc SPIE Int Soc Opt Eng 7961.796158 (February 13, 2011).
PMID
22267985
Source
pubmed
Published In
Proceedings of SPIE - The International Society for Optical Engineering
Volume
7961
Issue
796158
Publish Date
2011
DOI
10.1117/12.878809

Characterization of image quality for 3D scatter-corrected breast CT images

The goal of this study was to characterize the image quality of our dedicated, quasi-monochromatic spectrum, cone beam breast imaging system under scatter corrected and non-scatter corrected conditions for a variety of breast compositions. CT projections were acquired of a breast phantom containing two concentric sets of acrylic spheres that varied in size (1-8mm) based on their polar position. The breast phantom was filled with 3 different concentrations of methanol and water, simulating a range of breast densities (0.79-1.0g/cc); acrylic yarn was sometimes included to simulate connective tissue of a breast. For each phantom condition, 2D scatter was measured for all projection angles. Scatter-corrected and uncorrected projections were then reconstructed with an iterative ordered subsets convex algorithm. Reconstructed image quality was characterized using SNR and contrast analysis, and followed by a human observer detection task for the spheres in the different concentric rings. Results show that scatter correction effectively reduces the cupping artifact and improves image contrast and SNR. Results from the observer study indicate that there was no statistical difference in the number or sizes of lesions observed in the scatter versus non-scatter corrected images for all densities. Nonetheless, applying scatter correction for differing breast conditions improves overall image quality.

Authors
Pachon, JH; Shah, J; Tornai, MP
MLA Citation
Pachon, JH, Shah, J, and Tornai, MP. "Characterization of image quality for 3D scatter-corrected breast CT images." Progress in Biomedical Optics and Imaging - Proceedings of SPIE 7961 (2011).
Website
http://hdl.handle.net/10161/7275
PMID
24236221
Source
scival
Published In
Proceedings of SPIE
Volume
7961
Publish Date
2011
DOI
10.1117/12.878808

Characterizing the contribution of cardiac and hepatic uptake in dedicated breast SPECT using tilted trajectories.

A small field of view, high resolution gamma camera has been integrated into a dedicated breast, single photon emission computed tomography (SPECT) device. The detector can be flexibly positioned relative to the breast and image beyond the chest wall, allowing the system to capture direct views of the heart and liver. The incomplete sampling of these organs creates artifacts in reconstructed images, complicating lesion detection. To understand the limits imposed on a 3D acquisition trajectory, sequential tilted trajectories at increasing polar tilt are utilized to collect data of anthropomorphic phantoms filled with aqueous (99m)Tc in a clinically realistic concentration ratio. The counts collected per projection between different scans and the SNR, contrast and resolution (FWHM) of two hot lesions were compared. As expected, the counts per projection increased when the camera had direct views of the heart and liver, but remained relatively constant at other angles. The SNR, contrast and FWHM were more affected by the insufficient sampling of the data by the large polar angles than by the cardiac and hepatic activity. An upper bound on polar tilt for each azimuthal position reduces the artifacts in the reconstructed images. Such trajectories were implemented to show artifact-free reconstructed images.

Authors
Perez, KL; Cutler, SJ; Madhav, P; Tornai, MP
MLA Citation
Perez, KL, Cutler, SJ, Madhav, P, and Tornai, MP. "Characterizing the contribution of cardiac and hepatic uptake in dedicated breast SPECT using tilted trajectories." Phys Med Biol 55.16 (August 21, 2010): 4721-4734.
PMID
20671354
Source
pubmed
Published In
Physics in Medicine and Biology
Volume
55
Issue
16
Publish Date
2010
Start Page
4721
End Page
4734
DOI
10.1088/0031-9155/55/16/007

Observer detection limits for a dedicated SPECT breast imaging system.

An observer-based contrast-detail study is performed in an effort to evaluate the limits of object detectability using a dedicated CZT-based breast SPECT imaging system under various imaging conditions. A custom geometric contrast-resolution phantom was developed that can be used for both positive ('hot') and negative contrasts ('cold'). The 3 cm long fillable tubes are arranged in six sectors having equal inner diameters ranging from 1 mm to 6 mm with plastic wall thicknesses of <0.25 mm, on a pitch of twice their inner diameters. Scans of the activity filled tubes using simple circular trajectories are obtained in a 215 mL uniform water filled cylinder, varying the rod:background concentration ratios from 10:1 to 1:10 simulating a large range of biological uptake ratios. The rod phantom is then placed inside a non-uniformly shaped 500 mL breast phantom and scans are again acquired using both simple and complex 3D trajectories for similarly varying contrasts. Summed slice and contiguous multi-slice images are evaluated by five independent readers, identifying the smallest distinguishable rod for each concentration and experimental setup. Linear and quadratic regression is used to compare the resulting contrast-detail curves. Results indicate that in a moderately low-noise 500 mL background, using the SPECT camera having 2.5 mm intrinsic pixels, the mean detectable rod was approximately 3.4 mm at a 10:1 ratio, degrading to approximately 5.2 mm with the 2.5:1 concentration ratio. The smallest object detail was observed using a 45 degrees tilted trajectory acquisition. The complex 3D projected sine wave acquisition, however, had the most consistent combined intra- and inter-observer results, making it potentially the best imaging approach for consistent results.

Authors
Cutler, SJ; Perez, KL; Barnhart, HX; Tornai, MP
MLA Citation
Cutler, SJ, Perez, KL, Barnhart, HX, and Tornai, MP. "Observer detection limits for a dedicated SPECT breast imaging system." Phys Med Biol 55.7 (April 7, 2010): 1903-1916.
PMID
20224159
Source
pubmed
Published In
Physics in Medicine and Biology
Volume
55
Issue
7
Publish Date
2010
Start Page
1903
End Page
1916
DOI
10.1088/0031-9155/55/7/008

Is SPECT or CT based attenuation correction more quantitatively accurate for dedicated breast SPECT acquired with non-traditional trajectories?

Attenuation correction is necessary for SPECT quantification. There are a variety of methods to create attenuation maps. For dedicated breast SPECT-CT imaging, it is unclear if either a SPECT- or CT-based attenuation map would provide the most accurate quantification and whether or not segmenting the different tissue types will have an effect on the quantification. For these experiments, 99mTc diluted in methanol and water filled geometric and anthropomorphic breast phantoms was imaged with a dedicated dual-modality SPECT-CT breast scanner. SPECT images were collected using a compact CZT camera with various 3D acquisition trajectories including vertical and 30 tilted parallel beam, and complex sinusoidal trajectories. CT images were acquired using a quasi-monochromatic x-ray source and CsI(T1) digital flat panel detector in a half-cone beam geometry. Measured scatter correction for SPECT and CT were implemented. To compare photon attenuation correction in the reconstructed SPECT images, various volumetric attenuation maps were derived from 1) uniform SPECT, 2) uniform CT, and 3) segmented CT, populated with different attenuation coefficient values. Comparisons between attenuation masks using phantoms consisting of materials with different attenuation values show that at 140 keV the differences in the attenuation between materials do not affect the quantification as much as the size and alignment of the attenuation map. The CT-based attenuation maps give quantitative values 30% below the actual value, but are consistent. The SPECT-based attenuation maps can provide within 10% accurate quantitative values, but are less consistent. © 2010 IEEE.

Authors
Perez, KL; Mann, SD; Pachon, JH; Madhav, P; Tornai, MP
MLA Citation
Perez, KL, Mann, SD, Pachon, JH, Madhav, P, and Tornai, MP. "Is SPECT or CT based attenuation correction more quantitatively accurate for dedicated breast SPECT acquired with non-traditional trajectories?." IEEE Nuclear Science Symposium Conference Record (2010): 2319-2324.
PMID
25999683
Source
scival
Published In
IEEE Nuclear Science Symposium Conference Record
Publish Date
2010
Start Page
2319
End Page
2324
DOI
10.1109/NSSMIC.2010.5874198

Investigating the dose distribution in the uncompressed breast with a dedicated CT mammotomography system

Authors
Crotty, DJ; Brady, SL; Jackson, DC; Toncheva, GI; Anderson, CE; Yoshizumi, TT; Tornai, MP
MLA Citation
Crotty, DJ, Brady, SL, Jackson, DC, Toncheva, GI, Anderson, CE, Yoshizumi, TT, and Tornai, MP. "Investigating the dose distribution in the uncompressed breast with a dedicated CT mammotomography system." 2010.
Source
wos-lite
Published In
Proceedings of SPIE - The International Society for Optical Engineering
Volume
7622
Publish Date
2010
DOI
10.1117/12.845433

Development of in vivo characterization of breast tissues through absolute attenuation coefficients using dedicated cone-beam CT

Authors
Madhav, P; Li, CM; Tornai, MP
MLA Citation
Madhav, P, Li, CM, and Tornai, MP. "Development of in vivo characterization of breast tissues through absolute attenuation coefficients using dedicated cone-beam CT." 2010.
Source
wos-lite
Published In
Proceedings of SPIE - The International Society for Optical Engineering
Volume
7622
Publish Date
2010
DOI
10.1117/12.845064

Evaluation of tilted cone-beam CT orbits in the development of a dedicated hybrid mammotomograph.

A compact dedicated 3D breast SPECT-CT (mammotomography) system is currently under development. In its initial prototype, the cone-beam CT sub-system is restricted to a fixed-tilt circular rotation around the patient's pendant breast. This study evaluated stationary-tilt angles for the CT sub-system that will enable maximal volumetric sampling and viewing of the breast and chest wall. Images of geometric/anthropomorphic phantoms were acquired using various fixed-tilt circular and 3D sinusoidal trajectories. The iteratively reconstructed images showed more distortion and attenuation coefficient inaccuracy from tilted cone-beam orbits than from the complex trajectory. Additionally, line profiles illustrated cupping artifacts in planes distal to the central plane of the tilted cone-beam, otherwise not apparent for images acquired with complex trajectories. This indicates that undersampled cone-beam data may be an additional cause of cupping artifacts. High-frequency objects could be distinguished for all trajectories, but their shapes and locations were corrupted by out-of-plane frequency information. Although more acrylic balls were visualized with a fixed-tilt and nearly flat cone-beam at the posterior of the breast, 3D complex trajectories have less distortion and more complete sampling throughout the reconstruction volume. While complex trajectories would ideally be preferred, negatively fixed-tilt source-detector configuration demonstrates minimally distorted patient images.

Authors
Madhav, P; Crotty, DJ; McKinley, RL; Tornai, MP
MLA Citation
Madhav, P, Crotty, DJ, McKinley, RL, and Tornai, MP. "Evaluation of tilted cone-beam CT orbits in the development of a dedicated hybrid mammotomograph." Phys Med Biol 54.12 (June 21, 2009): 3659-3676.
PMID
19478374
Source
pubmed
Published In
Physics in Medicine and Biology
Volume
54
Issue
12
Publish Date
2009
Start Page
3659
End Page
3676
DOI
10.1088/0031-9155/54/12/004

Characterizing the MTF in 3D for a Quantized SPECT Camera Having Arbitrary Trajectories.

The emergence of application-specific 3D tomographic small animal and dedicated breast imaging systems has stimulated the development of simple methods to quantify the spatial resolution or Modulation Transfer Function (MTF) of the system in three dimensions. Locally determined MTFs, obtained from line source measurements at specific locations, can characterize spatial variations in the system resolution and can help correct for such variations. In this study, a method is described to measure the MTF in 3D for a compact SPECT system that uses a 16 × 20 cm(2) CZT-based compact gamma camera and 3D positioning gantry capable of moving in different trajectories. Image data are acquired for a novel phantom consisting of three radioactivity-filled capillary tubes, positioned nearly orthogonally to each other. These images provide simultaneous measurements of the local MTF along three dimensions of the reconstructed imaged volume. The usefulness of this approach is shown by characterizing the MTF at different locations in the reconstructed imaged 3D volume using various (1) energy windows; (2) iterative reconstruction parameters including number of iterations, voxel size, and number of projection views; (3) simple and complex 3D orbital trajectories including simple vertical axis of rotation, simple tilt, complex circle-plus-arc, and complex sinusoids projected onto a hemisphere; and (4) object shapes in the camera's field of view. Results indicate that the method using the novel phantom can provide information on spatial resolution effects caused by system design, sampling, energy windows, reconstruction parameters, novel 3D orbital trajectories, and object shapes. Based on these measurements that are useful for dedicated tomographic breast imaging, it was shown that there were small variations in the MTF in 3D for various energy windows and reconstruction parameters. However, complex trajectories that uniformly sample the breast volume of interest were quantitatively shown to have slightly better spatial resolution performance than more simple orbits.

Authors
Madhav, P; Bowsher, JE; Cutler, SJ; Tornai, MP
MLA Citation
Madhav, P, Bowsher, JE, Cutler, SJ, and Tornai, MP. "Characterizing the MTF in 3D for a Quantized SPECT Camera Having Arbitrary Trajectories." IEEE Trans Nucl Sci 56.3 (June 1, 2009): 661-670.
PMID
21331301
Source
pubmed
Published In
IEEE Transactions on Nuclear Science
Volume
56
Issue
3
Publish Date
2009
Start Page
661
End Page
670
DOI
10.1109/TNS.2009.2013464

Towards quantification of dedicated breast SPECT using non-traditional acquisition trajectories

Quantification of radiotracer uptake in lesions can provide valuable information to physicians in deciding patient care or determining treatment efficacy. Physical processes (e.g. scatter, attenuation), detector/collimator characteristics, sampling and acquisition trajectories, and reconstruction artifacts contribute to an incorrect absolute measurement of tracer activity and distribution. For these experiments, a cylinder with three syringes of varying radioactivity concentration, and a fillable 800mL breast with two lesion phantoms containing aqueous 99mTc pertechnetate were imaged using the SPECT subsystem of the dual-modality SPECT-CT dedicated breast scanner. SPECT images were collected using a compact CZT camera with various 3D acquisitions including vertical axis of rotation, 30° tilted, and complex sinusoidal trajectories. Quantitative differences in the measured absolute activity values were investigated for each acquisition trajectory to determine the efficacy of an acquisition trajectory to quantify regions of focal uptake. With attenuation and scatter corrections applied, reconstruction image results showed that the measured average activity concentrations in the hot-spot areas corresponded to within 15% of the actual dose calibrator measured activity concentration. More complete sampling trajectories outperform incomplete tilted acquisition trajectories. ©2009 IEEE.

Authors
Perez, KL; Cutler, SJ; Madhav, P; Tornai, MP
MLA Citation
Perez, KL, Cutler, SJ, Madhav, P, and Tornai, MP. "Towards quantification of dedicated breast SPECT using non-traditional acquisition trajectories." IEEE Nuclear Science Symposium Conference Record (2009): 3866-3870.
Source
scival
Published In
IEEE Nuclear Science Symposium Conference Record
Publish Date
2009
Start Page
3866
End Page
3870
DOI
10.1109/NSSMIC.2009.5401917

Initial investigation of novel trajectories to improve chest wall imaging in a dedicated breast computed tomography system

In current dedicated breast computed tomography (mammotomography) systems, comfortable patient positioning on a stationary bed restricts the practicable range of source-detector trajectories, thus compromising the system's ability to adequately image the patient's anterior chest wall. This study examines the effect on detecting small, low-contrast lesion-like-spheres using limited angle x-ray source-detector trajectories and trajectories that intentionally raise the tomographic imaging system mid-acquisition. These modified acquisition paths may increase chest wall visualization, simplify the design of the imaging system and increase patient comfort by allowing the design of an improved patient bed. Thin walled balloons of various volumes filled with iodine act as surrogate high contrast lesions to initially investigate the effect of these novel trajectories. Then, stacks of 5mm acrylic spheres regularly spaced in concentric circles are placed in water to simulate a low contrast environment in a uniform scatter medium. 360° azimuthal scans are acquired at various bed heights with contiguous projections subsequently removed to create limited angle acquisitions from 240-360°. Projections from the different bed heights are interwoven to form trajectories that mimic discontinuously raising the imaging system mid-acquisition. The resulting iteratively reconstructed volumes are evaluated with an observer study. Initial images suggest that using limited angles and raising the system is possible while increasing the observer's ability to visualize objects near the chest wall. Based on the results of this study, an improved patient bed to facilitate chest wall imaging will be designed, and the feasibility of vertical system motion to increase imaged breast volume explored. © 2009 SPIE.

Authors
Crotty, DJ; McKinley, RL; Madhav, P; Cutler, SJ; Tornai, MP
MLA Citation
Crotty, DJ, McKinley, RL, Madhav, P, Cutler, SJ, and Tornai, MP. "Initial investigation of novel trajectories to improve chest wall imaging in a dedicated breast computed tomography system." Progress in Biomedical Optics and Imaging - Proceedings of SPIE 7258 (2009).
Source
scival
Published In
Proceedings of SPIE
Volume
7258
Publish Date
2009
DOI
10.1117/12.812500

Novel Patient Optimized Acquisition Trajectories for Dedicated Breast SPECT Imaging

Authors
Perez, KL; Cutler, SJ; Madhav, P; Tornai, MP; IEEE,
MLA Citation
Perez, KL, Cutler, SJ, Madhav, P, Tornai, MP, and IEEE, . "Novel Patient Optimized Acquisition Trajectories for Dedicated Breast SPECT Imaging." 2009.
Source
wos-lite
Published In
IEEE Conference Record - Nuclear Science Symposium & Medical Imaging Conference : IEEE Nuclear Science Symposium And Medical Imaging Conference. Proceedings
Publish Date
2009
Start Page
5388
End Page
+

Comparison of 2D Scintimammography and 3D Dedicated Breast SPECT Using A Compressible Breast Phantom and Lesions of Varying Size and Tracer Uptake

Authors
Cutler, SJ; Perez, KL; Madhav, P; Tornai, MP; IEEE,
MLA Citation
Cutler, SJ, Perez, KL, Madhav, P, Tornai, MP, and IEEE, . "Comparison of 2D Scintimammography and 3D Dedicated Breast SPECT Using A Compressible Breast Phantom and Lesions of Varying Size and Tracer Uptake." 2009.
Source
wos-lite
Published In
IEEE Conference Record - Nuclear Science Symposium & Medical Imaging Conference : IEEE Nuclear Science Symposium And Medical Imaging Conference. Proceedings
Publish Date
2009
Start Page
5399
End Page
+

Improved Chest Wall Imaging through Combined Complex Trajectories in Dedicated Dual Modality SPECT-CT Breast Molecular Imaging

Authors
Crotty, DJ; Cutler, SJ; McKinley, RL; Madhav, P; Perez, KL; Tornai, MP; IEEE,
MLA Citation
Crotty, DJ, Cutler, SJ, McKinley, RL, Madhav, P, Perez, KL, Tornai, MP, and IEEE, . "Improved Chest Wall Imaging through Combined Complex Trajectories in Dedicated Dual Modality SPECT-CT Breast Molecular Imaging." 2009.
Source
wos-lite
Published In
IEEE Conference Record - Nuclear Science Symposium & Medical Imaging Conference : IEEE Nuclear Science Symposium And Medical Imaging Conference. Proceedings
Publish Date
2009
Start Page
5409
End Page
+

Dynamic Laser-Guided Contouring for Dedicated Emission Mammotomography

Authors
Cutler, SJ; Crotty, DJ; Tornai, MP; IEEE,
MLA Citation
Cutler, SJ, Crotty, DJ, Tornai, MP, and IEEE, . "Dynamic Laser-Guided Contouring for Dedicated Emission Mammotomography." 2009.
Source
wos-lite
Published In
IEEE Conference Record - Nuclear Science Symposium & Medical Imaging Conference : IEEE Nuclear Science Symposium And Medical Imaging Conference. Proceedings
Publish Date
2009
Start Page
4062
End Page
4066

Improved chest wall imaging through combined complex trajectories in dedicated dual modality SPECT-CT breast molecular imaging

In the hybrid SPECT-CT breast imaging system currently in development in our lab, patient positioning is a practical compromise between comfort and a need to maximize the imaged volume of breast and chest wall. The integrated imaging system rotates under the patient, with the current CT system restricted to purely azimuthal trajectories at a fixed height, while the flexible SPECT system is capable of fully 3D positioning around the pendant breast. The current patient bed, designed with the aforementioned compromises in mind, separates the top of the CT cone beam from the chest wall, thus limiting the system's ability to image this important area. This study examines combined complex trajectories, including limited angle tomography for both modalities and raising the entire imaging system during the scan, to more effectively image lesions in or near the chest wall. While emphasizing new CT system trajectories, SPECT trajectories are also investigated to maximize the imaged volume while avoiding contact with the bed or patient. Various sized lesions filled with low and medium concentrations of "mTc activity (10:1 to 3:1) and CT contrast are imaged using different trajectories. Dual modality projections are post-processed to mimic limited angle trajectories or trajectories that raise the CT system for a portion of the scan. Reconstructed images from data sets with trajectories that removed 60° of SPECT and CT azimuthal data and trajectories combining limited angle acquisition with vertical system shift show a significant increase in observed breast volume while maintaining lesion visibility. Two task-based observer studies are used to further evaluate the visibility of small low-contrast lesions reconstructed with decreasing angular acquisitions and system shifting. Observer study results further indicate that limited angle trajectories and system shifting in mid-scan appear to improve chest wall imaging for this dual modality system. © 2008 IEEE.

Authors
Crotty, DJ; Cutler, SJ; McKinley, RL; Madhav, P; Perez, KL; Tornai, MP
MLA Citation
Crotty, DJ, Cutler, SJ, McKinley, RL, Madhav, P, Perez, KL, and Tornai, MP. "Improved chest wall imaging through combined complex trajectories in dedicated dual modality SPECT-CT breast molecular imaging." IEEE Nuclear Science Symposium Conference Record (2008): 5650-5656.
Source
scival
Published In
IEEE Nuclear Science Symposium Conference Record
Publish Date
2008
Start Page
5650
End Page
5656
DOI
10.1109/NSSMIC.2008.4774525

Comparison of 2D scintimammography and 3D dedicated breast SPECT using a compressible breast phantom and lesions of varying size and tracer uptake

This study aims to qualitatively and quantitatively compare 2D planar scintimammography imaging of the breast under various degrees of compression with uncompressed, dedicated 3D SPECT using dedicated acquisition trajectories. A 700 m L compressible anthropomorphic breast phantom containing small lesions was developed to compare 2D and 3D breast imaging. Thin walled, deformable lesions ranging from 40 to 500uL volume suspended on a thin plastic sheet in the phantom were used to mimic breast lesions undergoing different degrees of compression. Using a 16x20cm2 CZT-based gamma camera, 99mTc-scintimammography was performed for lOmin imaging times for compression thicknesses of 6 and 12cm (fully uncompressed) using a single mediolateral view. Dedicated breast SPECT was then performed for lOmin using the uncompressed breast acquired with a simple tilted rotation, and a complex 3D acquisition trajectory. Experimental variables include: (1) background torso contamination; (2) (in)homogeneous breast composition; and (3) low count (clinically relevant) and high count (low noise) images. The radioactivity lesion:background concentration ratio was varied from 12:1 down to 3:1. A comparison between the two modalities was made in a limited observer study with independent observers evaluating reconstructed images for the smallest detectable lesion and total number of lesions. Image quality, based on lesion SNRs and contrasts were also evaluated. SPECT images appear to yield observation of smaller and more simulated lesions than those seen in scintimammography, additionally with more than twice the SNR and contrast. Due to greater positioning flexibility of the SPECT system gantry, under a wide range of measurement conditions, statistically significantly (p<0.05) more lesions, smaller lesion sizes, and (3D) lesion locations were detected with dedicated breast SPECT than with compressed breast scintimammography. © 2008 IEEE.

Authors
Cutler, SJ; Perez, KL; Madhav, P; Tornai, MP
MLA Citation
Cutler, SJ, Perez, KL, Madhav, P, and Tornai, MP. "Comparison of 2D scintimammography and 3D dedicated breast SPECT using a compressible breast phantom and lesions of varying size and tracer uptake." IEEE Nuclear Science Symposium Conference Record (2008): 5640-5646.
Source
scival
Published In
IEEE Nuclear Science Symposium Conference Record
Publish Date
2008
Start Page
5640
End Page
5646
DOI
10.1109/NSSMIC.2008.4774523

Novel patient optimized acquisition trajectories for dedicated breast SPECT imaging

Novel acquisition trajectories developed for our dedicated breast SPECT camera move 3 dimensionally within a hemispherical volume, fully contouring a patient's pendent breast to provide a high quality, high resolution 3D functional image. Each unique trajectory, created in under a minute, is tailored for each breast of each subject to obtain the highest image quality for a particular study. If a suspected lesion location is known prior to the scan, a trajectory can be created with many close and direct views of the lesion. A torso phantom with an attached 1730 mL breast phantom containing a 2.1 mL (0.8cm radius) spherical lesion was filled with clinical levels of activity: heart:liver:torso: breast: lesion concentration ratio 12:12:1:1:6. A variety of novel acquisition trajectories were employed to image the lesion. Sequentially increasing tilted parallel beam trajectories investigated signals obtained from different polar angles for imaging the breast and chest wall with contamination from the heart and liver. These studies yielded a bound on polar positions for all azimuthal locations in order to minimize background contamination. Other trajectories were created to obtain the best lesion signal. This study shows sinusoidal trajectories can recover the breast's shape and image into the chest wall best. Changing the camera's starting position or subtracting projection views can reduce cardiac and hepatic contamination in the reconstructed image. However, more than one trajectory may provide equivalent image quality. Acquisition trajectories can be created to meet specific imaging goals which consider certain patient factors, such as breast size, lesion location and cardiac and hepatic uptake. © 2008 IEEE.

Authors
Perez, KL; Cutler, SJ; Madhav, P; Tornai, MP
MLA Citation
Perez, KL, Cutler, SJ, Madhav, P, and Tornai, MP. "Novel patient optimized acquisition trajectories for dedicated breast SPECT imaging." IEEE Nuclear Science Symposium Conference Record (2008): 5629-5634.
Source
scival
Published In
IEEE Nuclear Science Symposium Conference Record
Publish Date
2008
Start Page
5629
End Page
5634
DOI
10.1109/NSSMIC.2008.4774521

Dynamic laser-guided contouring for dedicated emission mammotomography

The dedicated breast CZT-based SPECT imaging system in our lab implements novel 3D camera trajectories that can minimize breast-detector separation, thus improving resolution and image quality. Current trajectories are manually customized for each patient by measuring breast-detector separations at several positions and interpolating. This study seeks to transition from this manual method to an automated contouring solution for routine patient SPECT imaging, given the vast array of uncompressed breast shapes in women. In the initial effort to model "typical" SPECT camera trajectories for patients, a sub-study was conducted of 103 MRI breast data sets to categorize the shape and size of uncompressed, pendant breasts. Obtained parameters include measured nipple-to-chest wall (mean=8.4cm), superior-inferior (mean=10.8cm), medial-lateral distances (mean=14.3cm), and estimated breast volume (mean=720mL). These images will be used as digital "phantoms" when utilizing computer models for orbit optimization and system development purposes. Automated breast surface contouring is implemented using a dual-layer, low divergence, ribbon laser feedback sensor system mounted along the edge of the SPECT camera. The upper and lower sensor layers consist of two laser-detector pairs that identify the region on the camera face that has been penetrated, defining a virtual plane. In both layers, receivers sense reduced signal intensity when the beam path is interrupted by the breast surface. The ROR can then be automatically adjusted such that the breast is within -tcm of the camera face, but no closer than O.5cm, thus safely keeping the camera face as close to breast as possible. Robustness of the contouring system is assessed using flexible anthropomorphic breast phantoms to model various pendant breast shapes and sizes. Initial results indicate that dynamic contouring both improves image quality and potentially adds comfort to the patient by shortening scan setup time. © 2008 IEEE.

Authors
Cutler, SJ; Crotty, DJ; Tornai, MP
MLA Citation
Cutler, SJ, Crotty, DJ, and Tornai, MP. "Dynamic laser-guided contouring for dedicated emission mammotomography." IEEE Nuclear Science Symposium Conference Record (2008): 4789-4793.
Source
scival
Published In
IEEE Nuclear Science Symposium Conference Record
Publish Date
2008
Start Page
4789
End Page
4793
DOI
10.1109/NSSMIC.2008.4774314

Experimental spectral measurements of heavy K-edge filtered beams for x-ray computed mammotomography.

A dual modality computed mammotomography (CmT) and single photon emission computed tomography (SPECT) system for dedicated 3D breast imaging is in development. Using heavy K-edge filtration, the CmT component narrows the energy spectrum of the cone-shaped x-ray beam incident on the patient's pendant, uncompressed breast. This quasi-monochromatic beam is expected to improve discrimination of tissue with similar attenuation coefficients while restraining absorbed dose to below that of dual view mammography. Previous simulation studies showed the optimal energy that maximizes dose efficiency for a 50/50% adipose/glandular breast is between 30 and 40 keV. This study experimentally validates these results using pre-breast and post-breast spectral measurements made under tungsten tube voltages between 40 and 100 kVp using filter materials with K-edge values ranging from 15 to 70 keV. Different filter material thicknesses are used, approximately equivalent to the 200th and 500th attenuating value layer (VL) thickness. Cerium (K = 40.4 keV) filtered post-breast spectra for 8-18 cm breasts are measured for a range of breast compositions. Figures of merit include mean beam energy, spectral full-width at tenth-maximum, beam hardening and dose for the range of breast sizes. Measurements corroborate simulation results, indicating that for a given dose, a 200th VL of cerium filtration may have optimal performance in the dedicated mammotomography paradigm.

Authors
Crotty, DJ; McKinley, RL; Tornai, MP
MLA Citation
Crotty, DJ, McKinley, RL, and Tornai, MP. "Experimental spectral measurements of heavy K-edge filtered beams for x-ray computed mammotomography." Phys Med Biol 52.3 (February 7, 2007): 603-616.
PMID
17228108
Source
pubmed
Published In
Physics in Medicine and Biology
Volume
52
Issue
3
Publish Date
2007
Start Page
603
End Page
616
DOI
10.1088/0031-9155/52/3/005

A contrast-detail comparison of computed mammotomography and digital mammography

We use a contrast-detail observer study to compare performance of a novel 3D computed mammotomography (CmT) system with a commercially developed full-field digital mammography (FFDM) system. A contrast-detail phantom comprised of uniform acrylic spheres of various diameters was developed and placed in a variety of mediums including uniform water (simulating low contrast lesions within a uniform background), water and acrylic yarn (simulating low contrast lesions with over/under-lying structure), oil only (simulating higher contrast lesions in a uniform background), and oil and acrylic yarn (simulating higher contrast lesions with over/under-lying structure). For CmT, the phantom was placed in a 14.6 cm diameter uncompressed breast phantom and projections acquired using a simple circular orbit, W-target tube, 60 kVp tube potential, 0.05 cm Ce filtration, 4 mAs per projection, and a CsI(Tl) digital x-ray detector. Reconstructions used an iterative OSTR algorithm. For FFDM, the phantom was placed in a 5.3-cm-thick compressed breast phantom. Single CC-view mammograms were acquired using a clinical W-target tube with 50 um Rh filtration, 28 kVp, photo-timed mAs per our clinical mammography operation, and a Selenium-based flat-panel detector (Mammomat Novation, Siemens). Six observers evaluated the images in terms of the number of detectable spheres. FFDM performed significantly better for the low contrast lesions in uniform water background (p<0.05). However, CmT performed significantly better for all other cases (p<0.05). Results indicate that CmT shows significant advantage in soft tissue detection over FFDM in otherwise low contrast dense breasts.

Authors
McKinley, RL; Tornai, MP; Floyd, CE; Samei, E
MLA Citation
McKinley, RL, Tornai, MP, Floyd, CE, and Samei, E. "A contrast-detail comparison of computed mammotomography and digital mammography." Progress in Biomedical Optics and Imaging - Proceedings of SPIE 6510.PART 1 (2007).
Source
scival
Published In
Proceedings of SPIE
Volume
6510
Issue
PART 1
Publish Date
2007
DOI
10.1117/12.713032

Comparison of reduced angle and fully 3D acquisition sequencing and trajectories for dual-modality mammotomography

A dual-modality SPECT-CT system for dedicated 3D breast cancer imaging is under development. Independent dedicated SPECT and CT imaging systems have been integrated onto a single gantry for uncompressed breast imaging. This study examines challenges and tradeoffs involved in integrating the acquisition procedures of two independent imaging systems into a single imaging protocol. The physical limitation of the rotating CT tube beneath the custom patient bed currently provides only a 294 degree scan with the bed low enough for the breast to be in the cone-beam CT field-of-view. The directly coupled SPECT system is therefore also limited if the scans are to be taken simultaneously or in an interleaved fashion. Thus, geometric phantoms are imaged to characterize image degradations due to reduced projection angles for both modalities. Two different acquisitions were performed: one with the central ray of the CT cone-beam aligned with the system's center of rotation and one offset from the center of rotation by 5cm. Various sized activity-filled lesions in an anthropomorphic breast phantom were imaged, first with uniform aqueous background activity and then with added acrylic pieces to simulate a non-uniform background. Interleaving the SPECT and CT acquisitions into a single scan was also investigated. Iterative reconstruction algorithms are used to reconstruct the data, and the SPECT and CT images are co-registered. Both the cold rod and breast data indicate that removing 75" of SPECT azimuthal data does not significantly reduce image quality. CT images were also minimally affected if the cone-beam is centrally aligned with the center of rotation, but degraded with the laterally offset cone-beam setup. In the course of these experiments, the patient bed was reconfigured with a larger central hole covered with flexible neoprene, gaining the ability to rotate completely around the breast and dramatically improving CT projection views through the chest wall. © 2007 IEEE.

Authors
Cutler, SJ; Madhav, P; Perez, KL; Crotty, DJ; Tornai, MP
MLA Citation
Cutler, SJ, Madhav, P, Perez, KL, Crotty, DJ, and Tornai, MP. "Comparison of reduced angle and fully 3D acquisition sequencing and trajectories for dual-modality mammotomography." IEEE Nuclear Science Symposium Conference Record 6 (2007): 4044-4050.
Source
scival
Published In
IEEE Nuclear Science Symposium Conference Record
Volume
6
Publish Date
2007
Start Page
4044
End Page
4050
DOI
10.1109/NSSMIC.2007.4437016

Initial patient study with dedicated dual-modality SPECT-CT mammotomography

Dual-modality SPECT-CT dedicated breast imaging offers great promise in the detection/staging of cancer and the monitoring of treatment therapies. The sequential acquisition with emission (nuclear) and transmission (x-ray) 3D imaging systems can aid in localizing the radioactive uptake of a tumor from the emission image by using the anatomical structure from the transmission image as a roadmap. Both independent SPECT and CT subsystems are mounted onto a single gantry that rotates around the vertical axis of a pendant, uncompressed breast. To evaluate the feasibility of this dedicated system, geometric phantoms and breast phantoms using fiducial markers were acquired to study the sampling and resolution properties and demonstrate the fusion of the functional-anatomical images. In addition, a preliminary investigation on the clinical performance of the system was done by imaging two women with confirmed breast cancer: one on the independent SPECT system and the other on the SPECT-CT system. Further patient hybrid imaging studies are in progress. This compact dedicated SPECT-CT system is capable of non-invasively providing complementary functional and anatomical fully-3D activity distribution information of the breast, and has the potential to help further enhance the visual and quantitative information over the independent systems. © 2007 IEEE.

Authors
Madhav, P; Cutler, SJ; Perez, KL; Crotty, DJ; McKinley, RL; Wong, TZ; Tornai, MP
MLA Citation
Madhav, P, Cutler, SJ, Perez, KL, Crotty, DJ, McKinley, RL, Wong, TZ, and Tornai, MP. "Initial patient study with dedicated dual-modality SPECT-CT mammotomography." IEEE Nuclear Science Symposium Conference Record 5 (2007): 3781-3787.
Source
scival
Published In
IEEE Nuclear Science Symposium Conference Record
Volume
5
Publish Date
2007
Start Page
3781
End Page
3787
DOI
10.1109/NSSMIC.2007.4436945

Initial development of a dual-modality SPECT-CT system for dedicated mammotomography

Dual-modality systems offer great promise in improving detection and evaluation of cancer through enhancement of the visual quality and quantitative accuracy of radionuclide imaging. A compact SPECT-CT system for dedicated 3D breast imaging is in development. The SPECT components include a 16×20cm2 CZT-based compact gamma camera with 2.5mm square pixels, attached to a goniometer with polar positioning capability. The CT component includes a heavily filtered W-target x-ray source producing a quasimonochromatic cone beam and CsI(T1) digital detector. Both systems are coupled to a common rotation stage and have a common field of view. The CT system has a stationary polar orientation, and is laterally offset from the center of rotation for imaging pendant uncompressed breasts that are larger than the detector's field of view. The constraints and performance of this initial configuration are being investigated. Previous measurements with combined system components show that optimal placement is limited by physical constraints rather than signal cross-contamination. Results on a combined system show that emission projection images are contaminated by x-ray scatter photons resulting in the reconstructed emission images having a higher signal level. Emission contamination also increases noise in the transmission image resulting in reducing the SNR in reconstructed CT images. Having both modalities on a single gantry is expected to simplify data acquisition, SPECTCT image registration, and necessary image corrections. © 2006 IEEE.

Authors
Madhav, P; Crotty, DJ; McKinley, RL; Tornai, MP
MLA Citation
Madhav, P, Crotty, DJ, McKinley, RL, and Tornai, MP. "Initial development of a dual-modality SPECT-CT system for dedicated mammotomography." IEEE Nuclear Science Symposium Conference Record 4 (2007): 2382-2386.
Source
scival
Published In
IEEE Nuclear Science Symposium Conference Record
Volume
4
Publish Date
2007
Start Page
2382
End Page
2386
DOI
10.1109/NSSMIC.2006.354392

Empirical effects of angular sampling and background content on image quality in dedicated breast SPECT

This study investigates the effects of varying the azimuthal and polar sampling of the acquisition trajectory with the dedicated breast SPECT imaging system developed in our lab. In addition, the frequency quality (density and distribution) of the background is considered. The SPECT system consists of a 16×20cm2 CZT gamma camera with 6.7% FWHM energy resolution at 140keV, which can accommodate fully 3D simple or complex trajectories about a pendant, uncompressed breast. Trajectories used in these studies are vertical axis of rotation, tilted parallel beam and sine wave projected onto a hemisphere. Various geometric and anthropomorphic phantoms containing lesions are imaged to evaluate the effects of sampling and background distributions on signal (lesion) visualization. In general, sufficient counting statistics limit the quality of the image and thus an optimization between the number of projections and the number of detected events is being explored. Reconstructed images of anthropomorphic breast phantoms did not appear to have distortion artifacts in regions inside the breast phantom containing a variety of spatial frequencies, but distortions did appear in some instances in the high frequency outer edge of the phantom in reconstructed images. © 2007 IEEE.

Authors
Perez, KL; Cutler, SJ; Tornai, MP
MLA Citation
Perez, KL, Cutler, SJ, and Tornai, MP. "Empirical effects of angular sampling and background content on image quality in dedicated breast SPECT." IEEE Nuclear Science Symposium Conference Record 4 (2007): 3065-3069.
Source
scival
Published In
IEEE Nuclear Science Symposium Conference Record
Volume
4
Publish Date
2007
Start Page
3065
End Page
3069
DOI
10.1109/NSSMIC.2007.4436777

3-D Contrast-detail analysis for dedicated emission mammotomography

An observer based 3D contrast-detail study is performed in an effort to evaluate the limits of object detectability for a dedicated CZT-based SPECT mammotomography imaging system under various imaging conditions. A novel, geometric contrast-resolution phantom was developed that can be used for both positive ("hot") and negative contrasts ("cold"). The 3cm long fillable tubes are arranged in six sectors having equal inner diameters ranging from 1mm to 6mm with plastic wall thicknesses of <0.25mm, on a pitch of twice their inner diameters. Scans using simple circular trajectories are first obtained of the activity filled tubes in a uniform water filled cylinder, first with no background activity, and then varying the rod:background concentration ratios from 10:1 to 1:10. The rod phantom is then placed inside a non-uniformly shaped breast phantom and scans are again acquired using both simple and complex 3D trajectories for similarly varying contrasts. Scan times are adjusted to account for radioactive decay, and both low and high noise data is obtained. An iterative OSEM reconstruction algorithm is used to reconstruct the data. Images are evaluated by six independent readers, identifying smallest distinguishable rod for each concentration and experimental setup. Results indicate that, using the SPECT camera having 2.5mm intrinsic pixels, the mean detectable size was ∼3.1mm at 10:1 ratio, degrading to ∼5.5mm with the 2.5:1 concentration ratio. Furthermore, there was little statistically significant difference (p<0.05) between cylinder vs. breast, simple vs. complex trajectories, or whether the rods appeared hot (10:1) or cold (1:10), indicating that data acquisition with the mammotomography system is quite robust. © 2006 IEEE.

Authors
Cutler, SJ; Perez, KL; Tornai, MP
MLA Citation
Cutler, SJ, Perez, KL, and Tornai, MP. "3-D Contrast-detail analysis for dedicated emission mammotomography." IEEE Nuclear Science Symposium Conference Record 5 (2007): 2954-2958.
Source
scival
Published In
IEEE Nuclear Science Symposium Conference Record
Volume
5
Publish Date
2007
Start Page
2954
End Page
2958
DOI
10.1109/NSSMIC.2006.356495

Evaluation of lesion distortion at various CT system tilts in the development of a hybrid system for dedicated mammotomography

A hybrid SPECT-CT system for dedicated 3D breast imaging (mammotomography) is currently under development. Each imaging system will be placed on top of a single rotation stage and moved in unison azimuthally, with the SPECT system additionally capable of polar and radial motions. In this initial prototype, the CT system will initially be positioned at a fixed polar tilt. Using a phantom with three tungsten wires, the MTF of the CT system was measured in 3D for different CT system tilts. A phantom with uniformly arranged 0.5cm diameter acrylic spheres was suspended in air in the CT field of view, and also placed at multiple locations and orientations inside an oil-filled breast phantom to evaluate the effect of CT system tilt on lesion visibility and distortion. Projection images were collected using various simple circular orbits with fixed polar tilts ranging between ±15°, and complex 3D saddle trajectories including combined polar and azimuthal motions at maximum polar tilt angles. Reconstructions were performed using an iterative reconstruction algorithm on 4×4 binned projection images with 0.508mm 3 voxels. There was minor variation in the MTF in the imaged volume for the CT system at all trajectories, potentially due to the use of an iterative reconstruction algorithm. Results from the spherical cross phantoms indicated that there was more reconstruction inaccuracy and geometric distortion in the reconstructed slices with simple circular orbits with fixed tilt in contrast to complex 3D trajectories. Line profiles further showed a cupping artifact in planes farther away from the flat plane of the x-ray cone beam placed at different tilts. However, this cupping artifact was not seen for images acquired with complex 3D trajectories. This indicated that cupping artifacts can also be caused by undersampled cone beam data. These findings generally indicate that despite insufficient sampling with the cone beam imaging geometry, it is possible to place the CT system at a stationary polar tilt with the CT tube positioned upward such that a patient can be comfortably placed above the system and allow complete sampling near the top of the pendant, uncompressed breast and chest wall. However, a complex 3D trajectory allows for more complete sampling of the entire image volume.

Authors
Madhav, P; Crotty, DJ; McKinley, RL; Tornai, MP
MLA Citation
Madhav, P, Crotty, DJ, McKinley, RL, and Tornai, MP. "Evaluation of lesion distortion at various CT system tilts in the development of a hybrid system for dedicated mammotomography." Progress in Biomedical Optics and Imaging - Proceedings of SPIE 6510.PART 1 (2007).
Source
scival
Published In
Proceedings of SPIE
Volume
6510
Issue
PART 1
Publish Date
2007
DOI
10.1117/12.713541

Investigating novel patient bed designs for use in a hybrid dual modality dedicated 3D breast imaging system

A hybrid SPECT-CT system for dedicated 3D breast cancer imaging (mammotomography) is in development. Using complex 3D imaging acquisition trajectories, the versatile integrated system will be capable of contouring and imaging an uncompressed breast suspended in a 3D volume located below a radio-opaque patient bed, providing co-registered volumetric anatomical and functional information. This study examines tradeoffs involved in the design of the patient bed to satisfy concomitant and competing technical and ergonomie requirements specific to this imaging paradigm. The complementary source-detector arrangement of the CT system is geometrically more restrictive than that of the single detector SPECT system. Additionally, the compact dimensions and size of the CT system components (primarily the x-ray tube) are key constraints on the bed design and so the focus is concentrated there. Using computer-aided design software, several design geometry options are examined to simultaneously consider and optimize the following parameters: image magnification, imaged breast volume, azimuthal imaging span, and patient comfort. Several CT system source to image distances are examined (55-80cm), as well as axial patient tilt up to 35°. An optimal patient bed design for a completely under-bed hybrid imaging system was determined. A 60cm SID, magnification factor of ∼1.5, and patient bed angled at ∼15° provided the optimal dimensions. Additional bed dimensions allow the CT projection beam to nearly entirely image the chest wall, however at the cost of reduced angular sampling for CT. Acquired x-ray mammotomographic image data is used to assess the feasibility of this reduced angle acquisition approach.

Authors
Crotty, DJ; Madhav, P; McKinley, RL; Tornai, MP
MLA Citation
Crotty, DJ, Madhav, P, McKinley, RL, and Tornai, MP. "Investigating novel patient bed designs for use in a hybrid dual modality dedicated 3D breast imaging system." Progress in Biomedical Optics and Imaging - Proceedings of SPIE 6510.PART 1 (2007).
Source
scival
Published In
Proceedings of SPIE
Volume
6510
Issue
PART 1
Publish Date
2007
DOI
10.1117/12.713764

Analysis of patient bed positioning in SPECT-CT imaging for dedicated mammotomography

Patient positioning on a bed is an integral part of accurate imaging for dedicated 3D breast imaging. For both dedicated breast SPECT (single photon emission computed tomography) and breast CT (computed tomography or computed mammotomography, CmT) which are under development in our lab, maximum access to the breast in the imaging system's field of view is required to obtain the largest imaged breast volume. Accurate bed positioning will be necessary as it may be integrated with a guided biopsy apparatus. Thus, a patient bed with flexible 3D positioning capability is being integrated into the various independent and hybrid 3D imaging systems. The customized bed has both manual and computer controlled positioning capability, and the accuracy and reproducibility of the system are being characterized. Computer controlled positioning and feedback provide seemingly reproducible results. However, gross movements may vary in their accuracy to the given input position. While linear with slopes near 1.0 and intercepts near 0.0cm, lateral (Y) movement translates less than the input amount, while axial (X) movement translates farther than the input amount. Vertical (Z) directional movement follows a quadratic shift with a small dc component with or without added weight on the table. A variety of patient imaging conditions along with x-ray image data are evaluated to demonstrate the reproducibility of positioning accuracy. Individual directional repositioning accuracy is found to be better than multiple, combined directional repositioning accuracy. Imaging results indicate a reproducibility (error) of less than 1mm, which may be suitable for SPECT imaging but perhaps not for higher resolution dedicated breast CT. However, for the independent SPECT system, bed motion is not necessary because the detector's line of sight can already acquire data at the chest wall.

Authors
Perez, KL; Madhav, P; Crotty, DJ; Tornai, MP
MLA Citation
Perez, KL, Madhav, P, Crotty, DJ, and Tornai, MP. "Analysis of patient bed positioning in SPECT-CT imaging for dedicated mammotomography." Progress in Biomedical Optics and Imaging - Proceedings of SPIE 6510.PART 2 (2007).
Source
scival
Published In
Proceedings of SPIE
Volume
6510
Issue
PART 2
Publish Date
2007
DOI
10.1117/12.713822

Performance of dedicated emission mammotomography for various breast shapes and sizes.

We evaluate the effect of breast shape and size and lesion location on a dedicated emission mammotomography system developed in our lab. The hemispherical positioning gantry allows ample flexibility in sampling a pendant, uncompressed breast. Realistic anthropomorphic torso (which includes the upper portion of the arm) and breast phantoms draw attention to the necessity of using unique camera trajectories (orbits) rather than simple circular camera trajectories. We have implemented several novel three-dimensional (3D) orbits with fully contoured radius-of-rotation capability for compensating for the positioning demands that emerge from different breast shapes and sizes. While a general orbit design may remain the same between two different breasts, the absolute polar tilt range and radius-of-rotation range may vary. We have demonstrated that using 3D orbits with increased polar camera tilt, lesions near the chest wall can be visualized for both large and small sized breasts (325 ml to 1,060 ml), for a range of intrinsic contrasts (three to ten times higher activity concentration in the lesion than breast background). Overall, nearly complete 3D acquisition schemes yield image data with relatively high lesion SNRs and contrasts and with minimal distortion of the uncompressed breast shape.

Authors
Brzymialkiewicz, CN; Tornai, MP; McKinley, RL; Cutler, SJ; Bowsher, JE
MLA Citation
Brzymialkiewicz, CN, Tornai, MP, McKinley, RL, Cutler, SJ, and Bowsher, JE. "Performance of dedicated emission mammotomography for various breast shapes and sizes." Phys Med Biol 51.19 (October 7, 2006): 5051-5064.
PMID
16985287
Source
pubmed
Published In
Physics in Medicine and Biology
Volume
51
Issue
19
Publish Date
2006
Start Page
5051
End Page
5064
DOI
10.1088/0031-9155/51/19/021

A novel method to characterize the MTF in 3D for computed mammotomography

A novel phantom has been developed to measure the modulation transfer function (MTF) in 3D for x-ray computed tomography. The phantom consists of three tungsten wires, positioned nearly orthogonal to each other. Simultaneous measurements of the MTF are taken at various locations along the three orthogonal reconstructed planes. Our computed mammotomography (CmT) system uses a Varian Paxscan 2520 digital x-ray detector which can be positioned anywhere in ∼2pi steradian band and can have arbitrary trajectories, With a half-cone beam geometry and with the phantom positioned near the center of rotation, projection images are acquired over 360 degrees, Various 3D orbits are evaluated including vertical axis of rotation and saddle. Reconstructions were performed using an iterative ordered-subsets transmission algorithm on rebinned projection images, using various numbers of iterations. Rotation of reconstructed slices isolated each wire into its own plane. At various locations along the length of each wire, corresponding MTFs were calculated from 1D line spread functions. Through measurement, accuracy of wire method was verified by comparison of the projection MTFs computed from a wire and a standard edge device. Results indicated minor variations in MTF among the three orthogonal planes, which imply a high degree of uniform sampling in the imaged volume. Findings indicate that the phantom can be used to assess the intrinsic image resolution in 3D as well as potential degradative effects of measurements in various media.

Authors
Madhav, P; McKinley, RL; Samei, E; Bowsher, JE; Tornai, MP
MLA Citation
Madhav, P, McKinley, RL, Samei, E, Bowsher, JE, and Tornai, MP. "A novel method to characterize the MTF in 3D for computed mammotomography." Progress in Biomedical Optics and Imaging - Proceedings of SPIE 6142 II (2006).
Source
scival
Published In
Proceedings of SPIE
Volume
6142 II
Publish Date
2006
DOI
10.1117/12.653393

Investigation of emission contamination in the transmission image of a dual modality computed mammotomography system

A dual modality SPECT/CT computed mammotomography (CmT) system for dedicated functional/structural breast imaging is under development. In simultaneous, dual-modality imaging, contamination of the transmission (x-ray) image by emission photons from the uncompressed, pendant breast and torso is an important consideration in the design of hybrid imaging hardware. The lack of a collimator on the transmission image detector implies increased geometric efficiency of primary and scattered emission photons from the breast and neighboring torso region that potentially increase transmission image noise. This study investigates the nature and extent of this cross contamination. Projection and tomographic x-ray images are obtained with and without emission activity in a realistic anthropomorphic torso and various breast phantoms, and also with and without lead shielding on the torso for a variety of x-ray exposure times. Results for emission-source contamination of transmission images are quantified in terms of a mean and standard deviation of regions of interest. There was an observed trend of increased contamination with increasing emission radioactivity in the projection images when the x-ray detector was located immediately beneath the torso phantom, but no discernible effect when the detector was lateral to (and beneath) the torso. Torso shielding mitigated this contamination somewhat. Indeed, in reconstructed CmT data, there was both a decrease in SNR and concomitant decrease in mean attenuation coefficient with increasing emission radioactivity contamination. These results are consistent with the expected increased noise due to a uniform emission irradiation of the detector and hence the resulting apparent increase in detected x-ray transmission events (which yield a lower reconstructed attenuation coefficient value). Despite the emission contamination in both projection and reconstructed images, the contamination is uncorrelated, and indeed no reconstruction artifacts were observed under the various measured conditions. This indicates that a simple contamination correction may be possible to the projection data prior to reconstruction.

Authors
Crotty, DJ; Bryzmialkiewicz, CN; McKinley, RL; Tornai, MP
MLA Citation
Crotty, DJ, Bryzmialkiewicz, CN, McKinley, RL, and Tornai, MP. "Investigation of emission contamination in the transmission image of a dual modality computed mammotomography system." Progress in Biomedical Optics and Imaging - Proceedings of SPIE 6142 II (2006).
Source
scival
Published In
Proceedings of SPIE
Volume
6142 II
Publish Date
2006
DOI
10.1117/12.654580

Preliminary investigation of dose for a dedicated mammotomography system

We use a previously reported, optimized quasi-monochromatic beam technique together with unique complex acquisition trajectories made possible with a novel, dedicated cone-beam transmission computed mammotomography (CmT) system to investigate effects of low dose imaging of pendant, uncompressed breasts. Investigators have used a guideline of dose for CmT type applications as that used for dual-view mammography (4-6 mGy for average breast size). This dose is somewhat arbitrary, and it may be possible to reduce this significantly without sacrificing image quality using our quasi-monochromatic x-ray beam, 3D complex acquisition orbits, and iterative reconstruction techniques. A low-scatter acrylic resolution phantom in various media, a breast phantom with sponge and oil-filled lesions, and a cadaver breast are used to evaluate the effect of lowered dose on resolution and image artifacts. Complex saddle acquisition trajectories (necessary to overcome cone-beam distortion) are carried out for total exposures of 96, 300, and 600 mAs over 240 projections. These exposures relate approximately to 1/10 th, 1/3 rd, and 2/3 of the standard dual view mammography dose for an average sized 50% adipose/glandular breast. Iterative reconstruction uses an OSTR algorithm with 0.125 mm 3 voxels. Image artifacts increased as dose was reduced but did not appear to greatly degrade image quality except at the lowest contrast tested (1% absolute contrast). As expected, noise increased as dose was reduced. However, this did not appear to affect resolution for rods in air (high contrast), nor rods in oil (20% absolute contrast). Resolution was reduced for rods in water (1% absolute contrast) due to increased prevalence of image artifacts as well as increased noise. Breast phantom imaging of soft lesions in a highly glandular breast (6% absolute contrast) clearly yielded the 60uL and all larger volume lesions. Preliminary biological breast tissue results illustrate excellent subjective image quality at all dose levels tested. Results indicate that our quasi-monochromatic beam together with complex orbit capability and iterative reconstruction has the potential to provide sufficient image quality for practical 3D mammotomography of uncompressed breasts at significantly lower dose than dual view mammography. This is nominally a 2-fold improvement over other approaches using circular orbits and broader spectral x-ray beams. While simple image filtering (post-reconstruction smoothing) could improve noise quality, improvements in image artifact correction and scatter correction are required to more accurately determine the lower limits on dose. A contrast-detail study is also warranted with a greater variety of lesion sizes and contrasts.

Authors
McKinley, RL; Tornai, MP
MLA Citation
McKinley, RL, and Tornai, MP. "Preliminary investigation of dose for a dedicated mammotomography system." Progress in Biomedical Optics and Imaging - Proceedings of SPIE 6142 I (2006).
Source
scival
Published In
Proceedings of SPIE
Volume
6142 I
Publish Date
2006
DOI
10.1117/12.654095

Experimental spectral measurements of heavy K-edge filtered beams for X-ray computed mammotomography

A compact, dual modality computed mammotomography (CmT) and single photon emission computed tomography (SPECT) system for dedicated 3D breast imaging is in development. The CmT component utilizes novel, heavy K-edge filtration to practicably narrow the energy spectrum of the cone-shaped x-ray beam incident on the patient's pendant, uncompressed breast. This quasi-monochromatic beam in CmT is expected to improve discrimination of tissue with very similar attenuation coefficients while restraining dose levels to below that of existing dual view mammography. Our previous extensive simulation studies showed the optimal energy range that provides maximum dose efficiency for a 50/50 adipose/glandular breast is in the 35-40keV range. This current study aims to experimentally validate previous simulation results. Here, experimental pre-breast and post-breast collimated x-ray beam spectral measurements are made under tube operating voltages between 40-100kVp using filter materials from Z= 13-74, with K-edge values spanning that of Ce (K=40.4keV), and using different attenuating thicknesses of filter material, approximately equivalent to the 200 th and 500 th attenuating value layer (VL) thickness. Ce-filtered post breast spectra for 8cm to 18cm breasts are measured for a range of breast adipose/glandular compositions. Evaluated figures of merit include mean beam energy, spectral full-width at tenth-maximum, beam hardening and dose for the range of breast sizes. Measurements are shown to corroborate the simulations, and both indicate that for a given dose a 200 th VL of Ce filtration may have the most optimal performance in the dedicated mammotomography paradigm.

Authors
Crotty, DJ; McKinley, RL; Tornai, MP
MLA Citation
Crotty, DJ, McKinley, RL, and Tornai, MP. "Experimental spectral measurements of heavy K-edge filtered beams for X-ray computed mammotomography." Progress in Biomedical Optics and Imaging - Proceedings of SPIE 6142 II (2006).
Source
scival
Published In
Proceedings of SPIE
Volume
6142 II
Publish Date
2006
DOI
10.1117/12.654611

Initial comparison of registration and fusion of SPECT-CmT mammotomography images

A hybrid, dual modality single photon emission computed tomography (SPECT) and x-ray computed mammotomography (CmT) scanner for dedicated breast and axillary imaging is under development. CmT imaging provides high resolution anatomical images, whereas SPECT provides functional images albeit with coarser resolution. As is being seen clinically in whole body imaging, integration of the images is expected to enhance (visually) and improve (with attenuation correction of SPECT) information provided by either modality for the detection, characterization and potentially staging of breast cancer. The registration of these images considers variations in object positions between the different modalities and imaging parameters (pixel size, conditions of acquisition, scan limitations). Automatic methods can be used which find the geometric transformations of the different imaging modalities involved. Here we demonstrate the initial stages of iterative 2-dimensional registration and fusion of SPECT with parallel beam geometry and CmT with offset cone-beam acquisition geometry for mammotomography with images acquired and reconstructed independently on each system. Two registration algorithms are considered: the first is an intrinsic correlation, Mutual Information (MI) method based on intrinsic image content; the second is a rigid body transform method, Iterative Closest Point (ICP) method based on identification of fiducial markers visible to both emission (SPECT) and transmission (CmT) imaging modalities. Experiments include use of a geometric resolution/frequency phantom imaged under different conditions, and two different anthropomorphic breast phantom sizes (325 and 935mL). Initial results with the geometric phantom demonstrate that MI can be misled by highly symmetric features, and ICP using control points is more accurate to within fractions of a voxel. Initial breast phantom studies indicate that object size and SPECT resolution limitations may contribute to registration errors.

Authors
Dura, E; Madhav, P; Cutler, SJ; Turkington, TG; Tornai, MP
MLA Citation
Dura, E, Madhav, P, Cutler, SJ, Turkington, TG, and Tornai, MP. "Initial comparison of registration and fusion of SPECT-CmT mammotomography images." Progress in Biomedical Optics and Imaging - Proceedings of SPIE 6144 II (2006).
Source
scival
Published In
Proceedings of SPIE
Volume
6144 II
Publish Date
2006
DOI
10.1117/12.654477

Analysis of a novel offset cone-beam computed mammotomography system geometry for accomodating various breast sizes.

We evaluate a newly developed dedicated cone-beam transmission computed mammotomography (CmT) system configuration using an optimized quasi-monochromatic cone beam technique for attenuation correction of SPECT in a planned dual-modality emission and transmission system for pendant, uncompressed breasts. In this study, we perform initial CmT acquisitions using various sized breast phantoms to evaluate an offset cone-beam geometry. This offset geometry provides conjugate projections through a full 360 degree gantry rotation, and thus yields a greatly increased effective field of view, allowing a much wider range of breast sizes to be imaged without truncation in reconstructed images. Using a tungsten X-ray tube and digital flat-panel X-ray detector in a compact geometry, we obtained initial CmT scans without shift and with the offset geometry, using geometrical frequency/resolution phantoms and two different sizes of breast phantoms. Acquired data were reconstructed using an ordered subsets transmission iterative algorithm. Projection images indicate that the larger, 20 cm wide, breast requires use of a half-cone-beam offset scan to eliminate truncation artifacts. Reconstructed image results illustrate elimination of truncation artifacts, and that the novel quasi-monochromatic beam yields reduced beam hardening. The offset geometry CmT system can indeed potentially be used for structural imaging and accurate attenuation correction for the functional dedicated breast SPECT system.

Authors
McKinley, RL; Tornai, MP; Brzymialkiewicz, C; Madhav, P; Samei, E; Bowsher, JE
MLA Citation
McKinley, RL, Tornai, MP, Brzymialkiewicz, C, Madhav, P, Samei, E, and Bowsher, JE. "Analysis of a novel offset cone-beam computed mammotomography system geometry for accomodating various breast sizes." Phys Med 21 Suppl 1 (2006): 48-55.
PMID
17645994
Source
pubmed
Published In
Physica Medica
Volume
21 Suppl 1
Publish Date
2006
Start Page
48
End Page
55
DOI
10.1016/S1120-1797(06)80024-4

Physica Medica: Preface

Authors
Levin, CS; Tornai, MP; Pani, R; Garibaldi, F; Mankoff, DA
MLA Citation
Levin, CS, Tornai, MP, Pani, R, Garibaldi, F, and Mankoff, DA. "Physica Medica: Preface." Physica Medica 21.SUPPL. 1 (2006): 1--.
Source
scival
Published In
Physica Medica
Volume
21
Issue
SUPPL. 1
Publish Date
2006
Start Page
1-
DOI
10.1016/S1120-1797(06)80010-4

Patient Bed Design for an Integrated SPECT-CT Dedicated Mammotomography System

Authors
Crotty, DJ; Madhav, P; McKinley, RL; Tornai, MP; IEEE,
MLA Citation
Crotty, DJ, Madhav, P, McKinley, RL, Tornai, MP, and IEEE, . "Patient Bed Design for an Integrated SPECT-CT Dedicated Mammotomography System." 2006.
Source
wos-lite
Published In
IEEE Conference Record - Nuclear Science Symposium & Medical Imaging Conference : IEEE Nuclear Science Symposium And Medical Imaging Conference. Proceedings
Publish Date
2006
Start Page
3915
End Page
3919

Initial study of quasi-monochromatic X-ray beam performance for X-ray computed mammotomography

Authors
McKinley, RL; Tornai, MP; Samei, E; Bradshaw, ML
MLA Citation
McKinley, RL, Tornai, MP, Samei, E, and Bradshaw, ML. "Initial study of quasi-monochromatic X-ray beam performance for X-ray computed mammotomography." IEEE TRANSACTIONS ON NUCLEAR SCIENCE 52.5 (October 2005): 1243-1250.
Source
wos-lite
Published In
IEEE Transactions on Nuclear Science
Volume
52
Issue
5
Publish Date
2005
Start Page
1243
End Page
1250
DOI
10.1109/TNS.2005.0857629

Evaluation of fully 3-D emission mammotomography with a compact cadmium zinc telluride detector.

A compact, dedicated cadmium zinc telluride (CZT) gamma camera coupled with a fully three-dimensional (3-D) acquisition system may serve as a secondary diagnostic tool for volumetric molecular imaging of breast cancers, particularly in cases when mammographic findings are inconclusive. The developed emission mammotomography system comprises a medium field-of-view, quantized CZT detector and 3-D positioning gantry. The intrinsic energy resolution, sensitivity and spatial resolution of the detector are evaluated with Tc-99m (140 keV) filled flood sources, capillary line sources, and a 3-D frequency-resolution phantom. To mimic realistic human pendant, uncompressed breast imaging, two different phantom shapes of an average sized breast, and three different lesion diameters are imaged to evaluate the system for 3-D mammotomography. Acquisition orbits not possible with conventional emission, or transmission, systems are designed to optimize the viewable breast volume while improving sampling of the breast and anterior chest wall. Complications in camera positioning about the patient necessitate a compromise in these two orbit design criteria. Image quality is evaluated with signal-to-noise ratios and contrasts of the lesions, both with and without additional torso phantom background. Reconstructed results indicate that 3-D mammotomography, incorporating a compact CZT detector, is a promising, dedicated breast imaging technique for visualization of tumors < 1 cm in diameter. Additionally, there are no outstanding trajectories that consistently yield optimized quantitative lesion imaging parameters. Qualitatively, imaging breasts with realistic torso backgrounds (out-of-field activity) substantially alters image characteristics and breast morphology unless orbits which improve sampling are utilized. In practice, the sampling requirement may be less strict than initially anticipated.

Authors
Brzymialkiewicz, CN; Tornai, MP; McKinley, RL; Bowsher, JE
MLA Citation
Brzymialkiewicz, CN, Tornai, MP, McKinley, RL, and Bowsher, JE. "Evaluation of fully 3-D emission mammotomography with a compact cadmium zinc telluride detector." IEEE Trans Med Imaging 24.7 (July 2005): 868-877.
PMID
16011316
Source
pubmed
Published In
IEEE Transactions on Medical Imaging
Volume
24
Issue
7
Publish Date
2005
Start Page
868
End Page
877

Initial study of quasi-monochromatic x-ray beam performance for x-ray computed mammotomography

We evaluate the feasibility, benefits, and operating parameters of a quasimonochromatic beam for a newly developed x-ray cone beam computed mammotomography application. The value of a near monochromatic x-ray source for fully 3D dedicated mammotomography is the expected improved ability to separate tissues with very small differences in attenuation coefficients while maintaining dose levels at or below that of existing dual view mammography. In previous studies, simulations for a range of tungsten tube potentials, K-edge filter materials, filter thicknesses, and a 12 cm uncompressed breast, with a digital flat-panel CsI(Tl) detector model, indicated that thick, rare earth filter materials may provide optimized image quality. Figures of merit computed included: lesion contrast under different filtering conditions; ratio of measured lesion contrast with and without filtering; and exposure efficiency (SNR 2/exposure). Initial experiments are performed with a custom built x-ray mammotomography system, cerium foil filters, and plastic breast and lesion tissue-equivalent slabs. Simulation results showed that tube potentials of 50-70 kVp with filters of Z = 57-63 yielded quasimonochromatic x-ray spectra with improved FOMs. Initial experimental measurements corroborate simulation results in that, relative trends and rank order of contrast ratios and exposure efficiency were in agreement. These studies show that this approach can be implemented practically with simple hardware and yield improved exposure efficiency versus the unfiltered or minimally filtered case. © 2005 IEEE.

Authors
McKinley, RL; Toraai, MP; Samei, E; Bradshaw, ML
MLA Citation
McKinley, RL, Toraai, MP, Samei, E, and Bradshaw, ML. "Initial study of quasi-monochromatic x-ray beam performance for x-ray computed mammotomography." IEEE Transactions on Nuclear Science 52.5 I (2005): 1243-1250.
Source
scival
Published In
IEEE Transactions on Nuclear Science
Volume
52
Issue
5 I
Publish Date
2005
Start Page
1243
End Page
1250
DOI
10.1109/TNS.2005.857629

Anthropomorphic breast phantoms for preclinical evaluation with transmission or emission imaging

With the development of several classes of dedicated emission and transmission imaging technologies utilizing ionizing radiation for improved breast cancer detection and in vivo characterization, it is extremely useful to have available anthropomorphic breast phantoms in a variety of shapes, sizes and malleability prior to clinical imaging. These anthropomorphic phantoms can be used to evaluate the implemented imaging approaches given a known quantity, the phantom, and to evaluate the variability of the measurement due to the imaging system chain. Thus, we have developed a set of fillable and incompressible breast phantoms ranging in volume from 240 to 1730mL with nipple-to-chest distances from 3.8 to 12cm. These phantoms are mountable and exchangeable on either a uniform chest plate or anthropomorphic torso phantom containing tissue equivalent bones and surface tissue. Another fillable ∼700mL breast phantom with solid anterior chest plate is intentionally compressible, and can be used for direct comparisons between standard planar imaging approaches using mild-to-severe compression, partially compressed tomosynthesis, and uncompressed computed mammotomography applications. These phantoms can be filled with various fluids (water and oil based liquids) to vary the fatty tissue background composition. Shaped cellulose sponges with two cell densities are fabricated and can be added to the breasts to simulate connective tissue. Additionally, microcalcifications can be simulated by peppering slits in the sponges with oyster shell fragments. These phantoms have a utility in helping to evaluate clinical imaging paradigms with known input object parameters using basic imaging characterization, in an effort to further evaluate contemporary and next generation imaging tools. They may additionally provide a means to collect known data samples for task based optimization studies.

Authors
Tornai, MP; McKinley, RL; Brzymialkiewicz, CN; Cutler, SJ; Crotty, DJ
MLA Citation
Tornai, MP, McKinley, RL, Brzymialkiewicz, CN, Cutler, SJ, and Crotty, DJ. "Anthropomorphic breast phantoms for preclinical evaluation with transmission or emission imaging." Progress in Biomedical Optics and Imaging - Proceedings of SPIE 5746.II (2005): 825-834.
Source
scival
Published In
Proceedings of SPIE
Volume
5746
Issue
II
Publish Date
2005
Start Page
825
End Page
834
DOI
10.1117/12.596094

Design and development of a fully-3D dedicated x-ray computed mammotomography system

Our effort to implement a volumetric x-ray computed mammotomography (CmT) system dedicated to imaging breast disease comprises: demonstrated development of a quasi-monochromatic x-ray beam providing minimal dose and other optimal imaging figures of merit; new development of a compact, variable field-of-view, fully-3D acquisition gantry with a digital flat-panel detector facilitating more nearly complete sampling of frequency space and the physical breast volume; incorporation of iterative ordered-subsets transmission (OSTR) image reconstruction allowing modeling of the system matrix. Here, we describe the prototype 3D gantry and demonstrate initial system performance. Data collected on the prototype gantry demonstrate the feasibility of using OSTR with realistic reconstruction times. The gantry consists of a rotating W-anode x-ray tube using ultra-thick K-edge filtration, and an ∼20×25cm 2 digital flat-panel detector located at <60cm SID. This source/detector combination can be shifted laterally changing the location of the central ray relative to the system center-of-rotation, hence changing the effective imaging field-of-view, and is mounted on a goniometric cradle allowing <50° polar tilt, then on a 360° azimuthal rotation stage. Combined, these stages provide for positioning flexibility in a banded region about a sphere, facilitating simple circle-plus-arc-like trajectories, as well as considerably more complex 3D trajectories. Complex orbits are necessary to avoid physical hindrances from the patient while acquiring the largest imaging volume of the breast. The system capabilities are demonstrated with fully-3D reconstructed images of geometric sampling and resolution phantoms, a fabricated breast phantom containing internal features of interest, and a cadaveric breast specimen. This compact prototype provides flexibility in dedicated, fully-SD CmT imaging of healthy and diseased breasts.

Authors
Tornai, MP; McKinley, RL; Brzymialkiewicz, CN; Madhav, P; Cutler, SJ; Crotty, DJ; Bowsher, JE; Samei, E; Jr, CEF
MLA Citation
Tornai, MP, McKinley, RL, Brzymialkiewicz, CN, Madhav, P, Cutler, SJ, Crotty, DJ, Bowsher, JE, Samei, E, and Jr, CEF. "Design and development of a fully-3D dedicated x-ray computed mammotomography system." Progress in Biomedical Optics and Imaging - Proceedings of SPIE 5745.I (2005): 189-197.
Source
scival
Published In
Proceedings of SPIE
Volume
5745
Issue
I
Publish Date
2005
Start Page
189
End Page
197
DOI
10.1117/12.595636

Comparison of compact gamma cameras with 1.3- And 2.0-mm quantized elements for dedicated emission mammotomography

In an effort to image smaller breast lesions, two compact gamma cameras with different intrinsic Nal(Tl) pixel sizes are evaluated for use in the application specific emission tomography (ASET) system for dedicated mammotomographic emission imaging. Comparison measurements were made with two scintillator arrays having 1.3 × 1.3 × 6 mm 3 or 2.0 × 2.0 × 6 mm 3 elements on exactly the same set of PMTs, electronics and control/processing hardware. Uniformity, sensitivity and energy resolution were assessed with flood field phantoms. Spatial resolution measurements included: a 99mTc (140 keV) activity filled capillary tube imaged in planar mode from 1-10 cm distance; two such tubes separated by 2 cm were also imaged with simple circular tomography from 3-7 cm radii-of-rotation (RORs); and a 99m Tc filled mini cold-rod phantom was imaged at 5 cm ROR with a simple circular orbit. Finally, a freely suspended and uniformly filled 950 mL breast phantom containing four tillable lesions (4-10 mm dia) was imaged with a lesion-to-uniform-background activity concentration ratio of 15:1, using simple and complex three-dimensional (3-D) orbits and minimal RORs. The measured sensitivity varied by the crystal fill-factor; uniformity had <4% variability; and mean energy resolutions of each camera were <12% full-width at half-maximum (FWHM). The planar spatial resolutions correspond to calculated values, with smaller pixels yielding 2%-13% better resolution with decreasing separation distance; tomographic results ranged from 3.2-5.2 mm FWHM at 3-7 cm, with nominally better contrast-resolution for the smaller pixel camera. Consistent with signal detection characteristics for these measurement conditions, quantitative SNRs and contrasts from lesion imaging with the uniform breast background illustrate better overall performance under nearly all conditions and for all lesions for the larger pixel camera. © 2005 IEEE.

Authors
Tornai, MP; Brzymialkiewicz, CN; Bradshaw, ML; Bowsher, JE; Patt, BE; Iwanczyk, JS; Li, J; MacDonald, LR
MLA Citation
Tornai, MP, Brzymialkiewicz, CN, Bradshaw, ML, Bowsher, JE, Patt, BE, Iwanczyk, JS, Li, J, and MacDonald, LR. "Comparison of compact gamma cameras with 1.3- And 2.0-mm quantized elements for dedicated emission mammotomography." IEEE Transactions on Nuclear Science 52.5 I (2005): 1251-1256.
Source
scival
Published In
IEEE Transactions on Nuclear Science
Volume
52
Issue
5 I
Publish Date
2005
Start Page
1251
End Page
1256
DOI
10.1109/TNS.2005.858192

Investigation of cone-beam acquisitions implemented using a novel dedicated mammotomography system with unique arbitrary orbit capability

We investigate cone-beam acquisitions implemented on a novel dedicated cone-beam transmission computed mammotomography (CmT) system with unique arbitrary orbit capability for pendant, uncompressed breasts. We use a previously reported optimized quasi-monochromatic beam technique together with orbits made possible with a novel CmT gantry system, to evaluate Vertical-Axis-Of-Rotation (VAOR), Circle-Plus-Two-Arcs (CP2A), and Saddle trajectories. Acquisition parameters include: W target, 60 kVp tube potential, 100th VL Nd filtration, 1.25 mAs, 55 cm SID, Csl(Tl) digital flat panel x-ray detector, and 7.7cm diameter uniform disc (Défrise) and resolution phantoms. Complex orbits were also performed for a realistic breast phantom. Reconstructions used an iterative ordered subsets transmission (OSTR) algorithm with 4×4 binned projections, 8 subsets, and 10 iterations, with 0.125 mm 3 voxels. We evaluate the results for image artifacts, distortion, and resolution. Reconstructed images of the disc coronal and sagittal slices show significant distortion of the discs and phantom interfaces away from the central plane of the conebeam for VAOR, less distortion for CP2A, and minimal distortion for the complex 3D Saddle orbit. Resolution phantoms indicate no loss of resolution with the Saddle orbit, with the smallest 1.1mm diameter rods clearly resolved. Other image artifacts such as streaking were also significantly reduced in the Saddle orbit case. Results indicate that arbitrary orbits of pendant uncompressed breasts using cone-beam acquisitions and OSTR iterative reconstructions can be successfully implemented for dedicated CmT to improve angular sampling with significant reduction in distortion and other image artifacts. This capability has the potential to improve the performance of dedicated CmT by adequately sampling the breast and anterior chest volumes of prone patients with pendant, uncompressed breasts.

Authors
McKinley, RL; Brzymialkiewicz, CN; Madhav, P; Tornai, MP
MLA Citation
McKinley, RL, Brzymialkiewicz, CN, Madhav, P, and Tornai, MP. "Investigation of cone-beam acquisitions implemented using a novel dedicated mammotomography system with unique arbitrary orbit capability." Progress in Biomedical Optics and Imaging - Proceedings of SPIE 5745.I (2005): 609-617.
Source
scival
Published In
Proceedings of SPIE
Volume
5745
Issue
I
Publish Date
2005
Start Page
609
End Page
617
DOI
10.1117/12.596089

A framework for optimising the radiographic technique in digital X-ray imaging.

The transition to digital radiology has provided new opportunities for improved image quality, made possible by the superior detective quantum efficiency and post-processing capabilities of new imaging systems, and advanced imaging applications, made possible by rapid digital image acquisition. However, this transition has taken place largely without optimising the radiographic technique used to acquire the images. This paper proposes a framework for optimising the acquisition of digital X-ray images. The proposed approach is based on the signal and noise characteristics of the digital images and the applied exposure. Signal is defined, based on the clinical task involved in an imaging application, as the difference between the detector signal with and without a target present against a representative background. Noise is determined from the noise properties of uniformly acquired images of the background, taking into consideration the absorption properties of the detector. Incident exposure is estimated or otherwise measured free in air, and converted to dose. The main figure of merit (FOM) for optimisation is defined as the signal-difference-to-noise ratio (SdNR) squared per unit exposure or (more preferably) dose. This paper highlights three specific technique optimisation studies that used this approach to optimise the radiographic technique for digital chest and breast applications. In the first study, which was focused on chest radiography with a CsI flat-panel detector, a range of kV(p) (50-150) and filtration (Z = 13-82) were examined in terms of their associated FOM as well as soft tissue to bone contrast, a factor of importance in digital chest radiography. The results indicated that additive Cu filtration can improve image quality. A second study in digital mammography using a selenium direct flat-panel detector indicated improved SdNR per unit exposure with the use of a tungsten target and a rhodium filter than conventional molybdenum target/molybdenum filter techniques. Finally, a third study focusing on cone-beam computed tomography of the breast using a CsI flat-panel detector indicated that high Z filtration of a tungsten target X-ray beam can notably improve the signal and noise characteristics of the image. The general findings highlight the fact that the techniques that are conventionally assumed to be optimum may need to be revisited for digital radiography.

Authors
Samei, E; Dobbins, JT; Lo, JY; Tornai, MP
MLA Citation
Samei, E, Dobbins, JT, Lo, JY, and Tornai, MP. "A framework for optimising the radiographic technique in digital X-ray imaging." Radiat Prot Dosimetry 114.1-3 (2005): 220-229.
PMID
15933112
Source
pubmed
Published In
Radiation Protection Dosimetry
Volume
114
Issue
1-3
Publish Date
2005
Start Page
220
End Page
229
DOI
10.1093/rpd/nch562

Characterizing the MTF in 3D for a quantized SPECT camera having arbitrary trajectories

The Modulation Transfer Function (MTF) in 3D is examined for a compact SPECT system capable of moving in different trajectories. A novel phantom has been developed to allow simultaneous measurements of the MTF oriented along three orthogonal axes for dedicated SPECT. The phantom consists of three capillary tubes filled with radioactivity, positioned nearly orthogonally to each other. The evaluated imaging system is a 16×20cm2 CZT-based compact gamma camera with 2.5mm square pixels having a hexagonal close-packed collimator on its front surface. Projection data are acquired with the phantom positioned in air and in various uniformly cylindrical and non-uniformly breast-shaped water scattering media in the camera's field of view. Various source-to-collimator distances are evaluated using simple and more complex orbital trajectories about the phantom including: vertical axis of rotation, tilted parallel beam, circle-plus-arc, and a sinusoid projected onto a hemisphere. Using data collected with an ±8% energy window about the 99mTc 140keV photopeak, images are reconstructed with an iterative ordered subsets expectation maximization algorithm for different iterations, reconstructed voxel sizes and sampling schemes. After reconstruction, each line is rotated into its own plane that is mutually orthogonal to the other two lines, and reoriented with coordinates obtained from 2D Radon transform. One dimensional line spread functions and corresponding MTFs are evaluated along the various segments of each capillary tube. Results indicate small variations in the MTFs, with complex orbits having slightly better performance in scatter conditions. © 2005 IEEE.

Authors
Madhav, P; Brzymialkiewicz, CN; Cutler, SJ; Bowsher, JE; Tornai, MP
MLA Citation
Madhav, P, Brzymialkiewicz, CN, Cutler, SJ, Bowsher, JE, and Tornai, MP. "Characterizing the MTF in 3D for a quantized SPECT camera having arbitrary trajectories." IEEE Nuclear Science Symposium Conference Record 3 (2005): 1722-1726.
Source
scival
Published In
IEEE Nuclear Science Symposium Conference Record
Volume
3
Publish Date
2005
Start Page
1722
End Page
1726
DOI
10.1109/NSSMIC.2005.1596652

Towards patient imaging with dedicated emission mammotomography

A patient bed was recently developed and subsequent modifications made for 3D, pendant breast imaging with a dedicated emission mammotomography system that incorporates a discretized 16×20cm2 CZT gamma camera with 2.5mm pixels. Goals for these experiments include: (1) designing acquisition orbits to minimize effects from complications that arise with patient positioning; (2) determining whether axillary imaging is possible in this configuration; and (3) determining an amount of system tilt to adequately image the breast. Data was initially acquired with Tc-99m-filled anthropomorphic breast and torso phantoms for each of three cases: activity in the breast only; activity in the breast and torso; activity in both, with lead shielding placed on the pallet (to mimic an intended custom-designed lead-lined pallet). Projection data were acquired using both simple and complex 3D orbits. We have found that acquisition orbits can be modified to accommodate the bed's physical hindrances and still recover most of the volume of interest, while minimizing distortion and artifacts in the reconstructed images. Overall, the results indicate this approach could be a beneficial diagnostic tool to aid in the characterization of lesions. © 2005 IEEE.

Authors
Brzymialkiewicz, CN; McKinley, RL; Tornai, MP
MLA Citation
Brzymialkiewicz, CN, McKinley, RL, and Tornai, MP. "Towards patient imaging with dedicated emission mammotomography." IEEE Nuclear Science Symposium Conference Record 3 (2005): 1519-1523.
Source
scival
Published In
IEEE Nuclear Science Symposium Conference Record
Volume
3
Publish Date
2005
Start Page
1519
End Page
1523
DOI
10.1109/NSSMIC.2005.1596607

Investigating the effects of energy resolution in dedicated emission mammotomography

This study probes the recent debate over the necessity for good energy resolution for uncompressed breast, 3D lesion imaging with dedicated single photon emission mammotomography. Here, the imaging system consists of a commercial, discretized CZT gamma camera having ∼6% FWHM intrinsic energy resolution (at 140keV) and intrinsic spatial resolution corresponding to the 2.5mm square pixilation, and is used on a fully-3D positioning gantry. Wider energy windows are used on list mode acquired data as a surrogate for having otherwise identical detection systems with poorer energy resolution characteristics. Scans using simple circular trajectories are first obtained of an aqueous Tc-99m filled mini resolution cold-rod phantom at various radii-of-rotation, and also immersed in a larger uniform water bath. Multiple 3D orbits about Tc-99m filled anthropomorphic breast and torso phantoms are acquired, with the breast containing two large lesions. The list mode data files were multiply processed to obtain images of varying energy window widths (from symmetric 6% to an asymmetric 18% (-12+6)) but with the same projection image count density. Counts were randomly subsampled from the entire list mode data set in order to maintain equivalent levels of count density for several bootstrap realizations. All data was then reconstructed using OSEM for various iterations. Profiles were obtained from the cold rod images, and regions of interest were drawn in and about the spherical lesions to determine signal-tonoise ratios and contrasts for each iteration. Results clearly illustrate both visual and quantitative differences between the various energy windows, with smaller energy windows (corresponding to better energy resolution) having better image quality. © 2005 IEEE.

Authors
Cutler, SJ; Brzymialkiewicz, CN; Tornai, MP
MLA Citation
Cutler, SJ, Brzymialkiewicz, CN, and Tornai, MP. "Investigating the effects of energy resolution in dedicated emission mammotomography." IEEE Nuclear Science Symposium Conference Record 5 (2005): 2537-2541.
Source
scival
Published In
IEEE Nuclear Science Symposium Conference Record
Volume
5
Publish Date
2005
Start Page
2537
End Page
2541
DOI
10.1109/NSSMIC.2005.1596856

Optimizing orientation of SPECT and cone beam CT detectors through quantification of cross contamination in a dual modality mammotomography system

A compact, dual modality SPECT/CT system for dedicated 3D breast imaging is in development. A major consideration in determining the relative placement of the SPECT and CT detectors is minimizing cross contamination. The transmission contamination of the emission image is investigated here using a 16×20cm2 quantized CZT SPECT camera located at various orientations relative to the 20×25cm2 CsI(Tl) CT detector, with a pendant, water-filled breast phantom placed in the common field-of-view. This arrangement is repeated with and without 99mTc emission radioactivity in the breast, with the breast laterally offset from the central ray of the x-ray cone-beam in a half-cone beam configuration. Planar transmission projections use a quasi-monochromatic (35keV mean energy, 20% FWHM) x-ray beam, with an exposure equivalent to 1/360, 1/180, 1/90 of the total exposure of dual view, screening mammography; these fractional exposures are used due to the requirement of multiple images necessary for CT data acquisition and ∼360 projection exposures are expected. Images and energy spectra acquired from the SPECT projections are used to quantify contamination from the x-ray beam. With the offset CT acquisition geometry, initial results show x-ray scatter contamination of the emission camera is limited to photons well below the 140keV photopeak. Pulse pile-up is not a concern, with the instantaneous x-ray scatter flux. Transmission contamination in the energy windowed emission image is negligible (<0.5%) for any SPECT camera position (polar orientation and azimuthal contamination) and various measured breast sizes (325 -1500mL). Optimal placement of the detectors is found to be more a function of physical constraints than x-ray transmission contamination. © 2005 IEEE.

Authors
Crotty, DJ; Bryzmialkiewicz, CN; McKinley, RL; Tornai, MP
MLA Citation
Crotty, DJ, Bryzmialkiewicz, CN, McKinley, RL, and Tornai, MP. "Optimizing orientation of SPECT and cone beam CT detectors through quantification of cross contamination in a dual modality mammotomography system." IEEE Nuclear Science Symposium Conference Record 3 (2005): 1672-1676.
Source
scival
Published In
IEEE Nuclear Science Symposium Conference Record
Volume
3
Publish Date
2005
Start Page
1672
End Page
1676
DOI
10.1109/NSSMIC.2005.1596641

Intraoperative Probes and Imaging Probes

© 2004 Elsevier Inc. All rights reserved.This chapter provides an overview of counting and imaging probes, which are used to obtain count measurements and images during surgery. This chapter begins with the history of development of intraoperative probes. These have been employed to assist in the detection and removal of tumors since the 1950s. The intraoperative imaging probes have been developed to see the details of the detected activity, giving the potential of using the technique in a low-contrast environment. Intraoperative probes are now established as clinical devices. The basic principles of intraoperative probe detectors and many variations of the gas detector, solid-state detector and scintillation detector are discussed in this chapter. The usefulness of procedures using an intraoperative probe must be considered in terms of a measurement system. This system consists of the radiation detector, the radioisotope, and the compound that is labeled. These probes also have a commercial infrastructure to support their continued use, and there is ongoing research, both commercial and academic, that ensures continued progress and renewed interest in this slowly developing field.

Authors
Hoffman, EJ; Tornai, MP; Janecek, M; Patt, BE; Iwanczyk, JS
MLA Citation
Hoffman, EJ, Tornai, MP, Janecek, M, Patt, BE, and Iwanczyk, JS. "Intraoperative Probes and Imaging Probes." Emission Tomography: The Fundamentals of PET and SPECT. November 18, 2004. 335-358.
Source
scopus
Publish Date
2004
Start Page
335
End Page
358
DOI
10.1016/B978-012744482-6.50020-X

Simulation study of a quasi-monochromatic beam for x-ray computed mammotomography.

The purpose of this simulation study was to evaluate the feasibility, benefits, and potential operating parameters of a quasi-monochromatic beam from a tungsten-target x-ray source yielding projection images. The application is intended for newly developed cone beam computed mammotomography (CmT) of an uncompressed breast. The value of a near monochromatic x-ray source for a fully 3D CmT application is the expected improved ability to separate tissues with very small differences in attenuation coefficients. The quasi-monochromatic beam is expected to yield enhanced tomographic image quality along with a low dose, equal to or less than that of dual view x-ray mammography. X-ray spectra were generated with a validated projection x-ray simulation tool (XSpect) for a range of tungsten tube potentials (40-100 kVp), filter materials (Z=51-65), and filter thicknesses (10th to 1000th value layer determined at 60 kVp). The breast was modeled from ICRU-44 breast tissue specifications, and a breast lesion was modeled as a 0.5 cm thick mass. The detector was modeled as a digital flat-panel detector with a 0.06 cm thick CsI x-ray absorption layer. Computed figures of merit (FOMs) included the ratio of mean beam energy post-breast to pre-breast and the ratio of lesion contrasts for edge-located and center-located lesions as indices of breast beam hardening, and SNR2/exposure and SNR2/dose as indices of exposure and dose efficiencies. The impact of optimization of these FOMs on lesion contrast is also examined. For all simulated filter materials at each given attenuation thickness [10th, 100th, 500th, 1000th value layers (VLs)], the mean and standard deviation of the pre-breast spectral full-width at tenth-maximum (FWTM) were 16.1 +/- 2.4, 10.3 +/- 2.2, 7.3 +/- 1.4, and 6.5 +/- 1.5 keV, respectively. The change in beam width at the tenth maximum from pre-breast to post-breast spectra ranged from 4.7 to 1.1 keV, for the thinnest and thickest filters, respectively. The higher Z filters (Z=57-63) produced a quasi-monochromatic beam that allowed the widest tube potential operating range (50-70 kVp) while maintaining minimal beam hardening and maximal SNR2/exposure and SNR2/dose, and providing a contrast greater than that obtained in the unfiltered case. Figures of merit improved with increasing filter thickness, with diminishing returns beyond the 500th value layer attenuation level. Operating parameters required to produce optimal spectra, while keeping exposures equal to that of dual view mammography, are within the capability of the commercial x-ray tube proposed for our experimental study, indicating that use of these highly attenuating filters is viable. Additional simulations comparing Mo/Mo, Mo/Rh, and W/Rh target/filter combinations indicate that they exhibit significantly lower SNR2/exposure than the present approach, precluding them from being used for computed mammotomography, while maintaining dose limitations and obtaining sufficient SNR. Beam hardening was also much higher in the existing techniques (17%-42%) than for our technique (2%). Simulations demonstrate that this quasi-monochromatic x-ray technique may enhance tissue separation for a newly developed cone beam computed mammotomography application for an uncompressed breast.

Authors
McKinley, RL; Tornai, MP; Samei, E; Bradshaw, ML
MLA Citation
McKinley, RL, Tornai, MP, Samei, E, and Bradshaw, ML. "Simulation study of a quasi-monochromatic beam for x-ray computed mammotomography." Med Phys 31.4 (April 2004): 800-813.
PMID
15124997
Source
pubmed
Published In
Medical physics
Volume
31
Issue
4
Publish Date
2004
Start Page
800
End Page
813
DOI
10.1118/1.1668371

Feasibility of a beta-gamma digital imaging probe for radioguided surgery

Authors
Tipnis, SV; Nagarkar, VV; Shestakova, I; Gaysinskiy, V; Entine, G; Tornai, MP; Stack, BC
MLA Citation
Tipnis, SV, Nagarkar, VV, Shestakova, I, Gaysinskiy, V, Entine, G, Tornai, MP, and Stack, BC. "Feasibility of a beta-gamma digital imaging probe for radioguided surgery." IEEE TRANSACTIONS ON NUCLEAR SCIENCE 51.1 (February 2004): 110-116.
Source
wos-lite
Published In
IEEE Transactions on Nuclear Science
Volume
51
Issue
1
Publish Date
2004
Start Page
110
End Page
116
DOI
10.1106/TNS.2003.823022

Measurements of an optimized beam for x-ray computed mammotomography

Simulation results from previous studies indicate that a quasi-monochromatic x-ray beam can be produced using a newly developed beam filtration technique. This technique utilizes heavy filtration with novel high Z filter materials having k-edges just above those of CsI, producing a near monochromatic beam with mean energy optimized for detection. The value of a near monochromatic x-ray source for a fully 3D tomography application is the expected improved ability to separate tissues with very small differences in attenuation coefficients for a range of uncompressed breast sizes while maintaining dose levels at or below existing dual view mammography. In this study, we experimentally investigate a set of filter materials (Al, Cu, Ag, Ce, W, and Pb), filter thicknesses (10 th, 100 th, and 200 th VL), and tube potentials (40-80 kVp) using a newly constructed test apparatus. Initial experimental results corroborate simulations and indicate that this approach can improve image quality (SNR) at constant dose. Al, Cu, W, and Pb provide optimal exposure efficiency results at 60 kVp and above. Decreasing relative improvements are observed above 100 th VL filter thickness at 78 cm SID. Results are obtained without significant tube heating (except at 40 kVp). In addition, simulations indicate significant reductions in beam hardening. This optimized beam will be incorporated into a novel cone-beam x-ray computed mammotomography sub-system together with an emission tomograph in a dual modality CT/SPECT application specific emission and transmission tomography system for fully 3D uncompressed breast imaging.

Authors
McKinley, RL; Samei, E; Brzymialkiewicz, CN; Tornai, MP; Floyd, CE
MLA Citation
McKinley, RL, Samei, E, Brzymialkiewicz, CN, Tornai, MP, and Floyd, CE. "Measurements of an optimized beam for x-ray computed mammotomography." Proceedings of SPIE - The International Society for Optical Engineering 5368.1 (2004): 311-319.
Source
scival
Published In
Proceedings of SPIE - The International Society for Optical Engineering
Volume
5368
Issue
1
Publish Date
2004
Start Page
311
End Page
319
DOI
10.1117/12.536033

Development of an optimal X-ray beam for dual-mode emission and transmission mammotomography

The development of an optimal x-ray beam for dual-mode emission and transmission mammotomography for evaluation of breast lesions is discussed. The idealized operating parameters for the quasi-monochromatic beam were determined by evaluating a beam hardening figure of merit (FOM) along with quantitative spectral characteristics. Filters with atomic numbers (Z) from 51-65 with 10th to 1000th value attenuating layer thicknesses were modeled, while considering the tube loading limitations. Results show that using a tungsten target, increased tube potential and infiltration can yield minimal beam hardening with improved exposure efficiency and contrast for various thicknesses of uncompressed breasts.

Authors
McKinley, RL; Tornai, MP; Samei, E; Bradshaw, ML
MLA Citation
McKinley, RL, Tornai, MP, Samei, E, and Bradshaw, ML. "Development of an optimal X-ray beam for dual-mode emission and transmission mammotomography." Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 527.1-2 (2004): 102-109.
Source
scival
Published In
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
Volume
527
Issue
1-2
Publish Date
2004
Start Page
102
End Page
109
DOI
10.1016/j.nima.2004.03.084

Feasibility of a beta-gamma digital imaging probe for radioguided surgery

We report here on a novel design of a digital, intraoperative imaging probe intended for use in radio-guided surgical procedures in conjunction with radiolabels such as 131I and 18F. The probe allows the user to rapidly localize tumors by detecting the highly penetrating gamma rays, and then image the tumor with the short-range beta rays. The system provides a rapid, high-resolution, image of the interrogated area, fulfilling the need for clear delineation of tumors during radio-guided surgical procedures. The beta imaging sensor consists of a micro-columnar CsI(Tl) scintillator screen capable of providing very high detection efficiency, high light output and excellent spatial resolution coupled to a CCD via a flexible, coherent fiberoptic bundle. The gamma sensor is a shielded piece of crystalline CsI(Tl) coupled to a photodiode located behind the image sensitive front end. The feasibility of this design was studied by separately testing the beta imaging and gamma detection components. The operation of the components was characterized with intrinsic performance measurements of count rates, signal-to-noise ratios, spatial resolution, as well as time for acquiring useful images using radionuclide and anthropomorphic phantoms.

Authors
Tipnis, SV; Nagarkar, VV; Shestakova, I; Gaysinskiy, V; Entine, G; Tornai, MP; Jr, BCS
MLA Citation
Tipnis, SV, Nagarkar, VV, Shestakova, I, Gaysinskiy, V, Entine, G, Tornai, MP, and Jr, BCS. "Feasibility of a beta-gamma digital imaging probe for radioguided surgery." IEEE Transactions on Nuclear Science 51.1 I (2004): 110-116.
Source
scival
Published In
IEEE Transactions on Nuclear Science
Volume
51
Issue
1 I
Publish Date
2004
Start Page
110
End Page
116
DOI
10.1109/TNS.2003.823022

3D data acquisition sampling strategies for dedicated emission mammotomography for various breast sizes

The dedicated emission mammotomography system developed in our lab is in preparation for initial patient studies. As a preliminary step, we evaluate the effect of breast size and lesion location on this paradigm. The hemispherical positioning gantry allows ample flexibility in sampling a pendant, uncompressed breast. Recently acquired, realistic anthropomorphic torso (which includes the upper portion of the arm) and breast phantoms emphasize the necessity of employing unique camera trajectories (orbits) rather than simple VAOR camera trajectories. Several novel 3D orbits have been implemented with fully contoured radius-of-rotation capability to compensate for the positioning demands that are required for different breast sizes. While a general orbit design may remain the same between two different breasts, the absolute polar tilt range and ROR range may vary. We have demonstrated that with increased polar camera tilt, employing 3D data acquisition camera trajectories, lesions near the chest wall can be visualized for both large and small sized breasts. © 2004 IEEE.

Authors
Brzymialkiewicz, CN; Tornai, MP; McKinley, RL; Cutler, SJ; Bowsher, JE
MLA Citation
Brzymialkiewicz, CN, Tornai, MP, McKinley, RL, Cutler, SJ, and Bowsher, JE. "3D data acquisition sampling strategies for dedicated emission mammotomography for various breast sizes." IEEE Nuclear Science Symposium Conference Record 4 (2004): 2596-2600.
Source
scival
Published In
IEEE Nuclear Science Symposium Conference Record
Volume
4
Publish Date
2004
Start Page
2596
End Page
2600

Erratum: Simulation study of a quasi-monochromatic beam for x-ray computed mammotomography (Medical Physics (2004) 31 (800-813))

Authors
McKinley, RL; Tornai, MP; Samei, E; Bradshaw, ML
MLA Citation
McKinley, RL, Tornai, MP, Samei, E, and Bradshaw, ML. "Erratum: Simulation study of a quasi-monochromatic beam for x-ray computed mammotomography (Medical Physics (2004) 31 (800-813))." Medical Physics 31.11 (2004): 3163--.
Source
scival
Published In
Medical physics
Volume
31
Issue
11
Publish Date
2004
Start Page
3163-
DOI
10.1118/1.1809766

Comparison of scintimammography and dedicated emission mammotomography

Using a 16 cm × 20 cm medium field of view CZT camera and a compressible breast phantom containing deformable lesions of various sizes and activity concentrations, a detailed comparison is made between 2D, planar scintimammography utilizing various degrees of breast compression and fully 3D, dedicated, uncompressed breast SPECT, or emission mammotomography. A 700 mL compressible anthropomorphic breast phantom attached to a chest plate was developed in order to compare 2D and 3D emission (or transmission) imaging of a breast containing small lesions in the same phantom, while providing physical attributes that mimic realistic imaging conditions including hindrances that could limit otherwise ideal imaging of an isolated breast phantom. Thin walled, fillable, deformable lesions from 40 to 500 microL volume suspended on narrow polyethylene tubing are used so that their shape would change with different degrees of breast compression and also to provide minimal lesion wall and support thicknesses. Experiments were performed with low noise, and lesion-to-background concentration ratios range from 3:1 to 12:1. Scintimammography is performed for equivalent times for compression thicknesses from 6 cm to 12 cm (fully uncompressed) using a single medio-Iateral view, and mammotomography is performed for the uncompressed breast for vertical axis of rotation, simple tilted parallel beam, and a trajectory based on a 3-lobed sinusoid projected onto a hemisphere. Image quality, based on lesion SNRs and contrasts, as well as degree of sampled breast volume are evaluated. Dedicated mammotomgroaphy appears to be nearly twice as effective as planar scintimammography under these measurement conditions. © 2004 IEEE.

Authors
Tornai, MP; Brzymialkiewicz, CN; Cutler, SJ; Madhav, P
MLA Citation
Tornai, MP, Brzymialkiewicz, CN, Cutler, SJ, and Madhav, P. "Comparison of scintimammography and dedicated emission mammotomography." IEEE Nuclear Science Symposium Conference Record 5 (2004): 2818-2822.
Source
scival
Published In
IEEE Nuclear Science Symposium Conference Record
Volume
5
Publish Date
2004
Start Page
2818
End Page
2822

Investigation of full-field CZT detector for emission mammotomography

Authors
Archer, CN; Tornai, MP
MLA Citation
Archer, CN, and Tornai, MP. "Investigation of full-field CZT detector for emission mammotomography." 2004.
Source
wos-lite
Published In
IEEE Conference Record - Nuclear Science Symposium & Medical Imaging Conference : IEEE Nuclear Science Symposium And Medical Imaging Conference. Proceedings
Publish Date
2004
Start Page
2667
End Page
2671
DOI
10.1109/NSSMIC.2003.1352437

Implementation and initial characterization of acquisition orbits with a dedicated emission mammotomograph

Authors
Archer, CN; Tornai, MP; Bowsher, JE; Metzler, SD; Pieper, BC; Jaszczak, RJ
MLA Citation
Archer, CN, Tornai, MP, Bowsher, JE, Metzler, SD, Pieper, BC, and Jaszczak, RJ. "Implementation and initial characterization of acquisition orbits with a dedicated emission mammotomograph." IEEE TRANSACTIONS ON NUCLEAR SCIENCE 50.3 (June 2003): 413-420.
Source
wos-lite
Published In
IEEE Transactions on Nuclear Science
Volume
50
Issue
3
Publish Date
2003
Start Page
413
End Page
420
DOI
10.1109/TNS.2003.812433

Initial X-ray design considerations for application specific emission and transmission tomography (ASETT) of the breast.

Authors
Bradshaw, ML; McKinley, RL; Samei, E; Archer, CN; Tornai, MP
MLA Citation
Bradshaw, ML, McKinley, RL, Samei, E, Archer, CN, and Tornai, MP. "Initial X-ray design considerations for application specific emission and transmission tomography (ASETT) of the breast." JOURNAL OF NUCLEAR MEDICINE 44.5 (May 2003): 287P-287P.
Source
wos-lite
Published In
Journal of nuclear medicine : official publication, Society of Nuclear Medicine
Volume
44
Issue
5
Publish Date
2003
Start Page
287P
End Page
287P

Mammotomography with pinhole incomplete circular orbit SPECT.

UNLABELLED: Dedicated mammotomography with pinhole incomplete circular orbit (PICO) SPECT imaging of an uncompressed pendant breast was evaluated with small, very-high-stopping-power pinhole apertures. Comparisons were made with planar pinhole scintimammography. Enhanced 3-dimensional imaging performance with very-high-stopping-power apertures is thought to ultimately yield improved sensitivities for lesion detection and identification in breast disease. METHODS: Pinhole collimators made of high-density and high atomic number (184)W or depleted (238)U, with aperture diameters from 1 to 4 mm, were used to image 0.6- and 1.0-cm-diameter spherical lesions in a pendulous, uncompressed breast phantom in planar and PICO-SPECT modes. The breast was centered on the horizontal axis of rotation of an incomplete circular orbit. Lesion, breast and body, and myocardial activities (L:B:M) were included in the phantoms to simulate clinical imaging conditions with (99m)Tc (140 keV). Lesion contrasts and signal-to-noise ratios (SNRs) for all apertures were determined for near clinical acquisition times for L:B:M ratios of 12:1:20 and 7:1:25. A set of minidisks inserted in the breast phantom was scanned to determine sampling limitations at depth from the nipple. In an initial study, a patient with biopsy-confirmed breast carcinoma was injected with 960 MBq (99m)Tc-tetrofosmin and scanned 2 h later with planar pinhole and PICO-SPECT techniques. RESULTS: Overall, for PICO-SPECT imaging there were small differences in measured counting rate sensitivity (4.9%) and lesion contrast (8.8%) with larger SNR differences (20.8%) between tungsten and depleted uranium pinhole materials at this energy and these lesion sizes. Backgrounds from simulated myocardial uptake had minor contributions in all reconstructed image volumes because of the rapid sensitivity fall-off for pinhole apertures. An optimal aperture diameter between 2 and 3 mm was determined from peak SNR, indicating that these aperture sizes may have the best performance for lesions as small as 0.6 cm in diameter with activity concentration ratios of (99m)Tc similar to those currently seen in patients. Both lesions were visualized with PICO-SPECT better than with planar pinhole imaging, with respective contrast improvements >20 times the values obtained from planar imaging for the same pinholes. In the patient study, higher contrast (>6) visualization of the active tumor periphery was obtained with PICO-SPECT than with planar imaging. CONCLUSION: These results indicate that the enhanced spatial resolution of smaller apertures outweighs the loss in sensitivity in small lesion identification with PICO-SPECT. Although the imaging differences between investigated aperture types are small and some limitations to this imaging approach exist, dedicated PICO-SPECT of the breast appears to be an improved technique compared with conventional planar pinhole scintimammography. This technique provides enhanced contrast and SNR for imaging small lesions with the high-resolution pinhole apertures along with 3-dimensional localization of the lesions.

Authors
Tornai, MP; Bowsher, JE; Jaszczak, RJ; Pieper, BC; Greer, KL; Hardenbergh, PH; Coleman, RE
MLA Citation
Tornai, MP, Bowsher, JE, Jaszczak, RJ, Pieper, BC, Greer, KL, Hardenbergh, PH, and Coleman, RE. "Mammotomography with pinhole incomplete circular orbit SPECT." J Nucl Med 44.4 (April 2003): 583-593.
PMID
12679403
Source
pubmed
Published In
Journal of nuclear medicine : official publication, Society of Nuclear Medicine
Volume
44
Issue
4
Publish Date
2003
Start Page
583
End Page
593

Detectors

Diagnostic Nuclear Medicine, Fourth Edition. Edited by M.P. Sandler, R.E. Coleman, J. A. Patton. F.J.Th. Wackers, A. Gottschalk. Lippincott Williams & Wilkins, Philadelphia 2003. RENAL NUCLEAR MEDICINE BRUCE J. BARRON E .

Authors
Tornai, MP; Turkington, TG
MLA Citation
Tornai, MP, and Turkington, TG. "Detectors." Diagnostic Nuclear Medicine. Philadelphia: Lippincott Williams & Wilkins, 2003. 21-29. (Chapter)
Source
manual
Publish Date
2003
Start Page
21
End Page
29

A 3D gantry single photon emission tomograph with hemispherical coverage for dedicated breast imaging

A three-dimensional gantry single photon emission tomograph with hemispherical coverage for dedicated breast imaging was discussed. Projections with all photopeak window and camera tilt conditions were reconstructed with an ordered subsets expectation maximization (OSEM) algorithm capable of reconstructing arbitrary tomographic orbits. Results showed that contrasts increased while signal-to-noise ratio (SNR) decreased with OSEM reconstruction.

Authors
Tornai, MP; Bowsher, JE; Archer, CN; Peter, J; Jaszczak, RJ; MacDonald, LR; Patt, BE; Iwanczyk, JS
MLA Citation
Tornai, MP, Bowsher, JE, Archer, CN, Peter, J, Jaszczak, RJ, MacDonald, LR, Patt, BE, and Iwanczyk, JS. "A 3D gantry single photon emission tomograph with hemispherical coverage for dedicated breast imaging." Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 497.1 (2003): 157-167.
Source
scival
Published In
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
Volume
497
Issue
1
Publish Date
2003
Start Page
157
End Page
167
DOI
10.1016/S0168-9002(02)01906-X

Optimizing beam quality for X-ray computed mammotomography

The purpose of this study was to determine the optimum beam quality in terms of kVp and filtration for a tungsten-target x-ray source for a newly developed cone beam computed mammotomography application. The optimized beam is expected to yield enhanced image quality along with a low dose, equal to or less than that of dual view x-ray mammography. X-ray spectra were computer generated for a range of tube potentials, filter materials, and filter and breast thicknesses. The uncompressed breast was modeled from 8, 12, and 16 cm thick tissue, and breast lesions were modeled as a 0.5 cm thick striated muscle mass and a 0.02 cm thick microcalcification. The detector was modeled as a digital flat-panel detector with a 0.06 cm thick CsI x-ray absorption layer. Figures of merit computed included the ratio of the mean beam energy post-breast to pre-breast as an index of beam hardening, ratio of lesion contrasts with and without filtering, and SNR2/exposure. Tube potentials between 50 and 70 kVp provided continuous spectra that, when filtered with Z-filters between 56 and 62 yielded quasi-monochromatic x-ray spectra with optimal SNR2/exposure and contrast while providing minimum beam hardening. Figures of merit improve with increasing filter thickness, but diminishing returns are seen beyond the 500th value attenuation layer. While uncompressed breast thickness affected absolute values of the measurement criteria, they had little effect on beam hardening and contrast ratio and did not alter the optimal operating range. Filter thickness near the 500th value layer is expected to be well within the operating range for an intended commercial x-ray tube, indicating that these highly attenuating filters can provide superior performance for mammotomography.

Authors
McKinley, RL; Tornai, MP; Samei, E; Bradshaw, ML
MLA Citation
McKinley, RL, Tornai, MP, Samei, E, and Bradshaw, ML. "Optimizing beam quality for X-ray computed mammotomography." Proceedings of SPIE - The International Society for Optical Engineering 5030 II (2003): 575-584.
Source
scival
Published In
Proceedings of SPIE - The International Society for Optical Engineering
Volume
5030 II
Publish Date
2003
Start Page
575
End Page
584
DOI
10.1117/12.480231

Implementation and initial characterization of acquisition orbits with a dedicated emission mammotomograph

While contemporary clinical single photon emission computed tomography (SPECT) scanners are limited to a horizontal axis of rotation about the patient, the compact application specific emission tomography (ASET) system overcomes physical proximity limitations of clinical scanners and allows for fully three-dimensional movement in an inverted hemisphere about the pendant breast through combined variable radius of rotation (ROR) and polar and azimuthal angular positioning. With these three degrees of freedom, the ASET can provide trajectories that satisfy Orlov's sampling criterion while maintaining a small ROR, necessary to minimize resolution degradation. One class of orbits investigated here consists of combinations of circular orbits and up to 60° arcs. Orbits are evaluated for image quality, including sampling and resolution characterization, utilizing both cold disk and cold rod emission phantoms, and quantitated contrasts and signal-to-noise ratios (SNRs) of small lesions located in a breast phantom with and without additional torso phantom backgrounds. The reconstructed cold disk and cold rod results indicate that all tested orbits in this class completely sample the volume and provide near equal resolution recovery. Furthermore, results from all orbits yielded higher contrasts and/or SNRs for the breast lesions compared with simple vertical-axis-of-rotation acquisitions, and nearly an order of magnitude better than those from uncompressed planar imaging.

Authors
Archer, CN; Tornai, MP; Bowsher, JE; Metzler, SD; Pieper, BC; Jaszczak, RJ
MLA Citation
Archer, CN, Tornai, MP, Bowsher, JE, Metzler, SD, Pieper, BC, and Jaszczak, RJ. "Implementation and initial characterization of acquisition orbits with a dedicated emission mammotomograph." IEEE Transactions on Nuclear Science 50 III.2 (2003): 413-420.
Source
scival
Published In
IEEE Transactions on Nuclear Science
Volume
50 III
Issue
2
Publish Date
2003
Start Page
413
End Page
420

Comparison of compact gamma cameras with 1.3mm and 2.0mm quantized elements for dedicated emission mammotomography

In an effort to image smaller breast lesions, two compact gamma cameras with different intrinsic NaI(TI) pixel sizes are evaluated for use in the Application Specific Emission Tomography system for mammotomographic emission imaging. Comparison measurements were made with two scintillator arrays with 1.3×1.3×6mm 3 or 2.0×2.0×6mm 3 elements on exactly the same set of PMTs, electronics and control/processing hardware. Uniformity, sensitivity and energy resolution were assessed with flood field phantoms. Spatial resolution measurements included: a 99mTe (140keV) activity filled capillary tube imaged in planar mode from 1 - 10cm distance; two such tubes separated by 2cm were also imaged with simple circular tomography from 3 - 7cm radii-of-rotation (RORs); and a 99mTc filled mini-cold rod phantom was imaged at 5cm ROR with a simple circular orbit Finally, a freely suspended and uniformly filled 950ml breast phantom containing four fillable lesions (4 - 10mm dia) was imaged with a lesion-to-uniform-background activity concentration ratio of 15:1, using simple and complex 3D orbits and minimal RORs. The measured sensitivity varied by the crystal fill-factor; uniformity had <4% variability; and mean energy resolutions of each camera were ≤12% full-width at half-maximum (FWHM). The planar spatial resolutions correspond to calculated values, with smaller pixels yielding 2 - 13% better resolution with decreasing distance, corroborating the change from collimator-limited to intrinsic resolution with decreasing separation distance; tomographic results ranged from 3.2 - 5.2mm FWHM at 3 - 7cm, with nominally better contrast-resolution for the smaller pixel camera. Consistent with signal detection characteristics for these measurement conditions, quantitative SNRs and contrasts from lesion imaging with the uniform breast background illustrate better overall performance under nearly all conditions and for all lesions for the larger pixel camera.

Authors
Tornai, MP; Archer, CN; Bradshaw, ML; Bowsher, JE; Patt, BE; Iwanczyk, JS; Li, J; MacDonald, LR
MLA Citation
Tornai, MP, Archer, CN, Bradshaw, ML, Bowsher, JE, Patt, BE, Iwanczyk, JS, Li, J, and MacDonald, LR. "Comparison of compact gamma cameras with 1.3mm and 2.0mm quantized elements for dedicated emission mammotomography." IEEE Nuclear Science Symposium Conference Record 3 (2003): 1886-1890.
Source
scival
Published In
IEEE Nuclear Science Symposium Conference Record
Volume
3
Publish Date
2003
Start Page
1886
End Page
1890

Simulation study of quasi-monochromatic X-ray beam performance for X-ray computed mammotomography given various breast compositions and lesion sizes

A quasi-monochromatic X-ray computed mammo-tomograph (XCT) system is under development. The importance of a near-monochromatic x-ray beam is that tissues of close attenuation coefficients are expected to be more easily separable compared with those from a standard filtered beam. Understanding the behavior of beam hardening, lesion contrast (enhancement), and exposure efficiency for the complete range of breast compositions allows assessment of the feasibility of such an XCT system. In this study, investigated design parameters include tube operating potential and filtration under various combinations of uncompressed breast and lesion thicknesses and breast compositions in order to optimize performance. The simulated X-ray beam was generated from a tungsten target using cone beam imaging geometry. Simulations were run for 10-20% incremental breast compositions of adipose and glandular breast tissue for 8-16cm thick uncompressed breasts with 1-10mm thick soft lesions. For 60-70kVp tube potentials (corresponding to 35-40keV mean energy) with ∼500 th value attenuating layer of Ce filtration, minimal beam hardening was <5%, optimal lesion contrast enhancement was 5-10% for 12 and 16cm breasts of all compositions and lesion sizes. Beyond 60% adipose tissue composition, heavy filtration decreases lesion contrast for the thinnest breast. Optimal exposure efficiency was also seen in this operating range, with better absolute values obtained for thinner breasts of all compositions and thicker lesions in this mammotomographic application. Thus, development of a suitable quasi-monochromatic x-ray beam is possible with commercially available equipment and high-Z K-edge filtration, and can yield optimal characteristics for dedicated mammotomography.

Authors
Bradshaw, ML; McKinley, RL; Tornai, MP; Samei, E
MLA Citation
Bradshaw, ML, McKinley, RL, Tornai, MP, and Samei, E. "Simulation study of quasi-monochromatic X-ray beam performance for X-ray computed mammotomography given various breast compositions and lesion sizes." IEEE Nuclear Science Symposium Conference Record 3 (2003): 1850-1854.
Source
scival
Published In
IEEE Nuclear Science Symposium Conference Record
Volume
3
Publish Date
2003
Start Page
1850
End Page
1854

Initial study of quasi-monochromatic X-ray beam performance for X-ray computed mammotomography

We evaluate the feasibility, benefits, and operating parameters of a quasi-monochromatic beam for a newly developed X-ray cone beam computed mammotomography application. The value of a near monochromatic X-ray source for a fully 3D tomography application is the expected improved ability to separate tissues with very small differences in attenuation coefficients while maintaining dose level at or below existing dual view mammography. X-ray spectra were simulated for a range of tungsten tube potentials, K-edge filter materials, filter thicknesses, and a 12 cm uncompressed breast. The detector was modeled as a digital flat-panel CsI(Tl) detector. Figures of merit computed included: ratio of mean beam energy post-breast to pre-breast; ratio of measured lesion contrasts with and without filtering; and exposure efficiency (SNR 2/exposure). Initial experiments were performed with a commercially available X-ray tube/generator system, Ce foil filters, and plastic breast and lesion tissue-equivalent slabs. Simulation results showed that tube potentials of 50-70 kVp with filters of Zr=57-63 yielded quasi-monochromatic X-ray spectra with optimal FOMs. Initial experimental measurements with Ce foil filters corroborate simulation results. Simulations and initial experiments with one type of filter show that this approach can improve image quality while reducing exposure, and will be implemented in our multi-modality X-ray CT/SPECT computed mammotomography system.

Authors
McKinley, RL; Tornai, MP; Samei, E; Bradshaw, ML
MLA Citation
McKinley, RL, Tornai, MP, Samei, E, and Bradshaw, ML. "Initial study of quasi-monochromatic X-ray beam performance for X-ray computed mammotomography." IEEE Nuclear Science Symposium Conference Record 4 (2003): 2999-3003.
Source
scival
Published In
IEEE Nuclear Science Symposium Conference Record
Volume
4
Publish Date
2003
Start Page
2999
End Page
3003

Non-invasive 3-dimensional molecular imaging of early breast cancer with a dedicated mammotomograph.

Authors
Tornai, MP; Archer, CN; Bowsher, JE
MLA Citation
Tornai, MP, Archer, CN, and Bowsher, JE. "Non-invasive 3-dimensional molecular imaging of early breast cancer with a dedicated mammotomograph." 2003.
Source
wos-lite
Published In
Breast Cancer Research and Treatment
Volume
82
Publish Date
2003
Start Page
S60
End Page
S60

A novel silicon array designed for intraoperative charged particle imaging.

A novel Si-PIN imaging array is under investigation for a charged particle (beta, positron, or alpha) sensitive intraoperative camera to be used for (residual) tumor identification during surgery. This class of collimator-less nuclear imaging device has a higher signal response for direct interactions than its scintillator-optical detector-based counterparts. Monte Carlo simulations with 635 keV betas were performed, yielding maximum and projected ranges of 1.64 and 0.55 mm in Si. Up to 90% of these betas were completely absorbed in the first 0.30 mm. Based on these results, 300 microm thick prototype Si detector arrays were designed in a 16 x 16 crossed-grid arrangement with 0.8 mm wide orthogonal strips on 1.0 mm pitch. A NIM- and CAMAC-based high-density data acquisition and processing system was used to collect the list mode data. The system was calibrated by comparisons of measured spectra to energy deposition simulations or by direct measurement of various >100 keV conversion electron or beta emitters. Mean electronic noise per strip was <3.6 keV FWHM at room temperature. When detecting positrons, which have an accompanying 511 keV annihilation background, the flood irradiated beta/gamma ratio was approximately 40, indicating that beta images could be made without the use of background rejection techniques. The intrinsic spatial resolution corresponds to the 1 x 1 mm2 pixel size, and measurements of beta emitting point and line sources yielded FWHM resolutions of 1.5 (lateral) and 2.5 mm (diagonal), respectively, with the larger widths due to particle range blurting effects. Deconvolution of the finite source size yielded intrinsic resolutions that corresponded to the image pixel size. Transmission images of circle and line phantoms with various hole sizes and pitch were resolved with either pure beta or positron irradiation without a background correction. This novel semiconductor imaging device facilitates high charged particle and low gamma sensitivity, high signal/noise ratio, and allows for compact design to potentially aid surgical guidance by providing in situ images of clinical relevance.

Authors
Tornai, MP; Patt, BE; Iwanczyk, JS; Tull, CR; MacDonald, LR; Hoffman, EJ
MLA Citation
Tornai, MP, Patt, BE, Iwanczyk, JS, Tull, CR, MacDonald, LR, and Hoffman, EJ. "A novel silicon array designed for intraoperative charged particle imaging." Med Phys 29.11 (November 2002): 2529-2540.
PMID
12462719
Source
pubmed
Published In
Medical physics
Volume
29
Issue
11
Publish Date
2002
Start Page
2529
End Page
2540
DOI
10.1118/1.1514241

Feasibility of application specific emission & transmission tomography (ASETT) of the breast.

Authors
Tornai, MP; Bowsher, JE; Archer, CN; Jaszczak, RJ
MLA Citation
Tornai, MP, Bowsher, JE, Archer, CN, and Jaszczak, RJ. "Feasibility of application specific emission & transmission tomography (ASETT) of the breast." JOURNAL OF NUCLEAR MEDICINE 43.5 (May 2002): 12P-12P.
Source
wos-lite
Published In
Journal of nuclear medicine : official publication, Society of Nuclear Medicine
Volume
43
Issue
5
Publish Date
2002
Start Page
12P
End Page
12P

Modeling the axial extension of a transmission line source within iterative reconstruction via multiple transmission sources.

Reconstruction algorithms for transmission tomography have generally assumed that the photons reaching a particular detector bin at a particular angle originate from a single point source. In this paper, we highlight several cases of extended transmission sources, in which it may be useful to approach the estimation of attenuation coefficients as a problem involving multiple transmission point sources. Examined in detail is the case of a fixed transmission line source with a fan-beam collimator. This geometry can result in attenuation images that have significant axial blur. Herein it is also shown, empirically, that extended transmission sources can result in biased estimates of the average attenuation, and an explanation is proposed. The finite axial resolution of the transmission line source configuration is modeled within iterative reconstruction using an expectation-maximization algorithm that was previously derived for estimating attenuation coefficients from single photon emission computed tomography (SPECT) emission data. The same algorithm is applicable to both problems because both can be thought of as involving multiple transmission sources. It is shown that modeling axial blur within reconstruction removes the bias in the average estimated attenuation and substantially improves the axial resolution of attenuation images.

Authors
Bowsher, JE; Tornai, MP; Peter, J; González Trotter, DE; Krol, A; Gilland, DR; Jaszczak, RJ
MLA Citation
Bowsher, JE, Tornai, MP, Peter, J, González Trotter, DE, Krol, A, Gilland, DR, and Jaszczak, RJ. "Modeling the axial extension of a transmission line source within iterative reconstruction via multiple transmission sources." IEEE Trans Med Imaging 21.3 (March 2002): 200-215.
PMID
11989845
Source
pubmed
Published In
IEEE Transactions on Medical Imaging
Volume
21
Issue
3
Publish Date
2002
Start Page
200
End Page
215
DOI
10.1109/42.996339

Parallel-beam tilted-head analytic SPECT reconstruction: Derivation and comparison with OSEM

Parallel-beam tilted-head single photon emission computed tomography (TH-SPECT) was previously implemented on a SPECT system for its potential to image breast lesions and nearby axilla of seated, upright women. All TH-SPECT reconstructions will contain artifacts since the tilted orbit does not satisfy the Orlov sampling criteria. However, it is not clear which reconstruction method, if any, is better suited for TH-SPECT data. Here a geometric derivation of the ramp filter for tilted parallel-beam geometries is presented. A filtered backprojection (FBP) algorithm, using this filter, was then implemented and compared with an iterative ordered subsets expectation maximization (OSEM) algorithm, using TH-SPECT data. A breast scan at various tilt angles was simulated and used to generate a noise versus bias study for both methods. Contrast and signal-to-noise ratio (SNR) values, as well as axial elongation present in all TH-SPECT reconstructions, were characterized using a mini-Defrise disk phantom placed inside a fillable breast phantom and imaged from 0 to 15° head tilt. A fillable breast phantom containing lesions was also imaged with a system dedicated to prone breast SPECT from 0 to 30° to evaluate the effects of incomplete sampling due to greater tilt angles. FBP noise versus bias studies indicated a greater increase in bias with tilt angle compared to OSEM reconstructions. At small tilt angles about the mini-Defrise disk phantom, poorer contrasts were obtained with FBP compared to OSEM at similar noise levels. All reconstructions of the fillable breast phantom indicated axial elongation at greater tilt angles, although FBP reconstructions displayed an increase in stretching distortions of the breast. OSEM SNR and contrast values were higher at all degrees of tilt. In conclusion, measured results indicate OSEM TH-SPECT reconstruction provides better contrast and SNR values and may offer better shape and uniform activity distribution of the breast compared to FBP methods.

Authors
Pieper, BC; Bowsher, JE; Tornai, MP; Archer, CN; Jaszczak, RJ
MLA Citation
Pieper, BC, Bowsher, JE, Tornai, MP, Archer, CN, and Jaszczak, RJ. "Parallel-beam tilted-head analytic SPECT reconstruction: Derivation and comparison with OSEM." IEEE Transactions on Nuclear Science 49 I.5 (2002): 2394-2400.
Source
scival
Published In
IEEE Transactions on Nuclear Science
Volume
49 I
Issue
5
Publish Date
2002
Start Page
2394
End Page
2400
DOI
10.1109/TNS.2002.803781

SPECT breast imaging combining horizontal and vertical axes of rotation

Vertical-axis-of-rotation (VAOR) geometries, in which a gamma camera orbits a pendulous breast of a prone patient, have been proposed for SPECT breast imaging. Dedicated VAOR systems would be advantageous since they allow for minimal radius of rotation around the breast, which improves resolution-sensitivity tradeoffs, and there is less attenuation and scatter between the breast and the camera. However, the torso may not be viewed at enough angles to estimate contamination from torso activity. Also, VAOR geometries may involve camera tilt to scan for tumors near the chest wall. These tilted VAOR projections may be insufficient to establish even breast activity alone. Thus, we investigated the utility of designing VAOR systems to function inside some general-purpose horizontal-axis-of-rotation (HAOR) scanners, with the HAOR scanner orbiting a 192° angular range posteriorly, alleviating the insufficient-data problems. We simulated the expected projection data from six various-sized lesions with different activity concentrations in the breast and axilla, additionally considering the contribution from background activity from the torso. The data were then statistically reconstructed considering 360° HAOR, VAOR plus small additional arcs and combined HAOR-VAOR orbits, and the results were compared with the known activity concentration distribution. Substantial improvement in the noise versus bias was observed in the breast and axilla, an important and otherwise difficult region to image.

Authors
Metzler, SD; Bowsher, JE; Tornai, MP; Pieper, BC; Peter, J; Jaszczak, RJ
MLA Citation
Metzler, SD, Bowsher, JE, Tornai, MP, Pieper, BC, Peter, J, and Jaszczak, RJ. "SPECT breast imaging combining horizontal and vertical axes of rotation." IEEE Transactions on Nuclear Science 49.1 I (2002): 31-36.
Source
scival
Published In
IEEE Transactions on Nuclear Science
Volume
49
Issue
1 I
Publish Date
2002
Start Page
31
End Page
36
DOI
10.1109/TNS.2002.998677

Observer studies of cardiac lesion detectability with triple-head 360° versus dual-head 180° SPECT acquisition using simulated projection data

The purpose of this study is to evaluate cardiac lesion detectability with triple-head 360° versus dual-head 180° myocardial perfusion SPECT scans with equal acquisition time. The channelized Hotelling observer (CHO) and human observers were used. A male and a female voxelized cardiac-torso phantoms were used to generate the 360° and the 180° projection data. A cold lesion was placed in eight different locations of myocardium and had a lesion contrast of 25%. Sixteen time frames of the cardiac cycle were averaged to create the cardiac motion blurring to simulate the clinical ungated scan. Sufficient Poisson noise was added to set the area under the receiver operating characteristic (ROC) curve (A z) to be between 0.75 and 0.85 in a pilot study and to simulate the clinical case where dual-head 180° and triple-head 360° scans both have the same total acquisition time. For each lesion location, multiple realizations of lesion-present and of lesion-absent data were generated. Five-iteration ordered subsets expectation maximization with eight subsets was used to reconstruct the data. There was no attenuation correction (AC) in reconstruction with images used in the human study, while CHO was applied on images both reconstructed with and without AC. A three-dimensional Hann filter with 0.7 times the Nyquist frequency was used to smooth the reconstructed images. For images reconstructed without AC, both the CHO and the human observer study showed better detection performance for the 180° scan, especially for the female phantom. For images reconstructed with AC, the CHO study showed better detection performance for the 360° scan, especially for the female phantom. The CHO results demonstrated the detection performance with 360° scan was improved more than with 180° scan after AC.

Authors
Chen, M; Peter, J; Jaszczak, RJ; Gilland, DR; Bowsher, JE; Tornai, MP; Metzler, SD
MLA Citation
Chen, M, Peter, J, Jaszczak, RJ, Gilland, DR, Bowsher, JE, Tornai, MP, and Metzler, SD. "Observer studies of cardiac lesion detectability with triple-head 360° versus dual-head 180° SPECT acquisition using simulated projection data." IEEE Transactions on Nuclear Science 49 I.3 (2002): 655-660.
Source
scival
Published In
IEEE Transactions on Nuclear Science
Volume
49 I
Issue
3
Publish Date
2002
Start Page
655
End Page
660
DOI
10.1109/TNS.2002.1039545

Transmission Imaging with a Compact Gamma Camera: Initial Results for Mammotomography

A dedicated single photon emission prototype imaging system is intended for fully 3D Application Specific Emission and Transmission Tomography (ASETT), where one specific application is dedicated breast imaging. In breast imaging, this dual-modality system may be useful for (1) improving detectability of low contrast lesions with x-ray CT imaging, (2) emission quantification using the transmission images, and (3) better interpretation of the reconstructed emission data by facilitating objective region selection. Each imaging component needs independent development, optimization and characterization. The prototype SPECT component using a NaI(Tl) based gamma camera has been built and initially evaluated with small, low contrast breast lesions; resolution and sampling issues are under investigation with the arbitrary orbits possible with the hemispherical positioning capability. This emission component has been demonstrated to be a novel and viable approach to dedicated mammotomography with high lesion signal-to-noise and contrast. Geometrical feasibility studies are investigated herein for transmission mammotomography. The studies use the emission gamma camera with 2×2×6 mm3 crystals with and without detector collimation, with single photon 99mTc 140 keV sources for the pendant breast geometry. Transmission data are acquired with simple vertical axis of rotation (with 0° polar tilt, 360° azimuthal acquisition). Phantom measurements are made with acrylic/air mini-rod and mini-tube resolution phantoms, and an anthropomorphic breast phantom containing 0.6 and 1.0 cm diameter water-filled, acrylic lesions. All data were reconstructed with ordered subsets expectation maximization. Initial transmission images are also shown with a recently acquired digital flat-panel x-ray detector illuminated with a nuclear source. This detector is intended for use in the final design of the dedicated x-ray transmission instrument.

Authors
Tornai, MP; Archer, CN; Bowsher, JE; McKinley, RL; Jaszczak, RJ
MLA Citation
Tornai, MP, Archer, CN, Bowsher, JE, McKinley, RL, and Jaszczak, RJ. "Transmission Imaging with a Compact Gamma Camera: Initial Results for Mammotomography." IEEE Nuclear Science Symposium and Medical Imaging Conference 3 (2002): 1597-1601.
Source
scival
Published In
IEEE Nuclear Science Symposium and Medical Imaging Conference
Volume
3
Publish Date
2002
Start Page
1597
End Page
1601

Initial Investigation of Circle-Plus-Arc Orbit Variants with a Dedicated Emission Mammotomograph

A dedicated emission mammotomograph, uniquely capable of imaging in a hemisphere, is utilized to image the breast by way of complex acquisition orbits, completely sampling most of the breast. Orbits such as the circle-plus-arc (CPA) in particular provide for extended viewing times in a specific portion of the breast. This is advantageous in that as a diagnostic rather than screening imaging tool, a long duration of the camera trajectory may be distinctly positioned in the quadrant where the lesion is suspected. However, orbit modifications that distribute the scan time more evenly over the breast may also be effective. As the trajectories conform to the shape of the breast, including dynamic radius-of-rotation control, resolution degradation is minimized. However, for both the arc and the circular portion of the orbit, increased background contamination may result since the line-of-sight of the single photon camera can view unscattered primary radiation, particularly from cardiac and hepatic sources. The effect of azimuthal position of the arc, as well as the degree of the arc, on image quality is investigated by measurements of lesion signal-to-noise ratios and contrasts. Additionally, because the resolution characteristics of the CPA are not uniform throughout breast quadrants, the implementation of a modified orbit, in the shape of a 3D cloverleaf is investigated through measurements of the breast phantom alone with lesions of varying radioactive concentrations, and with additional torso backgrounds. These initial results indicate that polar tilt does affect image quality, with low polar tilt showing little variation in SNRs and contrasts, while increasing tilt decreases SNRs and contrasts by ∼2x when torso background is present. Considering the effect of azimuthal arc location, θ=45° yields the highest SNRs and contrasts for the locations at which SNR was evaluated. Both cloverleaf orbits yield comparable SNRs and contrasts to the CPA orbits.

Authors
Archer, CN; Tornai, MP; Bowsher, JE; Bradshaw, ML
MLA Citation
Archer, CN, Tornai, MP, Bowsher, JE, and Bradshaw, ML. "Initial Investigation of Circle-Plus-Arc Orbit Variants with a Dedicated Emission Mammotomograph." IEEE Nuclear Science Symposium and Medical Imaging Conference 2 (2002): 1118-1122.
Source
scival
Published In
IEEE Nuclear Science Symposium and Medical Imaging Conference
Volume
2
Publish Date
2002
Start Page
1118
End Page
1122

Observer studies of cardiac lesion detectability with triple-head 360° vs. dual-head 180° SPECT acquisition using simulated projection data

The purpose of this study is to evaluate cardiac lesion detectability with triple-head 360-degree versus dual-head 180-degree myocardial perfusion SPECT scans with equal acquisition time. The channelized Hotelling observer (CHO) and human observers were used. A male and a female voxelized four-dimensional cardiac-torso phantoms were used to generate the 360-degree and the 180-degree projection data. A cold lesion was placed in 8 different locations of myocardium and had a lesion contrast of 25%. Sufficient poisson noise was added to set the area under the ROC curve (A z) to be between 0.75 to 0.85 in a pilot study, and to simulate the clinical case where dual-head 180-degree and triple-head 360-degree both have the same total scan time. For each lesion location, 100 realizations of lesion-present and of lesion-absent data were generated. Five-iteration OSEM was used to reconstruct the data with no attenuation correction. A 3D Hann filter with 0.7 times the Nyquist frequency was used to smooth the reconstructed images. The CHO showed a higher lesion detectability index d′ for the 180-degree data. The human observer study showed a slightly better detection performance of the 180-degree scan, especially for the female phantom, but the differences were not statistically significant (at the P = 0.05 level).

Authors
Chen, M; Peter, J; Jaszczak, RJ; Gilland, DR; Bowsher, JE; Tornai, MP; Metzler, SD
MLA Citation
Chen, M, Peter, J, Jaszczak, RJ, Gilland, DR, Bowsher, JE, Tornai, MP, and Metzler, SD. "Observer studies of cardiac lesion detectability with triple-head 360° vs. dual-head 180° SPECT acquisition using simulated projection data." IEEE Nuclear Science Symposium and Medical Imaging Conference 4 (2002): 2229-2233.
Source
scival
Published In
IEEE Nuclear Science Symposium and Medical Imaging Conference
Volume
4
Publish Date
2002
Start Page
2229
End Page
2233

Feasibility of a Beta-Gamma Digital Imaging Probe for Radioguided Surgery

We report here on a novel design of a digital, intraoperative imaging probe intended for use in radio-guided surgical procedures in conjunction with radiolabels such as 131I and 18F. The probe allows the user to rapidly localize tumors by detecting the highly penetrating gamma rays, and then image the tumor with the short-range beta rays. The system provides a rapid, high-resolution, image of the interrogated area, fulfilling the need for clear delineation of tumors during radio-guided surgical procedures. The beta imaging sensor consists of a microcolumnar CsI(TI) scintillator screen capable of providing very high detection efficiency, high light output and excellent spatial resolution coupled to a CCD via a flexible, coherent fiberoptic bundle. The gamma sensor is a shielded piece of crystalline CsI(TI) coupled to a photodiode located behind the image sensitive front end. The feasibility of this design was studied by separately testing the beta imaging and gamma detection components. The operation of the components was characterized with intrinsic performance measurements of count rates, signal-to-noise ratios, spatial resolution, as well as time for acquiring useful images using radionuclide and anthropomorphic phantoms.

Authors
Tipnis, SV; Nagarkar, VV; Shestakova, I; Gaysinskiy, V; Entine, G; Tornai, MP; Stack, BC
MLA Citation
Tipnis, SV, Nagarkar, VV, Shestakova, I, Gaysinskiy, V, Entine, G, Tornai, MP, and Stack, BC. "Feasibility of a Beta-Gamma Digital Imaging Probe for Radioguided Surgery." IEEE Nuclear Science Symposium and Medical Imaging Conference 1 (2002): 43-47.
Source
scival
Published In
IEEE Nuclear Science Symposium and Medical Imaging Conference
Volume
1
Publish Date
2002
Start Page
43
End Page
47

A compact dedicated device for dual modality radionuclide imaging of the breast with an application specific emission and transmission tomograph (ASETT)

Authors
Tornai, MP; Bowsher, JE; Archer, CN; Peter, J; Macdonald, LR; Patt, BE
MLA Citation
Tornai, MP, Bowsher, JE, Archer, CN, Peter, J, Macdonald, LR, and Patt, BE. "A compact dedicated device for dual modality radionuclide imaging of the breast with an application specific emission and transmission tomograph (ASETT)." RADIOLOGY 221 (November 2001): 555-555.
Source
wos-lite
Published In
Radiology
Volume
221
Publish Date
2001
Start Page
555
End Page
555

Dedicated breast imaging with an ASET: Application specific emission tomograph.

Authors
Tornai, MP; Bowsher, JE; Archer, CN; Peter, J; MacDonald, LR; Patt, BE; Iwanczyk, JS; Jaszczak, RJ; Coleman, RE
MLA Citation
Tornai, MP, Bowsher, JE, Archer, CN, Peter, J, MacDonald, LR, Patt, BE, Iwanczyk, JS, Jaszczak, RJ, and Coleman, RE. "Dedicated breast imaging with an ASET: Application specific emission tomograph." JOURNAL OF NUCLEAR MEDICINE 42.5 (May 2001): 97P-97P.
Source
wos-lite
Published In
Journal of nuclear medicine : official publication, Society of Nuclear Medicine
Volume
42
Issue
5
Publish Date
2001
Start Page
97P
End Page
97P

Dedicated PICO-SPECT: An approach to clinical breast imaging.

Authors
Tornai, MP; Bowsher, JE; Jaszczak, RJ; Greer, KL; Hardenbergh, PH; Coleman, RE
MLA Citation
Tornai, MP, Bowsher, JE, Jaszczak, RJ, Greer, KL, Hardenbergh, PH, and Coleman, RE. "Dedicated PICO-SPECT: An approach to clinical breast imaging." JOURNAL OF NUCLEAR MEDICINE 42.5 (May 2001): 207P-208P.
Source
wos-lite
Published In
Journal of nuclear medicine : official publication, Society of Nuclear Medicine
Volume
42
Issue
5
Publish Date
2001
Start Page
207P
End Page
208P

An EM algorithm for estimating SPECT emission and transmission parameters from emissions data only.

A maximum-likelihood (ML) expectation-maximization (EM) algorithm (called EM-IntraSPECT) is presented for simultaneously estimating single photon emission computed tomography (SPECT) emission and attenuation parameters from emission data alone. The algorithm uses the activity within the patient as transmission tomography sources, with which attenuation coefficients can be estimated. For this initial study, EM-IntraSPECT was tested on computer-simulated attenuation and emission maps representing a simplified human thorax as well as on SPECT data obtained from a physical phantom. Two evaluations were performed. First, to corroborate the idea of reconstructing attenuation parameters from emission data, attenuation parameters (mu) were estimated with the emission intensities (lambda) fixed at their true values. Accurate reconstructions of attenuation parameters were obtained. Second, emission parameters lambda and attenuation parameters mu were simultaneously estimated from the emission data alone. In this case there was crosstalk between estimates of lambda and mu and final estimates of lambda and mu depended on initial values. Estimates degraded significantly as the support extended out farther from the body, and an explanation for this is proposed. In the EM-IntraSPECT reconstructed attenuation images, the lungs, spine, and soft tissue were readily distinguished and had approximately correct shapes and sizes. As compared with standard EM reconstruction assuming a fix uniform attenuation map, EM-IntraSPECT provided more uniform estimates of cardiac activity in the physical phantom study and in the simulation study with tight support, but less uniform estimates with a broad support. The new EM algorithm derived here has additional applications, including reconstructing emission and transmission projection data under a unified statistical model.

Authors
Krol, A; Bowsher, JE; Manglos, SH; Feiglin, DH; Tornai, MP; Thomas, FD
MLA Citation
Krol, A, Bowsher, JE, Manglos, SH, Feiglin, DH, Tornai, MP, and Thomas, FD. "An EM algorithm for estimating SPECT emission and transmission parameters from emissions data only." IEEE Trans Med Imaging 20.3 (March 2001): 218-232.
PMID
11341711
Source
pubmed
Published In
IEEE Transactions on Medical Imaging
Volume
20
Issue
3
Publish Date
2001
Start Page
218
End Page
232
DOI
10.1109/42.918472

Investigation of microcolumnar scintillators on an optical fiber coupled compact imaging system

A compact imaging system with a novel front-end detector is under investigation and development. Unique aspects of this collimatorless system include the use of thin arrays of many thousands of microcolumnar (<10 μm diameter) CsI front-end scintillators that are coupled through a four-times reducing fiber-optic (FO) bundle to a metal-channel multianode position sensitive photodetector. The tested arrays are 140 or 200 μm tall on faceplates of plane glass, FO, and FO with statistical extramural absorbers (EMAs). The highly discrete nature of the scintillator microcolumn arrays ensures very fine intrinsic spatial resolution, limited by the particle penetration and backscatter in the detector assembly. Their retro-reflector-tipped front ends facilitate light propagation toward the photodetector, ensuring good light collection. Monte Carlo simulations confirmed the limiting nature of beta particle penetration on measurable resolution. With this system, absolute light output was higher for the taller arrays, which indicates that these sizes are below the optimum for light output and energy absorption from the energetic beta particles; even taller scintillators, however, would suffer from increased backgrounds from annihilation radiation with positron detection. While MTF measurements with an X-ray source and microslit indicate the best response with the arrays on FO + EMA substrates, measurements with high and medium (1.7 MeV and 635 keV) energy beta line sources yield the best responses with the plane glass substrate, indicating that energy thresholding affects resolution in the classical way, even with these highly miniaturized arrays. Experiments with complex positron emission distributions along with large gamma-ray backgrounds, as may be expected during surgery, yield images with small background contamination and no distortions.

Authors
Tornai, MP; Archer, CN; Weisenberger, AG; Wojcik, R; Popov, V; Majewski, S; Keppel, CE; Levin, CS; Tipnis, SV; Nagarkar, VV
MLA Citation
Tornai, MP, Archer, CN, Weisenberger, AG, Wojcik, R, Popov, V, Majewski, S, Keppel, CE, Levin, CS, Tipnis, SV, and Nagarkar, VV. "Investigation of microcolumnar scintillators on an optical fiber coupled compact imaging system." IEEE Transactions on Nuclear Science 48.3 II (2001): 637-644.
Source
scival
Published In
IEEE Transactions on Nuclear Science
Volume
48
Issue
3 II
Publish Date
2001
Start Page
637
End Page
644
DOI
10.1109/23.940139

Breast tumor imaging using a tiltable head SPECT camera

As a test bed for dedicated breast single-photon emission computed tomography (SPECT) cameras that are under development, a general purpose SPECT system with two tiltable heads was used to image fillable breast and torso phantoms containing multiple lesions. Breast, liver, and myocardial activity were included in order to simulate direct contamination and Compton scattering expected in clinical scans. The tiltable-head SPECT (TH-SPECT) data were reconstructed using an OS-EM algorithm which accounted for the tilted geometry. High-count planar images were acquired for comparison with TH-SPECT. In order to characterize axial blurring effects inherent with TH-SPECT reconstructions, two cylindrical disk Defrise phantoms, one large Defrise phantom and one mini-Defrise phantom placed inside the fillable breast phantom, were imaged at various tilt angles. Results indicate an increase in axial blurring with greater tilt angle. Reconstructions of the combined fillable breast and torso phantoms containing two 1.15 ml lesions, one centered axially and one proximal to the anterior chest wall within the breast, were most clearly visible in the 30° reconstructed TH-SPECT images, providing lesion signal-to-noise ratio (SNR) and contrast improvements of nearly three times compared to the high-count planar images.

Authors
Pieper, BC; Bowsher, JE; Tornai, MP; Peter, J; Greer, K; Jaszczak, RJ
MLA Citation
Pieper, BC, Bowsher, JE, Tornai, MP, Peter, J, Greer, K, and Jaszczak, RJ. "Breast tumor imaging using a tiltable head SPECT camera." IEEE Transactions on Nuclear Science 48.4 II (2001): 1477-1482.
Source
scival
Published In
IEEE Transactions on Nuclear Science
Volume
48
Issue
4 II
Publish Date
2001
Start Page
1477
End Page
1482
DOI
10.1109/23.958383

Physical phantom evaluation of EM-IntraSPECT (EMIS) algorithm for non-uniform attenuation correction in cardiac imaging

The purpose of this study was to evaluate performance of the EM-IntraSPECT (EMIS) algorithm for non-uniform attenuation correction in the chest EMIS is a maximum-likelihood expectation maximization (MLEM) algorithm for simultaneously estimating SPECT emission and attenuation parameters from emission data alone. EMIS uses the activity within the patient as transmission tomography sources, with which attenuation coefficients can be estimated. A thorax phantom with a normal heart was used. The activity images reconstructed by EMIS were compared to images reconstructed using a conventional MLEM with a fixed uniform attenuation map. Uniformity of normal heart was improved with EMIS as compared to a conventional MLEM.

Authors
Krol, A; Bowsher, JE; Feiglin, DH; Gagne, GM; Hellwig, BJ; Tornai, MP; Thomas, FD
MLA Citation
Krol, A, Bowsher, JE, Feiglin, DH, Gagne, GM, Hellwig, BJ, Tornai, MP, and Thomas, FD. "Physical phantom evaluation of EM-IntraSPECT (EMIS) algorithm for non-uniform attenuation correction in cardiac imaging." Proceedings of SPIE - The International Society for Optical Engineering 4322.2 (2001): 934-938.
Source
scival
Published In
Proceedings of SPIE - The International Society for Optical Engineering
Volume
4322
Issue
2
Publish Date
2001
Start Page
934
End Page
938
DOI
10.1117/12.430966

Uranium pinhole collimators for 511-keV photon SPECT imaging of small volumes

Depleted uranium (DU) pinhole collimators are evaluated for small-volume SPECT imaging of 511-keV gammas, with a view toward small-animal imaging. Tungsten (W) pinholes are examined for comparison. Line source measurements show planar full-width at half-maximum(FWHM) as low as 6.5 mm for a 1-mm DU pinhole, with SPECT system FWHM of 5.0 mm at 43-mm ROR and 6.7 mm at 69-mm ROR. Planar FWHM is smaller for DU than for W pinholes but is insensitive to aperture size for pinholes of 1-3 mm diameter at this energy for the collimators studied. These trends indicate penetration at pinhole edges, as confirmed by LSF shape and full-width at tenth-maximum trends. In SPECT scans of rod phantoms at 71-mm ROR, DU pinholes were only barely able to resolve cold rods as large as 4.7 mm (center-to-center spacing = 2× diameter). For both F-18 alone and F-18 imaged along with Tc-99m, 3.9-mm hot rods were resolved. Tc-99m scans resolved 2.3-mm rods with F-18 present and 1.5-mm rods without F-18. DU pinhole SPECT at 511 keV does not currently match the spatial resolution of high-resolution positron emission tomography (PET) but is open to improvement and, unlike PET, is capable of simultaneous multiple-isotope acquisitions.

Authors
Tenney, CR; Tornai, MP; Smith, MF; Turkington, TG; Jaszczak, RJ
MLA Citation
Tenney, CR, Tornai, MP, Smith, MF, Turkington, TG, and Jaszczak, RJ. "Uranium pinhole collimators for 511-keV photon SPECT imaging of small volumes." IEEE Transactions on Nuclear Science 48.4 II (2001): 1483-1489.
Source
scival
Published In
IEEE Transactions on Nuclear Science
Volume
48
Issue
4 II
Publish Date
2001
Start Page
1483
End Page
1489
DOI
10.1109/23.958384

Implementation and initial characterization of acquisition orbits about a pendulous breast using the ASET system

The goal of the Application Specific Emission Tomography (ASET) system is to image small (≤ 1 cm diameter) lesions and lesions of low activity uptake in a pendulous breast reference frame with high contrast and signal-to-noise ratio (SNR). While contemporary clinical SPECT scanners are limited to a horizontal axis of rotation about the patient, the compact ASET system overcomes physical proximity limitations of clinical scanners and allows for fully 3D movement in an inverted hemisphere about the breast through combined variable radius of rotation (ROR), polar and azimuthal angular positioning. With these three degrees of freedom, the ASET can traverse orbits that satisfy Orlov's sampling criterion while maintaining a small ROR, necessary to minimize resolution degradation. One class of orbits consisting of combinations of simple circular orbits and up to 60° arcs that can be implemented for the ASET system includes tilted parallel beam (TPB), circle-plus-arc, incomplete moustache, incomplete circular orbit, and spiral-plus-arcs. Each collects sufficient or nearly sufficient data for activity reconstruction of the pendant breast volume. Initial ordered subsets expectation maximization reconstructed ASET data acquired with the TPB orbit at various tilt angles yields insufficiently sampled images, since TPB at polar tilt angles > 0° does not satisfy Orlov's criteria. Artifacts present in these images are partly due to cardiac and hepatic contamination and also incomplete sampling, which the more complete orbits are designed to overcome. Each orbit is evaluated for image quality, including sampling and resolution characterization with cold disk and cold rod phantoms, and quantitated SNR and contrast of small lesions located in a breast with additional torso backgrounds.

Authors
Archer, CN; Tornai, MP; Bowsher, JE; Metzler, SD; Pieper, BC; Jaszczak, RJ; MacDonald, LR; Patt, BE; Iwanczyk, JS
MLA Citation
Archer, CN, Tornai, MP, Bowsher, JE, Metzler, SD, Pieper, BC, Jaszczak, RJ, MacDonald, LR, Patt, BE, and Iwanczyk, JS. "Implementation and initial characterization of acquisition orbits about a pendulous breast using the ASET system." IEEE Nuclear Science Symposium and Medical Imaging Conference 3 (2001): 1323-1327.
Source
scival
Published In
IEEE Nuclear Science Symposium and Medical Imaging Conference
Volume
3
Publish Date
2001
Start Page
1323
End Page
1327

SPECT breast imaging using more nearly complete orbits and combined pinhole-parallel-beam collimation

Two novel pinhole orbits for SPECT breast imaging are investigated using noise-free analytically simulated projection data. The two orbits are designed to more nearly completely sample the breast region while also maintaining close proximity of the pinhole to the breast. The two orbits involve the same trajectory but different angular orientations for the pinhole. For both orbits the pinhole traverses two half circles, which from an anterior perspective thus appear to have the shape of an "X". The orbits differ in that in one case the pinhole is tilted toward a single point throughout the orbit whereas in the other case it is untilted. It is found that both orbits remove the distortions characteristic of purely transverse, single-half-circle orbits. Also investigated is the use of parallel-beam collimators on the remaining cameras of triple-headed SPECT scanners. It is found that these additional parallel-beam measurements greatly improve estimates of torso activity. Determining whether parallel-beam measurements improve estimates of breast activity will require additional studies involving clinical levels of noise in the projection data.

Authors
Bowsher, JE; Tornai, MP; Metzler, SD; Peter, J; Jaszczak, RJ
MLA Citation
Bowsher, JE, Tornai, MP, Metzler, SD, Peter, J, and Jaszczak, RJ. "SPECT breast imaging using more nearly complete orbits and combined pinhole-parallel-beam collimation." IEEE Nuclear Science Symposium and Medical Imaging Conference 3 (2001): 1328-1330.
Source
scival
Published In
IEEE Nuclear Science Symposium and Medical Imaging Conference
Volume
3
Publish Date
2001
Start Page
1328
End Page
1330

Parallel-beam tilted-head analytic SPECT reconstruction

Parallel-beam Tilted-Head SPECT (TH-SPECT) was previously implemented on a SPECT system for its potential to image breast lesions and nearby axilla of seated, upright women. All TH-SPECT reconstructions will contain artifacts since the tilted orbit does not satisfy the Orlov sampling criteria. However, it is not clear which reconstruction method, if any, is better suited for TH-SPECT data. Here a geometric derivation of the ramp filter for tilted parallel-beam geometries is presented. A new filter is then heuristically suggested, specifically designed to boost frequencies near the unmeasured null space present in all TH-SPECT geometries. This filter, H(ν″, τ″), was combined with the ramp filter and then implemented and compared with an iterative Ordered Subsets Expectation Maximization (OSEM) algorithm and a ramp-only FBP algorithm, using TH-SPECT data. Contrast values as well as axial elongation present in all TH-SPECT reconstructions were characterized using a mini-Defrise disk phantom placed inside a fillable breast phantom and imaged from 0-15 degree head tilt. At small tilt angles about the mini-Defrise disk phantom, contrasts were generally equal between H(ν″, τ″)-filtered FBP and OSEM reconstructions compared at similar noise values, and poorer contrasts were obtained for ramp-only FBP results. In conclusion, measured results indicate OSEM reconstruction may offer better shape and uniform activity distribution of the breast compared to FBP methods. H(ν″, τ″)-filtered TH-SPECT FBP, however, performed more comparably to OSEM than ramp-only FBP methods, and other similar filtering techniques may provide even greater improvements.

Authors
Pieper, BC; Bowsher, JE; Tornai, MP; Archer, CN; Jaszczak, RJ
MLA Citation
Pieper, BC, Bowsher, JE, Tornai, MP, Archer, CN, and Jaszczak, RJ. "Parallel-beam tilted-head analytic SPECT reconstruction." IEEE Nuclear Science Symposium and Medical Imaging Conference 3 (2001): 1313-1317.
Source
scival
Published In
IEEE Nuclear Science Symposium and Medical Imaging Conference
Volume
3
Publish Date
2001
Start Page
1313
End Page
1317

A novel application specific emission tomograph (ASET) for breast imaging

A novel, dedicated and compact single photon ASET dedicated to pendant-breast nuclear medicine-based lesion imaging is developed. The prototype ASET system utilizes a compact gamma camera mounted on a support with variable radius-of-rotation, which is coupled to a polar goniometric cradle, all on an azimuthal vertical axis-of-rotation stage. The combination of radial, polar and azimuthal motions can achieve nearly any contiguous 3D acquisition orbit on an inverted hemispherical domain of the pendant breast reference frame. Tomographic resolution and volume sampling considerations were evaluated with cold rod and disk phantoms imaged with simple orbits, with the projection data reconstructed using an OSEM algorithm which accounts for the arbitrary Euler angles of the camera's vantage. With parallel-beam collimation, the 3.1 mm cold rods were visualized with the smallest radius-of-rotation; increasing polar tilt angle demonstrated insufficient sampling of the Orlov volume for the highly symmetric cold disk phantom, but can be ameliorated by the complex 3D orbits possible with the system. An uncompressed breast phantom containing Tc-99m and 0.6 and 1.0 cm diameter hot lesions was affixed to an anthropomorphic torso phantom with total activity concentration ratios for lesions: breast+body : cardiac+liver of 11:1:19. Despite insufficient sampling with simple orbits about the volume, as well as torso background contamination, the hot lesions were easily visualized on the uniform breast background, yielding signal-to-noise ratios and contrasts which were >9 times higher than for planar data; scatter correction further increased the SNR and contrast improvements. This new, compact, dedicated ASET imaging system has the potential of providing valuable, fully 3D, functional imaging information about small (lt;1cm), otherwise indeterminate breast lesions as an adjunct to diagnostic mammography.

Authors
Tornai, MP; Bowsher, JE; Archer, CN; Peter, J; MacDonald, LR; Patt, BE; Iwanczyk, JS; Jaszczak, RJ; Coleman, RE
MLA Citation
Tornai, MP, Bowsher, JE, Archer, CN, Peter, J, MacDonald, LR, Patt, BE, Iwanczyk, JS, Jaszczak, RJ, and Coleman, RE. "A novel application specific emission tomograph (ASET) for breast imaging." IEEE Nuclear Science Symposium and Medical Imaging Conference 2 (2001): 1161-1165.
Source
scival
Published In
IEEE Nuclear Science Symposium and Medical Imaging Conference
Volume
2
Publish Date
2001
Start Page
1161
End Page
1165

Investigation of large field-of-view transmission imaging for SPECT attenuation compensation with Gd-153, Tc-99m and Ce-139 sources

Authors
Tornai, MP; Jaszczak, RJ; Gilland, DR; Coleman, RE; Ooie, Y; Taguchi, M; Enos, G
MLA Citation
Tornai, MP, Jaszczak, RJ, Gilland, DR, Coleman, RE, Ooie, Y, Taguchi, M, and Enos, G. "Investigation of large field-of-view transmission imaging for SPECT attenuation compensation with Gd-153, Tc-99m and Ce-139 sources." IEEE TRANSACTIONS ON NUCLEAR SCIENCE 47.3 (June 2000): 1182-1191.
Source
wos-lite
Published In
IEEE Transactions on Nuclear Science
Volume
47
Issue
3
Publish Date
2000
Start Page
1182
End Page
1191
DOI
10.1109/23.856567

Fast-timing silicon photodetectors

Authors
Patt, BE; Iwanczyk, JS; Tull, CR; Segal, JD; MacDonald, LR; Tornai, MP; Kenney, CJ; Hoffman, EJ
MLA Citation
Patt, BE, Iwanczyk, JS, Tull, CR, Segal, JD, MacDonald, LR, Tornai, MP, Kenney, CJ, and Hoffman, EJ. "Fast-timing silicon photodetectors." IEEE TRANSACTIONS ON NUCLEAR SCIENCE 47.3 (June 2000): 957-964.
Source
wos-lite
Published In
IEEE Transactions on Nuclear Science
Volume
47
Issue
3
Publish Date
2000
Start Page
957
End Page
964
DOI
10.1109/23.856726

Analytical versus voxelized phantom representation for Monte Carlo simulation in radiological imaging.

Monte Carlo simulations in nuclear medicine, with accurately modeled photon transport and high-quality random number generators, require precisely defined and often detailed phantoms as an important component in the simulation process. Contemporary simulation models predominantly employ voxel-driven algorithms, but analytical models offer important advantages. We discuss the implementation of ray-solid intersection algorithms in analytical superquadric-based complex phantoms with additional speed-up rejection testing for use in nuclear medicine imaging simulations, and we make comparisons with voxelized counterparts. Comparisons are made with well-known cold rod:sphere and anthropomorphic phantoms. For these complex phantoms, the analytical phantom representations are nominally several orders of magnitude smaller in memory requirements than are voxelized versions. Analytical phantoms facilitate constant distribution parameters. As a consequence of discretizing a continuous surface into finite bins, for example, time-dependent voxelized phantoms can have difficulties preserving accurate volumes of a beating heart. Although virtually no inaccuracy is associated with path calculations in analytical phantoms, the discretization can negatively impact the simulation process and results. Discretization errors are apparent in reconstructed images of cold rod:sphere voxel-based phantoms because of a redistribution of the count densities in the simulated objects. These problems are entirely avoided in analytical phantoms. Voxelized phantoms can accurately model detailed human shapes based on segmented computed tomography (CT) or magnetic resonance imaging (MRI) images, but analytical phantoms offer advantages in time and accuracy for evaluation and investigation of imaging physics and reconstruction algorithms in a straightforward and efficient manner.

Authors
Peter, J; Tornai, MP; Jaszczek, RJ
MLA Citation
Peter, J, Tornai, MP, and Jaszczek, RJ. "Analytical versus voxelized phantom representation for Monte Carlo simulation in radiological imaging." IEEE Trans Med Imaging 19.5 (May 2000): 556-564.
PMID
11021699
Source
pubmed
Published In
IEEE Transactions on Medical Imaging
Volume
19
Issue
5
Publish Date
2000
Start Page
556
End Page
564
DOI
10.1109/42.870266

Breast tumor imaging using a tiltable head SPECT camera

An axially Tiltable-Head SPECT (TH-SPECT) system with 2 heads was used to image tillable breast and torso phantoms containing multiple lesions at various tilt angles. Breast, liver, and myocardial activity were included in order to simulate direct contamination and Compton scattering expected in clinical scans. High count planar images were acquired for comparison with TH-SPECT, and the TH-SPECT data was reconstructed using an OS-EM algorithm which accounted for the tilted geometry. In order to characterize axial blurring effects inherent with TH-SPECT reconstructions, two cylindrical disk Defrise phantoms, one large Defrise phantom and one mini-Defrise phantom placed inside the fillable breast phantom, were imaged at various tilt angles. Reconstructions of the combined fillable breast and torso phantoms containing two 1.15 ml lesions, one centered axially and one proximal to the anterior chest wall within the breast, were most clearly visible in the 30° reconstructed TH-SPECT images compared to the high-count planar images, providing lesion SNR and contrast improvements of nearly three times.

Authors
Pieper, BC; Bowsher, JE; Tornai, MP; Peter, J; Greer, K; Jaszczak, RJ
MLA Citation
Pieper, BC, Bowsher, JE, Tornai, MP, Peter, J, Greer, K, and Jaszczak, RJ. "Breast tumor imaging using a tiltable head SPECT camera." IEEE Nuclear Science Symposium and Medical Imaging Conference 3 (2000): 22/77-22/81.
Source
scival
Published In
IEEE Nuclear Science Symposium and Medical Imaging Conference
Volume
3
Publish Date
2000
Start Page
22/77
End Page
22/81

SPECT breast imaging combining horizontal and vertical axes of rotation

Vertical axis of rotation (VAOR) geometries in which the patient lies prone with one pendulous breast, and a gamma camera orbits the breast have been proposed for SPECT breast imaging. Dedicated VAOR systems are advantageous for several reasons. They allow for minimal radius of rotation around the breast, which improves resolution-sensitivity trade-offs, but the torso is not viewed at enough angles to estimate torso activity. Also, VAOR geometries may involve a tilt to scan for tumors near the chest wall. These tilted VAOR projections may be insufficient to establish even breast activity alone. We investigated the utility of designing VAOR systems to function inside some general-purpose horizontal axis of rotation (HAOR) scanner, with the HAOR scanner orbiting a 192° angular range posteriorly, alleviating the insufficient-data problems. We simulated the expected projection data from 6 lesions in the breast and axilla, considering the contribution from background activity in the torso. The data were then reconstructed considering HAOR-only, VAOR-only and combined HAOR-VAOR orbits and compared with the known activity concentration distribution. Substantial improvement in the noise-vs-bias curve was observed in the chest wall near the breast, an important and otherwise difficult region to image.

Authors
Metzler, SD; Bowsher, JE; Tornai, MP; Pieper, BC; Peter, J; Jaszczak, RJ
MLA Citation
Metzler, SD, Bowsher, JE, Tornai, MP, Pieper, BC, Peter, J, and Jaszczak, RJ. "SPECT breast imaging combining horizontal and vertical axes of rotation." IEEE Nuclear Science Symposium and Medical Imaging Conference 3 (2000): 22/72-22/76.
Source
scival
Published In
IEEE Nuclear Science Symposium and Medical Imaging Conference
Volume
3
Publish Date
2000
Start Page
22/72
End Page
22/76

Effects of pinhole material and aperture size on lesion contrast and SNR in breast SPECT

Pinhole collimators made of depleted uranium-238 (DU) and tungsten alloy (VV) with aperture diameters from 1 - 4 mm were used to image <0.6 ml breast lesions in a pendulous breast reference frame, centered on the axis-of-rotation. with incomplete circular orbit (ICO <180 deg) SPECT. Breast, body and myocardial activity were included in the phantoms to simulate clinical imaging conditions. The background from the DU aperture was <12% contribution to the emission photopeak, and was inversely proportional to aperture size. Scans performed for clinical counting times included lesion:background ratios of 12:1 and 7:1. Contrast and signal-to-noise ratios (SNR) were better with smaller apertures, and measurements indicate that 2 - 3 mm apertures may have the best performance down to 0.11 ml lesions with near clinical uptake ratios of Tc-99m compounds. Contrast generally decreased for increasing aperture diameter, indicating that the enhanced spatial resolution may outweigh the loss in sensitivity in small lesion identification with ICO breast SPECT. Dedicated pinhole ICO SPECT of the breast appears to be a dramatically improved technique over conventional planar breast scintimammography, providing enhanced contrast and SNR for imaging smaller lesions with the dedicated high resolution pinholes.

Authors
Tornai, MP; Bowsher, JE; Pieper, BC; Jaszczak, RJ
MLA Citation
Tornai, MP, Bowsher, JE, Pieper, BC, and Jaszczak, RJ. "Effects of pinhole material and aperture size on lesion contrast and SNR in breast SPECT." IEEE Nuclear Science Symposium and Medical Imaging Conference 3 (2000): 22/16-22/20.
Source
scival
Published In
IEEE Nuclear Science Symposium and Medical Imaging Conference
Volume
3
Publish Date
2000
Start Page
22/16
End Page
22/20

Investigation of micro-columnar scintillators on an optical fiber coupled compact imaging system

A compact imaging system with a novel front-end detector is under investigation and development. Unique aspects of this collimator-less system include the use of many thousands of micro-columnar (<10 μm diameter) CsI front-end scintillators (140 and 200 microns tall on faceplates of plane glass, fiber optics (FO), and FO with statistical extramural absorbers (EMA)) that are coupled through a 4 times reducing FO bundle to a metal-channel multianode position sensitive photo-detector. The highly discrete nature of the scintillator micro-column arrays ensures very fine intrinsic spatial resolution, limited by the particle penetration and backscatter in the detector assembly, while their retro-reflector-tipped front-ends facilitate light propagation towards the photo-detector. Monte Carlo simulations confirmed the limiting nature of particle penetration on measurable resolution. With this system, absolute light output was highest for the taller arrays, which contradicts results of using much larger, quantized scintillators in other applications. While MTF measurements with an x-ray source indicate the best response with the arrays on FO+EMA substrates, measurements with high and medium (1.7 MeV and 635 keV) energy beta line sources yield the best responses with the plane glass substrate indicating that energy thresholding affects resolution in the classical way, even with these highly miniaturized arrays. Further experiments of complex positron emission distributions along with large gamma ray backgrounds yield images with minimal background contamination and no distortions.

Authors
Tornai, MP; Brzymialkiewicz, CN; Weisenberger, AG; Wojcik, R; Popov, V; Majewski, S; Keppel, CE; Levin, CS; Tipnis, SV; Nagarkar, VV
MLA Citation
Tornai, MP, Brzymialkiewicz, CN, Weisenberger, AG, Wojcik, R, Popov, V, Majewski, S, Keppel, CE, Levin, CS, Tipnis, SV, and Nagarkar, VV. "Investigation of micro-columnar scintillators on an optical fiber coupled compact imaging system." IEEE Nuclear Science Symposium and Medical Imaging Conference 3 (2000): 21/19-21/23.
Source
scival
Published In
IEEE Nuclear Science Symposium and Medical Imaging Conference
Volume
3
Publish Date
2000
Start Page
21/19
End Page
21/23

Investigation of large fffild-of-vlew transmission imaging for spect attenuation compensation with GO-153, TC-99m and CE-139 sources

A recently developed, large field-of-view (FOV), dual head SPECT system was investigated for fast sequential fan-beam (FB) transmission computed tomography (TCT) with various transmission sources. For TCT, the system utilizes a fixed line source at the 77 cm focal line of a symmetric FB collimator. The TCT maps arc used for non-uniform attenuation compensation (NUAC) of Tc-99m myocardial SPECT. The heads each have three degrees of freedom (transaxial tilt, radial linear and transaxial linear travel). When the heads are tilted and height adjusted to accommodate different size FOVs (34-53 cm diameter), the symmetric FB geometry only samples part of the FOV. Thus, with full 360 degree acquisitions, the pseudo-asymmetric FB TCT detector utilizes measured conjugate views to avoid truncation artifacts without sacrificing spatial resolution, and minimizes emission contamination compared with other TCT geometries. Transmission line source energies of 100 to 166 keV (Irani Gd-153, Tc-99m, and Ce-139 line sources) were utilized with rod and sphere, and anthropomorphic phantoms. The TCT images were reconstructed with iterative ordered subsets estimation maximization (OSEM). Comparisons were made between the emission reconstructions utilizing filtered backprojection (without and with iterative and multiplicative Chang NUAC) and OSEM (without and with NUAC). Based on a derived noise equivalent count rate determination of the three sources, the highest energy yet weakest intensity TCT source outperforms the other sources in the primary myocardial region of interest by approximately a factor of two. The emission contamination for the highest energy transmission source was an order of magnitude smaller than for the other sources with this acquisition geometry. These line sources each demonstrate the potential for suitably compensated images and quantitative myocardial activity profiles with this geometry. Higher energy transmission sources in particular result in more physically accurate attenuation maps useful for SPECT quantitation. © 2000 IEEE.

Authors
Tornai', MP; Jaszczak, RJ; Gilland, DR; Coleman, RE; Ooie, Y; Taguchi, M; Enos, G
MLA Citation
Tornai', MP, Jaszczak, RJ, Gilland, DR, Coleman, RE, Ooie, Y, Taguchi, M, and Enos, G. "Investigation of large fffild-of-vlew transmission imaging for spect attenuation compensation with GO-153, TC-99m and CE-139 sources." IEEE Transactions on Nuclear Science 47.3 PART 3 (2000): 1182-1191.
Source
scival
Published In
IEEE Transactions on Nuclear Science
Volume
47
Issue
3 PART 3
Publish Date
2000
Start Page
1182
End Page
1191

Intraoperative probes and imaging probes.

Intraoperative probes have been employed to assist in the detection and removal of tumors for more than 50 years. For a period of about 40 years, essentially every detector type that could be miniaturized had been tested or at least suggested for use as an intraoperative probe. These detectors included basic Geiger-Müller (GM) tubes, scintillation detectors, and even state-of-the-art solid state detectors. The radiopharmaceuticals have progressed from (32)PO(4)(-) injections for brain tumors to sophisticated monoclonal antibodies labeled with iodine-125 for colorectal cancers. The early work was mostly anecdotal, primarily interdisciplinary collaborations between surgeons and physical scientists. These collaborations produced a few publications, but never seemed to result in an ongoing clinical practice. In the mid 1980s, several companies offered basic gamma-detecting intraoperative probes as products. This led to the rapid development of radioimmunoguided surgery (RIGS) and sentinel node detection as regularly practiced procedures to assist in the diagnosis and treatment of cancer. In recent years intraoperative imaging probes have been developed. These devices add the ability to see the details of the detected activity, giving the potential of using the technique in a low-contrast environment. Intraoperative probes are now established as clinical devices, they have a commercial infrastructure to support their continued use, and there is ongoing research, both commercial and academic, that would seem to ensure continued progress and renewed interest in this slowly developing field.

Authors
Hoffman, EJ; Tornai, MP; Janecek, M; Patt, BE; Iwanczyk, JS
MLA Citation
Hoffman, EJ, Tornai, MP, Janecek, M, Patt, BE, and Iwanczyk, JS. "Intraoperative probes and imaging probes." Eur J Nucl Med 26.8 (August 1999): 913-935. (Review)
PMID
10436207
Source
pubmed
Published In
European journal of nuclear medicine
Volume
26
Issue
8
Publish Date
1999
Start Page
913
End Page
935

Small-animal PET: advent of a new era of PET research.

Authors
Tornai, MP; Jaszczak, RJ; Turkington, TG; Coleman, RE
MLA Citation
Tornai, MP, Jaszczak, RJ, Turkington, TG, and Coleman, RE. "Small-animal PET: advent of a new era of PET research." J Nucl Med 40.7 (July 1999): 1176-1179.
PMID
10405139
Source
pubmed
Published In
Journal of nuclear medicine : official publication, Society of Nuclear Medicine
Volume
40
Issue
7
Publish Date
1999
Start Page
1176
End Page
1179

Effect and correction of detector sag in SPECT systems.

Authors
Peter, J; Gilland, DR; Bowsher, JE; Tornai, MP; Jaszczak, RJ
MLA Citation
Peter, J, Gilland, DR, Bowsher, JE, Tornai, MP, and Jaszczak, RJ. "Effect and correction of detector sag in SPECT systems." JOURNAL OF NUCLEAR MEDICINE 40.5 (May 1999): 285P-285P.
Source
wos-lite
Published In
Journal of nuclear medicine : official publication, Society of Nuclear Medicine
Volume
40
Issue
5
Publish Date
1999
Start Page
285P
End Page
285P

Ultra-high resolution SPECT images with uranium pinhole collimators.

Authors
Tenney, CR; Smith, MF; Tornai, MP; Jaszczak, RJ
MLA Citation
Tenney, CR, Smith, MF, Tornai, MP, and Jaszczak, RJ. "Ultra-high resolution SPECT images with uranium pinhole collimators." JOURNAL OF NUCLEAR MEDICINE 40.5 (May 1999): 34P-34P.
Source
wos-lite
Published In
Journal of nuclear medicine : official publication, Society of Nuclear Medicine
Volume
40
Issue
5
Publish Date
1999
Start Page
34P
End Page
34P

Evaluation of transmission source collimation for SPECT attenuation compensation

Authors
Tornai, MP; Bowsher, JE; Stone, CD; Gilland, DR; Jaszczak, RJ; Enos, G; IEEE, ; IEEE, ; IEEE,
MLA Citation
Tornai, MP, Bowsher, JE, Stone, CD, Gilland, DR, Jaszczak, RJ, Enos, G, IEEE, , IEEE, , and IEEE, . "Evaluation of transmission source collimation for SPECT attenuation compensation." 1999.
Source
wos-lite
Published In
IEEE Conference Record - Nuclear Science Symposium & Medical Imaging Conference : IEEE Nuclear Science Symposium And Medical Imaging Conference. Proceedings
Publish Date
1999
Start Page
1368
End Page
1372

Uranium pinhole collimators for positron emission SPECT imaging of small volumes

Authors
Tenney, CR; Tornai, MP; Smith, MF; Turkington, TG; Jaszczak, RJ; IEEE, ; IEEE, ; IEEE,
MLA Citation
Tenney, CR, Tornai, MP, Smith, MF, Turkington, TG, Jaszczak, RJ, IEEE, , IEEE, , and IEEE, . "Uranium pinhole collimators for positron emission SPECT imaging of small volumes." 1999.
Source
wos-lite
Published In
IEEE Conference Record - Nuclear Science Symposium & Medical Imaging Conference : IEEE Nuclear Science Symposium And Medical Imaging Conference. Proceedings
Publish Date
1999
Start Page
1038
End Page
1042

High resolution CsI(Tl)/Si-PIN detector development for breast imaging

Authors
Patt, BE; Iwanczyk, JS; Tull, CR; Wang, NW; Tornai, MP; Hoffman, EJ
MLA Citation
Patt, BE, Iwanczyk, JS, Tull, CR, Wang, NW, Tornai, MP, and Hoffman, EJ. "High resolution CsI(Tl)/Si-PIN detector development for breast imaging." IEEE TRANSACTIONS ON NUCLEAR SCIENCE 45.4 (August 1998): 2126-2131.
Source
wos-lite
Published In
IEEE Transactions on Nuclear Science
Volume
45
Issue
4
Publish Date
1998
Start Page
2126
End Page
2131
DOI
10.1109/23.708319

A miniature phoswich detector for gamma-ray localization and beta imaging

Authors
Tornai, MP; Levin, CS; MacDonald, LR; Holdsworth, CH; Hoffman, EJ
MLA Citation
Tornai, MP, Levin, CS, MacDonald, LR, Holdsworth, CH, and Hoffman, EJ. "A miniature phoswich detector for gamma-ray localization and beta imaging." IEEE TRANSACTIONS ON NUCLEAR SCIENCE 45.3 (June 1998): 1166-1173.
Source
wos-lite
Published In
IEEE Transactions on Nuclear Science
Volume
45
Issue
3
Publish Date
1998
Start Page
1166
End Page
1173
DOI
10.1109/23.681996

Minimizing cardiac motion blurring and improving image signal-to-background using gated SPECT and statistically based 3D morphological deformations.

Authors
Tornai, MP; McCulloch, C; Jaszczak, RJ; Greer, KL; Johnson, VE; Coleman, RE
MLA Citation
Tornai, MP, McCulloch, C, Jaszczak, RJ, Greer, KL, Johnson, VE, and Coleman, RE. "Minimizing cardiac motion blurring and improving image signal-to-background using gated SPECT and statistically based 3D morphological deformations." JOURNAL OF NUCLEAR MEDICINE 39.5 (May 1998): 121P-121P.
Source
wos-lite
Published In
Journal of nuclear medicine : official publication, Society of Nuclear Medicine
Volume
39
Issue
5
Publish Date
1998
Start Page
121P
End Page
121P

A dual detector β-ray imaging probe with γ-ray background suppression for use in intra-operative detection of radiolabeled tumors

The basic concepts for a dual detector β+ imaging probe incorporating a method of γ-ray background suppression were evaluated. The test devices consisted of a 1.2 cm2 β+ imaging CaF2(Eu) scintillator disk optically coupled to a 1.7 mm thick, area-matched transparent diffuser disk, which in turn was coupled to sets of 2 × 2 or 4 × 4 mm2 by 10 mm long BGO, GSO or LSO scintillators, which acted as both γ-detectors as well as light guides for the CaF2(Eu) scintillation light, which in turn are attached to a fiber optic bundle coupled to a multichannel photomultiplier. Pulse shape discrimination allowed identification of the detector of interaction and coincidence between the two detectors allowed selection of β+ -only events. This type imaging detector system was shown to be capable of producing high-resolution images of β+ distributions while suppressing the events due to the 511 keV annihilation radiation background. GSO was found to be the detector of choice for this application. © 1998 Elsevier Science B.V. All rights reserved.

Authors
Hoffman, EJ; Tornai, MP; Levin, CS; MacDonald, LR; Holdsworth, CH
MLA Citation
Hoffman, EJ, Tornai, MP, Levin, CS, MacDonald, LR, and Holdsworth, CH. "A dual detector β-ray imaging probe with γ-ray background suppression for use in intra-operative detection of radiolabeled tumors." Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 409.1-3 (1998): 511-516.
Source
scival
Published In
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
Volume
409
Issue
1-3
Publish Date
1998
Start Page
511
End Page
516
DOI
10.1016/S0168-9002(97)01305-3

High resolution CsI(Tl)/Si-PIN detector development for breast imaging

High resolution multi-element (8×8) imaging arrays with collimators, size matched to discrete CsI(Tl) sdntillator arrays and Si-PIN photodetector arrays (PDA's) were developed as prototypes for larger arrays for breast imaging. Photodetector pixels were each 1.5 × 1.5 mm2 with 0.25 mm gaps. A 16-element quadrant of the detector was evaluated with a segmented CsI(Tl) scintillator array (1.5x1.5x6 mm3 segments with 0.25 mm septa) coupled to the silicon array. The scintillator thickness- of 6 mm corresponds to 85% total gamma efficiency at 140 keV. Pixel energy resolution of < 8% FWHM was obtained for Tc-99m (140 keV). Electronic noise was 41 e" RMS corresponding to a 3% FWHM contribution to the 140 keV photopeak. Detection efficiency uniformity (± o%) measured with a Tc-99m flood source was 4.3% for a ∼ 10% energy photopeak window. Spatial resolution was 1.53 mm FWHM and pitch was 1.75 mm as measured from the Co-57 (122 keV) line spread function. Signal to background was 34 and conlrasl ([max-iniii]/[max+min]) was 0.94. The energy resolution and spatial characteristics of the new imaging detector exceed those of other scintillator based imaging detectors. A camera based on this technology will allow: 1) Improved Compton scatter rejection; 2) Detector positioning in close proximity to the breast to increase signal to noise; 3) Improved spatial resolution; and 4) Improved efficiency compared to high resolution collimated gamma cameras for the anticipated compressed breast geometries. © 1998 IEEE.

Authors
Part, BE; Iwanczyk, JS; Rossington, C; Wang, NW; Tornai, MP; Huffman, EJ
MLA Citation
Part, BE, Iwanczyk, JS, Rossington, C, Wang, NW, Tornai, MP, and Huffman, EJ. "High resolution CsI(Tl)/Si-PIN detector development for breast imaging." IEEE Transactions on Nuclear Science 45.4 PART 2 (1998): 2126-2131.
Source
scival
Published In
IEEE Transactions on Nuclear Science
Volume
45
Issue
4 PART 2
Publish Date
1998
Start Page
2126
End Page
2131

A miniature phoswich detector for gamma-ray localization and beta imaging

A combined y-ray probe/imaging detector was created by modification of a beta imaging intra-operative probe. This phoswich detector consists of a thin CaF2(Eu) 1 imaging disk, coupled through a light diffuser to 7 or 19 parallelepiped highZ scintillation crystals arranged hexagonally in columns. These elements are either 2x2x10 mm3 or 4x4x10 mm3 LSO, GSO or BGO crystals, and act as both light guides for the imaging light and as intrinsic y detectors. The coincidence between the CaF2(Eu) and phoswich scintillators identifies + or trueevents and suppresses accompanying annihilation or background y events. The phoswich crystals are in turn coupled through optical fibers to a multi-channel PMT with positioning and discrimination electronics. Various characteristics of this novel imaging phoswich detector are investigated and presented for each of the phoswich combinations including: detector anisotropy, effects of time blocking and energy windows on phoswich imaging, intrinsic singles and phoswich spectral and spatial resolution characteristics, and phoswich imaging ability within y background environments. The performance characteristics of the assembled prototype devices demonstrate that in surgery, this device can be used three ways: (1) rapid localization of y emitting radionuclides with the modestly directional, self-collimated phoswich crystals; (2) high resolutionimaging or coarse (annihilation background corrupted) +imaging in singles mode; or (3) + imaging in coincidence mode with reduced y background contamination. © 1998 IEEE.

Authors
Tornai, MP; Levin, CS; MacDonald, LR; Holdsworth, CH; Hoffman, EJ
MLA Citation
Tornai, MP, Levin, CS, MacDonald, LR, Holdsworth, CH, and Hoffman, EJ. "A miniature phoswich detector for gamma-ray localization and beta imaging." IEEE Transactions on Nuclear Science 45.3 PART 2 (1998): 1166-1173.
Source
scival
Published In
IEEE Transactions on Nuclear Science
Volume
45
Issue
3 PART 2
Publish Date
1998
Start Page
1166
End Page
1173

A miniature phoswich detector for gamma-ray localization and beta imaging

Authors
TORNAI, M
MLA Citation
TORNAI, M. "A miniature phoswich detector for gamma-ray localization and beta imaging." IEEE Trans Nucl Sci 45 (1998): 1166-1173.
Source
cinii-english
Published In
IEEE Trans Nucl Sci
Volume
45
Publish Date
1998
Start Page
1166
End Page
1173

Design and performance of gamma and beta intra-operative imaging probes

Authors
Hoffman, EJ; Tornai, MP; Levin, CS; MacDonald, LR; Siegel, S
MLA Citation
Hoffman, EJ, Tornai, MP, Levin, CS, MacDonald, LR, and Siegel, S. "Design and performance of gamma and beta intra-operative imaging probes." PHYSICA MEDICA 13 (December 1997): 243-246.
Source
wos-lite
Published In
Physica Medica
Volume
13
Publish Date
1997
Start Page
243
End Page
246

A novel dual detector probe for gamma-ray guided intraoperative beta imaging.

Authors
Tornai, MP; Levin, CS; Hoffman, EJ; MacDonald, LR; Glass, EC; Essner, R; Black, KL
MLA Citation
Tornai, MP, Levin, CS, Hoffman, EJ, MacDonald, LR, Glass, EC, Essner, R, and Black, KL. "A novel dual detector probe for gamma-ray guided intraoperative beta imaging." JOURNAL OF NUCLEAR MEDICINE 38.5 (May 1997): 21-21.
Source
wos-lite
Published In
Journal of nuclear medicine : official publication, Society of Nuclear Medicine
Volume
38
Issue
5
Publish Date
1997
Start Page
21
End Page
21

Dedicated breast imaging system based on a novel solid state detector array

Authors
Patt, BE; Iwanczyk, JS; Tornai, MP; Hoffman, EJ; Rossington, C
MLA Citation
Patt, BE, Iwanczyk, JS, Tornai, MP, Hoffman, EJ, and Rossington, C. "Dedicated breast imaging system based on a novel solid state detector array." JOURNAL OF NUCLEAR MEDICINE 38.5 (May 1997): 535-535.
Source
wos-lite
Published In
Journal of nuclear medicine : official publication, Society of Nuclear Medicine
Volume
38
Issue
5
Publish Date
1997
Start Page
535
End Page
535

Compton scatter and X-ray crosstalk and the use of very thin intercrystal septa in high-resolution PET detectors

To improve spatial resolution, positron emission tomography (PET) systems are being developed with finer detector elements. Unfortunately, using a smaller crystal size increases intercrystal Compton scatter and X-ray escape crosstalk, causing positioning errors that can lead to degradation of image contrast. We investigated the use of extremely thin (<300 /urn) lead strips for passive shielding of this intercrystal crosstalk. Using annihilation gamma rays and small (2- and 3-mm wide) Bismuth Germanate (BGO) crystal detectors in coincidence, crosstalk studies were performed with either two small adjacent crystals [(one-dimensional) (1-D)] or one crystal inside a volume of BGO [(two-dimensional) (2-D)J. The fraction of Compton scattered events from one crystal into an adjacent one was reduced, on average, by a factor of 3.2 (2.2) in the 1-D experiment and by a factor of 3.0 (2.1) in 2-D one, with a 300 (ISO)-4m-thick lead strip in between the crystals and a 300-700-keV energy window in both crystals. We could not measure a reduction in bismuth X-ray crosstalk with the use of lead septa due to the production of lead X-rays of similar energy. The full-width at half-maximum (FWHM) of the coincident point-spread function (CPSF) was not significantly different for the 1- and 2-D studies, with or without the different septa in place. However, the FWTM was roughly 20% smaller with the 300-jum lead shielding in place. These results indicate that intercrystal crosstalk does not affect the positioning resolution at FWHM, but does affect the tails of the CPSF. Thus, without introducing any additional dead area, an insertion of very thin lead strips can reduce the extent of positioning errors. Reducing the intercrystal crosstalk in a high-resolution PET detector array could potentially improve tomographic image contrast in situations where intercrystal crosstalk plays a significant role in event mispositioning. -. © 1997 IEEE.

Authors
Levin, CS; Tornai, MP; Cherry, SR; MacDonald, LR; Huffman, EJ
MLA Citation
Levin, CS, Tornai, MP, Cherry, SR, MacDonald, LR, and Huffman, EJ. "Compton scatter and X-ray crosstalk and the use of very thin intercrystal septa in high-resolution PET detectors." IEEE Transactions on Nuclear Science 44.2 (1997): 218-224.
Source
scival
Published In
IEEE Transactions on Nuclear Science
Volume
44
Issue
2
Publish Date
1997
Start Page
218
End Page
224
DOI
10.1109/23.568809

Investigation of crystal geometries for fiber coupled gamma imaging intra-operative probes

CsI(Na), CsI(Tl) and Nal(Tl) scintillators coupled through optical fibers were investigated with simulations and measurements to evaluate their potential as gamma imaging intraoperative probes. Three coupling methods were employed: discrete crystals coupled one-to-one with the fibers; discrete crystals coupled through a light diffuser to an unmatched fiber array; and continuous crystals coupled directly to the fiber optic array. The discrete crystals were 4x4 element arrays ranging in size from 1x1x2.5 mm3 to 2x2x6 mm 3. CsI(Na) produced the best pulse height and single crystal energy resolution (44% at 140 keV) when coupled through fibers to the photodetector. All elements of the arrays were completely resolved, indicating that the intrinsic spatial resolution will be determined by the crystal size. The spatial resolution for the 12.5 mm φ × 3.5 mm continuous crystals was -1.33 mm FWHM. Preliminary imaging measurements faithfully reproduced the activity distributions and compared favorably with simulations. © 1997 IEEE.

Authors
Tornai, MP; Levin, CS; MacDonald, LR; Huffman, EJ
MLA Citation
Tornai, MP, Levin, CS, MacDonald, LR, and Huffman, EJ. "Investigation of crystal geometries for fiber coupled gamma imaging intra-operative probes." IEEE Transactions on Nuclear Science 44.3 PART 2 (1997): 1254-1261.
Source
scival
Published In
IEEE Transactions on Nuclear Science
Volume
44
Issue
3 PART 2
Publish Date
1997
Start Page
1254
End Page
1261
DOI
10.1109/23.596997

Discrete scintillator coupled mercuric iodide photodetector arrays for breast imaging

Multi-element (4x4) imaging arrays with high resolution collimators, size matched to discrete CsI(Tl) scintillator arrays and mercuric iodide photodetector arrays (HgI2 PDA) were developed as prototypes for larger 16×16 element arrays for breast imaging. The compact nature of the arrays allows detector positioning in close proximity to the breast to eliminate activity not in the line-of-sight of the collimator, thus reducing image background. Short collimators, size matched to <1.5xl.5 mm2 scintillators show a factor of 2 and 3.4 improvement in spatial resolution and efficiency, respectively, compared to high resolution collimated gamma cameras for the anticipated compressed breast geometries. Monte Carlo simulations, confirmed by measurements, demonstrated that scintillator length played a greater role in efficiency and photofraction for 140 keV gammas than cross sectional area, which affects intrinsic spatial resolution. Simulations also demonstrated that an increase in the ratio of scintillator area to length corresponds to an improvement in light collection. Electronic noise was below 40 e- RMS indicating that detector resolution was not noise limited. The high quantum efficiency and spectral match of prototype unity gain HgI2 PDAs coupled to 1x1x2.5 mm3 and 2x2x4 mm3 CsI(Tl) scintillators demonstrated energy resolutions of 9.4% and 8.8% FWHM at 140 keV, respectively, without the spectral tailing observed in standard high-Z, compound semiconductor detectors. Line spread function measurements matched the scintillator size and pitch, and small, complex phantoms were easily imaged. © 1997 IEEE.

Authors
Tornai, MP; Patt, BE; Iwanczyk, JS; Levin, CS; Hoffman, EJ
MLA Citation
Tornai, MP, Patt, BE, Iwanczyk, JS, Levin, CS, and Hoffman, EJ. "Discrete scintillator coupled mercuric iodide photodetector arrays for breast imaging." IEEE Transactions on Nuclear Science 44.3 PART 2 (1997): 1127-1133.
Source
scival
Published In
IEEE Transactions on Nuclear Science
Volume
44
Issue
3 PART 2
Publish Date
1997
Start Page
1127
End Page
1133
DOI
10.1109/23.596976

Gamma and beta intra-operative imaging probes

Small area (∼1.5 cm2) scintillation cameras for imaging gammas and betas using inter-changeable detector front ends were built and characterized. Components common to both emission imaging cameras include: (1) fiber optic bundles 2-3 m long, comprised of multi-clad fibers which connect the scintillation detector to (2) an MC-PMT; (3) parallel MC-PMT outputs feed a resistive positioning network and i-V converter/line driver network which produce balanced +X, -X, +Y, and -Y outputs; and (4) four ADCs and a Macintosh PC for system control and image display. The beta and gamma devices used distinct scintillation detectors which were characterized by both simulation and measurement. The beta camera utilized a 0.5 mm by 1.25 cm φ CaF2(Eu) scintillation crystal coupled, through a diffusing light guide, to 19 2-mm φ optical fibers. These front-end fibers are in turn coupled by a more flexible fiber bundle to the MC-PMT. CaF2(Eu) has high light output, high beta sensitivity, and low gamma sensitivity. Image signals are histogrammed and displayed after Anger logic computations are performed on digitized signals. The beta camera has <0.6 mm FWHM intrinsic resolution. The gamma camera concept was tested with matrices of discrete 1 x 1 mm2 and 2 x 2 mm2 CsI(Tl) and NaI(Tl) crystals of various lengths, and 3 mm thick continuous crystals. Configurations using 4 x 4 element matrices with one-to-one coupling between crystals and fiber channels, and light diffusers between each crystal matrix and fibers were evaluated. The continuous crystals were coupled directly to the fiber optics with signal and data processing analogous to the beta camera. Coupling of discrete crystals to fiber optics by both methods gave essentially perfect identification of the crystal of interaction, allowing spatial resolution to be defined by the crystal size and collimator. The continuous crystal gamma camera gave intrinsic resolution of ∼1.4 mm FWHM.

Authors
Hoffman, EJ; Tornai, MP; Levin, CS; MacDonald, LR; Siegel, S
MLA Citation
Hoffman, EJ, Tornai, MP, Levin, CS, MacDonald, LR, and Siegel, S. "Gamma and beta intra-operative imaging probes." Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 392.1-3 (1997): 324-329.
Source
scival
Published In
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
Volume
392
Issue
1-3
Publish Date
1997
Start Page
324
End Page
329
DOI
10.1016/S0168-9002(97)00247-7

Development of an intraoperative gamma camera based on a 256-pixel mercuric iodide detector array

A 256-element mercuric iodide (HgI2) detector array has been developed which is intended for use as an intraoperative gamma camera (IOGC). The camera is specifically designed for use in imaging gamma-emitting radiopharmaceuticals (such as 99m-Tc labeled Sestamibi) incorporated into brain tumors in the intraoperative surgical environment. The system is intended to improve the success of tumor removal surgeries by allowing more complete removal of subclinical tumor cells without removal of excessive normal tissue. The use of HgI2 detector arrays in this application facilitates construction of an imaging head that is very compact and has a high SNR. The detector is configured as a cross-grid array. Pixel dimensions are 1.25 mm squares separated by 0.25 mm. The overall dimension of the detector is 23.75 mm on a side. The detector thickness is 1 mm which corresponds to over 60% stopping at 140 keV. The array has good uniformity with average energy resolution of 5.2 ±2.9 % FWHM at 140 keV (best resolution was 1.9 % FWHM). Response uniformity (± cr) was 7.9 %. A study utilizing realistic tumor phantoms (uptake ratio varied from 2:1 to 100:1) in background (1 mCi/1) was conducted. SNR's for the reasonably achievable uptake ratio of 50:1 were 5.61 crwith 1 cm of background depth ("normal tissue") and 2.74 crwith 4 cm of background for a 6.3 μl tumor phantom (∼270 nCi at the time of the measurement). © 1997 IEEE.

Authors
Patt, BE; Tornai, MP; Iwanczyk, JS; Levin, CS; Huffman, EJ
MLA Citation
Patt, BE, Tornai, MP, Iwanczyk, JS, Levin, CS, and Huffman, EJ. "Development of an intraoperative gamma camera based on a 256-pixel mercuric iodide detector array." IEEE Transactions on Nuclear Science 44.3 PART 2 (1997): 1242-1248.
Source
scival
Published In
IEEE Transactions on Nuclear Science
Volume
44
Issue
3 PART 2
Publish Date
1997
Start Page
1242
End Page
1248
DOI
10.1109/23.596995

Annihilation y ray background characterization and rejection for a small beta camera used for tumor localization during surgery

We have developed a miniature (1.2 cm2) beta-ray camera prototype to assist a surgeon in locating the margins of a resected tumor. With this technique, one directly detects betas emitted from exposed radio-labeled tissue. When imaging positron emitting radiopharmaceuticals, annihilation gamma ray interactions in the detector can mimic those of the betas. The extent of the background contamination depends on the detector, geometry and the tumor specificity of the radiopharmaceutical. We have characterized the effects that annihilation gamma rays have on positron imaging with our small camera. We studied beta and gamma ray detection rates and imaging using small positron or electron sources directly exposed to the detector to simulate hot tumor remnants, and a cylinder filled with 18F to simulate annihilation background from the brain. For various ratios of phantom head/tumor activity, a background gamma rate of 2.0 cts/sec/μCi was measured in the CaF2(Eu) detector. We present two gammaray background rejection schemes that require a β-γ coincidence. The first configuration uses a high efficiency scintillator coincidence "shield", the second, a "phoswich". Results show that these coincidence methods work with ~99% gamma ray rejection efficiency. © 1997 IEEE.

Authors
Levin, CS; Tornai, MP; MacDonald, LR; Huffman, EJ
MLA Citation
Levin, CS, Tornai, MP, MacDonald, LR, and Huffman, EJ. "Annihilation y ray background characterization and rejection for a small beta camera used for tumor localization during surgery." IEEE Transactions on Nuclear Science 44.3 PART 2 (1997): 1120-1126.
Source
scival
Published In
IEEE Transactions on Nuclear Science
Volume
44
Issue
3 PART 2
Publish Date
1997
Start Page
1120
End Page
1126
DOI
10.1109/23.596975

PSPMT and photodiode designs of a small scintillation camera for imaging malignant breast tumors

We are investigating the concept of utilizing a small gamma ray scintillation camera to help identify and localize malignant breast tumors after a suspicious finding in a mammogram. Excellent sensitivity and specificity for malignant breast tumors has been achieved using conventional nuclear medicine scintillation cameras with certain 99mTc labeled radiopharmaceuticals. However, because of the large size, low image resolution and high cost of these devices, they are not ideal for use in breast imaging in a mammography suite. A dedicated miniaturized camera would allow imaging at angles that are physically impossible with the standard camera. These lateral views would not include the background activity from the heart and liver. In addition, with a potentially higher intrinsic resolution, shorter collimator and if breast compression is applied, a small camera could significantly improve the sensitivity and signal to noise ratio for the scintillation imaging method. We are exploring two different photodetector technologies for a small prototype camera development. The first uses a position sensitive photomultiplier (PSPMT) as the photodetector, the second, an array of silicon PIN photodiodes (PD). In this report, we present imaging results obtained with a NaI(Tl)-PSPMT design, and the design features, expected performance and relevant energy and position measurements obtained for a test CsI(Tl)-PD device. © 1997 IEEE.

Authors
Levin, CS; Hoffman, EJ; Tornai, MP; MacDonald, LR
MLA Citation
Levin, CS, Hoffman, EJ, Tornai, MP, and MacDonald, LR. "PSPMT and photodiode designs of a small scintillation camera for imaging malignant breast tumors." IEEE Transactions on Nuclear Science 44.4 PART 1 (1997): 1513-1520.
Source
scival
Published In
IEEE Transactions on Nuclear Science
Volume
44
Issue
4 PART 1
Publish Date
1997
Start Page
1513
End Page
1520
DOI
10.1109/23.632706

Design and performance of gamma and beta intra-operative imaging probes

A prototype small area scintillation camera capable of imaging both gammas and betas by use of inter-changeable detector front ends was characterized. In the camera's application, patients are injected with tumor seeking radiopharmaceuticals before surgery, during surgery the body of tumor is removed, and the residual tumor is located with gamma or beta imaging probes. Common elements of both types of camera include: (1) a 2-3 meter long fiber optic bundle, consisting of 19 sets of groups of three 0.9 mm diameter multiclad fibers that allow a flexible optical connection to the scintillator in addition to electrical isolation of the patient from the electronics, (2) fibers are connected to a Multi-Channel Photomultiplier (MC-PMT) which has 64 parallel channels, (3) the parallel PMT outputs feed a resistive divider network and an i-V converter/line driver network with gain adjustments, producing balanced + X, -X, + Y, and -Y outputs for analog image signals, (4) four ADCs connected to a Macintosh PC for digitizing and displaying the image. The beta camera utilized a 0.5 mm thick by 1.25 cm diam. CaF2(Eu) scintillation crystal coupled to 19 2-mm diameter multiclad optical fibers, which are in turn coupled by a longer fiber bundle to the MC-PMT The crystal is coupled to fibers through a diffusing light guide ensuring adequate distribution of scintillation light among fibers. Image signals are directly histogrammed and displayed after Anger logic computations are performed on analog signals. The gamma camera concept was tested with 3 mm thick continuous crystals and matrices of CsI(T1) as the system front end with the same fiber optic coupling as the beta camera, and data processing analogous to the beta camera. With the matrices of crystals, a configuration which used a light diffuser between the matrix and fiber optics was evaluated. The beta imaging probe produced images with 0.6 mm FWHM resolution and a flood field uniformity of ± 15%. The continuous crystal imaging probe gave intrinsic resolutions of 1.4 ± 0.2 mm FWHM at 122 keV. Flood field images, made with the diffuser between fiber optics and discrete crystals, completely resolved the 1 x 1 mm2 elements Intrinsic resolution as measured by a line spread function was 0.92 ± 0.03 mm FWHM.

Authors
Hoffman, EJ; Tornai, MP; Levin, CS; MacDonald, LR; Siegel, S
MLA Citation
Hoffman, EJ, Tornai, MP, Levin, CS, MacDonald, LR, and Siegel, S. "Design and performance of gamma and beta intra-operative imaging probes." Physica Medica 13.SUPPL. 1 (1997): 243-246.
Source
scival
Published In
Physica Medica
Volume
13
Issue
SUPPL. 1
Publish Date
1997
Start Page
243
End Page
246

Miniature phoswich detector for gamma-ray localization and beta imaging

A combined γ-ray probe/γ+ imaging detector was created through the modification of a beta imaging intra-operative probe. The phoswich detector consists of a thin CaF2(Eu) β+ imaging disk, coupled through a light diffuser to 7 or 19 parallel-piped high-Z scintillation crystals arranged hexagonally in columns. The performance characteristics of the assembled prototype devices demonstrate that in surgery, this device can be used for: the rapid localization of γ emitting radionuclides with the modestly directional, self-collimated phoswich crystals; high-resolution β- imaging or coarse β+ imaging in singles mode; or β+ imaging in coincidence mode with reduced γ background contamination.

Authors
Tornai, MP; Levin, CS; MacDonald, LR; Holdsworth, CH; Hoffman, EJ
MLA Citation
Tornai, MP, Levin, CS, MacDonald, LR, Holdsworth, CH, and Hoffman, EJ. "Miniature phoswich detector for gamma-ray localization and beta imaging." IEEE Nuclear Science Symposium & Medical Imaging Conference 2 (1997): 1028-1032.
Source
scival
Published In
IEEE Nuclear Science Symposium & Medical Imaging Conference
Volume
2
Publish Date
1997
Start Page
1028
End Page
1032

Characterization of fluor concentration and geometry in organic scintillators for in situ beta imaging

Authors
Tornai, MP; Hoffman, EJ; MacDonald, LR; Levin, CS
MLA Citation
Tornai, MP, Hoffman, EJ, MacDonald, LR, and Levin, CS. "Characterization of fluor concentration and geometry in organic scintillators for in situ beta imaging." IEEE TRANSACTIONS ON NUCLEAR SCIENCE 43.6 (December 1996): 3342-3347.
Source
wos-lite
Published In
IEEE Transactions on Nuclear Science
Volume
43
Issue
6
Publish Date
1996
Start Page
3342
End Page
3347
DOI
10.1109/23.552749

Design of a small scintillation camera with photodiode readout for imaging malignant breast tumors.

Authors
Levin, CS; Hoffman, EJ; Tornai, MP; MacDonald, LR
MLA Citation
Levin, CS, Hoffman, EJ, Tornai, MP, and MacDonald, LR. "Design of a small scintillation camera with photodiode readout for imaging malignant breast tumors." JOURNAL OF NUCLEAR MEDICINE 37.5 (May 1996): 200-200.
Source
wos-lite
Published In
Journal of nuclear medicine : official publication, Society of Nuclear Medicine
Volume
37
Issue
5
Publish Date
1996
Start Page
200
End Page
200

Characterization and rejection of annihilation gamma-ray background for a surgical beta ray camera that utilizes positron emitting radiopharmaceuticals

Authors
Levin, CS; Tornai, MP; MacDonald, LR; Hoffman, EJ
MLA Citation
Levin, CS, Tornai, MP, MacDonald, LR, and Hoffman, EJ. "Characterization and rejection of annihilation gamma-ray background for a surgical beta ray camera that utilizes positron emitting radiopharmaceuticals." JOURNAL OF NUCLEAR MEDICINE 37.5 (May 1996): 303-303.
Source
wos-lite
Published In
Journal of nuclear medicine : official publication, Society of Nuclear Medicine
Volume
37
Issue
5
Publish Date
1996
Start Page
303
End Page
303

Design considerations and initial performance of a 1.2 cm2 beta imaging intra-operative probe

A novel small area beta (β±) detector is under development for nuclear emission imaging of surgically exposed, radiolabeled tumor beds. The imaging device front-end consists of a 0.5 mm thick by 1.25 cm diameter CaF2(Eu) scintillator disk coupled to a rigid bundle of 2 mm diameter double clad optical fibers through a polystyrene light diffuser. The detector area (1.2 cm2) was determined by the requirement of introducing the probe into small cavities, e.g. during neuro-surgical lesion resection, but large enough to produce images of clinical significance. Flexible back-end optical fibers (1.9 m long) were coupled to the front-end components allowing ∼75 photoelectrons to be detected for mean beta energies of 250 keV, indicating that sufficient signal can be obtained with clinical beta emitters (e.g. 18F, 131I). The long flexible fibers guide the scintillation light to a Philips XP1700 series, fiber optic faceplate, Multi-Channel PMT. The parallel MC-PMT outputs arc fed into a variable gain, charge divider network and an i-V pre-amplifier/line driver network, whose resulting four outpuls are digitized and histogrammed with standard Anger positioning logic. The various components in the imaging chain were evaluated and optimized by both simulations and measurements. Line spread functions measured in the 10.8 mm FOV were 0.50 mm ±0.038 mm and 0.55 mm ±0.065 mm FWHM in X and Y, respectively. A 20% variation in pulse height and minimal variation in spatial resolution was observed. The differential image uniformity was measured to be ±15.6% with ∼150 cts/pixel. Preliminary images show excellent reproduction of phantom activity distributions. © 1996 IEEE.

Authors
Tornai, MP; MacDonald, LR; Levin, CS; Siegel, S; Hoffman, EJ
MLA Citation
Tornai, MP, MacDonald, LR, Levin, CS, Siegel, S, and Hoffman, EJ. "Design considerations and initial performance of a 1.2 cm2 beta imaging intra-operative probe." IEEE Transactions on Nuclear Science 43.4 PART 1 (1996): 2326-2335.
Source
scival
Published In
IEEE Transactions on Nuclear Science
Volume
43
Issue
4 PART 1
Publish Date
1996
Start Page
2326
End Page
2335
DOI
10.1109/23.531898

Optimizing light collection from thin scintillators used in a beta-ray camera for surgical use

We are developing a 1-2 cm2 area camera for imaging the distribution of beta-emitting radiopharmaceuticals at the surface of tissue exposed during surgery. The front end consists of a very thin continuous or segmented scintillator sensitive to betas (positrons or electrons) of a few hundred keV, yet insensitive to gamma rays. The light from the scintillator is piped through clear fibers to the photon detector (PD). This approach requires that a sufficient number of scintillation photons be transported from the scintillator, through the fibers to the PD. The scintillator. reflector, surface treatments, geometry, fiber light guides, and optical couplings must be optimized. We report here on efforts made to optimize the light collection from < 3 mm thick plastic and CaF2(Eu) scintillators into clear fibers using experimental measurements and computer simulations. We measured that with a 1.25 cm diameter, 0.5 mm thick optimized CaF2(Eu) disk coupled to a 5 cm long bundle of clear optical fibers, on average, ∼250 photoelectrons are produced at a PMT photocathode for a 204Tl beta flood source (Emax = 763 keV). This corresponds to a sufficient number of photoelectrons for ∼ 1 mm resolution imaging capabilities for the proposed camera. © 1996 IEEE.

Authors
Levin, CS; MacDonald, LR; Tornai, MP; Hoffman, EJ; Park, J
MLA Citation
Levin, CS, MacDonald, LR, Tornai, MP, Hoffman, EJ, and Park, J. "Optimizing light collection from thin scintillators used in a beta-ray camera for surgical use." IEEE Transactions on Nuclear Science 43.3 PART 2 (1996): 2053-2060.
Source
scival
Published In
IEEE Transactions on Nuclear Science
Volume
43
Issue
3 PART 2
Publish Date
1996
Start Page
2053
End Page
2060
DOI
10.1109/23.507268

Mercuric iodide photodetector arrays for gamma-ray imaging

We have developed a novel detector device, namely: a mercuric iodide photodetector array (HgI2 PDA) to be used with a scintillating crystal for X-ray and gamma-ray imaging. A HgI2 PDA prototype with 16-pixels has been evaluated with segmented scintillators (CsI(Tl)) coupled to the HgI2 PDA. Pixel energy resolution of 9.4% FWHM has been obtained at 122 keV for a 4 mm thick scintillator corresponding to 72% stopping at 140 keV, and pixel energy resolution of 11% FWHM has been obtained at 122 keV with the 10 mm thick scintillator.

Authors
Patt, BE; Iwanczyk, JS; Wang, YJ; Tornai, MP; Levin, CS; Hoffman, EJ
MLA Citation
Patt, BE, Iwanczyk, JS, Wang, YJ, Tornai, MP, Levin, CS, and Hoffman, EJ. "Mercuric iodide photodetector arrays for gamma-ray imaging." Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 380.1-2 (1996): 295-300.
Source
scival
Published In
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
Volume
380
Issue
1-2
Publish Date
1996
Start Page
295
End Page
300
DOI
10.1016/S0168-9002(96)00492-5

Investigation of crystal geometries for fiber coupled gamma imaging intra-operative probes

In this work, gamma sensitive intra-operative imaging detectors using CsI(Na), CsI(Tl) and NaI(Tl) scintillators coupled through optical fibers were investigated with simulations and measurements. Three coupling methods were employed between the detectors and optical fiber imaging array: discrete crystals coupled one-to-one with the fibers; discrete crystals coupled through a light diffuser to an unmatched fiber array; and continuous, light sharing crystals coupled directly to the fiber optic array. The discrete crystals were arranged in 4×4 element arrays of sizes ranging from 1×1×2.5 mm3 up to 2×2×6 mm3. CsI(Na) had the best pulse height and single crystal energy resolution (44% at 140 keV) when coupled through fibers to the MC-PMT photodetector. All discrete arrays were completely resolved, indicating that the intrinsic spatial resolution corresponded to the crystal size. The spatial resolution for the 12.5 mm φ×3.5 mm continuous crystals was approximately 1.2 mm FWHM, with relative pulse heights of 1.5 to 5.5 times lower than for the discrete array detectors.

Authors
Tornai, MP; Levin, CS; MacDonald, LR; Hoffman, EJ
MLA Citation
Tornai, MP, Levin, CS, MacDonald, LR, and Hoffman, EJ. "Investigation of crystal geometries for fiber coupled gamma imaging intra-operative probes." IEEE Nuclear Science Symposium & Medical Imaging Conference 2 (1996): 1135-1139.
Source
scival
Published In
IEEE Nuclear Science Symposium & Medical Imaging Conference
Volume
2
Publish Date
1996
Start Page
1135
End Page
1139

PSPMT and PIN diode designs of a small scintillation camera for imaging malignant breast tumors

We are investigating the concept of utilizing a small gamma ray scintillation camera to help identify and localize malignant breast tumors after a suspicious finding in a mammogram. We are exploring two different photodetector technologies for a small prototype camera development. The first uses a position sensitive photomultiplier (PSPMT) as the photodetector, the second, an array of silicon PIN diodes (PD). In this report, we present imaging results obtained with a NaI(Tl)-PSPMT design, and the design features, expected performance and relevant energy measurements obtained for the CsI(Tl)-PD based device.

Authors
Levin, CS; Hoffman, EJ; Tornai, MP; MacDonald, LR
MLA Citation
Levin, CS, Hoffman, EJ, Tornai, MP, and MacDonald, LR. "PSPMT and PIN diode designs of a small scintillation camera for imaging malignant breast tumors." IEEE Nuclear Science Symposium & Medical Imaging Conference 2 (1996): 1196-1200.
Source
scival
Published In
IEEE Nuclear Science Symposium & Medical Imaging Conference
Volume
2
Publish Date
1996
Start Page
1196
End Page
1200

Characterization of fluor concentration and geometry in organic scintillators for in situ beta imaging

Development of a small area (1-2 cm2 ) in situ beta imaging device includes optimization of the front end scintillation detector, which is fiber optically coupled to a remote photon detector. Thin plastic scintillation detectors, which are sensitive to charged particles, are the ideal detectors due to the low sensitivity to ambient gamma backgrounds. The light output of a new binary plastic scintillator was investigated with respect to increasing concentrations of the fluor (0.5-2.0% by weight) and varying thickness cylindrical configurations of the intended imaging detector. The fluor had an emission maximum increasing from 431 to 436 nm with increasing fluor concentration. The decay time(s) had two components (0.38 and 1.74 ns). There was an ~20% increase in light output with increasing fluor concentration, measured with both 204T1 betas and conversion electrons from 207Bi. The highest light output of this new scintillator was measured to be ~30% lower than BC404. Simulations predicted the 1.5 mm scintillator thickness at which light output and energy absorption for ~700 keV electrons (e.g., from 204T1, 18F) were maximized, which corresponded with measurements. As beta continua are relatively featureless, energy calibration for the thin scintillators was investigated using Landau distributions, which appear as distinct peaks in the spectra. As the scintillators were made thinner, gamma backgrounds were shown to linearly decrease. © 1996 IEEE.

Authors
Tornai, MP; Huffman, EJ
MLA Citation
Tornai, MP, and Huffman, EJ. "Characterization of fluor concentration and geometry in organic scintillators for in situ beta imaging." IEEE Transactions on Nuclear Science 43.6 PART 2 (1996): 3342-3347.
Source
scival
Published In
IEEE Transactions on Nuclear Science
Volume
43
Issue
6 PART 2
Publish Date
1996
Start Page
3342
End Page
3347

Annihilation gamma ray background characterization and rejection for a positron camera

We have developed a miniature (1.2 cm2) beta-ray camera prototype to assist a surgeon in locating and removing the margins of a resected tumor. When imaging positron emitting radiopharmaceuticals, annihilation gamma ray interactions in the detector can mimic those of the betas. The extent of the background contamination depends on the detector, geometry and tumor specificity of the radiopharmaceutical. We have characterized the effects that annihilation gamma rays have on positron imaging with the camera. We studied beta and gamma ray detection rates and imaging using small positron or electron sources directly exposed to the detector to simulate hot tumor remnants and a cylinder filled with 18F to simulate annihilation background from the brain. For various ratios of phantom brain/tumor activity, a annihilation gamma rate of 1.8 cts/sec/μCi was measured in the CaF2(Eu) detector. We present two gamma-ray background rejection schemes that use a β-γ coincidence. Results show that the coincidence methods works with approximately 99% gamma ray rejection efficiency.

Authors
Levin, CS; Tornai, MP; MacDonald, LR; Hoffman, EJ
MLA Citation
Levin, CS, Tornai, MP, MacDonald, LR, and Hoffman, EJ. "Annihilation gamma ray background characterization and rejection for a positron camera." IEEE Nuclear Science Symposium & Medical Imaging Conference 2 (1996): 1044-1048.
Source
scival
Published In
IEEE Nuclear Science Symposium & Medical Imaging Conference
Volume
2
Publish Date
1996
Start Page
1044
End Page
1048

Discrete scintillator coupled mercuric iodide photodetector arrays for breast imaging

Multi-element (4×4) imaging arrays with high resolution collimators, size matched to discrete CsI(Tl) scintillator arrays and mercuric iodide photodetector arrays (HgI2 PDA) are under development as prototypes for larger 16×16 element arrays. The compact nature of the arrays allows detector positioning in proximity to the breast to eliminate activity not in the line-of-sight of the collimator, thus reducing image background. Short collimators, size matched to ≤1.5×1.5 mm2 scintillators show a factor of 2 and 3.4 improvement in spatial resolution and efficiency, respectively, compared to high resolution collimated gamma cameras for the anticipated compressed breast geometries. Monte Carlo simulations, confirmed by measurements, demonstrated that scintillator length played a greater role in efficiency and photofraction for 140 keV gammas than cross sectional area, which affects intrinsic spatial resolution. Simulations also demonstrated that an increase in the ratio of scintillator area to length corresponds to an improvement in light collection. Electronic noise was below 40 e- RMS indicating that detector resolution was not noise limited. The high quantum efficiency and spectral match of prototype unity gain HgI2 PDAs coupled to 1×1×2.5 mm3 and 2×2×4 mm3 CsI(Tl) scintillators demonstrated energy resolutions of 9.4% and 8.8% FWHM at 140 keV, respectively, without the spectral tailing observed in standard high-Z, compound semi-conductor detectors. Line spread function measurements matched the scintillator size and pitch, and small, complex phantoms were easily imaged.

Authors
Tornai, MP; Patt, BE; Iwanczyk, JS; Levin, CS; Hoffman, ES
MLA Citation
Tornai, MP, Patt, BE, Iwanczyk, JS, Levin, CS, and Hoffman, ES. "Discrete scintillator coupled mercuric iodide photodetector arrays for breast imaging." IEEE Nuclear Science Symposium & Medical Imaging Conference 2 (1996): 1034-1038.
Source
scival
Published In
IEEE Nuclear Science Symposium & Medical Imaging Conference
Volume
2
Publish Date
1996
Start Page
1034
End Page
1038

INVESTIGATION OF THE PHYSICAL ASPECTS OF BETA-IMAGING PROBES USING SCINTILLATING FIBERS AND VISIBLE-LIGHT PHOTON COUNTERS

Authors
MACDONALD, LR; TORNAI, MP; LEVIN, CS; PARK, J; ATAC, M; CLINE, DB; HOFFMAN, EJ
MLA Citation
MACDONALD, LR, TORNAI, MP, LEVIN, CS, PARK, J, ATAC, M, CLINE, DB, and HOFFMAN, EJ. "INVESTIGATION OF THE PHYSICAL ASPECTS OF BETA-IMAGING PROBES USING SCINTILLATING FIBERS AND VISIBLE-LIGHT PHOTON COUNTERS." IEEE TRANSACTIONS ON NUCLEAR SCIENCE 42.4 (August 1995): 1351-1357.
Source
wos-lite
Published In
IEEE Transactions on Nuclear Science
Volume
42
Issue
4
Publish Date
1995
Start Page
1351
End Page
1357
DOI
10.1109/23.467855

COLLECTION OF SCINTILLATION LIGHT FROM SMALL BGO CRYSTALS

Authors
CHERRY, SR; SHAO, YP; TORNAI, MP; SIEGEL, S; RICCI, AR; PHELPS, ME
MLA Citation
CHERRY, SR, SHAO, YP, TORNAI, MP, SIEGEL, S, RICCI, AR, and PHELPS, ME. "COLLECTION OF SCINTILLATION LIGHT FROM SMALL BGO CRYSTALS." IEEE TRANSACTIONS ON NUCLEAR SCIENCE 42.4 (August 1995): 1058-1063.
Source
wos-lite
Published In
IEEE Transactions on Nuclear Science
Volume
42
Issue
4
Publish Date
1995
Start Page
1058
End Page
1063
DOI
10.1109/23.467749

Comparison of PET detector modules employing rectangular and round photomultiplier tubes

We have compared the high resolution BGO detector blocks from the EXACT HR PET system which use two dual-cathode rectangular photomultiplier (PM) tubes with a new block design, the EXACT HR PLUS, which uses four round PM tubes. Despite the lower coupling area between photocathode and scintillator, the HR PLUS block compares favorably with the HR block. The energy resolution averages 20% for the HR PLUS block and 23% for the HR block, with efficiency variations of 17% in both blocks. Additional measurements were carried out on the HR PLUS block to characterize depth of interaction effects and cross-talk between elements. Coincidence line spread function measurements had a FWHM of 3.0 mm in the axial direction and 2.9 mm in the transaxial direction. In light of these results, limitations of the BGO block design are discussed and some solutions proposed.

Authors
Cherry, SR; Tornai, MP; Levin, CS; Siegel, S; Hoffman, EJ; Andreaco, MS; Williams, CW
MLA Citation
Cherry, SR, Tornai, MP, Levin, CS, Siegel, S, Hoffman, EJ, Andreaco, MS, and Williams, CW. "Comparison of PET detector modules employing rectangular and round photomultiplier tubes." IEEE Transactions on Nuclear Science 42.4 pt 1 (1995): 1064-1068.
Source
scival
Published In
IEEE Transactions on Nuclear Science
Volume
42
Issue
4 pt 1
Publish Date
1995
Start Page
1064
End Page
1068

Development of a mercuric iodide detector array for medical imaging applications

A nineteen element mercuric iodide (HgI2) detector array has been developed as a prototype for a larger (169 element) array, which is intended for use as an intra-operative gamma camera (IOGC). This work is motivated by the need for identifying and removing residual tumor cells after the removal of bulk tumor, while sparing normal tissue. Prior to surgery, a tumor seeking radiopharmaceutical is injected into the patient, and the IOGC is used to locate and map out the radioactivity. The IOGC can be used with commercially available radioisotopes such as 201Tl, 99mTc, and 123I which have low energy X- and gamma-rays. The use of HgI2 detector arrays in this application facilitates construction of an imaging head that is very compact and has a high signal-to-noise ratio. The prototype detectors were configured as discrete pixel elements joined by fine wires into novel pseudo crossed-grid arrays to promote improved electric field distribution compared with previous designs, and to maximize the fill factor for the expected circular probe shape. Pixel dimensions are hexagonal with 1.5 mm and 1.9 mm diameters separated by 0.2 mm thick lead septa. The overall detectors are hexagonal with a diameter of ∼1 cm. The sensitive detector thickness is 1.2 mm, which corresponds to >99% efficiency at 59 keV and 67% efficiency at 140 keV. Row, column, and pixel spectra have been measured on the prototypical detector array. Energy resolution was found to vary with the width of the row/column coincidence window that was applied. With the low edge of the coincidence window at 30% below the photopeak, pixel energy resolutions of 2.98% and 3.88% FWHM were obtained on the best individual pixels at 59 keV (241Am) and 140 keV (99mTc), respectively. To characterize this array as an imaging device, the spatial response of the pixels was measured with stepped point sources. The spatial response corresponded well with the pixel geometry, indicating that the spatial resolution was determined by the pixel geometry. © 1995.

Authors
Patt, BE; Iwanczyk, JS; Tornai, MP; Levin, CS; Hoffman, EJ
MLA Citation
Patt, BE, Iwanczyk, JS, Tornai, MP, Levin, CS, and Hoffman, EJ. "Development of a mercuric iodide detector array for medical imaging applications." Nuclear Inst. and Methods in Physics Research, A 366.1 (1995): 173-182.
Source
scival
Published In
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
Volume
366
Issue
1
Publish Date
1995
Start Page
173
End Page
182
DOI
10.1016/0168-9002(95)00479-3

Small-area fiber-coupled scintillation camera for imaging beta-ray distributions intraoperatively

A small area, imaging, scintillation probe is being developed for locating small amounts of radio-labeled malignant tissue during surgery. Preliminary in brain surgery, avoiding the removal of excess tissue is a priority. It is possible to locate the main body of a brain tumor both before and during surgery, but once the bulk of the tumor is excised the identification of residual malignant tissue is difficult. A probe that covers an area of 1-2 cm 2 with an intrinsic resolution of 1-2 mm could locate small tumor masses that pose a threat of recurrence of the disease, and prevent removal of healthy tissue. A pre-operative injection of tumor seeking, beta emitting radiopharmaceutical (e.g. 18fluorodeoxyuridine-FDUR-) will label the tumor. The limited range of beta-rays ensures proximity upon successful detection. Plastic scintillators are used for beta detection, and visible light photon counters (VLPCs) detect the scintillation light. For maneuverability in and around the surgical cavity, the scintillators are coupled to the VLPCs via 2 m of optical fiber. An imaging device can cover the tissue bed in a time compatible with surgery, as opposed to a single element detector on the order of 1-2 mm in size with comparable resolution. An imager also distinguishes high background rates (such as from annihilation gammas in FDUR) and concentrations of activity.

Authors
MacDonald, LR; Tornai, MP; Levin, CS; Park, J; Atac, M; Cline, DB; Hoffman, EJ
MLA Citation
MacDonald, LR, Tornai, MP, Levin, CS, Park, J, Atac, M, Cline, DB, and Hoffman, EJ. "Small-area fiber-coupled scintillation camera for imaging beta-ray distributions intraoperatively." Proceedings of SPIE - The International Society for Optical Engineering 2551 (1995): 92-101.
Source
scival
Published In
Proceedings of SPIE - The International Society for Optical Engineering
Volume
2551
Publish Date
1995
Start Page
92
End Page
101

Investigation of the physical aspects of beta imaging probes using scintillating fibers and visible light photon counters

We are developing a hand-held imaging probe intended for intra-operative use. This probe is to be used after the bulk of a tumor has been removed. It will locate residual malignant tissue labeled by a pre-operative injection of a tumor-seeking radiopharmaceutical. The device presented here is a prototype system that consists of a 4 × 8 array of 925μm diameter plastic scintillating fibers. The imaging array is coupled to Visible Light Photon Counters (VLPCs) via 2 meters of optical fiber. We have obtained an intrinsic spatial resolution of < 1.0 mm with a highly collimated beta source, and a 2.0 mm resolution with a 1 mm, uncollimated source. Standard deviations of the relative gain and sensitivity over the 32 imaging elements were found to be 9.6% and 11.7% of the mean, respectively.

Authors
MacDonald, LR; Tornai, MP; Levin, CS; Park, J; Atac, M; Cline, DB; Hoffman, EJ
MLA Citation
MacDonald, LR, Tornai, MP, Levin, CS, Park, J, Atac, M, Cline, DB, and Hoffman, EJ. "Investigation of the physical aspects of beta imaging probes using scintillating fibers and visible light photon counters." IEEE Transactions on Nuclear Science 42.4 pt 1 (1995): 1351-1357.
Source
scival
Published In
IEEE Transactions on Nuclear Science
Volume
42
Issue
4 pt 1
Publish Date
1995
Start Page
1351
End Page
1357

Collection of scintillation light from small BGO crystals

We propose to develop a high resolution positron emission tomography (PET) detector designed for animal imaging. The detector consists of a 2-D array of small bismuth germanate (BGO) crystals coupled via optical fibers to a multi-channel photomultiplier tube (MC-PMT). Though this approach offers several advantages over the conventional BGO block design, it does require that a sufficient number of scintillation photons be transported from the crystal, down the fiber and into the PMT. In this study we use simulations and experimental data to determine how to maximize the signal reaching the PMT. This involves investigating factors such as crystal geometry, crystal surface treatment, the use of reflectors, choice of optical fiber, coupling of crystal to the optical fiber and optical fiber properties. Our results indicate that using 2 × 2 ×10 mm BGO crystals coupled to 30 cm of clad optical fiber, roughly 50 photoelectrons are produced at the PMT photocathode for a 511 keV interaction. This is sufficient to clearly visualize the photopeak and provide adequate timing resolution for PET. Based on these encouraging results, a prototype detector will now be constructed.

Authors
Cherry, SR; Shao, Y; Tornai, MP; Siegel, S; Ricci, AR; Phelps, ME
MLA Citation
Cherry, SR, Shao, Y, Tornai, MP, Siegel, S, Ricci, AR, and Phelps, ME. "Collection of scintillation light from small BGO crystals." IEEE Transactions on Nuclear Science 42.4 pt 1 (1995): 1058-1063.
Source
scival
Published In
IEEE Transactions on Nuclear Science
Volume
42
Issue
4 pt 1
Publish Date
1995
Start Page
1058
End Page
1063

Design considerations and initial performance of a 1.2cm2 beta imaging intra-operative probe

A novel small area beta detector is under development for nuclear emission imaging of surgically exposed radiolabeled tumor beds. The detector size (1.2 cm2) is determined by the requirement to introduce the probe into small cavities, e.g. during neuro-surgical lesion resection, but large enough to produce images of clinical significance. The various components of the imaging chain are optimized by both simulation and measurements.

Authors
Tornai, MP; MacDonald, LR; Levin, CS; Siegel, S; Hoffman, EJ
MLA Citation
Tornai, MP, MacDonald, LR, Levin, CS, Siegel, S, and Hoffman, EJ. "Design considerations and initial performance of a 1.2cm2 beta imaging intra-operative probe." IEEE Nuclear Science Symposium & Medical Imaging Conference 3 (1995): 1791-1795.
Source
scival
Published In
IEEE Nuclear Science Symposium & Medical Imaging Conference
Volume
3
Publish Date
1995
Start Page
1791
End Page
1795

Optimizing light collection from thin scintillators used in a beta-ray camera for surgical use

We are developing a 1-2 cm2 area camera for imaging the distribution of beta emitting radiopharmaceuticals at the surface of tissue exposed during surgery. The front end consists of a very thin continuous or segmented scintillator sensitive to betas (positrons or electrons) of a few hundred keV, yet insensitive to gamma rays. The light from the scintillator is piped away through clear fibers into the photon detector (PD). We report here on efforts made to optimize the light collection from < 3 mm thick plastic and CaF2(Eu) scintillators into clear fibers using experimental measurements and computer simulations.

Authors
Levin, CS; MacDonald, LR; Tornai, MP; Hoffman, EJ; Park, J
MLA Citation
Levin, CS, MacDonald, LR, Tornai, MP, Hoffman, EJ, and Park, J. "Optimizing light collection from thin scintillators used in a beta-ray camera for surgical use." IEEE Nuclear Science Symposium & Medical Imaging Conference 3 (1995): 1796-1800.
Source
scival
Published In
IEEE Nuclear Science Symposium & Medical Imaging Conference
Volume
3
Publish Date
1995
Start Page
1796
End Page
1800

Characterization of flour concentration and geometry in organic scintillators for in situ beta imaging

Development of a small area (1-2 cm2) in situ beta imaging device includes optimization of the front end scintillation detector which is fiber optically coupled to a remote photon detector. Thin plastic scintillation detectors, which are sensitive to charge particles, are the ideal detectors due to the low sensitivity to ambient gamma backgrounds. The light output of a new binary plastic scintillator was investigated with respect to increasing concentrations of the flour ([0.5] to [2.0%] by weight), and varying thickness cylindrical configurations of the intended imaging detector. The new flour had an emission maximum increasing from 431 to 436 nm with increasing flour concentration. The decay time(s) had two components (0.38, 1.74 nsec). There was an approx.20% increase in light output with increasing flour concentration, measured with both 204Tl betas and conversion electrons from 207Bi. The highest light output of this new scintillator was measured to be approx.30% lower than BC404. Simulations predicted the 1.5 mm scintillator thickness at which light output and energy absorption for approx.700 keV electrons (e.g. from 204Tl, 18F) were maximized, which corresponded with measurements. As beta continua are relatively featureless, energy calibration for the thin scintillators was investigated using Landau distributions, which appear as distinct peaks in the spectra. As the scintillators were made thinner, gamma backgrounds were shown to linearly decrease.

Authors
Tornai, MP; Hoffman, EJ; MacDonald, LR; Levin, CS
MLA Citation
Tornai, MP, Hoffman, EJ, MacDonald, LR, and Levin, CS. "Characterization of flour concentration and geometry in organic scintillators for in situ beta imaging." IEEE Nuclear Science Symposium & Medical Imaging Conference 3 (1995): 1632-1636.
Source
scival
Published In
IEEE Nuclear Science Symposium & Medical Imaging Conference
Volume
3
Publish Date
1995
Start Page
1632
End Page
1636

Compton scatter and x-ray crosstalk and the use of very thin inter-crystal septa in high resolution PET detectors

To improve spatial resolution, PET systems are being developed with finer detector elements. Unfortunately, using smaller crystal sizes increases inter-crystal Compton scatter and bismuth x-ray and (to a lesser degree) electron escape crosstalk, causing positioning errors that lead to degradation of image contrast. We investigated the use of extremely thin (≤ 300 μm) lead strips for passive shielding of this inter-crystal crosstalk. Using annihilation photons and small (2 and 3 mm wide) BGO crystals in coincidence, crosstalk studies were performed with either two small adjacent crystals (1-D) or one crystal inside a volume of BGO (2-D). The fraction of Compton scattered events from one crystal into an adjacent one was reduced, on average, by a factor of 3.2 (2.2) in the 1-D experiment and by a factor of 3.0 (2.1) in 2-D, with a 300 (150) μm thick lead strip in between the crystals and a 300-700 keV energy window in both crystals. We could not measure a reduction in bismuth x-ray crosstalk with the use of lead septa because of the production of lead x-rays. The width of the coincident point spread function was not significantly different for the 1- and 2-D studies, with or without the different thickness septa in place. These results indicate that intercrystal crosstalk does not affect the positioning resolution. A simple insertion of very thin lead strips may significantly reduce the inter-crystal scattering crosstalk of a high resolution PET system, thereby ultimately improving image contrast, without introducing a dead area.

Authors
Levin, CS; Tornai, MP; Cherry, SR; MacDonald, LR; Hoffman, EJ
MLA Citation
Levin, CS, Tornai, MP, Cherry, SR, MacDonald, LR, and Hoffman, EJ. "Compton scatter and x-ray crosstalk and the use of very thin inter-crystal septa in high resolution PET detectors." IEEE Nuclear Science Symposium & Medical Imaging Conference 2 (1995): 1036-1040.
Source
scival
Published In
IEEE Nuclear Science Symposium & Medical Imaging Conference
Volume
2
Publish Date
1995
Start Page
1036
End Page
1040

Investigation of the physical aspects of beta imaging probes using scintillating fibers and visible light photon counters

We are developing a hand held imaging probe intended for intra-operative use. This probe is to be used after the bulk of tumor has been removed. It will locate residual malignant tissue labeled by a pre-operative injection of a tumor seeking radiopharmaceutical. The device presented here is a prototype system that consists of a 4 × 8 array of 925μm diameter plastic scintillating fibers. The imaging array is coupled to Visible Light Photon Counters (VLPCs) via 2 meters of optical fiber. We have obtained an intrinsic spatial resolution of 1.0 mm with a highly collimated beta source, and a 2.0 mm resolution with a 1 mm, uncollimated source. Standard deviations of the relative gain and sensitivity over the 32 imaging elements were found to be 9.6% and 11.7% of the mean, respectively.

Authors
MacDonald, LR; Tornai, MP; Levin, CS; Park, J; Atac, M; Cline, DB; Hoffman, EJ
MLA Citation
MacDonald, LR, Tornai, MP, Levin, CS, Park, J, Atac, M, Cline, DB, and Hoffman, EJ. "Investigation of the physical aspects of beta imaging probes using scintillating fibers and visible light photon counters." IEEE Nuclear Science Symposium & Medical Imaging Conference 3 (1995): 1380-1384.
Source
scival
Published In
IEEE Nuclear Science Symposium & Medical Imaging Conference
Volume
3
Publish Date
1995
Start Page
1380
End Page
1384

POSITIONING AND ENERGY RESPONSE OF PET BLOCK DETECTORS WITH DIFFERENT LIGHT SHARING SCHEMES

Authors
TORNAI, MP; GERMANO, G; HOFFMAN, EJ
MLA Citation
TORNAI, MP, GERMANO, G, and HOFFMAN, EJ. "POSITIONING AND ENERGY RESPONSE OF PET BLOCK DETECTORS WITH DIFFERENT LIGHT SHARING SCHEMES." IEEE TRANSACTIONS ON NUCLEAR SCIENCE 41.4 (August 1994): 1458-1463.
Source
wos-lite
Published In
IEEE Transactions on Nuclear Science
Volume
41
Issue
4
Publish Date
1994
Start Page
1458
End Page
1463
DOI
10.1109/23.322931

Effect of refraction index and light sharing on detector element identification for 2D detector modules in Positron Emission Tomography

Relationships among indices of refraction (n) of scintillation detectors, light sharing among discrete detector elements and accuracy of detector element identification in Positron Emission Tomography (PET) 2-D detector arrays were examined with theory and experiment. Mismatches between the index of refraction of scintillators and the glass of photomultipliers (PMT) were seen to lead to nonlinear relationships between crystal position and ratio (positioning) signals derived from PMTs. Insight is provided into the empirically derived use of light sharing among elements of the crystals in PET 2-D array detectors to compensate for this nonlinear response. © 1994.

Authors
Tornai, MP; Hoffman, EJ; Cherry, SR
MLA Citation
Tornai, MP, Hoffman, EJ, and Cherry, SR. "Effect of refraction index and light sharing on detector element identification for 2D detector modules in Positron Emission Tomography." Nuclear Inst. and Methods in Physics Research, A 348.2-3 (1994): 618-622.
Source
scival
Published In
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
Volume
348
Issue
2-3
Publish Date
1994
Start Page
618
End Page
622

Positioning and energy response of pet block detectors with different light sharing schemes

Two state-of-the-art modular PET block detectors using either discrete or pseudo-discrete BGO crystals coupled to two dual PMTs, utilizing different light sharing schemes, were evaluated. Both detectors were approximately 30 mm thick, while each element of the GE 6 × 6 block detector was 4 mm × 8.4 mm, and each element of the CTI 8 × 7 block detector was 2.8 mm × 5.8 mm. In addition to measurements with gamma sources, the detectors were also irradiated with a Sr/Y-90 beta source to evaluate the performance of the block detectors without inter-element scatter of annihilation photons. The best and worst energy resolutions of individual elements at 511 keV were 21.8% and 44.2% for the GE detector, and 22.7% and 42.5% for the CTI detector. The peak to valley ratios in the detector identification ratio histograms were generally better than 3 to 1. Measurements with beta sources indicate that light sharing in both detectors is a large component of event mispositioning along with inter-detector scatter of the annihilation photons.

Authors
Tornai, MP; Germano, G; Hoffman, EJ
MLA Citation
Tornai, MP, Germano, G, and Hoffman, EJ. "Positioning and energy response of pet block detectors with different light sharing schemes." IEEE Transactions on Nuclear Science 41.4 pt 1 (1994): 1458-1463.
Source
scival
Published In
IEEE Transactions on Nuclear Science
Volume
41
Issue
4 pt 1
Publish Date
1994
Start Page
1458
End Page
1463
DOI
10.1109/23.322931

Positioning and energy response of PET block detectors with different light sharing schemes

Two state-of-the-art modular PET block detectors using either discrete or pseudo-discrete BGO crystals coupled to two dual PMTs, utilizing different light sharing schemes, were evaluated. Both detectors were approximately 30 mm thick, while each element of the GE 6 × 6 block detector was 4 mm × 8.4 mm, and each element of the CTI 8 × 7 block detector was 2.8 mm × 5.8 mm. In addition to measurements with gamma sources, the detectors were also irradiated with a Sr/Y-90 beta source to evaluate the performance of the block detectors without inter-element scatter of annihilation photons. The best and worst energy resolutions of individual elements at 511 keV were 21.8% and 44.2% for the GE detector, and 22.7% and 42.5% for the CTI detector. The peak to valley ratios in the detector identification ratio histograms were generally better than 3 to 1. Measurements with beta sources indicate that light sharing in both detectors is a large component of event mispositioning along with inter-detector scatter of the annihilation photons.

Authors
Tornai, MP; Germano, G; Hoffman, EJ
MLA Citation
Tornai, MP, Germano, G, and Hoffman, EJ. "Positioning and energy response of PET block detectors with different light sharing schemes." IEEE Nuclear Science Symposium & Medical Imaging Conference pt 2 (1994): 1126-1130.
Source
scival
Published In
IEEE Nuclear Science Symposium & Medical Imaging Conference
Issue
pt 2
Publish Date
1994
Start Page
1126
End Page
1130

EFFECT OF INDEX OF REFRACTION ON DETECTOR ELEMENT IDENTIFICATION IN PET BLOCK DETECTORS

Authors
TORNAI, MP; HOFFMAN, EJ
MLA Citation
TORNAI, MP, and HOFFMAN, EJ. "EFFECT OF INDEX OF REFRACTION ON DETECTOR ELEMENT IDENTIFICATION IN PET BLOCK DETECTORS." JOURNAL OF NUCLEAR MEDICINE 34.5 (May 1993): P180-P180.
Source
wos-lite
Published In
Journal of nuclear medicine : official publication, Society of Nuclear Medicine
Volume
34
Issue
5
Publish Date
1993
Start Page
P180
End Page
P180

Detection and quantitation of 17F formation during the cyclotron production of 13N

The positron emitter 17F has been identified for the first time as a radioactive contaminant formed during 13N production. It was determined that 17F made up 18% of the short-lived radioactivity previously thought to be exclusively 15O. Mathematical deconvolution of decay curve data was employed as a complement to radioanalytical techniques. The nuclidic composition of the effluents from the proton bombardment of (a) water, (b) dilute ethanol and (c) 13C powder/water slurry was determined and compared with previous literature values. © 1992.

Authors
Tornai, M; Bishop, A; Satyamurthy, N; Kleck, J
MLA Citation
Tornai, M, Bishop, A, Satyamurthy, N, and Kleck, J. "Detection and quantitation of 17F formation during the cyclotron production of 13N." International Journal of Radiation Applications and Instrumentation. Part 43.7 (1992): 841-846.
PMID
1321098
Source
scival
Published In
International Journal of Radiation Applications and Instrumentation. Part A, Applied Radiation and Isotopes
Volume
43
Issue
7
Publish Date
1992
Start Page
841
End Page
846
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Research Areas:

  • Absorption
  • Algorithms
  • Biophysics
  • Breast
  • Breast Neoplasms
  • Calibration
  • Cesium
  • Computer Simulation
  • Computers
  • Cone-Beam Computed Tomography
  • Electrons
  • Equipment Design
  • Gamma Cameras
  • Humans
  • Image Interpretation, Computer-Assisted
  • Mammography
  • Miniaturization
  • Monitoring, Intraoperative
  • Phantoms, Imaging
  • Radiation Dosage
  • Radiographic Image Enhancement
  • Radiographic Image Interpretation, Computer-Assisted
  • Radiography
  • Radiography, Thoracic
  • Radiology
  • Research
  • Scattering, Radiation
  • Scintillation Counting
  • Scintillation cameras
  • Semiconductors
  • Sensitivity and Specificity
  • Stochastic Processes
  • Subtraction Technique
  • Systems Integration
  • Tissue Distribution
  • Tomography, Emission-Computed, Single-Photon
  • Tomography, X-Ray Computed
  • Tungsten
  • X-Ray Intensifying Screens
  • X-Rays