B. Bendriem - Academia.edu (original) (raw)
Papers by B. Bendriem
1996 IEEE Nuclear Science Symposium. Conference Record, 1996
Using the Utah scatter phantom with different density media and activity proportions, we tested t... more Using the Utah scatter phantom with different density media and activity proportions, we tested the accuracy of quantification in the 2D and 3D modes of acquisition of the new ECAT Exact HR+ tomograph. The influence of radioactive sources outside the Field Of View (FOV) was also investigated, using different bed positions. We measured the activities in regions of interest drawn
Proceedings., International Conference on Image Processing, 1995
Presents a method to make dynamic image analysis by image fusion. This method is unsupervised and... more Presents a method to make dynamic image analysis by image fusion. This method is unsupervised and does not require previous knowledge of the number of relevant parameters as in statistical methods. It uses set operations to segment recursively a given region if at any following time this region appears not to be homogeneous. This algorithm has been tested with success
Physics in Medicine and Biology, 1995
Hybrid methods have been known for a long time as very efficient algorithms for attenuation corre... more Hybrid methods have been known for a long time as very efficient algorithms for attenuation correction in single-photon emission computed tomography, but only recently have efforts been made to formulate them with more rigorous mathematics. This has allowed us to explain their efficiency in terms of approximate inversion, and to establish a convergence condition. The present study focuses on the convergence problem and emphasizes the question of symmetry. Hybrid method operators are not symmetrical; therefore the convergence condition is not easily verified. New schemes based on a modified conjugate gradient method are presented. Convergence is proved and performances are shown to be at least as good as the standard hybrid schemes on perfect and noisy simulated data.
Journal of Cerebral Blood Flow & Metabolism, 1999
Several algorithms have been proposed to improve positron emission tomography quantification by c... more Several algorithms have been proposed to improve positron emission tomography quantification by combining anatomical and functional information in a pixel-by-pixel correction scheme. The precision of these methods when applied to real data depends on the precision of the manifold correction steps, such as full-width half-maximum modeling, magnetic resonance imaging-positron emission tomography registration, tissue segmentation, or background activity estimation. A good understanding of the influence of these parameters thus is critical to the effective use of the algorithms. In the current article, the authors present a monodimensional model that allows a simple theoretical and experimental evaluation of correction imprecision. The authors then assess correction robustness in three dimensions with computer simulations, and evaluate the validity of regional SD as a correction performance criterion.
IEEE Transactions on Nuclear Science, 1998
Using the Utah scatter phantom with media of different densities and activity proportions, the au... more Using the Utah scatter phantom with media of different densities and activity proportions, the authors tested the accuracy of quantitation in the two-dimensional (2-D) and three-dimensional (3-D) modes of acquisition of the ECAT EXACT HR+ tomograph. The influence of radioactive sources outside the field of view (FOV) was also investigated, using different bed positions. The authors measured the activities in
Journal of nuclear medicine : official publication, Society of Nuclear Medicine, 1996
PET is potentially very useful for the accurate in vivo quantitation of time-varying biological d... more PET is potentially very useful for the accurate in vivo quantitation of time-varying biological distributions of radiolabeled antibodies over several days. The short half-lives of most commonly used positron-emitting nuclides make them unsuitable for this purpose. Iodine-124 is a positron emitter with a half-life of 4.2 days and appropriate chemical properties. It has not been widely used because of a complex decay scheme including several high energy gamma rays. However, measurements made under realistic conditions on several different PET scanners have shown that satisfactory imaging and quantitation can be achieved. Whole-body and head-optimized scanners with different detectors (discrete BGO, block BGO and BaF2 time-of-flight), different septa and different correction schemes were used. Measurements of resolution, quantitative linearity and the ability to quantitatively image spheres of different sizes and activities in different background activities were made using phantoms. C...
The American journal of psychiatry, 1990
To assess the effects of chronic cocaine intoxication on dopamine receptors in human subjects, th... more To assess the effects of chronic cocaine intoxication on dopamine receptors in human subjects, the authors evaluated [18F]N-methylspiroperidol binding using positron emission tomography in 10 cocaine abusers and 10 normal control subjects. Cocaine abusers who had been detoxified for 1 week or less showed significantly lower values for uptake of [18F]N-methylspiroperidol in striatum than the normal subjects, whereas the cocaine abusers who had been detoxified for 1 month showed values comparable to those obtained from normal subjects. The authors conclude that postsynaptic dopamine receptor availability decreases with chronic cocaine abuse but may recover after a drug-free interval.
1996 IEEE Nuclear Science Symposium. Conference Record, 1996
The aim of this work was to optimize the [18F]FDG cerebral protocol for 3D PET acquisitions on th... more The aim of this work was to optimize the [18F]FDG cerebral protocol for 3D PET acquisitions on the EXACT HR+. We compared the noise equivalent counts (NEC) and the quantitation of 2D and 3D acquisitions both performed in 7 patients. The 2D and 3D scans were acquired sequentially during respectively 20 and 5 minutes after an injection of 160 to 255 MBq of [18F]FDG. A plasma input function was measured in three patients. The NEC analysis indicated that the optimal dose of [18F]FDG was close to 200 MBq for a 3D brain acquisition. Using this dose, a 3.5-fold increase in NEC was obtained in 3D compared to 2D allowing thus the acquisition time to be reduced to 6 minutes without any loss of NEC. First results in three subjects indicated slightly higher regional cerebral metabolism rate of the glucose (rCMRglc) in 3D than in 2D: the slope of the linear regression onto the 3D versus 2D rCMRglc values equaled 1.07±0.008, 1.04±0.006 and 1.07±0.005 (p<0.0001). The discrepancy between 2D and 3D values may be due in part to an overestimation of the scatter in 2D and to an undercorrection for the scatter component originating from out of FOV sources in 3D
![Research paper thumbnail of Regional distribution and kinetics of haloperidol binding in human brain: A pet study with [18F]haloperidol](https://attachments.academia-assets.com/46038504/thumbnails/1.jpg)
](Synapse, 1992
The regional distribution and the kinetics of haloperidol uptake in human brain were examined usi... more The regional distribution and the kinetics of haloperidol uptake in human brain were examined using [18Flhaloperidol and PET in 9 controls and 5 schizophrenics while on haloperidol medication and after haloperidol washout. The regional distribution of [lsFIN-methylspiroperidol, a tracer for D, receptors, was measured in 1 normal subject for comparison. The uptake of [lsFlhaloperidol in the whole brain in normals was high (6.6% of the injected dose at 2 hr), and regional distribution was much more extensive than could be accounted for by the distribution of dopamine D, receptors. In normals, the cerebellum, basal ganglia, and thalamus showed a greater concentration than the cortex, and there was minimal clearance of "F from the brain during the 10-hr period of the study. Medicated schizophrenics showed a total brain uptake of 4.0% and had a significant clearance of [lsF]haloperidol from brain and a higher concentration of [18F]haloperidol in plasma. After withdrawal from medication, [18Flhaloperidol clearance from brain became slower than while on medication. These results are discussed in terms of the pharmacokinetics of haloperidol in the human brain and its binding to dopamine D, receptors and to sigma receptors. o
Journal of Neuroscience Research, 1990
Muscarinic cholinergic M1 and M2 receptors in young and aged adult male volunteers were studied u... more Muscarinic cholinergic M1 and M2 receptors in young and aged adult male volunteers were studied using [N-11C-methyl]-benztropine, a specific muscarinic cholinergic receptor ligand, and high resolution positron emission tomography (PET). A regionally specific pattern of decreased binding was observed in aged volunteers. Using two separate methods of data analysis, thalamic, hippocampal and cerebellar regions showed no decreases in the apparent specific binding of [N-11C-methyl]-benztropine while frontal, parietal, temporal and occipital cortices as well as the corpus striatum showed age related changes in binding that declined (in 82 yrs old subject) to about 50% of the value obtained from the youngest volunteer (19 yrs). These data suggest that regions high in muscarinic receptor density, the corpus striatum and the cortical mantle, show a greater rate of decline than those areas that have a relatively low number of muscarinic receptors. Furthermore, this study demonstrates the usefulness of PET and [N-11C-methyl]-benztropine for assessing age related regional changes in muscarinic cholinergic receptor binding in the living human brain.
IEEE Transactions on Nuclear Science, 2001
Planar large field-of-view gamma camera detectors in coincidence imaging are characterized by a h... more Planar large field-of-view gamma camera detectors in coincidence imaging are characterized by a high singles count rate, leading to a high acquired random coincidence rate. The authors propose and compare two methods to correct the random coincidences that account for the variation of the random count rate during the detector rotation. One method consists of using a uniform distribution for
IEEE Transactions on Nuclear Science, 1998
In positron imaging, image quality depends on scatter, random and coincidence rate. It is known t... more In positron imaging, image quality depends on scatter, random and coincidence rate. It is known that noise equivalent count (NEC) rate is a good indicator of image quality and that it helps optimizing acquisition parameters. We measured the NEC curve with a SophyCamera DST (SMV) using a 20 cm cylinder phantom filled with 18F (59 MBq). The field of view
IEEE Transactions on Medical Imaging, 1991
The accurate measurement of the concentration of a radioisotope in small structures with positron... more The accurate measurement of the concentration of a radioisotope in small structures with positron emission tomography (PET) requires a correction for quantitation loss due to the partial volume effect and the effect of scattered radiation. To evaluate errors associated with measures in the human basal ganglia (BG), a unilateral model of the BG has been inserted in a 20-cm cylinder. The recovery coefficient (RC=measured activity/true activity) for the BG phantom has been measured on a CTI tomograph with different background concentrations (contrast) and at different axial locations in the gantry. The BG was visualized on four or five slices, depending on its position in the gantry and on the contrast used. The RC was 0.75 with no background (contrast equal to 1.0). Increasing the relative radioactivity concentration in the background increased the RC from 0.75 to 2.00 when the contrast was -0.7 (BG<background). The RC was also affected by the size and the shape of the region of interest (ROI) used (RC from 0.75 to 0.67 with ROI size from 0.12 to 1.41 cm(2)). These results show that accurate RC correction depends not only on the volume of the structure but also on its contrast with its surroundings, as well as on the selection of the ROI.
Proceedings of IEEE Symposium on Computer-Based Medical Systems (CBMS), 2000
1996 IEEE Nuclear Science Symposium. Conference Record, 1996
We present a new dynamic myocardial phantom designed to evaluate SPECT and PET imaging in systoli... more We present a new dynamic myocardial phantom designed to evaluate SPECT and PET imaging in systolic and diastolic conditions. The phantom includes a thoracic attenuating media and the myocardial wall thickness varying during the scan can be performed. In this study the phantom was used with three different wall thickness characteristic of a systolic, end-diastolic and pathologic end-diastolic condition. The myocardium was filled with ""' Tc, 18F and Gd and imaged by SPECT, PET and MRI. SPECT attenuation correction was performed using a modified PET transmission. A bull's eyes image was obtained for all data and wall ROI were then drawn for analysis. Using MRI ,as a reference, error from PET, SPECT and attenuation corrected SPECT were calculated. Systolic PET performances agree with MRI. Quantitation loss due to wall thickness reduction compared to the systole. Attenuation correction in SPECT leads to significant decrease of the error both in systole (from 29% to 14%) and diastole (35% to 22%). This is particulary sensitive for septum and inferior walls. SPECT residual errors (14% in systole and 22% in pathologic end-diastole) are likely caused by scatter, noise and depht dependant resolution effect. The results obtained with this dynamical phantom demonstrate the quantitation improvement achieved in SPECT with attenuation correction and also reinforce the need for variable resolution correction in addition to attenuation correc:tion.
2000 IEEE Nuclear Science Symposium. Conference Record (Cat. No.00CH37149), 2000
This aiticlc reports on PET-mode transaxial spatial rcsolution for a new hybrid PET/SPECT system.... more This aiticlc reports on PET-mode transaxial spatial rcsolution for a new hybrid PET/SPECT system. This systciii is based on a rotating dual-head tomograph using LSO/Nal scintillators and is capable of depth-of-interaction (DOI) measurement. For this LSO PET/SPECT, each detector head contains two 84x 120 planar arrays of crystalsone array NaI, the other LSO. LSO and Nal crystals are each 0 . 4 4~0 . 4 4~1 cm. In PET mode, each head is radially offset 36 cm from FOV center. Relative orientation of the two heads is 158 degrees. Dual-level DO[ discriminates LSO versus Nal by scintillation pulse decay time. While significant for good image resolution, dual-level DO1 isolates gamma detection only to the ( 1 cni) long axis depth of each individual crystal. Critical to delivery of excellent spatial resolution are additional methods to precisely characterize the depth of the centroid of the probability of gamma interaction along the crystal long axis. This depth is measured to +/-0.01 cm for each of 4 planar arrays and applied for more accurate LOR positioning in super-fast real-time rebinning hardware. With DO1 and measured centroid depth applied, FWHM transaxial spatial resolution is 0.4 cm at FOV center and 0.6 cm at I O cni off center. Without DOI, resolution degrades as much as 33%.
2000 IEEE Nuclear Science Symposium. Conference Record (Cat. No.00CH37149), 2000
In this work the authors compare the impact of the acquisition mode (2D vs. 3D) on the performanc... more In this work the authors compare the impact of the acquisition mode (2D vs. 3D) on the performance of human observers in detecting and localizing tumors. They use a non-Monte Carlo simulator to rapidly generate multiple realizations of ideal data with added spherical lesions and with accurate noise properties, thus avoiding the confounding effect of residual biases. The simulated 2D
Medical Imaging 1994: Image Processing, 1994
ABSTRACT
IEEE Symposium Conference Record Nuclear Science 2004., 2004
In Positron Emission Tomography (PET) the concept of Noise Equivalent Count Rate (NEC) is a measu... more In Positron Emission Tomography (PET) the concept of Noise Equivalent Count Rate (NEC) is a measure of image quality. It has been shown that the local signal-to-noise ratio in the images reflects the global signal-to-noise ratio, which, in turn, can be related to the NEC. Factors that affect the NEC include the scanner geometry and scintillator material. The peak NEC has long been considered an indicator of PET scanner performance, whereas the sensitivity, represented by the slope of the NEC curve at the origin is equally important. This initial slope is proportional to the true coincidence sensitivity times the factor (1-SF), where SF is the scatter fraction. The peak NEC value is a strong function of scanner geometry and scintillator material, scatter fraction, system dead time and random coincidence fraction. The scatter fraction depends mainly on the low level discriminator setting of the system. Access to time-offlight information may have a strong impact on the signal-tonoise properties and hence on the NEC performance. However, this work will focus specifically on the effect of the scintillator properties on the NEC, in particular the stopping power, light output, decay time and the interaction with the electronics. Three scintillators have been compared, the standard BGO, the fast high density LSO and a new fast, high light yield scintillator LaBr 3 . The scintillators have been compared for the fixed scanner geometry of the ECAT EXACT.
1996 IEEE Nuclear Science Symposium. Conference Record, 1996
Using the Utah scatter phantom with different density media and activity proportions, we tested t... more Using the Utah scatter phantom with different density media and activity proportions, we tested the accuracy of quantification in the 2D and 3D modes of acquisition of the new ECAT Exact HR+ tomograph. The influence of radioactive sources outside the Field Of View (FOV) was also investigated, using different bed positions. We measured the activities in regions of interest drawn
Proceedings., International Conference on Image Processing, 1995
Presents a method to make dynamic image analysis by image fusion. This method is unsupervised and... more Presents a method to make dynamic image analysis by image fusion. This method is unsupervised and does not require previous knowledge of the number of relevant parameters as in statistical methods. It uses set operations to segment recursively a given region if at any following time this region appears not to be homogeneous. This algorithm has been tested with success
Physics in Medicine and Biology, 1995
Hybrid methods have been known for a long time as very efficient algorithms for attenuation corre... more Hybrid methods have been known for a long time as very efficient algorithms for attenuation correction in single-photon emission computed tomography, but only recently have efforts been made to formulate them with more rigorous mathematics. This has allowed us to explain their efficiency in terms of approximate inversion, and to establish a convergence condition. The present study focuses on the convergence problem and emphasizes the question of symmetry. Hybrid method operators are not symmetrical; therefore the convergence condition is not easily verified. New schemes based on a modified conjugate gradient method are presented. Convergence is proved and performances are shown to be at least as good as the standard hybrid schemes on perfect and noisy simulated data.
Journal of Cerebral Blood Flow & Metabolism, 1999
Several algorithms have been proposed to improve positron emission tomography quantification by c... more Several algorithms have been proposed to improve positron emission tomography quantification by combining anatomical and functional information in a pixel-by-pixel correction scheme. The precision of these methods when applied to real data depends on the precision of the manifold correction steps, such as full-width half-maximum modeling, magnetic resonance imaging-positron emission tomography registration, tissue segmentation, or background activity estimation. A good understanding of the influence of these parameters thus is critical to the effective use of the algorithms. In the current article, the authors present a monodimensional model that allows a simple theoretical and experimental evaluation of correction imprecision. The authors then assess correction robustness in three dimensions with computer simulations, and evaluate the validity of regional SD as a correction performance criterion.
IEEE Transactions on Nuclear Science, 1998
Using the Utah scatter phantom with media of different densities and activity proportions, the au... more Using the Utah scatter phantom with media of different densities and activity proportions, the authors tested the accuracy of quantitation in the two-dimensional (2-D) and three-dimensional (3-D) modes of acquisition of the ECAT EXACT HR+ tomograph. The influence of radioactive sources outside the field of view (FOV) was also investigated, using different bed positions. The authors measured the activities in
Journal of nuclear medicine : official publication, Society of Nuclear Medicine, 1996
PET is potentially very useful for the accurate in vivo quantitation of time-varying biological d... more PET is potentially very useful for the accurate in vivo quantitation of time-varying biological distributions of radiolabeled antibodies over several days. The short half-lives of most commonly used positron-emitting nuclides make them unsuitable for this purpose. Iodine-124 is a positron emitter with a half-life of 4.2 days and appropriate chemical properties. It has not been widely used because of a complex decay scheme including several high energy gamma rays. However, measurements made under realistic conditions on several different PET scanners have shown that satisfactory imaging and quantitation can be achieved. Whole-body and head-optimized scanners with different detectors (discrete BGO, block BGO and BaF2 time-of-flight), different septa and different correction schemes were used. Measurements of resolution, quantitative linearity and the ability to quantitatively image spheres of different sizes and activities in different background activities were made using phantoms. C...
The American journal of psychiatry, 1990
To assess the effects of chronic cocaine intoxication on dopamine receptors in human subjects, th... more To assess the effects of chronic cocaine intoxication on dopamine receptors in human subjects, the authors evaluated [18F]N-methylspiroperidol binding using positron emission tomography in 10 cocaine abusers and 10 normal control subjects. Cocaine abusers who had been detoxified for 1 week or less showed significantly lower values for uptake of [18F]N-methylspiroperidol in striatum than the normal subjects, whereas the cocaine abusers who had been detoxified for 1 month showed values comparable to those obtained from normal subjects. The authors conclude that postsynaptic dopamine receptor availability decreases with chronic cocaine abuse but may recover after a drug-free interval.
1996 IEEE Nuclear Science Symposium. Conference Record, 1996
The aim of this work was to optimize the [18F]FDG cerebral protocol for 3D PET acquisitions on th... more The aim of this work was to optimize the [18F]FDG cerebral protocol for 3D PET acquisitions on the EXACT HR+. We compared the noise equivalent counts (NEC) and the quantitation of 2D and 3D acquisitions both performed in 7 patients. The 2D and 3D scans were acquired sequentially during respectively 20 and 5 minutes after an injection of 160 to 255 MBq of [18F]FDG. A plasma input function was measured in three patients. The NEC analysis indicated that the optimal dose of [18F]FDG was close to 200 MBq for a 3D brain acquisition. Using this dose, a 3.5-fold increase in NEC was obtained in 3D compared to 2D allowing thus the acquisition time to be reduced to 6 minutes without any loss of NEC. First results in three subjects indicated slightly higher regional cerebral metabolism rate of the glucose (rCMRglc) in 3D than in 2D: the slope of the linear regression onto the 3D versus 2D rCMRglc values equaled 1.07±0.008, 1.04±0.006 and 1.07±0.005 (p<0.0001). The discrepancy between 2D and 3D values may be due in part to an overestimation of the scatter in 2D and to an undercorrection for the scatter component originating from out of FOV sources in 3D
Synapse, 1992
The regional distribution and the kinetics of haloperidol uptake in human brain were examined usi... more The regional distribution and the kinetics of haloperidol uptake in human brain were examined using [18Flhaloperidol and PET in 9 controls and 5 schizophrenics while on haloperidol medication and after haloperidol washout. The regional distribution of [lsFIN-methylspiroperidol, a tracer for D, receptors, was measured in 1 normal subject for comparison. The uptake of [lsFlhaloperidol in the whole brain in normals was high (6.6% of the injected dose at 2 hr), and regional distribution was much more extensive than could be accounted for by the distribution of dopamine D, receptors. In normals, the cerebellum, basal ganglia, and thalamus showed a greater concentration than the cortex, and there was minimal clearance of "F from the brain during the 10-hr period of the study. Medicated schizophrenics showed a total brain uptake of 4.0% and had a significant clearance of [lsF]haloperidol from brain and a higher concentration of [18F]haloperidol in plasma. After withdrawal from medication, [18Flhaloperidol clearance from brain became slower than while on medication. These results are discussed in terms of the pharmacokinetics of haloperidol in the human brain and its binding to dopamine D, receptors and to sigma receptors. o
Journal of Neuroscience Research, 1990
Muscarinic cholinergic M1 and M2 receptors in young and aged adult male volunteers were studied u... more Muscarinic cholinergic M1 and M2 receptors in young and aged adult male volunteers were studied using [N-11C-methyl]-benztropine, a specific muscarinic cholinergic receptor ligand, and high resolution positron emission tomography (PET). A regionally specific pattern of decreased binding was observed in aged volunteers. Using two separate methods of data analysis, thalamic, hippocampal and cerebellar regions showed no decreases in the apparent specific binding of [N-11C-methyl]-benztropine while frontal, parietal, temporal and occipital cortices as well as the corpus striatum showed age related changes in binding that declined (in 82 yrs old subject) to about 50% of the value obtained from the youngest volunteer (19 yrs). These data suggest that regions high in muscarinic receptor density, the corpus striatum and the cortical mantle, show a greater rate of decline than those areas that have a relatively low number of muscarinic receptors. Furthermore, this study demonstrates the usefulness of PET and [N-11C-methyl]-benztropine for assessing age related regional changes in muscarinic cholinergic receptor binding in the living human brain.
IEEE Transactions on Nuclear Science, 2001
Planar large field-of-view gamma camera detectors in coincidence imaging are characterized by a h... more Planar large field-of-view gamma camera detectors in coincidence imaging are characterized by a high singles count rate, leading to a high acquired random coincidence rate. The authors propose and compare two methods to correct the random coincidences that account for the variation of the random count rate during the detector rotation. One method consists of using a uniform distribution for
IEEE Transactions on Nuclear Science, 1998
In positron imaging, image quality depends on scatter, random and coincidence rate. It is known t... more In positron imaging, image quality depends on scatter, random and coincidence rate. It is known that noise equivalent count (NEC) rate is a good indicator of image quality and that it helps optimizing acquisition parameters. We measured the NEC curve with a SophyCamera DST (SMV) using a 20 cm cylinder phantom filled with 18F (59 MBq). The field of view
IEEE Transactions on Medical Imaging, 1991
The accurate measurement of the concentration of a radioisotope in small structures with positron... more The accurate measurement of the concentration of a radioisotope in small structures with positron emission tomography (PET) requires a correction for quantitation loss due to the partial volume effect and the effect of scattered radiation. To evaluate errors associated with measures in the human basal ganglia (BG), a unilateral model of the BG has been inserted in a 20-cm cylinder. The recovery coefficient (RC=measured activity/true activity) for the BG phantom has been measured on a CTI tomograph with different background concentrations (contrast) and at different axial locations in the gantry. The BG was visualized on four or five slices, depending on its position in the gantry and on the contrast used. The RC was 0.75 with no background (contrast equal to 1.0). Increasing the relative radioactivity concentration in the background increased the RC from 0.75 to 2.00 when the contrast was -0.7 (BG<background). The RC was also affected by the size and the shape of the region of interest (ROI) used (RC from 0.75 to 0.67 with ROI size from 0.12 to 1.41 cm(2)). These results show that accurate RC correction depends not only on the volume of the structure but also on its contrast with its surroundings, as well as on the selection of the ROI.
Proceedings of IEEE Symposium on Computer-Based Medical Systems (CBMS), 2000
1996 IEEE Nuclear Science Symposium. Conference Record, 1996
We present a new dynamic myocardial phantom designed to evaluate SPECT and PET imaging in systoli... more We present a new dynamic myocardial phantom designed to evaluate SPECT and PET imaging in systolic and diastolic conditions. The phantom includes a thoracic attenuating media and the myocardial wall thickness varying during the scan can be performed. In this study the phantom was used with three different wall thickness characteristic of a systolic, end-diastolic and pathologic end-diastolic condition. The myocardium was filled with ""' Tc, 18F and Gd and imaged by SPECT, PET and MRI. SPECT attenuation correction was performed using a modified PET transmission. A bull's eyes image was obtained for all data and wall ROI were then drawn for analysis. Using MRI ,as a reference, error from PET, SPECT and attenuation corrected SPECT were calculated. Systolic PET performances agree with MRI. Quantitation loss due to wall thickness reduction compared to the systole. Attenuation correction in SPECT leads to significant decrease of the error both in systole (from 29% to 14%) and diastole (35% to 22%). This is particulary sensitive for septum and inferior walls. SPECT residual errors (14% in systole and 22% in pathologic end-diastole) are likely caused by scatter, noise and depht dependant resolution effect. The results obtained with this dynamical phantom demonstrate the quantitation improvement achieved in SPECT with attenuation correction and also reinforce the need for variable resolution correction in addition to attenuation correc:tion.
2000 IEEE Nuclear Science Symposium. Conference Record (Cat. No.00CH37149), 2000
This aiticlc reports on PET-mode transaxial spatial rcsolution for a new hybrid PET/SPECT system.... more This aiticlc reports on PET-mode transaxial spatial rcsolution for a new hybrid PET/SPECT system. This systciii is based on a rotating dual-head tomograph using LSO/Nal scintillators and is capable of depth-of-interaction (DOI) measurement. For this LSO PET/SPECT, each detector head contains two 84x 120 planar arrays of crystalsone array NaI, the other LSO. LSO and Nal crystals are each 0 . 4 4~0 . 4 4~1 cm. In PET mode, each head is radially offset 36 cm from FOV center. Relative orientation of the two heads is 158 degrees. Dual-level DO[ discriminates LSO versus Nal by scintillation pulse decay time. While significant for good image resolution, dual-level DO1 isolates gamma detection only to the ( 1 cni) long axis depth of each individual crystal. Critical to delivery of excellent spatial resolution are additional methods to precisely characterize the depth of the centroid of the probability of gamma interaction along the crystal long axis. This depth is measured to +/-0.01 cm for each of 4 planar arrays and applied for more accurate LOR positioning in super-fast real-time rebinning hardware. With DO1 and measured centroid depth applied, FWHM transaxial spatial resolution is 0.4 cm at FOV center and 0.6 cm at I O cni off center. Without DOI, resolution degrades as much as 33%.
2000 IEEE Nuclear Science Symposium. Conference Record (Cat. No.00CH37149), 2000
In this work the authors compare the impact of the acquisition mode (2D vs. 3D) on the performanc... more In this work the authors compare the impact of the acquisition mode (2D vs. 3D) on the performance of human observers in detecting and localizing tumors. They use a non-Monte Carlo simulator to rapidly generate multiple realizations of ideal data with added spherical lesions and with accurate noise properties, thus avoiding the confounding effect of residual biases. The simulated 2D
Medical Imaging 1994: Image Processing, 1994
ABSTRACT
IEEE Symposium Conference Record Nuclear Science 2004., 2004
In Positron Emission Tomography (PET) the concept of Noise Equivalent Count Rate (NEC) is a measu... more In Positron Emission Tomography (PET) the concept of Noise Equivalent Count Rate (NEC) is a measure of image quality. It has been shown that the local signal-to-noise ratio in the images reflects the global signal-to-noise ratio, which, in turn, can be related to the NEC. Factors that affect the NEC include the scanner geometry and scintillator material. The peak NEC has long been considered an indicator of PET scanner performance, whereas the sensitivity, represented by the slope of the NEC curve at the origin is equally important. This initial slope is proportional to the true coincidence sensitivity times the factor (1-SF), where SF is the scatter fraction. The peak NEC value is a strong function of scanner geometry and scintillator material, scatter fraction, system dead time and random coincidence fraction. The scatter fraction depends mainly on the low level discriminator setting of the system. Access to time-offlight information may have a strong impact on the signal-tonoise properties and hence on the NEC performance. However, this work will focus specifically on the effect of the scintillator properties on the NEC, in particular the stopping power, light output, decay time and the interaction with the electronics. Three scintillators have been compared, the standard BGO, the fast high density LSO and a new fast, high light yield scintillator LaBr 3 . The scintillators have been compared for the fixed scanner geometry of the ECAT EXACT.