The Experts below are selected from a list of 195 Experts worldwide ranked by ideXlab platform
Michael A. King - One of the best experts on this subject based on the ideXlab platform.
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Estimation of attenuation maps from scatter and Photopeak window single photon-emission computed tomographic images of technetium 99m-labeled sestamibi☆☆☆
Journal of Nuclear Cardiology, 1997Co-Authors: Tinsu Pan, Michael A. King, S T Dahlberg, Der Shan Luo, B J VillegasAbstract:Background In single photon-emission computed tomographic imaging of the chest, nonuniform attenuation correction requires use of a patient-specific attenuation map. The aim of this study was to determine whether an estimate of the regions of the lungs and nonpulmonary tissues of the chest could be obtained by segmenting the Photopeak and Compton scatter window images in a phantom and in patients to estimate patient-specific attenuation maps.
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Segmentation of the Body and Lungs from Compton Scatter and Photopeak Window Data in SPECT
1996Co-Authors: Tinsu Pan, Michael A. King, D.j. De Vries, Michael LjungbergAbstract:In SPECT imaging of the chest, nonuniform attenu- ation correction requires use of a patient specific attenuation (p) map. Such a map can be obtained by estimating the regions of 1) the lungs and 2) the soft tissues and bones, and then assigning an appropriate value of attenuation coefficient (p) to each region. We proposed a method to segment such regions from the Compton scatter and Photopeak window SPECT slices of Tc-99m Sestamibi studies. The Compton scatter slices are used to segment the body outline and to estimate the regions of the lungs. Locations of the back bone and sternum are estimated from the Photopeak window slices to assist in the segmentation. To investigate the accuracy of using Compton scatter slices in estimating the regions of the body and the lungs, a Monte-Carlo SPECT simulation of an anthropomorphic phantom with an activity distribution and noise characteristics similar to patient data was conducted. Energy windows of various widths were simulated for use in locating a suitable Compton scatter window for imaging. The effects of attenuation correction using a p map based on segmentation were also studied. The results demonstrated for the activity and p maps studied herein that: 1) reasonable contrast could be obtained from Compton scatter data for the segmentation of the lung regions, 2) true positive rates of 99% and 89% for determining the body and lung regions, respectively, with total error rates of 4% and 29%, could be achieved, 3) usage of a p map based on segmentation for attenuation correction improved relative quantification over filtered backprojection, 4) variations in the assigned p value of 40% smaller or 40% larger in the lung regions had an insignificant impact on the results of relative quantification, 5) a wide energy window away from the Photopeak window for recording scattered events could benefit both the segmentation of the lung regions and the attenuation correction of the activity in the myocardium region, and 6) usage of a smaller
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Window Selection for Dual Photopeak Window Scatter Correction in Tc-99m
1994Co-Authors: Daniel J. De Vries, Michael A. KingAbstract:Abstmct-The width and placement of the windows for the dual Photopeak window (DPW) scatter subtraction method for Tc-99m imaging is investigated in order to obtain a method that is stable on a multihead detector system for single photon emission computed tomography (SPECT) and is capable of providing a good scatter estimate for extended objects. For various window pairs, stability and noise were examined with experiments using a SPECT system, while Monte Carlo simulations were used to predict the accuracy of scatter estimates for a variety of objects and to guide the development of regression relations for various window pairs. The DPW method that resulted from this study was implemented with a symmetric 20% Photopeak window composed of a 15% asymmetric Photopeak window and a 5% lower window abutted at 7 keV below the peak. A power function regression was used to relate the scatter-to-total ratio to the lower window-to-total ratio at each pixel, from which an estimated scatter image was calculated. DPW demonstrated good stability, achieved by abutting the two windows away from the peak. Performance was assessed and compared with Compton window subtraction (CWS). For simulated extended objects, DPW generally produced a less biased scatter estimate than the commonly used CWS method with k = 0.5. In aquisitions of a clinical SPECT phantom, contrast recovery was comparable for both DPW and CWS; however, DPW showed greater visual contrast in clinical SPECT bone studies.
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Window selection for dual Photopeak window scatter correction in Tc-99m imaging
IEEE Transactions on Nuclear Science, 1994Co-Authors: Daniel J. De Vries, Michael A. KingAbstract:The width and placement of the windows far the dual Photopeak window (DPW) scatter subtraction method for Tc-99m imaging is investigated in order to obtain a method that is stable on a multihead detector system for single photon emission computed tomography (SPECT) and is capable of providing a good scatter estimate for extended objects. For various window pairs, stability and noise were examined with experiments using a SPECT system, while Monte Carlo simulations were used to predict the accuracy of scatter estimates for a variety of objects and to guide the development of regression relations for various window pairs. The DPW method that resulted from this study was implemented with a symmetric 20% Photopeak window composed of a 15% asymmetric Photopeak window and a 5% lower, window abutted at 7 keV below the peak. A power function regression was used to relate the scatter-to-total ratio to the lower window-to-total ratio at each pixel, from which an estimated scatter image was calculated. DPW demonstrated good stability, achieved by abutting the two windows away from the peak. Performance was assessed and compared with Compton window subtraction (CWS). For simulated extended objects, DPW generally produced a less biased scatter estimate than the commonly used CWS method with k=0.5. In acquisitions of a clinical SPECT phantom, contrast recovery was comparable for both DPW and CWS; however, DPW showed greater visual contrast in clinical SPECT bone studies. >
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A Monte Carlo investigation of the dual Photopeak window scatter correction method (SPECT)
IEEE Transactions on Nuclear Science, 1993Co-Authors: George Hademenos, M. Ljungberg, Michael A. King, S.j. GlickAbstract:Results from a Monte Carlo investigation of the dual Photopeak window (DPW) scatter correction method are presented for point and extended sources of Tc-99m in both homogeneous and nonhomogeneous attenuating media. The DPW method uses the ratio of counts in two nonoverlapping energy windows within the Photopeak region as input to a regression relation. A pixel-by-pixel estimate of the scatter in the summed windows is obtained and subtracted to yield an estimate of the primary. An approximately tenfold decrease in the scatter fraction and an excellent agreement with the shape of the true scatter distribution were observed. >
N. S. Aly - One of the best experts on this subject based on the ideXlab platform.
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Direct Analytical Method to Calculate Photopeak Efficiency and Photopeak Attenuation Coefficient of NaI(Tl) Well-Type Detector
World Journal of Nuclear Science and Technology, 2016Co-Authors: Kholud. S. Almugren, Mahmoud I. Abbas, Eman M. El-bayoumi, N. S. AlyAbstract:In this paper full-energy peak (Photopeak) efficiency and Photopeak attenuation coefficient of 3'' × 3'' NaI(Tl) well-type scintillation detector were calculated using gamma-rayisotropic radiating point sources (with photon energy: 0.245, 0.344, 0.662, 0.779, 0.964, 1.1732, 1.333 and 1.408 MeV) placed outside the detector well. These energies were obtained from 152Eu, 137Cs and 60Co. The relations between the full energy peak efficiency and Photopeak attenuation coefficients, were plotted vs. photon energy at different sources to detector distance, and it found that the full energy peak efficiency decreased by increasing the distance between the source and the detector.
B J Villegas - One of the best experts on this subject based on the ideXlab platform.
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Estimation of attenuation maps from scatter and Photopeak window single photon-emission computed tomographic images of technetium 99m-labeled sestamibi.
Journal of nuclear cardiology : official publication of the American Society of Nuclear Cardiology, 1997Co-Authors: T S Pan, M A King, D S Luo, S T Dahlberg, B J VillegasAbstract:In single photon-emission computed tomographic imaging of the chest, nonuniform attenuation correction requires use of a patient-specific attenuation map. The aim of this study was to determine whether an estimate of the regions of the lungs and nonpulmonary tissues of the chest could be obtained by segmenting the Photopeak and Compton scatter window images in a phantom and in patients to estimate patient-specific attenuation maps. The Photopeak and scatter window slices from 16 consecutive 99mTc-labeled sestamibi perfusion studies were segmented interactively. In these studies, visually reasonable regions could be obtained by estimating a "cold" lung region from scatter window data with additional anatomic information of the myocardium region, the backbone and sternum locations, the liver, and the rib cage from the Photopeak window data. In an anthropomorphic torso phantom study and a patient study, comparison was made between the attenuation maps based on segmentation of the emission images and transmission imaging with a slant-hole collimator. It was determined that good agreement in the estimation of the body regions can be achieved with segmentation of the emission images in both the phantom and patient data. Attenuation correction using the maximum-likelihood expectation maximization method was performed on the phantom and the patient data. In both studies, attenuation correction with the segmented attenuation map improved uniformity of the inferior wall region in comparison with the other walls. The estimation of patient-specific attenuation maps by segmenting the scatter and Photopeak window slices of 99mTc-labeled sestamibi studies may be a way of reducing the loss of specificity due to attenuation artifacts. The potential limitations on the accuracy of correction inherent in the method due to the estimation of the regions and assignment of the attenuation coefficients need to be determined further, and the method needs to be further automated before it can be considered for routine clinical use.
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Estimation of attenuation maps from scatter and Photopeak window single photon-emission computed tomographic images of technetium 99m-labeled sestamibi☆☆☆
Journal of Nuclear Cardiology, 1997Co-Authors: Tinsu Pan, Michael A. King, S T Dahlberg, Der Shan Luo, B J VillegasAbstract:Background In single photon-emission computed tomographic imaging of the chest, nonuniform attenuation correction requires use of a patient-specific attenuation map. The aim of this study was to determine whether an estimate of the regions of the lungs and nonpulmonary tissues of the chest could be obtained by segmenting the Photopeak and Compton scatter window images in a phantom and in patients to estimate patient-specific attenuation maps.
Mahmoud I. Abbas - One of the best experts on this subject based on the ideXlab platform.
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Direct Analytical Method to Calculate Photopeak Efficiency and Photopeak Attenuation Coefficient of NaI(Tl) Well-Type Detector
World Journal of Nuclear Science and Technology, 2016Co-Authors: Kholud. S. Almugren, Mahmoud I. Abbas, Eman M. El-bayoumi, N. S. AlyAbstract:In this paper full-energy peak (Photopeak) efficiency and Photopeak attenuation coefficient of 3'' × 3'' NaI(Tl) well-type scintillation detector were calculated using gamma-rayisotropic radiating point sources (with photon energy: 0.245, 0.344, 0.662, 0.779, 0.964, 1.1732, 1.333 and 1.408 MeV) placed outside the detector well. These energies were obtained from 152Eu, 137Cs and 60Co. The relations between the full energy peak efficiency and Photopeak attenuation coefficients, were plotted vs. photon energy at different sources to detector distance, and it found that the full energy peak efficiency decreased by increasing the distance between the source and the detector.
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Direct mathematical calculation of the Photopeak efficiency for gamma rays in cylindrical NaI(Tl) detectors
AIP Conference Proceedings, 1999Co-Authors: Mahmoud I. Abbas, M. BassiouniAbstract:A direct mathematical formalism for the determination of the Photopeak (full energy peak) efficiency and the photofraction (peak to total ratio) of cylindrical (2R×L) NaI(Tl) scintillation detectors is deduced. The results have been compared with previous computational treatments. The comparison of our calculated data with the published experimental values shows a very satisfactory agreement in most of the practical energy region.
Kholud. S. Almugren - One of the best experts on this subject based on the ideXlab platform.
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Direct Analytical Method to Calculate Photopeak Efficiency and Photopeak Attenuation Coefficient of NaI(Tl) Well-Type Detector
World Journal of Nuclear Science and Technology, 2016Co-Authors: Kholud. S. Almugren, Mahmoud I. Abbas, Eman M. El-bayoumi, N. S. AlyAbstract:In this paper full-energy peak (Photopeak) efficiency and Photopeak attenuation coefficient of 3'' × 3'' NaI(Tl) well-type scintillation detector were calculated using gamma-rayisotropic radiating point sources (with photon energy: 0.245, 0.344, 0.662, 0.779, 0.964, 1.1732, 1.333 and 1.408 MeV) placed outside the detector well. These energies were obtained from 152Eu, 137Cs and 60Co. The relations between the full energy peak efficiency and Photopeak attenuation coefficients, were plotted vs. photon energy at different sources to detector distance, and it found that the full energy peak efficiency decreased by increasing the distance between the source and the detector.