Pub Date : 1995-10-21DOI: 10.1109/NSSMIC.1995.500255
R. Freifelder, J. Karp
The authors present a design of a PET scanner dedicated to breast imaging. The scanner uses two 2-dimensional position sensitive NaI(Tl) detectors, each with 16 PMTs, placed above and below the breast to detect tumors. The design combines high spatial resolution (3.5 mm) to detect small tumors (/spl ap/0.1 cc), high sensitivity and good energy resolution to suppress scatter background and to detect low contrast masses. Additional views of the breast and lymph nodes will be possible. Simulations show that the proposed design has better lesion detectability than a general purpose whole-body PET scanner. Detector thickness, position algorithms, surface treatments of the NaI(Tl) and PMT arrangements will ensure good performance under high countrate conditions and particularly at the edges of the detector closest to the body. A preliminary investigation of different iterative reconstruction algorithms with limited angle datasets show promise in obtaining good image quality and tumor detectability, the scanner's primary design goals. Simulation results are compared to preliminary phantom measurements.
{"title":"A dedicated PET scanner for breast cancer","authors":"R. Freifelder, J. Karp","doi":"10.1109/NSSMIC.1995.500255","DOIUrl":"https://doi.org/10.1109/NSSMIC.1995.500255","url":null,"abstract":"The authors present a design of a PET scanner dedicated to breast imaging. The scanner uses two 2-dimensional position sensitive NaI(Tl) detectors, each with 16 PMTs, placed above and below the breast to detect tumors. The design combines high spatial resolution (3.5 mm) to detect small tumors (/spl ap/0.1 cc), high sensitivity and good energy resolution to suppress scatter background and to detect low contrast masses. Additional views of the breast and lymph nodes will be possible. Simulations show that the proposed design has better lesion detectability than a general purpose whole-body PET scanner. Detector thickness, position algorithms, surface treatments of the NaI(Tl) and PMT arrangements will ensure good performance under high countrate conditions and particularly at the edges of the detector closest to the body. A preliminary investigation of different iterative reconstruction algorithms with limited angle datasets show promise in obtaining good image quality and tumor detectability, the scanner's primary design goals. Simulation results are compared to preliminary phantom measurements.","PeriodicalId":409998,"journal":{"name":"1995 IEEE Nuclear Science Symposium and Medical Imaging Conference Record","volume":"73 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122789705","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1995-10-21DOI: 10.1109/NSSMIC.1995.510369
B. Baumbaugh, J. Bishop, N. Biswas, L. Coney, J. Marchant, E. Masterson, R. Ruchti, T. Stavish, J. Warchoł, M. Wayne
We have designed, constructed, and operated a small cryostem which supports the operation of 32 channels of visible light photon counters (HISTE-IV VLPCs). The VLPCs are situated within a small enclosure which can be lowered into a 30-100 liter dewar. The enthalpy of the boil-off helium keeps the VLPCs cold, and allows the system to be operated with stability for many days within the desired temperature range of 6.0 K-7.5 K. The cryostem is instrumented with clear fiber waveguides which transport the light from an optical connector situated at the top of the cryostem and outside of the dewar to the photosensors at cryogenic temperatures within the dewar. Electrical signals from the VLPCs are amplified at room temperature using QPA02 preamplifiers. Details of design and performance are reviewed.
我们设计、构建并运行了一个支持32通道可见光光子计数器(hste - iv vlpc)操作的小型系统。vlpc位于一个小的外壳内，可以降低到30-100升杜瓦瓶。蒸发氦的焓使vlpc保持低温，并允许系统在6.0 K-7.5 K的期望温度范围内稳定运行许多天。该系统配备了透明光纤波导，它将光从位于系统顶部和杜瓦瓶外部的光学连接器传输到杜瓦瓶内低温下的光传感器。来自vlpc的电信号在室温下使用QPA02前置放大器进行放大。详细的设计和性能进行了审查。
{"title":"Small cryostem for operation of visible light photon counters (VLPC)","authors":"B. Baumbaugh, J. Bishop, N. Biswas, L. Coney, J. Marchant, E. Masterson, R. Ruchti, T. Stavish, J. Warchoł, M. Wayne","doi":"10.1109/NSSMIC.1995.510369","DOIUrl":"https://doi.org/10.1109/NSSMIC.1995.510369","url":null,"abstract":"We have designed, constructed, and operated a small cryostem which supports the operation of 32 channels of visible light photon counters (HISTE-IV VLPCs). The VLPCs are situated within a small enclosure which can be lowered into a 30-100 liter dewar. The enthalpy of the boil-off helium keeps the VLPCs cold, and allows the system to be operated with stability for many days within the desired temperature range of 6.0 K-7.5 K. The cryostem is instrumented with clear fiber waveguides which transport the light from an optical connector situated at the top of the cryostem and outside of the dewar to the photosensors at cryogenic temperatures within the dewar. Electrical signals from the VLPCs are amplified at room temperature using QPA02 preamplifiers. Details of design and performance are reviewed.","PeriodicalId":409998,"journal":{"name":"1995 IEEE Nuclear Science Symposium and Medical Imaging Conference Record","volume":"272 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122831220","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1995-10-21DOI: 10.1109/NSSMIC.1995.504323
E. Beuville, P. Barale, F. Bieser, W. Hearn, S. Klein, M. Lisa, T. Noggle, H. Ritter, C. Vu, H. Wieman
A 16 channel low noise amplifier shaper has been designed for the STAR particle detector of the RHIC accelerator. The STAR Amplifier-Shaper (SAS) includes a pole/zero network which cancels the long tail of the Time Projection Chamber (TPC) signal. The tail correction can be adjusted depending on the type of gas used in the TPC. The SAS equivalent noise charge is 900 e/sub RMS//sup -/,, with 25 pf detector capacitance (the test board having 7.7 pF of parasitic capacitance), and with 80 ns shaping time (step response). The measured noise slope is 13.7 e/sub RMS//sup -//pF. The shaper pulse FWHM is adjusted at 180 ns (detector response) with /spl plusmn/4% variation over the entire dynamic range. The shaping time and the tail correction are adjusted with external voltages using MOS resistors. The gain is 16 mV/fC with a linearity of 4%. The crosstalk is about 0.36% which have a negligible effect on the position resolution. The circuit also includes an on-chip calibration system in which the test input charge is controlled by a DC voltage. The output buffer drives a 2 V swing on 50 pF output load for a total power consumption of less than 750 mW (/spl plusmn/5 Volt supply). On-chip protection diodes have also been integrated. The full custom chip has been integrated in the CMOS ORBIT 1.2 /spl mu/m technology with double polysilicon capacitors.
{"title":"A low noise amplifier-shaper with tail correction for the STAR detector","authors":"E. Beuville, P. Barale, F. Bieser, W. Hearn, S. Klein, M. Lisa, T. Noggle, H. Ritter, C. Vu, H. Wieman","doi":"10.1109/NSSMIC.1995.504323","DOIUrl":"https://doi.org/10.1109/NSSMIC.1995.504323","url":null,"abstract":"A 16 channel low noise amplifier shaper has been designed for the STAR particle detector of the RHIC accelerator. The STAR Amplifier-Shaper (SAS) includes a pole/zero network which cancels the long tail of the Time Projection Chamber (TPC) signal. The tail correction can be adjusted depending on the type of gas used in the TPC. The SAS equivalent noise charge is 900 e/sub RMS//sup -/,, with 25 pf detector capacitance (the test board having 7.7 pF of parasitic capacitance), and with 80 ns shaping time (step response). The measured noise slope is 13.7 e/sub RMS//sup -//pF. The shaper pulse FWHM is adjusted at 180 ns (detector response) with /spl plusmn/4% variation over the entire dynamic range. The shaping time and the tail correction are adjusted with external voltages using MOS resistors. The gain is 16 mV/fC with a linearity of 4%. The crosstalk is about 0.36% which have a negligible effect on the position resolution. The circuit also includes an on-chip calibration system in which the test input charge is controlled by a DC voltage. The output buffer drives a 2 V swing on 50 pF output load for a total power consumption of less than 750 mW (/spl plusmn/5 Volt supply). On-chip protection diodes have also been integrated. The full custom chip has been integrated in the CMOS ORBIT 1.2 /spl mu/m technology with double polysilicon capacitors.","PeriodicalId":409998,"journal":{"name":"1995 IEEE Nuclear Science Symposium and Medical Imaging Conference Record","volume":"48 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130193834","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1995-10-21DOI: 10.1109/NSSMIC.1995.500275
G. Klein, X. Teng, B. Reutter, R. Huesman, W. Jagust, T. Budinger
Volume of interest extraction for radionuclide and anatomical measurements requires correct identification of the anatomical feature being studied. We have developed a toolset for specifying 3D volumes-of-interest (VOIs) on a multislice Positron Emission Tomography (PET) dataset. The software is particularly suited for specifying cerebral cortex VOIs that represent a particular gyrus or mid-brain structure. A registered 3D magnetic resonance image (MRI) dataset is used to provide high-resolution anatomical information, both as oblique 2D sections and as volume renderings of a segmented cortical surface. Because most clinicians can readily identify specific sulci from high-quality renderings of the cortical surface, a crucial step in quickly identifying sulci in 2D sectional data is providing a feedback mechanism between the renderings and the section data. Our toolkit provides this mechanism by calculating a full depth map and transformation matrix for volume renderings of the cortex. A region drawing environment is then possible where the position of a main drawing cursor on a 2D section can be simultaneously mirrored on the rendered views. The feedback is further enhanced by displaying the projection of the main cursor position on any number of auxiliary 2D sections oriented at orthogonal slicing angles with respect to the principal 2D section. Complete VOIs are specified by drawing a stack of 2D contours subsequently filed together to form closed triangular mesh surface models.
{"title":"A 3D navigational environment for specifying positron emission tomography volumes-of-interest","authors":"G. Klein, X. Teng, B. Reutter, R. Huesman, W. Jagust, T. Budinger","doi":"10.1109/NSSMIC.1995.500275","DOIUrl":"https://doi.org/10.1109/NSSMIC.1995.500275","url":null,"abstract":"Volume of interest extraction for radionuclide and anatomical measurements requires correct identification of the anatomical feature being studied. We have developed a toolset for specifying 3D volumes-of-interest (VOIs) on a multislice Positron Emission Tomography (PET) dataset. The software is particularly suited for specifying cerebral cortex VOIs that represent a particular gyrus or mid-brain structure. A registered 3D magnetic resonance image (MRI) dataset is used to provide high-resolution anatomical information, both as oblique 2D sections and as volume renderings of a segmented cortical surface. Because most clinicians can readily identify specific sulci from high-quality renderings of the cortical surface, a crucial step in quickly identifying sulci in 2D sectional data is providing a feedback mechanism between the renderings and the section data. Our toolkit provides this mechanism by calculating a full depth map and transformation matrix for volume renderings of the cortex. A region drawing environment is then possible where the position of a main drawing cursor on a 2D section can be simultaneously mirrored on the rendered views. The feedback is further enhanced by displaying the projection of the main cursor position on any number of auxiliary 2D sections oriented at orthogonal slicing angles with respect to the principal 2D section. Complete VOIs are specified by drawing a stack of 2D contours subsequently filed together to form closed triangular mesh surface models.","PeriodicalId":409998,"journal":{"name":"1995 IEEE Nuclear Science Symposium and Medical Imaging Conference Record","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133123662","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1995-10-21DOI: 10.1109/NSSMIC.1995.510479
R. Guillemaud, P. Hugonnard, R. Sauze, P. Grangeat
Attenuation compensation is an important issue for SPECT imaging. For this purpose transmission measurements can be acquired on a gamma, but the acquisitions are usually truncated. The truncation results in large artifacts in the attenuation map when reconstructed with usual filtered-backprojection algorithms. These artifacts prevents good attenuation correction of emission map. The authors propose a new efficient method for truncation correction which is based on an iterative reconstruction/reprojection algorithm using extended projections and constraints on the reconstructed map. Extended projections are a combination of truncated and reprojected projections with a continuity constraint at the truncation edge. The constraints on the attenuation map are based on object model. The first one is a large elliptical model, with positivity constraints. During the iterative reconstruction process, the model is refined to a have geometric shape closer to the patient's outline. The refining is an active contour segmentation technique. Additional constraints on the attenuation factors can finally be incorporated. Results on truncation correction obtained for simulated and experimental data are presented and the effect on attenuation compensation in emission reconstruction is discussed.
{"title":"Truncation artifact correction of attenuation map with iterative and model based reconstruction","authors":"R. Guillemaud, P. Hugonnard, R. Sauze, P. Grangeat","doi":"10.1109/NSSMIC.1995.510479","DOIUrl":"https://doi.org/10.1109/NSSMIC.1995.510479","url":null,"abstract":"Attenuation compensation is an important issue for SPECT imaging. For this purpose transmission measurements can be acquired on a gamma, but the acquisitions are usually truncated. The truncation results in large artifacts in the attenuation map when reconstructed with usual filtered-backprojection algorithms. These artifacts prevents good attenuation correction of emission map. The authors propose a new efficient method for truncation correction which is based on an iterative reconstruction/reprojection algorithm using extended projections and constraints on the reconstructed map. Extended projections are a combination of truncated and reprojected projections with a continuity constraint at the truncation edge. The constraints on the attenuation map are based on object model. The first one is a large elliptical model, with positivity constraints. During the iterative reconstruction process, the model is refined to a have geometric shape closer to the patient's outline. The refining is an active contour segmentation technique. Additional constraints on the attenuation factors can finally be incorporated. Results on truncation correction obtained for simulated and experimental data are presented and the effect on attenuation compensation in emission reconstruction is discussed.","PeriodicalId":409998,"journal":{"name":"1995 IEEE Nuclear Science Symposium and Medical Imaging Conference Record","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133778392","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1995-10-21DOI: 10.1109/NSSMIC.1995.500265
M.X.H. Yan, J. Karp
An algorithm is described for estimating attenuation length in 3D from sinogram or projection data, by which 3D attenuation correction can be performed in brain PET imaging for given attenuation coefficients. The algorithm begins with the estimation of scalp contours from sinogram data, based on optimal thresholding, spline smoothing and interpolation and backprojection. A cubic B-spline surface is then introduced to accurately describe the scalp surface by the least squares fitting to the stacked 2D estimated scalp contours. Due to the use of this surface model, an efficient and accurate technique is developed for estimation of a distance between two intersecting points formed by an arbitrary projection ray and the scalp surface. This fully automated and fast algorithm has been applied to sinogram and projection data collected using PENN-PET scanners. It has the potential to be used in routine clinical PET imaging.
{"title":"A fully automated algorithm for estimating attenuation length in 3D from projection data","authors":"M.X.H. Yan, J. Karp","doi":"10.1109/NSSMIC.1995.500265","DOIUrl":"https://doi.org/10.1109/NSSMIC.1995.500265","url":null,"abstract":"An algorithm is described for estimating attenuation length in 3D from sinogram or projection data, by which 3D attenuation correction can be performed in brain PET imaging for given attenuation coefficients. The algorithm begins with the estimation of scalp contours from sinogram data, based on optimal thresholding, spline smoothing and interpolation and backprojection. A cubic B-spline surface is then introduced to accurately describe the scalp surface by the least squares fitting to the stacked 2D estimated scalp contours. Due to the use of this surface model, an efficient and accurate technique is developed for estimation of a distance between two intersecting points formed by an arbitrary projection ray and the scalp surface. This fully automated and fast algorithm has been applied to sinogram and projection data collected using PENN-PET scanners. It has the potential to be used in routine clinical PET imaging.","PeriodicalId":409998,"journal":{"name":"1995 IEEE Nuclear Science Symposium and Medical Imaging Conference Record","volume":"145 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133884293","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1995-10-21DOI: 10.1109/NSSMIC.1995.501922
J. MacDonald, K. Wells, R. Ott
A digital autoradiography system, incorporating a cooled scientific charge coupled device (CCD) is in development at the Physics Department of the Institute of Cancer Research (ICR). The ICR system is designed to image /spl beta/-particles and low energy X-rays from radiolabelled biological tissue samples, utilising direct irradiation of the CCD. This prototype system displays position resolution of 30 /spl mu/m over an area of /spl sim/4 cm/sup 2/. System response is linear over a dynamic range of at least 10/sup 4/, with signal to noise ratio approaching 300. The different components of system noise are discussed,along with the optimisation of integration times to minimise their effect. The potential application of the system to "multimodality" imaging-the automatic registration of optical and radionuclide images of a stained tissue sample-is discussed.
{"title":"Preliminary results from a novel CCD-based imaging system for biomedical applications","authors":"J. MacDonald, K. Wells, R. Ott","doi":"10.1109/NSSMIC.1995.501922","DOIUrl":"https://doi.org/10.1109/NSSMIC.1995.501922","url":null,"abstract":"A digital autoradiography system, incorporating a cooled scientific charge coupled device (CCD) is in development at the Physics Department of the Institute of Cancer Research (ICR). The ICR system is designed to image /spl beta/-particles and low energy X-rays from radiolabelled biological tissue samples, utilising direct irradiation of the CCD. This prototype system displays position resolution of 30 /spl mu/m over an area of /spl sim/4 cm/sup 2/. System response is linear over a dynamic range of at least 10/sup 4/, with signal to noise ratio approaching 300. The different components of system noise are discussed,along with the optimisation of integration times to minimise their effect. The potential application of the system to \"multimodality\" imaging-the automatic registration of optical and radionuclide images of a stained tissue sample-is discussed.","PeriodicalId":409998,"journal":{"name":"1995 IEEE Nuclear Science Symposium and Medical Imaging Conference Record","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123122523","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1995-10-21DOI: 10.1109/NSSMIC.1995.510493
Y. Weng, G. L. Zeng, G. Gullberg
In single photon emission computed tomography (SPECT), photon attenuation within the body is a major factor contributing to the quantitative inaccuracy in measuring the in vivo distribution of radioactivity. Usually the attenuation of the body is not uniform, but for brain imaging, it can be a good approximation to assume that the attenuation is uniformly distributed. For 2D parallel-beam geometry, an exact convolution backprojection algorithm to reconstruct image from attenuated Radon transform with constant attenuation had been developed by Tretiak and Metz (1980). The algorithm can be modified for attenuated fan-beam projections. Unlike the attenuated parallel-beam projections, the filter for attenuated fan-beam projections is no longer spatially invariant, instead, it is a space-variant filter. The algorithm with this spatially variant filter will take more computation time than the algorithm with convolution, but is an exact algorithm. This algorithm has been implemented and simulated using a mathematical phantom. Compared with parallel-beam reconstructions, fan-beam reconstructions have the same image quality.
{"title":"Analytical inversion formula for attenuated fan-beam projections","authors":"Y. Weng, G. L. Zeng, G. Gullberg","doi":"10.1109/NSSMIC.1995.510493","DOIUrl":"https://doi.org/10.1109/NSSMIC.1995.510493","url":null,"abstract":"In single photon emission computed tomography (SPECT), photon attenuation within the body is a major factor contributing to the quantitative inaccuracy in measuring the in vivo distribution of radioactivity. Usually the attenuation of the body is not uniform, but for brain imaging, it can be a good approximation to assume that the attenuation is uniformly distributed. For 2D parallel-beam geometry, an exact convolution backprojection algorithm to reconstruct image from attenuated Radon transform with constant attenuation had been developed by Tretiak and Metz (1980). The algorithm can be modified for attenuated fan-beam projections. Unlike the attenuated parallel-beam projections, the filter for attenuated fan-beam projections is no longer spatially invariant, instead, it is a space-variant filter. The algorithm with this spatially variant filter will take more computation time than the algorithm with convolution, but is an exact algorithm. This algorithm has been implemented and simulated using a mathematical phantom. Compared with parallel-beam reconstructions, fan-beam reconstructions have the same image quality.","PeriodicalId":409998,"journal":{"name":"1995 IEEE Nuclear Science Symposium and Medical Imaging Conference Record","volume":"51 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132550415","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1995-10-21DOI: 10.1109/NSSMIC.1995.500250
G. K. Gregoriou, B. Tsui, E. Frey, D. Lalush
In recent years, the quantitative accuracy of reconstructed SPECT images has been enhanced by compensating for photon attenuation using attenuation maps obtained from transmission CT data. The quality and quantitative accuracy of transmission CT images are affected by artifacts due to truncation of the projection data. In this study, the effect of data sampling on the quantitative accuracy of transmission CT images reconstructed from truncated projections has been investigated. Parallel-beam projections with different sets of acquisition parameters were simulated. In deciding whether a set of acquisition parameters (in terms of the number of linear and angular samples) provided sufficient sampling, use was made of the singular value decomposition of the projection matrix. The results of the study indicate that for noise-free data the ring artifact which is present in images reconstructed using iterative algorithms can be reduced or completely eliminated provided that the sampling is sufficient and an adequate number of iterations is performed. Reconstructions using the singular value decomposition were obtained and correlated very well with the reconstructions obtained using iterative algorithms. When the singular value decomposition indicated the presence of a null space, the iterative reconstruction methods failed to recover the object. The quantitative accuracy of the reconstructed attenuation maps depends on the sampling and is better as the number of angles and/or the number of projection bins is increased. Furthermore, the higher the degree of truncation the larger the number of iterations required in order to obtain accurate attenuation maps. In the presence of noise, the number of iterations required for the best compromise of noise and image detail is decreased with increased noise level and higher degree of truncation. Finally, the use of the body contour as support in the reconstructions resulted in quantitatively superior reconstructed images.
{"title":"Artifacts and sampling requirement in transmission CT reconstruction with truncated projection data","authors":"G. K. Gregoriou, B. Tsui, E. Frey, D. Lalush","doi":"10.1109/NSSMIC.1995.500250","DOIUrl":"https://doi.org/10.1109/NSSMIC.1995.500250","url":null,"abstract":"In recent years, the quantitative accuracy of reconstructed SPECT images has been enhanced by compensating for photon attenuation using attenuation maps obtained from transmission CT data. The quality and quantitative accuracy of transmission CT images are affected by artifacts due to truncation of the projection data. In this study, the effect of data sampling on the quantitative accuracy of transmission CT images reconstructed from truncated projections has been investigated. Parallel-beam projections with different sets of acquisition parameters were simulated. In deciding whether a set of acquisition parameters (in terms of the number of linear and angular samples) provided sufficient sampling, use was made of the singular value decomposition of the projection matrix. The results of the study indicate that for noise-free data the ring artifact which is present in images reconstructed using iterative algorithms can be reduced or completely eliminated provided that the sampling is sufficient and an adequate number of iterations is performed. Reconstructions using the singular value decomposition were obtained and correlated very well with the reconstructions obtained using iterative algorithms. When the singular value decomposition indicated the presence of a null space, the iterative reconstruction methods failed to recover the object. The quantitative accuracy of the reconstructed attenuation maps depends on the sampling and is better as the number of angles and/or the number of projection bins is increased. Furthermore, the higher the degree of truncation the larger the number of iterations required in order to obtain accurate attenuation maps. In the presence of noise, the number of iterations required for the best compromise of noise and image detail is decreased with increased noise level and higher degree of truncation. Finally, the use of the body contour as support in the reconstructions resulted in quantitatively superior reconstructed images.","PeriodicalId":409998,"journal":{"name":"1995 IEEE Nuclear Science Symposium and Medical Imaging Conference Record","volume":"45 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131789489","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1995-10-21DOI: 10.1109/NSSMIC.1995.510400
D. Brajnik, S. Korpar, G. medin, M. Starič, A. Stanovnik
The highly radiotoxic /sup 90/Sr cannot be determined by /spl gamma/-spectrometry as /sup 90/Sr and its daughter /sup 90/Y are both pure /spl beta/-emitters. Cherenkov radiation of the relatively high energy /spl beta/-particles from /sup 90/Y (E/sub /spl beta///sup max/=2.27 MeV) allows for discrimination or at least for strong suppression of the lower energy /spl beta/-emitters. The contribution of both may then be determined from /sup 90/Y if their ratio is known. Measurements of efficiencies with a silica aerogel radiator (n=1.055), show a steep dependence on the /spl beta/ end-point energy above threshold (E/sub /spl beta///sup th/=1.09 MeV). Possible contributions from /spl beta/-emitters other than /sup 90/Y in the sample may be detected by the shape of the pulse height spectrum. Using a multiwire proportional chamber in coincidence and plastic scintillation counters in anticoincidence reduces the background, so environmental activities down to about 1 Bq of /sup 90/Sr//sup 90/Y may be detected in a few hours of measurement of a thin sample (air filter or sediment).
{"title":"Detection of /sup 90/Sr//sup 90/Y with Cherenkov radiation","authors":"D. Brajnik, S. Korpar, G. medin, M. Starič, A. Stanovnik","doi":"10.1109/NSSMIC.1995.510400","DOIUrl":"https://doi.org/10.1109/NSSMIC.1995.510400","url":null,"abstract":"The highly radiotoxic /sup 90/Sr cannot be determined by /spl gamma/-spectrometry as /sup 90/Sr and its daughter /sup 90/Y are both pure /spl beta/-emitters. Cherenkov radiation of the relatively high energy /spl beta/-particles from /sup 90/Y (E/sub /spl beta///sup max/=2.27 MeV) allows for discrimination or at least for strong suppression of the lower energy /spl beta/-emitters. The contribution of both may then be determined from /sup 90/Y if their ratio is known. Measurements of efficiencies with a silica aerogel radiator (n=1.055), show a steep dependence on the /spl beta/ end-point energy above threshold (E/sub /spl beta///sup th/=1.09 MeV). Possible contributions from /spl beta/-emitters other than /sup 90/Y in the sample may be detected by the shape of the pulse height spectrum. Using a multiwire proportional chamber in coincidence and plastic scintillation counters in anticoincidence reduces the background, so environmental activities down to about 1 Bq of /sup 90/Sr//sup 90/Y may be detected in a few hours of measurement of a thin sample (air filter or sediment).","PeriodicalId":409998,"journal":{"name":"1995 IEEE Nuclear Science Symposium and Medical Imaging Conference Record","volume":"189 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131987729","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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