Pub Date : 2012-10-01DOI: 10.1109/NSSMIC.2012.6551506
A. Karpikov, H. Tagare, T. Mulnix, J. Gallezot, A. Sinusas, Chi Liu, R. Carson
Generation of parametric images of myocardial blood flow (MBF) from dynamic PET requires a reproducible and reliable method to obtain left and right ventricular time-activity curves. We propose the use of Independent Component Analysis (ICA) on PET temporal information to segment the image data into three categories: right ventricle (RV), left ventricle (LV) and myocardium. ICA is an established signal processing technique that assumes that the dynamic signal in each voxel is a linear mixture of signals from statistically independent sources. The mixing process is due to cardiac motion and partial volume effects. Due to its ability to find the intensity of the underlying sources, ICA generates a 3D map of the mixing coefficients that allows the segmentation of structures. Dynamic cardiac PET data were acquired with a Siemens Biograph mCT PET/CT scanner using Rb-82 and [15O]water in nonhuman primate and pigs with injections of different activities. The Dice similarity coefficient (DSC) was used to compare the segmentations between scans of different species with different tracers. The LV and RV regions were used to calculate input functions for kinetic analysis and MBF estimation. Pairwise comparisons of the segmentations between different [15O]water PET scans gave DSC of 0.91 ± 0.09 and 0.92±0.08 for the RV and LV segmentations, respectively. For Rb-82 PET scans, the DSC values were of 0.89 ± 0.09 and 0.85±0.10 for RV and LV. We used contrast CT as a gold standard for the LV and RV segmentations. Pairwise comparisons of the segmentations between different contrast CT and Rb-82 PET scans gave DSC of 0.86 ± 0.09 and 0.85±0.09 for the RV and LV, respectively. Our work shows the reliability and reproducibility of the results of the segmentation algorithm. High quality parametric images of MBF and the kinetic parameters were obtained. These results suggest that ICA may be useful to extract time-activity curves for kinetic MBF analysis. The effects of partial volume on input TAC determination were also evaluated.
{"title":"Myocardial blood flow from dynamic PET using Independent Component Analysis","authors":"A. Karpikov, H. Tagare, T. Mulnix, J. Gallezot, A. Sinusas, Chi Liu, R. Carson","doi":"10.1109/NSSMIC.2012.6551506","DOIUrl":"https://doi.org/10.1109/NSSMIC.2012.6551506","url":null,"abstract":"Generation of parametric images of myocardial blood flow (MBF) from dynamic PET requires a reproducible and reliable method to obtain left and right ventricular time-activity curves. We propose the use of Independent Component Analysis (ICA) on PET temporal information to segment the image data into three categories: right ventricle (RV), left ventricle (LV) and myocardium. ICA is an established signal processing technique that assumes that the dynamic signal in each voxel is a linear mixture of signals from statistically independent sources. The mixing process is due to cardiac motion and partial volume effects. Due to its ability to find the intensity of the underlying sources, ICA generates a 3D map of the mixing coefficients that allows the segmentation of structures. Dynamic cardiac PET data were acquired with a Siemens Biograph mCT PET/CT scanner using Rb-82 and [15O]water in nonhuman primate and pigs with injections of different activities. The Dice similarity coefficient (DSC) was used to compare the segmentations between scans of different species with different tracers. The LV and RV regions were used to calculate input functions for kinetic analysis and MBF estimation. Pairwise comparisons of the segmentations between different [15O]water PET scans gave DSC of 0.91 ± 0.09 and 0.92±0.08 for the RV and LV segmentations, respectively. For Rb-82 PET scans, the DSC values were of 0.89 ± 0.09 and 0.85±0.10 for RV and LV. We used contrast CT as a gold standard for the LV and RV segmentations. Pairwise comparisons of the segmentations between different contrast CT and Rb-82 PET scans gave DSC of 0.86 ± 0.09 and 0.85±0.09 for the RV and LV, respectively. Our work shows the reliability and reproducibility of the results of the segmentation algorithm. High quality parametric images of MBF and the kinetic parameters were obtained. These results suggest that ICA may be useful to extract time-activity curves for kinetic MBF analysis. The effects of partial volume on input TAC determination were also evaluated.","PeriodicalId":187728,"journal":{"name":"2012 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS/MIC)","volume":"84 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130133300","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 : 2012-10-01DOI: 10.1109/NSSMIC.2012.6551403
M. Pizzichemi, E. Auffray, R. Chipaux, G. Cucciati, Nicolas Di Vara, A. Ghezzi, Riccardo Iaconelli, P. Lecoq, M. Lucchini, A. Knapitsch, M. Paganoni, K. Pauwels
The extensive use of scintillating crystals in medical imaging field is generating a growing interest in Monte Carlo simulation of light transportation and photon collection inside inorganic materials. The critical parameters under study which affect the performance of medical devices are the number of photons collected per unit of energy deposited (light yield), the energy resolution, the effect of dimensions and surface state and the time profiles of the scintillation process. Moreover, most of the crystals used in Positron Emission Tomography (PET) applications, such as lutetium orthosilicate (LSO), are anisotropic, potentially influencing the performances. In particular the recent development of time of flight PET scanners requires a detailed knowledge of timing profiles of the crystals in terms of time of arrival of single photons, scintillation rise and decay times. Furthermore the effort towards innovative endoscopic probe for PET examination requires an extensive analysis of the effect of the dimensions of small crystals on the parameters mentioned. Different simulation tools are employed nowadays for detailed studies of interaction of particles in inorganic materials and tracing of the scintillating photons produced. In particular our attention is focused on SLitrani and Geant4. SLitrani is a general purpose Monte-Carlo program simulating light propagation, developed for high energy experiments, in particular in the frame of the CMS experiment at LHC. Its most advanced characteristics is the ability to handle anisotropic materials, thus retaining a quite general application. Geant4 is a general purpose Monte Carlo toolkit widely used in high energy physics, astroparticle physics and nuclear physics, which includes an optical physics process category to simulate the production and propagation of light. In the frame of the Crystal Clear Collaboration, we have been developing and testing innovative scintillation technologies for medical applications, and with this respect Monte Carlo techniques are powerful tools for investigating the performances of our setups. In order to validate and accurately describe the inorganic crystals developed we have been comparing the performances of the SLitrani and Geant4 frameworks, and started a preliminary comparison with experimental results obtained in our laboratories.
{"title":"Ray tracing simulations in scintillators: A comparison between SLitrani and Geant4","authors":"M. Pizzichemi, E. Auffray, R. Chipaux, G. Cucciati, Nicolas Di Vara, A. Ghezzi, Riccardo Iaconelli, P. Lecoq, M. Lucchini, A. Knapitsch, M. Paganoni, K. Pauwels","doi":"10.1109/NSSMIC.2012.6551403","DOIUrl":"https://doi.org/10.1109/NSSMIC.2012.6551403","url":null,"abstract":"The extensive use of scintillating crystals in medical imaging field is generating a growing interest in Monte Carlo simulation of light transportation and photon collection inside inorganic materials. The critical parameters under study which affect the performance of medical devices are the number of photons collected per unit of energy deposited (light yield), the energy resolution, the effect of dimensions and surface state and the time profiles of the scintillation process. Moreover, most of the crystals used in Positron Emission Tomography (PET) applications, such as lutetium orthosilicate (LSO), are anisotropic, potentially influencing the performances. In particular the recent development of time of flight PET scanners requires a detailed knowledge of timing profiles of the crystals in terms of time of arrival of single photons, scintillation rise and decay times. Furthermore the effort towards innovative endoscopic probe for PET examination requires an extensive analysis of the effect of the dimensions of small crystals on the parameters mentioned. Different simulation tools are employed nowadays for detailed studies of interaction of particles in inorganic materials and tracing of the scintillating photons produced. In particular our attention is focused on SLitrani and Geant4. SLitrani is a general purpose Monte-Carlo program simulating light propagation, developed for high energy experiments, in particular in the frame of the CMS experiment at LHC. Its most advanced characteristics is the ability to handle anisotropic materials, thus retaining a quite general application. Geant4 is a general purpose Monte Carlo toolkit widely used in high energy physics, astroparticle physics and nuclear physics, which includes an optical physics process category to simulate the production and propagation of light. In the frame of the Crystal Clear Collaboration, we have been developing and testing innovative scintillation technologies for medical applications, and with this respect Monte Carlo techniques are powerful tools for investigating the performances of our setups. In order to validate and accurately describe the inorganic crystals developed we have been comparing the performances of the SLitrani and Geant4 frameworks, and started a preliminary comparison with experimental results obtained in our laboratories.","PeriodicalId":187728,"journal":{"name":"2012 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS/MIC)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130142376","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 : 2012-10-01DOI: 10.1109/NSSMIC.2012.6551738
Takahiro Matsumoto, T. Yamaya, E. Yoshida, F. Nishikido, N. Inadama, H. Murayama, M. Suga
We are developing a novel PET detector with 3D isotropic resolution, the X'tal cube. Our original idea was to cover all 6 surfaces of a segmented crystal block with multi-pixel photon counters (MPPCs) for effective scintillation photon acquisition. On the other hand, modification toward practical use is important in terms of assembling efficiency and production costs. In addition, when the X'tal cubes are arranged to form a PET scanner, insensitive inter-detector gaps made by the MPPC arrays should not be too wide or better yet, they should be removed. Therefore, reducing the number of faces to be connected to the MPPCs has become our top priority. In this paper, we evaluated the effect of reducing the number of MPPCs on positioning accuracy through numerical simulations. We optimized the X'tal cube in terms of the gap material of crystal segments and the number of MPPC connection faces. We simulated the X'tal cube with (3.0 mm)3 crystal segments; the crystal block was composed of 6 × 6 × 6 array of (3.0 mm)3 LGSO crystals. Each surface of the crystal block was covered with a 4 × 4 array of MPPCs, each of which had a 3.0 × 3.0 mm2 active area. Outer surfaces of the crystal block, except for the partitions that the MPPCs were arranged on, were covered with reflectors. For material between crystal elements, we compared optical glue and air gap. The air gap showed better crystal identification performance than the optical glue, although good crystal identification performance was obtained even with optical glue for the 6-face MPPC connection. We showed that the number of MPPC connection faces could be reduced to two when the gap material was air.
{"title":"Simulation study to optimize the number of photo-detection faces and inter-crystal materials for the X'tal cube PET detector","authors":"Takahiro Matsumoto, T. Yamaya, E. Yoshida, F. Nishikido, N. Inadama, H. Murayama, M. Suga","doi":"10.1109/NSSMIC.2012.6551738","DOIUrl":"https://doi.org/10.1109/NSSMIC.2012.6551738","url":null,"abstract":"We are developing a novel PET detector with 3D isotropic resolution, the X'tal cube. Our original idea was to cover all 6 surfaces of a segmented crystal block with multi-pixel photon counters (MPPCs) for effective scintillation photon acquisition. On the other hand, modification toward practical use is important in terms of assembling efficiency and production costs. In addition, when the X'tal cubes are arranged to form a PET scanner, insensitive inter-detector gaps made by the MPPC arrays should not be too wide or better yet, they should be removed. Therefore, reducing the number of faces to be connected to the MPPCs has become our top priority. In this paper, we evaluated the effect of reducing the number of MPPCs on positioning accuracy through numerical simulations. We optimized the X'tal cube in terms of the gap material of crystal segments and the number of MPPC connection faces. We simulated the X'tal cube with (3.0 mm)3 crystal segments; the crystal block was composed of 6 × 6 × 6 array of (3.0 mm)3 LGSO crystals. Each surface of the crystal block was covered with a 4 × 4 array of MPPCs, each of which had a 3.0 × 3.0 mm2 active area. Outer surfaces of the crystal block, except for the partitions that the MPPCs were arranged on, were covered with reflectors. For material between crystal elements, we compared optical glue and air gap. The air gap showed better crystal identification performance than the optical glue, although good crystal identification performance was obtained even with optical glue for the 6-face MPPC connection. We showed that the number of MPPC connection faces could be reduced to two when the gap material was air.","PeriodicalId":187728,"journal":{"name":"2012 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS/MIC)","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134043704","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 : 2012-10-01DOI: 10.1109/NSSMIC.2012.6551724
E. Berg, A. Goertzen
When developing new detectors for positron emission tomography (PET) imaging it is necessary to characterize the performance in terms of spatial and timing resolution in order to understand how the detector performs relative to existing technology. With the move toward time-of-flight PET (TOF PET) due to its benefits for clinical imaging, characterization of the timing performance of PET detectors is taking on an increased importance. We present a probe designed to facilitate the simultaneous measurement of spatial and timing resolution of a PET detector using an electronically collimated beam of 511 keV photons. The design of the probe uses two Multi-Pixel Photon Counting (MPPC) single pixel detectors. The first, used to generate the timing signal, is coupled to a plastic scintillator containing an embedded positron emitting source. The second MPPC detector is coupled to a single LYSO crystal and is used to electronically collimate the 511 keV photon beam. Several features are built into the probe to facilitate the characterization of a PET detector under test including: 1) the two MPPC detectors are mounted on an arm that can be rotated in 15° steps in order to allow characterization of spatial and timing resolution as a function of 511 keV photon beam incidence angle; 2) the effective size of the 511 keV photon beam can be varied by changing the distance between the two MPPC detectors, thus changing the geometric magnification (or minification) of the beam; 3) the probe can be used to acquire a flood irradiation timing measurement if only the output of the MPPC coupled to the plastic scintillator is used or the beam can be collimated by taking a coincidence with the LYSO detector.
{"title":"A MPPC based tool for timing and spatial resolution characterization of PET detectors","authors":"E. Berg, A. Goertzen","doi":"10.1109/NSSMIC.2012.6551724","DOIUrl":"https://doi.org/10.1109/NSSMIC.2012.6551724","url":null,"abstract":"When developing new detectors for positron emission tomography (PET) imaging it is necessary to characterize the performance in terms of spatial and timing resolution in order to understand how the detector performs relative to existing technology. With the move toward time-of-flight PET (TOF PET) due to its benefits for clinical imaging, characterization of the timing performance of PET detectors is taking on an increased importance. We present a probe designed to facilitate the simultaneous measurement of spatial and timing resolution of a PET detector using an electronically collimated beam of 511 keV photons. The design of the probe uses two Multi-Pixel Photon Counting (MPPC) single pixel detectors. The first, used to generate the timing signal, is coupled to a plastic scintillator containing an embedded positron emitting source. The second MPPC detector is coupled to a single LYSO crystal and is used to electronically collimate the 511 keV photon beam. Several features are built into the probe to facilitate the characterization of a PET detector under test including: 1) the two MPPC detectors are mounted on an arm that can be rotated in 15° steps in order to allow characterization of spatial and timing resolution as a function of 511 keV photon beam incidence angle; 2) the effective size of the 511 keV photon beam can be varied by changing the distance between the two MPPC detectors, thus changing the geometric magnification (or minification) of the beam; 3) the probe can be used to acquire a flood irradiation timing measurement if only the output of the MPPC coupled to the plastic scintillator is used or the beam can be collimated by taking a coincidence with the LYSO detector.","PeriodicalId":187728,"journal":{"name":"2012 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS/MIC)","volume":"58 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134535804","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 : 2012-10-01DOI: 10.1109/NSSMIC.2012.6551722
Elisabeth Stuhler, G. Platsch, M. Weih, J. Kornhuber, T. Kuwert, D. Merhof
Gaussian mixture (GM) models can be applied for statistical classification of various types of dementia. As opposed to linear boundaries, they do not only provide the class membership of a case, but also a measure of its probability. This enables an improved interpretation and classification of neurodegenerative dementia datasets which comprise various stages of the disease, and also mixed forms of dementia. In this work, GM models are applied to a total number of 103 technetium-99methylcysteinatedimer (99mTc-ECD) SPECT datasets of asymptomatic controls (CTR), as well as Alzheimer's disease (AD) and frontotemporal dementia (FTD) patients in early or moderate stages of the disease. Prior to classification, multivariate analysis is applied: Principal component analysis (PCA) is used for dimensionality reduction, followed by a differentiation of the datasets via multiple discriminant analysis (MDA). A GM model on the resulting discrimination plane is constructed by computing the GM distribution associated with the underlying training set. The posterior probabilities of each case indicate its class membership probability. The performance of GM models for classification is assessed by bootstrap resampling and cross validation. Accuracy and robustness of the method are evaluated for different numbers of principal components (PCs), and furthermore the detection rate of dementia in early stages is calculated. The GM model outperfomes classification with linear boundaries in both predicted accuracy and detection rate of early dementia, and is equally robust.
{"title":"Classification of neurodegenerative dementia by Gaussian mixture models applied to SPECT images","authors":"Elisabeth Stuhler, G. Platsch, M. Weih, J. Kornhuber, T. Kuwert, D. Merhof","doi":"10.1109/NSSMIC.2012.6551722","DOIUrl":"https://doi.org/10.1109/NSSMIC.2012.6551722","url":null,"abstract":"Gaussian mixture (GM) models can be applied for statistical classification of various types of dementia. As opposed to linear boundaries, they do not only provide the class membership of a case, but also a measure of its probability. This enables an improved interpretation and classification of neurodegenerative dementia datasets which comprise various stages of the disease, and also mixed forms of dementia. In this work, GM models are applied to a total number of 103 technetium-99methylcysteinatedimer (99mTc-ECD) SPECT datasets of asymptomatic controls (CTR), as well as Alzheimer's disease (AD) and frontotemporal dementia (FTD) patients in early or moderate stages of the disease. Prior to classification, multivariate analysis is applied: Principal component analysis (PCA) is used for dimensionality reduction, followed by a differentiation of the datasets via multiple discriminant analysis (MDA). A GM model on the resulting discrimination plane is constructed by computing the GM distribution associated with the underlying training set. The posterior probabilities of each case indicate its class membership probability. The performance of GM models for classification is assessed by bootstrap resampling and cross validation. Accuracy and robustness of the method are evaluated for different numbers of principal components (PCs), and furthermore the detection rate of dementia in early stages is calculated. The GM model outperfomes classification with linear boundaries in both predicted accuracy and detection rate of early dementia, and is equally robust.","PeriodicalId":187728,"journal":{"name":"2012 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS/MIC)","volume":"108 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131509514","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 : 2012-10-01DOI: 10.1109/NSSMIC.2012.6551934
Yi Gu, C. Levin
This study presents results from two 3-D position-sensitive dual-CZT photon detector modules designed for a high-resolution small animal PET system. Each module comprises a stack of two 40 mm × 40 mm × 5 mm monolithic CZT crystals metalized with a cross-strip electrode pattern that achieves better than 1 mm resolution. In contrast to our prior work focusing on single-crystal CZT performance, this study investigated the impact of detector packaging and module construction on detector performance. This study measured five module-level characteristics; the corresponding findings are as follows. First, the study measured the fraction of event triggers potentially induced by intra-module cross-talk, i.e. occurrence of simultaneous triggers on anode or cathode strips of one detector and the corresponding electrode strips on another detector across the thin flex circuit. This was measured to be 1.51±0.34% for anode channels and 6.40±1.21 % for cathode channels - sufficiently low not to be of specific concern for PET imaging. Second, detector photon sensitivity is maintained at detector-detector boundaries, with the edge anode strip detecting approximately equal number of events as other anode strips. Third, the anode energy resolution in dual-module configuration was measured to be 6.18±0.87% and 4.38±0.67% - slightly degraded from previous studies of an individual detector crystal due to either increased anode stray capacitance or crystal variances, or both. Fourth, stray capacitance on cathode channels was seen to increase the readout noise level by a factor of -2.8 for a free-standing dual-detector module, and by a factor of -4.8 for two stacked dual-detector modules. This revealed the need to increase the cathode-cathode separation across flex circuits and the use of a lower dielectric constant flex substrate. Finally, a survey of noisy, intermittent or disconnected electrode channels highlighted the need for tight control of the module assembly process.
{"title":"Characterization of inter-detector effects in a 3-D position-sensitive dual-CZT detector modules for PET","authors":"Yi Gu, C. Levin","doi":"10.1109/NSSMIC.2012.6551934","DOIUrl":"https://doi.org/10.1109/NSSMIC.2012.6551934","url":null,"abstract":"This study presents results from two 3-D position-sensitive dual-CZT photon detector modules designed for a high-resolution small animal PET system. Each module comprises a stack of two 40 mm × 40 mm × 5 mm monolithic CZT crystals metalized with a cross-strip electrode pattern that achieves better than 1 mm resolution. In contrast to our prior work focusing on single-crystal CZT performance, this study investigated the impact of detector packaging and module construction on detector performance. This study measured five module-level characteristics; the corresponding findings are as follows. First, the study measured the fraction of event triggers potentially induced by intra-module cross-talk, i.e. occurrence of simultaneous triggers on anode or cathode strips of one detector and the corresponding electrode strips on another detector across the thin flex circuit. This was measured to be 1.51±0.34% for anode channels and 6.40±1.21 % for cathode channels - sufficiently low not to be of specific concern for PET imaging. Second, detector photon sensitivity is maintained at detector-detector boundaries, with the edge anode strip detecting approximately equal number of events as other anode strips. Third, the anode energy resolution in dual-module configuration was measured to be 6.18±0.87% and 4.38±0.67% - slightly degraded from previous studies of an individual detector crystal due to either increased anode stray capacitance or crystal variances, or both. Fourth, stray capacitance on cathode channels was seen to increase the readout noise level by a factor of -2.8 for a free-standing dual-detector module, and by a factor of -4.8 for two stacked dual-detector modules. This revealed the need to increase the cathode-cathode separation across flex circuits and the use of a lower dielectric constant flex substrate. Finally, a survey of noisy, intermittent or disconnected electrode channels highlighted the need for tight control of the module assembly process.","PeriodicalId":187728,"journal":{"name":"2012 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS/MIC)","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131542367","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 : 2012-10-01DOI: 10.1109/NSSMIC.2012.6551148
M. Tabata, I. Adachi, Y. Hatakeyama, H. Kawai, T. Morita, K. Nishikawa, T. Sumiyoshi
This paper presents the recent progress in the development of large-area hydrophobic silica aerogels for use as radiators in the aerogel-based ring-imaging Cherenkov (A-RICH) counter that will be installed in the forward end cap of the Belle II detector. The proximity-focusing A-RICH counter is designed to identify charged pions and kaons and to have a separation capability of more than 4σ at momenta up to 4 GeV/c. In a focusing-dual-layer radiator with different refractive indices, a prototype A-RICH counter satisfied the required performance using our conventional aerogel tiles with refractive indices n of 1.045 and 1.055, transmission lengths ΛT of 30-40 mm, and designed final dimensions of 18 × 18 × 2 cm3. Moreover, we achieved better π/K separation performance using n ~ 1.06 aerogels with relatively small dimensions but long transmission length (ΛT > 50 mm) produced by a novel pin-drying method. We need to fill the large end cap area of 3.5 m2 with two-layer aerogel tiles and to minimize the number of tiles with realistic dimensions to reduce the tile boundaries, at which the number of detected photoelectrons decreases. Therefore, we studied large area aerogel production by both conventional and pin-drying methods as a key to achieving high performance over the actual detector. This paper discusses the crack-free yield, optical transparency, and uniformity in refractive index within a monolith of recently produced large area aerogels.
{"title":"Development of large area silica aerogel used as RICH radiator for the Belle II experiment","authors":"M. Tabata, I. Adachi, Y. Hatakeyama, H. Kawai, T. Morita, K. Nishikawa, T. Sumiyoshi","doi":"10.1109/NSSMIC.2012.6551148","DOIUrl":"https://doi.org/10.1109/NSSMIC.2012.6551148","url":null,"abstract":"This paper presents the recent progress in the development of large-area hydrophobic silica aerogels for use as radiators in the aerogel-based ring-imaging Cherenkov (A-RICH) counter that will be installed in the forward end cap of the Belle II detector. The proximity-focusing A-RICH counter is designed to identify charged pions and kaons and to have a separation capability of more than 4σ at momenta up to 4 GeV/c. In a focusing-dual-layer radiator with different refractive indices, a prototype A-RICH counter satisfied the required performance using our conventional aerogel tiles with refractive indices n of 1.045 and 1.055, transmission lengths ΛT of 30-40 mm, and designed final dimensions of 18 × 18 × 2 cm3. Moreover, we achieved better π/K separation performance using n ~ 1.06 aerogels with relatively small dimensions but long transmission length (ΛT > 50 mm) produced by a novel pin-drying method. We need to fill the large end cap area of 3.5 m2 with two-layer aerogel tiles and to minimize the number of tiles with realistic dimensions to reduce the tile boundaries, at which the number of detected photoelectrons decreases. Therefore, we studied large area aerogel production by both conventional and pin-drying methods as a key to achieving high performance over the actual detector. This paper discusses the crack-free yield, optical transparency, and uniformity in refractive index within a monolith of recently produced large area aerogels.","PeriodicalId":187728,"journal":{"name":"2012 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS/MIC)","volume":"115 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131566341","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 : 2012-10-01DOI: 10.1109/NSSMIC.2012.6551061
E. Min, Mincheol Ko, Yongkwon Kim, J. Joung, Kisung Lee
A spectrum of a radio isotope (RI) contains a single or multiple photo-peaks and radio-activities of all energy levels. These characteristics of each RI source are measured by radiation monitor (RM) systems. However, if the radiation count is extremely low and source to detector distance is too far, we cannot acquire good spectroscopic results for RI identification by RM devices while we still able to measure some counting statistics. Thus, precise peak detection in noisy spectrums is one of the most important tasks in the RM system. In this study, we developed an accurate peak detection method based on wavelet decomposition followed by principal component analysis. We used a discrete wavelet transform (DWT) for reduction of unnecessary high frequency noises in low counts spectrums. To reduce effect of a background radiation, we made a background template using a pre-measured background spectrum and calculated square errors for suppressing a background of low energy levels and maintaining true photo-peaks. Finally, we analyzed pre-processed data and detected photo-peaks using PCA. We measured Cesium 137(Cs-137) and Barium 133(Ba133) with 1 and 10 micro curies collected from the various distance. Each spectrum was collected for a second and total 60 sets were stored for each isotope. Results of our research show that the proposed algorithm achieves high sensitivity and specificity, proving that the algorithm is appropriate for RM systems.
{"title":"A peak detection in noisy spectrum using principal component analysis","authors":"E. Min, Mincheol Ko, Yongkwon Kim, J. Joung, Kisung Lee","doi":"10.1109/NSSMIC.2012.6551061","DOIUrl":"https://doi.org/10.1109/NSSMIC.2012.6551061","url":null,"abstract":"A spectrum of a radio isotope (RI) contains a single or multiple photo-peaks and radio-activities of all energy levels. These characteristics of each RI source are measured by radiation monitor (RM) systems. However, if the radiation count is extremely low and source to detector distance is too far, we cannot acquire good spectroscopic results for RI identification by RM devices while we still able to measure some counting statistics. Thus, precise peak detection in noisy spectrums is one of the most important tasks in the RM system. In this study, we developed an accurate peak detection method based on wavelet decomposition followed by principal component analysis. We used a discrete wavelet transform (DWT) for reduction of unnecessary high frequency noises in low counts spectrums. To reduce effect of a background radiation, we made a background template using a pre-measured background spectrum and calculated square errors for suppressing a background of low energy levels and maintaining true photo-peaks. Finally, we analyzed pre-processed data and detected photo-peaks using PCA. We measured Cesium 137(Cs-137) and Barium 133(Ba133) with 1 and 10 micro curies collected from the various distance. Each spectrum was collected for a second and total 60 sets were stored for each isotope. Results of our research show that the proposed algorithm achieves high sensitivity and specificity, proving that the algorithm is appropriate for RM systems.","PeriodicalId":187728,"journal":{"name":"2012 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS/MIC)","volume":"48 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131573291","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 : 2012-10-01DOI: 10.1109/NSSMIC.2012.6551232
K. Kasinski, R. Kleczek, P. Grybos, R. Szczygiel
Modern High Energy Physics experiments require more functionality from the multichannel readout circuits which in conjunction with strict limits on power consumption, area occupation and low noise performance set new requirements in the analog front-end electronics design. We discuss the applicability issues and design challenges of a constant-current discharge time-over-threshold (ToT) processing chain for readout of the large capacitance silicon strip detectors. The conclusions are based on measurement results of two prototype ASICs: TOTOl, TOT02. The revealed non-idealities and issues have been identified and are briefly presented in this paper. Moreover, an idea for charge amplifiaction, measurement and timestamping is proposed as a possible remedy for presented matters. This conception uses two cascaded amplifiers and exploits advantages of two different feedback circuits to eliminate the negative impact of a large detector capacitance on the performance of ToT processing while keeping the power consumption at low level.
{"title":"Time-over-threshold processing implementation for silicon detectors with large capacitances","authors":"K. Kasinski, R. Kleczek, P. Grybos, R. Szczygiel","doi":"10.1109/NSSMIC.2012.6551232","DOIUrl":"https://doi.org/10.1109/NSSMIC.2012.6551232","url":null,"abstract":"Modern High Energy Physics experiments require more functionality from the multichannel readout circuits which in conjunction with strict limits on power consumption, area occupation and low noise performance set new requirements in the analog front-end electronics design. We discuss the applicability issues and design challenges of a constant-current discharge time-over-threshold (ToT) processing chain for readout of the large capacitance silicon strip detectors. The conclusions are based on measurement results of two prototype ASICs: TOTOl, TOT02. The revealed non-idealities and issues have been identified and are briefly presented in this paper. Moreover, an idea for charge amplifiaction, measurement and timestamping is proposed as a possible remedy for presented matters. This conception uses two cascaded amplifiers and exploits advantages of two different feedback circuits to eliminate the negative impact of a large detector capacitance on the performance of ToT processing while keeping the power consumption at low level.","PeriodicalId":187728,"journal":{"name":"2012 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS/MIC)","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132934807","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 : 2012-10-01DOI: 10.1109/NSSMIC.2012.6551949
N. Gary, Shiang Teng, A. Tiwari, Haori Yang
In this paper we are presenting a unique approach to solve the thermal background problem encountered in semiconductor nuclear detectors. Our approach addresses above challenge by making a shift from 'electronic detection mechanism' to 'spintronic detection mechanism'. The proposed methodology is based on the hypothesis that the electromagnetic field associated with the incident nuclear radiation will interact with the spin of the electrons (injected from a ferromagnetic electrode into a semiconductor channel) via the Rashba spin-orbit interaction mechanism. This interaction will result in a precession in the spin polarization of the electrons and as a result the current collected by another ferromagnetic electrode (which will be aligned either parallel or anti-parallel to the first electrode) will change. So, in contrast to traditional semiconductor detectors, where the radiation sensing mechanism depends on the generation and collection of charge carriers, in spintronic detectors, the radiation sensing mechanism will be based on the quantum mechanical precession of the spin of electrons.
{"title":"Room-temperature solid-state radiation detectors based on spintronics","authors":"N. Gary, Shiang Teng, A. Tiwari, Haori Yang","doi":"10.1109/NSSMIC.2012.6551949","DOIUrl":"https://doi.org/10.1109/NSSMIC.2012.6551949","url":null,"abstract":"In this paper we are presenting a unique approach to solve the thermal background problem encountered in semiconductor nuclear detectors. Our approach addresses above challenge by making a shift from 'electronic detection mechanism' to 'spintronic detection mechanism'. The proposed methodology is based on the hypothesis that the electromagnetic field associated with the incident nuclear radiation will interact with the spin of the electrons (injected from a ferromagnetic electrode into a semiconductor channel) via the Rashba spin-orbit interaction mechanism. This interaction will result in a precession in the spin polarization of the electrons and as a result the current collected by another ferromagnetic electrode (which will be aligned either parallel or anti-parallel to the first electrode) will change. So, in contrast to traditional semiconductor detectors, where the radiation sensing mechanism depends on the generation and collection of charge carriers, in spintronic detectors, the radiation sensing mechanism will be based on the quantum mechanical precession of the spin of electrons.","PeriodicalId":187728,"journal":{"name":"2012 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS/MIC)","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129396504","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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