Pub Date : 2020-10-31DOI: 10.1109/NSS/MIC42677.2020.9508096
Logan J. Forth, H. Gibbard, Stephanie Biddlecombe, Isabel Braddock, C. Crean, J. C. Khong, Mingqing Wang, R. Speller, K. Choy, P. Sellin, R. Moss
Metal-halide perovskite materials have begun to attract much attention recently for their potential use in radiation detection applications. This interest is mainly due to their favourable semi-conductive properties, high electron density, ease of manufacture and relatively low cost compared to popular detector materials. In this paper we investigate inorganic caesium lead bromide (CsPbBr3). Polycrystalline powder samples were produced by solution growth and simple ‘sandwich’ devices were fabricated. The powder was manually ground and then pressed to form pellets of a few mm thickness. Gold planar electrodes were deposited on the top and bottom perovskite surfaces by evaporation and were connected to an external circuit. We have made comparative measurements of the photoluminescence (PL), dark current and temporal radiation response. The PL measurements showed stable emissions centred at 525 nm for CsPbBr3’ which is typical of these materials and within a useful range for this application. A CsPbBr3 device was exposed to X-rays and demonstrates a good increase in photocurrent over the dark current under both positive and negative bias with a sensitivity of 33.8 µCGy−1aircm−2and the temporal response was determined to be ~40 ms by measuring the photocurrent decay after X-ray illumination.
{"title":"Polycrystalline Perovskite X-ray Detectors","authors":"Logan J. Forth, H. Gibbard, Stephanie Biddlecombe, Isabel Braddock, C. Crean, J. C. Khong, Mingqing Wang, R. Speller, K. Choy, P. Sellin, R. Moss","doi":"10.1109/NSS/MIC42677.2020.9508096","DOIUrl":"https://doi.org/10.1109/NSS/MIC42677.2020.9508096","url":null,"abstract":"Metal-halide perovskite materials have begun to attract much attention recently for their potential use in radiation detection applications. This interest is mainly due to their favourable semi-conductive properties, high electron density, ease of manufacture and relatively low cost compared to popular detector materials. In this paper we investigate inorganic caesium lead bromide (CsPbBr3). Polycrystalline powder samples were produced by solution growth and simple ‘sandwich’ devices were fabricated. The powder was manually ground and then pressed to form pellets of a few mm thickness. Gold planar electrodes were deposited on the top and bottom perovskite surfaces by evaporation and were connected to an external circuit. We have made comparative measurements of the photoluminescence (PL), dark current and temporal radiation response. The PL measurements showed stable emissions centred at 525 nm for CsPbBr3’ which is typical of these materials and within a useful range for this application. A CsPbBr3 device was exposed to X-rays and demonstrates a good increase in photocurrent over the dark current under both positive and negative bias with a sensitivity of 33.8 µCGy−1aircm−2and the temporal response was determined to be ~40 ms by measuring the photocurrent decay after X-ray illumination.","PeriodicalId":6760,"journal":{"name":"2020 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC)","volume":"30 1","pages":"1-3"},"PeriodicalIF":0.0,"publicationDate":"2020-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90482268","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 : 2020-10-31DOI: 10.1109/NSS/MIC42677.2020.9507747
M. Aresti, A. Cardini, A. Lai, A. Loi, G. Cossu, M. Garau, A. Lampis, G. Betta, G. Forcolin
In the next generation of experiments at the future high luminosity particle colliders, the identification of the interaction and decay vertices will be an extremely difficult task because of the very large number of particles that will be produced at each bunch crossing. LHC experiments have shown that new vertex detectors with single-hit time resolutions of the order of 10 ps will allow to recover the current tracking and vertexing capabilities. The TimeSPOT project is developing 3D trench-based silicon pixel detectors with a time resolution below 30 ps. Initial beam test with a first sensors batch has showed that these detectors fulfill and even exceed these expectations. To carefully study their performances and optimize their design, it is important to precisely measure sensors time response over their active area. This paper summarize the preliminary measurements of this sensors developed within the TimeSPOT project performed in our laboratory, using a custom laser-based setup to deposit a known energy in specific regions of the pixel sensitive volume, allowing us to estimate the performances of these sensors under charge-particle illumination.
{"title":"Laboratory Characterization of Innovative 3D Trench-design Silicon Pixel Sensors Using a Sub-Picosecond Precision Laser-Based Testing Equipment","authors":"M. Aresti, A. Cardini, A. Lai, A. Loi, G. Cossu, M. Garau, A. Lampis, G. Betta, G. Forcolin","doi":"10.1109/NSS/MIC42677.2020.9507747","DOIUrl":"https://doi.org/10.1109/NSS/MIC42677.2020.9507747","url":null,"abstract":"In the next generation of experiments at the future high luminosity particle colliders, the identification of the interaction and decay vertices will be an extremely difficult task because of the very large number of particles that will be produced at each bunch crossing. LHC experiments have shown that new vertex detectors with single-hit time resolutions of the order of 10 ps will allow to recover the current tracking and vertexing capabilities. The TimeSPOT project is developing 3D trench-based silicon pixel detectors with a time resolution below 30 ps. Initial beam test with a first sensors batch has showed that these detectors fulfill and even exceed these expectations. To carefully study their performances and optimize their design, it is important to precisely measure sensors time response over their active area. This paper summarize the preliminary measurements of this sensors developed within the TimeSPOT project performed in our laboratory, using a custom laser-based setup to deposit a known energy in specific regions of the pixel sensitive volume, allowing us to estimate the performances of these sensors under charge-particle illumination.","PeriodicalId":6760,"journal":{"name":"2020 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC)","volume":"80 2","pages":"1-6"},"PeriodicalIF":0.0,"publicationDate":"2020-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91422952","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 : 2020-10-31DOI: 10.1109/NSS/MIC42677.2020.9507850
Xiao Liu, Hui Liu, Li Cheng, Zheng Gu, R. Yao, Yaqiang Liu
Many medical radionuclides can emit cascade photons sequentially, yet commercial imaging equipment like PET or SPECT don't make use of this information. We have developed a cascade gamma emission imager system to detect the cascade photons in coincidence for those radionuclide imaging. In previous study, reasonable reconstruction images could be obtained using coincidence event based MLEM (CE-MLEM) but with a low signal-to-noise ratio (SNR), caused by the poor sensitivity of the coincidence event. In this work, we proposed an MLEM with mixed events (ME-MLEM) reconstruction method based on the coincidence events incorporated with the simultaneously detected single photons to improve the SNR while maintaining the spatial resolution. A myocardial phantom filled with 1 mCi 177Lu3+ solution was scanned for 1 hour on our prototype setup. 1.36xl04 coincidence events and 8.27×107 single photons were acquired under a 25.6 ns CTW and 10.8%/14.6% @ 208/113 KeV energy window. CE-MLEM, single photon based MLEM (SP-MLEM), and ME-MLEM with a 0.001 weighting factor between coincidence events and single photons were then used for the image reconstruction. The results showed the potential for ME-MLEM to improve the image SNR while keeping the same spatial resolution as CE-MLEM. Our results demonstrated that our system's image quality could be improved when combined coincidence events and single photons together.
{"title":"An MLEM Reconstruction Method with Mixed Events Based on a Cascade Gamma Emission Imager System","authors":"Xiao Liu, Hui Liu, Li Cheng, Zheng Gu, R. Yao, Yaqiang Liu","doi":"10.1109/NSS/MIC42677.2020.9507850","DOIUrl":"https://doi.org/10.1109/NSS/MIC42677.2020.9507850","url":null,"abstract":"Many medical radionuclides can emit cascade photons sequentially, yet commercial imaging equipment like PET or SPECT don't make use of this information. We have developed a cascade gamma emission imager system to detect the cascade photons in coincidence for those radionuclide imaging. In previous study, reasonable reconstruction images could be obtained using coincidence event based MLEM (CE-MLEM) but with a low signal-to-noise ratio (SNR), caused by the poor sensitivity of the coincidence event. In this work, we proposed an MLEM with mixed events (ME-MLEM) reconstruction method based on the coincidence events incorporated with the simultaneously detected single photons to improve the SNR while maintaining the spatial resolution. A myocardial phantom filled with 1 mCi 177Lu3+ solution was scanned for 1 hour on our prototype setup. 1.36xl04 coincidence events and 8.27×107 single photons were acquired under a 25.6 ns CTW and 10.8%/14.6% @ 208/113 KeV energy window. CE-MLEM, single photon based MLEM (SP-MLEM), and ME-MLEM with a 0.001 weighting factor between coincidence events and single photons were then used for the image reconstruction. The results showed the potential for ME-MLEM to improve the image SNR while keeping the same spatial resolution as CE-MLEM. Our results demonstrated that our system's image quality could be improved when combined coincidence events and single photons together.","PeriodicalId":6760,"journal":{"name":"2020 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC)","volume":"11 1","pages":"1-3"},"PeriodicalIF":0.0,"publicationDate":"2020-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79203501","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 : 2020-10-31DOI: 10.1109/NSS/MIC42677.2020.9508105
R. Twyman, S. Arridge, Bangti Jin, B. Hutton, L. Brusaferri, K. Thielemans
Penalised PET image reconstruction methods are often accelerated with the use of only a subset of the data at each update. It is known that many subset algorithms, such as Ordered Subset Expectation Maximisation, do not converge to a single solution but to a limit cycle, which can lead to variations between subsequent image estimates. A new class of stochastic variance reduction optimisation algorithms have been recently proposed for general optimisation problems. These methods aim to reduce the subset update variance by incorporating previous subset gradients into the update direction computation. This work applies three of these algorithms to iterative PET penalised reconstruction and exhibits superior performance to standard deterministic reconstruction methods after only a few epochs.
{"title":"Stochastic Variance Reduction Optimisation Algorithms Applied to Iterative PET Reconstruction","authors":"R. Twyman, S. Arridge, Bangti Jin, B. Hutton, L. Brusaferri, K. Thielemans","doi":"10.1109/NSS/MIC42677.2020.9508105","DOIUrl":"https://doi.org/10.1109/NSS/MIC42677.2020.9508105","url":null,"abstract":"Penalised PET image reconstruction methods are often accelerated with the use of only a subset of the data at each update. It is known that many subset algorithms, such as Ordered Subset Expectation Maximisation, do not converge to a single solution but to a limit cycle, which can lead to variations between subsequent image estimates. A new class of stochastic variance reduction optimisation algorithms have been recently proposed for general optimisation problems. These methods aim to reduce the subset update variance by incorporating previous subset gradients into the update direction computation. This work applies three of these algorithms to iterative PET penalised reconstruction and exhibits superior performance to standard deterministic reconstruction methods after only a few epochs.","PeriodicalId":6760,"journal":{"name":"2020 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC)","volume":"15 1","pages":"1-2"},"PeriodicalIF":0.0,"publicationDate":"2020-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79714187","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 : 2020-10-31DOI: 10.1109/NSS/MIC42677.2020.9507815
Eric W. Petersen, Wei Zhao, A. Goldan
Current clinical positron emission tomography scanners are distinguished by their large, circular detector rings - necessary to minimize spatial blue from parallax and Compton scattering within the detector. Recent advances in detector capability, specifically depth-of-interaction (DOI) localization and Compton scatter recovery, enable alternative detector designs that are more conformal to the human body. In particular, the Prism- PET detector - a single-ended detector with a segmented light guide - has demonstrated potential in both DOI localization and Compton recovery. With this in mind, we propose a hexagonal detector geometry, Arc-PET, and develop analytical expressions to quantify the geometric efficiency and spatial resolution of the detector.
{"title":"Arc-PET: Cost-Effective Whole-Body Scanner with High Sensitivity and High Spatial Resolution","authors":"Eric W. Petersen, Wei Zhao, A. Goldan","doi":"10.1109/NSS/MIC42677.2020.9507815","DOIUrl":"https://doi.org/10.1109/NSS/MIC42677.2020.9507815","url":null,"abstract":"Current clinical positron emission tomography scanners are distinguished by their large, circular detector rings - necessary to minimize spatial blue from parallax and Compton scattering within the detector. Recent advances in detector capability, specifically depth-of-interaction (DOI) localization and Compton scatter recovery, enable alternative detector designs that are more conformal to the human body. In particular, the Prism- PET detector - a single-ended detector with a segmented light guide - has demonstrated potential in both DOI localization and Compton recovery. With this in mind, we propose a hexagonal detector geometry, Arc-PET, and develop analytical expressions to quantify the geometric efficiency and spatial resolution of the detector.","PeriodicalId":6760,"journal":{"name":"2020 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC)","volume":"3 1","pages":"1-4"},"PeriodicalIF":0.0,"publicationDate":"2020-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88567678","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 : 2020-10-31DOI: 10.1109/NSS/MIC42677.2020.9507987
L. Abbene, F. Principato, G. Gerardi, A. Buttacavoli, S. Altieri, C. Gong, N. Protti, M. Bettelli, N. S. Amadè, S. Zanettini, A. Zappettini, N. Auricchio, S. del Sordo, E. Caroli
Intense research activities have been carry out in the development of room temperature gamma ray spectroscopic imagers, aiming to compete with the excellent energy resolution of high-purity germanium (HPGe) detectors (0.3 % FWHM at 662 keV) obtained after cryogenic cooling. Cadmium-zinc-telluride (CZT) detectors equipped with pixel, strip and virtual Frisch-grid electrode structures represented an appealing solution for room temperature measurements. In this work, we present the performance of new high-resolution CZT drift strip detectors (19.4 x 19.4 x 6 mm3), recently fabricated at IMEM-CNR of Parma (Italy) in collaboration with due2lab company (Reggio Emilia, Italy). The detectors, working in planar transverse field (PTF) irradiation geometry, are able to perform 3D positioning and energy measurement of X rays and gamma rays: 2D positioning through cross-strip electrode patterns on the cathode/anode electrodes and the third coordinate by exploiting the C/A ratio and/or the drift time. A 32-channel digital electronics was used to process and analyze the zoo of collected/induced charge pulses from the strips. Excellent room temperature energy resolution (0.9 % FWHM at 662 keV)characterizes the detectors, after the application of a new correction technique. These activities follow the goals of two Italian research projects (3DCaTM and 3CaTS projects funded by ASI and INFN, respectively) on the development of spectroscopic X-ray and gamma ray imagers (10 keV-1MeV) for medical and astrophysical applications.
为了与低温冷却后获得的高纯锗(HPGe)探测器(662 keV时0.3% FWHM)的优异能量分辨率相竞争，在室温伽马能谱成像仪的开发方面开展了大量的研究活动。配备像素、条带和虚拟Frisch-grid电极结构的碲化镉锌(CZT)探测器代表了一种具有吸引力的室温测量解决方案。在这项工作中，我们介绍了新的高分辨率CZT漂移条探测器(19.4 x 19.4 x 6 mm3)的性能，该探测器最近在意大利帕尔马的IMEM-CNR与due2lab公司(意大利雷焦艾米利亚)合作制造。该探测器工作在平面横向场(PTF)辐照几何结构中，能够对X射线和伽马射线进行三维定位和能量测量;通过阴极/阳极电极上的交叉带电极图案进行二维定位;通过利用C/A比和/或漂移时间进行第三坐标定位。利用32通道数字电子学处理和分析了从条带中收集/感应的电荷脉冲。在应用了一种新的校正技术后，探测器具有优异的室温能量分辨率(662 keV时0.9 % FWHM)。这些活动遵循两个意大利研究项目(分别由ASI和INFN资助的3DCaTM和3CaTS项目)的目标，即开发用于医疗和天体物理应用的光谱x射线和伽马射线成像仪(10kv - 1mev)。
{"title":"New results on high-resolution 3-D CZT drift strip detectors","authors":"L. Abbene, F. Principato, G. Gerardi, A. Buttacavoli, S. Altieri, C. Gong, N. Protti, M. Bettelli, N. S. Amadè, S. Zanettini, A. Zappettini, N. Auricchio, S. del Sordo, E. Caroli","doi":"10.1109/NSS/MIC42677.2020.9507987","DOIUrl":"https://doi.org/10.1109/NSS/MIC42677.2020.9507987","url":null,"abstract":"Intense research activities have been carry out in the development of room temperature gamma ray spectroscopic imagers, aiming to compete with the excellent energy resolution of high-purity germanium (HPGe) detectors (0.3 % FWHM at 662 keV) obtained after cryogenic cooling. Cadmium-zinc-telluride (CZT) detectors equipped with pixel, strip and virtual Frisch-grid electrode structures represented an appealing solution for room temperature measurements. In this work, we present the performance of new high-resolution CZT drift strip detectors (19.4 x 19.4 x 6 mm3), recently fabricated at IMEM-CNR of Parma (Italy) in collaboration with due2lab company (Reggio Emilia, Italy). The detectors, working in planar transverse field (PTF) irradiation geometry, are able to perform 3D positioning and energy measurement of X rays and gamma rays: 2D positioning through cross-strip electrode patterns on the cathode/anode electrodes and the third coordinate by exploiting the C/A ratio and/or the drift time. A 32-channel digital electronics was used to process and analyze the zoo of collected/induced charge pulses from the strips. Excellent room temperature energy resolution (0.9 % FWHM at 662 keV)characterizes the detectors, after the application of a new correction technique. These activities follow the goals of two Italian research projects (3DCaTM and 3CaTS projects funded by ASI and INFN, respectively) on the development of spectroscopic X-ray and gamma ray imagers (10 keV-1MeV) for medical and astrophysical applications.","PeriodicalId":6760,"journal":{"name":"2020 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC)","volume":"4 1","pages":"1-3"},"PeriodicalIF":0.0,"publicationDate":"2020-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88798189","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 : 2020-10-31DOI: 10.1109/NSS/MIC42677.2020.9508049
Owen A. Anderson, L. Bläckberg, S. Sajedi, H. Sabet, L. Furenlid
New laser-induced optical-barrier technology designed to reduce depth-of-interaction blurring requires a new calibration approach. Calibration by using a collimated beam of gamma rays to acquire a mean detector response function is important for maximum-likelihood estimation of interaction location. We have designed and built a 5-axis calibration stage to meet this need. The calibration system is able to move independently in 3 linear and 2 rotational dimensions to allow for complete control of collimated beam position and direction. This allows us to simulate gamma rays coming through a pinhole from any angle in the field of view. The need for precision in the movements between positions of the system motivated the use of a probe to map out the detector. Collision detection and automation in the software simplifies and speeds up the calibration process.
{"title":"A 5-Axis Calibration Stage for Depth-of-Interaction-Correcting Scintillation Crystals","authors":"Owen A. Anderson, L. Bläckberg, S. Sajedi, H. Sabet, L. Furenlid","doi":"10.1109/NSS/MIC42677.2020.9508049","DOIUrl":"https://doi.org/10.1109/NSS/MIC42677.2020.9508049","url":null,"abstract":"New laser-induced optical-barrier technology designed to reduce depth-of-interaction blurring requires a new calibration approach. Calibration by using a collimated beam of gamma rays to acquire a mean detector response function is important for maximum-likelihood estimation of interaction location. We have designed and built a 5-axis calibration stage to meet this need. The calibration system is able to move independently in 3 linear and 2 rotational dimensions to allow for complete control of collimated beam position and direction. This allows us to simulate gamma rays coming through a pinhole from any angle in the field of view. The need for precision in the movements between positions of the system motivated the use of a probe to map out the detector. Collision detection and automation in the software simplifies and speeds up the calibration process.","PeriodicalId":6760,"journal":{"name":"2020 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC)","volume":"20 1","pages":"1-3"},"PeriodicalIF":0.0,"publicationDate":"2020-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87332685","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 : 2020-10-31DOI: 10.1109/NSS/MIC42677.2020.9507797
Xi Zhang, Baihezi Ye, S. Xie, Weijie Tao, Zhixiang Zhao, Qiu Huang, Jianfeng Xu, Q. Peng
The purpose of this study is to develop a PET detector with a 0.5 mm crystal size for high-resolution preclinical PET imaging. The methods to improve the decoding performances of the detectors, including the wedge-shaped light guides with different thicknesses, different methods to suppress the dark count noises in the SiPMs and different methods to calculate the flood maps, were investigated. The experimental results show that the PET detector developed in this study achieved an extraordinary decoding performance. The ratio of background “noise” in the flood map to the total events is about 40%. The simulation study shows that the intrinsic intra-crystal Compton scatters contribute to 30.32% of the background “noise”. Thus, the optical design of the detector and the electronics and algorithms to generate the flood maps only introduced 10% the background “noise”. We are currently constructing a high-resolution preclinical PET imager using 12 detectors.
{"title":"Preliminary Optimized Design of a High-resolution PET Detector with a 0.5 mm Crystal Size","authors":"Xi Zhang, Baihezi Ye, S. Xie, Weijie Tao, Zhixiang Zhao, Qiu Huang, Jianfeng Xu, Q. Peng","doi":"10.1109/NSS/MIC42677.2020.9507797","DOIUrl":"https://doi.org/10.1109/NSS/MIC42677.2020.9507797","url":null,"abstract":"The purpose of this study is to develop a PET detector with a 0.5 mm crystal size for high-resolution preclinical PET imaging. The methods to improve the decoding performances of the detectors, including the wedge-shaped light guides with different thicknesses, different methods to suppress the dark count noises in the SiPMs and different methods to calculate the flood maps, were investigated. The experimental results show that the PET detector developed in this study achieved an extraordinary decoding performance. The ratio of background “noise” in the flood map to the total events is about 40%. The simulation study shows that the intrinsic intra-crystal Compton scatters contribute to 30.32% of the background “noise”. Thus, the optical design of the detector and the electronics and algorithms to generate the flood maps only introduced 10% the background “noise”. We are currently constructing a high-resolution preclinical PET imager using 12 detectors.","PeriodicalId":6760,"journal":{"name":"2020 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC)","volume":"38 1","pages":"1-2"},"PeriodicalIF":0.0,"publicationDate":"2020-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90614400","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 : 2020-10-31DOI: 10.1109/NSS/MIC42677.2020.9507861
A. Gonzalez-Montoro, S. Pourashraf, M. S. Lee, J. Cates, Zhixiang Zhao, C. Levin
Incorporating 511 keV photon time-of-flight (TOF) information in PET enables a significant boost in reconstructed image signal-to-noise ratio (SNR). This SNR boost depends on the 511 keV photon pair coincidence time resolution (CTR) of the PET system, which is determined by several factors including properties of the scintillation crystal and photodetector, crystal-to-sensor coupling configurations, and reflective materials. The goal of the present work is to achieve 100 picoseconds (ps) CTR for > 2-fold additional improvement in reconstructed image SNR compared to state-of-the-art PET systems that currently have 250–400 ps CTR. A critical parameter to optimize in achieving this goal is the optical reflector's influence on light collection and transit time to the photodetector. For the experimental set-up, we made use of PET detector elements based on both 3×3×10 and 3×3×20 mm3 LGSO crystals coupled to an array of SiPMs by using a novel “side-readout” configuration. We have tested the CTR performance by applying four different reflector materials to the crystal surfaces namely: Enhanced Specular Reflector (ESR), Teflon, BaSO4 paint and TiO2 paint. In addition, we have also evaluated the influence of the scintillation crystal length on the CTR performance by testing 3×3×10mm3 and 3×3×20mm3 LGSO crystals.
{"title":"Study of optical reflectors used in scintillation detectors that achieve 100 ps coincidence time resolution for TOF-PET","authors":"A. Gonzalez-Montoro, S. Pourashraf, M. S. Lee, J. Cates, Zhixiang Zhao, C. Levin","doi":"10.1109/NSS/MIC42677.2020.9507861","DOIUrl":"https://doi.org/10.1109/NSS/MIC42677.2020.9507861","url":null,"abstract":"Incorporating 511 keV photon time-of-flight (TOF) information in PET enables a significant boost in reconstructed image signal-to-noise ratio (SNR). This SNR boost depends on the 511 keV photon pair coincidence time resolution (CTR) of the PET system, which is determined by several factors including properties of the scintillation crystal and photodetector, crystal-to-sensor coupling configurations, and reflective materials. The goal of the present work is to achieve 100 picoseconds (ps) CTR for > 2-fold additional improvement in reconstructed image SNR compared to state-of-the-art PET systems that currently have 250–400 ps CTR. A critical parameter to optimize in achieving this goal is the optical reflector's influence on light collection and transit time to the photodetector. For the experimental set-up, we made use of PET detector elements based on both 3×3×10 and 3×3×20 mm3 LGSO crystals coupled to an array of SiPMs by using a novel “side-readout” configuration. We have tested the CTR performance by applying four different reflector materials to the crystal surfaces namely: Enhanced Specular Reflector (ESR), Teflon, BaSO4 paint and TiO2 paint. In addition, we have also evaluated the influence of the scintillation crystal length on the CTR performance by testing 3×3×10mm3 and 3×3×20mm3 LGSO crystals.","PeriodicalId":6760,"journal":{"name":"2020 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC)","volume":"10 1","pages":"1-3"},"PeriodicalIF":0.0,"publicationDate":"2020-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90729551","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 : 2020-10-31DOI: 10.1109/NSS/MIC42677.2020.9507825
M. Nazari, Isaac Shiri, H. Zaidi
Clear cell renal cell carcinoma (ccRCC) is one of the most aggressive histologic subtype of RCC. In this study, we developed and evaluated a Bayesian network as a prognostic model using computed tomography (CT) radiomic features and clinical information to predict the risk of death within 5 years for ccRCC patients. Seventy patients who had abdominal CT scans with delayed post-contrast phase and outcome data were enrolled. 3D volumes of interest (VOIs) covering the whole tumor on CT images were manually delineated. Image preprocessing techniques including, wavelet, Laplacian of Gaussian, and resampling of the intensity values to 32, 64 and 128 bin levels were applied on all VOIs. Different radiomic features, including shape, first-order, and texture features were extracted from the VOIs. For features selection, we first used the z-score method to normalize all image features, then the relevant features were selected based on mutual information (MI) criteria. The patients were divided into a low- and high-risk group based on survival or death at 5 years after surgery, respectively. Bayesian networks were used as a classifier for risk stratification. The model was evaluated using the area under the curve (AUC), sensitivity, specificity, and accuracy by 1000 bootstra resampling. The Bayesian model with Laplacian of Gaussian (LOG) filter showed the best predictive performance in this cohort with an AUC, sensitivity, specificity, and accuracy of 0.94, 85 %, 94%, and 89%, respectively. The results of the current study indicated that prognostic models based on radiomic features are very promising tools for risk stratification for ccRCC patients.
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