Pub Date : 2012-10-01DOI: 10.1109/NSSMIC.2012.6551116
K. Sakasai, K. Toh, T. Nakamura, K. Takakura, C. Konno, Y. Iwamoto
Storage characteristics of mixtures of polyethylene powder and photostimulable phosphors such as KCI:EuH with low gamma-ray sensitivity were investigated in order to improve the spatial resolution when the mixtures were applied to fast neutron imaging. The maximum photostimulated luminescence yields were obtained at a KCI:EuH weight ratio of about 0.8 when the mixtures were irradiated by fast neutron with an energy of 14.8 MeV. These experimental results well agreed with theoretical predictions by Monte Carlo simulation using PHITS code. Estimated spatial resolution of the optimal mixture sample was 0.068 mm that was better than that obtained by conventional methods where the radiators are set in front of the phosphors. These mixtures will be usable for fast neutron imaging.
{"title":"Storage characteristics of mixtures of KCl:Eu2+ phosphors and polyethylene powder by irradiation of fast neutrons","authors":"K. Sakasai, K. Toh, T. Nakamura, K. Takakura, C. Konno, Y. Iwamoto","doi":"10.1109/NSSMIC.2012.6551116","DOIUrl":"https://doi.org/10.1109/NSSMIC.2012.6551116","url":null,"abstract":"Storage characteristics of mixtures of polyethylene powder and photostimulable phosphors such as KCI:EuH with low gamma-ray sensitivity were investigated in order to improve the spatial resolution when the mixtures were applied to fast neutron imaging. The maximum photostimulated luminescence yields were obtained at a KCI:EuH weight ratio of about 0.8 when the mixtures were irradiated by fast neutron with an energy of 14.8 MeV. These experimental results well agreed with theoretical predictions by Monte Carlo simulation using PHITS code. Estimated spatial resolution of the optimal mixture sample was 0.068 mm that was better than that obtained by conventional methods where the radiators are set in front of the phosphors. These mixtures will be usable for fast neutron imaging.","PeriodicalId":187728,"journal":{"name":"2012 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS/MIC)","volume":"29 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":"117086019","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}
Dual-head flat-panel positron emission tomography (PET) is the dedicated system for small-animal imaging because of its high spatial resolution and detection sensitivity. Unlike the conventional ring-based PET system, the dual-head system is versatile and can be reconfigured readily to accommodate different sample sizes and/or to achieve an optimal system performance. However, the unique imaging geometry also leads to severe depth-of-interaction (DOl) blurring. Monte Carlo simulation has been employed to account for DOl effects in the system response matrix with high accuracy, but the long simulation times make routine search for an optimal configuration impractical. To facilitate the system optimization while considering the parallax error, we employ an efficient numerical method to model the DOl effect in the system matrix for image reconstruction and accelerate the computation with the graphics processing units (GPUs). Among the system response matrices corresponding to different geometric configurations, a favorable one can be selected by exploiting the statistical detection theory. Computer simulation studies were carried out to validate and quantitatively evaluate the proposed method.
{"title":"Image reconstruction and signal detectability in dual-head small animal PET","authors":"Yu-Jiun Kao, Chun-Hao Kao, Yun Dong, C. Kao, Chin-Tu Chen, Weichung Wang, Cheng-Ying Chou","doi":"10.1109/NSSMIC.2012.6551784","DOIUrl":"https://doi.org/10.1109/NSSMIC.2012.6551784","url":null,"abstract":"Dual-head flat-panel positron emission tomography (PET) is the dedicated system for small-animal imaging because of its high spatial resolution and detection sensitivity. Unlike the conventional ring-based PET system, the dual-head system is versatile and can be reconfigured readily to accommodate different sample sizes and/or to achieve an optimal system performance. However, the unique imaging geometry also leads to severe depth-of-interaction (DOl) blurring. Monte Carlo simulation has been employed to account for DOl effects in the system response matrix with high accuracy, but the long simulation times make routine search for an optimal configuration impractical. To facilitate the system optimization while considering the parallax error, we employ an efficient numerical method to model the DOl effect in the system matrix for image reconstruction and accelerate the computation with the graphics processing units (GPUs). Among the system response matrices corresponding to different geometric configurations, a favorable one can be selected by exploiting the statistical detection theory. Computer simulation studies were carried out to validate and quantitatively evaluate the proposed method.","PeriodicalId":187728,"journal":{"name":"2012 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS/MIC)","volume":"5 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":"128609304","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.2012.6551106
M. F. Koskinas, F. W. Lacerda, I. M. Yamazaki, F. Toledo, M. N. Takeda, M. S. Dias
The present work aims the standardization of 68Ga, a positron emitter of short half-life used in PET (Positron Emission Tomography). The 68Ga standardization was performed in a triple 4πβ-γ coincidence system that consists of a thin window gas-flow proportional counter (PC) in 4π geometry coupled to a NaI(TI) scintillator and a HPGe crystal, for gamma-ray detection. The data acquisition was carried out by means of a Software Coincidence System (SCS) developed at the Nuclear Metrology Laboratory (Laboratorio de Metrologia Nuclear - LMN) at the IPEN-CNEN/SP. The final results were obtained from a multiple curve fitting applying a covariance matrix methodology combining experimental results with those determined by the Monte Carlo simulation.
68Ga是一种短半衰期正电子发射体，用于PET(正电子发射断层扫描)的标准化研究。68Ga标准化在一个4π三重β-γ符合系统中进行，该系统由一个4π几何形状的薄窗气体流动比例计数器(PC)与一个NaI(TI)闪烁体和一个HPGe晶体耦合组成，用于伽马射线检测。数据采集由IPEN-CNEN/SP的核计量实验室(Laboratory de Metrologia Nuclear - LMN)开发的软件重合系统(SCS)进行。将实验结果与蒙特卡罗模拟结果相结合，采用协方差矩阵法进行多次曲线拟合，得到最终结果。
{"title":"Standardization of 68Ga by means of a 4πβ-γ Software Coincidence System","authors":"M. F. Koskinas, F. W. Lacerda, I. M. Yamazaki, F. Toledo, M. N. Takeda, M. S. Dias","doi":"10.1109/NSSMIC.2012.6551106","DOIUrl":"https://doi.org/10.1109/NSSMIC.2012.6551106","url":null,"abstract":"The present work aims the standardization of 68Ga, a positron emitter of short half-life used in PET (Positron Emission Tomography). The 68Ga standardization was performed in a triple 4πβ-γ coincidence system that consists of a thin window gas-flow proportional counter (PC) in 4π geometry coupled to a NaI(TI) scintillator and a HPGe crystal, for gamma-ray detection. The data acquisition was carried out by means of a Software Coincidence System (SCS) developed at the Nuclear Metrology Laboratory (Laboratorio de Metrologia Nuclear - LMN) at the IPEN-CNEN/SP. The final results were obtained from a multiple curve fitting applying a covariance matrix methodology combining experimental results with those determined by the Monte Carlo simulation.","PeriodicalId":187728,"journal":{"name":"2012 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS/MIC)","volume":"16 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":"128715427","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.2012.6551849
Sangtae Ahn, H. Qian, R. Manjeshwar
Joint reconstruction of activity and attenuation maps from emission data only, while being a long-standing problem in emission tomography, has been gaining recent interests because of its application to MR-based attenuation correction in PET/MR scanners where CT images are not available. Furthermore, recent studies showed that TOF (time-of-flight) information can substantially reduce, or completely remove in theory, crosstalk artifacts, which had been one of the hurdles preventing joint reconstruction techniques from being used clinically. Nonetheless, estimating both activity and attenuation from TOF emission data is a computationally challenging nonconvex optimization problem with high-dimensional data size. Therefore, as a tool for investigating and optimizing the joint estimation techniques for clinical use, we need numerical algorithms that are derived in a principled way and guaranteed to converge to a solution. Here, in a PL (penalized-likelihood) framework, we present a block alternating MM (minorization maximization) algorithm, which is provably globally convergent although the PL objective function is nonconcave. By using linear parameterization of attenuation maps, the algorithm applies to a variety of scenarios, depending on the type of and the degree of prior information, in a unified way. In addition, we provide a proof of the uniqueness of solutions to joint estimation problems for a continuous-space TOF PET system whose TOF kernels do not need to be Gaussian.
{"title":"Convergent iterative algorithms for joint reconstruction of activity and attenuation from time-of-flight PET data","authors":"Sangtae Ahn, H. Qian, R. Manjeshwar","doi":"10.1109/NSSMIC.2012.6551849","DOIUrl":"https://doi.org/10.1109/NSSMIC.2012.6551849","url":null,"abstract":"Joint reconstruction of activity and attenuation maps from emission data only, while being a long-standing problem in emission tomography, has been gaining recent interests because of its application to MR-based attenuation correction in PET/MR scanners where CT images are not available. Furthermore, recent studies showed that TOF (time-of-flight) information can substantially reduce, or completely remove in theory, crosstalk artifacts, which had been one of the hurdles preventing joint reconstruction techniques from being used clinically. Nonetheless, estimating both activity and attenuation from TOF emission data is a computationally challenging nonconvex optimization problem with high-dimensional data size. Therefore, as a tool for investigating and optimizing the joint estimation techniques for clinical use, we need numerical algorithms that are derived in a principled way and guaranteed to converge to a solution. Here, in a PL (penalized-likelihood) framework, we present a block alternating MM (minorization maximization) algorithm, which is provably globally convergent although the PL objective function is nonconcave. By using linear parameterization of attenuation maps, the algorithm applies to a variety of scenarios, depending on the type of and the degree of prior information, in a unified way. In addition, we provide a proof of the uniqueness of solutions to joint estimation problems for a continuous-space TOF PET system whose TOF kernels do not need to be Gaussian.","PeriodicalId":187728,"journal":{"name":"2012 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS/MIC)","volume":"17 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":"129244825","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.2012.6551568
Uttam M. Shrestha, F. Alhassen, Youngho Seo, E. Botvinick, G. Gullberg
Modeling of data from a dynamic acquisition is complicated by the combination of camera motion, organ motion, and the time-varying nature of the radionuclide distribution being imaged which results in inconsistent projection data sets. Our approach is to estimate the time varying radionuclide distribution directly from projection data. Entire tomographic slices or volumes are represented by a multiresolution spatiotemporal parameterization. The heart is modeled using spatiotemporal model that takes into account changes in the deformation of the heart as well as changes in the intensity of the signal caused by uptake and washout of the radiopharmaceutical from the heart and motion of the camera. We have developed an algorithm to reconstruct the continuous kinetics of the radiopharmaceutical by using spatiotemporal basis functions when the cardiac cycle of the heart is uniformly gated. The temporal basis functions are chosen to reflect the optimal tracer dynamics while the gate basis functions are assumed to be periodic with respect to the beating of the heart. Our preliminary results show that the fast gantry rotation of the SPECT camera can delineate the proper positioning of the myocardium in the reconstructed image while the 'out of phase' slow camera rotation smear out the motion of the heart.
{"title":"Reconstruction of gated dynamic cardiac SPECT data using spatiotemporal basis functions","authors":"Uttam M. Shrestha, F. Alhassen, Youngho Seo, E. Botvinick, G. Gullberg","doi":"10.1109/NSSMIC.2012.6551568","DOIUrl":"https://doi.org/10.1109/NSSMIC.2012.6551568","url":null,"abstract":"Modeling of data from a dynamic acquisition is complicated by the combination of camera motion, organ motion, and the time-varying nature of the radionuclide distribution being imaged which results in inconsistent projection data sets. Our approach is to estimate the time varying radionuclide distribution directly from projection data. Entire tomographic slices or volumes are represented by a multiresolution spatiotemporal parameterization. The heart is modeled using spatiotemporal model that takes into account changes in the deformation of the heart as well as changes in the intensity of the signal caused by uptake and washout of the radiopharmaceutical from the heart and motion of the camera. We have developed an algorithm to reconstruct the continuous kinetics of the radiopharmaceutical by using spatiotemporal basis functions when the cardiac cycle of the heart is uniformly gated. The temporal basis functions are chosen to reflect the optimal tracer dynamics while the gate basis functions are assumed to be periodic with respect to the beating of the heart. Our preliminary results show that the fast gantry rotation of the SPECT camera can delineate the proper positioning of the myocardium in the reconstructed image while the 'out of phase' slow camera rotation smear out the motion of the heart.","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":"129477196","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.2012.6551254
C. R. Brambilla, G. Hoff
This work provides a critical analysis of the point source methodology applied in nuclear medicine radioactivity waste management routine. To evaluate the point source approximation used in the practice to determine the activity and its effect on activity and storage time was used deterministic and Monte Carlo calculations. The first step of this work was to validate the Monte Carlo Geant4 toolkit using measurements with standard calibration sources. After that the deterministic and Monte Carlo calculation was performed. In a realistic geometry the waste is not a point source but a box of dimensions (30.5 x 31.5 x 25.0) cm3. The impact on activity estimation comparing the real source point to the box geometry was observed from 20% up to 800% depending on the distance between the source and the detector and the selected radionuclide. The simple case evaluated in this work considering different radioisotopes proves that uses the point source approximation cause significant influence on the activity estimation. However it does not have significant impact in the storage time. The non significant influence in time storage can be explained by the activity limits recommend to release the radioactive waste that is significant smaller than the initial activity and the exponential behavior of the radioactive decay associated to value of the physical disintegration constant for the radionuclide commonly used on nuclear medicine applications.
本文对点源方法在核医学放射性废物管理中的应用进行了批判性分析。为了评估在实践中使用的点源近似来确定活度及其对活度和存储时间的影响，使用了确定性和蒙特卡罗计算。这项工作的第一步是使用带有标准校准源的测量来验证Monte Carlo Geant4工具包。然后进行了确定性计算和蒙特卡罗计算。在现实的几何形状中，废物不是点源，而是一个尺寸(30.5 x 31.5 x 25.0) cm3的盒子。根据源与探测器和所选放射性核素之间的距离，将实际源点与盒几何形状进行比较，观察到对活度估计的影响从20%到800%不等。考虑不同放射性同位素的简单实例证明，采用点源近似对活度估算有显著影响。但对储存时间影响不大。对时间储存的不显著影响可以解释为，建议释放的放射性废物的活度限值明显小于初始活度，以及与核医学应用中常用的放射性核素的物理衰变常数值相关的放射性衰变的指数行为。
{"title":"Evaluation of the solid radioactive waste activity in nuclear medicine: Definition of shape factors to real geometries","authors":"C. R. Brambilla, G. Hoff","doi":"10.1109/NSSMIC.2012.6551254","DOIUrl":"https://doi.org/10.1109/NSSMIC.2012.6551254","url":null,"abstract":"This work provides a critical analysis of the point source methodology applied in nuclear medicine radioactivity waste management routine. To evaluate the point source approximation used in the practice to determine the activity and its effect on activity and storage time was used deterministic and Monte Carlo calculations. The first step of this work was to validate the Monte Carlo Geant4 toolkit using measurements with standard calibration sources. After that the deterministic and Monte Carlo calculation was performed. In a realistic geometry the waste is not a point source but a box of dimensions (30.5 x 31.5 x 25.0) cm3. The impact on activity estimation comparing the real source point to the box geometry was observed from 20% up to 800% depending on the distance between the source and the detector and the selected radionuclide. The simple case evaluated in this work considering different radioisotopes proves that uses the point source approximation cause significant influence on the activity estimation. However it does not have significant impact in the storage time. The non significant influence in time storage can be explained by the activity limits recommend to release the radioactive waste that is significant smaller than the initial activity and the exponential behavior of the radioactive decay associated to value of the physical disintegration constant for the radionuclide commonly used on nuclear medicine applications.","PeriodicalId":187728,"journal":{"name":"2012 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS/MIC)","volume":"46 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":"129484115","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.2012.6551626
M. Budassi, M. Purschke, J. Fried, T. Cao, S. Stoll, E. Gualtieri, J. Karp, P. O'connor, D. Schlyer, C. Woody, P. Vaska
A new PET system has been developed for the purposes of simultaneous PET/MR whole body rodent imaging in conjunction with a Varian large-bore 9.4T MRI system with a commercial Insight birdcage coil. The detector and readout technology is based on that developed for the RatCAP PET system, resulting in a highly robust and compact design that is compatible with MRI systems at the highest field strength. Testing of the full readout chain has shown a successful implementation of both modalities, with indications of only modest cross-interference on MRI image quality or PET detection efficiency. The final design cycle is complete, and supports operation of the full system with upgrades to the data acquisition electronics, firmware, and software. First results from the complete PET system will be presented, including preliminary imaging and tests of interference between modalities.
{"title":"First results from the BNL/Penn PET-MRI system for whole body rodent imaging at 9.4T","authors":"M. Budassi, M. Purschke, J. Fried, T. Cao, S. Stoll, E. Gualtieri, J. Karp, P. O'connor, D. Schlyer, C. Woody, P. Vaska","doi":"10.1109/NSSMIC.2012.6551626","DOIUrl":"https://doi.org/10.1109/NSSMIC.2012.6551626","url":null,"abstract":"A new PET system has been developed for the purposes of simultaneous PET/MR whole body rodent imaging in conjunction with a Varian large-bore 9.4T MRI system with a commercial Insight birdcage coil. The detector and readout technology is based on that developed for the RatCAP PET system, resulting in a highly robust and compact design that is compatible with MRI systems at the highest field strength. Testing of the full readout chain has shown a successful implementation of both modalities, with indications of only modest cross-interference on MRI image quality or PET detection efficiency. The final design cycle is complete, and supports operation of the full system with upgrades to the data acquisition electronics, firmware, and software. First results from the complete PET system will be presented, including preliminary imaging and tests of interference between modalities.","PeriodicalId":187728,"journal":{"name":"2012 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS/MIC)","volume":"1857 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":"129891747","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.2012.6551740
J. Cabello, J. Gillam, J. Oliver, J. Barrio, M. Rafecas, G. Llosá
Increased sensitivity is one of the major challenges in novel detector development. While pixelated crystals are standard, the use of continuous crystals can provide increased active volume and thus sensitivity. Accurate estimation of the interaction positions of photons in continuous crystals requires a sophisticated algorithm. Additionally, including depth of interaction (Dol) in the reconstruction process can mitigate parallax effects near the edges of field of view, therefore Dol estimation is highly desirable. In this work, the interaction position coordinates in 3D are estimated adapting an already existing analytical model to our system with no additional hardware, training data sets or Monte Carlo simulations. The algorithm is implemented in a two-detector-head system comprised of continuous crystals coupled to SiPM arrays. Acquired data is stored in list-mode where the continuous nature of the interaction position is preserved. For image reconstruction, since the crystal is continuous, pre-computation of the system matrix elements would require discretization of the detected measurements. To avoid data discretization the system matrix elements are calculated on-the-fly. Spatial information is later on retained in the reconstruction algorithm by using a Siddon-like algorithm where the ray end-points correspond to the estimated interaction positions in continuous space, introducing the interaction position estimation uncertainty in the calculation of the system matrix elements. Reconstruction using continuous data is compared to reconstruction using artificially discretized data. Results show that the spatial resolution measured from a reconstructed point source using ML-EM obtained with a continuous crystal is superior to the spatial resolution obtained with a pixelated crystal.
{"title":"Monolithic crystals on SiPM arrays in a prototype system with depth of interaction estimation","authors":"J. Cabello, J. Gillam, J. Oliver, J. Barrio, M. Rafecas, G. Llosá","doi":"10.1109/NSSMIC.2012.6551740","DOIUrl":"https://doi.org/10.1109/NSSMIC.2012.6551740","url":null,"abstract":"Increased sensitivity is one of the major challenges in novel detector development. While pixelated crystals are standard, the use of continuous crystals can provide increased active volume and thus sensitivity. Accurate estimation of the interaction positions of photons in continuous crystals requires a sophisticated algorithm. Additionally, including depth of interaction (Dol) in the reconstruction process can mitigate parallax effects near the edges of field of view, therefore Dol estimation is highly desirable. In this work, the interaction position coordinates in 3D are estimated adapting an already existing analytical model to our system with no additional hardware, training data sets or Monte Carlo simulations. The algorithm is implemented in a two-detector-head system comprised of continuous crystals coupled to SiPM arrays. Acquired data is stored in list-mode where the continuous nature of the interaction position is preserved. For image reconstruction, since the crystal is continuous, pre-computation of the system matrix elements would require discretization of the detected measurements. To avoid data discretization the system matrix elements are calculated on-the-fly. Spatial information is later on retained in the reconstruction algorithm by using a Siddon-like algorithm where the ray end-points correspond to the estimated interaction positions in continuous space, introducing the interaction position estimation uncertainty in the calculation of the system matrix elements. Reconstruction using continuous data is compared to reconstruction using artificially discretized data. Results show that the spatial resolution measured from a reconstructed point source using ML-EM obtained with a continuous crystal is superior to the spatial resolution obtained with a pixelated crystal.","PeriodicalId":187728,"journal":{"name":"2012 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS/MIC)","volume":"156 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":"129216035","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.2012.6551058
Jianping Cheng, B. Yu, Ziran Zhao, Xuewu Wang
Cosmic-ray muon radiography is a novel method to detect high-Z materials in thick shield, and the reconstruction algorithm is the key point of this technique. In this paper, we have improved the traditional maximum likelihood algorithm, using EM method to get the estimation and OS technique to accelerate, and using the result from the Point of Closest Approach algorithm as the initial value. Having done the simulated numerical experiments in three dimensional space, we get some preliminary reconstruction results. This new method will be embedded into platform program and expanded into widely practical applications in muon tomography.
{"title":"Study of 3D reconstruction algorithm used in cosmic-ray muon radiography","authors":"Jianping Cheng, B. Yu, Ziran Zhao, Xuewu Wang","doi":"10.1109/NSSMIC.2012.6551058","DOIUrl":"https://doi.org/10.1109/NSSMIC.2012.6551058","url":null,"abstract":"Cosmic-ray muon radiography is a novel method to detect high-Z materials in thick shield, and the reconstruction algorithm is the key point of this technique. In this paper, we have improved the traditional maximum likelihood algorithm, using EM method to get the estimation and OS technique to accelerate, and using the result from the Point of Closest Approach algorithm as the initial value. Having done the simulated numerical experiments in three dimensional space, we get some preliminary reconstruction results. This new method will be embedded into platform program and expanded into widely practical applications in muon tomography.","PeriodicalId":187728,"journal":{"name":"2012 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS/MIC)","volume":"54 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":"129235226","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.2012.6551424
Jinyuan Wu
Usually, transmission lines such as coaxial cables, twist pair cables, printed circuit board traces etc. are carefully terminated to eliminate reflections when transmitting important signals such as system clocks. However, if appropriately designed, the reflection signal from the un-terminated cable end carries useful information which can be utilized to improve system performance. In this paper, multi-tap transmission lines with one open end are studied for clock distribution. When trapezoidal clock pulses with sufficiently long rising and falling ramps are fed into such a transmission line, the timing skews at different taps due to propagation delays can be compensated naturally as a result of the superposition of the transmitting and reflecting signals. Higher order effect due to resistive loss of the transmission lines is also discussed and the curve shapes of the raising/falling ramps for reducing higher order skews are derived and tested. Measurements are made on actual cables to validate this clock distribution scheme.
{"title":"The trapezoidal clocking","authors":"Jinyuan Wu","doi":"10.1109/NSSMIC.2012.6551424","DOIUrl":"https://doi.org/10.1109/NSSMIC.2012.6551424","url":null,"abstract":"Usually, transmission lines such as coaxial cables, twist pair cables, printed circuit board traces etc. are carefully terminated to eliminate reflections when transmitting important signals such as system clocks. However, if appropriately designed, the reflection signal from the un-terminated cable end carries useful information which can be utilized to improve system performance. In this paper, multi-tap transmission lines with one open end are studied for clock distribution. When trapezoidal clock pulses with sufficiently long rising and falling ramps are fed into such a transmission line, the timing skews at different taps due to propagation delays can be compensated naturally as a result of the superposition of the transmitting and reflecting signals. Higher order effect due to resistive loss of the transmission lines is also discussed and the curve shapes of the raising/falling ramps for reducing higher order skews are derived and tested. Measurements are made on actual cables to validate this clock distribution scheme.","PeriodicalId":187728,"journal":{"name":"2012 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS/MIC)","volume":"135 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":"129297666","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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