Pub Date : 2020-10-31DOI: 10.1109/NSS/MIC42677.2020.9508057
Tao Feng, Hongdi Li, Yizhang Zhao, N. Omidvari, Yang Lv, Elizabeth Li, Debin Hu, Y. Abdelhafez, J. Schmall, R. Badawi, S. Cherry
For a dedicated brain scan, the carotid artery is the best location for acquiring an image-based input function. With improvements in PET spatial resolution, accurate quantitation may be achieved with PET data alone. With the ability to cover both the carotid artery and the thorax at high spatial resolution, the uEXPLORER datasets provide a unique opportunity to develop and validate input functions in multiple regions such as the carotid artery. The regions containing the carotid arteries were first manually identified using reconstructed images consisting of the first 60 seconds of data post-injection. The image-based point spread function (PSF) was measured using off-center phantom scans to approximate the locations of the carotid artery. The same reconstruction approach was used for both the phantom scans and the volunteer scans. The structure of the carotid artery at each slice was generated using a deconvolution approach. An additional constraint of a uniform activity distribution within the carotid artery was added in the deconvolution approach. The acquired carotid artery structure was then applied to the dynamic frames (1-hour data) from volunteer scans for partial volume correction to acquire the input function (CA-IF). The input function from the descending aorta (DA-IF) was also extracted as a gold standard. The area-under-curve (AUC) ratio between the two input functions was used to evaluate the accuracy of the method. Without correction, there was a significant visual difference between CA-IF and the DA-IF, which was reduced dramatically after correction. The quantitation difference was dramatically reduced with the proposed correction method. The AUC ratio between the two input functions was 0.78+-0.04 (original), and was 1.00+-0.03 after correction, suggesting much improved quantitative accuracy. The results demonstrated that with improved image resolution and sensitivity, it is possible to accurately acquire the input function from carotid arteries without reliance on extra anatomical imaging approaches such as MRI.
{"title":"Development and Validation of an Accurate Input Function from Carotid Arteries using the uEXPLORER","authors":"Tao Feng, Hongdi Li, Yizhang Zhao, N. Omidvari, Yang Lv, Elizabeth Li, Debin Hu, Y. Abdelhafez, J. Schmall, R. Badawi, S. Cherry","doi":"10.1109/NSS/MIC42677.2020.9508057","DOIUrl":"https://doi.org/10.1109/NSS/MIC42677.2020.9508057","url":null,"abstract":"For a dedicated brain scan, the carotid artery is the best location for acquiring an image-based input function. With improvements in PET spatial resolution, accurate quantitation may be achieved with PET data alone. With the ability to cover both the carotid artery and the thorax at high spatial resolution, the uEXPLORER datasets provide a unique opportunity to develop and validate input functions in multiple regions such as the carotid artery. The regions containing the carotid arteries were first manually identified using reconstructed images consisting of the first 60 seconds of data post-injection. The image-based point spread function (PSF) was measured using off-center phantom scans to approximate the locations of the carotid artery. The same reconstruction approach was used for both the phantom scans and the volunteer scans. The structure of the carotid artery at each slice was generated using a deconvolution approach. An additional constraint of a uniform activity distribution within the carotid artery was added in the deconvolution approach. The acquired carotid artery structure was then applied to the dynamic frames (1-hour data) from volunteer scans for partial volume correction to acquire the input function (CA-IF). The input function from the descending aorta (DA-IF) was also extracted as a gold standard. The area-under-curve (AUC) ratio between the two input functions was used to evaluate the accuracy of the method. Without correction, there was a significant visual difference between CA-IF and the DA-IF, which was reduced dramatically after correction. The quantitation difference was dramatically reduced with the proposed correction method. The AUC ratio between the two input functions was 0.78+-0.04 (original), and was 1.00+-0.03 after correction, suggesting much improved quantitative accuracy. The results demonstrated that with improved image resolution and sensitivity, it is possible to accurately acquire the input function from carotid arteries without reliance on extra anatomical imaging approaches such as MRI.","PeriodicalId":6760,"journal":{"name":"2020 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC)","volume":"55 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":"84875516","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/MIC42677.2020.9507968
Maxime Toussaint, R. Lecomte, J. Dussault
It was recently demonstrated that using ultra-fast Time-of-Flight (ToF) in positron emission tomography can mitigate the blur induced by the detector size. In another study, it was also observed that resolution beyond the expected Gaussian blur of annihilation photon acolinearity (APA) could be achieved, even though APA was not modeled in the system matrix. This incongruity is further investigated in this work. With perfect ToF resolution, the resulting response function is shown to be the product between the expected Gaussian APA and the 1/r function. A 2D scanner with 1-mm wide detectors and 2-mm ToF resolution is used to further explore the issue. Simulation of point sources shows that the reconstructed profiles were indeed not Gaussian. A Hot Spots phantom was also simulated to evaluate qualitatively the scanner resolving power and, again, resolution beyond the expected 0.0044R, R being the scanner radius, was achieved. These results highlight that the spatial response function induced by neglecting APA in the reconstruction scheme is sharper than expected, approaching an 1/r shape, when ultra-fast ToF is available.
{"title":"Annihilation Photon Acolinearity with Ultra-fast ToF-PET","authors":"Maxime Toussaint, R. Lecomte, J. Dussault","doi":"10.1109/NSS/MIC42677.2020.9507968","DOIUrl":"https://doi.org/10.1109/NSS/MIC42677.2020.9507968","url":null,"abstract":"It was recently demonstrated that using ultra-fast Time-of-Flight (ToF) in positron emission tomography can mitigate the blur induced by the detector size. In another study, it was also observed that resolution beyond the expected Gaussian blur of annihilation photon acolinearity (APA) could be achieved, even though APA was not modeled in the system matrix. This incongruity is further investigated in this work. With perfect ToF resolution, the resulting response function is shown to be the product between the expected Gaussian APA and the 1/r function. A 2D scanner with 1-mm wide detectors and 2-mm ToF resolution is used to further explore the issue. Simulation of point sources shows that the reconstructed profiles were indeed not Gaussian. A Hot Spots phantom was also simulated to evaluate qualitatively the scanner resolving power and, again, resolution beyond the expected 0.0044R, R being the scanner radius, was achieved. These results highlight that the spatial response function induced by neglecting APA in the reconstruction scheme is sharper than expected, approaching an 1/r shape, when ultra-fast ToF is available.","PeriodicalId":6760,"journal":{"name":"2020 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC)","volume":"174 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":"85184850","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/MIC42677.2020.9507793
Haoran Chang, Rhodri L. Smith, S. Paisey, R. Boutchko, D. Mitra
Previously, we have shown that an image location, size, or even constant attenuation factor may be estimated by deep learning from the images Radon transformed representation. In this project, we go a step further to estimate a few other mathematical transformation parameters under Radon transformation. The motivation behind the project is that many medical imaging problems are related to estimating similar invariance parameters. Such estimations are typically performed after image reconstruction from detector images that are in the Radon transformed space. The image reconstruction process introduces additional noise of its own. Deep learning provides a framework for direct estimation of required information from the detector images. A specific case we are interested in is dynamic nuclear imaging, where the quantitative estimations of the target tissues are queried. Motion inherent in biological systems, e.g., in vivo imaging with breathing motion, may be modeled as a transformation in the spatial domain. Motion is particularly prevalent in dynamic imaging, while tracer dynamics in the imaged object are a second source of transformation in the time domain. Our neural network model attempts to discern the two types of transformation (motion and intensity variation dynamics), i.e., tries to learn one type of transformation, ignoring the other.
{"title":"Deep Learning Image Transformation under Radon Transform","authors":"Haoran Chang, Rhodri L. Smith, S. Paisey, R. Boutchko, D. Mitra","doi":"10.1109/NSS/MIC42677.2020.9507793","DOIUrl":"https://doi.org/10.1109/NSS/MIC42677.2020.9507793","url":null,"abstract":"Previously, we have shown that an image location, size, or even constant attenuation factor may be estimated by deep learning from the images Radon transformed representation. In this project, we go a step further to estimate a few other mathematical transformation parameters under Radon transformation. The motivation behind the project is that many medical imaging problems are related to estimating similar invariance parameters. Such estimations are typically performed after image reconstruction from detector images that are in the Radon transformed space. The image reconstruction process introduces additional noise of its own. Deep learning provides a framework for direct estimation of required information from the detector images. A specific case we are interested in is dynamic nuclear imaging, where the quantitative estimations of the target tissues are queried. Motion inherent in biological systems, e.g., in vivo imaging with breathing motion, may be modeled as a transformation in the spatial domain. Motion is particularly prevalent in dynamic imaging, while tracer dynamics in the imaged object are a second source of transformation in the time domain. Our neural network model attempts to discern the two types of transformation (motion and intensity variation dynamics), i.e., tries to learn one type of transformation, ignoring the other.","PeriodicalId":6760,"journal":{"name":"2020 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC)","volume":"37 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":"82189389","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/MIC42677.2020.9507745
V. Nagarkar, S. Miller, M. Marshall, C. Brown, C. Sosa, Bipin Singh, L. D'Aries
Federal agencies including DOE (NNSA), CWMD, and DTRA all play a vital role in the U.S. government's efforts to prevent, counter, and respond to a terrorist or other adversary with a nuclear or radiological device. To support its functions and foundational capabilities across nonproliferation, counterterrorism, and emergency response mission areas, these agencies need advanced sensors and instrumentation that may be used to rapidly identify threats and get the information needed to plan a response. At RMD we are developing the tools and techniques that will address some of these mission needs. One ongoing effort involves the development of a portable, high spatial resolution, combined neutron/X-ray radiography detector. The detector is capable of high sensitivity imaging of fast neutrons, thermal neutrons, and high energy X-rays, and will permit data analysis for material identification purposes. The key enabling technology for such a detector is the fabrication of a large area scintillator converter that can simultaneously detect fast neutrons, thermal neutrons, and hard X-rays, with the highest possible efficiency. To preserve spatial resolution the scintillator is microstructured to minimize the traditional trade-off between the detection efficiency and spatial resolution. Additionally, the scintillator should be sufficiently bright for enhanced signal-to-noise-ratio (SNR), and its fabrication method should be amenable for producing large area sensors. We are investigating several approaches to realize such sensors. Here, we report preliminary results on a portable flat panel based large area detector measuring 25 cm × 30 cm in active imaging area, and an intrinsic spatial resolution of 139 µm. The report also includes scintillator design approaches, GEANT4 simulations of scintillator response to various radiation types, and experimental imaging data taken using thermal neutrons, fast neutrons between 1 MeV to 40 MeV, and hard X-rays up to 400 kV. The performance of the detector as a whole has been evaluated at ORNL and NIST neutron beam lines.
{"title":"High Resolution Combined Neutron/X-ray Imaging Detector","authors":"V. Nagarkar, S. Miller, M. Marshall, C. Brown, C. Sosa, Bipin Singh, L. D'Aries","doi":"10.1109/NSS/MIC42677.2020.9507745","DOIUrl":"https://doi.org/10.1109/NSS/MIC42677.2020.9507745","url":null,"abstract":"Federal agencies including DOE (NNSA), CWMD, and DTRA all play a vital role in the U.S. government's efforts to prevent, counter, and respond to a terrorist or other adversary with a nuclear or radiological device. To support its functions and foundational capabilities across nonproliferation, counterterrorism, and emergency response mission areas, these agencies need advanced sensors and instrumentation that may be used to rapidly identify threats and get the information needed to plan a response. At RMD we are developing the tools and techniques that will address some of these mission needs. One ongoing effort involves the development of a portable, high spatial resolution, combined neutron/X-ray radiography detector. The detector is capable of high sensitivity imaging of fast neutrons, thermal neutrons, and high energy X-rays, and will permit data analysis for material identification purposes. The key enabling technology for such a detector is the fabrication of a large area scintillator converter that can simultaneously detect fast neutrons, thermal neutrons, and hard X-rays, with the highest possible efficiency. To preserve spatial resolution the scintillator is microstructured to minimize the traditional trade-off between the detection efficiency and spatial resolution. Additionally, the scintillator should be sufficiently bright for enhanced signal-to-noise-ratio (SNR), and its fabrication method should be amenable for producing large area sensors. We are investigating several approaches to realize such sensors. Here, we report preliminary results on a portable flat panel based large area detector measuring 25 cm × 30 cm in active imaging area, and an intrinsic spatial resolution of 139 µm. The report also includes scintillator design approaches, GEANT4 simulations of scintillator response to various radiation types, and experimental imaging data taken using thermal neutrons, fast neutrons between 1 MeV to 40 MeV, and hard X-rays up to 400 kV. The performance of the detector as a whole has been evaluated at ORNL and NIST neutron beam lines.","PeriodicalId":6760,"journal":{"name":"2020 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC)","volume":"3 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":"79509555","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/MIC42677.2020.9507858
V. Viswanath, M. Daube-Witherspoon, A. Pantel, M. Parma, M. Werner, J. Karp
Long axial field-of-view (AFOV) PET scanners have valuable benefits for both clinical and research applications. Thus far, two of these scanners are currently operational in the US: the 194-cm uExplorer at UC Davis and the PennPET Explorer at the University of Pennsylvania. We had previously reported performance metrics and human imaging studies on the 64-cm PennPET Explorer and have recently completed extending the AFOV of the scanner to a 5-ring, 112-cm system. We extended the NEMA metrics to scanners longer than 65-cm and performed sensitivity, count rate, spatial resolution, and contrast recovery measurements on the 5-ring system. The sensitivity of the system was 104 kcps/MBq; the peak NEC measured with a 20×70 cm count rate phantom was 1.6 Mcps @ 39 kBq/cc; the axial spatial resolution degraded slightly for the 62° acceptance angle; and the contrast recovery did not degrade as a function of increased axial acceptance angle. Therefore, extending the axial length of the PennPET Explorer from 64 cm to 112 cm, while expanding the acceptance angle, resulted in gains in sensitivity and count rate with minimal degradations in spatial resolution and no degradation of contrast recovery.
{"title":"Performance Benefits of Extending the AFOV of PET Scanners","authors":"V. Viswanath, M. Daube-Witherspoon, A. Pantel, M. Parma, M. Werner, J. Karp","doi":"10.1109/NSS/MIC42677.2020.9507858","DOIUrl":"https://doi.org/10.1109/NSS/MIC42677.2020.9507858","url":null,"abstract":"Long axial field-of-view (AFOV) PET scanners have valuable benefits for both clinical and research applications. Thus far, two of these scanners are currently operational in the US: the 194-cm uExplorer at UC Davis and the PennPET Explorer at the University of Pennsylvania. We had previously reported performance metrics and human imaging studies on the 64-cm PennPET Explorer and have recently completed extending the AFOV of the scanner to a 5-ring, 112-cm system. We extended the NEMA metrics to scanners longer than 65-cm and performed sensitivity, count rate, spatial resolution, and contrast recovery measurements on the 5-ring system. The sensitivity of the system was 104 kcps/MBq; the peak NEC measured with a 20×70 cm count rate phantom was 1.6 Mcps @ 39 kBq/cc; the axial spatial resolution degraded slightly for the 62° acceptance angle; and the contrast recovery did not degrade as a function of increased axial acceptance angle. Therefore, extending the axial length of the PennPET Explorer from 64 cm to 112 cm, while expanding the acceptance angle, resulted in gains in sensitivity and count rate with minimal degradations in spatial resolution and no degradation of contrast recovery.","PeriodicalId":6760,"journal":{"name":"2020 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC)","volume":"110 1","pages":"1-7"},"PeriodicalIF":0.0,"publicationDate":"2020-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79642590","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/MIC42677.2020.9507741
Zahra Ashouri, A. Groll, C. Levin
Including accurate modeling of the point spread function (PSF) in positron emission tomography (PET) reconstruction algorithms results in improvements in image spatial resolution and contrast. In this work, we sampled the PSF in our first-generation radio-frequency brain dedicated PET insert for simultaneous PET/MR imaging using a 100 µCi NEMA standard 250 µm diameter Na-22 point source at 13 different positions within a subsection of the system field of view (FoV). The acquired list mode data was converted into the canonical sinogram format from which the spatial positioning of the source and standard deviations were calculated. The subset was then used to extrapolate the PSF for the full system FoV. This model was then fed as an input parameter into a graphical processing unit based ordered subset expectation maximization (OSEM) reconstruction algorithm and used to generate reconstructed images with and without spatially varying PSF modeling for the Na-22 point source and a Hoffman brain phantom. Results indicate that for point source reconstruction, the FWHM of the horizontal profile of the point source is smaller with spatially variant PSF especially closer to the edges. Effect of spatially varying PSF modeling is also presented with Hoffman phantom reconstruction and CNR value has increased with spatially varying PSF.
{"title":"PET Reconstruction with a Spatially Varying Point Spread Function for a Brain Dedicated PET Insert for PET/MR","authors":"Zahra Ashouri, A. Groll, C. Levin","doi":"10.1109/NSS/MIC42677.2020.9507741","DOIUrl":"https://doi.org/10.1109/NSS/MIC42677.2020.9507741","url":null,"abstract":"Including accurate modeling of the point spread function (PSF) in positron emission tomography (PET) reconstruction algorithms results in improvements in image spatial resolution and contrast. In this work, we sampled the PSF in our first-generation radio-frequency brain dedicated PET insert for simultaneous PET/MR imaging using a 100 µCi NEMA standard 250 µm diameter Na-22 point source at 13 different positions within a subsection of the system field of view (FoV). The acquired list mode data was converted into the canonical sinogram format from which the spatial positioning of the source and standard deviations were calculated. The subset was then used to extrapolate the PSF for the full system FoV. This model was then fed as an input parameter into a graphical processing unit based ordered subset expectation maximization (OSEM) reconstruction algorithm and used to generate reconstructed images with and without spatially varying PSF modeling for the Na-22 point source and a Hoffman brain phantom. Results indicate that for point source reconstruction, the FWHM of the horizontal profile of the point source is smaller with spatially variant PSF especially closer to the edges. Effect of spatially varying PSF modeling is also presented with Hoffman phantom reconstruction and CNR value has increased with spatially varying PSF.","PeriodicalId":6760,"journal":{"name":"2020 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC)","volume":"37 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":"84355498","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/MIC42677.2020.9507969
Chen Hu, Jiang Li, B. Jiang, Liyuan Zhang, R. Zhu
Because of its potential low cost, bright and fast LuAG scintillating ceramics have attracted a broad interest in the HEP community. One crucial issue for its application at future high energy colliders is its radiation hardness against hadrons, including both neutrons and protons. LuAG ceramics were irradiated at LANSCE and CERN up to 6.7×1015neq/cm2 and 1.2×1015 p/cm2 respectively, and are found to have a factor of two better radiation hardness than LYSO crystals. Ca2+ codoping in LuAG ceramics improves the fast to total ratio and the radiation hardness against hadrons.
{"title":"Neutron and Proton-Induced Radiation Damage in LuAG Scintillating Ceramics","authors":"Chen Hu, Jiang Li, B. Jiang, Liyuan Zhang, R. Zhu","doi":"10.1109/NSS/MIC42677.2020.9507969","DOIUrl":"https://doi.org/10.1109/NSS/MIC42677.2020.9507969","url":null,"abstract":"Because of its potential low cost, bright and fast LuAG scintillating ceramics have attracted a broad interest in the HEP community. One crucial issue for its application at future high energy colliders is its radiation hardness against hadrons, including both neutrons and protons. LuAG ceramics were irradiated at LANSCE and CERN up to 6.7×1015neq/cm2 and 1.2×1015 p/cm2 respectively, and are found to have a factor of two better radiation hardness than LYSO crystals. Ca2+ codoping in LuAG ceramics improves the fast to total ratio and the radiation hardness against hadrons.","PeriodicalId":6760,"journal":{"name":"2020 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC)","volume":"81 6 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":"85310162","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/MIC42677.2020.9508058
S. Butalla, M. Hohlmann
The LHe is currently undergoing a high luminosity upgrade, which is set to increase the instantaneous luminosity by at least a factor of five. This luminosity increase will result in a higher muon flux rate in the forward region and overwhelm the current trigger system of the CMS experiment. The MEO, a gas electron multiplier detector, is proposed for the Phase-2 Muon System Upgrade for the CMS experiment to help increase the muon acceptance and to control the Level 1 muon trigger rate. A recent design iteration of this detector features GEM foils that are segmented on both sides, which helps to lower the probability of high voltage discharges. However, during preliminary testing of the chamber, substantial crosstalk between readout sectors was observed. Here, we investigate, characterize, and quantify the crosstalk present in the detector, and also estimate the performance of the chamber as a result of this crosstalk via simulation results of the detector dead time, efficiency loss, and frontend electronics response. The results of crosstalk via signals produced by applying a square voltage pulse directly on the readout strips of the detector with a signal generator are summarized. We also present the efficacy of mitigation strategies including bypass capacitors and increasing the area of the HV segments on the third GEM foil in the detector. We find that the crosstalk is a result of capacitive coupling between the readout strips on the readout board and between the readout strips and the bottom of the third GEM foil. Our results show that the crosstalk generally follows a pattern where the largest magnitude of crosstalk is within the same azimuthal readout segment in the detector, and in the next-nearest horizontal segments in eta. Generally, the bypass capacitors and increased area of the HV segments successfully lower the crosstalk in the sectors where they are located; on average, we observe a maximum decrease of crosstalk in sectors previously experiencing crosstalk from (1.66±0.03)% to (1.11±0.02)% with all HV segments connected in parallel on the bottom of the third GEM foil, with the addition of an HV low-pass filter connected to this electrode, and an HV divider. However, with these mitigation strategies, we also observe slightly increased crosstalk (≨ 0.4%) in readout sectors farther away.
{"title":"Investigation and Mitigation of Crosstalk in the Prototype ME0 GEM Detector for the Phase-2 Muon System Upgrade of the CMS Experiment: On behalf of the CMS Muon Group","authors":"S. Butalla, M. Hohlmann","doi":"10.1109/NSS/MIC42677.2020.9508058","DOIUrl":"https://doi.org/10.1109/NSS/MIC42677.2020.9508058","url":null,"abstract":"The LHe is currently undergoing a high luminosity upgrade, which is set to increase the instantaneous luminosity by at least a factor of five. This luminosity increase will result in a higher muon flux rate in the forward region and overwhelm the current trigger system of the CMS experiment. The MEO, a gas electron multiplier detector, is proposed for the Phase-2 Muon System Upgrade for the CMS experiment to help increase the muon acceptance and to control the Level 1 muon trigger rate. A recent design iteration of this detector features GEM foils that are segmented on both sides, which helps to lower the probability of high voltage discharges. However, during preliminary testing of the chamber, substantial crosstalk between readout sectors was observed. Here, we investigate, characterize, and quantify the crosstalk present in the detector, and also estimate the performance of the chamber as a result of this crosstalk via simulation results of the detector dead time, efficiency loss, and frontend electronics response. The results of crosstalk via signals produced by applying a square voltage pulse directly on the readout strips of the detector with a signal generator are summarized. We also present the efficacy of mitigation strategies including bypass capacitors and increasing the area of the HV segments on the third GEM foil in the detector. We find that the crosstalk is a result of capacitive coupling between the readout strips on the readout board and between the readout strips and the bottom of the third GEM foil. Our results show that the crosstalk generally follows a pattern where the largest magnitude of crosstalk is within the same azimuthal readout segment in the detector, and in the next-nearest horizontal segments in eta. Generally, the bypass capacitors and increased area of the HV segments successfully lower the crosstalk in the sectors where they are located; on average, we observe a maximum decrease of crosstalk in sectors previously experiencing crosstalk from (1.66±0.03)% to (1.11±0.02)% with all HV segments connected in parallel on the bottom of the third GEM foil, with the addition of an HV low-pass filter connected to this electrode, and an HV divider. However, with these mitigation strategies, we also observe slightly increased crosstalk (≨ 0.4%) in readout sectors farther away.","PeriodicalId":6760,"journal":{"name":"2020 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC)","volume":"75 1","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":"83803483","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/MIC42677.2020.9508097
J. Jeong, Jae Chang Kim, J. Son, K. Pak, Yong Kyun Kim, Ju Hahn Lee
The Rare Isotope Science Project was launched in December 2011, and a heavy-ion accelerator complex in Korea, named RAON, has been designed, including a muon facility for muon spin rotation, relaxation, and resonance (μSR). In this study, the graphite target in RAON was designed to have a rotating ring shape and was cooled by radiative heat transfer, which presents advantages in the cool-down process such as a low-temperature gradient in the target and no necessity of a liquid coolant-cooling system. Monte-Carlo simulations and ANSYS calculations were performed to optimize the proton beam size and the dimensions of the target to produce a sufficient number of surface muons in a thermally stable condition. A comparison between the simulation and the experimental data was also included in this paper in order to obtain a reliable result. The expected number of surface muons was 6.942×108 with a 100 kW proton beam and Δp/p~5%. The maximum temperature was 2012 °K and the maximum stress in the target was 8.1598 kPa with the 400 kW proton beam, which guarantees safety during the replacement cycle of the target.
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Pub Date : 2020-10-31DOI: 10.1109/NSS/MIC42677.2020.9508093
Diana Jeong, Li Tao, Zander Adams, Yushin Kim, C. Levin
With a goal to achieve less than 10 picosecond (ps) coincidence time resolution for advancing time-of-flight positron emission tomography (TOF-PET), we seek to leverage the effects of transient free carriers generated from 511 keV interactions in a material. Most ultrafast optics methods rely on many excitation particles with a priori information on their arrival times. However, in PET it is critical to find a way to sensitively detect single, randomly emitted 511 keV annihilation photons from the ionization it produces. We investigate two ways to increase the signal: employing probe laser wavelength in the mid-IR and confining the probe beam to match the size of ionization tracks created by the 511 keV photons. We observed a continued decrease of 2% in transmission of the mid-IR probe beam (8μm) in a 10 X 10 X 1 mm3 Cadmium Telluride crystal with 511 keV annihilation irradiation over 300 seconds. The trend was reversed when the radiation source is removed, and reached the previous baseline transmission in 800 seconds. For confining the interaction volume to match the probe beam diameter, we revised a previously investigated interferometry approach to use a focused beam and did not apply a bias voltage across the detector crystal. With a 405nm laser diode as an excitation source, a shift of 43% in transmitted signal voltage was observed, and with Am-241 alpha source irradiation, a 1% shift was measured. With the improved sensitivity, these findings provide insights into possible methods of detecting single 511 keV events.
为了实现小于10皮秒(ps)的符合时间分辨率，以推进飞行时间正电子发射断层扫描(TOF-PET)，我们试图利用材料中511 keV相互作用产生的瞬态自由载流子的影响。大多数超快光学方法依赖于许多具有其到达时间先验信息的激发粒子。然而，在PET中，找到一种方法来灵敏地探测它产生的电离中随机发射的511 keV湮灭光子是至关重要的。我们研究了两种增加信号的方法:采用中红外探测激光波长和限制探测光束以匹配511 keV光子产生的电离轨迹的大小。我们观察到在511 keV湮灭辐照300秒后，中红外探测光束(8μm)在10 X 10 X 1 mm3碲化镉晶体中的透射率持续下降2%。当辐射源被移除后，这一趋势发生了逆转，在800秒内达到了之前的基线传输。为了限制相互作用体积以匹配探测光束直径，我们修改了先前研究的干涉测量方法，使用聚焦光束，并且不在探测器晶体上施加偏置电压。以405nm激光二极管作为激发源，观察到传输信号电压偏移43%，在Am-241 α源照射下，测量到传输信号电压偏移1%。随着灵敏度的提高，这些发现为检测单个511 keV事件的可能方法提供了见解。
{"title":"Approaches for Measuring Fast Modulation of Optical Properties Induced by 511keV Photon Interactions","authors":"Diana Jeong, Li Tao, Zander Adams, Yushin Kim, C. Levin","doi":"10.1109/NSS/MIC42677.2020.9508093","DOIUrl":"https://doi.org/10.1109/NSS/MIC42677.2020.9508093","url":null,"abstract":"With a goal to achieve less than 10 picosecond (ps) coincidence time resolution for advancing time-of-flight positron emission tomography (TOF-PET), we seek to leverage the effects of transient free carriers generated from 511 keV interactions in a material. Most ultrafast optics methods rely on many excitation particles with a priori information on their arrival times. However, in PET it is critical to find a way to sensitively detect single, randomly emitted 511 keV annihilation photons from the ionization it produces. We investigate two ways to increase the signal: employing probe laser wavelength in the mid-IR and confining the probe beam to match the size of ionization tracks created by the 511 keV photons. We observed a continued decrease of 2% in transmission of the mid-IR probe beam (8μm) in a 10 X 10 X 1 mm3 Cadmium Telluride crystal with 511 keV annihilation irradiation over 300 seconds. The trend was reversed when the radiation source is removed, and reached the previous baseline transmission in 800 seconds. For confining the interaction volume to match the probe beam diameter, we revised a previously investigated interferometry approach to use a focused beam and did not apply a bias voltage across the detector crystal. With a 405nm laser diode as an excitation source, a shift of 43% in transmitted signal voltage was observed, and with Am-241 alpha source irradiation, a 1% shift was measured. With the improved sensitivity, these findings provide insights into possible methods of detecting single 511 keV events.","PeriodicalId":6760,"journal":{"name":"2020 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC)","volume":"402 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":"80597500","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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