Pub Date : 2013-10-01DOI: 10.1109/nssmic.2013.6829815
P. Pani
After more than 3 years of successful operation at the LHC, we report on the operation and performance of the Semi-Conductor Tracker (SCT) functioning in a high luminosity, high radiation environment. The SCT is part of the inner tracking system of the ATLAS experiment at CERN and is constructed of 4088 silicon detector modules for a total of 6.3 million strips. We find 99.3% of the SCT modules are operational, noise occupancy and hit efficiency exceed the design specifications; the alignment is very close to the ideal to allow on-line track reconstruction and invariant mass determination. We will report on the operation and performance of the detector including an overview of the issues encountered. The observables employed to monitor online and offline the quality and the performance of the data acquired by the SCT will be described and discussed.
{"title":"Performance and operation experience of the ATLAS Semiconductor Tracker","authors":"P. Pani","doi":"10.1109/nssmic.2013.6829815","DOIUrl":"https://doi.org/10.1109/nssmic.2013.6829815","url":null,"abstract":"After more than 3 years of successful operation at the LHC, we report on the operation and performance of the Semi-Conductor Tracker (SCT) functioning in a high luminosity, high radiation environment. The SCT is part of the inner tracking system of the ATLAS experiment at CERN and is constructed of 4088 silicon detector modules for a total of 6.3 million strips. We find 99.3% of the SCT modules are operational, noise occupancy and hit efficiency exceed the design specifications; the alignment is very close to the ideal to allow on-line track reconstruction and invariant mass determination. We will report on the operation and performance of the detector including an overview of the issues encountered. The observables employed to monitor online and offline the quality and the performance of the data acquired by the SCT will be described and discussed.","PeriodicalId":246351,"journal":{"name":"2013 IEEE Nuclear Science Symposium and Medical Imaging Conference (2013 NSS/MIC)","volume":"114 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124370913","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 : 2013-10-01DOI: 10.1109/NSSMIC.2013.6829629
Y. Fujimoto, T. Yanagida, Y. Futami
Dosimetric, and scintillation properties of undoped sapphire (Al2O3) single crystal fabricated by different methods of the Czochralski (Cz) and the Bridgman were investigated. In X-ray induced radioluminescence spectra, they showed emission peaks at 240 and 300 nm due to exciton and F+ centers, respectively. Scintillation decay times of F+ center was fast around few ns. As a dosimetric property, from 0.01 to 2 Gy X-ray was exposed to them and they exhibited a thermally stimulated luminescence (TSL) with a good linearity. The glow peaks of them were similar, 150, 250, and 325 °C. In TSL, the Bridgeman sample represented only F-center emission while the Cz sample showed F at 400 nm and F+ at 300 nm centers emission.
{"title":"Fabrication process dependency of dosimetric and scintillation properties of sapphire crystals","authors":"Y. Fujimoto, T. Yanagida, Y. Futami","doi":"10.1109/NSSMIC.2013.6829629","DOIUrl":"https://doi.org/10.1109/NSSMIC.2013.6829629","url":null,"abstract":"Dosimetric, and scintillation properties of undoped sapphire (Al2O3) single crystal fabricated by different methods of the Czochralski (Cz) and the Bridgman were investigated. In X-ray induced radioluminescence spectra, they showed emission peaks at 240 and 300 nm due to exciton and F+ centers, respectively. Scintillation decay times of F+ center was fast around few ns. As a dosimetric property, from 0.01 to 2 Gy X-ray was exposed to them and they exhibited a thermally stimulated luminescence (TSL) with a good linearity. The glow peaks of them were similar, 150, 250, and 325 °C. In TSL, the Bridgeman sample represented only F-center emission while the Cz sample showed F at 400 nm and F+ at 300 nm centers emission.","PeriodicalId":246351,"journal":{"name":"2013 IEEE Nuclear Science Symposium and Medical Imaging Conference (2013 NSS/MIC)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127873874","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 : 2013-10-01DOI: 10.1109/NSSMIC.2013.6829010
L. Tran, D. Bolst, S. Guatelli, D. Prokopovich, Y. C. Keat, M. Petasecca, M. Lerch, M. Reinhard, A. Fazzi, E. Sagia, S. Agosteo, N. Matsufuji, A. Rosenfeld
The response of ΔE-E telescope in C12 ion beam at defined positions within the Bragg peak at different depths with 0.5mm step was studied using Geant4 Monte Carlo toolkit. The microdosimetric spectra derived from ΔE stage response using assumption that average chord is 1.8 μm along with simulated scatter plots for the same points. It was demonstrated that microdosimetric spectra is changing dramatically within 0.5 mm depth increments close to and at distal part of the BP that is impossible to observe with TEPC. Fragments (He4, He3, Li7, Be9, B11) and neutrons contributed to microdosimetric spectra and to YD have been analyzed for each position.
{"title":"High spatial resolution microdosimetry with ΔE-E detector on C-12 beam: Monte Carlo simulations","authors":"L. Tran, D. Bolst, S. Guatelli, D. Prokopovich, Y. C. Keat, M. Petasecca, M. Lerch, M. Reinhard, A. Fazzi, E. Sagia, S. Agosteo, N. Matsufuji, A. Rosenfeld","doi":"10.1109/NSSMIC.2013.6829010","DOIUrl":"https://doi.org/10.1109/NSSMIC.2013.6829010","url":null,"abstract":"The response of ΔE-E telescope in C<sup>12</sup> ion beam at defined positions within the Bragg peak at different depths with 0.5mm step was studied using Geant4 Monte Carlo toolkit. The microdosimetric spectra derived from ΔE stage response using assumption that average chord is 1.8 μm along with simulated scatter plots for the same points. It was demonstrated that microdosimetric spectra is changing dramatically within 0.5 mm depth increments close to and at distal part of the BP that is impossible to observe with TEPC. Fragments (He<sup>4</sup>, He<sup>3</sup>, Li<sup>7</sup>, Be<sup>9</sup>, B<sup>11</sup>) and neutrons contributed to microdosimetric spectra and to YD have been analyzed for each position.","PeriodicalId":246351,"journal":{"name":"2013 IEEE Nuclear Science Symposium and Medical Imaging Conference (2013 NSS/MIC)","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127880723","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 : 2013-10-01DOI: 10.1109/NSSMIC.2013.6829713
G. Gerganov, K. Mitev
The quantitative comparison of liquid scintillation counting spectra and subsequent identification of regions of statistically significant differences can be very useful in activity determination by liquid scintillation counting (LSC). The objective of this work is to present two approaches for quantitative comparison of LSC spectra and to evaluate their performance. The proposed techniques are based on statistical analysis of the difference spectrum of the two spectra. The first algorithm employs thresholding to evaluate the statistically significant differences, while the second one employs the Grubbs' statistical test for outliers combined with a prior application of a variance stabilizing transformation. The performance of the two methods is tested with experimental data obtained in dedicated measurement with a LS counter. We conclude that the proposed techniques show good potential for identification of regions of statistically significant differences between liquid scintillation spectra and are applicable in problems related to comparison and analysis of LSC spectra.
{"title":"Quantitative comparison of liquid scintillation counting spectra","authors":"G. Gerganov, K. Mitev","doi":"10.1109/NSSMIC.2013.6829713","DOIUrl":"https://doi.org/10.1109/NSSMIC.2013.6829713","url":null,"abstract":"The quantitative comparison of liquid scintillation counting spectra and subsequent identification of regions of statistically significant differences can be very useful in activity determination by liquid scintillation counting (LSC). The objective of this work is to present two approaches for quantitative comparison of LSC spectra and to evaluate their performance. The proposed techniques are based on statistical analysis of the difference spectrum of the two spectra. The first algorithm employs thresholding to evaluate the statistically significant differences, while the second one employs the Grubbs' statistical test for outliers combined with a prior application of a variance stabilizing transformation. The performance of the two methods is tested with experimental data obtained in dedicated measurement with a LS counter. We conclude that the proposed techniques show good potential for identification of regions of statistically significant differences between liquid scintillation spectra and are applicable in problems related to comparison and analysis of LSC spectra.","PeriodicalId":246351,"journal":{"name":"2013 IEEE Nuclear Science Symposium and Medical Imaging Conference (2013 NSS/MIC)","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126320042","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 : 2013-10-01DOI: 10.1109/NSSMIC.2013.6829376
J. Johansson, J. Teuho, J. Lindén, U. Tuna, T. Tolvanen, V. Saunavaara, M. Teräs
Choice of the PET scanner and image reconstruction parameters have significant impact in quantitative positron-emission tomography (PET). Hoffman phantom is probably the most widely used test object for assessing this impact in brain PET studies. In high-resolution PET, however, it's usability is questionable due to lesser partial-volume effect. Futhermore, Hoffman phantom is cylindrical and does not offer realistic attenuation effect for the skull. In the current work we used a novel brain phantom that was produced using a 3D-printer, and provides realistic head contour and skull attenuation effect. We scanned the phantom with latest generation whole-body PET/MR (Philips Ingenuity TF) and PET/CT (GE Discovery 690) scanners and in a brain dedicated high-resolution scanner (Siemens HRRT) to evaluate it's usability for intra- and inter-scanner comparisons with regard to PET brain imaging. In all scanners reconstruction algorithm choice and number of iterations had significant impact on anatomical gray matter ROI values. As compared to the HRRT, whole-body scanners showed 3% to 15% (Philips Ingenuity TF) and 0% to 5% (GE D690) negative biases in gray matter ROIs, when iterative reconstruction with high number of iterations but without resolution modeling was used. Whereas, low number of iterations in Philips Ingenuity yielded negative biases of 7% to 19%, but inclusion of resolution modeling in GE D690 yielded 19% to 7% higher values. In the HRRT count statistics related negative bias of up to 6% was seen, when iterative reconstruction without resolution modeling was used. We conclude that the new three-dimensional brain phantom is suitable for assessing the impact of reconstruction parameters both within and between scanners. However, the lack of ground truth values hampers the interpretation of the results, and furthermore, the small differences we saw between whole-body and brain-dedicated scanners might be due to limited resolution of the 3D-printing.
{"title":"Image quantification in high-resolution PET assessed with a new anthropomorphic brain phantom","authors":"J. Johansson, J. Teuho, J. Lindén, U. Tuna, T. Tolvanen, V. Saunavaara, M. Teräs","doi":"10.1109/NSSMIC.2013.6829376","DOIUrl":"https://doi.org/10.1109/NSSMIC.2013.6829376","url":null,"abstract":"Choice of the PET scanner and image reconstruction parameters have significant impact in quantitative positron-emission tomography (PET). Hoffman phantom is probably the most widely used test object for assessing this impact in brain PET studies. In high-resolution PET, however, it's usability is questionable due to lesser partial-volume effect. Futhermore, Hoffman phantom is cylindrical and does not offer realistic attenuation effect for the skull. In the current work we used a novel brain phantom that was produced using a 3D-printer, and provides realistic head contour and skull attenuation effect. We scanned the phantom with latest generation whole-body PET/MR (Philips Ingenuity TF) and PET/CT (GE Discovery 690) scanners and in a brain dedicated high-resolution scanner (Siemens HRRT) to evaluate it's usability for intra- and inter-scanner comparisons with regard to PET brain imaging. In all scanners reconstruction algorithm choice and number of iterations had significant impact on anatomical gray matter ROI values. As compared to the HRRT, whole-body scanners showed 3% to 15% (Philips Ingenuity TF) and 0% to 5% (GE D690) negative biases in gray matter ROIs, when iterative reconstruction with high number of iterations but without resolution modeling was used. Whereas, low number of iterations in Philips Ingenuity yielded negative biases of 7% to 19%, but inclusion of resolution modeling in GE D690 yielded 19% to 7% higher values. In the HRRT count statistics related negative bias of up to 6% was seen, when iterative reconstruction without resolution modeling was used. We conclude that the new three-dimensional brain phantom is suitable for assessing the impact of reconstruction parameters both within and between scanners. However, the lack of ground truth values hampers the interpretation of the results, and furthermore, the small differences we saw between whole-body and brain-dedicated scanners might be due to limited resolution of the 3D-printing.","PeriodicalId":246351,"journal":{"name":"2013 IEEE Nuclear Science Symposium and Medical Imaging Conference (2013 NSS/MIC)","volume":"94 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126232281","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 : 2013-10-01DOI: 10.1109/NSSMIC.2013.6829087
M. Streun, H. Nöldgen, A. Erven, S. España, L. Jokhovets, R. Marcinkowski, C. Peters, M. Ramm, N. Schramm, P. Wüstner, S. Vandenberghe, G. Kemmerling, S. van Waasen
A typical high resolution PET detector consists of a matrix of scintillator elements which are connected to a light guide in order to spread the light onto the pixels of a photo detector. In this work we introduce a matrix that works without light guide but has defined internal light leaks in order to allow controlled light sharing between the individual scintillator elements. This is especially useful when used together with the Philips digital SiPM DPC 3200. We show that better position determination is achieved and in addition higher count rates should be possible compared to a classical light guide solution.
{"title":"PET scintillator arrangement on digital SiPMs","authors":"M. Streun, H. Nöldgen, A. Erven, S. España, L. Jokhovets, R. Marcinkowski, C. Peters, M. Ramm, N. Schramm, P. Wüstner, S. Vandenberghe, G. Kemmerling, S. van Waasen","doi":"10.1109/NSSMIC.2013.6829087","DOIUrl":"https://doi.org/10.1109/NSSMIC.2013.6829087","url":null,"abstract":"A typical high resolution PET detector consists of a matrix of scintillator elements which are connected to a light guide in order to spread the light onto the pixels of a photo detector. In this work we introduce a matrix that works without light guide but has defined internal light leaks in order to allow controlled light sharing between the individual scintillator elements. This is especially useful when used together with the Philips digital SiPM DPC 3200. We show that better position determination is achieved and in addition higher count rates should be possible compared to a classical light guide solution.","PeriodicalId":246351,"journal":{"name":"2013 IEEE Nuclear Science Symposium and Medical Imaging Conference (2013 NSS/MIC)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126506180","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 : 2013-10-01DOI: 10.1109/NSSMIC.2013.6829371
J. Bian, Kai Yang, E. Sidky, J. Boone, Xiaochuan Pan
Current dedicated breast-CT prototypes use analytic-based algorithms such as FDK for image reconstruction, which require a large number of densely sampled views. Because the total imaging dose delivered to a patient in a breast-CT scan is kept about the same as that in a typical two-view mammography exam, the use of a large number of views thus can lead to projection data of low SNR and images with high noise, which makes reconstruction improvement challenging. Recently, there exists increased interest in development and evaluation of optimization-based (i.e. iterative) image reconstruction algorithms for low-dose cone-beam CT (CBCT). In the work, we focus on investigation of optimization-based image reconstruction for low-dose breast CT by tailoring a TV-minimization-based algorithm, adaptive-steep-descent (ASD)-projection-onto-convex-set (POCS) algorithm, for image reconstruction from low-SNR patient data. We performed inverse-crime studies for verifying if the algorithm is solving the designed optimization program, and studied the effect of optimization program parameter, ε, on the reconstruction images. We also studied the change of image power spectra with ε and iteration numbers. The results indicate that optimization-based algorithms may improve image quality over analytic-based algorithm for low-dose dedicated breast CT.
{"title":"Optimization-based image reconstruction from low-dose patient breast CT Data","authors":"J. Bian, Kai Yang, E. Sidky, J. Boone, Xiaochuan Pan","doi":"10.1109/NSSMIC.2013.6829371","DOIUrl":"https://doi.org/10.1109/NSSMIC.2013.6829371","url":null,"abstract":"Current dedicated breast-CT prototypes use analytic-based algorithms such as FDK for image reconstruction, which require a large number of densely sampled views. Because the total imaging dose delivered to a patient in a breast-CT scan is kept about the same as that in a typical two-view mammography exam, the use of a large number of views thus can lead to projection data of low SNR and images with high noise, which makes reconstruction improvement challenging. Recently, there exists increased interest in development and evaluation of optimization-based (i.e. iterative) image reconstruction algorithms for low-dose cone-beam CT (CBCT). In the work, we focus on investigation of optimization-based image reconstruction for low-dose breast CT by tailoring a TV-minimization-based algorithm, adaptive-steep-descent (ASD)-projection-onto-convex-set (POCS) algorithm, for image reconstruction from low-SNR patient data. We performed inverse-crime studies for verifying if the algorithm is solving the designed optimization program, and studied the effect of optimization program parameter, ε, on the reconstruction images. We also studied the change of image power spectra with ε and iteration numbers. The results indicate that optimization-based algorithms may improve image quality over analytic-based algorithm for low-dose dedicated breast CT.","PeriodicalId":246351,"journal":{"name":"2013 IEEE Nuclear Science Symposium and Medical Imaging Conference (2013 NSS/MIC)","volume":"57 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126553032","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 : 2013-10-01DOI: 10.1109/NSSMIC.2013.6829361
Xiaofei Xu, Liang Li, Li Zhang, Qingli Wang
The introduction of flat-panel detectors into the cone-beam computed tomography (CBCT) has a lot of benefits. Metallic implants have higher attenuation coefficient and it form shadows in the raw projection data. This shadow will cause streak artifacts which influence image quality and it is still a challenge to reduce the metal artifacts. There are many algorithms to reduce the metal artifacts and projection data preprocessing method is much more efficient. The vital step of this method is to segment the metal shadows in projection data. The goal of this paper is to find a method to segment the metal projection. In this problem, it is difficult to segment the projection only once to get a good result. But it is easy to find background regions that contains the metal projection and former regions which is inside the metal projection. Segmentation based on random walks utilizes the two regions and calculates every pixel's probability that it first reaches the former regions. Based on the obtained probability values, metal shadows are segmented. In comparison with other methods, the algorithm based on random walks gives the best result and it shows the clear boundary of metal projection. Modify the metal projection with total variation (TV) inpainting model, the reconstruction image quality has improved and the nearby soft- tissue regions are much clearer.
{"title":"A metal projection segmentation algorithm based on Random walks for dental CBCT metal artifacts correction","authors":"Xiaofei Xu, Liang Li, Li Zhang, Qingli Wang","doi":"10.1109/NSSMIC.2013.6829361","DOIUrl":"https://doi.org/10.1109/NSSMIC.2013.6829361","url":null,"abstract":"The introduction of flat-panel detectors into the cone-beam computed tomography (CBCT) has a lot of benefits. Metallic implants have higher attenuation coefficient and it form shadows in the raw projection data. This shadow will cause streak artifacts which influence image quality and it is still a challenge to reduce the metal artifacts. There are many algorithms to reduce the metal artifacts and projection data preprocessing method is much more efficient. The vital step of this method is to segment the metal shadows in projection data. The goal of this paper is to find a method to segment the metal projection. In this problem, it is difficult to segment the projection only once to get a good result. But it is easy to find background regions that contains the metal projection and former regions which is inside the metal projection. Segmentation based on random walks utilizes the two regions and calculates every pixel's probability that it first reaches the former regions. Based on the obtained probability values, metal shadows are segmented. In comparison with other methods, the algorithm based on random walks gives the best result and it shows the clear boundary of metal projection. Modify the metal projection with total variation (TV) inpainting model, the reconstruction image quality has improved and the nearby soft- tissue regions are much clearer.","PeriodicalId":246351,"journal":{"name":"2013 IEEE Nuclear Science Symposium and Medical Imaging Conference (2013 NSS/MIC)","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128055856","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 : 2013-10-01DOI: 10.1109/NSSMIC.2013.6829314
Y. Lemaréchal, J. Bert, N. Boussion, E. Le Fur, D. Visvikis
In brachytherapy, dosimetric plans are routinely calculated with the TG43 formalism which considers the patient as a simple water box. However, accurate modelling of the physical processes considering patient heterogeneity using Monte Carlo (MC) methods is currently too time-consuming and computationally demanding to be routinely used. As a solution we implemented an accurate and fast MC simulation based on Geant4 on graphics processing units (GPU) for brachytherapy applications. Existing approaches using GPU architecture for brachytherapy MC simulations suffer from numerous approximations including, the use of virtual seed bound to a phase space file to define dwell sources, or removing voxel within the CT image to include seed density. Within the proposed framework such approximations have been removed. A comparison between dosimetric plans based on the current clinical standard (TG43) and the proposed full MC simulation led to substantial differences due to the TG43 related approximations assuming the patient as a water box. Finally, the proposed dosimetry platform is capable of providing accurate dose distributions within one minute, which is compatible for a clinical routine usage.
{"title":"Monte Carlo simulations on GPU for brachytherapy applications","authors":"Y. Lemaréchal, J. Bert, N. Boussion, E. Le Fur, D. Visvikis","doi":"10.1109/NSSMIC.2013.6829314","DOIUrl":"https://doi.org/10.1109/NSSMIC.2013.6829314","url":null,"abstract":"In brachytherapy, dosimetric plans are routinely calculated with the TG43 formalism which considers the patient as a simple water box. However, accurate modelling of the physical processes considering patient heterogeneity using Monte Carlo (MC) methods is currently too time-consuming and computationally demanding to be routinely used. As a solution we implemented an accurate and fast MC simulation based on Geant4 on graphics processing units (GPU) for brachytherapy applications. Existing approaches using GPU architecture for brachytherapy MC simulations suffer from numerous approximations including, the use of virtual seed bound to a phase space file to define dwell sources, or removing voxel within the CT image to include seed density. Within the proposed framework such approximations have been removed. A comparison between dosimetric plans based on the current clinical standard (TG43) and the proposed full MC simulation led to substantial differences due to the TG43 related approximations assuming the patient as a water box. Finally, the proposed dosimetry platform is capable of providing accurate dose distributions within one minute, which is compatible for a clinical routine usage.","PeriodicalId":246351,"journal":{"name":"2013 IEEE Nuclear Science Symposium and Medical Imaging Conference (2013 NSS/MIC)","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125597686","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 : 2013-10-01DOI: 10.1109/NSSMIC.2013.6829598
A. Cardini, V. Fanti, A. Lai
We are investigating the possibility of using Silicon Avalanche Photo Detectors (both in proportional and in Geiger mode) to readout inorganic scintillators operated at cryogenic temperatures. Such detectors, that need to operate close to LHe temperatures and in a magnetic field of a few Tesla, was proposed by our group as a way to built an active polarized target to be used for neutrino physics, for the searches of axions and CP violation, as suggested by some theoretical papers. In the present work we have investigated in some details the performance of Hamamatsu MPPCs down to LHe temperature, to verify the temperature range of usability of these devices. Measurement of the most important parameters will be presented: quantum efficiency, dark current, dark rate, gain. These results will be compared to what we measured on Large Area Silicon APDs operating in the same temperature range.
{"title":"Performance of avalanche photodetectors at cryogenic temperatures: Operations of MPPCs at temperatures below 77 K","authors":"A. Cardini, V. Fanti, A. Lai","doi":"10.1109/NSSMIC.2013.6829598","DOIUrl":"https://doi.org/10.1109/NSSMIC.2013.6829598","url":null,"abstract":"We are investigating the possibility of using Silicon Avalanche Photo Detectors (both in proportional and in Geiger mode) to readout inorganic scintillators operated at cryogenic temperatures. Such detectors, that need to operate close to LHe temperatures and in a magnetic field of a few Tesla, was proposed by our group as a way to built an active polarized target to be used for neutrino physics, for the searches of axions and CP violation, as suggested by some theoretical papers. In the present work we have investigated in some details the performance of Hamamatsu MPPCs down to LHe temperature, to verify the temperature range of usability of these devices. Measurement of the most important parameters will be presented: quantum efficiency, dark current, dark rate, gain. These results will be compared to what we measured on Large Area Silicon APDs operating in the same temperature range.","PeriodicalId":246351,"journal":{"name":"2013 IEEE Nuclear Science Symposium and Medical Imaging Conference (2013 NSS/MIC)","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125649183","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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