Time-encoded imaging is useful for identifying potential special nuclear materials and other radioactive sources at a distance.In this study,a large field-of-view time-encoded imager was developed for gamma-ray and ne...Time-encoded imaging is useful for identifying potential special nuclear materials and other radioactive sources at a distance.In this study,a large field-of-view time-encoded imager was developed for gamma-ray and neutron source hotspot imaging based on a depth-of-interaction(DOI)detector.The imager primarily consists of a DOI detector system and a rotary dual-layer cylindrical coded mask.An EJ276 plastic scintillator coupled with two SiPMs was designed as the DOI detector to increase the field of view and improve the imager performance.The difference in signal time at both ends and the log of the signal amplitude ratio were used to calculate the interaction position resolution.The position resolution of the DOI detector was calibrated using a collimated Cs-137 source,and the full width at half maximum of the reconstruction position of the Gaussian fitting curve was approximately 4.4 cm.The DOI detector can be arbitrarily divided into several units to independently reconstruct the source distribution images.The unit length was optimized via Am-Be source-location experiments.A multidetector filtering method is proposed for image denoising.This method can effectively reduce image noise caused by poor DOI detector position resolution.The vertical field of view of the imager was(-55°,55°)when the detector was placed in the center of the coded mask.A DT neutron source at 20 m standoff could be located within 2400 s with an angular resolution of 3.5°.展开更多
Purpose Coded aperture imaging was a widely used imaging method for radiation sources.However,the traditional gamma camera based on two-dimensional projection information for coded aperture imaging ignored the influen...Purpose Coded aperture imaging was a widely used imaging method for radiation sources.However,the traditional gamma camera based on two-dimensional projection information for coded aperture imaging ignored the influence of the interaction depth of particles and detectors on the projection information,which reduced the imaging quality of the camera to some extent.Therefore,a method of correcting the coded gamma camera based on the interaction depth of particles and detectors is proposed to improve the location accuracy of detectors.Methods The camera developed in this work uses a 7×7 YSO crystal array coupled with two 7×7 Si-PM arrays.The crystal is evenly divided into 11 parts in the depth direction,with a voxel size of 3×3×3 mm3.The coded mask is a 13×13 array,which is a mosaic of two cycles of 7×7 modified uniformly redundant array mask.The depth resolution of the detector is obtained via the subsurface laser engraving dual-end readout method.After obtaining the three-dimensional position information of the interaction point the projection information obtained by the detector is layered,and the image is reconstructed.According to the spatial position information of the detector and the coded mask,the corresponding field of view of each layer of the detector is calculated,and the reconstructed image of each layer is amplified and superimposed according to the ratio of the field of view to obtain the reconstructed image combined with the depth information.Results and conclusion According to Monte Carlo simulation and radiation source imaging experiment results,this method can effectively improve the positioning ability of the detector.For the experimental scenario mentioned in the paper,the location accuracy can be improved by up to 1.54°.展开更多
Background The Circular Electron-Positron Collider(CEPC)is aimed for precision measurements of the Higgs boson properties and the electroweak parameters.The achievable precision will be largely dependent on the contro...Background The Circular Electron-Positron Collider(CEPC)is aimed for precision measurements of the Higgs boson properties and the electroweak parameters.The achievable precision will be largely dependent on the controlled level of radiation backgrounds,which requires an optimized design of the interaction region to assure the optimal performance of both the accelerator and the detectors.Purpose In this article,the latest results on the radiation backgrounds are reported based on the accelerator parameters and the detector design presented in the CEPC conceptual design reports.Method For the different sources of radiation backgrounds,simulation steps consisting of generation,tracking,and detector simulation were performed.Radiation backgrounds from the processes of synchrotron radiation,pair production,radiative Bhabha scattering,beam gas Bremsstrahlung scattering,and beam thermal photon scattering were considered for the accel-erator operating at the different centre-of-mass energies(HZ threshold,WW threshold,and Z pole).Possible mitigation methods of masks and/or collimators were introduced to suppress the radiation backgrounds,together with the careful opti-mization of the interaction region design.With the improved tracking methods during simulation,the accuracy and reliability of the results were improved.In addition,the radiation backgrounds on the CEPC vertex detector were estimated,and the pair-production was found to be the most important source.Result In the worst case of operation at the Z pole,the vertex detector would have to withstand a total ionization dose of 5.6 Mrad per year and a non-ionization energy loss(shown in 1 MeV neutron equivalent)of 1.06×10^(13)n_(eq)/cm^(2)per year.展开更多
Purpose We developed a low-complexity,high-resolution depth-of-interaction(DOI)capable positron emission tomography(PET)detector and tested its performance to prove that it can be applied to practical PET instruments....Purpose We developed a low-complexity,high-resolution depth-of-interaction(DOI)capable positron emission tomography(PET)detector and tested its performance to prove that it can be applied to practical PET instruments.Methods The detector module consists of a 24×24 LYSO crystal matrix,each with dimension of 1.04×1.04×15mm^(3),optically coupled to an 8×8 SiPM photo-sensor array with TOFPET2 ASIC single-ended readout.By only adding a light guide at the top of the crystal to reflect scintillation light back to the SiPM array,the continuous DOI information is extracted using a light sharing and redirection encoding method without adding system complexity.Results The crystal array with 9-to-1 coupling between scintillators and photo-sensors can be clearly separated in the flood image.The other detector performance in terms of DOI resolution,energy resolution and coincidence time resolution are measured on average as 4.1 mm,15.0%and 432 ps,respectively.Conclusion The test results confirm that the light sharing and redirection DOI encoding method can provide reasonably high DOI resolution without deteriorating other performance,even for highly pixelated PET detectors readout with commercially available ASIC chip.It has great potential for applications in future pre-clinical and organ-dedicated PET scanners.展开更多
Standard compact scheme and upwinding compact scheme have high order accuracy and high resolution,but cannot capture the shock which is a discontinuity.This work developed a modified upwinding compact scheme which use...Standard compact scheme and upwinding compact scheme have high order accuracy and high resolution,but cannot capture the shock which is a discontinuity.This work developed a modified upwinding compact scheme which uses an effective shock detector to block compact scheme to cross the shock and a control function to mix the flux with WENO scheme near the shock.The new scheme makes the original compact scheme able to capture the shock sharply and,more importantly,keep high order accuracy and high resolution in the smooth area which is particularly important for shock boundary layer and shock acoustic interactions.Numerical results show the scheme is successful for 2-D Euler and 2-D Navier-Stokes solvers.The examples include 2-D incident shock,2-D incident shock and boundary layer interaction.The scheme is robust,which does not involve case related parameters.展开更多
目的探讨气象因素与湖州市心脑血管疾病的关系,并建立医学气象预报模型对心脑血管疾病发病水平进行预测。方法收集湖州市中心医院和湖州市第一人民医院2006～2007年门诊就诊资料和同期该地区气象资料,采用Spearman相关分析,并用自动交...目的探讨气象因素与湖州市心脑血管疾病的关系,并建立医学气象预报模型对心脑血管疾病发病水平进行预测。方法收集湖州市中心医院和湖州市第一人民医院2006～2007年门诊就诊资料和同期该地区气象资料,采用Spearman相关分析,并用自动交互检测方法(AID)建立预报模型,数据处理用SPSS10.0和SAS EM 4.1统计软件。结果我市心脑血管疾病发病冬春季高于夏秋季节,其发病与日平均气压、平均气温、最低气温、日较差、水汽压、降水量、日照时数等气象因子存在相关性,按周建立了气象因素与心脑血管疾病预报模型和四个预警等级,模型拟合值为0.279。结论心脑血管疾病发病与气象因素密切相关,按周建立预警、预测模型效果较好。展开更多
基金supported by the National Natural Science Foundation of China(Nos.11975121,12205131)the Fundamental Research Funds for the Central Universities(No.lzujbky-2021-sp58)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYCX22_0354)。
文摘Time-encoded imaging is useful for identifying potential special nuclear materials and other radioactive sources at a distance.In this study,a large field-of-view time-encoded imager was developed for gamma-ray and neutron source hotspot imaging based on a depth-of-interaction(DOI)detector.The imager primarily consists of a DOI detector system and a rotary dual-layer cylindrical coded mask.An EJ276 plastic scintillator coupled with two SiPMs was designed as the DOI detector to increase the field of view and improve the imager performance.The difference in signal time at both ends and the log of the signal amplitude ratio were used to calculate the interaction position resolution.The position resolution of the DOI detector was calibrated using a collimated Cs-137 source,and the full width at half maximum of the reconstruction position of the Gaussian fitting curve was approximately 4.4 cm.The DOI detector can be arbitrarily divided into several units to independently reconstruct the source distribution images.The unit length was optimized via Am-Be source-location experiments.A multidetector filtering method is proposed for image denoising.This method can effectively reduce image noise caused by poor DOI detector position resolution.The vertical field of view of the imager was(-55°,55°)when the detector was placed in the center of the coded mask.A DT neutron source at 20 m standoff could be located within 2400 s with an angular resolution of 3.5°.
基金supported by the National Natural Science Foundation of China under Grant Nos.12005234 and 12105307.
文摘Purpose Coded aperture imaging was a widely used imaging method for radiation sources.However,the traditional gamma camera based on two-dimensional projection information for coded aperture imaging ignored the influence of the interaction depth of particles and detectors on the projection information,which reduced the imaging quality of the camera to some extent.Therefore,a method of correcting the coded gamma camera based on the interaction depth of particles and detectors is proposed to improve the location accuracy of detectors.Methods The camera developed in this work uses a 7×7 YSO crystal array coupled with two 7×7 Si-PM arrays.The crystal is evenly divided into 11 parts in the depth direction,with a voxel size of 3×3×3 mm3.The coded mask is a 13×13 array,which is a mosaic of two cycles of 7×7 modified uniformly redundant array mask.The depth resolution of the detector is obtained via the subsurface laser engraving dual-end readout method.After obtaining the three-dimensional position information of the interaction point the projection information obtained by the detector is layered,and the image is reconstructed.According to the spatial position information of the detector and the coded mask,the corresponding field of view of each layer of the detector is calculated,and the reconstructed image of each layer is amplified and superimposed according to the ratio of the field of view to obtain the reconstructed image combined with the depth information.Results and conclusion According to Monte Carlo simulation and radiation source imaging experiment results,this method can effectively improve the positioning ability of the detector.For the experimental scenario mentioned in the paper,the location accuracy can be improved by up to 1.54°.
文摘Background The Circular Electron-Positron Collider(CEPC)is aimed for precision measurements of the Higgs boson properties and the electroweak parameters.The achievable precision will be largely dependent on the controlled level of radiation backgrounds,which requires an optimized design of the interaction region to assure the optimal performance of both the accelerator and the detectors.Purpose In this article,the latest results on the radiation backgrounds are reported based on the accelerator parameters and the detector design presented in the CEPC conceptual design reports.Method For the different sources of radiation backgrounds,simulation steps consisting of generation,tracking,and detector simulation were performed.Radiation backgrounds from the processes of synchrotron radiation,pair production,radiative Bhabha scattering,beam gas Bremsstrahlung scattering,and beam thermal photon scattering were considered for the accel-erator operating at the different centre-of-mass energies(HZ threshold,WW threshold,and Z pole).Possible mitigation methods of masks and/or collimators were introduced to suppress the radiation backgrounds,together with the careful opti-mization of the interaction region design.With the improved tracking methods during simulation,the accuracy and reliability of the results were improved.In addition,the radiation backgrounds on the CEPC vertex detector were estimated,and the pair-production was found to be the most important source.Result In the worst case of operation at the Z pole,the vertex detector would have to withstand a total ionization dose of 5.6 Mrad per year and a non-ionization energy loss(shown in 1 MeV neutron equivalent)of 1.06×10^(13)n_(eq)/cm^(2)per year.
基金This work was supported by the National Natural Science Foundation of China[Grant Number 11735013].
文摘Purpose We developed a low-complexity,high-resolution depth-of-interaction(DOI)capable positron emission tomography(PET)detector and tested its performance to prove that it can be applied to practical PET instruments.Methods The detector module consists of a 24×24 LYSO crystal matrix,each with dimension of 1.04×1.04×15mm^(3),optically coupled to an 8×8 SiPM photo-sensor array with TOFPET2 ASIC single-ended readout.By only adding a light guide at the top of the crystal to reflect scintillation light back to the SiPM array,the continuous DOI information is extracted using a light sharing and redirection encoding method without adding system complexity.Results The crystal array with 9-to-1 coupling between scintillators and photo-sensors can be clearly separated in the flood image.The other detector performance in terms of DOI resolution,energy resolution and coincidence time resolution are measured on average as 4.1 mm,15.0%and 432 ps,respectively.Conclusion The test results confirm that the light sharing and redirection DOI encoding method can provide reasonably high DOI resolution without deteriorating other performance,even for highly pixelated PET detectors readout with commercially available ASIC chip.It has great potential for applications in future pre-clinical and organ-dedicated PET scanners.
基金This work is supported by AFRL VA Summer Faculty Research Program.The authors thank Drs.Poggie,Gaitonde,Visbal for their support through VA Summer Faculty Program.
文摘Standard compact scheme and upwinding compact scheme have high order accuracy and high resolution,but cannot capture the shock which is a discontinuity.This work developed a modified upwinding compact scheme which uses an effective shock detector to block compact scheme to cross the shock and a control function to mix the flux with WENO scheme near the shock.The new scheme makes the original compact scheme able to capture the shock sharply and,more importantly,keep high order accuracy and high resolution in the smooth area which is particularly important for shock boundary layer and shock acoustic interactions.Numerical results show the scheme is successful for 2-D Euler and 2-D Navier-Stokes solvers.The examples include 2-D incident shock,2-D incident shock and boundary layer interaction.The scheme is robust,which does not involve case related parameters.
文摘目的探讨气象因素与湖州市心脑血管疾病的关系,并建立医学气象预报模型对心脑血管疾病发病水平进行预测。方法收集湖州市中心医院和湖州市第一人民医院2006～2007年门诊就诊资料和同期该地区气象资料,采用Spearman相关分析,并用自动交互检测方法(AID)建立预报模型,数据处理用SPSS10.0和SAS EM 4.1统计软件。结果我市心脑血管疾病发病冬春季高于夏秋季节,其发病与日平均气压、平均气温、最低气温、日较差、水汽压、降水量、日照时数等气象因子存在相关性,按周建立了气象因素与心脑血管疾病预报模型和四个预警等级,模型拟合值为0.279。结论心脑血管疾病发病与气象因素密切相关,按周建立预警、预测模型效果较好。
