In recent years,graphics processing units(GPUs)have been applied to accelerate Monte Carlo(MC)simulations for proton dose calculation in radiotherapy.Nonetheless,current GPU platforms,such as Compute Unified Device Ar...In recent years,graphics processing units(GPUs)have been applied to accelerate Monte Carlo(MC)simulations for proton dose calculation in radiotherapy.Nonetheless,current GPU platforms,such as Compute Unified Device Architecture(CUDA)and Open Computing Language(OpenCL),suffer from cross-platform limitation or relatively high programming barrier.However,the Taichi toolkit,which was developed to overcome these difficulties,has been successfully applied to high-performance numerical computations.Based on the class II condensed history simulation scheme with various proton-nucleus interactions,we developed a GPU-accelerated MC engine for proton transport using the Taichi toolkit.Dose distributions in homogeneous and heterogeneous geometries were calculated for 110,160,and 200 MeV protons and were compared with those obtained by full MC simulations using TOPAS.The gamma passing rates were greater than 0.99 and 0.95 with criteria of 2 mm,2%and 1 mm,1%,respectively,in all the benchmark tests.Moreover,the calculation speed was at least 5800 times faster than that of TOPAS,and the number of lines of code was approximately 10 times less than those of CUDA or OpenCL.Our study provides a highly accurate,efficient,and easy-to-use proton dose calculation engine for fast prototyping,beamlet calculation,and education purposes.展开更多
Monte Carlo transport simulations of a full-core reactor with a high-fidelity structure have been made possible by modern-day computing capabilities. Performing transport–burnup calculations of a full-core model typi...Monte Carlo transport simulations of a full-core reactor with a high-fidelity structure have been made possible by modern-day computing capabilities. Performing transport–burnup calculations of a full-core model typically includes millions of burnup areas requiring hundreds of gigabytes of memory for burnup-related tallies. This paper presents the study of a parallel computing method for full-core Monte Carlo transport–burnup calculations and the development of a thread-level data decomposition method. The proposed method decomposes tally accumulators into different threads and improves the parallel communication pattern and memory access efficiency. A typical pressurized water reactor burnup assembly along with the benchmark for evaluation and validation of reactor simulations model was used to test the proposed method.The result indicates that the method effectively reduces memory consumption and maintains high parallel efficiency.展开更多
The first-principles calculations based on density functional theory combined with cluster expansion techniques and Monte Carlo （MC） simulations were used to study the phase diagrams of both wurtzite （WZ） and zinc...The first-principles calculations based on density functional theory combined with cluster expansion techniques and Monte Carlo （MC） simulations were used to study the phase diagrams of both wurtzite （WZ） and zinc-blende （ZB） Cdl_xZnxS alloys. All formation energies are positive for WZ and ZB Cdl-xZnxS alloys, which means that the Cdl-xZnxS alloys are unstable and have a tendency to phase separation. For WZ and ZB Cdl_xZnxS alloys, the consolute temperatures are 655 K and 604 K, respectively, and they both have an asymmetric miscibility gap. We obtained the spatial distributions of Cd and Zn atoms in WZ and ZB Cd0.sZn0.sS alloys at different temperatures by MC simulations. We found that both WZ and ZB phases of Cdo.sZn0.sS alloy exhibit phase segregation of Cd and Zn atoms at low temperature, which is consistent with the phase diagrams.展开更多
The influence of dose variation due to heterogeneities in narrow photon beams used in stereotactic radiosurgery has been investigated. Since the lateral electronic disequilibrium and existence of steep dose gradients ...The influence of dose variation due to heterogeneities in narrow photon beams used in stereotactic radiosurgery has been investigated. Since the lateral electronic disequilibrium and existence of steep dose gradients in small fields and the presence of heterogeneities can intensify these problems, in this study the effects of heterogeneities on 6 MV small photon beams produced by circular cone collimators with 5, 10, 15, 20 and 30 mm diameters are investigated. The heterogeneities include 3 cm Cork with density of 0.2 g/cm3 instead of lung and 3 cm Polytetrafluoroethylene (P.T.F.E) with density of 2.2 g/cm3 as bone. The measurements were carried out with EBT2 gafchromic and EDR2 radiographic films. Simulation was done by MCNP Monte Carlo Code (MCNP5). The depth dose curves in heterogeneous phantom were compared with homogeneous phantom. A good agreement was obtained within film and Monte Carlo calculations in presence of low density heterogeneity and also in the presence of high density heterogeneity. Monte Carlo results showed good agreement after stopping power correction.展开更多
Neutral particle energy spectra in the HT-7 tokamak are calculated by using the Monte Carlo method. It can reproduce the spectra measured in experiment. Differences of neutral particle energy spectra in higher and low...Neutral particle energy spectra in the HT-7 tokamak are calculated by using the Monte Carlo method. It can reproduce the spectra measured in experiment. Differences of neutral particle energy spectra in higher and lower electron density plasma are discussed. Results show that the ion temperature given by neutral particle energy spectra is lower than the real ion temperature, but the deviation is within 10% if the ion temperature is less than 800 eV and thecentral chord-averaged electron density does not exceed 3 ×1013 cm-3. But for ion temperature higher than 1000 eV at the central chord-averaged density limit up to 5 ×1013 cm-3, the neutral particle energy spectra can still give the ion temperature within 10% deviation.展开更多
A few CT-based voxel phantoms were produced to investigate the sensitivity of Monte Carlo simulations of X-ray beam and electron beam to the proportions of elements and the mass densities of the materials used to expr...A few CT-based voxel phantoms were produced to investigate the sensitivity of Monte Carlo simulations of X-ray beam and electron beam to the proportions of elements and the mass densities of the materials used to express the patient’s anatomical structure. The human body can be well outlined by air, lung, adipose, muscle, soft bone and hard bone to calculate the dose distribution with Monte Carlo method. The effects of the calibration curves established by using various CT scanners are not clinically significant based on our investigation. The deviation from the values of cumulative dose volume histogram derived from CT-based voxel phantoms is less than 1% for the given target.展开更多
Previous results show that the floating reference theory(FRT)is an effective tool to reduce the infuence of interference factors on noninvasive blood glucose sensing by near infrared spectros-copy(NIRS).It is the key ...Previous results show that the floating reference theory(FRT)is an effective tool to reduce the infuence of interference factors on noninvasive blood glucose sensing by near infrared spectros-copy(NIRS).It is the key to measure the floating reference point(FRP)precisely for the application of FRT.Monte Carlo(MC)simulation has been introduced to quantitatively in-vestigate the effects of positioning errors and light source drifts on measuring FRP.In this article,thinning and calculating method(TCM)is proposed to quantify the positioning error.Mean-while,the normalization process(NP)is developed to significantly reduce the error induced by light source drift.The results according to TCM show that 7 purm deviations in positioning can generate about 10.63%relative error in FRP.It is more noticeable that 1%fluctuation in light source intensity may lead to 12.21%relative errors.Gratifyingly,the proposed NP model can effectively reduce the error caused by light source drift.Therefore,the measurement system for FRPs must meet that the positioning error is less than 7 purm,and the light source drift is kept within 1%.Furthermore,an improvement for measurement system is proposed in order to take advantage of the NP model.展开更多
在释光年代学上,剂量率代表样品埋藏过程中单位时间内吸收的辐射剂量,其估计直接影响到埋藏年代的可靠性。误差传递公式(Quadratic propagation of uncertainty)常用于剂量率误差估计。由于计算剂量率涉及到众多参数复杂的非线性运算,...在释光年代学上,剂量率代表样品埋藏过程中单位时间内吸收的辐射剂量,其估计直接影响到埋藏年代的可靠性。误差传递公式(Quadratic propagation of uncertainty)常用于剂量率误差估计。由于计算剂量率涉及到众多参数复杂的非线性运算,造成基于误差传递公式的误差估计过程繁琐复杂。本文以粗颗粒石英矿物为例介绍了剂量率计算过程及误差估计方法,使用蒙特卡罗误差传递法(Monte Carlo error propagation)模拟了剂量率计算过程中多参数不确定性耦合误差,编写了执行随机剂量率模拟运算的开源R程序,并通过实测数据展示了该技术的应用。相对于应用误差传递公式法估计剂量率误差,Monte Carlo方法具有直观灵活、简便科学的特点,这种随机策略在分析科学领域具有广泛的适用性。展开更多
基金supported by the National Natural Science Foundation of China (Nos.11735003,11975041,and 11961141004)。
文摘In recent years,graphics processing units(GPUs)have been applied to accelerate Monte Carlo(MC)simulations for proton dose calculation in radiotherapy.Nonetheless,current GPU platforms,such as Compute Unified Device Architecture(CUDA)and Open Computing Language(OpenCL),suffer from cross-platform limitation or relatively high programming barrier.However,the Taichi toolkit,which was developed to overcome these difficulties,has been successfully applied to high-performance numerical computations.Based on the class II condensed history simulation scheme with various proton-nucleus interactions,we developed a GPU-accelerated MC engine for proton transport using the Taichi toolkit.Dose distributions in homogeneous and heterogeneous geometries were calculated for 110,160,and 200 MeV protons and were compared with those obtained by full MC simulations using TOPAS.The gamma passing rates were greater than 0.99 and 0.95 with criteria of 2 mm,2%and 1 mm,1%,respectively,in all the benchmark tests.Moreover,the calculation speed was at least 5800 times faster than that of TOPAS,and the number of lines of code was approximately 10 times less than those of CUDA or OpenCL.Our study provides a highly accurate,efficient,and easy-to-use proton dose calculation engine for fast prototyping,beamlet calculation,and education purposes.
基金supported by the Innovation Foundation of the Chinese Academy of Sciences(No.CXJJ-16Q231)the National Natural Science Foundation of China(No.11305203)+3 种基金the Special Program for Informatization of the Chinese Academy of Sciences(No.XXH12504-1-09)the Anhui Provincial Special Project for High Technology Industrythe Special Project of Youth Innovation Promotion Association of Chinese Academy of Sciencesthe Industrialization Fund
文摘Monte Carlo transport simulations of a full-core reactor with a high-fidelity structure have been made possible by modern-day computing capabilities. Performing transport–burnup calculations of a full-core model typically includes millions of burnup areas requiring hundreds of gigabytes of memory for burnup-related tallies. This paper presents the study of a parallel computing method for full-core Monte Carlo transport–burnup calculations and the development of a thread-level data decomposition method. The proposed method decomposes tally accumulators into different threads and improves the parallel communication pattern and memory access efficiency. A typical pressurized water reactor burnup assembly along with the benchmark for evaluation and validation of reactor simulations model was used to test the proposed method.The result indicates that the method effectively reduces memory consumption and maintains high parallel efficiency.
基金supported by the National Natural Science Foundation of China(Grant Nos.11164014 and 11364025)Gansu Science and Technology Pillar Program,China(Grant No.1204GKCA057)
文摘The first-principles calculations based on density functional theory combined with cluster expansion techniques and Monte Carlo （MC） simulations were used to study the phase diagrams of both wurtzite （WZ） and zinc-blende （ZB） Cdl_xZnxS alloys. All formation energies are positive for WZ and ZB Cdl-xZnxS alloys, which means that the Cdl-xZnxS alloys are unstable and have a tendency to phase separation. For WZ and ZB Cdl_xZnxS alloys, the consolute temperatures are 655 K and 604 K, respectively, and they both have an asymmetric miscibility gap. We obtained the spatial distributions of Cd and Zn atoms in WZ and ZB Cd0.sZn0.sS alloys at different temperatures by MC simulations. We found that both WZ and ZB phases of Cdo.sZn0.sS alloy exhibit phase segregation of Cd and Zn atoms at low temperature, which is consistent with the phase diagrams.
文摘The influence of dose variation due to heterogeneities in narrow photon beams used in stereotactic radiosurgery has been investigated. Since the lateral electronic disequilibrium and existence of steep dose gradients in small fields and the presence of heterogeneities can intensify these problems, in this study the effects of heterogeneities on 6 MV small photon beams produced by circular cone collimators with 5, 10, 15, 20 and 30 mm diameters are investigated. The heterogeneities include 3 cm Cork with density of 0.2 g/cm3 instead of lung and 3 cm Polytetrafluoroethylene (P.T.F.E) with density of 2.2 g/cm3 as bone. The measurements were carried out with EBT2 gafchromic and EDR2 radiographic films. Simulation was done by MCNP Monte Carlo Code (MCNP5). The depth dose curves in heterogeneous phantom were compared with homogeneous phantom. A good agreement was obtained within film and Monte Carlo calculations in presence of low density heterogeneity and also in the presence of high density heterogeneity. Monte Carlo results showed good agreement after stopping power correction.
文摘Neutral particle energy spectra in the HT-7 tokamak are calculated by using the Monte Carlo method. It can reproduce the spectra measured in experiment. Differences of neutral particle energy spectra in higher and lower electron density plasma are discussed. Results show that the ion temperature given by neutral particle energy spectra is lower than the real ion temperature, but the deviation is within 10% if the ion temperature is less than 800 eV and thecentral chord-averaged electron density does not exceed 3 ×1013 cm-3. But for ion temperature higher than 1000 eV at the central chord-averaged density limit up to 5 ×1013 cm-3, the neutral particle energy spectra can still give the ion temperature within 10% deviation.
基金The project supported by the An Hui Natural Science Foundation (No. 01043601)
文摘A few CT-based voxel phantoms were produced to investigate the sensitivity of Monte Carlo simulations of X-ray beam and electron beam to the proportions of elements and the mass densities of the materials used to express the patient’s anatomical structure. The human body can be well outlined by air, lung, adipose, muscle, soft bone and hard bone to calculate the dose distribution with Monte Carlo method. The effects of the calibration curves established by using various CT scanners are not clinically significant based on our investigation. The deviation from the values of cumulative dose volume histogram derived from CT-based voxel phantoms is less than 1% for the given target.
基金the National High Technology Research and Development Program of China(863 Program:2012AA022602)the 111 Project(B07014)and Tianjin Natural Science Foundation(No.16JCZDJC31200).
文摘Previous results show that the floating reference theory(FRT)is an effective tool to reduce the infuence of interference factors on noninvasive blood glucose sensing by near infrared spectros-copy(NIRS).It is the key to measure the floating reference point(FRP)precisely for the application of FRT.Monte Carlo(MC)simulation has been introduced to quantitatively in-vestigate the effects of positioning errors and light source drifts on measuring FRP.In this article,thinning and calculating method(TCM)is proposed to quantify the positioning error.Mean-while,the normalization process(NP)is developed to significantly reduce the error induced by light source drift.The results according to TCM show that 7 purm deviations in positioning can generate about 10.63%relative error in FRP.It is more noticeable that 1%fluctuation in light source intensity may lead to 12.21%relative errors.Gratifyingly,the proposed NP model can effectively reduce the error caused by light source drift.Therefore,the measurement system for FRPs must meet that the positioning error is less than 7 purm,and the light source drift is kept within 1%.Furthermore,an improvement for measurement system is proposed in order to take advantage of the NP model.
文摘在释光年代学上,剂量率代表样品埋藏过程中单位时间内吸收的辐射剂量,其估计直接影响到埋藏年代的可靠性。误差传递公式(Quadratic propagation of uncertainty)常用于剂量率误差估计。由于计算剂量率涉及到众多参数复杂的非线性运算,造成基于误差传递公式的误差估计过程繁琐复杂。本文以粗颗粒石英矿物为例介绍了剂量率计算过程及误差估计方法,使用蒙特卡罗误差传递法(Monte Carlo error propagation)模拟了剂量率计算过程中多参数不确定性耦合误差,编写了执行随机剂量率模拟运算的开源R程序,并通过实测数据展示了该技术的应用。相对于应用误差传递公式法估计剂量率误差,Monte Carlo方法具有直观灵活、简便科学的特点,这种随机策略在分析科学领域具有广泛的适用性。
