共查询到20条相似文献,搜索用时 250 毫秒
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核医学治疗中为了制定合理的治疗方案需要对患者进行个体化剂量评估。本研究通过计算患者的体素级剂量分布,对分化型甲状腺癌患者的131I SPECT图像及CT图像进行了精准定量分析,利用体素S因子方法、直接蒙特卡罗方法和GPU蒙特卡罗方法计算了核医学患者体素级剂量分布。体素S因子方法相比于蒙特卡罗方法,在上呼吸道内部、肺部、骨骼等与水密度差异大的位置表现出剂量结果的差异,在肺和骨骼的最大差异达到40%,且在组织的交界处差异明显,在距离源分布较远位置的剂量相对于蒙特卡罗结果有一定低估。GPU蒙特卡罗方法与直接蒙特卡罗方法计算结果一致,并实现了400倍的加速比。综上所述,体素级剂量计算能获得亚器官区域和肿瘤区域的剂量不均匀分布,直接蒙特卡罗方法相比于体素S因子方法能够实现更精确的剂量计算,GPU程序能有效加速蒙特卡罗计算。 相似文献
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在辐射环境质量监测中,多能核素的级联符合相加效应是影响γ能谱活度测量准确性的重要因素之一,为了提高待测样品分析的准确性,对结果进行符合相加修正是十分必要的。以152Eu核素为例,根据峰总比不变性特点,获得探测器峰总比拟合公式,联合符合相加修正公式,全能峰效率公式,计算了152Eu核素的符合相加修正因子,进一步采用Genie 2000符合相加蒙特卡罗程序对液体体源的152Eu核素进行了符合相加修正。点源的修正结果与真值的相对偏差小于6%,体源修正结果与真值的相对偏差在±4%以内。通过点源符合相加修正因子与源到探测器距离的线性关系,可以得到符合相加效应可忽略的最小测量距离;体源样品的符合相加修正结果表明:同一介质的样品,高度越高,符合相加修正因子越小;自吸收效应会在低能端对样品的有效立体角产生较大影响,从而影响样品的符合相加修正因子。峰总比不变性与衰变纲图相结合的数值修正方法,不需要对不同位置处的点源总效率进行测量,与蒙特卡罗程序法相比,该方法无需对探测器进行工厂表征,不用对体源介质、密度和形状等参数进行描述;舍弃级联符合较... 相似文献
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开发了一个基于中国女性彩色解剖断层图像的体素剂量学模型VPCF,并用FLUKA程序计算了光子能量在0.02~10 MeV范围内的20个能量点、外照射方向为腹背向(AP)、背腹向(PA)的组织或器官剂量转换因子和有效剂量转换系数,并与ICRP 74号报告的推荐值、CRAM和Regina的计算值进行了比较.结果表明:VPCF有些器官(如膀胱)的剂量转换因子与ICRP 74号出版物差别较大;有效剂量转换系数的差别不如器官或组织的剂量转换因子明显;VPCF的有效剂量转换系数要大于ICRP 74号出版物推荐值、CRAM和Regina的计算值. 相似文献
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放射治疗的X光透射剂量中含有不同强度的模体散射线,影响其临床应用.本文基于实验方法在不同条件下测量6 MV X线射野中心轴及离轴位置的透射剂量分布,从中提取原射线剂量,计算得到相应的散射线剂量,分析透射剂量中原射线和模体散射线的大小,研究不同条件下透射剂量中模体散射线分布的物理特性. 相似文献
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《中国原子能科学研究院年报》2001,(1)
为了开展反应堆压力容器中子辐照损伤、射线辐照生物效应等方面的研究,研究了蒙特卡罗通量计算技巧,建立了形成大范围粒子的精细通量分布的快速方法,并可以根据介质的不同转换为剂量场分布。 利用上述手段,进行了大探伤加速器实时成像技术中的研究和体部伽玛刀准直器辅助设计中的应用。 基于人体内剂量场计算的粒子源组织间三维立体定向肿瘤治疗计划系统也正在研制中,很快将投放市场。 相似文献
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放射性核素153Sm诱导不同肿瘤细胞凋亡及相关基因表达研究 总被引:4,自引:0,他引:4
采用细胞抑制率实验、光镜、电镜、流式细胞仪和免疫组化方法研究了^153Sm作用于前列腺癌PC—3细胞、乳腺癌ER—75—30细胞和肺癌A549细胞后对细胞的抑制作用,诱导肿田细胞凋亡的时间剂量效应关系和周期依赖性以及凋亡相关基因bcl—2和bax蛋白在其中的表达情况。结果显示,^153Sm对3种肿田细胞有明显的杀伤作用,能诱导肿田细胞产生凋亡的形态学变化,并且随着浓度的增大和时间的延长,凋亡率增加,且呈时间剂量和周期依赖性。比1—2表达减弱,bax表达增强,细胞阻滞于G2/M期,bcl—2和bax基因均参与^153Sm诱导细胞凋亡过程。3种细胞对^153Sm的敏感性由高到低依次为PC—3细胞、ER—75—30细胞和A549细胞。 相似文献
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钐-153标记的多胺甲基膦酸化合物的研究 总被引:1,自引:1,他引:0
合成了8种有机胺膦酸类配位体,进行了与153Sm的配位试验,研究了酸度、温度、时间等条件的影响,得到了最佳标记条件,并进行了小鼠体内生物分布试验。结果表明,其中4种配合物在骨中有较高的浓集,注射后2h骨的摄取率均在20%·g-1以上,骨与肌肉的摄取比接近200,这与目前临床应用的153SmEDTMP基本一致,因此具有药用价值,值得进一步研究。 相似文献
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Xiaokang ZHANG 《等离子体科学和技术》2022,24(9):95603
PyNE R2S is a mesh-based R2S implementation with the capability of performing shutdown dose rate (SDR) analysis directly on CAD geometry with Cartesian or tetrahedral meshes. It supports advanced variance reduction for fusion energy systems. However, the assumption of homogenized materials of PyNE R2S with a Cartesian mesh throughout a mesh voxel introduces an approximation in the case where a voxel covers multiple non-void cells. This work implements a sub-voxel method to add fidelity to PyNE R2S with a Cartesian mesh during the process of activation and photon source sampling by performing independent inventory calculations for each cell within a mesh voxel and using the results of those independent calculations to sample the photon source more precisely. PyNE sub-voxel R2S has been verified with the Frascati Neutron Generator (FNG)-ITER and ITER computational shutdown dose rate benchmark problems. The results for sub-voxel R2S show satisfactory agreement with the experimental values or reference results. PyNE sub-voxel R2S has been applied to the shutdown dose rate calculation of the Chinese Fusion Engineering Testing Reactor (CFETR). In conclusion, sub-voxel R2S is a reliable tool for SDR calculation and obtains more accurate results with the same voxel size than voxel R2S. 相似文献
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《Journal of Nuclear Science and Technology》2013,50(12):1518-1525
The MCDB Monte Carlo Dosimetry Code for Brain Tumors has been developed for Boron Neutron Capture Therapy (BNCT). This code system includes a medical preprocessor, a Monte Carlo dose calculation and a postprocessor. The center point method is used to determine the material and density in each voxel. For dose calculations, a fast particle track technique is developed for the voxel model. This technique is valid for the single-voxel model as well as the multivoxel model. The material matrix and mesh tally matrix are designed for reducing the initialization and tally times. The same dose results as MCNP are achieved. MCDB is faster by a factor of 2:7~3:5 in computational speed with respect to MCNP. Furthermore, MCDB can do parallel computation. It meets the clinical requirements for precision and time. 相似文献
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Thermal neutron capture cross sections for the Sm(n,γ)Sm and Sm(n,γ)Sm reactions at 0.0536 eV energy
M.S. Uddin M.H. Chowdhury S.M. Hossain M.A. Islam S.H. Mubin S.M. Yunus 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2008,266(22):4855-4861
The neutron capture cross sections for the 152Sm(n,γ)153Sm and 154Sm(n,γ)155Sm reactions at 0.0536 eV neutron energy were measured using an activation technique based on the TRIGA Mark-II research reactor, relative to the reference reaction 197Au(n,γ)198Au. The activity was measured nondestructively using gamma-ray spectroscopy. Our measured values at this neutron energy are the first ones and are compared with 1/v based evaluated cross sections reported in the ENDF/B-VII and JENDL-3.3 libraries. The measured value for the 152Sm(n,γ)153Sm reaction is 0.28% lower than JENDL-3.3 and 0.48% higher than ENDF/B-VII. Our value for the production of 155Sm is about 3% and 2.3% higher than the evaluated value with ENDF/B-VII and JENDL-3.3 at 0.0536 eV, respectively. 相似文献
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JIANG Shu-Bin LUO Shun-Zhong LIU Guo-Ping DENG Hou-Fu BING Wen-Zeng WANG Wen-Jin WEI Hong-Yuan HUShu 《核技术(英文版)》2003,14(2)
TTHMP (triethylenetetraaminehexamethylenephosphonic acid) was labeled with 153Sm. The labeling condition, stability, mole ratio of 153Sm to TTHMP, rabbit bone imaging and bio-distribution of 153Sm-TTHMP in mice were investigated. The results showed that weak basie media and high concentration ligands were favorable to form 153Sm-TTHMP; labeling compounds were stable at pH 7 in 7 days. The results also indicated that the chemical mole ratio of 153Sm-TTHMP is n(153Sm) : n(TTHMP) = 1 : 1 and skeleton uptake of 153Sm-TTHMP is high((13.96±3.51)%/g at 1h post injection and (13.54±2.98)%/g at 48h post injection), while the non-target tissue uptake is relatively low, so 153Sm-TTHMP is a promising bone tumor therapeutic agent. 相似文献