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CT检查个体化辐射剂量估算研究现状 总被引:1,自引:0,他引:1
2011年和2014年美国医学物理学会分别发布204号和220号报告,描述基于个体体征估算CT受检者的辐射剂量。204号报告介绍应用受检者前后径和左右径等描述个体体征,220号报告介绍用水当量直径描述受检者的体型特异性,利用体型特异性的转换因子估算CT扫描受检者体型相关的辐射剂量(SSDE)。近年来,国外一系列的文章在SSDE方面进行了深入的研究,本文首先介绍两则报告的主要内容,并对SSDE在儿童和成年人群CT检查诊断参考水平的制定、CT断层图像的质量、受检者器官剂量和有效剂量的估算方面的研究现状进行综述,为开展国内SSDE相关研究和应用提供参考。 相似文献
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辐射屏蔽计算是核电厂辐射防护设计和审评的重要内容之一。国际屏蔽计算软件对中国实行"出口封锁",制约了我国核电辐射屏蔽审核计算能力,因此,研发了具有自主知识产权的基于蒙特卡罗方法的辐射屏蔽专用蒙特卡罗软件RShieldMC(Radiation Shielding Monte Carlo)。为了验证RShieldMC程序,进行中子注量率计算的准确性和适用性,利用秦山一期反应堆结构与辐照监督管相关参数,通过RShieldMC可视化前处理模块建立辐照监督管屏蔽计算模型,计算秦山一期反应堆辐照监督管堆芯中平面和上焊缝处的中子注量率。RShieldMC程序计算结果与辐照监督管实验测量值以及MCNP(Monte Carlo N-Particle)、JMCT-S(J Monte Carlo Transport)、TORT(Three-dimensional Neutron/Photon Transport)程序计算结果符合较好,验证了RShieldMC软件在中子注量率计算中的可用性及正确性。 相似文献
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探讨医院级各部位CT扫描辐射剂量及成人CT检查诊断剂量水平。采集2018年2月—2019年1月本院在GE Light Speed 16 CT设备上进行诊断性CT检查的全部成年人共15 440例的CT检查数据,按照检查部位进行分类,统计各部位的容积剂量指数(CTDIvol)、剂量长度乘积(DLP)。使用SPSS 19统计软件分析CTDIvol、DLP的四分位数并计算有效剂量(ED)。结果表明,各部位CTDIvol的诊断剂量参考水平(DRL)值为:颅脑87.75 mGy、肺部8.09 mGy、上下腹15.82 mGy、上下腹盆腔15.79 mGy;各部位DLP的诊断剂量参考水平(DRL)值为:颅脑1 053.03 mGy·cm、肺部245.19 mGy·cm、上下腹269.96 mGy·cm、上下腹盆腔835.20 mGy·cm。研究中发现肺部CTDIvol、DLP的DRL值(分别为8.09 mGy、245.19 mGy·cm)低于我国其他地区和其他国家的DRL值;60岁以下患者肺部CT检查CTDIvol、DLP的DRL值低于8.09 mGy、245.19 mGy·cm,60岁以上患者肺部CT检查CTDIvol、DLP的DRL值高于8.09 mGy、245.19 mGy·cm。通过研究可以确定医院级各部位CT检查辐射剂量及成人CT检查诊断剂量水平,能为优化CT检查扫描技术和监测辐射剂量提供基础。 相似文献
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探讨成人在70 kVp副鼻窦CT检查中降低有效辐射剂量的同时,获取最佳图像质量的新一代多模型迭代算法(Adaptive Statistical Iterative Reconstruction-V,Asir-V)的权重。本研究对20例成人患者进行副鼻窦Revolution CT检查,采用70 kVp、230 mA条件下进行螺旋CT扫描,扫描完成后对每例患者的原始数据采用不同权重(0,20%,40%,60%,80%,100%)的后置新一代多模型迭代算法(Adaptive Statistical Iterative Reconstruction-V,Asir-V)重建的方法,共获得120幅图像,并对每例6组图像进行客观评价及主观评分。客观评价包括噪声(standard deviations, SD)和对比噪声比(contrast noise ratio,CNR),主观评价由2名评价医生对图像质量评分并对两者的主观一致性进行评价。每例患者扫描完成后,记录其剂量长度乘积(dose-length product,DLP)和CT容积剂量指数(CT dose index volume,CTDIvol),并计算其平均有效辐射剂量(effective dose,ED)。客观评价结果表明不同权重的Asir-V图像噪声随着Asir-V权重的提升而降低,CNR值随着Asir-V权重的提升而升高,且有效辐射剂量ED较常规头颈部CT检查的平均辐射剂量明显减少;主观评价结果表明不同权重的Asir-V图像评分不同,在Asir-V 60% 时评分最高,且2名医生主观评价一致性好。结合主客观评价结果,认为在70 kVp、230 mA成人副鼻窦Revolution CT检查中,Asir-V 60%的图像既可满足临床诊断的需要,也可明显降低有效辐射剂量。 相似文献
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基于Monte Carlo方法的释光测年剂量率误差估计 总被引:1,自引:0,他引:1
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。 相似文献
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分析GEANT4应用发射断层(GEANT4 Application for Tomographic Emission,GATE)在模拟人体体素模型剂量转换系数的应用,为计算基于体素模型的光子辐射场中的剂量提供一种新路径。GATE是基于GEANT4开发并广泛应用于模拟正电子发射断层成像(Positron Emission Tomography,PET)、单光子发射计算机断层成像(Single Photon Emission Computed Tomography,SPECT)等成像系统以及放射治疗的蒙特卡罗模拟软件。用自编的MATLAB程序将人体体素模型KTMAN-2的体素数据逆转为断层影像(Computed Tomography,CT),再由VV软件将CT转换为GATE体素模型文件,在GATE和MCNPX(Monte Carlo N-Particle e Xtended)中模拟6种标准照射方式下、0.01~10 Me V能量范围内23种单能光子在人体内的输运,得到一系列的光子器官剂量转换系数,将两者的计算结果进行对比,并将结果和ICRP 74、ICRP 116号出版物的推荐值进行比较。GATE和MCNPX的计算结果具有很好的一致性,除质量很小的器官(垂体、扁桃体、甲状腺等),其它器官的差异都在3%以内;对于某些器官在某些照射条件下,所得结果和ICRP 74、ICRP 116号出版物的推荐值一致,但在某些照射条件本文结果与ICRP 74、ICRP 116出版物的推荐值存在较大差异。GATE为基于体素模型的剂量计算提供了一种新方法;本文计算的剂量转换系数对于分析亚洲人个体与ICRP参考人之间光子剂量转换系数的差异具有重要意义。 相似文献
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多排(层)螺旋CT的辐射剂量表达及其影响因素探讨 总被引:9,自引:0,他引:9
多排(层)螺旋CT反映了放射学影像设备与技术的最新进展.它的迅速推广应用有益于临床医学诊断,但同时也增加了受检者医疗照射,随之可能增加一定的电离辐射风险.然而相应的放射防护监测及评价的前提是准确表达并测量其辐射剂量.因此本文侧重辐射剂量学角度,从总结归纳多排(层)螺旋CT的主要特点入手;系统评述X射线CT所致辐射剂量的表征量及其测量或估算方法;进而分析探讨影响多排(层)螺旋CT扫描所致辐射剂量的主要因素.显然,正确掌握这些X射线CT所致辐射剂量的表达及其测量与评价方法,进而统筹兼顾优化提高影像质量与合理降低受检者剂量,已经成为放射防护学界、医学物理学界、临床医学放射学界以及医疗器械研发部门等共同关注的重点和热点. 相似文献
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C.C. Ferreira J.W. Vieira A.F. Maia 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2009,267(20):3447-3455
We have evaluated the utilization of five X-ray spectra codes for Monte Carlo (MC) simulations of computed tomography (CT) examinations. Four codes (Xcomp5r, X-raytbc, X-rayb&m and Srs-78) are semi-empiricals and one is based on MC methods (EGSnrc/BEAM Monte Carlo code). The X-ray spectra calculated by the semi-empirical codes were compared with the X-ray spectrum calculated by the EGSnrc/BEAM MC code. The absorbed doses to each organ or tissue were also compared. The calculated doses, and its respective organs, for which occurs the greatest disagreement, as well as the calculated doses for the testes and red bone marrow (two important organs used for calculating effective dose) were presented. The results obtained in this work are in good agreement with those obtained by Ay [M.R. Ay, S. Sarkar, M. Shahriari, D. Sardari, H. Zaidi, Assessment of different computational models for generation of X-ray spectra in diagnostic radiology and mammography, Med. Phys. 32 (2005) 1660], mainly for the bremsstrahlung distribution. Also, it was noted that the total characteristic X-rays produced by the EGSnrc/BEAM MC code increases with the increase of voltage more intensely than with the Xcomp5r, X-raytbc and Srs-78 codes. Comparison between the absorbed dose to each organ or tissue showed that, for X-ray spectra with additional filtration, the code based on Tucker et al. is in agreement with EGSnrc/BEAM MC code. But, for X-ray spectra without additional filtration the code based on Tucker et al. model presented the strong disagreement with EGSnrc/BEAM MC code. 相似文献
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为准确地得到γ射线的辐射剂量,对G(E)函数法和Gravel算法处理能谱-剂量的转换效果进行了研究。根据实际应用需求,采取蒙特卡罗方法模拟获取了?50 mm×50 mm NaI(Tl)探测器的Gravel法响应矩阵,并使用Matlab得到探测器的G(E)函数。使用NaI(Tl)探测器和多道谱仪系统测量标准源的能谱,分别使用G(E)法和Gravel法计算剂量值并与理论值进行比较,同时在计算过程中总结对比了两种方法的特点。 相似文献
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《Journal of Nuclear Science and Technology》2013,50(9):964-971
Conversion from tooth enamel dose to organ doses was analyzed to establish a method of retrospective individual dose assessment against external photon exposure by electron spin resonance (ESR) dosimetry. Dose to tooth enamel was obtained by Monte Carlo calculations using a modified MIRD-type phantom with a teeth part. The calculated tooth enamel doses were verified by measurements with thermo-luminescence dosimeters inserted in a physical head phantom. Energy and angular dependences of tooth enamel dose were compared with those of other organ doses. Additional Monte Carlo calculations were performed to study the effect of human model on the tooth enamel dose with a voxel-type phantom, which was based on computed tomography images of the physical phantom. The data derived with the modified MIRD-type phantom were applied to convert from tooth enamel dose to organ doses against external photon exposure in a hypothesized field, where scattered radiation was taken into account. The results indicated that energy distribution of photons incident to a human body is required to evaluate precisely an individual dose based on ESR dosimetry for teeth. 相似文献
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Takuma Noto Kazuaki Kosako Takashi Nakamura 《Journal of Nuclear Science and Technology》2020,57(8):898-904
ABSTRACT An effective dose calculation method is important in the design of efficient shields in radiation facilities. Some analytical methods have been shown to provide a simple and quick design analysis; however, no suitable method exists that can be applied to a room located directly under an X-ray irradiation room. We propose a new analytical method that uses the multiple reflection ratio predetermined by a Monte Carlo simulation and the differential dose albedo given by the Chilton–Huddleston semi-empirical equation. Our method is verified by comparison with the Monte Carlo simulation, performed for the case of an electron linac facility with an accelerated energy of 10 MeV, where the shielding floor has a thickness of 1.6–2.0 m and the downstairs room has a height of 0.5–1.5 m. The difference between the effective X-ray doses in the downstairs room calculated via the proposed analytical method and the Monte Carlo simulation is less than 25% when the horizontal distance from the X-ray beam to the evaluation point exceeds 3 m and the evaluation point is set at half of the height of the room. The new analytical method can be efficiently and accurately applied to the calculation of the effective dose. 相似文献
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提出了一种简便的CdZnTe探测器能谱-剂量转换函数(G(E)函数)的计算方法。峰形拟合函数被用于表征CdZnTe探测器对γ射线的低能拖尾,峰形拟合函数的参数通过实验测量获取,并通过拟合得到其随能量变化的关系。Monte-Carlo模拟计算得到的探测器理想沉积谱,经峰形拟合函数卷积得到了修正的模拟能谱,修正的模拟能谱与实际测量能谱吻合较好。基于修正的模拟能谱计算得到了CdZnTe探测器的G(E)函数。标准辐射场中的实验结果表明,用G(E)函数加权积分计算的周围剂量当量率与约定真值基本一致。 相似文献
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