基于蒙特卡罗模拟的^(235)U分布对肺计数器探测效率的影响  

A Monte Carlo simulation-based study of ^(235)U distribution effect on lung counter detection efficiency

作　　者：刘婕 纪云龙 许旭 张晓敏 李大伟 张宇心 宁静 Liu Jie;Ji Yunlong;Xu Xu;Zhang Xiaomin;Li Dawei;Zhang yuxin;Ning Jing(Academy of Military Medical Sciences,Academy of Military Sciences,Beijing 100039,China)

机构地区：[1]军事科学院军事医学研究院,北京100039

出　　处：《中华放射医学与防护杂志》2025年第3期223-228,共6页Chinese Journal of Radiological Medicine and Protection

摘　　要：目的探究由于体内代谢引起的核素随时间分布变化对使用肺计数法测量体内放射性污染的影响。方法以单次吸入含有^(235)U气溶胶为例,结合国际放射防护委员会(ICRP)核素代谢隔室模型,计算核素在体内的分布随时间变化。使用Geant4模拟计算软件对肺计数器进行无源效率刻度,获得感兴趣组织或器官对肺计数器计数的贡献,研究核素分布对肺计数方法的影响。结果吸入放射性核素后所经历的时间以及核素的理化状态影响着核素在体内分布状态,从而影响了肺计数器的探测效率。粒径小的放射性微粒在肺部初始滞留量较高,吸入活性中值空气动力学直径(ADAM)1μm的放射性微粒在肺部滞留量对肺计数器计数贡献份额高于ADAM为5μm的放射性核素。F型化合物在呼吸系统内代谢速率较快,当摄入8 h后核素在肺部滞留份额对肺计数器贡献份额不超过30%;而M型和S型化合物则在摄入后3 d内放射性微粒主要沉积在鼻咽区,随着核素的代谢廓清,肺部对肺计数器贡献份额增加,3 d后贡献份额始终保持在80%以上。结论不同理化性质的放射性物质在体内代谢情况不同,测量的时间不同,对应的核素在体内的分布不同,在进行内污染测量估算时,避免未考虑核素分布而造成内照射剂量的高估。Objective To investigate the effect of nuclide distribution with time from the in vivo metabolism based on measurement of radioactive contamination using lung counting method.Methods The distribution of nuclides in the body with time was calculated on a basis of a single inhalation of aerosols containing ^(235)U and the International Commission of Radiological Protection(ICRP)nuclide metabolism compartment model.A passive efficiency calibration of the lung counter,was performed using the simulation and calculation software Geant4 to obtain the contribution of the tissue or organs of interest to the lung counter,and to investigate the effect of the nuclide distribution on the lung counting method.Results The time elapsed after inhalation of radionuclides,as well as their physicochemical state,has the effect on their distribution in the body and on the detection efficiency of the lung counter.Radionuclides with smaller particulate sizes have a higher initial retention in the lungs,and those with an activity median aerodynamic diameter(ADAM)of 1μm contributed more fraction to the lung counter than those with an ADAM of 5μm.F-type compounds were metabolized more rapidly by the respiratory system,and after 8 h of ingestion,nuclides were distributed in the lungs.F-type compounds were metabolized in the respiratory system at a relatively fast rate,and 8 h after inhalation,the fraction of nuclides retained in the lung contributed no more than 30%to the lung counter.Within 3 d after ingestion of M-type and S-type compounds,radioactive particulats largely deposites in the nasopharyngeal region.With biological metabolization and clearance,the fraction contributed by lung to counter is in rising,and the fraction to the lung counter typically remained larger than 80%after 3 d.Conclusions Radionuclide metabolization in the body varies with their physicochemical properties and measurement time and site.For estimating internal contamination,consideration should be given to the distribution of nuclides,in order to avoid the ove

关 键 词：蒙特卡罗模拟 生物动力学模型 放射性内污染 探测效率 

分 类 号：R73[医药卫生—肿瘤]