摘要目的 研究光子外照射事故下人体的剂量重建方法,并在局部剂量分布层面上验证方法的准确性.方法 基于开源蒙特卡罗代码Geant4,使用国际辐射防护委员会(ICRP) 103号建议书推荐的人体体素模型,研究外照射事故照射条件下的剂量重建方法,实现全身平均吸收剂量、器官吸收剂量和局部剂量分布的评价.为了对建立的方法进行验证,使用组织等效的物理仿真模型ART;通过CT扫描,建立起其分辨率为1.57 mm×1.57 mm×10.00mm的体素模型;在标准辐射场下进行一系列热释光剂量计(TLD)照射实验,比较实验和剂量重建模拟的结果.结果 实验测量值的综合相对不确定度为10.9％,剂量重建模拟值的综合相对不确定度在非组织交界面处为7.10％,在组织交界面处为16.6％.对451个测量点位进行统计分析,模拟值除以测量值的均值为0.972,标准差为0.083 8,在0.95 ～ 1.05,0.90～1.10和0.80～1.20范围内的比例分别为49.2％,79.4％和96.4％.结论 基于人体体素模型的蒙特卡罗剂量重建方法无论在全身或器官层面,还是在局部剂量分布层面都满足实际使用的精度要求,可作为外照射事故下对受照者进行剂量评估的有力工具,为诊断和救治提供支持.

abstractsObjective To study the method of dose reconstruction in human body under the photon external radiation accident condition,and to verify the accuracy of the method for the local dose distribution.Methods Based on the open source Monte Carlo tool kit Geant 4 and using the human voxel phantom recommended by ICRP Publication 103,the dose reconstruction method under the condition of external radiation accident was studied to evaluate the average absorbed dose,organ absorbed dose and local dose distribution.To validate the code,several irradiation experiments were implemented in some standard radiation fields by putting TLDs in the tissue equivalent physical phantom ART.A voxel phantom was used to reconstruct the radiation doses,which was created based on the CT scan image of the ART phantom with resolution of 1.57 mm× 1.57 mm× 10.00 mm.The result of experiment were compared with those of dose reconstruction simulation.Results The relative uncertainty of the measured values was 10.9％.The relative uncertainty of the dose reconstruction simulation values was 7.10％ at the non-tissueinterface area and 16.6％ at the tissue-interface area.For 451 measuring points,the average of the simulated value divided by the measured value was 0.972,with the standard deviation of 0.083 8.In the range of 0.95-1.05,0.90-1.10 and 0.80-1.20,and the proportions were 49.2％,79.4％ and 96.4％,respectively.Conclusions The method of Monte Carlo dose reconstruction based on human voxel phantom meets the accuracy requirement of actual uses both at the whole body or organ level and at the local dose distribution level.It can be used as a powerful tool for dose assessment of the exposed people in an external radiation accidents and provide support for diagnosis and treatment.