质子治疗室感生放射性及屏蔽材料影响分析

Analysis of induced radiation and shielding materials in proton therapy room

目的分析质子固定束治疗室内感生放射性剂量分布及屏蔽材料的影响。为质子治疗辐射防护及屏蔽材料选择提供依据。方法利用FLUKA模拟质子固定束治疗室内感生放射性剂量分布、剂量随时间的变化情况及不同混凝土材料的影响。结果质子治疗室内感生放射性剂量分布主要集中于靶周边,且冷却3~5 min后剂量迅速降为停止照射时刻的5~10倍。混凝土中感生放射性会在主射束末端靠近屏蔽体内侧形成剂量略高区域,混凝土中Fe、O、H、等元素含量对治疗室内感生放射性剂量有显著影响(P<0.01),且治疗室内感生放射性剂量与Fe元素含量呈负相关。结论质子治疗室内治疗后的患者、空气和屏蔽材料的感生放射性均是工作人员外照射剂量的主要来源,采取时间的防护方式最为有效。在不考虑施工难度等因素,从外照射防护效果和感生放射性剂量贡献的影响上分析,在质子治疗室的屏蔽材料选择上含Fe较多的重混凝土为最优选择。

Objective To analyze the dose distribution of induced radiation in fixed proton beam therapy room and the influence of shielding materials,and to provide a basis for radiation protection and shielding material selection in proton therapy.Methods FLUKA was used to simulate the dose distribution of induced radiation in fixed proton beam therapy room,the dose over time,and the influence of different concrete materials.Results The dose of induced radiation was mainly concentrated around the target,and the dose rapidly decreased to 1/5-1/10 of the value at the time of stopping irradiation after cooling for 3-5 min.The induced radiation in concrete formed a slightly higher dose area at the end of the main beam near the inner side of the shield.The content of Fe,O,and H in concrete had significant effects on induced radiation(P<0.01),and the dose was negatively correlated with the content of Fe.Conclusion The patients after proton therapy as well as the induced radiation in air and shielding materials are the main sources of external radiation dose for workers,and waiting for a period of time is the most effective way to protect the staff.Without considering the difficulty in construction and based on the analysis of shielding materials in protection against external irradiation and their influence on induced radiation,heavy concrete with a relatively high level of Fe is the best choice of the shielding material for proton therapy room.