【摘要】 医用电子直线加速器产生的X射线已广泛应用于放射治疗过程,X射线与机头中的高Z物质(铅、钨、铜和铁)发生(γ,n),(γ,2n)反应产生一定量的中子,引起与治疗无关的中子剂量。本文对工作在15MV能量档的Prim μs-M型医用电子直线加速器在标准照射野10cm×10cm内治疗平面的光中子剂量分布,进行了Monte-Carlo模拟,并使用CR39固体核径迹探测器和中子气泡探测器(NBD)进行了实验测量。研究发现,测量与模拟的中子剂量之间最大偏差约±30%,其最主要的原因是由于"加速器产生的光核中子与物质发生非弹性散射反应"而逐步降低能量,产生了低于上述两种探测器阈能(100keV)的中子,使测量值比模拟值偏低。研究结果为X射线放射治疗中减低污染中子剂量的优化设计提供了基础数据。更多还原

【Abstract】 X-rays produced by medical accelerator have been widely used in radiotherapy.During the process of therapy,a certain level of photonuclear neutrons are produced by the (γ,n) and (γ,2n) reactions of the X-rays and surrounding materials.The neutron dose distribution caused by the Prim μs-M linac at 15 MV in the standard exposure field of 10 cm×10 cm was M-C simulated,and measured at the treatment plane by CR-39 solid state nuclear track detector and neutron bubble detector (NBD).The results show that the measured neutron doses are lower than the simulated ones by up to 30%.The main reason for this difference is that the neutrons with energies below 100 keV produced by inelastic scattering of fast neutrons with surrounding materials are below the threshold energies of both detectors,and thus not detected.These results provide some basis for the optimal design of the facility shielding aiming at controllable and minimized contaminating neutron dose.更多还原