摘要
目的:放射治疗过程中金属植入物会对体内剂量分布造成影响,这种影响主要表现为散射电子背向散射造成的金属植入物入射面处剂量增强和由于金属植入物阻挡造成的出射面处剂量衰减。本文主要研究金属植入物入射面处剂量增强的影响因素及作用规律。方法:利用蒙特卡罗粒子输运程序MCNP建立内部含有金属块的水箱模型,通过改变金属植入物材质、厚度、宽度、在水箱中的深度、测量点距金属表面距离以及入射光子能量、照射面积等因素参数,研究以上因素对背散射因子的影响规律,并根据射线与物质相互作用原理进行物理分析。结果:通过模拟计算得到背散射因子与以上影响因素的关系。结论:(1)背散射因子对金属植入物的材质、厚度、测量点距金属表面的距离以及入射线束的能量等因素变化较敏感,而对金属植入物在水箱中的深度、宽度以及照射面积等因素的变化不太敏感。(2)研究结果与前人实验结果相近,证明MCNP程序能够很好地用于研究金属植入物入射面处的剂量扰动问题。
Objective： Metal implants would affect the dose distribution in the body when radiotherapy, this effect is mainly characterized by dose enhancement at the incident surface of metal implants caused by backscattering of scattered electron and dose attenuation at the exit of surface due to the block of metal implant.This paper mainly studies the factors and effect laws of dose enhancement of implant metal on incident surface. Methods： First, using MCNP Monte Carlo particle transport program establish a model with a metal block inside a water-filled phantom, then do research on the effect laws of material, thickness, width, depth in the water phantom of the metal implant and distance of measuring point f^om metal surface, as well as the incident photon energy, exposure area and other factors to the backscattering factor, And make physics analysis basing on the principle of interaction between radiation and matter. Results： Obtain the relation of backscattering factor with the foregoing factors through simulation and calculation. Conclusions： （1） Backscattering factor is sensitive to factors such as material, thickness, distance of measuring point from metal surface, as well as energy of incident beam, while show insensitive to depth of metal implants in the water phantom, width and exposure area and so on.（2）Results in this paper are similar to the previous experimental results, indicating MCNP program can be perfectly applied to research the problem of dose perturbation on the inci dent surface of metal implant.
出处
《中国医学物理学杂志》
CSCD
2013年第5期4373-4377,共5页
Chinese Journal of Medical Physics
