放疗中高次散射X线对剂量计算结果影响分析

目的 分析放疗中X线的高次散射对剂量计算结果的影响,解决将2次散射光子及高次散射光子对剂量贡献问题修正到1次散射光子散射剂量贡献中的可能性,为建立快速蒙特卡罗剂量计算方法提供支持。方法 采用X线与物质的作用截面理论和蒙特卡罗方法计算结果,分析1次、2次和高次散射X线对剂量计算精确度影响相对重要性。结果 ≥2次的高次散射对剂量的影响很小,并且可通过一小的修正系数被修正到1次散射X线的贡献中。结论 只追踪原射线和1次散射X线剂量贡献就可获得临床满意的剂量计算精确度,如用蒙特卡罗方法建立1次散射X线散射光子注量角分布和光子平均能量散射角分布模型数据库,将有助于提高临床剂量的蒙特卡罗计算效率。

The analyzing to the effects of high-order scattered X-ray to dose calculation in radiotherapy

Objective To analyze the effects of high-order scattered X-ray in dose calculation in radiotherapy, to resolve the problem of correcting the dose contribution of secondary and high-order scattering X-ray to the primary scattered X ray, and to provide a support for photon fast dose calculation method of Monte Carlo. Methods By the theory of cross-section in interaction between X-ray with material and Monte Carlo calculating results, to analysis the relative importance of primary scattered X-ray, secondary and high-order scattered of X-ray in dose calculation. Results The contribution of secondary and high-order scattered X-ray to dose calculation was very small, it can be corrected to the primary scattered X-ray with a correction factor. Conclusions The results show that we can obtain a precise dose calculation for radiotherapy by only to tracking the contribution of primary X-rays and primary scattering X-ray, so, to establishing the database for primary scattering X-ray by Monte Carlo methods is important for fast dose calculation of Monte Carlo method.