医用电子直线加速器机头散射X射线的分析

The analysis calculation for the scattering from medical electron linac head structure

本文介绍了一种用于医用电子直线加速器机头的结构部件上产生的散射X射线能量注量分布的解析计算方法。该方法是在蒙特卡罗模拟计算得到的初级X射线能谱的基础上,通过康普顿散射的Klein—Nishina公式计算得到的。考虑的主要散射源为机头内的初级准直器和均整块。我们用这个方法研究了北京医疗器械研究所生产的6MeV BJ-6加速器的机头散射情况并和实验测量结果进行了比较。比较的结果还包括均整块和初级准直器的散射与射野大小及离开X射线源距离之间的关系。比较结果表明:该解析计算方法对计算机头散射问题是可行的。

The paper introduced an analysis formula lor the calculation of the scattering effects on head structure of medical electron accelerator. This calculation was based on the Monte Carlo simulated primary X-ray spectrum, and the formula of Klein-Nishina was used for the calculation for the scattered spectra mainly scattered from primary collimator and energy spreader. Using the formaula and the method the scattering effects were systematically investigated for the 6 MeV BJ-6 linac Produced by Beijing Medical Equipment Institute. The presented results also include the relations between scattering factors with therapeutical fields and the distances of primary X-ray source and target plane. All the results showed that this calculation is reliable and useful for estimation of the scattering in head structure of Linac for the dose calculation for radiotherapy.