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用蒙特卡罗应用程序EGSnrc模拟计算了60Coγ射线、6–MV的点源光子束在有限宽非均匀模体中,不同射野条件下中心轴上的剂量分布情况,利用剂量扰动因子(Dose perturbation factor,DPF)定量研究了剂量增强或减弱效应的强度。DPF即不均匀介质模体中某点的剂量与均匀水模体中同一空间位置点处的剂量值之比。模拟结果表明,剂量扰动效应的强弱程度取决于多种因素,如射线的能量、射野的尺寸和入射介质的尺寸。另外,无论是在骨等效介质中,还是在肺等效介质中,剂量增强或减弱效应随射野尺寸的变化并不是线性的。
Dose perturbation (Dose perturbation) of 60Coγ-ray and 6-MV point-source photon beam in the central axis of a finite-width inhomogeneous phantom was calculated by Monte Carlo application EGSnrc. factor, DPF) quantified the intensity of dose-enhancing or attenuating effects. The DPF is the ratio of the dose at a point in an inhomogeneous matrix to the dose at the same spatial point in a homogeneous water phantom. Simulation results show that the degree of dose perturbation depends on many factors, such as the energy of the radiation, the size of the radiation field, and the size of the incident medium. In addition, dose-enhancing or attenuating effects are not linear with field size changes in both bone-equivalent and lung-equivalent media.