基于蒙特卡罗方法的XHA600D医用电子直线加速器的入射电子束参数研究

使用蒙特卡罗方法研究入射电子束参数对XHA600D医用电子直线加速器产生的剂量分布的影响，并确定优化的入射电子束参数。根据厂商提供的XHA600D加速器治疗头的几何、材料参数，使用蒙特卡罗程序EGSnrc对不同的入射电子束参数进行模拟并记录其在水模体中产生的剂量分布，将模拟结果与测量结果进行比较。模拟的入射电子束参数包括平均能量、径向强度分布、角度展宽和能量展宽；实验测量数据包括4 cm×4 cm、10 cm×10 cm、30 cm×30 cm射野条件下的百分深度剂量与离轴剂量。结果表明当入射电子束的平均能量为6 MeV、径向强度的半高宽(Full Width at Half Maximum, FWHM)为0.25 cm、角度展宽为0.15°时，模拟结果和测量结果吻合非常好。这些参数可以作为建立适用于XHA600D加速器的TPS(Treatment Planning System)剂量计算模型的基础参数。

The Study of Incident Electron Beam Parameters of XHA600D Medical Linear Accelerator Based on Monte Carlo Method

This study investigated the influence of incident electron beam parameters on dose distribution generated by the XHA600D accelerator based on Monte Carlo method, and then determined the optimal incident electron beam parameters. According to the geometric and material parameters of XHA600D accelerator treatment head provided by the manufacturer, the dose distributions in the water phantom generated by different incident electron beam parameters were simulated and recorded using Monte Carlo code EGSnrc, and the simulated dose distributions were compared with the measured results. The simulated incident electron beam parameters include mean energy, radial intensity distribution, angular divergency and energy spread. The experimental measurements include percentage depth doses and off-axis doses for 4 cm×4 cm, 10 cm×10 cm, 30 cm×30 cm fields. The results show that the simulated data are in excellent agreement with the measurements when the mean energy is monoenergetic 6 MeV, the FWHM(Full Width at Half Maximum) radial intensity is 0.25 cm and the angular divergency is 0.15°. These parameters can be used as the basic parameters to establish the dose calculation model of TPS(Treatment Planning System) for XHA600D accelerator.