质子束流蒙特卡罗模型的建立及对脊形滤波器的探究

目的:探究脊形滤波器结构对质子束流展宽的影响。方法:利用蒙特卡罗程序FLUKA建立质子束流模型,并进行验证。模拟质子束流通过三棱柱型（A型）和金字塔型（B型）两种脊形滤波器,比较使用和不使用脊形滤波器的模拟值:束流前端最大剂量50%到束流末端最大剂量50%的宽度（E50-D50）、束流前端80%到束流末端80%的宽度（E80-D80）及束流末端80%到束流末端20%的宽度（D80-D20）。结果:根据模型计算出的121.1 MeV质子对应的模拟值绘制的积分深度剂量曲线与实际测量的积分深度剂量曲线,E50、E70和D80位置偏差不超过0.06 mm;A型相比B型将E50-D50平均多展宽了0.80 mm,将E80-D80 平均多展宽了0.27 mm,将D80-D20 平均多展宽了0.08 mm。结论:建立的质子束流蒙特卡罗模型合理,三棱柱型（A型）脊形滤波器展宽质子束流的效果更好。

Monte Carlo simulation of proton beams and investigation on ripple filters

Objective To explore the effect of ripple filter structure on the broadening of proton beams. Methods Monte Carloprogram FLUKAwas used to establish a proton beam model, and the model was verified. The situations that proton beams passedthrough triangular prism type (A-type) and pyramid type (B-type) ripple filters were simulated, and the simulation data when theripple filter was used or not were compared. The simulation data included the width between 50% of the maximum dose of thebeam entrance and 50% of the maximum dose of the distal beam (E50-D50), the width between 80% of the maximum dose of thebeam entrance and 80% of the maximum dose of the distal beam (E80-D80) and the width between 80% of the maximum doseof the distal beam and 20% of the maximum dose of the distal beam (D80-D20). Results The difference of E50, E70 and D80between the integral depth dose curve plotted according to the simulation value of 121.1 MeV proton calculated by the model andthe actually measured integral depth dose curve was no more than 0.06 mm. The E50-D50, E80-D80 and D80-D20 broadenedbyA-type ripple filter was 0.80, 0.27 and 0.08 mm wider than those broadened by B-type ripple filter. Conclusion The Monte Carlomodel of proton beams is proved to be reasonable, and the triangular prism type (A-type) ripple filter has better effect on broadeningthe proton beams.