X线蒙特卡洛算法与有限元笔形束算法在旋转容积调强放疗计划中的剂量学比较

Dosimetric comparison of X-ray voxel Monte Carlo and finite size pencil beam dose calculation algorithm for volumetric modulated arc therapy planning

目的:比较Monaco治疗计划系统X线蒙特卡洛算法(X-ray voxel Monte Carlo,XVMC)和有限元笔形束算法(finite size pencil beam,FSPB)在食管癌和直肠癌旋转容积调强放疗计划中的剂量学差异。方法:选取7例食管癌和7例直肠癌旋转容积调强放疗计划,分别使用XVMC算法和FSPB算法进行剂量计算,比较靶区和危及器官的剂量分布差异。结果:XVMC算法的剂量计算值均高于FSPB算法,在食管癌的靶区和脊髓、直肠癌的靶区和危及器官,各项指标差值都小于3%,肺的各项指标差值最大达到10%。结论:在临床旋转容积调强治疗中,尤其是计算区域含有低密度组织较多的病例,优先推荐更为精确的XVMC算法进行剂量计算。

Objective To compare the dosimetric differences between finite size pencil beam （FSPB） and X-ray voxel Monte Carlo （XVMC） in Monaco treatment planning system for volumetric modulated arc therapy （VMAT） planning of esophageal cancer and rectal cancer. Methods For 7 esophageal cancer patients and 7 rectal cancer patients, VMAT treatment plans with FSPB and XVMC were preformed respectively. The differences of dose distribution to targets and organs at risk （OAR） were determined. Results The dose calculated by XVMC was higher than that by FSPB. For targets and spinal cord of esophageal cancer, targets and organs at risk of rectal cancer, the differences between XVMC and FSPB were less than 3%, and maximum difference to the lung reached 10%. Conclusion In clinical VMAT treatment, especially for the cases with calculation area including many low density tissues, XVMC algorithm gains the priority of dose calculation for its accuracy.