通量平滑度对左乳癌保乳术后容积旋转调强放疗剂量学的影响

Effect of fluence smoothing on dosimetry of volume rotation intensity modulated radiotherapy after breast-conserving surgery for left breast cancer

目的:对比Monaco计划系统的蒙特卡罗算法中3种通量平滑度参数在左乳癌保乳术后容积调强中剂量学的差异。方法:选取左乳癌保乳术后患者15例,采用Monaco计划系统在相同的优化条件下分别使用低、中、高3种通量平滑度进行VMAT计划设计,比较三组计划的靶区及危及器官剂量学参数。结果:三组计划的靶区D_(2)、D_(98)、D_(95)、CI、HI等各项参数以及脊髓D_(max)相比差异均无统计学意义;高组得到的左肺V_(5)、V_(10)、V_(20)、V_(30)和D_(mean)以及心脏的V_(5)和D_(mean)均低于中组和低组,其中左肺V_(5)、D_(mean)、心脏V_(5)、D_(mean)的差异均有统计学意义(P<0.05);与低组相比,中组的左肺V_(5)、V_(10)、V_(20)、V_(30)和D_(mean)以及心脏D_(mean)均降低,但差异均无统计学意义(P>0.05);中组和高组的右肺V_(5)、心脏D_(mean)均低于低组,右肺D_(mean)高于低组,但差异均无统计学意义(P>0.05);高组的子野数与中组、低组相比均显著降低,分别降低了5.8%和7.5%,差异均有统计学意义(t=7.405、5.215,P<0.05);中组的子野数低于低组1.7%,差异有统计学意义(t=3.826,P<0.05);低组、中组和高组的平均机器跳数为913.61 MU、938.76 MU和777.29 MU,高组与中组和低组相比分别减少了17.2%和14.9%,差异有统计学意义(t=6.954、12.516,P<0.05)。结论:左乳癌保乳术后VMAT中建议采用高通量平滑度。

Objective:Comparison of dosimetric differences of three fluence smoothing parameters in Monte Carlo algorithm of Monaco treatment planning system(TPS)in volume intensity modulation after breast-conserving surgery for left breast cancer.Methods:Fifteen patients with left breast cancer after breast-conserving surgery were selected.The Monaco TPS was used to design the VMAT plan with the fluence smoothing of low,medium and high respectively under the same optimized conditions.The dosimetric parameters of the target area and endangered organs of the three groups were compared.Results:There was no significant difference in D_(max) of the cord and D_(2),D_(98),D_(95),CI,HI and other parameters of the target among the three groups.There was no significant difference in D_(max) of the cord and D_(2),D_(98),D_(95),CI,HI and other parameters of the target among the three groups.The V_(5),V_(10),V_(20),V_(30) and D_(mean) of the left lung and the V_(5),D_(mean) of the heart in the high group were lower than those in the other two groups,and there were significant differences in the V_(5),D_(mean) of left lung and heart(P<0.05).Compared with the low group,the V_(5),V_(10),V_(20),V_(30) and D_(mean) of the left lung and the D_(mean) of the heart in the medium group were all decreased,but the difference was not statistically significant(P>0.05).The V_(5),V_(10),V_(20),V_(30) and D_(mean) of left lung and the V_(5),D_(mean) of heart in the medium group were lower than those in the low group,but there was no significant difference.The V_(5) and D_(mean) of right lung in both the medium and the high group were lower than those in the low group,and D_(mean) of right lung was higher than that in the low group,but the difference was not statistically significant(P>0.05).The number of segments in the high group was significantly lower than that in the medium and the low group(5.8% and 7.5%,respectively,t=7.405,5.215,P<0.05),and the number of segments in the medium group was 1.7% lower than that in the low group,the difference was statistically significant(t=3.826,P<0.05).The average number of machine unit in the three groups were 913.61 MU,938.76 MU and 777.29 MU respectively,and that in the high group decreased by 17.2% and 14.9% compared with the middle and low groups.The difference was statistically significant(t=6.954,12.516,P<0.05).Conclusion:VMAT plans optimized with high fluence smoothing are recommended in the treatment of patients after breast-conserving surgery for left breast cancer.