左侧乳腺癌保乳术后VMAT与dMLC-IMRT的剂量学差异研究

Dosimetric difference between VMAT and dMLC-IMRT after breast-conserving surgery for left-sided breast cancer

目的:探讨左侧乳腺癌保乳术后容积旋转调强放疗(volume modulated arc therapy,VMAT)和动态多叶光栅调强放疗(dynamic multi-leaf collimator intensity modulated radiation therapy,d MLC-IMRT)的剂量学差异,以为患者治疗提供更优的治疗方案。方法:回顾性选取某院放疗科收治的15例左侧乳腺癌保乳术后患者的临床资料,为每位患者设计连续弧容积旋转调强放疗(continue volume modulated arc therapy,c VMAT)、分段切线弧容积旋转调强放疗(tangent volume modulated arc therapy,t VMAT)和d MLC-IMRT 3组计划,比较3组计划肿瘤靶区和危及器官的剂量学参数。采用SPSS 25.0软件进行统计学分析。结果:3组计划肿瘤靶区剂量分布均满足临床需求,D_(2)、Dmean、适形性指数(conformity index,CI)、均匀性指数(homogeneity index,HI)差异均具有统计学意义,机器跳数差异无统计学意义。对于D_(2),d MLC-IMRT组高于c VMAT组和t VMAT组;对于Dmean,d MLC-IMRT组低于t VMAT组和c VMAT组;对于CI,c VMAT组最优,t VMAT组次之。在低剂量区域中,对于患侧肺受照体积,c VMAT组和t VMAT组均高于d MLC-IMRT组;对于心脏受照体积,t VMAT组明显低于c VMAT组和d MLC组,c VMAT组略高于d MLC-IMRT组。在高剂量区域中,对于患侧肺受照体积,c VMAT组和t VMAT组低于d MLC-IMRT组,t VMAT组高于c VMAT组;对于心脏受照体积,c VMAT组和t VMAT组低于d MLC-IMRT组,t VMAT组和c VMAT组差异无统计学意义。结论:左侧乳腺癌保乳术后调强放疗计划设计中,VMAT相对于d MLC-IMRT肿瘤靶区的适形性较好,对危及器官心脏、肺有着更优的保护。

Objective To investigate the dosimetric difference between volume modulated arc therapy(VMAT)and dynamic multi-leaf collimator intensity modulated radiation therapy(dMLC-IMRT)after breast-conserving surgery for left-sided breast cancer so as to optimize the treatment plan for the patient.Methods The clinical data of 15 patients admitted to the radiothe-rapy department of some hospital after breast-conserving surgery for left-sided breast cancer were selected retrospectively.Three groups of plans were designed for each patient,including continue volume modulated arc therapy(cVMAT),tangent volume modulated arc therapy(tVMAT)and dMLC-IMRT plans,and then compared in terms of the dosimetric parameters of the tumor target areas and organs at risk.SPSS 25.0 software was used for statistical analysis.Results The three groups had the dose distribution of the tumor target areas meet clinical requirements,which had significant differences between the values of D_(2),Dmean,conformity index(CI)and homogeneity index(HI),while the difference between the numbers of monitor units were not statistically significant.The dMLC-IMRT group had higher D_(2) value while lower Dmean than the cVMAT and tVMAT groups;for CI the cVMAT behaved the best in the three groups,followed by the tVMAT group.In the low-dose region,the cVMAT and tVMAT groups had larger illuminated volumes of the affected lung than the dMLC-IMRT group;the tVMAT group had the smallest illuminated volume of heart in the three groups,and the cVMAT group had the illuminated volume of heart slightly higher than that of the dMLC-IMRT group.In the high-dose region,the cVMAT and tVMAT groups had smaller illuminated volumes of the affected lung than the dMLC-IMRT group,and the illuminated volume of the affected lung of the tVMAT group was larger than that of the cVAMT group;the dMLC-IMAT group had the largest illuminated volume of heart in the three groups,and the differences between the tVMAT and cVMAT groups were not statistically significant.Conclusion In the design of intensity-modulated radiotherapy plans after breast-conserving surgery for left-sided breast cancer,VMAT behaves better than dMLC-IMRT in conformability to the tumor target area and protection of heart and lung at risk.