等效均匀剂量在乳腺癌保乳术后调强放射治疗优化中的应用

The application of EUD in the optimization of IMRT for breast cancer post breast-conserving surgery

目的:研究乳腺癌保乳术后调强放射治疗(IMRT)中等效均匀剂量(EUD)在计划优化中改善计划靶区(PTV)和危及器官(OAR)剂量分布的作用。方法:选取医院收治的15例早期乳腺癌保乳术后行全乳调强放射治疗患者。使用EclipseTPS进行计划设计,根据PTV和OAR按不同的优化方法分为PTV组、PTV+EUD组和PTV+OAR+EUD组3组进行计划设计。PTV组对PTV及OAR进行剂量体积(DV)优化;PTV+EUD组对PTV进行DV和等效均匀剂量(EUD)优化,OAR进行DV优化;PTV+OAR+EUD组对PTV及OAR进行DV和EUD优化。比较分析3组计划PTV和OAR的剂量分布。结果:PTV+EUD组PTV适形性指数(CI)和均匀性指数(HI)优于PTV组,V105体积降低26.8%,差异有统计学意义(t=5.002,t=5.668,t=6.74;P<0.05);PTV+OAR+EUD组PTV的CI和HI劣于PTV组,V105增加36.4%,差异有统计学意义(t=4.154,t=-4.265,t=-3.102;P<0.05)。PTV+EUD组同侧肺V20、平均肺部剂量(MLD)高于PTV组计划,差异有统计学意义(t=-5,t=-3.914;P<0.05);PTV+OAR+EUD组低于PTV组计划,差异有统计学意义(t=5.95,t=7.182;P<0.05)。PTV+EUD组心脏V40、V30高于PTV组,差异有统计学意义(t=-4.098,t=-3.924;P<0.05)。PTV+OAR+EUD组低于PTV组,差异有统计学意义(t=2.73,t=3.8;P<0.05)。PTV+EUD组的健侧乳腺V5高于PTV组,差异有统计学意义(t=-2.938;P<0.05);PTV+OAR+EUD组健侧乳腺Dmean低于PTV组,差异有统计学意义(t=2.351,P<0.05)。结论:PTV使用EUD优化可提高靶区CI、HI和靶区覆盖度,但增加了OAR的受照体积和平均受照剂量。PTV和OAR同时使用EUD优化,在靶区CI、HI和靶区覆盖度满足临床要求的同时降低OAR的受照体积和平均受照剂量。

Objective:To study the effect of equivalent uniform dose(EUD)that improved the dose distribution of planned target volume(PTV)and organ at risk(OAR)in the optimization of intensity modulated radiation therapy(IMRT)for breast cancer post breast-conserving surgery.Methods:15 patients with early breast cancer who underwent IMRT post breast-conserving surgery were selected.Eclipse TPS was used for planning design.According to different optimization methods of PTV and OAR,they were divided into PTV group,PTV+EUD group and PTV+OAR+EUD group to implement planning design.The dose volume(DV)was optimized for PTV and OAR in PTV group,and the DV and EUD were optimized for PTV and DV was optimized for OAR in PTV+EUD group,and DV and EUD were optimized for PTV and OAR in PTV+OAR+EUD group.The dose distribution of planed PTV and OAR among three groups were compared and analyzed.Results:The conformation index(Cl)and homogeneity index(HI)of PTV+EUD group were significantly better than those of PTV group,and the V105 of PTV+EUD group was significantly decreased by 26.8%compared with that of PTV group(t=5.002,t=5.668,t=6.74,P<0.05).The Cl and HI of PTV in PTV+OAR+EUD group were significantly lower than those in the PTV group,and the V105 of PTV+OAR+EUD group was significantly increased by 36.4%compared with that of PTV group(t=4.154,t=-4.265,t=-3.102,P<0.05).And the V20 of ipsilateral lung and mean lung dose(MLD)of PTV+EUD group were significantly higher than those of PTV group(t=-5,t=-3.914,P<0.05),and those of PTV+OAR+EUD group were significantly lower than those of PTV group(t=5.95,t=7.182,.P<0.05).And the V40 and V30 of heart of PTV+EUD group were significantly higher than those of PTV group(t=-4.098,t=-3.924,P<0.05).And the V40 and V30 of heart of PTV+OAR+EUD group were significantly lower than those of PTV group(t=2.73,t=3.8,P<0.05).V5 of healthy breast of PTV+EUD group was significantly higher than that of PTV group(t=-2.938,P<0.05).The Dmean of healthy breast of PTV+OAR+EUD group was significantly lower than that of PTV group(t=2.351,P<0.05).Conclusion:EUD optimization of PTV can improve Cl,HI and the coverage of target area,but it increases the exposure volume and average exposure dose of OAR.EUD optimization is used in both PTV and OAR can reduce the exposure volume and average exposure dose of OAR while the CI,HI of target area and the coverage of target areas can meet the clinical requirements.