高级别脑胶质瘤术后VMAT与IMRT剂量学比较

摘要

目的:比较高级别脑胶质瘤(HGG)术后采用不同拉弧数量容积旋转调强放疗(VMAT)和不同照射野数量逆向调强放疗(IMRT)在靶区和危及器官的剂量学差异及效率的高低.方法:收集HGG病例资料10例,采用Oncentra治疗计划系统对每个病例分别设计5、7、9野IMRT计划和单弧、双弧VMAT(VMAT1、VMAT2)计划,处方剂量为计划靶区(PTV):60 Gy/30 f.(1)比较5、7、9野IMRT计划间PTV和各危及器官的剂量学差异.(2)研究5野IMRT、VMAT1和VMAT2计划间PTV适形指数(CI)、均匀性指数(HI)和危及器官受照量等剂量学差异,比较机器跳数、优化时间和治疗时间等效率参数的差异.结果:(1)5、7、9野IMRT计划:3组计划PTV的CI、HI及各危及器官的最高受量均无统计学差异(p0.05).(2)5野IMRT、VMAT1和VMAT2计划:靶区CI分别为0.617±0.076、0.715±0.084和0.731±0.806,有统计学差异(P=0.007),VMAT1和VMAT2组相当,均好于5野IMRT组;靶区HI、最高剂量、最小剂量和D95％无统计学差异(P＞0.05);所有危及器官的最高剂量均无统计学差异(P＞0.05).(3)3组计划的机器跳数有统计学差异(P=0.004);计划的优化时间:5野IMRT最快,但VMAT技术耗时;治疗时间:VMAT1最快,只需(3.7±0.5)min,3组计划间有统计学差异(P＜0.05).结论:在HGG术后放疗中,射野数≥5的IMRT计划在PTV和危及器官剂量分布差异不显著;与5野IMRT计划相比,尽管VMAT计划优化时间稍长,但显著提高PTV的CI,且VMAT1计划还具有机器跳数少、治疗时间短的优势.%Objective To compare the dosimetric differences in target areas and organs-at-risk (OAR) and the efficiency between volumetric modulated arc therapy (VMAT) and intensity-modulated radiotherapy (IMRT) for postoperative high-grade glioma (HGG).Methods Oncentra treatment planning system was used to design 5-,7-,9-field IMRT plans and single-and double-arc VMAT (VMAT1 and VMAT2) for 10 postoperative HGG patients.In each plans,the prescription dose was 60 Gy/30 ffor planning target volume (PTV).The dosimetric differences in PTV and OAR were compared among 5-,7-,9-field IMRT plans.The conformity index (CI),homogeneity index (HI) of PTV,the dose of OAR,monitor units,treatment time and optimizing time were compared among 5-field IMRT,VMAT1 and VMAT2 plans.Results No statistical differences were found in the CI and HI of PTV,and the maximum dose (Dma,) of OAR among 5-,7-,9-field IMRT plans (P＞0.05).VMAT1 and VMAT2 plans showed similar CI of target areas,0.715±0.084 and 0.731±0.806,respectively,better than 0.617±0.076 in 5-field IMRT plan (comparison among 3 plans,P=0.007).No statistical differences were found in the HI,D minimum dose and D95％of target areas,and the Dmaxof OAR among 5-field IMRT,VMAT1 and VMAT2 plans (P＞0.05).Statistical differences were found in monitor units among 5-field IMRT,VMAT1 and VMAT2 plans (P=0.004).Optimizing time was shortest in 5-field IMRT plan,longest in VMAT2 plan.The treatment time in VMAT1 plan was only (3.7±0.5) min,with statistical differences among three plans (P＜0.05).Conclusion For the postoperative HGG patients,IMRT plans with the number of fields less than 5 doesn't show statistical differences in the dose distribution in PTV and OAR.Compared with 5-field IMRT plan,VMAT plan needs longer optimizing time,but achieves better CI in PTV,and VMAT1 has the advantages of smaller monitor units and shorter treatment time.