论文部分内容阅读
目的 比较有均整器(FF)和无均整器(FFF)模式下非共面VMAT单发脑肿瘤剂量学参数,探索加速器进行立体定向放射外科(SRS)的合适评估方法.方法 对10例单发颅内肿瘤患者进行回顾分析,均采用非共面VMAT技术,处方剂量25 Gy.配对t检验两种治疗方案适形指数(CI)、梯度指数(GI50、GI25)、梯度、正常脑组织V10和V12、照射时间差异.结果 FFF-VMAT和FF-VMAT的GI50分别为2.91±0.34和3.07±0.35,GI25分别为6.91±0.28和7.35±0.27,梯度分别为(0.57±0.07) cm和(0.61±0.08)cm(P＜0.05),CI相近(P＞0.05);正常脑组织剂量分别为(160.64±43.64) cGy和(174.27±53.98) cGy,V10分别为(45.35±30.32)％和(48.37±30.88)％,V12分别为(36.69±25.15)％和(39.48±25.37)％(P＜0.05).结论 FFF模式非共面VMAT脑瘤时可获得比较好的剂量分布,能较好地保护正常组织,同时增加GI指数及梯度参数可以对SRS治疗计划进行更全面评估.“,”Objective To compare relevant dosimetric parameters of non-coplanar volumetric modulated arc therapy (VMAT) in treating brain tumors in conventional flattening filter (FF) or flattening filter-free (FFF) delivery mode,aiming to explore the appropriate evaluation method of accelerator for stereotactic radiosurgery (SRS).Methods Clinical data of 10 patients with single cranial tumor were retrospectively analyzed.All patients received non-coplanar VMAT at a prescription dose of 25 Gy in 1 fraction.Dosimetric parameters including conformity index (CI),heterogeneity index (HI),gradient index (GI50,GI25),gradient,volume of the brain tissue receiving larger than 10 Gy and 12 Gy (V10 and V12) and beam-on time were statistically compared between two treatment plans by paired sample t-test.Results When FFF-VMAT was compared with FF-VMAT in SRS for intracranial tumors,Paddick gradient index GI50 was 2.91±0.34 vs.3.07±0.35,6.91±0.28 vs.7.35±0.27 for GI25,(0.57±0.07) cm vs.(0.61±0.08) cm for gradient,respectively (all P＜0.05),whereas CI did not significantly differ (P＞0.05).For the normal brain tissues,the average dose was (160.64±43.64) cGy vs.(174.27± 53.98) cGy,(45.35± 30.32) ％ vs.(48.37± 30.88) ％ for V10 and (36.69±25.15) ％ vs.(39.48±25.37) ％ for V12,respectively (all P＜0.05).Conclusions Non-coplanar VMAT in FFF delivery mode can improve dose distribution and normal brain tissue sparing in the treatment of intracranial single tumors.Meanwhile,supplement of GI index and gradient index can implement comprehensive evaluation of the SRS planning.