基于Trilogy-HD非均整与均整模式脑膜瘤容积调强放疗的剂量学对比

Dosimetric comparison of volumetric intensity modulated radiotherapy for meningioma based on Trilogy-HD FFF and FF mode

目的对比非均整(flatting-filter-free,FFF)和均整(flatting-filter,FF)射束模式下脑膜瘤容积调强放疗(Volumetric Modulated Arc Therapy,VMAT)计划的剂量学差异,为FFF模式临床应用提供参考。方法选取首都医科大学附属北京天坛医院已行FF模式VMAT计划治疗的74例脑膜瘤患者作为研究对象,基于Trilogy-HD加速器FF、FFF模式6MV X线另行设计两组VMAT计划;比较其计划靶区(planning target volume,PTV)、危及器官(organs at risk,OARs)、计算体积Body的剂量学差异;比较两组VMAT计划的跳数(monitor unit,MU)和剂量验证γ通过率。结果两组VMAT计划均能满足临床要求;FFF组计划PTV处方剂量覆盖度体积V 95%、近似最小剂量D 98%、平均剂量D MEAN、近似最大剂量D 2%、处方剂量均匀性指数HI、处方剂量适形指数CI均好于FF组计划,其中有D 2%、HI差异有统计学意义。FFF组计划脑干D MAX/D MEAN、左右晶状体D MAX、左右视神经D MAX、视交叉D MAX、垂体D MAX明显更低,差异有显著统计学意义。FFF组计划Body V 30、V 20、V 10、V 5体积范围更小,有显著统计学意义。FFF组计划较FF组计划Mu数均值增加了23Mu,差异有统计学意义,但没有降低治疗效率。两组计划剂量验证通过率均满足临床要求(3%2 mm、10%剂量阈值,γ通过率≥90%),但FFF组计划验证通过率均值较FF组计划低0.81%,差异有显著统计学意义。结论FFF和FF模式脑膜瘤VMAT计划均能满足临床要求;FFF模式VMAT计划能提供更优的靶区剂量,同时能降低危及器官和正常组织受照剂量。

Objective To compare the dosimetric differences of the flatting-filter-free(FFF)and flatting-filter(FF)beam mode volumetric modulated arc therapy(VMAT)plans for meningioma,and to provide a reference for the clinical application of FFF mode.Methods A total of 74 patients with meningioma who had undergone FF mode VMAT plans in Beijing Tiantan Hospital,Capital Medical University were selected as the research objects,and two sets of VMAT plans were designed based on FF and FFF mode 6MV X-rays.The dosimetric differences of planning target volume(PTV),organs at risk(OARs),and calculated volume“Body”were compared;The number of plans’Mu,plans’dose verificationγpass rates of the two groups were compared.Results Both sets of plans could meet the clinical requirements;The prescribed dose coverage volume V 95%,approximate minimum dose D 98%,average dose D MEAN,approximate maximum dose D 2%,prescription dose homogeneity index(HI),and prescription dose conformal index(CI)of PTV in the FFF group were better than those in the FF group,the differences in D 2%and HI were statistically significant.The FFF group had significantly lower brainstem D MAX/D MEAN,left and right lens D MAX,left and right optic nerve D MAX,chiasm D MAX and pituitary D MAX,and the difference was statistically significant.In the FFF group,the volume range of Body V 30/V 20/V 10/V 5 was smaller,which was statistically significant.Compared with the FF group,the mean Mu number of FFF group increased by 23 Mus,which was a statistically significant difference,but did not reduce the treatment efficiency.Theγpass rate of plans’dose verification in both groups met the clinical requirements(3%2 mm,10%dose threshold,γpass rate≥90%),but the averageγpass rate of FFF group was 0.81%lower than that in FF group,and the difference was statistically significant.Conclusions Both FFF and FF mode VMAT plans for meningioma can meet the clinical requirements.The VMAT plans with FFF mode provide a better target dose while reducing the dose of exposure to OARs and normal tissues.