容积旋转调强计划遮挡技术应用于早期鼻腔NK/T细胞淋巴瘤的剂量学研究

Avoidance technique applied in volumetric modulated arc therapy for early-stage nasal natural killer/T-cell lymphoma:a dosimetric study

目的:比较3种容积旋转调强计划(VMAT)的剂量学差异,探讨VMAT遮挡技术对早期鼻腔NK/T细胞淋巴瘤的剂量学影响。方法:选取20例早期鼻腔NK/T细胞淋巴瘤患者,分别设计无晶体遮挡(VMAT-OFF)计划、晶体半遮挡(VMAT-E)计划和晶体全遮挡(VMAT-E&E)计划,评估3组计划的计划靶区体积(PTV)和危及器官(OARs)剂量学参数,评估机器跳数(MU)和SCIMOCA通过率(3%/2 mm)。结果:3种计划的靶区剂量分布均能满足临床要求,PTV的D_(2%)、D_(98%)、V_(95%)、均匀性指数、适形度指数均无统计学差异;在MU方面,VMAT-OFF<VMAT-E<VMAT-E&E(P<0.05);在OARs晶体(D_(max)、D_(mean))方面,VMAT-E&E<VMAT-OFF(P<0.05),VMAT-E&E<VMAT-E(P<0.05),D_(max)和D_(mean)均无统计学差异;靶区、晶体和计划的SCIMOCA通过率(3%/2 mm)都高于95%且无统计学差异。结论:VMAT-E&E计划的MU较高,但在保护晶体方面更有优势。

Objective To compare the dosimetric differences among 3 different volumetric modulated arc therapy(VMAT)plans,and to explore the dosimetric effects of VMAT avoidance technique on early-stage nasal natural killer/T-cell lymphoma.Methods Twenty patients with early-stage nasal natural killer/T-cell lymphoma were enrolled in the study,and 3 kinds of plans,namely no lens avoidance plan(VMAT-OFF),lens half-avoidance(VMAT-E)and lens avoidance plan(VMAT-E&E),were designed for each patients.The dosimetric parameters of planning target volume(PTV)and organs-atrisk were compared among 3 kinds of groups,and meanwhile,monitor units(MU)and SCIMOCA passing rate(3%/2 mm)were evaluated.Results The target dose distribution in 3 kinds of plans all met the prescribed dose requirements.There was no statistically difference in the D_(2%),D_(98%),V_(95%),homogeneity index and conformity index of PTV.MU was highest in VMATE&E,followed by VMAT-E and VMAT-OFF(P<0.05).The D_(max) and D_(mean) to lens in VMAT-E&E were lower than those in VMAT-OFF(P<0.05)and VMAT-E(P<0.05),and no statistically difference was found in the D_(max) and D_(mean) to other OAR.The SCIMOCA passing rate(3%/2 mm)of PTV,lens and plans were all higher than 95%,without statistical differences.Conclusion Although VMAT-E&E has relatively higher MU,it has more advantages in lens sparing.