3台医科达加速器束流匹配后互换执行容积旋转调强放射治疗计划的剂量准确性分析

目的:探讨放疗科3台加速器束流匹配后互换执行容积旋转调强放射治疗（VMAT）计划的准确性。方法:随机选取18例头颈部、胸腹部和盆腔部患者，采用Synergy1、Synergy2和VersaHD 3台加速器模型分别制作VMAT放疗计划PlanSynergy1，PlanSynergy1和PlanVersaHD。同一VMAT计划（6 MV X射线）分别在3台加速器执行，采用电离室和Delta4分别测量绝对点剂量误差和相对三维剂量γ通过率（3 mm/3%）。互换执行VMAT计划后，点剂量和相对剂量的测量结果与治疗计划系统（TPS）计算的结果比较，评估3台加速器束流匹配后VMAT计划互换执行的可行性。结果:PlanSynergy1计划分别在Synergy1、Synergy2、VersaHD执行时，测得的点剂量与TPS计算的偏差分别为-0.27%±0.87%、-0.88%±1.74%和0.37%±2.18%，测量的相对剂量与TPS计算相比，γ通过率分别为99.84%±0.31%、98.89%±1.32%和99.16%±1.12%；PlanSynergy2计划分别在Synergy1、Synergy2、VersaHD执行时测得的点剂量与TPS计算的偏差分别为0.24%±1.98%、0.15%±1.97%和-0.09%±0.66%，测量的相对剂量与TPS计算相比，γ通过率分别为98.75%±1.38%、99.77%±0.42%和99.41%±1.66%；PlanVersaHD计划分别在Synergy1、Synergy2、VersaHD执行时测得的点剂量与TPS计算的偏差分别为-0.57%±1.07%、-0.42%±2.10%和-1.55%±1.62%，测量的相对剂量与TPS计算相比，γ通过率分别为97.79%±1.61%、98.75%±1.37%和99.78%±0.60%。在3台加速器互换执行VMAT计划中，点剂量偏差均在3%以内，相对剂量偏差的γ通过率均在95%以上，均满足临床要求。结论:3台医科达加速器束流（6 MV X射线）匹配后可互换执行VMAT计划。

Analysis of dose accuracy for swapping VMAT plan across 3 Elekta beam-matched linear accelerators

Abstract: Objective To investigate the possibility of swapping volumetric modulated arc therapy (VMAT) plan across 3 beam-matched linear accelerators. Methods Synergy1, Synergy2 and VersaHD were used to generate VMAT plans named PlanSynergy1, PlanSynergy1 and PlanVersaHD for 18 cases with the tumor located in head and neck, chest and abdomen, or pelvis. The same VMAT plan (6 MV X-ray) was executed sequentially on 3 accelerators. The absolute point dose error and relative three-dimensional dose distribution with gamma passing rate (3 mm/3%) measured by ion chamber and Delta4 were compared with the results calculated by treatment planning system for assessing the feasibility of swapping VMAT radiotherapy plan across 3 beam-matched linear accelerators. Results The deviations between measured point dose of PlanSynergy1 executed on 3 accelerators (Synergy1, Synergy2 and VersaHD) and TPS calculation were (-0.27±0.87)%, (-0.88±1.74)% and (0.37±2.18)%, respectively and the comparison between measured relative dose and TPS calculation showed that the gamma passing rates were (99.84±0.31)%, (98.89±1.32)% and (99.16±1.12)%, respectively. For PlanSynergy2, the deviations between measured point dose and TPS calculation were (0.24±1.98)%, (0.15±1.97)% and (-0.09±0.66)%, respectively and the gamma passing rates of relative dose were (98.75±1.38)%, (99.77±0.42)% and (99.41±1.66)%, respectively. For PlanVersaHD, the deviations between measured point dose and TPS calculation were (-0.57±1.07)%, (-0.42±2.10)% and (-1.55±1.62)%, respectively the gamma passing rates of relative dose were (97.79±1.61)%, (98.75±1.37)% and (99.78±0.60)%, respectively. When VMAT plan was swapped across 3 Elekta beam-matched linear accelerators, the point dose deviations were within the range of ±3%, and the gamma passing rate of relative doses were higher than 95%, meeting clinical requirements. Conclusion VMAT plan can be swapped across 3 Elekta linear accelerators after beam match (6 MV X-ray).