两台直线加速器束流匹配后模型验证与稳定性评估

Model verification and stability assessment of two beam-matched linear accelerators

目的:探讨在已经完成束流匹配的医科达Synergy和VersaHD医用直线加速器上进行患者治疗计划互换的可行性。方法:将治疗计划系统(TPS)模型数据与两台加速器采集数据进行一维Gamma通过率分析。选取在医院治疗的20例肿瘤患者不同部位治疗计划,按计划复杂程度分为复杂计划组和简单计划组,每组10例,在两台加速器上6个月内分4次测量。比较两台加速器的照射野百分深度剂量(PDD)、离轴比(OAR)曲线及输出因子(OUF)以及患者治疗计划的二维Gamma通过率。结果:Synergy加速器与TPS模型数据相比,除采集数据中5 cm×5 cm照射野Inline方向5 cm深度(PDD)的OAR曲线Gamma通过率为92.7%以外,其余照射野PDD和OAR的Gamma通过率均>95%,两台加速器的OUF与TPS模型计算的OUF的最大偏差为-0.51%。两组患者计划验证结果中,Synergy和Versa HD加速器2 mm/2%、2 mm/3%和3 mm/3%标准下Gamma通过率的差异均无统计学意义。复杂计划组和简单计划组不同时间点测量的Gamma通过率的差异均无统计学意义(H=2.477,H=2.451;P>0.05)。结论:尽管TPS模型与加速器采集数据在PDD、OAR和OUF上有一定的细微差异,但这些差异对两台加速器的计划验证Gamma通过率均未产生明显影响,临床上可以实现患者计划互换执行,但需要对束流匹配的加速器增加必要的质量控制措施。

Objective:To explore the feasibility of conducting interchange of treatment plan of patients on the beammatched Elekta Synergy linear accelerator and Versa HD linear accelerator.Methods:The model data of treatment planning system(TPS)and the collected data of two accelerators were used to implement one-dimensional Gamma pass rate analysis.The treatment plans of different sites of 20 patients with tumor who admitted to hospital were selected,and they were divided into complex plan group and simple plan group according to the complexity of plan,with 10 cases in each group.They received 4 measurements on two accelerators within 6 months.The percent depth dose(PDD),off-axis ratio(OAR)curve and output factor(OUF)of the two accelerators were compared,as well as the two-dimensional gamma pass rates of treatment plans of patients.Results:Compared with TPS model data,the Gamma pass rate of PDD and OAR of other radiation fields of Synergy accelerator were larger than 95%except that of 5cm PDD and OAR curve on Inline direction of 5cm×5cm radiation field in collecting data was 92.7%.And the maximum deviation of OUF between each accelerator and TPS model was-0.51%.In the verified results of treatment plans of two groups,the differences of Gamma pass rates between Synergy and Versa HD were no significant under 2mm/2%,2mm/3%and 3mm/3%standard.The differences of Gamma pass rates between complex plan group and simple plan group were no significant at different point-in-times(H=2.477,H=2.451,P>0.05).Conclusion:There are a certain of subtle differences between the TPS model and the collected data of accelerators in PDD,OAR and OUF,while these differences don’t cause significant influences on the Gamma pass rates of plan verifications of two accelerators.The execution of interchange of treatment plan of patients can be realized in clinical practice,but the beam-matched accelerator need is added necessary measurements of quality control.