鼻咽癌VMAT两种TPS设置参数选择比较

目的 考察不同的计划设置参数对两种TPS VMAT计划质量与执行效率的影响,为临床计划优化提供参考依据。方法 随机选取25例鼻咽癌病例进行VMAT计划设计,在TPS-1和TPS-2中分别采用相同目标条件,并设定多个设置参数限制条件组进行优化,比较各组计划的靶区和OAR剂量分布、机器跳数和照射时间。对符合正态分布的数据采用配对t检验或单因素方差分析,不符合上述条件的采用非参数Wilcoxon符号秩检验或非参数Friedman检验。结果 增加子野数目可提高TPS-1计划的剂量分布质量和减少机器跳数,同时增加照射时间(子野数目>120以后影响减弱);但对TPS-2的计划几乎没有影响。与单弧照射比较,TPS-1的双弧计划质量相近但照射时间增加了70.6%(P=0.000);TPS-2的双弧计划剂量分布更好,脊髓D_max、D_mean分别比下降了3.9%、13.7%(P=0.000、0.000),同时机器跳数和照射时间分别增加了11.7%和31.2%(P=0.000、0.000)。最大和最小剂量率均对两种TPS的VMAT计划质量影响很小,提高最大或最小剂量率均可使计划的照射时间下降但后者机器跳数会增加(P=0.000、0.000)。结论 计划参数的设置对两种TPS的 VMAT计划质量和执行效率的影响有明显差异,对不同TPS进行单独测试可以帮助确定各系统的最佳参数设置。

Comparison of planning parameter selection for volumetric modulated arc therapy of nasopharyngeal carcinoma in two different treatment planning systems

Objective To investigate the impact of planning parameter settings on plan quality and delivery efficiency of VMAT for nasopharyngeal carcinoma with two treatment planning systems (TPS),as references for clinic plan optimization. Methods 25 patients with nasopharyngeal carcinoma were selected and planned for SIB-VMAT treatment. The same planning aims were used in the two kinds of TPS (TPS-1 and TPS-2).Multiple planning parameters were set for plan optimization. Dose distribution to the target volumes and organs at risk,monitor unit (MU) and delivery time were compared. Paired t-test or one-way ANOVA was used for the data which was in accordance to normal distribution;otherwise,nonparametric Wilcoxon signed rank test or nonparametric Friedman test was used. Results More segments lead to better plan quality and less MU but longer delivery time (Minor impact was observed when segment number was larger than 120) in TPS-1,while it had little impact on both plan quality and delivery efficiency in TPS-2.Comparing to single-arc plans,dual-arc VMAT achieved no significant benefit in plan quality but had more MU and longer delivery time in TPS-1(P=0.000).However,dual-arc VMAT plans had better dose distribution in TPS-2,decreased the maximum and mean dose for spinal cord in 3.9% and 13.7% respectively (P=0.000,0.000).Changing the settings of maximum or minimum dose rate did not affect the plan quality in both of the tested TPSs. Increasing the maximum or minimum dose rate reduced the delivery time but the latter increased the number of MU (P=0.000,0.000). Conclusions VMAT plan quality and delivery efficiency is affected significantly and differently by planning parameter settings for two TPSs. Trial test should be conducted for different TPS to determine the optimal parameter settings.