IMRT、VMAT和混合IMRT技术在颅脑多发转移瘤同步加量放疗中的剂量学研究

Dosimetric comparison of simultaneous integrated boost with intensity-modulated radiotherapy, volumetric modulated arc therapy, and hybrid intensity-modulated radiotherapy in patients with multiple brain metastases

目的 比较颅脑多发转移瘤同步加量放疗中不同照射技术对靶区和OAR剂量学差异,为其临床放疗技术选择提供数据参考。方法 随机选取本院行全脑同步加量放疗的10例颅脑多发转移瘤患者的定位影像数据,分别设计动态IMRT、双弧VMAT和混合IMRT （Hybrid-IMRT）计划,Hybrid-IMRT计划在适形计划基础上分别进行3野、4野固定野逆向调强叠加优化。行双尾配对Wilcoxon符号秩和检验法比较3类放疗计划在靶区剂量（CI、HI）、OAR受量（Dmean、Dmax））的剂量学差异和机器跳数、执行时间方面的差异。结果 VMAT计划颅脑转移灶靶区CI优于IMRT、Hybrid-IMRT计划（P=0.04、0.00）,HI差异无统计学意义（P〉0.05）;IMRT与Hybrid-IMRTCI、HI差异均无统计学意义（P〉0.05）。Hybrid-IMRT两种计划中的眼晶状体、眼球受量均低于动态IMRT （P均=0.00）,而脑干和视神经的受量在3种技术中均相近（P〉0.05）。在机器跳数和执行时间方面VMAT〈Hybrid-IMRT〈IMRT （P均=0.00）。结论 3类技术均可以满足临床要求,VMAT计划执行效率最高。Hybrid-IMRT可以在保证靶区剂量的前提下更好的保护眼晶状体和眼球,与IMRT相比降低了机器跳数,为颅脑多发转移瘤放疗计划设计提供了一个可以思考和借鉴的思路。

Objective To evaluate the impact of simultaneous integrated boost （SIB） with different radiotherapy plans on the dosimetry of the target volume and organs at risk （OAR） in patients with multiple brain metastases （MBM）, and to provide a basis for the selection of an optimal clinical radiotherapy. Methods Ten patients with MBM who were treated with whole-brain SIB radiotherapy were randomly selected in this analysis. The local imaging data from the enrolled patients were re-planned with dynamic intensity-modulated radiotherapy （dynamic IMRT）, dual-arc volumetric modulated arc therapy （dual-arc VMAT）, and hybrid-IMRT （h-IMRT）. h-IMRT plan was created by inversely optimizing 3 and 4 fixed fields of IMRT based on conformal radiotherapy. Two-tailed Wilcoxon matched pairs signed rank sum test was performed to analyze the differences between the three radiotherapy plans in the conformity index （CI） and homogeneity index （HI） of the planning target volumes （PTV）, Dmean and Dmax of OAR, monitor units （MU）, and delivery time. Results CI of PTVs with VMAT plan was better than that with IMRT and h-IMRT plans （P=0.04,0.00）, and no significant difference in HI was observed between the three plans （P〉0.05）. There were no significant differences in CI and HI between 3 and 4 fields in dynamic IMRT （P〉0.05）. h-IMRT 3-and 4-field plans had significantly reduced doses to the eye lens and eyeballs than dynamic IMRT and VMAT plans （all P=0.00）, and the three plans had similar doses to the brainstem and optic nerve （P〉0.05）. As for the MHs and delivery time, dynamic IMRT and VMAT plans showed the highest and lowest value, respectively （all P=0.00）. Conclusions All the three plans meet the clinical requirements. VMAT shows the highest treatment efficiency. H-IMRT protects the eye lens and eyeballs more effectively while maintaining the doses to the PTV, with reduced MU compared with IMRT. These offer a reference for designing the radiotherapy plan in MBM patients.