旋转调强与固定野逆向调强放疗在颅脑多发转移瘤中的剂量学比较研究

目的 比较旋转调强(RapidArc)与固定野调强(IMRT)放疗在颅脑多发转移瘤中的剂量学差异。方法 针对10例多发脑转移瘤患者分别设计3种放疗计划:固定野逆向调强(IMRT),RapidArc单弧旋转调强(RA1),双弧旋转调强(RA2)。在保证计划均满足临床要求前提下,分别比较3种计划的靶区剂量分布、危及器官及靶区外正常组织的受照剂量、机器跳数以及治疗时间,探讨其剂量学差异。结果 3种计划均满足临床要求,在靶区适形度和均匀性方面,RA2计划优于IMRT(Z＝-2.803、-2.094,P<0.05)和RA1(Z＝-2.448、-2.191,P＜0.05),RA1计划与IMRT计划差别不大。RA1、RA2计划中的双侧晶体、双侧眼球、脑干的最大剂量均显著低于IMRT(Z＝-2.803～-2.191,P <0.05)。RA2计划评估的双侧视神经最大剂量均显著低于IMRT(Z＝-2.293、-2.701,P<0.05)。RA1、RA2计划中的机器跳数相对于IMRT平均分别减少了43%和24%,缩短了治疗时间。结论 单弧和双弧旋转调强计划均可达到或优于IMRT计划的靶区剂量分布,能更好地降低部分危及器官的受照剂量,同时可以显著降低机器跳数和治疗实施时间。

Dosimetric comparison of fixed field intensity modulated radiation therapy and RapidArc volumetric modulated arc therapy in treatment of multiple intracranial metastases

Objective To evaluate the performace of fixed field Intensity modulated radiation therapy (IMRT) and RapidArc in the radiotherapy for multiple intracranial metastases. Methods The clinical data of 10 patients with multiple intracranial metastases, 8 male and 2 female, aged 65-73, were used to design 3 plans:fixed field IMRT, RapidArc with single Arc (RA1), and RapidArc with double Arc (Arc 2). Dose-volume-histogram analysis was used to compare dose results, monitor unit, and delivery time. Results All 3 plans met the clinical requirements. The best target conformity and homogeneity were observed in the RA2 plan (Z=-2.803,-2.904,P<0.05) and there were no statistical differences between the IMRT plan and RA1 plan. The maximum doses to the lens, eyes, and brainstem of the two RapidArc plans were all significantly lower than those of the IMRT plan(Z=-2.803--2.191,P<0.05), and the maximum dose to the optic nerves of the RA2 plan was significantly lower than that of the IMRT plan (Z=-2.293,-2.701,P<0.05). Compared with the IMRT plan, the average monitor units of the RA1 and RA2 plans were reduced by 29% and 24%, respectively, and the delivery time of these plans were significantly shorter by 84% and 69%, respectively. Conclusions Compared to the IMRT plan, RapidArc plans with single or double Arcs show similar or better effects in the target dose distribution, reduction of irradiation doses on organs at risk and,moreover, significant decrease of the monitor units and delivery time.