脑转移瘤同期加量混合调强放疗与调强放疗的剂量学比较

Dosimetric comparison of Hybrid-IMRT vs IMRT for radiotherapy with simultaneous integrated boost for brain metastases

目的:探讨同时运用三维适形与调强的混合调强放疗(Hybrid-IMRT)与调强放疗(IMRT)用于脑转移瘤同期加量的剂量学差异。方法:选取20例进行头颅放疗的患者,分别设计Hybrid-IMRT计划和IMRT计划。Hybrid-IMRT计划包括全脑行三维适形(两野对穿)3 600 cGy/20 F、脑转移灶行IMRT同期加量至5 000 cGy/20 F;IMRT计划全程运用IMRT给予全脑照射3 600 cGy/20 F、脑转移灶5 000 cGy/20 F。在满足临床要求的前提下,比较两组计划靶区的均匀性指数、适形度指数、平均剂量和机器跳数,危及器官脑干、视神经、晶体、视交叉、眼球的最大剂量和平均剂量。结果:两种计划均能满足临床要求。Hybrid-IMRT计划的PGTV均匀性优于IMRT计划(P<0.001);Hybrid-IMRT计划的脑干、视交叉、左右晶体的最大剂量与平均剂量,左右眼球的平均剂量以及左右视神经的最大剂量均低于IMRT计划(P<0.05);Hybrid-IMRT计划的机器跳数比IMRT计划减少了约70%(P<0.001)。结论:两种计划均能满足临床要求,Hybrid-IMRT计划相较IMRT计划靶区剂量更加均匀,治疗时间缩短,也能更好地保护危及器官。

Objective To explore the dosimetric differences between intensity-modulated radiotherapy(IMRT)and Hybrid-IMRT which combining three-dimensional conformal radiotherapy and IMRT for radiotherapy with simultaneous integrated boost for brain metastases.Methods Hybrid-IMRT plan and IMRT plan were designed for 20 patients with brain metastases.Hybrid-IMRT plan included 3600 cGy/20 F to the whole brain by 2 horizontal irradiation fields in three-dimensional conformal radiotherapy and 5000 cGy/20 F to brain metastases by IMRT with simultaneous integrated boost.In IMRT plan,3600 cGy/20 F was given to the whole brain and 5000 cGy/20 F to brain metastases.On the premise of meeting the clinical requirements,the dosimetric parameters between Hybrid-IMRT and IMRT were compared.The dosimetric parameters included the conformity index(CI),homogeneity index and mean dose of target areas,monitor units,the maximum dose and mean dose of organs-at-risk such as brain stem,optic nerves,lens,optic chiasm and eyeballs.Results Both IMRT plan and Hybrid-IMRT plan met the clinical requirements.The homogeneity index of PGTV in Hybrid-IMRT plan was lower than IMRT plan(P<0.001).The maximum dose and mean dose of brain stem,optic chiasm and lens,and the mean dose of eyeballs and the maximum dose of optic nerves in Hybrid-IMRT plan were lower than those in IMRT plan(P<0.05).Moreover,the monitor units in Hybrid-IMRT plan was decreased by about 70%as compared with IMRT plan(P<0.001).Conclusion Both plans meet the clinical requirements,but Hybrid-IMRT plan is advantageous over IMRT plan in homogeneity index,treatment time and organs-at-risk sparing.