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

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。

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

Abstract: 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 3 600 cGy/20 F to the whole brain by 2 horizontal irradiation fields in three-dimensional conformal radiotherapy and 5 000 cGy/20 F to brain metastases by IMRT with simultaneous integrated boost. In IMRT plan, 3 600 cGy/20 F was given to the whole brain and 5 000 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.