Zeng Huaqu, Zhong MinZhi, Chen Zongyou, Tang Shukui, Wen Zunbei
Radiotherapy Center, Gaozhou People's Hospital, Gaozhou, China.
Department of Radiology, Guangzhou Red Cross Hospital, Guangzhou, China.
Front Oncol. 2025 Jan 23;14:1428329. doi: 10.3389/fonc.2024.1428329. eCollection 2024.
The aim of this study was to investigate the dosimetric differences between non-coplanar volumetric modulated arc therapy (VMAT) and non-coplanar fixed-field intensity-modulated radiotherapy (IMRT) in hippocampus-avoidance whole-brain radiation therapy with a simultaneous integrated boost (HA-WBRT+SIB) for brain metastases using the Monaco treatment planning system (TPS).
A total of 22 patients with brain metastases were retrospectively enrolled. Two radiotherapy treatment plans were designed for each patient: non-coplanar VMAT and non-coplanar fixed field IMRT. The dose distribution of targets and organs at risk (OAR), the number of monitor units (MUs), and pre-treatment plan verification were compared between the two plans while meeting the prescribed dose requirements of the target volume.
There were no significant differences in V, V, D, heterogeneity index (HI) and conformity index (CI) of target PGTV between the two plans (>0.05). For PTV-brain-SIB, there was no significant difference in D between IMRT and VMAT (=0.103). VMAT significantly improved the V of PTV-brain-SIB (<0.001), decreased HI (=0.003), and increased CI (<0.001). There were no significant differences in the D to the brain stem, left and right lens, optic chiasm, pituitary gland, and left and right hippocampus between the two plans (>0.05). Compared with IMRT, VMAT significantly reduced the D to the left and right eyes (<0.001) and significantly increased the D to the right inner ear (=0.010). There was no significant difference in the D to the left inner ear between VMAT and IMRT (=0.458). Compared with IMRT, VMAT significantly reduced the D to the left optic nerve (=0.006), but significantly increased the D to the right optic nerve (=0.001). There was no significant difference in the D to the left and right hippocampus between VMAT and IMRT (>0.05), but VMAT significantly increased the D (<0.05) compared with IMRT. Compared with VMAT, IMRT significantly reduced the MU (<0.001) but VMAT has a higher treatment efficiency than IMRT, with an average reduction of 41 seconds (294.1 ± 16.4 s for VMAT, 335.8 ± 34.9 s for IMRT, <0.001). Under the conditions of 3%/2 mm, and 2%/2 mm, the gamma passing rate of the IMRT QA was improved compared to VMAT, with an average increase of 0.6%, =0.013, and 1.7%, <0.001, respectively.
Both non-coplanar VMAT and non-coplanar fixed field IMRT based on the Monaco TPS produce clinically acceptable results for HA-WBRT+SIB in patients with brain metastases. Compared with IMRT, VMAT has better dose distribution in the target volume and treatment efficiency, but IMRT can better protect the hippocampus and reduce the number of MUs.
本研究旨在使用Monaco治疗计划系统（TPS），调查在海马避让全脑放疗同步推量（HA-WBRT+SIB）治疗脑转移瘤中，非共面容积调强弧形放疗（VMAT）与非共面固定野调强放疗（IMRT）之间的剂量学差异。
回顾性纳入22例脑转移瘤患者。为每位患者设计两个放射治疗计划：非共面VMAT和非共面固定野IMRT。在满足靶区规定剂量要求的同时，比较两个计划之间靶区和危及器官（OAR）的剂量分布、监测单位（MU）数量以及治疗前计划验证情况。
两个计划之间靶区PGTV的V、V、D、异质性指数（HI）和适形指数（CI）无显著差异（>0.05）。对于PTV-脑-SIB，IMRT和VMAT之间的D无显著差异（=0.103）。VMAT显著提高了PTV-脑-SIB的V（<0.001），降低了HI（=0.003），并增加了CI（<0.001）。两个计划之间对脑干、左右晶状体、视交叉、垂体以及左右海马的D无显著差异（>0.05）。与IMRT相比，VMAT显著降低了对左右眼的D（<0.001），并显著增加了对右内耳的D（=0.010）。VMAT和IMRT之间对左内耳的D无显著差异（=0.458）。与IMRT相比，VMAT显著降低了对左视神经的D（=0.006），但显著增加了对右视神经的D（=0.001）。VMAT和IMRT之间对左右海马的D无显著差异（>0.05），但与IMRT相比，VMAT显著增加了D（<0.05）。与VMAT相比，IMRT显著减少了MU（<0.001），但VMAT的治疗效率高于IMRT，平均减少41秒（VMAT为294.1±16.4秒，IMRT为335.8±34.9秒，<0.001）。在3%/2 mm和2%/2 mm条件下，IMRT的QA伽马通过率相比VMAT有所提高，平均分别提高0.6%（=0.013）和1.7%（<0.001）。
基于Monaco TPS的非共面VMAT和非共面固定野IMRT在脑转移瘤患者的HA-WBRT+SIB治疗中均产生了临床可接受的结果。与IMRT相比，VMAT在靶区剂量分布和治疗效率方面更好，但IMRT能更好地保护海马并减少MU数量。
