Eclipse计划系统计算网格大小对脑胶质瘤VMAT计划影响分析

Analysis of the Impact of Eclipse Planning System Computational Grid Size on VMAT Planning for Glioma

目的比较Eclipse计划系统计算网格大小对脑胶质瘤容积旋转调强治疗(Volume Modulated Arc Therapy,VMAT)计划质量的影响,为临床诊疗提供依据。方法回顾性选取2021年9月至2022年6月我院收治的行VMAT计划的胶质瘤患者33例,在优化参数相同的条件下,对所有患者分别用1.25、2.50、5.00 mm计算网格设计3组VMAT计划(1.25 mm组、2.50mm组、5.00mm组)。比较3组VMAT计划的靶区剂量学参数[临床靶区(Clinical Tumor Volume,CTV)、计划靶区(Planning Target Volume,PTV)]、机器跳数、危及器官受量和计划优化时间。结果5.00 mm组躯干D_(max)、CTV D_(max)均显著高于1.25 mm组和2.50 mm组,1.25 mm组的PTV D_(min)、CTV D_(min)均显著高于2.50 mm组和5.00 mm组。3组危及器官受量和机器跳数比较差异均无统计学意义(P>0.05)。1.25 mm组与2.50 mm组、5.00 mm组的CTV D_(min)、PTV D_(min)靶区剂量相对偏差较大,其他靶区剂量参数相对偏差较小。1.25 mm组与2.50 mm组、5.00 mm组的左侧晶体、左侧视神经、右侧视神经的相对偏差较大。1.25 mm组与2.50 mm组、5.00 mm组的机器跳数相对偏差均较小。1.25 mm组计划优化时间明显短于2.50mm组和5.00mm组。结论脑胶质瘤放射治疗中,Eclipse计划系统选用不同计算网格会引起VMAT PTV及危及器官产生剂量方面的差异。从计划质量与优化时间综合考虑,建议采用2.50 mm的计算网格来进行VMAT计划设计,但需注意小网格会导致体积较小的危及器官受量增高,因此选取小网格优化时,建议适当增大危及器官限量权重来降低危及器官受量。

Objective To compare the effect of Eclipse planning system calculation grid size on the quality of volume modulated arc radiotherapy(VMAT)plan for glioma,and to provide a basis for clinical diagnosis and treatment.Methods Atotal of 33 patients with glioma who received VMAT program in our hospital from September 2021 to June 2022 were retrospectively selected.Under the same optimization parameters,three VMAT plans(1.25 mm group,2.50 mm group,5.00 mm group)were designed using 1.25,2.50,and 5.00 mm computational grid respectively for all patients.The target area dosimetry parameters[clinical tumor volume(CTV),planning target volume(PTV)],monitor units,organs at risk dose,and plan optimization time of three VMAT plans were compared.Results The D_(max) and CTV D_(max) of trunk in 5.00 mm group were significantly higher than those in 1.25 mm group and 2.50 mm group.The PTV D_(min) and CTV D_(min) of the 1.25 mm group were significantly higher than those of the 2.50 mm group and 5.00 mm group.There were no significant differences in organs at risk dose and monitor units among the three groups(P>0.05).The relative deviations of CTV D_(min) and PTV D_(min) in 1.25 mm group were larger than those in 2.50 mm group and 5.00 mm group,while the relative deviations of other target dose parameters were smaller.The relative deviation of left lens,left optic nerve and right optic nerve in 1.25 mm group were greater than that in 2.50 mm group and 5.00 mm group.The relative deviation of monitor units in 1.25 mm group was small compared with 2.50 mm group and 5.00 mm group.The optimal planning time of 1.25 mm group was significantly shorter than that of 2.50 mm group and 5.00 mm group.Conclusion In glioma radiotherapy,the use of different computational grids in the Eclipse planning system can cause differences in the VMAT program target area and the dose of organs at risk.From the comprehensive consideration of plan quality and optimization time,it is recommended to use a 2.50 mm computing grid for VMAT plan design.But it should be noted that a small grid will lead to an increase in the capacity of small organs at risk.Therefore,when selecting a small grid for optimization,it is recommended to appropriately increase the limited weight of organs at risk to reduce the capacity of organs at risk.