基于改进非共面容积旋转调强海马保护全脑放疗的剂量学研究

Dosimetric study on improved non-coplanar volumetric modulated arc therapy for hippocampal avoidance whole-brain radiotherapy

目的:对已有的非共面容积旋转调强(VMAT)海马保护全脑放疗(HA-WBRT)方法进行改进,比较改进的非共面VMAT计划与非共面、共面VMAT计划在HA-WBRT中的剂量学差异。方法:选取15例颅外肿瘤脑转移需行WBRT的患者,分别对每例患者设计改进非共面、非共面和共面VMAT计划,并对3种计划的靶区、危及器官剂量以及加速器MU值和治疗时间进行比较。结果:改进非共面VMAT计划与非共面、共面VMAT计划相比,改进非共面VMAT计划靶区适形性和剂量梯度的差异无统计学意义(P>0.05),但靶区剂量均匀性略差于另外两种计划。在海马体组织Dmax、Dmin、Dmean3项剂量参数上,改进非共面计划可分别控制在约14.37、8.40和10.80 Gy,显著小于非共面和共面计划相应值(P<0.05);其它危及器官如晶体、视神经等剂量均控制在临床安全剂量范围内,各计划之间差异不显著;改进非共面计划MU值和治疗时间均大于非共面计划和共面计划,差异有统计学意义(P<0.05)。结论:相较于非共面和共面VMAT计划,本研究改进的非共面VMAT方法在HA-WBRT中能更进一步降低海马组织的受照剂量,为临床实施HA-WBRT时提供一种切实可行的治疗方案。

Objective To improve the non-coplanar volumetric modulated arc therapy(VMAT)for hippocampal avoidance whole-brain radiotherapy(HA-WBRT),and to compare dosimetric differences among improved non-coplanar VMAT,noncoplanar VMAT and coplanar VMAT for HA-WBRT.Methods Fifteen patients scheduled for WBRT for brain metastasis from extracranial tumors were enrolled in the study,and 3 different kinds of plans,namely improved non-coplanar VMAT,non-coplanar VMAT and coplanar VMAT plans,were designed for each patient.The doses delivered to target areas and organs-at-risk,monitor unit and treatment time were compared among 3 different kinds of plans.Results There were no statistical differences among 3 different kinds of plans in conformity index and gradient index(P>0.05),but improved noncoplanar VMAT plan had a higher homogeneity index than the other two kinds of plans.The Dmax,Dmin and Dmean of hippocampus in improved non-coplanar VMAT plans could be limited to 14.37,8.40 and 10.80 Gy,respectively,which were significantly lower than those in non-coplanar VMAT plans and coplanar plans(P<0.05).The doses delivered to other organsat-risk,such as lens and optic nerves,were within the range of clinical safe dose,and no statistical significance was found among different plans.The monitor unit and treatment time of improved non-coplanar VMAT plans were both greater than those of non-coplanar VMAT plans and coplanar VMAT plans,with statistical differences(P<0.05).Conclusion Compared with non-coplanar VMAT and coplanar VMAT,improved non-coplanar VMAT for HA-WBRT can further reduce the dose delivered to hippocampus,providing a practicable treatment strategy for the clinical application of HA-WBRT.