摘要目的 基于容积旋转弧形调强放疗(VMAT)技术,对肝癌立体定向放疗(SABR)方案进行评估,并结合图像引导技术及呼吸管理技术,分析执行中患者位置误差.方法 回顾性分析接受基于VMAT技术的SABR治疗并配合自主深呼气末屏气技术(vDEBH)进行呼吸管理的15例肝癌患者.VMAT计划采用2个部分弧,对治疗方案评估剂量参数,比较VMAT与调强放疗技术(IMRT)的计划质量差异.所有优化方案均经质量保证(QA)验证,包括点剂量和面剂量验证、机器跳数(MU)和出束时间记录.每次治疗时,锥形束CT(CBCT)影像采集2次,包括治疗前1次评估两次治疗问误差和治疗结束后1次评估当次治疗内位移.结果 VMAT和IMRT优化方案的各剂量学参数均满足临床治疗要求,差异无统计学意义(P＞0.05);相比IMRT,VMAT方案的平均MU降低了28.1％(t=3.064,P＜0.05),且治疗时间缩短了31.6％(t=2.278,P＜O.05).CBCT图像引导结果显示,采用vDEBH技术可有效减少当次治疗内的位置误差,各方向上的偏移均控制在可容许范围内(＜3 mm).结论 基于VMAT技术的肝癌SABR治疗计划在靶区体积剂量分布和正常组织受量等剂量学表现与IMRT技术相当,可行性良好且在治疗效率方面优势明显.

abstractsObjective To investigate the feasibility and plan quality of the image-guided volumetric modulated arc therapy (VMAT) based voluntary deep exhale breath-holding technique in the stereotactic ablative body radiotherapy (SABR) for liver tumors.Methods Fifteen patients with liver tumors were involved in this study.All patients were immobilized with voluntary deep exhale breath hold (vDEBH) combined with real-time position management (RPM) respiratory gating system.Treatment was planned using VMAT with 2 modified partial arc and re-planned using intensity modulated radiation therapy (IMRT) technique for comparison.Dosimetric parameters were calculated for plan quality assessment.Quality assurance studies included absolute dose and multiple planar dose verifications,total monitor units and delivery time analysis.Daily cone beam computed tomography imaging was used to verify the motions.Results There were no significant dosimetric differences between VMAT and conventional IMRT plans (P ＞0.05).Both techniques were able to minimize doses to organs at risk including normal liver,kidneys,spinal cord,and stomach.However,the average monitor units with VMAT were significantly lower 28.1％ than those with IMRT(t =3.064,P ＜0.05).The average beam-on time in VMAT plans was 31.6％ shorter than that in IMRT plans(t =2.278,P ＜ 0.05).Conclusions The utilization of VMAT in the treatment planning of SABR for liver tumors under breath control mode has better dosimetrics.In comparison to conventional IMRT plans,VMAT plans have higher efficiency and feasibility.