容积调强技术在食管癌放疗中的剂量学研究

Dosimetric study on the volumetric modulated arc therapy in the radiotherapy of esophageal cancer

目的研究旋转容积调强VMAT与固定野调强IMRT在食管癌放疗中的剂量学差异。方法 2014年6月~2015年8月入组食管癌患者30例。用瓦利安Eclipse10.0计划系统分别设计单弧VMAT（Arc1）、双弧VMAT（Arc2）、和9野IMRT计划。比较三组计划在平均剂量体积直方图、靶区剂量覆盖率、危及器官和正常组织保护等方面的剂量学差异,并比较三组计划的总机器跳数（MU）和治疗时间。结果 VMAT（Arc2）靶区剂量分布均匀性（HI）和矩形度（CI）较其他两种要好（P〈0.05）。危及器官方面：VMAT（Arc1）与VMAT（Arc2）比较,VMAT（Arc2）对双肺、脊髓Dmax保护优于VMAT（Arc1）;VMAT（Arc2）、与IMRT9野比较,VMAT（Arc2）对心脏Dmean、脊髓Dmax保护优于IMRT 9野;治疗时间方面：VMAT（Arc1）时间最短,需时90s,VMAT（Arc2）所需时间190~200s,IMRT 9野平均所需时间680s。结论 VMAT（Arc1）、VMAT（Arc2）、与IMRT 9野三种计划都满足临床要求。对于瓦利安Eclipse10.0计划系统VMAT（Arc2）临床使用上较普遍。

Objective To explore the dosimetric differences between volumetric modulated arc therapy（VMAT） and intensity modulated radiation therapy（IMRT） in the radiotherapy of esophageal cancer. Methods 30 patients with esophageal cancers during June 2014 and August 2015 were recruited. The single arc VMAT（Arc 1） plan, double arc VMAT（Arc2） plan, and IMRT 9 fields plan were designed by Varian Eclipse 10.0 planning system. The dosimetric differences of average dose volume histogram, target section dose distribution, organ damage, and normal tissue protections of the three plans were compared. The total monitor unit（MU） numbers and treatment time of the three plans were compared. Results The homogeneity index（HI） and conformal index（CI） of VMAT（Arc2） plan were better than the other two plans（P 0.05）. In terms of organ damage, the VMAT（Arc2） plan＇s Dmax protections of double lung and spinal cord were better than those of VMAT（Arc1） plan, the VMAT（Arc2） plan＇s Dmean protection of heart and Dmax protection of spinal cord were better than those of IMRT 9 fields. In terms of treatment time, the VMAT（Arc1） plan needed the shortest time—evenly 90 seconds, the VMAT（Arc2） plan lasted for 190 to 200 seconds, and IMRT 9 fields evenly lasted for 680 seconds. Conclusion All the VMAT（Arc1） plan, VMAT（Arc2） plan and IMRT 9 fields plan can satisfy the clinical dosimetric requirements, while the VMAT（Arc2） is more common for clinical practice according to Varian Eclipse 10.0 planning system.