颈段及胸上段食管癌调强放射治疗计划的比较

目的：射野数目的多少在调强放射计划中直接影响着靶区的适形性（conformity）,均匀度（uniformity）以及对周围危及器官（organs at risk,OAR）的保护。本文就颈段及胸上段食管癌,对不同射野数目进行调强放射治疗计划的比较。方法：回顾继往颈段及胸上段食管癌病例,从中挑选5位患者,运用5,7,9个射野的调强放射治疗计划,同时对IMRT的靶区运用200 cGy/fx,30fx总共60 Gy剂量,比较在这个给定相同的剂量的条件下,通过剂量体积直方图（dose volumehistograms,DVH）,等剂量曲线分布（iso-dose distributions）以及靶区的适形指数（conformity index,CI）等来比较各个计划中计划靶区（planning target volume,PTV）,以及危及器官（OARs）的剂量学差异。结果：随着射野数目的增加靶区适形度以及等剂量线分布越来越好。7、9个射野对肺的损伤也不像想象中那么大。甚至7、9野的IMRT在肺的V20更低。结论：相比5个射野的IMRT计划,7个射野能提供更好的适形度和均匀性,以及对肺组织的保护;而相比9野计划,7个射野能运用更短的治疗时间和更少的加速器跳数（monitor unite,MU）,减少器官运动对靶区剂量的影响。

Comparison of Intensity-modulated Radiation Therapy(IMRT)for Cervical and Upper Thoracic Esophageal Carcinoma

Objective：The number of beams in intensity-modulated radiation therapy（IMRT） directly works on the dose conformity,dose uniformity of planning target volume（PTV） and the dose to the organs at risk（OAR）.This paper compares different IMRT plans with variable beams arrangements for cervical and upper thoracic esophageal carcinoma.Methods：Treatment plans,which were IMRT plans with 5,7 or 9 beams,were analyzed for 5 patients with cervical and upper thoracic esophageal carcinoma.With the same prescribed dose which was given to 60 Gy/30fx,the dose-volume histogram（DVH）,dose distribution and conformity index were used to compare these treatment plans.Results：The CI to the target and iso-distribution were improved with the beam number increased.The 7 or 9 beams IMRT plans did results in lower V20 in total lung.Conclusions：Comparing to IMRT plans with 5 beams,IMRT plans with 7 beams produced better CI and uniformity,and lower lung sparing;comparing to IMRT plans with 9 beams,IMRT plans with 7 beams reduced the time of treatments and the monitor unit（MU）.And the effects of motion on the dose distribution of PTV were diminutive.