鼻咽癌调强放疗“处方剂量”外区域的剂量差异性研究

[目的]观察调强放疗（IMRT）计划中规定处方剂量（致死剂量DT70Gy及预防剂量DT56Gy）的等剂量曲线外围邻近组织的剂量变化,评价不同医师对靶区勾画的差异所造成的的剂量学影响。[方法]20例初诊鼻咽癌患者,按照IMRT的治疗流程予以靶区勾画及计划设计。将IMRT计划中70Gy及56Gy的等剂量曲线所包含的体积范围定义为V70及V56。围绕V70及V56分别均匀外扩0.5cm及1cm所包含的体积范围,并＂挖除＂原有V70及V56部分分别形成的＂戒指状＂体积部分,定义为V70＋0.5,V70＋1及V56＋0.5,V56＋1。分别绘制V70＋0.5,V70＋1及V56＋0.5,V56＋1的剂量体积直方图（DVH）,同时分别计算D50、D95。[结果]V70＋0.5、V70＋1、V56＋0.5和V56＋1的D50分别为65.94Gy、62.28Gy、51.51Gy和47.03Gy;D95分别为58.86Gy、49.66Gy、38.87Gy和29.03Gy。[结论]IMRT治疗计划中,处方剂量外0.5～1cm处区域存在较高的放射剂量,靶区勾画差异所引起的＂剂量缺失＂并不显著。

The Dose Difference of Outside Region of Prescribed Dose in IMRT for Nasopharyngeal Carcinoma

[Purpose] To observe the dose variability to the tissue outside the isodose curve of the prescribed dose (the tumoricidal dose DT70Gy and the prophylaxis dose DT56Gy) in IMRT plan to nasopharyngeal carcinoma, to evaluate the dosimetric impact of inter-observer contouring variation. [Methods] Twenty cases with pathologically confirmed nasopharyngeal carcinoma underwent IMRT, target delineation and program design according to the procedure. The tissue volume enclose by the isodose curve of the prescribed dose...