鼻咽癌三维适形和调强放疗过程中头部与颈部摆位误差比较研究

A study of the positioning errors of head and neck in the process of intensity modulation radiated therapy of nasopharyngeal carcinoma

目的探讨鼻咽癌三维适形、调强放疗过程中头部和颈部摆位误差是否存在差异。方法选择中晚期鼻咽癌（T2-4N1-3M0期）患者19例，头颈肩热塑面罩固定，将等中心点置于鼻咽腔附近。由三维激光灯在面罩上定出左、中、右原始十字标志点，并贴上直径约为0．3mm的铅珠作为显像标记，然后CT扫描。将CT图像通过网络传至Peacock逆向计划系统进行计划设计，然后实施治疗。治疗1—6周每周在CT模拟机进行重复扫描，扫描及固定和摆位方法都与进行计划CT时相同。将每周验证体位重复性CT图像与计划CT图像通过读图软件进行比较，并利用双独立样本t检验头、颈部摆位误差。结果左右、上下、头脚方向上颈部摆位误差分别为（2．44±2．24）、（2．05±1．42）、（1．83±-1．53）mm，头部摆位误差分别为（1．05±0．87）、（1．23±1．05）、（1．17±1．55）mm；颈部和头部的摆位误差差异有统计学意义（t=-6．58、-5．28、-3．42，P=0．000、0．000、0．001）。左右、上下、头脚方向上颈部系统误差分别是头部的2．33、1．67、1．56倍，颈部随机误差分别是头部的2．57、1．34、0．99倍。结论鼻咽癌三维适形、调强放疗过程中采用头颈肩热塑面罩固定情况下，颈部的摆位误差大于头部。

Objective To investigate the positioning errors of head and neck during intensitymodulated radiation therapy of nasopharyngeal carcinoma. Methods Nineteen patients with middleadvanced nasopharyngeal carcinoma （T2-4 N1-3 M0 ）, treated by intensity-modulated radiation therapy, underwent repeated CT during their 6-week treatment course. All the patients were immobilized by head- neck-shoulder thermoplastic mask. We evaluated their anatomic landmark coordinated in a total of 66 repeated CT data sets and respective x , y , z shifts relative to their position in the planning CT . Results The positioning error of the neck was 2. 44 mm ±2. 24 mm,2. 05 mm± 1.42 mm,1.83 mm± 1.53 mm in x, y, zrespectively. And that of the head was 1.05 mm ±0.87 mm,1.23 mm ±1.05 mm,1. 17 mm ±1.55 mm respectively. The positioning error between neck and head have respectively statistical difference （ t = - 6. 58, - 5.28, - 3.42 ,P = 0. 000,0. 000,0. 001 ）. The system error of the neck was 2. 33,1.67 and 1.56 higher than that of the head, respectively in left-right, vertical and head-foot directions ; and the random error of neck was 2. 57,1.34 and 0. 99 higher than that of head respectively. Conclusions In the process of the intensity-modulated radiation therapy of nasopharyngeal carcinoma, with the immobilization by headneck-shoulder thermoplastic mask, the positioning error of neck is higher than that of head.