鼻咽癌适形调强放射治疗中计划靶体积不确定度的研究  

Design Planning Target Volumes (PTVs) in Intensity-modulated Radiotherapy for Nasopharyngeal Carcinoma

作　　者：林承光[1] 李国文[2] 林刘文[1] 吴裕起[1] 萧达宜[1] 赵充[1] 卢泰祥[1] 崔念基[1] 

机构地区：[1]华南肿瘤学国家重点实验室 [2]郑州大学第一附属医院光子刀放疗中心,河南郑州450052

出　　处：《癌症》2007年第2期200-203,共4页Chinese Journal of Cancer

基　　金：吴阶平医学基金;卫生部科研基金(No.WKJ2005-3-006-11)~~

摘　　要：背景与目的:鼻咽癌的适形调强放疗为减少正常组织的放射损伤,提高患者的生存质量提供了契机。但是,高度适形的治疗技术使肿瘤和正常组织之间的剂量梯度变得非常陡峭,每日的摆位不确定度对理想化的治疗计划产生的影响也会因此而加大。本研究探讨使用热塑面罩固定时,该治疗过程的摆位不确定度,以及为补偿这种不确定度需要在临床靶体积周围所加的安全边界的大小。方法:选取首次做适形调强放疗的早期鼻咽癌患者19例。每周进行一次CT重复扫描,方法与做治疗计划时完全相同。共获取85次扫描参数。通过读图软件对每周扫描的CT图像与计划设计的CT图像进行比较,求出每次摆位与首次定位时感兴趣的解剖标记点在三维方向上的差异。结果:19例患者的85次扫描参数比较,不同解剖骨性标记点在X、Y、Z方向的绝对位移值分别为(0.89±0.69)mm、(0.82±0.79)mm、(0.95±1.24)mm。矢量位移的系统误差分别为0.94mm、1.00mm、1.32mm,随机误差分别为0.87mm、0.80mm、1.04mm。等中心点的三维矢量位移的平均值为1.87mm,95%可信区间为2.03～7.24mm,平均值3.82mm。结论:对早期鼻咽癌患者的适形调强放疗,其X、Y、Z轴向上由临床靶体积统一外扩3.00mm形成临床靶体积-计划靶体积安全边界来弥补由于体位固定的不确定度对靶区剂量分布造成的影响应该是足够的。BACKGROUND ＆ OBJECTIVE. Intensity-modulated radiotherapy （IMRT） may help to diminish radiation-induced normal tissue damage and improve quality of life of nasopharyngeal carcinoma （NPC） patients, However, highly conformal treatment techniques commonly establish steep dose gradients between tumor and normal tissues, therefore, daily setup variations can significantly compromise the ultimate precision of idealized IMRT delivery, This study was to investigate the setup accuracy of thermoplastic masks used for immobilizing NPC patients treated by simultaneous integrated boost IMRT, and to determine adequate margins to account for those uncertainties, METHODS：Nineteen patients with early stage （T1-2N0M0） NPC received CT scan weekly during their 6-week treatment course of fractionated IMRT. A total of 85 scanning parameters were obtained, The differences in anatomic landmark coordinates in 3-dimensional directions between daily setup and the first day setup were calculated through comparing the CT images with Osiris software, RESULTS：Mean target isocenter translation was （0,89＋0,69） mm in x-direction, （0,82＋0.79） mm in y-direction, and （0.95＋1,24） mm in z-direction. The systematic errors were 0,94 mm, 1.00 mm, and 1.32 mm. The random errors were 0,87 mm, 0,80 mm, and 1,04 mm, The mean total magnitude vector of isocenter motion was 1,87 mm; the 95% confidence interval （CI） was 2.03-7.24 mm. CONCLUSION： During IMRT for early stage nasopharyngeal carcinoma, setting appropriate margin of planning target volume （PTV） by widening 3 mm from clinical target volume （CTV） in x, y, z directions will be sufficient to compensate for the dosimetric uncertainty of target areas due to patient setup error, The measured data in the present study should enable the user of this kind of thermoplastic mask to assign appropriate margins for the generation of planning target volumes （PTVs）.

关 键 词：鼻咽肿瘤 适形调强放疗 计划靶体积 随机误差 系统误差 

分 类 号：R739.63[医药卫生—肿瘤]