【摘要】 目的本研究探讨使用热塑面罩固定的鼻咽癌患者,在治疗过程的摆位不确定度。方法选择首次放疔的早期鼻咽癌患者19例,仰卧体位,个体化泡沫头枕,热塑面膜固定,将等中心点置于鼻咽腔附近,由三维激光灯在而罩上定出左、中、右3个原始十字标志点,并贴上直径约为0．3 mm的铅珠作为显像标记,然后行CT扫描。将CT图像通过网络传到Peacock的逆向计划系统进行计划设计,然后实施治疗。在治疗的一至六周,每周在CT模拟机进行重复扫描,共85次,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的CT图像与计划CT图像通过读图软件进行比较。结果通过对19例患者的85次重复CT与计划CT比较,得出使用本面罩系统时,等中心点的平均位置坐标为(-0．84,+0．65,+0．01)mm；不同解剖骨性标记点在x、y、z 3个轴向的绝对位移值分别为(0．89±0．69),(0．82±0．79),(0．95±1．24)mm；等中心点三维矢量位移的平均值为1．87mm；等中心点三维矢量位移的95%可信区间(CI)最大值7．24mm,最小值2．03mm,平均值3．82mm；第一周到第三周等中心点二维矢量位移95%CI的平均值是4．17mm,第四周到第六周的平均值是5．12mm。结论使用连续CT多次重复扫描的方法来研究鼻咽癌治疗过程中的摆位不确定度是可行的。更多还原

【Abstract】 Objective This study is to investigate the set-up accuracy of thermoplastic mask used for immobilization of nasopharyngeal carcinoma (NPC) patients being treated by Intensity Modulated Radia- tion Therapy (IMRT).Methods Nineteen patients with early stage nasopharyngeal carcinoma (T1- T2N0M0),treated by fractionated intensity-modulated radiation therapy,underwent repeated CTs during their 6-week treatment course.We evaluated their anatomic landmark coordinates in a total of 85 repeated CT data sets and respective x,y and z shifts relative to their position in the 19 treatment-planning reference CTs.Results The translation in x,y,and z-axes with their mean value derived from both positive and negative set-up errors was-0.84 mm(x-axis),+0.65 mm(y-axis) and +0.01 mm(z-axis).Mean target isocenter translation was (0.89±0.69) mm,(0.82±0.79) mm,(0.95±1.24) mm in x,y and z-direc- tions,respectively.The mean total magnitude vector and 95% CI of isocenter motion were 1.87 mm and 4.65 mm.The data measured over the 6-week fractionated course of treatment revealed a slight deterioration of isocenter accuracy.The 95% CI,considered by us to be a valuable parameter for characterizing the sys- tem,of 4.17 mm for measurement within the first 3 weeks increased to 5.12 mm in the last 3 weeks of treat- ment.Conclusions The sequential CT scanning is a pronounced valuable method of evaluating the quality of departmental specific patient positioning procedures.The thermoplastic mask is eyed as well suited tool for immobilization and repositioning of NPC patients receiving intensity-modulated radiation therapy.更多还原