摘要目的：应用千伏级锥形束CT（CBCT）对比分析头颈部肿瘤放疗中头枕+头颈肩面膜、真空气垫+头颈肩面膜两种体位固定技术的摆位误差。方法随机选取60例接受诊断及治疗的头颈部肿瘤患者（头枕+头颈肩面膜组29例、真空气垫+头颈肩面膜组31例），治疗过程中每周行1次CBCT扫描，将所获取的CBCT图像与计划CT图像进行配准，得到左右、上下、前后方向的摆位线性误差，采用独立t检验对比两组数据的差异性。结果头枕+头颈肩面膜组在左右、上下、前后方向的摆位线性误差分别为：（0．07±1．70）、（0．45±1．53）、（0．39±1．62） mm，真空气垫+头颈肩面膜组在左右、上下、前后方向的摆位线性误差分别为：（-0．05±1．39）、（0．13±1．37）、（0．08±1．25） mm。两组在左右方向上的摆位线性误差比较差异无统计学意义（t=0．729， P>0．05），在上下和前后方向上的差异有统计学意义（t=2．093、2．039， P均<0．05）。结论两种固定方式中头颈部肿瘤真空气垫+头颈肩面膜固定的患者摆位误差小，体位重复性好。

abstractsObjective To analyze the setup errors of two immobilization techniques (pillow +head-and-neck shoulder mask and vacuum bag + head-and-neck shoulder mask)with KV- cone beam computed tomography ( CBCT ) for head-and-neck cancer radiotherapy . Methods Sixty head-and-neck cancer patients who diagnosed and treated in Panyu central hospital were randomly selected and divided into two groups(29 patients of pillow + head-and-neck shoulder mask group and 31 patients of vacuum bag + head-and-neck shoulder mask group). CBCT was weekly carried out before treatment delivery. Then, the CBCT images were matched with the planned CT images in order to get the setup errors in left-right, superior-inferior and anterior-posterior directions. Independent t-test was used to evaluate the differences. Results In the pillow+head-and-neck shoulder mask group, the average setup errors values in the left-right, superior-inferior and anterior-posterior directions were(0.07±1.70), (0.45±1.53), (0.39± 1.62) mm, respectively. Also in the vacuum bag+head-and-neck shoulder mask group, the average setup errors values were (-0.05 ±1.39), (0.13 ±1.37), (0.08 ±1.25) mm, respectively. And in the left -right direction, there was no statistically significant difference (t=0.729, P>0.05). While, in the superior-inferior and anterior-posterior directions, both of which had statistically significant difference(t=2.093 and 2.039, both P<0.05). Conclusion The vacuum bag+head-and-neck shoulder mask fixed technique was more accurate when compared to the pillow+head-and-neck shoulder mask fixation method, which has the smaller setup errors and the better position repeatability.