【摘要】 目的　使用实时照射野成像系统监测胸部放射治疗时的摆位误差 ,定量分析治疗机床面 (网状支架 )和模拟机床面 (平板 )不一致时误差的分布情况、移位的几率和程度 ,并评价固定器的价值。方法　用正交摄影法随机采集 30例胸部肿瘤放射治疗时的正侧位照射野图像共计 389幅 ,并与同期相应的模拟定位片相比较 ,分别测量解剖参考点的纵向、横向和垂直方向的移动度。结果　各方向摆位误差的分布均近似正态分布 ,横向和纵向的系统误差值较小 (大约为 1～ 2mm) ,随机误差相似。垂直方向无固定组的系统误差值平均为 - 6 .8mm ,固定组为 - 1.5mm ,两组间差异有显著性意义(u =6 .0 7,P =0 .0 0 0 )。无固定组的随机误差较大 ,垂直下陷的几率显著高于固定组 (χ2 =12 .36 ,P =0 .0 0 1)。结论　治疗床面的下垂是造成系统摆位误差的一个重要原因 ,必须及时加以纠正 ,使用适当的固定器有助于提高摆位精度更多还原

【Abstract】 Objective We have monitored the set up errors of radiotherapy for thoracic cancer using ontime imaging system. The discrepancy of couch top between treatment machine (net bracket) and simulator (plate) was observed. Set up errors were analyzed quantitively according to variable distribution, ratio and extent of displacement. Methods Three hundred eighty nine orthogonal portal images of 30 patients were compared to the simulation films. Set up deviation in lateral, longitudinal and vertical direction were measured respectively. The systematic and random errors were evaluated. Results The distribution of set up errors in each direction approximated a normal distribution. The systematic error in lateral and longitudinal was lower with a mean of 1～2 mm, and however, it was 6.8 mm in vertical direction without immobilization device as compared to 1.5 mm with immobilization device. The random error was larger and ratio of vertical displacement was higher without immobilization. Conclusions The decline of treatment couch top (with net bracket) could result in a larger systematic error with a mean of 6.8 mm. We must pay attention to the coordination of couch top between treatment machine and simulator when radiation field is set. The use of immobilization device during thoracic radiotherapy is able to improve the geometrical quality.更多还原