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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
Objective To use the real-time radiation field imaging system to monitor the setup error during chest radiotherapy and quantitatively analyze the distribution of error, the probability and degree of displacement when the treatment machine tool face (mesh support) and the simulated machine tool face (flat plate) are inconsistent, and evaluate The value of the fixture. Methods A total of 389 images of positive lateral irradiation fields in 30 cases of thoracic tumor radiotherapy were randomly collected by orthogonal radiography, and the longitudinal, lateral, and vertical directions of the anatomical reference points were measured and compared with the corresponding analog locators in the same period. Mobility. Results The distribution of errors in all directions was approximately normal distribution. The horizontal and vertical system error values were small (approximately 1 to 2 mm) and the random errors were similar. The systematic errors in the non-fixed group in the vertical direction averaged -6.8mm, and in the fixed group -1.5mm. There was a significant difference between the two groups (u = 6.0, P = 0.00). The random errors of the non-fixed group were larger, and the probability of vertical subsidence was significantly higher than that of the fixed group (χ 2 =12.36, P =0. 0 0 1). Conclusion Treatment of bed sag is an important cause of system setup error. It must be corrected in time. Using appropriate holders can help improve the accuracy of the setup.