光学表面监测系统与CBCT确定左侧乳腺癌深吸气屏气放疗误差的比较

目的 建立本单位应用光学表面监测系统(OSMS)门控技术在左侧乳腺癌深吸气屏气(DIBH)放疗的基本流程,比较应用OSMS与CBCT确定左侧乳腺癌DIBH放疗摆位误差的一致性。方法 20例左侧乳腺癌患者采用DIBH方法治疗,OSMS与模拟定位DIBH体表外轮廓配准,CBCT扫描与模拟定位CT配准各记录得到误差数据,数据包括左右(x)、上下(y)、前后(z)方向平移误差和旋转误差Rx、Ry、Rz。采用Pearson法分析两者相关性,Bland-Altman法检验两者一致性。结果 两种方法呈正相关,x、y、z方向平移误差以及Rx、Ry、Rz方向旋转误差的相关系数分别为0.84、0.74、0.84、0.65、0.41、0.54(P<0.01),95%CI值分别为-0.37~0.42 cm、-0.39~0.41 cm、-0.29~0.49cm和-2.9°~1.4°、-2.6°~1.4°、-2.4°~2.5°,均<5mm和3°。20例左侧乳腺癌DIBH放疗患者系统误差<0.18cm,随机误差<0.24cm。结论 左侧乳腺癌DIBH放疗中应用OSMS与CBCT两种方式确定与模拟定位状态误差具有一致性,CBCT图像引导基础上使用无辐射的OSMS验证位置信息是安全可靠的。

Comparison of the performance of two methods to determine set-up errors for DIBH patients with left sided breast cancer in radiotherapy

Objective To establish the basic procedures of the application of optical surface monitoring system (OSMS) in the deep inspiration breath hold (DIBH) radiotherapy for patients with left sided breast cancer and compare the performance of OSMS and cone-beam CT (CBCT) in the determination of the set-up errors of DIBH radiotherapy for patients with left sided breast cancer. Methods Twenty patients with left sided breast cancer received DIBH radiotherapy. Through the registration of CBCT images with the planning CT images,and the registration of OSMS radiography images with the outer contour of the body surface,translational set-up errors and rotational errors were determined along the lateral-medial (Rx), superior-inferior (Ry) and anterior-posterior (Rz) directions. Pearson correlation analysis was performed to evaluate the correlation of the set-up errors determined by two methods,and Bland-Altman plot analysis was used to assess the coincidence of these two methods. Results Two methods were positively correlated. The Rz volume was 0.84,0.74 and 0.84 in the x,y and z directions,and 0.65,0.41 and 0.54 in the Rx,Ry and Rz directions,respectively (all P<0.01). The 95%CI of agreement were within preset 5 mm tolerance (-0.37-0.42cm,-0.39-0.41cm,-0.29-0.49cm) in x,y and z directions for two methods. The 95%CI of agreement were within preset 3 ° tolerance -2.9°-1.4°,-2.6°-1.4°,-2.4°-2.5°in Rx,Ry and Rz directions for two methods. The system errors of 20 patients with left sided breast cancer receiving DIBH radiotherapy were <0.18cm and the random errors were <0.24cm. Conclusions OSMS is equivalent to CBCT in the determination and stimulation of set-up errors for patients with left sided breast cancer receiving DIBH radiotherapy. The combination of CBCT and OSMS is a safe and reliable method.