ExacTrac X-射线图像引导系统在体部肿瘤放疗中的摆位误差和残余误差分析

目的 通过对体部肿瘤放射治疗的ExacTrac X-射线图像的回顾性分析，了解患者群体的摆位误差和残余误差分布情况，研究六维放射治疗床修正摆位误差的必要性和有效性。方法 通过配准数字重建图像（DRR）和ExacTrac图像引导系统拍摄的正交kV级验证像的骨性解剖结构，计算患者3个方向的平移误差和旋转误差以及对应的残余误差。结果 平移摆位误差为x（左右方向）：（2.27±2.02）mm，y（头脚方向）：（4.49±2.52）mm，z（腹背方向）：（2.27±1.37）mm；旋转摆位误差为Rx（矢状面）：（1.02±0.73）°，Ry（横断面）：（0.67±0.68）°，Rz（冠状面）：（0.76±0.84）°。残余平移误差x（r）：（0.27±0.48）mm，y（r）：（0.37±0.45）mm，z（r）：（0.22±0.30）mm；残余旋转误差为Rx（r）：（0.17±0.33）°，Ry（r）：（0.14±0.34）°，Rz（r）：（0.16±0.28）°。结论 对于体部放射治疗的患者，旋转误差和平移误差是同时存在的，不仅需要校准平移误差，旋转误差也不容忽视。ExacTrac X-射线图像引导系统能够有效纠正六自由度的摆位误差，并保证残余误差在较小的范围内，保证了体部肿瘤放疗的治疗精度。

Analysis of the setup errors and residual errors for ExacTrac X-ray image-guidance system for radiotherapy of somal tumors

Objective To retrospectively analyze the setup error in radiotherapy of somal tumors and body metastases using the ExacTrac X-ray portal image, and to evaluate the feasibility and effectiveness of 6D setup error correction in body radiotherapy. Methods The translational and rotational setup errors were calculated by registering the bony structures on the ExacTrac X- setup images to that of the digitally reconstructed setup images, and the corresponding residual errors were calculated together. Results The translational and rotational setup errors in the x (left-right), y (superior-inferior), z (anterior-posterior) and Rx (sagittal), Ry (transverse), Rz (coronal) directions were(2.27±2.02)mm, (4.49±2.52)mm, (2.27±1.37) mm and (1.02±0.73)°, (0.67±0.68)°, (0.76±0.84)°, respectively. The residual translational and rotational setup errors in the x(r), y(r), z(r) and Rx(r), Ry(r), Rz(r) directions were(0.27±0.48)mm,(0.37±0.45)mm, (0.22±0.30)mm and (0.17±0.33)°, (0.14±0.34)°, (0.16±0.28)°respectively. Conclusions Besides the translational setup errors, a certain amount of rotational setup errors exist in radiotherapy of somal tumors and body metastases. By using the 6D setup error correction of the ExacTrac system, a translational less than 0.4 mm and rotational setup errors less than 0.2° could be achieved.