ExacTrac系统在颅脑肿瘤放疗摆位中的应用

Application of ExacTrac system in the positioning of brain tumor radiotherapy

目的使用ExacTrac与OBI系统对颅内肿瘤进行图像引导放疗,并用锥形束CT(CBCT)验证ExacTrac系统移床修正后的结果,评估ExacTrac系统在颅脑肿瘤放射治疗中的摆位精度。方法选取2017年1月至2018年1月中山大学附属第一医院收治的28例颅脑肿瘤放疗患者作为研究对象。先利用三维激光系统摆位,用ExacTrac系统拍摄两幅交叉的X线图像,得到三维平移误差X(左右)、Y(进出)、Z(升降)和对应的旋转误差Rx、Ry、Rz,进行六维移床修正后,再使用ExacTrac系统验证修正后的位置并在加速器上进行CBCT扫描。记录ExacTrac修正前、后以及CBCT的摆位误差并统计分析。结果ExacTrac系统修正前X、Y、Z三个方向的平移误差分别为(-0.38±1.38)mm、(0.30±1.37)mm、(-0.55±1.12)mm,修正后的误差为(0.02±0.31)mm、(0.01±0.25)mm、(-0.03±0.27)mm,其对应的旋转误差分别为(-0.18±1.08)°、(0.35±1.60)°、(0.21±1.11)°和(0.06±0.19)°、(0.01±0.23)°、(-0.03±0.30)°,修正前后比较,差异有统计学意义(P<0.05)。CBCT验证ExacTrac修正后的误差为(0.26±0.59)mm、(-0.42±0.55)mm、(0.22±0.53)mm,均不超过±1 mm。结论ExacTrac系统配合六维床可明显降低摆位误差,提高治疗精度,是一种在颅脑肿瘤放射治疗中可靠的图像引导方法。

Objective To apply ExacTrac and OBI systems to perform image-guided radiotherapy for intracranial tumors,and cone beam CT(CBCT)to verify the results of the ExacTrac system moving bed correction,and evaluate the positioning accuracy of the ExacTrac system in brain tumor radiotherapy.Methods Twenty-eight patients with craniocerebral tumor radiotherapy in the First Affiliated Hospital of Sun Yat-sen University from January 2017 to January 2018 were selected as the research objects.First the three-dimensional laser system was used to position,and the ExacTrac system was used to take two cross X-ray images to obtain the three-dimensional translation error X(Left and right),Y(in and out),Z(up and down)and the corresponding rotation errors Rx,Ry,Rz.After the correction of the six-dimensional bed movement,the ExacTrac system was used to verify the corrected position and perform a CBCT scan on the accelerator.The setting errors of ExacTrac before and after correction,and CBCT were recorded and statistically analyzed.Results The translation errors in the X,Y,and Z directions of the ExacTrac system before correction were(-0.38±1.38)mm,(0.30±1.37)mm,and(-0.55±1.12)mm.The corrected error was(0.02±0.31)mm,(0.01±0.25)mm,and(-0.03±0.27)mm.The corresponding rotation errors were(-0.18±1.08)°,(0.35±1.60)°,(0.21±1.11)°,(0.06±0.19)°,(0.01±0.23)°,and(-0.03±0.30)°,and they were compared before and after correction,with statistically significant differences(P<0.05).CBCT verified that the corrected error of ExacTrac was(0.26±0.59)mm,(-0.42±0.55)mm,(0.22±0.53)mm,all of which did not exceed±1 mm.Conclusion The ExacTrac system combined with the six-dimensional bed can significantly reduce the positioning error and improve the treatment accuracy.It is a reliable image guidance method in the radiotherapy of brain tumors.