ExacTrac X线图像引导系统在胸部肿瘤治疗应用的初步评估

Preliminary Assessment on the Application of ExacTrac X Ray Image Guide System for the Therapy of Thoracic Tumor

目的:比较红外线标记及X射线图像引导系统配合6维移动治疗床进行摆位在胸部肿瘤调强放射治疗应用的精度,评估各自的应用可行性。方法:选择8例胸部肿瘤调强放疗的患者,应用红外线标记进行摆位后,采用ExacTrac X线图像引导系统拍摄交叉X线射野照片,与计划的数字重建射野图像进行匹配,得到前者在X、Y、Z三个方向的平移误差和绕三个方向中心轴的旋转误差(6D误差),并进行摆位修正。在摆位修正后再以X线图像验证患者体位的6D误差。结果:红外线标记摆位在X、Y、Z三个方向的平移误差分别为(1.64±1.42)mm、(2.35±1.89)mm、(2.81±1.74)mm,绕X、Y、Z轴的旋转误差分别为(0.96±0.87)°、(1.27±1.05)°、(1.42±0.99)°。经X线图像引导修正摆位后X、Y、Z方向的平移误差分别为(0.28±0.11)mm、(0.43±0.14)mm、(0.43±0.14)mm,绕X、Y、Z轴旋转误差均小于0.5°。X线图像引导修正摆位后的3个线性误差和3个旋转误差均明显小于单纯红外线标记摆位的误差,差异有统计学意义(P<0.01)。结论:应用ExacTrac X线图像引导系统配合6维移动治疗床在胸部肿瘤调强放射治疗是可行的,并可明显减小患者治疗的位置误差。

Objective： To compare the accuracy of the infrared markers with the X ray image guide system, cooperating with the six degree mobile treatment bed in Intensity Modulated Radiation Therapy（IMRT） for thoracic tumor while positioning. And to assess the application feasibility of these two ways. Methods ： Eight patients with thoracic tumor accepting IMRT were chosen. The cross X-ray radiation field photos taken by ExacTrac X-ray image guide system were matched with the DRR after positioning with the infrared markers. Then the motion errors on X ,Y and Z directions and rotation errors （6D errors） were obtained and corrected. After that, the 6D errors of the patients were verified using the x-ray image guide system again. Results： The errors occurred in the infrared markers positioning on X ,Y ,Z directions were（ 1.64 ± 1.42）mm,（2. 35 ± 1.89）mm and（2. 81 ± 1.74）mm respectively, and the rotation errors spinning X, Y, Z axis were （0. 96 ± 0. 87 ） °, （ 1.27 ± 1.05 ） ° and （ 1.42 ± 0. 99 ） ° respectively. After verified by the x-ray image guide system, the position errors on X,Y,Z directions were（0. 28 ± 0. 11 ）mm, （0. 43 ± 0. 14）mm and （0.43 ± 0. 14）mm respectively, and the rotation errors were all less than 0. 5°. The three position errors and the three rotation errors verified by the x-ray image guide were obviously less than which verified by the infrared markers. The differences were significant（P 〈 0. 01 ）. Conclusion： It is feasible to use ExacTrac X-ray image guide system cooperating with the six degree mobile treatment bed in IMRT for the therapy of thoracic tumors with markedly reduced position errors of the treatment.