应用锥形束CT分析调强放疗中头颈部肿瘤的摆位误差

背景与目的：采用锥形束CT（Cone-beam computed tomography,CBCT）影像技术研究本院头颈部肿瘤调强放射治疗中的摆位误差,并计算出CTV的外扩边界PTV的范围。方法：应用Varian图像引导放疗系统（Image-guided radiation therapy,IGRT）治疗头颈部肿瘤31例,每周均获取锥形束断层扫描（CBCT）各一次,将CBCT图像和计划CT图像及其靶中心匹配,获得靶中心x、y、z方向的误差,分析误差及其分布规律。CTV到PTV外扩边界的大小由公式：2.5∑＋0.7σ计算得出,其中∑为系统误差,σ为随机误差。结果：得出本院头颈部肿瘤PTV的理论边界x、y、z（左右、头脚、前后）方向上分别为：1.9mm,1.6mm,1.3mm。结论：通过CBCT测量摆位误差并进行调整可提高患者摆位精度,为外扩CTV边界提供了理论依据,使治疗计划的实施更精确。

Setup errors in image-guided radiotherapy for head and neck tumors analyzed by cone-beam computed tomography

Objective：This work was to research the Setup Errors in Image-guided Radiotherapy for Head and Neck Tumors by cone-beam CT（Cone-beam computed tomography,CBCT） imaging technology,and calculate CTV safety margins of PTV.Methods ：31 patients were treated with Varian image guided radiotherapy system（IGRT）.All patients had received cone beam computed tomography（kv-CBCT）once a week.The acquired CBCT images were compared with planning CT and errors of isocenter positions on x, y,z axes were obtained and analyzed.CTV margin should be calculated with the formula 2.5E ＋0.7σ  means Systematic Error,σ means Random Error.Results：The margin of PTV of head and neck cancer in three directions（x,y,z）was 1.9 mm,1.6mm,1.3mm respectively.Conclusion： Measurement of setup error delivery using CBCT scan combined with on-line correction could improve the patient setup precision and may make our design of radiotherapy system more scientific and normal.