图像引导放疗锥束CT与计划CT不同配准方法精度研究

目的 验证CBCT图像引导系统骨性和灰度配准算法的精度和适用范围,为临床提供参考依据。方法 使用仿真人头颈和胸腹体模,模拟三维方向摆位偏移并在完成每次摆位时获取CBCT图像。用IGRT系统的骨性和灰度配准方法分别配准计划CT图像与各次摆位CBCT图像,得到体模在x、y、z方向偏移量。分析两种配准方法的精度和重复性,并行配对t检验。结果 头颈体模骨性和灰度配准在x、y、z轴向的误差分别为(－0.65±0.22) mm和(－0.70±0.17) mm (P=0.00)、(1.02±0.27) mm和(0.90±0.20) mm (P=0.00)、(1.46±0.53) mm和(1.47±0.47) mm (P=0.54);胸腹体模的分别为(0.82±0.33) mm和(0.79±0.18) mm (P=0.03)、(2.45±1.17) mm和(1.61±0.84) mm (P=0.00)、(1.44±3.25) mm和(0.19±1.11) mm (P=0.00)。结论 灰度配准精度和稳定性高于骨性配准,头颈部配准精度稍优于胸腹部,临床使用时应分别进行测试并根据治疗精度要求选择合适方法并修正误差。

Accuracy study of different registration methods for cone beam CT and planning CT in image-guided radiation therapy

Objective To evaluate the accuracy of image registration based on bony structure (RBS) and grey-scale (RGS) in positioning correction of radiation treatment, and their reliability in clinical application. Methods Setup errors of anthropomorphic phantom (chest& abdomen, head& neck) were simulated with x-, y-, z-directions. CBCT images were acquired for each simulation and registered with planning CT. using bony structure and grey-scale registration separately. Geometry accuracy of all registration were then obtained and analyzed. Results The errors of RBS and RGS in x-,y-,z-directions were (－0.65±0.22) mm and (－0.70±0.17) mm (P=0.00),(1.02±0.27) mm and (0.90±0.20) mm (P=0.00),(1.46±0.53) mm and (1.47±0.47) mm (P=0.54) for head& neck positioning;with (0.82±0.33) mm and (0.79±0.18) mm (P=0.03),(2.45±1.17) mm and (1.61±0.84) mm (P=0.00),(1.44±3.25) mm and (0.19±1.11) mm (P=0.00) for chest& abdomen positioning. Conclusions RGS is more accurate and stable than RBS. The accuracy of image registration is a little better for head& neck than that for chest& abdomen. The algorithms of image registration used in clinical application needs to be tested independently and the systematic error needs to be corrected before applying in different treatment techniques according to their accuracy requirement.