X射线容积成像系统配准方式对中下段食管癌放疗体位验证的影响

目的 探讨X射线容积成像系统不同配准方式对中下段食管癌放射治疗中摆位误差的影响，为食管癌放射治疗提供参考。方法 随机选取63名中下段食管癌患者，对其首次治疗时XVI系统获取的重建图像，分别选择灰度配准和骨性配准方式进行系统自动配准，得到2种方法在x（左右）、y（头脚）、z（前后）方向的3个平移误差和3个旋转误差值并进行统计分析。结果 灰度配准在x、z方向的平移误差小于骨性配准（x方向t=-2.78,z方向t=-2.15,P <0.05），在y方向差异无统计学意义（P> 0.05）。3个旋转方向配准误差值均小于1°且灰度配准小于骨性配准，但差异无统计学意义（P> 0.05）。结论 对于中下段食管癌放疗建议选择灰度配准，实际工作中在自动配准后还应经人工确认或微调，同时除平移误差外也应关注旋转误差。

Effects of X-ray volume imaging registration methods on position verification for radiotherapy in treatment of middle/lower-segment esophageal cancer

Objective To compare the set up errors derived from different registration methods of the X-ray volume imaging (XVI) system for radiotherapy in the treatment of middle/lower-segment esophageal cancer, and to provide a reference for radiation treatment of esophageal cancer. Methods We randomly selected 63 patients with middle/lower-segment esophageal cancer, and obtained their reconstructed XVI images at the first therapy to perform automatic registration with gray-value and bone registration methods. We acquired and compared the three translation errors (along x [left to right], y [head to feet], and z [front to back] axes) and three rotation errors (around the x, y, and z axes) derived from the two registration methods. Results Gray-value registration had significantly smaller translation errors along the x and z axes than bone registration (x azes t = −2.78, z azes t = −2.15, P < 0.05), but there was no significant difference along the y axes (P > 0.05). The rotation errors around the three axes were all smaller than 1°, and were smaller with gray-value registration than with bone registration, but without significant differences (P > 0.05). Conclusion We recommend gray-value registration for radiotherapy in the treatment of middle/lower-segment esophageal cancer. Manual verification or fine-tuning is recommended after automatic registration in clinical practice. Besides translation errors, rotation errors should also be paid attention to.