鼻咽癌进行图像引导放疗时不同配准方法对体位校正的影响

目的探讨鼻咽癌进行图像引导放疗时不同图像配准方法对体位校正的影响。方法用不同的图像配准方法,对37例鼻咽癌患者在进行图像引导放疗时所获得的47对电子射野影像（EPID）和计划系统生成的数字重建图像（DRR）进行配准分析。方法A：系统自动选择窗宽窗位后进行图像灰度配准。方法B：系统自动选择窗宽窗位后以第一颈椎体前缘中点作为配准点进行自动配准。方法C：在方法A的基础上手动调节窗宽窗位后进行图像灰度配准。方法D：在方法B的基础上手动调节窗宽窗位后,再以第一颈椎体前缘中点作为配准点进行自动配准。在四种不同配准方式下,分别得靶区在X和Y轴方向的摆位误差,再用SPSS13.0统计软件对所得结果进行配对样本t检验。结果方法A与B、B与D相比,靶区在X、Y轴上的摆位误差均有显著差异（P〈0.05）;方法A与C、C与D相比,靶区在X、Y轴上的摆位误差均无差异（P〉0.05）。结论鼻咽癌进行图像引导放疗时,基于图像灰度的摆位误差校正与基于第一颈椎体前缘中点摆位误差校正差异明显。

Effect of Different Image Matching Methods on the Position Correction for Nasopharyngeal Carcinoma Patients Underwent Image Guided Radiation Therapy

Objective To investigate the effects of different image matching methods on the position correction for nasopharyngeal carcinoma patients underwent image guided radiation therapy （IGRT）. Methods 47 pairs of digitally reconstructed radiograph （DRR） images generated by the treatment planning system and port images taken by electronic portal imaging device （EPID） during the course of set up, which come from 37 nasopharyngeal carcinoma patients underwent IGRT, were analyzed by four different image matching methods. Method A：the DRR and EPID images were matched at window width and level automatically chosen by the system, which were based on image gray-scale. Method B：the midpoin of anterior border of first cervical vertebra on DRR and EPID images were matched at automatical window width and level. Method C and D are similar with method A and B, respectively. But manual adjustment of window width and level is allowed. The setup errors of different matching methods on X, Y axes were compared with each other by t test with SPSS13.0 software. Results The setup errors on X, Y axes are significantly different for method A vs. B or B vs. D （P〉0.05）. But no significant difference for method A vs. C or C vs. D （P〈0.05）. Conclusion The setup errors based on image gray-scale and midpoint of anterior border of first cervical vertebra for nasopharyngeal carcinoma patients underwent IGRT are obviously different.