2D／3D影像配准在鼻咽癌放疗中的应用

目的：研究2D/3D像配准方法对鼻咽癌放疗中计划靶区PTV外扩距离的影响。方法应用OBI （On Board Image，OBI）系统获取2D影像（kV图像和PV图像）和3D影像（CBCT图像），将获取的2D和3D影像分别经DRR配准系统和模拟定位CT进行图像配准，确定前后、头脚、左右3个方向上的摆位误差，再由2种PTV外扩公式计算3个方向上的PTV外扩距离。结果2D和3D影像配准的PTV外扩值有所不同。kV，PV，CBCT三者配准误差相互比较P〉0.05，无统计学意义。结论kV图像和PV图像和CBCT图像都能很好地验证照射野位置。CBCT图像可以分析三维方向的影像误差，降低了2D图像影像重叠产生的摆位误差的影响。

Application of 2D/3D Image Registration in the Radiotherapy of Nasopharyngeal Carcinoma

Objective To study the effect of 2D/3D image registration on the extended distance of planning target volume （PTV） in the radiotherapy of nasopharyngeal carcinoma （NPC）. Methods Using OBI system to obtain two-dimensional images （kV images and PV images） and three-dimensional images （CBCT images）. Then registering 2D and 3D images by using DRR registration system and simulation positioning CT respectively to get the set-up errors of VRT, LNG, LAT. Then calculating the values of PTV extended distance of VRT, LNG, LAT with two kinds of PTV expansion formulas. Results The values of PTV extended distance between 2D and 3D images are different while there is no signiifcance in registration errors among kV, PV, CBCT images （P〉0.05）. Conclusion Both of 2D images （kV images and PV images） and 3D images （CBCT images） can verify the radiation field well. 3D image errors can be analyzed with CBCT images, which can reduce the inlfuence of set-up errors caused by image overlapping of 2D images.