立位脊柱三维重建技术在椎体轴向旋转角测量中的应用研究

Application of the standing spine three-dimensional reconstruction technology in the measurement of vertebral axial rotation

目的利用基于双平面X线的立位脊柱三维重建技术定量测量椎体轴向旋转角(Vertebral Axial Rotation,VAR)。并初步判断立位三维重建下测量VAR的精度。方法对一位主诉为腰痛的病人,加用标定装置拍摄腰椎正侧位X线片,标定装置上有数个小钢珠做成的已知三维坐标的标定点。依据Nash-Moe法,在平片上寻找出存在轴向旋转的椎体,运用相关软件,提取旋转椎体的VAR测量相关点在正侧位平片上投影点的二维坐标和平片上正侧位成像各自标定点的二维坐标。根据立位三维重建的基本原理,重建出VAR测量相关点的三维坐标。定量测量VAR,并和Nash-Moe法的测量结果进行对比,初步判断测量精度。结果发现1个存在轴向旋转的椎体,位于第3腰椎(Lumber vertebrae,L),Nash-Moe分度为1度,测量VAR为+2.3°。方向与双侧椎弓根形状变化一致,但数值不在Nash-Moe法(L_2-L_4,1度)相对应的旋转范围5-15°之内。结论本实验在国内率先利用基于双平面X线的立位脊柱三维重建技术定量测量出VAR,但测量精度需要进一步提高。

Objective To measure the vertebral axial rotation （VAR） using the standing spine three-dimensional reconstruction technology based on biplanar X-ray images, and to judge the accu- racy of VAR measurement using the standing spine three-dimensional reconstruction technology pre- liminarily. Methods One patient with the chief complaint of low back pain took the lumbar antero- posterior and lateral X-ray examination with the calibration device. On the calibration device, there were some calibration points made of small steel ball with known three dimensional coordinates. Using the related software, extracted two dimensional coordinates of VAR measuring points projections in the anteroposterior and lateral radiographs of the rotary vertebrae based on Nash-Moe method and cali- bration points of the anteroposterior and lateral imaging in the radiographs. According to the basic principles of the standing spine three-dimensional reconstruction, the three dimensional coordinates of the VAR measuring points were reconstructed. The VAR was measured quantitatively by the defini- tion. 3＇he measurement result was compared with the Nash-Moe method to determine the measurement accuracy preliminarily. Results Only one rotary vertebra was found （L3, ＋degree based on Nash-Moe method）. VAR was measured as ＋2.3°. The direction was correct, but the value was not in the rotation range given by the Nash-Moe method. Conclusions The VAR is measured quantitatively using the standing Spine three-dimensional reconstruction technology based on biplanar X-ray images first in China. However, the measurement accuracy needs to be further improved.