Validation of the non-stereo corresponding points stereoradiographic 3D reconstruction technique

Several 3D reconstruction techniques deriving from stereoradiographic DLT h ave been presented during the last 15 years, but these techniques have usua lly been limited in accuracy because of the small number of corresponding a natomical landmarks identified on both radiographs. A new technique has rec ently been proposed to perform 30 reconstruction of the spine using not onl y the stereo-corresponding anatomical landmarks (seen on both frontal and s agittal X-ray films) but also some non-stereo-corresponding ones. This tech nique (called non-stereo-corresponding points or NSCP) has already been use d for cervical dry vertebrae. In the present study, we focus on the validat ion of this technique for lumbar vertebrae by comparing four techniques: di rect measurement, CT scan, 30 reconstruction by stereoradiography using a d irect linear transformation (DLT) algorithm and the NSCP technique. The acc uracy of the NSCP technique was also evaluated on different vertebral regio ns. The global results show mean errors of 1.1mm and maximum of 7.8mm with regard to direct measurements. These mean errors are close to those obtaine d using 30 reconstructions from CT scan using 1mm cuts.