3-D reconstruction of the spine from biplanar radiographs based on contour matching using the Hough transform.

The purpose of this study was to develop and evaluate a method for three-dimensional (3-D) reconstruction of the spine from biplanar radiographs. The approach was based on vertebral contour matching for estimating vertebral orientations and locations. Vertebral primitives were initially positioned under constraint of the 3-D spine midline, which was estimated from manually identified control points. Vertebral orientations and locations were automatically adjusted by matching projections of 3-D primitives with vertebral edges on biplanar radiographs based on the generalized Hough transform technique with a deformation tolerant matching strategy. We used graphics processing unit to accelerate reconstruction. Accuracy and precision were evaluated using radiographs from 15 scoliotic patients and a spine model in 24 poses. On in vivo radiographs, accuracy was within 2.8° for orientation and 2.4 mm for location; precision was within 2.3° for orientation and 2.1 mm for location. results were slightly better on model radiographs than on in vivo radiographs but without significance (p>0.05). The duration for user intervention was less than 2 min, and the computation time was within 3 min. Results indicated the method's reliability. It is a promising tool to determine 3-D spinal geometry with acceptable user interaction.