Estimating vertebral orientation from biplanar radiography based on contour matching

This paper proposed an approach for estimating 3D orientation of a vertebra given its 3D model and 2D biplanar radiographs. The estimation was based on the Hough transform technique to match the projections of the standard 3D primitive with the vertebral contours in biplanar radiographs, where the projected contours were generated from the 3D model by sampling the viewing sphere with a hierarchical scheme. The average computing time was 9.5 minutes. Seventeen vertebral models were used to evaluate the accuracy of the proposed method. Results showed that the mean of the estimation errors was 3.9o. It indicates that this approach may help orthopedic surgeons measure the vertebral orientation from 2D radiographs for better assessment of scoliosis.