Model-based Estimation of Vertebrae from Uncalibrated Bi-Planar XRays

This paper presents a method and preliminary study for estimating the location of vertebrae from uncalibrated bi-planar radiographs. The method uses the axis/angle representation of rotations and exact analytic derivatives for optimising the objective function. Multiple vertebral models are incorporated in a single procedure. Results are shown on both real data in vivo and on simulated data. No ground truth for the real data is available, but sensible results are produced by the method in comparison with a method using numeric derivatives. Simulation results show that the method is robust to Gaussian errors in the landmarks and degrades gracefully as these errors increase.