Uncalibrated X-Ray Stereo Reconstruction

We describe a novel application of uncalibrated stereo reconstruction to Roentgen Stereophotogrammetry Analysis (RSA). In RSA, stereo X-ray images are taken of a bone containing a prosthesis (e.g. a replacement knee) and a number of metal markers. The aim is to recover the relative position of the prosthesis and markers in 3D. Accuracy in previous RSA methods has been limited by two factors: manual feature selection and an assumption that camera calibration parameters are known to high precision this is not the case in practice. Furthermore, the manual processing is slow and tedious. We report progress towards developing a fully automatic RSA system. New algorithms are described for automatically localising marker points in X-ray images to sub-pixel accuracy, and using them to reconstruct accurate 3D positions using robust statistical methods. Preliminary experiments give excellent results.