The precision of radiostereometric measurements. Manual vs. digital measurements.

X-Ray Photogrammetry. Basic Geometry and Quality

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.

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Dan Talmage

Papers

Uncalibrated x-ray stereo reconstruction