Analytic calibration of cone-beam scanners

We are investigating a direct analytic method of determining all geometric calibration parameters for a cone-beam scanner. Each projection is independently calibrated using a common calibration object that remains fixed in the laboratory frame. We make no assumptions or restrictions on the path of the cone vertex (e.g. the X-ray source) or the movement of the detector but we do assume a known field-of-view common to all views. The method uses a calibration object consisting of 30 small balls lying on 3 orthogonal concentric circles and one additional ball at the center of the calibration object. From parametrizations of the 3 image ellipses it is possible to analytically obtain expressions for all the calibration parameters. Using simulations we present our first results with this method, and by adding uncertainty to the locations of the projected balls, we determine the stability of the method. Our ultimate goal is to develop a completely automated calibration procedure requiring no user intervention whatsoever, and providing a seamless link to the reconstruction procedure