A. Ladikos, W. Wein Geometric calibration using bundle adjustment for cone-beam computed tomography devices SPIE Medical Imaging, February 2012, San Diego, USA. (bib)
	In this paper we present a novel geometric calibration procedure for cone-beam computed tomography (CBCT) devices with arbitrary geometry using a calibration phantom containing steel beads. In contrast to typical calibration procedures the position of the beads does not have to be known precisely as it is also recovered during calibration. In addition, the arrangement of the beads inside the phantom is very flexible and does not have to follow hard constraints. The bead centers are extracted with subpixel precision from the projection images while taking the absorption properties of the calibration phantom into account. Based on the recovered center positions and phantom geometry, the projection geometry is computed for every projection image. This geometry can be arbitrary and does not have to lie on a specific path, e.g. a circle. This allows to calibrate devices with reproducible mechanical errors in the gantry movement. We present an evaluation of the point extraction and the calibration procedure on ground-truth data and show reconstruction results on a device calibrated using the proposed calibration method.
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