CALIBRATION METHOD FOR RING ARTIFACT CORRECTION IN NON-IDEAL ISOCENTRIC 3D ROTATIONAL X-RAY SCANNER SYSTEMS USING A CALIBRATION PHANTOM BASED ROTATION CENTER FINDING ALGORITHM
The present invention refers to 3D rotational X-ray imaging systems for use in computed tomography (CT) and, more particularly, to a fast, accurate and mathematically robust calibration method for determining the effective center of rotation (I) in not perfectly isocentric 3D rotational C-arm systems and eliminating substantially circular ring artifacts (RA) which arise when using such a CT scanner system for acquiring a set of 2D projection images of an object of interest to be three- dimensionally reconstructed. For this purpose, a C-arm based rotational CT scanner comprising at least one radiation detector (D) having an X-radiation sensitive surface ex- posed to an X-ray beam emitted by at least one X-ray tube (S), each rotating along a non-ideal circular trajectory (TF, TCD) about an object of interest to be three- dimensionally reconstructed from a set of 2D projection images is used for providing geometrical calibration data by scanning a calibration phantom from a plurality of distinct projection directions and calculating, for each projection direction, the 3D positions of the X-ray tubes focal spot and the X-ray detectors center. For approximating the exact 3D position and angular direction of the axis of rotation about which the at least one X- ray tube and the at least one radiation detector rotate, a circular regression technique using a number of mathematically robust least squares fits is applied.La présente invention concerne des systèmes dimagerie à rayons X rotationnels 3D destinés à être utilisés en tomodensitométrie (TDM). Plus particulièrement, linvention concerne un procédé d’étalonnage rapide, précis et mathématiquement robuste, permettant de déterminer le centre efficace de rotation (I) dans des systèmes darceau rotationnels 3D isocentriques non parfaits, et déliminer des artéfacts danneau sensiblement circulaires (RA) qui apparaissent lors de lutilisation dun tel système de TDM. Linvention vise à permettre lacquisition dun ensemble dimages de
