CALIBRATION METHOD FOR RING ARTEFACT CORRECTION IN NON-IDEAL ISOCENTRIC THREE-DIMENSIONAL ROTATIONAL X-RAY SCANNER SYSTEMS USING CALIBRATION PHANTOM BASED ROTATION CENTRE FINDING ALGORITHM

摘要

FIELD: physics.;SUBSTANCE: invention relates to three-dimensional (3D) rotational X-ray imaging systems for use in computed tomography. A pre-calibration method for eliminating substantially circular ring artefacts during 3D image reconstruction in a non-ideal isocentric 3D rotational X-ray scanner system comprises scanning a calibration phantom while moving an X-ray tube and an X-ray detector along a non-ideal circular trajectory, for each projection direction, calculating the 3D position of the focal spot of the X-ray tube and the 3D position of the centre of the X-ray detector from the obtained 2D projection images of the phantom, and determining, from the set of geometric calibration data obtained from the 3D calibration procedure performed based on the calculated 3D position data, 3D coordinates of the effective rotation centre around which the non-ideal isocentric 3D rotational X-ray scanner system rotates. A 3D rotational X-ray scanner system with a C-shaped arm comprises a calibration unit for the calibration method and an additional reconstruction for the reconstruction method. A computer-readable medium contains commands which enable to perform calibration and reconstruction on the 3D rotational X-ray scanner system. The 3D coordinates of the effective rotation centre are used for calibration of the scanner system or 3D image reconstruction.;EFFECT: use of the invention improves image quality by facilitating correction of circular ring artefacts.;14 cl, 5 dwg