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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
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
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机译：基于基于校准幻影的旋转中心查找算法的非理想等角3D旋转X射线扫描仪系统中伪影校正的校准方法
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摘要
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 tube's focal spot and the X-ray detector's 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.
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