Geometric qualification for robot CT with flexible trajectories

Abstract

Robot CT systems bring great flexibility to X-ray CT based inspection scans. The system geometry needs to be well calibrated in order to avoid serious artifacts in the reconstructed volume. However, conventional calibration methods are normally designed for circular paths, which may be insufficient for a robot CT system. This paper proposes a phantom based geometric qualification method which supports nearly any view points. This is achieved by automatically mapping 3D-2D features based on collinear markers. The position and orientation of the X-ray focal spot and the detector are determined for each image of the reference phantom. This can be used for the CT reconstructions of later scans with the same trajectory. It is also possible to use the acquired geometries parameters to calibrate the underlying robots. The approach is validated on experimentally acquired data and the uncertainty is estimated by a Monte-Carlo based method.