Calibration of the Circle-plus-Arc Trajectory

In this paper, a novel calibration method for C-arm cone-beam (CB) scanners is presented which allows the calibration of the circle-plus-arc trajectory. The circle-plus-arc trajectory has been investigated recently for exact image reconstruction and is especially well suited for C-arm systems. The main idea is the separation of the trajectory into two segments (circle segment and arc segment) which are calibrated independently. For each trajectory segment, a calibration phantom is placed in an optimal way. The calibration results are then combined by computing the transformation the phantom experienced inbetween the independent runs. This combination can be done in a postprocessing step by using the singular value decomposition (SVD). The method works for any calibration procedure in which the phantom has a favored orientation with respect to a trajectory segment. Results are presented for both, simulated as well as real data acquired with a Siemens AXIOM Artis C-arm system.