PI-partner based motion detection and motion artifact reduction

We present an algorithm for helical cone-beam CT, which can detect motion based on the analysis of so-called PI-partners. For each object point, the two independent measurements of the line integral along the PI-line of this object point are considered. It is shown in a simulation study that a difference in these two values correlates well with the occurrence of motion artifacts, if no redundant data are used for the reconstruction. Compared with other projection based motion detection techniques, our approach does not require any rebinning or approximations and it provides a spatially resolved motion estimate and works also in the case of truncated projections. The motion detection method can be readily applied to other complete trajectories like the saddle trajectory.