Using an MRI distortion transfer function to characterize the ghosts in motion-corrupted images

Motion artefact suppression remains an active topic in MRI. In this paper, the authors suggest that certain nonrigid, or spatially variant, characteristics of motion of an object can be represented by extending the work of Mitsa et al. (1989). This empirical extension uses a ghost distortion transfer function (GTDF) applied to the k-space (frequency domain) data. The authors demonstrate the variety of ghost characteristics that can be generated from various two-dimensional (2-D) GTDF´s. The distortion transfer function for periodic motion along the Z-axis can be determined from the nonoverlapped portions of the ghost and central image. It required a GDTF with the shape of a belt bandpass filter to produce an image corresponding to the ghosts of a volunteer´s abdomen image corrupted by unknown respiratory motion artefacts. The preliminary results of a composite method of motion artefact suppression are presented. The artefact suppression was successful for ghost images described by a GDTF have a low-pass nature, but less successful with ghosts have a GDTF of a bandpass nature.