Non-rigid correction of interleaving artefacts in pelvic MRI

This paper presents a novel method to reduce the effects of interleaving motion artefacts in single-plane MR scanning of the pelvic region without the need for k-space information. Interleaved image (or multipacket) acquisition is frequently used to reduce cross-talk and scanning time during full pelvic MR scans. Patient motion during interleaved acquisition can result in non-linear "staircase" imaging artefacts which are most visible on sagittal and coronal reconstructions. These artefacts can affect the segmentation of organs, registration, and visualization. A fast method has been implemented to replace artefact affected slices in a packet with interpolated slices based on Penney et al (2004) whose method involves the registration of neighbouring slices to obtain correspondences, followed by linear interpolation of voxel intensities along the displacement fields. This interpolation method has been applied to correct motion affected MRI volumes by firstly creating a new volume where every axial slice from the artefact affected packet is removed and replaced with an interpolated slice and then secondly for each of these slices, 2D non-rigid registration is used to register each original axial slice back to its matching interpolated slice. Results show visible improvements in artefacts particularly in sagittal and coronal image reconstructions, and should result in improved intensity based non-rigid registration results between MR scans (for example for atlas based automatic segmentation). Further validation was performed on simulated interleaving artefacts which were applied to an artefact free volume. Results obtained on prostate cancer radiotherapy treatment planning contouring were inconclusive and require further investigation.