Intra-subject multi-slab registration: Application to hippocampal ultra-high resolution imaging at 7T

Magnetic Resonance Imaging (MRI) of anatomical structures usually requires a compromise between acquisition time and image resolution. In fact higher resolutions require longer acquisition times which may result in movement artifacts that alter image quality. With the progress of high field imaging, visualizing microstructural details of anatomical structures became possible. In the case of the hippocampus, which is a brain structure involved in memory, visualizing the inner structure of the hippocampus would allow a better characterization of Alzheimer disease and temporal lobe epilepsy. However quantifying the inner structure of the hippocampus requires at-most 300 μm in-plane resolutions; this yields long acquisitions sensitive to movement artifacts. In this work we propose a method to reduce movement artifacts for ultra-high resolution imaging. To do so, the long MR acquisition is split into shorter sub-slabs that are then registered to a low resolution short acquisition in order to reconstruct a 3D-consistent high resolution volume. This procedure is illustrated for ultra-high resolution imaging of the hippocampus inner structure at 7T. The registration method proved robust on 37 subjects.