A regularized reconstruction pipeline for high-definition diffusion MRI in challenging regions incorporating a per-shot image correction

Abstract

Purpose: Diffusion MRI is of interest for clinical research and diagnosis. Whereas high- resolution DWI/DTI is hard to achieve by single-shot methods, interleaved acquisitions can deliver these if motion and/or folding artefacts are overcome. Thanks to its ability to provide zoomed, folding-free images, spatially encoded MRI can fulfill these requirements. This is here coupled with a regularized reconstruction and parallel receive methods, to deliver a robust scheme for human DWI/DTI at mm and sub-mm resolutions. Methods: Each shot along the spatially encoded dimension was reconstructed separately to retrieve per-shot phase maps. These shots, together with coil sensitivities, were combined with spatially encoded quadratic phase-encoding matrices associated to each shot, into single global operators. Their originating images were then iteratively computed aided by l1 and l2 regularization methods. When needed, motion-corrupted shots were discarded and replaced by redundant information arising from parallel imaging. Results: Full-brain DTI experiments at 1 mm and restricted brain DTIs with 0.75 mm nominal in-plane resolutions were acquired and reconstructed successfully by the new scheme. These 3 Tesla spetiotemporally encoded results compared favorably with EPI counterparts based on segmented and selective excitation schemes provided with the scanner. Conclusion: A new procedure for achieving high-definition diffusion-based MRI was developed and demonstrated.