Submillimeter diffusion MRI using in-plane segmented 3D multi-slab EPI and a denoiser-regularized reconstruction

Motivation: Submillimeter diffusion MRI is desirable for neuroscientific research but suffers from intrinsically low SNR. Goal(s): To achieve submillimeter isotropic resolution in-vivo diffusion MRI with superior SNR and minimal blurring and distortion. Approach: We quantify the effective resolution and SNR for high-resolution diffusion-weighted EPI, based on which a 3D Fourier encoding-based acquisition with in-plane segmented multi-slab EPI at 7T and a denoiser-regularized reconstruction framework are developed. Results: In-vivo whole-brain experiments at 0.61 mm isotropic resolution reveal more detailed microstructure compared to 1.05 mm data, which also demonstrates great consistency with a previous post-mortem study. The acquired data also exhibit great anatomical fidelity. Impact: Our study achieves 3D Fourier-encoded 0.61 mm isotropic resolution whole-brain in-vivo diffusion MRI with minimal blurring and distortion and superior SNR, showing great potential to reveal more detailed depiction of microstructure of the living human brain and advance neuroscientific research.