Accelerated B0 Mapping and Distortion Correction in Ultra-Low Field MRI Using Locally Low-Rank Reconstruction

Motivation: Low-field MRI systems are promising tools for accessible medical imaging but are highly sensitive to B0 inhomogeneities, especially in portable environments where external disturbances may affect magnetic fields. Goal(s): This study aimed to develop a method for accelerated B0 mapping and distortion correction in ultra-low field MRI, maintaining image quality while reducing scan time. Approach: We used a locally low-rank (LLR) reconstruction approach on two undersampled (R=2) datasets with shifted and unshifted TEs for B0 mapping and distortion correction. Results: LLR reconstruction provided high-quality distortion-corrected images comparable to fully-sampled (R=1) acquisitions, even under extreme inhomogeneity from simulated external magnetic disturbances. Impact: This approach enables faster, distortion-corrected imaging for low-field MRI in varied settings, expanding its potential for accessible, portable medical imaging in remote and resource-limited environments.