Achieving 2D sub-millimeter images using Phase-Encoded Frequency-modulated Rabi Encoded Echoes in a B0 gradientless inhomogeneous 0.5T magnet

Motivation: MRI is the gold standard diagnostic technique, yet it is widely inaccessible - techniques to reduce its cost often drop its image quality. Goal(s): Developing B1-encoded MRI pulse sequences that are immune to field inhomogeneity could enable the design of affordable, effective, and silent systems while retaining clinical-value. Approach: We propose a 2D B1 encoding sequence in a two-channel Tx/Rx system with perpendicular and decoupled surface coils. The experiments are carried out in an inhomogeneous 0.5T permanent magnet. Results: Experiments show phantom details with 0.2mm resolution using FFT and model-based reconstruction without any B0 gradients available. Impact: 2D FREE's results highlight the potential to enable high-resolution imaging despite large magnetic field inhomogeneities and no B0-gradient hardware. These advancements could enable new low-cost architectures that are effective and affordable, making MRI more accessible to the world.