Robust fat fraction mapping in the presence of magnetic field inhomogeneities with phase-cycled bSSFP

Motivation: The current implementation of fat fraction quantification based on phase-cycled bSSFP suffers from water-fat swaps due to magnetic field inhomogeneities. Goal(s): To develop an approach to simultaneously estimate magnetic field inhomogeneities and fat fraction maps from phase-cycled bSSFP data to avoid water fat swaps. Approach: Phase-cycled bSSFP-based B0 and fat fraction maps were compared with multi-echo gradient-echo (MEGRE)-based maps. Results: Phase-cycled bSSFP-based B0 and fat fraction estimations matched with the reference and significantly increased the quality of fat fraction maps. The method avoided water-fat swaps, even in regions with large field inhomogeneities. Impact: Mapping and correcting magnetic field inhomogeneities improves phase-cycled bSSFP fat fraction mapping, enabling its use in complex anatomical regions such as liver and potentially broadening its applicability in low-SNR settings as low-field MRI, where fat fraction mapping is typically challenging.