Navigator-free water/fat separation for multi-shot diffusion-weighted EPI using structured low-rank reconstruction

Multi-shot EPI readout-approaches provide high spatial resolution at reduced geometric distortions and improved SNR in diffusion weighted imaging (DWI). As a specific challenge, physiological motion induces shot-to-shot phase variations and needs specific handling, e.g., using additionally measured phase navigators, data-driven phase estimation and/or low-rank regularizations. Furthermore, good fat-suppression is also needed in DWI, making the use of chemical-shift encoding interesting. In this work, a structured low-rank-based water/fat separation pipeline is proposed to jointly estimate water/fat images while correcting motion-induced phase variations with improved time efficiency. In-vivo examples from different anatomies demonstrate improved water/fat separation compared to conventional approaches.