Simultaneous 3D , , and fat-signal-fraction mapping with respiratory-motion correction for comprehensive liver tissue characterization at 0.55 T.

Purpose: To develop a framework for simultaneous three-dimensional (3D) mapping of , , and fat signal fraction in the liver at 0.55 T.

Methods: The proposed sequence acquires four interleaved 3D volumes with a two-echo Dixon readout. and are encoded into each volume via preparation modules, and dictionary matching allows simultaneous estimation of , , and for water and fat separately. 2D image navigators permit respiratory binning, and motion fields from nonrigid registration between bins are used in a nonrigid respiratory-motion-corrected reconstruction, enabling 100% scan efficiency from a free-breathing acquisition. The integrated nature of the framework ensures the resulting maps are always co-registered.

Results: , , and fat-signal-fraction measurements in phantoms correlated strongly (adjusted ) with reference measurements. Mean liver tissue parameter values in 10 healthy volunteers were , , and for , , and fat signal fraction, giving biases of , , and percentage points, respectively, when compared to conventional methods.

Conclusion: A novel sequence for comprehensive characterization of liver tissue at 0.55 T was developed. The sequence provides co-registered 3D , , and fat-signal-fraction maps with full coverage of the liver, from a single nine-and-a-half-minute free-breathing scan. Further development is needed to achieve accurate proton-density fat fraction (PDFF) estimation in vivo.