Simultaneous 3D T1$$ {\mathrm{T}}_1 $$, T2$$ {\mathrm{T}}_2 $$, and fat‐signal‐fraction mapping with respiratory‐motion correction for comprehensive liver tissue characterization at 0.55 T

Abstract

PurposeTo develop a framework for simultaneous three‐dimensional (3D) mapping of , , and fat signal fraction in the liver at 0.55 T.MethodsThe 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.ConclusionA 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.