Simultaneous 3D T1, T2 and fat-signal-fraction mapping with respiratory-motion correction for comprehensive liver tissue characterization at 0.55?T

Abstract

Purpose: To develop a framework for simultaneous three-dimensional (3D)mapping of T1 , T2 , and fat signal fraction in the liver at 0.55 T.Methods: The proposed sequence acquires four interleaved 3D volumes witha two-echo Dixon readout. T 1 and T 2 are encoded into each volume via prepa-ration modules, and dictionary matching allows simultaneous estimation of T 1 ,T2 , and M0 for water and fat separately. 2D image navigators permit respiratorybinning, and motion fields from nonrigid registration between bins are used in anonrigid respiratory-motion-corrected reconstruction, enabling 100% scan effi-ciency from a free-breathing acquisition. The integrated nature of the frameworkensures the resulting maps are always co-registered.Results: T1 , T2 , and fat-signal-fraction measurements in phantoms correlatedstrongly (adjusted r2 > 0.98) with reference measurements. Mean liver tissueparameter values in 10 healthy volunteers were 427 ± 22, 47.7 ± 3.3 ms, and7 ± 2% for T1 , T 2 , and fat signal fraction, giving biases of 71, ?30.0 ms, and ?5percentage points, respectively, when compared to conventional methods.Conclusion: A novel sequence for comprehensive characterization of livertissue at 0.55 T was developed. The sequence provides co-registered 3D T 1 ,T2 , and fat-signal-fraction maps with full coverage of the liver, from a singlenine-and-a-half-minute free-breathing scan. Further development is needed toachieve accurate proton-density fat fraction (PDFF) estimation in vivo.K E Y W O R D Sliver, low-field MR, motion correction, NAFLD, quantitative imagingRadhouene Neji and René M. Botnar contributed equally to this work.This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided theoriginal work is properly cited.© 2024 The Author(s). Magnetic Resonance in Medicine published by Wiley Periodicals LLC on behalf of International Society for Magnetic Resonance in Medicine.Magn Reson Med. 2024;92:2433–2446. wileyonlinelibrary.com/journal/mrm 2433