Validation of a motion-robust 2D sequential technique for quantification of hepatic proton density fat fraction during free breathing

Abstract

Background: Current chemical-shift-encoded (CSE) MRI techniques for measuring hepatic proton density fat fraction (PDFF) are sensitive to motion artifacts.

Purpose: Initial validation of a motion-robust 2D-sequential CSE-MRI technique for quantification of hepatic PDFF.

Study type: Phantom study and prospective in vivo cohort.

Population: Fifty adult patients (27 women, 23 men, mean age 57.2 years).

Field strength/sequence: 3D, 2D-interleaved, and 2D-sequential CSE-MRI acquisitions at 1.5T.

Assessment: Three CSE-MRI techniques (3D, 2D-interleaved, 2D-sequential) were performed in a PDFF phantom and in vivo. Reference standards were 3D CSE-MRI PDFF measurements for the phantom study and single-voxel MR spectroscopy hepatic PDFF measurements (MRS-PDFF) in vivo. In vivo hepatic MRI-PDFF measurements were performed during a single breath-hold (BH) and free breathing (FB), and were repeated by a second reader for the FB 2D-sequential sequence to assess interreader variability.

Statistical tests: Correlation plots to validate the 2D-sequential CSE-MRI against the phantom and in vivo reference standards. Bland-Altman analysis of FB versus BH CSE-MRI acquisitions to evaluate robustness to motion. Bland-Altman analysis to assess interreader variability.

Results: Phantom 2D-sequential CSE-MRI PDFF measurements demonstrated excellent agreement and correlation (R² > 0.99) with 3D CSE-MRI. In vivo, the mean (±SD) hepatic PDFF was 8.8 ± 8.7% (range 0.6-28.5%). Compared with BH acquisitions, FB hepatic PDFF measurements demonstrated bias of +0.15% for 2D-sequential compared with + 0.53% for 3D and +0.94% for 2D-interleaved. 95% limits of agreement (LOA) were narrower for 2D-sequential (±0.99%), compared with 3D (±3.72%) and 2D-interleaved (±3.10%). All CSE-MRI techniques had excellent correlation with MRS (R² > 0.97). The FB 2D-sequential acquisition demonstrated little interreader variability, with mean bias of +0.07% and 95% LOA of ± 1.53%.

Data conclusion: This motion-robust 2D-sequential CSE-MRI can accurately measure hepatic PDFF during free breathing in a patient population with a range of PDFF values of 0.6-28.5%, permitting accurate quantification of liver fat content without the need for suspended respiration.

Level of evidence: 1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;48:1578-1585.

Keywords: hepatic steatosis; liver; magnetic resonance imaging; motion; motion artifact; proton density fat fraction.