Linearity, Bias, and Precision of Hepatic Proton Density Fat Fraction Measurements by Using MR Imaging: A Meta-Analysis

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A meta-analysis of pooled data collected from 28 published studies demonstrated excellent linearity, negligible bias, and high precision of proton density fat fraction measurements by using MR imaging across different field strengths, imager manufacturers, and reconstruction methods.


To determine the linearity, bias, and precision of hepatic proton density fat fraction (PDFF) measurements by using magnetic resonance (MR) imaging across different field strengths, imager manufacturers, and reconstruction methods.

Materials and Methods

This meta-analysis was performed in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. A systematic literature search identified studies that evaluated the linearity and/or bias of hepatic PDFF measurements by using MR imaging (hereafter, MR imaging–PDFF) against PDFF measurements by using colocalized MR spectroscopy (hereafter, MR spectroscopy-PDFF) or the precision of MR imaging–PDFF. The quality of each study was evaluated by using the Quality Assessment of Studies of Diagnostic Accuracy 2 tool. De-identified original data sets from the selected studies were pooled. Linearity was evaluated by using linear regression between MR imaging–PDFF and MR spectroscopy-PDFF measurements. Bias, defined as the mean difference between MR imaging–PDFF and MR spectroscopy-PDFF measurements, was evaluated by using Bland-Altman analysis. Precision, defined as the agreement between repeated MR imaging–PDFF measurements, was evaluated by using a linear mixed-effects model, with field strength, imager manufacturer, reconstruction method, and region of interest as random effects.


Twenty-three studies (1679 participants) were selected for linearity and bias analyses and 11 studies (425 participants) were selected for precision analyses. MR imaging–PDFF was linear with MR spectroscopy-PDFF (R2 = 0.96). Regression slope (0.97; P < .001) and mean Bland-Altman bias (−0.13%; 95% limits of agreement: −3.95%, 3.40%) indicated minimal underestimation by using MR imaging–PDFF. MR imaging–PDFF was precise at the region-of-interest level, with repeatability and reproducibility coefficients of 2.99% and 4.12%, respectively. Field strength, imager manufacturer, and reconstruction method each had minimal effects on reproducibility.


MR imaging–PDFF has excellent linearity, bias, and precision across different field strengths, imager manufacturers, and reconstruction methods.

© RSNA, 2017

Online supplemental material is available for this article.

An earlier incorrect version of this article appeared online. This article was corrected on October 2, 2017.


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Article History

Received March 9, 2017; revision requested April 21; revision received May 4; accepted June 5; final version accepted June 8.
Published online: Sept 11 2017
Published in print: Feb 2018