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

Abstract

Purpose 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. Results 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 (R = 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. Conclusion 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.

Proton density fat fraction MRI of vertebral bone marrow: Accuracy, repeatability, and reproducibility among readers, field strengths, and imaging platforms

“…Only small, although statistically significant, differences were observed among the three MR imagers for both readers. Particularly, there was a trend for slightly higher PDFF values on the Philips scanners compared with those on the GE platform, which is consistent with the results from a recent large‐scaled meta‐analysis . The reason for these findings is uncertain at this point, but two factors could possibly account for this observation: first, incompletely corrected T 1 ‐bias is thought to be a significant source of error in chemical shift‐encoding‐based fat quantification and may induce PDFF overestimation, as outlined below.…”

“…In patients, previous studies on steatosis quantification have shown high linear correlation and small mean bias in MRI‐determined PDFF ranging from 0.9–3.7% across two and three different MRI platforms. In our study, the reproducibility of MRI‐determined PDFF in lumbar bone marrow was comparable to or even better than that reported for liver fat quantification, possibly owing to the inherent heterogeneity of steatosis across the liver (ie, because of different ROI locations) . Only small, although statistically significant, differences were observed among the three MR imagers for both readers.…”

“…In this study, MRS‐determined PDFF of the third lumbar vertebra (L3) served as the reference standard for PDFF estimation. MRS has generally been accepted as the noninvasive reference standard for quantifying tissue fat concentration, used in both epidemiologic studies and randomized controlled clinical trials to derive the highest level of evidence . Repeatability was defined as the agreement between repeated measurements under near‐identical conditions.…”

“…PDFF is an objective MRI‐based measure of an inherent tissue property and can be defined as the density of hydrogen protons attributable to fat, normalized by the total hydrogen proton density from all mobile proton species . While MRI‐determined PDFF has been proven as a reliable noninvasive quantitative imaging biomarker (QIB) for the assessment of liver steatosis, its impact on bone marrow fat quantification is a significant, yet not so well‐explored issue. Owing to the distinct microarchitectural characteristics of the bone, it is important to validate the precision of MRI‐determined PDFF for bone marrow fat quantification for several reasons: first, bone marrow adipose tissue is not homogeneously distributed within the trabecular bone matrix and can exhibit a wider range of fat content than most visceral organs, ranging from 0–80% .…”

Diurnal Variation of Proton Density Fat Fraction in the Liver Using Quantitative Chemical Shift Encoded MRI

“…Over the last decade, emerging quantitative magnetic resonance imaging (MRI) biomarkers of hepatic steatosis such as proton density fat fraction (PDFF) have been developed, measured using confounder‐corrected chemical shift‐encoded MRI (CSE‐MRI). There has been a tremendous amount of work evaluating the bias, precision, reproducibility, and repeatability of CSE‐MRI to quantify PDFF in the liver . Despite this work there is a relative paucity of data investigating the variation of liver PDFF during the day, between days, as well as variation in liver PDFF resulting from hydration status and meals.…”