Accuracy and precision of proton density fat fraction measurement across field strengths and scan intervals: A phantom and human study

Background Complex‐based chemical shift imaging‐based magnetic resonance imaging (CSE‐MRI) is emerging as a preferred method for noninvasively quantifying proton density fat fraction (PDFF), a promising quantitative imaging biomarker (QIB) for longitudinal hepatic steatosis measurement. Purpose To determine linearity, bias, repeatability, and reproducibility of the PDFF measurement using CSE‐MRI (CSE‐PDFF) across scan intervals, MR field strengths, and readers in phantom and nonalcoholic fatty liver disease (NAFLD) patients. Study Type Institutional Review Board (IRB)‐approved prospective. Subjects Fat‐water phantom and 20 adult patients. Field Strength/Sequence 1.5 T and 3.0 T MR systems and a commercially available CSE‐MRI sequence (IDEAL‐IQ). Assessment Two independent readers measured CSE‐PDFF of fat‐water phantom and NAFLD patients across two field strengths and scan intervals (same‐day and 2‐week) each and in a combination of both. MR spectroscopy‐based PDFF (MRS‐PDFF) was used as the reference standard for phantom PDFF. Statistical Tests Linearity and bias of measurement were evaluated by linear regression analysis and Bland–Altman plots, respectively. Repeatability and reproducibility were assessed by coefficient of variance and repeatability / reproducibility coefficients (RC). The intraclass correlation coefficient was used to validate intra‐ and interobserver agreements. Results CSE‐PDFF showed high linearity and small bias (–0.6–0.4 PDFF%) with 95% limits of agreement within ±2.9 PDFF% across field strengths, 2‐week interscan period, and readers in the clinical scans. CSE‐PDFF was highly repeatable and reproducible both in phantom and clinical scans, with the largest observed RC across field strengths and 2‐week interscan period being 3 PDFF%. Data Conclusion CSE‐PDFF is a robust QIB with high linearity, small bias, and excellent repeatability/reproducibility. A change of more than 3 PDFF% across field strengths within 2 weeks of scan interval likely reflects a true change, which is well within the clinically acceptable range. Level of Evidence : 3 Technical Efficacy : Stage 2 J. Magn. Reson. Imaging 2019;50:305–314.