Accurate and spatially stable quantification of hepatic steatosis using ultrasound-derived fat fraction in metabolic dysfunction-associated steatotic liver disease (MASLD): a prospective magnetic resonance imaging-proton density fat fraction (MRI-PDFF) study

Background: Accurate and noninvasive quantification of hepatic steatosis is essential for managing metabolic dysfunction-associated steatotic liver disease (MASLD). This study evaluated the diagnostic accuracy, spatial stability, and clinical correlates of ultrasound-derived fat fraction (UDFF) in MASLD patients. Methods: In this prospective study of an Asian population, we enrolled 109 patients with MASLD and 20 healthy controls. UDFF was measured across hepatic segments V-VIII, with the mean value (UDFF mean) calculated. Magnetic resonance imaging-proton density fat fraction (MRI-PDFF) served as the reference standard. Diagnostic performance, agreement, and determinants were assessed using receiver operating characteristic (ROC) curves, Bland-Altman analysis, and multivariable regression. Results: UDFF mean increased stepwise with MRI-PDFF-defined steatosis grades (P<0.0001). The areas under the curve (AUCs) for detecting ≥S1, ≥S2, and S3 steatosis were 1.00, 0.99, and 0.99, respectively. Optimal cut-off values were 5.09%, 11.18%, and 18.46%. UDFF demonstrated excellent reproducibility with an intraclass correlation coefficient (ICC) of 0.98 and showed no significant systematic bias on Bland-Altman analysis. Alanine aminotransferase (ALT), gamma-glutamyl transferase (GGT), age, and sex were independently associated with UDFF (all P<0.05). Conclusions: UDFF provides a stable and accurate ultrasound-based assessment of hepatic fat burden in MASLD, with excellent agreement with MRI-PDFF and high spatial reproducibility, supporting its clinical utility for noninvasive risk stratification and longitudinal monitoring.