Factors affecting assessment of liver steatosis with quantitative ultrasound

Objectives We aim to observe the diagnostic performance of quantitative ultrasound and their factors affecting assessment of liver steatosis with tissue attenuation imaging (TAI), and tissue scatter distribution imaging (TSI) in patients with non-alcoholic fatty liver disease (NAFLD). Materials We performed liver TAI, TSI ultrasound measurements with Samsung RS85 Prestige ultrasound system and prospectively enrolled 101 participants with suspected NAFLD. As a reference, magnetic resonance imaging proton-density-fat-fraction (MRI-PDFF) was performed, and patients were divided into ≤5%, 5%-10%, and ≥10% of MRI-PDFF groups. Kruskal-Wallis test with post-hoc Dunn's test was used to compare the TAI and TSI values between the three steatosis groups. Spearman's correlation analysis was used to determine correlation between TAI, TSI, and MRI-PDFF. Simple and multiple linear regression analysis were performed to identify independent predictors. The diagnostic performance of TAI, TSI was interpreted with area under the receiver operating characteristic curve (AUC). The intraclass correlation coefficient (ICC) was calculated to assess interobserver reliability. Results Kruskal-Wallis test showed significant difference between both steatosis groups (p<0.0001). Both TAI (ρ=0.78, p<0.001) and TSI (ρ=0.68, p<0.001) showed significant correlation with MRI-PDFF. MRI-PDFF proved to be an independent predictor of TAI (β=1.03; p<0.001), while both MRI-PDFF (β=50.9; p<0.001) and liver stiffness measures with shear wave elastography (β=-0.86; p<0.001) were independent predictors of TSI when adjusted for body mass index and liver capsule-to-skin distance. TAI overperformed TSI in the detection of both ≥5% MRI-PDFF (AUC=0.89 vs. 0.87) and ≥10% (AUC=0.93 vs. 0.86). Interobserver correlation analysis showed excellent reproducibility of TAI (ICC=0.95) and moderate reproducibility of TSI (ICC=0.73). Conclusions In a linear regression analysis MRI-PDFF was a significant independent predictor of both TAI and TSI while liver stiffness had weak but significant influence on TSI. Both TAI and TSI were reproducible methods for diagnosing fatty liver disease.