Quantitative Ultrasound Assessment of Hepatic Steatosis

Abstract

Background/aims: Non-alcoholic fatty liver disease (NAFLD) is widespread chronic disease of the live in humans with the prevalence of 30% of the United States population.^1,2 The goal of the study is to validate the performance of quantitative ultrasound algorithms in the assessment of hepatic steatosis in patients with suspected NAFLD.

Methods: This prospective study enrolled a total of 31 patients with clinical suspicion of NAFLD to receive liver fat measurements by quantitative ultrasound and reference MRI measurements (proton density fat-fraction, PDFF). The following ultrasound (US) parameters based on both raw ultrasound RF (Radio Frequency) data and 2D B-mode images of the liver were analyzed with subsequent correlation with MRI-PDFF: hepatorenal index, acoustic attenuation coefficient, Nakagami coefficient parameter, shear wave viscosity, shear wave dispersion and shear wave elasticity. Ultrasound parameters were also correlated with the presence of hypertension and diabetes.

Results: The mean (± SD) age and body mass index of the patients were 49.03 (± 12.49) and 30.12 (± 6.15), respectively. Of the aforementioned ultrasound parameters, the hepatorenal index and acoustic attenuation coefficient showed a strong correlation with MRI-PDFF derivations of hepatic steatosis, with r-values of 0.829 and 0.765, respectively. None of the remaining US parameters showed strong correlations with PDFF. Significant differences in Nakagami parameters and acoustic attenuation coefficients were found in those patients with and without hypertension.

Conclusions: Hepatorenal index and acoustic attenuation coefficient correlate well with MRI-PDFF-derived measurements of hepatic steatosis. Quantitative ultrasound is a promising tool for the diagnosis and assessment of patients with NAFLD.

Keywords: ALT, alanine aminotransferase; AST, aspartate aminotransferase; BMI, body mass index; DICOM, digital imaging and communications in medicine; HIPAA, health insurance portability and accountability act; HRI, hepatorenal index; Hgb A1C, hemoglobin A1C (glycated hemoglobin); IQ, in-phase quadrature; IR, insulin resistance; LDL, low-density lipoprotein; MRI-PDFF, magnetic resonance imaging - proton density fat-fraction; NAFLD, non-alcoholic fatty liver disease; NASH, non-alcoholic steatohepatitis; RF, raw radio frequency; ROI, regions of interest; SD, standard deviation; T2DM, type 2 diabetes mellitus; US, ultrasound; liver fat quantification; non-alcoholic fatty liver disease; ultrasound.

Figure 1

Hepatorenal index DICOM and RF. A. Severe liver steatosis, HRI is 4.32 (PDFF = 25.4%). The difference in echogenicity between liver and renal cortical tissues is visibly significant. B. Healthy liver, HRI is 0.95 (PDFF = 1.3%). There is poor differentiation of echogenicity between liver and renal cortical tissues.

Figure 2

Images of acoustic Attenuation coefficient. A. Severe liver steatosis, AttenQ = 0.80 dB/MHz/cm (PDFF = 25.4%). B. Healthy liver, AttenQ = 0.46 dB/MHz/cm (PDFF = 1.3%).

Figure 3

Images of Nakagami parameters. A. Severe liver steatosis, Nakagami m = 0.95 (PDFF = 25.4%). B. Healthy liver, Nakagami m = 0.78 (PDFF = 1.3%).

Figure 4

MRI-PDFF images. A. Severe liver steatosis (PDFF = 25.4%), B. Normal liver (PDFF = 1.3%).

Figure 5

There is a strong correlation between hepatorenal index (HRI) and MRI-PDFF (r > 0.7).

Figure 6

There is a strong correlation between acoustic attenuation and MRI-PDFF (r > 0.7).