Nonalcoholic Fatty Liver Disease: US-based Acoustic Radiation Force Impulse Elastography

Purpose: To investigate the clinical usefulness of ultrasonography-based acoustic radiation force impulse (ARFI) elastography (ie, ARFI sonoelastography) in patients with a diagnosis of nonalcoholic fatty liver disease (NAFLD) and compare ARFI sonoelastography results with transient sonoelastography and serum fibrosis marker test results. Materials and Methods: Written informed consent was obtained from all subjects, and the local ethics committee approved the study. Fifty-four patients with a liver biopsy-confirmed diagnosis of NAFLD (mean age, 50.6 years +/- 13.7) were examined. All patients with NAFLD and healthy volunteers underwent ARFI sonoelastography, transient sonoelastography, and serum liver fibrosis marker testing (hyaluronic acids, type IV collagen 7 S domain). Ten healthy volunteers underwent ARFI sonoelastography. ARFI sonoelastography results were compared with liver biopsy findings, the reference standard. ARFI sonoelastography findings were compared with liver biopsy, transient sonoelastography, and serum fibrosis marker test results. Student t testing was used for univariate comparisons; Kruskal-Wallis testing, for assessments involving more than two independent groups; and areas under the receiver operating characteristic curve (A(z)), to assess the sensitivity and specificity of ARFI sonoelastography for detection of stage 3 and stage 4 fibrosis. Results: Median velocities in the patients with NAFLD were 1.040 m/sec for those with stage 0 fibrosis, 1.120 m/sec for those with stage 1, 1.130 m/sec for those with stage 2, 1.780 m/sec for those with stage 3, and 2.180 m/sec for those with stage 4. The A(z) for the diagnosis of hepatic fibrosis stages 3 or higher was 0.973 (optimal cutoff value, 1.77 m/sec; sensitivity, 100%; specificity, 91%), while that for the diagnosis of stage 4 fibrosis was 0.976 (optimal cutoff value, 1.90 m/sec; sensitivity, 100%; specificity, 96%). Significant correlations between median velocity measured by using ARFI sonoelastography and the following parameters were observed: liver stiffness measured with transient sonoelastography (r = 0.75, P < .0001), serum level of hyaluronic acid (r = 0.459, P = .0009), and serum level of type IV collagen 7 S domain (r = 0.445, P = .0015). Conclusion: There is a significant positive correlation between median velocity measured by using ARFI sonoelastography and severity of liver fibrosis in patients with NAFLD. The results of ARFI sonoelastography were similar to those of transient sonoelastography. (C) RSNA, 2010