Quantitative measurement of ultrasound attenuation and Hepato-Renal Index in Non-Alcoholic Fatty Liver Disease

Abstract

The aim of this study was to non-invasively explore new methods of ultrasound attenuation measurements in livers of patients with Non-Alcoholic-Fatty-Liver-Disease (NAFLD) and to measure the liver tissue elasticity. Sixteen patients with NAFLD, twelve patients with liver fibrosis and fifteen healthy subjects were included. Echo Levels (ELs) in dB were measured at 2 and 7 cm depths in the right liver to calculate the attenuation. ELs were measured in liver and right kidney tissue to calculate the Hepato-Renal Index (HRI). This index was calculated both as a difference, HRI-diff; (EL Liver -EL Kidney) and HRI-ratio; (EL Liver / EL Kidney) using built-in software of the ultrasound scanner. Liver tissue elasticity was measured using transient elastography (TE, Fibroscan®). NAFLD and liver fibrosis were confirmed by liver biopsy. We found that HRI- diff was significantly higher in the NAFLD group compared with healthy subjects, 6.2 dB (0.8-11.4) vs.1. 9 dB (0.0-6.1), p=0.012. HRI- ratio was significantly lower between the same two groups, 0.9 dB (0.8-1.02) vs.1.01 dB (0.9-1.12), and p<0.0001. TE, ELs and liver size showed significant differences between NAFLD patients and healthy controls. Between patients with fibrosis and NAFLD the differences were significant for TE, liver size and attenuation. Intra- and interobserver correlation and agreement of ELs were good. Measurements of liver tissue using HR-Indexes, ultrasound attenuation, and tissue elasticity may be useful methods to differentiate objectively between steatosis and healthy and quantify the differences.