Liver steatosis and steato-hepatitis have become major global health care issues. Recently, the scope of Non-Alcoholic Fatty Liver Disease (NAFLD) was extended to Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD), to include the metabolic side of the disease. Fat accumulation in hepatocytes (steatosis) can lead to the development of liver inflammation, which is crucial for the progression to fibrosis. Noninvasive assessment is essential for both initial diagnosis and follow-up. Although various biomarkers are under evaluation, larger clinical trials are still needed.

The reference biomarkers for liver assessment derive from magnetic resonance imaging: MR-PDFF for the quantification of liver steatosis and MR-Elastography (MR-E) for fibrosis. Despite their accuracy, MRI techniques face limitations including availability and patient tolerance, particularly in teenagers and heavily obese patients.

The acoustic attenuation coefficient is a tissue-dependent physical property that quantifies how much the acoustic intensity drops in unit of distance. As ultrasound travels through soft tissue, absorption and scattering reduce the acoustic intensity. This coefficient can be measured and is linked to liver steatosis, as increased liver fat leads to more acoustic beam attenuation. Shear wave elastography (SWE) measures tissue elasticity in kPa by generating and tracking shear waves in the tissue. Their speed is directly linked to the tissue stiffness: faster shear waves suggest stiffer tissue. SWE can assess liver fibrosis which hardens the liver.

Ultrasounds parameters such as the attenuation of the ultrasound beam (US-ATI) and the tissue stiffness from shear wave elastography (SWE) can be quantified on commercial scanners and are correlated to steatosis and fibrosis grades, respectively. US-ATI and SWE are widely available and could offer an alternative to MRI techniques (MR-PDFF, MR-E). The reliability of both magnetic resonance and ultrasound exams depends on measurement variability. This study aims to evaluate the variability of MR-PDFF, MR-E, US-ATI and SWE in assessing MASLD.