Quantitative assessment of fatty liver using ultrasound attenuation imaging

Non-alcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease, with an incidence of 20-40% worldwide, making it a major healthcare problem. Because NAFLD can progress to liver fibrosis and cirrhosis through non-alcoholic steatohepatitis, early detection and monitoring of hepatic steatosis are essential for management of NAFLD patients. Even though conventional B-mode ultrasound (US) has been widely used for the evaluation of NAFLD owing to its safety and easy accessibility, its subjective nature and limited accuracy in detecting mild steatosis are major limitations. To overcome the current limitations of conventional B-mode US, attenuation imaging (ATI) based on two-dimensional B-mode US has been developed. ATI can quantitatively assess the degree of hepatic steatosis by calculating the attenuation coefficient, which reflects the degree of US beam attenuation transmitted into the liver tissue. After the first study was published in 2019, several clinical studies using ATI to evaluate hepatic steatosis have reported promising results. In this review, the basic physics, measurement protocol, and reported diagnostic accuracy of ATI in evaluating hepatic steatosis will be discussed.