Noninvasive imaging biomarkers for liver steatosis in NAFLD: present and future

Non-alcoholic fatty liver disease is currently the most common chronic liver disease, affecting up to 25% of the world's population. Simple fatty liver, in which fat is deposited in the liver without fibrosis, has been regarded as a benign disease in the past, but it is now known to be prognostic. In the future, more emphasis should be placed on the quantification of liver fat. Traditionally, fatty liver has been assessed by histological evaluation, which requires an invasive examination, but technological innovations have made it possible to evaluate fatty liver by noninvasive imaging methods such as ultrasonography, computed tomography, and magnetic resonance imaging. In addition, quantitative as well as qualitative measurements for the detection of fatty liver have become available. In this review, we summarize currently used qualitative evaluations of fatty liver and discuss quantitative evaluations that are expected to further develop in the future.