The development of MRI-based measures of liver fat (PDFF) has received great attention in the last 10 years. Although MRS-based measures have been long been feasible, MRI has the advantages related to whole-liver imaging and greater distributability. These techniques are now available from the major MRI vendors and are being offered by a variety of imaging labs for use in multi-center clinical trials.

Much of the excitement around PDFF measures was motivated by the rising prevalence of non-alcoholic steatohepatitis (NASH), a metabolic disease characterized by abnormal triglyceride (fat) deposition in the liver which leads to liver inflammation, fibrosis, cirrhosis, and ultimately liver failure and/or liver cancer. It was hoped that measures of PDFF would be helpful in the diagnosis and characterization of NASH, and in particular the differentiation between NASH and non-alcoholic fatty liver (NAFL), a state in which abnormal triglyceride deposition is present in the liver, but the downstream effects which lead to morbidity and mortality do not develop.

As drug development for NASH has continued, there is a growing awareness that NASH may simply represent a particular phenotype of the metabolic syndrome, which can also manifest with obesity, diabetes mellitus, coronary artery disease, and peripheral atherosclerosis. Many drugs developed for the treatment of individual phenotypes have been found to have efficacy against other components of the metabolic syndrome, for example some drugs designed for control of blood glucose also can normalize LFTs and lead to reductions in liver fat content.

Some of the focus in fatty liver imaging has shifted toward imaging changes in metabolism, for example in attempting to assess the proportions of saturated and unsaturated fatty acids present in hepatic steatosis, or in measuring location of abdominal fat deposition and relative proportions of fat and skeletal muscle. These developments may herald a paradigm shift form imaging isolated processes to measuring metabolic changes that reflect the overall health of the patient.