Rapid Imaging Assessment of the Liver Using Multiparametric Magnetic Resonance

Obesity per se as a cause of liver dysfunction and failure has been well studied. However, although it is a very common disease, at present the only reliable way to diagnose it is with percutaneous liver biopsy. This is painful and not without risk, as the liver is a highly vascular organ. Even with ultrasound guidance, it is still a diagnostic test that is underused as it carries a 1:1000 risk of serious adverse events (eg bleeding, infection, bowel perforation) because it is invasive. Moreover, the patients requiring the test often have impaired clotting of their blood due to liver dysfunction, and so are at higher risk of bleeding, and need to be observed in hospital for a few hours after the procedure. This adds to the cost of the procedure. As a result of these factors, liver biopsy is not used in all patients for whom NAFLD, NASH or other liver disease are suspected, unless the patients have clinically moderate to severe disease.

With the increasing prevalence of obesity in the community, NASH and NAFLD are becoming increasingly common, and there is a need for a reliable, feasible and cost-effective non-invasive diagnostic tool for these conditions. Moreover, they often coexist with other liver diseases (eg tumours, or autoimmune liver disease). There are approximately 1.5million UK adults with mild to moderate liver disease which, at present, cannot be ascertained non-invasively.

Developments in magnetic resonance medicine may allow us to accurately diagnose liver fibrosis, using the amount of extracellular fluid (ECF) as a biomarker for fibrosis. T1 mapping of the liver can reliably show differences in ECF content and thereby allow quantification of the degree of liver fibrosis. In conjunction with MR spectroscopy and T2* mapping for concurrent interpretation of lipid and iron content, this will allow rapid non-invasive diagnosis of the type and/or severity of many common liver diseases (NAFLD/NASH, hepatitis, iron overload).