Distinction between pure steatosis and NASH using fat quantification method in combination with liver intravoxel incoherent motion imaging in MRI at 3.0T

In the past decade, the incidence rise of obesity, particularly of childhood obesity (1), diabetes and lipid metabolism disorders involved an epidemic increase of Non-Alcoholic Fatty Liver Diseases (NAFLD) prevalence which was estimated at 33.6 % in the USA (2) and between 20 and 30 % in Europe (3). In about 20 % of cases, NAFLD evolves to its aggressive form known as Non-Alcoholic SteatoHepatitis (NASH) and characterized by inflammation and fibrosis in addition to steatosis. Many of these patients may lead to cirrhosis, the end-stage of liver fibrosis. Complications such as hepatic decompensation, portal hypertension and hepatocellular carcinoma (HCC) are becoming a growing public health concern. Fat content quantification and distinction between pure steatosis and NASH is clinically important and drive the therapeutic strategy. While histology after liver biopsy is the gold standard for liver steatosis diagnosis to distinguish between NASH and pure steatosis, inherent risk with a recognized morbidity and mortality renders this method unsuitable and problematic for longitudinal clinical monitoring, particularly on children (4). Furthermore, liver biopsies have other limitations such as cost, inter-observer variability and sampling errors (5). For these reasons, non-invasive and cost effective quantification methods have been developed to quantify liver fat content (6,7). These latter allow an accurate quantification of fat content but are inadequate to separate between pure steatosis and NASH. On another hand, intra-voxel incoherent motion imaging (IVIM) has been proposed to asses liver fibrosis (8). Thus, the aim of this study was to evaluate the combination of liver IVIM and a MRI fat quantification method at 3.0 T to make the distinction between NASH and pure steatosis.