An Approach to Graphically Evaluate Steatosis in Non-Alcoholic Fatty Liver Disease

Introduction Hepatic steatosis affects 30% of the adult population in the western world [1] and is characteristic of many chronic liver diseases. Currently, the gold-standard to determine the severity of liver disease, including steatosis, is liver biopsy, which is an invasive procedure prone to sampling error due to small specimen size (less than 1/50,000 of the liver) [2]. A major pitfall in the assessment of steatosis is its heterogeneous distribution. While MRI provides a non-invasive alternative to liver biopsy for quantification of steatosis with opposed-phase T1-weighted GRE imaging [3], the method depends on manually drawn regions of interest and cumbersome mathematical equations. Furthermore, quantification is affected by placement of regions of interest and could be misleading in the assessment of disease progression. The aim of this study was to develop a color mapping technique based on liver signal intensity loss on inand out-of-phase images to readily and accurately assess the steatosis grade and heterogeneity. Methods 38 patients diagnosed with non-alcoholic fatty liver disease (NAFLD, 20 men and 18 women; mean age 44 years, range 11-73) and 20 healthy volunteers (10 men and 10 women; mean age 31 years, range 22-48) underwent MRI using a 1.5T GE scanner. Coronal breath-hold T1-weighted dual fast gradient echo sequences were acquired of the abdomen (TR/TE 90/4.2 and 2.1 ms; flip angle 75°; slice/gap 8/1 mm; matrix 256x128-192, NEX 1). Patients underwent a liver biopsy for steatosis grading within 3 months of the MRI scan (average 23.7 days, median 12 days, range 0-83 days). The number of subjects with steatosis grades 0, 1, 2 and 3 were 5, 7, 11 and 15, respectively.