Liver steatosis quantification using magnetic resonance imaging: a prospective comparative study with liver biopsy.

BACKGROUND AND AIMS To prospectively determine the accuracy of liver fat quantification with magnetic resonance imaging (MRI). PATIENTS AND METHODS The population consisted of 40 patients (mean age, 52.5 years; range, 23-78 years). The same day, all patients underwent MRI and ultrasonography-guided liver biopsy. The histological evaluation of steatosis was performed by an experienced liver pathologist blinded to the MRI results. On T1-weighted in- and opposed-phase images, one radiologist, experienced in abdominal imaging, blinded to the clinical and pathological results, recorded signal intensity (SI) by mean regions of interest placed at same locations in both phases. Fat-water ratio was obtained by dividing SI of liver in opposed-phase sequence by SI of liver in in-phase sequence. The fat-water ratio and the histological grade of steatosis were compared by linear regression. Receiver operating characteristic curve was used to define the sensitivity and specificity of fat-water ratio as a diagnostic tool for evaluation of steatosis. RESULTS Diagnoses were nonalcoholic fatty liver disease (n = 25), alcoholic liver disease (n = 10), cholangiopathy (n = 2), and autoimmune hepatitis (n = 3). Fatty liver infiltration was present in 80% of patients. The mean (SD) percentage of fatty hepatocytes was 38.7% (29.2). Fat-water ratio and steatosis grade were highly correlated (r = 0.852, P < 0.0001). Sensitivity and specificity of fat-water ratio to detect fatty infiltration greater than 20% were 96% and 93%, respectively. CONCLUSIONS This prospective study demonstrates that MRI can be proposed as a noninvasive method to screen and quantify liver steatosis.