MRI arterial enhancement fraction in hepatic fibrosis and cirrhosis

OBJECTIVE. Fibrosis leads to altered liver hemodynamics. The arterial enhancement fraction, which is defined as the ratio of hepatic arterial perfusion to the total hepatic perfusion, can provide noninvasive assessment of hepatic perfusion. The aim of this study was to show that the arterial enhancement fraction values correlate with histopathologic stage of liver fibrosis, thus providing a reliable noninvasive radiologic alternative to liver biopsy for the detection and staging of hepatic fibrosis. MATERIALS AND METHODS. We evaluated hepatic fibrosis stage (denoted by Metavir score [F]) and arterial enhancement fraction of patients who underwent standard triphasic liver MRI and liver biopsy within 1 year from January 2005 to December 2010. Prototype software was used to calculate the arterial enhancement fraction. Statistical analysis included nonparametric tests and area under the receiver operating characteristic curve (AUC). RESULTS. One hundred fourteen patients (69 men and 45 women; median age, 52.5 years) were divided into groups according to the Metavir score. The mean arterial enhancement fraction was 24.2% ± 11.6% for F0, 35.2% ± 18.7% for F1, 30.2% ± 12.5% for F2, 37.5% ± 16.4% for F3, and 59.8% ± 16.6% for F4. The mean arterial enhancement fraction values differed significantly between Metavir scores (p < 0.001) and showed a positive correlation with Metavir score (r = 0.693; p < 0.001). The optimal mean arterial enhancement fraction cutoffs were 32.96% or more (AUC = 0.8343) for detection of mild fibrosis, 33.33% or more (AUC = 0.8524) for detection of moderate fibrosis, 38.43% or more (AUC = 0.8819) for detection of severe fibrosis, and 45.76% or more (AUC = 0.9161) for detection of cirrhosis. CONCLUSION. Arterial enhancement fraction using triple-phase MRI can provide a reliable noninvasive method to assess hepatic fibrosis.