Diagnostic value of morphological enhancement patterns in the hepatobiliary phase of gadoxetic acid-enhanced MRI to distinguish focal nodular hyperplasia from hepatocellular adenoma.

To describe the different morphological enhancement patterns of focal nodular hyperplasia (FNH) and hepatocellular adenoma (HCA) in the hepatobiliary phase (HBP) of gadoxetic acid-enhanced MRI (Gd-EOB-DTPA MRI) and to determine their added value in their differential diagnosis. A retrospective analysis of imaging findings in 185 benign hepatocellular lesions (154 FNH; 31 HCA) in 108 patients who underwent Gd-EOB-DTPA MRI was performed by two independent reviewers. Six patterns on HBP were recorded: 1) homogeneous enhancement; 2) peripheral ring-like enhancement with hypointense central core; 3) peripheral ring-like enhancement with hyperintense central core; 4) central core enhancement with hypointense periphery; 5) heterogeneous enhancement; and 6) the absence of enhancement. Peripheral ring-like enhancement with hypointense central core and peripheral ring-like enhancement with hyperintense central core showed the highest specificity for the diagnosis of FNH (100% and 96.8%, respectively). The absence of enhancement and central core enhancement with hypointense periphery were only present in 0.6% and 1.9% of FHN, respectively. All other patterns were observed with similar frequencies in FNH (22.1% to 26.6%). Six HCA showed contrast uptake on the HBP: homogeneous (6.5%), peripheral ring-like enhancement with hyperintense central core (3.2%) and heterogeneous (9.7%). Both FNH and HCA may demonstrate enhancement in the HBP of Gd-EOB-DTPA MRI, limiting its specificity. A significant improvement in specificity can be achieved by the evaluation of morphological enhancement patterns: Peripheral ring-like enhancement with hypointense or hyperintense central core was highly specific for FNH diagnosis. On the other hand, the absence of HBP enhancement makes the diagnosis of FNH unlikely.