Hepatocellular Adenoma and Focal Nodular Hyperplasia: Value of Gadoxetic Acid-enhanced MR Imaging in Differential Diagnosis.

Purpose: To retrospectively evaluate the utility of gadoxetic acid-enhanced magnetic resonance (MR) imaging in the differential diagnosis of hepatocellular adenoma (HCA) and focal nodular hyperplasia (FNH). Materials and Methods: This study had institutional review board approval; the requirement for informed consent was waived. Eighty-two patients (58 patients with FNH and 24 patients with HCAs) with 111 lesions were included in the study. There were 74 female patients and eight male patients (mean age, 41.9 years ± 13.2 [standard deviation]; age range, 11-78 years). Two readers reviewed all images in terms of signal intensity (SI) features on unenhanced, dynamic, and hepatobiliary phase images. For quantitative analysis, contrast enhancement ratio (CER), lesion-to-liver contrast (LLC), and SI ratio on dynamic and hepatobiliary phase images were calculated. Results: The CER of FNH in the arterial phase (mean, 94.3\% ± 33.2) was significantly higher than that of HCAs (mean, 59.3\% ± 28.1) (P < .0001). During the hepatobiliary phase, the LLC of FNH showed minimally positive values (mean, 0.05 ± 0.01) and that of HCAs demonstrated strong negative values (mean, -0.67 ± 0.24) (P < .0001). The area under the receiver operating characteristic curve of the hepatobiliary phase SI ratio for differentiation of the two tumors was 0.97, and a sensitivity of 92\% and specificity of 91\% were found with a cutoff value of 0.87. Among six FNH lesions that showed atypical hypointensity during the hepatobiliary phase, four had a large central scar, one contained a substantial fat component, and one had abundant radiating fibrous septa. Three HCAs were isointense during the hepatobiliary phase owing to severe hepatic steatosis. Conclusion: Gadoxetic acid-enhanced MR imaging facilitates the differentiation of FNH from HCA. © RSNA, 2012 Supplemental material: http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.11101742/-/DC1.