Small hypervascular hepatocellular carcinoma: limited value of portal and delayed phases on dynamic magnetic resonance imaging

BACKGROUND: Characterization of small nodules in the cirrhotic liver is always challenging in clinical practice. In the differential diagnosis of small hypervascular lesions, it has been reported that portal venous or delayed hypointensity is a useful sign to characterize hepatocellular carcinomas (HCCs) during dynamic magnetic resonance (MR) imaging. However, few studies have assessed the diagnostic value of this sign. PURPOSE: To determine the diagnostic value of portal-phase (PP) and delayed-phase (DP) images for the diagnosis of small hypervascular HCCs during intravenous (IV) contrast-enhanced dynamic MR imaging of cirrhotic liver. MATERIAL AND METHODS: A total of 69 small (6-20 mm) hypervascular HCCs in 53 cirrhotic patients were subjected to a retrospective analysis of the signal intensities (hypo-, iso-, or hyperintense) and rim enhancement on PP and 5-min DP images from three-phased dynamic MR imaging according to the pre-contrast T1- and T2-weighted imaging features. After exclusion of 33 subcapsular wedge-shaped pseudolesions and three hemangiomas by typical imaging features, 74 centrally located small hypervascular benign or pseudolesions were used as a control group for comparative analyses. RESULTS: The sensitivities of PP hypointensity, DP hypointensity, and rim enhancement in the diagnosis were 11%, 29%, and 18%, respectively, for 6-10-mm hypervascular HCCs, and 42%, 63%, and 58%, respectively, for 16-20-mm lesions. After exclusion of the 48 lesions showing T2-weighted hyperintensity (HCCs, n = 39; benign lesions, n = 9), the overall sensitivity for diagnosis of small hypervascular HCCs decreased (8.3%, 25.0%, and 8.3%, respectively). CONCLUSION: Although DP provides a better sensitivity than PP, both PP and DP have very limited diagnostic value for diagnosis of small hypervascular HCCs during dynamic MR imaging of the cirrhotic liver.ope