Gadoxetic acid-enhanced magnetic resonance imaging: Hepatocellular carcinoma and mimickers

Gadoxetic acid, a hepatocyte-specific magnetic resonance imaging (MRI) contrast agent, has emerged as an important tool for hepatocellular carcinoma (HCC) diagnosis. Gadoxetic acid-enhanced MRI is useful for the evaluation of early-stage HCC, diagnosis of HCC precursor lesions, and highly sensitive diagnosis of HCC. Furthermore, functional information provided by gadoxetic acid-enhanced MRI can aid in the characterization of focal liver lesions. For example, whereas lesions lack functioning hepatocytes appear hypointense in the hepatobiliary phase, preserved or enhanced expression of organic anion transporting polypeptides in some HCCs as well as focal nodular hyperplasia lead to hyperintensity in the hepatobiliary phase; and a targetoid appearance on transitional phase or hepatobiliary phase imaging can be helpful for identifying the histopathological composition of tumors. While gadoxetic acid-enhanced MRI may improve the sensitivity of HCC diagnosis and provide new insights into the characterization of focal liver lesions, there are many challenges associated with its use. This article reviews the pros and cons of HCC diagnosis with gadoxetic acid-enhanced MRI and discuss some clues in the radiological differentiation of HCC from HCC mimickers.

Failure of hepatocellular carcinoma surveillance: inadequate echogenic window and macronodular parenchyma as potential culprits

PURPOSE: The purpose of this study was to examine the associations between ultrasonography (US) quality and clinical outcomes in patients undergoing surveillance for hepatocellular carcinoma. METHODS: Between 2008 and 2013, 155 patients were diagnosed with liver cancer during regular surveillance by positive US results (US group, n=82) or by computed tomography (CT) or magnetic resonance image (MRI) scanning as alternative modalities (CT/MRI group, n=73). The quality of the echogenic window, macronodularity of the liver parenchyma, and occurrence of surveillance failure (initial tumor diagnosis beyond the Milan criteria or at Barcelona Clinic Liver Cancer stage B or C) were evaluated. Overall survival was compared according to whether surveillance failure occurred. RESULTS: The patients in the CT/MRI group with negative US results had a higher proportion of parenchymal macronodularity on US than those in the US group (79.5% vs. 63.4%, P=0.028). Surveillance failure tended to be more common in the US group than in the CT/MRI group (40.2% vs. 26.0% by the BCLC staging system [P=0.061]). In the US group, surveillance failure occurred more frequently when the echogenic window was inadequate (50.0% vs. 19.4% by the Milan criteria [P=0.046]). Significantly poorer 5-year overall survival was associated with surveillance failure (P≤0.001). CONCLUSION: Parenchymal macronodularity hindered the detection of early-stage tumors during US surveillance. Using an alternative imaging modality may help prevent surveillance failure in patients with macronodular parenchyma on US. Supplemental surveillance strategies than US may also be necessary when the echogenic window is inadequate.