Gadoxetic acid-enhanced MRI of hepatocellular carcinoma: Value of washout in transitional and hepatobiliary phases

Background: Current Liver Imaging Reporting and Data System guidelines define the washout appearance of gadoxetic acid-enhanced MRI only during the portal venous phase. Defining washout only during the portal venous phase may lead to lower sensitivity for diagnosis of hepatocellular carcinoma (HCC). Purpose: To compare the diagnostic performances of three gadoxetic acid-enhanced MRI criteria for HCC according to the phases during which washout appearance was determined. Materials and Methods: In this retrospective study, patients with a hepatic nodule detected at US surveillance for HCC from January to December 2012 underwent gadoxetic acid-enhanced MRI. Three diagnostic MRI criteria for HCC were defined according to the phases during which washout appearance was observed, with the presence of arterial phase hyperenhancement and hypointensity noted (a) only during the portal venous phase, with washout confined to the portal venous phase; (b) during the portal venous phase or transitional phase, with washout extended to the transitional phase; or (c) during the portal venous, transitional, or hepatobiliary phase, with washout extended to the hepatobiliary phase. If a nodule showed marked T2 hyperintensity or a targetoid appearance, it was precluded from the diagnosis of HCC. The sensitivity and specificity were compared by using a generalized estimating equation. Results: A total of 178 patients were included (mean age 6 standard deviation, 55.3 years 6 9.1) with 203 surgically confirmed hepatic nodules (186 HCCs and 17 non-HCCs) measuring 3.0 cm or smaller. The sensitivity with washout extended to the hepatobiliary phase (95.2% [177 of 186]) was better than that with washout extended to the transitional phase (90.9% [169 of 186]; P = .01) and washout confined to the portal venous phase (75.3% [140 of 186]; P , .01). The specificity with extensions of washout to the transitional phase and hepatobiliary phase (82% [14 of 17] for both) was similar to that obtained with washout confined to the portal venous phase (94.1% [16 of 17]) (P = .47). Conclusion: After exclusion of typical hemangiomas and nodules with a targetoid appearance, extending washout appearance to the transitional or hepatobiliary phase (instead of restricting it to the portal venous phase) allowed higher sensitivity without a reduction in specificity.