Noninvasive diagnosis of hepatocellular carcinoma on gadoxetic acid-enhanced MRI: can hypointensity on the hepatobiliary phase be used as an alternative to washout?

OBJECTIVES: To determine which dynamic phase(s) of gadoxetic acid-enhanced MRI is most appropriate to assess "washout" in the noninvasive diagnosis of hepatocellular carcinoma (HCC) based on hemodynamic pattern.
METHODS: In this retrospective cohort study, 288 consecutive patients with chronic liver disease presented with 387 arterially enhancing nodules (292 HCCs, 95 non-HCCs) (≥1 cm) on gadoxetic acid-enhanced MRI. All HCCs were confirmed by histopathology or by their typical enhancement pattern on dynamic liver CT. MR imaging diagnosis of HCC was made using criteria of arterial enhancement and hypointensity relative to the surrounding parenchyma (1) on the portal-venous phase (PVP), (2) on the PVP and/or transitional phase (TP), or (3) on the PVP and/or TP, and/or hepatobiliary phase (HBP).
RESULTS: For the noninvasive diagnosis of HCC, criterion 1 provided significantly higher specificity (97.9%; 95% confidence interval, 92.6 - 99.7%) than criteria 2 (86.3%; 77.7 - 92.5%), or 3 (48.4%; 38.0 - 58.9%). Conversely, higher sensitivity was obtained with criterion 3 (93.8%; 90.4 - 96.3%) than with criterion 2 (86.6%; 82.2 - 90.3%) or 1 (70.9%; 65.3 - 76.0%).
CONCLUSIONS: To make a sufficiently specific diagnosis of HCC using gadoxetic acid-enhanced MRI based on typical enhancement features, washout should be determined on the PVP alone rather than combined with hypointensity on the TP or HBP. KEY POINTS: • Gadoxetic acid-enhanced MRI enhancement features can be used to diagnose HCC. • Washout should be determined on the PVP alone for high specificity. • Hypointensity on the TP or HBP increases sensitivity but lowers specificity.