Diagnostic accuracy of gadoxetic acid enhanced MR for small hypervascular hepatocellular carcinoma and the concordance rate of Liver Imaging Reporting and Data System (LI-RADS)

Background & aims To assess diagnostic accuracy of gadoxetic acid enhanced MR for small hypervascular hepatocellular carcinoma (HCC) detected by C-arm CT and concordance rate of Liver Imaging Reporting and Data System (LI-RADS). Methods In this retrospective study, we recruited 4,544 patients suspected of having HCC underwent C arm CT from November 2008 to May 2013. Among these patients, gadoxetic acid enhanced MR was performed in 167 patients with HCC (n = 379; 257 > 1 cm, 122 <= 1 cm). HCC was confirmed by MR, CT, or follow-up images. Two radiologists graded likelihood of HCC and assessed MR features. Jackknife alternative free-response receiver operating characteristic (JAFROC) analysis was performed. All HCCs were evaluated concordance rate of LI-RADS. Results Mean JAFROC figure of merit for large (> 1-cm) HCC was 0.948, while that for small HCC was 0.787 with fair agreement (K = 0.409). Mean sensitivity and positive predictive value (PPV) were 91% and 90% for large HCC versus 63.0% and 79% for small HCC, respectively. Seventeen of 122 small HCCs (13.9%) were not visible on MR. Among 379 HCCs, 99 met LR-5, and 259 met LR-4. Common features for small HCC included arterial enhancement (81.9%), hepatobiliary phase hypointensity (80.3%), and delayed washout (72.9%). Conclusion Diagnostic accuracy of gadoxetic acid enhanced MR imaging for small, hypervascular HCCs (Mean figure of merit = 0.787) was still low compared with large HCC (Mean figure of merit = 0.948). LR-5 and LR-4 covered 94% (358/379) of the HCCs.