Diagnostic Performance of Gadoxetic Acid-enhanced Liver MR Imaging in the Detection of HCCs and Allocation of Transplant Recipients on the Basis of the Milan Criteria and UNOS Guidelines: Correlation with Histopathologic Findings

Purpose: To determine whether hepatobiliary phase (HBP) imaging can improve the diagnostic performance of gadoxetic acid-enhanced liver magnetic resonance (MR) imaging in the detection of hepatocellular carcinomas (HCCs) and to investigate the accuracy of gadoxetic acid-enhanced MR imaging in the allocation of transplant recipients on the basis of the Milan criteria and United Network for Organ Sharing (UNOS) guidelines. Materials and Methods: This retrospective study had institutional review board approval; the requirement for informed consent was waived. Between June 2008 and June 2011, 63 patients who underwent liver transplantation (LT) were included. All patients underwent a gadoxetic acid-enhanced 3.0-T MR imaging examination of the liver that included HBP images obtained 20 minutes after contrast material administration. Two abdominal radiologists independently assessed two MR imaging data sets to detect HCCs: Set 1 included unenhanced and gadoxetic acid-enhanced dynamic images, and set 2 also included HBP images. Patients were allocated into three groups: Those who did not meet the Milan criteria, those who did meet the Milan criteria with additional priority according to UNOS guidelines, and those who did meet the Milan criteria without additional priority. Diagnostic performance of each data set in depicting HCCs was compared by using jackknife alternative free-response receiver operating characteristics (JAFROCs). Sensitivity and accuracy of patient allocation were compared by using generalized estimating equations. Results: Sixty-three HCCs were found in 36 of 63 patients. Eight patients were classified as not meeting Milan criteria, 12 as meeting Milan criteria with additional priority, and 43 as meeting Milan criteria without additional priority. For the detection of HCCs, reader-averaged figures of merit estimated with JAFROCs were 0.761 for set 1 and 0.791 for set 2 (P < .001). Addition of HBP images significantly improved sensitivity for the detection of HCCs, particularly 1-2-cm HCCs (six [20.7%] vs 13 [44.8%] of 29 [P = .008] for reader 1 and eight [27.6%] vs 12 [41.4%] of 29 [P = .041] for reader 2). Accuracy of patient allocation was 88.9% for set 1 and 92.1% for set 2 (P = .151). Conclusion: Addition of HBP images can significantly improve the diagnostic performance of gadoxetic acid-enhanced liver MR imaging in the detection of 1-2-cm HCCs in liver transplantation candidates. In addition, gadoxetic acid-enhanced MR imaging showed 92.1% accuracy in patient allocation on the basis of the Milan criteria and UNOS guidelines. (C) RSNA, 2014