Added Value of sequentially performed gadoxetic acid-enhanced liver MRI for the diagnosis of small (10-19 mm) or atypical hepatic observations at contrast-enhanced CT: A prospective comparison.

BACKGROUND: Small hepatocellular carcinomas (HCCs) often show atypical features at cross-sectional imaging, yet there is no preferred recommendation for the diagnosis or characterization of small observations (10-19 mm) at present.

PURPOSE: To determine the added value of sequentially performed gadoxetic acid-enhanced liver MRI for contrast-enhanced computed tomography (CECT)-detected small (10-19 mm) or atypical hepatic observations ≥20 mm in the diagnosis of HCC.

STUDY TYPE: Prospective, cross-sectional, intraindividual comparison.

POPULATION: In all, 110 patients at high risk of developing HCC.

FIELD STRENGTH/SEQUENCE: 1.5T and 3T/T1 -weighted imaging.

ASSESSMENT: Hepatic observations were classified into HCCs or benign non-HCCs based on imaging features of arterial phase hyperenhancement (APHE) and portal or delayed washout at CT or APHE and portal washout at MRI. Final diagnoses were established using a composite algorithm and diagnostic performances of MRI and CT were compared in all observations. In addition, in a subgroup of histologically confirmed observations and stable benign observations during follow-up (n = 94), sensitivity and specificity of MRI were compared between the aforementioned criteria and LR-5 of Liver Imaging Reporting and Data System v2014.

STATISTICAL TEST: χ2 test.

RESULTS: MRI provided higher sensitivity than CT (62.2% vs. 27.0%, P = 0.0001) while maintaining specificity (97.2%, each) at the per-patient level. Among 124 observations, 10-19 mm in size, MRI showed significantly higher sensitivity in diagnosing HCCs (62.5%, 50/80) than CT (25%, 20/80, P < 0.0001) with comparable specificity (97.7% [43/44], each). However, seven atypical observations (≥20 mm) at CT remained atypical at MRI. In the subgroup analysis, the diagnostic criteria of APHE and portal washout showed a significantly higher sensitivity (44.2%, 19/43) than LR-5 (23.2%, 10/43, P = 0.004), without compromising specificity (97.7% vs. 95.5%).

DATA CONCLUSION: Sequentially performed gadoxetic acid-enhanced MRI provided added value to CECT for the diagnosis of HCCs in small observations by improving sensitivity while maintaining specificity.

LEVEL OF EVIDENCE: 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018.