Optimal lexicon of gadoxetic acid-enhanced magnetic resonance imaging for the diagnosis of hepatocellular carcinoma modified from LI-RADS

Purpose To define the optimal lexicon of major imaging findings on gadoxetic acid-enhanced MRIs to diagnose HCC to improve diagnostic performance of the LI-RADS. Methods Two hundred forty-one hepatic lesions (149 HCC, six other malignancies, 86 benign lesions) in 177 treatment-naive patients at risk of HCC who underwent gadoxetic acid-MRIs from January 2013 to December 2015 were retrospectively reviewed using either histopathological or follow-up imaging findings as a standard reference. Two board-certified radiologists independently evaluated the imaging features and categorized the nodules based on the original and the following modified definitions in LI-RADS: (1) washout appearance in the portal venous phase (PVP) only versus that in the PVP or transitional phase, and (2) enhancing capsule only versus enhancing or non-enhancing capsule. Diagnostic performance and inter-observer agreement of LR-5 were assessed and compared between the algorithms using generalized estimation equation. Results The sensitivity [79.2% (95% confidence interval 71.9, 85.0)] and accuracy [84.6% (79.5, 88.7)] of LR-5 were significantly higher for modified lexicon compared with original LI-RADS [60.4% (52.3, 67.9) and 73.9% (67.9, 79.0); P < 0.001 in all cases]. There was no significant difference in specificity [93.5% (86.2, 97.0) and 95.7% (89.0, 98.4); P = 0.153]. Subgroups of lesions < or >= 2 cm showed similar tendencies. Inter-observer agreement for capsule appearance was fair to moderate, whereas that for other imaging findings was good to excellent. Conclusions Compared to original LI-RADS, LI-RADS with modified lexicon showed higher sensitivity for the diagnosis of HCC using gadoxetic acid-MRI, with similar specificity.