Utility of Liver Imaging Reporting and Data System v2018 Ancillary Features for the Diagnosis of Hepatocellular Carcinoma in LR-4 Lesions Using Contrast-enhanced Magnetic Resonance Imaging

Objective: To evaluate the diagnostic performance of Liver Imaging Reporting and Data System (LI-RADS) version 2018 ancillary features for the diagnosis of hepatocellular carcinoma (HCC) from LR-4 ('probably HCC') lesions using gadoxetic acid-enhanced magnetic resonance imaging. Methods: This retrospective study evaluated 166 LR-4 lesions including ancillary features in 114 high-risk cases imaged with gadoxetic acid-enhanced magnetic resonance imaging between March 2015 and December 2017. Two radiologists evaluated the imaging features using LI-RADS v2018. All lesions were confirmed as HCC or benign lesions by pathological assessment or >2 years of follow-up imaging. The diagnostic contribution of ancillary features was assessed using simple and multivariable logistic regression and generalised estimating equations. Results: In all, 114 HCCs (68.7%) and 52 benign lesions (31.3%) were confirmed. Simple logistic regression analysis revealed that mild to moderate T2 hyperintensity (p = 0.014), restricted diffusion (p < 0.001), and intralesional fat (p = 0.018) were statistically significant for differentiating HCCs from benign lesions; however, multivariable logistic analysis revealed that only restricted diffusion was statistically significant (adjusted odds ratio = 9.703, p < 0.001). Restricted diffusion had lower sensitivity (48.2%) and higher specificity (90.4%) for the diagnosis of HCC; however, the diagnostic values improved when combined with mild to moderate T2 hyperintensity and hepatobiliary phase hypointensity (sensitivity: 73.8%, specificity: 80.8%). Conclusion: Among ancillary LI-RADS v2018 imaging features, restricted diffusion is the diagnostic feature most accurately distinguishing HCCs from benign abnormalities in LR-4 lesions.