Second-line Sonazoid-enhanced ultrasonography for Liver Imaging Reporting and Data System category 3 and 4 on gadoxetate-enhanced magnetic resonance imaging

Purpose: This study investigated the utility of second-line contrast-enhanced ultrasonography (CEUS) using Sonazoid in Liver Imaging Reporting and Data System category 3 (LR-3) and 4 (LR-4) observations on gadoxetate-enhanced magnetic resonance imaging (MRI). Methods: This retrospective study included LR-3 or LR-4 observations on gadoxetate-enhanced MRI subsequently evaluated with CEUS from 2013 to 2017. The presence of MRI features, CEUS-arterial phase hyperenhancement (CEUS-APHE), and Kupffer phase defect (KPD) was evaluated. Multivariable logistic regression analysis was performed to identify significant imaging features associated with the diagnosis of hepatocellular carcinoma (HCC). The optimal diagnostic criteria were investigated using the McNemar test. Results: In total, 104 patients with 104 observations (63 HCCs) were included. The presence of both CEUS-APHE and KPD on CEUS enabled the additional detection of 42.3% (11/26) of LR-3 HCCs and 78.4% (29/37) of LR-4 HCCs. Transitional phase (TP) hypointensity (adjusted odds ratio [OR], 10.59; P<0.001), restricted diffusion (adjusted OR, 7.55; P=0.004), and KPD (adjusted OR, 7.16; P=0.003) were significant imaging features for HCC diagnosis. The presence of at least two significant imaging features was optimal for HCC diagnosis (sensitivity, specificity, and accuracy: 88.9%, 78.1%, and 84.6%, respectively), with significantly higher sensitivity than the presence of both CEUS-APHE and KPD (sensitivity, specificity, and accuracy: 63.5% [P=0.001], 92.7% [P=0.077], and 75.0% [P=0.089], respectively). Conclusion: The combined interpretation of gadoxetate-enhanced MRI and second-line CEUS using Sonazoid, focusing on TP hypointensity, restricted diffusion, and KPD, may be optimal for further characterizing LR-3 and LR-4 observations.