Nonhypervascular Hypointense Nodules at Gadoxetic Acid-enhanced MR Imaging in Chronic Liver Disease: Diffusion-weighted Imaging for Characterization

Purpose: To compare the diagnostic performance of magnetic resonance (MR) imaging features, including those on diffusion-weighted (DW) and T2-weighted images, in differentiating between hypovascular hepatocellular carcinoma (HCC) and dysplastic nodules seen as hypointense nodules at hepatobiliary phase gadoxetic acid-enhanced MR imaging. Materials and Methods: The institutional review board approved this retrospective study and waived the need to obtain informed patient consent. There were 53 patients (39 men and 14 women; age range, 32-75 years) with histologically proven hypovascular HCCs (n = 25) and/or dysplastic nodules (n = 31) who underwent gadoxetic acid-enhanced MR imaging at 3.0-T between March 2011 and January 2014. Images of 25 HCCs and 31 dysplastic nodules were analyzed for nodule size; signal intensity on T1- and T2-weighted, portal venous phase, and DW (b value = 800 sec/mm(2)) images; and intralesional fat. Correlations between the hyperintensity grade of lesions and the liver-to-lesion signal intensity ratio at T2-weighted and DW imaging were determined by means of analysis with generalized estimating equations. Results: Hyperintensity at T2-weighted and DW imaging and hypointensity in the portal venous phase were significant features for differentiating hypovascular HCCs from dysplastic nodules (P < .05). The sensitivity of DW imaging tended to be higher than that of T2-weighted imaging (72.0% [18 of 25] vs 40.0% [10 of 25]; P = .008 for grade 2 and 3 hyperintensity). Use of the parameter of hyperintensity similar to or slightly lower than the signal intensity of the spleen on DW images (b value = 800 sec/mm(2)) yielded a specificity of 100% (31 of 31) for the diagnosis of hypovascular HCC by differentiating it from a dysplastic nodule. Conclusion: Hyperintensity at DW imaging could be a useful MR imaging feature for differentiating hypovascular HCCs from dysplastic nodules seen as hypointense nodules at gadoxetic acid-enhanced MR imaging.