Objective: The purpose of this study was to define imaging features that may help characterize hyperintense lesions seen in the hepatobiliary phase of gadoxetic acid-enhanced hepatic MRI examinations.
Materials and methods: This retrospective study included 48 hyperintense nodules depicted on gadoxetic acid disodium-enhanced hepatobiliary phase MR images: 16 hepatocellular carcinomas (HCCs), 14 lesions of focal nodular hyperplasia, and 18 benign nodules associated with cirrhosis. Two observers independently reviewed hepatobiliary phase images and recorded the shape, margin, focal defects in contrast uptake, nodule-in-nodule pattern of uptake, central scar, internal septation, and presence of a hypointense rim around the lesion. Interobserver agreement was assessed with kappa statistics, and consensus opinions were reached by conference. For quantitative analysis, one observer measured lesion-to-liver contrast ratio (signal intensity of tumor divided by signal intensity of liver) on hepatobiliary phase images. Logistic regression analysis was used to determine the value of individual clinical and MR findings in prediction of malignancy.
Results: Compared with benign lesions, hyperintense HCC more commonly had focal defects in uptake (68.8% vs 3.1%, respectively; p < 0.001), nodule-in-nodule appearance (75.0% vs 0%, p < 0.001), absence of a central scar (100% vs 46.9%, p < 0.001), internal septation (50.0% vs 3.1%, p < 0.001), and a hypointense rim (75.0% vs 15.6%, p < 0.001) on hepatobiliary phase MR images. The mean contrast ratios of HCC (1.31) and benign lesions (1.28) were not significantly different (p = 0.63). Multiple logistic regression analysis showed that a focal defect in contrast uptake (p = 0.025) and a hypointense rim (p = 0.019) were significant predictors of HCC, having odds ratios of 36.8 (95% CI, 1.56-870.0) and 17.5 (1.60-191.4).
Conclusion: On gadoxetic acid-enhanced MR images, hyperintense nodules can be differentiated with several imaging characteristics, especially a focal defect in contrast uptake and a hypointense rim, that indicate the diagnosis of hyperintense HCC.