Objective: The purpose of this study was to determine the finding most predictive for characterizing hypervascular hepatocellular carcinoma (HCC) measuring 1 cm or less at gadoxetic acid-enhanced MRI that includes diffusion-weighted images.
Materials and methods: In this retrospective study, between May 2008 and June 2009, 66 patients with 108 hypervascular HCCs 1 cm or smaller underwent gadoxetic acid-enhanced 3-T MRI that included diffusion-weighted images. The diagnosis of HCC was determined by surgical resection in 32 cases, percutaneous biopsy in three cases, or interval growth to larger than 1 cm on follow-up images in accordance with the American Association for the Study of Liver Diseases guidelines in 73 cases. MRI findings of HCC and 33 benign hypervascular lesions in a control group were analyzed by two radiologists in consensus. They based their assessments on the presence or absence of the following five findings: hyperintensity on T2-weighted images, hyperintensity on diffusion-weighted images with low b values, washout pattern, capsular enhancement, and hypointensity on gadoxetic acid-enhanced hepatobiliary phase images. The findings were compared by use of univariate and multivariate analyses.
Results: No HCC with capsular enhancement was found. Fifty-seven HCCs (52.8%) had four findings, 36 (33.3%) had three, nine (8.3%) had two findings, and six (5.6%) had one finding. Univariate analysis showed significant differences between the HCC and control groups with respect to four findings (p < 0.0001). Multivariate analysis showed that hyperintensity on T2-weighted (p < 0.0001) and diffusion-weighted (p = 0.0081) images were statistically significant MRI findings for predicting HCC.
Conclusion: Hyperintensity on both T2- and diffusion-weighted images is helpful in the diagnosis of hypervascular HCC smaller than 1 cm in diameter.