Gd-EOB-DTPA-ENHANCED MAGNETIC RESONANCE IMAGING: DIFFERENTIATION BETWEEN FOCALNODULAR HYPERPLASIA AND HEPATOCELLULAR ADENOMA

Gadoxetic acid (Gd-EOB-DTPA) is a contrast media used in magnetic resonance imaging (MRI) for the detection and characterization of hepatic lesions. It shows combined properties of extracellular and biliary excretion, with 50% of the administered dose eliminated by the hepatobiliary pathway. One of its applications, therefore, is the characterization of focal hepatic lesions, including those of hepatocellular nature, such as focal nodular hyperplasia and hepatocellular adenoma. Patients with focal nodular hyperplasia (FNH) are usually asymptomatic and rarely reveal complications. In other hand, hepatocellular adenoma may suffer complications, such as intraperitoneal or intratumoral (sometimes massive) bleeding and the possible progression to malignancy. Objectives: To determine the value of MRI with Gd-EOB-DTPA in characterizing hepatic lesions, particularly in the differentiation between HNF and AHC. Material and methods: A retrospective study was carried out by investigating cases of FNH and HCA referred for MR evaluation with Gd-EOB-DTPA in the Department of Radiology of the University Hospitals of Coimbra (HUC) between August 2009 and December 2010. We evaluated 32 patients, 24 with FNH and 8 AHC. The diagnosis was established by histology, follow-up or agreement between imaging methods. In order to evaluate the enhancement after contrast administration in the hepatobiliary phase, we calculated the values of Signal-to-noise ratio (SNR), Contrast-to-noise ratio (CNS) and percentage of enhancement. Statistical analysis was performed with SPSS, version 18, and the tests were evaluated at a significance level of 5%. Results: The SNR and CNR after contrast is significantly different for the two types of lesion (p <0.001 and p = 0.03, respectively), with higher values for both parameters in the group of focal nodular hyperplasia. As for the % of enhancement, there is a statistically significant difference between groups (p = 0.006), again with the FNH group presenting higher values. There are significant differences in both groups among the studies pre-and post-contrast for the CNR (FNH: p <0.001; adenoma: p = 0.017), but for the SNR of the lesion the difference manifests in the HNF group (p <0,001); the CNR values increase in FNH and decrease in hepatocellular adenoma, while for the SNR of the lesion post-contrast values are higher than pre-contrast, in both groups. Conclusions: Magnetic resonance imaging with hepatospecific contrast is a valuable method for characterization of benign hepatic lesions, helping to differentiate FNH from HCA, based on the different patterns of uptake and retention of Gd-EOB-DTPA.