An update on clinical applications of hepatospecific contrast media in magnetic resonance imaging of liver parenchyma.

Hepatobiliary-specific contrast agents are now widely used in magnetic resonance imaging (MRI) of liver parenchyma. As extracellular fluid agents, they provide informations regarding lesion vascularity and their use in the hepatobiliary or delayed phase (DPI), and give additional data regarding hepatocyte presence and function. The aim of this article is to review the recent literature about MRI using hepatobiliary-specific contrast agents and to discuss benefits and limits of their clinical applications. Since November 2008, hepatobiliary contrast agents were routinely employed in our Institution for the characterization of equivocal liver lesions detected by other imaging modalities, and for the evaluation of hepatic nodules in liver cirrhosis. The informations provided are particularly relevant for the detection of metastases, for the differentiation between focal nodular hyperplasia (FNH) and hepatocellular adenoma (HCA), and for the detection and differentiation between dysplastic nodules (DNs) and hepatocellular carcinoma (HCC) in the cirrhotic liver. The role in the cirrhosis grading and the quantification of liver function is still controversial. Finally, their biliary excretion allows evaluation of anatomy and function of the biliary tree. According to our and reported data, hepatobiliary contrast agents are able to improve liver lesions detection and characterization; their introduction in clinical practice has improved MRI diagnostic efficacy/accuracy, allowing to decrease the number of invasive diagnostic procedures.

Enhancement patterns of intrahepatic mass-forming cholangiocarcinoma at multiphasic computed tomography and magnetic resonance imaging and correlation with clinicopathologic features.

OBJECTIVE: Incidence of intrahepatic mass-forming cholangiocarcinoma (IMCC) is increasing worldwide, especially in patients with chronic liver disease. The small and the histologically well-differentiated IMCCs in chronic liver disease could be arterially hypervascular lesions with/without washout on computed tomography (CT) and magnetic resonance imaging (MRI), mimicking typical hepatocellular carcinoma (HCC). The aim of this work is to evaluate contrast enhancement (CE) patterns of IMCCs at quadri-phasic multidetector CT (4-MDCT) and MRI, using imaging-clinicopathologic correlation. PATIENTS AND METHODS: The 4-MDCT and MR images of 56 histologically confirmed IMCCs were retrospectively evaluated for tumor morphology and enhancement features. Enhancement pattern was defined according to the behavior of the nodule in arterial (AP), portal venous (PVP) and equilibrium phases (EP), and dynamic pattern was described according to enhancement progression throughout the different phases. Arterial and dynamic enhancement patterns were correlated with chronic liver disease, tumor size and histological differentiation. RESULTS: Most of the nodules were peripherally hyperenhancing (50%) on AP, and partially hyperenhancing on PVP (67.9%) and EP (80.3%). Forty-six (82.1%) IMCCs showed progressive CE, 7 (12.5%) stable CE and 3 (5.4%) wash-out. In normal liver there were 34 nodules with progressive and 3 with stable CE, whereas in chronic liver disease there were 12 IMCCs with progressive, 4 with stable and 3 with washout pattern (p = 0.01); IMCCs with progressive CE were more differentiated than IMCCs with stable CE and wash-out (p = 0.02). CONCLUSIONS: The most prevalent enhancement pattern of IMCCs was arterial rim enhancement followed by progressive and concentric filling. The stable and the washout patterns were more frequent in poorly differentiated IMCCs. Contrast washout was observed only in IMCCs emerging in chronic liver disease with a risk of misdiagnosis with HCC.

Differentiating hepatocellular carcinoma from dysplastic nodules at gadobenate dimeglumine-enhanced hepatobiliary-phase magnetic resonance imaging.

PURPOSE: We evaluated whether the addition of delayed phase imaging (DPI) gadobenate dimeglumine-enhanced MRI to dynamic postcontrast imaging improves the characterization of small hepatocellular carcinoma (HCC) and the differentiation between HCC, high grade dysplastic nodules (HGDN), and low grade dysplastic nodules (LGDN). METHODS: Twenty-five cirrhotic patients with 30 nodules (16 HCC, 8 HGDNs, and 6 LGDNs; maximum size of 3 cm) were included in this retrospective study. The diagnostic reference standard was histology. All the patients underwent MRI both prior to and following intravenous administration of gadobenate dimeglumine. The lesions were classified as hypointense, isointense, hyperintense on DPI for qualitative assessment. In the quantitative analysis the relative tumor-liver contrast to noise ratio (CNR) of the lesions on DPI was calculated. RESULTS: All HCCs were hypointense on DPI while only 8 (57.1%) of 14 DNs were hypointense and only 1 of 6 (16.6%) LGDNs was hypointense. There was a statistically significant difference in the hypointensity on DPI between HCCs and DNs (p = 0.003) in the qualitative analysis but not in the CNR values while there was a strong statistically significant difference in the hypointensity on DPI in the qualitative (p = 0.00001) and quantitative analysis (p < 0.05) between LGDNs and the group obtained by unifying HGDNs and HCCs. CONCLUSION: DPI is helpful in differentiating HCCs and HGDNs from LGDNs. Demonstration of hypointensity on DPI should raise the suspicion of HGDN or hypovascular HCC in the case of nodules with atypical dynamic pattern.