Focal liver lesions detection and characterization: The advantages of gadoxetic acid-enhanced liver MRI

Abstract

Since its clinical introduction, several studies in literature have investigated gadolinium ethoxybenzhyl diethylenetriaminepentaacetic acid or gadoxetic acid (Gd-EOB-DTPA) properties. Following contrast injection, it provides dynamic vascular phases (arterial, portal and equilibrium phases) and hepatobiliary phase, the latter due to its uptake by functional hepatocytes. The main advantages of Gd-EOB-DTPA of focal liver lesion detection and characterization are discussed in this paper. Namely, we focus on the possibility of distinguishing focal nodular hyperplasia (FNH) from hepatic adenoma (HA), the identification of early hepatocellular carcinoma (HCC) and the pre-operative assessment of metastasis in liver parenchyma. Regarding the differentiation between FNH and HA, adenoma typically appears hypointense in hepatobiliary phase, whereas FNH is isointense or hyperintense to the surrounding hepatic parenchyma. As for the identification of early HCCs, many papers recently published in literature have emphasized the contribution of hepatobiliary phase in the characterization of nodules without a typical hallmark of HCC. Atypical nodules (no hypervascularizaton observed on arterial phase and/or no hypovascular appearance on portal phase) with low signal intensity in the hepatobiliary phase, have a high probability of malignancy. Finally, regarding the evaluation of focal hepatic metastases, magnetic resonance pre-operative assessment using gadoxetic acid allows for more accurate diagnosis.

Keywords: Carcinoma; Gadolinium diethylenetriaminepentaacetic acid; Hepatocellular; Image enhancement; Liver; Magnetic resonance imaging.

Figure 1

Typical imaging features of focal nodular hyperplasia in a 29-year-old woman. Gadoxetic acid-enhanced magnetic resonance imaging; axial images (A-D) were obtained in dynamic phases and hepatobiliary phase. A shows a solid circumscribed mass (white arrow), lobulated in contour, with a central scar (black arrow); the lesion is hyperintense on the arterial phase (A) and persists slightly hyperintense in the portal and venous phases (B and C respectively). In hepatobiliary phase (D) the mass is slightly hyperintense or isointense to the surrounding liver. The presence of biliary canaliculi, even if not functioning, leads to retention of gadoxetic acid in comparison to the surrounding parenchyma.

Figure 2

Magnetic resonance imaging of a small focal nodular hyperplasia. Arterial, venous and hepatobiliary phases (A, B and C), acquired in a 44-year-old woman shows the typical enhancement of a small focal nodular hyperplasia (white arrows). The lesion is located in the fourth liver segment, between medium and left sovrahepatic vein. In hepatobiliary phase (C) the lesion is slightly hyperintense to the surrounding liver parenchyma, due to uptake of hepatospecific contrast.

Figure 3

Imaging features of a typical hepatocellular carcinoma. Axial magnetic resonance images show a hypervascular lesion in the arterial phase (A, white arrow), located in the top of the liver, with wash-out clearly in the portal venous phase (B, white arrow). This enhancement pattern represents the typical morphological hallmark of hepatocellular carcinoma. The nodule has an increased arteriolar supply and reduced portal vascularization. In hepatobiliary phase, the lesion appears hypointense to the surrounding liver parenchyma.

Figure 4

Imaging features of a small hepatocellular carcinoma. The lesion (white arrow), located in the fifth segment of right hepatic lobe, is detectable in the arterial and hepatobiliary phase. It has hypervascular appearance in arterial phase (A), without evident wash-out in the portal phase (B). The lesion is hypointense in the hepatobiliary phase (C). As reported in literature, the low or absence of gadolinium ethoxybenzhyl diethylenetriaminepentaacetic acid or gadoxetic acid uptake could precede the decrease of portal vascularization in malignant differentiation.