A new lipophilic gadolinium chelate as a tissue-specific contrast medium for MRI.

Gd-Ethoxybenzyl-DTPA (Gd-EOB-DTPA) is a highly water-soluble paramagnetic contrast agent. Due to its protein binding of about 10% and its lipophilic residue, Gd-EOB-DTPA exhibits both renal (30% of the dose) and hepatobiliary (70%) excretion in rats. Despite its lipophilic character, the compound displays a low toxicity (LD50 = 7.5 mmol/kg). T1-relaxivity of 5.3 liters mmol-1 s-1 in water, 8.7 liters mmol-1 s-1 in plasma, and 16.9 liters mmol-1 s-1 in rat liver together with the hepatocellular uptake explain the liver-specific contrast enhancement of Gd-EOB-DTPA. The diagnostic dose is considerably lower than the amount of Magnevist used in abdominal imaging. The preclinical studies suggest its clinical role as being a hepatobiliary contrast agent for MRI.