A gadolinium coordination entity that consists of Gd(3+) coordinated to 3,6,9-triazaundecadiamide in which each of the amide nitrogens is substituted by a 2-methoxyethyl group and in which the nitrogens at positions 3, 6, and 9 are each substituted by carboxylatomethyl group. The gadolinium is coordinated to the three tertiary amino groups as well as to the carboxylate groups. A white odourless powder that is freely soluble in water, gadoversetamide has paramagnetic properties and is used as a contrast agent in magnetic resonance imaging. It distributes mainly in extracellular fluid, but does not cross the blood-brain barrier. It is used particularly in imaging the brain, spine and liver.