Fig. 1.

Gadolinium-based contrast agents (GBCAs) consist of a central paramagnetic Gadolinium (Gd 3+) chelated to a ligand, preventing direct toxicity from free Gd3+. The biochemical structure of the types of ligands are illustrated: a Linear agents, with an elongated organic molecular ligand wrapping around the ion and b Macrocyclic agents, which form a cage-like ligand structure with the ion trapped in the central cavity