Abstract
Gadolinium-based contrast agents (GBCA) have been standardly intravenously applied to improve visibility of MRI examinations since 1988, when gadopentetate dimeglumine (Magnevist(R)) was approved for clinical practice. Gadolinium itself is a heavy metal, highly toxic in biological systems.
Therefore, gadolinium must be bound to ligands for the purpose of contrast agents. GBCA consist of gadolinium ion and a chelating molecule, which could be cyclic or linear.
The macrocyclic molecule pre-organizes the rigid ring to cage the gadolinium ion, which offers better protection and binding of gadolinium ion. Linear chelates with a flexible open chain are less stable and provide weaker link of the gadolinium ion.
The rate of gadolinium dissociation from the macrocyclic ligands is remarkably slower than their dissociation from the linear chelates