Abstract
Gadolinium(III)-based contrast agents (GBCAs) have been extensively used in magnetic resonance imaging (MRI) in clinical practice since 1988, largely because they can dramatically improve contrast between healthy and diseased tissues. GBCAs are complexes of Gd(III) in which the metal ion is encapsulated in a cavity of linear (open-chain) or macrocyclic ligands. Although the safety statistics of GBCAs are in general excellent, nephrogenic systemic fibrosis (NSF) observed in a small subset of patients with poor kidney function after the administration of linear GBCAs and more recently, gadolinium deposition in various tissues (e.g., brain, bone) raised safety concerns. In this review we briefly describe the physical principles of MRI, the background of NSF, environmental concerns of gadolinium as well as related regulatory actions. The robustness of commercial GBCAs in terms of stability and inertness and innovative research to develop safer and more effective new GBCAs, as well as smart/responsive contrast agents (SCAs) (pH-, hypoxia-sensitive CAs, enzyme activated systems) will also be discussed.
