Introduction to the gadolinium class

Among the many paramagnetic substances, gadolinium ions [Gd(III)] exhibit one of the strongest degrees of proton-relaxation enhancement, which can be applied advantageously to selectively enhance diseases tissues on MR images. Such enhancement often proves the difference between suggestive and conclusive MR diagnostic studies. Chelation of the metal to organic ligands enhances safety and facilitates diagnostically useful tissue distribution and renal clearance. Chelates confer the further advantage of enabling gadolinium to be joined with carrier molecules, which can, in turn, foster tissue- or even antigen-specific targeting of contrast agents. Cost and relative biologic-tolerance profiles may prove to be key factors for distinguishing agents with similar distributions in clinical practice.