Soluble Paramagnetic Chelates and Stabilized Colloidal Particle Solutions of Iron Oxides as Contrast Agents for Magnetic Resonance Imaging

The development of contrast agents shortening the relaxation times of protons began more than 20 years ago in order to improve the capability of diagnosing disease by means of magnetic resonance imaging (MRI). A variety of extracellular and tissue specific contrast agents were developed based on two types of molecules. One type was related to soluble paramagnetic chelates and the other type to stabilized colloidal particle solutions of iron oxides. The chelate or metal complex of gadopentetate dimeglumine was the pioneering magnetic resonance (MR) contrast agent used in 1988. Chemical modifications of this chelate and the design of new chelates led to tissue or blood pool specificity in MRI. Similarly, modifications in coating materials and variations in size of iron oxide particles allowed for tissue specificity or blood pool properties in MRI. Both types of contrast agents offer excellent perspectives for clinical MRI and for molecular imaging.