Paramagnetic agents for contrast-enhanced NMR imaging: a review

The use of paramagnetic agents for contrast enhancement may extend the diagnostic potential of nuclear magnetic resonance (NMR) imaging. Proton relaxation is enhanced in targeted organ systems after either oral or intravenous administration of suitable paramagnetic agents. A decrease in T1 and T2, the spin-lattice and spin-spin relaxation times, can then be observed as an increase in signal intensity on NMR imaging. Initial investigations have focused on development of agents incorporating either paramagnetic ions or stable free radicals. Principles in development and application are illustrated with examples from experiments using the Vanderbilt Technicare 0.5 T NMR imager.