Characterisation of magnetic resonance imaging (MRI) contrast agents using NMR relaxometry

This contribution describes the use of Fast Field-cycling relaxometry (FFC-NMR) for the characterisation of Gd(III)- and Mn(II)-based contrast agents for MRI. Through a series of selected examples, we analyse the role of different structural and dynamic parameters on ¹ H relaxivity and on the shape of the ¹ H Nuclear Magnetic Relaxation Dispersion (NMRD) profiles. The amplitude and shape of the profiles is affected by the number of water molecules coordinated to the metal ion, the water exchange rate, the rotational correlation time of the complex and the relaxation of the electron spin. As a result, ¹ H NMRD profiles represent a powerful tool for the understanding of the properties of MRI contrast agent candidates at the molecular level.