Characterising Contrast Agents for Magnetic Resonance Imaging

In Magnetic Resonance Imaging (MRI), complexes of Gd3+ are very often used as contrast agents to locally accelerate relaxation of water protons. The theoretical models developed to quantitatively describe this phenomenon involve parameters which determine the spin-lattice relaxation for the complexes. Their values can be obtained by simulating a series of EPR spectra recorded at different frequencies over a range of temperatures. These studies reveal the factors determining the efficacy of the complexes and can be used to optimise their structure.