The visualisation of the distribution of nuclear spins (usually water) in a body by using a magnetic field gradient (
NMR imaging). A similar technique, but less widely used, is to visualise the distribution of paramagnetic centres (
EPR imaging).
Source:
PAC, 1997, 69, 1251. 'Glossary of terms used in bioinorganic chemistry (IUPAC Recommendations 1997)' on page 1284 (https://doi.org/10.1351/pac199769061251)