A method of electron spin resonance enhanced MRI using a physiologically tolerable paramagnetic substance comprises generating an image from a data set produced by manipulation of enhanced FID signals detected under at least two different sets of operational parameters including the timing of the exposure of the subject and optionally also the amplitude and frequency distribution of the ESR stimulating radiations, the manipulation producing a normalized signal representative of the difference between signals under said different operational parameters. In other embodiments the method comprises imaging the distribution of two or more paramagnetic substances within the subject, the first substance having a generally invariant ESR transition and the second substance having an ESR transition the frequency or linewidth of which varies according to location in the subject, or comprises sequentially exposing the subject to a first radiation of at least two ESR transition stimulating frequencies and a second radiation of frequency for stimulating coupled nuclear SR transitions. <IMAGE>
Improvements in and relating to magnetic resonance imaging