Method of electron spin resonance enhanced MRI

A method of electron spin resonance enhanced magnetic resonance imaging of a paramagnetic substance-containing sample, said method comprising:

• (i) in repeated first pulse sequences, sequentially exposing said sample to a first radiation of at least two frequencies selected to stimulate electron spin resonance transitions in said sample and therebetween to 180.degree. pulses of a second radiation of a frequency selected to stimulate coupled nuclear spin resonance transitions in said sample and subsequently further exposing said sample to at least one pulse of a second radiation whereby to cause the sample to emit magnetic resonance signals from which a difference signal (.DELTA.A) image of said sample may be generated;
• (ii) in repeated second pulse sequences interleaved with said first pulse sequences, exposing said sample to said first and second radiations as in said first pulse sequences but with the omission of said 180.degree. second radiation pulses whereby to cause said sample to emit magnetic resonance signals from which a normalizing (A) image of said sample may be generated;
• (iii) detecting magnetic resonance signals emitted from said sample in said first and second pulse sequences;
• and (iv) generating a normalized difference (.DELTA.A/A) image from the detected magnetic resonance signals.