Composition of positive and negative contrast agents for electron spin resonance enhanced magnetic resonance imaging

A method of generating a magnetic resonance image of a sample, said method comprising exposing said sample to pulses of a first radiation of a frequency selected to excite nuclear spin transitions in selected nuclei in said sample, detecting a signal from said sample and generating a said image from said detected signal, said method further comprising introducing into said sample a first paramagnetic contrast agent and exposing said sample to a second radiation of a frequency selected to excite an electron spin transition of said first contrast agent coupled to nuclear spin transitions of at least some of said selected nuclei whereby to enhance the signal therefrom, characterised in that said method also comprises introducing into said sample a second contrast agent having at least one transition in the esr spectrum thereof whereby to reduce the enhancement of said signal by said first contrast agent to increase contrast in different parts of the generated magnetic image of the sample.

A method of generating a magnetic resonance image of a sample, said method comprising exposing said sample to pulses of a first radiation of a frequency selected to excite nuclear spin transitions in selected nuclei in said sample, detecting a signal from said sample and generating a said image from said detected signal, said method further comprising introducing into said sample a first paramagnetic contrast agent and exposing said sample to a second radiation of a frequency selected to excite an electron spin transition of said first contrast agent coupled to nuclear spin transitions of at least some of said selected nuclei whereby to enhance the signal therefrom, characterised in that said method further comprises introducing into said sample a second contrast agent wherein said first contrast agent has an electron spin resonance transition with a linewidth of 1 Gauss or less and wherein said second contrast agent has an electron spin resonance transition with a linewidth of 3 Gauss or more.

A method of generating a magnetic resonance image of a sample, said method comprising exposing said sample to pulses of a first radiation of a frequency selected to excite nuclear spin transitions in selected nuclei in said sample, detecting signal from said sample and generating a said image from said detected signal, said method further comprising introducing into said sample a first paramagnetic contrast agent and exposing said sample to a second radiation of a frequency selected to excite an electron spin transition of said first contrast agent coupled to nuclear spin transitions of at least some of said selected nuclei whereby to enhance the signal therefrom, characterised in that said method further comprises introducing into said sample a second contrast agent wherein said first contrast agent comprises a stable free radical and wherein said second contrast agent comprises a paramagnetic metal species.

A method of generating a magnetic resonance image of a sample, said method comprising exposing said sample to pulses of a first radiation of a frequency selected to excite nuclear spin transitions in selected nuclei in said sample, detecting signal from said sample and generating a said image from said detected signal, said method further comprising introducing into said sample a first paramagnetic contrast agent and exposing said sample to a second radiation of a frequency selected to excite an electron spin transition of said first contrast agent coupled to nuclear spin transitions of at least some of said selected nuclei whereby to enhance the signal therefrom, characterised in that said method also comprises introducing into said sample a second contrast agent having at least one transition in the esr spectrum thereof wherein the ratio of the linewidth of the esr transition of said second agent to that of said first agent is at least 1.5:1.

A method of generating a magnetic resonance image of a sample, said method comprising exposing said sample to pulses of a first radiation of a frequency selected to excite nuclear spin transitions in selected nuclei in said sample, detecting signal from said sample and generating a said image from said detected signal, said method further comprising introducing into said sample a first paramagnetic contrast agent and exposing said sample to a second radiation of a frequency selected to excite an electron spin transition of said first contrast agent coupled to nuclear spin transitions of at least some of said selected nuclei whereby to enhance the signal therefrom, characterised in that said method further comprises introducing into said sample a second contrast agent having at least one transition in the esr spectrum thereof, wherein said first and second contrast agents are so selected that the degree of stimulability by said second radiation of said first contrast agent is greater than that of said second contrast agent.