Nuclear magnetic resonance method and apparatus

Claim 1

A method of determining the spatial distribution of a quantity relating to a chosen element across a slice of a body comprising: exciting nuclear magnetic resonance for said element preferentially in said slice of said body; applying first and second pulsed magnetic gradient fields having magnetic field gradients in first and second mutually orthogonal directions in the plane of said slice to produce phase dispersion in said resonance along said first and second directions respectively; and analysing resulting free induction decay signals; characterised by stepping the value of the gradient of said first field through a range of first values, for each of said first values stepping the value of the gradient of said second field through a range of second values and measuring the free induction decay signal after each set of one first and second field pulses to form a set of free induction decay signals; subjecting said set of signals to a two dimensional Fourier Transform process with respect to said first and second directions, and to an additional Fourier Transform process with respect to time to obtain chemical shift spectra for said chosen element at each of a plurality of different locations in said slice.

Claim 2

A method of determining the spatial distribution of a quantity relating to a chosen element across a slice of a body comprising: exciting nuclear magnetic resonance for said element preferentially in said slice of said body; applying first and second pulsed magnetic gradient fields having magnetic field gradients in first and second mutually orthogonal directions in the plane of said slice to produce phase dispersion in said resonance along said first and second directions respectively; and analysing resulting free induction decay signals; characterised by stepping the value of the gradient of said first field through a range of first values, for each of said first values stepping the value of the gradient of said second field through a range of second values and measuring the free induction decay signal after each set of one first and second field pulses to form a set of free induction decay signals; subjecting said set of signals to a two dimensional Fourier Transform process with respect to said first and second directions, and to an additional Fourier Transform process with respect to time to obtain chemical shift spectra for said chosen element at each of a plurality of different locations in said slice.

Claim 5

A method according to either of the preceding claims in which after each step a magnetic field pulse is applied which is effective to cause spin echoes.

Claim 6

An apparatus for determining the spatial distribution of a quantity relating to a chosen element across a slice of a body comprising: means arranged to excite nuclear magnetic resonance for said element preferentially in said slice of said body; means arranged to apply first and second pulsed magnetic gradient fields having magnetic field gradients in first and second mutually orthogonal directions in the plane of said slice; and means for analysing resultant free induction decay signals; characterised in that said means for applying said first and second pulsed fields is arranged to step the value of the gradient of said first field through a range of first values and step the value of the gradient of said second field through a range of second values for each of said first values; and in that said means for analysing comprises means for measuring the free induction decay signal after each set of one first and second field pulses to form a set of free induction decay signals, and means for subjecting said set of signals to a two dimensional Fourier Transform process with respect to said first and second directions, and to an additional Fourier Transform process with respect to time so as to obtain chemical shift spectra for said chosen element at each of a plurality of different locations in said slice.

Claim 7

An apparatus for determining the spatial distribution of a quantity relating to a chosen element across a slice of a body comprising: means arranged to excite nuclear magnetic resonance for said element preferentially in said slice of said body; means arranged to apply first and second pulsed magnetic gradient fields having magnetic field gradients in first and second mutually orthogonal directions in the plane of said slice; and means for analysing resultant free induction decay signals; characterised in that said means for applying said first and second pulsed fields is arranged to step the value of the gradient of said first field through a range of first values and step the value of the gradient of said second field through a range of second values for each of said first values; and in that said means for analysing comprises means for measuring the free induction decay signal after each set of one first and second field pulses to form a set of free induction decay signals, and means for subjecting said set of signals to a two dimensional Fourier Transform process with respect to said first and second directions, and to an additional Fourier Transform process with respect to time so as to obtain chemical shift spectra for said chosen element at each of a plurality of different locations in said slice.

Claim 8

An apparatus arranged to perform a method of determining the spatial distribution of a quantity relating to a chosen element over a volume within a body comprising: means for exciting nuclear magnetic resonance for said element within said volume; means for applying first, second and third pulsed magnetic gradient fields having magnetic field gradients within said volume in first, second and third mutually orthogonal directions; and means for analysing resulting free induction decay signals; characterised in that said means for applying said first, second and third pulsed fields is arranged to step the value of the gradient of said first field through a range of first values, step the value of the gradient of said second field through a range of second values for each value of said first value, and step the value of the gradient of said third field through a range of third values for each of said second value; and in that said means for analysing comprises means for measuring the free induction decay signal after each set of one first, second and third field puls-es to form a set of free induction decay signals, and means for subjecting said set of signals to a three dimensional Fourier Transform process, and to an additional Fourier Transform process.with respect to time so as to obtain chemical shift spectra for said chosen element at each of a plurality of locations in said volume.

Claim 9

An apparatus arranged to perform a method of determining the spatial distribution of a quantity relating to a chosen element over a volume within a body comprising: means for exciting nuclear magnetic resonance for said element within said volume; means for applying first, second and third pulsed magnetic gradient fields having magnetic field gradients within said volume in first, second and third mutually orthogonal directions; and means for analysing resulting free induction decay signals; characterised in that said means for applying said first, second and third pulsed fields is arranged to step the value of the gradient of said first field through a range of first values, step the value of the gradient of said second field through a range of second values for each value of said first value, and step the value of the gradient of said third field through a range of third values for each of said second value; and in that said means for analysing comprises means for measuring the free induction decay signal after each set of one first, second and third field puls-es to form a set of free induction decay signals, and means for subjecting said set of signals to a three dimensional Fourier Transform process, and to an additional Fourier Transform process.with respect to time so as to obtain chemical shift spectra for said chosen element at each of a plurality of locations in said volume.