Selective volume method for performing localized NMR spectroscopy
AssigneeGeneral Electric Company
InventorPaul A. Bottomley
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Abstract
Selective irradiation is used to isolate a planar slice of nuclear spins in a nuclear magnetic resonance (NMR) sample. Selective radio frequecy pulses, applied in the presence of magnetic field gradients, are then employed to define a smaller sensitive volume in a predetermined region of the isolated planar slice. An NMR spin echo signal produced by excited nuclear spins situated in the thusly localized volume is observed in the absence of magnetic field gradients and, upon Fourier transformation, yields the desired localized chemical shift spectra.
Claims23
A method of performing localized NMR chemical shift spectroscopy comprising the steps of:
- (a) positioning an NMR sample in a homogeneous magnetic field directed along an axis thereof;
- (b) irradiating said NMR sample with a first RF pulse in the presence of a first magnetic field gradient so as to isolate a plurality of nuclear spins in a planar slice of said NMR sample;
- (c) applying a second RF pulse having a predetermined frequency content in the presence of a second magnetic field gradient so as to excite a fraction of said nuclear spins situated in a predetermined strip-like region of said planar slice oriented perpendicular to the direction of said second magnetic field gradient;
- (d) applying a third RF pulse having a predetermined frequency content in the presence of a third magnetic field gradient so as to invert nuclear spins in a predetermined volume of said strip-like region, said inverted nuclear spins producing a spin echo signal;
- and
- (e) sensing said spin echo signal in the absence of magnetic field gradients such that Fourier transformation of said spin echo signal yields a localized chemical shift spectrum from said predetermined volume.
A method of performing localized NMR chemical shift spectroscopy comprising the steps of:
- (a) positioning an NMR sample in a homogeneous magnetic field directed along an axis thereof;
- (b) irradiating said NMR sample with a first RF pulse in the presence of a first magnetic field gradient so as to excite a plurality of nuclear spins in a planar slice of said NMR sample;
- (c) applying a magnetic field gradient having a direction opposite to that of said first magnetic field gradient and a fraction of the magnitude thereof so as to rephase said plurality of nuclear spins;
- (d) applying a second RF pulse in the presence of a second magnetic field gradient so as to invert a fraction of said nuclear spins situated in a first region of said planar slice oriented perpendicular to the direction of said second magnetic field gradient;
- (e) applying a third RF pulse in the presence of a third magnetic field gradient so as to invert a plurality of nuclear spins situated in a second region of said planar slice oriented perpendicular to the direction of said third magnetic field gradient such that said first and second regions overlap forming a sensitized volume;
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- (f) sensing in the absence of magnetic field gradients a spin echo signal produced by nuclear spins in said sensitized volume, wherein Fourier transformation of said spin echo signal yields a localized chemical shift spectrum from said sensitized volume.
Dependencies are inferred from the claim text.