Abstract: Use of a switch at the end of a .lambda./4 cable inserted between the Rf coil and ground allows the coil to be tuned and detuned at will. This detune switch essentially eliminates coupling between adjacent coils permitting operation of multiple transmit coils at the same frequency. These switches have been employed to prove a previously proposed method of complete sensitive-volume localization using multiple Rf coils and depth pulse schemes. The example illustrated is the case of two coaxial coplanar surface coils. There are important uses in in-vivo spectroscopy.

Abstract: A method of obtaining an NMR spectrum from a first region lying wholly within a second region of a sample material, comprises obtaining a signal indicative of a first NMR spectrum from substantially all of the second region of the sample material applying to the sample a magnetic field gradient, and simultaneously applying to the sample an Rf perturbing pulse having an amplitude and a frequency distribution such as to perturb nuclear spins in the said first region, but not outside it, removing the magnetic field gradient, and thereafter obtaining from the sample a signal indicative of a second NMR spectrum before relaxation of the perturbed spins in the said first region, and comparing the said first and second signals to obtain a difference spectrum attributable to the said region.Three separate perturbing pulses are preferably employed, each in the presence of a corresponding field gradient.

Abstract: A radiofrequency transducer, for nuclear magnetic resonance spectroscopy, comprising a radiofrequency transmission line formed into a loop, having terminals for the connection of a radiofrequency source or receiver thereto in such a manner that the transmission properties of the loop counteract the impedance due to its loop geometry. The transducer may comprise first and second elongate conductors (1,2) spaced by a dielectric material (3), for example polytetrafluoroethylene, and shaped to form the said loop, terminals (4,5) for the two conductors being provided at opposite ends of the loop.

Abstract: A method of obtaining an NMR spectrum from a sample comprising the steps of: maintaining a static magnetic field along an axis which is homogeneous over at least a small volume constituting part of a sample applying a gradient to said magnetic field which varies in one direction orthogonal to said axis while applying an rf pulse to the sample to saturate all nuclei in the said volume except for a slab lying in a plane normal to the said one direction replacing the said gradient by a second gradient to said magnetic field which varies in a second direction orthogonal to said axis and said one direction while applying an rf pulse to the sample to saturate all nuclei in the said volume except for a slab lying in a plane normal to the said second direction, whereby nuclei in a narrow column extending parallel to the said axis have their spins left undisturbed replacing the second gradient by a third gradient to said static magnetic field which varies in a direction parallel to said axis while applying an rf pulse

Abstract: A method of determining or imaging fats in a non .sup.13 C enriched biological sample, particularly human tissue comprising subjecting the sample to a magnetic field, irradiating the sample with radiofrequency electromagnetic radiation, obtaining from the sample an electrical signal indicative of the radiofrequency absorption of the sample in the magnetic field at a frequency corresponding to the .sup.13 C NMR resonance frequency for --(CH.sub.2).sub.n --, filtering the signal to exclude components due to absorption by the sample attributable to carbon atoms other than those present as --(CH.sub.2).sub.n -- and determining from the intensity of the absorption the fat content of the sample, or applying to the signal an imaging technique to determine the fat distribution in the sample. .sup.1 H decoupling is preferably employed to increase signal-to-noise ratio.The method is useful in the diagnosis of certain fat-related diseases, such as muscular dystrophy.

Abstract: A method of obtaining an NMR spectrum from a sample comprising the steps of: maintaining a static magnetic field along an axis which is homogeneous over at least a small volume constituting part of a sample applying a gradient to said magnetic field which varies in one direction orthogonal to said axis while applying an rf pulse to the sample to saturate all nuclei in the said volume except for a slab lying in a plane normal to the said one direction replacing the said gradient by a second gradient to said magnetic field which varies in a second direction orthogonal to said axis and said one direction while applying an rf pulse to the sample to saturate all nuclei in the said volume except for a slab lying in a plane normal to the said second direction, whereby nuclei in a narrow column extending parallel to the said axis have their spins left undisturbed replacing the second gradient by a third gradient to said static magnetic field which varies in a direction parallel to said axis while applying an rf pulse