Abstract: The invention provides RF field coils and detector coils for an NMR machine. The two coils are specially designed for their respective purpose, the transmit coil (5, 6) being rectangular and the received coil (7-11) substantially elliptical with defined axis ratios and spacing in the z-direction being by projection of equi-spaced conductors on to the ellipse.

Abstract: The invention provides an investigation of chemical shift for an element, for example phosphorus, in a region of a body, in one example resonance is preferentially in a line in a slice of the body. Frequency dispersion down the line is produced by a pulsed field having a switched gradient so that the frequency distribution is in steps. This allows a chemical dispersion in each limited region of the line without overlap with adjacent regions. The measured FID signals are Fourier transformed to give a spatial and chemical analysis of the line.Alternatively resonance is excited in a slice and lines selected by a pulsed gradient which gives chemical dispersion as well as spatial dispersion between the lines after Fourier Transformation. This is repeated for many different directions of the pulsed gradient to allow analysis of a chemical line by convolution techniques to give a picture for the slice.

Abstract: The invention is related to the so-called "echo-planar" method of NMR imaging. In that method a resonance is first excited in a slice and then two orthogonal gradients provided dispersion in the slice. One gradient is pulsed to space the frequencies of spins in adjacent strips allowing the other gradient to provide dispersion down the strips. It is now proposed to pulse the second gradient so that the dephasing down each strip is also in steps. The FID signals (including rephasing signals) for each distinct element so produced can then be put in an array and two-dimensionally Fourier transformed to yield the desired output for each element.

Abstract: In an NMR examining arrangement for producing an image of a region, generally a planar slice, of a body, it has been suggested to derive, from the resonance signals, a plurality of values, for strips in the slice, and then to convolve them with a convolution function to be suitable for back projection in the manner known for x-ray signals. In this invention it is proposed to modulate the resonance signals with a suitable function and then to Fourier transform them but not to convolve them. The modulation function is chosen to give after Fourier transformation the same effect as the convolution would have given. It is suggested that the modulation function should be the inverse Fourier Transform of the desired convolution function.

Abstract: For NMR purposes a uniform magnetic field has been produced by field coils. It is known to use a cosinusoidal distribution to produce a uniform field. However, a large-diameter low-inductance coil is required for NMR and it is difficult to wind a small number of turns cosinusoidally. It is proposed to use two cosinusoidal coils providing unequal and opposing fields, the required field being the resultant and the combined inductance being less than either coil individually. The coils may have different winding densities or may be at different radii or both.

Abstract: In a NMR pulse sequence dispersion caused by inhomogeneity in the steady axial magnetic field may be reduced by applying a 180.degree. `spin-echo` RF pulse. However, whereas it is possible in known pulse sequences to apply a 90.degree. RF pulse in the presence of a selected gradient and to phase correct it adequately, this is not true for the 180.degree. pulse needed in a simple echo system (or the multiple pulses of more complex systems). It has been thought that a 180.degree. pulse could not then be use. It is proposed to apply the 90.degree. H.sub.1 pulse in the absence of an axial field gradient. For this purpose it is desirable to apply the RF field and sense the resonance with different coils. The RF coils should be of substantially greater extent in the axial direction than the resonance sensing coils.