Abstract: In order to increase the efficiency with which NMR information is received, the peak amplitude of the received NMR signal is reduced. This reduction is obtained by varying the phase of the nuclear spin systems which produce the NMR signal. The phase variation may be obtained by applying a spatially inhomogeneous rf pulse. It may alternatively be obtained by applying a tailored rf pulse having either an amplitude spectrum or a phase spectrum which varies with frequency. It may alternatively be obtained by applying gradient pulses. The phase variation may be produced at one or more of several times during the data acquisition. In addition to reducing the peak amplitude of the NMR signal, the phase variation results in reduced noise from an FFT performed during processing.

Abstract: The phase encoding of NMR information is performed using rf pulse sequences. The rf pulse sequences produce a substantially continuous phase variation cross the resonant frequency range of the atoms of an object in order to perform phase encoding. Some of the pulses may be tailored pulses, with each tailored rf pulse including frequencies which cover a bounded continuous frequency range. Either the phase or the amplitude of each tailored rf pulse varies with frequency across this continuous range. If the amplitude is linearly variant across the range, the phase is constant, but if the phase is linearly variant across the range, the amplitude is constant. The tailored rf pulses may be applied in the presence of pulsed magnetic gradient fields of the conventional type to produce the phase variation.

Abstract: In the disclosed pulse and gradient switching sequences, refocusing pulses are timed to provide spectral encoding so that a resulting series of spin echoes each include both spatial and spectral information for chemical shift imaging. Atoms within an object are excited and may then be spatially encoded, as by a phase encoding gradient. A series of refocusing pulses is then applied, each followed by an observation gradient field. Each of the refocusing pulses after the first one may be displaced in time relative to the observation gradients in order to provide spectral encoding. In an alternative embodiment for limited spectral resolution of fat and water, the observation gradients may also be timed so that echoes may be added to compensate for the decreasing amplitudes of the successive spin echoes.

Abstract: A radio frequency (rf) coil for an NMR device is disclosed in which at least two active sections each have a ground end connected to a common potential and a drive end opposite the ground end. The rf coil also includes at least one transmission line section for coupling the drive ends of two of the active sections. The coil is tuned to a resonant frequency by a variable capacitor connected to the drive end of one of the active sections. Two active sections may be arranged opposite each other about an axis and connected by a half wavelength transmission line to provide a linearly polarized magnetic field. Four active sections may be arranged 90.degree. apart from each other in a quadrature coil to provide a circularly polarized magnetic field. Each active section may include two wires, each connected at one end to a lower ground ring and having an opposite end adjacent an upper ground ring which provides a ground plane.

Abstract: Measurement of magnetic field distributions is performed using a method based on the nuclear magnetic resonance (NMR) technique of Pourier imaging. By selecting objects which limit the spatial distribution of the NMR observable nuclei, images can be obtained which allow easy interpretation of the magnetic field distribution and facilitate rapid shimming of magnets. A method for providing a convenient display of field data is provided, as well as chemical shift imaging with correction for static field inhomogeneity. Results from these field plots are used as corrections for static field inhomogeniety when obtaining a chemical shift image. A method for localized spectral analysis from the chemical shift image is also provided.