Technicare Corporation

National Research Development Corporation

Waldo S Hinshaw

Russell A Compton

David M Kramer

Robert C Gauss

Arnold H Lent

William Stanley Moore

The null point in the gradient field of an NMR imaging system is offset from its nominal position in the static magnetic field by application of a bias field to the gradient field. The bias field produces a substantially uniform offset in the field intensity at every point in the gradient field. Alternatively, null point offset may be achieved by controllably superimposing two gradient fields of separately located null points.

Offset gradient fields in nuclear magnetic resonance imaging systems

The effects of particle motion or flow within a sample may be measured by applying a motion-encoding gradient to the sample, along with spatial encoding gradients. The motion-encoding gradient applies two gradient fields of respective opposite sense to the spins of the sample so as to encode motion as a net phase component resulting from the two fields. Two image data sequences, one with motion encoding and one without, may be compared to measure the effects of motion, or a plurality of image data sequences may be taken, each with a different value motion-encoding gradient. A Fourier transformation performed on the sequence data in the latter case with respect to the variation in the motion-encoding gradient pulses will yield a plurality of images, each representing the amount of material which exhibits a different velocity.

Nuclear magnetic resonance flow imaging

Spatially discriminated information is obtained by appropriate processing of data derived from a series of pulsed N.M.R. operations performed with a magnetic field exhibiting a linear gradient whose magnitude is different for each operation. In obtaining a two-dimensional image of spin density distribution, coil sets (5 and 6) are used to generate magnetic field components giving x and y gradients, the former being changed stepwise in magnitude and the latter being fixed. For each value of x gradient, the sample (1) is irradiated with pulsed r.f. energy, resultant N.M.R. signals being detected by phase-sensitive detectors (19 and 20) whose outputs are regularly sampled by A-D converters (25 and 26). Processing of the complete sampled data by a computer (12) involves both Fourier transformation with respect to x gradient magnitude and Fourier transformation with respect to time. For sectional images a third coil set (7) is used to generate a component giving an alternating z gradient and the irradiation consists of a train of pulses.

Investigation of samples by N.M.R. techniques

Apparatus for generating and detecting magnetic field components oscillating at a radio frequency in a direction transverse to a static magnetic field in a nuclear-magnetic-resonance (NMR) system. The apparatus has a plurality of conductive elements spaced from one another and from the axis along which the static magnetic field is directed. The relative amplitudes of alternating currents in the conductive elements are controlled to generate a spatially uniform field. A preferred embodiment uses a standing wave in a coil assembly to control relative current amplitudes, which takes advantage of the current-phase characteristics of such waves. Detection of RF magnetic fields results from an EMF generated in the coil assembly in response to the time-varying magnetic field; the high Q of the coil assembly enhances detection properties.

Distributed phase RF coil

A method of analyzing and apparatus for analyzing materials comprising subjecting a sample of the material to a non-homogeneous magnetic field having a predetermined time-dependency with respect to the sample such that a localized volume of the sample is subjected to a field the time dependent variation of which is unique with respect to the remainder of the sample. The sample is irradiated with radio-frequency energy to cause gyromagnetic resonance in the sample, and electrical energy produced by gyromagnetic resonance in the localized volume is measured.

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Richmond Heights, OH, United States of America

Waldo S Hinshaw