Abstract: A magnetic resonance apparatus including an r.f. coil arrangement (13) for detecting and/or exciting magnetic resonance in a body in use of the apparatus, the coil arrangement comprising a cylindrical coil (25) and two saddle coils (29) which are disposed in register on opposite sides of the cylindrical coil and conform to the surface of the cylindrical coil.In use of the apparatus the coil arrangement is disposed with the axes of the coils lying in a plane orthogonal to the direction of a static field applied to the body.

Abstract: A magnetic resonance method and apparatus for the microscopic examination of an internal region of a body (3) wherein a probe (25) is located in the body adjacent the region during the examination, and spatial encoding of r.f. signals resulting for excitation of magnetic resonance in the region is effected by a magnetic field gradient produced in the region by a coil arrangement carried by the probe.

Abstract: A magnetic resonance imaging apparatus using a transverse magnet system (29) and having a patient handling arrangement (31, 33) which allows transport of a patient into the magnet system by first moving the patient in a direction (A) at right angles to the head-to-toe axis (B) of the patient. The patient's position in the magnet system may then be adjusted by movement in the head-to-toe axis direction. The area required to accommodate the apparatus is reduced compared with apparatus wherein patient transport is effected solely in the patient's head-to-toe axis direction.

Abstract: A coil (17) for use as a surface r.f. coil in magnetic resonance apparatus comprising a conductor (25) wound helically to form a coil of overall laminar form with the parts of the conductor on one main face (29) more closely spaced to one another than are the parts of the conductor on the other main face (31). The coil is used to induce or detect an r.f. field locally in a body under investigation by positioning it with the main face having the more closely spaced conductor parts adjacent the body. The closer spacing improves coupling to the body while allowing the coil to be thinner, and therefore less bulky, than a coil of comparable performance with the same conductor part spacing on both main faces.

Abstract: A magnetic resonance method comprising the steps of exciting magnetic resonance in nuclei in a planar region of a body, applying a first gradient magnetic field having a periodically reversing gradient in a first direction across the region in conjunction with a series of pulses of a second gradient magnetic field in a second direction across the region orthogonal to the first direction, progressively decreasing the time between successive pulses of the second gradient, sensing resonance signals from the nuclei, and subjecting the resonance signals to a two-dimensional Fourier Transform process to acquire data relating to the region of the body. In the method the time between successive pulses of the second gradient is decreased in such a manner as to avoid acquisition of data in respect of areas in the corners of a rectangular matrix defined by the first and second gradient fields.

Abstract: A method of reducing the effects of eddy currents produced by a gradient magnetic field pulse pattern applied to a body in a magnetic resonance method by selecting the rates of change of magnetic flux produced during the edges of the or each pulse of the pulse pattern in relation to the times elapsing between the edges and the time constants of the eddy currents.

Abstract: An r.f. antenna for use in a magnetic resonance method or apparatus comprising two sub-systems (17A, 17B) each comprising a relatively large area conductor means (29A, 29B) and a return current path conductor means (33A, 33B) which together act as a transmission line tuned to the frequency of the r.f. The two sub-systems are placed on opposite sides of a body (7) under examination with the large area conductor means in facing relationship, and when used to apply an r.f. field to the body, are excited so that the r.f. currents in the two large area conductor means at any given instant are in opposite directions. The large area conductor means of each sub-system may be planar or convexly or concavely curved, and may comprise a single sheet of conducting material or an array of conducting strips in spaced relationship.

Abstract: An RF coil arrangement (23) in a magnetic resonance apparatus wherein a static magnetic field for application to a body under examination is produced in a gap (3) between a pair of pole pieces (5). The RF coil arrangement comprises at least one coil (45 or 47) having a first part (49,51) fixed secured to a part (5) of the apparatus adjacent the gap and a further part (53) which is detachably electrically connected to the first part to provide easy access to the gap when placing in, or removing from, the gap a body to be imaged. The further part of the coil may be wholly detachable from the first part or pivotally mounted on a first portion (49) of the first part and detachable from a second portion (51) of the first part on pivotal movement of the further part with respect to the first portion of the first part.

Abstract: A magnet arrangement for producing a magnet field in a gap (3) between a pair of pole pieces (1), e.g. to provide the main magnetic field for application to a subject for magnetic resonance imaging, wherein adjacent the pole pieces the magnet core 15 has sections 17 of restricted cross-sectional area which serve to improve the homogeneity of the field in the gap.

Abstract: A magnet system (1) for a nuclear magnetic resonance (NMR) imaging apparatus comprising a magnetic core arrangement (7, 13, 15) shaped to provide two or more discrete gaps (3, 5) of different sizes in which objects to be imaged may be placed, the magnetic field across each gap being produced by a single drive coil arrangement (9) associated with the core arrangement. A system providing gaps of different sizes, for different types of NMR examination is thus provided at relatively low cost compared with using a separate magnet system for each type of examination.

Abstract: A method of nuclear magnetic resonance imaging wherein motion artifacts in the image are reduced by compensating for variations in the coupling between the RF transmitter and/or detector coils (9A, 9B and/or 10A, 10B) and the body (43) being imaged due to movement of the body. Compensation is suitably effected by measuring the position of the body (43) with respect to a datum immediately prior to each excitation of nuclear spins in the body and setting the amplitude of the applied RF excitation pulse B (90.degree.) and the detector sensitivity in dependence on the measured position.

Abstract: A method of operating an electromagnet arrangement comprising a main electromagnet and a number of correction coils for applying correction fields to the field produced by the main electromagnet to produce a resultant desired homogeneous magnetic field in a given volume. The method comprises obtaining the least squares fit values for the correction coil currents and, if the required current in any coil lies outside a range of permissible values for that coil current, following a special procedure to find the best selection of coil currents consistent with the permissible currents in the coils.

Abstract: A method, and an apparatus for performing the method, are described, for imaging a region of a body using NMR in which part of the region is moving with a motion such that its displacement with respect to time is a nonmonotonic function during the time period over which NMR data signals are collected. The data signals are collected in an order dependent on the motion such that motion artifacts are reduced.

Abstract: An NMR spectroscopy method monitors a component of a sample, the component having two resonances in coupled together different spectral regions. The first resonance lies in a region including a resonance of a second component of a sample while the second resonance lies in a spectral region including a resonance of a third component of the sample. Two spin-echo pulse sequences each consisting of pulses of a predetermined frequency are applied, the spin-echo resonance spectra together being used to obtain the second resonance of the first component with the resonance of the third component suppressed.

Abstract: A coil arrangement for producing a magnetic field of high homogeneity, such as is required in magnetic resonance imaging, comprising a single pair of identical annular coils (17A, 17B) disposed coaxially in spaced relationship and a pair of annular members (19A, 19B) of ferromagnetic material disposed coaxially with the coils, symmetrically with respect to the plane which perpendicularly intersects the axis of the coils centrally between them. The coils and ferromagnetic members have dimensions and are relatively positioned so that, with the coils carrying equal energizing currents, the more significant spherical harmonic coefficients are eliminated.

Abstract: A multi-pulse radio frequency signal sequence includes a 90.degree. excitation pulse (50) and at least a first 180.degree. refocusing pulse (52) and a second 180.degree. refocusing pulse (54). The excitation pulse and first refocusing pulse are separated by a duration A and the first and second refocusing pulses are separated by A+B. A free induction decay (60) follows the excitation pulse, a first spin echo (62) occurs a duration A after the first refocusing pulse and a second spin echo (64) occurs the duration B after the second refocusing pulse. A first read gradient (90) is applied between the excitation and first refocusing pulses; a second read gradient (92) is applied between the first refocusing pulse and the first spin echo; a third read gradient (94) is applied between the first spin echo and the second refocusing pulse; and a fourth read gradient (96) is applied between the second refocusing pulse and the second spin echo. Because the 90.degree. and 180.degree.

Abstract: A nuclear magnetic resonance imaging method and apparatus using the Hahn spin echo technique wherein dephasing of spins due to selection field gradients (G1x, G2x, G3x) applied during the radio frequency excitation pulses (B1 (90.degree.), B2 (90.degree.), B3 (90.degree.) of the Hahn technique is corrected solely by magnetic field gradients (-G'x, -G2'x) applied before the last radio frequency excitation pulse.

Abstract: In a steady state free precession (SFP) magnetic resonance imaging method, after each pulse of an applied train of phase coherent RF pulses which excite magnetic resonance spins in a region of a body being examined, magnetic field gradients are applied to encode the excited spins and the encoded spins are detected, and at least one further magnetic field gradient is then applied to rephase the spins by the time the next RF pulse is applied.

Abstract: An NMR chemical shift imaging method and apparatus wherein a number of experiments are performed with different encoding gradients sufficient to obtain a desired spatial resolution in the image, and each of said number of experiments is repeated for each of a number of different delay times between excitation and the start of data collection sufficient to obtain a desired chemical shift resolution in the image.

Abstract: A phantom for use in assessing the performance of an NMR imaging apparatus which enables quantitative assessments of image slice width and spatial resolution under different conditions of contrast to be made, and which enables an assessment of overall performance of the apparatus to be made to facilitate comparison of the performance of the apparatus when operating in different modes. The structure and methods of use of the phantom are described.