Abstract: A method of producing a waveguide and a coupling transducer for connecting the waveguide to a load is disclosed. The method comprises: forming a series of similar circuits each circuit comprising two capacitors and at least one inductor section, the circuits being coupled to together to form the waveguide; and removing one of the capacitors and at least part of the at least one inductor section from one of the circuits to form the coupling transducer.

Abstract: A probe 1, for use with magnetic resonance imaging apparatus, which is designed to be inserted into and removed from a patient and which comprises a former 2 upon which an r.f. coil 3 is mounted is characterised in that the former also carries at least one transducer or sensor 6-9 by which the targeting of energy relating to an interventional procedure to an area in the vicinity of the transducer may be controlled both as to position and strength.

Abstract: A pair of annular magnets (10) generate a vertical magnetic flux field through an imaging volume (12). The flux is focused by a pair of Rose rings (26) of high cobalt steel. A high order shim set includes a plurality of permanently magnetized or magnetized iron rings (32a, 32b, 32c, 32d) which cooperatively interact with the magnet assembly to optimize the homogeneity of the magnetic flux through the imaging volume. One of the permanent magnetic rings (32d), is mounted with an opposite polarity relative to the others. The magnetized rings are mounted in a non-ferrous, electrically insulating support structure (34) such that gradient coils (50) can be positioned behind the permanent magnet rings. A flux return path (14, 16, 18, 20, 22, 24) provides a low flux resistant path from adjacent the Rose ring at one side of the imaging volume remotely around the imaging volume to a position adjacent the Rose ring at the other side of the imaging volume.

Abstract: A region of interest of a subject (20) on a subject support (18) is positioned above a ferrous pedestal (16, 116) that is supported on a ferrous floor yoke portion (76, 176). A lower imaging coil assembly (50) including a lower gradient coil (52), a radio frequency coil (54), and a lower pole piece (58) are disposed between the pedestal and a region of interest of the subject. An upper imaging coil assembly (40) including an annular gradient coil (42, 142) and an upper annular pole piece (44, 144) is supported from a ceiling ferrous yoke member (74, 174). The upper imaging coil assembly is supported by supports (70, 170) which are moved by drives (72, 78, 172) to raise and lower the upper imaging coil assembly. A laser gauging system (80, 180) gauges the position of the upper imaging coil assembly such that, with a control circuit (82), the upper imaging coil assembly is accurately repositioned at preselected imaging positions.

Abstract: A magnetic resonance imaging scanner includes a pair of opposing pole pieces (20, 20') disposed symmetrically about an imaging volume (24) facing one another. The pair of opposing pole pieces (20, 20') includes a first ferrous pole piece (20) which has a front side (22) facing the imaging volume (24) and a back side (28). Also included is a second ferrous pole piece (20') which also has a front side (22) facing the imaging volume (24) and a back side (28). A magnetic flux return path (30) extends, remotely from the imaging volume (24), between a point adjacent the back side 28 of the first pole piece (20) and a point adjacent the back side 28' of the second pole piece (20)'. A source of magnetic flux generates a magnetic flux through the imaging volume (24), the pair of opposing pole pieces (20, 20'), and the magnetic flux return path (30). An array of annular hoops (40) and (40') are integrated with the pair of opposing pole pieces (20, 20') for homogenizing the magnetic flux through the imaging volume (24).

Abstract: A magnetic resonance imaging suite is sheathed with plates (32, 34, 36) of iron or other ferrous material. The plates define projections (42, 44, 54, 54', 68) in alignment with each other on opposite ceiling and floor or wall surfaces. A pair of magnetic pole pieces (10, 10'; 50, 50'; 60, 60') are surrounded by superconducting electromagnetic coils (12, 12'; 52, 52'; 62, 62'). The pole pieces are positioned between the ferrous plates in axial alignment. When current flows through the electromagnetic coils, magnetic flux flows between the pole pieces. The ferrous wall sheathing or other ferrous constructions define a flux return path. The pole pieces are magnetically attracted toward each other and are each magnetically mirrored in and attracted toward the adjacent ferrous flux return path.

Abstract: A magnetic resonance imaging apparatus (10) includes a couch (54) for supporting a region of interest of a subject (44) being examined in an examination region. A main magnet for generating a substantially uniform temporally constant main magnetic field through the examination region includes a stationary pole piece (24), a movable pole piece (22), a ferrous flux return path (26), and a magnetic flux generator that selectively generates magnetic flux that flows between the pole pieces (22, 24) through the examination region and through the ferrous flux return path (26) which connects the pole pieces (22, 24). The stationary pole piece (24) is arranged adjacent a first side of the examination region.

Abstract: In magnetic resonance imaging (MRI) apparatus in which weight considerations and accessibility of the patient result in a magnet 1 with a large bore 2, in order to enable spectroscopy or other activities requiring large magnetic fields to nevertheless be carried out, a small magnet 4 with its own cryostat can be moved from an inoperative position A to an operative position B, in which the large magnet acts as a shield winding for the small magnet.

Abstract: A magnetic resonance imaging suite is sheathed with plates (32, 34, 36) of iron or other ferrous material. The plates define projections (42, 44, 54, 54', 68) in alignment with each other on opposite ceiling and floor or wall surfaces. A pair of magnetic pole pieces (10, 10'; 50, 50'; 60, 60') are surrounded by superconducting electromagnetic coils (12, 12'; 52, 52'; 62, 62'). The pole pieces are positioned between the ferrous plates in axial alignment. When current flows through the electromagnetic coils, magnetic flux flows between the pole pieces. The ferrous wall sheathing or other ferrous constructions define a flux return path. The pole pieces are magnetically attracted toward each other and are each magnetically mirrored in and attracted toward the adjacent ferrous flux return path.

Abstract: In a magnet system, e.g. for use in a magnetic resonance apparatus, wherein a magnetic field is produced in a gap between pole pieces (5) joined by a yoke (7) by an electric drive coil arrangement carried on the yoke, stabilisation against variations in the field in the gap is provided by a stabilising arrangement (43) wherein over a section of its length the yoke is divided into a plurality of discrete parallel finger-like portions (45) each of which is surrounded by a separate ring (47) of superconducting non-magnetic material.

Abstract: A probe (3) for use in in vivo imaging of a microscopic internal region (1) of a patient's body using magnetic resonance techniques incorporates a member (7) having a surface having a pattern of projections (9) formed thereon. In use the surface contacts the surface of the region to trap between the projections molecules in the region, thereby to restrict diffusion of the molecules and so improve resolution of the image obtained.

Abstract: A radio frequency signal detector coil arrangement (17) for a magnetic resonance apparatus comprising a planar coil (25) and an annular magnetic flux rejecting arrangement (25) disposed coaxially with the planar coil, on one side thereof, which reduces the sensitivity of the planar coil to signals from sources remote from the axis of the planar coil. One embodiment of the flux reducing arrangement comprises an annular superconducting member (35) disposed between the planar coil and the body (31). In other embodiments it comprises an arrangement of coils which conform to a tubular surface coaxial with the planar coil, and electrically connected therewith.

Abstract: In imaging an internal region of the human body, using optical or NMR techniques, a high resolution image is produced by imaging a layer of material formed on the region of interest which conforms to the surface of the region. The material is preferably a lipid, introduced into the body and positioned adjacent the region of interest using a probe.

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: In a magnetic resonance apparatus, motion artifacts in data obtained are reduced by transmitting, during data collection, an r.f. signal of known amplitude and of a frequency different from that of the spins excited for imaging, and utilizing a signal induced by that r.f. signal in a coil (45A,45B) positioned adjacent the data signal detector means (10A,10B) to effect an alteration of the signal produced by the detector means (10A,10B) such as to reduce the motion artifacts.

Abstract: A method of determining the proportions of different components of material in a duct comprises exciting nuclear magnetic spins of nuclei of a species common to the components in a region of the duct and utilizing the resulting free induction decay (FID) signal. The nuclear spins are excited simultaneously in the components and the proportions are determined by measuring the phase of the FID signal relative to a phase datum. The method finds particular application for measuring the proportions of oil and water in material obtained from a sub-sea oil well.

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 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 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.