Abstract: A material having magnetic permeability at r.f. frequency, for example a microstructured magnetic material has a magnetic permeability of negative value but unity magnitude over a particular r.f. frequency range. The singularity in the flux pattern has the result that magnetic resonant disturbances in a plane C,E normal to the line C,D are focussed into a plane D,F also normal to the line C,D and vice versa. This is particularly applicable to magnetic resonance apparatus, since the material can be used to transfer the r.f. magnetic flux distribution in a target region in a patient, for example at C,E to D,F where the flux may be directly measured by receive coils. Equally, transmit coils may generate flux to be focussed into the target region by the material. Magnetic resonance apparatus may be constructed which does not require gradient coils, and r.f. hypothermia may be carried out in a focussed way, minimising damage to surrounding tissue.

Abstract: Microstructure materials which can be tuned to a particular range of r.f. frequencies to display particular magnetic permeabilities have been proposed. A typical material is made of an array of capacitive elements e.g. spirals or rolls of conducting material on a non-conducting substrate. These materials can be used as a guide which is effective for the particular band of frequencies to which it is tuned. In one example, the rolls (2a to 2c) guide magnetic flux along ducts (1, 2, 3) while rolls (4a, 5a) guide magnetic flux along ducts (4, 5). Flux can thus be guided upwardly along duct (2), along ducts (4 and 5), and down ducts (1, 3), or vice versa.

Abstract: A pad which has a magnetic permeability greater than that of free space at the frequency of nuclear magnetic resonance but which is non-magnetic in steady magnetic fields is disposed between an RF coil and the surface of a patient. The pad is surmounted by a block having similar properties. Two further pads extend from the ends of the block to the surface of the patient. The pads and block guide magnetic flux, which is indicative of magnetic resonant active nuclei in the patient, towards an RF coil which is spaced apart from the surface of the patient/object under examination.

Abstract: A structure (40) with switchable magnetic properties comprises: an array of capacitive elements (44) in which each capacitive element (44) includes a low resistance conducting path and is such that a magnetic component (H) of electromagnetic radiation (12) lying within a predetermined frequency band induces an electrical current (j) to flow around said path and through said associated element (44). The size of the elements (44) and their spacing (&agr;) apart are selected such as to provide a predetermined permeability (&mgr;) in response to said received electromagnetic radiation (12). Each capacitive element (44) comprises a plurality of stacked planar sections (42) each or which comprises at least two concentric spiral conducting members or tracks (46, 48) which are electrically insulated from each other. A switchable permittivity material, such as Barium Strontium Titanate (BST) is provided between the tracks.

Abstract: Microstructured materials which can be tuned to a particular range of r.f. frequencies to display particular magnetic permeabilities have been proposed. A typical material is made of an array of capacitive elements e.g. spirals or rolls of conducting material on a non-conducting substrate. These materials can be used as screening material which is effective for the particular band of frequencies to which it is tuned. In one example, the rolls 2 to 5 are orientated normal to the face of the screen 1, which reflects or absorbs the magnetic vector of electromagnetic radiation impinging normal onto the reflector face.

Abstract: A material having magnetic permeability at r.f. frequency, for example a microstructured magnetic material has a magnetic permeability of negative value but unity magnitude over a particular r.f. frequency range. The singularity in the flux pattern has the result that magnetic resonant disturbances in a plane C,E normal to the line C,D are focussed into a plane D,F also normal to the line C,D and vice versa. This is particularly applicable to magnetic resonance apparatus, since the material can be used to transfer the r.f. magnetic flux distribution in a target region in a patient, for example at C,E to D,F where the flux may be directly measured by receive coils. Equally, transmit coils may generate flux to be focussed into the target region by the material. Magnetic resonance apparatus may be constructed which does not require gradient coils, and r.f. hypothermia may be carried out in a focussed way, minimising damage to surrounding tissue.

Abstract: In magnetic resonance imaging apparatus, an array of coils (7, 8, 9, 10) is used to receive magnetic resonance signals from a desired region of a patient. Screens 11 to 13 and 14 and 15 are provided between the coils and at the ends of the array of coils to control the sensitive region A of each coil but, in accordance with the invention, the screening properties of the screens is controllable so that for example the screens may be made inoperative beneath the plane of the array of coils so that each has the field of view B, in order to vary the properties produced by the array. Other uses of screens are described.

Abstract: In magnetic resonance imaging apparatus, an array of coils (7, 8, 9, 10) is used to receive magnetic resonance signals from a desired region of a patient. Screens 11 to 13 and 14 and 15 are provided between the coils and at the ends of the array of coils to control the sensitive region A of each coil but, in accordance with the invention, the screening properties of the screens is controllable so that for example the screens may be made inoperative beneath the plane of the array of coils so that each has the field of view B, in order to vary the properties produced by the array. Other uses of screens are described.

Abstract: A structure (40) with switchable magnetic properties comprises: an array of capacitive elements (44) in which each capacitive element (44) includes a low resistance conducting path and is such that a magnetic component (H) of electromagnetic radiation (12) lying within a predetermined frequency band induces an electrical current (j) to flow around said path and through said associated element (44). The size of the elements (44) and their spacing (a) apart are selected such as to provide a predetermined permeability (&mgr;) in response to said received electromagnetic radiation (12). Each capacitive element (44) comprises a plurality of stacked planar sections (42) each of which comprises at least two concentric spiral conducting members or tracks (46, 48) which are electrically insulated from each other. A switchable permittivity material, such as Barium Strontium Titanate (BST) is provided between the tracks.

Abstract: Microstructure materials which can be tuned to a particular range of r.f. frequencies to display particular magnetic permeabilities have been proposed. A typical material is made of an array of capacitive elements e.g. spirals or rolls of conducting material on a non-conducting substrate. These materials can be used as a guide which is effective for the particular band of frequencies to which it is tuned. In one example, the rolls (2a to 2c) guide magnetic flux along ducts (1, 2, 3) while rolls (4a, 5a) guide magnetic flux along ducts (4, 5). Flux can thus be guided upwardly along duct (2), along ducts (4 and 5), and down ducts (1, 3), or vice versa.

Abstract: Microstructured materials which can be tuned to a particular range of r.f. frequencies to display particular magnetic permeabilities have been proposed. A typical material is made of an array of capacitive elements e.g. spirals or rolls of conducting material on a non-conducting substrate. These materials can be used as screening material which is effective for the particular band of frequencies to which it is tuned. In one example, the rolls 2 to 5 are orientated normal to the face of the screen 1, which reflects or absorbs the magnetic vector of electromagnetic radiation impinging normal onto the reflector face.

Abstract: An electrically-controllable liquid crystal filter device comprises two partially-reflecting substrate structures mounted substantially parallel to each other with a space therebetween to form a Fabry-Perot filter. A layer of ferroelectric liquid crystal material is disposed in the space, the liquid crystal material being switchable, by application of an electric field, between different refractive index values whereby the device is switchable between transmissive and reflective states for light of a particular narrow wavelength band. The spacing of the substrate structures is selected in relation to the wavelength of light to be transmitted, such that the Fabry-Perot filter operates in a low order state, which may be the first order.