Marconi Optical Components Limited

Ericsson Ab

Koninklijke Phillips Electronics N.v.

Marconi UK Intellectual Property Limited

Michael Charles Keogh Wiltshire

Ian R Young

John Brian Pendry

Joseph Vilmos Hajnal

David John Gilderdale

David James Larkman

Robert Ian Young

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.

Material having magnetic permeability at R.F. frequency

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 (to) guide magnetic flux along ducts () while rolls () guide magnetic flux along ducts (). Flux can thus be guided upwardly along duct (), along ducts (and), and down ducts (), or vice versa.

Guides for r.f. magnetic flux

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.

Magnetic resonance apparatus including an rf magnetic flux guiding structure for improving the signal-to-noise ratio

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

Structure with switchable magnetic properties

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 to are orientated normal to the face of the screen , which reflects or absorbs the magnetic vector of electromagnetic radiation impinging normal onto the reflector face.

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High Wycombe, United Kingdom

Michael Charles Keogh Wiltshire