General Electric Company

William D Barber

Evangelos Trifon Laskaris

Bulent Aksel

Christopher Judson Hardy

Peter B Roemer

Michele Dollar Ogle

Paul Shadforth Thompson

Xianrui Huang

Ronald Dean Watkins

Kenneth William Rohling

Kathleen Melanie Amm

Peter G Frischmann

John F Schenck

Paul St Mark Shadforth Thompson

Johannes Martinus Van Oort

Steven G Karr

Harvey E Cline

Charles L Dumoulin

George E Possin

Matthew N O'Donnell

Jeffrey Wayne Eberhard

William A Edelstein

Robert David Darrow

William E Lorensen

Kiruba Sivasubramaniam

Richard Andrew Ranze

Joseph Leagrand Mundy

Gerald J Carlson

Raymond A Sigsbee

Kirby Gannett Vosburgh

Jish M Wang

Norman C Gittinger

James R Whitten

Thomas M Cipolla

Arthur C Chen

Walter H Berninger

Samuel M Blumenfeld

Richard L St Peters

Cornelius Jan Von Morze

A composite sealed vessel is provided. The vessel includes a non-metallic, generally cylindrical inner containment piece, a non-metallic, generally cylindrical outer containment piece disposed around the inner containment piece. A pair of non-metallic flanges are disposed at ends of the inner and outer containment pieces to form a closed structure defining a cavity therein. The vessel also includes a metallic external lining disposed over the closed structure to form a leak-tight pressure boundary.

Thin metal layer vacuum vessels with composite structural support

A cryogenically cooled radiofrequency (RF) coil structure for use in Magnetic Resonance Imaging (MRI) and method for cryogenically cooling RF coils are provided. The cryogenically cooled RF coil structure comprises a sealed structure constructed of non-conducting material and adapted for containing a cooling substance and at least one RF coil disposed integrally in contact with the sealed structure such that sealed structure and integrally disposed RF coil are disposed about an object to be imaged.

Cryogenically cooled radiofrequency coil array for magnetic resonance imaging

Methods and apparatus for fabricating a magnetic resonance imaging (MRI) gradient coil for generating magnetic field gradients are provided. The method includes determining a pattern of gradient current paths on a surface using a set of stream functions oriented in at least one of a z-gradient, a y-gradient; and an x-gradient, and arranging conductive material to define a current path that conforms to the determined gradient current paths.

Methods and systems for fabricating magnetic resonance gradient coils

An imaging system including at least one pole piece is described. The at least one pole piece includes at least two grain-oriented sheets that are stacked together, where a direction of easy magnetization of a first of the at least two grain-oriented sheets is different than a direction of easy magnetization of a second of the at least two grain-oriented sheets.

Systems and methods for fabricating pole pieces for magnetic resonance imaging systems

Briefly in accordance with one aspect, the present technique provides a method for heating a permanent magnet in a magnetic resonance imaging system. The method for heating a permanent magnet includes directly heating a surface of the permanent magnet using a surface heater. The present technique also provides a system for heating a permanent magnet in a magnetic resonance imaging system. The system includes a surface heater configured to directly heat a surface of the permanent magnet.

Method and apparatus for maintaining thermal stability of permanent magnets in MRI systems

A method is presented for manufacturing laminate tile metal pole pieces for an MRI. Each laminate tile has a trapezoidal or annular sector shape. The trapezoidal shape allows the tiles to be attached side by side to form a multiple concentric annular array pole piece without using oddly shaped edge filler tiles needed to fill a circular pole piece with square tiles. The pole piece is made by placing a plurality of tiles into a mold and filling the mold with an adhesive substance to bind the plurality of tiles into a unitary tile body. The unitary tile body is then removed from the mold and attached to a pole piece base to form the pole piece. The mold cavity surface preferably has a non-uniform contour. The bottom surface of the unitary tile body forms a substantially inverse contour of the mold cavity surface contour.

Method of making a pole piece for an MRI

A laminate tile pole piece for an MRI, a method and a mold for manufacturing laminate tile metal pole pieces for an MRI. Each laminate tile has a trapezoidal or annular sector shape. The trapezoidal shape allows the tiles to be attached side by side to form a multiple concentric annular array pole piece without using oddly shaped edge filler tiles needed to fill a circular pole piece with square tiles. The pole piece is made by placing a plurality of tiles into a mold and filling the mold with an adhesive substance to bind the plurality of tiles into a unitary tile body. The unitary tile body is then removed from the mold and attached to a pole piece base to form the pole piece. The mold cavity surface preferably has a non-uniform contour. The bottom surface of the unitary tile body forms a substantially inverse contour of the mold cavity surface contour.

Mold for bonding MRI pole piece tiles and method of making the mold

A laminate tile pole piece for an MRI. Each laminate tile has a trapezoidal or annular sector shape. The trapezoidal shape allows the tiles to be attached side by side to form a multiple concentric annular array pole piece without using oddly shaped edge filler tiles needed to fill a circular pole piece with square tiles. The pole piece is made by placing a plurality of tiles into a mold and filling the mold with an adhesive substance to bind the plurality of tiles into a unitary tile body. The unitary tile body is then removed from the mold and attached to a pole piece base to form the pole piece. The mold cavity surface preferably has a non-uniform contour. The bottom surface of the unitary tile body forms a substantially inverse contour of the mold cavity surface contour.

Laminate tile pole piece for an MRI, a method manufacturing the pole piece and a mold bonding pole piece tiles

An MRI system includes a magnet which produces the main polarizing magnetic field. Variations in strength of this field are corrected by a temperature compensation system that calculates a compensating flux needed to maintain the field at constant strength. The compensating flux is calculated from changes in sensed magnet temperature and a magnet temperature coefficient. One or more correction coils are wound around the magnet and driven with the current necessary to produce the compensating flux.

Temperature compensated NMR magnet and method of operation therefor

A laminate tile pole piece for an MRI, a method and an apparatus for manufacturing laminate tile metal pole pieces for an MRI. Each laminate tile has a trapezoidal or annular sector shape. The trapezoidal shape allows the tiles to be attached side by side to form a multiple concentric ring pole piece without using oddly shaped edge filler tiles needed to fill a circular pole piece with square tiles. The laminate tiles are formed by unwinding a metal ribbon, guiding the ribbon through an adhesive bath, winding the ribbon on a polygonal bobbin, such as a rectangular bobbin, to form a coil with at least one flat side, removing the coil from the bobbin, cutting the coil into laminate bars and shaping the laminate bars into trapezoidal or annular sector shaped laminate tiles. The apparatus contains an adhesive bath, a polygonal shaped bobbin, bobbin side plates for guiding the ribbon onto the bobbin and pressure plates for controlling the thickness of the coil. The apparatus also contains a cutting tool for cutting the coil into laminate bars after the coil is removed from the bobbin and a water jet to shape the laminate bars into trapezoidal or annular sector shaped laminate tiles.

Laminate tiles for an MRI system and method and apparatus for

Pole faces for an open magnetic resonance (MR) imaging system are constructed from a number of blocks having laminate sheets. The laminate sheets of the blocks are aligned, such that they are parallel to the flux of an applied time-changing magnetic field. Each laminate sheet is constructed of an amorphous material such that there is no predominant magnetic field alignment. This construction reduces eddy currents induced in the pole faces, and reduces residual magnetization, thereby reducing artifacts in an acquired image.

Low eddy current and low hysteresis magnet pole faces in MR imaging

The invention is directed to a gradient coil assembly for MR imaging which includes a gradient coil set comprising inner and outer gradient coils, the inner gradient coil located within the outer gradient coil and surrounding or otherwise proximate to an imaging volume. The system further includes means for selectively energizing the inner and outer gradient coils to generate a resultant gradient field in the imaging volume. The energized inner and outer gradient coils are also disposed to collectively generate an eddy current field component in a region between the outer coil and a conductive structure spaced-apart therefrom when the inner gradient coil is displaced along an axis from a specified position with respect to the outer gradient coil. A compensation coil is selectively positioned with respect to the inner and outer gradient coils, and means are provided for applying a compensation current to the compensation coil to generate a magnetic field which substantially cancels the eddy current component, the compensation current and the displacement of the inner coil along the axis from the specified position having a specified relationship.

Misalignment compensation for MR gradient coil assembly

A magnetic field gradient apparatus for use in a magnetic resonance (MR) imaging system employing open magnets allows access to a patient while the patient is being imaged. The magnetic field gradient apparatus employs two gradient coil assemblies and a gradient coil amplifier. Each gradient coil assembly has a gradient coil carrier with at least one gradient coil disposed on it. Each gradient coil carrier is comprised of a cylinder with a flange at one end. The gradient coil assemblies are positioned in the bore of each ring of the open magnet and spaced apart from each other allowing access to the patient. The gradient coil amplifier provides current through the gradient coils to create a magnetic field gradient which has high linearity inside an imaging volume. A coil is disposed on cylinders which surround each gradient coil assembly and fit inside the bore of each ring which acts as an active shield and minimizing eddy currents in conductors outside the gradient coil assemblies.

Open gradient coils for magnetic resonance imaging

A magnetic resonance (MR) imaging system for use in a medical procedure employs an open main magnet allowing access to a portion of a patient within an imaging volume, for producing a main magnetic field over the imaging volume; a set of open gradient coils which provide magnetic fields gradients over the imaging volume without restricting access to the imaging volume; a radiofrequency coil set for transmitting RF energy into the imaging volume to nutate nuclear spins within the imaging volume and receive an MR response signal from the nuclear spins; and a pointing device for indicating the position and orientation of a plane in which an image is to be acquired; an image control means for operating power supplies for the gradient coils and the RF coils to acquire an MR signal from the desired imaging plane; and a computation unit for constructing an image of the desired imaging plane. The MR imaging system is intended to operate to provide images to a physician during medical procedures to guide the physician in his procedures.

Magnetic resonance imaging system with pointing device

A method for minimizing the inhomogeneity of a static magnetic field, produced by a main magnet, over a selected arbitrary volume, by operation of a plurality N of shimming coils each independently producing an associated shimming magnetic field having an associated inhomogeneity which is a function of spatial location over that same volume, uses the steps of: measuring the magnitude of the main magnet field, in the absence of all shimming fields, at a plurality of locations X.sub.i upon the surface of an imaginary sphere enclosing the arbitrary volume; measuring the polarity and magnitude of each of the N shimming fields, with respect to the polarity and magnitude of a D.C. current flowing through the associated shimming coil, at the same plurality of locations X.sub.i upon the imaginary sphere surface; determining the weighted mean-square variation of the total field at each of another plurality of points Y.sub.i within the volume of said imaginary sphere; and (d) selecting the current magnitudes and polarities for each of the N shimming coils to provide each of the N associated shimming fields with magnitude and polarity to minimize the inhomogeneity of the main magnetic field in the arbitrary volume. The set of weighting coefficients may be selected to all be equal, or to emphasize at least one desired region of the arbitrary volume.

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Ballston Lake, NY, United States of America

William D Barber