Showing papers by "Evangelos Trifon Laskaris published in 1999"

Open supercondutive magnet having shielding

Abstract: An open superconductive magnet useful in magnetic resonance imaging (MRI) applications. The magnet has two spaced-apart assemblies and preferably has a "C" shape. Each assembly has: a vacuum enclosure having a longitudinal axis and surrounding a bore; a magnetizable pole piece located within the bore and outside the vacuum enclosure; and a superconductive main coil, a superconductive shielding coil, and a magnetizable ring positioned within the vacuum enclosure. There is no magnetizable solid path between the two pole pieces. Preferably, the ring is positioned longitudinally between the main and shielding coils.

Laminate tiles for an MRI system and method and apparatus for manufacturing the laminate tiles

Abstract: 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.

Shielded and open superconductive magnet

Abstract: An open superconductive magnet useful in magnetic resonance imaging (MRI) applications. The magnet has two spaced apart assemblies, wherein each assembly has a superconductive shielding coil spaced longitudinally outward and apart from a superconductive main coil. A magnetizable pole piece is spaced apart from the coils, has a radially-outer portion at least partially radially overlapping the main coil, and has a longitudinally-inner portion which projects longitudinally inward past the longitudinally outer end of the main coil.

Magnet having a shim for a laminated pole piece

Abstract: A magnet having an imaging volume, a pole piece with a laminated portion including a first surface hole, a non-magnetizable first insert with an internally-threaded hole, and a first shim with a shape of an externally-threaded bolt. The first insert is positioned in the first surface hole and is attached to the pole piece. The first shim is threaded into the hole of the first insert. Additional shims for additional inserts for additional surface holes are used to shim the magnet to reduce magnetic field inhomogeneities in the imaging volume.

Apparatus and method for a superconductive magnet with pole piece

Abstract: A magnet, such as an open magnetic-resonance-imaging (MRI) magnet) has a first assembly including a superconductive main coil and a magnetizable pole piece which, during magnet operation, has a temperature equal to generally the temperature of the main coil. In one example, a cryogenic-fluid (e.g., liquid helium) dewar encloses the main coil, and the dewar has an interior surface defined in part by a surface portion of the pole piece. A method for providing a homogeneous imaging volume for a magnet includes steps to construct the above-described magnet.

Open magnet having shielding

Abstract: An open magnet useful in magnetic resonance imaging (MRI) applications. The magnet has two spaced-apart assemblies. Each assembly has a shielding coil located longitudinally outward from a main coil, a magnetizable member not carrying an electric current and spaced apart from and proximate the main and shielding coils, and a magnetizable pole piece spaced apart from the magnetizable member: The method of the invention generates a magnetic field in a first area between the two assemblies while shielding a second area not between the two assemblies from a stray magnetic field by creating the previously-described open magnet.

Open and shielded supercondutive magnet

Abstract: An open superconductive magnet useful in magnetic resonance imaging (MRI) applications. The magnet has two spaced apart assemblies, wherein each assembly has a magnetizable pole piece and a magnetizable ring radially spaced outwardly apart from, and at least partially longitudinally overlapping, the pole piece. A superconductive main coil is positioned radially between the pole piece and the ring. A superconductive shielding coil is positioned radially outward from the superconductive main coil and longitudinally outward from the longitudinally outer end of the ring.

Open superconductive magnet having a cryocooler coldhead

Abstract: An open magnet has vertically aligned first and second assemblies each with at least one superconductive main coil. At least one support member is vertically aligned and attached to, the first and second assemblies. At least one cryocooler coldhead is aligned generally horizontally and has a housing which is attached to, and receives weight-bearing support from, one of the first and second assemblies.

Open magnet with floor mount

Abstract: A vertically-aligned open magnet includes first and second (i.e., top and bottom) assemblies each having a longitudinally-extending and vertically-aligned axis, a superconductive main coil, and a vacuum enclosure enclosing the main coil. At least one support beam has a first end attached to the first assembly and has a second end attached to the second assembly. An annularly-cylindrical support skirt is coaxially aligned with the axes, has a first longitudinal end attached to the second assembly and has a second longitudinal end supportable by a floor.

Pole piece assembly and open magnet having same

Abstract: A magnet pole piece assembly has first and second pole pieces and at least one support member. The pole pieces have longitudinally aligned and facing surface recesses. The support member has a central segment and first and second end segments abuttingly and metallurgically attached to the central segment. The first and second end segments are positioned within a corresponding surface recess of the first and second pole piece and are abuttingly and metallurgically attached to the corresponding pole piece. An open magnet adds main coils to the magnet pole piece assembly.

Magnet having shielding

Abstract: A magnet, such as a closed, superconductive, magnetic-resonance-imaging (MRI) magnet, includes a main coil and includes a shielding coil positioned radially outward from the main coil. A magnetizable member is positioned radially outward from the main coil and radially inward from the shielding coil to supplement the strength, and increase the homogeneity of, the magnetic field created, at least in part, by the main coil and to supplement the shielding provided, at least in part, by the shielding coil.

Superconductive magnet having a tube suspension assembly

Abstract: A superconductive magnet includes a cryogenic vessel enclosing superconductive coils, a thermal shield enclosing the cryogenic vessel, a vacuum enclosure enclosing the thermal shield, a tube suspension assembly having a plurality of tubes located between respective ones of the cryogenic vessel, thermal shield and vacuum enclosure and axially overlapped and interconnected with the cryogenic vessel, thermal shield and vacuum enclosure and the tubes forming bonded joints with one another, and a plurality of locking clip arrangements attached to and having portions at least partially overlapping the bonded joints of the tubes of the suspension assembly so as to reinforce and strengthen the bonded joints.

Magnet including shielding

Abstract: A magnet, such as a closed, superconductive, magnetic-resonance-imaging (MRI) magnet includes a main coil, a correction coil, and a shielding coil positioned radially outward from the main and correction coils. Two magnetizable members are positioned radially outward from the main and correction coils and radially inward from the shielding coil to shorten the magnet, to supplement the strength, and increase the homogeneity of, the magnetic field created, at least in part, by the main and correction coils and to supplement the shielding provided, at least in part, by the shielding coil.

Laminated composite shell assembly with joint bonds

Abstract: A laminated composite shell assembly includes composite shells assembled together and having joint bonds connecting the assembly with an external structure and pinch rings assembled to the shells adjacent the joint bonds so as to reinforce the same The composite shells and pinch rings are cylindrical in configuration and made of layers of graphite-epoxy material having fibers oriented in desired stacking sequences The shells and pinch rings are concentrically assembled in a desired sequence with some of the shells being adapted to perform a structural load bearing function while others of the shells are adapted to perform a load transfer function and with the pinch rings adapted to perform additional stiffening as well as load redistributing and transfer functions in the regions of the joint bonds between the assembled shells and the external structure

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

Abstract: There iscribed a laminate tile pole piece (50) for an MRI (71-77) and a method and a mold for manufacturing laminate tile metal pole pieces (50) for an MRI. Each laminate tile(42) has a trapezoidal or annular sector shape. The trapezoidal shape allows the tiles (42) to be attached side by side to form a multiple concentric annular array pole piece (50) without using oddly shaped edge filler tiles needed to fill a circular pole piece with square tiles. The pole piece (50) is made by placing a plurality of tiles (42) into a mold (100) and filling the mold (100) with an adhesive substance to bind the plurality of tiles (42) into a unitary tile body (120). The unitary tile body (120) is then removed from the mold (100) and attached to a pole piece base (51) to form the pole piece (50). The mold cavity surface (101) preferably has a non-uniform contour (110). The bottom surface of the unitary tile body (120) forms a substantially inverse contour(114) of the mold cavity surface contour (110)

Laminated composite shell assembly for magnet applications

Abstract: A uniform stiffness laminated composite shell assembly includes a plurality of composite shells. The shells are made of layers of laminates of graphite-epoxy material having fibers oriented in various stacking sequences for performing different functions in the assembly. The shells are concentrically assembled in a desired sequence with some of the adjacent ones of the shells being at least equal to or greater in axial length than others thereof and with some of the shells being adapted to perform a structural load bearing function while others of the shells being adapted to perform a load transfer function. The desired sequence of shells of the composite shell assembly provides enhanced thermal insulating properties and efficient load distributing properties for enabling use of the assembly as a tube suspension in a superconductive magnet.

Magnet with shielding

Abstract: A magnet, such as a closed, superconductive, magnetic-resonance-imaging (MRI) magnet includes a main coil, a magnetizable article, and a shielding coil positioned radially outward from the main coil and magnetizable article. Two magnetizable members are positioned radially outward from the main coil and magnetizable article and radially inward from the shielding coil to supplement the strength, and increase the homogeneity of, the magnetic field created, at least in part, by the main coil and magnetizable article and to supplement the shielding provided, at least in part, by the shielding coil.

Magnetic pole piece for magnetic resonance imaging device and method and mold for manufacturing magnetic pole piece

Abstract: PROBLEM TO BE SOLVED: To provide a method and a mold for manufacturing a laminated tile magnetic pole piece and a laminated tile metallic magnetic pole piece for MRI. SOLUTION: Respective laminated tiles 42 are formed into a trapezoidal or annular sectorial shape. By the shape, the tiles can be attached horizontally side by side and many concentric annular array bodies are formed. Thus, without using an edge part filling tile in an incomplete shape required at the time of filling a circular magnetic pole piece with quadrilateral tiles, this magnetic pole piece 50 is formed. In order to form the magnetic pole piece, by arranging the plural number of the tiles in this mold and filling the mold with an adhesive material, the plural number of the tiles are connected and an integrated tile main body is formed. Then, by taking out the integrated tile main body from the mold and attaching it to the base part 51 of the magnetic pole piece, the magnetic pole piece is formed.

Design method for assembly composed of curved structure

Abstract: PROBLEM TO BE SOLVED: To provide the design method of an assembly composed of one or more curved structures (cylinders for instance) constituted of plural laminated composite material layers respectively provided with fiber arrangement directions. SOLUTION: The assembly is modeled in a digital computer program for calculating the response of the assembly to a prescribed load based on the value of the fiber arrangement direction of respective layers first (220). Then, the value of the fiber arrangement direction of the respective layers is decided corresponding to genetic algorithm relating to a composite material for executing a genetic operation (like substitution) to the value of a previous time (230). Such a procedure is repeated until an appropriate response is obtained by the computer program (250). This method is extended so as to geometrically divide the assembly into sections and then decide the number of the layers in the respective sections. COPYRIGHT: (C)2000,JPO

Open type superconducting magnet

Abstract: PROBLEM TO BE SOLVED: To provide an open type superconducting magnet being useful for the usage of a magnetic resonance imaging(MRI). SOLUTION: The magnet 10 is provided with two separated assembling bodies 12 and 30. The respective assembling bodies are provided with superconducting shielding coils 22 and 32 which are arranged at the outer side in a vertical direction compared with superconducting main coils 14 and 32. Magnetization possible magnetic polar pieces 24 and 42 are arranged to be separated from the main coils and the shielding coils, provided with radius direction outer parts 26 and 44 to be overlapped with the superconducting main coils at least partially in a radius direction and also provided with vertical direction inner parts 28 and 66 which are projected inward in the vertical direction over the vertical direction outer ends 20 and 38 of the superconducting main coils.