Abstract: A magnet apparatus for a magnetic resonance imaging system, the magnet apparatus includes a vacuum vessel, a helium vessel disposed within the vacuum vessel and a thermal shield disposed between the vacuum vessel and the helium vessel. A set of passive compensation coils are disposed within the vacuum vessel or the helium vessel and used to compensate for magnetic field distortion caused by mechanical vibrations within the magnet apparatus.

Abstract: A magnet apparatus for a magnetic resonance imaging system, the magnet apparatus includes a cylindrical vacuum vessel, a closed loop cooling system disposed within the vacuum vessel and a cylindrical thermal shield disposed between the vacuum vessel and the closed loop cooling system. A set of passive compensation coils are disposed within the vacuum vessel and used to compensate for magnetic field distortion caused by mechanical vibrations within the magnet apparatus.

Abstract: A gradient coil apparatus for a magnetic resonance imaging (MRI) system includes an inner gradient coil assembly comprising at least one inner gradient coil and an outer gradient coil assembly comprising at least one outer gradient coil. At least one gradient coil interconnect is coupled to the inner gradient coil and the outer gradient coil. The gradient coil interconnect includes a wire assembly comprising a plurality of conductors. The wire assembly has a first end electrically coupled to the outer gradient coil assembly and a second end electrically coupled to the inner gradient coil. The gradient coil interconnect also includes a reinforcement material disposed around a portion of the wire assembly.

Abstract: A gradient coil apparatus for a magnetic resonance imaging (MRI) system includes an inner gradient coil assembly and an outer gradient coil assembly disposed around the inner gradient coil assembly. The outer gradient coil assembly has an outer surface, a first end and a second end. The gradient coil apparatus also includes a force balancing apparatus disposed around the outer surface of the outer gradient coil assembly. In one embodiment, the force balancing apparatus includes an active force balancing coil disposed around the outer surface of the outer gradient coil assembly. In another embodiment, the force balancing apparatus includes a first passive conducting strip disposed around the first end of the outer gradient coil assembly and a second passive conducting strip disposed around the second end of the outer gradient coil assembly.

Abstract: A magnet apparatus for a magnetic resonance imaging system, the magnet apparatus includes a cylindrical vacuum vessel, a closed loop cooling system disposed within the vacuum vessel and a cylindrical thermal shield disposed between the vacuum vessel and the closed loop cooling system. A set of passive compensation coils are disposed within the vacuum vessel and used to compensate for magnetic field distortion caused by mechanical vibrations within the magnet apparatus.

Abstract: A gradient coil apparatus for a magnetic resonance imaging (MRI) system includes an inner gradient coil assembly and an outer gradient coil assembly disposed around the inner gradient coil assembly. The outer gradient coil assembly has an outer surface, a first end and a second end. The gradient coil apparatus also includes a force balancing apparatus disposed around the outer surface of the outer gradient coil assembly. In one embodiment, the force balancing apparatus includes an active force balancing coil disposed around the outer surface of the outer gradient coil assembly. In another embodiment, the force balancing apparatus includes a first passive conducting strip disposed around the first end of the outer gradient coil assembly and a second passive conducting strip disposed around the second end of the outer gradient coil assembly.

Abstract: A gradient coil apparatus for a magnetic resonance imaging (MRI) system includes an inner gradient coil assembly comprising at least one inner gradient coil and an outer gradient coil assembly comprising at least one outer gradient coil. At least one gradient coil interconnect is coupled to the inner gradient coil and the outer gradient coil. The gradient coil interconnect includes a wire assembly comprising a plurality of conductors. The wire assembly has a first end electrically coupled to the outer gradient coil assembly and a second end electrically coupled to the inner gradient coil. The gradient coil interconnect also includes a reinforcement material disposed around a portion of the wire assembly.

Abstract: A shim coil design technique determines a position and a geometry of a room temperature (RT) shim coil to provide both a desired field homogeneity and a desired B0 field setting time. The simultaneous satisfaction of both field homogeneity and field settling time is achieved without a reduction of flux leakage from the shim coil, modification of main magnet protection circuitry, and without necessarily decoupling of the shim coil from the overall main magnet.

Abstract: A Magnetic Resonance Imaging (MRI) system is disclosed. The MRI system includes a cryogenic magnet assembly with a cryogenic vessel housing a superconducting magnet. Disposed radially inboard of the cryogenic magnet assembly are a gradient coil module and a plurality of room temperature steel rings proximate to the gradient coil module. A field of view is defined by at least the superconducting magnet, the gradient coil module, and the plurality of room temperature steel rings. In response to the superconducting magnet being energized, the room temperature steel rings create high order harmonics that serve to expand the magnetic field homogeneity FOV, and low order harmonics that tend to degrade the magnetic field homogeneity within the FOV. The low order harmonics are compensated for by the cryogenic magnet assembly.

Abstract: A magnetic resonance imaging system (10) includes a superconducting magnet (14) that generates a static magnetic field. A gradient coil assembly (50) with an associated patient bore enclosure (18) and a gradient coil (52) that generates a gradient magnetic field in the patient bore (18). A static field-shaping coil (11) resides between the superconducting magnet (14) and the patient bore (18) and supplements the static magnetic field.

Abstract: A Magnetic Resonance Imaging (MRI) system 50 is provided including a superconducting magnet coil assembly 54. The magnet coil assembly 54 includes a superconducting magnet 82 and forms an imaging volume 60. The superconducting magnet 82 generates a polarizing field in the imaging volume 60. A readout magnet 106 generates a readout field in the imaging volume 60. A controller 102 is electrically coupled to the readout magnet 106 and pulses the readout magnet 106 to generate a uniform magnetic field through the imaging volume 60. A method for performing the same is also provided.

Abstract: A gradient compensation system comprising a magnet assembly, at least one field-generating gradient coil operable for generating magnetic field gradients in three orthogonal coordinates, and at least one gradient compensation coil positioned adjacent to the magnet assembly and operable for generating a magnetic field to compensate for leakage fields. A system for eliminating image distortion in magnetic resonance imaging comprising a magnet assembly comprising an imaging gradient coil and an imaging volume, and at least one gradient compensation coil positioned adjacent to the magnet assembly operable for generating gradient compensation fields in response to the magnetic field change.

Abstract: A Magnetic Resonance Imaging (MRI) magnet field instability simulator (80) is provided. The simulator includes a rigid body motion generator (82) that simulates motion of one or more MRI system components. An eddy current analyzer (84) generates a magnetic stiffness and damping signal and an electromagnetic transfer function in response to the motions and a cryostat material properties signal. A mechanical model generator (86) generates a mechanical disturbance signal and a mechanical model of one or more MRI system components in response to the motions and the magnetic stiffness and damping signal. A structural analyzer (88) generates a motion signal in response to the mechanical model. A field instability calculator (90) generates a field instability signal in response to the electromagnetic transfer function and the motion signal. A method of performing the same is also provided.

Abstract: A gradient compensation system comprising a magnet assembly, at least one field-generating gradient coil operable for generating magnetic field gradients in three orthogonal coordinates, and at least one gradient compensation coil positioned adjacent to the magnet assembly and operable for generating a magnetic field to compensate for leakage fields. A system for eliminating image distortion in magnetic resonance imaging comprising a magnet assembly comprising an imaging gradient coil and an imaging volume, and at least one gradient compensation coil positioned adjacent to the magnet assembly operable for generating gradient compensation fields in response to the magnetic field change.

Abstract: A Magnetic Resonance Imaging (MRI) system 50 is provided including a superconducting magnet coil assembly 54. The magnet coil assembly 54 includes a superconducting magnet 82 and forms an imaging volume 60. The superconducting magnet 82 generates a polarizing field in the imaging volume 60. A readout magnet 106 generates a readout field in the imaging volume 60. A controller 102 is electrically coupled to the readout magnet 106 and pulses the readout magnet 106 to generate a uniform magnetic field through the imaging volume 60. A method for performing the same is also provided.

Abstract: A Magnetic Resonance Imaging (MRI) magnet field instability simulator (80) is provided. The simulator includes a rigid body motion generator (82) that simulates motion of one or more MRI system components. An eddy current analyzer (84) generates a magnetic stiffness and damping signal and an electromagnetic transfer function in response to the motions and a cryostat material properties signal. A mechanical model generator (86) generates a mechanical disturbance signal and a mechanical model of one or more MRI system components in response to the motions and the magnetic stiffness and damping signal. A structural analyzer (88) generates a motion signal in response to the mechanical model. A field instability calculator (90) generates a field instability signal in response to the electromagnetic transfer function and the motion signal. A method of performing the same is also provided.

Abstract: A mechanical stabilizer-tuned damper is attachable to the first upper magnet assembly of a high field open magnet, which magnet includes a first upper magnet assembly, a lower second magnet assembly and at least one non-magnetizable support beam therebetween. The mechanical stabilizer-tuned damper reduces the dynamic response of the magnet. A connecting device is provided which consists of a threaded rod mounted to an attachment bracket through a linear bearing and vibration mount. A series of non-magnetic and extremely low conductivity plates of various weights are attachable to the rod to change the mass and the tuning frequency of the damper. The location and size of the mechanical stabilizer-tuned damper are determined to balance the frequency of the field oscillation and physical room. The direction of orientation depends upon the direction of motion to be dampened or controlled.

Abstract: Magnetic field homogeneity correction system including coils for a superconducting magnet assembly are wound on the same coil forms as the axially spaced main magnet coils such that they are superimposed radially to simplify the system including design requirements for associated passive shimming and reduce transverse magnetic forces therebetween, and improve magnetic field homogeneity.

Abstract: A shielded and open magnetic resonance imaging (MRI) magnet having two spaced-apart, generally toroidal-shaped superconductive coil assemblies. Each coil assembly has a coil housing containing a generally annular-shaped superconductive main and a radially-outwardly spaced-apart shielding coil carrying electric currents in opposing directions. Preferably, supplemental shielding is provided with the addition of: a generally annular permanent magnet configuration internal to, or external of, the coil housings; a generally-non-permanently-magnetized external ferromagnetic shield having at least a portion positioned longitudinally between the coil housings, an external resistive coil; or combinations thereof.

Abstract: A lightweight passive magnetic shielding system for a mobile magnetic resonance imaging (MRI) superconducting magnet is provided to enable transportation of the MRI while at superconducting operation within the regulations limiting the strength of the stray magnetic field of the MRI magnet and the weight of the vehicle including the MRI system.