Abstract: Radio frequency (RF) shields used with magnetic resonance imaging (MRI) apparatus may experience gradient field induced eddy currents and RF field induced eddy currents. These eddy currents can cause the RF shield to heat up at an undesirable rate. RF shields are designed to have a desired degree of RF shielding and a desired heating attribute. Design goals for RF shields include gradient field transparency and RF field opacity, both of which can be influenced by eddy currents. Example methods identify a gradient field that will induce eddy currents and identify an RF field that will induce eddy currents. If a region on the RF shield is identified where the desired heating attribute will not be achieved, then a pattern of axial cuts and azimuthal cuts can be made in the RF shield to reduce gradient eddy current heating in the RF shield while maintaining desired RF shielding.

Abstract: Radio frequency (RF) shields used with magnetic resonance imaging (MRI) apparatus may experience gradient field induced eddy currents and RF field induced eddy currents. These eddy currents can cause the RF shield to heat up at an undesirable rate. RF shields are designed to have a desired degree of RF shielding and a desired heating attribute. Design goals for RF shields include gradient field transparency and RF field opacity, both of which can be influenced by eddy currents. Example methods identify a gradient field that will induce eddy currents and identify an RF field that will induce eddy currents. If a region on the RF shield is identified where the desired heating attribute will not be achieved, then a pattern of axial cuts and azimuthal cuts can be made in the RF shield to reduce gradient eddy current heating in the RF shield while maintaining desired RF shielding.

Abstract: Active resistive shim coil assemblies may be used in magnetic resonance imaging (MRI) systems to reduce in-homogeneity of the magnetic field in the imaging volume. Disclosed embodiments may be used with continuous systems, gapped cylindrical systems, or vertically gapped systems. Disclosed embodiments may also be used with an open MRI system and can be used with an instrument placed in the gap of the MRI system. An exemplary embodiment of the active resistive shim coil assembly of the present disclosure includes active resistive shim coils each operable to be energized by separate currents through a plurality of power channels. In some embodiments, the disclosed active resistive shim coil assemblies allow for various degrees of freedom to shim out field in-homogeneity.

Abstract: Active resistive shim coil assemblies may be used in magnetic resonance imaging (MRI) systems to reduce in-homogeneity of the magnetic field in the imaging volume. Disclosed embodiments may be used with continuous systems, gapped cylindrical systems, or vertically gapped systems. Disclosed embodiments may also be used with an open MRI system and can be used with an instrument placed in the gap of the MRI system. An exemplary embodiment of the active resistive shim coil assembly of the present disclosure includes active resistive shim coils each operable to be energized by separate currents through a plurality of power channels. In some embodiments, the disclosed active resistive shim coil assemblies allow for various degrees of freedom to shim out field in-homogeneity.

Abstract: Radio frequency (RF) shields used with magnetic resonance imaging (MRI) apparatus may experience gradient field induced eddy currents and RF field induced eddy currents. These eddy currents can cause the RF shield to heat up at an undesirable rate. RF shields are designed to have a desired degree of RF shielding and a desired heating attribute. Design goals for RF shields include gradient field transparency and RF field opacity, both of which can be influenced by eddy currents. Example methods identify a gradient field that will induce eddy currents and identify an RF field that will induce eddy currents. If a region on the RF shield is identified where the desired heating attribute will not be achieved, then a pattern of axial cuts and azimuthal cuts can be made in the RF shield to reduce gradient eddy current heating in the RF shield while maintaining desired RF shielding.

Abstract: The present invention relates to a method of discretization of the continuous current solution of a gradient coil design that allows satisfaction of the target field quality characteristics as well as other characteristics such as minimization of the energy/inductance, minimization of the residual eddy current effect, minimization of the thrust forces on the coil and cold shields, coil resistance thus the power dissipated by the coil, etc. The method of optimized gradient coil design can be applied to the design of axial or transverse gradient coils. The method of this invention includes the steps of defining at least one, and more commonly numerous performance characteristics of the desired gradient coil, concurrently varying discretization parameters to develop numerous possible hypothetical gradient coil designs, evaluating the designs to determine whether the defined performance characteristics are met by each design and selecting one design.

Abstract: The present invention relates to a method of discretization of the continuous current solution of a gradient coil design that allows satisfaction of the target field quality characteristics as well as other characteristics such as minimization of the energy/inductance, minimization of the residual eddy current effect, minimization of the thrust forces on the coil and cold shields, coil resistance thus the power dissipated by the coil, etc. The method of optimized gradient coil design can be applied to the design of axial or transverse gradient coils. The method of this invention includes the steps of defining at least one, and more commonly numerous performance characteristics of the desired gradient coil, concurrently varying discretization parameters to develop numerous possible hypothetical gradient coil designs, evaluating the designs to determine whether the defined performance characteristics are met by each design and selecting one design.

Abstract: A magnetic resonance imaging apparatus includes a main magnet (12) for generating a main magnetic field in an examination region (14), a plurality of gradient coils (22) for setting up magnetic field gradients in the main field, an RF transmit coil for transmitting RF signals into the examination region to excite magnetic resonance in a subject disposed therein, and an RF receive coil (16) for receiving RF signals from the subject. The RF receive coil includes a first loop (101) and a second loop (102), the first and second loops being disposed substantially in a similar plane (x-z). Also included is a signal combiner (120) for combining the signals received by the first and second loops in quadrature.

Abstract: A magnetic resonance imaging apparatus includes a main magnet (12) for generating a main magnetic field in an examination region (14), a plurality of gradient coils (22) for setting up magnetic field gradients in the main field, an RF transmit coil for transmitting RF signals into the examination region to excite magnetic resonance in a subject disposed therein, and an RF receive coil (16) for receiving RF signals from the subject. The RF receive coil includes a first loop (101) and a second loop (102), the first and second loops being disposed substantially in a similar plane (x-z). Also included is a signal combiner (120) for combining the signals received by the first and second loops in quadrature.

Abstract: A gradient coil for a magnetic resonance imaging apparatus (10) includes a primary coil (16) defining an inner cylindrical surface (60), and shield coil (18) or coils defining a coaxial outer cylindrical surface (62). Coil jumps (74) connect the primary and shield coils (16, 18). The coil jumps (74) define a non-planar current-sharing surface (64) extending between inner and outer contours (66, 68) that coincide with the inner and outer cylindrical surfaces (60, 62), respectively. The coil (16, 18, 74) defines a current path that passes across the current sharing surface (64) between the inner and outer contours (66, 68) a plurality of times. Optionally, some primary coil turns (70) are electrically interconnected to define an isolated primary sub coil (P2) that together with a second shield (S2, S2?, S2?) enables a discretely or continuously selectable field of view.

Abstract: A localized coil (30) is disposed in the temporally constant magnetic field of a magnetic resonance imaging system. The localized coil is designed in five steps: a static problem formulation step, a static current solution step, a discretization step, a current loop connection step, and a high frequency solution step. One radio frequency coil designed by this process to be carried on a circularly cylindrical former includes two coil sections (60, 62) disposed on opposite sides of the dielectric former. Each of the two coil sections includes a pair of inner loops (64.sub.1, 64.sub.2) disposed symmetrically relative to a z=0 plane of symmetry and a second pair of loops (68.sub.1, 68.sub.2) also disposed symmetrically about the plane of symmetry. To raise self-resonance frequency, the inner and outer loops are connected in parallel. The resonance frequency is fine-tuned with reactive elements (66.sub.1, 66.sub.2).