Abstract: A method of correcting active shimming element of a magnetic resonance device, including providing a set of correction values for each shimming element for a given N sub volumes, wherein N is an integer number greater than or equal to 1, detecting irregularities in the magnetic field of the sample regions, optimizing all the shimming elements according to the set of correction values, assessing the regularity of the corrected magnetic field, and reiterating the process until field uniformity is achieved, such that an accurate magnetic resonance measurement of the sample is achieved after a minimum number of iterations.

Abstract: A method and apparatus for local grading shielding includes a gradient shield loop having a plurality of arcs positioned adjacent to a superconducting magnet coil. The plurality of arcs magnetically couple with a gradient magnetic field generated by a magnetic field gradient to locally shield the superconducting magnet coil.

Abstract: A MRI shim element includes a plurality of thin wires extending substantially parallel to each other wherein each wire has cross sectional dimensions less than ?sk, wherein ?sk is the wire's skin depth.

Abstract: A magnetic resonance imaging apparatus includes: a static magnetic field generating unit which generates a static magnetic field, a measuring unit which measures the strength distribution characteristic of the static magnetic field, a determination unit which determines correction amounts for first- to nth-order (n is a natural number of more than one) components of the strength distribution characteristic of the static magnetic field by fixing the correction amount for at least one of specific component which are part of the first- to nth-order components at a predetermined amount and determining the correction amounts for other components than the specific components on the basis of the strength distribution characteristic, and a correction magnetic field generating unit which generates correction magnetic fields to correct the static magnetic field on the basis of the correction amounts.

Abstract: In a method and magnetic resonance system for generating a homogenous, radio-frequency excitation field in a spatial examination volume of the magnetic resonance system for a subject examination, the magnetic resonance system having a body coil comprised of N resonator segments or groups and a control and evaluation device for the separate activation of the individual resonator segments electromagnetically decoupled from one another, separate excitation of each individual resonator segment using defined excitation parameters ensue with an examination subject located in the magnetic resonance system and the respective segment-specific or group specific magnetic field distributions in the examination volume are determined. The segment-specific or group-specific magnetic field distributions are computationally superimposed to determine a overall field distribution in the examination volume.

Abstract: A method for determining construction parameters of magnet structures designed to generate magnetic fields in predetermined volumes of space, comprising the steps of: a) defining a predetermined volume of space in which a static magnetic field is to be generated; b) defining the nominal strength and profile of the magnetic field in said predetermined volume of space; c) mathematically describing the nominal magnetic field on the surface of and/or in said predetermined volume of space by using a polynomial expansion of the magnetic field-describing function, which provides a series of coefficients; d) determining the size, geometry and relative position in space of the means for generating said nominal magnetic field, with respect to the volume of space in and on which the desired, i.e. nominal magnetic field, is defined.

Abstract: An apparatus for shimming the magnetic field generated by a magnet arrangement of a magnetic resonance imaging (MRI) system, has a number of shim devices of substantially similar cross-sectional dimensions, at least some of the shim devices exhibiting differing ferromagnetic characteristics. A structure body has an elongate, tubular channel cross-sectionally dimensioned to serially receive the shim devices in a predetermined sequence to provide a required distribution of the ferromagnetic characteristics in relation to said magnetic field, the channel being of length sufficient to accommodate the shim devices serially in said predetermined sequence. The shim devices are presented at the entrance of the channel in the sequence, and are forced into the channel in the sequence by pressurized fluid directed toward the entrance.

Abstract: A magnetic resonance imaging (MRI) magnet having a first section and a second section is disclosed. The first section has a first housing, and a first set of magnet coils arranged about a common axis that include coils proximate the common axis. The second section has a second housing, and a second set of magnet coils arranged about the common axis where the coils are radially displaced from the common axis. The second section is connected to but axially displaced a distance “d” from the first section.

Abstract: A method includes heating a MRI shim with a heater to reduce a temperature rise per unit of time during a gradient operation of a MRI system.

Abstract: In order to suppress fringe field due to the magnetic field generated from shield coils along the center axis of main coils and the shield coils that are disposed with their center axes being identical, when reducing fringe field to the outside of a magnet apparatus using the shield coils, the magnet apparatus is configured so that the radii of the main coils are approximately equal to or smaller than the radii of the shield coils, the radii of auxiliary coils are smaller than the radii of the shield coils, the distance between the two main coils is smaller than the distance between the two shield coils, and the distance between the two shield coils is smaller than the distance between the two auxiliary coils.

Abstract: A magnetic field generating device is disclosed having an arrangement of permanent magnets, each permanent magnet (PM) having a north end and a south end, and each aligned in the same north-south orientation. The PM arrangement is configured to have a surface at the north polarity end, a surface at the south polarity end, or a surface at both ends. A layer of ferromagnetic material is securely disposed at one of the surfaces of the PM arrangement, the layer having a thickness equal to or less than about 15 millimeters.

Abstract: In a magnet system utilizing a pair of magnet bodies each having a cylindrical hollow, by effectively utilizing the hollow spaces of the magnet bodies, the ability of adjusting through magnetic shims the magnetic-field homogeneity of a homogeneous static-magnetic-field space region is enhanced. Two magnet bodies each incorporating a group of superconductive coils and each having a cylindrical hollow are arranged opposing each other; the first ring-shaped magnetic shim is arranged in the cylindrical hollow of the one magnet body, concentrically with the first group of superconductive coils; and the second ring-shaped magnetic shim is arranged inside the first ring-shaped magnetic shim, concentrically with the first group of superconductive coils.

Abstract: A magnetic resonance imaging apparatus and the magnet apparatus thereof comprise plural pairs of magnetic field generation sources, arranged face to face with each other, for forming a magnetic field space 3; and magnetic field homogeneity adjusting apparatuses 17 and 18 for providing homogeneity adjustment of the magnetic field formed in the magnetic field space 3. The magnetic field homogeneity adjusting apparatuses 17 and 18 contain a plurality of tapped holes 24 for installing a magnetic field homogeneity adjusting member 26 of smaller volume in a plate-formed tray made of a non-magnetic substance; and a plurality of mounts 25 for installing the magnetic field homogeneity adjusting member 27 of greater volume, these mounts being formed over the area containing a plurality of through-holes for permitting installation of a magnetic field homogeneity adjusting member 26 of smaller volume, whereby major magnetic field adjusting work can be performed independently of minor magnetic field adjusting work.

Abstract: An open magnetic resonance imaging (MRI) device is provided with at least one main coil for generating a magnetic field for imaging a volume, and at least one shaping coil. The at least one shaping coil is positioned relative to the at least one main coil to shape the magnetic field in the volume.

Abstract: In a magnetic resonance system and an operating method therefor, a B1 field distribution of a radio-frequency antenna is measured in at least one part of a examination volume of the magnetic resonance system, and then the RF pulses emitted by the radio-frequency antenna are optimized, based on the determined B1 field distribution, for homogenization in a specific volume. An effective volume within the examination volume is determined beforehand for each applied RF pulse and, based on the determined B1 field distribution, the appertaining RF pulse is individually adjusted such that the B1 field is homogenized within the effective volume of the RF pulse.

Abstract: A method and system for homogenizing a main magnetic field of a magnetic resonance imaging (“MRI”) system includes obtaining a main magnetic field distribution generated by the MRI system, obtaining at least one shim magnetic field distribution generated by at least one shim coil of the MRI system, and determining a corresponding shim current based on a relationship between the main magnetic field distribution and the at least one shim magnetic field distribution.

Abstract: A first room-temperature space is formed penetrating through a cryostat along a center axis of a split-type multi-layer cylindrical superconducting coil system which has a ratio of the maximum empirical magnetic field to the central magnetic field of not larger than 1.3 and is horizontally arranged such that the center axis of the coil is in the horizontal direction, a room-temperature shim coil system is arranged in said first room-temperature space to improve the homogeneity of the magnetic field, a second room-temperature space is formed penetrating through the cryostat and passing through the center of said split gap in the vertical direction, and a sample to be measured and an NMR probe having a solenoid-type probe coil are inserted in said second room-temperature space. Further, the NMR analyzer has a new function constituted by a system for irradiating and detecting the electromagnetic waves having wavelengths of shorter than 0.1 mm.

Abstract: A shielded superconducting MRI magnet system uses a multi-layer shielded coil design. By splitting the magnet coils into a plurality of coil layers, an increased number of degrees of freedom is achieved which, in turn, permits minimization of the overall length of the magnet while nevertheless avoiding excessive magnet field and stress values in the coils. A compact coil system is thereby designed which also satisfies the plurality of MRI requirements with regard to sufficiently large investigational volume, magnet field strength, acceptable homogeneity, and magnet stray field limitation while achieving sufficiently low maximum coil B field strengths and stress values to avoid quenches and maintain the structural integrity of the magnet.

Abstract: The present invention has been made in order to decrease vibrations of gradient-magnetic-field coils in a magnetic apparatus for a magnetic resonance imaging diagnosis system so as to improve the image quality of magnetic resonance images. The magnetic apparatus includes: a superconductive electromagnet having pairs of superconductive coils for generating a uniform static magnetic field region, a pair of vacuum containers each for housing one of the superconductive coils of each of the pairs thereof, and a vacuum container connecting member for connecting the pair of vacuum containers; and a pair of gradient-magnetic-field coils for generating a gradient magnetic field having a gradient in a uniform static magnetic field region.

Abstract: The present invention is intended to provide a magnet apparatus obviating the necessity of shield coils designed to suppress eddy currents. The magnet apparatus has gradient coils disposed in a bore of a cylindrical superconducting magnet, and includes a cylindrical structure that is realized with a combination of tiles made of a high-permeability material and that is interposed between the internal surface of the superconducting magnet and the external surface of the gradient coils. The tiles made of a high-permeability material are laminates made of a high-permeability material. The high-permeability material is a silicon steel plate or an amorphous magnetic material.

Abstract: The invention relates to a method for shimming a main magnetic field in a magnetic resonance device. The method comprises the steps of generating at least one spatially selective radio frequency pulse (RF) for exciting nuclear spin magnetization within a restricted region of the examination volume of the magnetic resonance device, acquiring a magnetic resonance signal (ES) that is sensitive to the homogeneity of the main magnetic field, and applying electric currents (SZ, SX, SY) to a shim coil arrangement of the magnetic resonance device such that the main magnetic field is adjusted in accordance to the properties of the acquired magnetic resonance signal (ES).

Abstract: A magnet for an NMR an analyzer includes a superconductor coil which is operated under a permanent current mode so as to generate a magnetic field in a space surrounded by the superconductor coil, and which enables a sample to be inserted into a measurement space in the magnetic space for analization. The superconductor coil includes a first access port for enabling access to the measurement space and a second access port for enabling insertion of the sample into the measurement space in a direction different from a direction of the first access port. An effective diameter of the first access port is larger than an effective diameter of the second access port when the effective diameters of the first and second access ports are defined as a diameter of a cylinder that is insertable into the first and second access ports.

Abstract: The system describes a means and a method for stabilizing the magnetic field generated in the measuring volume of a high-resolution magnetic resonance spectrometer having an actively shielded magnet coil (4) which is located in a cryostat (2) and which is superconductingly short-circuited. The system comprises a compensation coil (12) which is decoupled from the magnet coil (4), and is disposed on the shielding coil (4b) of the magnet coil (4).

Abstract: An actively shielded superconducting magnet coil system (1) for generating a magnetic field in a working volume (6), which is rotationally symmetric about a z-axis, comprising a radially inner main field winding (5) and a radially outer shielding winding (7), and an electrically highly conductive shielding cylinder (radially inner shielding cylinder) (8a/8b) which is disposed radially inside the main field winding (5) or between main field winding (5) and the shielding winding (7) is characterized in that at least one further electrically highly conductive shielding cylinder (9) is disposed radially outside the shielding winding (7). The inventive magnet coil system prevents generation of a fringe field flash in the outer region of the magnet coil system in case of a quench.

Abstract: The present invention provides a magnet assembly (30a, 30b) comprising a pair of drive coils (31a, 31b; 32a, 32b; 33a, 33b) symmetrically disposed with respect to a reference plane. The reference plane is located approximately equidistant between the drive coils. Each of the drive coils has a current flowing through it which is in the opposite sense to the current flowing through the other drive coil, such that a primary magnetic field is generated in a plane which is parallel to and substantially coincident with the reference plane. The assembly may comprise further compensating coils (44a, 45a, 46a) which are configured to generate a magnetic field to improve homogeneity of the primary magnetic field. The drive coils and the compensating coils are generally in the shape of a racetrack and are preferably superconducting coils.

Abstract: At least one superconducting shim coil is wound around a cylinder member disposed approximately coaxially with a group of superconducting main coils, and the positions in the winding center locus in an axial direction change approximately in accordance with a function where a sine or cosine function with a cycle of (360/m) degrees (m; an integer of one or more) in a circumferential direction is mixed with a sine or cosine function with a cycle of (360/(m+2)) degrees.

Abstract: Systems, methods and apparatus are provided through which inhomogeneity in a magnetic field is reduced by invoking electromagnetic mutual inductance between a main coil and another coil.

Abstract: To access a measurement space located at the center of the magnet, an access port is provided in the direction of the magnet's axis, a clearance is provided in the coil winding portion, and another access port passes through the clearance so that a sample can be positioned perpendicularly to the coil axis. According to this configuration, an access port passing through the coil winding portion can be smaller than the access port passing through the coil axis, a sample is inserted from the access port, and a probe is inserted from the access port passing through the magnet axis, and thus the clearance can be minimized.

Abstract: An actively shielded superconducting magnet having a dipole shim coil for adjusting and fine-tuning an external or far fringe magnetic field produced by a main coil of the magnet. An active shield coil is coupled to the main coil in reverse polarity and produces a magnetic field when energized that opposes the far fringe field to substantially reduce the far fringe field. The dipole shim coil is electrically isolated from the active shield and main coils of superconducting magnet, and produces a magnetic field when energized that provides for the fine adjustment of any residual far fringe field.

Abstract: An MRI apparatus includes magnet members for compensating the magnetic field which are disposed to a thermal shield system of the superconducting apparatus. The magnet members for compensating the magnetic field are disposed at positions where temperature change in the vacuum chamber is not transferred to the interior of the vacuum chamber.

Abstract: The projection of magnetic gradient fields useful in Magnetic Resonance Imaging where projection of a gradient outside of a field generating assembly allows imaging of samples which will not physically fit inside the coil confines. The linearity of the projected gradient field is improved by arranging the position of the magnetic field generating coil conductors such that the second derivative of a gradient component is equal to zero. In one practical example the linearity is improved by providing a first circular coil which is positioned so that its center is offset along the axis of the field generating coil assembly by a distance equal to half the radius of the coil. In another example a pair of current carrying wires are selectively positioned offset from a region of interest.

Abstract: Systems, methods and apparatus are provided through which in some embodiments drift of a magnetic field of a magnetic resonance imaging (MRI) system is reduced by including a drift compensation coil which accumulates current at a rate proportional to the decay in the primary coil via its electromagnetic mutual inductance to the primary coil. In some embodiments, the drift compensation coil includes reverse turns at an outer radius, to significantly reduce any exacerbation of the fringe field during a quench of the primary coil. In further embodiments, the actively shielded drift compensation coil is complemented with a non-coupling external disturbance shield coil.

Abstract: The present invention discloses a permanent magnet for magnetic resonance, which is used for a magnetic resonance imaging apparatus for medical diagnosis. The permanent magnet of the present comprises permanent magnetic material; pole heads; plates for eliminating vortex (i.e. eddy currents); rings for homogenizing the magnetic field; gradient coils; and a yoke, said yoke of the permanent magnet has an integral and substantially C-shaped structure formed with two columns and is an open type configuration. This invention fully ensures the parallelism of the lower and upper poles, greatly improves the mechanical strength of the yoke, and results in a good magnetic uniformity and a consistent magnetic current.

Abstract: In a method and magnetic resonance system for homogenization of the B1 field for a magnetic resonance data acquisition with a number of iteration steps. An iteration step includes the following sub-steps: Measurement data are acquired that represent a B1 field distribution in at least one part of the examination volume of the magnetic resonance system. A B1 homogeneity analysis based on the acquired measurement data is automatically implemented. A specific homogenization action is automatically selected from among a number of possible homogenization actions based on the B1 homogeneity analysis, or the iterative homogenization method is ended if the diagnosed homogeneity is sufficient for an intended magnetic resonance measurement. The selected homogenization action is implemented.

Abstract: A magnetic resonance apparatus has a basic field magnet with an interior bore having a bulge therein. A mass augmentation device is disposed in the bulge, and is composed of a number of assembled individual segments. The mass augmentation device reduces the propagation of mechanical oscillations that are produced during operation of the magnetic resonance apparatus, and which otherwise would produce unwanted noise.

Abstract: A magnetic resonance imaging (MRI) device includes an inner gradient coil assembly proximate a patient positioning area, an outer gradient coil assembly proximate a magnet assembly, and a damping layer sandwiched between the inner and outer gradient coil assemblies.

Abstract: A magnetic resonance imaging system is provided in which the two contradictory requirements, i.e., enhancing the feeling of being not confined by enlarging the subject-insertion space and decreasing magnetomotive force of the superconductive coils by bringing the superconductive coils as close as possible to a subject, can be met in a good balance.

Abstract: In a magnetic resonance imaging apparatus, a transmitting/receiving coil is attached to a patient at a region of interest and disposed within a static magnetic field, a radio-frequency magnetic field, and a gradient magnetic field and an image of the patient is obtained. A tabletop is used to move the patient in the static field in a horizontal direction within a horizontal plane and up and down in a direction that is perpendicular to the horizontal plane, a patient couch controller causing the tabletop to move, based on the position of the region of interest obtained from the image, so that the position of the region of interest is caused to coincide in three dimensions with the center of the static magnetic field and/or the gradient magnetic field.

Abstract: An MRI apparatus having an open structure includes a static magnetic field generating magnet including magnetic field generating sources arranged above and below an imaging space and magnetic field fluctuation reducing plates arranged inside the magnet. Gradient magnetic field coils are fixed to the static magnetic field generating magnet so as to not be in contact with the magnetic field fluctuation reducing plates. When the strength of the magnetic field generated by the static magnetic field generating magnet fluctuates due to vibration of the gradient magnetic field coils or other devices during an imaging operation of the MRI apparatus, an eddy current is generated on the magnetic field fluctuation reducing plates in response to the magnetic field fluctuation components. Magnetic flux which cancels the static magnetic field fluctuation components is generated due to this eddy current, and consequently, a time-sequentially stable static magnetic field can be obtained.

Abstract: A magnetic field generator for producing a homogenous magnetic field region. The magnetic field generator comprises: a plurality of main magnet coils arranged in a cylindrical fashion; a plurality of shielding coils arranged in a cylindrical fashion, and located radially outward of the plurality of magnets; and wherein the main magnet coils and shielding coils are configured to shape a magnetic field which comprises at least one low fringe field region when in operation. A method for designing an MRI system that produces a low fringe field region. The method comprises: defining a solution space; defining a field of view, a center field and homogeneity requirements; defining fringe field requirements; and running an optimization algorithm to determine coil positions.

Abstract: A cryogen pressure vessel assembly for a superconducting magnet comprises an inner former, an outer former, and an outer shell. The inner former has a plurality of superconducting magnet coils wound thereon, and the outer former has a plurality of bucking coils wound thereon. The inner former, the outer former, and the outer shell form a fluid boundary for a cryogen. In one aspect, a pressure face is formed on at least one of the coil formers, and a radial slot for receiving wires entering and exiting a coil is disposed in the pressure face. A plurality of wire clamps are positioned in the radial slot, with each wire clamp in the plurality of wire clamps including: a front face extending coplanar with the pressure face, a rear face opposite the front face, the rear face contacting a back surface of the radial slot, and a recess formed in the rear face, the recess forming a channel for passage of the wires.

Abstract: The invention concerns a method for charging an actively shielded magnet coil arrangement (20) comprising a first partial region (21) which can be superconductingly short-circuited using an additional switch (23), and a second partial region (22), wherein the two partial regions (21, 22) generate dipole moments of different signs. The magnetic fringe field B* is measured close to the desired operating state of the arrangement (20) and operating currents are determined for each of the two partial regions (21, 22) at which the overall magnetic field B is free from an additional dipole moment caused by production tolerances to permit setting of the theoretically optimum fringe field, irrespective of production tolerances.

Abstract: A magnetic resonance imaging apparatus and method having a magnet assembly, which provides substantially flat surfaces of constant magnetic field outside the assembly and a set of magnetic field gradients. One-, two-, and three-dimensional images are rendered. The static magnetic field is virtually uniform within horizontal degrees of freedom and decreases monotonically in a direction away from the surface. An RF probe, for example, a coil, located adjacent the surface, produces a field substantially perpendicular to the static magnetic field. A magnetic field gradient is set to horizontally scan a given level within the sensitive volume. Received magnetic resonance signals are detected by the coil for a depth corresponding to the excitation frequency. As the tuning and excitation frequency is switched to lower values, signals are generated for layers progressively farther from the surface. The RF probe is automatically tuned.

Abstract: A secondary coil circuit for use with a multi-section protected superconductive magnet coil circuit is disclosed herein. The secondary coil circuit includes two circuit nodes, a ramping switch electrically connected between the two circuit nodes, and a number of secondary coils electrically connected between the two circuit nodes. The secondary coils are made of wire having substantially superconductive capability when cooled below a characteristic critical temperature level and conducting electric current below a characteristic critical current level. The secondary coils are sized and positioned relative to the superconductive magnet coils situated in the individual sections of the multi-section protected superconductive magnet coil circuit so as to functionally cooperate with the multi-section protected superconductive magnet coil circuit in producing and maintaining a magnetic field that is substantially homogeneous.

Abstract: Magnet assembly for use in medical magnetic resonance imaging includes means for increasing flux generation in the gap region to provide the capability of scanning smaller volume regions of a patient at increased levels of scanning resolution. The means for increasing flux generation is mechanical or electromagnetic, is coupled to each of the polar regions and maintains the gap region sufficiently large and unobstructed to allow for access to the patient by several persons during scanning. Tapered outer walls of the polar region proximate the gap region further enhance accessibility to the patient during scanning.

Abstract: The invention concerns a method for charging a magnet arrangement (20) comprising a first partial region (21) which can be superconductingly short-circuited via an additional switch (23), and a second partial region (22), wherein the two partial regions (21, 22) generate, in an investigational volume (8), gradients of second order having different signs. A magnetic field dependence B* is measured close to the desired operating state of the magnet arrangement (20) and operating currents are determined for each of the two partial regions (21, 22) at which the overall magnetic field B in the volume (8) under investigation is freed from a magnetic field gradient of second order. These operating currents are set thereby taking into consideration the inductive coupling of the partial regions (21, 22) through initially charging of the overall magnet arrangement (20) and, after closing of the additional switch (23), through continuation of charging only in the second partial region (22).

Abstract: Provided is a circular pole piece that contributes to simplification of work and a reduction in costs and that has no gap created among adjoining blocks. A circular pole piece is manufactured by circularly arranging laminate blocks each having numerous hexagonal directional magnetic steel sheet tiles layered. Since heteromorphic soft magnetic material tiles are unnecessary, work can be simplified and the cost of the circular pole piece can be reduced. Moreover, the laminate blocks can be arranged substantially circularly without a gap among adjoining blocks.

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 receiver for a resonance signal of a magnetic resonance imaging system generates a baseband signal for image processing by dividing a raw resonance signal among multiple parallel channels, each amplified at a respective gain. A digital channel selector determines, at any given moment, a lowest-distortion channel to be further processed. Amplitude and phase error compensation are handled digitally using complex multipliers, which are derived by a calibration, based on a simple Larmor oscillator, which can be done without the need for a sample and without repeating when measurement conditions are changed. One of the important benefits of the invention is that it provides for gain selection without repeated calibration steps. This is particularly important in systems that employ fast imaging techniques such as fast spin echo, where the invention can speed imaging substantially.

Abstract: A solid-state nuclear magnetic resonance probe that includes multiple sample spinning systems and detection coils is disclosed. The probe can be repositioned within the bore of the magnet to selectively maximize the throughput and sensitivity of the instrument by acquiring a spectrum from one sample at a time while at least one other sample is at or returning to an equilibrium spin state. Methods for the utilization of the probe are also disclosed.