Abstract: In an apparatus and method for magnetic resonance imaging, an imaging field (B.sub.p) and a pre-polarization field (B.sub.p) are generated by means of electromagnetic coils ALC in an air gap between pole pieces of a magnet core. The pole pieces are designed such that, as the current in the coils is increased, the field strength increases only in the central area between pole pieces up to the strength (B.sub.p) of the pre-polarization field. This is due to the saturation of the edge zones of pole pieces that restricts the increase of field strength in the edge zones of the air gap.

Abstract: In a magnet system, e.g. for use in a magnetic resonance apparatus, wherein a magnetic field is produced in a gap between pole pieces (5) joined by a yoke (7) by an electric drive coil arrangement carried on the yoke, stabilisation against variations in the field in the gap is provided by a stabilising arrangement (43) wherein over a section of its length the yoke is divided into a plurality of discrete parallel finger-like portions (45) each of which is surrounded by a separate ring (47) of superconducting non-magnetic material.

Abstract: A subject receiving bore (12) of a magnetic resonance apparatus has an axial length to diameter ratio of less than 1.75:1 and preferably about 2:1. The temporally constant magnetic field generated by superconducting magnets (10) surrounding the bore have various magnetic field harmonic distortions generally in the Z1-Z18 range. Shim trays (80) are disposed longitudinally around the bore (12). Each shim tray contains a number of shim pockets (84) which receive ferrous shims for shimming the magnetic field in the bore (12). An initialization system (60) calibrates the initial magnetic field within the bore (12). An initial shim distribution is determined which shims the inhomogeneous magnetic field toward a target more homogeneous magnetic field. An optimization system (66) determines a residual magnetic field from a difference between the present inhomogeneous magnetic field of the bore and the target magnetic field.

Abstract: An apparatus for monitoring characteristics of rock cores using NMR. The apparatus is provided with a clad permanent magnet for generating a magnetic field having a saddle profile. The magnetic field is sufficiently uniform within a working volume to enable an NMR experiment to be performed. Rock cores are conveyed along a path about which the magnet is arranged. The cores pass through the working volume of the magnetic field orthogonally to the saddle profile of the magnetic field. An NMR experiment to monitor oil bearing rock characteristics, such as porosity is carried out on a portion of the rock core within the working volume.

Abstract: A superconductive magnet with magnetic shielding has an annularly-cylindrical-shaped housing whose first end wall and outer cylindrical wall are magnetizable (e.g., iron) walls and whose inner cylindrical wall is a non-magnetizable wall. At least one main superconductive coil is positioned within the housing and carries an electric current in a first (e.g., clockwise) direction. A first resistive (e.g., copper) deflection coil is positioned outside the housing radially proximate the outer cylindrical wall and longitudinally closer to the first end wall than to a midpoint located between the two end walls. The first deflection coil carries an electric current in an opposite direction to the first direction so that its magnetic field longitudinally pushes the stray magnetic field of the superconductive coil(s), which leaves the magnet's bore, inward to be captured by the iron first end wall.

Abstract: A superconductive magnet with magnetic shielding has an annularly-cylindrical-shaped housing whose first end wall and outer cylindrical wall are magnetizable (e.g., iron) walls and whose inner cylindrical wall is a non-magnetizable wall. At least one main superconductive coil is positioned within the housing and carries an electric current in a first (e.g., clockwise) direction. An annular first permanent magnet is positioned outside the housing longitudinally proximate the first end wall. The first permanent magnet has a number of equivalent ampere turns and has a magnetic field direction oriented parallel to the axis pointing towards the second end wall so that its magnetic field longitudinally pulls the stray magnetic field of the superconductive coil(s), which leaves the magnet's bore, inward to be captured by the iron first end wall.

Abstract: Convenient side access to an image volume located within a two-pole, two-column main magnet of an MRI system is provided by rotating the symmetry axis of the magnet to be non-perpendicular with respect to the longitudinal axis of the patient transport and/or otherwise displacing the two column structures of the magnetic circuit so as to permit open and unobstructed access to the image volume along a direction perpendicular to the longitudinal axis of the patient transport.

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.

Abstract: A magnet assembly comprises a pair of substantially aligned, spaced apart first magnets (1,2) having like poles facing each other. A second magnet (3) is positioned adjacent the space between the first magnets with its magnetic axis transverse to the alignment axis of the first magnets (1,2). A magnetic field of sufficient homogeneity to perform a nuclear magnetic resonance process is generated in a working region.

Abstract: In an NMR tomograph with superconducting main field coil (10) and large transverse access opening a compensation of inhomogeneities of the static magnetic field without hindering the axial and transverse access to the investigational volume (V) can be effected by the following elements:ferromagnetic homogeneity elements (20) which are arranged on the surface of the room temperature bore on both sides of the transverse access opening;at least four superconducting correction coils (C.sub.1 and C.sub.4) which can be separately supplied with current and which are coaxial to the main field coil (10), whereby each correction coil (C.sub.1 through C.sub.4) comprises at least two partial coils (C.sub.1i, C.sub.1a through C.sub.4i, C.sub.4a), whereby all partial coils of all correction coils (C.sub.1 through C.sub.4) are cylindrical coils coaxial to a common axis (z) having a diameter less than the inner diameter (d.sub.a2) of the outer field coil (1a, 1b), whereby in each correction coil one partial coil (C.sub.

Abstract: A magnet system for nuclear magnetic resonance (NMR) imaging volume has two magnet coils (S1, S2) arranged on both sides of an investigational volume coaxially relative to a z axis running through the center of the investigational volume and assuming positions relative to the center of the investigational volume of z.sub.S1 and z.sub.S2 with average separations r.sub.S1 and r.sub.S2 from the z axis. During operation, currents flow through the coils in the same direction. The system is characterized by ferromagnetic rings (R11 and R21) provided for on each of the two magnet coils (S1, S2) arranged closer to the center of the investigational volume than the corresponding neighboring magnet coil (S1 or S2). The rings (R11, R21) are positioned and dimensioned in such a fashion that the magnetic field in the center of the investigational volume can be rendered homogeneous up to 8th order. The axial separation g.sub.

Abstract: Magnetic resonance apparatus includes an essentially cylindrical magnet system (2) for generating a steady magnetic field (H) in a measurement space (28), a coil system (4) for generating gradient fields in the measurement space, and at least one RF coil (10) which is arranged in the immediate vicinity of the measurement space. In order to increase the homogeneity of the main magnetic field (H), approximately annular first elements (44) of a magnetically conductive material are provided within the magnet system (2) so as to extend coaxially with respect to the axis (9) of the magnet system. In order to minimize the amount of magnetically conductive material required, the first elements (44) are situated in the immediate vicinity of the RF coil (10).

Abstract: An open magnetic resonance imaging (MRI) magnet having two generally toroidal-shaped superconductive coil assemblies spaced apart by generally spaced-apart and generally parallel inter-coil-assembly posts. Each coil assembly has associated with it a generally annular-shaped superconductive shielding assembly and at least two spaced-apart assembly posts each having one end attached to the coil assembly and another end attached to the shielding assembly The shielding coil within the shielding assembly has an inner diameter greater than the outer diameter of the main coil within the coil assembly. A cryocooler coldhead cools the entire magnet. Magnetic shielding is achieved while maintaining the openness of the open magnet.

Abstract: A magnetic field generating apparatus has a hollow permanent magnet formed of a plurality of permanent magnet elements arranged to have a polygonal section. Magnetization directions of the end portions of the hollow permanent magnet in its longitudinal direction are made different from those of the central portion thereof so that the magnetic field generated in a predetermined region in the hollow space of the permanent magnet is increased as compared with a case where the magnetizations of the hollow permanent magnet are all directed in the same direction.

Abstract: A pancake magnetic resonance imaging (MRI) magnet having a superconductive coil assembly including a toroidal-shaped coil housing containing a superconductive main coil set and a radially spaced-apart superconductive supplemental coil set. The main coil set includes a first main coil located radially towards the circumferential outside surface which faces away from the bore, and the supplemental coil set includes three radially spaced-apart supplemental coils located radially towards the circumferential outside surface which faces towards the bore. The first main coil and the middle supplemental coil each carry an equal electric current in a first direction while the other two supplemental coils each carry the same electric current in the opposite direction. Such coil arrangement produces an imaging volume longitudinally wider than the longitudinal thickness of the magnet.

Abstract: The apparatus comprises a magnet system which is rotationally symmetrically arranged about a central axis (9) and which comprises a superconducting inner coil system (1) for generating a steady magnetic field in a measurement space (5) within the magnet system, and also comprises an outer coil system (7) which is arranged so as to be coaxial with the inner coil system and which is electrically connected in series therewith in order to shield the environment from the magnetic field generated by the inner coil system. The magnet system can be bridged by of a superconducting persistent current switch (33) and comprises a superconducting shunt (37) which bridges a pan of the magnet system which is situated between first and second connection points (39, 41).

Abstract: A magnetic resonance gantry (A) includes a magnet (12) which generates a uniform magnetic field in a thin (under 15 cm thick) imaging volume (10). Gradient coils (30) and radio frequency coils (20) transmit radio frequency and gradient magnetic field pulses of conventional imaging sequences into the imaging volume. A patient support surface (42) moves a patient continuously through the imaging volume as the pulses of the magnetic resonance sequence are applied. A tachometer (52) monitors movement of the patient. A frequency scaler (54) scales the frequency of the RF excitation pulses applied by the transmitter (22) and the demodulation frequency of the receiver (26) in accordance with the patient movement such that the selected slice moves in synchrony with the patient through the imaging volume. The slice select gradient is indexed after magnetic resonance signals to generate a full set of views for reconstruction into a two-dimensional image representation of the slice are generated.

Abstract: A method for using ferromagnetic shims to reduce the inhomogeneity of the magnetic field in a Diameter Spherical Volume (DSV) in the bore of a Magnetic Resonance Imaging (MRI) device is provided. More specifically, a magnetic field is established within the bore of the MRI device. An operator defines the DSV. The strength of the magnetic field is measured at the surface of the DSV. A Legendre polynomial is derived to model the inhomogeneity in the magnetic field in the DSV. A set of coefficients for the harmonic terms of the polynomial is calculated from the field strength measurements and segregated into three separate groups for evaluation. Each group of terms expresses field inhomogeneity in a unique set of spatial dimensions.

Abstract: A magnetic resonance imaging (MRI) magnet having an annularly cylindrical-shaped vacuum enclosure with a longitudinal axis, first and second longitudinal ends, a first larger diameter bore extending from the first towards the second longitudinal end, and a second smaller diameter bore extending from the second longitudinal end to the first bore. First and second superconductive coils are placed in the vacuum enclosure with the first coil generally circumferentially surrounding the first bore and the second coil circumferentially surrounding the second bore, wherein the radial distance of the radially innermost portion of the second coil from the axis is smaller than the radius of the first bore. The first longitudinal end of the vacuum enclosure fits over a patient's shoulders with the patient's head at least partially passing through the first bore and extending into the second bore for MRI brain imaging.

Abstract: A nuclear spin resonance (NMR) measuring device, in particular an NMR tomography apparatus with a preferentially superconducting main field coil which is capable of producing, within a measurement volume whose center is coincident with the origin of a Cartesian coordinate system x, y, z, a homogeneous static magnetic field B.sub.0 in the direction of the z-axis of this coordinate system and with a tesseral gradient coil system for the production of magnetic gradient fields with a largely linear dependence within the measuring volume in a direction perpendicular to the z-axis, whereby the gradient coil system comprises at least four largely identical saddle-type partial coils arranged symmetrically with radial and axial separations from the coordinate origin, the partial coils each exhibiting two electrically conducting segments which run about the z-axis in the azimuthal direction one segment (21) of which has as small a radial separation r.sub.1 and the other segment (22) as large a radial separation r.sub.

Abstract: An open access MRI magnet includes a ferromagnetic frame open on at least two sides and having upper and lower end plates and at least two support columns. A superconducting coil assembly is mounted to each end plate for generating a magnetic flux field in a patient receiving area located between the end plates. Each superconducting coil assembly includes a toroidal vacuum tight vessel, insulation, and one or more temperature shields mounted within the vacuum tight vessel. One or more coils of superconducting wire is wound within the vacuum vessel, and is coupled to a power source and to a persistent switch for maintaining a constant flow of current with no power consumption. A return path for the flux is provided by the end plates and support posts of the frame.

Abstract: A magnet is specially designed for the creation of an extremely uniform magnetic field in a small volume for use in MRI mammography. A disk of ferromagnetic material has a surface having a well adapted to receive the object to be examined and lined with a solenoidal coil which provides the basic magnetic field. Uniformity is increased by three additional coils surrounding the solenoidal coil and placed in annular slots surrounding the well. Of these three additional coils, the middle one generates a magnetic field in the well which opposes the basic magnetic field, and the others supplement the basic magnetic field. The ampereturns of the three additional coils are selected to maximize uniformity of the magnetic field in the well.

Abstract: An MRI magnet arrangement comprises, an annular electromagnet defined by a coil, an annular shim of magnetic material coaxially disposed within the coil, first permanent magnet means having a field, the direction of which is the same as the field of the coil, disposed coaxially within the said shim and second permanent magnet means disposed coaxially within the said first permanent magnet means, the field of which is arranged to be opposite in direction to the field produced by the said first permanent magnet means, the arrangement being such that the magnetic field produced in an imaging volume within the said second permanent magnet means is substantially homogeneous.

Abstract: A magnetic resonance imaging (MRI) magnet having an annularly cylindrical-shaped vacuum enclosure with a longitudinal axis, first and second longitudinal ends, a first larger diameter bore extending from the first towards the second longitudinal end, and a second smaller diameter bore extending from the second longitudinal end to the first bore. First and second superconductive coils are placed in the vacuum enclosure with the first coil generally circumferentially surrounding the first bore and the second coil circumferentially surrounding the second bore, wherein the radial distance of the radially innermost portion of the second coil from the axis is smaller than the radius of the first bore. The second longitudinal end of the vacuum enclosure fits on a patient's shoulders with the patient's head passing through the second bore and extending into the first bore for MRI brain imaging.

Abstract: An extremely efficient magnet system having a comparatively large angle of aperture can be obtained for magnetic resonance imaging by a reduction of fields of all orders in a common approach affecting active and passive as well as positive and negative oriented coil elements. Passive soft-magnetic ring segments are arranged in two pairs and located within a plurality of larger diameter active magnetic coils. The active coils include a central coil and outer coils wherein the outer coils are smaller than the central coil. The coils are in a helium Dewar vessel and arranged such that the system has an aperture of about 90.degree.. The central active coil may have a larger radius than the smaller outer coils.

Abstract: To improve the homogeneity of the basic magnetic field generated in a nuclear magnetic resonance tomography unit, an iterative shimming method includes the steps of generating a pulse sequence in the form of a bipolar gradient pulse train in the examination volume, and entering the echo signals which are acquired into a measured matrix. A correlation coefficient of the echo signals of at least a part of the rows of the measurement matrix is formed with respect to a reference row. The shim current through at least one shim coil in the tomography apparatus is then varied in a manner causing the correlation coefficient to increase. These steps are repeated until the correlation coefficient reaches a selected value which is large enough to indicate that an adequate basic field homogeneity has been achieved.

Abstract: An improved magnetic field generating device for use with a medical nuclear magnetic resonance tomographic device (MRI). The device comprises a magnetic circuit formed of a pair of magnetic pole pieces connected by yoke members in opposite relationship with each other leaving a space sufficient to accommodate therebetween an object receiving a medical inspection. According to the present invention, a super-conductive coil is wound around one of the pairs of magnetic pole pieces and the dimensional relationship between the two magnetic pole pieces is varied in a variety of ways to reduce the magnetic field imbalance, with the advantages that the magnetic flux distribution becomes highly uniform throughout the space between the pair of magnetic pole pieces, the patient entering the space has no oppressive sensation and the manufacturing cost can be reduced to a considerable degree.

Abstract: The invention relates to a magnet apparatus for producing a uniform magnetic field for magnetic resonance imaging (MRI). The magnet apparatus is of the type having a pair of permanent magnet discs each of which has a hole in a central region and a yoke structure in which the magnet discs are held opposite to each other. For each magnet disc the yoke structure has an aperture which is in alignment with the hole in the magnet disc. As is usual, a pair of pole plates are attached to the opposite faces of the magnet discs, respectively, so as to produce a uniform magnetic field in a space between the two magnet discs. To ease visual observation of the object of imaging in the afore-mentioned space, such as the head part of a human body, the pole plate on each magnet disc is formed with a hole which is in alignment with the hole in the magnet disc. A video camera can be used. According to the need small pole pieces are attached to the surfaces of the holed pole plates to keep uniformity of the magnetic field.

Abstract: Superconducting electromagnets suitable for use in the NMR tomography of human organs, and a method of making the same, are disclosed. Each of the disclosed electromagnets are constructed according to a structured coils methodology, where the desired field at locations within the volume of interest and, optionally, outside of the location of the coils is selected; the current magnitude and polarity for a plurality of coil elements locations are then optimized, by way of a computer program, to provide the desired field magnitude at the locations. The magnet construction results in a plurality of coils of varying current polarity, and of irregular shape and size, optimized to provide the uniform field.

Abstract: An MRI system has a magnet configuration that provides access for a surgeon or other personnel to perform procedures on a patient under support of real time MRI image. The magnet system uses a plurality of C-shape solenoidal magnets oriented to form an imaging volume in a central region of the magnets so that the magnetic flux from each magnet contributes to the magnetic field in the imaging volume. The configuration provides a high strength field in the imaging volume. The MRI system has a gradient coil for providing a magnetic field gradient in the imaging volume and an Rf coil for providing an Rf signal in the imaging volume. Preferably, the Rf coil also receives NMR signals from a specimen in the imaging volume.

Abstract: The magnet contains a magnetic yoke and two pole shoes between which a magnetic field of high homogeneity is formed. The pole shoes are provided with special pole piece device. Each pole piece device is spaced from a base part facing the yoke by a narrow correction air gap. In accordance with the invention, each pole piece device contains two plate-like pole piece elements which are parallel to each other and spaced apart by a gap of predetermined width. In this connection, the plate element facing the base part has a relative permeability (.mu..sub.r 1) which is smaller by at least a factor of 5 than the plate element facing the useful volume, the relative permeability (.mu..sub.r 2) of which element is at least 10,000.

Abstract: A superconducting magnet suitable for use in magnetic resonance imaging applications is disclosed. A plurality of driving coils are located around a cylindrical bore, for generating an axial magnetic field therein. At the ends of the magnet, within the same cryostat as the driving coils, first and second shielding coils are located, each carrying a current of opposite polarity relative to the driving coils. The location, size, and current in the coils are determined by a methodology in which the error between the desired field and the simulated field is minimized at target locations within the bore and outside of the bore. A flux return is disposed in the gap between the first and second shielding coils, so that the shielding coils inject return magnetic flux into the flux return. The flux return may be of iron, or may consist of a superconducting coil. The resulting magnet has relatively low superconductor cost as well as relatively low weight, due to the efficient use of both superconductor and iron.

Abstract: For calculating the magnetic field inhomogeneity, a gradient echo sequence or a spin echo sequence having a non-central 180.degree. radio-frequency pulse is first carried out. The nuclear magnetic resonance signal thus acquired is Fourier-transformed and the phase curve of the nuclear spins in a given region is identified. This is multiply repeated in different projections. The phase curves that are obtained are analyzed with a fit method and the coefficients of the spherical, harmonic functions describing the field distribution are identified therefrom. The current to be supplied to the individual shim coils and an offset current for the gradient coils can thus be calculated.

Abstract: This invention relates to a pole face design for superconducting magnets of the type that are C-shaped. Such structures of this type, generally, employ pole faces which homogenize the magnet field within the imaging volume.

Abstract: A magnetic resonance imaging apparatus includes a magnet for generating a static magnetic field, a gradient coil for generating a gradient magnetic field in a measurement space, and a vibration damping means which includes a container and granular material disposed in the container. The vibration damping means is installed with a supporting bolt between the gradient coil and a supporting means. Since the gradient coil is supported at a constant position without any vibration and deformation, the magnetic resonance imaging apparatus generates an accurate image signal without any acoustic noise.

Abstract: A plurality of measurements are made with a probe containing a material sample with a known frequency spectrum. The probe is positioned in one spot in the magnet bore in the presence of a field gradient along a predetermined axis. Prior to each measurement, the gradient strength is increased by a predetermined constant amount. The resulting measurement values are mathematically manipulated to yield a set of values which can be used to set the shim coil currents based on known equations for the field generated by each shim coil. The method can be used with a material sample with a simple NMR spectrum or a complex NMR spectrum. If a sample with a complex NMR spectrum is employed in the measurement, the spectral complexity can be removed by deconvolution during the manipulation of the measurement values.

Abstract: A magnet device for MRI system is provided with a main coil assembly including a plurality of ring-like main coils wound around a reel element and a sub-coil assembly including at least one pair of ring-like sub-coils wound around the reel element. All the coils are arranged symmetric with respect to an axial direction of the reel element. The sub-coils are disposed at axially inner predetermined positions apart from the axial outermost main coils. A coil driving element, provided in the device, makes the main coils generate a main magnetic field in the space and makes the sub-coils generate a magnetic field inverse to the main magnetic field to form a high-uniform static magnetic field as a diagnostic space. Magnetomotive forces of the main coils and sub-coils are adjusted so that the diagnostic space having a longer radial axis than its longitudinal axis is formed in the cylindrical space.

Abstract: A magnetic field correction device for producing a uniform field within a coil includes non-magnetic tubes attached on a cylinder at specific circumferential angles .psi. to accommodate the non-magnetic tubes therein. Each of the magnetic shims consists of two rod members of predetermined lengths and transverse sectional area ratio. The end angles and the sectional area ratio A.sub.2 /A.sub.1 of the two rods satisfy specific relationships.

Abstract: A permanent magnet for nuclear magnetic resonance imaging that provides an intense and highly homogeneous magnetic magnetic field is disclosed. The magnet is made up of a set of rings having two sub-sets of rings of permanently magnetized polygonal blocks, wherein the rings of a sub-set of rings are substantially concentric. In addition, the rings of the two sub-sets are complementary in terms of magnetization. Each ring of a sub-set is separated from its complementary ring by a space that is substantially the same for all pairs of complementary rings. The rings have a regular polygonal structure and are made up of blocks that also have regular polygonal shapes.

Abstract: A magnetic field generating assembly having at least two magnetic fields in the same sense. The generators are arranged such that, in use in a working region external to the generators, the resultant magnetic field exhibits a gradient extending in a first direction and at least second order variations in the fields in directions transverse to the first direction within the working region are substantially balanced such that an NMR experiment can be performed on a sample within the working region in accordance with the related method. The magnetic electrical field generators are substantially coaxial electrical coils, wherein the axis extends in the first direction.

Abstract: An active shield magnet has a plurality of screening coils which each have a small number of turns in comparison with the number of turns of the main magnet coil assemblies and which are connected in series in a closed loop to reduce the effect of disturbing influences in a working volume of the magnet.

Abstract: In a method for the production of a magnet coil arrangement which can create a predetermined magnet field B and has a minimal inductance L. The magnetic field B to be generated is expanded in spherical harmonics with coefficients C.sub.n,m and a field error .DELTA. B=f.sub.1 (C.sub.n,m) is defined fixing the deviation of the magnet field profile of the coil arrangement to be calculated from the given magnet field B within a volume and, if necessary, further parameters P=f.sub.2 (C.sub.n,m) are predefined, whereby the value of P which is calculated with a particular set of coefficients C.sub.n,m is within predetermined limits. By defining limits for technically relevant parameters and their variation as well as by giving the desired minimum inductance, the procedure achieves a high flexibility in conjunction with independent optimization of the parameters, in particular field errors, minimum inductance and current density oscillations.

Abstract: This invention relates to an apparatus and method for providing passive shimming for a superconducting magnet of the type that has a relatively small imaging volume. Such structures of this type, generally, provide the proper amount of passive shimming for a relatively small imaging volume.

Abstract: A C-shaped superconducting magnet for use in magnetic resonance imaging (MRI) equipment is disclosed. The magnet includes flux concentrators on opposing sides of the gap, for generating a vertical field therein; the flux concentrators include a plurality of coils, for carrying current in opposing directions, so as to generate an inwardly directed field to compensate for the gap. Injection correctors, each consisting of a horizontal coil, are disposed adjacent the flux concentrators. A flux return body, for example a superconducting solenoid or an iron yoke, provides a return path on the opposite side of the magnet from the gap. Flux deflectors guide return flux in a curved path from the flux return body to the injection correctors.

Abstract: Apparatus for cancelling magnetic fields for cancelling a leakage magnetic field from a static magnetic field generation assembly are disposed outside the static magnetic field generation assembly. A magnetic shield made of a magnetic substance is disposed between the static magnetic field generating assembly and the cancelling magnetic field apparatus. The cancelling magnetic field generation apparatus is of a cryostatless type.

Abstract: This invention relates to a superconducting magnet of the type that has a relatively small imaging volume. Such structures of this type, generally, allow the operator to image human limbs without the use of a larger, more costly superconducting magnet.

Abstract: A superconducting magnetic imaging apparatus includes a vacuum vessel (40) having a central helium reservoir (48) in which superconducting magnetic coil windings (44) are maintained at a superconducting temperature. The vacuum vessel defines an internal bore (42) within which a self-shielded gradient coil assembly (14) and an RF coil (22) are received. The self-shielded coil assembly includes an inner former (60) which defines an imaging region (12) within which an imaged portion of the patient are received. X and y-gradient coils having winding patterns (62) are bonded to the former (60) forming an integral structure. A z-gradient coil (70) is mounted to mechanical reinforcement structure (72) to be held in a spaced relationship from the x and y-gradient coils with an air gap (74) in between. This facilitates the dissipation of heat generated by the large current pulses applied to the x and y-gradient coils.

Abstract: The invention relates to a novel magnetic resonance imaging apparatus. The nuclei, protons or the paramagnetic electrons of an imaged object are cyclically polarized during a period of about one second with a permanent magnet which is then quickly shifted away from the imaged object in a permanent magnet carrier tube, so that the field of the permanent magnet would not have an interfering effect on the immediately following signal-collection for MRI-imaging. The permanent magnet can be manipulated or shifted back and forth in the tube either magnetically, pneumatically, hydraulically or mechanically. The apparatus also includes another permanent magnet or a resistive magnet coil couple, which is located in the tube near the opposite end of the tube, and which generates a homogeneous magnetic field within the imaged area.

Abstract: A superconducting means for MRI including seven to nine small superconducting coils situated in such a manner that the number of turns of these coils becomes progressively greater towards the outside, and preventing the occurrence of 2nd to 16th order inhomogeneous fields.

Abstract: An open architecture Magnetic Resonance Imaging Magnet with a pair of spaced annular superconducting magnet assemblies utilizing a cantilevered main magnet coil and correction magnet coil within each assembly.