Bruker Analytische Messtechnik Gmbh

Bruker Analytische Mebtechnik Gmbh

Kernforschungszentrum Karlsruhe Gmbh

Wolfgang H Muller

Bertold Knuttel

Michael Westphal

Gunther R Laukien

Arne Kasten

Gerhard Roth

Tony W Keller

Wolfgang Lehmann

Franz Graf

Peter Turowski

Wolfgang Stautner

Arne Kastep

A gradient system for a nuclear spin resonance (NMR) tomograph with a main magnet system producing a homogeneous magnetic field directed along a z-axis inside a measuring volume, wherein the main magnet system provides access to the measuring volume along the z-axis and transversely to the z-axis, and wherein the gradient system comprises two first partial gradient systems which are located at opposite sides of a central plane perpendicular to the z-axis, across the measuring volume. At least one of the two partial gradient systems is movable between at least two positions along the z-axis. In this way, with a small constructional size and with a simple manufacturing procedure, a gradient system is obtained with high performance capability with respect to generated gradient strength for given ampere turns, high linearity of the generated gradient fields, minimum inductance and minimum electrical resistance of the conductor segments.

Gradient system for an NMR tomograph

A magnet system for a nuclear spin tomograph having at least one field producing magnet coil S.sub.1 with radius r.sub.s1 arranged in a middle plane which produces a homogeneous magnetic field in an investigational volume directed along a z-axis perpendicular to the middle plane, is characterized in that at least one, preferentially at least two, ferromagnetic rings R.sub.i with radius r.sub.Ri are provided in the middle plane concentric to the magnetic coil S.sub.1. A system of this kind can be substantially more compact in construction than conventional systems with equal produced field strength. In addition substantially reduced currents are required through the coil or coils for field production.

NMR slice coil

In a magnetic shielding for a superconducting magnetic coil (2) arranged on the inside of a cryostat (1) and having a vertical axis for the production of a static magnetic field with a homogeneity of &lt;10.sup.-7 in an investigational volume (V) of a nuclear magnetic resonance (NMR) spectrometer, the shielding is a room shielding located at a separation from the cryostat (1), which includes at least two ferromagnetic, horizontally arranged plates (3, 4) of which one is arranged below and other above the cryostat (1), whereby the separation of the upper plate (3) from the center of the investigational volume (V) is approximately 1.5 to 3 times, preferentially approximately twice, as large as the separation (h) of the lower plate (4) from the center of the investigational volume (V), and vertical ferromagnetic side elements (5) are provided for which magnetically connect the upper plate (3) and the lower plate (4) and the upper plate (3) contains 1.5 times to 3 times, preferentially twice as much ferromagnetic material as the lower plate (4 ). In this fashion the magnetic field homogeneity is maintained and no significant forces occur during operation of the magnetic coil (2).

Ferromagnetic room shielding for the superconducting high field magnet

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.S of both magnetic coils (S1, S2) assumes a value between 1/4 and 3/4, preferentially 1/2 of the sum r.sub.S1 and r.sub.S2 of the average separations of both magnetic coils (S1, S2) from the z axis and the axial separation g.sub.R of both rings (R11, R21) is slightly, e.g. up to 15%, smaller than the axial separation g.sub.S between both magnet coils (S1, S2). The rings (R11, R21) are at least partially integrated into the coils. The system is compact, highly homogeneous and enjoys low power consumption while exhibiting good transverse and axial access.

Magnet system for NMR tomography

A system for the generation of magnetic gradient fields which intermittently overlap the static magnetic field of a nuclear-spin tomograph, with at least one pair of gradient coils, powered from a power supply, through which current flows in series when in operation and which generate, in a predefined volume under examination, a gradient magnetic field that varies at least approximately in linear fashion with position in one direction, is characterized in that each gradient coil (A, B) has one set with at least one first winding zone (S1) and one set with at least one second winding zone (S2), which have terminals (16, 17; 18, 19) that are separate from one another, in such a way that the winding zones can be easily be connected to and separated from one another in varying ways. The user can thereby modify the properties of the gradient system.

Gradient-generation system, nuclear spin tomograph, and process for the

Magnet system with superconducting field coils

Winding configuration for a cryomagnet

In an NMR magnet system for generating a highly homogeneous magnetic field of high field strength, with at least one superconducting magnet coil which is arranged in a first chamber of a cryostat in supercooled liquid helium at a temperature of less than 4.2K, with the cryostat having at least one further chamber containing liquid helium that is essentially at atmospheric pressure with a temperature of approximately 4.2K, the first chamber is connected to the further chamber in such a way that the supercooled liquid helium located in the first chamber is also essentially at atmospheric pressure. A refrigerator with which the liquid helium can be cooled to a temperature T&lt;&lt;4.2K, especially to T.apprxeq.1.8-2.3K, is provided in the first chamber.

NMR magnet system with superconducting coil in a helium bath

A magnet winding in a air coil configuration with windings made from conducting elements which surrounds a magnetic field axis and is wound in at least two layers with at least one layer transition, is characterized in that, in an angular region about the magnetic field axis which includes a layer transition, the radial separation from the magnetic field axis of at least the radially innermost winding of a respective layer is less than that in the other angular region. In this manner, it is, to a large extent, possible to compensate for the magnetic field breach resulting from the 'thinning' of the effective active conducting elements of the innermost winding in the region of the layer transition.

Magnet winding with layer transition compensation

A nuclear magnetic resonance spectrometer, in particular a nuclear spin tomograph serving to investigate biological samples, comprising a magnetic coil for generating a substantially homogeneous magnetic field in a volume under examination, and a set of shim coils for eliminating any remaining inhomogeneities of the magnetic field is characterized in that at least one additional electric conductor, preferably an additional shim coil, is provided which may be arranged in the volume under examination, in the direct vicinity of the sample, that the additional conductor is designed in such a way that it will generate an inhomogeneous magnetic field when loaded with current, and that it can be loaded with currents of a type generating inhomogeneous magnetic fields which will eliminate, at least partially, and in a selected area in the sample, local field inhomogeneities resulting from susceptibility variations within the sample, for example. This enables the accuracy of the spectroscopy results to be improved.

Nuclear magnetic resonance spectrometer

A magnet coil (30) comprises at least one first winding made of wire (34) which is superconductive at operating temperature and at least one second winding made of normally conductive wire (36). In addition, means are provided for supplying a current into the second winding, which is completely dead during superconductive operation of the magnet coil (30), when at least certain sections of the superconductive wire (34) assume the normally conductive state. In order to accelerate the spatial propagation of this transition in the magnet coil (30) and at the same time to provide the possibility to use low-cost wires having a relatively small proportion, related to the cross-sectional area, of normally conductive material, the first and the second winding are connected in parallel electrically.

Superconductor and normally conductive spaced parallel connected windings

An electromagnet system for nuclear spin tomography comprises a ferromagnetic yoke (41), two pole pieces (42, 43) arranged on the said yoke (41) with their pole faces (51, 52) facing each other, and at least one excitation coil (47, 48). The pole pieces (42, 43) delimit an air gap (44) having a diameter-to-width ratio of less than 2.5. There is arranged in the area of each of the pole faces (51, 52) formed by the pole pieces (42, 43) at least one substantially two-dimensional supplementary coil (55, 56, 57, 58) whose number of ampere turns is between 0.1% and 10% of the number of ampere turns of the excitation coil (47, 48). The excitation and supplementary coils generate together in the air gap (44) a magnetic field (B) which exhibits a homogeneity better than 10.sup.-4 in a spherical volume having a diameter equal to half the value of the width (H) of the air gap.

Electromagnet system for nuclear spin tomography

An electromagnet for generating the constant magnetic field required in NMR tomography includes a superconductive coil system consisting of at least one circular cylindrical field coil (1) and at least one correction coil (2, 3) concentric with the field coil. The coil system is enclosed in a ferromagnetic cylindrical shell (13) whose influence on the homogeneity of the magnetic field is compensated by the particular dimensioning of the field and correction coils. The magnetic field is produced by the coil system (1, 2, 3) in the interior space defined by it, which space is accessible and suitable to receive the body presented for examination. The cylindrical shell (13) may be closed at its ends by ring-shaped ferromagnetic plates (14). The cylindrical shell (13), complete with plates (14), may directly form the exterior wall of the Dewar.

Electromagnet for NMR tomography

An electromagnet for producing the constant magnetic field required in NMR tomography comprises a coil system (1, 2, 3, 4) of the Helmholtz double coil type. The coil system is enclosed in, and supported by, a stable cylindrical shell (5). The influence exerted by the cylindrical shell (5) on the homogeneity of the magnetic field, which is generated by the coil system in an accessible interior space defined by it and suitable to receive the body to be examined, is compensated by the particular dimensioning of the field and error coils (1, 2, 3, 4). The cylindrical shell (5) is best made of a ferromagnetic material having low electric conductivity and is constructed of a plurality of axially serially disposed annular discs (6) which are preferably divided into sectors.

A cooling apparatus for a low temperature magnet system includes a superconducting magnet coil (32) which encircles a test space (36). The magnet coil (32) is surrounded by at least one intermediate shield (26, 29) and is contained in an evacuated outer shell (22). On the outer shell (22) is a motor driven refrigerator (11) which actively cools the at least one intermediate shield (26, 29) by means of a cooling arm (18) extending through the outer shell (22). For compensating the disturbing fields emitted by the motorized drive of the refrigerator (11) a sensing device is provided for picking up these magnetic and/or mechanical disturbing signals. The sensor signal controls at least one coil (62) for compensating the disturbing field effective in the test space (36).

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Karlsruhe, Germany

Wolfgang H Muller