Active shielded cylindrical gradient coil system with passive RF shielding for NMR devices.

专利摘要:
The invention relates to an actively shielded cylindrical NMR gradient coil system which generates a Z-gradient field and comprises an active shielding coil (2), the main gradient coil (1a, 1b) being symmetrical about at least two in the z-direction about a first axial length (L1) Partial coil systems axially spaced apart from the center of the measuring volume are constructed colinearly with the z-axis and are constructed from electrical conductor sections wound around the z-axis with a maximum outer radius R1gradient o ut m ax, wherein an active shielding coil of electrical conductors has a minimum inner radius R1shield is constructed in m in about the z-axis, and where R1shield in m in> R1gradient out max, is characterized in that in a hollow cylindrical portion on the first axial length (L1) symmetrical to the center in a radius range between a minimum inner radius R1 gradient in min of the main gradient coil and R1shield in m in no electrical Are provided conductor elements of the gradient coil system, and that a passive RF shield (3) is provided, which is composed of at least three electrically interconnected sections, of which two sections are arranged with a maximum outer radius R1hf out ma x about the z-axis, while therebetween a third subsection is arranged with a second axial length (L2) and a minimum inner radius R2hf in m in and a maximum outer radius R2hf out max about the z-axis, where R1hf out max <R1gradient in min and R1gradient out ma x <R2hf in min <R2hf out max and L2 <L1.
公开号:CH707701B1
申请号:CH00384/14
申请日:2014-03-14
公开日:2018-06-29
发明作者:Freytag Nicolas
申请人:Bruker Biospin Ag；
IPC主号:

专利说明:

Description: [0001] The invention relates to an actively shielded cylindrical gradient coil system for use in an MR (= magnetic resonance) spectrometer with a main field magnet which generates a main magnetic field aligned in the direction of a z-axis, wherein the gradient coil system flows in current flow in one of the z-axis. Axis traversed by the measured volume generates a z-gradient field whose zero crossing lies in the center of the measuring volume, and wherein the gradient coil system has at least one main gradient coil and at least one active shielding coil, wherein the main gradient coil of at least two in the z-direction by a length L1 symmetrical to the center of the measuring volume axially spaced apart cylindrical sub-coil systems is constructed, the axes of which run col-linear with the z-axis, wherein the cylindrical sub-coil systems at least partially electrically wound with a maximum outer radius R1 gradientoutmax about the z-axis conductor sections are constructed, wherein at least one of the active shielding of electrical conductors on a minimum inner radius R1shieldinmm is constructed around the z-axis, and wherein Rlshieldjn "1" 1> R1gradientoUtmax.
Such a gradient coil system for an imaging NMR apparatus has become known, for example, from US Pat. No. 5,296,810.
Background of the Invention A modern nuclear magnetic resonance (NMR) spectrometer consists of a superconducting electromagnet for generating a strong static magnetic field, a shim system for homogenizing the static magnetic field, and an NMR probe containing at least one transmit / receive coil system for emitting RF Pulses and receiving the signals, a measuring sample and a gradient coil system for generating pulsed field gradients. In addition, the NMR spectrometer includes the necessary apparatus for generating and detecting the electrical signals that are generated or detected in the aforementioned components.
Most modern NMR probes contain actively shielded gradient coil systems for generating a Z-gradient field, in rare cases also for the generation of X, Y, and Z gradient fields. The active shielding is necessary because many NMR pulse sequences require a fast switching of the gradient fields, which leads to the induction of eddy currents in the surrounding metallic structures (in particular the outer sheath of the measuring heads, the carrier for the shim system and the various, partly in the case of unshielded gradient coil systems) cryogenically cooled metallic elements of superconducting magnet systems and cryo-shim systems The goal of active shielding is to minimize the eddy currents and to minimize the measuring artifacts caused by the remaining eddy currents in the measuring volume Properties of the gradient coil system and include both phase errors and spectral broadening of the NMR lines to be received.
In the prior art actively shielded gradient coil systems are usually made so that the turns of the gradient coils and the associated Abschirmspulen come to rest on two different radii per gradient. The turns on the inner radius are used for the generation of the gradient field, the outer radius responsible for the shielding of the gradient fields to the outside. In part, certain linearization tasks can be taken over by the turns on the outer diameter and come to lie part of the shield in the outermost axial regions of the inner cylinder.
This design principle has great advantages in the production and calculation of the gradient coils. In particular, the manufacturing simplifies, since in the construction of gradient coils of cut electrically conductive tubes, foils, sheets, PCB material or the coating and patterning on cylindrical substrates only two tubular objects must be aligned with each other. For multi-layer gradient coils additional radial and axial positioning must be performed, which usually reduce the yield in the production.
In particular, in Z-Gradientenspulensystemen there is the possibility to choose a design for the gradient, in which the distribution of the electrical conductors of the main gradient coil has an axial distance symmetrical to the center of the measuring volume. Depending on the design, this may also be valid for the active gradient shields. Examples of the occupancy of such gradients can be found e.g. in US Pat. No. 4,733,189.
The turns of the gradients are usually connected in series in order to ensure a constant current through all conductors can. Parallel interconnection would result in fluctuations of the gradient field by varying the currents of different partial spurs, in particular if the temperatures of the individual conductors during operation vary due to inhomogeneous cooling, different conductor lengths and resistors given thereby. However, there are also parallel shadows in practice, but require a greater effort in the generation and control of the gradient currents.
To make the galvanic connection between the two symmetrical halves of the main gradient coil and the active shielding coil, it is common to lay them through the central region in which they are spaced, the conductor for connection either coaxial with the cylinder axis or can run in any curve. Examples of curved profiles can be found in US Pat. No. 7,109,712 B2 or in US Pat. No. 6,456,076 B1.
Examples of straight courses can be found e.g. in the initially-quoted US Pat. No. 5,296,810 or in the documents cited as state of the art in US Pat. No. 6,456,076 B1 or in US Pat. No. 7,109,712 B2.
In the prior art, in addition to the tubular gradient coil systems, other geometries exist in which the turns of the main and / or Abschirmgradientenspulen come to lie on more complex surfaces.
Gradients are known from US-A 5 512 828, consisting of a main gradient coil and an active shielding coil, wherein the distance between the two coils is greater in areas remote from the center than in the areas in the vicinity of the center.
US Pat. No. 5,939,882 discloses a gradient coil system in which the full space is not occupied by the gradient coils. However, this is a modification of a biplanar gradient coil system on curved surfaces rather than a cylindrical gradient coil system. In the area of the RF coils, a filling of the space with gradient coils is provided for at least part of the xy plane.
US 6,933,723 B2 shows a gradient coil system in which the main gradient coil is set back in the region of the RF coil. Here, 218/221 the symmetry axes x and z, 211 represent the magnets for generating a static magnetic field, 212 the active shielding coil of the gradient coil system, 213/213 'the main gradient coil of the gradient coil system and 219 the RF coil. Neither the description nor the figures describe an RF shield for limiting the volume accessible to the RF, so it must be assumed that there is no RF shielding in this arrangement.
Idem is found in US 7,852,083 B2, but here an RF shield is described explicitly, which granted by the recessed portion of the main gradient coil the RF coil system, a larger volume and thus increases the performance of the RF coil system (or the Gradients in the region outside the central region allows a greater distance between the gradient coil and the shielding coil and thus increases the efficiency of the gradient coils with respect to a conventional gradient coil system). The RF shield follows the shape of the main gradient coil, which has a larger radius r2> r1 in the area of the RF coils than outside the active RF range.
Common to the documents US 7 852 083 B2 and US 6 933 723 B2, that the gradient coils each extend over the full length of the z-axis or even have an overlap region in which exist on two radii turns of the gradient coils. There is no axial region in which the main gradient coils have no turns.
From US 7 057 391 B1 a magnetic system with integrated gradient (3) and RF coil (4) is known, are embedded in the gradient and coil in a bulge of the magnet. The aim is to use «unused» space for the efficient generation of the static magnetic field. Gradient, RF coil and possibly RF shielding seem to be made cylindrical.
From US-A 6 154 110 a gradient coil system for open MRI magnets is known, in which the gradient coils and the shielding coils are interrupted in a central region. However, no RF shield can be mounted in the same area, otherwise the open system would be closed by the RF shield. It is in principle a modification of biplanar gradient coil systems.
In US-A 5,600,245 local gradient coil systems are presented, which enclose the RF coil while leaving an opening in the RF coil free. However, these gradient coils are not actively shielded coils and they can only work in combination with a main gradient coil and serve only to locally amplify the gradient field.
From US-A-5 406 204 a gradient coil system is known which includes an RF shield which in certain embodiments is arranged at different radii. The turns of the Z gradient coil are laid in grooves of a carrier in one embodiment. RF shielding is laid either on the surface of the carrier and into the grooves, outside the Z gradient coil, or both in the grooves and outside the Z gradient coil.
The depth of the grooves largely corresponds to the thickness of the Z gradient turns. It should be noted that the outer surface of the RF shield with the outer surface of the Z gradient windings should form a largely flat surface for receiving the X and Y gradient windings.
The thickness of the gradient turns is classified as negligible compared to the large diameters of the gradient coil system (60-90mm). This can also be seen in particular from FIGS. 1 to 3 of US Pat. No. 5,406,204: The illustrated graduation of the RF shield in the grooves of the Z gradient windings moves only in the range of approximately 0.5-1% of their Radius. Due to this slight variation of the radius is also explicitly stated that the grooves for the functionality of the invention have no meaning and the Z-gradient can be laminated without significant losses in performance on a continuous RF shield with a constant radius. It appears that the filling of the grooves tends to be more for manufacturing reasons than for performance reasons.
From the document is not directly clear how the galvanic connections between the individual turns of the Z-gradient coil are executed. However, it should be noted that the design of the X, Y and Z-Gra serving coils preferably according to the patent application no. 07/942 521 succeed. From this application, the cited publication US-A5 296 810 developed, in which for a Z-gradient, a serial shading of the turns is also represented by the central region. It is therefore to be understood that in US-A-5,406,204 over the full length of the gradient coil system electrical conductors exist on the radii of the main and shield coils of the X, Y and Z gradient coils. Because the X and Y gradient coils are adhered to the Z-gradient coil, it will be appreciated that in one embodiment with grooves, a coaxial groove must also exist that establishes the electrical connection between the two halves of the main gradient coil.
Modern NMR probes are typically made with actively shielded gradient coil systems for generating pulsed field gradients. In contrast to sensors for nuclear magnetic resonance methods (= MRI), most of these gradient coil systems are only uniaxial gradient coil systems, in particular Z gradients, in which the most uniform gradient of the magnetic field is applied along the z direction, the z direction being the direction of the static magnetic field is defined. The effect of this gradient field on a spin / is a rotation about the z-axis by an angle yiGz, where G is the gradient amplitude and Y | is the gyromagnetic relationship of the spin. By applying a field gradient, a phase factor of the magnetization coded along the gradient axis can be induced. In rare cases, however, gradient coil systems are also used to generate a plurality of gradient fields, in particular X, Y, Z gradient fields, as are customary for MRI.
For nuclear magnetic resonance spectroscopy, it is customary to produce measuring heads with integrated pulsed field gradient coils. In this case, both the measuring heads and the gradient coil systems are usually cylindrical or hollow cylindrical, in particular circular cylinder-shaped variants being used. These gradient coil systems are usually applied to (circular) cylindrical supports and their conductors occupy substantially the full cylinder surface area. In rarer cases, and especially for very high gradient systems requiring liquid cooling, the gradient systems are separated from the probes.
There are various methods for producing gradient coil systems: either they are wound from wire, with the wires usually being fixed in grooves in the carriers, or they are cut from usually metallic tubes, foils or electrically coated carriers or onto flexible ones Printed circuit boards or sheets or foils and then applied to carriers.
The gradient windings can be created in two different ways: the so-called "lane change winding" or the "spiral winding". For the sake of simplicity, the following discussion is limited to Z-gradient coil systems, but applies as far as possible to all other gradient coil systems.
For a Z-gradient coil system, the turns are in "lane changing" except for a small section each on a z-position. In the small section, a transition is made from one z position to the next. In "spiral winding", the z position is continuously occupied. Wire gradients, in particular, are generally designed as "lane change windings", since the grooves can not be produced spirally with great precision or only with great effort. However, due to the easier calculation of the gradient design, differently produced gradient types are usually produced as "lane change windings".
In order to produce a Z-gradient field, a main gradient coil is needed, which usually has a symmetry with respect to the xy-plane. In order to be able to generate the gradient field, however, the direction of rotation of the current in the two half-spaces must be opposite. Usually, the two gradient halves are connected in series by means of a galvanic connection through the center, wherein this connection is laid on the same radius as the actual gradient windings.
For most NMR applications actively shielded Z-gradient coil systems are used, due to the necessary short gradient recovery times pay special attention to the shielding of the gradient to the outside and their interaction with the magnetic and shim system and the RF coil systems must be placed inside. Active shielded gradient coil systems usually consist of at least one main gradient coil and one shielding coil, wherein the shielding coil completely envelops the main gradient coil. In particular, the shielding coils are usually made longer than the main gradient coils. Since the assignment of the gradient coils for technical reasons usually takes place only on cylinder jacket surfaces and not on the end faces of the cylinder, the missing end faces can be compensated for at least in part by extending the shielding coils. Furthermore, usually parts of the axial shield are designed on the cylinder shell of the main gradient coil.
As well as for MRI, the highest possible and most efficient field gradients are required in NMR spectroscopy. In particular, the second point requires that the radial distance between the main gradient coil and the shielding coil must be made as large as possible. However, since the outer dimensions are defined by the bore of the magnet system, this can only be achieved by reducing the radius of the main gradient coil with respect to the fixed outer radius of the shield coil.
An NMR probe is not primarily characterized by the gradient coil system contained in it, since it is designed in particular for transmitting and receiving RF signals. This is done with RF coil or resonator systems tuned to the resonant frequencies of the nuclear spins to be measured in a given static magnetic field. The reduction of the radius of the main gradient coils therefore has a lower limit, which is given by the volume necessary for an efficient operation of the RF coil system in the interior.
Basically, there are two ways to combine RF coil and gradient coil systems in a measuring head: Either both systems share the same space, i. E. they are not separated from each other electromagnetically, or the available space is divided into an area for the gradient coil system (gradient area) and a room for the HF system (HF area). In the latter case, an RF shield is drawn between coils and gradient coil system.
The advantages and disadvantages of the two concepts are as follows: Unshielded gradient coil systems do not or hardly limit the volume available to the HF in comparison to a measuring head without gradient coil system. An inserted RF shielding reduces the performance of the RF system. essential, since on the RF shield Abschirmströme must flow, which act on the one hand dissipative and thus reduce the quality of the RF system, and on the other generate the RF magnetic field opposing field and thus reduce the generated magnetic field amplitude per unit current in the measurement volume. Thus, the sensitivity of a RF shielded probe decreases with respect to a probe without RF shielding.
However, since an unshielded gradient coil system in the radio frequency range has a broad spectrum of natural resonances and these, in particular in the case of Tripleaxis gradient, can couple partially massive with the RF coil system, the use of gradient coil systems without RF shielding in the Usually very expensive or even impossible. Couplings between eigenmodes of the gradient and the RF coil systems can z.T. generate significantly higher losses in Q and magnetic field amplitude per unit current than would produce a corresponding RF shield.
To circumvent this dilemma, the radii of the gradient coil systems are usually chosen as large as possible in order to accept the smallest possible losses due to RF shielding. However, this results in a lower efficiency of the gradient coil system, which must be bought with higher currents and / or higher inductance and higher dissipation during operation.
The device according to the invention In contrast, the object of the present invention is to improve an actively shielded gradient coil system of the type described at the outset with the simplest possible technical means such that the available space in the measuring head can be converted into an HF range and a gradient range by RF shielding is divided, wherein the volume of the RF range is maximized while maintaining the performance of the gradient coil system.
According to the invention this object is achieved in a hollow cylindrical section on the axial length L1 symmetrical to the center of the measuring volume in a radius range between a minimum inner radius R1gradientmin of the main gradient coil and Rlshieldjn "in a surprisingly easy to implement, but very effective manner 1, there are no electrical conductor elements of the gradient coil system, and that a passive RF shield is provided, which is composed of at least three electrically interconnected sections, of which two sections are arranged with a maximum outer radius R1hfoutmax about the z-axis, while between these two sections are arranged a third section with an axial length L2 and a minimum inner radius RZhfjn "1" 1 and a maximum outer radius R2hfoutmax about the z-axis, where: R1 hfoutmax <R1 gradientinmin and R1 gradientoUtmax <R2hfinmin <R2hfoutmax and L2 <L1.
DETAILED DESCRIPTION OF THE INVENTION WITH EMBODIMENTS [0039] In particular when actively shielded Z-gradient coil systems are used, it is not absolutely necessary to cover the full cylinder jacket surface or cylinder jacket surfaces on various radii over the full z-range, as in the case of the gradient coil systems in the prior art the technique is common. The highest current densities must be generated in the region of the reversal points of the gradient field, which as a rule must be outside the range of the RF coil systems in order to be able to ensure a sufficient length of the gradient field over the active region of the NMR system. In the axial region in which the RF coil systems come to lie, additional turns may be necessary to achieve better linearity of the Z gradient field along the Z axis, with the possibility of burdening some of the linearization by turns of the gradient shield coil to perform the shielding effect. In addition, the additional turns necessary for the linearization can be laid on a different radius than that of the main gradient coil.
In addition, for the usual dimensions of nuclear magnetic resonance spectroscopy, it is sufficient to add a single pair of gradient coils to the pair of main gradient coils to achieve sufficient linearity for the Z gradient across the measurement volume.
In addition to the usual optimization goals of a gradient coil system for minimal inductance, maximum efficiency, linearity over a certain volume, external shielding and recovery properties given internal and external diameters, specifications are thus made for volumes that need to be free from conductors. In order to keep the central area free of electrical conductors, the main gradient coil can be made up of two or more separate sub-coil systems. The electrical leads for each of the sub-coil systems are guided axially in the space between the main gradient coils and the shielding coil to the nearer end of the gradient, without crossing the central area. Now all sub-coil systems of the gradient including the shielding coil (s) can be connected in series.
A gradient coil system according to the invention accordingly has a cylindrical section in a central region which does not contain any conductor elements of the gradient coil system and has a maximum external radius which is greater than the minimum internal radius of the main gradient coil conductor elements. In addition to the actual gradient windings, this also includes the lead wires or connecting wires between the individual turns of the gradient coils. In particular, the outer radius of this cylindrical portion is only slightly smaller than or equal to the minimum inner radius of the shielding coil in this axial region.
This free space in the center of the gradient coil system can now be used to insert a passive RF shielding whose radius R2 in a central region over a length L2 is greater than the radius R1 in the outer regions (in particular the region the highest current density of the main gradient Teilspulensys-systems). To achieve this, the RF shield is made up of at least three sections that are electrically connected together. By electrical connection is meant in this context either a galvanic connection or an electromagnetic connection. Electromagnetically connected are two conductor elements, if they have a significant electromagnetic coupling, which comes about in particular by capacitive or inductive coupling. It can be achieved by discrete or distributed capacitively and / or inductively acting elements. Distributed capacitive elements may e.g. be performed as isolated for isolation by dielectric layers, overlapping electrical conductors.
Since at least one transmitting and / or receiving coil system is mounted in the central region of an NMR measuring head, the volume available to it is less severely limited by the RF shielding according to the invention than in the prior art. With comparable performance of the gradient coil system, this leads to a higher performance of the transmitting and / or receiving coil system than in an NMR measuring head according to the prior art.
In particular, the required pulse angles can be achieved when transmitting with lower pulse powers, which reduces thermal effects. Furthermore, the sensitivity and thus the signal to noise ratio of the measuring head during reception is improved.
In the following, preferred embodiments and developments of the invention with their modes of action and particular advantages are described: A particularly preferred embodiment of the gradient coil system according to the invention is characterized in that the following applies: R2hfoutmax <R1shieldinmin.
It is thus achieved that the shielding coil of the gradient coil system is made of one piece, e.g. on a single carrier, can be made. This simplifies the assembly and alignment of the partial coil systems of the main gradient coil to the shielding coil during manufacture.
Particular advantages are also offered by an embodiment of the gradient coil system according to the invention in which: R2hfinmm> 1.1-R1gradientoutmax and R2hfoutmax> 0.8 * R1shieldinmm.
With these dimensions, a significant increase in the performance of the transmitting and / or receiving coil system can be achieved.
In a further preferred embodiment, R2hfinmin> R1 gradientoutmax + 3 mm and R2hfoutmax> R1shieldinmin - 3 mm.
With the usual dimensions of the gradient coil system of an NMR probe with R2 approximately in the range 33 mm <R2 <40 mm and R1 approximately in the range 18 mm <R1 <25 mm, these dimensions result in a significant increase in the performance of the transmit and / or receive Coil system with respect to a NMR probe according to the prior art.
A class of embodiments of the gradient coil system according to the invention is characterized in that the electrical conductor sections wound around the z-axis are constructed from wires with a preferably round cross-section. This is particularly easy to manufacture, e.g. by inserting grooves in a support into which wires are wound. Wires with a round cross-section can be mounted even easier than wires with any, in particular square, cross-section. Rectangular cross section wires optimize the current density per unit volume in round wire design.
In an alternative class of embodiments, the electrical conductor sections wound around the z-axis are constructed of ribbon conductors. As a strip conductor to be understood wires whose cross-section has a width to height ratio that differs significantly from 1, especially for a height to width or width to height ratio greater than 1.5 have. Particularly preferred are conductors with a width to height ratio greater 2. Bandleiter can minimize the electrical resistance of the gradient system for a given radial dimension or allow a smaller conductor spacing in the axial direction for a given electrical resistance.
A further, likewise alternative class of embodiments is characterized in that the electrical conductor sections wound around the z-axis are constructed of dielectric carriers coated with an electrically conductive layer. A precise and at the same time cost-effective production of gradient coil systems is possible by structuring (for example laser structuring, but also wet-chemical methods) of carriers coated with electrically conductive layers. The manual effort can be minimized and the reproducibility maximized. Suitable supports are ceramic materials, plastics, glasses and ground single crystals. When a carrier material having high thermal conductivity (for example, aluminum nitride, aluminum oxide, silicon or silicon carbide as a ceramic or single crystal) is used, the carrier can also perform the heat transfer for cooling thereof in addition to the function of mechanical positioning and stabilization of the electrical conductors. This is particularly advantageous in the case of cryogenically cooled gradient coil systems.
Also preferred are embodiments of the gradient coil system according to the invention, in which at least two of the pairs of axially spaced-apart cylindrical partial coil systems of the main gradient coil have different minimum inner radii R 1 gradient T min, R 2 gradient T min, R 3 gradient T min. In these embodiments, e.g. Coils are incorporated for linearization of the gradient, which only minimally reduce the available space for the RF area when the RF shield follows the profile of the ladder of the gradient coil system.
In further advantageous embodiments, it is provided that at least two sections of the passive RF shield have different minimum inner radii R1hfinmm, R2hfinmm, R3hfinmm, R4hfinmm. This allows the RF range to be maximized when using a gradient having at least two pairs of axially spaced cylindrical sub-coil systems having different minimum inner radii. In addition, an "indentation" of the RF shielding can thus only be made in the region of conductors of a partial coil system of the main gradient coil. This maximizes the RF range and thus the performance of the NMR transmit / receive coil systems.
Furthermore, embodiments are also preferred in which at least one of the cylindrical partial coil systems is constructed from a plurality of electrical conductor sections wound over one another in the radial direction. As superposed conductors, conductors are to be understood which are mounted on several radii at approximately the same z-position. This provides the ability to design higher current densities in a z-position with constant conductor width. This reduces the resistance of the gradient coils, reduced in terms of designs with locally reduced conductor widths, and simplifies the design. Compared to a "smeared" occupancy by conductors, the space occupied by the conductors of the main gradient coil is also minimized, which is no longer available for the HF range.
Also advantageous is a class of embodiments, which are characterized in that the cylindrical Teilspulensysteme the main gradient coil and the at least one active Abschirmspule are completely bordered by a supply port of the passive RF shield. As a result, on the one hand, the electromagnetic couplings between the gradient coils and the transmitting / receiving coil systems can be minimized or reduced to zero, on the other hand, possibly detectable NMR signal of gradient materials (eg 1H or 13C signal of insulation of the electrical conductors, adhesives, support materials etc.) are minimized or reduced to zero.
These embodiments of the gradient coil system according to the invention can be further developed in that the radially inner surfaces and the axial end faces of the cylindrical partial coil systems of the main gradient coil and the radially outer surfaces and the axial end faces of the at least one active shielding coil are enclosed by the passive RF shield. As a result, the gradient coil system is completely enclosed by the RF shield, so that couplings and basic signal can be minimized or eliminated.
An alternative class of embodiments is characterized in that the passive RF shield is spatially shaped to enclose an RF-dense space region from which RF radiation can not escape to the outside. In this embodiment, the RF range is sharply demarcated, so that couplings with the outside space can be efficiently minimized and no basic NMR signal can be received from the outside space.
The two classes of embodiments described above can advantageously be further developed by virtue of RF sealing of the passive RF shield by capacitive overlapping of elements of the passive RF shield and / or by soldering and / or by pressing and / or by Gluing is effected with electrically conductive adhesive. This makes it possible to inexpensively produce an HF-dense grading of the passive RF shield from several parts.
Gradientenspulensystem according to any one of the preceding claims, characterized in that the passive RF shield (3) is mounted on a support, in particular by vapor deposition and / or sputtering and / or CVD and / or electroplating, and / or printing and / or painting and / or sticking. This allows to efficiently apply an RF shield in a manufacturing step on the inside and / or outside of a substrate. Furthermore, the electrically conductive layer applied in this way can be easily and precisely patterned in a further step in a pattern which allows the lowest possible shielding currents when switching gradient fields.
A further preferred embodiment is characterized in that at least two of the electrically interconnected sections are arranged cylindrically symmetric about the z-axis with a maximum outer radius R1hfoutmax, between these two sections a third section with an axial length L2 and a minimum inner radius R2hfinmm and a maximum outer radius R2hfoutmax is arranged about the z-axis, and that between the third section and the two other sections each have a transition section, in particular in the form of a cone-shaped element, arranged on an axial length L8 arranged on different radii Connecting sections together. This embodiment is particularly suitable when the passive RF shield is applied to a carrier by means of coating methods, since no surfaces need to be coated or structured perpendicular to the cylinder axis or sharp edges.
In the context of the present invention, finally, also an MR spectrometer with a gradient coil system with the above-described inventive modifications, which is characterized in that an RF transmitting and / or receiving coil system is provided which falls within the Radius R2hfinmm is arranged on an axial length L3 <L2 symmetrical to the center of the measuring volume. If the increased radius cavity of the passive RF shield has a greater length than the RF transmit and / or receive coil systems, the performance of the latter can be further improved.
Further advantages of the invention will become apparent from the description and the drawing. The drawings do not necessarily depict the various features to scale. Likewise, the features listed above and those listed further may be used individually or in any combination. The embodiments shown and described are not to be understood as exhaustive enumeration, but rather have exemplary character for the description of the invention.
It shows:
1 shows a schematic cross section through a first embodiment of the actively screened cylindrical gradient coil system according to the invention, which is of a particularly simple construction:
FIG. 2 shows an embodiment of the gradient coil system according to the invention comprising a transmitting and / or receiving coil system; FIG.
3 shows an embodiment with a main gradient coil consisting of three pairs of partial coil systems at different radii and a passive RF shield with three sections at different radii;
4 shows a further gradient coil system according to the invention, in which the partial coil systems of the main gradient coil are each manufactured from a plurality of layers of conductors and the HF shield defines indentations in the region of the conductors;
5 shows an embodiment of the gradient coil system according to the invention, which is completely enclosed by the passive RF shielding;
FIG. 6 shows a gradient coil system according to the invention, which is completely enclosed by the passive RF shield, wherein the shield coil consists of two partial coil systems spaced apart in a central region; FIG.
FIG. 7 shows an embodiment with RF-sealed HF range; FIG.
FIG. 8 a shows an RF shield for a gradient coil system according to the invention, which is applied on the outside of a carrier; FIG. and
Fig. 8b, an RF shield, which is applied to the outside of a carrier, wherein the transition between the two radii of the RF shield is made conical.
In the following detailed description, for purposes of explanation and not limitation, embodiments disclosing specific details are set forth in order to provide a thorough understanding of the present teachings. However, it will be apparent to those skilled in the art having read the present disclosure that other embodiments in accordance with the present teachings which depart from the specific details disclosed herein remain within the scope of the appended claims. Furthermore, descriptions of devices and methods known from the prior art may be omitted for the sake of clarity. Such methods and devices are obviously within the scope of the present teachings.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. The defined terms are in addition to technical and scientific meanings of the defined terms as commonly understood and accepted in the art of the present teachings.
The terms "one, one, one" and "the, the" include both singular and plural forms unless the context clearly dictates otherwise. Thus, for example, "one device" includes one device and / or multiple devices.
The terms "essential" or "substantially" as used in the specification and the appended claims mean "within acceptable limits or degrees".
The term "about" means "within an acceptable limit or amount for one of ordinary skill in the art." For example, "about the same" means that one of ordinary skill in the art would consider the elements being compared to be the same.
The use of the term "particular" merely highlights a subset of a set without explicitly limiting the population of the set. Thus, e.g. the set "cylinder, in particular circular cylinder", the amount of all cylinders of any cross-sectional area and highlights only those with circular cross-sectional area as particularly suitable.
An actively shielded gradient coil system according to the invention for use in an MR spectrometer with a main field magnet which generates a main magnetic field aligned in the direction of a z-axis is arranged cylindrically about the z-axis and consists of a main gradient coil consisting of at least two cylindrical Teilspulensystemen, at least one cylindrical Abschirmspule and at least one passive RF shield, wherein the at least two Teilspulensysteme the main gradient coil of electrical conductors are constructed on a radius R1 gradient, and in the z-direction over an axial length L1 from each other beab are standing, and the at least one shielding coil of electrical conductors on a radius Rlshield is constructed.
In many embodiments, in particular with electrical conductor elements made of wire, the radial extent of the main gradient coil and the shielding coil is so large that the difference between the minimum inner diameter and the maximum outer diameter is not more than approximately the same. For this reason, a minimum inner radius R1 gradient ^ 1 ™ or Rlshieldm1 ™ as well as a maximum outer radius R1gradientoutmax or R1shield0utmax are respectively allocated for the embodiments with non-negligible radial dimensions. For circular cylindrical gradient coil systems, in particular, the minimum inner radius is equal to the inner radius and the maximum outer radius is equal to the outer radius. For embodiments, in particular circular cylindrical, with approximately equal inner and outer radii of the sub-coils, R1 gradient tmin = R1 gradient T max = R1 gradient should be considered.
In this case, the following conditions apply: ## EQU1 ## The main gradient coil can be embodied within the shielding coil, which enables easy assembly during manufacture but also enables production on a single support for the shielding coil and the shielding coil Technically, this condition is necessary for the separation of the functionality in field generation in an interior, in particular in the measurement volume and active shielding of the gradient field in an external space, in particular outside the NMR probe.
In addition, R1shieldoutmax is determined by the maximum possible dimensions of the gradient coil system, which can still be installed in the NMR probe or in the shim system of the MR spectrometer. R1 gradient inmin is determined by the requirements of the performance of the gradient coil system as well as the dimensions and performance of the transmit and / or receive coil system.
The gradient coil system also consists of at least one sectionally cylindrical passive RF shield whose electrically conductive elements are located within at least two minimum inner radii Rih-finmm and two maximum outer radii Rihfoutmax, where i is a natural number greater than / equal to two. Analogous to the radii of the gradient coils should be considered in the case of approximately the same inner and outer radii as Rihfinmin = Rih-foutmax = Rihf, which is particularly true for thin, circular cylindrical RF shields is met.
The RF shield is made up of at least three sections, wherein two of these sections have the radius R1hf and between them a third section with an axial length L2 is inserted symmetrically to the center of the measuring volume on the radius R2hf.
For the radii of the passive RF shield, the following conditions apply: R1outmax <R2hfinmin, R1hfoutmax <R1 gradientin1 ™ * and R1 gradientoUtmax * <R2hfjnmm. In addition, for the axial dimensions L2 <L1. This results in an actively shielded gradient coil system with a passive RF shield, which has a bulge to the outside in a central area. Since at least one transmitting and / or receiving coil system is located in this central region of the NMR measuring head, its performance is increased by increasing the available volume compared to the NMR measuring heads of the prior art with cylindrical RF shielding on the radius R1 hf improved.
Particularly preferred is an embodiment consisting of a main gradient coil comprising exactly two sub-coil systems and a single shielding coil, wherein the passive RF shield has as small a radial distance from the shielding coil in a central region and in the edge regions the smallest possible radial distance to the Having gradient coils.
For this embodiment, in addition to the above-mentioned conditions, R2hfoutmax <R1shieldinmin. This embodiment is technically as simple as possible to realize and allows to provide a large volume for the RF coil systems and at the same time provides no restriction for the positioning of the conductor elements of the shielding coil. This ensures efficient shielding of the gradient fields to the outside become. If the shielding coil is mounted on a carrier and this has a small wall thickness, this embodiment represents only a small loss of performance of the transmitting and / or receiving coil system. It is shown schematically as a section in Fig. 1.
The production of such a gradient coil system can be carried out particularly preferably from the following sections: 1. From four components, consisting of an RF shield on a support, two partial coil systems of the main gradient coil on a respective tubular support and a shielding coil on another tubular support. This manufacturing method can be applied to all common methods for the production of gradient systems. In particular, it is suitable for wire wound gradients, but also for electrically conductive coated carrier. In producing the gradient chips from cut metal tubes, the above-mentioned carriers account for at least a portion of the elements. 2. Three components each consisting of one or more Teitspulensystemen the main gradient coil on the inside and half of the shielding coil (cut through the xy plane) on the outside and an RF shield on a support. It should be noted that the fabrication of a shielding coil of two halves is considered to be substantially equal to fabrication on a single cylindrical support when the two halves are substantially in contact in the central portion. This manufacturing method reduces the number of degrees of freedom in the positioning of the components and can thus minimize waste, if the correct positioning of the conductor elements can be ensured on the two carriers manufacturing technology. 3. The gradient coil system can be fabricated on the inside and outside of a single carrier into which the RF shield is inserted. Here, the RF shield is usually composed of individual parts or applied to an insulating layer in the interior of the gradient coil. This production method is particularly suitable for electrically conductive coated carrier and allows by means of mechanical production, a high yield of the gradient without time-consuming positioning of the main gradient coil to Abschirmspule. 4. Another possibility is to manufacture the gradient coil system on the inside and outside of a "half-shell-shaped" carrier cut along the longitudinal axis. Here, in particular, the design of the gradient system can be designed so that no or only a few galvanic connections between the "half shells" are needed. This can e.g. can be achieved by a multiple change of current between the main gradient coil and the shielding coil over the cutting edge. The RF shield may be fabricated on a third carrier which is inserted into the two half shells or applied to an insulating layer inside the half shells.
Other manufacturing methods consisting of more elements, in particular for RF shielding, may also have merit under certain circumstances, especially if the RF shield is not made from a continuous, thin, electrically conductive layer, but from sections with capacitive coupling between adjacent elements.
In another preferred embodiment, the outer radius of the RF shield in a central portion of the length L2 can also be greater than the inner radius of the active shielding coil, i. E. R2hfoutmax> R1shieldinmm. This is possible if in the design of the gradient a central region of the length L6 is provided, in which neither the main gradient coil nor the shielding coil has conductor elements. In this case, the volume for the transmit and / or receive coil systems is maximized, but typically the efficiency of the active gradient shield is reduced somewhat so that with fast switching of the gradient field (s) more eddy currents in the electrically conductive structures with radii greater than R1shieldoutmax be induced. This must be counteracted by using appropriate materials with high electrical resistance or non-conductive materials in the environment of the gradient coil system or by adapted design of the gradient, the eddy currents generated with little effect on the measurement volume. In general, furthermore, R2hfoutmax = R1shieldoutmax · [0085] Furthermore, an embodiment in which the length L2 is greater than the length L3 of at least one transmitting and / or receiving coil system is particularly preferred. This allows the lowest performance loss through RF shielding while providing high efficiency of the gradient coil system. In Fig. 2, such a gradient coil system is shown schematically in its simplest form. An NMR probe typically includes more than one transmit and / or receive coil system. The length L3 refers to the magnetic length of one of these coil systems. There are various definitions for the magnetic length of transmit and / or receive coil systems, but they may be considered to be approximately the same in the context of this invention. One of these magnetic length definitions is the half-value length of the RF magnetic field on the z-axis.
Another embodiment provides that the sub-coil systems of the main gradient coil to more than one and the RF shield are made on more than two radii. This has the advantage of having more flexibility for the conception of the gradient, improving the linearity and shielding of the gradient and at the same time further increasing the volume available for the HF range given the specifications for the gradient coil system.
In Fig. 3, a gradient coil system is shown schematically, in which the RF shield over the length L2 has an inner radius R2hfinmm. On two sections lying symmetrically to the center of the measuring volume with L2 / 2 <Izl <L4 / 2 it has a radius R3hf, where R3hfoutmax <R2hfin'r "n. Over the remaining length, the HF-shield has a radius R1hf, where In this example, R1hfoutmax <RShfjn "1" 1. Basically, further grading of the RF shielding is possible and these need not be symmetrical to the magnetic center of the measuring head.
A further preferred embodiment provides for a low area occupation by the partial coil systems of the main gradient coil. This further maximizes the volume for the RF range. This lower surface coverage can be achieved in particular if several layers of conductors are stacked radially one above the other. This is an advantageous embodiment, in particular for wire-wound gradients, since it is technically easy to solve by making grooves in a support for receiving the gradient wires and wrapping the gradient tightly packed in these grooves. Alternatively, it is possible to work with multilayer PCBs or to nested several layers of tubes into one another. In this case, any radius occupied by the conductor should be considered as an independent gradient coil on radius R1 gradient, where i is a natural number (positive integer). The z-positions of different sub-coil systems can therefore also overlap.
Such a gradient coil system is shown schematically in section in FIG. 4, wherein in this specific embodiment the HF shield has the radius R2hf in an interval -L2 / 2 <z <L2 / 2, in two further intervals L2 / 2 <Izl <L4 / 2 the radius R3hf, in the intervals L4 / 2 <Izl <L5 / 2 the radius R4hf and over the remaining length the radius R1 hf. In Fig. 4, R2hf = R4hf. However, this need not apply and serves only to illustrate a particularly preferred embodiment. In general, all radii can be performed differently. In addition, in Fig. 4, the axial extent of the various gradient coils at approximately the same z-position drawn the same size. This need not be guaranteed in the general case, but is e.g. to realize wire gradients particularly easy when wires are wound in grooves. Another easy way to create a wire gradient is to wind the wires in "tightest ball packing" so that every other layer contains one less wire and has half a wire diameter offset.
Not only the reduction of the coupling between the transmitting and / or receiving coil system and the gradient coil system is relevant for certain applications of NMR, but also the suppression of the NMR background signal e.g. of wire or conductor insulations, adhesives or substrate material in the gradient. This basic signal is generated by the excitation and reception of NMR signals. At best, it leads to a reproducibly altered baseline of the NMR spectra, which can be numerically corrected. This is especially the case when the fundamental signal is weak and the NMR lines are very broad. In the worst case, however, the fundamental signal contains relatively narrow narrow NMR lines that can not be corrected. In order to avoid this background signal as completely as possible, it is appropriate to completely separate the gradient coil system from the HF range. For this purpose, it may be necessary to enclose the gradient inside, outside and frontally by means of an RF shield. In the area of the gradient feed line, an RF shield can likewise be provided in order to prevent coupling or reception of basic signal in this area. It should be noted here that usually only components with almost identical static magnetic field can contribute to the fundamental NMR signal, because otherwise the Larmor frequency of the nuclei of the background is so strongly shifted with respect to the spectrum to be measured that they lie outside the measurement frequencies come because the static field of the main magnets has a largely symmetrical to the measuring range plateau, which falls outside steeply.
Fig. 5 schematically illustrates a variant of this embodiment in which the gradient coil system is completely enclosed in an RF shield. In this case, the RF shield consists of elements 3a on the inside of the gradient coil system, elements 3b on the end faces and elements 3c on the outside of the gradient coil system and an enclosure 6 of the gradient feed lines. The RF shield forms a closed
Gradient area 7, in which substantially no RF radiation can penetrate, as long as the RF shielding achieves a sufficiently high attenuation of the RF radiation. This can be achieved particularly well by a galvanically closed RF shield if the conductor thickness has multiple penetration depths at the relevant frequencies and temperatures. Alternatively, a structured RF shield can be designed so that it has sufficient RF leakage at the relevant frequencies. However, structured shielding is generally not sufficiently RF-tight at all frequencies to completely prevent artifacts due to the fundamental signal.
End-face and cylinder shell-shaped elements may e.g. by capacitive overlap, soldering, crimping, gluing with conductive adhesive, etc., in order to ensure the HF-tightness of the shielding at a required level.
FIG. 6 shows an embodiment in which the RF shielding is designed such that R2hfoutmax> R1shieldoutmax applies to the central region of the RF shield (3d). As a result, the volume of the RF range relevant for the performance of the transmitting and / or receiving coil systems can be increased even further. In order to achieve this, the shielding coil in the middle must have a symmetrical region with a length L6 that does not contain any conductors. In this case, the radius R2hfoutmax is the same radius that the RF shield would have for an NMR probe without integrated gradient coil system or with a non-RF shielded gradient coil system.
To integrate an RF-dense RF shield in the gradients that prevents e.g. NMR fundamental signals of materials outside the actual RF range can be received, as an alternative to the variants presented above, in which the fundamental signal generating material is "wrapped" by means of RF shielding, and the RF range also closed to the outside become. In this case, the RF range is so encapsulated that no signal outside this range can be received. For this purpose, the front surfaces of the RF area must be sealed as far as possible HF-tight. As a rule, a measuring sample must be introduced into the measuring head, but this can only be done on one side completely. The closing of the insertion opening may e.g. be performed by a waveguide, which is operated below its cutoff frequency and thereby has exponential attenuation for the RF waves. This is shown schematically in FIG. 7. Furthermore, the RF feed lines must be introduced by the RF shield so that they can not produce radiation in the outer space.
In a particularly preferred embodiment, the RF shield is applied to a substrate (e.g., by vapor deposition, sputtering, CVD, electroplating, gluing, clamping, printing or painting). This has the advantage that no internal coatings must be performed and the RF shield must be applied only to outsides. This is technically much easier to realize. Similarly, structuring the RF shield on an outer sheath is technically easier. Through structuring, the "recovery behavior" of the gradient coil system can be improved, since the eddy currents induced in the RF shielding can only occur to a lesser extent due to galvanic interruptions of the RF shielding. For this purpose, a variety of different variants are known from the literature, which can be adapted to the geometry of the invention. The embodiment of the RF shield according to the invention explicitly includes all concepts known from the prior art for executing a passive RF shielding.
For use in NMR, due to the typical dimensions, the performance of electrical connections between the individual sections of the RF shield, but in particular their galvanic connection, e.g. by soldering when mounted on the outer soap of a carrier much easier to perform than on the inside of a carrier. Likewise, an RF shield structured on a printed circuit board (PCB) may simply be applied to a substrate from outside, e.g. by gluing or clamping.
Further, the support material may be made of a material having high thermal conductivity (alumina, aluminum nitride, silicon nitride or silicon carbide as a ceramic, polycrystalline or monocrystal, e.g., sapphire) so that there is a possibility to efficiently cool the RF shield. This is essential especially for measuring heads with cryogenically cooled RF coil systems in order to minimize the noise contribution of the RF shield. Furthermore, it is also advantageous for gradients that must operate at high currents, since cooling during operation, e.g. can be done by embedded in the substrate or applied to the substrate cooling liquid lines. As a result, the duty cycle and permissible maximum current of a gradient according to the invention can be increased.
Particularly easy to manufacture is an RF shield on a substrate when the transitions between the different radii of the RF shield are chamfered, since then a coating can be technically much easier to implement. The bevel may be tapered, but may also include more complicated geometries.
The presented in the context of this invention shaping the passive RF shield can be combined with the various implementation options for the reduction of eddy currents on RF shields according to the prior art. However, particularly preferred are thin metallic layers which have no or only a few slots. The term "thin" is to be understood as meaning a metallic layer if the layer thickness d is of the same order of magnitude as the electrical penetration depth δ in the relevant frequency range, i. 0 <d <10 δ, but especially 0 <d <δ.
For slotted shields, capacitive connections between the individual conductive elements are preferably made as capacitive overlaps across the slots. This minimizes the radial dimensions. Furthermore, capacitive overlaps with low dielectric layer thicknesses are to be preferred, since the remaining magnetic flux through the remaining gaps is smaller than with capacitive connections with the same capacitance values, but with a greater distance between the conductive elements. For larger RF shields, the capacitive connections can also be carried out by means of capacitors, which allows greater flexibility in the selection of the elements.
A-1 f electric conductor sections of the partial coil systems of a main gradient coil 2; 2a-2c active shielding coils 3 passive RF shielding 3a-3e sections of the passive RF shielding 4 RF transmitting and / or receiving coil system zz-axis
Variables list L1 Length of the axial spacing between the sub-coil systems of the main gradient coil where there are no conductor elements between R1 gradient Tmin and FHshieldjn "1" 1 L2 Axial length of the third sub-section of the RF shield L3 Axial length of the RF transmit and / or Receiving coil system L4, axial length 5 different areas of the RF shield L6 axial spacing of the two partial coil systems of the shielding coil
Ft1gradientinmm minimum inner radius of the main gradient coil
Ft1 gradientoutmax maximum outer radius of the main gradient coil
Ft1shieldinmin minimum inner radius of the shielding coil R1 hfoutmax maximum outer radius of the at least two sections of the RF shield R2hfinmin minimum inner radius of the third (central) section of the RF shield R2hfoutmax maximum outer radius of the third (central) section of the RF shield R2gradientinmm minimum inner radius of a second partial coil system of Major gradient coil R3gradientinmm Minimum inner radius of a third partial coil system of the main gradient coil Rihfinmm (ie N) Minimum internal radii of the different sections of the RF shield
Reference List [1] US-A 5 296 810 [2] US-A 4,733,189 [3] US 7,109,712 B2 [4] US 6,456,076 B1 [5] US-A 5,512,828

权利要求:
Claims (17)
[1]
[6] US Pat. No. 5,939,882 [7] US Pat. No. 6,933,723 B2 [8] US Pat. No. 7,852,083 B2 [9] US Pat. No. 7,057,391 B1 [10] US Pat. No. 6,154,110 [11] US Pat. No. 5,600 245 [12] US-A 5 406 204 claims
An actively shielded cylindrical gradient coil system for use in a magnetic resonance spectrometer with a main field magnet which generates a z-axis aligned main magnetic field, the gradient coil system producing a z gradient field when current flows through a measurement volume traversed by the z axis The gradient coil system has at least one main gradient coil and at least one active shielding coil (2; 2a, 2b, 2c), the main gradient coil being axially symmetrical from at least two in the z-direction by a length L1 symmetrical to the center of the measurement volume is constructed of spaced-apart cylindrical part coil systems whose axes are collinear with the z-axis, wherein the cylindrical part coil systems at least partially from with a maximum outer radius R1gradientoUtmax about the z-axis wound electrical conductor sections (1a, 1b, 1a, 1c, 1d, 1f; 1a, 1d), wherein at least one of the active shielding coils (2; 2a) is constructed of electrical conductors on a minimum inner radius R1shieldinmin about the z-axis, and wherein Rlshieldjn "1" 1> R1 gradientoutmax, characterized in that in a hollow cylindrical portion on the axial length L1 symmetrical to the center of the measuring volume in a radius range between a minimum inner radius R1 gradientjn "1" 1 of the main gradient coil and R1shieldinmin there are no electrical conductor elements of the gradient coil system, and that a passive RF shield (3) is provided is, which is composed of at least three electrically interconnected subsections (3a, 3b, 3c), of which two subsections (3a, 3c) are arranged with a maximum outer radius R1hfoutmax about the z-axis, while between these two subsections (3a, 3c) a third section (3b) having an axial length L2 and a minimum inner radius R2hfinmin and egg a maximum outer radius R2hfoutmax about the z-axis is arranged, where: R1hfoutmax <R1 gradient1 ™ and R1gradientoutmax <R2hfinmm <R2hfoutmax and L2 <L1.
[2]
2. gradient coil system according to claim 1, characterized in that the following applies: R2hf0Utmax <R1shieldinmin.
[3]
3. gradient coil system according to claim 1 or 2, characterized in that the following applies: R2hfjnmin> 1.1 · R1gradientoutmax and R2hfoutmax> 0.8 · R1shieldinmin.
[4]
4. Gradientenspulensystem according to any one of the preceding claims, characterized in that the following applies: R2hfinmin> R1gradientoutmax + 3 mm and R2hfoutmax> R1shieldinmin - 3 mm.
[5]
5. gradient coil system according to one of claims 1 to 4, characterized in that the wound around the z-axis electrical conductor sections (1a, 1b, 1a, 1c, 1 d, 1f, 1a, 1d) are constructed of wires with preferably round cross-section ,
[6]
6. gradient coil system according to one of claims 1 to 4, characterized in that the wound around the z-axis electrical conductor sections (1a, 1b, 1a, 1c, 1 d, 1f, 1a, 1d) are constructed of strip conductors.
[7]
7. Gradientenspulensystem according to one of claims 1 to 4, characterized in that the wound around the z-axis electrical conductor sections (1a, 1b, 1a, 1c, 1 d, 1f, 1a, 1d) of dielectric layer coated with a dielectric Carriers are constructed.
[8]
8. gradient coil system according to any one of the preceding claims, characterized in that at least two of the pairs of axially spaced-apart cylindrical part coil systems of the main gradient coil have different minimum inner radii (R1gradientinmin, R2gradientinmm, R3gradientinmin).
[9]
9. Gradientenspulensystem according to any one of the preceding claims, characterized in that at least two sections (3a, 3b, 3c, 3d) of the passive RF shield (3) have different minimum inner radii (R1hfinmin, R2hfinmin, R3hfinmin, R4hfinmin).
[10]
10. Gradientenspulensystem according to any one of the preceding claims, characterized in that at least one of the cylindrical part coil systems of a plurality in the radial direction übereinandergewwickelten electrical conductor sections (1a, 1b, 1a, 1c, 1 d, 1f, 1a, 1d) is constructed.
[11]
11. Gradientenspulensystem according to any one of the preceding claims, characterized in that the cylindrical Teilspulensysteme the main gradient coil and the at least one active Abschirmspule (2; 2a, 2b, 2c) are completely enclosed except for a feed opening of the passive RF shield (3).
[12]
12. gradient coil system according to claim 11, characterized in that the radially inner surfaces and the axial end faces of the cylindrical Teilspulensysteme the main gradient coil and the radially outer surfaces and the axial end faces of the at least one active Abschirmspule (2, 2a, 2b, 2c) of the passive RF shield (3) are enclosed.
[13]
13. Gradientenspulensystem according to one of claims 1 to 10, characterized in that the passive RF shield (3) spatially shaped so that it encloses an RF-dense space area from which RF radiation can not escape to the outside.
[14]
14 gradient coil system according to one of claims 11 to 13, characterized in that an RF-tightness of the passive RF shield (3) by capacitive overlapping of elements of the passive RF shield (3) and / or by soldering and / or by pressing and / or by gluing with electrically conductive adhesive is effected.
[15]
15. Gradientenspulensystem according to any one of the preceding claims, characterized in that the passive RF shield (3) is mounted on a support, in particular by vapor deposition and / or sputtering and / or CVD and / or electroplating and / or printing and / or Paint and / or stick on.
[16]
16. gradient coil system according to any one of the preceding claims, characterized in that at least two of the electrically interconnected subsections (3a, 3c) are arranged cylindrically symmetric about the z-axis with a maximum outer radius R1hfoutmax, wherein between these two sections (3a, 3c) third subsection (3b) having an axial length L2 and a minimum inner radius R2hfinmm and a maximum outer radius R2hfoutmax about the z-axis, and that between the third subsection (3b) and the two other subsections (3a, 3c) each have a transition section (3d, 3e), in particular in the form of a cone-shaped element, is arranged, which connects on an axial length L8 arranged on different radii sections (3a, 3b and 3c, 3b) with each other.
[17]
17. Magnetic resonance spectrometer with a gradient coil system according to one of claims 1 to 16, characterized in that an RF transmitting and / or receiving coil system (4) is provided which is symmetrical within the radius R2hfinmin on an axial length L3 <L2 is arranged to the center of the measuring volume.

类似技术:

---

公开号 | 公开日 | 专利标题

---

DE102013204952B3|2014-05-15|Active shielded cylindrical gradient coil system with passive RF shielding for NMR devices

---

DE10118835C2|2003-03-13|Superconducting resonators for applications in NMR

---

EP0073375B1|1986-12-03|High-frequency device in a nuclear spin resonance apparatus

---

DE102005047883B4|2008-11-20|Nuclear magnetic resonance measuring head comprising at least two coils / resonator arrangements with reduced coupling

---

DE19733574C2|2000-04-06|Superconducting hybrid resonator for receiving NMR signals

---

DE10124465A1|2002-11-21|Transmission and receiver coil for a magnetic resonance imaging instrument with an arrangement of independently adjustable resonator segments forming a body coil that allows complete control of the HF field distribution

---

DE102006017438A1|2007-10-25|Resonator for magnetic resonance applications

---

DE3237250A1|1983-05-05|CIRCUIT-CONCENTRATED RESONATOR

---

EP1746432B1|2008-03-12|Rf shield with reduced coupling to the rf resonator system

---

DE60118993T2|2007-05-10|About the NMR probe distributed capacitive bays

---

DE4414371C2|1997-10-23|Diagnostic magnetic resonance device

---

DE102010041202B4|2014-03-06|Magnetic resonance apparatus, reflector array and high-frequency shielding system for a magnetic resonance apparatus

---

EP0156979A1|1985-10-09|High-frequency antenna arrangement in a nuclear magnetic resonance tomography apparatus and method for its operation

---

DE102012203343B3|2013-07-11|Gradient coil system with correction windings and method for their preparation

---

DE102004007291A1|2005-09-08|Hybrid magnet arrangement

---

DE202013012810U1|2020-01-22|Device for generating and maintaining a plasma for plasma processing

---

DE69831983T2|2006-07-27|Reduction of eddy currents in &#34;fingerprint&#34; gradient coils for magnetic resonance imaging

---

DE102005013293B4|2008-10-02|Magnetic resonance system with a high-frequency source

---

DE102011006157B4|2016-06-16|Double tuned RF resonator

---

DE202010003162U1|2010-05-27|Traveling wave magnetic resonance imaging antenna device

---

DE4104079C2|1994-12-08|Probe head for NMR tomography

---

EP0157924B1|1987-11-04|High-frequency antenna arrangement in a nuclear magnetic resonance tomography apparatus and method for its operation

---

EP0204104A2|1986-12-10|Resonator arrangement

---

DE102004012058B4|2009-04-02|Producer of time-variable magnetic fields of a magnetic resonance apparatus and magnetic resonance apparatus with the producer

---

DE102016204733B4|2019-05-09|CW maser with electromagnetic resonant circuit

同族专利:

---

公开号 | 公开日

---

DE102013204952B3|2014-05-15|

---

CN104062612B|2017-04-12|

---

CN104062612A|2014-09-24|

---

US9817096B2|2017-11-14|

---

GB201404827D0|2014-04-30|

---

CH707701A2|2014-09-30|

---

JP2014230739A|2014-12-11|

---

US20140285201A1|2014-09-25|

---

GB2514467A|2014-11-26|

---

JP5837954B2|2015-12-24|

---

GB2514467B|2018-11-14|

引用文献:

---

公开号 | 申请日 | 公开日 | 申请人 | 专利标题

---

---

US4733189A|1986-06-03|1988-03-22|Massachusetts Institute Of Technology|Magnetic resonance imaging systems|

---

US5296810A|1992-03-27|1994-03-22|Picker International, Inc.|MRI self-shielded gradient coils|

---

US5406204A|1992-03-27|1995-04-11|Picker International, Inc.|Integrated MRI gradient coil and RF screen|

---

DE4324021C2|1993-07-17|1996-05-30|Bruker Analytische Messtechnik|Therapy tomograph|

---

US5600245A|1993-10-08|1997-02-04|Hitachi, Ltd.|Inspection apparatus using magnetic resonance|

---

DE4422782C2|1994-06-29|1998-02-19|Siemens Ag|Actively shielded transverse gradient coil for magnetic resonance imaging devices|

---

DE4425997C1|1994-07-22|1996-01-25|Bruker Analytische Messtechnik|Divisible, movable gradient system for NMR tomographs|

---

JP3654463B2|1996-03-29|2005-06-02|株式会社日立メディコ|Magnetic resonance imaging system|

---

DE19653449C2|1996-12-20|1999-11-11|Siemens Ag|Gradient coil arrangement for a magnetic resonance imaging device|

---

JP2002200055A|2000-12-28|2002-07-16|Toshiba Medical System Co Ltd|Magnetic resonance imaging apparatus|

---

US6456076B1|2001-01-31|2002-09-24|The Trustees Of The University Of Pennsylvania|Z gradient shielding coil for canceling eddy currents|

---

DE10202986A1|2002-01-26|2003-07-31|Philips Intellectual Property|Coil system for an MR apparatus and MR apparatus with such a coil system|

---

US6885194B2|2002-05-03|2005-04-26|Ge Medical Systems Global Technology Company, Llc|Method and apparatus for minimizing gradient coil and rf coil coupling|

---

JP4146745B2|2003-03-07|2008-09-10|株式会社日立メディコ|Magnetic resonance imaging system|

---

US7141974B2|2003-08-25|2006-11-28|William A Edelstein|Active-passive electromagnetic shielding to reduce MRI acoustic noise|

---

CN100541653C|2003-09-02|2009-09-16|Nxp股份有限公司|Be used to comprise the active shielding of the circuit of magnetic-sensitive material|

---

DE10345767B4|2003-10-01|2006-05-18|Siemens Ag|Magnetic resonance apparatus with a cavity and with a gradient coil system arranged in the cavity|

---

DE10352381B4|2003-11-10|2009-07-30|Siemens Ag|Producer of time-variable magnetic fields of a magnetic resonance apparatus and magnetic resonance apparatus with the producer|

---

JP2005160842A|2003-12-04|2005-06-23|Hitachi Medical Corp|Magnetic resonance imaging apparatus|

---

JP4639763B2|2004-11-12|2011-02-23|三菱電機株式会社|Magnetic resonance imaging system|

---

US7880467B2|2005-06-09|2011-02-01|Aspect Magnet Technologies Ltd.|Packed array of MRI/NMR devices and an MRI/NMR method of analyzing adjacent lines of goods simultaneously|

---

US8514043B2|2005-09-14|2013-08-20|General Electric Company|Systems and methods for passively shielding a magnetic field|

---

JP5285596B2|2006-03-22|2013-09-11|コーニンクレッカフィリップスエレクトロニクスエヌヴィ|Shielded MULTIX coil array for parallel high field MRI|

---

WO2007119726A1|2006-04-14|2007-10-25|Hitachi Medical Corporation|Magnetic resonance imaging device and gradient magnetic field coil|

---

US7375526B2|2006-10-20|2008-05-20|Edelstein William A|Active-passive electromagnetic shielding to reduce MRI acoustic noise|

---

WO2008075614A1|2006-12-21|2008-06-26|Hitachi, Ltd.|Nuclear magnetic resonance measuring device and coil unit|

---

US8487269B2|2007-02-28|2013-07-16|Siemens Aktiengesellschaft|Combined radiation therapy and magnetic resonance unit|

---

DE102008007245B4|2007-02-28|2010-10-14|Siemens Aktiengesellschaft|Combined radiotherapy and magnetic resonance device|

---

JP5159145B2|2007-04-06|2013-03-06|株式会社東芝|Shield coil and magnetic resonance imaging apparatus|

---

US7753165B2|2007-12-21|2010-07-13|Robert Bosch Gmbh|Device and method for active noise cancellation in exhaust gas channel of a combustion engine|

---

US8754644B2|2008-06-20|2014-06-17|The University Of Queensland|MRI apparatus and method with moving field component|

---

CA2760055C|2009-07-15|2021-04-06|Viewray Incorporated|Method and apparatus for shielding a linear accelerator and a magnetic resonance imaging device from each other|

---

GB2484529B|2010-10-15|2012-09-19|Siemens Ag|Beam deflection arrangement within a combined radiation therapy and magnetic resonance unit|

---

GB2507792B|2012-11-12|2015-07-01|Siemens Plc|Combined MRI and radiation therapy system|JP6366940B2|2014-01-09|2018-08-01|キヤノンメディカルシステムズ株式会社|Magnetic resonance imaging system|

---

GB2563557B|2016-03-09|2021-11-17|Synaptive Medical Inc|Reducing magnetic field instabilities caused by oscillations of a mechanical cryocooler in magnetic resonance systems|

---

US10295631B2|2016-04-29|2019-05-21|Schlumberger Technology Corporation|Composite noise shield for magnetic resonance tools|

---

KR20180007745A|2016-07-14|2018-01-24|에너브레인|Method for manufacturing thin film type coil unit for camera actuator|

---

EP3415940B1|2017-06-14|2019-07-31|Siemens Healthcare GmbH|Mr-high frequency shielding unit.|

---

DE102018206643A1|2018-04-27|2019-10-31|Siemens Healthcare Gmbh|Gradient coil unit for a magnetic resonance device|

法律状态:
2019-10-31| PFA| Name/firm changed|Owner name: BRUKER SWITZERLAND AG, CH Free format text: FORMER OWNER: BRUKER BIOSPIN AG, CH |

优先权:

---

申请号 | 申请日 | 专利标题

---

DE102013204952.8A|DE102013204952B3|2013-03-20|2013-03-20|Active shielded cylindrical gradient coil system with passive RF shielding for NMR devices|

---