CN219759314U

CN219759314U - Passive shimming structure

Info

Publication number: CN219759314U
Application number: CN202322260127.4U
Authority: CN
Inventors: 曾范昊; 王兆连; 王前; 张义廷; 齐玉宁
Original assignee: Weifang Xinli Superconducting Magnet Technology Co ltd
Current assignee: Weifang Xinli Superconducting Magnet Technology Co ltd
Priority date: 2023-08-22
Filing date: 2023-08-22
Publication date: 2023-09-26
Anticipated expiration: 2033-08-22

Abstract

The utility model discloses a passive shimming structure which comprises a superconducting magnet, a plurality of mounting clamping strips and a drawer assembly, wherein the mounting clamping strips are uniformly arranged on the inner wall of the superconducting magnet along the circumferential direction of the superconducting magnet, the mounting clamping strips extend along the axial direction of the superconducting magnet, a shimming channel is formed between any two adjacent mounting clamping strips, and the drawer assembly is used for being arranged in the shimming channel. The passive shimming structure disclosed by the utility model is characterized in that the shimming channel is manufactured in the inner cavity of the superconducting magnet by installing the clamping strips, so that the drawer component can be fixed on the inner wall of the superconducting magnet, the influence of the length and the heating value of the gradient coil caused by the installation of the drawer component in the gradient coil is avoided, and the passive shimming structure is especially suitable for the condition that the shimming channel is not suitable for being arranged in the gradient coil.

Description

Passive shimming structure

Technical Field

The utility model relates to the technical field of nuclear magnetic resonance imaging, in particular to a passive shimming structure.

Background

With the development and maturation of magnetic resonance technology, magnetic resonance imaging devices are widely used in the clinical medical field. The magnetic resonance imaging superconducting magnet is a core component of magnetic resonance imaging equipment, and the size of the magnetic field uniformity of a central spherical region of the superconducting magnet directly influences the imaging effect of an image.

The uniformity of the magnetic field of the magnetic resonance superconducting magnet in the central spherical region is about hundreds of PPM after the manufacture is finished, which cannot meet the basic requirement of clear imaging, and the uniformity of the central magnetic field is generally required to be less than tens of PPM, so that the smaller the PPM is, the clearer the imaging is. There is therefore a need for using shimming techniques to meet the homogeneity of the magnetic field in the centre of MRI (magnetic resonance imaging ) superconducting magnets. The conventional shimming technology is mainly divided into a passive shimming technology and an active shimming technology.

As shown in fig. 1, in the conventional passive shimming technique, a gradient coil 20 is disposed in a superconducting magnet 100, a plurality of (generally 24) rectangular shimming channels are uniformly distributed in the circumferential direction of the gradient coil 20, each shimming channel is provided with a shimming drawer 30 as shown in fig. 2, a plurality of blank spaces are disposed on the shimming drawer, the positions and thicknesses of silicon steel sheets used for placing the blank spaces are determined according to the distribution of a magnetic field and the simulation calculation of shimming software, and the simulation calculation and adjustment are repeated for several times to finally enable the uniformity of the central magnetic field of the superconducting magnet to meet the use requirement.

The mode is accurate in positioning, convenient to install and good in shimming effect, but the gradient coil is required to have a sufficient length (generally greater than three times the diameter of a central magnetic field area of the superconducting magnet, and the gradient coil is required to be symmetrically arranged relative to the superconducting magnet), and the heating value of the gradient coil during operation cannot be too high, otherwise the shimming effect is affected.

Therefore, how to protect the passive shimming structure from the length and the heating value of the gradient coil is a technical problem to be solved by those skilled in the art.

Disclosure of Invention

In view of the above, the present utility model is directed to a passive shimming structure, so that the passive shimming structure is not affected by the length and the heating value of the gradient coil.

In order to achieve the above purpose, the present utility model provides the following technical solutions:

a passive shimming structure comprising:

a superconducting magnet;

the mounting clamping strips are uniformly arranged on the inner wall of the superconducting magnet in the circumferential direction, extend along the axial direction of the superconducting magnet, and form a shimming channel between any two adjacent mounting clamping strips;

the drawer component is used for being arranged in the shimming channel.

Optionally, in the passive shimming structure, two sides of the mounting clamping strip far away from one end of the superconducting magnet are provided with mounting bosses, an embedded groove is formed between the mounting bosses and the superconducting magnet, and the embedded groove is communicated with the shimming channel;

two sides of the drawer component are provided with embedding parts for being embedded into the embedding grooves.

Optionally, in the passive shimming structure, the superconducting magnet and the mounting clip are welded.

Optionally, in the passive shimming structure, two sides of the mounting clip facing one end of the superconducting magnet are chamfered.

Optionally, in the passive shimming structure, a welding avoidance hole for a welding tool to pass through is formed in the mounting boss.

Optionally, in the passive shimming structure, the drawer assembly includes:

the shimming strip is provided with a plurality of storage tanks for placing silicon steel sheets;

the cover plate is connected with the shimming strips and used for blocking the storage groove;

the mounting plate is connected to the two ends of the shimming strip, and the mounting plate is used for being connected with the mounting clamping strip.

Optionally, in the passive shimming structure described above, the shimming strip and the mounting plate are in a unitary structure or a split structure.

Optionally, in the passive shimming structure, a disassembly hole for allowing a disassembly tool to pass through to eject the silicon steel sheet out of the storage tank is formed at the bottom of the storage tank.

Optionally, in the passive shimming structure, the cover plate is connected with the shimming strip through countersunk screws; and/or the number of the groups of groups,

the terminal surface of installation card strip be provided with be used for with the bolt hole that the mounting panel is connected.

Optionally, in the passive shimming structure described above, the shimming strips, the cover plate and the mounting plate are all made of epoxy plates.

The passive shimming structure comprises a superconducting magnet, mounting clamping strips and a drawer assembly, wherein the mounting clamping strips are uniformly arranged on the inner wall of the superconducting magnet along the circumferential direction of the superconducting magnet, the mounting clamping strips extend along the axial direction of the superconducting magnet, a shimming channel is formed between any two adjacent mounting clamping strips, and the drawer assembly is used for being arranged in the shimming channel.

Compared with the prior art, the passive shimming structure provided by the utility model has the advantages that the shimming channel is manufactured in the inner cavity of the superconducting magnet through the mounting clamping strips, so that the drawer component can be fixed on the inner wall of the superconducting magnet, the influence of the length and the heating value of the gradient coil due to the fact that the drawer component is mounted in the gradient coil is avoided, and the passive shimming structure is especially suitable for the condition that the shimming channel is not suitable for being formed in the gradient coil.

Drawings

In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the utility model, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a schematic diagram of a prior art passive shimming structure;

FIG. 2 is a schematic diagram of a prior art shimming drawer;

FIG. 3 is a schematic diagram of a passive shimming structure disclosed in an embodiment of the present utility model;

FIG. 4 is a schematic diagram of a mounting clip according to an embodiment of the present utility model;

FIG. 5 is a schematic view of a drawer assembly according to an embodiment of the present utility model;

fig. 6 is a schematic view of a mounting structure of a mounting clip and drawer assembly according to an embodiment of the present utility model.

Wherein 20 is a gradient coil, and 30 is a shimming drawer;

100 is a superconducting magnet;

200 is an installation clamping strip, 210 is a clamping strip body, 211 is a threaded connecting hole, 212 is a bolt hole, 220 is an installation boss, and 221 is a welding avoidance port;

300 is a drawer assembly, 310 is a shimming strip, 311 is a storage tank, 312 is an embedded part, 320 is a cover plate, 321 is a countersunk head screw, 330 is a mounting plate, and 331 is a connecting piece.

Detailed Description

The core of the utility model is to disclose a passive shimming structure, so that the passive shimming structure is free from the influence of the length and the heating value of the gradient coil.

Hereinafter, embodiments will be described with reference to the drawings. Furthermore, the embodiments shown below do not limit the summary of the utility model described in the claims. The whole contents of the constitution shown in the following examples are not limited to the solution of the utility model described in the claims.

Wherein, in the description of the embodiments of the present utility model, unless otherwise indicated, "/" means or, for example, a/B may represent a or B; "and/or" herein is merely an association relationship describing an association object, and means that three relationships may exist, for example, a and/or B may mean: a exists alone, A and B exist together, and B exists alone. In addition, in the description of the embodiments of the present utility model, "plurality" means two or more than two.

The terms "first" and "second" are used below for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature.

Referring to fig. 3, the passive shimming structure disclosed in the embodiment of the present utility model includes a superconducting magnet 100, a plurality of mounting clamping bars 200 and a drawer assembly 300, wherein the mounting clamping bars 200 are uniformly arranged on the inner wall of the superconducting magnet 100 along the circumferential direction of the superconducting magnet 100, the mounting clamping bars 200 extend along the axial direction of the superconducting magnet 100, a shimming channel is formed between any two adjacent mounting clamping bars 200, and the drawer assembly 300 is used for being arranged in the shimming channel.

Compared with the prior art, the passive shimming structure disclosed by the embodiment of the utility model makes a shimming channel in the inner cavity of the superconducting magnet 100 through the mounting clamping strip 200, so that the drawer assembly 300 can be fixed on the inner wall of the superconducting magnet 100, the influence of the length and the heating value of the gradient coil caused by the fact that the drawer assembly 300 is mounted in the gradient coil is avoided, and the passive shimming structure is particularly suitable for the condition that the shimming channel is not suitable for being arranged in the gradient coil.

The passive shimming structure disclosed in embodiments of the present utility model structurally separates the drawer assembly 300 from the gradient coils such that the gradient coils have more arrangements relative to the installed position of the superconducting magnet 100, such as an asymmetric arrangement relative to the superconducting magnet 100.

Referring to fig. 6, the mounting bars 200 and drawer assembly 300 are generally 24 in number, and alternate and are wound into a ring-like configuration within the superconducting magnet 100.

The following mounting clip 200/mounting boss 220 is directed to an end of the superconducting magnet 100 facing the inner wall of the superconducting magnet 100.

In a specific embodiment of the present disclosure, as shown in fig. 4, mounting bosses 220 are disposed on two sides of one end of the mounting clip 200 away from the superconducting magnet 100, an insertion groove is formed between the mounting bosses 220 and the inner wall of the superconducting magnet 100, the insertion groove is communicated with the shimming channel, insertion portions 312 for being inserted into the insertion groove are disposed on two sides of the drawer assembly 300, and the drawer assembly 300 can be primarily fixed in the shimming channel by mounting and matching the insertion portions 312 with the insertion grooves.

In the passive shimming installation process, the installation clamping strips 200 may be fixed on the inner wall of the superconducting magnet 100, then the drawer assembly 300 is inserted from the end of the shimming channel, and finally the drawer assembly 300 and the superconducting magnet 100 and/or the installation clamping strips 200 are fixed.

Wherein the fixing of the drawer assembly 300 to the superconducting magnet 100 needs to consider the influence of the fixing means on the magnetic field. In addition, after the subsequent gradient coil is mounted to the inner cavity of the superconducting magnet, the water pipe, the electric wire, etc. of the gradient coil are routed and fixed on the end surface of the superconducting magnet 100, and if the fixing device is also located on the end surface of the superconducting magnet 100, interference may be caused between the fixing device and the routing of the gradient coil, so that the drawer assembly 300 and the mounting clip 200 are generally fixed.

Referring to fig. 4, the mounting clip 200 has a T-shaped cross section, and both sides of the drawer assembly 300 are provided with protruding steps as the fitting portions 312 fitted with the mounting clip 200.

The minimum distance between the drawer assembly 300 and the inner wall of the superconducting magnet 100 is kept within 1-2 mm, so that the drawer assembly 300 can be normally used, the gap can be ensured to smoothly slide into a shimming channel, and the influence of the position deviation of the silicon steel sheet caused by the gap on actual shimming is small.

The mounting clip 200 and the mounting boss 220 may be integrally formed, and in one embodiment, the mounting clip 200 includes a clip body 210 and the mounting boss 220.

The mounting clip 200 disclosed in the embodiment of the utility model can be mounted and fixed with the superconducting magnet 100 by adopting various modes such as welding, bolting and the like, wherein the welding mode has the advantages of simple and convenient mounting and low cost.

In order to realize the welded connection between the installation clamping strip 200 and the superconducting magnet 100, one end of the installation clamping strip 200 facing the superconducting magnet 100 is an installation end, and both sides of the installation end are provided with chamfer structures, so that the welding space between the installation clamping strip 200 and the superconducting magnet 100 can be reserved by the chamfer structures, and the influence of the welding seam on the installation of the drawer assembly 300 in a shimming channel due to the fact that the welding seam enters the embedded groove area is avoided.

Referring to fig. 4, a welding avoidance hole 221 through which a welding tool passes is provided in the mounting boss 220, and in the welding process, the welding tool may approach the welding position of the mounting clip 200 and the superconducting magnet 100 from the welding avoidance hole 221, so as to realize welding of the mounting clip 200 and the superconducting magnet 100.

Specifically, the mounting clip 200 is welded to the superconducting magnet 100 by spot welding, and is not welded by full-length welding, so that welding deformation is reduced on the premise of ensuring the connection strength. After the welding position is determined, a welding avoidance hole 221 is machined in the mounting boss 220 and the clip strip body 210.

The mounting clip 200 is made of the same material as the superconducting magnet 100, typically 304 stainless steel or 316 stainless steel, to facilitate the welding operation.

Referring to fig. 4, the end surface of the installation clip 200 facing the inner wall of the superconducting magnet 100 may be a planar structure or a curved surface structure attached to the inner wall of the superconducting magnet 100, where the installation clip 200 of the planar structure has a light weight and a low production difficulty, while the installation clip 200 of the curved surface structure is affected by the machining error of the superconducting magnet 100, and when the machining error is superimposed with the welding error, the installation accuracy of the installation clip 200 is reduced, and the machining cost of the installation clip 200 of the curved surface structure is increased.

In a particular embodiment of the present disclosure, as shown in fig. 5, the drawer assembly 300 includes a shim bar 310, a cover plate 320, and a mounting plate 330. The shimming strip 310 is provided with a plurality of storage slots 311 for placing silicon steel sheets, and the cover plate 320 is connected with the shimming strip 310 and used for blocking the storage slots 311 so as to fix the silicon steel sheets in the storage slots 311. Mounting plates 330 are attached to the ends of the shim bars 310, and the mounting plates 330 are used to connect the shim bars 310 to the mounting clip bars 200. After the drawer assembly 300 is inserted into the shimming channel, the drawer assembly 300 and the mounting clip 200 are fixed by the mounting plate 330, and the fixing of the drawer assembly 300 is completed.

Wherein the shim bars 310 and the mounting plate 330 may be of unitary construction or of split construction. When shim bar 310 and mounting plate 330 are split type structure, shim bar 310 and mounting plate 330 pass through connecting piece 331 bolted connection, and installation card strip 200 and mounting plate 330 are bolted connection too, and in the time of the follow-up installation, conveniently repair through mounting plate 330 when the phenomenon of hole site misalignment appears.

The end face of the mounting clip 200 is provided with a bolt hole 212 for connecting with the mounting plate 330 through a connecting piece 331, and the mounting clip 200/clip body 210 is penetrated with a threaded connecting hole 211 for connecting with a positioning tool.

In order to secure the connection strength, a plurality of connection holes are provided on the mounting plate 330, wherein the connection holes at both ends are used for connection of the shim bars 310, and the connection hole in the middle is used for connection with the mounting plate 330.

The shim bars 310 can be prepared by processing a plurality of storage grooves 311 uniformly arranged on a long epoxy plate, and the structures of the storage grooves 311 and the embedded parts 312 are not interfered with each other.

The cover plate 320 may be made of a thin epoxy plate, and a ring of connecting holes are formed on the edge of the plate surface to be detachably connected with the shim bars 310.

In order to facilitate taking out the silicon steel sheet from the storage groove 311, a disassembly hole is formed in the bottom of the storage groove 311, and a disassembly tool can pass through the disassembly hole to eject the silicon steel sheet out of the storage groove 311, wherein the disassembly tool can be a push rod or the like.

The dismounting hole can also be a buckling groove which is communicated with the storage groove 311 and is formed at the opening end of the shimming strip 310, but the scheme has a requirement on the distance between the storage grooves 311, and the positions of the buckling grooves are required to be reserved, so that the number of the storage grooves 311 on the same length is reduced, and the storage amount of the silicon steel sheets is reduced.

Cover plate 320 is connected to shim bars 310 via countersunk screws 321 to ensure that countersunk screws 321 are not higher than the surface of cover plate 320, thereby not affecting the installation of drawer assembly 300 in the shim channel.

Further, since a large number of countersunk screws 321 need to be screwed into the cover plate 320, if there is a situation that the countersunk screws 321 are not assembled in place, the countersunk screws 321 are higher than the surface of the cover plate 320, so that the smoothness of the assembly process is affected, the countersunk screws 321 are made of plastic materials, if the countersunk screws are forcibly dragged, the countersunk screws and the cover plate 320 are damaged, further, the silicon steel sheets in the drawer assembly 300 are scattered on the inner wall of the superconducting magnet 100, and the absorbed silicon steel sheets are difficult to remove due to large magnetic force, therefore, in combination with fig. 6, one end of the drawer assembly 300 provided with the cover plate 320 is far away from the inner wall of the superconducting magnet 100 than the other end, and a gap capable of carrying out fault tolerance on the assembly of the countersunk screws 321 is reserved between the drawer assembly 300 and the outer wall of the gradient coil.

In the preparation process of the passive shimming structure, firstly, the mounting clamping strips 200 are welded on the inner wall surface of the superconducting magnet 100 through scribing or positioning tools, then the thickness and the position of the silicon steel sheet required to be placed by the shimming strips 310 at each position are calculated through shimming software, then the silicon steel sheet is placed into the storage groove 311 according to the calculation result, the storage groove 311 is filled with plastic sheets, the cover plate 320 is fastened on the shimming strips 310 through cross-slot countersunk screws 321 of nonmagnetic materials, then the mounting plates 330 are fastened on the end surfaces of the shimming strips 310 through nonmagnetic common screws, finally, the shimming drawer assembly 300 is inserted into a shimming channel formed by the adjacent mounting clamping strips 200 (and the inner cavity surface of the superconducting magnet 100), the magnetic field uniformity at that moment is measured, if the requirements are not met, the thickness and the position of the silicon steel sheet are continuously calculated and adjusted through the shimming software, and the magnetic field uniformity can reach below 10PPM generally 3-5 times, and the use requirements are met.

The terms first and second and the like in the description and in the claims, are used for distinguishing between different objects and not for describing a particular sequential order. Furthermore, the terms "comprise" and "have," as well as any variations thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to the listed steps or elements but may include steps or elements not expressly listed.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present utility model. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the utility model. Thus, the present utility model is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A passive shimming structure comprising:

a superconducting magnet (100);

the installation clamping strips (200) are uniformly arranged on the inner wall of the superconducting magnet (100) along the circumferential direction of the superconducting magnet (100), the installation clamping strips (200) extend along the axial direction of the superconducting magnet (100), and a shimming channel is formed between any two adjacent installation clamping strips (200);

a drawer assembly (300) for positioning within the shim channel.

2. The passive shimming structure according to claim 1, characterized in that mounting bosses (220) are provided on both sides of the mounting clip (200) away from one end of the superconducting magnet (100), and an embedded groove is formed between the mounting bosses (220) and the superconducting magnet (100), and the embedded groove is communicated with the shimming channel;

two sides of the drawer assembly (300) are provided with embedding parts (312) for being embedded in the embedding grooves.

3. The passive shimming structure according to claim 2, characterized in that the superconducting magnet (100) and the mounting clip (200) are welded together.

4. A passive shimming structure according to claim 3, characterized in that the end of the mounting clip (200) facing the superconducting magnet (100) is a mounting end, both sides of which are provided with chamfers.

5. A passive shim construction as claimed in claim 3, characterized in that the mounting boss (220) is provided with a weld relief opening (221) for a welding tool to pass through.

6. The passive shimming structure of claim 1, characterized in that the drawer assembly (300) comprises:

the shimming strip (310) is provided with a plurality of storage grooves (311) for placing silicon steel sheets;

a cover plate (320) connected with the shimming strips (310) and used for blocking the storage groove (311);

and the mounting plates (330) are connected to two ends of the shimming strip (310), and the mounting plates (330) are used for being connected with the mounting clamping strips (200).

7. The passive shim structure of claim 6, wherein the shim bars (310) and the mounting plate (330) are of unitary or split construction.

8. The passive shimming structure according to claim 6, characterized in that a bottom of the storage slot (311) is provided with a dismounting hole for a dismounting tool to pass through to eject the silicon steel sheet out of the storage slot (311).

9. The passive shim structure of claim 6, wherein the cover plate (320) is connected to the shim bar (310) by a countersunk screw (321); and/or the number of the groups of groups,

the mounting plate (330) is connected with the mounting clamping strip (200) through a connecting piece (331), and a bolt hole (212) matched with the connecting piece (331) is formed in the end face of the mounting clamping strip (200).

10. The passive shim structure of claim 6, wherein the shim bars (310), the cover plate (320), and the mounting plate (330) are each fabricated from an epoxy plate.