Dumbbell magnet structure and magnetic resonance imaging system

Abstract

The application discloses a dumbbell-shaped magnet structure and a magnetic resonance imaging system, and relates to the technical field of magnets. The first end magnet comprises at least one first magnet assembly, the first magnet assembly comprises at least two layers of first annular magnets which are sequentially sleeved; the middle magnet comprises at least one second magnet assembly, the second magnet assembly comprises at least one layer of second annular magnets, and the multiple layers of second annular magnets of each second magnet assembly are sequentially sleeved; the second end magnet comprises at least one third magnet assembly, and each third magnet assembly comprises at least two layers of third annular magnets which are sequentially sleeved; the number of layers of the first annular magnets of each first magnet assembly is more than the number of layers of the second annular magnets of each second magnet assembly, and the number of layers of the third annular magnets of each third magnet assembly is more than the number of layers of the second annular magnets of each second magnet assembly; and the magnet structure is in a dumbbell shape. The application can improve the uniformity of the magnetic field distribution and better meet the spatial requirements of the magnetic resonance imaging system imaging.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of magnets, in particular to a dumbbell-shaped magnet structure and a magnetic resonance imaging system. BACKGROUND

[0002] Magnetic resonance imaging (MRI) has the advantages of zero radiation exposure and good soft tissue imaging contrast, and is widely used in the observation of nervous system, musculoskeletal system and tumor, etc. The main magnet as the most basic component of the magnetic resonance imaging system, its performance will directly affect the quality of the magnetic resonance image.

[0003] The existing main magnet is mainly divided into superconducting electromagnetic type and permanent magnet type. The superconducting electromagnetic type main magnet is more easy to realize high field strength, so as to improve the imaging quality, but the cost of the superconducting electromagnetic type main magnet is high, and the rare liquid helium needs to be supplemented regularly, so the maintenance cost is high, which seriously restricts the popularization of magnetic resonance. In comparison, the permanent magnet type main magnet is generally made of rare earth permanent magnet material, which is low in cost and easy to popularize. In addition, the permanent magnet type main magnet also has the advantages of low power consumption and low maintenance cost; but the magnetic field uniformity of the permanent magnet type main magnet is poor, and the magnetic resonance imaging system based on the permanent magnet type main magnet usually has poor imaging quality, so the research on the permanent magnet type main magnet with high uniformity can reduce the cost of the magnetic resonance imaging system, improve the total number of magnetic resonance deployment on the social surface, and thus improve the overall throughput of the magnetic resonance detection, so as to facilitate the popularization of magnetic resonance.

[0004] Among them, the Halbach array magnet structure is generally composed of a plurality of magnetic blocks made of permanent magnet material according to a special designed spatial distribution, which can enhance the field strength in a unit direction by using the special arrangement of the magnet units. The traditional dumbbell-shaped magnet structure is cylindrical, and at the opening ends of the cylindrical dumbbell-shaped magnet structure, there is a lack of adjacent magnets to support the concentration of the magnetic field, so the magnetic field cannot be completely guided and concentrated like in the middle of the dumbbell-shaped magnet structure, resulting in the dispersion of the magnetic field at the opening ends and the interruption of the magnetic flux path, and thus part of the magnetic field cannot be effectively shielded, and the magnetic field lines will escape at the end, forming magnetic leakage. SUMMARY

[0005] The purpose of the present application is to provide a dumbbell-shaped magnet structure and a magnetic resonance imaging system to solve the problems existing in the prior art, which can reduce magnetic leakage and improve the uniformity of the magnetic field distribution; and can better meet the spatial requirements of the magnetic resonance imaging system imaging.

[0006] To achieve the above purpose, the present application provides the following scheme:

[0007] The present application provides a dumbbell-shaped magnet structure, comprising a magnet structure, the magnet structure comprising a first end magnet, a middle magnet and a second end magnet arranged in sequence, wherein:

[0008] The first end magnet comprises at least one first magnet assembly, each of the first magnet assembly comprising at least two layers of first annular magnets arranged in sequence;

[0009] The middle magnet comprises at least one second magnet assembly, each of the second magnet assembly comprising at least one layer of second annular magnets, the multiple layers of the second annular magnets of each of the second magnet assembly arranged in sequence;

[0010] The second end magnet comprises at least one third magnet assembly, each of the third magnet assembly comprising at least two layers of third annular magnets arranged in sequence; the first annular magnet, the second annular magnet and the third annular magnet are all annular Halbach array magnets; the number of layers of the first annular magnet of each of the first magnet assembly is more than the number of layers of the second annular magnet of each of the second magnet assembly, a plane perpendicular to the center line of the first magnet assembly is a first plane, the projection of the outer rim of each of the first magnet assembly on the first plane is located outside the projection of the outer rim of each of the second magnet assembly on the first plane; the number of layers of the third annular magnet of each of the third magnet assembly is more than the number of layers of the second annular magnet of each of the second magnet assembly, the projection of the outer rim of each of the third magnet assembly on the first plane is located outside the projection of the outer rim of each of the second magnet assembly on the first plane.

[0011] Preferably, the center lines of all the first annular magnets, all the second annular magnets and all the third annular magnets are collinear.

[0012] Preferably, a plane perpendicular to the center line of the first magnet assembly is a first plane, the projection of the first annular magnet of the outermost circle of each of the first magnet assembly on the first plane is located outside the projection of each of the second magnet assembly on the first plane; the projection of the third annular magnet of the outermost circle of each of the third magnet assembly on the first plane is located outside the projection of each of the second magnet assembly on the first plane.

[0013] Preferably, the projection of the first annular magnet of the innermost circle of each of the first magnet assembly on the first plane is located inside the projection of each of the second magnet assembly on the first plane; the projection of the third annular magnet of the innermost circle of each of the third magnet assembly on the first plane is located inside the projection of each of the second magnet assembly on the first plane.

[0014] Preferably, the second magnet assembly is multiple.

[0015] Preferably, the lengths of the first annular magnets of each of the first magnet assemblies along the first magnet assembly center line are the same, the lengths of the second annular magnets of each of the second magnet assemblies along the second magnet assembly center line are the same, and the lengths of the third annular magnets of each of the third magnet assemblies along the third magnet assembly center line are the same.

[0016] Preferably, the magnet structure is a symmetric piece that is symmetric in the length direction of the magnet structure.

[0017] Preferably, the spacing between the first end magnet and the middle magnet along the first end magnet center line is a first spacing, the spacing between the second end magnet and the middle magnet along the first end magnet center line is a second spacing, the spacing between two adjacent first magnet assemblies along the first end magnet center line is a third spacing, the spacing between two adjacent second magnet assemblies along the first end magnet center line is a fourth spacing, and the spacing between two adjacent third magnet assemblies along the first end magnet center line is a fifth spacing, and the first spacing, the second spacing, the third spacing, the fourth spacing, and the fifth spacing are the same.

[0018] Preferably, the first annular magnets of each of the first magnet assemblies are four layers, the second annular magnets of each of the second magnet assemblies are two layers, and the third annular magnets of each of the third magnet assemblies are four layers.

[0019] The present application provides a magnetic resonance imaging system, comprising a main magnet, which is the dumbbell-shaped magnet structure.

[0020] The present application has the following technical effects relative to the prior art:

[0021] The application provides a dumbbell-shaped magnet structure and a magnetic resonance imaging system, a first end magnet comprises at least one first magnet assembly, each first magnet assembly comprises at least two layers of first annular magnets which are sequentially sleeved, a middle magnet comprises at least one second magnet assembly, each second magnet assembly comprises at least one layer of second annular magnets, and the multiple layers of second annular magnets of each second magnet assembly are sequentially sleeved, and a second end magnet comprises at least one third magnet assembly, each third magnet assembly comprises at least two layers of third annular magnets which are sequentially sleeved, the first annular magnet, the second annular magnet and the third annular magnet are annular Halbach array magnets, the number of layers of the first annular magnet of each first magnet assembly is more than the number of layers of the second annular magnet of each second magnet assembly, a plane perpendicular to the center line of the first magnet assembly is a first plane, and the projection of the outer ring edge of each first magnet assembly on the first plane is located outside the projection of the outer ring edge of each second magnet assembly on the first plane, and the number of layers of the third annular magnet of each third magnet assembly is more than the number of layers of the second annular magnet of each second magnet assembly, and the projection of the outer ring edge of each third magnet assembly on the first plane is located outside the projection of the outer ring edge of each second magnet assembly on the first plane.

[0022] The middle magnet is used to generate a high-intensity magnetic field, and the first end magnet and the second end magnet are used to reduce the magnetic leakage phenomenon and improve the magnetic field uniformity, and the principle is that, because the number of layers of the first annular magnet of each first magnet assembly is more than the number of layers of the second annular magnet of each second magnet assembly, and the number of layers of the third annular magnet of each third magnet assembly is more than the number of layers of the second annular magnet of each second magnet assembly, at least one layer of first annular magnet and at least one layer of third annular magnet are added at the two ends of the cylindrical Halbach array magnet, the annular magnets added at the two ends can help guide the magnetic flux, so that a closed magnetic flux path is formed at the opening of the two ends of the dumbbell-shaped magnet structure, thereby reducing the leakage of the magnetic field lines and helping to keep the magnetic field concentrated inside the coil or magnet, the annular magnets added at the two ends can compensate for the end effect and reduce the weakening of the magnetic field strength caused by the opening of the two ends of the dumbbell-shaped magnet structure. By applying an additional magnetic field at the two ends of the dumbbell-shaped magnet structure, the magnetic leakage can be offset, so that the magnetic field distribution inside the dumbbell-shaped magnet structure and the working area is more uniform. At the same time, the magnet structure is in the shape of a dumbbell, that is, a compensation magnet is added outside the outer end of the magnet structure, a compensation magnet with a larger thickness can be added outside according to requirements, the number of compensation magnets in the inner cavity of the magnet structure is reduced, or the compensation magnet is avoided to be arranged in the inner cavity of the magnet structure, in the case that the size of the middle magnet is constant, the size of the inner cavity of the dumbbell-shaped magnet structure is larger, and the magnetic resonance imaging system can better perform imaging through the magnetic field in the inner cavity of the magnet structure. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description only constitute some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0024] Figure 1 Front view of the dumbbell-shaped magnet structure provided for Embodiment 1;

[0025] Figure 2 Cross-sectional view of A-A in Figure 1

[0026] Cross-sectional view of B-B in Figure 3 Figure 1 Left view of the first end magnet provided for Embodiment 1;

[0027] Figure 4 Left view of the middle magnet provided for Embodiment 1;

[0028] Figure 5 Left view of the second end magnet provided for Embodiment 1;

[0029] Figure 6 In the drawings: 100, dumbbell-shaped magnet structure; 1, first magnet assembly; 101, first annular magnet; 2, second magnet assembly; 201, second annular magnet; 3, third magnet assembly; 301, third annular magnet; 4, magnetic block. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments only constitute some embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0031] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments only constitute some embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0032] The present application aims to provide a dumbbell-shaped magnet structure and a magnetic resonance imaging system to solve the problems in the prior art, reduce magnetic leakage, and improve the uniformity of magnetic field distribution, and better meet the spatial requirements of the magnetic resonance imaging system.

[0033] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application will be further described in detail below with reference to the drawings and specific embodiments.

[0034] Embodiment 1

[0035] As​Figures 1 to 6As shown, the embodiment provides a dumbbell-shaped magnet structure 100, which comprises a magnet structure including a first end magnet, a middle magnet and a second end magnet arranged in sequence, wherein: the first end magnet comprises at least one first magnet assembly 1, each first magnet assembly 1 comprising at least two layers of first annular magnets 101 arranged in sequence; the middle magnet comprises at least one second magnet assembly 2, each second magnet assembly 2 comprising at least one layer of second annular magnets 201, and the multiple layers of second annular magnets 201 of each second magnet assembly 2 are arranged in sequence; the second end magnet comprises at least one third magnet assembly 3, each third magnet assembly 3 comprising at least two layers of third annular magnets 301 arranged in sequence; the first annular magnets 101, the second annular magnets 201 and the third annular magnets 301 are all annular Halbach array magnets; the number of layers of the first annular magnets 101 of each first magnet assembly 1 is greater than the number of layers of the second annular magnets 201 of each second magnet assembly 2, a plane perpendicular to the center line of the first magnet assembly 1 is a first plane, and the projection of the outer rim of each first magnet assembly 1 on the first plane is located outside the projection of the outer rim of each second magnet assembly 2 on the first plane; the number of layers of the third annular magnets 301 of each third magnet assembly 3 is greater than the number of layers of the second annular magnets 201 of each second magnet assembly 2, and the projection of the outer rim of each third magnet assembly 3 on the first plane is located outside the projection of the outer rim of each second magnet assembly 2 on the first plane, i.e. the magnet structure is in a dumbbell shape with small middle and large ends. Among them, the middle magnet is used to generate a high-strength magnetic field; the first end magnet and the second end magnet are used to reduce the magnetic leakage phenomenon and improve the uniformity of the magnetic field, and the principle is that: since the number of layers of the first annular magnets 101 of each first magnet assembly 1 is greater than the number of layers of the second annular magnets 201 of each second magnet assembly 2, and the number of layers of the third annular magnets 301 of each third magnet assembly 3 is greater than the number of layers of the second annular magnets 201 of each second magnet assembly 2, it is equivalent to adding at least one layer of first annular magnets 101 and at least one layer of third annular magnets 301 at both ends of the cylindrical Halbach array magnet, and the annular magnets added at both ends can help guide the magnetic flux, so that a closed magnetic flux path is formed at the opening of both ends of the magnet structure, thereby reducing the leakage of magnetic field lines and helping to keep the magnetic field concentrated inside the coil or magnet; the annular magnets added at both ends can compensate for the end effect and reduce the weakening of the magnetic field strength due to the opening of both ends of the magnet structure. By applying an additional magnetic field at both ends of the magnet structure, the magnetic leakage can be offset, and a more uniform magnetic field distribution can be maintained inside the magnet structure and in the working area.Meanwhile, the magnet structure is dumbbell-shaped, that is, compensation magnets are added outside the outer ends of the magnet structure, larger-thickness compensation magnets can be added outside as required, too many compensation magnets are not added in the inner cavity of the magnet structure, or the compensation magnets are not arranged in the inner cavity of the magnet structure, the inner cavity of the dumbbell-shaped magnet structure 100 is larger in size under the condition that the sizes of the middle magnets are constant, and the magnet structure inner cavity magnetic field can better perform magnetic resonance imaging system imaging.

[0036] In the embodiment, the center lines of all the first annular magnets 101, all the second annular magnets 201 and all the third annular magnets 301 are collinear.

[0037] In the embodiment, a plane perpendicular to the center line of the first magnet assembly 1 is a first plane, the projection of the outermost ring of the first annular magnet 101 of each first magnet assembly 1 on the first plane is located outside the projection of each second magnet assembly 2 on the first plane; the projection of the outermost ring of the third annular magnet 301 of each third magnet assembly 3 on the first plane is located outside the projection of each second magnet assembly 2 on the first plane.

[0038] In the embodiment, the projection of the innermost ring of the first annular magnet 101 of each first magnet assembly 1 on the first plane is located inside the projection of each second magnet assembly 2 on the first plane; the projection of the innermost ring of the third annular magnet 301 of each third magnet assembly 3 on the first plane is located inside the projection of each second magnet assembly 2 on the first plane. It should be noted that, in order to ensure the size of the inner cavity of the magnet structure, the inner cavity of the magnet structure is not easy to add too many compensation magnets, and as a feasible implementation manner, the first annular magnet 101 and the third annular magnet 301 protruding from the inner wall of the middle magnet are both one layer.

[0039] In the embodiment, the second magnet assembly 2 is multiple.

[0040] In the embodiment, the lengths of all the first annular magnets 101 of each first magnet assembly 1 along the center line of the first magnet assembly 1 are the same, the lengths of all the second annular magnets 201 of each second magnet assembly 2 along the center line of the second magnet assembly 2 are the same, and the lengths of all the third annular magnets 301 of each third magnet assembly 3 along the center line of the third magnet assembly 3 are the same.

[0041] In the embodiment, the magnet structure is a symmetric piece symmetrical in the length direction of the magnet structure, that is, the cross section at the middle of the length direction of the magnet structure is a symmetry plane of the magnet structure, which can ensure the uniformity of the magnetic field.

[0042] As a feasible implementation, the spacing of the first end magnet and the middle magnet along the first end magnet center line is a first spacing, the spacing of the second end magnet and the middle magnet along the first end magnet center line is a second spacing, the spacing of the adjacent two first magnet assemblies 1 along the first end magnet center line is a third spacing, the spacing of the adjacent two second magnet assemblies 2 along the first end magnet center line is a fourth spacing, and the spacing of the adjacent two third magnet assemblies 3 along the first end magnet center line is a fifth spacing. The first spacing, the second spacing, the third spacing, the fourth spacing and the fifth spacing are the same.

[0043] In the embodiment, the first annular magnet 101 of each first magnet assembly 1 is four layers, the second annular magnet 201 of each second magnet assembly 2 is two layers, and the third annular magnet 301 of each third magnet assembly 3 is four layers. As a preferred embodiment, the first magnet assembly 1 and the third magnet assembly 3 are two, and the second magnet assembly 2 is four.

[0044] In the embodiment, each first annular magnet 101, each second annular magnet 201 and each third annular magnet 301 are all formed by combining a plurality of magnetic blocks 4 with the same shape and different magnetization directions to form an annular magnet. The first annular magnet 101, the second annular magnet 201 and the third annular magnet 301 are all multi-layered, which is beneficial to reduce the volume of a single magnetic block 4 and facilitate processing and manufacturing. When an annular magnet is formed by combining smaller magnetic blocks 4, the space utilization can be increased. Specifically, as shown in the figure, the cross section of the magnetic block 4 is rectangular, and the number of magnetic blocks 4 of the annular magnet gradually increases from the inner circle to the outer circle, thereby increasing the space utilization. Figures 2 to 6

[0045] Embodiment 2

[0046] The embodiment provides a magnetic resonance imaging system, which comprises a main magnet, and the main magnet is the dumbbell-shaped magnet structure 100 in the embodiment 1.

[0047] The principles and implementation manners of the present application are described by using specific examples in the present application. The above embodiment is only used to help understand the method and core idea of the present application. Meanwhile, for those skilled in the art, according to the idea of the present application, the specific implementation manner and application range can be changed. In conclusion, the content of the present application should not be understood as a limitation of the present application.​

Claims

1. A dumbbell-shaped magnet structure comprising a magnet structure, characterized by: The magnet structure comprises a first end magnet, a middle magnet and a second end magnet arranged in sequence, wherein: The first end magnet comprises at least one first magnet assembly, each of the first magnet assemblies comprising at least two layers of first annular magnets arranged in sequence; The middle magnet comprises at least one second magnet assembly, each of the second magnet assemblies comprising at least one layer of second annular magnets arranged in sequence; The second end magnet comprises at least one third magnet assembly, each of the third magnet assemblies comprising at least two layers of third annular magnets arranged in sequence; the first annular magnets, the second annular magnets and the third annular magnets are all annular Halbach array magnets; the number of layers of the first annular magnets of each of the first magnet assemblies is greater than the number of layers of the second annular magnets of each of the second magnet assemblies, a plane perpendicular to the center line of each of the first magnet assemblies is a first plane, and the projection of the outer rim of each of the first magnet assemblies on the first plane is located outside the projection of the outer rim of each of the second magnet assemblies on the first plane; the number of layers of the third annular magnets of each of the third magnet assemblies is greater than the number of layers of the second annular magnets of each of the second magnet assemblies, and the projection of the outer rim of each of the third magnet assemblies on the first plane is located outside the projection of the outer rim of each of the second magnet assemblies on the first plane.

2. The dumbbell magnet structure of claim 1, wherein: The center lines of all the first annular magnets, all the second annular magnets and all the third annular magnets are collinear.

3. The dumbbell magnet structure of claim 1, wherein: The projection of the outermost layer of the first annular magnets of each of the first magnet assemblies on the first plane is located outside the projection of each of the second magnet assemblies on the first plane; the projection of the outermost layer of the third annular magnets of each of the third magnet assemblies on the first plane is located outside the projection of each of the second magnet assemblies on the first plane.

4. The dumbbell magnet structure of claim 3, wherein: The projection of the innermost layer of the first annular magnets of each of the first magnet assemblies on the first plane is located inside the projection of each of the second magnet assemblies on the first plane; the projection of the innermost layer of the third annular magnets of each of the third magnet assemblies on the first plane is located inside the projection of each of the second magnet assemblies on the first plane.

5. The dumbbell magnet structure of claim 1, wherein: The second magnet assemblies are a plurality of.

6. The dumbbell magnet structure of claim 1, wherein: The lengths of all the first annular magnets of each of the first magnet assemblies along the center line of the first magnet assemblies are the same, the lengths of all the second annular magnets of each of the second magnet assemblies along the center line of the second magnet assemblies are the same, and the lengths of all the third annular magnets of each of the third magnet assemblies along the center line of the third magnet assemblies are the same.

7. The dumbbell magnet structure of claim 1, wherein: The magnet structure is a symmetric piece symmetrical in the length direction of the magnet structure.

8. The dumbbell magnet structure of claim 7, wherein: The spacing between the first end magnet and the middle magnet along the first end magnet centerline is a first spacing, the spacing between the second end magnet and the middle magnet along the first end magnet centerline is a second spacing, the spacing between two adjacent first magnet assemblies along the first end magnet centerline is a third spacing, the spacing between two adjacent second magnet assemblies along the first end magnet centerline is a fourth spacing, and the spacing between two adjacent third magnet assemblies along the first end magnet centerline is a fifth spacing, wherein the first spacing, the second spacing, the third spacing, the fourth spacing, and the fifth spacing are the same.

9. The dumbbell magnet structure of claim 1, wherein: The first annular magnet of each first magnet assembly is four layers, the second annular magnet of each second magnet assembly is two layers, and the third annular magnet of each third magnet assembly is four layers.

10. A magnetic resonance imaging system, characterized by: The application also provides a main magnet, which is the dumbbell-shaped magnet structure according to any one of claims 1-9.

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