Three-dimensional Halbach magnet for magnetic resonance

Abstract

The utility model relates to a three-dimensional Halbach magnet for magnetic resonance, which belongs to the technical field of magnetic resonance, and comprises a two-dimensional Halbach magnetic steel combination which is a circular ring formed by enclosing n pieces of magnetic steel in a Halbach array, n being an even number greater than 2; the first three-dimensional Halbach magnetic steel combination and the second three-dimensional Halbach magnetic steel combination are arranged on the two sides of the two-dimensional Halbach magnetic steel combination respectively, each of the first three-dimensional Halbach magnetic steel combination and the second three-dimensional Halbach magnetic steel combination is a circular ring defined by n pieces of magnetic steel in a Halbach array, and n is an even number larger than 2; wherein the first three-dimensional Halbach magnetic steel combination and the second three-dimensional Halbach magnetic steel combination comprise inclined magnetic steel with a magnetic axial component. Compared with the prior art, the distribution curve of the magnetic field intensity on the central axis on the height H of the magnet is compressed into a peak shape, so that the central magnetic field intensity is improved, and the magnetic field non-uniformity is improved.

Description

Technical Field

[0001] This utility model relates to the field of magnetic resonance technology, specifically to a three-dimensional Halbach magnet for magnetic resonance. Background Technology

[0002] Most existing Halbach array-based magnet structures are two-dimensional, while compact magnetic resonance magnets focus only on very small target regions, such as a sphere with a diameter of 5 mm or less at the center of the magnet, considering magnetic field strength B and magnetic field inhomogeneity. Two-dimensional Halbach magnet structures exhibit uniform magnetism only along their axis within an infinitely long magnet; along the axis of a finite-length magnet, the magnetic distribution is dome-shaped.

[0003] Patent CN218768932U discloses a high-strength uniform field magnet with a three-layer two-dimensional Halbach magnet structure. Specifically, it adds bottom magnets at both ends of a traditional Halbach magnet to enhance the magnetic field strength and uniformity in the working air gap. The outer diameter of the bottom magnets can be different from (smaller than) the outer diameter of the main magnet to reduce the cost of rare-earth permanent magnet materials. This patent achieves a central magnetic field strength that is more than 12% higher than existing technologies when using the same weight of magnets. However, to obtain good magnetic field non-uniformity, existing patents' two-dimensional Halbach magnet structures have larger magnet lengths, greater weight, larger volume, higher costs, and are difficult to miniaturize. Utility Model Content

[0004] To overcome the shortcomings of two-dimensional Halbach magnet structures, such as large length, weight, volume, high cost, and difficulty in miniaturization, this invention provides a three-dimensional Halbach magnet for magnetic resonance, which can enhance the central magnetic field strength and improve magnetic field inhomogeneity.

[0005] The objective of this utility model can be achieved through the following technical solutions:

[0006] A three-dimensional Halbach magnet for magnetic resonance imaging includes:

[0007] A two-dimensional Halbach magnet assembly, consisting of n magnets arranged in a Halbach array to form a ring, where n is an even number greater than 2;

[0008] The first three-dimensional Halbach magnet assembly and the second three-dimensional Halbach magnet assembly are respectively set on both sides of the two-dimensional Halbach magnet assembly. The first three-dimensional Halbach magnet assembly and the second three-dimensional Halbach magnet assembly are both formed by n magnets arranged in a Halbach array to form a ring, where n is an even number greater than 2.

[0009] The first three-dimensional Halbach magnet assembly and the second three-dimensional Halbach magnet assembly include oblique magnets that include a magnetic axial component.

[0010] Specifically, in a two-dimensional Halbach magnet assembly, the magnets only have magnetic components along the XY axis, while in a three-dimensional Halbach magnet assembly, in addition to having magnetic components along the XY axis, there is also a magnetic component along the Z axis. The magnetic component along the Z axis compresses the distribution curve of the magnetic field strength on the central axis along the magnet height H into a mountain peak shape, thereby increasing the central magnetic field strength.

[0011] Furthermore, the three-dimensional Halbach magnet also includes an outer cylinder disposed around the two-dimensional Halbach magnet assembly, the first three-dimensional Halbach magnet assembly, and the second three-dimensional Halbach magnet assembly, as well as a first end plate and a second end plate disposed on both sides of the outer cylinder.

[0012] Furthermore, the first end plate and the second end plate are respectively threaded to both sides of the outer cylinder.

[0013] Furthermore, the first end plate is an end plate made of a non-magnetic material.

[0014] Furthermore, the second end plate is an end plate made of a non-magnetic material.

[0015] Furthermore, limiting spacers are provided on both sides of the two-dimensional Halbach magnet assembly and between it and the first three-dimensional Halbach magnet assembly and the second three-dimensional Halbach magnet assembly, respectively.

[0016] Furthermore, the limiting spacer is a spacer made of non-magnetic material.

[0017] Furthermore, the magnets in the two-dimensional Halbach magnet assembly are rare-earth permanent magnets.

[0018] Furthermore, the magnets in the first three-dimensional Halbach magnet assembly are rare-earth permanent magnets.

[0019] Furthermore, the magnets in the second three-dimensional Halbach magnet assembly are rare-earth permanent magnets.

[0020] Compared with the prior art, this utility model replaces the first two-dimensional Halbach magnet combination and the third two-dimensional Halbach magnet combination in the prior art with the first three-dimensional Halbach magnet combination and the second three-dimensional Halbach magnet combination, respectively. The oblique magnets with magnetic axial components in the first three-dimensional Halbach magnet combination and the second three-dimensional Halbach magnet combination can contribute to the three-dimensional Halbach magnet for magnetic resonance, compressing the distribution curve of the magnetic field strength on the central axis at the magnet height H into a mountain peak shape, thereby increasing the central magnetic field strength and improving the magnetic field non-uniformity. Attached Figure Description

[0021] Figure 1 This is a cross-sectional view of a three-dimensional Halbach magnet used for magnetic resonance in the embodiment;

[0022] Figure 2 This is a three-dimensional view of the Halbach magnet used for magnetic resonance in the embodiment;

[0023] Figure 3 This is a schematic diagram showing the magnetization direction of the three-dimensional Halbach magnet used for magnetic resonance in the embodiment;

[0024] Figure 4 This is a top view of the three-dimensional Halbach magnet used for magnetic resonance in the embodiment;

[0025] Figure 5 This is a left view of the three-dimensional Halbach magnet used for magnetic resonance in the embodiment;

[0026] Figure 6 This is a front view of the three-dimensional Halbach magnet used for magnetic resonance in the embodiment;

[0027] Figure 7 This is a right view of the three-dimensional Halbach magnet used for magnetic resonance in the embodiment;

[0028] Figure 8 This is a rear view of the three-dimensional Halbach magnet used for magnetic resonance in the embodiment;

[0029] Figure 9 This is a perspective view of the first three-dimensional Halbach magnet assembly of the three-dimensional Halbach magnet used in the embodiment for magnetic resonance.

[0030] Figure 10 This is a top view of the first three-dimensional Halbach magnet assembly of the three-dimensional Halbach magnet used in the embodiment for magnetic resonance.

[0031] Figure 11 This is a front view of the first three-dimensional Halbach magnet assembly of the three-dimensional Halbach magnet used in the embodiment for magnetic resonance.

[0032] Figure 12 This is a left view of the first three-dimensional Halbach magnet assembly of the three-dimensional Halbach magnet used in the embodiment for magnetic resonance.

[0033] Figure 13 This is a perspective view of a two-dimensional Halbach magnet assembly of a three-dimensional Halbach magnet used in magnetic resonance in the embodiment;

[0034] Figure 14 This is a top view of a two-dimensional Halbach magnet assembly of a three-dimensional Halbach magnet used in the magnetic resonance embodiment;

[0035] Figure 15 This is a perspective view of the second three-dimensional Halbach magnet assembly of the three-dimensional Halbach magnet used in the magnetic resonance embodiment;

[0036] Figure 16 This is a top view of the second three-dimensional Halbach magnet assembly of the three-dimensional Halbach magnet used in the magnetic resonance embodiment;

[0037] Figure 17 This is a front view of the second three-dimensional Halbach magnet assembly of the three-dimensional Halbach magnet used in the embodiment for magnetic resonance.

[0038] Figure 18 This is a left view of the second three-dimensional Halbach magnet assembly of the three-dimensional Halbach magnet used in the embodiment for magnetic resonance.

[0039] Figure 19 A diagram showing the magnetic field contribution of a two-dimensional Halbach magnet in the prior art;

[0040] Figure 20 This is a diagram showing the magnetic field contribution of a three-dimensional Halbach magnet used for magnetic resonance in this embodiment.

[0041] The numbers in the diagram indicate: 1-First three-dimensional Halbach magnet assembly; 2-Two-dimensional Halbach magnet assembly; 3-Second three-dimensional Halbach magnet assembly; 4-Outer cylinder; 5-Limiting spacer; 6-First end plate; 7-Second end plate. Detailed Implementation

[0042] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0043] Example

[0044] To overcome the drawbacks of two-dimensional Halbach magnet structures, such as large length, weight, volume, high cost, and difficulty in miniaturization, this embodiment provides a three-dimensional Halbach magnet for magnetic resonance imaging. The specific structure is shown in [reference needed]. Figure 1-18 ,include:

[0045] A two-dimensional Halbach magnet assembly 2, consisting of n magnets arranged in a Halbach array to form a ring, where n is an even number greater than 2; the two-dimensional Halbach magnet assembly 2 is used to provide the main magnetic field for a three-dimensional Halbach magnet for magnetic resonance.

[0046] The first three-dimensional Halbach magnet assembly 1 and the second three-dimensional Halbach magnet assembly 3 are respectively set on both sides of the two-dimensional Halbach magnet assembly 2. The first three-dimensional Halbach magnet assembly 1 and the second three-dimensional Halbach magnet assembly 3 are both formed by n magnets arranged in a Halbach array to form a ring, where n is an even number greater than 2.

[0047] The first three-dimensional Halbach magnet assembly 1 and the second three-dimensional Halbach magnet assembly 3 include oblique magnets with magnetic axial components. Under the combined action of the first three-dimensional Halbach magnet assembly 1 and the second three-dimensional Halbach magnet assembly 3, the magnetic field intensity distribution curve of the main magnetic field direction on the axis of the magnetic resonance three-dimensional Halbach magnet is compressed into a mountain peak-shaped magnetic field intensity distribution curve, which greatly improves the magnetic field intensity of the product or maintains the original magnetic field intensity, reduces the product volume and weight, saves costs, and is conducive to the miniaturization of the whole machine.

[0048] Specifically, in the two-dimensional Halbach magnet assembly, all magnets have magnetic components only in the XY axes, see... Figure 13-14 The three-dimensional Halbach magnet assembly has magnetic components not only along the XY axes but also along the Z axis, see [reference needed]. Figure 9-12 , Figure 15-18 The magnetic component along the Z-axis compresses the distribution curve of the magnetic field strength along the central axis at the magnet height H into a mountain peak shape, thereby increasing the central magnetic field strength. For example... Figure 2 As shown, the three-dimensional Halbach magnet assembly includes axial magnets with the magnetic direction along the axis, horizontal magnets with the magnetic direction along the horizontal direction, and oblique magnets whose magnetic direction can be decomposed into a magnetic axial component and a magnetic horizontal component that intersects with the magnetic direction of the horizontal magnet.

[0049] In this embodiment, the three-dimensional Halbach magnet further includes an outer cylinder 4 disposed around the two-dimensional Halbach magnet assembly 2, the first three-dimensional Halbach magnet assembly 1, and the second three-dimensional Halbach magnet assembly 3, and a first end plate 6 and a second end plate 7 respectively disposed on both sides of the outer cylinder 4. The outer cylinder 4 is used to protect and fix the magnet; the first end plate 6 is used to fix the upper magnet to prevent displacement due to magnetic repulsion and to provide fixing holes for parts in the magnet cavity; the second end plate 7 is used to fix the lower magnet to prevent displacement due to magnetic repulsion and to provide a positioning reference for the magnet.

[0050] In this embodiment, the first end plate 6 and the second end plate 7 are threadedly connected to both sides of the outer cylinder 4, respectively.

[0051] In this embodiment, the first end plate 6 is an end plate made of non-magnetic material; the second end plate 7 is an end plate made of non-magnetic material.

[0052] In this embodiment, limiting spacers 5 are provided on both sides of the two-dimensional Halbach magnet assembly 2 between the first three-dimensional Halbach magnet assembly 1 and the second three-dimensional Halbach magnet assembly 3, respectively; the limiting spacers 5 are spacers made of non-magnetic material, used to maintain interlayer positioning and prevent misalignment or damage of the interlayer magnets.

[0053] In this embodiment, the magnets in the two-dimensional Halbach magnet assembly 2 are rare-earth permanent magnets; the magnets in the first three-dimensional Halbach magnet assembly 1 are rare-earth permanent magnets; and the magnets in the second three-dimensional Halbach magnet assembly 3 are rare-earth permanent magnets.

[0054] In existing technology, the distribution curve of the magnetic field strength along the central axis of a two-dimensional Halbach magnet at the magnet height H is dome-shaped, see... Figure 19 In this embodiment, the three-dimensional Halbach magnet replaces the existing first two-dimensional Halbach magnet assembly with a first three-dimensional Halbach magnet assembly 1, and the existing third two-dimensional Halbach magnet assembly with a second three-dimensional Halbach magnet assembly 3. The oblique magnets with magnetic axial components in both the first three-dimensional Halbach magnet assembly 1 and the second three-dimensional Halbach magnet assembly 3 contribute to the magnet's structure, compressing the magnetic field strength distribution curve along the magnet height H on the central axis into a peak shape. This reduces the magnetic field strength in useless areas and increases the magnetic field strength in the target area, thereby reducing product size and weight, saving costs, and facilitating overall miniaturization. Figure 20 .

[0055] Specifically, this embodiment compares the three-dimensional Halbach magnet used in magnetic resonance with a traditional integral Halbach magnet. Under the same external dimensions, the central magnetic field strength of this embodiment is 811.32 mt and the magnetic field inhomogeneity (ppm) is 677.91, while the central magnetic field strength of the traditional integral Halbach magnet is 718.44 mt and the ppm is 918.66. Therefore, it can be seen that the central magnetic field strength and ppm of this embodiment are superior to those of the traditional integral Halbach magnet.

[0056] The three-dimensional Halbach magnet used in this embodiment for magnetic resonance imaging is compared with Chinese patent application number 202221488061.3, entitled "A High-Intensity Uniform Field Magnet." With the same external dimensions, the central magnetic field strength of this embodiment is 811.32 mt, and the magnetic field inhomogeneity (ppm) is 677.91, while the central magnetic field strength of the aforementioned patented magnet is 804.81 mt, and the ppm is 2248.97. Therefore, the central magnetic field strength of this embodiment is not significantly different from that of the aforementioned patented magnet, while the ppm is significantly better.

[0057] The above description is merely a preferred embodiment of this utility model and is not intended to limit the utility model in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of this utility model without departing from its technical solution shall still fall within the protection scope of this utility model.

Claims

1. A three-dimensional Halbach magnet for magnetic resonance, characterized in that, include: Two-dimensional Halbach magnet assembly (2), which consists of n magnets arranged in a Halbach array to form a ring, where n is an even number greater than 2; The first three-dimensional Halbach magnet assembly (1) and the second three-dimensional Halbach magnet assembly (3) are respectively set on both sides of the two-dimensional Halbach magnet assembly (2). The first three-dimensional Halbach magnet assembly (1) and the second three-dimensional Halbach magnet assembly (3) are both formed by n magnets arranged in a Halbach array to form a ring, where n is an even number greater than 2. The first three-dimensional Halbach magnet assembly (1) and the second three-dimensional Halbach magnet assembly (3) include oblique magnets with magnetic axial components.

2. A three-dimensional Halbach magnet for magnetic resonance according to claim 1, characterized in that, The three-dimensional Halbach magnet also includes an outer cylinder (4) disposed around the two-dimensional Halbach magnet assembly (2), the first three-dimensional Halbach magnet assembly (1) and the second three-dimensional Halbach magnet assembly (3), as well as a first end plate (6) and a second end plate (7) disposed on both sides of the outer cylinder (4).

3. A three-dimensional Halbach magnet for magnetic resonance according to claim 2, characterized in that, The first end plate (6) and the second end plate (7) are threaded to both sides of the outer cylinder (4).

4. A three-dimensional Halbach magnet for magnetic resonance according to claim 2, characterized in that, The first end plate (6) is an end plate made of non-magnetic material.

5. A three-dimensional Halbach magnet for magnetic resonance according to claim 2, characterized in that, The second end plate (7) is an end plate made of non-magnetic material.

6. A three-dimensional Halbach magnet for magnetic resonance according to claim 1, characterized in that, Limiting spacers (5) are provided on both sides of the two-dimensional Halbach magnet assembly (2) between the first three-dimensional Halbach magnet assembly (1) and the second three-dimensional Halbach magnet assembly (3).

7. A three-dimensional Halbach magnet for magnetic resonance according to claim 6, characterized in that, The limiting spacer (5) is made of non-magnetic material.

8. A three-dimensional Halbach magnet for magnetic resonance according to claim 1, characterized in that, The magnets in the two-dimensional Halbach magnet assembly (2) are rare earth permanent magnets.

9. A three-dimensional Halbach magnet for magnetic resonance according to claim 1, characterized in that, The magnets in the first three-dimensional Halbach magnet assembly (1) are rare earth permanent magnets.

10. A three-dimensional Halbach magnet for magnetic resonance according to claim 1, characterized in that, The magnets in the second three-dimensional Halbach magnet assembly (3) are rare earth permanent magnets.

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