CN112435824A - Magnet device and magnetic resonance imaging equipment - Google Patents
Magnet device and magnetic resonance imaging equipment Download PDFInfo
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- CN112435824A CN112435824A CN202011163240.5A CN202011163240A CN112435824A CN 112435824 A CN112435824 A CN 112435824A CN 202011163240 A CN202011163240 A CN 202011163240A CN 112435824 A CN112435824 A CN 112435824A
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- 238000002595 magnetic resonance imaging Methods 0.000 title claims abstract description 26
- 238000003384 imaging method Methods 0.000 claims abstract description 22
- 239000000463 material Substances 0.000 claims abstract description 12
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- 230000003068 static effect Effects 0.000 claims description 42
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 18
- 229910052742 iron Inorganic materials 0.000 claims description 9
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F7/00—Magnets
- H01F7/02—Permanent magnets [PM]
- H01F7/0273—Magnetic circuits with PM for magnetic field generation
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/05—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves
- A61B5/055—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
- G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
- G01R33/38—Systems for generation, homogenisation or stabilisation of the main or gradient magnetic field
- G01R33/383—Systems for generation, homogenisation or stabilisation of the main or gradient magnetic field using permanent magnets
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
- G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F7/00—Magnets
- H01F7/02—Permanent magnets [PM]
- H01F7/0273—Magnetic circuits with PM for magnetic field generation
- H01F7/0278—Magnetic circuits with PM for magnetic field generation for generating uniform fields, focusing, deflecting electrically charged particles
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Abstract
The present invention relates to a magnet device and a magnetic resonance imaging apparatus, the magnet device including: the two yokes are spaced and oppositely arranged; the two permanent magnets serving as magnetic field sources are respectively arranged on the opposite inner surfaces of the two yokes, the permanent magnets are of cylindrical structures, the magnetic orientations of the permanent magnets are axial, and the magnetic orientation directions of the two permanent magnets are the same; the two polar plates are respectively arranged on the opposite inner surfaces of the two permanent magnets, and an imaging space is formed between the two polar plates; the two shimming rings are respectively arranged on the opposite inner surfaces of the two polar plates; wherein, the shimming ring part or all is made of permanent magnet material. The magnet device and the magnetic resonance imaging equipment provided by the invention can obviously enlarge the range of an imaging area, thereby reducing the whole weight of the magnet device, reducing the production cost and facilitating the movement and installation of the magnetic resonance imaging equipment.
Description
Technical Field
The present invention relates to the field of magnetic resonance imaging technology, and more particularly, to a magnet device and a magnetic resonance imaging apparatus.
Background
The Magnetic Resonance Imaging (MRI) equipment can be used for scanning all parts of a human body, has no ionizing radiation damage to the human body, has clear soft tissue structure display, and can be used for diagnosing diseases of all parts of the whole body. The magnet is a core component in a magnetic resonance imaging apparatus for generating the main magnetic field necessary for magnetic resonance imaging.
There are three types of magnets currently used in clinical magnetic resonance imaging equipment: permanent magnet, superconducting magnet. The permanent magnet body utilizes a permanent magnetic material to generate a magnetic field, so that the operation and maintenance cost is low, and the manufacturing cost is relatively low.
As shown in fig. 1, a common permanent magnet for magnetic resonance consists of a yoke 1 ', a permanent magnet material 2', a pole plate 3 'and a shim ring 4', and through the interaction of these parts, a region with a relatively uniform magnetic field is formed between the two pole plates, and this region is an imaging region that can be used for magnetic resonance imaging, and the relatively larger this region of the same magnet, the higher the usage rate of the weight of the magnet, that is, the lighter the magnet can be made in the case of the same imaging region.
Due to the physical characteristics of the magnetic field, if no shimming ring is arranged, the magnetic field in the space between the two polar plates can be rapidly reduced from the center to the outside, the shimming ring has the function of adjusting the uniformity of the magnetic field in the imaging space, so that the magnetic field in the area close to the shimming ring is increased, and the area with relatively uniform magnetic field is formed in the center of the two polar plates for magnetic resonance imaging.
The shimming rings are usually made of soft magnetic materials, the arrangement of the shimming rings is very critical to the design of the magnet, and the larger the diameter of the shimming ring is, the larger the imaging area is, and the larger the volume and the weight of the magnet are. However, the heavy weight of the magnet will make the system difficult to move and install, and the cost will be greatly increased.
Disclosure of Invention
In view of the above, the present invention provides a magnet device and a magnetic resonance imaging apparatus, which are intended to solve the problems in the prior art.
According to a first aspect of the present invention, there is provided a magnet apparatus comprising:
the two yokes are spaced and oppositely arranged;
the two permanent magnets serving as magnetic field sources are respectively arranged on the opposite inner surfaces of the two yokes, the permanent magnets are of cylindrical structures, the magnetic orientations of the permanent magnets are axial, and the magnetic orientation directions of the two permanent magnets are the same;
the two polar plates are respectively arranged on the opposite inner surfaces of the two permanent magnets, and an imaging space is formed between the two polar plates;
the two shimming rings are respectively arranged on the opposite inner surfaces of the two polar plates;
wherein, the shimming ring part or all is made of permanent magnet material.
Preferably, the magnet device further comprises a static magnetic shielding box, the static magnetic shielding box is of a hollow box structure, and the yoke, the magnetic pole, the pole plate and the shimming ring are all arranged inside the static magnetic shielding box.
Preferably, the static magnetic shielding box is provided with at least one opening for the entrance and exit of a patient into and out of the static magnetic shielding box.
Preferably, the static magnetic shielding box is of a one-layer or multi-layer structure; when the static magnetic shielding box is of a multilayer structure, the distance between two adjacent box structures of the static magnetic shielding box is 30-100mm, and each layer of box structure of the static magnetic shielding box is made of pure iron materials.
Preferably, the shimming rings comprise an inner shimming ring and an outer shimming ring, the inner shimming ring is arranged to be close to the outer shimming ring, the inner shimming ring is made of soft magnetic materials, and the outer shimming ring is made of permanent magnetic materials.
Preferably, the shimming rings are formed by connecting a plurality of shimming ring units with the same size end to end, the cross sections of the shimming ring units perpendicular to the axial direction of the permanent magnet are isosceles trapezoids, and the shimming rings are sequentially connected together to form a polygonal annular structure.
Preferably, each shimming ring unit comprises a vertical plate, a mounting plate and a magnetic material block, the mounting plate and the vertical plate are mutually perpendicular and connected to form a mounting seat of an L-shaped structure, the magnetic material block is detachably connected to the mounting seat, and the mounting seat is fixedly connected to the pole plate through a screw.
Preferably, the surface of the mounting plate facing the vertical plate is provided with a guide block in an outward protruding manner, the cross section of the guide block is in a dovetail shape, the guide block extends in a direction parallel to the vertical plate, the surface of the magnetic material block facing the mounting plate is provided with a guide groove which is recessed inwards and matched with the guide block, and the magnetic material block is connected to the guide block of the mounting plate in a sliding manner through the guide groove.
Preferably, a sliding rail is respectively arranged on the surface of the mounting plate facing the vertical plate and the surface of the vertical plate facing the mounting plate, the two sliding rails are arranged in parallel, sliding grooves matched with the sliding rails are respectively arranged on the surfaces of the magnetic material block facing the mounting plate and the vertical plate, and the magnetic material block is slidably connected to the mounting base through the two sliding grooves.
According to a second aspect of the invention, there is provided a magnetic resonance imaging apparatus comprising a magnet arrangement as described above.
According to the magnet device and the magnetic resonance imaging equipment provided by the invention, the shimming ring part or all shimming ring parts are made of the permanent magnetic material, compared with the shimming ring made of the soft magnetic material, the magnet device can obviously enlarge the imaging area range, and the imaging area range in a larger range can be obtained under the condition that the permanent magnet with the same volume and weight is used as a magnetic field source. Therefore, under the condition of obtaining a certain required imaging area range, the whole weight of the magnet device can be reduced by using the magnet device, the production cost is reduced, and the magnetic resonance imaging equipment is convenient to move and install.
Drawings
The above and other objects, features and advantages of the present invention will become more apparent from the following description of the embodiments of the present invention with reference to the accompanying drawings.
Fig. 1 is a schematic structural view of a conventional magnet device.
Fig. 2 shows a schematic structural view of a magnet device according to an embodiment of the present invention.
Fig. 3 is a partial enlarged view at B in fig. 2.
Fig. 4 shows a perspective view of a magnet device according to an embodiment of the present invention.
Fig. 5 shows the result of the simulation calculation of the magnetic field distribution in the imaging zone of the magnet assembly using shim rings of soft magnetic material.
Fig. 6 shows the result of the simulation calculation of the magnetic field distribution in the imaging zone of the magnet assembly using shim rings of 85% permanent magnetic material.
Fig. 7 shows a schematic structural view of shim rings in a magnet arrangement according to an embodiment of the invention.
Fig. 8 shows a schematic structural view of shim ring units in a magnet arrangement according to an embodiment of the invention.
Fig. 9 shows a schematic structural view of shim ring units in a magnet arrangement according to another embodiment of the invention.
In the figure: the magnetic shield type permanent magnet shim plate comprises a yoke iron 1, a permanent magnet 2, a polar plate 3, a shim ring 4, an inner shim ring 41, an outer shim ring 42, a shim ring unit 400, a vertical plate 401, a magnetic material block 402, a mounting plate 403, a guide block 404, a guide groove 405, a slide rail 406, a slide groove 407, a static magnetic shield box 5 and an opening 51.
Detailed Description
Various embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Like elements in the various figures are denoted by the same or similar reference numerals. For purposes of clarity, the various features in the drawings are not necessarily drawn to scale.
The invention provides a magnet device, which comprises two yokes 1, two permanent magnets 2, two polar plates 3 and two shimming rings 4. The two yokes 1 are arranged oppositely at a preset distance; the two permanent magnets 2 are used as magnetic field sources and are respectively arranged on the opposite inner surfaces of the two yokes 1, the permanent magnets 2 are in cylindrical structures, the magnetic orientations of the permanent magnets 2 are axial, and the magnetic orientation directions of the two permanent magnets 2 are the same; the two polar plates 3 are respectively arranged on the opposite inner surfaces of the two permanent magnets 2, an imaging space A is formed between the two polar plates 3, and the imaging space A is used for a patient to enter for magnetic resonance imaging; two shimming rings 4 are respectively arranged on the opposite inner surfaces of the two polar plates 3, wherein part or all of the shimming rings 4 are made of permanent magnetic materials.
In this embodiment, the shimming rings 4 are partially made of a permanent magnetic material, as shown in fig. 2 and 3, the shimming rings 4 include an inner shimming ring 41 and an outer shimming ring 42, the inner shimming ring 41 is disposed adjacent to the outer shimming ring 42, the inner shimming ring 41 is made of a soft magnetic material, and the outer shimming ring 42 is made of a permanent magnetic material. The inner shim ring 41 made of soft magnetic material is arranged at the inner side, so that when the magnetic resonance imaging is carried out, the gradient magnetic field passes through the outer shim ring 42 to cause adverse effects on the magnetic resonance imaging system. Of course, this can also be avoided in other ways, for example, by designing the gradient coils such that the gradient fields are very small, the effect being negligible, for example, by software, etc.
By partially or totally manufacturing the shimming ring 4 of the magnet device by adopting a permanent magnet material, a larger imaging area range can be obtained under the condition that the permanent magnet 2 with the same volume and weight is used as a magnetic field source. In this embodiment, two magnet assemblies having permanent magnets of the same volume and mass are subjected to simulation calculation, the shimming rings of the first magnet assembly are all made of soft magnetic material pure iron, the shimming rings of the second magnet assembly are provided with shimming rings of the same external dimensions, about 4% of the volume of the shimming rings is made of permanent magnetic material, the remaining 15% of the volume of the shimming rings is made of soft magnetic material pure iron, and the soft magnetic material is arranged on the inner side of the permanent magnetic material. Through simulation calculation, the simulation calculation results are shown in fig. 5 and fig. 6, wherein fig. 5 is a schematic diagram of the magnetic field distribution of the first magnet device, and the magnetic field distribution on the X axis with the center of the pole plate as the origin can be seen as a trend that the magnetic field distribution always descends along the X axis, the diameter of the imaging region is not more than 150mm, and a large amount of work is required during passive shimming; fig. 6 is a schematic diagram of the magnetic field distribution of the second magnet device, and the magnetic field distribution on the X-axis with the center of the pole plate as the origin can be seen, where the magnetic field distribution first tends to rise along the X-axis and then to fall, and the diameter of the imaging region is expected to reach 260mm or more. Of course, the first magnet assembly can be improved by increasing the height or diameter of the shimming rings, but the size of the opening between the shimming rings and the weight are inevitably lost, the design of the whole magnet assembly is very disadvantageous, and the magnetic field distribution lines are flattened by increasing the shimming rings, no more energy is introduced, only the magnetic field distribution is changed, the central magnetic field is inevitably reduced, and the equivalent level of the magnetic field distribution of the magnet assembly cannot be achieved.
For the existing magnet device, as the shimming ring 4 is made of soft magnetic materials (such as pure iron, carbon steel, cast steel and the like), the pole plate 3 is connected with the shimming ring only by common bolts, and the connection is simple and has no potential safety hazard. The shimming ring 4 is partially or completely made of permanent magnetic materials, and because the magnetic materials are very high in hardness and are not suitable for processing holes, threads and the like, the existing bolt connection mode cannot be adopted, and some difficulties are caused to the installation of the shimming ring 4. The common magnetic materials are generally adhered in an installation mode, but the adhering process is complex and long in process, the surface needs to be cleaned to remove oil, the adhesive is uniform and appropriate in thickness, the adhesive is solidified to meet certain requirements on temperature, humidity and solidifying time, safety accidents can be caused by small errors in each step, the adhesive is adhered to the surface, the service life of the adhesive is prolonged, the adhesive force of the adhesive can be reduced along with the time, and the potential safety hazard can be caused.
In the magnet device, the shimming rings 4 are formed by connecting a plurality of shimming ring units 400 with the same size end to end, the cross sections of the shimming ring units 400 perpendicular to the axial direction of the permanent magnet 2 are isosceles trapezoids, and the shimming rings 4 are sequentially connected together to form a polygonal annular structure. The shimming ring 4 is deformed into a polygonal annular structure, the overall performance of the magnet is not influenced, particularly when the number of the shimming ring units 400 is large, the multi-annular structure is close to an annular structure, the processing of magnetic materials can be simplified, the circular arc surface does not need to be processed, and the structure of the shimming ring 4 in the magnet device is shown in fig. 7. Further, each shim ring unit 400 comprises a vertical plate 401, a mounting plate 403 and a magnetic material block 402, the mounting plate 403 and the vertical plate 401 are mutually perpendicular and connected to form a mounting seat of an L-shaped structure, the magnetic material block 402 is detachably connected to the mounting seat, and the mounting seat is fixedly connected to the pole plate 3 through screws. The vertical plate 401, the mounting plate 403 and the magnetic material are connected together to form a shimming ring unit 400 with an isosceles trapezoid cross section in a block structure. Referring to fig. 8 and 9, a threaded hole is formed in the mounting plate 403, a countersunk screw hole corresponding to the threaded hole is formed in the pole plate 3, and the mounting plate 403 is fixedly connected to the pole plate 3 by a countersunk screw. In this embodiment, a gap for connecting the mounting seat is formed in the edge of the surface of the pole plate 3 facing the shimming ring 4 along the circumferential direction, the depth of the gap is equal to the thickness of the mounting plate 403, and the length of the gap along the radial direction of the pole plate 3 is equal to the sum of the length of the mounting plate 403 and the thickness of the vertical plate 401, so that the shimming ring unit 400 and the pole plate 3 can be conveniently connected, and the connecting surface of the magnetic material block 402 and the mounting plate 403 is coplanar with the surface of the pole plate 3 on which the gap is formed. In this embodiment, a guide block 404 protrudes outward from the surface of the mounting plate 403 facing the vertical plate 401, the cross section of the guide block 404 is dovetail-shaped, the guide block 404 extends in a direction parallel to the vertical plate 401, a guide groove 405 matched with the guide block 404 is recessed inward from the surface of the magnetic material block 402 facing the mounting plate 403, and the magnetic material block 402 is slidably connected to the guide block 404 of the mounting plate 403 through the guide groove 405. In this embodiment, the dovetail groove in the dovetail shape of the magnetic material block 402 may be processed by wire cutting, which is a common processing method for magnetic materials. The guide block 404 on the mounting plate 403 can prevent the magnetic material from moving along the radial direction of the pole plate 3, and can also prevent the material from moving along the up-and-down direction, so that the magnetic connecting block is connected to the guide block 404 of the mounting plate 403 through the guide groove 405, and the mounting plate 403 is connected to the pole plate 3 through a screw, thereby omitting the complex process of gluing, increasing the connection reliability and eliminating the potential safety hazard.
In another embodiment of the present invention, a sliding rail 406 is respectively disposed on a surface of the mounting plate 403 facing the vertical plate 401 and a surface of the vertical plate 401 facing the mounting plate 403, the two sliding rails 406 are disposed in parallel with each other, sliding grooves 407 matching with the sliding rails 406 are respectively disposed on surfaces of the magnetic material block 402 facing the mounting plate 403 and the vertical plate 401, and the magnetic material block 402 is slidably connected to the mounting base through the two sliding grooves 407. In this embodiment, the cross section of the slide rail 406 is rectangular, and the slide slot 407 on the magnetic material block 402 is also processed by wire cutting. The mounting plate 403 and the two slide rails 406 on the vertical plate 401 are used in cooperation, the slide rails 406 on the mounting plate 403 can prevent the magnetic material from moving along the radial direction of the pole plate 3, and the slide rails 406 on the vertical plate 401 can prevent the material from moving along the up-and-down direction. The rectangular slide rail 406 and the slide slot 407 in this embodiment are easier to manufacture than the dovetail-shaped guide block 404 and the dovetail-shaped guide slot 405, and can achieve the same technical effect.
Further, the magnet device of the present invention further includes a static magnetic shield box 5, the static magnetic shield box 5 has a hollow box structure, and the yoke 1, the magnetic pole, the pole plate 3, and the shim ring 4 are all provided in the hollow structure inside the static magnetic shield box 5. The static magnetic shielding box 5 can reduce the leakage of the static magnetic field of the magnet, reduce the influence of the magnet on surrounding magnetically sensitive people and equipment, improve the field intensity of the magnet, improve the utilization efficiency of the permanent magnet and reduce the cost. The static magnetic shield box 5 is provided with at least one opening 51, and the opening 51 is used for the patient to enter and exit the static magnetic shield box 5. Referring to fig. 4, in the present embodiment, the magnetostatic shield box 5 has an opening 51 in the direction into the imaging space, the opening 51 being used for the entrance and exit of the patient into and out of the magnetostatic shield box 5; in other alternative embodiments, two or more openings 51 are provided in the static magnetic shielding box 5 to allow a patient to enter and exit the static magnetic shielding box 5 through a plurality of different openings 51 in certain application scenarios.
The static magnetic shield box 5 may be selectively designed into one or more layers according to the requirements of the magnet. When the static magnetic shielding box 5 is of a multilayer structure, the distance between two adjacent box structures of the static magnetic shielding box 5 is 30-100mm, and each layer of box structure of the static magnetic shielding box 5 is made of pure iron materials. As shown in fig. 4, in the present embodiment, the static magnetic shielding box 5 has a double-layer structure, the static magnetic field outside the static magnetic shielding box 5 does not exceed 50Gs due to the double-layer shielding of the static magnetic shielding box 5, the two-layer box structures of the static magnetic shielding box 5 are both made of pure iron material with a thickness of 4mm, the distance between the two-layer box structures is 60mm, and the two-layer box structures are not connected by magnetic conduction. Because pure iron is also a good conductor material, the static magnetic shielding box 5 can also play a role of electromagnetic shielding, and the influence of external interference on magnetic resonance imaging is reduced. Experiments prove that the static magnetic shielding box 5 can increase the field intensity by about 6.5 percent and reduce the range of a 5Gs safety zone by about 20 percent. The range of the 5Gs safety zone can be further reduced by increasing the structural layer number or the thickness of the box body of the static magnetic shielding box according to needs, and even the safety zone below 5Gs is completely arranged outside the static magnetic shielding box, so that the central field intensity of the magnet is further increased.
The invention also provides a magnetic resonance imaging apparatus comprising a magnet arrangement as described above.
In summary, according to the magnet device and the magnetic resonance imaging apparatus provided by the present invention, the shimming ring part or all of the shimming ring part is made of the permanent magnetic material, and compared with the shimming ring made of the soft magnetic material, the magnet device can significantly increase the imaging area range, and can obtain a larger imaging area range under the condition that the permanent magnet with the same volume and weight is used as the magnetic field source. Therefore, under the condition of obtaining a certain required imaging range, the whole weight of the magnet device can be reduced by using the magnet device, the production cost is reduced, and the movement and the installation of the magnetic resonance imaging equipment are also convenient. The static magnetic shielding box can reduce the leakage of a static magnetic field of the magnet, reduce the influence of the magnet on surrounding magnetically sensitive people and equipment, improve the field intensity of the magnet, improve the utilization efficiency of the permanent magnet and reduce the cost, and can also play a role in electromagnetic shielding and reduce the influence of external interference on magnetic resonance imaging.
It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
Finally, it should be noted that: it should be understood that the above examples are only for clearly illustrating the present invention and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications of the invention may be made without departing from the scope of the invention.
Claims (10)
1. A magnet assembly, comprising:
the two yokes are spaced and oppositely arranged;
the two permanent magnets serving as magnetic field sources are respectively arranged on the opposite inner surfaces of the two yokes, the permanent magnets are of cylindrical structures, the magnetic orientations of the permanent magnets are axial, and the magnetic orientation directions of the two permanent magnets are the same;
the two polar plates are respectively arranged on the opposite inner surfaces of the two permanent magnets, and an imaging space is formed between the two polar plates;
the two shimming rings are respectively arranged on the opposite inner surfaces of the two polar plates;
wherein, the shimming ring part or all is made of permanent magnet material.
2. The magnet assembly of claim 1, further comprising a static magnetic shield box having a hollow box structure, wherein the yoke, the magnetic poles, the pole plate, and the shim rings are disposed inside the static magnetic shield box.
3. A magnet assembly as claimed in claim 2, wherein the static magnetic shielding cage is provided with at least one opening for ingress and egress of a patient into and out of the static magnetic shielding cage.
4. A magnet assembly as claimed in claim 3, wherein the static magnetic shield box is of one or more layers;
when the static magnetic shielding box is of a multilayer structure, the distance between two adjacent box structures of the static magnetic shielding box is 30-100mm, and each layer of box structure of the static magnetic shielding box is made of pure iron materials.
5. The magnet assembly of claim 1, wherein the shim rings include an inner shim ring and an outer shim ring, the inner shim ring being disposed against the outer shim ring, the inner shim ring being made of a soft magnetic material, and the outer shim ring being made of a permanent magnetic material.
6. The magnet device according to claim 5, wherein the shimming rings are formed by connecting a plurality of shimming ring units with the same size end to end, the cross section of each shimming ring unit perpendicular to the axial direction of the permanent magnet is isosceles trapezoid, and the shimming rings are connected together in sequence to form a polygonal annular structure.
7. The magnet device according to claim 6, wherein each shim ring unit comprises a vertical plate, a mounting plate and a magnetic material block, the mounting plate and the vertical plate are vertically connected with each other to form a mounting seat with an L-shaped structure, the magnetic material block is detachably connected to the mounting seat, and the mounting seat is fixedly connected to the pole plate through a screw.
8. The magnet device according to claim 7, wherein a guide block is arranged on the surface of the mounting plate, which faces the vertical plate, in a protruding manner, the cross section of the guide block is in a dovetail shape, the guide block extends in a direction parallel to the vertical plate, a guide groove matched with the guide block is arranged on the surface of the magnetic material block, which faces the mounting plate, in a recessed manner, and the magnetic material block is slidably connected to the guide block of the mounting plate through the guide groove.
9. The magnet device according to claim 7, wherein a sliding rail is respectively disposed on a surface of the mounting plate facing the vertical plate and a surface of the vertical plate facing the mounting plate, the two sliding rails are disposed parallel to each other, sliding grooves matched with the sliding rails are respectively disposed on surfaces of the magnetic material block facing the mounting plate and the vertical plate, and the magnetic material block is slidably connected to the mounting base through the two sliding grooves.
10. A magnetic resonance imaging apparatus, characterized in that it comprises a magnet arrangement according to any one of claims 1-9.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202011163240.5A CN112435824A (en) | 2020-10-27 | 2020-10-27 | Magnet device and magnetic resonance imaging equipment |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202011163240.5A CN112435824A (en) | 2020-10-27 | 2020-10-27 | Magnet device and magnetic resonance imaging equipment |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN112435824A true CN112435824A (en) | 2021-03-02 |
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