CN101191828B - Full-open permanent magnetism magnetic body for magnetic resonance image-forming - Google Patents
Full-open permanent magnetism magnetic body for magnetic resonance image-forming Download PDFInfo
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- 229910052761 rare earth metal Inorganic materials 0.000 claims description 11
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Abstract
The invention discloses a full-open permanent magnet for MRI, wherein the permanent magnet comprises: full-open main structure of a rectangular structure composed of two vertical yokes arranged left and right symmetrically and two transverse yokes arranged up and down symmetrically with an air gap zone of the permanent magnetic positioned in the middle of the full-open main structure; up and down two parallel opposite main poles which are respectively arranged on the sides close to the air gap zone of and connected with the up and down two transverse yokes; and up and down two parallel opposite pole plates which are respectively arranged on the sides close to the air gap zone of and connected with the up and sown two main poles. The invention enormously reduces the weight of the yokes, improves the shimming efficiency and increases the openness of the magnetic field.
Description
Technical field
The present invention relates to be used in the medicine equipment permanent-magnet technical field of medical diagnosis, particularly a kind of full-open permanent magnetism magnetic body for magnetic resonance image-forming.
Background technology
Magnetic resonance imaging (MRI) equipment is the medical diagnostic apparatus that has grown up since the eighties in last century, obtain to its no wound the image of any tomography in partes corporis humani position, can obtain soft-tissue image clearly, obtain human anatomy information, be current the discovery and diagnosis early-stage cancer and the state-of-the-art clinical diagnostic device of other multiple diseases, all come into one's own at international medical community and technos.
Magnet is one of nucleus equipment of MR imaging apparatus, and its every performance index are directly connected to the signal to noise ratio (S/N ratio) of magnetic resonance equipment system, are determining the quality of image to a certain extent.Magnet is divided into superconduct, and resistance or electromagnetism are often led type, three kinds of permanent-magnet types.
Wherein, permanent-magnet type MRI is reliable, need not the auxiliary equipment of keeping ultralow temperature, energy savings, and price, operating cost and maintenance cost are all lower, become the main flow in this kind equipment of present China.
The permanent-magnet that is used for the MRI system can be divided into enclosed and open two kinds.Wherein the former comprises four post symmetric forms etc., and the latter comprises the asymmetric and single-column C type of twin columns etc.
The developing direction of main magnet shape is: open, comfortable, press close to patient.Common permanent-magnet mostly is the structure of C type at present.The patent No. be 94115507.2 Granted publications number for CN 1041969C and the patent No. be 00239177.5 Granted publication number for the Chinese patent of CN 2430698Y and application number be 09/386146 Granted publication number for the United States Patent (USP) of US 6340888B1 has disclosed different C type permanent-magnet main structures, application number is that 10/233539 Granted publication number has disclosed a kind of two column type permanent-magnet main structures afterwards for the United States Patent (USP) of US 2003/0020578A1.The deficiency of these structures is:
1) C type physical construction causes the yoke part will bear the total weight of the permanent magnetism main pole and the top crown group on top, also has the acting force that attracts each other between two main poles simultaneously, so it is the shear stress of last yoke inside is very big, higher to the material and the dimensional requirement of this part.
2) C type magnet structure is asymmetric, makes the perform region less than normal near a side magnetic field of vertical yoke, and uniformity of magnetic field is caused adverse effect.
3) C type yoke makes the permanent magnetism main pole on top become cantilever design, and when equipment was subjected to the external world or the mechanical disturbance of self, magnetic pole more easily vibrated, thereby influences the stability and the homogeneity of perform region, magnetic field.
4) because the stress of last yoke inside is had relatively high expectations, generally all select the higher steel of intensity for use, and the magnetic permeability of steel is not high, so the cross-sectional area of yoke is had higher requirement, causes the volume of yoke too huge, makes that finally the general assembly (TW) of magnet is very big.
Therefore, along with the enhancing of field intensity, not only the use amount of permanent magnetic material increases, and the use amount of yoke also significantly increases, and the weight that how to alleviate yoke then becomes the important techniques problem.In addition, improve shimming efficient, and increase the magnetic field openness so that operation in the clinical practice and diagnosis and treatment etc. also are permanent-magnet type MRI problem demanding prompt solutions.
Summary of the invention
(1) technical matters that will solve
In view of this, fundamental purpose of the present invention is to provide a kind of full-open permanent magnetism magnetic body for magnetic resonance image-forming, to alleviate the weight of yoke, improves shimming efficient, and increases the openness in magnetic field.
(2) technical scheme
For achieving the above object, technical scheme of the present invention is achieved in that
A kind of full-open permanent magnetism magnetic body for magnetic resonance image-forming, this permanent-magnet comprises:
By two vertical yokes that are symmetrically arranged and two up and down the horizontal yoke of symmetric arrangement being of constituting flat wide hollow structure the full open model main structure, the air gap district of this permanent-magnet is positioned at the middle part of described full open model main structure;
Be positioned at up and down two horizontal yokes near air gap district one side and respectively with two two parallel relative main poles up and down that horizontal yoke links together up and down;
Be positioned at up and down two main poles near air gap district one side and respectively with two two groups of parallel relative last bottom crown groups up and down that main pole links together up and down.
Described full open model main structure sees from the front and is flat wide hollow, two parallel positioned opposite of horizontal yoke up and down, about two parallel positioned opposite of vertical yoke; Described two vertical yokes are clipped between two horizontal yokes, and are symmetrically arranged in the far-end of horizontal yoke; By the taper bolt location, be connected between vertical yoke and the horizontal yoke through screw rod.
Described vertical yoke or horizontal yoke are forged to make by electrical pure iron and are formed, method to vertical yoke or horizontal yoke employing computer simulation design magnetic structure, magnetic flux density is than the material of lower part in the removal yoke, do not cause under the saturated prerequisite of material magnetic flux satisfied, make magnetic flux inner concentrated, alleviate the general assembly (TW) of yoke to yoke.
Described two horizontal yokes are left-right symmetric, front and back symmetry and laterally zygomorphic structure, and stepped construction is adopted in outside of two far-ends about it; From the front, laterally two ends, the yoke left and right sides become stepped away from a side of vertical yoke, the ladder number is three to four, and the thickness of each ladder is 1/4th to 1/3rd of horizontal yoke gross thickness, and the length of each ladder is a thirtieth to 1/15th of horizontal yoke total length.
Described two horizontal yoke center sections have been removed the part material away from a side of main pole, and the horizontal yoke behind the removal material still keeps left-right symmetric, front and back symmetrical structure; From the front, do not consider the staircase structure of horizontal yoke two far-ends, laterally the center section thickness minimum of yoke, for total thickness 1/3rd to 2/3rds between, to two far-ends, its thickness increases gradually, until equating with total thickness from the center section of horizontal yoke; The center section of horizontal yoke behind the described removal material connects horizontal yoke on its fore-and-aft direction, be of a size of 2/3rds of main pole external diameter on left and right directions.
The described center section of having removed the horizontal yoke of part material, from the front, its surface away from main pole one side forms a recessed platform, and its left and right directions minimum length is 1/5th of a main pole external diameter, and it connects horizontal yoke at fore-and-aft direction; Described platform is 1/2nd of a horizontal yoke gross thickness with the vertical distance of horizontal yoke end face; Laterally yoke by removing material, respectively forms three planes in the both sides of platform away from the surface of main pole one side.
The described center section of having removed the horizontal yoke of part material, from the front, its surface away from main pole one side forms trapezoidal depression, its inboard base is shorter, length is 1/5th of main pole external diameter, base, outside length is 4/5ths of main pole external diameter, and trapezoidal height is 1/2nd of a horizontal yoke total thickness; The removal of described ladder material has formed three facets at the upper surface of horizontal yoke.
The xsect of described vertical yoke is trapezoidal, and narrow limit is towards the inboard of described full open model main structure, and broadside is towards the outside of full open model main structure; At the center with main pole is in the horizontal section in the center of circle, and described xsect is that the trapezoidal shared central angle of vertical yoke is less than 1/10.
Described main pole profile is cylindrical, is arranged between horizontal yoke and the pole plate, by bonding the forming of numerous Nd-Fe-B rare-earth permanent magnet magnetic patch groups; Described Nd-Fe-B rare-earth permanent magnet magnetic patch group is built and is bonded together along the main pole short transverse by the identical little magnetic patch of one pile of xsect, and the height of magnetic patch group equals the vertical distance between horizontal yoke and the pole plate; Magnetic patch group near the main pole center section in the described Nd-Fe-B rare-earth permanent magnet magnetic patch group is the square-section, and the magnetic patch group of close main pole circumferential section then is the cross section of sector crosssection or other shapes.
Described go up the bottom crown group by screw respectively with up and down laterally yoke is connected, the screw of described connection pole plate group and horizontal yoke passes main pole; The described bottom crown group that goes up all comprises pole plate, complete cycle polar ring and non-complete cycle polar ring, and three's external diameter is identical and less than the main pole external diameter, material is the electrical pure iron of high magnetic permeability; Last bottom crown is with laterally yoke is parallel, and two-plate is parallel to each other and relatively, is furnished with the complete cycle polar ring that the cross section is the L type in its side near air gap, and one side of its L type is close to pole plate, and the barbed portion of L type is towards the inboard; In the side of complete cycle polar ring near air gap, being furnished with the cross section is the non-complete cycle polar ring of rectangle; The anchor ring of this non-complete cycle polar ring and complete cycle polar ring is close to, and arranges in the left-right symmetric face symmetria bilateralis of magnet main structure; In the horizontal section, be the center of circle with the center of main pole, the central angle of each non-complete cycle polar ring between 40 ° to 70 °, thickness complete cycle polar ring thickness 1/8th to 1/4th between; Be connected by circumferential screw between described polar ring and the pole plate, constituting outside surface is the pole plate group of cylinder; Wherein, the complete cycle polar ring is used to raise the close value of magnetic of air gap edge, non-complete cycle polar ring be used for further revising since the layout of vertical yoke with the magnetic flux of perform region to the both sides field weakening that the direction attraction of vertical yoke causes, improve the uniformity coefficient in magnetic field in the air gap.
(3) beneficial effect
From technique scheme as can be seen, the present invention has following beneficial effect:
1, the present invention is just at the MRI permanent-magnet of prior art, a kind of symmetrical far-end twin columns structure is provided, basis magnetic field symmetry and be easy to shimming, physical construction is stable, quality is less relatively, can guarantee the full-open permanent magnetism magnetic body for magnetic resonance image-forming of certain magnetic field openness, has alleviated the weight of yoke greatly, improve shimming efficient, and increased the openness in magnetic field.
2, this full-open permanent magnetism magnetic body for magnetic resonance image-forming provided by the invention, by adopting the design of left-right symmetric and front and back symmetry, more stable on physical construction, simultaneously also help improving the magnetic field homogeneity and the stability of magnet perform region, avoid because the image disruption that structural vibration causes.
3, this full-open permanent magnetism magnetic body for magnetic resonance image-forming provided by the invention, by adopting the method for computer simulation design magnetic structure, removed in the yoke magnetic flux density than the material of lower part, do not cause under the saturated prerequisite of material magnetic flux satisfied, make magnetic flux inner concentrated, alleviated the general assembly (TW) of yoke simultaneously greatly to yoke.
4, this full-open permanent magnetism magnetic body for magnetic resonance image-forming provided by the invention is compared with existing C type permanent-magnet, with still less mass distribution on more large-area ground, the magnet quality that makes unit area ground bear reduces, to the ground load-bearing requirement reduction relatively of infield.
5, this full-open permanent magnetism magnetic body for magnetic resonance image-forming provided by the invention, because the magnet main structure is symmetric design, and polar ring also be the layout of symmetry, so magnet forms the field, basis of symmetry in the perform region, so shimming is simple and easy relatively.
6, this full-open permanent magnetism magnetic body for magnetic resonance image-forming provided by the invention, in the horizontal section, center with main pole is the center of circle, the vertical shared central angle of yoke is less than 1/10, make the openness in magnetic field increase, increased usage space effectively, solved the narrow problem of sick bed width when adopting C type magnet, give the openness and the comfort level of patient's maximum simultaneously, for medical personnel's clinical manipulation provides more spaces.
7, this full-open permanent magnetism magnetic body for magnetic resonance image-forming provided by the invention, be arranged in pole plate and raised the close value of magnetic of air gap edge near the complete cycle polar ring of a side of air gap, be arranged in that the complete cycle polar ring is further revised near the non-complete cycle polar ring of air gap side because the layout of vertical yoke causes both sides field weakening from the magnetic flux of perform region to the direction attraction of vertical yoke, thereby effectively improved the uniformity coefficient in magnetic field in the air gap.
Description of drawings
The outside drawing of the full-open permanent magnetism magnetic body for magnetic resonance image-forming that provides according to first embodiment of the invention is provided Fig. 1;
The front view of the full-open permanent magnetism magnetic body for magnetic resonance image-forming that provides according to first embodiment of the invention is provided Fig. 2;
The vertical view of the full-open permanent magnetism magnetic body for magnetic resonance image-forming that provides according to first embodiment of the invention is provided Fig. 3;
The following main pole that provides according to first embodiment of the invention and the sectional view of bottom crown group are provided Fig. 4;
The outside drawing of the bottom crown group that provides according to first embodiment of the invention is provided Fig. 5;
The full-open permanent magnetism magnetic body for magnetic resonance image-forming magnetic flux synoptic diagram of Fig. 6 for providing according to first embodiment of the invention;
The outside drawing of the full-open permanent magnetism magnetic body for magnetic resonance image-forming that provides according to second embodiment of the invention is provided Fig. 7;
The front view of the full-open permanent magnetism magnetic body for magnetic resonance image-forming that provides according to second embodiment of the invention is provided Fig. 8.
Embodiment
For making the purpose, technical solutions and advantages of the present invention clearer, below in conjunction with specific embodiment, and with reference to accompanying drawing, the present invention is described in more detail.
This full-open permanent magnetism magnetic body for magnetic resonance image-forming provided by the invention, comprise: by two vertical yokes that are symmetrically arranged and two up and down the horizontal yoke of symmetric arrangement constitute, see the full open model main structure that is flat wide hollow structure from the front, the air gap district of this permanent-magnet is positioned at the middle part of described full open model main structure; Be positioned at up and down two horizontal yokes near air gap district one side and respectively with two two parallel relative main poles up and down that horizontal yoke links together up and down; Be positioned at up and down two main poles near air gap district one side and respectively with two two groups of parallel relative last bottom crown groups up and down that main pole links together up and down.
Wherein, described full open model main structure sees from the front and is flat wide hollow, two parallel positioned opposite of horizontal yoke up and down, about two parallel positioned opposite of vertical yoke.Two vertical yokes are clipped between two horizontal yokes, and are symmetrically arranged in the far-end of horizontal yoke.By the taper bolt location, be connected between vertical yoke and the horizontal yoke through screw rod.
Vertical yoke or horizontal yoke are forged to make by electrical pure iron and are formed, method to vertical yoke or horizontal yoke employing computer simulation design magnetic structure, magnetic flux density is than the material of lower part in the removal yoke, do not cause under the saturated prerequisite of material magnetic flux satisfied, make magnetic flux inner concentrated, alleviate the general assembly (TW) of yoke to yoke.
Two horizontal yokes are left-right symmetric, front and back symmetry and laterally zygomorphic structure, and stepped construction is adopted in outside of two far-ends about it.From the front, laterally two ends, the yoke left and right sides become stepped away from a side of vertical yoke, the ladder number is three to four, and the thickness of each ladder is 1/4th to 1/3rd of horizontal yoke gross thickness, and the length of each ladder is a thirtieth to 1/15th of horizontal yoke total length.
Two horizontal yoke center sections have been removed the part material away from a side of main pole, and the horizontal yoke behind the removal material still keeps left-right symmetric, front and back symmetrical structure.From the front, do not consider the staircase structure of horizontal yoke two far-ends, laterally the center section thickness minimum of yoke, for total thickness 1/3rd to 2/3rds between, to two far-ends, its thickness increases gradually, until equating with total thickness from the center section of horizontal yoke.
The center section of horizontal yoke behind the described removal material connects horizontal yoke on its fore-and-aft direction, be of a size of 2/3rds of main pole external diameter on left and right directions.
The xsect of described vertical yoke is trapezoidal, and narrow limit is towards the inboard of described full open model main structure, and broadside is towards the outside of full open model main structure.
At the center with main pole is in the horizontal section in the center of circle, described xsect be the trapezoidal shared central angle of vertical yoke less than 1/10, make the openness in magnetic field increase, for patient's bed provides open relatively space.
The main pole profile is cylindrical, is arranged between horizontal yoke and the pole plate group, by bonding the forming of numerous Nd-Fe-B rare-earth permanent magnet magnetic patch groups.Nd-Fe-B rare-earth permanent magnet magnetic patch group is built and is bonded together along the main pole short transverse by the identical little magnetic patch of one pile of xsect, and the height of magnetic patch group equals the vertical distance between horizontal yoke and the pole plate.Magnetic patch group near the main pole center section in the Nd-Fe-B rare-earth permanent magnet magnetic patch group is the square-section, and the magnetic patch group of close main pole circumferential section then is the cross section of sector crosssection or other shapes.
Last bottom crown group by screw respectively with up and down laterally yoke is connected, the screw that connects pole plate group and horizontal yoke passes main pole.Last bottom crown group all comprises pole plate, complete cycle polar ring and non-complete cycle polar ring, and three's external diameter is identical and less than the main pole external diameter, material is the electrical pure iron of high magnetic permeability.Last bottom crown is with laterally yoke is parallel, and two-plate is parallel to each other and relatively, is furnished with the complete cycle polar ring that the cross section is the L type in its side near air gap, and one side of its L type is close to pole plate, and the barbed portion of L type is towards the inboard.In the side of complete cycle polar ring near air gap, being furnished with the cross section is the non-complete cycle polar ring of rectangle.The anchor ring of this non-complete cycle polar ring and complete cycle polar ring is close to, and arranges in the left-right symmetric face symmetria bilateralis of magnet main structure.In the horizontal section, be the center of circle with the center of main pole, the central angle of each non-complete cycle polar ring between 40 ° to 70 °, thickness complete cycle polar ring thickness 1/8th to 1/4th between.
Be connected by circumferential screw between polar ring and the pole plate, constituting outside surface is the pole plate group of cylinder.Wherein, the complete cycle polar ring is used to raise the close value of magnetic of air gap edge, non-complete cycle polar ring is used for further revising because the layout of vertical yoke causes both sides field weakening from the magnetic flux of perform region to the direction attraction of vertical yoke, thereby improves the uniformity coefficient in magnetic field in the air gap.
Embodiment one
In the present embodiment, the static magnetic field strength of magnetic resonance imaging perform region is 4000 Gausses, and the main pole material is a Nd-Fe-B rare-earth permanent magnet, and the remainder material of magnet is an electrical pure iron.The key dimension of magnet main structure is: height overall 1900mm, long 2800mm, wide 650mm, bee-line between two vertical yoke 1a, 1b is 1900mm, bee-line between two horizontal yoke 2a, 2b is 1100mm, up and down between polar ring apart from 450mm, perform region 10 sphere diameter 400mm, uniformity of magnetic field is less than 20ppm, and the magnet general assembly (TW) is less than 16 tons.
As shown in Figure 1, the outside drawing of the full-open permanent magnetism magnetic body for magnetic resonance image-forming that provides according to first embodiment of the invention is provided Fig. 1.Its upper and lower two horizontal yoke 2a, 2b are parallel to each other relatively, and left and right two vertical yoke 1a, 1b divide the far-end between two horizontal yoke 2a, 2b.
As shown in Figure 2, the front view of the full-open permanent magnetism magnetic body for magnetic resonance image-forming that provides according to first embodiment of the invention is provided Fig. 2.Wherein, laterally yoke 2a, 2b and vertical yoke 1a, 1b use four screw rod 7a, 7b (not drawing among the figure) to connect respectively by two taper bolt 8a, 8b (not drawing among the figure) location again.Four yokes constitute the full open model main structure jointly.Compare C type structure, the shear stress of superposed horizontal yoke inside is less relatively in this structure.When being subjected to the mechanical disturbance of equality strength, this kind structural vibrations is violent not as C type structure, has avoided to a certain extent because the vibration of physical construction causes magnetic field homogeneity destroyed.
As shown in Figure 3, the vertical view of the full-open permanent magnetism magnetic body for magnetic resonance image-forming that provides according to first embodiment of the invention is provided Fig. 3.The xsect of vertical yoke 1a, 1b is trapezoidal, and its narrow limit is towards full open model main structure inboard, and broadside is towards the full open model main structure outside.In the horizontal section, be the center of circle with the center of main pole, the vertical shared central angle of yoke is about 27 °, and this makes the openness in magnetic field increase, for patient's bed provides open relatively space.
The horizontal yoke 2a on top is identical with the horizontal yoke 2b structure of bottom, is the center symmetric arrangement with main structure horizontal symmetrical face, only one is described here.Laterally yoke 2a is left-right symmetric, front and back symmetrical structure, two far-ends are away from the side of vertical yoke 1a, 1b about it, it is upside, be cut into stepped, the ladder number is three, and from top to bottom the thickness of each ladder is respectively 3/8ths, 3/8ths and 1/4th of horizontal yoke 2a gross thickness; The length of each ladder is respectively a thirtieth and 1/15th of horizontal yoke 2a total length from outside to inside.
Laterally yoke 2a center section has been removed the part material away from the side of main pole 3a, and the horizontal yoke behind the removal material still keeps left-right symmetric, front and back symmetrical structure.From the front, laterally the upper surface of the yoke 2a center section surface of main pole one side (promptly away from) forms a recessed platform 12a after removing the part material, its left and right directions minimum length is about 1/5th of main pole 3a external diameter, and it connects horizontal yoke 2a at fore-and-aft direction.Platform 12a is about 1/2nd of horizontal yoke 2a total thickness with the vertical distance of horizontal yoke 2a end face.Laterally the upper surface of the yoke 2a surface of main pole one side (promptly away from) by removing material, respectively forms three plane 13a, 13b, 13c and 13a ', 13b ', 13c ' in the both sides of platform 12a.Wherein, the intersection of the intersection of plane 13b and plane 11a and plane 13b ' and plane 11a ' all is parallel to the bilateral symmetry plane of main structure, also is parallel to the pole-face of main pole 3a.Distance between these two intersections is about 4/5ths of main pole 3a external diameter.The intersection of plane 13a, 13c, 13a ', 13c ' and platform 12a is 15 ° with the angle of the bilateral symmetry plane of main structure all.As shown in Figure 1.
The horizontal yoke 2a on top has parallel with it pole plate group near a side of air gap, and the top crown group links to each other with horizontal yoke 2a by screw 5a.The top crown group comprises pole plate 4a, complete cycle polar ring 6a and non-complete cycle polar ring 9a, and three's external diameter is identical.
The structure of bottom crown group is identical with the top crown group, as Fig. 4 and shown in Figure 5.The following main pole that provides according to first embodiment of the invention and the sectional view of bottom crown group are provided Fig. 4, and the outside drawing of the bottom crown group that provides according to first embodiment of the invention is provided Fig. 5.
Upper and lower pole plate group is parallel to each other and relatively.Near a side of air gap the cross section being arranged at pole plate 4a is the complete cycle polar ring 6a of " L " type, and one side of its " L " type is close to pole plate 4a, and the barbed portion of " L " type is towards the inboard.Complete cycle polar ring 6a is connected with pole plate 4a by screw.In the side of complete cycle polar ring 6a near air gap, being furnished with the cross section is the non-complete cycle polar ring 9a of rectangle, is connected with the complete cycle polar ring by screw.Non-complete cycle polar ring 9a arranges that in the left-right symmetric face symmetria bilateralis of magnet main structure the anchor ring of this non-complete cycle polar ring 9a and complete cycle polar ring 6a is close to, as shown in Figure 3.In the horizontal section, be the center of circle with the center of main pole, the central angle alpha of each non-complete cycle polar ring is 60 °, thickness is about 1/8th of complete cycle polar ring.The effect of complete cycle polar ring 6a is to raise the close value of the magnetic of air gap edge, non-complete cycle polar ring 9a then further revises because vertical yoke 1a, 1b cause both sides field weakening from the magnetic flux of perform region 10 to the direction attraction of vertical yoke, thereby improves the uniformity coefficient in magnetic field in the air gap.
Main pole 3a profile is cylindrical, is arranged between horizontal yoke 2a and the pole plate 4a.Main pole 3a is by bonding the forming of numerous Nd-Fe-B rare-earth permanent magnet magnetic patch groups (not drawing among the figure).Each magnetic patch group is built and is bonded together along the main pole short transverse by the identical little magnetic patch of one pile of xsect, and the height of magnetic patch group equals the vertical distance between horizontal yoke 2a and the pole plate 4a.Magnetic patch group near main pole 3a center section is the square-section, and the magnetic patch group of close main pole 3a circumferential section then is the cross section of sector crosssection or other shapes.
As shown in Figure 6, the full-open permanent magnetism magnetic body for magnetic resonance image-forming magnetic flux synoptic diagram of Fig. 6 for providing according to first embodiment of the invention.The magnetic circuit of present embodiment is closed, and 10 the polarity of the magnetic field points upwards in the perform region is used for imaging.Magnetic flux passes through top crown 4a successively, goes up main pole 3a, then divide left and right two-way through upper lateral yoke 2a, vertical yoke 1a, 1b and lower, transverse yoke 2b, be pooled to down main pole 3b again, get back to perform region 10, form the magnetic structure of a closure through bottom crown 4b.
Because magnet is symmetrical structure, (a) only described the field flux distribution situation of right-hand part among Fig. 6, and its left side is symmetry with it.When not removing the part material of horizontal yoke 2a, (b) describes in the distribution situation such as Fig. 6 of its interior flux.When not removing material, laterally the center section of yoke 2a is more sparse away from the side magnetic flux of main pole 3a as can be seen, and after clipping the material of this part, magnetic flux is then inner concentrated to yoke.Laterally the right-hand member of yoke 2a is not cut into when stepped, the magnetic flux of its end is more sparse, and some magnetic flux has arrived extraneous space via the side of horizontal yoke 2a, cause unnecessary flux loss, and be cut under the stair-stepping situation, magnetic flux is then inner concentrated to yoke, and has reduced unnecessary flux loss.As can be seen, after removing through the part material, the field flux distribution of yoke inside is more reasonable, has utilized the magnetic property of yoke more fully, and has alleviated the weight of yoke to a certain extent.
Embodiment two
In the present embodiment, describe with reference to Fig. 7 and Fig. 8.Wherein, the outside drawing of the full-open permanent magnetism magnetic body for magnetic resonance image-forming that provides according to second embodiment of the invention is provided Fig. 7, and the front view of the full-open permanent magnetism magnetic body for magnetic resonance image-forming that provides according to second embodiment of the invention is provided Fig. 8.Concrete magnet structure and embodiment one are similar, only the first half are illustrated here.
Two far-ends are away from the side of vertical yoke 1a, 1b about horizontal yoke 2a, be upside, be cut into steppedly that the ladder number is three, the thickness of each ladder is 1/3rd of horizontal yoke 2a gross thickness, and the length of each ladder is 1/15th of horizontal yoke 2a total length.
Laterally yoke 2a has parallel with it pole plate group near a side of air gap, and the top crown group links to each other with horizontal yoke 2a by double-screw bolt 5a.The top crown group comprises pole plate 4a, complete cycle polar ring 6a and non-complete cycle polar ring 9a, and three's external diameter is identical.The structure of bottom crown group is identical with the top crown group, as Fig. 4 and shown in Figure 5.Upper and lower pole plate group is parallel to each other and relatively.Near a side of air gap the cross section being arranged at pole plate 4a is the complete cycle polar ring 6a of " L " type, and one side of its " L " type is close to pole plate 4a, and the barbed portion of " L " type is towards the inboard.Complete cycle polar ring 6a is connected with pole plate 4a by screw.In the side of complete cycle polar ring 6a near air gap, being furnished with the cross section is the non-complete cycle polar ring 9a of rectangle, is connected with the complete cycle polar ring by screw.This non-complete cycle polar ring 9a arranges that in the left-right symmetric face symmetria bilateralis of magnet main structure the anchor ring of this non-complete cycle polar ring 9a and complete cycle polar ring 6a is close to, as shown in Figure 3.In the horizontal section, be the center of circle with the center of main pole, the central angle alpha of each non-complete cycle polar ring is 50 °, thickness is about 1/4th of complete cycle polar ring.
Above-described specific embodiment; purpose of the present invention, technical scheme and beneficial effect are further described; institute is understood that; the above only is specific embodiments of the invention; be not limited to the present invention; within the spirit and principles in the present invention all, any modification of being made, be equal to replacement, improvement etc., all should be included within protection scope of the present invention.
Claims (9)
1. a full-open permanent magnetism magnetic body for magnetic resonance image-forming is characterized in that, this permanent-magnet comprises:
By two vertical yokes that are symmetrically arranged and two up and down the horizontal yoke of symmetric arrangement being of constituting flat wide hollow structure the full open model main structure, the air gap district of this permanent-magnet is positioned at the middle part of described full open model main structure;
Be positioned at up and down two horizontal yokes near air gap district one side and respectively with two two parallel relative main poles up and down that horizontal yoke links together up and down;
Be positioned at up and down two main poles near air gap district one side and respectively with two two groups of parallel relative last bottom crown groups up and down that main pole links together up and down;
Wherein, this full open model main structure sees from the front and is flat wide hollow, two parallel positioned opposite of horizontal yoke up and down, about two parallel positioned opposite of vertical yoke; Two horizontal yokes are left-right symmetric, front and back symmetry and laterally zygomorphic structure, and stepped construction is adopted in outside of two far-ends about it; From the front, laterally two ends, the yoke left and right sides become stepped away from a side of vertical yoke, the ladder number is three to four, and the thickness of each ladder is 1/4th to 1/3rd of horizontal yoke gross thickness, and the length of each ladder is a thirtieth to 1/15th of horizontal yoke total length.
2. full-open permanent magnetism magnetic body for magnetic resonance image-forming according to claim 1 is characterized in that, described two vertical yokes are clipped between two horizontal yokes, and is symmetrically arranged in the far-end of horizontal yoke; By the taper bolt location, be connected between vertical yoke and the horizontal yoke through screw rod.
3. full-open permanent magnetism magnetic body for magnetic resonance image-forming according to claim 1 and 2, it is characterized in that, described vertical yoke or horizontal yoke are forged to make by electrical pure iron and are formed, method to vertical yoke or horizontal yoke employing computer simulation design magnetic structure, magnetic flux density is than the material of lower part in the removal yoke, do not cause under the saturated prerequisite of material magnetic flux satisfied, make magnetic flux inner concentrated, alleviate the general assembly (TW) of yoke to yoke.
4. full-open permanent magnetism magnetic body for magnetic resonance image-forming according to claim 1, it is characterized in that, described two horizontal yoke center sections have been removed the part material away from a side of main pole, and the horizontal yoke behind the removal material still keeps left-right symmetric, front and back symmetrical structure; From the front, do not consider the staircase structure of horizontal yoke two far-ends, laterally the center section thickness minimum of yoke, for total thickness 1/3rd to 2/3rds between, to two far-ends, its thickness increases gradually, until equating with total thickness from the center section of horizontal yoke;
The center section of horizontal yoke behind the described removal material connects horizontal yoke on its fore-and-aft direction, be of a size of 2/3rds of main pole external diameter on left and right directions.
5. full-open permanent magnetism magnetic body for magnetic resonance image-forming according to claim 4, it is characterized in that, the described center section of having removed the horizontal yoke of part material, from the front, its surface away from main pole one side forms a recessed platform, its left and right directions minimum length is 1/5th of a main pole external diameter, and it connects horizontal yoke at fore-and-aft direction; Described platform is 1/2nd of a horizontal yoke gross thickness with the vertical distance of horizontal yoke end face; Laterally yoke by removing material, respectively forms three planes in the both sides of platform away from the surface of main pole one side.
6. full-open permanent magnetism magnetic body for magnetic resonance image-forming according to claim 4, it is characterized in that, the described center section of having removed the horizontal yoke of part material, from the front, its surface away from main pole one side forms trapezoidal depression, and its inboard base is shorter, and length is 1/5th of main pole external diameter, base, outside length is 4/5ths of main pole external diameter, and trapezoidal height is 1/2nd of a horizontal yoke total thickness; The removal of described ladder material has formed three facets at the upper surface of horizontal yoke.
7. full-open permanent magnetism magnetic body for magnetic resonance image-forming according to claim 1 is characterized in that, the xsect of described vertical yoke is trapezoidal, and narrow limit is towards the inboard of described full open model main structure, and broadside is towards the outside of full open model main structure.
8. full-open permanent magnetism magnetic body for magnetic resonance image-forming according to claim 1 is characterized in that, described main pole profile is cylindrical, is arranged between horizontal yoke and the pole plate, by bonding the forming of numerous Nd-Fe-B rare-earth permanent magnet magnetic patch groups;
Described Nd-Fe-B rare-earth permanent magnet magnetic patch group is built and is bonded together along the main pole short transverse by the identical little magnetic patch of one pile of xsect, and the height of magnetic patch group equals the vertical distance between horizontal yoke and the pole plate;
Magnetic patch group near the main pole center section in the described Nd-Fe-B rare-earth permanent magnet magnetic patch group is the square-section, and the magnetic patch group of close main pole circumferential section then is the cross section of sector crosssection or other shapes.
9. full-open permanent magnetism magnetic body for magnetic resonance image-forming according to claim 1 is characterized in that, described go up the bottom crown group by screw respectively with up and down laterally yoke is connected, the screw of described connection pole plate group and horizontal yoke passes main pole;
The described bottom crown group that goes up all comprises pole plate, complete cycle polar ring and non-complete cycle polar ring, and three's external diameter is identical and less than the main pole external diameter, material is the electrical pure iron of high magnetic permeability;
Last bottom crown is with laterally yoke is parallel, and two-plate is parallel to each other and relatively, is furnished with the complete cycle polar ring that the cross section is the L type in its side near air gap, and one side of its L type is close to pole plate, and the barbed portion of L type is towards the inboard;
In the side of complete cycle polar ring near air gap, being furnished with the cross section is the non-complete cycle polar ring of rectangle; The anchor ring of this non-complete cycle polar ring and complete cycle polar ring is close to, and arranges in the left-right symmetric face symmetria bilateralis of magnet main structure; In the horizontal section, be the center of circle with the center of main pole, the shared central angle of each non-complete cycle polar ring between 40 ° to 70 °, thickness complete cycle polar ring thickness 1/8th to 1/4th between;
Be connected by circumferential screw between described polar ring and the pole plate, constituting outside surface is the pole plate group of cylinder; Wherein, the complete cycle polar ring is used to raise the close value of magnetic of air gap edge, non-complete cycle polar ring be used for further revising since the layout of vertical yoke with the magnetic flux of perform region to the both sides field weakening that the direction attraction of vertical yoke causes, improve the uniformity coefficient in magnetic field in the air gap.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102680925B (en) * | 2011-03-17 | 2015-04-08 | 上海爱立峰医疗科技有限公司 | 360-degree-open magnet for permanent magnet type medical magnetic resonance imaging system |
| CN102677918A (en) * | 2011-03-17 | 2012-09-19 | 上海爱立峰医疗科技有限公司 | Integral magnetic resonance medical treatment room |
| CN103860178B (en) * | 2014-03-21 | 2016-04-06 | 沈阳中北真空磁电科技有限公司 | A kind of permanent magnet for nuclear magnetic resonance imaging instrument |
| CN103892834B (en) * | 2014-03-21 | 2016-05-25 | 沈阳中北真空磁电科技有限公司 | A kind of permanent magnet for NMR imaging instrument |
| CN105761874A (en) * | 2016-04-22 | 2016-07-13 | 北京理工大学 | Uniform magnetic field device for measuring speed of explosive detonation product particles |
| CN107515525B (en) * | 2017-09-12 | 2023-04-25 | 飞亚达精密科技股份有限公司 | Antimagnetic performance testing device and magnetizing structure thereof |
| CN108303663B (en) * | 2018-01-23 | 2020-07-03 | 山东迈格尼医疗科技有限公司 | Double-air-gap open type magnetic resonance imaging magnet |
| CN109870665A (en) * | 2019-01-31 | 2019-06-11 | 佛山瑞加图医疗科技有限公司 | Permanent magnetic field generating device, assemble method and MR imaging apparatus |
| CN109872859A (en) * | 2019-01-31 | 2019-06-11 | 佛山瑞加图医疗科技有限公司 | Magnet apparatus and MR imaging apparatus |
| CN110411546A (en) * | 2019-07-30 | 2019-11-05 | 北京华特克林科技有限公司 | A kind of check weighing vibrating string type sensor |
| CN114184990B (en) * | 2021-11-29 | 2024-01-05 | 深圳航天科技创新研究院 | Magnet for magnetic resonance imaging and method for optimizing iron yoke |
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| CN201017740Y (en) * | 2006-11-22 | 2008-02-06 | 北京万东医疗装备股份有限公司 | Permanent magnetism magnetic body for full open type magnetic resonance image-forming |
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