CN100485829C - Permanent magnet, magnet device for MRI comprising the permanent magnet, and method for fabricating same - Google Patents
Permanent magnet, magnet device for MRI comprising the permanent magnet, and method for fabricating same Download PDFInfo
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- CN100485829C CN100485829C CNB2006100572913A CN200610057291A CN100485829C CN 100485829 C CN100485829 C CN 100485829C CN B2006100572913 A CNB2006100572913 A CN B2006100572913A CN 200610057291 A CN200610057291 A CN 200610057291A CN 100485829 C CN100485829 C CN 100485829C
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Abstract
The invention discloses a permanent magnet and forming method of MRI magnetic device, which contains column of permanent magnetic material, wherein the column is distributed into magnetic core and magnetic case along radial direction on the same axle; the magnetic core is suited on the magnetic case, whose magnetic direction is axial; the magnetic direction of magnetic case is axial from one end of column of paralleling magnetic direction to the other end of vertical magnetic direction step by step. The invention can produce working field strength over 0.5-0.6 tesla for MRI.
Description
Technical field
The invention relates to a kind of permanent-magnet and the MRI magnet apparatus that comprises this magnet, and the manufacture method of this permanent-magnet and MRI usefulness magnet apparatus.
Background technology
MRI (magnetic resonance imager) is the medical imaging diagnostic device that begins to enter the practical stage 1980s, is current one of the state-of-the-art clinical diagnostic imaging equipment of early-stage cancer and other multiple diseases of finding and diagnose.The operation principle of MRI is: human body is placed the magnetic field of particular design, use the hydrogen nuclei in the radio-frequency (RF) magnetic field pulse excitation human body then, cause hydrogen nuclei resonance, and absorb energy; After stopping radio-frequency pulse, hydrogen nuclei sends the radio signal by characteristic frequency, and the energy that absorbs is discharged, and is included by the receiver that human body is outer, handles obtaining image through electronic computer.
Critical piece among the MRI is the magnet apparatus that is used to produce space magnetic field.In order to obtain clear real image, the patient is accurately diagnosed the working area field that MRI requires magnet apparatus wherein can produce even distribution, have enough field intensity.
MRI can be divided into high field pattern (the service area field intensity is more than 3 teslas), middle field pattern (the service area field intensity is 1 ± 0.5 tesla) and low field pattern (the service area field intensity is 0.4 tesla and following) usually according to function and picture quality.The service area field intensity is high more, and the signal to noise ratio of signal is just high more, and it is more clear just to obtain, and comprises the more image of abundant information.Therefore, compare with low field pattern MRI, high field pattern and middle field pattern MRI have very big advantage.
At present, MRI has superconducting magnet and permanent-magnet with the magnet that often uses in the magnet apparatus.The magnetic field that superconducting magnet produces is stronger, but its manufacturing cost is very expensive, and complex structure, so not only price height, operating cost and maintenance cost are also high for the MRI of use superconducting magnet.Use the MRI of permanent-magnet not have these shortcomings, but work magnetic field must improve, so that its overall performance is close to superconducting MRI.
Fig. 1 is the schematic diagram of the MRI of use permanent-magnet of the prior art with magnet apparatus, and Fig. 2 a to Fig. 2 d then shows the external shape of the permanent-magnet that uses among Fig. 1.
As shown in Figure 1, the MRI of existing use permanent-magnet comprises yoke 1, last permanent-magnet 2, following permanent-magnet 3, goes up pole shoe 4 and following pole shoe 5 with magnet apparatus, wherein go up permanent-magnet 2 and following permanent-magnet 3 and be connected to the two ends up and down of yoke 1 and opposed up and down, last pole shoe 4 and following pole shoe 5 are separately positioned on the end face of permanent-magnet 2 and following permanent-magnet 3, have air gap 6 between last pole shoe 4 and following pole shoe 5.Among Fig. 1, the arrow in the last permanent-magnet 2 (perhaps descending permanent-magnet 3) is represented the direction of magnetization of this magnet, and the arrow in the air gap 6 is represented the working area field direction that produces.
Shown in Fig. 2 a to Fig. 2 d, use in the magnet apparatus at existing MRI, permanent-magnet 2 is the one-piece type cylinder body shapes that are made of the identical permanent magnetic material of the direction of magnetization, for example cylindrical, hollow cylindrical, polygon prismatic, hollow is polygon prismatic, the direction of magnetization of permanent magnetic material and the parallel axes of cylinder are shown in the arrow in each permanent-magnet 2.
MRI magnet apparatus shown in above-mentioned Fig. 1 is open C-shape structure.In addition, also has the MRI magnet apparatus of other structure in the prior art, for example four-column type structure, two pole structures etc.Above-mentioned MRI can be with reference to IEEE TRANSACTIONS OF APPLIEDSUPERCONDUCTIVITY with magnet apparatus, VOL.14, NO.2, JUNE 2004, perhaps the content of the MAGNETIC RESONANCEIMAGING chapter 1 1.3.1 of the second edition of being write by M.T.Vlaardingerbroek and J.A.den Boer joint.
In the prior art, MRI has only 0.4 tesla and following with the service area field intensity of magnet apparatus, so this MRI is low field pattern, the MRI of middle field pattern and high field pattern generally will use superconducting magnet.Therefore, though permanent-magnet MRI low price, open good, use the MRI structure of permanent-magnet also simple relatively, but the field intensity in the magnetic field that is produced by permanent-magnet is on the low side, if produce bigger working area field intensity, then need to use the permanent magnetism magnetic material of excess, make permanent-magnet and comprise that the MRI of this permanent-magnet is very heavy.For example, if reach the standard that the service area field intensity is the middle field pattern MRI of 1 ± 0.5 tesla, need the permanent-magnet of 6～12 tons of weight.Therefore, in the prior art, still do not use the middle field pattern MRI of permanent-magnet.Because the service area field intensity of the MRI of existing use permanent-magnet is lower, therefore, the signal to noise ratio of signal is low, can not move high-speed plus series, therefore compares with superconducting MRI, and image definition is not enough, and information category that obtains and content are also few.
In addition, permanent-magnet and the magnet apparatus that is used for MRI put down in writing at many pieces of patent documentations.For example: CN 1116311A discloses a kind of field generator for magnetic that is used for MR imaging apparatus; CN2404130Y discloses a kind of magnet apparatus that is used for magnetic resonance imaging system; CN 2430698Y discloses a kind of C type magnetic resonance imaging permanent-magnet that does not have blocking magnetic pole; CN 1371000A discloses a kind of completely opened magnetic resonant imaging instrument; CN 1400473A discloses a kind of magnetic resonance imaging system permanent magnet assembly; CN 2542225Y discloses a kind of two column open C type permanent-magnet type magnetic resonance magnets; CN1491613A discloses a kind of assembly method of magnetic part of the magnetic field generation device that is used for magnetic resonance imaging; CN 1588582A discloses a kind of thin slice shape magnetic field completely opened magnetic resonant imaging instrument master magnet.
Yet, the same with MRI shown in Figure 1, the disclosed permanent-magnet of above-mentioned document or comprise that also there is the lower shortcoming of service area field intensity in the magnetic imaging instrument of permanent-magnet, the service area field intensity has only 0.4 tesla and following, in can not being applied to field pattern MRI or do not belong in field pattern MRI.Therefore, keeping that openness is constant, under the prerequisite that magnetic material use quantity and magnet key dimension and total weight are constant, how to improve the magnetic field intensity of permanent-magnet, obtaining having more, the permanent magnetism MRI magnet of high workload district field intensity becomes the difficult problem in this area.
Summary of the invention
First purpose of the present invention provides a kind of permanent-magnet that can produce strong service area field intensity.
Second purpose of the present invention provides a kind of MRI magnet apparatus that comprises this permanent-magnet with strong service area field intensity.
The 3rd purpose of the present invention provides a kind of manufacture method of permanent-magnet.
The 4th purpose of the present invention provides a kind of formation method of using the MRI of permanent-magnet with magnet apparatus.
According to a first aspect of the invention, permanent-magnet provided by the invention comprises the cylinder that is made of permanent magnetic material, and wherein, described cylinder radially is divided into magnetic core and magnetosheath, and magnetic core and magnetosheath are coaxial, and magnetic core is sleeved in the magnetosheath; The direction of magnetization of described magnetic core is axially, and the direction of magnetization of described magnetosheath is for being stepwise change from the end direction parallel with the direction of magnetization of magnetic core to the other end direction vertical with the direction of magnetization of magnetic core axially along cylinder.
According to a second aspect of the invention, the MRI magnet apparatus of use permanent-magnet provided by the invention, comprise yoke, go up permanent-magnet and following permanent-magnet and go up pole shoe and following pole shoe, wherein: go up permanent-magnet and comprise the cylinder that constitutes by permanent magnetic material, wherein, described cylinder radially is divided into magnetic core and magnetosheath, and magnetic core and magnetosheath are coaxial, and magnetic core is sleeved in the magnetosheath; The direction of magnetization of described magnetosheath is stepwise change from the end direction parallel with the direction of magnetization of magnetic core to the other end direction vertical with the direction of magnetization of magnetic core axially along cylinder, and the direction of magnetization of magnetosheath upper end is that axially the direction of magnetization of lower end is for radially inside; Following permanent-magnet comprises the cylinder that is made of permanent magnetic material, and wherein, described cylinder radially is divided into magnetic core and magnetosheath, and magnetic core and magnetosheath are coaxial, and magnetic core is sleeved in the magnetosheath; The direction of magnetization of described magnetosheath is for being stepwise change from the end direction parallel with the direction of magnetization of magnetic core to the other end direction vertical with the direction of magnetization of magnetic core axially along cylinder, and the direction of magnetization of magnetosheath upper end is for radially outward, and the direction of magnetization of lower end is axial.
According to a third aspect of the present invention, the invention provides a kind of manufacture method of permanent-magnet, this method comprises: forming the direction of magnetization is axial magnetic core; Form magnetosheath; And magnetic core closely is sleeved in this magnetosheath, the direction of magnetization that makes described magnetosheath is stepwise change from the end direction parallel with the direction of magnetization of magnetic core to the other end direction vertical with the direction of magnetization of magnetic core axially along cylinder.
According to a fourth aspect of the present invention, the invention provides a kind of formation method of using the MRI of permanent-magnet with magnet apparatus, this magnet apparatus comprises yoke, last permanent-magnet and following permanent-magnet, and last pole shoe and following pole shoe, wherein: the described formation method that goes up permanent-magnet comprises that forming the direction of magnetization is axial downward magnetic core, form magnetosheath, and magnetic core closely is sleeved in this magnetosheath, making the direction of magnetization of described magnetosheath is stepwise change from the end direction parallel with the direction of magnetization of magnetic core to the other end direction vertical with the direction of magnetization of magnetic core along the axial of cylinder, the direction of magnetization of magnetosheath upper end is that the direction of magnetization of lower end is for radially inside axially downwards; And the described formation method of permanent-magnet down comprises that forming the direction of magnetization is axial downward magnetic core, form magnetosheath, and magnetic core closely is sleeved in this magnetosheath, making the direction of magnetization of described magnetosheath is stepwise change from the end direction parallel with the direction of magnetization of magnetic core to the other end direction vertical with the direction of magnetization of magnetic core along the axial of cylinder, the direction of magnetization of magnetosheath upper end is for radially outward, and the direction of magnetization of lower end is axially downwards.
The described pole shoe of going up radially is divided into pole piece and utmost point cover, and pole piece and utmost point cover are coaxial, and pole piece closely is sleeved in the utmost point cover; The direction of magnetization of utmost point cover is radially inside; Described pole shoe down radially is divided into pole piece and utmost point cover, and pole piece and utmost point cover are coaxial, and pole piece is sleeved in the utmost point cover; The direction of magnetization of utmost point cover radially outward.
Therefore, by technique scheme of the present invention, permanent-magnet of the present invention is compared with existing permanent-magnet, under situation, can provide higher field intensity with essentially identical size and shape, maximally utilise the potential of permanent-magnet, therefore, the service area field intensity that permanent-magnet is provided reaches more than 0.5～0.6 tesla, permanent-magnet can be applied among the middle field pattern MRI.
Description of drawings
Fig. 1 uses the schematic diagram of the MRI of permanent-magnet with magnet apparatus in the prior art;
Fig. 2 a to Fig. 2 d is the external shape of the permanent-magnet of use in the displayed map 1;
Fig. 3 a to Fig. 3 d is the external shape that shows permanent-magnet of the present invention;
Fig. 3 e to Figure 31 is the generalized section that shows permanent-magnet of the present invention, wherein shows the direction of magnetization of permanent-magnet;
Fig. 4 a to Fig. 4 d is the external shape that shows the permanent-magnet of first embodiment of the invention;
Fig. 4 e is the generalized section that shows the permanent-magnet of first embodiment of the invention, wherein shows the direction of magnetization;
Fig. 5 a to Fig. 5 d is the external shape that shows the permanent-magnet of second embodiment of the invention;
Fig. 5 e is the schematic diagram that shows a string magnetic lobe in the permanent-magnet of second embodiment of the invention, wherein shows the direction of magnetization;
Fig. 6 is the schematic diagram of MRI of the present invention with magnet apparatus, has wherein used permanent-magnet of the present invention;
Fig. 7 a and Fig. 7 b are the schematic diagrames of a kind of execution mode of used pole shoe among Fig. 6;
Fig. 8 is the schematic diagram of the another kind of execution mode of used pole shoe among Fig. 6.
Description of reference numerals
1 yoke
Permanent-magnet on 2
3 times permanent-magnets
Pole shoe on 4
5 times pole shoes
6 air gaps
21,31 magnetic cores
22,32 magnetosheaths
210,310 through holes
221,321 magnetospheres
222,322 magnetic lobes
41,51 pole pieces
42,52 utmost point covers
420,520 magnetic lobes
Embodiment
Describe principle of the present invention and illustrative embodiments with reference to the accompanying drawings in detail.
According to a first aspect of the invention, extremely shown in Figure 31 as Fig. 3 a, the invention provides a kind of permanent-magnet, this permanent-magnet comprises the cylinder that is made of permanent magnetic material, wherein, described cylinder radially is divided into magnetic core 21 and magnetosheath 22, and magnetic core 21 and magnetosheath 22 are coaxial, and magnetic core 21 is sleeved in the magnetosheath 22; The direction of magnetization of described magnetic core 21 is axially, and the direction of magnetization of described magnetosheath 22 is for being stepwise change from the end direction parallel with the direction of magnetization of magnetic core 21 to the other end direction vertical with the direction of magnetization of magnetic core 21 axially along cylinder.
Fig. 3 e to Figure 31 has shown the multiple arrangement form of magnetic core 21 and magnetosheath 22 direction of magnetizations in the permanent-magnet of the present invention respectively, and wherein dotted arrow is represented the direction of magnetization of magnetic core 21, and solid arrow is represented the direction of magnetization of magnetosheath 22.
In Fig. 3 e to Fig. 3 h, the direction of magnetization of magnetic core 21 is identical with the direction of magnetization of magnetosheath 22 1 ends.As shown in the figure, the direction of magnetization of magnetic core 21 is axially downwards, and the direction of magnetization of magnetosheath 22 1 ends is all axially downwards, and the direction of magnetization of the other end is for radially.The direction of magnetization of magnetosheath 22 from an end axially down to the other end radially between present stepwise change.
In Fig. 3 g to Fig. 3 h, the direction of magnetization of magnetic core 21 is opposite with the direction of magnetization of magnetosheath 22 1 ends.As shown in the figure, the direction of magnetization of magnetic core 21 is axially downwards, and the direction of magnetization of magnetosheath 22 1 ends is all axially upwards, and the direction of magnetization of the other end is for radially.The direction of magnetization of magnetosheath 22 from an end axially upward to the other end radially between present stepwise change.
To shown in Figure 31, can also have multiple arrangement between the direction of magnetization of the direction of magnetization of magnetic core 21 and magnetosheath 22 as Fig. 3 e.
Shown in Fig. 3 e, the direction of magnetization of magnetic core 21 is that wherein Z represents the axis of magnetic core axially downwards.The direction of magnetization of magnetosheath 22 upper ends is that the direction of magnetization of lower end is for radially outward axially downwards.The direction of magnetization of magnetosheath 22 changes for stepping from top to bottom.That is, the direction of magnetization of magnetosheath upper end is axially downwards, and the direction of magnetization of any is for outside a little downwards from the magnetosheath upper end then, and the direction of magnetization of any is more outside downwards again, and when arriving the magnetosheath lower end at last, the direction of magnetization is changed into radially outward fully.The direction of magnetization of magnetosheath 22 from the upper end axially down to the lower end radially outward between be stepping change, i.e. transition gradually.
Shown in Fig. 3 f, the permanent-magnet among permanent-magnet and Fig. 3 e is basic identical, and difference only is the direction of magnetization of magnetosheath 22 lower ends for radially inside, and promptly the direction of magnetization of magnetosheath 22 is from axially downward the radially inside of lower end of changing into gradually of upper end.
Shown in Fig. 3 g, permanent-magnet among permanent-magnet and Fig. 3 e is basic identical, difference only is that the reversal of magnetism of magnetosheath 22 upper ends is for radially outward, the direction of magnetization of lower end then is axially downwards, promptly the direction of magnetization of magnetosheath 22 from the upper end radially outward change into gradually the lower end axially downwards.
Shown in Fig. 3 h, the permanent-magnet among permanent-magnet and Fig. 3 g is basic identical, and difference only is the direction of magnetization of magnetosheath 22 upper ends for radially inside, and promptly the direction of magnetization of magnetosheath 22 is from radially inside the axially downward of lower end of changing into gradually of upper end.
Fig. 3 i is basic identical to permanent-magnet and the permanent-magnet shown in Fig. 3 e to Fig. 3 h shown in Figure 31, and difference only is that magnetosheath 22 1 ends are that the axial direction of magnetization is opposite with the axial direction of magnetization of magnetic core 21.That is, if the direction of magnetization of magnetic core 21 is axially downwards, then magnetosheath 22 1 ends are that the axial direction of magnetization then makes progress for axial.
The shape of magnetic core 21 of the present invention and magnetosheath 22 is not particularly limited, magnetic core 21 can be that regular shape also can be irregularly shaped, is erose other cylinders as cylinder, hollow circular cylinder, polygon prism, equilateral polygon prism, the polygon prism of hollow, the equilateral polygon prism of hollow, oval cylinder or cross section.Magnetosheath 22 can be that regular shape also can be irregularly shaped, as cylindrical sleeves, polygon prismatic sleeve, equilateral polygon prismatic sleeve, cylindroid sleeve or irregular other cylinder sleeve of shape of cross section.Fig. 3 a to Fig. 3 d has exemplarily provided the profile of several permanent-magnets of the present invention.
Shown in Fig. 3 a, magnetic core 21 forms cylinder, and magnetosheath 22 forms cylinder, and magnetic core 21 is sleeved in the magnetosheath 22.In order clearly to show, show the gap between magnetic core 21 and the magnetosheath 22 in the drawings, but in actual product, magnetic core 21 generally is very closely to be sleeved in the magnetosheath 22.
Shown in Fig. 3 b, the permanent-magnet difference among permanent-magnet and Fig. 3 a only is that magnetic core 21 forms hollow circular cylinder, and promptly the center of magnetic core 21 is formed with the through hole 210 of axial perforation.
Shown in Fig. 3 c, magnetic core 21 forms polygon prism, and magnetosheath 22 also forms polygon prismatic sleeve, and magnetic core 21 very relevantly is sleeved in the magnetosheath 22.
Shown in Fig. 3 d, the permanent-magnet difference among permanent-magnet and Fig. 3 c only is that magnetic core 21 centers are formed with the through hole 210 of axial perforation.
Shown in Fig. 3 c and 3d, described polygon prism and/or polygon prismatic sleeve can be equilateral polygon prism and/or equilateral polygon prismatic sleeve.
In addition, the outer cylinder of the outer cylinder of magnetic core 21 and magnetosheath 22 can be of similar shape (shown in Fig. 3 a to Fig. 3 d), also can have different shape (not shown)s, for example magnetic core 21 is a cylinder, the inner cylinder of magnetosheath 22 is cylindrical, but outer cylinder can be for polygon prismatic or oval, or the like.Those skilled in the art can be used in combination the magnetic core and the magnetosheath of existing any cylinder body shape as required.
According to the present invention, magnetic core 21 can use identical or different permanent magnetic material manufacturings with magnetosheath 22.Permanent magnetic material can be selected existing any permanent magnetic material for use, for example sintered NdFeB, bonding rare earth permanent magnet, Rare-Earth Cobalt, permanent magnetic ferrites etc.
In order to optimize the performance of permanent-magnet, the size of described magnetic core and magnetosheath preferably can satisfy following conditions, and for example: the diameter of described magnetic core can be 1 to 5 with the ratio of height, is preferably 3.4 to 4; The thickness of described magnetosheath can be 10% to 80%, is preferably 50% to 55%; The thickness of described magnetosheath is 0.05 to 2 with the ratio of height, is preferably 1.5 to 1.7.
A preferred embodiment of the invention, magnetosheath 22 can comprise a plurality of magnetospheres 221 in the axial direction, shown in Fig. 4 a to Fig. 4 d.By this structure, can realize easily that the axial magnetized direction of magnetosheath 22 upper ends changes into the diametrical magnetization direction of magnetosheath 22 lower ends gradually, the stepping that promptly realizes the direction of magnetization of magnetosheath 22 changes, and (comprise that some layer thickness is zero by each magnetosphere being elected as different-thickness, and use different magnetic materials, the step-length of control step.
As shown in the figure, each magnetosphere 221 forms annular cover, and promptly magnetosphere 221 is to be formed by the plane cutting perpendicular to a series of illusions of magnetic core 21 axis.Can have identical size between each magnetosphere 221 in the magnetosheath 22, also can have different sizes, promptly each magnetosphere 221 height each other can equate, also can be different.The thickness of some magnetosphere can be taken as zero under some situation.
The present invention does not have special requirement for size, quantity and the material of the magnetosphere in the magnetosheath 22 221.For example, the height of each magnetosphere can be 0%～30% of magnetosheath height, is preferably 10% to 20%; The quantity of magnetosphere can be 1 to 10, is preferably 5 to 6; The material of each magnetosphere can mutually the samely also can differ from one another, and can be selected from sintered NdFeB, bonded rare earth permanent magnetic, Rare-Earth Cobalt, permanent magnetic ferrites etc.
Fig. 4 e schematically shows the profile of a kind of permanent-magnet of the present invention, and wherein dotted arrow is represented the direction of magnetization of magnetic core 21, and solid arrow is represented the direction of magnetization of each magnetosphere 221.
Shown in Fig. 4 e, each magnetosphere 221 has the direction of magnetization separately, and from topmost magnetosphere to bottom magnetosphere, the direction of magnetization is that stepping changes.Therefore, stack together up and down in order, just can realize easily that the stepping of magnetosheath 22 from the direction of magnetization of upper end to the direction of magnetization of lower end changes by the magnetosphere 221 that will have the different direction of magnetizations.
According to another kind of preferred implementation of the present invention, each magnetosphere 221 of described magnetosheath 22 can also upwards comprise a plurality of magnetic lobes 222 week, shown in Fig. 5 a to Fig. 5 d, thereby further facilitate the diametrical magnetization direction that the axial magnetized direction that realizes magnetosheath 22 upper ends is changed into magnetosheath 22 lower ends gradually, realize that promptly the stepping of the direction of magnetization of magnetosheath 22 changes.
As shown in the figure, described each magnetic lobe 222 is to be formed by a series of plane cutting through magnetic core 21 axis.Magnetic lobe 222 in each magnetosphere 221 can have identical size, also can have different sizes, and all the magnetic lobes 222 in all magnetospheres 221 also can have identical size or different sizes.
The present invention does not have special requirement for size, quantity and the material of magnetic lobe 222.For example, the magnetic lobe quantity of each magnetosphere can be 16 to 64, is preferably 16 to 32; Can align in the axial direction between the magnetic lobe of each magnetosphere to arrange and also can not line up arrangement; The material of each magnetic lobe can mutually the samely also can differ from one another.
Fig. 5 e schematically shows the row longitudinal flux lobe 222 in the magnetosheath 22, and wherein Z represents the axis of permanent-magnet, and dotted arrow is represented the direction of magnetization of magnetic core, and solid arrow is represented the direction of magnetization of magnetic lobe 222.Each magnetic lobe 222 has unique separately direction of magnetization.Each magnetic lobe is stacked together up and down in order, can realize of the stepping change of the direction of magnetization of a row magnetic lobe easily, thereby realize that easily magnetosheath 22 changes with respect to the stepping of the direction of magnetization of magnetic core 21 with respect to the direction of magnetization of magnetic core.
According to a second aspect of the invention, as shown in Figure 6, the invention provides a kind of MRI magnet apparatus, this magnet apparatus comprises yoke 1, last permanent-magnet 2, following permanent-magnet 3, goes up pole shoe 4 and following pole shoe 5, wherein:
Last permanent-magnet 2 comprises the cylinder that is made of permanent magnetic material, and wherein, described cylinder radially is divided into magnetic core 21 and magnetosheath 22, and magnetic core 21 and magnetosheath 22 are coaxial, and magnetic core 21 closely is sleeved in the magnetosheath 22; The direction of magnetization of described magnetic core 21 is axially downwards, the direction of magnetization of described magnetosheath 22 is stepwise change from the end direction parallel with the direction of magnetization of magnetic core 21 to the other end direction vertical with the direction of magnetization of magnetic core 21 axially along cylinder, the direction of magnetization of magnetosheath 22 upper ends is that the direction of magnetization of lower end is for radially inside axially downwards;
Following permanent-magnet 3 comprises the cylinder that is made of permanent magnetic material, and wherein, described cylinder radially is divided into magnetic core 31 and magnetosheath 32, and magnetic core 31 and magnetosheath 32 are coaxial, and magnetic core 31 closely is sleeved in the magnetosheath 32; The direction of magnetization of described magnetic core 31 is axially downwards, the direction of magnetization of described magnetosheath 32 is stepwise change from the end direction parallel with the direction of magnetization of magnetic core 31 to the other end direction vertical with the direction of magnetization of magnetic core 31 axially along cylinder, the direction of magnetization of magnetosheath 32 upper ends is for radially outward, and the direction of magnetization of lower end is axially downwards.
MRI magnet apparatus shown in Figure 6 is a kind of execution mode of MRI provided by the invention with magnet apparatus, and this device is the improvement on the basis of magnet apparatus shown in Figure 1, and improvements have been to utilize the above-mentioned permanent-magnet of the present invention.
Need to prove in addition, shown in Figure 1 only is the structure that a kind of MRI relatively more commonly used of the prior art uses magnet apparatus, therefore the present invention is not limited to this specific structure shown in Fig. 6, and can adopt the structure of other any appropriate of the prior art, the structure described in described each list of references of background technology part of the present invention.
According to this ad hoc structure shown in Figure 6 MRI of the present invention is elaborated with magnet apparatus below.
With in the magnet apparatus, the effect of yoke 1 is as the path of magnetic pole magnetic flux and as the skeleton of whole magnet at MRI.
Last permanent-magnet 2 and following permanent-magnet 3 can use the described permanent-magnet of first aspect present invention respectively.
Get back to Fig. 1 and Fig. 2 a to Fig. 2 d once more, use in the magnet apparatus at existing MRI, because the direction of magnetization of last permanent-magnet 2 and following permanent-magnet 3 is parallel to its axis direction, so magnetic flux some process air gap 6 by last permanent- magnet 2 and 3 generations of following permanent-magnet, and another part magnetic flux will be walked around air gap 6, for example overflow, therefore generally can not surpass 0.4 tesla as resulting field intensity in the air gap 6 of service area from the magnet peripheral surface.
Therefore, the present invention is in order to improve the field intensity in the air gap 6, the structure of the permanent-magnet that uses carried out above-mentioned improvement, and above-mentioned permanent-magnet is applied in this magnet apparatus, thereby can obtain field intensity more than 0.5～0.6 tesla in air gap 6.Its principle is, in the above-mentioned permanent-magnet of the present invention, can effectively restrain the magnetic flux escape that magnetic core produces by the direction of magnetization of magnetosheath, thereby can effectively increase the service area field intensity, be i.e. field intensity in the air gap 6.
According to a kind of preferred implementation of the present invention, shown in Fig. 7 a and Fig. 7 b, MRI provided by the invention is with in the magnet apparatus, and the described pole shoe 4 of going up radially is divided into pole piece 41 and utmost point cover 42, and it is 42 coaxial that the pole piece 41 and the utmost point overlap, and pole piece 41 is sleeved in the utmost point cover 42; The direction of magnetization of utmost point cover 42 is radially inside.That is, the direction of magnetization of this utmost point cover 42 is consistent with the direction of magnetization of descending most magnetosphere 222 of last permanent-magnet 2.Described down pole shoe 5 radially is divided into pole piece 51 and utmost point cover 52, and it is 52 coaxial that the pole piece 51 and the utmost point overlap, and pole piece 51 is sleeved in the utmost point cover 52; The direction of magnetization of utmost point cover 52 radially outward.That is, the direction of magnetization of this utmost point cover 52 is consistent with the direction of magnetization that goes up most magnetosphere 322 of following permanent-magnet 3.
Described pole piece can be selected from certain combination of carbon steel, engineering pure iron and they and silicon steel sheet, iron based nano crystal, and the material range of choice of described utmost point cover can be identical with magnetosheath.
Adopt pole shoe of the present invention, because the utmost point cover in the pole shoe can effectively suppress the magnetic flux escape that magnetic core 21 produces, thereby can effectively increase the service area field intensity, i.e. field intensity in the air gap 6.
As shown in Figure 8, under the preferable case, the described utmost point is enclosed within circumferentially and is made of a plurality of magnetic lobes 420, and each magnetic lobe 420 is similar in the above-mentioned permanent-magnet magnetic lobe 221 in the magnetosphere 22 that connects utmost point cover at aspects such as size, quantity, materials, can self correspondence.
The effect of last pole shoe 4 and following pole shoe 5 is: pole piece can homogenizing its deviation of each local magnetic property in permanent magnetism cylinder after one's death, the shirt rim of pole piece can make working area field roughly even.The shape of pole shoe 4,5 is generally the circular plate type of band shirt rim.
According to a third aspect of the present invention, the invention provides a kind of manufacture method of permanent-magnet, this method comprises: forming the direction of magnetization is axial magnetic core 21; Form magnetosheath 22; And magnetic core 21 closely is sleeved in this magnetosheath 22, the direction of magnetization that makes described magnetosheath is stepwise change from the end direction parallel with the direction of magnetization of magnetic core to the other end direction vertical with the direction of magnetization of magnetic core axially along cylinder.
Magnetic core is shaped by the fritter gummed earlier, each magnetic lobe layering is sat in the right seat then, embed assigned position, all little magnetic patch and magnetic lobe feed to advance under manual or pneumatic situation, to finish by non magnetic mechanical arm enough bold on the mechanics, thereby can realize engaging of magnetic core and magnetosheath.
According to a fourth aspect of the present invention, the invention provides the manufacture method of a kind of MRI with magnet apparatus, this magnet apparatus comprises yoke 1, goes up permanent-magnet 2 and following permanent-magnet 3, goes up pole shoe 4 and following pole shoe 5, wherein:
The described formation method that goes up permanent-magnet 2 comprises that forming the direction of magnetization is axial downward magnetic core 21, form magnetosheath 22, and magnetic core 21 closely is sleeved in this magnetosheath 22, making the direction of magnetization of described magnetosheath is stepwise change from the end direction parallel with the direction of magnetization of magnetic core to the other end direction vertical with the direction of magnetization of magnetic core along the axial of cylinder, the direction of magnetization of magnetosheath 22 upper ends is that the direction of magnetization of lower end is for radially inside axially downwards; And
The described formation method of permanent-magnet 3 down comprises that forming the direction of magnetization is axial downward magnetic core 31, form magnetosheath 32, and magnetic core 31 closely is sleeved in this magnetosheath 32, making the direction of magnetization of described magnetosheath is stepwise change from the end direction parallel with the direction of magnetization of magnetic core to the other end direction vertical with the direction of magnetization of magnetic core along the axial of cylinder, the direction of magnetization of magnetosheath 32 upper ends is for radially outward, and the direction of magnetization of lower end is axially downwards.
The manufacture method of last permanent-magnet and following permanent-magnet can be realized according to the manufacture method of the permanent-magnet of third aspect of the present invention.(can describe) with reference to the manufacture method of permanent-magnet
Last pole shoe and following pole shoe upwards can comprise pole piece and utmost point cover in week, and the manufacture method of pole piece generally is the magnetic lobe that constitutes utmost point cover to be fed with mechanical arm enter the position, and is fixing then.The manufacture method of utmost point cover generally is to make with the Digit Control Machine Tool process equipment.
Utmost point cover can upwards comprise a plurality of magnetic lobes week, and the manufacture method of these magnetic lobes can be identical with the manufacture method of magnetic lobe in the above-mentioned permanent-magnet.
Annexation and connection means between each parts of magnet apparatus can adopt prior art, do not repeat them here.
Further specify advantage of the present invention below by embodiment and Comparative Examples.
Embodiment:
Step 1: using sintered neodymium iron boron material to make the direction of magnetization is axial downward cylinder shape magnetic core, and the height of this magnetic core is 25cm, and diameter is 80cm;
Step 2: use sintered neodymium iron boron material to make 5 batches every batch 8 same magnetic lobe, the height of each magnetic lobe is 5cm, and the radial thickness of magnetic lobe is 20cm.Wherein, the direction of magnetization of the 1st batch of magnetic lobe is all axially downwards, the direction of magnetization of the 2nd batch of magnetic lobe is with respect to 25 degree that axially slope inwardly, the direction of magnetization of the 3rd batch of magnetic lobe is with respect to 50 degree that axially slope inwardly, the direction of magnetization of the 4th batch of magnetic lobe is with respect to 75 degree that axially slope inwardly, the direction of magnetization of the 5th batch of magnetic lobe is with respect to 90 degree that axially slope inwardly, and is promptly radially inside;
Step 3: 8 magnetic lobes of each batch are put in place upwards using mechanical arm to feed in week, be linked to be a circle and constitute a magnetosphere, to be sleeved on the magnetic core from the top down up to the radially inner order that changes gradually from axially downward according to the direction of magnetization by 5 magnetospheres that the magnetic lobe constitutes then, thereby form first permanent-magnet;
Step 4: using sintered neodymium iron boron material to make the direction of magnetization is axial downward cylinder shape magnetic core, and the height of this magnetic core is 25cm, and diameter is 80cm;
Step 5: use sintered neodymium iron boron material to make 5 batches every batch 8 same magnetic lobe, the height of each magnetic lobe is 5cm, and the radial thickness of magnetic lobe is 20cm.The direction of magnetization of the 1st batch of magnetic lobe is all axially downwards, the direction of magnetization of the 2nd batch of magnetic lobe is with respect to axial outward-dipping 25 degree, the direction of magnetization of the 3rd batch of magnetic lobe is with respect to axial outward-dipping 50 degree, the direction of magnetization of the 4th batch of magnetic lobe is with respect to axial outward-dipping 75 degree, the direction of magnetization of the 5th batch of magnetic lobe is with respect to axial outward-dipping 90 degree, radially outward promptly;
Step 6: 8 magnetic lobes of each batch are put in place upwards using mechanical arm to feed in week, be linked to be a circle and constitute a magnetosphere, then 5 magnetospheres that will constitute by the magnetic lobe according to the direction of magnetization from radially outward until the axially downward order that changes gradually be sleeved on the magnetic core from the top down, thereby form second permanent-magnet;
Step 7: using the engineering pure iron to make the direction of magnetization is axial downward cylindrical pole piece, and the height of this pole piece is 10cm, and diameter is 80cm;
Step 8: using sintered neodymium iron boron material to make the direction of magnetization is radially inner 8 same magnetic lobes, and the height of this magnetic lobe is 10cm, and radical length is 20cm;
Step 9: produced above-mentioned 8 magnetic lobes use mechanical arm is fed the circumferential utmost point cover of formation that puts in place, and the pole piece that step 1 is made is sleeved in this utmost point cover then, thereby forms first pole shoe;
Step 10: using the engineering pure iron to make the direction of magnetization is axial downward cylindrical pole piece, and the height of this pole piece is 10cm, and diameter is 80cm;
Step 11: using sintered neodymium iron boron material to make the direction of magnetization is radially outer 8 same magnetic lobes, and the height of this magnetic lobe is 10cm, and radical length is 80cm;
Step 12: produced above-mentioned 8 magnetic lobes use mechanical arm is fed the circumferential utmost point cover of formation that puts in place, and the pole piece that step 1 is made is sleeved in this utmost point cover then, thereby forms second pole shoe;
Step 13: first pole shoe and second pole shoe are respectively installed on relative two end faces of first and second permanent-magnets, detect the field intensity in the air gap then, the field intensity size that obtains is 0.5 tesla.
Comparative example:
(material is sintered NdFeB using existing single cylinder, highly be 25cm, diameter is 120cm) the MRI of permanent-magnet with in the magnet apparatus, (material is the engineering pure iron to use existing single discoideus pole shoe, highly be 10cm, diameter is 120cm), this pole shoe is respectively installed on the opposing end surface of the permanent-magnet up and down in the comparative example 1, detect the field intensity in the air gap, the field intensity size that obtains is 0.37 tesla.
Therefore, from above-mentioned data as can be seen, use structure of the present invention, because leakage field is suppressed comprehensively, the magnetic usefulness of permanent magnetic material is not fully exerted, so compare with the magnet of existing formation technology, can be in that to keep the magnet openness constant, magnetic material gross weight is substantially constant, under the constant substantially situation of magnet gross weight and overall dimension, the powerful width of cloth of magnet yard is promoted.
Claims (20)
1, a kind of permanent-magnet, this magnet comprises the cylinder that is made of permanent magnetic material, and wherein, described cylinder radially is divided into magnetic core and magnetosheath, and magnetic core and magnetosheath are coaxial, and magnetic core closely is sleeved in the magnetosheath; The direction of magnetization of described magnetic core be cylinder axially, the direction of magnetization of described magnetosheath be along cylinder axial from the end direction parallel with the direction of magnetization of magnetic core to the other end direction stepwise change vertical with the direction of magnetization of magnetic core.
2, permanent-magnet as claimed in claim 1, wherein, being shaped as of described magnetic core is cylindrical or polygon prismatic.
3, permanent-magnet as claimed in claim 1, wherein, the diameter of described magnetic core is 1 to 5 with the ratio of height.
4, permanent-magnet as claimed in claim 1, wherein, the thickness of described magnetosheath is 10% to 80% of described magnetic core radius.
5, permanent-magnet as claimed in claim 1, wherein, the thickness of described magnetosheath is 0.05 to 2 with the ratio of height.
6, permanent-magnet as claimed in claim 1, wherein, described magnetosheath comprises a plurality of magnetospheres in the axial direction.
7, permanent-magnet as claimed in claim 6, wherein, each magnetosphere of described magnetosheath is upwards comprising a plurality of magnetic lobes week.
8, a kind of MRI magnet apparatus, comprise yoke, last permanent-magnet, following permanent-magnet, go up pole shoe and following pole shoe, wherein, last permanent-magnet and following permanent-magnet comprise the cylinder that is made of permanent magnetic material respectively, wherein, described cylinder radially is divided into magnetic core and magnetosheath, and magnetic core and magnetosheath are coaxial, and magnetic core closely is sleeved in the magnetosheath; The direction of magnetization of described magnetic core be cylinder axially, the direction of magnetization of described magnetosheath be along cylinder axial from the end direction parallel with the direction of magnetization of magnetic core to the other end direction stepwise change vertical with the direction of magnetization of magnetic core, and,
The direction of magnetization of the magnetic core of last permanent-magnet is axially downwards, and the direction of magnetization of magnetosheath upper end is that the direction of magnetization of lower end is for radially inside axially downwards;
The direction of magnetization of the magnetic core of following permanent-magnet is axially downwards, and the direction of magnetization of magnetosheath upper end is for radially outward, and the direction of magnetization of lower end is axially downwards.
9, magnet apparatus as claimed in claim 8, wherein, described magnetosheath comprises a plurality of magnetospheres in the axial direction.
10, magnet apparatus as claimed in claim 9, wherein, each magnetosphere of described magnetosheath is upwards comprising a plurality of magnetic lobes week.
11, magnet apparatus as claimed in claim 8, wherein:
The described pole shoe of going up radially is divided into pole piece and utmost point cover, and pole piece and utmost point cover are coaxial, and pole piece closely is sleeved in the utmost point cover; The direction of magnetization of utmost point cover is radially inside;
Described pole shoe down radially is divided into pole piece and utmost point cover, and pole piece and utmost point cover are coaxial, and pole piece is sleeved in the utmost point cover; The direction of magnetization of utmost point cover radially outward.
12, magnet apparatus as claimed in claim 11, wherein, the described utmost point is enclosed within and upwards comprises a plurality of magnetic lobes week.
13, a kind of manufacture method of permanent-magnet, this method comprises:
Forming the direction of magnetization is axial magnetic core;
Form magnetosheath; And
Magnetic core closely is sleeved in this magnetosheath, and making the direction of magnetization of magnetosheath is stepwise change from the end direction parallel with the direction of magnetization of magnetic core to the other end direction vertical with the direction of magnetization of magnetic core along the axial of cylinder.
14, method as claimed in claim 13, wherein, described magnetosheath comprises a plurality of magnetospheres in the axial direction.
15, method as claimed in claim 14, wherein, each magnetosphere of described magnetosheath is upwards comprising a plurality of magnetic lobes week.
16, a kind of MRI manufacture method of magnet apparatus, this method comprises the two ends up and down that last permanent-magnet and following permanent-magnet are respectively installed to yoke, and will go up on the opposing end surface that pole shoe and following pole shoe be respectively installed to permanent-magnet and following permanent-magnet, wherein, last permanent-magnet and following permanent-magnet comprise the cylinder that is made of permanent magnetic material respectively, and wherein, described cylinder radially is divided into magnetic core and magnetosheath, magnetic core and magnetosheath are coaxial, and magnetic core closely is sleeved in the magnetosheath; The direction of magnetization of described magnetic core be cylinder axially, the direction of magnetization of described magnetosheath be along cylinder axial from the end direction parallel with the direction of magnetization of magnetic core to the other end direction stepwise change vertical with the direction of magnetization of magnetic core, and,
The direction of magnetization of the magnetic core of last permanent-magnet is axially downwards, and the direction of magnetization of magnetosheath upper end is that the direction of magnetization of lower end is for radially inside axially downwards;
The direction of magnetization of the magnetic core of following permanent-magnet is axially downwards, and the direction of magnetization of magnetosheath upper end is for radially outward, and the direction of magnetization of lower end is axially downwards.
17, method as claimed in claim 16, wherein, described magnetosheath comprises a plurality of magnetospheres in the axial direction.
18, method as claimed in claim 17, wherein, each magnetosphere of described magnetosheath is upwards comprising a plurality of magnetic lobes week.
19, method as claimed in claim 16, wherein;
The described pole shoe of going up radially is divided into pole piece and utmost point cover, and pole piece and utmost point cover are coaxial, and pole piece closely is sleeved in the utmost point cover; The direction of magnetization of utmost point cover is radially inside;
Described pole shoe down radially is divided into pole piece and utmost point cover, and pole piece and utmost point cover are coaxial, and pole piece is sleeved in the utmost point cover; The direction of magnetization of utmost point cover radially outward.
20, method as claimed in claim 19, wherein, the described utmost point is enclosed within and upwards comprises a plurality of magnetic lobes week.
Priority Applications (6)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB2006100572913A CN100485829C (en) | 2005-06-10 | 2006-03-09 | Permanent magnet, magnet device for MRI comprising the permanent magnet, and method for fabricating same |
| US11/411,808 US7365623B2 (en) | 2005-06-10 | 2006-04-27 | Permanent magnet, magnetic device for use in MRI including the same, and manufacturing processes thereof |
| JP2008515030A JP4773515B2 (en) | 2005-06-10 | 2006-06-02 | PERMANENT MAGNET, MAGNETIC DEVICE WITH PERMANENT MAGNET FOR USE IN MRI AND MANUFACTURING METHOD THEREOF |
| PCT/CN2006/001191 WO2006131060A1 (en) | 2005-06-10 | 2006-06-02 | Permanent magnet, magnetic device for use in mri including the same and manufanufacturing processes thereof |
| AT06742078T ATE533064T1 (en) | 2005-06-10 | 2006-06-02 | PERMANENT MAGNET FOR MAGNETIC RESONANCE IMAGING |
| EP06742078A EP1889087B1 (en) | 2005-06-10 | 2006-06-02 | Permanent magnet for magnetic resonance imaging |
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| Application Number | Priority Date | Filing Date | Title |
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| CN200510075185.3 | 2005-06-10 | ||
| CN200510075185 | 2005-06-10 | ||
| CN200510077392.2 | 2005-06-23 | ||
| CNB2006100572913A CN100485829C (en) | 2005-06-10 | 2006-03-09 | Permanent magnet, magnet device for MRI comprising the permanent magnet, and method for fabricating same |
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| CN1877757A CN1877757A (en) | 2006-12-13 |
| CN100485829C true CN100485829C (en) | 2009-05-06 |
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| CN104376958A (en) * | 2014-11-21 | 2015-02-25 | 国网重庆市电力公司电力科学研究院 | Permanent magnet device |
| 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 |
| 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 |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3153215A (en) * | 1958-10-15 | 1964-10-13 | Westinghouse Electric Corp | Magnetic core structure |
| CN1233342A (en) * | 1996-10-15 | 1999-10-27 | Abb动力T&D股份有限公司 | Magnetic core structure |
| CN2430698Y (en) * | 2000-06-20 | 2001-05-16 | 中油管道京磁新材料有限责任公司 | C shape magnetic resonance imaging permanent magnet without blocking magnetic pole |
| CN1400473A (en) * | 2001-07-27 | 2003-03-05 | 武汉宏建电气技术有限公司 | Permanent magnet device for nuclear magnetic resonane imaging system and magnetic material distribution in it |
| CN2692130Y (en) * | 2004-03-05 | 2005-04-13 | 李永炳 | Fluid pulse magnelization device |
-
2006
- 2006-03-09 CN CNB2006100572913A patent/CN100485829C/en not_active Expired - Fee Related
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3153215A (en) * | 1958-10-15 | 1964-10-13 | Westinghouse Electric Corp | Magnetic core structure |
| CN1233342A (en) * | 1996-10-15 | 1999-10-27 | Abb动力T&D股份有限公司 | Magnetic core structure |
| CN2430698Y (en) * | 2000-06-20 | 2001-05-16 | 中油管道京磁新材料有限责任公司 | C shape magnetic resonance imaging permanent magnet without blocking magnetic pole |
| CN1400473A (en) * | 2001-07-27 | 2003-03-05 | 武汉宏建电气技术有限公司 | Permanent magnet device for nuclear magnetic resonane imaging system and magnetic material distribution in it |
| CN2692130Y (en) * | 2004-03-05 | 2005-04-13 | 李永炳 | Fluid pulse magnelization device |
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