CN101281239A - Permanent magnetic body used for magnetic resonance imaging and manufacturing method thereof - Google Patents
Permanent magnetic body used for magnetic resonance imaging and manufacturing method thereof Download PDFInfo
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- CN101281239A CN101281239A CNA2008101122890A CN200810112289A CN101281239A CN 101281239 A CN101281239 A CN 101281239A CN A2008101122890 A CNA2008101122890 A CN A2008101122890A CN 200810112289 A CN200810112289 A CN 200810112289A CN 101281239 A CN101281239 A CN 101281239A
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Abstract
Disclosed is a permanent magnetism magnetic body for magnetic resonance imaging, whose main magnetic body is formed by overlapping a plurality of magnetic body rings in echelonment distribution along the longitudinal axis. The magnetic body ring is divided into a plurality of magnetic petals along the radial direction, the magnetization direction of the magnetic petal on random transverse cross-section is in a 360 degrees marching type variation around the longitudinal axis; the magnetization direction of the magnetic petal on random one-half longitudinal section is in a marching type variation along the central shaft, and the tangent lines of the magnetization direction of every magnetic petal are in a continuous distribution. The main magnetic field magnetization direction of the magnetic body ring at the shaft center point is in axial direction. The method for manufacturing the permanent magnetism magnetic body includes: forming magnetic petals by right and left overlapping the main pole in the radial direction; forming magnetic body rings based on the magnetization direction of magnetic petals in the radial direction, according to the 360 degrees marching type variation sequence around the longitudinal axis; and forming the main magnetic body by overlapping the magnetic body rings along the longitudinal axis.
Description
Technical field
The present invention relates to magnetic resonance imaging system, particularly a kind of permanent-magnet and manufacture method thereof that is used for magnetic resonance imaging.
Background technology
Magnetic resonance imaging can provide high spatial resolution, unlimited penetration depth and very good soft tissue contrast, and dissection location, splendid space, so magnetic resonance imaging has the incomparable advantage of other iconography technology.Novel magnetic resonance imaging requires higher magnetic field intensity, higher spatial resolution.For improving magnetic field intensity, superconducting magnet is a selection beyond doubt.But superconducting magnet manufacturing, operation and maintenance cost height.Permanent-magnet is lower because of its reliable operation, price, does not need auxiliary device, and operation and maintenance are simple, and advantages such as energy savings more and more obtain paying attention to.
Conventional permanent-magnet can be divided into two big classes: open and closed.Wherein the typical case of open magnet representative is a C type magnet; The type that closed magnet comprises is more, and " mouth " font, upright post type, " worker " font, ball-type, column type or the like are arranged.Compare with open magnet, closed magnet exists magnetic field good stability, uniformity coefficient height, leakage field is little and advantages such as simple are made in installation.The principle that magnet design is followed is: field intensity is high as far as possible; Magnetic field is even as far as possible; Do not allow obvious leakage field; Weight is light as far as possible.Therefore, we at first consider to adopt enclosed construction design magnet.Traditional closed-in construction magnet is made of yoke, main magnetic patch and pole-face.Because edge effect have only the air gap center can obtain magnetic field of high uniformity, and magnetic field, air gap marginarium is uneven.In order to obtain unevenness less than 10 among a small circle in the air gap center
-4Magnetic field of high uniformity, the ratio of pole-face width and air gap height need reach 4-8, promptly magnet need be done very greatly.In order to reduce the magnet cost, 1984, U.S. Field Effect company developed a kind of follow-on permanent-magnet.It is to be combined into a polygon toroidal magnet with the some different trapezoidal magnetic patch of direction of magnetization, and ring inside is the air gap district.Because without yoke, this magnet weight is lighter, the consumption of magnetic patch material also is lower than above-mentioned common permanent-magnet.But because the direction of magnetization difference in each trapezoidal magnetic patch, processing and manufacturing is difficulty relatively.And the working point is inconsistent everywhere in the magnetic patch, and many magnetic patch are in the less working point of magnetic energy level, thereby the consumption of magnetic patch material is still quite big.Chinese patent CN85103498 is the improvement structure of the common frame magnet that the iron yoke is arranged.This structure has adopted the polygon toroidal magnet structure of U.S. Field Effect company, kept magnetic patch simple shape in the common permanent-magnet structure (mostly being square and triangle), be convenient to processing and manufacturing, have shaped as frame yoke formation closed magnetic path thereby magnetic flux can not drain to advantages such as yoke outside.Compare with common permanent-magnet structure, increased leak stopping magnetic patch and side magnetic patch, improved the magnetic field homogeneity at air gap place.The permanent-magnet that is applied to magnetic resonance imaging the earliest is the QED Beta 3000 that U.S. Fonar company manufactures and designs, and its work magnetic is close to be 3000 Gausses, is magnetic source with permanent magnetic ferrites material, and gross weight almost reaches 100 tons.Calculate according to relevant law of magnetism, if when adopting the close magnet of the QED Beta 3000 of Chinese patent CN85103498 manufacturing technology index and Fonar company, estimate that gross weight will be above 60 tons, absolute weight is still very big, and owing to added side magnetic patch and leak stopping magnetic patch, the processing of magnet and installation are complicated more.Chinese patent CN1042795 is the structure of another improved iron-free yoke, adopts the strontium calcium ferrite as magnetic source, and magnetic is close when being 1500 Gausses, and weight reaches 9 tons, but the stray field scope is bigger.The another kind of magnet of medical college of New York University development (see IEEE Transaction on Magnetics, Vol.Mag-25, No.5, P3904-3906) assembled by the permanent magnets of difformity, different magnetizing directions, processing and installation are all very complicated.Though Chinese patent 200420009046.1 and 200420047676.8 all is an enclosed construction, field intensity all is difficult to the level that reaches higher.
In this class magnet, relatively more classical magnet structure is Halbach.In the Halbach structure, the magnetic direction of each piece magnet steel is all followed in theory
Distribute.This structure is very practical and economical, basically routine replaced low electromagnet (＜1.8T), especially be fit to the small-sized magnet of Design Laboratory.It is B that the magnetic field intensity of Halbach cylindrical magnets is calculated formula
Z=μ
0Mlog (R
Ext/ R
Int), the magnetic field intensity of ball-type magnet is calculated formula and is
From formula as can be seen, no matter column type or ball-type, the field intensity of this magnet can reach infinitely great in theory.But in fact, because permanent magnetic material works in degree of depth magnetic saturation and second quadrant demagnetization part of the back magnetic hysteresis loop that magnetizes, when field intensity reach a certain height, magnet can suffer the strong demagnetizing effect of magnetic material high-coercive force, finally field intensity is limited in about about 2.5T, even does not reach 2T.Obviously this traditional permanent-magnet design is difficult to further improve magnetic field intensity.
Summary of the invention
For overcoming the shortcoming of prior art, the present invention proposes a kind of follow-on permanent-magnet and manufacture method thereof that is used for magnetic resonance imaging.
Magnetic resonance imaging permanent-magnet provided by the invention comprises yoke, main magnet and upper and lower pole shoe.It is characterized in that main magnet is made of a plurality of magnet rings; Magnet ring is a loop configuration, radially is divided into a plurality of magnetic lobes, and the direction of magnetization of magnetic lobe on any xsect is for to be 360 ° of stepwise change around the longitudinal axis; The direction of magnetization of each magnetic lobe on any 1/2nd longitudinal sections is along the central shaft stepwise change, and the tangent line of each magnetic lobe direction of magnetization is the continuity distribution; The main field direction of magnetization of magnet ring in the axle center is axial.
Main magnet is a closed ring structure, and the main field direction of magnetization in the axle center is axial; Main magnet is formed by stacking up and down along the stepped distribution of the longitudinal axis by a plurality of magnet rings; The direction of magnetization of the main magnet of stack gained on any xsect is for to be 360 ° of stepwise change around the longitudinal axis, direction of magnetization on any 1/2nd longitudinal sections is along 360 ° of stepwise change of central shaft, and the tangent line of the direction of magnetization of each rank magnet ring is the continuity distribution on same 1/2nd longitudinal sections; The axial length of main magnet is greater than the maximum radial length of magnet ring; Yoke is wrapped in the periphery of whole main magnet; Upper and lower pole shoe is positioned at two ends of main magnet imaging region, for imaging region provides uniform magnetic field.
The invention provides the manufacture method of a kind of magnetic resonance imaging, it is characterized in that, at first permanent magnetic material is carried out line and be cut into magnetic patch, magnetize then, splice in order, glue together, make main pole according to the magnetic patch direction of magnetization with permanent-magnet; The main pole of one or more direction of magnetization gradual change is stack to the left and right in the footpath, is formed on any 1/2nd longitudinal sections direction of magnetization along the central shaft stepwise change, and the tangent line of direction of magnetization is the magnetic lobe that continuity distributes; According to the magnetic lobe uniqueness of direction of magnetization diametrically, by the order that is 360 ° of stepwise change around the longitudinal axis, the main field direction of magnetization that is formed on a center is axial magnet ring again.
Along the order of 360 ° of stepwise change of central shaft,, form the main magnet of enclosed annular according to direction of magnetization on any 1/2nd longitudinal sections along the longitudinal axis each rank magnet ring that superposes up and down; Upper and lower pole shoe is fixed on the imaging end face of main magnet; Again with the stepped distribution of inside surface, and the soft magnet yoke ferropexy that the exponent number of the progression of ladder and magnet ring adapts is in main magnet periphery.
By technique scheme of the present invention, permanent-magnet provided by the invention is compared with existing permanent-magnet, under situation with essentially identical size and shape, field intensity can reach several teslas, there is not obvious leakage field, consumptive material is few, and is in light weight, used the potential of permanent-magnet to greatest extent.Therefore, this permanent-magnet can not only be used to carry out magnetic resonance imaging, but also can be used for small-sized, the high field magnet of other needs, and magnet is convenient to any situation mobile and that safeguard.
Description of drawings
Fig. 1 is the synoptic diagram of magnet ring vertical section structure of the present invention;
Fig. 2 a, Fig. 2 b are magnet ring of the present invention longitudinal section axial step-by-step movement direction of magnetization synoptic diagram;
Fig. 3 a, Fig. 3 b are magnet ring radial section synoptic diagram of the present invention;
Fig. 4 a to Fig. 4 j is the shape synoptic diagram of magnet ring magnetic lobe radial section of the present invention;
Fig. 5 is master's magnet vertical section structure synoptic diagram of the present invention;
Fig. 6 is each rank magnet ring synoptic diagram of master's magnet of the present invention longitudinal section;
Fig. 7 is master's magnet of the present invention longitudinal section axial step-by-step movement direction of magnetization synoptic diagram;
Fig. 8 a, Fig. 8 b are the vertical section structure synoptic diagram of permanent-magnet device of the present invention;
Among the figure: 1 yoke, 2 main magnets, pole shoe about in the of 3,4 imaging regions, the access way of 5 imaging objects, 21 magnet rings, 211 magnetic lobes, 212 magnetic holes, 213 main poles.
Embodiment
Further specify the present invention below in conjunction with the drawings and specific embodiments.
According to first content of the present invention, as shown in Figures 1 to 4, the invention provides a kind of magnet ring 21 of loop configuration, described loop configuration magnet ring 21 radially is divided into a plurality of magnetic lobes 211, and the direction of magnetization of described magnetic lobe 211 on any xsect is for to be 360 ° of stepwise change around the longitudinal axis; The direction of magnetization of described each magnetic lobe 211 on any 1/2nd longitudinal sections is along the central shaft stepwise change, and the tangent line of each direction of magnetization is the continuity distribution; The main field direction of magnetization of described loop configuration magnet ring 21 in the axle center is axial.
Fig. 2 a and Fig. 2 b are the longitudinal section axial step-by-step movement direction of magnetization synoptic diagram of magnet ring 21 of the present invention.Shown in Fig. 2 a and Fig. 2 b, direction of magnetization on magnet ring of the present invention 21 any 1/2nd longitudinal sections is for being stepwise change along the direction of magnetization of central shaft from the direction of magnetization of an end to the other end, and the tangent line of each direction of magnetization that is changing is continuity and distributes.This magnetization trend can be to change clockwise from top to bottom along central shaft, also can be to change counterclockwise from top to bottom along central shaft.Fig. 2 a and Fig. 2 b have only shown wherein a kind of situation of change.When shown in Fig. 2 a and Fig. 2 b during along the clockwise from top to bottom 360 ° of stepwise change of central shaft, the main field direction of resulting magnet ring 21 upwards; Otherwise during along the counterclockwise from top to bottom 360 ° of stepwise change of central shaft, the main field of resulting magnet ring 21 is directed downwards.
The direction of magnetization of each magnetic lobe 211 is by the magnetization situation decision of its component units main pole 213 in the magnet ring 21 of the present invention.The magnetic lobe 211 of the main pole 213 of the one or more direction of magnetization gradual change direction of magnetization of stack formation to the left and right gradual change in the footpath.Shown in Fig. 2 a, 212 places, magnetic hole, promptly the direction of magnetization of axle center is vertically upward; The both sides in magnetic hole 212, along with the distance between main pole 213 and the magnetic hole 212 strengthens gradually, the direction of magnetization of main pole 213 is by the outside clockwise progressive off-axis center of direction of approaching vertically upward.Shown in Fig. 2 b, 212 places, magnetic hole, promptly the direction of magnetization of axle center is vertically upward; The both sides in magnetic hole 212, along with the distance between main pole 213 and the magnetic hole 212 strengthens gradually, the direction of magnetization of main pole 213 is by the outside counterclockwise progressive off-axis center of direction of approaching vertically upward.
Fig. 3 a and Fig. 3 b are and the radial section synoptic diagram of Fig. 2 a and the corresponding magnet ring 21 shown in the present of Fig. 2 b, there is shown the direction of magnetization of each magnetic lobe around longitudinal axis stepwise change.Each magnetic lobe 211 direction of magnetization diametrically has uniqueness, the direction of magnetization of all the magnetic lobes 211 on the same xsect is finished around 360 ° of stepwise change of the longitudinal axis, wherein the arrow of each direction of magnetization can point to circumference by the axle center, shown in Fig. 3 a, also can point to the axle center, shown in Fig. 3 b by circumference.
The present invention is for the size of magnetic lobe 211, and quantity and material do not have special requirement.The size of magnetic lobe 211 can be determined according to the size of needed magnet ring 21 and the size of imaging region 4.The field intensity of magnet ring 21 requires high more, and the desired imaging region 4 of imaging object is big more, and the size of magnetic lobe 211 will be big more thereupon.The quantity of magnetic lobe 211 is principle with the magnet ring 21 that can form sealing diametrically.Can be 2 or a plurality of in theory.The material of magnetic lobe 211 can be selected existing any permanent magnetic material for use, as: sintered NdFeB, bonded rare earth permanent magnetic, Rare-Earth Cobalt, permanent magnetic ferrites etc.
The magnetic lobe 211 that Fig. 1 also schematically illustrates magnet ring is formed by stacking about radially by a plurality of main poles 213.The quantity of 211 pairs of main poles 213 of described each magnetic lobe does not have special requirement, can be one or more in theory.Size, thickness, the material of 211 pairs of main poles 213 of each magnetic lobe do not have special requirement.The size of each main pole 213 can be identical, also can be different.The thickness of each main pole 213 can be identical, also can be different.The main pole 213 of all magnetic lobes 211 can have identical thickness, also can have different thickness.Each main pole 213 can be selected identical permanent magnetic material for use according to the distribution of local magnetic field, also can select different permanent magnetic materials for use.Permanent magnetic material can be selected existing any permanent magnetic material for use, as: sintered NdFeB, bonded rare earth permanent magnetic, Rare-Earth Cobalt, permanent magnetic ferrites etc.
The present invention does not have special requirement for the shape of magnetic lobe 211.Magnetic lobe 211 in each magnet ring 21 can be of similar shape, and also can have different shapes.The inside surface of described magnetic lobe 211 can be point-like, linearity, circular-arc, polyline shaped, curve-like; The outside surface of described magnetic lobe 211 can be linearity, circular-arc, polyline shaped, curve-like.Therefore, the radial section of described magnetic lobe 211 can be fan-shaped, triangle, sharp cone distal, trapezoidal, arc, flat taper, in square any one, or other arbitrary shape, exemplarily provided the radial section synoptic diagram of several magnet ring magnetic of the present invention lobe 211 as Fig. 4 a, Fig. 4 b, Fig. 4 c, Fig. 4 d, Fig. 4 e, Fig. 4 f, Fig. 4 g, Fig. 4 h, Fig. 4 i and Fig. 4 j.
There is no particular limitation for the shape of described magnet ring 21 in the present invention.Wherein, the appearance of described magnet ring 21 can be that regular shape also can be irregularly shaped, as: any one in cylindrical, conical, polygon prismatic, polygon pyramid, the shaped as frame or xsect are erose any one cylinder; Wherein, the interior table shape of described magnet ring 21 can be that regular shape also can be irregularly shaped, is erose any one cylinder as any one or xsect in cylindrical, conical, polygon prismatic, polygon pyramid, the shaped as frame.Fig. 3 a and Fig. 3 b have demonstrated the radial section synoptic diagram of the magnet ring 21 under wherein a kind of magnetic lobe 211 shapes, and this moment, the shape of each magnetic lobe 211 was identical, big or small identical, and the surfaces externally and internally of magnet ring 21 is all the column type of rule.
The present invention provides a kind of magnetic resonance imaging magnet apparatus that adopts above-mentioned magnet ring 21 simultaneously, and this magnet apparatus comprises yoke 1, main magnet 2 and upper and lower pole shoe 3.
Wherein, described main magnet 2 is an enclosed construction, and the main field direction of magnetization in the axle center is axial; Described main magnet 2 is formed by stacking up and down along the stepped distribution of the longitudinal axis by above-mentioned a plurality of magnet rings 21; The direction of magnetization of the main magnet 2 of stack gained on any xsect is for to be 360 ° of stepwise change around the longitudinal axis, direction of magnetization on any 1/2nd longitudinal sections is along 360 ° of stepwise change of central shaft, and the tangent line of the direction of magnetization of each rank magnet ring 21 is the continuity distribution on same 1/2nd longitudinal sections; The axial length of described main magnet 2 is greater than the maximum radial length of magnet ring 21.
Fig. 5 to Fig. 7 has schematically shown the structure and the magnetization situation thereof of master's magnet 2 of the present invention.This magnetization trend can be to change clockwise from top to bottom along central shaft on any 1/2nd longitudinal sections, also can be to change counterclockwise from top to bottom along central shaft.Fig. 7 has only shown wherein a kind of situation of change.When as shown in Figure 7 along the clockwise from top to bottom 360 ° of stepwise change of central shaft, the magnetic direction of resulting main magnet 2 upwards, otherwise during along the counterclockwise from top to bottom 360 ° of stepwise change of central shaft, the magnetic direction of resulting main magnet 2 is downward.
Main magnet 2 among the present invention is formed by stacking up and down along the stepped distribution of the longitudinal axis by above-mentioned a plurality of magnet rings 21, wherein, the direction of magnetization of described each magnet ring 21 on any 1/2nd longitudinal sections is to change along the step-by-step movement of the longitudinal axis from the direction of magnetization of an end to the direction of magnetization of the other end, and direction of magnetization and the angle of the longitudinal axis of each magnet ring 21 on same 1/2nd longitudinal sections is the wave band formula and distributes, and bears jointly from 0 ° to 360 ° wave band formula to change.By the order of each magnet ring 21 by the direction of magnetization gradual change stacked together up and down, just can realize easily that the direction of magnetization of main magnet 2 from the direction of magnetization of an end to the other end changes along 360 ° of step-by-step movements of central shaft.
Fig. 5 schematically illustrates the stepped distribution between each rank magnet ring 21 in the main magnet 2, and this stepped distribution can be complete symmetry mode or rotational symmetry mode or asymmetric.
Fig. 6 has not only demonstrated the stepped distribution between each rank magnet ring 21 in the main magnet 2, and has demonstrated each rank magnet ring 21 and comprise a plurality of magnetic lobes 211 diametrically, and each magnetic lobe 211 can contain one or more main poles 213.
Described main magnet 2 does not have special requirement for size, thickness and the material of each rank magnet ring 21.Each magnet ring 21 can have identical size, also can have different sizes.The thickness of each magnet ring 21 can be identical, also can be different.Each magnet ring 21 can be selected identical permanent magnetic material for use, also can select different permanent magnetic materials for use.Permanent magnetic material can be selected existing any permanent magnetic material for use, as: sintered NdFeB, bonded rare earth permanent magnetic, Rare-Earth Cobalt, permanent magnetic ferrites etc.
There is no particular limitation for the shape of described main magnet 2 in the present invention.The shape of each rank magnet ring 21 has determined the shape of main magnet 2 jointly.The appearance of described main magnet 2 can be that regular shape also can be irregularly shaped, Fig. 7 has demonstrated the longitudinal cross-section synoptic diagram of the main magnet 2 under wherein a kind of magnetic lobe 211 shapes, this moment, the shape of each magnetic lobe 211 was identical, big or small identical, the surfaces externally and internally of each rank magnet ring 21 is all the column type of rule, and the appearance of main magnet 2 is then got by the stepped distribution of a plurality of right cylinders.
Magnetic resonance imaging magnet apparatus shown in Fig. 8 a to 8b is a kind of embodiment of magnet apparatus of the present invention.
Shown in Fig. 8 a, Fig. 8 b, magnetic resonance imaging of the present invention is with in the magnet apparatus, the effect of yoke 1 is to be used for forming magnetic circuit, the magnetic field at 4 places, Enhanced Imaging zone, shielding leakage field, and can be used for fixing each rank magnet ring 21, strengthen main magnet 2 structural stability, provide sizable convenience for the installation of whole magnet apparatus.
Yoke 1 of the present invention is selected the soft magnetic material of high saturation for use, and material can be carbon steel or engineering pure iron.The structure of yoke 1 is arranged by the profile of main magnet 2.The inside surface of yoke 1 is determined by the outside surface of main magnet 2 in the magnet apparatus of the present invention, stepped distribution, and the magnetosphere number of the progression of ladder and magnet ring 21 adapts.Described yoke 1 can be an integral structure with respect to each magnet ring 21, also can be the assembly type structure, can also have some other auxiliary part.Described yoke 1 is wrapped in the periphery of whole main magnet 2.
Institute is noted that in the magnet apparatus of the present invention that main magnet 2 is being parallel on the main field direction, and the magnet two ends are enclosed constructions, and imaging region 4 is positioned at the center of main magnet 2, shown in Fig. 8 a and 8b.In Fig. 8 b, on perpendicular to the main field direction, main magnet 2 is pass-through type structures, exists a passage 5 to be used for picking and placeing imaging object.This passage 5 also may reside on the other direction vertical with main field.
Pole shoe 3 is made of the soft magnetic material of high saturation up and down, and its material can be selected from certain combination of carbon steel, engineering pure iron and they and siliconized plate, iron based nano crystal.Pole shoe 3 is positioned at two ends of imaging region up and down, for imaging region 4 provides uniform magnetic field as well as possible, to reach the purpose that can directly carry out magnetic resonance imaging.
According to second content of the present invention, the invention provides a kind of manufacture method of magnet ring, this method comprises: the main pole 213 that forms difformity, different direction of magnetization; Be formed on direction of magnetization on any 1/2nd longitudinal sections and be the magnetic lobe 211 that continuity distributes along the tangent line of central shaft stepwise change and direction of magnetization; According to the uniqueness of magnetic lobe 211 direction of magnetization on xsect, radially assemble a plurality of magnetic lobes 211, the main field direction of magnetization that is formed on a center is axial magnet ring 21.
According to magnetic lobe 211 uniqueness of direction of magnetization diametrically,, each magnetic lobe 211 along radially placing, is fixed through rivet again, formed magnet ring 21 at last by the order that is 360 ° of stepwise change around the longitudinal axis (shown in Fig. 3 a and Fig. 3 b).
The present invention provides a kind of magnetic resonance imaging of adopting above-mentioned magnet ring 21 manufacture method with magnet apparatus simultaneously, and this magnet apparatus comprises yoke 1, main magnet 2, pole shoe 3 up and down.
The formation method of wherein said main magnet 2 comprise according on any 1/2nd longitudinal sections direction of magnetization along the longitudinal axis from 0 ° to 360 ° the stepping order of subrane, stacked up and down each rank magnet ring 21 just can form the main magnet 2 of enclosed annular easily.The magnetization trend of winner of institute magnet 2 can be to change clockwise from top to bottom along central shaft, also can be to change counterclockwise from top to bottom along central shaft.Stepped distribution between each rank magnet ring 21 of main magnet 2, this stepped distribution can be axisymmetric, also can be non-axial symmery shape.
The manufacture method of main magnet 2 can be realized according to the manufacture method of the above-mentioned magnet ring 21 of the present invention.
In the magnet apparatus of the present invention, the manufacturing of pole shoe 3 can obtain by machining.Pole shoe is installed on the opposing end surface of main magnet imaging region 4 up and down.
In the magnet apparatus of the present invention, yoke 1 is composed of multiple units.The unit number of yoke 1 is identical with the exponent number of magnet ring 21, and the inside surface of the yoke 1 also outside surface with corresponding magnet ring 21 with it is corresponding one by one.Each yoke unit directly obtains by machining, and yoke is wrapped in the periphery of each magnet ring 21.Assemble a plurality of magnet rings 21 at last, be formed into the picture magnet apparatus.
Further specify advantage of the present invention below by embodiment.
Embodiment:
Step 1: use NdFeB material to make 7 batches every batch 8 identical magnetic lobes, wherein the height of 6 batches of magnetic lobes is 55mm, and the height of 1 batch of magnetic lobe is 20mm.Wherein, the 1st batch of magnetic lobe and the 7th batch of magnetic lobe thickness are 40mm, and 1 grade of main pole is only arranged, and main pole is selected magnetic energy level magnetic material placed in the middle for use; The 2nd batch of magnetic lobe and the 6th batch of magnetic lobe thickness are 80mm, are made of 2 grades of main poles, select magnetic energy level magnetic material placed in the middle for use from the near main pole of axle, select the lower magnetic material of magnetic energy level for use from axle main pole far away; The 3rd batch of magnetic lobe and the 5th batch of magnetic lobe thickness are 120mm, are made of 3 grades of main poles, select the higher magnetic material of magnetic energy level for use from the near main pole of axle, and the main pole in the middle of being positioned at is selected the lower magnetic material of magnetic energy level for use, selects magnetic energy level magnetic material placed in the middle for use from axle main pole farthest; The 4th batch of magnetic lobe is positioned at imaging region, and thickness is 106.5mm, is made of 2 grades of main poles, selects the lower magnetic material of magnetic energy level for use from the near main pole of axle, selects the higher magnetic material of magnetic energy level for use from axle main pole far away.
Step 2: the direction of magnetization that makes the 1st batch of 1 grade of main pole in the magnetic lobe is with respect to axial outward-dipping 30 degree; The direction of magnetization of the 2nd batch of 2 grades of main poles in the magnetic lobe is outwards spent with respect to axial outward-dipping 30 degree and 60 successively by the axle center; The direction of magnetization of the 3rd batch of 3 grades of main poles in the magnetic lobe is outwards spent with respect to axial outward-dipping 60 degree, 120 degree and 150 successively by the axle center; The direction of magnetization that makes the 4th batch of 1 grade of main pole in the magnetic lobe is with respect to axioversion 180 degree; The direction of magnetization of the 5th batch of 3 grades of main poles in the magnetic lobe is outwards spent with respect to 60 degree that axially slope inwardly, 120 degree and 150 successively by the axle center; The direction of magnetization of the 6th batch of 2 grades of main poles in the magnetic lobe is outwards spent with respect to 30 degree and 60 that axially slope inwardly successively by the axle center; The direction of magnetization that makes the 7th batch of 1 grade of main pole in the magnetic lobe is with respect to 30 degree that axially slope inwardly.
Step 3: use the engineering pure iron to make 3 groups (2 every group, and between any two size and profile are identical) the conductive magnetic yoke iron hoop, the upper end of the 1st group of yoke is that diameter is that 120mm, height are that the plectane of 50mm, lower end are that internal diameter is that 80mm, external diameter are that 120mm, height are the cylinder ring of 25mm; The upper end of the 2nd group of yoke is that internal diameter is that 80mm, external diameter are that 200mm, height are that the cylinder ring of 30mm, lower end are that internal diameter is that 160mm, external diameter are that 200mm, height are the cylinder ring of 25mm; The upper end of the 3rd group of yoke is that internal diameter is that 160mm, external diameter are that 360mm, height are that the cylinder ring of 30mm, lower end are that internal diameter is that 240mm, external diameter are that 360mm, height are the cylinder ring of 65mm.
Step 4: with the yoke ring according to its external diameter from small to large more from big to small order be symmetry shape successively and be screwed from top to bottom, keep a back cover plectane this moment.
Step 5: with 8 magnetic lobes of the 1st batch according to its direction of magnetization around the order of the longitudinal axis 360 degree stepwise change along radially feeding in the yoke ring topmost, at this moment, on the plectane of yoke ring occupies.In like manner, feed the 2nd batch, the 3rd batch, the 4th batch, the 5th batch, the 6th batch, the 7th batch magnetic lobe successively in order, the last back cover yoke plectane that keeps of encapsulation just obtains from top to bottom direction of magnetization along the closed annular magnet system of axial 360 degree stepwise change.
Step 6: detect the magnetic field intensity in the air gap, the magnitude of field intensity that obtains is 3.4 teslas.
The longitudinal length of the resulting permanent-magnet of present embodiment is 450mm, and radical length is 360mm, and imaging region is that high 27mm, bottom surface diameter are the cylinder of 20mm.
Therefore, from above-mentioned data as can be seen, use structure of the present invention and manufacture method, make the usefulness of permanent magnetic material be not fully exerted, leakage field is suppressed comprehensively, so compare with the magnet of existing formation technology, can be in that to keep the magnet openness constant, under the substantially constant situation of magnet gross weight, significantly improve the magnet field intensity, save magnetic material expense.
Claims (5)
1, a kind of permanent-magnet that is used for magnetic resonance imaging comprises yoke (1), main magnet (2) and upper and lower pole shoe (3); It is characterized in that main magnet (2) is made of a plurality of magnet rings (21); Magnet ring (21) is a loop configuration, radially is divided into a plurality of magnetic lobes (211), and the direction of magnetization of magnetic lobe (211) on any xsect is for to be 360 ° of stepwise change around the longitudinal axis; The direction of magnetization of each magnetic lobe (211) on any 1/2nd longitudinal sections is along the central shaft stepwise change, and the tangent line of each magnetic lobe (211) direction of magnetization is the continuity distribution; The main field direction of magnetization of magnet ring (21) in the axle center is axial; Main magnet (2) is a closed ring structure, and the main field direction of magnetization in the axle center is axial; Main magnet (2) is formed by stacking up and down along the stepped distribution of the longitudinal axis by a plurality of magnet rings (21); The direction of magnetization of the main magnet (2) of stack gained on any xsect is for to be 360 ° of stepwise change around the longitudinal axis, direction of magnetization on any 1/2nd longitudinal sections is along 360 ° of stepwise change of central shaft, and the tangent line of the direction of magnetization of each rank magnet ring (21) is the continuity distribution on same 1/2nd longitudinal sections; The axial length of main magnet (2) is greater than the maximum radial length of magnet ring (21); Yoke (1) is wrapped in the periphery of whole main magnet (2); Upper and lower pole shoe (3) is positioned at two ends of main magnet imaging region (4), for imaging region (4) provides uniform magnetic field.
2, permanent-magnet as claimed in claim 1 is characterized in that, described magnet ring (21) is made up of a plurality of magnetic lobes (211) diametrically, magnetic lobe (211) be distributed in imaging region (4) around.
3, permanent-magnet as claimed in claim 1 is characterized in that, the appearance of described magnet ring (21) is a kind of in cylindrical conical or polygon prismatic or polygon pyramid or the shaped as frame; The interior table of magnet ring (21) is shaped as a kind of in cylindrical conical or polygon prismatic or polygon pyramid or the shaped as frame.
4, a kind of described manufacture method that is used for the permanent-magnet of magnetic resonance imaging of claim 1 of making, it is characterized in that, at first permanent magnetic material is carried out line and be cut into magnetic patch, magnetize then, splice in order, glue together according to the magnetic patch direction of magnetization, make main pole (213); The main pole of one or more direction of magnetization gradual change (213) is stack to the left and right in the footpath, is formed on any 1/2nd longitudinal sections direction of magnetization along the central shaft stepwise change, and the tangent line of direction of magnetization is the magnetic lobe (211) that continuity distributes; According to magnetic lobe (211) uniqueness of direction of magnetization diametrically, by the order that is 360 ° of stepwise change around the longitudinal axis, the main field direction of magnetization that is formed on a center is axial magnet ring (21) again.
5, as the said manufacture method that is used for the permanent-magnet of magnetic resonance imaging of claim 4, it is characterized in that, according on any 1/2nd longitudinal sections direction of magnetization along the order of 360 ° of stepwise change of central shaft, along the longitudinal axis each rank magnet ring (21) that superposes up and down, form enclosed main magnet (2); Pole shoe (3) is fixed on the imaging end face of main magnet up and down; Again with the stepped distribution of inside surface, and the soft magnetism yoke (1) that the exponent number of the progression of ladder and magnet ring (21) adapts is fixed on main magnet (2) periphery.
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| CN2008101122890A CN101281239B (en) | 2008-05-22 | 2008-05-22 | Permanent magnetic body used for magnetic resonance imaging and manufacturing method thereof |
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| CN101281239B CN101281239B (en) | 2012-02-08 |
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101901663A (en) * | 2010-03-03 | 2010-12-01 | 中国科学院电工研究所 | Dipolar permanent magnet and manufacturing method thereof |
| CN102331588A (en) * | 2011-08-03 | 2012-01-25 | 中国石油大学(北京) | Nuclear magnetic resonance logging instrument as well as probe magnet and probe thereof |
| CN101620260B (en) * | 2009-07-31 | 2012-07-04 | 河南理工大学 | Permanent-magnetic hierarchical testing device for content of magnetic substance powder |
| CN105280368A (en) * | 2015-10-10 | 2016-01-27 | 宁波韵升股份有限公司 | Manufacturing method for laminated magnetic steel |
| CN107316729A (en) * | 2017-06-15 | 2017-11-03 | 中国科学院近代物理研究所 | The method of magnetic ring component and manufacture magnetic ring component |
| CN114184990A (en) * | 2021-11-29 | 2022-03-15 | 深圳航天科技创新研究院 | Magnet for magnetic resonance imaging and optimization method of iron yoke |
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2008
- 2008-05-22 CN CN2008101122890A patent/CN101281239B/en not_active Expired - Fee Related
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101620260B (en) * | 2009-07-31 | 2012-07-04 | 河南理工大学 | Permanent-magnetic hierarchical testing device for content of magnetic substance powder |
| CN101901663A (en) * | 2010-03-03 | 2010-12-01 | 中国科学院电工研究所 | Dipolar permanent magnet and manufacturing method thereof |
| CN102331588A (en) * | 2011-08-03 | 2012-01-25 | 中国石油大学(北京) | Nuclear magnetic resonance logging instrument as well as probe magnet and probe thereof |
| CN102331588B (en) * | 2011-08-03 | 2014-08-06 | 中国石油大学(北京) | Nuclear magnetic resonance logging instrument as well as probe magnet and probe thereof |
| CN105280368A (en) * | 2015-10-10 | 2016-01-27 | 宁波韵升股份有限公司 | Manufacturing method for laminated magnetic steel |
| CN107316729A (en) * | 2017-06-15 | 2017-11-03 | 中国科学院近代物理研究所 | The method of magnetic ring component and manufacture magnetic ring component |
| CN114184990A (en) * | 2021-11-29 | 2022-03-15 | 深圳航天科技创新研究院 | Magnet for magnetic resonance imaging and optimization method of iron yoke |
| 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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| CN101281239B (en) | 2012-02-08 |
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