CN1389177A - Medical magnetic resonance system and its eddy current eliminator - Google Patents
Medical magnetic resonance system and its eddy current eliminator Download PDFInfo
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- CN1389177A CN1389177A CN 01113084 CN01113084A CN1389177A CN 1389177 A CN1389177 A CN 1389177A CN 01113084 CN01113084 CN 01113084 CN 01113084 A CN01113084 A CN 01113084A CN 1389177 A CN1389177 A CN 1389177A
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- eddy current
- gradient coil
- magnetic resonance
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Abstract
The present invention relates to a medical nuclear magnetic resonance imaging system and its device for elimianting eddy current. It includes upright columns and imaging space, and the upper and lower two sides of the imaging space are respectively symmetrically equipped with gradient coil, machine head, magnetic body and electrode plate in turn, the outer side of the gradient coil is matched with uniform field ring, which it is characterized by that between machine head and gradient coil a device for eliminating eddy current is set, so that the induced current of gradient coil can directly act on the eddy current eliminating device, its machine head does not produce eddy current so as to shorten gradient rising time and improve imaging quality.
Description
The invention belongs to the mr imaging technique field, particularly relate to the device of a kind of medical magnetic resonance imaging system and elimination eddy current thereof.
In background technology, comprise column and imaging space in the medical magnetic resonance imaging system, be symmetrically arranged with gradient coil, head, magnetic and pole plate successively in the both sides up and down of imaging space, gradient coil is centered on mutually by grading ring.The imaging of medical magnetic resonance is the strong fast-changing gradient fields of stack on magnetostatic field very uniformly, and these gradient fields are that the gradient coil by the current impulse that is loaded with accurate control produces, and the imaging volume has been determined in the space at gradient fields place.Gradient coil is made up of three groups of coils, has represented X, Y, three directions of Z respectively, and relation is orthogonal between them.Because gradient coil is near head, produce the eddy current of X, Y, three directions of Z applying fail to be convened for lack of a quorum on the head induction of big Pulse Electric on the gradient coil, their relation that also is orthogonal each other, direction is opposite with the gradient current direction.The size of eddy current is decided by the size of the pulse current that applies on the gradient coil, and the electric current that the applies maelstrom of healing is also bigger, and vice versa.The life period of eddy current is decided by the length of eddy current flow path, and the time that the shorter eddy current in path exists is shorter, and the eddy current life period is shorter, and the faradic time of its generation is shorter, and just shorter to the influence time of magnetostatic field, the picture quality that finally obtains is just high.In medical examination, people require more and more higher to the gradient fields in the medical magnetic resonance imaging, the gradient pulse electric current is increasing, cause the eddy current on the pole plate also more and more big, the result is gradient rising edge time lengthening, magnetic resonance system miopragia, image quality decrease, therefore, the solution eddy current problem has become the key in the nuclear magnetic resonance.
Have in the magnetic resonance imaging system of vertical magnetic field in style of opening, usually adopt at the head external coating to have the amorphous metal mixture coating of certain elimination venturi effect or with the method for amorphous metal material head, to reach the purpose that reduces eddy current.It is better that this method is eliminated the effect of eddy current, but cost an arm and a leg, complex process, cost be high, is difficult to generally use popularization.
For example: put down in writing a kind of " being used for reducing the device of the eddy current of MR imaging apparatus " on the patent application document of disclosed publication number CN110971A on the 31st in May nineteen ninety-five, this device is made up of C shape magnet, pole shoe, permanent magnet and gradient coil.Near the gradient coil place, adopt ferruginous thin slice to be made for the lip-deep laminated insulation dish of pole shoe very, the structure of dish has two kinds: in the planar orientation of rim pole-shoe face that part of, they are made of the annular slab that cuts into from iron plate; In the part that the axle along pole-shoe face is orientated, they are made of the ring with banded iron plate spiral coiled.The thin plate-like or the ring-type ferromagnetic parts that are stacked to by multilamellar are housed on the pole shoe surface, and each layer is by lacquer or fixing glue and adjacently situated surfaces point insulating.On these layers, cut out narrow radial slot before the closed assembly, to reduce eddy current.Groove in the adjacent layer is indexed into and does not overlap, thereby causes even magnetic flux on all directions.
On the patent application document of disclosed publication number CN 1252977A on May 17th, 2000, put down in writing " magnetic pole strength of the low magnetic hysteresis of the eddy current in the nuclear magnetic resonance ", it has pole piece, that each pole piece has is respect to one another, be defined as the volumetrical pole-face of picture, excitation unit with magnet exciting coil and pole piece, described pole-face comprises a plurality of magnetic piece with lamination, each lamination is made of the amorphous ferromagnetic material, described lamination is separated by substrate and combines in this substrate, and the arrangement of lamination is arranged essentially parallel to institute's pole-face.This structure has reduced induced eddy current in pole-face, has also reduced remanent magnetization simultaneously, thereby can improve the quality of image.
More than the numerical procedure of two pieces of described reduction eddy current of disclosed patent application document, there is not to solve the problem of the mobile path length of eddy current, the magnetic field that its vortex induction electric current produces to magnetostatic field to influence the persistent period still longer, need further to improve to eliminate vortex device and just can better improve picture quality.
The objective of the invention is to solve magnetic field that eddy current that the gradient pulse induction by current produces produces influence and the eddy current of gradient rise time the problem that influences to magnetostatic field on head, provide a kind of simple in structure, make easily, can eliminate vortes interference, improve the medical magnetic resonance imaging system of picture quality and eliminate the device of eddy current.
The object of the present invention is achieved like this: it comprises column and imaging space, both sides up and down at imaging space are symmetrically arranged with gradient coil, head, magnetic and pole plate successively, matching with grading ring in the outside of gradient coil, it is characterized in that being provided with between described head and the gradient coil device that eddy current is eliminated.
The device that the alleged eddy current of the present invention is eliminated, comprise metallic laminations layer and insulating barrier, it is characterized in that described metallic laminations layer is at least two-layer, there is insulating barrier to be separated by between the adjacent metal lamination layer, the metallic laminations layer is rearranged by the metallic laminations bar, the metallic laminations bar forms by sheet metal is superimposed, and the metallic laminations bar in the adjacent metal lamination layer is and intersects the shape setting.
Because the present invention has adopted the structure that the eddy current cancellation element is set between head and gradient coil, it is isolated gradient coil and pole plate, when when applying gradient, having big pulse current to pass through in the gradient coil, the faradic current of gradient coil directly acts on the eddy current cancellation element, do not produce eddy current on the head, thereby solved magnetic field that eddy current that the gradient pulse induction by current produces produces influence and the eddy current of gradient rise time the problem that influences on head to magnetostatic field, shorten the gradient rise time, improved image quality.
In conjunction with the accompanying drawings and embodiments, this utility model is further described as follows:
Fig. 1 is a structural representation of the present invention
Fig. 2 is one of structural representation sketch map of eliminating vortex device
Fig. 3 is two of the structural representation sketch map of eliminating vortex device
Fig. 4 is the structural representation of metallic laminations bar
With reference to accompanying drawing: the present invention includes column 4 and imaging space 12, be symmetrically arranged with gradient coil 3 and gradient coil 8 successively in the both sides up and down of imaging space 12; Head 5 and head 10; Magnetic 2 and magnetic 7; Pole plate 1 and pole plate 9, match with grading ring 13,11 in the outside of gradient coil 3,8, described gradient coil 3,8, head 5,10, magnetic 2,7 and pole plate 1,9 all join with column 4 and are close to mutually, between described head 5 and gradient coil 3, be provided with eddy current cancellation element 602, be provided with eddy current cancellation element 601 between head 9 and the gradient coil 8, column 4 is all made by metal material with head 1,9, and column 4 can constitute magnetic loop in use; Pole plate the 1, the 9th is made by metal material, has good permeability; Magnetic is a permanent magnet material, and it can produce magnetostatic field; Gradient coil 3,8 are made by the metal copper material, grading ring 11,13 are made by metal material, it can carry out shimming to magnetostatic field, eliminate vortex device 6 and adopt the permeability height, the metal material that remanent magnetism is few is made, the device 6 that the alleged eddy current of the present invention is eliminated, it comprises metallic laminations layer 15,19 and insulating barrier 16, described metallic laminations layer is generally layer 2-4, adjacent metal lamination layer 15, there is insulating barrier 16 to be separated by between 19, metallic laminations layer 15,19 are rearranged by metallic laminations bar 20, metallic laminations bar 20 forms adjacent metal lamination layer 15 by sheet metal 201 usefulness insulation viscose glue 21 bondings, metallic laminations bar 20 orthogonal thereto shape settings in 19.Sheet metal 201 employing pcrmeability height, the stalloy that remanent magnetism is few are made, and its thickness is 0.1-0.4mm, and width is 5-12mm, and length is not less than 10mm, and length also can be determined by the position that grading ring limits.Because the elimination vortex device 6 among the present invention can separate gradient coil and pole plate, thereby when when executing gradient, having big pulse current to pass through in the gradient coil, the faradic current of gradient coil acts directly on the device 6 of eliminating eddy current, make and do not produce eddy current on the head, the rising of gradient is not subjected to the effect of eddy current retardance, therefore, the gradient rise time is just short, ensured magnetostatic field stability, improved the performance and the picture quality of medical magnetic resonance imaging system.
Claims (3)
1, a kind of medical magnetic resonance imaging system, comprise column and imaging space, both sides up and down at imaging space are symmetrically arranged with gradient coil, head, magnetic and pole plate successively, matching with grading ring in the outside of gradient coil, it is characterized in that being provided with between described head and the gradient coil device that eddy current is eliminated.
2, a kind of medical magnetic resonance imaging system is eliminated the device of eddy current, comprise metallic laminations layer and insulating barrier, it is characterized in that described metallic laminations layer is at least two layers, there is insulating barrier to be separated by between the adjacent metal lamination layer, the metallic laminations layer is rearranged by the metallic laminations bar, the metallic laminations bar forms by sheet metal is superimposed, and the metallic laminations bar in the adjacent metal lamination layer is and intersects the shape setting.
3, medical magnetic resonance imaging system according to claim 2 is eliminated the device of eddy current, it is characterized in that described sheet metal adopts pcrmeability height, stalloy that remanent magnetism is few to make, and its thickness is 0.1-0.4mm, and width is 5-12mm, and length is not less than 10mm.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 01113084 CN1389177A (en) | 2001-06-06 | 2001-06-06 | Medical magnetic resonance system and its eddy current eliminator |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 01113084 CN1389177A (en) | 2001-06-06 | 2001-06-06 | Medical magnetic resonance system and its eddy current eliminator |
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| CN1389177A true CN1389177A (en) | 2003-01-08 |
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| CN 01113084 Pending CN1389177A (en) | 2001-06-06 | 2001-06-06 | Medical magnetic resonance system and its eddy current eliminator |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100431489C (en) * | 2004-06-22 | 2008-11-12 | 中国科学院电工研究所 | Magnet polar plate of magnetic resonance |
| CN102403081A (en) * | 2010-09-17 | 2012-04-04 | 通用电气公司 | Magnet assembly and manufacturing method thereof |
| CN101897586B (en) * | 2008-11-06 | 2012-09-12 | 株式会社东芝 | MRI apparatus, bed device for MRI apparatus and table top of bed device for MRI apparatus |
| CN103654787A (en) * | 2012-09-24 | 2014-03-26 | 三星电子株式会社 | Magnetic resonance imaging (MRI) apparatus and manufacturing method thereof |
| CN103892834A (en) * | 2014-03-21 | 2014-07-02 | 沈阳中北真空磁电科技有限公司 | Permanent magnet used for nuclear magnetic resonance imager |
-
2001
- 2001-06-06 CN CN 01113084 patent/CN1389177A/en active Pending
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100431489C (en) * | 2004-06-22 | 2008-11-12 | 中国科学院电工研究所 | Magnet polar plate of magnetic resonance |
| CN101897586B (en) * | 2008-11-06 | 2012-09-12 | 株式会社东芝 | MRI apparatus, bed device for MRI apparatus and table top of bed device for MRI apparatus |
| CN102403081A (en) * | 2010-09-17 | 2012-04-04 | 通用电气公司 | Magnet assembly and manufacturing method thereof |
| CN103654787A (en) * | 2012-09-24 | 2014-03-26 | 三星电子株式会社 | Magnetic resonance imaging (MRI) apparatus and manufacturing method thereof |
| CN103654787B (en) * | 2012-09-24 | 2017-12-15 | 三星电子株式会社 | MR imaging apparatus and its manufacture method |
| CN103892834A (en) * | 2014-03-21 | 2014-07-02 | 沈阳中北真空磁电科技有限公司 | Permanent magnet used for nuclear magnetic resonance imager |
| CN103892834B (en) * | 2014-03-21 | 2016-05-25 | 沈阳中北真空磁电科技有限公司 | A kind of permanent magnet for NMR imaging instrument |
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