JPH01115348A - Magnetic resonance imaging apparatus - Google Patents
Magnetic resonance imaging apparatusInfo
- Publication number
- JPH01115348A JPH01115348A JP62271756A JP27175687A JPH01115348A JP H01115348 A JPH01115348 A JP H01115348A JP 62271756 A JP62271756 A JP 62271756A JP 27175687 A JP27175687 A JP 27175687A JP H01115348 A JPH01115348 A JP H01115348A
- Authority
- JP
- Japan
- Prior art keywords
- magnetic field
- magnet
- main magnet
- superconductor
- generated
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 238000002595 magnetic resonance imaging Methods 0.000 title claims description 11
- 239000002887 superconductor Substances 0.000 claims abstract description 19
- 230000003068 static effect Effects 0.000 claims abstract description 15
- 239000007788 liquid Substances 0.000 claims description 10
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 8
- 239000002826 coolant Substances 0.000 claims description 6
- 239000001307 helium Substances 0.000 claims description 6
- 229910052734 helium Inorganic materials 0.000 claims description 6
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 claims description 6
- 238000001816 cooling Methods 0.000 claims description 5
- 229910052757 nitrogen Inorganic materials 0.000 claims description 4
- 239000004020 conductor Substances 0.000 abstract description 4
- 229910052751 metal Inorganic materials 0.000 abstract description 4
- 239000002184 metal Substances 0.000 abstract description 4
- 239000000523 sample Substances 0.000 abstract description 4
- 239000000919 ceramic Substances 0.000 abstract description 2
- 238000001208 nuclear magnetic resonance pulse sequence Methods 0.000 abstract description 2
- 239000000463 material Substances 0.000 abstract 1
- 238000000034 method Methods 0.000 description 4
- 238000010586 diagram Methods 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910010293 ceramic material Inorganic materials 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000005284 excitation Effects 0.000 description 1
- 238000007710 freezing Methods 0.000 description 1
- 230000008014 freezing Effects 0.000 description 1
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 1
- 239000010931 gold Substances 0.000 description 1
- 229910052737 gold Inorganic materials 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000005057 refrigeration Methods 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
Abstract
Description
【発明の詳細な説明】
［発明の目的］
（産業上の利用分野）
本発明は、磁気共鳴イメージング装２（以下ＭＲＩ装置
という）に関し、特に静磁場発生用の主磁石として用い
る超電導磁石の改良に関する。[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a magnetic resonance imaging device 2 (hereinafter referred to as an MRI device), and particularly relates to an improvement of a superconducting magnet used as a main magnet for generating a static magnetic field. Regarding.
（従来の技術）
従来、超電導磁石を静磁場発生用に構成してなる超電導
ＭＲＩ装置においては、超電導磁石の主要構成部材であ
る超電導体を絶対零度近傍の液体ヘリウムにより冷却し
、この極低温冷却状態で超電導磁石を稼動させていた。(Prior art) Conventionally, in a superconducting MRI apparatus in which a superconducting magnet is configured to generate a static magnetic field, the superconductor, which is the main component of the superconducting magnet, is cooled with liquid helium at a temperature close to absolute zero. Superconducting magnets were operating in this state.
更に、超電導体を直接的に冷却する液体ヘリウム及びこ
の液体ヘリウムの周囲に充填させる液体窒素の充填容器
を、熱伝導性が高く極低温乃至真空状態にも耐え１ｑる
組成としたステンレス、アルミニウム等の金属により製
作した。Furthermore, the containers filled with liquid helium that directly cools the superconductor and liquid nitrogen that is filled around the liquid helium are made of stainless steel, aluminum, etc., which have a composition that has high thermal conductivity and can withstand extremely low temperatures and vacuum conditions. Manufactured from metal.
しかしながら、このような超電導磁石により形成される
静磁場発生空間には、傾斜磁場コイルが配置されており
、この傾斜磁場コイルから発生される傾斜磁場を静磁場
に重畳印加した時、超電導磁石の容器中に渦電流が生じ
るという弊害があった。However, a gradient magnetic field coil is arranged in the static magnetic field generation space formed by such a superconducting magnet, and when the gradient magnetic field generated from this gradient magnetic field coil is applied superimposed on the static magnetic field, the container of the superconducting magnet The problem was that eddy currents were generated inside.
（発明が解決しようとする問題点）
即ち、従来の超電導ＭＲＩ装置の場合においては、超電
導磁石により静１４１ＪＪＡを発生させている際、傾斜
磁場コイルより傾斜ｌ１ｆｉ場が発生されると超電導磁
石の容器中に渦電流、が誘起される。(Problems to be Solved by the Invention) In other words, in the case of a conventional superconducting MRI apparatus, when a static 141JJA is generated by a superconducting magnet, when a gradient l1fi field is generated from a gradient magnetic field coil, the container of the superconducting magnet Eddy currents are induced inside.
この渦電流は、傾斜磁場コイルによる傾斜磁場と反対向
きの磁場を発生させ、傾斜磁場の強度を低下させること
になる。This eddy current generates a magnetic field in the opposite direction to the gradient magnetic field produced by the gradient magnetic field coil, thereby reducing the strength of the gradient magnetic field.
そこで、従来は、渦電流によって生じる反対向きの磁場
を打消すように傾斜磁場コイルに対してあらかじめ大き
な電流を供給し、所望の磁場強度を得るという手段を採
用していた。Conventionally, therefore, a method has been adopted in which a large current is supplied in advance to the gradient magnetic field coils so as to cancel out the oppositely directed magnetic fields generated by the eddy currents, thereby obtaining the desired magnetic field strength.
しかし、この手段によると、傾斜磁場コイルに電流を供
給するための電源を大がかりのものとしなければならな
いという不具合があった。However, this method has the disadvantage that it requires a large-scale power source for supplying current to the gradient magnetic field coils.
また、傾斜磁場コイルと超電導磁石との間の距離を大ぎ
くするという手段も採用されており、この場合、傾斜ｔ
ａ場ココイル大きさは中に入る被検体の大きさによって
小さくすることに限度があるため、超′Ｎｉ導磁石が著
しく大型化されるという不具合があった。In addition, a method of increasing the distance between the gradient magnetic field coil and the superconducting magnet has also been adopted; in this case, the gradient t
Since there is a limit to reducing the size of the a-field cocoil depending on the size of the subject to be examined, there is a problem in that the super'Ni conductive magnet becomes extremely large.
これらの対策の他にも渦電流を打消すための種々の手段
が提案されているが、何れも本質的に渦電流を消失させ
るものはな（、何らかのパワーを必要とするという問題
点があった。In addition to these measures, various methods have been proposed to cancel eddy currents, but none of them essentially eliminate eddy currents (although they do have the problem of requiring some kind of power). Ta.
本発明の目的は、傾斜磁場コイルにより傾斜磁場を発生
したとき渦電流の発生するのを回避することができる静
磁場発生用の超電導磁石を構成してなるＭＲＩ装置を提
供することにある。An object of the present invention is to provide an MRI apparatus configured with a superconducting magnet for static magnetic field generation that can avoid generation of eddy currents when gradient magnetic fields are generated by gradient magnetic field coils.
［発明の構成１
（問題点を解決するための手段）
本発明は、上記の目的を）１成するため、静磁場発生用
の主磁石として、液体ヘリウム、液体窒素等の極低温冷
却媒体による６汀１温度を越える高温下で超電導現象が
生じる超電導体を主要構成部材とした超電導磁石を構成
してなることを要旨とする。[Structure 1 of the Invention (Means for Solving the Problems)] In order to achieve the above object, the present invention uses a cryogenic cooling medium such as liquid helium or liquid nitrogen as the main magnet for generating a static magnetic field. The gist of the present invention is to constitute a superconducting magnet whose main component is a superconductor that exhibits a superconducting phenomenon at a high temperature exceeding 6.1.
（作用）
本発明による構成であれば、超電導磁石の主要構成部材
の超電導体を冷却する条件を緩和させても、その超電導
体に超電導用９が生じるから、超電導体の冷却媒体の充
填容器を金属導体としなければならないという従来の条
件を回避することができる。(Function) With the configuration according to the present invention, even if the conditions for cooling the superconductor, which is the main component of the superconducting magnet, are relaxed, superconductor 9 is generated in the superconductor, so the container filled with the cooling medium for the superconductor is The traditional requirement of having to use metal conductors can be avoided.
そして、超電導体が冷却媒体で冷却することなく超電導
現象が生じる超電導体であれば、冷却媒体の充填容器は
不必要となる。If the superconductor is a superconductor in which the superconducting phenomenon occurs without being cooled with a cooling medium, a container filled with the cooling medium is unnecessary.
（実施例）
第２図は、本発明が適用されるＭＲＩＩＩｆの概略を示
す構成図である。(Example) FIG. 2 is a configuration diagram showing an outline of MRIIf to which the present invention is applied.
このＭＲＩ装置は、静磁場発生用の主磁石１と、この主
磁石１により得られるｉｆ？’！ｉ場下でへ周波励起パ
ルス（ＲＦパルス）の発信及び磁気共鳴信号（ＭＲ倍信
号の受信を行うプローブ２と、主磁石１による静磁場ｘ
、ｙ、ｚの各軸方向等の傾斜磁場を重畳印加するための
各傾斜磁場コイル３と、これらプローブ２及び各傾斜磁
場コイル３をパルスシーケンスに従って制御するととも
に、ＭＲ倍信号信号処理を行う制御用コンピュータ４と
、・ＣＲＴ等のモニタ５とを備えている。This MRI apparatus includes a main magnet 1 for generating a static magnetic field, and an if? obtained by this main magnet 1. '! A probe 2 transmits a frequency excitation pulse (RF pulse) and receives a magnetic resonance signal (MR multiplied signal) under an i field, and a static magnetic field generated by the main magnet 1
, y, z axis directions, etc., and controls these probes 2 and gradient magnetic field coils 3 according to a pulse sequence, and performs MR multiplication signal processing. 4, and a monitor 5 such as a CRT.
このようなＭＲＩ装置に対しての主磁石１に適用される
超電導体は、液体ヘリウム、液体窒素等の極低温冷却媒
体による冷却温度、好ましくは摂氏零度以上の常温で超
電導現象が生じるセラミックス材料からなる。The superconductor applied to the main magnet 1 of such an MRI apparatus is made of a ceramic material that exhibits a superconducting phenomenon at a temperature cooled by a cryogenic cooling medium such as liquid helium or liquid nitrogen, preferably at room temperature above zero degrees Celsius. Become.
この超電導体をコイル状に巻回するなどして磁場発生を
可能にした超電導磁石構成の主磁石１であれば、超電導
体を冷１．１１する条件が緩和されることになる。その
ため、断面形状がρ１えば第１図に示す如く超電導体の
コイル１０を介在させた外側シールド１１及び内側シー
ルド１２からなり、内側シールド１２内に冷ｕ１媒体を
充填づるようにしてなる充填容器として、非金属のセラ
ミックスやプラスブック樹脂を成型加工した容器を適用
することができる。特に、摂氏零度以上の常温で超電導
現象が生じる超電導体を主磁石に適用する場合、上記の
冷７ＪＩ媒体の充填容器を用いなくても済む。If the main magnet 1 has a superconducting magnet structure in which magnetic field generation is possible by winding this superconductor into a coil, the conditions for cooling the superconductor will be relaxed. Therefore, if the cross-sectional shape is ρ1, as shown in FIG. , a container molded from non-metallic ceramics or plus book resin can be applied. In particular, when a superconductor that exhibits a superconducting phenomenon at normal temperatures above zero degrees Celsius is used as the main magnet, it is not necessary to use the container filled with the cold 7JI medium described above.
このように、本発明の一実施例では超電導磁石構成の主
磁石１に金属導体が全く使用されていないから、超電導
磁石構成の主磁石１により静磁場を発生させている際、
各傾斜磁場コイル３より傾斜磁場が発生されたとき、超
電導磁石構成の主磁石１には渦電流が全く生じない。As described above, in one embodiment of the present invention, since no metal conductor is used in the main magnet 1 having a superconducting magnet structure, when a static magnetic field is generated by the main magnet 1 having a superconducting magnet structure,
When a gradient magnetic field is generated from each gradient magnetic field coil 3, no eddy current is generated in the main magnet 1 having a superconducting magnet structure.
そのため、各傾斜磁場コイル３から発生される傾斜磁場
が渦電流により打消作用されるという不具合が解）肖さ
れる。従って、各傾斜磁場コイル３へ給電する傾斜磁場
電源のパワーが従来よりも小さく設定された傾斜磁場電
源を使用することができる。Therefore, the problem that the gradient magnetic field generated from each gradient magnetic field coil 3 is canceled by the eddy current is solved. Therefore, it is possible to use a gradient magnetic field power source whose power is set smaller than that of the conventional power source for feeding power to each gradient magnetic field coil 3.
また、超電導磁石構成の主磁石１と各傾斜磁場フィル３
との間に無駄なスペースを設ける必要がなくなり、従っ
て、主磁石１を可及的に小型化することができる。In addition, a main magnet 1 having a superconducting magnet configuration and each gradient magnetic field filter 3
There is no need to provide a wasted space between the main magnet 1 and the main magnet 1. Therefore, the main magnet 1 can be made as small as possible.
また、超電導体のコイル１０に超電導状態が生じる温度
がどの程度であるかによって適宜に冷却設備を設置する
ことも必要となるが、例えば常温で超電導現象が生じる
物質で超電導体のコイル１０を構成した場合には、通常
の冷凍、冷蔵用の冷却設備で冷Ｗ状態を確保することが
できる。It is also necessary to install appropriate cooling equipment depending on the temperature at which the superconductor coil 10 becomes superconducting. For example, the superconductor coil 10 may be made of a substance that exhibits superconductivity at room temperature. In this case, a cold W state can be ensured using ordinary cooling equipment for freezing and refrigeration.
［発明の効果］
以上説明したように、本発明は、静磁場発生用の主磁石
として、金ｆｌ導体を非使用とした超電導磁石を構成す
るから、傾斜磁場コイルから傾斜磁場が発生されたとき
、超電導磁石での渦電流発生を防＋ｈすることができる
。[Effects of the Invention] As explained above, the present invention constitutes a superconducting magnet that does not use a gold fl conductor as the main magnet for generating a static magnetic field, so that when a gradient magnetic field is generated from a gradient magnetic field coil, , the generation of eddy currents in superconducting magnets can be prevented.
第１図は本発明の一実施例の要部構成を示ケ所面図、第
２図は本発明が適用されるＭＲＩ装置の概略を示す構成
図である。
１・・・主磁石 ２・・・プローブ３・・・
傾斜磁場コイル
４・・・制御用コンピュータ
５・・・モニタ １０・・・コイル１１・・・
外側シールド １２・・・内側シールド代理人 弁理士
則 近 憲 佑FIG. 1 is a plan view showing the main structure of an embodiment of the present invention, and FIG. 2 is a block diagram schematically showing an MRI apparatus to which the present invention is applied. 1... Main magnet 2... Probe 3...
Gradient magnetic field coil 4... Control computer 5... Monitor 10... Coil 11...
Outer Shield 12... Inner Shield Agent Patent Attorney Noriyuki Chika
Claims (2)
体窒素等の極低温冷却媒体による冷却温度を越える高温
下で超電導現象が生じる超電導体を主要構成部材とした
超電導磁石を構成してなることを特徴とする磁気共鳴イ
メージング装置。(1) The main magnet for generating a static magnetic field is a superconducting magnet whose main component is a superconductor that exhibits a superconducting phenomenon at a high temperature exceeding the cooling temperature using a cryogenic cooling medium such as liquid helium or liquid nitrogen. A magnetic resonance imaging device characterized by:
現象が生じる超電導体を主要構成部材としたことを特徴
とする特許請求の範囲第１項記載の磁気共鳴イメージン
グ装置。(2) The magnetic resonance imaging apparatus according to claim 1, wherein the superconducting magnet has a superconductor as a main component that exhibits a superconducting phenomenon at normal temperatures above zero degrees Celsius.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP62271756A JPH01115348A (en) | 1987-10-29 | 1987-10-29 | Magnetic resonance imaging apparatus |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP62271756A JPH01115348A (en) | 1987-10-29 | 1987-10-29 | Magnetic resonance imaging apparatus |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH01115348A true JPH01115348A (en) | 1989-05-08 |
Family
ID=17504400
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP62271756A Pending JPH01115348A (en) | 1987-10-29 | 1987-10-29 | Magnetic resonance imaging apparatus |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH01115348A (en) |
-
1987
- 1987-10-29 JP JP62271756A patent/JPH01115348A/en active Pending
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