JPH0215834B2 - - Google Patents
Info
- Publication number
- JPH0215834B2 JPH0215834B2 JP58158563A JP15856383A JPH0215834B2 JP H0215834 B2 JPH0215834 B2 JP H0215834B2 JP 58158563 A JP58158563 A JP 58158563A JP 15856383 A JP15856383 A JP 15856383A JP H0215834 B2 JPH0215834 B2 JP H0215834B2
- Authority
- JP
- Japan
- Prior art keywords
- magnetic
- magnetic field
- magnet
- circuit
- magnet pieces
- 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.)
- Expired - Lifetime
Links
- 239000000463 material Substances 0.000 claims description 10
- 230000035699 permeability Effects 0.000 claims description 5
- 238000003780 insertion Methods 0.000 claims description 3
- 230000037431 insertion Effects 0.000 claims description 3
- 238000013421 nuclear magnetic resonance imaging Methods 0.000 claims description 3
- 239000000696 magnetic material Substances 0.000 claims description 2
- 238000010586 diagram Methods 0.000 description 7
- 230000005415 magnetization Effects 0.000 description 5
- 238000005481 NMR spectroscopy Methods 0.000 description 4
- 230000004907 flux Effects 0.000 description 4
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 3
- 238000003384 imaging method Methods 0.000 description 3
- 229910000859 α-Fe Inorganic materials 0.000 description 3
- 229910000976 Electrical steel Inorganic materials 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000004033 plastic Substances 0.000 description 2
- 239000011230 binding agent Substances 0.000 description 1
- 239000003990 capacitor Substances 0.000 description 1
- 239000010941 cobalt Substances 0.000 description 1
- 229910017052 cobalt Inorganic materials 0.000 description 1
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 229910052761 rare earth metal Inorganic materials 0.000 description 1
- 150000002910 rare earth metals Chemical class 0.000 description 1
- 229920001169 thermoplastic Polymers 0.000 description 1
- 239000004416 thermosoftening plastic Substances 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
- G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
- G01R33/38—Systems for generation, homogenisation or stabilisation of the main or gradient magnetic field
- G01R33/387—Compensation of inhomogeneities
- G01R33/3873—Compensation of inhomogeneities using ferromagnetic bodies ; Passive shimming
Landscapes
- Physics & Mathematics (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- General Physics & Mathematics (AREA)
- Magnetic Resonance Imaging Apparatus (AREA)
Description
【発明の詳細な説明】
本発明は、核磁気共鳴（nuclear magnetic
resonance：以下NMRと略す）イメージング装
置に使用される磁界発生装置に関する。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to nuclear magnetic resonance
Resonance (hereinafter abbreviated as NMR) relates to a magnetic field generating device used in an imaging device.
従来からNMRイメージング装置は知られてい
る。このような装置に関し、NMRイメージング
に必要な安定で均一な基底磁界Hoを得ようとす
るにおいて、電磁石を用いる必要性は必ずしも存
在せず、既に永久磁石を用いることが提案されて
いる。ところが、何分にも人体をくぐらせ得る位
の太い内径若しくは幅の空間を主磁束占有空間と
するような巨大な永久磁石を作ろうとすると、物
の量だけでも大変なことになるのみならず、着磁
をどうやつて効果的に行うかという問題に直面
し、着磁のためのコイルやパルス電源だけでもと
んでもないものになつてしまう。 NMR imaging devices have been known for a long time. Regarding such a device, when trying to obtain a stable and uniform base magnetic field Ho necessary for NMR imaging, it is not necessarily necessary to use an electromagnet, and the use of a permanent magnet has already been proposed. However, if you try to make a huge permanent magnet whose main magnetic flux occupies a space with an inner diameter or width that is large enough to allow a human body to pass through it for several minutes, it will not only be difficult due to the amount of material involved, but also the size of the magnet. However, we were faced with the problem of how to effectively achieve magnetization, and even just a coil and a pulsed power supply for magnetization would be unbelievable.
この目的に利用され得る永久磁石の構造として
は、人体の体軸と直交する方向の基底磁界Hcを
用いるならば所謂馬蹄形乃至Ｕ形、Ｃ形等に類す
る片側磁気回路式のものでよいが、それらの成す
基底磁界Hcは均一性の点でさほど優れていない
ことから、それらを２つ並べた如き両側磁気回路
式のものも利用され、このものの方が優れた均一
度を得やすい。しかし、磁石材料自身を中空円筒
状に形成するならば着磁のやり方如何でその軸方
向にも又軸とは直交する方向にも基底磁界Hcを
発生させることができ、その均一度は着磁の分布
に応じて、又、それを調節することにより、かな
り優れたものとすることができる。このような円
筒磁石はモータ、発電機乃至ガルバノメータ等の
回転機の用途に既に汎用されている。材料として
は、その目的のフエライトでもよいし、又、所謂
プラスチツク磁石、即ち希土類コバルト系の磁石
材料の粉末を高濃度に熱可塑性プラスチツク等を
バインダーとして固めたもの等が適合している。
しかるに、巨大な馬蹄形や円筒形のものを一気に
作り上げることは難しいので、円環を多数積み上
げるとか、電磁軟鉄やケイ素鋼板のラミネーシヨ
ンの磁気回路乃至ポールピースを併用するとかの
工夫が必要となる。それでも尚、組立後の有効な
着磁という問題が残る。 As for the structure of the permanent magnet that can be used for this purpose, if the base magnetic field Hc in the direction perpendicular to the body axis of the human body is used, a one-sided magnetic circuit type similar to the so-called horseshoe shape, U shape, C shape, etc. may be used. Since the base magnetic field Hc formed by these magnets is not very good in terms of uniformity, a double-sided magnetic circuit type in which two of them are arranged side by side is also used, and it is easier to obtain excellent uniformity. However, if the magnet material itself is formed into a hollow cylindrical shape, the base magnetic field Hc can be generated in the axial direction or in the direction perpendicular to the axis, depending on the method of magnetization. Depending on the distribution of , and by adjusting it, it can be made considerably superior. Such cylindrical magnets are already widely used in rotating machines such as motors, generators, and galvanometers. The material may be ferrite for the purpose, or a so-called plastic magnet, that is, a material made by hardening a powder of a rare earth cobalt magnet material at a high concentration using a thermoplastic or the like as a binder, is suitable.
However, it is difficult to create a huge horseshoe or cylindrical shape all at once, so it is necessary to devise measures such as piling up many rings or using magnetic circuits or pole pieces laminated with electromagnetic soft iron or silicon steel sheets. Nevertheless, the problem of effective magnetization after assembly still remains.
本発明は、このような点に鑑みてなされたもの
で、その目的は、本質的に組立、製作及び着磁と
その修正が容易であつて、磁気回路併用式の磁界
発生装置を提供することにある。 The present invention has been made in view of these points, and its purpose is to provide a magnetic field generating device that is essentially easy to assemble, manufacture, magnetize, and modify, and that is combined with a magnetic circuit. It is in.
この目的を達成する本発明は、核磁気共鳴イメ
ージング装置において、外部磁気回路を磁気抵抗
の少ない透磁率の良い物質で形成された閉回路と
し、目的とする基底磁界Hcを印加する空間にお
いてその外部磁気回路を閉口せしめ、その端面に
各磁石片同士の間に所定の〓間を形成して磁石片
を略一様に多数分布せしめ、且つこれらの磁石片
にはすべて又は適当な比率でその一部にネジ穴を
設け該ネド穴に高透磁率の非永久磁石材料からな
るシヤント用コアを螺合させ、該コアの挿入長を
調整することにより起磁力の強さを調整する手段
を設けてなることを特徴とするものである。 The present invention achieves this object by making the external magnetic circuit a closed circuit formed of a material with low magnetic resistance and high magnetic permeability in a nuclear magnetic resonance imaging apparatus, and in which the external magnetic circuit is formed in a space where the target base magnetic field Hc is applied. The magnetic circuit is closed, and a predetermined gap is formed between each magnet piece on the end face, so that a large number of magnet pieces are distributed substantially uniformly, and all or a suitable ratio of the magnet pieces are distributed. A screw hole is provided in the part, and a shunt core made of a non-permanent magnetic material with high magnetic permeability is screwed into the screw hole, and means is provided for adjusting the strength of the magnetomotive force by adjusting the insertion length of the core. It is characterized by:
以下、図面を参照し本発明を詳細に説明する。 Hereinafter, the present invention will be explained in detail with reference to the drawings.
本発明では、小形の磁石を多数用い、磁束が斎
一する向きになるように磁気回路の一端面に並べ
て、大きな面としての起磁力を実現する。その様
子を第１図に示す。即ち、ケイ素鋼板の巻鉄芯の
円筒（外部磁気回路）或いはフエライトで成る円
筒１の内面に、磁石片２を、すべての磁束が斎一
する向きに貼付ける。この磁石片２は板厚状或い
は高さの低い円筒状等で、フエライトマグネツト
或いはプラスチツク磁石で成り、各磁石片２同士
はその間隙が少なくとも磁石片の高さよりも小な
る関係で配置され、フラツクスのバイパスを少な
くする。磁石片２の分布が第２図の如くcos2θに
従うならば、内部に生じる基底磁界Hcは均一に
なる。尚、特にcos2θに従わずとも適当に左右に
別れて分布させれば中央部では均一な磁場とな
る。更に、円筒１内の軸方向に相当な距離（例え
ば内径70cm以上の円筒の場合、内径の２倍程度の
距離）にわたつて上述の如き磁石片配列をとるな
らば、ｚ軸方向（軸方向）の均一度も十分確保で
きる。第３図はこの場合において更に均一度の向
上を図つたものである。即ち、円筒の端の方の磁
石の分布密度を上げておくことにより円筒外に漏
れて出る分を含めてｚ方向の基底磁界Hcの分布
を均一化することができる。尚、磁石の分布密度
でなく電磁石的に補正するようにしてもよい。 In the present invention, a large number of small magnets are used and arranged on one end surface of a magnetic circuit so that the magnetic flux is uniform, thereby realizing magnetomotive force as a large surface. The situation is shown in Figure 1. That is, the magnet pieces 2 are attached to the inner surface of a cylinder 1 made of a silicon steel plate wound iron core (external magnetic circuit) or a cylinder 1 made of ferrite in a direction in which all the magnetic flux is uniform. The magnet pieces 2 have a thick plate shape or a cylindrical shape with a low height, and are made of ferrite magnets or plastic magnets, and the magnet pieces 2 are arranged such that the gap between them is at least smaller than the height of the magnet pieces, Reduce flux bypass. If the distribution of the magnet pieces 2 follows cos 2 θ as shown in FIG. 2, the base magnetic field Hc generated inside will be uniform. Note that even if the magnetic field does not particularly follow cos 2 θ, if the magnetic field is distributed appropriately to the left and right, a uniform magnetic field will be obtained in the center. Furthermore, if the magnet pieces are arranged as described above over a considerable distance in the axial direction within the cylinder 1 (for example, in the case of a cylinder with an inner diameter of 70 cm or more, the distance is about twice the inner diameter), ) can also ensure sufficient uniformity. FIG. 3 shows an attempt to further improve the uniformity in this case. That is, by increasing the distribution density of the magnets toward the end of the cylinder, it is possible to make the distribution of the base magnetic field Hc in the z direction uniform, including the part that leaks out of the cylinder. Note that the correction may be performed electromagnetically instead of using the distribution density of the magnets.
又、第４図の如く、更に基底磁界Hc修正用コ
イル４１と信号検出用コイル４２等とも複合化す
ることができる。 Further, as shown in FIG. 4, it can be further combined with a base magnetic field Hc correction coil 41, a signal detection coil 42, etc.
第５図は馬蹄形の外部磁気回路５１の開口部に
磁石片２を取付けたものであり、上記と同様に基
底磁界Hcを得るものである。更に、第６図は双
Ｕ字形の磁気回路６１に磁石片２を補助ポールピ
ース６２を介して接合したものである。 FIG. 5 shows a magnet piece 2 attached to the opening of a horseshoe-shaped external magnetic circuit 51 to obtain a base magnetic field Hc in the same manner as above. Further, in FIG. 6, a magnet piece 2 is joined to a double U-shaped magnetic circuit 61 via an auxiliary pole piece 62.
第７図は見掛け上の起磁力を調節することがで
きるようにした磁石素片の構成を示す図である。
即ち、永久磁石材料のブロツクの中央部にネジ穴
７２を設け、このネジ穴に永久磁石材料ではない
が透磁率の高い材料でなるシヤント用コア７１
（オネジとなつている）を入れる。このコア７１
の挿入深さを調節することにより見掛け上の磁界
（外部へ有効に出てゆく磁界）を調節することが
できる。このような構成の磁石素片をすべて又は
適当な個数毎に配列し、その各々を巧みに調整す
ることにより、所望の起磁力分布を磁気回路の開
口部の壁に分布せしめることができ、もつて均一
な基底磁界Hcを永久磁石により実現することが
できる。 FIG. 7 is a diagram showing the configuration of a magnet piece that allows the apparent magnetomotive force to be adjusted.
That is, a screw hole 72 is provided in the center of a block of permanent magnet material, and a shunt core 71 made of a material with high magnetic permeability, which is not a permanent magnet material, is inserted into this screw hole.
(has a male screw). This core 71
By adjusting the insertion depth of the magnetic field, the apparent magnetic field (the magnetic field that effectively exits to the outside) can be adjusted. By arranging all or an appropriate number of magnet pieces with such a configuration and skillfully adjusting each piece, it is possible to distribute the desired magnetomotive force distribution on the wall of the opening of the magnetic circuit. A uniform base magnetic field Hc can be realized using a permanent magnet.
第８図は上記の如き磁石片を磁気回路の端面に
接合した後に、これを着磁するための着磁装置の
構成図である。図中、８１は着磁コイルで、磁石
片２の外周を取り囲むような薄肉の円筒又は四角
筒状に形成されている。この着磁コイル８１は、
直流電源８２で充電されたコンデンサ８３にスイ
ツチ８４を介して接続されている。着磁は、コイ
ルの中に磁石片をとらえて、スイツチを瞬間的に
オンとし、コイルに瞬時的に電流を流し、磁石片
を磁化して行われる。各磁石片について同様に行
い、永久磁石を形成する。 FIG. 8 is a configuration diagram of a magnetizing device for magnetizing a magnet piece as described above after it is bonded to an end face of a magnetic circuit. In the figure, reference numeral 81 denotes a magnetizing coil, which is formed into a thin cylindrical or rectangular cylindrical shape so as to surround the outer periphery of the magnet piece 2. This magnetizing coil 81 is
It is connected via a switch 84 to a capacitor 83 charged by a DC power supply 82 . Magnetization is performed by capturing a piece of magnet in a coil, turning on a switch momentarily, and instantly passing current through the coil to magnetize the piece of magnet. Do the same for each magnet piece to form a permanent magnet.
以上説明したように、本発明によれば、組立、
製作及び着磁とその修正が容易である。又、個々
に調整可能なネジ形式シヤント用コアからなる起
磁力調整手段を有する磁石片を多数個分布してい
るため、３次元的な空間にて均一な磁界を容易に
実現することができる。 As explained above, according to the present invention, assembly,
It is easy to manufacture, magnetize, and modify. In addition, since a large number of magnet pieces each having a magnetomotive force adjustment means made of individually adjustable screw-type shunt cores are distributed, a uniform magnetic field can be easily achieved in a three-dimensional space.
第１図は本発明に係る磁界発生装置の一実施例
を示す構成図、第２図は磁石片の分布の磁界の関
係を説明するための説明図、第３図乃至第６図は
本発明の他の実施例を示す構成図、第７図は磁石
素片の他の実施例を示す説明図、第８図は着磁装
置の構成図である。
１……外部磁気回路、２……磁石片、７１……
コア。
FIG. 1 is a configuration diagram showing one embodiment of a magnetic field generating device according to the present invention, FIG. 2 is an explanatory diagram for explaining the relationship between the distribution of magnet pieces and the magnetic field, and FIGS. 3 to 6 are diagrams according to the present invention. FIG. 7 is an explanatory diagram showing another embodiment of the magnet piece, and FIG. 8 is a diagram showing the configuration of a magnetizing device. 1... External magnetic circuit, 2... Magnet piece, 71...
core.
Claims (1)
磁気回路を磁気抵抗の少ない透磁率の良い物質で
形成された閉回路とし、目的とする基底磁界Ho
を印加する空間においてその外部磁気回路を閉口
せしめ、その端面に、各磁石片同士の間に所定の
〓間を形成して磁石片を略一様に多数分布せし
め、且つこれら磁石片にはすべて又は適当な比率
でその一部にネジ穴を設け該ネジ穴に高透磁率の
非永久磁石材料からなるシヤント用コアを螺合さ
せ、該コアの挿入長を調整することにより起磁力
の強さを調整する手段を設けてなることを特徴と
する核磁気共鳴イメージング装置の磁界発生装
置。1 In nuclear magnetic resonance imaging equipment, the external magnetic circuit is a closed circuit made of a material with low magnetic resistance and high permeability, and the target base magnetic field Ho
The external magnetic circuit is closed in the space in which the magnetic field is applied, and a predetermined gap is formed between each magnet piece on the end face thereof, and a large number of magnet pieces are distributed almost uniformly, and all of these magnet pieces are Alternatively, the strength of the magnetomotive force can be increased by providing screw holes in some of them at an appropriate ratio, screwing a shunt core made of a non-permanent magnetic material with high magnetic permeability into the screw hole, and adjusting the insertion length of the core. 1. A magnetic field generating device for a nuclear magnetic resonance imaging apparatus, characterized in that the magnetic field generating device is provided with means for adjusting.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP58158563A JPS6050442A (en) | 1983-08-30 | 1983-08-30 | Magnetic-field generator for nuclear-magnetic- resonance imaging apparatus |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP58158563A JPS6050442A (en) | 1983-08-30 | 1983-08-30 | Magnetic-field generator for nuclear-magnetic- resonance imaging apparatus |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS6050442A JPS6050442A (en) | 1985-03-20 |
| JPH0215834B2 true JPH0215834B2 (en) | 1990-04-13 |
Family
ID=15674430
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP58158563A Granted JPS6050442A (en) | 1983-08-30 | 1983-08-30 | Magnetic-field generator for nuclear-magnetic- resonance imaging apparatus |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS6050442A (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS61264242A (en) * | 1985-05-17 | 1986-11-22 | Shimadzu Corp | Fine regulating device for magnetic field distribution of electromagnet for mri |
| FR2598809B1 (en) * | 1986-05-13 | 1988-07-22 | Thomson Cgr | MAGNETIC FIELD HOMOGENEITY CORRECTOR BLOCK AND MAGNET PROVIDED WITH SUCH BLOCKS |
| FR2609206B1 (en) * | 1986-12-30 | 1992-02-14 | Thomson Cgr | MAGNETIC CORRECTIVE DEVICE FOR MAGNETIC FIELD INHOMOGENEITIES IN A MAGNET |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5150499A (en) * | 1974-10-28 | 1976-05-04 | Hitachi Ltd |
-
1983
- 1983-08-30 JP JP58158563A patent/JPS6050442A/en active Granted
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5150499A (en) * | 1974-10-28 | 1976-05-04 | Hitachi Ltd |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS6050442A (en) | 1985-03-20 |
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