JPH06290934A - Magnetic field generator for magnetic resonance imaging apparatus - Google Patents
Magnetic field generator for magnetic resonance imaging apparatusInfo
- Publication number
- JPH06290934A JPH06290934A JP5093934A JP9393493A JPH06290934A JP H06290934 A JPH06290934 A JP H06290934A JP 5093934 A JP5093934 A JP 5093934A JP 9393493 A JP9393493 A JP 9393493A JP H06290934 A JPH06290934 A JP H06290934A
- Authority
- JP
- Japan
- Prior art keywords
- yoke
- magnetic field
- fixed
- field generator
- magnet blocks
- 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.)
- Granted
Links
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、核磁気共鳴（ＮＭＲ）
現象を利用して被検体の検査部位の断層像を得る磁気共
鳴イメージング装置（以下「ＭＲＩ装置」という）に用
いられる永久磁石を使用した磁界発生装置に関し、特に
被検体を位置させる空隙内の静磁場の均一度を調整する
のが容易なＭＲＩ装置の磁界発生装置に関する。FIELD OF THE INVENTION The present invention relates to nuclear magnetic resonance (NMR).
The present invention relates to a magnetic field generator using a permanent magnet used in a magnetic resonance imaging apparatus (hereinafter, referred to as “MRI apparatus”) that obtains a tomographic image of a test region of a subject by utilizing a phenomenon, and particularly relates to a static magnetic field in a space where a subject is positioned. The present invention relates to a magnetic field generator for an MRI apparatus in which it is easy to adjust the homogeneity of the magnetic field.
【０００２】[0002]
【従来の技術】ＭＲＩ装置は、ＮＭＲ現象を利用して被
検体中の所望の検査部位における核スピンの密度分布，
緩和時間分布等を計測して、その計測信号を演算処理
し、上記検査部位の断層像として画像表示するものであ
る。ここで、人体などの空間的に広い範囲を計測対象と
する場合には、直径３０〜５０cmの球空間からなる計測
空間内において０.０５〜２Ｔ(テスラ；１テスラは１
０,０００ ガウス）程度の静磁場を数１０ppm 以下の均
一度で発生させる磁界発生装置が必要である。ここで、
上記計測空間内の任意の点において発生した静磁場の均
一度は、 均一度＝任意の点の磁場強度−中心磁場強度／中心磁場
強度×１０6(ppm） で表される。このような磁界発生装置としては、従来か
ら常電導磁石，超電導磁石，永久磁石の三方式が用いら
れている。2. Description of the Related Art An MRI apparatus utilizes a nuclear magnetic resonance (NMR) phenomenon to obtain a nuclear spin density distribution at a desired inspection site in an object.
The relaxation time distribution and the like are measured, the measurement signal is arithmetically processed, and an image is displayed as a tomographic image of the inspection site. Here, when measuring a spatially wide range such as a human body, 0.05-2T (Tesla; 1 Tesla is 1
A magnetic field generator that can generate a static magnetic field of about 2,000 Gauss) with a uniformity of several tens of ppm or less is required. here,
The homogeneity of the static magnetic field generated at any point in the measurement space is represented by: homogeneity = magnetic field strength at any point−central magnetic field strength / central magnetic field strength × 10 6 (ppm). As such a magnetic field generation device, three methods of a normal conducting magnet, a superconducting magnet and a permanent magnet have been conventionally used.
【０００３】永久磁石を用いた従来のＭＲＩ装置の磁界
発生装置の一例は、特開昭62−104011号公報に記載され
ている。これを図４を参照して説明する。この磁界発生
装置は、継鉄を使用せずに永久磁石から成る複数の磁石
ブロック１1〜１8が環状に配置され、この環状配置内の
空隙Ｃに略均一な静磁界を発生するものである。上記各
磁石ブロック１1〜１8の磁化方向は、例えば図４におい
て各矢印方向で示すように設定されており、この全体に
より被検体が挿入される空隙Ｃ内に例えば矢印Ａで示す
垂直上向きの静磁場を発生するようになっている。An example of a conventional magnetic field generator for an MRI apparatus using a permanent magnet is described in Japanese Patent Laid-Open No. 62-104011. This will be described with reference to FIG. In this magnetic field generator, a plurality of magnet blocks 11 to 18 made of permanent magnets are annularly arranged without using a yoke, and a substantially uniform static magnetic field is generated in a void C in the annular arrangement. is there. The magnetization direction of each magnet blocks 1 1 to 1 8, for example, FIG and 4 are set as shown by the arrows directions in a vertical upward as indicated by the gap in the C which the subject is inserted by the entire example arrow A It is designed to generate a static magnetic field.
【０００４】上記の磁界発生装置における静磁場の調整
手段としては、上記各磁石ブロック１1〜１8はその対向
する平行な面が上記環状配置の中心に対し例えば正八角
形をなすように配置されており、これらの各磁石ブロッ
ク１1〜１8が互いに略直角な二つの方向２，３において
それぞれの位置を独立に移動調整でき、さらに上記二つ
の方向２，３のうち少なくとも一つの方向を軸心として
各磁石ブロック１1〜１8を独立に回動調整できるように
なっていた。As means for adjusting the static magnetic field in the above-mentioned magnetic field generator, each of the magnet blocks 11 to 18 is arranged so that the parallel surfaces facing each other form, for example, a regular octagon with respect to the center of the annular arrangement. and which each of these magnet blocks 1 1 to 1 8 in two directions 2 and 3 substantially perpendicular to each other can move adjust their position independently of the further at least one direction among the two directions 2,3 as axis had so each magnet blocks 1 1 to 1 8 can be rotated independently adjusted.
【０００５】ここで、図４において、紙面に平行な水平
方向をＸ方向とし、紙面に垂直な水平方向をＹ方向と
し、このＸＹ平面に垂直な上向き方向をＺ方向とする
と、このＺ方向が矢印Ａで示す静磁場の磁界発生方向と
なる。このような状態で、図４に示す静磁場の均一度の
歪みは、ルジャンドル関数の展開項Ｘ，Ｙ，ＸＹ，
Ｚ1 ，Ｚ2，Ｚ3などの各項と関係している。上記Ｚ1 項
の歪みは、Ｚ座標に比例して生じる歪みで、Ｚ座標値と
磁場強度が比例するものである。また、Ｚ2 項の歪み
は、Ｚ座標の２乗に比例して磁場強度が変化する。さら
に、Ｘ，Ｙ項の歪みは、Ｘ，Ｙ座標にのみ依存する歪み
である。そして、実際の磁界発生装置で発生する静磁場
では、これらの歪みが合成されて生じている。In FIG. 4, if the horizontal direction parallel to the paper surface is the X direction, the horizontal direction perpendicular to the paper surface is the Y direction, and the upward direction perpendicular to the XY plane is the Z direction, then this Z direction is The direction of the static magnetic field is indicated by the arrow A. In such a state, the distortion of the homogeneity of the static magnetic field shown in FIG. 4 becomes the expansion terms X, Y, XY, of the Legendre function.
It is related to each term such as Z 1 , Z 2 and Z 3 . The strain of the Z 1 term is a strain that occurs in proportion to the Z coordinate, and the Z coordinate value and the magnetic field strength are proportional. The distortion of the Z 2 term changes the magnetic field strength in proportion to the square of the Z coordinate. Furthermore, the distortion of the X and Y terms is the distortion that depends only on the X and Y coordinates. Then, in a static magnetic field generated by an actual magnetic field generator, these distortions are combined and generated.
【０００６】また、永久磁石を用いた従来の磁界発生装
置の他の例としては、図５に示すように、多角形筒状に
形成された継鉄５と、この継鉄５の複数の内壁面にそれ
ぞれ固着され中心部に被検体が入り得る空隙Ｃを形成す
るように配置された永久磁石から成る複数の磁石ブロッ
ク１1〜１6とを備え、上記空隙Ｃ内に均一な静磁界Ａを
発生させるようにしたものがある。このような磁界発生
装置において、上記空隙Ｃ内の静磁場の均一度の歪みに
ついて実験的に調べてみたら、上記各磁石ブロック１1
〜１6のうち一つの磁石ブロックを上下又は左右に移動
することにより、上記ルジャンドル関数の展開項の複数
の項の歪みを調整できることが分かった。As another example of the conventional magnetic field generator using a permanent magnet, as shown in FIG. 5, a yoke 5 formed in a polygonal cylindrical shape and a plurality of yokes 5 are provided. A plurality of magnet blocks 11 to 16 each composed of a permanent magnet and fixed to the wall surface so as to form a space C into which a subject can enter, and a uniform static magnetic field A is provided in the space C. There are some that are designed to generate. In such a magnetic field generator, when the distortion of the homogeneity of the static magnetic field in the air gap C is experimentally investigated, the magnet blocks 1 1
It has been found that the distortion of a plurality of terms of the expansion term of the Legendre function can be adjusted by moving one magnet block out of 16 up and down or left and right.
【０００７】このことから、ある項の歪みを補正したい
場合は、関連する複数の磁石ブロックを移動して調整し
なければならないことからわかる。特に、前述のＺ2 項
の歪みは、継鉄５の上部内壁面に固着された複数の磁石
ブロック１3〜１5の総てを上下に移動する調整が有効で
あることがわかった。From this, it can be understood from the fact that in order to correct the distortion of a certain term, it is necessary to move and adjust a plurality of related magnet blocks. In particular, it has been found that the above-mentioned distortion of the Z 2 term is effective in adjusting all of the plurality of magnet blocks 1 3 to 15 fixed to the upper inner wall surface of the yoke 5 to move up and down.
【０００８】[0008]
【発明が解決しようとする課題】しかし、上記図４又は
図５に示す磁界発生装置においては、各磁石ブロック間
の磁気特性（残留磁束密度，磁化方向）の不均一性や、
装置組立時に生じる不均一性によって発生する静磁場の
不均一性を、上記各磁石ブロックを独立して移動及び回
転することで調整していたので、ある一つの磁石ブロッ
クを一方向に移動して調整した場合は複数の不均一度項
が変化することとなり、一つの不均一度項を調整する場
合に複数の磁石ブロックの移動量をうまく組み合わせな
がら調整しなければならないものであって。従って、調
整作業が複雑となると共に、調整に長時間を要するもの
であった。また、各磁石ブロックを独立して移動する
と、それぞれの磁石ブロックの移動時に移動量誤差を含
み、各磁石ブロック間の釣り合いがくずれ、水平方向に
依存した歪みなど他の歪みを引き起こすという問題があ
った。However, in the magnetic field generator shown in FIG. 4 or FIG. 5, the magnetic characteristics (residual magnetic flux density, magnetization direction) between the magnet blocks are not uniform,
Since the inhomogeneity of the static magnetic field generated by the inhomogeneity generated when assembling the device was adjusted by independently moving and rotating each of the magnet blocks, it is possible to move one magnet block in one direction. If adjusted, a plurality of inhomogeneity terms will change, and when adjusting one inhomogeneity term, the movement amounts of a plurality of magnet blocks must be properly combined and adjusted. Therefore, the adjustment work becomes complicated and the adjustment requires a long time. In addition, if each magnet block is moved independently, there is a problem that the movement amount error is included when each magnet block moves, the balance between the magnet blocks is lost, and other distortions such as horizontal-dependent distortion occur. It was
【０００９】そこで、本発明では、このような問題点に
対処し、被検体を位置させる空隙内にて主として磁界発
生方向の静磁場の均一度を調整するのが容易なＭＲＩ装
置の磁界発生装置を提供することを目的とする。In view of the above, the present invention addresses such problems and makes it easy to adjust the homogeneity of the static magnetic field mainly in the direction of the magnetic field in the space where the subject is positioned. The purpose is to provide.
【００１０】[0010]
【課題を解決するための手段】上記目的を達成するため
に、本発明によるＭＲＩ装置の磁界発生装置は、多角形
筒状に形成された継鉄と、この継鉄の複数の内壁面にそ
れぞれ固着され中心部に被検体が入り得る空隙を形成す
るように配置された永久磁石から成る複数の磁石ブロッ
クを備え、上記空隙内に均一な静磁界を発生させる磁気
共鳴イメージング装置の磁界発生装置において、上記継
鉄をその筒の長手方向に沿って略半分に分割すると共
に、その分割箇所を高磁性率の部材から成る調整板でそ
れぞれ結合し、かつこれらの調整板による結合箇所にて
上記複数の磁石ブロックを固着した一方の分割継鉄に対
し、同じく複数の磁石ブロックを固着した他方の分割継
鉄を移動調整可能としたものである。In order to achieve the above object, a magnetic field generator for an MRI apparatus according to the present invention has a polygonal cylindrical yoke and a plurality of inner wall surfaces of the yoke. In a magnetic field generator of a magnetic resonance imaging apparatus, comprising a plurality of magnet blocks, which are fixed and are arranged so as to form a void into which a subject can enter, and which generate a uniform static magnetic field in the void. , The yoke is divided into approximately half along the longitudinal direction of the cylinder, and the divided portions are respectively connected by adjusting plates made of a member having a high magnetic susceptibility, and the plurality of connecting portions are connected by the adjusting plates. With respect to one of the split yokes to which the magnet block is fixed, the other split yoke to which the plurality of magnet blocks are similarly fixed can be moved and adjusted.
【００１１】[0011]
【作用】このように構成されたＭＲＩ装置の磁界発生装
置は、筒の長手方向に沿って略半分に分割すると共にそ
の分割箇所を高磁性材の部材から成る調整板でそれぞれ
結合した継鉄を、上記調整板による結合箇所にて内壁面
に複数の磁石ブロックを固着した一方の分割継鉄に対
し、同じく複数の磁石ブロックを固着した他方の分割継
鉄を移動調整可能とすることにより、上記継鉄及び複数
の磁石ブロックで囲まれた中心部の空隙内の静磁場の均
一度を調整する。これにより、主として磁界発生方向の
静磁場の均一度の調整を容易とすることができる。In the magnetic field generator of the MRI apparatus constructed as described above, the yoke is divided into approximately half along the longitudinal direction of the cylinder, and the divided portions are joined by adjusting plates made of a member of high magnetic material. , By making it possible to adjust the movement of the other split yoke that also has a plurality of magnet blocks fixed to the one split yoke that has a plurality of magnet blocks fixed to the inner wall surface at the connection point by the adjusting plate, The homogeneity of the static magnetic field in the central void surrounded by the yoke and the plurality of magnet blocks is adjusted. This makes it easy to adjust the uniformity of the static magnetic field mainly in the magnetic field generation direction.
【００１２】[0012]
【実施例】以下、本発明の実施例を添付図面に基づいて
詳細に説明する。図１は本発明によるＭＲＩ装置の磁界
発生装置の実施例を示す正面側から見た中央縦断面図で
あり、図２は図１の右側面図である。この磁界発生装置
は、永久磁石を使用して被検体を挿入する空隙内に均一
な静磁界を発生させるもので、図１に示すように、継鉄
６と、複数の磁石ブロック１1〜１6とを備えて成る。Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. 1 is a central longitudinal cross-sectional view showing an embodiment of a magnetic field generator of an MRI apparatus according to the present invention as seen from the front side, and FIG. 2 is a right side view of FIG. This magnetic field generator generates a uniform static magnetic field in a space into which a subject is inserted by using a permanent magnet. As shown in FIG. 1, a yoke 6 and a plurality of magnet blocks 11 to 1 are used. 6 and.
【００１３】上記継鉄６は、複数の磁石ブロック１1〜
１6と共に磁気回路を形成する部材となるもので、軟質
磁性材で例えば六角形筒状に形成されている。ここで、
上記継鉄６は、その筒の長手方向に沿って中心部で略半
分に分割され、上側の部材が上継鉄６ａとされ、下側の
部材が下継鉄６ｂとされている。そして、上記上継鉄６
ａの複数の内壁面にて、水平な部分の内側には矩形断面
を有する直方体状の磁石ブロック１4 が固着され、その
両側の斜めの部分の内側にはほぼ三角形断面を有する柱
状の磁石ブロック１3，１5がそれぞれ固着されている。
また、下継鉄６ｂの複数の内壁面にて、水平な部分の内
側には矩形断面を有する直方体状の磁石ブロック１1 が
固着され、その両側の斜めの部分の内側にはほぼ三角形
断面を有する柱状の磁石ブロック１2，１6がそれぞれ固
着されている。上下の磁石ブロック１1，１4は発生する
静磁場の磁界方向Ａと同方向の磁化方向を持ち、また上
継鉄６ａの両側の磁石ブロック１3，１5は磁場中心から
斜め外向きの磁化方向を持ち、さらに下継鉄６ｂの両側
の磁石ブロック１2，１6は磁場中心に向う斜め内向きの
磁化方向を持っている。この場合、上記各磁石ブロック
１2〜１6の磁化方向は、最適な静磁界を発生するように
それぞれ決められる。The yoke 6 has a plurality of magnet blocks 11 to.
It becomes a member that forms a magnetic circuit together with 16 and is made of a soft magnetic material, for example, in the shape of a hexagonal cylinder. here,
The yoke 6 is divided into approximately half at the central portion along the longitudinal direction of the cylinder, and the upper member is the upper yoke 6a and the lower member is the lower yoke 6b. And the above-mentioned iron iron 6
by a plurality of inner wall surfaces of a, rectangular parallelepiped magnet block 1 4 having a rectangular cross section is secured on the inner side of the horizontal portion, columnar magnet block having a generally triangular cross-section on the inside of the oblique portion of the sides 1 3 and 1 5 are fixed respectively.
Further, in a plurality of inner wall surface of the lower yoke 6b, the inside of the horizontal portion is fixed magnet block 1 1 rectangular having a rectangular cross-section, a substantially triangular cross-section on the inside of the oblique portion of the sides The columnar magnet blocks 1 2 and 1 6 that it has are respectively fixed. Upper and lower magnet block 1 1, 1 4 has a magnetization direction of the magnetic field direction A in the same direction of the static magnetic field generated, and both sides of the magnet block 1 3 above yoke 6a, 1 5 are oblique outwardly from the center of the magnetic field The magnet blocks 1 2 and 1 6 on both sides of the lower yoke 6b have a magnetization direction that is obliquely inward toward the center of the magnetic field. In this case, the magnetization direction of each magnet block 1 2-1 6 is determined respectively so as to generate an optimal static magnetic field.
【００１４】このような状態で、上記２分割された継鉄
６の上継鉄６ａと下継鉄６ｂとは、その分割箇所におい
て調整板７，８でそれぞれ結合されている。これらの調
整板７，８は、上記上継鉄６ａと下継鉄６ｂとを磁気的
につなぐもので、磁界発生装置としての磁路形成の妨げ
にならないような高磁性率の部材、例えば純鉄などを用
いて、図１に示すように上継鉄６ａ及び下継鉄６ｂの間
にまたがり、図２に示すように継鉄６の長手方向にわた
って伸びている。そして、まず、下継鉄６ｂの両側面部
において、該下継鉄６ｂに左右の調整板７，８を固定用
ねじ９，１０；１１，１２を水平方向に締め付けて固定
する。次に、これらの調整板７，８の内側面上部に上継
鉄６ａの両側下端部を合致させ、上記各調整板７，８の
上部に水平方向に穿設されたねじ挿通孔を固定用ねじ１
３，１４をそれぞれ通して締め付けることにより、各調
整板７，８に上継鉄６ａを固定する。ただし、上記調整
板７，８に穿設された固定用ねじ１３，１４のねじ挿通
孔は、その断面形が上下に長い長円形とされており、上
記固定用ねじ１３，１４が上記ねじ挿通孔内で締め付け
固定される位置により、下継鉄６ｂと上継鉄６ａ、及び
それらに固着された各磁石ブロック間の間隔が決められ
る。In this state, the upper yoke 6a and the lower yoke 6b of the yoke 6 divided into two are connected by the adjusting plates 7 and 8 at the divided portions. These adjusting plates 7 and 8 are for magnetically connecting the upper yoke 6a and the lower yoke 6b, and are members having a high magnetic rate that do not hinder the formation of a magnetic path as a magnetic field generator, such as a pure magnetic member. As shown in FIG. 1, it spans between the upper yoke 6a and the lower yoke 6b using iron or the like, and extends in the longitudinal direction of the yoke 6 as shown in FIG. Then, first, on both side surfaces of the lower yoke 6b, the left and right adjusting plates 7, 8 are fixed to the lower yoke 6b by horizontally tightening fixing screws 9, 10, 11 and 12. Next, the lower end portions on both sides of the upper yoke 6a are aligned with the inner surface upper portions of these adjusting plates 7 and 8, and the screw insertion holes formed in the upper portion of the adjusting plates 7 and 8 in the horizontal direction are fixed. Screw 1
The upper yoke 6a is fixed to each of the adjusting plates 7 and 8 by tightening the screws 3 and 14 respectively. However, the screw insertion holes of the fixing screws 13 and 14 formed in the adjusting plates 7 and 8 have an oval cross section whose shape is vertically long, and the fixing screws 13 and 14 are inserted into the screw inserting holes. The distance between the lower yoke 6b and the upper yoke 6a, and the magnet blocks fixed to them is determined by the position where they are clamped and fixed in the hole.
【００１５】さらに、上記上継鉄６ａの両側下端部に
は、調整用ねじ１５，１６が上下方向に螺合されてい
る。この調整用ねじ１５，１６は、下継鉄６ａと上継鉄
６ａとの間隔を調整するためのもので、その下端部は平
らな面に形成されて各調整板７，８の上端面に当接され
ている。そして、この調整用ねじ１５，１６を締め付け
たり、ゆるめたりすることにより、上継鉄６ａ及びこれ
に固着された各磁石ブロック１3〜１5が上下移動可能と
されている。以上のような状態で、図１に示すように、
各磁石ブロック１1〜１6で囲まれた中心部に、被検体が
入り得る空隙Ｃが形成され、上記各磁石ブロック１1〜
１6の磁化方向の合成として、上記空隙Ｃ内に矢印Ａで
示す方向に静磁界が発生することとなる。Further, adjusting screws 15 and 16 are vertically screwed to the lower end portions on both sides of the upper yoke 6a. The adjusting screws 15 and 16 are for adjusting the distance between the lower yoke 6a and the upper yoke 6a, and the lower end portion of the adjusting screw 15 and 16 is formed into a flat surface so that the upper end surfaces of the adjusting plates 7 and 8 can be adjusted. Abutted. Then, or tightening the adjustment screw 15 and 16, by loosen, upper yoke 6a and the magnet block 1 3 to 1 5 secured thereto is a vertically movable. In the above state, as shown in FIG.
In the center surrounded by the magnet blocks 1 1 to 1 6, the gap C to obtain contains the object is formed, each of magnet blocks 1 1
As a combination of the 16 magnetization directions, a static magnetic field is generated in the void C in the direction indicated by the arrow A.
【００１６】図２に示す右側面図から明らかように、上
記調整板７，８で上継鉄６ａと下継鉄６ｂとを結合する
箇所に螺合される固定用ねじ９〜１４と、調整用ねじ１
５，１６とは、添字ａを付して示すように筒状の継鉄６
の前部に取り付けられるものと、添字ｂを付して示すよ
うに中央部に取り付けられるものと、添字ｃを付して示
すように後部に取り付けられるものとがある。従って、
継鉄６の左右両側面では合計６箇所のねじ結合箇所があ
る。そして、磁界発生装置を組み立てるときには、最初
に図１において固定用ねじ９，１０及び１１，１２の系
列で下継鉄６ｂに調整板７，８を固定しておくと、上継
鉄６ａを上下移動する際にねじをゆるめなくてよい。ま
た、下継鉄６ｂと上継鉄６ａとの間隔を決める調整用ね
じ１５，１６の系列を締め込む量はできるだけ同じにす
るとよい。As is apparent from the right side view shown in FIG. 2, fixing screws 9 to 14 screwed to the connecting points of the upper yoke 6a and the lower yoke 6b with the adjusting plates 7 and 8 and adjusting screws. Screw 1
5 and 16 are tubular yokes 6 as indicated by the subscript a.
There are those attached to the front part, those attached to the central part as indicated by the subscript b, and those attached to the rear part as indicated by the subscript c. Therefore,
There are a total of 6 screw connection points on the left and right side surfaces of the yoke 6. When assembling the magnetic field generator, first, the adjusting plates 7 and 8 are fixed to the lower yoke 6b with the series of fixing screws 9, 10 and 11, 12 in FIG. You do not have to loosen the screws when moving. Further, it is preferable that the series of the adjusting screws 15 and 16 for determining the interval between the lower yoke 6b and the upper yoke 6a be tightened as much as possible.
【００１７】次に、このように構成された磁界発生装置
において、上継鉄６ａの上下移動について図１を参照し
て説明する。始めに、上継鉄６ａに調整板７，８を固定
している固定用ねじ１３，１４をゆるめる。各磁石ブロ
ック１1〜１6はほぼ上向きの磁化方向を持つために、上
下の磁石ブロックは互いに引き合う。そのため、これら
のねじ１３，１４をゆるめた後に、調整用ねじ１５，１
６で上継鉄６ａ及び下継鉄６ｂの引き合う力を支えなけ
ればならない。調整用ねじ１５，１６は、上下継鉄６
ａ，６ｂの引き合う力を支えられる材質及び太さとされ
ている。そして、上継鉄６ａを上に移動する時は、調整
用ねじ１５，１６を締め込み、調整板７，８との間隔を
広げて、上継鉄６ａと下継鉄６ｂの間隔を広げる。逆
に、上継鉄６ａを下に移動する時は、調整用ねじ１５，
１６をゆるめて上下継鉄６ａ，６ｂの間隔を狭めればよ
い。この上下移動の調整後に、上下継鉄６ａ，６ｂの固
定をより安定させるために、前記固定用ねじ１３，１４
を締めて、上継鉄６ａを固定する。この１連の作業を、
左右の調整板７，８について繰返し６カ所行う。Next, the vertical movement of the upper yoke 6a in the magnetic field generator thus constructed will be described with reference to FIG. First, the fixing screws 13 and 14 fixing the adjusting plates 7 and 8 to the upper yoke 6a are loosened. Since each of the magnet blocks 1 1 to 16 has a substantially upward magnetization direction, the upper and lower magnet blocks attract each other. Therefore, after loosening these screws 13 and 14, the adjustment screws 15 and 1
6 must support the pulling force of the upper yoke 6a and the lower yoke 6b. The adjusting screws 15 and 16 are the upper and lower yokes 6.
The material and thickness are such that they can support the attractive forces of a and 6b. When the upper yoke 6a is moved upward, the adjusting screws 15 and 16 are tightened to widen the gap between the adjusting plates 7 and 8 and widen the gap between the upper yoke 6a and the lower yoke 6b. On the contrary, when moving the upper yoke 6a downward, the adjusting screw 15,
16 may be loosened to narrow the gap between the upper and lower yokes 6a and 6b. After adjusting the vertical movement, in order to stabilize the upper and lower yokes 6a and 6b more stably, the fixing screws 13 and 14 are used.
To fix the upper iron 6a. This series of work
Repeat 6 times for the left and right adjusting plates 7 and 8.
【００１８】上記の移動操作において上下継鉄６ａ，６
ｂを一体化して上下移動するために、左右６カ所の調整
用ねじ１５，１６の回転量を一定する必要がある。回転
量にばらつきがある場合は、水平(Ｘ，Ｙ)方向に依存す
る歪みなどを引き起こす可能性がある。従って、例えば
ダイヤルゲージを上下継鉄６ａ，６ｂ間にセットし、上
継鉄６ａの移動量を調整用ねじ１５，１６の位置で測定
しておけば、水平に移動させることができる。これによ
って、前述のＺ2 の不均一度項が調整できる。また、図
２に示す前部の調整用ねじ１６ａ(１５ａ)と後部のねじ
１６ｃ(１５ｃ)の値を異ならせると、Ｙ項の調整ができ
る。なお、本発明の主旨からは、主継鉄６ａ及び下継鉄
６ｂは複数に分割され、各々が相対的に移動できるよう
になっていてもよい。In the above moving operation, the upper and lower yokes 6a, 6
In order to integrally move b and move it up and down, it is necessary to keep the amount of rotation of the adjusting screws 15 and 16 at the six left and right positions constant. If there is variation in the amount of rotation, there is a possibility of causing distortion depending on the horizontal (X, Y) direction. Therefore, if, for example, a dial gauge is set between the upper and lower yokes 6a and 6b and the movement amount of the upper yoke 6a is measured at the position of the adjusting screws 15 and 16, it can be moved horizontally. Thereby, the above-mentioned nonuniformity term of Z 2 can be adjusted. Further, the Y term can be adjusted by making the values of the front adjusting screw 16a (15a) and the rear adjusting screw 16c (15c) shown in FIG. 2 different. In addition, from the gist of the present invention, the main yoke 6a and the lower yoke 6b may be divided into a plurality of pieces, and each of them may be relatively movable.
【００１９】図３は本発明の他の実施例を示す正面側か
ら見た中央縦断面図である。この実施例は、継鉄６′を
四角形筒状に形成し、この筒の長手方向に沿って中心部
で略半分に分割され、上側の部材が上継鉄６ａ′とさ
れ、下側の部材が下継鉄６ｂ′とされている。そして、
上記上継鉄６ａ′の複数の内壁面にて、水平な部分の内
側には矩形断面を有する直方体状の磁石ブロック１4 が
固着され、その両側で左右に相対する面には三角形断面
を有する柱状の磁石ブロック１3，１5がそれぞれ固着さ
れている。また、下継鉄６ｂ′の複数の内壁面にて、水
平な部分の内側には矩形断面を有する直方体状の磁石ブ
ロック１1 が固着され、その両側で左右に相対する面に
は三角形断面を有する柱状の磁石ブロック１2，１6がそ
れぞれ固着されている。上下の磁石ブロック１1，１4は
発生する静磁場の磁界方向Ａと同方向の磁化方向を持
ち、また上継鉄６ａ′の両側の磁石ブロック１3，１5は
磁場中心から外向きの磁化方向を持ち、さらに下継鉄６
ｂ′の両側の磁石ブロック１2，１6 は磁場中心に向う
内向きの磁化方向を持っている。この場合、上記各磁石
ブロック１2〜１6の磁化方向は、最適な静磁界を発生す
るようにそれぞれ決められる。FIG. 3 is a central longitudinal sectional view showing another embodiment of the present invention as seen from the front side. In this embodiment, the yoke 6'is formed in a quadrangular cylinder shape, and is divided into approximately half along the longitudinal direction of the cylinder at the central portion, the upper member being the upper yoke 6a ', and the lower member. Is referred to as a subordinate iron 6b '. And
By a plurality of inner wall surfaces of the upper yoke 6a ', on the inner side of the horizontal portion is fixed is rectangular parallelepiped magnet block 1 4 having a rectangular cross-section, have a triangular cross-section on the opposite surface to the left and right on both sides Columnar magnet blocks 1 3 and 1 5 are fixed to each other. Further, in a plurality of inner wall surface of the lower yoke 6b ', on the inner side of the horizontal portion is fixed magnet block 1 1 rectangular having a rectangular cross-section, a triangular cross-section on the opposite surface to the left and right on both sides The columnar magnet blocks 1 2 and 1 6 that it has are respectively fixed. The upper and lower magnet blocks 1 1 and 1 4 have a magnetization direction that is the same as the magnetic field direction A of the static magnetic field that is generated, and the magnet blocks 1 3 and 1 5 on both sides of the upper iron 6a ′ are directed outward from the center of the magnetic field. It has a magnetizing direction, and is a lower iron 6
The magnet blocks 1 2 and 1 6 on both sides of b ′ have an inward magnetization direction toward the center of the magnetic field. In this case, the magnetization direction of each magnet block 1 2-1 6 is determined respectively so as to generate an optimal static magnetic field.
【００２０】このような状態で、上記２分割された継鉄
６′の上継鉄６ａ′と下継鉄６ｂ′とは、その分割箇所
において図１と同様の考え方により調整板７，８でそれ
ぞれ結合されている。従って、図１に示す実施例と同様
に、調整用ねじ１５，１６を締め付けたり、ゆるめたり
することにより、上継鉄６ａ′及びこれに固着された各
磁石ブロック１3〜１5が上下移動可能とされている。そ
して、上継鉄６ａ′の上下移動の移動操作についても、
図１に示す実施例と同様に行えばよい。In such a state, the upper yoke 6a 'and the lower yoke 6b' of the yoke 6'divided into two parts are separated by the adjusting plates 7 and 8 at the divided portions according to the same idea as in FIG. Each is combined. Therefore, similarly to the embodiment shown in FIG. 1, or tightening the adjustment screws 15 and 16, by loosen, each magnet is secured on the yoke 6a 'and to block 1 3 to 1 5 move up and down It is possible. And for the movement operation of the vertical movement of the upper iron 6a ′,
It may be performed in the same manner as the embodiment shown in FIG.
【００２１】なお、図１及び図３において、調整板７，
８の固定用ねじ９，１０；１１，１２を通す孔には、ね
じ山を設けてもよい。また、上記調整板７，８は、上下
継鉄６ａ，６ｂと別体のものとして示したが、これに限
らず例えば下継鉄６ｂに調整板７，８を一体化させた構
造としてもよい。この場合は、固定用ねじ９，１０；１
１，１２は不要である。さらに、以上の説明では、下継
鉄６ｂに対する上継鉄６ａの上下移動は、調整用ねじ１
５，１６を用いたねじ機構としているが、本発明はこれ
に限らず、上下移動が可能であれば他の駆動機構を用い
てもよい。Incidentally, in FIGS. 1 and 3, the adjusting plate 7,
Threads may be provided in the holes through which the fixing screws 9, 10; Further, although the adjusting plates 7 and 8 are shown as being separate from the upper and lower yokes 6a and 6b, the structure is not limited to this, and the adjusting plates 7 and 8 may be integrated with the lower yoke 6b. . In this case, the fixing screws 9, 10; 1
1 and 12 are unnecessary. Further, in the above description, the vertical movement of the upper yoke 6a relative to the lower yoke 6b is performed by the adjustment screw 1
Although the screw mechanism using 5 and 16 is used, the present invention is not limited to this, and another drive mechanism may be used as long as vertical movement is possible.
【００２２】[0022]
【発明の効果】本発明は以上のように構成されたので、
筒の長手方向に沿って略半分に分割すると共にその分割
箇所を高磁性材の部材から成る調整板でそれぞれ結合し
た継鉄を、上記調整板による結合箇所にて内壁面に複数
の磁石ブロックを固着した一方の分割継鉄に対し、同じ
く複数の磁石ブロックを固着した他方の分割継鉄を移動
調整可能とすることにより、上記継鉄及び複数の磁石ブ
ロックで囲まれた中心部の空隙内の静磁場の均一度を調
整することができる。従って、磁場均一度の調整作業が
容易となり、調整を短時間で終了させることができる。
また、各磁石ブロックを上継鉄又は下継鉄と共に一体化
して移動することにより、各磁石ブロック間の釣り合い
をくずさず、他の歪みを引き起こすことなく静磁場の均
一度を調整することができる。Since the present invention is constructed as described above,
The yoke is divided into approximately half along the longitudinal direction of the cylinder, and the divided parts are joined by adjusting plates each made of a member of high magnetic material, and a plurality of magnet blocks are attached to the inner wall surface at the connecting parts by the adjusting plates. By making it possible to move and adjust the other split yoke to which one magnet block is fixed, the other split yoke, which is also fixed to a plurality of magnet blocks, can be adjusted. The homogeneity of the static magnetic field can be adjusted. Therefore, the adjustment work of the magnetic field homogeneity becomes easy, and the adjustment can be completed in a short time.
Further, by moving each magnet block integrally with the upper yoke or the lower yoke, it is possible to adjust the homogeneity of the static magnetic field without breaking the balance between the magnet blocks and causing other distortion. .
【図１】本発明によるＭＲＩ装置の磁界発生装置の実施
例を示す正面側から見た中央縦断面図。FIG. 1 is a central longitudinal sectional view showing an embodiment of a magnetic field generator of an MRI apparatus according to the present invention as seen from the front side.
【図２】図１の右側面図。FIG. 2 is a right side view of FIG.
【図３】本発明の他の実施例を示す正面側から見た中央
縦断面図。FIG. 3 is a central vertical cross-sectional view seen from the front side, showing another embodiment of the present invention.
【図４】従来のＲＭＩ装置の磁界発生装置の一例を示す
正面図。FIG. 4 is a front view showing an example of a magnetic field generator of a conventional RMI device.
【図５】従来の磁界発生装置の他の例を示す正面側から
見た中央縦断面図。FIG. 5 is a central vertical cross-sectional view showing another example of a conventional magnetic field generator as seen from the front side.
【符号の説明】 １1〜１6 磁石ブロック ６ 継鉄 ６′ 継鉄 ６ａ 上継鉄 ６ａ′ 上継鉄 ６ｂ 下継鉄 ６ｂ′ 下継鉄 ７ 調整板 ８ 調整板 ９〜１４ 固定用ねじ １５ 調整用ねじ １６ 調整用ねじ Ｃ 空隙 Ａ 静磁場の方向[Explanation of reference signs] 1 1 to 16 Magnet block 6 Yoke 6'Yoke 6a Upper iron 6a 'Upper iron 6b Lower iron 6b' Lower iron 7 Adjustment plate 8 Adjustment plate 9-14 Fixing screw 15 Adjustment screw 16 Adjustment screw C Air gap A Static magnetic field direction
───────────────────────────────────────────────────── フロントページの続き (51)Int.Cl.5 識別記号 庁内整理番号 ＦＩ 技術表示箇所 8203−2Ｇ Ｇ０１Ｒ 33/22 Ａ ─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. 5 Identification code Internal reference number FI technical display location 8203-2G G01R 33/22 A
Claims (1)
の複数の内壁面にそれぞれ固着され中心部に被検体が入
り得る空隙を形成するように配置された永久磁石から成
る複数の磁石ブロックとを備え、上記空隙内に均一な静
磁界を発生させる磁気共鳴イメージング装置の磁界発生
装置において、上記継鉄をその筒の長手方向に沿って略
半分に分割すると共に、その分割箇所を高磁性率の部材
から成る調整板でそれぞれ結合し、かつこれらの調整板
による結合箇所にて上記複数の磁石ブロックを固着した
一方の分割継鉄に対し、同じく複数の磁石ブロックを固
着した他方の分割継鉄を移動調整可能としたことを特徴
とする磁気共鳴イメージング装置の磁界発生装置。1. A yoke which is formed in a polygonal cylindrical shape, and a permanent magnet which is fixed to a plurality of inner wall surfaces of the yoke and is arranged so as to form a void in the center thereof into which a subject can enter. In a magnetic field generator of a magnetic resonance imaging apparatus comprising a plurality of magnet blocks and generating a uniform static magnetic field in the air gap, the yoke is divided into approximately half along the longitudinal direction of the cylinder, and the division is performed. The parts were joined by adjusting plates made of high magnetic material, and the magnet blocks were fixed to the split yokes where the magnet blocks were fixed at the connecting parts by these adjusting plates. A magnetic field generator for a magnetic resonance imaging apparatus, wherein the other split yoke is movable and adjustable.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP09393493A JP3171721B2 (en) | 1993-03-30 | 1993-03-30 | Magnetic field generator for magnetic resonance imaging |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP09393493A JP3171721B2 (en) | 1993-03-30 | 1993-03-30 | Magnetic field generator for magnetic resonance imaging |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH06290934A true JPH06290934A (en) | 1994-10-18 |
| JP3171721B2 JP3171721B2 (en) | 2001-06-04 |
Family
ID=14096269
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP09393493A Expired - Fee Related JP3171721B2 (en) | 1993-03-30 | 1993-03-30 | Magnetic field generator for magnetic resonance imaging |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3171721B2 (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2001326118A (en) * | 1999-11-16 | 2001-11-22 | Sumitomo Special Metals Co Ltd | Magnetic pole unit, its assembling method, and magnetic field generating apparatus |
| US6340888B1 (en) | 1998-09-02 | 2002-01-22 | Sumitomo Special Metals Co., Ltd. | Magnetic field generator for MRI |
| CN100350522C (en) * | 2004-05-18 | 2007-11-21 | 北京泰杰磁电研究所 | Magnetic resonant image-forming magnetic body and forming method thereof |
| JP2009544946A (en) * | 2006-07-26 | 2009-12-17 | フォルシュングスツェントルム・ユーリッヒ・ゲゼルシャフト・ミット・ベシュレンクテル・ハフツング | Device for applying a magnetic field to a sample |
| JP2018072332A (en) * | 2016-10-31 | 2018-05-10 | セニス エージー | Calibration tool for calibrating magnetic sensor |
-
1993
- 1993-03-30 JP JP09393493A patent/JP3171721B2/en not_active Expired - Fee Related
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6340888B1 (en) | 1998-09-02 | 2002-01-22 | Sumitomo Special Metals Co., Ltd. | Magnetic field generator for MRI |
| JP2001326118A (en) * | 1999-11-16 | 2001-11-22 | Sumitomo Special Metals Co Ltd | Magnetic pole unit, its assembling method, and magnetic field generating apparatus |
| CN100350522C (en) * | 2004-05-18 | 2007-11-21 | 北京泰杰磁电研究所 | Magnetic resonant image-forming magnetic body and forming method thereof |
| JP2009544946A (en) * | 2006-07-26 | 2009-12-17 | フォルシュングスツェントルム・ユーリッヒ・ゲゼルシャフト・ミット・ベシュレンクテル・ハフツング | Device for applying a magnetic field to a sample |
| JP2018072332A (en) * | 2016-10-31 | 2018-05-10 | セニス エージー | Calibration tool for calibrating magnetic sensor |
Also Published As
| Publication number | Publication date |
|---|---|
| JP3171721B2 (en) | 2001-06-04 |
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