JP3171721B2 - Magnetic field generator for magnetic resonance imaging - Google Patents
Magnetic field generator for magnetic resonance imagingInfo
- Publication number
- JP3171721B2 JP3171721B2 JP09393493A JP9393493A JP3171721B2 JP 3171721 B2 JP3171721 B2 JP 3171721B2 JP 09393493 A JP09393493 A JP 09393493A JP 9393493 A JP9393493 A JP 9393493A JP 3171721 B2 JP3171721 B2 JP 3171721B2
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- yoke
- magnetic field
- magnet blocks
- magnet
- field generator
- Prior art date
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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。BACKGROUND OF THE INVENTION 1. 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 an “MRI apparatus”) that obtains a tomographic image of an examination part of a subject using a phenomenon, and particularly to a static magnetic field in a gap where a subject is located. The present invention relates to a magnetic field generator for an MRI apparatus that can easily adjust the uniformity of a 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 an NMR phenomenon to measure a nuclear spin density distribution at a desired examination site in a subject.
The relaxation time distribution and the like are measured, the measurement signal is subjected to arithmetic processing, and an image is displayed as a tomographic image of the inspection site. Here, when a spatially wide range such as a human body is to be measured, 0.05 to 2T (tesla; 1 tesla is 1) in a measurement space composed of a spherical space having a diameter of 30 to 50 cm.
A magnetic field generator for generating a static magnetic field of about 000 gauss) with a uniformity of several tens of ppm or less is required. here,
The uniformity of the static magnetic field generated at an arbitrary point in the measurement space is represented by: uniformity = magnetic field intensity at an arbitrary point−central magnetic field intensity / central magnetic field intensity × 10 6 (ppm). Conventionally, three types of such magnetic field generators are used: a normal conducting magnet, a superconducting magnet, and a permanent magnet.
【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 Application Laid-Open No. 62-1004011. 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 gap 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 A static magnetic field is generated.
【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 magnetic field generator, the magnet blocks 11 to 18 are arranged such that their opposing parallel surfaces 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, the Z direction is This is the direction in which the static magnetic field is generated as indicated by arrow A. In such a state, the distortion of the uniformity of the static magnetic field shown in FIG. 4 is caused by the expansion terms X, Y, XY, and Legendre functions.
It is related to each term such as Z 1 , Z 2 , and Z 3 . The distortion of the Z 1 term is a distortion generated in proportion to the Z coordinate, and the Z coordinate value is proportional to the magnetic field strength. The distortion of the Z 2 term changes the magnetic field strength in proportion to the square of the Z coordinate. Further, the distortion of the X and Y terms is a distortion that depends only on the X and Y coordinates. 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 a 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 yoke 5 A plurality of magnet blocks 11 to 16 each comprising permanent magnets fixed to the wall surface and arranged so as to form a gap C into which a subject can enter in the center, and a uniform static magnetic field A in the gap C. There is something that causes it to occur. In such a magnetic field generating device, when the distortion of the uniformity of the static magnetic field in the air gap C is experimentally examined, it is found that each of the magnet blocks 11 1
It has been found that the distortion of a plurality of expansion terms of the Legendre function can be adjusted by moving one of the magnet blocks up to 16 up or 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 seen that when it is desired to correct the distortion of a certain term, it is necessary to move and adjust a plurality of related magnet blocks. In particular, the distortion of the foregoing Z 2 term, it was found that adjustment to move all up and down the plurality of magnet blocks 1 3 to 1 5 fixed to the upper inner wall surface of the yoke 5 are valid.
【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 non-uniformity of the magnetic characteristics (residual magnetic flux density, magnetization direction) between the magnet blocks,
Since the non-uniformity of the static magnetic field caused by the non-uniformity generated at the time of assembling the apparatus was adjusted by independently moving and rotating each of the magnet blocks, moving one magnet block in one direction. When the adjustment is made, a plurality of non-uniformity terms change, and when one non-uniformity term is adjusted, the adjustment must be made while combining the moving amounts of the plurality of magnet blocks well. Therefore, the adjustment work becomes complicated and the adjustment takes a long time. In addition, when each magnet block is moved independently, there is a problem that the movement of each magnet block includes a movement amount error, the balance between the magnet blocks is lost, and other distortions such as distortion depending on the horizontal direction are caused. 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 a problem, and makes it easy to adjust the uniformity of the static magnetic field mainly in the direction in which the magnetic field is generated in the gap where the subject is located. 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な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
継鉄を略半分に分割し、その分割箇所を結合すると共に
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
を移動調整可能とする調整部材を備えたものである。In order to achieve the above object, a magnetic field generator for an MRI apparatus according to the present invention comprises a polygonal cylindrical yoke and a plurality of inner wall surfaces of the yoke. A magnetic block comprising a plurality of permanent magnet blocks fixedly arranged to form a gap into which a subject can enter in a central portion, wherein the magnet block generates a uniform static magnetic field in the gap; In the above, the yoke is divided into approximately half, the divided portions are combined, and the other divided yoke to which the plurality of magnet blocks are fixed is moved and adjusted with respect to one divided yoke to which the plurality of magnet blocks are fixed. It is provided with an adjusting member that can be used.
【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。The magnetic field generator of the MRI apparatus constructed as described above divides the yoke into approximately half along the longitudinal direction of the cylinder and joins the divided portions with an adjusting plate made of a high magnetic material. By allowing the other divided yoke to which a plurality of magnet blocks are fixed to be movable and adjustable, with respect to one divided yoke to which a plurality of magnet blocks are fixed to the inner wall surface at the joint by the adjustment plate, The uniformity of the static magnetic field in the central space surrounded by the yoke and the plurality of magnet blocks is adjusted. Thereby, it is possible to easily 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。DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a central longitudinal sectional view of an embodiment of a magnetic field generator of an MRI apparatus according to the present invention as viewed from the front side, and FIG. 2 is a right side view of FIG. This magnetic field generator uses a permanent magnet to generate a uniform static magnetic field in a gap into which a subject is inserted. As shown in FIG. 1, a yoke 6 and a plurality of magnet blocks 11 to 1 are used. And 6 .
【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 includes a plurality of magnet blocks 11 1 to 11.
A member that forms a magnetic circuit together with 16 is made of a soft magnetic material, for example, in a hexagonal cylindrical shape. here,
The yoke 6 is divided substantially in half at the center along the longitudinal direction of the cylinder, and the upper member is an upper yoke 6a and the lower member is a lower yoke 6b. And, the above-mentioned upper yoke 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, 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 columnar magnet blocks 1 2, 1 6 with is fixed, respectively. 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 it has a magnetization direction, on both sides of the magnet block 1 2, 1 6 below yoke 6b further has a magnetization direction oblique 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 above-mentioned two divided yoke 6 are connected to each other by adjusting plates 7 and 8 at the divided portions. These adjusting plates 7 and 8 magnetically connect the upper yoke 6a and the lower yoke 6b, and have a high magnetic susceptibility such as a pure magnetic material that does not hinder the formation of a magnetic path as a magnetic field generator. Using iron or the like, it straddles between the upper yoke 6a and the lower yoke 6b as shown in FIG. 1, 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 adjustment plates 7, 8 are fixed to the lower yoke 6b by horizontally tightening fixing screws 9, 10, 11 and 12 in the horizontal direction. Next, the lower ends of both sides of the upper yoke 6a are aligned with the upper inner surfaces of these adjusting plates 7 and 8, and screw insertion holes drilled horizontally in the upper portions of the adjusting plates 7 and 8 are used for fixing. Screw 1
The upper yoke 6a is fixed to each of the adjusting plates 7, 8 by tightening the through holes 3 and 14, respectively. However, the screw insertion holes of the fixing screws 13 and 14 formed in the adjustment plates 7 and 8 have an oval cross section that is long vertically, and the fixing screws 13 and 14 have the screw insertion 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 tightened 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 screwed to the lower ends on both sides of the upper yoke 6a in the vertical direction. These adjusting screws 15 and 16 are for adjusting the distance between the lower yoke 6a and the upper yoke 6a, and the lower ends thereof are formed as flat surfaces and are provided on the upper surfaces of the respective adjusting plates 7 and 8. Has been 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 space 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 can be seen from the right side view shown in FIG. 2, fixing screws 9 to 14 screwed to the positions where the upper yoke 6a and the lower yoke 6b are joined by the adjusting plates 7, 8 are provided. Screw 1
5 and 16 are cylindrical yoke 6 as shown by the suffix a.
Are attached to the center as indicated by the suffix b, and are attached to the rear as indicated by the suffix c. Therefore,
There are a total of six screw joints on the left and right sides of the yoke 6. When assembling the magnetic field generator, first, the adjusting plates 7, 8 are fixed to the lower yoke 6b in the series of the fixing screws 9, 10, 11 and 12 in FIG. You do not need to loosen the screws when moving. Further, the amount of tightening of the series of adjusting screws 15 and 16 for determining the distance between the lower yoke 6b and the upper yoke 6a should be as equal 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 configured as described above will be described with reference to FIG. First, the fixing screws 13 and 14 for fixing the adjustment plates 7 and 8 to the upper yoke 6a are loosened. For each magnet blocks 1 1 to 1 6 having substantially upward magnetization direction, the upper and lower magnet block attract each other. Therefore, after loosening these screws 13, 14, the adjusting screws 15, 1
6 must support the attractive force of the upper yoke 6a and the lower yoke 6b. The adjusting screws 15 and 16 are
It is made of a material and a thickness capable of supporting the attracting force of a and 6b. When moving the upper yoke 6a upward, the adjusting screws 15 and 16 are tightened to widen the gap between the adjustment plates 7 and 8, thereby widening the gap between the upper yoke 6a and the lower yoke 6b. Conversely, when moving the upper yoke 6a downward, the adjusting screws 15,
16 may be loosened to reduce the distance between the upper and lower yokes 6a, 6b. After the adjustment of the vertical movement, in order to further stabilize the fixing of the upper and lower yokes 6a, 6b, the fixing screws 13, 14 are used.
To fix the upper yoke 6a. This series of work,
The operation is repeated six times for the left and right adjustment 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 move up and down integrally with b, the amount of rotation of the adjusting screws 15 and 16 at six locations on the left and right needs to be constant. When there is a variation in the amount of rotation, there is a possibility that distortion depending on the horizontal (X, Y) direction or the like may be caused. Therefore, for example, if the dial gauge is set between the upper and lower yokes 6a and 6b, and the amount of movement of the upper yoke 6a is measured at the positions of the adjusting screws 15 and 16, it can be moved horizontally. As a result, the aforementioned non-uniformity term of Z 2 can be adjusted. When the value of the front adjustment screw 16a (15a) and the value of the rear screw 16c (15c) shown in FIG. 2 are made different, the Y term can be adjusted. Note that, from the gist of the present invention, the main yoke 6a and the lower yoke 6b may be divided into a plurality of parts, each of which 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 viewed from the front side. In this embodiment, a yoke 6 'is formed in the shape of a quadrangular cylinder, and is divided substantially in half at the center along the longitudinal direction of the cylinder. The upper member is an upper yoke 6a', and the lower member is a lower member. Is the lower 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 block 1 3, 1 5 are fixed respectively. 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 columnar magnet blocks 1 2, 1 6 with is fixed, respectively. 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 of the upper yoke 6a ', 1 5 from the center of the magnetic field of the outward It has a magnetization direction, and has a lower iron 6
b either side of the magnet block 1 2, 1 6 'has the magnetization direction in toward inward to 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' are divided by the adjusting plates 7 and 8 at the divided portions in the same manner as in FIG. Each is joined. 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 about the moving operation of the vertical movement of the upper yoke 6a ',
What is necessary is just to carry out similarly to the Example 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。In FIGS. 1 and 3, the adjusting plates 7,
Screw holes may be provided in the holes through which the fixing screws 9, 10; 11, 12 of 8 are passed. Although the adjusting plates 7 and 8 are shown as being separate from the upper and lower yokes 6a and 6b, the present invention is not limited to this. For example, 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 with respect to the lower yoke 6b is caused by the adjustment screw 1
Although a 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 it can move up and down.
【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。The present invention has been configured as described above.
A plurality of magnet blocks are divided into approximately half along the longitudinal direction of the cylinder, and the divided portions are joined with an adjusting plate made of a member of high magnetic material. With respect to one of the fixed divided yokes, the other divided yoke to which a plurality of magnet blocks are fixed can also be moved and adjusted, so that the gap between the center portion surrounded by the yoke and the plurality of magnet blocks is reduced. The uniformity of the static magnetic field can be adjusted. Therefore, the adjustment work of the magnetic field uniformity becomes easy, and the adjustment can be completed in a short time.
In addition, by moving each magnet block integrally with the upper yoke or the lower yoke, the uniformity of the static magnetic field can be adjusted without breaking the balance between the respective magnet blocks and without 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 viewed 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 longitudinal sectional view showing another embodiment of the present invention as viewed from the front side.
【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 longitudinal sectional view showing another example of the conventional magnetic field generator as viewed from the front side.
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1 1 to 1 6 Magnet block 6 Yoke 6 'Yoke 6a Upper yoke 6a' Upper yoke 6b Lower yoke 6b 'Lower yoke 7 Adjustment plate 8 Adjustment plate 9 to 14 Fixing screw 15 Adjusting screw 16 Adjustment Screw C Air gap A Static magnetic field direction
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な
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、上記継鉄を略半分に分割し、その分割箇
所を結合すると共に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する調整部材を備
え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 formed in a polygonal cylindrical shape, and a permanent magnet fixed to a plurality of inner wall surfaces of the yoke and arranged so as to form a gap into which a subject can enter in a central portion. In a magnetic field generator for 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, and
And fixed the above multiple magnet blocks
Multiple magnet blocks are also fixed to one split yoke
An adjustment member is provided to make the other split yoke moveable and adjustable.
Magnetic field of a magnetic resonance imaging apparatus characterized by the following:
Generator.
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 JPH06290934A (en) | 1994-10-18 |
| JP3171721B2 true 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) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2000139874A (en) | 1998-09-02 | 2000-05-23 | Sumitomo Special Metals Co Ltd | Magnetic field generator for mri |
| JP4813645B2 (en) * | 1999-11-16 | 2011-11-09 | 日立金属株式会社 | Magnetic pole unit, method for assembling the same, and magnetic field generator |
| 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 |
| DE102006034472A1 (en) * | 2006-07-26 | 2008-01-31 | Forschungszentrum Jülich GmbH | Device for applying a magnetic field to a sample |
| EP3315983B1 (en) * | 2016-10-31 | 2020-06-03 | Senis AG | Calibration tool for calibrating a magnetic sensor |
-
1993
- 1993-03-30 JP JP09393493A patent/JP3171721B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH06290934A (en) | 1994-10-18 |
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