JP3435821B2 - Static magnetic field generator for magnetic resonance imaging - Google Patents
Static magnetic field generator for magnetic resonance imagingInfo
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- JP3435821B2 JP3435821B2 JP17484294A JP17484294A JP3435821B2 JP 3435821 B2 JP3435821 B2 JP 3435821B2 JP 17484294 A JP17484294 A JP 17484294A JP 17484294 A JP17484294 A JP 17484294A JP 3435821 B2 JP3435821 B2 JP 3435821B2
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- magnetic field
- static magnetic
- coil
- static
- field generator
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Description
【発明の詳細な説明】Detailed Description of the Invention
【０００１】[0001]
【産業上の利用分野】本発明は、磁気共鳴イメージング
装置（以下、ＭＲＩ装置と略称）用の静磁場発生装置に
係り、特に、奥行き長が短く、また、漏洩磁場が少ない
ことにより、設置条件が緩和されたＭＲＩ装置用の静磁
場発生装置に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a static magnetic field generator for a magnetic resonance imaging apparatus (hereinafter abbreviated as MRI apparatus), and in particular, it has a short depth and a small leakage magnetic field, so that the installation condition can be improved. The present invention relates to a static magnetic field generator for an MRI apparatus in which the magnetic field is relaxed.
【０００２】[0002]
【従来の技術】ＭＲＩ装置は、ＮＭＲ（核磁気共鳴）現
象を利用して計測した信号を演算処理することで、被検
体中の核スピンの密度分布、緩和時間分布等を断層像と
して画像表示するものである。このＮＭＲ現象を発生さ
せるためには、空間的、時間的に一様な強度と方向を持
った静磁場が必要である。具体的には、直径３００〜５
００mm程度の空隙に、０．０４〜２テスラ（Ｔ）の強度
と数１０ｐｐｍ程度以下の均一度を持った静磁場が要求
される。静磁場を発生させるための静磁場発生装置は、
永久磁石あるいは、超伝導コイルや常電導コイルを用い
たものの３種類に大別できる。本発明は、超伝導コイル
あるいは常電導コイルを用いた静磁場発生装置に関する
ものである。2. Description of the Related Art An MRI apparatus displays a density distribution, relaxation time distribution, etc. of nuclear spins in a subject as a tomographic image by processing a signal measured by utilizing an NMR (nuclear magnetic resonance) phenomenon. To do. In order to generate this NMR phenomenon, a static magnetic field having a spatially and temporally uniform intensity and direction is required. Specifically, diameter 300 to 5
A static magnetic field having a strength of 0.04 to 2 Tesla (T) and a homogeneity of several tens of ppm or less is required for a void of about 00 mm. A static magnetic field generator for generating a static magnetic field is
It can be roughly classified into three types, that is, a permanent magnet, a superconducting coil, or a normal conducting coil. The present invention relates to a static magnetic field generator using a superconducting coil or a normal conducting coil.
【０００３】図６に、従来技術による超伝導コイルを用
いた静磁場発生装置の構成を表す縦断面図を示す。通例
に従い、被検体１００を挿入する奥行き方向をＺ方向、
上下をＹ方向、左右をＸ方向とする直交座標系を用いて
説明する。超伝導コイル１０は被検体１００の周りに、
Ｚ方向軸を中心としてソレノイド状に巻いてある。この
超伝導コイル１０により、被検体を含む計測空間１１０
内に均一で強力な、Ｚ方向の向きを持った静磁場Ｂ0を
発生させている。FIG. 6 is a vertical cross-sectional view showing the structure of a static magnetic field generator using a conventional superconducting coil. According to the customary practice, the depth direction in which the subject 100 is inserted is the Z direction,
An orthogonal coordinate system in which the upper and lower sides are the Y direction and the left and right sides are the X direction will be described. The superconducting coil 10 surrounds the subject 100,
It is wound like a solenoid around the Z-axis. The superconducting coil 10 allows the measurement space 110 including the subject to be measured.
A uniform and strong static magnetic field B 0 having a Z direction is generated therein.
【０００４】一般には、超伝導コイル１０を幾つかのブ
ロックに分け、複数のコイルの組（図６においては、１
０ａ〜１０ｄの４組）で静磁場を発生している。各コイ
ルの組１０ａ〜１０ｄの線材の巻き数と配置位置を適切
に選ぶことで、磁場の均一度と発生効率を向上させてい
る。In general, the superconducting coil 10 is divided into several blocks, and a set of a plurality of coils (in FIG.
A static magnetic field is generated by 4 sets of 0a to 10d). By appropriately selecting the number of turns and the arrangement position of the wire rods of each coil set 10a to 10d, the uniformity of the magnetic field and the generation efficiency are improved.
【０００５】また、現在のＭＲＩ用の静磁場発生装置に
使用可能な超伝導コイルは、極低温下で用いる必要があ
る。そのために、超伝導コイルの線材は冷却容器３０の
中に収め、液体ヘリウム等を用いて冷却している。勿
論、常電導コイルを使用する場合には、この冷却容器は
不要である。Further, the superconducting coil usable in the current static magnetic field generator for MRI needs to be used at an extremely low temperature. Therefore, the wire rod of the superconducting coil is placed in the cooling container 30 and cooled with liquid helium or the like. Of course, when using the normal conducting coil, this cooling container is unnecessary.
【０００６】[0006]
【発明が解決しようとする課題】このような超伝導コイ
ル或いは常電導コイルを用いた静磁場発生装置は、被検
体１１０を計測空間１１０内に移動させるために円筒状
の計測空間の両側に開口４０（４０ａ、４０ｂ）が設け
られている。この開口部から磁場が装置の外部に漏れだ
すために、装置内の磁場強度は開口部に近づくにつれて
急激に低下する。A static magnetic field generator using such a superconducting coil or normal conducting coil has openings on both sides of a cylindrical measurement space for moving the subject 110 into the measurement space 110. 40 (40a, 40b) are provided. Since the magnetic field leaks from the opening to the outside of the device, the magnetic field strength inside the device sharply decreases as it approaches the opening.
【０００７】既に述べたように、鮮明な断層画像を得る
ためには、計測空間１１０内に空間的、時間的に均一な
静磁場を発生させる必要がある。従って、計測空間内に
おける磁場の空間的な均一度を良くするためには、開口
４０を計測空間１１０から遠ざける、すなわち奥行き長
さを延ばす必要があった。このために、装置の設置場所
に長い奥行きが必要となり、装置の設置場所に面積的な
制限があった。この制限は、ＭＲＩ装置を車に搭載する
などの設置面積が限定される場合において、特に問題と
なる。As described above, in order to obtain a clear tomographic image, it is necessary to generate a spatially and temporally uniform static magnetic field in the measurement space 110. Therefore, in order to improve the spatial homogeneity of the magnetic field in the measurement space, it is necessary to keep the opening 40 away from the measurement space 110, that is, to extend the depth length. For this reason, a long depth is required for the installation location of the device, and the installation location of the device is limited in area. This limitation becomes a particular problem when the installation area is limited, such as when the MRI apparatus is mounted on a vehicle.
【０００８】また、ＭＲＩ用静磁場発生装置では、装置
の外部に漏洩する磁場（漏洩磁場）による影響が問題と
なる。ＣＲＴなどは１ガウス程度、ペースメーカなどは
５ガウス程度の磁場の影響を受けて、性能が劣化する。
従って、ＭＲＩ装置の周囲は磁場の管理区域として、人
間の立入りや機器の設置を制限する必要がある。この管
理区域をできるだけ狭くするためには、漏洩磁場を低減
する必要がある。Further, in the static magnetic field generator for MRI, the influence of the magnetic field (leakage magnetic field) leaking to the outside of the device becomes a problem. A CRT or the like is affected by a magnetic field of about 1 gauss, and a pacemaker or the like is affected by a magnetic field of about 5 gauss, and the performance is deteriorated.
Therefore, it is necessary to restrict human access and equipment installation around the MRI apparatus as a magnetic field control area. In order to make this controlled area as narrow as possible, it is necessary to reduce the leakage magnetic field.
【０００９】このために、従来技術では図７に示すよう
にコイルを２重に巻く構造を用いている。すなわち、上
で説明した計測空間に静磁場を発生するための主コイル
１０の外側に、主コイルが装置の外部に作り出す磁場と
逆向きの磁場を発生させるための打ち消しコイル１１を
設置している。両コイルのバランスをとることで、漏洩
磁場の低減を図っている。この構造では、径（Ｘ及び
Ｙ）方向の漏洩磁場に対しては低減効果を得られるが、
開口４０付近から外部に漏れる磁場の打ち消しは困難で
あり、径（Ｘ及びＹ）方向の漏洩磁場に比べて、奥行き
（Ｚ）方向の漏洩磁場の低減効果が小さいという問題が
あった。特に、被検体を計測空間に挿入するための寝台
機構が置かれた開口４０ａでは寝台機構の外側ではかな
り磁場強度が小さくなっているのに対し、その反対側の
開口４０ｂでは比較的大きな磁場強度の漏洩磁場が存在
するため、その低減が必要であった。For this reason, in the prior art, as shown in FIG. 7, a coil is double wound. That is, on the outside of the main coil 10 for generating a static magnetic field in the measurement space described above, the canceling coil 11 for generating a magnetic field in the opposite direction to the magnetic field generated by the main coil outside the apparatus is installed. . By balancing both coils, the leakage magnetic field is reduced. With this structure, a reduction effect can be obtained for the stray magnetic field in the radial (X and Y) directions.
It is difficult to cancel the magnetic field leaking from the vicinity of the opening 40 to the outside, and there is a problem that the effect of reducing the leak magnetic field in the depth (Z) direction is smaller than that in the radial (X and Y) direction. In particular, the magnetic field strength is considerably small outside the bed mechanism at the opening 40a where the bed mechanism for inserting the subject into the measurement space is placed, whereas the opening 40b on the opposite side has a relatively large magnetic field strength. Since there is a leaking magnetic field, it was necessary to reduce it.
【００１０】本発明は上記した問題点を解消し、装置の
奥行き（Ｚ）方向に漏洩する磁場強度を低減できる構造
のＭＲＩ用静磁場発生装置を提供することを目的とす
る。また本発明は、奥行き方向の全長を短くしたＭＲＩ
用静磁場発生装置を提供することを目的とする。また、
これにより磁場管理区域を削減し、狭い検査室にも設置
が可能で、周囲に磁場の影響を与えにくいＭＲＩ用静磁
場発生装置を提供することを目的とする。An object of the present invention is to solve the above-mentioned problems and to provide a static magnetic field generator for MRI having a structure capable of reducing the strength of the magnetic field leaking in the depth (Z) direction of the apparatus. Further, the present invention is an MRI in which the entire length in the depth direction is shortened.
An object of the present invention is to provide a static magnetic field generator for use. Also,
Accordingly, it is an object of the present invention to provide a static magnetic field generator for MRI that can reduce the magnetic field management area, can be installed in a small examination room, and is less likely to be affected by the magnetic field in the surroundings.
【００１１】[0011]
【課題を解決するための手段】上記目的を達成するため
に、複数の静磁場発生用コイルを用いて被検体を配置す
る測定空間内に前記被検体の体軸方向に円環状の静磁場
発生用コイルを複数配置し前記体軸方向に静磁場を発生
する磁気共鳴イメージング用静磁場発生装置において、
前記複数の静磁場発生用コイルのうち少なくとも１つの
静磁場発生用コイルの径を異ならせて配置したものであ
る。また、前記複数の静磁場発生用コイルは、前記被検
体の頭側に配置された静磁場発生用コイルの径が他の静
磁場発生用コイルの径よりも小さくしてもよいし、前記
静磁場発生用コイルの外側に漏洩磁場抑制手段を配置し
てもよい。さらに、複数の静磁場発生用コイルを用いて
被検体を配置する測定空間内に前記被検体の体軸方向に
円環状の静磁場発生用コイルを複数配置し前記体軸方向
に静磁場を発生する磁気共鳴イメージング用静磁場発生
装置において、前記複数の静磁場発生用コイルの径並び
に間隔を変えて配置したものである。In order to achieve the above-mentioned object, a static magnetic field is generated in an annular shape in the body axis direction of the subject in a measurement space in which the subject is placed using a plurality of static magnetic field generating coils. In a static magnetic field generator for magnetic resonance imaging, wherein a plurality of coils for magnetic field are arranged to generate a static magnetic field in the body axis direction,
At least one static magnetic field generating coil among the plurality of static magnetic field generating coils is arranged with different diameters. Further, the plurality of static magnetic field generating coils, the diameter of the static magnetic field generating coil disposed on the head side of the subject may be smaller than the diameter of the other static magnetic field generating coil, the static The leakage magnetic field suppressing means may be arranged outside the magnetic field generating coil. Further, a plurality of annular static magnetic field generating coils are arranged in the body axis direction of the subject in a measurement space in which the subject is arranged using a plurality of static magnetic field generating coils, and a static magnetic field is generated in the body axis direction. In the static magnetic field generator for magnetic resonance imaging described above, the plurality of static magnetic field generating coils are arranged with different diameters and intervals.
【００１２】さらに本発明の好適な態様においては、静
磁場発生装置の漏洩磁場を低減するために、静磁場発生
用コイルによって静磁場発生装置の外側に発生する磁場
と反対向きの磁場を発生するコイルを静磁場発生用コイ
ルの外部に配置するか、或いは静磁場発生用コイルの外
側に強磁性体を配置する。Further, in a preferred aspect of the present invention, in order to reduce the leakage magnetic field of the static magnetic field generator, the static magnetic field generating coil generates a magnetic field in a direction opposite to the magnetic field generated outside the static magnetic field generator. The coil is arranged outside the static magnetic field generating coil, or a ferromagnetic material is arranged outside the static magnetic field generating coil.
【００１３】[0013]
【作用】静磁場発生用コイルの径を異ならせることによ
り、比較的磁場強度の大きい漏洩磁場をなくし、磁場管
理区域を削減することができる。また、静磁場発生用コ
イルの径及び間隔を異ならせることで、測定空間の中心
位置を静磁場発生装置の奥行き方向の中心からずらすこ
とができ、奥行き方向の全長を短くすることができ、磁
場管理区域を削減及び設置箇所の制限を低減することが
できる。By changing the diameters of the static magnetic field generating coils, it is possible to eliminate the leakage magnetic field having a relatively large magnetic field strength and reduce the magnetic field management area. In addition, by making the diameter and interval of the static magnetic field generating coil different, the center position of the measurement space can be shifted from the center of the static magnetic field generator in the depth direction, and the total length in the depth direction can be shortened. It is possible to reduce the management area and the restrictions on installation locations.
【００１４】特に開口と反対側の端部を覆うように１又
は複数の静磁場発生用コイルを設けることにより、開口
と反対側の漏洩磁場を効果的に低減することができ、し
かも測定空間内に均一な磁場を形成することができる。
またさらに静磁場発生用コイルの外側に漏洩磁場防止用
コイルを設け、或いは強磁性体を設けることにより、漏
洩磁場低減効果を高めることができる。Particularly, by providing one or more static magnetic field generating coils so as to cover the end portion on the side opposite to the opening, the leakage magnetic field on the side opposite to the opening can be effectively reduced, and moreover, in the measurement space. It is possible to form a uniform magnetic field.
Further, the effect of reducing the leakage magnetic field can be enhanced by providing a leakage magnetic field preventing coil or a ferromagnetic material outside the static magnetic field generating coil.
【００１５】[0015]
【実施例】以下、本発明の実施例を図面に沿って具体的
に説明する。図１は本発明の一実施例を説明するための
ＭＲＩ用静磁場発生装置の断面図を示す。ここでも被検
体１００を挿入する奥行き方向をＺ方向、上下をＹ方
向、左右をＸ方向とする直交座標系を用いて説明する。Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a sectional view of a static magnetic field generator for MRI for explaining an embodiment of the present invention. Here, too, a description will be given using an orthogonal coordinate system in which the depth direction in which the subject 100 is inserted is the Z direction, the upper and lower sides are the Y direction, and the left and right sides are the X direction.
【００１６】本実施例においても、基本的には従来技術
と同様の冷却容器３０の中に収められた円環形状の超伝
導コイル１０を用いている。しかし、本実施例では、従
来例として示した図６の静磁場発生装置と異なり、被検
体１００を計測空間に挿入するために、計測空間のＺ方
向の一方の側のみに開口４０が設けられ、Ｚ方向の他方
の端部を覆うように直径の小さい超伝導コイル１０’を
配置している。被検体１００を静磁場発生装置の中に出
し入れするための寝台機構（図示せず）は、開口４０の
外側に設置されている。コイル１０及び１０’の線材の
巻き数と配置位置を適切に選ぶことで、計測空間内に均
一な磁場が発生するように構成される。この場合、奥側
の超伝導コイル１０’の直径を小さくしたことにより、
従来構造ではこの部分から外部に漏れ出していた磁場を
少なくでき、これにより、静磁場発生装置の奥に向かっ
ても磁場の低下が少なく、短い奥行きでも同等の磁場均
一度を達成できる。Also in this embodiment, basically, the annular superconducting coil 10 housed in the cooling container 30 similar to the prior art is used. However, in the present embodiment, unlike the static magnetic field generator of FIG. 6 shown as a conventional example, in order to insert the subject 100 into the measurement space, the opening 40 is provided only on one side in the Z direction of the measurement space. , A superconducting coil 10 'having a small diameter is arranged so as to cover the other end in the Z direction. A bed mechanism (not shown) for putting the subject 100 in and out of the static magnetic field generator is installed outside the opening 40. By appropriately selecting the number of windings and the arrangement position of the wire rods of the coils 10 and 10 ′, a uniform magnetic field is generated in the measurement space. In this case, by reducing the diameter of the superconducting coil 10 'on the back side,
In the conventional structure, it is possible to reduce the magnetic field leaking from this portion to the outside, so that the magnetic field does not decrease further toward the back of the static magnetic field generator, and the same magnetic field homogeneity can be achieved even at a short depth.
【００１７】このような構成において、寝台機構に位置
決めされた被検体１は寝台機構を予め設定された距離Ｚ
0移動させることにより、位置決めされた部位が計測空
間の中心位置に位置するようになっている。ここで、図
１の構成の静磁場発生装置ではその奥に向かっても高い
磁場均一度を維持しているので、測定空間１１０の中心
位置を静磁場発生装置の中心よりも奥に設定することが
できる。即ち、静磁場発生装置のＺ方向の長さをＬとす
るとき、開口４０から測定空間１１０の中心位置までの
距離Ｚ0を開口４０から静磁場発生装置の中心までの距
離Ｌ／２よりも、大きくすることができる。換言するな
らば、従来の装置では開口４０における磁場漏洩の影響
のない距離Ｚ0に静磁場発生装置の中心があったのに対
し（Ｚ0＝Ｌ／２）、距離Ｚ0を奥側にシフトできること
により装置全体の大きさを小さくすることができる。In such a structure, the subject 1 positioned on the bed mechanism has the bed mechanism set at a preset distance Z.
By moving it by 0 , the positioned part is located at the center position of the measurement space. Here, in the static magnetic field generator having the configuration of FIG. 1, since the high magnetic field homogeneity is maintained toward the back, the center position of the measurement space 110 should be set deeper than the center of the static magnetic field generator. You can That is, when the length of the static magnetic field generator in the Z direction is L, the distance Z 0 from the opening 40 to the center position of the measurement space 110 is smaller than the distance L / 2 from the opening 40 to the center of the static magnetic field generator. , Can be bigger. In other words, in the conventional device, the center of the static magnetic field generation device was at the distance Z 0 where there was no influence of magnetic field leakage at the opening 40 (Z 0 = L / 2), while the distance Z 0 was set to the back side. By being able to shift, the size of the entire device can be reduced.
【００１８】なお、図１では冷却装置３０を用いている
が、コイルの常電導コイルであって冷却が不要の場合に
は、もちろんこの冷却装置は必要ない。さらに、図１に
おいては、５組の超伝導コイル（内、２組が径の小さい
コイル）を示したが、この数は必要とする静磁場の特性
（強度、均一度）や製造原価に応じて適当に選択でき
る。Although the cooling device 30 is used in FIG. 1, this cooling device is, of course, not necessary when the coil is a normal conducting coil and cooling is unnecessary. Further, although FIG. 1 shows five sets of superconducting coils (of which two sets have small diameters), the number depends on the required static magnetic field characteristics (strength, homogeneity) and manufacturing cost. Can be selected appropriately.
【００１９】以上のように構成される静磁場発生装置
は、さらに装置全体の漏洩磁場を低減するとともに、開
口と反対側の漏洩磁場を開口側の漏洩磁場に比較して少
なくなるための手段（以下、漏洩磁場低減手段という）
を設けることができる。このための構成を図２及び図４
に示す。The static magnetic field generating device configured as described above further reduces the leakage magnetic field of the entire device and reduces the leakage magnetic field on the side opposite to the opening as compared with the leakage magnetic field on the opening side ( Hereinafter referred to as the leakage magnetic field reducing means)
Can be provided. The configuration for this is shown in FIGS.
Shown in.
【００２０】図２は漏洩磁場低減手段として、測定空間
１１０に静磁場を発生させるための超伝導コイル１０、
１０’の外側に、漏洩磁場を減少させることを目的とし
た打消しコイル１１を追加した構成を示すものである。
打消しコイル１１は、主磁場を作るためのコイル１０、
１０’と同様に、超伝導線あるいは常電導線を用いるこ
とができ、超伝導コイル１０、１０’が静磁場発生装置
の外側に発生する磁場を打ち消すような磁場を発生す
る。打消しコイル１１は、超伝導コイル１０の外側に配
置されるとともに、端部の超伝導コイル１０’を覆うよ
うに複数個配置される。このように打消しコイル１１を
付加することで、ＸＹ方向の漏洩磁場のみならず、Ｚ方
向に漏洩する磁場の領域の実質的に大幅に削減すること
ができる。FIG. 2 shows a superconducting coil 10 for generating a static magnetic field in the measurement space 110 as a leakage magnetic field reducing means.
A configuration is shown in which a canceling coil 11 for the purpose of reducing the leakage magnetic field is added to the outside of 10 '.
The canceling coil 11 is a coil 10 for creating a main magnetic field,
Similar to 10 ', a superconducting wire or a normal conducting wire can be used, and the superconducting coils 10, 10' generate a magnetic field that cancels the magnetic field generated outside the static magnetic field generator. The canceling coils 11 are arranged outside the superconducting coil 10 and a plurality of canceling coils 11 are arranged so as to cover the end superconducting coils 10 ′. By adding the canceling coil 11 in this manner, not only the leakage magnetic field in the XY directions but also the magnetic field region leaking in the Z direction can be substantially reduced.
【００２１】このことを図３に示すグラフを用いて説明
する。同図は、横軸にＺ方向の距離、縦軸に磁場強度を
とっている。横軸の原点Ｏは、静磁場発生装置のＺ方向
の中心位置である。原点Ｏ付近で強く均一であった磁場
は、中心から遠ざかるにつれて急激に減少する。特に
（−）方向では、中心軸近傍にまで打消しコイル１１が
設置されているので、磁場の減少の程度を大きくでき
る。一方、（＋）側、即ち開口４０側においては、従来
装置と同程度の減少の仕方となる。前述のように装置の
実際の使用状況においては、静磁場発生装置の（＋）Ｚ
側の外側には被検体１００を搭載するための寝台機構が
設置されており、この寝台機構が置かれた領域よりも外
側では、漏洩磁場も問題ない程度にまで減少している。
漏洩磁場が問題となるのは、寝台機構を含むＭＲＩ装置
の外側の領域であるから、（＋）Ｚ側の漏洩磁場は問題
となることが少ない。これに対し、（−）Ｚ側では漏洩
磁場が大きな問題となる得るが、上記構成により（−）
Ｚ側の漏洩磁場を大幅に減らすことができるので、全体
として磁場を管理すべき領域を実質的に大幅に削減でき
る。This will be described with reference to the graph shown in FIG. In this figure, the horizontal axis represents the distance in the Z direction, and the vertical axis represents the magnetic field strength. The origin O on the horizontal axis is the center position of the static magnetic field generator in the Z direction. The magnetic field that was strong and uniform near the origin O sharply decreases as it moves away from the center. Particularly (-) in the direction, the coil 11 cancel to the vicinity central axis that is disposed can be increased the degree of reduction of the magnetic field. On the other hand, on the (+) side, that is, on the side of the opening 40, the reduction method is the same as that of the conventional device. As described above, when the device is actually used, the (+) Z of the static magnetic field generator is used.
A bed mechanism for mounting the subject 100 is installed on the outer side of the side, and the leakage magnetic field is reduced to a level where there is no problem outside the area where the bed mechanism is placed.
Since the leakage magnetic field is a problem in the region outside the MRI apparatus including the bed mechanism, the leakage magnetic field on the (+) Z side is less likely to be a problem. On the other hand, the leakage magnetic field can be a big problem on the (−) Z side, but the above configuration causes the (−)
Since the leakage magnetic field on the Z side can be significantly reduced, the region where the magnetic field should be managed can be substantially reduced as a whole.
【００２２】このため、ＭＲＩ装置を使用施設に設置す
る際に、漏洩磁場に対する制限が大幅に緩和され、より
容易に設置することが可能となる。また、図２のように
漏洩磁場の打消しコイル１１を用いることで、次に述べ
る構成に比較して、静磁場発生装置全体の重量を低く押
えることができる。尚、図２では繁雑さを避けるために
冷却容器は図示していないが、静磁場発生用コイル１
０、１０’及び／又は打消しコイル１１が超伝導コイル
である場合には、冷却容器を設けることは言うまでもな
い。Therefore, when the MRI apparatus is installed in the facility where the MRI apparatus is installed, the restriction on the leakage magnetic field is greatly relaxed, and the MRI apparatus can be installed more easily. Further, by using the leakage magnetic field canceling coil 11 as shown in FIG. 2, the weight of the entire static magnetic field generation device can be kept low as compared with the configuration described below. Although a cooling container is not shown in FIG. 2 to avoid complexity, the static magnetic field generating coil 1
It goes without saying that if 0, 10 'and / or the cancellation coil 11 is a superconducting coil, a cooling vessel is provided.
【００２３】図４は、漏洩磁場低減手段の他の実施例を
示すもので、本実施例では漏洩磁場を打ち消すのに、コ
イルの代わりに鉄等の強磁性体１２を用いている。この
場合にも、図２の装置と同様に、強磁性体１２で超伝導
コイル１０、１０’を覆うことにより、装置のＸＹ方向
のみならず、特に（−）Ｚ側での漏洩磁場を大幅に削減
することが可能である。FIG. 4 shows another embodiment of the leakage magnetic field reducing means. In this embodiment, a ferromagnetic material 12 such as iron is used in place of the coil to cancel the leakage magnetic field. Also in this case, as in the device of FIG. 2, by covering the superconducting coils 10 and 10 ′ with the ferromagnetic material 12, not only the XY direction of the device but also the leakage magnetic field particularly on the (−) Z side is significantly increased. Can be reduced to.
【００２４】またこの実施例では、コイルの代わりに強
磁性体を用いることで、図２と同様の主コイル１０を用
いた場合に、測定空間内の磁場強度が高めることができ
る。従って、同じ静磁場強度の装置を製造する場合、図
２に示すコイルを用いた場合に比べ、製造原価を低減で
きるメリットがある。In this embodiment, by using a ferromagnetic material instead of the coil, when the main coil 10 similar to that shown in FIG. 2 is used, the magnetic field strength in the measurement space can be increased. Therefore, when manufacturing a device having the same static magnetic field strength, there is an advantage that the manufacturing cost can be reduced as compared with the case where the coil shown in FIG. 2 is used.
【００２５】さらに本発明の別の実施例を示すための断
面図を図５に示す。基本的な構造は図１に示したものと
同じであるが、この実施例では、開口４０と反対側、コ
イルの直径を小さくした奥行側端部に小さな穴５０を設
けている。常電導コイルの場合にはコイルを覆うガント
リにこのような穴５０を形成する。また超伝導コイルの
場合には冷却容器３０に穴５０をあける。穴５０を設け
ることによって、装置内に入ったときの被検体の恐怖感
を和らげることができ、画像撮影をスムーズに行うこと
ができる。図５の構成は、図２或いは図４に示す漏洩磁
場低減手段を設けた装置においても適用できる。FIG. 5 is a sectional view showing another embodiment of the present invention. Although the basic structure is the same as that shown in FIG. 1, in this embodiment, a small hole 50 is provided on the side opposite to the opening 40 and on the depth side end where the diameter of the coil is reduced. In the case of a normal conducting coil, such a hole 50 is formed in the gantry that covers the coil. In the case of a superconducting coil, a hole 50 is made in the cooling container 30. By providing the hole 50, it is possible to reduce the fear of the subject when he / she enters the apparatus, and it is possible to smoothly perform the image capturing. The configuration of FIG. 5 can also be applied to an apparatus provided with the leakage magnetic field reducing means shown in FIG. 2 or 4.
【００２６】[0026]
【発明の効果】以上説明したように、本発明のＭＲＩ装
置用静磁場発生装置によれば、複数の静磁場発生用コイ
ルを用いた静磁場発生装置において、静磁場発生コイル
の径並びに間隔を異ならせることにより、漏洩磁場が問
題となる奥行方向の漏洩磁場を効果的に抑制するととも
に、実質的に装置の奥行方向のサイズを小さくすること
を可能とし、これにより狭い検査室にも設置が可能で、
周囲の磁場の影響を与えにくいＭＲＩ装置用静磁場発生
装置を提供できる。さらに本発明のＭＲＩ装置用静磁場
発生装置によれば、静磁場発生用コイルの外側に漏洩磁
場を低減する手段を設けることにより、上記効果を更に
高めることが可能である。As described above, according to the static magnetic field generating apparatus for an MRI apparatus of the present invention, in the static magnetic field generating apparatus using a plurality of static magnetic field generating coils, the diameters and intervals of the static magnetic field generating coils are set. By making them different, it is possible to effectively suppress the leakage magnetic field in the depth direction where the leakage magnetic field becomes a problem, and it is possible to substantially reduce the size of the apparatus in the depth direction, which allows installation in a narrow examination room. Possible,
It is possible to provide a static magnetic field generator for an MRI apparatus that is less likely to be affected by the surrounding magnetic field. Further, according to the static magnetic field generator for an MRI apparatus of the present invention, the above effect can be further enhanced by providing a means for reducing the leakage magnetic field outside the static magnetic field generating coil.
【図１】 本発明による実施例を示すための断面図FIG. 1 is a sectional view showing an embodiment according to the present invention.
【図２】 本発明による別の実施例を示すための断面図FIG. 2 is a sectional view showing another embodiment according to the present invention.
【図３】 本発明を実施した場合の磁場分布を説明する
ためのグラフFIG. 3 is a graph for explaining a magnetic field distribution when the present invention is implemented.
【図４】 本発明によるさらに別の実施例を示すための
断面図FIG. 4 is a sectional view showing yet another embodiment according to the present invention.
【図５】 本発明によるさらに別の実施例を示すための
断面図FIG. 5 is a sectional view showing yet another embodiment according to the present invention.
【図６】 従来例による静磁場発生装置の一例を示すた
めの断面図FIG. 6 is a cross-sectional view showing an example of a conventional static magnetic field generator.
【図７】 別の従来例による静磁場発生装置の一例を示
すための断面図FIG. 7 is a sectional view showing an example of a static magnetic field generator according to another conventional example.
１０ 超伝導コイル（静磁場発生用コイル） １０’ 超伝導コイル（静磁場発生用コイル） １１ 打消しコイル（漏洩磁場低減手段） １２ 強磁性体（漏洩磁場低減手段） ４０ 開口 １００ 被検体 １１０ 測定空間 10 Superconducting coil (static magnetic field generating coil) 10 'superconducting coil (static magnetic field generating coil) 11 Canceling coil (Means for reducing leakage magnetic field) 12 Ferromagnet (Means for reducing leakage magnetic field) 40 openings 100 subject 110 measurement space
Claims (2)
体の体軸方向に円環状の静磁場発生用コイルを複数配置
し前記体軸方向に静磁場を発生する磁気共鳴イメージン
グ用静磁場発生装置において、前記被検体を前記測定空
間に挿入するための開口を一カ所にだけ設け、前記開口
側における静磁場発生用コイルの直径よりも小さい直径
をもつ静磁場発生用コイルを前記開口と反対側に備えた
ことを特徴とする磁気共鳴イメージング用静磁場発生装
置。1. The test object is placed in a measurement space in which the test object is placed.
Multiple annular magnetic field generation coils are arranged in the body axis direction
Magnetic resonance imager for generating a static magnetic field in the body axis direction
In the static magnetic field generator for magnetic field
There is only one opening for insertion between
Diameter smaller than the diameter of the static magnetic field generating coil on the side
A static magnetic field generating apparatus for magnetic resonance imaging , comprising a static magnetic field generating coil having the above-mentioned on the side opposite to the opening .
場抑制手段を配置したことを特徴とする請求項１乃至２
の何れか１項に記載の磁気共鳴イメージング用静磁場発
生装置。 2. A leakage magnetic field is provided outside the static magnetic field generating coil.
A field suppressing means is provided, and the field suppressing means is arranged.
The magnetic field generator for magnetic resonance imaging according to any one of
Raw equipment.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP17484294A JP3435821B2 (en) | 1994-07-05 | 1994-07-05 | Static magnetic field generator for magnetic resonance imaging |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP17484294A JP3435821B2 (en) | 1994-07-05 | 1994-07-05 | Static magnetic field generator for magnetic resonance imaging |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0819525A JPH0819525A (en) | 1996-01-23 |
| JP3435821B2 true JP3435821B2 (en) | 2003-08-11 |
Family
ID=15985615
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP17484294A Expired - Fee Related JP3435821B2 (en) | 1994-07-05 | 1994-07-05 | Static magnetic field generator for magnetic resonance imaging |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3435821B2 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AU2015306082B2 (en) * | 2014-08-18 | 2020-04-30 | Magnetica Limited | Magnet for head and extremity imaging |
-
1994
- 1994-07-05 JP JP17484294A patent/JP3435821B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0819525A (en) | 1996-01-23 |
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