JPH04343832A - Magnetic field generating device for magnetic resonance imaging device - Google Patents
Magnetic field generating device for magnetic resonance imaging deviceInfo
- Publication number
- JPH04343832A JPH04343832A JP3144083A JP14408391A JPH04343832A JP H04343832 A JPH04343832 A JP H04343832A JP 3144083 A JP3144083 A JP 3144083A JP 14408391 A JP14408391 A JP 14408391A JP H04343832 A JPH04343832 A JP H04343832A
- Authority
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- Japan
- Prior art keywords
- magnetic field
- coil
- field generating
- magnetic resonance
- resonance imaging
- Prior art date
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- Pending
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- 230000005291 magnetic effect Effects 0.000 title claims abstract description 139
- 238000002595 magnetic resonance imaging Methods 0.000 title claims abstract description 20
- 230000003068 static effect Effects 0.000 claims abstract description 32
- 238000001208 nuclear magnetic resonance pulse sequence Methods 0.000 claims description 2
- 230000000704 physical effect Effects 0.000 claims description 2
- 238000001514 detection method Methods 0.000 claims 1
- 238000003384 imaging method Methods 0.000 description 16
- 238000005481 NMR spectroscopy Methods 0.000 description 7
- 238000010586 diagram Methods 0.000 description 6
- 230000004907 flux Effects 0.000 description 5
- 238000012545 processing Methods 0.000 description 5
- 230000005540 biological transmission Effects 0.000 description 3
- 230000000694 effects Effects 0.000 description 2
- 235000021538 Chard Nutrition 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000017531 blood circulation Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000012937 correction Methods 0.000 description 1
- 238000013480 data collection Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000003302 ferromagnetic material Substances 0.000 description 1
- 238000007689 inspection Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
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- Magnetic Resonance Imaging Apparatus (AREA)
Abstract
Description
【０００１】0001
【産業上の利用分野】本発明は、核磁気共鳴現象を利用
して被検体の所望箇所を画像化する磁気共鳴イメージン
グ装置（以下、ＭＲＩ装置と称する）における静磁場発
生用の磁場発生装置に関する。[Field of Industrial Application] The present invention relates to a magnetic field generator for generating a static magnetic field in a magnetic resonance imaging apparatus (hereinafter referred to as an MRI apparatus) that images a desired location of a subject by utilizing nuclear magnetic resonance phenomena. .
【０００２】0002
【従来の技術】ＭＲＩ装置は、核磁気共鳴現象を利用し
て被検体中の所望の検査部位における原子核スピンの密
度分布、緩和時間分布等を計測して、その計測データか
ら被検体の断面を画像表示するものである。[Prior Art] An MRI apparatus uses the nuclear magnetic resonance phenomenon to measure the density distribution, relaxation time distribution, etc. of nuclear spins at a desired inspection site in a subject, and uses the measurement data to determine a cross section of the subject. It displays images.
【０００３】均一で強力な静磁場発生装置内に置かれた
被検体の原子核スピンは、静磁場の強さによって定まる
周波数（ラーモア周波数）で静磁場の方向を軸として歳
差運動を行なう。そこで、このラーモア周波数に等しい
周波数の高周波パルスを外部より照射すると、スピンが
励起され高いエネルギー状態に遷移する（核磁気共鳴現
象）。この照射を打ち切ると、スピンはそれぞれの状態
に応じた時定数でもとの低いエネルギー状態に戻り、こ
のときに外部に電磁波を放出する。これをその周波数に
同調した高周波受信コイルで検出する。このとき、空間
内に位置情報を負荷する目的で、３軸の傾斜磁場を静磁
場空間に印加する。この結果、空間内の位置情報を周波
数情報として捕らえることが可能である。Nuclear spins of an object placed in a uniform and strong static magnetic field generating device precess around the direction of the static magnetic field at a frequency (Larmor frequency) determined by the strength of the static magnetic field. Therefore, when a high-frequency pulse with a frequency equal to this Larmor frequency is applied from the outside, the spins are excited and transition to a higher energy state (nuclear magnetic resonance phenomenon). When this irradiation is stopped, the spins return to their original low energy state with a time constant depending on their state, and at this time they emit electromagnetic waves to the outside. This is detected by a high-frequency receiving coil tuned to that frequency. At this time, a three-axis gradient magnetic field is applied to the static magnetic field space for the purpose of loading position information in the space. As a result, it is possible to capture positional information in space as frequency information.
【０００４】ところで、この検出されるＮＭＲ信号の強
度は、現在使用されている磁場強度範囲内では、ほぼ静
磁場強度に比例することが知られている。つまり、静磁
場強度が高いＭＲＩ装置ではＳＮ比の高い画像が得られ
ることになる。（この詳細に関してはＨＯＵＬＴ＆ＲＩ
ＣＨＡＲＤの論文「Ｔｈｅ Ｓｉｇｎａｌ−ｔｏ−Ｎｏ
ｉｓｅ Ｒａｔｉｏ ｏｆ ｔｈｅ ＮｕｃｌｅａｒＭ
ａｇｎｅｔｉｃ Ｒｅｓｏｎａｎｃｅ Ｅｘｐｅｒｉｍ
ｅｎｔ」（ＪＯＵＲＮＡＬ ＯＦ ＭＡＧＮＥＴＩＣ
ＲＥＳＯＮＡＮＣＥ ２４，Ｐ７１−８５１９７６）を
参照。）また、ＭＲＩ装置ではこの静磁場の均一性も重
要であり、これが十分でないと撮像される画像に歪みや
ノイズを発生し、血流のイメージングなどの高機能化に
おいて大きな障害となる。従ってＭＲＩ装置の磁場発生
装置は被検体の撮像部位全体を包む範囲において、高い
均一度の高磁場を発生することが必要であり、このため
に超電導電磁石や大電流を流した電磁石あるいは高効率
の永久磁石が使用されている。By the way, it is known that the intensity of the detected NMR signal is approximately proportional to the static magnetic field intensity within the currently used magnetic field intensity range. In other words, an MRI apparatus with a high static magnetic field strength can obtain images with a high signal-to-noise ratio. (For details, please refer to HOULT&RI
CHARD's paper "The Signal-to-No
ise ratio of the NuclearM
agnetic resonance experiment
ent” (JOURNAL OF MAGNETIC
RESONANCE 24, P71-851976). ) Furthermore, in an MRI apparatus, the uniformity of the static magnetic field is also important, and if this is not sufficient, distortion and noise will occur in the captured image, which will be a major hindrance in improving functionality such as imaging of blood flow. Therefore, it is necessary for the magnetic field generator of an MRI apparatus to generate a highly uniform, high magnetic field in a range that encompasses the entire imaged area of the subject. Permanent magnets are used.
【０００５】[0005]
【発明が解決しようとする課題】このように磁場発生装
置の磁場強度とその均一性はＭＲＩ装置の性能を決定す
る要である。また、ＭＲＩ装置は人体の全部位の臨床に
有用であり、体幹部への適用を考えると、均一磁場空間
は４０ｃｍ球程度必要である。しかし、頭部撮像時にお
いては２５ｃｍ球程度の均一磁場空間があれば十分であ
り、これ以上の領域では均一性は必要がない。つまり、
体幹部の撮像時には視野が大きく信号量を確保でき、ま
た、体動の影響があるため高分解能も要求されず、静磁
場強度よりも磁場空間の均一度が最重要である。これに
対して、頭部の撮像や局所的な部位の撮像においては、
複雑な構造に対応するため高い分解能が要求され、ＳＮ
比が重要である。このためには少しでも高い静磁場が必
要であるが均一空間は狭くてよい。しかし、従来のＭＲ
Ｉ装置では被検体の全部位に適用するために広い均一空
間を重視しており、このため高い静磁場を得ることが困
難であった。As described above, the magnetic field strength of the magnetic field generator and its uniformity are key to determining the performance of the MRI apparatus. Furthermore, the MRI apparatus is useful in clinical practice for all parts of the human body, and when considering application to the trunk, a uniform magnetic field space of approximately 40 cm is required. However, when imaging the head, it is sufficient to have a uniform magnetic field space of about a 25 cm sphere, and uniformity is not necessary in a larger area. In other words,
When imaging the trunk of the body, the field of view is large and the amount of signal can be secured, and high resolution is not required because of the effects of body movement, and the homogeneity of the magnetic field space is more important than the static magnetic field strength. On the other hand, when imaging the head or localized areas,
High resolution is required to handle complex structures, and SN
The ratio is important. For this purpose, a static magnetic field as high as possible is required, but the uniform space may be narrow. However, conventional MR
The I device emphasizes a wide uniform space in order to apply it to all parts of the subject, and therefore it is difficult to obtain a high static magnetic field.
【０００６】本発明の目的は、静磁場強度を変化させる
ことにより良好な画像を得ることができるＭＲＩ装置を
提供することにある。An object of the present invention is to provide an MRI apparatus that can obtain good images by changing the static magnetic field strength.
【０００７】[0007]
【課題を解決するための手段】被検体を収容する空間に
超電導コイル、常電導コイルまたは永久磁石によって強
く均一な静磁場を形成する主磁場発生器と、前記被検体
にスライス傾斜磁場、リードアウト傾斜磁場及び位相エ
ンコード傾斜磁場を印加する傾斜磁場コイルと、前記被
検体の組織を構成する原子の原子核に磁気共鳴を起こさ
せる高周波パルスをある所定のパルスシーケンスで繰り
返し印加する照射コイルと、磁気共鳴信号を検出する受
信コイルと、前記検出信号を使って対象物体の物理的性
質を表わす画像を得る画像再構成手段とを備えたＭＲＩ
装置において、前記主磁場発生器の均一磁場空間内部に
局部的に前記主磁場発生器により形成される均一な静磁
場強度とは異なる均一な静磁場を形成すると共に局部的
な均一静磁場強度を任意に可変設定する補助磁場発生手
段を設ける。[Means for Solving the Problems] A main magnetic field generator that forms a strong and uniform static magnetic field using a superconducting coil, a normal conducting coil, or a permanent magnet in a space accommodating a subject, and a slice gradient magnetic field and a readout for the subject. a gradient magnetic field coil that applies a gradient magnetic field and a phase encoding gradient magnetic field; an irradiation coil that repeatedly applies a high-frequency pulse in a predetermined pulse sequence that causes magnetic resonance to the nuclei of atoms constituting the tissue of the subject; and a magnetic resonance coil. MRI comprising a receiving coil that detects a signal and an image reconstruction means that uses the detected signal to obtain an image representing the physical properties of the target object.
In the apparatus, a uniform static magnetic field different from the uniform static magnetic field strength formed by the main magnetic field generator is locally formed inside the uniform magnetic field space of the main magnetic field generator, and the local uniform static magnetic field strength is increased. An auxiliary magnetic field generating means that can be set arbitrarily and variably is provided.
【０００８】[0008]
【作用】主磁場発生器の均一磁場空間内部に補助磁場発
生手段を設け、主磁場発生器より形成される静磁場強度
と異なった静磁場を形成させる。また、補助磁場発生手
段により局部的な均一静磁場強度を任意に可変設定をす
る。[Operation] An auxiliary magnetic field generating means is provided inside the uniform magnetic field space of the main magnetic field generator to generate a static magnetic field different in intensity from the static magnetic field generated by the main magnetic field generator. Further, the local uniform static magnetic field strength can be arbitrarily and variably set by the auxiliary magnetic field generating means.
【０００９】[0009]
【実施例】以下、本発明を垂直磁場方式ＭＲＩ装置に適
用した際の実施例を添付図面に基づいて詳細に説明する
。図６は本発明に係るＭＲＩ装置の全体構成例を示す構
成図である。このＭＲＩ装置は、核磁気共鳴（ＮＭＲ）
現象を利用して被検体６の断層画像を得るもので、磁場
発生装置１０と、中央処理装置（以下、ＣＰＵと称する
）１１と、シーケンサ１２と、送信系１３と、傾斜磁場
発生系１４と、受信系１５と、信号処理系１６とからな
る。上記磁場発生装置１０は、被検体６の体軸方向と垂
直に且つ上記被検体６の周りのある広がりを持った空間
に強く均一な静磁場を発生させるもので、本実施例では
永久磁石による磁場発生手段を用いている。上記シーケ
ンサ１２は、ＣＰＵ１１の制御で動作し、被検体６の断
層画像のデータ収集に必要な種々の命令を送信系１３及
び傾斜磁場発生系１４並びに受信系１５に送るものであ
る。Embodiments Hereinafter, embodiments in which the present invention is applied to a vertical magnetic field type MRI apparatus will be described in detail with reference to the accompanying drawings. FIG. 6 is a configuration diagram showing an example of the overall configuration of an MRI apparatus according to the present invention. This MRI device uses nuclear magnetic resonance (NMR)
It obtains a tomographic image of the subject 6 by using the phenomenon, and includes a magnetic field generator 10, a central processing unit (hereinafter referred to as CPU) 11, a sequencer 12, a transmission system 13, and a gradient magnetic field generation system 14. , a receiving system 15, and a signal processing system 16. The magnetic field generator 10 generates a strong and uniform static magnetic field perpendicular to the body axis direction of the subject 6 and in a certain expanse of space around the subject 6, and in this embodiment, it uses a permanent magnet. A magnetic field generating means is used. The sequencer 12 operates under the control of the CPU 11 and sends various commands necessary for data collection of tomographic images of the subject 6 to the transmission system 13, gradient magnetic field generation system 14, and reception system 15.
【００１０】上記送信系１３は、高周波発生器１７と、
変調器１８と、高周波増幅器１９と、送信側の照射コイ
ル２０とからなり、上記高周波発生器１７から出力され
た高周波パルスをシーケンサ１２の命令に従って変調器
１８で変調し、この変調された照射パルスを高周波増幅
器１９で増幅した後に被検体６に近接して配置された照
射コイル２０に供給することにより、電磁波が被検体６
に照射されるようになっている。上記傾斜磁場発生系１
４は、Ｘ，Ｙ，Ｚの３軸方向に巻かれた傾斜磁場コイル
２１と、それぞれのコイルを駆動する傾斜磁場電源２２
とからなり、上記シーケンサ１２からの命令に従ってそ
れぞれのコイルの傾斜磁場電源２２を駆動することによ
り、Ｘ，Ｙ，Ｚの３軸方向の傾斜磁場Ｇｘ，Ｇｙ，Ｇｚ
を被検体６に印加するようになっている。この傾斜磁場
の加え方により、被検体６に対するスライス面を設定す
ることができる。The transmission system 13 includes a high frequency generator 17,
Consisting of a modulator 18, a high-frequency amplifier 19, and a transmitting-side irradiation coil 20, the modulator 18 modulates the high-frequency pulse output from the high-frequency generator 17 according to instructions from the sequencer 12, and the modulated irradiation pulse is The electromagnetic waves are amplified by a high frequency amplifier 19 and then supplied to an irradiation coil 20 placed close to the subject 6.
It is designed to be irradiated by The above gradient magnetic field generation system 1
4 is a gradient magnetic field coil 21 wound in the three axis directions of X, Y, and Z, and a gradient magnetic field power supply 22 that drives each coil.
By driving the gradient magnetic field power supply 22 of each coil according to the command from the sequencer 12, gradient magnetic fields Gx, Gy, Gz in the three axis directions of X, Y, and Z are generated.
is applied to the subject 6. Depending on how this gradient magnetic field is applied, a slice plane for the subject 6 can be set.
【００１１】上記受信系１５は、受信コイル９と、プリ
アンプ２３と、直交位相検波器２４と、Ａ／Ｄ変換器２
５とからなり、上記送信側の照射コイル２０から照射さ
れた電磁波による被検体６からの応答電磁波（ＮＭＲ信
号）は被検体６に近接して配置された受信コイル９で検
出され、プリアンプ２３及び直交位相検波器２４を介し
てＡ／Ｄ変換器２５に入力してデジタル量に変換され、
さらにシーケンサ１２からの命令によるタイミングで直
交位相検波器２４によりサンプリングされた二系統の収
集データとされ、その信号が信号処理系１６に送られる
ようになっている。この信号処理系１６は、ＣＰＵ１１
と、磁気ディスク２６及び磁気テープ２７等の記録装置
と、ＣＲＴ等のディスプレイ２８とからなり、上記ＣＰ
Ｕ１１でフーリエ変換、補正係数計算、画像再構成等の
処理を行ない、任意断面の信号強度分布あるいは複数の
信号に適当な演算を行なって得られた分布を画像化して
ディスプレイ２８に表示するようになっている。なお、
本図において、照射コイル２０と受信コイル９及び傾斜
磁場コイル２１は、被検体６の周りの空間に配置された
磁場発生装置１０の磁場空間内に配置されている。The receiving system 15 includes a receiving coil 9, a preamplifier 23, a quadrature phase detector 24, and an A/D converter 2.
5, the response electromagnetic wave (NMR signal) from the subject 6 due to the electromagnetic wave irradiated from the transmitting side irradiation coil 20 is detected by the receiving coil 9 disposed close to the subject 6, and the preamplifier 23 and It is input to the A/D converter 25 via the quadrature phase detector 24 and converted into a digital quantity,
Furthermore, two systems of collected data are sampled by a quadrature phase detector 24 at a timing according to a command from the sequencer 12, and the signals are sent to a signal processing system 16. This signal processing system 16 includes a CPU 11
, a recording device such as a magnetic disk 26 and a magnetic tape 27, and a display 28 such as a CRT.
Processing such as Fourier transformation, correction coefficient calculation, and image reconstruction is performed in U11, and the signal intensity distribution of an arbitrary cross section or the distribution obtained by performing appropriate calculations on a plurality of signals is converted into an image and displayed on the display 28. It has become. In addition,
In this figure, the irradiation coil 20, the reception coil 9, and the gradient magnetic field coil 21 are arranged in the magnetic field space of the magnetic field generator 10 arranged in the space around the subject 6.
【００１２】ここで本発明による磁場発生装置の外観図
を図１に示す。常電導コイルによる補助磁場発生手段１
は受信コイル９の上下にアーム５を介して配置され、被
検体用ベッド２９に固定される。このベッド２９が撮像
時に磁場発生装置１０の中央に撮像部が位置するように
挿入される。補助磁場発生手段１、受信コイル９、アー
ム５、ベッド２９は強磁性体を含まない材質で構成し、
磁場発生装置１０の磁場均一度を低下させないようにす
る。補助磁場発生手段１の常電導コイルに電流を流さな
い状態では、図２（Ａ）に示すように磁場発生装置１０
内部には永久磁石による主磁場発生器２より発生される
磁束３だけが存在するが、この磁束３を強める方向に補
助磁場発生手段１の常電導コイルに電流を流せば、図２
（Ｂ）に示すように磁束３を増加させることができる。
また、コイル電流を変えることによって磁束３の量を制
御できるので、撮像部位に応じて静磁場強度を任意に可
変することも可能である。FIG. 1 shows an external view of a magnetic field generator according to the present invention. Auxiliary magnetic field generation means 1 using a normally conducting coil
are arranged above and below the receiving coil 9 via arms 5, and fixed to the subject bed 29. This bed 29 is inserted so that the imaging section is located at the center of the magnetic field generating device 10 during imaging. The auxiliary magnetic field generating means 1, the receiving coil 9, the arm 5, and the bed 29 are made of a material that does not contain ferromagnetic material,
The magnetic field uniformity of the magnetic field generator 10 is not reduced. When no current is applied to the normally conductive coil of the auxiliary magnetic field generating means 1, the magnetic field generating device 10 as shown in FIG. 2(A)
Inside, only the magnetic flux 3 generated by the main magnetic field generator 2 made of permanent magnets exists, but if a current is passed through the normally conducting coil of the auxiliary magnetic field generating means 1 in a direction to strengthen this magnetic flux 3, the result as shown in FIG.
The magnetic flux 3 can be increased as shown in (B). Furthermore, since the amount of magnetic flux 3 can be controlled by changing the coil current, it is also possible to arbitrarily vary the static magnetic field strength depending on the imaging region.
【００１３】補助磁場発生手段１の常電導コイルの径が
小さいと、磁場の発生効率は高いが、均一空間は狭くな
る。このため、撮像領域に応じて補助磁場発生手段１の
大きさを変える必要が生じる。図３はこの一例であるが
比較的撮像領域の狭い頭部では頭部用受信コイル９ａの
上下に小径の常電導コイルによる補助磁場発生手段１ａ
を設置し、狭い空間に高い静磁場を発生させる。これに
対し、体幹部用受信コイル９ｂの上下には磁場発生効率
よりも均一領域を重視した径の大きな常電導コイルによ
る補助磁場発生手段１ｂを設置して、撮像に応じて使い
分けるようにする。また、受信コイル９の移動に伴って
補助磁場発生手段１も移動するような構造にすれば、使
い勝手を向上することができる。If the diameter of the normally conducting coil of the auxiliary magnetic field generating means 1 is small, the efficiency of magnetic field generation is high, but the uniform space becomes narrow. Therefore, it is necessary to change the size of the auxiliary magnetic field generating means 1 depending on the imaging area. FIG. 3 is an example of this, but in the case of a head where the imaging area is relatively narrow, auxiliary magnetic field generating means 1a using small-diameter normal conducting coils above and below the head receiving coil 9a.
installed to generate a high static magnetic field in a narrow space. On the other hand, auxiliary magnetic field generating means 1b are installed above and below the body trunk receiving coil 9b, and are made of normal conductive coils with a large diameter, placing more emphasis on a uniform area than on magnetic field generation efficiency, and are used selectively depending on the imaging. Further, if the structure is such that the auxiliary magnetic field generating means 1 also moves as the receiving coil 9 moves, usability can be improved.
【００１４】図４は本発明を超電導コイルによる水平磁
場発生装置１０に適用した例であるが、主磁場発生器２
は筒状の超電導コイル４であり、この中に入る被検体に
対して水平に静磁場を与える。補助磁場発生手段１は図
のように主磁場発生器２の働きによって、中央部では局
所的に強い水平方向の静磁場を得ることができる。同様
に図５に示す垂直磁場方式の磁場発生装置１０では永久
磁石を使用した主磁場発生器２の間隙に常電導コイルに
よる補助磁場発生手段１を対向して配置し、局所高磁場
を得ることが可能である。FIG. 4 shows an example in which the present invention is applied to a horizontal magnetic field generator 10 using superconducting coils.
is a cylindrical superconducting coil 4, which applies a static magnetic field horizontally to a subject entering the coil. As shown in the figure, the auxiliary magnetic field generating means 1 can obtain a locally strong horizontal static magnetic field at the center by the action of the main magnetic field generator 2. Similarly, in the vertical magnetic field type magnetic field generator 10 shown in FIG. 5, an auxiliary magnetic field generating means 1 made of a normal conductive coil is disposed facing the gap between the main magnetic field generator 2 using a permanent magnet to obtain a local high magnetic field. is possible.
【００１５】この補助磁場発生手段１は撮像部位によっ
て選択して使用する必要があるので、付け外しあるいは
電気的な断続を任意にできなければならない。このこと
から常電導コイルによる電磁石がその強度を任意に可変
でき、最適であると考えられる。この補助磁場発生手段
１は小範囲であるほど効率よく高磁場を発生しうるが、
均一度は低下し撮像範囲が狭くなるので撮像部位に応じ
て最適な大きさが存在する。従って、撮像部位に合わせ
て数種類用意することが望ましい。さらに、撮像部位を
この狭い均一空間内に納めるための補助磁場発生手段１
の移動手段が必要である。また、視野を小さくして撮像
する際は必然的に分解能が必要となり、静磁場が高いこ
とが望ましいので、撮像時の視野に応じてコイル電流を
視野内での均一度が低下しない範囲での最大磁場となる
ように制御して使用することも可能である。Since the auxiliary magnetic field generating means 1 needs to be used selectively depending on the region to be imaged, it must be possible to attach or detach it or to electrically disconnect it as desired. For this reason, an electromagnet using a normally conducting coil is considered to be optimal because its strength can be arbitrarily varied. This auxiliary magnetic field generating means 1 can generate a high magnetic field more efficiently in a smaller range.
Since uniformity decreases and the imaging range becomes narrower, there is an optimal size depending on the imaging region. Therefore, it is desirable to prepare several types according to the imaging site. Furthermore, an auxiliary magnetic field generating means 1 for accommodating the imaging region within this narrow uniform space.
transportation is required. In addition, when imaging with a small field of view, resolution is inevitably required, and a high static magnetic field is desirable. It is also possible to control and use the magnetic field so as to obtain the maximum magnetic field.
【００１６】[0016]
【発明の効果】以上述べたように本発明による磁場発生
装置では、補助磁場発生手段の付加をすると共に、撮像
領域に応じてこれの大きさを選択して使用する構造とし
たことによって、静磁場強度を可変設定することが可能
となり、ＳＮ比の高い良質なＭＲＩ画像を得ることがで
きる。Effects of the Invention As described above, the magnetic field generating device according to the present invention has a structure in which an auxiliary magnetic field generating means is added and the size of the auxiliary magnetic field generating means is selected depending on the imaging area. It becomes possible to variably set the magnetic field strength, and it is possible to obtain high-quality MRI images with a high signal-to-noise ratio.
【図１】補助磁場発生手段外観図[Figure 1] External view of auxiliary magnetic field generating means
【図２】補助磁場発生手段の作用説明図[Fig. 2] Diagram explaining the operation of the auxiliary magnetic field generating means
【図３】補助磁
場発生手段の選択使用説明図[Figure 3] Diagram for explaining the selection and use of auxiliary magnetic field generation means
【図４】水平磁場発生装置
の適用図[Figure 4] Application diagram of horizontal magnetic field generator
【図５】垂直磁場発生装置の適用図[Figure 5] Application diagram of vertical magnetic field generator
【図６】ＭＲＩ装置の適用図[Figure 6] Application diagram of MRI device
１ 補助磁場発生手段 ２ 主磁場発生器 ３ 磁束 ４ 超電導コイル ５ アーム ６ 被検体 ７ 常電導コイル ９ 受信コイル １０ 磁場発生装置 ２９ ベッド 1. Auxiliary magnetic field generation means 2 Main magnetic field generator 3 Magnetic flux 4 Superconducting coil 5 Arm 6 Subject 7 Normal conduction coil 9 Receiving coil 10 Magnetic field generator 29 Bed
Claims (2)
電導コイルまたは永久磁石によって強く均一な静磁場を
形成する主磁場発生器と、前記被検体にスライス傾斜磁
場、リードアウト傾斜磁場及び位相エンコード傾斜磁場
を印加する傾斜磁場コイルと、前記被検体の組織を構成
する原子の原子核に磁気共鳴を起こさせる高周波パルス
をある所定のパルスシーケンスで繰り返し印加する照射
コイルと、磁気共鳴信号を検出する受信コイルと、前記
検出信号を使って対象物体の物理的性質を表わす画像を
得る画像再構成手段とを備えた磁気共鳴イメージング装
置において、前記主磁場発生器の均一磁場空間内部に局
部的に前記主磁場発生器により形成される均一な静磁場
強度とは異なる均一な静磁場を形成する補助磁場発生手
段を備えたことを特徴とする磁気共鳴イメージング装置
用磁場発生装置。1. A main magnetic field generator that forms a strong and uniform static magnetic field in a space accommodating an object using a superconducting coil, a normal conducting coil, or a permanent magnet; A gradient magnetic field coil that applies an encoding gradient magnetic field, an irradiation coil that repeatedly applies a high-frequency pulse in a certain predetermined pulse sequence to cause magnetic resonance in the nuclei of atoms constituting the tissue of the subject, and detects a magnetic resonance signal. In a magnetic resonance imaging apparatus comprising a receiving coil and an image reconstruction means for obtaining an image representing physical properties of a target object using the detection signal, the 1. A magnetic field generator for a magnetic resonance imaging apparatus, comprising auxiliary magnetic field generating means for generating a uniform static magnetic field different from the uniform static magnetic field intensity formed by the main magnetic field generator.
する補助磁場発生手段を備えた請求項１に記載の磁気共
鳴イメージング装置用磁場発生装置。2. The magnetic field generating device for a magnetic resonance imaging apparatus according to claim 1, further comprising auxiliary magnetic field generating means for arbitrarily variably setting the local uniform static magnetic field strength.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3144083A JPH04343832A (en) | 1991-05-21 | 1991-05-21 | Magnetic field generating device for magnetic resonance imaging device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3144083A JPH04343832A (en) | 1991-05-21 | 1991-05-21 | Magnetic field generating device for magnetic resonance imaging device |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH04343832A true JPH04343832A (en) | 1992-11-30 |
Family
ID=15353855
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP3144083A Pending JPH04343832A (en) | 1991-05-21 | 1991-05-21 | Magnetic field generating device for magnetic resonance imaging device |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH04343832A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2003175012A (en) * | 2002-08-26 | 2003-06-24 | Ge Yokogawa Medical Systems Ltd | Mri system |
-
1991
- 1991-05-21 JP JP3144083A patent/JPH04343832A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2003175012A (en) * | 2002-08-26 | 2003-06-24 | Ge Yokogawa Medical Systems Ltd | Mri system |
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