JPH1147113A - Power supply unit and magnetic resonance imaging using the same - Google Patents
Power supply unit and magnetic resonance imaging using the sameInfo
- Publication number
- JPH1147113A JPH1147113A JP9224484A JP22448497A JPH1147113A JP H1147113 A JPH1147113 A JP H1147113A JP 9224484 A JP9224484 A JP 9224484A JP 22448497 A JP22448497 A JP 22448497A JP H1147113 A JPH1147113 A JP H1147113A
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- current
- power supply
- arbitrary waveform
- magnetic field
- load
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Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は電源装置に係わり、
特に大電力を要求される静磁場，傾斜磁場，高周波磁場
の発生に必要な各種電源に好適な電源装置及びこれを用
いた磁気共鳴イメージング装置（以下、ＭＲＩ装置とい
う）に関する。The present invention relates to a power supply device,
In particular, the present invention relates to a power supply device suitable for various power supplies required for generating a static magnetic field, a gradient magnetic field, and a high-frequency magnetic field requiring high power, and a magnetic resonance imaging apparatus (hereinafter, referred to as an MRI apparatus) using the same.
【０００２】[0002]
【従来の技術】ＭＲＩ装置は、静磁場中に置かれた検査
対象に高周波磁場をパルス状に印加し、検査対象から発
生する核磁気共鳴信号を検出し、この検出信号をもとに
スペクトルや画像を形成するものである。ＭＲＩ装置に
は、磁場発生コイルとして静磁場を発生する超電導コイ
ル，静磁場に重畳される傾斜磁場を発生するための傾斜
磁場コイル、さらに高周波磁場を発生するための高周波
コイルが備えられている。これら磁場発生コイルは所定
の磁場強度の磁場を発生するために印加電流の大きさと
タイミングを制御するための電源装置を備えている。こ
のようなＭＲＩ装置では、静磁場や傾斜磁場や高周波磁
場の磁場強度が最終的に得られる画像上のノイズや撮影
時間に大きく影響する。2. Description of the Related Art An MRI apparatus applies a high-frequency magnetic field in a pulsed manner to a test object placed in a static magnetic field, detects a nuclear magnetic resonance signal generated from the test object, and uses the detected signal to obtain a spectrum or the like. An image is formed. The MRI apparatus includes a superconducting coil for generating a static magnetic field as a magnetic field generating coil, a gradient magnetic field coil for generating a gradient magnetic field superimposed on the static magnetic field, and a high frequency coil for generating a high frequency magnetic field. These magnetic field generating coils include a power supply device for controlling the magnitude and timing of an applied current to generate a magnetic field having a predetermined magnetic field strength. In such an MRI apparatus, the magnetic field strength of a static magnetic field, a gradient magnetic field, or a high-frequency magnetic field greatly affects noise on an finally obtained image and imaging time.
【０００３】また、短時間で診断に有用な画像を得るた
めにＭＲＩ装置の磁場電源として大電流電源が必要にな
ってきている。このための電源装置を本発明者等は、特
開平８−２１１１３９号公報に提案している。この磁場
電源装置の出力電流値は磁場強度に直接影響するので、
最終的に得られるＭＲＩ画像への影響が大きく、このた
め高速応答，高精度の磁場電源装置が要求される。Further, in order to obtain images useful for diagnosis in a short time, a large current power supply is required as a magnetic field power supply of the MRI apparatus. The present inventors have proposed a power supply device for this purpose in Japanese Patent Application Laid-Open No. H8-111139. Since the output current value of this magnetic field power supply directly affects the magnetic field strength,
The influence on the finally obtained MRI image is large, and therefore, a high-speed response and high-precision magnetic field power supply device is required.
【０００４】そこで、磁場コイルに流れる電流（磁場コ
イル電流）を検出し、これが磁場コイル電流の目標値に
一致するように磁場コイル電流をフィードバック制御す
る機構を備えた電源装置が、特開平６−１０５８２３
号，特開平６−１８１９０５号，特開平６−２０９９１
３号，ＵＳＰ５，０１７，８７３，ＵＳＰ５，２７０，
６５７，ＵＳＰ５，０６３，３４９に提案されている。To solve this problem, Japanese Unexamined Patent Publication No. Hei 6 (1996) -1994 discloses a power supply device having a mechanism for detecting a current flowing through a magnetic field coil (magnetic field coil current) and performing feedback control of the magnetic field coil current so as to match the target value of the magnetic field coil current. 105823
JP-A-6-181905, JP-A-6-20991
No. 3, USP 5,017,873, USP 5,270,
657, USP 5,063,349.
【０００５】このような磁場電源装置を用いてＭＲＩ画
像を形成するに必要な磁場を発生するわけであるが、Ｍ
ＲＩ装置は非常に微弱な信号を受信し、その信号をもと
に画像を形成するために、対ノイズを考慮して上記磁場
電源装置はガントリー，受信コイル等が設置されている
検査室の外部に設置し、この検査室をシールドする（こ
れをシールドルームと呼ぶ）。そして、磁場電源装置が
発生するノイズが前記シールドルーム内の受信系に悪影
響を及ぼさないようにするために、磁場電源装置と磁場
コイルとの間にノイズフィルタを設けて、できるだけノ
イズの影響を受けない方法が特開平４−５８９３８号に
提案されている。[0005] A magnetic field necessary for forming an MRI image is generated by using such a magnetic field power supply.
The RI device receives a very weak signal and forms an image based on the signal. In consideration of noise, the above-mentioned magnetic field power supply is installed outside the inspection room where the gantry, the receiving coil, etc. are installed. And shield this inspection room (this is called a shield room). In order to prevent the noise generated by the magnetic field power supply device from affecting the receiving system in the shield room, a noise filter is provided between the magnetic field power supply device and the magnetic field coil, and the noise filter is affected by the noise as much as possible. No such method has been proposed in JP-A-4-58938.
【０００６】[0006]
【発明が解決しようとする課題】上述したように、出力
電流の大電流化，高速応答化，高精度化やノイズの影響
を極力受けない方法により、ＭＲＩ画像の画質向上を図
ってきたが、近年、さらなる撮影時間の短縮や高画質化
等の要求により、出力電流の増大や高速応答，高精度化
が必須である。As described above, the quality of MRI images has been improved by a method of increasing the output current, increasing the response speed, increasing the accuracy, and minimizing the influence of noise. In recent years, an increase in output current, high-speed response, and high accuracy are indispensable due to demands for further shortening of a photographing time and improvement of image quality.
【０００７】このため、これに伴って磁場電源装置から
発生するノイズも大きくなり、従来と同じノイズフィル
タを設ける方法では対応できない。すなわち、大電流化
に伴い増加するノイズを除去するためのノイズ除去比
（信号Ｓ／ノイズＮ）の高いノイズフィルタとこのノイ
ズフィルタの影響を受けない磁場コイル電流の検出及び
制御方法が必要となる。[0007] Accordingly, the noise generated from the magnetic field power supply device increases with this, and it cannot be coped with by the conventional method of providing a noise filter. That is, a noise filter having a high noise elimination ratio (signal S / noise N) for removing noise that increases with an increase in current and a method of detecting and controlling a magnetic field coil current unaffected by the noise filter are required. .
【０００８】一般に、ノイズフィルタは、コンデンサと
リアクトルをπ型に接続したもので構成され、これを磁
場電源装置と負荷であるシールドルーム内に配置された
磁場コイルとの間に接続し、前記コンデンサの一端をア
ースに接地する構成をとっている。In general, a noise filter is composed of a capacitor and a reactor connected in a π-shape, and is connected between a magnetic field power supply device and a magnetic field coil disposed in a shield room as a load. Is connected to the ground at one end.
【０００９】図７は、直流電源１と、任意波形の電流を
生成する任意波形生成手段２（半導体スイッチング素子
で構成、特開平４−５８９３８号を参照）と、コンデン
サとリアクトルで構成されたノイズフィルタ３０（コン
デンサ３０１，３０３，リアクトル３０２），３１（コ
ンデンサ３１１，３１３，リアクトル３１２）とをシー
ルドルーム４０の中に設置されたＭＲＩ装置の磁場コイ
ル５０に接続した例を示す図である。FIG. 7 shows a DC power supply 1, an arbitrary waveform generating means 2 for generating a current of an arbitrary waveform (constituted by a semiconductor switching element, see Japanese Patent Application Laid-Open No. 4-58938), and a noise composed of a capacitor and a reactor. FIG. 3 is a diagram illustrating an example in which filters 30 (capacitors 301 and 303 and a reactor 302) and 31 (capacitors 311 and 313 and a reactor 312) are connected to a magnetic field coil 50 of an MRI apparatus installed in a shield room 40.
【００１０】図７において、出力電流ＩP，ＩNはＡ点，
Ｂ点の電位差により、その大きさと方向が決定される。
このＡ点，Ｂ点はアースに対して電位が浮いており、不
定なのに対して、ノイズフィルタのコンデンサ３０１，
３０３，３１１，３１３の一端はアースに接続されてい
る。このため、Ａ点，Ｂ点からは前記コンデンサ３０
１，３０３，３１１，３１３に向かって周波数の高い交
流電流が流れる。この交流電流の発生はこのように構成
された電源装置ではやむえない現象である。In FIG. 7, output currents IP and IN are at point A,
The magnitude and direction are determined by the potential difference at point B.
The potentials at the points A and B are floating with respect to the ground and are indefinite.
One ends of 303, 311 and 313 are connected to the ground. For this reason, from the point A and the point B, the capacitor 30
High-frequency alternating current flows toward 1,303,311 and 313. The generation of the alternating current is a phenomenon that cannot be unavoidable in the power supply device configured as described above.
【００１１】この交流電流は、前記コンデンサの静電容
量に比例して大きくなるので、これまでは静電容量を小
さくすることで対応してきた。しかし、出力電流の大容
量化に伴い、前記ノイズフィルタの回路定数の見直しが
必須となった。このノイズフィルタのＳ／Ｎを高くする
ためには、前記コンデンサの静電容量とリアクトルのイ
ンダクタンスの値を適当に選定する必要があるが、特に
コンデンサの静電容量を大きくすれば効果的となること
が知られている。Since this alternating current increases in proportion to the capacitance of the capacitor, it has been conventionally handled by reducing the capacitance. However, with the increase in output current capacity, it has become necessary to review the circuit constants of the noise filter. In order to increase the S / N of the noise filter, it is necessary to appropriately select the capacitance of the capacitor and the inductance of the reactor. In particular, it is effective to increase the capacitance of the capacitor. It is known.
【００１２】しかし、これでは前記コンデンサに流れる
交流電流が増加してしまい、この電流成分が任意波形生
成手段２の出力電流ＩP，ＩNに重畳して、この出力電流
ＩP，ＩNの同相雑音（以下、コモンモードノイズ電流と
いう）が増加する。However, in this case, the AC current flowing through the capacitor increases, and this current component is superimposed on the output currents IP and IN of the arbitrary waveform generating means 2, and the common-mode noise of the output currents IP and IN (hereinafter referred to as "in-phase noise"). , Common mode noise current).
【００１３】そこで、前記任意波形生成手段２とノイズ
フィルタ３０，３１の間に電流検出器を入れて磁場コイ
ル電流を検出すると、この磁場コイル電流と共に前記コ
モンモードノイズ電流も検出してしまい、これをフィー
ドバックして磁場コイル電流を制御すると、この磁場コ
イル電流が変動し、これによって発生する磁場の強度が
不均一となる。Therefore, when a current detector is inserted between the arbitrary waveform generating means 2 and the noise filters 30 and 31 to detect the magnetic field coil current, the common mode noise current is detected together with the magnetic field coil current. Is fed back to control the magnetic field coil current, the magnetic field coil current fluctuates, and the intensity of the generated magnetic field becomes uneven.
【００１４】図８は磁場コイル電流と発生磁場の関係を
示す図である。磁場コイル電流にゆらぎが含まれない理
想的な場合には、磁場コイル電流と発生磁場の関係は
（１）のようになる。磁場コイル電流にゆらぎが含まれ
ると、この磁場コイル電流に含まれる前記コモンモード
ノイズ電流の振幅と周波数により、（２）のようにゲイ
ンが変わったり、（３）のように△Ｈのオフセット分が
重畳したりする。FIG. 8 shows the relationship between the magnetic field coil current and the generated magnetic field. In an ideal case where the fluctuations are not included in the magnetic field coil current, the relationship between the magnetic field coil current and the generated magnetic field is as shown in (1). If the magnetic field coil current includes fluctuations, the gain changes as shown in (2) or the ΔH offset as shown in (3) depending on the amplitude and frequency of the common mode noise current included in the magnetic field coil current. May be superimposed.
【００１５】これらは、最終的にはＭＲＩ画像のボケや
アーチファクト（被検体の実像の周辺にできる虚像）と
して現れ、画質を低下させる。対応策として電流検出手
段を前記ノイズフィルタの出力側、すなわちシールドル
ーム内の磁場コイルの近傍に設ける方法が考えれるが、
シールドルームの外に設置されている磁場コイイル電流
の制御装置と前記電流検出手段との距離が長くなり、こ
の間にノイズが混入するので、やはりノイズフィルタが
必要となって、上記と同様のコモンモードノイズを含ん
だ電流を検出することになる。These eventually appear as blurring or artifacts (virtual images formed around the real image of the subject) of the MRI image, deteriorating the image quality. As a countermeasure, a method is conceivable in which current detection means is provided on the output side of the noise filter, that is, in the vicinity of a magnetic field coil in a shield room.
The distance between the magnetic field coil current control device installed outside the shield room and the current detecting means becomes longer, and noise is mixed in the distance. Therefore, a noise filter is required, and the same common mode as described above is used. A current containing noise will be detected.
【００１６】そこで、本発明の目的は、シールドルーム
の入り口にノイズフィルタが設けられていても、電源装
置の出力電流である磁場コイル電流検出手段が雑音を検
出しないようにして、高精度の電源装置及びこの電源装
置を用いた高画質のＭＲＩ画像が得られる磁気共鳴イメ
ージング装置を提供することにある。Therefore, an object of the present invention is to provide a high-precision power supply by preventing magnetic field coil current detection means, which is the output current of a power supply device, from detecting noise even if a noise filter is provided at the entrance of a shield room. An object of the present invention is to provide an apparatus and a magnetic resonance imaging apparatus capable of obtaining a high-quality MRI image using the power supply apparatus.
【００１７】[0017]
【課題を解決するための手段】上記目的は、任意波形の
電流若しくは電圧を生成する任意波形生成手段の出力を
負荷に供給し、この負荷に流れる電流（負荷電流）を電
流検出手段で検出し、この電流検出手段で検出した電流
値を前記負荷電流の目標値と一致するように前記負荷電
流を制御する制御手段を備えた電源装置において、前記
任意波形生成手段と負荷との間にノイズフィルタを、前
記任意波形生成手段とノイズフィルタとの間に前記電流
検出手段を介設し、前記ノイズフィルタを介して前記電
源装置のアースに流入、流出する電流を打ち消す向きに
前記任意波形生成手段の出力電流を前記電流検出手段に
入力し、前記任意波形生成手段の出力電流の前記電流検
出手段への入力方向は、前記任意波形生成手段から出て
いく電流とこの任意波形生成手段に入ってくる電流と同
じ方向とすることによって達成される。（請求項１，請
求項２）An object of the present invention is to supply an output of an arbitrary waveform generating means for generating a current or voltage of an arbitrary waveform to a load, and to detect a current (load current) flowing through the load by a current detecting means. A power supply device having control means for controlling the load current so that the current value detected by the current detection means matches the target value of the load current, wherein a noise filter is provided between the arbitrary waveform generation means and the load. The current detection means is interposed between the arbitrary waveform generating means and the noise filter, and the arbitrary waveform generating means is arranged in such a direction as to cancel the current flowing into and out of the ground of the power supply device through the noise filter. The output current is input to the current detection means, and the input direction of the output current of the arbitrary waveform generation means to the current detection means depends on the current flowing out of the arbitrary waveform generation means and the current direction. It is accomplished by the same direction as the current entering the waveform generating means. (Claim 1, Claim 2)
【００１８】このように構成することによって、ノイズ
フィルタ内のコンデンサを介してアースに流入、流出す
る電流によって発生するコモンモードノイズ電流成分
を、上記電流検出方法により除去できるので、従来のよ
うなコモンモードノイズ電流が混入した検出電流値でフ
ィードバックされた結果、出力電流にゆらぎを生じると
いうことがなくなり、この電流が供給される負荷を好適
に制御できるという効果がある。With this configuration, the common mode noise current component generated by the current flowing into and out of the ground via the capacitor in the noise filter can be removed by the above-described current detection method. As a result of feeding back with the detected current value in which the mode noise current is mixed, the output current does not fluctuate, and the load to which this current is supplied can be suitably controlled.
【００１９】また、本発明は、上記電流検出手段に一組
のホール素子やカレントトランス等の非接触電流検出器
を用い、この非接触電流検出器に上記任意波形生成手段
から出ていく電流とこの任意波形生成手段に入ってくる
電流との方向が同じになるように入力するものである。
（請求項３） この構成では、電流検出手段として非接触電流検出器が
一組で良いので回路構成の簡単化や調整の簡単化に効果
がある。Further, according to the present invention, a non-contact current detector such as a set of Hall elements or a current transformer is used as the current detecting means, and the current flowing out of the arbitrary waveform generating means is used for the non-contact current detector. The input is made so that the direction of the current entering the arbitrary waveform generating means is the same as that of the current.
(Claim 3) In this configuration, a single non-contact current detector may be used as the current detection means, which is effective in simplifying the circuit configuration and the adjustment.
【００２０】さらに、本発明の上記電流検出手段は、こ
の電流検出手段の電流検出部に二組のホール素子やカレ
ントトランス等の非接触電流検出器を用い、これらの二
組の非接触電流検出器のうちの一方の非接触電流検出器
には前記任意波形生成手段から出ていく電流を入力し、
もう一方の非接触電流検出器には前記任意波形生成手段
に入ってくる電流を前記一方の非接触電流検出器に入力
する方向と同じ向きに入力し、これらの電流検出器の出
力を加算する演算手段から成る。（請求項４）Further, the current detecting means of the present invention uses two sets of non-contact current detectors, such as a Hall element and a current transformer, in the current detecting section of the current detecting means. The current coming out of the arbitrary waveform generating means is input to one of the non-contact current detectors of the detector,
To the other non-contact current detector, the current entering the arbitrary waveform generating means is input in the same direction as the input direction to the one non-contact current detector, and the outputs of these current detectors are added. It consists of arithmetic means. (Claim 4)
【００２１】この構成では、二組の非接触電流検出器を
必要とするが、上記一組の非接触電流検出器を用いる場
合にくらべて非接触電流検出器の電流定格が１／２です
むので、一組の電流検出器が小型となり電源装置への実
装がしやすくなる。In this configuration, two sets of non-contact current detectors are required, but the current rating of the non-contact current detector is halved as compared with the case of using the above-mentioned one set of non-contact current detectors. Therefore, the set of current detectors is small and easy to mount on a power supply device.
【００２２】さらに、本発明の上記電流検出手段は、こ
の電流検出手段に二組の抵抗器を用い、これらの二組の
抵抗器のうちの一方の抵抗器で前記任意波形生成手段か
ら出ていく電流による電圧降下を検出し、この電圧降下
と同じ極性となるようにもう一方の抵抗器で前記任意波
形生成手段に入ってくる電流による電圧降下を検出し、
これらの抵抗器に生じる電圧降下を加算する演算手段か
ら成る。（請求項５）Further, the current detecting means of the present invention uses two sets of resistors for the current detecting means, and one of the two sets of resistors is used to output from the arbitrary waveform generating means. The voltage drop due to the current flowing is detected, and the voltage drop due to the current entering the arbitrary waveform generating means is detected by the other resistor so as to have the same polarity as the voltage drop,
It consists of arithmetic means for adding the voltage drops occurring in these resistors. (Claim 5)
【００２３】この構成では、電流検出器に抵抗器を用い
ているため、高価な絶縁電流検出器を必要とせず、装置
の低コスト化に有利となる。さらに、本発明は、上記負
荷に磁場コイルを用い、この磁場コイル用の電源装置と
して、上記の電源装置を備えたものである。（請求項
６）In this configuration, since a resistor is used for the current detector, an expensive insulation current detector is not required, which is advantageous in reducing the cost of the device. Further, the present invention uses a magnetic field coil as the load, and includes the above-described power supply device as a power supply device for the magnetic field coil. (Claim 6)
【００２４】上記電源装置を磁気共鳴イメージング装置
の磁場コイル用電源とすることによって、上記任意波形
生成手段と磁場コイルとの間にノイズフィルタを設けて
も、検出された磁場コイル電流に前記ノイズフィルタに
よって生じるコモンモードノイズ電流を含まないように
することができる。したがって、磁場コイル電流を正確
に検出することができ、これをフィードバックして磁場
コイル電流の目標値に一致するように制御できるので、
従来のように、磁場コイル電流にゆらぎを生じて、発生
する磁場強度が変動するということがなくなる。これに
よって、ＭＲＩ画像の画質を改善することができ、より
安価で信頼性が高く、今後普及すると思われるＥＰＩ
（Echo Planner Imaging）などの高速シーケンスに対応
可能とすることができる。By using the power supply device as a power supply for the magnetic field coil of the magnetic resonance imaging apparatus, even if a noise filter is provided between the arbitrary waveform generating means and the magnetic field coil, the noise filter current is applied to the detected magnetic field coil current. It is possible not to include a common mode noise current caused by the above. Therefore, it is possible to accurately detect the magnetic field coil current and feed it back to control so as to match the target value of the magnetic field coil current.
As in the related art, the fluctuation of the magnetic field coil current does not cause the generated magnetic field intensity to fluctuate. This can improve the quality of MRI images, is cheaper, more reliable, and is expected to spread in the future.
(Echo Planner Imaging).
【００２５】さらに、本発明は、上記磁気共鳴イメージ
ング装置の磁場コイル，受信系等をシールドルームに設
置し、このシールドルームへの電源入力部近傍に上記ノ
イズフィルタを設けたものである。（請求項７）Further, according to the present invention, a magnetic field coil, a receiving system, and the like of the magnetic resonance imaging apparatus are installed in a shield room, and the noise filter is provided near a power input portion to the shield room. (Claim 7)
【００２６】このように構成することによって、上記電
源装置の任意波形生成手段等で発生する電磁波ノイズを
上記受信系で受信しないようにすることができるので、
ＭＲＩ画像の画質に悪影響を及ぼさないようにすること
ができる。With this configuration, it is possible to prevent electromagnetic wave noise generated by the arbitrary waveform generating means of the power supply device from being received by the receiving system.
The image quality of the MRI image can be prevented from being adversely affected.
【００２７】[0027]
【発明の実施の形態】以下、本発明の電源装置及びこれ
をＭＲＩ装置の傾斜磁場コイルに適用した実施例につい
て説明する。図１は任意波形生成手段の出力側にコモン
モードノイズ電流を低減できる電流検出手段を設けた電
源装置の第一の実施形態による回路構成図である。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a power supply device according to the present invention and an embodiment in which the power supply device is applied to a gradient coil of an MRI apparatus will be described. FIG. 1 is a circuit diagram of a first embodiment of a power supply device provided with a current detection unit capable of reducing a common mode noise current on the output side of an arbitrary waveform generation unit.
【００２８】直流電源１は任意波形生成手段２に直流電
圧を供給し、この任意波形生成手段２は電力用半導体ス
イッチング素子で構成された電力変換器で、任意波形の
電流を出力する。The DC power supply 1 supplies a DC voltage to the arbitrary waveform generating means 2, and the arbitrary waveform generating means 2 is a power converter composed of a power semiconductor switching element and outputs a current having an arbitrary waveform.
【００２９】任意波形生成手段２には、コモンモードノ
イズ電流を低減できる電流検出手段１０が接続され、こ
の電流検出手段１０にて検出された検出値Ｉdetは制御
回路２０に入力される。制御回路２０には目標電流値Ｉ
refが入力され、これと前記検出値Ｉdetが一致するよう
にフィードバック制御を行う。前記電流検出手段１０の
出力にはノイズフィルタ３０，３１を介して負荷である
傾斜磁場コイルが接続されている。ＭＲＩ装置はその受
信系に前記電源装置の任意波形生成手段２からのスイッ
チングノイズ等の混入を防ぐために受信系や磁場コイル
等をシールドルームの中にいれ、前記電源装置をこのシ
ールドルームの外部に設置し、このシールドルームの電
源入力部近傍に前記ノイズフィルタを接続する構成をと
るものである。The arbitrary waveform generating means 2 is connected to a current detecting means 10 capable of reducing a common mode noise current, and a detection value Idet detected by the current detecting means 10 is inputted to a control circuit 20. The control circuit 20 has the target current value I
ref is input, and feedback control is performed so that the ref matches the detected value Idet. A gradient magnetic field coil as a load is connected to the output of the current detecting means 10 via noise filters 30 and 31. The MRI apparatus includes a receiving system, a magnetic field coil, and the like in a shield room in order to prevent switching noise and the like from the arbitrary waveform generating means 2 of the power supply device into the reception system, and places the power supply device outside the shield room. The noise filter is installed near the power input section of the shield room.
【００３０】図２は、ノイズフィルタ３０，３１の構造
と流れる電流を示している。ノイズフィルタ３０，３１
は、コンデンサとリアクトル（ノイズフィルタ３０側の
コンデンサ３０１，３０３とリアクトル３０２、ノイズ
フィルタ３１側のコンデンサ３１１，３１３とリアクト
ル３１２）がπ型に接続されたもので、コンデンサ３０
１，３０３，コンデンサ３１１，３１３はアースに接地
されている。ここで、任意波形生成手段２からの往路に
流れる電流をＩP，復路に流れる電流をＩN，ノイズフィ
ルタ３０，３１のコンデンサ３０１，３１１に流れる電
流をＩC1，コンデンサ３０２，３１２に流れる電流をＩ
C2，傾斜磁場コイル５０に流れる電流をＩとすると、こ
れらの間には以下の関係式が成り立つ。 ＩP−ＩC1−ＩC2＝Ｉ （１） Ｉ−ＩC1−ＩC2＝ＩN （２） （１）より ＩP＝Ｉ＋ＩC1＋ＩC2 （３）FIG. 2 shows the structure of the noise filters 30 and 31 and the current flowing therethrough. Noise filters 30, 31
Is a capacitor and a reactor (the capacitors 301 and 303 and the reactor 302 on the noise filter 30 side and the capacitors 311 and 313 and the reactor 312 on the noise filter 31 side) are connected in a π-type.
1, 303 and capacitors 311 and 313 are grounded. Here, the current flowing in the forward path from the arbitrary waveform generating means 2 is represented by IP, the current flowing in the backward path is represented by IN, the current flowing through the capacitors 301 and 311 of the noise filters 30 and 31 is represented by IC 1 , and the current flowing through the capacitors 302 and 312 is represented by I P.
Assuming that I is the current flowing through C 2 and the gradient magnetic field coil 50, the following relational expression holds between them. IP-IC 1 -IC 2 = I (1) I-IC 1 -IC 2 = IN (2) (1) from IP = I + IC 1 + IC 2 (3)
【００３１】図３は電流検出手段１０の構造で、電流検
出器１１にはカレントトランス，ホール素子等の非接触
電流検出器を用い、これに被検出電流が流れる導体を貫
通して非接触で検出するものである。図３に示すよう
に、任意波形生成手段２の出力電流を磁場コイル５０に
供給する電気導体の往路と、折り返した復路の電気導体
をそれぞれ電流が同一方向に流れるように電流検出器１
１に貫通することで、以下の関係式が示すようにノイズ
フィルタ３０，３１に流れる電流ＩC1，ＩC2を打ち消す
ことができ、電流検出器１１は図４に示すよう磁場コイ
ルに流れる電流Ｉの２倍の電流値を検出することにな
る。 ＩP＋ＩN＝（Ｉ＋ＩC1＋ＩC2）＋（Ｉ−ＩC1−ＩC2）＝２Ｉ （４）FIG. 3 shows the structure of the current detecting means 10. A non-contact current detector such as a current transformer or a Hall element is used as the current detector 11, and the current flows through the conductor through which the current to be detected flows. It is to detect. As shown in FIG. 3, the current detector 1 supplies the output current of the arbitrary waveform generator 2 to the magnetic field coil 50 so that the current flows in the same direction in the forward direction of the electric conductor and in the folded electric conductor in the return direction.
1, the currents IC 1 and IC 2 flowing through the noise filters 30 and 31 can be canceled as shown by the following relational expression, and the current detector 11 outputs the current I C flowing through the magnetic field coil as shown in FIG. Will be detected. IP + IN = (I + IC 1 + IC 2) + (I-IC 1 -IC 2) = 2I (4)
【００３２】上記（４）で得られた電流検出器１１の出
力を増幅器１２に入力し、公知の演算手法を用いて前記
増幅器１２で前記電流検出器１１の出力を１／２にして
検出電流値Ｉdetを出力する。このように構成された電
流検出手段１０を備えることで、ノイズフィルタがある
場合でも検出電流値に含まれるコモンモードノイズ電流
を除去することができ、高精度に磁場コイル電流を検出
することができる。したがって、これによって制御され
る磁場コイル電流と発生磁場強度の関係は、図８の
（１）のようになり、従来の電流検出方法で生じていた
図８の（２）に示すゲイン変動や（３）に示すオフセッ
ト△Ｈのない特性となり、これを用いて形成されるＭＲ
Ｉ画像は、ボケやアーチファクト（被検体の実像の周辺
にできる虚像）のない高画質のＭＲＩ画像とすることが
できる。The output of the current detector 11 obtained in the above (4) is input to the amplifier 12, and the output of the current detector 11 is halved by the amplifier 12 using a known calculation method. Output the value Idet. With the provision of the current detecting means 10 configured as described above, the common mode noise current included in the detected current value can be removed even when there is a noise filter, and the magnetic field coil current can be detected with high accuracy. . Therefore, the relationship between the magnetic field coil current and the generated magnetic field intensity controlled by this is as shown in FIG. 8A, and the gain fluctuation shown in FIG. The characteristic shown in 3) has no offset ΔH, and the MR formed by using the characteristic is obtained.
The I image can be a high quality MRI image without blur or artifact (virtual image formed around the real image of the subject).
【００３３】図５に本発明の第２の実施形態による電流
検出手段１３の構造図を示す。電流検出器１４と１５の
２個の電流検出器を用い、電流検出器１４で検出した電
流値ＩPと、電流検出器１５で電流値ＩPとは逆向きに検
出した電流値ＩNを、加算器１６に入力するものであ
る。FIG. 5 shows a structural diagram of the current detecting means 13 according to the second embodiment of the present invention. Using two current detectors, current detectors 14 and 15, the current value IP detected by the current detector 14 and the current value IN detected by the current detector 15 in a direction opposite to the current value IP are added. 16 is input.
【００３４】加算器１６に入力した復路の検出電流値Ｉ
Nは、増幅率１の反転増幅器６０にて反転して、反転増
幅器６１に入力する。この反転増幅器６１に往路の検出
電流値ＩPも入力し、ＩPとＩNの両者を加算することに
よりコモンモードノイズ電流成分が打ち消される。前記
反転増幅器６１はその増幅率を１／２とすることによ
り、反転増幅器６１の出力は磁場コイル電流Ｉと等しい
値となる。The detected return current value I input to the adder 16
N is inverted by an inverting amplifier 60 having an amplification factor of 1 and input to an inverting amplifier 61. The forward path detection current value IP is also input to the inverting amplifier 61, and the addition of both IP and IN cancels the common mode noise current component. By setting the amplification factor of the inverting amplifier 61 to コ イ ル, the output of the inverting amplifier 61 has a value equal to the magnetic field coil current I.
【００３５】このように構成することで、第１の実施例
と同様にして高画質のＭＲＩ画像を得ることができる。
図５の第２の本実施形態に用いた電流検出器１４，１５
は図３の第１の実施形態に用いた電流検出器１１にくら
べて電流定格が１／２ですむので、電流検出器が小型と
なり電源装置への実装がしやすくなる。With this configuration, a high-quality MRI image can be obtained in the same manner as in the first embodiment.
The current detectors 14, 15 used in the second embodiment of FIG.
Since the current rating of the current detector is half that of the current detector 11 used in the first embodiment shown in FIG. 3, the current detector is small in size and can be easily mounted on a power supply device.
【００３６】図６は、第３の実施形態で、電流検出器に
抵抗器７０，７１を用いた例である。抵抗器７０，７１
の両端の電圧を検出して等価的に磁場コイル電流Ｉを検
出するもので、抵抗器７０で検出した電圧ＶPと、抵抗
器７１で検出した電圧ＶNを加算器２１に入力する。こ
の加算器２１に入力した検出電圧ＶP，ＶNは絶縁増幅器
６２，６３で絶縁し、この出力を反転増幅器６０，６１
にて増幅，加算して、第２の実施形態と同様にして検出
電流値Ｉdetを出力する。このように構成することによ
って、第１，第２の実施形態と同様にして高画質のＭＲ
Ｉ画像を得ることができる。また、第３の実施形態で
は、電流検出器に抵抗器を用いているため、高価な絶縁
電流検出器を必要とせず、装置の低コスト化に有利とな
る。FIG. 6 shows a third embodiment in which resistors 70 and 71 are used as current detectors. Resistors 70 and 71
The voltage VP detected by the resistor 70 and the voltage VN detected by the resistor 71 are input to the adder 21. The detection voltages VP and VN input to the adder 21 are insulated by isolation amplifiers 62 and 63, and the outputs are inverted by inverting amplifiers 60 and 61.
, And outputs the detected current value Idet in the same manner as in the second embodiment. With this configuration, a high-quality MR can be obtained in the same manner as in the first and second embodiments.
An I image can be obtained. Further, in the third embodiment, since a resistor is used as the current detector, an expensive insulation current detector is not required, which is advantageous for reducing the cost of the device.
【００３７】なお、第２，第３の実施形態では、加算器
１６，２１の反転増幅器等はアナログ回路で構成した
が、これに限定するものではなく、デジタル回路やマイ
クロコンピュータ等を用いて構成することも可能であ
る。In the second and third embodiments, the inverting amplifiers and the like of the adders 16 and 21 are constituted by analog circuits. However, the present invention is not limited to this, and is constituted by using digital circuits and microcomputers. It is also possible.
【００３８】[0038]
【発明の効果】以上で説明したように本発明によれば、
シールドルームの電源入力部近傍にノイズフィルタが設
けられていても、出力電流検出手段が雑音を検出しない
ようにして、高画質のＭＲＩ画像が得られる電源装置及
び、これを用いた磁気共鳴イメージング装置を提供する
ことができる。According to the present invention as described above,
Power supply device capable of obtaining high-quality MRI images by preventing output current detection means from detecting noise even if a noise filter is provided in the vicinity of a power supply input portion of a shield room, and magnetic resonance imaging apparatus using the same Can be provided.
【図１】本発明の第１の実施形態の電流検出手段を用い
た電源装置及びこれをＭＲＩ装置の傾斜磁場コイルに電
流を供給する全体回路構成図。FIG. 1 is a diagram illustrating a power supply device using a current detection unit according to a first embodiment of the present invention and an overall circuit configuration for supplying a current to a gradient coil of an MRI apparatus.
【図２】ノイズフィルタと電流を示す図。FIG. 2 is a diagram showing a noise filter and a current.
【図３】本発明の第１の実施形態による電流検出手段の
構造図。FIG. 3 is a structural diagram of a current detection unit according to the first embodiment of the present invention.
【図４】図３の電流検出手段の検出電流値を示す図。FIG. 4 is a view showing a detected current value of the current detecting means of FIG. 3;
【図５】本発明の第２の実施形態の電流検出手段の構造
図。FIG. 5 is a structural diagram of a current detecting unit according to a second embodiment of the present invention.
【図６】本発明の第３の実施形態の電流検出手段の構造
図。FIG. 6 is a structural diagram of a current detecting unit according to a third embodiment of the present invention.
【図７】コモンモードノイズ電流の発生メカニズムを示
す図。FIG. 7 is a diagram showing a generation mechanism of a common mode noise current.
【図８】磁場コイル電流と発生磁場強度の関係を示す
図。FIG. 8 is a diagram showing a relationship between a magnetic field coil current and a generated magnetic field intensity.
１ 直流電源 ２ 任意波形生成手段 １０，１３，２０ 電流検出手段 １１，１４，１５ 非接触電流検出器 １２ 増幅器 １６，２１ 加算器 ２０ 制御回路 ３０，３１ ノイズフィルタ ４０ シールドルーム ５０ 磁場コイル ７０，７１ 電流検出用抵抗 Reference Signs List 1 DC power supply 2 Arbitrary waveform generating means 10, 13, 20 Current detecting means 11, 14, 15 Non-contact current detector 12 Amplifier 16, 21 Adder 20 Control circuit 30, 31 Noise filter 40 Shield room 50 Magnetic field coil 70, 71 Current detection resistor
───────────────────────────────────────────────────── フロントページの続き (72)発明者 竹内 博幸 東京都千代田区内神田一丁目１番14号 株 式会社日立メディコ内 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroyuki Takeuchi 1-1-1 Uchikanda, Chiyoda-ku, Tokyo Inside Hitachi Medical Corporation
Claims (7)
任意波形生成手段の出力を負荷に供給し、この負荷に流
れる電流（負荷電流）を電流検出手段で検出し、この電
流検出手段で検出した電流値を前記負荷電流の目標値と
一致するように前記負荷電流を制御する制御手段を備え
た電源装置において、前記任意波形生成手段と負荷との
間にノイズフィルタを、前記任意波形生成手段とノイズ
フィルタとの間に前記電流検出手段を介設し、前記ノイ
ズフィルタを介して前記電源装置のアースに流入、流出
する電流を打ち消す向きに前記任意波形生成手段の出力
電流を前記電流検出手段に入力することを特徴とする電
源装置。An output of an arbitrary waveform generating means for generating a current or a voltage of an arbitrary waveform is supplied to a load, and a current (load current) flowing through the load is detected by a current detecting means, and the current is detected by the current detecting means. In a power supply device including a control unit that controls the load current so that a current value matches a target value of the load current, a noise filter is provided between the arbitrary waveform generation unit and a load, and the arbitrary waveform generation unit includes: The current detection means is interposed between the power supply device and the noise filter, and the output current of the arbitrary waveform generation means is supplied to the current detection means in a direction to cancel the current flowing into and out of the ground of the power supply device through the noise filter. A power supply characterized by inputting.
電流検出手段への入力方向は、前記任意波形生成手段か
ら出ていく電流とこの任意波形生成手段に入ってくる電
流との方向が同じであることを特徴とする請求項１に記
載の電源装置。2. An input direction of an output current of the arbitrary waveform generating means to the current detecting means is such that a direction of a current flowing out of the arbitrary waveform generating means and a direction of a current entering the arbitrary waveform generating means are the same. The power supply device according to claim 1, wherein
カレントトランス等の非接触電流検出器を用い、この非
接触電流検出器に前記任意波形生成手段から出ていく電
流とこの任意波形生成手段に入ってくる電流との方向が
同じになるように入力することを特徴とするとする請求
項２に記載の電源装置。3. A non-contact current detector, such as a set of Hall elements or a current transformer, is used as the current detecting means, and the current flowing from the arbitrary waveform generating means and the arbitrary waveform generating means are used in the non-contact current detector. 3. The power supply device according to claim 2, wherein the input is performed such that the direction of the current flowing into the means is the same as that of the current.
の電流検出部に二組のホール素子やカレントトランス等
の非接触電流検出器を用い、これらの二組の非接触電流
検出器のうちの一方の非接触電流検出器には前記任意波
形生成手段から出ていく電流を入力し、もう一方の非接
触電流検出器には前記任意波形生成手段に入ってくる電
流を前記一方の非接触電流検出器に入力する方向と同じ
向きに入力し、これらの電流検出器の出力を加算する演
算手段から成ることを特徴とする請求項２に記載の電源
装置。4. The current detection means uses two sets of non-contact current detectors, such as a Hall element and a current transformer, in a current detection section of the current detection means. The current coming out of the arbitrary waveform generating means is input to one non-contact current detector, and the current entering the arbitrary waveform generating means is inputted to the other non-contact current detector to the one non-contact current detector. 3. The power supply device according to claim 2, further comprising arithmetic means for inputting in the same direction as the direction of input to the current detector, and adding outputs of these current detectors.
に二組の抵抗器を用い、これらの二組の抵抗器のうちの
一方の抵抗器で前記任意波形生成手段から出ていく電流
による電圧降下を検出し、この電圧降下と同じ極性とな
るようにもう一方の抵抗器で前記任意波形生成手段に入
ってくる電流による電圧降下を検出し、これらの抵抗器
に生じる電圧降下を加算する演算手段から成ることを特
徴とする請求項２に記載の電源装置。5. The current detecting means uses two sets of resistors for the current detecting means, and outputs one of the two sets of resistors by a current flowing out of the arbitrary waveform generating means. A voltage drop is detected, a voltage drop due to a current flowing into the arbitrary waveform generating means is detected by the other resistor so as to have the same polarity as the voltage drop, and the voltage drops generated in these resistors are added. 3. The power supply device according to claim 2, comprising an arithmetic unit.
コイル用の電源装置として、請求項１乃至５に記載の電
源装置を備えたことを特徴とする磁気共鳴イメージング
装置。6. A magnetic resonance imaging apparatus, wherein a magnetic field coil is used for the load, and the power supply apparatus according to claim 1 is provided as a power supply apparatus for the magnetic field coil.
磁気共鳴イメージング装置の磁場コイル，受信系等をシ
ールドルームに設置し、このシールドルームへの電源入
力部近傍に前記ノイズフィルタを設けたことを特徴とす
る請求項６に記載の磁気共鳴イメージング装置。7. The magnetic resonance imaging apparatus according to claim 1, wherein a magnetic field coil, a receiving system, and the like of the magnetic resonance imaging apparatus are installed in a shielded room, and the noise filter is provided near a power input portion to the shielded room. The magnetic resonance imaging apparatus according to claim 6, wherein
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP22448497A JP4052696B2 (en) | 1997-08-07 | 1997-08-07 | Power supply apparatus and magnetic resonance imaging apparatus using the same |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP22448497A JP4052696B2 (en) | 1997-08-07 | 1997-08-07 | Power supply apparatus and magnetic resonance imaging apparatus using the same |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH1147113A true JPH1147113A (en) | 1999-02-23 |
| JP4052696B2 JP4052696B2 (en) | 2008-02-27 |
Family
ID=16814526
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP22448497A Expired - Fee Related JP4052696B2 (en) | 1997-08-07 | 1997-08-07 | Power supply apparatus and magnetic resonance imaging apparatus using the same |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP4052696B2 (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2008043042A (en) * | 2006-08-04 | 2008-02-21 | Sansha Electric Mfg Co Ltd | Power supply unit |
| KR101143852B1 (en) | 2009-09-23 | 2012-05-22 | 신경민 | RF generator frequency common-mode noise filter treatment |
| WO2023013235A1 (en) * | 2021-08-03 | 2023-02-09 | スミダコーポレーション株式会社 | Measurement apparatus and measurement method |
-
1997
- 1997-08-07 JP JP22448497A patent/JP4052696B2/en not_active Expired - Fee Related
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2008043042A (en) * | 2006-08-04 | 2008-02-21 | Sansha Electric Mfg Co Ltd | Power supply unit |
| KR101143852B1 (en) | 2009-09-23 | 2012-05-22 | 신경민 | RF generator frequency common-mode noise filter treatment |
| WO2023013235A1 (en) * | 2021-08-03 | 2023-02-09 | スミダコーポレーション株式会社 | Measurement apparatus and measurement method |
Also Published As
| Publication number | Publication date |
|---|---|
| JP4052696B2 (en) | 2008-02-27 |
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