JPH0475009B2 - - Google Patents
Info
- Publication number
- JPH0475009B2 JPH0475009B2 JP61162243A JP16224386A JPH0475009B2 JP H0475009 B2 JPH0475009 B2 JP H0475009B2 JP 61162243 A JP61162243 A JP 61162243A JP 16224386 A JP16224386 A JP 16224386A JP H0475009 B2 JPH0475009 B2 JP H0475009B2
- Authority
- JP
- Japan
- Prior art keywords
- gradient coil
- circuit
- waveform
- trapezoidal waveform
- gradient
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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- Magnetic Resonance Imaging Apparatus (AREA)
Description
【発明の詳細な説明】
〔産業上の利用分野〕
本発明は、イメージ装置の勾配コイルに矩形電
圧を印加して勾配磁場を発生させるイメージ装置
の勾配コイル励磁回路に関する。DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a gradient coil excitation circuit for an imaging device that applies a rectangular voltage to a gradient coil of the imaging device to generate a gradient magnetic field.
第３図はイメージ装置の勾配コイルの回路を示
す図、第４図は勾配コイルに印加する電圧波形を
示す図、第５図は勾配コイルの負荷電圧波形を示
す図である。
FIG. 3 is a diagram showing the circuit of the gradient coil of the image device, FIG. 4 is a diagram showing the voltage waveform applied to the gradient coil, and FIG. 5 is a diagram showing the load voltage waveform of the gradient coil.
NMR−CT（核磁気共鳴コンピユータ断層撮影
装置）やESR−CT（電子スピン共鳴コンピユー
タ断層撮影装置）等のイメージ装置の勾配コイル
励磁回路は、第３図に示すような等価回路で表す
ことができる。従来、かかるイメージ装置の勾配
磁場を発生させるには、勾配コイルＬに勾配電源
Vsから第４図に示すような矩形電圧波形を印加
している。理想的には、この矩形電圧波形の印加
によつて勾配磁場が得られる。 The gradient coil excitation circuit of an imaging device such as NMR-CT (Nuclear Magnetic Resonance Computerized Tomography) or ESR-CT (Electron Spin Resonance Computerized Tomography) can be represented by an equivalent circuit as shown in Figure 3. . Conventionally, in order to generate a gradient magnetic field in such an imaging device, a gradient power source is connected to a gradient coil L.
A rectangular voltage waveform as shown in FIG. 4 is applied from Vs. Ideally, a gradient magnetic field is obtained by applying this rectangular voltage waveform.
しかしながら、実際には第３図に示す勾配コイ
ルの等価回路に第４図に示すような矩形電圧波形
を印加すると、第５図に示すような負荷電圧波形
が測定される。このため勾配コイルＬの両端に
は、入力電圧の10倍ないし数百倍のインダクデイ
ブキツクと呼ばれる高電圧が発生する。このイン
ダクデイブキツクは、ノイズ発生源となりCT画
像の画質に悪い影響を与え、また、電源のトラブ
ルの原因になる。勾配コイルから発生する誘導起
電圧をコイルセンサーにてピツクアツプして積分
器で積分した電圧波形をオシロスコープにて観測
すると、第５図に示すようにインダクデイブキツ
クとリンギングが発生してコイルの両端は時間的
に約20ｍsecぐらい不安定な状態になつているこ
とが判る。この不安定な状態における異常電圧に
よりトランジスタ等の半導体素子その他の回路素
子を破壊に至らしめる場合も多い。
However, in reality, when a rectangular voltage waveform as shown in FIG. 4 is applied to the equivalent circuit of the gradient coil shown in FIG. 3, a load voltage waveform as shown in FIG. 5 is measured. Therefore, a high voltage called an inductor voltage is generated at both ends of the gradient coil L, which is 10 to several hundred times the input voltage. This inductor block becomes a source of noise, has a negative effect on the image quality of CT images, and can also cause problems with the power supply. When the induced electromotive force generated from the gradient coil is picked up by a coil sensor and the voltage waveform integrated by an integrator is observed with an oscilloscope, as shown in Figure 5, inductor wave kick and ringing occur, and both ends of the coil are It can be seen that the time is unstable for about 20 msec. Abnormal voltage in this unstable state often leads to destruction of semiconductor elements such as transistors and other circuit elements.
本発明は、上記の問題点を解決するものであつ
て、インダクデイブキツクの発生しない矩形電圧
波形を勾配コイルに印加できるイメージ装置の勾
配コイル励磁回路を提供することを目的とするも
のである。 SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems, and to provide a gradient coil excitation circuit for an imaging device that can apply a rectangular voltage waveform to a gradient coil without causing induction kick.
そのために本発明のイメージ装置の勾配コイル
励磁回路は、イメージ装置の勾配コイルの矩形電
圧を印加して勾配磁場を発生させるイメージ装置
の勾配コイル励磁回路であつて、矩形波形を台形
波形に変換する台形波形変換手段を備え、矩形電
圧を台形波形変換手段を通して勾配コイルに印加
するようにしたことを特徴とするものである。
To this end, the gradient coil excitation circuit of the imaging device of the present invention is a gradient coil excitation circuit of the imaging device that applies a rectangular voltage to the gradient coil of the imaging device to generate a gradient magnetic field, and converts the rectangular waveform into a trapezoidal waveform. The device is characterized in that it includes trapezoidal waveform converting means, and a rectangular voltage is applied to the gradient coil through the trapezoidal waveform converting means.
本発明のイメージ装置の勾配コイル励磁回路で
は、矩形波形を台形波形に変換して勾配コイルに
印加するので、その台形波形を不安定な状態に合
わせて調整することによつて、勾配コイルにおけ
るインダクデイブキツクとリンギングの発生を抑
えることができる。その結果、電気回路に発生す
るノズルを除去することができる。
In the gradient coil excitation circuit of the image device of the present invention, a rectangular waveform is converted into a trapezoidal waveform and applied to the gradient coil. Therefore, by adjusting the trapezoidal waveform to match the unstable state, the inductance in the gradient coil can be reduced. It is possible to suppress the occurrence of bumps and ringing. As a result, nozzles occurring in the electric circuit can be removed.
以下、実施例を図面を参照しつつ説明する。 Examples will be described below with reference to the drawings.
第１図は本発明に係るイメージ装置の勾配コイ
ル励磁回路の１実施例構成を示す図、第２図は台
形波形変換回路の１実施例を示す図である。図
中、１はパルス発生回路、２は勾配コイルコント
ロール回路、３は台形波形変換回路、４は勾配コ
イル電源回路、５は勾配コイル、３１と３２は増
幅器を示す。 FIG. 1 is a diagram showing an embodiment of the configuration of a gradient coil excitation circuit of an image device according to the present invention, and FIG. 2 is a diagram showing an embodiment of a trapezoidal waveform conversion circuit. In the figure, 1 is a pulse generation circuit, 2 is a gradient coil control circuit, 3 is a trapezoidal waveform conversion circuit, 4 is a gradient coil power supply circuit, 5 is a gradient coil, and 31 and 32 are amplifiers.
第１図において、パルス発生回路１は、例えば
NMR−CTのホストコンピユータよりコントロ
ールされイメージ測定に必要なパルス系列を発生
する回路であり、勾配コイルコントロール回路２
は、パルス発生回路１の出力信号からＸ軸コイ
ル、Ｙ軸コイル、Ｚ軸コイルに流す電流のタイミ
ングをコントロールする回路である。従来は、こ
の勾配コイルコントロール回路２の出力によつて
直接勾配コイル電源回路４を制御していたが、本
発明では、台形波形変換回路３を設け、Ｘ軸コイ
ル、Ｙ軸コイル、Ｚ軸コイルに流す電流のタイミ
ングに従つて矩形波形を台形波形に変換し、その
台形波形により勾配コイル電源回路４を制御す
る。勾配コイル電源回路４は、勾配コイル５に流
す電流を発生する定電流電源ユニツトであり、勾
配コイル５により勾配磁場を発生する。 In FIG. 1, the pulse generation circuit 1 includes, for example,
This is a circuit that is controlled by the NMR-CT host computer and generates the pulse sequence necessary for image measurement. Gradient coil control circuit 2
is a circuit that controls the timing of current flowing to the X-axis coil, Y-axis coil, and Z-axis coil from the output signal of the pulse generation circuit 1. Conventionally, the gradient coil power supply circuit 4 was directly controlled by the output of the gradient coil control circuit 2, but in the present invention, a trapezoidal waveform conversion circuit 3 is provided to control the X-axis coil, Y-axis coil, and Z-axis coil. The rectangular waveform is converted into a trapezoidal waveform according to the timing of the current flowing through the coil, and the gradient coil power supply circuit 4 is controlled by the trapezoidal waveform. The gradient coil power supply circuit 4 is a constant current power supply unit that generates a current to flow through the gradient coil 5, and the gradient coil 5 generates a gradient magnetic field.
矩形波形を台形波形に変換する台形波形変換回
路３の具体的な構成例を示したのが第２図であ
る。この台形波形変換回路では、第１の増幅器３
１に矩形波形を入力端子に供給し、その出力を他
方の入力端子に抵抗R1を介して帰還する。そし
て第１の増幅器３１の出力端子に抵抗R1，R2，
コンデンサＣの直列回路を接続し、抵抗R1とコ
ンデンサＣとの直列接続点を第２の増幅器３２の
入力端子に接続すると共にその出力を他方の入力
端子に帰還する。このように構成することによつ
て、第１の増幅器３１に矩形波形Ａを入力する
と、第２の増幅器３２から台形波形Ｂに変換され
た出力が得られる。 FIG. 2 shows a specific example of the configuration of the trapezoidal waveform conversion circuit 3 that converts a rectangular waveform into a trapezoidal waveform. In this trapezoidal waveform conversion circuit, the first amplifier 3
1, a rectangular waveform is supplied to the input terminal, and its output is fed back to the other input terminal via the resistor R1 . Then, resistors R 1 , R 2 ,
A series circuit of capacitors C is connected, and the series connection point of resistor R 1 and capacitor C is connected to the input terminal of the second amplifier 32, and its output is fed back to the other input terminal. With this configuration, when a rectangular waveform A is input to the first amplifier 31, an output converted to a trapezoidal waveform B is obtained from the second amplifier 32.
なお、台形波形の調整は、次のようにして行え
ばよい。すなわち、出力波形をオシロスコープで
観測して第５図に示す不安定な時間T1，T2を測
定する。次に第２図に示す台形波形変換回路の抵
抗R1，R2の比、及びコンデンサＣの容量値を変
化させて前記不安定時間分だけ台形波形の立ち上
がり時間を遅らせる。以上の手順をＸ軸、Ｙ軸、
Ｚ軸の各台形波形変換回路にて行う。 Note that the trapezoidal waveform may be adjusted as follows. That is, the output waveform is observed with an oscilloscope and the unstable times T 1 and T 2 shown in FIG. 5 are measured. Next, the ratio of resistors R 1 and R 2 of the trapezoidal waveform conversion circuit shown in FIG. 2 and the capacitance value of capacitor C are changed to delay the rise time of the trapezoidal waveform by the unstable time. The above steps are performed on the X axis, Y axis,
This is done in each Z-axis trapezoidal waveform conversion circuit.
次に、本発明による台形波形変換回路を各Ｘ
軸、Ｙ軸、Ｚ軸に追加したことによる、その回路
の有効性について説明する。 Next, the trapezoidal waveform conversion circuit according to the present invention is
The effectiveness of the circuit by adding it to the axis, Y axis, and Z axis will be explained.
実際に静磁場中で勾配コイルに台形波形変換回
路を使用しないで矩形波形により勾配コイルに励
磁電圧を印加した時の勾配コイル負荷電圧は、先
に述べた第５図に示すような波形となる。それに
対して、本発明により実際に台形波形変換回路を
使用して、台形波形により静磁場中で勾配コイル
に励磁電圧を印加した時には、ほぼ矩形の勾配コ
イル負荷電圧波形が得られる。従つて本発明によ
れば、勾配コイルのインダクテイブキツクとリン
ギングによる不安定な時間は取り除くことが出来
る。 When an excitation voltage is actually applied to the gradient coil in a static magnetic field with a rectangular waveform without using a trapezoidal waveform conversion circuit, the gradient coil load voltage has a waveform as shown in Figure 5 mentioned above. . On the other hand, when the trapezoidal waveform conversion circuit according to the present invention is actually used to apply excitation voltage to the gradient coil in a static magnetic field with a trapezoidal waveform, a substantially rectangular gradient coil load voltage waveform is obtained. According to the invention, therefore, the instability due to inductive kick and ringing of the gradient coils can be eliminated.
なお、本発明は、種々の変形が可能であり、上
記実施例に限定されるものではない。例えば上記
実施例では、NMR−CTの勾配コイルに適用し
てCT画像の画質を向上させる例を説明したが、
今後開発されるESR−CTの勾配コイルのコント
ロール部に同様の台形波形変換回路を追加するこ
とによつてESR−CTの画質向上にも利用できる
ことは勿論である。また、第２図に示す例では台
形波形変換回路を演算増幅器、抵抗、コンデンサ
を使つて構成したが、ROM等のメモリを使用し
て台形波形変換回路を構成しても良い。 Note that the present invention can be modified in various ways and is not limited to the above embodiments. For example, in the above embodiment, an example was explained in which the image quality of a CT image is improved by applying it to an NMR-CT gradient coil.
Of course, by adding a similar trapezoidal waveform conversion circuit to the gradient coil control section of ESR-CT that will be developed in the future, it can also be used to improve the image quality of ESR-CT. Further, in the example shown in FIG. 2, the trapezoidal waveform conversion circuit is configured using an operational amplifier, a resistor, and a capacitor, but the trapezoidal waveform conversion circuit may also be configured using a memory such as a ROM.
以上の説明から明らかなように、本発明によれ
ば、矩形電圧波形を台形波形に変換して勾配コイ
ルに印加するので、インダクテイブキツクやリン
ギングを除去できる。その結果、インダクテイブ
キツクに起因して電気回路に発生するノイズを除
去できるので、電源トラブルや回路素子の破壊を
防ぐことができると共に、NMR−CT（核磁気共
鳴コンピユータ断層撮影装置）やESR−CT（電
子スピン共鳴コンピユータ断層撮影装置）等のイ
メージ装置の画質の向上を図ることができる。さ
らには、勾配コイルの製作時のバラツキを完全に
補うことができ、CT画像の画質の向上を図るこ
とができる。
As is clear from the above description, according to the present invention, since a rectangular voltage waveform is converted into a trapezoidal waveform and applied to the gradient coil, inductive kicks and ringing can be eliminated. As a result, noise generated in electrical circuits due to inductive kicks can be removed, preventing power supply problems and circuit element destruction, as well as NMR-CT (Nuclear Magnetic Resonance Computer Tomography) and ESR - It is possible to improve the image quality of imaging devices such as CT (electron spin resonance computer tomography). Furthermore, it is possible to completely compensate for variations in the manufacturing process of gradient coils, and it is possible to improve the image quality of CT images.
第１図は本発明に係るイメージ装置の勾配コイ
ル励磁回路の１実施例構成を示す図、第２図は台
形波形変換回路の１実施例を示す図、第３図はイ
メージ装置の勾配コイルの回路を示す図、第４図
は勾配コイルに印加する電圧波形を示す図、第５
図は勾配コイルの負荷電圧波形を示す図である。
１……パルス発生回路、２……勾配コイルコン
トロール回路、３……台形波形変換回路、４……
勾配コイル電源回路、５……勾配コイル、３１と
３２……増幅器。
FIG. 1 is a diagram showing an embodiment of the configuration of a gradient coil excitation circuit of an imaging device according to the present invention, FIG. 2 is a diagram showing an embodiment of a trapezoidal waveform conversion circuit, and FIG. Figure 4 is a diagram showing the circuit, Figure 4 is a diagram showing the voltage waveform applied to the gradient coil, Figure 5 is a diagram showing the voltage waveform applied to the gradient coil.
The figure is a diagram showing a load voltage waveform of a gradient coil. 1... Pulse generation circuit, 2... Gradient coil control circuit, 3... Trapezoidal waveform conversion circuit, 4...
Gradient coil power supply circuit, 5...Gradient coil, 31 and 32...Amplifier.
Claims (1)
して勾配磁場を発生させるイメージ装置の勾配コ
イル励磁回路であつて、矩形波形を台形波形に変
換する台形波形変換手段を備え、矩形電圧を台形
波形変換手段を通して勾配コイルに印加するよう
にしたことを特徴とするイメージ装置の勾配コイ
ル励磁回路。1. A gradient coil excitation circuit for an imaging device that applies a rectangular voltage to a gradient coil of the imaging device to generate a gradient magnetic field, and includes trapezoidal waveform converting means for converting a rectangular waveform into a trapezoidal waveform, and converts the rectangular voltage into a trapezoidal waveform. A gradient coil excitation circuit for an imaging device, characterized in that the gradient coil excitation circuit is configured to apply voltage to the gradient coil through means.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP61162243A JPS6319136A (en) | 1986-07-10 | 1986-07-10 | Gradient coil exciting circuit of imaging apparatus |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP61162243A JPS6319136A (en) | 1986-07-10 | 1986-07-10 | Gradient coil exciting circuit of imaging apparatus |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS6319136A JPS6319136A (en) | 1988-01-26 |
| JPH0475009B2 true JPH0475009B2 (en) | 1992-11-27 |
Family
ID=15750708
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP61162243A Granted JPS6319136A (en) | 1986-07-10 | 1986-07-10 | Gradient coil exciting circuit of imaging apparatus |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS6319136A (en) |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4437053A (en) * | 1982-05-10 | 1984-03-13 | Diasonics (Nmr) Inc. | Gradient power supply |
| JPS6095337A (en) * | 1983-10-31 | 1985-05-28 | Hitachi Ltd | Nuclear magnetic resonance imaging apparatus |
| JPS62221341A (en) * | 1986-03-20 | 1987-09-29 | 株式会社東芝 | Magnetic resonance imaging apparatus |
-
1986
- 1986-07-10 JP JP61162243A patent/JPS6319136A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS6319136A (en) | 1988-01-26 |
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