JPS62168408A - Automatic resonance and matching device of antenna circuit for mri device - Google Patents
Automatic resonance and matching device of antenna circuit for mri deviceInfo
- Publication number
- JPS62168408A JPS62168408A JP26226085A JP26226085A JPS62168408A JP S62168408 A JPS62168408 A JP S62168408A JP 26226085 A JP26226085 A JP 26226085A JP 26226085 A JP26226085 A JP 26226085A JP S62168408 A JPS62168408 A JP S62168408A
- Authority
- JP
- Japan
- Prior art keywords
- standing wave
- wave ratio
- antenna circuit
- resonance
- antenna
- 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.)
- Pending
Links
- 239000003990 capacitor Substances 0.000 claims abstract description 36
- 238000010168 coupling process Methods 0.000 claims abstract description 14
- 238000005859 coupling reaction Methods 0.000 claims abstract description 14
- 230000008878 coupling Effects 0.000 claims abstract description 13
- 238000001228 spectrum Methods 0.000 description 6
- 238000000034 method Methods 0.000 description 4
- 238000005259 measurement Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 238000003384 imaging method Methods 0.000 description 2
- 238000009530 blood pressure measurement Methods 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 239000013256 coordination polymer Substances 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
Abstract
Description
【発明の詳細な説明】
〈産業上の利用分野〉
本発明は、ＭＲＩ装置用アンテナ回路の自動共振・整合
装置に関する。DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an automatic resonance/matching device for an antenna circuit for an MRI apparatus.
〈従来の技術〉
ＭＲＩ装置におけるアンテナ回路の共振とインピーダン
ス整合を調整する方法には、例えば、鞍型コイル状アン
テナに共振用可変キャパシタが並列接続されたタンク回
路にインピーダンス整合用のカップリング・キャパシタ
が直列接続されて成るアンテナ回路へ、電圧定在波比測
定器（例えば電圧定材液比測定ブリッジ）を介して高周
波電力を供給し、この測定器の出力を観測しながら共振
用キャパシタとカンプリング・キャパシタを調整する方
法がある。すなわち、アンテナ回路に供給する高周波の
周波数を所定の範囲で掃引すると、高周波電力供給ライ
ンに現れる電圧・定在波比が周波数によって変わるので
、電圧定在波比測定ブリッジの出力は、例えば第２図ｆ
ａ）に示すようなスペクトルを示す。図において紺軸は
電圧定在波比（Ｖ、Ｓ、Ｗ、Ｒ，）軸、横軸は周波数軸
である。また周波数軸上のｆｏは目的の共振周波数を示
す。この図によれば、スペクトルのピーク位置がｆＱよ
りずれており、またその落ち込みが非常に浅く、従って
アンテナ回路は共振点よりずれ、かつ、高周波電力供給
源とインピーダンス整合をしていない。<Prior Art> A method for adjusting the resonance and impedance matching of an antenna circuit in an MRI apparatus includes, for example, adding a coupling capacitor for impedance matching to a tank circuit in which a variable capacitor for resonance is connected in parallel to a saddle-shaped coil antenna. High-frequency power is supplied to the antenna circuit consisting of series-connected voltage standing wave ratio measuring instruments (for example, a voltage constant material liquid ratio measuring bridge), and while observing the output of this measuring instrument, the resonant capacitor and amplifier are connected in series. There are ways to tune ring capacitors. In other words, when the frequency of the high frequency wave supplied to the antenna circuit is swept over a predetermined range, the voltage/standing wave ratio appearing on the high frequency power supply line changes depending on the frequency, so the output of the voltage standing wave ratio measuring bridge is, for example, Figure f
A spectrum as shown in a) is shown. In the figure, the dark blue axis is the voltage standing wave ratio (V, S, W, R,) axis, and the horizontal axis is the frequency axis. Further, fo on the frequency axis indicates a target resonance frequency. According to this figure, the peak position of the spectrum is shifted from fQ, and the drop is very shallow, so the antenna circuit is shifted from the resonance point and is not impedance matched with the high frequency power supply source.
そこで共振用キャパシタとカンプリング・キャパシタの
両方を調節し、両キャパシタの容量値の組み合わせを変
えて、第２図（ｂ） （ｃ） （ｄｉおよび（ｅ）で代
表サレるような種々なパターンのスペクトルを求め、そ
の結果として同図（ｅ）のように、ピーク位置が目的の
共振周波数ｆＯに合致し、かつ、落ち込みが最も深いス
ペクトルを得ることにより、アンテナ回路をインピーダ
ンス整合の状態で共振させることができる。なお、以上
のようなスペクトルは、例えば、周波数−電圧変換器で
電圧に変換された高周波電力供給装置からの周波数信号
と、電圧定在波比測定ブリッジの検波出力電圧とを利用
して、ｘ−ｙレコーダや記録式ＣＲＴ等の記録装置に表
示される。Therefore, by adjusting both the resonance capacitor and the compling capacitor, and changing the combination of capacitance values of both capacitors, various patterns as shown in Fig. 2 (b), (c), (di and (e)) are created. As a result, as shown in the same figure (e), by obtaining a spectrum whose peak position matches the desired resonance frequency fO and whose dip is the deepest, the antenna circuit can be made to resonate in a state of impedance matching. The above spectrum can be obtained by combining, for example, a frequency signal from a high-frequency power supply device converted into voltage by a frequency-voltage converter and a detected output voltage of a voltage standing wave ratio measurement bridge. The information is displayed on a recording device such as an x-y recorder or a recording type CRT.
〈発明が解決しようとする問題点〉
共振用キャパシタとカップリング・キャパシタの容量値
の組み合せから第２図（ｅ）に示すような最適スペクト
ルを得るには非常に面倒なキャパシタ調節操作が必要で
ある。また、マイクロッコンピュータを用いて自動化す
ることも、採取すべきスペクトルデータの数が非常に多
いため、高速化が難しく、制御も複雑になる。<Problems to be solved by the invention> In order to obtain the optimum spectrum as shown in Fig. 2(e) from the combination of capacitance values of the resonance capacitor and the coupling capacitor, a very troublesome capacitor adjustment operation is required. be. Further, even if the process is automated using a microcomputer, the amount of spectrum data to be collected is extremely large, so it is difficult to increase the speed and control becomes complicated.
しかも、ＭＲＩ装置の場合、たとえ撮像条件が一定であ
っても、被検体が変わればその都度アンテナ回路の共振
とインピーダンス整合を再調整する必要がある。Moreover, in the case of an MRI apparatus, even if the imaging conditions are constant, whenever the subject changes, it is necessary to readjust the resonance and impedance matching of the antenna circuit.
本発明は、上記のような、従来技術に伴う欠点的問題に
解決を与える。The present invention provides a solution to the disadvantageous problems associated with the prior art, as described above.
〈問題点を解決するための手段〉
問題解決のため、本発明による装置においては、コイル
型アンテナと、可変容量ダイオードを用いた共振用キャ
パシタおよびカンプリング・キャパシタより成るタンク
回路に電圧定在波比測定器（例えば電圧定在波比測定ブ
リッジ）を介して、周波数が所定値に固定された高周波
電力を供給し、上記測定器の出力に応じて可変容量ダイ
オードの制御電圧を出力する制御手段が、同ブリッジの
出力電圧を最低値に保つよう、上記の共振用キャパシタ
とカップリング・キャパシタの容量を制御するよう構成
されている。<Means for solving the problem> In order to solve the problem, in the device according to the present invention, a voltage standing wave is applied to a tank circuit consisting of a coil antenna, a resonance capacitor using a variable capacitance diode, and a compling capacitor. Control means for supplying high frequency power whose frequency is fixed to a predetermined value via a ratio measuring device (for example, a voltage standing wave ratio measuring bridge) and outputting a control voltage for the variable capacitance diode according to the output of the measuring device. is configured to control the capacitance of the resonance capacitor and coupling capacitor so as to maintain the output voltage of the bridge at a minimum value.
〈作用〉
上記のようにアンテナ回路に供給される高周波の周波数
が所定値に固定されていることが、共振用キャパシタと
カップリング・キャパシタの両方を同時に調節して電圧
定在波比測定器の出力を最低にすることを可能にし、ア
ンテナ回路の調整操作の過程を簡単にしている。<Function> The fact that the frequency of the high frequency wave supplied to the antenna circuit is fixed at a predetermined value as described above makes it possible to adjust both the resonance capacitor and the coupling capacitor at the same time to measure the voltage standing wave ratio. It allows the output to be minimized and simplifies the process of adjusting the antenna circuit.
〈実施例〉 以下に本発明の実施例を第１図に基づいて説明する。<Example> An embodiment of the present invention will be described below based on FIG.
図において、例えば鞍型コイル状のアンテナ１は反直列
に接続された２個の可変容量ダイオード２ａ、２ｂ （
共振用キャパシタ２を形成している）と共にタンク回路
を形成し、この回路には、反直列に接続された２個の可
変容量ダイオード３ａ。In the figure, for example, a saddle-shaped coil-shaped antenna 1 has two variable capacitance diodes 2a, 2b (
(forming the resonant capacitor 2) forms a tank circuit, and this circuit includes two variable capacitance diodes 3a connected in anti-series.
３ｂから成るカップリング・キャパシタ３と電圧定在波
比測定ブリッジ１２とを介して、高周波発信器１３より
一定周波数の高周波電力が供給される。一方電圧定在波
比測定ブリッジの出力は、検波器１１と増幅器１０によ
って検波、増幅された後、Ａ−Ｄ変換器９でデジタル信
号化されてＣＰＵ８に入力される。また、ＣＰＵ８は可
変容量ダイオード制御用のデジタル信号を出力するが、
その信号はＤ−Ａ変換器６と７によって異なるアナログ
信号に変換され、これらのアナログ信号に基づいてダイ
オード制御回路４は可変容量ダイオード３ａおよび３ｂ
からなるカップリング・キャパシタ３の容量を制御し、
またダイオード制御回路５は可変容量ダイオード２ａお
よび２ｂから成る共振用キャパシタ２の容量を制御する
。High frequency power at a constant frequency is supplied from a high frequency oscillator 13 via a coupling capacitor 3 consisting of 3b and a voltage standing wave ratio measurement bridge 12. On the other hand, the output of the voltage standing wave ratio measurement bridge is detected and amplified by a detector 11 and an amplifier 10, and then converted into a digital signal by an AD converter 9 and input to the CPU 8. In addition, the CPU 8 outputs a digital signal for controlling the variable capacitance diode,
The signals are converted into different analog signals by D-A converters 6 and 7, and based on these analog signals, the diode control circuit 4 controls the variable capacitance diodes 3a and 3b.
controlling the capacitance of the coupling capacitor 3 consisting of
Further, the diode control circuit 5 controls the capacitance of the resonance capacitor 2 consisting of variable capacitance diodes 2a and 2b.
以上の回路構成において、先ずＣＰＵ８は、所定のプロ
グラムに基づく第１回目の制御デジタル信号を出力する
。その結果カップリングキャパシタ３と共振用キャパシ
タ２の容量が決定され、それに対応する電圧定在波比を
示す信号が電圧定在波圧測定ブリッジ１２より出力され
る。この信号が検波、増幅され、デジタル化されてＣＰ
Ｕ８に送られると、ＣＰＵは直ちに次の制御デジタル信
号を出力する。このような容量制御・電圧定在波比検出
サイクルが、カップリング・キャパシタ３と共振用キャ
パシタ２に対する所定の容量制御領域にわたって（り返
され、その過程で電圧定在波比の最小値が検知されると
、ＣＰＵ８は直ちに、このような電圧定在波比の最小値
に対応する制御デジタル信号を出力する状態に戻り、そ
の状態を持続する。このようにしてアンテナ１．共振用
キャパシタ２およびカップリング・キャパシタ３より成
るアンテナ回路の共振とインピーダンス整合が達成され
る。In the above circuit configuration, the CPU 8 first outputs a first control digital signal based on a predetermined program. As a result, the capacitances of the coupling capacitor 3 and the resonance capacitor 2 are determined, and a signal indicating the corresponding voltage standing wave ratio is outputted from the voltage standing wave pressure measurement bridge 12. This signal is detected, amplified, and digitized into the CP
Once sent to U8, the CPU immediately outputs the next control digital signal. Such a capacitance control/voltage standing wave ratio detection cycle is repeated over a predetermined capacitance control region for the coupling capacitor 3 and the resonance capacitor 2, and in the process, the minimum value of the voltage standing wave ratio is detected. Then, the CPU 8 immediately returns to the state of outputting the control digital signal corresponding to the minimum value of the voltage standing wave ratio, and maintains that state.In this way, the antenna 1, resonance capacitor 2, and Resonance and impedance matching of the antenna circuit consisting of the coupling capacitor 3 is achieved.
ところで、カップリングキャパシタと共振用キャパシタ
の容量がある値に設定されてから、電圧定在波比の値が
求められ、両キャパシタの容量が次の値に設定されるま
での時間は、各構成回路の応答・作動時間がμ秒のオー
ダーであることから、大きい目に見積もって全体で数ｍ
秒程度である。By the way, the time from when the capacitance of the coupling capacitor and the resonance capacitor is set to a certain value to when the value of the voltage standing wave ratio is calculated and the capacitance of both capacitors is set to the next value depends on each configuration. Since the response/operation time of the circuit is on the order of microseconds, the overall length is several meters.
It is about seconds.
従って容量変化のステップ数を１０００として、アンテ
ナ回路の調整に要する全時間は数秒程度である。Therefore, assuming that the number of capacitance change steps is 1000, the total time required for adjusting the antenna circuit is about several seconds.
〈発明の効果〉
以上の説明から明らかなように、本発明によればアンテ
ナ回路の共振とインピーダンスの調整が数秒程の極く短
い時間で完了するので、ＭＲｒ装置による撮像作業の能
率が大幅に向上する。また、調整操作はすべて電気的、
自動的に行われるので、遠隔操作も容易になる。<Effects of the Invention> As is clear from the above description, according to the present invention, the resonance of the antenna circuit and the adjustment of impedance can be completed in a very short time of about several seconds, which greatly improves the efficiency of imaging work by the MRr device. improves. In addition, all adjustment operations are electrical.
Since this is done automatically, remote control is also easy.
第１図は本発明実施例の回路構成を示すブロック図であ
る。第２図はアンテナ回路の共振とインピーダンス整合
の状況を説明する特性図である。
１−・・アンテナ
２・・−共振用キャパシタ
３−カップリング・キャパシタ
２ａ、２ｂ、３ａ、３ｂ−−一可変容量ダイオード４．
５−ダイオード制御回路
６．７−・−Ｄ−Ａ変換器
８・・−ＣＰＵ
９−・−Ａ−Ｄ変換器
１０・−・増幅器
１１−検波器
１２−電圧定在波比測定装置
１３−高周波発振器
特許出願人 株式会社島津製作所
代 理 人 弁理士 西１） 新
築２図
（Ｑ） （ｔ））
■５、ｗＲＶ、’Ｓ、、Ｗ、Ｒ
（ｃ） （ｃｊ
ンＶＳ、Ｗ、Ｒ
（（Ｚ）FIG. 1 is a block diagram showing the circuit configuration of an embodiment of the present invention. FIG. 2 is a characteristic diagram illustrating the state of resonance and impedance matching of the antenna circuit. 1--Antenna 2--Resonance capacitor 3-Coupling capacitors 2a, 2b, 3a, 3b--Variable capacitance diode 4.
5-Diode control circuit 6.7--D-A converter 8--CPU 9--A-D converter 10--Amplifier 11-Detector 12-Voltage standing wave ratio measuring device 13- High frequency oscillator patent applicant Shimadzu Corporation Representative Patent attorney Nishi 1) New construction 2 drawings (Q) (t)) ■5, wRV,'S,,W,R (c) (cj
VS, W, R ((Z)
Claims (1)
グ・キャパシタに可変容量ダイオードを用いたＭＲＩ装
置用アンテナ回路を、このアンテナ回路に高周波電力を
供給する送信器の周波数に対して、最適インピーダンス
整合状態で共振させる装置において、上記送信器の出力
と上記アンテナ回路からの反射波によって生ずる電圧定
在波を検出する電圧定在波比測定器と、この電圧定在波
比測定器の出力信号に応じて所定の可変容量ダイオード
制御信号を出力する装置とを有し、可変容量ダイオード
を用いた上記共振用キャパシタとカップリング・キャパ
シタの容量が、上記所定の可変容量ダイオード制御信号
によって制御されるよう構成されたことを特徴とする、
ＭＲＩ装置用アンテナ回路自動共振・整合装置。A device that makes an antenna circuit for an MRI device, which uses a variable capacitance diode as a resonance capacitor and an impedance matching coupling capacitor, resonate in an optimal impedance matching state with respect to the frequency of a transmitter that supplies high-frequency power to this antenna circuit. a voltage standing wave ratio measuring device for detecting a voltage standing wave generated by the output of the transmitter and a reflected wave from the antenna circuit; and a device for outputting a capacitance diode control signal, and the capacitance of the resonance capacitor and the coupling capacitor using a variable capacitance diode is configured to be controlled by the predetermined variable capacitance diode control signal. Characterized by
Antenna circuit automatic resonance/matching device for MRI equipment.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP26226085A JPS62168408A (en) | 1985-11-21 | 1985-11-21 | Automatic resonance and matching device of antenna circuit for mri device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP26226085A JPS62168408A (en) | 1985-11-21 | 1985-11-21 | Automatic resonance and matching device of antenna circuit for mri device |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPS62168408A true JPS62168408A (en) | 1987-07-24 |
Family
ID=17373306
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP26226085A Pending JPS62168408A (en) | 1985-11-21 | 1985-11-21 | Automatic resonance and matching device of antenna circuit for mri device |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS62168408A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2656698A1 (en) * | 1989-12-29 | 1991-07-05 | Vectavib | DEVICE FOR MEASURING VARIATIONS IN THE CAPACITY OF A CAPACITOR FORMING, IN PARTICULAR, A SENSOR. |
| US6707029B1 (en) | 1999-01-22 | 2004-03-16 | Citizen Watch Co., Ltd. | Optical displacement measuring apparatus having light receiving arrays |
-
1985
- 1985-11-21 JP JP26226085A patent/JPS62168408A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2656698A1 (en) * | 1989-12-29 | 1991-07-05 | Vectavib | DEVICE FOR MEASURING VARIATIONS IN THE CAPACITY OF A CAPACITOR FORMING, IN PARTICULAR, A SENSOR. |
| US5311140A (en) * | 1989-12-29 | 1994-05-10 | Societe D'applications Generales D'electricite Et De Mecanique Sagem | Circuit for measuring variations in the capacitance of a variable capacitor using a continuously rebalanced detection bridge |
| US6707029B1 (en) | 1999-01-22 | 2004-03-16 | Citizen Watch Co., Ltd. | Optical displacement measuring apparatus having light receiving arrays |
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