JPH0546509B2 - - Google Patents
Info
- Publication number
- JPH0546509B2 JPH0546509B2 JP59195450A JP19545084A JPH0546509B2 JP H0546509 B2 JPH0546509 B2 JP H0546509B2 JP 59195450 A JP59195450 A JP 59195450A JP 19545084 A JP19545084 A JP 19545084A JP H0546509 B2 JPH0546509 B2 JP H0546509B2
- Authority
- JP
- Japan
- Prior art keywords
- antenna
- loop
- receiving
- saddle
- frequency power
- 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
Links
- 239000003990 capacitor Substances 0.000 description 15
- 230000005684 electric field Effects 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 230000008054 signal transmission Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 1
- 230000001939 inductive effect Effects 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
- G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
- G01R33/32—Excitation or detection systems, e.g. using radio frequency signals
- G01R33/34—Constructional details, e.g. resonators, specially adapted to MR
- G01R33/34046—Volume type coils, e.g. bird-cage coils; Quadrature bird-cage coils; Circularly polarised coils
- G01R33/34069—Saddle coils
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
- G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
- G01R33/32—Excitation or detection systems, e.g. using radio frequency signals
- G01R33/36—Electrical details, e.g. matching or coupling of the coil to the receiver
- G01R33/3628—Tuning/matching of the transmit/receive coil
Description
【発明の詳細な説明】
(イ) 産業上の利用分野
本発明はNMR信号送・受信用アンテナに関す
る。DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to an antenna for transmitting and receiving NMR signals.
(ロ) 従来技術
ループ型のNMR信号送・受信用アンテナ、例
えば、NMR−CTに用いる鞍型コイル状に形成
されたアンテナにおいては、使用する高周波の波
長に対する鞍型コイルの相対的な寸法が大きくな
るにつれて、コイルの給・受電端とコイルの先端
との間での位相差が問題になり、それに伴うコイ
ル上での定在波の電流強度の分布に対応して、発
生する高周波磁場の均一度が低下するだけでな
く、被検体中の対象部位における磁場強度も低下
する。また、これにより高周波電場の被検体を貫
通する成分の強度が増すため、誘電体損失も増大
するようになる。以上のように、コイルが大型化
し、また、使用周波数が高くなるにつれ、コイル
のアンテナとしての性能が低下する。(b) Prior art In a loop-type NMR signal transmission/reception antenna, for example, an antenna formed in a saddle-shaped coil shape used for NMR-CT, the relative dimensions of the saddle-shaped coil with respect to the wavelength of the high frequency used are As the size increases, the phase difference between the feeding/receiving end of the coil and the tip of the coil becomes a problem, and the resulting high-frequency magnetic field changes in response to the distribution of the current strength of the standing wave on the coil. Not only is the uniformity reduced, but the magnetic field strength at the target site in the subject is also reduced. Furthermore, this increases the strength of the component of the high-frequency electric field that penetrates the object, and therefore the dielectric loss also increases. As described above, as the coil becomes larger and the frequency used becomes higher, the performance of the coil as an antenna deteriorates.
(ハ) 目的
本発明の目的は従来技術に伴う上記の欠点を排
除するため、アンテナを構成するループ状回路中
での電流強度分布を可変し得る手段を設けた、
NMR信号送・受信用アンテナを提供することに
ある。(c) Purpose An object of the present invention is to provide means for varying the current intensity distribution in a loop-shaped circuit constituting an antenna, in order to eliminate the above-mentioned drawbacks associated with the prior art.
The purpose of the present invention is to provide an antenna for transmitting and receiving NMR signals.
(ニ) 構成
以上の目的を達成するため、本発明は高周波信
号送・受信用のループ型アンテナであつて、アン
テナを構成するループ状に形成された回路中の、
高周波電力給・受電端から最遠隔の部位に可変リ
アクタンス素子を設けたことを特徴としている。(d) Structure In order to achieve the above object, the present invention is a loop antenna for transmitting and receiving high frequency signals, and in a loop-shaped circuit constituting the antenna,
A feature is that a variable reactance element is provided at the farthest point from the high-frequency power supply/receiver end.
(ホ) 実施例
以下に本発明の実施例を図面に基づいて説明す
る。(e) Examples Examples of the present invention will be described below based on the drawings.
第１図は鞍型コイル・ペア状に形成された
NMR−CT用アンテナに本発明を実施した場合
の構成を示す斜視図である。２つの鞍型コイル状
アンテナ回路１および１ａには、それぞれ高周波
電力給・受電端Ａ，Ｈおよびａ，ｈから見た最遠
隔部の端子DE間およびｄ，ｅ間にそれぞれ、容
量性リアクタンス素子としての可変キヤパシタ２
および２ａが挿入されている。なお、高周波電力
給・受電端に挿入されているキヤパシタ３および
３ａは共振用キヤパシタであつて、このアンテナ
回路全体の高周波電力入出力端子４，４ａに対し
て、例えば直列に接続されるべき整合用キヤパシ
タと共に、高周波電源ないしは受信部との間に共
振と整合の条件を満たすよう調節するためのキヤ
パシタである。 Figure 1 shows a pair of saddle-shaped coils.
FIG. 1 is a perspective view showing a configuration when the present invention is implemented in an NMR-CT antenna. In the two saddle-shaped coiled antenna circuits 1 and 1a, capacitive reactance elements are installed between terminals DE and d and e at the farthest points as seen from the high-frequency power feeding/receiving ends A, H and a, h, respectively. variable capacitor 2 as
and 2a are inserted. Note that the capacitors 3 and 3a inserted in the high frequency power supply/receiver end are resonance capacitors, and are matching capacitors to be connected in series, for example, to the high frequency power input/output terminals 4 and 4a of the entire antenna circuit. This capacitor is used to adjust the relationship between the high-frequency power source or the receiving section so as to satisfy the conditions of resonance and matching.
以上の構成において、端子４，４ａより、例え
ば高周波電力を供給する場合、キヤパシタ２およ
び２ａを調節して反射波の位相を適当に選べば、
アンテナの大きさが高周波の波長に比べて無視し
得ない程充分に大きい場合でも、第２図に示すよ
うに、鞍型ループ回路の直線部Ｂ−Ｃ，Ｆ−Ｇ，
ｂ−ｃおよびｆ−ｇの中央に電流定在波の腹をも
たらすことができる。即ち、第２図において
は、第１図の鞍型ループ回路１に、出力インピー
ダンスがＲの高周波電源６より、整合用キヤパシ
タ５を介して高周波電力が供給されている状態を
示す等価回路であり、およびはそれぞれ、鞍
型ループの直線部Ｃ−ＢおよびＦ−Ｇにおける電
流（実線）と電圧（点線）の定在波波形を示すグ
ラフである。図は鞍型ループ１における電流、電
圧の分布のみを示すが、鞍型ループ１ａについて
も同様な結果が得れることはもちろんである。 In the above configuration, when, for example, high frequency power is supplied from the terminals 4 and 4a, if the phase of the reflected wave is appropriately selected by adjusting the capacitors 2 and 2a,
Even if the size of the antenna is sufficiently large that it cannot be ignored compared to the wavelength of the high frequency, as shown in Fig. 2, the straight portions B-C, F-G,
An antinode of the current standing wave can be created at the center of b-c and f-g. That is, FIG. 2 is an equivalent circuit showing a state in which high-frequency power is supplied to the saddle-shaped loop circuit 1 of FIG. 1 from a high-frequency power supply 6 with an output impedance of R via a matching capacitor 5. , and are graphs showing the standing wave waveforms of current (solid line) and voltage (dotted line) in the straight portions CB and FG of the saddle loop, respectively. Although the figure only shows the distribution of current and voltage in the saddle loop 1, it goes without saying that similar results can be obtained for the saddle loop 1a.
第２図からわかるように、電流安定波の腹が鞍
型ループの直線部の中央にくるので、アンテナ中
央部において高周波磁場の値は最大となり、磁場
均一性もよくなる。また、電流定在波の腹は電圧
定在波の節と一致するので、アンテナ中央部にお
ける電場強度はゼロとなり、その近傍に位置すべ
き被検体中に生ずる誘電損失は最小となり、アン
テナの効率も増大する。なお、もしキヤパシタ
２，２ａがなければ、アンテナの寸法と使用高周
波の波長との関係によつては、極端な場合、電流
定在波の腹がループの先端部にくるようになり、
アンテナ中央部の高周波数磁場は弱く、かつ、不
均一になり、しかもそこで電場強度が最大となつ
て誘電体損失のみが増大するようなことにもな
る。 As can be seen from FIG. 2, since the antinode of the current stable wave is located at the center of the straight section of the saddle-shaped loop, the value of the high-frequency magnetic field becomes maximum at the center of the antenna, and the uniformity of the magnetic field is also improved. In addition, since the antinode of the current standing wave coincides with the node of the voltage standing wave, the electric field strength at the center of the antenna becomes zero, and the dielectric loss that occurs in the object that should be located near it is minimized, making the antenna efficient. also increases. Note that if the capacitors 2 and 2a are not provided, depending on the relationship between the dimensions of the antenna and the wavelength of the high frequency used, in extreme cases, the antinode of the current standing wave will be at the tip of the loop.
The high-frequency magnetic field at the center of the antenna is weak and non-uniform, and the electric field strength reaches its maximum there, causing only dielectric loss to increase.
また、本発明は第３図に示すように構成するこ
ともできる。この実施例においては、第１図に示
した実施例におけるキヤパシタ３および３ａが、
共通のキヤパシタ３ｂで置きかえられている。 Further, the present invention can also be configured as shown in FIG. In this embodiment, the capacitors 3 and 3a in the embodiment shown in FIG.
It has been replaced with a common capacitor 3b.
さらに、アンテナと高周波電源（または受信回
路）との間の接続は、第４図Ａ，ＢおよびＣに示
すように実施することもできる。第４図Ａにおい
ては第２図、第３図におけるキヤパシタ３（およ
び３ａ）が２個の直列キヤパシタで置きかえられ
ており、また、第２図Ｂではキヤパシタ３（およ
び３ａ）を挿入する代わりに、給・受電端部の弧
状回路の長さを変え、誘導性リアクタンスを調節
することにより整合がとられるようになつてい
る。またＣでは端子４および４ａの側にそれぞれ
整合用キヤパシタが接続されている。 Furthermore, the connection between the antenna and the high frequency power source (or receiving circuit) can also be implemented as shown in FIGS. 4A, B and C. In FIG. 4A, capacitor 3 (and 3a) in FIGS. 2 and 3 is replaced with two series capacitors, and in FIG. 2B, instead of inserting capacitor 3 (and 3a), , matching is achieved by changing the length of the arcuate circuit at the feeding and receiving ends and adjusting the inductive reactance. Further, at C, matching capacitors are connected to the terminals 4 and 4a, respectively.
(ヘ) 効果
以上の説明から明らかなように、本発明に、よ
るNMR信号送・受信用アンテナによれば、アン
テナの寸法および使用高周波の波長に関係なく、
電流定在波の腹の位置をアンテナ回路中の位置の
部位、特に、アンテナ回路の中央部にもたらすこ
とかできるため、例えば、NMR−CT用のアン
テナに適用して、高周波信号の効率のよい送・受
信が可能となる。(f) Effects As is clear from the above explanation, according to the NMR signal transmission/reception antenna according to the present invention, regardless of the dimensions of the antenna and the wavelength of the high frequency used,
Since the position of the antinode of the current standing wave can be brought to a position in the antenna circuit, in particular, to the center of the antenna circuit, it can be applied to an NMR-CT antenna, for example, to improve the efficiency of high-frequency signals. Sending/receiving becomes possible.
第１図は本発明実施例の構成を示す斜視図であ
る。第２図は上記実施例の作用を説明する図であ
る。第３図は本発明の他の実施例の構成を示す斜
視図である。第４図は本発明によるアンテナの
給・受電回路を示す図である。
１，１ａ…鞍型ループ回路、２，２ａ，２ｂ…
電流定在波位置調節用キヤパシタ、４，４ａ…ア
ンテナ入・出力端子。
FIG. 1 is a perspective view showing the configuration of an embodiment of the present invention. FIG. 2 is a diagram illustrating the operation of the above embodiment. FIG. 3 is a perspective view showing the configuration of another embodiment of the present invention. FIG. 4 is a diagram showing an antenna feeding/receiving circuit according to the present invention. 1, 1a...Saddle type loop circuit, 2, 2a, 2b...
Capacitor for adjusting current standing wave position, 4, 4a...Antenna input/output terminal.
Claims (1)
あつて、アンテナを構成するループ状に形成され
た回路中の、高周波電力給・受電端から最遠隔の
部位に可変リアクタンス素子を設けたことを特徴
とする、NMR信号送・受信用アンテナ。1. A loop-type antenna for transmitting and receiving high-frequency signals, characterized in that a variable reactance element is provided at the farthest point from the high-frequency power supply/receiver end in the loop-shaped circuit that constitutes the antenna. An antenna for transmitting and receiving NMR signals.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP59195450A JPS6173061A (en) | 1984-09-17 | 1984-09-17 | Antenna for nmr signal transmission and reception |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP59195450A JPS6173061A (en) | 1984-09-17 | 1984-09-17 | Antenna for nmr signal transmission and reception |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS6173061A JPS6173061A (en) | 1986-04-15 |
| JPH0546509B2 true JPH0546509B2 (en) | 1993-07-14 |
Family
ID=16341265
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP59195450A Granted JPS6173061A (en) | 1984-09-17 | 1984-09-17 | Antenna for nmr signal transmission and reception |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS6173061A (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2671364B2 (en) * | 1988-04-05 | 1997-10-29 | 株式会社日立製作所 | Inspection equipment using nuclear magnetic resonance |
| EP1617515B1 (en) * | 2004-07-13 | 2007-09-19 | TDK Corporation | PxM antenna for high-power, broadband applications |
| JP5182742B2 (en) * | 2007-08-14 | 2013-04-17 | 株式会社 Ｊｅｏｌ Ｒｅｓｏｎａｎｃｅ | NMR detector |
| CN105223526A (en) | 2015-09-25 | 2016-01-06 | 沈阳东软医疗系统有限公司 | A kind of radio-frequency sending coil impedance matching circuit and method |
-
1984
- 1984-09-17 JP JP59195450A patent/JPS6173061A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS6173061A (en) | 1986-04-15 |
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