JPH0542125A - Nuclear magnetic resonance device - Google Patents
Nuclear magnetic resonance deviceInfo
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- JPH0542125A JPH0542125A JP3200255A JP20025591A JPH0542125A JP H0542125 A JPH0542125 A JP H0542125A JP 3200255 A JP3200255 A JP 3200255A JP 20025591 A JP20025591 A JP 20025591A JP H0542125 A JPH0542125 A JP H0542125A
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- signal
- magnetic resonance
- nuclear magnetic
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Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、被検体中の水素や燐等
からの核磁気共鳴（以下、「ＮＭＲ」という）信号を測
定し、核の密度分布や緩和時間分布等を映像化する核磁
気共鳴装置に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention measures nuclear magnetic resonance (hereinafter referred to as "NMR") signals from hydrogen, phosphorus, etc. in an object to visualize nuclear density distribution and relaxation time distribution. The present invention relates to a nuclear magnetic resonance apparatus.
【０００２】[0002]
【従来の技術】従来、核磁気共鳴装置（以下ＭＲ装置と
呼ぶ）においては、被検体（例えば、人）の関心部位を
取り巻く各種の頭部用コイルや腹部用コイル、心臓等の
動きの影響を受けにくい表面コイル等を用い被検体の検
査、撮像が行われてきた。2. Description of the Related Art Conventionally, in a nuclear magnetic resonance apparatus (hereinafter referred to as an MR apparatus), various head coils or abdominal coils surrounding the region of interest of a subject (for example, a person), the influence of movement of the heart, etc. Examination and imaging of a subject have been performed by using a surface coil or the like that is hard to receive.
【０００３】上記表面コイルは、上記頭部用コイルや上
記腹部用コイルに比べ高感度であるが、視野が制限され
てしまい、脊椎等広範囲を検査する際には、上記表面コ
イルを移動させ、数回撮像せねばならず時間がかかると
いう問題が発生していた。Although the surface coil has higher sensitivity than the head coil and the abdominal coil, the field of view is limited, and the surface coil is moved when a wide area such as the spine is inspected. There has been a problem that it takes time to capture images several times.
【０００４】これに対して、複数個の表面コイルを各表
面コイルが隣接する表面コイルと相互結合しないよう適
度にオ−バラップさせて配列し、上記各表面コイルで受
信されたＮＭＲ信号を合成することにより実質的に視野
を広くする方法がある。この方法の原理については、特
表平２−５００１７５、特公平２−１３４３２号、ある
いはマグネティックレゾナンスインメディスン（ｍａｇ
ｎｅｔｉｃｒｅｓｏｎａｎｃｅ ｉｎ ｍｅｄｉｃｉｎ
ｅ）１６巻１９２頁から２２５頁（１９９０年）に記載
してある。On the other hand, a plurality of surface coils are arranged so as to be appropriately overlapped so that each surface coil does not mutually couple with an adjacent surface coil, and the NMR signals received by the surface coils are synthesized. Therefore, there is a method of substantially widening the field of view. The principle of this method is described in Japanese Patent Publication No. 2-500175, Japanese Patent Publication No. 2-3432, or Magnetic Resonance in Medicine (mag).
network resonance in medicin
e) 16 volumes 192 to 225 (1990).
【０００５】[0005]
【発明が解決しようとする課題】上記、従来の技術にお
いて、プローブ出力を単に合成して検出すると信号雑音
比（Ｓ／Ｎ）が向上しないことから、Ｓ／Ｎを上げるた
めに図１に示した従来例のごとく複数個のプローブ出力
をそれぞれ独自に検出しなければならなかった。そのた
め複数個の信号処理系が必要となり装置が複雑、かつ大
型、高額になるという問題があった。またプローブ出力
を時系列的に分割して１つの信号処理系で処理した場合
にはこれらの問題は解決できるものの撮像時間が長くな
るという問題が生じる。本発明はこのように複数個のプ
ローブ出力信号から画像を合成するＭＲ装置において、
Ｓ／Ｎが向上する信号合成方式を提案し、これを用いた
構成の簡単なＭＲ装置を提供することを目的とするもの
である。In the above-mentioned conventional technique, the signal-noise ratio (S / N) cannot be improved by simply combining and detecting the probe outputs. Moreover, as in the conventional example, it is necessary to independently detect a plurality of probe outputs. Therefore, a plurality of signal processing systems are required, and there is a problem that the device is complicated, large in size, and expensive. Further, when the probe output is divided in time series and processed by one signal processing system, although these problems can be solved, there is a problem that the imaging time becomes long. According to the present invention, in the MR device for synthesizing an image from a plurality of probe output signals as described above,
An object of the present invention is to propose a signal synthesizing method with improved S / N and to provide a simple MR device having the configuration using the signal synthesizing method.
【０００６】[0006]
【課題を解決するための手段】上記目的を達成する基本
的な特徴は、ＭＲ装置において、複数個の出力端を有す
る高周波プローブからの複数個の生体高周波信号を、各
々の出力に対応した複数個の増幅器で各々増幅後、該増
幅信号のそれぞれを周波数変換器により、互いに信号周
波数帯域が実質的に重ならない複数の周波数帯域の信号
に変換し、次に該それぞれの信号をそれぞれ帯域通過フ
ィルタによりフィルタリングし、その後該複数個の信号
を合成する手段を有することにある。The basic feature for achieving the above object is that in an MR apparatus, a plurality of biological high frequency signals from a high frequency probe having a plurality of output terminals are provided in a plurality of units corresponding to respective outputs. After being amplified by each of the amplifiers, each of the amplified signals is converted by the frequency converter into a signal of a plurality of frequency bands in which the signal frequency bands do not substantially overlap with each other, and then the respective signals are respectively band-pass filtered. And then combine the plurality of signals.
【０００７】[0007]
【作用】互いに信号周波数帯域が実質的に重ならない複
数の周波数帯域の信号に変換したのち、該それぞれの信
号をそれぞれ帯域通過フィルタによりフィルタリング
し、その後該複数個の信号を合成する手段を有するので
信号とノイズの分離が確実に行え、信号合成後のＳ／Ｎ
が劣化しない。The present invention has means for converting signals into a plurality of frequency bands whose signal frequency bands do not substantially overlap with each other, filtering the respective signals with a bandpass filter, and then synthesizing the plurality of signals. Signal and noise can be reliably separated, and S / N after signal synthesis
Does not deteriorate.
【０００８】[0008]
【実施例】以下、本発明を図１に示した実施例を用いて
詳細に説明する。本実施例は、複数個の出力端を有する
高周波プローブからの第１の周波数帯域群にある生体の
高周波信号を、各々の出力に対応した複数個の増幅器で
増幅後、それぞれを周波数変換する第１の複数個の周波
数変換器により第２の周波数帯域群にそれぞれの信号周
波数帯域が互いに実質的に重ならないように下げ、次に
複数の帯域通過フィルタにより該第２の周波数帯域群の
信号のそれぞれをフィルタリングし、その後該複数個の
信号を合成する手段を設けている。また該第２の周波数
帯域群の複数個の信号のそれぞれの中心周波数の相互の
隔たりが、該第１の周波数帯域群の複数個の信号のそれ
ぞれの中心周波数の相互の隔たりに比べ大きくなるよう
に設定している。The present invention will be described in detail below with reference to the embodiment shown in FIG. In the present embodiment, a high frequency signal of a living body in a first frequency band group from a high frequency probe having a plurality of output terminals is amplified by a plurality of amplifiers corresponding to respective outputs, and then frequency conversion is performed on each of them. A plurality of frequency converters to lower the signal frequency bands to the second frequency band group so that they do not substantially overlap each other, and then use a plurality of band pass filters to convert the signals of the second frequency band group. Means are provided for filtering each and then combining the plurality of signals. Further, the distance between the center frequencies of the plurality of signals in the second frequency band group is greater than the distance between the center frequencies of the plurality of signals in the first frequency band group. Is set to.
【０００９】図１は高周波プローブからの３個の出力信
号１−１〜１−３を同時に検出し合成する回路を示して
いる。ＭＲ装置の高周波プローブを構成するコイル１５
−１〜１５−３の出力信号１−１〜１−３は第１の信号
周波数をもち、これは生体原子核のラーモア周波数に正
確に一致する。ラーモア周波数はＭＲ装置の磁場強度と
生体中の注目している原子核で決まる。図２を用いてこ
れを説明する。垂直磁場方式のＭＲ装置を例にとると、
磁場強度は図示した静磁場（ｚ方向とする）の強度Ｈ０
と、静磁場と直交する方向ｘに強度分布をもつｚ方向磁
場を発生する傾斜磁場強度Ｈｇ（ｘ）の合成値である。
この時のラーモア周波数ｆは、 ｆ＝γ（Ｈｇ（ｘ）＋Ｈ０）／２π （１） である。γは原子核固有の磁気回転比でありプロトンで
は２６７ＭＨｚ／Ｔである。Ｈｇ（ｘ）は例えば視野中
心を０として傾きは一定であり、この傾きａは例えば
０．１ｍＴ／ｍ〜１０ｍＴ／ｍ（あるいは０．０１Ｇ／
ｃｍ〜１Ｇ／ｃｍ）程度である。ｘ方向の視野をＬとす
れば検出されるＭＲ信号の帯域Δｆは、 Δｆ＝γａＬ／２π （２） である。従って、例えば０．２Ｔの静磁場強度におい
て、比較的弱い傾斜磁場、例えば磁場強度０．５ｍＴ／
ｍを用いてプロトンを検出する場合、撮像視野を＋０．
３ｍ〜−０．３ｍ、計０．６ｍとすればＭＲ信号の周波
数は８．５ＭＨｚを中心として周波数帯域１２．７５ｋ
Ｈｚとなる。撮像視野を図２に示したようにコイル１５
−１〜１５−３の３個の表面コイルで等分して撮像する
場合、各コイルからの信号１−１〜１−３の中心周波数
は（１）式よりそれぞれ８．４９５７５ＭＨｚ、８．５
００００ＭＨｚ、８．５０４２５ＭＨｚである。また各
周波数帯域は（２）式より４．２５ｋＨｚである。すな
わち複数個のプローブの信号検出空間が異なるときには
対応する傾斜磁場強度がそれぞれ異なり検出する高周波
信号の周波数、第１の周波数、は各コイルで互いに僅か
に異なる。FIG. 1 shows a circuit for simultaneously detecting and synthesizing three output signals 1-1 to 1-3 from a high frequency probe. Coil 15 that constitutes the high frequency probe of the MR device
The output signals 1-1 to 1-3 of -1 to 15-3 have a first signal frequency, which exactly corresponds to the Larmor frequency of biological nuclei. The Larmor frequency is determined by the magnetic field strength of the MR device and the nucleus of interest in the living body. This will be described with reference to FIG. Taking a vertical magnetic field type MR device as an example,
The magnetic field strength is the strength H0 of the illustrated static magnetic field (in the z direction).
And a gradient magnetic field strength Hg (x) that generates a z-direction magnetic field having a strength distribution in a direction x orthogonal to the static magnetic field.
The Larmor frequency f at this time is f = γ (Hg (x) + H0) / 2π (1). γ is the gyromagnetic ratio peculiar to the nucleus, and is 267 MHz / T for protons. For example, Hg (x) has a constant inclination with the center of the field of view as 0, and this inclination a is, for example, 0.1 mT / m to 10 mT / m (or 0.01 G / m).
cm to 1 G / cm). If the visual field in the x direction is L, the band Δf of the MR signal detected is Δf = γaL / 2π (2). Therefore, for example, at a static magnetic field strength of 0.2 T, a relatively weak gradient magnetic field, for example, a magnetic field strength of 0.5 mT /
m to detect protons, the imaging field of view is +0.
If the total length is 3 m to -0.3 m, and the total is 0.6 m, the frequency of the MR signal is 12.75 k with a frequency band centering on 8.5 MHz.
It becomes Hz. As shown in FIG. 2, the field of view of the coil 15
When the image is equally divided by the three surface coils -1 to 15-3, the center frequencies of the signals 1-1 to 1-3 from the coils are 8.49575 MHz and 8.5, respectively, according to the equation (1).
0000 MHz and 8.50425 MHz. Further, each frequency band is 4.25 kHz according to the equation (2). That is, when the signal detection spaces of the plurality of probes are different, the corresponding gradient magnetic field strengths are different, and the frequency of the high-frequency signal to be detected and the first frequency are slightly different in each coil.
【００１０】以上では垂直磁場方式について説明した
が、水平磁場方式の場合についても検出信号の周波数に
ついて同様の説明ができることはいうまでもない。Although the vertical magnetic field method has been described above, it goes without saying that the same can be applied to the frequency of the detection signal in the case of the horizontal magnetic field method.
【００１１】図１に戻って、出力信号１−１〜１−３は
それぞれ増幅器２−１〜２−３で増幅される。典型的に
は増幅器のゲインは２０ｄＢから５０ｄＢ程度である。
増幅器の出力信号７−１〜７−３はそれぞれ第１の周波
数変換器３−１から３−３で第２の信号周波数の信号８
−１〜８−３に変換される。この第２の信号周波数は後
段の帯域通過フィルタの帯域と密接な関係を有し、本発
明ではこの周波数を、後述する該フィルタ帯域が容易に
取り扱える帯域になるように低い周波数にする。一例と
して高周波発生器１４の出力１２−１、１２−２、１２
−３の周波数をそれぞれ７．４００００ＭＨｚ、７．３
００００ＭＨｚ、７．２００００ＭＨｚとしこれらを周
波数変換器３−１から３−３の参照信号として入力する
とそれぞれ１．０９５７５ＭＨｚ、１．２００００ＭＨ
ｚ、１．３０４２５ＭＨｚの低周波信号が得られる。こ
の時に発生する約１６ＭＨｚの高調波は１ＭＨｚとは大
きく周波数が異なるので必要に応じて、良く知られたよ
うに低域通過フィルタ（図示していない）を用いて簡単
に除去できる。出力９−１から９−３の周波数帯域は、
信号１−１〜１−３の帯域に等しく（２）式より得られ
たように４．２５ｋＨｚである。しかしそれらの中心周
波数の差は第１の複数個の信号のそれぞれの中心周波数
の相互の隔たり（４．２５ｋＨｚ）に比べ１０４．２５
ｋＨｚと大きい。従ってそれぞれの信号に対して信号周
波数帯域以外の雑音を帯域通過フィルタ４−１から４−
３を用いて容易に除去できる。ここで雑音の除去は互い
に他の信号が存在する周波数帯域で除去できれば良いの
で、ゆるやかな特性の帯域フィルタ（１ＭＨｚにたいし
て１００ｋＨｚの分離でよい）を用いることが出来る。
帯域通過フィルタのＱ値は一般にｆ／Δｆで示される。
ここでｆは中心周波数、Δｆは周波数帯域である。本実
施例では、 Ｑ＝１ＭＨｚ／１０４．２５ｋＨｚ＝１０ （３） であり、例えば図３に示した帯域通過フィルタ回路のよ
うに一般に知られている技術で容易に作成できる。本実
施例では先に述べたように第２の周波数でのそれぞれの
信号の中心周波数の差が第１の複数個の信号のそれぞれ
の中心周波数の相互の隔たりに比べ十分大きいので、そ
れぞれの信号に対して信号周波数帯域以外の雑音を帯域
通過フィルタを用いて容易に除去できる。それぞれの中
心周波数の相互の隔たりが十分大きいので、（３）式で
与えられるＱ値が実現容易な値になっている。Returning to FIG. 1, the output signals 1-1 to 1-3 are amplified by the amplifiers 2-1 to 2-3, respectively. The gain of the amplifier is typically about 20 dB to 50 dB.
The output signals 7-1 to 7-3 of the amplifier are respectively output from the first frequency converters 3-1 to 3-3 by the signal 8 of the second signal frequency.
Converted to -1 to 8-3. This second signal frequency has a close relationship with the band of the band pass filter in the subsequent stage, and in the present invention, this frequency is set to a low frequency so that the filter band described later can be easily handled. As an example, the outputs 12-1, 12-2, 12 of the high frequency generator 14
-3 frequencies of 7.40000 MHz and 7.3, respectively.
If 0000 MHz and 7.20000 MHz are set and these are input as the reference signals of the frequency converters 3-1 to 3-3, they are 1.09575 MHz and 1.20000 MH, respectively.
A low frequency signal of z, 1.30425 MHz is obtained. Since the harmonics of about 16 MHz generated at this time have a frequency greatly different from 1 MHz, they can be easily removed as necessary by using a low-pass filter (not shown) as well known. The frequency bands of outputs 9-1 to 9-3 are
It is equal to the bands of the signals 1-1 to 1-3 and is 4.25 kHz as obtained from the equation (2). However, the difference in their center frequencies is 104.25 compared to the mutual separation (4.25 kHz) of the respective center frequencies of the first plurality of signals.
It is as large as kHz. Therefore, noise other than the signal frequency band is applied to each signal by the bandpass filters 4-1 to 4-
3 can be easily removed. Here, since it is sufficient to remove noise in a frequency band in which other signals exist, it is possible to use a band-pass filter having a gentle characteristic (separation of 100 kHz is sufficient for 1 MHz).
The Q value of the bandpass filter is generally represented by f / Δf.
Here, f is the center frequency, and Δf is the frequency band. In this embodiment, Q = 1 MHz / 104.25 kHz = 10 (3), which can be easily created by a generally known technique such as the bandpass filter circuit shown in FIG. In the present embodiment, as described above, the difference between the center frequencies of the respective signals at the second frequency is sufficiently larger than the distance between the respective center frequencies of the first plurality of signals, so that the respective signals On the other hand, noise outside the signal frequency band can be easily removed by using a bandpass filter. Since the respective center frequencies are sufficiently separated from each other, the Q value given by the equation (3) is a value that is easy to realize.
【００１２】以上の説明で第２の周波数は約１ＭＨｚで
あったが、これは本発明の趣旨の範囲で変更でき、例え
ば２０ｋＨｚ程度まで下げることも可能である。この時
のフィルタはよりゆるやかなフィルタ特性で良く実現が
容易である。In the above description, the second frequency is about 1 MHz, but this can be changed within the scope of the present invention, and it can be lowered to about 20 kHz, for example. The filter at this time has a gentler filter characteristic and is easy to realize.
【００１３】再び図１に戻って説明する。帯域通過フィ
ルタ４−１から４−３によりフィルタリングされた第２
の周波数の信号９−１から９−３は、合成器６で合成さ
れる。この結果合成された信号１１は周波数帯域が約１
ＭＨｚから１．３ＭＨｚの信号となる。合成信号の周波
数あたりのノイズは十分に小さく信号合成によるノイズ
の増大は無い。これは合成される信号群９−１から９−
３が、既に帯域通過フィルタ群４−１から４−３により
おのおの不要領域のノイズ除去がされているためであ
る。Returning to FIG. 1, the description will be continued. Second filtered by band pass filter 4-1 to 4-3
The signals 9-1 to 9-3 having the frequencies of are combined by the combiner 6. As a result, the synthesized signal 11 has a frequency band of about 1
Signals from MHz to 1.3 MHz are obtained. The noise per frequency of the combined signal is sufficiently small and there is no increase in noise due to the signal combination. This is the combined signal group 9-1 to 9-
3 is because the noises in the unnecessary regions have already been removed by the bandpass filter groups 4-1 to 4-3.
【００１４】すなわち、例えば、合成をアナログ的に行
っても信号のＳ／Ｎ比は良好である。従って、図には示
していないが、合成後の信号は１つのＡ／Ｄ変換器でア
ナログ／デジタル変換出来、そのデジタル信号は各種デ
ジタル信号処理されることが可能である。この場合、Ａ
／Ｄ変換器の数を従来例に比べて著しく削減でき装置が
小型化、低価格化できる。That is, for example, the S / N ratio of the signal is good even if the synthesis is performed in an analog manner. Therefore, although not shown in the figure, the combined signal can be analog / digital converted by one A / D converter, and the digital signal can be processed by various digital signals. In this case, A
The number of D / D converters can be significantly reduced compared to the conventional example, and the device can be downsized and the cost can be reduced.
【００１５】即ち、本実施例においてＡ／Ｄ変換器の個
数はコイル出力端の個数をｎとしたとき通常の検出でｎ
個未満でよい。また１つの出力にたいして実部と虚部に
それぞれ１個づつのＡ／Ｄ変換器が必要な直交位相検波
方式に本実施例の構成を用いた場合、Ａ／Ｄ変換器の個
数は２ｎ個未満でよい。That is, in the present embodiment, the number of A / D converters is n in the normal detection when the number of coil output terminals is n.
It may be less than the number. Further, when the configuration of the present embodiment is used for the quadrature phase detection method that requires one A / D converter for each real part and one imaginary part for one output, the number of A / D converters is less than 2n. Good.
【００１６】また該増幅後の信号を直ちにアナログデジ
タル変換すれば第１のフィルタリングにデジタルフィル
タの技術を利用できる。If the signal after the amplification is immediately converted into an analog signal, the digital filtering technique can be used for the first filtering.
【００１７】さらに該フィルタリングの後の該信号合成
のあと、合成された信号を更にフィルタリングする第２
のフィルタリング手段を有することにより信号成分を任
意に重み付けすることが出来、画像信号の合成の自由度
が増し均一な画像を得られる。この第２のフィルタリン
グ手段としてデジタルフィルタを用いることができる。A second step of further filtering the combined signal after the signal combining after the filtering
With the above filtering means, the signal components can be arbitrarily weighted, the degree of freedom in combining the image signals is increased, and a uniform image can be obtained. A digital filter can be used as the second filtering means.
【００１８】次にＭＲ装置の構造のブロック図、図４、
を用いて高周波発生器と帯域通過フィルタの制御方法を
説明する。被写体１６は静磁場発生部２３で動作される
磁石１９の作る静磁場中に配置される。また傾斜磁場コ
イル１８は傾斜磁場発生部２４により、励起高周波コイ
ル１７は励起高周波パルス発生部２１によりそれぞれ傾
斜磁場、高周波磁場を発生し、被写体に作用する。複数
個のコイルからなるコイル部１５は被写体からの高周波
磁場信号（ＭＲ信号）を受信する。この信号は図２の１
から１４でなる高周波信号処理合成部２０で処理合成さ
れその後信号処理部２２で画像処理や信号補正され表示
部２５でＭＲ画像（ＭＲＩやＭＲＳ、ＭＲＩＳなど）が
表示される。静磁場発生部２３、傾斜磁場発生部２４、
励起高周波パルス発生部２１、高周波信号処理合成部２
０、信号処理部２２、表示部２５は制御部２６で制御さ
れる。とくに制御部２６では傾斜磁場強度と高周波信号
処理時のパラメータを前述のように相互に最適化し制御
する。すなわち一般に傾斜磁場強度は本発明のフィルタ
以外の要因、例えば撮像シーケンスや撮像速度、視野に
より決定されるので、選択された傾斜磁場強度と視野に
したがって本発明で述べた高周波信号処理部のパラメー
タ、例えば帯域通過フィルタの帯域幅や中心周波数、高
周波発生器の信号周波数などを任意に設定することが可
能である。この場合フィルタには可変帯域のフィルタを
用いたり、フィルタを各チャンネルごとに複数個設けて
適宜切り替えても良い。Next, a block diagram of the structure of the MR device, FIG.
A method of controlling the high frequency generator and the bandpass filter will be described using. The subject 16 is placed in the static magnetic field created by the magnet 19 operated by the static magnetic field generator 23. Further, the gradient magnetic field coil 18 generates a gradient magnetic field and the excitation high frequency pulse generator 21 generates a gradient magnetic field and a high frequency magnetic field, respectively, which act on the subject. The coil unit 15 including a plurality of coils receives a high frequency magnetic field signal (MR signal) from a subject. This signal is 1 in FIG.
1 to 14 are processed and synthesized by the high frequency signal processing and synthesizing unit 20 and then image processing and signal correction are performed by the signal processing unit 22 and an MR image (MRI, MRS, MRIS, etc.) is displayed on the display unit 25. Static magnetic field generation unit 23, gradient magnetic field generation unit 24,
Excitation high-frequency pulse generator 21, high-frequency signal processing synthesizer 2
0, the signal processing unit 22, and the display unit 25 are controlled by the control unit 26. In particular, the control unit 26 mutually optimizes and controls the gradient magnetic field strength and the parameter at the time of high frequency signal processing. That is, in general, the gradient magnetic field strength is determined by factors other than the filter of the present invention, for example, the imaging sequence, the imaging speed, and the field of view, so the parameters of the high-frequency signal processing unit described in the present invention according to the selected gradient magnetic field strength and the field of view, For example, it is possible to arbitrarily set the band width and center frequency of the band pass filter, the signal frequency of the high frequency generator, and the like. In this case, a variable band filter may be used as the filter, or a plurality of filters may be provided for each channel and switched appropriately.
【００１９】本実施例で使われるコイルは例えばフェイ
ズドアレイコイルを用いることができる。また鞍型コイ
ル、バードケージコイル、スロッテドチューブレゾネー
タコイルなどに適用可能である。As the coil used in this embodiment, for example, a phased array coil can be used. It is also applicable to saddle type coils, birdcage coils, slotted tube resonator coils and the like.
【００２０】以上の説明では垂直磁場方式を例に採り、
説明したが水平磁場方式でも本発明が適用されることは
明らかである。また０．２Ｔの磁場強度で説明したが本
発明は他の磁場強度でも適用できる。傾斜磁場強度につ
いても実施例で記載した以外の強度についても適用でき
る。更にＭＲ装置の構成図は一実施例であり他の構成で
も本発明が適用できる。In the above description, the vertical magnetic field system is taken as an example,
Although described, it is clear that the present invention can be applied to the horizontal magnetic field method. Further, although the magnetic field strength of 0.2T has been described, the present invention can be applied to other magnetic field strengths. The gradient magnetic field strength can also be applied to strengths other than those described in the examples. Furthermore, the configuration diagram of the MR device is an example, and the present invention can be applied to other configurations.
【００２１】本実施例の効果は、低周波信号のそれぞれ
を複数の帯域通過フィルタによりフィルタリング処理す
る際、該複数個の信号のそれぞれの中心周波数の相互の
隔たりが大きいのでフィルタの特性が最適でなくとも信
号とノイズの分離が確実に行え、信号加算後のＳ／Ｎが
劣化しないことである。The effect of this embodiment is that when the low-frequency signals are filtered by a plurality of band-pass filters, the center frequencies of the plurality of signals are largely separated from each other, so that the filter characteristics are optimal. It is necessary to surely separate the signal and the noise, and the S / N after the signal addition is not deteriorated.
【００２２】次に第２の実施例を開示する。図５は本発
明をクォードラチャデテクション（ＱＤ）プローブの信
号合成に適用した一例である。Next, a second embodiment will be disclosed. FIG. 5 is an example in which the present invention is applied to signal synthesis of a quadrature detection (QD) probe.
【００２３】ＱＤプローブのＡポート及びＢポートから
の出力は互いにほぼ９０度ずれている。これらの出力信
号はそれぞれ前置増幅器２−Ａ、２−Ｂで増幅されたあ
と、位相シフタ５−Ａと位相シフタ５−Ｂで相互の位相
が適当にずれるように微調整される。ここでＡとＢの出
力の周波数帯域は、ＭＲＩ画像の視野と傾斜磁場強度か
ら決まりともに等しい。これらの等しい周波数帯域の信
号のうち片方の出力、ここではＢの出力をシンセサイザ
と混合器及び帯域フィルタからなる周波数変換器３を用
いて周波数変換する。Ａポートの出力と周波数変換され
たＢポートの出力を、それぞれ信号帯域以外のノイズを
除去する目的で帯域フィルタ４−Ａ、４−Ｂにそれぞれ
通し、加算器５６で信号合成する。合成は例えば抵抗合
成のような固定された重み付け合成で良い。合成後の信
号はＡＤ変換器によりサンプリング５８とＡＤ変換６０
の処理を受け、フーリエ変換器６２でフーリエ変換され
る。ＡポートとＢポートの信号はフーリエ変換後のデー
タでは異なる周波数帯域に現れるので容易に分離でき
る。ポートごとに分離されたデータ６４と６６ははそれ
ぞれの重み付け手段６８と７０により関数Ｇａ（ｋｚ）
とＧｂ（ｋｚ）で重み付けされる。更に合成器７２で
は、Ｂデータについて位相シフトによりＡデータと同一
の周波数帯域に移動し、Ａデータと合成して画像データ
７４を得る。本方式では両ポートの信号が合成されたあ
とにＡＤ変換が行われるので検出系が単純でその規模も
小さい。また直交位相検波の適用も容易であるなどの特
徴を持つ。この方式のＱＤプローブは従来方式のＱＤプ
ローブと異なりそれぞれのポートの信号をＡＤ変換後も
周波数的に分離した状態で有するため、ローデータ、ま
たは画像データ上での任意の重み付けや位相補正を個別
に行った後加算できる。従って均一な画像を容易に得る
ことが出きる。The outputs from the A and B ports of the QD probe are offset from each other by approximately 90 degrees. These output signals are amplified by the preamplifiers 2-A and 2-B, respectively, and then finely adjusted by the phase shifter 5-A and the phase shifter 5-B so that their mutual phases are appropriately shifted. Here, the frequency bands of the outputs of A and B are determined from the field of view of the MRI image and the gradient magnetic field strength and are equal. One of the outputs of these signals in the same frequency band, that is, the output of B, is frequency-converted using the frequency converter 3 including a synthesizer, a mixer, and a bandpass filter. The output of the A port and the frequency-converted output of the B port are respectively passed through bandpass filters 4-A and 4-B for the purpose of removing noise other than the signal band, and the adder 56 synthesizes the signals. The combination may be a fixed weighted combination such as resistance combination. The combined signal is sampled 58 and AD converted 60 by an AD converter.
And the Fourier transform is performed by the Fourier transformer 62. The signals of the A port and the B port appear in different frequency bands in the data after the Fourier transform, so they can be easily separated. The data 64 and 66 separated for each port are given a function Ga (kz) by weighting means 68 and 70, respectively.
And Gb (kz). Further, in the combiner 72, the B data is moved to the same frequency band as the A data by the phase shift, and is combined with the A data to obtain the image data 74. In this method, since the AD conversion is performed after the signals of both ports are combined, the detection system is simple and its scale is small. In addition, it is easy to apply quadrature detection. Unlike the conventional QD probe, this type of QD probe has the signals of each port in a frequency separated state even after AD conversion. Therefore, arbitrary weighting or phase correction on raw data or image data can be performed individually. You can add after going to. Therefore, a uniform image can be easily obtained.
【００２４】[0024]
【発明の効果】本発明に依れば、複数個の出力端を有す
る高周波プローブからの複数個の生体高周波信号を用い
てＭＲ画像を得る核磁気共鳴装置において、該信号を互
いに信号周波数帯域が実質的に重ならない複数の周波数
帯域の信号に変換したにち、該それぞれの信号をそれぞ
れ帯域通過フィルタによりフィルタリングし、その後該
複数個の信号を合成する手段を有するので信号とノイズ
の分離が確実に行え、信号合成後のＳ／Ｎが劣化しな
い。According to the present invention, in a nuclear magnetic resonance apparatus for obtaining an MR image using a plurality of biological high-frequency signals from a high-frequency probe having a plurality of output ends, the signals are provided in a signal frequency band of each other. After the signals are converted into signals in a plurality of frequency bands that do not substantially overlap, each of the signals is filtered by a band pass filter, and then the plurality of signals are combined, so that separation of the signal and the noise is ensured. Therefore, the S / N after signal combination does not deteriorate.
【図１】本発明の１実施例の主要部を示すブロック図。FIG. 1 is a block diagram showing a main part of one embodiment of the present invention.
【図２】実施例の各コイル出力の周波数を示す概念図。FIG. 2 is a conceptual diagram showing the frequency of each coil output of the embodiment.
【図３】実施例の帯域通過フィルタの回路図。FIG. 3 is a circuit diagram of a bandpass filter according to an embodiment.
【図４】実施例の装置全体構成を示すブロック図。FIG. 4 is a block diagram showing the overall configuration of the apparatus of the embodiment.
【図５】本発明の別の実施例を示すブロック図。FIG. 5 is a block diagram showing another embodiment of the present invention.
１−１〜１−３…高周波プローブの出力、２−１〜２−
３…増幅機、３−１〜３−３…周波数変換器、４−１〜
４−３…帯域通過フィルタ、６…合成器1-1 to 1-3 ... Output of high frequency probe, 2-1 to 2-
3 ... Amplifier, 3-1 to 3-3 ... Frequency converter, 4-1 to
4-3 ... band pass filter, 6 ... combiner
───────────────────────────────────────────────────── フロントページの続き (72)発明者 松永 良国 東京都国分寺市東恋ケ窪１丁目280番地 株式会社日立製作所中央研究所内 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ryokuni Matsunaga 1-280, Higashi Koikekubo, Kokubunji, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd.
Claims (9)
らの複数個の生体高周波信号を各々の出力に対応した複
数個の増幅器で各々増幅後、増幅信号のそれぞれを周波
数変換器により互いに信号周波数帯域が実質的に重なら
ない複数の周波数帯域の信号に変換し、次にそれぞれの
信号をそれぞれ帯域通過フィルタによりフィルタリング
し、その後該複数個の信号を合成する信号合成手段を有
する核磁気共鳴装置。1. A plurality of biological high-frequency signals from a high-frequency probe having a plurality of output terminals are respectively amplified by a plurality of amplifiers corresponding to respective outputs, and then the amplified signals are frequency-converted by a frequency converter. A nuclear magnetic resonance apparatus having signal synthesizing means for converting signals into a plurality of frequency bands whose bands do not substantially overlap each other, filtering the respective signals with a bandpass filter, and then synthesizing the plurality of signals.
理するものであり、れ且つ、該信号合成手段の合成出力
をアナログデジタル変換するアナログデジタル変換器を
有することを特徴とする請求項１の核磁気共鳴装置。2. The signal synthesizing means processes a signal in an analog manner, and has an analog-digital converter for analog-digital converting the synthesized output of the signal synthesizing means. Nuclear magnetic resonance apparatus.
高周波プローブの出力端の個数をｎとしたとき前記アナ
ログデジタル変換器の個数がｎ未満であることを特徴と
する核磁気共鳴装置。3. The nuclear magnetic resonance apparatus according to claim 2, wherein the number of the analog-digital converters is less than n when the number of output terminals of the high frequency probe is n.
イルの出力端の個数をｎとしたとき前記アナログデジタ
ル変換器の個数が２ｎ未満である直交位相検波方式の高
周波検出系を有する核磁気共鳴装置。4. The nuclear magnetic resonance apparatus according to claim 2, which has a quadrature phase detection type high frequency detection system in which the number of the analog-digital converters is less than 2n, where n is the number of output terminals of the coil. Magnetic resonance device.
らの第１の周波数帯域群にある生体の高周波信号を、各
々の出力に対応した複数個の増幅器で増幅後、それぞれ
を周波数変換する第１の複数個の周波数変換器により第
２の周波数帯域群にそれぞれの信号周波数帯域が互いに
実質的に重ならないように下げ、次に複数の帯域通過フ
ィルタにより該第２の周波数帯域群の信号のそれぞれを
フィルタリングし、その後該複数個の信号を合成する信
号合成手段を有することを特徴とする核磁気共鳴装置。5. A high-frequency signal of a living body in a first frequency band group from a high-frequency probe having a plurality of output terminals is amplified by a plurality of amplifiers corresponding to respective outputs and then frequency-converted. A plurality of frequency converters to lower the signal frequency bands to the second frequency band group so that they do not substantially overlap each other, and then use a plurality of band pass filters to convert the signals of the second frequency band group. A nuclear magnetic resonance apparatus comprising a signal synthesizing means for filtering each of them and then synthesizing the plurality of signals.
それぞれの中心周波数の相互の隔たりが、該第１の周波
数帯域群の複数個の信号のそれぞれの中心周波数の相互
の隔たりに比べ大きいことを特徴とする請求項５の核磁
気共鳴装置。6. The distance between the center frequencies of the plurality of signals in the second frequency band group is the distance between the center frequencies of the plurality of signals in the first frequency band group. The nuclear magnetic resonance apparatus according to claim 5, wherein the nuclear magnetic resonance apparatus is large in comparison.
信号合成手段の合成出力信号を更にフィルタリングする
フィルタリング手段を有することを特徴とする核磁気共
鳴装置。7. The nuclear magnetic resonance apparatus according to claim 5, further comprising filtering means for further filtering the combined output signal of the signal combining means.
複数の帯域通過フィルタもしくは前記合成出力信号を更
にフィルタリングするフィルタリング手段としてデジタ
ルフィルタを用いることを特徴とする核磁気共鳴装置。8. The nuclear magnetic resonance apparatus according to claim 7, wherein a digital filter is used as a filtering means for further filtering the plurality of band pass filters or the combined output signal.
空間内におかれた被検体に、高周波磁場を照射し、該被
検体の核磁気共鳴信号を発生させ、これをｘ方向とｙ方
向の直線高周波磁場検出コイルを組み合わせてｘ、ｙ平
面上の回転高周波磁場を検出する核磁気共鳴装置におい
て、該ｘ方向とｙ方向の直線高周波磁場検出コイルの受
信信号をそれぞれ増幅器により増幅し、ｘ方向若しくは
ｙ方向の増幅後の出力を周波数変換し互いに異なる周波
数帯域の信号としたのちに合成し、アナログデジタル変
換し、これらの異なる周波数帯域の信号をそれぞれ任意
の重み付け関数で重み付けした後、さらにｘ方向若しく
はｙ方向の信号を再び周波数変換し互いに同一の周波数
帯域の信号として合成する手段を有する核磁気共鳴装
置。9. An x, y, z in which a static magnetic field exists in the z direction.
A high frequency magnetic field is applied to a subject placed in a space to generate a nuclear magnetic resonance signal of the subject, which is combined with linear high frequency magnetic field detection coils in the x direction and the y direction on the x, y plane. In a nuclear magnetic resonance apparatus that detects a rotating high-frequency magnetic field, the received signals of the linear high-frequency magnetic field detecting coils in the x-direction and the y-direction are respectively amplified by an amplifier, and the outputs after the amplification in the x-direction or the y-direction are frequency-converted to be different from each other. After the signals in the frequency band are combined, the signals are analog-to-digital converted, the signals in these different frequency bands are weighted by arbitrary weighting functions, and then the signals in the x-direction or y-direction are frequency-converted again to make them identical to each other. A nuclear magnetic resonance apparatus having means for synthesizing as a signal in a frequency band.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3200255A JP2555233B2 (en) | 1991-08-09 | 1991-08-09 | Nuclear magnetic resonance equipment |
| US07/793,456 US5280246A (en) | 1990-11-16 | 1991-11-18 | Nuclear magnetic resonance apparatus |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3200255A JP2555233B2 (en) | 1991-08-09 | 1991-08-09 | Nuclear magnetic resonance equipment |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0542125A true JPH0542125A (en) | 1993-02-23 |
| JP2555233B2 JP2555233B2 (en) | 1996-11-20 |
Family
ID=16421334
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP3200255A Expired - Fee Related JP2555233B2 (en) | 1990-11-16 | 1991-08-09 | Nuclear magnetic resonance equipment |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2555233B2 (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2002143122A (en) * | 2000-11-09 | 2002-05-21 | Toshiba Corp | Magnetic resonance imaging equipment and method for collecting and processing mr signal |
| JP2008522651A (en) * | 2004-12-06 | 2008-07-03 | コーニンクレッカ フィリップス エレクトロニクス エヌ ヴィ | Method and apparatus for connecting receive coils in a magnetic resonance imaging scanner |
| US7400148B2 (en) | 2005-03-23 | 2008-07-15 | Kabushiki Kaisha Toshiba | MRI apparatus, signal selection method in MRI apparatus, and MRI method in magnetic resonance imaging apparatus |
| CN102200569A (en) * | 2010-03-23 | 2011-09-28 | 西门子公司 | Transmission method for magnetic resonance signal with dual frequency conversion |
-
1991
- 1991-08-09 JP JP3200255A patent/JP2555233B2/en not_active Expired - Fee Related
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2002143122A (en) * | 2000-11-09 | 2002-05-21 | Toshiba Corp | Magnetic resonance imaging equipment and method for collecting and processing mr signal |
| JP2008522651A (en) * | 2004-12-06 | 2008-07-03 | コーニンクレッカ フィリップス エレクトロニクス エヌ ヴィ | Method and apparatus for connecting receive coils in a magnetic resonance imaging scanner |
| US7400148B2 (en) | 2005-03-23 | 2008-07-15 | Kabushiki Kaisha Toshiba | MRI apparatus, signal selection method in MRI apparatus, and MRI method in magnetic resonance imaging apparatus |
| CN102200569A (en) * | 2010-03-23 | 2011-09-28 | 西门子公司 | Transmission method for magnetic resonance signal with dual frequency conversion |
Also Published As
| Publication number | Publication date |
|---|---|
| JP2555233B2 (en) | 1996-11-20 |
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