JPS6323785B2 - - Google Patents
Info
- Publication number
- JPS6323785B2 JPS6323785B2 JP56078973A JP7897381A JPS6323785B2 JP S6323785 B2 JPS6323785 B2 JP S6323785B2 JP 56078973 A JP56078973 A JP 56078973A JP 7897381 A JP7897381 A JP 7897381A JP S6323785 B2 JPS6323785 B2 JP S6323785B2
- Authority
- JP
- Japan
- Prior art keywords
- magnetic field
- static magnetic
- nuclear
- magnetic resonance
- linear 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
Links
- 230000003068 static effect Effects 0.000 claims description 37
- 238000005481 NMR spectroscopy Methods 0.000 claims description 26
- 238000005259 measurement Methods 0.000 claims description 25
- 238000003745 diagnosis Methods 0.000 claims description 5
- 238000012937 correction Methods 0.000 claims description 4
- 238000001514 detection method Methods 0.000 claims description 2
- 230000006698 induction Effects 0.000 claims description 2
- 230000005311 nuclear magnetism Effects 0.000 claims 1
- 239000000725 suspension Substances 0.000 claims 1
- 230000005284 excitation Effects 0.000 description 10
- 239000001257 hydrogen Substances 0.000 description 6
- 229910052739 hydrogen Inorganic materials 0.000 description 6
- 238000010586 diagram Methods 0.000 description 5
- 239000000523 sample Substances 0.000 description 5
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 4
- 150000002431 hydrogen Chemical class 0.000 description 4
- 230000002123 temporal effect Effects 0.000 description 3
- 230000000694 effects Effects 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000002223 garnet Substances 0.000 description 1
- 239000001307 helium Substances 0.000 description 1
- 229910052734 helium Inorganic materials 0.000 description 1
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
- 239000010421 standard material Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
- 230000001131 transforming effect Effects 0.000 description 1
Landscapes
- Magnetic Resonance Imaging Apparatus (AREA)
Description
【発明の詳細な説明】
(1) 発明の属する分野
本発明は、核磁気共鳴（以下「NMR」と称す
る）現象を利用して、生体内各組織の特定原子核
密度分布を被検体外部より無浸襲に測定し、医学
的診断のための情報を得る診断用NMR装置に関
するものである。[Detailed Description of the Invention] (1) Field of the Invention The present invention utilizes the phenomenon of nuclear magnetic resonance (hereinafter referred to as "NMR") to detect the density distribution of specific atomic nuclei in various tissues in a living body from outside the subject. The present invention relates to a diagnostic NMR device that performs invasive measurements to obtain information for medical diagnosis.
(2) 従来技術およびその問題点
NMR装置は、静磁場に対応したラジオ波周波
数での原子核の共鳴を測定する装置であり、特定
原子核（一般には水素原子核の場合が多い）分布
の高精度の測定が可能である。このため測定に使
用する静磁場としても高安定なものが必要とされ
る。すなわちNMRの測定中に印加している静磁
場が変動すると共鳴周波数がずれるため、測定誤
差が生ずる。このため、高安定な磁石用電源を用
い、且つ磁石本体および測定環境の温度制御を行
なうだけでなく、磁場を直接測定して、フイード
バツク制御を行なつている。磁場の測定方法とし
ては、NMR現象を用いるのが最適であり、理化
学用のNMR装置においては一部利用されている
が、生体の水素原子核等の密度分布像を得る診断
用NMR装置では、従来、次のような理由で
NMRによる磁場の測定が行なわれていなかつ
た。(2) Prior art and its problems NMR equipment is a device that measures the resonance of atomic nuclei at a radio frequency corresponding to a static magnetic field, and it measures the distribution of specific atomic nuclei (usually hydrogen nuclei) with high precision. Measurement is possible. Therefore, a highly stable static magnetic field is required for measurement. That is, if the static magnetic field applied during NMR measurement fluctuates, the resonance frequency shifts, resulting in measurement errors. For this reason, in addition to using a highly stable magnet power source and controlling the temperature of the magnet body and the measurement environment, the magnetic field is directly measured to perform feedback control. The best way to measure magnetic fields is to use the NMR phenomenon, and it is used in some physical and chemical NMR devices, but diagnostic NMR devices that obtain density distribution images of hydrogen nuclei in living organisms, etc. , for the following reasons
No magnetic field measurements were made using NMR.
(i) 密度分布測定領域等を特定するため線型傾斜
磁場を静磁場に重ねているため、位置により共
鳴周波数が異なり、NMR信号の周波数がある
幅をもつて拡がるため、静磁場の変動を明確に
は識別することができない。(i) Since a linear gradient magnetic field is superimposed on the static magnetic field to specify the density distribution measurement area, etc., the resonance frequency differs depending on the position, and the frequency of the NMR signal spreads over a certain range, making it possible to clearly identify the fluctuations in the static magnetic field. cannot be identified.
(ii) 対象原子核を水素以外とすると、被検体内に
異物（磁場測定用標準物質）を挿入しなければ
ならず、事実上測定中の磁場測定は行なえな
い。(ii) If the target atomic nucleus is other than hydrogen, a foreign object (standard material for magnetic field measurement) must be inserted into the subject, and magnetic field measurement cannot be performed during the actual measurement.
(iii) 対象原子核を水素とした場合には、測定画像
情報と同じ原子核を対象にしているので、同時
測定はできない。(iii) When the target atomic nucleus is hydrogen, simultaneous measurements are not possible because the target is the same nucleus as the measurement image information.
このため、例えば、特開昭54−156597号公報に
示された技術においては、別途にYIG（イツトリ
ウム―鉄―ガーネツト）同調発振器を磁場測定器
として用いている。 For this reason, for example, in the technique disclosed in Japanese Unexamined Patent Publication No. 156597/1984, a YIG (yttrium-iron-garnet) tuned oscillator is separately used as a magnetic field measuring device.
一方、超伝導磁石を永久モードで用いれば、磁
場の時間的変動はほとんど生じないが、現状では
磁石が高価になりすぎ、また常時液体ヘリウムで
冷却する必要があるため、構成が複雑でしかも保
守が容易でないなどの問題がある。 On the other hand, if superconducting magnets are used in permanent mode, there will be almost no temporal fluctuations in the magnetic field, but currently the magnets are too expensive and need to be constantly cooled with liquid helium, making the configuration complex and maintenance difficult. There are problems such as it is not easy.
(3) 本発明の目的
本発明は、比較的簡単な構成で静磁場の時間的
変動を効果的に補正し得る診断用NMR装置を提
供することを目的としている。(3) Purpose of the present invention The purpose of the present invention is to provide a diagnostic NMR apparatus that can effectively correct temporal fluctuations in a static magnetic field with a relatively simple configuration.
(4) 発明の概要
本発明は、一様静磁場に線型傾斜磁場を重ねて
被検体に印加し前記線型傾斜磁場を制御して前記
被検体に対する面状の投影部分および投影方向を
選択しつつ前記投影方向を逐次変更して前記被検
体のNMR信号を測定して前記面状の部分につい
ての多方向の特定原子核密度分布の投影情報を
得、この投影情報に基づいて前記被検体内の前記
面状の部分における特定原子核密度分布像を再構
成する診断用NMR装置において、前記被検体に
印加する一様静磁場を補正するための補助コイル
と、前記線型傾斜磁場の印加を停止させる手段
と、この手段により前記線型傾斜磁場が除去され
たときの前記一様静磁場中におけるNMRの検出
信号から自由誘導減衰（以下「FID」と称する）
信号の周波数を計測する周波数計測手段と、この
周波数計測手段の計測値を設定値と比較しこれら
の差に応じた出力を得る比較手段と、この比較手
段の出力に応じた電流を前記補助コイルに印加す
る電源回路とを具備し、投影情報収集の休止期間
に静磁場の変動を計測補正し、常に一定の静磁場
を得るものである。(4) Summary of the Invention The present invention involves applying a linear gradient magnetic field superimposed on a uniform static magnetic field to a subject, and controlling the linear gradient magnetic field to select a planar projection portion and projection direction on the subject. The projection direction is sequentially changed and the NMR signal of the object is measured to obtain projection information of the specific nuclear density distribution in multiple directions for the planar portion, and based on this projection information, the NMR signal in the object is measured. A diagnostic NMR apparatus for reconstructing a specific atomic nucleus density distribution image in a planar area, comprising: an auxiliary coil for correcting a uniform static magnetic field applied to the object; and means for stopping application of the linear gradient magnetic field. , Free induction decay (hereinafter referred to as "FID") is obtained from the NMR detection signal in the uniform static magnetic field when the linear gradient magnetic field is removed by this means.
A frequency measuring means for measuring the frequency of the signal, a comparing means for comparing the measured value of the frequency measuring means with a set value and obtaining an output according to the difference between them, and a current according to the output of the comparing means to be connected to the auxiliary coil. The device is equipped with a power supply circuit that applies power to the magnetic field, and measures and corrects fluctuations in the static magnetic field during the pause period of projection information collection to obtain a constant static magnetic field at all times.
(5) 発明の実施例
本発明の一実施例の構成図を第１図に示す。第
１図において、１は４個のコイルからなる電磁石
コイルであり、この電磁石コイル１により一様静
磁場をつくる。２はその電源である。３は前記静
磁場に沿う方向（Ｚ方向）に線型傾斜磁場をつく
る傾斜磁場用コイルであり、対をなすヘルムホル
ツ型コイルに逆方向に電流を流して傾斜磁場をつ
くるようにしている。４はその電源であり、この
電源４からコイル３に流す電流値は、デイジタル
計算機５により制御される。６は前記静磁場方向
（Ｚ方向）に沿い且つその方向に垂直な方向（ｘ
―ｙ方向）に傾斜する線型傾斜磁場をつくるため
のコイルであり、７はその電源で、電源４と同様
にデイジタル計算機５により制御される。８は励
起パルス（選択励起パルスおよび90゜パルス）を
発生する発振器であり、９は発振器８からの励起
パルスの送出とNMR信号の受信とを行なうデユ
プレクサである。１０はデユプレクサ９に接続さ
れ被検体に高周波磁場（励起パルス）をかけると
ともに被検体からNMR信号を検出するプローブ
ヘツドである。１１は検出NMR信号のFID信号
を増幅する増幅器である。前記デイジタル計算機
５はFID信号をＡ／Ｄ（アナログ―デイジタル）
変換し、記録積算した後に、これをフーリエ変換
して投影情報を得るとともに、さらにこの投影情
報から再構成像をつくる。１２はデイジタル計算
機５において得られた画像を表示する表示器であ
る。１３は各投影情報を得るための計測動作の合
い間に、線型傾斜磁場を止め、発振器８からデユ
プレクサ９、プローブヘツド１０を介して90゜パ
ルスを被検体に印加して、プローブヘツド１０、
デユプレクサ９を介して得られたFID信号の周波
数を計測し、且つ計測値と設定値との差をＤ／Ａ
（デイジタル―アナログ）変換する計測回路であ
る。１４は前記静磁場の変動を補償するための補
助コイルである。１５は補助コイル１４の電源で
あり、計測回路１３の出力に応じて補助コイル１
４に流す電流値を制御する。(5) Embodiment of the Invention A configuration diagram of an embodiment of the present invention is shown in FIG. In FIG. 1, reference numeral 1 denotes an electromagnetic coil consisting of four coils, and this electromagnetic coil 1 creates a uniform static magnetic field. 2 is its power source. Reference numeral 3 denotes a gradient magnetic field coil that creates a linear gradient magnetic field in the direction along the static magnetic field (Z direction), and the gradient magnetic field is created by passing current through the pair of Helmholtz coils in opposite directions. 4 is its power source, and the value of the current flowing from this power source 4 to the coil 3 is controlled by a digital computer 5. 6 is a direction (x
This is a coil for creating a linear gradient magnetic field tilted in the -y direction), and 7 is its power supply, which is controlled by the digital computer 5 similarly to the power supply 4. 8 is an oscillator that generates excitation pulses (selective excitation pulses and 90° pulses), and 9 is a duplexer that sends out the excitation pulses from the oscillator 8 and receives the NMR signal. A probe head 10 is connected to the duplexer 9 and applies a high frequency magnetic field (excitation pulse) to the subject and detects an NMR signal from the subject. 11 is an amplifier that amplifies the FID signal of the detected NMR signal. The digital computer 5 converts the FID signal into an A/D (analog-digital)
After being converted and recorded and integrated, this is subjected to Fourier transformation to obtain projection information, and a reconstructed image is further created from this projection information. 12 is a display device for displaying images obtained by the digital computer 5; 13 stops the linear gradient magnetic field between measurement operations to obtain each projection information, and applies a 90° pulse to the object from the oscillator 8 via the duplexer 9 and the probe head 10.
The frequency of the FID signal obtained through the duplexer 9 is measured, and the difference between the measured value and the set value is measured by D/A.
(Digital to analog) conversion measurement circuit. 14 is an auxiliary coil for compensating for fluctuations in the static magnetic field. 15 is a power supply for the auxiliary coil 14, and the auxiliary coil 1
4. Controls the current value flowing through 4.
第２図は計測回路１３の詳細な構成を示す構成
図である。第２図において、１３―１はコンパレ
ータ、１３―２はカウンタ、１３―３は引算回
路、１３―４はＤ／Ａ変換器である。 FIG. 2 is a configuration diagram showing the detailed configuration of the measurement circuit 13. In FIG. 2, 13-1 is a comparator, 13-2 is a counter, 13-3 is a subtraction circuit, and 13-4 is a D/A converter.
次にこのような構成における動作について述べ
る。 Next, the operation in such a configuration will be described.
Ｚ方向に沿う一様静磁場H0を電磁石コイル１
と電源２によつてつくり、Ｚ方向について傾斜し
た傾斜磁場GZをコイル３と電源４とでつくり、
これらを重畳してプローブヘツド１０の中に配置
された被検体に印加しておき、さらに発振器８、
デユプレクサ９とプローブヘツド１０によつて選
択励起パルスH1を前記被検体に印加する。ここ
で、選択励起パルスH1の周波数を前記静磁場に
対応する周波数値0に合わせておくと、選択励起
パルスH1の周波数幅Δに対応するスライス幅
ΔGの面状（板状）の部分の水素原子核が被検体
内で選択的に励起される。ここでスライスの中心
は傾斜磁場GZがゼロである位置となる。前記周
波数幅Δとスライス幅ΔGの関係は
π・Δ＝γ・ΔG
（但し、γは磁気回転比である。）
選択励起パルスH1印加後に、ｘ―ｙ平面に沿う
方向に傾斜をもつ線型傾斜磁場Gxyを、コイル６
と電源７によつて印加しつつFID信号を検出し、
増幅器１１で増幅した後、デイジタル計算機５
で、一定時間幅のサンプリングを行ないつつ、デ
イジタル変換して記録する。こうして、必要な回
数のFID信号を同様の処理によつて記録し、これ
らを積算すれば信号／雑音比の向上が実現でき
る。こうして得られた信号をフーリエ変換する
と、選択励起した部分内の水素原子核密度分布を
傾斜磁場Gxyの傾斜方向に投影した投影情報が得
られる。傾斜磁場Gxyをｘ―ｙ平面内で電気的に
回転させながら、順次投影情報を測定し、最後に
画像再構成を行なえば、被検体断面（前記面状部
分）内の水素原子核密度分布像が得られる。 A uniform static magnetic field H 0 along the Z direction is applied to electromagnet coil 1.
and a power source 2, and a gradient magnetic field G Z tilted in the Z direction is created by a coil 3 and a power source 4,
These signals are superimposed and applied to the object placed in the probe head 10, and then the oscillator 8,
A selective excitation pulse H 1 is applied to the object by means of a duplexer 9 and a probe head 10 . Here, if the frequency of the selective excitation pulse H 1 is adjusted to the frequency value 0 corresponding to the static magnetic field, a planar (plate-shaped) portion with a slice width ΔG corresponding to the frequency width Δ of the selective excitation pulse H 1 hydrogen nuclei are selectively excited within the subject. Here, the center of the slice is the position where the gradient magnetic field G Z is zero. The relationship between the frequency width Δ and the slice width ΔG is π・Δ=γ・ΔG (However, γ is the gyromagnetic ratio.) After applying the selective excitation pulse H1 , a linear shape with an inclination in the direction along the x-y plane Gradient magnetic field Gxy, coil 6
and detect the FID signal while applying it by the power supply 7,
After being amplified by the amplifier 11, the digital computer 5
The data is then digitally converted and recorded while sampling over a fixed time period. In this way, the signal/noise ratio can be improved by recording the required number of FID signals through the same processing and integrating them. By Fourier transforming the signal thus obtained, projection information is obtained in which the hydrogen nucleus density distribution within the selectively excited portion is projected in the gradient direction of the gradient magnetic field G xy . While electrically rotating the gradient magnetic field G xy in the xy plane, projection information is sequentially measured, and finally image reconstruction is performed to obtain a hydrogen nucleus density distribution image within the cross section of the object (the planar portion). is obtained.
ここで、各投影情報測定中に静磁場H0が変動
すると選択励起パルスによる選択面（部分）がＺ
方向にずれてしまい、再構成画像が歪んでしま
う。これを避けるために、投影情報測定の休止期
間すなわち測定の合い間に線型傾斜磁場GZ、Gxy
を止め、発振器８から90゜パルスを発生させ被検
体に印加する。この場合傾斜磁場が印加されてい
ないので選択励起されず、被検体中の水素原子核
からのFID信号が得られる。このFID信号は、単
一周波数の信号となる。このFID信号の波形を第
３図ａに示す。このFID信号を増幅器１１によつ
て増幅したのち、計測回路１３に入力する。この
FID信号はコンパレータ１３―１で基準電圧と比
較され第３図ｂに示すような波形のパルスとして
出力される。このパルス出力をカウンタ１３―２
で一定時間ずつ計数する。この計数値は、FID信
号の周波数に対応する。引算回路１３―３でこの
計数値から、設定静磁場の周波数値に対応する設
定カウント値を差引く。前記設定カウント値はデ
イジタル計算機５から与えられる。例えば、静磁
場が高い値に変動すると前記計数値が大きくな
り、差が正となる。逆に静磁場が低い値に変化す
ると、前記計数値が小さくなり、差が負となる。
この差分値をＤ／Ａ変換器１３―４によりアナロ
グ信号に変換して補助コイル電源１５に与え、補
助コイル１４に流す電流を制御して、全体の静磁
場を設定値に戻す。このようにして静磁場の時間
変動を比較的簡単にかつ、高い精度で安定に保つ
ことができる。第４図ａは静磁場が高くなつた場
合のFID信号波形、同図ｂは、設定条件のFID信
号つまり静磁場が設定状態にあるときのFID信号
波形、同図ｃは静磁場が低い場合のFID信号波形
である。 Here, when the static magnetic field H 0 changes during each projection information measurement, the selected surface (portion) by the selective excitation pulse changes to Z
direction, and the reconstructed image becomes distorted. To avoid this, linear gradient magnetic fields G Z , G xy are applied during the pause period of projection information measurement, that is, between measurements.
The oscillator 8 generates a 90° pulse and applies it to the subject. In this case, since no gradient magnetic field is applied, selective excitation is not performed, and FID signals from hydrogen nuclei in the specimen are obtained. This FID signal is a single frequency signal. The waveform of this FID signal is shown in FIG. 3a. After this FID signal is amplified by the amplifier 11, it is input to the measurement circuit 13. this
The FID signal is compared with a reference voltage by a comparator 13-1 and output as a pulse having a waveform as shown in FIG. 3b. This pulse output is sent to the counter 13-2.
Count for a certain period of time. This count value corresponds to the frequency of the FID signal. A subtraction circuit 13-3 subtracts a set count value corresponding to the frequency value of the set static magnetic field from this count value. The set count value is given from the digital computer 5. For example, when the static magnetic field changes to a high value, the count value increases and the difference becomes positive. Conversely, when the static magnetic field changes to a lower value, the count value becomes smaller and the difference becomes negative.
This difference value is converted into an analog signal by the D/A converter 13-4 and applied to the auxiliary coil power supply 15, and the current flowing through the auxiliary coil 14 is controlled to return the entire static magnetic field to the set value. In this way, time fluctuations in the static magnetic field can be kept stable relatively easily and with high precision. Figure 4a shows the FID signal waveform when the static magnetic field is high, Figure 4b shows the FID signal waveform under the setting conditions, that is, the FID signal waveform when the static magnetic field is in the set state, and Figure 4c shows the FID signal waveform when the static magnetic field is low. This is the FID signal waveform of
このようにして、投影情報の測定の休止期間に
傾斜磁場を切り90゜パルスによるFID信号の周波
数値から静磁場の短時間変動を測定し、補助コイ
ル１４に流す電流を制御して、静磁場の変動を打
ち消すことにより、高安定の磁石用電源を要する
ことなく、精度の高いNMR投影情報を得ること
が可能となる。 In this way, the gradient magnetic field is cut off during the pause period of the measurement of projection information, and short-term fluctuations in the static magnetic field are measured from the frequency value of the FID signal by the 90° pulse, and the current flowing through the auxiliary coil 14 is controlled to generate the static magnetic field. By canceling out the fluctuations in , it becomes possible to obtain highly accurate NMR projection information without requiring a highly stable power source for the magnet.
なお、上述において、電磁石の安定度が良好な
場合には、各投影毎に、補正信号を得る必要はな
く、予め設定した一定数の投影情報を得た後に行
なえばよい。この場合、全体の計測時間が短縮で
きるという利点が生ずる。 In addition, in the above description, if the stability of the electromagnet is good, it is not necessary to obtain a correction signal for each projection, and it is sufficient to perform the correction signal after obtaining a predetermined number of projection information. In this case, there is an advantage that the entire measurement time can be shortened.
また、得られるFID信号の周波数が低く、その
まま周波数計測をしたのでは、精度が低くなつて
しまう場合には、さらに別の補助コイルを追加し
て、静磁場の測定時にのみ、全体の静磁場をシフ
トさせ、FID信号の周波数を上げることによつ
て、精度を向上させることができる。また逆に、
静磁場の測定時にのみ、別の補助コイルに流す電
流を切ることによつて静磁場をシフトさせるよう
にしても、同様の効果が得られる。 In addition, if the frequency of the obtained FID signal is low and the accuracy will be low if you measure the frequency as is, add another auxiliary coil and measure the entire static magnetic field only when measuring the static magnetic field. The accuracy can be improved by shifting the FID signal and increasing the frequency of the FID signal. And vice versa,
A similar effect can be obtained by shifting the static magnetic field by cutting off the current flowing through another auxiliary coil only when measuring the static magnetic field.
この他、本発明はその要旨を変更しない範囲内
で種々変形して実施することができる。 In addition, the present invention can be implemented with various modifications without changing the gist thereof.
(6) 発明の効果
比較的簡単な構成であるにもかかわらず、静磁
場の時間的変動を高精度に測定し効果的な補正を
行なうことが可能となる。(6) Effects of the invention Despite the relatively simple configuration, it is possible to measure temporal fluctuations in the static magnetic field with high precision and perform effective correction.
第１図は本発明の一実施例の構成を模式的に示
す構成図、第２図は同実施例における計測回路の
具体的な構成図、第３図ａおよびｂならびに第４
図ａ〜ｃは同実施例の動作の説明のための波形図
である。
１…電磁石コイル、２…電磁石コイル１用電
源、３…Ｚ方向線型傾斜磁場コイル、４…傾斜磁
場コイル３用電源、５…デイジタル計算機、６…
ｘ―ｙ方向線型傾斜磁場コイル、７…傾斜磁場コ
イル６用電源、８…発振器、９…デユプレクサ、
１０…プローブヘツド、１１…増幅器、１２…表
示器、１３…計測回路、１３―１…コンパレー
タ、１３―２…カウンタ、１３―３…引算回路、
１３―４…Ｄ／Ａ変換器、１４…補助コイル、１
５…補助コイル用電源。
FIG. 1 is a block diagram schematically showing the configuration of an embodiment of the present invention, FIG. 2 is a specific block diagram of a measuring circuit in the embodiment, FIGS. 3 a and b, and 4.
Figures a to c are waveform diagrams for explaining the operation of the same embodiment. DESCRIPTION OF SYMBOLS 1...Electromagnetic coil, 2...Power source for electromagnetic coil 1, 3...Z-direction linear gradient magnetic field coil, 4...Power source for gradient magnetic field coil 3, 5...Digital computer, 6...
x-y direction linear gradient magnetic field coil, 7... power source for gradient magnetic field coil 6, 8... oscillator, 9... duplexer,
10... Probe head, 11... Amplifier, 12... Display, 13... Measurement circuit, 13-1... Comparator, 13-2... Counter, 13-3... Subtraction circuit,
13-4...D/A converter, 14...auxiliary coil, 1
5...Power supply for auxiliary coil.
Claims (1)
印加し前記線型傾斜磁場を制御して前記被検体に
対する面状の投影部分および投影方向を選択しつ
つ前記投影方向を逐次変更して前記被検体の核磁
気共鳴信号を測定して前記面状の部分についての
多方向の特定原子核密度分布の投影情報を得、こ
の投影情報に基づいて前記被検体内の前記面状の
部分における特定原子核密度分布象を再構成する
診断用核磁気共鳴装置において、前記被検体に印
加する一様静磁場を補正するための補助コイル
と、前記線型傾斜磁場の印加を停止させる手段
と、この手段により前記線型傾斜磁場が除去され
たときの前記一様静磁場中における核磁気共鳴の
検出信号から自由誘導減衰信号の周波数を計測す
る周波数計測手段と、この周波数計測手段の計測
値を設定値と比較しこれらの差に応じた出力を得
る比較手段と、この比較手段の出力に応じた電流
を前記補助コイルに印加する電源回路とを具備す
ることを特徴とする診断用核磁気共鳴装置。 ２ 特許請求の範囲第１項記載の診断用核磁気共
鳴装置において、補助コイルによる一様静磁場の
補正を、予定個数の投影情報の測定後の測定休止
期間毎に行なうことを特徴とする診断用核磁気共
鳴装置。 ３ 特許請求の範囲第１項または第２項に記載の
診断用核磁気共鳴装置において、周波数計測手段
による計測時にのみ一様静磁場の大きさを一様に
シフトさせる磁場シフト用補助コイルを設けたこ
とを特徴とする診断用核磁気共鳴装置。[Scope of Claims] 1. Applying a linear gradient magnetic field superimposed on a uniform static magnetic field to a subject, controlling the linear gradient magnetic field to select a planar projection portion and a projection direction with respect to the subject, and selecting the projection direction. is successively changed to measure the nuclear magnetic resonance signal of the object to obtain projection information of specific nuclear density distribution in multiple directions for the planar portion, and based on this projection information, the surface within the object is measured. In a nuclear magnetic resonance apparatus for diagnosis that reconstructs a specific nuclear density distribution phenomenon in a shaped part, an auxiliary coil for correcting a uniform static magnetic field applied to the subject, and means for stopping application of the linear gradient magnetic field. and a frequency measuring means for measuring the frequency of a free induction decay signal from a detection signal of nuclear magnetic resonance in the uniform static magnetic field when the linear gradient magnetic field is removed by this means, and a measured value of the frequency measuring means. nuclear magnetism for diagnosis, characterized in that it is equipped with a comparison means for comparing the value with a set value and obtaining an output according to the difference between them, and a power supply circuit for applying a current to the auxiliary coil according to the output of the comparison means. Resonator. 2. A nuclear magnetic resonance apparatus for diagnosis according to claim 1, characterized in that the correction of the uniform static magnetic field by the auxiliary coil is performed every measurement suspension period after the measurement of a predetermined number of projection information. nuclear magnetic resonance equipment. 3. In the nuclear magnetic resonance apparatus for diagnosis according to claim 1 or 2, an auxiliary coil for magnetic field shifting is provided to uniformly shift the magnitude of the uniform static magnetic field only during measurement by the frequency measuring means. A diagnostic nuclear magnetic resonance apparatus characterized by:
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP56078973A JPS57192541A (en) | 1981-05-25 | 1981-05-25 | Nuclear magnetic rosonance apparatus for diagnosis |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP56078973A JPS57192541A (en) | 1981-05-25 | 1981-05-25 | Nuclear magnetic rosonance apparatus for diagnosis |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS57192541A JPS57192541A (en) | 1982-11-26 |
| JPS6323785B2 true JPS6323785B2 (en) | 1988-05-18 |
Family
ID=13676839
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP56078973A Granted JPS57192541A (en) | 1981-05-25 | 1981-05-25 | Nuclear magnetic rosonance apparatus for diagnosis |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS57192541A (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS59142444A (en) * | 1983-02-04 | 1984-08-15 | Hitachi Ltd | Inspecting apparatus using nuclear magnetic resonance |
| US4685468A (en) * | 1983-03-18 | 1987-08-11 | Albert Macovski | NMR imaging system using field compensation |
| JPS59200947A (en) * | 1983-04-30 | 1984-11-14 | Toshiba Corp | Nuclear magnetic resonance video apparatus |
| JPS59230148A (en) * | 1983-06-13 | 1984-12-24 | Hitachi Ltd | Nmr imaging device |
| JPH01299543A (en) * | 1988-05-27 | 1989-12-04 | Hitachi Ltd | Inspecting method and device using nuclear magnetic resonance |
-
1981
- 1981-05-25 JP JP56078973A patent/JPS57192541A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS57192541A (en) | 1982-11-26 |
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