JPH0315443A - Inspection method using nuclear magnetic resonance - Google Patents

Abstract

PURPOSE:To obtain a distortionless signal from an interested region of arbitrary position and shape by simultaneously applying an inclined magnetic field and a selective high frequency pulse before execution of a procedure, in which subtraction of a signal, measured by inverting only the nuclear magnetization in the interested region, from a normal signal, in the case of obtaining local information from a part of an object through utilization of nuclear magnetic resonance. CONSTITUTION:In a coil for generating a static magnetic field, an inspection object 2 is arranged in the coil. A sequencer 3 feeds a command to an inclined magnetic field driver 4 and a high frequency oscillator 5 to apply an inclined magnetic field and a high frequency magnetic field. The high frequency magnetic field is applied to the inspection object 2 by a high frequency transmitter 8 via a high frequency modulator 6 and a high frequency amplifier 7. Operation for selectively saturating nuclear magnetism in one part of an object is executed by a plural number of times for a plurality of regions in a plurality of directions of the object, further an optimized pulse such as minimizing residual magnetization is used. A signal, generated from the inspection object, is received by a receiver 9, guided to pass through an amplifier 10, phase detector 11 and an AD converter 12, and fed to a CPU13, here a signal process is performed. The signal and a measuring condition can be also stored in a memory medium 14 as necessary.

Description

【発明の詳細な説明】 〔産業上の利用分野〕 本発明は、核磁気共鳴を川いて物体の内部情報を計？ｌ
１！Ｉする手法に関わり、特に信号量の大きな物体の一
部分から帰所的な情報を晶精度で計測する手法に関する
。[Detailed Description of the Invention] [Field of Industrial Application] The present invention uses nuclear magnetic resonance to measure internal information of an object. l
1! The present invention relates to methods for measuring I, and in particular to methods for measuring reductive information from a part of an object with a large amount of signal with crystal precision.

〔従来の技術〕[Conventional technology]

従来、物体の一部から局所的な情報を得るための手段と
して、関心領域の磁化のみを励起したり、マグネテイツ
ク　レソナンス　イン　メデインスン　第３巻　（１９
８６年）９６３〜９６９ペー（２） ジ（Ｍａｇｎｅｔｉｃ　ｌ｛ｅｓｏｎａｎｃｅ　ｉｎ　
Ｍｅｄ．ｉｃｊｎｅ　３　，（［３８６）ｐ９６３〜９
６９）に記載されでいるように領域外の磁化を飽和させ
るなど多くの提案がなされてきた。Conventionally, as a means to obtain local information from a part of an object, only the magnetization of the region of interest is excited, or
1986) pages 963-969 (2) Magnetic l{sonance in
Med. icjne 3, ([386) p963-9
Many proposals have been made, such as saturating the magnetization outside the region, as described in 69).

しかしどの方法にも、｛ｔ４号がひずんだり、釦』或外
から信号が掘れ込む勢といった欠点かあ−）た。However, all of these methods had drawbacks such as distortion of the t4, buttons, and the tendency for signals to be dug in from outside.

最も欠点の少ない方法として、ジャーナル　オブ　マグ
ネテイツク　レゾナンス　第６６巻（１　９　８　６年
）２８３〜２９４ページ（ＪｏｕｒｎａＪ　ｏＪＭａｇ
ｎｅｔｉｃ　Ｒｅｓｏｎａｎｃｅ　６６，　（１．９８
６）　ｐ２８：３〜２９４）に北載されている選択的な
核磁化の反転を利用した方法がノムく用いられできた。As the method with the fewest drawbacks, the Journal of Magnetic Resonance, Volume 66 (1986), pages 283-294 (JournaJ
netic Resonance 66, (1.98
6) The method using selective reversal of nuclear magnetization, which is published in p. 28:3-294, was widely used.

ごの方法では、まず第一段ＭＪｉとして物体企休の信号
を計測し、第二段階として関心領域の核磁化を渕択的に
反転した状態で物体全体の信号を計？ｌ１！ｌし、これ
らを引き算することにより局所情報を得る。しかし、こ
の方法では飴域外の信号レベルが尚い場合には装置のイ
・安定性の影響による信号のゆらきが大きくなり、引算
の後に領域外の信号が完今に７１！１このため、たとえ
はソサイエテイ　オフ　マクネデイツク　レゾナンス　
イン　メデインス　第六回年大会（　ＩＩ．　Ｈ　８’
７年）　第二巻　９６４ベーシ（Ｓｏｃｊｅｔｙ　ｏｆ
　ＭａＨｎｅｔｊｃ　ＲｅＳｏｎａｎｃＣｉｎ　Ｍｅｄ
ｉｃｊｎｅｓｊｘｔｈ　Ａｎｎｕａｌ　Ｍｅｅｔｊ．ｎ
ｇ（　１　９　８　”／　）　ＶｏＪ．ｕｍｅ　２ｐ　
９　６４）に記載されているように、引算する信号を計
Ｈｌｌｌするｒ′ｌｉｉに物体の一方向に幻して勾配を
持つ傾斜磁場とｌｉｉＪ時に選択的な＾）Ｉｊ閉波バル
スを印加することにより核磁化を飽和させて領城外の信
号を減少させるという方法が提案されていた。In this method, the first stage MJi measures the signal of the object, and the second stage measures the signal of the entire object while selectively inverting the nuclear magnetization in the region of interest. l1! local information is obtained by subtracting these values. However, with this method, if the signal level outside the candy area is still low, the signal fluctuation will increase due to the influence of the stability of the device, and after subtraction, the signal outside the area will be completely 71!1. , The parable is Society Off Maknedytsk Resonance.
In Medins 6th Annual Conference (II. H 8'
7 years) Volume 2 964 basis (Socjety of
MaHnetjc ReSonanCin Med
icjnesjxth Annual Meetj. n
g(198”/) VoJ.ume 2p
As described in 964), a gradient magnetic field with an phantom gradient in one direction of the object is applied to r'lii, which calculates the signal to be subtracted, and a selective ^)Ij closed-wave pulse is applied to r'lii. A method was proposed that would saturate nuclear magnetization by doing so, thereby reducing signals outside the castle.

〔発明が解決しようとずる課鯨〕[The problem that the invention tries to solve]

上記従来技術は、物体金体の関心領域の大きさの差か数
術ある場合に飴域外の信号を選択的に飽和するという操
作をネ了ってはいるが、物体の一方向に刻して行ってい
るたけであり、しかも一同のみの実Ｑｊであるため飴域
外の信号の代減効率が悪く、選択的な核磁化のｋ転を利
川して周所情報を得る場合に鎮城外からの信号の漏れ込
みを低減し切れないという問題があった。The above-mentioned conventional technology has an operation of selectively saturating signals outside the candy area when there is a difference in the size of the region of interest of the metal object, but it is possible to selectively saturate the signal outside the candy area, Moreover, since it is only the same real Qj, the efficiency of substituting signals outside the area is poor. There was a problem in that it was not possible to completely reduce the leakage of signals from.

また選択的な核磁化の飽和を行うための品ノ刈波（４） パルスとして、数稚類のパルスを用いでいるか、これら
のパルスは選択的な飽和を行おうとする領域のｕｌｔｉ
端の信号か残りやすいという問題かあ−Ｘ）た。In addition, several types of pulses can be used as Shinano-kari wave (4) pulses to selectively saturate nuclear magnetization, or these pulses can be
The problem is that the signal at the edge tends to remain.

本発咽の目的は、任怠の位ｊＱ！　，形状の関心領域か
ら企の無い信号が得られ、しかも全体のイ一号と局所化
した信号とのレベル差が大きい場合でも、領域外からの
信号の漏れ込みなしに局所情報を得る手段を提供するこ
とである。The purpose of this outburst is to get rid of it! , Even if an unintentional signal is obtained from the region of interest in the shape, and there is a large level difference between the overall A1 and the localized signal, we have developed a means to obtain local information without leaking signals from outside the region. It is to provide.

〔課題を解決するための手段〕[Means to solve the problem]

上記目的を達或するために、従来の技術の瑣で述べた選
択的な核磁化の反転を川いて局所情報を得る手法を実行
する前の段階として、関心領域外の複数の幀域の磁化を
選択的に飽和させるような高周波Ｓ場を傾斜磁場ととも
に順々に印加することを複数方向に対して複数回繰迦し
、物体全体から発生する信号レベルを効率良く小さくし
たものである。In order to achieve the above purpose, as a step before implementing the method of obtaining local information by selectively reversing nuclear magnetization as described in item (4) of the conventional technology, the magnetization of multiple regions outside the region of interest is The signal level generated from the entire object is effectively reduced by repeatedly applying a high-frequency S field that selectively saturates the object along with a gradient magnetic field multiple times in multiple directions.

また選択的な核磁化の飽和を行うためのｌｌ’ｆ＋　ｈ
′１１波パルスとして、残留磁化が最小となるようむ最
適化パルスを用いることにより、関心領域外の信号（５
） の低減効率を向上させるようにしたものである。Also, ll'f+h for selective nuclear magnetization saturation
By using an optimized pulse that minimizes the residual magnetization as the '11 wave pulse, the signal outside the region of interest (5
) is designed to improve the reduction efficiency of

〔作川〕[Sakukawa]

核磁気共鳴を川いて局所的な内部情報を得たい物体に対
して傾斜磁場をかけると、傾斜の方向に沿って核磁気共
鳴周波数が勾配をもつ。この状態で第２図の領域１の核
磁化のみを励起するような高周波磁場を印加する。励起
された磁化は傾斜磁場の影響で位相がバラバラになり、
この領域全体としての核磁化は零となって信号計８１リ
にかからない。When a gradient magnetic field is applied to an object from which local internal information can be obtained through nuclear magnetic resonance, the nuclear magnetic resonance frequency has a gradient along the direction of the gradient. In this state, a high frequency magnetic field is applied that excites only the nuclear magnetization in region 1 in FIG. 2. The phase of the excited magnetization becomes scattered due to the influence of the gradient magnetic field,
The nuclear magnetization of this region as a whole becomes zero and is not detected by the signal meter 81.

三次元の物体に対し複数の方向について上記の手順を順
々に施せば、関心領域外の全域にわたって信号を低減す
ることができ、物体全体から生しる信号レベルと関心領
域から生しる信号レベルは同程度になるので、磁化が緩
和現象によってＩ！ｊｌ復する前に従来技術のところで
連べた計測法を実行すれば、＊　ａｌｌ信号に漏れ込む
領域外の信号或分を効率良く低減することができる。ま
た、この選択飽和の過程を複数回繰り迦すことによって
１　１！！］の選択飽和では励起されずに残る核磁化を
飽和させ（６） ることかできる。By sequentially performing the above steps in multiple directions on a three-dimensional object, it is possible to reduce the signal over the entire area outside the region of interest, and the signal level generated from the entire object and the signal generated from the region of interest can be reduced. Since the levels are about the same, the magnetization changes to I! due to the relaxation phenomenon. If the measurement method described in the prior art section is performed before the signal is restored, it is possible to efficiently reduce a portion of the signal outside the region that leaks into the *all signal. Moreover, by repeating this selection saturation process multiple times, 1 1! ! ] can saturate the nuclear magnetization that remains unexcited (6).

また縦磁化のスライス形状が知形にほほ迦い最適化パル
スを知いることにより、第２図の領域↓の両端の核磁化
を残すことなく飽和することかできる。Furthermore, by knowing the optimization pulse in which the slice shape of the longitudinal magnetization is almost similar to the shape, it is possible to saturate the region ↓ in FIG. 2 without leaving the nuclear magnetization at both ends.

〔実施例〕〔Example〕

第３図は、物体の一部から局所情報を得るために用いる
核磁気共鳴を用いた検査製置の一例である。１は静磁場
を発生するコイルで、検企対象２をこの中に配置する。FIG. 3 is an example of an inspection setup using nuclear magnetic resonance, which is used to obtain local information from a part of an object. 1 is a coil that generates a static magnetic field, and the object 2 to be examined is placed inside this coil.

シーケンサ３は傾斜磁場ドライバ４，高周波発信器５に
命令を送り、｛ｌＪｉ斜磁揚および高周波磁場を印加す
る。高周波磁場は、高周波蛮調器６，高周波増幅器７を
経て高ｊ閉波送信器８により検査対象２に印力Ｕされる
ので、傾斜磁場の存在ドでは核磁化を部分的に飽和した
り、反転することかｉｊＪ能である。検査対象から発生
した信号は受信機９によって受波され、増幅器］０，位
相検波器１１，ＡＤ変換器１２を通ってＣ　Ｐ　Ｕ１３
に送られ、ここで信号処理を行う。必要に応こどもでき
る。The sequencer 3 sends commands to the gradient magnetic field driver 4 and the high-frequency oscillator 5 to apply {lJi diagonal magnetic lift and a high-frequency magnetic field. The high-frequency magnetic field is applied to the inspection object 2 by the high-j closed-wave transmitter 8 via the high-frequency modulator 6 and the high-frequency amplifier 7, so that in the presence of a gradient magnetic field, the nuclear magnetization may be partially saturated. It is possible to reverse it. The signal generated from the inspection object is received by a receiver 9, passes through an amplifier 0, a phase detector 11, and an AD converter 12, and then is sent to the CPU 13.
The signal is then sent to the station, where it undergoes signal processing. I can take care of children as needed.

第４図のような物体の一部分（関心領域ｌ）からノ０所
情報を得る場合には、例えば第１図のようなタイミング
で傾斜磁場および尚周波パルスを印力Ｎする。When obtaining location information from a part of the object (region of interest 1) as shown in FIG. 4, a gradient magnetic field and a frequency pulse are applied at the timing shown in FIG. 1, for example.

第１図の前半部分（αつ）は領域外の信号を抑圧するた
めの操作を示している。すなわち、第４図の物体の入方
向に対して勾配を持つような傾斜磁場を印加した状態で
領域外２の核磁化を励起するような高周波パルスを印加
し、その後傾斜ｍ場を利用してこの領域の核磁化を飽和
させる。上記操作で用いる高周波パルスには、たとえば
時間領域では、 ｓｊｎ（ｔ） ｐ（ｔ）＝ ｔ （一τ／２≦ｔ≦゛１“／２） となるようなｓｉｎ　ｃ　変調パルスを用いる。このよ
うにすると鎮域内の核磁化のみが選択的に飽和される。The first half (α) of FIG. 1 shows operations for suppressing signals outside the area. That is, a high-frequency pulse that excites the nuclear magnetization outside the region 2 is applied while applying a gradient magnetic field that has a gradient with respect to the direction of entry of the object in Figure 4, and then using the gradient m field. The nuclear magnetization in this region is saturated. As the high-frequency pulse used in the above operation, for example, in the time domain, a sin c modulation pulse such that sjn(t) p(t) = t (-τ/2≦t≦゛1″/2) is used. In this way, only the nuclear magnetization within the nuclear region is selectively saturated.

しかしこのパルスは特に領域境界付近にお留磁化が最小
となるようにｓｉｎｃｅ調パルスを最適化したパルスを
用いる方が良い。However, it is better to use a pulse that is an optimized since-tuned pulse so that the residual magnetization is minimized especially near the region boundary.

上記操作をＸ方向の関心領域外の別の部分に対しても行
い、さらにこれをＹ方向，Ｚ方向に辿珀する。この一連
の操作をたとえは二ｌＬｊＩ　ｍり逗す。The above operation is also performed on other parts outside the region of interest in the X direction, and is further traced in the Y and Z directions. This series of operations can be compared with two.

第工図の後半部分（■）では実行テーフル（第５図）に
従って第４図の関心飴域Ｆの核磁化を反転させる選択反
転パルスをｘ，ｙ，ｚ方向の傾斜磁場と同時に印加した
後、励起して８ｍりの信号を計測する。第５図でパルス
がＯＮの時には第１図の実線で示したように選択反転パ
ルスを印加し、ＯＦＦの時には第１図の点線で示したよ
うに選択反転パルスを印加しない。In the second half of the drawing (■), after applying a selective reversal pulse that reverses the nuclear magnetization in the area of interest F in Fig. 4 according to the execution table (Fig. 5) at the same time as gradient magnetic fields in the x, y, and z directions. , and measure the signal at 8 m. In FIG. 5, when the pulse is ON, a selective inversion pulse is applied as shown by the solid line in FIG. 1, and when it is OFF, the selective inversion pulse is not applied as shown by the dotted line in FIG.

上記操作（■）で用いる高周波パルスには、たとえば（
■）と同様にＳｌｎＯ盆調パルスなどを用いるが、最適
化パルスを用いるとさらに良い。For example, the high-frequency pulse used in the above operation (■) includes (
Similar to (2), a SlnO tone pulse is used, but it is even better to use an optimized pulse.

８回の計測で得られた信号を実行テーブル（第５図）の
符号が十の時には加算，一の時に減算することにより、
第４図の関心領域１の信号のみ８回積算した結果が得ら
れる。By adding the signals obtained from eight measurements when the code in the execution table (Figure 5) is 10 and subtracting it when the code is 1,
The result of integrating only the signal of the region of interest 1 in FIG. 4 eight times is obtained.

（９） 〔発四の効果〕 本発明では、選択反転パルスと信号の加滅算を用いて物
体の局所的な情報を得る場合に、物体の一部分の核磁化
を選択的に飽和する操作を物体の複数方向の複数の領域
に刻して複数回実行し、しかも残悄磁化か最小となるよ
うな最辿化パルスを用いるため領域外の信号を効率良く
抑圧することかできるので、この後関心鎮域の槓磁化を
反転させて計測した信号と通常の信号との減算から関心
領域の信号を求めるときに、関心飴域の信号と物体全体
の信号のレベル差が数桁あっても領域外から信号が漏れ
込むことなく、任意の位置，形状の領域から歪の無い信
号を計測することが出来る。(9) [Effect of 4th generation] In the present invention, when obtaining local information of an object using selective inversion pulses and signal addition, an operation of selectively saturating the nuclear magnetization of a part of the object is performed. By engraving multiple regions of the object in multiple directions and executing it multiple times, and using a retracing pulse that minimizes the residual magnetization, it is possible to efficiently suppress signals outside the region. When obtaining the signal of the region of interest by subtracting the signal measured by reversing the magnetization of the region of interest and the normal signal, even if there is a level difference of several orders of magnitude between the signal of the region of interest and the signal of the entire object, the region It is possible to measure undistorted signals from an arbitrary position and shape area without signals leaking from outside.

【図面の簡単な説明】[Brief explanation of drawings]

第１図は選択的に核磁化を飽和させる方法を示したパル
スタイミング図、第２図は本発四の原理の説明図、第３
図は本発明を実行するときに用いる核磁気共鳴を用いた
検杏装置の一例を示すブロック図、第４図は計ｉｌ＋Ｉ
Ｊする物体の一例を示す斜視図、第５図は選択反転パル
スを印加する時の実行（１０） テーブルを示す図である。 （１１） 第 ２ 品 ０紅仙 １− 猶 ３ 図 嘱 ４ 図Figure 1 is a pulse timing diagram showing the method of selectively saturating nuclear magnetization, Figure 2 is an explanatory diagram of the fourth principle of the present invention, and Figure 3
The figure is a block diagram showing an example of an examination apparatus using nuclear magnetic resonance used when carrying out the present invention, and FIG.
FIG. 5 is a perspective view showing an example of an object subject to J, and FIG. 5 is a diagram showing an execution (10) table when applying a selective inversion pulse. (11) 2nd item 0 Kosen 1- Yu 3 Figure 4 Figure

Claims (1)

【特許請求の範囲】 １、核磁気共鳴を用いて物体の一部分から局所情報を得
る場合に、関心領域の核磁化のみ反転して計測した信号
と通常の信号との減算を利用した手法を実行する前に、
傾斜磁場と選択的な高周波パルスを同時に印加すること
によつて関心領域外の複数の領域の核磁化を選択的に飽
和させて信号を減少させる操作を順々に実行する段階を
含むことを特徴とする核磁気共鳴を用いた検査方法。 ２、特許請求の範囲第１項に記載の核磁気共鳴を用いた
検査方法は、複数の領域の核磁化を選択的に飽和させる
上記の過程を複数回繰り返すことにより、信号減少の効
率を向上させることを特徴とする核磁気共鳴を用いた検
査方法。 ３、特許請求の範囲第１項に記載の核磁気共鳴を用いた
検査方法は、上記した関心領域外の核磁化を選択的に飽
和させる操作を三次元の物体にたいし、複数の方向につ
いて実行する段階を含むことを特徴とする核磁気共鳴を
用いた検査方法。 ４、特許請求の範囲第１項に記載の核磁気共鳴を用いた
検査方法は、上記選択的な飽和を行うために印加する高
周波パルスとして、残留磁化が最小となるような最適化
パルスを用いることを特徴とする核磁気共鳴を用いた検
査方法。[Claims] 1. When obtaining local information from a part of an object using nuclear magnetic resonance, a method is performed that utilizes subtraction between a signal measured by inverting only the nuclear magnetization of the region of interest and a normal signal. Before you do
characterized by comprising steps of sequentially performing operations for selectively saturating nuclear magnetization in a plurality of regions outside the region of interest to reduce the signal by simultaneously applying a gradient magnetic field and selective radio frequency pulses; An inspection method using nuclear magnetic resonance. 2. The inspection method using nuclear magnetic resonance according to claim 1 improves the efficiency of signal reduction by repeating the above process of selectively saturating nuclear magnetization in multiple regions multiple times. An inspection method using nuclear magnetic resonance characterized by: 3. The inspection method using nuclear magnetic resonance according to claim 1 performs the operation of selectively saturating the nuclear magnetization outside the region of interest on a three-dimensional object in a plurality of directions. 1. An inspection method using nuclear magnetic resonance, comprising the step of performing. 4. The inspection method using nuclear magnetic resonance according to claim 1 uses an optimized pulse that minimizes residual magnetization as the high-frequency pulse applied to perform the selective saturation. An inspection method using nuclear magnetic resonance characterized by: