JPH038215B2 - - Google Patents
Info
- Publication number
- JPH038215B2 JPH038215B2 JP60147034A JP14703485A JPH038215B2 JP H038215 B2 JPH038215 B2 JP H038215B2 JP 60147034 A JP60147034 A JP 60147034A JP 14703485 A JP14703485 A JP 14703485A JP H038215 B2 JPH038215 B2 JP H038215B2
- Authority
- JP
- Japan
- Prior art keywords
- signal
- magnetic field
- gradient
- time
- fid
- 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
- 238000000034 method Methods 0.000 claims description 22
- 238000005481 NMR spectroscopy Methods 0.000 claims description 18
- 238000005070 sampling Methods 0.000 claims description 4
- 238000001514 detection method Methods 0.000 claims description 2
- 238000003672 processing method Methods 0.000 claims 1
- 238000001208 nuclear magnetic resonance pulse sequence Methods 0.000 description 8
- 238000010586 diagram Methods 0.000 description 6
- 230000006870 function Effects 0.000 description 5
- 230000010355 oscillation Effects 0.000 description 4
- 230000005284 excitation Effects 0.000 description 2
- 238000003384 imaging method Methods 0.000 description 2
- 238000000691 measurement method Methods 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 238000003325 tomography Methods 0.000 description 2
- 238000004364 calculation method Methods 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- 238000012887 quadratic function Methods 0.000 description 1
- 230000009466 transformation 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
- G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
- G01R33/48—NMR imaging systems
- G01R33/54—Signal processing systems, e.g. using pulse sequences ; Generation or control of pulse sequences; Operator console
- G01R33/56—Image enhancement or correction, e.g. subtraction or averaging techniques, e.g. improvement of signal-to-noise ratio and resolution
- G01R33/565—Correction of image distortions, e.g. due to magnetic field inhomogeneities
- G01R33/56572—Correction of image distortions, e.g. due to magnetic field inhomogeneities caused by a distortion of a gradient magnetic field, e.g. non-linearity of a gradient magnetic field
Landscapes
- Physics & Mathematics (AREA)
- Nonlinear Science (AREA)
- Health & Medical Sciences (AREA)
- General Health & Medical Sciences (AREA)
- Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
- Radiology & Medical Imaging (AREA)
- Engineering & Computer Science (AREA)
- Signal Processing (AREA)
- High Energy & Nuclear Physics (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- General Physics & Mathematics (AREA)
- Magnetic Resonance Imaging Apparatus (AREA)
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（nuclear magnetic
resonance：以下これをNMRと略称する）現象
を利用して被検体内における特定原子核分布等を
被検体外部より知るようにしたNMR断層撮像装
置におけるNMR信号の測定方法の改善に関すも
のである。Detailed Description of the Invention (Industrial Field of Application) The present invention relates to nuclear magnetic resonance (nuclear magnetic resonance).
The present invention relates to an improvement in the method of measuring NMR signals in an NMR tomographic imaging device that utilizes resonance (hereinafter abbreviated as NMR) phenomenon to determine the distribution of specific atomic nuclei within a subject from outside the subject.
（従来の技術）
NMR断層撮像装置におけるNMR信号の観測
方法には、FID信号（自由誘導減衰信号）を観測
する方法と、エコー信号を観測する方法とがあ
る。第５図はFID信号を観測する場合のパルスシ
ーケンスを示す図、第６図はエコー信号を観測す
る場合のパルスシーケンスを示す図で、第６図に
おいては勾配磁場印加の様子については図示を省
略してある。(Prior Art) There are two methods of observing NMR signals in an NMR tomography apparatus: a method of observing an FID signal (free induction decay signal) and a method of observing an echo signal. Figure 5 is a diagram showing the pulse sequence when observing the FID signal, and Figure 6 is a diagram showing the pulse sequence when observing the echo signal. In Figure 6, the illustration of the gradient magnetic field application is omitted. It has been done.
FID信号観測の場合は、第５図のロに示すよう
にＺ勾配磁場を印加した状態で同図イに示すよう
に90゜パルスを印加して所定のスライスのスピン
を励起（選択励起）する。次に、Ｙ勾配磁場Gy
（ビユーごとにその大きさが変る）を与えて位相
エンコードを行う。続いて、読出し勾配用のＸ勾
配磁場を与え、この時点をFID信号の時間原点
（ｔ＝０）とし、そのFID信号をＴ時間にわたつ
て観測する。 In the case of FID signal observation, apply a Z gradient magnetic field as shown in Figure 5B, and apply a 90° pulse as shown in Figure 5A to excite spins in a predetermined slice (selective excitation). . Next, the Y gradient magnetic field Gy
(the size changes for each view) and performs phase encoding. Subsequently, an X-gradient magnetic field for a readout gradient is applied, and this time point is set as the time origin (t=0) of the FID signal, and the FID signal is observed over T time.
一方、エコー信号観測の場合は、90゜パルス印
加からNMR信号が発生するところまでは第５図
の場合と同様であるが、90゜パルス印加の後τ時
間経過したとき180゜パルスを印加し、分散中のス
ピンを180゜反転させる。これによりスピンは集束
しはじめ、前記180゜パルス印加よりτ時間経過し
た時点で最大となるようなエコー信号を発生す
る。このように発生するエコー信号の観測は、図
示のように180゜パルス印加の直後からエコー信号
が実質上なくなる時点までのTn期間行われる。 On the other hand, in the case of echo signal observation, the process from the application of the 90° pulse to the point where the NMR signal is generated is the same as in Figure 5, but the 180° pulse is applied when τ time has elapsed after the application of the 90° pulse. , flips the spin during dispersion by 180°. As a result, the spins begin to focus, generating an echo signal that reaches its maximum at the time τ after the application of the 180° pulse. Observation of the echo signal generated in this way is carried out for a period of T n from immediately after the application of the 180° pulse until the time when the echo signal substantially disappears, as shown in the figure.
（発明が解決しようとする問題点）
ところで、FID信号はエコー信号に比べて使い
難い点が幾つかあるため、従来は主としてエコー
信号の観測の方が用いられていた。しかし、単位
時間当りのＳ／Ｎで比較すると、T2緩和による
信号の低下や180゜パルスによる無駄時間が無いと
いう点でエコー信号よりもFID信号の方が優れて
いることが分る。(Problems to be Solved by the Invention) Incidentally, since FID signals have several points that are difficult to use compared to echo signals, conventionally, observation of echo signals has been mainly used. However, when compared in terms of S/N per unit time, it can be seen that the FID signal is superior to the echo signal in that there is no signal drop due to T 2 relaxation and no wasted time due to 180° pulses.
このような理由からFID信号を用いる方が望ま
しいが、FI信号利用には他に次のような問題が
ある。 For these reasons, it is preferable to use the FID signal, but there are other problems with using the FI signal.
２次元フーリエ変換を行うに際し、FID信号の
ピーク値とその位置（この位置はFID信号の観測
の際の時間原点になる。）とを正確に捕えてデー
タを処理する必要がある。エコー信号を用いる場
合は第６図に示されるようにNMR画像の２次元
フーリエ変換における直流成分（DC成分）がエ
コー信号のピーク（図のＰ点）として正確に得ら
れるので問題はないが、FID信号を用いた場合
は、DC成分がその先頭のデータに相当はするけ
れども、この部分ではピークとしての正確な位置
を求めることが困難な上、観測勾配の立上がりに
よる波形の乱れで正確な振幅を得ることもまた難
しいという問題があつた。 When performing two-dimensional Fourier transformation, it is necessary to accurately capture the peak value of the FID signal and its position (this position becomes the time origin when observing the FID signal) and process the data. When using an echo signal, there is no problem as the DC component in the two-dimensional Fourier transform of the NMR image can be accurately obtained as the peak of the echo signal (point P in the figure), as shown in Figure 6. When using an FID signal, although the DC component corresponds to the first data, it is difficult to find the exact position of the peak in this part, and the waveform is disturbed by the rise of the observation slope, making it difficult to determine the exact amplitude. There was also the problem that it was difficult to obtain.
本発明の目的は、この様な点に鑑み、FID信号
の時間原点の正確な位置を知ることができて、
FID信号からの検出データを基に正確な再構成画
像を得ることができるFID信号処理FID信号測定
方法を提供することにある。 In view of these points, an object of the present invention is to be able to know the exact position of the time origin of the FID signal,
An object of the present invention is to provide an FID signal processing FID signal measurement method that can obtain an accurate reconstructed image based on detection data from an FID signal.
（問題点を解決するための手段）
この様な目的を達成するために、本発明では、
選択励起後読出し勾配用の勾配磁場を与えて、発
生するFID信号を観測するようにした核磁気共鳴
信号の測定方法において、読出し勾配用の勾配磁
場印加に先立ち、その勾配磁場とは反対符号の勾
配を適宜の時間印加するようにし、FID信号をそ
の時間原点よりも少し手前から発生させて、FID
信号を検出し、時間原点近傍の複数のサンプリン
グ点から時間原点の正確な位置を推定し、時間原
点以降のFID信号の検出データと推定した時間原
点の位置を基に再構成断層像を求めるようにした
ことを特徴とする。(Means for solving the problem) In order to achieve such an objective, the present invention
In a nuclear magnetic resonance signal measurement method in which a gradient magnetic field for a readout gradient is applied after selective excitation and the generated FID signal is observed, prior to applying a gradient magnetic field for a readout gradient, a magnetic field of opposite sign to that of the gradient magnetic field is applied. Apply the gradient for an appropriate time, generate the FID signal a little before the origin at that time, and then
The system detects the signal, estimates the accurate position of the time origin from multiple sampling points near the time origin, and calculates a reconstructed tomographic image based on the detected data of the FID signal after the time origin and the estimated position of the time origin. It is characterized by the following.
（実施例）
以下図面を用いて本発明を実施例につき詳細に
説明する。第１図は本発明の方法を実施するため
のNMR断層撮像装置の要部構成図である。図に
おいて、１はマグネツトアセンブリで、内部には
対象物を挿入するための空間部分（孔）が設けら
れ、この空間部分を取巻くようにして、対象物に
一定の磁場を印加する主磁場コイルと、勾配磁場
を発生するための勾配磁場コイル（個別に勾配磁
場を発生することができるように構成されれたｘ
勾配磁場コイル、ｙ勾配磁場コイル及びｚ勾配磁
場コイル）と、対象物内の原子核のスピンを励起
するための高周波パルスを与えるRF送信コイル
と、対象物からのNMR信号を検出する受信用コ
イル等が配置されている。(Example) The present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram of the main parts of an NMR tomography apparatus for carrying out the method of the present invention. In the figure, 1 is a magnet assembly, inside which a space (hole) is provided for inserting an object, and a main magnetic field coil that surrounds this space and applies a constant magnetic field to the object. and a gradient magnetic field coil for generating a gradient magnetic field (x configured to be able to individually generate a gradient magnetic field)
gradient magnetic field coils, y gradient magnetic field coils, and z gradient magnetic field coils), RF transmitting coils that provide high-frequency pulses to excite the spins of atomic nuclei within the object, and receiving coils that detect NMR signals from the object, etc. is located.
主磁場コイルは主磁場電源２に、Gx，Gy，Gz
各勾配磁場コイルはGx，Gy，Gz勾配磁場駆動回
路３に、RF送信コイルはRF電力増幅器４に、
NMR信号の受信用コイルは前置増幅器５にそれ
ぞれ接続されている。１０はシーケンス記憶回路
で、勾配磁場や高周波磁場の発生シーケンスを制
御すると共に得られたNMR信号をＡ／Ｄ変換す
るときのタイミングを制御する。 The main magnetic field coil is connected to the main magnetic field power supply 2, Gx, Gy, Gz
Each gradient magnetic field coil is connected to a Gx, Gy, Gz gradient magnetic field drive circuit 3, and the RF transmitting coil is connected to an RF power amplifier 4.
The coils for receiving NMR signals are each connected to a preamplifier 5. 10 is a sequence storage circuit that controls the generation sequence of gradient magnetic fields and high-frequency magnetic fields, and also controls the timing when A/D converting the obtained NMR signal.
６はゲート変調回路、７は高周波信号を発生す
るRF発振回路である。ゲート変調回路６は、シ
ーケンス記憶回路１０からのタイミング信号によ
りRF発振回路７が出力した高周波信号を変調し、
高周波パルスを生成する。この高周波パルスは
RF電力増幅器４に与えられる。 6 is a gate modulation circuit, and 7 is an RF oscillation circuit that generates a high frequency signal. The gate modulation circuit 6 modulates the high frequency signal output by the RF oscillation circuit 7 using the timing signal from the sequence storage circuit 10,
Generates high frequency pulses. This high frequency pulse
RF power amplifier 4.
８は位相検波器で、RF発振回路７の出力信号
を参照して、受信用コイルで検出し前置増幅器５
を介して送られるNMR信号を位相検波する。 8 is a phase detector which refers to the output signal of the RF oscillation circuit 7, detects it with a receiving coil, and sends it to the preamplifier 5.
Detects the phase of the NMR signal sent via the
１１はＡ／Ｄ変換器で、位相検波器８を介して
得られたNMR信号（アナログ）をデイジタル信
号に変換する
１３は計算機を含む処理装置で、種々のスキヤ
ンを実現するためスキヤン条件をシーケンス記憶
回路１０に供給する機能や、Ａ／Ｄ変換器より入
力される観測データからスピン密度分布等に関す
る情報を画像に再構成する演算処理機能、操作コ
ンソール１２に対する情報の授受を行う機能など
を有する。 11 is an A/D converter, which converts the NMR signal (analog) obtained through the phase detector 8 into a digital signal. 13 is a processing device including a computer, which sequences scan conditions to realize various scans. It has a function of supplying data to the memory circuit 10, a calculation processing function of reconstructing information on spin density distribution, etc. into an image from observation data input from an A/D converter, a function of sending and receiving information to and from the operation console 12, etc. .
処理装置１３で得られた再構成像は表示装置９
において表示される。 The reconstructed image obtained by the processing device 13 is displayed on the display device 9.
Displayed in .
このような構成における動作を次に説明する。 The operation in such a configuration will be explained next.
第５図に示す従来のシーケンスにおいては、読出
し勾配（Ｘ勾配磁場）を印加した瞬間が時間原点
に相当している。しかし実際には読出し勾配の立
上がりに時間を要し、この間にスピンの位相が変
化するため、勾配が完全に立上がつた（したがつ
て信号が観測できるようになつた）時点ではすで
に時間原点からはずれてしまつている。また、勾
配の立上がり直後は、勾配磁場コイルと受信コイ
ルの結合状態により受信信号が乱れていることも
考えられ、データの正確さは保証されない。In the conventional sequence shown in FIG. 5, the moment when the readout gradient (X gradient magnetic field) is applied corresponds to the time origin. However, in reality, it takes time for the readout gradient to rise, and the spin phase changes during this time, so by the time the gradient has completely risen (and therefore the signal can be observed), the time origin has already been reached. It has drifted away from it. Further, immediately after the gradient rises, the received signal may be disturbed due to the coupling state of the gradient magnetic field coil and the receiving coil, and the accuracy of the data is not guaranteed.
本発明では第２図に示すように従来のシーケン
スとは読出し勾配（Ｘ勾配磁場）の印加が異なる
シーケンスでスキヤンを行うことにより時間原点
付近の正確なデータを得るようにし、第３図のよ
うに正確な時間原点を推定し、FID信号と時間原
点を基に画像再構成している。すなわち、FID観
測に先立つて、読出し勾配を僅かだけ反対方向に
印加しておく、このシーケンスによりFID信号を
時間原点の少し前から観測できるようになり、第
３図に示すように時間原点近傍の複数のサンプリ
ング点からの演算により、信号のピークとして時
間原点を確定できるようになる。また、△Ｔを適
当な長さにすれば、勾配の立上がり等による信号
の乱れもこの時間に納まり、正確な振幅の信号を
観測することができる。△Ｔは装置にもよるが数
百μsecないしし数msecでよく、これによる信号
観測時間の増大は無視できる。 In the present invention, as shown in Fig. 2, accurate data near the time origin is obtained by scanning in a sequence in which the readout gradient (X gradient magnetic field) is applied differently from the conventional sequence, and as shown in Fig. 3. The accurate time origin is estimated and the image is reconstructed based on the FID signal and the time origin. That is, prior to FID observation, a readout gradient is applied slightly in the opposite direction. This sequence allows the FID signal to be observed from a little before the time origin, and as shown in Figure 3, the readout gradient is applied in the opposite direction. By calculating from multiple sampling points, it becomes possible to determine the time origin as the peak of the signal. Furthermore, if ΔT is set to an appropriate length, signal disturbances due to the rise of the gradient, etc. will be contained within this time, and a signal with accurate amplitude can be observed. ΔT may be several hundred microseconds to several milliseconds, depending on the device, and the increase in signal observation time caused by this can be ignored.
このようなシーケンスはシーケンス記憶回路１
０に記憶されていて、シーケンス記憶回路１０に
より勾配磁場駆動回路３を制御することにより上
記のような勾配磁場印加が達成される。 Such a sequence is stored in the sequence memory circuit 1.
0, and by controlling the gradient magnetic field drive circuit 3 by the sequence storage circuit 10, application of the gradient magnetic field as described above is achieved.
さて、時間原点は信号がピークをとる位置であ
るが、一般にその点がサンプリング点と一致する
とは限らない。そこで、第３図に示すように、ピ
ーク近傍の数点S1，S2，S3に関して、適当な関数
（例えば２次関数等）Fnで近似して真のピークPt
を求めるのが望まみしい。また、フーリエ変換法
ではワープ量零でのビユーでのみ時間原点の検出
が可能なので、他のビユーではワープ量零のビユ
ーで決定した値を用いる。 Now, the time origin is the position where the signal peaks, but generally that point does not always coincide with the sampling point. Therefore, as shown in Fig. 3, several points S 1 , S 2 , and S 3 near the peak are approximated by an appropriate function (for example, a quadratic function) Fn to find the true peak Pt.
It is desirable to seek. Furthermore, in the Fourier transform method, since the time origin can be detected only in a view with a warp amount of zero, values determined in a view with a warp amount of zero are used in other views.
このようにして得られた正確なFIDデータは、
周波数空間の半分のデータであるので、実関数の
フーリエ変換の共役対称性を利用して残る半分の
データを作つて画像再構成をしたり、残る半分の
データを零としてフーリエ変換しその実数部を用
いて画像再構成したりする等の適当な方法により
画像化することができる。しかし、いずれの方法
を用いるにしても、正の時間領域すなわち周波数
空間の半分のデータを用いる画像再構成処理では
位相歪みを抑えるために時間原点の正確な位置を
得ることが重要である。画像化の方法は種々ある
が、フーリエ法再構成でアーテイフアクトの少な
い画像を得るための一つの方法として例えば次の
ような方法がある。 Accurate FID data obtained in this way is
Since the data is half of the frequency space, it is possible to use the conjugate symmetry of the Fourier transform of a real function to create the remaining half of the data and reconstruct the image, or to perform the Fourier transform with the remaining half of the data as zero and then calculate its real part. The image can be created by an appropriate method such as reconstructing the image using . However, whichever method is used, it is important to obtain an accurate position of the time origin in order to suppress phase distortion in image reconstruction processing that uses data in the positive time domain, that is, half of the frequency space. There are various imaging methods, and one method for obtaining an image with fewer artifacts using Fourier reconstruction is, for example, the following method.
FID信号の負の時間領域に零値を埋め込み、又
は零値があるものと見なして、FID信号を測定し
た際の磁場勾配の傾き方向により一方はそのまま
とし、他方は読出し時間軸が正負反転するように
複素画像をフーリエ変換し、更に主磁場不均一に
より生じた読出し方向の位置・濃度歪みを補正す
る。このようにして得られた２枚の画像を複素数
加算することで主磁場不均一の影響を少なくし、
絶対値処理又は位相回転等の画像処理で実数値画
像を得る。 By embedding a zero value in the negative time domain of the FID signal, or by assuming that there is a zero value, one is left as is, and the readout time axis is reversed depending on the direction of the magnetic field gradient when measuring the FID signal. The complex image is Fourier-transformed as shown in FIG. By adding complex numbers to the two images obtained in this way, the influence of the main magnetic field inhomogeneity is reduced,
A real value image is obtained by image processing such as absolute value processing or phase rotation.
なお、本発明の方法はフーリエ法のみでなく、
投影法（PR法）にも同様に用いることができる。
その際のパルスシーケンス例を第４図に示す。
PR法では、ビユーごとにプロジエクシヨン勾配
の方向を変えて（Ｘ勾配磁場とＹ勾配磁場とを変
化させて）スキヤンするが、本発明を実施するた
めには、信号観測に先立つて観測時と同じ角度で
符号が反対の勾配を印加するようにすればよい。
すなわち、例えばＹ勾配磁場としてGpr1を印加す
る場合では信号観測前に−kGpr1を印加し、Ｘ勾
配磁場としてGpr2を印加する場合は信号観測前に
−kGpr2を印加する。ただし、ｋは正の定数であ
り、Gpr1，Gpr2はビユーごとに変る磁場の強さで
ある。 Note that the method of the present invention is not limited to the Fourier method.
It can be similarly used for projection method (PR method).
An example of the pulse sequence at that time is shown in FIG.
In the PR method, scanning is performed by changing the direction of the projection gradient for each view (by changing the X gradient magnetic field and the Y gradient magnetic field). It is sufficient to apply a gradient with the same angle and opposite sign.
That is, for example, when applying G pr1 as the Y gradient magnetic field, -kG pr1 is applied before signal observation, and when applying G pr2 as the X gradient magnetic field, -kG pr2 is applied before signal observation. However, k is a positive constant, and G pr1 and G pr2 are the magnetic field strengths that change for each view.
（発明の効果）
以上説明したように、本発明によればFID信号
の時間原点付近の正確な位置を得ることができ
る。従つて、正の時間領域のデータであるFID信
号すなわち周波数空間の半分のデータによつて単
位時間あたりのＳ／Ｎが良好な画像を得られると
共に、位相歪みのない精度のよい画像を得ること
ができる。(Effects of the Invention) As explained above, according to the present invention, an accurate position near the time origin of the FID signal can be obtained. Therefore, it is possible to obtain an image with a good S/N ratio per unit time by using the FID signal, which is data in the positive time domain, that is, data in half of the frequency space, and to obtain a highly accurate image without phase distortion. Can be done.
第１図は本発明の方法を実施するためのNMR
断層撮像装置の一実施例を示す構成図、第２図は
本発明の方法を実施するためのパルスシーケンス
を示す図、第３図はFID信号のピーク値を曲線近
似する様子を説明するための図、第４図は本発明
の方法をPR法に適用した場合のパルスシーケン
スを示す図、第５図はFID信号観測に係る従来の
パルススシーケンスを示す図、第６図はエコー信
号観測に係る従来のパルスシーケンスを示す図で
ある。
１……マグネツトアセンブリ、２……主磁場電
源、３……勾配磁場駆動回路、４……RF電力増
幅器、５……前置増幅器、６……ゲート変調回
路、７……RF発振回路、８……位相検波器、９
……表示装置、１０……シーケンス記憶回路、１
１……Ａ／Ｄ変換器、１２……操作コンソール、
１３……処理装置。
Figure 1 shows NMR for carrying out the method of the present invention.
FIG. 2 is a diagram showing a pulse sequence for carrying out the method of the present invention, and FIG. 3 is a diagram for explaining how the peak value of an FID signal is approximated by a curve. Figure 4 shows the pulse sequence when the method of the present invention is applied to the PR method, Figure 5 shows the conventional pulse sequence for FID signal observation, and Figure 6 shows the pulse sequence for echo signal observation. FIG. 3 is a diagram showing such a conventional pulse sequence. DESCRIPTION OF SYMBOLS 1... Magnet assembly, 2... Main magnetic field power supply, 3... Gradient magnetic field drive circuit, 4... RF power amplifier, 5... Preamplifier, 6... Gate modulation circuit, 7... RF oscillation circuit, 8... Phase detector, 9
... Display device, 10 ... Sequence memory circuit, 1
1... A/D converter, 12... Operation console,
13... Processing device.
Claims (1)
後、読出し勾配用の勾配磁場を印加し、被検体の
再構成断層像を求めるためにFID信号を測定し処
理する核磁気共鳴信号の処理方法法において、 前記読出し勾配用の勾配磁場印加に先立ち、そ
の勾配磁場とは反対符号の勾配を適宜の時間印加
するようにし、FID信号をその時間原点よりも少
し手前から発生させて、FID信号を検出し、時間
原点近傍の複数のサンプリング点から時間原点の
正確な位置を推定し、時間原点以降のFIDの検出
データと推定した時間原点の位置を基に再構成断
層像を求めるようにした核磁気共鳴信号の処理方
法。[Claims] 1. After selectively exciting a desired slice plane of the object, a gradient magnetic field for a readout gradient is applied, and the FID signal is measured and processed to obtain a reconstructed tomographic image of the object. In the resonance signal processing method, prior to applying the gradient magnetic field for the readout gradient, a gradient with the opposite sign to the gradient magnetic field is applied for an appropriate time, and the FID signal is generated slightly before the time origin. Detects the FID signal, estimates the accurate position of the time origin from multiple sampling points near the time origin, and reconstructs a tomographic image based on the FID detection data after the time origin and the estimated position of the time origin. A method of processing nuclear magnetic resonance signals as required.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP60147034A JPS628046A (en) | 1985-07-04 | 1985-07-04 | Method for measuring nuclear magnetic resonance signal |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP60147034A JPS628046A (en) | 1985-07-04 | 1985-07-04 | Method for measuring nuclear magnetic resonance signal |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS628046A JPS628046A (en) | 1987-01-16 |
| JPH038215B2 true JPH038215B2 (en) | 1991-02-05 |
Family
ID=15421030
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP60147034A Granted JPS628046A (en) | 1985-07-04 | 1985-07-04 | Method for measuring nuclear magnetic resonance signal |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS628046A (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0614915B2 (en) * | 1988-03-03 | 1994-03-02 | 株式会社東芝 | Magnetic resonance imaging equipment |
| JP5132420B2 (en) * | 2008-05-20 | 2013-01-30 | 第一高周波工業株式会社 | FBG optical spectrum analyzer |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6029646A (en) * | 1983-02-25 | 1985-02-15 | Asahi Chem Ind Co Ltd | Device for obtaining signal containing information on spin-spin relaxation |
| JPS6095339A (en) * | 1983-09-09 | 1985-05-28 | ゼネラル・エレクトリツク・カンパニイ | Method of generating nmr image data |
-
1985
- 1985-07-04 JP JP60147034A patent/JPS628046A/en active Granted
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6029646A (en) * | 1983-02-25 | 1985-02-15 | Asahi Chem Ind Co Ltd | Device for obtaining signal containing information on spin-spin relaxation |
| JPS6095339A (en) * | 1983-09-09 | 1985-05-28 | ゼネラル・エレクトリツク・カンパニイ | Method of generating nmr image data |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS628046A (en) | 1987-01-16 |
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