JPH04336036A - Fourier transform imaging method - Google Patents
Fourier transform imaging methodInfo
- Publication number
- JPH04336036A JPH04336036A JP3105514A JP10551491A JPH04336036A JP H04336036 A JPH04336036 A JP H04336036A JP 3105514 A JP3105514 A JP 3105514A JP 10551491 A JP10551491 A JP 10551491A JP H04336036 A JPH04336036 A JP H04336036A
- Authority
- JP
- Japan
- Prior art keywords
- magnetic field
- fourier transform
- signal
- image
- magnetic resonance
- 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.)
- Pending
Links
- 238000003384 imaging method Methods 0.000 title claims description 10
- 238000005481 NMR spectroscopy Methods 0.000 abstract description 8
- 238000000034 method Methods 0.000 abstract description 6
- 238000002595 magnetic resonance imaging Methods 0.000 abstract description 3
- 238000005259 measurement Methods 0.000 description 16
- 238000010586 diagram Methods 0.000 description 5
- 230000009466 transformation Effects 0.000 description 4
- 238000001208 nuclear magnetic resonance pulse sequence Methods 0.000 description 2
- 230000003068 static effect Effects 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000013075 data extraction Methods 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 238000007689 inspection Methods 0.000 description 1
Landscapes
- Magnetic Resonance Imaging Apparatus (AREA)
- Image Processing (AREA)
- Image Analysis (AREA)
Abstract
Description
【０００１】0001
【産業上の利用分野】本発明は、ＮＭＲ断層像を高速に
撮影する際に、撮影と同時に画像再構成を行いリアルタ
イムに動画表示を行えるようにしたフーリエ変換イメー
ジングに関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to Fourier transform imaging in which, when NMR tomographic images are taken at high speed, image reconstruction is performed at the same time as the image is taken, and a moving image can be displayed in real time.
【０００２】0002
【従来の技術】通常のイメージングでは、数秒から十数
分程度の信号計測終了後に全ての計測信号データを使用
してフーリエ変換により画像再構成を行い、計測データ
と同分解能の２次元の画像データとして画像表示装置上
に表示を行う方法が一般化されている。[Prior Art] In normal imaging, after completing signal measurement for several seconds to more than ten minutes, all measured signal data is used to reconstruct an image by Fourier transform, and two-dimensional image data with the same resolution as the measured data is generated. A method of displaying images on an image display device has become common.
【０００３】例えば、心臓などのように動いている部分
を動画として表示を行う場合、信号計測を行うときに心
臓の心拍に同期をかけて各時相の計測を行い、全信号計
測終了後にフーリエ変換により画像再構成を行う。この
画像再構成後に各時相の画像データを順次表示し動画と
する。For example, when displaying a moving part such as the heart as a moving image, when performing signal measurement, each time phase is measured in synchronization with the heartbeat, and after all signal measurements are completed, Fourier Image reconstruction is performed by conversion. After this image reconstruction, the image data of each time phase is sequentially displayed to create a moving image.
【０００４】0004
【発明が解決しようとする課題】しかしながら、上記従
来例では、高速撮影法を用いて信号計測を行い、計測と
同時に画像再構成を行おうとすると、信号計測よりも画
像再構成に時間がかかるためリアルタイムな画像表示が
困難である。[Problems to be Solved by the Invention] However, in the above-mentioned conventional example, when signal measurement is performed using a high-speed imaging method and image reconstruction is attempted at the same time as the measurement, image reconstruction takes more time than signal measurement. Real-time image display is difficult.
【０００５】[0005]
【課題を解決するための手段】このような目的を達成す
るために、本発明は、フーリエ変換イメージング法にお
いて、信号計測時の分解能を画像再構成の時に任意に落
として再構成をできるようにしたものである。[Means for Solving the Problems] In order to achieve the above object, the present invention provides a Fourier transform imaging method that enables reconstruction by arbitrarily lowering the resolution during signal measurement during image reconstruction. This is what I did.
【０００６】[0006]
【作用】この発明においては、信号計測は高分解能で高
速に計測し、計測と同時に行う画像再構成は分解能を落
とし、フーリエ変換の計算点数を減少させて高速に画像
再構成を行い、リアルタイムに動画表示を行う、また、
画像再構成と同時に計測信号を保存し、必要な部分を計
測終了後に従来法と同様の画像再構成を行い高分解能の
動画表示を行うことができる。[Operation] In this invention, signal measurement is performed at high resolution and high speed, and image reconstruction performed at the same time as measurement reduces the resolution and reduces the number of Fourier transform calculation points to perform image reconstruction at high speed and in real time. Displays videos, and
The measurement signal is saved at the same time as the image is reconstructed, and after the measurement of the necessary portion is completed, the image is reconstructed in the same manner as in the conventional method, and a high-resolution moving image can be displayed.
【０００７】[0007]
【実施例】図１は、本発明の一実施例である磁気共鳴イ
メージング装置の構成の概要を示す構成図である。図に
おいて、超電導磁石１により静磁場が発生し、計算機３
は傾斜磁場電源２を駆動し超電導磁石１の空間内に傾斜
磁場（位置による強度の異なる磁場）を発生するように
なっている。また、計算機３は高周波送信器９を介して
高周波磁場を照射するようになっている。該高周波磁場
は、数１で示される周波数Ｗを集中的に有する。DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing an outline of the structure of a magnetic resonance imaging apparatus which is an embodiment of the present invention. In the figure, a static magnetic field is generated by a superconducting magnet 1, and a computer 3
drives the gradient magnetic field power supply 2 to generate a gradient magnetic field (a magnetic field whose strength differs depending on the position) within the space of the superconducting magnet 1. Further, the computer 3 is configured to irradiate a high frequency magnetic field via a high frequency transmitter 9. The high frequency magnetic field has a concentrated frequency W as shown in equation 1.
【０００８】[0008]
【数１】Ｗ＝γＨ
ここで、Ｗ：共鳴周波数
γ：磁気回転比
Ｈ：検査対象断面位置の磁場強度
これにより、検査対象の特定断面のみで磁気共鳴現象が
起こり、核スピンが励起される。励起された核スピンは
、核スピンの置かれた磁場強度に対応して前記数１で示
される周波数の高周波を放射する（核磁気共鳴信号）こ
の際断層面において、傾斜磁場を印加すると信号の周波
数は位置と対応する。これにより断面の核スピンを各々
の位置に対応づけて分離することができる。該核スピン
の信号は、前置増幅器５により増幅され、基準信号発生
器７により発生された基準信号と直交検波器６でミキシ
ングされ低周波信号に変換されて、さらにＡ／Ｄ変換器
８によってデジタル信号に変換され、計算機３に取り込
まれる。該核磁気共鳴信号は複数回取り込まれ、計算機
３内でフーリエ変換する事により断層画像が得られる。[Equation 1] W=γH Here, W: Resonance frequency γ: Magnetic rotation ratio H: Magnetic field strength at the cross-section position of the object to be inspected.As a result, a magnetic resonance phenomenon occurs only in a specific cross-section of the object of inspection, and nuclear spins are excited. . The excited nuclear spins emit a high frequency wave with a frequency shown by the equation 1 above (nuclear magnetic resonance signal) corresponding to the magnetic field strength in which the nuclear spins are placed (nuclear magnetic resonance signal).At this time, when a gradient magnetic field is applied on the tomographic plane, the signal changes. Frequency corresponds to position. This allows the nuclear spins in the cross section to be separated in association with their respective positions. The nuclear spin signal is amplified by a preamplifier 5, mixed with a reference signal generated by a reference signal generator 7 by a quadrature detector 6, converted to a low frequency signal, and further converted to a low frequency signal by an A/D converter 8. It is converted into a digital signal and taken into the computer 3. The nuclear magnetic resonance signal is captured multiple times and subjected to Fourier transformation within the computer 3 to obtain a tomographic image.
【０００９】このような概略構成の装置において、高速
撮影法と共に高速にフーリエ変換を行い動画表示する方
法を説明する。[0009] In the apparatus having such a general configuration, a method of displaying a moving image by performing high-speed Fourier transform together with a high-speed photographing method will be described.
【００１０】図２に一般的な高速撮影法のパルスシーケ
ンスを示す。まず、α°ＲＦパルス（高周波）およびＧ
ｓ（断面を決定するための傾斜磁場）により、被検体の
特定の断面内の核スピンを励起する。その直後にＧｐの
傾斜磁場を印加し断面内の位相エンコード方向に位置情
報を付加する。そして、断面内の周波数エンコード方向
の位置情報を付加するための傾斜磁場Ｇｒを印加しなが
ら、核磁気共鳴信号Ｓを取り込む。２次元フーリエ変換
イメージング法では、前記傾斜磁場Ｇｐの大きさを順次
変化させながら複数の核磁気共鳴信号を取り込む。FIG. 2 shows a pulse sequence for a general high-speed imaging method. First, α°RF pulse (high frequency) and G
s (gradient magnetic field for determining the cross section) excites nuclear spins within a specific cross section of the object. Immediately after that, a gradient magnetic field of Gp is applied to add position information in the phase encoding direction within the cross section. Then, a nuclear magnetic resonance signal S is captured while applying a gradient magnetic field Gr for adding position information in the frequency encoding direction within the cross section. In the two-dimensional Fourier transform imaging method, a plurality of nuclear magnetic resonance signals are captured while sequentially changing the magnitude of the gradient magnetic field Gp.
【００１１】本発明は、上記高速撮影法において計測信
号の分解能を任意に低下させて画像再構成を行うことを
特徴とする。The present invention is characterized in that image reconstruction is performed by arbitrarily lowering the resolution of the measurement signal in the above-mentioned high-speed imaging method.
【００１２】計測された上記２次元の核磁気共鳴信号Ｓ
は計算機３内で、図３に示す画像最構成のフローチャー
トにより２次元フーリエ変換される。その結果目的の画
像が得られる。図３に従い以下具体的に説明する。The measured two-dimensional nuclear magnetic resonance signal S
is subjected to two-dimensional Fourier transformation in the computer 3 according to the flowchart for image reconfiguration shown in FIG. As a result, the desired image is obtained. A detailed explanation will be given below according to FIG. 3.
【００１３】まず図３の１のように、検出された２次元
計測データから画像分解能低下の割合によりフーリエ変
換するデータを切り出す。具体的には図４に示すように
、２次元計測信号の中心からフーリエ変換に使用するす
るデータを切り出す。First, as shown in FIG. 3, data is extracted from the detected two-dimensional measurement data to be subjected to Fourier transform according to the rate of image resolution reduction. Specifically, as shown in FIG. 4, data to be used for Fourier transformation is extracted from the center of the two-dimensional measurement signal.
【００１４】次に図３の２及び３に示すように、切り出
した計測データの点数分の位相エンコード方向及び周波
数エンコード方向のフーリエ変換を行う。Next, as shown in 2 and 3 of FIG. 3, Fourier transform is performed in the phase encoding direction and frequency encoding direction for the number of points of the cut out measurement data.
【００１５】例えば、位相エンコード方向２５６点，周
波数エンコード方向２５６点の計測を行うとフーリエ変
換点数は６５５３６点であるが、もとのデータの１／２
を切り出した場合フーリエ変換の計算点数は、１６３８
４点と１／４になるため大幅にフーリエ変換にかかる時
間を短縮できる。For example, if 256 points in the phase encoding direction and 256 points in the frequency encoding direction are measured, the number of Fourier transform points is 65536, but it is 1/2 of the original data.
When cutting out, the number of calculation points for Fourier transform is 1638
Since the number of points is 4 and 1/4, the time required for Fourier transformation can be significantly reduced.
【００１６】また、高速フーリエ変換の性質上データ切
り出しの点数は、位相エンコード方向，周波数エンコー
ド方向とも２のべき乗にする必要がある。Furthermore, due to the nature of fast Fourier transform, the number of data extraction points must be a power of two in both the phase encoding direction and the frequency encoding direction.
【００１７】[0017]
【発明の効果】上記実施例から、本発明は、高速撮影法
による動画の画像再構成において、画像の分解能を低下
させフーリエ変換点数を減少させる事により高速に動画
を表示させる事が出来る。As can be seen from the above embodiments, the present invention can display a moving image at high speed by lowering the resolution of the image and reducing the number of Fourier transform points in image reconstruction of a moving image using a high-speed photographing method.
【００１８】本発明は、必要な部分は計測終了後に高分
解能で画像再構成を行い動画とする事が出来る。[0018] According to the present invention, necessary portions can be reconstructed with high resolution into a moving image after the measurement is completed.
【図１】本発明による磁気共鳴イメージング装置の概略
構成図である。FIG. 1 is a schematic configuration diagram of a magnetic resonance imaging apparatus according to the present invention.
【図２】高速撮影法の基本的なパルスシーケンスを示す
図である。FIG. 2 is a diagram showing a basic pulse sequence of high-speed imaging.
【図３】フーリエ変換法による画像再構成にフローチャ
ートを示す図である。FIG. 3 is a diagram showing a flowchart for image reconstruction using the Fourier transform method.
【図４】分解能低下、信号切り出し法を示す図である。FIG. 4 is a diagram showing a resolution reduction and signal extraction method.
１…超電導磁石（静磁場）、２…傾斜磁場電源、３…計
算機、４…検査対象（被検体）、５…前置増幅器、６…
直行検波器（混合器）、７…基準信号発生器、８…Ａ／
Ｄ変換器、９…高周波送信器。1... Superconducting magnet (static magnetic field), 2... Gradient magnetic field power supply, 3... Computer, 4... Test object (subject), 5... Preamplifier, 6...
Orthogonal detector (mixer), 7...Reference signal generator, 8...A/
D converter, 9...High frequency transmitter.
Claims (1)
に対し高周波を照射した後、前記被検体から放射される
共鳴信号を検出するまでの間に、１軸方向または互いに
直交する複数軸方向に沿った傾斜磁場を印加すると共に
、該傾斜磁場の時間積分を所定値に一致するように制御
する第１の手段と、検出した前記共鳴信号を計算機に取
り込む第２の手段と、前記傾斜磁場の時間積分量を変化
させながら、前記第１・第２の手段を繰り返して実行す
る第３の手段と、検出した前記共鳴信号に対して、１次
元または複数次元のフーリエ変換を行い、画像を得る第
４の手段と、からなるフーリエ変換イメージング法にお
いて、検出した前記共鳴信号に対して、画像分解能を低
下させ、高速にフーリエ変換を行う事を特徴とするフー
リエ変換イメージング法。Claim 1: After the nuclear spins of a subject placed in a uniform magnetic field are irradiated with high frequency waves and until the resonance signals emitted from the subject are detected, the nuclear spins are radiated in one axis direction or perpendicular to each other. a first means for applying a gradient magnetic field along a plurality of axial directions and controlling the time integral of the gradient magnetic field to match a predetermined value; a second means for importing the detected resonance signal into a computer; a third means for repeatedly performing the first and second means while changing the time integral amount of the gradient magnetic field; and performing a one-dimensional or multi-dimensional Fourier transform on the detected resonance signal. , and a fourth means for obtaining an image, the Fourier transform imaging method is characterized in that the detected resonance signal is subjected to Fourier transform at high speed by lowering the image resolution.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3105514A JPH04336036A (en) | 1991-05-10 | 1991-05-10 | Fourier transform imaging method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3105514A JPH04336036A (en) | 1991-05-10 | 1991-05-10 | Fourier transform imaging method |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH04336036A true JPH04336036A (en) | 1992-11-24 |
Family
ID=14409713
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP3105514A Pending JPH04336036A (en) | 1991-05-10 | 1991-05-10 | Fourier transform imaging method |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH04336036A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2010012294A (en) * | 2009-09-14 | 2010-01-21 | Toshiba Corp | Magnetic resonance imaging apparatus and processing method for magnetic resonance imaging collection data |
-
1991
- 1991-05-10 JP JP3105514A patent/JPH04336036A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2010012294A (en) * | 2009-09-14 | 2010-01-21 | Toshiba Corp | Magnetic resonance imaging apparatus and processing method for magnetic resonance imaging collection data |
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