JPH03121050A - Magnetic resonance imaging and device therefor - Google Patents

Abstract

PURPOSE:To permit the real-time observation for a moving body by carrying out the procedures of irradiating the high frequency pulse for excitation to a specific part of an inspected body, generating the inclined magnetic fields for slicing and reading in the specific directions, collecting the magnetic resonance signals, carrying out the first dimensional Fourier transformation and arranging the magnetic resonance signals in a specific direction of an image matrix, several times. CONSTITUTION:An inspected body P is set, and coordinates X, Y, and Z are defined in a body 1, and each sectional surface region S is sliced. A sequence is executed, and the obtained magnetic resonance signal is applied with the first dimensional Fourier transformation treatment by a first dimension FET processor 13, and the first dimensional projected data along the X-axis direction related to the sectional surface region S can be obtained. By repeating the procedures of data collection for the sectional surface region S and the first dimensional Fourier transformation treatment in number of times, the data is arranged in a specific direction of an image matrix on an image buffer 15, and a motion image in accordance with the lapse of time of the sectional surface region S is obtained. The motion image can be displayed as a moving image according to the lapse of time of the sectional surface region S on a display 12.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to magnetic resonance (MR) technology.
The present invention relates to a magnetic resonance imaging method and apparatus for obtaining morphological information and functional information such as spectroscopy of a subject using the phenomenon (sonance).

(Prior art) Magnetic resonance is a phenomenon in which an atomic nucleus with non-zero spin and magnetic moment placed in a static magnetic field resonantly absorbs and emits only electromagnetic waves of a specific frequency. The angular frequency ω shown in (ω.−2πν., .

niller-more frequency) ν It resonates with me.

ωo　1　γ　H.

Here, γ is the gyromagnetic ratio specific to the type of atomic nucleus,
Further, Ho is the static magnetic field strength.

An apparatus that performs biological diagnosis using the above-mentioned principle processes electromagnetic waves of the same frequency as above that are induced after the above-mentioned resonance absorption, and calculates nuclear density, longitudinal relaxation time T1. Transverse relaxation time T2. Diagnostic information that reflects information such as flow and chemical shift, such as slice images of a subject, can be obtained non-invasively.

Collecting diagnostic information by magnetic resonance can excite all parts of a subject placed in a static magnetic field and collect signals, but there are limitations in the equipment configuration and clinical requirements for imaging images. Therefore, in an actual device, a specific part is excited and its signal is collected.

In this case, the specific region to be imaged is generally a sliced region with a certain thickness;
Magnetic resonance signals (MR multiplied signals) of echo signals and FID signals from this slice site are collected by performing a data encoding process many times, and these data groups are subjected to image reconstruction processing using, for example, a two-dimensional Fourier transform method. By doing so, an image of the specific slice region is generated.

For the data acquisition and reconstruction method as the two-dimensional Fourier transform method mentioned above, the pulse spin-echo method as a normal method and the gradient-end field echo method as a high-speed method have been commonly used. There is an echo planar method etc. as a high-speed method.

Furthermore, all parts of the living body can be arbitrarily designated as imaging targets, that is, diagnostic targets, simply by electrical manipulation. In this case, if the object to be imaged is a stationary object that does not require time information, any of the above methods can be adopted, but if the object to be imaged is a high-speed moving object that moves on a second-by-second basis, such as the heart. In this case, data collection methods that require data time on the order of several seconds or less cannot be adopted, such as the pulse spin-echo method or the gradient-end field echo method.

Therefore, using the echo planar method, which requires data collection time in units of several seconds or less, it is possible to image high-speed moving objects that move on the order of seconds, but the echo planar method itself is based on hardware. Because the above issues remain to be solved, it has not yet reached the clinical practical level, and in the end, electrocardiogram-gated imaging using pulsed spin-echo method or gradient-end field echo method was used to obtain multi-temporal images. The current situation is that

(Problems to be Solved by the Invention) Even if images of high-speed moving bodies using such temporal images use data collected in a state where there is no arrhythmia, the resulting images are obtained by data editing. However, there was a problem in that it did not provide accurate clinical information.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a magnetic resonance imaging method and apparatus that enable real-time observation of a moving body.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above problems and achieve the objects, the present invention has a structure in which the following means are taken.

That is, the invention according to claim 1 irradiates the subject with an excitation high-frequency pulse for causing a magnetic resonance phenomenon in a specific region of the subject, and generates a slicing gradient magnetic field in the direction along the first axis. .

Next, a read gradient magnetic field is generated in a direction along a second axis orthogonal to the first axis to collect magnetic resonance signals, and the magnetic resonance signals are subjected to one-dimensional Fourier transform.

This magnetic resonance imaging method is characterized in that image information is obtained by executing a series of steps for arranging the converted data in a specific direction of an image matrix multiple times.

The invention according to claim 2 irradiates the subject with an excitation high frequency (Rus) for producing a magnetic resonance phenomenon in a specific region of the subject, and generates a gradient magnetic field for slicing in the direction along the first axis. 4. Next, read gradient magnetic fields are generated in the directions along the second and third axes perpendicular to the first axis to collect magnetic resonance signals, and this magnetic resonance signal is subjected to one-dimensional Fourier transform, and the converted data is This is a magnetic resonance imaging method characterized in that image information is obtained by executing a series of steps for arranging images in a specific direction on an image matrix multiple times.

The invention according to claim 3 includes a first means for causing a magnetic resonance phenomenon in a specific region of a subject; a magnetic resonance signal is induced from the region where the magnetic resonance phenomenon occurs by the first means; In a magnetic resonance imaging apparatus, the magnetic resonance imaging apparatus has a second means for imparting positional information upon acquisition, and a third means for generating image information having a two-dimensional image matrix based on the magnetic resonance signals collected by the second means. irradiating the specimen with an excitation high-frequency pulse for producing a magnetic resonance phenomenon in a specific region of the specimen, and generating a slicing gradient magnetic field in a direction along a first axis; The control procedure for collecting magnetic resonance signals by generating a read gradient magnetic field in a direction along at least one of the axis and the third axis is described in the first. the magnetic resonance signal obtained by executing the control procedure is subjected to one-dimensional Fourier transform;

The magnetic resonance imaging apparatus is characterized in that it includes a fourth means capable of arranging the converted data in a specific direction of the image matrix.

(Function) According to the invention claimed in claim 1, data collection does not require time, and a projection image of a specific cross section in one orthogonal axial direction can be observed every hour instead of a two-dimensional tomographic image. Real-time observation of moving objects becomes possible.

According to the invention according to claim 2, it is possible to observe not a two-dimensional tomographic image but a projected image of a specific cross section in any one axis direction every time without requiring time for data collection, so that real-time observation of a moving body can be performed. Observation becomes possible.

According to the invention according to claim 3, a fourth structure that utilizes the configuration for generating a two-dimensional tomographic image and has a relatively simple configuration is also provided.
By simply having the means, projection images of a specific cross section in an orthogonal direction or in any one axis direction can be observed every time without requiring time for data collection, and real-time observation of a moving body is possible.

(Example) An example of the magnetic resonance imaging method and apparatus according to the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of the magnetic resonance imaging apparatus of this embodiment, and FIGS. 2 and 3 (pulse sequence diagrams of the magnetic resonance imaging method executed by the magnetic resonance imaging apparatus of this embodiment, 4 and 5 are diagrams showing the data collection situation in the magnetic resonance imaging apparatus of this embodiment and the magnetic resonance imaging method of this embodiment, and FIGS. 6 and 7 are diagrams showing the magnetic resonance imaging of this embodiment. It is a figure which shows the imaging method and display example in the apparatus and the magnetic resonance imaging method of a present Example.

In FIG. 1, there is a static magnetic field magnet 2. - Gradient magnetic field coils that generate gradient magnetic fields along the X, Y, and Z axis directions 3. A probe 4 having a transmitter coil and a receiver coil is incorporated, and a space is formed inside these into which a subject (not shown) is introduced, and a magnetic field generated within the space generates a magnetic resonance phenomenon and generates a magnetic resonance signal. It is now possible to collect.

Further, the gradient magnetic field coil 3 is driven by a gradient magnetic field controller 5 and an amplifier 6, and the probe 4 is driven by a transmitter 7.
．． It is driven by receiver 8. Gradient magnetic field controller 5
．． Transmitter 7. The receiver 8 is under the control of a sequencer 9, which in turn is under the control of a computer system 10.

And probe 4. The magnetic resonance signals obtained through the receiver 8 are transmitted to the computer system 1 via the memory 11.
0, where image reconstruction processing is performed using two-dimensional and three-dimensional Fourier transform methods, and display is performed on the display 12.

The above configuration is the same as the conventional one, but in this embodiment, the probe 4. Receiver 8. A one-dimensional Fourier transform process is performed on the magnetic resonance signal obtained through the memory 11.
The dimensional FFT processor 13 performs the process, and the one-dimensional projection data that is the result of this processing is sent to the distributor 14. The image is supplied to the computer system 10 and display 12 through the image buffer 15.

Here, the memory 11, one-dimensional FFT processor 13, and distributor 14 are controlled by the sequencer 9.

In addition, the sequencer 9 can execute not only the conventional pulse spin echo method and gradient-end field echo method, but also the pulse sequences shown in Figs. 2 and 3 as well as Figs. 9 and 10. It is something that can be done.

The method shown in Figure 2 is a gradient-end field echo method that excludes a gradient magnetic field for phase encoding, and is described below.
The first method is called the motion imaging gradient-end field echo method.

Furthermore, the method shown in FIG. 3 is a pulse spin-echo method excluding the gradient magnetic field for phase encoding, and is hereinafter referred to as the first motion imaging pulse spin-echo method.

Note that G2 indicates a gradient magnetic field along the Z-axis direction, and GX indicates a gradient magnetic field along the Z-axis direction.
G indicates a gradient magnetic field along the axial direction, and G indicates a gradient magnetic field for slicing, GR indicates a gradient magnetic field for reading, and in this example, GZ indicates G
s, and Gx is GR. Therefore, there is no gradient magnetic field GY along the Y-axis direction and no gradient magnetic field G8 for phase encoding.

In addition, Hl is a high frequency pulse for refocusing magnetization during excitation, and generally has a flip angle of around 90'', and H2 is a high frequency pulse for refocusing magnetization during excitation, and generally has a flip angle of around 90''. It is around 180°.

Next, the operation of the apparatus and method configured as described above will be explained as a specific example with reference to FIGS. 4 to 7.

That is, as shown in FIG. 4, there is a subject P, and the coordinates X and Y shown in the figure are within the main body 1.

Z is defined and the illustrated cross-sectional area S (for example, the plane containing the heart)
Let's do slicing. Here, when the sequence shown in FIG. 2 or 3 is executed and the obtained magnetic resonance signal is subjected to one-dimensional Fourier transform processing by the one-dimensional FFT processor 13, as shown schematically in FIG. , one-dimensional projection data along the X-axis direction regarding the cross-sectional area S is obtained.

If the steps of data collection and one-dimensional Fourier transformation processing for the cross-sectional area S as described above are repeated many times, and the data is arranged in a specific direction of the image matrix MN on the image buffer 15, as shown in FIG. A morphological change image (motion image) Ml of the cross-sectional area S over time is obtained.

The motion image MI in this case is the cross-sectional area S
It contains the heart, chest wall, and lungs.

Display 12 displays dynamic images of the heart wall and chambers over time.
can be displayed on top.

As described above, according to this embodiment, by using the configuration for generating a two-dimensional tomographic image and also having a one-dimensional FFT processor 139, distributor 14, and image buffer 15, which have relatively simple configurations, Using the first motion imaging gradient-end field echo method and the first motion imaging pulse spin echo method, which do not require time for data collection, data can be collected in one orthogonal uniaxial direction for a specific cross section rather than a two-dimensional tomographic image. Since the projected image of the image can be observed every hour, real-time dynamic observation of a moving body such as the heart becomes possible.

Note that the data collection repetition time TR and echo time TE in the first motion imaging gradient-end field echo method and the first motion imaging pulse spin echo method.

By appropriately selecting parameters such as the flip angles of the high-frequency pulses H1 and H2, image information with different characteristics can be obtained, just as in the normal gradient-end field echo method and pulsed spin-echo method. .

In particular, in this clinical example, the heart is the subject of imaging, and the parameters relaxation time T1. Since the MR multiplication signal intensity differs due to the influence of T2 and blood flow, it is possible to clearly image not only the outer contour of the heart but also the inner contour. In addition, when adopting the first motion imaging pulse-spin echo method for the purpose of high-speed data collection,
It is preferable to use one in which the data collection repetition time TR is set short.

Furthermore, averaging may be used for one line of imaging data by averaging projection data of a plurality of times.

In the example described above, the data is projected onto the X-axis, which is one of the orthogonal axes, but as shown in FIG. 8, it is also possible to project onto the X'-axis having an angle θ. This can be done by distributing the read gradient magnetic field to the X and Y axes. That is, in the method shown in FIG. 9, the read gradient magnetic field G is set to X.

This is a gradient-end field echo method in which the gradient magnetic field for phase encoding is appropriately distributed on the Y axis and the gradient magnetic field for phase encoding is excluded.
The second motion imaging φ gradient end field echo method is called. The method shown in FIG. 10 is a pulse spin echo method in which the read gradient magnetic field Gs is appropriately distributed to the X and Y axes and the phase encode gradient magnetic field is excluded. This is called the pulse spin echo method.

, according to the above second motion imaging gradient-end field echo method and second motion imaging pulse spin echo method, X with an angle θ
It becomes possible to observe the real-time dynamics of a moving body along the ′ axis.

In addition, in the configuration shown in FIG. 1, instead of having a one-dimensional FFT processor 131, distributor 14□ image processor 15, an equivalent configuration is provided in the computer system 10 in terms of hardware or software. It's okay.

In addition, various modifications can be made without departing from the gist of the present invention.

[Effects of the Invention] As described above, the invention according to claim 1 irradiates the subject with an excitation high-frequency pulse for causing a magnetic resonance phenomenon in a specific region of the subject, and also irradiates the subject in a direction along the first axis. A slicing gradient magnetic field is generated, a read gradient magnetic field is generated in a direction along a second axis perpendicular to the first axis, a magnetic resonance signal is collected, this magnetic resonance signal is subjected to one-dimensional Fourier transform, and this This is a magnetic resonance imaging method characterized in that image information is obtained by executing a series of procedures for arranging transformed data in a specific direction of an image matrix many times.

According to the method invention, it is possible to observe a projection image of a specific cross section in the orthogonal uniaxial direction every time, rather than a two-dimensional tomographic image, without requiring time for data collection, so real-time observation of a moving body is possible. becomes.

Further, the invention according to claim 2 irradiates the subject with an excitation high-frequency pulse for causing a magnetic resonance phenomenon in a specific region of the subject, and also generates a gradient magnetic field for slicing in a direction along the first axis. 1. Next, read gradient magnetic fields are generated in directions along a second axis and a third axis perpendicular to the first axis to collect magnetic resonance signals, and this magnetic resonance signal is subjected to one-dimensional Fourier transform, and the converted data is A magnetic resonance imaging method is used, which is characterized by obtaining image information by executing a series of steps for arranging images in a specific direction in an image matrix many times.

According to the method invention, it is possible to observe a projection image of a specific cross section in any one axis direction every time, rather than a two-dimensional tomographic image, without requiring time for data collection, so real-time observation of a moving body is possible. becomes.

Furthermore, the invention according to claim 3 includes a first means for causing a magnetic resonance phenomenon in a specific region of a subject; and a magnetic resonance signal is induced from the region where the magnetic resonance phenomenon occurs by the first means; A magnetic resonance imaging apparatus comprising a second means for imparting position information when collecting signals, and a third means for generating image information including a two-dimensional image matrix based on the magnetic resonance signals collected by the second means, irradiating the subject with an excitation high-frequency pulse for causing a magnetic resonance phenomenon in a specific region of the subject, and generating a slicing gradient magnetic field in a direction along a first axis, which is then orthogonal to the first axis; The first and second means have a control procedure for generating a read gradient magnetic field in a direction along at least one of the second axis and the third axis to collect magnetic resonance signals, and the control procedure includes: The present invention is a magnetic resonance imaging apparatus characterized by comprising a fourth means capable of performing one-dimensional Fourier transform on a magnetic resonance signal obtained by the execution and arranging the transformed data in a specific direction of an image matrix.

According to the device of the present invention, by using the structure of a device for generating a two-dimensional tomographic image and also having a fourth means with a relatively simple structure, it is possible to obtain orthogonal information about a specific cross section without requiring time for data collection. Alternatively, a projected image in any one axis direction can be observed every time, making it possible to observe a moving body in real time.

Therefore, according to the present invention, it is possible to provide a magnetic resonance imaging method and apparatus that enable real-time observation of a moving body.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the magnetic resonance imaging apparatus of the present invention, and FIGS. 2 and 3 are pulse sequence diagrams of the magnetic resonance imaging method executed by the magnetic resonance imaging apparatus of the present embodiment. , FIG. 4 and FIG. 5 are diagrams showing the data collection situation in the magnetic resonance imaging apparatus of this embodiment and the magnetic resonance imaging method of this embodiment, and FIGS. 6 and 7 are diagrams showing the magnetic resonance imaging of this embodiment. 8 is a diagram showing the imaging method and display example in the apparatus and the magnetic resonance imaging method of this embodiment, FIG. 8 is a diagram showing the data collection situation in the magnetic resonance imaging method of another embodiment of the present invention, FIG. FIG. 10 is a pulse sequence diagram of a magnetic resonance imaging method executed by a magnetic resonance imaging apparatus according to another embodiment. DESCRIPTION OF SYMBOLS 1... Main body, 2... Static magnetic field magnet, 3... Gradient magnetic field coil, 4... Probe, 5... Gradient magnetic field controller, 6... Amplifier, 7... Transmitter, 8・・・
- Receiver, 9... Sequencer, 10... Computer system, 11... Memory, 12... Display, 13... One-dimensional FFT processor, 14... Distributor, 15... image buffer. Figure 2

Claims (3)

[Claims] (1) A high-frequency pulse for excitation to cause a magnetic resonance phenomenon in a specific region of the subject is irradiated to the subject, and a gradient magnetic field for slicing is generated in the direction along the first axis, and then a gradient magnetic field for slicing is generated in the direction along the first axis. A series of steps in which a read gradient magnetic field is generated in the direction along the orthogonal second axis, a magnetic resonance signal is collected, this magnetic resonance signal is subjected to one-dimensional Fourier transformation, and this transformed data is arranged in a specific direction of an image matrix. , a magnetic resonance imaging method characterized in that image information is obtained by performing it multiple times. (2) irradiating the subject with an excitation high-frequency pulse for causing a magnetic resonance phenomenon in a specific region of the subject, and generating a slicing gradient magnetic field in a direction along the first axis; Magnetic resonance signals are collected by generating gradient magnetic fields for reading in directions along the orthogonal second and third axes, subjected to one-dimensional Fourier transformation of the magnetic resonance signals, and converted data to a specific direction of the image matrix. A magnetic resonance imaging method characterized by obtaining image information by performing a series of arranging steps multiple times. (3) a first means for causing a magnetic resonance phenomenon in a specific region of the subject; and position information when the first means induces a magnetic resonance signal from the region where the magnetic resonance phenomenon occurs and collects the signal. and a third means for generating image information having a two-dimensional image matrix based on the magnetic resonance signals collected by the second means. irradiating the subject with an excitation high-frequency pulse for producing a magnetic resonance phenomenon and generating a slicing gradient magnetic field in a direction along the first axis;
The first and second means have a control procedure for generating a read gradient magnetic field in a direction along at least one of a second axis and a third axis perpendicular to the axis and collecting magnetic resonance signals, and A magnetic resonance imaging apparatus comprising a fourth means capable of performing one-dimensional Fourier transform on the magnetic resonance signals obtained by executing the control procedure and arranging the transformed data in a specific direction of an image matrix.