JPH04156825A - Mri device equipped with process to draw blood flow image using influx effect - Google Patents

Abstract

PURPOSE:To shorten the photographing time and provide a device, in which an image obtained assumes an angio image admitting direct observation, not by preparing angio image through a three-dimensional measurement performed previously, but by measuring the two-dimensional projected angio image directly. CONSTITUTION:To make rotation addition of unclear spin in a two-dimensional plane region having a certain thickness in an amount corresponding to the space coordinates, coding is made normally being divided in two directions X, Y. The X direction is designated as the frequency encode direction, while the Y direction is used as the phase encode direction. One-dimension measuring data of N samples are collected in the X-direction, and complex data of N+1 samples are obtained. Subjecting it to one-dimension Fourier transform will give information of one line of the applicable image. If such pieces of data are collected from a number of cross sections, they are represented by a single sheet of image. According to the present invention, two-dimensional blood vessel image due to direct projection is obtained, which eliminates the process of projecting from a three-dimensional blood vessel image onto a two-dimensional plane as conventional method, and the total processing time can be shortened to a great extent.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an NMR imaging apparatus (hereinafter referred to as MRI apparatus) that obtains a tomographic image of an object to be examined by utilizing nuclear magnetic resonance (hereinafter referred to as NMR) phenomenon. ).

[Prior Art] An MRI device obtains not only anatomical information, but also biochemical information, chemical shift information, and blood flow information, such as an image that visualizes the X-ray absorption coefficient obtained by an X-ray CT device. Because of this, it has attracted attention in recent years and is rapidly becoming popular.

Among them, the method of depicting blood flow signals using an MHI device is called MR angiography, which does not require a contrast agent unlike angiography using X-rays, and has no side effects on patients, so it is particularly suitable for clinical application. It's becoming popular. The present invention relates to MR angiography.

First, the MRI apparatus will be explained.

An MRI apparatus utilizes NMR phenomena to detect the density distribution of nuclear spins (hereinafter simply referred to as spins), relaxation time distribution (information regarding longitudinal relaxation time T1 or transverse relaxation time T2), etc. at a desired inspection site in a subject. The cross-sectional information of the subject is displayed as an image based on the measured data.

In this apparatus, as shown in FIG. 4, a subject 1 is placed in a static magnetic field generator 10 that generates a static magnetic field of about 0.02 to 2 Tesla. At this time, the spins in the subject perform precession around the direction of the static magnetic field at a frequency determined by the strength H of the static magnetic field. This frequency is called the Larmor frequency. Larmor frequency υ. is ν. =-H, (1) 2π Here, Ho: static magnetic field strength γ: has a unique value for each type of atomic nucleus expressed by the gyromagnetic ratio unique to the nuclide. Also, the angular velocity of Larmor precession is ω.

Then, ω. =2πν.

Because of the relationship, ω. =γH, (2) is given by

Now, the Larmor frequency ν of the atomic nucleus is to be measured by the high-frequency transmitting coil 20a. When the subject is irradiated with a high-frequency magnetic field having a frequency f equal to f, the spins are excited and transition to a higher energy level state. When this high-frequency magnetic field is cut off, the spins try to return to their original lower energy levels. This process is called relaxation phenomenon. The weak electromagnetic waves emitted at this time are received by the receiving coil 20b, and the amplifier 23
After amplifying the waveform with a filter and digitizing it with an A/D converter 25, the central processing unit 11 (hereinafter referred to as
(referred to as the CPU). The CPU II performs reconstruction calculations based on the obtained signals, and the calculated data is displayed on the display 28 as a tomographic image of the subject 1. The above-described high-frequency magnetic field is obtained by amplifying a signal sent out by the sequencer 12 controlled by the CPU II by the high-frequency amplifier 19 and sending the amplified signal to the high-frequency transmitting coil 20a.

By the way, in addition to the above-mentioned static magnetic field and high-frequency magnetic field, MR equipment uses a gradient magnetic field that generates a gradient magnetic field such that the relationship between spatial position and magnetic field strength is linear in order to identify positional information in space. A coil group 21 is equipped. These gradient magnetic field coil groups are supplied with current from a gradient magnetic field coil power supply 22 that operates based on signals from the sequencer 12, and generate gradient magnetic fields around the subject.

Next, I will briefly explain the principle of tomographic imaging in the MHI device. From a classical mechanical viewpoint, the spins in the static magnetic field H1 behave like a single bar magnet, and the Larmor frequency ν, which was mentioned earlier, It precesses around the direction of the static magnetic field (this direction is usually taken as the Z-axis). This frequency is given by equation (2) and is proportional to the static magnetic field strength. γ in equations (1) and (2) is called the gyromagnetic ratio, and is specific to the nuclide. The amount of spins in a unit pixel in the object is enormous, and each spin rotates with a random phase in the static magnetic field, so the X and Y direction components perpendicular to the static magnetic field direction cancel each other out, and the Z Macroscopic magnetization in only the direction remains. In this state, when a high frequency magnetic field H1 having a frequency equal to the Larmor frequency ν is irradiated in the X direction, the macroscopic magnetization starts to fall in the Y direction. This angle of inclination is proportional to the product of the intensity of the irradiated high-frequency magnetic field H1 and the irradiation time. When the high-frequency magnetic field is considered as a pulse, a case where the macroscopic magnetization is inverted by 90 degrees is a 90 degree pulse, and a case where the macroscopic magnetization is inverted by 18080 degrees is a 90 degree pulse, and one in which the macroscopic magnetization is inverted by 18080 degrees is a 90 degree pulse. This is called a 180 degree pulse.

Most of the commercially available MRI devices are
Images are taken using the dimensional Fourier transform imaging method. The principle of imaging will be explained based on the spin echo method, which is a typical method among these methods. This pulse sequence starts with 90
The macroscopic magnetization is tilted by 90 degrees. Immediately after the collapse, what can be regarded as macroscopic magnetization is subtly influenced by the interaction between spins and the surrounding magnetic environment, and the frequency of rotation of each spin differs slightly, so as time passes, the difference between each spin changes. A phase difference occurs. 18 in this condition
When the 'O degree pulse is irradiated, each spin is reversed in the rotating coordinate system, and the rotational speed of each spin continues to rotate at the same rate. Therefore, the relationship that was previously in the direction of mutual phase divergence is now in the direction of convergence. change. When fully converged, it forms an echo signal. At this time, if the time from the 90 degree pulse to the echo formation is the echo time TE, then it is desirable that the time from the 90 degree pulse to the 180 degree pulse be TE/2.

It is not possible to identify where in the static magnetic field a signal measured in this way is generated. Therefore, a gradient magnetic field whose spatial position changes linearly is used for identification. First, when a gradient magnetic field is applied to a spatially uniform static magnetic field, the spatial distance and magnetic field strength change linearly, so if you irradiate a high-frequency magnetic field according to the frequency of the place where you want to obtain a tomographic image during irradiation, Since only the portion that resonates with that frequency is excited, the excited plane is formed as a tomographic image. Next, when reading signals, if measurement is performed while applying a gradient magnetic field, the position can be discriminated with respect to one axis of the tomographic plane by Fourier transforming this. In the direction perpendicular to this axis,
A phase corresponding to the position is added by a gradient magnetic field having an inclination in this direction, and the position is similarly discriminated by Fourier transformation. In order to distinguish these three orthogonal axes in space, gradient magnetic field coil groups corresponding to the three axes are installed.

Regarding the above-mentioned MRI apparatus, please refer to "NMR Medicine" (Basic and Clinical) (Nuclear Magnetic Resonance Medical Research Gold Line, Maruzen Co., Ltd., published on January 20, 1980).

By the way, in an MRI apparatus, a set of gradient magnetic fields consisting of a pair of positive and negative gradient magnetic fields with the same gradient magnetic field strength and the same application time is called a flow encode pulse, and by its application, the nucleus of the stationary part is The spin returns its phase, but in some parts of the flow, a new phase is added. Therefore, signals in areas where there is flow, such as blood flow, disappear.

In order to restore this, it is sufficient to apply a gradient magnetic field that has a negative relationship with the above-mentioned phase. Therefore, by applying two sets of flow encode pulses in positive and negative pairs, it is possible to restore the phase of a portion where there is a flow. Such a method is called a gradient magnetic field moment zeroing method or a phase rephasing method.

For a method of depicting blood flow signals with high brightness by applying such a gradient magnetic field, see, for example, "Magnetic Re5onance Impressions".
ag-ing of the Body'', edit
d by D, D, 5tark and W, G.

Bradley, Jr., Raven Press,
New York (+987) or C, L, D
umoulin et al;”Three-Dime
ns ion-al Time-of-Flight
Magnetic Re5onance Angio-
graphy Using 5pin Sar, ura
tion”, Magnetic Re5onace i
n Medicine, 11. pp, 35-46 (
(1989) etc. for details.

When this gradient magnetic field moment zeroing method is applied to the gradient echo method, blood flow signals can be captured with high signals. In this method, images are acquired using the conventional two-dimensional Fourier transform method, and information on a large number of tomographic planes is obtained.
A dimensional blood vessel image (angiogram) is projected two-dimensionally and is provided for diagnosis by a doctor. This method requires an imaging time equal to the time required to obtain -2D images multiplied by the number of images to be captured.

As described above, with the conventional technology, an unnecessarily long imaging time is required even to obtain -2-dimensional MR angioimages.

[Problems to be Solved by the Invention] In the above-mentioned conventional technology, in order to obtain -2-dimensional MR angio images by performing projection processing from the 3-dimensional angio images, - degree 3-dimensional measurement is required. Therefore, the imaging time was long.

The purpose of the present invention is to shorten the imaging time by directly measuring a two-dimensional projected angio image, rather than creating an angio image by performing three-dimensional measurements in advance, and to directly The object of the present invention is to provide a device that provides an observable angioimage.

[Means for solving the problem] The above purpose is to set the number of phase encodes for normal image signal measurement to 1, degenerate the normally obtained two-dimensional image to one-dimensional in the phase encode direction, and perform a so-called line scan. By constructing a two-dimensional image by a collection of many degenerate line scans, and by adopting an imaging sequence that measures the blood flow area with high signals, the two-dimensional angio image can be directly measured. You can achieve what you want.

More specifically, means for applying a static magnetic field and a gradient magnetic field to an object to be inspected; means for applying a high frequency pulse to cause nuclear magnetic resonance in the nuclei of atoms constituting the tissue of the object; In a nuclear magnetic resonance imaging apparatus comprising a nuclear magnetic resonance signal detection means for detecting a signal due to resonance, and six means for Fourier transforming the nuclear magnetic resonance signal detected by the detection means to reconstruct an image. By providing a process in the pulse sequence to apply a gradient magnetic field to reverse the phase rotation of the blood flow, the inflowing blood flow is captured with a higher signal than the stationary part, and only the O encode is measured in the phase encode direction. If this is done for a large number of positions, a two-dimensional angioimage can be directly obtained.

[Operation] In general, currently commercially available MHI devices use protons as the target nuclide, and obtain information on the proton density and its relaxation time within the body to be inspected through measurement.

Now, let's consider drawing blood flow perpendicular to a two-dimensional cross section. When flowing nuclear spins are applied with a gradient magnetic field, they feel different resonance frequencies as they move in the direction of the gradient magnetic field being applied, so when viewed from the center resonance frequency, the flowing nuclear spins have a phase advance. You will feel a delay, or a phase rotation. Therefore, signal loss generally occurs in moving parts compared to signals in stationary parts.

In order to prevent this signal loss, it is sufficient to restore the phase lead/lag described above. Since the phase rotation of flowing nuclear spins is caused by the application of a gradient magnetic field, it is also possible to recover the phase return by applying a gradient magnetic field. FIG. 2 shows how the combination of applying a pair of positive and negative gradient magnetic fields affects the phase of nuclear spins. The lower part of the figure shows the phase effect on the nuclear spins of the application of a pair of positive and negative gradient magnetic fields. Since the nuclear spin in the stationary part does not move,
If the gradient magnetic field strength is the same on the positive side and the negative side, and the application time is also the same, the amount of phase rotation felt while the positive side gradient magnetic field is applied and the negative side gradient magnetic field are the same. The amount of phase rotation felt during the rotation is the same in magnitude and opposite in sign, so as a result, the phase rotation becomes zero.

However, for example, nuclear spins flowing at a constant speed V cumulatively receive different amounts of phase rotation as they move, and as a result are expressed as a square function of time, so after applying a pair of positive and negative gradient magnetic fields, the You will feel the phase φ expressed by equation 1.

φ= 2 πGvt t
(1)b Here, G is the strength of the gradient magnetic field, G is the application time of the gradient magnetic field on one side, and G is the time between the centers of gravity of the pair of positive and negative gradient magnetic fields. Due to this phase rotation, nuclear spins flowing like blood flow cause signal loss.

It is clear that this signal can be recovered by correcting the phase rotation. The upper part of FIG. 2 shows that in order to restore the amount of phase rotation felt by the flowing nuclear spins, the amount of phase rotation is returned to the original value, and the negative one of the combinations of the positive and negative pairs of gradient magnetic fields is The phase of the flowing nuclear spins is also made zero by applying it either before or after the gradient magnetic field and adding a negative phase as shown in the first equation. Of course, the phase of the nuclear spin in the stationary part is
Needless to say, it remains zero even after the pair of gradient magnetic fields are applied. This method is called gradient magnetic field moment zeroing method,
It is also called "Rephasing".

By correcting the phase rotation of the blood flow in which the signal has disappeared in this manner, the blood flow signal can be depicted as a high signal on the image. FIG. 3 shows a gradient echo method in which a phase return effect is added to the slice selection excitation axis and the signal readout axis.

In order to use it for MR angiography, it is necessary to improve the separation ability between the blood flow part and the stationary part.

Since the longitudinal relaxation time of tissue is usually long, if the repetition time TR is shorter than that, the stationary area will have a sufficiently low signal, so it is possible to increase the separation between the blood flow area and the stationary area. It is possible to visualize the flow with a high signal.

[Example] Hereinafter, an example of the present invention will be described in detail based on the accompanying drawings.

FIG. 4 is a block diagram showing an example of the overall configuration of a nuclear magnetic resonance imaging apparatus according to the present invention. This nuclear magnetic resonance imaging apparatus uses a nuclear magnetic resonance (NMR) phenomenon to obtain a tomographic image of a subject 1, and uses a static magnetic field generating magnet 1.
0, a central processing unit (hereinafter referred to as CPU) 11, a sequencer 12, a transmission system 13, a magnetic field gradient generation system 14, a reception system 15, and a signal processing system 16. The static magnetic field generating magnet 10 generates a strong and uniform static magnetic field around the subject 1 in the body axis direction or in a direction perpendicular to the body axis, and has a certain extent around the subject 1. A permanent magnet type, normal conduction type, or superconducting type magnetic field generating means is arranged in the space. The sequencer 12 operates under the control of the CPU II, and sends various commands necessary for data collection of tomographic images of the subject 1 to the transmission system 13, the magnetic field gradient generation system 14, and the reception system 15. The transmission system 13 includes a high-frequency oscillator 7, a modulator 18, a high-frequency amplifier 19, and a high-frequency coil 20a on the transmitting side.
The high-frequency pulse output from the high-frequency oscillator 17 is amplitude-modulated by the modulator 18 according to the command from the sequencer 12, and the amplitude-modulated high-frequency pulse is transmitted to the high-frequency amplifier 19.
The electromagnetic waves are amplified and then supplied to a high-frequency coil 20a placed close to the object 1 to be inspected, so that the object 1 to be inspected is irradiated with electromagnetic waves. The magnetic field gradient generation system 14 consists of gradient magnetic field coils 21 wound in the three axial directions of X, Y, and Z, and a gradient magnetic field power supply 22 that drives each coil. By driving the gradient magnetic field power supply 22 of
y and Gz are applied to the object 1 to be inspected.

Depending on how this gradient magnetic field is applied, a slice plane for the object 1 to be inspected can be set. The receiving system 15 includes a receiving-side high-frequency coil 20b, an amplifier 23, a quadrature phase detector 24, and an A/D converter 25.
The electromagnetic wave (NMR signal) in response to is detected by the high frequency coil 20b placed close to the test object l, and is sent to the amplifier 23.
and two bases of acquired data that are input to the A/D converter 25 via the quadrature phase detector 24 and converted into digital quantities, and further sampled by the quadrature phase detector 24 at the timing according to the command from the sequencer 12. The signal is sent to a signal processing system 16. This signal processing system 16 includes a CPU Ull and a magnetic disk 26.
and a storage device such as a magnetic tape 27, and a display 28 such as a CRT. The signal intensity distribution or the distribution obtained by performing appropriate calculations on a plurality of signals is converted into an image and displayed on the display 28. In addition, in FIG. 4, the high frequency coils 20a, 20b and the gradient magnetic field coil 21 on the transmitting side and receiving side
is arranged in the magnetic field space of the static magnetic field generating magnet 10 arranged in the space around the object 1 to be inspected.

FIG. 3 schematically represents a time sequence in gradient echo measurement used in the present invention. In FIG. 3, RF indicates the timing of radio frequency signal irradiation and the envelope for selective excitation. Gz indicates the timing of applying a gradient magnetic field in the slice direction. ay indicates a gradient magnetic field in the phase encoding direction. G
x indicates the timing of application of the frequency encode gradient magnetic field, and SIGNAL indicates the NMR signal to be measured. The bottom row shows the time sequence divided into sections 1 to 5. Note that the three axes X, Y, and Z are Cartesian coordinate axes that are orthogonal to each other. In section 1 in FIG. 3, a selective excitation pulse at an angle of 90 degrees or less is irradiated, and a gradient magnetic field in the slice direction is applied. In section 2, a negative gradient magnetic field in the slice selection direction is applied to restore the phase rotation at both ends of the slice, and at the same time prepare for the phase return effect in the slice direction in the next section 3. Furthermore, in section 2, a gradient magnetic field in the frequency encoding direction is applied so that a phase return effect occurs when measuring the echo signal. In section 3, a negative frequency encoding gradient magnetic field is applied. This is to dephase (invert the phase of) the nuclear spins in advance so that the time origin is at the center of section 5 when measuring the NMR signal in section 5. In section 4, only the negative frequency encoding gradient magnetic field is applied.

In section 5, a positive frequency encoding gradient magnetic field is applied and an NMR signal is measured.

To perform NMR imaging, as described above, an RF pulse is irradiated with a gradient magnetic field applied to the static magnetic field, and a gradient is applied to encode the NMR signal emitted from the inspection area of the object 1 as spatial information. Apply a magnetic field, NM
After measuring the R signal, the image is reconstructed.

To encode space, a gradient magnetic field is used, which takes advantage of the fact that the nuclear magnetic resonance frequency ω has a linear relationship with the magnetic field strength. In other words, if the linearity of the gradient magnetic field is maintained spatially, the relationship between the spatial position and frequency in the target region will be linear, and by simply Fourier transforming the NMR signal, which is time information, and replacing it with the frequency axis, the The image is reconstructed by utilizing the fact that position information of 1 is obtained.

Normally, images are reconstructed using a two-dimensional Fourier transform method, but in the present invention, images are reconstructed using a two-dimensional Fourier transform method.
In other words, integrated information is obtained. This method of measurement is also called line scanning. An image can be constructed by collecting a large number of line scans at equal intervals. A method of encoding space after the nuclear spins in a region having a certain thickness in the slice direction are excited by selective excitation will be described below.

In order to add rotation to the nuclear spin of a two-dimensional surface area with a certain thickness by an amount corresponding to the spatial coordinates, two
Encode by dividing into directions. According to FIG. 3, the X direction is divided into a frequency encoding direction, and the X direction is divided into a phase encoding direction.

In the frequency encoding direction, when reading the spin echo signal, the phase must be shifted by Nπ at both ends of the field of view, and if the frequency encoding time is Tx, then y Gx - D - Tx = N yr =
47) The following relationship must be satisfied. Here, γ
: The gyromagnetic ratio of the proton, which is the target nucleus (2,6751
x IO'rad/sec/Gauss)Gx/Frequency Encoding direction gradient magnetic field strength D = Field of view diameter N: Number of measurement samples.

Application of a gradient magnetic field in the frequency encoding direction means a method of encoding spatial coordinates in the X direction on the frequency axis.

In this way, N samples of one-dimensional measurement data are collected in the X direction. Usually, QPD is used for NMR signal measurement.
(Quadrature Phase Detection
On) method is used to collect the real and imaginary parts at the same time, so
Complex data of NXI samples is obtained. If this is subjected to one-dimensional Fourier transform, information on one line of the image can be obtained.

If such data is collected for many cross sections, 1
It can be formed as a single image.

In Fig. 3, as already explained in Fig. 2, the method for imaging flowing components such as blood flow with high signals is to use phase return based on a combination of two pairs of positive and negative gradient magnetic fields as the slice selection axis. It is applied to the frequency encode axis to depict blood flow, etc. with high signals.

Now, a pulse sequence that depicts blood flow with a high signal as shown in Fig. 3 is executed as an integrated line scan in the phase encoding direction, and the resonant frequency to be measured is
If images are taken so that the position changes by II, a single blood vessel image can be formed as a collection of the images. Conventionally, as shown in Figure 5, a large number of two-dimensional blood vessel images were measured, and the three images obtained were
The dimensional blood vessel images were projected into a two-dimensional image and used for diagnosis by doctors. However, this method requires about 20 minutes to capture a three-dimensional blood vessel image. For example, repetition time TR: 40m5. Number of phase encodes: 256. Number of slices = 64. Number of additions: 21.85 under two imaging conditions
minute imaging time is required. With this measurement, 64 two-dimensional blood vessel images are obtained. If the slice thickness is 1 m, this means that 64 images are obtained in the slice direction.

Conventionally, this was projected to obtain a two-dimensional blood vessel image, that is, an MR angio image.

In the present invention, since a directly projected two-dimensional blood vessel image is obtained, the imaging time for one blood vessel image is about 20 seconds, which can significantly reduce the time. Moreover, since the time required for projecting a three-dimensional blood vessel image onto a two-dimensional surface as in the conventional method is unnecessary, the overall processing time can be shortened from this point of view as well.

FIG. 1 shows how a blood vessel image is formed when one line scan is performed using the pulse sequence shown in FIG. 3 according to the present invention. When the gradient echo method with a short repetition time TR is used, the signal of the stationary part 32 is small and only the signal of the blood vessel 31 can be captured largely due to the TR being shorter than the longitudinal relaxation time of the tissue. If this line scan is performed 1 m at a time and a total of 256 measurements are taken, a two-dimensional projected blood vessel image can be directly captured. In this case, repetition time TR: 40ms, number of lines 256. Number of additions, 2
The imaging time is 20.48 seconds, and the patient restraint time is extremely short, and it can also be applied to breath-hold imaging of the abdomen, etc.
It can be said that the present invention is highly useful.

The method shown in FIG. 6 is preferably used when the method shown in FIG. 1 does not provide a sufficiently high separation ability between the signal of the stationary part and the signal of the blood flow part. In this method, measurement is performed using a sequence with a phase return effect and a sequence without it, and only blood vessel signals are extracted from the difference between the two. FIG. 6(a) shows a cross section of a human body. If the phase return effect is working sufficiently, the signal strength of the stationary part and the blood flow part will be about the same, so
When a line scan is performed and the profile of the signal is viewed, a cross-sectional profile Sg1 in which the position of the blood vessel is unknown is obtained, as shown in FIG. 6(b). Next, when a line scan is performed with a sequence that does not include the phase return effect, the profile becomes as shown in FIG. , can be done. Since the height DR, which indicates the signal intensity of the stationary portion, is considered to be equal in both cases, by subtracting (C) from (b), a blood vessel profile as shown in FIG. 6(d) can be obtained. In this way, by measuring the line scan while shifting the line scan by 1 mm, a two-dimensional projected blood vessel image can be directly captured.

FIG. 7 shows a pulse sequence for blood vessel imaging using the above-mentioned difference. The first half is a phase-insensitive sequence section with a phase return effect, and the second half is a phase-sensitive sequence section without a phase return effect. The designations in FIG. 7 are the same as in FIG. 3. The first half of FIG. 7 is the same as FIG. 3. In the latter half, while irradiating the RF selective excitation pulse in section 6, a gradient magnetic field Gx for slice selection is applied. In section 7, the phase rotation at both ends in the slice direction is restored by applying a negative gradient magnetic field in the slice direction. Furthermore, in section 8, a negative frequency encoding direction gradient magnetic field is applied to bring the center of echo signal imaging to the center of the signal measurement time. In section 9, N
Measure the MR signal. By subtracting the signals of the first half and the second half obtained in this way, only the blood vessel image can be obtained.

FIG. 8 shows a method of collecting a large amount of line information obtained by line scanning in this way and composing it as an image. 1st
If the line information shown in the figure is measured by line scanning with a certain thickness, for example, at 1 mm intervals, and lined up with the correct positional correspondence, a large number of lines can be obtained as shown in the bird track diagram at the top of Figure 8. A two-dimensional image is formed from the line information. The lower part of FIG. 8 shows the state of the image viewed from the front. In this way, a two-dimensional blood vessel image is obtained from information from a large number of line scans.

FIG. 9 shows the process of acquiring a blood vessel image after collecting a large number of line information obtained by line scanning and configuring it as an image. By subtracting image processing 1 based on a set of line scans taken in a sequence without a phase return effect from image processing based on a set of line scans taken in a sequence with a phase return effect, the projected two-dimensional blood vessel image is obtained. ■
1 is obtained.

[Effects of the Invention] According to the present invention, the blood vessel image, which was previously measured three-dimensionally, is directly measured two-dimensionally by measuring only the O-encoding direction in the phase encoding direction during measurement, thereby reducing the measurement time. Not only is this possible, but also the process of projecting and converting a three-dimensional blood vessel image into a two-dimensional image can be omitted, which is effective in significantly shortening the patient restraint time.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the characteristics of the measurement method of the present invention, Figure 2 is a diagram showing the phase rotation of nuclear spins by the method of applying a gradient magnetic field, and Figure 3 is a diagram showing the phase return effect that depicts blood vessels with high signals. Fig. 4 is a block diagram showing an example of the overall configuration of the NMR imaging apparatus according to the present invention, and Fig. 5 shows a blood vessel image obtained by conventional three-dimensional measurement into two-dimensional image. Figure 6 is a diagram showing a method of drawing a blood vessel image by difference. Figure 7 is a diagram showing a method of drawing a blood vessel image using a gradient echo method when drawing blood vessels with and without a phase reversal effect. FIG. 8 is a pulse sequence diagram; FIG. 8 is a diagram showing a method of creating a two-dimensional blood vessel image from line scan information; FIG. 9 is a diagram showing how the method of the present invention is realized by differential measurement. ■...Object, 10...Static magnetic field generating magnet, It...
・Central processing unit, I2...Sequencer, I3...Transmission system, 14...Magnetic field gradient generation system, 15...Reception system, 1
6... Signal processing system, 17... High frequency oscillator, 18.
... Modulator, I9... High frequency amplifier, 20a... Transmitting side high frequency coil, 20b... Receiving side high frequency coil,
21... Gradient magnetic field coil, 22... Gradient magnetic field power supply,
23... Amplifier, 24... Quadrature phase detector, 25...
... A/D converter, 26... Magnetic disk, 27...
- Magnetic tape, 28... Display, 31... Blood vessel section, 32... Stationary section.蓼2 口＜kL Liquid Nail Di #8 eyes 2nd -7c ixL Sugabul #q Ro J3'' 1 Rade Gai Izumi

Claims (1)

[Scope of Claims] 1. Means for applying a static magnetic field and gradient magnetic field to an object to be inspected, and means for applying a high-frequency pulse to cause nuclear magnetic resonance in the nuclei of atoms constituting the tissue of the object to be inspected. , magnetic resonance imaging comprising: nuclear magnetic resonance signal detection means for detecting the signal due to the nuclear magnetic resonance; and means for Fourier transforming the nuclear magnetic resonance signal detected by the detection means to reconstruct an image. In a (MRI) device, by providing a pulse sequence with a process of applying a gradient magnetic field to reverse the phase rotation of the blood flow, the inflowing blood flow is captured with a higher signal than the stationary part, and the incoming blood flow is captured in the phase encoding direction with a higher signal. An MRI apparatus equipped with a process of drawing blood flow using an inflow effect, characterized in that imaging time is shortened by measuring only 0 encode and obtaining information on a large number of cross sections according to the required area. 2. In claim 1, a large number of tomographic plane information is measured three-dimensionally in the slice direction by measuring only 0 encodes as the number of phase encodes and applying a slice encode gradient magnetic field, and An MRI apparatus includes a process of depicting blood flow by an inflow effect characterized by obtaining integrated information. 3. means for applying a static magnetic field and a gradient magnetic field to the object to be inspected; means for applying a high-frequency pulse to cause nuclear magnetic resonance in the nuclei of atoms constituting the tissue of the object to be inspected; A magnetic resonance imaging (MRI) apparatus comprising a nuclear magnetic resonance signal detection means for detecting a signal, and a means for Fourier transforming the nuclear magnetic resonance signal detected by the detection means to reconstruct an image, A pulse sequence is used to apply a gradient magnetic field to restore the phase rotation of the blood flow, and a pulse sequence is used to apply a gradient magnetic field to restore the phase rotation of the blood flow, and by the difference between the two, the blood flow is captured with a higher signal than the stationary part. At the same time, the process of drawing blood flow using the inflow effect is characterized by shortening the imaging time by measuring only 0 encode in the phase encoding direction and obtaining information on multiple cross sections depending on the required area. MRI equipment equipped with