JPH0767851A - Fluid measuring method by mri device - Google Patents

Abstract

PURPOSE:To measure a speed variation of a fluid by high time resolution, and also, to derive a variation of acceleration by high time resolution by using the MRI device. CONSTITUTION:In an area in which a fluid flows, the face for intersecting with a flow is selected and excited by a first high frequency magnetic field 11, and selected and excited by a second high frequency magnetic field 13 in the direction being orthogonal to the face excited by a first high frequency magnetic field, and thereafter, a lead-out gradient magnetic field 16 is impressed repeatedly along the direction of the flow, while inverting the polarity of amplitude, and at least two or more of echo signals S2 whose phase variation of magnetization by a speed of the fluid is corrected are generated. From a moving distance of the fluid in a projection image generated from these echo signals S2 and an echo signal generation interval, flow velocity at the time when each echo signal is generated is derived.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluid measuring method in an MRI apparatus, and more particularly to a method for measuring velocity change with high time resolution.

[0002]

2. Description of the Related Art Conventionally, as a fluid measuring method in an MRI apparatus, David A Feinberg, Lawrence Crooks, John
Hoenninger, et al. Pulsatile Blood Velocity in Hum
an Arteries Displayed by Magnetic Resonance Imagin
g: Radiology 153-177 (1984), the time of flight method is generally known. This is to measure the fluid excited on the upstream side on the downstream side. That is, in the region where the fluid flows, the plane intersecting with the flow is selectively excited by the first high-frequency magnetic field,
After selective excitation by the second high-frequency magnetic field in a direction parallel or orthogonal to the plane selectively excited by the first high-frequency magnetic field, a read-out gradient magnetic field is applied to obtain an echo signal from the fluid that has been excited twice. .

[0003]

In such a conventional fluid measuring method, one flow velocity is obtained by one excitation by applying the first and second high-frequency magnetic fields, so that a plurality of flow velocity is obtained. In order to obtain, it was necessary to repeat the cycle of excitation and signal measurement, and there was a problem that the measurement time was long. Further, in order to measure the acceleration, it is necessary to have information on the velocity at least at two or more places, and the accuracy improves as the time interval becomes shorter. However, in the conventional fluid measurement method, the velocity information at two or more places can be obtained at a short time interval. It was difficult to get information.

The present invention solves such a problem of the conventional fluid measurement method and can obtain a plurality of velocity information of a fluid by only one excitation, and the velocity change can be measured with high time resolution. The purpose is to provide. Further, the present invention is
An object of the present invention is to provide a fluid measurement method capable of obtaining a two-dimensional image of a fluid by repeating a measurement sequence while changing the encoding gradient magnetic field in increments of one encoding step. Further, according to the present invention, by combining two measurement steps, it is possible to obtain a plurality of pieces of information regarding the velocity and acceleration of the fluid and a plurality of pieces of information regarding the velocity, and it is possible to extract the information regarding the acceleration from these pieces of information. The purpose is to provide.

[0005]

The above object of the present invention is to apply a high frequency pulse and then repeatedly apply a read-out gradient magnetic field while inverting the polarity of the amplitude to obtain at least two echo signals containing information on the velocity. It is achieved by continuously generating one or more pieces. That is, in the first aspect of the fluid measuring method of the present invention, in the region where the fluid flows, a surface intersecting with the flow is selectively excited by the first high-frequency magnetic field, and is selectively excited by the first high-frequency magnetic field. After being selectively excited by a second high-frequency magnetic field in the orthogonal direction, a read-out gradient magnetic field is applied along the flow direction while inverting the polarity of the amplitude, and an echo in which the phase change of the magnetization due to the velocity of the fluid is corrected At least two signals are generated, a projected image is created from each echo signal, the flow velocity at the time of each echo signal generation is obtained from the moving distance of the fluid in the projected image and the time interval of the echo signal generation, and from the change of the flow velocity It is to obtain the acceleration.

In a second aspect of the fluid measuring method of the present invention, a plane intersecting with a flow is selectively excited by a first high frequency magnetic field in a region where a fluid flows, and is parallel to a plane excited by the first high frequency magnetic field. A first step of selectively exciting the orthogonal plane with a second high-frequency magnetic field; a second step of applying an encode gradient magnetic field in a direction perpendicular to the flow direction after the selective excitation by the first step; A read-out gradient magnetic field is applied repeatedly while reversing the polarity of the amplitude along the direction, and at least two echo signals in which the phase change of the magnetization due to the velocity of the fluid is corrected are generated. , While repeating the application amount of the encoding gradient magnetic field in increments of one encoding step, and after applying the first high-frequency magnetic field in each sequence, the same time Using rows of echo signal generated by the image reconstruction, to obtain image.

A third aspect of the fluid measuring method of the present invention is
The same measurement process is repeated by changing the amplitude of the readout gradient magnetic field in the fluid measurement method according to the first aspect, and the echo signal in which the phase change of the magnetization due to the velocity and acceleration of the fluid is corrected is obtained in the first measurement process. In the second measuring step, an echo signal in which the phase change of magnetization due to the velocity of the fluid is corrected is obtained, and the acceleration component of the fluid is extracted by taking the difference between the projected images of these echo signals.

Furthermore, a fourth aspect of the fluid measuring method of the present invention is
The same measurement process is repeated by changing the amplitude of the readout gradient magnetic field in the fluid measurement method according to the second aspect, and an image including the velocity and acceleration components of the fluid obtained in the first measurement process and the image obtained in the second measurement process are obtained. The acceleration component of the fluid is extracted by taking the difference from the image containing the velocity component of the fluid.

[0009]

In the fluid measuring method according to the present invention, in the region where the fluid flows, the plane intersecting with the flow is selectively excited by the first high frequency magnetic field, and the direction parallel or orthogonal to the plane selectively excited by the first high frequency magnetic field. In addition, the region of the fluid to be traced is limited by the selective excitation by the second high frequency magnetic field. Next, a read-out gradient magnetic field is repeatedly applied along the flow direction while inverting the polarity of the amplitude, thereby continuously generating an echo signal containing information about the velocity of the fluid. Furthermore, a projection image is created from each echo signal, and the flow velocity at the time of generation of each echo signal is obtained from the moving distance of the fluid in the projection image and the time interval of echo signal generation. Thereby, the change in the velocity of the fluid can be measured with high time resolution. By adding a cycle of applying an encode gradient magnetic field to this measuring method, a two-dimensional image including the velocity component of the fluid can be obtained.

By properly selecting the amplitude of the readout gradient magnetic field for inverting the polarity of the amplitude, an echo signal in which the phase change of the magnetization due to the acceleration and velocity of the fluid is corrected can be obtained. By taking the difference between the projection image created from this echo signal and the projection image from the echo signal in which the phase change of the magnetization due to the velocity of the fluid is corrected, the direct acceleration information can be measured with high time resolution.

[0011]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 3 shows M to which the fluid measuring method of the present invention is applied.
1 shows an overall configuration of an RI apparatus, which is a static magnetic field generating magnet 1 for generating a static magnetic field in a space in which a subject 7 is placed.
And a gradient magnetic field generator 2 for generating a gradient magnetic field in this space
And a program for transmitting high frequency pulses and detecting signals.
A power source 4 for the gradient magnetic field generator 2, a transceiver 5 for transmitting high frequency pulses and receiving signals, and an operation controller 6 for controlling these and performing a predetermined operation based on the received signals. It consists of

The static magnetic field generating magnet 1 is for generating a uniform static magnetic field having a normal magnetic field strength of 0.1 T to 4.7 T around the subject 7, and a superconducting magnet or a permanent magnet is used as the magnet. . The gradient magnetic field generation unit 2 is for providing gradients to the strength of the magnetic field along the direction of the static magnetic field and two directions perpendicular thereto, and three gradient magnetic fields Gx, Gy, Gz.
It has three sets of coils for generating. The tomographic plane can be set by the method of applying the gradient magnetic field. High frequency professional
The probe 3 can be moved to a region of the subject 7 to be imaged, and generates a high frequency magnetic field with a normal frequency of 4 MHz to 200 MHz. In FIG. 3, the probe 3 is shown to be used for transmission and reception, but these may be prepared as separate probes. The control of these gradient magnetic fields and the control of the high frequency pulse and signal acquisition are performed via the arithmetic control unit 6 according to the pulse sequence.

In such an MRI apparatus, the gradient magnetic field generating coil 2 and the high frequency probe 3 are driven by a pulse sequence controlled by the arithmetic control unit 6 to apply a predetermined pulsed high frequency magnetic field to the subject 7. After selectively exciting a region of interest of the subject 7, a read-out gradient magnetic field is applied, and the high frequency magnetic field (NMR signal) generated from the subject 7 is detected by the high frequency probe 3.

By applying a read-out gradient magnetic field, the fluid undergoes a phase change φ in its magnetization. This phase φ is given by the following equation.

[0015]

[Equation 1]

In the equation, T is the time when the gradient magnetic field Gz is applied, γ is a value specific to the nuclide (eg, proton) detected by the gyromagnetic ratio, and r ₀ is the nuclear spin excited by the high frequency magnetic field. The first position, v is the velocity of the fluid.
When a gradient magnetic field composed of a pair of positive and negative (a pair of gradient magnetic fields with opposite polarities of amplitude and the same magnetic field strength) is applied, the phase returns in the stationary part and an echo signal is generated, but in the part where there is a flow, the phase The added echo signal disappears. Therefore, by applying two sets of read-out gradient magnetic fields, the phase of the fluid portion is returned and a velocity-corrected echo signal can be obtained. In the fluid measuring method of the present invention, at least two or more velocity-corrected echo signals are generated by repeatedly applying such a gradient magnetic field whose amplitude polarity is reversed.

These echo signals are received by the receiving section 5,
After performing image processing such as Fourier transform and image reconstruction and predetermined calculation, the velocity and acceleration of the fluid are obtained. The obtained image and the calculation result are displayed on a display unit (not shown).
Next, the first pulse sequence according to the fluid measurement method of the present invention will be described.
An example will be described. Here, as shown in FIG. 4, blood flowing in the blood vessel is assumed to flow in the XZ plane.

In this pulse sequence, as shown in FIG. 1, first, an exciting (90 °) high frequency pulse 11 and a gradient magnetic field (Gz) 12 for inclining the magnetic field strength in the z direction are applied in a pulse shape to form a region of interest. To excite. A region of interest can be selectively excited by simultaneously applying a high frequency pulse and a gradient magnetic field. Next, at time t ₀ after the application of the high frequency pulse 11, the reversal (180 °) high frequency pulse 13 and the gradient magnetic field (Gy) 14 for inclining the magnetic field strength in the y direction are applied in a pulse shape, and the high frequency pulse 11 generates Excite the plane orthogonal to the excited plane.

At time t ₁ after the application of the high frequency pulse 13, a gradient magnetic field (Gz) 16 for gradient of the magnetic field strength in the z direction is applied as a readout gradient magnetic field for T time.
Thereafter, the application of the gradient magnetic field is repeated every 2T time while inverting the polarity of the amplitude, that is, the direction of the gradient. During this period, an echo signal is generated every time the total amount of the products of the gradient of the readout gradient magnetic field (Gz) and the application time becomes zero. As shown in FIG. 4, the high-frequency pulse 11 is generated in the area where the echo signal is generated.
At the intersecting portion 41 of the planes excited respectively by the high frequency pulse 13 and
It flows out along the direction of flow over time.

Here, the echo signal during the period when the gradient magnetic field (Gz) is negative is S ₁ , and the echo signal during the period when the gradient magnetic field (Gz) is positive is S _2, and a set of echo signals generated first ( Focusing on S ₁ ) 17 and (S ₂ ) 18, the peak phase change of S ₁

[0021]

[Equation 2]

Is satisfied. Here, γ is the gyromagnetic ratio, r is the position of the nuclear spin, and v is the velocity of the fluid. In this equation, the integral of the term including r does not become 0 in the interval 0 to 2T, so
This corresponds to the case where the phase change due to the velocity component of the fluid is emphasized. Also, regarding the phase change during the peak of S ₂ ,

[0023]

[Equation 3]

The following holds. In this formula, the integral of the term containing r
Is 0 in the interval 0 to 4T, so it depends on the velocity component of the fluid.
This corresponds to the case where the phase change is corrected. That is, the echo signal
S₂As a high frequency pulse 11 and a high frequency pulse 13
The signals from the excited portion 41 and the fluid 42 are obtained
It Such an echo signal S₁And S₂The relationship between
All echo signals S that occur ₁, S₂Is always established between
Then, the signal that emphasized the influence of speed and the influence of speed were corrected.
The signals will alternate. Where signal S₂Is 4
Since it occurs at T intervals, information about the velocity of the fluid 41
It is possible to track at 4T intervals. Obtained signal S
₂Is transformed into a one-dimensional projection image by Fourier transform.
It

FIG. 5 shows a projected image of S ₂ . This is a state in which the fluid moves over time.
1 represents a stationary part, and 42 represents a fluid part. Since t ₁ + 4T time has elapsed from the first excitation to the first generation of S ₂ , the fluid moves to the position r ₁ with respect to the stationary portion.
Therefore, the average flow velocity v ₁ of the fluid portion during this period is r ₁ / (t
₁ + 4T). Next, the second generated S ₂ has further passed 4T time from the first generation of S ₂ , so the fluid at the initial position r ₁ moves to the position r ₂ . Thus the average flow velocity v ₂ from the position r ₁ to the position r ₂ is (r ₂ -
r ₁ ) / 4T. The average acceleration a ₁ can be obtained from the average flow velocities v ₁ and v _{2 at} these two points. Similarly, the velocity can be sequentially obtained from the position change of the fluid in the projection images at the adjacent times, and the acceleration can be sequentially obtained from the speed change.

Although the above description is for obtaining a one-dimensional projection image, a two-dimensional projection image can be obtained by adding a cycle of applying an encode gradient magnetic field to the measuring method of the first embodiment. it can. A second embodiment of the present invention will be described as a fluid measuring method for obtaining a two-dimensional projection image. In the second embodiment, the high frequency pulse 13 in FIG.
Application (first step) and readout gradient magnetic field 16
Is applied (third step), the pulsed magnetic field (Gx) 15 whose magnetic field strength changes in the x direction is applied (second step). This gradient magnetic field (Gx) has a function of adding information on the position along the x direction to the phase of the echo signal, and is therefore called an encode gradient magnetic field. The encoding gradient magnetic field strength is changed by one encoding step, and the execution of this pulse sequence (processes from the first to third steps) is repeated.

In the course of this one-time pulse sequence, the echo signal in which S ₁ and S ₂ are alternately generated is obtained as described in the first embodiment. Among the signals of S ₂ obtained at each repetition of the pulse sequence, signals having the same time from the application of the high frequency pulse 11 to the signal generation and different application amounts of the encoding gradient magnetic field (Gx) are used as a set of data (echo signal). Column). The data of each set is image-reconstructed by a two-dimensional Fourier transform to obtain a two-dimensional projection image. Figure 7
The two-dimensional projection image thus obtained is shown in FIG. The obtained projection image represents a two-dimensional projection image in which the fluid is traced at a time resolution of 4T intervals as in the first embodiment. From these projection images, the velocity of the fluid, Acceleration can be calculated.

The fluid measuring method of the present invention further provides a method for directly observing the acceleration component. A third embodiment of such a fluid measuring method will be described. In the pulse sequence based on this fluid measurement method, as shown in FIG.
A 0 ° high-frequency pulse 21 and a gradient magnetic field (Gz ₁ ) 22 are applied in a pulse shape to excite the region of interest. Next, at time t ₀ after the application of the high frequency pulse 21, the 180 ° high frequency pulse 24 and the gradient magnetic field (Gy) 25 are applied in a pulse shape to excite the plane orthogonal to the plane excited by the high frequency pulse 21. .

At time t ₁ after the application of the high frequency pulse 24, the gradient magnetic field (Gz ₁ ) 27 is applied for 2 (√ (2) −1) T time. After that, the application of the gradient magnetic field (Gz ₁ ) is repeated while inverting the polarity of the amplitude with the combination of 2T, 2T, and 4 (√ (2) −1) T time. During this time, the gradient magnetic field (Gz ₁ )
An echo signal is generated each time the total amount of the products of the slope and the application time becomes zero. The above-mentioned time interval is a value selected so that the phase change becomes zero during the application of the gradient magnetic field that is inverted the third time. That is, when the echo signal generated first is S ₃ , the echo signal generated second is S ₄ , and the echo signal generated third is S ₅ , these signals S ₃ , S
_The following equations hold for the phase changes of ₄ and S ₅ during the peak.

[0030]

[Equation 4]

[0031]

[Equation 5]

[0032]

[Equation 6]

Here, in the case of equations (4) and (5),
Although the influence of the speed and the acceleration is emphasized, the influence of the speed and the acceleration is corrected in the case of the equation (6).
That is, the echo signal S ₅ is obtained from the portion 41 excited by the high-frequency pulse 11 and the high-frequency pulse 13 and the fluid 42 flowing out from the portion 41. The relationship between these signals S ₃ , S ₄ and S ₅ always holds among all the signals S ₃ , S ₄ and S ₅ that are generated thereafter, and S ₅ is 4√ (2).
Since it occurs at T intervals, it is possible to trace information about the velocity and acceleration of the fluid portion at 4√ (2) T intervals. Since the signal S ₅ is corrected for the influence of the acceleration and the velocity, in order to extract the information of only the acceleration, it is sufficient to subtract the velocity information therefrom.

By the way, in the pulse sequence shown in the first embodiment, since the echo signal S ₂ in which the influence of only the velocity is corrected is generated, the information of only the acceleration can be taken out by using this echo signal S _2. it can. Therefore, the echo signal S ₂ is obtained by re-measuring the same region using the readout gradient magnetic field Gz ₁ . However, under the same imaging conditions as those for obtaining the signal S ₅ at the time of measurement again, the signal S ₅ is generated at 4√2T intervals, whereas the signal S ₂ is generated at 4T intervals. There is a timing difference. Therefore, 1 / √ a gradient field strength of the gradient magnetic field (Gz ₂₎ with respect to the gradient magnetic field (Gz ₂₎
(2) By performing the double modulation, as shown in FIG.
₅ and S ₂ can be generated at the same timing.

In the second measurement for obtaining the echo signal S ₂ in which the influence of only the velocity is corrected, first, the high frequency pulse 21 and the gradient magnetic field (Gz ₂ ) 23 are applied in a pulse shape to the region of interest. To excite. Next, the high frequency pulse 21
At time t ₀ after the application of, the high frequency pulse 24 and the gradient magnetic field (Gy) 25 are applied in a pulse shape to excite the plane orthogonal to the plane excited by the high frequency pulse 21. Further, at time t ₁ after applying the high frequency pulse 24, the gradient magnetic field (Gz ₂ ) 28 is applied for √ (2) T time. Thereafter, the application of the gradient magnetic field (Gz ₂ ) is repeated while inverting the polarity of the amplitude every 2√ (2) T time. During this period, the signal S ₁ and the signal S ₂ are alternately generated every time the total amount of the product of the gradient of the gradient magnetic field (Gz ₂ ) and the application time becomes 0. That is, the signal S ₂ is generated at the interval of 4√ (2) T like the signal S ₅ .

As described above, since the signal S ₂ is corrected for the influence of the fluid velocity and the signal S ₅ is corrected for the influence of the fluid velocity and acceleration, the obtained signals of S ₂ and S ₅ are obtained. After converting each row into a one-dimensional projected image by Fourier transform, the difference between the projected image of S _{2 and} the projected image of S _{5 at} the same time from the application of the high-frequency magnetic field 21 is calculated.
As shown in, the acceleration component at the required time can be extracted.

Although the third embodiment described above is for obtaining a one-dimensional projection image, a case for obtaining a two-dimensional projection image will be described as a fourth embodiment. In the fourth embodiment, similarly to the second embodiment in FIG. 2, the encoding is performed between the application of the high frequency pulse 24 (first step) and the application of the readout gradient magnetic fields 27 and 28 (third step). Gradient magnetic field (G
x) 26 is applied in a pulse form (second step). This encoding gradient magnetic field strength is changed by one encoding step, and the execution of this pulse sequence (first to third steps) is repeated.

Here, in the first measurement, the gradient magnetic field (G
In each signal sequence of S ₅ obtained by z ₁ ), signals having the same time from the application of the high frequency pulse 21 to the signal generation and different application amounts of the encoding gradient magnetic field are set as one set of data. In addition, in each signal sequence of S ₂ obtained by the gradient magnetic field (Gz ₂ ) in the second measurement, one set of signals having the same time from the application of the high frequency pulse 11 to the signal generation and different application amounts of the encoding gradient magnetic field is used. Data. The image of each set of data is reconstructed by two-dimensional Fourier transform to obtain a two-dimensional projection image. By taking the difference between the projected image of the signal S _{2 and} the projected image of the signal S _{5 at} the same time from the application of the high-frequency magnetic field 21, the acceleration component at that time can be extracted as shown in FIG.

In the above embodiments, the case where two high frequency magnetic fields for selectively exciting a region are applied in directions orthogonal to each other has been described, but the fluid measuring method of the present invention is excited by the two high frequency magnetic fields. The planes may be parallel. Further, the configuration of the MRI apparatus to which the present invention is applied can be freely changed within the scope of the present invention.

[0040]

As is clear from the above description, according to the fluid measuring method of the present invention, the readout gradient magnetic field is repeatedly applied to the selectively excited fluid portion while reversing the polarity of the magnetic field, Since the echo signal whose influence is corrected is continuously generated, there is an effect that velocity and acceleration can be measured with high time resolution. Further, according to the fluid measuring method of the present invention, by appropriately selecting the amplitude of the readout gradient magnetic field applied repeatedly, it is possible to continuously generate an echo signal in which the influence of velocity and acceleration is corrected. Thus, acceleration information can be directly obtained with high time resolution.

[Brief description of drawings]

FIG. 1 is a diagram showing pulse sequences of first and second embodiments of the present invention.

FIG. 2 is a diagram showing pulse sequences of third and fourth embodiments of the present invention.

FIG. 3 is a diagram showing a schematic configuration of an MRI apparatus to which the present invention is applied.

FIG. 4 is a schematic diagram for explaining each example.

FIG. 5 is a schematic diagram showing a one-dimensional projection image of an echo signal obtained in the first embodiment.

FIG. 6 is a schematic diagram showing a one-dimensional projection image of an echo signal obtained in the third embodiment.

FIG. 7 is a schematic diagram showing a two-dimensional projection image of an echo signal obtained in the second embodiment.

FIG. 8 is a schematic diagram showing a two-dimensional projected image of an echo signal obtained in the fourth embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Static magnetic field generation magnet 2 ... Gradient magnetic field generation part 3 ... High frequency probe 5 ... Transmitter and receiver 6 ... Computation control part 7 ... Subject 41 ... Excitation area 42 ... Fluid

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location G01P 13/00 E 7507-4C A61B 5/05 376 G01N 24/00 D

Claims (4)

[Claims] 1. In a region where a fluid flows, a plane intersecting with a flow is selectively excited by a first high frequency magnetic field, and a second high frequency magnetic field is applied in a direction parallel or orthogonal to the plane excited by the first high frequency magnetic field. After selective excitation, a readout gradient magnetic field is repeatedly applied along the flow direction while inverting the polarity of amplitude, and at least two echo signals in which the phase change of magnetization due to the velocity of the fluid is corrected are generated. A fluid measuring method using an MRI apparatus, wherein a projection image is created from an echo signal, and a flow velocity at each echo signal generation is obtained from a moving distance of a fluid in the projection image and an echo signal generation time interval. 2. In a region where a fluid flows, a plane intersecting with the flow is selectively excited by a first high frequency magnetic field, and a plane parallel or orthogonal to the plane excited by the first high frequency magnetic field,
A first step of selectively exciting with a second high-frequency magnetic field; a second step of applying an encode gradient magnetic field in a direction perpendicular to the flow direction after the selective excitation by the first step; and reading along the flow direction. A third step of repeatedly applying an out gradient magnetic field while inverting the polarity of the amplitude to generate at least two echo signals in which the phase change of the magnetization due to the velocity of the fluid is corrected; The MRI is characterized in that the image is reconstructed using a sequence of echo signals generated at the same time after the first high-frequency magnetic field is applied in each sequence by changing the amount of application of the signal by one encoding step and obtaining an image. Fluid measurement method with a device. 3. In a region where a fluid flows, a plane intersecting with the flow is selectively excited by a first high frequency magnetic field, and a plane parallel or orthogonal to the plane excited by the first high frequency magnetic field,
After being selectively excited by the second high-frequency magnetic field, a read-out gradient magnetic field is repeatedly applied along the flow direction while inverting the polarity of the amplitude, and an echo signal in which the phase change of the magnetization due to the velocity and acceleration of the fluid is corrected is obtained. A first measurement step of generating at least two or more, and further the region
A plane intersecting with the flow is selectively excited by the first high-frequency magnetic field, and a plane parallel or orthogonal to the plane selectively excited by the first high-frequency magnetic field is selectively excited by the second high-frequency magnetic field, and then along the flow direction. A read-out gradient magnetic field is repeatedly applied while inverting the polarity of the amplitude to generate at least two echo signals in which the phase change of the magnetization due to the velocity is corrected, and a first high-frequency magnetic field. At the same time after the application of, the projected image of the echo signal in which the phase change of the magnetization due to the velocity and the acceleration obtained in the first measurement step is corrected, and the phase of the magnetization according to the velocity obtained in the second measurement step. A fluid measuring method by an MRI apparatus, wherein an acceleration component of the fluid is extracted by taking a difference between projected images of echo signals whose changes are corrected. 4. In a region where a fluid flows, a plane intersecting with the flow is selectively excited by a first high frequency magnetic field, and a second high frequency magnetic field is applied in a direction parallel or orthogonal to the plane excited by the first high frequency magnetic field. A first step of selective excitation, a second step of applying an encoding gradient magnetic field in a direction perpendicular to the flow direction after the selective excitation, and a polarity of amplitude of a readout gradient magnetic field is reversed along the flow direction. The sequence (A) consisting of a third step in which at least two echo signals in which the phase change of the magnetization due to the velocity and acceleration of the fluid is corrected is repeatedly applied while the application amount of the encoding gradient magnetic field is 1 Echo signals generated at the same time after the first high-frequency magnetic field is applied in each sequence (A) by repeating the encoding steps while changing the encoding steps. A first measurement step of image reconstruction using the further the region, the plane crossing the flow first
First excitation by the second high frequency magnetic field in a direction parallel or orthogonal to the plane excited by the first high frequency magnetic field, and perpendicular to the flow direction after the selective excitation. The second step of applying the encoding gradient magnetic field in various directions and the echo in which the phase change of the magnetization due to the velocity of the fluid is corrected by repeatedly applying the readout gradient magnetic field along the flow direction while inverting the polarity of the amplitude. The sequence (B) including the third step of generating at least two signals is repeated while changing the application amount of the encoding gradient magnetic field by one encoding step, and the first high frequency magnetic field application in each sequence (B) is performed. A second measurement step of reconstructing an image using a train of echo signals generated at the same time later,
At the same time after applying the high-frequency magnetic field, the difference between the image containing the velocity and acceleration components of the fluid obtained in the first measurement step and the image containing the velocity component obtained in the second measurement step is obtained. A method for measuring a fluid by an MRI apparatus, characterized in that the acceleration component of the fluid is extracted.