JPH0515513A - Fluid imaging method by MRI apparatus - Google Patents

Abstract

(57) [Summary] [Purpose] A blood flow projection image is obtained at high speed using the echo planar method. The echo signal train generated by a read-out gradient magnetic field that excites a region of interest and is applied with repeated inversion of amplitude polarity is used to detect an echo signal 25 in which a phase change of magnetization due to a flow is emphasized and a magnetization signal due to the flow. The echo signals 26 whose phase changes have been corrected are separated and individually image-reconstructed, and then a blood flow projection image is obtained by subtraction.
At this time, in the second stage, a pulse sequence is used in which the read-out gradient magnetic field 24 is added with a read-out gradient magnetic field (shaded portion 27) in which the polarity of the amplitude is inverted from 2T time before the time T ₀ to after the T time. As a result, the echo signal A12 generated in the first stage and the echo signal B13 generated in the second stage have the same phase change due to the static magnetic field inhomogeneity and the attenuation amount due to the lateral relaxation.
Since these effects are offset, an accurate and high-speed fluid imaging method can be realized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluid imaging method by an MRI apparatus, and more particularly to a fluid imaging method by an MRI apparatus suitable for blood flow imaging in a human body.

[0002]

2. Description of the Related Art Conventionally, as a blood flow imaging method using an MRI apparatus, subtraction of two images, that is, an image obtained by a pulse sequence that feels flow and an image obtained by a pulse sequence that does not feel flow, As typified by an example of extracting only a blood flow portion, a method of obtaining a target image from a plurality of images having different properties is generally known. As one of the methods, for example, “Magnetic Resonance in Medicine 12 (198
9), pp. 1-13 (Magnetic Resonance InMedicine 1
2, pp. 1-13 (1989) ”. This method is performed twice, when the magnetic field waveform of the readout gradient magnetic field is set to a flow encode pulse in which the phase change of the magnetization due to the flow is emphasized and to the flow compensate pulse in which the phase change of the magnetization due to the flow is corrected. The blood flow image is obtained by subtraction of the image obtained by the measurement. Also, as a method of reducing the number of data samplings by half without lowering the resolution,
The half encoding method is known. This is because when the image data is a real number, the measurement data on the phase space are in a complex conjugate relationship with each other, and only half the area of the phase space is measured, and the remaining data is obtained by calculation. Is. For this method, for example, "D.A. Feinberg, J.D. Hale, J.C.
Watts, LK Kalfman & A. Mark: 'Herving M.I.R. Imaging Time Bi-Conjugation: Demonstration at 3.5K G' (Radiology, 16
1, 2, 527-531 (1986) (DAFein
berg, JDHale, JCWatts, LKKaufman and A.Mark: 'Ha
lving MR imaging time by conjugation: Demonstration
at 3.5KG '(Radiorogy, 161,2, pp.527-531 (1986)) "
In detail.

[0003]

In the above-mentioned conventional technique, the waveforms of the read gradient magnetic field are different between the pulse sequence that senses the flow and the pulse sequence that does not sense the flow, and therefore two measurements are required. In addition, since signal measurement is performed by repeating excitation of magnetization and application of a gradient magnetic field, the measurement time is long, and measurement is required twice. Therefore, there is a problem in obtaining a blood flow image of a dynamic part such as the heart. It was The object of the present invention is to improve such a problem, and after applying a high frequency pulse, apply a readout gradient magnetic field while reversing the polarity of the amplitude, and use an imaging method for continuously generating an echo signal. MR that can obtain blood flow images
An object of the present invention is to provide a fluid imaging method using the I device.

[0004]

In order to achieve the above object, in a fluid imaging method using an MRI apparatus of the present invention, in a first step, a region of interest in which a fluid flows is selectively excited to read in a direction perpendicular to a projection direction. By applying the out gradient magnetic field while reversing the polarity of the amplitude, and by applying the encode gradient magnetic field in the direction perpendicular to both the projection direction and the readout direction, an echo signal in which the phase change of the magnetization due to the flow is emphasized is obtained. , An echo signal in which the phase change of the magnetization due to the flow is corrected is alternately generated, and the signals are sequentially sampled to form a first signal sequence, and in the second stage, the region of interest is selectively excited again to project. A readout gradient magnetic field added with a flow encode pulse is applied in the vertical and vertical directions while inverting the polarity of the amplitude, and it is applied in both the projection direction and the readout direction. By applying an encoding gradient magnetic field in the direct direction, an echo signal in which the phase change of the magnetization due to the flow is emphasized and an echo signal in which the phase change of the magnetization due to the flow is corrected are generated alternately and sequentially sampled. And a second signal sequence, and in the third stage, from those signal sequences, the echo signal comrades in which the phase change of the magnetization due to the flow is emphasized and the echo signal comrades in which the phase change of the magnetization due to the flow is corrected are combined. The feature is that a projection image of a fluid is obtained by canceling the effects of static magnetic field inhomogeneity and lateral relaxation by separately performing image reconstruction and performing subtraction on the obtained image.

[0005]

In the present invention, in the echo planar method, which is a typical ultrafast imaging method, the read-out gradient magnetic field waveform applied by inverting the polarity of the amplitude is obtained by alternately combining the flow encode pulse and the flow compensate pulse. Because of the different waveforms, the fact that the sequentially generated echo signals S ₁ and S ₂ have different properties with respect to the flow is utilized. That is, a signal sequence obtained in the same manner as the conventional one in the first stage and a signal sequence obtained in the second stage using the readout gradient magnetic field added with the flow encode pulse are combined with echo signals of different properties to obtain a signal. After obtaining the columns {S ₁ } and {S ₂ }, they are separately image reconstructed and subtracted. by this,
A blood flow projection image can be obtained at high speed by using the echo planar method.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is a schematic diagram showing an outline of an MRI apparatus to which the fluid imaging method of the present invention is applied, and FIG. 3 is a schematic diagram showing a blood vessel to be measured in one embodiment of the present invention. This device includes a coil 1 for generating a static magnetic field, a gradient magnetic field generator 2 for generating a gradient magnetic field, a probe 3 for transmitting a high frequency pulse and receiving an echo signal, a power source 4 for a gradient magnetic field and a high frequency pulse, It is composed of a computer 5. Further, the gradient magnetic field generator 2 has gradients for inclining the strength of the magnetic field along the three directions of the direction of the static magnetic field (z direction) and two directions (x direction and y direction) perpendicular thereto. It has three sets of coils that generate a magnetic field. Note that these gradient magnetic fields are called Gx, Gy, and Gz. Further, the control of these gradient magnetic fields and the control of the high frequency pulse and the signal acquisition are performed via the computer 5 in accordance with the pulse sequence. Further, in this embodiment, as shown in FIG.
It is assumed that blood flowing therein flows in the region of interest 8 on the xy plane.

Next, the operation and procedure of fluid imaging in the first embodiment of the present invention will be described. Figure 1
FIG. 4 is a pulse sequence diagram showing a fluid imaging method according to the first embodiment of the present invention, and FIG. 4 is an explanatory diagram of a signal train obtained by the first step in the phase space of the first embodiment of the present invention. In this embodiment, a gradient magnetic field is applied to the region of interest 8 in the first and second steps, and the signal sequence is rearranged and the image is reconstructed in the third step. In the first stage, first, the high frequency pulse 21 is applied, and the gradient magnetic field Gz for inclining the magnetic field strength in the z direction is applied in a pulse form to excite the region to be measured. In this way, the region of interest can be selectively excited by applying the high frequency pulse and the gradient magnetic field at the same time. The high frequency pulse 21
Is generally a 90 ° pulse, but a pulse with a smaller flip angle (α °) may be used. Next, high frequency pulse 2
At time T ₀ after 1 is applied, the gradient magnetic field Gx whose magnetic field strength changes in the x direction is applied for a time T as indicated by 24.
After that, the application of the gradient magnetic field Gx is continuously repeated while inverting the polarity of the amplitude of Gx, that is, the direction of the gradient every time 2T. Gx is called a read-out gradient magnetic field. Further, at time T ₀ + T, the gradient magnetic field Gy that causes the magnetic field strength to be inclined in the y direction is applied for a time t shorter than the time T as indicated by 23. After that, the application of the gradient magnetic field Gy is repeated every time 2T with the amplitude of the same polarity for each time t.
Note that Gy has a function of adding information on the position along the y direction to the phase of the echo signal, and is therefore called an encode gradient magnetic field. During this period, an echo signal (signal A12) is generated each time the total amount of the product (G × T) of the amplitude of the readout gradient magnetic field and the application time becomes zero. There are two types of echo signals. The echo signal during the positive Gx period is shown as S ₁ and the echo signal during the negative Gx period is shown as S ₂ . In general, the phase change of the echo signal due to the application of the gradient magnetic field is represented by Expression 1 where γ is the gyromagnetic ratio, r is the position, and v is the velocity.

[Equation 1] Here, the first set of echo signals S ₁ 25 and S ₂ 26
Focusing on ( ₁₎ , the phase change at the peak of S ₁ due to the application of the read-out gradient magnetic field is expressed by Expression 1 as Expression 2 below.

[Equation 2] This corresponds to the case where the phase change due to the velocity component of the fluid using the flow encode pulse is emphasized. Further, the phase change at the peak of S ₂ due to the application of the read-out gradient magnetic field is expressed by Expression 3.

[Equation 3] This corresponds to the case where the phase change due to the velocity component of the fluid is corrected by using the flow compensating pulse. That is, by continuously applying the inverted readout gradient magnetic field polarity, and the echo signal S ₂ which phase change is corrected by the phase change is emphasized echo signal S ₂ and the velocity component due to the velocity component is alternately You can see that it occurs.
Therefore, information about the flow can be retrieved by using S ₁ and S ₂ . From the signal A12 thus obtained, alternately generated signals S ₁ and S ₂ are sequentially sampled, and a signal train as shown in FIG. 4 is stored in the computer 5.
Next, the second stage will be described. FIG. 5 shows the first of the present invention.
FIG. 7 is an explanatory diagram of a signal sequence obtained in the second stage in the phase space of the example of FIG. In the second stage, as shown by the hatched portion in FIG. 1, with respect to the read-out gradient magnetic field Gx applied from T ₀ in the first stage, from 2T time before that,
A pulse sequence to which a read-out gradient magnetic field 27 whose amplitude polarity is inverted after T time is added is used. Therefore, the time T ₀ needs to be longer than the time 2T. After that, similarly to the first step, the application of the gradient magnetic field Gx is continuously repeated while reversing the polarity of the amplitude of Gx every time 2T. Further, at time T ₀ + T, a gradient magnetic field Gy that causes the magnetic field strength to be inclined in the y direction is applied for a time t shorter than time T, as in 23. After that, the application of the gradient magnetic field Gy is repeated every time 2T with the amplitude of the same polarity for each time t.
In this case, at time T ₀ , the total amount of the product (G × T) of the amplitude of the added readout gradient magnetic field 27 and the application time becomes 0, so that the echo signal SD28 is generated. This is not used for image reconstruction as a dummy signal, but it can be used for position detection of the subject or the like in some cases. Furthermore, at time T ₀ + 2T, the total amount of the product of the amplitude of the readout gradient magnetic field and the application time (G × T) becomes 0 again, so that an echo signal is generated, but this signal is as shown in Equation 3. Is S ₂ in which the phase change due to the velocity component is corrected.
After that, S ₁ and S ₂ are alternately generated as shown by the signal B13. However, the order of generation of the signals after the time T ₀ + 2T is replaced with that in the case of the first stage, and the echo signal during the negative period of Gx is S ₁ and the echo signal during the positive period of Gx is S ₂
Is shown. Thus, the alternately generated signals S ₁ and S ₂
Are sequentially sampled and stored in the computer 5 as a signal sequence as shown in FIG. Here, considering the echo signal generated in the first stage and the echo signal generated in the second stage at the same time after the excitation of the magnetization, since the time after the excitation is the same, the phase due to the non-uniformity of the static magnetic field is considered. The amount of signal attenuation due to change and lateral relaxation is equal. Therefore, by taking a difference between these signals, the influence of the static magnetic field inhomogeneity, the influence of the lateral relaxation, etc. are completely canceled, and since the applied encoding gradient magnetic field amounts are equal, the equations 2 and 3 to 4 Only the phase difference due to the flow represented by is left.

[Equation 4] That is, comparing the signals at the same time in the first stage and the second stage, two signals having different information regarding the flow are obtained at the same position in the phase space. The same position in the phase space means that the applied encode gradient magnetic field amount and the read out magnetic field amount are the same for the two signals. Therefore, regarding the signal example obtained by the above two processes, the signal sequence {S ₁ } in the first stage is changed to the signal sequence {S ₂ } in the second stage, or the signal sequence {S ₂ } in the first stage is changed. It can be replaced with the signal sequence {S ₁ } in the second stage. Therefore,
In the third stage, first, these signals are rearranged.
FIG. 6 shows the first stage and the second stage in the first embodiment of the present invention.
FIG. 7 is an explanatory diagram of the signal sequence {S ₁ } exchanged from the stage, FIG. 7 is an explanatory diagram of the signal sequence {S ₂ } exchanged from the first stage and the second stage in the first embodiment of the present invention, and FIG. First invention
Of the image (1) obtained from the image reconstruction of the signal sequence {S ₁ } in the above embodiment, and FIG. 9 is obtained from the image reconstruction of the signal sequence {S ₂ } in the second embodiment of the present invention. FIG. 10 is an explanatory diagram of the image (2), and FIG. 10 is a blood flow projection image diagram obtained by subtraction of the image (1) and the image (2) in the first embodiment of the present invention. In this embodiment, as shown in FIG. 6, one phase space is configured by a signal sequence {S ₁ }, and
As shown in FIG. 7, the other phase space is formed by the signal sequence {S ₂ }. From the signal sequences {S ₁ } and {S ₁ } separated in this way, the signal change in the sampling time direction of each echo signal indicates position information in the x direction, and S ₁ ,
Since the signal change in each repeating direction of S ₂ indicates the position information in the y direction, by performing Fourier transform in both directions,
Images are individually reconstructed to obtain two types of images (image (1) and image (2)). As described above, the obtained image (1) is an image in which the signal is attenuated by the velocity component of the fluid, and image (2) is an image in which the influence of the velocity component of the fluid is corrected. Therefore, as shown in FIG. 3, when the region of interest 8 across which the blood vessel 7 crosses is selected, the image (1) becomes as shown in FIG. 8 and the image (2) becomes as shown in FIG. 9. And
If these subtractions are performed, as shown in FIG.
An image of only the velocity component, that is, the blood flow portion is obtained. Although the present embodiment describes the case where the half-encoding method is used, it is clear that the imaging method of the present invention is also effective for the full-encoding method. That is, as indicated by the dotted line, the Gy pulse 20 of FIG.
_By applying in advance within the period of ₀ , imaging by the full encoding method becomes possible.

Next, the operation and procedure of fluid imaging in the second embodiment of the present invention will be described. Figure 11
FIG. 7 is a pulse sequence diagram showing a fluid imaging method according to the second embodiment of the present invention. In the first stage of the present embodiment, first, as in the first embodiment, the high frequency pulse 2
1 and the pulse 22 of the z-direction gradient magnetic field Gz are applied to excite the region to be measured, and time T ₀ after the high-frequency pulse is applied.
Then, the pulse 24 'of the readout gradient magnetic field Gx is applied for T time. After that, the application of the readout gradient magnetic field Gx is continuously repeated while inverting the polarity of the amplitude every 2T. However, in this embodiment, the change in the Gx amplitude is sinusoidal. Such an application of the read-out gradient magnetic field is continuously repeated, and at the time T ₀ + T, the encode gradient magnetic field Gy for gradient of the magnetic field strength in the y direction is set to 2
3 is applied for a time t shorter than the time T, and then 2
The application of the encode gradient magnetic field is repeated every T for t time with the same polarity amplitude. During this period, an echo signal is generated each time the time-integrated value of the readout gradient magnetic field becomes zero.
Here, as in the first embodiment, the echo signal S ₁ is a signal in which the phase change due to the velocity component is emphasized, and the echo signal S ₂ is a signal in which the phase change due to the velocity component is corrected. The echo signals S ₁ and S ₂ thus alternately generated are stored in the computer 5 as signal sequences {S ₁ } and {S ₂ }, respectively. Next, in the second stage, as in the first embodiment, as shown in FIG.
As indicated by the shaded area of No. 1, with respect to the readout gradient magnetic field Gx24 ′ applied from time T ₀ in the first stage,
The read-out gradient magnetic field Gx having a sinusoidal waveform in which the polarity of the amplitude is inverted from 2T time before that time to 2T time after that,
Add like 7 '. Thereafter, similarly to the first step, the application of the gradient magnetic field Gx is continuously repeated while reversing the polarity of the amplitude of Gx every time 2T, and at the time T ₀ + T.
Gradient magnetic field Gy that causes the magnetic field strength to be inclined at
Is applied for a time t shorter than the time T as in 23, and thereafter, the application of the gradient magnetic field Gy is repeated every time 2T with the amplitude of the same polarity for the time t. In this case, since the time integrated value of the readout gradient magnetic field applied at time T ₀ becomes 0, the echo signal SD is generated, but this is a dummy signal. Further, at time T ₀ + 2T, since the time integration value of the readout gradient magnetic field becomes 0 again, an echo signal is generated, but this signal is S ₂ in which the phase change due to the velocity component is corrected. After that, as in the first stage, S ₁ and S ₂ are alternately generated. However, the order of generation of signals after time T ₀ + 2T is switched between the first stage and the second stage, and the echo signal during the negative period of Gx is S ₁ and the echo signal during the positive period of Gx is S ₂ . Shows. The alternately generated signals S ₁ and S ₂ are sampled and stored in the computer 5 as signal sequences {S ₁ } and {S ₂ }.
Next, as the third stage, similarly to the first embodiment, the signal sequence {S ₁ } in the first stage is changed to the signal sequence {S ₂ } in the second stage, or the signal sequence {S ₂ in the first stage. by replacing} to signal sequence {S _1} in the second stage, a phase space defined by only the signal sequence {S _1}, is separated into a formed phase space by only the signal sequence {S _2}. Further, these are individually image-reconstructed to obtain images (1) and (2) similar to those shown in FIGS. 8 and 9. In the image reconstruction, unequal interval sampling in the phase space of the echo signal caused by the fact that the readout gradient magnetic field is not rectangular or trapezoidal is corrected. Then, the image (1) and the image (2) are subtracted to obtain the image of only the blood flow portion shown in FIG.

Next, the operation and procedure of fluid imaging in the third embodiment of the present invention will be described. 12
FIG. 7 is a pulse sequence diagram showing a fluid imaging method according to a third embodiment of the present invention. In the first stage of the present embodiment, as in the first embodiment, first, the 90 ° pulse 4
The gradient magnetic field Gz42 in which the magnetic field strength changes in the 1 and Z directions is applied to selectively excite the region to be measured, and further 180 °
A pulse 43 and a gradient magnetic field Gz44 are applied to reverse the magnetic field in the selected region. After that, similar to the first embodiment,
From time T ₀ after the application of the 180 ° high frequency pulse, the pulse 24 of the readout gradient magnetic field Gx is applied for the time T. Then, the application of the readout gradient magnetic field Gx is continuously repeated while reversing the polarity of the amplitude every 2T. Further, at time T ₀ + T, the encode gradient magnetic field Gy for inclining the magnetic field strength in the y direction is applied for a time t shorter than the time T, as in 23, and thereafter, the gradient magnetic field is incremented by the time t at the amplitude of the same polarity every time 2T. The application of Gy is repeated. During this time, an echo signal is generated every time the product (G × T) of the amplitude of the readout gradient magnetic field and the application time becomes zero. The echo signals S ₁ and S ₂ alternately generated are stored in the computer 5 as signal sequences {S ₁ } and {S ₂ }, respectively. In the second stage,
Similar to the first embodiment, a read-out gradient magnetic field Gx27 shown by the shaded area is added. The echo signal SD generated first is a dummy signal. After that, the alternately generated echo signals S ₁ and S ₂ are stored in the computer 5 as signal sequences {S ₁ } and {S ₂ }, respectively. However, the order of occurrence of S ₁ and S ₂ is interchanged with that of the first stage. In the third stage, the first
In the same manner as in the above embodiment, the signal sequence {S ₁ } in the first stage is changed to the signal sequence {S ₂ } in the second stage or the signal sequence {S ₂ } in the first stage is changed to the signal sequence {S ₂ in the second stage. ₁ } to separate into a phase space composed only of the signal sequence {S ₁ } and a phase space composed only of the signal sequence {S ₂ }. Further, these are individually image-reconstructed to obtain the image (1) and the image (2) shown in FIGS. 8 and 9. Then, the image (1) and the image (2) are subtracted to obtain an image of only the blood flow portion shown in FIG. Although the present embodiment describes the case where the magnetic field waveform of the read-out gradient magnetic field is rectangular, as in the second embodiment shown in FIG.
Even if the magnetic field waveform of the readout gradient magnetic field is made sinusoidal,
The same effect can be obtained.

[0010]

According to the present invention, in an ultrahigh-speed imaging method, two kinds of signals having different properties with respect to flow, which are alternately generated by applying a read-out gradient magnetic field in which amplitude inversion is repeated, are separated, and the velocity of a fluid is separated. Since the two images, the image in which the component is attenuated and the image in which the velocity component of the fluid is corrected, are obtained, a fluid imaging method capable of extracting the fluid portion at high speed can be realized.

[0011]

[Brief description of drawings]

FIG. 1 is a pulse sequence diagram showing a fluid imaging method according to a first embodiment of the present invention.

FIG. 2 is an MR to which the fluid imaging method of the present invention is applied.
It is a block diagram which shows the outline of I apparatus.

FIG. 3 is a schematic diagram showing a blood vessel to be measured in one example of the present invention.

FIG. 4 is a first diagram of the first embodiment of the present invention in the phase space;
It is explanatory drawing of the signal sequence obtained by the step.

FIG. 5 is a second diagram in the phase space of the first embodiment of the present invention.
It is explanatory drawing of the signal sequence obtained by the step.

FIG. 6 is a first stage and a second stage in the first embodiment of the present invention.
It is an illustration of a signal sequence {S _1} interchanged from step.

FIG. 7 is a first stage and a second stage in the first embodiment of the present invention.
It is an illustration of a signal sequence {S _2} interchanged from step.

FIG. 8 is a signal sequence {S ₁ } according to the first embodiment of the present invention.
FIG. 7 is an explanatory diagram of image (1) obtained by image reconstruction of FIG.

FIG. 9 is a signal sequence {S ₂ } according to the second embodiment of the present invention.
FIG. 5 is an explanatory diagram of an image (2) obtained by image reconstruction of FIG.

FIG. 10 is a blood flow projection image diagram obtained by subtraction of image (1) and image (2) in the first example of the present invention.

FIG. 11 is a pulse sequence diagram showing a fluid imaging method according to the second embodiment of the present invention.

FIG. 12 is a pulse sequence diagram showing a fluid imaging method according to a third embodiment of the present invention.

[Explanation of symbols]

1 static magnetic field coil 2 gradient magnetic field generator 3 probe 4 power supply 5 computer 6 subject 7 blood vessel 8 region of interest 12 signal generated in the first stage 13 signal generated in the second stage 20 encoding gradient magnetic field when the full encoding method is applied Pulse 21 high frequency pulse 22 pulse in z-direction gradient magnetic field 23 pulse in read-out gradient magnetic field 24 pulse in encode gradient magnetic field 24 'pulse in encode gradient magnetic field 25 echo signal (S ₁ ) 26 echo signal (S ₂ ) 27 read-out gradient magnetic field Pulse (flow encode pulse) 27 'Readout gradient magnetic field pulse (flow encode pulse) 28 Dummy signal 41 High frequency pulse 42 z direction gradient magnetic field pulse 43 High frequency pulse 44 z direction gradient magnetic field pulse

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number FI Technical indication location 9118-2J G01N 24/08 Y (72) Inventor Ryuichi Suzuki 1-280, Higashi Koikeku, Kokubunji, Tokyo Stock Central Research Laboratory of Hitachi, Ltd.

Claims (5)

[Claims] 1. In a fluid imaging method using an MRI apparatus, a region of interest in which a fluid flows is selectively excited, and a readout gradient magnetic field is applied in the direction perpendicular to the projection direction while inverting the polarity of the amplitude, and the projection direction and the readout. By applying an encoding gradient magnetic field in a direction perpendicular to any of the directions, an echo signal in which the phase change of the magnetization due to the flow is emphasized and an echo signal in which the phase change of the magnetization due to the flow is corrected are alternately generated. , The echo signals are sequentially sampled to form a first signal sequence, the region of interest is selectively excited again, and the polarity of the amplitude of the readout gradient magnetic field added with the flow encode pulse is inverted in the direction perpendicular to the projection direction. Flow by applying an encoding gradient magnetic field in a direction perpendicular to both the projection direction and the readout direction. An echo signal in which the phase change of the magnetization due to is and an echo signal in which the phase change of the magnetization due to the flow is corrected are alternately generated, and the echo signals are sequentially sampled to form a second signal sequence. From the row, echo signal comrades in which the phase change of the magnetization due to the flow is emphasized,
Fluid imaging by an MRI apparatus, characterized in that echo signals whose magnetization phase changes due to flow are corrected are combined, image reconstruction is performed separately, and the resulting images are subtracted to obtain a projected image of the fluid. Method. 2. The fluid imaging by the MRI apparatus according to claim 1, wherein after the region of interest is excited by applying a 90 ° high frequency pulse, an 180 ° inversion high frequency pulse is applied to generate an echo signal. Method. 3. The M according to claim 1, wherein the magnetic field waveform of the readout gradient magnetic field is sinusoidal.
A fluid imaging method using an RI apparatus. 4. When applying the encode gradient magnetic field,
The fluid imaging method by the MRI apparatus according to claim 1, wherein the half-encoding method is applied. 5. The flow encode pulse is applied so that the polarity is inverted at a time T from 2T (T: a positive number) time before the application time of the readout gradient magnetic field, and the read-out gradient magnetic field is applied after the application. By applying so that the polarities are inverted at the time T, the sampling order of the emphasized echo signal and the correction echo signal at the same time after the ROI excitation is reversed in the first signal sequence and the second signal sequence. A fluid imaging method using the MRI apparatus according to any one of claims 1 to 4.