JPH11113874A - Magnetic resonance image pickup method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively restrain a chemical shift-artifact by generating plural echoes at a time interval when a phase of a fat signal in the echoes changes by a specific angle when a magnetic resonance image is picked up by an echo planner method. SOLUTION: An almost cylindrical gradient coil part 4 and a body coil part 6 are coaxially arranged inside a magnetostatic field generating part 2, and an RF signal is imparted to the body coil part 6 from a transmission part 12, and an RF magnetic field is generated, and an in vivo spin of an examinee 8 is excited. A spin echo signal is detected by the body coil part 6, and its detecting signal is received, and is inputted to a computer 18 after A/D conversion, and here, two-dimensional inverse Fourier transform is performed on data on a two-dimensional Fourier space, and an image of the examinee 8 is reconstituted. In this case, it is controlled so that an echo is generated in an echo space coincident with time when a phase of a fat signal changes by 180 deg., and a chemical shift-artifact is restrained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic resonance imaging method and apparatus, and more particularly, to an echoplanar.
The present invention relates to a magnetic resonance imaging method and a magnetic resonance imaging apparatus for executing an echo planar method.

[0002]

2. Description of the Related Art Magnetic resonance imaging by an echo planar method, that is, echo planar imaging.
ging: EPI) is, for example, a pulse sequence shown in FIG. 11 and a 90 ° pulse as shown in FIG.
, And the spin is reversed by a 180 ° pulse. Then, as shown in FIGS. 3B and 3C, the readout gradient magnetic field (readout gradient) is rapidly and alternately changed, and the phase encode gradient magnetic field (readout gradient) is changed. By applying a phase encode gradient, an echo signal as shown in FIG.

[0003] The echo signal is digital data (digital d).
Ata) is collected in memory, and the image is reconstructed by two-dimensional inverse Fourier transform of the echo data.

[0004] The echo signal (fat signal) generated from the fat portion of the subject has a lower frequency than the echo signal generated from the water portion due to a chemical shift. Image shift (chemical shift ar
tifact)), the suppression of the fat signal is performed.

[0005] Suppression of the fat signal is performed by exciting the signal with an RF (radio frequency) signal that matches the frequency of the fat signal in advance to saturate the fat signal, or selectively by using an RF signal that matches the water signal. This is done by excitation.

[0006]

The above-described selective excitation of the fat signal or the water signal causes the non-uniformity of the main magnetic field or the RF signal.
Depending on the capability of the excitation system, appropriate selective excitation is not always performed. Therefore, the water signal often disappears or the suppression of the fat signal tends to be insufficient.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to realize a magnetic resonance imaging method and apparatus using an echo planar method that effectively suppresses chemical shift artifacts. .

[0008]

[Means for Solving the Problems]

(1) A first aspect of the present invention for solving the above-mentioned problem is that, when magnetic resonance imaging is performed by the echo planar method, a plurality of echoes are generated at time intervals at which the phase of a fat signal in the echo changes by 180 °. And

(2) According to a second aspect of the present invention, in performing magnetic resonance imaging by the echo planar method, a plurality of echoes are generated within a time when a phase of a fat signal in the echo changes by 360 °. It is characterized by the following.

(3) According to a third aspect of the present invention, there is provided a static magnetic field forming means for forming a static magnetic field in a space accommodating a subject, a gradient magnetic field forming means for forming a gradient magnetic field in the space, High-frequency magnetic field forming means for forming a high-frequency magnetic field in the space, measuring means for measuring a magnetic resonance signal from the space, image generating means for generating an image based on the magnetic resonance signal measured by the measuring means, and echo In performing the planar method, imaging control means for generating a plurality of echoes at time intervals at which the phase of a fat signal in an echo changes by 180 ° by controlling the gradient magnetic field forming means and the high-frequency magnetic field forming means, It is characterized by doing.

(4) According to a fourth aspect of the present invention, there is provided a static magnetic field forming means for forming a static magnetic field in a space accommodating a subject, a gradient magnetic field forming means for forming a gradient magnetic field in the space, High-frequency magnetic field forming means for forming a high-frequency magnetic field in the space, measuring means for measuring a magnetic resonance signal from the space, image generating means for generating an image based on the magnetic resonance signal measured by the measuring means, and echo In performing the planar method, imaging control means for generating a plurality of echoes within a time when the phase of a fat signal in an echo changes by 360 ° by controlling the gradient magnetic field forming means and the high frequency magnetic field forming means, It is characterized by doing.

(Operation) In the first invention or the third invention, a plurality of echoes sequentially obtained by the echo planar method include a fat signal whose phase changes by 180 °. As a result, the chemical shift artifact moves to both ends of the FOV (field of view) on the reconstructed image.

Further, in the second invention or the fourth invention,
Multiple echoes sequentially obtained by the echo planar method are:
The phase of the fat signal changes by 360 ° over all echoes. As a result, the displacement of the fat image on the reconstructed image falls within one pixel.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiment.

FIG. 1 shows a block diagram of a magnetic resonance imaging apparatus. This device is an example of an embodiment of the present invention. An example of an embodiment relating to the device of the present invention is shown by the configuration of the present device. An example of an embodiment relating to the method of the present invention is shown by the operation of the present apparatus.

(Configuration) The configuration of the present apparatus will be described. As shown in FIG. 1, in the present apparatus, a substantially cylindrical static magnetic field generating section 2 forms a uniform static magnetic field (main magnetic field) in its internal space. The static magnetic field generation unit 2 is an example of an embodiment of a static magnetic field forming unit according to the present invention.

Inside the static magnetic field generating section 2, a gradient coil section 4 and a body coil section each having a substantially cylindrical shape are provided.
The parts 6 are arranged sharing a central axis. The subject 8 is placed in a generally cylindrical space formed inside the body coil portion 6.
Are carried in by carrying means (not shown).

A gradient driving unit 10 is connected to the gradient coil unit 4. The gradient coil unit 4 and the gradient driving unit 10
It is an example of embodiment of the gradient magnetic field formation means in this invention. The gradient driving unit 10 supplies a driving signal to the gradient coil unit 4 to generate a gradient magnetic field. The generated gradient magnetic fields are of three types: a slice gradient magnetic field, a read-out (read out) gradient magnetic field, and a phase encode (phase encode) gradient magnetic field.

The transmitting section 12 is connected to the body coil section 6. The body coil section 6 and the transmitting section 12 are an example of an embodiment of the high-frequency magnetic field forming means in the present invention. The transmission unit 12 supplies a drive signal (RF signal) to the body coil unit 6 to generate an RF magnetic field, thereby exciting spins in the body of the subject 8.

A magnetic resonance signal generated by the excited spin is detected by the body coil unit 6. The receiving unit 14 is connected to the body coil unit 6. The receiving unit 14 receives the signal detected by the body coil unit 6.

The receiving unit 14 has an analog / digital (ana
(log-to-digital) The conversion unit 16 is connected. The body coil section 6, the receiving section 14, and the analog / digital conversion section 16 are an example of an embodiment of the measuring means in the present invention. The analog-to-digital converter 16 converts an output signal of the receiver 14 into a digital signal.

The computer 18 receives a digital signal from the analog-to-digital converter 16 and stores it in a memory (not shown). A data space is formed in the memory. This data space constitutes a two-dimensional Fourier space. The computer 18 performs a two-dimensional inverse Fourier transform on the data in the two-dimensional Fourier space to reconstruct an image of the subject 8. The computer 18 is an example of an embodiment of an image generating unit according to the present invention.

The control unit 20 is connected to the computer 18. The computer 18 and the control unit 20 are an example of an embodiment of an imaging control unit according to the present invention. The control unit 20 includes a gradient driving unit 10, a transmission unit 12, and a reception unit 14.
And an analog / digital conversion unit 16. The control unit 20 includes a gradient driving unit 10, a transmission unit 12, and a reception unit 14 based on a command given from the computer 18.
And the analog-to-digital converter 16 are respectively controlled.

A display unit 22 and an operation unit 24 are connected to the computer 18. The display unit 22 is a computer 18
Various types of information including reconstructed images output from are displayed. The operation unit 24 is operated by an operator, and inputs various commands and information to the computer 18.

(Operation) The operation of the present apparatus will be described. First E
The PI will be described, and then the removal of chemical shift artifacts will be described. FIG. 2 shows an example of a pulse sequence based on the echo planar method. This pulse sequence is for collecting a spin echo.

In the figure, the horizontal axis represents time, and the vertical axis represents signal intensity. (A) RF pulse and echo signal, (b) readout gradient magnetic field (readout gradient) and dephase gradient magnetic field (dephase gradient), (c)
Indicates a phase encoding gradient magnetic field (phase encoding gradient). Illustration of the slice gradient magnetic field is omitted. The echo signal has a much lower signal strength than the RF pulse, but has the same amplitude for convenience. The same applies to other pulse sequences described later.

The sequence of the RF pulses indicates the operation of the transmitting unit 12. The sequence of the readout gradient and the phase encode gradient indicates the operation of the gradient driving unit 10. The same applies to other pulse sequences described later.

FIG. 3 conceptually shows the behavior of spin. In the figure, x ', y', z 'indicate three mutually perpendicular coordinate axes in the rotating coordinate system. Hereinafter, FIGS. 2 and 3
The operation will be described with reference to FIG.

As shown in FIG. 2, at time t1, 90
The excitation of the spin is performed by the ° pulse. As a result, as shown in FIG. 3A, the spins oriented in the z ′ direction fall by 90 ° and are oriented in the y ′ direction.

Next, at time t2, a dephase gradient and a phase encode gradient are applied for a predetermined time. As a result, the phases of the spins are dispersed (dephased) as shown in FIG.

Next, at time t3, the spin is inverted by a 180 ° pulse. Thereby, as shown in FIG. 3C, the direction of the spin in the y ′ direction is reversed. Next, at time t4, a readout gradient is applied. The readout gradient keeps a constant value until its polarity is inverted at time t6. The phase change of the spin continues during the application period of the readout gradient, and the dispersed phase converges as shown in FIG.

At time t5 on the way, the integrated value of the readout gradient becomes equal to the integrated value of the dephase gradient applied at time t2, and the phases of the spins are aligned as shown in FIG. At this point, the first peak of the magnetic resonance signal (spin echo signal) occurs.

After time t5, as shown in FIG. 3 (f), the phase is dispersed due to the continuation of the phase change of the spin, and the echo signal is attenuated. The echo signal is read during the readout gradient application period from time t4 to t6. The reading of the echo signal is performed by the system of the body coil unit 6-the receiving unit 14-the analog / digital converting unit 16-the computer 18. The same applies hereinafter.

The echo signal in this period is shown in FIG. 4 when the time axis is enlarged. However, the echo signal is shown not in a precise waveform diagram but in a conceptual diagram. As shown in the figure, the amplitude of the echo signal gradually increases from time t4 to t5, reaches a peak, and decreases from time t5 to time t6.

Returning to FIG. 2, a phase encoding gradient is applied for a short time in accordance with the polarity reversal of the readout gradient at time t6.
Steps are performed, and phase encoding for the next view is performed. This phase encoding gradient is called a blip pulse.

The generation and readout of the echo signal of the second view are performed according to the negative readout gradient from time t6 to time t8. The absolute value of the amplitude of the readout gradient of the negative polarity is the same as the amplitude of the positive polarity. The time from time t6 to t8 is equal to the time from time t4 to t6.

With the readout gradient, the phase of the dispersed spin is pulled back as shown in FIG. As a result, the phase changes in the direction opposite to the arrow in FIG. 3F, and the state shown in FIG. 3E is reached, and further, the state shown in FIG. However,
The direction of the spin phase change is opposite to the direction of the arrow.

For this reason, the echo signal reaches a peak at time t7 and attenuates therefrom to time t8. Time t6
The integrated value of the readout gradient from time t5 to time t7 is calculated at time t5
From the integrated value of the readout gradient from t to t6. Thus, an echo signal similar to that shown in FIG. 4 is read.

In the same manner, the inversion of the polarity of the readout gradient and the application of the blip pulse are repeated, and FIG.
By repeating (e) → (f) → (e) → (f) → (d)..., Echo signals of a plurality of views are sequentially generated and read out. The echo peaks are arranged at regular time intervals (echo space) along the time axis. The echo peak changes along an envelope env as indicated by a broken line, for example, according to the amount of phase encoding.

With the reading of the echo signal, the collection of echo data proceeds along a predetermined trajectory in the two-dimensional Fourier space. This is shown in FIG. In FIG. 5, k is a two-dimensional Fourier space. This is also called k-space. kx and ky are two coordinate axes orthogonal to each other in the two-dimensional Fourier space, kx is a frequency axis (readout axis), and ky is a phase axis (phase encode axis).

Trajectory trj for echo data collection
Starts from the point of kx = -100, ky = 100, for example. The unit of the coordinates is%. kx = −100 corresponds to the left end of the echo signal shown in FIG. ky = 100
Is the phase encoding amount of the echo signal shown in FIG. This is determined by the phase encoding gradient at time t2.

With the readout of the echo signal of the first view (collection of echo data) during the readout period from time t4 to time t6, the trajectory trj reaches kx = 100 along the arrow. A point at kx = 0 in the middle corresponds to a time point t5, and a peak value is collected here.

The trajectory is lowered by one step by the phase encoding at time t6.
During the readout period of the second view from 6 to t8, data collection for the next echo takes place, and the trajectory trj reaches kx = -100 along the arrow. The point of kx = 0 in the middle corresponds to the time point of time t7,
Here, peak values are collected.

Similarly, the data is collected in the two-dimensional Fourier space k along the kx axis while sequentially shifting downward along the ky axis every time phase encoding is performed. Thus, echo data for the entire two-dimensional Fourier space k is collected. The total number of views is, for example, 256.

An image is reconstructed by the computer 18 based on such echo data. Image reconstruction is performed by two-dimensional inverse Fourier transform. The above is
Although this is an example of EPI using spin echo, EPI using gradient echo can also be performed.

FIG. 6 shows an EP based on a gradient echo.
3 shows a pulse sequence of I. As shown in the figure, spins are excited by an α ° (eg, 90 °) pulse at time t1, a phase encode gradient is applied for a predetermined time at time t2, and a negative dephase gradient is applied at time t3. At time t4, a readout gradient is applied.

The readout gradient maintains a constant value until the polarity is inverted at time t6. At time t5 on the way, the integrated value of the readout gradient cancels the integrated value of the dephase gradient from time t3 to t4, and at this time, the first peak of the echo signal (gradient echo signal) occurs.
The echo signal attenuates after time t5.

The reading of the echo signal is performed during the period from time t4 to time t6. The echo signal in this period is the same as that shown in FIG. 4 if the time axis is enlarged.
That is, as shown in FIG.
From t to t5, the amplitude gradually increases and reaches a peak,
The amplitude attenuates from time t5 to time t6.

Returning to FIG. 6, a blip pulse is applied in accordance with the polarity reversal of the readout gradient at time t6, and the phase encoding is advanced by one step. The readout of the echo signal of the second view is performed according to the negative readout gradient from time t6 to time t8. The absolute value of the readout gradient amplitude is the same as the positive polarity amplitude. The time from time t6 to t8 is equal to the time from time t4 to t6. The echo signal reaches a peak at time t7, and then attenuates from time t8 to time t8. The integrated value of the readout gradient from time t6 to t7 cancels the integrated value of the readout gradient from time t5 to t6. Thus, an echo signal similar to that shown in FIG. 4 is read.

In the same manner, the polarity inversion of the readout gradient and the application of the blip pulse are repeated, and echo signals of a plurality of views are sequentially read. As a result, FIG.
The same echo signal sequence as in the case (1) is read. Therefore, data collection in the two-dimensional Fourier space is performed in the same manner as that shown in FIG. 5, and an image is reconstructed by performing a two-dimensional inverse Fourier transform.

Next, the removal of the chemical shift artifact will be described. The echo signal (fat signal) generated from the fat portion of the subject 8 has a different frequency from the echo signal (water signal) generated from the water portion due to a chemical shift. Changes over time.

The phase of the fat signal is 180 ° when viewed from the water signal.
The (π radian) changing time is given by the following equation.

[0053]

(Equation 1)

Here, γ: magnetic rotation ratio δ: chemical shift of fat T: static magnetic field strength For example, when the static magnetic field strength is 1.5T, tδ is 2.3.
mS. Focusing on such a relationship, in the present apparatus, under the control of the control unit 20, imaging is performed with a pulse sequence in which the echo space matches tδ. Such a pulse sequence is formed by appropriately adjusting the dephase gradient and the readout gradient in the pulse sequence shown in FIG. 2 or FIG.

Specifically, in FIG. 2, by adjusting the dephase amount by the dephase gradient applied at time t2 and the readout gradient applied after time t4,
The time from the application time of the readout gradient (for example, time t4) to the time when the echo peak occurs (for example, time t5) is set to tδ / 2.

Similarly, in FIG. 6, by adjusting the dephase gradient applied at time t3 and the readout gradient applied after time t4, the peak of the echo starts from the application time of the readout gradient (for example, time t4). The time until the point of occurrence (for example, time t5) is set to tδ / 2.

When spin echo signals having an echo space of tδ are sequentially collected, the fat signal contained in each echo changes in phase by π sequentially. As a result, as shown in FIG. 5 as the fat phase (1), in the k space, the phase change of the fat signal between adjacent trajectories becomes π, and the fat signal has a Nyquist frequency in the phase axis direction. become.

Assuming that the number of views of all data collected in the k space is N, data that changes by n periods along the phase axis ky is ghost (ghost) at a position separated by a distance given by the following equation in the real space. ) Is known to occur.

[0059]

(Equation 2)

Here, the FOV is the size of the real space given by the field of view, that is, the reconstructed image.
Because the fat signal has the Nyquist frequency, (2)
In the equation, n = N / 2. Therefore, the ghost due to the fat signal occurs at the position of d = (FOV) / 2.

If this is illustrated, for example, as shown in FIG. 7 (a), when a subject consisting of a water portion and a fat portion surrounding the water portion is imaged at the center of the FOV, the reconstructed image shows (b) in FIG. As shown in ()), the fat image is driven to both ends of the FOV. Therefore, by setting the FOV to about twice the image display range, the fat image can be prevented from being displayed on the screen. That is, an image free of chemical shift artifacts can be obtained.

When the static magnetic field is a low magnetic field of, for example, about 0.2 T, the value of tδ is about 17.3 mS. Setting the echo space to such a time is not practical because the signal attenuation increases. Therefore, when the static magnetic field strength is low, imaging is performed by the following pulse sequence.

FIGS. 8 and 9 show pulse sequences suitable for a low magnetic field, respectively. FIG. 8 shows a pulse sequence for spin echo, and FIG. 9 shows a pulse sequence for gradient echo.

As shown in both figures, the pulse sequence is configured so that the time to collect all echoes is within 2tδ. When the static magnetic field strength is, for example, 0.2T, 2tδ is 3
4.6 mS.

The number of echoes collected by one RF excitation is represented by Et.
When t is set, the echo space is 2tδ / Ett. 8 and 9, the dephase gradient and the readout gradient are set so as to realize such an echo space.

When the echo data is collected in this manner, the phase of the fat signal in the k-space becomes 360 ° along the phase axis ky as shown in FIG. 5 as fat phase (2).
(2π radians).

That is, the phase change of the fat signal throughout one view is within one cycle. This is the case where n = 1 or less in equation (2), whereby the ghost occurrence position is within (FOV) / N, that is, within one pixel.

When the value of N is 256, for example, the displacement within one pixel is hardly noticeable on the display screen. Therefore, in the reconstructed image, as shown in FIG. 7 (c), the fat image is displayed substantially without any displacement, and virtually no chemical shift artifact occurs.

When it is difficult to collect all echoes of, for example, 256 views within the time of 2tδ, a method of collecting the echoes in plural times by the number of echoes that can be collected within the time of 2tδ is used. This is a multi-shot EP
Called I.

FIG. 10 is a conceptual diagram of the multi-shot EPI. As shown in the figure, by the first RF excitation (shot), echo data is collected at intervals of a plurality of steps of phase encoding in the direction of the phase axis, as indicated by the solid line trajectory.

Such data collection is performed by using FIG. 8 or FIG.
In the pulse sequence shown in (1), this can be performed by appropriately adjusting the dephase amount and the phase encode amount.

Next, in the second shot, as shown by the dashed line, the phase encode is performed in the phase axis direction.
Echo data is collected along a trajectory translated by a step. Such data collection is also shown in FIG.
Alternatively, it can be performed by adjusting the amount of dephase and the amount of phase encoding in the pulse sequence shown in FIG.

In the same manner, data is collected along the trajectory that fills the space between the third shot and the fourth shot. Data collection for each shot is 2
Each is performed within the same time within tδ. As a result, the phase change of the fat signal included in the echo data is within 2π throughout all views, and the chemical shift artifact in the reconstructed image virtually does not occur.

In the above, an example of EPI in which echo data is collected over the entire k-space has been described. For example, echo data is collected only in half of the k-space in the phase axis direction, and the fractional Fourier is collected.
The image may be reconstructed by the urie) method. This is preferred in terms of shortening TE.

[0075]

As described above in detail, according to the present invention, in one aspect, in performing magnetic resonance imaging by the echo planar method, an echo is generated at a time interval at which the phase of a fat signal in the echo changes by 180 °. Therefore, it is possible to realize a magnetic resonance imaging method and apparatus using an echo planar method that effectively suppresses chemical shift artifacts.

In another aspect, a plurality of echoes are collected within the time when the phase of the fat signal in the echo changes by 360 °. Therefore, the echo planer method that effectively suppresses chemical shift artifacts is used. A magnetic resonance imaging method and apparatus can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram of a device according to an example of an embodiment of the present invention.

FIG. 2 is a diagram showing a pulse sequence executed by the device according to the embodiment of the present invention;

FIG. 3 is a conceptual diagram of spin behavior when a spin echo method is executed.

FIG. 4 is a conceptual diagram of an echo signal read by a device according to an embodiment of the present invention;

FIG. 5 is a conceptual diagram of data collection in a two-dimensional Fourier space by an apparatus according to an embodiment of the present invention.

FIG. 6 is a diagram showing a pulse sequence executed by the device according to the embodiment of the present invention;

FIG. 7 is a conceptual diagram showing removal of chemical shift artifacts in the apparatus according to an embodiment of the present invention.

FIG. 8 is a diagram showing a pulse sequence executed by the apparatus according to the embodiment of the present invention;

FIG. 9 is a diagram showing a pulse sequence executed by the apparatus according to an embodiment of the present invention.

FIG. 10 is a conceptual diagram of data collection in a two-dimensional Fourier space by an apparatus according to an embodiment of the present invention.

FIG. 11 is a diagram showing a pulse sequence of EPI.

[Explanation of symbols]

 2 Static magnetic field generation unit 4 Gradient coil unit 6 Body coil unit 8 Subject 10 Gradient driving unit 12 Transmitting unit 14 Receiving unit 16 Analog-digital converting unit 18 Computer 20 Control unit 22 Display unit 24 Operation unit

Claims (4)

[Claims] 1. A magnetic resonance imaging method, wherein when performing magnetic resonance imaging by an echo planar method, a plurality of echoes are generated at time intervals at which the phase of a fat signal in the echo changes by 180 °. 2. The magnetic resonance imaging method according to claim 1, wherein a plurality of echoes are generated within a time when the phase of the fat signal in the echo changes by 360 ° when performing the magnetic resonance imaging by the echo planar method. 3. A static magnetic field forming means for forming a static magnetic field in a space accommodating a subject, a gradient magnetic field forming means for forming a gradient magnetic field in the space, and a high frequency magnetic field forming means for forming a high frequency magnetic field in the space. A measuring unit that measures a magnetic resonance signal from the space; an image generating unit that generates an image based on the magnetic resonance signal measured by the measuring unit; and, when executing an echo planar method, the gradient magnetic field forming unit and Imaging control means for generating a plurality of echoes at time intervals at which the phase of the fat signal in the echo changes by 180 ° by controlling the high-frequency magnetic field forming means,
A magnetic resonance imaging apparatus comprising: 4. A static magnetic field forming means for forming a static magnetic field in a space accommodating a subject, a gradient magnetic field forming means for forming a gradient magnetic field in the space, and a high frequency magnetic field forming means for forming a high frequency magnetic field in the space. A measuring unit that measures a magnetic resonance signal from the space; an image generating unit that generates an image based on the magnetic resonance signal measured by the measuring unit; and, when executing an echo planar method, the gradient magnetic field forming unit and An imaging control unit that generates a plurality of echoes within a time when a phase of a fat signal in an echo changes by 360 ° by controlling the high-frequency magnetic field forming unit;
A magnetic resonance imaging apparatus comprising: