KR101949491B1 - Device and method for generating magnetic resonance imaging - Google Patents

Abstract

A method for generating a magnetic resonance image according to an embodiment of the present invention includes acquiring a magnetic resonance signal as an imaging pulse train for a plurality of slices is applied to a target object, obtaining a refocusing pulse Obtaining a free induction decay (FID) signal by applying a calibration pulse string in which the phase of the FID signal is inverted to a target object, subtracting and correcting the FID signal from the magnetic resonance signal, And generating a magnetic resonance image based on the resonance signal.

Description

TECHNICAL FIELD [0001] The present invention relates to a magnetic resonance imaging method and a magnetic resonance imaging method,

The present invention relates to a method of generating a magnetic resonance image and a magnetic resonance imaging apparatus thereof, and more particularly, to a method of generating a magnetic resonance image in which artifacts according to a free induction decay (FID) signal are removed .

The spin echo technique is the most widely used technique in magnetic resonance imaging (MIR). After a 90-degree excitation pulse, a 180-degree refocusing pulse is applied to a target object to acquire and image an echo signal. Such a spin-echo technique is attracting attention because it can generate images with excellent SNR (signal to noise ratio) and contrast.

On the other hand, in order to shorten the scan time, the spin echo technique is developed by applying a plurality of refocusing pulses after a 90-degree excitation pulse is applied. However, when the re-focusing pulses having a 180 DEG flip angle are continuously applied to a target object, stability problems arise as the Specific Absorption Rate (SAR) absorbed by the subject increases. Accordingly, various accelerating techniques are intentionally being developed in such a way as to apply refocusing pulses with a flip angle smaller than 180 degrees. However, if the flip angles of the re-focusing pulses are intentionally adjusted to less than 180 degrees due to instability of the system or intentionally to solve the SAR problem, an unintended free induction decay (FID) signal And the FID signal acts as an artifact in the magnetic resonance image, thereby lowering the SNR of the image. Therefore, in recent years, studies have been actively carried out to maintain the SNR and contrast of the spin echo technique while securing the safety of the subject.

Conventionally, artifacts have been removed by adding the original image and the phase-inverted image by repeating scanning by applying a phase-inverted refocusing pulse to each slice after scanning each slice. However, since the above method performs repetitive scans for each slice, there is a disadvantage that the scan time excessively increases when the number of slices increases.

Korean Patent Publication No. 10-1560463 (entitled " Magnetic Resonance Image Acquisition Method for Removing Artifacts and Undesired Signals in Magnetic Resonance Imaging System Using Off-Resonance Radio Frequency Pulse)

SUMMARY OF THE INVENTION It is an object of the present invention to provide a magnetic resonance imaging apparatus and a magnetic resonance imaging apparatus, And a method therefor.

Also, some embodiments of the present invention are directed to quantifying the FID signal without unduly increasing the scan time.

As a technical means for achieving the above technical object, a first aspect of the present invention is a method for acquiring a magnetic resonance signal, comprising: acquiring an MR signal as an imaging pulse train for a plurality of slices is applied to a target object; Acquiring a free induction decay (FID) signal by applying a calibration pulse string in which a phase of a refocusing pulse is inverted to one of a plurality of slices, to a target object; Subtracting and correcting the FID signal in the magnetic resonance signal; And generating a magnetic resonance image based on the magnetic resonance signal in which the FID signal is subtracted and corrected.

According to a second aspect of the present invention, there is provided a magnetic resonance imaging apparatus including a memory for storing a program for instructing pulse train information with an MRI scanner and generating a magnetic resonance image from a magnetic resonance signal received from an MRI scanner, Thereby providing a video device. At this time, the processor obtains the magnetic resonance signal by applying the imaging pulse string for the plurality of slices, acquires the FID signal by applying a calibration pulse string in which the phase of the refocusing pulse is inverted to one slice of the plurality of slices, Subtracts and corrects the FID signal in the resonance signal, and generates a magnetic resonance image based on the magnetic resonance signal in which the FID signal is subtracted and corrected.

A third aspect of the present invention provides a computer-readable recording medium on which a program for implementing the method of the first aspect is recorded.

According to the above-described object of the present invention, by adding a calibration pulse string that takes one TR in various high-speed pulse strings based on the spin echo technique, the safety problem of the subject is solved without excessively increasing the scan time High SNR and contrast can be maintained.

1 is a view showing a magnetic resonance imaging apparatus according to an embodiment of the present invention.
FIG. 2 is a flowchart illustrating a magnetic resonance imaging method according to an embodiment of the present invention.
3 is an example showing an area where an FID signal is radiated by an imaging pulse train according to an embodiment of the present invention.
FIG. 4 illustrates a method of extracting an FID signal according to an embodiment of the present invention. Referring to FIG.
5 is a diagram illustrating a result of extracting an FID signal by applying a calibration pulse sequence to one slice included in a phantom according to an embodiment of the present invention.
FIG. 6 is a diagram illustrating a result of generating an artifact-free magnetic resonance image according to an FID signal using the FID signal extracted in FIG. 5 according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, which will be readily apparent to those skilled in the art. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

Throughout the specification, when a part is referred to as being "connected" to another part, it includes not only "directly connected" but also "electrically connected" with another part in between . Also, when a part is referred to as "including " an element, it does not exclude other elements unless specifically stated otherwise.

In the present specification, "MRI (Magnetic Resonance Imaging)" means an image of a target object obtained using the nuclear magnetic resonance principle.

Further, the term "image" or " image " refers to multi-dimensional data consisting of discrete elements. It means that a plurality of pixels in a two-dimensional image and a plurality of voxels .

Also, the "object" is an object of imaging of a magnetic resonance imaging apparatus, and may include a person, an animal, or a part thereof. The subject may also include various organs such as heart, brain or blood vessels or various types of phantoms.

The term "user" may be, but is not limited to, a medical professional such as a doctor, a nurse, a medical imaging specialist, or a device repair technician.

The term "pulse sequence (or pulse sequence)" means a signal repeatedly applied in a magnetic resonance imaging apparatus. The pulse sequence may include a repetition time (TR) or an echo time (Time to Echo, TE) as a time parameter of the RF pulse.

Hereinafter, embodiments of a magnetic resonance imaging apparatus will be described with reference to the accompanying drawings.

1 is a view showing a magnetic resonance imaging apparatus according to an embodiment of the present invention.

The magnetic resonance imaging apparatus 1 may include an MRI scanner 10, a signal processing unit 20, a monitoring unit 40, a control unit 50, and an interface unit 60.

The MRI scanner 10 forms a magnetic field and generates a resonance phenomenon with respect to an atomic nucleus. A magnetic resonance image is photographed when the object is positioned inside the MRI scanner 10. The MRI scanner 10 includes a main magnet 12, a gradient coil 14, an RF coil 16 and the like, through which a static magnetic field and a gradient magnetic field are formed, and an RF signal is radiated toward a target object.

The main magnet 12, the gradient coil 14 and the RF coil 16 are arranged in the MRI scanner 10 according to a predetermined direction. The object is positioned on a table that can be inserted into the cylinder along the horizontal axis of the cylinder and the object can be positioned inside the bore of the MRI scanner 10 as the table moves.

The main magnet 12 generates a static magnetic field that aligns the direction of the magnetic dipole moment of the nuclei included in the object in a predetermined direction.

The gradient coil 14 includes an X-coil, a Y-coil, and a Z-coil that generate mutually orthogonal X-axis, Y-axis, and Z-axis gradient magnetic fields. The gradient coil 14 induces different resonance frequencies for the respective parts of the object so that position information of each part of the object can be obtained.

The RF coil 16 can radiate an RF signal to a target object and receive a magnetic resonance image signal emitted from the target object. The RF coil 16 outputs an RF signal having the same frequency as the frequency of the carrot motion toward the nucleus of the car wash motion, and can receive the magnetic resonance image signal emitted from the target body.

For example, the RF coil 16 generates an RF signal having a frequency corresponding to the atomic nucleus, and applies the RF signal to the object, in order to transition the atomic nucleus from a low energy state to a high energy state. Thereafter, when the RF coil 16 stops transmitting the RF signal, the atomic nucleus to which the electromagnetic wave has been applied transits from a high energy state to a low energy state and emits an electromagnetic wave having a Lamor frequency, and the RF coil 16 And receives the corresponding electromagnetic wave signal.

The RF coil 16 includes a transmitting RF coil for transmitting an RF signal having a radio frequency corresponding to the type of the atomic nucleus and a receiving RF coil for receiving electromagnetic waves emitted from the atomic nucleus.

Further, the RF coil 16 may be fixed to the MRI scanner 10, or may be detachable. The removable RF coil 16 may be implemented in the form of a head RF coil, a chest RF coil, a leg RF coil, a neck RF coil, a shoulder RF coil, a wrist RF coil, and an ankle RF coil, which may be coupled to a part of a target object .

The MRI scanner 10 can provide various information to a user or a target through a display, and can include a display 18 disposed on the outside and a display (not shown) disposed on the inside.

The signal processing unit 20 controls a gradient magnetic field formed inside the MRI scanner 10 according to a predetermined MR pulse sequence (i.e., a pulse train), and can control the transmission and reception of an RF signal and a magnetic resonance image signal.

The signal processing section 20 may include a gradient magnetic field amplifier 22, a switching section 24, an RF transmission section 26 and an RF reception section 28.

The gradient magnetic field amplifier 22 drives the gradient coil 14 included in the MRI scanner 10 and outputs a pulse signal for generating a gradient magnetic field under the control of the gradient magnetic field control unit 44 to the gradient coil 14, . By controlling the pulse signals supplied from the oblique magnetic field amplifier 22 to the gradient coil 14, gradient magnetic fields in the X axis, Y axis, and Z axis directions can be synthesized.

The RF transmitting unit 26 supplies RF pulses to the RF coil 16 to drive the RF coil 16. [ The RF receiver 28 receives the MRI image signal transmitted by the RF coil 16 after receiving the RF signal.

The switching unit 24 can adjust the transmission and reception directions of the RF signal and the magnetic resonance image signal. For example, during a transmit operation, an RF signal is applied to an object through an RF coil 16, and during a receive operation, a magnetic resonance image signal from a subject is received via the RF coil 16. [ The switching unit 24 is controlled in switching operation by a control signal from the RF control unit 46. [

The interface unit 30 may instruct the control unit 40 to transmit the pulse sequence information according to an operation of the user and may transmit a command for controlling the operation of the entire MRI system. The interface unit 30 may include an image processing unit 36, an output unit 34, and an input unit 32 for processing a magnetic resonance image signal received from the RF receiving unit 38.

The image processor 36 can process the MR image signal received from the RF receiver 38 to generate MR image data for the object 10.

The image processor 36 applies various signal processing such as amplification, frequency conversion, phase detection, low frequency amplification, filtering, and the like to the MRI image signal received by the RF receiver 38.

The image processing unit 36 can arrange the digital data in the k space, for example, and reconstruct the image data into two-dimensional or three-dimensional Fourier transformed data.

In addition, various signal processes applied to the magnetic resonance image signal by the image processing unit 36 can be performed in parallel. For example, a plurality of magnetic resonance image signals may be reconstructed into image data by applying signal processing in parallel to a plurality of magnetic resonance image signals received by the multi-channel RF coil.

The output unit 34 can output the image data or the reconstructed image data generated by the image processing unit 36 to the user. The output unit 54 may output information necessary for a user to operate the MRI system, such as a UI (user interface), user information, or object information. The output unit 54 may include a speaker, a printer, or various image display means.

The user can input object information, parameter information, scan condition, pulse sequence, information on image synthesis and calculation of difference through the input unit 32. The input unit 32 may include a keyboard, a mouse, a trackball, a voice recognition unit, a gesture recognition unit, a touch screen, and the like, and may include various input devices within a range obvious to those skilled in the art.

The control unit 40 includes a sequence control unit 42 for controlling a sequence of signals formed in the MRI scanner 10 and a scanner control unit 48 for controlling the MRI scanner 10 and the devices mounted on the MRI scanner 10, . ≪ / RTI >

The sequence control unit 42 includes an inclination magnetic field control unit 44 for controlling the gradient magnetic field amplifier 22 and an RF control unit 46 for controlling the RF transmission unit 26, the RF reception unit 28 and the switching unit 24. [ do. The sequence control unit 42 can control the gradient magnetic field amplifier 22, the RF transmission unit 26, the RF reception unit 28 and the switching unit 24 according to the pulse sequence received from the interface unit 30. [ The pulse sequence includes all information necessary for controlling the gradient magnetic field amplifier 22, the RF transmitter 26, the RF receiver 28 and the switching unit 24, and for example, a pulse applied to the gradient coil 24 the intensity of the pulse signal, the application time, the application timing, and the like.

The monitoring unit 50 monitors or controls devices mounted on the MRI scanner 10 or the MRI scanner 10. The monitoring unit 50 may include a system monitoring unit 52, an object monitoring unit 54, a table control unit 56, and a display control unit 58.

The system monitoring unit 52 monitors the state of the static magnetic field, the state of the gradient magnetic field, the state of the RF signal, the state of the RF coil, the state of the table, the state of the device for measuring the body information of the object, You can monitor and control the state of the compressor.

The object monitoring unit 54 monitors the state of the object and may be a camera for photographing the movement or position of the object, a respiration measuring unit for measuring the respiration of the object, an ECG measuring unit for measuring the electrocardiogram of the object, And a temperature measuring device for measuring temperature.

The table control unit 56 controls the movement of the table in which the object is located. The table control unit 56 can control the movement of the table in synchronization with the sequence control signal output by the sequence control unit 42. [ For example, in moving imaging of a subject, the table control unit 56 may move the table in accordance with the sequence control, thereby causing the FOV (field of view) of the MRI scanner to move to the target object Can be photographed.

The display control unit 58 controls on / off of a display located outside and inside of the MRI scanner 10 or a screen to be output to the display. When the speaker is located inside or outside the MRI scanner 10, the display controller 58 may control on / off of the speaker or sound to be output through the speaker.

The MRI scanner 10, the RF coil 16, the signal processing unit 20, the monitoring unit 50, the control unit 40 and the interface unit 30 may be connected to each other wirelessly or wired, (Not shown) for synchronizing the clocks of the mobile stations. Communication between the MRI scanner 10, the RF coil 16, the signal processing unit 20, the monitoring unit 50, the control unit 40 and the interface unit 30 is performed by a high-speed digital communication unit such as LVDS (Low Voltage Differential Signaling) Interface, an asynchronous serial communication such as a universal asynchronous receiver transmitter (UART), a hypo-synchronous serial communication, or a CAN (Controller Area Network) can be used. A communication method can be used.

The magnetic resonance imaging apparatus 1 according to the embodiment of the present invention is characterized by the configuration of the interface unit 30. [ At this time, the interface unit 30 may be implemented as a separate computing device, and performs operations of generating a magnetic resonance image based on the memory and the processor mounted on the computing device.

At this time, a program for generating a magnetic resonance image is stored in the memory. A memory is a nonvolatile storage device that keeps stored information even when no power is supplied, and a volatile storage device that requires power to maintain stored information.

The processor instructs the pulse train information including the refocusing pulses of 180 degrees or less according to the execution of the program stored in the memory, and then generates a magnetic resonance image using the magnetic resonance signal emitted from the object. At this time, the magnetic resonance signal may be image data including a plurality of frames representing a space according to a time flow in the space-time encoding region (k, t-space).

As described above with reference to FIG. 1, in order to generate a magnetic resonance signal according to a pulse train command, the MRI scanner 10 adjusts another magnetic field by using an electromagnetic pulse while fixing one magnetic field, (not shown). Then, the MRI scanner 10 can obtain a magnetic resonance signal with respect to the space-time domain by forming a magnetic field based on the plurality of gradient coils 14.

As described above, the processor of the MRI apparatus 1 can receive the signal obtained from the MRI scanner 10. The magnetic resonance imaging apparatus 1 can generate a magnetic resonance image in which artifacts according to the FID signal are removed using the magnetic resonance signal obtained from the MRI scanner 10. [

FIG. 2 is a flowchart illustrating a magnetic resonance imaging method according to an embodiment of the present invention.

Referring to FIG. 2, the magnetic resonance imaging apparatus 1 acquires magnetic resonance signals by applying imaging pulse sequences for a plurality of slices to a target object (S110). Here, the imaging pulse train may be various pulse trains based on a spin echo technique and is configured to include a plurality of refocusing pulses having a fixed and / or variable flip angle of 180 degrees or less. The imaging pulse train may be based on, for example, fast spin echo (FSE), turbo spin echo (TSE), grayscale (Gradient and Spin echo, GRASE), or a combination thereof.

On the other hand, when the echo train length (ETL) of the imaging pulse train is long and configured to have a short echo spacing (ESP), it is preferable to use a re-focusing pulse having a short duration of the pulse. At this time, since the duration of the pulse is inversely proportional to the spatial bandwidth of the pulse, it is preferable to use a pulse corresponding to the field of view (FOV) in the slice direction or having a larger spatial bandwidth. Accordingly, the re-focusing pulse according to an exemplary embodiment of the present invention may be a wide-bandwidth (i.e., wide-band) refocusing pulse that may include all of a plurality of slices to be imaged, Lt; / RTI >

On the other hand, as shown in FIG. 3, a free induction decay (FID) signal generated by a wide-band refocusing pulse or a non-selective refocusing pulse includes a slice area 301, Direction FOV of the received signal.

Generally, the FID signal is an unstable signal generated as the magnetized nuclei are dephased. In order to solve the unstable case of the system or the SAR problem, the imaging pulse string is intentionally made to have a flip angle smaller than 180 degrees Including focusing pulses unintentionally occurs and affects the final image. That is, the magnetic resonance imaging apparatus 1 receives a magnetic resonance signal including an FID signal as well as an echo signal by using a refocusing pulse of 180 or less, and the FID signal acts on the image as artifact Thereby reducing the SNR and contrast of the image. Therefore, the magnetic resonance imaging apparatus 1 performs the following operation to remove the FID signal from the magnetic resonance signal acquired through the imaging pulse string, thereby preventing the SNR and contrast of the image from dropping.

First, the magnetic resonance imaging apparatus 1 acquires an FID signal by applying a calibration pulse string in which the phase of the re-focusing pulse is inverted to one of a plurality of slices, as a target object (S120). At this time, the calibration pulse train takes one TR and can be applied before the imaging pulse train or after the imaging pulse train is applied. Alternatively, the calibration pulse train may be applied in the middle of the imaging pulse train. For example, as shown in FIG. 4, after the imaging pulse sequence for one slice is applied, the calibration pulse sequence 420 in which the phase of the re-focusing pulse included in the imaging pulse sequence 410 of the slice is reversed It can be applied as a target object.

The magnetic resonance imaging apparatus 1 acquires the first magnetic resonance signal including the echo signal 401 and the FID signal 402a for the slice through the imaging pulse train 410 and then outputs the first magnetic resonance signal including the calibration pulse string 420 To obtain a second magnetic resonance signal comprising an echo signal 401 for the same slice and a phase-inverted FID signal 402b. Thereafter, the magnetic resonance imaging apparatus 1 can extract the FID signal 402a from which the echo signal 401 has been removed by subtracting the first magnetic resonance signal and the second magnetic resonance signal.

5 is a diagram showing a result of extracting an FID signal 530 by applying a calibration pulse string to one slice included in a phantom according to an embodiment of the present invention. At this time, it is assumed that the phantom is divided into first to fifth slices 610 to 650 as shown in FIG. 6, and the calibration pulse sequence is applied to the third slice 630. In other words, the first magnetic resonance signal 510 shows imaging of the magnetic resonance signal obtained through the imaging pulse train of the third slice 630, and the second magnetic resonance signal 520 is the imaging signal of the re- And the magnetic resonance signal obtained through the calibration pulse string obtained by inverting the phases of the magnetic resonance signals.

3, since the extracted FID signal 530 is radiated from a region wider than the third slice 630, the FID signal 530, which can be generated by the imaging pulse sequences of the first to fifth slices 610 to 650, .

Referring again to FIG. 2, the MRI apparatus 1 subtracts and corrects the FID signal from the obtained magnetic resonance signal (S130). Thereby, the magnetic resonance imaging apparatus 1 can extract an echo signal suitable for imaging by removing the FID signal from the magnetic resonance signal.

Thereafter, the magnetic resonance imaging apparatus 1 generates a magnetic resonance image based on the magnetic resonance signal whose FID signal is subtracted and corrected (S140). That is, the magnetic resonance imaging apparatus 1 generates a magnetic resonance image using an echo signal, thereby solving the SAR problem for a target object, and generating a magnetic resonance image having a high SNR and a high contrast.

The imaging pulse sequence may include excitation pulses that simultaneously magnetize two or more slices based on multi-band multi-slice imaging.

FIG. 6 is a diagram illustrating a result of generating an artifact-free magnetic resonance image according to an FID signal using the FID signal extracted in FIG. 5 according to an embodiment of the present invention. That is, the magnetic resonance imaging apparatus 1 subtracts and corrects the FID signal 530 obtained using the third slice 630 from the magnetic resonance signals obtained from the first to fifth slices 610 to 650, The artifacts according to the FID signal 530 can be removed from the slices 610 to 650. [

As described above, the MRI apparatus 1 according to the disclosed embodiment adds a calibration pulse string that requires one TR to increase the stability problem generated in the fast pulse train based on the spin echo technique without excessively increasing the scan time At the same time, it is possible to maintain high SNR and contrast which are advantages of the spin echo technique.

One embodiment of the present invention may also be embodied in the form of a recording medium including instructions executable by a computer, such as program modules, being executed by a computer. Computer readable media can be any available media that can be accessed by a computer and includes both volatile and nonvolatile media, removable and non-removable media. The computer-readable medium may also include computer storage media. Computer storage media includes both volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data.

It will be understood by those skilled in the art that the foregoing description of the present invention is for illustrative purposes only and that those of ordinary skill in the art can readily understand that various changes and modifications may be made without departing from the spirit or essential characteristics of the present invention. will be. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. For example, each component described as a single entity may be distributed and implemented, and components described as being distributed may also be implemented in a combined form.

The scope of the present invention is defined by the appended claims rather than the detailed description and all changes or modifications derived from the meaning and scope of the claims and their equivalents are to be construed as being included within the scope of the present invention do.

1: Magnetic Resonance Imaging Device
10: MRI Scanner
20: Signal processor
30:
40:
50: Monitoring section

Claims (9)

A method for generating a magnetic resonance imaging (MRI)
Acquiring a magnetic resonance signal as an imaging pulse train for a plurality of slices is applied to the object;
Acquiring a free induction decay (FID) signal by applying a calibration pulse train in which a phase of a refocusing pulse is inverted to one of the plurality of slices to the object;
Subtracting the FID signal from the magnetic resonance signal; And
And generating a magnetic resonance image based on the magnetic resonance signal in which the FID signal is subtracted and corrected. The method according to claim 1,
The step of acquiring the FID signal
Acquiring a first magnetic resonance signal including an echo signal and an FID signal by applying an imaging pulse train for the one slice to a target;
Obtaining a second magnetic resonance signal including an echo signal and a phase-inverted FID signal by applying a calibration pulse string inverted in phase of a refocusing pulse included in the imaging pulse string to the object; And
And subtracting the second magnetic resonance signal from the first magnetic resonance signal to extract the FID signal. The method according to claim 1,
Wherein the imaging pulse train comprises a plurality of refocusing pulses having a flip angle of 180 degrees or less. The method of claim 3,
Wherein the plurality of refocusing pulses have a variable flip angle or a fixed flip angle. The method of claim 3,
Wherein the calibration pulse sequence takes one TR (repetition time). The method according to claim 1,
Wherein the spatial bandwidth of the refocusing pulse included in the imaging pulse sequence corresponds to the FOV in the slice direction. In a magnetic resonance imaging apparatus,
A memory for storing a program for instructing pulse train information by an MRI scanner and generating a magnetic resonance image from a magnetic resonance signal received from the MRI scanner;
And a processor for executing the program,
The processor
Applying an imaging pulse train to a plurality of slices to acquire a magnetic resonance signal and applying a calibration pulse string in which a phase of a refocusing pulse is inverted to one slice of the plurality of slices, Decay, FID) signal,
And subtracts the FID signal from the magnetic resonance signal to generate a magnetic resonance image based on the subtraction-corrected magnetic resonance signal. 8. The method of claim 7,
The processor
Acquiring a first magnetic resonance signal including an echo signal and an FID signal by applying an imaging pulse train for the one slice, applying a calibration pulse string in which the phase of the refocusing pulse included in the imaging pulse string is inverted, Acquires a second magnetic resonance signal including a phase-inverted FID signal, and subtracts a second magnetic resonance signal from the first magnetic resonance signal to extract an FID signal. A computer-readable recording medium on which a program for implementing the method according to any one of claims 1 to 6 is recorded.

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