JP4751210B2 - Magnetic resonance imaging system - Google Patents

Description

The present invention relates to a magnetic resonance imaging equipment using fast spin echo (FSE) method.

  In this type of magnetic resonance imaging apparatus, the phase shift of the spin echo is detected by prescan. In the main scan, the detected phase shift is corrected.

For example, in the technique disclosed in Patent Document 1, spin echoes from which phase encoding (PE) is removed are collected, and zeroth-order and first-order phase differences between the first and second echoes are measured. The zero-order phase difference is corrected mainly by the RF phase, and the first-order phase difference is corrected by adding a correction pulse to the gradient magnetic field pulse in the readout direction.
U.S. Patent 6,369,568

  The magnitude of the correction pulse is theoretically determined using, for example, a trapezoidal approximation model. However, the amount of change in the gradient magnetic field may vary due to the effects of eddy currents and vibrations even when a fixed correction pulse is added. In particular, unshielded gradient coils and / or open magnets are greatly affected by eddy currents and vibrations, and variation in gradient magnetic field variation is significant.

  For this reason, if the correction pulse uniquely determined according to the measured phase difference is used, the phase difference may not be completely corrected. If the phase difference remains, there is a risk of causing sensitivity unevenness.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a magnetic resonance imaging apparatus capable of correcting a primary phase difference with high accuracy.

  In order to achieve the above object, the first aspect of the present invention provides a gradient magnetic field coil that generates a gradient magnetic field for reading when a read pulse is supplied, and supply means for supplying the read pulse to the gradient magnetic field coil. And a magnetic resonance imaging apparatus that performs imaging by the fast spin echo method, prior to the main scan for collecting imaging data, the odd-numbered first spin echo and the even-numbered second A collecting means for collecting a spin echo and an odd-numbered third spin echo or an even-numbered fourth spin echo generated after the first and second spin echoes; and In the acquisition period, a basic pulse is supplied to the gradient coil as the reading pulse, and one of the third or fourth spin echoes is supplied. The unit sensitivity pulse is supplied to the gradient coil as the reading pulse during the period from the end of the period of collecting the spin echo to the start of the period of collecting the third or fourth spin echo. A first control unit that controls the supply unit; a first measurement unit that measures a shift amount between a peak position of the first spin echo and a peak position of the second spin echo; Second measuring means for measuring the shift amount of the peak position of the third spin echo with respect to the peak position of the spin echo or the shift amount of the peak position of the fourth spin echo with respect to the peak position of the second spin echo; , Peak positions of the first spin echo and the second spin echo based on the shift amount, the energy amount of the unit sensitivity pulse, and the shift amount. A means for determining a correction energy amount for correcting a deviation of the correction energy, and supplying the basic pulse as the reading pulse to the gradient magnetic field coil during the main scan, and separately, a correction pulse for the correction energy amount And second control means for controlling the supply means so as to be supplied to the gradient coil as the reading pulse.

In order to achieve the above object, the second aspect of the present invention provides a gradient magnetic field coil that generates a gradient magnetic field for reading when a read pulse is supplied, and supply means for supplying the read pulse to the gradient magnetic field coil. The gradient magnetic field generated by the basic pulse of the reading pulse in a pre-scan prior to the main scan for collecting imaging data in a magnetic resonance imaging apparatus that performs imaging by a high-speed spin echo method The main scan based on the spin echo obtained by using the gradient magnetic field generated by the read pulse configured by adding a unit sensitivity pulse to the basic pulse and the unit pulse. Means for obtaining the magnitude of the correction pulse at the time, and in the main scan, the temporal position relative to the RF pulse is the unit sense. The same position as the pulse, and means for obtaining the spin echo using the gradient magnetic field the correction pulse of magnitude the obtained generated by the reading pulse that is configured in addition to the basic pulse.

  According to the present invention, it is possible to correct a primary phase difference with high accuracy.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing a configuration of a magnetic resonance imaging apparatus (hereinafter referred to as an MRI apparatus) according to the present embodiment. The MRI apparatus shown in FIG. 1 includes a static magnetic field magnet 1, a gradient magnetic field coil 2, a gradient magnetic field power supply 3, a bed 4, a bed control unit 5, a whole body RF coil 6, a transmission unit 7, a reception unit 8, a hybrid circuit 9, and a computer. A system 10 is provided.

  The static magnetic field magnet 1 has a hollow cylindrical shape and generates a uniform static magnetic field in an internal space. As the static magnetic field magnet 1, for example, a permanent magnet, a superconducting magnet or the like is used.

  The gradient magnetic field coil 2 has a hollow cylindrical shape and is disposed inside the static magnetic field magnet 1. The gradient magnetic field coil 2 is a combination of three types of coils corresponding to the X, Y, and Z axes orthogonal to each other. The gradient magnetic field coil 2 generates a gradient magnetic field in which the above three coils are individually supplied with electric current from the gradient magnetic field power supply 3 and the magnetic field intensity changes along the X, Y, and Z axes. The Z-axis direction is, for example, the same direction as the static magnetic field. The gradient magnetic fields of the X, Y, and Z axes correspond to, for example, the slice selection gradient magnetic field Gs, the phase encoding gradient magnetic field Ge, and the readout gradient magnetic field Gr, respectively. The slice selection gradient magnetic field Gs arbitrarily determines an imaging section. The phase encoding gradient magnetic field Ge changes the phase of the magnetic resonance signal in accordance with the spatial position. The readout gradient magnetic field Gr changes the frequency of the magnetic resonance signal in accordance with the spatial position.

  The subject P is inserted into the cavity of the gradient coil 2 while being placed on the top plate 41 of the bed 4. The top plate 41 is driven by the bed control unit 5 and moves in the longitudinal direction and the vertical direction. Usually, the bed 4 is installed such that the longitudinal direction thereof is parallel to the central axis of the static magnetic field magnet 1.

  The whole body RF coil 6 is disposed inside the gradient magnetic field coil 2. The whole body RF coil 6 receives a high frequency pulse (RF pulse) from the transmitter 7 and generates a high frequency magnetic field. The whole body RF coil 6 receives a magnetic resonance signal emitted from the subject P.

  The transmission unit 7 includes an oscillation unit, a phase selection unit, a frequency conversion unit, an amplitude modulation unit, and a high frequency power amplification unit. The oscillation unit generates a high-frequency signal having a resonance frequency unique to the target nucleus in the static magnetic field. The phase selection unit selects the phase of the high-frequency signal. The frequency conversion unit converts the frequency of the high-frequency signal output from the phase selection unit. The amplitude modulation unit modulates the amplitude of the high-frequency signal output from the frequency modulation unit, for example, according to a sync function. The high frequency power amplification unit amplifies the high frequency signal output from the amplitude modulation unit. As a result of the operation of each of these units, the transmission unit 7 transmits an RF pulse corresponding to the Larmor frequency.

  The whole body RF coil 6 is disposed inside the gradient magnetic field coil 2. The whole body RF coil 6 includes a plurality of RF coils that receive magnetic resonance signals radiated from the subject P due to the influence of the high-frequency magnetic field. Magnetic resonance signals output from the plurality of RF coils are input to the receiving unit 8.

  The receiving unit 8 includes a pre-stage amplifier, a phase detector, and an analog / digital converter. The preamplifier amplifies the magnetic resonance signal output from the hybrid circuit 9. The phase detector detects the phase of the magnetic resonance signal output from the preamplifier. The analog-digital converter converts the signal output from the phase detector into a digital signal.

  The hybrid circuit 9 supplies the high-frequency pulse transmitted from the transmission unit 7 to the whole-body RF coil 6 during the transmission period. The hybrid circuit 9 supplies the signal output from the whole-body RF coil 6 to the receiving unit 8 during the reception period. The transmission period and the reception period are instructed from the computer system 10. The hybrid circuit 9 can be connected to a local RF coil. When the local RF coil is connected, the hybrid circuit 9 supplies a high-frequency pulse to either the whole-body RF coil or the local RF coil, and outputs a signal that either the whole-body RF coil or the local RF coil outputs. The signal is supplied to the receiving unit 8. The computer system 10 instructs whether to select the whole body RF coil or the local RF coil.

  The computer system 10 includes an interface unit 101, a data collection unit 102, a reconstruction unit 103, a storage unit 104, a display unit 105, an input unit 106, and a control unit 107.

  The interface unit 101 is connected to the gradient magnetic field power source 3, the bed control unit 5, the transmission unit 7, the reception unit 8, and the hybrid circuit 9. The interface unit 101 inputs and outputs signals exchanged between these connected units and the computer system 10.

  The data collection unit 102 collects digital signals output from the reception unit 8. The data collection unit 102 stores the collected digital signal in the storage unit 104 as magnetic resonance signal data.

  The reconstruction unit 103 performs post-processing, that is, reconstruction processing such as Fourier transform, on the magnetic resonance signal data stored in the storage unit 104, and obtains spectrum data or image data of the desired nuclear spin in the subject P. Ask.

  The storage unit 104 stores magnetic resonance signal data and spectrum data or image data for each patient.

  The display unit 105 displays spectrum data or image data and other various information under the control of the control unit 107. A display device such as a liquid crystal display can be used for the display unit 105.

  The input unit 106 receives various commands and information input from the operator. As the input unit 106, a pointing device such as a mouse or a trackball, a selection device such as a mode change switch, or an input device such as a keyboard can be used as appropriate.

  The control unit 107 includes a CPU, a memory, and the like, and comprehensively controls the MRI apparatus according to the present embodiment. Further, the control unit 107 serves as means for realizing some functions as described below in addition to means for realizing functions generally provided in the MRI apparatus. One of the functions described above executes a pre-scan prior to the main scan. One of the functions is to measure the phase difference X between the first and second spin echoes acquired by the pre-scan. One of the functions is to add a unit sensitivity pulse of a certain magnitude to a gradient magnetic field pulse (RO pulse) that generates a readout gradient magnetic field for reading the third spin echo in the pre-scan. The gradient magnetic field power supply 3 is controlled. The magnitude of the unit sensitivity pulse is, for example, such that if the hardware is complete, the echo should shift by one pixel. One of the functions described above measures the phase difference Δ between the first and third spin echoes. One of the above functions calculates the magnitude of the correction pulse for correcting the phase difference X based on the magnitude of the unit sensitivity pulse and the phase difference Δ. Further, one of the above functions is to control the gradient magnetic field power supply 3 so as to add the correction pulse having the calculated magnitude to each of the RO pulses for generating the gradient magnetic field for reading each spin echo during the main scan. To do.

  Next, the operation of the MRI apparatus configured as described above will be described. Since the operation for obtaining the image of the subject P is the same as the conventional one, the description thereof is omitted here. In the following, characteristic operations according to the present invention will be described.

  This MRI apparatus performs the main scan by the FSE method. The main scan is a scan for collecting k-space data for imaging. In the FSE method, a plurality of flop pulses are given after one flip pulse to create a spin echo train. At this time, each spin echo is made to correspond to a different line in the k space by giving different phase encodings to the respective spin echoes. Thus, the FSE method collects a plurality of different views in one excitation.

  In the FSE method, if the waveforms of the RF pulse and the gradient magnetic field signal repeated after the flop pulse are symmetric, the first type spin echo α and the second type spin echo β are alternately displayed in the MR signal. Two echo components appearing are observed. This assumption is also satisfied in many cases. These two echo components are called a spin echo component and a stimulated echo component, respectively.

  In principle, the phase difference between the flip pulse and the flop pulse is 90 °, and the gradient magnetic field for read-out after the flip pulse is transmitted and for read-out after the flop pulse is transmitted. When the area (moment) ratio to the gradient magnetic field is 1: 2, the spin echo α in the spin echo component and the spin echo β in the stimulated echo component, and further the spin echo β in the spin echo component and the spin echo α in the stimulated echo component And, the peak position and the phase at this peak position coincide with each other.

  However, even if an RF pulse having a phase difference of 90 ° is supplied to the whole body RF coil 6, the flip pulse and the flop pulse are not aligned due to hardware imperfections and / or zero-order components of eddy currents. The phase difference may not be 90 °. Moreover, even if a read-out pulse (RO pulse) having an area (moment) ratio of 1: 2 is supplied to the gradient coil 2, the area (moment) ratio of the gradient magnetic field for read-out does not become 1: 2. There is.

  Therefore, prior to performing the main scan, the control unit 107 performs a pre-scan. The prescan determines the phase of the RF pulse for setting the phase difference between the flip pulse and the flop pulse to 90 ° and the correction amount of the RO pulse for setting the area (moment) ratio of the gradient magnetic field to 1: 2. This is a scan for collecting data used for the test. This pre-scan may be performed in order to collect only the data for the above-mentioned use, and is common with a known scan for collecting data used to determine the correction amount of the spoiler pulse and the flow compensation pulse. It is also good.

  In the prescan, a method of extracting only the spin echo component is adopted. As a method for extracting only the spin echo component, a known method can be used.

  For example, US Pat. No. 5,818,229 discloses a first shot in which the phase of a flop pulse is “π, π, π, π, π, π,...” And “π, −π, π, −π”. , Π, −π,... ””, It is shown that only the spin echo component can be extracted by adding the signals acquired in the second shot. This method requires two-shot acquisition, and it is necessary that the behavior of the gradient magnetic field after the flop pulse is constant, but this can be easily realized.

  In addition, “Errors in T2 Estimation Using Multislice Multiple Echo Imaging, Magnetic Resonance in Medicine 4, pp34-47 (1987) APCrawley and RM Henkelman” includes a small pulse in the phase encoding (PE) direction, “△ PE, − A method of spoiling a stimulated echo component by applying ΔPE, 2ΔPE, −2ΔPE,... Is shown.

  In the pre-scan, when the phase of the RF pulse for transmitting the flip pulse is 0 °, the phase of the RF pulse for transmitting the flop pulse is 90 °. As shown in FIG. 2, the RO pulse after the first and second flop pulses after the flip pulse is only a basic pulse determined to have an area (moment) twice that of the RO pulse after the flip pulse. Is done. As shown in FIG. 2, a unit sensitivity pulse is added to the RO pulse after the third flop pulse before the basic pulse. The unit sensitivity pulse has a constant area (moment) U. The area (moment) of the RO pulse may be adjusted by either the intensity or the duration.

  The control unit 107 executes the process shown in FIG. 3 when pre-scanning is being performed or after pre-scanning is finished.

  In step Sa1, the control unit 107 determines the first, second and third spin echoes (hereinafter referred to as the first echo, the second echo and the third echo) from the data collected by the pre-scan. S1 (k), s2 (k), and s3 (k). In step Sa2, the control unit 107 performs Fourier transform on the first echo s1 (k), the second echo s2 (k), and the third echo s3 (k), respectively, and results of conversion S1 (r), S2 ( r) and S3 (r) are obtained.

  In step Sa3, the control unit 107 obtains the evaluation function S2 ′ (r) by subtracting the phase component of S1 (r) from S2 (r). In step Sa4, the control unit 107 obtains the zero-order component φ and the first-order component X1 in the read-out direction in the phase distribution curve of the phase component included in S2 ′ (r). In order to obtain the zero-order component φ and the first-order component X1, Ahn method (CB Ahn and ZH Cho, “A new phase correction method in NMR imaging based on autocorrelation and histogram analysis,” IEEE Trans. Med. Imag., vol. MI-6, pp.32-36, Mar. 1987) can be used.

  The primary component X1 obtained in step Sa4 is proportional to the amount of deviation Δ1 between the peak position P1 of the first echo and the peak position P2 of the second echo as shown in FIG. That is, obtaining the primary component X1 is equivalent to measuring the shift amount Δ1. The zero-order component φ is proportional to the difference between the phase of the first echo at the peak position P1 and the phase of the second echo at the peak position P2. That is, obtaining the zero-order component φ is equivalent to measuring the phase difference between the peak of the first echo and the peak of the second echo.

  In step Sa5, the control unit 107 obtains the evaluation function S3 ′ (r) by subtracting the phase component of S1 (r) from S3 (r). In step Sa6, the control unit 107 obtains a primary component X2 in the read-out direction in the phase distribution curve of the phase component included in S3 ′ (r). In order to obtain the primary component X2, a known method such as the Ahn method can be used.

  If the RO pulse is only the basic pulse, the peak position of the third echo is the peak position P1 of the first echo. However, here, the peak position P3 of the third echo shifts from the peak position P1 as shown in FIG. 2 due to the influence of the change in the gradient magnetic field due to the unit sensitivity pulse. This shift amount Δ2 is proportional to the primary component X2 obtained in step Sa6. That is, obtaining the primary component X2 is equivalent to measuring the shift amount Δ2.

  The phase difference between the peak of the first echo and the peak of the second echo, the shift amount Δ1 or the shift amount Δ2 can also be directly measured from an echo that is not subjected to Fourier transform. However, since the accuracy of such measurement is generally not sufficient, measurement based on the zeroth-order component or the first-order component is preferable.

In step Sa7, the control unit 107 obtains the area (moment) Y of the correction pulse of the RO pulse by the following equation.
Y = X1 / X2 × U
In step Sa8, the control unit 107 obtains the flop pulse phase correction amount δ by the following equation.
δ = φ / 2
In the main scan following the pre-scan, the control unit 107 controls the transmission unit 7 so that the phase of the flop pulse is changed by an angle corresponding to the correction amount δ. Thereby, the phase at the peak of the odd-numbered echo and the phase at the peak of the even-numbered echo substantially coincide. Note that the phase at the peak of the echo can be corrected by changing the gradient magnetic field in the slice direction.

  Further, in the main scan, the control unit 107 tilts so that a correction pulse having the area (moment) Y determined as described above is added to each RO pulse for reading each spin echo as shown in FIG. The magnetic field power supply 3 is controlled. The area (moment) of the correction pulse may be adjusted by either the intensity or the duration. However, since the adjustment of the duration is poor due to the influence of eddy current, it is desirable to adjust the area (moment) of the correction pulse according to the intensity. The position where the correction pulse is added in each RO pulse is the same as the position where the unit sensitivity pulse is added. That is, in this embodiment, as shown in FIG. 2, the unit sensitivity pulse is added to the front side of the basic pulse, so that the correction pulse is also added to the front side of each basic pulse as shown in FIG. The correction pulse may be separated from the basic pulse.

  Further, when a spoiler pulse or a flow compensation pulse is added to the basic pulse in the RO pulse of the main scan, the area (moment) of these pulses may be increased by Y.

  As described above, according to the present embodiment, by measuring the difference Δ2 in the peak position between the third pulse and the first pulse read using the gradient magnetic field generated by the RO pulse to which the unit sensitivity pulse is added. The shift amount of the peak position of the spin pulse by the unit sensitivity pulse is actually measured. Based on the actual measurement result, the intensity of the correction pulse necessary for correcting the shift amount Δ1 of the peak position between the first pulse and the second pulse is calculated. As a result, even if the gradient magnetic field coil 2 changes its gradient magnetic field due to the influence of various conditions such as eddy current and vibration, it is possible to calculate an appropriate correction pulse intensity considering such a change in gradient magnetic field. By adding a correction pulse having such an appropriate intensity to the RO pulse, the gradient magnetic field area (moment) between the flip pulse and the first flop pulse and the gradient magnetic field area between the flop pulse and the flop pulse ( The moment can be adjusted to be exactly 1: 2. As a result, sensitivity unevenness and ringing can be prevented and high-accuracy imaging can be performed.

  Unshielded gradient coils and / or open magnets are greatly affected by eddy currents and vibrations, and variations in gradient magnetic field variations are significant. According to this embodiment, such variations are appropriate. Can be corrected. Therefore, this embodiment is particularly effective when a non-shield type is adopted as the gradient coil 2.

  This embodiment can be variously modified as follows.

  The correction pulse can be added to the rear side of the basic pulse as shown in FIG. In this case, the unit sensitivity pulse is added behind the basic pulse for reading the second echo as shown in FIG.

  The shift amount Δ1 only needs to be a shift amount between the peak positions of the spin echo α and the spin echo β. Therefore, for example, the phase difference between the second echo and the third echo is measured. What is necessary is just to measure the deviation | shift amount of the peak position between arbitrary spin echoes and even-numbered arbitrary spin echoes. However, the unit sensitivity pulse is not added to the front side of the basic pulse for reading the echo used for measuring the deviation amount Δ1.

  The unit sensitivity pulse may be included in a basic pulse for reading another odd-numbered spin echo. The unit sensitivity pulse may be added to the basic pulse for reading an even-numbered arbitrary spin echo. However, the unit sensitivity pulse is added after the basic pulse for reading the spin echo used for measuring the shift amount Δ1. When a unit sensitivity pulse is added to the basic pulse for reading the even-numbered spin echo, the peak position between the spin-echo and the even-numbered spin echo used for measuring the shift amount Δ1 is calculated. The shift amount Δ2 is measured as the shift amount.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment.

The figure which shows the structure of the magnetic resonance imaging apparatus which concerns on one Embodiment of this invention. The figure which shows a mode of adding a unit sensitivity pulse to a readout pulse, and the phase relationship of the 1st thru | or 3rd echo. 2 is a flowchart of processing for the control unit in FIG. 1 to determine an energy amount of a correction pulse in a main scan. The figure which shows a mode that a correction pulse is added to a readout pulse. The figure which shows the modification of the addition form of a correction pulse. The figure which shows the modification of the addition form of a unit sensitivity pulse.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Static magnetic field magnet, 2 ... Gradient magnetic field coil, 3 ... Gradient magnetic field power supply, 4 ... Sleeper, 5 ... Sleeper control part, 6 ... Whole body RF coil, 7 ... Transmitter, 8 ... Receiving part, 9 ... Hybrid circuit, 10 DESCRIPTION OF SYMBOLS Computer system 101 ... Interface part 102 ... Data collection part 103 ... Reconstruction part 104 ... Storage part 105 ... Display part 106 ... Input part 107 ... Control part

Claims (5)

Magnetic resonance comprising a gradient coil for generating a gradient magnetic field for reading when a reading pulse is supplied, and a supply means for supplying the reading pulse to the gradient magnetic field coil, and performing imaging by a high-speed spin echo method In the imaging device,
Prior to the main scan for collecting imaging data, odd-numbered first spin echoes, odd-numbered second spin echoes, and odd-numbered ones generated after the first and second spin echoes Collecting means for collecting the third spin echo or the even-numbered fourth spin echo;
During the collection period of the spin echo by the collection means, a basic pulse is supplied to the gradient magnetic field coil as the reading pulse, and there is a period for collecting the spin echo immediately before the third or fourth spin echo. A first control unit that controls the supply unit to supply a unit sensitivity pulse as the reading pulse to the gradient magnetic field coil during a period from the end to the start of the period for collecting the third or fourth spin echo. Control means,
First measuring means for measuring a shift amount between a peak position of the first spin echo and a peak position of the second spin echo;
Measuring a shift amount of a peak position of the third spin echo with respect to a peak position of the first spin echo or a shift amount of a peak position of the fourth spin echo with respect to a peak position of the second spin echo; Measuring means,
Based on the shift amount, the energy amount of the unit sensitivity pulse, and the shift amount, a correction energy amount for correcting a peak position shift between the first spin echo and the second spin echo is determined. Means,
In the main scan, the basic pulse is supplied to the gradient magnetic field coil as the reading pulse, and separately, the correction pulse of the correction energy amount is supplied to the gradient magnetic field coil as the reading pulse. A magnetic resonance imaging apparatus comprising: a second control unit that controls the supply unit. The first control means controls the supply means to add the unit sensitivity pulse to the front side of the basic pulse in the collection period of the third or fourth spin echo,
2. The magnetic resonance imaging apparatus according to claim 1, wherein the second control unit controls the supply unit to add the correction pulse to each front side of the basic pulse in the main scan. The first control unit controls the supply unit to add the unit sensitivity pulse to the rear side of the basic pulse in the collection period of the spin echo immediately before the third or fourth spin echo. ,
2. The magnetism according to claim 1, wherein the second control unit controls the supply unit to add the correction pulse to the rear side of each of the basic pulses in the spin echo acquisition period. Resonance imaging device.   The collecting means collects the first spin echo as the first spin echo, the second spin echo as the second spin echo, and the third spin echo as the third spin echo. The magnetic resonance imaging apparatus according to claim 1. Magnetic resonance comprising a gradient coil for generating a gradient magnetic field for reading when a reading pulse is supplied, and a supply means for supplying the reading pulse to the gradient magnetic field coil, and performing imaging by a high-speed spin echo method In the imaging device,
In the pre-scan prior to the main scan for collecting imaging data, the spin echo obtained by using the gradient magnetic field generated by the basic pulse of the reading pulse and the unit sensitivity pulse are added to the basic pulse. Means for determining the magnitude of the correction pulse at the time of the main scan based on the spin echo obtained by using the gradient magnetic field generated by the reading pulse configured as described above,
In the main scan, the time position relative to the RF pulse is the same position as the unit sensitivity pulse, and the reading pulse generated by adding the correction pulse of the calculated magnitude to the basic pulse is used. And a means for obtaining a spin echo using a gradient magnetic field.

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