JP5523696B2 - Magnetic resonance imaging system - Google Patents

Description

  The present invention magnetically excites a subject's nuclear spin with a radio frequency (RF) signal of a Larmor frequency, and re-images the nuclear magnetic resonance (NMR) signal generated by this excitation. This is related to the magnetic resonance imaging (MRI) devices that are configured, and in particular, the phase correction echo signal overflows due to the acquisition of the phase correction data separately from the imaging data and the imaging method with phase correction. In addition, the present invention relates to a magnetic resonance imaging apparatus that performs imaging by setting a reception gain appropriate for an echo signal for imaging in a shorter time.

  Magnetic resonance imaging is an imaging method in which a nuclear spin of a subject placed in a static magnetic field is magnetically excited with an RF signal having a Larmor frequency, and an image is reconstructed from an MR signal generated by the excitation.

  One of the pulse sequences used for this magnetic resonance imaging is FSE (Fast Spin Echo) method. When performing imaging by the FSE method, a phase correction pulse sequence for collecting phase correction data and an imaging pulse sequence for collecting imaging data are generally executed. The MR signal for phase correction collected by executing the pulse sequence for phase correction is used for phase correction of the MR signal for imaging acquired by executing the pulse sequence for imaging. That is, for example, based on the MR signal for phase correction, the MR signal for imaging is phase-corrected. In addition, the imaging pulse sequence is finely adjusted based on the phase correction MR signal so that the imaging MR signal to be acquired is acquired after phase correction, and the phase is determined by executing the finely adjusted imaging pulse sequence. In some cases, corrected MR signals for imaging are collected.

  In this case, since the phase correction pulse sequence is executed without adding phase encoding, an MR signal whose intensity is higher than the MR signal collected by executing the imaging pulse sequence with the phase encoding pulse added is a phase correction pulse. It will be collected by the execution of the sequence. Therefore, conventionally, the receiving gain of the receiving system is set so that no overflow occurs in the receiving system with reference to the maximum signal strength of the MR signal for phase correction.

  FIG. 1 is a diagram for explaining a conventional reception gain setting method in the case of imaging by the FSE method.

  In FIG. 1, the vertical axis represents MR signal strength S, and the horizontal axis represents time. Further, the curve in FIG. 1 shows the temporal signal intensity change of the MR echo signal sequence for phase correction collected sequentially by the execution of the pulse sequence for phase correction. As shown in FIG. 1, the signal intensity of the MR echo signals Ne1, Ne2, Ne3,... For phase correction is attenuated according to the attenuation curve of T2 relaxation (lateral relaxation), so the first MR echo signal Ne1 for phase correction The signal intensity S1 is the maximum.

  On the other hand, the signal intensity S of the MR echo signal for imaging decreases as the phase encoding amount increases. Therefore, the signal intensity Sc of the MR echo signal is maximized in an effective echo time (effective TE: effective echo time) corresponding to a phase encoding amount of zero.

  Here, a comparison between the maximum signal intensity S1 of the MR echo signal Ne1 for phase correction and the maximum signal intensity Sc of the MR echo signal for imaging is as shown in FIG. That is, the maximum signal strength S1 of the MR echo signal Ne1 for phase correction is the maximum signal strength of the MR echo signal for imaging, except when the initial MR echo signal for imaging is collected with the phase encoding amount set to zero. Bigger than Sc. Therefore, the reception gain in the reception system that amplifies the MR signal is set with reference to the maximum signal intensity S1 of the MR echo signal Ne1 for phase correction.

  However, if the reception gain is set with reference to the maximum signal intensity S1 of the MR echo signal Ne1 for phase correction so that the high-intensity MR signal collected by the phase correction pulse sequence does not overflow in the reception system, the imaging pulse sequence The reception gain is too low for the low-intensity imaging MR signal collected by the above. For this reason, there is a problem that MR signals for imaging cannot be collected with high accuracy by effectively using the dynamic range of an A / D (analog to digital) converter in the receiving system. That is, the intensity resolution of the sampled MR signal is reduced.

  Conversely, when the reception gain in the receiving system is set based on the maximum signal intensity Sc of the MR echo signal for imaging, as described above, the range of the MR echo signal intensity for phase correction can be handled by the A / D converter. This causes the problem of overflowing and overflowing.

Therefore, prior to the execution of the phase correction pulse sequence, a technique for executing the phase correction pulse sequence and the imaging pulse sequence as a preparatory scan has been proposed (see, for example, Patent Document 1). In this technology, the flip angle that can reduce the intensity of the MR signal collected by the phase correction pulse sequence to the same level as the intensity of the MR signal for imaging is achieved by executing the phase correction pulse sequence and the imaging pulse sequence. It is obtained based on the intensity of each collected MR signal. In other words, the signal intensity of the MR signal for phase correction collected by adding the phase encoding and the MR signal for phase correction collected without adding phase encoding is measured, and the signal of the MR signal for phase correction is measured. The flip angle of the phase correction sequence is obtained based on the ratio between the intensity and the signal intensity of the MR signal for imaging. Then, a phase correction pulse sequence is executed at the obtained flip angle.
Japanese Patent No. 3806645

  However, with the technology that executes the phase correction pulse sequence and imaging pulse sequence as a preparatory scan prior to the execution of the conventional phase correction pulse sequence, the MR signal for phase correction is not exceeded the maximum input intensity of the receiving system. While achieving the purpose of collecting MR signals for imaging at an appropriate reception gain while collecting, it is necessary to perform at least three preparatory scans (pre-scans) before the imaging scan as the so-called main scan. Become. For this reason, there is a problem that the total imaging time, that is, the inspection time is extended.

  In particular, when imaging by the FSE method is performed in one shot, the ratio of the preparation scan time to the total imaging time is 3/4. For this reason, shortening of the preparation scan time is required to improve the inspection efficiency.

  The present invention has been made in order to cope with such a conventional situation. The phase correction echo signal overflows due to the imaging method including the phase correction by collecting the phase correction data separately from the imaging data. It is another object of the present invention to provide a magnetic resonance imaging apparatus capable of performing imaging by setting a reception gain appropriate for an echo signal for imaging in a shorter time.

In the magnetic resonance imaging apparatus according to the present invention, in the phase correction pulse sequence for collecting the magnetic resonance data for phase correction, the phase correction data for collecting the magnetic resonance data for phase correction from the subject with the first reception gain. In the imaging means and the imaging pulse sequence for collecting magnetic resonance data for imaging, the magnetic resonance data for imaging is collected from the subject with a second reception gain, and the magnetic resonance data for imaging is collected. Imaging means for performing imaging of the subject by performing phase correction processing based on the magnetic resonance data for phase correction , the imaging means collecting the phase correction collected by the pulse sequence for phase correction Among the plurality of magnetic resonance signals for imaging, the imaging pulse sequence Phase encoding amount to determine the second reception gain based on the intensity of the collected magnetic resonance signals in the zero timing in cans,
It is characterized by this.

  In the magnetic resonance imaging apparatus according to the present invention, the phase correction echo signal is not overflowed by the imaging method including the phase correction by collecting the phase correction data separately from the imaging data, and the imaging echo Imaging can be performed by setting an appropriate reception gain for a signal in a shorter time.

  Embodiments of a magnetic resonance imaging apparatus according to the present invention will be described with reference to the accompanying drawings.

(Configuration and function)
FIG. 2 is a block diagram showing an embodiment of the magnetic resonance imaging apparatus according to the present invention.

  The magnetic resonance imaging apparatus 20 includes a cylindrical static magnetic field magnet 21 that forms a static magnetic field and a shim coil 22, a gradient magnetic field coil 23, and an RF coil 24 that are provided inside the static magnetic field magnet 21. This is a built-in configuration.

  In addition, the magnetic resonance imaging apparatus 20 includes a control system 25. The control system 25 includes a static magnetic field power supply 26, a gradient magnetic field power supply 27, a shim coil power supply 28, a transmitter 29, a receiver 30, a sequence controller 31, and a computer 32. The gradient magnetic field power source 27 of the control system 25 includes an X-axis gradient magnetic field power source 27x, a Y-axis gradient magnetic field power source 27y, and a Z-axis gradient magnetic field power source 27z. In addition, the computer 32 includes an input device 33, a display device 34, an arithmetic device 35, and a storage device 36.

  The static magnetic field magnet 21 is connected to a static magnetic field power supply 26 and has a function of forming a static magnetic field in the imaging region by a current supplied from the static magnetic field power supply 26. In many cases, the static magnetic field magnet 21 is composed of a superconducting coil, and is connected to the static magnetic field power supply 26 at the time of excitation and supplied with current. It is common. In some cases, the static magnetic field magnet 21 is composed of a permanent magnet and the static magnetic field power supply 26 is not provided.

  A cylindrical shim coil 22 is coaxially provided inside the static magnetic field magnet 21. The shim coil 22 is connected to the shim coil power supply 28, and is configured such that a current is supplied from the shim coil power supply 28 to the shim coil 22 to make the static magnetic field uniform.

  The gradient magnetic field coil 23 includes an X-axis gradient magnetic field coil 23 x, a Y-axis gradient magnetic field coil 23 y, and a Z-axis gradient magnetic field coil 23 z, and is formed in a cylindrical shape inside the static magnetic field magnet 21. A bed 37 is provided inside the gradient magnetic field coil 23 as an imaging region, and the subject P is set on the bed 37. The RF coil 24 may not be built in the gantry but may be provided near the bed 37 or the subject P.

  The gradient magnetic field coil 23 is connected to a gradient magnetic field power supply 27. The X-axis gradient magnetic field coil 23x, the Y-axis gradient magnetic field coil 23y, and the Z-axis gradient magnetic field coil 23z of the gradient magnetic field coil 23 are respectively an X-axis gradient magnetic field power source 27x, a Y-axis gradient magnetic field power source 27y, and a Z-axis gradient magnetic field coil 27z. It is connected to the magnetic field power supply 27z.

  The X-axis gradient magnetic field power source 27x, the Y-axis gradient magnetic field power source 27y, and the Z-axis gradient magnetic field power source 27z are supplied with currents supplied to the X-axis gradient magnetic field coil 23x, the Y-axis gradient magnetic field coil 23y, and the Z-axis gradient magnetic field coil 23z, respectively. In the imaging region, a gradient magnetic field Gx in the X-axis direction, a gradient magnetic field Gy in the Y-axis direction, and a gradient magnetic field Gz in the Z-axis direction can be formed, respectively.

  The RF coil 24 is connected to the transmitter 29 and the receiver 30. The RF coil 24 receives the RF signal from the transmitter 29 and transmits it to the subject P, and receives the NMR signal generated along with the excitation of the nuclear spin inside the subject P by the RF signal to the receiver 30. Has the function to give.

  On the other hand, the sequence controller 31 of the control system 25 is connected to the gradient magnetic field power source 27, the transmitter 29, and the receiver 30. The sequence controller 31 has control information necessary for driving the gradient magnetic field power supply 27, the transmitter 29, and the receiver 30, for example, operation control information such as the intensity, application time, and application timing of the pulse current to be applied to the gradient magnetic field power supply 27. And the gradient magnetic field power source 27, the transmitter 29, and the receiver 30 are driven according to the stored predetermined sequence to drive the X-axis gradient magnetic field Gx, the Y-axis gradient magnetic field Gy, and the Z-axis gradient magnetic field. It has the function of generating Gz and RF signals.

  In addition, the sequence controller 31 is configured to receive raw data, which is complex data obtained by detection of an NMR signal and A / D (analog to digital) conversion in the receiver 30, and supply the raw data to the computer 32. The

  For this reason, the transmitter 29 is provided with a function of applying an RF signal to the RF coil 24 based on the control information received from the sequence controller 31, while the receiver 30 detects the NMR signal received from the RF coil 24. Then, by executing required signal processing and A / D conversion, a function of generating raw data that is digitized complex data and a function of supplying the generated raw data to the sequence controller 31 are provided.

  Further, the computer 32 is provided with various functions by executing the program stored in the storage device 36 of the computer 32 by the arithmetic unit 35. However, a specific circuit having various functions may be provided in the magnetic resonance imaging apparatus 20 regardless of the program.

  FIG. 3 is a functional block diagram of the computer 32 shown in FIG.

  The computer 32 functions as an imaging condition setting unit 40, a sequence controller control unit 41, a k-space database 42, an image reconstruction unit 43, an image database 44, an image processing unit 45, and a phase correction unit 46 by a program. The imaging condition setting unit 40 includes a phase correction data reception gain setting unit 40A, a reception gain storage unit 40B, an imaging data reception gain setting unit 40C, and a sequence correction unit 40D.

  The imaging condition setting unit 40 has a function of setting imaging conditions including a pulse sequence and an MR signal reception gain based on instruction information from the input device 33, and giving the set imaging conditions to the sequence controller control unit 41. In particular, in the imaging condition setting unit 40, phase correction necessary for setting imaging conditions for imaging scans for collecting imaging data, phase correction processing for imaging data, or imaging conditions for imaging scans is required. A function for setting imaging conditions for a preparatory scan for collecting data for use.

  Imaging pulse sequences for imaging scans and phase correction pulse sequences for preparatory scans, such as FSE sequences, EPI (echo planar imaging) sequences, PROPELLER (Periodically Rotated Overlapping ParallEL Lines with Enhanced Reconstruction) sequences, etc. In addition, multi-echo data collection is performed, and pulse sequences in which the intensity of the MR signal for phase correction collected by the preparation scan and the intensity of the MR signal for imaging are different from each other are used. Hereinafter, the FSE sequence will be described as an example, but the same applies to other sequences.

  FIG. 4 is a diagram showing an example of a phase correction pulse sequence of the FSE method set in the imaging condition setting unit 40 shown in FIG.

  In FIG. 4, the horizontal axis indicates time, RF is the transmitted RF pulse, Gss, Gpe, and Gro are gradient magnetic field pulses for slice selection (SS) and phase encode (PE), respectively. ECHO represents a gradient magnetic field pulse, a gradient magnetic field pulse for readout (RO), and ECHO represents a received MR echo signal for phase correction.

  As shown in FIG. 4, in the FSE sequence for collecting data for phase correction, the excitation RF pulse R with a flip angle of 90 ° and the gradient magnetic field pulse Gss for slice selection are followed by 1 with a flip angle of 180 °. The first RF inversion pulse P1 and the gradient magnetic field pulse Gss for slice selection are applied. Then, the first echo signal Ne1 for phase correction is acquired by applying the gradient magnetic field pulse Gro for reading.

  Next, the second RF inversion pulse P2 and the slice selection gradient magnetic field pulse Gss are applied, and the readout gradient magnetic field pulse Gro is applied to obtain the second echo signal Ne2 for phase correction. . Similarly, the gradient magnetic field pulses Gss for slice selection are sequentially applied together with the RF inversion pulses P3, P4, P5,..., And the echo signals Ne3, Ne4 for phase correction are applied by applying the gradient magnetic field pulse Gro for reading. , Ne5,… are acquired.

  In the phase correction pulse sequence, the phase encoding gradient magnetic field pulse is not applied. This is because phase correction measures a phase shift that does not depend on phase encoding for each echo signal, and finely adjusts the gradient magnetic field waveform of the imaging pulse sequence or the phase of the RF transmission pulse based on the measured phase shift of the echo signal. This is because it consists of a process of correcting the phase of imaging data.

  FIG. 5 is a graph showing temporal changes in the intensity of the phase correction echo signal shown in FIG.

  In FIG. 5, the vertical axis indicates the intensity S of the echo signal for phase correction, and the horizontal axis indicates time. Further, the curve in FIG. 5 shows the temporal signal intensity change of the echo signal for phase correction.

  As shown in FIG. 5, since the signal intensity of the echo signals Ne1, Ne2, Ne3,... For phase correction attenuates according to the attenuation curve of T2 relaxation (lateral relaxation), the signal of the first echo signal Ne1 for phase correction The intensity S1 is the maximum.

  Here, for the sake of simplicity, the signal value of each echo signal for phase correction is represented as a single value. However, since the echo signal is actually composed of signals at a plurality of points sampled in the readout direction, a plurality of values are used. Has the value of The signal value of the echo signal shown in FIG. 5 indicates the maximum value among a plurality of signal values at all sampling points of the echo signal, and the signal value of the echo signal is similarly shown as a single value in the following description. .

  Furthermore, for the sake of simplicity, the echo signal is expressed as an absolute value, but in reality, two signals of the real part and the imaginary part, which have positive and negative values, are echoed by quadrature detection using two phase-sensitive detectors. Collected as a signal.

  FIG. 6 is a diagram illustrating an example of an imaging pulse sequence of the FSE method set in the imaging condition setting unit 40 illustrated in FIG.

  In FIG. 6, the horizontal axis represents time, RF represents an RF pulse to be transmitted, Gss, Gpe, and Gro each represent a gradient magnetic field pulse for slice selection, a gradient magnetic field pulse for phase encoding, and a gradient magnetic field pulse for reading. ECHO indicates a received MR echo signal for imaging.

  The FSE sequence shown in FIG. 6 sequentially collects echo signals from one high frequency side of the k space toward the low frequency side, then collects echo signals at the center of the k space, and then from the other low frequency side of the k space. The example in the case of collecting echo signals sequentially toward the high frequency side is shown.

  In the imaging pulse sequence using the FSE sequence shown in FIG. 6, the excitation RF pulse R with a flip angle of 90 ° and the gradient magnetic field pulse Gss for slice selection are followed by the first RF inversion pulse P1 with a flip angle of 180 °. And the gradient magnetic field pulse Gss for slice selection is applied. Next, the first gradient magnetic field pulse Gp1e for phase encoding is applied. Then, by applying a readout gradient magnetic field pulse Gro, the first echo signal e1 for imaging is acquired. Thereafter, a rewind pulse Gp1r having the same area and reverse polarity as the first gradient magnetic field pulse Gp1e for phase encoding is applied.

  Next, the second RF inversion pulse P2 and the gradient magnetic field pulse Gss for slice selection are applied, followed by the second gradient magnetic field pulse Gp2e for phase encoding, and the readout gradient magnetic field pulse Gro is applied. The echo signal e2 for the second imaging is acquired. Thereafter, a rewind pulse Gp2r having the same area and opposite polarity as the second gradient magnetic field pulse Gp2e for phase encoding is applied.

  Similarly, the gradient magnetic field pulse Gss for slice selection is sequentially applied together with the n (n = 3, 4, 5,...) Th RF inversion pulse Pn. Next, the nth phase encoding gradient magnetic field pulse Gpne is applied, and then the readout gradient magnetic field pulse Gro is applied, whereby the nth imaging echo signal en is acquired. Thereafter, a rewind pulse Gpnr having the same area and opposite polarity as the n-th phase encoding gradient magnetic field pulse Gpne is applied.

  In the example of the imaging pulse sequence shown in FIG. 6, the areas of the third phase encoding gradient magnetic field pulse Gp3e and the third rewind pulse Gp3r are both zero. Therefore, the third echo signal e3 becomes imaging data at the center of the k space. The echo time (TE: echo time) at which the echo signal e3 at the center of the k space is collected is called effective TE (TEeff). The effective TE reflects the T2 relaxation contrast of the image.

  FIG. 7 is a graph showing temporal changes in the intensity of the echo signal for imaging shown in FIG.

  In FIG. 7, the vertical axis indicates the intensity S of the echo signal for imaging, and the horizontal axis indicates time. Further, the curve in FIG. 7 shows the temporal signal intensity change of the echo signal for imaging.

  As shown in FIG. 7, the signal intensity S of the echo signals e1, e2, e3,... For imaging decreases as the amount of phase encoding corresponding to the area of the gradient magnetic field pulse for phase encoding increases. Therefore, the signal intensity Sc of the echo signal e3 at the center of the k-space acquired with the phase encoding amount being zero in the effective TE (TEeff) is maximized.

  The phase correction data reception gain setting unit 40A of the imaging condition setting unit 40 has a function of setting an appropriate reception gain when collecting phase correction echo signals by executing the phase correction pulse sequence as described above. . The imaging data reception gain setting unit 40C has a function of setting an appropriate reception gain when collecting echo signals for imaging by executing the imaging pulse sequence as described above.

  That is, the imaging condition setting unit 40 has a function of independently setting the reception gain when collecting the echo signal for phase correction and the reception gain when collecting the echo signal for imaging. The imaging condition setting unit 40 is configured to control the reception gain in the receiver 30 by giving the set reception gain to the receiver 30 through the sequence controller control unit 41 and the sequence controller 31. However, the imaging condition setting unit 40 may control the reception gain in components other than the receiver 30.

  FIG. 8 is a block diagram showing an example of a detailed configuration of the receiver 30 shown in FIG.

  As shown in FIG. 8, the receiver 30 is configured by connecting an amplifier 30A, a frequency converter 30B, and an A / D converter 30C in series. An RF coil 24 is connected to the amplifier 30A on the input side of the receiver 30, and a computer 32 is connected to the A / D converter 30C on the output side through the sequence controller 31. The amplifier 30 </ b> A is connected to the computer 32 through the sequence controller 31 and is configured to be able to adjust the reception gain (amplification factor) according to a control signal from the computer 32.

  The amplifier 30A has a function of amplifying the MR echo signal input to the receiver 30 with the reception gain set according to the control signal from the computer 32 and outputting the amplified signal to the frequency converter 30B. The frequency converter 30B has a function of converting the frequency of the MR echo signal input from the amplifier 30A into a frequency that can be converted from a Larmor frequency to a digital signal and outputting the frequency to the A / D converter 30C. The A / D converter 30C has a function of converting the MR echo signal input from the frequency converter 30B into a digital signal that can be processed by the computer 32 and outputting the digital signal to the computer 32 through the sequence controller 31.

  However, there is a maximum processable value in the input signal of the A / D converter 30C, and an input signal exceeding the maximum value is not converted correctly. In other words, overflow occurs. For this reason, the reception gain of the amplifier 30A is adjusted according to the intensity of a signal input to an arbitrary amplifier connected to the preceding stage of the A / D converter 30C, for example, the amplifier 30A of the receiver 30.

  That is, the imaging condition setting unit 40 is configured so that the echo signal does not overflow in the A / D converter 30C of the receiver 30 and the echo signal is input to the A / D converter 30C with a larger signal strength. A control signal is supplied to the amplifier 30A through the sequence controller control unit 41 and the sequence controller 31 so that the reception gain of the amplifier 30A becomes the set reception gain and the function of setting the reception gain as the imaging condition. And a function to control.

  Here, a method for determining an appropriate reception gain when collecting echo signals for phase correction will be described.

  The appropriate reception gain for collecting the echo signal for phase correction is the intensity of the echo signal collected with a sufficiently small reception gain that does not cause an overflow by executing a sequence that can be regarded as the same or the same as the pulse sequence for phase correction. Can be determined based on Therefore, the imaging condition setting unit 40 is also provided with a function for setting imaging conditions for a preparation scan for obtaining a reception gain for collecting echo signals for phase correction.

  For example, the reception gain for collecting the echo signal for obtaining the reception gain for collecting the echo signal for phase correction can be set to the minimum value. Thereby, it is possible to prevent the A / D converter 30C from overflowing even if a signal having any expected strength is received.

  Next, the maximum signal strength is measured among the signal strengths of the echo signal sequence collected without adding phase encoding by executing the phase correction pulse sequence with the reception gain as the minimum value, and based on the measured maximum signal strength. Thus, the reception gain for collecting the echo signal for phase correction can be determined. Note that the echo signal collected without adding the phase encoding is attenuated according to the attenuation curve of T2 relaxation, so that the maximum signal intensity is the signal intensity S0 of the first echo signal.

  More specifically, the reception gain for collecting the echo signal for phase correction is G1, the maximum signal strength of the echo signal collected without adding phase encoding is S0, and the A / D conversion of the echo signal with the maximum signal strength S0 When the input voltage to the converter 30C is V1 [V] and the maximum voltage that can be handled by the A / D converter 30C is Vmax [V], in order to use the dynamic range of the A / D converter 30C most effectively, The reception gain of the amplifier 30A is multiplied by Vmax / V1 so that the voltage of the echo signal having the maximum signal intensity S0 input to the A / D converter 30C is the same as the maximum voltage Vmax that can be handled by the A / D converter 30C. That's fine.

That is, when the reception gain is expressed in dB and the initial reception gain G0 is 0 [dB], the appropriate reception gain G1 for collecting the echo signal for phase correction is a known general formula relating to voltage or current. It can be determined by the equation (1).
[Equation 1]
G1 = 0 + 20 · log ₁₀ (Vmax / V1) [dB] (1)
However, in practice, the MR signal intensity varies at each measurement timing due to various factors such as movement of the subject P and hardware stability. For this reason, a few dB margin k is provided to collect the echo signal for phase correction so that the A / D converter 30C does not overflow even if the MR signal intensity fluctuates, as shown in equation (2). It is desirable to determine an appropriate reception gain G1 for use. This margin k can be determined empirically by a test scan or the like for each apparatus.
[Equation 2]
G1 = 0 + 20 · log ₁₀ (Vmax / V1)-k [dB] (2)
Since the input voltage V1 to the A / D converter 30C is determined by the maximum signal strength S0 of the echo signal when the reception gain is the initial value G0, an appropriate reception gain for collecting the echo signal for phase correction is used. G1 can be expressed as G1 = f1 (S0) as a function f1 of the maximum signal strength S0 of the echo signal when the reception gain is the initial value G0.

  On the other hand, the appropriate reception gain G1 for collecting the echo signal for phase correction may be a preset value Gpr determined in advance. If an appropriate reception gain G1 for collecting an echo signal for phase correction is set to the preset value Gpr, a preparation scan for determining the reception gain G1 is not necessary. That is, the number of preparation scans required before the imaging scan can be reduced from two to one. For this reason, the total inspection time can be shortened.

  The preset value Gpr can be, for example, the minimum value (0 [dB]) of the reception gain. That is, when the echo signal collected without setting the reception gain to the minimum value and adding the phase encoding has sufficient intensity resolution to execute the phase correction processing, as described above, There is no need to reset the reception gain G1 for collecting echo signals to an appropriate value and execute the phase correction pulse sequence. Therefore, the minimum value of the reception gain can be directly used as the reception gain G1 for collecting the echo signal for phase correction.

  If the intensity of the received echo signal can be estimated to some extent, a reception gain larger than the minimum value that can be set by the system can be prepared as the preset value Gpr. The magnitude of the intensity of the received echo signal varies depending on imaging conditions such as a receiving coil used for imaging, an imaging area, a slice thickness, an imaging cross-sectional direction, and a pulse sequence type. Therefore, the maximum value that the magnitude of the intensity of the received echo signal can be taken for each imaging condition such as the receiving coil used for imaging, imaging area, slice thickness, imaging cross-sectional direction, pulse sequence type, etc. is experimental or experienced. Can be estimated. Even if an echo signal having the maximum signal intensity for each imaging condition is input to the A / D converter 30C, the A / D converter 30C does not overflow, and the echo signal for each imaging condition performs a phase correction process. Therefore, an appropriate reception gain preset value Gpr having sufficient intensity resolution can be determined.

  Furthermore, not only the reception gain G1 for collecting the echo signal for phase correction but also the reception gain for the preparation scan for collecting the echo signal for determining the reception gain G1 for collecting the echo signal for phase correction. The initial value G0 can be a preset value Gpr of the reception gain instead of the minimum value. That is, 0 [dB] in Equation (1) or Equation (2) can be set as the preset value Gpr. In this case, since the first preparation scan can be executed using a more appropriate reception gain, it is possible to determine the reception gain G1 for collecting the echo signal for phase correction more accurately and appropriately. Become.

  For this reason, an appropriate reception gain preset value Gpr is received for each of a plurality of parameters of imaging conditions such as a receiving coil used for imaging, an imaging area, a slice thickness, an imaging cross-sectional direction, and a pulse sequence type. It is stored in the gain storage unit 40B. The phase correction data reception gain setting unit 40A then sets an appropriate reception gain preset value stored in the reception gain storage unit 40B in order to determine an appropriate reception gain G1 for collecting phase correction echo signals. It is configured so that it can be obtained by referring to Gpr.

  As described above, the function for determining the appropriate reception gain G1 for collecting the phase correction echo signal is provided in the phase correction data reception gain setting unit 40A. That is, the phase correction data reception gain setting unit 40A acquires the echo signal collected by the phase correction pulse sequence to which no phase encoding is added from the k-space database 42, and based on the intensity of the echo signal, the phase correction echo signal For determining the appropriate reception gain G1 for the acquisition and / or parameters of the imaging conditions such as the receiving coil used for imaging input from the input device 33, imaging area, slice thickness, imaging cross-sectional direction, pulse sequence type, etc. Is obtained from the reception gain storage unit 40B and set to an appropriate reception gain G1 for collecting echo signals for phase correction.

  Next, a method for determining an appropriate reception gain Gc when collecting echo signals for imaging will be described.

  The appropriate reception gain Gc for collecting the echo signal for imaging is the phase correction data acquired by executing the phase correction pulse sequence with the reception gain G1 appropriately set by the phase correction data reception gain setting unit 40A. Can be determined based on the intensity of the echo signal. That is, the intensity of the echo signal for phase correction collected at the effective TE timing of the imaging pulse sequence is measured, and an appropriate reception gain Gc for collecting the echo signal for imaging is determined based on the measured intensity. be able to.

  FIG. 9 is a diagram showing the intensity Sc of the echo signal for phase correction collected at the effective TE timing of the imaging pulse sequence measured by the imaging condition setting unit 40 shown in FIG.

  In FIG. 9, the vertical axis indicates the intensity S of the echo signal for phase correction, and the horizontal axis indicates time. Further, the curve in FIG. 9 shows the temporal signal intensity change of the echo signal for phase correction.

  As shown in FIG. 9, the signal intensity of the phase correction echo signals Ne1, Ne2, Ne3,... Attenuates according to the attenuation curve of T2 relaxation (lateral relaxation).

  Here, in the imaging pulse sequence using the FSE sequence as shown in FIG. 6, the gradient magnetic field pulse for phase encoding is applied before the collection of the echo signal, but the gradient for phase encoding is collected after the collection of the echo signal. A rewind pulse having the same area as the magnetic field pulse but having the opposite polarity is applied. For this reason, the influence of the gradient magnetic field pulse for phase encoding is removed immediately before the application of each 180 ° RF inversion pulse.

  Accordingly, the intensity of the echo signal for imaging at the center of k-space collected at the effective TE with the phase encoding amount set to zero is the timing of the effective TE without applying the gradient magnetic field pulse for phase encoding with the same reception gain. This is equivalent to the intensity of the echo signal for phase correction collected in step. Further, the intensity of the echo signal for imaging at the center of k-space collected by the effective TE is the maximum signal intensity Sc as shown in FIG. Therefore, the intensity of the echo signal for phase correction collected at the timing of effective TE can be regarded as the maximum signal intensity Sc of the echo signal for imaging collected with the same reception gain.

  Therefore, an appropriate reception gain Gc for collecting the echo signal for imaging can be determined as follows based on the intensity Sc of the echo signal for phase correction collected at the timing of the effective TE. That is, the input voltage to the A / D converter 30C of the echo signal for phase correction of the intensity Sc collected at the timing of the effective TE is Vc [V], and the maximum voltage that can be handled by the A / D converter 30C is Vmax [ V], in order to use the dynamic range of the A / D converter 30C most effectively, the reception gain of the amplifier 30A is multiplied by Vmax / Vc and the maximum signal intensity Sc input to the A / D converter 30C is set. The voltage of the echo signal for imaging should be the same as the maximum voltage Vmax that can be handled by the A / D converter 30C.

More specifically, the appropriate reception gain Gc for collecting the echo signal for imaging is the reception gain G1 [dB] for collecting the echo signal for phase correction, and the input voltage Vc to the A / D converter 30C. It can be determined from the maximum input voltage Vmax according to equation (3).
[Equation 3]
Gc = G1 + 20 · log ₁₀ (Vmax / Vc) [dB] (3)
However, in order to prevent the A / D converter 30C from overflowing even if the intensity of the MR signal fluctuates, a margin k of several dB is provided to collect an echo signal for imaging as shown in Equation (4). It is desirable to determine an appropriate reception gain Gc.
[Equation 4]
Gc = G1 + 20 · log ₁₀ (Vmax / Vc)-k [dB] (4)
When the reception gain G1 [dB] for collecting the echo signal for phase correction is set to the minimum value 0 [dB] of the reception gain, Equation (3) and Equation (4) ) And formula (5-2).
[Equation 5]
Gc = 20 ・ log ₁₀ (Vmax / Vc) [dB] (5-1)
Gc = 20 ・ log ₁₀ (Vmax / Vc)-k [dB] (5-2)
Further, since the input voltage Vc to the A / D converter 30C is determined by the signal intensity Sc at the timing of the effective TE when the reception gain is G1, an appropriate reception gain Gc for collecting echo signals for imaging is The function fc of the signal strength Sc at the effective TE timing when the reception gain is G1 can be expressed as Gc = fc (Sc).

  The function of determining an appropriate reception gain Gc for collecting an echo signal for imaging in this way is provided in the imaging data reception gain setting unit 40C as described above. Therefore, the imaging data reception gain setting unit 40C is also provided with a function of acquiring a phase correction echo signal collected from the k-space database 42 without adding phase encoding.

  The echo signal for phase correction is used not only for determining an appropriate reception gain Gc for collecting an echo signal for imaging, but also for phase correction that is originally intended for use. Phase correction methods include post-processing phase correction processing for imaging echo signals collected by the imaging pulse sequence, and the gradient magnetic field waveform of the imaging pulse sequence and the phase of the transmitted RF pulse. There is a method for receiving an echo signal for imaging whose phase is corrected by performing the adjustment.

  Therefore, the sequence correction unit 40D of the imaging condition setting unit 40 has a function of acquiring an echo signal for phase correction from the k-space database 42, and a gradient magnetic field of an imaging pulse sequence based on the acquired echo signal for phase correction. A function to finely adjust the waveform and phase of the transmission RF pulse is provided.

  Further, the phase correction unit 46 acquires the phase correction echo signal and the imaging echo signal from the k-space database 42, and performs phase correction processing of the imaging echo signal based on the phase correction echo signal. And a function of writing an echo signal for imaging after the phase correction processing in the k-space database 42.

  The sequence controller control unit 41 has a function of controlling driving by giving the sequence controller 31 imaging conditions including a pulse sequence and a reception gain acquired from the imaging condition setting unit 40 based on scan disclosure information from the input device 33. . In addition, the sequence controller control unit 41 has a function of acquiring an echo signal as raw data from the sequence controller 31 and arranging the acquired echo signal in the k space formed in the k space database 42. Therefore, the k-space database 42 stores the echo signal for phase correction and the echo signal for imaging generated in the receiver 30 as k-space data.

  The image reconstruction unit 42 takes in k-space data for imaging after phase correction processing from the k-space database 42 and performs image reconstruction processing including Fourier transformation (FT) to reconstruct the image data. And a function of writing image data obtained by reconstruction into the image database 44. For this reason, the image database 44 stores the image data reconstructed by the image reconstruction unit 43.

  The image processing unit 45 has a function of acquiring image data from the image database 44 and performing necessary image processing to generate display image data, and a function of causing the display device 34 to display the generated display image data. .

(Operation and action)
Next, the operation and action of the magnetic resonance imaging apparatus 20 will be described.

  FIG. 10 is a flowchart showing a procedure for capturing an image of the subject P by executing two preparation scans and an imaging scan for setting the reception gain by the magnetic resonance imaging apparatus 20 shown in FIG. Reference numerals with numerals in the figure indicate the steps of the flowchart.

  First, in step S1, the reception gain is set to the initial value G0 by the phase correction data reception gain setting unit 40A. The initial value G0 can be a minimum value 0 [dB] or a preset value Gpr corresponding to the imaging condition. When the preset value Gpr is used, the reception gain storage unit 40B is searched by the phase correction data reception gain setting unit 40A, and the preset value Gpr corresponding to the imaging condition is acquired.

  Next, in step S2, in order to determine the reception gain G1 for collecting the echo signal for phase correction, for example, a phase correction pulse sequence without adding a phase encode pulse as shown in FIG. The first preparation scan is executed by the phase correction pulse sequence at the initial value G0 of the reception gain set at 40.

  For this purpose, the subject P is set on the bed 37 in advance, and a static magnetic field is formed in the imaging region of the static magnetic field magnet 21 (superconducting magnet) excited by the static magnetic field power supply 26. Further, a current is supplied from the shim coil power supply 28 to the shim coil 22, and the static magnetic field formed in the imaging region is made uniform.

  Then, when an instruction to start the preparation scan is given from the input device 33 to the sequence controller control unit 41, the sequence controller control unit 41 receives the imaging condition including the initial value G0 of the reception gain and the phase correction pulse sequence from the imaging condition setting unit 40. Is given to the sequence controller 31. The sequence controller 31 drives the gradient magnetic field power source 27, the transmitter 29, and the receiver 30 according to the imaging conditions acquired from the sequence controller control unit 41, thereby forming a gradient magnetic field in the imaging region where the subject P is set, An RF signal is generated from the RF coil 24. Further, the reception gain in the amplifier 30A of the receiver 30 is controlled by the control signal to become the initial value G0 of the reception gain.

  Then, the NMR signal generated by nuclear magnetic resonance inside the subject P is received by the RF coil 24 and given to the receiver 30. The receiver 30 receives the NMR signal from the RF coil 24, performs necessary signal processing, and then performs A / D conversion to generate raw data that is an NMR signal of digital data. The receiver 30 gives the generated raw data to the sequence controller 31. The sequence controller 31 provides the raw data to the sequence controller control unit 41, and the sequence controller control unit 41 arranges the raw data as k-space data in the k-space formed in the k-space database 42.

  Here, since the reception gain is set to a sufficiently small initial value G0 so that an echo signal that is not phase-encoded does not overflow even if it is input to the A / D converter 30C, an overflow in the A / D converter 30C is avoided. Is done.

  Next, in step S3, the phase correction data reception gain setting unit 40A acquires the echo signal sequence collected by the phase correction pulse sequence from the k-space database 42 at the initial value G0 of the reception gain, and the maximum signal intensity. Measure S0. Since the echo signal sequence collected by the phase correction pulse sequence is collected without applying the phase encoding gradient magnetic field, it becomes the signal intensity of the first echo signal with the least attenuation due to T2 relaxation.

  Next, in step S4, the phase correction data reception gain setting unit 40A may input the phase correction echo signal to the A / D converter 30C based on the measured maximum signal intensity S0 of the echo signal. The reception gain G1 for collecting the echo signal for phase correction is determined so that the echo signal for phase correction is input to the A / D converter 30C with a larger signal intensity without overflow. Specifically, the reception gain G1 for collecting the echo signal for phase correction can be calculated by Expression (1) or Expression (2).

  Next, in step S5, in order to collect the echo signal for phase correction, the second preparation scan is executed by the phase correction pulse sequence with the reception gain G1 for collecting the echo signal for phase correction. . This phase correction pulse sequence is the same as that executed in step S2, and the second preparation scan can be executed in the same flow as in step S2.

  Here, the reception gain G1 does not overflow even if a phase-corrected echo signal that is not phase-encoded is input to the A / D converter 30C, and is input to the A / D converter 30C with a larger signal strength. It is set optimally. For this reason, an overflow in the A / D converter 30C can be avoided, and the dynamic range of the A / D converter 30C can be effectively used to collect an echo signal for phase correction that is possible for a good signal intensity. .

  The echo signal train for phase correction collected in this way is stored in the k-space database 42. Then, based on the intensity of the echo signal for phase correction, an appropriate reception gain Gc for collecting the echo signal for imaging is determined separately from the reception gain G1 for collecting the echo signal for phase correction. It becomes possible.

  Therefore, in step S6, the imaging data reception gain setting unit 40C acquires the echo signal sequence for phase correction from the k-space database 42, and executes the execution TE (TEeff) of the acquired echo signal sequence for phase correction. The intensity Sc of the echo signal for phase correction collected at the timing is measured. The intensity Sc of the echo signal for phase correction collected at the timing of this execution TE (TEeff) is the maximum signal intensity of the echo signal collected with the phase encoding amount set to zero by the imaging pulse sequence with phase encoding added. Can be considered equal.

  Therefore, the echo signal for phase correction collected at the timing of execution TE (TEeff) does not overflow even if it is input to the A / D converter 30C, and is input to the A / D converter 30C with a larger signal strength. The reception gain determined to be an appropriate reception gain Gc for collecting an echo signal for imaging.

Therefore, in step S7, the imaging data reception gain setting unit 40C calculates the equation (3) based on the intensity Sc of the phase correction echo signal collected at the timing of execution TE (TEeff).
), Expression (4), Expression (5-1), or Expression (5-2), the reception gain Gc for collecting the echo signal for imaging is set.

  On the other hand, in the case where fine adjustment of the imaging pulse sequence is performed as the phase correction processing of the echo signal, that is, when the echo signal for imaging is collected in a phase-corrected state, in step S8 The sequence correction unit 40D acquires the echo signal for phase correction from the k-space database 42, and uses the acquired echo signal for phase correction to finely adjust the gradient magnetic field waveform of the imaging pulse sequence and the phase of the transmission RF pulse. Make adjustments.

  Accordingly, the imaging condition setting unit 40 sets the reception gain Gc for collecting the imaging pulse sequence and the imaging echo signal.

  Next, in step S9, an imaging scan is executed by an imaging pulse sequence with a reception gain Gc for collecting imaging echo signals. Then, the echo signal for imaging is collected in the same flow as when the echo signal for phase correction is collected. The acquired echo signal sequence for imaging is stored in the k-space database 42.

  Here, the reception gain Gc is optimally set so that it does not overflow even if an echo signal for imaging is input to the A / D converter 30C, and is input to the A / D converter 30C with a larger signal strength. Yes. For this reason, an overflow in the A / D converter 30C can be avoided, and the dynamic range of the A / D converter 30C can be effectively used to collect an echo signal for imaging with a good signal intensity.

  Next, when performing phase correction on the collected echo signal as the phase correction processing of the echo signal, in step S10, the phase correction unit 46 extracts the echo signal for phase correction and the echo for imaging from the k-space database 42. The signal is acquired, and the phase correction process of the echo signal for imaging is performed based on the echo signal for phase correction. Then, the echo signal for imaging after the phase correction process is written in the k-space database 42.

  Next, in step S11, image data is generated by image reconstruction processing and necessary image processing for the echo signal for imaging, and the generated image data is displayed.

  Specifically, the image reconstruction unit 42 obtains an echo signal for imaging after the phase correction process from the k-space database 42 and performs image reconstruction process to reconstruct and reconstruct the image data. The obtained image data is written into the image database 44. Next, the image processing unit 45 takes in the image data from the image database 44, performs necessary image processing to generate display image data, and causes the display device 34 to display the generated display image data.

  In this way, by setting the reception gain so that the dynamic range of the A / D converter 30C can be used effectively for the execution of the phase correction pulse sequence and the imaging pulse sequence, the reception gain can be reduced. Thus, the signal strength of the phase correction echo signal is prevented while preventing the overflow of the A / D converter 30C due to the input of the echo signal for phase correction having a relatively large signal strength to the A / D converter 30C. It is possible to prevent a decrease in intensity resolution of a relatively small echo signal for imaging.

  Further, by setting the reception gain G1 for collecting the echo signal for phase correction to the preset value Gpr corresponding to the imaging condition, the number of preparation scans can be reduced from two to one.

  FIG. 11 is a flowchart showing a procedure for capturing an image of the subject P by performing one preparation scan and imaging scan for setting the reception gain by the magnetic resonance imaging apparatus 20 shown in FIG. Reference numerals with numerals in the figure indicate the steps of the flowchart. Steps similar to those in FIG. 10 are denoted by the same reference numerals and description thereof is omitted.

  In step S20 in FIG. 11, the reception gain G1 for collecting the echo signal for phase correction is set to the preset value Gpr corresponding to the imaging condition. That is, the reception gain storage unit 40B is searched by the phase correction data reception gain setting unit 40A, the preset value Gpr corresponding to the imaging condition is acquired, and the acquired preset value Gpr is used for collecting the echo signal for phase correction. Set to receive gain G1.

  Then, using the reception gain G1 for collecting echo signals for phase correction set in this way, image data can be generated and displayed in the same flow as in steps S5 to S11 in FIG.

  In this way, if the reception gain G1 for collecting the echo signal for phase correction is set to the preset value Gpr corresponding to the imaging conditions, the reception gain Gc of the pulse sequence for imaging is set by executing one preparation scan. It becomes possible to do.

  That is, the magnetic resonance imaging apparatus 20 as described above measures the intensity of the signal collected at the timing of execution TE in the phase correction echo signal sequence collected by the phase correction pulse sequence to which no phase encoding is added. The reception gain for imaging is determined based on the signal strength.

(effect)
For this reason, according to the magnetic resonance imaging apparatus 20, for the echo signal for phase correction in a shorter time, the reception gain is set so as not to exceed the upper limit of the input signal intensity in the reception system, while the echo signal for imaging is set. Therefore, it is possible to set an optimum reception gain that can provide sufficient intensity resolution. That is, in the conventional technique, at least three preparation scans are necessary. According to the magnetic resonance imaging apparatus 20, an appropriate reception gain can be determined by executing at least two preparation scans. it can. For this reason, the number of preparation scans can be reduced from three to two. Further, the total imaging time and data processing time are reduced, leading to an increase in imaging efficiency.

  Further, when an approximate minimum reception gain is known in advance so that the A / D converter 30C does not overflow even if an echo signal for phase correction is input to the A / D converter 30C, or an initial value of the reception gain is set. If the echo signal for phase correction can be collected with the intensity resolution necessary for phase correction even if the minimum value is set, the preparation scan for determining the reception gain for the echo signal for phase correction may be omitted. it can. That is, it is possible to determine an appropriate reception gain for the imaging echo signal only by measuring the intensity of the signal collected at the timing corresponding to execution TE or TE in the phase correction echo signal sequence. In this case, since the number of preparation scans is one, the inspection time can be further shortened.

The figure explaining the setting method of the conventional receiving gain in the case of imaging by FSE method. 1 is a configuration diagram showing an embodiment of a magnetic resonance imaging apparatus according to the present invention. FIG. 3 is a functional block diagram of the computer shown in FIG. 2. The figure which shows an example of the pulse sequence for phase correction of the FSE method set in the imaging condition setting part shown in FIG. The graph which shows the time change of the intensity | strength of the echo signal for phase correction shown in FIG. The figure which shows an example of the pulse sequence for imaging of the FSE method set in the imaging condition setting part shown in FIG. The graph which shows the time change of the intensity | strength of the echo signal for imaging shown in FIG. The block diagram which shows an example of the detailed structure of the receiver shown in FIG. The figure which shows the intensity | strength of the echo signal for phase correction collected in the timing of effective TE of the pulse sequence for imaging measured in the imaging condition setting part shown in FIG. FIG. 3 is a flowchart showing a procedure for capturing an image of a subject by executing two preparation scans and imaging scans for setting a reception gain by the magnetic resonance imaging apparatus shown in FIG. 2. 3 is a flowchart showing a procedure for capturing an image of a subject by performing one preparation scan and imaging scan for setting a reception gain by the magnetic resonance imaging apparatus shown in FIG. 2.

Explanation of symbols

20 Magnetic Resonance Imaging Device 21 Magnet for Static Magnetic Field 22 Shim Coil 23 Gradient Magnetic Field Coil 24 RF Coil 25 Control System 26 Static Magnetic Field Power Supply 27 Gradient Magnetic Field Power Supply 28 Shim Coil Power Supply 29 Transmitter 30 Receiver 30A Amplifier 30B Frequency Converter 30C A / D Conversion Device 31 sequence controller 32 computer 33 input device 34 display device 35 arithmetic device 36 storage device 37 bed 40 imaging condition setting unit 40A phase correction data reception gain setting unit 40B reception gain storage unit 40C imaging data reception gain setting unit 40D sequence correction Unit 41 Sequence controller control unit 42 k-space database 43 Image reconstruction unit 44 Image database 45 Image processing unit 46 Phase correction unit P Subject

Claims (9)

In a phase correction pulse sequence for collecting magnetic resonance data for phase correction, phase correction data collection means for collecting the magnetic resonance data for phase correction from a subject with a first reception gain ;
In the imaging pulse sequence for collecting magnetic resonance data for imaging, the magnetic resonance data for imaging is collected from the subject with a second reception gain, and the phase for the magnetic resonance data for imaging is collected. An imaging means for performing imaging of the subject by performing phase correction processing based on magnetic resonance data for correction ;
With
The imaging means is a magnetic resonance signal collected at a timing when a phase encoding amount becomes zero in the imaging pulse sequence among the plurality of magnetic resonance signals for phase correction collected in the phase correction pulse sequence. Determining the second reception gain based on the intensity of
A magnetic resonance imaging apparatus. The phase correction data collection means is a maximum value of signal intensity of a magnetic resonance signal sequence collected by a second phase correction pulse sequence that does not add phase encoding with a third reception gain different from the first reception gain. The magnetic resonance imaging apparatus of claim 1, wherein the magnetic resonance imaging apparatus is configured to determine the first reception gain on the basis of the frequency. A reception gain storage means for storing a reception gain value corresponding to the imaging condition;
The phase correction data collection means collects the magnetic resonance collected by the second phase correction pulse sequence that does not add phase encoding with the third reception gain acquired from the reception gain storage means according to the imaging conditions of the imaging. The magnetic resonance imaging apparatus according to claim 1, wherein the first reception gain is determined based on a maximum value of signal intensity of a signal sequence. A reception gain storage means for storing a reception gain value corresponding to the imaging condition;
2. The magnetic resonance imaging apparatus according to claim 1, wherein the phase correction data collection unit is configured to set a reception gain acquired from the reception gain storage unit according to an imaging condition of the imaging as the first reception gain. . The reception gain storage means stores a value of a reception gain according to an imaging condition using at least one of a reception coil used for imaging, an imaging area, a slice thickness, an imaging cross-sectional direction, and a pulse sequence type as a parameter. The magnetic resonance imaging apparatus according to claim 3 or 4, which is configured. The imaging means performs multi-echo data collection with phase correction, and performs the imaging based on pulse sequences having different signal intensities between the magnetic resonance data for phase correction and the magnetic resonance data for imaging. The magnetic resonance imaging apparatus of claim 1, configured to perform. The magnetic resonance imaging apparatus according to claim 6 , wherein the imaging unit is configured to perform the imaging based on any of a Fast Spin Echo sequence, an echo planar imaging sequence, and a Periodically Rotated Overlapping ParallEL Lines with Enhanced Reconstruction sequence. The magnetic resonance imaging apparatus according to claim 1, wherein the imaging unit is configured to perform the phase correction process by adjusting the pulse sequence for imaging based on the magnetic resonance data for phase correction. The imaging means is configured to perform the phase correction processing by correcting the phase of the magnetic resonance data for imaging collected by the imaging pulse sequence based on the magnetic resonance data for phase correction. The magnetic resonance imaging apparatus according to claim 1.

Images