WO2016149888A1

WO2016149888A1 - Magnetic resonance imaging method and device

Info

Publication number: WO2016149888A1
Application number: PCT/CN2015/074786
Authority: WO
Inventors: 邹超; 钟耀祖; 刘新; 郑海荣
Original assignee: 中国科学院深圳先进技术研究院
Priority date: 2015-03-20
Filing date: 2015-03-20
Publication date: 2016-09-29

Abstract

A magnetic resonance imaging method and a magnetic resonance imaging device. The magnetic resonance imaging method comprises: alternately collecting an echo translation signal and a time inversion steady-state precession signal within adjacent repetition periods by periodically executing a magnetic resonance imaging impulse sequence, wherein the magnetic resonance imaging impulse sequence comprises a first level selection gradient (A), a second level selection gradient (B), a third level selection gradient (C), a fourth level selection gradient (D) and a fifth level selection gradient (E) which are applied to a level selection direction, and satisfy M_B + M_C = M_D + M_E, M_A/2 + M_B + M_C + M_A + M_D = 0, and M_A/2 + M_D + M_E - M_B = 0. By means of the magnetic resonance imaging method, an echo translation signal and a time inversion steady-state precession signal can be collected at the same time, a required repetition period is short, the quality of an obtained image is good, and the magnetic resonance imaging method is convenient and fast.

Description

Magnetic resonance imaging method and device

Technical field

Embodiments of the present invention relate to the field of magnetic resonance imaging technology, and in particular, embodiments of the present invention relate to a magnetic resonance imaging method and apparatus.

Background technique

This section is intended to provide a background or context for the embodiments of the invention set forth in the claims. The description herein is not admitted to be prior art as it is included in this section.

Time-reversed Fast Imaging with Steady-State Precession (time reversed FISP, or PSIF, or Contrast Enhanced Fourier Acquired Steady state, CE-FAST) signal is a heavy T2-weighted gradient echo signal . Compared with the traditional fast spin echo T2-weighted signal, it has the advantages of fast acquisition speed and low selective absorption rate.

The Echo Shift (ES) signal is a heavy T2* weighted gradient echo signal with long echo time (TE) and is also sensitive to phase changes, usually used for magnetic resonance. Real-time monitoring areas such as temperature imaging.

At present, the industry usually uses two different magnetic resonance imaging pulse sequences to separately acquire time-reversed steady-state precession signals and echo translation signals.

Summary of the invention

In some real-time monitoring fields, in order to obtain temperature information and organize T2 change information, it is necessary to simultaneously collect echo translation signals and time-reversed steady-state precession signals. Currently, the industry uses two different magnetic resonance imaging pulse sequences to separately acquire the above two. The way the signal is used does not meet this need.

To this end, an improved magnetic resonance imaging method is highly desirable to meet the need to simultaneously acquire an echo translation signal and a time-reversed steady state precession signal.

In this context, embodiments of the present invention are directed to providing a magnetic resonance imaging method and apparatus.

In a first aspect of the embodiments of the present invention, a magnetic resonance imaging method is provided, for example, which may include:

Performing a step periodically according to a duty cycle until the total number of cycles for performing the step reaches a preset number of phase codes;

While periodically performing the steps, filling the k-space with the obtained time-reversed steady-state precession signal and the echo translation signal;

After the filling is completed, performing Fourier transform on the data of the k space to obtain a magnetic resonance image;

The steps include sub-step 11 to sub-step 18:

Sub-step 11, applying a radio frequency pulse while applying a first level selection gradient A;

Sub-step 12, applying a second level selection gradient B, a first phase encoding gradient U, and a first readout pre-dispersion gradient F;

Sub-step 13, applying a first readout gradient G, simultaneously acquiring a magnetic resonance signal, and performing analog-to-digital conversion on the currently acquired magnetic resonance signal to obtain a time-reversed steady-state precession signal;

Sub-step 14, applying a first readout back-concentration gradient H, a first back-concentration gradient V, and a third-level selection gradient C;

Sub-step 15, applying the radio frequency pulse while applying a first layer selection gradient A;

Sub-step 16, applying a fourth level selection gradient D, a first phase encoding gradient U, and a second readout pre-dispersion gradient J;

Sub-step 17, applying a second readout gradient P, simultaneously acquiring a magnetic resonance signal, and performing analog-to-digital conversion on the currently acquired magnetic resonance signal to obtain an echo translation signal;

Sub-step 18, applying a second readout back-concentration gradient Q, a first back-concentration gradient V, and a fifth-level selection gradient E;

The first layer selection gradient A, the second layer selection gradient B, the third layer selection gradient C, the fourth layer selection gradient D, and the fifth layer selection gradient E are all applied to the layer selection direction, and satisfy the following relationship:

M _B +M _C =M _D +M _E ,

M _A /2+M _B +M _C +M _A +M _D =0,

M _A /2+M _D +M _E -M _B =0,

M _A is the moment at which the gradient _A is selected at the first level.

M _B is the moment of the second level selecting the gradient B,

M _C is the moment at which the third level selects the gradient C,

M _D is the moment of the fourth level selecting the gradient D,

M _E is the moment at which the gradient _E is selected at the fifth level.

The first phase encoding gradient U and the first back-concentration gradient V are both applied to the phase encoding direction, and satisfy the following relationship:

M _U =-M _V ,

M _U is the moment of the first phase encoding gradient U,

M _V is the moment of the first back convergence gradient V;

The first readout pre-dispersion phase gradient F, the first readout gradient G, the first readout back-concentration gradient H, the second readout pre-dispersion phase gradient J, the second readout gradient P, and the second readout back The poly gradient Q is applied to the readout direction and satisfies the following relationship:

The first readout pre-dispersion phase gradient F, the first readout back-concentration gradient H is opposite to the polarity of the first readout gradient G, the second readout pre-dispersion gradient J, and the second readout back-convergence gradient Q Opposite to the polarity of the second readout gradient P,

M _F +M _G +M _H =0,

M _J +M _P +M _Q =0,

M _F is the first moment to read the pre-dispersion phase gradient F,

M _G is the moment of the first readout gradient G,

M _H is the moment at which the first readback gradient _H is read,

M _J is the moment of the second readout pre-dispersion gradient J,

M _P is the moment of the second readout gradient P,

M _Q is the moment of the second readout convergence gradient Q;

The duty cycle includes two repetition periods;

When the step is performed, the sub-steps 11 to 14 are sequentially performed in the first repetition period of the work cycle, and the sub-steps 15 to 18 are sequentially performed in the second repetition period of the work cycle. Alternatively, the sub-step 15 to the sub-step 18 are sequentially executed in the first repetition period of the work cycle, and the sub-step 11 to the sub-step 14 are sequentially executed in the second repetition period of the work cycle; and each completion For one duty cycle, the moments of the first phase encoding gradient U and the first back-concentration gradient V are changed.

In a second aspect of the embodiments of the present invention, a magnetic resonance imaging apparatus is provided, which may include, for example, a processor, a gradient coil, a pulse transmitting coil, a pulse receiving coil, an analog to digital converter, and an output device;

The processor includes:

a first processing unit configured to control the pulse transmitting coil to emit a radio frequency pulse while controlling the gradient coil to apply a first layer selection gradient A;

a second processing unit, configured to control the gradient coil to apply a second layer selection gradient B, a first phase encoding gradient U, and a first readout pre-dispersion gradient F;

a third processing unit configured to control the gradient coil to apply a first readout gradient G while controlling the pulse receiving coil to acquire a magnetic resonance signal, and controlling the analog to digital converter to perform a mode on the currently acquired magnetic resonance signal Number conversion to obtain a time-reversed steady-state precession signal;

a fourth processing unit, configured to control the gradient coil to apply a first readout back-concentration gradient H, a first back-concentration gradient V, and a third-level selection gradient C;

a fifth processing unit, configured to control the pulse transmitting coil to emit a radio frequency pulse while controlling the gradient coil to apply a first level selection gradient A;

a sixth processing unit, configured to control the gradient coil to apply a fourth layer selection gradient D, a first phase encoding gradient U, and a second readout pre-dispersion phase gradient J;

a seventh processing unit configured to control the gradient coil to apply a second readout gradient P while controlling the pulse receiving coil to acquire a magnetic resonance signal, and controlling the analog to digital converter to perform a mode on the currently acquired magnetic resonance signal Number conversion to obtain an echo translation signal;

The eighth processing unit is configured to control the gradient coil to apply a second readout back-concentration Q, a first back-concentration gradient V, and a fifth-level selection gradient E;

M _B +M _C =M _D +M _E ,

M _A /2+M _B +M _C +M _A +M _D =0,

M _A /2+M _D +M _E -M _B =0,

M _A is the moment at which the gradient _A is selected at the first level.

M _B is the moment of the second level selecting the gradient B,

M _C is the moment at which the third level selects the gradient C,

M _D is the moment of the fourth level selecting the gradient D,

M _E is the moment at which the gradient _E is selected at the fifth level;

M _U =-M _V ,

M _U is the moment of the first phase encoding gradient U,

M _V is the moment of the first back convergence gradient V;

M _F +M _G +M _H =0,

M _J +M _P +M _Q =0,

M _F is the first moment to read the pre-dispersion phase gradient F,

M _G is the moment of the first readout gradient G,

M _H is the moment at which the first readback gradient _H is read,

M _J is the moment of the second readout pre-dispersion gradient J,

M _P is the moment of the second readout gradient P,

M _Q is the moment of the second readout convergence gradient Q;

The processor further includes:

The execution unit is configured to periodically operate according to a duty cycle, the work cycle includes two repetition periods, and the execution unit sequentially triggers the first processing unit to the fourth processing unit in the first repetition period of the working period thereof The fifth processing unit to the eighth processing unit are sequentially triggered in the second repetition period of the working cycle, or the execution unit sequentially triggers the fifth processing unit to the eighth processing unit in the first repetition period of the working cycle. And triggering the first processing unit to the fourth processing unit in sequence in the second repetition period of the working cycle;

a loop unit configured to control the execution unit to periodically operate until a total number of cycles completed by the execution unit reaches a preset number of phase codes, wherein the cycle unit changes each time the execution unit completes one duty cycle a moment of the first phase encoding gradient U and the first back convergence gradient V;

a clock, providing a clock signal to the execution unit and the loop unit, so that the execution unit and the loop unit determine a start time and an end time of each repetition period;

a filling unit configured to fill a k-space with a time-reversed steady-state precession signal and an echo translation signal obtained by the analog-to-digital converter;

a Fourier transform unit, configured to perform Fourier transform on the data in the filled k-space to obtain a magnetic resonance image;

The output device is arranged to output the magnetic resonance image.

A magnetic resonance imaging method and apparatus according to an embodiment of the present invention can simultaneously acquire an echo translation signal and a time reversal steady state precession signal in an adjacent repetition period by periodically performing a magnetic resonance imaging pulse sequence to achieve simultaneous acquisition. For the purpose of the two signals, further, the magnetic resonance imaging is performed by using the collected echo translation signal and the time-reversed steady-state precession signal; the magnetic resonance imaging method of the embodiment of the invention requires a short repetition period and the acquired signal The high signal-to-noise ratio and good image quality are a convenient and fast method for magnetic resonance imaging.

DRAWINGS

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments will be briefly described below. It is obvious that the drawings in the following description are only the present invention. For some embodiments, other drawings may be obtained from those of ordinary skill in the art without departing from the drawings.

Figure 1 schematically shows a magnetic resonance imaging pulse sequence of an embodiment of the present invention;

Fig. 2 schematically shows another magnetic resonance imaging pulse sequence of an embodiment of the present invention;

FIG. 3 is a schematic structural view showing a magnetic resonance imaging apparatus according to an embodiment of the present invention; FIG.

FIG. 4 is a schematic structural diagram of a processor according to an embodiment of the present invention; FIG.

Figure 5 is a schematic illustration of a duty cycle of an embodiment of the present invention;

Figure 6 is a schematic illustration of another duty cycle of an embodiment of the present invention;

FIG. 7 is a schematic flow chart showing a magnetic resonance imaging method according to an embodiment of the present invention; FIG.

Figure 8 is four magnetic resonance images obtained in an exemplary embodiment of an embodiment of the present invention.

detailed description

The principles and spirit of the present invention are described below with reference to a few exemplary embodiments. It is to be understood that the embodiments are presented only to enable those skilled in the art to understand the invention. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Those skilled in the art will appreciate that embodiments of the present invention can be implemented as a system, apparatus, device, method, or computer program product. Accordingly, the present disclosure may be embodied in the form of full hardware, complete software (including firmware, resident software, microcode, etc.), or a combination of hardware and software.

According to an embodiment of the present invention, a magnetic resonance imaging method and apparatus are proposed.

In this article, you need to understand:

1. The letters A, B, C, D, E, F, G, H, J, P, Q, U, V, S, T in the text and in the drawings are only used for differentiation without any meaning. .

2. Gradient: includes a gradient applied to the layer selection direction, a gradient applied to the phase encoding direction, and a gradient applied to the readout direction.

3. The first level selects the gradient A: is applied to the layer selection direction, cooperates with the radio frequency pulse to excite a certain layer of the living body (ie, the excitation layer), and the first layer selects the duration of the gradient A and the gradient field changes with time. The function is determined by parameters such as the thickness of the excitation layer and the bandwidth of the RF pulse.

3. The first phase encoding gradient U: applied to the phase encoding direction for two-dimensional magnetic resonance imaging, so that the spins in the same two-dimensional plane in the excitation layer have different initial phases to distinguish different voxels s position.

4. The first back-concentration gradient V: applied to the phase encoding direction for two-dimensional magnetic resonance imaging to recombine the phase of the spins in the same two-dimensional plane in the excitation layer, the first convergence gradient V It has the same intensity and opposite polarity as the first phase encoding gradient U.

5. The second phase encoding gradient S: applied to the layer selection direction for three-dimensional magnetic resonance imaging, so that the spins in the excitation layer perpendicular to the two-dimensional plane have different initial phases to distinguish different two-dimensional flat.

6. The second back-concentration gradient T: applied to the layer selection direction for three-dimensional magnetic resonance imaging to recombine the phases of the spins in the excitation layer perpendicular to the two-dimensional plane, the second convergence gradient T and The second phase encoding gradient S has the same intensity and opposite polarity.

7. Number of Phase Coding: Depending on the resolution of the magnetic resonance image, the total number of cycles in which the execution unit periodically operates (or the total number of cycles in which the magnetic resonance pulse sequence is periodically executed) corresponds to the number of phase encodings.

8. The first readout gradient G: cooperates with the RF receiving coil to acquire a time-reversed steady-state precession signal. The duration of the first readout gradient G and the gradient field as a function of time are determined by the number of sampling points, the acquisition bandwidth, and The parameters such as the size of the field of view in the readout direction are determined.

9. The second readout gradient P: cooperates with the RF receiving coil to acquire the echo translation signal, and the duration of the second readout gradient P and the gradient field as a function of time are determined by the number of sampling points, the acquisition bandwidth, and the readout direction. The parameters such as the size of the field of view are determined.

10. Output device: output magnetic resonance image, which can be a device such as a display or a printer.

Summary of invention

Currently in the field of magnetic resonance imaging, two different magnetic resonance imaging pulse sequences are usually used to separately acquire time-reversed steady-state precession signals and echo-translation signals, but in some real-time monitoring fields, in order to obtain temperature information and organization The T2 change information requires simultaneous acquisition of the echo translation signal and the time-reversed steady-state precession signal. Currently, the industry uses two different magnetic resonance imaging pulse sequences to separately acquire the above two signals, which cannot meet this requirement.

To this end, the present invention provides a magnetic resonance imaging method in which an echo translation signal and time reversal stabilization can be alternately acquired in adjacent repetition periods by periodically performing a magnetic resonance imaging pulse sequence. The state precession signal, further, fills the k-space with the two acquired signals, and performs Fourier transform on the filled k-space to obtain a corresponding magnetic resonance image.

Referring to FIG. 1 , which is a magnetic resonance imaging pulse sequence executed by the present invention, the process of performing the magnetic resonance imaging pulse sequence shown in FIG. 1 may include the following steps (first acquiring a time-reversed steady-state precession signal in an adjacent repetition period) , then collect the echo translation signal):

Step S11, applying a radio frequency pulse while applying a first level selection gradient A;

Step S12, applying a second level selection gradient B, a first phase encoding gradient U, and a first readout pre-dispersion gradient F;

Step S13, applying a first readout gradient G, and simultaneously acquiring a magnetic resonance signal to obtain a time-reversed steady-state precession signal;

Step S14, applying a first readout back-concentration gradient H, a first back-concentration gradient V, and a third-level selection gradient C;

Step S15, applying the radio frequency pulse while applying the first layer selection gradient A;

Step S16, applying a fourth level selection gradient D, a first phase encoding gradient U, and a second readout pre-dispersion phase gradient J;

Step S17, applying a second readout gradient P, and simultaneously acquiring a magnetic resonance signal to obtain an echo translation signal;

In step S18, a second readout back-concentration gradient Q, a first back-concentration gradient V, and a fifth-level selection gradient E are applied.

In FIG. 1, the first layer selection gradient A, the second layer selection gradient B, the third layer selection gradient C, the fourth layer selection gradient D, and the fifth layer selection gradient E are all applied to the layer selection direction, and satisfy the following relationship:

M _B +M _C =M _D +M _E ,

M _A /2+M _B +M _C +M _A +M _D =0,

M _A /2+M _D +M _E -M _B =0.

Optionally, the magnetic resonance imaging pulse sequence used in the present invention may also be in the form shown in FIG. 2. The process of performing the magnetic resonance imaging pulse sequence shown in FIG. 2 may include the following steps (collecting in an adjacent repetition period) Echo panning signal, and then collecting time reversal steady-state precession signal):

Step s11, applying the radio frequency pulse while applying the first layer selection gradient A;

Step s12, applying a fourth level selection gradient D, a first phase encoding gradient U, and a second readout pre-dispersion gradient J;

Step s13, applying a second readout gradient P, and simultaneously acquiring a magnetic resonance signal to obtain an echo translation signal;

Step s14, applying a second readout back-concentration gradient Q, a first back-concentration gradient V, and a fifth-level selection gradient E;

Step s15, applying a radio frequency pulse while applying a first level selection gradient A;

Step s16, applying a second level selection gradient B, a first phase encoding gradient U, and a first readout pre-dispersion phase gradient F;

Step s17, applying a first readout gradient G, and simultaneously acquiring a magnetic resonance signal to obtain a time-reversed steady-state precession signal;

In step s18, a first readout back-concentration gradient H, a first back-concentration gradient V, and a third-level selection gradient C are applied.

In FIG. 2, the first layer selection gradient A, the second layer selection gradient B, the third layer selection gradient C, the fourth layer selection gradient D, and the fifth layer selection gradient E are all applied to the layer selection direction, and satisfy the following relationship:

M _B +M _C =M _D +M _E ,

M _A /2+M _B +M _C +M _A +M _D =0,

M _A /2+M _D +M _E -M _B =0.

Having described the basic principles of the invention, various non-limiting embodiments of the invention are described in detail below.

Application scenario overview

In the magnetic resonance imaging process, the magnetic resonance imaging apparatus applies a radio frequency pulse and a magnetic field gradient to the living body according to the magnetic resonance imaging pulse sequence to cause precession and energy level transition of the nucleus in the living tissue, and the magnetic resonance imaging apparatus detects the nucleus here. The magnetization vector generated during the motion is used as the magnetic resonance signal, and finally the magnetic resonance imaging is performed using the magnetic resonance signal.

The magnetic resonance imaging apparatus may be of any of the following types: permanent magnet or electromagnetic (classified according to magnetic field generation), open magnet type, closed magnet type or special shape magnet type (according to the shape of the main magnet), Low field, midfield, high field, or ultra high field strength type (according to the field strength of the main magnet).

Exemplary device

A magnetic resonance imaging apparatus according to an exemplary embodiment of the present invention will be described below in conjunction with an application scenario.

It should be noted that the above application scenarios are only shown to facilitate understanding of the spirit and principle of the present invention, and embodiments of the present invention are not limited in this respect. Rather, embodiments of the invention may be applied to any scenario that is applicable.

For example, referring to FIG. 3, it is a schematic structural diagram of a magnetic resonance imaging apparatus according to an embodiment of the present invention. As shown in FIG. 3, the magnetic resonance imaging apparatus may include a processor 31, a gradient coil 32, a pulse transmitting coil 33, a pulse receiving coil 34, an analog to digital converter 35, and an output device 36.

Referring to FIG. 4, the processor 31 has 31 bodies, which may include: a first processing unit 311, a second processing unit 312, a third processing unit 313, a fourth processing unit 314, a fifth processing unit 315, a sixth processing unit 316, and a Seven processing unit 317, eighth processing unit 318, and execution unit 31-Z, loop unit 31-X, clock 31-S, padding unit 31-T, and Fourier transform unit 31-F.

The working process of the magnetic resonance imaging apparatus provided by the embodiment of the present invention is as follows:

The operator activates the magnetic resonance imaging apparatus, and the magnetic resonance imaging apparatus follows various parameters set by the operator (eg, the field of view of the readout direction, the thickness of the excitation layer, the resolution of the magnetic resonance image, the flip angle of the radio frequency pulse, and the repetition Start working, such as the duration of the cycle.

After startup, the loop unit 31-X and the execution unit 31-Z determine the start time and end time of each repetition period based on the clock 31-S signal supplied from the clock 31-S, and the loop unit 31-X controls the execution unit 31-Z. It works periodically and counts the cycles completed by the execution unit until the total number of cycles completed by the execution unit reaches the preset number of phase codes. The execution unit 31-Z experiences two repetition periods per periodic operation. For convenience of introduction, the following execution unit 31-Z is called a work cycle (including two repetition periods) once per periodic operation, which is described below with reference to FIG. The specific process of each duty cycle of the execution unit 31-Z, as shown in FIG. 5, represents the time direction from left to right.

(1) The execution unit 31-Z triggers the first processing unit 311 at the start of the first repetition period. Immediately after the triggering, the first processing unit 311 controls the pulse transmitting coil 33 to emit a radio frequency pulse while controlling the gradient coil 32 to apply the first layer selection gradient A in the slice selection direction.

(2) After the execution unit 31-Z triggers the first processing unit 311, the second processing unit 312 is triggered. Immediately after the triggering, the second processing unit 312 controls the gradient coil 32 to apply the second layer selection gradient B in the slice selection direction, the first phase encoding gradient U in the phase encoding direction, and the first readout pre-distribution in the readout direction. Phase gradient F.

(3) After the execution unit 31-Z triggers the second processing unit 312, the third processing unit 313 is triggered. The third processing unit 313 immediately controls the gradient coil 32 to apply the first readout gradient G in the readout direction after the trigger, while controlling the pulse receiving coil 34 to acquire the magnetic resonance signal, and controlling the analog to digital converter 35 to the currently acquired magnetic The resonant signal is analog-to-digital converted to obtain a time-reversed steady-state precession signal.

(4) After the execution unit 31-Z triggers the third processing unit 313, the fourth processing unit 314 is triggered. The fourth processing unit 314 immediately controls the gradient coil 32 to apply a first readout back-concentration gradient H in the readout direction, a first back-concentration gradient V in the phase-encoding direction, and a third-level selection in the slice selection direction. Gradient C.

At this point, the first repetition period ends and the second repetition period is entered.

(5) The execution unit 31-Z triggers the fifth processing unit 315 at the beginning of the second repetition period. The fifth processing unit 315 controls the pulse transmitting coil 33 to emit a radio frequency pulse immediately after the trigger, while controlling the gradient coil 32 to apply the first layer selection gradient A in the slice selection direction.

(6) After the execution unit 31-Z triggers the fifth processing unit 315, the sixth processing unit 316 is triggered. After the triggering, the sixth processing unit 316 immediately controls the gradient coil 32 to apply the fourth layer selection gradient D in the layer selection direction, the first phase encoding gradient U in the phase encoding direction, and the second reading in the read direction. A pre-dispersion gradient J is derived.

(7) After the execution unit 31-Z triggers the sixth processing unit 316, the seventh processing unit 317 is triggered. The seventh processing unit 317 immediately controls the gradient coil 32 to apply the second readout gradient P in the readout direction after the trigger, while controlling the pulse receiving coil 34 to acquire the magnetic resonance signal, and controlling the analog to digital converter 35 to the currently acquired magnetic resonance. The signal is analog-to-digital converted to obtain an echo translation signal.

(8) After the execution unit 31-Z triggers the seventh processing unit 317, the eighth processing unit 318 is triggered. The eighth processing unit 318, after triggering, immediately controls the gradient coil 32 to apply a second readout backgrading gradient Q in the readout direction, a first backscattering gradient V in the phase encoding direction, and a fifth level selection in the slice selection direction. Gradient E.

At this point, the second repetition period also ends, and the execution unit 31-Z enters the next duty cycle.

In the duty cycle shown in Figure 5, each gradient needs to meet the following conditions:

M _B +M _C =M _D +M _E

_{_{M A / 2 + M B +}} M C + M A + M D = 0

M _A /2+M _D +M _E -M _B =0

M _U =-M _V

M _F +M _G +M _H =0

M _J +M _P +M _Q =0

M _A is the moment at which the gradient _A is selected at the first level.

M _B is the moment of the second level selecting the gradient B,

M _C is the moment at which the third level selects the gradient C,

M _D is the moment of the fourth level selecting the gradient D,

M _E is the moment at which the gradient _E is selected at the fifth level.

M _U is the moment of the first phase encoding gradient U,

M _V is the moment of the first back-concentration gradient V,

M _F is the first moment to read the pre-dispersion phase gradient F,

M _G is the moment of the first readout gradient G,

M _H is the moment at which the first readback gradient _H is read,

M _J is the moment of the second readout pre-dispersion gradient J,

M _P is the moment of the second readout gradient P,

M _Q is the moment of the second readout convergence gradient Q,

And, the first readout pre-dispersion gradient F, the first readout back-concentration gradient H and the polarity of the first readout gradient G are opposite, the second readout pre-dispersion gradient J, and the second readout back-convergence gradient Q It is opposite to the polarity of the second readout gradient P.

While the execution unit 31-Z is operating periodically, the filling unit 31-T fills the k-space with the time-reversed steady-state precession signal and the echo-translation signal obtained by the analog-to-digital converter 35, respectively.

After the filling of the k-space is completed, the Fourier transform unit 31-F performs a Fourier transform on the data in the k-space filled with the time-reversed steady-state precession signal to obtain a magnetic resonance corresponding to the time-reversed steady-state precession signal. The image, and the Fourier transform unit 31-F performs Fourier transform on the data in the k-space filled with the echo translation signal to obtain a magnetic resonance image corresponding to the echo translation signal.

Finally, output device 36 outputs the two magnetic resonance images.

It should be noted that, in order to make the acquired time reversal steady state precession signal and echo translation signal cover the entire k space for the purpose of two-dimensional imaging, the circulation unit 31-X periodically works in the control execution unit 31-Z. At the same time, it is also responsible for the following work: each time the execution unit 31-Z completes a duty cycle, the cycle unit 31-X changes the moments of the first phase encode gradient U and the first back-convergence gradient V, that is, in any one working cycle The first phase encoding gradient U is the same as the first back-concentration gradient V, and the first phase encoding gradient U and the first back-concentration gradient V undergo a change every time a duty cycle is experienced.

In the duty cycle shown in FIG. 5, the time reversal steady state precession signal is acquired in the first repetition period, and the echo translation signal is acquired in the second repetition period.

Optionally, in the working cycle of the execution unit 31-Z, the echo translation signal may also be acquired in the first repetition period, and the time-reversed steady-state precession signal is acquired in the second repetition period, which is described below in conjunction with FIG. Types of work cycles.

(1) The execution unit 31-Z triggers the fifth processing unit 315 at the beginning of the second repetition period. The fifth processing unit 315 controls the pulse transmitting coil 33 to emit a radio frequency pulse immediately after the trigger, while controlling the gradient coil 32 to apply the first layer selection gradient A in the slice selection direction.

(2) After the execution unit 31-Z triggers the fifth processing unit 315, the sixth processing unit 316 is triggered. After the triggering, the sixth processing unit 316 immediately controls the gradient coil 32 to apply the fourth layer selection gradient D in the layer selection direction, the first phase encoding gradient U in the phase encoding direction, and the second reading in the read direction. A pre-dispersion gradient J is derived.

(3) After the execution unit 31-Z triggers the sixth processing unit 316, the seventh processing unit 317 is triggered. The seventh processing unit 317 immediately controls the gradient coil 32 to apply the second readout gradient P in the readout direction after the trigger, while controlling the pulse receiving coil 34 to acquire the magnetic resonance signal, and controlling the analog to digital converter 35 to the currently acquired magnetic resonance. The signal is analog-to-digital converted to obtain an echo translation signal.

(4) After the execution unit 31-Z triggers the seventh processing unit 317, the eighth processing unit 318 is triggered. The eighth processing unit 318, after triggering, immediately controls the gradient coil 32 to apply a second readout backgrading gradient Q in the readout direction, a first backscattering gradient V in the phase encoding direction, and a fifth level selection in the slice selection direction. Gradient E.

(5) The execution unit 31-Z triggers the first processing unit 311 at the start of the first repetition period. Immediately after the triggering, the first processing unit 311 controls the pulse transmitting coil 33 to emit a radio frequency pulse while controlling the gradient coil 32 to apply the first layer selection gradient A in the slice selection direction.

(6) After the execution unit 31-Z triggers the first processing unit 311, the second processing unit 312 is triggered. Immediately after the triggering, the second processing unit 312 controls the gradient coil 32 to apply the second layer selection gradient B in the slice selection direction, the first phase encoding gradient U in the phase encoding direction, and the first readout pre-distribution in the readout direction. Phase gradient F.

(7) After the execution unit 31-Z triggers the second processing unit 312, the third processing unit 313 is triggered. The third processing unit 313 immediately controls the gradient coil 32 to apply the first readout gradient G in the readout direction after the trigger, while controlling the pulse receiving coil 34 to acquire the magnetic resonance signal, and controlling the analog to digital converter 35 to the currently acquired magnetic The resonant signal is analog-to-digital converted to obtain a time-reversed steady-state precession signal.

(8) After the execution unit 31-Z triggers the third processing unit 313, the fourth processing unit 314 is triggered. The fourth processing unit 314 immediately controls the gradient coil 32 to apply a first readout back-concentration gradient H in the readout direction, a first back-concentration gradient V in the phase-encoding direction, and a third-level selection in the slice selection direction. Gradient C.

In the duty cycle shown in Figure 6, each gradient also needs to meet the following conditions:

M _B +M _C =M _D +M _E

M _A /2+M _B +M _C +M _A +M _D =0

M _A /2+M _D +M _E -M _B =0

M _U =-M _V

M _F +M _G +M _H =0

M _J +M _P +M _Q =0

It should be noted that, when the execution unit 31-Z periodically operates, the duty cycle shown in FIG. 5 may always be used, or the duty cycle shown in FIG. 6 may always be used, and the time shown in FIG. 5 may also be used. Work cycle, sometimes using the work cycle shown in Figure 6.

If the Free Induction Decay (FID) signal of the RF pulse continues to the time of acquiring the magnetic resonance signal because it is not completely attenuated, it will cause interference to the acquired magnetic resonance signal. Optionally, in order to make the free induction attenuation signal of the radio frequency pulse does not affect the acquisition of the magnetic resonance signal, the first layer selection gradient A, the second layer selection gradient B, and the fourth layer selection gradient D also satisfy the following conditions:

|M _A /2+M _B |≥|M _A /2|,|M _A /2+M _D |≥|M _A /2| (Condition 1)

Optionally, in order to satisfy the above condition 1, the first layer selection gradient A, the second layer selection gradient B, the third layer selection gradient C, the fourth layer selection gradient D, and the fifth layer selection gradient E may satisfy the following relationship:

M _B =-M _A ,

M _C =-M _A /2,

M _D =0,

M _E = -3M _A /2.

Optionally, in order to satisfy the above condition 1, the first layer selection gradient A, the second layer selection gradient B, the third layer selection gradient C, the fourth layer selection gradient D, and the fifth layer selection gradient E may also satisfy the following relationship. :

M _B =M _A /2,

M _C =-M _A /2,

M _D = -3M _A /2,

M _E = 3M _A /2.

In order to ensure that the two magnetic resonance images finally obtained (corresponding to the time-reversed steady-state precession signal and the echo translation signal respectively) have the same resolution and have a better flow compensation effect, optionally, the first The readout pre-diffusion phase gradient F, the first readout gradient G, the first readout back-concentration gradient H, the second readout pre-dispersion phase gradient J, the second readout gradient P, and the second readout back-convergence gradient Q are satisfied The relationship is as follows: M _F = M _J = M _H = M _Q = - M _G /2 = -M _P /2.

In order to obtain a three-dimensional magnetic resonance image, optionally, when the second processing unit 312 and the sixth processing unit 316 are triggered, the gradient coil 32 is further controlled to apply a second phase encoding gradient S in the slice selection direction, the fourth processing unit 314 and the When the eight processing unit 318 is triggered, the gradient coil 32 is further controlled to apply a second convergence gradient T in the layer selection direction; wherein the moment M _{s of the} second phase encoding gradient S and the moment M T of the second convergence gradient _T satisfy the following relationship :M _s =−M _T , and, in order to make the acquired time reversal, the steady state precession signal and the echo translation signal cover the entire k space in three dimensions for the purpose of three-dimensional imaging, and the cyclic unit 31-X is executed in control. While the unit 31-Z is working periodically, it is also responsible for changing the moments of the second phase encoding gradient S and the second back convergence gradient T each time the execution unit 31-Z completes one duty cycle, that is, It is said that the first phase encoding gradient U and the first back-concentration gradient V are the same in any one working cycle, and the first phase encoding gradient U and the first back-concentration gradient V are changed once every one working cycle.

Exemplary method

Having described the apparatus of the exemplary embodiment of the present invention, next, a magnetic resonance imaging method of an exemplary embodiment of the present invention will be described with reference to FIGS. 1, 2, and 7.

FIG. 7 is a schematic flow chart of a magnetic resonance imaging method according to an embodiment of the present invention. The flow of the magnetic resonance imaging method will be described below with reference to the figure.

Step 701, starting the magnetic resonance imaging apparatus.

Step 702, the processor reads various parameters, such as: a field of view of the readout direction, a thickness of the excitation layer, a resolution of the magnetic resonance image, a flip angle of the radio frequency pulse, a duration of the repetition period, a number of codes of the phase encoding, and What type of duty cycle is used by the execution unit (first acquisition of the time-reversed steady-state precession signal, acquisition of the echo translation signal, or acquisition of the echo translation signal and acquisition of the time-reversed steady-state precession signal).

Step 703, the execution unit determines the type of the current work cycle according to the read parameter (alternative), if it is of the type shown in FIG. 5 (first collects the time reversal steady state precession signal and collects the echo translation signal) Then, step 704 is performed, if it is of the type shown in FIG. 6 (the acquisition time reversal steady state precession signal is acquired after the echo translation signal is first collected), then Go to step 705. Optionally, the parameter may be set such that the execution unit always works according to the duty cycle as shown in FIG. 5, or may always work according to the work cycle as shown in FIG. 6, and may also work as shown in FIG. Periodic work, sometimes working according to the work cycle shown in Figure 6.

Step 704 includes:

In step 7041, the pulse transmitting coil applies a radio frequency pulse, and the gradient coil applies a first level selection gradient A in the layer selection direction.

Step 7042, the gradient coil applies a second level selection gradient B in the layer selection direction, a first phase encoding gradient U in the phase encoding direction, and a first readout pre-dispersion gradient F in the read direction. Alternatively, the gradient coil may also apply a second phase encoding gradient S in the slice selection direction and a second back condensation gradient T in the slice selection direction.

Step 7043, the gradient coil applies a first readout gradient G in the readout direction, and the pulse receiving signal acquires the magnetic resonance signal, and the analog-to-digital converter performs analog-to-digital conversion on the currently acquired magnetic resonance signal to obtain a time-reversed steady state. Dynamic signal.

In step 7044, the gradient coil applies a first readout back-concentration gradient H in the readout direction, a first back-concentration gradient V in the phase-encoding direction, and a third-level selection gradient C in the slice-selection direction. Step 705 includes:

Step 7051, the pulse transmitting coil applies the radio frequency pulse, and the gradient coil applies a first layer selection gradient A in the layer selection direction.

Step 7052, the gradient coil applies a fourth level selection gradient D in the layer selection direction, a first phase encoding gradient U in the phase encoding direction, and a second readout pre-scatter phase gradient J in the readout direction. Alternatively, the gradient coil may also apply a second phase encoding gradient S in the slice selection direction and a second back condensation gradient T in the slice selection direction.

Step 7053, the gradient coil applies a second readout gradient P in the readout direction, and the pulse receiving coil acquires the magnetic resonance signal, and the analog-to-digital converter performs analog-to-digital conversion on the currently acquired magnetic resonance signal to obtain an echo translation signal;

In step 7054, the gradient coil applies a second readout convergence gradient Q in the readout direction, a first backscatter gradient V in the phase encoding direction, and a fifth layer selection gradient E in the slice selection direction.

Step 706, the filling unit fills the k-space with the time-reversed steady-state precession signal that has been acquired, and fills the k-space with the echo translation signal that has been acquired.

Step 707, the Fourier transform unit determines whether the k-space is filled in real time, and if the filling is completed, performs Fourier transform on the data in the k-space to obtain a corresponding magnetic resonance image.

Step 708: The loop unit determines, according to the read parameters, whether the total number of cycles completed by the execution unit reaches the number of codes of the phase encoding. If not, step 709 is performed, and if so, the magnetic resonance imaging ends.

Step 709, changing the moments of the first phase encoding gradient U and the first back convergence gradient V, and returning to step 703. Optionally, when the second phase encoding gradient S and the second back-concentration gradient T are applied in step 704 or step 705, step 709 also needs to change the moments of the second phase encoding gradient S and the second back-concentration gradient T.

Exemplary implementation case

Having described the apparatus and method of the exemplary embodiment of the present invention, next, the magnetic resonance image effect obtained by the exemplary embodiment of the present invention will be described with reference to FIG.

This exemplary embodiment performed three magnetic resonance imaging processes using the same magnetic resonance imaging device, namely:

1. Using the exemplary method of the present invention to simultaneously acquire a time-reversed steady state precession signal and an echo translation signal to obtain a magnetic resonance image as shown in (a) and (b) of FIG.

2. The time-reversed steady-state precession signal is acquired by using the magnetic resonance imaging pulse sequence commonly used in the industry, and the magnetic resonance image shown in (c) of FIG. 8 is obtained.

3. The echo translation signal is acquired by using the magnetic resonance imaging pulse sequence commonly used in the industry, and the magnetic resonance image shown in (d) of FIG. 8 is obtained.

When the magnetic resonance imaging apparatus performs the above three magnetic resonance imaging processes, the same parameters are:

Field of view in the readout direction: 384mm

Field of view in the phase direction: 384mm

Excitation layer thickness: 5mm

Magnetic resonance image resolution: 384*384

Flip angle of RF pulse: 20degree

Repeat period: 4.5ms

Echo time: 2.35ms

Acquisition bandwidth: 592Hz/Dixel

It should be noted that although several elements of the magnetic resonance imaging apparatus are mentioned in the above detailed description, such division is merely not mandatory. In fact, according to an embodiment of the invention, two or more of the units described above Features and functions can be embodied in one unit. Conversely, the features and functions of one unit described above may be further divided into multiple units.

Furthermore, although the operation of the method of the present invention is described in a particular order in the figures, this is not a requirement or implied that the operations must be performed in the specific order, or all the operations shown must be performed to achieve the desired results. Additionally or alternatively, certain steps may be omitted, multiple steps being combined into one step, and/or one step being broken down into multiple steps.

While the spirit and principles of the present invention have been described with reference to the specific embodiments of the present invention, it is understood that the invention is not limited to the specific embodiments disclosed. Benefits, this division is only for the convenience of expression. The invention is intended to cover various modifications and equivalents

Those skilled in the art can also understand that the various illustrative logical blocks, units, and steps listed in the embodiments of the present invention can be implemented by electronic hardware, computer software, or a combination of the two. To clearly illustrate the interchangeability of hardware and software, the various illustrative components, units and steps described above have generally described their functions. Whether such functionality is implemented by hardware or software depends on the design requirements of the particular application and the overall system. A person skilled in the art can implement the described functions using various methods for each specific application, but such implementation should not be construed as being beyond the scope of the embodiments of the present invention.

The various illustrative logic blocks, or units, or devices described in the embodiments of the invention may be implemented by general purpose processors, digital signal processors, application specific integrated circuits (ASICs), field programmable gate arrays or other programmable logic. Devices, discrete gate or transistor logic, discrete hardware components, or any combination of the above are designed to implement or operate the functions described. A general purpose processor may be a microprocessor. Alternatively, the general purpose processor may be any conventional processor, controller, microcontroller, or state machine. The processor may also be implemented by a combination of computing devices, such as a digital signal processor and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a digital signal processor core, or any other similar configuration. achieve.

The steps of the method or algorithm described in the embodiments of the present invention may be directly embedded in hardware, a software module executed by a processor, or a combination of the two. The software modules can be stored in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium in the art. Illustratively, the storage medium can be coupled to the processor such that the processor can read information from the storage medium and can write information to the storage medium. Optionally, the storage medium can also be integrated To the processor. The processor and the storage medium may be disposed in an ASIC, and the ASIC may be disposed in the user terminal. Alternatively, the processor and the storage medium may also be disposed in different components in the user terminal.

In one or more exemplary designs, the above-described functions described in the embodiments of the present invention may be implemented in hardware, software, firmware, or any combination of the three. If implemented in software, these functions may be stored on a computer readable medium or transmitted as one or more instructions or code to a computer readable medium. Computer readable media includes computer storage media and communication media that facilitates the transfer of computer programs from one place to another. The storage medium can be any available media that any general purpose or special computer can access. For example, such computer-readable media can include, but is not limited to, RAM, ROM, EEPROM, CD-ROM or other optical disk storage, disk storage or other magnetic storage device, or any other device or data structure that can be used for carrying or storing Other media that can be read by a general purpose or special computer, or a general purpose or special processor. In addition, any connection can be appropriately defined as a computer readable medium, for example, if the software is from a website site, server, or other remote source through a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL) Or wirelessly transmitted in, for example, infrared, wireless, and microwave, is also included in the defined computer readable medium. The disks and discs include compact disks, laser disks, optical disks, DVDs, floppy disks, and Blu-ray disks. Disks typically replicate data magnetically, while disks typically optically replicate data with a laser. Combinations of the above may also be included in a computer readable medium.

Claims

A magnetic resonance imaging method, comprising:

Performing a step periodically according to a duty cycle until the total number of cycles for performing the step reaches a preset number of phase codes;

While periodically performing the steps, filling the k-space with the obtained time-reversed steady-state precession signal and the echo translation signal;

After the filling is completed, performing Fourier transform on the data of the k space to obtain a magnetic resonance image;

The steps include sub-step 11 to sub-step 18:

Sub-step 11, applying a radio frequency pulse while applying a first level selection gradient A;

Sub-step 12, applying a second level selection gradient B, a first phase encoding gradient U, and a first readout pre-dispersion gradient F;

Sub-step 13, applying a first readout gradient G, simultaneously acquiring a magnetic resonance signal, and performing analog-to-digital conversion on the currently acquired magnetic resonance signal to obtain a time-reversed steady-state precession signal;

Sub-step 14, applying a first readout back-concentration gradient H, a first back-concentration gradient V, and a third-level selection gradient C;

Sub-step 15, applying the radio frequency pulse while applying a first layer selection gradient A;

Sub-step 16, applying a fourth level selection gradient D, a first phase encoding gradient U, and a second readout pre-dispersion gradient J;

Sub-step 17, applying a second readout gradient P, simultaneously acquiring a magnetic resonance signal, and performing analog-to-digital conversion on the currently acquired magnetic resonance signal to obtain an echo translation signal;

Sub-step 18, applying a second readout back-concentration gradient Q, a first back-concentration gradient V, and a fifth-level selection gradient E;

The first layer selection gradient A, the second layer selection gradient B, the third layer selection gradient C, the fourth layer selection gradient D, and the fifth layer selection gradient E are all applied to the layer selection direction, and satisfy the following relationship:

M B +M C =M D +M E ,

M A /2+M B +M C +M A +M D =0,

M A /2+M D +M E -M B =0,

M A is the moment at which the gradient A is selected at the first level.

M B is the moment of the second level selecting the gradient B,

M C is the moment at which the third level selects the gradient C,

M D is the moment of the fourth level selecting the gradient D,

M E is the moment at which the gradient E is selected at the fifth level.

The first phase encoding gradient U and the first back-concentration gradient V are both applied to the phase encoding direction, and satisfy the following relationship:

M U =-M V ,

M U is the moment of the first phase encoding gradient U,

M V is the moment of the first back convergence gradient V;

The first readout pre-dispersion phase gradient F, the first readout gradient G, the first readout back-concentration gradient H, the second readout pre-dispersion phase gradient J, the second readout gradient P, and the second readout back The poly gradient Q is applied to the readout direction and satisfies the following relationship:

The first readout pre-dispersion phase gradient F, the first readout back-concentration gradient H is opposite to the polarity of the first readout gradient G, the second readout pre-dispersion gradient J, and the second readout back-convergence gradient Q Opposite to the polarity of the second readout gradient P,

M F +M G +M H =0,

M J +M P +M Q =0,

M F is the first moment to read the pre-dispersion phase gradient F,

M G is the moment of the first readout gradient G,

M H is the moment at which the first readback gradient H is read,

M J is the moment of the second readout pre-dispersion gradient J,

M P is the moment of the second readout gradient P,

M Q is the moment of the second readout convergence gradient Q;

The duty cycle includes two repetition periods;

When the step is performed, the sub-steps 11 to 14 are sequentially performed in the first repetition period of the work cycle, and the sub-steps 15 to 18 are sequentially performed in the second repetition period of the work cycle. Alternatively, the sub-step 15 to the sub-step 18 are sequentially executed in the first repetition period of the work cycle, and the sub-step 11 to the sub-step 14 are sequentially executed in the second repetition period of the work cycle; and each completion For one duty cycle, the moments of the first phase encoding gradient U and the first back-concentration gradient V are changed.
The magnetic resonance imaging method according to claim 1, wherein the first layer selection gradient A, the second layer selection gradient B, and the fourth layer selection gradient D further satisfy the following relationship:

|M A /2+M B |≥|M A /2|,

|M A /2+M D |≥|M A /2|.
The magnetic resonance imaging method according to claim 2, wherein the first layer selection gradient A, the second layer selection gradient B, the third layer selection gradient C, the fourth layer selection gradient D, and the fifth layer selection gradient E Meet the following relationship:

M B =-M A ,

M C =-M A /2,

M D =0,

M E = -3M A /2.
The magnetic resonance imaging method according to claim 2, wherein the first layer selection gradient A, the second layer selection gradient B, the third layer selection gradient C, the fourth layer selection gradient D, and the fifth layer selection gradient E Meet the following relationship:

M B =M A /2,

M C =-M A /2,

M D = -3M A /2,

M E = 3M A /2.
The magnetic resonance imaging method according to claim 1, wherein said first readout pre-dispersion gradient F, first readout gradient G, first readout back-concentration gradient H, second readout pre-dispersion gradient J, the second readout gradient P, and the second readout convergence gradient Q satisfy the following relationship:

M F = M J = M H = M Q = - M G /2 = -M P /2.
The magnetic resonance imaging method according to claim 1, wherein

The sub-step 12 and sub-step 16 further include: applying a second phase encoding gradient S in the layer selection direction;

The sub-step 14 and sub-step 18 further include: applying a second back-concentration gradient T in the layer selection direction;

The second phase encoding gradient S and the second back convergence gradient T satisfy the following relationship:

M S =-M T ,

M S is the moment of the second phase encoding gradient S,

M T is the moment of the second back convergence gradient T;

The magnetic resonance imaging method further includes changing a moment of the second phase encoding gradient S and the second back convergence gradient T every time one duty cycle is completed.
A magnetic resonance imaging apparatus, comprising: a processor, a gradient coil, a pulse transmitting coil, a pulse receiving coil, an analog to digital converter, and an output device;

The processor includes:

a first processing unit configured to control the pulse transmitting coil to emit a radio frequency pulse while controlling the gradient coil to apply a first layer selection gradient A;

a second processing unit, configured to control the gradient coil to apply a second layer selection gradient B, a first phase encoding gradient U, and a first readout pre-dispersion gradient F;

a third processing unit configured to control the gradient coil to apply a first readout gradient G while controlling the pulse receiving coil to acquire a magnetic resonance signal, and controlling the analog to digital converter to perform a mode on the currently acquired magnetic resonance signal Number conversion to obtain a time-reversed steady-state precession signal;

a fourth processing unit, configured to control the gradient coil to apply a first readout back-concentration gradient H, a first back-concentration gradient V, and a third-level selection gradient C;

a fifth processing unit, configured to control the pulse transmitting coil to emit a radio frequency pulse while controlling the gradient coil to apply a first level selection gradient A;

a sixth processing unit, configured to control the gradient coil to apply a fourth layer selection gradient D, a first phase encoding gradient U, and a second readout pre-dispersion phase gradient J;

a seventh processing unit configured to control the gradient coil to apply a second readout gradient P while controlling the pulse receiving coil to acquire a magnetic resonance signal, and controlling the analog to digital converter to perform a mode on the currently acquired magnetic resonance signal Number conversion to obtain an echo translation signal;

The eighth processing unit is configured to control the gradient coil to apply a second readout back-concentration Q, a first back-concentration gradient V, and a fifth-level selection gradient E;

The first layer selection gradient A, the second layer selection gradient B, the third layer selection gradient C, the fourth layer selection gradient D, and the fifth layer selection gradient E are all applied to the layer selection direction, and satisfy the following relationship:

M B +M C =M D +M E ,

M A /2+M B +M C +M A +M D =0,

M A /2+M D +M E -M B =0,

M A is the moment at which the gradient A is selected at the first level.

M B is the moment of the second level selecting the gradient B,

M C is the moment at which the third level selects the gradient C,

M D is the moment of the fourth level selecting the gradient D,

M E is the moment at which the gradient E is selected at the fifth level;

The first phase encoding gradient U and the first back-concentration gradient V are both applied to the phase encoding direction, and satisfy the following relationship:

M U =-M V ,

M U is the moment of the first phase encoding gradient U,

M V is the moment of the first back convergence gradient V;

The first readout pre-dispersion phase gradient F, the first readout gradient G, the first readout back-concentration gradient H, the second readout pre-dispersion phase gradient J, the second readout gradient P, and the second readout back The poly gradient Q is applied to the readout direction and satisfies the following relationship:

The first readout pre-dispersion phase gradient F, the first readout back-concentration gradient H is opposite to the polarity of the first readout gradient G, the second readout pre-dispersion gradient J, and the second readout back-convergence gradient Q Opposite to the polarity of the second readout gradient P,

M F +M G +M H =0,

M J +M P +M Q =0,

M F is the first moment to read the pre-dispersion phase gradient F,

M G is the moment of the first readout gradient G,

M H is the moment at which the first readback gradient H is read,

M J is the moment of the second readout pre-dispersion gradient J,

M P is the moment of the second readout gradient P,

M Q is the moment of the second readout convergence gradient Q;

The processor further includes:

The execution unit is configured to periodically operate according to a duty cycle, the work cycle includes two repetition periods, and the execution unit sequentially triggers the first processing unit to the fourth processing unit in the first repetition period of the working period thereof The fifth processing unit to the eighth processing unit are sequentially triggered in the second repetition period of the working cycle, or the execution unit sequentially triggers the fifth processing unit to the eighth processing unit in the first repetition period of the working cycle. And triggering the first processing unit to the fourth processing unit in sequence in the second repetition period of the working cycle;

a loop unit configured to control the execution unit to periodically operate until a total number of cycles completed by the execution unit reaches a preset number of phase codes, wherein the cycle unit changes each time the execution unit completes one duty cycle a moment of the first phase encoding gradient U and the first back convergence gradient V;

a clock, providing a clock signal to the execution unit and the loop unit, so that the execution unit and the loop unit determine a start time and an end time of each repetition period;

a filling unit configured to fill a k-space with a time-reversed steady-state precession signal and an echo translation signal obtained by the analog-to-digital converter;

a Fourier transform unit, configured to perform Fourier transform on the data in the filled k-space to obtain a magnetic resonance image;

The output device is arranged to output the magnetic resonance image.
The magnetic resonance imaging apparatus according to claim 7, wherein said first layer selection gradient A, second layer selection gradient B, and fourth layer selection gradient D further satisfy the following relationship:

|M A /2+M B |≥|M A /2|,

|M A /2+M D |≥|M A /2|.
The magnetic resonance imaging apparatus according to claim 8, wherein said first layer selection gradient A, second layer selection gradient B, third layer selection gradient C, fourth layer selection gradient D, fifth layer selection gradient E Meet the following relationship:

M B =-M A ,

M C =-M A /2,

M D =0,

M E = -3M A /2.
The magnetic resonance imaging apparatus according to claim 8, wherein said first layer selection gradient A, second layer selection gradient B, third layer selection gradient C, fourth layer selection gradient D, fifth layer selection gradient E Meet the following relationship:

M B =M A /2,

M C =-M A /2,

M D = -3M A /2,

M E = 3M A /2.
The magnetic resonance imaging apparatus according to claim 7, wherein said first readout pre-dispersion gradient F, first readout gradient G, first readout back-concentration gradient H, second readout pre-dispersion gradient J, the second readout gradient P, and the second readout convergence gradient Q satisfy the following relationship:

M F = M J = M H = M Q = - M G /2 = -M P /2.
The magnetic resonance imaging apparatus according to claim 7, wherein

The second processing unit and the sixth processing unit are further configured to: control the gradient coil to apply a second phase encoding gradient S;

The fourth processing unit and the eighth processing unit are further configured to: control the gradient coil to apply a second back-concentration gradient T;

The second phase encoding gradient S and the second back convergence gradient T are all applied to the layer selection direction, and the following relationship is satisfied:

M S =-M T ,

M S is the moment of the second phase encoding gradient S,

M T is the moment of the second back convergence gradient T;

The loop unit is further configured to change the moments of the second phase encoding gradient S and the second back convergence gradient T each time the execution unit completes one duty cycle.