Magnetic resonance frequency calibration method and magnetic resonance device

Abstract

The invention relates to a magnetic resonance frequency calibration method and a magnetic resonance device.The method is applied to the magnetic resonance device.The method comprises the steps that an imaging sequence and a calibration sequence are applied to an imaging object; the calibration sequence is located between two adjacent imaging sequences; the imaging sequence is a functional magnetic resonance elastography sequence; obtaining a first echo signal and a second echo signal corresponding to the current calibration sequence, and determining a frequency drift amount according to the first echo signal and the second echo signal; and calibrating the reference frequency of the magnetic resonance device according to the frequency drift amount, and applying an imaging sequence adjacent to the current calibration sequence to the imaging object based on the calibrated reference frequency. According to the magnetic resonance frequency calibration method provided by the invention, calibration of the reference frequency of the magnetic resonance device with short repetition time can be realized.

Description

Technical Field

[0001] The present application relates to the field of imaging technology, and in particular to a magnetic resonance frequency calibration method and a magnetic resonance device. Background Art

[0002] When using a magnetic resonance device for long-term sequence scanning, the vibration caused by the continuous switching of the current will generate heat, which will cause the reference frequency of the magnetic resonance device to drift. The accuracy of the reference frequency will directly affect the quality of the scanned image. For example, the drift of the reference frequency will cause the image position to shift, the fat suppression effect is poor, etc., which will affect the research results based on the image. Especially for imaging sequences that require a very short repetition time, such as functional magnetic resonance elastography (fMRE) sequences, the signal of the magnetic resonance component is weak and easily affected by the interference of the reference frequency. However, traditional technologies lack a method for calibrating the frequency drift of magnetic resonance equipment that requires a very short repetition time. Summary of the invention

[0003] Based on this, it is necessary to provide a magnetic resonance frequency calibration method and a magnetic resonance device that can calibrate the frequency drift of a magnetic resonance device with a very short repetition time in order to solve the above technical problems.

[0004] In a first aspect, the present application provides a magnetic resonance frequency calibration method, which is applied to a magnetic resonance device, and the method comprises:

[0005] Applying an imaging sequence and a calibration sequence to an imaging subject; the calibration sequence is located between two adjacent imaging sequences; and the imaging sequence is a functional magnetic resonance elastography sequence;

[0006] Acquire a first echo signal and a second echo signal corresponding to a current calibration sequence, and determine a frequency drift amount according to the first echo signal and the second echo signal;

[0007] The reference frequency of the magnetic resonance device is calibrated according to the frequency drift amount, and an imaging sequence adjacent to the current calibration sequence is applied to the imaging subject based on the calibrated reference frequency.

[0008] In one embodiment, a first radio frequency pulse of the imaging sequence is the same as a second radio frequency pulse of the calibration sequence, and a first repetition time of the imaging sequence is the same as a second repetition time of the calibration sequence.

[0009] In one embodiment, applying the imaging sequence to an imaging subject comprises:

[0010] A first radio frequency pulse is applied to the imaging subject, and a first gradient is applied to the imaging subject.

[0011] In one embodiment, the first gradient includes a first slice selection gradient, a phase encoding gradient, a first readout encoding gradient, and a motion encoding gradient, applying a first radio frequency pulse to the imaging object, and applying the first gradient to the imaging object includes:

[0012] Applying a first slice selection gradient while applying a first radio frequency pulse to the imaging object;

[0013] After applying the first layer selection gradient, applying a motion coding gradient to the imaged object;

[0014] After applying the motion encoding gradient, a phase encoding gradient and a first readout encoding gradient are applied to the imaging object.

[0015] In one embodiment, applying a calibration sequence to an imaging subject comprises:

[0016] A second radio frequency pulse is applied to the imaging subject, and a second gradient is applied to the imaging subject.

[0017] In one embodiment, the second gradient includes a second slice selection gradient and a second readout encoding gradient, applying a second radio frequency pulse to the imaging object, and applying the second gradient to the imaging object includes:

[0018] applying a second slice selection gradient while applying a second radio frequency pulse to the imaging object;

[0019] A second readout encoding gradient is applied to the imaging object.

[0020] In one embodiment, determining the frequency drift amount according to the first echo signal and the second echo signal includes:

[0021] Converting the first echo signal and the second echo signal respectively to obtain a first complex signal and a second complex signal in a complex domain;

[0022] determining a phase difference according to the first complex signal and the second complex signal;

[0023] The frequency drift amount is determined according to the phase difference and the time difference between the first echo signal and the second echo signal.

[0024] In one embodiment, calibrating the reference frequency of the magnetic resonance device according to the frequency drift includes:

[0025] Acquiring a reference frequency and an initial frequency offset of a magnetic resonance device;

[0026] The calibrated reference frequency is determined according to the reference frequency, the initial frequency offset and the frequency drift.

[0027] In one embodiment, the method further comprises:

[0028] The third echo signal corresponding to each imaging sequence is acquired, and the third echo signal is reconstructed to obtain a magnetic resonance image of the imaging object.

[0029] In a second aspect, an embodiment of the present application provides a magnetic resonance device, including a magnetic resonance component and a control component, wherein the control component is communicatively connected to the magnetic resonance component; the control component is used to execute the steps of the method provided in the first aspect above.

[0030] In a third aspect, the present application further provides a magnetic resonance frequency calibration device, the device comprising:

[0031] An applying module, used for applying an imaging sequence and a calibration sequence to an imaging object; the calibration sequence is located between two adjacent imaging sequences; and the imaging sequence is a functional magnetic resonance elastography sequence;

[0032] An acquisition module, used for acquiring a first echo signal and a second echo signal corresponding to a current calibration sequence, and determining a frequency drift amount according to the first echo signal and the second echo signal;

[0033] The reference frequency of the magnetic resonance device is calibrated according to the frequency drift, and an imaging sequence adjacent to the current calibration sequence is applied to the imaging subject based on the calibrated reference frequency.

[0034] In a fourth aspect, the present application further provides a computer device, the computer device comprising a memory and a processor, the memory storing a computer program, and the processor implementing the steps of the method provided in the first aspect above when executing the computer program.

[0035] In a sixth aspect, the present application further provides a computer-readable storage medium, wherein a computer program is stored on the computer-readable storage medium, and when the computer program is executed by a processor, the steps of the method provided in the first aspect are implemented.

[0036] In a seventh aspect, the present application further provides a computer program product, including a computer program, which implements the steps of the method provided in the first aspect when executed by a processor.

[0037] The magnetic resonance frequency calibration method and magnetic resonance device are applied to the magnetic resonance device. The method applies an imaging sequence and a calibration sequence to the imaging object; the calibration sequence is located between two adjacent imaging sequences; the imaging sequence is a functional magnetic resonance elastic imaging sequence; the first echo signal and the second echo signal corresponding to the current calibration sequence are obtained, and the frequency drift is determined according to the first echo signal and the second echo signal; the reference frequency of the magnetic resonance device is calibrated according to the frequency drift, and the imaging sequence adjacent to the current calibration sequence is applied to the imaging object based on the calibrated reference frequency. In this embodiment, the frequency drift can be determined according to the first echo signal and the second echo signal corresponding to the current calibration sequence obtained, and the reference frequency of the magnetic resonance device can be calibrated by the frequency drift. In addition, the calibration sequence applied to the imaging object is between two imaging sequences, that is, after a complete imaging sequence scan is completed, the calibration sequence scan is performed, and then the next imaging sequence scan is performed, so that the imaging sequence scan can be performed using the reference frequency calibrated by the frequency drift corresponding to the calibration sequence, which can realize real-time calibration of the reference frequency of the magnetic resonance device, and the influence of the calibration sequence on the time resolution can be ignored, thereby improving the practicality of the magnetic resonance frequency calibration method. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 A diagram showing an application environment of a magnetic resonance frequency calibration method in one embodiment;

[0039] Figure 2 A schematic diagram of a process flow of a magnetic resonance frequency calibration method in one embodiment;

[0040] Figure 3 A schematic diagram of a process flow of a magnetic resonance frequency calibration method in another embodiment;

[0041] Figure 4 A schematic diagram of an imaging sequence and a calibration sequence in one embodiment;

[0042] Figure 5 A schematic diagram of a process flow of a magnetic resonance frequency calibration method in another embodiment;

[0043] Figure 6 A schematic diagram of a process flow of a magnetic resonance frequency calibration method in another embodiment;

[0044] Figure 7 A schematic diagram of a process flow of a magnetic resonance frequency calibration method in another embodiment;

[0045] Figure 8 A schematic diagram of a process flow of a magnetic resonance frequency calibration method in another embodiment;

[0046] Fig. 9is a schematic structural diagram of a magnetic resonance frequency calibration device in one embodiment;

[0047] Fig.10 FIG. 4 is a diagram showing the internal structure of a computer device in one embodiment. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0049] The serial numbers assigned to the components in this article, such as "first", "second", etc., are only used to distinguish the objects described and do not have any order or technical meaning.

[0050] First, before specifically introducing the technical solutions of the embodiments disclosed in the present application, the background technology or technical evolution context on which the embodiments of the present application are based is introduced. In the field of magnetic resonance imaging, when a magnetic resonance device is used for long-term sequence scanning, heat will be generated due to the vibration caused by the continuous switching of the current, which will cause the reference frequency of the magnetic resonance device to drift. The accuracy of the reference frequency directly affects the quality of the scanned image. For example, it will cause image position offset, poor fat suppression effect, etc., which will affect the research results of the staff based on the image. In particular, for imaging sequences with a very short repetition time (TR) (TR about 50ms) required during magnetic resonance imaging, such as functional magnetic resonance elastography (fMRE) sequences, the steady-state signal is very weak and easily disturbed by the reference frequency drift. However, in the traditional technology, a method for calibrating the frequency drift of a magnetic resonance device with a very short repetition time is determined. In this regard, the present application provides a magnetic resonance frequency calibration method.

[0051] The magnetic resonance frequency calibration method provided in the present application can be applied to a magnetic resonance device, the structure of which is as follows: Figure 1 As shown, it includes a magnetic resonance component 104 and a control component 103. The control component 103 can communicate with the magnetic resonance component 104 through a network. The control component 103 can be, but is not limited to, various personal computers, laptops, and tablet computers.

[0052] The technical solution of the present application and how the technical solution of the present application solves the technical problem are described in detail below with specific embodiments.

[0053] In one embodiment, Figure 2As shown, a magnetic resonance frequency calibration method is provided. This embodiment uses the method applied to a control component in a magnetic resonance device as an example. In this embodiment, the method includes the following steps:

[0054] Step 200: applying an imaging sequence and a calibration sequence to an imaging subject; the calibration sequence is located between two adjacent imaging sequences. The imaging sequence is a functional magnetic resonance elastography sequence;

[0055] The imaging object may be an animal body or an imaging phantom. The magnetic resonance component in the magnetic resonance device has a small aperture and can provide a high field strength. After the imaging object is placed on the carrying component (scanning bed) of the magnetic resonance component, the control component sends a control signal to the magnetic resonance component to control the magnetic resonance component to apply an imaging sequence and a calibration sequence to the imaging object. The calibration sequence is located between two adjacent imaging sequences. In other words, after the control component controls the magnetic resonance component to apply the first imaging sequence to the imaging object, the first calibration sequence is applied, the second imaging sequence is applied, and the second calibration sequence is applied, and in this order, the scanning imaging of the imaging object is completed. The signal collected under the imaging sequence is used for imaging, and the signal collected under the calibration sequence is used for calibration. This embodiment does not limit the specific types of imaging sequences and calibration sequences, as long as their functions can be achieved. Among them, the imaging sequence applied by the magnetic resonance component to the imaging object is a functional magnetic resonance elastic imaging sequence that requires a very short repetition time.

[0056] Step 210: Acquire a first echo signal and a second echo signal corresponding to the current calibration sequence, and determine a frequency drift amount according to the first echo signal and the second echo signal.

[0057] After the control component controls the magnetic resonance component to apply the imaging sequence and the calibration sequence to the imaging object, the magnetic resonance component will collect the first echo signal and the second echo signal corresponding to the current calibration sequence. That is, after applying the calibration sequence to the imaging object once, the first echo signal and the second echo signal corresponding to the calibration sequence are collected. The magnetic resonance component sends the collected first echo signal and the second echo signal to the control component. In other words, the calibration sequence is a dual gradient echo calibration sequence. Under the dual gradient echo calibration sequence, the first echo signal and the second echo signal generated by the imaging object can be collected.

[0058] After acquiring the first echo signal and the second echo signal of the imaging object, the control component can determine the frequency drift amount of the reference frequency of the magnetic resonance component according to the first echo signal and the second echo signal. That is, the frequency difference between the first frequency of the magnetic resonance component corresponding to the first echo signal and the second frequency of the magnetic resonance component corresponding to the second echo signal in the current scanning time period. This embodiment does not limit the specific method of determining the frequency drift amount according to the first echo signal and the second echo signal, as long as its function can be achieved.

[0059] In an optional embodiment, the control component can determine the first frequency of the magnetic resonance component corresponding to the first scanning moment according to the first echo signal, and can determine the second frequency of the magnetic resonance component corresponding to the second scanning moment according to the second echo signal; and determine the frequency drift amount according to the frequency difference between the first frequency and the second frequency. The time period between the first scanning moment and the second time moment is the current scanning time period.

[0060] Step 220: calibrate the reference frequency of the magnetic resonance device according to the frequency drift, and apply an imaging sequence adjacent to the current calibration sequence to the imaging subject based on the calibrated reference frequency.

[0061] The reference frequency of the magnetic resonance device refers to the center frequency of the magnetic resonance component in the magnetic resonance device before scanning. After determining the frequency drift of the magnetic resonance component, the control component calibrates the reference frequency of the magnetic resonance component in the magnetic resonance device according to the frequency drift to obtain the calibrated reference frequency.

[0062] In an optional embodiment, the control component determines the calibrated reference frequency by determining the sum of the reference frequency and the frequency drift amount.

[0063] After determining the calibrated reference frequency, the control component applies the next imaging sequence to the imaging object based on the calibrated reference frequency, that is, the frequency of the radio frequency pulses in the next imaging sequence applied is the same as the calibrated reference frequency. The next imaging sequence refers to an imaging sequence adjacent to the current calibration sequence.

[0064] In an optional embodiment, a first imaging sequence and a first calibration sequence are applied to the imaging object, and a first echo signal and a second echo signal corresponding to the first calibration sequence are obtained, so that a frequency drift corresponding to the first calibration sequence can be determined; the sum of the frequency drift and a reference frequency is calculated to obtain a calibrated reference frequency; the calibrated reference frequency is determined as a new reference frequency, and a second imaging sequence and a second calibration sequence are applied to the imaging object based on the new reference frequency; and the above steps are repeated until the scanning of the imaging object is completed.

[0065] The magnetic resonance frequency calibration method provided in the embodiment of the present application is applied to a magnetic resonance device. The method applies an imaging sequence and a calibration sequence to an imaging object; the calibration sequence is located between two adjacent imaging sequences; the imaging sequence is a functional magnetic resonance elastic imaging sequence; the first echo signal and the second echo signal corresponding to the current calibration sequence are obtained, and the frequency drift is determined according to the first echo signal and the second echo signal; the reference frequency of the magnetic resonance device is calibrated according to the frequency drift, and an imaging sequence adjacent to the current calibration sequence is applied to the imaging object based on the calibrated reference frequency. In this embodiment, the frequency drift can be determined according to the first echo signal and the second echo signal corresponding to the current calibration sequence obtained, and the reference frequency of the magnetic resonance device can be calibrated by the frequency drift. In addition, the calibration sequence applied to the imaging object is between two imaging sequences, that is, after a complete imaging sequence scan is completed, the calibration sequence scan is performed, and then the next imaging sequence scan is performed, so that the imaging sequence scan can be performed using the reference frequency calibrated by the frequency drift corresponding to the calibration sequence, which can realize real-time calibration of the reference frequency of the magnetic resonance device, and the influence of the calibration sequence on the time resolution can be ignored, thereby improving the practicality of the magnetic resonance frequency calibration method.

[0066] In one embodiment, the first radio frequency pulse of the imaging sequence is the same as the second radio frequency pulse of the calibration sequence, and the first repetition time of the imaging sequence is the same as the second repetition time of the calibration sequence.

[0067] The first radio frequency pulse of the imaging sequence applied to the imaging object is the same as the second radio frequency pulse applied to the imaging object. Specifically, the type of the first radio frequency pulse is the same as the type of the second radio frequency pulse, and the relevant parameters of the first radio frequency pulse are the same as the relevant parameters of the second radio frequency pulse. For example, the flip angle of the first radio frequency pulse is the same as the flip angle of the second radio frequency pulse, the bandwidth of the first radio frequency pulse is the same as the bandwidth of the second radio frequency pulse, and the frequency of the first radio frequency pulse is the same as the frequency of the second radio frequency pulse.

[0068] The type of radio frequency pulse may include non-selective radio frequency pulse, selective radio frequency pulse, hard pulse, soft pulse and adiabatic pulse, etc. The type of the first radio frequency pulse and the type of the second radio frequency pulse may be any one of them.

[0069] The calibration sequence is located between the first imaging sequence and the second imaging sequence, and the first repetition time of the imaging sequence refers to the time period between the center of the first radio frequency pulse of the first imaging sequence and the center of the second radio frequency pulse of the calibration sequence. The calibration sequence is adjacent to the first imaging sequence. The second repetition time of the calibration sequence refers to the time period between the center of the second radio frequency pulse of the calibration sequence and the center of the first radio frequency pulse of the second imaging sequence. The calibration sequence is adjacent to the second imaging sequence. The first repetition time of the imaging sequence is the same as the second repetition time of the radio frequency pulse. The first repetition time and the second repetition time are approximately 50 ms.

[0070] In this embodiment, the first radio frequency pulse of the imaging sequence applied to the imaging object is the same as the second radio frequency pulse of the calibration sequence applied, and the first repetition time of the imaging sequence is the same as the second repetition time of the calibration sequence, so that the steady state of the signal obtained by long-term scanning can be maintained, thereby improving the accuracy of the determined frequency drift amount, so as to achieve accurate calibration of the reference frequency of the magnetic resonance device, and further improve the quality of the image after imaging.

[0071] In one embodiment, an implementation method of applying an imaging sequence to an imaging object includes:

[0072] A first radio frequency pulse is applied to the imaging subject, and a first gradient is applied to the imaging subject.

[0073] The applied imaging sequence includes a first radio frequency pulse and a first gradient. The control component generates a control signal to the magnetic resonance component, and the magnetic resonance component applies the first radio frequency pulse to the imaging object based on the control signal to excite the hydrogen nuclei in the imaging object so that it produces a magnetic resonance phenomenon; and applies the first gradient to the imaging object to excite the hydrogen nuclei at a fixed position in the imaging object to achieve positioning. This embodiment does not limit the specific types of the applied first radio frequency pulse and the first gradient, as long as their functions can be achieved.

[0074] In one embodiment, the first gradient applied to the imaging object may include a first slice selection gradient, a phase encoding gradient, a first readout encoding gradient, and a motion encoding gradient. In this case, Figure 3 As shown, an implementation method of applying a first radio frequency pulse to an imaging object and applying a first gradient to the imaging object includes the steps of:

[0075] Step 300: Apply a first slice selection gradient while applying a first radio frequency pulse to an imaging object.

[0076] The control component applies a first layer selection gradient to the imaging object while controlling the magnetic resonance component to apply a first radio frequency pulse to the imaging object. The first layer selection gradient is a linearly changing magnetic field applied along a certain axial direction of the imaging object (usually the Z axis, i.e., the up and down direction of the imaging object) on the basis of the main magnetic field. After applying the first radio frequency pulse and the first layer selection gradient to the imaging object, the hydrogen nuclei at different layers of the imaging object are in different magnetic field intensities and their Larmor frequencies are also different. When the frequency of the first radio frequency pulse matches the Larmor frequency of a certain layer of hydrogen nuclei, only the hydrogen nuclei at this layer are excited, thereby achieving layer selection. Applying the first layer selection gradient while applying the first radio frequency pulse means that the first radio frequency pulse is applied during the time period when the first layer selection gradient is applied to the object, and it is not required that the start time of applying the first radio frequency pulse is the same as the start time of applying the first layer selection gradient, and the end time of applying the first radio frequency pulse is the same as the end time of applying the first layer selection gradient.

[0077] Step 310: After applying the first layer selection gradient, applying a motion coding gradient to the imaging object.

[0078] Motion encoding gradients are mainly used to encode and measure the motion of objects in the imaging subject. The basic principle is based on the sensitivity of magnetic resonance signals to magnetic field changes and phase changes caused by object motion.

[0079] After controlling the magnetic resonance component to apply the first slice selection gradient, the control component applies a motion encoding gradient to the imaging object. The motion encoding gradient may be applied immediately after the first slice selection gradient is applied, or the motion encoding gradient may be applied after a first preset time interval after the first slice selection gradient is applied. The gradient direction of the motion encoding gradient may be the same as or different from the axial direction of the first slice selection gradient. Figure 4 As shown, in the selected layer gradient G ss , phase encoding gradient G PE , read out the encoding gradient G RO Motion encoding gradients are applied in all axial directions.

[0080] Step 320: After applying the motion encoding gradient, applying a phase encoding gradient and a first readout encoding gradient to the imaging object.

[0081] The phase encoding gradient can be used to determine the position of hydrogen nuclei in another direction (usually the y-axis, i.e. the front-to-back direction of the imaging object) within the imaging plane of the imaging object. After the first RF pulse excitation, phase encoding gradients of different intensities are applied at different time points, so that the phases of hydrogen nuclei at different y-axis positions change to different degrees. After each application of phase encoding gradients of different intensities, a set of data is collected. After multiple changes in the phase encoding gradient intensity and data collection, sufficient information can be obtained to construct the spatial information of the image in the y-axis direction. Figure 4 As shown, phase encoding gradients of different intensities are applied sequentially according to the order of the arrows.

[0082] The first readout encoding gradient, also known as the first frequency encoding gradient, can be used to apply a linearly changing magnetic field gradient in a specific direction (usually the left and right direction of the imaging object, i.e., the x-axis direction) on the imaging layer selected by the RF pulse excitation. This can make the hydrogen nuclei at different positions generate magnetic resonance signals of different frequencies, and the spatial position of the hydrogen nuclei in the specific direction can be determined based on the magnetic resonance signal.

[0083] After controlling the magnetic resonance component to apply the motion encoding gradient, the control component applies the phase encoding gradient and the first readout encoding gradient to the imaging object. The phase encoding gradient and the first readout encoding gradient may be applied directly after the motion encoding gradient is applied, that is, the end time of the motion encoding gradient is the start time of the phase encoding gradient and the first readout encoding gradient; or the phase encoding gradient and the first readout encoding gradient may be applied at an interval of a second preset time after the motion encoding gradient is applied.

[0084] The phase encoding gradient includes a first phase encoding gradient and a second phase encoding gradient. The direction of the first phase encoding gradient is opposite to that of the second phase encoding gradient. Both the first phase encoding gradient and the second phase encoding gradient are linear gradients. The start time of applying the first phase encoding gradient is the same as the start time of applying the first readout encoding gradient. The start time of applying the second phase encoding gradient can be the same as the end time of applying the first readout encoding gradient, or the second phase encoding gradient can be applied after the end time of applying the first readout gradient and after a third preset time. Figure 4 As shown, the phase encoding gradient includes a first phase encoding gradient close to the motion encoding gradient and a second phase encoding gradient far from the motion encoding gradient. The first phase encoding gradient includes a plurality of phase encoding gradients of different strengths sequentially applied in a first direction according to the order of arrows; the second phase encoding gradient includes a plurality of phase encoding gradients of different strengths sequentially applied in a second direction according to the order of arrows, and the first direction is opposite to the second direction.

[0085] In this embodiment, a first layer selection gradient is applied while applying a first radio frequency pulse to the imaging object; a motion encoding gradient is applied to the imaging object after applying the first layer selection gradient; and a phase encoding gradient and a first readout encoding gradient are applied to the imaging object after applying the motion encoding gradient. In this way, spatial information in various directions of a certain imaging layer of the imaging object can be acquired by applying the radio frequency pulse, the first layer selection gradient, the motion encoding gradient, the phase encoding gradient and the first readout encoding gradient, thereby facilitating the subsequent acquisition of an accurate image of the imaging object.

[0086] In one embodiment, an implementation of applying a calibration sequence to an imaging subject includes:

[0087] A second radio frequency pulse is applied to the imaging subject, and a second gradient is applied to the imaging subject.

[0088] The calibration sequence applied to the imaging object includes a second radio frequency pulse and a second gradient. After the current scanning imaging is completed by applying the imaging sequence to the imaging object, the calibration sequence is applied to the imaging object. The magnetic resonance component applies the second radio frequency pulse to the object based on the control signal sent by the control component, and applies the second gradient to the imaging object to excite the hydrogen nuclei at fixed positions in the imaging object. The description of the second radio frequency pulse can refer to the specific description of the first radio frequency pulse in the above embodiment, and will not be repeated here.

[0089] In one embodiment, the second gradient applied to the imaging object may include a second layer selection gradient and a second readout encoding gradient. Figure 5 As shown, an implementation method involving applying a second radio frequency pulse to an imaging object and applying a second gradient to the imaging object includes the steps of:

[0090] Step 500: applying a second slice selection gradient while applying a second radio frequency pulse to the imaging object.

[0091] The control component applies a second layer selection gradient to the imaging object while controlling the magnetic resonance component to apply the first radio frequency pulse to the imaging object. The gradient magnitude of the second layer selection gradient may be the same as or different from the gradient magnitude of the first layer selection gradient, and the application duration of the second layer selection gradient may be the same as or different from the application duration of the first layer selection gradient. The description of the second layer selection gradient may refer to the description of the first layer selection gradient in the above embodiment, and will not be repeated here.

[0092] Step 510: Apply a second readout encoding gradient to the imaging object.

[0093] The control component controls the magnetic resonance component to apply a second readout encoding gradient to the imaging object, including a first readout encoding sub-gradient and a second readout encoding sub-gradient applied sequentially. The intensity of the first readout encoding sub-gradient may be the same as the intensity of the second readout encoding sub-gradient, and the duration of the second readout encoding sub-gradient may be the same as the duration of the second readout encoding sub-gradient. The intensity of the first readout encoding sub-gradient may be the same as or different from the intensity of the first readout encoding gradient; the duration of the first readout encoding sub-gradient may be the same as or different from the duration of the first readout encoding gradient. The description of the first readout encoding sub-gradient and the second readout encoding sub-gradient may refer to the description of the first readout encoding gradient in the above embodiment, and will not be repeated here. Figure 4As shown, the type of the second radio frequency pulse RF of the calibration sequence is the same as the type of the first radio frequency pulse of the imaging sequence, and the flip angle is the same, both of which are The calibration sequence includes applying a first readout encoder gradient and a second readout encoder gradient in sequence. The first readout encoder gradient corresponds to the collected first echo signal Echo, and the second readout encoder gradient corresponds to the collected second echo signal Echo.

[0094] In this embodiment, a second layer selection gradient is applied while a second radio frequency pulse is applied to the imaging object; a second readout encoding gradient is applied to the imaging object, so that spatial information of a certain imaging layer of the imaging object can be obtained, thereby facilitating subsequent acquisition of a calibration signal and realizing calibration of the reference frequency of the magnetic resonance component in the magnetic resonance device.

[0095] In an optional embodiment, the first gradient of the imaging sequence further includes a first dephasing gradient, and the second gradient of the calibration sequence further includes a second dephasing gradient. The first dephasing gradient and the second dephasing gradient can be applied in at least one of the axial directions of the slice selection gradient, the axial direction of the phase encoding gradient, and the axial direction of the readout encoding gradient. Figure 4 As shown, in the imaging sequence, the gradient applied after the first readout encoding gradient is a dephasing gradient. In the calibration sequence, the gradient applied in the axial direction of the phase encoding gradient is a dephasing gradient. The first dephasing gradient applied in the imaging sequence can remove redundant gradient signals in the imaging process. The second dephasing gradient applied in the calibration sequence can remove redundant gradient signals in the calibration process, thereby improving the accuracy of calibrating the reference frequency of the magnetic resonance component in the magnetic resonance device, thereby improving the quality of the magnetic resonance image of the determined imaging object.

[0096] In one embodiment, Figure 6 As shown, it is related to an implementation method of determining the frequency drift amount according to the first echo signal and the second echo signal, and the implementation method includes:

[0097] Step 600: Convert the first echo signal and the second echo signal respectively to obtain a first complex signal and a second complex signal in a complex domain.

[0098] The first echo signal is a signal collected based on the first readout coder gradient, and the second echo signal is a signal collected based on the second readout coder gradient. After acquiring the first echo signal and the second echo signal, the control component performs Fourier transform on the first echo signal to obtain a first complex signal in the complex domain, and performs Fourier transform on the second echo signal to obtain a second complex signal in the complex domain.

[0099] Assume that the first echo signal is recorded as E n，1 , the second echo signal is recorded as En，2 , perform Fourier transform on the first echo signal to obtain the first complex signal E n，3 , perform Fourier transform on the second echo signal to obtain the second complex signal E n，4 The first complex signal can be expressed as: , the second complex signal can be expressed as . where n represents the number of times the calibration sequence is applied.

[0100] Step 610: Determine a phase difference according to the first complex signal and the second complex signal.

[0101] After determining the first complex signal and the second complex signal, the control component determines a phase difference between the first complex signal and the second complex signal. Specifically, the phase difference can be obtained by conjugate multiplication, and the phase difference can be expressed as: .

[0102] Step 620: Determine the frequency drift amount according to the phase difference and the time difference between the first echo signal and the second echo signal.

[0103] The time difference between the first echo signal and the second echo signal refers to the time difference between the peak of the first echo signal and the peak of the second echo signal. After determining the phase difference between the first complex signal and the second complex signal, the control component can determine the frequency drift amount according to the phase difference and the time difference between the first echo signal and the second echo signal. Specifically, the direct correspondence between the frequency f and the phase angle θ can be expressed as , represents the time difference between the first echo signal and the second echo signal. The frequency drift can be expressed as .

[0104] In this embodiment, the first complex signal and the second complex signal are converted respectively to obtain the first complex signal and the second complex signal in the complex domain; the phase difference is determined according to the first complex signal and the second complex signal; the frequency drift is determined according to the phase difference and the time difference between the first echo signal and the second echo signal. This method for determining the frequency drift is quick and easy to implement, and can improve the practicability of the magnetic resonance frequency calibration method.

[0105] In one embodiment, Figure 7 As shown, it is related to an implementation method of calibrating the reference frequency of the magnetic resonance device according to the frequency drift, and the steps of the implementation method include:

[0106] Step 700: Obtain a reference frequency and an initial frequency offset of a magnetic resonance device.

[0107] The reference frequency of the magnetic resonance device can be the center frequency set by the magnetic resonance device after leaving the factory, or it can be pre-set by the technician. The frequency of the first radio frequency pulse applied to the imaging object needs to be the same as the reference frequency to produce the magnetic resonance phenomenon. The initial frequency offset can be the frequency error of the magnetic resonance device calculated by the staff.

[0108] The reference frequency and initial frequency offset of the magnetic resonance device may be pre-stored in the memory of the control component, and the control component directly obtains them from the memory when needed.

[0109] Step 710: Determine a calibrated reference frequency according to the reference frequency, the initial frequency offset and the frequency drift.

[0110] After acquiring the reference frequency and initial frequency offset of the magnetic resonance device and determining the frequency drift, the control component calibrates the reference frequency according to the initial frequency offset and the frequency drift to obtain the calibrated reference frequency.

[0111] Assuming that the reference frequency is F, the initial frequency offset is f0, and the frequency drift amount determined after applying the first calibration sequence is f1, the reference frequency after calibration, that is, the reference frequency based on which the second imaging sequence is applied, can be expressed as F2=F+f1-f0. By analogy, the frequency drift amount determined after applying the nth calibration sequence is fn, and the reference frequency after calibration, that is, the reference frequency based on which the imaging sequence is applied for the n+1th time, can be expressed as: Fn+1=F'+fn-f0, where F' represents the reference frequency based on which the imaging sequence is applied for the n-1th time.

[0112] In this embodiment, the reference frequency and the initial frequency offset of the magnetic resonance device are used; the reference frequency is calibrated according to the initial frequency offset and the frequency drift to obtain the calibrated reference frequency. This not only can realize the calibration of the reference frequency, but also, in the process of calibration, the initial frequency offset of the magnetic resonance device is taken into consideration, which can improve the accuracy of the calibration of the reference frequency, thereby improving the practicability of the magnetic resonance frequency calibration method.

[0113] In one embodiment, the method further comprises:

[0114] The third echo signal corresponding to each imaging sequence is acquired, and the third echo signal is reconstructed to obtain a magnetic resonance image of the imaging object.

[0115] The control component collects the third echo signals corresponding to each imaging sequence when controlling the magnetic resonance component to apply the imaging sequence to the imaging object, specifically, when applying the first readout encoding gradient. After acquiring the third echo signals corresponding to each imaging sequence, the control component performs image reconstruction processing on each third echo signal to obtain a magnetic resonance image of the imaging object. Specifically, performing Fourier transform on each third echo signal can determine a two-dimensional magnetic resonance image of the imaging object, and performing image matching on the two-dimensional images determined by all the third echo signals can obtain a three-dimensional magnetic resonance image of the imaging object.

[0116] In this embodiment, the third echo signal corresponding to each imaging sequence is acquired and reconstructed to obtain a magnetic resonance image of the imaging object. When a calibration sequence is applied before the imaging sequence, the acquired third echo signal corresponding to the imaging object is more accurate, thereby improving the quality of the magnetic resonance image of the imaging object finally determined.

[0117] See also Figure 8 An embodiment of the present application provides a magnetic resonance frequency calibration method, which is applied to a magnetic resonance device. The magnetic resonance device includes a magnetic resonance component and a control component. The control component is used to perform the following steps:

[0118] Step 800: applying a first imaging sequence and a first calibration sequence to an imaging subject; the first imaging sequence includes a first radio frequency pulse, a first slice selection gradient, a motion encoding gradient, a phase encoding gradient, and a first readout encoding gradient, and the first calibration sequence includes a second radio frequency pulse, a second slice selection gradient, a first readout encoding sub-gradient, and a second readout encoding sub-gradient; the first radio frequency pulse of the first imaging sequence is the same as the second radio frequency pulse of the first calibration sequence, and the first repetition time of the first imaging sequence is the same as the second repetition time of the first calibration sequence; the first imaging sequence is a functional magnetic resonance elastography sequence;

[0119] Step 810: Acquire a first echo signal and a second echo signal corresponding to a first calibration sequence;

[0120] Step 820, performing Fourier transform on the first echo signal and the second echo signal respectively to obtain a first complex signal and a second complex signal;

[0121] Step 830: determine a phase difference between the first complex signal and the second complex signal, and determine a frequency drift amount according to the phase difference and a time difference between the first echo signal and the second echo signal;

[0122] Step 840, obtaining a reference frequency and an initial frequency offset of the magnetic resonance device;

[0123] Step 850: calibrate the reference frequency according to the initial frequency offset and the frequency drift to obtain a calibrated reference frequency;

[0124] Step 860: Use the calibrated reference frequency as the new reference frequency, apply the second imaging sequence and the second calibration sequence to the imaging object, use the second imaging sequence as the new first imaging sequence, use the second calibration sequence as the new first calibration sequence, and return to execute steps 810-850.

[0125] In one embodiment, Figure 1 As shown, a magnetic resonance device is provided, which includes a magnetic resonance component 104 and a control component 103. The control component 103 is in communication connection with the magnetic resonance component 104, and the control component 103 is used to execute the steps of the method provided in the above embodiment.

[0126] It should be understood that, although the various steps in the flowcharts involved in the above-mentioned embodiments are displayed in sequence according to the indication of the arrows, these steps are not necessarily executed in sequence according to the order indicated by the arrows. Unless there is a clear explanation in this article, the execution of these steps does not have a strict order restriction, and these steps can be executed in other orders. Moreover, at least a part of the steps in the flowcharts involved in the above-mentioned embodiments can include multiple steps or multiple stages, and these steps or stages are not necessarily executed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a part of the steps or stages in other steps.

[0127] Based on the same inventive concept, the embodiment of the present application also provides a magnetic resonance frequency calibration device for implementing the magnetic resonance frequency calibration method involved above. The implementation scheme for solving the problem provided by the device is similar to the implementation scheme recorded in the above method, so the specific limitations in one or more embodiments of the magnetic resonance frequency calibration device provided below can refer to the limitations of the magnetic resonance frequency calibration method above, and will not be repeated here.

[0128] In one embodiment, Fig. 9 As shown, a magnetic resonance frequency calibration device 10 is provided, comprising: an application module 11, an acquisition module 12 and a calibration module 13, wherein:

[0129] The applying module 11 is used to apply an imaging sequence and a calibration sequence to the imaging object; the calibration sequence is located between two adjacent imaging sequences; and the imaging sequence is a functional magnetic resonance elastography sequence.

[0130] The acquisition module 12 is used to acquire the first echo signal and the second echo signal corresponding to the current calibration sequence, and determine the frequency drift according to the first echo signal and the second echo signal.

[0131] The calibration module 13 is used to calibrate the reference frequency of the magnetic resonance device according to the frequency drift, and apply an imaging sequence adjacent to the current calibration sequence to the imaging subject based on the calibrated reference frequency.

[0132] In one embodiment, the first radio frequency pulse of the imaging sequence is the same as the second radio frequency pulse of the calibration sequence, and the first repetition time of the imaging sequence is the same as the second repetition time of the calibration sequence.

[0133] In one embodiment, the applying module 11 comprises a first applying unit. The first applying unit is used to apply a first radio frequency pulse to the imaging object and to apply a first gradient to the imaging object.

[0134] In one embodiment, the first applying unit is specifically used to apply a first layer selection gradient while applying a first radio frequency pulse to the imaging object; after applying the first layer selection gradient, apply a motion encoding gradient to the imaging object; after applying the motion encoding gradient, apply a phase encoding gradient and a first readout encoding gradient to the imaging object.

[0135] In one embodiment, the applying module 11 comprises a second applying unit. The second applying unit is used to apply a second radio frequency pulse to the imaging object and to apply a second gradient to the imaging object.

[0136] In one embodiment, the second applying unit is specifically configured to apply a second slice selection gradient while applying a second radio frequency pulse to the imaging object; and apply a second readout encoding gradient to the imaging object.

[0137] In one embodiment, the acquisition module 12 is specifically used to convert the first echo signal and the second echo signal respectively to obtain the first complex signal and the second complex signal in the complex domain; determine the phase difference according to the first complex signal and the second complex signal; determine the frequency drift according to the phase difference and the time difference between the first echo signal and the second echo signal.

[0138] In one embodiment, the calibration module 13 is specifically used to obtain a reference frequency and an initial frequency offset of the magnetic resonance device; and determine a calibrated reference frequency according to the reference frequency, the initial frequency offset and the frequency drift.

[0139] In one embodiment, the acquisition module 12 is further used to acquire the third echo signal corresponding to each imaging sequence, and to reconstruct the third echo signal to obtain a magnetic resonance image of the imaging object.

[0140] Each module in the magnetic resonance frequency calibration device can be implemented in whole or in part by software, hardware, or a combination thereof. Each module can be embedded in or independent of a processor in a computer device in the form of hardware, or can be stored in a memory in a computer device in the form of software, so that the processor can call and execute operations corresponding to each module.

[0141] In one embodiment, a computer device is provided, whose internal structure diagram can be as follows: Fig.10 As shown. The computer device includes a processor, a memory, a communication interface, a display screen and an input device connected through a system bus. Among them, the processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The communication interface of the computer device is used to communicate with an external terminal in a wired or wireless manner, and the wireless manner can be achieved through WIFI, a mobile cellular network, NFC (near field communication) or other technologies. When the computer program is executed by the processor, a magnetic resonance frequency calibration method is implemented. The display screen of the computer device can be a liquid crystal display screen or an electronic ink display screen, and the input device of the computer device can be a touch layer covered on the display screen, or a key, trackball or touchpad set on the computer device shell, or an external keyboard, touchpad or mouse, etc.

[0142] Those skilled in the art will understand that Fig.10 The structure shown in the figure is only a block diagram of a part of the structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than those shown in the figure, or combine certain components, or have a different arrangement of components.

[0143] In one embodiment, a computer device is provided, including a memory and a processor, wherein a computer program is stored in the memory, and when the processor executes the computer program, the following steps are implemented:

[0144] Applying an imaging sequence and a calibration sequence to an imaging subject; the calibration sequence is located between two adjacent imaging sequences; and the imaging sequence is a functional magnetic resonance elastography sequence;

[0145] Acquire a first echo signal and a second echo signal corresponding to a current calibration sequence, and determine a frequency drift amount according to the first echo signal and the second echo signal;

[0146] The reference frequency of the magnetic resonance device is calibrated according to the frequency drift amount, and an imaging sequence adjacent to the current calibration sequence is applied to the imaging subject based on the calibrated reference frequency.

[0147] In one embodiment, the first radio frequency pulse of the imaging sequence is the same as the second radio frequency pulse of the calibration sequence, and the first repetition time of the imaging sequence is the same as the second repetition time of the calibration sequence.

[0148] In one embodiment, when the processor executes the computer program, the processor further implements the following steps: applying a first radio frequency pulse to the imaging object, and applying a first gradient to the imaging object.

[0149] In one embodiment, when the processor executes the computer program, the following steps are also implemented: applying a first layer selection gradient while applying a first radio frequency pulse to the imaging object; applying a motion encoding gradient to the imaging object after applying the first layer selection gradient; and applying a phase encoding gradient and a first readout encoding gradient to the imaging object after applying the motion encoding gradient.

[0150] In one embodiment, when the processor executes the computer program, the processor further implements the following steps: applying a second radio frequency pulse to the imaging subject, and applying a second gradient to the imaging subject.

[0151] In one embodiment, when the processor executes the computer program, the following steps are further implemented: applying a second slice selection gradient while applying a second radio frequency pulse to the imaging object; and applying a second readout encoding gradient to the imaging object.

[0152] In one embodiment, when the processor executes the computer program, the following steps are also implemented: converting the first echo signal and the second echo signal respectively to obtain the first complex signal and the second complex signal in the complex domain; determining the phase difference according to the first complex signal and the second complex signal; determining the frequency drift amount according to the phase difference and the time difference between the first echo signal and the second echo signal.

[0153] In one embodiment, when the processor executes the computer program, the following steps are also implemented: obtaining a reference frequency and an initial frequency offset of the magnetic resonance device; and determining a calibrated reference frequency according to the reference frequency, the initial frequency offset and the frequency drift.

[0154] In one embodiment, when the processor executes the computer program, the following steps are further implemented: acquiring a third echo signal corresponding to each imaging sequence, and reconstructing the third echo signal to obtain a magnetic resonance image of the imaging object.

[0155] In one embodiment, a computer-readable storage medium is provided, on which a computer program is stored, and when the computer program is executed by a processor, the following steps are implemented:

[0156] Applying an imaging sequence and a calibration sequence to an imaging subject; the calibration sequence is located between two adjacent imaging sequences; and the imaging sequence is a functional magnetic resonance elastography sequence;

[0157] Acquire a first echo signal and a second echo signal corresponding to a current calibration sequence, and determine a frequency drift amount according to the first echo signal and the second echo signal;

[0158] The reference frequency of the magnetic resonance device is calibrated according to the frequency drift amount, and an imaging sequence adjacent to the current calibration sequence is applied to the imaging subject based on the calibrated reference frequency.

[0159] In one embodiment, the first radio frequency pulse of the imaging sequence is the same as the second radio frequency pulse of the calibration sequence, and the first repetition time of the imaging sequence is the same as the second repetition time of the calibration sequence.

[0160] In one embodiment, when the computer program is executed by the processor, the computer program further implements the following steps: applying a first radio frequency pulse to the imaging subject, and applying a first gradient to the imaging subject.

[0161] In one embodiment, when the computer program is executed by the processor, the following steps are also implemented: applying a first layer selection gradient while applying a first radio frequency pulse to the imaging object; applying a motion encoding gradient to the imaging object after applying the first layer selection gradient; and applying a phase encoding gradient and a first readout encoding gradient to the imaging object after applying the motion encoding gradient.

[0162] In one embodiment, when the computer program is executed by the processor, the computer program further implements the following steps: applying a second radio frequency pulse to the imaging subject, and applying a second gradient to the imaging subject.

[0163] In one embodiment, when the computer program is executed by the processor, the following steps are further implemented: applying a second slice selection gradient while applying a second radio frequency pulse to the imaging object; and applying a second readout encoding gradient to the imaging object.

[0164] In one embodiment, when the computer program is executed by the processor, the following steps are also implemented: converting the first echo signal and the second echo signal respectively to obtain the first complex signal and the second complex signal in the complex domain; determining the phase difference based on the first complex signal and the second complex signal; determining the frequency drift amount based on the phase difference and the time difference between the first echo signal and the second echo signal.

[0165] In one embodiment, when the computer program is executed by the processor, the following steps are further implemented: obtaining a reference frequency and an initial frequency offset of the magnetic resonance device; and determining a calibrated reference frequency according to the reference frequency, the initial frequency offset and the frequency drift.

[0166] In one embodiment, when the computer program is executed by the processor, the following steps are further implemented: acquiring a third echo signal corresponding to each imaging sequence, and reconstructing the third echo signal to obtain a magnetic resonance image of the imaging object.

[0167] In one embodiment, a computer program product is provided, comprising a computer program, which, when executed by a processor, implements the following steps:

[0168] Applying an imaging sequence and a calibration sequence to an imaging subject; the calibration sequence is located between two adjacent imaging sequences; and the imaging sequence is a functional elastic imaging sequence;

[0169] Acquire a first echo signal and a second echo signal corresponding to a current calibration sequence, and determine a frequency drift amount according to the first echo signal and the second echo signal;

[0170] The reference frequency of the magnetic resonance device is calibrated according to the frequency drift amount, and an imaging sequence adjacent to the current calibration sequence is applied to the imaging subject based on the calibrated reference frequency.

[0171] In one embodiment, the first radio frequency pulse of the imaging sequence is the same as the second radio frequency pulse of the calibration sequence, and the first repetition time of the imaging sequence is the same as the second repetition time of the calibration sequence.

[0172] In one embodiment, when the computer program is executed by the processor, the computer program further implements the following steps: applying a first radio frequency pulse to the imaging subject, and applying a first gradient to the imaging subject.

[0173] In one embodiment, when the computer program is executed by the processor, the following steps are also implemented: applying a first layer selection gradient while applying a first radio frequency pulse to the imaging object; applying a motion encoding gradient to the imaging object after applying the first layer selection gradient; and applying a phase encoding gradient and a first readout encoding gradient to the imaging object after applying the motion encoding gradient.

[0174] In one embodiment, when the computer program is executed by the processor, the computer program further implements the following steps: applying a second radio frequency pulse to the imaging subject, and applying a second gradient to the imaging subject.

[0175] In one embodiment, when the computer program is executed by the processor, the following steps are further implemented: applying a second slice selection gradient while applying a second radio frequency pulse to the imaging object; and applying a second readout encoding gradient to the imaging object.

[0176] In one embodiment, when the computer program is executed by the processor, the following steps are also implemented: converting the first echo signal and the second echo signal respectively to obtain the first complex signal and the second complex signal in the complex domain; determining the phase difference based on the first complex signal and the second complex signal; determining the frequency drift amount based on the phase difference and the time difference between the first echo signal and the second echo signal.

[0177] In one embodiment, when the computer program is executed by the processor, the following steps are further implemented: obtaining a reference frequency and an initial frequency offset of the magnetic resonance device; and determining a calibrated reference frequency according to the reference frequency, the initial frequency offset and the frequency drift.

[0178] In one embodiment, when the computer program is executed by the processor, the following steps are further implemented: acquiring a third echo signal corresponding to each imaging sequence, and reconstructing the third echo signal to obtain a magnetic resonance image of the imaging object.

[0179] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to the memory, database or other medium used in the embodiments provided in this application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetoresistive random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. As an illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM). The database involved in each embodiment provided in this application may include at least one of a relational database and a non-relational database. Non-relational databases may include distributed databases based on blockchains, etc., but are not limited to this. The processor involved in each embodiment provided in this application may be a general-purpose processor, a central processing unit, a graphics processor, a digital signal processor, a programmable logic device, a data processing logic device based on quantum computing, etc., but are not limited to this.

[0180] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0181] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A magnetic resonance frequency calibration method, characterized in that: Applied to a magnetic resonance device, the method comprises: Applying an imaging sequence and a calibration sequence to an imaging subject; the calibration sequence is located between two adjacent imaging sequences; the imaging sequence is a functional magnetic resonance elastography sequence; Acquire a first echo signal and a second echo signal corresponding to a current calibration sequence, and determine a frequency drift amount according to the first echo signal and the second echo signal; The reference frequency of the magnetic resonance device is calibrated according to the frequency drift, and an imaging sequence adjacent to the current calibration sequence is applied to the imaging subject based on the calibrated reference frequency.

2. The method according to claim 1, characterized in that: The first radio frequency pulse of the imaging sequence is the same as the second radio frequency pulse of the calibration sequence, and the first repetition time of the imaging sequence is the same as the second repetition time of the calibration sequence.

3. The method according to claim 1 or 2, characterized in that: Applying the imaging sequence to the imaging subject comprises: A first radio frequency pulse is applied to the imaging subject, and a first gradient is applied to the imaging subject.

4. The method according to claim 3, characterized in that The first gradient includes a first slice selection gradient, a phase encoding gradient, a first readout encoding gradient, and a motion encoding gradient. The applying of a first radio frequency pulse to the imaging object and applying the first gradient to the imaging object include: Applying the first slice selection gradient while applying the first radio frequency pulse to the imaging object; After applying the first layer selection gradient, applying the motion coding gradient to the imaging object; After applying the motion encoding gradient, the phase encoding gradient and the first readout encoding gradient are applied to the imaging object.

5. The method according to claim 1 or 2, characterized in that: Applying the calibration sequence to the imaging subject comprises: A second radio frequency pulse is applied to the imaging subject, and a second gradient is applied to the imaging subject.

6. The method according to claim 5, characterized in that The second gradient includes a second slice selection gradient and a second readout encoding gradient, and applying a second radio frequency pulse to the imaging object and applying the second gradient to the imaging object include: applying the second slice selection gradient while applying the second radio frequency pulse to the imaging object; The second readout encoding gradient is applied to the imaging object.

7. The method according to claim 1 or 2, characterized in that: The determining the frequency drift amount according to the first echo signal and the second echo signal includes: Converting the first echo signal and the second echo signal respectively to obtain a first complex signal and a second complex signal in a complex domain; determining a phase difference according to the first complex signal and the second complex signal; The frequency drift amount is determined according to the phase difference and the time difference between the first echo signal and the second echo signal.

8. The method according to claim 1 or 2, characterized in that: The step of calibrating the reference frequency of the magnetic resonance device according to the frequency drift comprises: Acquiring the reference frequency and initial frequency offset of the magnetic resonance device; The calibrated reference frequency is determined according to the reference frequency, the initial frequency offset and the frequency drift.

9. The method according to claim 1 or 2, characterized in that: The method further comprises: A third echo signal corresponding to each of the imaging sequences is acquired, and the third echo signal is reconstructed to obtain a magnetic resonance image of the imaging object.

10. A magnetic resonance device, characterized in that: The method comprises a magnetic resonance component and a control component, wherein the control component is communicatively connected with the magnetic resonance component; the control component is used to execute the steps of the method according to any one of claims 1 to 9.

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