Magnetic resonance frequency calibration method and magnetic resonance apparatus

Abstract

The application relates to a magnetic resonance frequency calibration method and a magnetic resonance device. The method is applied to a magnetic resonance device, and the method comprises the following steps: applying 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 elastography sequence; a first echo signal and a second echo signal corresponding to the current calibration sequence are acquired, and a frequency drift amount 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 amount, and an imaging sequence adjacent to the current calibration sequence is applied to the imaging object based on the calibrated reference frequency. The magnetic resonance frequency calibration method provided by the application can realize calibration of the reference frequency of a magnetic resonance device with a short repetition time.

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

[0002] When a long-time sequence scan is performed using a magnetic resonance device, heat is generated due to vibration caused by continuous switching of current, and thus the reference frequency of the magnetic resonance device drifts. The accuracy of the reference frequency directly affects the quality of the image obtained by scanning, for example, drift of the reference frequency causes image position offset, poor fat suppression effect, and the like, thereby affecting the research results of the staff based on the image. In particular, imaging sequences with very short repetition times are required, such as functional magnetic resonance elastography (fMRE) sequences, the signal of the magnetic resonance component is weak and is easily affected by reference frequency interference. However, there is a lack of methods for calibrating the frequency drift of magnetic resonance devices with very short repetition times in the prior art. SUMMARY

[0003] Therefore, it is necessary to provide a magnetic resonance frequency calibration method and a magnetic resonance device capable of calibrating 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 applied to a magnetic resonance device, the method comprising:

[0005] applying 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 elastography sequence;

[0006] 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;

[0007] 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.

[0008] In one of the embodiments, 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.

[0009] In one of the embodiments, applying the imaging sequence to the imaging object comprises:

[0010] applying a first radio frequency pulse to the imaging object, and applying a first gradient to the imaging object.

[0011] In one of the embodiments, the first gradient comprises a first slice selection gradient, a phase encoding gradient and a first readout encoding gradient, and a motion encoding gradient, the first radio frequency pulse is applied to the imaging object, and the first gradient is applied to the imaging object, comprising:

[0012] The first slice selection gradient is applied to the imaging object while the first radio frequency pulse is applied to the imaging object;

[0013] The motion encoding gradient is applied to the imaging object after the first slice selection gradient is applied;

[0014] The phase encoding gradient and the first readout encoding gradient are applied to the imaging object after the motion encoding gradient is applied.

[0015] In one of the embodiments, the calibration sequence is applied to the imaging object, comprising:

[0016] The second radio frequency pulse is applied to the imaging object, and the second gradient is applied to the imaging object.

[0017] In one of the embodiments, the second gradient comprises a second slice selection gradient and a second readout encoding gradient, the second radio frequency pulse is applied to the imaging object, and the second gradient is applied to the imaging object, comprising:

[0018] The second slice selection gradient is applied to the imaging object while the second radio frequency pulse is applied to the imaging object;

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

[0020] In one of the embodiments, the frequency drift amount is determined according to the first echo signal and the second echo signal, comprising:

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

[0022] The phase difference is determined according to the first complex signal and the second complex signal;

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

[0024] In one of the embodiments, the reference frequency of the magnetic resonance device is calibrated according to the frequency drift amount, comprising:

[0025] The reference frequency of the magnetic resonance device and an initial frequency offset are obtained;

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

[0027] In one of the embodiments, the method further comprises:

[0028] The third echo signals corresponding to each imaging sequence are acquired, and the third echo signals are 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, comprising a magnetic resonance assembly and a control assembly, the control assembly being in communication connection with the magnetic resonance assembly; the control assembly is configured to execute the steps of the method provided in the first aspect.

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

[0031] The application module is configured to apply 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 elastography sequence;

[0032] The acquisition module is configured to acquire first echo signals and second echo signals corresponding to the current calibration sequence, and determine a frequency drift amount based on the first echo signals and the second echo signals.

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

[0034] In a fourth aspect, the present application further provides a computer device, which comprises a memory and a processor, the memory stores a computer program, and the processor executes the computer program to realize the steps of the method provided in the first aspect.

[0035] In a sixth aspect, the present application further provides a computer readable storage medium. The computer readable storage medium stores a computer program, and the computer program is executed by a processor to realize the steps of the method provided in the first aspect.

[0036] In a seventh aspect, the present application further provides a computer program product. The computer program product comprises a computer program, and the computer program is executed by a processor to realize the steps of the method provided in the first aspect.

[0037] The magnetic resonance frequency calibration method and the magnetic resonance device, the method is applied to the 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 elastography sequence; a first echo signal and a second echo signal corresponding to the current calibration sequence are obtained, and a frequency drift amount 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 amount, 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 amount can be determined according to the first echo signal and the second echo signal corresponding to the current calibration sequence, and the reference frequency of the magnetic resonance device can be calibrated through the frequency drift amount. 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 is performed using the reference frequency calibrated based on the frequency drift amount corresponding to the calibration sequence. The reference frequency of the magnetic resonance device can be calibrated in real time, and the influence of the calibration sequence on the time resolution can be ignored, and the practicability of the magnetic resonance frequency calibration method is improved. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 An application environment diagram of the magnetic resonance frequency calibration method in one embodiment;

[0039] Figure 2 A step flowchart of the magnetic resonance frequency calibration method in one embodiment;

[0040] Figure 3 A step flowchart of the magnetic resonance frequency calibration method in another embodiment;

[0041] Figure 4 An imaging sequence and a calibration sequence diagram in one embodiment;

[0042] Figure 5 A step flowchart of the magnetic resonance frequency calibration method in another embodiment;

[0043] Figure 6 A step flowchart of the magnetic resonance frequency calibration method in another embodiment;

[0044] Figure 7 A step flowchart of the magnetic resonance frequency calibration method in another embodiment;

[0045] Figure 8 A step flowchart of the magnetic resonance frequency calibration method in another embodiment;

[0046] Figure 9A structural schematic diagram of a magnetic resonance frequency calibration device in an embodiment;

[0047] Figure 10 An internal structure diagram of a computer device in an embodiment. DETAILED DESCRIPTION

[0048] In order to make the purposes, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application.

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

[0050] First, before specifically introducing the technical solutions of the disclosed embodiments of the present application, the background technology or technical evolution context based on which the embodiments of the present application are introduced. In the field of magnetic resonance imaging, when using a magnetic resonance device to perform a long-time sequence scan, the device will heat up due to the vibration caused by the continuous switching of the current, and then the reference frequency of the magnetic resonance device will drift. The accuracy of the reference frequency directly affects the quality of the image obtained by scanning. For example, it can cause image position offset, poor fat suppression effect, etc., thereby affecting the research results of the researchers based on the image. Especially for imaging sequences that require a very short repetition time (TR) (TR is about 50 ms) in the magnetic resonance imaging process, such as functional magnetic resonance elastography (fMRE) sequence, the steady-state signal is very weak and is easily disturbed by the reference frequency drift. However, in the traditional technology, a method for calibrating the frequency drift of a magnetic resonance device that requires a very short repetition time is determined. In view of this, the present application provides a magnetic resonance frequency calibration method.

[0051] The magnetic resonance frequency calibration method provided by the present application can be applied to a magnetic resonance device, and the structure of the magnetic resonance device is as shown in Figure 1 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, notebook computers and tablet computers.

[0052] The technical solutions of the present application and how the technical solutions of the present application solve the technical problems will be described in detail below with specific embodiments.

[0053] In an embodiment, as Figure 2As shown, a magnetic resonance frequency calibration method is provided, and the embodiment takes the method applied to a control component in a magnetic resonance device as an example. The method comprises the following steps:

[0054] Step 200, applying 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 elastography sequence;

[0055] The imaging object can be an animal body or an imaging phantom. The magnetic resonance component in the magnetic resonance device is a small-bore component, which can provide a high field strength. After the imaging object is placed on a bearing component (a scan 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 a first imaging sequence to the imaging object, a first calibration sequence is applied, then a second imaging sequence is applied, and a second calibration sequence is applied. In this order, the scan imaging of the imaging object is completed. The signal acquired under the imaging sequence is used for imaging, and the signal acquired under the calibration sequence is used for calibration. The specific types of the imaging sequence and the calibration sequence are not limited in the embodiment, as long as the functions thereof can be realized. The imaging sequence applied by the magnetic resonance component to the imaging object is a functional magnetic resonance elastography sequence with a very short repetition time.

[0056] Step 210, acquiring 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.

[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 acquires a first echo signal and a second echo signal corresponding to the current calibration sequence. That is, after applying a calibration sequence to the imaging object, the first echo signal and the second echo signal corresponding to the calibration sequence are acquired. The magnetic resonance component sends the acquired first echo signal and second echo signal to the control component. That is, 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 acquired.

[0058] After the control component acquires the first echo signal and the second echo signal of the imaging object, the frequency drift amount of the reference frequency of the magnetic resonance component can be determined 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 scan time period. The specific method of determining the frequency drift amount according to the first echo signal and the second echo signal is not limited in the embodiment, as long as the function thereof can be realized.

[0059] In an optional embodiment, the control component can determine a first frequency of the magnetic resonance component corresponding to the first scanning moment according to the first echo signal, and determine a 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 scanning moment is the current scanning time period.

[0060] Step 220: 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.

[0061] The reference frequency of the magnetic resonance device refers to the center frequency of the magnetic resonance component before the magnetic resonance component in the magnetic resonance device performs scanning. After the control component determines the frequency drift amount 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 amount, and obtains 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 the control component determines 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 pulse in the next imaging sequence applied is the same as the calibrated reference frequency. The next imaging sequence refers to the imaging sequence adjacent to the current calibration sequence.

[0064] In an optional embodiment, the first echo signal and the second echo signal corresponding to the first calibration sequence are obtained according to the application of the first imaging sequence and the first calibration sequence to the imaging object, the frequency drift amount corresponding to the first calibration sequence can be determined, the sum of the frequency drift amount and the reference frequency is calculated to obtain the calibrated reference frequency, the calibrated reference frequency is determined as a new reference frequency, the second imaging sequence and the 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 embodiments 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 elastography sequence. A first echo signal and a second echo signal corresponding to the current calibration sequence are acquired, and a frequency drift amount 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 amount, and the imaging sequence adjacent to the current calibration sequence is applied to the imaging object based on the calibrated reference frequency. In the embodiments, the frequency drift amount can be determined according to the acquired first echo signal and second echo signal corresponding to the current calibration sequence, and the reference frequency of the magnetic resonance device can be calibrated through the frequency drift amount. 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. In this way, the imaging sequence scan can be performed using the reference frequency calibrated based on the frequency drift amount corresponding to the calibration sequence, the reference frequency of the magnetic resonance device can be calibrated in real time, and the influence of the calibration sequence on the time resolution can be ignored, thereby improving the practicability 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 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 related parameters of the first radio frequency pulse are the same as the related 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 the radio frequency pulse can include a non-selective radio frequency pulse, a selective radio frequency pulse, a hard pulse, a soft pulse, an adiabatic pulse, and the like. The type of the first radio frequency pulse and the type of the second radio frequency pulse can be any of the above.

[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 a time period between a center of the first radio frequency pulse of the first imaging sequence and a 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 a time period between the center of the second radio frequency pulse of the calibration sequence and a 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 about 50 ms.

[0070] In the 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 time scanning can be maintained, and thus the accuracy of the determined frequency drift amount can be improved, so as to realize accurate calibration of the reference frequency of the magnetic resonance device, and thus the quality of the image after imaging can be improved.

[0071] In one embodiment, an implementation of applying an imaging sequence to an imaging object is involved, and the implementation comprises:

[0072] applying a first radio frequency pulse to the imaging object, and applying a first gradient to the imaging object.

[0073] The applied imaging sequence comprises the first radio frequency pulse and the 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 to generate 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 realize positioning. The embodiment does not limit the specific types of the applied first radio frequency pulse and the first gradient, as long as the functions thereof can be realized.

[0074] In one embodiment, the applied first gradient to the imaging object can comprise a first slice selection gradient, a phase encoding gradient and a first readout encoding gradient, and a motion encoding gradient. In this case, as shown in the following, an implementation of applying a first radio frequency pulse to an imaging object and applying a first gradient to the imaging object comprises: Figure 3

[0075] Step 300, applying a first slice selection gradient while applying a first radio frequency pulse to the imaging object.

[0076] ​The control component applies a first radio frequency (RF) pulse to the imaging object simultaneously with the magnetic resonance imaging (MRI) assembly. The first slice-selective gradient is a linearly varying magnetic field applied along a specific axis of the imaging object (typically the Z-axis, i.e., the vertical direction of the imaging object) based on the main magnetic field. After applying the first RF pulse and the first slice-selective gradient, the magnetic field strength and Larmor frequency of hydrogen nuclei in different layers of the imaging object differ. When the frequency of the first RF pulse matches the Larmor frequency of a hydrogen nucleus in a particular layer, only the hydrogen nuclei in that layer are excited, thus achieving slice selection. Applying the first slice-selective gradient simultaneously with the first RF pulse means that the first RF pulse is applied during the same time period as the first slice-selective gradient is applied to the object; it is not required that the start and end times of the first RF pulse and the first slice-selective gradient are the same.

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

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

[0079] After the control component applies the first slice-selective gradient to the magnetic resonance imaging (MRI) unit, it applies a motion-coded gradient to the imaging object. This motion-coded gradient can be applied immediately after the first slice-selective gradient, or it can be applied after a first preset time interval. The direction of the motion-coded gradient can be the same as or different from the axis of the first slice-selective gradient. Figure 4 As shown, in the selected layer gradient G ss Phase encoding gradient G PE Read out the encoded gradient G RO Motion coding gradients are applied in all axial directions.

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

[0081] Phase-encoded gradients can be used to determine the positions of hydrogen nuclei in another direction (usually the y-axis, i.e., the front-to-back direction of the imaged object) within the imaging plane. After the first radio frequency pulse excitation, phase-encoded gradients of different intensities are applied at different time points, causing varying degrees of phase change in the hydrogen nuclei at different y-axis positions. A set of data is collected after each application of a different phase-encoded gradient intensity. After repeatedly changing the phase-encoded gradient intensity and collecting data, sufficient information can be obtained to construct the spatial information of the image along the y-axis.Figure 4 As shown, different intensity phase encoding gradients are applied in sequence according to the arrow order.

[0082] The first readout encoding gradient, also referred to as the first frequency encoding gradient. Through the first readout encoding gradient, a linearly changing magnetic field gradient can be applied in a specific direction (usually the left-right direction of the imaging object, i.e., the x-axis direction) of the selected imaging layer excited by the radio frequency pulse, so that hydrogen nuclei at different positions produce magnetic resonance signals of different frequencies, and the spatial position of the hydrogen nuclei in the specific direction can be determined according to the magnetic resonance signals.

[0083] The control component applies the phase encoding gradient and the first readout encoding gradient to the imaging object after the magnetic resonance component applies the motion encoding gradient. The phase encoding gradient and the first readout encoding gradient can 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 can be applied after the motion encoding gradient is applied, with a second preset time interval.

[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 the direction of the second phase encoding gradient, and the first phase encoding gradient and the second phase encoding gradient are both linearly changing 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 gradient, or the second phase encoding gradient can be applied after the end time of the first readout gradient with a third preset time interval. As shown, 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 away from the motion encoding gradient. The first phase encoding gradient includes a plurality of phase encoding gradients of different intensities applied in sequence in a first direction according to the arrow order; the second phase encoding gradient includes a plurality of phase encoding gradients of different intensities applied in sequence in a second direction according to the arrow order, the first direction and the second direction are opposite.

[0085] In this embodiment, by applying the first slice selection gradient to the imaging object at the same time as applying the first radio frequency pulse; applying the motion encoding gradient to the imaging object after applying the first slice selection gradient; and applying the phase encoding gradient and the first readout encoding gradient to the imaging object after applying the motion encoding gradient, the spatial information of each direction of a certain imaging layer of the imaging object can be obtained by applying the radio frequency pulse, the first slice selection gradient, the motion encoding gradient, the phase encoding gradient and the first readout encoding gradient, so as to facilitate subsequent acquisition of accurate images of the imaging object.

[0086] In one embodiment, an implementation related to applying a calibration sequence to the imaging subject, the implementation comprises:

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

[0088] The calibration sequence applied to the imaging subject comprises the second radio frequency pulse and the second gradient. After completing the current scan imaging by applying the imaging sequence to the imaging subject, the calibration sequence is applied to the imaging subject. The magnetic resonance component applies the second radio frequency pulse to the imaging subject and applies the second gradient to the imaging subject based on the control signal sent by the control component to excite the hydrogen nuclei at the fixed position in the imaging subject. The description of the second radio frequency pulse can refer to the specific description of the first radio frequency pulse in the above embodiments, which will not be repeated here.

[0089] In one embodiment, the second gradient applied to the imaging subject can comprise a second slice selection gradient and a second readout encoding gradient. In this case, as Figure 5 shown, an implementation related to applying a second radio frequency pulse to the imaging subject, and applying a second gradient to the imaging subject, the implementation comprises the steps of:

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

[0091] The control component controls the magnetic resonance component to apply a second slice selection gradient to the imaging subject while controlling the magnetic resonance component to apply a first radio frequency pulse to the imaging subject. The gradient strength of the second slice selection gradient can be the same as or different from the gradient strength of the first slice selection gradient, and the application duration of the second slice selection gradient can be the same as or different from the application duration of the first slice selection gradient. The description of the second slice selection gradient can refer to the description of the first slice selection gradient in the above embodiments, which will not be repeated here.

[0092] Step 510, applying a second readout encoding gradient to the imaging subject.

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

[0094] In the embodiment, by applying the second radio frequency pulse to the imaging object at the same time as applying the second slice selection gradient, and applying the second readout encoding gradient to the imaging object, the spatial information of a certain imaging layer of the imaging object can be obtained, so that the subsequent calibration signal can be obtained, and the calibration of the reference frequency of the magnetic resonance component in the magnetic resonance device is realized.

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

[0096] In an embodiment, as shown in Figure 6 An implementation of determining the frequency drift amount according to the first echo signal and the second echo signal includes:

[0097] Step 600, respectively, the first echo signal and the second echo signal are converted to obtain the first complex signal and the second complex signal in the complex domain.

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

[0099] Suppose the first echo signal is denoted as E n，1 , and the second echo signal is denoted as En，2 The first complex signal E n，3 The second complex signal E n，4 The first complex signal can be expressed as: The second complex signal can be expressed as Wherein, n represents the number of applying the calibration sequence.

[0100] Step 610, determining the phase difference according to the first complex signal and the second complex signal.

[0101] The control component determines the phase difference between the first complex signal and the second complex signal after determining 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, determining the frequency drift 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. The control component determines the frequency drift according to the phase difference and the time difference between the first echo signal and the second echo signal after determining the phase difference between the first complex signal and the second complex signal. Specifically, the direct correspondence between the frequency f and the phase angle θ can be expressed as , The time difference between the first echo signal and the second echo signal, and the frequency drift can be expressed as .

[0104] In this embodiment, by respectively converting the first echo signal and the second echo signal, the first complex signal and the second complex signal in the complex domain are obtained; 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, so that the method for determining the frequency drift is fast and easy to implement, and the practicability of the magnetic resonance frequency calibration method can be improved.

[0105] In one embodiment, as Figure 7 shown, an implementation mode related to calibrating the reference frequency of the magnetic resonance device according to the frequency drift, the steps of the implementation mode include:

[0106] Step 700, obtaining the reference frequency of the magnetic resonance device and the initial frequency bias.

[0107] The reference frequency of the magnetic resonance device can be a center frequency set after the magnetic resonance device is shipped, or can be set by a technician in advance. The frequency of the first radio frequency pulse applied to the imaging object needs to be the same as the reference frequency to generate a magnetic resonance phenomenon. The initial frequency offset can be a frequency error existing in the magnetic resonance device calculated by the worker.

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

[0109] Step 710, determining the calibrated reference frequency according to the reference frequency, the initial frequency offset and the frequency drift amount.

[0110] After the control component obtains the reference frequency and the initial frequency offset of the magnetic resonance device, and determines the frequency drift amount, the reference frequency is calibrated according to the initial frequency offset and the frequency drift amount, and the calibrated reference frequency can be obtained.

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

[0112] In the embodiment, the reference frequency of the magnetic resonance device and the initial frequency offset are obtained, the reference frequency is calibrated according to the initial frequency offset and the frequency drift amount, and the calibrated reference frequency is obtained. In this way, not only the calibration of the reference frequency can be realized, but also the initial frequency offset of the magnetic resonance device is considered in the calibration process, 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] Obtaining the third echo signal corresponding to each imaging sequence, and reconstructing the third echo signal to obtain a magnetic resonance image of the imaging object.

[0115] The control component acquires the third echo signals corresponding to the imaging sequences during controlling the magnetic resonance component to apply the imaging sequences to the imaging object, specifically, when the first readout encoding gradient is applied. After acquiring the third echo signals corresponding to the imaging sequences, the control component performs image reconstruction processing on the third echo signals, and a magnetic resonance image of the imaging object can be obtained. 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 all the two-dimensional images determined by the third echo signals can obtain a three-dimensional magnetic resonance image of the imaging object.

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

[0117] Please refer to Figure 8 An embodiment of the present application provides a magnetic resonance frequency calibration method, applied to a magnetic resonance device, the magnetic resonance device comprising a magnetic resonance component and a control component, the control component being configured to perform the following steps:

[0118] Step 800, applying a first imaging sequence and a first calibration sequence to an imaging object; the first imaging sequence comprises 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 comprises 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, acquiring a first echo signal and a second echo signal corresponding to the 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, determining a phase difference between the first complex signal and the second complex signal, and determining a frequency drift according to the phase difference and a time difference between the first echo signal and the second echo signal;

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

[0123] Step 850, calibrating the reference frequency according to the initial frequency offset and the frequency drift amount to obtain a calibrated reference frequency;

[0124] Step 860, taking the calibrated reference frequency as a new reference frequency, applying a second imaging sequence and a second calibration sequence to the imaging object, taking the second imaging sequence as a new first imaging sequence, taking the second calibration sequence as a new first calibration sequence, and returning to execute steps 810-850.

[0125] In one embodiment, as shown in FIG. 1, Figure 1 A magnetic resonance device is provided, which includes a magnetic resonance assembly 104 and a control assembly 103, the control assembly 103 being in communication connection with the magnetic resonance assembly 104, and the control assembly 103 being configured to execute the steps of the method provided by the above-mentioned embodiments.

[0126] It should be understood that, although each step in the flowchart involved in each of the above-mentioned embodiments is displayed in sequence according to the arrow, these steps are not necessarily executed in sequence according to the arrow. Unless otherwise specified herein, the execution of these steps is not strictly limited in sequence, and these steps can be executed in other sequences. Moreover, at least part of the steps in the flowchart involved in each of the above-mentioned embodiments can include multiple steps or stages, which are not necessarily executed at the same time, but can be executed at different times, and the execution sequence of these steps or stages is not necessarily sequential, but can be executed alternately or alternately with at least part of other steps or steps or stages in other steps.

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

[0128] In one embodiment, as shown in FIG. 1, Figure 9 A magnetic resonance frequency calibration device 10 is provided, which includes an application module 11, an acquisition module 12, and a calibration module 13, wherein:

[0129] The application module 11 is configured 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 configured to acquire the first echo signal and the second echo signal corresponding to the current calibration sequence, and determine the frequency drift amount according to the first echo signal and the second echo signal.

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

[0132] In an 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 an embodiment, the application module 11 includes a first application unit. The first application unit is configured to apply the first radio frequency pulse to the imaging object, and apply the first gradient to the imaging object.

[0134] In an embodiment, the first application unit is specifically configured to apply the first slice selection gradient while applying the first radio frequency pulse to the imaging object; apply the motion encoding gradient to the imaging object after applying the first slice selection gradient; and apply the phase encoding gradient and the first readout encoding gradient to the imaging object after applying the motion encoding gradient.

[0135] In an embodiment, the application module 11 includes a second application unit. The second application unit is configured to apply the second radio frequency pulse to the imaging object, and apply the second gradient to the imaging object.

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

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

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

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

[0140] The modules in the magnetic resonance frequency calibration device can be implemented by software, hardware, or a combination thereof. The modules can be embedded in a processor in a computer device in hardware or independent of the processor, or stored in a memory in the computer device in software, so that the processor can call and execute the operations of the modules.

[0141] In one embodiment, a computer device is provided, and an internal structure diagram of the computer device can be as shown in Figure 10 The computer device includes a processor, a memory, a communication interface, a display screen, and an input device connected by a system bus. The processor of the computer device is configured 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 running the operating system and the computer program in the non-volatile storage medium. The communication interface of the computer device is configured to perform wired or wireless communication with an external terminal. The wireless communication can be achieved by WIFI, mobile cellular network, NFC (Near Field Communication), or other technologies. The computer program is executed by the processor to implement a magnetic resonance frequency calibration method. The display screen of the computer device can be a liquid crystal display screen or an electronic ink display screen. The input device of the computer device can be a touch layer overlaid on the display screen, or a key, trackball, or touchpad arranged on the shell of the computer device, or an external keyboard, touchpad, or mouse, etc.

[0142] Those skilled in the art can understand that Figure 10 The structure shown in the above embodiment is only a block diagram of part of the structure related to the scheme of the present application, and does not limit the computer device to which the scheme of the present application is applied. Specifically, the computer device can 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, the memory storing a computer program, and the processor executing the computer program to implement the following steps:

[0144] applying 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 elastography sequence;

[0145] 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;

[0146] calibrating a 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.

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

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

[0149] In one embodiment, the processor further implements the following steps when executing the computer program: applying the first slice selection gradient to the imaging object while applying the first radio frequency pulse to the imaging object; applying the motion encoding gradient to the imaging object after applying the first slice selection gradient; applying the phase encoding gradient and the first readout encoding gradient to the imaging object after applying the motion encoding gradient.

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

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

[0152] In one embodiment, the processor further implements the following steps when executing the computer program: converting the first echo signal and the second echo signal to obtain a first complex signal and a second complex signal in a complex domain, respectively; determining a phase difference based on the first complex signal and the second complex signal; and determining the frequency drift based on the phase difference and a time difference between the first echo signal and the second echo signal.

[0153] In one embodiment, the processor further implements the following steps when executing the computer program: obtaining a reference frequency of the magnetic resonance device and an initial frequency offset; and determining a calibrated reference frequency based on the reference frequency, the initial frequency offset, and the frequency drift.

[0154] In one embodiment, the processor further implements the following steps when executing the computer program: obtaining 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, and the computer readable storage medium stores a computer program. The computer program is executed by a processor to implement the following steps:

[0156] applying 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 elastography sequence;

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

[0158] calibrating a reference frequency of the magnetic resonance apparatus according to the frequency drift amount, and applying an imaging sequence adjacent to the current calibration sequence 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, the computer program, when executed by the processor, further implements the following steps: applying the first radio frequency pulse to the imaging subject, and applying the first gradient to the imaging subject.

[0161] In one embodiment, the computer program, when executed by the processor, further implements the following steps: applying the first slice selection gradient to the imaging subject while applying the first radio frequency pulse to the imaging subject; applying the motion encoding gradient to the imaging subject after applying the first slice selection gradient; and applying the phase encoding gradient and the first readout encoding gradient to the imaging subject after applying the motion encoding gradient.

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

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

[0164] In one embodiment, the computer program, when executed by the processor, further implements the following steps: converting the first echo signal and the second echo signal to obtain a first complex signal and a second complex signal in a complex domain, respectively; determining a phase difference according to the first complex signal and the second complex signal; and determining the frequency drift amount according to the phase difference and a time difference between the first echo signal and the second echo signal.

[0165] In one embodiment, the computer program, when executed by the processor, further implements the following steps: obtaining a reference frequency of the magnetic resonance apparatus and an initial frequency bias; and determining the calibrated reference frequency according to the reference frequency, the initial frequency bias, and the frequency drift amount.

[0166] In one embodiment, the computer program, when executed by the processor, further implements the following steps: acquiring third echo signals corresponding to each imaging sequence, and reconstructing the third echo signals 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 the processor, implements the following steps:

[0168] applying the imaging sequences and the calibration sequence to the imaging object; the calibration sequence is located between two adjacent imaging sequences; the imaging sequence is a functional elastography sequence;

[0169] acquiring first echo signals and second echo signals corresponding to the current calibration sequence, and determining the frequency drift amount according to the first echo signals and the second echo signals;

[0170] calibrating a 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.

[0171] 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.

[0172] In one embodiment, the computer program, when executed by 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.

[0173] In one embodiment, the computer program, when executed by the processor, further implements the following steps: applying a first slice selection gradient to the imaging object while applying the first radio frequency pulse to the imaging object; applying a motion encoding gradient to the imaging object after applying the first slice 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, the computer program, when executed by the processor, further implements the following steps: applying a second radio frequency pulse to the imaging object, and applying a second gradient to the imaging object.

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

[0176] In one embodiment, the computer program, when executed by the processor, further implements the following steps: 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 the phase difference according to the first complex signal and the second complex signal; and determining the frequency drift according to the phase difference and a time difference between the first echo signal and the second echo signal.

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

[0178] In one embodiment, the computer program, when executed by the processor, further implements the following steps: obtaining a third echo signal corresponding to each imaging sequence, and performing reconstruction processing on 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. The computer program can be stored in a non-volatile computer readable storage medium, and when the computer program is executed, the processes of the above-mentioned embodiments of the methods can be included. Any reference to memory, database or other medium used in the embodiments provided in the present 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 storage, high-density embedded non-volatile memory, resistive memory (ReRAM), magnetoresistive random access memory (MRAM), ferroelectric 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 but not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM), etc. The database involved in the embodiments provided in the present application can include at least one of a relational database and a non-relational database. The non-relational database can include a distributed database based on a block chain, etc., without being limited thereto. The processor involved in the embodiments provided in the present application can be a general-purpose processor, a central processing unit, a graphics processing unit, a digital signal processor, a programmable logic device, a data processing logic device based on quantum computing, etc., without being limited thereto.

[0180] Any combination of the technical features of the above embodiments can be made. In order to make the description simple, all possible combinations of the technical features in the above embodiments are not described, however, as long as the combination of the technical features does not exist, it should be considered as the scope of the present application.

[0181] The above embodiments only express several implementation manners of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent of the present application. It should be pointed out that for ordinary skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the scope of protection of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

Claims

1. A magnetic resonance frequency calibration method, characterized in that, Applied to a magnetic resonance imaging device, the method includes: An imaging sequence and a calibration sequence are applied to the imaging object; the calibration sequence is located between two adjacent imaging sequences; the imaging sequence is a functional magnetic resonance elastography sequence; 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; the calibration sequence is a dual-gradient echo calibration sequence. Obtain the first echo signal and the second echo signal corresponding to the current calibration sequence, and determine the frequency drift based on 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.

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

3. The method according to claim 2, characterized in that, The first gradient includes a first layer selection gradient, a phase coding gradient, a first readout coding gradient, and a motion coding gradient. Applying a first radio frequency pulse to the imaging object and applying the first gradient to the imaging object includes: While applying the first radio frequency pulse to the imaging object, the first layer selection gradient is applied; After applying the first layer selection gradient, the motion coding gradient is applied to the imaging object; After applying the motion-coded gradient, the phase-coded gradient and the first readout-coded gradient are applied to the imaging object.

4. The method according to claim 1, characterized in that, Applying the calibration sequence to the imaging object includes: A second radio frequency pulse is applied to the imaging object, and a second gradient is applied to the imaging object.

5. The method according to claim 4, characterized in that, The second gradient includes a second layer selection gradient and a second readout coding gradient. Applying a second radio frequency pulse to the imaging object and applying the second gradient to the imaging object includes: Simultaneously with applying the second radio frequency pulse to the imaging object, the second layer selection gradient is applied; The second readout coding gradient is applied to the imaging object.

6. The method according to claim 1, characterized in that, Determining the frequency drift based on the first echo signal and the second echo signal includes: The first echo signal and the second echo signal are converted respectively to obtain the first complex signal and the second complex signal in the complex domain; The phase difference is determined based on the first complex signal and the second complex signal; The frequency drift is determined based on the phase difference and the time difference between the first echo signal and the second echo signal.

7. The method according to claim 1, characterized in that, The calibration of the reference frequency of the magnetic resonance device based on the frequency drift includes: Obtain the reference frequency and initial frequency offset of the magnetic resonance device; The calibrated reference frequency is determined based on the reference frequency, the initial frequency offset, and the frequency drift.

8. The method according to claim 1, characterized in that, The method further includes: The third echo signal corresponding to each imaging sequence is acquired, and the third echo signal is reconstructed to obtain the magnetic resonance image of the imaging object.

9. A magnetic resonance device, characterized in that, It includes a magnetic resonance assembly and a control assembly, the control assembly being communicatively connected to the magnetic resonance assembly; the control assembly is used to perform the steps of the method as described in any one of claims 1-8.

10. A magnetic resonance frequency calibration device, characterized in that, Applied to a magnetic resonance imaging (MRI) device, the device includes: An application module is used to apply 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 elastography sequence; 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; the calibration sequence is a dual-gradient echo calibration sequence. The acquisition module is used to acquire the first echo signal and the second echo signal corresponding to the current calibration sequence, and determine the frequency drift based on the first echo signal and the second echo signal. The calibration module is used to calibrate the reference frequency of the magnetic resonance device according to the frequency drift, and to apply an imaging sequence adjacent to the current calibration sequence to the imaging object based on the calibrated reference frequency.

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