Magnetic resonance frequency calibration methods, computer equipment, and magnetic resonance systems

Abstract

This application relates to a magnetic resonance frequency calibration method, a computer device, and a magnetic resonance system. The method, applied to a magnetic resonance system, includes applying at least two imaging sequences to an imaging object and acquiring at least two calibration echo signals of the imaging object based on the at least two imaging sequences; determining a frequency drift based on the at least two calibration echo signals; calibrating the system frequency of the magnetic resonance system based on the frequency drift; and applying the calibrated system frequency as the new system frequency to the imaging object using the next imaging sequence; the next imaging sequence is the next imaging sequence following the imaging sequences corresponding to the at least two calibration echo signals. Using the magnetic resonance frequency calibration method provided in this application can improve the accuracy of frequency calibration.

Description

Technical Field

[0001] This application relates to the field of imaging technology, and in particular to a magnetic resonance frequency calibration method, computer equipment, and magnetic resonance system. Background Technology

[0002] During long-duration sequential scans using magnetic resonance imaging (MRI) equipment, the vibrations caused by the continuous switching of current generate heat, leading to frequency drift in the system. The accuracy of the system frequency directly affects the quality of the resulting images. For example, frequency drift can cause image position shifts and poor fat suppression.

[0003] In traditional techniques, a pre-scanning sequence (gradient double echo sequence) is typically used for scanning, and echo signals are acquired to calculate the system frequency drift and calibrate the system frequency.

[0004] However, for imaging sequences that require very short repetition times, traditional methods for calibrating the system frequency are inaccurate. Summary of the Invention

[0005] Therefore, it is necessary to provide a magnetic resonance frequency calibration method, computer equipment, and magnetic resonance system that can improve the accuracy of frequency calibration in response to the above-mentioned technical problems.

[0006] In a first aspect, this application provides a magnetic resonance frequency calibration method applied to a magnetic resonance system, the method comprising:

[0007] Apply at least two imaging sequences to the imaging object; and based on the at least two imaging sequences, acquire at least two calibration echo signals of the imaging object;

[0008] The frequency drift is determined based on at least two calibration echo signals;

[0009] The system frequency of the magnetic resonance system is calibrated based on the frequency drift, and the calibrated system frequency is used as the new system frequency to apply the next imaging sequence to the imaging object; the next imaging sequence is the next imaging sequence after at least two calibrated echo signals.

[0010] In one embodiment, the imaging sequence includes an imaging subsequence, which includes a radio frequency pulse, a slice selection gradient, a first phase coding gradient, a second phase coding gradient, and a first readout coding gradient. Applying at least two imaging sequences to the imaging object includes:

[0011] For each applied imaging sequence, a layer-selective gradient is applied simultaneously with the application of a radio frequency pulse to the imaging object;

[0012] After applying the layer selection gradient, a first phase coding gradient and a first readout coding gradient are applied to the imaging object;

[0013] After applying the first readout coding gradient, a second phase coding gradient is applied to the imaging object; the direction of the first phase coding gradient is opposite to the direction of the second phase coding gradient.

[0014] In one embodiment, the imaging sequence further includes a calibration subsequence, which includes a second readout encoded gradient, applies at least two imaging sequences to the imaging object, and further includes:

[0015] For each applied imaging sequence, a second readout coding gradient is applied to the imaging object after the second phase coding gradient is applied.

[0016] In one embodiment, the method further includes:

[0017] The imaging signal is acquired based on the first readout coding gradient applied to the imaging object;

[0018] Image reconstruction is performed based on the imaging signal to obtain the magnetic resonance image of the imaging object.

[0019] In one embodiment, the imaging sequence further includes a dephasing gradient, applying at least two imaging sequences to the imaging object, and further includes:

[0020] For each applied imaging sequence, a dephasing gradient is applied to the imaging object after the second readout coding gradient is applied.

[0021] In one embodiment, based on at least two imaging sequences, at least two calibration echo signals of the imaging object are acquired, including:

[0022] For each imaging sequence, a calibration echo signal is obtained based on a second readout coding gradient applied to the imaging object.

[0023] In one embodiment, determining the frequency drift based on at least two calibration echo signals includes:

[0024] Determine the first calibration echo signal and the second calibration echo signal from at least two calibration echo signals;

[0025] Fourier transforms are performed on the first calibration echo signal and the second calibration echo signal respectively to obtain the first complex signal and the second complex signal;

[0026] The phase difference is determined based on the first complex signal and the second complex signal;

[0027] The frequency drift is determined based on the phase difference and the time when the second calibration echo signal is generated.

[0028] In one embodiment, calibrating the system frequency of the magnetic resonance system based on the frequency drift includes:

[0029] The system frequency of the magnetic resonance system is obtained, and the system frequency is calibrated according to the frequency drift to obtain the calibrated system frequency.

[0030] Secondly, one embodiment of this application provides a magnetic resonance frequency calibration device for use in a magnetic resonance system, the device comprising:

[0031] An acquisition module is used to apply at least two imaging sequences to the imaging object; and based on the at least two imaging sequences, acquire at least two calibration echo signals of the imaging object;

[0032] The frequency drift is determined based on at least two calibration echo signals;

[0033] The system frequency of the magnetic resonance system is calibrated based on the frequency drift, and the calibrated system frequency is used as the new system frequency to apply the next imaging sequence to the imaging object; the next imaging sequence is the next imaging sequence after at least two calibrated echo signals.

[0034] Thirdly, one embodiment of this application provides a computer device including a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the steps of the method provided in the first aspect above.

[0035] Fourthly, one embodiment of this application provides a magnetic resonance system, including a magnetic resonance device and a control device, wherein the control device is communicatively connected to the magnetic resonance device; the control device is used to perform the steps of the method provided in the first aspect above.

[0036] Fifthly, this application also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the method provided in the first aspect above.

[0037] In a seventh aspect, this application also provides a computer program product. The computer program product includes a computer program that, when executed by a processor, implements the steps of the method provided in the first aspect above.

[0038] The aforementioned magnetic resonance frequency calibration method, computer equipment, and magnetic resonance system are described. This method, applied to a magnetic resonance system, involves applying at least two imaging sequences to an imaging object and acquiring at least two calibration echo signals based on these sequences. A frequency drift is determined based on the at least two calibration echo signals. The system frequency of the magnetic resonance system is calibrated according to the frequency drift, and the calibrated system frequency is used as the new system frequency to apply the next imaging sequence to the imaging object. The next imaging sequence is the sequence following the one corresponding to the at least two calibration echo signals. In this embodiment, the frequency drift determined based on the acquired at least two calibration echo signals enables the calibration of the magnetic resonance system's system frequency. Furthermore, the at least two calibration echo signals are acquired during the imaging sequence, eliminating the need for a pre-scanning sequence to the imaging object, thus avoiding disruption of signal steady-state and improving the accuracy of the determined frequency drift. Moreover, acquiring calibration echo signals during the imaging sequence improves the efficiency of frequency calibration, enabling accurate, efficient, and real-time calibration of the magnetic resonance system's system frequency, thereby enhancing the practicality of the magnetic resonance frequency calibration method. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the pre-scanning sequence in one embodiment;

[0040] Figure 2 This is a schematic diagram of the structure of a magnetic resonance system in one embodiment;

[0041] Figure 3 This is a schematic flowchart of a magnetic resonance frequency calibration method in one embodiment;

[0042] Figure 4 This is a flowchart illustrating the steps of a magnetic resonance frequency calibration method in another embodiment;

[0043] Figure 5 This is a schematic diagram of an imaging sequence in one embodiment;

[0044] Figure 6 This is a flowchart illustrating the steps of a magnetic resonance frequency calibration method in another embodiment;

[0045] Figure 7 This is a flowchart illustrating the steps of a magnetic resonance frequency calibration method in another embodiment;

[0046] Figure 8 This is a flowchart illustrating the steps of a magnetic resonance frequency calibration method in another embodiment;

[0047] Figure 9 This is a schematic diagram of the magnetic resonance calibration device in one embodiment;

[0048] Figure 10 This is an internal structural diagram of a computer device in one embodiment. Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0050] The serial numbers assigned to components in this article, such as "first" and "second", are used only to distinguish the objects being described and have no sequential or technical meaning.

[0051] First, before introducing the technical solutions of the embodiments disclosed in this application, the background technology or technological evolution on which the embodiments of this application are based will be introduced. In the field of magnetic resonance imaging, when using magnetic resonance equipment for long-term sequential scanning, the vibration caused by the continuous switching of current will generate heat, which will lead to system frequency drift. The accuracy of the system frequency directly affects the quality of the scanned image. For example, system frequency drift can lead to image position shift, poor fat suppression effect, etc., which will affect the research results of researchers based on the image. In traditional technology, in order to avoid the system frequency drift from reducing image quality, the system frequency is usually calibrated. For example, gradient dual-echo sequences are usually used for field drift calibration. This method uses a pre-scan sequence to scan and collect echo signals, calculates the amount of system frequency drift, and modifies the system frequency used in subsequent scans. The pre-scan sequence is as follows: Figure 1 As shown, RF represents radio frequency pulse, G SS G represents the gradient of selected layers. PE G represents the phase-encoded gradient. RO This represents the readout encoded gradient, and Echo represents the acquired echo signal. The flip angle of the radio frequency pulse in the imaging sequence is... The flip angle of the RF pulses in the pre-scan sequence is Within the repetition time (TR) corresponding to the imaging sequence, a pre-scan sequence is applied, and corresponding echo signals E1 and E2 are acquired. The system frequency drift is calculated based on echo signals E1 and E2. However, this pre-scan sequence introduces additional signal fluctuations, disrupting the steady state of the acquired magnetic resonance signal. This is especially true in imaging sequences requiring short TRs, where the steady-state signal is weak and more susceptible to interference. To reduce the impact of the pre-scan sequence on the signal steady state, acquisition is typically performed after a complete scan sequence is completed; that is, echo signals are acquired after each averaging or repetitive acquisition to calibrate the field drift. However, this method of calibrating the field drift is inefficient and inaccurate. Therefore, this application provides a magnetic resonance frequency calibration method.

[0052] The magnetic resonance frequency calibration method provided in this application can be applied to magnetic resonance systems, the structure of which is as follows: Figure 2 As shown, the device includes a magnetic resonance imaging (MRI) device 104 and a control device 103. The control device 103 can communicate with the MRI device 104 via a network. The MRI device 104 can be functional magnetic resonance elastography (fMRE). The control device 103 can be, but is not limited to, various personal computers, laptops, and tablets.

[0053] The technical solution of this application and how the technical solution of this application solves the technical problem are described in detail below with specific embodiments.

[0054] In one embodiment, such as Figure 3 As shown, a magnetic resonance frequency calibration method is provided. This embodiment illustrates the application of this method to a control device in a magnetic resonance system. In this embodiment, the method includes the following steps:

[0055] Step 300: Apply at least two imaging sequences to the imaging object; and based on the at least two imaging sequences, acquire at least two calibration echo signals of the imaging object.

[0056] The imaging object can be an animal body or an imaging phantom. After the imaging object is placed on the carrier component (scanning bed) of the magnetic resonance imaging (MRI) device, the control device in the MRI system sends a control signal to the MRI device. Based on the received control signal, the MRI device applies at least two imaging sequences to the imaging object; that is, it sequentially applies a first imaging sequence, a second imaging sequence, a third imaging sequence, etc., until the scanning of the imaging object is completed. The number of imaging sequences applied can be set according to the user's scanning needs; this embodiment does not impose any limitations on this.

[0057] After applying at least two imaging sequences to the imaging object, the magnetic resonance imaging (MRI) device acquires calibration echo signals corresponding to the imaging object based on each applied imaging sequence. This means at least two calibration echo signals can be acquired, and these acquired signals are sent to the control device. The number of acquired calibration echo signals is the same as the number of imaging sequences applied to the imaging object. In other words, according to the control signal, after applying the first imaging sequence to the imaging object, the MRI device can acquire the first calibration echo signal based on the first imaging sequence; after applying the second imaging sequence, it can acquire the second calibration echo signal based on the second imaging sequence; after applying the third imaging sequence, it can acquire the third calibration echo signal based on the third imaging sequence, and so on, acquiring multiple calibration echo signals.

[0058] Step 310: Determine the frequency drift based on at least two calibration echo signals.

[0059] After receiving at least two calibration echo signals from the magnetic resonance imaging (MRI) device, the control device determines the frequency drift based on these two signals. This embodiment does not limit the specific method used to determine the frequency drift based on at least two calibration echo signals, as long as the function is achieved.

[0060] In an optional embodiment, it is assumed that the control device receives two calibration echo signals, and can determine the first frequency and the second frequency of the two calibration echo signals respectively, and determine the frequency drift based on the frequency difference between the first frequency and the second frequency.

[0061] Step 320: Calibrate the magnetic resonance system according to the frequency drift, and apply the calibrated system frequency as the new system frequency to the imaging object for the next imaging sequence. The next imaging sequence is the next imaging sequence following at least two calibration echo signals.

[0062] The system frequency of a magnetic resonance (MRI) system refers to the reference frequency of the MRI equipment, also known as the center frequency of the MRI system. This reference frequency can be set at the factory or preset by technicians. The frequency of the imaging sequence applied to the imaging object needs to be set according to the reference frequency of the MRI equipment.

[0063] After determining the frequency drift, the control device calibrates the system frequency of the magnetic resonance imaging (MRI) device based on this drift, thus obtaining the calibrated system frequency. This embodiment does not limit the specific method used to calibrate the system frequency based on the frequency drift, as long as the function is achieved.

[0064] After determining the calibrated system frequency, the control device uses this calibrated system frequency as the new system frequency of the magnetic resonance imaging (MRI) device. Based on this new system frequency, the control device applies the next imaging sequence to the imaging object. In other words, the control device acquires the latest calibration echo signal from the two calibration echo signals used to determine the frequency drift, and controls the MRI device to apply the next imaging sequence corresponding to the latest calibration echo signal to the imaging object. For example, if the imaging sequences corresponding to the two calibration echo signals used to determine the frequency drift are the first imaging sequence applied to the imaging object and the nth imaging sequence applied to the imaging object, the control device sends a control signal to the MRI device to apply the (n+1)th imaging sequence to the imaging object based on the new system frequency. Based on the (n+1)th imaging sequence applied to the imaging object, the control device acquires the (n+1)th calibration echo signal of the imaging object and returns to execute steps 310 and 320 above until the scanning of the imaging object is completed.

[0065] In an optional embodiment, the control device sends a control signal to the magnetic resonance imaging (MRI) device. Based on the received control signal, the MRI device applies a first imaging sequence and a second imaging sequence to the imaging object, and acquires a first calibration echo signal corresponding to the first imaging sequence and a second calibration echo signal corresponding to the second imaging sequence. The MRI device then sends both the first and second calibration echo signals to the control device. The control device determines the frequency drift based on the first and second calibration echo signals, calibrates the system frequency of the MRI device based on the frequency drift, and uses the calibrated system frequency as the new system frequency to control the MRI device to apply a third imaging sequence to the imaging object, acquiring a third calibration echo signal corresponding to the third imaging sequence. The control device uses the second calibration echo signal as the new first calibration echo signal and the third calibration echo signal as the new second calibration echo signal, then returns to the previous steps of determining the frequency drift based on the first and second calibration echo signals and calibrating the system frequency of the MRI device based on the frequency drift. These steps are repeated until the scanning of the imaging object is complete.

[0066] The magnetic resonance frequency calibration method provided in this application is applied to a magnetic resonance system. This method involves applying at least two imaging sequences to the imaging object and acquiring at least two calibration echo signals based on these sequences; determining the frequency drift based on the at least two calibration echo signals; calibrating the system frequency of the magnetic resonance system based on the frequency drift; and applying the calibrated system frequency as the new system frequency to the imaging object using the next imaging sequence. The next imaging sequence is the sequence following the one corresponding to the at least two calibration echo signals. In this embodiment, the frequency drift determined based on the acquired at least two calibration echo signals can be used to calibrate the system frequency of the magnetic resonance system. Furthermore, the at least two calibration echo signals are acquired during the imaging sequence, eliminating the need for a pre-scanning sequence and preventing disruption of signal steady-state, thus improving the accuracy of the determined frequency drift. Moreover, acquiring calibration echo signals during the imaging sequence improves the efficiency of frequency calibration, enabling accurate, efficient, and real-time calibration of the magnetic resonance system's frequency, thereby enhancing the practicality of the magnetic resonance frequency calibration method.

[0067] In one embodiment, the imaging sequence includes an imaging subsequence, which includes a radio frequency pulse, a layer selection gradient, a first phase coding gradient, a second phase coding gradient, and a first readout coding gradient.

[0068] In this embodiment, the frequency of the radio frequency (RF) pulse is the same as the system frequency of the magnetic resonance imaging (MRI) device. The RF pulse type can be any of the following: non-selective RF pulse, selective RF pulse, hard pulse, soft pulse, and adiabatic pulse. This embodiment does not limit the type of RF pulse in the imaging sequence, nor its related parameters such as flip angle and bandwidth, as long as the function can be achieved.

[0069] The layer selection gradient is a linearly varying magnetic field applied along a certain axis of the imaging object (usually the Z-axis, i.e., the vertical direction of the imaging object) based on the main magnetic field. This embodiment does not impose restrictions on the intensity and duration of the layer selection gradient.

[0070] The direction of the first phase coding gradient is opposite to that of the second phase coding gradient. The first readout coding gradient is also called the first frequency coding gradient. The first readout coding gradient can be used to apply a linearly varying magnetic field gradient in a specific direction (usually the left-right direction of the imaging object, i.e., the x-axis direction) on a selected imaging plane by exciting a radio frequency pulse. This can cause hydrogen nuclei at different locations to generate magnetic resonance signals of different frequencies. The spatial position of the hydrogen nuclei in that specific direction can be determined based on the magnetic resonance signal.

[0071] In the case where the imaging sequence includes an imaging subsequence, and the imaging subsequence includes a radio frequency pulse, a slice selection gradient, a first phase coding gradient, a second phase coding gradient, and a first readout coding gradient, such as Figure 4 As shown, an implementation method involves applying at least two imaging sequences to an imaging object, the steps of which include:

[0072] Step 400: For each applied imaging sequence, apply a radio frequency pulse to the imaging object while simultaneously applying a layer-selective gradient.

[0073] When the control device controls the magnetic resonance imaging (MRI) device to apply each imaging sequence to the imaging object, the control device first controls the MRI device to apply a slice-selective gradient to the imaging object simultaneously with the application of a radio frequency (RF) pulse. Applying a slice-selective gradient simultaneously with the application of an RF pulse means that a first RF pulse is applied within the time period during which the slice-selective gradient is applied to the imaging object. The start time of the RF pulse application and the start time of the slice-selective gradient application can be the same or different; the end time of the RF pulse application and the end time of the slice-selective gradient application can also be the same or different.

[0074] After applying a radio frequency pulse and a slice-selective gradient to the imaging object, the hydrogen atoms in different layers of the object and the strength of the magnetic resonance magnetic field are different, resulting in different Larmor frequencies. When the frequency of the radio frequency pulse matches the Larmor frequency of the hydrogen nuclei in a certain layer, only the hydrogen nuclei in that layer are excited, thus achieving slice selection.

[0075] Step 410: After applying the layer selection gradient, apply the first phase coding gradient and the first readout coding gradient to the imaging object.

[0076] 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 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 5 As shown, in the order of the arrows, first phase coding gradients of different intensities are applied sequentially. The first phase coding gradient is the phase coding gradient that is close to the layer selection gradient.

[0077] After applying a slice-selective gradient to the imaging target using the magnetic resonance imaging (MRI) device, the control device applies a first phase-coding gradient and a first readout-coding gradient to the imaging target. The MRI device can apply the first phase-coding gradient and the first readout-coding gradient directly after applying the slice-selective gradient. That is, the end time of the slice-selective gradient is the start time of the first phase-coding gradient and the first readout-coding gradient; alternatively, it can apply the first phase-coding gradient and the first readout-coding gradient at a first preset time interval after applying the slice-selective gradient. The start time of applying the first phase-coding gradient is the same as the start time of applying the first readout-coding gradient. Figure 5 As shown, after applying the layer selection gradient, the first phase coding gradient and the first readout coding gradient are applied directly.

[0078] Step 420: After applying the first readout coding gradient, apply the second phase coding gradient to the imaging object; the direction of the first phase coding gradient is opposite to the direction of the second phase coding gradient.

[0079] After applying a first readout coding gradient to the imaging object using the magnetic resonance imaging (MRI) device, the control device applies a second phase coding gradient to the imaging object. The start time of applying the second phase coding gradient can be the same as the end time of applying the first readout coding gradient, or it can be applied after the end time of applying the first readout gradient, at a second preset time interval. Figure 5 As shown, the first phase coding gradient is the phase coding gradient close to the layer selection gradient, and the second phase coding gradient is the phase coding gradient far from the layer selection gradient. The first phase coding gradient includes multiple phase coding gradients of different intensities applied sequentially in the first direction according to the arrow order; the second phase coding gradient includes multiple phase coding gradients of different intensities applied sequentially in the second direction according to the arrow order, with the first and second directions being opposite.

[0080] In this embodiment, for each applied imaging sequence, a layer-selective gradient is applied simultaneously with an RF pulse to the imaging object; after applying the layer-selective gradient, a first phase-coding gradient and a first readout-coding gradient are applied to the imaging object; after applying the first readout-coding gradient, a second phase-coding gradient is applied to the imaging object; the direction of the first phase-coding gradient is opposite to the direction of the second phase-coding gradient. In this way, by applying imaging sub-sequences to the imaging object, spatial information of a certain imaging layer of the imaging object in several directions can be obtained, facilitating the subsequent acquisition of accurate images of the imaging object.

[0081] In one embodiment, the imaging sequence further includes a calibration subsequence, which includes a second readout-coded gradient. That is, the imaging sequence includes an imaging subsequence for imaging and a calibration subsequence for frequency calibration. The intensity of the second readout-coded gradient may be the same as or different from the intensity of the first readout-coded gradient, and the duration of the second readout-coded gradient may be the same as or different from the duration of the first readout-coded gradient. A description of the second readout-coded gradient can be found in the description of the first readout-coded gradient in the above embodiments.

[0082] When the imaging sequence includes a calibration subsequence that includes a second readout encoded gradient, implementations involving applying at least two imaging sequences to the imaging object also include:

[0083] For each applied imaging sequence, a second readout coding gradient is applied to the imaging object after the second phase coding gradient is applied.

[0084] When the control device applies each imaging sequence to the imaging object using the magnetic resonance imaging (MRI) device, it applies a second readout coding gradient to the imaging object after applying the second phase coding gradient. The start time of the second readout coding gradient can be the same as the end time of the second phase coding gradient; that is, the second readout coding gradient is applied directly after the second phase coding is applied to the imaging object. Alternatively, the start time of the second readout coding gradient can be different from the end time of the second phase coding gradient. In other words, the second readout coding gradient is applied after a third preset time interval following the end time of the second phase coding gradient.

[0085] In this embodiment, for each applied imaging sequence, after applying a second phase coding gradient to the imaging object, a second readout coding gradient is applied to the imaging object to facilitate the acquisition of calibration echo signals based on the second readout coding gradient. The calibration echo signals are then used to determine the frequency drift and to calibrate the system frequency of the magnetic resonance device.

[0086] In one embodiment, such as Figure 6 As shown, the method further includes the following steps:

[0087] Step 600: Acquire the imaging signal based on the first readout coding gradient applied to the imaging object.

[0088] When the control device controls the magnetic resonance imaging (MRI) device to apply a first readout coding gradient to the imaging object, it acquires the imaging signal of the imaging object based on the first readout coding gradient and sends the imaging signal to the control device. When multiple imaging sequences are applied to the imaging object, multiple imaging signals can be acquired, and the number of imaging signals is the same as the number of first readout coding gradients in the applied imaging sequences. For example... Figure 5As shown, the acquisition time period of the imaging signals (i.e., echo signals E1,1 and En,1) corresponds to the time period during which the first readout coding gradient is applied. Figure 5 In the middle, TE1 represents the time when the echo signal E1,1 was generated.

[0089] Step 610: Reconstruct the image based on the imaging signal to obtain the magnetic resonance image of the imaging object.

[0090] After receiving the imaging signal, the control device performs image reconstruction to obtain the magnetic resonance image of the object being imaged. This embodiment does not limit the specific method used for image reconstruction based on the imaging signal, as long as the function can be achieved. Optionally, the control device can determine the magnetic resonance image of the object by performing a Fourier transform on the imaging signal.

[0091] When multiple imaging signals are received, image reconstruction can be performed on each imaging signal to obtain a two-dimensional magnetic resonance image of the imaging object; image matching of all two-dimensional magnetic resonance images can obtain a three-dimensional magnetic resonance image of the imaging object.

[0092] In this embodiment, an imaging signal is acquired based on a first readout coding gradient applied to the imaging object; an image is reconstructed based on the imaging signal to obtain a magnetic resonance image of the imaging object. Since the imaging sequence is applied based on a calibrated system frequency, the imaging signal acquired based on the imaging object is more accurate, thereby improving the quality of the final determined magnetic resonance image of the imaging object.

[0093] In one embodiment, the imaging sequence further includes a asphaltral gradient, in which case the implementation involving applying at least two imaging sequences to the imaging object also includes:

[0094] For each applied imaging sequence, a dephasing gradient is applied to the imaging object after the second readout coding gradient is applied.

[0095] When the control device applies each imaging sequence to the imaging object using the magnetic resonance imaging (MRI) device, it applies a astigmatic gradient to the imaging object after applying the second readout coding gradient. The MRI device can apply the astigmatic gradient directly after applying the second readout coding gradient, i.e., the end time of the second readout coding gradient is the start time of the astigmatic gradient; alternatively, the MRI device can apply the astigmatic gradient at a fourth preset time interval after applying the second readout coding gradient. The astigmatic gradient can be applied along at least one axis direction: the axis direction of the slice selection gradient, the axis direction of the first and second phase coding gradients, and the upper limit of the axis directions of the first and second readout coding gradients. Figure 5As shown, the gray gradient represents the applied isophagic gradient, which is applied along the axial directions corresponding to the layer selection gradient, the first phase coding gradient, and the first readout coding gradient. This embodiment does not limit the intensity, duration, or axial direction of the applied isophagic gradient, as long as its function is achieved.

[0096] In this embodiment, for each applied imaging sequence, after applying the second readout coding gradient to the imaging object, a dephasing gradient is applied to the imaging object. This dephasing gradient removes redundant signals during the imaging process, thereby improving the accuracy of system frequency calibration and the quality of the magnetic resonance image of the determined imaging object. Ultimately, this improves the accuracy of research results obtained by researchers studying magnetic resonance images.

[0097] In one embodiment, an implementation involves acquiring at least two calibration echo signals of an imaging object based on at least two imaging sequences. This implementation includes:

[0098] For each imaging sequence, a calibration echo signal is obtained based on a second readout coding gradient applied to the imaging object.

[0099] For each imaging sequence applied by the magnetic resonance imaging (MRI) device to the imaging object, the control device, while controlling the MRI device to apply a second readout coding gradient to the imaging object, acquires a calibration echo signal based on the second readout coding gradient and sends the calibration echo signal to the control device. For example... Figure 5 As shown, the calibration echo signals E1,2 and En,2 are calibrated. Figure 5 In the diagram, TE2 represents the time when the calibration echo signal E1,2 was generated, and TE3 represents the time when the calibration echo signal En,2 was generated.

[0100] In this embodiment, for each imaging sequence, a calibration echo signal is acquired based on a second readout coding gradient applied to the imaging object. This means the calibration echo signal is acquired during the imaging sequence, eliminating the need for a pre-scan sequence applied to the imaging object, thus preserving the signal steady state and improving the accuracy of the determined frequency drift. This enables accurate, efficient, and real-time calibration of the magnetic resonance system's frequency.

[0101] In one embodiment, such as Figure 7 As shown, an implementation method for determining the frequency drift based on at least two calibration echo signals is described, the steps of which include:

[0102] Step 700: Determine the first calibration echo signal and the second calibration echo signal from at least two calibration echo signals.

[0103] After receiving at least two calibration echo signals, the control device can determine the first calibration echo signal and the second calibration echo signal from the received calibration echo signals.

[0104] Specifically, if the control device receives only two calibration echo signals, it directly designates these two signals as the first and second calibration echo signals, respectively. The two calibration echo signals received by the control device can be two calibration echo signals corresponding to two adjacent imaging sequences, or two calibration echo signals corresponding to imaging sequences spaced a preset number apart. For example, the first calibration echo signal might be the calibration echo signal corresponding to the first imaging sequence applied to the imaging object, and the second calibration echo signal might be the calibration echo signal corresponding to the nth imaging sequence applied to the imaging object, where n is a natural number greater than 2. If the control device receives more than two calibration echo signals, it sorts the received calibration echo signals according to their acquisition time from earliest to latest, obtaining the earliest acquired calibration echo signal and the latest acquired calibration echo signal, and designating them as the first and second calibration echo signals, respectively. In other words, the earliest acquired calibration echo signal can be designated as the first calibration echo signal, and the latest acquired calibration echo signal as the second calibration echo signal.

[0105] Step 710: Perform Fourier transform on the first calibration echo signal and the second calibration echo signal respectively to obtain the first complex signal and the second complex signal.

[0106] After determining the first calibration echo signal and the second calibration echo signal, the control device performs a Fourier transform on the first calibration echo signal to obtain the first complex signal in the complex domain, and performs a Fourier transform on the second calibration echo signal to obtain the second complex signal in the complex domain.

[0107] Assuming the first calibration echo signal is E1,2 and the second echo signal is En,2, performing a Fourier transform on the first calibration echo signal yields a first complex signal E3, and performing a Fourier transform on the second calibration echo signal yields a second complex signal E4. The first complex signal can be expressed as: The second complex signal can be represented as Where n represents the number of times the imaging sequence is applied.

[0108] Step 720: Determine the phase difference based on the first complex signal and the second complex signal.

[0109] After determining the first complex signal and the second complex signal, the control device determines the phase difference between the two signals. Specifically, the phase difference can be obtained through conjugate multiplication, and can be expressed as: .

[0110] Step 730: Determine the frequency drift based on the phase difference and the time when the second calibration echo signal is generated.

[0111] The generation time of the second calibration echo signal refers to the time interval between the peak of the radio frequency pulse in the imaging sequence corresponding to the second calibration echo signal and the peak of the second calibration echo signal. After determining the phase difference between the first and second complex signals, the control device can determine the frequency drift based on this phase difference and the generation time of the second calibration echo signal. Specifically, the direct relationship between frequency f and phase angle θ can be expressed as follows: , The time at which the second calibration echo signal is generated, and the frequency drift, can be expressed as: .

[0112] In this embodiment, a first calibration echo signal and a second calibration echo signal are determined from at least two calibration echo signals; Fourier transforms are performed on the first and second calibration echo signals respectively to obtain a first complex signal and a second complex signal; the phase difference is determined based on the first and second complex signals; and the frequency drift is determined based on the phase difference and the time when the second calibration echo signal was generated. This method for determining the frequency drift is quick and easy to implement, improving the efficiency of determining the frequency drift and thus enhancing the practicality of the magnetic resonance frequency calibration method.

[0113] In one embodiment, an implementation for calibrating the system frequency of a magnetic resonance device based on a frequency drift includes:

[0114] The system frequency of the magnetic resonance imaging (MRI) device is obtained, and the system frequency is calibrated according to the frequency drift to obtain the calibrated system frequency.

[0115] The system frequency of a magnetic resonance system, i.e. the system frequency of the magnetic resonance device in the magnetic resonance system, can be pre-stored in the memory of the control device, and the control device can directly retrieve it from the memory when needed.

[0116] After acquiring the system frequency of the magnetic resonance imaging (MRI) device, the control equipment calibrates the system frequency based on the determined frequency drift, thus obtaining the calibrated system frequency. Specifically, the sum of the system frequency and the frequency drift can be calculated to determine the calibrated system frequency. Assuming the system frequency is F, the calibrated system frequency can be expressed as Fn = F + .

[0117] In an optional embodiment, the magnetic resonance imaging (MRI) device has an initial frequency bias. This initial frequency bias can be a frequency error in the MRI device calculated by the operator. In this case, another implementation of calibrating the system frequency of the MRI system based on the frequency drift includes calibrating the system frequency based on the frequency drift and the initial frequency bias to obtain the calibrated system frequency. Specifically, the calibrated system frequency can be obtained by calculating the sum of the system frequency and the frequency drift, and then subtracting the initial frequency bias from this sum. Assuming the initial frequency bias is f0, the calibrated system frequency can be expressed as Fn = F + -f0.

[0118] In this embodiment, the system frequency of the magnetic resonance system is obtained, and the system frequency is calibrated according to the frequency drift to obtain the calibrated system frequency. This method of determining the calibrated system frequency is quick and easy to implement, which can improve the efficiency of determining the calibrated system frequency and thus improve the practicality of the magnetic resonance frequency calibration method.

[0119] Please see Figure 8 This application provides a magnetic resonance frequency calibration method, applied to a magnetic resonance system, the magnetic resonance system including a magnetic resonance device, the method comprising:

[0120] Step 800: Apply a first imaging sequence to the imaging object, and obtain a first calibration echo signal based on the first calibration subsequence in the first imaging sequence;

[0121] Step 810: Apply a second imaging sequence to the imaging object, and obtain a second calibration echo signal based on the second calibration subsequence in the second imaging sequence;

[0122] Step 820: Perform Fourier transform on the first calibration echo signal and the second calibration echo signal respectively to obtain the first complex signal and the second complex signal;

[0123] Step 830: Determine the phase difference based on the first complex signal and the second complex signal; and determine the frequency drift based on the phase difference and the time when the second calibration echo signal is generated.

[0124] Step 840: Obtain the system frequency of the magnetic resonance device and calibrate the system frequency according to the frequency drift to obtain the calibrated system frequency;

[0125] Step 850: Apply the calibrated system frequency as the new system frequency to the imaging object and return to steps 800-840 as the new first imaging sequence until the scanning of the imaging object is completed.

[0126] It should be understood that although the steps in the flowcharts of the embodiments described above are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the embodiments described above may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages of other steps.

[0127] Based on the same inventive concept, this application also provides a magnetic resonance frequency calibration device for implementing the magnetic resonance frequency calibration method described above. The solution provided by this device is similar to the implementation described in the above method; therefore, the specific limitations in one or more embodiments of the magnetic resonance frequency calibration device provided below can be found in the limitations of the magnetic resonance frequency calibration method described above, and will not be repeated here.

[0128] In one embodiment, such as Figure 9 As shown, a magnetic resonance frequency calibration device 10 is provided, including: an acquisition module 11, a determination module 12, and a calibration module 13, wherein:

[0129] The acquisition module 11 is used to apply at least two imaging sequences to the imaging object; and to acquire at least two calibration echo signals of the imaging object based on the at least two imaging sequences.

[0130] Determine module 12, which is used to determine the frequency drift based on at least two calibration echo signals.

[0131] The calibration module 13 is used to calibrate the system frequency of the magnetic resonance system according to the frequency drift, and apply the calibrated system frequency as the new system frequency to the imaging object for the next imaging sequence; the next imaging sequence is the next imaging sequence of at least two calibration echo signals.

[0132] In one embodiment, the imaging sequence includes an imaging subsequence, which includes a radio frequency pulse, a slice selection gradient, a first phase coding gradient, a second phase coding gradient, and a first readout coding gradient. The acquisition module 11 includes a first application unit. The first application unit is configured to, for each applied imaging sequence, apply a radio frequency pulse to the imaging object while simultaneously applying a slice selection gradient; after applying the slice selection gradient, apply the first phase coding gradient and the first readout coding gradient to the imaging object; and after applying the first readout coding gradient, apply the second phase coding gradient to the imaging object; the direction of the first phase coding gradient is opposite to the direction of the second phase coding gradient.

[0133] In one embodiment, the imaging sequence further includes a calibration subsequence, which includes a second readout coding gradient, and the acquisition module 11 further includes a second application unit. The second application unit is used to apply a second readout coding gradient to the imaging object for each applied imaging sequence after applying the second phase coding gradient.

[0134] In one embodiment, the magnetic resonance frequency calibration device 10 includes a reconstruction module. The reconstruction module is used to acquire an imaging signal based on a first readout coding gradient applied to the imaging object; and to reconstruct an image based on the imaging signal to obtain a magnetic resonance image of the imaging object.

[0135] In one embodiment, the acquisition module 11 further includes a third application unit. The third application unit is used to apply a dephasing gradient to the imaging object for each applied imaging sequence after applying a second readout coding gradient.

[0136] In one embodiment, the acquisition module 11 is specifically used to acquire a calibration echo signal for each imaging sequence based on a second readout coding gradient applied to the imaging object.

[0137] In one embodiment, the determining module 12 is specifically configured to determine a first calibration echo signal and a second calibration echo signal from at least two calibration echo signals; perform Fourier transforms on the first calibration echo signal and the second calibration echo signal respectively to obtain a first complex signal and a second complex signal; determine the phase difference based on the first complex signal and the second complex signal; and determine the frequency drift based on the phase difference and the time when the second calibration echo signal was generated.

[0138] In one embodiment, the calibration module 13 is specifically used to obtain the system frequency of the magnetic resonance system and calibrate the system frequency according to the frequency drift to obtain the calibrated system frequency.

[0139] Each module in the aforementioned magnetic resonance frequency calibration device can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in hardware within or independently of the processor in a computer device, or stored in software within the memory of a computer device, so that the processor can call and execute the corresponding operations of each module.

[0140] In one embodiment, a computer device is provided, the internal structure of which can be shown as follows: Figure 10 As shown, the computer device includes a processor, memory, communication interface, display screen, and input devices connected via a system bus. The processor provides computing and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs stored in the non-volatile storage media. The communication interface is used for wired or wireless communication with external terminals; wireless communication can be achieved through Wi-Fi, mobile cellular networks, NFC (Near Field Communication), or other technologies. When executed by the processor, the computer program implements a magnetic resonance frequency calibration method. The display screen can be an LCD screen or an e-ink screen. The input devices can be a touch layer covering the display screen, buttons, a trackball, or a touchpad on the computer device's casing, or an external keyboard, touchpad, or mouse.

[0141] Those skilled in the art will understand that Figure 10 The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the computer device to which the present application is applied. Specific computer devices may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0142] In one embodiment, a computer device is provided, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to perform the following steps:

[0143] Apply at least two imaging sequences to the imaging object; and based on the at least two imaging sequences, acquire at least two calibration echo signals of the imaging object;

[0144] The frequency drift is determined based on at least two calibration echo signals;

[0145] The system frequency of the magnetic resonance system is calibrated based on the frequency drift, and the calibrated system frequency is used as the new system frequency to apply the next imaging sequence to the imaging object; the next imaging sequence is the next imaging sequence after at least two calibrated echo signals.

[0146] In one embodiment, the processor, when executing the computer program, further implements the following steps: for each applied imaging sequence, applying a radio frequency pulse to the imaging object while simultaneously applying a layer selection gradient; after applying the layer selection gradient, applying a first phase coding gradient and a first readout coding gradient to the imaging object; after applying the first readout coding gradient, applying a second phase coding gradient to the imaging object; the direction of the first phase coding gradient is opposite to the direction of the second phase coding gradient.

[0147] In one embodiment, the processor, when executing the computer program, further implements the following steps: for each applied imaging sequence, after applying the second phase coding gradient, applying a second readout coding gradient to the imaging object.

[0148] In one embodiment, when the processor executes the computer program, it further performs the following steps: acquiring an imaging signal based on a first readout coding gradient applied to the imaging object; and reconstructing an image based on the imaging signal to obtain a magnetic resonance image of the imaging object.

[0149] In one embodiment, the processor, when executing the computer program, further implements the following steps: for each applied imaging sequence, after applying a second readout coding gradient, applying a dephasing gradient to the imaging object.

[0150] In one embodiment, the processor, when executing the computer program, further performs the following steps: for each imaging sequence, acquiring a calibration echo signal based on a second readout coding gradient applied to the imaging object.

[0151] In one embodiment, when the processor executes the computer program, it further performs the following steps: determining a first calibration echo signal and a second calibration echo signal from at least two calibration echo signals; performing Fourier transforms on the first calibration echo signal and the second calibration echo signal respectively to obtain a first complex signal and a second complex signal; determining a phase difference based on the first complex signal and the second complex signal; and determining a frequency drift based on the phase difference and the time when the second calibration echo signal was generated.

[0152] In one embodiment, when the processor executes the computer program, it further performs the following steps: acquiring the system frequency of the magnetic resonance system and calibrating the system frequency according to the frequency drift to obtain the calibrated system frequency.

[0153] In one embodiment, a computer-readable storage medium is provided having a computer program stored thereon, the computer program performing the following steps when executed by a processor:

[0154] Apply at least two imaging sequences to the imaging object; and based on the at least two imaging sequences, acquire at least two calibration echo signals of the imaging object;

[0155] The frequency drift is determined based on at least two calibration echo signals;

[0156] The system frequency of the magnetic resonance system is calibrated based on the frequency drift, and the calibrated system frequency is used as the new system frequency to apply the next imaging sequence to the imaging object; the next imaging sequence is the next imaging sequence after at least two calibrated echo signals.

[0157] In one embodiment, when the computer program is executed by the processor, it further implements the following steps: for each applied imaging sequence, applying a radio frequency pulse to the imaging object while applying a layer selection gradient; after applying the layer selection gradient, applying a first phase coding gradient and a first readout coding gradient to the imaging object; after applying the first readout coding gradient, applying a second phase coding gradient to the imaging object; the direction of the first phase coding gradient is opposite to the direction of the second phase coding gradient.

[0158] In one embodiment, when the computer program is executed by the processor, it further performs the following steps: for each applied imaging sequence, after applying the second phase coding gradient, applying a second readout coding gradient to the imaging object.

[0159] In one embodiment, when the computer program is executed by the processor, it further performs the following steps: acquiring an imaging signal based on a first readout coding gradient applied to the imaging object; and reconstructing an image based on the imaging signal to obtain a magnetic resonance image of the imaging object.

[0160] In one embodiment, when the computer program is executed by the processor, it further performs the following steps: for each applied imaging sequence, after applying a second readout coding gradient, applying a dephasing gradient to the imaging object.

[0161] In one embodiment, when the computer program is executed by the processor, it further performs the following steps: for each imaging sequence, acquiring a calibration echo signal based on a second readout coding gradient applied to the imaging object.

[0162] In one embodiment, when the computer program is executed by a processor, it further performs the following steps: determining a first calibration echo signal and a second calibration echo signal from at least two calibration echo signals; performing Fourier transforms on the first calibration echo signal and the second calibration echo signal respectively to obtain a first complex signal and a second complex signal; determining a phase difference based on the first complex signal and the second complex signal; and determining a frequency drift based on the phase difference and the time when the second calibration echo signal was generated.

[0163] In one embodiment, when the computer program is executed by the processor, it further performs the following steps: acquiring the system frequency of the magnetic resonance system and calibrating the system frequency according to the frequency drift to obtain the calibrated system frequency.

[0164] In one embodiment, a computer program product is provided, including a computer program that, when executed by a processor, performs the following steps:

[0165] Apply at least two imaging sequences to the imaging object; and based on the at least two imaging sequences, acquire at least two calibration echo signals of the imaging object;

[0166] The frequency drift is determined based on at least two calibration echo signals;

[0167] The system frequency of the magnetic resonance system is calibrated based on the frequency drift, and the calibrated system frequency is used as the new system frequency to apply the next imaging sequence to the imaging object; the next imaging sequence is the next imaging sequence after at least two calibrated echo signals.

[0168] In one embodiment, when the computer program is executed by the processor, it further implements the following steps: for each applied imaging sequence, applying a radio frequency pulse to the imaging object while applying a layer selection gradient; after applying the layer selection gradient, applying a first phase coding gradient and a first readout coding gradient to the imaging object; after applying the first readout coding gradient, applying a second phase coding gradient to the imaging object; the direction of the first phase coding gradient is opposite to the direction of the second phase coding gradient.

[0169] In one embodiment, when the computer program is executed by the processor, it further performs the following steps: for each applied imaging sequence, after applying the second phase coding gradient, applying a second readout coding gradient to the imaging object.

[0170] In one embodiment, when the computer program is executed by the processor, it further performs the following steps: acquiring an imaging signal based on a first readout coding gradient applied to the imaging object; and reconstructing an image based on the imaging signal to obtain a magnetic resonance image of the imaging object.

[0171] In one embodiment, when the computer program is executed by the processor, it further performs the following steps: for each applied imaging sequence, after applying a second readout coding gradient, applying a dephasing gradient to the imaging object.

[0172] In one embodiment, when the computer program is executed by the processor, it further performs the following steps: for each imaging sequence, acquiring a calibration echo signal based on a second readout coding gradient applied to the imaging object.

[0173] In one embodiment, when the computer program is executed by a processor, it further performs the following steps: determining a first calibration echo signal and a second calibration echo signal from at least two calibration echo signals; performing Fourier transforms on the first calibration echo signal and the second calibration echo signal respectively to obtain a first complex signal and a second complex signal; determining a phase difference based on the first complex signal and the second complex signal; and determining a frequency drift based on the phase difference and the time when the second calibration echo signal was generated.

[0174] In one embodiment, when the computer program is executed by the processor, it further performs the following steps: acquiring the system frequency of the magnetic resonance system and calibrating the system frequency according to the frequency drift to obtain the calibrated system frequency.

[0175] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium. When executed, the computer program can include the processes of the embodiments described above. Any references to memory, databases, or other media 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), magnetic 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. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM). The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, etc., and are not limited to these.

[0176] The technical features of the above embodiments can be combined in any way. For the sake of brevity, 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.

[0177] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A magnetic resonance frequency calibration method, characterized in that, Applied to a magnetic resonance system, the method includes: At least two imaging sequences are applied to the imaging object; and based on the at least two imaging sequences, at least two calibration echo signals of the imaging object are obtained; the imaging sequences include imaging sub-sequences for imaging and calibration sub-sequences for frequency calibration; the imaging sub-sequences include a radio frequency pulse, a slice gradient, a first phase coding gradient, a second phase coding gradient and a first readout coding gradient, and the calibration sub-sequences include a second readout coding gradient; The frequency drift is determined based on the at least two calibration echo signals; The system frequency of the magnetic resonance system is calibrated according to the frequency drift, and the calibrated system frequency is used as the new system frequency to apply the next imaging sequence to the imaging object; the next imaging sequence is the next imaging sequence corresponding to the at least two calibration echo signals. The application of at least two imaging sequences to the imaging object includes: For each of the applied imaging sequences, the layer-selective gradient is applied simultaneously with the radio frequency pulse applied to the imaging object; After applying the layer selection gradient, the first phase coding gradient and the first readout coding gradient are applied to the imaging object; After applying the first readout coding gradient, the second phase coding gradient is applied to the imaging object; the direction of the first phase coding gradient is opposite to the direction of the second phase coding gradient. For each of the applied imaging sequences, after applying the second phase-encoding gradient, the second readout-encoding gradient is applied to the imaging object; The step of calibrating the system frequency of the magnetic resonance system based on the frequency drift includes: calculating the sum between the system frequency and the frequency drift to obtain the calibrated system frequency.

2. The method according to claim 1, characterized in that, The method further includes: An imaging signal is acquired based on the first readout coding gradient applied to the imaging object; Image reconstruction is performed based on the imaging signal to obtain a magnetic resonance image of the imaging object.

3. The method according to claim 1, characterized in that, The imaging sequence further includes a astigmatic gradient, and applying the at least two imaging sequences to the imaging object also includes: For each of the applied imaging sequences, the asphalt gradient is applied to the imaging object after the second readout coding gradient is applied.

4. The method according to claim 3, characterized in that, The acquisition of at least two calibration echo signals of the imaged object based on at least two imaging sequences includes: For each of the imaging sequences, the calibration echo signal is obtained based on the second readout coding gradient applied to the imaging object.

5. The method according to any one of claims 1-4, characterized in that, Determining the frequency drift based on the at least two calibration echo signals includes: The first calibration echo signal and the second calibration echo signal are determined from the at least two calibration echo signals; Perform Fourier transforms on the first calibration echo signal and the second calibration echo signal respectively to obtain a first complex signal and a second complex signal; 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 when the second calibration echo signal is generated.

6. The method according to any one of claims 1-4, characterized in that, Determining the frequency drift based on the at least two calibration echo signals includes: Determine the first and second frequencies of the two calibration echo signals; The frequency drift is determined based on the frequency difference between the first frequency and the second frequency.

7. The method according to any one of claims 1-4, characterized in that, The step of calculating the sum between the system frequency and the frequency drift to obtain the calibrated system frequency includes: Obtain the initial frequency offset of the magnetic resonance system, calculate the sum between the system frequency and the frequency drift, and subtract the initial frequency offset from the sum between the system frequency and the frequency drift to obtain the calibrated system frequency.

8. A magnetic resonance frequency calibration device, characterized in that, The device includes: An acquisition module is configured to apply at least two imaging sequences to an imaging object; and based on the at least two imaging sequences, acquire at least two calibration echo signals of the imaging object; the imaging sequences include an imaging sub-sequence for imaging and a calibration sub-sequence for frequency calibration; the imaging sub-sequence includes a radio frequency pulse, a slice selection gradient, a first phase coding gradient, a second phase coding gradient and a first readout coding gradient, and the calibration sub-sequence includes a second readout coding gradient; The determination module is used to determine the frequency drift based on the at least two calibration echo signals; The calibration module is used to calibrate the system frequency of the magnetic resonance system according to the frequency drift, and apply the calibrated system frequency as the new system frequency to the imaging object for the next imaging sequence; the next imaging sequence is the next imaging sequence corresponding to the at least two calibration echo signals. The acquisition module includes a first application unit and a second application unit. The first application unit is configured to apply the radio frequency pulse to the imaging object and apply the slice selection gradient simultaneously for each applied imaging sequence; after applying the slice selection gradient, apply the first phase coding gradient and the first readout coding gradient to the imaging object; after applying the first readout coding gradient, apply the second phase coding gradient to the imaging object; the direction of the first phase coding gradient is opposite to the direction of the second phase coding gradient. The second application unit is configured to apply the second readout coding gradient to the imaging object after applying the second phase coding gradient for each applied imaging sequence. The calibration module is specifically used to calculate the sum between the system frequency and the frequency drift to obtain the calibrated system frequency.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes a computer program, it implements the steps of the method according to any one of claims 1-7.

10. A magnetic resonance system, characterized in that, It includes a magnetic resonance imaging (MRI) device and a control device, wherein the control device is communicatively connected to the MRI device; the control device is used to perform the steps of the method as described in any one of claims 1-7.

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