Delay determination method, device and system of magnetic resonance system and storage medium

Abstract

The invention provides a delay determination method, device and system of a magnetic resonance system and a storage medium, and the method comprises the steps: carrying out the image collection of a target object based on a preset echo interval, and obtaining a first echo phase image, a second echo phase image and a third echo phase image, the first echo phase image and the third echo phase image are acquired based on a frequency coding gradient magnetic field of the first polarity; determining a first phase difference image corresponding to a single echo interval based on the first echo phase image and the third echo phase image; superposing the first echo phase image and the first phase difference image to obtain a reference phase image corresponding to the second echo phase image; and determining delay information of the magnetic resonance system based on the reference phase image and the second echo phase image. Based on the scheme of the invention, the delay information of the magnetic resonance system can be accurately determined.

Description

Technical Field

[0001] This application relates to the field of magnetic resonance technology, and in particular to a method, apparatus, system and storage medium for determining the delay of a magnetic resonance system. Background Technology

[0002] Magnetic resonance imaging (MRI) systems are widely used in medical diagnostics and scientific research. They acquire information about the internal structure of objects by utilizing the resonance properties of atomic nuclei's magnetic moments in a magnetic field. In practical applications, MRI systems involve complex signal acquisition and processing, and delays may occur during operation. These delays cause deviations between the acquired signals and the expected timing, thus affecting image quality or the accuracy of data processing results. Therefore, determining the delay in an MRI system is a crucial technical problem that needs to be solved. Summary of the Invention

[0003] This application provides a method, apparatus, system, and storage medium for determining the delay of a magnetic resonance system. The method can accurately determine the delay information of a magnetic resonance system.

[0004] In a first aspect, a method for determining the time delay of a magnetic resonance imaging (MRI) system is provided, wherein a target object is placed in the imaging region of the MRI system, and the method includes:

[0005] Based on the preset echo interval, the target object is image acquired to obtain the first echo phase image, the second echo phase image and the third echo phase image. The first echo phase image and the third echo phase image are acquired based on the frequency-coded gradient magnetic field of the first polarity.

[0006] Based on the first echo phase image and the third echo phase image, determine the first phase difference image corresponding to a single echo interval;

[0007] The first echo phase image and the first phase difference image are superimposed to obtain the reference phase image corresponding to the second echo phase image;

[0008] The delay information of the magnetic resonance system is determined based on the reference phase image and the second echo phase image.

[0009] In conjunction with the first aspect, in some possible implementations, image acquisition of the target object is performed based on a preset echo interval to obtain a first echo phase image, a second echo phase image, and a third echo phase image. The first echo phase image and the third echo phase image are acquired based on a frequency-coded gradient magnetic field of a first polarity, including: exciting magnetic resonance signals in the imaging layer of the target object based on a preset layer-selective gradient magnetic field and a radio frequency signal; acquiring the first echo signal at the first echo time, the second echo signal at the second echo time, and the third echo signal at the third echo time based on the magnetic resonance signal and the preset echo interval, the phase-coded gradient magnetic field, and the frequency-coded gradient magnetic field, where the time interval between the first echo time and the second echo time, and the time interval between the second echo time and the third echo time are both echo intervals; and acquiring the first echo phase image corresponding to the first echo signal, the second echo phase image corresponding to the second echo signal, and the third echo phase image corresponding to the third echo signal.

[0010] In conjunction with the first aspect and the above implementation methods, in some possible implementation methods, based on the magnetic resonance signal and a preset echo interval, a phase encoding gradient magnetic field, and a frequency encoding gradient magnetic field, the acquisition of a first echo signal at a first echo time, a second echo signal at a second echo time, and a third echo signal at a third echo time includes: at the first echo time, encoding the magnetic resonance signal based on the preset phase encoding gradient magnetic field and a frequency encoding gradient magnetic field of the first polarity to acquire the first echo signal; at the second echo time after the preset echo interval of the first echo time, encoding the magnetic resonance signal based on the phase encoding gradient magnetic field and a preset frequency encoding gradient magnetic field of the second polarity to acquire the second echo signal, wherein the first polarity is opposite to the second polarity; at the third echo time after the echo interval of the second echo time, encoding the magnetic resonance signal based on the phase encoding gradient magnetic field and the frequency encoding gradient magnetic field of the first polarity to acquire the third echo signal.

[0011] In conjunction with the first aspect and the above implementation methods, in some possible implementation methods, obtaining the first echo phase image corresponding to the first echo signal, the second echo phase image corresponding to the second echo signal, and the third echo phase image corresponding to the third echo signal includes: performing Fourier transform processing on the first echo signal, the second echo signal, and the third echo signal respectively to obtain the first echo complex image corresponding to the first echo signal, the second echo complex image corresponding to the second echo signal, and the third echo complex image corresponding to the third echo signal; and extracting phase components from the first echo complex image, the second echo complex image, and the third echo complex image respectively to obtain the first echo phase image corresponding to the first echo signal, the second echo phase image corresponding to the second echo signal, and the third echo phase image corresponding to the third echo signal.

[0012] In combination with the first aspect and the above implementation methods, in some possible implementation methods, determining the first phase difference image corresponding to a single echo interval based on the first echo phase image and the third echo phase image includes: performing phase difference calculation processing on the first echo phase image and the third echo phase image to obtain a second phase difference image; dividing the phase value in the second phase difference image by two to obtain the first phase difference image corresponding to a single echo interval.

[0013] Combining the first aspect and the above implementation methods, in some possible implementation methods, the delay information of the magnetic resonance system is determined based on the reference phase image and the second echo phase image, including: performing phase difference calculation processing on the reference phase image and the second echo phase image to obtain a third phase difference image; performing inverse Fourier transform processing on the third phase difference image to obtain the signal distribution in K space; determining the peak position of the signal distribution in K space in the frequency coding direction; and determining the delay information of the magnetic resonance system based on the offset distance between the peak position and the preset center position in K space in the frequency coding direction.

[0014] Combining the first aspect and the above implementation methods, in some possible implementation methods, the magnetic resonance system includes a gradient transmission subsystem and a radio frequency receiving subsystem; after determining the delay information of the magnetic resonance system based on the reference phase image and the second echo phase image, it further includes: determining the delay compensation parameters of the magnetic resonance system according to the delay information; configuring the parameters of the magnetic resonance system according to the delay compensation parameters, so that the magnetic resonance system compensates for the gradient delay of the gradient transmission subsystem and the acquisition delay of the radio frequency receiving subsystem according to the delay compensation parameters.

[0015] Secondly, a delay determination device for a magnetic resonance system is provided, wherein a target object is placed in the imaging region of the magnetic resonance system, and the device includes:

[0016] The acquisition unit is used to acquire images of the target object based on a preset echo interval, and to obtain a first echo phase image, a second echo phase image and a third echo phase image. The first echo phase image and the third echo phase image are acquired based on a frequency-coded gradient magnetic field of the first polarity.

[0017] The first determining unit is used to determine the first phase difference image corresponding to a single echo interval based on the first echo phase image and the third echo phase image;

[0018] The superposition unit is used to superimpose the first echo phase image and the first phase difference image to obtain a reference phase image corresponding to the second echo phase image;

[0019] The second determining unit is used to determine the delay information of the magnetic resonance system based on the reference phase image and the second echo phase image.

[0020] Thirdly, a magnetic resonance system is provided, the magnetic resonance system comprising:

[0021] Memory, used to store executable program code;

[0022] The processor is used to call and run executable program code from memory, so that the magnetic resonance system performs any of the above-mentioned delay determination methods for the magnetic resonance system.

[0023] Fourthly, a computer-readable storage medium is provided, which stores a computer program that, when executed, implements the delay determination method for a magnetic resonance system as described above.

[0024] The beneficial effects of the technical solutions provided by some embodiments of this application include at least the following: First, images of the target object are acquired based on a preset echo interval to obtain a first echo phase image, a second echo phase image, and a third echo phase image; wherein, the first echo phase image and the third echo phase image are acquired using the same first polarity frequency-coded gradient magnetic field, and the phase difference between them is mainly caused by the uniformity of the gradient magnetic field in each direction of the magnetic resonance system. Further, a first phase difference image corresponding to a single echo interval is calculated based on the first echo phase image and the third echo phase image; then, the first echo phase image and the first phase difference image are superimposed to obtain a reference phase image corresponding to the second echo phase image; finally, the delay information of the magnetic resonance system is determined based on the difference between the reference phase image and the second echo phase image, which enables the delay information to more accurately reflect the actual state of the uniformity of the gradient magnetic field in each direction, thereby improving the accuracy of the delay information. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a timing diagram for determining delay using a related technology provided in an embodiment of this application;

[0027] Figure 2 This is a flowchart illustrating a method for determining the delay of a magnetic resonance system according to an embodiment of this application;

[0028] Figure 3 This is a schematic diagram of a process for acquiring multiple echo phase images provided in an embodiment of this application;

[0029] Figure 4This is a schematic diagram of a process for acquiring multiple echo signals provided in an embodiment of this application;

[0030] Figure 5 This is an example schematic diagram of image acquisition provided in an embodiment of this application;

[0031] Figure 6 This is a schematic flowchart illustrating a process for obtaining an echo phase image corresponding to an echo signal, provided in an embodiment of this application.

[0032] Figure 7 This is a schematic diagram of a process for obtaining a first phase difference image provided in an embodiment of this application;

[0033] Figure 8 This is a flowchart illustrating a method for determining delay information provided in an embodiment of this application;

[0034] Figure 9 This is a schematic diagram of a delay compensation process provided in an embodiment of this application;

[0035] Figure 10 This is a first echo phase image provided in an embodiment of this application;

[0036] Figure 11 This is a second echo phase image provided in an embodiment of this application;

[0037] Figure 12 This is a third echo phase image provided in an embodiment of this application;

[0038] Figure 13 This is a second phase difference image provided in an embodiment of this application;

[0039] Figure 14 This is a first phase difference image provided in an embodiment of this application;

[0040] Figure 15 This is a reference phase image provided in an embodiment of this application;

[0041] Figure 16 This is a third phase difference image provided in an embodiment of this application;

[0042] Figure 17 This is a schematic diagram of a signal distribution in K-space provided in an embodiment of this application;

[0043] Figure 18 This is an enlarged schematic diagram of the signal distribution center in K-space provided in an embodiment of this application;

[0044] Figure 19 This is a delay-compensated first echo phase reference image provided in an embodiment of this application;

[0045] Figure 20 This is a delay-compensated second echo phase reference image provided in an embodiment of this application;

[0046] Figure 21 This is a schematic diagram of the structure of a delay determination device for a magnetic resonance system provided in an embodiment of this application;

[0047] Figure 22 This is a schematic diagram of the structure of a magnetic resonance system provided in an embodiment of this application. Detailed Implementation

[0048] To make the features and advantages of this application more apparent and understandable, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0049] In the following description, when referring to the accompanying drawings, the same numbers in different drawings denote the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0050] Hereinafter, the terms "first" and "second" are used for descriptive purposes only and should not be construed as implying or suggesting relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.

[0051] The following will provide a detailed description of each example. It should be noted that the order of description of the following embodiments is not intended to limit the preferred order of the embodiments.

[0052] Magnetic resonance imaging (MRI) is a widely used imaging system in medical diagnosis and scientific research. It acquires information about the internal structure of an object by utilizing the resonance properties of the magnetic moments of atomic nuclei in a magnetic field. In related technologies, an MRI system can include a core control module, a radio frequency (RF) transmission subsystem, an RF receiving subsystem, and a gradient transmission subsystem. The core control module coordinates the operation of each subsystem; the RF transmission subsystem generates and transmits RF signals; the RF receiving subsystem receives and processes MRI signals; and the gradient transmission subsystem generates the gradient magnetic field required for spatial localization. Specifically, during MRI imaging, the core control module coordinates the operation of each subsystem. The RF transmission subsystem transmits RF signals to the target object; the gradient transmission subsystem applies slice-selective gradient magnetic fields, phase-encoded gradient magnetic fields, and frequency-encoded gradient magnetic fields; and the RF receiving subsystem acquires MRI signals, collectively achieving spatial localization and image reconstruction.

[0053] Please see Figure 1 , Figure 1 A timing diagram for the delay was determined for the relevant technology. First, a positive-polarity trapezoidal layer selection gradient magnetic field was applied in the layer selection direction, and simultaneously, an radio frequency (RF) signal was transmitted through the RF transmitting subsystem to excite a magnetic resonance signal at a specific layer. Immediately afterwards, a layer selection gradient magnetic field with the same waveform but opposite polarity as the positive-polarity trapezoidal layer selection gradient magnetic field was applied, i.e., an anti-polarity trapezoidal layer selection gradient magnetic field, and a data acquisition window was set at the flat segment of this anti-polarity trapezoidal layer selection gradient magnetic field. Ideally, the peak value of the acquired magnetic resonance signal should appear at the center point t0_1 of the flat segment of the anti-polarity trapezoidal layer selection gradient magnetic field. However, due to the inductive effect of the gradient coil in the gradient transmitting subsystem and the capacitive characteristics of the gradient filter, which cause a delay in the establishment of the gradient magnetic field, as well as the transmission delay of the signal transmission link and the conversion delay of the analog-to-digital converter in the RF receiving subsystem, the actual peak value of the acquired magnetic resonance signal appears at time t1. The time difference Δt between t0_1 and t1 is the delay information of the magnetic resonance system.

[0054] It can be seen that, based on Figure 1 The current delay determination scheme has the following drawbacks: First, the inhomogeneity of the static main magnetic field in magnetic resonance imaging (MRI) causes a frequency shift in the MRI signal. This frequency shift further leads to cumulative changes in the signal phase, thus affecting the accurate determination of the MRI signal peak position. Although related techniques attempt to partially compensate for the inhomogeneity of the slice selection direction by alternately applying positive and negative polarity slice selection gradient magnetic fields, this method does not take into account the interference of gradient magnetic field inhomogeneities in other directions. Especially in multi-echo gradient echo imaging, this inaccurate delay measurement leads to distortion of image phase information, affecting the accuracy of subsequent image reconstruction. Therefore, there is an urgent need for a scheme that can consider the interference of gradient magnetic field inhomogeneities in multiple directions and accurately determine the delay of the MRI system.

[0055] To address the aforementioned issues, the solution provided in this application mainly includes: firstly, image acquisition of the target object based on a preset echo interval to obtain a first echo phase image, a second echo phase image, and a third echo phase image; wherein, the first echo phase image and the third echo phase image are acquired using the same first polarity frequency-coded gradient magnetic field, and the phase difference between them is mainly caused by the uniformity of the gradient magnetic field in each direction of the magnetic resonance system. Further, a first phase difference image corresponding to a single echo interval is calculated based on the first echo phase image and the third echo phase image; then, the first echo phase image and the first phase difference image are superimposed to obtain a reference phase image corresponding to the second echo phase image; finally, the delay information of the magnetic resonance system is determined based on the difference between the reference phase image and the second echo phase image, enabling the delay information to more accurately reflect the actual state of the uniformity of the gradient magnetic field in each direction, thereby improving the accuracy of the delay information.

[0056] The following will combine Figure 2 - Figure 20 This application provides a detailed description of the delay determination method for the magnetic resonance system provided in the embodiments.

[0057] Please see Figure 2 , Figure 2 This is a flowchart illustrating a method for determining the delay of a magnetic resonance system, provided as an embodiment of this application. Figure 2 As shown, the method in this application embodiment may include the following steps S101-S104, wherein a target object is placed in the imaging region of the magnetic resonance system.

[0058] S101, based on the preset echo interval, image acquisition is performed on the target object to obtain a first echo phase image, a second echo phase image and a third echo phase image. The first echo phase image and the third echo phase image are acquired based on the frequency-coded gradient magnetic field of the first polarity.

[0059] Specifically, in this embodiment, the imaging region of the magnetic resonance system refers to the spatial range within the uniform magnetic field region inside the magnet aperture used to place the object under test and acquire signals. It should be noted that the imaging region of the magnetic resonance system contains a target object, which can be any object with stable nuclear magnetic resonance characteristics. For example, the target object can be a copper sulfate water phantom. The advantage of using a copper sulfate water phantom is that it has uniform relaxation characteristics and stable signal intensity, providing a reliable phase measurement reference.

[0060] Furthermore, the echo interval involved in this embodiment refers to a fixed time interval between the center points of two adjacent echo signals. During image acquisition, the magnetic resonance system emits radio frequency signals to the target object and applies gradient magnetic fields in multiple directions. The gradient magnetic fields in multiple directions include at least a frequency-encoded gradient magnetic field in the frequency encoding direction, or, in addition, a layer-selection gradient magnetic field in the layer-selection direction and a phase-encoded gradient magnetic field in the phase encoding direction.

[0061] Regarding the process of acquiring images of a target object based on a preset echo interval to obtain a first echo phase image, a second echo phase image, and a third echo phase image, some possible implementations include: firstly, transmitting a layer-selective radio frequency pulse, and simultaneously applying a layer-selective gradient magnetic field in the layer-selective direction to excite magnetic resonance signals in a specific layer of the target object; subsequently, applying a phase-encoding gradient magnetic field in the phase-encoding direction and a frequency-encoding gradient magnetic field in the frequency-encoding direction for spatial encoding; furthermore, sequentially acquiring the first echo signal, the second echo signal, and the third echo signal according to the preset echo interval; and processing each acquired echo signal to obtain the first echo phase image corresponding to the first echo signal, the second echo phase image corresponding to the second echo signal, and the third echo phase image corresponding to the third echo signal. Here, the time interval between the first echo time and the second echo time, and the time interval between the second echo time and the third echo time are all considered as the echo interval. Alternatively, the time interval between any two adjacent echo phase images in the first, second, and third echo phase images can be considered as the preset echo interval.

[0062] Regarding the application of a frequency coding gradient magnetic field in the frequency coding direction, in some possible implementations, a frequency coding gradient magnetic field of the first polarity can be applied continuously in the frequency coding direction; in other possible implementations, a frequency coding gradient magnetic field of the first polarity and the second polarity can be applied alternately in the frequency coding direction, wherein the first polarity and the second polarity are opposite. It is understood that the first polarity can be either positive or negative. If the first polarity is positive, then the second polarity is negative; similarly, if the first polarity is negative, then the second polarity is positive.

[0063] It should be noted that the first and third echo phase images were acquired based on a frequency-coded gradient magnetic field of the first polarity. That is, when acquiring the first and third echo signals, the frequency-coded gradient magnetic field maintained its first polarity, while when acquiring the second echo signal, it adopted a second polarity, opposite to the first polarity. This acquisition method, which alternately applies frequency-coded gradient magnetic fields of different polarities, results in the first and third echo phase images having the same frequency-coded gradient magnetic field polarity characteristics, while the second echo phase image has opposite frequency-coded gradient magnetic field polarity characteristics.

[0064] S102, based on the first echo phase image and the third echo phase image, determine the first phase difference image corresponding to a single echo interval.

[0065] Specifically, the first phase difference image involved in this embodiment represents the amount of phase change caused by the inhomogeneity of the gradient magnetic field in each direction in the magnetic resonance system within a single echo interval. This amount of phase change excludes the influence of frequency coding gradient magnetic field polarity switching and acquisition delay, and only reflects the cumulative effect of magnetic field uniformity on signal phase.

[0066] In some possible implementations, the phase difference between the first and third echo phase images can be calculated pixel-by-pixel to obtain a second phase difference image. Since there are two echo intervals between the first and third echo phase images, the phase change in the second phase difference image reflects the cumulative phase change caused by the magnetic field uniformity within the two echo intervals. Subsequently, dividing the phase value of each pixel in the second phase difference image by two yields the first phase difference image corresponding to a single echo interval.

[0067] In some possible implementations, the first and third echo phase images can first be complex-ized to obtain complex first and third echo images. Specifically, the phase value of each pixel in the phase image is converted into a complex number, where the real part is the cosine of the corresponding phase value and the imaginary part is the sine of the corresponding phase value. Then, the conjugate product of the complex first and third echo images is calculated to obtain the complex second phase difference image. By extracting the phase components from the complex second phase difference image, the second phase difference image is obtained. Finally, the phase values ​​in the second phase difference image are divided by two to obtain the first phase difference image corresponding to a single echo interval. It should be noted that this implementation ensures the accuracy of the phase difference calculation through complex number operations.

[0068] It is understandable that a mapping relationship exists between the first echo phase image, the third echo phase image, and the first phase difference image. This mapping relationship can be implemented not only based on the methods described above, but also based on relevant machine learning models. For example, the first echo phase image and the third echo phase image can be input into a pre-trained machine learning model to obtain the first phase difference image output by the model. In addition, the mapping relationship between the first echo phase image, the third echo phase image, and the first phase difference image can be implemented in other ways, which will not be listed here.

[0069] S103, superimpose the first echo phase image and the first phase difference image to obtain the reference phase image corresponding to the second echo phase image.

[0070] Specifically, the reference phase image involved in this embodiment represents the phase distribution characteristics that the second echo phase image should possess under ideal delay conditions. It can be understood that the reference phase image excludes the influence of the magnetic resonance system delay and only contains the phase change component caused by the magnetic field homogeneity, which can be used as a benchmark for evaluating the deviation of the actual second echo phase image.

[0071] In some possible implementations, the first echo phase image and the first phase difference image can be complex-ized to obtain a first echo complex image and a first phase difference complex image. Specifically, the phase value of each pixel in the first echo phase image is converted into a complex form, where the real part is the cosine of the corresponding phase value and the imaginary part is the sine of the corresponding phase value; the phase value of each pixel in the first phase difference image is also converted into a complex form. Then, the product of the first echo complex image and the first phase difference complex image is calculated to obtain a reference complex image. By extracting the phase components from the reference complex image, the reference phase image corresponding to the second echo phase image can be obtained. It should be noted that this implementation ensures the accuracy of phase superposition through complex number operations.

[0072] In some possible implementations, the phase values ​​of the first echo phase image and the first phase difference image can be added pixel by pixel to obtain an initial reference phase image. Since phase values ​​have periodic characteristics, when the addition result exceeds the phase period range, the phase values ​​need to be periodically adjusted to fall within the standard phase interval. Subsequently, spatial smoothing processing can be performed on the initial reference phase image to eliminate possible local phase jumps, ultimately obtaining the reference phase image corresponding to the second echo phase image. It should be noted that this implementation method ensures the continuity and reliability of the reference phase image through phase period adjustment and spatial smoothing processing.

[0073] It is understandable that there is a mapping relationship between the first echo phase image, the first phase difference map, and the reference phase image. This mapping relationship can be implemented not only based on the methods described above, but also based on relevant machine learning models. For example, the first echo phase image and the first phase difference map can be input into a pre-trained machine learning model to obtain the reference phase image output by the model. In addition, the mapping relationship between the first echo phase image, the first phase difference map, and the reference phase image can be implemented in other ways, which will not be listed here.

[0074] S104, based on the reference phase image and the second echo phase image, determines the time delay information of the magnetic resonance system.

[0075] Specifically, the delay information involved in this embodiment represents the signal acquisition time deviation caused by the combined effect of multiple delays in the magnetic resonance system, wherein the multiple delays include, but are not limited to, the gradient delay of the gradient transmission subsystem and the acquisition delay of the radio frequency receiving subsystem.

[0076] In some possible implementations, the phase difference is first calculated pixel-by-pixel on the reference phase image and the second echo phase image to obtain a third phase difference image. Further, an inverse Fourier transform is performed on the third phase difference image to obtain the signal distribution in K-space. In an ideal, delay-free state, the signal peak in K-space should be located at a predetermined center position along the frequency encoding direction; when system delay exists, the signal peak will shift along the frequency encoding direction. By calculating the ratio of this shift distance to the sampling rate along the frequency encoding direction, the delay time of the magnetic resonance system can be accurately determined.

[0077] In some possible implementations, the second echo phase image can be acquired based on the frequency-coded gradient magnetic field of the second polarity, while the reference phase image is the ideal phase distribution calculated based on the frequency-coded gradient magnetic field of the first polarity. Therefore, the phase change in the third phase difference image reflects the phase deviation caused by the switching of the frequency-coded gradient magnetic field polarity and the system delay.

[0078] In this embodiment, images of the target object are first acquired based on a preset echo interval, resulting in a first echo phase image, a second echo phase image, and a third echo phase image. The first and third echo phase images are acquired using the same frequency-coded gradient magnetic field with the same first polarity, and the phase difference between them is mainly caused by the uniformity of the gradient magnetic field in each direction within the magnetic resonance system. Further, a first phase difference image corresponding to a single echo interval is calculated based on the first and third echo phase images. Then, the first echo phase image and the first phase difference image are superimposed to obtain a reference phase image corresponding to the second echo phase image. Finally, the time delay information of the magnetic resonance system is determined based on the difference between the reference phase image and the second echo phase image. This allows the time delay information to more accurately reflect the actual state of the uniformity of the gradient magnetic field in each direction, thereby improving the accuracy of the time delay information.

[0079] Please see Figure 3 This document provides a flowchart illustrating the process of acquiring multiple echo phase images, as described in an embodiment of this application. Figure 3 As shown, the method in this embodiment may include the following steps S201-S203, and steps S201-S203 may be used as a method for... Figure 2 The detailed steps of step S101 in the illustrated embodiment.

[0080] S201, based on a preset layer-selective gradient magnetic field and radio frequency signal, excites magnetic resonance signals in the imaging layer of the target object.

[0081] S202, based on the magnetic resonance signal and the preset echo interval, phase-coded gradient magnetic field, and frequency-coded gradient magnetic field, acquires the first echo signal at the first echo time, the second echo signal at the second echo time, and the third echo signal at the third echo time. The time interval between the first echo time and the second echo time, and the time interval between the second echo time and the third echo time are all echo intervals.

[0082] S203, acquire the first echo phase image corresponding to the first echo signal, the second echo phase image corresponding to the second echo signal, and the third echo phase image corresponding to the third echo signal.

[0083] Specifically, in this embodiment, the selected layer gradient magnetic field refers to a spatially positioned gradient magnetic field applied along the direction of the main magnetic field, used to selectively excite the imaging layer at a specific location in the target object; the radio frequency signal refers to an electromagnetic wave pulse with a specific frequency and power, used to excite the magnetic resonance phenomenon of atomic nuclei in the target object; the imaging layer refers to a two-dimensional planar region in the target object jointly defined by the selected layer gradient magnetic field and the radio frequency signal; the echo interval refers to a fixed time interval between the center points of two adjacent echo signals; the phase encoding gradient magnetic field refers to a gradient magnetic field applied in the spatial dimension perpendicular to the layer selection direction and the frequency encoding direction, used to achieve spatial encoding in the phase dimension; and the frequency encoding gradient magnetic field refers to a gradient magnetic field applied when reading the echo signal, used to achieve spatial encoding in the frequency dimension.

[0084] It should be noted that the frequency-encoded gradient magnetic field mentioned above can also be regarded as the reading gradient magnetic field, and the frequency encoding direction can also be regarded as the reading direction. This naming method reflects its role in reading echo signals.

[0085] To perform time-delay measurements, a magnetic resonance signal is first excited in the imaging layer of the target object based on a preset layer-selective gradient magnetic field and a radio frequency (RF) signal. In some possible implementations, after placing the target object in the imaging region of the magnetic resonance system, a layer-selective gradient magnetic field of preset amplitude and duration is applied in the layer-selective direction through a gradient emission subsystem, while a radio frequency (RF) signal with a specific center frequency and bandwidth is emitted through an RF emission subsystem. The combined effect of these two methods causes the atomic nuclei at a specific location in the target object to undergo magnetic resonance.

[0086] Then, based on the magnetic resonance signal and preset echo intervals, phase-encoded gradient magnetic fields, and frequency-encoded gradient magnetic fields, the first echo signal at the first echo time, the second echo signal at the second echo time, and the third echo signal at the third echo time are acquired. In some possible implementations, after exciting the magnetic resonance signal, a preset phase-encoded gradient magnetic field is applied in the phase-encoded direction, and a preset frequency-encoded gradient magnetic field is applied in the frequency-encoded direction. Specifically, a frequency-encoded gradient magnetic field of the first polarity is applied at the first echo time and the first echo signal is acquired; a frequency-encoded gradient magnetic field of the same polarity as the first or second polarity is applied at the second echo time and the second echo signal is acquired; and a frequency-encoded gradient magnetic field of the first polarity is applied again at the third echo time and the third echo signal is acquired. It should be noted that maintaining an equal echo interval between the acquisition times of the three echo signals ensures the regularity of phase changes.

[0087] Further, the first echo phase image corresponding to the first echo signal, the second echo phase image corresponding to the second echo signal, and the third echo phase image corresponding to the third echo signal are acquired. In some possible implementations, the acquired first, second, and third echo signals are subjected to analog-to-digital conversion and digital signal processing, including but not limited to filtering, amplification, and digital down-conversion. Subsequently, a two-dimensional Fourier transform is performed on the processed digital signals to obtain the first, second, and third echo complex images. Finally, the phase components are extracted from the three complex images to generate the first, second, and third echo phase images.

[0088] In addition, in some possible implementations, echo phase image acquisition can be completed using either 3D or 2D image data acquisition. For example, in this embodiment, the imaging layer can be one of multiple layers in 3D image data acquisition or a single layer in 2D image data acquisition. In 3D image data acquisition mode, the magnetic resonance system spatially encodes multiple consecutive layers by applying a phase-encoding gradient magnetic field in a selected layer direction. In this case, the imaging layer refers to a layer among the multiple encoded layers that is jointly excited by a specific selected layer gradient magnetic field and a radio frequency signal. In 2D image data acquisition mode, the magnetic resonance system images only a single fixed layer; in this case, the imaging layer refers to that single acquisition layer. Regardless of whether 3D or 2D image data acquisition mode is used, this embodiment ensures that the imaging layer has a clear geometric location and a uniform signal excitation effect by controlling the parameters of the selected layer gradient magnetic field and the radio frequency signal. In particular, in the 3D image data acquisition mode, although phase encoding is involved in multiple layers, the signal excitation and echo acquisition process of each imaging layer independently follow the method of this embodiment. Through the precise coordination of the layer-selective gradient magnetic field and the radio frequency signal, the spatial selectivity and phase consistency of the signals at each layer are guaranteed, providing an accurate phase information basis for subsequent time delay measurement.

[0089] In this embodiment, firstly, a magnetic resonance signal in the imaging layer of the target object is excited based on a preset layer-selective gradient magnetic field and a radio frequency signal, ensuring the spatial positioning accuracy of the signal source. Then, based on the magnetic resonance signal and preset echo intervals, phase-encoded gradient magnetic fields, and frequency-encoded gradient magnetic fields, the first echo signal at the first echo time, the second echo signal at the second echo time, and the third echo signal at the third echo time are acquired while maintaining the echo interval. The first and third echo signals are acquired using the same frequency-encoded gradient magnetic field of the same polarity. Finally, the first echo phase image, the second echo phase image, and the third echo phase image corresponding to the three echo signals are acquired respectively. In this way, by fixing the echo interval to ensure the regularity of phase change, and by using the same frequency-encoded gradient magnetic field of the same polarity to acquire the first and third echo phase images, the influence of magnetic field uniformity introduced from multiple directions can be eliminated. The combination of the three echo phase images can provide more accurate phase change information, providing a reliable data foundation for subsequent delay determination.

[0090] Please see Figure 4 This document provides a flowchart illustrating the process of acquiring multiple echo signals, as described in an embodiment of this application. Figure 4 As shown, the method in this embodiment may include the following steps S301-S303, and steps S301-S303 may be used as a method for... Figure 3 The detailed steps of step S202 in the illustrated embodiment.

[0091] S301, at the first echo time, the magnetic resonance signal is encoded based on the preset phase encoding gradient magnetic field and the frequency encoding gradient magnetic field of the first polarity to acquire the first echo signal.

[0092] S302, at the second echo time after a preset echo interval following the first echo time, the magnetic resonance signal is encoded based on the phase-encoded gradient magnetic field and the preset second polarity frequency-encoded gradient magnetic field to acquire the second echo signal, where the first polarity is opposite to the second polarity.

[0093] S303, at the third echo time after the echo interval following the second echo time, the magnetic resonance signal is encoded based on the phase-coded gradient magnetic field and the frequency-coded gradient magnetic field of the first polarity to acquire the third echo signal.

[0094] Specifically, the determination of the time delay in a magnetic resonance system may be affected by cross-term eddy currents, which refer to the fluctuations in magnetic field uniformity in the direction perpendicular to a switching of a directional gradient magnetic field. These fluctuations cause changes in the phase of the magnetic resonance signal, thus affecting the accuracy of the time delay measurement. It is understandable that if... Figure 1The related techniques shown determine the time delay information of the magnetic resonance system. However, since only the slice gradient magnetic field in the slice selection direction is used for measurement, the influence of cross-term eddy currents in the phase encoding and frequency encoding directions cannot be eliminated. Therefore, this related technique also fails to eliminate the influence of cross-term eddy currents.

[0095] Based on this, this embodiment employs alternating application of frequency-coded gradient magnetic fields of different polarities to achieve gradient magnetic field switching. Correspondingly, the phase-coded gradient magnetic field and the layer-selection gradient magnetic field perpendicular to them will generate periodically changing eddy current magnetic fields due to cross-coupling effects. Acquiring multiple echo signals under these conditions ensures that the influence of cross-term eddy currents can be effectively separated and eliminated in subsequent data processing.

[0096] During the first echo time, the magnetic resonance signal is encoded based on a preset phase-encoding gradient magnetic field and a frequency-encoding gradient magnetic field of the first polarity to acquire the first echo signal. In some possible implementations, after exciting the magnetic resonance signal, a phase-encoding gradient magnetic field of preset amplitude and duration is first applied in the phase-encoding direction, while a frequency-encoding gradient magnetic field of the first polarity is applied in the frequency-encoding direction. The two work together to spatially encode the magnetic resonance signal. The frequency-encoding gradient magnetic field of the first polarity can adopt a trapezoidal waveform, including a rising edge, a flat segment, and a falling edge, maintaining a stable magnetic field strength near the center point of the first echo time. The first echo signal is acquired within this time window by the radio frequency receiving subsystem, ensuring that the signal has clear spatial encoding characteristics.

[0097] In the second echo time, after a preset echo interval following the first echo time, the magnetic resonance signal is encoded based on the phase-coded gradient magnetic field and a preset second-polarity frequency-coded gradient magnetic field to acquire the second echo signal. In some possible implementations, the parameters of the phase-coded gradient magnetic field are kept constant, while the polarity of the frequency-coded gradient magnetic field is switched to a second polarity opposite to the first polarity. The waveform of this second-polarity frequency-coded gradient magnetic field remains symmetrical to that of the first polarity. It should be noted that the switching process between the first and second polarities must consider the response time of the gradient system to ensure that the polarity conversion is completed before the second echo time. The second echo signal, which has the same phase-coding characteristics as the first echo signal but with the opposite frequency-coding polarity, is acquired by the radio frequency receiving subsystem within the second echo time window.

[0098] In the third echo time, after the echo interval following the second echo time, the magnetic resonance signal is encoded based on the phase-coded gradient magnetic field and the frequency-coded gradient magnetic field of the first polarity to acquire the third echo signal. In some possible implementations, the frequency-coded gradient magnetic field is switched back to the first polarity, and its waveform parameters are consistent with the first-polarity frequency-coded gradient magnetic field applied initially. The third echo signal, which has the same frequency-coded polarity characteristics as the first echo signal, is acquired within the third echo time window by the radio frequency receiving subsystem, forming a symmetrical signal acquisition mode. It is important to emphasize that the acquisition time points of the three echo signals strictly maintain the same echo interval to ensure the linear accumulation characteristic of the phase change.

[0099] In this embodiment, three echo signals are acquired by alternately applying frequency-coded gradient magnetic fields of different polarities. This ensures that the influence of cross-term eddy currents exhibits the same pattern in the first and third echo signals, but the opposite pattern in the second echo signal. This symmetrical acquisition method provides a data foundation for subsequent elimination of the cross-term eddy current influence through phase difference calculation.

[0100] Based on the above Figure 3 , Figure 4 For the illustrated embodiment, please refer to [link / reference]. Figure 5 , Figure 5This is an example schematic diagram of an image acquisition method provided in an embodiment of this application. Exemplarily, firstly, a magnetic resonance signal in the imaging layer of the target object is excited based on a preset slice gradient magnetic field Gslice and a radio frequency (RF) signal. The slice gradient magnetic field Gslice includes a slice gradient portion Gzrf1 during RF excitation, a combined or compensated gradient Gzcomb, and a phase-encoded gradient Gzp in the slice selection direction. The slice gradient portion Gzrf1 is applied synchronously during the application of the RF signal to achieve slice selection. Subsequently, the combined or compensated gradient Gzcomb is applied to counteract eddy current effects and magnetic field inhomogeneities. Finally, the phase-encoded gradient Gzp in the slice selection direction is applied to complete phase encoding in the slice selection direction. Simultaneously, multi-echo signal acquisition is performed based on the magnetic resonance signal and preset echo interval ESP, phase-encoded gradient magnetic field Gphase, and frequency-encoded gradient magnetic field Gread. The phase-encoded gradient magnetic field Gphase includes an initial application portion Gy1 and an ending application portion Gy1r. The frequency-encoded gradient magnetic field Gread includes an initial application portion Gx1, a first flat segment Gxw1 (corresponding to the first polarity), a second flat segment Gxw2 (corresponding to the second polarity, which is opposite to the first polarity), a third flat segment Gxw3 (corresponding to the first polarity), and an ending application portion Gxk. During the first echo time, the magnetic resonance signal is encoded based on the initial application portion Gy1 of the phase-encoded gradient magnetic field Gphase and the first flat segment Gxw1 (first polarity) of the frequency-encoded gradient magnetic field Gread to acquire the first echo signal echo1. In the second echo time, after the preset echo interval ESP following the first echo time, while keeping the parameters of the phase-encoding gradient magnetic field Gphase unchanged, the frequency-encoding gradient magnetic field Gread is switched to the second flat segment -Gxw2 (second polarity) to encode the magnetic resonance signal and acquire the second echo signal echo2. At this time, the polarity of the frequency-encoding gradient magnetic field Gread is opposite to the first polarity. In the third echo time, after the echo interval ESP following the second echo time, the frequency-encoding gradient magnetic field Gread is switched back to the third flat segment Gxw3 (first polarity) to encode the magnetic resonance signal and acquire the third echo signal echo3. At this time, the polarity of the frequency-encoding gradient magnetic field Gread returns to the first polarity. In the above process, the flat segments Gxw1 (first polarity), -Gxw2 (second polarity), and Gxw3 (first polarity) of the frequency-encoding gradient magnetic field Gread alternately switch polarities to achieve multi-echo acquisition. The acquisition time points of the three echo signals echo1, echo2, and echo3 maintain the same echo interval ESP to ensure the regularity of phase changes. In addition, the echo time TE is defined as the time interval from the center point of the radio frequency signal RF to the center point of the first echo signal echo1, which affects the T2* (or T2-star, used to describe the time constant of lateral magnetization decay) weight of the image.The repetition time TR is defined as the time interval from the start of the layer-selection gradient portion Gzrf1 to the end of the phase-encoded gradient Gzp, the phase-encoded gradient magnetic field Gphase, and the frequency-encoded gradient magnetic field Gread, where the application portion Gy1r ends and the application portion Gxk ends. It controls the longitudinal magnetization recovery and influences the T1 (or T-, a physical parameter describing the longitudinal magnetization recovery process) weight of the image. Through this timing design, it can be ensured that the first and third echo phase images are acquired using the same first polarity frequency-encoded gradient magnetic field. The phase difference between them is mainly caused by the uniformity of the gradient magnetic fields in each direction within the magnetic resonance system, providing a reliable data foundation for accurately determining the delay information.

[0101] Please see Figure 6 This document provides a flowchart illustrating the process of obtaining an echo phase image corresponding to an echo signal, as described in an embodiment of this application. Figure 6 As shown, the method in this embodiment may include the following steps S401-S402, and steps S401-S402 may be used as a method for... Figure 3 The detailed steps of step S203 in the illustrated embodiment.

[0102] S401, perform Fourier transform processing on the first echo signal, the second echo signal and the third echo signal respectively to obtain the first echo complex image corresponding to the first echo signal, the second echo complex image corresponding to the second echo signal and the third echo complex image corresponding to the third echo signal.

[0103] S402, phase components are extracted from the first echo complex image, the second echo complex image, and the third echo complex image respectively to obtain the first echo phase image corresponding to the first echo signal, the second echo phase image corresponding to the second echo signal, and the third echo phase image corresponding to the third echo signal.

[0104] Specifically, the Fourier transform processing involved in this embodiment refers to the mathematical operation process of converting a time-domain signal into a frequency-domain representation; the complex image refers to two-dimensional image data that simultaneously contains real and imaginary components; the phase component extraction refers to the processing process of separating phase information from the complex image; and the echo phase image refers to a two-dimensional image that retains only the phase information.

[0105] First, Fourier transforms are performed on the first, second, and third echo signals respectively. In some possible implementations, the acquired first, second, and third echo signals are first preprocessed, including but not limited to signal amplification, filtering, and baseline correction. Then, a one-dimensional Discrete Fourier Transform (DFT) is performed on the preprocessed signals along the frequency encoding direction and the phase encoding direction, or a two-dimensional DFT is directly performed, to obtain the complex images of the first, second, and third echoes. It should be noted that each pixel in the complex image contains two components: a real part and an imaginary part. The real part represents the in-phase component of the signal, and the imaginary part represents the quadrature component.

[0106] Next, phase components are extracted from the first, second, and third echo complex images, respectively. In some possible implementations, for each pixel in the complex image, the ratio of its imaginary part to its real part is calculated, and then the corresponding phase value is obtained by applying the arctangent function. Arranging the phase values ​​of all pixels according to their original spatial positions constitutes the corresponding echo phase image.

[0107] In this embodiment, the original time-domain signal is converted into a complex image with clear spatial coding characteristics by performing Fourier transform on the three echo signals respectively. Furthermore, the phase components are accurately extracted from the complex images to obtain the phase images corresponding to each of the three echo signals. In this way, the spatial positioning information and phase change characteristics of the echo signals can be preserved in the phase images, providing an accurate data foundation for subsequent delay determination based on phase difference calculation.

[0108] Please see Figure 7 This document provides a flowchart illustrating the process of acquiring a first phase difference image, as described in an embodiment of this application. Figure 7 As shown, the method in this embodiment may include the following steps S501-S502, and steps S501-S502 may be used as a method for... Figure 2 The detailed steps of step S102 in the illustrated embodiment.

[0109] S501, perform phase difference calculation on the first echo phase image and the third echo phase image to obtain the second phase difference image;

[0110] S502, divide the phase value in the second phase difference image by two to obtain the first phase difference image corresponding to a single echo interval.

[0111] Specifically, the phase difference calculation process involved in this embodiment refers to the process of performing a difference operation on the phase values ​​of corresponding pixels in two phase images; the second phase difference image refers to a two-dimensional distribution image of the phase difference between the first echo phase image and the third echo phase image; the first phase difference image corresponding to a single echo interval refers to a two-dimensional image reflecting the phase change within a single echo interval after normalization processing.

[0112] First, phase difference calculation is performed on the first and third echo phase images. In some possible implementations, the phase difference value of corresponding pixels in the first and third echo phase images can be calculated pixel by pixel. Specifically, for each pixel location, the phase value of the first echo phase image is subtracted from the phase value of the third echo phase image to obtain the phase difference value at that location. The phase difference values ​​of all pixels are arranged according to their original spatial positions to form the second phase difference image. It should be noted that this implementation ensures the spatial resolution of the phase difference through pixel-by-pixel calculation.

[0113] Next, the phase values ​​in the second phase difference image are divided by two. In some possible implementations, the phase values ​​in the second phase difference image can be divided pixel by pixel. Since there are two echo intervals between the first and third echo phase images, the second phase difference image reflects the cumulative phase change within those two echo intervals. Dividing the phase value of each pixel by two yields the phase change corresponding to a single echo interval. After processing all pixels, the first phase difference image is obtained.

[0114] In this embodiment, a second phase difference image reflecting the phase change within two echo intervals is obtained by performing phase difference calculation on the first and third echo phase images. Furthermore, the phase value in the second phase difference image is divided by two to obtain the first phase difference image corresponding to a single echo interval. Thus, by inferring the phase change of a single echo interval from the phase change between two echo intervals, the accuracy of phase change measurement can be effectively improved, providing a reliable data foundation for subsequent accurate calculation of the reference phase image.

[0115] Please see Figure 8 This document provides a flowchart illustrating the process of determining delay information in an embodiment of this application. Figure 8 As shown, the method in this embodiment may include the following steps S601-S604, and steps S601-S604 may be used as a method for... Figure 2 The detailed steps of step S104 in the illustrated embodiment.

[0116] S601, perform phase difference calculation on the reference phase image and the second echo phase image to obtain the third phase difference image;

[0117] S602, Perform inverse Fourier transform on the third phase difference image to obtain the signal distribution in K space;

[0118] S603, determine the peak position of the signal distribution in the K space along the frequency coding direction;

[0119] S604 determines the delay information of the magnetic resonance system based on the offset distance between the peak position and the preset center position of the K space in the frequency coding direction.

[0120] Specifically, in this embodiment, the third phase difference image refers to the two-dimensional distribution image of the phase difference between the second echo phase image and the reference phase image; the inverse Fourier transform processing refers to the mathematical operation process of converting the spatial domain image back to the K-space signal distribution; the K-space signal distribution refers to the original data distribution of the nuclear magnetic resonance signal in the two-dimensional space formed by the frequency encoding direction and the phase encoding direction; the peak position refers to the location of the data point with the highest intensity in the K-space signal; the preset center position refers to the theoretical center point position of K-space in the frequency encoding direction; and the offset distance refers to the number of data point intervals between the peak position and the preset center position.

[0121] First, the phase difference between the reference phase image and the second echo phase image is calculated. In some possible implementations, the phase difference between corresponding pixels in the reference phase image and the second echo phase image can be calculated pixel by pixel. Specifically, for each pixel location, the phase value of the reference phase image is subtracted from the phase value of the second echo phase image to obtain the phase difference value at that location. The phase difference values ​​of all pixels are arranged according to their original spatial positions to form the third phase difference image. It should be noted that this phase difference value reflects the phase deviation caused by the frequency coding gradient magnetic field polarity switching and system delay. In another implementation, the reference phase image and the second echo phase image can be converted into complex numbers first, and the third phase difference complex image can be obtained through complex conjugate multiplication. Then, the phase components can be extracted from this complex image to generate the third phase difference image.

[0122] Secondly, the third phase difference image is processed using an inverse Fourier transform. In some possible implementations, a two-dimensional discrete inverse Fourier transform algorithm can be used to process the third phase difference image. Specifically, firstly, the phase value of each pixel in the third phase difference image is converted into a complex number, where the real part is the cosine of the corresponding phase value and the imaginary part is the sine of the corresponding phase value. Then, a one-dimensional inverse Fourier transform is performed on this complex image along both the frequency encoding direction and the phase encoding direction, or a two-dimensional inverse Fourier transform is performed directly to obtain the signal distribution in K-space. It is important to emphasize that this signal distribution reflects the actual positional offset of the original acquired signal in K-space.

[0123] Next, the peak positions of the signal distribution in K-space along the frequency coding direction are determined. In some possible implementations, the signal intensity in K-space can be scanned along the frequency coding direction to find the location of the data point with the largest signal amplitude. Specifically, the signal magnitude of each data point along the frequency coding direction can be calculated, and the peak position can be determined by comparing the magnitude values.

[0124] Finally, the delay information of the magnetic resonance system is determined based on the offset distance between the peak position and the preset center position in the K-space along the frequency coding direction. In some possible implementations, the number of data point intervals between the peak position and the preset center position can be calculated first. Then, based on the sampling rate in the frequency coding direction and the image matrix size, the number of data point intervals can be converted into a time offset, which is then used as the delay information of the magnetic resonance system. In another implementation, a mapping relationship between the offset distance and the time offset can be established using data tables, databases, etc. Given a fixed offset distance, the corresponding time offset can be determined based on this mapping relationship, and this time offset can then be used as the delay information of the magnetic resonance system.

[0125] In this embodiment, a third phase difference image reflecting the system delay effect is obtained by calculating the phase difference between the second echo phase image and the reference phase image. This phase difference information is then converted back to the K-space signal distribution using an inverse Fourier transform, accurately capturing the actual center offset during signal acquisition. By analyzing the offset distance between the K-space signal peak position and the theoretical center position, the time offset can be determined and used as the delay information of the magnetic resonance system. Thus, this method achieves precise measurement of the delay information of the magnetic resonance system through the conversion relationship between phase information and the K-space signal, avoiding the problems of magnetic field inhomogeneity and cross-term eddy current interference in related technologies, and providing a reliable basis for delay compensation of the magnetic resonance system.

[0126] Please see Figure 9 This document provides a schematic diagram of a delay compensation process in an embodiment of this application. Figure 9 As shown, the method in this embodiment may include the following steps S701-S702, and steps S701-S702 may be performed in... Figure 2 The illustrated embodiment is executed after step S104, wherein the magnetic resonance system includes a gradient emission subsystem and a radio frequency receiving subsystem.

[0127] S701, determine the delay compensation parameters of the magnetic resonance system based on the delay information;

[0128] S702 configures the parameters of the magnetic resonance system according to the delay compensation parameters, so that the magnetic resonance system can compensate for the gradient delay of the gradient transmission subsystem and the acquisition delay of the radio frequency receiving subsystem according to the delay compensation parameters.

[0129] Specifically, the delay compensation parameters involved in this embodiment refer to the set of configuration parameters used to correct the timing deviation of each subsystem in the magnetic resonance system; the gradient delay of the gradient transmission subsystem refers to the lag of the gradient magnetic field establishment time relative to the preset timing; the acquisition delay of the radio frequency receiving subsystem refers to the lag of the signal acquisition time caused by the signal receiving and processing link relative to the preset timing; parameter configuration refers to the process of writing the calculated delay compensation parameters into the storage unit of the magnetic resonance system and activating the application.

[0130] First, the delay compensation parameters of the magnetic resonance system are determined based on the delay information. In some possible implementations, the delay information may include the gradient delay component of the gradient transmission subsystem and the acquisition delay component of the radio frequency receiving subsystem. Specifically, the delay information can be decomposed into gradient delay components and acquisition delay components through a preset mapping relationship, where the gradient delay component is used to compensate for timing deviations in the gradient transmission subsystem, and the acquisition delay component is used to compensate for timing deviations in the radio frequency receiving subsystem. Further, gradient compensation parameters are generated based on the gradient delay components, which may include gradient waveform pre-trigger time, gradient amplifier response time compensation value, etc.; acquisition compensation parameters are generated based on the acquisition delay components, which may include signal acquisition window offset, analog-to-digital conversion trigger advance, etc. It is understood that the delay compensation parameters of the magnetic resonance system include the aforementioned gradient compensation parameters and acquisition compensation parameters.

[0131] Secondly, the magnetic resonance system is configured with parameters based on delay compensation parameters. In some possible implementations, gradient compensation parameters can be written into the storage unit of the gradient transmission subsystem to adjust the trigger timing of gradient waveform generation, aligning the actual establishment time of the gradient magnetic field with the preset timing. Specifically, the gradient compensation parameters can be configured as the gradient waveform pre-trigger time, i.e., triggering the gradient current amplifier before the preset gradient application time to compensate for the delay caused by the gradient coil inductance and gradient filter capacitance. Simultaneously, acquisition compensation parameters are written into the storage unit of the RF receiving subsystem to adjust the opening time of the signal acquisition window, aligning the actual center time of signal acquisition with the preset acquisition time. Specifically, the acquisition compensation parameters can be configured as the signal acquisition window offset, i.e., opening the signal acquisition window before the preset acquisition time to compensate for the delay caused by the signal transmission link and analog-to-digital conversion.

[0132] In this embodiment, by decomposing the delay information into gradient delay components and acquisition delay components, and generating corresponding delay compensation parameters for each, precise timing correction can be performed on different subsystems of the magnetic resonance system. By writing the compensation parameters into the control registers of the gradient transmission subsystem and the radio frequency receiving subsystem, the timing of gradient waveform triggering and signal acquisition windows is adjusted, ensuring that the actual time of gradient magnetic field establishment and signal acquisition is strictly aligned with the preset timing. Thus, this method, through a subsystem compensation strategy, achieves independent correction of the delays of the gradient transmission subsystem and the radio frequency receiving subsystem, avoiding the residual timing errors caused by hybrid compensation in related technologies, and providing a precise timing basis for multi-echo gradient echo imaging of the magnetic resonance system.

[0133] Based on the above embodiments, combined with Figures 10 to 20 This application proposes a comprehensive process for determining the delay information of a magnetic resonance system, as described in its embodiments. Figure 10 This is the phase image of the first echo. Figure 11 This is the second echo phase image. Figure 12 This is the phase image of the third echo. Figure 13 This is the second phase difference image. Figure 14 This is the first phase difference image. Figure 15 For reference phase image, Figure 16 This is the third phase difference image. Figure 17 This is a schematic diagram of the signal distribution in K-space. Figure 18 This is a magnified schematic diagram of the signal distribution center in K-space. Figure 19 This is the phase reference image of the first echo after time delay compensation. Figure 20 This is the second echo phase reference image after time delay compensation.

[0134] Specifically, firstly, an image of the target object is acquired based on a preset echo interval to obtain a first echo phase image (e.g., Figure 10 (as shown), second echo phase image (as shown) Figure 11 (as shown) and the third echo phase image (as shown) Figure 12 (As shown). The first and third echo phase images were acquired using a frequency-coded gradient magnetic field of the first polarity, while the second echo phase image was acquired using a frequency-coded gradient magnetic field of the opposite polarity. The time intervals between these three echo phase images were preset echo intervals to ensure the regularity of phase changes.

[0135] Next, the first echo phase image ( Figure 10 ) and third echo phase image ( Figure 12 Phase difference calculations are performed to obtain a second phase difference image reflecting the phase change within two echo intervals (e.g., ...). Figure 13As shown). Since the second phase difference image contains the cumulative phase change of two echo intervals, dividing its phase value by two yields the first phase difference image corresponding to a single echo interval (as shown). Figure 14 (As shown). It can be understood that this first phase difference image characterizes the amount of phase change within a single echo interval caused by multidirectional gradient magnetic field inhomogeneities.

[0136] Furthermore, the first echo phase image ( Figure 10 ) and the first phase difference image ( Figure 14 The images are then overlaid to generate a reference phase image (e.g., the second echo phase image) corresponding to the second echo phase image. Figure 15 (As shown). This reference phase image reflects the phase distribution characteristics that the second echo phase image should possess under ideal, time-delay-free conditions. By comparing the reference phase image ( Figure 15 ) and the actual acquired second echo phase image ( Figure 11 ), and perform phase difference calculation to obtain the third phase difference image (e.g. Figure 16 As shown in the image, this third phase difference image highlights the phase deviation caused by the switching of the frequency-coded gradient magnetic field polarity and the system delay.

[0137] To determine the specific delay information, the third phase difference image ( Figure 16 Perform inverse Fourier transform processing to obtain the signal distribution in K space (e.g., Figure 17 As shown). By magnifying and observing the central region of K-space (e.g.) Figure 18 As shown in the figure, the offset of the signal peak position relative to the preset center position can be clearly identified, that is, the time offset of the magnetic resonance system can be obtained, and the time offset can be further determined as the delay information of the magnetic resonance system.

[0138] Finally, the magnetic resonance system is compensated and configured based on the determined delay information. Figure 19 and Figure 20 The first and second echo phase reference images after delay compensation are shown respectively. It can be seen that the phase distribution after compensation exhibits good symmetry and consistency, which verifies the compensation effect.

[0139] In some possible implementations, a copper sulfate water model is used as the target object, placed in the imaging region at the center of the magnetic resonance system. Three echo images are acquired according to a preset time sequence, with the echo interval set to ESP. Specific acquisition parameters are configured as follows: a field of view of 360mm in the frequency encoding direction, a field of view of 288mm in the phase encoding direction, a slice thickness of 3mm, a total of 22 slices, an oversampling rate of 27.27% in the slice selection direction, an acquisition bandwidth of 166.67kHz, and a resolution of 256 in the frequency encoding direction. Under this parameter configuration, when the system gradient switching rate is not less than 80mT / m / s, the echo interval ESP can reach 1.9ms. This specific parameter setting ensures that, in a superconducting magnetic resonance system with compliant magnetic field homogeneity, under an echo interval of 1.9ms, the phase difference between different echoes is mainly due to phase rollover caused by gradient delay, rather than phase changes caused by magnetic field homogeneity.

[0140] In some potential applications, the delay information determined in this embodiment can significantly improve the accuracy of multi-echo gradient echo imaging in the grading of fatty liver and the diagnosis of heavy metal deposition. In fatty liver grading, multi-echo gradient echo images are acquired using compensated delay parameters. Based on the chemical shift frequency shift component of the fat signal and the phase change of the water signal, the fat fraction in liver tissue can be accurately calculated. Because delay compensation eliminates image phase errors, the resulting fat fraction is less affected by magnetic field inhomogeneity and metal deposition, meeting the stringent clinical requirements for fatty liver grading. In the diagnosis of heavy metal deposition, the compensated relaxation time measurement error is reduced, enabling the differentiation between normal liver tissue and iron-overloaded tissue. In particular, for the diagnosis of early, mild iron deposition, this embodiment can improve detection sensitivity because delay compensation significantly improves the phase linearity of the multi-echo signal, effectively avoiding measurement deviations caused by phase rollover in related technologies. These improvements stem from delay compensation optimizing the phase reliability of the multi-echo image, ensuring that the fat-water separation algorithm and relaxation time fitting are not affected by system timing errors.

[0141] In this embodiment, by employing a multi-echo gradient echo imaging sequence and alternately applying frequency-coded gradient magnetic fields of different polarities, and utilizing the phase relationship between the three echo phase images, the effects of multi-directional gradient magnetic field inhomogeneities and cross-term eddy currents can be simultaneously eliminated. Specifically, the first and third echo phase images are acquired using frequency-coded gradient magnetic fields of the same polarity, ensuring that their phase difference only reflects the phase accumulation caused by magnetic field homogeneity; while the second echo phase image is acquired using frequency-coded gradient magnetic fields of opposite polarity, so that the effects of cross-term eddy currents are canceled out during phase difference calculation. This symmetrical acquisition and processing method ensures that the final determined delay information is not affected by multi-directional gradient magnetic field inhomogeneities and cross-term eddy currents, significantly improving the accuracy and reliability of delay measurements in the magnetic resonance system.

[0142] The following will combine Figure 21 The delay determination device for the magnetic resonance system provided in the embodiments of this application will be described in detail. It should be noted that... Figure 21 The delay determination device of the magnetic resonance system in the present application is used to perform the operation of this application. Figure 2 - Figure 20 The methods shown in the embodiments are illustrated for ease of explanation, showing only the parts relevant to the embodiments of this application. For specific technical details not disclosed, please refer to this application. Figure 2 - Figure 20 The illustrated embodiment. Specifically, a target object is placed in the imaging region of the magnetic resonance system. The delay determination device 800 of the magnetic resonance system may include an acquisition unit 801, a first determination unit 802, a superposition unit 803, and a second determination unit 804, as detailed below:

[0143] The acquisition unit 801 is used to acquire images of the target object based on a preset echo interval, and to obtain a first echo phase image, a second echo phase image and a third echo phase image. The first echo phase image and the third echo phase image are acquired based on the frequency-coded gradient magnetic field of the first polarity.

[0144] The first determining unit 802 is used to determine the first phase difference image corresponding to a single echo interval based on the first echo phase image and the third echo phase image;

[0145] The superposition unit 803 is used to superimpose the first echo phase image and the first phase difference image to obtain a reference phase image corresponding to the second echo phase image;

[0146] The second determining unit 804 is used to determine the delay information of the magnetic resonance system based on the reference phase image and the second echo phase image.

[0147] Optionally, in some embodiments, the acquisition unit 801 can be used to: excite magnetic resonance signals in the imaging layer of the target object based on a preset layer-selective gradient magnetic field and a radio frequency signal; acquire a first echo signal at a first echo time, a second echo signal at a second echo time, and a third echo signal at a third echo time based on the magnetic resonance signal and preset echo intervals, phase-coded gradient magnetic fields, and frequency-coded gradient magnetic fields, wherein the time interval between the first echo time and the second echo time, and the time interval between the second echo time and the third echo time are both echo intervals; and acquire a first echo phase image corresponding to the first echo signal, a second echo phase image corresponding to the second echo signal, and a third echo phase image corresponding to the third echo signal.

[0148] Optionally, in some embodiments, the acquisition unit 801 can be used to: encode the magnetic resonance signal based on a preset phase encoding gradient magnetic field and a frequency encoding gradient magnetic field of a first polarity to acquire a first echo signal at a first echo time; encode the magnetic resonance signal based on a preset echo interval after the first echo time at a second echo time to acquire a second echo signal at a second echo time, wherein the first polarity is opposite to the second polarity; and encode the magnetic resonance signal based on a preset phase encoding gradient magnetic field and a frequency encoding gradient magnetic field of a first polarity after the second echo time at a third echo time to acquire a third echo signal at a third echo time.

[0149] Optionally, in some embodiments, the acquisition unit 801 can be used to: perform Fourier transform processing on the first echo signal, the second echo signal, and the third echo signal respectively to obtain a first echo complex image corresponding to the first echo signal, a second echo complex image corresponding to the second echo signal, and a third echo complex image corresponding to the third echo signal; and extract phase components from the first echo complex image, the second echo complex image, and the third echo complex image respectively to obtain a first echo phase image corresponding to the first echo signal, a second echo phase image corresponding to the second echo signal, and a third echo phase image corresponding to the third echo signal.

[0150] Optionally, in some embodiments, the first determining unit 802 may be used to: perform phase difference calculation processing on the first echo phase image and the third echo phase image to obtain a second phase difference image; divide the phase value in the second phase difference image by two to obtain a first phase difference image corresponding to a single echo interval.

[0151] Optionally, in some embodiments, the second determining unit 804 may be used to: perform phase difference calculation processing on the reference phase image and the second echo phase image to obtain a third phase difference image; perform inverse Fourier transform processing on the third phase difference image to obtain the signal distribution in K space; determine the peak position of the signal distribution in K space in the frequency coding direction; and determine the delay information of the magnetic resonance system based on the offset distance between the peak position and the preset center position in K space in the frequency coding direction.

[0152] Optionally, in some embodiments, the magnetic resonance system includes a gradient transmission subsystem and a radio frequency receiving subsystem; the delay determination device 800 of the magnetic resonance system can be used to: determine the delay compensation parameters of the magnetic resonance system based on the delay information; and configure the magnetic resonance system according to the delay compensation parameters so that the magnetic resonance system compensates for the gradient delay of the gradient transmission subsystem and the acquisition delay of the radio frequency receiving subsystem according to the delay compensation parameters.

[0153] For the effects achievable in this embodiment, please refer to the relevant embodiments of the delay determination method for the magnetic resonance system described above, which will not be repeated here.

[0154] This embodiment also provides a computer-readable storage medium storing computer program code. When the computer program code is run on a computer, the computer executes the above-described related method steps to implement the delay determination method for a magnetic resonance system provided in the above embodiment.

[0155] The storage medium may include: read-only memory (ROM), random access memory (RAM), disk or optical disk, etc.

[0156] Since the instructions stored in the storage medium can execute the steps in any of the delay determination methods for magnetic resonance systems provided in the embodiments of this application, the beneficial effects that any of the delay determination methods for magnetic resonance systems provided in the embodiments of this application can achieve can be realized. For details, please refer to the previous embodiments, which will not be repeated here.

[0157] Accordingly, this application also provides a magnetic resonance system 900. Please refer to... Figure 22 , Figure 22 This is a schematic diagram of the structure of a magnetic resonance system 900 provided in an embodiment of this application. The magnetic resonance system 900 includes a processor 901 and a memory 902. The processor 901 and the memory 902 are electrically connected.

[0158] The processor 901 is the control center of the magnetic resonance system 900. It connects various parts of the entire magnetic resonance system through various interfaces and lines. By running or calling computer programs stored in the memory 902, and calling data stored in the memory 902, it performs various functions of the magnetic resonance system and processes data, thereby monitoring the magnetic resonance system as a whole.

[0159] The memory 902 can be used to store software programs and modules. The processor 901 executes various functional applications and determines the delay of the magnetic resonance system by running the computer programs and modules stored in the memory 902. The memory 902 may mainly include a program storage area and a data storage area. The program storage area may store the operating system, computer programs required for at least one function, etc.; the data storage area may store data created according to the use of the magnetic resonance system, etc.

[0160] Furthermore, memory 902 may include high-speed random access memory, and may also include non-volatile memory, such as at least one disk storage device, flash memory device, or other volatile solid-state storage device. Accordingly, memory 902 may also include a memory controller to provide processor 901 with access to memory 902.

[0161] In this embodiment, a target object is placed in the imaging area of ​​the magnetic resonance system 900. The processor 901 in the magnetic resonance system 900 loads the instructions corresponding to the processes of one or more computer programs into the memory 902 according to the following steps, and the processor 901 runs the computer programs stored in the memory 902 to achieve various functions, as follows:

[0162] Based on the preset echo interval, the target object is image acquired to obtain the first echo phase image, the second echo phase image and the third echo phase image. The first echo phase image and the third echo phase image are acquired based on the frequency-coded gradient magnetic field of the first polarity.

[0163] Based on the first echo phase image and the third echo phase image, determine the first phase difference image corresponding to a single echo interval;

[0164] The first echo phase image and the first phase difference image are superimposed to obtain the reference phase image corresponding to the second echo phase image;

[0165] The delay information of the magnetic resonance system is determined based on the reference phase image and the second echo phase image.

[0166] Optionally, when the processor 901 performs image acquisition on the target object based on a preset echo interval to obtain a first echo phase image, a second echo phase image, and a third echo phase image, wherein the first echo phase image and the third echo phase image are acquired based on a frequency-coded gradient magnetic field of the first polarity, the processor 901 specifically performs the following: excites the magnetic resonance signal of the imaging layer in the target object based on a preset layer-selective gradient magnetic field and a radio frequency signal; acquires the first echo signal at a first echo time, the second echo signal at a second echo time, and the third echo signal at a third echo time based on the magnetic resonance signal and the preset echo interval, the phase-coded gradient magnetic field, and the frequency-coded gradient magnetic field, wherein the time interval between the first echo time and the second echo time, and the time interval between the second echo time and the third echo time are both echo intervals; and acquires the first echo phase image corresponding to the first echo signal, the second echo phase image corresponding to the second echo signal, and the third echo phase image corresponding to the third echo signal.

[0167] Optionally, when the processor 901 executes the acquisition of the first echo signal at the first echo time, the second echo signal at the second echo time, and the third echo signal at the third echo time based on the magnetic resonance signal and preset echo intervals, phase encoding gradient magnetic fields, and frequency encoding gradient magnetic fields, it specifically performs the following: at the first echo time, the magnetic resonance signal is encoded based on the preset phase encoding gradient magnetic field and the frequency encoding gradient magnetic field of the first polarity to acquire the first echo signal; at the second echo time after the preset echo interval following the first echo time, the magnetic resonance signal is encoded based on the phase encoding gradient magnetic field and the preset frequency encoding gradient magnetic field of the second polarity to acquire the second echo signal, wherein the first polarity is opposite to the second polarity; at the third echo time after the echo interval following the second echo time, the magnetic resonance signal is encoded based on the phase encoding gradient magnetic field and the frequency encoding gradient magnetic field of the first polarity to acquire the third echo signal.

[0168] Optionally, when the processor 901 executes the process of acquiring the first echo phase image corresponding to the first echo signal, the second echo phase image corresponding to the second echo signal, and the third echo phase image corresponding to the third echo signal, it specifically performs the following: performing Fourier transform processing on the first echo signal, the second echo signal, and the third echo signal respectively to obtain the first echo complex image corresponding to the first echo signal, the second echo complex image corresponding to the second echo signal, and the third echo complex image corresponding to the third echo signal; and extracting phase components from the first echo complex image, the second echo complex image, and the third echo complex image respectively to obtain the first echo phase image corresponding to the first echo signal, the second echo phase image corresponding to the second echo signal, and the third echo phase image corresponding to the third echo signal.

[0169] Optionally, when the processor 901 executes the process of determining the first phase difference image corresponding to a single echo interval based on the first echo phase image and the third echo phase image, it specifically performs the following: performing phase difference calculation processing on the first echo phase image and the third echo phase image to obtain a second phase difference image; dividing the phase value in the second phase difference image by two to obtain the first phase difference image corresponding to a single echo interval.

[0170] Optionally, when the processor 901 determines the delay information of the magnetic resonance system based on the reference phase image and the second echo phase image, it specifically performs the following: performing phase difference calculation processing on the reference phase image and the second echo phase image to obtain a third phase difference image; performing inverse Fourier transform processing on the third phase difference image to obtain the signal distribution in K space; determining the peak position of the signal distribution in K space in the frequency coding direction; and determining the delay information of the magnetic resonance system based on the offset distance between the peak position and the preset center position in K space in the frequency coding direction.

[0171] Optionally, after the processor 901 executes the following steps: the magnetic resonance system includes a gradient transmission subsystem and an radio frequency receiving subsystem; and after determining the delay information of the magnetic resonance system based on a reference phase image and a second echo phase image, the processor 901 specifically performs the following: determining the delay compensation parameters of the magnetic resonance system based on the delay information; and configuring the parameters of the magnetic resonance system according to the delay compensation parameters, so that the magnetic resonance system compensates for the gradient delay of the gradient transmission subsystem and the acquisition delay of the radio frequency receiving subsystem according to the delay compensation parameters.

[0172] For the effects achievable in this embodiment, please refer to the relevant embodiments of the delay determination method for the magnetic resonance system described above, which will not be repeated here.

[0173] In the embodiments provided in this application, it should be understood that the disclosed apparatus and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another apparatus, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0174] For the delay determination device of the magnetic resonance system in this application embodiment, its functional modules can be integrated into a processing chip, or each module can exist physically separately, or two or more modules can be integrated into one module. The integrated module can be implemented in hardware or as a software functional module. If the integrated module is implemented as a software functional module and sold or used as an independent product, it can also be stored in a computer-readable storage medium.

[0175] The delay determination method, apparatus, system, and storage medium of the magnetic resonance system provided in the embodiments of this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The above embodiments are only for the purpose of helping to understand the method and its core ideas; at the same time, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A method for determining the delay of a magnetic resonance system, characterized in that, The target object is placed in the imaging region of the magnetic resonance system, and the method includes: Based on a preset echo interval, the target object is image acquired to obtain a first echo phase image, a second echo phase image, and a third echo phase image. The first echo phase image and the third echo phase image are acquired based on a frequency-coded gradient magnetic field of the first polarity. Based on the first echo phase image and the third echo phase image, a first phase difference image corresponding to a single echo interval is determined; The first echo phase image and the first phase difference image are superimposed to obtain the reference phase image corresponding to the second echo phase image; Based on the reference phase image and the second echo phase image, the delay information of the magnetic resonance system is determined.

2. The method according to claim 1, characterized in that, The image acquisition of the target object based on a preset echo interval yields a first echo phase image, a second echo phase image, and a third echo phase image. The first echo phase image and the third echo phase image are acquired based on a frequency-coded gradient magnetic field of a first polarity, including: The magnetic resonance signal in the imaging layer of the target object is excited based on the preset layer-selective gradient magnetic field and radio frequency signal. Based on the magnetic resonance signal and the preset echo interval, phase-coded gradient magnetic field, and frequency-coded gradient magnetic field, the first echo signal at the first echo time, the second echo signal at the second echo time, and the third echo signal at the third echo time are acquired. The time interval between the first echo time and the second echo time, and the time interval between the second echo time and the third echo time are all the echo interval. Acquire the first echo phase image corresponding to the first echo signal, the second echo phase image corresponding to the second echo signal, and the third echo phase image corresponding to the third echo signal.

3. The method according to claim 2, characterized in that, The acquisition of the first echo signal at the first echo time, the second echo signal at the second echo time, and the third echo signal at the third echo time, based on the magnetic resonance signal and a preset echo interval, phase-encoded gradient magnetic field, and frequency-encoded gradient magnetic field, includes: During the first echo time, the magnetic resonance signal is encoded based on a preset phase-encoded gradient magnetic field and a frequency-encoded gradient magnetic field of the first polarity to acquire the first echo signal; At the second echo time after a preset echo interval following the first echo time, the magnetic resonance signal is encoded based on the phase-encoded gradient magnetic field and the preset second polarity frequency-encoded gradient magnetic field to acquire the second echo signal, wherein the first polarity is opposite to the second polarity. At the third echo time after the echo interval following the second echo time, the magnetic resonance signal is encoded based on the phase-encoded gradient magnetic field and the frequency-encoded gradient magnetic field of the first polarity to acquire the third echo signal.

4. The method according to claim 2, characterized in that, The step of acquiring the first echo phase image corresponding to the first echo signal, the second echo phase image corresponding to the second echo signal, and the third echo phase image corresponding to the third echo signal includes: Fourier transform is performed on the first echo signal, the second echo signal, and the third echo signal respectively to obtain the first echo complex image corresponding to the first echo signal, the second echo complex image corresponding to the second echo signal, and the third echo complex image corresponding to the third echo signal. Phase components are extracted from the first complex echo image, the second complex echo image, and the third complex echo image to obtain the first echo phase image corresponding to the first echo signal, the second echo phase image corresponding to the second echo signal, and the third echo phase image corresponding to the third echo signal.

5. The method according to claim 1, characterized in that, Determining the first phase difference image corresponding to a single echo interval based on the first echo phase image and the third echo phase image includes: The phase difference between the first echo phase image and the third echo phase image is calculated to obtain the second phase difference image; Divide the phase value in the second phase difference image by two to obtain the first phase difference image corresponding to a single echo interval.

6. The method according to claim 1, characterized in that, The step of determining the time delay information of the magnetic resonance system based on the reference phase image and the second echo phase image includes: The reference phase image and the second echo phase image are processed by phase difference calculation to obtain a third phase difference image; The third phase difference image is subjected to inverse Fourier transform processing to obtain the signal distribution in K space; Determine the peak position of the signal distribution in the K-space along the frequency coding direction; The delay information of the magnetic resonance system is determined based on the offset distance between the peak position and the preset center position of the K space in the frequency encoding direction.

7. The method according to claim 1, characterized in that, The magnetic resonance system includes a gradient emission subsystem and a radio frequency receiving subsystem; after determining the delay information of the magnetic resonance system based on the reference phase image and the second echo phase image, it further includes: Determine the delay compensation parameters of the magnetic resonance system based on the delay information; The magnetic resonance system is configured with parameters according to the delay compensation parameters so that the magnetic resonance system can compensate for the gradient delay of the gradient transmission subsystem and the acquisition delay of the radio frequency receiving subsystem according to the delay compensation parameters.

8. A delay determination device for a magnetic resonance system, characterized in that, A target object is placed in the imaging region of the magnetic resonance system, and the device includes: The acquisition unit is used to acquire images of the target object based on a preset echo interval, and to obtain a first echo phase image, a second echo phase image and a third echo phase image. The first echo phase image and the third echo phase image are acquired based on a frequency-coded gradient magnetic field of a first polarity. The first determining unit is configured to determine a first phase difference image corresponding to a single echo interval based on the first echo phase image and the third echo phase image; The superposition unit is used to superimpose the first echo phase image and the first phase difference image to obtain a reference phase image corresponding to the second echo phase image; The second determining unit is used to determine the delay information of the magnetic resonance system based on the reference phase image and the second echo phase image.

9. A magnetic resonance system, characterized in that, The magnetic resonance system includes: Memory, used to store executable program code; A processor for calling and running the executable program code from the memory, causing the magnetic resonance system to perform the method as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed, implements the method as described in any one of claims 1 to 7.

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