Magnetic resonance b0 eddy current compensation method, device and storage medium

Abstract

The application relates to the field of magnetic resonance, and discloses a magnetic resonance B0 eddy current compensation method, device and storage medium, which comprises the following steps: acquiring parameters of a scanning sequence; dividing each repetition time TR into p time segments to obtain a total of p+1 time points; calculating p sets of B0 eddy current compensation values by using the gradient waveform, multiple sets of B0 eddy current amplitude constants and multiple sets of B0 eddy current time constants; using the gradient waveform, multiple sets of B0 eddy current amplitude constants, multiple sets of B0 eddy current time constants and the B0 eddy current compensation value of a first specified time point, responding to the fact that the first specified time point is an echo signal receiving time point, using the B0 eddy current phase compensation value of the first specified time point to perform phase compensation on the echo signal of the first specified time point, and obtaining a compensated first magnetic resonance signal. The application accelerates B0 eddy current compensation through a modular partial preprocessing mode, and meets the requirements of real-time speed, low consumption and high precision.

Description

Technical Field

[0001] This application relates to the field of magnetic resonance, and in particular to a magnetic resonance BO eddy current compensation method, apparatus and storage medium. Background Technology

[0002] Magnetic resonance refers to the phenomenon of spin magnetic resonance. Its meaning is broad, encompassing nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR), or electron spin resonance. In everyday life, the term "magnetic resonance" refers to magnetic resonance imaging (MRI), a type of imaging device used for medical examinations that utilizes the NMR phenomenon.

[0003] Wherever a changing magnetic field exists, it will induce an electric current in nearby conductors. Because these currents rotate like eddies in a river, they are called "eddies." Eddies reduce the speed and efficiency of gradient switching. Changing gradients generate eddies, causing distortion of the gradients themselves along the X, Y, and Z axes. They also cause a shift in the B0 master magnetic field, which can lead to artifacts and other problems in the image. Summary of the Invention

[0004] To address the issue of image artifacts caused by the shift of the B0 main magnetic field, this application provides a magnetic resonance B0 eddy current compensation method, apparatus, and storage medium.

[0005] This application provides a magnetic resonance B0 eddy current compensation method, which adopts the following technical solution: Firstly, a magnetic resonance B0 eddy current compensation method is provided, including: Obtain the parameters of the sequence to be scanned; the parameters include: repetition time TR, gradient waveform G, and multiple sets of B0 eddy current amplitude constants A. ij and multiple sets of B0 eddy current time constants T ij ; Each repetition time TR is divided into p time segments to obtain a total of p+1 time points within each repetition time TR; Using the gradient waveform G and multiple sets of B0 eddy current amplitude constants A ij and multiple sets of B0 eddy current time constants T ij The eddy current compensation coefficient D of p set B0 is calculated. ij (n), E ij (n) and F ij (n), and the B0 eddy current phase compensation coefficient K ij (n), M ij (n) and N ij (n); here, 1≤n≤p; Using the nth set of B0 eddy current compensation coefficients D ij (n), E ij (n) and F ij(n) Calculate the eddy current compensation value B0 at the corresponding time point. ij (t n ); Here, 1≤n≤p; When n=0, B0 ij (t0) = 0; Using the B0 eddy current phase compensation coefficient K of the nth set ij (n), M ij (n), N ij (n) and the B0 eddy current compensation value B0 at the time point preceding the first specified time point. ij (t n The B0 eddy current phase compensation value at the first specified time point is calculated. Here, 1 ≤ n ≤ p; when n = 0, In response to the first specified time point being the echo signal reception time point, the B0 eddy current phase compensation value at the first specified time point is used. Phase compensation is performed on the echo signal at the first specified time point to obtain the compensated first magnetic resonance signal.

[0006] Secondly, a magnetic resonance B0 eddy current compensation method is also provided, including: Obtain the parameters of the sequence to be scanned; the parameters include: repetition time TR, gradient waveform G, and multiple sets of B0 eddy current amplitude constants A. ij and multiple sets of B0 eddy current time constants T ij ; Each repetition time TR is divided into p time segments to obtain a total of p+1 time points within each repetition time TR; Using the gradient waveform G and multiple sets of B0 eddy current amplitude constants A ij and multiple sets of B0 eddy current time constants T ij The eddy current compensation coefficient D of p set B0 is calculated. ij (n), E ij (n) and F ij (n), and the B0 eddy current phase compensation coefficient K ij (n), M ij (n) and N ij (n); here, 1≤n≤p; Using the nth set of B0 eddy current compensation coefficients D ij (n), E ij (n) and F ij (n) Calculate the eddy current compensation value B0 at the corresponding time point. ij (t n ); Here, 1≤n≤p; When n=0, B0 ij (t0) = 0; Using the B0 eddy current phase compensation coefficient K of the nth setij (n), M ij (n), N ij (n) and the B0 eddy current compensation value B0 at the time point preceding the first specified time point. ij (t n The B0 eddy current phase compensation value at the first specified time point is calculated. Here, 1 ≤ n ≤ p; when n = 0, Using the eddy current compensation value B0 ij (t n Given 0≤n≤p and gyromagnetic ratio γ, the B0 eddy current frequency correction value Δω(t) at the second specified time point is calculated. n ); In response to the second specified time point being the first radio frequency signal transmission time, the B0 eddy current phase compensation value at the second specified time point is used. Phase compensation is performed on the first radio frequency signal at the second specified time point; the B0 eddy current frequency correction value Δω(t) at the second specified time point is used. n The first radio frequency signal is frequency corrected to obtain a compensated and corrected second radio frequency signal. The second radio frequency signal is transmitted, and a second magnetic resonance signal compensated for the B0 eddy current is received, generated by the second radio frequency signal and the gradient waveform G.

[0007] Preferred options also include: The eddy current compensation value B0 at the (p+1)th time point within each repetition time TR is... ij (t n ) and B0 eddy current phase compensation value The eddy current compensation value B0 at the first time point of the next repetition time TR. ij (t n ) and B0 eddy current phase compensation value Using the B0 eddy current compensation value B0 at the first time point of the next repetition time TR ij (t n ) and B0 eddy current phase compensation value And the p-set B0 eddy current compensation coefficient D ij (n), E ij (n) and F ij (n), and the B0 eddy current phase compensation coefficient K ij (n), M ij (n) and N ij (n) is used as a basis to calculate the B0 eddy current phase compensation value at the third specified time point within the next repetition time TR. and / or B0 eddy current frequency correction value Δω(t)n ), used to compensate or correct the radio frequency signal or echo signal at the third specified time point within the next repetition time TR.

[0008] Preferably, after dividing each repeated time TR into p time segments to obtain a total of p+1 time points, the method further includes: The p+1 time points should include: s radio frequency transmission times and r echo reception times; and p+1 ≥ s + r; preferably, the nth set of B0 eddy current compensation coefficients D is used. ij (n), E ij (n) and F ij (n) Calculate the eddy current compensation value B0 at the corresponding time point. ij (t n ); Here, 1≤n≤p; When n=0, B0 ij (t0) = 0; including: The gradient waveform G is split into a fixed waveform Ge and a waveform Ga whose amplitude varies with the period; and G = Ge + Ga; Using the fixed waveform portion Ge, the eddy current compensation value B0 generated by the change of the fixed waveform Ge within each time segment is calculated. ij (t n The coefficient D required in the formula ij (n), the calculation formula is as follows: In the above formula, i represents multiple sets of B0 eddy current amplitude constants A ij Or multiple sets of B0 eddy current time constants T ij The number of gradients, j represents the three gradient axes X, Y, and Z; t n-1 To t n , represents any one of the n time segments; For the initial t n-1 The remaining portion of the eddy current generated at time t is calculated as it decays over time, yielding the eddy current portion from t onwards. n-1 to t n The eddy current compensation value B0 that decays with time after the time gradient waveform G disappears. ij (t n The required coefficient E in the formula ij (n), the calculation formula is as follows: The amplitude varies with the periodic waveform Ga, and the result is obtained from t n-1 to t n The eddy current compensation value B0 is generated by the amplitude varying with the period of the waveform. ij (tn The required coefficient F in the formula ij (n), the calculation formula is as follows: In the above formula, Ga1 is the waveform of Ga after normalization; Calculate t n The eddy current compensation value B0 at time point B0 ij (t n ),include: B0 ij (t n ) = D ij (n)+E ij (n)·B0 ij (t n-1 )+F ij (n)·|Ga| j Where the eddy current compensation value B0 at time t0 is... ij (t0) defaults to zero.

[0009] Preferably, the B0 eddy current phase compensation coefficient K of the nth set is used. ij (n), M ij (n), N ij (n) and the B0 eddy current compensation value B0 at the time point preceding the first specified time point. ij (t n The B0 eddy current phase compensation value at the first specified time point is calculated. Here, 1 ≤ n ≤ p; when n = 0, include: The gradient waveform G is split into a fixed waveform Ge and a waveform Ga whose amplitude varies with the period; and G = Ge + Ga; for the fixed waveform Ge, the B0 eddy current phase compensation value generated by the change of the fixed waveform Ge in each time segment is calculated. The coefficient K required in the formula ij (n), the calculation formula is as follows: In the above formula, i represents the number of multiple sets of eddy current compensation parameters, j represents the three gradient axes X, Y, and Z; t n-1 To t n , represents any time segment within the n time segments; γ is the gyromagnetic ratio; For the initial t n-1 The remaining portion of the eddy current generated at time t is calculated as it decays over time, yielding the eddy current portion from t onwards. n-1 to t n The B0 eddy current phase compensation value that decays with time after the time gradient waveform G disappears. The coefficient M required in the formula ij (n), the calculation formula is as follows: Calculate Ga, the amplitude-period-varying waveform portion of the gradient signal, to obtain the amplitude from t. n-1 to t n The B0 eddy current phase compensation value is generated by the waveform portion of the amplitude varying with the period. The coefficient N required in the formula ij (n), the calculation formula is as follows: The B0 eddy current phase compensation value is calculated at either the first specified time point or the second specified time point. The calculation formula is as follows: Wherein is the B0 eddy current phase compensation value at time t0 The default value is zero; m represents the m groups of B0 eddy current amplitude constants A. ij Or m groups of B0 eddy current time constant T ij .

[0010] Preferably, the use of B0 eddy current compensation value B0 ij (t n Given 0≤n≤z and gyromagnetic ratio γ, the B0 eddy current frequency correction value Δω(t) at the second specified time point is calculated. n The calculation formula is as follows: m represents the m sets of B0 eddy current amplitude constants A ij Or m groups of B0 eddy current time constant T ij .

[0011] Thirdly, a magnetic resonance B0 eddy current compensation device is also provided, comprising: Acquisition module: used to acquire parameters of the sequence to be scanned; the parameters include: repetition time TR, gradient waveform G, and multiple sets of B0 eddy current amplitude constants A. ij and multiple sets of B0 eddy current time constants T ij ; Segmentation module: used to divide each repeated time TR into p time segments, to obtain a total of p+1 time points within each repeated time TR; First calculation module: used to utilize the gradient waveform G and multiple sets of B0 eddy current amplitude constants A ij and multiple sets of B0 eddy current time constants T ij The eddy current compensation coefficient D of p set B0 is calculated. ij (n), E ij (n) and Fij (n), and the B0 eddy current phase compensation coefficient K ij (n), M ij (n) and N ij (n); Here, 1≤n≤p; Using the nth set of B0 eddy current compensation coefficients D ij (n), E ij (n) and F ij (n) Calculate the eddy current compensation value B0 at the corresponding time point. ij (t n ); Here, 1≤n≤p; When n=0, B0 ij (t0) = 0; Second calculation module: used to utilize the B0 eddy current phase compensation coefficient K of the nth set. ij (n), M ij (n), N ij (n) and the B0 eddy current compensation value B0 at the time point preceding the first specified time point. ij (t n The B0 eddy current phase compensation value at the first specified time point is calculated. Here, 1 ≤ n ≤ p; when n = 0, First compensation module: Used to, in response to a first specified time point being the echo signal reception time point, utilize the B0 eddy current phase compensation value at the first specified time point. Phase compensation is performed on the echo signal at the first specified time point to obtain the compensated first magnetic resonance signal.

[0012] Fourthly, a magnetic resonance B0 eddy current compensation device includes: Acquisition module: used to acquire parameters of the sequence to be scanned; the parameters include: repetition time TR, gradient waveform G, and multiple sets of B0 eddy current amplitude constants A. ij and multiple sets of B0 eddy current time constants T ij ; Segmentation module: used to divide each repeated time TR into p time segments, to obtain a total of p+1 time points within each repeated time TR; First calculation module: used to utilize the gradient waveform G and multiple sets of B0 eddy current amplitude constants A ij and multiple sets of B0 eddy current time constants T ij The eddy current compensation coefficient D of p set B0 is calculated. ij (n), E ij (n) and F ij (n), and the B0 eddy current phase compensation coefficient K ij (n), M ij (n) and N ij (n); Here, 1≤n≤p; Using the nth set of B0 eddy current compensation coefficients Dij (n), E ij (n) and F ij (n) Calculate the eddy current compensation value B0 at the corresponding time point. ij (t n ); Here, 1≤n≤p; When n=0, B0 ij (t0) = 0; The third calculation module is used to utilize the B0 eddy current phase compensation coefficient K of the nth set. ij (n), M ij (n), N ij (n) and the B0 eddy current compensation value B0 at the time point preceding the first specified time point. ij (t n The B0 eddy current phase compensation value at the first specified time point is calculated. Here, 1 ≤ n ≤ p; when n = 0, Fourth calculation module: used to utilize the B0 eddy current compensation value B0 ij (t n Given 0≤n≤z and gyromagnetic ratio γ, the B0 eddy current frequency correction value Δω(t) at the second specified time point is calculated. n ); Second compensation module: used to respond to the second specified time point being the transmission time of the first radio frequency signal, and utilize the B0 eddy current phase compensation value at the second specified time point. Phase compensation is performed on the first radio frequency signal at the second specified time point; the B0 eddy current frequency correction value Δω(t) at the second specified time point is used. n The first radio frequency signal is frequency corrected to obtain a compensated and corrected second radio frequency signal. First receiving module: used to transmit the second radio frequency signal and receive the second magnetic resonance signal compensated for the B0 eddy current generated by the second radio frequency signal and the gradient waveform G.

[0013] Fifthly, a computer-readable storage medium is also provided, comprising: storing a computer program that can be loaded by a processor and execute the methods described in any of the above technical solutions.

[0014] In summary, this application includes at least one of the following beneficial technical effects: This application accelerates B0 eddy current compensation through modular partial preprocessing, taking into account the requirements of real-time speed, low power consumption, and high accuracy. Attached Figure Description

[0015] Figure 1 This is a step diagram of the first embodiment of a magnetic resonance B0 eddy current compensation method; Figure 2This is a step diagram of a second embodiment of a magnetic resonance B0 eddy current compensation method; Figure 3 This is a step diagram of the third embodiment of a magnetic resonance B0 eddy current compensation method; Figure 4 This is a step diagram of the fourth embodiment of a magnetic resonance B0 eddy current compensation method; Figure 5 This is a logic diagram of a magnetic resonance B0 eddy current compensation device; Figure 6 This is a logic diagram of another magnetic resonance B0 eddy current compensation device.

[0016] Explanation of reference numerals in the attached drawings: 1. A magnetic resonance B0 eddy current compensation device; 2. Another magnetic resonance B0 eddy current compensation device; 11. Acquisition module; 12. Segmentation module; 13. First calculation module; 14. Second calculation module; 15. First compensation module; 21. Acquisition module; 22. Segmentation module; 23. First calculation module; 24. Third calculation module; 25. Fourth calculation module; 26. Second compensation module; 27. First receiving module. Detailed Implementation

[0017] To make the purpose, technical solution, and advantages of this application clearer, the following description is provided in conjunction with the appendix. Figure 1 To be continued Figure 6 The present application will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the application.

[0018] Current B0 eddy current compensation technology is mainly hardware-based. The spectrometer outputs a B0 signal to a shimming power supply, which drives the B0 coil to generate a B0 compensation magnetic field, thus performing physical compensation. The advantage is that it accurately reproduces the physical process and provides comprehensive compensation; the disadvantages are that it has high hardware requirements and is costly.

[0019] In existing technologies, adding a Boolean eddy current compensation coil to the main magnetic field increases the cost of additional hardware. Furthermore, since the Boolean eddy current compensation coil generates its magnetic field by receiving a simulated Boolean eddy current compensation signal, this simulated signal is typically affected by temperature. When the temperature changes, the magnitude of the Boolean eddy current compensation signal drifts or fluctuates, causing a change in the field strength of the Boolean eddy current compensation magnetic field, thus affecting the accuracy of compensating for the magnetic resonance center frequency.

[0020] The technical solution provided in this application achieves the technical effect of B0 eddy current compensation by compensating the gradient signal through software. This is unaffected by ambient temperature and also reduces hardware costs.

[0021] Firstly, such as Figure 1As shown, a magnetic resonance B0 eddy current compensation method is provided, including: S11: Obtain the parameters of the sequence to be scanned; the parameters include: repetition time TR, gradient waveform G, and multiple sets of B0 eddy current amplitude constants A. ij and multiple sets of B0 eddy current time constants T ij The parameters of the sequence to be scanned include the gradient signals of the X, Y, and Z axes to be transmitted, as well as the radio frequency signals. In this embodiment, the gradient signals of the X, Y, and Z axes in the sequence, as well as the repetition time TR and multiple sets of B0 eddy current amplitude constants A are mainly utilized. ij and multiple sets of B0 eddy current time constants T ij ; Perform calculations to obtain the compensation phase.

[0022] S12: Divide each repetition time TR into p time segments to obtain a total of p+1 time points within each repetition time TR; the repetition time TR is the time elapsed from the appearance of the first radio frequency signal in the scanned sequence to the appearance of the same radio frequency signal in the next cycle. Typically, the repetition time TR can be defined as a phase time utilizing both magnetic and radio frequency signals. Dividing the repetition time TR yields p+1 time points, which can be either the radio frequency signal transmission time or the magnetic resonance signal echo reception time.

[0023] S14: Utilizing the nth set of B0 eddy current compensation coefficients D ij (n), E ij (n) and F ij (n) Calculate the eddy current compensation value B0 at the corresponding time point. ij (t n ); Here, 1≤n≤p; When n=0, B0 ij (t0) = 0; Since eddy currents will always be generated within the operating time range of the magnetic resonance system, compensation for the eddy currents is required for each time point.

[0024] S15: Utilizing the B0 eddy current phase compensation coefficient K of the nth set ij (n), M ij (n), N ij (n) and the B0 eddy current compensation value B0 at the time point preceding the first specified time point. ij (t n The B0 eddy current phase compensation value at the first specified time point is calculated. Here, 1 ≤ n ≤ p; when n = 0, To compensate for the eddy current at time B0 at the first specified time, the eddy current compensation value B0 at the first specified time point must first be obtained. ij (t nFurthermore, 0 ≤ n ≤ z; for the time point n = 0, the eddy current compensation value B0 at that point is... ij (t n If p = 100, then to calculate the B0 eddy current compensation value at time point n = 50, it is necessary to calculate the B0 eddy current compensation value B0 at a total of 50 time points from n = 1 to n = 50. ij (t n Then, using the eddy current compensation value B0 at n=50... ij (t n The B0 eddy current phase compensation value at point n=50 was calculated. Although, in the end, only the eddy current compensation value B0 at n=50 was used. ij (t n This is used to calculate the eddy current compensation value B0 at that point. ij (t n However, the previous B0 eddy current compensation values ​​from n=1 to n=49 were... ij (t n It utilizes the previous B0 eddy current compensation value B0 one by one. ij (t n Get the current eddy current compensation value B0. ij (t n ), and so on, the obtained B0 eddy current compensation value B0 for n=50. ij (t n The value of eddy current compensation (B0) at that time point is B0. ij (t n ).

[0025] S16: In response to the first specified time point being the echo signal reception time point, utilize the B0 eddy current phase compensation value at the first specified time point. Phase compensation is performed on the echo signal at the first specified time point to obtain the compensated first magnetic resonance signal. The compensated first magnetic resonance signal cancels out the influence of the B0 eddy current and can accurately reflect the echo signal at that time point.

[0026] Secondly, such as Figure 2 As shown, a magnetic resonance B0 eddy current compensation method is also provided, including: S21: Obtain the parameters of the sequence to be scanned; the parameters include: repetition time TR, gradient waveform G, and multiple sets of B0 eddy current amplitude constants A. ij and multiple sets of B0 eddy current time constants T ij ; S22: Divide each of the repeated times TR into p time segments to obtain a total of p+1 time points within each of the repeated times TR; S23: Utilizing the gradient waveform G and multiple sets of B0 eddy current amplitude constants A ij and multiple sets of B0 eddy current time constants T ij The eddy current compensation coefficient D of p set B0 is calculated. ij (n), E ij (n) and F ij (n), and the B0 eddy current phase compensation coefficient K ij (n), M ij (n) and N ij (n); here, 1≤n≤p; S24: Utilizing the nth set of B0 eddy current compensation coefficients D ij (n), E ij (n) and F ij (n) Calculate the eddy current compensation value B0 at the corresponding time point. ij (t n ); Here, 1≤n≤p; When n=0, B0 ij (t0) = 0; Using the B0 eddy current phase compensation coefficient K of the nth set ij (n), M ij (n), N ij (n) and the B0 eddy current compensation value B0 at the time point preceding the first specified time point. ij (t n The B0 eddy current phase compensation value at the first specified time point is calculated. Here, 1 ≤ n ≤ p; when n = 0, S25: Utilizing the B0 eddy current compensation value B0 ij (t n ), 0≤n≤z, gyromagnetic ratio γ, calculate the B0 eddy current frequency correction value Δω(t) at the second specified time point. n In this embodiment, if we want to obtain the B0 eddy current frequency correction value Δω(t) at n=50... n The eddy current compensation values ​​B0 from n=0 to n=50 still need to be obtained sequentially. ij (t n Then, the B0 eddy current frequency correction value Δω(t) at n=50 is calculated and obtained. n ).

[0027] S26: In response to the second specified time point being the radio frequency signal transmission time, utilize the B0 eddy current phase compensation value at the second specified time point. Phase compensation is performed on the radio frequency signal at the second specified time point; the B0 eddy current frequency correction value Δω(t) at the second specified time point is used. nThe radio frequency signal is frequency-corrected to obtain a compensated second radio frequency signal. In this embodiment, the second specified time point is set as the radio frequency signal transmission time. After the radio frequency signal is transmitted, it resonates with the magnetic signal, exciting hydrogen protons to generate a magnetic resonance signal. Therefore, the radio frequency signal excitation resonance process will also affect the generation of B0 eddy currents. This effect can be avoided by performing phase compensation or frequency correction on the radio frequency signal.

[0028] S27: Transmit the second radio frequency signal and receive the second magnetic resonance signal compensated for the B0 eddy current generated by the second radio frequency signal and the gradient waveform G.

[0029] Preferred, such as Figure 3 As shown, it also includes: S31: Set the B0 eddy current compensation value B0 at the (p+1)th time point within each repetition time TR. ij (t n ) and B0 eddy current phase compensation value The eddy current compensation value B0 at the first time point of the next repetition time TR. ij (t n ) and B0 eddy current phase compensation value In this embodiment, for example, the eddy current compensation value B0 at the last time point of the first repetition time TR is... ij (t n ) and B0 eddy current phase compensation value The eddy current compensation value B0 at the first time point of the second repetition time TR. ij (t n ) and B0 eddy current phase compensation value That is, the B0 eddy current compensation value B0 continues from each time point of the first repetition time TR. ij (t n ) and B0 eddy current phase compensation value

[0030] S32: Utilize the B0 eddy current compensation value B0 at the first time point of the next repetition time TR. ij (t n ) and B0 eddy current phase compensation value And the p-set B0 eddy current compensation coefficient D ij (n), E ij (n) and F ij (n), and the B0 eddy current phase compensation coefficient K ij (n), M ij (n) and N ij (n) is used as a basis to calculate the B0 eddy current phase compensation value at the third specified time point within the next repetition time TR. and / or B0 eddy current frequency correction value Δω(t) n This is used to compensate or correct the radio frequency signal or echo signal at the third specified time point within the next repetition time TR. In this embodiment, the calculation steps are the same as those in the first repetition time TR, also utilizing the B0 eddy current phase compensation value. It can be used to compensate for echoes or radio frequency signals, or to correct the frequency of radio frequency signals.

[0031] Preferred, such as Figure 4 As shown, the step of dividing each repeated time TR into p time segments to obtain a total of p+1 time points, further includes: S13: The p+1 time points should include: s radio frequency transmission times and r echo reception times; and p+1 ≥ s + r; after dividing the repetition time TR, p+1 time points are obtained; each time point is separate; it can be set as radio frequency transmission time or echo reception time; the division is based on the specific sequence waveform. The s radio frequency transmission times and r echo reception times can be interspersed among each other to facilitate echo phase compensation, radio frequency phase compensation, and radio frequency correction.

[0032] Preferably, the nth set of B0 eddy current compensation coefficients D ij (n), E ij (n) and F ij (n) Calculate the eddy current compensation value B0 at the corresponding time point. ij (t n ); Here, 1≤n≤p; When n=0, B0 ij (t0) = 0; including: The gradient waveform G is split into a fixed waveform Ge and a waveform Ga whose amplitude varies with the period; and G = Ge + Ga; using the fixed waveform Ge, the eddy current compensation value B0 generated by the change of the fixed waveform Ge in each time segment is calculated. ij (t n The coefficient D required in the formula ij (n), the calculation formula is as follows: In the above formula, i represents multiple sets of B0 eddy current amplitude constants A ij Or multiple sets of B0 eddy current time constants T ij The number of gradients, j represents the three gradient axes X, Y, and Z; t n-1 To t n , represents any one of the n time segments; For the initial t n-1The remaining portion of the eddy current generated at time t is calculated as it decays over time, yielding the eddy current portion from t onwards. n-1 to t n The eddy current compensation value B0 that decays with time after the time gradient waveform G disappears. ij (t n The required coefficient E in the formula ij (n), the calculation formula is as follows: The amplitude varies with the periodic waveform Ga, and the result is obtained from t n-1 to t n The eddy current compensation value B0 is generated by the amplitude varying with the period of the waveform. ij (t n The required coefficient F in the formula ij (n), the calculation formula is as follows: In the above formula, Ga1 is the waveform of Ga after normalization; Calculate t n The eddy current compensation value B0 at time point B0 ij (t n ),include: B0 ij (t n ) = D ij (n)+E ij (n)·B0 ij (t n-1 )+F ij (n)·|Ga| j Where the eddy current compensation value B0 at time t0 is... ij (t0) defaults to zero.

[0033] The eddy current compensation value B0 at each time point can be calculated using the above formula. ij (t n The coefficients D at each time point in the formula ij (1) E ij (1) F ij (1), coefficient D ij (2) E ij (2) F ij (2), ..., coefficient D ij (s+r), E ij (s+r), F ij (s+r).

[0034] Preferably, the use of the nth set of B0 eddy current phase compensation coefficient K ij (n), Mij (n), N ij (n) and the B0 eddy current compensation value B0 at the time point preceding the first specified time point. ij (t n The B0 eddy current phase compensation value at the first specified time point is calculated. Here, 1 ≤ n ≤ p; when n = 0, include: The gradient waveform G is split into a fixed waveform Ge and a waveform Ga whose amplitude varies with the period; and G = Ge + Ga; For the fixed waveform portion Ge, the B0 eddy current phase compensation value generated by the change of the fixed waveform Ge within each time segment is calculated. The coefficient K required in the formula ij (n), the calculation formula is as follows: In the above formula, i represents the number of multiple sets of eddy current compensation parameters, j represents the three gradient axes X, Y, and Z; t n-1 To t n , represents any time segment within the n time segments; γ is the gyromagnetic ratio; For the initial t n-1 The remaining portion of the eddy current generated at time t is calculated as it decays over time, yielding the eddy current portion from t onwards. n-1 to t n The B0 eddy current phase compensation value that decays with time after the time gradient waveform G disappears. The coefficient M required in the formula ij (n), the calculation formula is as follows: Calculate Ga, the amplitude-period-varying waveform portion of the gradient signal, to obtain the amplitude from t. n-1 to t n The B0 eddy current phase compensation value is generated by the waveform portion of the amplitude varying with the period. The coefficient N required in the formula ij (n), the calculation formula is as follows: The B0 eddy current phase compensation value at each time point can be calculated using the above formula. The coefficient K for each time period in the formula ij (1) M ij (1), N ij (1), coefficient K ij (2) M ij (2), N ij (2), ..., coefficient K ij (s+r), Mij (s+r), N ij (s+r).

[0035] The computer will input the parameters of the sequence to be scanned and the coefficients D at each time point. ij (1) E ij (1) F ij (1) K ij (1) M ij (1), N ij (1), coefficient D ij (2) E ij (2) F ij (2) K ij (2) M ij (2), N ij (2), ..., coefficient D ij (s+r), E ij (s+r), F ij (s+r), K ij (s+r), M ij (s+r), N ij (s+r) is sent to the spectrometer.

[0036] Using the above formula, as the sequence is scanned, the spectrometer can calculate t1, t2, ..., t in real time. s+r Eddy current compensation value B0 at time B0 ij (t1), B0 ij (t2), ..., B0 ij (t s+r ).

[0037] B0 ij (t1)=D ij (1)+E ij (1)·B0 ij (t0)+F ij (1)·|Ga| j B0 ij (t2)=D ij (2)+E ij (2)·B0 ij (t1)+F ij (2)·|Ga| j ... B0 ij (t s+r ) = D ij (s+r)+E ij (s+r)·B0 ij (t s+r-1 )+Fij (s+r)·|Ga| j The B0 eddy current phase compensation value is calculated at either the first specified time point or the second specified time point. The calculation formula is as follows: Wherein is the B0 eddy current phase compensation value at time t0 The default value is zero; m represents the m groups of B0 eddy current amplitude constants A. ij Or m groups of B0 eddy current time constant T ij .

[0038] Using the above formulas, the spectrometer can calculate t1, t2, ..., t in real time. s+r Eddy current phase compensation value at time B0

[0039] ... Where K ij (1) M ij (1) N ij (1) is the B0 eddy current phase compensation value during the time period t0-t1. The coefficient K required in the formula ij (2) M ij (2) N ij (2) is the B0 eddy current phase compensation value during the time period t1-t2. The coefficient K required in the formula ij (s+r), M ij (s+r), N ij (s+r) is t s+r-1 -t s+r B0 eddy current phase compensation value over time period The coefficients required in the formula.

[0040] Preferably, the use of B0 eddy current compensation value B0 ij (t n Given 0≤n≤z and gyromagnetic ratio γ, the B0 eddy current frequency correction value Δω(t) at the second specified time point is calculated. n The calculation formula is as follows: m represents the m sets of B0 eddy current amplitude constants A ij Or m groups of B0 eddy current time constant T ij .

[0041] Thirdly, such as Figure 5 As shown, a magnetic resonance B0 eddy current compensation device 1 is also provided, comprising: Acquisition module 11: used to acquire parameters of the sequence to be scanned; the parameters include: repetition time TR, gradient waveform G, and multiple sets of B0 eddy current amplitude constants A. ij and multiple sets of B0 eddy current time constants T ij ; Segmentation module 12: used to divide each of the repeated time TRs into p time segments, and obtain a total of p+1 time points within each of the repeated time TRs; First calculation module 13: used to utilize the gradient waveform G and multiple sets of B0 eddy current amplitude constants A ij and multiple sets of B0 eddy current time constants T ij The eddy current compensation coefficient D of p set B0 is calculated. ij (n), E ij (n) and F ij (n), and the B0 eddy current phase compensation coefficient K ij (n), M ij (n) and N ij (n); Here, 1≤n≤p; Using the nth set of B0 eddy current compensation coefficients D ij (n), E ij (n) and F ij (n) Calculate the eddy current compensation value B0 at the corresponding time point. ij (t n ); Here, 1≤n≤p; When n=0, B0 ij (t0) = 0; Second calculation module 14: used to utilize the B0 eddy current phase compensation coefficient K of the nth set. ij (n), M ij (n), N ij (n) and the B0 eddy current compensation value B0 at the time point preceding the first specified time point. ij (t n The B0 eddy current phase compensation value at the first specified time point is calculated. Here, 1 ≤ n ≤ p; when n = 0, First compensation module 15: Used to, in response to a first specified time point being the echo signal reception time point, utilize the B0 eddy current phase compensation value at the first specified time point. Phase compensation is performed on the echo signal at the first specified time point to obtain the compensated first magnetic resonance signal.

[0042] Fourthly, such as Figure 6 As shown, another magnetic resonance B0 eddy current compensation device 2 is also provided, comprising: Acquisition module 21: used to acquire parameters of the sequence to be scanned; the parameters include: repetition time TR, gradient waveform G, and multiple sets of B0 eddy current amplitude constants A. ij and multiple sets of B0 eddy current time constants T ij ; Segmentation module 22: used to divide each of the repeated time TRs into p time segments, and obtain a total of p+1 time points within each of the repeated time TRs; First calculation module 23: used to utilize the gradient waveform G and multiple sets of B0 eddy current amplitude constants A ij and multiple sets of B0 eddy current time constants T ij The eddy current compensation coefficient D of p set B0 is calculated. ij (n), E ij (n) and F ij (n), and the B0 eddy current phase compensation coefficient K ij (n), M ij (n) and N ij (n); Here, 1≤n≤p; Using the nth set of B0 eddy current compensation coefficients D ij (n), E ij (n) and F ij (n) Calculate the eddy current compensation value B0 at the corresponding time point. ij (t n ); Here, 1≤n≤p; When n=0, B0 ij (t0) = 0; Third calculation module 24: used to utilize the B0 eddy current phase compensation coefficient K of the nth set. ij (n), M ij (n), N ij (n) and the B0 eddy current compensation value B0 at the time point preceding the first specified time point. ij (t n The B0 eddy current phase compensation value at the first specified time point is calculated. Here, 1 ≤ n ≤ p; when n = 0, Fourth calculation module 25: Used to utilize the eddy current compensation value B0. ij (t n Given 0≤n≤z and gyromagnetic ratio γ, the B0 eddy current frequency correction value Δω(t) at the second specified time point is calculated. n ); Second compensation module 26: Used to compensate for the B0 eddy current phase value at the second specified time point in response to the first radio frequency signal transmission time at the second specified time point. Phase compensation is performed on the first radio frequency signal at the second specified time point; the B0 eddy current frequency correction value Δω(t) at the second specified time point is used.n The first radio frequency signal is frequency corrected to obtain a compensated and corrected second radio frequency signal. First receiving module 27: used to transmit the second radio frequency signal and receive the second magnetic resonance signal compensated for the B0 eddy current generated by the second radio frequency signal and the gradient waveform G.

[0043] Fifthly, a computer-readable storage medium is also provided, comprising: storing a computer program that can be loaded by a processor and execute any of the methods described in the above technical solutions.

[0044] In summary, this application includes at least one of the following beneficial technical effects: This application accelerates B0 eddy current compensation through modular partial preprocessing, taking into account the requirements of real-time speed, low power consumption, and high accuracy.

[0045] The above are all preferred embodiments of this application and are not intended to limit the scope of protection of this application. Any feature disclosed in this specification (including the abstract and drawings) may be replaced by other equivalent or similar features unless specifically stated otherwise. That is, unless specifically stated otherwise, each feature is only one example of a series of equivalent or similar features.

Claims

1. A magnetic resonance BO eddy current compensation method, characterized in that, include: Obtain the parameters of the sequence to be scanned; the parameters include: repetition time TR, gradient waveform G, and multiple sets of B0 eddy current amplitude constants A. ij and multiple sets of B0 eddy current time constants T ij ; Each repetition time TR is divided into p time segments to obtain a total of p+1 time points within each repetition time TR; Using the gradient waveform G and multiple sets of B0 eddy current amplitude constants A ij and multiple sets of B0 eddy current time constants T ij The eddy current compensation coefficient of p set B0 was calculated. and B0 eddy current phase compensation coefficient Here, ; Using the nth set of B0 eddy current compensation coefficients The B0 eddy current compensation value at the corresponding time point was calculated. Here, When n=0, =0; Using the B0 eddy current phase compensation coefficient of the nth set The B0 eddy current compensation value of the time point preceding the first specified time point The B0 eddy current phase compensation value at the first specified time point is calculated. Here, When n=0, =0; In response to the first specified time point being the echo signal reception time point, the B0 eddy current phase compensation value at the first specified time point is used. Phase compensation is performed on the echo signal at the first specified time point to obtain the compensated first magnetic resonance signal; Using the nth set of B0 eddy current compensation coefficients The B0 eddy current compensation value at the corresponding time point was calculated. Here, When n=0, =0; includes: The gradient waveform G is split into a fixed waveform Ge and a waveform Ga whose amplitude varies with the period; and G = Ge + Ga; Using the fixed waveform Ge, the B0 eddy current compensation value generated by the change of the fixed waveform Ge within each time segment is calculated. The coefficients required in the formula The calculation formula is as follows: In the above formula, , where i is the amplitude constant A of multiple sets of B0 eddy currents. ij Or multiple sets of B0 eddy current time constants T ij The number of gradients, j represents the three gradient axes X, Y, and Z; t n-1 To t n , represents any time segment within n time segments; For the initial t n-1 The remaining portion of the eddy current generated at time t is calculated as it decays over time, yielding the eddy current portion from t onwards. n-1 to t n The eddy current compensation value of B0 that decays with time after the time gradient waveform G disappears. The coefficients required in the formula The calculation formula is as follows: The amplitude of the waveform Ga, which varies with the period, is calculated to obtain the amplitude from t. n-1 to t n The B0 eddy current compensation value is generated by the waveform portion of the amplitude changing with the period at any given moment. The coefficients required in the formula The calculation formula is as follows: In the above formula, Ga1 is the waveform of Ga after normalization; Calculate t n B0 eddy current compensation value at time point ,include: The eddy current compensation value of B0 at time t0 The default value is zero; Using the B0 eddy current phase compensation coefficient of the nth set The B0 eddy current compensation value of the time point preceding the first specified time point The B0 eddy current phase compensation value at the first specified time point is calculated. Here, When n=0, =0; includes: The gradient waveform G is split into a fixed waveform Ge and a waveform Ga whose amplitude varies with the period; and G = Ge + Ga; For the fixed waveform portion Ge, the B0 eddy current phase compensation value generated by the change of the fixed waveform Ge within each time segment is calculated. The coefficients required in the formula The calculation formula is as follows: In the above formula, , where i is the number of multiple sets of eddy current compensation parameters, j is the three gradient axes X, Y, and Z; t n-1 To t n , represents any time segment within the n time segments; γ is the gyromagnetic ratio; For the initial t n-1 The remaining portion of the eddy current generated at time t is calculated as it decays over time, yielding the eddy current portion from t onwards. n-1 to t n The B0 eddy current phase compensation value that decays with time after the time gradient waveform G disappears. The coefficients required in the formula The calculation formula is as follows: )； Calculate Ga, the amplitude-period-varying waveform portion of the gradient signal, to obtain the amplitude from t. n-1 to t n The B0 eddy current phase compensation value is generated by the waveform portion of the amplitude varying with the period. The coefficients required in the formula The calculation formula is as follows: ； The B0 eddy current phase compensation value is calculated at either the first specified time point or the second specified time point. The calculation formula is as follows: The B0 eddy current phase compensation value at time t0 The default value is zero; m represents the m groups of B0 eddy current amplitude constants A. ij Or m groups of B0 eddy current time constant T ij .

2. The magnetic resonance BO eddy current compensation method according to claim 1, characterized in that, include: Using B0 eddy current compensation value , And the gyromagnetic ratio γ, to calculate the B0 eddy current frequency correction value at the second specified time point. ; In response to the second specified time point being the first radio frequency signal transmission time, the B0 eddy current phase compensation value at the second specified time point is used. Phase compensation is performed on the first radio frequency signal at the second specified time point; the B0 eddy current frequency correction value at the second specified time point is used. The first radio frequency signal is frequency corrected; a compensated and corrected second radio frequency signal is obtained. The second radio frequency signal is transmitted, and a second magnetic resonance signal compensated for the B0 eddy current is received, generated by the second radio frequency signal and the gradient waveform G.

3. The magnetic resonance B0 eddy current compensation method according to claim 2, characterized in that, Also includes: The B0 eddy current compensation value at the (p+1)th time point within each repetition time TR. and B0 eddy current phase compensation value B0 eddy current compensation value as the first time point of the next repetition time TR and B0 eddy current phase compensation value ; Using the B0 eddy current compensation value at the first time point of the next repetition time TR and B0 eddy current phase compensation value and the p-set B0 eddy current compensation coefficient and B0 eddy current phase compensation coefficient Based on this, the B0 eddy current phase compensation value at the third specified time point within the next repetition time TR is calculated. and / or B0 eddy current frequency correction value It is used to compensate or correct the radio frequency signal or echo signal at the third specified time point within the next repetition time TR.

4. A magnetic resonance BO eddy current compensation method according to claim 1 or 2, characterized in that, The step of dividing each repeated time TR into p time segments to obtain a total of p+1 time points, further includes: The p+1 time points should include: s radio frequency transmission times and r echo reception times; and p+1 ≥ s + r.

5. The magnetic resonance BO eddy current compensation method according to claim 2, characterized in that, The use of B0 eddy current compensation value , And the gyromagnetic ratio γ, to calculate the B0 eddy current frequency correction value at the second specified time point. The calculation formula is as follows: m represents the amplitude constant A of the m groups of B0 eddy currents. ij Or m groups of B0 eddy current time constant T ij .

6. A magnetic resonance B0 eddy current compensation device, used to implement the magnetic resonance B0 eddy current compensation method as described in claim 1, characterized in that, include: Acquisition module: used to acquire parameters of the sequence to be scanned; the parameters include: repetition time TR, gradient waveform G, and multiple sets of B0 eddy current amplitude constants A. ij and multiple sets of B0 eddy current time constants T ij ; Segmentation module: used to divide each repeated time TR into p time segments, to obtain a total of p+1 time points within each repeated time TR; First calculation module: used to utilize the gradient waveform G and multiple sets of B0 eddy current amplitude constants A ij and multiple sets of B0 eddy current time constants T ij The eddy current compensation coefficient of p set B0 was calculated. and B0 eddy current phase compensation coefficient Here, ; Utilizing the nth set of B0 eddy current compensation coefficients The B0 eddy current compensation value at the corresponding time point was calculated. Here, When n=0, =0; Second calculation module: used to utilize the B0 eddy current phase compensation coefficient of the nth set. The B0 eddy current compensation value of the time point preceding the first specified time point The B0 eddy current phase compensation value at the first specified time point is calculated. Here, When n=0, =0; First compensation module: Used to, in response to a first specified time point being the echo signal reception time point, utilize the B0 eddy current phase compensation value at the first specified time point. Phase compensation is performed on the echo signal at the first specified time point to obtain the compensated first magnetic resonance signal.

7. A magnetic resonance B0 eddy current compensation device, used to implement the magnetic resonance B0 eddy current compensation method as described in claim 2, characterized in that, include: Acquisition module: used to acquire parameters of the sequence to be scanned; the parameters include: repetition time TR, gradient waveform G, and multiple sets of B0 eddy current amplitude constants A. ij and multiple sets of B0 eddy current time constants T ij ; Segmentation module: used to divide each repeated time TR into p time segments, to obtain a total of p+1 time points within each repeated time TR; First calculation module: used to utilize the gradient waveform G and multiple sets of B0 eddy current amplitude constants A ij and multiple sets of B0 eddy current time constants T ij The eddy current compensation coefficient of p set B0 was calculated. and B0 eddy current phase compensation coefficient Here, ; Utilizing the nth set of B0 eddy current compensation coefficients The B0 eddy current compensation value at the corresponding time point was calculated. Here, When n=0, =0; The third calculation module is used to utilize the B0 eddy current phase compensation coefficient of the nth set. The B0 eddy current compensation value of the time point preceding the first specified time point The B0 eddy current phase compensation value at the first specified time point is calculated. Here, When n=0, =0; Fourth calculation module: used to utilize B0 eddy current compensation value , And the gyromagnetic ratio γ, to calculate the B0 eddy current frequency correction value at the second specified time point. ; Second compensation module: used to respond to the second specified time point being the transmission time of the first radio frequency signal, and utilize the B0 eddy current phase compensation value at the second specified time point. Phase compensation is performed on the first radio frequency signal at the second specified time point; the B0 eddy current frequency correction value at the second specified time point is used. The first radio frequency signal is frequency corrected; a compensated and corrected second radio frequency signal is obtained. First receiving module: used to transmit the second radio frequency signal and receive the second magnetic resonance signal compensated for the B0 eddy current generated by the second radio frequency signal and the gradient waveform G.

8. A computer-readable storage medium, characterized in that, include: The computer program is stored that can be loaded by a processor and execute the method as described in any one of claims 1 to 5.

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