Method, apparatus, electronic device and storage medium for determining radio frequency delay

Abstract

The present application provides a method, an apparatus, an electronic device, and a storage medium for determining a radio frequency delay. The method includes: applying a spatial saturation pulse outside a target region to saturate the background magnetization vector outside the target region; applying a radio frequency pulse to the target region and collecting magnetic resonance signals according to a bipolar gradient applied to the target region; determining the radio frequency delay according to the time difference between the first moment when the target waveform generates a first peak and the second moment when the ideal waveform generates a first peak. Through the above method, the embodiments of the present application do not need to repeatedly measure by an exhaustive method, can directly obtain the radio frequency delay, and improve the measurement efficiency.

Description

Technical Field

[0001] The present application relates to the field of magnetic resonance technology. Specifically, it relates to a method, device, electronic device, and storage medium for determining a radio frequency delay. Background Art

[0002] In magnetic resonance imaging, the radio frequency delay is the delay of the radio frequency pulse relative to the gradient. The measurement of the radio frequency delay is a very critical system calibration technology, and the accuracy of its delay measurement determines the quality of the image.

[0003] The inventors found in their research that in the prior art, by utilizing the sensitivity of the water excitation pulse to the radio frequency delay, and by gradually stepping the radio frequency delay value little by little, the uniformity of the multi-layer diffusion imaging under water excitation is measured to determine whether the radio frequency delay is correct. That is, in the prior art, new radio frequency delay values need to be continuously listed, and experiments and verifications are carried out on the newly listed radio frequency delay values. A measurement method similar to exhaustively listing radio frequency delay values and then repeatedly verifying is used to find the most accurate radio frequency delay value, resulting in a long measurement time and low measurement efficiency. Summary of the Invention

[0004] In view of this, embodiments of the present application provide a method, device, electronic device, and storage medium for determining a radio frequency delay to improve the measurement efficiency.

[0005] In a first aspect, an embodiment of the present application provides a method for determining a radio frequency delay, the method including:

[0006] Applying a spatial saturation pulse to the outside of the target area to saturate the background magnetization vector outside the target area, and at the same time applying a slice selection gradient and a spoiling gradient for spatial saturation in cooperation with the spatial saturation pulse;

[0007] Applying a radio frequency pulse to the target area, and collecting magnetic resonance signals according to the bipolar gradient applied to the target area; the magnetic resonance signals are the Fourier transform of the magnetization vector in the target area; the magnetization vector is generated by the radio frequency pulse exciting the protons in the target area;

[0008] Determining the radio frequency delay according to the time difference between the first moment when the target waveform generates the first peak and the second moment when the ideal waveform generates the first peak; the target waveform is obtained by mirroring the waveform of the magnetic resonance signal on the time coordinate; the ideal waveform is the waveform of the radio frequency pulse without delay.

[0009] In a feasible implementation, the gradients in the bipolar gradient include a slice selection gradient and a readout gradient; the magnitudes of the slice selection gradient and the readout gradient are equal, the directions are opposite, and the application times are the same;

[0010] Apply a radio frequency pulse to a target region and acquire magnetic resonance signals according to a bipolar gradient applied to the target region, including:

[0011] Apply the radio frequency pulse to the target region to excite protons in the target region to generate the magnetization vector when the slice selection gradient is positive and read out the magnetic resonance signal when the amplitude of the readout gradient is negative; the slice selection gradient and the readout gradient are on the same axis;

[0012] Based on the characteristics of the bipolar gradient, acquire the magnetic resonance signal when the amplitude of the readout gradient is negative.

[0013] In a feasible implementation, the gradient magnetic field in the bipolar gradient is set in a preselected target direction; the target direction includes: the X direction, the Y direction, and the Z direction;

[0014] The magnetic resonance signal acquired by the bipolar gradient is generated on the gradient magnetic field in the target direction.

[0015] In a feasible implementation, before determining the radio frequency delay, the method further includes:

[0016] Obtain a complex signal of a waveform obtained by mirror flipping the waveform of the magnetic resonance signal on the abscissa;

[0017] When the target direction is the X direction or the Y direction, use the waveform formed by the imaginary part signal in the complex signal as the target waveform;

[0018] When the target direction is the Z direction, use the waveform formed by the real part signal in the complex signal as the target waveform.

[0019] In a feasible implementation, before determining the radio frequency delay, the method further includes:

[0020] Fit the target waveform to obtain a denoised target waveform.

[0021] In a second aspect, an embodiment of the present application further provides a device for determining radio frequency delay, and the device includes:

[0022] A saturation unit for applying a spatial saturation pulse to the outside of the target region to saturate the background magnetization vector outside the target region, and simultaneously applying a slice selection gradient and a scrambling gradient for spatial saturation in cooperation with the spatial saturation pulse;

[0023] An excitation unit, configured to apply a radio frequency pulse to a target region and collect a magnetic resonance signal according to a bipolar gradient applied to the target region; the magnetic resonance signal is the Fourier transform of the magnetization vector in the target region; the magnetization vector is generated by the radio frequency pulse exciting protons in the target region.

[0024] A determination unit, configured to determine a radio frequency delay according to the time difference between the first moment when the target waveform generates the first peak and the second moment when the ideal waveform generates the first peak; the target waveform is obtained by mirroring the waveform of the magnetic resonance signal on the time coordinate; the ideal waveform is the waveform of the radio frequency pulse without delay.

[0025] In a feasible implementation, the gradient in the bipolar gradient includes a slice selection gradient and a readout gradient; the magnitudes of the slice selection gradient and the readout gradient are equal, the directions are opposite, and the application times are the same.

[0026] The excitation unit is configured to:

[0027] Apply the radio frequency pulse to the target region to excite protons in the target region to generate the magnetization vector when the slice selection gradient is positive and read out the magnetic resonance signal when the magnitude of the readout gradient is negative; the slice selection gradient and the readout gradient are on the same axis.

[0028] Based on the characteristics of the bipolar gradient, collect the magnetic resonance signal when the magnitude of the readout gradient is negative.

[0029] In a feasible implementation, the gradient magnetic field in the bipolar gradient is set in a preselected target direction; the target direction includes: X direction, Y direction, Z direction.

[0030] The magnetic resonance signal collected by the bipolar gradient is generated on the gradient magnetic field in the target direction.

[0031] In a feasible implementation, the device further includes:

[0032] An acquisition unit, configured to acquire a complex signal of the waveform obtained by mirroring the waveform of the magnetic resonance signal on the abscissa before determining the radio frequency delay.

[0033] A first adjustment unit, configured to use the waveform formed by the imaginary part signal in the complex signal as the target waveform when the target direction is the X direction or the Y direction.

[0034] A second adjustment unit, configured to use the waveform formed by the real part signal in the complex signal as the target waveform when the target direction is the Z direction.

[0035] In a feasible embodiment, the device further includes:

[0036] A fitting unit, configured to fit the target waveform to obtain a denoised target waveform before determining the radio frequency delay.

[0037] In a third aspect, an embodiment of the present application further provides an electronic device, including: a processor, a storage medium, and a bus. The storage medium stores machine-readable instructions executable by the processor. When the electronic device runs, the processor communicates with the storage medium through the bus. The processor executes the machine-readable instructions to perform the steps of the method according to any one of the first aspects.

[0038] In a fourth aspect, an embodiment of the present application further provides a computer-readable storage medium, on which a computer program is stored. When the computer program is run by a processor, it performs the steps of the method according to any one of the first aspects.

[0039] A method, device, electronic device, and storage medium for determining radio frequency delay provided by an embodiment of the present application saturate the background magnetization vector outside the target area by applying a spatial saturation pulse outside the target area; ensure that the signal outside the target area is saturated, apply a radio frequency pulse to the target area, and collect magnetic resonance signals according to the bipolar gradient applied to the target area; the magnetic resonance signal is the Fourier transform of the magnetization vector in the target area; the magnetization vector is generated by the radio frequency pulse exciting protons in the target area; determine the radio frequency delay according to the time difference between the first moment when the target waveform generates the first peak and the second moment when the ideal waveform generates the first peak; the target waveform is obtained by mirroring and flipping the waveform of the magnetic resonance signal on the time coordinate; the ideal waveform is the waveform of the radio frequency pulse without delay. Through the above method, according to the relationship between the magnetic resonance signal and the magnetization vector generated by the radio frequency pulse exciting the protons in the target area, the waveform of the magnetic resonance signal is flipped to obtain the target waveform, and then the radio frequency delay is determined according to the time difference between the target waveform and the ideal waveform generating the peak. Compared with the prior art that needs to exhaust radio frequency delay values and conduct repeated experiments, the embodiment of the present application does not need to repeatedly verify by exhaustion, can directly obtain the radio frequency delay, and improves the measurement efficiency.

[0040] To make the above objects, features, and advantages of the present application more obvious and understandable, the following specifically enumerates preferred embodiments and, in conjunction with the accompanying drawings, makes a detailed description as follows. Description of the Drawings

[0041] To more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the accompanying drawings required for the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0042] Figure 1 It shows a sequence block diagram of a radio frequency delay measurement provided by an embodiment of the present application.

[0043] Figure 2 It shows a flowchart of a method for determining radio frequency delay provided by an embodiment of the present application.

[0044] Figure 3 It shows a flowchart of a method for determining a target waveform provided by an embodiment of the present application.

[0045] Figure 4 It shows a schematic structural diagram of a device for determining radio frequency delay provided by an embodiment of the present application.

[0046] Figure 5 It shows a schematic structural diagram of an electronic device provided by an embodiment of the present application. Detailed implementation manners

[0047] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the accompanying drawings in the embodiments of the present application. It should be understood that the accompanying drawings in the present application only serve the purposes of illustration and description, and are not used to limit the protection scope of the present application. Additionally, it should be understood that the schematic drawings are not drawn to actual scale. The flowcharts used in the present application show the operations implemented according to some embodiments of the present application. It should be understood that the operations in the flowchart may not be implemented in sequence, and steps without logical context relationships may be reversed or implemented simultaneously. Moreover, those skilled in the art can add one or more other operations to the flowchart or remove one or more operations from the flowchart under the guidance of the content of the present application.

[0048] In addition, the described embodiments are only some embodiments of the present application, rather than all embodiments. The components of the embodiments of the present application described and illustrated in the accompanying drawings here can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application claimed, but only represents the selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative efforts belong to the protection scope of the present application.

[0049] It should be noted in advance that the term "including" will be used in the embodiments of the present application to indicate the presence of the features stated thereafter, but does not exclude the addition of other features.

[0050] Figure 1 A sequence block diagram for radio frequency delay measurement provided by an embodiment of the present application is shown. Figure 1 It includes: radio frequency pulses, gradient Z, gradient Y, and gradient X. When applying a spatial saturation pulse, a spatial selection gradient and a scrambling gradient for cooperating with the saturation pulse are applied on gradient Z, gradient Y, and gradient X; when applying a radio frequency pulse to be measured, the selection gradient and the readout gradient in the bipolar gradient are applied on the same axis (such as the X axis), where Figure 1 the gradients represented by G and -G have the same magnitude and opposite directions. When the selection gradient is at the magnitude of G, a radio frequency pulse to be measured with a duration of τ is applied to excite and generate a magnetization vector; when the readout gradient is at the magnitude of -G (i.e., having the same magnitude and opposite direction as the selection gradient and the same application duration of τ), a magnetic resonance signal is acquired within the application duration of τ. The parameters in gradient Z and gradient Y are preset and stored, and can be changed according to user requirements.

[0051] Figure 2 A flowchart of a method for determining radio frequency delay provided by an embodiment of the present application is shown. In combination with Figure 1 the sequence block diagram in it, the embodiments of the present application are described. As Figure 2 shown, the method is implemented through the following steps:

[0052] Step 101, apply a spatial saturation pulse outside the target area to saturate the background magnetization vector outside the target area, and at the same time apply a selection gradient and a scrambling gradient for spatial saturation in cooperation with the spatial saturation pulse.

[0053] Specifically, the target area is a water film area with a preset target size, that is, the region of interest in the field of magnetic resonance technology. The target area is spatially represented as a three-dimensional spatial shape, including shapes such as a cube and a cuboid.

[0054] Spatial saturation technology is an imaging technique that applies a non-selective pre-saturation radiofrequency pulse to all tissues in a certain area before the excitation of the radiofrequency pulse, so that the longitudinal magnetization is completely saturated. Subsequently, the excitation and data acquisition of the target area are immediately carried out, so that the tissues in the saturated area cannot generate signals. That is, the spatial saturation pulse is a pre-warning and radiofrequency pulse applied outside the target area. By setting the parameters, emission direction, and emission position of the spatial saturation pulse, a target area that is not affected by the spatial saturation pulse is formed. The size of the target area is related to the position where the spatial saturation pulse is applied. For example, six groups of spatial saturation pulses are set above, below, left, right, front, and back of the target area, so that the spatial saturation pulse completely saturates the longitudinal magnetization outside the target area, without causing interference and influence to the target area, so that the magnetization vector can be excited in the limited and smaller target area, ensuring magnetic field uniformity.

[0055] In the embodiment of the present application, the length, width, and height of the set target area are all 20 mm. The embodiment of the present application does not limit the size of the target area and can be changed accordingly according to actual needs. For example, the length, width, and height of the target area are adjusted to 20 mm, 30 mm, and 30 mm respectively; or adjusted to 30 mm, 30 mm, and 30 mm.

[0056] Step 102: Apply a radiofrequency pulse to the target area and collect magnetic resonance signals according to the bipolar gradient applied to the target area; the magnetic resonance signal is the Fourier transform of the magnetization vector in the target area; the magnetization vector is generated by the radiofrequency pulse exciting the protons in the target area.

[0057] Specifically, a radiofrequency pulse is applied to the water film in the target area. The radiofrequency pulse generates a magnetization vector by exciting the water film (i.e., the protons in the water film) in the target area, and performs a Fourier transform on the magnetization vector to obtain a magnetic resonance signal. In the embodiment of the present application, the magnetic resonance signal is collected through the bipolar gradient applied to the target area.

[0058] Among them, when applying a radiofrequency pulse to the protons in the target area, according to the small-angle approximation principle, the magnetization vector generated by exciting the protons in the target area can be obtained. In magnetic resonance imaging, the gradient magnetic field is turned on when selecting a specific slice. A radiofrequency pulse with a certain bandwidth and the slice selection gradient magnetic field act together to achieve the selection of tissue slices. The gradient magnetic fields located in the X, Y, and Z directions in space are G X 、G Y 、G Z , which can be used to select the cross-section, sagittal plane, and coronal plane respectively. Combining two of them can be used to select the inclined plane, and combining all three can be used to select the double-inclined slice. In the embodiment of the present application, the above steps 101 and 102 can set the bipolar gradient according to the gradient magnetic field in any one direction.

[0059] In an embodiment of the present application, taking the example of setting a bipolar gradient on a gradient magnetic field in the Z direction, the magnetization vector is represented by M(τ, r), where τ represents time and r represents the slice selection gradient as G Z , M(τ, r) is the magnetization vector generated by exciting the water film in the target area after a time τ when a radio frequency pulse is applied to the target area due to the slice selection gradient G Z in the slice z to excite the target area

[0060]

[0061] i represents the imaginary unit (√-1) in complex numbers; s represents the time variable; ω(G, r) represents the slice selection excitation frequency, γ is the gyromagnetic ratio, B1(s) is the radio frequency pulse, and a corresponding delay will be generated during the process of exciting the radio frequency pulse B1(s) in the gradient. The relationship between the slice selection excitation frequency ω(G, r) and the slice selection gradient G Z is as follows:

[0062] ω(G, r) = γG Z ;

[0063] S(t) is the magnetic resonance signal collected through the bipolar gradient within the time τ. The magnetic resonance signal S(t) is obtained after performing a Fourier transform on the magnetization vector M(τ, r). The relationship between the magnetic resonance signal S(t) and the magnetization vector M(τ, r) is:

[0064]

[0065] where t is the time variable in the magnetic resonance signal S(t), and Δω(r) represents the off-resonance frequency, represents the transverse relaxation rate under an inhomogeneous magnetic field. Therefore, after applying a spatial saturation pulse to the outside of the target area, the target area can be considered as a region with a uniform magnetic field. Thus, the off-resonance effect in the target area can be ignored, that is, Δω(r)≈0, then substituting Δω(r)≈0, into the formula:

[0066]

[0067] we get:

[0068] S(t) ∝ ∫M(τ, r)e -i(ω(G,r))t dz;

[0069] Then substituting the formula into the formula S(t) ∝ ∫M(τ, r)e -i(ω(G,r))t dz, we can obtain:

[0070] S(t) ∝ B1(τ - t);

[0071] Among them, the relationship between B1(τ - t) and the waveform of the radio frequency pulse B1(s) is that the ordinate is equal and the abscissa is the opposite of each other. That is, the waveform of the signal B1(τ - t) is obtained by mirroring the waveform of the radio frequency pulse B1(s) in time (mirroring on the abscissa). Then, in the above formula, the magnetic resonance signal S(t) is proportional to B1(τ - t), which is equal to the magnetic resonance signal S(t) being proportional to the radio frequency pulse B1(s) flipped in time on the abscissa. Therefore, the signal obtained by mirroring the magnetic resonance signal in time is the actual radio frequency delay waveform.

[0072] The relationship between the magnetic resonance signal and the radio frequency pulse is discussed by the above method. That is, after obtaining the magnetic resonance signal, the radio frequency delay signal with a delay generated during the actual application of the radio frequency pulse in the magnetic resonance imaging process can be obtained according to the magnetic resonance signal, and the waveform corresponding to the radio frequency delay signal is the radio frequency delay waveform.

[0073] It should be noted that before the implementation of the embodiments of the present application, it is necessary to correct the gradient delay to ensure that the gradients in the X, Y, and Z directions and the radio frequency pulse are synchronized.

[0074] Step 103: Determine the radio frequency delay according to the time difference between the first moment when the target waveform generates the first peak and the second moment when the ideal waveform generates the first peak; the target waveform is obtained by mirroring the waveform of the magnetic resonance signal on the time coordinate; the ideal waveform is the waveform of the radio frequency pulse without delay.

[0075] Specifically, since the magnetic resonance signal S(t) is proportional to the signal B1(τ - t), after the magnetic resonance signal is collected through step 102, the radio frequency delay waveform is the target waveform obtained by mirroring the waveform corresponding to the magnetic resonance signal S(t) in time. In the ideal case, the waveform of the radio frequency pulse without delay forms. In the target time period after applying the radio frequency pulse, the moment when the ideal waveform generates the first peak is the 0 moment (the second moment), and the moment when the target waveform generates the first peak (i.e., the first moment) is the actual moment when the radio frequency delay signal generates the peak. According to the time difference between the first moment and the second moment, the specific value of the radio frequency delay is determined. For example, in the target time period, the first moment when the target waveform generates the first peak is 60 us, and the second moment when the ideal waveform generates the first peak is 0 us, then the radio frequency delay is 60 us (60 us - 0 us).

[0076] The abscissa of the target waveform represents the fluctuation time of the waveform, and the ordinate represents the fluctuation amplitude of the waveform. The target waveform is obtained by mirror - flipping the waveform of the magnetic resonance signal on the abscissa. That is, after obtaining the waveform of the magnetic resonance signal, the center point at the center position of the waveform of the magnetic resonance signal on the horizontal axis is determined. The straight line parallel to the ordinate passing through this center point is used as the target line, and the waveform of the magnetic resonance signal is mirror - flipped according to this target line to obtain the target waveform.

[0077] For example, multiple coordinates of the magnetic resonance signal waveform in the coordinate system are: (1, 20), (2, 30), (3, 40), (4, 50); then the corresponding multiple coordinates after flipping the magnetic resonance signal waveform on the abscissa are: (1, 50), (2, 40), (3, 60), (4, 20).

[0078] In the embodiments of the present application, cross - correlation calculation is performed on the target waveform and the ideal waveform to determine the RF delay according to the cross - correlation function. In actual operations, the RF delay between the target waveform and the ideal waveform can also be determined. The embodiments of the present application do not limit the method for determining the delay between the two waveforms.

[0079] In a feasible implementation scheme, the gradients in the bipolar gradient include a slice - selection gradient and a read - out gradient; the amplitudes of the slice - selection gradient and the read - out gradient are equal in magnitude and opposite in direction, and the application time is the same; when performing step 102 of applying an RF pulse to the target area and collecting magnetic resonance signals according to the bipolar gradient applied to the target area, the following steps are included:

[0080] Step 104, applying the RF pulse to be measured to the target area to generate the magnetization vector by exciting the protons in the target area with the slice - selection gradient and reading out the magnetic resonance signal when the amplitude of the read - out gradient is negative; the slice - selection gradient and the read - out gradient are on the same axis; the slice - selection gradient is the gradient magnetic field for setting the bipolar gradient; based on the characteristics of the bipolar gradient, the magnetic resonance signal is collected when the amplitude of the read - out gradient is negative.

[0081] Specifically, the slice - selection gradient includes a rise time, a flat - top time, and a fall time; the read - out gradient includes a rise time, a flat - top time, and a fall time; the fall time of the slice - selection gradient is connected end - to - end with the rise time of the read - out gradient. When the fall time of the slice - selection gradient ends, the rise time of the read - out gradient starts, and the slice - selection gradient is switched to the read - out gradient. During the flat - top time of the slice - selection gradient, an RF pulse is applied through the slice - selection gradient to excite the magnetization vector. After the slice - selection gradient is switched to the read - out gradient, the magnetic resonance signal is collected during the flat - top time of the read - out gradient.

[0082] A method for determining radio frequency delay provided by an embodiment of the present application saturates the background magnetization vector outside the target area by applying a spatial saturation pulse outside the target area; ensures that the signal outside the target area is saturated, applies a radio frequency pulse to the target area, and acquires a magnetic resonance signal according to the bipolar gradient applied to the target area; the magnetic resonance signal is the Fourier transform of the magnetization vector in the target area; the magnetization vector is generated by the radio frequency pulse exciting the protons in the target area; determines the radio frequency delay according to the time difference between the first moment when the target waveform generates the first peak and the second moment when the ideal waveform generates the first peak; the target waveform is obtained by mirror-inverting the waveform of the magnetic resonance signal on the time coordinate; the ideal waveform is the waveform of the radio frequency pulse without delay. Through the above method, according to the relationship between the magnetic resonance signal and the magnetization vector generated by the radio frequency pulse exciting the protons in the target area, the waveform of the magnetic resonance signal is inverted to obtain the target waveform, so that the radio frequency delay is determined according to the time difference between the target waveform and the ideal waveform generating the peak. Compared with the prior art scheme that needs to exhaust radio frequency delay values and conduct repeated experiments, the embodiment of the present application does not need to repeatedly verify by exhaustion, can directly obtain the radio frequency delay, and improves the measurement efficiency.

[0083] In a feasible implementation, the gradient magnetic field in the bipolar gradient is set in a preselected target direction; the target directions include: the X direction, the Y direction, and the Z direction; the magnetic resonance signal acquired by the bipolar gradient is generated on the gradient magnetic field in the target direction. The X direction corresponds to gradient X, the Y direction corresponds to gradient Y, and the Z direction corresponds to gradient Z.

[0084] In a feasible implementation, Figure 3 The flowchart of a method for determining a target waveform provided by an embodiment of the present application is shown. Before performing step 103 to determine the radio frequency delay, as Figure 3 shown, the method further includes the following steps:

[0085] Step 201, acquire the complex signal of the waveform obtained by mirror-inverting the waveform of the magnetic resonance signal on the abscissa.

[0086] Specifically, after mirror-inverting the waveform of the magnetic resonance signal on the abscissa, according to steps 102-step 103, the obtained waveform is the waveform of the radio frequency delay signal. The magnetic resonance signal is a complex signal, and the complex signal includes a real part signal and an imaginary part signal. In a feasible implementation provided by an embodiment of the present application, the magnitudes of the real part signal and the imaginary part signal in the magnetic resonance signal (complex signal) are the same, and the phases differ by 90 degrees.

[0087] When the gradient magnetic field in the bipolar gradient is set in a preselected target direction, in order to ensure a more accurate target waveform in each gradient magnetic field direction and distinguish the signals obtained from the gradient magnetic fields in different target directions, if the target direction is the X direction or the Y direction, go to step 202; if the target direction is the Z direction, go to step 203. Specifically:

[0088] Step 202, when the target direction is the X direction or the Y direction, use the waveform formed by the imaginary part signal in the complex signal as the target waveform.

[0089] Specifically, select the waveform formed by the imaginary part signal in the complex signal used to represent the magnetic resonance signal as the target waveform, so that the waveform formed by the imaginary part signal is used as the target waveform in step 103, in order to determine the radio frequency delay based on the first moment when the peak value is generated by this target waveform.

[0090] Step 203, when the target direction is the Z direction, use the waveform formed by the real part signal in the complex signal as the target waveform.

[0091] Specifically, select the waveform formed by the real part signal in the complex signal used to represent the magnetic resonance signal as the target waveform, so that the waveform formed by the real part signal is used as the target waveform in step 103, in order to determine the radio frequency delay based on the first moment when the peak value is generated by this target waveform.

[0092] In a feasible implementation, before performing step 103, the method further includes: fitting the target waveform to obtain a denoised target waveform.

[0093] Specifically, after obtaining the target waveform, the target waveform contains noise. In order to filter the noise in the target waveform, by fitting the target waveform, a denoised target waveform is obtained, so as to exclude the interference of noise before determining the radio frequency delay and make the obtained data more accurate.

[0094] Figure 4 The structural schematic diagram of a device for determining radio frequency delay provided by an embodiment of the present application is shown. As Figure 4 shown, the device includes: a saturation unit 301, an excitation unit 302, and a determination unit 303.

[0095] The saturation unit 301 is used to apply a spatial saturation pulse to the outside of the target area to saturate the background magnetization vector outside the target area, and at the same time apply a selection layer gradient and a scrambling gradient for spatial saturation in cooperation with the spatial saturation pulse. 9]

[0096] An excitation unit 302 is configured to apply a radio frequency pulse to a target region and collect a magnetic resonance signal according to a bipolar gradient applied to the target region; the magnetic resonance signal is the Fourier transform of the magnetization vector in the target region; the magnetization vector is generated by the radio frequency pulse exciting the protons in the target region.

[0097] A determination unit 303 is configured to determine a radio frequency delay according to the time difference between the first moment when the target waveform generates the first peak and the second moment when the ideal waveform generates the first peak; the target waveform is obtained by mirroring and flipping the waveform of the magnetic resonance signal on the time coordinate; the ideal waveform is the waveform of the radio frequency pulse without delay.

[0098] In a feasible implementation, the gradient in the bipolar gradient includes a slice selection gradient and a readout gradient; the magnitudes of the slice selection gradient and the readout gradient are equal and the directions are opposite, and the application times are the same.

[0099] The excitation unit is configured to:

[0100] Apply the radio frequency pulse to the target region to excite the protons in the target region to generate the magnetization vector when the slice selection gradient is positive and read out the magnetic resonance signal when the magnitude of the readout gradient is negative; the slice selection gradient and the readout gradient are on the same axis.

[0101] Based on the characteristics of the bipolar gradient, collect the magnetic resonance signal when the magnitude of the readout gradient is negative.

[0102] In a feasible implementation, the gradient magnetic field in the bipolar gradient is set in a preselected target direction; the target directions include: the X direction, the Y direction, and the Z direction.

[0103] The magnetic resonance signal collected by the bipolar gradient is generated on the gradient magnetic field in the target direction.

[0104] In a feasible implementation, the device further includes:

[0105] An acquisition unit is configured to acquire a complex signal of the waveform obtained by mirroring and flipping the waveform of the magnetic resonance signal on the abscissa before determining the radio frequency delay.

[0106] A first adjustment unit is configured to use the waveform formed by the imaginary part signal in the complex signal as the target waveform when the target direction is the X direction or the Y direction.

[0107] A second adjustment unit is configured to use the waveform formed by the real part signal in the complex signal as the target waveform when the target direction is the Z direction.

[0108] In a feasible embodiment, the device further includes:

[0109] A fitting unit, configured to fit the target waveform to obtain a denoised target waveform before determining the radio frequency delay.

[0110] A device for determining radio frequency delay provided by an embodiment of the present application saturates the background magnetization vector outside the target area by applying a spatial saturation pulse outside the target area; ensures that the signal outside the target area is saturated, applies a radio frequency pulse to the target area, and acquires a magnetic resonance signal according to a bipolar gradient applied to the target area; the magnetic resonance signal is the Fourier transform of the magnetization vector in the target area; the magnetization vector is generated by the radio frequency pulse exciting protons in the target area; determines the radio frequency delay according to the time difference between the first moment when the target waveform generates the first peak and the second moment when the ideal waveform generates the first peak; the target waveform is obtained by mirroring and flipping the waveform of the magnetic resonance signal on the time coordinate; the ideal waveform is the waveform of the radio frequency pulse without delay. Through the above device, according to the relationship between the magnetic resonance signal and the magnetization vector generated by the radio frequency pulse exciting protons in the target area, the waveform of the magnetic resonance signal is flipped to obtain the target waveform, and thus the radio frequency delay is determined according to the time difference between the target waveform and the ideal waveform when generating peaks. Compared with the prior art scheme that needs to exhaust radio frequency delay values and conduct repeated experiments, the embodiment of the present application does not need to repeatedly verify by exhaustion, can directly obtain the radio frequency delay, and improves the measurement efficiency.

[0111] Figure 5 FIG. shows a schematic structural diagram of an electronic device provided by an embodiment of the present application, including: a processor 401, a storage medium 402, and a bus 403. The storage medium 402 stores machine-readable instructions executable by the processor 401. When the electronic device runs a method for determining radio frequency delay as in the embodiment, the processor 401 communicates with the storage medium 402 through the bus 403, and the processor 401 executes the machine-readable instructions to execute the steps as in the embodiment.

[0112] In the embodiment, the storage medium 402 can also execute other machine-readable instructions to execute other methods as in the embodiment. For the specific method steps and principles of execution, refer to the description of the embodiment, and details are not repeated here.

[0113] In several embodiments provided by the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. The device embodiments described above are merely illustrative. For example, the division of the modules is only a logical function division. In actual implementation, there may be other division methods. For another example, multiple modules or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the displayed or discussed couplings or direct couplings or communication connections to each other can be through some communication interfaces. The indirect couplings or communication connections of the devices or modules can be in electrical, mechanical or other forms.

[0114] The modules described as separate components may or may not be physically separated. The components shown as modules may or may not be physical units, that is, they can be located in one place or distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0115] In addition, in each embodiment of the present application, the functional units can be integrated in a processing unit, or each unit can exist physically alone, or two or more units can be integrated in one unit.

[0116] If the functions are implemented in the form of software function units and sold or used as independent products, they can be stored in a non-volatile computer-readable storage medium executable by a processor. Based on this understanding, the technical solution of the present application, in essence, or the part that contributes to the prior art, or a part of this technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to enable a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in each embodiment of the present application. The foregoing storage medium includes: various media such as USB flash drives, mobile hard disks, ROM, RAM, magnetic disks, or optical discs that can store program codes.

[0117] The above is only the specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present application, and all should be covered by the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for determining radio frequency delay, characterized in that The method includes: Applying a spatial saturation pulse outside the target region to saturate the background magnetization vector outside the target region, and simultaneously applying a slice selection gradient and a spoiling gradient for spatial saturation in cooperation with the spatial saturation pulse; Applying a radio frequency pulse to the target region, and acquiring a magnetic resonance signal according to a bipolar gradient applied to the target region; the magnetic resonance signal is the Fourier transform of the magnetization vector in the target region; the magnetization vector is generated by the radio frequency pulse exciting protons in the target region; Determining a radio frequency delay according to the time difference between the first moment when the target waveform generates a first peak and the second moment when the ideal waveform generates a first peak; the target waveform is obtained by mirror-inverting the waveform of the magnetic resonance signal on the time coordinate; the ideal waveform is the waveform of the radio frequency pulse without delay; The gradient magnetic field in the bipolar gradient is set in a preselected target direction; the target direction includes: the X direction, the Y direction, and the Z direction; The magnetic resonance signal acquired by the bipolar gradient is generated on the gradient magnetic field in the target direction; Before determining the radio frequency delay, the method further includes: Obtaining a complex signal of a waveform obtained by mirror-inverting the waveform of the magnetic resonance signal on the abscissa; When the target direction is the X direction or the Y direction, using the waveform formed by the imaginary part signal in the complex signal as the target waveform; When the target direction is the Z direction, using the waveform formed by the real part signal in the complex signal as the target waveform.

2. The method according to claim 1, wherein The gradient in the bipolar gradient includes a slice selection gradient and a readout gradient; the magnitudes of the slice selection gradient and the readout gradient are equal, the directions are opposite, and the application times are the same; Applying a radio frequency pulse to the target region and acquiring a magnetic resonance signal according to the bipolar gradient applied to the target region includes: Applying the radio frequency pulse to the target region to excite protons in the target region to generate the magnetization vector when the slice selection gradient is positive and read out the magnetic resonance signal when the magnitude of the readout gradient is negative; the slice selection gradient and the readout gradient are on the same axis; Based on the characteristics of the bipolar gradient, acquiring the magnetic resonance signal when the magnitude of the readout gradient is negative.

3. The method according to claim 1, characterized in that, Before determining the radio frequency delay, the method further includes: Fitting the target waveform to obtain a denoised target waveform.

4. A device for determining radio frequency delay, characterized in that, The device includes: A saturation unit for applying a spatial saturation pulse outside the target region to saturate the background magnetization vector outside the target region, and simultaneously applying a slice selection gradient and a spoiling gradient for spatial saturation in cooperation with the spatial saturation pulse; An excitation unit, configured to apply a radio frequency pulse to a target region and acquire a magnetic resonance signal according to a bipolar gradient applied to the target region; the magnetic resonance signal is the Fourier transform of the magnetization vector in the target region; the magnetization vector is generated by the radio frequency pulse exciting protons in the target region; the gradient magnetic field in the bipolar gradient is set in a preselected target direction; the target direction includes: the X direction, the Y direction, and the Z direction; the magnetic resonance signal acquired by the bipolar gradient is generated on the gradient magnetic field in the target direction; A determination unit, configured to determine a radio frequency delay according to the time difference between the first moment when the target waveform generates the first peak and the second moment when the ideal waveform generates the first peak; the target waveform is obtained by mirror-inverting the waveform of the magnetic resonance signal in the time coordinate; the ideal waveform is the waveform of the radio frequency pulse without delay; An acquisition unit, configured to acquire a complex signal of the waveform obtained by mirror-inverting the waveform of the magnetic resonance signal in the abscissa before determining the radio frequency delay; A first adjustment unit, configured to use the waveform formed by the imaginary part signal in the complex signal as the target waveform when the target direction is the X direction or the Y direction; A second adjustment unit, configured to use the waveform formed by the real part signal in the complex signal as the target waveform when the target direction is the Z direction.

5. An electronic device, characterized in that, Comprising: A processor, a storage medium, and a bus. The storage medium stores machine-readable instructions executable by the processor. When the electronic device runs, the processor communicates with the storage medium through the bus, and the processor executes the machine-readable instructions to perform the steps of the method for determining the radio frequency delay according to any one of claims 1 to 3.

6. A computer-readable storage medium, characterized in that, A computer program is stored on the computer-readable storage medium, and when the computer program is run by the processor, it performs the steps of the method for determining the radio frequency delay according to any one of claims 1 to 3.

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