WO2021203705A1 - 梯度场控制方法、装置、磁共振成像设备及介质 - Google Patents

梯度场控制方法、装置、磁共振成像设备及介质 Download PDF

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WO2021203705A1
WO2021203705A1 PCT/CN2020/129197 CN2020129197W WO2021203705A1 WO 2021203705 A1 WO2021203705 A1 WO 2021203705A1 CN 2020129197 W CN2020129197 W CN 2020129197W WO 2021203705 A1 WO2021203705 A1 WO 2021203705A1
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gradient
band
new
signal
area value
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PCT/CN2020/129197
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English (en)
French (fr)
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王海峰
邹莉娴
梁栋
刘新
郑海荣
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深圳先进技术研究院
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
    • G01R33/48—NMR imaging systems
    • G01R33/4818—MR characterised by data acquisition along a specific k-space trajectory or by the temporal order of k-space coverage, e.g. centric or segmented coverage of k-space
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
    • G01R33/38—Systems for generation, homogenisation or stabilisation of the main or gradient magnetic field
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
    • G01R33/443—Assessment of an electric or a magnetic field, e.g. spatial mapping, determination of a B0 drift or dosimetry

Definitions

  • This application belongs to the field of magnetic resonance technology, and in particular relates to a gradient field control method, device, magnetic resonance imaging equipment, and computer-readable storage medium.
  • Magnetic resonance imaging Magnetic Resonance Imaging, MRI
  • MRI Magnetic Resonance Imaging
  • MRI Magnetic Resonance Imaging
  • the protons in the target body After the application of the radio frequency pulse is stopped, the protons in the target body generate magnetic resonance MR signals during the relaxation process, and the usable MR signals can be obtained through processing procedures such as receiving the MR signal, spatial encoding, and image reconstruction.
  • each signal contains full-layer information, so it is necessary to encode the magnetic resonance signal in space, that is, frequency encoding and phase encoding.
  • the MR signal collected by the receiving coil is actually a radio wave with spatially coded information, which is an analog signal, it needs to be converted into digital information through analog-to-digital conversion, and then the digital information is filled into the K-space, and finally the corresponding Digital dot matrix.
  • the K-space is closely related to the spatial positioning of the magnetic resonance signal.
  • the K-space is also called Fourier space, which is the filling space of the original digital information of the MR signal with the spatial positioning coding information.
  • Each MR image has its corresponding K-space data dot matrix. Through the Fourier transform of the K-space data, the spatial positioning coding information in the original digital data can be decoded, and different frequencies, phases and phases can be decomposed.
  • MR digital signals of different frequencies, phases and signal strengths are allocated to the corresponding pixels to obtain the MR image data, that is, the MR image is reconstructed.
  • Fourier transform is the process of transforming the original data lattice of K space into the MR image lattice.
  • a gradient field needs to be applied in the static magnetic field environment.
  • the gradient field is used in the process of magnetic resonance imaging to cooperate with the excitation of radio frequency pulses to realize the selection of imaging area and the imaging goal
  • the MR signal generated on the body performs the encoding of the spatial position.
  • three sets of gradient coils are continuously switched in the on and off states, and in space, such as coordinates X, Y, Z Gradient magnetic fields are generated in three directions to construct a gradient field environment.
  • the gradient field component must quickly reach the maximum power, and the phase encoding gradient and the slice selection gradient must be quickly disconnected before the readout gradient is turned on.
  • the polarity of the gradient field will switch quickly, and during the fast switching process, the metal wires in the gradient coil will vibrate violently, which will generate a lot of noise.
  • the band stop filter can be used to suppress the frequency band components with high sound pressure level of the gradient waveform, but this solution needs to collect the sound pressure in the gradient coil and then calculate The frequency response function then filters out the specific frequency band sound produced by the gradient coil when switching the gradient field. It can be seen that, in the existing magnetic resonance imaging technology, when reducing the noise in the gradient field switching process, there is a problem that the noise reduction scheme is more complicated and the cost is higher.
  • the embodiments of the present application provide a gradient field control method, device, magnetic resonance imaging equipment, and computer-readable storage medium to solve the problem of reducing noise in the gradient field switching process in the existing magnetic resonance imaging technology. At this time, there is a problem that the noise reduction scheme is more complicated and the cost is higher.
  • the first aspect of the embodiments of the present application provides a gradient field control method, including:
  • control parameters are used to describe the gradient waveform of the signal to be adjusted
  • the second area value of the new gradient band is the same as the first area value of the new platform band.
  • the sum of the first area value is equal to the target area value
  • the gradient field is controlled based on a target signal gradient waveform composed of the new gradual waveband and the new platform waveband.
  • control parameter includes a gradient function used to describe the gradient waveform of the signal to be adjusted
  • the scan sequence parameters include: K-space size, K-space unit size, gyromagnetic ratio of nuclei, scanning field of view, bandwidth, sampling time, and the number of sampling points associated with the sampling time.
  • the determining the target area value of the gradient waveform of the signal to be adjusted according to the scan sequence parameter and the control parameter includes:
  • the target area value of the gradient waveform of the signal to be adjusted is measured and calculated by the following formula
  • k(t) is the position in K space at the sampling time t; ⁇ is the gyromagnetic ratio of the nucleus; G(t′) is the gradient function; k is the K space size; N is The number of sampling points; ⁇ k is the size of the K-space unit; FOV is the scanning field of view; A is the target area value; BW is the bandwidth.
  • the adjusting the waveform amplitude of the platform waveband according to the preset amplitude adjustment parameter to obtain a new platform waveband includes:
  • sampling time includes the duration of the platform band and the duration of the gradual band
  • the number of sampling points includes the number of first sampling points corresponding to the duration of the platform band, and the number of the first sampling points corresponding to the duration of the gradual band The number of second sampling points;
  • the smoothly adjusting the gradual waveband based on the target area value and the first area value of the new platform waveband to obtain a new gradual waveband includes:
  • the gradual change band includes a plurality of continuous gradual changes within the duration of the gradual change band
  • the smoothly adjusting the gradient band based on the adjustment area value to obtain a new gradient band includes:
  • X(t) is the new transition point
  • t is the time in the duration of the transition band
  • w is the adjustment factor, and 0 ⁇
  • Xn(t) represents the value of X(t) Normalized result
  • G0 is the amplitude value of the gradient point
  • G(t) is the amplitude value of the new gradient point
  • a plurality of the new gradient points form a new gradient band
  • a plurality of the new gradient points The sum of the amplitude values of the gradient points is equal to the adjusted area value.
  • the method further includes:
  • the target gradient function and the control parameter are associated and stored in a preset database.
  • a second aspect of the embodiments of the present application provides a gradient field control device, including:
  • the first acquiring unit is used to acquire preset scan sequence parameters and control parameters; wherein, the control parameters are used to describe the gradient waveform of the signal to be adjusted;
  • the first determining unit is configured to determine the target area value of the gradient waveform of the signal to be adjusted according to the scan sequence parameter and the control parameter; wherein the gradient waveform of the signal to be adjusted includes a plateau band and a gradient band;
  • the first adjustment unit is configured to adjust the waveform amplitude of the platform waveband according to the preset amplitude adjustment parameter to obtain a new platform waveband;
  • the second adjustment unit is configured to smoothly adjust the gradient band based on the target area value and the first area value of the new platform band to obtain a new gradient band; wherein the value of the new gradient band is The sum of the second area value and the first area value is equal to the target area value;
  • the execution unit is configured to control the gradient field based on the target signal gradient waveform composed of the new gradual waveband and the new platform waveband.
  • a third aspect of the embodiments of the present application provides a magnetic resonance imaging device, including a memory, a processor, and a computer program stored in the memory and running on the magnetic resonance device, and the processor executes the The computer program implements the steps of the gradient field control method provided by the first solution.
  • the fourth aspect of the embodiments of the present application provides a computer-readable storage medium that stores a computer program that, when executed by a processor, implements the gradient field control method provided by the first solution Various steps.
  • the fifth aspect of the embodiments of the present application provides a computer program product.
  • the computer program product runs on a magnetic resonance device
  • the magnetic resonance device executes each of the gradient field control methods described in any one of the above-mentioned first aspects. step.
  • the gradient field control method provided by the embodiment of the present application obtains preset scan sequence parameters and control parameters. Since the control parameters can be used to describe the gradient waveform of the signal to be adjusted, it can be determined according to the scan sequence parameters and control parameters.
  • the target area value of the gradient waveform of the signal to be adjusted, and the gradient waveform of the signal to be adjusted includes the plateau band and the gradient band. The greater the drop of the signal inflection point represented by the gradient band, the greater the noise in the gradient field switching process.
  • the amplitude adjustment parameter to adjust the waveform amplitude of the platform band of the signal gradient waveform to be adjusted, and then smoothly adjust the gradient band based on the target area value and the first area value of the new platform band to obtain a new gradient band, thereby reducing the original
  • the drop of the signal inflection point represented by the gradient band, and finally the gradient field is controlled based on the target signal gradient waveform composed of the new gradient band and the new platform band, which can realize the noise reduction of the noise caused by switching the gradient place during the magnetic resonance imaging process Processing, there is no need to collect the noise generated in the gradient field switching process, and then match the corresponding noise reduction signal to perform the noise reduction operation, which simplifies the noise reduction scheme and saves the noise reduction cost.
  • FIG. 1 is an implementation flowchart of a gradient field control method provided by an embodiment of the present application
  • FIG. 2 is a schematic diagram of the implementation principle of the overall solution of this application.
  • FIG. 3 is an implementation flowchart of a gradient field control method provided by another embodiment of the present application.
  • FIG. 4 is a structural block diagram of a gradient field control device provided by an embodiment of the present application.
  • Fig. 5 is a structural block diagram of a magnetic resonance imaging device according to another embodiment of the present application.
  • FIG. 1 is an implementation flowchart of a gradient field control method provided by an embodiment of the present application.
  • the gradient field control method is used for gradient field switching control in the magnetic resonance imaging process, and its execution subject is the magnetic resonance imaging device.
  • the gradient field control method shown in Fig. 1 includes the following steps:
  • S11 Acquire preset scan sequence parameters and control parameters; wherein, the control parameters are used to describe the gradient waveform of the signal to be adjusted.
  • the scan sequence parameter is used to describe the collection window, that is, the time period for data collection. Since there is an association relationship between the acquisition window and the control parameter in time sequence, that is, there is an overlap area in the time sequence between the gradient waveform of the signal to be adjusted described by the control parameter and the acquisition window, so the overlap area is the time period for data acquisition.
  • the control parameter is a control parameter that controls the gradient field, that is, a control parameter that controls the gradient field switching in the magnetic resonance imaging process, so the gradient waveform described by the control parameter is the gradient waveform of the signal to be adjusted.
  • the hydrogen protons in the target body are excited to generate Magnetic resonance phenomenon.
  • a static magnetic field environment it is also necessary to construct a gradient field, which is used for selective excitation to select the imaging area during the magnetic resonance imaging process, and to encode the spatial position of the MR signal generated on the imaging target.
  • the gradient waveform of the signal to be adjusted described by the control parameter is a signal waveform used to control the switching of the gradient magnetic field.
  • Figure 2 shows a schematic diagram of the implementation principle of the overall solution.
  • the signal gradient waveform presented by the control parameters has a relatively sharp inflection point, such as points P1 and P2 in Figure 2, and the parameter signal corresponding to the sharp inflection point causes noise Therefore, in order to reduce the noise in the gradient field switching process, it is necessary to adjust the sharp inflection point in the gradient waveform of the signal to be adjusted.
  • the scan sequence parameters and the control parameters are obtained. Since the control parameters can be used to describe the gradient waveform of the signal to be adjusted, the control parameters can be imaged, and the control parameters can be analyzed and adjusted more effectively. Provide a way and basis for improving the overall plan. It should be understood that in all the embodiments of the present application, adjusting the gradient waveform of the signal to be adjusted is actually adjusting the control parameter.
  • Scenario 1 In the process of magnetic resonance imaging, when a preset instruction for selecting an imaging area is detected, the preset scan sequence parameters and control parameters are acquired.
  • the preset scan sequence parameters and control parameters are acquired.
  • Scenario 2 If a preset instruction for adjusting the control parameters is detected, then the preset scan sequence parameters and control parameters are acquired.
  • the preset instruction for adjusting the control parameters is triggered to obtain the preset scan sequence parameters and control parameters.
  • the adjustment of the control parameters can be done during the use of the magnetic resonance imaging equipment, or when the magnetic resonance imaging equipment is adjusted. Make adjustments when debugging.
  • the preset scan sequence parameters and control parameters can be pre-stored in the database of the magnetic resonance imaging equipment.
  • the corresponding parameters can be obtained from the database according to the magnetic resonance imaging strategy corresponding to the control instruction. Scanning sequence parameters and control parameters.
  • S12 Determine the target area value of the gradient waveform of the signal to be adjusted according to the scan sequence parameter and the control parameter; wherein the gradient waveform of the signal to be adjusted includes a plateau band and a gradient band.
  • the gradient waveform of the signal to be adjusted can be used to characterize the corresponding relationship between the control parameter and time, that is, different time points correspond to different amplitude values.
  • the amplitude values of multiple discrete sampling points are connected on the coordinate to form the signal gradient waveform to be adjusted, and each amplitude value is accumulated in the continuous time period to obtain the signal gradient waveform to be adjusted The target area value.
  • the scan sequence parameters are used to describe the acquisition window.
  • the data collection period and data content are used to characterize the position of the collected data in K space.
  • the target area value of the signal gradient waveform to be adjusted is determined according to the scan sequence parameters and the control parameters.
  • the target area value is not the complete area value of the signal gradient waveform to be adjusted, but the signal gradient waveform to be adjusted and the acquisition window
  • the timing of the platform band a of the signal gradient waveform to be adjusted completely overlaps with the timing of the acquisition window a'described by the scan sequence parameters, that is, the effective acquisition data and the effective acquisition period represented by the acquisition window are different from those of the acquisition window a'.
  • the plateau band a and the gradient band (a1, a2) in the signal gradient waveform 201 to be adjusted are distinguished by the sampling time, that is, the sampling corresponding to the gradient band (a1, a2)
  • the time is from time 1 to time 2, and from time 3 to time 4.
  • the sampling period corresponding to platform band a is from time 2 to time 3.
  • time 0 to time 1 belong to the preparation time, and time 4 to time 5 are the end time, they are not included in the sampling window.
  • the two bands a1 and a2 before and after the platform band a contain two critical value points, that is, the inflection point P1 and the inflection point P2 that change drastically, when the gradient waveform of the signal to be adjusted is adjusted, the band a1 and the band a2 are changed. It is recognized as a gradual band, and the platform band is a.
  • the gradual band is composed of two bands containing the critical value endpoints before and after the platform band. That is, the gradual band can be regarded as the two bands before and after the platform band, and in each gradual band Both contain threshold endpoints.
  • the specific shape of the gradient waveform of the signal to be adjusted depends on the control parameter, that is, the control parameter is a series of relationship data between the gradient amplitude value and time.
  • the abscissa can represent time and the ordinate can be Represents the gradient amplitude value, and the gradient waveform of the signal to be adjusted can be drawn. Since the control parameter can draw the corresponding gradient waveform of the signal to be adjusted in the coordinate system, part of the data in the control parameter can be replaced with a gradient function describing the gradient waveform of the signal to be adjusted.
  • control parameters include a gradient function used to describe the gradient waveform of the signal to be adjusted;
  • scan sequence parameters include: K-space size, K-space unit size, gyromagnetic ratio of nuclei, and scanning field of view , Bandwidth, sampling time, and the number of sampling points associated with the sampling time.
  • Step S12 may specifically include:
  • the target area value of the gradient waveform of the signal to be adjusted is measured and calculated by the following formula
  • k(t) is the position in K space at the sampling time t; ⁇ is the gyromagnetic ratio of the nucleus; G(t′) is the gradient function; k is the K space size; N is The number of sampling points; ⁇ k is the size of the K-space unit; FOV is the scanning field of view; A is the target area value; BW is the bandwidth.
  • the K-space size is the product of the number of sampling points and the K-space unit size, and the K-space unit size ⁇ k has a reciprocal relationship with the scanning field of view FOV; N is the number of sampling points, and N is greater than 0 Integer.
  • K-space is also called Fourier space, which is the filling space of the original digital data of the MR signal with spatial positioning coding information.
  • Each MR image has its corresponding K-space data dot matrix.
  • the Fourier transform of the data can decode the spatial positioning coding information in the original digital data, and decompose MR signals of different frequencies, phases and amplitudes. Different frequencies and phases represent different spatial positions, and the amplitude represents MR signal intensity, that is, Fourier transform, is the process of transforming the original data lattice of K-space into a magnetic resonance image lattice.
  • the area where the gradient waveform of the signal to be adjusted and the acquisition window overlap in time sequence is used to characterize the effective data acquisition period and data content, that is, to characterize the position of the collected data in K-space, through the above formula, combined with scanning
  • the conversion relationship between the K-space size, the K-space unit size, the gyromagnetic ratio of the nucleus, the scanning field of view, bandwidth, sampling time, and the number of sampling points associated with the sampling time included in the sequence parameters can be determined to be adjusted
  • the target area value of the gradient waveform of the signal to be adjusted is used to characterize the position of the collected data in k-space, in order to ensure that the position of the data in the k-space remains unchanged, the The signal gradient waveform is adjusted, and the obtained area value of the new signal gradient waveform is equal to the target area value of the signal gradient waveform to be adjusted.
  • the preset amplitude adjustment parameter can be an increment or multiple of the waveform amplitude of the platform waveband, that is, the waveform amplitude of the platform waveband is adjusted by increasing its waveform amplitude value on the basis of the original waveform amplitude of the platform waveband. size.
  • the increment is an increment value greater than 0.
  • the preset amplitude adjustment parameter is a multiple of the waveform amplitude of the platform band, the The multiple is a multiple greater than 1.
  • the gradient waveform of the signal to be adjusted is adjusted, specifically, the band with a sharp inflection point in the gradient waveform of the signal to be adjusted is smoothed, and in order to ensure the area value enclosed by the new trapezoidal band after adjustment It is equal to the target area value of the gradient waveform of the signal to be adjusted. Therefore, adjusting the waveform amplitude of the platform band according to the preset amplitude adjustment parameter is to increase the waveform amplitude of the platform band to compensate for the partial area loss after smoothing.
  • the waveform amplitude of the new platform band b is greater than the waveform amplitude of the original platform band a.
  • the gradient waveform 201 of the signal to be adjusted is adjusted, after smoothing the band with a sharp inflection point, part of the area is lost, and the waveform of the new platform band b is obtained through configuration, because its amplitude is greater than the waveform amplitude of the original platform band a , It can compensate for some area lost after smoothing.
  • step S13 may include:
  • the new platform amplitude value is the sum of the original platform amplitude value and the adjustment parameter. Since the sampling process of the gradient field belongs to discrete sampling, that is, the plateau band and the gradient band in the gradient waveform of the signal to be adjusted respectively correspond to sampling times, that is, sampling points, and the gradient function can be used to describe the entire gradient waveform of the signal to be adjusted, Therefore, the sampling time or the number of sampling points can determine the platform waveband and the gradual waveband, and the platform amplitude value of the platform waveband can be determined by combining the gradient function.
  • the process of adjusting the gradient waveform of the signal to be adjusted is to first adjust the amplitude value of the platform band, and then adjust the gradient band based on the new platform band obtained after adjustment. . Since the amplitude value corresponding to each sampling time or sampling point in the new platform band is higher than the original amplitude value, there is a gap between the new platform band and the unadjusted gradient band. In order to ensure that the adjusted gradient waveform can be larger The original characteristics of the signal gradient waveform to be adjusted are retained to a certain extent, so the gradual waveband is smoothly adjusted, even if it can be smoothly and continuously traveled with the new signal gradient waveform of the new platform waveband.
  • S14 Perform smooth adjustment on the gradient waveband based on the target area value and the first area value of the new platform waveband to obtain a new gradient waveband; wherein, the second area value of the new gradient waveband is the same as The sum of the first area value is equal to the target area value.
  • the target area value is the area of the signal gradient waveform to be adjusted.
  • the first area value is the area on the time and amplitude coordinate axes of the new platform band, and is also the accumulation of the amplitude values of all sampling points of the new platform band.
  • the first area value is the area value of the new platform band, which is also the cumulative sum of the amplitude values corresponding to each sampling point on the new platform band
  • the second area value is the area value of the new gradient band, which is also The cumulative sum of the amplitude values corresponding to each sampling point on the new gradual band.
  • the area of the new signal gradient waveform composed of the new platform band and the new gradient band must be the same as the target area of the signal gradient waveform to be adjusted.
  • the sum of the second area value and the first area value of the new gradual waveband is equal to the target area as a limiting condition to smoothly adjust the gradual waveband.
  • the sampling time includes the duration of the platform band and the duration of the gradual band;
  • the number of sampling points includes the number of first sampling points corresponding to the duration of the platform band, and The number of second sampling points corresponding to the duration of the gradual band;
  • step S14 may include:
  • the first area value is the area on the time and amplitude coordinate axis of the new platform band
  • the amplitude value of each point on the new platform waveband is greater than the amplitude value of each point on the original platform waveband Therefore, in order to ensure that the area enclosed by the adjusted gradient waveform is consistent with the target area of the signal gradient waveform to be adjusted, when smoothly adjusting the gradient band, it is necessary to consider the difference between the target area and the first area value of the new platform band The difference. That is, after smooth adjustment of the gradient band, the cumulative sum of the amplitude values of all sampling points on the new gradient band is equal to the difference between the target area and the first area value.
  • the gradual change band includes a plurality of gradual change points that are continuous within the duration of the gradual change band; the smooth adjustment of the gradual change band based on the adjustment area value is performed to obtain a new
  • the gradient bands include:
  • X(t) is the new transition point
  • t is the time in the duration of the transition band
  • w is the adjustment factor, and 0 ⁇
  • Xn(t) represents the value of X(t) Normalized result
  • G0 is the amplitude value of the gradient point
  • G(t) is the amplitude value of the new gradient point
  • a plurality of the new gradient points form a new gradient band
  • a plurality of the new gradient points The sum of the amplitude values of the gradient points is equal to the adjusted area value.
  • X(t) is a new gradient point
  • the value range of w is related to the relative position of the gradient point in the platform band, that is, multiple new gradient points show an upward trend over time, or multiple new gradients
  • the point shows a downward trend with time, which is related to the relative position of the gradient point in the plateau band.
  • the value of the adjustment factor w is between 0 and 1, that is, 0 ⁇ w ⁇ 1; when the time t of X(t) is After the arrival of the platform band, the adjustment factor w ranges between -1 and 0, that is, -1 ⁇ w ⁇ 0.
  • the gradient bands (a1, a2) in the gradient waveform 201 of the signal to be adjusted may be the bands containing the critical inflection points (P1, P2) corresponding to the sampling points, and the gradient band (a1, a2) can be the same as the platform waveband, that is, both waveband a1 and waveband a2 have the same amplitude value as the platform waveband a.
  • the amplitude value of each new gradient point on the new gradient band (b1, b2) is different.
  • the band b1 and the band b2 are different.
  • the amplitude values corresponding to all sampling time points are different.
  • the target signal gradient waveform 202 composed of the new platform band b and the new gradual band (b1, b2) is obtained, and its area is equal to
  • the target area of the signal gradient waveform 201 to be adjusted is the same.
  • the adjustment of the a1 band should be a gradual upward trend adjustment over time, and then the b1 band is obtained, so when the X(t) It is in the a1 band at time t, and the adjustment factor w has a value range between 0 and 1. Since the gradual changes in the a2 band are all after the plateau band, the adjustment to the a2 band should gradually decrease over time. The trend is adjusted to obtain the b2 band. Therefore, when the time t of X(t) is in the a2 band, the adjustment factor w has a value range between -1 and 0.
  • step S15 the area of the target signal gradient waveform is equal to the target area of the signal gradient waveform to be adjusted. Therefore, the position of the K-space represented by the area of the target signal gradient waveform is the same position as the position of the K-space represented by the target area .
  • the gradient field is controlled by using the new control parameter corresponding to the target signal gradient waveform to control the gradient field to switch.
  • control parameter is a control parameter that controls the gradient field switching
  • adjusting the gradient waveform of the signal to be adjusted described in the control parameter is actually adjusting the control parameter, so based on the adjustment obtained
  • the target signal gradient waveform composed of the new gradual band and the new platform band corresponds to the adjusted control parameters. Therefore, the control gradient field based on the target signal gradient waveform composed of the new gradual band and the new platform band is based on the target signal gradient waveform
  • the corresponding adjusted control parameter controls the gradient field for switching operations.
  • the gradient field control method obtains preset scan sequence parameters and control parameters. Since the control parameters can be used to describe the gradient waveform of the signal to be adjusted, the control parameters are based on the scan sequence parameters and control. The parameter can determine the target area value of the gradient waveform of the signal to be adjusted, and the gradient waveform of the signal to be adjusted includes the plateau band and the gradient band.
  • the drop of the signal inflection point represented by the original gradual band is reduced, and finally the gradient field is controlled based on the target signal gradient waveform composed of the new gradual band and the new platform band, which can realize the switching of the gradient field during the magnetic resonance imaging process.
  • the noise is processed for noise reduction, without the need to collect the noise generated during the gradient field switching process, and then match the corresponding noise reduction signal to perform the noise reduction operation, which simplifies the noise reduction scheme and saves the noise reduction cost.
  • FIG. 3 is a flowchart of an implementation of a gradient field control method provided by another embodiment of the present application. Compared with the embodiment corresponding to FIG. 1, the gradient field control method provided in this embodiment further includes S21 to S22 after step S15. The details are as follows:
  • the target gradient function is a function derived based on the gradient waveform of the target signal. That is, after recombining the new gradient band and the new platform band, the target signal gradient wave is obtained, and the target gradient function can be obtained based on the target signal gradient wave.
  • the sampling time point in the gradient function G(t′) corresponding to the gradient waveform of the signal to be adjusted corresponds to a sharply changing inflection point, it is easy to cause a large noise when the gradient field is switched.
  • the amplitude value of the platform waveform is increased, the gradient waveform is smoothly adjusted, and finally the new gradient band is recombined with the new platform band to obtain the target signal gradient wave, based on the target signal
  • the gradient waveform can be used to obtain the target gradient function. Because the gradient waveform represented by the target gradient function is the target signal gradient waveform, and there is no sharp amplitude inflection point in the waveform, it will not produce a large noise.
  • the target gradient function and the control parameter are associated and stored in the preset database.
  • the corresponding control parameter can be directly obtained from the preset database.
  • the target gradient function that is, the target gradient function corresponding to the gradient waveform after adjustment, can directly control the gradient field.
  • the gradient field control method obtains preset scan sequence parameters and control parameters. Since the control parameters can be used to describe the gradient waveform of the signal to be adjusted, the control parameters are based on the scan sequence parameters and control. The parameter can determine the target area value of the gradient waveform of the signal to be adjusted, and the gradient waveform of the signal to be adjusted includes the plateau band and the gradient band.
  • the drop of the signal inflection point represented by the original gradual band is reduced, and finally the gradient field is controlled based on the target signal gradient waveform composed of the new gradual band and the new platform band, which can realize the switching of the gradient field during the magnetic resonance imaging process.
  • the noise is processed for noise reduction, without the need to collect the noise generated during the gradient field switching process, and then match the corresponding noise reduction signal to perform the noise reduction operation, which simplifies the noise reduction scheme and saves the noise reduction cost.
  • the target signal gradient waveform or the corresponding target gradient function can be searched from the preset database to perform gradient field switching control.
  • FIG. 4 is a structural block diagram of a gradient field control device provided by an embodiment of the present application.
  • the units included in the gradient field control device are used to execute the steps in the embodiment corresponding to FIG. 1 and FIG. 3.
  • the gradient field control device 400 includes: a first acquisition unit 41, a first determination unit 42, a first adjustment unit 43, a second adjustment unit 44, and an execution unit 45. in:
  • the first acquiring unit 41 is configured to acquire preset scan sequence parameters and control parameters; wherein, the control parameters are used to describe the gradient waveform of the signal to be adjusted.
  • the first determining unit 42 is configured to determine the target area value of the gradient waveform of the signal to be adjusted according to the scan sequence parameter and the control parameter; wherein the gradient waveform of the signal to be adjusted includes a plateau band and a gradient band.
  • the first adjustment unit 43 is configured to adjust the waveform amplitude of the platform waveband according to the preset amplitude adjustment parameter to obtain a new platform waveband.
  • the second adjustment unit 44 is configured to smoothly adjust the gradient band based on the target area value and the first area value of the new platform band to obtain a new gradient band; wherein, the new gradient band The sum of the second area value of and the first area value is equal to the target area value.
  • the execution unit 45 is configured to control the gradient field based on the target signal gradient waveform composed of the new gradual waveband and the new platform waveband.
  • control parameters include a gradient function used to describe the gradient waveform of the signal to be adjusted;
  • scan sequence parameters include: K-space size, K-space unit size, gyromagnetic ratio of nuclei, and scanning field of view , Bandwidth, sampling time, and the number of sampling points associated with the sampling time.
  • the first determining unit 42 is specifically configured to calculate the target area value of the gradient waveform of the signal to be adjusted using the following formula;
  • k(t) is the position in K space at the sampling time t; ⁇ is the gyromagnetic ratio of the nucleus; G(t′) is the gradient function; k is the K space size; N is The number of sampling points; ⁇ k is the size of the K-space unit; FOV is the scanning field of view; A is the target area value; BW is the bandwidth.
  • the first adjustment unit 43 is specifically configured to determine the platform amplitude value of the platform waveband according to the gradient function; adjust the platform amplitude value according to preset amplitude adjustment parameters to obtain a new platform amplitude value Wherein, the amplitude value of the new platform waveband is equal to the sum of the platform amplitude value and the adjustment parameter; the new platform waveband is obtained according to the new platform amplitude value.
  • the sampling time includes the duration of the platform band and the duration of the gradient band; the number of sampling points includes the number of first sampling points corresponding to the duration of the platform band, and the number of sampling points corresponding to the duration of the gradient band. The number of second sampling points corresponding to the band duration.
  • the second adjustment unit 44 is specifically configured to obtain the number of the first sampling points; identify the product of the number of the first sampling points and the new platform amplitude value as the first area value; The difference between the target area value and the first area value is used to obtain an adjusted area value; and the gradient waveband is smoothly adjusted based on the adjusted area value to obtain a new gradient waveband.
  • the gradient waveband includes a plurality of gradient points that are continuous within the duration of the gradient waveband; the second adjustment unit 44 is specifically configured to:
  • X(t) is the new transition point
  • t is the time in the duration of the transition band
  • w is the adjustment factor, and 0 ⁇
  • Xn(t) represents the value of X(t) Normalized result
  • G0 is the amplitude value of the gradient point
  • G(t) is the amplitude value of the new gradient point
  • a plurality of the new gradient points form a new gradient band
  • a plurality of the new gradient points The sum of the amplitude values of the gradient points is equal to the adjusted area value.
  • the gradient field control device 400 further includes: a second determining unit 46 and a storage unit 47. specifically:
  • the second determining unit 46 is configured to determine a target gradient function corresponding to the target signal gradient waveform.
  • the storage unit 47 is configured to store the target gradient function and the control parameter in a preset database in association with each other.
  • the solution provided in this embodiment obtains preset scan sequence parameters and control parameters. Since the control parameters can be used to describe the signal gradient waveform to be adjusted, the scan sequence parameters and control parameters can be used to determine the Adjust the target area value of the signal gradient waveform, and the signal gradient waveform to be adjusted includes the plateau band and the gradient band.
  • the amplitude adjustment parameter adjusts the waveform amplitude of the platform band of the signal gradient waveform to be adjusted, and then smoothly adjusts the gradient band based on the target area value and the first area value of the new platform band to obtain a new gradient band, thereby reducing the original gradient
  • the target signal gradient waveform or the corresponding target gradient function can be searched from the preset database to perform gradient field switching control.
  • Fig. 5 is a structural block diagram of a magnetic resonance imaging device according to another embodiment of the present application.
  • the magnetic resonance imaging device 5 of this embodiment includes a processor 50, a memory 51, and a computer program 52 stored in the memory 51 and running on the processor 50, such as gradient field control. Method of procedure.
  • the processor 50 executes the computer program 52, the steps in the embodiments of the above-mentioned gradient field control methods are implemented, such as S11 to S15 shown in FIG. 1.
  • the processor 50 executes the computer program 52
  • the functions of the units in the embodiment corresponding to FIG. 4 are realized, for example, the functions of the units 41 to 45 shown in FIG. 4, please refer to the corresponding implementation in FIG. 5 for details The relevant description in the example will not be repeated here.
  • the computer program 52 may be divided into one or more units, and the one or more units are stored in the memory 51 and executed by the processor 50 to complete the application.
  • the one or more units may be a series of computer program instruction segments capable of completing specific functions, and the instruction segments are used to describe the execution process of the computer program 52 in the magnetic resonance imaging device 5.
  • the computer program 52 may be divided into a first acquisition unit, a first determination unit, a first adjustment unit, a second adjustment unit, and an execution unit, and the specific functions of each unit are as described above.
  • the magnetic resonance device may include, but is not limited to, a processor 50 and a memory 51.
  • FIG. 5 is only an example of the magnetic resonance imaging device 5, and does not constitute a limitation on the magnetic resonance imaging device 5. It may include more or less components than shown in the figure, or combine certain components, or Different components, for example, the magnetic resonance device may also include input and output devices, network access devices, buses, and so on.
  • the so-called processor 50 may be a central processing unit (Central Processing Unit, CPU), other general-purpose processors, digital signal processors (Digital Signal Processor, DSP), application specific integrated circuits (Application Specific Integrated Circuit, ASIC), Ready-made programmable gate array (Field-Programmable Gate Array, FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc.
  • the general-purpose processor may be a microprocessor or the processor may also be any conventional processor or the like.
  • the memory 51 may be an internal storage unit of the magnetic resonance imaging device 5, for example, a hard disk or a memory of the magnetic resonance imaging device 5.
  • the memory 51 may also be an external storage device of the magnetic resonance imaging device 5, such as a plug-in hard disk equipped on the magnetic resonance imaging device 5, a smart memory card (Smart Media Card, SMC), and a secure digital (Secure Digital). Digital, SD) cards, flash cards, etc.
  • the memory 51 may also include both an internal storage unit of the magnetic resonance imaging device 5 and an external storage device.
  • the memory 51 is used to store the computer program and other programs and data required by the magnetic resonance device.
  • the memory 51 can also be used to temporarily store data that has been output or will be output.

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Abstract

一种梯度场控制方法、装置(400)、磁共振成像设备(5)及介质，其中，一种梯度场控制方法，通过获取预先设定的扫描序列参数与控制参数，根据扫描序列参数与控制参数，可以确定待调整信号梯度波形(201)的目标面积值(A)，其中，待调整信号梯度波形(201)包括平台波段(a)与渐变波段(a1, a2)，按照预设幅度调整参数调整待调整信号梯度波形(201)的平台波段(a)的波形幅度，再基于目标面积值(A)与新的平台波段(b)的第一面积值，对渐变波段(a1,a2)进行平滑调整得到新的渐变波段(b1,b2)，降低了原有渐变波段(a1,a2)所表征的信号拐点(P1,P2)的落差，无需对梯度场切换过程中产生的噪音进行采集，再匹配相应的降噪信号进行降噪操作，简化了降噪方案且节约了降噪成本。

Description

梯度场控制方法、装置、磁共振成像设备及介质 技术领域
本申请属于磁共振技术领域，尤其涉及一种梯度场控制方法、装置、磁共振成像设备及计算机可读存储介质。
背景技术
磁共振成像技术(Magnetic Resonance Imaging，MRI)是通过对静磁场中的目标体施加特定频率的射频脉冲，使该目标体中的氢质子受到激励而发生磁共振现象。在停止施加射频脉冲后，目标体中的质子在弛豫过程中产生磁共振MR信号，通过对该MR信号的接收、空间编码和图像重建等处理过程，即可获得可用的MR信号。由于磁共振过程中，每一个信号都含有全层的信息，因此需要对磁共振信号进行空间定位编码，即频率编码和相位编码。具体地，因为接收线圈采集到的MR信号实际是带有空间编码信息的无线电波，属于模拟信号，所以需要经过模数转换变成数字信息，再将数字信息填充到K空间，最后得到相应的数字点阵。其中，K空间与磁共振信号的空间定位息息相关，该K空间也叫傅里叶空间，是带有空间定位编码信息的MR信号原始数字信息的填充空间。每一幅MR图像都有其相应的K空间数据点阵，通过对K空间的数据进行傅里叶转换，就能对原始数字数据中的空间定位编码信息进行解码，分解出不同频率、相位和幅度的MR信号，不同的频率和相位代表不同的空间位置，而幅度则代表MR信号强度。把不同频率、相位及信号强度的MR数字信号分配到相应的像素中，就得到MR图像数据，也即重建出了MR图像。傅里叶变换就是把K空间的原始数据点阵转变成MR图像点阵的过程。
在使用磁共振成像技术进行扫描成像的过程中，需要在静磁场环境中施加一个梯度场，该梯度场用于磁共振成像过程中配合射频脉冲的激励实现成像区 域的选择，以及对成像的目标体上产生的MR信号进行空间位置的编码。现有的磁共振成像设备中，用于制造梯度场环境的梯度场组件中，通过三组梯度线圈不断地在接通、断开状态下切换，并在空间中，如坐标X、Y、Z三个方向上产生梯度磁场，从而构建出梯度场环境。由于磁共振成像设备在工作过程中，梯度场组件必须快速地到达最大功率，而且相位编码梯度与层面选择梯度必须在读出梯度接通前快速地断开。有时梯度场的极性还会快速地切换，而在快速切换过程中，梯度线圈中的金属丝之间会产生剧烈地震动，进而产生较大的噪声。
虽然现有技术中在解决磁共振成像过程中的噪音问题时，可以通过使用带阻滤波器来抑制梯度波形声压级高的频带成分，但是该方案需要采集梯度线圈中的声压，然后计算频率响应函数进而滤除梯度线圈在切换梯度场时说产生的特定频段声音。由此可见，现有的磁共振成像技术中，在降低梯度场切换过程中的噪音时，存在降噪方案较复杂且成本较高的问题。
发明内容
有鉴于此，本申请实施例提供了一种梯度场控制方法、装置、磁共振成像设备及计算机可读存储介质，以解决现有的磁共振成像技术中，在降低梯度场切换过程中的噪音时，存在降噪方案较复杂且成本较高的问题。
本申请实施例的第一方面提供了一种梯度场控制方法，包括：
获取预先设定的扫描序列参数与控制参数；其中，所述控制参数用于描述待调整信号梯度波形；
根据所述扫描序列参数与所述控制参数，确定所述待调整信号梯度波形的目标面积值；其中，所述待调整信号梯度波形包括平台波段与渐变波段；
按照预设幅度调整参数调整所述平台波段的波形幅度，得到新的平台波段；
基于所述目标面积值与所述新的平台波段的第一面积值，对所述渐变波段进行平滑调整，得到新的渐变波段；其中，所述新的渐变波段的第二面积值与 所述第一面积值之和等于所述目标面积值；
基于所述新的渐变波段与所述新的平台波段组成的目标信号梯度波形，控制所述梯度场。
进一步的，所述控制参数包括用于描述所述待调整信号梯度波形的梯度函数；
所述扫描序列参数包括：K空间尺寸、K空间单元尺寸、原子核的旋磁比、扫描视野、带宽、采样时间，以及与所述采样时间关联的采样点个数。
进一步的，所述根据所述扫描序列参数与所述控制参数，确定所述待调整信号梯度波形的目标面积值，包括：
通过以下公式测算出所述待调整信号梯度波形的目标面积值；
Figure PCTCN2020129197-appb-000001
k＝N·Δk；
Figure PCTCN2020129197-appb-000002
Figure PCTCN2020129197-appb-000003
其中，k(t)为所述采样时间为t时刻的K空间位置；γ为所述原子核的旋磁比；G(t′)为所述梯度函数；k为所述K空间尺寸；N为所述采样点个数；Δk为所述K空间单元尺寸；FOV为所述扫描视野；A为所述目标面积值；BW为所述带宽。
进一步的，所述按照预设幅度调整参数调整所述平台波段的波形幅度，得到新的平台波段，包括：
根据所述梯度函数确定所述平台波段的平台幅度值；
按照预设幅度调整参数调整所述平台幅度值，得到新的平台幅度值；其中，所述新的平台波段的幅度值等于所述平台幅度值与所述调整参数之和；
根据所述新的平台幅度值得到所述新的平台波段。
进一步的，所述采样时间包括平台波段持续时间与渐变波段持续时间；所述采样点个数包括与所述平台波段持续时间对应的第一采样点个数，以及与所 述渐变波段持续时间对应的第二采样点个数；
所述基于所述目标面积值与所述新的平台波段的第一面积值，对所述渐变波段进行平滑调整，得到新的渐变波段，包括：
获取所述第一采样点个数；
将所述第一采样点个数与所述新的平台幅度值的乘积，识别为所述第一面积值；
测算所述目标面积值与所述第一面积值之差，得到调整面积值；
基于所述调整面积值对所述渐变波段进行平滑调整，得到新的渐变波段。
进一步的，所述渐变波段包括在所述渐变波段持续时间内连续的多个渐变点；
所述基于所述调整面积值对所述渐变波段进行平滑调整，得到新的渐变波段，包括：
获取所述渐变波段持续时间；
基于所述渐变波段持续时间确定多个渐变点；
通过以下公式调整每个所述渐变点的幅度值，得到多个新的渐变点；
X(t)＝1-exp(-w*t)；
G(t)＝G0*Xn(t)；
其中，X(t)为所述新的渐变点；t为所述渐变波段持续时间中的时刻；w为调节因子，且0<|w|<1；Xn(t)表征X(t)的归一化结果；G0为所述渐变点的幅度值；G(t)为所述新的渐变点的幅度值；多个所述新的渐变点组成新的渐变波段，且多个所述新的渐变点的幅度值之和等于所述调整面积值。
进一步的，所述方法还包括：
确定与所述目标信号梯度波形对应的目标梯度函数；
将所述目标梯度函数与所述控制参数关联存储至预设数据库中。
本申请实施例的第二方面提供了一种梯度场控制装置，包括：
第一获取单元，用于获取预先设定的扫描序列参数与控制参数；其中，所 述控制参数用于描述待调整信号梯度波形；
第一确定单元，用于根据所述扫描序列参数与所述控制参数，确定所述待调整信号梯度波形的目标面积值；其中，所述待调整信号梯度波形包括平台波段与渐变波段；
第一调整单元，用于按照预设幅度调整参数调整所述平台波段的波形幅度，得到新的平台波段；
第二调整单元，用于基于所述目标面积值与所述新的平台波段的第一面积值，对所述渐变波段进行平滑调整，得到新的渐变波段；其中，所述新的渐变波段的第二面积值与所述第一面积值之和等于所述目标面积值；
执行单元，用于基于所述新的渐变波段与所述新的平台波段组成的目标信号梯度波形，控制所述梯度场。
本申请实施例的第三方面提供了一种磁共振成像设备，包括存储器、处理器以及存储在所述存储器中并可在所述磁共振设备上运行的计算机程序，所述处理器执行所述计算机程序时实现第一方案提供的梯度场控制方法的各步骤。
本申请实施例的第四方面提供了一种计算机可读存储介质，所述计算机可读存储介质存储有计算机程序，所述计算机程序被处理器执行时实现第一方案提供的梯度场控制方法的各步骤。
本申请实施例的第五方面提供了一种计算机程序产品，当计算机程序产品在磁共振设备上运行时，使得磁共振设备执行上述第一方面中任一项所述的梯度场控制方法的各步骤。
实施本申请实施例提供的一种梯度场控制方法、装置、磁共振成像设备及计算机可读存储介质具有以下有益效果：
本申请实施例提供的一种梯度场控制方法，通过获取预先设定的扫描序列参数与控制参数，由于控制参数能够用于描述待调整信号梯度波形，因此根据扫描序列参数与控制参数，可以确定待调整信号梯度波形的目标面积值，且待调整信号梯度波形包括平台波段与渐变波段，由于该渐变波段所表征的信号拐 点落差越大，梯度场切换过程中的噪音就越大，因此按照预设幅度调整参数调整待调整信号梯度波形的平台波段的波形幅度，再基于目标面积值与新的平台波段的第一面积值，对渐变波段进行平滑调整得到新的渐变波段，进而降低了原有渐变波段所表征的信号拐点的落差，最后基于新的渐变波段与新的平台波段组成的目标信号梯度波形控制梯度场，即可实现在磁共振成像过程中对切换梯度场所导致的噪音进行降噪处理，无需对梯度场切换过程中产生的噪音进行采集，再匹配相应的降噪信号进行降噪操作，简化了降噪方案且节约了降噪成本。
此外，按照预设幅度调整参数调整待调整信号梯度波形的平台波段的波形幅度，再基于目标面积值与新的平台波段的第一面积值，调整渐变波段得到新的渐变波段，使得新的渐变波段与新的平台波段组成的目标信号梯度波形，保持有待调整信号梯度波形的目标面积值不变的情况下，尽可能保留平台波段，也即实现最大化地保留控制参数同时，降低梯度切换剧烈带来的噪声问题。
附图说明
为了更清楚地说明本申请实施例中的技术方案，下面将对实施例或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本申请的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动性的前提下，还可以根据这些附图获得其他的附图。
图1是本申请实施例提供的一种梯度场控制方法的实现流程图；
图2是本申请整体方案实现原理示意图；
图3是本申请另一实施例提供的一种梯度场控制方法的实现流程图；
图4是本申请实施例提供的一种梯度场控制装置结构框图；
图5是本申请另一实施例提供的一种磁共振成像设备的结构框图。
具体实施方式
为了使本申请的目的、技术方案及优点更加清楚明白，以下结合附图及实施例，对本申请进行进一步详细说明。应当理解，此处所描述的具体实施例仅仅用以解释本申请，并不用于限定本申请。
请参阅图1，图1是本申请实施例提供的一种梯度场控制方法的实现流程图。本实施例中，梯度场控制方法用于在磁共振成像过程中的梯度场切换控制，其执行主体为磁共振成像设备。
如图1所示的梯度场控制方法包括以下步骤：
S11：获取预先设定的扫描序列参数与控制参数；其中，所述控制参数用于描述待调整信号梯度波形。
在步骤S11中，扫描序列参数用于描述采集窗口，也即进行数据采集的时间段。由于采集窗口与控制参数在时序上存在关联关系，也即控制参数所描述的待调整信号梯度波形与采集窗口之间在时序上存在重叠区域，因此该重叠区域为数据采集的时间段。控制参数为控制梯度场的控制参数，也即控制磁共振成像过程中梯度场切换的控制参数，因此该控制参数所描述的梯度波形为待调整信号梯度波形。
需要说明的是，在磁共振成像过程中，通过构建一个静磁场环境，再对静磁场中的目标体如人体，施加某种特定频率的射频脉冲，使目标体中的氢质子受到激励而发生磁共振现象。在静磁场环境下，还需要构建一个梯度场，该梯度场用于在磁共振成像过程中做选择激励以选择成像区域，以及对成像的目标体上产生的MR信号进行空间位置的编码。现有的磁共振成像设备中，用于制造梯度场环境的梯度场组件中，通过三组梯度线圈不断地在接通、断开状态下切换，并在空间中产生梯度磁场。在本申请的所有实施例中，控制参数所描述的待调整信号梯度波形，是用于控制梯度磁场切换的信号波形。
图2示出了整体方案实现原理示意图。如图2所示，在实际应用中，由于控制参数所呈现出来的信号梯度波形存在较为剧烈的拐点，如图2中的点P1与点P2，而该剧烈拐点所对应的参数信号就是导致噪音的原因，因此为了降低 梯度场切换过程中的噪音，需要对该待调整信号梯度波形中的剧烈拐点进行调整。
在本实施例中，获取扫描序列参数与控制参数，由于控制参数能够用于描述待调整信号梯度波形，因此将该控制参数进行图像化，能够更多好地对控制参数进行分析和调整，也是为对整体方案进行改进提供途径和基础。应当理解的是，在本申请的所有实施例中，对待调整信号梯度波形进行调整，实际上是对控制参数进行调整。
至于何时获取预先设定的扫描序列参数与控制参数，可以包括但不仅限于以下两个场景。
场景1：若在进行磁共振成像的过程中，检测到用于选择成像区域的预设指令时，获取预先设定的扫描序列参数与控制参数。
例如，在对目标体进行磁共振成像的过程中，当通过选择不同的信号激励进而对目标体的成像区域进行选择时，获取预先设定的扫描序列参数与控制参数。
场景2：若检测到用于对控制参数进行调整的预设指令，则获取预先设定的扫描序列参数与控制参数。
例如，在向磁共振成像设备导入控制方案后，通过触发用于对控制参数进行调整的预设指令，进而获取预先设定的扫描序列参数与控制参数。
应当理解的是，在实际应用中，由于磁共振成像过程的自动化程度较高，因此对控制参数进行调整，可以是在使用磁共振成像设备的过程中进行调整，或者是在对磁共振成像设备进行调试时进行调整。预先设定的扫描序列参数与控制参数，可以预先存储在磁共振成像设备的数据库中，获取扫描序列参数与控制参数时，可以根据控制指令所对应的磁共振成像策略，从数据库中获取相应的扫描序列参数与控制参数。
S12：根据所述扫描序列参数与所述控制参数，确定所述待调整信号梯度波形的目标面积值；其中，所述待调整信号梯度波形包括平台波段与渐变波段。
在步骤S12中，待调整信号梯度波形能够用于表征控制参数与时间之间的对应关系，也即不同的时间点对应不同的幅度值。连续的时间段内，多个离散的采样点的幅度值在坐标上相连即形成了待调整信号梯度波形，且各幅度值在连续的时间段内进行累加，即可得到该待调整信号梯度波形的目标面积值。
需要说明的是，扫描序列参数用于描述采集窗口，该采集窗口与待调整信号梯度波形在时序上存在重叠，而待调整信号梯度波形与采集窗口在时序上重叠的区域，用于表征有效的数据采集时段和数据内容，也即用于表征采集到的数据在K空间上的位置。
在本实施例中，根据扫描序列参数与控制参数确定待调整信号梯度波形的目标面积值，该目标面积值并非待调整信号梯度波形的完整面积值，而是待调整信号梯度波形与采集窗口在时序重叠部分的面积值，也即待调整信号梯度波形的中有效的数据采集波段。
如图2所示，待调整信号梯度波形的平台波段a的时序与扫描序列参数所描述的采集窗口a’的时序完全重叠，也即采集窗口所表征的有效采集数据和有效采集时段，与待调整信号梯度波形的平台波段a对应。
如图2所示，在本实施例中，待调整信号梯度波形201中的平台波段a与渐变波段(a1、a2)是由采样时间进行区分，也即渐变波段(a1、a2)对应的采样时间为时刻1至时刻2，以及时刻3至时刻4，平台波段a对应的采样时段为时刻2至时刻3。
如图2所示，由于时刻0至时刻1属于准备时刻，时刻4至时刻5为结束时刻，因此不纳入采样窗口范围内。由于平台波段a的前后两个波段a1与a2，都包含有两个临界值点，也即变化剧烈的拐点P1与拐点P2，因此在对待调整信号梯度波形进行调整时，波段a1与波段a2被识别为渐变波段，平台波段则为a。
可以理解的是，无论是中平台波段还是渐变波段，都可以是由点组成的线。在待调整信号梯度波形中，渐变波段则由平台波段的前后两段包含有临界值端 点的波段所组成，也即可以将渐变波段视为平台波段的前后两段波段，且每段渐变波段中都包含有临界值端点。
在实际应用中，待调整信号梯度波形的具体形状取决于控制参数，也即控制参数是一系列梯度幅度值与时间之间的关系数据，在坐标系中，可以将横坐标代表时间，纵坐标代表梯度幅度值，即可绘制出待调整信号梯度波形。由于控制参数可以在坐标系中绘制出相应的待调整信号梯度波形，因此控制参数中的部分数据可以用描述待调整信号梯度波形的梯度函数所代替。
作为本实施例一种可能实现的方式，控制参数包括用于描述所述待调整信号梯度波形的梯度函数；扫描序列参数包括：K空间尺寸、K空间单元尺寸、原子核的旋磁比、扫描视野、带宽、采样时间，以及与所述采样时间关联的采样点个数。步骤S12具体可以包括：
通过以下公式测算出所述待调整信号梯度波形的目标面积值；
Figure PCTCN2020129197-appb-000004
k＝N·Δk；
Figure PCTCN2020129197-appb-000005
Figure PCTCN2020129197-appb-000006
其中，k(t)为所述采样时间为t时刻的K空间位置；γ为所述原子核的旋磁比；G(t′)为所述梯度函数；k为所述K空间尺寸；N为所述采样点个数；Δk为所述K空间单元尺寸；FOV为所述扫描视野；A为所述目标面积值；BW为所述带宽。
在本实施例中，K空间尺寸为采样点个数K空间单元尺寸的乘积，K空间单元尺寸Δk则与扫描视野FOV之间为倒数关系；N为采样点个数，且N为大于0的整数。
需要说明的是，K空间也叫傅里叶空间，是带有空间定位编码信息的MR信号原始数字数据的填充空间，每一幅MR图像都有其相应的K空间数据点阵，对K空间的数据进行傅里叶转换，就能对原始数字数据中的空间定位编码信息 进行解码，分解出不同频率、相位和幅度的MR信号，不同的频率和相位代表不同的空间位置，而幅度则代表MR信号强度，也即傅里叶变换就是把K空间的原始数据点阵转变成磁共振图像点阵的过程。由于待调整信号梯度波形与采集窗口在时序上重叠的区域，用于表征有效的数据采集时段和数据内容，也即用于表征采集到的数据在K空间上的位置，通过上述公式，结合扫描序列参数中所包括的K空间尺寸、K空间单元尺寸、原子核的旋磁比、扫描视野、带宽、采样时间，以及与采样时间关联的采样点个数之间换算关系，即可确定出待调整信号梯度波形的目标面积值。
在本申请的所有实施例中，由于待调整信号梯度波形的目标面积值用于表征采集到的数据在K空间上的位置，因此为了确保数据在K空间上的位置保持不变，在对待调整信号梯度波形进行调整，所得到的新的信号梯度波形的面积值与待调整信号梯度波形的目标面积值相等。
S13：按照预设幅度调整参数调整所述平台波段的波形幅度，得到新的平台波段。
在步骤S13中，预设幅度调整参数可以为平台波段的波形幅度的增量或者倍数，也即调整平台波段的波形幅度，是在平台波段原有的波形幅度的基础上增加其波形幅度值的大小。
需要说明的是，当预设幅度调整参数为平台波段的波形幅度的增量时，该增量为大于0的增量数值，当预设幅度调整参数为平台波段的波形幅度的倍数时，该倍数为大于1的倍数。
在本申请的所有实施例中，对待调整信号梯度波形进行调整，具体是对待调整信号梯度波形中具有剧烈拐点的波段进行平滑处理，而为了保证调整后的新的梯形波段所围成的面积值与待调整信号梯度波形的目标面积值相等，因此按照预设幅度调整参数调整平台波段的波形幅度，是为了通过增加平台波段的波形幅度，进而补偿因平滑处理后损失的部分面积。
如图2所示，新的平台波段b的波形幅度大于原有的平台波段a的波形幅 度。且由于对待调整信号梯度波形201进行调整，将具有剧烈拐点的波段进行平滑处理后，损失部分面积，通过配置得到新的平台波段b的波形，因为其幅度大于原有的平台波段a的波形幅度，能够补偿因平滑处理后损失的部分面积。
作为本实施例一种可能实现的方式，步骤S13可以包括：
根据所述梯度函数确定所述平台波段的平台幅度值；按照预设幅度调整参数调整所述平台幅度值，得到新的平台幅度值；其中，所述新的平台波段的幅度值等于所述平台幅度值与所述调整参数之和；根据所述新的平台幅度值得到所述新的平台波段。
在本实施例中，新的平台幅度值为原有的平台幅度值与调整参数之和。由于梯度场的采样过程属于离散型采样，也即待调整信号梯度波形中的平台波段与渐变波段分别对应有采样时间，也即采样点，且梯度函数能够用于描述整个待调整信号梯度波形，因此采样时间或采样点个数，即可确定出平台波段和渐变波段，结合梯度函数则可确定出的平台波段的平台幅度值。
需要说明的是，在本申请的所有实施例中，对待调整信号梯度波形进行调整的过程，是先对平台波段进行幅度值调整，再基于调整后得到的新的平台波段，对渐变波段进行调整。由于新的平台波段中，每个采样时间或采样点对应的幅度值都高于原始幅度值，因此新的平台波段与未调整的渐变波段之间存在落差，为了确保调整后梯度波形能够较大程度地保留待调整信号梯度波形的原有特性，因此对渐变波段进行平滑调整，也即使其能够与新的平台波段之间平滑且连贯行程新的信号梯度波形。
S14：基于所述目标面积值与所述新的平台波段的第一面积值，对所述渐变波段进行平滑调整，得到新的渐变波段；其中，所述新的渐变波段的第二面积值与所述第一面积值之和等于所述目标面积值。
在步骤S14中，目标面积值为待调整信号梯度波形的面积。第一面积值为新的平台波段的在时间与幅度坐标轴上的面积，也是新的平台波段的所有采样点的幅度值累加。
需要说明的是，第一面积值为新的平台波段的面积值，也是新的平台波段上每个采样点对应幅度值的累加之和；第二面积值为新的渐变波段的面积值，也是新的渐变波段上每个采样点对应幅度值的累加之和。为了保持待调整信号梯度波形所表征的K空间的数据位置不变，新的平台波段与新的渐变波段组成的新的信号梯度波形，其面积必须与待调整信号梯度波形的目标面积，因此在对渐变波段进行平滑调整时，以新的渐变波段的第二面积值与第一面积值之和等于目标面积，作为限制条件对渐变波段进行平滑调整。
作为本实施例一种可能实现的方式，所述采样时间包括平台波段持续时间与渐变波段持续时间；所述采样点个数包括与所述平台波段持续时间对应的第一采样点个数，以及与所述渐变波段持续时间对应的第二采样点个数；步骤S14可以包括：
获取所述第一采样点个数；将所述第一采样点个数与所述新的平台幅度值的乘积，识别为所述第一面积值；测算所述目标面积值与所述第一面积值之差，得到调整面积值；基于所述调整面积值对所述渐变波段进行平滑调整，得到新的渐变波段。
在本实施例中，由于第一面积值为新的平台波段的在时间与幅度坐标轴上的面积，而新的平台波段上各个点的幅度值均大于原有平台波段上各个点的幅度值，因此为了确保调整后梯度波形所围成很的面积与待调整信号梯度波形的目标面积一致，在对渐变波段进行平滑调整时，需要考虑目标面积与新的平台波段的第一面积值之间的差值。也即对渐变波段进行平滑调整后，新的渐变波段上所有采样点的幅度值的累加之和，等于目标面积与第一面积值之间的差值。
在实际应用中，由于已经获悉了对渐变波段进行平滑调整的限制条件，也即新的渐变波段的第二面积值与第一面积值之和等于目标面积，因此在其他实施例中，可以通过配置相应的条件函数或者方程组，描述该限制条件，进而实现对渐变波段进行平滑调整。
作为本实施例一种可能实现的方式，所述渐变波段包括在所述渐变波段持 续时间内连续的多个渐变点；所述基于所述调整面积值对所述渐变波段进行平滑调整，得到新的渐变波段，包括：
获取所述渐变波段持续时间；
基于所述渐变波段持续时间确定多个渐变点；
通过以下公式调整每个所述渐变点的幅度值，得到多个新的渐变点；
X(t)＝1-exp(-w*t)；
G(t)＝G0*Xn(t)；
其中，X(t)为所述新的渐变点；t为所述渐变波段持续时间中的时刻；w为调节因子，且0<|w|<1；Xn(t)表征X(t)的归一化结果；G0为所述渐变点的幅度值；G(t)为所述新的渐变点的幅度值；多个所述新的渐变点组成新的渐变波段，且多个所述新的渐变点的幅度值之和等于所述调整面积值。
需要说明的是，X(t)为新的渐变点，w的取值范围与渐变点位于平台波段相对位置有关，也即多个新的渐变点随时间呈上升趋势，或者多个新的渐变点随时间呈下降趋势，与渐变点位于平台波段相对位置有关。
在本实施例中，当X(t)的t时刻处于平台波段到来之前，调节因子w取值范围在0与1之间，也即0<w<1；当X(t)的t时刻处于平台波段到来之后，调节因子w取值范围在-1与0之间，也即-1<w<0。
如图2所示，在本申请的所有实施例中，待调整信号梯度波形201中的渐变波段(a1、a2)可以为包含临界拐点(P1、P2)对应采样点的波段，且该渐变波段(a1、a2)可以与平台波段相同，也即波段a1与波段a2都与平台波段a的幅度值相同。与待调整信号梯度波形201中的渐变波段不同的是，新的渐变波段(b1、b2)上每个新的渐变点的幅度值都不相同，如图2所示，波段b1和波段b2上所有采样时间点对应的幅度值均不相同，通过对待调整信号梯度波形201进行调整，得到由新的平台波段b与新的渐变波段(b1、b2)组成的目标信号梯度波形202，其面积与待调整信号梯度波形201的目标面积相同。
如图2所示，由于在a1波段中的渐变点均在平台波段到来之前，也即对 a1波段的调整应当是随时序逐渐上升的趋势调整，进而得到b1波段，因此当X(t)的t时刻处于在a1波段中，调节因子w取值范围在0与1之间；由于在a2波段中的渐变点均在平台波段到来之后，也即对a2波段的调整应当是随时序逐渐下降的趋势调整，进而得到b2波段，因此当X(t)的t时刻处于在a2波段中，调节因子w取值范围在-1与0之间。
需要说明的是，本实施例在对待调整信号梯度波形中的渐变波段进行调整时，只是将部分平台波段划定为渐变波段，连同待调整信号梯度波形中的拐点进行平滑调整，能够在保证大部分平台波段不变的条件下，实现对渐变波段的平滑处理，消除信号梯度波形中的剧烈拐点，使得新的平台波段与新的渐变波段之间能够平滑过渡，从消除梯度场切换过程中的噪音。
S15：基于所述新的渐变波段与所述新的平台波段组成的目标信号梯度波形，控制所述梯度场。
在步骤S15中，目标信号梯度波形的面积与待调整信号梯度波形的目标面积相等，因此目标信号梯度波形的面积所表征的K空间的位置，与目标面积所表征的K空间的位置为同一位置。
需要说明的是，基于新的渐变波段与新的平台波段组成的目标信号梯度波形，控制梯度场，是利用目标信号梯度波形对应的新的控制参数，控制梯度场进行切换。
在本申请的所有实施例中，由于控制参数是控制梯度场切换的控制参数，对控制参数所描述的待调整信号梯度波形进行调整，实际上是对该控制参数进行调整，因此基于调整后得到新的渐变波段与新的平台波段组成的目标信号梯度波形，对应调整后的控制参数，故基于新的渐变波段与新的平台波段组成的目标信号梯度波形控制梯度场，就是基于目标信号梯度波形对应的调整后的控制参数控制梯度场进行切换操作。
以上可以看出，本实施例提供的一种梯度场控制方法，通过获取预先设定的扫描序列参数与控制参数，由于控制参数能够用于描述待调整信号梯度波形， 因此根据扫描序列参数与控制参数，可以确定待调整信号梯度波形的目标面积值，且待调整信号梯度波形包括平台波段与渐变波段，由于该渐变波段所表征的信号拐点落差越大，梯度场切换过程中的噪音就越大，因此按照预设幅度调整参数调整待调整信号梯度波形的平台波段的波形幅度，再基于目标面积值与新的平台波段的第一面积值，对渐变波段进行平滑调整得到新的渐变波段，进而降低了原有渐变波段所表征的信号拐点的落差，最后基于新的渐变波段与新的平台波段组成的目标信号梯度波形控制梯度场，即可实现在磁共振成像过程中对切换梯度场所导致的噪音进行降噪处理，无需对梯度场切换过程中产生的噪音进行采集，再匹配相应的降噪信号进行降噪操作，简化了降噪方案且节约了降噪成本。
此外，按照预设幅度调整参数调整待调整信号梯度波形的平台波段的波形幅度，再基于目标面积值与新的平台波段的第一面积值，调整渐变波段得到新的渐变波段，使得新的渐变波段与新的平台波段组成的目标信号梯度波形，保持有待调整信号梯度波形的目标面积值不变的情况下，尽可能保留平台波段，也即实现最大化地保留控制参数同时，降低梯度切换剧烈带来的噪声问题。
请参阅图3，图3是本申请另一实施例提供的一种梯度场控制方法的实现流程图。相对于图1对应的实施例，本实施例提供的梯度场控制方法在步骤S15之后还包括S21～S22。详述如下：
S21：确定与所述目标信号梯度波形对应的目标梯度函数。
S22：将所述目标梯度函数与所述控制参数关联存储至预设数据库中。
在本实施例中，目标梯度函数是基于目标信号梯度波形所得出的函数。也即，将新的渐变波段与新的平台波段进行重组后，得到目标信号梯度波，基于该目标信号梯度波即可得出目标梯度函数。
需要说明的是，由于待调整信号梯度波形对应的梯度函数G(t′)中，采样时间点对应有变化剧烈的拐点，因此容易导致梯度场切换时产生较大噪音。而通过对待调整信号梯度波形进行调整后，将平台波形的幅度值增加，将渐变波形 平滑调整，最后将新的渐变波段与新的平台波段进行重组后，得到目标信号梯度波，基于该目标信号梯度波形即可得出目标梯度函数，由于该目标梯度函数所表征的梯度波形为目标信号梯度波形，且该波形中没有剧烈的幅度值拐点，因此不会在控制梯度场切换时产生较大的噪声。
应当理解的是，将目标梯度函数与控制参数关联存储至预设数据库中，当再次需要对控制参数对应的待调整信号梯度波形进行调整时，可以直接根据控制参数从预设数据库中获取相应的目标梯度函数，也即调整之后梯度波形所对应的目标梯度函数，即可直接进行梯度场控制。
以上可以看出，本实施例提供的一种梯度场控制方法，通过获取预先设定的扫描序列参数与控制参数，由于控制参数能够用于描述待调整信号梯度波形，因此根据扫描序列参数与控制参数，可以确定待调整信号梯度波形的目标面积值，且待调整信号梯度波形包括平台波段与渐变波段，由于该渐变波段所表征的信号拐点落差越大，梯度场切换过程中的噪音就越大，因此按照预设幅度调整参数调整待调整信号梯度波形的平台波段的波形幅度，再基于目标面积值与新的平台波段的第一面积值，对渐变波段进行平滑调整得到新的渐变波段，进而降低了原有渐变波段所表征的信号拐点的落差，最后基于新的渐变波段与新的平台波段组成的目标信号梯度波形控制梯度场，即可实现在磁共振成像过程中对切换梯度场所导致的噪音进行降噪处理，无需对梯度场切换过程中产生的噪音进行采集，再匹配相应的降噪信号进行降噪操作，简化了降噪方案且节约了降噪成本。
此外，按照预设幅度调整参数调整待调整信号梯度波形的平台波段的波形幅度，再基于目标面积值与新的平台波段的第一面积值，调整渐变波段得到新的渐变波段，使得新的渐变波段与新的平台波段组成的目标信号梯度波形，保持有待调整信号梯度波形的目标面积值不变的情况下，尽可能保留平台波段，也即实现最大化地保留控制参数同时，降低梯度切换剧烈带来的噪声问题。
此外，通过确定与目标信号梯度波形对应的目标梯度函数，再将改目标梯 度函数与控制参数关联存储至预设数据库中，使得在下次采用与控制参数一直的信号对梯度场进行控制时，无需重复梯度波形的调整步骤，即可从预设数据库中查找目标信号梯度波形或者与其对应的目标梯度函数进行梯度场切换控制。
请参阅图4，图4是本申请实施例提供的一种梯度场控制装置的结构框图。本实施例中该梯度场控制装置包括的各单元用于执行图1与图3对应的实施例中的各步骤。具体请参阅图1与图3以及图1与图3所对应的实施例中的相关描述。为了便于说明，仅示出了与本实施例相关的部分。参见图4，梯度场控制装置400包括：第一获取单元41、第一确定单元42、第一调整单元43、第二调整单元44以及执行单元45。其中：
第一获取单元41，用于获取预先设定的扫描序列参数与控制参数；其中，所述控制参数用于描述待调整信号梯度波形。
第一确定单元42，用于根据所述扫描序列参数与所述控制参数，确定所述待调整信号梯度波形的目标面积值；其中，所述待调整信号梯度波形包括平台波段与渐变波段。
第一调整单元43，用于按照预设幅度调整参数调整所述平台波段的波形幅度，得到新的平台波段。
第二调整单元44，用于基于所述目标面积值与所述新的平台波段的第一面积值，对所述渐变波段进行平滑调整，得到新的渐变波段；其中，所述新的渐变波段的第二面积值与所述第一面积值之和等于所述目标面积值。
执行单元45，用于基于所述新的渐变波段与所述新的平台波段组成的目标信号梯度波形，控制所述梯度场。
作为本申请一实施例，所述控制参数包括用于描述所述待调整信号梯度波形的梯度函数；所述扫描序列参数包括：K空间尺寸、K空间单元尺寸、原子核的旋磁比、扫描视野、带宽、采样时间，以及与所述采样时间关联的采样点个数。
作为本申请一实施例，第一确定单元42具体用于，通过以下公式测算出所 述待调整信号梯度波形的目标面积值；
Figure PCTCN2020129197-appb-000007
k＝N·Δk；
Figure PCTCN2020129197-appb-000008
Figure PCTCN2020129197-appb-000009
其中，k(t)为所述采样时间为t时刻的K空间位置；γ为所述原子核的旋磁比；G(t′)为所述梯度函数；k为所述K空间尺寸；N为所述采样点个数；Δk为所述K空间单元尺寸；FOV为所述扫描视野；A为所述目标面积值；BW为所述带宽。
作为本申请一实施例，第一调整单元43具体用于，根据所述梯度函数确定所述平台波段的平台幅度值；按照预设幅度调整参数调整所述平台幅度值，得到新的平台幅度值；其中，所述新的平台波段的幅度值等于所述平台幅度值与所述调整参数之和；根据所述新的平台幅度值得到所述新的平台波段。
作为本申请一实施例，所述采样时间包括平台波段持续时间与渐变波段持续时间；所述采样点个数包括与所述平台波段持续时间对应的第一采样点个数，以及与所述渐变波段持续时间对应的第二采样点个数。
第二调整单元44具体用于，获取所述第一采样点个数；将所述第一采样点个数与所述新的平台幅度值的乘积，识别为所述第一面积值；测算所述目标面积值与所述第一面积值之差，得到调整面积值；基于所述调整面积值对所述渐变波段进行平滑调整，得到新的渐变波段。
作为本申请一实施例，所述渐变波段包括在所述渐变波段持续时间内连续的多个渐变点；第二调整单元44具体用于，
获取所述渐变波段持续时间；
基于所述渐变波段持续时间确定多个渐变点；
通过以下公式调整每个所述渐变点的幅度值，得到多个新的渐变点；
X(t)＝1-exp(-w*t)；
G(t)＝G0*Xn(t)；
其中，X(t)为所述新的渐变点；t为所述渐变波段持续时间中的时刻；w为调节因子，且0<|w|<1；Xn(t)表征X(t)的归一化结果；G0为所述渐变点的幅度值；G(t)为所述新的渐变点的幅度值；多个所述新的渐变点组成新的渐变波段，且多个所述新的渐变点的幅度值之和等于所述调整面积值。
作为本申请一实施例，梯度场控制装置400，还包括：第二确定单元46与存储单元47。具体地：
第二确定单元46，用于确定与所述目标信号梯度波形对应的目标梯度函数。
存储单元47，用于将所述目标梯度函数与所述控制参数关联存储至预设数据库中。
以上可以看出，本实施例提供的方案，通过获取预先设定的扫描序列参数与控制参数，由于控制参数能够用于描述待调整信号梯度波形，因此根据扫描序列参数与控制参数，可以确定待调整信号梯度波形的目标面积值，且待调整信号梯度波形包括平台波段与渐变波段，由于该渐变波段所表征的信号拐点落差越大，梯度场切换过程中的噪音就越大，因此按照预设幅度调整参数调整待调整信号梯度波形的平台波段的波形幅度，再基于目标面积值与新的平台波段的第一面积值，对渐变波段进行平滑调整得到新的渐变波段，进而降低了原有渐变波段所表征的信号拐点的落差，最后基于新的渐变波段与新的平台波段组成的目标信号梯度波形控制梯度场，即可实现在磁共振成像过程中对切换梯度场所导致的噪音进行降噪处理，无需对梯度场切换过程中产生的噪音进行采集，再匹配相应的降噪信号进行降噪操作，简化了降噪方案且节约了降噪成本。
此外，按照预设幅度调整参数调整待调整信号梯度波形的平台波段的波形幅度，再基于目标面积值与新的平台波段的第一面积值，调整渐变波段得到新的渐变波段，使得新的渐变波段与新的平台波段组成的目标信号梯度波形，保持有待调整信号梯度波形的目标面积值不变的情况下，尽可能保留平台波段，也即实现最大化地保留控制参数同时，降低梯度切换剧烈带来的噪声问题。
此外，通过确定与目标信号梯度波形对应的目标梯度函数，再将改目标梯度函数与控制参数关联存储至预设数据库中，使得在下次采用与控制参数一直的信号对梯度场进行控制时，无需重复梯度波形的调整步骤，即可从预设数据库中查找目标信号梯度波形或者与其对应的目标梯度函数进行梯度场切换控制。
图5是本申请另一实施例提供的一种磁共振成像设备的结构框图。如图5所示，该实施例的磁共振成像设备5包括：处理器50、存储器51以及存储在所述存储器51中并可在所述处理器50上运行的计算机程序52，例如梯度场控制方法的程序。处理器50执行所述计算机程序52时实现上述各个梯度场控制方法各实施例中的步骤，例如图1所示的S11至S15。或者，所述处理器50执行所述计算机程序52时实现上述图4对应的实施例中各单元的功能，例如，图4所示的单元41至45的功能，具体请参阅图5对应的实施例中的相关描述，此处不赘述。
示例性的，所述计算机程序52可以被分割成一个或多个单元，所述一个或者多个单元被存储在所述存储器51中，并由所述处理器50执行，以完成本申请。所述一个或多个单元可以是能够完成特定功能的一系列计算机程序指令段，该指令段用于描述所述计算机程序52在所述磁共振成像设备5中的执行过程。例如，所述计算机程序52可以被分割成第一获取单元、第一确定单元、第一调整单元、第二调整单元以及执行单元，各单元具体功能如上所述。
所述磁共振设备可包括，但不仅限于，处理器50、存储器51。本领域技术人员可以理解，图5仅仅是磁共振成像设备5的示例，并不构成对磁共振设备5的限定，可以包括比图示更多或更少的部件，或者组合某些部件，或者不同的部件，例如所述磁共振设备还可以包括输入输出设备、网络接入设备、总线等。
所称处理器50可以是中央处理单元(Central Processing Unit，CPU)，还可以是其他通用处理器、数字信号处理器(Digital Signal Processor，DSP)、专用集成电路(Application Specific Integrated Circuit，ASIC)、现成可编程门阵列 (Field-Programmable Gate Array，FPGA)或者其他可编程逻辑器件、分立门或者晶体管逻辑器件、分立硬件组件等。通用处理器可以是微处理器或者该处理器也可以是任何常规的处理器等。
所述存储器51可以是所述磁共振成像设备5的内部存储单元，例如磁共振设备5的硬盘或内存。所述存储器51也可以是所述磁共振成像设备5的外部存储设备，例如所述磁共振成像设备5上配备的插接式硬盘，智能存储卡(Smart Media Card，SMC)，安全数字(Secure Digital，SD)卡，闪存卡(Flash Card)等。进一步地，所述存储器51还可以既包括所述磁共振成像设备5的内部存储单元也包括外部存储设备。所述存储器51用于存储所述计算机程序以及所述磁共振设备所需的其他程序和数据。所述存储器51还可以用于暂时地存储已经输出或者将要输出的数据。
以上所述实施例仅用以说明本申请的技术方案，而非对其限制；尽管参照前述实施例对本申请进行了详细的说明，本领域的普通技术人员应当理解：其依然可以对前述各实施例所记载的技术方案进行修改，或者对其中部分技术特征进行等同替换；而这些修改或者替换，并不使相应技术方案的本质脱离本申请各实施例技术方案的精神和范围，均应包含在本申请的保护范围之内。

Claims (10)

  1. 一种梯度场控制方法，其特征在于，包括：
    获取预先设定的扫描序列参数与控制参数；其中，所述控制参数用于描述待调整信号梯度波形；
    根据所述扫描序列参数与所述控制参数，确定所述待调整信号梯度波形的目标面积值；其中，所述待调整信号梯度波形包括平台波段与渐变波段；
    按照预设幅度调整参数调整所述平台波段的波形幅度，得到新的平台波段；
    基于所述目标面积值与所述新的平台波段的第一面积值，对所述渐变波段进行平滑调整，得到新的渐变波段；其中，所述新的渐变波段的第二面积值与所述第一面积值之和等于所述目标面积值；
    基于所述新的渐变波段与所述新的平台波段组成的目标信号梯度波形，控制所述梯度场。
  2. 根据权利要求1所述的梯度场控制方法，其特征在于，所述控制参数包括用于描述所述待调整信号梯度波形的梯度函数；
    所述扫描序列参数包括：K空间尺寸、K空间单元尺寸、原子核的旋磁比、扫描视野、带宽、采样时间，以及与所述采样时间关联的采样点个数。
  3. 根据权利要求2所述的梯度场控制方法，其特征在于，所述根据所述扫描序列参数与所述控制参数，确定所述待调整信号梯度波形的目标面积值，包括：
    通过以下公式测算出所述待调整信号梯度波形的目标面积值；
    Figure PCTCN2020129197-appb-100001
    k＝N·Δk；
    Figure PCTCN2020129197-appb-100002
    Figure PCTCN2020129197-appb-100003
    其中，k(t)为所述采样时间为t时刻的K空间位置；γ为所述原子核的旋磁 比；G(t′)为所述梯度函数；k为所述K空间尺寸；N为所述采样点个数；Δk为所述K空间单元尺寸；FOV为所述扫描视野；A为所述目标面积值；BW为所述带宽。
  4. 根据权利要求2所述的梯度场控制方法，其特征在于，所述按照预设幅度调整参数调整所述平台波段的波形幅度，得到新的平台波段，包括：
    根据所述梯度函数确定所述平台波段的平台幅度值；
    按照预设幅度调整参数调整所述平台幅度值，得到新的平台幅度值；其中，所述新的平台波段的幅度值等于所述平台幅度值与所述调整参数之和；
    根据所述新的平台幅度值得到所述新的平台波段。
  5. 根据权利要求4所述的梯度场控制方法，其特征在于，所述采样时间包括平台波段持续时间与渐变波段持续时间；所述采样点个数包括与所述平台波段持续时间对应的第一采样点个数，以及与所述渐变波段持续时间对应的第二采样点个数；
    所述基于所述目标面积值与所述新的平台波段的第一面积值，对所述渐变波段进行平滑调整，得到新的渐变波段，包括：
    获取所述第一采样点个数；
    将所述第一采样点个数与所述新的平台幅度值的乘积，识别为所述第一面积值；
    测算所述目标面积值与所述第一面积值之差，得到调整面积值；
    基于所述调整面积值对所述渐变波段进行平滑调整，得到新的渐变波段。
  6. 根据权利要求5所述的梯度场控制方法，其特征在于，所述渐变波段包括在所述渐变波段持续时间内连续的多个渐变点；
    所述基于所述调整面积值对所述渐变波段进行平滑调整，得到新的渐变波段，包括：
    获取所述渐变波段持续时间；
    基于所述渐变波段持续时间确定多个渐变点；
    通过以下公式调整每个所述渐变点的幅度值，得到多个新的渐变点；
    X(t)＝1-exp(-w*t)；
    G(t)＝G0*Xn(t)；
    其中，X(t)为所述新的渐变点；t为所述渐变波段持续时间中的时刻；w为调节因子，且0<|w|<1；Xn(t)表征X(t)的归一化结果；G0为所述渐变点的幅度值；G(t)为所述新的渐变点的幅度值；多个所述新的渐变点组成新的渐变波段，且多个所述新的渐变点的幅度值之和等于所述调整面积值。
  7. 根据权利要求1至6任一项所述的梯度场控制方法，其特征在于，所述方法还包括：
    确定与所述目标信号梯度波形对应的目标梯度函数；
    将所述目标梯度函数与所述控制参数关联存储至预设数据库中。
  8. 一种梯度场控制装置，其特征在于，包括：
    第一获取单元，用于获取预先设定的扫描序列参数与控制参数；其中，所述控制参数用于描述待调整信号梯度波形；
    第一确定单元，用于根据所述扫描序列参数与所述控制参数，确定所述待调整信号梯度波形的目标面积值；其中，所述待调整信号梯度波形包括平台波段与渐变波段；
    第一调整单元，用于按照预设幅度调整参数调整所述平台波段的波形幅度，得到新的平台波段；
    第二调整单元，用于基于所述目标面积值与所述新的平台波段的第一面积值，对所述渐变波段进行平滑调整，得到新的渐变波段；其中，所述新的渐变波段的第二面积值与所述第一面积值之和等于所述目标面积值；
    执行单元，用于基于所述新的渐变波段与所述新的平台波段组成的目标信号梯度波形，控制所述梯度场。
  9. 一种磁共振成像设备，其特征在于，所述磁共振设备包括存储器、处理器以及存储在所述存储器中并可在所述磁共振设备上运行的计算机程序，所述 处理器执行所述计算机程序时实现如权利要求1至7任一项所述梯度场控制方法的步骤。
  10. 一种计算机可读存储介质，所述计算机可读存储介质存储有计算机程序，其特征在于，所述计算机程序被处理器执行时实现如权利要求1至7任一项所述梯度场控制方法的步骤。
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