A method, system, and storage medium for compensating magnetic resonance radio frequency transmission fields.

Abstract

This application relates to a method, system, and storage medium for compensating for the radio frequency (RF) transmission field of magnetic resonance (MRI). It addresses the problem that as the strength of the MRI master magnetic field increases, the wavelength of the RF wave shortens, making image problems caused by RF field inhomogeneity particularly significant at high fields. The method includes: acquiring information on the inhomogeneity distribution of the transmission field in the xy-plane caused by applying a time-varying RF field; analyzing and determining a matrix gradient coil driving current group adapted to the RF field inhomogeneity distribution information in the xy-plane based on the correspondence between different driving current groups of the matrix gradient coil and the generated gradient magnetic field, and the RF field inhomogeneity distribution information in the xy-plane; and activating the determined matrix gradient coil driving current group to apply a gradient to the xy-plane, compensating for the inhomogeneity generated by the transmission field in the xy-plane. This application has the following effect: reducing the impact of image problems caused by RF field inhomogeneity at high fields (>3T).

Description

Technical Field

[0001] This application relates to the technical field of magnetic resonance imaging, and more particularly to a compensation system and storage medium for a magnetic resonance radio frequency emission field. Background Technology

[0002] Magnetic resonance imaging (MRI), a non-invasive imaging technique, can reveal the internal hierarchical structure of objects and has been widely used in fields such as medical diagnosis, biological research, and materials research.

[0003] A magnetic resonance imaging (MRI) system comprises a stable, uniform main magnetic field, a gradient magnetic field for spatial encoding, and radio frequency (RF) components. Therefore, the hardware of a classic MRI system mainly consists of three parts: (1) the main magnet; (2) the gradient coil system; and (3) the RF coil system. The gradient coil system is a set of coils used for tomographic imaging, providing a means to select slices of the target image by using a magnetic field that varies with spatial coordinates. The gradient coil system consists of linear gradient coils in the x, y, and z directions, used for slice selection, frequency encoding, and phase encoding. Each gradient coil requires a driving device, such as a power amplifier, to provide a controllable current. The driving device can adjust the gradient value of the magnetic field generated by the gradient coil by changing the magnitude of the current.

[0004] In magnetic resonance imaging, the emitted electromagnetic field (B1+) generated by the radio frequency coil system is used to excite tissue to produce a specific angle of reversal. The inhomogeneity of the emitted field usually brings certain spatial changes to the signal-to-noise ratio and contrast of the image.

[0005] Regarding the aforementioned technologies, the inventors discovered the following drawbacks: As the strength of the main magnetic field of magnetic resonance increases, the center frequency becomes higher, which means that the frequency of the radio frequency wave required to generate resonance becomes higher. When the frequency increases, the wavelength of the radio frequency wave becomes shorter (c = f * L, and the propagation speed c is constant). Therefore, under high field conditions (>3T), the image problems caused by the non-uniformity of the transmission field become particularly significant. Summary of the Invention

[0006] To reduce the impact of image problems caused by non-uniformity of the transmission field under high field conditions (>3T), this application provides a magnetic resonance radio frequency transmission field compensation system and storage medium.

[0007] In a first aspect, this application provides a compensation for a magnetic resonance radio frequency emission field, including:

[0008] To obtain information on the non-uniformity distribution of the emitted field in the xy plane caused by applying a time-varying radio frequency field;

[0009] Based on the correspondence between different driving current groups of the matrix gradient coil and the generated gradient magnetic field, and the correspondence between the non-uniformity distribution information of the transmitting field in the xy plane and the required gradient magnetic field, the driving current group of the matrix gradient coil adapted to the non-uniformity distribution information of the transmitting field in the xy plane is analyzed and determined.

[0010] The analyzed and determined matrix gradient coil drive current group is activated to compensate for the non-uniformity of the emission field in the xy plane.

[0011] By adopting the above technical solution, it is possible to analyze the high-order spatial distribution magnetic field that needs to be compensated based on the non-uniform distribution information of the transmission field in the xy plane, and effectively analyze and determine the matrix gradient coil driving current group that is suitable for the non-uniform distribution information of the transmission field in the xy plane, thereby effectively realizing the compensation of the transmission field.

[0012] Optionally, obtaining information on the non-uniformity distribution of the emission field in the xy plane includes:

[0013] Acquire the applied radio frequency pulses within a preset time range and define how the radio frequency pulses change over time;

[0014] Based on the applied radio frequency pulse within a preset time range, the non-uniformity of the transmission field in the xy plane is excited, and the distribution map of the non-uniformity of the radio frequency field as a function of space is obtained as information on the non-uniformity distribution of the transmission field in the xy plane.

[0015] By adopting the above technical solution, a method for obtaining information on the non-uniformity distribution of the transmission field in the xy plane is specifically disclosed. After this series of radio frequency pulses are applied, non-uniformity will be excited in the xy plane. Moreover, the specific non-uniformity of the xy plane can also be characterized by the radio frequency field non-uniformity distribution map.

[0016] Optionally, based on the applied radio frequency pulse within a preset time range, the non-uniformity of the transmission field in the xy plane is excited, and the distribution map of the non-uniformity of the radio frequency field varying with space is obtained using the real flip angle imaging method.

[0017] Optionally, the matrix gradient coil drive current set, which is adapted to the non-uniformity distribution information of the transmitting field in the xy plane, includes:

[0018] Based on the correspondence between the non-uniform distribution information of the emission field in the xy plane and the required gradient magnetic field, query the gradient magnetic field required to be generated by the matrix gradient coil driving current group.

[0019] If found, the gradient magnetic field required to generate by the gradient coil driving current group of the query matrix will be used as the gradient magnetic field determined in this analysis.

[0020] If no results are found, the magnetic field generated by each unit of the gradient array under a unit current is taken as the basis, and the applied current is the weight parameter of each basis. The gradient magnetic field adapted to the non-uniformity distribution information of the emission field in the xy plane is determined by multi-channel compensation method and used as the gradient magnetic field determined in this analysis.

[0021] Based on the correspondence between different driving current groups of the matrix gradient coil and the resulting gradient magnetic field, and the gradient magnetic field determined in this analysis, the driving current group of the matrix gradient coil corresponding to the required gradient magnetic field is determined.

[0022] By adopting the above technical solution, the system first analyzes whether there is a gradient magnetic field in the past that can compensate for the non-uniformity of the transmission field in the xy plane. If it exists, the existing gradient magnetic field is used as the gradient magnetic field determined in this analysis. If it does not exist, the system uses a multi-channel compensation method to analyze and determine the gradient magnetic field that is compatible with the non-uniformity distribution information of the transmission field in the xy plane. Finally, the system matches a suitable matrix gradient coil drive current group according to the gradient magnetic field determined in the analysis.

[0023] Optionally, the gradient magnetic field adapted to the non-uniformity distribution information of the emission field in the xy plane, determined by multi-channel compensation method, includes the following:

[0024] Analyze whether the approximate flip angle falls within the preset angle range;

[0025] If so, the multi-channel compensation method will be analyzed and determined based on the correspondence between the preset angle range and the multi-channel compensation method, and will be used as the multi-channel compensation method in this study.

[0026] The non-uniform gradient magnetic field generated by the compensated emission field in the xy plane was determined by using the multi-channel compensation method.

[0027] By adopting the above technical solution, it is fully considered that when the approximate flip angle is small, the component Mz of the magnetization vector after excitation can be approximated as the initial magnetization vector M0 at a small flip angle. Under this condition, the corresponding multi-channel compensation method can be effectively determined, thereby effectively analyzing and determining the non-uniform gradient magnetic field generated by the compensation emission field in the xy plane.

[0028] Optional multi-channel compensation methods include:

[0029]

[0030] Where i is the imaginary unit, γ is the gyromagnetic ratio constant, and M + B1 is the transverse magnetization vector, which is the excitation profile in the z-direction. + F is a time-varying radio frequency field. -1This is a Fourier transform operation, where M0 is the initial magnetization vector, e is the generated phase term, G is the gradient, r is the coordinate vector, and τ is the coordinate vector. rf Where Nc is the duration of the radio frequency pulse, I is the number of channels in the matrix gradient, and Nc is the number of channels in the matrix gradient. k φ is the control current of the k-th channel. k Let α(x,y) represent the magnetic field distribution of the k-th channel under unit current driving, where α(x,y) is the spatial variation term.

[0031] By adopting the above technical solution and the above multi-channel compensation method, compared with the previous method of approximating compensation by a series of low-order gradients with secondary distribution, the duration of radio frequency pulses is reduced.

[0032] Secondly, this application provides a compensation system for a magnetic resonance radio frequency emission field, comprising:

[0033] A magnetic resonance radio frequency transmission field compensation system, comprising:

[0034] The acquisition module is used to acquire information on the non-uniformity distribution of the emission field in the xy plane caused by the application of a time-varying radio frequency field;

[0035] The analysis and determination module is used to analyze and determine the matrix gradient coil driving current group that is suitable for the non-uniform distribution information of the transmitter field in the xy plane, based on the correspondence between different driving current groups of the matrix gradient coil and the generated gradient magnetic field, and the correspondence between the non-uniform distribution information of the transmitter field in the xy plane and the required gradient magnetic field.

[0036] The execution module is used to start the analyzed and determined matrix gradient coil drive current group to compensate for the non-uniformity of the emission field in the xy plane.

[0037] By adopting the above technical solution, the acquisition module and the analysis and determination module can analyze the high-order spatial distribution magnetic field that needs to be compensated for the non-uniform distribution information of the transmission field in the xy plane, effectively analyze and determine the matrix gradient coil driving current group that is suitable for the non-uniform distribution information of the transmission field in the xy plane, and finally effectively realize the compensation of the transmission field through the execution module.

[0038] Optionally, the analysis and determination module includes:

[0039] The query module is used to query the gradient magnetic field required by the matrix gradient coil driving current group based on the correspondence between the non-uniform distribution information of the emission field in the xy plane and the required gradient magnetic field.

[0040] The classification execution module is used to determine the gradient magnetic field based on the query results. If the query is found, the gradient magnetic field generated by the gradient coil driving current group of the query matrix is ​​used as the gradient magnetic field determined in this analysis. If the query is not found, the magnetic field generated by each unit of the gradient array under unit current is used as the basis, and the applied current is the weight parameter of each basis. The multi-channel compensation method is used to analyze and determine the gradient magnetic field that is adapted to the non-uniformity distribution information of the emission field in the xy plane, and this is used as the gradient magnetic field determined in this analysis.

[0041] The matrix gradient coil drive current group determination module is used to analyze and determine the matrix gradient coil drive current group corresponding to the required gradient magnetic field based on the correspondence between different drive current groups of the matrix gradient coil and the generated gradient magnetic field, and the gradient magnetic field determined in this analysis.

[0042] By adopting the above technical solution, the query module first analyzes whether there is a gradient magnetic field in the history that can compensate for the non-uniformity of the transmission field in the xy plane. Then, the classification execution module analyzes the gradient magnetic field according to the execution results. The specific analysis is as follows: if it exists, the existing gradient magnetic field is used as the gradient magnetic field determined in this analysis. If it does not exist, the multi-channel compensation method is used to analyze and determine the gradient magnetic field that is suitable for the non-uniformity distribution information of the transmission field in the xy plane. Finally, the matrix gradient coil drive current group determination module matches a suitable matrix gradient coil drive current group according to the analyzed and determined gradient magnetic field.

[0043] Thirdly, this application provides a computer storage medium, comprising:

[0044] A computer storage medium includes a program that, when loaded and executed by a processor, implements compensation for the magnetic resonance radio frequency emission field as described in the first aspect.

[0045] By adopting the above technical solution and retrieving the program, it is possible to analyze the high-order spatial distribution magnetic field that needs to be compensated based on the non-uniform distribution information of the transmission field in the xy plane, and effectively analyze and determine the matrix gradient coil driving current group that is suitable for the non-uniform distribution information of the transmission field in the xy plane, thereby effectively realizing the compensation of the transmission field.

[0046] In summary, the beneficial technical effects of this application are as follows:

[0047] 1. Effectively compensates for the non-uniformity of the emission field in the xy plane, so that layer selection and uniform excitation in the xy plane are finally achieved in the z direction; 2. The gradient descent method is used to effectively shorten the duration of the radio frequency pulse, thereby shortening the scanning time. Attached Figure Description

[0048] Figure 1This is a flowchart illustrating a method for compensating a magnetic resonance radio frequency emission field according to an embodiment of this application.

[0049] Figure 2 This is a schematic diagram illustrating the process of obtaining information on the non-uniform distribution of the launch field in the xy plane according to another embodiment of this application.

[0050] Figure 3 This is a schematic diagram of the process for analyzing and determining the matrix gradient coil drive current group adapted to the non-uniform distribution information of the transmitting field in the xy plane, according to another embodiment of this application.

[0051] Figure 4 This is a schematic diagram of the process of determining the matrix gradient coil drive current group adapted to the non-uniform distribution information of the transmitting field in the xy plane using a multi-channel compensation method according to another embodiment of this application.

[0052] Figure 5 This is an example diagram of radio frequency pulses that change over time.

[0053] Figure 6 This is an example diagram of the non-uniform distribution of the radio frequency field after the radio frequency pulse is applied.

[0054] Figure 7 This is a schematic diagram of the overall structure of the matrix gradient coil.

[0055] Figure 8 This is a schematic diagram of the overall structure of the coil unit of a matrix gradient coil.

[0056] Figure 9 This is a system block diagram of a magnetic resonance radio frequency emission field compensation system according to an embodiment of this application.

[0057] Figure 10 This is a system block diagram of the analysis and determination module in the embodiments of this application.

[0058] In the diagram, 1 is the acquisition module; 2 is the analysis and determination module; 3 is the execution module; 4 is the query module; 5 is the classification execution module; and 6 is the matrix gradient coil drive current group determination module. Detailed Implementation

[0059] The present application will be further described in detail below with reference to the accompanying drawings.

[0060] Reference Figure 1 The compensation for a magnetic resonance radio frequency emission field disclosed in this application includes:

[0061] Step S100: Obtain information on the non-uniformity distribution of the emission field in the xy plane caused by applying a time-varying radio frequency field.

[0062] Reference Figure 2The acquisition of information on the non-uniform distribution of the launch field in the xy plane includes:

[0063] Step S110: Obtain the applied radio frequency pulse within a preset time range and define the change of the radio frequency pulse over time.

[0064] Among them, the radio frequency pulse is the RF pulse. The RF pulse itself is an electromagnetic wave, which satisfies the characteristics of a wave and changes over time. Figure 5 The preset time range can be 5 minutes or 10 minutes, or other times.

[0065] Step S120: According to the applied radio frequency pulse within a preset time range, the non-uniformity of the transmission field in the xy plane is excited, and the non-uniformity distribution map of the radio frequency field that varies with space is obtained as the non-uniformity distribution information of the transmission field in the xy plane.

[0066] The non-uniformity of the transmission field in the xy plane and the distribution of radio frequency field non-uniformity are static and do not change with time, but vary with space. See the attached diagram for details. Figure 6 .

[0067] It should be noted that the non-uniformity of the emission field in the xy plane is excited by the applied radio frequency pulse within the preset time range, and the distribution map of the non-uniformity of the radio frequency field that varies with space is obtained by the real flip angle imaging method.

[0068] Step S200: Based on the correspondence between different driving current groups of the matrix gradient coil and the generated gradient magnetic field, and the correspondence between the non-uniformity distribution information of the transmitting field in the xy plane and the required gradient magnetic field, analyze and determine the matrix gradient coil driving current group that is suitable for the non-uniformity distribution information of the transmitting field in the xy plane.

[0069] Among them, the matrix gradient coil reference Figure 7 As shown, the matrix ladder coil consists of forty largely identical coil units. Specific coil units are shown in the image. Figure 8 Each of the 40 coil units is independently controlled by a separate drive source, and different sets of drive currents can generate a highly free magnetic field in space. Due to the non-uniform distribution of the emission field, it typically exhibits a nonlinear and high-order magnetic field.

[0070] The analysis of the matrix gradient coil drive current group adapted to the non-uniform distribution information of the transmitting field in the xy plane is as follows: Based on the correspondence between the non-uniform distribution information of the transmitting field in the xy plane and the required gradient magnetic field, the required gradient magnetic field is determined, and the matrix gradient coil drive current group is determined by querying the correspondence between different drive current groups of the matrix gradient coil and the generated gradient magnetic field.

[0071] Step S300: Start the matrix gradient coil drive current group determined by the analysis to compensate for the non-uniformity of the emission field in the xy plane.

[0072] Specifically, the start-up of the matrix gradient coil driving current group determined by the analysis is as follows: each coil unit is driven independently by a determined current. Through the change of the current of each coil unit, a nonlinear gradient with spatiotemporal variation, i.e., a high-order spatially distributed magnetic field, is generated, which can well compensate for high-order inhomogeneity.

[0073] The implementation principle of this embodiment is as follows:

[0074] When the transmission field exhibits non-uniformity in the xy plane, the system analyzes and determines the matrix gradient coil driving current group that is compatible with the non-uniformity distribution information of the transmission field in the xy plane, based on the non-uniformity distribution information corresponding to the non-uniformity of the transmission field in the xy plane, and the correspondence between different driving current groups of the matrix gradient coil and the generated gradient magnetic field. The system then effectively compensates for the non-uniformity of the transmission field in the xy plane by driving the corresponding matrix gradient coil driving current group.

[0075] exist Figure 1 In step S200, further consideration is given to scenarios where the correspondence between the non-uniform distribution information of the transmitting field in the xy plane and the required gradient magnetic field cannot be found during the analysis and determination of the matrix gradient coil driving current group. In such cases, further analysis of the gradient magnetic field is required to determine a suitable matrix gradient coil driving current group. See [link to relevant documentation] for details. Figure 3 The illustrated embodiments are described in detail.

[0076] Reference Figure 3 The matrix gradient coil drive current group, which is analyzed and determined to be adapted to the non-uniform distribution information of the emission field in the xy plane, includes:

[0077] Step S210: Based on the correspondence between the non-uniformity distribution information of the emission field in the xy plane and the gradient magnetic field to be generated, query the gradient magnetic field to be generated by the matrix gradient coil driving current group.

[0078] The query for the gradient magnetic field required by the matrix gradient coil driving current group is as follows: taking the non-uniformity distribution information of the emission field in the xy plane as the query object, the gradient magnetic field required by the matrix gradient coil driving current group is obtained from the preset correspondence between the non-uniformity distribution information of the emission field in the xy plane and the required gradient magnetic field.

[0079] Step S220: The retrieved matrix gradient coil drive current group is used as the matrix gradient coil drive current group adapted to the non-uniform distribution information of the emission field in the xy plane.

[0080] The query for the matrix gradient coil drive current group is as follows: taking the gradient magnetic field to be generated by the matrix gradient coil as the query object, the matrix gradient coil drive current group is retrieved from the preset database that stores the correspondence between different drive current groups of matrix gradient coils and the generated gradient magnetic field.

[0081] Step S230: The magnetic field generated by each unit of the gradient array under a unit current is used as a basis, and the applied current is the weight parameter of each basis. The gradient magnetic field adapted to the non-uniformity distribution information of the emission field in the xy plane is determined by multi-channel compensation method.

[0082] Step S240: Based on the correspondence between different driving current groups of the matrix gradient coil and the generated gradient magnetic field, and the gradient magnetic field determined in this analysis, analyze and determine the matrix gradient coil driving current group corresponding to the required gradient magnetic field.

[0083] The analysis and determination of the matrix gradient coil driving current group corresponding to the required gradient magnetic field is as follows: Taking the gradient magnetic field determined in this analysis as the query object, the matrix gradient coil driving current group is retrieved from the preset database that stores the correspondence between different driving current groups of matrix gradient coils and the generated gradient magnetic field.

[0084] The implementation principle of this embodiment is as follows:

[0085] First, based on the correspondence between the non-uniform distribution information of the emission field in the xy plane and the required gradient magnetic field, the required gradient magnetic field is queried. If it is not found, the gradient array with the best compensation effect is selected through multi-channel compensation method, so as to more accurately determine the matrix gradient coil driving current group.

[0086] exist Figure 3 In step S240, further consideration is given to the gradient descent method used in the matrix gradient coil drive current group, which is adapted to the non-uniform distribution information of the emission field in the xy plane. This method needs to take into account the applicable range of the approximate flip angle. See [link to relevant documentation] for details. Figure 4 The illustrated embodiments are described in detail.

[0087] Reference Figure 4 The matrix gradient coil drive current group, adapted to the non-uniform distribution information of the transmitting field in the xy plane, was determined using a multi-channel compensation method as follows:

[0088] Step S241: Analyze whether the approximate flip angle falls within the preset angle range. If yes, proceed to step S242.

[0089] The preset angle range can be (10, 30) degrees, or other angle ranges.

[0090] Specifically, the necessity of approximately flipping the corner into a preset angle range is explained as follows:

[0091] First, there is an equation used to describe the physical laws of magnetic resonance, called the Bloch equation, as follows:

[0092]

[0093] The equation includes the radio frequency field B1 and the layer selection gradient G in the z direction. The above equation can be rewritten in fractional form as follows:

[0094]

[0095] At this point, assuming a small approximate flip angle θ (<30 degrees), the following approximation holds:

[0096]

[0097] That is, the component Mz of the magnetization vector after excitation in the z direction can be approximated as the initial magnetization vector M0 at a small flip angle. Under the above selection, it is fully considered that the phenomenon of non-uniformity of the emission field excitation may occur in any xyz direction / plane. However, the z direction is usually used as a layer selection (non-3D sequence). The non-uniformity is not so significant in a very narrow layer thickness, especially when the small flip angle is satisfied. The non-uniformity of the excitation plane can be regarded as the non-uniformity of the xy plane.

[0098] Step S242: Based on the correspondence between the preset angle range and the multi-channel compensation method, analyze and determine the multi-channel compensation method, which will be used in this case.

[0099] Among them, the multi-channel compensation method includes:

[0100]

[0101] Where i is the imaginary unit, γ is the gyromagnetic ratio constant, and M + B1 is the transverse magnetization vector, which is the excitation profile in the z-direction. + F is a time-varying radio frequency field. -1 This is a Fourier transform operation, where M0 is the initial magnetization vector, e is the generated phase term, G is the gradient, r is the coordinate vector, and τ is the coordinate vector. rf Where Nc is the duration of the radio frequency pulse, I is the number of channels in the matrix gradient, and Nc is the number of channels in the matrix gradient. k φ is the control current of the k-th channel. k Let α(x,y) represent the magnetic field distribution of the k-th channel under unit current driving, where α(x,y) is the spatial variation term.

[0102] Specifically, the acquisition of the multi-channel compensation method depends on equation (1), which is explained in detail below: the magnetization vector M of the xy component x and M y Combined with the B1 component in the xy direction as follows; M + ≡M x +iM y B1+≡B 1x +iB 1y ;

[0103] Therefore, equation (1) simplifies to:

[0104]

[0105] Solving for:

[0106]

[0107] in:

[0108] 2D problems are essentially extensions of 1D problems; therefore, we discuss 1D layer selection problems here. When selecting layers, the gradient in the z-direction needs to be enabled, using a conventional linear layer selection gradient. Therefore, the specific formula for the gradient descent method can be derived from equation (2):

[0109]

[0110] From equation (3), we can see that the transverse magnetization vector M + That is, the excitation profile in the z-direction and the radio frequency field B1 have a Fourier transformation relationship. This correspondence holds under the assumption of a small flip angle (<30 degrees). The α(x, y) multiplied on the right side of the equation is a spatial variation term, which is the part that is to be offset by changing the magnitude of the gradient G in the xy plane and the spatial variation, so that the excitation profile M+(r) is more uniform in the xy plane.

[0111] Step S243: The non-uniform gradient magnetic field generated by the compensation emission field in the xy plane is analyzed and determined using the multi-channel compensation method determined by the analysis.

[0112] Reference Figure 9 This application also provides a compensation system for magnetic resonance radio frequency transmission fields.

[0113] A magnetic resonance radio frequency emission field compensation system includes:

[0114] Acquisition module 1 is used to acquire information on the non-uniformity distribution of the emission field in the xy plane caused by applying a time-varying radio frequency field;

[0115] The analysis and determination module 2 is used to analyze and determine the matrix gradient coil driving current group that is suitable for the non-uniform distribution information of the transmitter field in the xy plane, based on the correspondence between different driving current groups of the matrix gradient coil and the generated gradient magnetic field, and the correspondence between the non-uniform distribution information of the transmitter field in the xy plane and the required gradient magnetic field.

[0116] Execution module 3 is used to start the matrix gradient coil drive current group determined by analysis to compensate for the non-uniformity of the emission field in the xy plane.

[0117] Reference Figure 10 The analysis and determination module includes:

[0118] The query module 4 is used to query the gradient magnetic field required by the matrix gradient coil driving current group based on the correspondence between the non-uniform distribution information of the emission field in the xy plane and the required gradient magnetic field.

[0119] The classification execution module 5 is used to determine the gradient magnetic field based on the query results. If the query is found, the gradient magnetic field generated by the gradient coil driving current group of the query matrix is ​​used as the gradient magnetic field determined in this analysis. If the query is not found, the magnetic field generated by each unit of the gradient array under unit current is used as the basis, and the applied current is the weight parameter of each basis. The multi-channel compensation method is used to analyze and determine the gradient magnetic field that is adapted to the non-uniformity distribution information of the emission field in the xy plane, and this is used as the gradient magnetic field determined in this analysis.

[0120] The matrix gradient coil drive current group determination module 6 is used to analyze and determine the matrix gradient coil drive current group corresponding to the required gradient magnetic field based on the correspondence between different drive current groups of the matrix gradient coil and the generated gradient magnetic field, and the gradient magnetic field determined in this analysis.

[0121] This application also provides a computer storage medium.

[0122] A computer storage medium includes components capable of being loaded and executed by a processor to implement, for example... Figures 1 to 4 The procedure for compensating the magnetic resonance radio frequency emission field.

[0123] The embodiments described in this specific implementation are preferred embodiments of this application and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A method for compensating for a magnetic resonance radio frequency emission field, characterized in that, include: To obtain information on the non-uniformity distribution of the emitted field in the xy plane caused by applying a time-varying radio frequency field; Based on the correspondence between different driving current groups of the matrix gradient coil and the generated gradient magnetic field, and the correspondence between the non-uniformity distribution information of the transmitting field in the xy plane and the required gradient magnetic field, the driving current group of the matrix gradient coil adapted to the non-uniformity distribution information of the transmitting field in the xy plane is analyzed and determined. The analyzed and determined matrix gradient coil drive current group is activated to compensate for the non-uniformity of the emission field in the xy plane; The analysis determined the matrix gradient coil drive current group adapted to the non-uniform distribution information of the emission field in the xy plane, including: Based on the correspondence between the non-uniform distribution information of the emission field in the xy plane and the required gradient magnetic field, query the gradient magnetic field required to be generated by the matrix gradient coil driving current group. If found, the gradient magnetic field required to generate by the gradient coil driving current group of the query matrix will be used as the gradient magnetic field determined in this analysis. If no results are found, the magnetic field generated by each unit of the gradient array under a unit current is taken as the basis, and the applied current is the weight parameter of each basis. The gradient magnetic field adapted to the non-uniformity distribution information of the emission field in the xy plane is determined by multi-channel compensation method and used as the gradient magnetic field determined in this analysis. Based on the correspondence between different driving current groups of the matrix gradient coil and the resulting gradient magnetic field, and the gradient magnetic field determined in this analysis, the driving current group of the matrix gradient coil corresponding to the required gradient magnetic field is determined. The gradient magnetic field, adapted to the non-uniformity distribution information of the emission field in the xy plane, was determined using a multi-channel compensation method, including the following: Analyze whether the approximate flip angle falls within the preset angle range; If so, the multi-channel compensation method will be analyzed and determined based on the correspondence between the preset angle range and the multi-channel compensation method, and will be used as the multi-channel compensation method in this study. The non-uniform gradient magnetic field generated by the compensated emission field in the xy plane was analyzed and determined using the multi-channel compensation method determined by the analysis. Multi-channel compensation methods include: ； in, The imaginary unit, It is the gyromagnetic ratio constant. This is the transverse magnetization vector, which is the excitation profile in the z-direction. For a time-varying radio frequency field, The initial magnetization vector, The exponent term is the generated phase term, where For coordinate vectors, The duration of the radio frequency pulse. The number of channels for the gradient of the matrix. This represents the control current for the k-th channel. This represents the magnetic field distribution of the k-th channel under unit current driving. This is a spatial variation term.

2. The method for compensating a magnetic resonance radio frequency transmission field according to claim 1, characterized in that, The acquisition of information on the non-uniformity distribution of the launch field in the xy plane includes: Acquire the applied radio frequency pulses within a preset time range and define how the radio frequency pulses change over time; Based on the applied radio frequency pulse within a preset time range, the non-uniformity of the transmission field in the xy plane is excited, and the distribution map of the non-uniformity of the radio frequency field as a function of space is obtained as information on the non-uniformity distribution of the transmission field in the xy plane.

3. The method for compensating a magnetic resonance radio frequency transmission field according to claim 2, characterized in that, Based on the applied radio frequency pulses within a preset time range, the non-uniformity of the emission field in the xy plane is excited, and the distribution map of the non-uniformity of the radio frequency field as a function of space is obtained using the real flip angle imaging method.

4. A compensation system for a magnetic resonance radio frequency transmission field, characterized in that, The method for compensating the magnetic resonance radio frequency emission field as described in claim 1 includes: The acquisition module (1) is used to acquire information on the non-uniformity distribution of the transmission field in the xy plane caused by applying a time-varying radio frequency field; The analysis and determination module (2) is used to analyze and determine the matrix gradient coil driving current group that is compatible with the non-uniform distribution information of the transmitter field in the xy plane, based on the correspondence between different driving current groups of the matrix gradient coil and the generated gradient magnetic field, the correspondence between the non-uniform distribution information of the transmitter field in the xy plane and the required gradient magnetic field. The execution module (3) is used to start the matrix gradient coil drive current group determined by the analysis to compensate for the non-uniformity of the emission field in the xy plane.

5. The magnetic resonance radio frequency emission field compensation system according to claim 4, characterized in that, The analysis and determination module (2) includes: The query module (4) is used to query the gradient magnetic field required to be generated by the matrix gradient coil driving current group based on the correspondence between the non-uniform distribution information of the emission field in the xy plane and the gradient magnetic field to be generated. The classification execution module (5) is used to determine the gradient magnetic field based on the query results. If the query is found, the gradient magnetic field generated by the gradient coil driving current group of the query matrix is ​​used as the gradient magnetic field determined in this analysis. If the query is not found, the magnetic field generated by each unit of the gradient array under the unit current is used as the basis, and the applied current is the weight parameter of each basis. The multi-channel compensation method is used to analyze and determine the gradient magnetic field that is adapted to the non-uniformity distribution information of the emission field in the xy plane, and it is used as the gradient magnetic field determined in this analysis. The matrix gradient coil drive current group determination module (6) is used to analyze and determine the matrix gradient coil drive current group corresponding to the required gradient magnetic field based on the correspondence between different drive current groups of the matrix gradient coil and the generated gradient magnetic field, and the gradient magnetic field determined in this analysis.

6. A computer storage medium, characterized in that, Includes a program that, when loaded and executed by a processor, implements the method for compensating the magnetic resonance radio frequency emission field as described in any one of claims 1 to 3.

Images