A gradient coil design method and device, electronic equipment and storage medium

Abstract

The application discloses a gradient coil design method and device, electronic equipment and a storage medium, applied to the technical field of superconducting magnetic resonance imaging systems, in order to solve the problems of large coil inductance and decreased magnetic field climbing rate, the gradient coil is an axisymmetric gradient coil, the method can obtain a triangular grid corresponding to the skeleton surface by discretizing the skeleton surface to be wired, then further performs flow function calculation according to the triangular grid, determines the corresponding initial flow function distribution, minimizes the flow function extreme value as a first objective function, and combines the first preset boundary condition to perform first nonlinear programming on the initial flow function distribution to obtain a new flow function distribution; and the parameter information of the gradient coil is determined according to the new flow function distribution. In the application, the flow function extreme value is taken as the first objective function, the flow function distribution is optimized, the inductance is minimized, the linearity of the gradient magnetic field is improved, and the demand of the fast imaging scene is better met.

Description

Technical Field

[0001] This invention relates to the field of superconducting magnetic resonance imaging systems, and in particular to a design method, apparatus, electronic device, and storage medium for gradient coils. Background Technology

[0002] In superconducting magnetic resonance imaging (MRI) systems, gradient coils are the core components for spatial localization, and their performance directly determines the resolution, speed, and image quality of the imaging. Gradient coils typically contain three dimensions: x, y, and z. Each dimension's coil consists of a main coil and a shielding coil. Key evaluation metrics include gradient field strength, gradient linearity, magnetic field creep rate, and eddy current interference level.

[0003] From a structural perspective, the coils in the x and y dimensions are mostly distributed in a butterfly shape on the surface of the skeleton, which is a two-dimensional linear spatial distribution. The number of variables is large and the computational complexity is high during the optimization process. However, the gradient coils in the z dimension have axisymmetry, which can be simplified to a one-dimensional linear distribution problem. This characteristic allows them to significantly reduce the number of variables in the optimization design and significantly improve computational efficiency and optimization accuracy. Therefore, it has become one of the key directions for gradient coil optimization.

[0004] In the design of gradient coils (especially z-axis coils), related technologies have not incorporated minimizing inductance into the optimization objective. This may result in coils with excessively high inductance, leading to a decrease in the magnetic field rise rate. The rise rate is a key indicator affecting imaging speed; a lower rise rate will prolong imaging time, making it difficult to meet the needs of rapid imaging scenarios (such as dynamic organ imaging and emergency imaging). Summary of the Invention

[0005] The purpose of this invention is to provide a design method, apparatus, electronic device, and computer-readable storage medium for gradient coils, which minimizes inductance during use and improves the linearity of the gradient magnetic field, thereby better meeting the needs of rapid imaging scenarios.

[0006] To address the aforementioned technical problems, the embodiments of the present invention provide the following technical solutions.

[0007] This invention provides a method for designing a gradient coil, wherein the gradient coil is an axisymmetric gradient coil, and the method includes:

[0008] Discretize the skeleton surface to be wired to obtain a triangular mesh corresponding to the skeleton surface;

[0009] Stream function calculations are performed based on the triangular mesh to determine the corresponding initial stream function distribution;

[0010] Minimizing the extreme value of the stream function is taken as the first objective function. Combined with the first preset boundary conditions, the initial stream function distribution is subjected to a first nonlinear programming to obtain a new stream function distribution.

[0011] The parameter information of the gradient coil is determined based on the new stream function distribution.

[0012] In one implementation, determining the parameter information of the gradient coil based on the new stream function distribution includes:

[0013] The contour lines are determined based on the new stream function distribution;

[0014] The number of turns of the gradient coil and the initial position of each turn are determined based on the contour lines described above.

[0015] The input current is minimized as the second objective function. Combined with the second preset boundary conditions, a second nonlinear programming is performed on the initial position of each coil turn to obtain the target current of the gradient coil and the final position information of each coil turn.

[0016] In one implementation, the first preset boundary condition includes:

[0017] The constraints include the magnitude of the first magnetic field deviation, the boundary stream function value, and the difference in stream functions between adjacent points.

[0018] In one implementation, the constraint on the magnitude of the first magnetic field deviation includes: ,in, Let x represent the magnetic field sensitivity matrix generated by the stream function basis functions at the nth grid point at the mth grid point, and let x represent the stream function value at the grid point. Indicates the target magnetic field value. Indicates the deviation value of the magnetic field;

[0019] The boundary flow function value constraints include: , This represents the stream function value corresponding to the t-th grid point on the boundary;

[0020] The adjacent point flow function difference constraint includes: ,in, This represents the difference in stream function values ​​between adjacent grid points. This represents the maximum value of the difference in the flow function between adjacent grid points.

[0021] In one implementation, the second preset boundary condition includes:

[0022] The second constraint includes the magnitude of the magnetic field deviation, the length constraint of the gradient coil, and the coil spacing constraint.

[0023] In one embodiment, the second magnetic field deviation magnitude constraint includes ,in, Indicates in The magnetic field generated when a current I is passed through the coil at that location. Let I represent the coordinate of the nth turn of the coil on the Z-axis, and let I represent the current flowing through the coil.

[0024] The gradient coil length constraint includes Where L represents the length of the skeleton;

[0025] The coil spacing constraint includes , where d represents the preset minimum distance.

[0026] In one implementation, the step of calculating the stream function based on the triangular mesh to determine the corresponding initial stream function distribution includes:

[0027] The flow function of the triangular mesh is calculated using the boundary element method to obtain the corresponding initial flow function distribution.

[0028] In another aspect, the present invention provides a design apparatus for a gradient coil, wherein the gradient coil is an axisymmetric gradient coil, and the apparatus includes:

[0029] The first processing module is used to discretize the skeleton surface to be wired to obtain a triangular mesh corresponding to the skeleton surface.

[0030] The first determining module is used to calculate the stream function based on the triangular mesh and determine the corresponding initial stream function distribution;

[0031] The optimization module is used to take minimizing the extreme value of the stream function as the first objective function, and perform a first nonlinear programming on the initial stream function distribution in combination with the first preset boundary conditions to obtain a new stream function distribution;

[0032] The second determining module is used to determine the parameter information of the gradient coil based on the new stream function distribution.

[0033] In another aspect, the present invention provides an electronic device, comprising:

[0034] Memory, used to store computer programs;

[0035] A processor is used to implement the steps of the gradient coil design method as described above when executing the computer program.

[0036] In another aspect, the present invention provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the gradient coil design method described above.

[0037] As can be seen from the above technical solutions, the embodiments of the present invention have the following advantages:

[0038] This invention provides a method for designing a gradient coil, which is an axisymmetric gradient coil. The method discretizes the skeleton surface to be wired, obtaining a triangular mesh corresponding to the skeleton surface. Then, stream function calculation is performed based on this triangular mesh to determine the corresponding initial stream function distribution. Minimizing the stream function extremum is then used as the first objective function. A first nonlinear programming is performed on the initial stream function distribution using a first preset boundary condition to obtain a new stream function distribution. The parameter information of the gradient coil is determined based on the new stream function distribution. Therefore, this application uses the stream function extremum as the first objective function. By optimizing the stream function distribution to minimize inductance, the linearity of the gradient magnetic field can be improved, thus better meeting the needs of fast imaging scenarios.

[0039] Furthermore, the present invention also provides corresponding implementation devices, electronic devices, and computer-readable storage media for the design method of gradient coils, further making the method more practical, and the devices, electronic devices, and computer-readable storage media have corresponding advantages. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the prior art and embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1 A flowchart illustrating a gradient coil design method provided in an embodiment of the present invention;

[0042] Figure 2 This is a schematic diagram of an initial stream function distribution according to an embodiment of the present invention;

[0043] Figure 3 This is a schematic diagram of a gradient coil design device provided in an embodiment of the present invention. Detailed Implementation

[0044] This invention provides a design method, apparatus, electronic device, and computer-readable storage medium for gradient coils, which minimizes inductance during use and improves the linearity of the gradient magnetic field, thereby better meeting the needs of rapid imaging scenarios.

[0045] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0046] Please refer to Figure 1 , Figure 1 This is a flowchart illustrating a gradient coil design method according to an embodiment of the present invention. In this gradient coil design method, the gradient coil is an axisymmetric gradient coil, and the method includes the following steps S110 to S130.

[0047] S110: Discretize the skeleton surface to be wired to obtain a triangular mesh corresponding to the skeleton surface.

[0048] It should be noted that in practical applications, the gradient coil wiring is performed on a skeleton surface with a certain radius. This can be achieved by discretizing the skeleton surface, dividing it into triangular meshes. In other words, the surface of the coil skeleton to be wired is discretized, dividing the continuous skeleton surface into several triangular mesh units. Triangular meshes have the advantages of strong geometric adaptability and high computational accuracy, and can accurately fit the curved surface shape of the skeleton (such as cylindrical or arc-shaped skeletons), providing an accurate geometric model for subsequent stream function calculations and magnetic field analysis.

[0049] During discretization, the mesh density needs to be adjusted according to the size and curvature of the skeleton: a finer mesh is used in areas with greater skeleton curvature (such as the transition areas at both ends) to ensure geometric accuracy; the mesh size can be appropriately increased in areas with gentle curvature to balance computational accuracy and efficiency. The final result is a triangular mesh that perfectly corresponds to the skeleton surface, with each mesh cell containing three vertices (mesh points) and their corresponding coordinate information.

[0050] It should also be noted that the current density distribution on the skeleton surface can be approximated by the basis functions of the discrete stream function at the grid points. This transforms the analytical solution of the continuous function into a discretized algebraic equation, which can be expressed as:

[0051] ;

[0052] in, Let n be the stream function basis function. , Let N represent any point on the grid, and N represent the total number of grid points. Any point can be represented as... Continuous current density J( The stream function value I is approximated at each grid point. n By superimposing these expressions and substituting them into Biot's law, expressions for inductance, power consumption, and torque, we can obtain the corresponding systems of algebraic equations.

[0053] S120: Calculate the stream function based on the triangular mesh to determine the corresponding initial stream function distribution.

[0054] It should be noted that, in this embodiment of the application, the boundary element method can be used to calculate the stream function of the triangular mesh obtained in S110 to determine the initial stream function distribution (e.g., Figure 2 (As shown). Among them, the boundary element method is an efficient numerical method for calculating electromagnetic field problems. Its core principle is to solve the boundary integral equation, which only requires calculation of the mesh (boundary) on the surface of the skeleton, without considering the entire solution domain, thus greatly reducing the amount of computation. It is especially suitable for magnetic field analysis of axisymmetric structures.

[0055] In stream function calculation, the physical meaning of the stream function is to characterize the distribution trend of current, and its contour lines correspond to the wiring path of the coil. Using the boundary element method, the initial stream function value at each grid point can be calculated based on a preset target magnetic field (such as a uniform gradient field), forming an initial stream function distribution covering the entire skeleton surface, providing basic data for subsequent optimization.

[0056] The current density distribution on the skeleton surface can be approximated by the basis functions of the discrete stream function at the grid points. This transforms the analytical solution of the continuous function into a discretized algebraic equation, which can be expressed as:

[0057] .

[0058] By comprehensively considering factors such as gradient linearity, power consumption, inductance size, and torque, the problem originally considering only gradient linearity can be transformed into a solvable regularized least squares problem. For example, the regularized expression for inductance is as follows:

[0059] ;where A nm This represents the magnetic field sensitivity matrix generated by the stream function basis functions at n grid points at m points, where x represents the stream function value at each grid point, and x is equivalent to the aforementioned I. n Since the stream function value is unknown, we denote it as x, b as the target magnetic field value, λ as the regularization coefficient (an empirical value), and T as the transpose. H represents the L2 norm. nnThe inductance matrix is ​​represented by a minimum solution, which represents the distribution of the stream function value at the grid points. Then, by interpolation, the distribution of contour lines with the same difference is found, which represents the current line distribution of the conductor on the frame. In this embodiment, the value of λ is only an empirical value and cannot be guaranteed to be optimal. Furthermore, when dividing contour lines according to the same difference, the main coil and the shielding coil need to carry the same current, and dividing the contour lines may result in the main coil and the shielding coil not having an integer number of turns. Generally, rounding is necessary, but this error can cause deviations in the actual magnetic field distribution. Therefore, in this embodiment, to reduce coil inductance and improve the ramp-up rate, the stream function distribution calculated directly from the triangular grid is determined as the initial stream function distribution.

[0060] S130: Taking the minimization of the stream function extremum as the first objective function, and combining it with the first preset boundary conditions, perform the first nonlinear programming on the initial stream function distribution to obtain a new stream function distribution.

[0061] It should be noted that in this embodiment, "minimizing the extreme value of the stream function" is used as the first objective function. Combined with the first preset boundary conditions, a first nonlinear programming is performed on the initial stream function distribution to obtain an optimized new stream function distribution. The core purpose of this stage is to improve the linearity of the subsequent magnetic field and reduce the magnetic field deviation by constraining the extreme values ​​and distribution characteristics of the stream function.

[0062] It can be understood that the extrema of the stream function (the difference between the maximum and minimum values) directly affect the uniformity of the current distribution. For example, excessively large extrema can lead to excessively high local current density, generating eddy current interference and magnetic field distortion; excessively small extrema may fail to meet the target magnetic field strength requirements. Therefore, minimizing the extrema of the stream function as the objective function can achieve a balance between current distribution and magnetic field performance. Furthermore, since the magnitude of the stream function's extrema represents the inductance, the smaller the extrema of the stream function, the fewer the number of turns, and the lower the inductance.

[0063] S140: Determine the parameter information of the gradient coil based on the new stream function distribution.

[0064] It is understood that, in the embodiments of this application, after obtaining the new stream function distribution, the parameter information of the gradient coil can be further determined based on the new stream function distribution, so as to design the gradient coil based on the parameter information. This can minimize the inductance of the designed gradient coil and improve the linearity of the gradient magnetic field, thereby better meeting the needs of fast imaging scenarios.

[0065] Understandably, this application addresses the problem in related technologies where, when dividing contour lines according to the same difference, the main coil and shielding coil need to carry the same current, leading to non-integer turns in the main coil and shielding coil, resulting in deviations in the actual magnetic field distribution. In practical applications, the final parameters of the gradient coil (target current, number of turns, and final position of each turn) can be determined through a process of "contour line extraction - initial parameter determination - second nonlinear programming." The specific process is as follows:

[0066] The contour lines were determined based on the new stream function distribution;

[0067] The number of turns of the gradient coil and the initial position of each turn are determined based on the contour lines.

[0068] The input current is minimized as the second objective function. Combined with the second preset boundary conditions, a second nonlinear programming is performed on the initial position of each coil turn to obtain the target current of the gradient coil and the final position information of each coil turn.

[0069] It should be noted that, since the contour lines of the stream function represent the equivalent path of the current, in this embodiment, several contour lines can be extracted first based on the new stream function distribution (the number of contour lines corresponds to the number of turns of the coil). The geometric shape and position of each contour line directly determine the wiring path of a turn of the coil. Based on this, the number of turns of the gradient coil (the number of contour lines) and the initial position of each turn of the coil can be determined (i.e., the coordinates of the contour lines on the surface of the frame, such as the coordinates in the Z-axis direction (Z...). n )).

[0070] Furthermore, in this embodiment, "minimizing the input current" is used as the second objective function. Combined with the second preset boundary conditions, a second nonlinear programming is performed on the initial position of each coil turn, thereby obtaining the target current of the coil and the final position information of each coil turn. It is understandable that the core reason for choosing "minimizing current" as the objective function in this embodiment is that the coil inductance is positively correlated with the current. Under the premise of satisfying the target magnetic field strength, minimizing the current can indirectly reduce the coil inductance, thereby increasing the magnetic field creep rate (creep rate is inversely proportional to inductance); at the same time, a smaller current can reduce the coil's heat loss and improve system stability.

[0071] In other words, in this embodiment of the application, a new coil position distribution (Z) can be determined by dividing the contour lines with the same difference. n Thus, the number of turns in coil z is a fixed value. After determining the number of turns, we will use the coil position distribution (Z) obtained from the first optimization. n ) as the initial value (Z0) for the second optimization n The purpose of the second optimization is to determine the coil position Z.n As an optimization variable, the optimized result is the position of the coil in our project. There is no need to divide the contour lines, thus avoiding the problem of non-integer turns. The mathematical expression of the second nonlinear programming is: min f2=I, where f2 represents the second objective function.

[0072] In one implementation, during the first nonlinear programming phase in S130, the first preset boundary conditions may include:

[0073] First magnetic field deviation magnitude constraint, boundary flow function value constraint, and adjacent point flow function difference constraint;

[0074] The constraint on the magnitude of the first magnetic field deviation includes: ,in, Let x represent the magnetic field sensitivity matrix generated by the stream function basis functions at the nth grid point at the mth grid point, and let x represent the stream function value at the grid point. Indicates the target magnetic field value. Indicates the deviation value of the magnetic field;

[0075] The boundary flow function value constraint includes: , This indicates that the stream function value at the t-th grid point on the boundary is 0, preventing current from flowing out of the boundary and ensuring no current leakage at the skeleton boundary, thus improving the magnetic field containment. This boundary condition is used to fix the stream function value at the skeleton boundary to avoid magnetic field distortion caused by boundary effects.

[0076] The flow function difference constraint between adjacent points includes: ,in, This represents the difference in stream function values ​​between adjacent grid points. This represents the maximum value of the difference in flow function between adjacent grid points (set according to the current carrying capacity of the conductor to avoid excessive local current). This boundary condition is used to limit the rate of change of the flow function between adjacent grid points, avoiding uneven current distribution caused by abrupt changes in the flow function.

[0077] It should be noted that the mathematical expression for the first nonlinear programming stage in this embodiment may include: minf = max(x). The first boundary conditions include: and .

[0078] In this embodiment, the purpose of the first preset boundary condition is to minimize the extremum of the stream function, i.e., minimize the inductance, under the premise that the magnetic field distribution satisfies the gradient field linearity (first magnetic field deviation magnitude constraint) and the line spacing that can be achieved in engineering (constraint condition 3), thus obtaining the stream function distribution with the minimum inductance value.

[0079] Understandably, by using the first nonlinear programming method (such as sequential quadratic programming or interior point method), under the premise of satisfying the above-mentioned first preset boundary conditions, the extreme value of the stream function is minimized, and the optimized new stream function distribution is finally obtained, providing a high-quality stream function basis for subsequent coil parameter determination.

[0080] In one implementation, the second preset boundary condition for the second nonlinear programming stage in this application embodiment may include:

[0081] The second constraint includes the magnitude of the magnetic field deviation, the length constraint of the gradient coil, and the coil spacing constraint.

[0082] The second magnetic field deviation magnitude constraint includes ,in, Indicates in The magnetic field generated when a current I is passed through the coil at that location. Let I represent the coordinate of the nth turn of the coil on the Z-axis, and let I represent the current flowing through the coil.

[0083] The gradient coil length constraint includes Where L represents the length of the skeleton;

[0084] The coil spacing constraint includes , where d represents the preset minimum distance.

[0085] It should be noted that the second preset boundary conditions in the second nonlinear programming stage may include , and ,in, It can be calculated and written directly using Biosavart's law. This constraint is used to limit the deviation between the magnetic field generated by the actual coil after it is energized and the target magnetic field, thus ensuring the accuracy of the magnetic field distribution. This constraint means that the coil wiring cannot exceed the length L of the frame, which limits the total length of the coil in the Z-axis direction, prevents the coil from exceeding the frame's range, ensures matching with the frame size, and guarantees the feasibility of assembly. This constraint states that the spacing between each coil turn must be greater than the minimum achievable spacing d in engineering, thus limiting the minimum spacing between adjacent coil turns to meet engineering processing and insulation requirements. Using this second constraint, the final position Z of the coil can be obtained in the second nonlinear programming stage. n And the required current I.

[0086] Taking Table 1 below as an example, the final optimized results are compared with traditional design methods in terms of linearity, line spacing, and resistance. The method provided in this application embodiment is superior to traditional design methods.

[0087] Table 1. Parameter table of this application and conventional methods

[0088]

[0089] This invention also provides a corresponding apparatus for the gradient coil design method, further enhancing the practicality of the method. The apparatus can be described from both a functional module perspective and a hardware perspective. The gradient coil design apparatus provided by this invention is described below. This apparatus is used to implement the gradient coil design method provided by this invention. In this embodiment, the gradient coil design apparatus may include or be divided into one or more program modules. These program modules are stored in a storage medium and executed by one or more processors to complete the gradient coil design method disclosed in the above embodiments. The program module referred to in this invention is a series of computer program instruction segments capable of performing a specific function, which is more suitable than the program itself for describing the execution process of the gradient coil design apparatus in the storage medium. The following description will specifically introduce the functions of each program module in this embodiment. The gradient coil design apparatus described below corresponds to the gradient coil-based design method described above. Please refer to... Figure 3 This application discloses a gradient coil design apparatus, wherein the gradient coil is an axisymmetric gradient coil, and the apparatus includes:

[0090] The first processing module 11 is used to discretize the skeleton surface to be wired to obtain a triangular mesh corresponding to the skeleton surface.

[0091] The first determining module 12 is used to perform stream function calculation based on the triangular mesh and determine the corresponding initial stream function distribution;

[0092] Optimization module 13 is used to take minimizing the extreme value of the stream function as the first objective function, and perform a first nonlinear programming on the initial stream function distribution in combination with the first preset boundary conditions to obtain a new stream function distribution;

[0093] The second determining module 14 is used to determine the parameter information of the gradient coil based on the new stream function distribution.

[0094] In one embodiment, the second determining module 14 includes:

[0095] The first determining unit is used to determine each contour line based on the new stream function distribution;

[0096] The second determining unit is used to determine the number of turns of the gradient coil and the initial position of each turn of the coil based on each contour line.

[0097] The first processing unit is used to minimize the input current as the second objective function, and to perform a second nonlinear programming on the initial position of each coil turn in combination with the second preset boundary conditions, so as to obtain the target current of the gradient coil and the final position information of each coil turn.

[0098] In one implementation, the first preset boundary condition includes:

[0099] The constraints include the magnitude of the first magnetic field deviation, the boundary stream function value, and the difference in stream functions between adjacent points.

[0100] In one implementation, the constraint on the magnitude of the first magnetic field deviation includes: ,in, Let x represent the magnetic field sensitivity matrix generated by the stream function basis functions at the nth grid point at the mth grid point, and let x represent the stream function value at the grid point. Indicates the target magnetic field value. Indicates the deviation value of the magnetic field;

[0101] Boundary flow function value constraints include: , This represents the stream function value corresponding to the t-th grid point on the boundary;

[0102] The flow function difference constraint between adjacent points includes: ,in, This represents the difference in stream function values ​​between adjacent grid points. This represents the maximum value of the difference in the flow function between adjacent grid points.

[0103] In one implementation, the second preset boundary condition includes:

[0104] The second constraint includes the magnitude of the magnetic field deviation, the length constraint of the gradient coil, and the coil spacing constraint.

[0105] In one implementation, the second magnetic field deviation magnitude constraint includes ,in, Indicates in The magnetic field generated when a current I is passed through the coil at that location. Let I represent the coordinate of the nth turn of the coil on the Z-axis, and let I represent the current flowing through the coil.

[0106] Gradient coil length constraints include Where L represents the length of the skeleton;

[0107] Coil spacing constraints include , where d represents the preset minimum distance.

[0108] In one implementation, the first determining module 12 is configured to:

[0109] The boundary element method is used to calculate the stream function of the triangular mesh, and the corresponding initial stream function distribution is obtained.

[0110] It should be noted that the gradient coil design apparatus provided in this application embodiment has the same beneficial effects as the gradient coil design method provided in the above embodiments, and the gradient coil design method involved in this application embodiment can be referred to the above embodiments, which will not be repeated here.

[0111] Based on the above embodiments, the present invention also provides an electronic device, comprising:

[0112] Memory, used to store computer programs;

[0113] A processor is used to implement the steps of the gradient coil design method as described above when executing the computer program.

[0114] Based on the above embodiments, the present invention also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps of the gradient coil design method described above.

[0115] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0116] It should also be noted that, in this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0117] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for designing a gradient coil, characterized in that, The gradient coil is an axisymmetric gradient coil, and the method includes: Discretize the skeleton surface to be wired to obtain a triangular mesh corresponding to the skeleton surface; Stream function calculations are performed based on the triangular mesh to determine the corresponding initial stream function distribution; Minimizing the extreme value of the stream function is taken as the first objective function. Combined with the first preset boundary conditions, the initial stream function distribution is subjected to a first nonlinear programming to obtain a new stream function distribution. The parameter information of the gradient coil is determined based on the new stream function distribution; wherein: The step of determining the parameter information of the gradient coil based on the new stream function distribution includes: The contour lines are determined based on the new stream function distribution; The number of turns of the gradient coil and the initial position of each turn are determined based on the contour lines described above. The input current is minimized as the second objective function. Combined with the second preset boundary conditions, the initial position of each coil is subjected to a second nonlinear programming to obtain the target current of the gradient coil and the final position information of each coil. The second preset boundary conditions include: second magnetic field deviation magnitude constraint, gradient coil length constraint, and coil spacing constraint; The second magnetic field deviation magnitude constraint includes ,in, Indicates in The magnetic field generated when a current I is passed through the coil at that location. Let I represent the coordinate of the nth turn of the coil on the Z-axis, and let I represent the current flowing through the coil. The gradient coil length constraint includes Where L represents the length of the skeleton; The coil spacing constraint includes , where d represents the preset minimum distance.

2. The gradient coil design method according to claim 1, characterized in that, The first preset boundary conditions include: The constraints include the magnitude of the first magnetic field deviation, the boundary stream function value, and the difference in stream functions between adjacent points.

3. The gradient coil design method according to claim 2, characterized in that, The first magnetic field deviation magnitude constraint includes: ,in, Let x represent the magnetic field sensitivity matrix generated by the stream function basis functions at the nth grid point at the mth grid point, and let x represent the stream function value at the grid point. Indicates the target magnetic field value. Indicates the deviation value of the magnetic field; The boundary flow function value constraints include: , This represents the stream function value corresponding to the t-th grid point on the boundary; The adjacent point flow function difference constraint includes: ,in, This represents the difference in stream function values ​​between adjacent grid points. This represents the maximum value of the difference in the flow function between adjacent grid points.

4. The gradient coil design method according to any one of claims 1 to 3, characterized in that, The step of calculating the stream function based on the triangular mesh and determining the corresponding initial stream function distribution includes: The boundary element method is used to calculate the stream function of the triangular mesh to obtain the corresponding initial stream function distribution.

5. A design device for a gradient coil, characterized in that, The gradient coil is an axisymmetric gradient coil, and the device includes: The first processing module is used to discretize the skeleton surface to be wired to obtain a triangular mesh corresponding to the skeleton surface. The first determining module is used to calculate the stream function based on the triangular mesh and determine the corresponding initial stream function distribution; The optimization module is used to take minimizing the extreme value of the stream function as the first objective function, and perform a first nonlinear programming on the initial stream function distribution in combination with the first preset boundary conditions to obtain a new stream function distribution; The second determining module is used to determine the parameter information of the gradient coil based on the new stream function distribution; wherein: The second determining module includes: The first determining unit is used to determine each contour line based on the new stream function distribution; The second determining unit is used to determine the number of turns of the gradient coil and the initial position of each turn of the coil based on each of the contour lines. The first processing unit is used to minimize the input current to a second objective function, and perform a second nonlinear programming on the initial position of each coil in combination with a second preset boundary condition to obtain the target current of the gradient coil and the final position information of each coil. The second preset boundary conditions include: second magnetic field deviation magnitude constraint, gradient coil length constraint, and coil spacing constraint; The second magnetic field deviation magnitude constraint includes ,in, Indicates in The magnetic field generated when a current I is passed through the coil at that location. Let I represent the coordinate of the nth turn of the coil on the Z-axis, and let I represent the current flowing through the coil. The gradient coil length constraint includes Where L represents the length of the skeleton; The coil spacing constraint includes , where d represents the preset minimum distance.

6. An electronic device, characterized in that, include: Memory, used to store computer programs; A processor for executing the computer program to implement the steps of the gradient coil design method as described in any one of claims 1 to 4.

7. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, implements the steps of the gradient coil design method as described in any one of claims 1 to 4.

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