Inner ear electric field intensity distribution simulation analysis method and system based on vestibular magnetic stimulation

Abstract

The invention discloses an inner ear electric field intensity distribution simulation analysis method and system based on vestibular magnetic stimulation, and relates to the field of biomedical engineering simulation. The method comprises the following steps: firstly, constructing a craniocerebral model, an inner ear model and an electroencephalogram electrode model, importing the craniocerebral model and the inner ear model into finite element analysis software, and constructing a magnetic stimulation coil model through the finite element analysis software; secondly, simulating and generating an electromagnetic field changing along with time according to a Maxwell equation set; and finally, according to the actual electromagnetic characteristics of the brain and inner ear tissues, sequentially carrying out mesh generation on the brain model, the inner ear model, the magnetic stimulation coil model and the electroencephalogram electrode model, and executing simulation calculation. The influence of different stimulation modes on the inner ear stimulation effect is compared through simulation, valuable reference and basis are provided for a vestibular magnetic stimulation experiment in reality, and further development and application of the vestibular magnetic stimulation technology are expected to be promoted.

Description

Technical Field

[0001] The present invention relates to the technical field of biomedical engineering simulation, and in particular to a method and system for simulating and analyzing the distribution of inner ear electric field intensity based on vestibular magnetic stimulation. Background Art

[0002] Magnetic Vestibular Stimulation (MVS) is a neurophysiological technique that non-invasively stimulates the vestibular system. It stimulates the vestibular system by generating an alternating magnetic field through a coil placed on the surface of the mastoid behind the human ear. The human vestibular organ is located in the inner ear and is an important control organ and sensory organ for the body's balance. Studies have shown that repetitive vestibular magnetic stimulation can promote brain adaptation and recovery from vestibular lesions.

[0003] The vestibular magnetic stimulation device is mainly composed of a capacitor circuit and a stimulation coil. The capacitor circuit generates a pulse current. When the current passes through the stimulation coil, an alternating magnetic field is generated. This magnetic field can pass through the skin and skull to reach the vestibular organ, causing the alternating magnetic field to generate an induced electric field in the vestibule, thereby activating the vestibular organ.

[0004] Common magnetic stimulation coils include circular coils, figure-8 coils, H coils, and biconical coils. Circular coils and figure-8 coils are mainly used to stimulate the superficial cortical layer of the brain, while biconical coils and H coils are mainly used to stimulate deep areas of the brain. The distance between the vestibular organ and the surface of the human skin will vary due to individual differences, but the outermost part of the vestibular organ is about 3.5-4.5 cm away from the center of the external auditory canal and about 2.5-3.5 cm away from the mastoid behind the ear. From the perspective of stimulation distance, the vestibular organ can be stimulated using a circular coil or a figure-8 coil. Since the volume of the vestibular organ that can receive stimulation is limited and the vestibular organ is connected to the cochlea, it is easy to stimulate the cochlea of ​​the inner ear of the human body during magnetic stimulation. Therefore, a figure-8 coil is used for focusing considerations.

[0005] When the current direction of the stimulation coil is constant, the direction of the induced current acting on the stimulation area is opposite to the current direction of the stimulation coil. Studies have shown that different stimulation directions will affect the stimulation effect of the motor cortex. Through research, it is found that the induced current in the posterior-front, anterior-posterior and lateral-medial directions of the brain can produce different patterns of downward impulses. Therefore, the electric field strength in the stimulation area will change. When the 8-shaped coil is stimulating, the change in the inclination direction of the coil will affect the induced electric field in the stimulation area, thereby affecting the stimulation effect. In experiments, transcranial magnetic stimulation is often combined with electroencephalography to observe the stimulation effect, but the electroencephalography electrodes will change the current conduction path between the scalp and the cerebral cortex and interfere with the magnetic field generated by the coil. Based on this, the present invention proposes a simulation analysis method and system for the distribution of inner ear electric field intensity based on vestibular magnetic stimulation. Summary of the invention

[0006] In view of the deficiencies in the prior art, the technical problem to be solved by the present invention is to provide a method and system for simulating and analyzing the distribution of inner ear electric field intensity based on vestibular magnetic stimulation.

[0007] The present invention solves the technical problem by adopting the following technical solution:

[0008] On the one hand, the present invention provides a method for simulating and analyzing the distribution of inner ear electric field intensity based on vestibular magnetic stimulation, characterized in that it comprises the following steps:

[0009] S1. Construct a cranial brain model, an inner ear model and an EEG electrode model, import the cranial brain model and the inner ear model into the finite element analysis software, and build a magnetic stimulation coil model through the finite element analysis software;

[0010] S2. Pre-configure the magnetic field in the finite element analysis software, introduce the Maxwell basic equations, pass current through the magnetic stimulation coil, and simulate the electromagnetic field that changes with time according to the Maxwell basic equations; set different stimulation methods and configure the solver parameters;

[0011] S3. According to the actual electromagnetic properties of the brain and inner ear tissues, the material properties of different tissues are configured in the brain model and the inner ear model;

[0012] S4. The brain model, inner ear model, magnetic stimulation coil model and EEG electrode model are meshed in turn, and simulation calculations are performed. The electric field strength distribution of the inner ear model under different conditions is calculated according to the preset stimulation method. The simulation calculation results are correlated with the EEG electrode model to evaluate the influence of the EEG electrodes on the inner ear electric field distribution and stimulation effect.

[0013] Furthermore, step S1 includes the following contents:

[0014] S11, obtaining image data of the subject by scanning with medical imaging technology, and importing the image data into image processing software to extract a three-dimensional geometric model;

[0015] S12, processing the three-dimensional geometric model using model repair software to obtain a standard three-dimensional geometric model;

[0016] S13, importing the standard three-dimensional geometric model into finite element analysis software to construct a cranial brain model and an inner ear model;

[0017] S14, constructing an EEG electrode model in a lead manner based on a real brain model according to the pre-configured electrodes;

[0018] S15. Import the skull and brain model and the inner ear model into the finite element analysis software, and build a magnetic stimulation coil model using the finite element analysis software.

[0019] Further, step S2 includes the following contents:

[0020] S21. Pre-configure the magnetic field in the finite element analysis software;

[0021] S22. In the setting of magnetic field, the differential form of Maxwell's basic equations is introduced; the expression of Maxwell's basic equations is:

[0022]

[0023] In the formula, is the differential operator, H is the magnetic field intensity vector; J is the current density vector; is the partial derivative operator, D is the electric flux density; E is the electric field intensity vector; B is the magnetic induction intensity vector; t is the time; ρ is the charge density;

[0024] S23, creating a geometry of the vestibular magnetic stimulation coil in the magnetic stimulation coil model, and setting the input of the conductivity and current of the vestibular magnetic stimulation coil;

[0025] S24, running finite element analysis software, observing and recording changes in magnetic field and electric field;

[0026] S25. Simulate different stimulation methods, observe the distribution of the electromagnetic field under different stimulation methods, and configure the parameters of the solver.

[0027] Furthermore, the material properties of the different tissues include electrical conductivity, relative dielectric constant and relative magnetic permeability.

[0028] Further, step S4 includes the following contents:

[0029] S41, meshing different brain models, inner ear models, magnetic stimulation coil models and EEG electrode models respectively;

[0030] S42. Based on the meshed brain model, inner ear model, magnetic stimulation coil model and EEG electrode model, analyze the magnetic field distribution generated by different magnetic stimulation coil models, compare the differences, and select the best magnetic stimulation coil model construction method;

[0031] S43, rotating the optimal magnetic stimulation coil model under the coil plane, obtaining data of the induced electric field on the inner ear under different stimulation directions, and analyzing the influence on the inner ear stimulation effect;

[0032] The stimulation directions include the upper direction, the upper left direction, the left direction, the lower left direction, the lower direction, the lower right direction, the right direction and the upper right direction. Then the electric field strength of the inner ear model under each stimulation direction is calculated. Each coil stimulation direction is obtained by rotating the previous stimulation direction 45° counterclockwise on the plane where the coil is located.

[0033] S44, keeping the midpoint of the vestibular magnetic stimulation coil unchanged, obtaining data on the inner ear induced electric field at different tilt angles by changing the coil plane of the optimal magnetic stimulation coil model, and analyzing the influence on the inner ear stimulation effect;

[0034] S45. Correlate the analysis results with the EEG electrode model to evaluate the impact of the EEG electrodes on the inner ear electric field distribution and stimulation effect.

[0035] On the other hand, the present invention also provides an inner ear electric field intensity distribution simulation analysis system based on vestibular magnetic stimulation, including a magnetic stimulation coil model construction module, an electromagnetic field configuration and simulation module, a material property configuration module, and a mesh generation and simulation calculation module;

[0036] A magnetic stimulation coil model building module is used to build a cranial brain model, an inner ear model and an EEG electrode model, import the cranial brain model and the inner ear model into the finite element analysis software, and build a magnetic stimulation coil model through the finite element analysis software;

[0037] The electromagnetic field configuration and simulation module is used to pre-configure the magnetic field in the finite element analysis software, introduce Maxwell's basic equations, pass current through the vestibular magnetic stimulation coil, and simulate the electromagnetic field that changes with time according to Maxwell's basic equations; set different stimulation methods and configure the solver parameters;

[0038] A material property configuration module is used to configure the material properties of different tissues in the brain model and the inner ear model according to the actual electromagnetic properties of the brain and inner ear tissues;

[0039] The meshing and simulation calculation module is used to mesh the brain model, inner ear model, magnetic stimulation coil model and EEG electrode model in turn, and perform simulation calculations. According to the preset stimulation method, the electric field strength distribution of the inner ear model under different conditions is calculated, and the simulation calculation results are correlated with the EEG electrode model to evaluate the influence of the EEG electrodes on the inner ear electric field distribution and stimulation effect.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] The present invention focuses on the key factors that need to be paid attention to when vestibular magnetic stimulation acts on the vestibular area of ​​the inner ear, and uses advanced simulation technology to conduct an in-depth analysis of these factors. During the simulation process, a cranial model, an inner ear model, and a magnetic stimulation coil model are constructed, and detailed parameter configurations are performed on these models. First, the characteristics of the conventional 8-shaped coil under different construction methods are compared. Through a detailed comparison of the magnetic field strength, the S-type is preferably selected as the construction method of the 8-shaped coil in the present invention. This choice significantly improves the stimulation effect; secondly, the influence of the stimulation direction on the inner ear stimulation effect is deeply analyzed. By comparing the electric field strength of the inner ear model under different stimulation directions, it is finally determined that the upward direction is the best stimulation direction. This finding provides strong support for optimizing the stimulation strategy; in addition, different inclination angles are also explored. The simulation results show that when the coil is as parallel as possible to the skin surface near the mastoid for stimulation, even a small tilt will not have a significant effect on the stimulation effect. This conclusion provides important guidance for actual operations. Finally, the effect of brain electrodes on the inner ear stimulation effect is evaluated. The simulation results clearly show that when the mastoid is selected as the stimulation target, the induced electric field strength of the inner ear is minimally affected by the EEG, and this effect is independent of the magnitude of the stimulation intensity. This finding provides a strong guarantee for ensuring the stability and reliability of the stimulation effect. In summary, the present invention compares the effects of different stimulation methods on the inner ear stimulation effect through simulation, which provides a valuable reference and basis for actual vestibular magnetic stimulation experiments, and is expected to promote the further development and application of vestibular magnetic stimulation technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is the overall flow chart of the method;

[0043] Figure 2 It is the structural diagram of the system;

[0044] Figure 3 It is a flowchart for building a three-dimensional finite element simulation model;

[0045] Figure 4 It is a model diagram of the brain and inner ear;

[0046] Figure 5 This is the structural diagram of the figure 8 coil;

[0047] Figure 6 This is a schematic diagram of building an EEG electrode model on a cranial brain model;

[0048] Figure 7 is the axis magnetic field distribution diagram;

[0049] Figure 8 is the horizontal magnetic field distribution diagram;

[0050] Fig. 9It is a schematic diagram of the axis and horizontal line of the figure 8 coil;

[0051] Fig.10 This is a schematic diagram of the current direction and stimulation direction of the figure-8 coil;

[0052] Fig.11 is a schematic diagram of the stimulation coil at different tilt angles;

[0053] Fig.12 It is a schematic diagram of the average induced electric field strength of the right inner ear before and after the construction of the EEG electrode;

[0054] Fig.13 It is a schematic diagram of the average induced electric field strength of the left inner ear before and after the construction of the EEG electrode;

[0055] Fig.14 This is the electric field distribution diagram of the right inner ear under different stimulation directions;

[0056] Fig.15 This is the electric field distribution diagram of the left inner ear under different stimulation directions;

[0057] Fig.16 This is the electric field distribution diagram of the right inner ear at different tilt directions;

[0058] Fig.17 This is the electric field distribution diagram of the left inner ear at different tilt directions;

[0059] In the figure: 1. Magnetic stimulation coil model building module; 2. Electromagnetic field configuration and simulation module; 3. Material property configuration module; 4. Mesh generation and simulation calculation module. DETAILED DESCRIPTION

[0060] Specific embodiments are given below in conjunction with the accompanying drawings. The specific embodiments are only used to introduce the technical solutions of the present invention in detail and are not intended to limit the protection scope of the present application.

[0061] The present invention provides a method for simulating and analyzing the electric field intensity distribution of the inner ear based on vestibular magnetic stimulation, comprising the following steps:

[0062] S1. Construct a cranial brain model, an inner ear model and an EEG electrode model, import the cranial brain model and the inner ear model into the finite element analysis software, and build a magnetic stimulation coil model through the finite element analysis software;

[0063] S11, obtaining image data of the subject by scanning with medical imaging technology, and importing the image data into image processing software to extract a three-dimensional geometric model;

[0064] S12, processing the three-dimensional geometric model using model repair software to obtain a standard three-dimensional geometric model;

[0065] S13, importing the standard three-dimensional geometric model into finite element analysis software to construct a cranial brain model and an inner ear model;

[0066] S14, constructing an EEG electrode model in a lead manner based on a real brain model according to the pre-configured electrodes;

[0067] S15. Import the skull and brain model and the inner ear model into the finite element analysis software, and build a magnetic stimulation coil model using the finite element analysis software.

[0068] This embodiment is mainly realized by biomedical engineering modeling and electromagnetic field finite element analysis; before modeling, the real cranial brain model and inner ear model need to use medical imaging technology (such as CT, MRI, etc.) to scan the image data of the subject, and import the image data into image processing software (such as Mimics, etc.) to extract the three-dimensional geometric model. Then, the three-dimensional geometric model is processed by model repair software (Geomagic Studio, etc.) to obtain a standard three-dimensional geometric model. Finally, the standard three-dimensional geometric model is imported into finite element analysis software (such as Comsol, etc.) to complete the establishment of the real cranial brain model and inner ear model, and obtain the cranial brain model and inner ear model. The magnetic stimulation coil used in this simulation is a 70mm human 8-shaped coil of a repetitive transcranial magnetic stimulator (Magstim Rapid2), and the single-sided coil is wound with 9 turns. The coil conductor thickness is about 1.25mm, the height is 6mm, the impedance spacing is about 0.75mm, the spacing between the two wings is about 1mm, and the inner and outer radii of the single-sided coil are 28mm and 45.25mm respectively. At present, the traditional figure-8 coil model can be constructed in three ways according to the different overall structures: ring-shaped figure-8 coil; spiral symmetrical figure-8 coil; spiral S-shaped figure-8 coil. Among them, the ring-shaped figure-8 coil is mostly used for optimization research, so the figure-8 coil construction methods mainly considered in this simulation are spiral symmetrical type and spiral S type. The present invention builds a traditional EEG electrode model and places 32 electrode leads on the scalp of a real cranial model.

[0069] S2. Pre-configure the magnetic field in the finite element analysis software, introduce the Maxwell basic equations, pass current through the vestibular magnetic stimulation coil, and simulate the electromagnetic field that changes with time according to the Maxwell equations; set different stimulation methods and configure the solver parameters;

[0070] S21. Pre-configure the magnetic field in the finite element analysis software;

[0071] S22. In the magnetic field setting, the differential form of Maxwell's basic equations is introduced;

[0072] S23, creating a geometry of the vestibular magnetic stimulation coil in the magnetic stimulation coil model, and setting the input of the conductivity and current of the vestibular magnetic stimulation coil;

[0073] S24, running finite element analysis software, observing and recording changes in magnetic field and electric field;

[0074] S25. Simulate different stimulation methods, observe the distribution of the electromagnetic field under different stimulation methods, and configure the parameters of the solver.

[0075] Preferably, the frequency of the current is 3571 Hz.

[0076] It should be explained that the physical field selected by the present invention is a magnetic field, and the frequency of the current passed through the vestibular magnetic stimulation coil is 3571 Hz. At this time, the wavelength is much larger than the size of the cranial model, so the magnetic field under the 8-shaped coil can be approximated as a quasi-static field. When the current is passed through the magnetic stimulation coil, a time-varying electromagnetic field is generated. In the isotropic model, both the magnetic field and the induced electric field satisfy the Maxwell basic equations.

[0077] Preferably, the expression of the Maxwell basic equations is:

[0078]

[0079] The magnetic field generated around the coil can be obtained according to the following expression:

[0080]

[0081] The constitutive relation expression of the added material is:

[0082] D=εE

[0083] B=μH

[0084] J=σE

[0085] In the formula, is the differential operator, H is the magnetic field intensity vector; J is the current density vector; D is the electric flux density; E is the electric field intensity vector; B is the magnetic induction intensity vector; t is the time; ρ is the charge density; μ0 is the spatial magnetic permeability; I(t) is the coil current; r0 is the coil radius; R(r0) is the unit tangent vector of the radius where the coil is located; r is the charge density; μ is the magnetic permeability of the medium; ε is the dielectric constant of the medium.

[0086] S3. According to the actual electromagnetic properties of the brain and inner ear tissues, the material properties of different tissues are configured in the brain model and the inner ear model, including electrical conductivity, relative dielectric constant and relative magnetic permeability;

[0087] It should be explained that the human tissue and coil in the simulation have conductive properties, and the electrical characteristic parameters of the human tissue will change due to the influence of the electromagnetic field. The magnetic field frequency generated by the reference repetitive transcranial magnetic stimulator is 3571 Hz. The model material properties selected in this paper according to this magnetic field frequency are shown in Table 1;

[0088] Table 1 Electrical characteristic parameters of simulation model

[0089]

[0090] S4, meshing the cranial brain model, inner ear model, magnetic stimulation coil model and EEG electrode model in turn, and performing simulation calculations, calculating the electric field intensity distribution of the inner ear model under different conditions according to the preset stimulation method, and correlating the simulation calculation results with the EEG electrode model to evaluate the influence of the EEG electrodes on the inner ear electric field distribution and stimulation effect;

[0091] S41, meshing different brain models, inner ear models, magnetic stimulation coil models and EEG electrode models respectively;

[0092] S42. Based on the meshed brain model, inner ear model, magnetic stimulation coil model and EEG electrode model, analyze the magnetic field distribution generated by different magnetic stimulation coil models, compare the differences, and select the best magnetic stimulation coil model construction method;

[0093] S43, rotating the optimal magnetic stimulation coil model under the coil plane, obtaining data of the induced electric field on the inner ear under different stimulation directions, and analyzing the influence on the inner ear stimulation effect;

[0094] S44, keeping the midpoint of the vestibular magnetic stimulation coil unchanged, obtaining data on the inner ear induced electric field at different tilt angles by changing the coil plane of the optimal magnetic stimulation coil model, and analyzing the influence on the inner ear stimulation effect;

[0095] S45. Correlate the analysis results with the EEG electrode model to evaluate the impact of the EEG electrodes on the inner ear electric field distribution and stimulation effect.

[0096] It should be explained that the cranial brain model includes four regions: skin, skull, cerebrospinal fluid and brain parenchyma. In the present invention, a unified mesh is performed as a whole, and the meshing accuracy is selected to be refined; because the inner ear model is the main analysis model in the simulation analysis, the meshing accuracy is selected to be finer; since the size of the mosquito coil is too small, insufficient meshing accuracy will cause deformation of the overall mesh of the coil model, so the meshing accuracy of the coil model is selected to be ultrafine; the air domain model does not affect the calculation results. In order to simplify the simulation calculation task, the meshing accuracy of the air domain model is selected to be normal; the electrode model is set to normal in the meshing.

[0097] By analyzing the magnetic field distribution generated by the three 8-shaped coil construction models, the differences are compared, and finally the appropriate 8-shaped coil construction method is selected according to the simulation results. The current directions of the left and right wing coils of the 8-shaped coil model are opposite, and the current direction of the right wing coil is counterclockwise, and the current size is set to 1000A. The analysis selects the frequency domain and adds coil geometry analysis.

[0098] A three-dimensional coordinate system is established with the symmetrical center point of the 8-shaped coil as the origin, and the cross section at 1 / 2 of the thickness of the 8-shaped coil is set as the XOY plane of the three-dimensional coordinate system Z=0. mm is selected as the length unit. At this time, the upper and lower planes of the coil are located at the Z=3mm and Z=-3mm planes of the coordinate system respectively. A line segment with an endpoint 100mm away from the coil and perpendicular to the 8-shaped coil and the center point of the coil is selected as the axis of the 8-shaped coil. A line segment located 5mm below the coil and parallel to the horizontal symmetry axis of the 8-shaped coil is selected as the horizontal line of the 8-shaped coil. The axis is located on the Z axis, and the horizontal line is parallel to the X axis. The axis and the horizontal line are relative to the position of the coil.

[0099] The model is simulated, and the magnitude of the magnetic field strength on the axis and horizontal line of the 8-shaped coil under different construction methods is calculated.

[0100] On the axis of the 8-shaped coil, the magnetic field intensity increases as it approaches the coil, but due to the influence of the height of the 8-shaped coil, when the Z axis approaches the origin, the magnetic field intensity is approximately 0. When close to the coil, the S-shaped coil has the largest magnetic field intensity. When away from the coil, the magnetic field intensity of the 8-shaped coil of the two construction methods decreases, and the decreasing trend is approximately the same. On the horizontal line of the 8-shaped coil, the magnetic field intensity is symmetrically distributed, and there is a peak value near the center of the coil, and there is another peak value at a distance of about 70mm from the center of the coil. On the horizontal line, the symmetrical coil and the S-shaped coil have approximately the same magnetic field intensity size and trend. In order to better react to the stimulation effect, the present invention selects the S-shaped coil construction method.

[0101] The present invention selects mastoid as the stimulation target, and selects electric field strength as a variable to measure the stimulation effect. In the simulation analysis, the electric field strength variable of the vestibular organ is related to two factors, one is the stimulation direction of the coil, and the other is the direction of the current in the coil. In fact, the current direction of the 8-shaped coil is from top to bottom to the inner side of the coil, that is, the horizontally placed 8-shaped coil, wherein the current direction of the left wing coil is clockwise, and the current direction of the right wing coil is counterclockwise. At this time, the upper side of the coil is set as the stimulation direction. When placing the 8-shaped coil, the midpoint of the two wings of the 8-shaped coil is placed at the mastoid position, and is 5mm apart from the skin surface. Adjust the placement position of the 8-shaped coil so that the coil surface is as parallel as possible to the skin surface near the mastoid.

[0102] Preferably, the step of rotating the optimal magnetic stimulation coil model under the coil plane, acquiring data of the induced electric field on the inner ear under different stimulation directions, and analyzing the influence on the inner ear stimulation effect comprises the following steps:

[0103] S431, the direction of the plane where the magnetic stimulation coil model is located is rotated to the upper direction, the upper left direction, the left direction, the lower left direction, the lower direction, the lower right direction, the right direction and the upper right direction respectively, and then the electric field strength of the inner ear model under each stimulation direction is calculated, and each coil stimulation direction is obtained by rotating the previous stimulation direction 45° counterclockwise on the plane where the coil is located;

[0104] S432. Analyze the electric field intensity distribution of the inner ear model under several different stimulation directions.

[0105] Preferably, the correlating analysis of the analysis results with the EEG electrode model to evaluate the influence of the EEG electrodes on the inner ear electric field distribution and stimulation effect comprises the following steps:

[0106] S451, respectively passing currents of different magnitudes into the magnetic stimulation coil model, and calculating the average induced electric field strength of the left and right inner ear models before and after the EEG electrode model is built;

[0107] S452. Based on the average induced electric field strength of the inner ear before and after the construction of the EEG electrode model, analyze the effect of EEG electrodes on inner ear stimulation under different stimulation intensities.

[0108] It should be explained that the 8-shaped coil is rotated under the coil plane to adjust the stimulation direction. In this simulation, a total of eight stimulation directions are analyzed to analyze the stimulation effect of the inner ear, namely, the upper left direction, the left direction, the lower left direction, the lower direction, the lower right direction, the right direction and the upper right direction, and the electric field strength of the inner ear model is calculated under each stimulation direction. The stimulation direction here refers to the direction of the plane where the 8-shaped coil is located. Each coil stimulation direction is obtained by rotating the previous stimulation direction 45° counterclockwise on the plane where the coil is located.

[0109] In the finite element analysis software, the current flowing through the two wing coils in the built 8-shaped coil model is set to 100A. Because the inner ear models on the left and right sides of the human body are mirror-symmetrical, for the convenience of simulation discussion, the stimulation direction is based on the stimulation direction marked on the right side of the human body. The actual stimulation direction on the left side and the marked stimulation direction are mirror-symmetrical. The change in the electric field strength modulus is shown in Table 2. Among them, E1max represents the maximum value of the electric field strength modulus of the right inner ear model; E2max represents the maximum value of the electric field strength modulus of the left inner ear model; E1avg represents the average value of the electric field strength modulus of the right inner ear model; E2avg represents the average value of the electric field strength modulus of the left inner ear model. The electric field strength distribution of the inner ear model under 8 different stimulation directions.

[0110] As shown in Table 2, when the stimulation direction is upward, the Emax and Eavg of the inner ear are both the largest, and the simulation results of the left and right inner ear models are the same. It is worth noting that because the left and right inner ears of the real human head are not completely symmetrical, the induced electric field strength of the left and right inner ear models is not completely equal. Figure 8 It can be seen that when the mastoid is selected as the stimulation target, the stimulation site of the 8-shaped coil is mainly located in the vestibule of the inner ear. When the stimulation direction is directly upward and directly downward, the induced electric field generated in the vestibule of the inner ear model is relatively uniform. In this analysis, the directly upward direction is selected as the stimulation direction of the coil.

[0111] Table 2 Maximum and average electric field strength of the inner ear under different stimulation directions (V·m -1 )

[0112]

[0113]

[0114] In experimental analysis, transcranial magnetic stimulation is often used in combination with EEG, and the height of the EEG electrode is about 5mm. Because of the influence of the EEG electrode line, the coil needs to be placed about 10mm away from the stimulation target when combined with the EEG device. In the finite element analysis software of the present invention, the 8-shaped coil is kept parallel to the skin surface near the mastoid and the coil is translated outward by 10mm. At this time, due to the influence of the coil housing, the distance between the midpoint of the 8-shaped coil and the mastoid is 15mm. The midpoint of the coil is kept unchanged, and the tilt direction is changed by changing the plane of the coil. The present invention sets up four tilt directions, namely, tilting upward, tilting downward, tilting to the left, and tilting to the right, wherein the tilt angle is set to 15°.

[0115] The influence of different tilt angles on the induced electric field of the inner ear was analyzed in the finite element analysis software. The current flowing into the coil was kept at 100 A, and the tilt direction was based on the tilt direction marked on the 8-shaped coil model on the right side of the human body. The calculation results of the left and right inner ear models are shown in Table 3, which shows the distribution of the induced electric field of the left and right inner ears.

[0116] As shown in Table 3, although the maximum and average values ​​of the electric field strength of the left and right inner ears are the largest when the figure-8 coil model is tilted to the left, the deviation of the electric field strength does not exceed 10% compared with when it is not tilted. Therefore, when the mastoid is selected as the stimulation target to stimulate the inner ear, the smaller tilt angle of the figure-8 coil will not greatly affect the stimulation effect. Fig.10It can be seen that the results of the 8-shaped coil when tilted in different directions are the same as when not tilted. The main stimulation area in the inner ear is still the vestibular body and semicircular canals of the inner ear vestibule. Therefore, when the mastoid is selected as the stimulation target for vestibular magnetic stimulation experiments, a small degree of tilt of the coil is allowed. It is worth noting that the tilt angle of 15° is selected as the measurement standard here, mainly due to the limitations of the stimulation distance and EEG electrodes, and the 8-shaped coil cannot be tilted to a greater extent.

[0117] Table 3 Maximum and average electric field strength of the inner ear at different tilt directions / (V·m -1 )

[0118]

[0119] In the 8-shaped coil model, currents of 100A, 200A, 300A, 400A and 500A were respectively passed, and the average induced electric field strength of the left and right inner ear models before and after the construction of the EEG electrode model was calculated. The influence of the EEG electrodes on the inner ear stimulation effect under different stimulation intensities was analyzed. The average induced electric field strength of the left and right inner ears decreased after the EEG electrodes were built, but the decrease did not exceed 5%. It can be seen that although the addition of EEG electrodes will change the current conduction path between the scalp and the cerebral cortex and the magnetic field generated by the interference coil, when the mastoid is selected as the stimulation target, since there are not too many EEG electrodes around the 8-shaped coil, the stimulation effect of the inner ear is not greatly affected after the electrode model is constructed. Moreover, the decrease in the average induced electric field strength remains unchanged as the stimulation intensity increases, that is, the increase in the current passed through the coil. It can be seen that when the mastoid is selected as the stimulation target to stimulate the inner ear, the addition of EEG electrodes will not greatly affect the stimulation effect on the inner ear, and the degree of influence will not change with the change of the stimulation intensity.

[0120] The present invention also provides an inner ear electric field intensity distribution simulation analysis system based on vestibular magnetic stimulation, comprising a magnetic stimulation coil model construction module 1, an electromagnetic field configuration and simulation module 2, a material property configuration module 3 and a mesh generation and simulation calculation module 4;

[0121] A magnetic stimulation coil model building module 1 is used to build a cranial brain model, an inner ear model and an EEG electrode model, import the cranial brain model and the inner ear model into a finite element analysis software, and build a magnetic stimulation coil model through the finite element analysis software;

[0122] Electromagnetic field configuration and simulation module 2 is used to pre-configure the magnetic field in the finite element analysis software, introduce the Maxwell basic equations, pass current through the vestibular magnetic stimulation coil, and simulate the electromagnetic field that changes with time according to the Maxwell equations; set different stimulation methods and configure the parameters of the solver;

[0123] The material property configuration module 3 is used to configure the material properties of different tissues in the brain model and the inner ear model according to the actual electromagnetic properties of the brain and inner ear tissues;

[0124] The mesh generation and simulation calculation module 4 is used to mesh the cranial brain model, inner ear model, magnetic stimulation coil model and EEG electrode model in turn, and perform simulation calculations, calculate the electric field strength distribution of the inner ear model under different conditions according to the preset stimulation method, correlate the simulation calculation results with the EEG electrode model, and evaluate the influence of the EEG electrodes on the inner ear electric field distribution and stimulation effect.

[0125] In summary, the present invention focuses on the key factors that need to be paid attention to when vestibular magnetic stimulation acts on the vestibular area of ​​the inner ear, and uses advanced simulation technology to conduct an in-depth analysis of these factors. During the simulation process, a cranial model, an inner ear model and a magnetic stimulation coil model are constructed, and detailed parameter configurations are performed on these models; first, the characteristics of the conventional 8-shaped coil under different construction methods are compared, and through a detailed comparison of the magnetic field strength, the S-type is preferably selected as the construction method of the 8-shaped coil in the present invention. This choice significantly improves the stimulation effect; secondly, the influence of the stimulation direction on the inner ear stimulation effect is deeply analyzed, and by comparing the electric field strength of the inner ear model under different stimulation directions, it is finally determined that the upward direction is the best stimulation direction. This finding provides strong support for optimizing the stimulation strategy; in addition, different inclinations are also explored. The influence of angle on the inner ear stimulation effect; the simulation results show that when the coil is stimulated as parallel as possible to the skin surface near the mastoid, even a small tilt will not have a significant effect on the stimulation effect. This conclusion provides important guidance for actual operations; finally, the influence of brain electrodes on the inner ear stimulation effect is evaluated; the simulation results clearly show that when the mastoid is selected as the stimulation target, the induced electric field strength of the inner ear is minimally affected by the EEG, and this influence is independent of the magnitude of the stimulation intensity; this finding provides a strong guarantee for ensuring the stability and reliability of the stimulation effect; in summary, the present invention compares the effects of different stimulation methods on the inner ear stimulation effect through simulation, provides a valuable reference and basis for actual vestibular magnetic stimulation experiments, and is expected to promote the further development and application of vestibular magnetic stimulation technology.

[0126] Any matters not described in the present invention are applicable to the prior art.

Claims

1. A method for simulating and analyzing the electric field intensity distribution of the inner ear based on vestibular magnetic stimulation, characterized in that: The following steps are involved: S1. Construct a cranial brain model, an inner ear model and an EEG electrode model, import the cranial brain model and the inner ear model into the finite element analysis software, and build a magnetic stimulation coil model through the finite element analysis software; S2. Pre-configure the magnetic field in the finite element analysis software, introduce the Maxwell basic equations, pass current through the magnetic stimulation coil, and simulate the electromagnetic field that changes with time according to the Maxwell basic equations; set different stimulation methods and configure the solver parameters; S3. According to the actual electromagnetic properties of the brain and inner ear tissues, the material properties of different tissues are configured in the brain model and the inner ear model; S4. The brain model, inner ear model, magnetic stimulation coil model and EEG electrode model are meshed in turn, and simulation calculations are performed. The electric field strength distribution of the inner ear model under different conditions is calculated according to the preset stimulation method. The simulation calculation results are correlated with the EEG electrode model to evaluate the influence of the EEG electrodes on the inner ear electric field distribution and stimulation effect.

2. The inner ear electric field intensity distribution simulation analysis method based on vestibular magnetic stimulation according to claim 1, characterized in that: Step S1 includes the following contents: S11, obtaining image data of the subject by scanning with medical imaging technology, and importing the image data into image processing software to extract a three-dimensional geometric model; S12, processing the three-dimensional geometric model using model repair software to obtain a standard three-dimensional geometric model; S13, importing the standard three-dimensional geometric model into finite element analysis software to construct a cranial brain model and an inner ear model; S14, constructing an EEG electrode model in a lead manner based on a real brain model according to the pre-configured electrodes; S15. Import the skull and brain model and the inner ear model into the finite element analysis software, and build a magnetic stimulation coil model using the finite element analysis software.

3. The inner ear electric field intensity distribution simulation analysis method based on vestibular magnetic stimulation according to claim 1, characterized in that: Step S2 includes the following contents: S21. Pre-configure the magnetic field in the finite element analysis software; S22. In the setting of magnetic field, the differential form of Maxwell's basic equations is introduced; the expression of Maxwell's basic equations is: In the formula, is the differential operator, H is the magnetic field intensity vector; J is the current density vector; is the partial derivative operator, D is the electric flux density; E is the electric field intensity vector; B is the magnetic induction intensity vector; t is the time; ρ is the charge density; S23, creating a geometry of the vestibular magnetic stimulation coil in the magnetic stimulation coil model, and setting the input of the conductivity and current of the vestibular magnetic stimulation coil; S24, running finite element analysis software, observing and recording changes in magnetic field and electric field; S25. Simulate different stimulation methods, observe the distribution of the electromagnetic field under different stimulation methods, and configure the parameters of the solver.

4. The inner ear electric field intensity distribution simulation analysis method based on vestibular magnetic stimulation according to claim 1, characterized in that: The material properties of the different tissues include electrical conductivity, relative permittivity and relative magnetic permeability.

5. The inner ear electric field intensity distribution simulation analysis method based on vestibular magnetic stimulation according to claim 1, characterized in that: Step S4 includes the following contents: S41, meshing different brain models, inner ear models, magnetic stimulation coil models and EEG electrode models respectively; S42. Based on the meshed brain model, inner ear model, magnetic stimulation coil model and EEG electrode model, analyze the magnetic field distribution generated by different magnetic stimulation coil models, compare the differences, and select the best magnetic stimulation coil model construction method; S43, rotating the optimal magnetic stimulation coil model under the coil plane, obtaining data of the induced electric field on the inner ear under different stimulation directions, and analyzing the influence on the inner ear stimulation effect; The stimulation directions include the upper direction, the upper left direction, the left direction, the lower left direction, the lower direction, the lower right direction, the right direction and the upper right direction. Then the electric field strength of the inner ear model under each stimulation direction is calculated. Each coil stimulation direction is obtained by rotating the previous stimulation direction 45° counterclockwise on the plane where the coil is located. S44, keeping the midpoint of the vestibular magnetic stimulation coil unchanged, obtaining data on the inner ear induced electric field at different tilt angles by changing the coil plane of the optimal magnetic stimulation coil model, and analyzing the influence on the inner ear stimulation effect; S45. Correlate the analysis results with the EEG electrode model to evaluate the impact of the EEG electrodes on the inner ear electric field distribution and stimulation effect.

6. A simulation and analysis system for inner ear electric field intensity distribution based on vestibular magnetic stimulation for implementing any of the methods described in claims 1 to 5, characterized in that: The system includes a magnetic stimulation coil model building module, an electromagnetic field configuration and simulation module, a material property configuration module, and a mesh generation and simulation calculation module; A magnetic stimulation coil model building module is used to build a cranial brain model, an inner ear model and an EEG electrode model, import the cranial brain model and the inner ear model into the finite element analysis software, and build a magnetic stimulation coil model through the finite element analysis software; The electromagnetic field configuration and simulation module is used to pre-configure the magnetic field in the finite element analysis software, introduce Maxwell's basic equations, pass current through the vestibular magnetic stimulation coil, and simulate the electromagnetic field that changes with time according to Maxwell's basic equations; set different stimulation methods and configure the solver parameters; A material property configuration module is used to configure the material properties of different tissues in the brain model and the inner ear model according to the actual electromagnetic properties of the brain and inner ear tissues; The meshing and simulation calculation module is used to mesh the brain model, inner ear model, magnetic stimulation coil model and EEG electrode model in turn, and perform simulation calculations. According to the preset stimulation method, the electric field strength distribution of the inner ear model under different conditions is calculated, and the simulation calculation results are correlated with the EEG electrode model to evaluate the influence of the EEG electrodes on the inner ear electric field distribution and stimulation effect.

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