A transcranial magnetic stimulation device based on super material resonator enhanced magnetic field

Abstract

The application relates to a transcranial magnetic stimulation device based on a metamaterial resonator for enhancing a magnetic field, which comprises pulse circuit system, a metamaterial resonator and a transcranial magnetic stimulation coil, wherein the metamaterial resonator comprises a multilayer spiral metal wire structure, a high-flux magnetic powder core and a laminated capacitor structure. The scheme provided by the application can improve the maximum intracranial electric field intensity by more than 40%, reduce the heat generation by more than 50%, and improve the stimulation depth and focusing property under the condition of the same power supply voltage; meanwhile, the required series resonant compensation capacitor on the coil side can be greatly reduced (to less than 30 mu F), which significantly reduces the volume of the energy storage capacitor and is a key factor for promoting the miniaturization and portability of the whole device.

Description

Technical Field

[0001] This invention relates to the field of medical device technology, and in particular to a transcranial magnetic stimulation device based on a metamaterial resonator to enhance the magnetic field. Background Technology

[0002] Transcranial magnetic stimulation (TMS) is a non-invasive bio-neuromodulation technique that typically uses a coil carrying an alternating current to generate a time-varying magnetic field. This magnetic field induces an electric field within the brain, causing biocurrents to be conducted in the tissues, thereby modulating brain metabolism and neural electrical activity. In the field of TMS, it is usually necessary to generate a sufficiently strong alternating magnetic field (frequency in the kHz range, magnetic field strength in the vicinity of the stimulator in the hundreds of mT range) in a specific region near the brain.

[0003] However, when traditional energized coils or solenoids operate in the kHz frequency band, they often need to be connected to a high-voltage pulse circuit to apply an extremely high voltage to the coil, thereby generating a large current on the order of kA to produce a sufficiently strong magnetic field. This leads to problems such as large system size and high power consumption.

[0004] The above content is only used to help understand the technical solution of the present invention and does not represent an admission that the above content is prior art. Summary of the Invention

[0005] The main objective of this invention is to provide a transcranial magnetic stimulation device based on a metamaterial resonator to enhance the magnetic field, thereby addressing the aforementioned technical problems in the prior art.

[0006] To achieve the above objectives, the present invention provides a transcranial magnetic stimulation device based on a metamaterial resonator to enhance the magnetic field, the transcranial magnetic stimulation device based on a metamaterial resonator to enhance the magnetic field includes: Pulse circuit system; Metamaterial resonators, including: A multi-layered spiral metal wire structure, which is nested and connected sequentially along the radial direction, with the winding directions of the multi-layered spiral metal wire structure being the same; A high-flux magnetic powder core is located in the central axial region of the multilayer helical metal wire structure. The initial permeability of the high-flux magnetic powder core is 147, and its saturation magnetic flux density is 1.5T. A multilayer capacitor structure includes a dielectric layer with a relative permittivity greater than 4400 at room temperature and in the kHz frequency band. The multilayer capacitor structure is located on top of the multilayer spiral metal wire structure and the high-flux magnetic powder core. The multilayer capacitor structure is not in contact with the high-flux magnetic powder core. One of the metal electrodes of the multilayer capacitor structure is electrically connected to the innermost spiral metal wire structure of the multilayer spiral metal wire structure, and the other metal electrode is electrically connected to the outermost spiral metal wire structure of the multilayer spiral metal wire structure. A transcranial magnetic stimulation coil is electrically connected to the pulse circuit system, and the transcranial magnetic stimulation coil is sleeved around the multi-layer spiral metal wire structure; The metamaterial resonator is not connected to the transcranial magnetic stimulation coil and the pulse circuit system. When an alternating current is applied to the transcranial magnetic stimulation coil, the metamaterial resonator is excited to resonate, and the magnetic field generated by the resonance is used to stimulate the human brain.

[0007] Preferably, in the transcranial magnetic stimulation device, the axial height of the multilayer spiral metal wire structure is h; the cross-sectional shape of the spiral metal wire in each layer of the spiral metal wire structure is rectangular, with a width of w and a thickness of d. m The inner radius of the i-th layer of the spiral metal wire structure is r. i The number of turns in the i-th layer is N i ; The high magnetic flux powder core is a cylinder with a height of h. c The radius is r c ; r c <r i <r i+1 h c ≤h, N i w < h, d m <r i+1 -r i . Preferably, in the transcranial magnetic stimulation device, the transcranial magnetic stimulation coil is a figure-eight coil, which includes two adjacent circular coils, and the current flowing through the two circular coils is in opposite directions. The metamaterial resonator is of two types, and the two metamaterial resonators are respectively housed in corresponding transcranial magnetic stimulation coils.

[0008] Preferably, in the transcranial magnetic stimulation device, the bottoms of the two circular coils form an adjustable preset angle, which is used to adapt to the surface of the human brain. The preset angle can be adjusted from 0 to 25 degrees.

[0009] Preferably, in the transcranial magnetic stimulation device, the pulse circuit system includes two identical pulse generating circuits, which output sinusoidal waveform pulses with adjustable pulse width at a specific frequency; Two circular coils are connected to two sets of pulse generating circuits respectively, and the pulses that excite the two circular coils have a sinusoidal waveform; The excitation pulses of the two circular coils have opposite current directions; The frequency of the sinusoidal pulse matches the overall resonant frequency of the transcranial magnetic stimulation coil and the metamaterial resonator after coupling.

[0010] Preferably, in the transcranial magnetic stimulation device, when an alternating current flows through the transcranial magnetic stimulation coil, the alternating magnetic field generated by the transcranial magnetic stimulation coil excites the resonance of the metamaterial resonator, and the resonant frequency of the metamaterial resonator is f1, where f1 is: ; Among them, L s The equivalent inductance of the metamaterial resonator is the inductance provided by the multilayer spiral metal wires surrounding the magnetic core; C s The equivalent capacitance of the metamaterial resonator, i.e., the capacitance provided by the stacked capacitor structure.

[0011] Preferably, in the transcranial magnetic stimulation device, the metamaterial resonator further includes an insulating support, the multilayer spiral metal wire structure is wrapped around the insulating support, and the stacked capacitor structure and the high magnetic flux powder core are respectively fixed on the insulating support.

[0012] Preferably, in the transcranial magnetic stimulation device, the stacked capacitor structure includes multiple ceramic dielectric sheets with silver-plated electrodes on both sides, and the multiple ceramic dielectric sheets are alternately stacked in two interlocking comb-shaped metal electrodes.

[0013] Preferably, in the transcranial magnetic stimulation device, the resonant angular frequency of the transcranial magnetic stimulation coil coupled with the metamaterial resonator is... The capacitor C connected in series in the transcranial magnetic stimulation coil circuit of the pulse circuit system c It is determined according to the following calculation method: The total complex impedance on the coil side under steady-state conditions is: (1) Taking the transcranial magnetic stimulation coil as the source and the complex impedance introduced by the metamaterial resonator into the circuit containing the transcranial magnetic stimulation coil as the load, when the voltage across the circuit containing the transcranial magnetic stimulation coil is fixed, the magnetic field generated by the metamaterial resonator is strongest when the following condition is met: (2) (3) Calculated using formula (2) ; C is calculated using formula (3). c ; Z represents the total complex impedance on the coil side under steady-state conditions. Z c Let be the complex impedance of the circuit containing the coil. ; Z s The complex impedance of the equivalent circuit of the metamaterial resonator is given. ; L c The inductance of a single circular transcranial magnetic stimulation coil; C c The series capacitance of the circuit containing the coil; R c The equivalent series resistance of a single circular transcranial magnetic stimulation coil; L s The equivalent inductance of a metamaterial resonator; C s The equivalent capacitance of the metamaterial resonator; R s This is the equivalent series resistance of the metamaterial resonator; M1 and These are the mutual inductance and mutual resistance of a single circular transcranial magnetic stimulation coil and its metamaterial resonator on the same side; M2 and These represent the mutual inductance and mutual resistance between two circular transcranial magnetic stimulation coils, respectively. M3 and These are the mutual inductance and mutual resistance of a single circular transcranial magnetic stimulation coil and its metamaterial resonator on the other side; M4 and These represent the mutual inductance and mutual resistance between two metamaterial resonators, respectively. This refers to the resonant angular frequency after the transcranial magnetic stimulation coil is coupled to the metamaterial resonator. ; f is the resonant frequency after the transcranial magnetic stimulation coil is coupled with the metamaterial resonator; i is the imaginary unit; Preferably, in the transcranial magnetic stimulation device, the frequency of the sine wave output by the pulse circuit system and the lifetime / linewidth of the coupling mode are determined according to the following formula: The time-domain equation satisfied by the voltage across the circuit containing the coil and the equivalent capacitance of the metamaterial resonator is as follows: (4) in, ; Introducing state vectors: (5) Equation (4) can be transformed into: (6) Where X and C1 are the coefficient matrices introduced by the substitution; ; ; matrix The real and imaginary parts are separated. The imaginary part is diagonalized, and the diagonal element is the two resonant angular frequencies after the transcranial magnetic stimulation coil is coupled with the metamaterial resonator. The real part is also transformed accordingly to obtain the lifetime / linewidth factor of the two coupling modes. The lower of the two resonant frequencies is taken as the frequency of the sine wave output by the pulse circuit system. U Cc This refers to the voltage divided by the capacitance of the circular transcranial magnetic stimulation coil circuit; U Cs The voltage divided by the equivalent capacitance of the metamaterial resonator circuit; R is the resistance matrix; C is the capacitance matrix; L is the inductance matrix; X is a coefficient matrix that satisfies ; C1 is the coefficient matrix, satisfying ; U C The vector is composed of the voltages obtained from the capacitance of the circular transcranial magnetic stimulation coil circuit and the equivalent capacitance of the metamaterial resonator circuit. U is the power supply voltage of the circular transcranial magnetic stimulation coil circuit; U is a vector consisting of the power supply voltages of the circular transcranial magnetic stimulation coil circuit and the metamaterial resonator circuit (here the metamaterial resonator is passive, and its equivalent circuit power supply voltage is 0); a is the state vector used to describe the resonant amplitude; t represents time.

[0014] The present invention has at least the following beneficial effects: The transcranial magnetic stimulation (TMS) device provided by this invention includes a pulse circuit system, a metamaterial resonator, and a TMS coil. The metamaterial resonator comprises a multilayer spiral metal wire structure, a high-flux magnetic powder core, and a stacked capacitor structure. The multilayer spiral metal wire structure is arranged and connected in a radially nested manner, with the winding directions of the multilayer spiral metal wire structure being the same. The high-flux magnetic powder core is located in the central axial region of the multilayer spiral metal wire structure, and the initial permeability of the high-flux magnetic powder core is 147, and the saturation magnetic flux density is 1.5T. The stacked capacitor structure includes a dielectric layer with a relative permittivity greater than 4400 at room temperature and in the kHz frequency band. The stacked capacitor structure is located on top of the multilayer spiral metal wire structure and the high-flux magnetic powder core, and the... The metal electrodes of the stacked capacitor structure are perpendicular to the top surface of the high-flux magnetic powder core. The stacked capacitor structure is not in contact with the high-flux magnetic powder core. One of the metal electrodes of the stacked capacitor structure is electrically connected to the innermost spiral metal wire structure of the multi-layered spiral metal wire structure, and the other metal electrode is electrically connected to the outermost spiral metal wire structure of the multi-layered spiral metal wire structure. The transcranial magnetic stimulation coil is electrically connected to the pulse circuit system and is sleeved around the multi-layered spiral metal wire structure. The metamaterial resonator is not connected to the transcranial magnetic stimulation coil or the pulse circuit system. When an alternating current flows through the transcranial magnetic stimulation coil, it excites the resonance of the metamaterial resonator. The magnetic field generated by this resonance is used to stimulate the human brain. In this way, a strong magnetic field can be generated by exciting the resonant mode of the metamaterial resonator using the transcranial magnetic stimulation coil. A stronger magnetic field intensity can be generated at the same operating voltage and frequency, increasing the intracranial electric field intensity by more than 28%. This mechanism effectively reduces the operating voltage of the device at the same stimulation intensity, thereby effectively reducing the dependence on high-voltage drive circuits. Furthermore, with the voltage amplitude across the transcranial magnetic stimulation coil fixed, using a coil to excite a metamaterial resonator can effectively reduce the current in the coil compared to directly using a coil to generate a magnetic field, significantly reducing ohmic losses (by more than 50%), thereby better alleviating the heating problem of the stimulator. Furthermore, theoretical analysis of the equivalent circuit of the transcranial magnetic stimulation coil-excited resonator shows that, when the conjugate matching condition of the resonant wireless transmission system—where the transcranial magnetic stimulation coil excites a metamaterial resonator—is satisfied, the required series resonant capacitance on the coil side can be significantly reduced (down to less than 30 μF). This allows for a significant reduction in the size of the energy storage capacitor, a key factor driving the miniaturization and portability of the entire device. Furthermore, the design of embedding a metamaterial resonator within the figure-eight coil not only maintains its original focusing advantage, but also allows the metamaterial resonator to induce a redistribution of the electromagnetic field in space using its resonant modes, which helps improve the depth index of the stimulus. Attached Figure Description

[0015] Figure 1 A schematic diagram of the stimulator structure, consisting of a transcranial magnetic stimulation coil and a metamaterial resonator, in the transcranial magnetic stimulation device provided in an embodiment of the present invention. Figure 2 This is a schematic diagram of the transcranial magnetic stimulation device provided in an embodiment of the present invention in an application scenario; Figure 3 The equivalent circuit diagram of the transcranial magnetic stimulation coil and metamaterial resonator provided in the embodiments of the present invention; Figure 4 The curve showing the relationship between the magnetic induction intensity at the center of the bottom surface of a metamaterial resonator and the frequency when excited by a circular coil carrying a unit current. Figure 5 The curve showing the relationship between the magnetic induction intensity at the center of the bottom surface of a metamaterial resonator and the frequency when excited by a circular coil with voltage across the circuit containing the coil. Figure 6 The magnetic induction intensity distribution of the metamaterial resonator provided in the embodiment of the present invention in the longitudinal section (xz plane) under the excitation of a circular transcranial magnetic stimulation coil; Figure 7 The magnetic induction intensity distribution of the metamaterial resonator provided in the embodiment of the present invention in the longitudinal section (xy plane) under the excitation of a circular transcranial magnetic stimulation coil; Figure 8 The magnetic field strength distribution is shown in the cross-section (xy plane) 10 mm below the intersection of the two transcranial magnetic stimulation coils. Figure 9 The figure-eight coil is shown as the electric field intensity along the center line of a human brain sphere model decays with depth, with and without a resonator.

[0016] The objectives, features, and advantages of this invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0017] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The present invention will be described in detail below with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0018] In this embodiment of the invention, the term "and / or" describes the relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. The character " / " generally indicates that the preceding and following associated objects have an "or" relationship.

[0019] It should be noted that the terms "first," "second," etc., in the specification, claims, and drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0020] In this embodiment of the invention, the term "multiple" refers to two or more, and other quantifiers are similar.

[0021] In this invention, unless otherwise stated, directional terms such as "upper," "lower," "top," and "bottom" are generally used in relation to the direction shown in the accompanying drawings, or in relation to the vertical, perpendicular, or gravitational direction of the component itself; similarly, for ease of understanding and description, "inner" and "outer" refer to the inner and outer contours of each component itself, but the above directional terms are not intended to limit this invention.

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the various embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details are presented in the embodiments of the present invention to facilitate a better understanding of the invention. However, the technical solutions claimed in the present invention can be implemented even without these technical details and various variations and modifications based on the following embodiments. The division of the following embodiments is for ease of description and should not constitute any limitation on the specific implementation of the present invention. The various embodiments can be combined with and referenced by each other without contradiction.

[0023] Metamaterials are artificial structures composed of subwavelength scale units with specific structures. According to the equivalent medium theory, through specific design, electromagnetic metamaterials can have arbitrary permittivity and permeability, and possess exotic electromagnetic properties that natural materials do not have. Therefore, metamaterials can achieve higher degrees of freedom in the control of electromagnetic fields / electromagnetic waves.

[0024] However, at low frequencies, periodic metamaterial structures are no longer suitable due to their large size and losses. More compact metamaterial resonators have gradually attracted researchers' attention. Metamaterial resonators are subwavelength devices with specific resonant modes, composed of artificial structures made of materials such as metals and dielectrics. They resonate under the excitation of an electromagnetic field at a specific frequency, thereby inducing the spatial distribution of the electromagnetic field. Metamaterial resonators have been applied in technologies such as magnetic resonance imaging in the MHz band, but have not yet been applied in the field of transcranial magnetic stimulation (TMS) at even lower frequencies (kHz band). To reduce the resonant frequency of the metamaterial resonator to the kHz band while maintaining structural compactness, the metamaterial resonator provided in this invention uses a multi-layered spiral core to increase structural inductance, employs a high-dielectric-constant ceramic material as the dielectric layer 2, and designs a stacked structure to increase structural capacitance. This significantly reduces the operating frequency of the metamaterial resonator, enabling it to be applied to more low-frequency scenarios such as TMS.

[0025] Some solutions employ specific resonant circuit designs to drive coils and directly generate strong magnetic fields. Resonant circuits fall under the category of circuits, which are conductive loops composed of power sources, electrical / electronic components, and wires, used for the transmission and distribution of electrical energy, as well as the transmission and processing of signals. A resonant circuit is an AC circuit containing specific inductors, capacitors, and resistors. Under the excitation of an AC power source at a specific frequency, the voltage and current of the entire circuit reach phase, exhibiting pure resistance—that is, reaching a resonant state. Furthermore, methods that directly energize coils to generate magnetic fields to stimulate the human brain typically require applying extremely high voltages to the coils to achieve the stimulation threshold of transcranial magnetic stimulation (TMS), generating extremely high currents (on the order of kiloamperes). This results in high power consumption, low energy efficiency, and significant heat generation, and also requires large capacitors (providing capacitance ranging from tens to hundreds of microfarads). Some solutions use multiple resonant circuits to stimulate multiple coils. Although optimizing the circuit topology reduces the voltage / current required to generate the same stimulation intensity, it still directly uses coils to generate magnetic fields. The method used in this invention is fundamentally different.

[0026] Other proposals suggest transcranial magnetic stimulation systems based on the principle of magnetic resonance coupling or magnetic negative metamaterials. However, the structural design of the metamaterial resonator proposed in this invention is completely different, and the achievable stimulation intensity enhancement factor (under the same voltage / current conditions) far exceeds that of such transcranial magnetic stimulation systems based on the principle of magnetic resonance coupling.

[0027] Furthermore, compared to traditional transcranial magnetic stimulation systems based on the principle of magnetic resonance coupling or magnetic negative supermaterials, this invention increases the intracranial electric field intensity by more than 40% under the same voltage. While increasing the stimulation intensity and reducing the power supply voltage, the value of the resonant compensation capacitor required in series on the coil side can be significantly reduced (down to less than 30 μF). This significantly reduces the volume of the energy storage capacitor, which is a key factor driving the miniaturization and portability of the entire device.

[0028] Furthermore, transcranial magnetic stimulation (TMS) devices based on magnetic resonant coupling typically stimulate the human brain by using a source coil to excite a resonant coil, as illustrated in patent CN107469233A. However, the circuit containing the resonant coil in this device is connected to a lumped capacitance element. The TMS device of this invention stimulates the human brain by using a source coil to excite a metamaterial resonator. Moreover, the equivalent capacitance of the resonator provided by this invention is provided by the design of a multilayer capacitor structure and a high-dielectric ceramic material, not by a lumped capacitance element.

[0029] Furthermore, existing transcranial magnetic stimulation (TMS) devices based on magnetic resonant coupling have simple coil designs and lack optimization for coil winding losses. The TMS device of this invention considers the additional losses (or additional resistance) introduced by the skin effect and proximity effect in the metal wire at kHz frequencies, as well as the additional losses introduced by the coupling between the coil and the resonator. A detailed and comprehensive theoretical analysis and simulation optimization of the entire system are performed, thereby achieving better electromagnetic field enhancement and producing a higher stimulation intensity for the human brain.

[0030] Furthermore, the metamaterial resonator of the transcranial magnetic stimulation device of the present invention includes a high-flux magnetic powder core. The magnetic core enhances the coupling between the transcranial magnetic stimulation coil and the metamaterial resonator, while making the spatial distribution of the magnetic field more concentrated, thereby improving the magnetic field strength in local areas (especially the area near the bottom surface of the magnetic core).

[0031] Existing transcranial magnetic stimulation (TMS) devices based on magnetic resonant coupling, such as patent CN107469233A, treat the source coil and resonant coil as independent when designing circuit parameters and determining the resonant frequency, neglecting the strong coupling between them. This approach is flawed. The coupling between the source coil and the resonant coil causes the overall resonant frequency to deviate from the resonant frequency of the circuit containing both the source and resonant coils. The mutual inductance between them introduces impedance, reducing the current intensity in the coils per unit voltage, thus resulting in a lower stimulation intensity for the human brain. In determining the circuit parameters and resonant frequency, this invention treats the transcranial magnetic stimulation coil and the coupled metamaterial resonator as a whole, fully considering the effects of coupling. Without changing the resonator's structural parameters, it determines the overall resonant frequency of the coil and resonator after coupling and the series resonant capacitance required for the coil circuit based on the conjugate matching method (or the maximum power transfer theorem). This determines the source current frequency and series resonant capacitance that enable the metamaterial resonator to generate the strongest magnetic field. Therefore, compared with patent CN107469233A and other related patents on transcranial magnetic stimulation devices with magnetic resonance coupling, it can produce a stronger stimulation intensity.

[0032] To further verify the technical effects of this invention, this invention compares the stimulation intensity produced by two methods—including a resonant coil and not including a resonant coil (i.e., directly stimulating the human brain with a source coil)—with related patents on transcranial magnetic stimulation devices based on magnetic resonant coupling, under a fixed source coil current. For example: Patent CN107469233A describes a magnetic resonant coupled four-leaf coil where the magnetic field is doubled per unit current compared to a coil without a resonant coil. Patent CN107174741A describes a magnetic resonant coupling orthogonal figure-eight coil that includes a resonant coil, which, compared to a coil without a resonant coil, increases the magnetic field per unit current by 3 times, and in local areas by 3.6 times. Patent CN105435371A describes a magnetic resonant coupling figure-eight coil that includes a resonant coil, which, compared to a coil without a resonant coil, increases the local magnetic field per unit current by nearly nine times. The patent CN105251124A magnetic resonant coupling transcranial magnetic stimulation system, which includes a resonant coil, increases the local magnetic field per unit current by about 9 times compared to the system without a resonant coil. Patent CN119345611A proposes a transcranial magnetic stimulation coil design based on a magnetically negative metamaterial. This design constructs an electromagnetic metamaterial with an equivalent magnetic permeability of negative. Compared to direct coil stimulation, the stimulation intensity per unit current can be increased by about 2 times.

[0033] Experimental results show that the above patents do not increase the stimulation intensity by more than 10 times under a unit current.

[0034] The present invention provides the following results regarding the stimulation intensity produced by stimulating the human brain using a system that excites a resonator with a source coil and by directly stimulating the human brain with a source coil, under two conditions: fixed source coil current and fixed source coil circuit power supply voltage. When the source coil current is fixed, for example, when the amplitude (peak value) of the coil current is fixed at 100 A, the magnetic induction intensity at the center of the bottom surface of the resonator is strongest at the current frequency of 5.74 kHz, reaching 0.869 T. Directly using the source coil to excite the magnetic induction intensity at the center of the bottom surface of the human brain results in 20.6 mT, an improvement of about 42 times, which is much higher than previous patents.

[0035] Previous patents related to transcranial magnetic stimulation (TMS) devices based on magnetic resonant coupling rarely discussed the effect of increasing stimulation intensity under a fixed source coil circuit power supply voltage. However, increasing stimulation intensity under a fixed source coil circuit power supply voltage is crucial for designing low-voltage, low-power, miniaturized, and highly safe TMS devices. In the coupling system of the source coil and resonant coil, the mutual inductance between them causes the resonant coil to introduce additional impedance into the circuit containing the source coil. This introduced impedance increases significantly near the resonant coil's own resonant frequency, resulting in an extremely high power supply voltage required to fix the source coil current. Therefore, the stimulation intensity enhancement effect under a fixed current in previous patents related to TMS devices based on magnetic resonant coupling comes at the cost of a significantly higher source coil circuit power supply voltage, increasing the size and cost of the device's power supply and hindering miniaturization. This invention significantly improves upon this aspect.

[0036] This invention provides a transcranial magnetic stimulation device based on a metamaterial resonator to enhance the magnetic field, such as... Figure 1 As shown, the transcranial magnetic stimulation device includes a pulse circuit system, a metamaterial resonator, a transcranial magnetic stimulation coil 9, and a structural support (not shown in the figure).

[0037] The metamaterial resonator includes a multilayer spiral metal wire structure, a high-flux magnetic powder core 8, and a stacked capacitor structure.

[0038] The stacked capacitor structure includes a left electrode 1 and a right electrode 3. Multi-layered spiral metal wire structures are nested and connected radially, with the winding directions of the multi-layered spiral metal wire structures all in the same direction. The winding directions of the multi-layered spiral metal wire structures can all be clockwise or counterclockwise. Having the same winding direction allows the mutual inductance between different layers of spiral metal wire structures to positively contribute to the overall inductance, thereby achieving high inductance within a small volume and ensuring that the magnetic fields generated by the current in each layer are superimposed in phase axially to enhance the local magnetic field. Too few layers of the multi-layered spiral metal wire structure result in a small inductance, failing to reduce the resonant frequency; too many layers result in a significant increase in the overall resistance, leading to a low magnetic field strength per unit voltage. Therefore, in some embodiments, the multi-layered spiral metal wire structure has four layers, thus providing sufficient magnetic field strength while offering a large inductance, thereby achieving the optimal effect of reducing the resonant frequency.

[0039] Metamaterial resonators are artificial structural units composed of metals / dielectrics at the subwavelength scale, possessing various resonant modes. When excited by electromagnetic waves or fields of a specific frequency, the resonant modes of a metamaterial resonator are excited, inducing a redistribution of the electromagnetic field (near-field) within a localized region, particularly achieving a significant enhancement of the electromagnetic field in a specific area. Metamaterial resonators are generally passive devices. In the kHz frequency band, they can be used in conjunction with energized coils, utilizing the magnetic field generated by the coil to excite the resonant modes of the metamaterial resonator, thereby significantly enhancing the magnetic field strength in the target region (under the same current on the coil side, the magnetic field strength in some regions can be increased by tens of times). The enhancement effect of metamaterial resonators on the electromagnetic field depends on the field distribution of the resonant modes; therefore, by modifying the resonator's structural design, resonators with specific resonant mode field distributions can be designed.

[0040] Additionally, it should be noted that a certain spacing (generally 1 to 5 mm) needs to be set between different layers of spiral metal wire structures. This can control the additional losses caused by proximity effect, reduce structural resistance, and reduce the influence of parasitic capacitance.

[0041] The radius of the outermost spiral metal wire structure of the multi-layer spiral metal wire structure is r, and the axial height of the multi-layer spiral metal wire structure is h; the cross-sectional shape of the spiral metal wire in each layer of the spiral metal wire structure is rectangular, with a width of w and a thickness of d. m The radius of the i-th layer of the spiral metal wire structure is r i The number of turns in the i-th layer is N i In some embodiments, the spiral metal wire structure is made of solid copper flat wire, and the cross-sectional area of ​​the spiral metal wires in different layers is the same, with each layer having a rectangular cross-section.

[0042] Table 1 illustrates an embodiment of a multi-layered spiral metal wire structure. The structure consists of four layers, with all four layers wound in the same direction (either clockwise or counter-clockwise). The inner radii of the spiral metal wires, from smallest to largest, are r1, r2, r3, and r4, and the number of turns is N1, N2, N3, and N4, respectively. The different layers are connected sequentially: the bottom of the innermost spiral metal wire 4 is connected to the bottom of the second spiral structure 5; the top of the second spiral structure 5 is connected to the top of the third spiral structure 6; and the bottom of the third spiral structure 6 is connected to the bottom of the outermost spiral structure 7.

[0043] Table 1. An embodiment of a multilayer spiral metal wire structure. Table 2 illustrates one embodiment of the high-flux magnetic powder core 8. The high-flux magnetic powder core 8 is located in the central axial region of the multilayer spiral metal wire structure. In Table 2, the initial permeability of the high-flux magnetic powder core 8 is 147, and its saturation magnetic flux density is 1.5T. In some embodiments, the high-flux magnetic powder core 8 uses a mixture of iron-nickel powder, specifically High Flux 147mu. The high-flux magnetic powder core 8 made of the above-mentioned material has a high saturation magnetic flux density, making it more suitable for strong magnetic field stimulation scenarios. Placing it at the center of the multilayer spiral metal wire structure can significantly improve the overall inductance of the structure, while also making the spatial distribution of the magnetic field more concentrated, generating a stronger magnetic field in the target area under the same current conditions. The high-flux magnetic powder core 8 is cylindrical in shape with a height of h. c The radius is r c The distance between the top surface of the high-flux magnetic powder core 8 and the stacked capacitor structure is d. cl ;r c <r i <r i+1 h c <h, N i w < h, d m <r i+1 -r i .

[0044] Table 2 Parameters of an embodiment of high flux magnetic powder core 8 Table 3 illustrates one embodiment of the stacked capacitor structure. The stacked capacitor structure includes a dielectric layer 2 with a relative permittivity greater than 4400 at room temperature and in the kHz frequency band. The stacked capacitor structure is located on top of the multilayer spiral metal wire structure and the high-flux magnetic powder core 8. The stacked capacitor structure is not in contact with the high-flux magnetic powder core 8. One metal electrode of the stacked capacitor structure (e.g., the left electrode 1) is electrically connected to the innermost spiral metal wire structure 4 of the multilayer spiral metal wire structure, and the other metal electrode (e.g., the right electrode 3) is electrically connected to the outermost spiral metal wire structure 7 of the multilayer spiral metal wire structure. The stacked capacitor structure includes multiple ceramic dielectric sheets with silver-plated electrodes on both sides, which are alternately stacked in two interlocking comb-shaped metal electrodes. In some embodiments, the metal electrodes of the stacked capacitor structure (typically the left electrode 1 and the right electrode 3) are perpendicular to the top surface of the high-flux magnetic powder core 8, and the ceramic dielectric sheets are PZT ceramic. Two comb-shaped metal electrodes are respectively connected to silver-plated layers of the same polarity, equivalent to multiple parallel-plate capacitors connected in parallel, thereby providing high capacitance in a compact space. In some embodiments, the ceramic dielectric sheet of the multilayer capacitor structure is a PZT-5h ceramic sheet with a dielectric constant of 4500.

[0045] Table 3 Parameters of an embodiment of the multilayer capacitor structure Table 4 illustrates one embodiment of the transcranial magnetic stimulation coil 9. The transcranial magnetic stimulation coil 9 is a circular coil. The transcranial magnetic stimulation coil 9 is electrically connected to the pulse circuit system and is sleeved around the multi-layered spiral metal wire structure.

[0046] Table 4. Parameters of one embodiment of transcranial magnetic stimulation coil 9 When an alternating current is applied to the transcranial magnetic stimulation coil 9, the alternating magnetic field generated by the transcranial magnetic stimulation coil 9 excites the resonance of the metamaterial resonator. The resonant frequency of the metamaterial resonator is f1, where f1 is: (1) Among them, L s The equivalent inductance of the metamaterial resonator is the inductance provided by the multilayer spiral metal wires surrounding the magnetic core; C s The equivalent capacitance of the metamaterial resonator, i.e., the capacitance provided by the stacked capacitor structure.

[0047] like Figure 2As shown, the transcranial magnetic stimulation coil 9 includes a left circular transcranial magnetic stimulation coil 21 and a right circular transcranial magnetic stimulation coil 22, which together form a figure-eight transcranial magnetic stimulation coil. The figure-eight transcranial magnetic stimulation coil includes two adjacent circular coils (i.e., the left circular transcranial magnetic stimulation coil 21 and the right circular transcranial magnetic stimulation coil 22), with the current flowing through the two coils in opposite directions. The metamaterial resonator is two in number, with the two metamaterial resonators (left metamaterial resonator 11 and right metamaterial resonator 12) respectively housed within the corresponding left circular transcranial magnetic stimulation coil 21 and right circular transcranial magnetic stimulation coil 22. Correspondingly, the pulse circuit system includes two identical pulse circuits, each connected to one of the two circular coils (i.e., the left circular transcranial magnetic stimulation coil 21 and the right circular transcranial magnetic stimulation coil 22), with the current in the circuits containing the two circular coils having equal amplitude and opposite directions. The optimal frequency of the sinusoidal pulse current should correspond to the overall resonant frequency of the transcranial magnetic stimulation coil 9 after coupling with the metamaterial resonator. Specifically, the pulse circuit system includes two identical pulse circuits, which output sinusoidal pulses with adjustable pulse width; two circular coils are respectively connected to the two pulse circuits, and the electrical pulses that excite the two circular coils have sinusoidal waveforms; the current directions of the excitation pulses of the two circular coils are opposite; the frequency of the sinusoidal pulse matches the overall resonant frequency of the transcranial magnetic stimulation coil 9 and the metamaterial resonators (left metamaterial resonator 11 and right metamaterial resonator 12) after coupling.

[0048] The bottoms of the two circular coils form an adjustable preset angle, which is used to adapt to the surface of the human brain. The adjustable range of the preset angle is 0 to 25 degrees. The two circular coils are energized with currents in opposite directions, creating a high-intensity, highly focused magnetic field near their intersection. Preferably, the transcranial magnetic stimulation coil 9 is wound with low-AC-loss Litz wire and encapsulated with epoxy resin to enhance structural stability.

[0049] The metamaterial resonator is not electrically connected to the transcranial magnetic stimulation coil 9 and the pulse circuit system. When an alternating current is applied to the transcranial magnetic stimulation coil 9, the transcranial magnetic stimulation coil 9 and the metamaterial resonator as a whole are excited to resonate. The magnetic field generated by the resonance is used to stimulate the human brain.

[0050] The multi-layered spiral metal wire structure is wrapped around the insulating support, and the stacked capacitor structure and the high-flux magnetic powder core 8 are respectively fixed to the insulating support. The structural support can be, but is not limited to, made of plastic (such as nylon) through 3D printing. Preferably, the insulating structural support is made of lightweight, high-strength, high-temperature resistant, and low-expansion coefficient carbon fiber or other novel materials. The structural support allows for free adjustment of the included angle between the bottom surfaces of the two circular transcranial magnetic stimulation coils 9.

[0051] With the voltage across the circuit containing the transcranial magnetic stimulation coil 9 fixed, the current frequency at which the current amplitude on the metamaterial resonator reaches its maximum and the optimal series resonant capacitance on the coil side can be determined by equivalent circuit theory. Specifically, the resonant angular frequency after the transcranial magnetic stimulation coil 9 is coupled to the metamaterial resonator... and the capacitor C connected in series in the 9th circuit of the transcranial magnetic stimulation coil c It is determined according to the following calculation method: The equivalent circuit of the coupling system between the transcranial magnetic stimulation coil 9 and the metamaterial resonator is as follows: Figure 3 The total complex impedance on the coil side under steady-state conditions is: (2) Taking the transcranial magnetic stimulation coil as the source and the complex impedance introduced by the metamaterial resonator into the circuit containing the transcranial magnetic stimulation coil as the load, when the voltage across the circuit containing the transcranial magnetic stimulation coil is fixed, the magnetic field generated by the metamaterial resonator is strongest when the following condition is met: (3) (4) Calculated using formula (3) ; C is calculated using formula (4). c ; Z represents the total complex impedance on the coil side under steady-state conditions. Z c Let be the complex impedance of the circuit containing the coil. ; Z s The complex impedance of the equivalent circuit of the metamaterial resonator is given. ; L c The inductance of a single circular transcranial magnetic stimulation coil; C c The series capacitance of the circuit containing the coil; R c The equivalent series resistance of a single circular transcranial magnetic stimulation coil; L s The equivalent inductance of a metamaterial resonator; Cs The equivalent capacitance of the metamaterial resonator; R s This is the equivalent series resistance of the metamaterial resonator; M1 and These are the mutual inductance and mutual resistance of a single circular transcranial magnetic stimulation coil and its metamaterial resonator on the same side; M2 and These represent the mutual inductance and mutual resistance between two circular transcranial magnetic stimulation coils, respectively. M3 and These are the mutual inductance and mutual resistance of a single circular transcranial magnetic stimulation coil and its metamaterial resonator on the other side; M4 and These represent the mutual inductance and mutual resistance between two metamaterial resonators, respectively. This refers to the resonant angular frequency after the transcranial magnetic stimulation coil is coupled to the metamaterial resonator. ; f is the resonant frequency after the transcranial magnetic stimulation coil is coupled with the metamaterial resonator; i is the imaginary unit; Table 5 illustrates the simulation results of various electrical parameters of the transcranial magnetic stimulation coil 9 and the metamaterial resonator around 4.61 kHz when using the parameters provided in Tables 1 to 4.

[0052] Table 5. Electrical parameters of the transcranial magnetic stimulation coil 9 and the metamaterial resonator Based on the above results, the resonant frequency of the metamaterial resonator (considering the coupling between resonators) is 5.78 kHz. With a fixed current amplitude of 100 A in the circuit containing transcranial magnetic stimulation coil 9, the simulation results of the magnetic flux density versus frequency at 10 mm below the intersection of the two transcranial magnetic stimulation coils are as follows: Figure 4 The magnetic field is strongest at a current frequency of 5.74 kHz, reaching 0.869 T. If a metamaterial resonator is not placed inside the transcranial magnetic stimulation coil 9, and the current amplitude of the circuit containing the transcranial magnetic stimulation coil 9 is fixed at 100 A, the magnetic induction intensity at 10 mm below the intersection of the two transcranial magnetic stimulation coils is only 20.6 mT. It can be seen that adding a metamaterial resonator to the transcranial magnetic stimulation coil 9 under a fixed current condition can increase the magnetic field strength at a specific location by about 42 times.

[0053] With a voltage amplitude of 100 V across the fixed transcranial magnetic stimulation coil 9, and a series capacitor C in the circuit containing the transcranial magnetic stimulation coil 9... cWith both coils at 28.1 μF, the simulation results of the magnetic field strength versus frequency at 10 mm below the intersection of the two transcranial magnetic stimulation coils are as follows: Figure 5 The magnetic flux density is strongest at a current frequency of 4.56 kHz, reaching 0.949 T. If a metamaterial resonator is not placed inside the transcranial magnetic stimulation coil 9, the inductance (excluding the magnetic core) of the coil 9 is 12.4 μH, and the mutual inductance between the coils is 0.99 μH. Therefore, the series capacitance of the circuit containing the coils at the same frequency should be 21.0 μF. The magnetic flux density at 10 mm below the intersection of the two transcranial magnetic stimulation coils is 0.733 T. It is evident that adding a metamaterial resonator to the transcranial magnetic stimulation coil 9 can increase the magnetic field strength generated by the stimulator per unit voltage (by 29.5%). Simultaneously, the required matching capacitance of the transcranial magnetic stimulation coil 9 is significantly reduced, which is beneficial for minimizing the size of the circuit module.

[0054] Furthermore, when the voltage amplitude across the fixed coil is 100 V and no metamaterial resonator is placed inside the transcranial magnetic stimulation coil 9, the current amplitude in the coil reaches as high as 3209 A, and the heat generated per unit time under steady state is 161 kJ. When a metamaterial resonator is placed inside the transcranial magnetic stimulation coil 9, the current amplitudes in the coil and the resonator are 1605 A and 402 A, respectively, and the heat generated per unit time under steady state is 77 kJ. It can be seen that using a coil to excite a metamaterial resonator can effectively reduce the current in the coil compared to directly using a coil to generate a magnetic field, and the ohmic loss is reduced by 52%, thereby better alleviating the heating problem of the stimulator.

[0055] In some implementations, the resonant mode frequency and mode lifetime / linewidth after the transcranial magnetic stimulation coil 9 is coupled to the metamaterial resonator are determined as follows: The time-domain equation satisfied by the voltage across the circuit containing the coil and the equivalent capacitance of the metamaterial resonator is as follows: (5) in, ; Introducing state vectors: (6) Equation (4) can be transformed into: (7) Where X and C1 are the coefficient matrices introduced by the substitution; ; ; U Cc This refers to the voltage divided by the capacitance of the circular transcranial magnetic stimulation coil circuit; UCs The voltage divided by the equivalent capacitance of the metamaterial resonator circuit; R is the resistance matrix; C is the capacitance matrix; L is the inductance matrix; X is a coefficient matrix that satisfies ; C1 is the coefficient matrix, satisfying ; U C The vector is composed of the voltages obtained from the capacitance of the circular transcranial magnetic stimulation coil circuit and the equivalent capacitance of the metamaterial resonator circuit. U is the power supply voltage of the circular transcranial magnetic stimulation coil circuit; U is a vector consisting of the power supply voltages of the circular transcranial magnetic stimulation coil circuit and the metamaterial resonator circuit (here the metamaterial resonator is passive, and its equivalent circuit power supply voltage is 0); a is the state vector used to describe the resonant amplitude; t represents time.

[0056] matrix The real and imaginary parts are separated. The imaginary part is diagonalized, and the diagonal element is the two resonant angular frequencies after the transcranial magnetic stimulation coil is coupled with the metamaterial resonator. The real part is also transformed accordingly to obtain the lifetime / linewidth factor of the two coupling modes. The lower of the two resonant frequencies is taken as the frequency of the sine wave output by the pulse circuit system. It should be noted that metamaterial resonators may have multiple different resonant modes at higher frequencies. Since the current frequency of transcranial magnetic stimulation (TMS) is relatively low (kHz band) and the magnetic field penetration depth of the fundamental mode is the greatest, this invention only utilizes the fundamental mode of the metamaterial resonator to enhance the magnetic field. It is important to note that the orientation of the TMS coil 9 used to excite the resonator is not arbitrary. To ensure the mode is excited most effectively, the axis of the TMS coil 9 should be parallel to the axis of the helix of the metamaterial resonator.

[0057] Preferably, given the sinusoidal amplitude and pulse width of the pulse circuit system output, the curve of the current changing with time in the multilayer spiral metal wire structure of the transcranial magnetic stimulation coil and metamaterial resonator is determined according to formulas (6) and (7).

[0058] Unlike traditional transcranial magnetic stimulation (TMS) methods that optimize electromagnetic field distribution by altering coil design, this invention utilizes the metamaterial resonator to induce a spatial redistribution of the electromagnetic field through its resonant modes. Therefore, the method of using the TMS coil 9 to excite the metamaterial resonator and then using the metamaterial resonator to stimulate the human brain not only enhances the intensity of TMS but also alters the spatial distribution of the electromagnetic field, thereby helping to improve indicators such as the stimulation depth of the coil.

[0059] To further verify the effectiveness of the present invention, the following evaluation index was used: Stimulation intensity index Half-value depth Focus .

[0060] Stimulus intensity index The electric field strength is defined as the maximum value of the electric field strength in the human brain when a voltage of 100 V is applied to the circuit containing the coil. It is used to measure the ability of a stimulator to generate an electromagnetic field. Half-value depth Defined as the maximum stimulation intensity of the electric field in the human brain. The distance from half of the deepest point to the surface of the human brain; Focus Defined as ,in The electric field strength in the human brain is greater than the maximum stimulus intensity. The volume of half of the region. The smaller the value, the better the coil's focus on stimulating the human brain; conversely, the larger the value, the better. The larger the value, the worse the stimulus focus.

[0061] The electromagnetic field distribution generated by the transcranial magnetic stimulation coil 9 containing the metamaterial resonator can be solved using electromagnetic simulation software such as Comsol or CST.

[0062] Figure 6 The diagram illustrates the magnetic flux density distribution in a longitudinal section (xz plane) of the metamaterial resonator provided in this embodiment of the invention under excitation by a circular transcranial magnetic stimulation coil 9 (with a voltage of 100V across the coil circuit). Figure 7 This is a magnetic field strength distribution diagram in the longitudinal section (yz plane). Figure 8 This is a map showing the magnetic induction intensity distribution in a cross-section (xy plane) 10 mm below the intersection of two transcranial magnetic stimulation coils.

[0063] In electromagnetic simulation, a multi-layered spherical shell model can be used to simulate the human brain, and then the stimulation intensity, half-value depth, and focusing degree of the coil can be determined based on the simulation results.

[0064] The specific parameters of the human brain spherical model 10 are described as follows: The radius of the human brain spherical model 10 is 100 mm; The region corresponds to white matter, with an electrical conductivity of 0.126 S / m and a relative permittivity of 120; The region corresponds to gray matter, with an electrical conductivity of 0.276 S / m and a relative permittivity of 120; The region corresponds to gray matter, with an electrical conductivity of 1.654 S / m and a relative permittivity of 60; The region corresponds to the skull, with an electrical conductivity of 0.010 S / m and a relative permittivity of 80; The region corresponds to the skin, with a conductivity of 0.465 S / m and a relative permittivity of 120; Please see Figure 2 Two identical circular transcranial magnetic stimulation coils 9 (left circular transcranial magnetic stimulation coil 21 and right circular transcranial magnetic stimulation coil 22) are placed adjacent to each other and are supplied with currents of the same amplitude in opposite directions, forming a figure-eight coil. Figure 2 The white arrow in the middle indicates the direction of the current in the coil; In the simulation, the bottom surface of the left circular transcranial magnetic stimulation coil 21 and the bottom surface of the left metamaterial resonator 11 are located on the same plane, and the bottom surface of the right circular transcranial magnetic stimulation coil 22 and the bottom surface of the right metamaterial resonator 12 are located on the same plane. During stimulation, the distance between these two planes and the surface of the human brain is 5 mm. The two coils forming the figure-eight coil (left circular transcranial magnetic stimulation coil 21 and right circular transcranial magnetic stimulation coil 22) do not need to be placed parallel to each other. The planes on which their bases lie can have an angle (similar to a biconical coil) to allow them to be closer to the surface of the human brain, resulting in stronger and deeper stimulation. In some embodiments, the angle between the planes on which the bases of the two coils lie can be 40° (i.e., the angle between the plane on which the bases of the coils lie and the xy plane is 20°).

[0065] Table 6 is... Figure 2 The figure-eight coil shown presents simulation results for the stimulation intensity, half-value depth, and focusing degree of a multilayer spherical human brain model under two conditions: without a resonator and with a resonator.

[0066] Table 6 Simulation Results As can be seen from Table 6, when the voltage amplitude of the circuit where the transcranial magnetic stimulation coil 9 is located is fixed, placing a metamaterial resonator inside the transcranial magnetic stimulation coil 9 can increase the intracranial electric field intensity by 42.3%, significantly improve the half-value depth of stimulation, and also improve the focusing ability to a certain extent.

[0067] The decay curve of intracranial electric field intensity with depth is shown in the figure. Figure 9 As shown, Figure 9 The relationship between the electric field strength and depth on the intracranial central line (the line connecting the center of the figure-eight coil and the center of the human brain sphere model 10) is shown when the voltage amplitude of the circuit containing the transcranial magnetic stimulation coil 9 is 100 V and the frequency is 4.5 kHz, with and without a metamaterial resonator placed inside the transcranial magnetic stimulation coil 9.

[0068] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A transcranial magnetic stimulation device based on a metamaterial resonator to enhance the magnetic field, characterized in that, include: Pulse circuit system; Metamaterial resonators, including: A multi-layered spiral metal wire structure, which is nested and connected sequentially along the radial direction, with the winding directions of the multi-layered spiral metal wire structure being the same; A high-flux magnetic powder core is located in the central axial region of the multilayer helical metal wire structure. The initial permeability of the high-flux magnetic powder core is 147, and its saturation magnetic flux density is 1.5T. A multilayer capacitor structure includes a dielectric layer with a relative permittivity greater than 4400 at room temperature and in the kHz frequency band. The multilayer capacitor structure is located on top of the multilayer spiral metal wire structure and the high-flux magnetic powder core. The multilayer capacitor structure is not in contact with the high-flux magnetic powder core. One of the metal electrodes of the multilayer capacitor structure is electrically connected to the innermost spiral metal wire structure of the multilayer spiral metal wire structure, and the other metal electrode is electrically connected to the outermost spiral metal wire structure of the multilayer spiral metal wire structure. A transcranial magnetic stimulation coil is electrically connected to the pulse circuit system, and the transcranial magnetic stimulation coil is sleeved around the multi-layer spiral metal wire structure; The metamaterial resonator is not connected to the transcranial magnetic stimulation coil and the pulse circuit system. When an alternating current is applied to the transcranial magnetic stimulation coil, the metamaterial resonator is excited to resonate, and the magnetic field generated by the resonance is used to stimulate the human brain.

2. The transcranial magnetic stimulation device as described in claim 1, characterized in that, The multi-layer spiral metal wire structure has an axial height of h; the cross-sectional shape of the spiral metal wire in each layer of the spiral metal wire structure is rectangular, with a width of w and a thickness of d. m The inner radius of the i-th layer of the spiral metal wire structure is r. i The number of turns in the i-th layer is N i ; The high magnetic flux powder core is a cylinder with a height of h. c The radius is r c ; r c <r i <r i+1 ,h c ≤h,N i w<h,d m <r i+1 -r i 。 3. The transcranial magnetic stimulation device as described in claim 1, characterized in that, The transcranial magnetic stimulation coil is a figure-eight coil, which includes two adjacent circular coils with opposite current directions. The metamaterial resonator is of two types, and the two metamaterial resonators are respectively housed in corresponding transcranial magnetic stimulation coils.

4. The transcranial magnetic stimulation device as described in claim 3, characterized in that, The bottoms of the two circular coils form an adjustable preset angle, which is used to adapt to the surface of the human brain; The preset angle can be adjusted from 0 to 25 degrees.

5. The transcranial magnetic stimulation device as described in claim 3, characterized in that, The pulse circuit system includes two identical pulse generating circuits, which output sinusoidal waveform pulses with adjustable pulse width at a specific frequency. Two circular coils are connected to two sets of pulse generating circuits respectively, and the pulses that excite the two circular coils have a sinusoidal waveform; The excitation pulses of the two circular coils have opposite current directions; The frequency of the sinusoidal pulse matches the overall resonant frequency of the transcranial magnetic stimulation coil and the metamaterial resonator after coupling.

6. The transcranial magnetic stimulation device as described in claim 3, characterized in that, When an alternating current flows through the transcranial magnetic stimulation coil, the alternating magnetic field generated by the transcranial magnetic stimulation coil excites the resonance of the metamaterial resonator. The resonant frequency of the metamaterial resonator is f1, where f1 is: ； Among them, L s The equivalent inductance of the metamaterial resonator is the inductance provided by the multilayer spiral metal wires surrounding the magnetic core; C s The equivalent capacitance of the metamaterial resonator, i.e., the capacitance provided by the stacked capacitor structure.

7. The transcranial magnetic stimulation device as described in claim 1, characterized in that, The metamaterial resonator also includes an insulating support, the multilayer spiral metal wire structure is wrapped around the insulating support, and the stacked capacitor structure and the high-flux magnetic powder core are respectively fixed on the insulating support.

8. The transcranial magnetic stimulation device as described in claim 1, characterized in that, The stacked capacitor structure includes multiple ceramic dielectric sheets with silver-plated electrodes on both sides, which are alternately stacked in two interlocking comb-shaped metal electrodes.

9. The transcranial magnetic stimulation device as described in claim 1, characterized in that, The resonant angular frequency ω of the transcranial magnetic stimulation coil coupled with the metamaterial resonator and the capacitor C connected in series in the transcranial magnetic stimulation coil circuit of the pulse circuit system. c It is determined according to the following calculation method: The total complex impedance on the coil side under steady-state conditions is: ；（1） Taking the transcranial magnetic stimulation coil as the source and the complex impedance introduced by the metamaterial resonator into the circuit containing the transcranial magnetic stimulation coil as the load, when the voltage across the circuit containing the transcranial magnetic stimulation coil is fixed, the magnetic field generated by the metamaterial resonator is strongest when the following condition is met: ；（2） ； （3） ω is calculated using formula (2); C is calculated using formula (3). c ; Z represents the total complex impedance on the coil side under steady-state conditions. Z c Let be the complex impedance of the circuit containing the coil. ; Z s The complex impedance of the equivalent circuit of the metamaterial resonator is given. ; L c The inductance of a single circular transcranial magnetic stimulation coil; C c The series capacitance of the circuit containing the coil; R c The equivalent series resistance of a single circular transcranial magnetic stimulation coil; L s The equivalent inductance of a metamaterial resonator; C s The equivalent capacitance of the metamaterial resonator; R s This is the equivalent series resistance of the metamaterial resonator; M1 and χ1 are the mutual inductance and mutual resistance of a single circular transcranial magnetic stimulation coil and its metamaterial resonator on the same side, respectively. M2 and χ2 are the mutual inductance and mutual resistance between two circular transcranial magnetic stimulation coils, respectively; M3 and χ3 are the mutual inductance and mutual resistance of a single circular transcranial magnetic stimulation coil and its metamaterial resonator on the other side, respectively. M4 and χ4 are the mutual inductance and mutual resistance between two metamaterial resonators, respectively; ω is the resonant angular frequency after the transcranial magnetic stimulation coil is coupled with the metamaterial resonator, ω=2πf; f is the resonant frequency after the transcranial magnetic stimulation coil is coupled with the metamaterial resonator; i is the imaginary unit.

10. The transcranial magnetic stimulation device as described in claim 9, characterized in that, The frequency of the sine wave output by the pulse circuit system and the lifetime / linewidth of the coupling mode are determined using the following formulas: The time-domain equation satisfied by the voltage across the circuit containing the coil and the equivalent capacitance of the metamaterial resonator is as follows: ；（4） in, ; Introducing state vectors: ；（5） Equation (4) can be transformed into: ；（6） Where X and C1 are the coefficient matrices introduced by the substitution; ； ； matrix The real and imaginary parts are separated. The imaginary part is diagonalized, and the diagonal element is the two resonant angular frequencies after the transcranial magnetic stimulation coil is coupled with the metamaterial resonator. The real part is also transformed accordingly to obtain the lifetime / linewidth factor of the two coupling modes. The lower of the two resonant frequencies is taken as the frequency of the sine wave output by the pulse circuit system. U Cc This refers to the voltage divided by the capacitance of the circular transcranial magnetic stimulation coil circuit; U Cs The voltage divided by the equivalent capacitance of the metamaterial resonator circuit; R is the resistance matrix; C is the capacitance matrix; L is the inductance matrix; X is a coefficient matrix that satisfies ; C1 is the coefficient matrix, satisfying ; U C The vector is composed of the voltages obtained from the capacitance of the circular transcranial magnetic stimulation coil circuit and the equivalent capacitance of the metamaterial resonator circuit. U is the power supply voltage of the circular transcranial magnetic stimulation coil circuit; U is a vector consisting of the power supply voltages of the circular transcranial magnetic stimulation coil circuit and the metamaterial resonator circuit (here the metamaterial resonator is passive, and its equivalent circuit power supply voltage is 0); a is the state vector used to describe the resonant amplitude; t represents time.

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