A transcranial magnetic stimulation device, a transcranial magnetic stimulation system and a method

Abstract

The present application discloses a transcranial magnetic stimulation device, a transcranial magnetic stimulation system and a method, which include a stimulation driving control module and a magnetic signal generating component. The magnetic signal generating component is used to be fixedly connected to the head and emit electromagnetic waves to the target area. The magnetic signal generating component includes a first and a second electromagnetic generating coil groups, which respectively include two first coils and two second coils with the same structure, and respectively form a pair of dual-focus magnetic stimulation coil pairs to perform magnetic stimulation on the target area. Among them, the central axes of the two first coils and the two second coils coincide, and the diameters of the first coil and the second coil are different. The stimulation driving control module performs timing control of the driving current on the first coil or the second coil respectively according to the preset coil stimulation intensity and stimulation timing. Since the magnetic stimulation is precisely controlled by two groups of dual-focus magnetic stimulation coil groups, the transcranial magnetic stimulation is more accurate, the stimulation depth and the stimulation range are more controllable, and the complications caused by magnetic stimulation are greatly reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of biomedical engineering, and particularly relates to a transcranial magnetic stimulation device, a transcranial magnetic stimulation system and a method. Background Art

[0002] Transcranial Magnetic Stimulation (TMS) is an important technology in the field of biomedical engineering. It is a technology based on the principle of electromagnetic induction of the brain electric field. Through high-field pulsed electromagnetic fields, it can penetrate the skull and act on nerve tissues at deeper positions for nerve stimulation and nerve regulation. Moreover, it does not require a device to be installed by penetrating the skin, and has advantages such as non-invasive and painless. The magnetic field used for TMS can have an intensity and density sufficient to depolarize neurons. And when TMS pulses are repeatedly applied, when the parameters of magnetic stimulation (frequency, amplitude, pulse width, pulse width gradient, etc.) are selected, transcranial magnetic stimulation can regulate the excitability of the cerebral cortex, and even regulate the excitability of the cortex throughout the stimulation period. In the past few decades, the application of TMS in studying the cognition of various nervous system and mental diseases, the relationship between brain behavior and pathophysiology has increased rapidly.

[0003] In the existing transcranial magnetic stimulation systems applied in the prior art, during actual use, transcranial magnetic stimulation may have adverse side effects such as slight pain, discomfort, mental fluctuations, fainting, syncope, and even induce epileptic seizures. The main reasons for these adverse side effects are that the stimulation range area of TMS is large, and the selection of magnetic stimulation power and magnetic stimulation method is inappropriate, etc. Among them, the most important reason is that the magnetic stimulation target is not accurately positioned, and it cannot accurately target the magnetic stimulation target or area for accurate positioning, and thus cannot achieve accurate quantitative and range-defined magnetic stimulation. Summary of the Invention

[0004] The main technical problem to be solved by the present invention is how to achieve accurate quantitative, controllable stimulation depth and controllable stimulation range of magnetic stimulation during deep magnetic stimulation of transcranial magnetic stimulation.

[0005] According to a first aspect, in one embodiment, a transcranial magnetic stimulation device is provided, including a stimulation driving control module and a magnetic signal generating component;

[0006] The magnetic signal generating component is used to be fixedly connected to the head through a positioning and fixing connection device, and emit electromagnetic waves into the target area in the head to perform magnetic stimulation on the target area;

[0007] The magnetic signal generating component includes a first electromagnetic generating coil group and a second electromagnetic generating coil group;

[0008] The first electromagnetic generating coil group includes two first coils with the same structure. The two first coils are symmetrically arranged about the center on the positioning and fixing connection device, and the center of symmetry is located at the center point of the positioning and fixing connection device. The second electromagnetic generating coil group includes two second coils with the same structure. The two second coils are symmetrically arranged about the center on the positioning and fixing connection device, and the center of symmetry is located at the center point of the positioning and fixing connection device. The diameter of the second coil is smaller than that of the first coil.

[0009] The two first coils of the first electromagnetic generating coil group form a pair of dual-focus magnetic stimulation coils, which emit electromagnetic waves towards the center of symmetry to perform magnetic stimulation on the target area.

[0010] The two second coils of the second electromagnetic generating coil group form a pair of dual-focus magnetic stimulation coils, which emit electromagnetic waves towards the center of symmetry to perform magnetic stimulation on the target area.

[0011] The central axes of the two first coils coincide with the central axes of the two second coils.

[0012] The stimulation driving and control module is electrically connected to the two first coils of the first electromagnetic generating coil group and the two second coils of the second electromagnetic generating coil group respectively. The stimulation driving and control module is used to perform timing control of the driving current on the first coil and / or the second coil according to the preset coil stimulation intensity and stimulation timing sequence.

[0013] According to a second aspect, in an embodiment, a transcranial magnetic stimulation device is provided, which includes a stimulation driving and control module and a magnetic signal generating component.

[0014] The magnetic signal generating component is used to be fixedly connected to the head through the positioning and fixing connection device and emit electromagnetic waves into the target area in the head to perform magnetic stimulation on the target area.

[0015] The magnetic signal generating component includes three first electromagnetic generating coil groups. Each first electromagnetic generating coil group includes two first coils with the same structure. The two first coils are symmetrically arranged about the center on the positioning and fixing connection device, and the center of symmetry is located at the center point of the positioning and fixing connection device.

[0016] The central axes of the two first coils of each first electromagnetic generating coil group are coplanar.

[0017] The two first coils of each first electromagnetic generating coil group form a pair of dual-focus magnetic stimulation coils, which emit electromagnetic waves towards the center of symmetry to perform magnetic stimulation on the target area.

[0018] The stimulation driving and control module is electrically connected to the two first coils of each of the first electromagnetic coil groups; the stimulation driving and control module is configured to perform timing control of the driving current on the two first coils according to a preset coil stimulation intensity and stimulation timing.

[0019] According to a third aspect, in an embodiment, a transcranial magnetic stimulation device is provided, including a stimulation driving and control module and a magnetic signal generating component;

[0020] The magnetic signal generating component is configured to be fixedly connected to the head through a positioning and fixing connection device, and emit electromagnetic waves into a target area in the head to perform magnetic stimulation on the target area;

[0021] The magnetic signal generating component includes four first electromagnetic coil groups; each of the first electromagnetic coil groups includes two first coils with the same structure, and the two first coils are symmetrically arranged about a center on the positioning and fixing connection device, and the center of symmetry is located at the center point of the positioning and fixing connection device;

[0022] The outer circles of one of the first coils in the four first electromagnetic coil groups have a common tangent point;

[0023] The two first coils of each of the first electromagnetic coil groups form a pair of dual-focus magnetic stimulation coil pairs, and emit electromagnetic waves towards the center of symmetry to perform magnetic stimulation on the target area;

[0024] The stimulation driving and control module is electrically connected to the two first coils of each of the first electromagnetic coil groups; the stimulation driving and control module is configured to perform timing control of the driving current on the two first coils according to a preset coil stimulation intensity and stimulation timing.

[0025] According to a fourth aspect, in an embodiment, a transcranial magnetic stimulation system is provided, including:

[0026] An image acquisition module, configured to acquire medical image data; the medical image data includes images of a target area to be magnetically stimulated inside the head and images of a marker area for target positioning;

[0027] A model reconstruction module, configured to perform three-dimensional reconstruction on the medical image data to obtain a virtual three-dimensional model; the virtual three-dimensional model includes a three-dimensional model of the target area after three-dimensional reconstruction of the target area, and the virtual three-dimensional model further includes a three-dimensional model of the marker area after three-dimensional reconstruction of the marker area;

[0028] A positioning and fixing connection device, configured to establish a spatial positioning coordinate system and fixedly connect the head in the spatial positioning coordinate system;

[0029] A target point coordinate acquisition module, configured to establish a correspondence between the three-dimensional model of the landmark area in the virtual three-dimensional model and the landmark area in the spatial positioning coordinate system, and based on the spatial position relationship between the three-dimensional model of the landmark area and the three-dimensional model of the target area in the virtual three-dimensional model, fixedly set the target area to be magnetically stimulated inside the skull at the center point of the positioning and fixing connection device, and use this center point as the target coordinate;

[0030] It further includes the transcranial magnetic stimulation device according to the first aspect, the second aspect or the third aspect; the transcranial magnetic stimulation device is configured to emit electromagnetic waves to the target area to perform magnetic stimulation on the target area.

[0031] According to the fifth aspect, in one embodiment, a transcranial magnetic stimulation method is provided, including:

[0032] Obtain medical image data; the medical image data includes images of the target area to be magnetically stimulated inside the skull and images of the landmark area for target positioning;

[0033] Perform three-dimensional reconstruction on the medical image data to obtain a virtual three-dimensional model; the virtual three-dimensional model includes the three-dimensional model of the target area after three-dimensional reconstruction of the target area, and the virtual three-dimensional model further includes the three-dimensional model of the landmark area after three-dimensional reconstruction of the landmark area;

[0034] Establish a spatial positioning coordinate system through a positioning and fixing connection device, and fixedly connect the skull in the spatial positioning coordinate system;

[0035] Establish a correspondence between the three-dimensional model of the landmark area in the virtual three-dimensional model and the landmark area in the spatial positioning coordinate system, and then based on the spatial position relationship between the three-dimensional model of the landmark area and the three-dimensional model of the target area in the virtual three-dimensional model, fixedly set the target area to be magnetically stimulated inside the skull at the center point of the positioning and fixing connection device, and use this center point as the target coordinate;

[0036] Fix the transcranial magnetic stimulation device to the positioning and fixing connection device;

[0037] Emit electromagnetic waves to the target area through the transcranial magnetic stimulation device to perform magnetic stimulation on the target area.

[0038] According to the transcranial magnetic stimulation device of the above embodiment, since the magnetic stimulation is precisely controlled by two groups of dual-focus magnetic stimulation coil groups, the transcranial magnetic stimulation is more accurate, the stimulation range is more controllable, and the complications caused by magnetic stimulation are greatly reduced.

[0039] According to the transcranial magnetic stimulation system of the above embodiments, since the target area in the depth of the brain is accurately positioned based on medical images, and then the magnetic stimulation intensity is accurately controlled by the dual-focus magnetic stimulation coil, the transcranial magnetic stimulation is more accurate and the stimulation range is more controllable. On the premise of greatly improving the treatment effect of transcranial magnetic stimulation, the complications caused by magnetic stimulation are reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a schematic structural connection diagram of a transcranial magnetic stimulation system in an embodiment;

[0041] Figure 2 It is a schematic structural connection diagram of a transcranial magnetic stimulation device in an embodiment;

[0042] Figure 3 It is a schematic structural diagram of a magnetic signal generating component in an embodiment;

[0043] Figure 4 It is a schematic structural connection diagram of a transcranial magnetic stimulation device in an embodiment;

[0044] Figure 5 It is a schematic structural diagram of a positioning and fixing connection device in an embodiment;

[0045] Figure 6 It is a schematic structural diagram of a circular guide rail in an embodiment;

[0046] Figure 7 It is a schematic flowchart of a transcranial magnetic stimulation method in an embodiment;

[0047] Figure 8 It is a schematic structural diagram of a magnetic signal generating component in another embodiment;

[0048] Figure 9 It is a schematic structural diagram of a magnetic signal generating component in another embodiment;

[0049] Figure 10 It is a schematic diagram of timing control and driving of a transcranial magnetic stimulation device in an example;

[0050] Figure 11 It is a schematic structural connection diagram of a central control system in another example;

[0051] Figure 12 It is a schematic flowchart of a multi-objective optimization algorithm in another embodiment;

[0052] Figure 13 It is a schematic diagram of transcranial magnetic stimulation in an embodiment;

[0053] Figure 14 It is a schematic diagram of magnetic stimulation timing control of a magnetic stimulation device in an embodiment;

[0054] Figure 15 Schematic diagram of the connection of the spherical fixing bracket in an embodiment;

[0055] Figure 16 Schematic diagram of the connection of the spherical fixing bracket in an embodiment. Detailed implementation manners

[0056] The present invention will be further described in detail below in conjunction with the accompanying drawings through specific implementation manners. Similar elements in different implementation manners are labeled with related similar element numbers. In the following implementation manners, many detailed descriptions are provided to enable a better understanding of the present application. However, those skilled in the art can easily recognize that some of the features can be omitted in different situations, or can be replaced by other elements, materials, or methods. In some cases, some operations related to the present application are not shown or described in the specification to avoid overwhelming the core part of the present application with excessive descriptions. For those skilled in the art, it is not necessary to describe these related operations in detail, and they can fully understand the related operations based on the description in the specification and general technical knowledge in the art.

[0057] In addition, the features, operations, or characteristics described in the specification can be combined in any suitable manner to form various implementation manners. At the same time, the steps or actions in the method description can also be reordered or adjusted in a manner obvious to those skilled in the art. Therefore, the various sequences in the specification and drawings are only for clearly describing a certain embodiment and do not mean that they are the necessary sequences, unless it is stated that a certain sequence must be followed.

[0058] The serial numbers assigned to the components herein, such as "first", "second", etc., are only used to distinguish the described objects and do not have any sequential or technical meanings. And the "connection" and "coupling" mentioned in the present application, unless otherwise specified, both include direct and indirect connections (couplings).

[0059] In the prior art, the usual depth of transcranial magnetic brain stimulation is generally about 1 - 3 centimeters, which can only stimulate the superficial regions of the brain and is difficult to reach the deep regions of the brain such as the frontal lobe, thalamus, cingulate gyrus, putamen, caudate nucleus, hippocampus, ventral striatum, and amygdala, or it is difficult to perform precise magnetic stimulation on the deep regions of the brain. Just by increasing the magnetic field intensity of the transcranial magnetic stimulation coil, adverse effects such as headache, fainting, and even induced epilepsy limit the application of transcranial magnetic brain stimulation. It is of great significance to urgently develop a new type of transcranial magnetic stimulation device with the ability of deep brain magnetic stimulation or deep focused magnetic stimulation function.

[0060] In TMS technology, brief magnetic pulses are used to cause depolarization of targeted neurons in the brain using Faraday's law of electromagnetic induction. When TMS is performed in a repetitive manner (termed rTMS), long-term potentiation-like or depression-like effects can be achieved. Conventional magnetic stimulation techniques and coils are mostly designed for surface stimulation of brain tissue but generally cannot deliver deeper stimulation. Since surface stimulation does not elicit effective stimulation of the ventral prefrontal cortex and other reward- and emotion-related brain structures such as the nucleus accumbens (ventral striatum), it is predictable that deeper brain stimulation may be more effective in treating major depressive disorder and other psychiatric and neurological diseases. Stimulating deep brain regions (dTMS), termed deep TMS, requires high intensity and accuracy, which cannot be achieved by current available conventional magnetic stimulators using standard coil configurations without causing undesirable side effects such as seizures or other problems associated with overstimulating cortical regions. In the past, the rTMS procedure could not directly stimulate targets more than 2 cm below the skull surface. Deep rTMS technology is being developed to improve the depth penetration of the electromagnetic field using H-coils, where multiple windings are arranged such that the magnetic fields generated thereby are summed together to allow direct simulation up to 4 cm below the skull surface.

[0061] Over the past decade, advances in functional imaging have identified specific brain regions with altered activity and volume associated with specific psychiatric symptoms and signs, which may bridge the theoretical gap between the diseases of psychiatry and the diseases of neurology for both patients and caregivers (Downar and Daskalakis 2013; Zhang et al., 2014). Corresponding advances in bioengineering have enabled non-invasive modulation of these altered brain regions via dTMS, thus forming an effective and logical treatment widely used in psychiatric patients and overall reducing the stigma of mental illness.

[0062] Although deep stimulation can also be accomplished with large circular coils or double-cone coils, their electromagnetic fields decay more severely than those of H-coils and to reach deep targets, higher intensities must be used on the surface than with H-coils (Roth et al., 2007; Pell et al., 2011). Higher intensities may be unpleasant and potentially unsafe for patients. The H-coil stimulates a wider area than the figure-eight coil, which eliminates the need for imaging and neuronavigation; without navigation, conventional rTMS misses the target in 27 - 32% of patients, making conventional rTMS treatment expensive due to the high number needed to achieve remission (number needed to treat, NNT) (Johnson et al., 2013; George et al., 2010). The H-coil stimulates a larger area (18 cm compared to 3 cm for conventional coils) 3 compared to 3 cm for conventional coils, it is 18 cm3 ) and the ability of deeper structures are the reasons for effectively treating dTMS synchronously with the H-coil.

[0063] In an embodiment of the present invention, a transcranial magnetic stimulation system is disclosed, which includes an image acquisition module, a model reconstruction module, a positioning and fixing connection device, a target coordinate acquisition module, and a magnetic stimulation device. The image acquisition module is used to acquire medical image data, the model reconstruction module is used to perform three-dimensional reconstruction on the medical image data to obtain a virtual three-dimensional model, the positioning and fixing connection device is used to establish a spatial positioning coordinate system and fix and connect the head in the spatial positioning coordinate system, the target coordinate acquisition module is used to obtain the coordinate values of the target area to be magnetically stimulated inside the head in the spatial positioning coordinate system according to the virtual three-dimensional model, and the transcranial magnetic stimulation device is used to perform magnetic stimulation on the target area. Due to the precise positioning of the target area in the depth of the brain based on medical images and the precise control of the magnetic stimulation intensity through the dual-focus magnetic stimulation coil, the transcranial magnetic stimulation is more accurate and the stimulation range is more controllable. On the premise of greatly improving the treatment effect of transcranial magnetic stimulation, the complications caused by magnetic stimulation are reduced, which is of great significance in the research of brain science and neuroscience.

[0064] Embodiment 1

[0065] Please refer to Figure 1 , which is a schematic structural connection diagram of a transcranial magnetic stimulation system in an embodiment. The transcranial magnetic stimulation system includes an image acquisition module 1, a model reconstruction module 2, a positioning and fixing connection device 3, a target coordinate acquisition module 4, and a transcranial magnetic stimulation device 5. The image acquisition module 1 is used to acquire medical image data. The medical image data includes the images of the target area to be magnetically stimulated inside the head and the images of the marker area for target positioning. The model reconstruction module 2 is used to perform three-dimensional reconstruction on the medical image data to obtain a virtual three-dimensional model. The virtual three-dimensional model includes the three-dimensional model of the target area after three-dimensional reconstruction of the target area, and the virtual three-dimensional model also includes the three-dimensional model of the marker area after three-dimensional reconstruction of the marker area. The positioning and fixing connection device 3 is used to establish a spatial positioning coordinate system and fix and connect the head in the spatial positioning coordinate system. The target coordinate acquisition module 4 is used to establish a correspondence between the three-dimensional model of the marker area in the virtual three-dimensional model and the marker area in the spatial positioning coordinate system, and based on the spatial position relationship between the three-dimensional model of the marker area and the three-dimensional model of the target area in the virtual three-dimensional model, fix the target area to be magnetically stimulated inside the head at the center point of the positioning and fixing connection device, and use this center point as the target coordinate. The transcranial magnetic stimulation device 5 is used to emit electromagnetic waves to the target area to perform magnetic stimulation on the target area.

[0066] Please refer to Figure 2, which is a schematic structural connection diagram of a transcranial magnetic stimulation device in an embodiment. The transcranial magnetic stimulation device 5 includes a stimulation driving control module 51 and a magnetic signal generating component 52. The magnetic signal generating component 52 is used to be fixedly connected to the head through a positioning and fixing connection device 3 and emit electromagnetic waves into the target area in the head to perform magnetic stimulation on the target area.

[0067] Please refer to Figure 3 , which is a schematic structural diagram of a magnetic signal generating component in an embodiment. The magnetic signal generating component includes a first electromagnetic generating coil group and a second electromagnetic generating coil group. The first electromagnetic generating coil group includes two first coils 11 with the same structure. The two first coils 11 are symmetrically arranged about the center on the positioning and fixing connection device 3, and the center of symmetry is located at the center point 10 of the positioning and fixing connection device 3. The second electromagnetic generating coil group includes two second coils 12 with the same structure. The two second coils 12 are symmetrically arranged about the center on the positioning and fixing connection device 3, and the center of symmetry is located at the center point 10 of the positioning and fixing connection device 3. The diameter of the second coil 12 is smaller than that of the first coil 11. The two first coils 11 of the first electromagnetic generating coil group form a pair of dual-focus magnetic stimulation coil pairs to emit electromagnetic waves to the center of symmetry to perform magnetic stimulation on the target area. The two second coils 12 of the second electromagnetic generating coil group form a pair of dual-focus magnetic stimulation coil pairs to emit electromagnetic waves to the center of symmetry to perform magnetic stimulation on the target area. The central axes of the two first coils 11 coincide with the central axes of the two second coils 12. The stimulation driving control module 51 is electrically connected to the two first coils 11 of the first electromagnetic generating coil group and the two second coils 12 of the second electromagnetic generating coil group respectively. The stimulation driving control module 51 is used to perform timing control of the driving current on the first coil and / or the second coil according to a preset coil stimulation intensity and stimulation timing.

[0068] Please refer to Figure 4 , which is a schematic structural connection diagram of a transcranial magnetic stimulation device in an embodiment. In one embodiment, an enhanced transcranial magnetic stimulation coil group (such as the first electromagnetic generating coil group) is formed by multiple coils with a specific layout to achieve enhanced magnetic stimulation of brain tissues at a specific depth. By using multiple coils arranged at specific positions to form a compensating transcranial magnetic stimulation coil group (such as the second electromagnetic generating coil group), it is possible to achieve a leading preventive stimulation of the cerebral cortex and adjacent tissues on the path between the enhanced transcranial magnetic stimulation coil and the target site, modulate the excitability and inhibitory properties of the cortical tissue, and prevent epilepsy and other adverse side effects caused by the focused stimulation of the enhanced transcranial magnetic stimulation coil group on the target area.

[0069] The stimulation-driven control module includes an enhanced transcranial magnetic stimulation coil group, a compensating transcranial magnetic stimulation coil group, a magnetoencephalogram detection device, a transcranial magnetic coil control driving device, and a central control system module. The enhanced transcranial magnetic stimulation coil group realizes enhanced and focused stimulation of deeper target parts of the brain. The compensating transcranial magnetic stimulation coil group can realize the leading preventive stimulation of the cerebral cortex on the path between the enhanced transcranial magnetic stimulation coil group and the target part, modulate the excitability and inhibitory of the cortical tissue, and prevent epilepsy and other adverse side effects caused by the focused stimulation of the enhanced transcranial magnetic stimulation coil group on the target area. The magnetoencephalogram detection device detects the magnetic view of the brain to guide the position arrangement and excitation of the enhanced transcranial magnetic stimulation coil group and the compensating transcranial magnetic stimulation coil group. The transcranial magnetic control driving device is responsible for driving and timing control of the enhanced transcranial magnetic stimulation coil group and the compensating transcranial magnetic stimulation coil group. The central control system is responsible for the operation of the entire enhanced deep-focus transcranial magnetic stimulation device.

[0070] In one embodiment, the enhanced transcranial magnetic stimulation coil and the compensating transcranial magnetic stimulation coil group adopt multiple working modes. Preferably, in Mode 1, the compensating transcranial magnetic stimulation coil group stimulates alone, mainly used for the restorative magnetic stimulation of the deep target brain area after the enhanced transcranial magnetic stimulation coil stimulates. Preferably, in Mode 2, it is an asynchronous stimulation mode of the enhanced transcranial magnetic stimulation coil and the compensating transcranial magnetic stimulation coil group. The compensating transcranial magnetic stimulation coil group first stimulates a certain amount of magnetic pulses alone, generally 100 - 300 pulses. Immediately afterwards, the enhanced transcranial magnetic stimulation coil stimulates a certain amount of stimulation pulses alone, generally more than 1000 pulses. Finally, the compensating transcranial magnetic stimulation coil group stimulates a certain amount of stimulation pulses alone again, generally not less than 500 pulses. This mode is generally applied in the early and late stages of treatment. Preferably, in Mode 3, it is a synchronous stimulation mode of the enhanced transcranial magnetic stimulation coil and the compensating transcranial magnetic stimulation coil group. In this mode, the enhanced transcranial magnetic stimulation coil and the compensating transcranial magnetic stimulation coil group stimulate the target area simultaneously. There are no strict requirements for the stimulation modes (frequency, intensity, number of pulses, etc.) of the enhanced transcranial magnetic stimulation coil and the compensating transcranial magnetic stimulation coil group. As long as the stimulation magnetic pulses of the compensating transcranial magnetic stimulation coil group are 0.35 pulse widths - 0.75 pulse widths ahead of the stimulation magnetic pulses of the enhanced transcranial magnetic stimulation coil, it can realize the pre-stimulation of the deep target brain area by the compensating transcranial magnetic stimulation coil group and the effective superposition of the stimulation of the enhanced transcranial magnetic stimulation coil, realize the enhanced stimulation of the deep target brain area, and also realize the pre-stimulation of the adjacent area of the deep target brain area by the compensating transcranial magnetic stimulation coil group, and trigger the propagation of the adjacent expected stimulation effect to the deep target brain area, and then realize the effective superposition with the subsequent stimulation of the enhanced transcranial magnetic stimulation coil, realize the enhanced stimulation of the deep target brain area. This mode is preferably applied in the middle stage of treatment.

[0071] In one embodiment, the effective diameter of the first coil is 200 mm, the size of the copper wire wound around the coil is 3 ✕ 2 mm², and the number of turns is 20 - 60 turns.

[0072] Please refer to Figure 5 , which is a schematic structural diagram of a positioning and fixing connection device in an embodiment. The positioning and fixing connection device includes a spherical fixing frame that can be disassembled into two identical hemispherical shapes. At least one circular guide rail 31 is provided on the spherical fixing frame, and the center of each circular guide rail 31 is located on the same straight line passing through the center point of the spherical fixing frame. The first electromagnetic generating coil group is fixedly connected to the positioning and fixing connection device through the circular guide rail 31.

[0073] In one embodiment, three circular guide rails 31 are provided on the spherical fixing frame, and the circular planes where each circular guide rail 31 is located form an angle of 60 degrees with each other.

[0074] Please refer to Figure 6 , which is a schematic structural diagram of a circular guide rail in an embodiment. At least two coil fixing interfaces 32 are provided on each circular guide rail 31, and each coil fixing interface 32 is evenly distributed on the circular guide rail 31. The coil fixing interface 32 is used to fixedly connect the first coil and the circular guide rail 31.

[0075] In one embodiment, the shape of the first coil is oval, circular or figure-eight. In one embodiment, the shape of the second coil is oval, circular or figure-eight.

[0076] In one embodiment, the transcranial magnetic stimulation device is used to perform timing control of the driving current on two first coils or one of the first coils simultaneously according to a preset coil stimulation intensity and stimulation timing sequence. The acquisition formula for the coil stimulation intensity includes:

[0077] B = 0.5×μ 0 ×N×I×R 2 ×[R 2 + (d / 2 + x) 2 -（3 / 2） ;

[0078] μ 0 = 4×π×10 -7 Tm / A;

[0079] wherein, N is the number of turns of the first coil, I is the coil current, R is the radius of the effective equivalent circular area of the first coil, x is the distance from the central symmetry point of the first coil to the center of the effective circle of the first coil, and d is the width of the first coil.

[0080] Please refer to Figure 7 , which is a schematic flowchart of a transcranial magnetic stimulation method in an embodiment. In one embodiment of the present application, a transcranial magnetic stimulation method is also disclosed, including:​

[0081] Step 110, obtain medical image data.

[0082] The medical image data includes the image of the target area to be magnetically stimulated inside the skull and the image of the landmark area for target positioning.

[0083] Step 120, obtain a virtual three-dimensional model.

[0084] Perform three-dimensional reconstruction on the medical image data to obtain a virtual three-dimensional model. The virtual three-dimensional model includes the three-dimensional model of the target area after three-dimensional reconstruction of the target area, and the virtual three-dimensional model also includes the three-dimensional model of the landmark area after three-dimensional reconstruction of the landmark area.

[0085] Step 130, establish a spatial positioning coordinate system.

[0086] Establish a spatial positioning coordinate system through a positioning and fixing connection device, and fix the skull in the spatial positioning coordinate system.

[0087] Step 140, obtain the target position.

[0088] Establish a corresponding relationship between the three-dimensional model of the landmark area in the virtual three-dimensional model and the landmark area in the spatial positioning coordinate system. Then, based on the spatial position relationship between the three-dimensional model of the landmark area and the three-dimensional model of the target area in the virtual three-dimensional model, fix the target area to be magnetically stimulated inside the skull at the center point of the positioning and fixing connection device, and use this center point as the target position.

[0089] Step 150, connect the transcranial magnetic stimulation device.

[0090] Fix and connect the transcranial magnetic stimulation device to the positioning and fixing connection device.

[0091] Step 160, start magnetic stimulation.

[0092] Emit electromagnetic waves from the transcranial magnetic stimulation device to the center point of the positioning and fixing connection device to perform magnetic stimulation on the target area.

[0093] In the embodiment of the present application, the disclosed transcranial magnetic stimulation method first performs three-dimensional reconstruction on the acquired medical image data; then establishes a corresponding relationship between the reconstructed virtual three-dimensional model and the spatial positioning coordinate system of the positioning and fixing connection device; then, according to the spatial position relationship between the landmark area three-dimensional model and the target area three-dimensional model in the virtual three-dimensional model, sets the target area to be magnetically stimulated inside the skull at the center point of the positioning and fixing connection device; finally, fixedly connects the transcranial magnetic stimulation device to the positioning and fixing connection device, so as to emit electromagnetic waves from the transcranial magnetic stimulation device to the center point of the positioning and fixing connection device to achieve magnetic stimulation of the target area. Since the target area deep in the brain is accurately positioned based on medical images, and the magnetic stimulation intensity is precisely controlled by the dual-focus magnetic stimulation coil, the transcranial magnetic stimulation is more accurate, and the stimulation depth and range are more controllable. On the premise of greatly improving the treatment effect of transcranial magnetic stimulation, the complications caused by magnetic stimulation are reduced.

[0094] The transcranial magnetic stimulation device disclosed in this embodiment includes a stimulation driving control module and a magnetic signal generating component. The magnetic signal generating component is used to be fixedly connected to the skull and emit electromagnetic waves to the target area. The magnetic signal generating component includes a first and a second electromagnetic generating coil groups, each of which includes two structurally identical first coils and second coils, and respectively constitutes a pair of dual-focus magnetic stimulation coil pairs to perform magnetic stimulation on the target area. Among them, the central axes of the two first coils and the two second coils coincide, and the diameters of the first coil and the second coil are different. The stimulation driving control module performs sequential control of the driving current on the first coil or the second coil according to the preset coil stimulation intensity and stimulation timing. Since the magnetic stimulation is precisely controlled by two sets of dual-focus magnetic stimulation coil groups, the transcranial magnetic stimulation is more accurate, the stimulation range is more controllable, and the complications caused by magnetic stimulation are greatly reduced.

[0095] Embodiment Two

[0096] Please refer to Figure 8, which is a schematic structural diagram of the magnetic signal generating component in another embodiment. The transcranial magnetic stimulation device includes a stimulation driving control module and a magnetic signal generating component. The magnetic signal generating component is used to be fixedly connected to the head through a positioning and fixing connection device, and emit electromagnetic waves into the target area in the head to perform magnetic stimulation on the target area. The magnetic signal generating component includes three first electromagnetic generating coil groups. Each first electromagnetic generating coil group includes two first coils 11 with the same structure. The two first coils 11 are symmetrically arranged on the positioning and fixing connection device 3, and the center of symmetry is located at the center point of the positioning and fixing connection device 3. The central axes of the two first coils 11 in the three first electromagnetic generating coil groups are coplanar. The two first coils 11 in each first electromagnetic generating coil group form a dual-focus magnetic stimulation coil pair to emit electromagnetic waves to the center of symmetry to perform magnetic stimulation on the target area. The stimulation driving control module is electrically connected to the two first coils 11 in each first electromagnetic generating coil group respectively. The stimulation driving control module is used to perform timing control of the driving current on each first coil 11 according to the preset coil stimulation intensity and stimulation timing.

[0097] Embodiment III

[0098] Please refer to Figure 9 , which is a schematic structural diagram of the magnetic signal generating component in another embodiment. The transcranial magnetic stimulation device includes a stimulation driving control module and a magnetic signal generating component. The magnetic signal generating component is used to be fixedly connected to the head through a positioning and fixing connection device, and emit electromagnetic waves into the target area in the head to perform magnetic stimulation on the target area. The magnetic signal generating component includes four first electromagnetic generating coil groups. Each first electromagnetic generating coil group includes two first coils 11 with the same structure. The two first coils 11 are symmetrically arranged on the positioning and fixing connection device 3, and the center of symmetry is located at the center point of the positioning and fixing connection device 3. There are common tangent points on the outer circles of one of the first coils 11 in the four first electromagnetic generating coil groups. The two first coils 11 in each first electromagnetic generating coil group form a dual-focus magnetic stimulation coil pair to emit electromagnetic waves to the center of symmetry to perform magnetic stimulation on the target area. The stimulation driving control module is electrically connected to the two first coils 11 in each first electromagnetic generating coil group respectively. The stimulation driving control module is used to perform timing control of the driving current on each first coil 11 according to the preset coil stimulation intensity and stimulation timing.

[0099] In one embodiment, the transcranial magnetic stimulation system further includes a magnetic view detection device, which includes a magnetometer array module, a magnetic view data processing module, and a magnetic view display module for detecting the magnetic view of the brain. The magnetometer array module includes a 48-channel atomic magnetometer array and a fixture. The magnetic view data processing module receives the magneto-electric signals of the brain detected by the magnetometer array module, performs intelligent processing, and generates a brain magnetic view. The magnetic view display module is used to display the brain magnetic view calculated by the magnetic view data processing module.

[0100] Please refer to Figure 10 , which is a schematic diagram of the timing control and driving of a transcranial magnetic stimulation device in an example. The stimulation driving control module includes a transcranial magnetic control driving device, which includes the control driving of an enhanced transcranial magnetic stimulation coil pair and the driving and control of a compensating transcranial magnetic stimulation coil pair. Specifically, it includes a timing generation module, a coil current mode generation module, and a driving control module. The timing generation module generates the driving excitation timing of the enhanced transcranial magnetic stimulation coil and the compensating transcranial magnetic stimulation coil, and can generate independent excitation timing for a single coil or combined excitation timing for multiple coils. The coil current mode generation module sets the output current intensity, frequency, and waveform of the driving circuit, and can generate an independent current mode for a single coil driving module or a combined synchronous current mode for multiple coil driving modules. The driving control module generates a driving current for driving a single coil according to a specific timing and current mode, or can also generate a combined driving current for driving multiple coils.

[0101] Please refer to Figure 11, which is a schematic structural connection diagram of the central control system in another example. The transcranial magnetic stimulation system includes a central control system, which includes a brain magnetic view processing module, a timing pattern calculation module, a brain magnetic view pattern library, a pattern evaluation module based on a multi-objective optimization algorithm with regional characteristics, and a system coordination control module. The brain magnetic view processing module is responsible for intelligently processing the brain magnetic view detected by the magnetic view detection device to obtain an intelligent status report. The timing pattern calculation module, based on the brain magnetic view status characteristics of the target stimulation site to be stimulated, and the brain magnetic view status characteristics of the brain cortex sites adjacent to the path between the magnetic stimulation coil and the target stimulation site to be stimulated, the pattern evaluation module based on the multi-objective optimization algorithm with regional characteristics, in combination with the brain magnetic view pattern library, comprehensively calculates the optimal stimulation patterns of the enhanced transcranial magnetic stimulation coil and the compensation transcranial magnetic stimulation coil. The brain magnetic view pattern library module records the authoritative transcranial magnetic stimulation excitation patterns in the industry. The pattern evaluation module based on the multi-objective optimization algorithm with regional characteristics can, based on the magnetic view characteristics of the target stimulation area, the brain magnetic view status characteristics of the brain cortex sites adjacent to the path between the magnetic stimulation coil and the target stimulation site to be stimulated, and the excitation magnetic field parameter characteristics of the magnetic stimulation coil, calculate multiple possible optimized stimulation patterns, and compare and evolve and optimize them with all the authoritative stimulation patterns stored in the brain magnetic view pattern library module to obtain multiple preferred stimulation patterns for the transcranial magnetic control drive device to preferably adopt. The system coordination control module controls the operation of the entire enhanced deep-focus transcranial magnetic stimulation device and comprehensively optimizes all the authoritative patterns and the current executed stimulation patterns in the brain magnetic view pattern library by using a multi-objective particle swarm optimization algorithm based on fast convergence, selects multiple optimized stimulation patterns for the specific target stimulation area, optimizes and updates the brain magnetic view pattern library, and uses them as the preferred stimulation patterns for subsequent stimulation.

[0102] Please refer to Figure 12 , which is a schematic flow diagram of the multi-objective optimization algorithm in another embodiment. The multi-objective optimization algorithm with regional characteristics adopted by the pattern evaluation module based on the multi-objective optimization algorithm with regional characteristics includes:

[0103] Step 1, generate an initial trial magnetic stimulation pattern;

[0104] Step 2, evaluate the initial magnetic stimulation pattern and initialize pbest (the target optimal magnetic stimulation pattern);

[0105] Step 3, from i = 1 to NP (the number of populations, NP is an integer greater than or equal to 8), for the pbest of the i-th trial magnetic stimulation pattern, identify the nearest nsize neighborhood optima (based on the principle of the lowest cost and the highest benefit of the trial magnetic stimulation pattern);

[0106] Step 4, update the optimization progress speed of the trial magnetic stimulation pattern. The formula for obtaining the update speed is:

[0107] ;

[0108] ;

[0109] Among them, is a random number uniformly distributed within the range of [0, 4.1 / nsize], is the sum of is the j-th nearest neighboring test magnetic stimulation pattern that is the individual optimal for the i-th test magnetic stimulation pattern;

[0110] Step Five, update the position of the test magnetic stimulation pattern, and the update formula is:

[0111] ;

[0112] Step Six, evaluate the newly generated test magnetic stimulation pattern;

[0113] Step Seven, update the pbest of the i-th test magnetic stimulation pattern, and end the loop;

[0114] Step Eight, if the termination condition is met, end; otherwise, go to Step Three.

[0115] Please refer to Figure 13 , which is a schematic diagram of transcranial magnetic stimulation in an embodiment. The transcranial magnetic stimulation device includes two first electromagnetic generating coil groups. One first electromagnetic generating coil group includes Coil 1 and Coil 2, and the other first electromagnetic generating coil group includes Coil 3 and Coil 4. The two first electromagnetic generating coil groups respectively form a dual-focusing type deep magnetic stimulation coil group. According to the magnetic stimulation focusing principle of the dual-focusing type deep magnetic stimulation coil group, taking a circular coil as an example, the magnetic field intensity generated by a group of dual-focusing type deep magnetic stimulation coil groups is approximately:

[0116] B 1 = 0.5 × μ 0 × N 1 × I 1 × R 1 2 × [R 1 2 + (d 1 / 2 + x 1 ) 2 -（3 / 2） ;

[0117] Among them, x 1 is the distance from a point on the axis to the center of a coil, and the magnetic field direction is along the axis.

[0118] ​The magnetic field intensity generated by another set of dual-focusing deep magnetic stimulation coil sets is approximately:

[0119] B 2 = 0.5 × μ 0 × N 2 × I 2 × R 2 2 × [R 2 2 + (d 2 / 2 + x 2 ) 2 -（3 / 2） ;

[0120] where x 2 is the distance from a point on the axis to the center of a coil, and the magnetic field direction is along the axis.

[0121] The spatial intersection of the axes of the two sets of dual magnetic stimulation coil sets is the maximum focusing point of the magnetic field intensity, and the magnetic field magnitude at the focusing point is:

[0122] B = (B 1 2 + B 2 2 + 2 × B 1 × B 2 × cosα) 1 / 2 ;

[0123] where α is the angle between the two axes. The position of the focusing point is completely determined by the axis intersection of the dual magnetic stimulation coil sets, and it is very easy to determine the stimulation depth (position of the focusing point) and intensity (synthesized magnetic field intensity at the focusing point) of magnetic stimulation.

[0124] Please refer to Figure 14 , which is a schematic diagram of the magnetic stimulation timing control of a magnetic stimulation device in an embodiment. The stimulation drive control module includes timing control and drive circuit 1, timing control and drive circuit 2, and timing control and drive circuit 3. The two first coils are fully synchronous magnetic stimulation coils, and the timing and magnitude of the current are obtained by shunting from timing control and drive circuit 1, which are timing 1 and drive current I1 respectively. The two second coils are fully synchronous magnetic stimulation coils, and the timing and magnitude of the current are obtained by shunting from timing control and drive circuit 2, which are timing 2 and drive current I2 respectively. In one embodiment, timing 1 and timing 2 can be the same or different. In one embodiment, drive current I1 and drive current I2 can be the same or different. The stimulation drive control module can intelligently stimulate the first coil and the second coil to achieve intelligent control of the magnetic field intensity and direction at a specific point.

[0125] Please refer to Figure 15 ​, which is a schematic diagram of the connection of the spherical fixing bracket in an embodiment. After the spherical fixing bracket is fixedly connected to the skull, the first coil is positioned in front of and behind the head. In one embodiment, one hemispherical frame of the spherical fixing bracket is arranged in front of the forehead (in front of the prefrontal lobe), and the other hemispherical frame is arranged at the back of the head. The two hemispherical frames are at the same horizontal height or form an angle of no more than 15 degrees with the horizontal plane.

[0126] Please refer to Figure 16 , which is a schematic diagram of the connection of the spherical fixing bracket in an embodiment. After the spherical fixing bracket is fixedly connected to the skull, the first coil is positioned on the left and right sides of the head. In one embodiment, one hemispherical frame of the spherical fixing bracket is arranged on the left side of the skull, and the other hemispherical frame is arranged on the right side of the skull. The two hemispherical frames are at the same horizontal height or form an angle of no more than 15 degrees with the horizontal plane.

[0127] In one embodiment, the value of the driving current is from 1 A to 10 kA. In one embodiment, the frequency of the time sequence is from 1 kHz to 10 kHz. The two first coils generate an electric field in the head sufficient to depolarize cortical neurons.

[0128] In one embodiment, the target area for which the magnetic stimulation device pre-performs magnetic stimulation includes one of the following: frontal lobe, thalamus, cingulate gyrus, putamen, caudate nucleus, hippocampus, ventral striatum, and amygdala.

[0129] The present invention adopts a precise and dexterous structural design, realizes the controllability of the stimulation depth of transcranial magnetic coil stimulation, and realizes the controllability of the magnetic stimulation focus of coil magnetic stimulation; based on the intelligent control of the coil current, the intelligent control of the intensity and direction of the magnetic stimulation focus of transcranial magnetic coil stimulation can be realized, which can provide precise stimulation treatment in transcranial magnetic stimulation therapy and can provide a powerful tool for the research of brain science and neuroscience.

[0130] Those skilled in the art can understand that all or part of the functions of the various methods in the above embodiments can be implemented in a hardware manner or in a computer program manner. When all or part of the functions in the above embodiments are implemented in a computer program manner, the program can be stored in a computer-readable storage medium, which may include: read-only memory, random access memory, magnetic disks, optical disks, hard disks, etc. The above functions can be realized by a computer executing the program. For example, the program is stored in the memory of the device, and when the processor executes the program in the memory, the above-mentioned all or part of the functions can be realized. In addition, when all or part of the functions in the above embodiments are implemented in a computer program manner, the program can also be stored in a storage medium such as a server, another computer, a magnetic disk, an optical disk, a flash drive or a mobile hard disk, and saved to the memory of the local device by downloading or copying, or the system of the local device is updated with a version. When the processor executes the program in the memory, all or part of the functions in the above embodiments can be realized.

[0131] The above uses specific examples to elaborate on the present invention, which is only used to help understand the present invention and is not intended to limit the present invention. For those skilled in the art to which the present invention pertains, according to the idea of the present invention, several simple deductions, deformations or substitutions can also be made.

Claims

1. A transcranial magnetic stimulation device, characterized in that, it includes a stimulation driving control module and a magnetic signal generating component; the magnetic signal generating component is used to be fixedly connected to the skull through a positioning and fixing connection device, and emit electromagnetic waves into the target area in the skull to perform magnetic stimulation on the target area; the magnetic signal generating component includes a first electromagnetic generating coil group and a second electromagnetic generating coil group; the first electromagnetic generating coil group includes two first coils with the same structure. The two first coils are symmetrically arranged about the center on the positioning and fixing connection device, and the center of symmetry is located at the center point of the positioning and fixing connection device; the second electromagnetic generating coil group includes two second coils with the same structure. The two second coils are symmetrically arranged about the center on the positioning and fixing connection device, and the center of symmetry is located at the center point of the positioning and fixing connection device; the diameter of the second coil is smaller than that of the first coil; the two first coils of the first electromagnetic generating coil group form a pair of dual-focus magnetic stimulation coil pairs to emit electromagnetic waves towards the center of symmetry to perform magnetic stimulation on the target area; the two second coils of the second electromagnetic generating coil group form a pair of dual-focus magnetic stimulation coil pairs to emit electromagnetic waves towards the center of symmetry to perform magnetic stimulation on the target area; the central axes of the two first coils coincide with the central axes of the two second coils; the stimulation driving control module is electrically connected to the two first coils of the first electromagnetic generating coil group and the two second coils of the second electromagnetic generating coil group respectively; the stimulation driving control module is used to perform timing control of the driving current on the first coil and / or the second coil according to a preset coil stimulation intensity and stimulation timing; the first electromagnetic generating coil group is used to perform enhanced magnetic stimulation on brain tissues at a specific depth, and the second electromagnetic generating coil group is used to perform pilot preventive stimulation on the cerebral cortex and adjacent tissues on the path between the first electromagnetic generating coil group and the target site or perform restorative magnetic stimulation on brain tissues at a specific depth.

2. A transcranial magnetic stimulation device, characterized in that, it includes a stimulation driving control module and a magnetic signal generating component; the magnetic signal generating component is used to be fixedly connected to the skull through a positioning and fixing connection device, and emit electromagnetic waves into the target area in the skull to perform magnetic stimulation on the target area; the magnetic signal generating component includes four first electromagnetic generating coil groups; each first electromagnetic generating coil group includes two first coils with the same structure. The two first coils are symmetrically arranged about the center on the positioning and fixing connection device, and the center of symmetry is located at the center point of the positioning and fixing connection device; the outer circles of one of the first coils in the four first electromagnetic generating coil groups have a common tangent point; each of the two first coils of each first electromagnetic generating coil group forms a pair of dual-focus magnetic stimulation coil pairs to emit electromagnetic waves towards the center of symmetry to perform magnetic stimulation on the target area; The stimulation driving control module is electrically connected to the two first coils of each of the first electromagnetic coil groups; the stimulation driving control module is used to perform timing control of the driving current on each of the first coils according to a preset coil stimulation intensity and stimulation timing.

3. A transcranial magnetic stimulation system Characterized in that it includes: An image acquisition module, configured to acquire medical image data; the medical image data includes images of the target area to be magnetically stimulated inside the skull and images of the landmark area for target positioning; A model reconstruction module, configured to perform three-dimensional reconstruction on the medical image data to obtain a virtual three-dimensional model; the virtual three-dimensional model includes the three-dimensional model of the target area after three-dimensional reconstruction of the target area, and the virtual three-dimensional model also includes the three-dimensional model of the landmark area after three-dimensional reconstruction of the landmark area; A positioning and fixing connection device, configured to establish a spatial positioning coordinate system and fixedly connect the skull in the spatial positioning coordinate system; A target coordinate acquisition module, configured to establish a correspondence between the three-dimensional model of the landmark area in the virtual three-dimensional model and the landmark area in the spatial positioning coordinate system, and based on the spatial position relationship between the three-dimensional model of the landmark area and the three-dimensional model of the target area in the virtual three-dimensional model, fixedly set the target area to be magnetically stimulated inside the skull at the center point of the positioning and fixing connection device, and use this center point as the target coordinate; It further includes the transcranial magnetic stimulation device according to any one of claims 1 to 2; the transcranial magnetic stimulation device is configured to emit electromagnetic waves to the target area to perform magnetic stimulation on the target area.

4. The transcranial magnetic stimulation system according to claim 3, Characterized in that the positioning and fixing connection device includes a spherical fixing frame that can be disassembled into two identical hemispherical shapes, and at least one circular guide rail is provided on the spherical fixing frame, and the center of each circular guide rail is located on the same straight line passing through the center point of the spherical fixing frame; the first electromagnetic coil group is fixedly connected to the positioning and fixing connection device through the circular guide rail.

5. The transcranial magnetic stimulation system according to claim 4, Characterized in that three circular guide rails are provided on the spherical fixing frame, and the circular planes where each circular guide rail is located are at an angle of 60 degrees to each other; at least two coil fixing interfaces are provided on each circular guide rail, and each coil fixing interface is evenly distributed on the circular guide rail, and the coil fixing interface is used to fixedly connect the first coil and the circular guide rail.

6. The transcranial magnetic stimulation system according to claim 3, Characterized in that the shape of the first coil is oval or circular.

7. The transcranial magnetic stimulation system according to claim 3, Characterized in that the acquisition formula of the coil stimulation intensity includes: B = 0.5×μ 0 ×N×I×R 2 ×[R 2 +(d / 2 + x) 2 -（3 / 2） ;​ μ 0 = 4×π×10 -7 Tm / A; where N is the number of turns of the first coil, I is the coil current, R is the radius of the effective equivalent circular area of the first coil, x is the distance from the central symmetry point of the first coil to the center of the effective circle of the first coil, and d is the width of the first coil.

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