A method of inducing field direction controllable magnetic intervention

Abstract

The application discloses a magnetic intervention method for inducing controllable field direction, and belongs to the technical field of noninvasive nerve regulation. t S100, calculating the current i needed to be passed in for generating a unit directional vector electric field at a target point P 1j , i 2j , i 3j , j=1, 2, …n, same below. S200, decomposing a vector electric field E needed at the target point into three base vector directions to obtain electric field component sizes E1, E2 and E3; S300, calculating currents for generating the electric field components E1, E2 and E3 at the target point, I 1j =E1i 1j , I 2j =E2i 2j , I 3j =E3i 3j . S400, superimposing the currents of the three current passing modes to obtain the synthetic current I j =I 1j +I 2j +I 3j =E1i 1j +E2i 2j +E3i 3j needed to be passed in for each coil of a coil set, that is, generating the needed electric field E at the target point to perform specific directional stimulation.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for inducing field direction controllable magnetic intervention, belonging to the technical field of non-invasive neural modulation. BACKGROUND

[0002] Magnetic intervention is a neural modulation technology, whose basic principle is to pass pulse current in the coil to generate a magnetic field that can penetrate the barrier tissues such as scalp and skull, induce an electric field in the brain, and then induce an induced current to change the membrane potential of neurons, activate neurons, and produce a series of physiological effects. Due to its non-invasive and safe characteristics, this technology is widely used in clinical routine electrophysiological examination, treatment of nervous system diseases and brain science research.

[0003] In the existing coil topology design of the magnetic intervention method, most of the attention is paid to the spatial distribution of the induced electric field amplitude, and the focusing degree and penetration depth are studied. However, the effect of magnetic intervention is not only related to the strength of the induced electric field, but also closely related to the direction of the induced electric field acting on neurons.

[0004] The mechanism of magnetic intervention technology is not clear, and effective intervention of deep brain is still difficult. The neurons in the deep brain nuclei are complex in direction and type, and different types of neurons have different sensitivity and activation thresholds to the direction of electric field. Controlling the strength and direction of the induced electric field can improve the effectiveness and selectivity of deep neuron stimulation.

[0005] The existing coil, such as the 8-shaped coil with consistent electric field direction at the current convergence, although the direction of the induced electric field is changed by rotating the original position, but this method is not flexible for controlling the direction of the electric field, and can only change the direction in the plane. When the position of the 8-shaped coil is changed to achieve three-dimensional electric field direction change, the 8-shaped coil must be away from the original stimulation target, and the strength of the electric field will decay rapidly, which cannot achieve the stimulation effect of neuron activation. Therefore, a new stimulation method and coil structure are needed to realize the direction controllable magnetic intervention. SUMMARY

[0006] The present application proposes a method for inducing field direction controllable magnetic intervention to solve the problem that in the prior art, the strength of the electric field decays rapidly when the position of the coil is changed, which cannot achieve the stimulation effect of neuron activation.

[0007] A method for inducing field direction controllable magnetic intervention, the method for inducing field direction controllable magnetic intervention comprises the following steps:

[0008] S100, calculating the current i required to pass in the target point P t to generate a unit directional vector electric field 1j , i 2j , i 3j, j = 1, 2, … n, same below.

[0009] S200, decompose the required vector electric field E at the target point into three base vector directions to obtain electric field component sizes E1, E2, E3;

[0010] S300, calculate the electric current I that can generate electric field components E1, E2, E3 at the target point 1j = E1i 1j , I 2j = E2i 2j , I 3j = E3i 3j .

[0011] S400, superimpose the currents of the three energizing modes to obtain the required composite current I of each coil of the coil group j = I 1j + I 2j + I 3j = E1i 1j +E2i 2j +E3i 3j , that is, generate the required electric field E at the target point to perform specific directional stimulation.

[0012] Further, before S100, it also includes:

[0013] S000, construct a magnetic intervention coil group.

[0014] Further, in S000, it specifically includes the following steps:

[0015] S001, construct a three-dimensional space;

[0016] S002, the target point P t is located in the three-dimensional space, and q wires with one end point intersecting are arranged above the target point P t , and the wires all form an angle with the xoy plane, and the angles with the positive direction of the z axis are θ1, θ2, … θ q , respectively.

[0017] S003, close the other end of the q wires with one end point intersecting by connecting wires in the form of line segments or polygons to form a magnetic intervention coil group, and the coils of the magnetic intervention coil group have n.

[0018] Further, in S100, the magnetic intervention coil group is energized with the following energizing modes:

[0019] When the first energizing mode, the current in each coil is I 11 , I 12 , I 13 , …, I 1j , …, I1n , thereby generating an induced electric field E1;

[0020] In the second energizing mode, the current in each coil is I 21 , I 22 , I 23 , …, I 2j , …, I 2n , thereby generating an induced electric field E2;

[0021] In the third energizing mode, the current in each coil is I 31 , I 32 , I 33 , …, I 3j , …, I 3n , thereby generating an induced electric field E3.

[0022] Further, in S200, specifically:

[0023] The coil group under each energizing mode is below the target point P t generates a combined induced electric field E1(a1, b1, c1), E2(a2, b2, c2), E3(a3, b3, c3), and the three induced electric fields are not coplanar, i.e., E1, E2, and E3 are linearly independent, wherein,

[0024]

[0025] Further, in S300, specifically:

[0026] The corresponding unit direction vector electric field e1 = E1 / |E1|, e2 = E2 / |E2|, e3 = E3 / |E3| is obtained, and the current size needed to generate a unit direction vector electric field at the target point,

[0027] i 11 = I 11 / |E1|, i 12 = I 12 / |E1|, i 13 = I 13 / |E1|, …, i 1j = I 1j / |E1|, …, i 1n = I 1n / |E1|;

[0028] i 21 = I 21 / |E2|, i 22 = I 22 / |E2|, i 23 = I 23 / |E2|, …, i 2j = I2j |E2|,..., i 2n = I 2n |E2|; i

[0029] i 31 = I 31 |E3|, i 32 = I 32 |E3|, i 33 = I 33 |E3|,..., i 3j = I 3j |E3|,..., i 3n = I 3n |E3|.

[0030] Further, in S400, specifically: according to the superposition principle of the field, the three direction base vector electric field at the target point is combined to form a unit electric field e in any direction in space,

[0031] e = λ1e1+ λ2e2+ λ3e3,

[0032] 0 ≤ λ i ≤ 1

[0033] Correspondingly, the currents in each coil are also superimposed,

[0034] i1= λ1i 11 + λ2i 21 + λ3i 31

[0035] i2= λ1i 12 + λ2i 22 + λ3i 32

[0036] i3= λ1i 13 + λ2i 23 + λ3i 33

[0037] ...

[0038] i j = λ1i 1j + λ2i 2j + λ3i 3j

[0039] ...

[0040] i n = λ1i n + λ2i 2n + λ3i 3n

[0041] Adjust the ratio between the currents flowing through the coils in the coil group i1:i2:i3:...:ij : i n , i.e. control the direction of the target point electric field e, overall adjust the size of the single flow ki1, ki2, ki3, …: ki j , i.e. ki n , i.e. adjust the size of the target point electric field ke.

[0042] The present application has the following beneficial effects: the magnetic intervention method with controllable induction field direction of the present application breaks through the design concept of the existing coil, can control the direction of the induced electric field at the target point in three-dimensional space by changing the current without moving the coil, and then provide flexible, accurate and directional intervention for neurons according to the electromagnetic field activation mechanism of neurons, provide means for non-invasive selective intervention of neurons, and help to improve the accuracy and effectiveness of magnetic intervention. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 is the projection of the coil center structure in the xoy plane, wherein, Figure 1 (a) is a two-line structure form, Figure 1 (b) is a three-line structure form, Figure 1 (c) is a q-line structure form;

[0044] Figure 2 is a coil center structure diagram;

[0045] Figure 3 is an example diagram of passing current;

[0046] Figure 4 is a magnetic intervention coil group in the form of four rectangles;

[0047] Figure 5 is an implementation method of the induced electric field direction control, wherein, Figure 5 (a) is a power supply mode 1, Figure 5 (b) is a power supply mode 2, Figure 5 (c) is a power supply mode 3, Figure 5 (d) is a power supply mode 4;

[0048] Figure 6 is the electric field distribution diagram on the cross section under each power supply mode;

[0049] Figure 7 is the electric field distribution on the cross section when the synthetic current is passed and the electric field value of the target point, wherein, Figure 7 (a) is E, Figure 7 (b) is the x-direction component of E, Figure 7 (c) is the y-direction component of E, Figure 7 (d) is the z-direction component of E;

[0050] Figure 8are shown in the form of five triangles, Figure 8 (a) are in the form of four quadrilaterals, Figure 8 (b) are in the form of four triangles, Figure 8 (c) are in the form of three triangles, Figure 8 (d) are in the form of five triangles, Figure 8 (e) are in the form of three hexagons. DETAILED DESCRIPTION

[0051] The technical solutions in the embodiments of the present application will be apparently and completely described in conjunction with the drawings of the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0052] Referring to Figure 1 The present application proposes a magnetic intervention method with controllable induced field direction, which comprises the following steps:

[0053] S100, calculating the current i required to generate a unit directional vector electric field at a target point P t , i 1j , i 2j , i 3j , j = 1, 2, … n, same below.

[0054] S200, decomposing the required vector electric field E at the target point into three base vector directions to obtain electric field component sizes E1, E2, E3;

[0055] S300, calculating the current I capable of generating electric field components E1, E2, E3 at the target point, 1j = E1i 1j , I 2j = E2i 2j , I 3j = E3i 3j .

[0056] S400, superimposing the currents of the three energizing modes to obtain the required composite current I j = I 1j + I 2j + I 3j = E1i 1j + E2i 2j + E3i 3j of each coil of the coil set, i.e. generating the required electric field E at the target point for specific directional stimulation.

[0057] Further, before S100, it further comprises:

[0058] S000, constructing a magnetic intervention coil set.

[0059] Further, in S000, the following steps are specifically included:

[0060] S001, constructing a three-dimensional space;

[0061] S002, target point P t In the three-dimensional space, q wires with one end point intersection are arranged above the target point P t , and the wires are all at an angle with the xoy plane, and the angles with the positive direction of the z axis are θ1, θ2, … θ q , respectively.

[0062] S003, by using a connecting wire in the form of a line segment or a polygon to close the other end of the q wires with one end point intersection, a magnetic intervention coil set is formed, and the coils of the magnetic intervention coil set have n.

[0063] Specifically, the physical principle of the magnetic intervention technology is Maxwell's equations, and the time-varying electromagnetic field generated by the pulse current of the coil can be regarded as a magnetic quasi-static field. In the air domain, the induced electric field and the current have the following relationship:

[0064]

[0065]

[0066]

[0067] In the formula, A is the vector magnetic potential, E is the induced electric field, Idl is the current element, r is the distance from the current element to the point to be solved, and μ0 is the vacuum permeability.

[0068] From the above formula, it can be seen that the induced electric field is parallel to the current element Idl, and the directions are opposite. Based on the relationship between the current and the electric field direction and the superposition principle of the field, the coil set structure for realizing the control of the electric field in space in any direction can be constructed by the intersecting currents above the target point P t . In order to obtain an electric field in any direction in a three-dimensional space, three non-coplanar basis vectors are needed to provide the electric field components in the x, y, and z directions of the Cartesian coordinate system.

[0069] Further, in S100, the magnetic intervention coil set is energized in the following manner:

[0070] In the first energizing mode, the currents in the coils are I 11 , I 12 , I 13 , …, I 1j , …, I 1n , thereby generating an induced electric field E1;

[0071] The current in each coil in the second energizing mode is I 21 , I 22 , I 23 , I 2j , I 2n , thereby generating an induced electric field E2;

[0072] The current in each coil in the third energizing mode is I 31 , I 32 , I 33 , I 3j , I 3n , thereby generating an induced electric field E3.

[0073] Specifically, an electric field in an arbitrary direction is constructed on a two-dimensional plane. For example, Figure 1 is the projection of the center structure of the coil group on the xoy plane, and the intersection of the wires is located directly above the target point. The wire structure alone or coinciding as a straight line cannot bring about the x and y direction electric field components, and cannot construct a coil structure on the plane through which the electric field direction is controllable by the current. The wire structure diverging from the center of the target point by 2, 3, …, q wires can bring about the x and y components on the plane, so that an electric field in an arbitrary direction can be synthesized in the xoy plane.

[0074] In order to generate an electric field in an arbitrary direction in three-dimensional space, the coil needs to generate an electric field component in the z direction, so the wire needs to form a certain angle with the xoy plane. Therefore, the coil structure is a three-dimensional structure rather than a planar structure, as shown in Figure 2 The angles between the wires and the positive direction of the z axis are θ1, θ2, … θ q .

[0075] By connecting the wire segments with a polygon to close the wire, a coil group structure with controllable induced field direction is obtained. The number q of intersecting wires above the target point corresponds to the number n of coil groups.

[0076] The implementation principle of the magnetic intervention method with controllable induced field direction is as follows: the current in each coil in the coil group is I 11 , I 12 , I 13 , I 1j , I 1n in the first energizing mode, I 21 , I 22 , I 23 , I 2j , I 2n , I 31 , I 32 , I33 , …, I 3j , …, I 3n (As Figure 3 For example, m = 1, 2, 3 represent the energizing mode.

[0077] Further, in S200, specifically:

[0078] Each coil group under each energizing mode is below the intersection of the coil target point P t Synthetic induced electric field E1(a1, b1, c1), E2(a2, b2, c2), E3(a3, b3, c3) are generated, three induced electric fields are not coplanar, that is, E1, E2, E3 are linearly independent, wherein,

[0079]

[0080] Further, in S300, specifically:

[0081] Get the corresponding unit direction vector electric field, e1 = E1 / |E1|, e2 = E2 / |E2|, e3 = E3 / |E3|, and the current size needed to generate a unit direction vector electric field at the target point,

[0082] i 11 = I 11 / |E1|, i 12 = I 12 / |E1|, i 13 = I 13 / |E1|, …, i 1j = I 1j / |E1|, …, i 1n = I 1n / |E1|;

[0083] i 21 = I 21 / |E2|, i 22 = I 22 / |E2|, i 23 = I 23 / |E2|, …, i 2j = I 2j / |E2|, …, i 2n = I 2n / |E2|;

[0084] i 31 = I 31 / |E3|, i 32 = I 32 / |E3|, i 33 = I 33 / |E3|, …, i 3j = I3j | i3 |,..., i 3n = I 3n | i3 |.

[0085] Further, in S400, specifically: according to the superposition principle of the field, the three direction base vector electric field at the target point is superimposed to get the unit electric field e in any direction in space,

[0086] e = λ1e1+ λ2e2+ λ3e3,

[0087] 0≤ λ i ≤1

[0088] Correspondingly, the current in each coil is also superimposed,

[0089] i1= λ1i 11 + λ2i 21 + λ3i 31

[0090] i2= λ1i 12 + λ2i 22 + λ3i 32

[0091] i3= λ1i 13 + λ2i 23 + λ3i 33

[0092] ...

[0093] i j = λ1i 1j + λ2i 2j + λ3i 3j

[0094] ...

[0095] i n = λ1i n + λ2i 2n + λ3i 3n

[0096] Adjust the ratio between the currents flowing through the coils in the coil group i1: i2: i3:... : i j :... : i n , that is, control the direction of the electric field e at the target point, adjust the size of the single current ki1, ki2, ki3,... : ki j ,... : ki n , that is, adjust the size of the electric field ke at the target point.

[0097] For example Figure 8, the coil group can have various forms, and the following describes the implementation of the magnetic intervention method for controlling the direction of the induced electric field in the form of a quadrilateral four-coil group in the air domain. The coil group structure is shown in Fig. 1, which is composed of four identical rectangles, and has a "book" structure. The side length of the rectangle is a and b. No. 1 and No. 2 coils are coplanar, No. 3 and No. 4 coils are coplanar, and the two coplanar coils form a wing. The angle between the plane of each wing coil and the negative direction of the z-axis is α, and the coil group has a symmetrical structure, that is, the angle between the two wings is 2α. Figure 4

[0098] The current flowing through the coil group in the first energization mode is I 11 , I 12 , I 13 , I 14 , and the current has the same magnitude I 11 = I 12 = I 13 = I 14 , and the current direction is clockwise, clockwise, counterclockwise, and counterclockwise, respectively, as viewed from the positive direction of the z-axis. The current flowing through the coil group in the second and third energization modes also has the same magnitude I 21 = I 22 = I 23 = I 24 , I 31 = I 32 = I 33 = I 34 , and the current direction is shown in Fig. 3. Figure 5

[0099] In the air domain, the direction of the induced electric field is opposite to that of the current. Fig. 4 shows the electric field distribution at a certain cross section below the coil under the three energization modes, the current has a magnitude of 1 A, the frequency is 2500 Hz, the side length a and b are both 70 mm, and the angle is 60°. Table 1 shows the electric field values at the target point under the three energization modes, which only brings the electric field in the x, y, and z directions at the target point. Figure 6

[0100]

[0101] Table 1 shows the induced electric field values at the target point (0, 0, -0.08) under the three energization modes.

[0102] Note: m = 1, 2, 3 is the energization mode; the current clockwise as viewed from the positive direction of the z-axis is positive, and the counterclockwise is negative, and the same applies below.

[0103] From this, the current required to generate a unit basis vector electric field at the target point can be calculated, as shown in Table 2.

[0104]

[0105] ​​​Table 2 Current required to produce unit base vector electric field at target point (0, 0, -0.08)

[0106] Take the example of producing a vector electric field E (2, 1, -1) V / m at the target point, the components of the base vector direction are E1 = 2, E2 = 1, E3 = -1, I j = 2i 1j + i 2j - i 3j (j = 1, 2, 3, 4), the synthetic current required to be passed through the coil set is (I1, I2, I3, I4) = (1.61 x 10 3 , -4.27 x 10 3 , 6.59 x 10 3 , -3.93 x 10 3 ) A.

[0107] As Figure 7 the cross-sectional electric field distribution containing the target point when the synthetic current is passed, the electric field value produced at the target point (0, 0, -0.08) is consistent with the expectation.

[0108] In a calculation domain with complex medium and complex boundary, the finite element calculation method can be used to calculate the induced electric field, and the electric field base vector and the passed current can also be calibrated by actual measurement.

[0109] The above implementation examples are only used to help understand the method of the present application and its core idea. For those skilled in the art, according to the idea of the present application, several improvements and refinements can be made in the specific implementation manner and application range, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A magnetic intervention method with controllable induced field direction, characterized in that, The magnetic intervention method with controllable induced field direction includes the following steps: S100, Calculation at the target point P t The current required to generate a unit direction vector electric field at a point i 1j , i 2j 、i 3j , j =1, 2, ... n The same applies below; S200, the required vector electric field at the target point. E Decompose the electric field along the three basis vectors to obtain the magnitudes of the electric field components. E 1. E 2. E 3; S300, Calculate the electric field components that can be generated at the target point. E 1. E 2. E 3 current, I 1j =E 1 i 1j , I 2j =E 2 i 2j , I 3j =E 3 i 3j； S400. The currents from the three energizing methods are superimposed to obtain the combined current required to be supplied to each coil of the coil group. I j = I 1j + I 2j + I 3j = E 1 i 1j + E 2 i 2j + E 3 i 3j That is, to generate the required electric field at the target point. E To provide specific directional stimulation; Prior to S100, it also includes: S000, Construct a magnetic interference coil assembly; In S000, the specific steps include: S001. Constructing a three-dimensional space; S002, Target P t Located in the three-dimensional space, at the target point P t Top settings q A series of wires that intersect at one end, and all of the wires are connected to... x o y The plane forms an angle with, and with z The angles between the positive axes are respectively θ 1. θ 2. ... θ q ; S003, Connecting by using line segments or polygonal connecting wires q The other ends of the wires that meet at their endpoints are closed, forming a magnetic interference coil group. The coils of the magnetic interference coil group have... n indivual; Specifically, in S200: The target point is located below the coil intersection under each energizing method. P t Generates a synthesized induced electric field E 1 ( a 1, b 1, c 1) E 2 ( a 2, b 2, c 2) E 3 ( a 3, b 3, c 3) The three induced electric fields are not coplanar, that is... E 1, E 2, E 3. Linearly independent, where, ； Specifically, in S300: The corresponding unit direction vector electric field is obtained. e 1= E 1 / |E 1|, e 2= E 2 / |E 2|, e 3= E 3 / |E 3|, and the magnitude of the current required to generate a unit-direction vector electric field at the target point, i 11 = I 11 / |E 1|、 i 12 = I 12 / |E 1|、 i 13 = I 13 / |E 1|、…、 i 1j = I 1j / |E 1|、…、 i 1n = I 1n / |E 1|； i 21 = I 21 / |E 2|、 i 22 = I 22 / |E 2|、 i 23 = I 23 / |E 2|、…、 i 2j = I 2j / |E 2|、…、 i 2n = I 2n / |E 2|； i 31 = I 31 / |E 3|、 i 32 = I 32 / |E 3|、 i 33 = I 33 / |E 3|、…、 i 3j = I 3j / |E 3|、…、 i 3n = I 3n / |E 3|； In S400, specifically: based on the superposition principle of fields, the electric fields of the three basis vectors at the target point are used to synthesize a unit electric field in any direction in space. e , ， 0≤λ i ≤1 Correspondingly, the currents in each coil are also superimposed. i 1=λ1 i 11 +λ2 i 21 +λ3 i 31 i 2=λ1 i 12 +λ2 i 22 +λ3 i 32 i 3=λ1 i 13 +λ2 i 23 +λ3 i 33 … … i j =λ1 i 1j +λ2 i 2j +λ3 i 3j … … i n =λ1 i n +λ2 i 2n +λ3 i 3n Adjusting the ratio of the currents flowing through the coils in the coil group i 1: i 2: i 3:…: i j :…: i n That is, controlling the electric field output at the target point e The direction, and the overall adjustment of the single flow size ki 1, ki 2, ki 3, ...: ki j , ...: ki n That is, adjusting the magnitude of the electric field at the target point. ke .

2. The magnetic intervention method with controllable induced field direction according to claim 1, characterized in that, In S100, current is energized in the magnetic interference coil assembly in the following manner: In the first energizing method, the current in each coil is: I 11 , I 12 , I 13 … I 1j … I 1n This generates an induced electric field. E 1; In the second energizing method, the current in each coil is: I 21 , I 22 , I 23 … I 2j … I 2n This generates an induced electric field. E 2; In the third energizing method, the current in each coil is: I 31 , I 32 , I 33 … I 3j … I 3n This generates an induced electric field. E 3.

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