A method for transcranial magnetic stimulation coil surface electric field identification

Abstract

The application provides a transcranial magnetic stimulation coil surface electric field identification method, which comprises the following steps: obtaining the measurement value of the electric field or the magnetic field on the surface of the transcranial magnetic stimulation coil, and drawing a closed energy distribution curve on the shell of the transcranial magnetic stimulation coil according to the projection of the measurement value on the shell of the transcranial magnetic stimulation coil. In use, the energy curve of the high-energy part is aligned with the treatment site of the patient, so that the energy utilization of the transcranial magnetic stimulation coil is improved, and better treatment effect is achieved.

Description

Technical Field

[0001] This invention relates to the technical field of biomedical engineering, and more particularly to a method for marking the electric field on the surface of a transcranial magnetic stimulation coil. Background Technology

[0002] Transcranial magnetic stimulation (TMS) is a treatment method in the brain and neurology field that uses time-varying pulsed electromagnetic fields to generate induced electric fields that act on the cerebral cortex and nervous system, affecting brain metabolism and neural electrical activity, thereby triggering a series of physiological and biochemical reactions. The TMS coil determines the pulsed magnetic field characteristics of the TMS device, and further determines the induced electric field characteristics of the brain's neural action area.

[0003] Currently, transcranial magnetic stimulation (TMS) coils are positioned relatively accurately at the treatment site using precise positioning mechanisms or magnetic stimulation navigation robots. However, the electric field distribution of the TMS coil itself is currently unknown in these devices or instruments, making it impossible to effectively apply the peak energy released by the TMS coil to the treatment site. This reduces the treatment effect and wastes a significant amount of energy. Summary of the Invention

[0004] The purpose of this invention is to provide a method for marking the electric field on the surface of a transcranial magnetic stimulation coil, so as to overcome the problem that the high-energy part of the transcranial magnetic stimulation coil cannot be aligned with the affected area in the existing technology.

[0005] The objective of this invention is achieved through the following steps, which include:

[0006] Step S1: Obtain the measurement value of the electric field distribution on the surface of the transcranial magnetic stimulation coil;

[0007] Step S2: Based on the projection of the measurement value onto the outer shell of the transcranial magnetic stimulation coil, draw a closed energy distribution curve on the outer shell of the transcranial magnetic stimulation coil.

[0008] The method for obtaining the metric value of the electric field on the surface of the transcranial magnetic stimulation coil in step S1 is as follows:

[0009] Magnetic vector potential of transcranial magnetic stimulation coil at various positions in cylindrical coordinate system for:

[0010]

[0011] In the formula

[0012]

[0013] Wherein, the cylindrical coordinates of the field origin are (r', θ', z'), the coordinates of each point around the transcranial magnetic stimulation coil in the cylindrical coordinate system are (r, θ, z), μ0 is the vacuum permeability, I is the current through the transcranial magnetic stimulation coil, S is the cross-sectional area of ​​the transcranial magnetic stimulation coil, and N is the number of turns of the transcranial magnetic stimulation coil.

[0014] Substituting the obtained magnetic vector potential into the following formula, the induced electric field generated by the transcranial magnetic stimulation coil at this location is obtained as follows: .

[0015] The closed energy distribution curves are equidistant from each other.

[0016] The closed energy distribution curve is labeled with the electric field ratio value.

[0017] The distances between the closed energy distribution curves are not the same.

[0018] The energy distribution curve is either an electric field distribution curve or a magnetic field distribution curve.

[0019] The electric field ratio values ​​fall within the same closed electric field distribution loop within the set range.

[0020] The steps for obtaining the measurement value of the electric field on the surface of the transcranial magnetic stimulation coil are as follows:

[0021] S1.1 Import the parameters of the coil in cylindrical coordinate system;

[0022] S1.2, Peak operating current and rate of change of the input coil;

[0023] S1.3 Determine the target plane of the coil and generate the target point matrix;

[0024] S1.4 Calculate the induced electric field value of the coil according to the formula;

[0025] S1.5 Obtain the three-dimensional induced electric field distribution diagram of the coil.

[0026] This invention plots an energy curve on the outer shell of a transcranial magnetic stimulation (TMS) coil based on the electric field distribution. During use, the high-energy portion of the energy curve is aligned with the patient's treatment area to improve the utilization of the TMS coil's electric field energy, thereby achieving better therapeutic effects. Furthermore, by calculating the electric field distribution around the TMS coil, the method for obtaining the electric field on the coil's surface is simplified, and the errors between the calculated and measured data are minimized. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 Flowchart of the program for solving the induced electric field. Figure 2 The three-dimensional electric field distribution diagram of the ring-shaped transcranial magnetic stimulation coil in Example 1. Figure 3 The closed electric field distribution curve is obtained by projecting a circular transcranial magnetic stimulation coil onto a plane. Figure 4 The energy distribution curve of the annular transcranial magnetic stimulation coil in Example 1 was obtained from the contour map. Figure 5 This is a three-dimensional view of the transcranial magnetic stimulation device of Example 1. Figure 6 The image shows the energy distribution curve of the annular transcranial magnetic stimulation coil in Example 2. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Example 1

[0031] A method for marking the electric field on the surface of a transcranial magnetic stimulation coil includes:

[0032] Step S1, obtaining the measurement value of the electric field on the surface of the transcranial magnetic stimulation coil, is as follows:

[0033] S1.1 Import the parameters of the coil in the cylindrical coordinate system, namely the height value of the circular coil and the width value of the circular coil. In this embodiment, the circular coil is a single-layer disc-shaped structure formed by multiple turns of wires concentrically wrapped in a plane. The coil parameters selected in this embodiment are: inner diameter 30mm, outer diameter 108mm, height 6mm, and a total of 18 turns.

[0034] S1.2, Input the peak operating current of the coil and its rate of change to determine the current I at different times;

[0035] S1.3 Determine the target plane of the coil and generate the target point matrix, that is, determine that the current of the circular coil is located in the z=-a and z=a plane, where a is half of the height of the circular coil, the inner and outer surfaces of the circular coil are defined by coordinates r'=R0-b and r=R0+b, where b is half of the width of the circular coil, the cylindrical coordinates of the field origin are (r', θ', z'), and the coordinates of each point around the circular current in the cylindrical coordinate system are (r, θ, z). Select each coordinate point within the upper and lower radius a range of the circular coil current plane in the cylindrical coordinate system, as well as within the range r' and r range of the circular coil current plane. The interval between the selected coordinate points is 1mm both vertically and horizontally.

[0036] S1.4 Calculate the induced electric field value of the coil according to the formula;

[0037] Substituting the coordinates of the selected points of the circular current in the cylindrical coordinate system into the following formula, we can obtain the magnetic vector potential at those points. :

[0038]

[0039] In the formula

[0040]

[0041] Substituting the magnetic vector potential obtained at this coordinate point into the following formula, the induced electric field at this point is obtained as follows: .

[0042] Where μ0 is the vacuum permeability, I is the current passing through the transcranial magnetic stimulation coil at the current time point, S is the cross-sectional area of ​​the transcranial magnetic stimulation coil, the coil cross-sectional area = (outer diameter - inner diameter) × height ÷ 2, and N is the number of turns of the transcranial magnetic stimulation coil.

[0043] S1.5. Based on the coordinates of each point in the selected cylindrical coordinate system and the electric field value, draw a three-dimensional induced electric field distribution diagram of the circular coil.

[0044] Step S2, as follows Figure 4 and Figure 5 The maximum induced electric field value generated by the transcranial magnetic stimulation coil at each of the above coordinate points is obtained as maxE. The selected coordinate points are grouped according to the electric field quantification value of each coordinate point being 98%, 90%, 80%, 70%, 60%, up to 0% of maxE, and then projected onto the outer shell of the transcranial magnetic stimulation coil. Points within the same group with the same projection radius are connected to form closed energy distribution curves. The distances between these closed electric field distribution curves are not uniform. Figure 4The area between the two 98% values ​​shown is the region of induced electric field corresponding to the operator's use of the coil for treatment, which is the region where the therapeutic energy of the transcranial magnetic stimulation coil is most effective.

[0045] Example 2

[0046] A method for marking the electric field on the surface of a transcranial magnetic stimulation coil includes:

[0047] Step S1: The method for obtaining the metric value of the electric field on the surface of the transcranial magnetic stimulation coil is as follows:

[0048] S1.1 Import the parameters of the coil in the cylindrical coordinate system, namely the height value of the circular coil and the width value of the circular coil. In this embodiment, the circular coil is formed by the wires concentrically wrapped around a plane, and the coil parameters are the same as in embodiment 1.

[0049] S1.2, Input the peak operating current of the coil and its rate of change to determine the current I at different times;

[0050] S1.3 Determine the target plane of the coil and generate the target point matrix, that is, determine that the current of the circular coil is located in the z=-a and z=a plane, where a is half of the height of the circular coil, the inner and outer surfaces of the circular coil are defined by coordinates r'=R0-b and r=R0+b, where b is half of the width of the circular coil, i.e., the distance between the innermost and outermost coils, the cylindrical coordinates of the field origin are (r', θ', z'), and the coordinates of each point around the circular current in the cylindrical coordinate system are (r, θ, z). Select each coordinate point within the upper and lower radius a range of the circular coil current plane in the cylindrical coordinate system, as well as within the range r' and r range of the circular coil current plane. The interval between the selected coordinate points is 1mm both vertically and horizontally.

[0051] S1.4 Calculate the induced electric field value of the coil according to the formula;

[0052] Substituting the coordinates of the selected points of the circular current in the cylindrical coordinate system into the following formula, we can obtain the magnetic vector potential at those points. :

[0053]

[0054] In the formula

[0055]

[0056] Substituting the magnetic vector potential obtained at this coordinate point into the following formula, the induced electric field at this point is obtained as follows: .

[0057] Where μ0 is the vacuum permeability, I is the current passing through the transcranial magnetic stimulation coil at the current time point, and S is the cross-sectional area of ​​the transcranial magnetic stimulation coil.

[0058] S1.5. Based on the coordinates of each point in the selected cylindrical coordinate system and the electric field value, draw a three-dimensional induced electric field distribution diagram of the circular coil.

[0059] Step S2: Figure 6 As shown, the inner and outer diameters of the transcranial magnetic stimulation coil are evenly divided into closed energy distribution curves with diameters of 40mm, 50mm, 60mm, 70mm, 80mm, 90mm, and 100mm, with equal radial intervals of 5mm. Points whose coordinate projections of the concentric circles are the same as or differ from the coordinates of the points by no more than 5%-15% are selected. The ratios of the induced electric field value at the point to the maximum induced electric field value maxE generated by the transcranial magnetic stimulation coil are marked on the concentric circles, such as 77.7%, 89.9%, 97%, 99.9%, 98.7%, 93.3%, and 83.4% of maxE.

[0060] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for marking the electric field on the surface of a transcranial magnetic stimulation coil, characterized in that, The steps are as follows: Step S1.1: Import the height and width of the circular coil in the cylindrical coordinate system. The circular coil is a single-layer disc-shaped structure formed by multiple turns of wires concentrically wrapped in a plane. S1.2, The peak operating current of the induction coil and its rate of change; S1.3 Determine the target plane of the coil and generate the target point matrix, that is, determine that the current of the circular coil is located in the z=-a and z=a plane, where a is half of the height of the circular coil, the inner and outer surfaces of the circular coil are defined by coordinates r'=R0-b and r=R0+b, where b is half of the width of the circular coil, the cylindrical coordinates of the field origin are (r', θ', z'), and the coordinates of each point around the circular current in the cylindrical coordinate system are (r, θ, z). Select each coordinate point within the upper and lower radius a range of the circular coil current plane in the cylindrical coordinate system, as well as within the range r' and r range of the circular coil current plane. The interval between the selected coordinate points is 1mm both vertically and horizontally. S1.4 Calculate the induced electric field value of the coil according to the formula; Substituting the coordinates of the selected points of the circular current in the cylindrical coordinate system into the following formula, we can obtain the magnetic vector potential at those points. : In the formula Substituting the magnetic vector potential obtained at this coordinate point into the following formula, the induced electric field at this point is obtained as follows: ; Where μ0 is the vacuum permeability, I is the current through the transcranial magnetic stimulation coil, S is the cross-sectional area of ​​the transcranial magnetic stimulation coil, and N is the number of turns of the transcranial magnetic stimulation coil. S1.

5. Based on the coordinates of each point in the selected cylindrical coordinate system and the electric field value, draw a three-dimensional induced electric field distribution diagram of the circular coil. Step S2: Obtain the maximum induced electric field value maxE generated by the transcranial magnetic stimulation coil at each of the above coordinate points. Group the selected coordinate points according to the electric field measurement value of the coordinate point being 98%, 90%, 80%, 70%, 60%, up to 0% of maxE, and then project the parameters of the coordinate point in the cylindrical coordinate system onto the outer shell of the transcranial magnetic stimulation coil. Connect the coordinate points in the same group with the same projection radius to form a closed energy distribution curve. When the operator uses the coil for treatment, the area between the energy distribution curves marking 98% of the maximum magnetic induced electric field value on the transcranial magnetic stimulation coil is taken as the area where the treatment energy is most effective.

2. The method for marking the electric field on the surface of a transcranial magnetic stimulation coil according to claim 1, characterized in that, The closed energy distribution curves are equidistant from each other.

3. The method for marking the electric field on the surface of a transcranial magnetic stimulation coil according to claim 2, characterized in that, The closed energy distribution curve is labeled with the electric field ratio value.

4. The method for marking the electric field on the surface of a transcranial magnetic stimulation coil according to claim 1, characterized in that, The distances between the closed energy distribution curves are not the same.

5. A method for marking the electric field on the surface of a transcranial magnetic stimulation coil according to any one of claims 1 to 4, characterized in that, The energy distribution curve is either an electric field distribution curve or a magnetic field distribution curve.

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