Disclosure of Invention
To solve at least one of the technical problems in the prior art to a certain extent, the present invention provides an 8-shaped transcranial magnetic stimulation coil, a magnetic stimulation device and a magnetic stimulation system.
The technical scheme adopted by the invention is as follows:
a figure-8 transcranial magnetic stimulation coil comprising:
the 8-shaped coil comprises two through holes;
the soft magnetic core is arranged in the center of the 8-shaped coil, is U-shaped and comprises two columns and a cross beam connected with the two columns, and the two columns are respectively arranged in the two through holes;
the magnetic shielding layer is arranged on one side of the 8-shaped coil, an opening is formed in the magnetic shielding layer, and the position of the opening corresponds to that of the soft magnetic core.
Furthermore, the opening is rectangular, the length of the opening is parallel to the line of the beam, and the length of the opening is perpendicular to the line of the beam;
the width of the opening is adjustable in size.
Further, in a cross section of the through hole, a center of the column is located between the center of the through hole and an edge of the through hole.
Further, in the cross section of the through hole, the area of the column is far smaller than that of the through hole.
Furthermore, the soft magnetic core is made of a material with high magnetic permeability and high saturation magnetization.
Further, the soft magnetic core is a homogeneous U-shaped magnetic core, a magnetic core formed by stacking a plurality of layers of iron-based soft magnetic sheets or a magnetic core formed by stacking a plurality of layers of amorphous strips.
Further, the cylinder is a cylinder, a polygonal prism or a polygonal pyramid.
Further, the shape of the through hole is circular, oval or polygonal.
The other technical scheme adopted by the invention is as follows:
a transcranial magnetic stimulation device comprising:
the transcranial magnetic stimulation coil is realized by adopting the 8-shaped transcranial magnetic stimulation coil;
and the power supply is used for providing alternating current with preset frequency for the transcranial magnetic stimulation coil.
The other technical scheme adopted by the invention is as follows:
a transcranial magnetic stimulation system comprises a box body and a plurality of transcranial magnetic stimulation devices which are placed in the box body.
The invention has the beneficial effects that: the invention effectively reduces the induction electric field intensity in other directions except the magnetic core direction through the magnetic shielding layer, thereby providing the stimulation precision of the transcranial magnetic stimulation coil.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention. The step numbers in the following embodiments are provided only for convenience of illustration, the order between the steps is not limited at all, and the execution order of each step in the embodiments can be adapted according to the understanding of those skilled in the art.
In the description of the present invention, it should be understood that the orientation or positional relationship referred to in the description of the orientation, such as the upper, lower, front, rear, left, right, etc., is based on the orientation or positional relationship shown in the drawings, and is only for convenience of description and simplification of description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention.
In the description of the present invention, the meaning of a plurality of means is one or more, the meaning of a plurality of means is two or more, and larger, smaller, larger, etc. are understood as excluding the number, and larger, smaller, inner, etc. are understood as including the number. If the first and second are described for the purpose of distinguishing technical features, they are not to be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated or implicitly indicating the precedence of the technical features indicated.
In the description of the present invention, unless otherwise explicitly limited, terms such as arrangement, installation, connection and the like should be understood in a broad sense, and those skilled in the art can reasonably determine the specific meanings of the above terms in the present invention in combination with the specific contents of the technical solutions.
As shown in fig. 1 and 2, the present embodiment provides an 8-shaped transcranial magnetic stimulation coil, comprising:
the 8-shaped coil 2 comprises two through holes;
the soft magnetic core 1 is arranged at the central position of the 8-shaped coil 2, the soft magnetic core 1 is U-shaped and comprises two columns and a cross beam for connecting the two columns, and the two columns are respectively arranged in the two through holes;
and the magnetic shielding layer 3 is arranged on one side of the 8-shaped coil 2, and an opening is arranged on the magnetic shielding layer 3, and the position of the opening corresponds to the position of the soft magnetic core 1.
In this embodiment the distribution of the electric field distribution in the direction of the core (i.e. in the z-x plane of the three-dimensional model in fig. 1) can be effectively changed by the soft magnetic core, improving the stimulation accuracy in this direction, but not significantly for stimulation in the direction perpendicular to the core, i.e. through the symmetry axis of the three-dimensional model and parallel to the y-z plane. In order to improve the stimulation precision in the x-axis direction (adding a magnetic core) and the stimulation precision in the y-axis direction at the same time, the embodiment proposes to add a magnetic shielding layer between the head and the coil, and improve the stimulation precision of the 8-shaped coil in the y-axis direction by adjusting the opening size (w) of the magnetic shielding layer in the y-axis direction.
In some alternative embodiments, the cross-section of the coils of the figure-8 coil is not limited to shapes such as rectangular, oval, multi-strand coils, and the like.
In some alternative embodiments, the coil of the figure-8 coil is not limited in particular, such as a single-strand loop figure-8 coil, a multi-strand loop figure-8 coil, a disk-shaped figure-8 coil with a connecting portion for placing a U-shaped magnetic core to limit the width, and the like.
In some alternative embodiments, the overall structure of the coils of the figure-8 coil is not limited, and includes a figure-8 coil with two coils on the same plane, a figure-8 coil with a specific included angle between two coils, and the like.
FIG. 1 is a model diagram for analyzing the effect of a 8-shaped transcranial magnetic stimulation coil on the stimulation effect, wherein the diagram comprises: a soft magnetic core 1, a figure-8 coil 2, a magnetic shielding layer and a simplified head model 4. The head model used a 95mm radius sphere to represent the intracranial tissue (represented by the electromagnetic parameters of interstitial fluid) and a 5mm shell outside the sphere to represent the skull. The relative magnetic conductivity, the electric conductivity and the relative dielectric constant of the skull are respectively 0.99, 0.01S/m and 13.50; the relative magnetic permeability, the electric conductivity and the dielectric constant of the tissue fluid are respectively 0.99, 4.0S/m and 80.0.
As shown in FIG. 3, this cross-section is the y-z cross-section of FIG. 1; the stimulation precision of different coils is evaluated by the electric field distribution of the electric field along the measuring line, and the strength of the induction field generated by the 8-shaped coil on the measuring line is maximum under the electric field (E)1) The electric field intensity at θ is Eθ. Using Eθ/E1Evaluation of stimulus accuracy in the y-axis direction, Eθ/E1The faster the decrease with increase in θ indicates that the stimulation accuracy in the y-axis direction is more concentrated directly below the coil, i.e., the stimulation accuracy is higher.
By analyzing the distribution of the electric field on the surface of the intracranial tissue on the measuring line, the influence of the openings of the shielding layers with different sizes on the 8-shaped coil stimulation effect is compared. The influence of different opening sizes on the stimulation depth of the 8-shaped TMS coil is compared by analyzing the distribution condition of the intracranial electric field intensity at different depths on the central axis of the model. Since the electric field distribution along the magnetic core direction, i.e. in the x direction of the three-dimensional model, can be adjusted by adjusting the size of the magnetic core, and the position right below the magnetic core is usually the target area for stimulation, the present embodiment needs to ensure that the opening length l of the magnetic shielding layer along the x-axis direction is slightly larger than the size of the magnetic core, and the electric field intensity generated by the coil loop part (and the position far from the magnetic core) is reduced on the premise that the induced electric field near the magnetic core is not significantly affected.
In some alternative embodiments, the center of the post is between the center of the through hole and the sides of the through hole in the cross section of the through hole. On the cross section of the through hole, the area of the column body is far smaller than that of the through hole.
In the embodiment, a small-sized soft magnetic core is arranged at the center of the 8-shaped coil, the 8-shaped coil and the soft magnetic core are eccentric, and the purpose of improving the stimulation precision of the 8-shaped coil along the direction of the magnetic core is achieved by matching the soft magnetic core and the 8-shaped coil; as shown in fig. 1, the center position of the figure-8 coil refers to a position where two coils in the figure-8 coil are connected. As shown in fig. 1, the eccentricity between the figure-8 coil and the soft magnetic core means: the center of the through hole of the 8-shaped coil is not coincident with the center of the column. When the magnetic core is concentric with the 8-shaped coil, the magnetic core can reduce the current intensity in the coil without influencing the stimulation effect, but can not improve the precision of the electric field distribution generated in the head model. Based on this, the magnetic core of the present embodiment can reduce the current intensity in the coil without affecting the precursor of the stimulation effect, but cannot improve the accuracy of the electric field distribution generated in the head model.
In the process of transcranial magnetic stimulation, alternating current with specific frequency is introduced into the 8-shaped TMS coil (namely the 8-shaped coil), and due to the fact that the frequency of the alternating current is low, the TMS coil can be considered to work in a quasi-static environment, and therefore the magnetic field around the coil can be analyzed through a magnetostatically related theory. Similarly, the magnetization process of a soft magnetic core with high permeability and high saturation magnetization can be magnetized in a quasi-static environment.
Under the action of external magnetic field, the isotropic magnetic material is magnetized, and the magnetic induction intensity after magnetization and the relative magnetic permeability mu of the B magnetic materialrProportional, it can be expressed as:
B=μ0μrH (1)
here, B is the magnetic induction after magnetization of the material; mu.s0Is a vacuum magnetic conductivity; mu.srIs the relative permeability of the magnetic material; h is the magnetic field strength in the environment where the material is located.
Typically, the permeability of magnetic materials can be very high, such as the μ of silicon steelrCan reach 7000 to 10000, fullAnd the magnetization intensity can reach 1.9-2.0T. Therefore, a soft magnetic core with high magnetic conductivity and high saturation magnetization is added in the center of the 8-shaped coil, and strong magnetic induction can be generated under a very small external magnetic field. Therefore, the magnetic material with high magnetic conductivity is added into the 8-shaped coil, the magnetic field distribution around the TMS coil is adjusted, and the stimulation precision of the TMS coil is improved.
In order to verify the influence of the soft magnetic shielding layer on the stimulation effect of the 8-shaped TMS coil, a spherical model is used for simulating head tissues, the spherical radius of the head tissues is 95mm, the electric conductivity is 4S/m, and the relative magnetic conductivity is 1; the surface of the sphere is provided with a shell with the thickness of 5mm to represent the skull, the electrical conductivity is 0.01S/m, and the relative magnetic permeability is 0.99. The influence of the magnetic shielding layer on the stimulation effect of the TMS coil is evaluated by using the attenuation condition of the electric field on the surface of the intracranial tissue along the measuring line and the central axis, and the electric field is attenuated more quickly along the increasing of the included angle theta between the measuring line and the axis, which means that the electric field intensity is more concentrated near the axis; the faster the decay with increasing depth on the central axis indicates that the coil can stimulate to a shallower depth.
Fig. 1 shows a figure-8 TMS coil with a U-shaped magnetic core and a magnetic shielding layer with a rectangular opening. The part of placing in 8 font TMS coil inside in the model is radius 8mm, and the cylinder of height 23mm is by a length 42mm, and the width is 16mm, and thickness is 10 mm's cube between two cylinders. The opening is left in the magnetic shielding layer under the magnetic core, and the opening is l along the size of x axle direction, and the opening size is w along the y axle direction, in the model of subsequent calculation shielding layer opening to the influence of intracranial electric field, keeps l 100mm unchangeable, analyzes the influence of opening size to intracranial electric field intensity through changing the size w of opening on the y axle direction.
Referring to fig. 4 and 5, fig. 4 and 5 show the distribution of the intracranial electric field on the measurement line and the central axis when the size w of the opening of the shielding layer is changed by using the finite element method, and the electric field strength is normalized in order to visually compare the influence of the size of the opening on the stimulation effect. Fig. 4 shows the influence of the w on the electric field distribution on the intracranial tissue surface measurement line, and as w increases, the decay rate of the electric field intensity on the arc line decreases, so that the size of w needs to be reduced as much as possible to ensure the stimulation precision in the y-axis direction of the three-dimensional model. FIG. 5 shows the influence of the magnitude of w on the electric field distribution on the central axis of the three-dimensional model, and as w increases, the electric field attenuation speed on the axis decreases, but the influence of w on the electric field attenuation on the central axis is not obvious.
Fig. 6 is for adding the influence of shielding layer electric field distribution on the camber line in the y axle direction, and along with theta increases, when adding w ═ 50 mm's shielding layer, the decay rate of electric field along the camber line is faster, consequently compares the coil that does not have magnetic shielding layer, can realize more accurate stimulation.
In summary, compared with the existing transcranial magnetic stimulation coil, the transcranial magnetic stimulation coil of the embodiment has the following beneficial effects:
(1) the embodiment provides a transcranial magnetic stimulation coil with an eccentric structure, and the accuracy of stimulation of an 8-shaped coil along the direction of a magnetic core can be improved by matching 8-shaped coils with different sizes.
(2) The U-shaped magnetic core is added at the center of the 8-shaped TMS coil, the magnetic shielding layer with an opening is arranged near the magnetic core, and the stimulation precision of the 8-shaped TMS coil on other areas except the direction along the magnetic core is improved by adjusting the size and the shape of the opening of the magnetic shielding layer.
(3) Through the combination of the properly designed magnetic shielding layer structure and the magnetic shielding layer and the magnetic core, the stimulation precision of the coil is further effectively improved on the premise of not influencing the stimulation depth of the 8-shaped TMS coil.
The present embodiments also provide a transcranial magnetic stimulation device, comprising:
the transcranial magnetic stimulation coil is realized by adopting the 8-shaped transcranial magnetic stimulation coil;
and the power supply is used for providing alternating current with preset frequency for the transcranial magnetic stimulation coil.
The transcranial magnetic stimulation device of the embodiment has a corresponding relationship with the 8-shaped transcranial magnetic stimulation coil, so that the function and effect of the 8-shaped transcranial magnetic stimulation coil are achieved.
The embodiment also provides a transcranial magnetic stimulation system, which comprises a box body and a plurality of transcranial magnetic stimulation devices arranged in the box body.
The transcranial magnetic stimulation system of the embodiment has a corresponding relationship with the 8-shaped transcranial magnetic stimulation coil, so that the function and effect of the 8-shaped transcranial magnetic stimulation coil are achieved.
In the foregoing description of the specification, reference to the description of "one embodiment/example," "another embodiment/example," or "certain embodiments/examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
While embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that: various changes, modifications, substitutions and alterations can be made to the embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.
While the preferred embodiments of the present invention have been illustrated and described, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.