Tms coil and tms system

Abstract

The present invention relates to a coil (10) for transcranial magnetic stimulation of a human brain (28), which coil is designed and configured to generate an alternating magnetic field, comprising: at least one electrical line (12) having a first end and a second end, on each of which a feed-in connection (14, 16) is arranged for feeding electrical energy to the coil (10), and which comprises at least four windings which, at least in portions, are at different distances from the adjacent winding; and an insulating structure, made of a non-conductive material, to be placed on the head of a person (30) to be treated, which insulating structure is arranged underneath the windings of the electrical line (12) such that the insulating structure electrically insulates the line from the head of a person to be treated; wherein the coil (10) comprises two groups (18, 20) of windings: a first group (18) comprises inner windings; a second group (20) comprises outer windings; and a first surface is formed by a first surface surrounding the first group (18) of windings and a second surface is formed by a second surface surrounding the second group (18) of windings; and the second surface is at least 1.5 times as large as the first surface.

Description

[0001] TMS coil and TMS system

[0002] The present invention relates to a coil for the transcranial magnetic stimulation of a human brain and a corresponding system comprising such a coil and a corresponding method.

[0003] Transcranial magnetic stimulation is a non-invasive treatment method for the human brain and is used for a variety of therapeutic purposes. For example, it can be used effectively to treat affective disorders, particularly clinical depression, obsessive-compulsive disorder, and post-traumatic stress disorder.

[0004] The mode of action of transcranial magnetic stimulation is essentially based on the fact that neurons and neuronal circuits in defined brain areas, which may themselves comprise multiple neurons and are also referred to as neuronal excitation circuits, are stimulated from the outside using an externally generated alternating (electro)magnetic field, so that the stimulated neutrons in turn emit signals. The resulting signals are forwarded and processed by other neurons and neuronal circuits in the brain. By using defined parameters to generate the alternating magnetic field for neuron stimulation, neurons and neuronal circuits can be neuromodulated as needed. The result is that neuromodulated neurons and neuronal circuits process, in particular, endogenous signals, i.e., the body's own signals, in a modified manner over the long term and beyond the duration of the treatment.This has a positive effect on the therapeutic treatment of the aforementioned disorders. A significant advantage is that treatment with transcranial magnetic stimulation eliminates the need for additional psychotropic medications, which are known to have negative effects on human well-being. Transcranial magnetic stimulation is the subject of extensive research, particularly with regard to the biophysical modeling of neurostimulation and the spatial-physiological modeling of the brain areas to be stimulated. For the technological background of the invention, reference is made to the scientific article by Goetz & Deng (2017) "The development and modeling of devices and paradigms for transcranial stimulation," International Review of Psychiatry, 29:2, 115-145 [doi: 10.1080 / 09540261.2017.1305949], the content of which is incorporated into the disclosure of this application.

[0005] To generate the alternating magnetic field, coils with multiple turns are used in a conventional manner. However, one challenge is to design the coil so that the field characteristics of the alternating magnetic field are optimally adapted to the areas of the human brain to be stimulated. Conventional coils therefore have turns with complex, partially overlapping geometries, which can generate very high field strengths locally at other, undesired locations. These can harm the patient or at least represent a side effect for the patient. In addition, the high field strengths require complex cooling. Finally, the complex winding geometries also make the conventional coils expensive.

[0006] In particular, special coils are used specifically for stimulating the cortical surface of the brain. Some are designed for focal points in the primary motor cortex or the dorsolateral prefrontal cortex, for example, and generate very concentrated, focal electric fields at these or these locations and low electric field strengths outside them. Other coils activate neurons in a large, well-defined cortical area, which includes, for example, the DLPFC, and have correspondingly more extensive areas with high electric field strengths, possibly also with a specific electric field direction. All have in common that the stimulated area is well-defined with a specific minimum electric field strength, and in other areas, a certain electric field strength is not exceeded to minimize side effects.Certain (neuro-)physiological effects and corresponding procedures for generating them are often tied to a specific spatial field distribution, which can be generated by different coils, but whose field distribution in the brain is sufficiently similar.

[0007] Against this background, a person skilled in the art is faced with the task of creating a coil, in particular a TMS coil, and a system and method by means of which the implementation of transcranial magnetic stimulation can be improved and, in particular, simplified with regard to handling. Particularly preferred is a cost-effective method for creating a TMS coil suitable for cost-effective operation.

[0008] The above object is achieved by a coil for the transcranial magnetic stimulation of a human brain, which is designed and configured to generate an alternating magnetic field, comprising: at least one electrical line with a first end and a second end, at each of which a feed connection for supplying the coil with electrical energy is arranged, and which has at least four turns with, at least in sections, different distances from the adjacent turn; and an insulation structure made of a non-conductive material for application to a head of a person to be treated, which insulation structure is arranged below the turns of the electrical line in such a way that the insulation structure electrically insulates the line from the head of a person to be treated, wherein the coil comprises two groups of turns; a first group comprises inner turns; a second group comprises outer turns;and a first surface is formed by a first surface enclosing the first group of turns; and a second surface is formed by a second surface enclosing the second group of turns; and the second surface is at least 1.5 times the size of the first surface.;

[0009] The above object is further achieved by a system for transcranial magnetic stimulation of a human brain, comprising: a coil as defined above; and a control device for controlling the coil to form an alternating magnetic field by means of the coil.

[0010] Finally, the above object is achieved by a method for transcranial magnetic stimulation of a human brain by means of a coil as defined above or by means of a system as defined above, comprising the steps:

[0011] Arranging the insulation structure of the coil in an environment of a head of a person to be treated; and

[0012] Forming an alternating magnetic field for transcranial magnetic stimulation of the brain of the person to be treated by controlling the coil. By means of an electrical line with at least four turns, which at least in sections have a different distance from the adjacent turn, a coil with an advantageous geometry can be created in a technically simple manner. Distances between turns according to the invention can, for example, refer to gaps between turns, but also distances between the centers of the cross sections of the corresponding turns. An insulating structure enables increased safety during treatment with such a coil, since an energy input in the form of electrical energy from the coil to the person to be treated can be prevented. The insulating structure can, in particular, be a layer of lacquer arranged around the turns of the coil. In other words, the coil can be lacquered.It is understood that the coil can also be encapsulated with an insulator, such as a resin, or wrapped with an insulator. In particular, the insulation structure can also be designed in the form of a plate and arranged only on the side of the coil facing the head of the person being treated during treatment.

[0013] Despite the simple geometry, two groups of windings with at least four windings can generate a magnetic field comparable to existing TMS coils. In particular, comparable or even better stimulation results can be achieved. It has been shown that a coil with this type of design can stimulate individual regions of the human brain more specifically. This advantageous design allows for reduced production costs and cooling requirements for such a coil.

[0014] By means of a second surface which is at least 1.5 times as large as the first surface, in a departure from previous concepts, a flat coil can be created with a geometry adapted to the stimulation of a human brain with regard to the alternating magnetic field generated by the coil. The geometry makes it possible to create a coil which is easy to handle, cost-effective to manufacture, and multifunctional, i.e. which can be used by different people. In particular, a coil can be created which is energy-efficient to operate. An area enclosing the windings is preferably to be understood as a closed area in which the windings lie, in particular as a smallest area which, at its boundary, largely rests against the winding. In particular, the enclosing area can be understood as the smallest area which completely covers the winding.For example, the enclosing can be formed by directly connecting two ends of a turn.

[0015] By combining two groups of windings with an area ratio of 1 to at least 1.5 and with a varying distance from the adjacent winding, at least in some sections, a weight-optimized TMS coil with improved handling can be created. The advantageous interaction of the area ratio and the variable spacing configuration allows for the generation of an alternating magnetic field suitable for transcranial magnetic stimulation. Passive cooling of the TMS coil is preferably possible, which contributes to both improved handling and lower operating and production costs. Furthermore, passive cooling enables a broader range of applications.

[0016] In a preferred embodiment, the coil is curved and, in one dimension, is curved with an average arc length of less than 2TT / 3 rad (120°), preferably less than TT / 2 rad (90°) and particularly preferably less than TT / 2 rad (60°) relative to a center of the curvature, or in two dimensions, is curved with an average solid angle of less than TT sr (steradian), preferably less than 2 / 3 TT sr and particularly preferably less than TT / 2 sr. In addition, the radius of curvature of the curvature is at least 60 mm, preferably at least 85 mm and particularly preferably at least 110 mm. By curving the coil, an advantageous introduction of the alternating magnetic field into the brain for stimulation can occur despite a simple geometry. In particular, this makes it possible to create a coil that can be produced efficiently and cost-effectively and allows simplified handling.A curvature makes it easier to position the coil on the head of a patient. In particular, the curvature described above can be used to find a compromise between coil manufacturability and achievable field strength.

[0017] Particularly preferably, the coil windings are arranged in a planar manner. This allows for the creation of a technically efficient and cost-effective coil. A coil can be created that allows for easy handling yet precise alignment. Such a coil is preferably suitable for stimulation in which the coil is guided as a handheld device.

[0018] In particular, it is conceivable for individual groups of coil turns to be arranged in a planar manner, in particular in one plane, whereby the individual planes can be offset from one another. For example, one of these planes can be spaced from another of these planes by up to 10 mm in the normal direction in both directions.

[0019] Advantageously, the turns of the electrical line between the feed connections are arranged without kinks. Additionally or alternatively, at least one turn has a negative curvature in at least one area. By kink-free is meant in particular that a function that describes the course of the turns between the feed connections is continuously differentiable everywhere. A negative curvature is meant that a tangent to a function describing the turn intersects the turn or the function. A negative curvature or a negative radius of curvature means in particular that a tangent to the turn of the electrical line would intersect this turn of the electrical line. If the turn does not have a negative radius of curvature, no tangent can be found for this turn that intersects this turn. The mechanical stability of the coil can be increased by kink-free turns.Particularly in hand-held coils, damage to the coil in the event of accidental dropping or impact can be advantageously counteracted. By having at least one region in which the winding has a negative curvature, a coil with a highly variable geometry can be created that can be optimized to generate the desired alternating magnetic field. In particular, this flexibility in the geometry enables the creation of a compact coil with a sufficiently high field strength and field geometry of the alternating magnetic field.

[0020] Advantageously, the electrical line comprises between four and twenty turns. Additionally or alternatively, the coil has an inductance in the range from 4 pH to 5 mH, preferably in the range from 5 pH to 500 pH, and particularly preferably in the range from 5 pH to 30 pH. Further additionally or alternatively, the coil has an electrical resistance in the range from 1 mQ to a maximum of 1,000 mQ, preferably in the range from 2.5 mQ to a maximum of 750 mQ, and particularly preferably in the range from 5 mQ to 50 mQ. The above-claimed ranges for the turns, the electrical resistance, and the inductance make it possible to create a highly variable coil that can be optimally tailored to a specific application. In particular, a coil can be created that can be operated in an energy-efficient manner and preferably requires less cooling. Preferably, a coil can be created that can be manufactured and operated cost-effectively.

[0021] Particularly preferably, the second area is at least 1.75 times, preferably at least 2 times, and particularly preferably at least 2.5 times, the size of the first area. These advantageous ratios allow the alternating magnetic field and a magnetic vector potential to be further defined. In particular, a region of the human brain can be stimulated more precisely without simultaneously stimulating regions that should not be stimulated.

[0022] Advantageously, the coil has a single electrical conductor forming the windings. The windings are preferably arranged without overlap. This further simplifies the manufacture of the coil. Because the individual conductor tracks do not overlap, the interaction between the individual conductor tracks can be reduced and the efficiency of the coil can be increased. Furthermore, a coil can be created that is inexpensive and quick to manufacture.

[0023] In a further advantageous embodiment, the windings have at least two different center points. The center point is understood to be the point with the shortest distance to all sections of a winding. In particular, the center point can also be a center of gravity of a winding. A winding is preferably understood to be a 360° revolution of the electrical line. It is understood that the line does not necessarily have to form a circle, but can take on other geometric shapes. Consequently, viewed from a center point of the winding, only one conductor track is arranged in each direction. The first group preferably has a different center point than the second group, wherein the center points of the individual windings of a group are each essentially the same.In particular, different center points enable the formation of an asymmetric magnetic field so that stimulation can be spatially limited more precisely.

[0024] Preferably, the centers of the at least two surfaces are at least 20 mm apart, preferably at least 30 mm apart, and particularly preferably at least 40 mm apart. Furthermore, several turns forming a first surface can have a common center, while simultaneously several turns forming a second surface can also form a common center.

[0025] Further preferably, the turns of the electrical line have a direction-dependent asymmetry, with a first asymmetry with respect to a first direction in the coil plane, which preferably comprises different conductor densities of the electrical line, and a second asymmetry with respect to a second direction running perpendicular to the first direction in the coil plane, which second direction preferably comprises different bending radii of the electrical line. The term "coil plane" is understood to mean, in particular, the plane or surface in which the turns of the electrical line are located. It is understood that this can be understood to mean a curved and / or bent plane or curved surface. By means of a direction-dependent asymmetry, the alternating magnetic field formed can be further specified, so that highly precise stimulation can be carried out by means of the coil.In particular, the asymmetries in different, preferably perpendicular, directions enable a highly precise determination and formation of the magnetic field.

[0026] The control unit can comprise a voltage source and / or a current source and, in particular, have two connections via which the coil can be supplied with electrical energy. In particular, the control unit can have a function generator, which is particularly designed to generate periodic electrical signals with user-defined parameters such as signal shape, pulse duration, frequency, or amplitude in order to generate a desired alternating magnetic field. The control unit can be designed to control the coil, in particular, with current pulses having a pulse duration of a maximum of 5 ms, in particular a maximum of 1 ms, for example between 50 ps and 350 ps, ​​preferably between 10 ps and 1000 ps, ​​in particular between 120 ps and 400 ps, ​​so that the field characteristics of the magnetic field to be generated can be optimized.The control unit can be configured to generate a magnetic flux density of at least 1 T and / or an electric field strength of at least 10 V / m, in particular at least 50 V / m, preferably at least 100 V / m, through the coil. The control unit can be configured to apply a voltage, in particular a variable voltage, of at least 100 V, in particular of at least 1000 V, to the coil.

[0027] The electrical conductor forming the coil's windings can have different cross-sections in different sections. Furthermore, several conductor sections can comprise different materials, such as copper, aluminum, or other metals or electrical conductors. In particular, it is conceivable for one section to be stamped, waterjet cut, or laser cut, while another section is manufactured using a different manufacturing technique. These sections are then joined together to form the coil's electrical conductor.

[0028] Due to the advantageous geometry of the coil, there are points from which the current flows in the same direction.

[0029] Windings can be formed that not only curve inwards, but also outwards at times or in sections.

[0030] In particular, the different geometries of the individual windings can form indentations or lagoons, i.e. areas free of conductors and at least partially surrounded by conductors. A vector describing the direction of one or both of the surrounding conductors can therefore have a double change of sign in the second path derivative. In particular, the respective current in both conductors surrounding an indentation or lagoon points in the same direction. A current pointing in the same direction is to be understood in particular as meaning that there is at least one point in each of the conductors surrounding an indentation or lagoon at which a vector describing the current flow points in the same direction.

[0031] Preferably, there are at least two clusters or groups of coils, with the coils in the groups spanning similar areas to each other and representatives from different groups spanning different areas.

[0032] The windings of the coil can be arranged such that at least two surface regions are formed which are surrounded by windings on all sides, wherein a first surface region is surrounded on at least two opposite sides by windings whose respective current points in the same direction, and a second surface region is surrounded on at least two opposite sides by windings whose respective current points in opposite directions. Preferably, the first surface region has windings on two further opposite sides whose currents point in opposite directions. These two surface regions preferably do not overlap and / or are also preferably not intersected by any winding. Preferably, one surface region, preferably each of the surface regions, comprises at least one tenth, particularly preferably at least one seventh, of the total surface area of ​​the coil enclosed by the outermost winding.By sides of turns whose respective current points in the same (opposite) direction, it is to be understood in particular that there is at least one point in each of the opposite turns enclosing the surface area in which a vector describing the current flow points in the same (opposite) direction.

[0033] The invention is described and explained in more detail below using selected embodiments in conjunction with the accompanying drawings. They show:

[0034] Figure 1 is a schematic simplified representation of a coil for transcranial magnetic stimulation in a plan view;

[0035] Figure 2 shows a section through the coil according to Figure 1 along the section plane A;

[0036] Figure 3 shows a system for transcranial magnetic stimulation of a human brain comprising a coil according to Figures 1 and 2 and a control device;

[0037] Figures 4a to 4i show diagrams of various coil geometries for coils according to the invention for transcranial magnetic stimulation in a plan view;

[0038] Figure 5 schematically shows a simulated magnetic field strength during magnetic stimulation using a coil according to the invention; and Figure 6 schematically shows the steps of a method according to the invention for transcranial magnetic stimulation of a human brain.

[0039] Figure 1 shows a simplified schematic representation of a coil 10 for transcranial magnetic stimulation (TMS) of a human brain. The coil 10 comprises an electrical line 12 that forms several turns. Feed connections 14, 16 are arranged at both ends of the electrical line 12 to connect the coil 10 to a control unit (not shown) so that the coil 10 can be controlled. The electrical line 12 forms a first group 18 with inner turns, i.e., turns with smaller bending radii, and a second group 20 of outer turns, i.e., turns with larger bending radii.

[0040] The first group 18 approximately encloses an area that is at least 1.5 times smaller than the area enclosed by the second group 20. An enclosing area of ​​the second group 20 is therefore 1.5 times as large as an enclosing area of ​​the first group 18.

[0041] Furthermore, the first group 18 and the second group 20 each have different center points, wherein the center points for turns of a group in the example shown are substantially the same and are each shown as "X" in the figure.

[0042] In Figure 1, a section plane A with viewing direction is also shown.

[0043] Figure 2 shows schematically a section through the coil 10 at the cutting plane A.

[0044] The same reference numerals refer to the same features and are not explained in more detail in Figure 2 and the following figures.

[0045] In the example shown, the conductor cross-section of the electrical line 12 is the same for all windings. It is understood that this is a simplified representation, and different conductor cross-sections may be provided.

[0046] Furthermore, it is understood that instead of the planar or flat geometry shown, a curved geometry is also conceivable, which in particular comprises a radius of curvature of at least 60 mm, in the case of a curvature in one dimension less than TT / 2 rad (90°) arc length or in the case of a curvature in two dimensions on average a solid angle of less than TT sr.

[0047] Figure 3 schematically shows an embodiment of a system 22 for transcranial magnetic stimulation with a coil 10, in particular a coil according to Figures 1 and 2, and a control unit 24.

[0048] The control unit 24 is connected to the feed connections of the coil 10 by means of two conductors. It is understood that the supply lines to the feed connections preferably contribute little or nothing to an alternating magnetic field 26 generated by the coil 10. This can be achieved, for example, by shielding the supply lines.

[0049] The alternating magnetic field 26 of the coil 10 acts on the human brain 28 of a person 30 to be treated.

[0050] The control unit 24 is designed to generate an alternating current whose parameters, such as frequency and amplitude, are user-adjustable. The alternating current fed by the control unit 24 flows through the electrical conductor 12 of the coil 10.

[0051] It is understood that the parameters of the alternating magnetic field 26 can be varied by the parameters of the alternating current flowing through the conductor 12. Furthermore, the parameters of the alternating magnetic field are determined by the geometry of the windings of the electrical conductor 12 of the coil 10. For reasons of clarity, an insulating structure of the coil 10 is not shown in Figures 1 to 3. This insulating structure is arranged between the person 30 to be treated and the surface of the line 12 facing the person 30 to be treated and electrically insulates the line 12 from the person 30 to be treated. This prevents the person 30 to be treated from suffering an electric shock, even if the coil 10 is touched. Furthermore, the mechanical stability of the coil 10 can be increased by the insulating structure.

[0052] In Figures 4a to 4i, diagrams 32 show different courses 34 of the electrical conductor 12 of the coil 10 in plan view.

[0053] The Y-axis of Figure 32 runs from approximately +80 cm to approximately -40 cm in 20 cm increments. The X-axis runs from approximately -80 cm to approximately +80 cm in 20 cm increments. Each square of a grid shown in Figure 32 for better orientation therefore covers an area of ​​20 cm x 20 cm.

[0054] Figure 4a shows a pattern 34 with five turns, with the first group 18 of inner turns comprising essentially 2.5 turns and the second group 20 of outer turns also comprising approximately 2.5 turns. The winding direction is predominantly co-rotational. Consequently, there are no reverse windings.

[0055] The inner coils form an oval, egg-shaped, or pear-shaped configuration. The coils each have a slight indentation on the side with the larger Y value.

[0056] The outer coils each have indentations approximately centrally in the X direction. In addition, the individual coils of the outer coils have one or two indentations in the negative Y direction.

[0057] Figure 4b shows a six-turn pattern 34. This pattern is similar to the pattern shown in Figure 4a, with the inner group of turns having an additional turn with a similar pattern to the other turns in this group.

[0058] Figure 4c shows another pattern 34 with seven turns. Unlike Figure 4b, the pattern 34 shown in Figure 4c includes one more outer turn. Furthermore, the indentations of the outer turns in the X direction are more pronounced than in Figure 4b.

[0059] Figure 4d shows a further pattern 34 with eight turns. In contrast to the pattern 34 shown in Figure 4c, the pattern 34 according to Figure 4d has one more outer turn. The innermost outer turn of the pattern 34 according to Figure 4d has very pronounced indentations in the X-direction and Y-direction, so that a minimum distance in the X-direction between two conductor tracks of the innermost turn of the group of outer turns is approximately 40 cm and a minimum distance of this turn in the Y-direction is approximately 20 cm. In a region of this turn that encloses the group of inner turns, the turn has a roughly oval or pear-shaped pattern. In a region not enclosing the group of inner turns, the turn has a peanut-like shape.

[0060] Figure 4e shows a further configuration 34 of an electrical conductor 12. Unlike the embodiment shown in Figure 4c, the configuration 34 according to Figure 4e has one more outer turn and one more inner turn. The turns extend similarly to the configuration 34 shown in Figure 4c.

[0061] Figures 4f to 4i show various courses 34 which are similar to the course 34 shown in Figure 4d. These diagrams show courses 34 in which, with ascending figure numbering, the course 34 comprises one more turn. The number of inner turns and outer turns is alternately increased by 1, with the inner turns each having a similar course to that in the previously shown figures and the outer turns each having a substantially hexagonal course with indentations in the X and Y directions, with the hexagon comprising an approximately square base with a section drawn upwards on the upper side, i.e. in the negative Y direction. The course 34 according to Figure 4f comprises one more outer turn than the course 34 shown in Figure 4e. The course 34 shown in Figure 4g comprises one more inner turn than the course 34 according to Figure 4f.The course 34 according to Figure 4h comprises one more inner turn than the course 34 shown in Figure 4g. The course 34 shown in Figure 4h comprises one more inner turn than the course 34 shown in Figure 4g.

[0062] Figure 5 schematically shows a standardized simulated electric field strength in a human brain 28. The scale ranges from 0 to 2, with the range from 0 to 1 grayed out, and stronger simulated electric fields in delimited areas 40 from 1 to 2 shown in black and white. Standardized field strengths in the range from 1 are shown in white, and standardized field strengths in the range from 2 are shown in black. Standardized field strengths in a range between 1 and 2 in areas 40 are shown in shades of gray.

[0063] Figure 6 schematically shows the steps of a method according to the invention for the transcranial magnetic stimulation of a human brain by means of a coil 10 as previously shown in the figures or by means of a system according to Figure 3.

[0064] In a first step S1, the insulation structure of the coil 10 is arranged in an environment of a head of a person 30 to be treated.

[0065] In a second step S2, an alternating magnetic field 26 is formed for transcranial magnetic stimulation of the brain 28 of the person 30 to be treated by controlling the coil as previously explained with reference to Figure 3. The invention has been comprehensively described and explained with reference to the drawings and the description. The description and explanation are to be understood as exemplary and not restrictive. The invention is not limited to the disclosed embodiments. Other embodiments or variations will become apparent to those skilled in the art upon use of the present invention and upon careful analysis of the drawings, the disclosure, and the following patent claims.

[0066] In the claims, the words "comprising" and "having" do not exclude the presence of further elements or steps. The undefined article "a" or "an" does not exclude the presence of a plurality. A single element or unit can perform the functions of several of the units recited in the claims. An element, unit, device, and system can be partially or completely implemented in hardware and / or software. The mere mention of some measures in several different dependent claims should not be understood to mean that a combination of these measures cannot also be used advantageously. Reference signs in the claims are not to be understood as limiting.

Claims

Patent claims 1. A coil (10) for the transcranial magnetic stimulation of a human brain (28), which is designed and configured to generate an alternating magnetic field (26), comprising: at least one electrical line (12) with a first end and a second end, at each of which a feed connection (14, 16) for supplying the coil (10) with electrical energy is arranged, and which has at least four turns with, at least in sections, different distances from the adjacent turns; and an insulation structure made of a non-conductive material for contact with the head of a person to be treated (30), which is arranged below the turns of the electrical line (12) such that the insulation structure electrically insulates the line from the head of a person to be treated, wherein the coil (10) comprises two groups (18, 20) of turns; a first group (18) comprises inner turns; a second group (20) comprises outer turns;and a first surface is formed by a first winding enclosing the first group (18), and a second surface is formed by a second winding enclosing the second group (18); and the second surface is at least 1.5 times as large as the first surface.; Coil (10) according to the preceding claim, wherein the coil (10) is formed with a curvature and is curved in one dimension on average with less than 2TT / 3 rad (120°) arc length, preferably less than TT / 2 rad (90°) arc length and particularly preferably less than TT / 3 rad (60°) arc length, relative to a center of the curvature, or in two dimensions on average with a solid angle of less than TT sr (steradian), preferably less than 2 / 3 TT sr and particularly preferably less than TT / 2 sr; and a radius of curvature of the curvature is at least 60 mm, preferably at least 85 mm and particularly preferably at least 110 mm. Coil (10) according to claim 1, wherein the turns of the coil (10) are arranged planarly. Coil (10) according to one of the preceding claims, wherein the windings between the feed connections (14, 16) are arranged without kinks; and / or comprises at least one winding in at least one region in which the winding has a negative curvature.Coil (10) according to one of the preceding claims, wherein the electrical line (12) comprises between 4 and 20 turns; the coil (10) has an inductance in the range of 4 pH to 5 mH, preferably in the range of 5 pH to 500 pH and particularly preferably in the range of 5 pH to 30 pH; and / or. the coil (10) has an electrical resistance in the range from 1 mQ to a maximum of 1000 mQ, preferably in the range from 2.5 mQ to a maximum of 750 mQ, and particularly preferably in the range from 5 mQ to 50 mQ. Coil (10) according to one of the preceding claims, wherein the second area is at least 1.75 times, preferably at least 2 times, and particularly preferably at least 2.5 times, as large as the first area. Coil (10) according to one of the preceding claims, wherein the coil (10) has exactly a single electrical line (12) which forms the windings; and wherein the windings are preferably arranged without overlap. Coil (10) according to one of the preceding claims, wherein the windings of the electrical line (12) have at least two different center points.Coil (10) according to one of the preceding claims, wherein the turns of the electrical line (12) have a direction-dependent asymmetry, comprising: a first asymmetry with respect to a first direction in the coil plane, which preferably comprises different conductor densities of the electrical line (12); and a second asymmetry with respect to a second direction running perpendicular to the first direction, in the coil plane, which preferably comprises different bending radii of the electrical line (12). A system (22) for the transcranial magnetic stimulation of a human brain (28), comprising: a coil (10) according to any one of the preceding claims; and a control device (24) for controlling the coil (10) in order to generate an alternating magnetic field (26) by means of the coil (10). A method for the transcranial magnetic stimulation of a human brain (28) using a coil (10) according to any one of claims 1 to 9 or using a system (22) according to claim 10, comprising the steps: Arranging (S1) the insulation structure of the coil (10) in an environment of a head of a person to be treated (30); and Forming (S2) an alternating magnetic field (26) for transcranial magnetic stimulation of the brain (28) of the person to be treated (30) by controlling the coil (10).

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