JP2012125546A - Magnetic coil, and transcranial magnetic stimulation system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic coil capable of efficiently producing an eddy current of required intensity at a limited place by relatively simple constitution by devising a coil form, and a transcranial magnetic stimulation system.SOLUTION: The magnetic coil 20 includes a plurality of coiled conductor parts 20J and 20K to form a magnetic field in which a pair of the coiled conductor parts 20J and 20K is configured such that the coil center Jc of the winding of one coiled conductor part 20J is made eccentric in the direction approaching the coil center Kc of the winding of the other coiled conductor part 20K.

Description

  The present invention relates to a magnetic coil that generates a magnetic field, in particular, a magnetic coil composed of a plurality of spiral conducting wire portions, or a magnetic coil in which a plurality of spiral conducting wire portions are three-dimensionally arranged around a predetermined axis, and such magnetism. The present invention relates to a transcranial magnetic stimulation device including a coil.

In recent years, interest in transcranial magnetic stimulation therapy has increased as a treatment method for many patients with neurological diseases for which drug treatment is not always effective. In this transcranial magnetic stimulation therapy, treatment and / or alleviation of symptoms can be achieved by applying magnetic stimulation to a specific part of the brain (for example, nerve in the brain) by a magnetic field generation source placed on the scalp surface of the patient. Unlike conventional electrical stimulation methods that use indwelling electrodes that require craniotomy and have a very strong resistance to the patient, this is a relatively new treatment that is non-invasive and requires less burden on the patient. It is expected to spread.
In addition to treatment, transcranial magnetic stimulation is used for the purpose of diagnosis of neurological diseases, and transcranial magnetic stimulation devices for diagnosis have been put into practical use. Furthermore, since magnetic stimulation can induce or temporarily block the activity of a specific part of the brain, it is also being used in basic brain function research.

As a specific method of such transcranial magnetic stimulation therapy, a current is passed through a treatment coil placed on the surface of a patient's scalp to generate a pulsed magnetic field, and a local vortex is generated in the skull using the principle of electromagnetic induction. A method is known in which a current is generated to stimulate a nerve in the brain immediately below the coil (see, for example, Patent Document 1).
In this patent document 1, it is confirmed that refractory neuropathic pain is effectively reduced by transcranial magnetic stimulation treatment performed by such a method, and more accurate local stimulation realizes a higher pain reduction effect. Has been. However, it has also been clarified that the optimal stimulation site varies slightly depending on the individual patient.

Moreover, in the said patent document 1, when the above-mentioned transcranial magnetic stimulation treatment is performed, it will be clarified that the pain alleviation effect lasts for several hours but does not last for several days or more. ing. Therefore, it is considered desirable from the viewpoint of pain reduction to perform the above-mentioned therapy continuously every day if possible without leaving much time interval. In order to be able to perform such continuous treatment without imposing excessive physical and temporal burdens on the patient, continuous repeated treatment at home or in a nearby clinic Ideally it should be possible.
However, conventionally, it is assumed that all magnetic stimulation devices used for transcranial magnetic stimulation therapy are used in relatively large hospitals and research institutions for examination and research by skilled specialists, etc. It is quite large and expensive. For this reason, not only is the cost burden excessive at a patient's individual home or a relatively small clinic or clinic, but it is generally difficult to secure an installation space.

  A magnetic stimulation device used for transcranial magnetic stimulation therapy uses a magnetic coil for treatment for generating an eddy current in the skull using the principle of electromagnetic induction, and a drive circuit for supplying a current to be supplied to the magnetic coil. The coil drive device is provided as a main part, and this coil drive device occupies most of the weight and size of the entire device. Therefore, if the coil driving device can be reduced in size, the magnetic stimulation device can be substantially reduced in size.

  One of the most effective measures to reduce the size of the coil drive device is to increase the efficiency of magnetic field generation by the magnetic coil, so that the eddy current of the required strength can be applied to the target site in the brain even with a drive circuit with lower output. It may be possible to wake up. If a lower output drive circuit can be applied, not only the drive circuit itself can be downsized, but also its related parts can be downsized, which greatly contributes to downsizing and cost reduction of the entire coil drive device. be able to.

  Although not directly conscious of the miniaturization of the coil drive device, the above-mentioned Patent Document 1 discloses a so-called so-called “8” shape in which two circular spiral coil portions are arranged on the same plane. The use of figure-8 spiral coils for transcranial magnetic stimulation therapy has been introduced. This 8-shaped spiral coil has a maximum induced current density just below the point corresponding to the intersection of the 8-characters, and is suitable for efficiently providing localized stimulation.

International Publication No. 2007/123147

  However, conventionally, the coil drive device used for transcranial magnetic stimulation therapy has been produced on the premise that it is used in a considerably large-scale medical institution, and thus has high output and high function. The total weight is excessive (for example, about 70 kg), and since the power consumption is large, electrical work is required at the time of installation, such as a large size and high production cost, and a relatively large installation space is required. There was a problem that the installation cost was high. For this reason, particularly when considering installation in the patient's home or a relatively small clinic or clinic, it is not only excessively costly, but it is generally difficult to secure installation space. It was.

As described above, increasing the efficiency of magnetic field generation by a magnetic coil so that an eddy current having a required strength can be generated even with a drive circuit having a lower output is to reduce the size of the coil drive device. It is valid.
It should be noted that increasing the magnetic field generation efficiency by the magnetic coil in this way so that a strong eddy current can be obtained at a specific location is not only necessary for a therapeutic coil used in magnetic stimulation therapy but also at a limited location. It is equally important for other various types of magnetic coils that are required to generate eddy currents. Furthermore, not only when the coil driving device is downsized, but also from the viewpoint of energy saving. Meaningful.

  Accordingly, the present invention provides a magnetic coil and a transcranial magnetic stimulation device capable of efficiently generating an eddy current having a required strength in a limited location with a relatively simple configuration by devising a coil form. This is done as a basic purpose.

  The inventors of the present application, while pursuing earnest research and development to achieve such an object, connect the vortex center and the center of the outer peripheral shape by decentering the vortex center of the spiral coil from the center of the outer peripheral shape of the spiral coil. Along the straight line, the density of the induced current generated by energization of the coil is also biased due to the density of the coil winding spacing, and by utilizing such a bias of the induced current density effectively As a result, it has been found that a strong eddy current can be generated in a limited specific location even when the current value is the same as compared with the case where the induced current density is relatively uniform and has no bias.

FIG. 26 shows a magnetic coil 90 in which two spiral conducting wire portions are arranged side by side in a plan view and the vortex center of each spiral conducting wire portion is decentered, so that the target site in the brain of the patient's head Mh has a required strength. FIG. 27 is an explanatory view schematically showing a case of inducing eddy current. FIG. 27 shows a brain of a patient's head Mh using a so-called 8-shaped spiral coil 110 instead of the magnetic coil 90. It is explanatory drawing which shows typically the case where the eddy current of required intensity | strength is induced | guided | derived to the target site | part of an inside.
As shown in these figures, the path of the current induced in the brain is close to the shape in which the winding shapes of the coils 90 and 110 are projected onto the brain.

In the case of the conventional 8-shaped spiral coil 110 shown in FIG. 27, the spiral conducting wire portions 110J and 110K are concentrically wound. However, in the case of the magnetic coil 90 shown in FIG. The conducting wire portions 110J and 110K are configured by decentering in the direction in which the vortex centers of the windings approach each other, that is, the vortex centers of the spiral conducting wire portions 90J and 90K are the outer peripheral shapes of the spiral conducting wire portions 90J and 90K. By decentering from the center of the coil to the center side, the coil winding interval is close on the center side, and the density of the induced current generated by energizing the coil 90 is also increased on the center side. As a result, as compared with the case of the conventional 8-shaped spiral coil 110 shown in FIG. 27, the stimulation current induced in the brain is also concentrated in the center, and the target site can be stimulated with a high current density. Alternatively, the magnetic coil 90 can be operated with a smaller coil current to obtain the same stimulation current density at the target site.

  In this way, the inventors of the present invention can use the bias of the induced current density caused by decentering the vortex center of the coil spiral conductor part from the center of the outer shape of the coil to make a specific identification even if the current value is the same. Focusing on the fact that a strong eddy current can be generated in a location, the invention has led to the invention of a magnetic coil that can efficiently generate an eddy current of a required strength in a limited location with a relatively simple configuration. is there.

  A magnetic coil according to a first invention of the present application is a magnetic coil configured by a plurality of spiral conducting wire portions and generating a magnetic field, and at least one set of the spiral conducting wire portions has a winding of one spiral conducting wire portion. The vortex center is decentered in the direction approaching the vortex center of the winding of the other spiral conducting wire portion.

  A magnetic coil according to a second invention of the present application is a magnetic coil for generating a magnetic field, in which a plurality of spiral conductive wire portions are three-dimensionally arranged around a predetermined axis, and at least one set of spiral conductive wire portions. Is characterized in that the vortex center of the winding of one spiral conducting wire portion is decentered in a direction approaching the vortex center of the winding of the other spiral conducting wire portion.

  In these cases, the one set of spiral conducting wire portions may be configured such that a part of one spiral conducting wire portion overlaps a part of the other spiral conducting wire portion substantially in parallel with each other.

  In this case, the overlapping portion may overlap until the outer peripheral portion of one spiral conducting wire portion reaches or near the vortex center of the winding of the other spiral conducting wire portion.

In the above case, the one set of spiral conducting wire portions may be inclined so as to form a mountain shape with a predetermined angle therebetween.
Or in the above case, you may comprise by curved surfaces, such as a part of cylindrical surface and a part of spherical surface, so that said 1 set of spiral conducting wire part may follow the surface of a patient's head.

  Moreover, in the above case, the outer peripheral shape of the spiral conducting wire part is preferably circular.

  Further, in the above case, the plurality of spiral conducting wire portions may be wound using a conducting wire having a quadrangular cross-sectional shape.

Alternatively, the plurality of spiral conducting wire portions may be wound up using a conducting wire configured by bringing a number of metal wires close to each other.
Alternatively, the plurality of spiral conducting wire portions may be wound up by using a conducting wire formed by laminating a tape-like conducting wire after being electrically insulated.

  A transcranial magnetic stimulation device according to a third invention of the present application is a transcranial magnetic stimulation device including a therapeutic magnetic coil having at least one set of spiral conductors for generating an eddy current in a patient's skull. The spiral conducting wire portion is formed with a curved surface along the surface shape of the patient's head.

  In this case, the curved surface may be a part of a cylindrical surface.

  Alternatively, the curved surface may be a part of a spherical surface.

  In the above transcranial magnetic stimulation apparatus, the at least one set of spiral conducting wire portions is configured such that the vortex center of the winding of one spiral conducting wire portion is decentered in a direction approaching the vortex center of the winding of the other spiral conducting wire portion. May be.

  A transcranial magnetic stimulation device according to a third invention of the present application is provided with a therapeutic magnetic coil having a therapeutic magnetic coil having at least one set of spiral conductors for generating an eddy current in a patient's skull. A) a case for accommodating each of the at least one set of spiral conducting wire portions individually or as a whole, and b) a cover attached to the case so that a gap is formed between the case, c) Force an air flow for cooling the case from an air inlet provided in a predetermined part of the cover to an air outlet provided in another part of the cover via the gap. And an air circulation means for circulation.

  In this case, it is preferable that the gap is provided at least on the side of the case close to the patient's head.

  In particular, it is more preferable that the gap is provided on both the side close to the patient's head of the case and the opposite side thereof.

  According to the first invention of the present application, in the magnetic coil composed of a plurality of spiral conducting wire portions, at least one set of spiral conducting wire portions, the vortex center of the winding of one spiral conducting wire portion is that of the other spiral conducting wire portion. Since it is configured to be decentered in the direction approaching the vortex center of the winding, the spacing between the coil windings becomes dense along the straight line connecting the vortex center of one spiral conducting wire portion and the center of the outer peripheral shape. Become. As a result, when an induced current is generated by energizing the coil, a region with a high induced current density is generated corresponding to the density of the coil winding interval of one spiral conductor, and a strong brain is generated in this region. Irritation is obtained. In other words, for a magnetic coil composed of a plurality of spiral conducting wire portions, a brain stimulation with a required intensity can be efficiently generated at a limited location with a relatively simple configuration simply by devising the shape and arrangement of each spiral conducting wire portion. be able to.

  According to the second invention of the present application, in a magnetic coil in which a plurality of spiral conductor portions are three-dimensionally arranged around a predetermined axis, at least one set of spiral conductor portions is wound on one spiral conductor portion. Since the vortex center of the wire is decentered in the direction approaching the vortex center of the winding of the other spiral conducting wire portion, along the straight line connecting the vortex center of one spiral conducting wire portion and the center of the outer peripheral shape, Density occurs in the interval between the coil windings. As a result, when an induced current is generated by energizing the coil, a region with a high induced current density is generated corresponding to the density of the coil winding interval of one spiral conductor, and a strong brain is generated in this region. Irritation is obtained. In other words, even in a magnetic coil in which a plurality of spiral conducting wire portions are three-dimensionally arranged around a predetermined axis, a relatively simple configuration that only devise the shape and arrangement of each spiral conducting wire portion can be used in a limited location. The brain stimulation with the required intensity can be generated efficiently.

  In these cases, the one set of spiral conducting wire portions is configured such that a part of one spiral conducting wire portion overlaps a part of the other spiral conducting wire portion substantially in parallel with each other, thereby overlapping the overlapping portions. Then, the density of the induced current generated when the coil is energized becomes higher, and a stronger brain stimulation can be obtained.

  In particular, the overlapping portion is configured so that the outer peripheral portion of one spiral conducting wire portion overlaps to the vortex center of the winding of the other spiral conducting wire portion or the vicinity thereof, so that the coil windings are closely spaced. The two can be overlapped with each other in the widest range, and a strong eddy current can be obtained more efficiently.

  In the above case, the surface shape of the object having a mountain shape (such as a human head) is formed by inclining the pair of spiral conducting wire portions so as to form a mountain shape across a predetermined angle. As a result, it is possible to generate an induced current so that more efficient magnetic field generation can be realized. Alternatively, in the above case, even if the spiral conducting wire part is configured by a curved surface such as a part of a cylindrical surface or a part of a spherical surface along the surface of the patient's head, the magnetic field can be generated efficiently. can do.

  Also, in the above case, by making the outer peripheral shape of the spiral conducting wire portion circular, the magnetic coil having the spiral conducting wire portion having a shape that has the highest versatility and can also suppress the electrical resistance during energization is low. The same effects as those described above can be achieved.

  Further, in the above case, the plurality of spiral conducting wire portions are formed by winding up a conducting wire having a quadrangular cross-sectional shape, so that the cross-sectional area can be increased even when the coil winding interval is the same as in the case of a circular cross-section. A large amount of current can be ensured and flowed, and more efficient magnetic field generation can be realized.

  Alternatively, in the above case, the plurality of spiral conducting wire portions are wound up using a conducting wire configured by bringing a number of metal wires close to each other, thereby increasing the flexibility of the coil winding and facilitating the formation of the spiral conducting wire portion. It can be carried out. Alternatively, in the above case, the same effect can also be obtained by winding up the plurality of spiral conducting wire portions using a conducting wire that is formed by laminating a tape-like conducting wire after being electrically insulated. .

  According to the third invention of the present application, since the spiral conductor portion of the magnetic coil for treatment forms a curved surface along the surface shape of the patient's head, an induced current is generated along the surface shape of the patient's head. And more efficient magnetic field generation can be realized.

  In this case, by forming the curved surface by a part of a cylindrical surface, it is possible to realize efficient magnetic field generation with a simple configuration.

  Alternatively, by forming the curved surface from a part of a spherical surface, it is possible to realize a more efficient magnetic field generation with a simple configuration.

  In the above transcranial magnetic stimulation apparatus, the at least one set of spiral conducting wire portions is configured such that the vortex center of the winding of one spiral conducting wire portion is decentered in a direction approaching the vortex center of the winding of the other spiral conducting wire portion. By doing so, the space | interval of a coil winding will arise along the straight line which connects the vortex center of one spiral conducting wire part, and the center of an outer periphery shape. As a result, when an induced current is generated by energizing the coil, a region with a high induced current density is generated corresponding to the density of the coil winding interval of one spiral conductor, and a strong brain is generated in this region. Irritation is obtained. In other words, for a magnetic coil composed of a plurality of spiral conducting wire portions, a brain stimulation with a required intensity can be efficiently generated at a limited location with a relatively simple configuration simply by devising the shape and arrangement of each spiral conducting wire portion. be able to.

  Further, according to the fourth invention of the present application, an air flow is forcibly circulated in a gap formed between a case housing the spiral conducting wire portion of the therapeutic magnetic coil and a cover attached to the case. Thus, the case can be cooled, so that the spiral conducting wire portion of the magnetic coil that generates heat accompanying the magnetic stimulation treatment can be effectively cooled, and even higher frequency magnetic stimulation can be performed without any problem.

  In this case, by providing the gap at least on the side of the case close to the patient's head, the side of the magnetic coil close to the patient's head can be reliably cooled.

  In particular, by providing the gap on both the side close to the patient's head of the case and the opposite side, the entire magnetic coil can be cooled to obtain a higher cooling effect.

It is explanatory drawing which shows roughly the whole structure of the magnetic stimulation apparatus which concerns on this embodiment. It is a perspective view which expands and shows the coil unit of the said magnetic stimulator. It is a top view which expands and shows the magnetic coil of the said coil unit. It is explanatory drawing which shows the form of the said magnetic coil typically. It is a figure for demonstrating verification of the effect of the magnetic coil which concerns on the Example of this invention by computer simulation. In the said computer simulation, it is a figure which displays the eddy current density distribution inside the spherical body which simulates a brain on the straight line parallel to a coil surface. In the said computer simulation, it is a figure which displays the eddy current density distribution inside the spherical body which simulates a brain on the straight line perpendicular | vertical to a coil surface. It is a figure which shows after the said eddy current density distribution is normalized by the maximum value. In the said computer simulation, it is a figure which displays the electric field distribution obtained from the result on the straight line 2 cm above the spherical body which simulates a brain. It is a top view which shows an example of a trial manufacture coil. It is explanatory drawing which shows an example of the drive circuit of the said trial manufacture coil. It is a perspective view which shows an example of the prototype coil manufactured by the method of inserting a conducting wire in the groove dug in the case. It is a perspective view which shows an example of the trial manufacture coil provided with the flow path for forced air cooling. It is a figure which illustrates the inductance and electrical resistance of the said trial manufacture coil. It is a perspective view which shows the search coil used for the experiment of a magnetic field measurement. It is a figure which shows an example of the recording waveform of an oscilloscope in the experiment of the said magnetic field measurement. It is a figure which shows the waveform of the generated magnetic field calculated | required from the recording waveform of the said oscilloscope. It is a figure which shows the waveform of the coil electric current calculated | required from the experiment of magnetic field measurement, and the waveform of a generated magnetic field. It is a figure which shows the numerical analysis result of the magnetic field distribution of the generated magnetic field. It is a figure which shows distribution of the strength of the magnetic field on the plane of y = 0 calculated | required by the said numerical analysis. It is a figure which shows an example of the temperature change of a coil when magnetic stimulation is performed with high frequency. It is explanatory drawing which shows typically the form of the eccentric spiral coil which concerns on the 1st modification of the said embodiment. It is a front view which shows typically the form of the eccentric spiral coil which concerns on the 2nd modification of the said embodiment. It is a front view which shows typically the form of the eccentric spiral coil which concerns on the 3rd modification of the said embodiment. It is a front view which shows typically the form of the eccentric spiral coil which concerns on the 4th modification of the said embodiment. It is explanatory drawing which shows typically the case where an eddy current is induced | guided | derived in a patient's brain by the magnetic coil which arrange | positioned two spiral conducting wire parts side by side in planar view, and made the vortex center of each spiral conducting wire part eccentric. It is explanatory drawing which shows typically the case where an eddy current is induced | guided | derived in a patient's brain using a conventional type 8 figure spiral coil. It is explanatory drawing which shows the calculation model for calculating | requiring the eddy current in a brain and the inductance of a coil by computer simulation. It is a figure which shows an example of the contour map of the magnetic flux density around the coil obtained from computer simulation. It is a top view which shows three types of coils from which eccentricity differs. In a computer simulation, it is a figure which illustrates the change of the electrical property of a coil when the eccentric degree of a coil, an outer diameter, an internal diameter, and the number of turns are each changed. It is a schematic diagram which shows an example of the magnetic coil provided with the four spiral conducting wire parts arrange | positioned at four leaf shape. It is a schematic diagram which shows an example of the magnetic coil provided with four spiral conducting wire parts arranged in three dimensions. It is a schematic diagram which shows an example of the magnetic coil provided with five spiral conducting wire parts arranged in three dimensions. It is a schematic diagram which shows another example of the magnetic coil provided with five spiral conducting wire parts arranged in three dimensions.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings, taking as an example a case where the present invention is applied to a magnetic coil used as a therapeutic coil in a magnetic stimulation apparatus used for transcranial magnetic stimulation therapy.
In the following description, terms indicating a specific direction (for example, “up”, “down”, “left”, “right”, and other terms including them, “clockwise direction”, “counterclockwise” ”) Is used to facilitate understanding of the invention with reference to the drawings, and the present invention should not be construed as being limited by the meaning of these terms. Moreover, in the magnetic coil demonstrated below, the same code | symbol is used for the same or similar component.

  FIG. 1 is an explanatory diagram schematically showing the overall configuration of a magnetic stimulation apparatus according to this embodiment used for transcranial magnetic stimulation therapy. In this figure, a magnetic stimulation apparatus (hereinafter simply referred to as “apparatus” as appropriate) that is indicated by the numeral 1 as a whole is a scalp of a patient M (subject) who is fixedly seated on a treatment chair 2. Treatment and / or alleviation of symptoms is achieved by applying magnetic stimulation to nerves in the brain by a magnetic coil (treatment coil) 20 included in a coil unit 5 disposed on the surface.

The magnetic coil 20 generates a dynamic magnetic field for applying magnetic stimulation to at least a specific part of the brain of the patient M, and can be operated to be displaceable with respect to the surface of the head Mh of the patient M. It is fixed in the unit 5.
In FIG. 1, after the coil unit 5 is gripped and the therapeutic coil 20 is displaced along the patient's scalp and the coil 20 is positioned, the coil 20 is not moved carelessly. More preferably, the state where the coil unit 5 is fixed to the holder fixture 3 is shown.

The magnetic stimulation device 1 includes a coil driving device 10 including a coil driving circuit (not shown) in order to control the supply of current pulses to the magnetic coil 20. The coil driving device 10 and the magnetic coil 20 are electrically connected to each other via a cable 16.
The coil drive device 10 includes a main body case 11 formed in, for example, a substantially rectangular parallelepiped box shape, and a terminal portion 12 to which the device-side connector 17 of the cable 16 is coupled to the main body case 11, and an operator uses the coil drive device. Operation switch section 13 for performing on / off (ON / OFF) operation of 10, output display section 14 for displaying the intensity of current flowing through the magnetic coil 20, the charging voltage of the internal capacitor, the percentage value with respect to the maximum charging voltage, etc. Etc. are provided. Although not specifically shown, the coil driving device 10 is configured such that the intensity of the magnetic stimulation by the magnetic coil 20 and the setting of the current pulse that determines the cycle, the setting of the pulse waveform, the pulse interval, the number of pulses, etc. It is configured to be performed by an operator.

  The coil unit 5 includes a coil case 6 that covers the periphery of the magnetic coil 20, as shown in an enlarged view in FIG. A terminal block 7 to which the coil side connector 18 of the cable 16 is coupled may be formed in the coil case 6. Instead of providing the terminal block 7 as described above, as shown in FIG. 3, the lead portions 22J and 22K of the coil winding 21 extended from the coils 20J and 20K, the magnetic coil 20, and a drive circuit (not shown). A grip 9 that houses the cores 16J and 16K of the cable 16 that connects the two may be provided. In this case, the core members 16J and 16K of the cable 16 are arranged so that a bending line in which a plurality of thin conductors are bundled (more preferably, a twisting line in which a plurality of bundled thin conductors are wound in a paper bag shape) so as to bend easily. The lead portions 22 </ b> J and 22 </ b> K of the coil winding 21 and the core members 16 </ b> J and 16 </ b> K of the cable 16 are connected inside the grip 9.

The coil case 6 plays a role of preventing electric shock by ensuring insulation between the winding of the magnetic coil 20 and the patient M, and positions the magnetic coil 20 in a predetermined mold (not shown). The resin material 8 having the required characteristics in the molten state (at least electrical insulation and heat resistance up to about 100 ° C.) is filled in the mold and solidified, thereby being integrated with the magnetic coil 20. Formed. Thus, by integrally forming with the resin 8, the winding 21 of the magnetic coil 20 is securely fixed in the coil case 6, and deformation such as distortion of the winding shape (that is, the coil shape) is generated. Can also be suppressed.
As another method of forming the magnetic coil 20, a spiral groove can be carved in the coil case 6 and the winding 21 can be fitted into this groove. In this case, since it is not necessary for the coil 20 itself to maintain an eccentric spiral complicated shape, the magnetic coil 20 can be easily manufactured. Further, when the magnetic coil 20 is formed by fitting the winding 21 in the groove as described above, the forming operation can be performed more easily when the winding 21 has a square cross section than the circular cross section.

In the present embodiment, the magnetic coil 20 is a magnetic coil that includes a plurality (two in this embodiment) of spiral conducting wire portions 20J and 20K and generates a magnetic field, and at least one set (in this embodiment, Since there are two spiral conducting wire portions, one set) of the spiral conducting wire portions 20J and 20K, the vortex center Jc or Kc of the winding of one spiral conducting wire portion 20J or 20K is the winding of the other spiral conducting wire portion 20K or 20J. It is configured to be eccentric in the direction approaching the vortex center Kc or Jc.
More specifically, in this embodiment, the magnetic coil 20 is configured so that a plurality (two in this embodiment) of circular spiral spiral conductors 20J and 20K are substantially side by side in a plan view. It is arranged and arranged. Thus, by arranging the two spiral conducting wire portions 20J and 20K so as to be substantially side by side in a plan view, when the coil 20 is energized, the two spiral conducting wire portions 20J and 20K are closest to each other. A strong eddy current can be obtained, and this is suitable for efficiently providing localized stimulation.

  4 (a) to 4 (c) are explanatory views schematically showing the form of the magnetic coil 20, FIG. 4 (a) is a plan view of the magnetic coil 20, and FIG. 4 (b) shows the magnetic coil 20 with an arrow 4b. , 4b seen from the direction of arrow (front view), FIG. 4C is a view of the magnetic coil 20 seen from the direction of arrows 4c, 4c (side view).

  As shown in FIGS. 4 (a) to 4 (c), in the present embodiment, in particular, each of the spiral conducting wire portions 20J and 20K has an outer peripheral shape of each of the spiral conducting wire portions 20J and 20K. The center is decentered by a predetermined amount from the centers Js and Ks. Moreover, these two spiral conductor portions 20J and 20K are arranged such that the distance Dc between the vortex centers Jc and Kc is smaller than the distance Ds between the outer peripheral centers Js and Ks (Dc <Ds). . That is, in this case, the vortex centers Jc and Kc of the spiral conducting wire portions 20J and 20K are decentered in the direction in which the vortex centers Jc and Kc approach each other by (Ds−Dc) / 2, respectively. .

  As described above, the two spiral conducting wire portions 20J and 20K arranged substantially side by side in a plan view have the vortex centers Jc and Kc of the spiral conducting wire portions 20J and 20K being the outer peripheral shapes of the spiral conducting wire portions 20J and 20K. Since each of the spiral conducting wire portions 20J and 20K is decentered by a predetermined amount from the centers Js and Ks, along the straight lines Lcs respectively connecting the vortex centers Jc and Kc and the outer peripheral centers Js and Ks, The space between the coil windings 21 is sparse and dense. In addition, the two spiral conductor portions 20J and 20K are arranged such that the distance Dc between the vortex centers Jc and Kc is smaller than the distance Ds between the outer peripheral centers Js and Ks. The parts with a close spacing of 21 are arranged close to each other.

  With this arrangement, when the magnetic coil 20 is energized to generate an induced current, regions having a high induced current density correspond to the density of the coil windings 21 of the spiral conductor portions 20J and 20K. It occurs in close proximity, and strong brain stimulation is obtained in this close location. That is, with respect to the magnetic coil 20 having the two spiral conductor portions 20J and 20K, a brain having a required strength in a limited place with a relatively simple configuration that only devise the shape and arrangement of the spiral conductor portions 20J and 20K. Stimulation can be generated efficiently.

  As a result, even with a smaller coil drive current, that is, with a lower output coil drive circuit (not shown), an eddy current having a required intensity can be generated in the target site in the brain of the patient's head Mh. . By using a lower output drive circuit, the drive circuit itself can be reduced in size as well as related components, and the coil drive device 10 as a whole can be greatly reduced in size and cost. be able to. In addition, since power consumption can be reduced, it is possible to eliminate the need for electrical work during installation. That is, the coil drive device 10 can contribute to miniaturization, cost reduction, space saving, improved installation, and energy saving.

Moreover, in the present embodiment, preferably, the two adjacent spiral conducting wire portions 20J and 20K are arranged such that parts of the spiral conducting wire portions 20J and 20K overlap each other substantially in parallel.
By adopting such a configuration, in the overlapping portion 20Q, the density of the induced current generated when the coil 20 is energized becomes higher, and it becomes possible to obtain a stronger brain stimulation.

Furthermore, in this case, more preferably, two adjacent spiral conductor portions 20J and 20K are arranged such that, with respect to the overlapping portion 20Q, the outer peripheral portion of one spiral conductor portion is at or near the vortex center of the other spiral conductor portion. It is arranged so as to overlap. That is, the outer periphery of one (left side in the figure) of the spiral conducting wire part 20J reaches the vicinity of the vortex center Kc of the other (right side in the figure) spiral part 20K (more specifically, the vortex center Kc is Up to the inner periphery of the substantially circular space portion, and conversely, until the outer periphery of the right spiral conductor 20K reaches the vicinity of the vortex center Jc of the left spiral conductor 20J (more specifically, It is comprised so that it may overlap to the inner periphery of the substantially circular space part containing the vortex center Jc.
By adopting such a configuration, the portions where the coil windings 21 are closely spaced can be overlapped in the widest range, and a strong eddy current can be obtained more efficiently.

  In addition, when a part of adjacent spiral conducting wire portions is overlapped, the outer circumference of one spiral conducting wire portion reaches the vortex center of the other spiral conducting wire portion or on the outer circumference of the substantially circular space portion including the vortex center. Both spiral conductor portions may be arranged so as to overlap each other. Or you may arrange | position so that the outer peripheral part of one spiral conducting wire part may overlap to the vicinity of a vortex center in the range which does not reach the inner periphery of the substantially circular space part containing the vortex center of the other spiral conducting wire part. Furthermore, it can be configured such that a part of the adjacent spiral conducting wire portions overlaps each other regardless of the positional relationship between the outer peripheral portion of one spiral conducting wire portion and the vortex center of the other spiral conducting wire portion.

[Verification by computer simulation]
With respect to the magnetic coil according to the present invention, the effect of configuring the vortex center of each spiral conducting wire portion to be decentered by a predetermined amount from the center of the outer peripheral shape of the spiral conducting wire portion was verified using a computer simulation technique.
Next, verification by this computer simulation will be described with reference to FIG.

  Although the brain has a complex three-dimensional structure, it was simulated with a simple sphere in order to make it easier to see the effect of “eccentricity” at the center of the vortex of each spiral conductor. The magnetic field generated by the magnetic coil has spatial symmetry, and in order to reduce the amount of calculation using the symmetry, a calculation model Nm1 in which a sphere is divided into eight parts was created. Furthermore, in order to reduce the amount of calculation, the central part was cut out to obtain a final brain model. The portion corresponding to the brain was assigned 0.106 S / m, which is the gray matter conductivity at a frequency of 3.15 kHz.

  There are skulls and scalp around the actual brain, but the skull has a very low conductivity compared to the brain, and as long as only the current distribution in the brain is considered, the skull and its outer side are approximate. Tissue can be modeled as an insulator. Although not shown in FIG. 5, a layer having zero conductivity and one relative permeability is provided around the brain to model the skull, surrounding tissue, air, and the like. The number of elements of the model Nm1 is 17160.

  On the 1/8 sphere model Nm1 that simulates the brain, for each of the two spiral conducting wire portions 30J and 30K, the vortex center is eccentric by a predetermined amount from the center of the outer peripheral shape of the spiral conducting wire portion, and the two spirals The magnetic coil 30 corresponding to the embodiment of the present invention in which the conducting wire portions 30J and 30K are arranged so that the distance between the vortex centers is smaller than the distance between the centers of the outer peripheral shapes (hereinafter referred to as “eccentric spiral coil” as appropriate). And a magnetic coil 100 corresponding to a comparative example provided with two conventional concentric spiral conductors 100J and 100K.

  The actual coil is wound in a spiral shape, but for the sake of simplification of model creation, approximation was performed with a set of circular rings. Both the two coils 30 and 100 had an outer diameter of 100 mm, an inner diameter of 20 mm, and a winding number of 10 times. In order to further increase the concentration of the induced current in the brain, the left and right windings are partially overlapped (that is, they are overlapped in plan view). The winding wire has a width of 2 mm and a height of 6 mm, and the eccentric spiral coil 30 is eccentric to the limit where adjacent windings come into contact with each other at the center. 36 elements are divided in the circumferential direction of each ring. A drive current of 4.6 kA (kiloamperes) generally required for brain stimulation was applied to each of the magnetic coils 30 and 100.

  The magnetic field generated by the magnetic coils 30 and 100 at the position of each calculation element constituting the brain and the surrounding insulator layer was calculated based on Bio-Savart's law. Subsequently, the induced current distribution inside the conductor simulating the brain was calculated by the finite element method. For the analysis, commercially available electromagnetic field analysis software PHOTO-EDDYjω was used. The pulse width in the magnetic stimulation is about 317 μs, and the frequency obtained by taking the reciprocal is 3.15 kHz. Therefore, an AC electromagnetic field analysis was performed on the assumption that the magnetic coils 30 and 100 were supplied with an AC current of this frequency.

As a result of the calculation, a convergent solution was obtained, and a strong current was induced in the surface layer portion of the sphere just below the central portion of the magnetic coils 30 and 100. Maximum current density inside the sphere, a conventional coil 100 of the comparative example (see FIG. 5 (a)) is 8.5A / ^{m 2,} an eccentric spiral coil 30 of the present invention embodiment 9.3A / ^{m 2} met It was. By decentering the vortex center of the spiral conductor portion from the center of the outer shape of the spiral conductor portion as in the present invention, the brain current density is increased by about 10%, and the effectiveness of the eccentric spiral coil can be verified. It was.

  In order to obtain a therapeutic effect by stimulating the brain in transcranial magnetic stimulation therapy, it is necessary to generate a current density in the brain above a certain threshold. For this purpose, the drive current of the magnetic coil required for this can be reduced by using the eccentric spiral coil 30 as compared with the case where the conventional coil 100 is used. This means that the stimulation efficiency of the magnetic coil is increased, and the stimulation current density in the brain necessary for obtaining a sufficient therapeutic effect can be achieved even with a coil drive circuit having a smaller output. In other words, if the eccentric spiral coil 30 is employed, the brain can be sufficiently stimulated even with a low-power coil drive circuit, so that smaller circuit components can be used, and the size and total size of the coil drive device including the coil drive circuit can be used. Weight can be reduced. In addition, a special power source with a large capacity is not required, and power can be supplied from a household outlet.

  That is, by adopting the eccentric spiral coil 30, it becomes possible to reduce the specifications and size of the components constituting the coil driving device, and to reduce the size and weight of the coil driving device that occupies most of the total weight of the magnetic stimulation device. It was confirmed that it is effective for cost reduction and installation improvement.

  The distribution of eddy current obtained by the simulation was plotted in a direction parallel to the coil surface (x direction) and a vertical direction (z direction). FIG. 6 shows the eddy current distribution in the direction parallel to the coil surface (x direction). It can be seen that in both the eccentric spiral coil and the conventional concentric coil, the strongest eddy current is obtained immediately below the center of the coil. Moreover, about the eddy current induced | guided | derived from an eccentric spiral coil, the width | variety (half-value half width) which an eddy current becomes a half of a maximum value was 2.43 cm. On the other hand, in the case of the conventional concentric coil, the half width at half maximum was 2.49 cm. FIG. 7 shows how the eddy current density is attenuated in the depth direction (−z direction). In any case, attenuation was observed with the distance from the coil. Similarly, when the half width was obtained, it was 1.86 cm for the eccentric spiral coil and 1.88 cm for the conventional concentric coil.

  In order to compare the current localization between the eccentric spiral coil and the conventional concentric coil, a graph was created by normalizing the eddy current density with the maximum value. FIG. 8A shows an eddy current distribution in the x direction at z = −0.5 cm. FIG. 8B shows the eddy current density distribution in the −z direction. From the two graphs, it was found that the localization of the eddy current distribution in the brain hardly changed in the direction parallel to the coil surface and in the depth direction.

  FIG. 9A shows the electric field distribution along the coil surface for the position of the skull or scalp 2 cm above the brain surface. From this, it can be seen that the electric field generated by the eccentric spiral coil is about 15% stronger than that of the conventional concentric coil. Moreover, in order to compare localization, the graph normalized by the maximum value is shown in FIG.9 (b). The half width at half maximum of the electric field induced from the eccentric spiral coil was 2.01 cm, and the half width at half maximum of the electric field induced from the concentric circular coil was 2.31 cm. Because the distance between the brain and the coil is large, there is almost no difference in the eddy current distribution in the brain in FIG. 8A, but the electric field in the vicinity of the coil is more localized in the eccentric spiral coil. Show.

  As described above, it was shown that the localization of eddy currents induced in the brain is almost the same between the eccentric spiral coil and the conventional concentric coil. In the treatment of intractable pain, the target of stimulation is the primary motor area of the brain. In this case, since local stimulation is required, it is considered that a higher spatial resolution of the stimulation is effective. However, in home treatment, high-precision coil positioning is not always possible. In currently available navigation systems, the error from the optimal position is within 5 mm, so it is desirable that the stimulus spatial resolution of the eccentric spiral coil be lower than 5 mm. The half width at half maximum of the eddy current density obtained from the analysis is about 2 cm, which satisfies this requirement.

[Prototype of coil 1]
A magnetic coil 40 shown in FIG. 10 was made on the basis of the proposed eccentric spiral shape. The spiral conductor portions 40J and 40K of the magnetic coil 20 have an outer diameter of 100 mm, an inner diameter of 20 mm, a winding number of 10 times, and a cross section of the conductor is a square of 2 mm × 6 mm. The shape of the winding 41 was designed by a function represented by the following equations (Equation 1) and (Equation 2).

  Here, the unit of x and y is mm, and θ is in the range of 0 ≦ θ ≦ 20π. The curve drawn by this function gives the locus of the center of the winding conductor 41. The winding length of the coil 40 is about 3.7 m. In the region near the center of the coil where the conductor is densely wound, the gap between adjacent conductors is 0.5 mm. In order to further increase the induced current, the left and right windings are overlapped. The gap between the upper and lower layers in the overlapping region is 1 mm.

The eccentric spiral shape is complicated, and it is not easy to maintain the shape by winding seamlessly from a single flat wire. Therefore, a processing method was adopted in which a winding was cut from a 6 mm thick copper plate by wire cutting like a mosquito coil. By this processing method, we succeeded in processing the shape of the coil with a shape and size with almost no distortion. When wire cutting is used, the winding can be processed automatically by a machine, which is suitable for mass production.
However, wire cutting is a processing method of cutting a shape in plan from a material plate, and therefore, in order to create a three-dimensional shape such as the current magnetic coil 40, it is necessary to divide it into a plurality of parts. . The coil shown in FIG. 10 is composed of a total of four parts including two coil windings on the left and right sides, and has three joint portions N1, N2, and N3. Two of the joints N1 and N2 are provided at the winding centers of the left and right spiral conductors 40J and 40K, and the other joint N3 is located below the right spiral conductor 40K. ing. In the central part of the coil where the conductors are dense, a small piece (not shown) of fiber reinforced plastic is inserted in the gap between the conductors to prevent electrical contact. A terminal block 47 is provided below the coil 40 so that the cable connecting the magnetic coil 40 and the drive circuit 49 (see FIG. 11) can be exchanged.

  The winding conductor 41 of the magnetic coil 40 was housed in a glass epoxy resin case 46, and the internal space was filled with an epoxy resin 48 to maintain the shape and ensure insulation. The outer dimension of the case body is 200 mm × 120 mm × 21 mm. The thickness of the case 46 at the bottom of FIG. 10 was set to 1 mm so that the distance between the winding conductor 41 and the brain could be shortened. A cable (not shown) having a length of 1 m was connected to the terminal block 47, a two-pole connector was attached to the tip, and the coil was completed. The cable used was a 4-core cable, and the current flowing in the positive and negative directions was assigned to each 2-core cable.

  As shown in FIG. 11, the basic configuration of the drive circuit 49 includes a power supply circuit 49A that generates a voltage required for each component from an AC voltage of 200V, and a booster circuit that generates a DC high voltage for charging the capacitor 49C. 49B, a capacitor 49C for accumulating charges supplied to the magnetic coil 40, a resistor 49D for adjusting the charging current of the capacitor 49C, and a semiconductor switch 49E for controlling the timing of pulse magnetic field generation. The semiconductor switch 49E has a thyristor and a diode connected in parallel in the opposite direction. After the thyristor is turned on by a control signal, a current of two phases, that is, a two-phase current flows through the magnetic coil 40.

  The case of the drive circuit 49 includes a connector for connecting a coil cable, a power switch, switches for controlling the stimulation operation, a dial for adjusting the charging voltage of the internal capacitor, and a scale for displaying a set value. The stimulation operation can be switched between a single shot, 5 pulses per second, and 10 pulses per second. When performing the repetitive operation, a timer is provided so as to cool down for 50 seconds after performing the stimulation operation for 10 seconds in order to suppress the heat generation of the magnetic coil 40. The total weight of the drive circuit 49 was 41 kg. A trigger input connector is also provided so that a stimulation operation synchronized with an external trigger can be performed.

[Coil prototype 2]
A second magnetic coil 20 shown in FIG. 3 was prototyped using a processing method different from the above-described wire cutting. A processing method was adopted in which the coil 20 is wound up from a single flat wire 21 having a cross section of 6 mm × 2 mm so that a seam is not formed. This method has an advantage that electrical resistance can be prevented from occurring at the joint. An eccentric spiral groove was dug in advance in a coil case 6 made of fiber reinforced plastic, and a flat conductor 21 was fitted into the groove to create the shape of the coil 20. By adopting this processing method, windings of any shape can be manufactured easily and with good reproducibility.
The function that gives the outer and inner curves of the groove of the case is expressed by the following equations (Equation 3) and (Equation 4) for the outer curve of the coil winding 20J in the left half of FIG.

  Further, the curve inside the coil winding 20J in the left half of FIG. 3 is expressed by the following equations (Equation 5) and (Equation 6).

  On the other hand, the outer curve of the right half coil winding 20K in FIG. 3 is expressed by the following equations (Equation 7) and (Equation 8).

  Further, the curve inside the coil winding 20K in the right half of FIG. 3 is expressed by the following equations (Equation 9) and (Equation 10).

  As shown in FIG. 12, the case 6 made of fiber reinforced plastic is divided into a total of four parts 6P, 6Q, 6R, and 6S on the coil body, and the grip 9 is another part. By adopting such a divided structure case, even a three-dimensional winding having an overlap can be manufactured. After the flat wire was fitted and assembled as a whole, it was filled with an epoxy resin and fixed. The core members 16J and 16K of the cable 16 that connect the magnetic coil 20 and the drive circuit (not shown) have a plurality of thin conductor wires bundled together (more preferably, a plurality of bundled thin conductor wires so as to bend easily. The lead wires 22J and 22K of the flat wire 21 extended from the coils 20J and 20K and the core members 16J and 16K of the cable 16 are formed on the grip 9. Connected internally.

  In order to obtain a sufficient therapeutic effect, it is necessary to perform magnetic stimulation at a high frequency of 5 times or more per second. Under such conditions, heat is generated in the magnetic coil. As a method of cooling the magnetic coil, a natural air cooling method in which fins are formed on the coil case to improve heat dissipation, a forced air cooling method in which the coil winding part is cooled by blowing air with a fan, near the coil winding. There are a natural convection liquid cooling method in which a fluid is filled and the fluid is circulated by thermal convection, and a forced convection liquid cooling method in which the fluid is circulated by an external pump. As the forced convection liquid cooling method, there are a method of forming a flow path in the case and a method of forming a tunnel-shaped flow path in the conductor of the coil and flowing the fluid through the flow path into the conductor. .

FIG. 13 shows an example of a prototype coil provided with a flow path for forced air cooling. Covers 23 </ b> P, 23 </ b> Q, and 23 </ b> R made of a total of three parts are attached to the outside of the case 6. The case 6 stores a plurality of spiral conducting wire portions of the magnetic coil individually or as a whole. A gap is formed between the case 6 and the covers 23P, 23Q, and 23R. The gap is formed in, for example, an air port 24 provided in the cover 23P and an air port 25 provided in the cover 23R, for example. Communicate. That is, the air port 24, the gaps between the case 6 and the covers 23P, 23Q, and 23R, and the air port 25 communicate with each other to form one flow path as a whole.
An air pump (not shown) provided with a fan for blowing air is connected to the air port 24 via a hose (not shown), and the air pumped by the air pump and blown by the fan is air. The air flows into the flow path from the opening 24, passes through the gaps between the case 6 and the covers 23P, 23Q, and 23R, and then flows out from the air opening 25. The magnetic coil in the case 6 can be forcibly cooled by the air flow. A vacuum cleaner or the like having a suction function may be connected to the air port 24 instead of an air pump having a blowing function. In this case, the air port 25 serves as an air inlet and the air port 24 serves as an air outlet. These air pumps having a blowing function or vacuum cleaners having a suction function constitute an air flow means for forcibly flowing a cooling air flow between the air ports 24 and 25 via the gap. Yes.

By adopting the above configuration, the air flow is forced into the gaps formed between the case 6 that houses the spiral conductor portion of the magnetic coil and the covers 23P, 23Q, and 23R that are attached to the case 6. Since the case 6 can be cooled by circulation, it is possible to effectively cool the spiral conductor portion of the magnetic coil that generates heat with the magnetic stimulation treatment, and to perform the magnetic stimulation more frequently without any trouble. it can.
Further, when such a cooling structure is provided, in order to reliably cool the side near the patient's head of the magnetic coil, the gap through which the cooling airflow flows is at least on the side near the patient's head of the case 6 It is preferable to provide in. Furthermore, by providing the gap on both the side close to the patient's head of the case 6 and the opposite side, the entire magnetic coil can be reliably cooled to obtain a higher cooling effect.

  In the above description, the spiral center of one set of spiral conductors is decentered in a direction approaching the center of the spiral of the other spiral conductor. However, the effect obtained by providing the above cooling structure is not limited to the case of the eccentric spiral coil, and even with a concentric spiral coil. It is clear from the above explanation that it is obtained. Accordingly, configurations using these concentric coils are also included in the present invention.

[Measurement of inductance and resistance]
In order to evaluate the electrical characteristics of the eccentric spiral coil according to the embodiment of the present invention, the inductance and resistance were measured. A magnetic coil 20 similar to that shown in FIG. 4 was used, and this magnetic coil 20 was connected to an LCR meter. The horizontal axis of FIG. 14 is the operating frequency of the LCR meter, and the vertical axis is the values of inductance and resistance. The inductance was about 11 to 12 μH, and no significant dependence on the frequency was observed. On the other hand, the resistance value decreased as the frequency increased. This is due to the fact that the effective area through which current flows decreases with increasing frequency, i.e. the skin effect.

[Experiment of magnetic field measurement]
Next, an experiment (magnetic field measurement) was performed to confirm that the eccentric spiral coil according to the embodiment of the present invention can generate a magnetic field as planned. Hereinafter, this magnetic field measurement experiment will be described.
<Measurement method>
In this experiment, a magnetic coil 20 similar to that shown in FIG. 4 is used, and this magnetic coil 20 is connected to a coil driving device (that is, a coil driving circuit inside it). A small search coil for magnetic field measurement was arranged. When a magnetic field is generated, a voltage is generated in the search coil according to the law of electromagnetic induction. This voltage waveform was recorded with an oscilloscope. Further, the current flowing through the magnetic coil 20 was recorded at the same time using a CT (current transformer) built in the coil drive circuit.

The search coil is a minute coil for detecting a magnetic field, and as shown in FIG. 15, for example, a copper wire having a diameter of 0.3 mm is wound around the tip of the acrylic pipe 26. The number of windings is 9 in total, 5 times for the inner layer and 4 times for the outer layer, and the effective diameter is 6.3 mm for the inner layer and 7.1 mm for the outer layer. From these values, the effective area of the search coil 25 is calculated to be 314.3 mm ² .
The search coil 25 was disposed at the following three measurement positions.
Measurement position A: vortex center Kc of the right spiral conductor portion 20K
Measurement position B: the center of the entire magnetic coil 20 (the midpoint between the left and right vortex centers Jc, Kc)
Measurement position C: vortex center Jc of the spiral conductor portion 20J on the left side

Further, in order to measure the attenuation of the magnetic field according to the distance from the magnetic coil 20, an acrylic block spacer is inserted between the magnetic coil 20 and the search coil 25, and the distance is set to 0 mm (the coil coil case 6 and the search coil 25. From the contact state) to 10 mm, 20 mm, and 30 mm. Therefore, the number of measurement points is 12. The coil coil case 6 has a thickness of 1 mm on the surface of the magnetic coil 20 to which the search coil 25 is applied.
The direction of the magnetic field vector is substantially the z direction (direction perpendicular to the coil surface) at the measurement positions A and C, and is substantially the x direction (left and right direction) at the measurement position B. Since the search coil 25 is sensitive to a magnetic field in a direction perpendicular to the coil surface, the search coil 25 is held so that the direction of the magnetic field vector and the surface of the search coil 25 are orthogonal to each other at each measurement position. I did it.
The oscilloscope used for the measurement is Tektronix TDS2014B and CT is Pearson model 4418.

<Measurement results>
FIG. 16 shows an example of output waveforms from the search coil 25 and the CT displayed on the oscilloscope in this magnetic field measurement experiment. The upper waveform is the output waveform from the search coil 25, and the lower waveform is the output waveform from the CT.
Assuming that the magnetic field at the position where the search coil 25 is placed is B (t), the voltage V (t) generated in the search coil 25 is given by the following equation (Equation 11).

Here, S is an effective area (314.3 mm ² ) of the search coil 25. The peak voltage of the search coil 25 was about 4V.

A voltage proportional to the current flowing through the magnetic coil 20 is generated from the CT, and the CT voltage and coil current can be converted by a coefficient of 0.001 V / A. The obtained peak current is 3.2 kA and the pulse width is 240 μs.
When Equation 11 is integrated, the following equation (Equation 12) is obtained.

  Based on the waveform recorded by the oscilloscope, numerical integration was performed to determine the waveform of the generated magnetic field in FIG. The peak magnetic flux density exceeding 400 mT (millitesla) was shown at measurement position A and distance 0 mm.

  Magnetic field measurement was also performed on the coil shown in FIG. 12 by the same method as the magnetic field measurement. FIG. 18 shows the waveform of the current flowing through the coil and the waveform of the magnetic field generated from the coil. In this magnetic field measurement, the search coil was placed at the measurement position A. A generated magnetic field of about 1.5 T was obtained for a coil current of about 6 kA at the peak value.

<Numerical analysis>
In order to verify the validity by comparing with the measurement results, numerical analysis of the generated magnetic field was performed.
FIG. 19 shows a numerical analysis result of the magnetic field distribution of the generated magnetic field. In the magnetic coil 20 shown in FIG. 19A, each spiral conducting wire portion 20J, 20K is approximated not by an actual spiral shape (spiral shape) but by a set of circular rings, which simplifies the analysis. It has been.
The magnetic field generated by each of the spiral conductor portions 20J and 20K can be calculated using the following mathematical formula.

That is, consider a case where a circular coil (spiral conductor) having a radius a is in a plane perpendicular to the z-axis with the origin as the center and a current of strength I is applied. The magnetic field vector generated at the position (x, y, z) or (r, θ, φ) by the coil is shown. Hereinafter, μ ₀ = 4π × 10 ⁻⁷ H / m is the magnetic permeability of vacuum, and the unit is MKSA unit.
The circular coil is divided into N elements in the circumferential direction. Each element is approximated by a straight line (line segment). The magnetic field generated at the position r = (x, y, z) by the n-th element at the position r = (x ′, y ′, z ′) is Bio Savart's law of the following equation (Equation 13). Given.

  Here, Δs = 2πa / N is the length of the line element, and the position r ′ is given by the following equations (Equation 14, Equation 15).

  t (r ′) is a unit vector representing the direction of the element, and is directed to the tangential direction of the circular coil, and is represented by the following equation (Equation 16).

  The magnetic field generated by the circular coil is the vector sum of the magnetic fields generated by the elements, and is expressed by the following equation (Equation 17).

  Based on the above, the magnetic field distribution is expressed by the following equation (Equation 18).

In FIG. 20, a circular coil having a radius a (a = 0.05 m) is in a plane perpendicular to the z-axis with the origin as the center, and a current having an intensity I (I = 2000 A) is applied. Is a distribution of the magnetic field strength B on the plane of y = 0, obtained using the equation (Equation 18), in the case where N is divided into N (N = 10) elements in the circumferential direction. Yes.
Here, the intensity B of the magnetic field _is obtained as ^{_{B = (B x 2 + B}} y 2 + B z 2) 1/2.

Referring to FIGS. 19B and 19C, the state where the right spiral conductor 20K overlaps the left spiral conductor 20J is also expressed in the analysis. A driving current of 3.2 kA was applied to the magnetic coil 20. As can be seen from FIG. 19B, the magnetic field is strong in the region where the right spiral conductor portion 20K and the left spiral conductor portion 20J overlap, and it can be seen that the magnetic field attenuates as the distance from this region increases. In FIGS. 19B and 19C, the length of the magnetic field vector (B _x ² + B _y ² + B _z ² ) ^½ is plotted by contour lines.

<Comparison of measurement results and analysis results>
Table 1 summarizes the measurement results and analysis results of the peak magnetic flux density at each measurement position.

磁束密度の測定結果と解析結果の比較

Comparison of magnetic flux density measurement results and analysis results

When the magnetic coil 20 and the search coil 25 are close, such as when the measurement distance is 0 mm, there is a discrepancy between the measurement result and the analysis result. However, as the measurement distance increases, both values become closer. As shown, the measurement distance of 30 mm was almost the same.
As can be seen from FIG. 19, the spatial change of the magnetic field becomes abrupt in the region close to the winding of the magnetic coil 20. Therefore, even if the position of the search coil 25 is slightly shifted, the measurement result is likely to fluctuate. In this measurement, since the search coil 25 was held by hand, positioning was not so precise, and errors were likely to occur. The analysis results in Table 1 show the magnetic flux density at the center point of the search coil 25, whereas the actual search coil 25 has a finite height and diameter. The magnetic field distribution is averaged and measured. This difference also causes a difference between the measurement result and the analysis result. Similarly, it can be said that the discrepancy is likely to occur in the vicinity of the magnetic coil 20 where the spatial change of the magnetic field is steep.

  From the above, it can be said that accurate evaluation becomes possible as the distance from the magnetic coil 20 increases. Since the measurement result and the analysis result showed close values at a measurement distance of 30 mm, it was judged that the manufactured magnetic coil was able to generate a magnetic field as planned.

[Measurement of heat generation]
The heat generation of the coil when the stimulus was output continuously was obtained from the experiment. The coil used is the same as that shown in FIG. The measuring instrument used a platinum resistance thermometer built in the coil and a thermography. The built-in platinum resistance temperature detector is embedded in the base of the grip of the coil and can measure the temperature inside the coil. Further, the thermography was fixed above the coil, and the surface temperature of the coil surface applied to the head, that is, the lower surface of FIG. 13 was measured, and the time change of the maximum temperature in the measured region was recorded. The coil of FIG. 13 is provided with a flow path for cooling by circulating air on the coil surface. In this experiment, measurement was performed with the cover for air cooling removed. The operation was performed by connecting a coil to the same drive unit used in the magnetic field measurement experiment.

The pattern of repeated stimulation was repeated for a maximum of 600 seconds with any one of the following <1> to <4> as a unit. The thermography was taken every 30 seconds, and the operation was stopped when the temperature exceeded 100 ° C. in consideration of the heat resistance of the plastic case.
<1> 5pps 50train
: A current of 5 pulses is applied for 10 seconds per second (there is a rest for 50 seconds).
<2> 5pps 100train
: A current of 5 pulses is applied for 20 seconds per second (after that, 40 seconds rest).
<3> 10pps 50train
: 10 pulses of current per second for 5 seconds (and rest for 55 seconds).
<4> 10pps 100train
: A current of 10 pulses is applied for 10 seconds per second (there is a rest for 50 seconds).

  FIG. 21 shows the experimental results. The horizontal axis represents the time (seconds) after the start of repeated stimulation, and the vertical axis represents temperature. It was found that the temperature changes depending on the coil location. That is, the temperature of the coil surface is close to the copper wire, which is a heating element, and heat is easily transmitted, so the temperature rises sharply. It was dull. On the same coil surface, the temperature was highest near the center where the copper wire was densely wound. On the other hand, at the time of rest, the surface that is in contact with air is more easily deprived of heat, and the thermography measurement results show a temperature drop, but the built-in sensor does not show a temperature drop.

In addition, in the operation pattern as described above, it was found that the stimulation frequency hardly affects the temperature increase, and the temperature increase is determined by the number of stimulations (train). Assuming 200 seconds after the start of stimulation as a steady state in the temperature rise of thermography, comparing the rise of 50 train and 100 train, the temperature rise for 50 train is about 6.3 ° C, and the temperature rise for 100 train is about 13 ° C. It was found that the temperature rise was proportional to the number of stimulations (train).
The above is a test for evaluating the capability as a device to the last, and in actual treatment, since this output is set to a few percent, the temperature rise as shown in FIG. 21 does not occur. In addition, since the coil of FIG. 13 is actually provided with a cooling mechanism, the temperature rise is actually kept lower.

  The above description is mainly about the eccentric spiral coil in which part of the spiral conducting wire part overlaps, but the magnetic coil according to the present invention is not limited to such a configuration, and its gist Various changes or improvements can be added without departing from the scope of the present invention. Hereinafter, various modifications will be described.

[First Modification]
22A to 22C are explanatory views schematically showing the form of the magnetic coil 50 according to the first modification of the present embodiment. FIG. 22A is a plan view of the magnetic coil 50, and FIG. (B) is an arrow view (front view) showing the magnetic coil 50 viewed from the directions of the arrows 11b and 11b, and FIG. 22 (c) is an arrow view showing the magnetic coil 50 viewed from the directions of the arrows 11c and 11c ( Side view).

As shown in FIGS. 22A to 22C, the eccentric spiral coil 50 according to the first modification is similar to that shown in FIGS. 4A to 4C, but 2 The magnetic wires shown in FIGS. 4A to 4C are that the spiral conductor portions 50J and 50K are arranged on the same plane and are arranged side by side without overlapping each other. It is different from the coil 20.
In this case, although the specific effect by providing the overlapping part cannot be obtained, the other effects of the eccentric spiral coil 20 can be enjoyed, and the magnetic coil 50 is arranged on the same plane, so that the magnetic coil 50 is arranged. Becomes flat, and the coil unit including the magnetic coil 50 can be formed thinner. Further, since there is no overlap, there is an advantage that the coil winding can be easily manufactured.

[Second Modification]
FIG. 23 is a front view schematically showing the form of the eccentric spiral coil 60 according to the second modification of the present embodiment.
The eccentric spiral coil 60 of the second modified example has a configuration in which the two spiral conducting wire portions 60J and 60K do not overlap each other as in the first modified example, but the surface of the patient's head Mh. The two spiral conducting wire portions 60J and 60K are inclined so as to form a mountain shape with a predetermined angle β between them so as to conform to the shape as much as possible.
By adopting such a configuration, the coil 60 can be arranged as much as possible along the surface shape of the patient's head Mh, and variation in the distance between the two can be suppressed and along the surface shape of the patient's head Mh. Thus, an induced current can be generated, and more efficient brain stimulation can be realized.
In this case, the surface of the patient head Mh and the coil 60 are formed by curving and rounding the coil 60 so as to better cope with the surface shape of the patient head Mh. The variation in the distance between the two can be more effectively suppressed.

[Third Modification]
FIG. 24 is a front view schematically showing the form of an eccentric spiral coil 70 according to a third modification of the present embodiment.
As in the case of the second modification, the eccentric spiral coil 70 of the third modification has a predetermined angle so that the two spiral conducting wire portions 70J and 70K are as close as possible to the surface shape of the patient head Mh. Although it inclines so as to form a mountain shape with β interposed therebetween, it further has a portion 70Q where two spiral conducting wire portions 70J and 70K overlap.

The overlapping portion 70Q is configured to be parallel by bending a part of the spiral conducting wire portions 70J and 70K.
By adopting such a form, in the overlapping portion 70Q, the density of the induced current generated when the coil is energized becomes higher, and a stronger magnetic field can be obtained. Further, the magnetic coil 70 can be arranged as much as possible along the surface shape of the patient's head Mh, and the induced current is generated along the surface shape of the patient's head Mh while suppressing the variation in distance between them. And more efficient brain stimulation can be realized. In addition, the portion 70Q where the two spiral conducting wire portions 70J and 70K overlap each other is formed by bending a part of each of the spiral conducting wire portions 70J and 70K so as to be parallel, and FIG. 24 and FIG. 23 are compared. As can be clearly seen, the magnetic coil 70 can be arranged more along the surface shape of the patient's head Mh.

[Fourth Modification]
FIG. 25 is a front view schematically showing a form of the eccentric spiral coil 80 according to the fourth modification example of the present embodiment.
The eccentric spiral coil 80 of the fourth modified example has a portion 80Q where two spiral conducting wire portions 80J and 80K overlap as in the case of the third modified example, but the spiral conducting wire portions 80J and 80K The curved surface is formed so as to follow the surface shape of the patient's head Mh as much as possible. This curved surface is, for example, a part of a cylindrical surface as shown in FIG. By setting it as such a curved surface, compared with the said 3rd modification, since the degree to which a coil adheres to the head surface increases, an eddy current can be induced effectively. Furthermore, if this curved surface is formed by a part of a spherical surface, the degree of close contact of the coil with the head surface can be further increased.

  In the above-described modification, a set of spiral conducting wire portions is configured to be eccentric in a direction in which the vortex center of one spiral conducting wire portion approaches the vortex center of the other spiral conducting wire portion. As a premise of the configuration of the “eccentric spiral coil”, a configuration in which a part of the coil is bent, a curved surface formed by a part of a cylindrical surface, and a curved surface formed by a part of a spherical surface have been described. However, the effect obtained by using the spiral coil having such a shape so that it conforms as much as possible to the surface shape of the patient's head is not limited to the case of the eccentric spiral coil, but is a concentric spiral coil. It is clear from the above explanation that the above can be obtained. Accordingly, configurations using these concentric coils are also included in the present invention.

  Among various values indicating the performance of the coil for magnetic stimulation, the strength of eddy current in the brain and the inductance of the coil are particularly important. Computer simulations have shown how brain eddy currents and inductances change when design parameters such as the outer and inner diameters of coils, the number of turns, and the degree of eccentricity are changed. As the standard dimensions of the eccentric spiral coil, the average diameter of the innermost circle is 20 mm (the inner diameter is 18 mm because the line width is 2 mm), and the average diameter of the outermost circle is 100 mm (the outer diameter is 2 mm because the line width is 2 mm). 102 mm), the number of turns was 10, and the degree of eccentricity was determined so that the gap between windings in the dense portion was 0.5 mm. Based on this parameter, the inner diameter, outer diameter, number of turns, and degree of eccentricity were independently changed. Other design parameters were fixed as shown in Table 2.

コイルの設計パラメータ

Coil design parameters

In transcranial magnetic stimulation treatment, it is necessary to perform stimulation frequently in order to obtain an effective therapeutic effect. In that case, the heat generation of the magnetic coil often becomes an operational restriction. The heat generation of the magnetic coil is proportional to the square of the current applied to the coil. Many parts in the drive circuit are selected according to the current. Therefore, a simulation was performed under the condition that the current is constant. Under this condition, a coil that can induce a strong eddy current in the brain can be determined to be an efficient coil.
The heat P of the coil can be calculated from the coil current I, the coil resistance R, the pulse width T, and the number of stimulations f per second by the following equation (Equation 19).

The simulation of the eddy current induced in the brain was performed by a method similar to the method described with reference to FIG. However, here, the conductor simulating the brain is not a 1/8 ball but a 1/4 ball. This increases the time required for the calculation, but improves the accuracy of the calculation.
FIG. 28 is an explanatory diagram showing a calculation model for obtaining the eddy current in the brain and the inductance of the coil by computer simulation. FIG. 28A shows a calculation model for analyzing the eddy current. In this simulation, in order to obtain the inductance of the coil, the distribution of the magnetic field generated around the coil when a unit current of 1 A (ampere) was applied to the coil was analyzed. A model representing a half of the coil as shown in FIG. 28B was placed inside a 160 mm × 80 mm × 100 mm rectangular parallelepiped representing air. The position of the coil was determined so that the cut surface of the coil was included in a 160 mm × 100 mm surface of a rectangular parallelepiped representing air. Using the finite element method, the distribution of the magnetic field inside this cuboid was calculated. All six outer peripheral surfaces of the model were given symmetric boundary conditions. The finite element for the calculation is a portion having the highest density and a size of about 2 mm.

  FIG. 29 is a diagram showing an example of a contour map of magnetic flux density around the coil obtained from the computer simulation. As shown in this figure, it can be seen that the magnetic flux density is attenuated as the distance from the coil increases. Based on this magnetic flux density, the inductance of the coil can be calculated by the following equation (Equation 20).

This equation represents the balance of magnetic energy, L is the inductance of the coil, I (= 1A) is the current applied to the coil, μ ₀ is the permeability of the vacuum, and B is the magnetic flux density. The integration on the right side is performed inside a rectangular parallelepiped representing air.
In an actual coil, in addition to the inductance of the coil body calculated from the equation (Equation 20), the cable connecting the coil and the drive circuit also has an inductance. Therefore, it is necessary to evaluate both by adding them together. is there. The inductance of the reciprocating two-conductor cable was calculated approximately using the following equation (Equation 21). In (Equation 21), r = 4.9 mm is the conductor outer diameter, D = 7 mm is the center-to-center distance, and l = 1.5 m is the cable length.

  In the drive circuit 49 shown in FIG. 1, the pulse width T, the charging voltage V of the capacitor, and the electrical resistance R of the coil and cable are expressed by the following equations (Equation 22), (Equation 23), and (Equation 24), respectively. I want.

  Here, the capacitance of the capacitor was set to 125 μF. The electric resistance was calculated from the resistivity of copper ρ = 16.78 μΩ · mm. The resistance is a value obtained by adding the coil body and the 1.5 m long cable.

  The degree of eccentricity of the coil is represented by the gap between the windings in the closest part. For concentric coils that are not eccentric, the gap is 2.44 mm. As the degree of eccentricity increases, the gap decreases, and ideally, the gap can be made almost zero. Actually, when a coated conductor is used, a gap corresponding to the thickness of the coating is required, and when using a conductor cut from a coating or a coil cut out from a copper plate, insulation is ensured. A gap is necessary. As a guide, it is preferable to provide a gap of 0.50 mm or more. FIG. 30 shows a concentric coil that is not eccentric, an eccentric spiral coil with a gap of 0.50 mm, and an eccentric spiral coil with a gap of 1.47 mm that is intermediate between them. The distance Dc between the vortex centers and the distance between the centers of the outer shapes are also shown.

  Next, the coil when the degree of eccentricity of the coil (that is, the gap between the windings of the closest part of the spiral conductor), the outer diameter of the spiral conductor, the inner diameter of the spiral conductor, and the number of turns of the spiral conductor is changed. The change of the electrical characteristics of was investigated. As the electrical characteristics of the coil, eddy current density, inductance, pulse width, voltage, resistance, and heat generation upon stimulation 5 times per second were examined.

Table 3 shows the change in the electrical characteristics of the coil when the degree of eccentricity of the coil, that is, the gap (mm) between the windings in the close-packed portion of the spiral conducting wire portion is changed.

Table 4 shows changes in the electrical characteristics of the coil when the outer diameter (mm) of the spiral conductor portion is changed.

Further, Table 5 shows changes in the electrical characteristics of the coil when the inner diameter (mm) of the spiral conductor portion is changed.

Further, Table 6 shows changes in the electrical characteristics of the coil when the number of turns (turns) of the spiral conducting wire portion is changed.

  FIG. 31 shows the electrical characteristics of the coil when the degree of eccentricity, outer diameter, inner diameter, and number of turns of the coil are changed as shown in Table 3, Table 4, Table 5, and Table 6, respectively. It is a figure which illustrates change. When the gap between the windings in the close-packed part is reduced, that is, when the degree of eccentricity is increased, the eddy current induced in the brain is increased, and the effectiveness of the eccentric spiral coil is shown again. In the coil design, it is desirable to make the gap between the windings of the closest part as small as possible within a range where insulation is maintained. Regarding the three design parameters of the outer diameter, the inner diameter, and the number of turns, it can be seen that the induced eddy current density, the inductance, and the charging voltage increase as these increase. The resistance increases as the winding length increases, but the change is within 2% due to the large contribution of the cable length.

  If it is considered that a coil capable of inducing strong eddy currents in the brain is an excellent coil compared under a condition where the coil current is constant, it is desirable that the outer diameter, inner diameter, and number of turns are larger. However, these cannot be increased without limit, and the pulse width and the charging voltage of the capacitor need to be within a certain range. As for the pulse width, since the evaluation of the therapeutic effect using the conventional magnetic stimulation apparatus is performed around 300 μs, it is necessary to start over from the evaluation of the therapeutic effect itself in the case of a pulse width that greatly deviates from this. Device development becomes difficult. If the accumulation of conventional knowledge in magnetic stimulation treatment is utilized, it is preferable to maintain a pulse width of around 300 μs. In addition, an increase in the charging voltage of the capacitor is not preferable because the safety risk increases, leading to an increase in the size of the apparatus. As a guide, it is preferable to keep the charging voltage at 2 kV or less. Further, since the necessary stimulus intensity varies depending on individual patients, it is necessary to have a predetermined amount of margin for these values. In the calculation result of FIG. 31, in any coil shape, the pulse width is about 300 μs and the charging voltage is 2 kV or less.

  When the outer diameter, the inner diameter, and the number of turns are increased by 10% based on the outer diameter of 102 mm, the inner diameter of 18 mm, and the number of turns of 10 times, the induced currents in the brain increase by 9%, 2%, and 9%, respectively. The charging voltage of the capacitor increases by 3.5%, 1.9% and 8.1%, respectively. That is, the increase in voltage with respect to improving the induced current in the brain by 10% is 3.9% when the outer diameter is changed, 9.5% when the inner diameter is changed, and when the number of turns is changed. 9.0%. Therefore, it is most preferable to increase the outer diameter in that the eddy current in the brain can be enhanced without causing an increase in voltage. On the other hand, when the outer diameter, the inner diameter, and the number of turns are reduced by 10% based on the outer diameter of 102 mm, the inner diameter of 18 mm, and the number of turns of 10 times, the induced currents in the brain are reduced by 14%, 2%, and 10%, respectively. . From these values, it is possible to understand the importance of appropriately selecting the coil design parameters.

When actually designing a coil, it is necessary to determine a number of parameters only with respect to the shape of the coil (the shape of the spiral conducting wire portion). Specifically, at least the following parameters must be determined.
<a> Basic shape of the spiral lead wire (round, square, square, etc.)
<B> Number and arrangement of spiral conducting wire portions <c> Height of the strand (conductor) <d> Width of the strand (conductor) <e> Outer diameter <f> Inner diameter <g> Number of turns <h> Degree of eccentricity <I> Degree of overlap <j> Angle of inclination between spiral conductors

  Computer simulation is a very effective means for evaluating the performance of a coil. However, when trying to find the optimum design of the coil, an approach that simply repeats computer simulation over a huge amount of these parameters is extremely difficult and practically impossible. Therefore, it is required to design using computer simulation in a limited and effective manner after showing a certain degree of preferred design direction based on electromagnetic considerations.

Regarding the “basic shape of the spiral conducting wire portion” in the <a> section, the basic shape is preferably a circle, particularly when the brain is the target of stimulation. There is a gap of about 3 cm between the coil conductor and the brain because there are a skull, a scalp, and a coil case for ensuring insulation. The nerves in the brain are further distributed to a depth of several centimeters. A round coil is most advantageous in reaching the magnetic field without being attenuated to such a depth. The larger the area surrounded by the coil, the more the magnetic field tends to reach deeper. However, the area surrounded by the conductive wire having a certain length is the largest. Therefore, the circular coil has the ability to reach the deepest part without attenuating the magnetic field.
Regarding the “number and arrangement of spiral conductors” in the section <b>, a coil including three or more spiral conductors is also an option if it can be combined with a drive circuit having a very large output. By providing three or more spiral conducting wire portions, the degree of freedom of design increases, and the eddy current in the brain can be brought closer to a desirable distribution. However, the effect of a coil having three or more spiral conducting wire portions is limited when reviewing the previous research results, compared to a coil having two spiral conducting wire portions. As the number of spiral conducting wire portions increases, the output required for the drive circuit increases. In particular, a magnetic field generating coil for home treatment is preferable in that a coil composed of two spiral conducting wire portions can be reduced in size.

Regarding the “height of the element wire (conductive wire)” in the item <c>, the higher the element wire (conductive wire), there is an advantage that the electric resistance can be reduced. On the other hand, for example, when a coil with overlapping spiral conductors such as the coil shown in FIG. 4 is manufactured, it is necessary to bend the wire in order to smoothly connect the layers having different heights. is there. If the wire is too high, a technical problem arises that bending becomes difficult. From experience, bending is relatively easy if the height is up to about 6 cm.
With respect to the “element wire (conductor) width” of <d>, the electrical resistance decreases if the element wire (conductor) is wide, so that the output of the drive circuit can be small. There is a problem that the degree of being able to do so decreases. If a width of about 2 mm is selected, the magnitude of heat generation calculated in [Equation 19] will be about 300 watts as a result, and the drive circuit can be designed with power consumption that can be fed from a household outlet.

The influence of the “outer diameter”, “inner diameter”, “number of turns”, and “degree of eccentricity” shown in the <e> to <h> items on the coil performance is not simple, but is a three-dimensional electromagnetic field analysis. Can be evaluated only after For these, optimization using computer simulation is extremely effective.
Regarding the “degree of overlap” in the item <i>, for example, as shown in FIG. 4 and the like, an overlapping portion may be provided up to a position where the outer periphery of one spiral conducting wire portion is in contact with the inner circumference of the other spiral conducting wire portion. preferable. Thereby, the current concentration at the central portion of the coil where the overlap is provided can be most enhanced.
The “angle of inclination between the spiral conducting wire portions” in the <j> section is selected in consideration of the ease of processing and the effect of stimulation. For example, when the coil is configured in a plane as shown in FIG. 4, the coil can be easily processed. On the other hand, if the design shown in FIG. 24 can be adopted, the efficiency of eddy current generation is improved. If an overlap is not provided between the spiral conducting wire portions of the coil, a shape as shown in FIG. 23 is also possible.

  As described above, it is possible to optimize the coil design by searching for a coil that can obtain the strongest eddy current in the brain within the range of allowable pulse width and capacitor charging voltage using computer simulation. it can. However, even if the design parameters to be examined in the simulation are narrowed down, it can still be said that the problem is that much labor is required. In addition, design parameters such as outer diameter, inner diameter, and number of turns are analyzed by selecting a finite number of combinations, and if there is an optimal value in the middle of the selected values, the accuracy of obtaining this optimal value is reduced. . By interpolating data using various numerical analysis methods, this optimal value can be estimated when there is an optimal value in the middle of a finite number of design parameters selected during computer simulation. .

  Further, the above description is for an eccentric spiral coil having a circular outer shape of the spiral conducting wire portion. However, in the present invention, the outer shape of the spiral conducting wire portion is an ellipse, an ellipse, a triangle, a quadrangle, or more. The present invention can also be effectively applied to magnetic coils having other various shapes such as a polygonal shape. In the case of a polygonal eccentric spiral coil such as a triangular or quadrangular outer shape of the spiral conducting wire part, there are two cases where it is biased in the direction of the corner and in the direction of the side. is there.

Furthermore, the number of spiral conducting wire portions is not limited to two, but may be three or four, or even more.
For example, FIG. 32 is a schematic diagram showing a magnetic coil 130 having four circular spiral conductor portions 130J, 130K, 130L, and 130M. The actual spiral conducting wire portions 130J to 130M are wound in a spiral shape (spiral shape). However, in the schematic diagram of FIG. 32, for simplification of the drawing, it is illustrated as a ring. The arrows indicate the current flow direction.

In the magnetic coil 130 shown in FIG. 32, the four spiral conducting wire portions 130J, 130K, 130L, and 130M are arranged in a four-leaf shape in plan view on the patient head Mh, and a part of each overlaps. Is arranged. Also in this case, at least one set of spiral conducting wire portions is configured to be eccentric so that the vortex center of the winding of one spiral conducting wire portion approaches the vortex center of the winding of the other spiral conducting wire portion. Corresponding to the density of the coil winding interval of the spiral conducting wire portion, a region having a high induced current density is generated, and strong brain stimulation is obtained in this region. In other words, for a magnetic coil composed of a plurality of spiral conducting wire portions, a brain stimulation with a required intensity can be efficiently generated at a limited location with a relatively simple configuration simply by devising the shape and arrangement of each spiral conducting wire portion. be able to.
In particular, all the four circular spiral conductor portions 130J, 130K, 130L, and 130M are configured to be eccentric so that the vortex center of the winding of the spiral conductor portion approaches the center passing through the z axis. The spiral conducting wire portion can be eccentric so that the vortex center of the winding of the spiral conducting wire portion approaches the vortex center of the winding of the other spiral conducting wire portion, and the highest effect can be obtained.

In addition, the present invention is not limited to the case where the plurality of spiral conducting wire portions are arranged substantially on one plane or with a slight inclination, but the plurality of spiral conducting wire portions are three-dimensionally around a predetermined axis. Even when it is arranged, it can be effectively applied.
FIG. 33 is a schematic diagram illustrating an example of a magnetic coil 150 including four spiral conducting wire portions arranged in three dimensions. In the schematic diagram of FIG. 33, the spiral conducting wire portions 150J, 150K, 150L, and 150M are illustrated as ellipses for the sake of simplicity of the drawing.
This magnetic coil 150 is of a so-called “slinky” type, and four elliptical spiral conductor portions 150J, 150K, 150L, and 150M are arranged in three dimensions around the axis Sa of the grip 159 connected to the cable 156. Yes.

Also in this case, at least one set of spiral conducting wire portions is configured to be eccentric so that the vortex center of the winding of one spiral conducting wire portion approaches the vortex center of the winding of the other spiral conducting wire portion. Corresponding to the density of the coil winding interval of the spiral conducting wire portion, a region having a high induced current density is generated, and strong brain stimulation is obtained in this region.
In particular, all the four spiral conducting wire portions 150J, 150K, 150L, and 150M are configured to be eccentric so that the vortex center of the winding of the spiral conducting wire portion approaches the center passing through the axis Sa. The spiral conducting wire portion can be eccentric so that the vortex center of the winding of the spiral conducting wire portion approaches the vortex center of the winding of the other spiral conducting wire portion, and the highest effect can be obtained.

FIG. 34 is a schematic diagram showing an example of a magnetic coil 170 including five spiral conductor portions 170J, 170K, 170L, 170M, and 170N arranged in three dimensions. In the schematic diagram of FIG. 34, the spiral conducting wire portions 170J, 170K, 170L, 170M, and 170N are imitated with an annular disk for the sake of simplicity of the drawing, and an arrow along each disk indicates a current flow. The direction is illustrated.
In this case, each spiral conducting wire portion 170J, 170K, 170L, 170M, 170N is three-dimensionally arranged with five spiral conducting wire portions 170J, 170K, 170L, 170M, 170N around an axis Sb parallel to the z axis. Yes.
Also in this case, at least one set of spiral conducting wire portions is configured to be eccentric so that the vortex center of the winding of one spiral conducting wire portion approaches the vortex center of the winding of the other spiral conducting wire portion. Corresponding to the density of the coil winding interval of the spiral conducting wire portion, a region having a high induced current density is generated, and strong brain stimulation is obtained in this region.

FIG. 35 is a schematic diagram illustrating an example of a magnetic coil 180 including five spiral conductor portions 180J, 180K, 180L, 180M, and 180N arranged in three dimensions. In the schematic diagram of FIG. 35, for the sake of concise and clear drawing, the three spiral conducting wire portions 180J, 180K, and 180M are imitated by a solid disk, and the two spiral conducting wire portions 180L and 180N are annular. The disc is imitated.
The magnetic coil 180 is based on a so-called eight-shaped coil, and five spiral conducting wire portions 180J, 180K, 180L, 180M, and 180N are three-dimensionally arranged around the axis Sc of the grip 189.
Also in this case, at least one set of spiral conducting wire portions is configured to be eccentric so that the vortex center of the winding of one spiral conducting wire portion approaches the vortex center of the winding of the other spiral conducting wire portion. Corresponding to the density of the coil winding interval of the spiral conducting wire portion, a region having a high induced current density is generated, and strong brain stimulation is obtained in this region.

  In the above description, the eccentricity of at least one set of spiral conducting wire portions is configured to be eccentric in the direction in which the vortex center of the winding of one spiral conducting wire portion approaches the vortex center of the winding of the other spiral conducting wire portion. Assuming that the “spiral coil” is configured, when three or more spiral conductor portions are arranged substantially on one plane or with a slight inclination, a plurality of spiral conductor portions are three-dimensionally formed around a predetermined axis. However, the effect obtained by arranging the spiral conducting wire portion in this way is not limited to the eccentric spiral coil, but concentric spirals. It is clear from the above description that even a coil can be obtained. Accordingly, configurations using these concentric coils are also included in the present invention.

  The above explanation was mainly about the magnetic coil for magnetic stimulation therapy used for transcranial magnetic stimulation therapy for neuropathic pain. However, magnetic stimulation therapy itself has other neurological and mental illnesses. The application to the treatment of organs other than the brain, such as urinary incontinence, is also progressing clinically from the early stage for the purpose of diagnosis, and it is actively used for basic research of brain function and brain science research. . Therefore, the present invention can be effectively applied in these fields. Further, the magnetic coil of the present invention can be applied to other fields such as thermotherapy using a magnetic coil and an electromagnetic field, and a nondestructive flaw detection method using eddy current.

  The present invention relates to a magnetic coil that generates a magnetic field, in particular, a magnetic coil composed of a plurality of spiral conducting wire portions, or a magnetic coil in which a plurality of spiral conducting wire portions are three-dimensionally arranged around a predetermined axis, and such magnetism. The present invention relates to a transcranial magnetic stimulation device provided with a coil, for example, as a magnetic coil for magnetic stimulation treatment used in transcranial magnetic stimulation therapy, and as a transcranial magnetic stimulation device equipped with such a magnetic coil. can do.

6 Case 20, 30, 40, 50, 60, 70, 80, 90 Magnetic coil 23P, 23Q, 23R Cover 24, 25 Air port 130, 150, 170, 180 Magnetic coil 20J, 30J, 50J, 60J, 70J, 80J Spiral conductor part 20K, 30K, 50K, 60K, 70K, 80K Spiral conductor part 130J-130M, 150J-150M Spiral conductor part 170J-170N, 180J-180N Spiral conductor part Dc Distance between vortex centers Ds Distance Jc, Kc Vortex center Jc, Js Center of outer shape

Claims (15)

A magnetic coil for generating a magnetic field composed of a plurality of spiral conductors;
The magnetism is characterized in that at least one set of spiral conducting wire portions is configured such that the vortex center of the winding of one spiral conducting wire portion is eccentric in a direction approaching the vortex center of the winding of the other spiral conducting wire portion. coil. A magnetic coil for generating a magnetic field, wherein a plurality of spiral conducting wire portions are arranged three-dimensionally around a predetermined axis,
The magnetism is characterized in that at least one set of spiral conducting wire portions is configured such that the vortex center of the winding of one spiral conducting wire portion is eccentric in a direction approaching the vortex center of the winding of the other spiral conducting wire portion. coil.   3. The one set of spiral conducting wire portions, wherein a part of one spiral conducting wire portion overlaps with a part of the other spiral conducting wire portion substantially in parallel with each other. Magnetic coil.   The outer peripheral part of one spiral conducting wire part overlaps to the vortex center of the winding of the other spiral conducting wire part or the vicinity thereof with respect to the one set of spiral conducting wire parts. Magnetic coil.   5. The magnetic coil according to claim 1, wherein the one set of spiral conducting wire portions is inclined so as to form a mountain shape with a predetermined angle interposed therebetween.   The magnetic coil according to any one of claims 1 to 5, wherein an outer peripheral shape of the at least one set of spiral conducting wire portions is circular.   The magnetic coil according to claim 1, wherein the plurality of spiral conducting wire portions are wound up by a conducting wire having a quadrangular cross-sectional shape.   The magnetic coil according to any one of claims 1 to 6, wherein the plurality of spiral conducting wire portions are wound up by a conducting wire configured by bringing together a large number of metal wires. A transcranial magnetic stimulation device comprising a therapeutic magnetic coil having at least one set of spiral conductors for generating eddy currents in a patient's skull,
The transcranial magnetic stimulation device characterized in that the spiral conducting wire part forms a curved surface so as to follow the surface shape of the patient's head.   The transcranial magnetic stimulation apparatus according to claim 9, wherein the curved surface is a part of a cylindrical surface.   The transcranial magnetic stimulation apparatus according to claim 9, wherein the curved surface is a part of a spherical surface.   The at least one set of spiral conducting wire portions is configured such that the vortex center of the winding of one spiral conducting wire portion is eccentric in a direction approaching the vortex center of the winding of the other spiral conducting wire portion. The transcranial magnetic stimulation device according to any one of claims 9 to 11. A transcranial magnetic stimulation device comprising a therapeutic magnetic coil having at least one set of spiral conductors for generating eddy currents in a patient's skull,
A case for storing each of the at least one set of spiral conducting wire portions individually or as a whole;
A cover attached to the case so that a gap is formed between the case and the case;
The air flow for cooling the case is forcibly distributed from the air inlet provided in a predetermined part of the cover to the air outlet provided in another part of the cover via the gap. Air circulation means
A transcranial magnetic stimulation device comprising:   The transcranial magnetic stimulation apparatus according to claim 13, wherein the gap is provided at least on the side of the case close to the patient's head.   The transcranial magnetic stimulation device according to claim 14, wherein the gap is provided on both the side close to the patient's head of the case and the opposite side thereof.

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