Bioelectrode

Abstract

There has been a demand for a bioelectrode with which it is possible to obtain vital information such as an electrocardiogram and brain waves by using X-rays without being captured in an X-ray image. This bioelectrode has: a base material for allowing X-rays to pass therethrough; a connection end region provided to the base material; a biological contact region provided at a different position of the base material from the connection end region with a lead region therebetween; and, from the inside of the connection end region to the inside of the biological contact region via the lead region, a metal wire-containing thin wire including a metal wire that has a diameter of 20 μm or less and is fixed to the base material. The bioelectrode can ensure conductivity and is not captured in an X-ray image.

Description

Biological electrode

[0001] The present invention relates to an electrode used by being attached to a living body, and particularly provides a biological electrode that is not imaged in X-ray photography.

[0002] Biological electrodes are useful devices attached to a living body, which are used not only for electrocardiogram monitoring during X-ray examination, catheter examination and surgery, but also for obtaining biological information when performing radiation therapy and examinations therefor. Conventionally, an electrode in which silver-silver chloride is formed on an electrode with a thickness of 10 to 20 microns and used as an electrode element (referred to as "silver-silver chloride electrode") has been used.

[0003] However, this electrode does not have X-ray permeability. Therefore, in order to obtain an accurate X-ray image, it was necessary to remove the electrode during imaging and reattach it after imaging, which was a cumbersome work. Accordingly, there has been a demand for a biological electrode that allows X-ray photography to be performed while it remains attached, and hardly casts a shadow on an X-ray image.

[0004] Patent Document 1 discloses that an electrode that is hardly imaged on an X-ray image can be obtained by using, as a lead wire, a carbon fiber having a fan-shaped protruding end with dendritically spread carbon fibers at the tip, and combining it with a silver-silver chloride conductive film (including a mesh-shaped one) having a thickness of 0.5 to 5 μm.

[0005] Japanese Unexamined Patent Publication No. 07-047058

[0006] However, even the biological electrode disclosed in Patent Document 1 has a problem that it appears as a shadow in an X-ray image when the resolution of X-ray photography is improved. Therefore, the problem that biological electrodes appear as shadows during X-ray photography has not yet been sufficiently solved.

[0007] Furthermore, it cannot be said that the biological electrode of Patent Document 1 is excellent in flexibility. Therefore, when the electrode is forced to deform such as "breaking" in order to follow the living body, there is a problem that it may be broken. Here, "breaking" refers to being bent at an acute angle. Also, even though the lead wire is made of carbon fiber, it cannot be said that it has sufficient flexibility. In addition, it cannot be said that it has stretchability that can alleviate the occurrence of wire breakage when pulled during work.

[0008] This invention was conceived in view of the above-mentioned problems, and provides a bioelectrode that is flexible and stretchable, and does not appear as a shadow, or appears very little, when X-ray imaging is performed while it is attached to a living body.

[0009] More specifically, the bioelectrode according to the present invention is characterized by comprising: a base material that transmits X-rays; a connection end region provided on the base material; a biocontact region provided at a different position on the base material via a lead region from the connection end region; and a metal wire-containing nanowire, including a metal wire fixed to the base material, extending from within the connection end region through the lead region to within the biocontact region.

[0010] The bioelectrode according to the present invention has a biocontact region that directly contacts the body and a connection end region that connects to the measuring instrument side, provided on a base material that does not appear in X-ray images. A metal wire with a diameter of 20 μm or less is arranged and fixed from one region to the other, so that it is conductive and does not appear in X-ray images.

[0011] Furthermore, because the diameter of the metal wire is very small, even if physical deformation such as "bending" occurs in the biocontact area, lead area, or connection end area of ​​the bioelectrode, the resulting curvature is small (large radius of curvature) relative to the diameter of the metal wire. This has the effect of making the risk of the metal wire breaking very small.

[0012] Furthermore, by using a material in which metal wire is twisted together with non-metallic fibers (also called "non-metallic wire"), the metal wire-containing fine wire can be treated as ordinary thread. Therefore, it has the effect of being able to sew and fix the metal wire to the base material. Moreover, when a material in which metal wire and non-metallic wire are twisted together is used as the metal wire-containing fine wire, even if the bioelectrode is pulled and deformed by stretching, the metal wire can also stretch as a thread to the extent of the twisting, and even if the bioelectrode as a whole is deformed by stretching, it has the effect of being less likely to break.

[0013] Furthermore, by using tungsten wire instead of metal wire, it becomes highly resistant to tension and will not break even when pulled.

[0014] This figure shows the configuration of a bioelectrode according to the present invention. This figure shows another shape of a bioelectrode according to the present invention. This figure shows the configuration of a metal wire-containing nanowire. This figure shows another configuration of a metal wire-containing nanowire. This figure shows another configuration of a metal wire-containing nanowire. This figure shows an example of how to sew a metal wire-containing nanowire onto a base material. This figure shows another configuration of a bioelectrode according to the present invention. This figure shows another configuration of a bioelectrode according to the present invention. This figure shows the arrangement of metal wires when taking an X-ray photograph of metal wires of different thicknesses. This figure shows a photograph showing the results of the X-ray imaging in Figure 9 and the brightness measurement results. This figure shows the arrangement of metal wires when taking an X-ray photograph of five metal wires of different thicknesses twisted together. This figure shows a photograph showing the results of the X-ray imaging in Figure 11 and the brightness measurement results. This figure shows a photograph showing the results of the X-ray imaging and brightness measurement results when multiple 13 μm thick tungsten wires are bundled together. This figure shows a photograph showing the results of the X-ray imaging and brightness measurement results when multiple 13 μm thick tungsten wires are twisted together in thread material. This figure shows the arrangement when taking an X-ray photograph of only the thread material. Figure 15 shows an X-ray photograph of the electrode and the results of brightness measurement. It also shows the configuration of the bioelectrode fabricated in the example. The diagram shows the connection to the human body. Finally, it shows a photograph illustrating electrocardiogram waveforms using electrodes with different wire spacings. The last photograph compares electrocardiogram waveforms using currently used electrodes (standard products) with those using the electrode of the present invention.

[0015] The bioelectrode according to the present invention will be described below with reference to drawings and examples. The following description illustrates one embodiment and one example, and the present invention is not limited to the following description. The following description may be modified without departing from the spirit of the invention. Furthermore, embodiments and examples obtained by appropriately combining the technical means disclosed in different embodiments and examples are also included within the technical scope of the present invention. All references cited herein are incorporated herein by reference. In this specification, when a numerical range is described as "A to B," it means "A or greater and B or less."

[0016] Figure 1 shows the configuration of a bioelectrode according to the present invention. The bioelectrode 1 is composed of a base material 10 and a metal wire-containing nanowire 12. The base material 10 is made of a material that does not appear as a shadow when X-rayed. Here, "not visible or not appearing" means that it is not visible to the human eye, and it is not required that its presence is not detectable in terms of electrical signals (even if there is a signal, it is below the noise level). This point is agreed upon throughout this specification.

[0017] Specifically, flat materials such as cloth, paper, textile fabrics, nonwoven fabrics, and plastics are preferably used, and more specifically, polymer materials such as polyurethane, silicone rubber, polyethylene, polypropylene, polyester, and nylon; natural materials such as rayon and cellulose; laminates of nonwoven fabric and polyurethane; laminates of cotton cloth and silicone rubber; and laminates of polyester nonwoven fabric and breathable film are preferably used. Flat materials that are thin, light, and flexible, with a thickness of about 50 μm to 3 mm, are particularly preferred. Furthermore, the base material 10 does not have to be a single material. For example, it may be constructed by laminating multiple materials in the thickness direction. Also, different materials may be used for each region, as described later.

[0018] These materials possess characteristics such as high X-ray transparency, flexibility, biocompatibility, the ability to be processed to a thickness of approximately 50 μm to 3 mm, sufficient strength for handling, and the possibility of making them breathable.

[0019] The shape of the base material 10 is not particularly limited, but a strip-like shape formed by opposing short sides and opposing long sides is preferably used. This is because one short side can be used as a connection end region 16 for connecting to a measuring instrument (not shown), and the other short side can be used as a bio-contact region 18 for contacting a living body. In other words, the base material 10 has a shape that allows the bio-contact region 18 and the connection end region 16 to be formed in regions that are far apart from each other.

[0020] The bio-contact area 18 is provided on the base material 10 and is the area that comes into contact with the living body. The bio-contact area 18 is also positioned in the area of ​​the living body that is irradiated with X-rays (this is called the "X-ray imaging area"). When bringing the bio-contact area 18 into contact with the living body, the bio-contact area 18 and the living body may be brought into contact via an electrolyte-containing gel or the like. The size and shape of the bio-contact area 18 are not particularly limited. Usually, an area of ​​about 1 cm square to 2 cm square is sufficient.

[0021] The connection end region 16 is provided on the base material 10 and is located away from the bio-contact region 18. Figure 1 shows a state in which the bio-contact region 18 is provided at one end of the base material 10 and the connection end region 16 is formed at the other end. The area between the bio-contact region 18 and the connection end region 16 becomes the lead region 20.

[0022] The lead region 20 between the bio-contact region 18 and the connection end region 16 should be long enough so that the connection end region 16 is sufficiently far from the X-ray imaging region where the bio-contact region 18 is located. In other words, the lead region 20 should be long enough so as not to interfere with examinations and treatments. Specifically, 15 cm or more is preferred, and 20 cm or more is more preferred. On the other hand, if it is too long, it will pick up noise in the environment in which it is used. Therefore, 200 cm or less is preferred, and 100 cm or less is more preferred.

[0023] The shapes of the connection end region 16, the lead region 20, and the bio-contact region 18 may each be different. Figure 2 shows examples of different shapes. In Figure 2, the connection end region 16 is roughly trapezoidal, the bio-contact region 18 is roughly circular, and the lead region 20 is rectangular. In this case, the materials constituting the connection end region 16, the lead region 20, and the bio-contact region 18 do not have to be the same as long as X-rays can pass through them, and the thickness of each region may also be different.

[0024] Furthermore, the metal wire-containing nanowires 12 do not necessarily have to be arranged in a straight line. Figure 2 shows a case where the angle of the metal wire-containing nanowires 12 changes in the bio-contact area 18. The metal wire-containing nanowires 12 may be curved in shape, as well as being composed of straight lines.

[0025] The metal wire-containing nanowire 12 is a nanowire containing a metal wire 12a (see Figure 3, described later) with a diameter that is not visible to X-rays. Experiments described later confirmed that metal wires 12a with a diameter of 20 μm or less do not appear as shadows in X-ray imaging equipment currently used in medical applications. Therefore, the bioelectrode 1 according to the present invention utilizes metal wires 12a with a diameter of 20 μm or less. There is no lower limit to the diameter of the metal wire 12, as long as it is manufactured and handleable. Currently, it is considered possible to manufacture metal wires with a diameter of approximately 2.5 μm.

[0026] The metal wire 12a should preferably have high conductivity and high rigidity or elasticity against tension. This is because it is preferable to use a material that can be stably formed into a wire even with a diameter of 20 μm or less and is less prone to breakage. For example, metals such as tungsten, molybdenum, stainless steel, titanium, copper, and beryllium, and alloys in which these metals are the main component (content (molar ratio) of 50% or more) can be suitably used. Tungsten is particularly suitable due to its excellent strength.

[0027] The metal wire-containing nanowire 12 is arranged through the lead region 20 from within the biological contact region 18 to the connection end region 16. There only needs to be one or more metal wire-containing nanowires 12 in the lead region 20. As will be described later, it is more preferable to arrange multiple metal wire-containing nanowires 12 in the lead region 20. However, when multiple wires are arranged, if adjacent metal wire-containing nanowires 12 are too close together, they may appear as a single metal wire in X-ray images. As will be described later in the examples, it is preferable to arrange the metal wire-containing nanowires 12 at a distance of 50 μm or more, preferably 100 μm or more, from each other. Furthermore, as will be described later in the examples, in the case of metal wires 12a with a diameter of 20 μm or less, even if multiple wires are twisted together, they may not appear in X-ray images.

[0028] The metal wire-containing nanowire 12 and the base material 10 can be fixed together using adhesive or the like. However, the metal wire 12a must be exposed in the bio-contact area 18 and the connection end area 16. Therefore, the bioelectrode 1 can be constructed by adhesively fixing the remaining parts. More specifically, when arranging the metal wire-containing nanowires 12 one by one on the base material 10, the starting and ending points of the metal wire-containing nanowires 12 and the lead area 20 can be bonded together.

[0029] If the metal wire-containing nanowire 12 is to be constructed solely from metal wires 12a with a diameter of 20 μm or less, the metal wires 12a must be handled directly, requiring precision during the process and making manufacturing difficult. Therefore, the metal wire-containing nanowire 12 can be constructed from metal wires 12a with a diameter of 20 μm or less and non-metallic wires 12b (hereinafter also referred to as "thread material 12b") that do not appear as shadows in X-ray imaging. In other words, a single metal wire-containing nanowire 12 may be constructed by combining thread material 12b (non-metallic wire 12b) made of a material that does not appear in X-ray images with one or more metal wires 12a.

[0030] The yarn material 12b includes, for example, natural fibers such as cotton, linen, wool, and silk; synthetic fibers such as polyester, nylon, acrylic, vinylon, polyolefin, para-aramid, meta-aramid, polyarylate, and polybenzoxazole; and regenerated fibers such as rayon. Water-soluble fiber yarns can also be used.

[0031] Figure 3(a) shows a conceptual diagram of a metal wire-containing fine wire 12 composed of a metal wire 12a and a thread material 12b. Here, one thread material 12b and one metal wire 12a are combined to form one metal wire-containing fine wire 12. If the metal wire-containing fine wire 12 is about the same thickness as sewing thread, it will be easy to handle. Specifically, a thickness of 50D (approximately 100S in cotton count) to 200D (approximately 27S in cotton count) is preferable. Note that "D" is denier and represents the weight (g) per 9000m.

[0032] In other words, arranging one metal wire-containing thin wire 12 with this configuration allows it to be handled in the same way as arranging a single ordinary thread, and from the standpoint of conductivity, it is equivalent to arranging only one metal wire 12a. This is a very suitable configuration for handling so that adjacent metal wires 12a do not come too close together. Furthermore, if the thread material 12b is a different color from the base material 10, it is preferable as it allows for visual confirmation of the arrangement of the metal wire-containing thin wire 12 and the base material 10. For example, the base material 10 may be black and the thread material 12b may be white.

[0033] Furthermore, by combining the metal wire 12a and the thread material 12b to form a single metal wire-containing fine wire 12, the metal wire 12a is exposed on the surface at various points on the metal wire-containing fine wire 12, ensuring conductivity. Alternatively, the thread material 12b and the metal wire 12a may be twisted together. When the metal wire-containing fine wire 12, including the metal wire 12a and the thread material 12b, is twisted as a whole, when the metal wire-containing fine wire 12 is pulled, it stretches by the amount of the twist, thus preventing the metal wire 12a from breaking midway.

[0034] In this specification, "twisted yarn" refers to a state in which multiple threads are twisted together to form a single metal wire-containing fine wire 12, and "bundle" refers to a state in which multiple threads are gathered together to form a single metal wire-containing fine wire 12, although a clear twist cannot be confirmed. These are also referred to as the "twisted state" and the "bundle state," respectively. For example, if, when viewed with an optical microscope that allows the metal wire 12a to be seen with the naked eye, it can be determined that there is no twist in the metal wire-containing fine wire 12 within the field of view, it may be considered a "bundle." In the bundle state, the metal wire 12a may separate from the thread material 12b, making it difficult to handle. However, as a metal wire-containing fine wire 12, the constraint on the metal wire 12a is loose, which is preferable for ensuring conductivity. Also, as shown in Figure 3(b), when the metal wire-containing fine wire 12 is pulled, the metal wire 12a has leeway from a loose state to a taut state. Therefore, breakage of the metal wire 12a when a tensile force is applied to the metal wire-containing fine wire 12 becomes less likely.

[0035] The "bundle" can be realized by methods such as twisting metal wire 12a and thread material 12b with water-soluble retaining thread 12k, fixing them to the base material 10, and then dissolving the retaining thread 12k, as described later.

[0036] Figure 4 shows another method for forming a metal wire-containing fine wire 12 by combining a metal wire 12a and a thread material 12b. When twisting the metal wire 12a and the thread material 12b, the metal wire 12a and the thread material 12b are used as core threads, and a retaining thread 12k is wound around the core threads. If this retaining thread 12k is made of water-soluble thread, after fixing the metal wire-containing fine wire 12 to the base material 10, only the retaining thread 12k can be dissolved to form a metal wire-containing fine wire 12 in the state shown in Figure 3(a) on the base material 10. In this case, a predetermined portion of the retaining thread 12k (for example, only the portion that comes into contact with the living body 18) may be dissolved.

[0037] Furthermore, by making both the thread material 12b and the retaining thread 12k water-soluble materials, it is possible to remove both the thread material 12b and the retaining thread 12k after fixing them to the base material 10, leaving only the metal wire 12a in the metal wire-containing fine wire 12. This allows for more reliable conductivity to be ensured for the bioelectrode 1.

[0038] When twisting thread material 12b and metal wire 12a as a core thread, it is best to twist the metal wire 12a in numbers of less than 10 (9 or fewer). This is because even if the diameter of the metal wire 12a is 20 μm or less, if the number of wires twisted simultaneously increases, it will appear as a shadow during X-ray imaging. Furthermore, as can be confirmed in the experiments described later, sufficient conductivity can be achieved for the bioelectrode 1 even without twisting so many metal wires simultaneously.

[0039] Alternatively, the thread material 12b may be used as a core thread, and the metal wire 12a may be twisted around it. Figure 5 illustrates this configuration. Figure 5(a) shows a metal wire-containing thin wire 12 in which there are two thread materials 12b and the metal wire 12a is wound around them. In this configuration, if the pitch 12ap of the metal wires 12a becomes too short, the metal wires 12a will come close together and appear as shadows during X-ray imaging. Figure 5(b) shows the case when the pitch 12ap is short. If this pitch 12ap is at least twice, preferably at least three times, and most preferably at least four times, the appearance of shadows during X-ray imaging can be suppressed.

[0040] Thus, by constructing the metal wire-containing fine wire 12 from thread material 12b and metal wire 12a, it becomes easy to place the metal wire 12a on the base material 10 and fix it with adhesive or the like. Furthermore, when the metal wire-containing fine wire 12 includes thread material 12b and the diameter of the metal wire-containing fine wire 12 is 50D or more, it becomes easily visible and can be handled in the same way as ordinary thread. In that case, it can also be fixed by sewing the metal wire-containing fine wire 12 to the base material 10.

[0041] The sewing method for the metal wire-containing fine wire 12 and the base material 10 can be basic sewing techniques such as running stitch, backstitch, half backstitch, and full backstitch, provided the metal wire 12a is 20 μm or less. On the other hand, sewing methods using upper and lower threads, which are unique to sewing machines, can also be used. With sewing using a lower thread, the sensitivity of the bio-contact area 18 increases as the sewing becomes denser, but the risk of it showing up in X-ray images also increases. Furthermore, it was confirmed that sufficient sensitivity can be obtained with a single-loop stitch for the bioelectrode 1. In addition, with a single-loop stitch using upper and lower threads, the metal wire-containing fine wire 12 is exposed almost continuously on both the front and back sides, so a wider contact area with the body can be secured compared to a running stitch.

[0042] Figure 6 shows examples of stitching methods. Figure 6(a) shows a running stitch, and Figure 6(b) shows a single chain stitch. Both Figures 6(a) and 6(b) are cross-sectional views of the base material 10, illustrating a portion of the lead region 20 between the bio-contact region 18 and the connecting end region 16. In the base material 10, the upward direction in the figure is considered the front side, and the opposite direction is considered the back side. The side on which the bio-contact region 18 is provided is considered the front side.

[0043] In Figure 6(a), a running stitch is used in which a single metal-reinforced thin wire 12 is sewn to the base material 10 while advancing the same distance on both the front and back sides. In this example, the length 30u on the front side and the length 30d on the back side are the same, but the length 30u on the front side may be longer than the length 30d on the back side.

[0044] Fig. 6(b) shows single-thread chain stitching using a sewing machine in the case where an upper thread 12UP and a lower thread 12DN are used. Here, the upper thread 12UP is reinforced, and the lower thread 12DN is sewn so as to fix the upper thread 12UP from the back side. Of course, the upper thread 12UP and the lower thread 12DN may be sewn with the same tension. When the upper thread 12UP and the lower thread 12DN are sewn with the same tension, the intersection 32 of the upper thread 12UP and the lower thread 12DN is arranged inside the base material 10.

[0045] The metal wire-containing fine wires 12 are sewn between the connection end region 16 and the living body contact region 18 of the base material 10. The sewing method is not particularly limited, but when sewing, it is preferable that adjacent metal wire-containing fine wires 12 are spaced apart by an interval equal to or larger than the thickness of the metal wire 12a. Further, it is preferable that a plurality of metal wire-containing fine wires 12 are sewn in the living body contact region 18 and the connection end region 16. This is because even if the metal wire 12a is broken at any position, the biological electrode 1 as a whole does not lose conductivity. For example, the method of sewing a plurality of metal wire-containing fine wires 12 as shown in Fig. 1 and Fig. 2 is one example of a sewing pattern.

[0046] Fig. 7 shows an example of sewing metal wire-containing fine wires 12 onto the base material 10. Fig. 7(a) is a plan view, and Fig. 7(b) is a cross-sectional view. This shows a state in which the direction from the connection end region 16 to the living body contact region 18 is regarded as the amplitude direction of a square wave, and the metal wire-containing fine wires 12 are sewn in a square wave pattern from the long side 12L1 toward the long side 12L2. Specifically, a starting point F1 is defined within the living body contact region 18, sewing is performed linearly to the inner part of the connection end region 16, and the sewing direction is changed in the width direction of the base material 10 at a turning point F2. Then, after sewing to F3, the sewing direction is changed toward the living body contact region 18, and sewing proceeds to F4 in the living body contact region 18. By repeating this, seams of the square wave-shaped metal wire-containing fine wires 12 are formed on the base material 10.

[0047] In the lead section 20, the number of metal wire-containing fine wires 12 when viewed in a direction perpendicular to the plane of the base 10 in the direction from the living body connection region 18 toward the connection end region 16 (the direction may be reversed) is referred to as the cross-sectional number. Further, the distance between the adjacent metal wire-containing fine wires 12 in this case is referred to as the adjacent wire spacing 12W. In the present invention, even if a single metal-containing fine wire 12 is fixed by reciprocating between the living body connection region 18 and the connection end region 16, it can be said that a plurality of metal wire-containing fine wires 12 are arranged between the connection end region 16 and the living body contact region 18 as long as there are a plurality of cross-sectional wires.

[0048] The adjacent wire spacing 12W between the metal wire-containing fine wires 12 may be set to a spacing such that the metal wires 12a in the metal wire-containing fine wires 12 are not visible on an X-ray image. As shown in the following examples, the spacing is preferably larger than 50 μm, at which a single metal wire 12a would be visible on an X-ray image. On the other hand, as can be seen from the following examples, it has been found that if the adjacent wire spacing 12W is too large, it will pick up noise and the like in the usage environment. Therefore, the adjacent wire spacing is desirably 1.0 mm (1000 μm) or less. It should be noted that the adjacent wire spacing does not need to be constant between each of the metal wire-containing fine wires 12 arranged in the lead section 20 as long as it is within the above-mentioned range.

[0049] It should be noted that a connector 40 for connection is shown in the connection end region 16. In FIG. 7(a), the connector 40 is shown as a perspective view with a one-dot chain line so that the stitches of the metal wire-containing fine wires 12 can be seen. The connector 40 is formed of a conductive material. For example, it is preferable to form the connector 40 from metal. However, in this case, the connector 40 does not allow X-rays to transmit therethrough, so this portion will appear as a shadow when X-ray imaged. Therefore, when the living body contact region 18 is contacted and fixed to a predetermined position of a living body, the lead region 20 is preferably formed long enough to allow the connector 40 to be positioned outside the field of view of X-ray imaging.

[0050] FIG. 7(b) is a cross-sectional view when the metal wire-containing fine wire 12 of FIG. 7(a) is subjected to single-thread chain stitching. When single-thread chain stitching is performed, the metal wire-containing fine wires 12 are arranged on the front side and the back side of the base material 10. The connector 40 is arranged so as to be in contact with the metal wire-containing fine wires 12 at the connection end region 16.

[0051] Figure 8 shows the base material 10 and metal wire-containing fine wire 12 shown in Figure 7, with additional components added. Figure 8(a) is a plan view, and Figure 8(b) is a cross-sectional view. A connector 40 is arranged in the connection end region 16 as in Figure 7. Furthermore, an electrode holder 42 with an electrode window 42w is formed in the bio-contact region 18. The electrode holder 42 is preferably made of a material that does not show up in X-ray images and has a certain degree of rigidity. For example, plastic can be suitably used.

[0052] When attaching the bioelectrode 1 to a living body, apply the electrolyte-containing gel to the electrode window 42w and then bring it into contact with the living body. The electrode holder 42 also covers the metal-containing nanowire 12DN on the back side of the base material 10. This is to prevent a short circuit from the metal-containing nanowire 12DN.

[0053] Furthermore, insulating films 44 may be formed on both the front and back sides of the lead region 20. The metal wire-containing nanowire 12 retains surface conductivity even when twisted together with the thread material 12b. This is to prevent short circuits in this area and to prevent breakage of the metal wire-containing nanowire 12 in the lead region 20. The insulating film 44 can be any insulating material such as plastic that does not appear as a shadow during X-ray imaging, and is more preferably made of a material that is easily deformable. This is to allow it to easily deform to conform to the surface shape of living organisms.

[0054] <Visibility by X-ray> Metal wire 12a was made of tungsten alloy wire, and thicknesses of 13 μm, 20 μm, 33 μm, and 50 μm were prepared. Referring to Figure 9, one tungsten alloy wire of each thickness was arranged in three rows, each 100 mm long and spaced 10 mm apart, and attached to a plastic frame. This was then X-rayed. Note that each thickness group was spaced 20 mm apart.

[0055] The equipment used for X-ray imaging was the RADspeed Pro radiography system (manufactured by Shimadzu Corporation) and the DR-ID 900PU FPD (manufactured by Fujifilm Corporation). The imaging conditions were set to tube voltages of 70kVp and 120kVp. Automatic exposure control (AEC) was used for exposure.

[0056] The Source-Surface Distance (SSD) from the X-ray source to the acrylic plate surface was 180 cm, the grid thickness was 12:1, and the irradiation field was 14 × 17. The analysis was performed using ImageJ, an open-source, public-domain image processing software.

[0057] Figure 10 shows the measurement results. Figure 10(a) is an X-ray image, and Figure 10(b) shows the brightness values ​​obtained by scanning the image signal from left to right in Figure 10(a). In each figure in Figure 10(b), the vertical axis represents the brightness value (arbitrary), and the horizontal axis represents the width (mm). Figures 10(a-1) and 10(b-1) are for a tube voltage of 70 kVp, and Figures 10(a-2) and 10(b-2) are for a voltage of 120 kVp. Figure 10(b-1) shows thicknesses of 13 μm, 20 μm, 33 μm, and 50 μm from left to right.

[0058] Referring to Figure 10(a), a visual inspection of this photograph revealed that the 13 μm thick tungsten alloy wire was not visible. While the 20 μm thick tungsten alloy wire was faintly discernible in some areas, most of it was invisible. Wires 33 μm or thicker could be visually identified, even individually. In Figure 10(a-1), although identification is not easy due to the diagram, white lines have been placed where metal wires of each thickness are located. As a result, it can be said that wires 20 μm or thinner are indistinguishable from those used in X-ray imaging for human photography. However, while wires 20 μm or thinner become invisible to X-rays, excessively thin wires become structurally weak and difficult to manufacture and handle. Therefore, a thickness of 1 μm or more, preferably 5 μm or more, is desirable.

[0059] Next, referring to Figure 10(b), a clear decrease in luminance signal was observed for tungsten alloy wires with diameters of 33 μm and 50 μm, but this could not be observed for the 13 μm tungsten alloy wire even at a tube voltage of 120 kVp. Since X-ray images are ultimately based on interpretation, the decrease in luminance signal should be considered as a reference, and the boundary for suitability as a bioelectrode 1 is considered to be when it is not visible to the naked eye. Therefore, it can be said that tungsten alloy wires with a diameter exceeding 20 μm are undesirable for use as bioelectrode 1.

[0060] <Effect of Multiple Wires: Different Thicknesses> Next, we will consider the case where multiple metal wires 12a are used. Five strands each of tungsten alloy wires with thicknesses of 13 μm, 20 μm, and 33 μm were twisted together, and the brightness values ​​of the X-ray images and video signals were examined. Figure 11 shows the relationship between the frame used in the experiment and the metal wires 12a. For each thickness of metal wire 12a, seven wires were placed along the length of the frame at intervals of 10 mm.

[0061] The results are shown in Figure 12. Figure 12(a) is an X-ray image, and Figure 12(b) shows the change in the brightness value of the video signal. The vertical axis represents the brightness value (arbitrary), and the horizontal axis represents the width (mm). Figures 12(a-1) and 12(b-1) show the case when the tube voltage is 70 kVp, and Figures 12(a-2) and 12(b-2) show the case when the tube voltage is 120 kVp.

[0062] In Figure 12, "13-5", "20-5", and "33-5" represent five strands of metal wire 12a with thicknesses of 13 μm, 20 μm, and 33 μm twisted together. Also, in Figure 12(a-1), white lines are placed where the frame and each metal wire 12a are positioned.

[0063] Referring to Figure 12, the difference between a yarn made of five strands of 20 μm thickness and a yarn made of five strands of 33 μm thickness was clearly visible. The arrows in Figure 12(a-2) indicate that the 20-5 and 33-5 samples were clearly visible. Furthermore, referring to Figure 12(b), a clear decrease in brightness values ​​was observed across the width of the 20-5 and 33-5 samples.

[0064] In contrast, sample 13-5 was not visible to the naked eye, and no decrease in brightness value was observed. Therefore, even when five 13 μm thick metal wires 12a were twisted together, they were not visible.

[0065] <Effect of multiple wires: 13 μm> It was found that metal wires 12a with a thickness of 20 μm or less are preferably used. Next, we investigated how thick a 13 μm metal wire 12a (tungsten alloy wire) could be made.

[0066] Metal-containing thin wires 12 were prepared by twisting together 10, 15, and 20 strands of tungsten alloy wire with a thickness of 13 μm. Three rows of these wires were attached to the frame shown in Figure 9, and the same experiment was conducted. The results are shown in Figure 13. Figure 13(a) is an X-ray image, and Figure 13(b) shows the change in the brightness value of the video signal. In the graph in Figure 13(b), the vertical axis represents the brightness value (arbitrary), and the horizontal axis represents the width (mm).

[0067] Referring to Figure 13(a), 10, 15, and 20 wires were all visually identifiable. Since they are difficult to see in the figure, white lines have been placed where the metal-containing thin wires 12 are located. Furthermore, a decrease in brightness values ​​was observed in the brightness signal. Therefore, it was found that even tungsten alloy wires with a thickness of 13 μm can become visible when bundled in groups of 10 or more.

[0068] Figure 14 shows bundles of tungsten alloy wires tied together with water-soluble vinylon thread. Structurally, this corresponds to the case in Figure 5(a) where reference numeral 12b is the tungsten alloy wire and reference numeral 12a is the water-soluble vinylon thread. Referring to Figure 14, Figure 14(a) is an X-ray image, and Figure 14(b) shows the change in the brightness value of the video signal. In the graph in Figure 14(b), the vertical axis represents the brightness value (arbitrary), and the horizontal axis represents the width (mm).

[0069] Referring to Figures 14(a) and 14(b), in both cases the metal-containing nanowire 12 could be recognized more clearly than in Figure 13.

[0070] <Thread Material> From the above, it was found that for 13 μm thick tungsten alloy wire to become invisible, the number of strands must be less than 10. Next, the visibility of polyester thread or water-soluble vinylon was investigated. One, two, and three strands of 50D (denier) polyester thread, one and two strands of 75D polyester thread, one strand of 150D polyester thread, and one strand of water-soluble vinylon were attached to a frame at intervals of 10 mm, and the decrease in brightness value was examined by visual inspection using photographs. In the case of multiple strands, they were twisted together.

[0071] Figure 15 shows the arrangement of the thread materials 12b during the experiment. Three samples each of the following were attached to the frame shown in Figure 9: one 50D polyester thread (labeled "Poly50D-1"), two 50D polyester threads (labeled "Poly50D-2"), three 50D polyester threads (labeled "Poly50D-3"), one 75D polyester thread (labeled "Poly75D-1"), two 75D polyester threads (labeled "Poly75D-2"), one 150D polyester thread (labeled "Poly150D-1"), and one water-soluble vinylon thread (labeled "WSV-1"). The X-ray imaging method is the same as in Figures 10 onward.

[0072] The results are shown in Figure 16. Figure 16(a) is an X-ray image, and Figure 16(b) shows the change in the brightness value of the video signal. In Figure 16, a white line is placed at the location of the thread material 12b. In the graph in Figure 16(b), the vertical axis is the brightness value (arbitrary), and the horizontal axis is the width (mm). In Figure 16, none of the thread materials 12b could be visually confirmed. Therefore, the thread material 12b can be selected from a relatively wide range of configurations for the bioelectrode 1.

[0073] <Electrode Performance> The bioelectrode 1 was fabricated as follows, as shown in Figure 17. A nonwoven fabric with a width of 25 mm, a length of 220 mm, and a thickness of 0.15 mm was used as the base material 10. The metal wire-containing fine wire 12 was made by twisting a 50D polyester and one φ13 μm tungsten wire as the core threads, with a 40D water-soluble vinylon thread as the binding thread 12k. This metal wire-containing fine wire 12 was sewn onto the base material 10 in a square wave pattern over a length of 200 mm. The sewing onto the base material 10 was done using a sewing machine with upper thread 12UP and lower thread 12DN. After sewing the metal wire-containing fine wire 12 onto the base material 10, the entire assembly was immersed in water to dissolve the binding thread 12k.

[0074] The bio-contact area 18 was defined as the 20 mm region from the end of one metal wire-containing nanowire 12, and the connecting end area 16 was defined as the 20 mm region from the end of the other metal wire-containing nanowire 12. As a result, the lead area 20 is 160 mm.

[0075] In Figure 17, the number of cross-sections is shown as N. Samples of bioelectrode 1 were prepared with 10 cross-sections (inter-line spacing: 1.5 mm), 15 cross-sections (inter-line spacing: 1 mm), and 30 cross-sections (inter-line spacing: 0.5 mm). These samples were designated as bioelectrode sample A, bioelectrode sample B, and bioelectrode sample C, respectively.

[0076] Figure 18 shows the attachment to the human body. Bioelectrode 1 was attached to the upper body of a 32-year-old male volunteer. An electrocardiograph 50, BSM-2401 patient monitor (Nihon Kohden, Tokyo, Japan), was used. For attachment, an electrolyte-containing gel was applied to the biocontact area 18 of bioelectrode 1 and it was then attached to the skin. Bioelectrode 1 was attached to T1 (anode) and T2 (cathode), and a standard electrode (a commercially available single-use disposable electrode; referred to as bioelectrode sample N) was attached to the T3 (ground) position.

[0077] In Figure 18, the two bioelectrodes 1 are represented as P1 and P2. The biocontact area 18, lead area 20, and connection end area 16 of each bioelectrode 1 are indicated in parentheses after the reference numerals P1 and P2. The biocontact area 18 is shown as a rectangle, and the lead area 20 as a curve. The connection end area 16 is shown as a curve following the lead area 20. In practice, the terminals of the connection end area 16 were attached to the electrocardiograph 50 using alligator clips 52a and 52b provided on the connector of the electrocardiograph 50, and connected to the electrocardiograph 50.

[0078] A typical electrode PN consists of a part PN (18) that attaches to the body, a lead wire PN (20), and a connecting terminal PN (16). The connecting terminal PN (16) is connected to the connector 52N of the electrocardiograph 50. This typical electrode PN is visible in X-ray images.

[0079] Figure 19 shows the electrocardiogram screen. Referring to Figure 19, Figure 19(a) shows the results for sample A, Figure 19(b) shows the results for sample B, and Figure 19(c) shows the results for sample C. In each figure, the horizontal axis is time and the vertical axis is millivolts (mV). In sample A (adjacent spacing 1.5 mm), an unstable output voltage was observed in the area indicated by the arrow, but stable output was obtained in sample B (adjacent wire spacing 1 mm) and sample C (adjacent wire spacing 0.5 mm). Therefore, it was found that it is preferable to use an adjacent wire spacing of 1 mm or less.

[0080] Figure 20 compares the output of sample C from Figure 19 with that of a disposable electrode conventionally used in clinical practice. Figure 20(a) shows a standard electrode (sample N), and Figure 20(b) shows sample C from Figure 19. Sample C, with a wire spacing of 0.5 mm, was able to obtain an output comparable to that of currently used electrodes.

[0081] Furthermore, since the metal wire-containing thin wire 12 used here contains only one tungsten wire with a diameter of 13 μm, it does not appear in X-ray photographs (or images) based on the results of the <X-ray visibility>. As described above, the bioelectrode 1 according to the present invention does not appear as a shadow in X-ray photography and can be used as an electrocardiogram electrode without issue.

[0082] The bioelectrode according to the present invention can be suitably used when it is desired to measure electrocardiograms or electroencephalograms while using X-rays.

[0083] 1 Bioelectrode 10 Base material 12 Fine wire containing metal wire 12a Metal wire 12b Thread material 12b Non-metallic wire 12k Retaining thread 12ap Pitch 12UP Upper thread 12DN Lower thread 12L1 Long side 12L2 Long side 12W Interconnection point 16 Connection end area 18 Biocontact area 20 Lead area 30u Front side length 30d Back side length 32 Intersection 40 Connector 42 Electrode holder 42w Electrode window 44 Insulating film 50 Electrocardiograph 52a Alligator clip

Claims

1. A bioelectrode comprising: a base material that transmits X-rays; a connection end region provided on the base material; a biocontact region provided at a different position on the base material via a lead region from the connection end region; and a metal wire containing a metal wire with a diameter of 20 μm or less, fixed to the base material, extending from within the connection end region through the lead region to within the biocontact region.

2. The bioelectrode according to claim 1, wherein a plurality of metal wire-containing nanowires are arranged in the lead region from the connection end region toward the biological contact region, and the spacing between adjacent metal wires is 50 μm or more and 1000 μm or less.

3. The bioelectrode according to claim 1 or 2, wherein the metal wire-containing fine wire is fixed by sewing it to the base material.

4. A bioelectrode according to claim 1 or 2, having an insulating region in which the metal wire-containing nanowire is insulated in a portion other than the bio-contact region.

5. The bioelectrode according to claim 1 or 2, wherein the metal wire-containing nanowire is composed of a metal wire and a non-metal wire, and the metal wire and the non-metal wire are twisted together.

6. The bioelectrode according to claim 1 or 2, wherein the metal wire-containing nanowire is composed of a metal wire and a non-metal wire, and the metal wire and the non-metal wire are fixed to the base material and are in a bundle.

7. The bioelectrode according to claim 1 or 2, wherein the metal wire-containing nanowire is composed of one to five tungsten alloy wires and non-metallic wires, each having a diameter of 13 μm.

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