Balloon catheter system having a balloon catheter

Abstract

This balloon catheter (1) comprises: a shaft having a distal end and a proximal end; a balloon (10) provided to the distal end section of the shaft (2); an insulating material disposed on the outer surface (11) of the balloon (10); a cauterizing electrode (25) disposed on the insulating material (20); and two or more impedance measurement electrodes (30) that have a smaller surface area than the cauterizing electrode (25), are disposed around the cauterizing electrode (25) on the insulating material (20), and measure impedance, wherein a straight line (38) that connects at least two measurement electrodes (30) to each other crosses the cauterizing electrode (25).

Description

[Technical field]

[0001] The present invention relates to a balloon catheter, and more particularly to a balloon catheter capable of cauterizing biological tissue and a system including the same. [Background technology]

[0002] In pulmonary vein isolation for the treatment of atrial fibrillation, an ablation catheter having a balloon is used. An ablation electrode is provided on the outer surface of the balloon. The tissue at the pulmonary vein opening can be ablated by inflating the balloon and bringing the ablation electrode into contact with the pulmonary vein opening and passing a high-frequency current through the ablation electrode. In order to check whether the ablation electrode is in contact with biological tissue such as the pulmonary vein, it has been proposed to provide an electrode on the outer surface of the balloon in addition to the ablation electrode.

[0003] Patent Document 1 discloses an electrophysiology catheter having a balloon including a membrane and a contact electrode supported on the outer surface of the membrane. The contact electrode is in electrical contact with the mouth of a lumen such as a pulmonary vein during an ablation procedure, and a current flows from the contact electrode to the mouth. Patent Document 1 also discloses that, in addition to the contact electrode, a plurality of separate island-like contact microelectrodes are provided, and the contact microelectrode is surrounded by a plurality of contact electrodes. Patent Document 2 discloses a system for detecting gaps in an ablation line by a microelectrode separate from the ablation electrode. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-94407 A [Patent Document 2] JP 2019-80926 A Summary of the Invention [Problem to be solved by the invention]

[0005] In order to cauterize a wide range of biological tissue at the same time, the cauterizing electrode is provided on the balloon so as to have a certain area. However, from the microelectrode arranged in the cauterizing electrode, it is sometimes difficult to grasp the detailed contact state between the cauterizing electrode and the biological tissue, such as whether the entire cauterizing electrode is in contact with the biological tissue or only a part of the cauterizing electrode is in contact with the biological tissue, and there is room for improvement. Therefore, the present invention aims to provide a balloon catheter and a balloon catheter system equipped with the same that can grasp the contact state between the cauterizing electrode and the biological tissue. [Means for solving the problem]

[0006] One embodiment of the balloon catheter of the present invention that has achieved the above object is a balloon catheter for cauterizing biological tissue, comprising a shaft having a distal end and a proximal end, a balloon provided at the distal part of the shaft, an insulating material disposed on the outer surface of the balloon, an ablation electrode disposed on the insulating material and cauterizing biological tissue by passing a high-frequency current therethrough, and two or more impedance measurement electrodes that have a smaller surface area than the ablation electrode and are disposed around the ablation electrode on the insulating material to measure impedance, and a straight line connecting at least two of the two or more impedance measurement electrodes crosses the ablation electrode. In the balloon catheter, two or more impedance measurement electrodes are disposed around the ablation electrode. Therefore, by measuring the impedance of each impedance measurement electrode, the contact state between each impedance measurement electrode and biological tissue can be detected. The specific contact state between the ablation electrode and biological tissue can be grasped from the detection result of the contact state between each impedance measurement electrode and biological tissue. Therefore, since the balloon catheter can be disposed at an appropriate position in the living body prior to ablation, ablation can be performed efficiently and the burden on the patient and the operator can be reduced.

[0007] In the balloon catheter, it is preferred that no impedance measuring electrode is completely surrounded by the ablation electrode.

[0008] In the above-mentioned balloon catheter, it is preferable that an insulating material is provided around at least one of the two or more impedance measuring electrodes, and that at least one of the two or more impedance measuring electrodes is insulated from the cauterizing electrode.

[0009] In the above balloon catheter, it is preferable that the shortest distance between one of the two or more impedance measuring electrodes and the ablation electrode is 1 / 5 or less of the shortest distance between two of the two or more impedance measuring electrodes.

[0010] It is preferable that the two or more impedance measurement electrodes include three or more impedance measurement electrodes, the ablation electrode has an overlapping region overlapping with a virtual region formed by the three or more impedance measurement electrodes, and the area of ​​the overlapping region occupies 70% or more of the area of ​​the ablation electrode. However, the virtual region is formed by defining the most proximal position located closest to the ablation electrode for each of the three or more impedance measurement electrodes arranged around the ablation electrode, and connecting the most proximal positions of the impedance measurement electrodes adjacent to each other in the circumferential direction of the ablation electrode with a straight line.

[0011] It is preferable that the two or more impedance measuring electrodes include three or more impedance measuring electrodes, the three or more impedance measuring electrodes including at least a first impedance measuring electrode, a second impedance measuring electrode, a third impedance measuring electrode, a fourth impedance measuring electrode, a fifth impedance measuring electrode, and a sixth impedance measuring electrode, the ablation electrode has a first overlapping area overlapping with a first virtual area formed by at least the first impedance measuring electrode, the second impedance measuring electrode, the third impedance measuring electrode, and the fourth impedance measuring electrode, and a second overlapping area overlapping with a second virtual area formed by at least the third impedance measuring electrode, the fourth impedance measuring electrode, the fifth impedance measuring electrode, and the sixth impedance measuring electrode, and the sum of the areas of the first overlapping area and the second overlapping area accounts for 70% or more of the area of ​​the ablation electrode. However, the first virtual region and the second virtual region are formed by defining the most proximal position located closest to the ablation electrode for each of three or more impedance measurement electrodes arranged around the ablation electrode, and connecting the most proximal positions of adjacent impedance measurement electrodes in the circumferential direction of the ablation electrode with a straight line.

[0012] In the above balloon catheter, it is preferable that the insulating material is a flexible substrate having a first surface and a second surface opposite the first surface, the first surface facing the outside of the balloon, and the cauterizing electrode is disposed on the second surface side of the insulating material.

[0013] The present invention also provides a balloon catheter system. The balloon catheter system according to one embodiment of the present invention has the balloon catheter, a measurement unit that measures impedance between one of the two or more impedance measurement electrodes and a cauterization electrode or between two different impedance measurement electrodes, and a control unit that is connected to the measurement unit and determines whether or not one of the two or more impedance measurement electrodes is in contact with a biological tissue using the impedance measurement result.

[0014] A balloon catheter system according to another embodiment of the present invention comprises the above-mentioned balloon catheter, a return electrode plate provided on the surface of a patient's body and through which a high-frequency current is passed between the return electrode plate and the ablation electrode, a measurement unit that measures the impedance between one of two or more impedance measurement electrodes and the return electrode plate, and a control unit that is connected to the measurement unit and uses the impedance measurement result to determine whether or not one of the two or more impedance measurement electrodes is in contact with biological tissue.

[0015] According to the balloon catheter system, the specific contact state between the cauterizing electrode and the biological tissue can be grasped from the detection result of the contact state between each impedance measurement electrode and the biological tissue. Therefore, the balloon catheter can be placed at an appropriate position in the living body prior to cauterization, so that cauterization can be performed efficiently and the burden on the patient and the operator can be reduced.

[0016] In the above-mentioned balloon catheter system, it is preferable that the control unit determines whether or not the cauterizing electrode is in contact with the biological tissue using a determination result of a contact state between at least one of the two or more impedance measuring electrodes and the biological tissue.

[0017] It is preferable that the two or more impedance measurement electrodes include three or more impedance measurement electrodes, the ablation electrode has an overlapping region overlapping with the virtual region formed by the three or more impedance measurement electrodes, and the control unit determines that the overlapping region of the ablation electrode has come into contact with the biological tissue when all of the three or more impedance measurement electrodes come into contact with the biological tissue. However, the virtual region is formed by defining the most proximal position located closest to the ablation electrode for each of the three or more impedance measurement electrodes arranged around the ablation electrode, and connecting the most proximal positions of the impedance measurement electrodes adjacent to each other in the circumferential direction of the ablation electrode with a straight line.

[0018] The two or more impedance measuring electrodes include three or more impedance measuring electrodes, the three or more impedance measuring electrodes including at least a first impedance measuring electrode, a second impedance measuring electrode, a third impedance measuring electrode, a fourth impedance measuring electrode, a fifth impedance measuring electrode, and a sixth impedance measuring electrode, and the ablation electrode includes a first overlapping area overlapping a first virtual area formed by at least the first impedance measuring electrode, the second impedance measuring electrode, the third impedance measuring electrode, and the fourth impedance measuring electrode, and a second overlapping area overlapping a first virtual area formed by at least the third impedance measuring electrode and the fourth impedance measuring electrode. It is preferable that the ablation electrode has a second overlapping area overlapping with a second virtual area formed by the first impedance measurement electrode, the fifth impedance measurement electrode and the sixth impedance measurement electrode, and the control unit determines that the first overlapping area of ​​the ablation electrode has come into contact with the biological tissue when the first impedance measurement electrode, the second impedance measurement electrode, the third impedance measurement electrode and the fourth impedance measurement electrode come into contact with the biological tissue, and determines that the second overlapping area of ​​the ablation electrode has come into contact with the biological tissue when the third impedance measurement electrode, the fourth impedance measurement electrode, the fifth impedance measurement electrode and the sixth impedance measurement electrode come into contact with the biological tissue.

[0019] It is preferable that the balloon catheter system further has a processing unit connected to the control unit, and the processing unit performs at least one of comparing the impedance between one of the two or more impedance measurement electrodes and the ablation electrode with a first reference value, comparing the impedance between two of the two or more impedance measurement electrodes with a second reference value, and comparing the impedance between one of the two or more impedance measurement electrodes and the return electrode with a third reference value, and the control unit uses a comparison result from the processing unit to determine whether or not one of the two or more impedance measurement electrodes is in contact with biological tissue.

[0020] It is preferable that the balloon catheter system further has a processing unit connected to the control unit, and the processing unit performs at least one of the following: a comparison of the impedance between one of the two or more impedance measurement electrodes and the ablation electrode before and after balloon expansion, a comparison of the impedance between two of the two or more impedance measurement electrodes before and after balloon expansion, and a comparison of the impedance between one of the two or more impedance measurement electrodes and the return electrode before and after balloon expansion, and the control unit uses a comparison result from the processing unit to determine whether or not one of the two or more impedance measurement electrodes is in contact with biological tissue.

[0021] It is preferable that the balloon catheter system is provided with a reference electrode at a position on the shaft surface proximal to the balloon, and the measurement unit further measures the impedance between one of the two or more impedance measurement electrodes and the reference electrode. Effect of the Invention

[0022] In the balloon catheter and balloon catheter system, two or more impedance measurement electrodes are arranged around the ablation electrode. Therefore, by measuring the impedance of each impedance measurement electrode, the contact state between each impedance measurement electrode and the biological tissue can be detected. From the detection result of the contact state between each impedance measurement electrode and the biological tissue, the specific contact state between the ablation electrode and the biological tissue can be grasped. Therefore, since the balloon catheter can be placed at an appropriate position in the living body prior to ablation, ablation can be performed efficiently and the burden on the patient and the operator can be reduced. [Brief description of the drawings]

[0023] [Figure 1] 1 is a side view (partial cross-sectional view) of a balloon catheter according to one embodiment of the present invention. [Diagram 2] 2 is a side view (partially sectional view) showing a modified example of the balloon catheter shown in FIG. [Diagram 3]2 is an enlarged cross-sectional view showing a modified example of the balloon catheter shown in FIG. 1. [Figure 4] FIG. 2 is a schematic diagram showing an example arrangement of an ablation electrode and two or more impedance measuring electrodes according to one embodiment of the present invention. [Diagram 5] 5 is a schematic diagram showing a modified arrangement of the cauterizing electrode and two or more impedance measuring electrodes shown in FIG. 4. [Figure 6] 5A and 5B are schematic diagrams illustrating another variation of the arrangement of the ablation electrode and two or more impedance measuring electrodes shown in FIG. 4. [Figure 7] 5 is a schematic diagram showing yet another modified example of the arrangement of the cauterizing electrode and the two or more impedance measuring electrodes shown in FIG. 4. [Figure 8] 5 is a schematic diagram showing yet another modified example of the arrangement of the cauterizing electrode and the two or more impedance measuring electrodes shown in FIG. 4. [Figure 9] 5 is a schematic diagram showing yet another modified example of the arrangement of the cauterizing electrode and the two or more impedance measuring electrodes shown in FIG. 4. [Figure 10] 1 illustrates a block diagram of a balloon catheter system according to an embodiment of the present invention. [Figure 11] 11 illustrates an example of a flowchart for determining a contact state between a cauterizing electrode and a biological tissue using the balloon catheter system illustrated in FIG. 10. [Figure 12] FIG. 11 is a block diagram showing a modified example of the balloon catheter system shown in FIG. [Figure 13] FIG. 13 is a block diagram showing a modified example of the balloon catheter system shown in FIG. 12. [Figure 14] 5 illustrates an example of a flowchart showing a second determination method according to an embodiment of the present invention. [Figure 15] 13 illustrates an example of a flowchart showing a third determination method according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] The present invention will be described in more detail below based on the following embodiments, but the present invention is not limited to the following embodiments, and can be modified as long as it meets the purpose described above and below, and all of these modifications are included in the technical scope of the present invention. In addition, hatching and component symbols may be omitted in each drawing for convenience, but in such cases, the specification and other drawings should be referred to. In addition, the dimensions of various components in the drawings may differ from the actual dimensions because priority is given to helping understand the features of the present invention.

[0025] 1. Balloon Catheter One embodiment of the balloon catheter of the present invention is a balloon catheter for cauterizing biological tissue, comprising a shaft having a distal end and a proximal end, a balloon provided at the distal part of the shaft, an insulating material disposed on the outer surface of the balloon, an ablation electrode disposed on the insulating material and cauterizing biological tissue by passing a high-frequency current therethrough, and two or more impedance measurement electrodes having a smaller surface area than the ablation electrode and disposed around the ablation electrode on the insulating material for measuring impedance, wherein a straight line connecting at least two of the two or more impedance measurement electrodes crosses the ablation electrode. In the balloon catheter, two or more impedance measurement electrodes are disposed around the ablation electrode. Therefore, by measuring the impedance of each impedance measurement electrode, the contact state between each impedance measurement electrode and biological tissue can be detected. The specific contact state between the ablation electrode and biological tissue can be grasped from the detection result of the contact state between each impedance measurement electrode and biological tissue. Therefore, since the balloon catheter can be disposed at an appropriate position in the living body prior to ablation, it is possible to efficiently perform ablation and reduce the burden on the patient and the surgeon.

[0026] The balloon catheter is an ablation catheter that cauterizes biological tissue. One example of the use of the balloon catheter is pulmonary vein isolation, which is one of the treatments for atrial fibrillation. In pulmonary vein isolation, an ablation electrode is provided on the outer surface of the balloon, the balloon is expanded, and the ablation electrode is brought into contact with the pulmonary vein opening, and a high-frequency current is passed through the ablation electrode to cauterize the pulmonary vein opening. This makes it possible to block the abnormal electrical pathway that causes atrial fibrillation.

[0027] The configuration of a balloon catheter will be described with reference to Fig. 1. Fig. 1 is a side view (partial cross-sectional view) of a balloon catheter according to one embodiment of the present invention. Fig. 1 shows an example of the configuration of an over-the-wire type balloon catheter in which a wire is inserted from the distal side to the proximal side of a shaft. The balloon catheter 1 has a shaft 2, a balloon 10, an insulating material 20, a cauterizing electrode 25, and two or more impedance measuring electrodes 30.

[0028] The shaft 2 has a distal end and a proximal end. A balloon 10 is provided at the distal portion of the shaft 2. A fluid supplier 52 such as a syringe for supplying a fluid to the inside of the balloon 10 is connected to the proximal portion of the shaft 2. In the present invention, the distal side of the balloon catheter 1 or the shaft 2 refers to the tip side in the longitudinal direction of the shaft 2 (in other words, the longitudinal axial direction of the shaft 2), which is the treatment target side. The proximal side of the balloon catheter 1 or the shaft 2 refers to the base end side in the longitudinal direction of the shaft 2, which is the hand side of the user (operator). Unless otherwise specified in the present invention, the inside and outside of the shaft 2 or the balloon 10 refer to the inside and outside in the radial direction of the shaft 2, and the inside in the radial direction of the shaft 2 refers to the side closer to the longitudinal axis center of the shaft 2.

[0029] The balloon catheter 1 is configured such that fluid is supplied from the fluid supplier 52 to the inside of the balloon 10 through the shaft 2. The balloon 10 can be expanded by supplying fluid to the inside of the balloon 10. The balloon 10 can be deflated by discharging fluid from the inside of the balloon 10. Although not shown, the fluid supplier 52 may include at least one of a heater that heats the fluid and a cooler that cools the fluid. The temperature of the fluid supplied from the fluid supplier 52 can be set or controlled as necessary.

[0030] Typically, the shaft 2 is provided therein with a flow path for the fluid to be supplied into the balloon 10 and a passage for inserting a wire that guides the progress of the shaft 2 within the body cavity. To facilitate good fluid flow, the flow path preferably extends in the longitudinal direction of the shaft 2. The shaft 2 may have a coaxial structure composed of at least a double tube, or may have a multi-lumen structure having multiple lumens.

[0031] The shaft 2 in FIG. 1 is composed of an inner tube 3 and an outer tube 4. The lumen of the inner tube 3 functions as a passage for inserting a wire. The space between the inner tube 3 and the outer tube 4 functions as a flow path for a fluid. In the distal portion of the shaft 2, the inner tube 3 extends from the distal end of the outer tube 4 and penetrates the balloon 10 in the longitudinal direction. As a result, the balloon 10 can be configured so that the distal portion is fixed to the inner tube 3 and the proximal portion is fixed to the outer tube 4.

[0032] In FIG. 1, the proximal part of the outer tube 4 of the shaft 2 is bifurcated, a fluid supplier 52 is connected to a first side of the bifurcation, and an operation unit 51 is disposed on a second side of the bifurcation. The operation unit 51 is connected to a proximal part of the inner tube 3. The second side of the bifurcation may be connected to a wire port or a cable connector. Although not shown, the shaft 2 and the fluid supplier 52 or the wire port may be connected via a connecting tube or connector. A wire can be inserted into the lumen of the shaft 2 from an opening (not shown) provided on the proximal side of the inner tube 3 of the shaft 2. The opening can also function as an inlet for injection of medicine or the like or an inlet for suction of fluids in the body or the like.

[0033] The shaft 2 is preferably flexible. This allows the shaft 2 to be deformed according to the shape of the body cavity. In order to maintain the shape, the shaft 2 is preferably elastic. The shaft 2 is preferably made of a resin, a metal, or a combination of a resin and a metal. Examples of the shaft 2 include a resin tube, a metal tube, a hollow body formed by arranging wires in a predetermined pattern, a hollow body having at least one of the inner and outer surfaces coated with resin, and a combination of these, for example, a combination of these connected in the longitudinal direction. The resin tube can be manufactured by extrusion molding, for example. Examples of the hollow body in which the wires are arranged in a predetermined pattern include a cylindrical body having a mesh structure formed by simply crossing or weaving the wires, and a coil in which the wires are wound. The wires may be one or more solid wires, or one or more twisted wires. The type of mesh structure is not particularly limited, and the number of turns and density of the coil are also not particularly limited. The mesh structure and the coil may be formed with a constant density over the entire longitudinal direction of the shaft 2, or may be formed so that the density varies depending on the position in the longitudinal direction of the shaft 2. To increase the flexibility of the metal tube, the outer surface of the metal tube may be provided with cuts or grooves, which may be linear, arcuate, annular, spiral, or a combination thereof.

[0034] By using a resin as the constituent material of the shaft 2, it becomes easier to impart flexibility and elasticity to the shaft 2. By using a metal as the constituent material of the shaft 2, it is possible to improve the deliverability of the balloon catheter 1. Examples of resins constituting the shaft 2 include polyamide resins, polyester resins, polyurethane resins, polyolefin resins, fluorine resins, vinyl chloride resins, silicone resins, natural rubber, synthetic rubber, and the like. These may be used alone or in combination of two or more. The resin constituting the shaft 2 may be either a thermoplastic resin or a thermosetting resin, but it is preferable to use a thermoplastic resin. Examples of metals constituting the shaft 2 include stainless steel such as SUS304 and SUS316, platinum, nickel, cobalt, chromium, titanium, tungsten, gold, Ni-Ti alloy, Co-Cr alloy, or a combination thereof. The shaft 2 may have a laminated structure made of different materials or the same material.

[0035] The balloon 10 in FIG. 1 has a distal fixing portion 12 fixed to the distal portion of the shaft 2, a proximal fixing portion 13 fixed to the shaft 2 at a position proximal to the distal fixing portion 12, and an expandable portion 14 located between the distal fixing portion 12 and the proximal fixing portion 13 and not fixed to the shaft 2. Since the balloon 10 is fixed to the shaft 2, the expandable portion 14 can be expanded by supplying a fluid to the balloon 10. The expandable portion 14 can be contracted by discharging a fluid from the balloon 10. In FIG. 1, the distal fixing portion 12 of the balloon 10 is fixed to the distal end of the inner tube 3 of the shaft 2, and the proximal fixing portion 13 of the balloon 10 is fixed to the distal end of the outer tube 4 of the shaft 2. The distal fixing portion 12 and the proximal fixing portion 13 of the balloon 10 can be fixed to the shaft 2 by a method such as welding or bonding with an adhesive.

[0036] In another embodiment not shown, the shaft 2 may have a multi-lumen structure having multiple lumens. The multi-lumen structure is a structure having multiple lumens arranged in the longitudinal direction inside one shaft and not overlapping with each other. The shaft 2 may have a first lumen extending in the longitudinal direction of the shaft 2, and a first side hole formed in the side wall of the shaft 2 at a position inside the balloon 10 and communicating with the first lumen. In this case, the fluid supplier 52 can be connected to the proximal side of the first lumen.

[0037] The balloon 10 can be manufactured by molding a resin. For example, the balloon 10 can be manufactured by placing an extruded resin tube in a mold and performing biaxial stretch blow molding. The balloon 10 can be formed into any shape by changing the shape of the mold. The balloon 10 can be manufactured by molding methods other than biaxial stretch blow molding, such as dip molding, injection molding, and compression molding.

[0038] Examples of resins constituting the balloon 10 include polyamide resins, polyester resins, polyurethane resins, polyolefin resins, vinyl chloride resins, silicone resins, natural rubber, synthetic rubber, and the like. These may be used alone or in combination of two or more. Among them, polyamide resins, polyester resins, and polyurethane resins are preferably used. From the viewpoint of thinning and flexibility of the balloon 10, elastomer resins can be used.

[0039] The membrane thickness of the balloon 10 before expansion can be, for example, 10 μm or more, 30 μm or more, or 50 μm or more, and is also permissible to be 150 μm or less, 120 μm or less, or 100 μm or less.

[0040] Examples of the fluid to be supplied to the inside of the balloon 10 include liquids such as physiological saline, contrast medium, or a mixture thereof, and gases such as air, nitrogen, and carbon dioxide gas.

[0041] The shape of the expandable portion 14 of the balloon 10 is not particularly limited, but may be a sphere, an oval sphere, a cylinder, a cone, a frustum, or a combination of these shapes.

[0042] The insulating material 20 is provided to hold the cauterizing electrode 25 and the two or more impedance measuring electrodes 30 on the balloon 10, and is a material that does not easily conduct electricity. The insulating material 20 is preferably flexible, so that it can follow the deformation of the balloon 10. Moreover, the insulating material 20 may have elasticity in order to maintain its shape.

[0043] The insulating material 20 is disposed on the outer surface 11 of the balloon 10. In particular, the insulating material 20 is preferably fixed to the outer surface 11 of the balloon 10, and more preferably fixed to the outer surface 11 of the expandable portion 14 of the balloon 10. The insulating material 20 may be directly or indirectly bonded to the outer surface 11 of the balloon 10. The insulating material 20 can be fixed to the outer surface 11 of the balloon 10 by a method such as welding or bonding with an adhesive.

[0044] The insulating material 20 may be disposed on only a part of the balloon 10, and may not be disposed over the entire outer surface 11 of the balloon 10. Also, the insulating material 20 may be fixed to only a part of the balloon 10, and may not be fixed over the entire outer surface 11 of the balloon 10. If the insulating material 20 is provided over a wide area of ​​the outer surface 11 of the balloon 10, the degree of deformation of the balloon 10 will be restricted by the flexibility of the insulating material 20. By providing the insulating material 20 partially on the balloon 10, the flexibility of the balloon 10 is ensured. The insulating material 20 may be a part of the membrane of the balloon 10. When the balloon 10 is made of an insulating material, the insulating material may be the balloon itself. The insulating material 20 may be a coating or print on the outer surface 11 of the balloon 10.

[0045] FIG. 2 shows a side view (partial cross-sectional view) of a modified example of the balloon catheter 1 shown in FIG. 1. As shown in FIG. 1, only one insulating material 20 may be provided on the balloon 10. On the other hand, as shown in FIG. 2, a plurality of insulating materials 20 may be provided on the balloon 10. As shown in FIG. 2, a plurality of insulating materials 20 may be arranged at different positions in the circumferential direction of the shaft 2. Although not shown, a plurality of insulating materials 20 may be arranged at different positions in the longitudinal direction of the shaft 2. A plurality of insulating materials 20 may be arranged at different positions in the longitudinal direction and circumferential direction of the shaft 2. By arranging a plurality of insulating materials 20, the cauterizing electrodes 25 can be arranged at various positions on the balloon 10 while ensuring the flexibility of the balloon 10.

[0046] Although the thicknesses of the insulating materials 20 may be different from each other, it is preferable that they are the same. This makes it easier to adjust the thicknesses of the cauterizing electrodes 25 arranged on the insulating materials 20 to the same thickness, and makes it easier to bring the cauterizing electrodes 25 into contact with the biological tissue to the same degree.

[0047] The insulating material 20 is preferably disposed at a position including the portion of the balloon 10 where the outer diameter is maximum when expanded. This makes it easier to dispose the cauterizing electrode 25 at the portion of the balloon 10 where the outer diameter is maximum when expanded, and makes it easier to bring the cauterizing electrode 25 into contact with biological tissue. The insulating material 20 may be disposed at a portion of the balloon 10 that faces the distal side of the balloon catheter 1 when expanded. This makes it possible to orient the cauterizing electrode 25 in the direction of travel of the balloon catheter 1, and makes it easier to bring the cauterizing electrode 25 into contact with biological tissue.

[0048] The insulating material 20 is preferably made of a resin. This ensures the electrical insulation of the insulating material 20 and makes it easier to fix the insulating material 20 to the balloon 10. Examples of the resin that constitutes the insulating material 20 include polyimide resin, polyamide resin, polyolefin resin, polyester resin, polycarbonate resin, and epoxy resin.

[0049] The shape of the insulating material 20 is not particularly limited, and may be a circle, an oval, a polygon, or a combination of these. In particular, it is preferable that the insulating material 20 has a long shape. This makes it easier to hold the cauterizing electrode 25 and the impedance measuring electrode 30 on the balloon 10 while ensuring the flexibility of the balloon 10. When multiple insulating materials 20 are provided on the balloon 10, the shapes of the multiple insulating materials 20 may be the same or different from each other.

[0050] 2, the insulating material 20 is a flexible base material 21 having a first surface 23 and a second surface 24 opposite to the first surface 23, and it is preferable that the first surface 23 faces the outside of the balloon 10 and the cauterizing electrode 25 is disposed on the second surface 24 side of the flexible base material 21. The flexibility of the insulating material 20 allows it to follow the deformation of the balloon 10. By disposing the cauterizing electrode 25 on the flexible base material 21 in this manner, it becomes easier to dispose the cauterizing electrode 25 on the balloon 10.

[0051] An example of the long insulating material 20 is a band-shaped flexible base material 21. The band-shaped flexible base material 21 has a longitudinal direction, a thickness direction (direction from the first surface 23 to the second surface 24), and a width direction perpendicular to both the longitudinal direction and the thickness direction.

[0052] A resin film or a resin sheet can be used as the flexible substrate 21. The flexible substrate 21 may be composed of a single layer or multiple layers.

[0053] The thickness of the flexible substrate 21 (i.e., film thickness or sheet thickness) is preferably 0.005 mm or more, 0.01 mm or more, or 0.02 mm or more. This allows the strength of the flexible substrate 21 to be secured even if the flexible substrate 21 is deformed. The thickness of the flexible substrate 21 is preferably 0.05 mm or less, 0.04 mm or less, or 0.03 mm or less. By limiting the thickness in this way, the profile of the balloon 10 when deflated can be made small.

[0054] The flexible substrate 21 may be thinner than the cauterizing electrode 25, but is preferably thicker than the cauterizing electrode 25. The flexible substrate 21 may be thinner than the impedance measuring electrode 30, but is preferably thicker. By forming the flexible substrate 21 to be thicker than these electrodes, it becomes easier to hold these electrodes on the balloon 10. The flexible substrate 21 may be thicker or thinner than the film thickness of the balloon 10 before expansion.

[0055] The width of the strip-shaped flexible base material 21 can be, for example, 1 mm or more, 3 mm or more, or 5 mm or more, or can be 10 mm or less, 8 mm or less.

[0056] The cauterizing electrode 25 is disposed on the insulating material 20 and is an electrode through which a high-frequency current is passed to cauterize biological tissue. More specifically, the cauterizing electrode 25 is fixed to the outer surface of the insulating material 20. The cauterizing electrode 25 is exposed on the surface of the balloon 10 so as to be able to come into contact with biological tissue.

[0057] The cauterizing electrode 25 may be used not only for cauterizing biological tissue but also for measuring the bioelectric potential. The bioelectric potential can be obtained, for example, by measuring the potential difference between the cauterizing electrode 25 and a reference electrode preferably provided in the balloon catheter 1. As the reference electrode, an electrode provided on the shaft 2 distal or proximal to the balloon 10, or a body surface electrode attached to the surface of the patient's body can be used.

[0058] A thin film of metal oxide or metal can be used as the cauterization electrode 25. This allows the cauterization electrode 25 to easily follow the deformation of the balloon 10.

[0059] The method of disposing the cauterizing electrode 25 on the insulating material 20 includes a method of providing a thin film on the insulating material 20 (preferably on the second surface 24 of the insulating material 20). The thin film can be formed by etching, vacuum deposition, sputtering, ion plating, plating, or coating.

[0060] When the cauterizing electrode 25 is in the form of a thin film, the thickness of the cauterizing electrode 25 may be, for example, 100 nm or more, 500 nm or more, or 1000 nm or more, and is also permissible to be 100 μm or less, 50 μm or less, or 30 μm or less.

[0061] The material constituting the cauterization electrode 25 only needs to be conductive, and may be, for example, a metal or a mixture containing a resin and a metal. Among them, it is preferable to use a conductive resin or a metal such as gold, silver, copper, platinum, a platinum-iridium alloy, stainless steel, or tungsten.

[0062] The shape of the cauterizing electrode 25 is not particularly limited, and may be a circle, an oval, a polygon, or a combination thereof. Figures 1 and 2 show an example in which the cauterizing electrode 25 is square.

[0063] Although not shown, the cauterizing electrode 25 is connected to a first conductor, which extends to the proximal side and is connected to the high-frequency generator 53. The cauterizing electrode 25 can be heated by applying a high-frequency electric field. As with the cauterizing electrode 25, the first conductor is preferably fixed to the insulating material 20. The high-frequency generator 53 may include a power supply circuit and a high-frequency oscillation circuit. Although not shown, an impedance matching circuit may be provided between the cauterizing electrode 25 and the high-frequency generator 53.

[0064] The first conductive wire is connected to a measuring unit 54 of the balloon catheter system 100, which will be described later. This allows a signal of the biopotential measured by the ablation electrode 25 to be sent to the measuring unit 54. The measuring unit 54 can measure the impedance between one of the two or more impedance measuring electrodes 30 and the ablation electrode 25.

[0065] The first conductive wire may be a conductive linear body such as a conductive wire, or may be a conductive material printed on the insulating material 20. The first conductive wire may be disposed on the inner surface of the balloon 10, between the balloon 10 and the insulating material 20, or on the outer surface of the insulating material 20. The first conductive wire may be a thin film of metal oxide or metal. For a method of forming a thin film of the first conductive wire on the insulating material 20, refer to the description of the method of forming a thin film of the cauterization electrode 25 on the insulating material 20. The first conductive wire may be disposed on the outer surface of the shaft 2, on the inner surface, in the thickened portion between the outer and inner surfaces, or within the lumen.

[0066] As shown in FIG. 1, only one ablation electrode 25 may be provided on the balloon 10, or as shown in FIG. 2, a plurality of ablation electrodes 25 may be provided on the balloon 10. The plurality of ablation electrodes 25 may be disposed at different positions in the longitudinal direction of the shaft 2. The plurality of ablation electrodes 25 may be disposed at different positions in the circumferential direction of the shaft 2, as shown in FIG. 2. The plurality of ablation electrodes 25 may be disposed at different positions in the longitudinal direction and circumferential direction of the shaft 2. By disposing the ablation electrodes 25 in this manner, it becomes easier to cauterize a wide range of biological tissue all at once.

[0067] The thicknesses of the plurality of cauterizing electrodes 25 may be different from each other, but are preferably the same. This makes it easier to grasp the contact state between the cauterizing electrodes 25 and the biological tissue. The materials constituting the plurality of cauterizing electrodes 25 may be different from each other, but are preferably the same from the viewpoint of making it easier to control the high-frequency current flowing through the cauterizing electrodes 25.

[0068] The shapes of the multiple cauterizing electrodes 25 may be different from one another, but from the viewpoint of making it easier for the multiple cauterizing electrodes 25 to come into uniform contact with the living tissue, it is preferable that the shapes are the same.

[0069] 1 and 2, one cauterizing electrode 25 may be provided on one insulating material 20. Although not shown, a plurality of cauterizing electrodes 25 may be provided on one insulating material 20.

[0070] The cauterizing electrode 25 can be disposed, for example, at a portion of the balloon 10 that has a maximum outer diameter when expanded, or at a portion that faces the distal side of the balloon catheter 1 when expanded. This makes it easier to bring the cauterizing electrode 25 into contact with biological tissue.

[0071] The impedance measuring electrode 30 is an electrode provided for measuring the impedance of biological tissue. The balloon catheter 1 has a surface area smaller than that of the cauterizing electrode 25, is arranged around the cauterizing electrode 25 on the insulating material 20, and has two or more impedance measuring electrodes 30 for measuring impedance. A straight line 38 connecting at least two of the two or more impedance measuring electrodes 30 crosses the cauterizing electrode 25. In FIG. 1, a first impedance measuring electrode 31 and a second impedance measuring electrode 32 are provided as the two or more impedance measuring electrodes 30, and a straight line 38 connecting the first impedance measuring electrode 31 and the second impedance measuring electrode 32 crosses the cauterizing electrode 25. The straight line 38 on the drawing is a virtual line. In the balloon catheter 1, two or more impedance measuring electrodes 30 are arranged around the cauterizing electrode 25. Therefore, by measuring the impedance of each impedance measuring electrode 30, the contact state between each impedance measuring electrode 30 and biological tissue can be detected. From the detection result of the contact state between each impedance measuring electrode 30 and the biological tissue, it is possible to grasp the specific contact state between the cauterizing electrode 25 and the biological tissue, for example, which part of the cauterizing electrode 25 is in contact. Therefore, since the balloon catheter 1 can be placed at an appropriate position in the living body prior to cauterization, cauterization can be performed efficiently and the burden on the patient and the surgeon can be reduced.

[0072] The biopotential can be measured using the impedance measuring electrode 30. The biopotential can be obtained by measuring the potential difference between the reference electrode, which is preferably provided on the balloon catheter 1, and the impedance measuring electrode 30. The obtained biopotential can be used to measure impedance. For measurement, it is necessary that each of the impedance measuring electrodes 30 is insulated.

[0073] Hereinafter, the impedance measuring electrode 30 may be simply referred to as the measuring electrode 30, the first impedance measuring electrode 31 as the measuring electrode 31, and the second impedance measuring electrode 32 as the measuring electrode 32. In the following description, these terms may be abbreviated in the same manner.

[0074] In FIG. 1, the straight line 38 is indicated by a dashed line. The two measurement electrodes 30 that define the straight line 38 are two measurement electrodes 30 arbitrarily selected from the measurement electrodes 30 that are arranged around the cauterizing electrode 25. When three or more measurement electrodes 30 are arranged around the cauterizing electrode 25, the two measurement electrodes 30 that define the straight line 38 may be adjacent to each other in the circumferential direction of the cauterizing electrode 25, or another measurement electrode 30 that does not define the straight line 38 may be arranged between the two measurement electrodes 30 that define the straight line 38 in the circumferential direction of the cauterizing electrode 25. The straight line 38 is a straight line that connects the outer edge of one measurement electrode 30 and the outer edge of the other measurement electrode 30 at the shortest distance. The straight line 38 is omitted in FIG. 2 and FIG. 4 to FIG. 9 described later.

[0075] A thin film of a metal oxide or metal can be used as the measurement electrode 30. This allows the measurement electrode 30 to easily follow the deformation of the balloon 10.

[0076] The method of arranging the measurement electrode 30 on the insulating material 20, the thickness, the constituent material, and the shape can be referred to in these descriptions of the cauterizing electrode 25. In order to facilitate the formation of the cauterizing electrode 25 and the measurement electrode 30, it is preferable that at least one of the method of arranging the measurement electrode 30 on the insulating material 20, the thickness, the constituent material, and the shape of the cauterizing electrode 25 and the measurement electrode 30 be the same.

[0077] Although not shown, the measurement electrode 30 is connected to a second conductor, which extends to the proximal side and is connected to the measurement unit 54. This allows a signal of the biopotential measured by the measurement electrode 30 to be sent to the measurement unit 54. As will be described later, the measurement unit 54 can measure the impedance between the measurement electrode 30 and the cauterizing electrode 25, between the two measurement electrodes 30, or between the measurement electrode 30 and the return electrode 29.

[0078] The second conductor may be a conductive line such as a conductive wire, or may be a conductive material printed on the insulating material 20. The second conductor may be disposed on the inner surface of the balloon 10, between the balloon 10 and the insulating material 20, or on the outer surface of the insulating material 20. Like the first conductor, the second conductor may be a thin film of metal oxide or metal. For a method of forming a thin film of the second conductor on the insulating material 20, refer to the description of the method of forming a thin film of the cauterization electrode 25 on the insulating material 20.

[0079] Although the position where the measurement electrode 30 is provided is not particularly limited, the measurement electrode 30 is preferably disposed at a position overlapping an enlarged area formed by enlarging the shape of the cauterizing electrode 25 by 1.5 times, and more preferably, the entire measurement electrode 30 is disposed within the enlarged area. Since the measurement electrode 30 is disposed near the cauterizing electrode 25, it becomes easier to grasp the contact state between the cauterizing electrode 25 and the biological tissue.

[0080] The measurement electrode 30 is preferably disposed at a distance from the ablation electrode 25. As a result, the measurement electrode 30 and the ablation electrode 25 are preferably insulated from each other. This allows the impedance between the measurement electrode 30 and the ablation electrode 25 to be measured. All of the two or more measurement electrodes 30 are preferably insulated from the ablation electrode 25.

[0081] The shortest distance between one of the two or more impedance measurement electrodes 30 and the cauterizing electrode 25 is preferably 1 / 5 or less of the shortest distance between two of the two or more impedance measurement electrodes 30, more preferably 1 / 8 or less of the shortest distance between the two measurement electrodes 30, and even more preferably 1 / 10 or less of the shortest distance between the two measurement electrodes 30. Since the measurement electrode 30 is disposed near the cauterizing electrode 25, it is easy to grasp the contact state of the cauterizing electrode 25 with the biological tissue from the measurement electrode 30. It is preferable that all of the two or more impedance measurement electrodes 30 are disposed so as to satisfy the above numerical range.

[0082] The shortest distance between one of the two or more measurement electrodes 30 and the cauterizing electrode 25 is preferably 1 / 30 or more of the shortest distance between two of the two or more measurement electrodes 30, more preferably 1 / 25 or more of the shortest distance between the two measurement electrodes 30, and even more preferably 1 / 20 or more of the shortest distance between the two measurement electrodes 30. This separates the measurement electrode 30 and the cauterizing electrode 25, so that they are insulated from each other. It is preferable that all of the two or more impedance measurement electrodes 30 are arranged so as to satisfy the above numerical range.

[0083] It is preferable that there is no impedance measurement electrode 30 that is entirely surrounded by the ablation electrode 25. If the measurement electrode 30 is entirely surrounded by the ablation electrode 25, it is difficult for the measurement electrode 30 to grasp which specific part of the ablation electrode 25 is in contact with the biological tissue. It is preferable that the measurement electrode 30 arranged on one insulating material 20 is not entirely surrounded by the ablation electrode 25 arranged on the insulating material 20. It is also preferable that all of the two or more measurement electrodes 30 arranged on one insulating material 20 are not entirely surrounded by the ablation electrode 25 arranged on the insulating material 20.

[0084] It is preferable that an insulating material 20 is provided around at least one of the two or more impedance measuring electrodes 30, and the at least one measuring electrode 30 is insulated from the ablation electrode 25. This allows the impedance between the measuring electrode 30 and the ablation electrode 25 to be measured. Note that a part of the insulating material 20 may be sandwiched between the measuring electrode 30 and the ablation electrode 25. FIG. 3 is an enlarged cross-sectional view showing a modified example of the balloon catheter 1 shown in FIG. 1. In FIG. 3, the insulating material 20 is provided around each of the two measuring electrodes 30, and the two measuring electrodes 30 are insulated from the ablation electrode 25.

[0085] The number of measurement electrodes 30 provided on one balloon 10 is not particularly limited as long as it is 2 or more, but from the viewpoint of making it easier to grasp the contact state between the cauterizing electrode 25 and the biological tissue, it is preferably 3 or more, more preferably 4 or more, and even more preferably 5 or more. Since the space around the cauterizing electrode 25 is limited, the number of measurement electrodes 30 provided on one balloon 10 is preferably 20 or less, more preferably 15 or less, and even more preferably 10 or less.

[0086] The surface area of ​​one measurement electrode 30 may be smaller than that of one cauterizing electrode 25. It is preferable that the total area of ​​all measurement electrodes 30 surrounding a cauterizing electrode 25 is smaller than the area of ​​the cauterizing electrode 25.

[0087] In order to easily detect the contact state between the measurement electrode 30 and the biological tissue, the area of ​​one measurement electrode 30 is preferably at least 1 / 100 of the area of ​​one cauterization electrode 25, more preferably at least 1 / 50, and even more preferably at least 1 / 20.

[0088] In order to make it easier to position the measurement electrodes 30 around the cauterizing electrodes 25, the area of ​​one measurement electrode 30 is preferably 1 / 4 or less than the area of ​​one cauterizing electrode 25, more preferably 1 / 5 or less, and even more preferably 1 / 8 or less.

[0089] The two or more measurement electrodes 30 are arranged at a distance from each other, so that the two or more measurement electrodes 30 are insulated from each other, thereby making it possible to measure the impedance between the two measurement electrodes 30.

[0090] The two or more measurement electrodes 30 may be arranged in line symmetry with respect to a line passing through the center of gravity of the cauterizing electrode 25. In addition, the two or more measurement electrodes 30 may be arranged in rotational symmetry with the center of gravity of the cauterizing electrode 25 as the center of rotation.

[0091] An example of the arrangement of the ablation electrode 25 and the measurement electrodes 30 will be described. FIG. 4 is a schematic diagram showing an example of the arrangement of the ablation electrode 25 and two or more impedance measurement electrodes 30 according to one embodiment of the present invention. Three or more measurement electrodes 30 may be arranged around the ablation electrode 25. In this case, the ablation electrode 25 has an overlapping area 45 overlapping with a virtual area 40 formed by three or more measurement electrodes 30, and it is preferable that the area of ​​the overlapping area 45 occupies 70% or more of the area of ​​the ablation electrode 25. However, the virtual area 40 is formed by defining the most proximal position located closest to the ablation electrode 25 for each of the three or more measurement electrodes 30 arranged around the ablation electrode 25, and connecting the most proximal positions of the measurement electrodes 30 adjacent to each other in the circumferential direction of the ablation electrode 25 with a straight line 39. By arranging the measurement electrodes 30 so that the overlapping area 45 is formed in this way, it becomes easier to grasp the contact state between the ablation electrode 25 and the living tissue. The straight line 39 may overlap at least a part of the straight line 38.

[0092] In FIG. 4, the first measurement electrode 31, the second measurement electrode 32, and the third measurement electrode 33 are arranged around the cauterizing electrode 25 as three or more measurement electrodes 30. The most proximal position 31a of the first measurement electrode 31, the most proximal position 32a of the second measurement electrode 32, and the most proximal position 33a of the third measurement electrode 33 are respectively defined. The most proximal positions 31a, 32a, and 33a of the three measurement electrodes 30 are connected by a straight line 39 to form a virtual region 40. In FIG. 4, the straight line 39 is shown by a dashed line, and the overlapping region 45 is shown by hatching. The virtual region 40 is a closed region on the balloon 10. The first measurement electrode 31, the second measurement electrode 32, and the third measurement electrode 33 are arranged side by side in the circumferential direction of the cauterizing electrode 25. In addition, when there are multiple most proximal positions located closest to the cauterizing electrode 25 for the measurement electrodes 30, the virtual region 40 can be formed by selecting any position from among them as the most proximal position. In this case, the most proximal position can be determined so that the virtual region 40 is the widest. When a plurality of virtual regions 40 are formed as described below, the most proximal position of the measurement electrode 30 used to form one virtual region 40 may be the same as or different from the most proximal position of the measurement electrode 30 used to form another virtual region 40.

[0093] It is more preferable that the area of ​​the overlapping region 45 occupies 73% or more, even more preferable that it occupies 75% or more, and even more preferable that it occupies 80% or more of the area of ​​the cauterizing electrode 25. By arranging the measurement electrode 30 in this manner, it becomes easier to grasp the contact state between the cauterizing electrode 25 and the biological tissue.

[0094] The area of ​​the overlapping region 45 may occupy 100%, 95% or less, or 90% or less of the area of ​​the cauterizing electrode 25. Arranging the measurement electrode 30 in this manner also makes it easier to grasp the contact state between the cauterizing electrode 25 and the biological tissue.

[0095] 5 to 7 are schematic diagrams showing other examples of the arrangement of the cauterizing electrode 25 and two or more measurement electrodes 30 shown in FIG. 4. In FIG. 5 to FIG. 6, the first measurement electrode 31, the second measurement electrode 32, the third measurement electrode 33, and the fourth measurement electrode 34 are arranged around the cauterizing electrode 25. As shown in FIG. 1 to FIG. 2, the cauterizing electrode 25 and the measurement electrode 30 may have the same shape but different sizes, and as shown in FIG. 4 to FIG. 7, the cauterizing electrode 25 and the measurement electrode 30 may have different shapes. In FIG. 1 to FIG. 2 and FIG. 4, the cauterizing electrode 25 is square-shaped, and in FIG. 5, the cauterizing electrode 25 is circular. By using such a shape, the cauterizing electrode 25 can be easily formed.

[0096] In FIG. 4, one virtual region 40 is formed by three measurement electrodes 30. On the other hand, in FIGS. 5 to 6, one virtual region 40 is formed by four measurement electrodes 30. The number of measurement electrodes 30 forming one virtual region 40 may be three or more, may be four or more, may be five or more, and may be, for example, twenty or less, fifteen or less, or ten or less. The virtual region 40 may be formed by all the measurement electrodes 30 arranged around the cauterizing electrode 25, or may be formed by any number of measurement electrodes 30.

[0097] Although not shown in the figures, one virtual region 40 may be formed by using any three of the four measurement electrodes 30 arranged in the circumferential direction of the cauterizing electrode 25 in Figs. 5 to 6, and multiple virtual regions 40 may be formed for one cauterizing electrode 25. By defining multiple virtual regions 40 in this way, multiple overlapping regions 45 can be provided for one cauterizing electrode 25. Therefore, the contact state between the cauterizing electrode 25 and the biological tissue can be grasped for each virtually divided region. For example, it becomes easy to grasp the detailed contact state, such as whether the entire cauterizing electrode 25 is in contact with the biological tissue or only a part of the cauterizing electrode 25 is in contact with the biological tissue.

[0098] The cauterizing electrode 25 may have a shape in which a part of a circle, an ellipse, or a polygon is cut out. In detail, the cauterizing electrode 25 can have a shape in which a part of the circumference of a circle, an ellipse, or a polygon is cut out. For example, in FIG. 6, the cauterizing electrode 25 has a cross shape in which the four corners of a square are cut out. By making the cauterizing electrode 25 have such a shape, the measurement electrode 30 can be placed in the cut-out portion. As a result, the measurement electrode 30 can be placed near the cauterizing electrode 25.

[0099] A slit 26 may be formed in a part of the cauterizing electrode 25, and the measurement electrode 30 may be disposed in the slit 26. In this case, the measurement electrode 30 may be disposed at a position including the center of gravity of the cauterizing electrode 25. FIG. 7 shows a substantially square cauterizing electrode 25 having a slit 26 extending from one side toward the center of gravity. It can also be said that the cauterizing electrode 25 is formed in a substantially U-shape. The slit width may be constant or may change midway. In FIG. 7, the slit width is wider in a portion close to the center of gravity of the cauterizing electrode 25, so that the measurement electrode 30 (the fifth impedance measurement electrode 35) can be easily disposed at a position including the center of gravity of the cauterizing electrode 25.

[0100] 7, five measurement electrodes 30 (a first measurement electrode 31, a second measurement electrode 32, a third measurement electrode 33, a fourth measurement electrode 34, and a fifth measurement electrode 35) are arranged adjacent to each other in the circumferential direction of the ablation electrode 25. A first virtual area 40A is formed by connecting the most proximal positions of the first measurement electrode 31, the second measurement electrode 32, and the fifth measurement electrode 35 with a straight line 39. The most proximal position of the fifth measurement electrode 35 with respect to the first measurement electrode 31 is different from the most proximal position with respect to the second measurement electrode 32, but multiple most proximal positions may be set for one measurement electrode 30. Similarly, a second virtual region 40B is formed by the second measurement electrode 32, the third measurement electrode 33, and the fifth measurement electrode 35, a third virtual region 40C is formed by the third measurement electrode 33, the fourth measurement electrode 34, and the fifth measurement electrode 35, and a fourth virtual region 40D is formed by the first measurement electrode 31, the fifth measurement electrode 35, and the fourth measurement electrode 34. In FIG. 7, since the slit 26 is formed in the cauterization electrode 25, five overlapping regions 45 are formed. In this way, the number of virtual regions 40 and the number of overlapping regions 45 may be different.

[0101] 8 and 9 are schematic diagrams showing other modified examples of the arrangement of the ablation electrode 25 and the two or more measurement electrodes 30 of the balloon catheter 1 shown in Fig. 4. Six or more measurement electrodes 30 may be arranged around the ablation electrode 25. In Fig. 8, the two or more measurement electrodes 30 include three or more measurement electrodes 30, and the three or more measurement electrodes 30 include at least a first impedance measurement electrode 31, a second impedance measurement electrode 32, a third impedance measurement electrode 33, a fourth impedance measurement electrode 34, a fifth impedance measurement electrode 35, and a sixth impedance measurement electrode 36. The cauterizing electrode 25 has a first overlapping region 45A overlapping with a first virtual region 40A formed by at least the first impedance measuring electrode 31, the second impedance measuring electrode 32, the third impedance measuring electrode 33, and the fourth impedance measuring electrode 34, and a second overlapping region 45B overlapping with a second virtual region 40B formed by at least the third impedance measuring electrode 33, the fourth impedance measuring electrode 34, the fifth impedance measuring electrode 35, and the sixth impedance measuring electrode 36. At this time, it is preferable that the sum of the areas of the first overlapping region 45A and the second overlapping region 45B occupies 70% or more of the area of ​​the cauterizing electrode 25. By defining a plurality of virtual regions 40 in this way, it is possible to grasp the contact state between the cauterizing electrode 25 and the living tissue for each virtually divided region. In addition, by setting the sum of the areas of the first overlapping region 45A and the second overlapping region 45B as described above, it becomes easier to grasp the contact state between the cauterizing electrode 25 and the living tissue.

[0102] It is more preferable that the sum of the areas of the multiple overlapping regions 45 account for 75% or more of the area of ​​the cauterization electrode 25, and even more preferable that it account for 80% or more, and it may also account for 100%, 98% or less, or 95% or less.

[0103] The first overlapping region 45A and the second overlapping region 45B may be arranged so as to overlap each other as shown in Fig. 8, or may be arranged separately from each other, although not shown. When multiple overlapping regions 45 overlap, care must be taken not to count the areas of the multiple overlapping regions 45 in the calculation of the sum of the areas of the multiple overlapping regions 45. For example, in Fig. 8, the sum of the area of ​​the first overlapping region 45A and the area of ​​the second overlapping region 45B excluding the part that overlaps with the first overlapping region 45A is the sum of the areas of the multiple overlapping regions 45.

[0104] As shown in FIG. 9, the cauterizing electrode 25 may have a central portion 27 extending in a first direction x, and a plurality of branch portions 28 extending from the central portion 27 in a second direction y perpendicular to the first direction x and arranged at a predetermined interval. The cauterizing electrode 25 having such a shape is highly flexible, so that the flexibility of the balloon 10 on which the cauterizing electrode 25 is provided can be maintained. In addition, it is easy to arrange the measurement electrode 30 and the through-hole for perfusion between the adjacent branch portions 28. Note that the first direction x is preferably the same as the direction from the distal end to the proximal end of the balloon 10. Note that in FIG. 9, the most proximal positions of each measurement electrode 30 forming the virtual region 40 (40A, 40B) are omitted. The first direction x of the cauterizing electrode 25 having the central portion 27 and the plurality of branch portions 28 is preferably arranged so as to be parallel to the direction from the distal end to the proximal end of the balloon 10.

[0105] Although not shown, a third overlapping region that partially overlaps at least one of the first overlapping region 45A and the second overlapping region 45B may be provided. For example, in the case of Figs. 8 to 9, a fifth virtual region is formed by connecting the most proximal positions of the first measurement electrode 31, the second measurement electrode 32, the third measurement electrode 33, the fourth measurement electrode 34, the fifth measurement electrode 35, and the sixth measurement electrode 36 with a straight line 39, and the cauterizing electrode 25 may have a third overlapping region that overlaps with the fifth virtual region. The fifth virtual region may be formed by all the measurement electrodes 30 arranged around the cauterizing electrode 25. By providing the fifth virtual region in this way, it becomes easier to grasp the contact state between the cauterizing electrode 25 and the living tissue.

[0106] 2. Balloon Catheter System The present invention also provides a balloon catheter system 100 including the balloon catheter 1 described above. Hereinafter, the balloon catheter system may be simply referred to as a system. FIG. 10 is a block diagram of a balloon catheter system 100 including the balloon catheter 1 shown in FIG. 1. As shown in FIG. 1 and FIG. 10, the system 100 preferably includes the balloon catheter 1, a measurement unit 54 that measures the impedance between one of the two or more impedance measurement electrodes 30 and the cauterization electrode 25 (hereinafter, sometimes referred to as a "first impedance"), and a control unit 55 that is connected to the measurement unit 54 and uses the measurement result of the first impedance to determine whether or not the one of the two or more impedance measurement electrodes 30 is in contact with a living tissue. From the detection result of the contact state between each measurement electrode 30 and the living tissue, the specific contact state between the cauterization electrode 25 and the living tissue can be grasped. Therefore, since the balloon catheter 1 can be placed at an appropriate position in the living body prior to cauterization, it is possible to efficiently perform cauterization and reduce the burden on the patient and the surgeon. In detail, when both the measurement electrode 30 and the ablation electrode 25 are in contact with the biological tissue, the portion between the measurement electrode 30 and the ablation electrode 25 is also likely to be in contact with the biological tissue, for example, the pulmonary vein wall. At this time, a current flows from the measurement electrode 30 to the ablation electrode 25 through the biological tissue. On the other hand, when at least one of the measurement electrode 30 and the ablation electrode 25 is not in contact with the biological tissue, the portion between the measurement electrode 30 and the ablation electrode 25 is likely to be in contact with the blood. At this time, a current flows from the measurement electrode 30 to the ablation electrode 25 through the blood. Since the electrical resistivity of blood is higher than that of biological tissue, when the measurement electrode 30 is in contact with the biological tissue, the impedance is lower than when it is not in contact. In this way, it is possible to determine whether the measurement electrode 30 is in contact with the biological tissue from the measurement result of the first impedance.

[0107] In the system 100 of Fig. 1, the contact state between the cauterizing electrode 25 and the living tissue can be determined by a method as shown in Fig. 11. Fig. 11 is a flowchart showing a method for determining the contact state between the cauterizing electrode 25 and the living tissue by the system 100 shown in Fig. 10.

[0108] The impedance (first impedance) between one of the two or more measurement electrodes 30 and the cauterizing electrode 25 is measured (step S1).

[0109] When the measurement of the impedance of all the measurement electrodes 30 is completed (Yes in step S2), it is determined whether or not all the measurement electrodes 30 are in contact with the biological tissue (step S3).

[0110] If the measurement of the impedance of all the measurement electrodes 30 has not been completed (No in step S2), the process returns to step S1, and the impedance between another measurement electrode 30 and the cauterizing electrode 25 is measured.

[0111] 11, when all the measurement electrodes 30 are in contact with the biological tissue (Yes in step S4), it is determined that the cauterizing electrode 25 is in contact with the biological tissue (step S5). When any one of the measurement electrodes 30 is not in contact with the biological tissue (No in step S4), it is determined that the cauterizing electrode 25 is not in contact with the biological tissue (step S6). However, the method of determining the contact state between the cauterizing electrode 25 and the biological tissue based on the contact state between the measurement electrodes 30 and the biological tissue is not limited to this method, and a determination method described later may also be adopted.

[0112] Although not essential, after step S6, it is preferable to change the position of the cauterization electrode 25 in the living body by at least moving the balloon catheter 1 back and forth or rotating it (step S7). After that, it is preferable to return to step S1 and measure the impedance again.

[0113] The system 100 of FIG. 10 may include the balloon catheter 1, a measurement unit 54 that measures the impedance between two of the two or more impedance measurement electrodes 30 (hereinafter, sometimes referred to as the "second impedance"), and a control unit 55 that is connected to the measurement unit 54 and uses the impedance measurement result to determine whether one of the two or more impedance measurement electrodes is in contact with the biological tissue. By measuring the second impedance in this manner, the specific contact state between the cauterizing electrode 25 and the biological tissue can be grasped. This is because the contact state between the cauterizing electrode 25 and the biological tissue can be determined by determining the contact state of the measurement electrode 30 with the biological tissue. In this case, the flowchart of FIG. 11 can be applied by measuring the second impedance instead of the first impedance in the above step S1.

[0114] FIG. 12 is a block diagram showing a modified example of the system 100 shown in FIG. 10. As shown in FIG. 12, the system 100 may include a counter electrode 29 provided on the body surface of a patient and through which a high-frequency current is applied between the counter electrode 29 and the cauterizing electrode 25, a measuring unit 54 for measuring an impedance between one of the two or more impedance measuring electrodes 30 and the counter electrode 29 (hereinafter, sometimes referred to as a "third impedance"), and a control unit 55 connected to the measuring unit 54 for determining whether or not one of the two or more impedance measuring electrodes 30 is in contact with a living tissue by using the measurement result of the impedance. By measuring the third impedance in this way, the specific contact state between the cauterizing electrode 25 and the living tissue can be grasped. In this case, the flowchart of FIG. 11 can be applied by measuring the third impedance instead of the first impedance in the above step S1.

[0115] The return electrode 29 may be an electrode pad that can be attached to the body surface of the patient. The electrode pad may have, for example, a conductive layer and an adhesive gel layer or a solid gel layer disposed on the conductive layer. For a description of the material constituting the conductive layer of the return electrode 29, the description of the material constituting the cauterizing electrode 25 may be referred to.

[0116] The measuring unit 54 measures at least one of the first impedance, the second impedance, and the third impedance. The first impedance can be measured based on the biopotentials measured by the measurement electrode 30 and the cauterizing electrode 25 of the target when a predetermined magnitude of AC current is applied to the living body. The second impedance can be measured based on the biopotentials measured by the two measurement electrodes 30 of the target, and the third impedance can be measured based on the biopotentials measured by the measurement electrode 30 and the return electrode 29 of the target.

[0117] An impedance measuring device such as an LCR meter can be used as the measuring unit 54. The measuring unit 54 can include an amplifier that amplifies the biosignal, an analog-to-digital converter, a filter for removing noise, and the like.

[0118] Fig. 13 is a block diagram showing a modified example of the system 100 shown in Fig. 12. As shown in Fig. 13, in the balloon catheter system 100, a reference electrode 48 is provided on the surface of the shaft 2 at a position proximal to the balloon 10, and the measurement unit 54 preferably further measures the impedance between one of the two or more impedance measurement electrodes 30 and the reference electrode 48. By providing a reference electrode, it is possible to measure the biopotential at the reference electrode 48, i.e., the impedance of the blood. It is preferable that the measurement unit 43 measures the impedance between the measurement electrode 30 and the reference electrode 48 for all the measurement electrodes 30.

[0119] The reference electrode 48 may be, for example, in the form of a ring, a ring with a slit in it that has a C-shaped cross section, or a coil formed by winding a wire in a spiral shape. In such a case, the reference electrode 48 can be disposed on the shaft 2 by crimping the reference electrode 48 to the shaft 2.

[0120] The reference electrode 48 is preferably disposed on the outer surface of the shaft 2. By disposing the reference electrode in this manner, it becomes easier to measure the impedance of the blood.

[0121] For the material constituting the reference electrode 48, the description of the material constituting the cauterizing electrode 25 can be referred to. The material constituting the reference electrode 48 may be the same as the material constituting the cauterizing electrode 25, or may be different from the material constituting the cauterizing electrode 25.

[0122] As shown in Fig. 10 and Figs. 12-13, in order to determine whether the measurement electrode 30 is in contact with the biological tissue in step S2, the system 100 may have a processing unit 56 connected to the control unit 55 and comparing the impedance with a reference value. By comparing the impedance with the reference value, it is possible to determine whether the measurement electrode 30 is in contact with the biological tissue. The processing unit 56 may perform processing other than the comparison of the measured impedance with the reference value, such as a filter processing for noise removal.

[0123] When the system 100 has a processing unit 56 connected to the control unit 55 as shown in Figures 10, 12 and 13, the processing unit 56 performs at least one of the following: comparing the impedance between one of the two or more impedance measurement electrodes 30 and the cauterization electrode 25 with a first reference value; comparing the impedance between two of the two or more impedance measurement electrodes 30 with a second reference value; and comparing the impedance between one of the two or more impedance measurement electrodes 30 and the return electrode 29 with a third reference value. The control unit 55 may use the comparison result in the processing unit 56 to determine whether or not the impedance measurement electrode 30 is in contact with biological tissue.

[0124] When the system 100 of FIG. 10 has a processing unit 56, the processing unit 56 preferably compares the impedance (first impedance) between one measurement electrode 30 and the cauterizing electrode 25 with a first reference value, or compares the impedance (second impedance) between two measurement electrodes 30 with a second reference value. By comparing the reference values ​​in this manner, it is possible to determine whether the measurement electrode 30 is in contact with the biological tissue. If each impedance is equal to or less than the respective reference value, it is possible to determine that the one measurement electrode 30 is in contact with the biological tissue. If the impedance exceeds the reference value, it is possible to determine that the one measurement electrode 30 is not in contact with the biological tissue. A preset impedance of the biological tissue can be used as the reference value. The first and second reference values ​​may be the same or different from each other.

[0125] 12 includes a processing unit 56, the processing unit 56 preferably compares the impedance (third impedance) between one measurement electrode 30 and the return electrode 29 with a third reference value. If the third impedance is equal to or less than the third reference value, it can be determined that the measurement electrode 30 is in contact with a biological tissue. If the third impedance exceeds the third reference value, it can be determined that the measurement electrode 30 is not in contact with a biological tissue.

[0126] The first reference value, the second reference value, and the third reference value used in the processing unit 56 may be stored in advance in the system 100, or may be supplied to the system 100 by a recording medium or the like.

[0127] As shown in FIG. 10, FIG. 12 to FIG. 13, when the system 100 has a processing unit 56 connected to the control unit 55, the processing unit 56 performs at least one of the following: a comparison of the impedance between one of the two or more impedance measurement electrodes 30 and the cauterization electrode 25 before and after the expansion of the balloon 10; a comparison of the impedance between two of the two or more impedance measurement electrodes 30 before and after the expansion of the balloon 10; and a comparison of the impedance between one of the two or more impedance measurement electrodes 30 and the return electrode 29 before and after the expansion of the balloon 10. It is preferable that the control unit 55 uses the comparison result in the processing unit 56 to determine whether or not one of the two or more impedance measurement electrodes 30 is in contact with the biological tissue. Before the expansion of the balloon 10, the measurement electrode 30 is not in contact with the biological tissue. Therefore, the impedance measured before the expansion of the balloon 10 can be said to be the impedance of the blood. By comparing the impedance measured after the expansion of the balloon 10 with the impedance of the blood as a reference value, it is possible to determine the contact state between the measurement electrode 30 and the biological tissue.

[0128] It is preferable that the control unit 55 determines whether or not the cauterizing electrode 25 is in contact with the living tissue by using a determination result of a contact state between at least one of the two or more impedance measuring electrodes 30 and the living tissue. In detail, the control unit 55 can determine the contact state between each measuring electrode 30 and the living tissue by using at least one of the first, second, and third impedances, for example. The control unit 55 can determine the contact state between the cauterizing electrode 25 and the living tissue by using the following first to third determination methods. FIG. 14 is an example of a flowchart showing the second determination method, and FIG. 15 is an example of a flowchart showing the third determination method.

[0129] The first and second discrimination methods show an example in which three or more impedance measurement electrodes 30 are arranged around one ablation electrode 25 as shown in Fig. 4 to Fig. 9. The ablation electrode 25 has an overlapping region 45 that overlaps with a virtual region 40 formed by the three or more impedance measurement electrodes 30. The virtual region 40 is formed by defining the most proximal position located closest to the ablation electrode 25 for each of the three or more impedance measurement electrodes 30 arranged around the ablation electrode 25, and connecting the most proximal positions of the impedance measurement electrodes 30 adjacent to each other in the circumferential direction of the ablation electrode 25 with a straight line 39.

[0130] (First Discrimination Method) The control unit 55 may determine that the overlapping region 45 of the ablation electrode 25 has come into contact with the biological tissue when at least two impedance measurement electrodes 30 have come into contact with the biological tissue. This makes it possible to determine that at least a part of the ablation electrode 25 has come into contact with the biological tissue. Note that the first determination method can be applied to the flowchart of FIG. 14 by replacing all impedance measurement electrodes 30 in each step of the second determination method described later with at least two impedance measurement electrodes.

[0131] (Second Discrimination Method) As shown in FIG. 14, when all the impedance measuring electrodes 30 are in contact with the biological tissue (Yes in step S4), the control unit 55 preferably determines that the overlapping region 45 of the cauterizing electrode 25 is in contact with the biological tissue (step S8). This allows the control unit 55 to grasp that a certain region of the cauterizing electrode 25 is in contact with the biological tissue. As a result, the cauterization can be performed efficiently. When all the measuring electrodes 30 are not in contact with the biological tissue (No in step S4), the control unit 55 may determine that the overlapping region 45 of the cauterizing electrode 25 is not in contact with the biological tissue (step S9). Although not essential, after step S9, the control unit 55 preferably changes the position of the cauterizing electrode 25 in the living body by at least moving the balloon catheter 1 forward or backward or rotating the balloon catheter 1 (step S10). After that, the control unit 55 preferably returns to step S1 and measures the impedance again.

[0132] (Third Discrimination Method) The third determination method can be applied when six or more impedance measurement electrodes 30 are arranged around one ablation electrode 25. For example, in FIG. 8, the three or more measurement electrodes 30 include at least a first measurement electrode 31, a second measurement electrode 32, a third measurement electrode 33, a fourth measurement electrode 34, a fifth measurement electrode 35, and a sixth measurement electrode 36. The ablation electrode 25 has a first overlapping region 45A overlapping with a first virtual region 40A formed by at least the first measurement electrode 31, the second measurement electrode 32, the third measurement electrode 33, and the fourth measurement electrode 34, and a second overlapping region 45B overlapping with a second virtual region 40B formed by at least the third measurement electrode 33, the fourth measurement electrode 34, the fifth measurement electrode 35, and the sixth measurement electrode 36. As shown in FIG. 15, when the first measurement electrode 31, the second measurement electrode 32, the third measurement electrode 33, and the fourth measurement electrode 34 are in contact with the biological tissue (Yes in step S11), the control unit 55 preferably determines that the first overlapping region 45A of the cauterizing electrode 25 is in contact with the biological tissue (step S12), and when the third measurement electrode 33, the fourth measurement electrode 34, the fifth measurement electrode 35, and the sixth measurement electrode 36 are in contact with the biological tissue (Yes in step S15), the control unit 55 preferably determines that the second overlapping region 45B of the cauterizing electrode 25 is in contact with the biological tissue (step S16). This allows the contact state between the cauterizing electrode 25 and the biological tissue to be determined for each virtually divided region, so that the specific contact state between the cauterizing electrode 25 and the biological tissue can be grasped. When the first to fourth measurement electrodes 31 to 34 are not in contact with the biological tissue (No in step S11), the control unit 55 may determine that the first overlapping region 45A is not in contact with the biological tissue (step S13). If the third to sixth measurement electrodes 33 to 36 are not in contact with the biological tissue (No in step S15), it may be determined that the second overlapping region 45B is not in contact with the biological tissue (step S17). Although not essential, it is preferable to change the position of the cauterizing electrode 25 in the living body after steps S13 and S17 (steps S14, 18). After that, it is preferable to return to step S1 and measure the impedance again.

[0133] In the third determination method, it is preferable that cauterization is performed when both the first overlap region 45A and the second overlap region 45B of the cauterization electrode 25 come into contact with the living tissue.

[0134] At least one of the functions of the system 100, for example, the functions of the control unit 55 and the processing unit 56, may be realized by hardware or software. Examples of the hardware include logic circuits formed in integrated circuits such as LSI (Large Scale Integration) and ASIC (Application Specific Integrated Circuit).

[0135] The system 100 may include a computer that executes instructions of a program, which is software for realizing at least one function of the control unit 55 and the processing unit 56. The computer preferably includes a processor and a computer-readable recording medium storing the program. The processor executes the program stored in the computer-readable recording medium, thereby realizing the above function. The processor may be a CPU (Central Processing Unit). The recording medium may be a ROM (Read Only Memory) or the like. The recording medium may also include a RAM (Random Access Memory). The program may be supplied to the computer via any transmission medium capable of transmitting the program. Examples of the transmission medium include a communication network and a communication line.

[0136] This application claims the benefit of priority based on Japanese Patent Application No. 2020-85151, filed on May 14, 2020. The entire contents of the specification of Japanese Patent Application No. 2020-85151, filed on May 14, 2020, are incorporated by reference into this application. [Explanation of symbols]

[0137] 1: Balloon catheter 2: shaft, 3: inner tube, 4: outer tube 10: balloon, 11: outer surface, 12: distal fixation portion, 13: proximal fixation portion, 14: expandable portion 20: Insulating material, 21: Flexible base material, 23: First surface, 24: Second surface 25: cauterization electrode, 26: slit, 27: center portion, 28: branch portion, 29: return electrode 30: impedance measurement electrode, 31: first impedance measurement electrode, 32: second impedance measurement electrode, 33: third impedance measurement electrode, 34: fourth impedance measurement electrode, 35: fifth impedance measurement electrode, 36: sixth impedance measurement electrode, 31a: most proximal position of the first impedance measurement electrode, 32a: most proximal position of the second impedance measurement electrode, 33a: most proximal position of the third impedance measurement electrode, 38: straight line connecting at least two impedance measurement electrodes, 39: straight line forming a virtual area 40: virtual area, 40A: first virtual area, 40B: second virtual area, 40C: third virtual area, 40D: fourth virtual area 45: overlapping region, 45A: first overlapping region, 45B: second overlapping region 48:Reference electrode 51: operation unit, 52: fluid supply unit, 53: high frequency generator, 54: measurement unit, 55: control unit, 56: processing unit 100: Balloon catheter system

Claims

1. A balloon catheter for cauterizing biological tissue, a shaft having a distal end and a proximal end; A balloon provided on a distal portion of the shaft; an insulating material disposed on an outer surface of the balloon; a cauterizing electrode disposed on the insulating material and configured to cauterize the biological tissue by passing a high-frequency current therethrough; two or more impedance measuring electrodes having a surface area smaller than that of the ablation electrode, disposed around the ablation electrode on the insulating material, and configured to measure impedance; a balloon catheter in which a straight line connecting at least two of the two or more impedance measurement electrodes crosses the ablation electrode; A measurement unit that measures impedance between one of the two or more impedance measurement electrodes and the cauterization electrode or between two different impedance measurement electrodes; a control unit connected to the measurement unit and configured to determine whether or not one of the two or more impedance measurement electrodes is in contact with a living tissue using a result of the impedance measurement, The control unit determines whether or not the ablation electrode is in contact with biological tissue using a determination result of a contact state between at least one of the two or more impedance measurement electrodes and biological tissue.

2. A balloon catheter for cauterizing biological tissue, a shaft having a distal end and a proximal end; A balloon provided on a distal portion of the shaft; an insulating material disposed on an outer surface of the balloon; a cauterizing electrode disposed on the insulating material and configured to cauterize the biological tissue by passing a high-frequency current therethrough; two or more impedance measuring electrodes having a surface area smaller than that of the ablation electrode, disposed around the ablation electrode on the insulating material, and configured to measure impedance; a balloon catheter in which a straight line connecting at least two of the two or more impedance measurement electrodes crosses the ablation electrode; A return electrode plate is provided on the patient's body surface and a high-frequency current is passed between the return electrode and the cauterization electrode; A measurement unit that measures the impedance between one of the two or more impedance measurement electrodes and the return electrode; a control unit connected to the measurement unit and configured to determine whether or not one of the two or more impedance measurement electrodes is in contact with a living tissue using a result of the impedance measurement, The control unit determines whether or not the ablation electrode is in contact with biological tissue using a determination result of a contact state between at least one of the two or more impedance measurement electrodes and biological tissue.

3. 3. The balloon catheter system according to claim 1, wherein no impedance measuring electrode is entirely surrounded by the ablation electrode.

4. The balloon catheter system according to any one of claims 1 to 3, wherein the insulating material is provided around at least one of the two or more impedance measuring electrodes, and at least one of the two or more impedance measuring electrodes is insulated from the ablation electrode.

5. The balloon catheter system according to any one of claims 1 to 4, wherein the shortest distance between one of the two or more impedance measuring electrodes and the ablation electrode is 1 / 5 or less of the shortest distance between two of the two or more impedance measuring electrodes.

6. The two or more impedance measuring electrodes include three or more impedance measuring electrodes, the ablation electrode has an overlap region that overlaps with a virtual region formed by the three or more impedance measuring electrodes; The balloon catheter system according to any one of claims 1 to 5, wherein the area of ​​the overlapping region occupies 70% or more of the area of ​​the ablation electrode. However, the virtual region is formed by defining the most proximal position of each of the three or more impedance measurement electrodes arranged around the ablation electrode, the most proximal position being located closest to the ablation electrode, and connecting the most proximal positions of adjacent impedance measurement electrodes in the circumferential direction of the ablation electrode with a straight line.

7. the two or more impedance measuring electrodes include three or more impedance measuring electrodes, the three or more impedance measuring electrodes including at least a first impedance measuring electrode, a second impedance measuring electrode, a third impedance measuring electrode, a fourth impedance measuring electrode, a fifth impedance measuring electrode, and a sixth impedance measuring electrode; the ablation electrode has a first overlapping region overlapping a first virtual region formed by at least the first impedance measurement electrode, the second impedance measurement electrode, the third impedance measurement electrode, and the fourth impedance measurement electrode, and a second overlapping region overlapping a second virtual region formed by at least the third impedance measurement electrode, the fourth impedance measurement electrode, the fifth impedance measurement electrode, and the sixth impedance measurement electrode; The balloon catheter system according to any one of claims 1 to 6, wherein the sum of the areas of the first overlapping region and the second overlapping region accounts for 70% or more of the area of ​​the ablation electrode. However, the first virtual region and the second virtual region are formed by defining the most proximal position located closest to the ablation electrode for each of the three or more impedance measurement electrodes arranged around the ablation electrode, and connecting the most proximal positions of the impedance measurement electrodes adjacent to each other in the circumferential direction of the ablation electrode with a straight line.

8. the insulating material is a flexible substrate having a first surface and a second surface opposite the first surface, the first surface facing an exterior of the balloon; The balloon catheter system according to any one of claims 1 to 7, wherein the cauterizing electrode is disposed on the second surface side of the insulating material.

9. The two or more impedance measuring electrodes include three or more impedance measuring electrodes, the ablation electrode has an overlap region that overlaps with a virtual region formed by the three or more impedance measuring electrodes; The balloon catheter system according to any one of claims 1 to 8, wherein the control unit determines that the overlapping area of ​​the ablation electrode is in contact with biological tissue when all of the three or more impedance measurement electrodes are in contact with biological tissue. However, the virtual region is formed by defining the most proximal position of each of the three or more impedance measurement electrodes arranged around the ablation electrode, the most proximal position being located closest to the ablation electrode, and connecting the most proximal positions of adjacent impedance measurement electrodes in the circumferential direction of the ablation electrode with a straight line.

10. the two or more impedance measuring electrodes include three or more impedance measuring electrodes, the three or more impedance measuring electrodes including at least a first impedance measuring electrode, a second impedance measuring electrode, a third impedance measuring electrode, a fourth impedance measuring electrode, a fifth impedance measuring electrode, and a sixth impedance measuring electrode; the ablation electrode has a first overlapping region overlapping a first virtual region formed by at least the first impedance measurement electrode, the second impedance measurement electrode, the third impedance measurement electrode, and the fourth impedance measurement electrode, and a second overlapping region overlapping a second virtual region formed by at least the third impedance measurement electrode, the fourth impedance measurement electrode, the fifth impedance measurement electrode, and the sixth impedance measurement electrode; 10. The balloon catheter system according to claim 9, wherein the control unit determines that the first overlapping region of the ablation electrodes is in contact with biological tissue when the first impedance measurement electrode, the second impedance measurement electrode, the third impedance measurement electrode, and the fourth impedance measurement electrode are in contact with biological tissue, and determines that the second overlapping region of the ablation electrodes is in contact with biological tissue when the third impedance measurement electrode, the fourth impedance measurement electrode, the fifth impedance measurement electrode, and the sixth impedance measurement electrode are in contact with biological tissue.

11. A processing unit connected to the control unit, The processing unit performs at least one of the following: a comparison of an impedance between one of the two or more impedance measurement electrodes and the cauterization electrode with a first reference value; a comparison of an impedance between two of the two or more impedance measurement electrodes with a second reference value; and a comparison of an impedance between one of the two or more impedance measurement electrodes and the return electrode with a third reference value; The balloon catheter system according to claim 2 , wherein the control unit determines whether or not one of the two or more impedance measuring electrodes is in contact with a living tissue, using a comparison result from the processing unit.

12. A processing unit connected to the control unit, The processing unit performs at least one of a comparison of impedance between one of the two or more impedance measurement electrodes and the ablation electrode before and after the expansion of the balloon, a comparison of impedance between two of the two or more impedance measurement electrodes before and after the expansion of the balloon, and a comparison of impedance between one of the two or more impedance measurement electrodes and the return electrode before and after the expansion of the balloon; The balloon catheter system according to claim 2 , wherein the control unit determines whether or not one of the two or more impedance measuring electrodes is in contact with a living tissue, using a comparison result from the processing unit.

13. A reference electrode is provided on the surface of the shaft at a position proximal to the balloon, The balloon catheter system according to any one of claims 1 to 12, wherein the measurement unit further measures the impedance between one of the two or more impedance measuring electrodes and the reference electrode.

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