Balloon catheter and balloon catheter system

Abstract

[Problem] The purpose of the present invention is to enable the identification of the surface temperature of a balloon at high precision. [Solution] A balloon catheter 15 comprises: a balloon 25; an outer cylinder shaft 30 that is connected to a proximal end 25b of the balloon 25; an inner cylinder shaft 35 that passes through the inside of the outer cylindrical shaft 30, extends into the balloon 25, and is connected to a distal end 25a of the balloon 25; and a heating member 40 that is disposed inside the balloon 25 and is for heating a liquid inside the balloon 25. A liquid feeding passage LP that leads into the balloon 25 is formed between the outer cylinder shaft and the inner cylinder shaft. A temperature sensor 45 is provided to the liquid feeding passage LP.

Description

[Technical Field]

[0001] The present invention relates to a balloon catheter and a balloon catheter system. [Background technology]

[0002] Catheter ablation therapy is a treatment method that uses a catheter inserted into the body to ablate a target site within the body. For example, by destroying the target site through ablation, diseases such as arrhythmia due to atrial fibrillation, endometriosis, and cancer are treated. As a catheter used in catheter ablation therapy, a balloon catheter having a balloon at its distal end is known, as disclosed in JP3611799B and JP4747141B.

[0003] When the balloon catheter is inserted into the body, the balloon is deflated and stretched in the longitudinal direction of the balloon catheter. Next, a liquid is supplied to the balloon catheter inserted into the body, and the balloon is expanded. The liquid inside the balloon is temperature-regulated, which allows the surface temperature of the balloon to be controlled. By contacting the balloon, which has been regulated to a predetermined surface temperature, with a circumferential target region, for example, a connection site of a vein to the atrium, the circumferential target region can be ablated in one go.

[0004] In treatments using balloon catheters, it is important to accurately grasp the surface temperature of the balloon. In this regard, the balloon catheters disclosed in JP3611799B and JP4747141B are provided with a temperature sensor for measuring the surface temperature of the balloon. However, in JP3611799B, a temperature sensor is attached to the inner surface of the balloon. However, it is not easy to stably install a temperature sensor on the surface of a balloon that expands from a deflated state. In this regard, JP4747141B proposes a two-layer balloon structure with a temperature sensor located between the layers. However, due to practical manufacturing difficulties in terms of fabricating the balloon, installing the heat-sensing part of the temperature sensor, and handling the temperature sensor lead wires, the balloon catheter of JP4747141B has not yet become widespread. In other words, it has been difficult to accurately determine the surface temperature of the balloon with conventional balloon catheters. DISCLOSURE OF THE INVENTION

[0005] The present invention has been made in consideration of the above points, and an object of the present invention is to make it possible to determine the surface temperature of a balloon with high accuracy.

[0006] The first balloon catheter of the present invention comprises a balloon, an outer cylindrical shaft connected to the proximal end of the balloon, an inner cylindrical shaft passing through the outer cylindrical shaft and extending into the balloon to connect to the distal end of the balloon, a heating element disposed within the balloon for heating a liquid within the balloon, and a temperature sensor disposed in a liquid supply path formed between the outer cylindrical shaft and the inner cylindrical shaft and leading to the inside of the balloon.

[0007] In the first balloon catheter of the present invention, the length along the longitudinal direction from the distal end of the outer cylindrical shaft to the temperature sensor may be 5 mm or more and 150 mm or less.

[0008] In the first balloon catheter of the present invention, the temperature sensor may be attached to the inner cylindrical shaft, the inner cylindrical shaft being movable relative to the outer cylindrical shaft, and when the inner cylindrical shaft has moved distally relative to the outer cylindrical shaft to expand the balloon, the temperature sensor may be located in the fluid transfer path between the outer cylindrical shaft and the inner cylindrical shaft.

[0009] In the first balloon catheter of the present invention, the temperature sensor may be attached to the outer cylindrical shaft.

[0010] In the first balloon catheter of the present invention, the temperature sensor may include a heat-sensing unit and a lead wire connected to the heat-sensing unit, the lead wire may be fixed to the inner cylindrical shaft or the outer cylindrical shaft, and the heat-sensing unit may be spaced apart from the inner cylindrical shaft and the outer cylindrical shaft.

[0011] The second balloon catheter of the present invention comprises a balloon, an outer cylindrical shaft connected to the proximal end of the balloon, an inner cylindrical shaft passing through the outer cylindrical shaft and extending into the balloon to connect to the distal end of the balloon, forming a liquid supply path between the outer cylindrical shaft and the inner cylindrical shaft leading to the inside of the balloon, a coil electrode disposed within the balloon that is energized at high frequency to apply a high-frequency current to the liquid within the balloon, thereby heating the liquid, and a temperature sensor disposed in a position where the high-frequency current is shielded.

[0012] The first balloon catheter system of the present invention may include either the first or second balloon catheter of the present invention described above, and a control device electrically connected to the temperature sensor and adjusting the output of the heating element based on the output of the temperature sensor.

[0013] A second balloon catheter system of the present invention may include either the first or second balloon catheter of the present invention described above, and a control device electrically connected to the temperature sensor and configured to determine the surface temperature of the balloon based on the output of the temperature sensor.

[0014] In the first and second balloon catheter systems of the present invention, the control device may have a display unit that displays the surface temperature.

[0015] In the first and second balloon catheter systems of the present invention, the control device may first determine a temperature fluctuation of the liquid in the liquid delivery path from the output of the temperature sensor, and then determine the surface temperature of the balloon based on the temperature fluctuation.

[0016] In the first and second balloon catheter systems of the present invention, the control device may first identify temperature fluctuations of the liquid in the liquid delivery path from the output of the temperature sensor, and then identify the maximum value of the temperature fluctuations as the surface temperature of the balloon.

[0017] The first and second balloon catheter systems of the present invention may further include an agitator that repeatedly supplies and discharges the liquid to and from the liquid feed path at a fixed cycle, and the control device may acquire an output from the temperature sensor at intervals shorter than the fixed cycle.

[0018] The third balloon catheter system of the present invention comprises either the first or second balloon catheter of the present invention described above, and an agitator that repeatedly supplies a predetermined amount of the liquid into the liquid feed path and discharges it from the liquid feed path at a constant cycle.

[0019] The first to third balloon catheter systems of the present invention further include a stirring device that repeatedly supplies a predetermined amount of the liquid to the liquid feed path and discharges it from the liquid feed path, and the length [mm] along the longitudinal direction from the distal end of the outer cylindrical shaft to the temperature sensor is set to the predetermined amount [mm 3] is the cross-sectional area of ​​the liquid transfer path [mm 2 ] may be set to be equal to or less than the value obtained by dividing by [ ].

[0020] In the first to third balloon catheter systems of the present invention, wiring electrically connected to the heating element and the control device is provided, the temperature sensor includes a lead wire electrically connected to the control device, the inner cylindrical shaft is movable relative to the outer cylindrical shaft, and both the wiring and the lead wire are attached to one of the outer cylindrical shaft and the inner cylindrical shaft, which are the same, and extend within the liquid delivery path.

[0021] According to the present invention, the surface temperature of a balloon can be determined with high accuracy. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is a diagram for explaining one embodiment, showing a balloon catheter system and a balloon catheter. [Figure 2] FIG. 2 is a diagram showing the distal end portion of the balloon catheter of FIG. 1 with the balloon inflated. [Figure 3] 2 is a diagram showing the distal end portion of the balloon catheter of FIG. 1 with the balloon in a deflated and expanded state. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 2. [Figure 5] 3 is a cross-sectional view taken along line VV in FIG. 2. [Figure 6] Temperature distribution at the distal end of a coaxial balloon catheter obtained by thermal fluid analysis using CAE. [Figure 7] Temperature distribution at the distal end of a non-coaxial balloon catheter obtained by thermal fluid analysis using CAE. [Figure 8] FIG. 2 is a diagram showing the distal end portion of the balloon catheter, illustrating the flow of liquid when the liquid is discharged from the liquid delivery path into the balloon. [Figure 9]FIG. 10 is a diagram showing the distal end portion of the balloon catheter, illustrating the flow of liquid when liquid is aspirated from inside the balloon into the liquid feed path. [Figure 10] FIG. 1 is a diagram for explaining an experimental method using a balloon catheter system. [Figure 11] FIG. 11 shows the distal end portion of the balloon catheter of FIG. 10. [Figure 12] FIG. 11 shows the distal end portion of the balloon catheter in a coaxial state in the experiment of FIG. 10 . [Figure 13] FIG. 11 shows the distal end portion of the balloon catheter in a non-coaxial state in the experiment of FIG. 10 . [Figure 14] 11 is a graph showing the measured values ​​of the temperature sensor and the surface temperature sensor obtained in the experiment of FIG. 10 (liquid volume: 10 ml, contrast medium dilution ratio: 1:2, coaxial state). [Figure 15] 11 is a graph showing the measured values ​​of the temperature sensor and the surface temperature sensor obtained in the experiment of FIG. 10 (liquid volume: 10 ml, contrast medium dilution ratio: 1:2, non-coaxial state). [Figure 16] 11 is a graph showing the measured values ​​of the temperature sensor and the surface temperature sensor obtained in the experiment of FIG. 10 (liquid volume: 10 ml, contrast medium dilution ratio: 1:3, coaxial state). [Figure 17] 11 is a graph showing the measured values ​​of the temperature sensor and the surface temperature sensor obtained in the experiment of FIG. 10 (liquid volume: 10 ml, contrast medium dilution ratio: 1:3, non-coaxial state). [Figure 18] 11 is a graph showing the measured values ​​of the temperature sensor and the surface temperature sensor obtained in the experiment of FIG. 10 (liquid volume: 20 ml, contrast medium dilution ratio: 1:3, coaxial state). [Figure 19] 11 is a graph showing the measured values ​​of the temperature sensor and the surface temperature sensor obtained in the experiment of FIG. 10 (liquid volume: 20 ml, contrast medium dilution ratio: 1:3, non-coaxial state). [Figure 20] 11 is a graph showing the measured values ​​of the temperature sensor and the surface temperature sensor obtained in the experiment of FIG. 10 (liquid volume: 20 ml, contrast medium dilution ratio: 1:2, coaxial state). [Figure 21]11 is a graph showing the measured values ​​of the temperature sensor and the surface temperature sensor obtained in the experiment of FIG. 10 (liquid volume: 20 ml, contrast medium dilution ratio: 1:2, non-coaxial state). [Figure 22] FIG. 1 is a diagram showing a balloon catheter system used in a first example. [Figure 23] FIG. 23 is a circuit block diagram of a control device used in the balloon catheter system of FIG. 22. [Figure 24] 24 is a flowchart showing a method for determining the surface temperature of the balloon from the detection result of the temperature sensor in the control device of FIG. 23. [Figure 25] 23 is a graph showing the actual measured values ​​of the temperature sensor and the surface temperature sensor in an experiment in which the balloon surface temperature identified from the detection results of the temperature sensor was set to 66°C using the balloon catheter system of FIG. 22. [Figure 26] FIG. 10 is a diagram showing a balloon catheter system used in the second example. [Figure 27] 10 is a flowchart showing a method for determining the surface temperature of a balloon from the detection results of a temperature sensor in a fourth specific example. DETAILED DESCRIPTION OF THE INVENTION

[0023] An embodiment of the present invention will be described below with reference to the drawings. For ease of illustration and understanding, the drawings accompanying this specification have been appropriately modified and exaggerated in scale and aspect ratio from the actual product. Furthermore, terms used in this specification that specify shapes, geometric conditions, and their degrees, such as "parallel," "orthogonal," and "identical," as well as values ​​of lengths and angles, are not limited to their strict meanings but are to be interpreted within a range within which similar functions can be expected.

[0024] 1 includes a balloon catheter 15, a control device 70, and a stirring device 75 connected to the balloon catheter 15. The balloon catheter 15 also includes a catheter body 20 having a longitudinal direction LD, and a handle 50 connected to the proximal end of the catheter body 20.

[0025] 2, the catheter main body 20 according to this embodiment includes a balloon 25, an outer cylindrical shaft 30 connected to the proximal end 25b of the balloon 25, an inner cylindrical shaft 35 connected to the distal end 25a of the balloon 25, and a heating member 40 disposed within the balloon 25. The inner cylindrical shaft 35 passes through the outer cylindrical shaft 30 and extends into the balloon 25. A liquid delivery path LP leading to the inside of the balloon 25 is formed between the outer cylindrical shaft 30 and the inner cylindrical shaft 35. The heating member 40 heats the liquid within the balloon 25.

[0026] In particular, the catheter main body 20 (balloon catheter 15) according to this embodiment is devised to enable highly accurate determination of the surface temperature of the balloon 25 filled with a heated liquid. Specifically, the temperature sensor 45 disposed in the liquid feed path LP acquires information relating to the temperature within the liquid feed path LP, and based on this information, the surface temperature of the balloon 25 can be detected with high accuracy.

[0027] The longitudinal direction LD of the catheter main body 20 is specified as the direction in which the central axes of the outer cylindrical shaft 30 and the inner cylindrical shaft 35 extending from the outer cylindrical shaft 30 extend. In this specification, the "distal" side used with respect to each component of the balloon catheter 15 and the catheter main body 20 means the side away from the operator (surgeon) of the handle 50 and the balloon catheter 15 along the longitudinal direction LD of the catheter main body 20, or in other words, the tip side. In addition, the "proximal" side used with respect to each component of the balloon catheter 15 and the catheter main body 20 means the side close to the operator (surgeon) of the handle 50 and the balloon catheter 15 along the longitudinal direction LD of the catheter main body 20, or in other words, the base end side.

[0028] The balloon catheter system 10 and the balloon catheter 15 will be described in further detail below. First, the catheter body 20 of the balloon catheter 15 will be described in detail. As described above, the catheter body 20 of the balloon catheter 15 according to this embodiment includes the balloon 25, the outer cylindrical shaft 30, the inner cylindrical shaft 35, the heating element 40, and the temperature sensor 45.

[0029] Of these, the outer cylindrical shaft 30 and the inner cylindrical shaft 35 are both configured in a tubular, typically cylindrical, shape. Therefore, the outer cylindrical shaft 30 and the inner cylindrical shaft 35 each form a lumen as an internal space. For example, a guide wire (not shown) is inserted into the lumen formed by the inner cylindrical shaft 35. The inner cylindrical shaft 35 is inserted into the lumen formed by the outer cylindrical shaft 30. In other words, the outer cylindrical shaft 30 and the inner cylindrical shaft 35 have a double-tube shaft configuration. The inner diameter of the outer cylindrical shaft 30 is larger than the outer diameter of the inner cylindrical shaft 35. Therefore, a lumen remains between the outer cylindrical shaft 30 and the inner cylindrical shaft 35. This lumen between the outer cylindrical shaft 30 and the inner cylindrical shaft 35 forms a liquid delivery path LP. As shown in FIG. 2, the liquid delivery path LP communicates with the inside of the balloon 25. The liquid delivery path LP also extends into the handle 50.

[0030] The lengths of the outer cylindrical shaft 30 and the inner cylindrical shaft 35 are preferably 500 mm or more and 1700 mm or less, and more preferably 600 mm or more and 1200 mm or less. The outer cylindrical shaft 30 and the inner cylindrical shaft 35 are preferably made of a flexible material with excellent antithrombogenicity. Examples of flexible materials with excellent antithrombogenicity include, but are not limited to, fluoropolymers, polyamides, polyurethane polymers, and polyimides. Furthermore, the outer cylindrical shaft 30 is preferably made by laminating layers of different flexible materials to achieve both slidability with the inner cylindrical shaft 35 and adhesiveness or heat-weldability with the balloon 25.

[0031] The outer diameter of the outer cylindrical shaft 30 is preferably 3.0 mm or more and 4.0 mm or less. The inner diameter of the outer cylindrical shaft 30 is preferably 2.5 mm or more and 3.5 mm or less. The outer diameter of the inner cylindrical shaft 35 is preferably 1.4 mm or more and 1.7 mm or less. The inner diameter of the inner cylindrical shaft 35 is preferably 1.1 mm or more and 1.3 mm or less.

[0032] A balloon 25 is connected to the outer cylindrical shaft 30 and the inner cylindrical shaft 35. The balloon 25 is formed so as to be expandable by filling it with a liquid and contractable by discharging the liquid. The balloon 25 preferably has a shape that can fit the target site (e.g., a blood vessel) to be treated. As an example, a spherical shape with a diameter of 15 mm to 40 mm can be adopted as the shape of the balloon 25 that fits the pulmonary vein junction of the left atrium. Here, the spherical shape includes a perfect sphere, an oblate spheroid, and an elongated spheroid, and also includes a nearly spherical shape.

[0033] The thickness of the balloon 25 is preferably 10 μm or more and 200 μm or less. Furthermore, a stretchable material with excellent antithrombotic properties is preferred as the material for the balloon 25, and specifically, a polyurethane-based polymer material or the like can be used. Examples of polyurethane-based polymer materials that can be used for the balloon 25 include thermoplastic polyether urethane, polyether polyurethane urea, fluorine polyether urethane urea, polyether polyurethane urea resin, and polyether polyurethane urea amide.

[0034] 2 and 3, in the illustrated catheter main body 20, the distal end (tip) 25a of the balloon 25 is fixed to the distal end (tip) 35a of the inner cylindrical shaft 35. The proximal end (base end) 25b of the balloon 25 is fixed to the distal end (tip) 30a of the outer cylindrical shaft 30. The balloon 25 can be connected to the outer cylindrical shaft 30 and the inner cylindrical shaft 35 by bonding or thermal welding.

[0035] The balloon 25 connected to the outer and inner cylindrical shafts 30 and 35 deforms as the outer and inner cylindrical shafts 30 and 35 move relative to each other in the longitudinal direction LD. In the illustrated example, the relative movement of the outer and inner cylindrical shafts 30 and 35 allows the size of the balloon 25 in the longitudinal direction LD to be adjusted. As shown in FIG. 3, as the inner cylindrical shaft 35 moves distally relative to the outer cylindrical shaft 30 in the longitudinal direction LD, the balloon 25 stretches in the longitudinal direction LD and becomes more tense. In the illustrated example, the distal movement range of the inner cylindrical shaft 35 relative to the outer cylindrical shaft 30 in the longitudinal direction LD is restricted by the balloon 25. As the inner cylindrical shaft 35 moves proximally relative to the outer cylindrical shaft 30 from the state shown in FIG. 3, the balloon 25 becomes relaxed. By introducing a liquid into the relaxed balloon 25, the balloon 25 can be inflated, as shown in FIG. 2. That is, the size of the balloon 25 in the longitudinal direction LD can be adjusted by moving the outer cylindrical shaft 30 and the inner cylindrical shaft 35 relative to each other.

[0036] Next, the heating element 40 will be described. The heating element 40 is disposed within the balloon 25. The heating element 40 is a member for heating the liquid filled within the balloon 25. As an example, a nichrome wire that generates heat by electrical resistance can be used as the heating element 40. As another example of the heating element 40, a coil electrode 41 can be used, as shown in FIGS. 2 and 3. By applying high-frequency current to the heating element 40 serving as the coil electrode 41, a high-frequency current flows between the coil electrode 41 and an externally disposed counter electrode 77 (FIG. 1), and the liquid located between the coil electrode 41 and the counter electrode 77 generates Joule heat. The counter electrode 77 is disposed, for example, on the back of the patient.

[0037] In the example shown in FIGS. 2 and 3 , the coil electrode 41 is provided on the inner cylindrical shaft 35 extending inside the balloon 25. The coil electrode 41 may be formed of a conductive wire wound around the inner cylindrical shaft 35. The coil electrode 41 is electrically connected to a wiring 42 for high-frequency current application. The wiring 42 extends to the handle 50 through the liquid transfer path LP, which serves as a lumen between the outer cylindrical shaft 30 and the inner cylindrical shaft 35. A specific example of the coil electrode 41 constituting the heating member 40 is a coil electrode formed by stripping the insulation-coated lead wire used for the wiring 42 and winding it around the inner cylindrical shaft 35. Since such a coil electrode 41 is formed integrally with the wiring 42, it is possible to effectively prevent problems such as wire breakage.

[0038] The diameter of the coil electrode 41 and the wiring 42 is preferably 0.1 mm or more and 1 mm or less, and more preferably 0.1 mm or more and 0.4 mm or less. Examples of conductive materials that form the coil electrode 41 and the wiring 42 include copper, silver, gold, platinum, and alloys thereof. To prevent short circuits, the wiring 42 is preferably configured such that the conductive linear portion is covered with an insulating film such as a fluoropolymer (see FIGS. 4 and 5).

[0039] Next, the temperature sensor 45 will be described. The temperature sensor 45 acquires information about the temperature of the liquid. In this embodiment, the temperature sensor 45 has a heat-sensing unit 46 disposed in the liquid feed path LP, which is located between the outer tubular shaft 30 and the inner tubular shaft 35. This temperature sensor 45 can acquire information about the temperature of the liquid in the liquid feed path LP. Furthermore, according to the inventors' investigations, the surface temperature of the balloon 25, which is important in ablation treatment using the balloon catheter system 10, can be determined with high accuracy based on the information acquired by the temperature sensor 45. Installing the temperature sensor 45 between the outer tubular shaft 30 and the inner tubular shaft 35 significantly simplifies the manufacture of the catheter body 20 compared to installing the temperature sensor 45 inside the balloon 25. Furthermore, compared to the balloon 25, which has a very thin wall and undergoes significant deformation during use, installing the temperature sensor 45 between the outer tubular shaft 30 and the inner tubular shaft 35 protects the temperature sensor 45 from external stress and provides stable support. That is, by installing the temperature sensor 45 in the liquid transfer path LP between the outer cylindrical shaft 30 and the inner cylindrical shaft 35, the quality and reliability of the balloon catheter system 10 and the balloon catheter 15 can be significantly improved.

[0040] For the purpose of determining the surface temperature of the balloon 25 with high accuracy, the preferred length DX along the longitudinal direction LD of the outer cylindrical shaft from the distal end 30a of the outer cylindrical shaft 30 to the heat-sensing portion 46 of the temperature sensor 45 strictly depends on the amount of liquid supplied and discharged by the stirring device 75, which will be described later. However, considering the dimensions of the balloon catheter 15 typically used in cardiac ablation treatment and the amount of liquid supplied and discharged from the stirring device 75, the length DX (see FIG. 2) from the distal end 30a of the outer cylindrical shaft 30 to the temperature sensor 45 is preferably 5 mm or more and 150 mm or less, and more preferably 10 mm or more and 20 mm or less.

[0041] Unless otherwise specified, the length DX from the distal end 30a of the outer cylindrical shaft 30 to the temperature sensor 45 is the length specified when the balloon 25 shown in Fig. 2 is inflated with a liquid. Similarly, unless otherwise specified, expressions such as "the temperature sensor 45 is located in the liquid feed path LP," "the temperature sensor 45 is located in the outer cylindrical shaft 30," and "the temperature sensor 45 is located between the outer cylindrical shaft 30 and the inner cylindrical shaft 35" are based on the assumption that the balloon 25 shown in Fig. 2 is inflated with a liquid.

[0042] A thermocouple or a thermistor can be used as the temperature sensor 45. A T-type thermocouple is particularly suitable as the temperature sensor 45. A T-type thermocouple can reduce the heat capacity of the heat-sensing part 46. Furthermore, by using a T-type thermocouple as the temperature sensor 45, the thermoelectromotive force is stabilized. Furthermore, a T-type thermocouple can detect a temperature range of 50°C or more and 80°C or less with high accuracy, making it particularly suitable for cardiac ablation treatment. Note that the temperature information acquired by the temperature sensor 45 is, for example, a potential acquired from a thermocouple or a resistance value acquired from a thermistor.

[0043] 2 and 3, the temperature sensor 45 typically has a heat-sensing portion 46 and a lead wire 47 electrically connected to the heat-sensing portion 46. In a temperature sensor 45 that is a thermocouple, the portion where dissimilar metals are connected forms the heat-sensing portion 46. In a temperature sensor 45 that is a thermistor, a ceramic element forms the heat-sensing portion 46. The lead wire 47 extends to the handle 50 through the liquid transfer path LP, which is a lumen between the outer cylindrical shaft 30 and the inner cylindrical shaft 35.

[0044] The diameter of the lead wire 47 is preferably 0.05 mm or more and 0.5 mm or less, and more preferably 0.05 mm or more and 0.3 mm or less. In the temperature sensor 45 as a thermocouple, for example, one lead wire 47 can be made of copper and the other lead wire 47 can be made of constantan. In this example, the heat-sensing unit 46 formed by joining the pair of lead wires 47 can function as a T-type thermocouple. To prevent short-circuiting of the pair of lead wires 47, it is preferable that an electrically insulating coating such as a fluoropolymer or enamel be provided, as shown in Figures 4 and 5.

[0045] In the illustrated example, the temperature sensor 45 is attached to the inner cylindrical shaft 35. As shown in FIGS. 2 to 4 , the lead wire 47 of the temperature sensor 45 is fixed to the inner cylindrical shaft 35, thereby attaching the temperature sensor 45 to the inner cylindrical shaft 35. The heat-sensing unit 46 is spaced apart from both the outer cylindrical shaft 30 and the inner cylindrical shaft 35. In other words, the heat-sensing unit 46 is not in contact with the outer cylindrical shaft 30 or the inner cylindrical shaft 35. This prevents the temperature of the outer cylindrical shaft 30 or the inner cylindrical shaft 35, which have large heat capacities, from deteriorating the responsiveness of the temperature sensor 45. This allows the temperature of the liquid in the liquid transfer path LP to be evaluated with high accuracy and high responsiveness using the temperature sensor 45. The fixing means 48 for fixing the lead wire 47 to the inner cylindrical shaft 35 is not particularly limited and various means can be used. In the illustrated example, a heat-shrinkable tube that shrinks when heated is used as the fixing means 48. However, the fixing means 48 is not limited to this example and various types of shrinkable tubes, adhesive tapes, adhesives, etc. can be used.

[0046] In the illustrated example, the wiring 42 is not attached to either the outer cylindrical shaft 30 or the inner cylindrical shaft 35, but this is not limiting and the wiring 42 may be attached to either the outer cylindrical shaft 30 or the inner cylindrical shaft 35. Preferably, both the wiring 42 and the lead wire 47 of the temperature sensor 45 are attached to the same one of the outer cylindrical shaft 30 and the inner cylindrical shaft 35. This specific example effectively prevents the wiring 42 and the lead wire 47, which both extend through the liquid feed path LP, from becoming entangled when the outer cylindrical shaft 30 and the inner cylindrical shaft 35 move relative to each other. This allows the heating element 40 to stably adjust the temperature of the liquid in the balloon and stably monitor the surface temperature of the balloon 25.

[0047] 3, even when the inner cylindrical shaft 35 has moved to the distal end in the longitudinal direction LD relative to the outer cylindrical shaft 30 to the maximum extent possible so that the balloon 25 is expanded, the temperature sensor 45 remains located within the outer cylindrical shaft 30. According to this specific example, the temperature sensor 45 can be located within the outer cylindrical shaft 30, regardless of the relative position of the inner cylindrical shaft 35 with respect to the outer cylindrical shaft 30. Therefore, the temperature sensor 45 can be stably protected by the outer cylindrical shaft 30, regardless of the relative position of the inner cylindrical shaft 35 with respect to the outer cylindrical shaft 30.

[0048] On the other hand, unlike the illustrated example, the temperature sensor 45 may be attached to the outer cylindrical shaft 30. For example, the lead wires 47 of the temperature sensor 45 may be fixed to the inner surface of the outer cylindrical shaft 30. According to this specific example, the temperature sensor 45 is located inside the outer cylindrical shaft 30, regardless of the relative position of the inner cylindrical shaft 35 with respect to the outer cylindrical shaft 30. Therefore, the temperature sensor 45 can be stably protected by the outer cylindrical shaft 30, regardless of the relative position of the inner cylindrical shaft 35 with respect to the outer cylindrical shaft 30.

[0049] Next, the handle 50 connected to the proximal side of the catheter main body 20 described above will be described. The handle 50 is the part that is grasped by the operator (surgeon) while using the balloon catheter system 10. Therefore, it is preferable that the handle 50 has a design that allows the operator to easily grasp and operate it with their hands. The material that constitutes the handle 50 is preferably a material with high chemical resistance, such as polycarbonate or ABS resin.

[0050] The handle 50 shown in Fig. 1 has a first handle section 51 and a second handle section 52 that are slidable relative to each other. The first handle section (front handle section) 51 is connected to the outer cylindrical shaft 30 of the catheter main body 20. The second handle section (rear handle section) 52 is connected to the inner cylindrical shaft 35 of the catheter main body 20. By moving the second handle section 52 relative to the first handle section 51, the inner cylindrical shaft 35 can be moved relative to the outer cylindrical shaft 30.

[0051] As shown in FIG. 1, the handle 50 also serves as a connection point between the balloon catheter 15 and other devices included in the balloon catheter system 10.

[0052] First, a connector 56 extends from the second handle portion 52. This connector 56 electrically connects the wiring 42 of the catheter main body 20 and the lead wire 47 of the temperature sensor 45 to an external control device 70. The connector 56 extends from one of multiple branch portions 52a provided on the second handle portion 52. When the wiring 42 and the lead wire 47 are connected to an external device (control device 70) via the same handle portion, it is preferable that the wiring 42 and the lead wire 47 be the same as each other, either the outer cylindrical shaft 30 or the inner cylindrical shaft 35, as described above, and that they are attached to the shaft (in the illustrated example, the inner cylindrical shaft 35) connected to the handle portion (in the illustrated example, the second handle portion 52). In this case, tangling and disconnection of the wiring 42 and the lead wire 47 can be more effectively avoided.

[0053] The connector 56 is preferably configured to effectively prevent incorrect connection. The connector 56 also preferably has excellent waterproof properties. The configuration of the connector 56 can be determined taking into consideration the convenience for the surgeon and design considerations. The connector 56 is preferably made of a material with high chemical resistance, similar to the handle 50, and suitable examples include polycarbonate or ABS resin.

[0054] The connector 56 may have a high-conductivity metal pin therein. The wiring 42 and the lead wire 47 can be electrically connected to the control device 70, which serves as a high-frequency power supply means, by connecting to this high-conductivity metal pin. However, the lead wire 47 of the temperature sensor 45 may be electrically connected to a device other than the control device 70, which serves as a high-frequency power supply means, such as a temperature indicator. The material of the high-conductivity metal pin included in the connector 56 is not particularly limited as long as it is a metal with high conductivity. Examples of the high-conductivity metal pin included in the connector 56 include copper, silver, gold, platinum, and alloys thereof. Furthermore, it is preferable that the exterior of the high-conductivity metal pin be protected with an electrically insulating and chemical-resistant material. Examples of the electrically insulating and chemical-resistant material include polysulfone, polyurethane-based polymer, polypropylene, and polyvinyl chloride.

[0055] The second handle portion 52 has branches 52b and 52c in addition to the branch 52a to which the connector 56 is connected. These branches 52b and 52c function as portions for supplying liquid to the lumen, which is the internal space of the inner cylindrical shaft 35, and as portions from which a guidewire inserted into the lumen of the inner cylindrical shaft 35 extends. During cardiac ablation treatment, a small amount of saline solution, approximately 100 ml per hour, is typically discharged into the body through the lumen of the inner cylindrical shaft 35. Discharging saline solution effectively prevents blood from flowing back into the lumen of the inner cylindrical shaft 35.

[0056] As shown in FIG. 1 , an extension tube 57 extends from the first handle portion 51. This extension tube 57 connects the liquid feed path LP of the catheter main body 20 to an external supply device 74 and an agitator 75. The extension tube 57 extends from a branch portion 51a provided in the first handle portion 51. The extension tube 57 is connected to the supply device 74 and the agitator 75 via a valve 58. In the illustrated example, by operating the valve 58, it is possible to select whether the supply device 74 or the agitator 75 is to be connected to the liquid feed path LP. A three-way stopcock can be used as the valve 58.

[0057] Next, the devices that constitute the balloon catheter system 10 together with the balloon catheter 15 described above, specifically the control device 70, the supply device 74, and the stirring device 75, will be described.

[0058] The illustrated control device 70 is electrically connected to the coil electrode 41 via wiring 42. The control device 70 has a high-frequency current control unit 70A that controls the application of high-frequency current to the coil electrode 41. In the illustrated example, the output from the heating member 40 is adjusted by controlling the application of high-frequency current to the coil electrode 41 with the high-frequency current control unit 70A. The high-frequency current control unit 70A can control the application of high-frequency current to the coil electrode 41 based on the surface temperature of the balloon 25 determined by a temperature calculation unit 70B (described later), or in accordance with preset processing, or in accordance with input from the operator.

[0059] The control device 70 is also electrically connected to the lead wire 47 of the temperature sensor 45. The control device 70 has a temperature calculation unit 70B that calculates information related to the temperature acquired by the inner cylindrical shaft 35. The temperature calculation unit 70B calculates the liquid temperature in the liquid transfer path LP based on the information related to the temperature acquired by the temperature sensor 45, and further estimates the surface temperature of the balloon 25 based on the calculated liquid temperature. The temperature calculation unit 70B may display the determined surface temperature of the balloon 25 on the display unit 71. The method for determining the surface temperature of the balloon 25 will be described in detail later.

[0060] Furthermore, the control device 70 has an agitator control section 70C that controls the agitator 75. The agitator control section 70C may be configured to display the control conditions of the agitator 75 on the display section 71.

[0061] The control device 70 is configured with hardware such as a CPU, for example. One or more of the high-frequency current control unit 70A, the temperature calculation unit 70B, and the stirring device control unit 70C included in the control device 70 may be configured as separate hardware, or a portion may be provided. At least a portion of the control device 70 may be configured with software. A portion of the control device 70 may be physically located separately. Furthermore, some of the components of the control device 70 may be capable of cooperating with other components by communication via a network. Furthermore, some of the components of the control device 70 may be located on a device that can communicate with other components via an external network, such as a server or database on a cloud.

[0062] Next, the supply device 74 will be described. The supply device 74 supplies liquid into the liquid feed path LP. By supplying liquid from the supply device 74 to the balloon 25 via the liquid feed path LP, the balloon 25 can be inflated as shown in FIG. 2. On the other hand, by discharging liquid from the balloon 25 via the liquid feed path LP from the supply device 74, the balloon 25 can also be deflated. The liquid supplied into the liquid feed path LP can typically be physiological saline. As shown in the figure, a syringe can be used as the supply device 74. However, a pump or the like can also be used as the supply device 74.

[0063] Next, the agitator 75 will be described. The agitator 75 is provided to agitate the liquid in the balloon 25. By agitating the liquid in the balloon 25, the heat supplied to the inside of the balloon 25 can be dispersed or uniformized, thereby adjusting the surface temperature of the balloon 25. The agitator 75 repeatedly supplies liquid to the liquid feed path LP and discharges liquid from the liquid feed path LP. As the agitator 75, a pump selected from the group consisting of a roller pump, a diaphragm pump, a bellows pump, a vane pump, a centrifugal pump, and a pump formed by a combination of a piston and a cylinder can be used.

[0064] The amount of liquid supplied to and discharged from the liquid feed path LP can be set to a constant amount (for example, 5 ml to 30 ml). Furthermore, the supply of liquid to and discharge of liquid from the liquid feed path LP may be repeated at a constant cycle (for example, 1 to 5 times per second). The amount of liquid supplied to and discharged from the liquid feed path LP may be adjusted by a control signal from the agitator control unit 70C described above or by direct input from the operator. Similarly, the cycle of the supply of liquid to and discharge of liquid from the liquid feed path LP may be adjusted by a control signal from the agitator control unit 70C described above or by direct input from the operator.

[0065] Next, an example of how to use the balloon catheter system 10 configured as above will be described.

[0066] First, the valve 58 is operated to connect the supply device 74 to the liquid feed path LP of the catheter main body 20 via the handle 50. Then, the supply device 74 is operated to introduce liquid into the liquid feed path LP, filling the balloon 25, the liquid feed path LP, and the extension tube 57 with liquid. Next, the inner cylindrical shaft 35 is moved distally (toward the tip) in the longitudinal direction LD relative to the outer cylindrical shaft 30, thereby expanding the balloon 25 as shown in FIG. 3. At this time, the outer cylindrical shaft 30 and the inner cylindrical shaft 35 can be moved relative to each other by operating the first handle portion 51 and the second handle portion 52 of the handle 50. Then, the catheter main body 20 with the balloon 25 expanded is inserted into the body.

[0067] Once the distal end of the catheter main body 20 has been guided to the vicinity of the target site (affected area), the inner cylindrical shaft 35 is moved proximally (toward the base end) in the longitudinal direction LD relative to the outer cylindrical shaft 30 to relax the balloon 25. Next, the valve 58 is operated to connect the supply device 74 to the liquid feed path LP of the catheter main body 20 via the handle 50. Thereafter, the supply device 74 is operated to introduce liquid into the liquid feed path LP, and the balloon 25 is inflated with the liquid, as shown in FIG.

[0068] Next, the valve 58 is operated to disconnect the supply device 74 from the liquid transfer path LP and connect the agitator 75 to the liquid transfer path LP. The agitator 75 is controlled by a control signal from the agitator control unit 70C of the control device 70. The agitator 75 repeatedly supplies a fixed amount of liquid to the liquid transfer path LP and discharges a fixed amount of liquid from the liquid transfer path LP at a fixed cycle. As a result, a fixed amount of liquid is discharged from the liquid transfer path LP into the balloon 25, and a fixed amount of liquid is sucked from the balloon 25 into the liquid transfer path L, repeatedly at a fixed cycle. As a result, the liquid in the balloon 25 is agitated.

[0069] Furthermore, the heating member 40 is controlled by a high-frequency current control unit 70A of the control device 70 to adjust the temperature of the liquid in the balloon 25. Specifically, high-frequency current is applied from the control device 70 between the coil electrode 41 constituting the heating member 40 and a counter electrode 77 placed outside the patient's body. As a result, a high-frequency current is generated between the coil electrode 41 and the counter electrode 77. However, by making the size of the coil electrode 41 significantly larger than the size of the counter electrode, the current density around the coil electrode 41 increases, and the liquid and contrast agent around the coil electrode 41 are heated by Joule heating.

[0070] A temperature sensor 45 is disposed near the coil electrode 41. However, the temperature sensor 45 is disposed not inside the balloon 25 but inside the outer cylindrical shaft 30, which is much thicker than the balloon 25. Therefore, the temperature sensor 45 can be shielded from the high-frequency current by the outer cylindrical shaft 30. This effectively prevents the temperature sensor 45 and the liquid around the temperature sensor 45 from being affected by the high-frequency current and experiencing a local temperature rise. In other words, the temperature sensor 45 can effectively be prevented from detecting an abnormal value.

[0071] In this manner, the liquid in the balloon 25 is heated and stirred. Then, the balloon 25 containing the heated liquid is pressed against the target site, and the target site is ablated. During ablation, the temperature sensor 45 disposed in the liquid feed path LP acquires information regarding the temperature of the liquid in the liquid feed path LP. The acquired information is calculated by the temperature calculation unit 70B of the control device 70. In particular, the temperature calculation unit 70B not only determines the temperature of the liquid in the region where the heat-sensing unit 46 of the temperature sensor 45 is disposed, but also can accurately determine the surface temperature of the balloon 25, as described below. The surface temperature of the balloon 25 determined with high accuracy by the temperature calculation unit 70B is displayed on the display unit 71, for example.

[0072] In other words, by using this balloon catheter system 10, the operator can perform ablation treatment while constantly and accurately monitoring the surface temperature of the balloon 25. Therefore, the operator can proceed with the treatment while adjusting the surface temperature of the balloon 25, which is the most important factor during ablation treatment, to an ideal temperature. As a result, the effectiveness of ablation treatment can be dramatically improved.

[0073] When ablation of the target area is complete, the energy supply to the heating element 40 is stopped. Furthermore, the valve 58 is operated to connect the supply device 74 to the liquid feed path LP of the catheter main body 20 via the handle 50, and the agitator 75 is disconnected from the liquid feed path LP. The supply device 74 is then used to discharge the liquid from the liquid feed path LP, thereby deflating the balloon 25. Next, the second handle portion 52 is operated to expand the deflated balloon 25 as shown in FIG. 3. The catheter main body 20 with the expanded balloon 25 is then removed from the body. This completes the procedure using the balloon catheter system 10.

[0074] Next, we will further explain in detail how the surface temperature of the balloon 25 can be detected with high accuracy by the temperature sensor 45, which has a heat-sensing part 46 arranged between the outer cylindrical shaft 30 and the inner cylindrical shaft 35 and acquires information about the temperature within the liquid delivery path LP.

[0075] First, FIGS. 6 and 7 show the results of a simulation of the temperature distribution inside the balloon 25 using CAE (computer-aided engineering). FIG. 6 shows the simulation results for a state in which the balloon 25 is pressed against the target site along the longitudinal direction LD (hereinafter simply referred to as the "coaxial state"). In the example shown in FIG. 6, the outer cylindrical shaft 30 is aligned in a substantially straight line with the inner cylindrical shaft 35 and the heating element 40 inside the balloon 25. On the other hand, FIG. 7 shows the simulation results for a state in which the balloon 25 is pressed against the target site from a direction inclined with respect to the longitudinal direction LD (hereinafter simply referred to as the "non-coaxial state"). In the example shown in FIG. 7, the outer cylindrical shaft 30 is significantly inclined with respect to the inner cylindrical shaft 35 and the heating element 40 inside the balloon 25.

[0076] The simulation results show that even if the liquid in the balloon 25 is stirred using the stirring device 75, a temperature gradient occurs in the liquid in the balloon 25 due to the placement of the heating element 40. When the coil electrode 41 is used as the heating element 40, the temperature distribution shows a tendency similar to that of the current density distribution. The temperature distribution in the balloon 25 is 5°C or more in the coaxial state shown in FIG. 6 and is approximately 5°C in the non-coaxial state shown in FIG. 7. Because the temperature distribution in the balloon 25 changes depending on factors such as the state in which the balloon 25 is pressed against the target site, it is considered difficult to determine the surface temperature of the balloon 25 based solely on information from a temperature sensor placed near the heating element 40 inside the balloon 25.

[0077] On the other hand, the temperature of the liquid in the region near the distal end 30a of the outer tubular shaft 30 where the temperature sensor 45 is disposed is different from the temperature of the liquid around the heating element 40, but is approximately equal to the surface temperature of the balloon 25, in both the coaxial state shown in Figure 6 and the non-coaxial state shown in Figure 7. First of all, from this point of view, it can be seen that by disposing the heat-sensing part 46 of the temperature sensor 45 between the outer tubular shaft 30 and the inner tubular shaft 35, the surface temperature of the balloon 25 can be detected with high accuracy.

[0078] The temperature gradient centered on the heating element 40 in the balloon 25 can occur not only in the heating element 40 that is expected to be resistance heated by the nichrome wire, but also in the heating element 40 that has a coil electrode 41 to which high frequency current is applied, as has been demonstrated by the simulation results. When high frequency current is applied to the coil electrode 41 and the counter electrode 77 outside the body, a high frequency current flows between the coil electrode 41 and the counter electrode 77. The high frequency current flows in this region because the resistivity of the liquid near the coil electrode 41 is high. (Current flowing) 2 × (resistance value of filling liquid) This Joule heat rapidly decreases as it moves away from the coil electrode 41. (Value of current flowing) 2 This is because the term "(flowing current value)" in "×(resistance value of filling liquid)" attenuates with the square of the distance. For example, in the simulation results of Figure 6, when the liquid temperature near the heating element 40 is 70°C, the balloon surface temperature drops to 65°C or below.

[0079] Next, the inventors of the present invention have also studied and experimented on the influence of agitation by the agitator 75, which repeatedly supplies and discharges the liquid, on the temperature of the liquid. The studies and experiments conducted by the inventors of the present invention will be described below.

[0080] When liquid is supplied from the stirring device 75 to the liquid feed path LP, the liquid is discharged from the distal end 30a of the outer cylindrical shaft 30 into the balloon 25, as shown in FIG. 8 . This stirs the liquid in the balloon 25, and the relatively high-temperature liquid around the heating element 40 moves to the surface of the balloon 25. In particular, in the illustrated example, the distal end 30a of the outer cylindrical shaft 30 opens toward the heating element 40. Therefore, the liquid is discharged from the distal end 30a of the outer cylindrical shaft 30 toward the heating element 40. This allows the heat around the heating element 40 to be efficiently diffused into the balloon 25.

[0081] On the other hand, when the agitator 75 discharges the liquid from the liquid transfer path LP, the liquid in the balloon 25 is sucked into the outer cylindrical shaft 30, as shown in FIG. 9 . At this time, the high-temperature liquid in the balloon 25 flows into the liquid transfer path LP. In particular, the inventors of the present invention have conducted extensive research and found that when liquid is sucked from the generally spherical balloon 25 into the liquid transfer path LP immediately after or in parallel with the ejection of liquid from the outer cylindrical shaft 30 toward the heating element 40 at the center of the balloon 25, if the heating element 40 is located at the center of the generally spherical balloon 25, the liquid flowing along the surface of the balloon 25 tends to easily flow into the liquid transfer path LP. Therefore, according to this embodiment, it is believed that the surface temperature of the balloon 25 can be determined with high accuracy by measuring the temperature of the liquid that has flowed into the liquid transfer path LP.

[0082] From this viewpoint, it is preferable that the heat-sensing portion 46 of the temperature sensor 45 is located near the distal end 30a of the outer cylindrical shaft 30. More specifically, it is preferable that the heat-sensing portion 46 is located in a region of the liquid feed path LP near the distal end 30a of the outer cylindrical shaft 30, into which the liquid in the balloon 25 is drawn when the agitator 75 suctions the liquid. This allows the temperature sensor 45 to detect the temperature of the liquid that was located near the surface of the balloon 25 immediately before the liquid was drawn in by the temperature sensor 45 in the outer cylindrical shaft 30. Specifically, the length DX (see FIG. 2) from the distal end 30a of the outer cylindrical shaft 30 to the temperature sensor 45 is set to the value of the liquid discharge amount [mm 3 ] is the cross-sectional area of ​​the liquid transport path LP [mm 2 It is preferable that the value be equal to or less than the value obtained by dividing by [

[0083] Furthermore, based on the considerations shown in FIGS. 8 and 9, it is expected that the temperature of the liquid detected by the temperature sensor 45 will differ between the state shown in FIG. 8 in which liquid is being discharged into the balloon 25 and the state shown in FIG. 9 in which liquid is being drawn from the balloon 25. Specifically, in the state shown in FIG. 8, the temperature sensor 45 measures the temperature of the liquid not heated by the heating element 40 located proximal to the temperature sensor 45, and therefore detects a lower temperature. On the other hand, in the state shown in FIG. 9, the temperature sensor 45 measures the liquid located inside the balloon 25, and therefore detects a higher temperature. In particular, considering the flow of liquid inside the balloon 25, it can be said that the temperature measured by the temperature sensor 45 in the state shown in FIG. 9 more accurately reflects the temperature of the surface of the balloon 25. These points are also verified by the experimental results of the present inventors, which will be described below.

[0084] Figure 10 shows the balloon catheter system 10 used in an experiment conducted to confirm the effect of stirring by the stirring device 75. In this experiment, the actual measured value of the surface temperature of the balloon 25 was compared with the actual measured value of the temperature of the liquid in the liquid transfer path LP, which was identified based on information acquired by the temperature sensor 45. In this experiment, the balloon catheter system 10 described above and shown in Figure 1 was used. However, the catheter body 20 was provided with an electrode temperature sensor 81 for measuring the temperature immediately adjacent to the coil electrode 41 and a surface temperature sensor 82 for directly measuring the temperature of the surface of the balloon 25.

[0085] As shown in Fig. 11, the electrode temperature sensor 81 is composed of a coil electrode 41 and an electrode temperature sensor wiring 43 sandwiched between the coil electrode 41 and the inner cylindrical shaft 35. The detection result of the electrode temperature sensor 81 is taken in by a temperature calculation unit 70B of the control device 70. A high-frequency current control unit 70A receives the calculation result of the temperature calculation unit 70B and controls the high-frequency current supply to the coil electrode 41 based on the information acquired by the electrode temperature sensor 81. Note that the electrode temperature sensor 81 is not shown in Fig. 10.

[0086] The surface temperature sensors 82 were film-like T-type thermocouples (approximately 5 × 15 mm, approximately 0.1 mm thick). Four surface temperature sensors 82 were attached to the balloon surface with 0.1 mm-thick polyimide tape. As shown in FIG. 11 , the four surface temperature sensors 82 were positioned at the center of the balloon 25 in the longitudinal direction (LD). The four surface temperature sensors 82 were also positioned on the balloon 25 at equal intervals in the circumferential direction around the central axis of the inner cylindrical shaft 35. The four surface temperature sensors 82 were electrically connected to a high-precision temperature logger 83 (manufacturer: HIOKI, model number: LR8431), and the surface temperature was determined by the temperature logger 83 based on information acquired by the surface temperature sensors 82. The average of the values ​​determined by the four surface temperature sensors 82 was used as the actual measured surface temperature of the balloon 25. Note that only two surface temperature sensors 82 are shown in FIG. 10 ; the remaining two are not shown.

[0087] In this experiment, ablation treatment was performed on a simulated living body 99 that simulated the left atrium pulmonary vein opening of a human body. The simulated living body 99 was immersed in physiological saline solution held in a water bath 85. During the experiment, a water bath stirrer 86 was used to stir the physiological saline solution in the water bath 85. A counter electrode 87 that generates a high-frequency current between itself and the coil electrode 41 of the catheter main body 20 was placed on the side wall of the water bath 85. The physiological saline solution in the water bath 85 was prepared by dissolving 0.9 wt% salt (sodium chloride) in water.

[0088] The liquid supplied from the supply device 74 into the liquid feed path LP and the balloon 25 was a physiological saline solution prepared by dissolving 0.9 wt% salt (sodium chloride) in water, with a contrast agent for X-ray imaging further mixed in. The amount of liquid injected into the balloon 25 was set to two levels: 10 mL and 20 mL, which are commonly used in actual ablation treatments. The contrast agent mixed in the liquid was Omnipaque (registered trademark) manufactured by Daiichi Sankyo Co., Ltd. The dilution ratio of the contrast agent was set to two levels: 1:2 and 1:3. Here, the dilution ratio of the contrast agent means "volume of physiological saline:volume of contrast agent."

[0089] Two postures were tested for the region near the distal end of the catheter main body 20, including the balloon 25 pressed against the simulated living body 99: a coaxial state shown in FIG. 12 and corresponding to FIG. 6, and a non-coaxial state shown in FIG. 13 and corresponding to FIG. 7. As shown in FIG. 12, in the coaxial state, the balloon 25 was pressed against the simulated living body 99, which is the target site, in the longitudinal direction LD. On the other hand, as shown in FIG. 13, in the non-coaxial state, the balloon 25 was pressed against the simulated living body 99 from a direction oblique to the longitudinal direction LD. In the non-coaxial state, the inner cylindrical shaft 35 was bent at an angle of 30° to 45°. In the non-coaxial state, the shape of the balloon 25 was not symmetrical about the outer cylindrical shaft 30 and the inner cylindrical shaft 35.

[0090] The agitator 75 was designed to supply and discharge the same liquid as that supplied into the liquid feed path LP and the balloon 25 to the liquid feed path LP at a drive frequency of 2 Hz. The amount of liquid supplied from the agitator 75 to the liquid feed path LP per one time and the amount of liquid discharged from the liquid feed path LP to the agitator 75 per one time were 780 mm 3 The cross-sectional area of ​​the liquid delivery path LP in the catheter body 20 used was 4.76 mm 2 On the other hand, the length DX (see FIG. 2) from the distal end 30a of the outer cylindrical shaft 30 to the temperature sensor 45 was set to 150 mm.

[0091] Based on the trends described above with reference to FIGS. 8 and 9, it is expected that the temperature fluctuation of the liquid in the liquid feed path LP will take on local maximum and minimum values ​​at intervals equal to the drive frequency of the agitator 75. More specifically, when the agitator 75 discharges liquid from the liquid feed path LP and the liquid is drawn into the liquid feed path LP from the balloon 25, the temperature of the heated high-temperature liquid is measured as a local maximum. Furthermore, when the agitator 75 supplies liquid to the liquid feed path LP and the liquid is ejected from the balloon 25 into the liquid feed path LP, the temperature of the low-temperature liquid remaining in the liquid feed path LP is measured as a local minimum. Therefore, in order to grasp the temperature fluctuation of the liquid in the liquid feed path LP, it is preferable to obtain the output of the temperature sensor 45 at intervals shorter than the drive frequency of the agitator 75. In this experiment, the drive frequency of the agitator 75 was set to 2 Hz, so it was expected that the temperature fluctuation would repeatedly take on local maximum values ​​every 0.5 seconds. Therefore, the output of the temperature sensor 45 was measured at intervals sufficiently shorter than 0.5 seconds, specifically, at intervals of 10 milliseconds. That is, the information from the temperature sensor 45 was calculated at time intervals of 1 / 50 of the drive period of the agitator 75 to calculate the liquid temperature in the liquid transfer path LP.

[0092] High frequency current control section 70A of control device 70 controlled the high frequency current supplied to coil electrode 41 so that the temperature of the liquid around coil electrode 41 was 70° C. The driving power was set to 150W.

[0093] As described above, simulation tests were conducted on the balloon catheter system 10 applied to the simulated living body 99 under eight different conditions, with the amount of liquid filled in the balloon 25, the dilution rate of the contrast agent, and the method of pressing the balloon 25 each being changed between two levels. The temperature measurements taken at 10-millisecond intervals by the temperature sensor 45 in each experiment, along with the temperature measurements taken by the surface temperature sensor 82, are shown in the graphs of FIGS. 14 to 21. In the graphs shown in FIGS. 14 to 21, the vertical axis represents temperature (°C), and the horizontal axis represents time (s) from the start of energization of the coil electrode 41 and the counter electrode 87. The graphs shown in FIGS. 14 to 21 show the measurement results from the start of energization of the high-frequency power until the surface temperature of the balloon 25 has sufficiently stabilized, specifically, from 150 to 200 seconds after the start of energization.

[0094] 14 to 21, the liquid temperature in the liquid transfer path LP measured by the temperature sensor 45 fluctuates with a period of approximately 0.5 seconds. This temperature fluctuation period is well matched to the period of liquid supply and discharge due to the 2 Hz drive frequency of the agitator 75. Furthermore, the actual surface temperature of the balloon 25 measured by the surface temperature sensor 82 is approximately the same as the maximum value of the temperature fluctuation measured by the temperature sensor 45. From this point of view, the temperature calculation unit 70B of the control device 70 can identify the maximum value of the temperature fluctuation line connecting the actual measured values ​​by the temperature sensor 45 (or the envelope connecting the maximum values) as the surface temperature of the balloon 25. Alternatively, the temperature calculation unit 70B of the control device 70 can first identify a triangular wave-shaped approximation curve from the actual measured values ​​by the temperature sensor 45, and then identify the maximum value of the temperature fluctuation approximation curve (or the envelope connecting the maximum values) as the surface temperature of the balloon 25. The surface temperature of the balloon 25 estimated in this way from the liquid temperature inside the outer tube shaft 30 had extremely high accuracy, and the error from the actual measured value measured by the surface temperature sensor 82 was approximately ±1°C.

[0095] Furthermore, the temperature of the liquid in the liquid feed path LP measured by the temperature sensor 45 fluctuated within a range of approximately 6°C to 9°C. Therefore, the temperature calculation unit 70B of the control device 70 may specify the surface temperature of the balloon 25 as a value obtained by adding a specific value between 3°C and 5°C to the average value of the liquid temperature in the liquid feed path LP actually measured by the temperature sensor 45. The surface temperature of the balloon 25 estimated from the liquid temperature in the outer cylindrical shaft 30 in this way also had extremely high accuracy, with an error of approximately ±1°C from the actual value measured by the surface temperature sensor 82.

[0096] 14 to 21, the following findings were obtained: First, regardless of the shape of the balloon, i.e., whether it was coaxial or non-coaxial, regardless of the amount of liquid filled in balloon 25, or regardless of the contrast agent dilution rate of the liquid filled in balloon 25, the maximum value (or the envelope connecting the maximum values) of the liquid temperature fluctuation in liquid feed path LP measured by temperature sensor 45 matched with the actual value of the balloon surface temperature measured by surface temperature sensor 82 with a high accuracy of approximately ±1°C.

[0097] Second, there is a temperature difference of approximately 5°C between the coaxial and non-coaxial states of the balloon surface temperature. That is, when the shape of the balloon is symmetrical with respect to the outer cylindrical shaft 30 and the inner cylindrical shaft 35, the liquid inside the balloon is well agitated, and the surface temperature of the balloon 25 increases. Conversely, when the shape of the balloon 25 is asymmetrical with respect to the outer cylindrical shaft 30 and the inner cylindrical shaft 35, the liquid inside the balloon is not agitated sufficiently, and the surface temperature of the balloon 25 does not increase. This tendency was observed regardless of the amount of liquid filled in the balloon 25 or the contrast agent dilution rate.

[0098] Regarding the amount of liquid filled in balloon 25, there was a tendency for the balloon surface temperature to decrease by about 2°C when the filling amount increased from 10 ml to 20 ml. However, regardless of the amount of liquid filled in balloon 25, the maximum value of the liquid temperature fluctuation in liquid feed path LP measured by temperature sensor 45 (or the envelope connecting the maximum values) agreed with a high accuracy of about ±1°C relative to the actual value of the balloon surface temperature measured by surface temperature sensor 82. Similarly, regardless of whether the contrast agent dilution ratio was 1:2 or 1:3, the maximum value of the liquid temperature fluctuation in liquid feed path LP measured by temperature sensor 45 (or the envelope connecting the maximum values) agreed with a high accuracy of about ±1°C relative to the actual value of the balloon surface temperature measured by surface temperature sensor 82, regardless of whether the contrast agent dilution ratio was 1:2 or 1:3.

[0099] To summarize the experimental results shown in FIGS. 14 to 21, the liquid temperature measured by the temperature sensor 45 reached a minimum value in response to the supply of liquid from the agitator 75 to the liquid feed path LP, and reached a maximum value in response to the discharge of liquid from the liquid feed path LP to the agitator 75. Continuously monitoring the peak (maximum) value of the liquid temperature detected by the temperature sensor 45 enabled the balloon surface temperature to be determined with high accuracy. Specifically, regardless of whether the balloon shape was coaxial or non-coaxial, and regardless of the amount of liquid filled in the balloon 25 or the contrast agent dilution rate, the maximum value (or the envelope connecting the maximum values) of the liquid temperature fluctuations in the liquid feed path LP measured by the temperature sensor 45 matched with a high accuracy of approximately ±1°C to the actual balloon surface temperature measured by the surface temperature sensor 82. Therefore, the surface temperature of the balloon 25, which is of utmost importance during ablation treatment, could be accurately detected, displayed, and used for control.

[0100] 14 to 21, the liquid temperature fluctuation in the liquid feed path LP reached maximum and minimum values ​​at the same cycle as the drive cycle of the agitator 75. The liquid temperature measured by the temperature sensor 45 reached minimum values ​​in response to the supply of liquid from the agitator 75 to the liquid feed path LP, and reached maximum values ​​in response to the discharge of liquid from the liquid feed path LP to the agitator 75. Continuously monitoring the peak values ​​(maximum values) of the liquid temperature detected by the temperature sensor 45 enabled the balloon surface temperature to be determined with high accuracy. Specifically, regardless of whether the balloon shape was coaxial or non-coaxial, and regardless of the amount of liquid filled in the balloon 25 or the contrast agent dilution rate, the maximum values ​​(or the envelope connecting the maximum values) of the liquid temperature fluctuation in the liquid feed path LP measured by the temperature sensor 45 were able to match the actual balloon surface temperature measured by the surface temperature sensor 82 with a high accuracy of approximately ±1°C. Therefore, the surface temperature of the balloon 25, which is the most important factor during ablation treatment, could be accurately detected, displayed, and used for control.

[0101] Furthermore, according to the above experimental results, in order to grasp the temperature fluctuations of the liquid in the liquid feed path LP, it is preferable to specify the liquid temperature by acquiring detection results (information acquired by the temperature sensor 45) from the temperature sensor 45 at time intervals that are shorter than the drive period of the agitator 75. It is more preferable to specify the liquid temperature by acquiring detection results from the temperature sensor 45 at time intervals that are shorter than half the drive period of the agitator 75. In this case, it is possible to detect the temperature at least once while the liquid temperature in the liquid feed path LP is decreasing, and it is also possible to detect the temperature at least once while the liquid temperature in the liquid feed path LP is increasing. Therefore, acquiring the output from the temperature sensor 45 at time intervals that are shorter than half the drive period of the agitator 75 to specify the liquid temperature is useful in grasping the average temperature of the liquid in the liquid feed path LP.

[0102] Similarly, it is preferable to specify the liquid temperature by obtaining detection results from the temperature sensor 45 at intervals less than 1 / 4 of the drive period of the agitator 75. In this case, the temperature can be detected at least twice while the liquid temperature in the liquid feed path LP is decreasing, and the temperature can be detected at least twice while the liquid temperature in the liquid feed path LP is increasing. Therefore, obtaining output from the temperature sensor 45 at time intervals less than 1 / 4 of the drive period of the agitator 75 to specify the liquid temperature is useful in understanding the profile of temperature fluctuations of the liquid in the liquid feed path LP.

[0103] Furthermore, in order to grasp the maximum value in the temperature fluctuation of the liquid in the liquid feed path LP, which is an indicator of the surface temperature of the balloon 25, the shorter the time interval for obtaining the detection result from the temperature sensor 45 and specifying the liquid temperature, the more accurate the detection accuracy. From this point of view, the time interval for obtaining the output of the temperature sensor 45 and specifying the liquid temperature is preferably less than 1 / 5 of the drive cycle of the agitator 75, more preferably less than 1 / 8 of the drive cycle of the agitator 75, and even more preferably less than 1 / 10 of the drive cycle of the agitator 75, and it is even more preferable to specify the liquid temperature continuously.

[0104] The "maximum" in the temperature fluctuation of the liquid calculated from the information acquired by the temperature sensor 45 refers to the temperature (°C) value when the temperature fluctuation over time changes from increasing to decreasing. The "maximum" may be identified from a polygonal linear fluctuation obtained by connecting temperature values ​​calculated at predetermined time intervals with a straight line, without being bound by the strict mathematical meaning, or from a continuous linear fluctuation (e.g., a triangular wave-like fluctuation) obtained by curve approximating the temperature values ​​calculated at predetermined time intervals. Similarly, the "minimum" in the temperature fluctuation of the liquid calculated from the information acquired by the temperature sensor 45 refers to the temperature (°C) value when the temperature fluctuation over time changes from decreasing to increasing. The "minimum" may be identified from a polygonal linear fluctuation obtained by connecting temperature values ​​calculated at predetermined time intervals with a straight line, without being bound by the strict mathematical meaning, or from a continuous linear fluctuation (e.g., a triangular wave-like fluctuation) obtained by curve approximating the temperature values ​​calculated at predetermined time intervals. Furthermore, the envelope curve connecting the maximum values ​​in the temperature fluctuation of a liquid as used in this specification means a line that sequentially connects the maximum values ​​of the temperature fluctuation in the form of a broken line or a continuous line, without being bound by the strict mathematical meaning.

[0105] Below, several specific examples included in the above-described embodiment will be described. In the following description of the specific examples and the drawings used in the description of the specific examples, parts that can be configured in the same way as in the above description will be designated by the same reference numerals as those used for the corresponding parts in the above description, and duplicated descriptions will be omitted.

[0106] <First specific example> (Production of balloon-equipped ablation catheter system) A polyurethane balloon 25 with a diameter of 30 mm and a thickness of 20 μm was produced by blow molding using a polyurethane tube. A polyurethane tube with an outer diameter of 3.6 mm, an inner diameter of 3.0 mm, and a length of 1000 mm was molded to form the outer cylindrical shaft 30. In addition, a polyamide tube with an outer diameter of 1.6 mm, an inner diameter of 1.2 mm, and a length of 1100 mm was molded to form the inner cylindrical shaft 35. A handle 50 was connected to the rear end (proximal end) of the outer cylindrical shaft 30 and the inner cylindrical shaft 35.

[0107] The wiring 42 was a copper wire with a diameter of 0.26 mm and a length of 1700 mm, coated with an electrically insulating coating made of perfluoroalkoxyalkane. 200 mm of the electrically insulating coating on the wiring 42 was stripped away, and the stripped wiring 42 was wound in a coil around the inner cylindrical shaft 35, starting from a position 25 mm from the tip (distal end) of the inner cylindrical shaft 35, to form a coil electrode 41 for applying high-frequency current. Polyurethane tubes were fixed by thermal welding to positions on the inner cylindrical shaft 35 adjacent to the coil electrode 41 on both sides in the longitudinal direction LD. The polyurethane tubes were provided to prevent the coil electrode 41 from shifting position on the inner cylindrical shaft 35.

[0108] A temperature sensor 45 was installed on the inner surface 10 mm from the tip (distal end) of the outer cylindrical shaft 30. A heat-shrinkable tube was placed on the inner cylindrical shaft 35 as fixing means 48. The heat-shrinkable tube was heated on the inner cylindrical shaft 35 so that the lead wires 47 of the temperature sensor 45 passed through the heat-shrinkable tube. The lead wires 47 were fixed to the inner cylindrical shaft 35 by the heat-shrinkable tube, which shrunk due to heating. The heat-sensitive part 46 of the temperature sensor 45, which was attached to the inner cylindrical shaft 35 using the fixing means 48, was separated from the outer cylindrical shaft 30 and the inner cylindrical shaft 35.

[0109] The tip (distal) portion of the inner cylindrical shaft 35 was inserted into the balloon 25, and the rear end (proximal end) of the balloon 25 was fixed to the tip (distal end) of the outer cylindrical shaft 30 by heat welding. In addition, the tip (distal end) of the balloon 25 was fixed to the inner cylindrical shaft 35 by heat welding.

[0110] The rear end of the wiring 42 electrically connected to the coil electrode 41 was passed through the liquid feed path LP between the outer cylindrical shaft 30 and the inner cylindrical shaft 35 and inside the handle 50, and was electrically connected to the high-frequency current control unit 70A of the control device 70. Similarly, the lead wire 47 of the temperature sensor 45 was passed through the liquid feed path LP and inside the handle 50, and was electrically connected to the temperature calculation unit 70B of the control device 70.

[0111] A valve 58 was attached to a branching portion of the handle 50 via an extension tube 57. A three-way stopcock was used as the valve 58. Furthermore, the valve 58 was connected to the agitator 75 via the extension tube 57. This created a path for transmitting the vibrations applied to the liquid from the agitator 75 to the liquid inside the balloon 25 via the extension tube 57, the handle 50, and the liquid feed path LP, thereby agitating the liquid.

[0112] (Control system and control method) In the above-described experiment using the balloon catheter system of FIG. 10 , information (electric potential) acquired by electrode temperature sensor 81 was input to temperature calculation unit 70B and high-frequency current control unit 70A of control device 70. Based on the temperature difference between the surface temperature of balloon 25 and the ambient temperature of coil electrode 41 being approximately 5°C, the surface temperature of balloon 25 was controlled to 65°C by adjusting the application of high-frequency voltage to coil electrode 41 to control the output of coil electrode 41 so that the liquid temperature around coil electrode 41, as determined from the information acquired by electrode temperature sensor 81, would be 70°C. Meanwhile, in the balloon catheter system 10 according to the first specific example, as shown in FIG. 22 , information (electric potential) acquired by temperature sensor 45 was input to temperature calculation unit 70B of control device 70. In temperature calculation unit 70B, the application of high-frequency voltage to coil electrode 41 from high-frequency current control unit 70A was adjusted to control the output of coil electrode 41 so that the surface temperature of balloon 25 calculated by temperature calculation unit 70B based on the information acquired by temperature sensor 45 would be 65°C. As described above, the temperature calculation unit 70B outputs the maximum value (peak value) of the temperature fluctuation of the liquid in the liquid transfer path LP, which is identified from the information acquired by the temperature sensor 45, as the surface temperature of the balloon 25. In the balloon catheter system 10 shown in Fig. 22, the high-frequency power control unit 70A, temperature calculation unit 70B, and agitation device control unit 70C are provided in a single housing. The high-frequency power control unit 70A, temperature calculation unit 70B, and agitation device control unit 70C may share at least a portion of their configuration (hardware).

[0113] A specific control method for the system according to the first example will be explained using the circuit block diagram shown in Fig. 23. The AC power input is input to a full-wave rectifier circuit via a power line filter to prevent the emission of power noise from the high-frequency power circuit. On the other hand, a switching regulator is built in to obtain a stabilized DC power supply for the logic circuits, including the CPU and FPGA.

[0114] The current output from the full-wave rectifier circuit is converted into a higher voltage direct current (usually 400V to 500V) by the next stage DC-DC converter, and is then converted into a square wave alternating current (usually with a frequency of 200KHz to 3MHz) by an RF switching circuit, which is a high-speed chopper circuit using a MOSFET (not shown).This conversion into alternating current makes it harmless to humans even if a current is passed through the human body between the coil electrode 41 of the heating member 40 and the counter electrode 77.

[0115] The information detected by the temperature sensor 45 is input to the temperature measurement circuit via lead wires 47 passing through the catheter body 20, and then input to a logic circuit including a CPU and FPGA that performs signal processing and control via an AD conversion circuit. The signal processing described below extracts the maximum value of the temperature fluctuation of the liquid in the liquid delivery path LP identified from the information acquired by the temperature sensor 45, as well as the envelope connecting the maximum values. This enables accurate detection and monitoring of the surface temperature of the balloon 25. Furthermore, the RF switching circuit is controlled so that the monitored surface temperature of the balloon 25 is always maintained at a desired temperature.

[0116] There are various methods for extracting an envelope curve connecting the maximum values ​​of the temperature fluctuation of the liquid in the liquid feed path LP identified from the information acquired by the temperature sensor 45. In the first specific example, the method shown in the flowchart of FIG. 24 was used. That is, the output from the temperature sensor 45 was converted into a digital temperature signal at 1-millisecond intervals by an AD conversion circuit. The output (referred to as T) of the temperature sensor 45, which was converted into a digital signal at 1-millisecond intervals, had its maximum value (referred to as MAX) recorded at the vibration period (500-millisecond interval) of the agitator 75 and used as a temperature control signal. That is, the maximum value used for the temperature control signal in the process shown in FIG. 24 was the maximum value in the broken line of temperature fluctuation obtained by connecting the liquid temperature values ​​in the liquid feed path LP periodically identified by the information from the temperature sensor 45 with a straight line, and this maximum value was used for control as the surface temperature of the balloon 25.

[0117] The current flowing between the coil electrode 41 and the opposing electrode 77 is constantly monitored and input into a logic circuit including a CPU and FPGA via an impedance measurement circuit and an AD conversion circuit, and a fail-safe mechanism is adopted that quickly turns off the high-frequency current if an unexpected situation occurs on the human body or during treatment when the high-frequency current is being applied.

[0118] In order to equalize the temperature inside the balloon, the operation of the agitator 75, which vibrates and agitates the liquid through the liquid supply path LP, as well as system settings and various interfaces with the operator (surgeon), are all performed by signals from logic circuits including a CPU and FPGA.

[0119] The experiment shown in FIG. 10 was conducted using the balloon catheter system 10 according to the first specific example described above. The simulated living body 99, water bath 85, water bath agitator 86, counter electrode 87, and surface temperature sensor 82 were the same as those used in the previous experiment. However, without using the electrode temperature sensor 81, high-frequency current was applied to the coil electrode 41 and counter electrode 87 to control the surface temperature of the balloon 25, estimated from the detection results of the temperature sensor 45, to 66.0°C. Other conditions for high-frequency current application included a frequency of 1.8 MHz and an applied high-frequency power of 150 W. The graph in FIG. 25 shows the temperature fluctuations of the liquid in the liquid delivery path LP determined from the information acquired by the temperature sensor 45 and the surface temperature fluctuations of the balloon 25 measured by the surface temperature sensor 82 during this experiment. As shown in FIG. 25, the maximum value of the temperature fluctuations of the liquid in the liquid delivery path LP determined from the information acquired by the temperature sensor 45 matched with extremely high accuracy the actual surface temperature of the balloon 25. Therefore, by controlling the high frequency current supply with the surface temperature of the balloon 25 as the control target, it is possible to set the surface temperature of the balloon 25 to a target value.

[0120] <Second specific example> Next, a second specific example of a balloon catheter system 10 is shown in FIG. 26 . The balloon catheter system 10 of the second specific example includes an electrode temperature sensor 81 mounted on the inner cylindrical shaft 35. The electrode temperature sensor 81 is a thermocouple, with one electrode being a coil electrode 41 mounted on the inner cylindrical shaft 35 and the other electrode being a conductive wire made of a different material from the coil electrode 41 but electrically connected to the coil electrode 41. In this balloon catheter system 10, the high-frequency current control unit 70A of the control device 70 controls the application of high-frequency current to the coil electrode 41 based on temperature information acquired by the electrode temperature sensor 81. This balloon catheter system 10 also includes a temperature sensor 45 disposed in the liquid supply path LP. This allows the operator (surgeon) to determine the surface temperature of the balloon 25, as determined above, from the information acquired by the temperature sensor 45. The determined surface temperature of the balloon 25 is displayed on the display unit 71 of the control device 70, allowing the operator to determine the surface temperature of the balloon 25 during surgery. The display unit 71 of the control device 70 also displays the liquid temperature around the heating member 40, which is determined from the detection result of the electrode temperature sensor 81.

[0121] The balloon catheter system 10 of the second specific example differs from the balloon catheter system 10 of the first specific example in that it includes two types of temperature sensors: an electrode temperature sensor 81 and a temperature sensor 45. In the second specific example, the surface temperature of the balloon 25 determined as described above from information acquired by the temperature sensor 45 can be displayed on the display unit 71 of the control device 70. In the second specific example, a digital temperature display is used as a means for displaying the surface temperature of the balloon 25. Meanwhile, the output from the heating element 40 can be controlled based on the temperature value determined by the electrode temperature sensor 81. Alternatively, the output from the heating element 40 can be controlled based on the temperature value determined by a sensor selected from the electrode temperature sensor 81 and the temperature sensor 45.

[0122] In the balloon catheter system 10 of the second specific example, the temperature of the liquid surrounding the coil electrode 41, which functions as the heating element 40, is controlled by the balloon catheter system 10 to a desired set temperature, so that the output of the heating element 40, which serves as the heating means, can be directly controlled, eliminating the need to determine the maximum value and envelope of the temperature fluctuation of the liquid identified from the output of the temperature sensor 45 and control the ablation catheter system using that signal, as was done in the first specific example. Therefore, it is possible to control the balloon catheter system 10 without affecting the control of the balloon catheter system 10 due to delays in signal processing in the temperature detection circuit, etc.

[0123] Furthermore, the balloon catheter system 10 of the second specific example is equipped with a display unit 71 that determines the maximum value and envelope of the temperature fluctuation of the liquid identified from the output of the temperature sensor 45 and displays them as digital or analog waveforms, thereby making it possible to notify the surgeon of the balloon surface temperature in real time.

[0124] <Third specific example> 27 shows a balloon catheter system 10 according to a third specific example. In the balloon catheter system 10 according to the third specific example, similar to the first specific example, information acquired by the temperature sensor 45 is input to the temperature calculation unit 70B of the control device 70, and the high-frequency current control unit 70A controls the high-frequency current supplied to the coil electrode 41 based on the liquid temperature determined from the information acquired by the temperature sensor 45, thereby controlling the output of the coil electrode 41. As in the first specific example, the maximum value of the liquid temperature fluctuation determined from the output of the temperature sensor 45 and the envelope connecting the maximum values ​​can be detected at a sufficiently fast speed, and the surface temperature of the balloon 25 can be determined with high accuracy from the temperature sensor 45.

[0125] On the other hand, the third specific example, like the second specific example, has an electrode temperature sensor 81 provided on the inner cylindrical shaft 35. A temperature calculation unit 70B of the control device 70 calculates the temperature of the liquid around the coil electrode 41 from information acquired by the electrode temperature sensor 81. This allows the control device 70 to monitor for the occurrence of a situation in which the liquid temperature identified based on information from the electrode temperature sensor 81 exceeds the boiling point of the liquid. When the liquid in the balloon 25 exceeds its boiling point, undesirable air bubbles are generated within the balloon 25. A high-frequency current control unit 70A of the control device 70 adjusts the high-frequency current applied to the coil electrode 41 to control the output of the coil electrode 41 so that air bubbles are not generated within the balloon 25.

[0126] <Fourth Specific Example> The fourth specific example has the same device and electrical circuit configuration as the balloon catheter system 10 according to the first specific example. However, the fourth specific example differs from the first specific example in the method for determining the surface temperature of the balloon 25 from the information acquired by the temperature sensor 45. In the fourth specific example, the average temperature of the liquid in the liquid delivery path LP determined from the information acquired by the temperature sensor 45 is calculated, and the value obtained by adding an offset value to this average value is determined as the surface temperature of the balloon 25.

[0127] According to the experimental results of the inventors described above, the fluctuation range of the liquid temperature in the liquid feed path LP measured by the temperature sensor 45 was approximately 6°C to 9°C. Therefore, the temperature calculation unit 70B of the control device 70 can specify the surface temperature of the balloon 25 by adding a specific value between 3°C and 5°C to the average value of the liquid temperature in the liquid feed path LP actually measured by the temperature sensor 45. The surface temperature of the balloon 25 estimated from the average value of the liquid temperature in the outer cylindrical shaft 30 in this manner also has extremely high accuracy, with an error of approximately ±1°C from the actual value measured by the surface temperature sensor 82. In the fourth specific example, the high-frequency current supplied to the coil electrode 41 is adjusted to control the output from the coil electrode 41 based on the surface temperature of the balloon 25 thus specified.

[0128] Figure 27 shows a flowchart for calculating the average value of the liquid temperature in the liquid supply path LP, calculated from information from the temperature sensor 45 used in the fourth specific example. The output of the temperature sensor 45 was converted to a digital signal at 1-millisecond intervals using an AD conversion circuit and captured as the shaft temperature sensor output (T). The output (T) of the temperature sensor 45 was calculated as a moving average every second, which was designated Tav. Furthermore, since the average value of the output of the temperature sensor 45 has an offset of approximately -4°C from the maximum value of the output of the temperature sensor 45, the value obtained by adding 4°C to Tav was used as the balloon surface temperature Tsu. The other control methods were the same as in the first specific example. Note that the method in the flowchart used here is merely one example for calculating the average value of the liquid temperature in the liquid supply path LP measured by the temperature sensor 45.

[0129] In the embodiment described above, the balloon catheter 15 includes a balloon 25, an outer cylindrical shaft 30 connected to the proximal end 25b of the balloon 25, an inner cylindrical shaft 35 passing through the outer cylindrical shaft 30, extending into the balloon 25 and connecting to the distal end 25a of the balloon 25, and forming a liquid feed path LP between the outer cylindrical shaft 30 and the inner cylindrical shaft 35, which leads into the balloon 25, and a heating element 40 disposed within the balloon 25 for heating the liquid within the balloon 25. In this balloon catheter 15, the surface temperature of the balloon 25 is strongly correlated with the temperature within the liquid feed path LP within the outer cylindrical shaft 30, which draws the liquid within the balloon 25. In particular, the liquid temperature in the region of the liquid feed path LP near the distal end 30a of the outer cylindrical shaft 30 is strongly correlated with the surface temperature of the balloon 25. In the embodiment described above, a temperature sensor 45 is provided between the outer cylindrical shaft 30 and the inner cylindrical shaft 35 to acquire information regarding the temperature within the liquid feed path LP. Because the surface temperature of the balloon 25 has a strong correlation with the temperature of the liquid in the liquid feed path LP into which the liquid in the balloon 25 flows, the surface temperature of the balloon 25 can be detected with high accuracy based on information acquired by the temperature sensor 45 in the liquid feed path LP. This significantly improves the effectiveness of ablation treatment using this balloon catheter 15. Furthermore, unlike the balloon 25, which undergoes significant deformation due to expansion and contraction, the outer cylindrical shaft 30 and inner cylindrical shaft 35 allow the temperature sensor 45 to be stably held within the liquid feed path LP.

[0130] In one specific example of the above-described embodiment, the length along the longitudinal direction LD from the distal end 30a of the outer cylindrical shaft 30 to the temperature sensor 45 is 5 mm or more and 150 mm or less. According to this specific example, when liquid is repeatedly discharged from the liquid feed path LP into the balloon 25 and sucked from the inside of the balloon 25 into the liquid feed path LP, the liquid inside the balloon 25, particularly the liquid near the surface of the balloon 25, is drawn into the outer cylindrical shaft 30, and the surface temperature of the balloon 25 can be evaluated with high accuracy by the temperature sensor 45 inside the outer cylindrical shaft 30.

[0131] In one specific example of the above-described embodiment, the temperature sensor 45 is attached to the inner cylindrical shaft 35, which is movable relative to the outer cylindrical shaft 30. Even when the inner cylindrical shaft 35 moves distally relative to the outer cylindrical shaft 30 and the balloon 25 is expanded, the temperature sensor 45 remains positioned within the liquid feed path LP between the outer cylindrical shaft 30 and the inner cylindrical shaft 35. According to this specific example, the temperature sensor 45 can be positioned within the liquid feed path LP between the outer cylindrical shaft 30 and the inner cylindrical shaft 35, regardless of the relative position of the inner cylindrical shaft 35 with respect to the outer cylindrical shaft 30. Therefore, the temperature sensor 45 can be stably protected by the outer cylindrical shaft 30, regardless of the relative position of the inner cylindrical shaft 35 with respect to the outer cylindrical shaft 30.

[0132] In one specific example of the above-described embodiment, the temperature sensor 45 may be attached to the outer cylindrical shaft 30. According to this specific example, the temperature sensor 45 is located inside the outer cylindrical shaft 30, regardless of the relative position of the inner cylindrical shaft 35 with respect to the outer cylindrical shaft 30. Therefore, the temperature sensor 45 can be stably protected by the outer cylindrical shaft 30, regardless of the relative position of the inner cylindrical shaft 35 with respect to the outer cylindrical shaft 30.

[0133] In one specific example of the above-described embodiment, the temperature sensor 45 includes a heat-sensing part 46 and a lead wire 47 connected to the heat-sensing part 46, the lead wire 47 is fixed to the inner cylindrical shaft 35 or the outer cylindrical shaft 30, and the heat-sensing part 46 is spaced apart from the inner cylindrical shaft 35 and the outer cylindrical shaft 30. According to this specific example, the temperature sensor 45 can be attached to the inner cylindrical shaft 35 or the outer cylindrical shaft 30 via the lead wire 47. On the other hand, since the heat-sensing part 46 is maintained in a non-contact state with the inner cylindrical shaft 35 and the outer cylindrical shaft 30, which have large heat capacities, it is possible to quickly and accurately grasp the temperature of the liquid in the liquid transfer path LP.

[0134] In one specific example of the above-described embodiment, the control device 70 first identifies temperature fluctuations of the liquid in the liquid feed path LP from information acquired by the temperature sensor 45, and then identifies the surface temperature of the temperature sensor 45 based on the identified temperature fluctuations. According to this specific example, as demonstrated in the above-described experiment, the surface temperature of the balloon 25 can be detected with high accuracy, thereby improving the effectiveness of the ablation treatment.

[0135] In one specific example of the above-described embodiment, the control device 70 first identifies the temperature fluctuation of the liquid in the liquid feed path LP from the information acquired by the temperature sensor 45, and then identifies the maximum value of the identified temperature fluctuation as the surface temperature of the balloon 25. According to this specific example, as demonstrated in the above-described experiment, the surface temperature of the balloon 25 can be detected with high accuracy, thereby improving the effectiveness of the ablation treatment.

[0136] In one specific example of the above-described embodiment, the balloon catheter system 10 includes an agitator 75 that repeatedly supplies and discharges liquid to and from the liquid feed path LP at a constant cycle. The controller 70 acquires information from the temperature sensor 45 at time intervals shorter than the constant cycle and performs calculations. According to this specific example, as demonstrated in the above-described experiment, the surface temperature of the balloon 25 can be detected with high accuracy, thereby improving the effectiveness of ablation treatment.

[0137] In one specific example of the above-described embodiment, the balloon catheter system 10 includes a stirring device 75 that repeatedly supplies and discharges a predetermined amount of liquid to and from the liquid feed path LP. The length [mm] along the longitudinal direction LD from the distal end 30a of the outer cylindrical shaft 30 to the temperature sensor 45 is a predetermined amount [mm 3 ] is the cross-sectional area of ​​the liquid transfer path [mm 2]. According to this specific example, when liquid is repeatedly discharged into the balloon 25 via the liquid feed path LP and suctioned from the balloon 25, the liquid near the surface of the balloon 25 can be drawn up to the area around the temperature sensor 45 in the outer cylindrical shaft 30. This allows the temperature sensor 45 in the outer cylindrical shaft 30 to evaluate the surface temperature of the balloon 25 with high accuracy.

[0138] In one specific example of the above-described embodiment, wiring 42 electrically connects the heating element 40 and the control device 70, and the temperature sensor 45 includes a lead wire 47 electrically connects the temperature sensor 45 to the control device 70. The inner cylindrical shaft 35 is movable relative to the outer cylindrical shaft 30. Both the wiring 42 and the lead wire 47 are attached to one of the outer cylindrical shaft 30 and the inner cylindrical shaft 35, and extend through the liquid transfer path LP. This specific example effectively prevents the wiring 42 and the lead wire 47, which both extend through the liquid transfer path LP, from becoming entangled when the inner cylindrical shaft 35 and the outer cylindrical shaft 30 move relative to each other. This allows the heating element 40 to stably adjust the temperature of the liquid in the balloon 25, and also allows the surface temperature of the balloon 25 to be stably monitored.

[0139] In the embodiment described above, the balloon catheter 15 includes the balloon 25, the outer cylindrical shaft 30 connected to the proximal end 25b of the balloon 25, the inner cylindrical shaft 35 passing through the outer cylindrical shaft 30, extending into the balloon 25 and connecting to the distal end 25a of the balloon 25, and forming a liquid supply path LP between the outer cylindrical shaft 30 and the inner cylindrical shaft 35 leading to the inside of the balloon 25, and the coil electrode 41 disposed within the balloon 25 and energized with high frequency to apply a high-frequency current to the liquid within the balloon 25 to heat the liquid. According to this embodiment, the liquid can be heated by applying a high-frequency current to the liquid. Meanwhile, the temperature sensor 45 is shielded from the high-frequency current, and therefore the temperature of the liquid within the balloon 25 can be detected with high accuracy, thereby improving the effectiveness of ablation treatment.

[0140] Although one embodiment has been described using a number of examples, these examples are not intended to limit the embodiment. The embodiment described above can be implemented in various other examples, and various omissions, substitutions, changes, additions, etc. can be made without departing from the spirit of the embodiment.

[0141] For example, in the above-described embodiment, one liquid transfer path LP is provided between the outer cylindrical shaft 30 and the inner cylindrical shaft 35, and liquid is supplied to the balloon 25 and discharged from the balloon 25 via this one liquid transfer path LP. However, this is not limited to this example, and two or more liquid transfer paths LP may be provided between the outer cylindrical shaft 30 and the inner cylindrical shaft 35. In this modification, the two or more liquid transfer paths LP may include a liquid supply path for supplying liquid into the balloon 25 and a liquid discharge path for discharging liquid from the balloon 25. In this modification, the surface temperature of the balloon 25 can also be determined with high accuracy by the temperature sensor 45 disposed in the liquid discharge path. [Industrial Applicability]

[0142] INDUSTRIAL APPLICABILITY The present invention can be used in a balloon catheter system and a balloon catheter for treating arrhythmia such as atrial fibrillation, endometriosis, cancer, and the like. [Explanation of symbols]

[0143] 10... Balloon catheter system, 15... Balloon catheter, 25... Balloon, 25a... Distal end, 25b... Proximal end, 30... Outer cylindrical shaft, 35... Inner cylindrical shaft, 40... Heating element, 41... Coil electrode, 42... Wiring, 45... Temperature sensor, 46... Heat-sensing part, 47... Lead wire, 70... Control device, 75... Stirring device, LD... Longitudinal direction, LP... Fluid delivery path, DX... Length

Claims

1. a balloon catheter including a balloon, an outer cylindrical shaft connected to a proximal end of the balloon, an inner cylindrical shaft passing through the outer cylindrical shaft and extending into the balloon to be connected to a distal end of the balloon, a heating element disposed within the balloon for heating a liquid within the balloon, and a temperature sensor disposed in a liquid supply path formed between the outer cylindrical shaft and the inner cylindrical shaft and communicating with the inside of the balloon; a control device electrically connected to the temperature sensor and adapted to determine the surface temperature of the balloon based on an output of the temperature sensor; a stirring device that repeatedly supplies the liquid to the liquid transfer path and discharges the liquid from the liquid transfer path at a constant cycle, the temperature sensor includes a heat-sensing unit and a lead wire connected to the heat-sensing unit, the heat-sensing unit being disposed in the liquid transfer path; The control device first determines temperature fluctuations of the liquid in the liquid delivery path from the output of the temperature sensor, and then determines the maximum value of the temperature fluctuations as the surface temperature of the balloon.

2. 2. The balloon catheter system according to claim 1, wherein the length along the longitudinal direction from the distal end of the outer cylindrical shaft to the heat-sensing portion is 5 mm or more and 150 mm or less.

3. the temperature sensor is attached to the inner cylindrical shaft; the inner cylindrical shaft is movable relative to the outer cylindrical shaft, 3. The balloon catheter system according to claim 1, wherein when the inner shaft moves distally relative to the outer shaft to expand the balloon, the heat-sensing part is located within the fluid supply path between the outer shaft and the inner shaft.

4. 3. The balloon catheter system according to claim 1, wherein the temperature sensor is attached to the outer cylindrical shaft.

5. 5. The balloon catheter system according to claim 1, wherein the lead wire is fixed to the inner cylindrical shaft or the outer cylindrical shaft, and the heat-sensing part is spaced apart from the inner cylindrical shaft and the outer cylindrical shaft.

6. a stirring device that repeatedly supplies a predetermined amount of the liquid to the liquid transfer path and discharges the liquid from the liquid transfer path, The length [mm] along the longitudinal direction from the distal end of the outer cylindrical shaft to the temperature sensor is ３ ] is the cross-sectional area of ​​the liquid transfer path [mm ２ 6. The balloon catheter system according to claim 1, wherein the value of the saturation coefficient is equal to or less than the value obtained by dividing by [0.01].

7. Wiring is provided to electrically connect the heating member and the control device, the temperature sensor includes leads electrically connected to the controller; the inner cylindrical shaft is movable relative to the outer cylindrical shaft, 7. The balloon catheter system according to claim 1, wherein both the wiring and the lead wire are attached to one of the outer cylindrical shaft and the inner cylindrical shaft, which are the same, and extend through the fluid delivery path.

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