Balloon catheter and catheter system

Abstract

The present invention comprises: a shaft 12; a balloon 14 provided to the shaft 12; and at least one heating member 16A, 16B capable of heating a fluid supplied into the balloon 14. The balloon 14 includes an expansion part 44 in which the at least one heating member 16A, 16B is disposed and which can be expanded by the fluid supplied therein. The expansion part 44 is provided with a pair of cone parts 48A, 48B respectively provided at end portions of the expansion part 44 in the axial direction, and a cylindrical part 50 provided between the pair of cone parts 48A, 48B. The at least one heating member 16A, 16B is disposed either at an overlapping position so as to overlap a corresponding cone part of the pair of cone parts 48A, 48B in the radial direction, or in a vicinity position that is an axial-direction position in the vicinity of the corresponding cone part.

Description

Balloon catheter and catheter system

[0001] The present disclosure relates to balloon catheters.

[0002] Patent Document 1 discloses a balloon catheter including a shaft, a balloon provided on the shaft, and a plurality of heating members capable of heating a fluid supplied into the balloon.

[0003] International Publication No. 2023 / 120680

[0004] A balloon catheter sometimes uses a cylindrical balloon having a pair of cone portions and a cylindrical portion disposed between the pair of cone portions. The present inventors have newly recognized the following problem when using such a cylindrical balloon. Specifically, depending on the position of the heating element within the balloon, when the heating element heats the fluid within the balloon, the fluid around the cone portion may not be sufficiently heated by the heating element, resulting in a large amount of low-temperature fluid remaining around the cone portion. This large amount of low-temperature fluid around the cone portion can result in significant temperature unevenness in the circumferential direction of the high-temperature fluid at the point heated by the heating element.

[0005] Therefore, one of the objects of the present disclosure is to provide a balloon catheter that can reduce temperature unevenness of the high-temperature fluid at the point heated by the heating member, which is caused by the low-temperature fluid around the cone portion of the balloon.

[0006] The balloon catheter of the present disclosure comprises a shaft, a balloon provided on the shaft, and at least one heating element capable of heating a fluid supplied into the balloon, wherein the balloon comprises an expansion section in which the at least one heating element is disposed and which can be expanded by a fluid supplied thereto, the expansion section comprising a pair of cone sections provided at both axial ends of the expansion section, and a tubular section provided between the pair of cone sections, and wherein the at least one heating element is disposed either at an overlapping position where it radially overlaps a corresponding one of the pair of cone sections, or at a nearby position which is an axial position near the corresponding cone section.

[0007] Fig. 3(A) is a schematic diagram illustrating a catheter system according to an embodiment; Fig. 3(B) is a schematic cross-sectional view illustrating a balloon according to an embodiment together with its surrounding structure; Fig. 3(A) is a diagram illustrating high-temperature fluid and low-temperature fluid in a balloon according to a reference embodiment, and Fig. 3(B) is a diagram illustrating convection occurring in the balloon according to the reference embodiment; Fig. 4(A) is a diagram illustrating high-temperature fluid and low-temperature fluid in a balloon according to an embodiment, and Fig. 4(B) is a diagram illustrating convection occurring in the balloon according to the embodiment; Fig. 5(A) is another diagram illustrating high-temperature fluid and low-temperature fluid in a balloon according to a reference embodiment, and Fig. 5(B) is another diagram illustrating convection occurring in the balloon according to the reference embodiment.

[0008] Hereinafter, an embodiment for implementing the balloon catheter of the present disclosure will be described. The same or equivalent elements will be given the same reference numerals, and redundant explanations will be omitted. In each drawing, for the sake of convenience, components will be omitted, enlarged, or reduced in size as appropriate. The drawings should be viewed in accordance with the orientation of the reference numerals.

[0009] Referring to Figure 1, the balloon catheter 10 includes a shaft 12, a balloon 14 attached to the shaft 12, heating members 16A and 16B capable of heating fluid supplied into the balloon 14, a handle device 18 attached to the proximal end portion of the shaft 12, and a temperature sensor 20 for detecting the temperature of the fluid within the balloon 14. The temperature sensor 20 is, for example, a thermocouple or a thermistor. In this specification, the direction along the centerline of the shaft 12 is simply referred to as the "axial direction," and the radial and circumferential directions relative to the centerline of the shaft 12 are simply referred to as the "radial direction" and the "circumferential direction." One axial side is also referred to as the proximal side, and the other axial side is also referred to as the distal side.

[0010] The balloon catheter 10 is used to treat biological tissue. To achieve this, the temperature of the fluid inside the balloon 14 is adjusted by heating the heating elements 16A and 16B, thereby adjusting the surface temperature of the balloon 14. Treatment using the balloon catheter 10 is performed by bringing the balloon 14, whose surface temperature has been adjusted, into contact with biological tissue. The treatment here is, for example, ablation of biological tissue, but specific examples are not particularly limited. Organs that are the target of this treatment include, for example, (1) digestive organs such as the intestinal tract and the hepatic duct, and (2) circulatory organs such as the heart and blood vessels.

[0011] The handle device 18 includes at least one handle 22A, 22B that can be grasped by the surgeon. In this embodiment, the handles 22A, 22B include a first handle 22A on the proximal side and a second handle 22B on the distal side. A connector 24 is attached to the first handle 22A via a tube.

[0012] The balloon catheter 10 is used as part of a catheter system 30. The catheter system 30 includes a control device 32 capable of controlling the heating operation by the heating members 16A and 16B, and a supply device 34 capable of supplying fluid into the balloon 14.

[0013] The control device 32 includes a power supply unit 32a and a control unit 32b. The power supply unit 32a is configured, for example, with a power supply circuit such as a regulator. The power supply unit 32a is electrically connected to the heating elements 16A and 16B via the connector 24 of the handle device 18 and conductors (not shown) provided in the shaft 12 and connected to the heating elements 16A and 16B. The power supply unit 32a supplies power to the heating elements 16A and 16B in a manner corresponding to the heating method of the heating elements 16A and 16B. In this embodiment, the heating elements 16A and 16B are used for bipolar heating. Here, bipolar heating refers to a method in which the fluid in the balloon 14 is heated by Joule heat generated by passing electricity between the pair of heating elements 16A and 16B. In this case, the power supply unit 32a supplies power to the pair of heating elements 16A and 16B so that electricity is passed between the pair of heating elements 16A and 16B.

[0014] The control unit 32b is configured with, for example, a microcomputer. The control unit 32b is electrically connected to the power supply unit 32a. The control unit 32b controls the heating operation of the fluid by the heating elements 16A and 16B by controlling the power supplied from the power supply unit 32a to the heating elements 16A and 16B. To achieve this, the control unit 32b controls the heating temperature, heating time, etc. of the heating elements 16A and 16B. The control unit 32b may control the heating operation of the heating elements 16A and 16B based on the temperature detected by the temperature sensor 20. The control mode of the control unit 32b to achieve this is not particularly limited. For example, the control unit 32b may control the heating temperature of the heating elements 16A and 16B so that the temperature of the fluid in the balloon 14 or the temperature of the balloon 14 detected by the temperature sensor 20 approaches a target temperature.

[0015] The supply device 34 may be configured using, for example, a syringe. The supply device 34 can supply fluid into the balloon 14 via at least a fluid port 18a provided in the handle device 18, in addition to a fluid lumen 42 (see FIG. 2) provided in the shaft 12. In this embodiment, the fluid port 18a is provided in the second handle 22B. The balloon 14 can be inflated by supplying fluid from the supply device 34 into the balloon 14 via the fluid lumen. This fluid may include, for example, gases, liquids, and semi-solids such as gels. This fluid may be, for example, a fluid that is liquid at room temperature and gels into a semi-solid when heated. This fluid may be, for example, a contrast agent containing methylcellulose or the like. Specific examples of the fluid are not limited to these examples and may include various liquids such as other contrast agents, saline, and sterilized water, as well as various gases such as air. The supply device 34 may discharge the fluid within the balloon 14 to the outside via a fluid lumen 42 of the shaft 12 or the like.

[0016] The catheter system 30 does not include a stirring device for stirring the fluid in the balloon 14. This stirring device is provided separately from the supply device 34. The stirring device is configured with a pump such as a roller pump, a diaphragm pump, or a bellows pump. The stirring device can stir the fluid in the balloon 14 by repeatedly discharging the fluid from the balloon 14 via the fluid lumen 42 of the shaft 12 and supplying the discharged fluid into the balloon 14. By not including such a stirring device, the configuration of the catheter system 30 can be simplified.

[0017] Referring to FIG. 2 , at least the distal end portion of the shaft 12 is inserted into the body. The shaft 12 is flexible and bendable. The shaft 12 is composed of at least one shaft member 40A, 40B. The shaft 12 of this embodiment includes the shaft members 40A, 40B, which are an outer shaft member 40A and an inner shaft member 40B inserted into the outer shaft member 40A. The inner shaft member 40B is pulled out from the distal end of the outer shaft member 40A and extends to the distal end of the shaft 12. The shaft 12 includes at least one fluid lumen 42 through which fluid supplied to the balloon 14 flows. In this embodiment, the fluid lumen 42 is formed between the outer shaft member 40A and the inner shaft member 40B, but the shaft member in which the fluid lumen 42 is formed is not particularly limited.

[0018] The balloon 14 includes an expansion section 44 that can be expanded by fluid supplied thereto, and sleeve sections 46 that are provided on both axial sides of the expansion section 44. Figures 1 and 2 show the expansion section 44 of the balloon 14 in an expanded state. Unless otherwise specified, the positional relationship of various components will be described based on the expansion section 44 of the balloon 14 being in an expanded state. The "expanded state" here refers to a state in which the expansion section 44 is expanded by applying a predetermined recommended expansion pressure to the expansion section 44. This recommended expansion pressure is the internal pressure that the manufacturer specifies as the pressure that should be applied to the balloon 14 to achieve a predetermined nominal diameter. Hereinafter, the terms "axially inner side" and "axially outer side" will be used to describe the positional relationship between the expansion section 44 of the balloon 14 and the heating elements 16A and 16B. Here, "axially inner" refers to the side axially approaching the axial center position C44 of the expansion portion 44 of the balloon 14, and "axially outer" refers to the side axially away from the axial center position C44.

[0019] Each sleeve portion 46 is attached to the shaft 12 by welding, adhesive, or the like. In this embodiment, the proximal sleeve portion 46 is attached to the outer shaft member 40A, and the distal sleeve portion 46 is attached to the inner shaft member 40B. The outer diameter of each sleeve portion 46 does not change before and after the inflation portion 44 of the balloon 14 is inflated.

[0020] The expansion section 44 includes a pair of cone sections 48A, 48B provided at both axial ends of the expansion section 44, and a cylindrical section 50 provided between the pair of cone sections 48A, 48B. A cylindrical balloon including the pair of cone sections 48A, 48B and the cylindrical section 50 is used as the balloon 14. Such a cylindrical balloon typically has higher hardness than a spherical balloon and has excellent expansion force during inflation. The balloon 14 is made of a material such as polyamide or PEBAX (registered trademark).

[0021] One of the pair of cone portions 48A, 48B is the proximal cone portion 48A on the proximal side, and the other is the distal cone portion 48B on the distal side. When the expansion section 44 is in an expanded state, the cone portions 48A, 48B gradually decrease in outer diameter as they extend axially outward. The specific shapes of the cone portions 48A, 48B are not particularly limited as long as they satisfy this condition. In this embodiment, the cone portions 48A, 48B are formed by a single conical surface whose rate of change in outer diameter is constant in the axial direction. Alternatively, the cone portions 48A, 48B may be formed by multiple conical surfaces whose rate of change in outer diameter is constant in the axial direction and whose rates of change are different from one another. Alternatively, the cone portions 48A, 48B may have a curved surface whose rate of change in outer diameter varies in the axial direction, or may be formed by combining at least one curved surface described herein with at least one conical surface. The shape of the cone portions 48A, 48B may be bowl-shaped, bullet-shaped, bell-shaped, funnel-shaped, horn-shaped, etc. The rate of change in outer diameter here refers to the rate of change in outer diameter per unit axial length.

[0022] The cylindrical portion 50 is provided in the middle of the expansion portion 44 and connects the pair of cone portions 48A, 48B. In this embodiment, the cylindrical portion 50 is cylindrical with a constant outer diameter in the axial direction. Alternatively, the cylindrical portion 50 may be cylindrical with a constant rate of change in outer diameter that is smaller than the rate of change in outer diameter of each of the pair of cone portions 48A, 48B. Here, "constant" is not limited to strict constant, but also includes the concept of approximately constant.

[0023] The heating members 16A, 16B are disposed within the expansion portion 44 of the balloon 14. In this embodiment, the heating members 16A, 16B are ring-shaped and surround the shaft 12. The shape of the heating members 16A, 16B is not particularly limited, and may be, for example, a coil shape that surrounds the shaft 12. The heating members 16A, 16B are fixed to a portion of the shaft 12 by various fixing means such as adhesive, welding, or swaging.

[0024] In this embodiment, the at least one heating element 16A, 16B includes first and second heating elements 16A, 16B spaced apart in the axial direction within the balloon 14. The first heating element 16A is located proximal to a central position C44 in the axial direction of the expansion portion 44 of the balloon 14, and the second heating element 16B is located distal to the central position C44. The heating elements 16A, 16B function as electrodes used for heating by electrical heating.

[0025] In this embodiment, the first heating element 16A corresponds to the proximal cone portion 48A, and the second heating element 16B corresponds to the distal cone portion 48B. The position where the heating elements 16A, 16B radially overlap the corresponding cone portions 48A, 48B is referred to as the overlapping position. The axial position where the heating elements 16A, 16B are near the corresponding cone portions 48A, 48B is referred to as the proximal position. In this case, at least one heating element 16A, 16B is disposed either at the overlapping position where it radially overlaps the corresponding cone portion 48A, 48B, or at a proximal position nearby. When disposing the heating elements 16A, 16B in the proximal or overlapping position, it is sufficient that they are disposed in a position where they do not come into contact with the balloon 14 when the balloon 14 is in an inflated state.

[0026] To satisfy the condition of "radially overlapping with the corresponding cone portion," the heating elements 16A, 16B do not need to radially overlap with the corresponding cone portion 48A, 48B over the entire circumferential range; they must radially overlap over at least a portion of the circumferential range. The axially outermost positions of the heating elements 16A, 16B are referred to as the outermost positions P16a, and the axially innermost positions of the corresponding cone portions 48A, 48B are referred to as the innermost positions P48a. This "innermost position" refers to the boundary between the cone portions 48A, 48B and the cylindrical portion 50. If the cylindrical portion 50 has a cylindrical shape with a constant outer diameter, the innermost position is the point where the cylindrical portion 50 begins to have a constant outer diameter midway from the cone portions 48A, 48B toward the cylindrical portion 50 in the axial direction. When the cylindrical portion 50 has a cylindrical shape with a constant rate of change in outer diameter, the point where the rate of change in outer diameter of the cylindrical portion 50 begins to be constant midway in the axial direction from the cone portions 48A, 48B toward the cylindrical portion 50 is the innermost position. In this case, the "overlapping position" also refers to the position where the outermost positions P16a of the heating elements 16A, 16B corresponding to the cone portions 48A, 48B are axially outward of the innermost positions P48a of the cone portions 48A, 48B. This overlapping position also includes a position where the innermost positions P48a of the cone portions 48A, 48B and the outermost positions P16a of the heating elements 16A, 16B corresponding to the cone portions 48A, 48B overlap in the radial direction. When arranging the heating elements 16A, 16B at the overlapping position, the relative axial positions of the heating elements 16A, 16B with respect to the corresponding cone portions 48A, 48B are not particularly limited.

[0027] Here, the "nearby position" is assumed to mean that the entire heating element 16A, 16B corresponding to the cone portion 48A, 48B is located axially inward of the cone portion 48A, 48B. The term "nearby" used to define the near position here refers to a position where the axial length Lp (see FIG. 3A ) from the innermost position P48a of the cone portion 48A, 48B to the outermost position P16a of the heating element 16A, 16B corresponding to the cone portion 48A, 48B is less than 0.20 × L. Here, "L" refers to the axial length (mm) of the tubular portion 50 of the balloon 14. The axial length L of the tubular portion 50 refers to the axial length from the innermost position P48a of the proximal cone portion 48A to the innermost position P16a of the distal cone portion 48B. The axial length L of the cylindrical portion 50 may be, for example, in the range of 5 mm to 50 mm, and preferably in the range of 10 mm to 30 mm, which is the usual clinical range.

[0028] The first heating member 16A is positioned either at an overlapping position where it radially overlaps the corresponding base cone portion 48A or at a nearby position. The second heating member 16B is positioned either at an overlapping position where it radially overlaps the corresponding distal cone portion 48B or at a nearby position. In other words, the first and second heating members 16A and 16B correspond to the respective cone portions 48A and 48B of the base cone portion 48A and the distal cone portion 48B, and are positioned either at an overlapping position or a nearby position corresponding to the corresponding cone portion 48A or 48B. In this embodiment, the first heating member 16A is positioned at an overlapping position corresponding to the base cone portion 48A, and the second heating member 16B is positioned at an overlapping position corresponding to the distal cone portion 48B.

[0029] This will be explained from another perspective. At least one heating member 16A, 16B is disposed in an overlapping position radially overlapping with the base-end cone portion 48A. In this embodiment, the first heating member 16A satisfies this condition. To satisfy this condition, the other heating members 16A, 16B do not have to overlap with the tip-end cone portion 48B in the radial direction. Furthermore, at least one heating member 16A, 16B is disposed in an overlapping position radially overlapping with the tip-end cone portion 48B. In this embodiment, the second heating member 16B satisfies this condition. To satisfy this condition, the other heating members 16A, 16B do not have to overlap with the base-end cone portion 48A in the radial direction.

[0030] Next, the background that led to the idea of ​​the balloon catheter 10 of the embodiment will be described, along with the effects of the balloon catheter 10.

[0031] Refer to FIG. 3A. This figure shows a portion of a balloon catheter 100 according to a reference embodiment. The balloon catheter 100 according to the reference embodiment differs from the balloon catheter 10 of the embodiment only in the positions of the first and second heating members 16A and 16B. Specifically, the first and second heating members 16A and 16B are positioned axially far inward from the cone portions 48A and 48B of the balloon 14. The first and second heating members 16A and 16B are positioned such that the axial length Lp from the innermost position P48a of the cone portions 48A and 48B to the outermost position P16a of the heating members 16A and 16B is 0.2 × L mm or greater. The first and second heating members 16A and 16B are positioned neither overlapping nor adjacent to the cone portions 48A and 48B. When a cylindrical balloon is used in this way, the common general technical knowledge at the time of filing stated that the heating members 16A, 16B should be positioned as far as possible axially inward from the cone portions 48A, 48B to avoid interference with the cone portions 48A, 48B of the balloon 14. The following describes the problems that arise when the heating members 16A, 16B are positioned in this way.

[0032] The fluid inside the balloon 14 is heated at a heating point Pa according to the heating method of the heating elements 16A, 16B. As a result, a high-temperature fluid is generated at the heating point Pa by the heating elements 16A, 16B. When heating using the bipolar method, the area between the pair of heating elements 16A, 16B is set as the heating point Pa, and the fluid inside the balloon 14 at the heating point Pa is heated almost uniformly. This is because a current with an almost uniform current density distribution flows between the pair of heating elements 16A, 16B, generating Joule heat of a magnitude according to the current density.

[0033] When the heating elements 16A and 16B are positioned far away from the cone portions 48A and 48B of the balloon 14, the fluid around the cone portions 48A and 48B is not sufficiently heated by the heating elements 16A and 16B, resulting in a large amount of low-temperature fluid being present at the points Pb around the cone portions 48A and 48B. Here, "low-temperature fluid" refers to a fluid that is colder than the high-temperature fluid present at the points Pa heated by the heating elements 16A and 16B. For ease of explanation, FIG. 3A shows only the main points Pb around the cone portions 48A and 48B where low-temperature fluid is steadily present. The same applies to the following FIGS. 4B and 5B.

[0034] Referring to FIG. 3B, consider a case where the axial direction of the shaft 12 is parallel to the horizontal at a certain point on the balloon 14. In this case, the high-temperature fluid at the point Pa heated by the heating elements 16A and 16B tends to rise in the direction Fa due to its relatively low density, while the low-temperature fluid at the point Pb around the cone portions 48A and 48B tends to descend in the direction Fb due to its relatively high density. This influence causes convection within the balloon 14 due to the temperature difference between the low-temperature fluid at the point Pb around the cone portions 48A and 48B and the high-temperature fluid at the point Pa heated by the heating elements 16A and 16B. This convection circulates, for example, from the upper portion Pa2 of the point Pa heated by the heating elements 16A and 16B to the upper portion within the cone portions 48A and 48B, to the lower portion within the cone portions 48A and 48B, and finally to the lower portion Pa1 of the point Pa heated by the heating elements 16A and 16B. In FIG. 3B, the arrows indicate the approximate direction of this convection. The same applies to the subsequent FIGS. 4(B) and 5(B).

[0035] When convection occurs due to the temperature difference between the high-temperature fluid and the low-temperature fluid, a portion of the high-temperature fluid at the heated area Pa by the heating elements 16A and 16B is partially cooled by the low-temperature fluid at the area Pb around the cone portions 48A and 48B. The further the heating elements 16A and 16B are axially inward from the cone portions 48A and 48B of the balloon 14, the greater the amount of low-temperature fluid at the area Pb around the cone portions 48A and 48B, thereby increasing the degree of cooling of the high-temperature fluid by the low-temperature fluid. As a result, when the heating elements 16A and 16B are positioned farther away from the cone portions 48A and 48B of the balloon 14, the circumferential temperature unevenness of the high-temperature fluid at the heated area Pa by the heating elements 16A and 16B (hereinafter simply referred to as the temperature unevenness of the high-temperature fluid) increases due to the low-temperature fluid around the cone portions 48A and 48B. In the illustrated example, the high-temperature fluid at the heated area Pa by the heating elements 16A and 16B is cooled by the low-temperature fluid. At this time, due to the influence of the circulation of the flow caused by the convection described above, the high-temperature fluid in the lower part Pa1 of the heated part Pa is first cooled to a higher degree by the low-temperature fluid, and then the high-temperature fluid in the upper part Pa2 of the heated part Pa is cooled to a lower degree by the low-temperature fluid. As a result, temperature unevenness occurs in the circumferential direction, which increases the temperature difference between the high-temperature fluid in the upper part Pa2 of the heated part Pa by the heating members 16A and 16B and the high-temperature fluid in the lower part Pa1.

[0036] The heat applied to the fluid within the balloon 14 by the heating elements 16A, 16B is continually absorbed by the fluid (air, body fluid, etc.), biological tissue, etc. present outside the balloon 14. Therefore, even if heating by the heating elements 16A, 16B continues, the temperature of the entire fluid within the balloon 14 does not become uniform, and a state in which the temperature distribution including the temperature unevenness described above occurs is steadily maintained. If such a state in which temperature unevenness occurs is steadily maintained, it can cause problems when treating biological tissue with the balloon 14 heated by the fluid, and therefore improvement in this state is desired.

[0037] (A) As a countermeasure to this problem, the inventors of the present application have recognized that it is effective to position at least one heating element 16A, 16B in either an overlapping or adjacent position with respect to the corresponding cone portion 48A, 48B, as shown in FIG. 3A. As a result, as is clear from a comparison of FIG. 3A and FIG. 4A, when heating the fluid in the balloon 14 using the heating elements 16A, 16B positioned in an overlapping position or the like, the amount of low-temperature fluid present at the point Pb around the cone portion 48A, 48B corresponding to the heating element 16A, 16B can be reduced compared to when this condition is not met. As a result, even if convection occurs due to a temperature difference between the low-temperature fluid present at the point Pb around the cone portion 48A, 48B and the high-temperature fluid present at the point Pa heated by the heating elements 16A, 16B, as shown in FIG. 4B, the degree of cooling of the high-temperature fluid by the low-temperature fluid can be reduced. As a result, this is advantageous in reducing temperature unevenness of the high-temperature fluid at the heated points Pa by the heating members 16A and 16B, which is caused by the low-temperature fluid at the points Pb around the cone portions 48A and 48B.

[0038] In this embodiment, the first and second heating elements 16A and 16B correspond to the respective cone portions 48A and 48B of the pair of cone portions 48A and 48B, and are disposed in either an overlapping position or a nearby position according to the corresponding cone portion 48A and 48B. This is advantageous in reducing temperature unevenness of the high-temperature fluid at the heated portion Pa by the first and second heating elements 16A and 16B, which is caused by the low-temperature fluid at the portion Pb around each of the pair of cone portions 48A and 48B.

[0039] In this embodiment, first and second heating elements 16A and 16B are used for bipolar heating. In this case, as described above, the fluid within the balloon 14 over a wide axial range, such as between the first and second heating elements 16A and 16B, is heated almost uniformly. Furthermore, in this embodiment, either of the first or second heating elements 16A and 16B is positioned in an overlapping or adjacent position corresponding to the corresponding cone portion 48A or 48B. This is advantageous in reducing temperature variations in the high-temperature fluid over a wide axial range between the first and second heating elements 16A and 16B, which are caused by the low-temperature fluid at the area Pb around the cone portion 48A or 48B. In particular, in this embodiment, the first and second heating elements 16A and 16B used for bipolar heating are positioned in an overlapping or adjacent position corresponding to the respective cone portion 48A or 48B. This is particularly advantageous in reducing temperature unevenness of the high-temperature fluid over a wide axial range between the first and second heating elements 16A and 16B, which is caused by the low-temperature fluid at the locations Pb around each of the cone portions 48A and 48B. In particular, bipolar heating heats the fluid in the balloon 14 almost uniformly between the pair of heating elements 16A and 16B. This, combined with other factors, makes it possible to significantly reduce temperature unevenness of the entire high-temperature fluid over a wide axial range between the pair of heating elements 16A and 16B.

[0040] In this embodiment, the heating elements 16A, 16B are arranged at overlapping positions that radially overlap the cone portions 48A, 48B. This significantly reduces the amount of low-temperature fluid in the areas Pb around the cone portions 48A, 48B corresponding to the heating elements 16A, 16B, compared to when the heating elements 16A, 16B are arranged in close proximity to each other, further reducing the degree of cooling of the high-temperature fluid by the low-temperature fluid. This is further advantageous in reducing temperature unevenness of the high-temperature fluid in the heated areas Pa of the heating elements 16A, 16B caused by the low-temperature fluid around the cone portions 48A, 48B.

[0041] Consider the objective of reducing the amount of cryogenic fluid in the area Pb around the cone portions 48A and 48B corresponding to the heating elements 16A and 16B. In relation to this objective, when the heating elements 16A and 16B are disposed in close proximity to each other, the axial length Lp described above is preferably as short as possible, and is preferably 0.10×L or less, and more preferably 0.050×L or less.

[0042] In this embodiment, the first heating member 16A is disposed at an overlapping position or a nearby position corresponding to the base-end cone portion 48A, which is advantageous in reducing temperature unevenness of the high-temperature fluid at the heated point Pa of the first heating member 16A caused by the low-temperature fluid around the base-end cone portion 48A.

[0043] In this embodiment, the second heating member 16B is disposed at an overlapping position or a nearby position corresponding to the tip cone portion 48B, which is advantageous in reducing temperature unevenness of the high-temperature fluid at the heated point Pa of the second heating member 16B caused by the low-temperature fluid around the tip cone portion 48B.

[0044] Consider the case where a heating method, such as a monopolar method, is used, in which only the periphery of the heating elements 16A and 16B is heated, with the heating elements 16A and 16B positioned in the same manner as in FIG. 3A. The monopolar method here refers to a method in which the fluid in the balloon 14 is heated by Joule heat generated by passing current between the return electrode outside the body and the heating elements 16A and 16B. In this case, as shown in FIG. 5A, the periphery of the heating elements 16A and 16B is designated as a heated area Pa, and a high-temperature fluid is generated at the heated area Pa. In this case, too, the fluid around the cones 48A and 48B is not sufficiently heated by the heating elements 16A and 16B, resulting in a large amount of low-temperature fluid being present at an area Pb around the cones 48A and 48B.

[0045] 5B , convection occurs within the balloon 14 due to the temperature difference between the low-temperature fluid at the area Pb around the cones 48A and 48B and the high-temperature fluid at the area Pa heated by the heating elements 16A and 16B. As a result, if the heating elements 16A and 16B are positioned far away from the cones 48A and 48B of the balloon 14, increasing the amount of low-temperature fluid around the cones 48A and 48B, the low-temperature fluid around the cones 48A and 48B will cause temperature unevenness in the high-temperature fluid at the area Pa heated by the heating elements 16A and 16B to increase. Even in the illustrated example, temperature unevenness occurs in the circumferential direction, increasing the temperature difference between the high-temperature fluid at the upper area Pa2 of the area Pa heated by the heating elements 16A and 16B and the high-temperature fluid at the lower area Pa1.

[0046] In this case, the heating elements 16A and 16B may be disposed in overlapping or adjacent positions corresponding to the cones 48A and 48B, as in the balloon catheter 10 of the embodiment. This reduces temperature unevenness of the high-temperature fluid at the heated area Pa by the heating elements 16A and 16B, which is caused by the low-temperature fluid at the area Pb around the cones 48A and 48B, although this is not shown.

[0047] In this case, if the axial length of the expansion portion 44 of the balloon 14 is increased, low-temperature fluid may be insufficiently heated at a point Pc between the heated points Pa of the first and second heating elements 16A and 16B. In this case, convection caused by the temperature difference between the low-temperature fluid at the point Pc between the first and second heating elements 16A and 16B and the high-temperature fluid at the heated points Pa of each heating element 16A and 16B may cause large temperature variations in the circumferential direction of the fluid at the point Pc. To reduce such temperature variations at the point Pc, it is sufficient to place another heating element 16A, 16B between the first and second heating elements 16A, 16B or shorten the axial length of the expansion portion 44 of the balloon 14.

[0048] Next, another feature of the balloon catheter 10 of this embodiment will be described. Consider the axial length Lb (mm) of the cone portions 48A, 48B corresponding to the heating elements 16A, 16B. This axial length Lb is the axial length from the innermost position P48a of the cone portions 48A, 48B to the outermost position P48b of the cone portions 48A, 48B, which is the axially outermost position of the cone portions 48A, 48B. This outermost position P48b of the cone portions 48A, 48B is the boundary between the cone portions 48A, 48B and the sleeve portion 46. In this case, this axial length Lb may be 5 mm or less. This allows for a moderate reduction in the amount of cryogenic fluid within the cone portions 48A, 48B corresponding to the heating elements 16A, 16B when heating the fluid within the balloon 14, compared to when this condition is not met. This is further advantageous in reducing circumferential temperature unevenness of the high-temperature fluid at the heated point Pa by the heating members 16A, 16B, which is caused by the low-temperature fluid around the cone portions 48A, 48B. This condition only needs to be satisfied by at least one of the pair of cone portions 48A, 48B. In this embodiment, this condition is satisfied by both of the pair of cone portions 48A, 48B. The lower limit value of the axial length Lb is not particularly limited and may be set appropriately within a range that is realistically achievable in manufacturing. From this perspective, the lower limit value of the axial length Lb may be, for example, 0.5 mm.

[0049] Consider the maximum outer diameter R44 (mm) of the expansion portion 44 when the balloon 14 is in an expanded state. The maximum outer diameter R44 here means the outer diameter at the maximum diameter. In this case, the maximum outer diameter R44 of the balloon 14 is preferably 10 mm or less. The advantages of this are explained below.

[0050] To suppress temperature unevenness of the fluid within the balloon 14, a stirring device is typically used to stir the fluid within the balloon 14. The present inventors have newly recognized that it is effective to arrange the heating elements 16A and 16B at overlapping or nearby positions corresponding to the cone portions 48A and 48B as described above, while setting the maximum outer diameter R44 of the balloon 14 to 10 mm or less. This makes it possible to reduce temperature unevenness of the high-temperature fluid at the heated point Pb by the heating elements 16A and 16B without using a stirring device. In particular, they have recognized that it is effective to arrange the pair of heating elements 16A and 16B used for bipolar heating at overlapping or nearby positions corresponding to the individual cone portions 48A and 48B, while setting the maximum outer diameter R44 of the balloon 14 to 10 mm or less. This makes it possible to reduce circumferential temperature unevenness of the high-temperature fluid between the pair of heating elements 16A and 16B, without using a stirring device. This is thought to be because the smaller the maximum outer diameter R44 of the balloon 14, the more the amount of fluid in the balloon 14 can be reduced, and therefore temperature unevenness is less likely to occur in the fluid in the balloon 14. This finding was obtained as a result of experimental and analytical studies conducted by the inventors of the present application.

[0051] Furthermore, setting the maximum outer diameter R44 of the balloon 14 to 10 mm or less is advantageous in reducing the maximum outer diameter R12 of the shaft 12. The maximum outer diameter R12 of the shaft 12 may be, for example, less than 3.7 mm. When the balloon catheter 10 is used in conjunction with an endoscope, the shaft 12 is inserted together with the balloon 14 into the endoscope channel. The minimum inner diameter of the endoscope channel is often 3.7 mm or greater. Setting the maximum outer diameter R44 of the balloon 14 to 10 mm or less and the maximum outer diameter R12 of the shaft 12 to less than 3.7 mm allows the balloon catheter 10 to be used in conjunction with many endoscopes. The lower limits of the maximum outer diameter R44 of the balloon 14 and the maximum outer diameter R12 of the shaft 12 are not particularly limited and may be set appropriately within a range that is practically achievable in manufacturing. From this perspective, the lower limit of the maximum outer diameter R44 may be, for example, 4 mm.

[0052] The axial length Lb of the cone portions 48A, 48B of the balloon 14 may be greater than 5 mm. The maximum outer diameter R44 of the balloon 14 may be greater than 10 mm, and the maximum outer diameter R12 of the shaft 12 may be greater than 3.7 mm. The maximum outer diameter R44 of the balloon 14 may be, for example, 4.0 mm or greater and 6.0 mm or less. This allows the balloon 14 to be easily inserted into the stricture when ablating a stricture in the bile duct using the balloon catheter 10. The axial lengths of the heating members 16A, 16B can be appropriately selected by those skilled in the art and are not particularly limited. The axial lengths of the heating members 16A, 16B may be set, for example, in the range of 1 to 2 mm, less than 1 mm, or greater than 2 mm.

[0053] Next, an example of an experiment conducted to support the above findings will be described. Here, an experiment was conducted using the catheter system 30 shown in Figure 1, in which the fluid supplied into the balloon 14 was heated by the heating elements 16A and 16B. The catheter system 30 does not include a stirring device.

[0054] This experiment was carried out in an environment where a contrast medium (specific heat: 3000 (J / kh·K)) was used as the fluid heated by heating members 16A and 16B, and air was present around balloon 14. In this experiment, the maximum outer diameter R44 of balloon 14 was 4 to 6 mm, the axial length L of tubular portion 50 of balloon 14 was 15 mm, and the axial length Lb of cone portions 48A and 48B was 2 mm.

[0055] In this experiment, the positions of the paired heating elements 16A and 16B relative to the cone portions 48A and 48B of the balloon 14 were determined under the following three conditions. All conditions were the same except for the positions of the heating elements 16A and 16B. (Reference Example) Each of the paired heating elements 16A and 16B was positioned such that the axial length Lp (see FIG. 3) from the corresponding cone portion 48A or 48B was 3 mm (= 0.20 × L). (Example 1) Each of the paired heating elements 16A and 16B was positioned such that the axial length Lp (see FIG. 3) from the corresponding cone portion 48A or 48B was 0.5 mm. (Example 2) Each of the paired heating elements 16A and 16B was positioned such that it radially overlapped with the corresponding cone portion 48A or 48B.

[0056] In this experiment, a pair of heating elements 16A and 16B was used for bipolar heating. This experiment was performed with a certain portion of the balloon 14 positioned horizontally in the axial direction. To evaluate the temperature unevenness of the heated portion by the heating elements 16A and 16B, temperature sensors were placed at the upper and lower ends of the expansion portion 44 of the balloon 14 at the axial center position C44, and the absolute difference in temperatures detected by each temperature sensor (= the absolute difference between the temperatures at the upper end and the lower end) was used for evaluation.

[0057] As a result, it was confirmed that the temperature variation was 5°C in the Reference Example, 2°C in Example 1, and 1°C in Example 2. These results confirm that by arranging the heating elements 16A and 16B corresponding to the cone portions 48A and 48B of the balloon 14 in overlapping or nearby positions, the temperature variation at the heated area Pa by the heating elements 16A and 16B can be reduced. This also confirms that arranging the heating elements 16A and 16B in overlapping positions can reduce the temperature variation at the heated area Pa by the heating elements 16A and 16B compared to arranging them in nearby positions. In other words, it can be said that this also confirms that by bringing the heating elements 16A and 16B closer to the outermost positions P48b of the cone portions 48A and 48B, the amount of low-temperature fluid at the area Pb around the cone portions 48A and 48B can be reduced, thereby reducing the temperature variation at the heated area Pa by the heating elements. It also supports the fact that, in order to reduce temperature unevenness in this way, stirring by a stirring device is not necessary if the maximum outer diameter R44 of the balloon 14 is the experimental condition.

[0058] Although not described here, it has been confirmed that a similar tendency exists even when the maximum outer diameter R44 of the balloon 14 is set to 4 mm to 6 mm. Furthermore, although not described here, it has also been confirmed by analytical techniques that a similar tendency exists under various conditions in which the dimensions of the balloon 14 and the positions of the heating members 16A and 16B are changed.

[0059] Next, variations of the components described above will be described.

[0060] The specific example of the shaft 12 is not particularly limited. The shaft 12 may be composed of, for example, only one shaft member, or may be composed of three or more shaft members. The positions of the connector 24, the fluid port 18a, and the like provided on the handle device 18 are not particularly limited. In the embodiment, an example in which the first handle 22A and the second handle 22B are provided separately has been described, but they may also be provided integrally. The catheter system 30 may include a stirring device provided separately from the supply device 34.

[0061] At least one heating element 16A, 16B may be used for monopolar heating. Multiple heating elements 16A, 16B may be used for both monopolar and bipolar heating. These monopolar and bipolar heating elements are direct resistance heating elements that directly heat the fluid within the balloon 14 by Joule heat generated in the fluid when electricity is applied to the fluid. The heating element 16A, 16B may be any heating element. For example, the heating element 16A, 16B may be an indirect resistance heating element that indirectly heats the fluid by Joule heat generated in the heating elements 16A, 16B when electricity is applied to the heating elements 16A, 16B.

[0062] To achieve the aforementioned effect (A), the number of heating elements 16A, 16B is not particularly limited. In addition to the two heating elements shown in the embodiment, the number may be one or three or more. When only a single heating element 16A, 16B is present, the heating element 16A, 16B only needs to correspond to one of the pair of cone elements 48A, 48B and be positioned in an overlapping or adjacent position corresponding to the corresponding cone element 48A, 48B. When two or more heating elements 16A, 16B are present, it is sufficient that at least one heating element 16A, 16B only needs to correspond to one of the cone elements 48A, 48B and be positioned in an overlapping or adjacent position corresponding to the corresponding cone element 48A, 48B. For example, only the first heating element 16A may be positioned in an overlapping or adjacent position corresponding to the proximal cone element 48A, and the second heating element 16B may be positioned in a location other than the overlapping or adjacent position corresponding to the distal cone element 48B. In addition, only the second heating member 16B may be positioned at an overlapping position or a nearby position corresponding to the tip-side cone portion 48B, and the first heating member 16A may be positioned at a location other than the overlapping position or nearby position corresponding to the base-side cone portion 48A.

[0063] The content of each component described in the above embodiments is an example. The abstract technical ideas should not be interpreted as being limited to the content of this specification. The content of each component described in the embodiments is subject to many design changes, such as modification, addition, and deletion. Contents subject to such design changes are emphasized by adding the notation "this embodiment" or "embodiment." However, design changes are also permitted even in content without such notation. Any combination of the above components is also valid.

[0064] The present disclosure relates to balloon catheters.

[0065] 10...balloon catheter, 12...shaft, 14...balloon, 16A...first heating element, 16B...second heating element, 30...catheter system, 32...control device, 34...supply device, 44...expansion portion, 48A...proximal cone portion, 48B...distal cone portion, 50...tubular portion.

Claims

1. A balloon catheter comprising: a shaft; a balloon provided on the shaft; and at least one heating element capable of heating a fluid supplied into the balloon; wherein the balloon has an expansion section in which the at least one heating element is disposed and which is expandable by a fluid supplied thereto; the expansion section having a pair of cone sections provided at both axial ends of the expansion section and a tubular section provided between the pair of cone sections; and wherein the at least one heating element is disposed either at an overlapping position where it radially overlaps a corresponding one of the pair of cone sections, or at a nearby position which is an axial position near the corresponding cone section.

2. The balloon catheter according to claim 1, wherein the at least one heating element includes a first heating element and a second heating element spaced apart in the axial direction, and at least one of the first heating element and the second heating element corresponds to one of the pair of cone elements and is disposed in either the overlapping position or the adjacent position depending on the corresponding cone element.

3. A balloon catheter according to claim 2, wherein the pair of cone portions includes a base-side cone portion and a tip-side cone portion, the first heating element is disposed at either the overlapping position or the adjacent position corresponding to the base-side cone portion, and the second heating element is disposed at either the overlapping position or the adjacent position corresponding to the tip-side cone portion.

4. The balloon catheter according to claim 2 or 3, wherein the first heating element and the second heating element are used for heating in a bipolar manner.

5. A balloon catheter according to any one of claims 1 to 4, wherein at least one of the heating elements is disposed in an overlapping position so as to overlap the corresponding cone portion in the radial direction.

6. A balloon catheter according to any one of claims 1 to 5, wherein the axial length of the cone portion corresponding to the heating element is 5 mm or less.

7. A balloon catheter according to any one of claims 1 to 6, wherein the maximum outer diameter of the expansion portion is 10 mm or less.

8. A catheter system comprising: a balloon catheter according to any one of claims 1 to 7; a control device capable of controlling the heating operation by the heating member; and a supply device capable of supplying a fluid into the balloon.

9. The catheter system according to claim 8, wherein the catheter system does not include a stirring device for stirring the fluid in the balloon that is provided separately from the supply device.

Images