catheter

Abstract

To provide a catheter that enables more accurate temperature measurement. [Solution] The catheter according to this disclosure comprises an outer balloon that is deformable between a first contracted state and a first expanded state and is tubular in the first expanded state, and an inner balloon that is positioned inside the outer balloon and is deformable between a second contracted state and a second expanded state and is tubular in the second expanded state, wherein in the first and second expanded states, the inner surface of the outer balloon and the outer surface of the inner balloon face each other, and the catheter further comprises a flexible substrate fixed to the inner surface of the outer balloon or the outer surface of the inner balloon, and at least one temperature sensor mounted on the flexible substrate.

Description

[[Technical Field]]

[0001] The present disclosure relates to a catheter. [[Background Art]]

[0002] For example, Patent Document 1 discloses a catheter for monitoring a biological environment such as an intr esophageal environment. The catheter includes one or more arm members and a temperature sensor provided on the arm member. [[Prior Art Literature]] [[Patent Literature]]

[0003] [[Patent Document 1]] Japanese Unexamined Patent Publication No. 2017-148524 [[Summary of the Invention]] [[Problem to be Solved by the Invention]]

[0004] In recent years, among catheters provided with a temperature sensor, there has been a demand for a catheter that enables more accurate temperature measurement with an inexpensive configuration.

[0005] An object of the present disclosure is to solve the above problem, and to provide a catheter including a temperature sensor that enables more accurate temperature measurement. [[Means for Solving the Problem]]

[0006] A catheter according to one aspect of the present disclosure comprises an outer balloon that is deformable between a first contracted state and a first expanded state and is tubular in the first expanded state, and an inner balloon that is located inside the outer balloon and is deformable between a second contracted state and a second expanded state and is tubular in the second expanded state, wherein in the first and second expanded states, the inner surface of the outer balloon and the outer surface of the inner balloon face each other, and the catheter further comprises a flexible substrate fixed to the inner surface of the outer balloon or the outer surface of the inner balloon, and at least one temperature sensor mounted on the flexible substrate. [Effects of the Invention]

[0007] According to this disclosure, it is possible to provide a catheter equipped with a temperature sensor that can measure temperature more accurately. [Brief explanation of the drawing]

[0008] [Figure 1] Perspective view of the expanded catheter of Embodiment 1 according to this disclosure [Figure 2] Perspective view of a catheter with an internal balloon. [Figure 3] Cross-sectional view of a catheter [Figure 4] Cross-sectional view of a catheter [Modes for carrying out the invention]

[0009] (Background leading to this disclosure) For example, a catheter with a temperature sensor on its arm is known. The user can insert the catheter into the esophagus and expand it, and the temperature sensor can measure the temperature inside the esophagus.

[0010] Since the catheter is inserted into the esophagus, accurate temperature measurement becomes difficult if the temperature sensor's insulation and waterproofing functions are not sufficiently guaranteed. To provide insulation and waterproofing functions to the temperature sensor, for example, a coating may be applied, but such a configuration increases the cost of the catheter.

[0011] Furthermore, if the temperature sensor comes into contact with the inner wall of the esophagus, there is a risk that the temperature sensor may detach from the catheter, making it difficult to measure the temperature at the point where it detached.

[0012] Therefore, the inventors investigated the configuration of a catheter that allows for more accurate temperature measurement with an inexpensive setup, leading to this disclosure.

[0013] Embodiment 1 of this disclosure will be described below with reference to the attached drawings. In addition, in each drawing, the elements are exaggerated to facilitate the explanation.

[0014] (Embodiment 1) [Overall structure] Figure 1 is a perspective view of the expanded catheter 1 according to Embodiment 1 of this disclosure. Figure 2 is a perspective view of the catheter 1 with the inner balloon 4 shown. Figures 3 and 4 are cross-sectional views of the catheter 1. Figures 3 and 4 show cross-sections taken in a direction perpendicular to the longitudinal direction L of the catheter 1.

[0015] As shown in Figure 1, catheter 1 is, for example, a balloon catheter used by being inserted into the esophagus.

[0016] As shown in Figures 2 and 3, the catheter 1 comprises an outer balloon 2, an inner balloon 4, a flexible substrate 6, a plurality of temperature sensors 8, and a sheath 10 (Figure 2).

[0017] <Outer balloon> The outer balloon 2 is a member that defines a space inside (the first space S1 described later) and is deformable between a first contracted state and a first expanded state by contracting and expanding the space. In the first expanded state, the outer balloon 2 is cylindrical. Here, "cylindrical" means having a cylindrical shape in part or all. The outer balloon 2 has a first cylindrical portion 21, an end 22 on one side in the longitudinal direction L of the first cylindrical portion 21, and an end 23 on the other side in the longitudinal direction L.

[0018] As shown in Figure 2, in the first deflated state, the first cylindrical portion 21 is a cylindrical portion having a central axis extending in the longitudinal direction L. The first cylindrical portion 21 may have an elongated shape extending in the longitudinal direction L. Therefore, the longitudinal direction L may also be referred to as the axial direction. In Embodiment 1, the dimension L1 of the first cylindrical portion 21 in the longitudinal direction L is larger than a dimension in a direction intersecting the longitudinal direction L, for example, a dimension in the width direction K orthogonal to the longitudinal direction L (i.e., the outer diameter D1).

[0019] In Embodiment 1, when viewed from the longitudinal direction L, the first cylindrical portion 21 has a circular cross-section. The first cylindrical portion 21 may have cross-sections of other shapes.

[0020] In the first deflated state, the end portions 22 and 23 each have a tapered shape whose cross-sectional area decreases in a direction away from the first cylindrical portion 21. That is, the end portions 22 and 23 each have a tapered shape. When viewed from the width direction K, the side surfaces of the end portions 22 and 23 are inclined at a constant angle.

[0021] As shown in Figure 4, the first cylindrical portion 21 has an outer surface 21A that can come into contact with a living body, and an opposite inner surface 21B.

[0022] In the first deflated state, the inner surface 21B defines a first space S1 on the inner side. The first space S1 is connected to an external fluid source and a pump (not shown), and fluid can flow into and out of the first space S1. By allowing fluid to flow into and out of the first space S1, the state of the outer balloon 2 is deformed between the first deflated state and the first expanded state. For example, fluid is caused to flow into and out of the first space S1 by a user's operation.

[0023] An inner balloon 4 is disposed inside the outer balloon 2. The inner balloon 4 is disposed in the first space S1 of the outer balloon 2. Accordingly, the catheter 1 has a double balloon structure.

[0024] <Inner Balloon> As shown in Figures 2 and 3, the inner balloon 4 is a member that defines a space inside (the second space S2 described later) and is deformable between a second contracted state and a second expanded state by contracting and expanding the space. The inner balloon 4 is cylindrical in the second expanded state. The inner balloon 4 has a second cylindrical portion 41, an end 42 on one side in the longitudinal direction L of the second cylindrical portion 41, and an end 43 on the other side in the longitudinal direction L.

[0025] As shown in Figure 2, in the second expanded state, the second cylindrical portion 41 is a cylindrical part having a central axis extending in the longitudinal direction L. In Embodiment 1, the second cylindrical portion 41 is arranged coaxially with the first cylindrical portion 21 inside the outer balloon 2. The second cylindrical portion 41 may be arranged on a different axis from the first cylindrical portion 21.

[0026] The second cylindrical portion 41 may have an elongated shape extending in the longitudinal direction L. In Embodiment 1, the dimension L2 of the second cylindrical portion 41 in the longitudinal direction L is larger than the dimension in the direction intersecting the longitudinal direction L, for example, the dimension in the width direction K perpendicular to the longitudinal direction L (i.e., the outer diameter D2).

[0027] In Embodiment 1, when viewed from the longitudinal direction L, the second cylindrical portion 41 has a circular cross-section, but the second cylindrical portion 41 may have a cross-section of a different shape.

[0028] In the second expanded state, the ends 42 and 43 have a tapered shape such that their cross-sectional area decreases in the direction away from the second cylindrical portion 41. The ends 42 and 43 have a tapered shape. When viewed from the width direction K, the sides of the ends 42 and 43 are inclined at a constant angle.

[0029] As described above, the shapes of the outer balloon 2 and the inner balloon 4 may be similar. Specifically, the measurement results obtained when measuring the shapes of the outer balloon 2 and the inner balloon 4 using a measuring device such as a 3D scanner are similar. For example, the shape of the inner balloon 4 is the shape of the outer balloon 2 scaled down by a predetermined scale factor.

[0030] As shown in Figure 4, in the first and second expanded states, the second cylindrical portion 41 has an outer surface 41A facing the inner surface 21B of the first cylindrical portion 21, and an inner surface 41B on the opposite side. With this configuration, the first space S1 is defined between the inner surface 21B of the first cylindrical portion 21 and the outer surface 41A of the second cylindrical portion 41.

[0031] Furthermore, because the shapes of the outer balloon 2 and the inner balloon 4 are similar, when the outer balloon 2 and the inner balloon 4 are in an expanded state, the distance G between the inner surface 21B of the first cylindrical portion 21 and the outer surface 41A of the second cylindrical portion 41 may be constant. For example, at least within the range of the second cylindrical portion 41 where the temperature sensor 8 is provided, the distance G between the inner surface 21B of the first cylindrical portion 21 and the outer surface 41A of the second cylindrical portion 41 is constant. With this configuration, it is easier to equalize the distance of the first space S1 through which heat from the living body passes, and it is easier to equalize the influence that heat from the living body receives when passing through the first space S1.

[0032] In the second expanded state, the inner surface 41B defines a second space S2 inside. The second space S2 is connected to an external fluid source and pump (not shown), and fluid can flow into and out of the second space S2. By allowing fluid to flow into and out of the second space S2, the state of the inner balloon 4 is deformed between the second contracted state and the second expanded state. For example, the fluid can be allowed to flow into and out of the second space S2 by user operation.

[0033] The second space S2 is sealed from the first space S1, and fluid movement between spaces S1 and S2 is suppressed. Specifically, the flow path connecting the second space S2 to the fluid source and pump is independent of the flow path connecting the first space S1 to the fluid source and pump. This configuration makes it easy to make the pressure P1 in the first space S1 and the pressure P2 in the second space S2 different.

[0034] In Embodiment 1, the expansion pressure P11 of the first space S1 in the first expansion state is smaller than the expansion pressure P12 of the second space S2 in the second expansion state. Specifically, the expansion pressure P11 of the first space S1 in the first expansion state is 0.5 times or less of the expansion pressure P12 of the second space S2 in the second expansion state. When using a syringe to inject air to expand the outer balloon 2 and the inner balloon 4, the expansion pressures P11 and P12 can be measured by providing a connector between the syringe and the outer balloon 2 and the inner balloon 4, and connecting a pressure sensor in parallel to the connector. The connector is, for example, a Y connector. Alternatively, the expansion pressures P11 and P12 may be calculated based on the amount of air injected into the outer balloon 2 and the inner balloon 4 by the syringe, or based on the volumes of the outer balloon 2 and the inner balloon 4.

[0035] For example, after inserting it into a living organism and increasing the pressures P1 and P2 in spaces S1 and S2 to the expanded pressure P12, the pressure P1 in the first space S1 is reduced to the expanded pressure P11 while maintaining the expanded pressure P12 in the second space S2.

[0036] Spaces S1 and S2 may be connected to a common fluid source or pump.

[0037] <Flexible circuit board> The flexible substrate 6 is a substrate on which electronic components (not shown) necessary for the catheter 1 to perform its function are mounted.

[0038] As shown in Figure 4, the flexible substrate 6 is fixed to the outer surface 41A of the second cylindrical portion 41 in the inner balloon 4. The flexible substrate 6 is fixed to the outer surface 41A, for example, with an adhesive.

[0039] When both the outer balloon 2 and the inner balloon 4 are in an expanded state, the flexible substrate 6 comes into contact with the inner surface 21B of the outer balloon 2. Specifically, the flexible substrate 6 comes into contact with the inner surface 21B in the area where the temperature sensor 8 (described later) is mounted.

[0040] The flexible substrate 6 may have a thickness smaller than the inner balloon 4 and a thickness larger than the outer balloon 2.

[0041] Multiple temperature sensors 8 are mounted on the flexible substrate 6. Since the flexible substrate 6 is fixed to the inner balloon 4, the flexible substrate 6 and temperature sensors 8 can be covered by the outer balloon 2. Therefore, even without applying a coating, direct contact between the flexible substrate 6 and temperature sensors 8 and living organisms is suppressed, and insulation and waterproofing can be ensured for the flexible substrate 6 and temperature sensors 8.

[0042] <Temperature sensor> Multiple temperature sensors 8 are sensors that can acquire temperature information around each temperature sensor 8. Examples of temperature sensors 8 include thermistors, chip thermistors, thermocouples, semiconductor sensors, or combinations thereof.

[0043] Multiple temperature sensors 8 are electrically connected to a control device (not shown) by wiring and are controlled by the control device. Temperature information measured by the multiple temperature sensors 8 is sent to the control device.

[0044] Multiple temperature sensors 8 are arranged on the flexible substrate 6 at intervals. The multiple temperature sensors 8 may be arranged at equal intervals in the longitudinal direction L and in the circumferential direction R around the longitudinal direction L. Alternatively, the multiple temperature sensors 8 may be arranged in a staggered pattern, offset in the longitudinal direction L or the circumferential direction R. The staggered arrangement prevents the temperature sensors 8 from overlapping when the inner balloon 4 is contracted. This makes it easier to contract the inner balloon 4 to a smaller size.

[0045] When the outer balloon 2 comes into contact with a living body, the temperature sensor 8 can acquire the temperature of the living body. Specifically, the temperature sensor 8 can acquire the temperature of the living body via the outer balloon 2 and the first space S1.

[0046] <Sheath> The sheath 10 is a cylindrical member capable of housing the deflated outer balloon 2 and inner balloon 4. When the outer balloon 2 and inner balloon 4 are housed in the sheath 10, the ends of the outer balloon 2 and inner balloon 4 may protrude from the sheath 10 in the longitudinal direction L. By pulling the protruding ends from the sheath 10, the user can easily pull out the outer balloon 2 and inner balloon 4.

[0047] By providing the sheath 10, it becomes easier to insert the catheter 1 into the patient.

[0048] Here, we will explain the outer balloon 2 and the inner balloon 4 in more detail, referring to Figure 4.

[0049] As shown in Figure 4, the inner diameter D11 of the first cylindrical portion 21 in the first expanded state is larger than the outer diameter D2 of the second cylindrical portion 41 in the second expanded state. The difference between the inner diameter D11 of the first cylindrical portion 21 and the outer diameter D2 of the second cylindrical portion 41 (i.e., the gap G) may be smaller than the outer diameter D2 of the second cylindrical portion 41. In Embodiment 1, the inner diameter D11 of the first cylindrical portion 21 is, for example, 20 mm, and the outer diameter D2 of the second cylindrical portion 41 is, for example, 12 mm. The inner diameter D11 and outer diameter D2 can be measured using an image dimension measuring instrument or a laser measuring instrument, etc.

[0050] Furthermore, the outer balloon 2 and the inner balloon 4 may differ in thickness. For example, if the main components of the outer balloon 2 and the inner balloon 4 are the same, the thickness t1 of the outer balloon 2 may be smaller than the thickness t2 of the inner balloon 4. In Embodiment 1, the thickness t1 of the outer balloon 2 is 0.9 times or less the thickness t2 of the inner balloon 4.

[0051] Furthermore, the outer balloon 2 and the inner balloon 4 may have different thermal conductivity. The outer balloon 2 may have a higher thermal conductivity than the inner balloon 4. In Embodiment 1, the thermal conductivity of the outer balloon 2 is 1.1 times or more that of the inner balloon 4.

[0052] Furthermore, the outer balloon 2 and the inner balloon 4 may have different elastic moduli. The outer balloon 2 may have a smaller elastic moduli than the inner balloon 4. In Embodiment 1, the elastic moduli of the outer balloon 2 are 0.9 times or less the elastic moduli of the inner balloon 4.

[0053] To make the thermal conductivity and elastic modulus of the outer balloon 2 and the inner balloon 4 different, the materials of the outer balloon 2 and the inner balloon 4 may be different. Specifically, the main components of the outer balloon 2 and the inner balloon 4 may be different. In this specification, materials other than the "main components" may be added to the outer balloon 2 and the inner balloon 4.

[0054] For example, to achieve different thermal conductivity, the main component of the outer balloon 2 is polyamide, polyurethane, polyamide elastomer, polyester elastomer, polyethylene terephthalate, fluorine-based elastomer, or silicone. On the other hand, the main component of the inner balloon 4 is polyurethane elastomer, polystyrene elastomer, or PEBAX. Furthermore, if the main component of the outer balloon 2 is something other than polyamide, the main component of the inner balloon 4 is polyamide.

[0055] For example, to create different elastic moduli, the main component of the outer balloon 2 is polyurethane, polyamide elastomer, polyester elastomer, polyurethane elastomer, polystyrene elastomer, fluorine elastomer, silicone, or latex. On the other hand, the main component of the inner balloon 4 is polyamide, PEBAX, or polyethylene terephthalate.

[0056] Furthermore, in order to make the thermal conductivity or elastic modulus different, the main components of the outer balloon 2 and the inner balloon 4 may be the same, while other properties of the outer balloon 2 and the inner balloon 4, such as thickness, may be made different.

[0057] [effect] The catheter 1 according to Embodiment 1 can achieve the following effects.

[0058] The catheter 1 comprises an outer balloon 2, an inner balloon 4, a flexible substrate 6, and at least one temperature sensor 8. The outer balloon 2 is deformable between a first contracted state and a first expanded state, and is tubular in the first expanded state. The inner balloon 4 is positioned inside the outer balloon 2 and is deformable between a second contracted state and a second expanded state, and is tubular in the second expanded state. In the first and second expanded states, the inner surface 21B of the outer balloon 2 and the outer surface 41A of the inner balloon 4 face each other. The flexible substrate 6 is fixed to the inner surface 21B of the outer balloon 2 or the outer surface 41A of the inner balloon 4. At least one temperature sensor 8 is mounted on the flexible substrate 6.

[0059] This configuration ensures insulation and waterproofing of the temperature sensor 8 even when it is covered by the outer balloon 2 and no coating is applied. Therefore, the simple and inexpensive structure ensures the insulation and waterproofing of the temperature sensor 8, enabling more accurate temperature measurement by the catheter 1. In addition, covering the temperature sensor 8 with the outer balloon 2 prevents the temperature sensor 8 from falling off and also prevents it from harming the body, thereby improving the safety of the catheter 1.

[0060] The catheter 1 further comprises a sheath 10 capable of accommodating the outer balloon 2 in a first deflated state. In the first expanded state, one end 22 of the outer balloon 2 in the longitudinal direction L has a tapered shape. In the second expanded state, one end 42 of the inner balloon 4 in the longitudinal direction has a tapered shape.

[0061] This configuration makes it easy to house the outer balloon 2 and the inner balloon 4 into the sheath 10.

[0062] In catheter 1, when viewed from the longitudinal direction L of the outer balloon 2, the inner diameter D11 of the outer balloon 2 in the first expansion state is larger than the outer diameter D2 of the inner balloon 4 in the second expansion state.

[0063] This configuration makes it easy to place the inner balloon 4 inside the outer balloon 2.

[0064] In catheter 1, the shape of the outer balloon 2 in the first expansion state and the shape of the inner balloon 4 in the second expansion state are similar.

[0065] This configuration makes it easy to maintain a constant distance between the outer balloon 2 and the inner balloon 4. Therefore, when the temperature sensor 8 is fixed to the outer surface 41A of the inner balloon 4 and heat from the body passes through the first space S1, it becomes easier to equalize the distance of the first space S1 through which the heat passes, and variations in the influence of the first space S1 on the heat can be suppressed. Consequently, the catheter 1 enables more accurate temperature measurement.

[0066] In catheter 1, the flexible substrate 6 is fixed to the outer surface 41A of the inner balloon 4. In the first expansion state, the inner surface 21B of the outer balloon 2 and the flexible substrate 6 fixed to the outer surface 41A of the inner balloon 4 come into contact.

[0067] This configuration allows heat from the body to be transferred more easily, improving measurement accuracy. Furthermore, it prevents the temperature sensor 8 mounted on the flexible substrate 6 from falling off.

[0068] In catheter 1, the outer balloon 2 has a higher thermal conductivity than the inner balloon 4.

[0069] This configuration allows heat from the body to pass more easily through the outer balloon 2 compared to the case where the outer balloon 2 has a lower thermal conductivity than the inner balloon 4, enabling more accurate temperature measurement by the catheter 1.

[0070] In catheter 1, the thermal conductivity of the outer balloon 2 is 1.1 times or more that of the inner balloon 4.

[0071] This configuration allows heat from the body to pass through the outer balloon 2 more easily.

[0072] In catheter 1, the main component of the outer balloon 2 is polyamide, polyurethane, polyamide elastomer, polyester elastomer, polyethylene terephthalate, fluorine-based elastomer, or silicone. The main component of the inner balloon 4 is polyamide, polyurethane elastomer, polystyrene elastomer, or PEBAX.

[0073] With this configuration, by appropriately selecting the material and / or thickness of the outer balloon 2, heat from the body can pass through the outer balloon 2 more easily.

[0074] In catheter 1, the main component of the outer balloon 2 and the main component of the inner balloon 4 are common, and the thickness t1 of the outer balloon 2 is smaller than the thickness t2 of the inner balloon 4.

[0075] This configuration allows the outer balloon 2 to deform more easily to conform to the shape of the body and to make better contact with the body, compared to cases where the outer balloon 2 has a greater thickness than the inner balloon 4. As a result, the catheter 1 can measure temperature more accurately.

[0076] In catheter 1, the thickness t1 of the outer balloon 2 is 0.9 times or less the thickness t2 of the inner balloon 4.

[0077] This configuration allows the outer balloon 2 to deform more easily to conform to the shape of the living body, making it easier to make contact with the body.

[0078] In catheter 1, the elastic modulus of the outer balloon 2 is smaller than that of the inner balloon 4.

[0079] This configuration makes it difficult for the outer balloon 2 to retain its shape during deflation, while the inner balloon 4 retains its shape easily. As a result, the inner balloon 4 deflates along its shape, and the outer balloon 2 deflates along the shape of the inner balloon 4, reducing the gap between the outer balloon 2 and the inner balloon 4 when deflated. Consequently, compared to the case where the outer balloon 2 has a higher modulus of elasticity than the inner balloon 4, the catheter 1 can be deflated to a smaller size, making it easier to insert into the body.

[0080] In catheter 1, the elastic modulus of the outer balloon 2 is 0.9 times or less the elastic modulus of the inner balloon 4.

[0081] This configuration allows catheter 1 to be further reduced in size.

[0082] In catheter 1, the main component of the outer balloon 2 is polyurethane, polyamide elastomer, polyester elastomer, polyurethane elastomer, polystyrene elastomer, fluorine elastomer, silicone, or latex. The main component of the inner balloon 4 is polyamide, PEBAX, or polyethylene terephthalate.

[0083] With this configuration, the catheter 1 can be further reduced in size by appropriately selecting the materials for the outer balloon 2 and the inner balloon 4.

[0084] In catheter 1, the expansion pressure P11 in the outer balloon 2 during the first expansion state is less than the expansion pressure P12 in the inner balloon 4 during the second expansion state.

[0085] This configuration makes it possible to suppress compression of surrounding tissues compared to when the expansion pressure P11 inside the outer balloon 2 is the same as that inside the inner balloon 4.

[0086] This disclosure is not limited to the embodiments described above, and can be implemented in various other forms.

[0087] In this specification, terms such as "First," "Second," etc., are used for illustrative purposes only and should not be understood as expressing or implying relative importance or ranking of technical features. Features designated as "First" or "Second" express or imply that they include one or more such features.

[0088] In Embodiment 1, an example was described in which the flexible substrate 6 is fixed to the inner balloon 4, but the invention is not limited to this. The flexible substrate 6 may also be fixed to the inner surface 21B of the first cylindrical portion 21 in the outer balloon 2. With this configuration, the temperature sensor 8 can acquire the temperature of the living body only through the first cylindrical portion 21.

[0089] In Embodiment 1, an example was described in which multiple temperature sensors 8 are mounted on a flexible substrate 6, but the invention is not limited to this. It is sufficient for at least one temperature sensor 8 to be mounted on the flexible substrate 6.

[0090] In Embodiment 1, an example was described in which the ends 22, 23, 42, and 43 on both sides in the longitudinal direction L of the cylindrical portions 21 and 41 have a tapered shape, but the invention is not limited to this. Only one end on the longitudinal direction L of the cylindrical portions 21 and 41 may have a tapered shape. For example, when the catheter 1 is housed in the sheath, only the ends 22 and 42 that are inserted into the sheath 10 before the cylindrical portions 21 and 41 may have a tapered shape.

[0091] In Embodiment 1, an example was described in which the outer balloon 2 and the inner balloon 4 differ in several respects, including thermal conductivity, elastic modulus, thickness, and material, but the invention is not limited to this. The outer balloon 2 and the inner balloon 4 only need to differ in at least one of the following: thermal conductivity, elastic modulus, thickness, and material. Alternatively, the outer balloon 2 and the inner balloon 4 may share the same thermal conductivity, elastic modulus, thickness, and material. In this case, the outer balloon 2 and the inner balloon 4 may differ in other characteristics.

[0092] While this disclosure is adequately described in relation to preferred embodiments with reference to the accompanying drawings, various variations and modifications will be obvious to those skilled in the art. Such variations and modifications should be understood to be included within the scope of this disclosure as defined by the accompanying claims. [Industrial applicability]

[0093] The catheter described herein is useful for inserting into a patient's body to measure temperature. [Explanation of Symbols]

[0094] 1 Catheter 2. Outer balloon 4. Inner balloon 6 Flexible circuit board 8. Temperature sensor 10 sheaths 21 First cylinder part 21A outer surface 21B Inner surface 22, 23 Ends 41 Second cylinder part 41A Outer surface 41B Inner surface 42, 43 End

Claims

1. It is deformable between a first contracted state and a first expanded state, and in the first expanded state, it has a tubular outer balloon, The inner balloon is positioned inside the outer balloon and is deformable between a second contracted state and a second expanded state, and is cylindrical in the second expanded state. In the first and second expanded states, the inner surface of the outer balloon and the outer surface of the inner balloon face each other. The catheter further comprises a flexible substrate fixed to the inner surface of the outer balloon or the outer surface of the inner balloon, and at least one temperature sensor mounted on the flexible substrate.

2. The system further comprises a sheath capable of accommodating the outer balloon in the first contracted state, In the first expanded state, one end of the outer balloon in the longitudinal direction has a tapered shape. The catheter according to claim 1, wherein in the second expanded state, one longitudinal end of the inner balloon has a tapered shape.

3. The catheter according to claim 1 or 2, wherein, when viewed from the longitudinal direction of the outer balloon, the inner diameter of the outer balloon in the first expanded state is larger than the outer diameter of the inner balloon in the second expanded state.

4. The catheter according to any one of claims 1 to 3, wherein the shape of the outer balloon in the first expanded state and the shape of the inner balloon in the second expanded state are similar.

5. The flexible substrate is fixed to the outer surface of the inner balloon, The catheter according to any one of claims 1 to 4, wherein the inner surface of the outer balloon in the first expanded state and the flexible substrate fixed to the outer surface of the inner balloon in the second expanded state are in contact.

6. The catheter according to any one of claims 1 to 5, wherein the outer balloon has a higher thermal conductivity than the inner balloon.

7. The catheter according to claim 6, wherein the thermal conductivity of the outer balloon is 1.1 times or more that of the inner balloon.

8. The main component of the outer balloon is polyamide, polyurethane, polyamide elastomer, polyester elastomer, polyethylene terephthalate, fluorine-based elastomer, or silicone. The catheter according to any one of claims 1 to 5, wherein the main component of the inner balloon is polyamide, polyurethane elastomer, polystyrene elastomer, or PEBAX.

9. The main component of the outer balloon and the main component of the inner balloon are common, The catheter according to any one of claims 1 to 5, wherein the thickness of the outer balloon is smaller than the thickness of the inner balloon.

10. The catheter according to claim 9, wherein the thickness of the outer balloon is 0.9 times or less the thickness of the inner balloon.

11. The catheter according to any one of claims 1 to 5, wherein the elastic modulus of the outer balloon is smaller than the elastic modulus of the inner balloon.

12. The catheter according to claim 11, wherein the elastic modulus of the outer balloon is 0.9 times or less the elastic modulus of the inner balloon.

13. The main component of the outer balloon is polyurethane, polyamide elastomer, polyester elastomer, polyurethane elastomer, polystyrene elastomer, fluorine-based elastomer, silicone, or latex. The catheter according to claim 11 or 12, wherein the main component of the inner balloon is polyamide, PEBAX, or polyethylene terephthalate.

14. The catheter according to any one of claims 1 to 13, wherein the pressure in the outer balloon in the first expanded state is less than the pressure in the inner balloon in the second expanded state.

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