catheter

Abstract

This invention provides a technology that achieves both flexibility and tear strength in a covering material that covers a restraining member provided on a balloon. [Solution] The balloon catheter 1 comprises a shaft 2 inserted into the body, a balloon 3 attached to the tip of the shaft 2 and expandable by an expansion fluid supplied from the proximal end of the shaft 2, an elastic band 4 wrapped around the outer circumference of the intermediate portion 32 between the tip 311 and the proximal end 331 of the balloon 3 to restrict the expansion of the balloon 3 in the intermediate portion 32, and a covering member having a Shore A hardness of 30 to 60 and covering the outer circumference of the elastic band 4.

Description

Technical Field

[0001] The present disclosure relates to a catheter, specifically a balloon catheter having a balloon that can be expanded inside the body.

Background Art

[0002] A catheter is a medical tube inserted into the body for examination and treatment. In particular, a catheter having a balloon that can be expanded inside the body is called a balloon catheter, and is used to expand dilated parts and stenotic parts in tubular organs inside the body such as blood vessels, tracheas, digestive tracts, common bile ducts, pancreatic ducts, etc., their connection parts (inlets and outlets), and holes formed inside the body for examination and treatment (for example, holes punctured from the stomach or duodenal bulb into the common bile duct).

[0003] In Patent Document 1, in order to reliably expand a stenotic part, an elastic band part is provided on the outer periphery of the middle part of the balloon. The balloon starts to expand from the shoulder parts on both sides of the band part, and the band part between the two shoulder parts forms a constricted waist part. Since the stenotic part to be expanded is supported from both sides by the previously expanded shoulder parts, it can stay at a position facing the waist part. When the balloon further expands in this state, the stenotic part is reliably expanded by the band part that elastically deforms and expands.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] After expanding the constricted area, the balloon, no longer needed, is deflated and removed from the body along with the shaft. To prevent the elastically deformed and expanded band portion, in other words, the restraining member, from detaching from the balloon and shaft, it is conceivable to cover the outer circumference of the restraining member with an elastically deformable covering member. This suppresses the detachment of the restraining member from the balloon and shaft when the balloon is deflated. When a covering member is provided on the outer circumference of the restraining member, the covering member is required to have the flexibility to follow the deformation of the balloon and the restraining member. In addition, the covering member is required to have high tear strength so that even if the covering member is damaged, the damage will not spread and tear during expansion.

[0006] This disclosure has been made in view of these circumstances, and its purpose is to provide a technology that achieves both flexibility and tear strength in a covering member that covers a restraining member provided on a balloon. [Means for solving the problem]

[0007] To solve the above problems, a catheter according to one embodiment of the present disclosure comprises a shaft inserted into the body; a balloon attached to the tip of the shaft and expandable by a fluid supplied from the proximal end of the shaft; a restraining member wrapped around the outer circumference of the intermediate portion between the tip and proximal ends of the balloon and restricting the expansion of the balloon in the intermediate portion; and a covering member having a Shore A hardness of 30 to 60 and covering the outer circumference of the restraining member.

[0008] Any combination of the above components, as well as any conversion of the expressions of this disclosure between methods, apparatus, systems, etc., are also valid forms of this disclosure. [Effects of the Invention]

[0009] The catheter of this disclosure makes it possible to achieve both flexibility and tear strength in the covering material. [Brief explanation of the drawing]

[0010] [Figure 1]A schematic overview of EPBD, which targets nipple dilation, is shown. [Figure 2] This is a side view showing the external appearance of the balloon catheter according to this embodiment. [Figure 3] This is a side view showing the external appearance of the balloon catheter according to this embodiment. [Figure 4] This is a cross-sectional view of the balloon catheter according to this embodiment. [Figure 5] A schematic diagram illustrates the expansion of the balloon and elastic band. [Figure 6] A schematic diagram of the manufacturing method for balloon catheters is shown. [Figure 7] Figures 7(A) to 7(D) show the relationship between the load applied to each test specimen and the amount of displacement during a tensile test. [Figure 8] Figures 8(A) to 8(D) show the relationship between the load applied to each test specimen and its expanded diameter during a tensile test. [Figure 9] This figure shows the results of the fatigue test. [Figure 10] Figures 10(A) to 10(D) show the relationship between the load applied to the elastic band specimen and the amount of displacement during a fatigue test. [Figure 11] Figures 11(A) to 11(D) show the relationship between the expansion pressure and the dimensions of the balloon and elastic band. [Figure 12] Figure 12(A) shows the maximum constriction expansion pressure, the maximum constriction expansion diameter of each part of the balloon, and the ratio of the band's maximum constriction expansion diameter to the balloon's maximum constriction expansion diameter. Figure 12(B) shows the difference in maximum constriction expansion diameter. Figure 12(C) shows the ratio of the balloon's maximum constriction expansion diameter to the maximum expansion diameter. [Modes for carrying out the invention]

[0011] The embodiments for carrying out this disclosure will be described in detail below with reference to the drawings. In the description and drawings, identical or equivalent components, members, and processes are denoted by the same reference numerals, and redundant descriptions are omitted. The scales and shapes of the illustrated parts are set for convenience to facilitate the description and are not to be interpreted restrictively unless otherwise specified. The embodiments are illustrative and do not limit the scope of this disclosure. Not all features or combinations thereof described in the embodiments are necessarily essential to the invention.

[0012] The catheter of this disclosure can be used to dilate any part to be dilated or narrowed in the body (for example, tubular organs in the body such as blood vessels, trachea, gastrointestinal tract, common bile duct, pancreatic duct, etc., their connections, or holes formed in the body for examination or treatment), but in this embodiment, endoscopic papillary balloon dilatation (EPBD) for dilating the papilla (ampulla of Vater or duodenal papilla) as the part to be dilated will be described as an example.

[0013] Figure 1 schematically shows an overview of EPBD targeting the papilla 91. An endoscope 10 equipped with a forceps channel 11 and a camera 12 is inserted into the duodenum 90 through the mouth. A balloon 3, which can be inflated with an expansion fluid supplied from its proximal end (oral side or lateral side) by mixing sterile distilled water or physiological saline with an appropriate contrast agent, is attached to the tip end (duodenum 90 side or internal side) of the tubular shaft 2 of the balloon catheter 1 inserted into the body through the forceps channel 11. Note that other liquids or gases such as air may be used as the expansion fluid if appropriate in light of the purpose of the examination or treatment.

[0014] Inside the common bile duct 92 and the pancreatic duct 93, which are the target sites for examination or treatment or the routes leading to them, a small-diameter guide wire 6 is pre-inserted through the forceps channel 11. There is a papilla 91 as an area to be dilated or an opening between the duodenum 90, the common bile duct 92, and the pancreatic duct 93. The guide wire 6, which has a sufficiently small diameter compared to the opening diameter of the papilla 91, can pass through the papilla 91 and enter the inside of the common bile duct 92 or the pancreatic duct 93. At this time, the operators of the endoscope 10 and the balloon catheter 1 can safely insert the guide wire 6 into the papilla 91 while checking the image obtained from the camera 12 arranged to face the papilla 91 on the side surface of the endoscope 10.

[0015] Inside the tubular shaft 2 of the balloon catheter 1, a long wire lumen (hole) through which the guide wire 6 can be inserted from the proximal end to the distal end is formed. With the guide wire 6 inserted into the inside of the common bile duct 92 or the pancreatic duct 93 via the papilla 91, by inserting the distal end of the wire lumen in the shaft 2 from the proximal end of the guide wire 6 outside the body, the balloon 3 at the distal end of the shaft 2 guided by the guide wire 6 heads towards the papilla 91. From the illustrated state, the shaft 2 is further advanced along the guide wire 6, and the balloon 3 that has reached the position of the papilla 91 is expanded with an expansion fluid to expand the papilla 91 from the inside. Thus, since the papilla 91, which is usually narrowed by the sphincter of Oddi (or the sphincter of the bile-pancreatic duct dilation part), expands, for example, a common bile duct stone formed in the common bile duct 92 can be effectively removed from the papilla 91.

[0016] After the papilla 91 is expanded, the unnecessary balloon 3 is contracted by discharging the expansion fluid outside the body and is taken out of the body together with the shaft 2 through the forceps channel 11. After the balloon catheter 1 is taken out of the body in this way, for another medical treatment such as removing a common bile duct stone from the papilla 91 into the duodenum 90 or outside the body as needed, another medical instrument such as another forceps or a choledochoscope is inserted into the expanded papilla 91 through the guide wire 6.

[0017] Figures 2 and 3 are side views showing the appearance of the balloon catheter 1 according to the present embodiment. In these figures, a balloon 3 is attached to the tip portion (left end portion) on the inside of the body of a long tubular shaft 2 that is inserted into the body from the right side (outside the body) toward the left side (inside the body). Figure 2 shows the balloon 3 in a fully contracted state, and Figure 3 shows the balloon 3 in a partially expanded state between the fully contracted state and the fully expanded state.

[0018] The proximal end side of the shaft 2, specifically the cross-section of the portion of the shaft 2 where the balloon 3 is not attached, is partitioned into two lumens, that is, a balloon expansion lumen 21A and a wire lumen 22A, as shown in Figure 4A which shows the cross-section A-A of Figure 2. In the illustrated example, a large-diameter expansion fluid tube 21 and a small-diameter guide wire tube 22 housed inside thereof are integrally formed. The balloon expansion lumen 21A is a space partitioned by the inner circumference of the expansion fluid tube 21 and the outer circumference of the guide wire tube 22, and the wire lumen 22A is a space partitioned by the inner circumference of the guide wire tube 22.

[0019] The balloon expansion lumen 21A communicates with a balloon expansion port 71 of a manifold 7 provided at the proximal end portion on the outside of the body of the shaft 2 (the right end portion in Figures 2 and 3). The expansion fluid supplied and discharged through the balloon expansion port 71 flows between the inside of the balloon 3 through the balloon expansion lumen 21A. Specifically, when the expansion fluid is supplied from the balloon expansion port 71, the expansion fluid flows into the balloon 3 through the balloon expansion lumen 21A, causing the balloon 3 to expand. Also, when the expansion fluid is discharged from the balloon expansion port 71, the expansion fluid flows out of the balloon 3 through the balloon expansion lumen 21A, causing the balloon 3 to contract.

[0020] Although not shown in the diagram, the expansion fluid tube 21 forming the balloon expansion lumen 21A has a tapered shape, and its small-diameter open end is inserted into the internal space 21B of the balloon 3. Through this open end, the expansion fluid tube 21 (balloon expansion lumen 21A) circulates the expansion fluid between itself and the internal space 21B of the balloon 3. The internal space 21B of the balloon 3 is shown in Figures 4B, 4C, and 4D, which show the BB, CC, and DD cross-sections in Figure 2 or Figure 3, respectively, as the space partitioned by the inner circumference of the balloon 3 and the outer circumference of the guide wire tube 22.

[0021] The wire lumen 22A communicates with the guidewire port 72 of the manifold 7, which is located at the proximal end of the shaft 2 on the outside of the body (the right end in Figures 2 and 3). Unlike the expansion fluid tube 21, which terminates in the internal space 21B of the balloon 3, the guidewire tube 22 forming the wire lumen 22A penetrates the internal space 21B of the balloon 3 to the tip side (the left end in Figures 2 and 3). Thus, a long wire lumen 22A is formed inside the tubular shaft 2 of the balloon catheter 1, penetrating from the guidewire port 72 at the proximal end to the open end 221 at the tip, through which the guidewire 6 can be inserted. As described above with respect to Figure 1, with the guidewire 6 inserted into the common bile duct 92 or pancreatic duct 93 via the papilla 91, the open end 221 of the guidewire tube 22, which is the tip of the wire lumen 22A, is inserted from the proximal end of the guidewire 6 on the outside of the body, causing the balloon 3 at the tip of the shaft 2, guided by the guidewire 6, to move toward the papilla 91.

[0022] The configuration of the tip of the balloon catheter 1, where balloon 3 is provided, will be described in more detail. As shown in Figures 4B and 4C, balloon 3 is attached to the outer circumference of the guide wire tube 22, which constitutes the tip of the shaft 2, in a folded, fully deflated state. Note that in Figures 4B and 4C, the internal space 21B between the inner circumference of balloon 3 in its fully deflated state and the outer circumference of the guide wire tube 22 is exaggerated, but in reality it is negligibly small. Therefore, the inner circumference of balloon 3 in its fully deflated state and the outer circumference of the guide wire tube 22 are in contact with almost no gap.

[0023] As shown in Figure 3, the balloon 3 comprises three parts with different expansion modes or configurations, namely, a tip-side tapered portion 31, an intermediate portion 32, and a base-side tapered portion 33, in order from the tip to the base. The tip-side tapered portion 31 is formed in a tapered shape, with the maximum expansion diameter increasing from the tip portion 311 of the balloon 3, which has approximately the same diameter as the outer circumference of the guide wire tube 22, to the intermediate portion 32. The base-side tapered portion 33 is formed in a tapered shape, with the maximum expansion diameter increasing from the base portion 331 of the balloon 3, which has approximately the same diameter as the outer circumference of the guide wire tube 22 (and the shaft 2, which is a combination of the small-diameter expansion fluid tube 21), to the intermediate portion 32.

[0024] In the illustrated example, the length of the tip-side tapered portion 31 and the length of the base-side tapered portion 33 are approximately equal in the direction connecting the tip (open end 221) and base end (guide wire port 72) of the shaft 2 (hereinafter referred to as the axial direction, longitudinal direction, or left-right direction, and the dimension in this direction is called length), but they may be significantly different. Also, in the illustrated example, the expanded diameter of the tip-side tapered portion 31 and the expanded diameter of the base-side tapered portion 33 are approximately equal at points equal to the distance from the tip 311 and base end 331, respectively, in any direction perpendicular to the axial direction (hereinafter referred to as the radial direction, expansion direction, or orthogonal direction, and the dimension in this direction is also called diameter or expanded diameter), but they may be significantly different. In the illustrated example, where the maximum expanded diameter of the base end 312 of the tip-side tapered portion 31 and the maximum expanded diameter of the tip 332 of the base-side tapered portion 33 are approximately equal, the intermediate portion 32 connecting the two portions in the axial direction becomes a straight pipe section with a substantially constant maximum expanded diameter.

[0025] As shown in Figures 3 and 4B, an annular elastic band 4 is wrapped around the outer circumference of at least a portion of the intermediate section 32 as a restraining member, limiting the expansion of the balloon 3 in the intermediate section 32. In the illustrated example, a strip-shaped elastic band 4 having a constant width or length in the axial direction is wrapped around the outer circumference of the central section 322 of the intermediate section 32. The tip-side straight tube section 321 of the intermediate section 32, which is closer to the tip than the central section 322, is not restricted in its expansion by the elastic band 4 and can therefore be easily expanded to a substantially constant maximum expansion diameter. Similarly, the base-side straight tube section 323 of the intermediate section 32, which is closer to the base than the central section 322, is not restricted in its expansion by the elastic band 4 and can therefore be easily expanded to a substantially constant maximum expansion diameter. On the other hand, since the central portion 322 of the intermediate portion 32 is restricted from expanding by the elastic band 4, the expansion diameter when the pressure of the expanding fluid inside the balloon 3 (internal space 21B) is below a predetermined value (e.g., less than 2 atm) is significantly smaller (e.g., 20% or more) than the expansion diameter of the easily expandable tip-side straight pipe portion 321 and base-side straight pipe portion 323.

[0026] In the following, the initial diameter of the inner circumference of the elastic band 4 when no expanding fluid is introduced is also referred to as the constraining diameter. When no expanding fluid is introduced, the outer circumference of the central part 322 of the balloon 3 is in a fully contracted state and is in contact with the inner circumference of the elastic band 4; therefore, in the following, the initial diameter of the balloon 3 (central part 322) is also referred to as the constraining diameter. When expanding fluid is introduced into the balloon 3 (internal space 21B), the elastic band 4 begins to elastically deform and expands from the constraining diameter or initial diameter. However, at least in the region where the pressure of the expanding fluid is less than the predetermined value mentioned above, the expansion speed of the tip-side straight pipe section 321 and the base-side straight pipe section 323 on both sides is greater, so the balloon 3 expands into a dumbbell shape with the central part 322 where the elastic band 4 is provided constricted relative to the tip-side straight pipe section 321 and the base-side straight pipe section 323. Note that the expansion diameter of the elastic band 4 differs depending on the position in the longitudinal direction, and the expansion diameter of both ends, which expand in conjunction with the tip-side straight pipe section 321 and the base-side straight pipe section 323, which expand easily, is larger than that of the central part.

[0027] The elastic band 4, formed from an elastomer such as rubber or any other elastic material, expands beyond its restraint diameter when an expanding fluid is introduced into the balloon 3 (internal space 21B), as the balloon 3 expands. Figures 3 and 5A show the state immediately after the elastic band 4 begins to expand after the expanding fluid is introduced into the balloon 3. At this time, the tip-side straight pipe section 321 and the base-side straight pipe section 323, whose expansion is not restricted by the elastic band 4, expand beyond the elastic band 4, while the diameter of the central section 322, whose expansion is restricted by the elastic band 4, is limited to an expansion diameter D1 that is slightly larger than the restraint diameter Dmin of the elastic band 4 (the inner diameter of the elastic band 4 in Figure 2). Also, since the pressure P1 of the expanding fluid inside the balloon 3 (internal space 21B) at this point is less than the predetermined value, the expansion diameter D1 is 20% or more smaller than the maximum expansion diameter Dmax of the tip-side straight pipe section 321 and the base-side straight pipe section 323 (D1 < 0.8 × Dmax).

[0028] As an example of dimensions, the maximum expansion diameter Dmax is between 7 mm and 15 mm (preferably between 8 mm and 12 mm), and the restraint diameter Dmin is between 1.5 mm and 2.5 mm (preferably between approximately 2 mm). Also, the diameter of the folded balloon 3 in the fully deflated state shown in Figure 2 is between 1.5 mm and 2.5 mm (preferably between approximately 1.8 mm), and the diameter of the shaft 2 on the proximal end side of the balloon 3 is between 1.5 mm and 3 mm (preferably between 2 mm and 2.5 mm).

[0029] As shown in Figures 3 and 5A, when the balloon 3 expands, a constricted portion with a small diameter (D1) is formed in the central portion 322 between the tip-side straight tube portion 321 and the base-side straight tube portion 323, which are expanded more than the elastic band 4. When the balloon 3 is expanded as shown in Figures 3 and 5A with the central portion 322 close to the nipple 91 to be expanded (Figure 1), the nipple 91, supported from both sides by the tip-side straight tube portion 321 and the base-side straight tube portion 323, which are expanded more than the elastic band 4, can remain facing the constricted portion (central portion 322). This constricted portion can effectively support the nipple 91 from both sides when the pressure of the expanded fluid is between 0.5 atm and 1.5 atm (preferably about 1.0 atm).

[0030] If the pressure of the expanding fluid inside the balloon 3 (internal space 21B) is increased to the predetermined value P2, the elastic band 4 expands to an expansion diameter D2, as shown in Figure 5B. Also, the tip side of the tip-side straight pipe section 321 and the base side of the base-side straight pipe section 323 expand to the maximum expansion diameter Dmax. At this time, the expansion diameter D2 of the central section 322 is 20% smaller than the maximum expansion diameter Dmax of the tip-side straight pipe section 321 and the base-side straight pipe section 323 (D2 = 0.8 × Dmax). Note that due to the elasticity of the balloon 3 itself, the maximum expansion diameter Dmax increases slightly in accordance with the pressure of the expanding fluid, but this can be ignored in practice. If the pressure of the expanding fluid is further increased from the state shown in Figure 5B (for example, between 2 atm and 6 atm), the central section 322 (elastic band 4), together with the tip-side straight pipe section 321 and the base-side straight pipe section 323, can expand to the maximum expansion diameter Dmax of the balloon 3 (intermediate section 32), as shown in Figure 5C. At a minimum, the difference between the expanded diameter of the elastic band 4 or the central section 322 and the expanded diameter (maximum expanded diameter) Dmax of the tip-side straight section 321 and the base-side straight section 323 is less than 20%.

[0031] At this time, the intermediate portion 32, including the central portion 322 around which the elastic band 4 is wound, becomes a straight tube that expands to a nearly constant maximum expansion diameter Dmax. In this way, the nipple 91 is reliably expanded by the elastic band 4 (central portion 322), which elastically deforms as the balloon 3 expands and expands to a size greater than the restraint diameter Dmin. Note that if the nipple 91 can be sufficiently expanded by the elastic band 4 expanded to an arbitrary diameter D2 that is greater than the restraint diameter Dmin and smaller than the maximum expansion diameter Dmax, as shown in Figure 5B, then the state in Figure 5B can be considered the final expansion state of the balloon 3, and it is not necessary to expand the elastic band 4 to the maximum expansion diameter Dmax as shown in Figure 5C. Note that the pressure of the expansion fluid inside the balloon 3 (internal space 21B) that determines the final expansion state is set as a recommended expansion pressure, for example, between 3 atm and 5 atm (preferably about 4 atm).

[0032] To ensure accurate positioning of the balloon 3 relative to the papilla 91, contrast agents mixed with the expansion fluid supplied into the balloon 3, and two contrast markers 222 and 223 placed on the outer circumference of the guidewire tube 22 at positions corresponding to both ends (312, 332) of the middle section 32 of the balloon 3 are utilized. The position of the balloon 3 relative to the papilla 91 and the expansion of the balloon 3 can be confirmed in real time by contrast-enhanced images taken with X-rays, etc., during the EPBD procedure.

[0033] In order to effectively hold a papilla 91 of a typical size in such an EPBD facing the constricted portion, it is preferable that the axial width or length of the elastic band 4 constituting the constricted portion be between 1 mm and 10 mm. Furthermore, in order to reduce the risk of the balloon 3, which is inserted into the common bile duct 92 via the papilla 91 and expands, compressing the pancreatic duct 93 and causing inflammation, it is preferable that the length of the balloon 3 be as small as possible. Conventionally, it was necessary to increase the length of the balloon 3 so that it would not come off the papilla 91 even if the expanded balloon 3 slipped, but in the balloon catheter 1 of this embodiment, the papilla 91 can be securely held by the constricted portion formed by the elastic band 4, so the length of the balloon 3 can be reduced. Specifically, the length of the intermediate portion 32 (straight tube portion), which is the effective length of the balloon 3, can be kept between 10 mm and 40 mm. Furthermore, it is preferable that the length of the intermediate portion 32 of the balloon 3 be between 10 mm and 40 mm.

[0034] In the above, an elastic band 4, which is an annular and band-shaped elastic member surrounding at least a portion of the outer circumference of the intermediate portion 32 (the central portion 322), was used as an example of a restraining member, but the restraining member is not limited to this. For example, the restraining member may be a plurality of elastic rings wound around at least a portion of the outer circumference of the intermediate portion 32, or a coil spring made of nickel-titanium alloy (NiTi) or the like wound spirally around at least a portion of the outer circumference of the intermediate portion 32. These elastic members only need to be members that generate a significant elastic force in the contraction direction when expanded by the pressure of the expanding fluid, and it is not required that they return completely to their original state (restraining diameter or initial diameter) after the expanding fluid is discharged. Therefore, some deformation (i.e., plastic deformation) may remain in the elastic member after the expanding fluid is discharged. Furthermore, the restraining member may be a member that does not have elasticity or has limited elasticity. For example, a plastic member made of metal or the like that can be plastically deformed by the expanding balloon 3 and expanded beyond the restraining diameter, but cannot be contracted once expanded, may be used as a restraining member. Alternatively, a rigid member that is substantially immovable and maintains its restraining diameter when the pressure of the expanded fluid inside the balloon 3 is below a predetermined value, and ruptures when the pressure of the expanded fluid inside the balloon 3 exceeds a predetermined value, may be used as the restraining member.

[0035] Furthermore, the restraining member, which is an elastic or plastic member, may be designed to rupture when the pressure of the expanding fluid inside the balloon 3 is further increased after it has elastically or plastically deformed to a predetermined diameter (for example, diameter D2 in Figure 5B). In this way, the central part 322, having lost the restraining member, automatically expands to the maximum expansion diameter Dmax as shown in Figure 5C (however, the elastic band 4 has ruptured), so the intermediate part 32 as a whole becomes a straight tube that has expanded to a substantially constant maximum expansion diameter Dmax. The covering member 5, which will be described next, covers the restraining member, including the plastically deformed plastic member and the fractured rigid member, from the outer circumference, thus preventing the restraining member from falling off the balloon 3 and shaft 2. In this way, the restraining member is prevented from falling into the body, making it possible to form the restraining member from materials that are not common in medical applications. Furthermore, by forming the restraining member (elastic band 4, etc.) from a material that does not transmit X-rays, the restraining member may be given a contrast-enhancing function similar to the contrast-enhancing markers 222 and 223 provided on the outer circumference of the guide wire tube 22.

[0036] Furthermore, the restraint member that remains within the covering member 5 can also function as an alignment marker (visibility part) visible through the camera 12 of the endoscope 10. Such a visibility part is provided in the middle part 32 of the balloon 3 (particularly the central part 322) and has features that make it visually distinguishable from other parts of the balloon 3 (e.g., the tip-side straight tube part 321, the proximal-side straight tube part 323, the tip-side tapered part 31, the proximal-side tapered part 33). For example, the elastic band 4 (restraint member) as a visibility part has a different color and / or pattern from other parts of the balloon 3. For example, since a typical balloon 3 is colorless or white and patternless, the elastic band 4 can be made to function as a visibility part that is visually distinguishable from the balloon 3 by adding a color other than white (gray or black) or any chromatic color and / or any pattern. The operator of the balloon catheter 1 can safely and reliably operate the balloon catheter 1 while visualizing the elastic band 4 as a visibility part that is distinguishable from the balloon 3 and target sites such as the papilla 91.

[0037] The visible portion is not limited to the elastic band 4 as a restraining member, but may also be formed on the balloon 3 or the covering member 5. When forming the visible portion as part of the balloon 3, the intermediate portion 32 (especially the central portion 322) where the visible portion should be formed may be given a different color or pattern from the other parts. Specifically, the material or properties of the area to be made visible in the balloon 3 may be changed from those of other parts to create a difference in color, pattern, etc., that is visually distinguishable from the other parts. When forming the visible portion on the covering member 5, a different color or pattern should be given to the position corresponding to the intermediate portion 32 (especially the central portion 322) of the balloon 3 where the visible portion should be formed. The visible portion can also be applied to balloon catheters 1 that do not have the elastic band 4 and / or the covering member 5. In this case, it is preferable to form a visible portion on the balloon 3 as described above, but an annular marker band that functions as a visible portion (but does not function as a restraining member) may be wrapped around the outermost circumference of the intermediate portion 32 (especially the central portion 322) of the balloon 3 in place of or in addition to the elastic band 4.

[0038] The covering member 5 covers the outer circumference of the elastic band 4 as shown in Figure 4B, and covers the outer circumference of the balloon 3 as shown in Figures 4C and 4D. The radial thickness of the covering member 5 (when not expanded) is, for example, about 75 μm, and the radial thickness of the elastic band 4 (when not expanded) is, for example, about 100 μm. The covering member 5 is a long, tubular elastic tube formed from any elastic material. In Figure 3, the tip of the covering member 5 (not shown) is fixed by a short fixing tube 51 made of thermoplastic elastomer or the like, covering the outer circumference of the guide wire tube 22 that extends from the tip 311 of the balloon 3 toward the tip. The base end of the covering member 5 is fixed by a short fixing tube 52 made of thermoplastic elastomer or the like, covering the outer circumference of the shaft 2 that extends from the base end 331 of the balloon 3 toward the base. Due to the difference in diameter between the small-diameter guide wire tube 22 at the tip and the large-diameter shaft 2 at the base, the diameter of the fixing tube 51 is smaller than the diameter of the fixing tube 52.

[0039] In this manner, both ends of the covering member 5, which is longer than the elastic band 4 and balloon 3, are fixed to the outer circumference of the shaft 2 (including the guide wire tube 22) on the tip and proximal ends of the elastic band 4. The covering member 5 may be shorter than the balloon 3, and both ends of the covering member 5 may be fixed to the outer circumference of the balloon 3 on the tip and proximal ends of the elastic band 4. For example, both ends of the covering member 5 may be fixed to the outer circumference of the tip tapered portion 31 and the proximal tapered portion 33, or to the outer circumference of the tip straight tube portion 321 and the proximal straight tube portion 323. In addition, in the balloon catheter 1, electrodes for medical procedures or measurements, or a tip (a member on which the open end 221 is formed) that constitutes the tip of the balloon catheter 1 or shaft 2 may be provided on the tip side of the balloon 3, and the covering member 5 may be fixed to the outer circumference of such electrodes (or part thereof) or tip.

[0040] In these cases, the covering member 5 covers not only the outer circumference of the elastic band 4 but also the outer circumference of the balloon 3 that is not wrapped with the elastic band 4, thus preventing the elastic band 4 and other restraining members from falling off the balloon 3. Furthermore, in the illustrated example, the covering member 5 covers not only the outer circumference of the elastic band 4 and the balloon 3 but also the outer circumference of the shaft 2 (including the guide wire tube 22) to which the balloon 3 is not attached, thus not only preventing the elastic band 4 and other restraining members from falling off the balloon 3 and the shaft 2, but also allowing the balloon 3 to be effectively deflated by the elasticity of the covering member 5 when the balloon catheter 1 is removed.

[0041] As described above, the covering member 5 is fixed to the outer circumference of the shaft 2 and / or balloon 3 at both ends, but not to the outer circumference of the balloon 3 and / or elastic band 4 at any other point. Therefore, as shown in Figure 4B, the elastic band 4, which is covered from the outside by the covering member 5, is not bonded to the inner circumference of the covering member 5. Similarly, the elastic band 4 is not bonded to the outer circumference of the inner balloon 3 (central portion 322). However, because the elastic band 4 is pressed against the balloon 3 from the outside by the elasticity of the covering member 5, it can remain in the desired position (central portion 322) and is prevented from falling off the balloon 3. In Patent Document 1, the band portion was welded to the balloon, but in this embodiment, there is no need to bond the elastic band 4 to the balloon 3 (and covering member 5), so the balloon catheter 1 can be manufactured economically. Furthermore, if the band portion is welded to the balloon as in Patent Document 1, there is a risk that the desired expansion of the balloon and band portion will be hindered at the welding point. In this embodiment, since the elastic band 4 and the balloon 3 are not welded or bonded together, they can expand as intended without interfering with each other.

[0042] The elastic covering member 5 holds the balloon 3 in a fully deflated state by pressing the balloon 3 and / or the elastic band 4 from the outside when the balloon 3 is not expanded, as shown in Figure 2. When the expansion fluid is supplied into the balloon 3 (internal space 21B) and the balloon 3 and / or the elastic band 4 expand, the covering member 5 elastically deforms and expands. The initial diameter or covering diameter (the inner diameter of the covering member 5 in a position where the elastic band 4 is not provided, as shown in Figure 4C) when the covering member 5 begins to elastically deform is smaller than the restraining diameter Dmin of the elastic band 4 shown in Figure 4B.

[0043] To achieve the expansion configuration of the balloon 3 and elastic band 4 shown in Figure 5, the balloon 3 is configured to have a higher modulus of elasticity than the elastic band 4, and the elastic band 4 is configured to have a higher modulus of elasticity than the covering member 5. Since the modulus of elasticity (also called Young's modulus) represents the resistance to deformation, the balloon 3 is less deformable than the elastic band 4, and the elastic band 4 is less deformable than the covering member 5. In other words, the covering member 5, elastic band 4, and balloon 3 are deformable in that order. The covering member 5, which is the most deformable, expands almost completely in accordance with the expansion of the inner balloon 3 and / or elastic band 4.

[0044] When expansion fluid is supplied to the balloon 3 (internal space 21B) in the fully contracted state shown in Figure 2, the balloon 3 begins to expand from its folded state, and the elastic band 4 wrapped around the central part 322 of the balloon 3 and the covering member 5 covering them expand in response. Figure 5A shows the state when the pressure of the expansion fluid inside the balloon 3 (internal space 21B) reaches P1. As described above, the balloon 3 expands into a dumbbell shape due to the tip-side straight pipe section 321 and the base-side straight pipe section 323 which expand significantly more than the central part 322, and the central part 322 which is limited to an expansion diameter D1 that is more than 20% smaller than the maximum expansion diameter Dmax.

[0045] If the pressure of the expanding fluid inside the balloon 3 (internal space 21B) is further increased to P2 (>P1) from the state shown in Figure 5A, the elastic band 4 will further deform elastically as shown in Figure 5B, expanding to a larger diameter than the expansion diameter D1 in Figure 5A, and the covering member 5 covering the elastic band 4 will also expand accordingly. The tapered portion 31 at the tip and the tapered portion 33 at the base of the balloon 3 had already expanded to their maximum expansion diameter at the time shown in Figure 5A, so even if the pressure of the expanding fluid is increased in Figure 5B, the balloon 3 will hardly expand any further due to its high elasticity. Also, the tip side of the straight tube portion 321 at the tip and the base side of the straight tube portion 323 at the base will expand to their maximum expansion diameter Dmax. If the pressure of the expanding fluid inside the balloon 3 (internal space 21B) is further increased to P3 (>P2) from the state shown in Figure 5B, the elastic band 4 will expand to its maximum expansion diameter Dmax as shown in Figure 5C, and the covering member 5 covering the elastic band 4 will also expand accordingly. Even if the pressure of the expanding fluid inside balloon 3 (internal space 21B) is further increased from the state shown in Figure 5C, balloon 3 hardly expands any further due to its high elasticity.

[0046] When the balloon catheter 1 is removed, the pressure of the expansion fluid inside the balloon 3 (internal space 21B) is reduced, and / or the expansion fluid is discharged from the balloon expansion port 71. The elasticity of the elastic band 4 and / or the covering member 5 effectively deflates the balloon 3, returning it to a state close to the fully deflated state shown in Figure 2 before expansion. In this case, the elastic band 4 functions as a deflation structure that causes the middle portion 32 (particularly the central portion 322) of the balloon 3 to deflate before the tip (including the tip-side straight tube portion 321) and the proximal portion (including the proximal-side straight tube portion 323) when the expansion fluid is discharged from the balloon 3. In other words, the elastic band 4 as a deflation structure increases the deflation rate of the middle portion 32 of the balloon 3 on which the deflation structure is provided, relative to the tip and proximal portions. As shown in Figure 5C, the elasticity of the elastic band 4 when expanded to its maximum expansion diameter Dmax may decrease from its initial state (for example, at the time shown in Figure 5A). However, the remaining elasticity at the time shown in Figure 5C allows the elastic band 4 to contract the middle section 32 first when the balloon 3 is deflated, and then the entire balloon 3 is effectively deflated by going through the same stages as in Figures 5B and 5A.

[0047] As described above, the elasticity of the elastic band 4 and / or covering member 5 effectively deflates the balloon 3, preventing it from becoming lodged in the forceps channel 11 (Figure 1) of the endoscope 10, and allowing the balloon catheter 1 to be easily removed. Furthermore, regardless of the expanded or contracted state of the balloon 3, the elastic band 4 is pressed against and held against the balloon 3 from the outside by the elasticity of the covering member 5, effectively preventing the elastic band 4 or other restraining members from falling off the balloon 3.

[0048] In Patent Document 1, where there was a possibility of the band portion detaching, it was necessary to make the elasticity of the band portion stronger than necessary to prevent detachment. However, in this embodiment, the function of preventing detachment is realized by the covering member 5, so there is no need to consider the risk of detachment when designing the elasticity, dimensions, shape, etc. of the elastic band 4, and it can be optimized solely to realize the desired expansion configuration as shown in Figure 5.

[0049] Figure 6 schematically shows the manufacturing method of the balloon catheter 1. In Figure 6A, the balloon 3 is attached to the outer circumference of the tip end of the shaft 2. The tip 311 of the balloon 3 is bonded to the outer circumference of the guide wire tube 22 of the shaft 2, sealing it to prevent leakage of the expansion fluid inside the balloon 3 (internal space 21B). The base end 331 of the balloon 3 is bonded to the outer circumference of the shaft 2, which has an expansion fluid tube 21 and a guide wire tube 22, as shown in Figure 4A, sealing it to prevent leakage of the expansion fluid inside the balloon 3 (internal space 21B). The guide wire tube 22 of the shaft 2 penetrates the entire length of the balloon 3, while the expansion fluid tube 21 terminates in the internal space 21B of the balloon 3, allowing the expansion fluid to flow between the internal space 21B of the balloon 3 and the guide wire tube 22 through its open end. As described above, the balloon 3, with both ends 311 and 331 bonded to the outer circumference of the shaft 2, is wound around the outer circumference of the shaft 2 and folded into multiple (for example, three) wing-like shapes.

[0050] In Figure 6B, the elastic band 4 is attached to the central part 322 of the folded balloon 3. For example, the tip of the guide wire tube 22 is inserted into the elastic band 4, and the elastic band 4 is slid down to the central part 322 of the balloon 3. At this time, it is not necessary to adhere the elastic band 4 to the outer circumference of the balloon 3 (central part 322). A lubricant such as silicone oil or silicone powder may be added or applied between the outer circumference of the balloon 3 and the inner circumference of the elastic band 4 to improve ease of assembly. In Figure 6C, a long tubular covering member 5 is attached to cover the folded balloon 3 and the elastic band 4, and its tip and base ends are fixed by fixing tubes 51 and 52. At this time, it is not necessary to adhere the covering member 5 to parts other than the tip 311 and base end 331 of the balloon 3 or to the outer circumference of the elastic band 4. A lubricant such as silicone oil or silicone powder may be added or applied between the outer circumference of the elastic band 4 and the inner circumference of the covering member 5 to improve ease of assembly.

[0051] As shown in Figure 4B, in this embodiment, the elastic band 4 and the covering member 5, both of which are elastic, were separate components, but they may also be integrally formed from the same elastic material. In this elastic member, the function of the elastic band 4 is achieved by making the thickness of the part corresponding to the central part 322 of the balloon 3 larger than that of other parts.

[0052] The covering member 5 has a Shore A hardness of 30 to 60. Examples of materials that make up such a covering member 5 include polyurethane with a Shore A hardness of 30 to 60, and silicone rubber with a Shore A hardness of 40 to 60. By setting the Shore A hardness of the covering member 5 to 30 to 60, it is possible to ensure the covering member 5's ability to follow the deformation caused by the expansion of the balloon 3 and elastic band 4, in other words, its flexibility, while also providing the covering member 5 with good tear strength. In short, it is possible to achieve both flexibility and tear strength in the covering member 5.

[0053] A metal member (not shown) may be placed at the tip opening of the forceps channel 11 to direct the advancement direction of the guide wire 6 and shaft 2 toward the papilla 91. When the covering member 5 passes through the tip opening of the forceps channel 11, it may be struck by the metal member and tear. However, if the covering member 5 has good tear strength, it is possible to prevent the tear from spreading and the covering member 5 from being completely torn when the covering member 5 expands together with the balloon 3 and elastic band 4.

[0054] Preferably, the Shore A hardness of balloon 3 is 80 or higher. Examples of materials constituting such balloon 3 include nylon elastomer and polyamide, which have a Shore A hardness of 80 or higher. By setting the Shore A hardness of balloon 3 to 80 or higher, it is possible to more reliably suppress excessive expansion and rupture of balloon 3 due to the inflow of the expanding fluid. The hardness of the material constituting balloon 3 is generally expressed in Shore D hardness. If the Shore A hardness of balloon 3 is 80 or higher, the Shore D hardness of balloon 3 is 30 or higher. Furthermore, the Shore D hardness of balloon 3 preferably has a lower limit of 40 or higher, 60 or higher, or 70 or higher, and an upper limit of 80 or lower, or 75 or lower.

[0055] Preferably, the Shore A hardness of the balloon 3 is higher than the Shore A hardness of the covering member 5, and the difference between the Shore A hardness of the balloon 3 and the Shore A hardness of the covering member 5 is 20 or more. This allows the balloon 3 to expand the constricted area while suppressing the covering member 5 from hindering the expansion of the balloon 3.

[0056] (Relationship between the strength and displacement of each component) The inventors evaluated the relationship between the strength and displacement of each component, the balloon 3, the restraining member, and the covering member 5, by tensile tests described below. Specifically, they first prepared a balloon 3 made of PEBAX, an elastic band 4 made of polyurethane, and a covering member 5 made of polyurethane. The elastic band 4 is an example of a restraining member. The balloon 3 was prepared with maximum expansion diameters Dmax set to 8 mm, 10 mm, 12 mm, and 15 mm. The elastic band 4 and covering member 5 were also prepared to correspond to each maximum expansion diameter Dmax. The maximum expansion diameter Dmax is the diameter of the tip-side straight tube section 321 and the proximal-side straight tube section 323 when fully expanded, and is generally stated on the product as a product specification for the balloon catheter 1. The size and material of each component before expansion are selected so as to obtain the set maximum expansion diameter Dmax.

[0057] Each component was cut to a width of 3 mm to create three annular test specimens (N1 to N3). The test specimen for balloon 3 was prepared by cutting the middle section 32. Each test specimen was set in a tensile testing machine, and a tensile test was performed until each specimen fractured. Specifically, a pair of chucks on the tensile testing machine were attached to each test specimen, and the pair of chucks were displaced in opposite directions to pull each specimen until it fractured. The chucks were metal V-clips with a wire diameter of 0.80 mm, and each test specimen was attached to the straight section of the V-clip. A load cell was then used to measure the load applied to each test specimen in relation to its displacement. The load applied to each test specimen can be considered as the strength of each specimen.

[0058] Figures 7(A) to 7(D) show the relationship between the load applied to each test specimen and the amount of displacement during a tensile test. Figure 7(A) shows the results for each member corresponding to a maximum expansion diameter of 8 mm. Figure 7(B) shows the results for each member corresponding to a maximum expansion diameter of 10 mm. Figure 7(C) shows the results for each member corresponding to a maximum expansion diameter of 12 mm. Figure 7(D) shows the results for each member corresponding to a maximum expansion diameter of 15 mm. In each figure, the displacement was defined as 0 when the test specimen was taut and without deflection, i.e., just before the load was applied to the test specimen, i.e., the distance between the chucks.

[0059] As shown in Figures 7(A) to 7(D), in all cases of maximum expansion diameter Dmax, the amount of displacement before rupture (hereinafter referred to as the maximum displacement) was greater for the covering member 5 than for the elastic band 4 and balloon 3, and greater for the elastic band 4 than for balloon 3. By setting the maximum displacement of each member in this way, the balloon 3 can be expanded into a dumbbell shape more reliably, and the covering member 5 can be made to follow the deformation of the balloon 3 and elastic band 4. The maximum displacement of the balloon 3 is preferably 10 mm or less.

[0060] Furthermore, in all cases of maximum expansion diameter Dmax, the load applied to each test specimen at maximum displacement, in other words, the strength of each test specimen at maximum displacement, was approximately the same for balloon 3 and elastic band 4, while the covering member 5 was lower than that of balloon 3 and elastic band 4. By setting the strength of each member in this way, it becomes possible to adopt a material more suitable for the role of each member. This makes it easier to impart the pressure resistance necessary to maintain the shape at maximum expansion to balloon 3 and elastic band 4. It also makes it easier to impart tear resistance and flexibility to covering member 5.

[0061] The balloon 3 and the covering member 5 are not adhered to each other except at both ends. Preferably, at least the intermediate portion 32 is not adhered to the covering member 5. More preferably, the tip-side tapered portion 31 and the base-side tapered portion 33 are also not adhered to the covering member 5. This makes it possible to suppress the deformation of the balloon 3 into a dumbbell shape from being hindered by the covering member 5.

[0062] It is preferable that no components, including stents or electrodes, are placed on the surface of the covering member 5. This prevents the balloon 3 from being hindered by such components. It also prevents the balloon 3, elastic band 4, or covering member 5 from being damaged by such components. Furthermore, it prevents the nipple 91 from being hindered by such components.

[0063] (Strength of each component at maximum expansion) The displacement amounts on the horizontal axis in Figures 7(A) to 7(D) were converted to the diameter of the specimen when expanded (hereinafter referred to as the expanded diameter) according to the conversion method described below. That is, when the specimen is supported by a pair of chucks, the total length of the specimen, i.e., the length from the end supported by one chuck to the end supported by the other chuck, is substantially equal to half the circumference of the specimen. Furthermore, when the specimen is pulled by a pair of chucks, it can be interpreted that the circumference length expands by twice the displacement amount of the specimen. Therefore, the displacement amount (mm) can be converted to the expanded diameter (mm) according to the formula: Expanded diameter = {(Total length + Displacement amount) × 2} / π.

[0064] The total length of the balloon 3 test specimen can be obtained, for example, by measuring the distance from one end to the other of the test specimen when it is pressed against a flat surface. The total lengths of the elastic band 4 test specimen and the covering member 5 test specimen can be obtained in the same way as the balloon 3 test specimen, or, if the tensile test has not yet been performed, they can be obtained from the product dimensions of the resin tubes used for the elastic band 4 and covering member 5, respectively.

[0065] Figures 8(A) to 8(D) show the relationship between the load applied to each test specimen and the expansion diameter during a tensile test. Figure 8(A) shows the results for each member corresponding to a maximum expansion diameter of 8 mm. Figure 8(B) shows the results for each member corresponding to a maximum expansion diameter of 10 mm. Figure 8(C) shows the results for each member corresponding to a maximum expansion diameter of 12 mm. Figure 8(D) shows the results for each member corresponding to a maximum expansion diameter of 15 mm. In Figures 8(A) to 8(D), the position of the expansion diameter at maximum expansion is indicated by the dashed vertical line.

[0066] As shown in Figures 8(A) to 8(D), in all cases of maximum expansion diameter Dmax, the load applied at maximum expansion, in other words, the strength at maximum expansion, was lower for the covering member 5 than for the balloon 3 and elastic band 4. The strength of the balloon 3 and elastic band 4 at maximum expansion is, for example, 5N to 25N. Alternatively, the strength of the balloon 3 and elastic band 4 at maximum expansion may be 5N to 20N, 5N to 12N, 6N to 11N, 7N to 10N, or 10N to 20N.

[0067] Preferably, at maximum expansion, the strength of the balloon 3 and the strength of the elastic band 4 are similar. This makes it easier to expand the central portion 322 to the same extent as the tip-side straight tube portion 321 and the base-side straight tube portion 323 at maximum expansion, thus changing from a dumbbell shape to a flat state without a constriction. The strength of the balloon 3 may be higher than the strength of the elastic band 4. Also, the strength of the covering member 5 at maximum expansion may be, for example, 5N or less, or 3N or less. Furthermore, the strength of the covering member 5 at maximum expansion may be 1 / 2 or less, 1 / 3 or less, or 1 / 4 or less of the strength of the balloon 3 at maximum expansion. In addition, the strength of the covering member 5 at maximum expansion may be 1 / 2 or less, 1 / 3 or less, or 1 / 4 or less of the strength of the elastic band 4 at maximum expansion.

[0068] (Deformation before and after expansion of elastic band 4) The inventors evaluated the degree of deformation of the elastic band 4 before and after expansion by conducting a fatigue test in which the elastic band 4 was repeatedly expanded to a state corresponding to the maximum expansion of the balloon 3, and then contracted. Specifically, it was assumed that when the balloon 3 reaches its maximum expansion diameter Dmax, the circumference of the elastic band 4 is substantially equal to the circumference of the balloon 3 at its maximum expansion. Furthermore, as described above, the total length of the test specimen is substantially equal to half the circumference of the test specimen. Therefore, in order to reproduce the expansion of the elastic band 4 corresponding to the maximum expansion of the balloon 3 in a tensile test, it is sufficient to pull the test specimen by half the amount by which the circumference of the test specimen increases until it reaches the circumference at maximum expansion.

[0069] Therefore, the half length of the circumference of balloon 3 at its maximum expanded diameter Dmax was calculated. For example, if the maximum expanded diameter Dmax is 15 mm, the half length is 15 × π / 2 = 23.6 mm. In addition, the distance between the chucks (hereinafter referred to as the initial distance) when no load is applied to the elastic band 4 test specimen was calculated from the inner diameter of the elastic band 4 test specimen before the tensile test (hereinafter referred to as the initial inner diameter). The initial inner diameter was obtained from the product dimensions of the resin tube used for the elastic band 4. For example, if the maximum expanded diameter is 15 mm, the initial inner diameter of the elastic band 4 test specimen is 2.1 mm as an example. In this case, the initial distance is 2.1 × π / 2 = 3.3 mm.

[0070] Then, the tensile distance of the test specimen required to achieve the state of the elastic band 4 corresponding to the maximum expansion of balloon 3 was calculated by subtracting the initial distance from half the circumference of balloon 3 at its maximum expansion diameter Dmax. For example, if the maximum expansion diameter Dmax is 15 mm, the tensile distance is 23.6 - 3.3 = 20.3 mm. If the maximum expansion diameter Dmax is 8 mm, the initial inner diameter of the elastic band 4 test specimen is 1.6 mm as an example, and the tensile distance is 10.1 mm. If the maximum expansion diameter Dmax is 10 mm, the initial inner diameter of the elastic band 4 test specimen is 1.8 mm as an example, and the tensile distance is 12.9 mm. If the maximum expansion diameter Dmax is 12 mm, the initial inner diameter of the elastic band 4 test specimen is 1.9 mm as an example, and the tensile distance is 15.9 mm.

[0071] Then, a pair of chucks were moved from an initial distance to the tensile distance at a travel speed of 100 mm / min, and then returned to the initial distance. This operation was considered one cycle, and this operation was performed 10 times. The total length of the test specimen after one cycle of this operation (hereinafter referred to as the post-test total length) was measured. The difference between the total length of the test specimen before the operation (hereinafter referred to as the initial total length) and the post-test total length was calculated, and this difference was defined as the permanent strain (mm) of the elastic band 4. The recovery rate (%) of the elastic band 4 was calculated according to the formula: recovery rate = {1 - (permanent strain / tensile distance)} × 100. Furthermore, the permanent strain rate (%) of the elastic band 4 was calculated according to the formula: permanent strain rate = {(initial total length + permanent strain) / initial total length} × 100. The maximum load (N) applied to the test specimen in the first cycle was also measured. In addition, the maximum load (N) applied to the test specimen during cycles 2 to 10 and the minimum load (N) applied to the test specimen during cycles 2 to 10 were measured. Furthermore, the average load (N) applied to the test specimen during cycles 2 to 10 was calculated.

[0072] Figure 9 shows the results of the fatigue test. Figures 10(A) to 10(D) show the relationship between the load applied to the elastic band 4 specimen and the amount of displacement during the fatigue test. Figure 10(A) shows the results for a specimen corresponding to a maximum expansion diameter of 8 mm. Figure 10(B) shows the results for a specimen corresponding to a maximum expansion diameter of 10 mm. Figure 10(C) shows the results for a specimen corresponding to a maximum expansion diameter of 12 mm. Figure 10(D) shows the results for a specimen corresponding to a maximum expansion diameter of 15 mm.

[0073] The elastic band 4 is required to have the desired elasticity or flexibility to follow the expansion of the balloon 3. Ideally, the elastic band 4 should return to its initial inner diameter when the balloon 3, which has expanded to its maximum expansion diameter Dmax, deflates. In other words, it is ideal that the elastic band 4 can follow the expansion of the balloon 3 solely through elastic deformation. For example, an elastic band 4 corresponding to a maximum expansion diameter of 8 mm should ideally be able to achieve a 5.0-fold expansion from an initial inner diameter of 1.6 mm to 8 mm solely through elastic deformation. Similarly, an elastic band 4 corresponding to a maximum expansion diameter of 15 mm should ideally be able to achieve a 7.14-fold expansion from an initial inner diameter of 2.1 mm to 15 mm solely through elastic deformation.

[0074] On the other hand, the elastic band 4 is required to exert a desired restraining force so that the balloon 3 becomes dumbbell-shaped during expansion. For example, the elastic band 4 is required to be able to withstand the pressure exerted by the expansion of the balloon 3 when the internal pressure of the balloon 3 is less than 2 atm to less than 4 atm, and to succumb to the pressure and expand together with the balloon 3 when the internal pressure is 2 atm or more to 4 atm or more. In order to give the elastic band 4 such a restraining force, it is necessary to construct the elastic band 4 from a material that has a certain degree of hardness or rigidity. However, as the hardness or rigidity of the elastic band 4 increases, it tends to lose its elasticity.

[0075] If the elasticity of the elastic band 4 decreases, it becomes difficult to achieve the above-mentioned expansion of more than five times through elastic deformation alone. If the elastic band 4 deforms beyond its elastic deformability range, it may not be able to return to its initial inner diameter when the balloon 3 deflates. In this case, there is a risk that the elastic band 4 will detach when the balloon 3 deflates. In contrast, in the balloon catheter 1 of this embodiment, the covering member 5 covers the balloon 3 and the elastic band 4, so it is possible to prevent the elastic band 4 from detaching from the balloon 3.

[0076] Therefore, a certain degree of plastic deformation of the elastic band 4 can be tolerated. This increases the freedom in material selection for the elastic band 4 and makes it easier to apply the desired restraining force to the elastic band 4. Thus, it becomes easier to deform the balloon 3 into a dumbbell shape. As a result, it is possible to more reliably prevent the balloon 3 from detaching from the papilla 91. In addition, by preventing the elastic band 4 from falling off with the covering member 5, the safety of the procedure using the balloon catheter 1 can be increased.

[0077] One could consider increasing the thickness of the elastic band 4 to balance elasticity and restraint, but this could lead to an increase in the diameter of the balloon catheter 1. Other materials that could balance elasticity and restraint include latex and isoprene, but these are difficult to process into thin walls of 100 μm or less. Therefore, this could also lead to an increase in the diameter of the balloon catheter 1. In contrast, the balloon catheter 1 of this embodiment, in which the elastic band 4 is covered with a covering member 5, can solve these problems.

[0078] The recovery rate of the elastic band 4 is preferably 65% ​​or more, more preferably 70% or more, and even more preferably 75% or more. Furthermore, the permanent deformation rate of the elastic band 4 is preferably 400% or less, more preferably 300% or less, and even more preferably 250% or less.

[0079] (Relationship between the dimensions of each part and the internal pressure of balloon 3) The inventors evaluated the relationship between the dimensions of each part of the balloon 3 when it is expanded and the internal pressure of the balloon 3 (hereinafter referred to as the expansion pressure) by expansion tests described below. Specifically, assemblies of the balloon 3, elastic band 4, and covering member 5 were prepared, each with a maximum expansion diameter Dmax set to 8 mm, 10 mm, 12 mm, and 15 mm. The balloon 3 was expanded by supplying expansion fluid from a fluid supply device to each balloon 3. The expansion pressure (atm) at that time was then measured. In this test, the pressure applied inside the balloon 3 by the fluid supply device was defined as the expansion pressure of the balloon 3.

[0080] Furthermore, while increasing the expansion pressure, the expansion diameters (mm) of the tip-side straight tube section 321, the base-side straight tube section 323, and the elastic band 4 were measured. The difference in diameter (mm) between the larger of the tip-side straight tube section 321 and the base-side straight tube section 323 (hereinafter referred to as the expansion diameter of the balloon section) and the expansion diameter of the elastic band 4 (hereinafter referred to as the expansion diameter of the band section) was calculated. In addition, the ratio (%) of the diameter difference to the expansion diameter of the balloon section (hereinafter referred to as the diameter difference / diameter ratio) was calculated.

[0081] Figures 11(A) to 11(D) show the relationship between the expansion pressure and the dimensions of the balloon 3 and elastic band 4. Figure 11(A) shows the results for an assembly with a maximum expansion diameter of 8 mm. Figure 11(B) shows the results for an assembly with a maximum expansion diameter of 10 mm. Figure 11(C) shows the results for an assembly with a maximum expansion diameter of 12 mm. Figure 11(D) shows the results for an assembly with a maximum expansion diameter of 15 mm. Note that each expansion diameter includes the wall thickness of the covering member 5, but for convenience, the wall thickness of the covering member 5 will be ignored in this explanation.

[0082] In assemblies with a maximum expansion diameter Dmax of 8 mm, it was confirmed that balloon 3 reached its maximum expansion diameter Dmax at an expansion pressure of 6 atm. In assemblies with maximum expansion diameters Dmax of 10 mm, 12 mm, and 15 mm, it was confirmed that balloon 3 reached its maximum expansion diameter Dmax at an expansion pressure of 4 atm. Furthermore, in all cases of maximum expansion diameter Dmax, the diameter difference / diameter ratio was 6.3% or less when the expansion pressure was 2 atm or higher. In other words, at expansion pressures of 2 atm or higher, there was virtually no constriction in balloon 3.

[0083] When balloon 3 was at its maximum expanded diameter Dmax, the diameter difference / diameter ratio was 4.0% or less. Therefore, it was confirmed that the nipple 91 could be reliably expanded. The diameter difference / diameter ratio when balloon 3 is at its maximum expanded diameter Dmax is preferably 10% or less, more preferably 8% or less, and even more preferably 6% or less.

[0084] Furthermore, in the aforementioned expansion test, the expansion pressure at which the diameter difference is maximum, that is, the expansion pressure at which the constriction of balloon 3 is maximum (hereinafter referred to as the maximum constriction expansion pressure), was identified. Specifically, as the expansion pressure gradually increases and exceeds a predetermined value, the internal pressure of balloon 3 exceeds the restraining force of the elastic band 4, and the central part 322 of balloon 3 begins to expand. In all cases of maximum expansion diameter Dmax, the central part 322 began to expand at approximately 0.70 atm or higher. Then, the expansion of the central part 322 stagnates at a certain point. In this test, the pressure at which the expansion stagnates was defined as the maximum constriction expansion pressure.

[0085] Furthermore, the expansion diameters (hereinafter referred to as the maximum constriction expansion diameter) of the tip-side straight tube section 321, the base-side straight tube section 323, and the elastic band 4 were measured when the internal pressure of balloon 3 was at the maximum constriction expansion pressure. The ratio (%) of the maximum constriction expansion diameter of the elastic band 4 to the larger of the maximum constriction expansion diameters of the tip-side straight tube section 321 and the base-side straight tube section 323 was calculated (hereinafter referred to as the band maximum constriction expansion diameter / balloon maximum constriction expansion diameter ratio). The difference (hereinafter referred to as the maximum constriction expansion diameter difference) between the maximum constriction expansion diameters of the tip-side straight tube section 321 and the base-side straight tube section 323 and the maximum constriction expansion diameter of the elastic band 4 was also calculated. Finally, the ratio (%) of the maximum constriction expansion diameters (hereinafter referred to as the balloon maximum constriction expansion diameter / maximum expansion diameter ratio) to the maximum expansion diameter Dmax was calculated.

[0086] Figure 12(A) shows the maximum constriction expansion pressure, the maximum constriction expansion diameter of each part of balloon 3, and the ratio of the band's maximum constriction expansion diameter to the balloon's maximum constriction expansion diameter. Figure 12(B) shows the difference in maximum constriction expansion diameter. Figure 12(C) shows the ratio of the balloon's maximum constriction expansion diameter to the maximum expansion diameter.

[0087] When the expansion pressure of balloon 3 reaches the maximum constriction expansion pressure, the ratio of the band's maximum constriction expansion diameter to the balloon's maximum constriction expansion diameter is preferably 40% or more, more preferably 50% or more, and even more preferably 70% or more. Furthermore, the ratio of the balloon's maximum constriction expansion diameter to the maximum expansion diameter is preferably 70% or more, more preferably 75% or more, and even more preferably 80% or more. Also, the ratio of the balloon's maximum constriction expansion diameter to the maximum expansion diameter may be 100% or less, 95% or less, or 90% or less.

[0088] The material, thickness, width, etc., of each component are appropriately adjusted to satisfy the preferred conditions derived from the tests described above.

[0089] The present disclosure has been described above based on embodiments. The embodiments are illustrative, and it will be understood by those skilled in the art that various modifications are possible in combinations of their components and processing processes, and that such modifications are also within the scope of the present disclosure.

[0090] This disclosure may be expressed as follows. Notwithstanding the dependencies between the items described below, each element of each item can be freely combined in any combination of each element of each embodiment and each variation described, as long as they do not contradict each other.

[0091] Item 1: A shaft that is inserted into the body, A balloon attached to the tip of the shaft and expandable by fluid supplied from the base end of the shaft, A restraining member is wrapped around the outer circumference of the intermediate portion between the tip and base of the balloon, and restricts the expansion of the balloon in the intermediate portion. The device comprises a covering member having a Shore A hardness of 30 or more and 60 or less, and covering the outer circumference of the restraining member. catheter. Item 2: The Shore A hardness of the balloon is higher than the Shore A hardness of the covering material, and the difference between the Shore A hardness of the balloon and the Shore A hardness of the covering material is 20 or more. The catheter described in item 1. Item 3: The Shore A hardness of the balloon is 80 or higher. A catheter as described in item 1 or 2. Item 4: The restraining member is not bonded to either the balloon or the covering member. A catheter as described in any of items 1 through 3. Item 5: When the balloon, restraining member, and covering member are each pulled until they break, the displacement of the covering member is greater than that of the balloon and the restraining member, and the displacement of the restraining member is greater than that of the balloon. A catheter as described in item 1 or 2. Item 6: The strength of the balloon and restraining member is higher than the strength of the covering member. A catheter as described in item 1 or 2. [Explanation of Symbols]

[0092] 1 Balloon catheter, 2 Shaft, 3 Balloon, 4 Elastic band, 5 Covering member, 32 Middle section, 311 Tip section, 331 Proximal section.

Claims

1. A shaft that is inserted into the body, A balloon attached to the tip end of the shaft and expandable by fluid supplied from the base end of the shaft, A restraining member is wrapped around the outer circumference of the intermediate portion between the tip and base of the balloon, and restricts the expansion of the balloon in the intermediate portion. The device comprises a covering member having a Shore A hardness of 30 or more and 60 or less, and covering the outer circumference of the restraining member. catheter.

2. The Shore A hardness of the balloon is higher than the Shore A hardness of the covering member, and the difference between the Shore A hardness of the balloon and the Shore A hardness of the covering member is 20 or more. The catheter according to claim 1.

3. The Shore A hardness of the balloon is 80 or higher. The catheter according to claim 1 or 2.

4. The restraining member is not bonded to either the balloon or the covering member. The catheter according to claim 1 or 2.

5. When each of the balloon, the restraining member, and the covering member is pulled until they break, the displacement of the covering member is greater than that of the balloon and the restraining member, and the displacement of the restraining member is greater than that of the balloon. The catheter according to claim 1 or 2.

6. The strength of the balloon and the restraining member is higher than the strength of the covering member. The catheter according to claim 1 or 2.

Images