Stent delivery device

Abstract

To provide a stent carrying device capable of more surely indwelling a stent in a desired part.SOLUTION: The stent delivery device 100 includes the elongated inner sheath 20 having the stent attachment portion 21 to which the stent 200 is attached in an exterior state at the time of delivering the stent 200, a partial section of the stent attachment portion 21 is the large-diameter portion 22 formed to have a larger diameter than the other section, the inner sheath 20 has the distal-side adjacent portion 26 and the proximal-side adjacent portion 27, and the size of the step 26a between the distal-side adjacent portion 26 and the distal-side end of the large-diameter portion 22 in the radial direction is defined as the first step size H1. When the size in the radial direction of the step 27a between the proximal side of the large-diameter portion 22 and the proximal side adjacent portion 27 is defined as a second step size H2, the second step size H1 is smaller than the first step size H2.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a stent delivery device. [Background technology]

[0002] An example of a stent delivery device used to place a stent in a body cavity is described in Patent Document 1. The stent delivery device of Patent Document 1 (referred to as a stent placement system in the document) has a long inner sheath with a stent mounting section (referred to as a holding section in the document) to which the stent is attached in an exterior state when the stent is delivered, and the outer diameter of the stent mounting section is constant regardless of its position in the axial direction. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7446280 Summary of the Invention [Problem to be solved by the invention]

[0004] According to the investigations of the present inventors, the stent delivery device of Patent Document 1 still has room for improvement in terms of the structure for more reliably placing the stent at the desired site.

[0005] The present invention has been made in view of the above problems, and aims to provide a stent delivery device that can more reliably place a stent at a desired site. [Means for solving the problem]

[0006] According to the present invention, there is provided a stent delivery device for delivering a stent into a body, comprising: a long inner sheath having a stent mounting portion to which the stent is mounted in an exterior state during delivery of the stent; A portion of the stent mounting section is a large diameter section formed to have a larger diameter than the other sections, the inner sheath has a distal adjacent portion which is a portion of the inner sheath adjacent to a distal side of the large diameter portion, and a proximal adjacent portion which is a portion of the inner sheath adjacent to a proximal side of the large diameter portion, a first step dimension is a radial dimension of a step between the distal adjacent portion and the distal end of the large diameter portion; When the dimension in the radial direction of the step between the proximal end of the large diameter portion and the proximal adjacent portion is defined as a second step dimension, A stent delivery device is provided in which the second step dimension is smaller than the first step dimension. [Effects of the Invention]

[0007] According to the present invention, the stent can be placed more reliably at the desired site. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic overall view of a stent delivery device according to an embodiment. [Figure 2] FIG. 2(a) is a side view showing the distal end of the stent delivery device according to the embodiment, and FIG. 2(b) is a partially enlarged view of part A shown in FIG. 2(a). [Figure 3] FIG. 3(a) is a side view schematically showing a state in which a stent is attached to an inner sheath in the embodiment, and FIG. 3(b) is a side view of the inner sheath in the embodiment. [Figure 4] FIG. 3(b) is a cross-sectional view taken along the line AA shown in FIG. [Figure 5] FIG. 2 is a side view showing a large diameter portion and its surrounding structure in the embodiment. [Figure 6] 6(a) is a partial enlarged view of part A shown in FIG. 5, FIG. 6(b) is a partial enlarged view of part B shown in FIG. 5, and FIG. 6(c) is a partial enlarged view of part C shown in FIG. [Figure 7] FIG. 1 is a schematic side view of a stent according to an embodiment. [Figure 8] Figures 8(a) and 8(b) are diagrams for explaining the operation of the stent delivery device of the embodiment, where Figure 8(a) shows the state in which the guide wire is inserted into the bile duct, and Figure 8(b) shows the state in which the distal end of the stent delivery device is inserted up to the vicinity of the bifurcation of the common hepatic duct. [Figure 9] Figures 9(a) and 9(b) are diagrams for explaining the operation of the stent delivery device according to the embodiment. Of these, Figure 9(a) shows a state in which the individual sheath portion of the inner sheath is exposed from the outer sheath, and Figure 9(b) shows a state in which the inner sheath has been further advanced from the state shown in Figure 9(a). [Figure 10] FIG. 10(a) is a side view schematically showing a state in which a stent is attached to an inner sheath in Modification 1, and FIG. 10(b) is a side view of the inner sheath in Modification 1. As shown in FIG. [Figure 11] 10 is a side view of the inner sheath in the first modification, viewed in a second direction. FIG. [Figure 12] 10 is a side view of the inner sheath in the first modification, viewed in a first direction. FIG. [Figure 13] FIG. 13(a) is a diagram showing the connecting member in Modification 1 as viewed from the distal side, and FIG. 13(b) is a diagram showing the connecting member in Modification 1 as viewed from the proximal side. [Figure 14] 14(a) is a cross-sectional view taken along line AA shown in FIG. 13(a), and FIG. 14(b) is a cross-sectional view taken along line BB shown in FIG. 13(a). [Figure 15] 10 is a side view of the inner sheath in Modification 2, showing the state when viewed in a second direction. FIG. [Figure 16] 10 is a side view of the inner sheath in Modification 2, viewed in a first direction. FIG. [Figure 17] FIG. 17(a) is a diagram showing the connecting member in Modification 2 as viewed from the distal side, and FIG. 17(b) is a diagram showing the connecting member in Modification 2 as viewed from the proximal side. [Figure 18]18(a) is a cross-sectional view taken along line AA shown in FIG. 17(a), and FIG. 18(b) is a cross-sectional view taken along line BB shown in FIG. 17(a). DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the present invention will be described with reference to Figures 1 to 9(b). In all the drawings, the same components are denoted by the same reference numerals, and the description thereof will be omitted where appropriate. The various components of the stent delivery device 100 of the present invention do not necessarily have to be independent entities. It is acceptable for multiple components to be formed as a single member, for one component to be formed from multiple members, for one component to be a part of another component, or for part of one component to overlap with part of another component. In the following description, the tip end side of the stent delivery device 100 is also referred to as the distal side, and its base end side as the proximal side. The distal end refers to a certain range including the distal end (the most distal end) and its periphery, and the proximal end refers to a certain range including the proximal end (the most proximal end) and its periphery. The directions toward the distal and proximal sides are also referred to as the tip-to-base direction or axial direction.

[0010] The stent delivery device 100 according to this embodiment is a stent delivery device that delivers a stent 200 into a body. As shown in Figures 2(a) and 2(b), the stent delivery device 100 is equipped with a long inner sheath 20 having a stent mounting portion 21 to which the stent 200 is mounted in an exterior state during delivery of the stent 200. A portion of the stent mounting portion 21 is a large diameter portion 22 formed with a larger diameter than the other portions, and the inner sheath 20 has a distal adjacent portion 26, which is the portion of the inner sheath 20 adjacent to the distal side of the large diameter portion 22, and a proximal adjacent portion 27, which is the portion of the inner sheath 20 adjacent to the proximal side of the large diameter portion 22. If the radial dimension of the step 26a between the distal adjacent portion 26 and the distal end of the large diameter portion 22 is defined as the first step dimension (dimension H1 shown in Figure 6(a)), and the radial dimension of the step 27a between the proximal end of the large diameter portion 22 and the proximal adjacent portion 27 is defined as the second step dimension (dimension H2 shown in Figure 6(b)), the second step dimension H2 is smaller than the first step dimension H1. Here, "the second step dimension H2 is smaller than the first step dimension H1" means that when the first step dimension H1 and the second step dimension H2 vary depending on the circumferential position, as in Modifications 1 and 2 described below, the average value of the second step dimension H2 is at least smaller than the average value of the first step dimension H1. Preferably, the maximum value of the second step dimension H2 is smaller than the minimum value of the first step dimension H1.

[0011] The stent delivery device 100 is used to place a stent 200 at a desired site in a body cavity. When placing the stent 200, as described below, the inner sheath 20, to which the stent 200 in a reduced diameter state is attached, is fed to the desired site in the body cavity while sliding from the proximal side to the distal side. Then, when the stent mounting portion 21 reaches the desired site, the stent 200 is transformed from the reduced diameter state to the expanded state. This places the stent 200 in place. After the stent 200 is placed, the inner sheath 20 is pulled proximally to remove it from the stent 200.

[0012] As described above, a portion of the stent mounting section 21 is the large diameter section 22 formed to have a larger diameter than the other sections. This allows the stent 200 to be well anchored to the large diameter portion 22, thereby restricting the stent 200 from being displaced in the axial direction relative to the stent mounting portion 21 as the inner sheath 20 moves backward (toward the proximal side) or forward (toward the distal side). Therefore, the stent 200 can be smoothly transported together with the inner sheath 20 to a desired site in a body cavity. Furthermore, in the inner sheath 20, the second step dimension H2, which is the step 27a between the proximal end of the large diameter portion 22 and the proximal adjacent portion 27, is smaller than the first step dimension H1, which is the step 26a between the distal adjacent portion 26 and the distal end of the large diameter portion 22. According to this configuration, when the inner sheath 20 is pulled out from the stent 200 after the stent 200 has been placed, it is possible to prevent the large diameter portion 22 from interfering with the stent 200. Furthermore, since the first step dimension H1 can be sufficiently ensured, the stent 200 is well anchored to the distal end of the large diameter portion 22, and the advancing force can be well transmitted to the stent 200 via the large diameter portion 22. Therefore, according to this embodiment, the stent 200 can be placed at a desired site more reliably.

[0013] As shown in Figures 3(a) and 7, the stent 200 has a main vessel 210 and a first branch vessel 220 and a second branch vessel 230 each branching off from a stent bifurcation portion 211, which is the distal end of the main vessel 210. As shown in FIG. 7, the main pipe 210, the first branch pipe 220 and the second branch pipe 230 are each formed, for example, in a cylindrical shape with a mesh structure. The lumen region of the main vessel 210 communicates with the lumen region of the first branch vessel 220 and the lumen region of the second branch vessel 230 at the distal end (stent bifurcation 211) of the main vessel 210, respectively. For example, the axial direction of the first branch vessel 220 and the axial direction of the second branch vessel 230 are both inclined relative to the axial direction of the main vessel 210, and the overall shape of the stent 200 is Y-shaped. In the present invention, the shape of the stent 200 is not limited to this example, and for example, the stent 200 may be composed of a single mesh-structured cylinder, the entirety of which may be formed in an approximately linear shape (I-shape). In the present invention, the stent 200 may also be a stent-graft, for example, comprising a tubular graft formed from a graft material.

[0014] As shown in Figure 3(a), the stent 200 is attached to the stent mounting section 21 in a reduced-diameter state while being restrained by a string member 240. One end (not shown) of the string member 240 is led out from the proximal side to the outside of the stent delivery device 100. Similarly, one end (not shown) of the wire member 250 is led out from the proximal side to the outside of the stent delivery device 100. In addition, a wire member 250 is fixed to the string member 240, and the string member 240 can be released from the stent 200 by pulling the wire member 250 out to the proximal side. This releases the string member 240 from restraint on the stent 200, and the stent 200 changes from the reduced-diameter state to the deployed state. More specifically, in this embodiment, the string member 240 and wire member 250 that restrain the first branch pipe 220 of the stent 200 and the string member 240 and wire member 250 that restrain the second branch pipe 230 are separate members. Therefore, the first branch pipe 220 and the second branch pipe 230 can be changed from the contracted state to the expanded state at different times. Note that Figure 3(a) schematically illustrates the stent 200, the string member 240, and the wire member 250. Furthermore, in Figure 2(a), the placement section of the stent 200 is illustrated by a two-dot chain line. Furthermore, for example, it is preferable that the ligated portions (not shown) of the string member 240 are disposed, in the tip-to-proximal direction, near and distal to a step 26a between the distal adjacent portion 26 and the distal end of the large diameter portion 22, and near and proximal to a step 27a between the proximal end of the large diameter portion 22 and the proximal adjacent portion 27. This allows the forward force to be transmitted to the stent 200 more effectively by the large diameter portion 22 and the ligated portions when the inner sheath 20 is advanced.

[0015] 1, a stent delivery device 100 includes, in addition to an inner sheath 20, an outer sheath 10 fitted over the inner sheath 20 so as to be slidable in the axial direction, an operation unit 90 to which the proximal end of the outer sheath 10 is fixed, a shaft 92 extending from the operation unit 90 toward the proximal end, and a shaft handle 91 to which the proximal end of the shaft 92 is fixed. Note that in Figures 2(a) and 2(b), the outer sheath 10 is selectively illustrated as a cross section taken along the axial center of the outer sheath 10. The stent 200 is housed in a reduced-diameter state between the inner circumferential surface of the outer sheath 10 and the outer circumferential surface of the inner sheath 20. Then, with the outer sheath 10 and the inner sheath 20 inserted into a desired site in a body cavity along a guidewire 300 (see FIG. 8(a) and the like), the operation section 90 is retracted together with the outer sheath 10 toward the shaft handle 91, and the stent mounting section 21 of the inner sheath 20 is exposed from the outer sheath 10. Then, by withdrawing the wire member 250 proximally and releasing the string member 240 restraining the stent 200, the stent 200 can be transformed from the reduced-diameter state to the expanded state and placed at the desired site. The reduced-diameter state of the stent 200 refers to a state in which the stent 200 is compressed in the radial direction to an extent that the stent 200 can be present within the outer sheath 10. The expanded-diameter state of the stent 200 refers to a state in which the diameter is at least larger than the reduced-diameter state, such as the natural state of the stent 200.

[0016] The outer sheath 10 is a long, hollow tubular member. As shown in Figures 2(a) and 2(b), the inner sheath 20 (in this embodiment, a first sheath 45 and a second sheath 47, which will be described later) is inserted into the lumen of the outer sheath 10, and the outer sheath 10 is slidable relative to the inner sheath 20 in its axial direction. In this embodiment, the inner and outer diameters of the outer sheath 10 are constant regardless of the position in the axial direction, and therefore the wall thickness of the outer sheath 10 is constant regardless of the position in the axial direction. However, the outer and inner diameters of the outer sheath 10 may differ depending on the position in the axial direction. The outer sheath 10 has, for example, a two-layer structure (not shown) including an inner layer and an outer layer disposed around the inner layer, and is configured by laminating the inner layer and the outer layer in that order from the axial center side of the outer sheath 10. A hydrophilic layer (not shown) may be formed on the surface of the outer layer. The material of the hydrophilic layer is not particularly limited, but examples thereof include hydrophilic resin materials such as maleic anhydride polymers such as polyvinyl alcohol (PVA) and copolymers thereof, and polyvinylpyrrolidone. This can reduce the sliding resistance when the outer sheath 10 is inserted into a body cavity of a living body. The inner layer is made of, for example, a fluorine-based thermoplastic polymer resin. The fluorine-based thermoplastic polymer material is not particularly limited, but may be polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), perfluoroalkoxy fluororesin (PFA), or the like. By making the inner layer out of such a fluorine-based polymer material, sliding resistance when the inner sheath 20 slides in the lumen of the outer sheath 10 is reduced. The outer layer may be made of, for example, a thermoplastic polymer material, such as polyimide (PI), polyamideimide (PAI), polyethylene terephthalate (PET), polyethylene (PE), polyamide (PA), polyamide elastomer (PAE), nylon elastomer such as polyether block amide (PEBA), polyurethane (PU), ethylene-vinyl acetate resin (EVA), polyvinyl chloride (PVC), or polypropylene (PP).

[0017] The inner diameter of the outer sheath 10 is set to a dimension larger than the outer diameter (maximum diameter) of the inner sheath 20. Therefore, the inner sheath 20 can be slidably inserted into the inner cavity of the outer sheath 10. More specifically, the inner diameter of the outer sheath 10 is not particularly limited, but is preferably 1 mm or more and 7 mm or less. The outer diameter of the outer sheath 10 is not particularly limited, but is preferably 1.5 mm or more and 8 mm or less. Furthermore, the total length of the outer sheath 10 is not particularly limited, but is preferably 500 mm or more and 2500 mm or less.

[0018] Furthermore, the outer sheath 10 includes a reinforcing layer (not shown) formed in a mesh shape by braiding metal wires, for example. The reinforcing layer is disposed, for example, from the distal end to the proximal end of the outer sheath 10. The outer sheath 10 is reinforced throughout by the reinforcing layer. The reinforcing layer may be formed of, for example, a metal wire wound in a coil shape, and may be disposed on, for example, a portion of the outer sheath 10 in the axial direction.

[0019] In this embodiment, a cylindrical radiopaque marker 55, for example, is embedded near the distal end of the outer sheath 10. The radiopaque marker 55 is made of an X-ray opaque material, such as platinum, tungsten, etc. By using the position of the radiopaque marker 55 as an index, the position of the distal end of the outer sheath 10 within the body cavity can be accurately recognized under X-ray (radiation) observation.

[0020] As shown in Figures 3(a) and 3(b), in this embodiment, the inner sheath 20 has a first sheath 45 that is inserted into the main tube 210 and the first branch tube 220 of the stent 200, and a second sheath 47 that is inserted into the main tube 210 and the second branch tube 230. The inner sheath 20 also has a sheath main portion 41 in which a first sheath 45 and a second sheath 47 are bundled together, and an individual sheath portion 43 that is located distal to a sheath branch portion 42 that is the distal end of the sheath main portion 41 and in which the first sheath 45 and the second sheath 47 are separated. Here, "bundled" means that the first sheath 45 and the second sheath 47 are constrained in an inseparable state from each other. Also, "separated" here means that the first sheath 45 and the second sheath 47 can bend in directions moving away from and toward each other. However, "separated" here also allows partial sections of the first sheath 45 and the second sheath 47 to be locally connected to each other in the individual sheath portion 43, as in Modifications 1 and 2 described below. More specifically, in the present embodiment, the inner sheath 20 further includes a third sheath 49 through which both the first sheath 45 and the second sheath 47 are inserted. The third sheath 49 is formed in a long tubular shape. A partial section of the first sheath 45 and a partial section of the second sheath 47 are inserted into the inner cavity of the third sheath 49 and bundled together. The distal end of the third sheath 49 terminates proximally relative to the distal ends of the first sheath 45 and the second sheath 47. In other words, the distal end portions of the first sheath 45 and the second sheath 47 each branch and extend distally from the distal end of the third sheath 49. In the inner sheath 20, the distal end of the third sheath 49 is the sheath branching section 42, the portion proximal to the distal end constitutes the sheath main section 41, and the portion distal to the distal end constitutes the individual sheath section 43. In this embodiment, the portion of the inner sheath 20 that is distal to the distal end of the third sheath 49 (individual sheath portion 43) is the stent mounting portion 21, and the entire stent 200 is fitted onto this stent mounting portion 21. As shown in FIG. 3( a), the stent 200 is attached to the inner sheath 20 in a state in which the first sheath 45 and the second sheath 47 of the individual sheath portion 43 are both inserted into the main tube 210, the first sheath 45 of the individual sheath portion 43 is inserted into the first branch tube 220, and the second sheath 47 of the individual sheath portion 43 is inserted into the second branch tube 230. 2(a) and 2(b), when inserted into the lumen of the outer sheath 10, the first sheath 45 and second sheath 47 of the individual sheath portion 43 extend approximately parallel to each other along the axial direction of the outer sheath 10. Similarly, the first branch tube 220, through which the first sheath 45 of the individual sheath portion 43 is inserted, and the second branch tube 230, through which the second sheath 47 of the individual sheath portion 43 is inserted, are also housed within the outer sheath 10 in a state of extending approximately parallel to each other along the axial direction. As shown in FIG. 3(a), when the individual sheath portion 43 is exposed from the outer sheath 10, the first sheath 45 and the second sheath 47 of the individual sheath portion 43 are bendable in directions moving away from and toward each other. However, the present invention is not limited to this example, and the inner sheath 20 may be configured as a single tubular body, for example.

[0021] The inner diameter and the outer diameter of the third sheath 49 are constant regardless of the position in the axial direction. 4, for example, in addition to the first sheath 45 and the second sheath 47, a fourth sheath 46a and a fifth sheath 46b are also inserted into the lumen of the third sheath 49. A wire member 250 that maintains the ligated state of the string member 240 is inserted into the fourth sheath 46a, and the string member 240 that restrains the stent 200 is inserted into the fifth sheath 46b. One end (not shown) of the wire member 250 is led out of the stent delivery device 100 via the fourth sheath 46a. The other end of the wire member 250 is led out from the distal end of the fourth sheath 46a toward the stent 200. One end (not shown) of the string member 240 is led out of the stent delivery device 100 via the fifth sheath 46b. The other end of the string member 240 is led out from the distal end of the fifth sheath 46b toward the stent 200. Each of the fourth sheath 46a and the fifth sheath 46b terminates in the axial direction at a position equivalent to or more proximal to the distal end of the third sheath 49. In other words, of the first sheath 45, the second sheath 47, the fourth sheath 46a, and the fifth sheath 46b, the first sheath 45 and the second sheath 47 constitute the individual sheath portion 43.

[0022] In this embodiment, each of the first sheath 45 and the second sheath 47 has a large diameter portion 22. More specifically, in the first sheath 45 of the individual sheath portion 43, a section corresponding to the first branch pipe 220 is the large diameter portion 22 (in this embodiment, first large diameter portions 22a and 22b shown in FIG. 3(b) and other figures), and in the second sheath 47 of the individual sheath portion 43, a section corresponding to the second branch pipe 230 is the large diameter portion 22 (in this embodiment, second large diameter portion 22c shown in FIG. 3(b) and other figures). Here, "corresponding to the first branch pipe 220" means that the stent 200 is disposed in the first branch pipe 220 when the stent 200 is attached to the stent mounting section 21, and similarly, "corresponding to the second branch pipe 230" means that the stent 200 is disposed in the second branch pipe 230 when the stent 200 is attached to the stent mounting section 21. This allows the first branch pipe 220 to be securely retained in the large diameter portion 22 (first large diameter portions 22a, 22b) of the first sheath 45, and the second branch pipe 230 to be securely retained in the large diameter portion 22 (second large diameter portion 22c) of the second sheath 47. This prevents the first branch pipe 220 from being displaced in the axial direction relative to the first sheath 45 when the first sheath 45 is retracted or advanced, and prevents the second branch pipe 230 from being displaced in the axial direction relative to the second sheath 47 when the second sheath 47 is retracted or advanced. This allows the first branch pipe 220, the second branch pipe 230, and the stent bifurcation 211 to be more reliably placed at the desired site.

[0023] As shown in FIG. 5, in this embodiment, the outer diameter of the large diameter portion 22 decreases toward the proximal side. According to this configuration, the second step dimension H2 can be made smaller while the first step dimension H1 is sufficiently ensured. Therefore, the stent 200 is well anchored to the distal end of the large diameter portion 22, and the advancing force can be well transmitted to the stent 200 via the large diameter portion 22. At the same time, when the inner sheath 20 is pulled out from the stent 200, interference of the large diameter portion 22 with the stent 200 can be more reliably prevented.

[0024] More specifically, large diameter section 22 (first large diameter sections 22a, 22b, second large diameter section 22c) has, for example, a first portion 23 located on the distal side and a second portion 24 located on the proximal side. Step 23a exists at the boundary between first portion 23 and second portion 24, and second portion 24 has a smaller diameter than first portion 23. According to this configuration, the second step dimension H2 can be made smaller while the first step dimension H1 is sufficiently ensured. Therefore, the stent 200 is satisfactorily locked to the distal end of the large diameter portion 22, and an advancing force can be effectively transmitted to the stent 200 via the large diameter portion 22. At the same time, when the inner sheath 20 is pulled out from the stent 200, interference of the large diameter portion 22 with the stent 200 can be more reliably prevented. Furthermore, since a sufficient outer diameter can be ensured over the entire first portion 23 in the tip-to-proximal direction, a frictional force can be applied to the stent 200 via the outer peripheral surface of the first portion 23, and an advancing force can be more effectively transmitted. It should be noted that the present invention is not limited to this example, and for example, the entire large diameter portion 22 may have a continuously decreasing diameter toward the proximal side.

[0025] The second portion 24, for example, gradually decreases in diameter toward the proximal side. According to this configuration, the second step dimension H2 can be further reduced while the first portion 23 ensures a sufficient first step dimension H1. Therefore, when the stent 200 is placed at a desired site, the advancing force can be effectively transmitted to the stent 200 via the large diameter portion 22. Furthermore, when the inner sheath 20 is pulled out from the stent 200 after the stent 200 has been placed, interference between the large diameter portion 22 and the stent 200 can be more reliably prevented. More specifically, the inner diameter of the second portion 24 is substantially constant regardless of the axial position, while the outer diameter of the second portion 24 gradually decreases toward the proximal side. Moreover, the inner diameter and the outer diameter of the first portion 23 are each substantially constant regardless of the position in the axial direction.

[0026] More specifically, in the present embodiment, the inner sheath 20 (in the present embodiment, each of the first sheath 45 and the second sheath 47) has an inner sheath body 31 and a large diameter portion-constituting tube 36 that is wrapped around the inner sheath body 31 and constitutes the large diameter portion 22. In the inner sheath body 31, the portion in the axial direction distal to the arrangement region of the large diameter portion constituting tube 36 constitutes the distal adjacent portion 26, and the portion proximal to the arrangement region of the large diameter portion constituting tube 36 constitutes the proximal adjacent portion 27. In the large diameter portion-forming tube 36, the wall thickness of the portion constituting the second portion 24 is smaller than the wall thickness T1 (see FIG. 6(a)) of the portion constituting the first portion 23. More specifically, the minimum value T2 (see FIG. 6(b)) of the wall thickness of the portion constituting the second portion 24 is smaller than at least the wall thickness T1 of the portion constituting the first portion 23. Preferably, the maximum value of the wall thickness of the portion constituting the second portion 24 is smaller than the wall thickness T1 of the portion constituting the first portion 23. According to such a configuration, the flexibility of the second portion 24 can be secured well, and therefore the kink resistance of the inner sheath 20 can be improved.

[0027] As shown in FIG. 6(c), a step 23a at the boundary between the first portion 23 and the second portion 24 is, for example, rounded. This makes it possible to prevent the step 23a at the boundary between the first portion 23 and the second portion 24 from interfering with the stent 200 when the inner sheath 20 is pulled out from the stent 200.

[0028] More specifically, the radial dimension of the step 23a at the boundary between the first portion 23 and the second portion 24 (hereinafter referred to as the seventh step dimension H3 (see Figure 6(c))) is, for example, smaller than the first step dimension H1 and larger than the second step dimension H2. Since the seventh step dimension H3 is smaller than the first step dimension H1, a portion (first portion 23) having a higher hardness than the other portions and a portion (second portion 24) having a lower hardness than the other portions change smoothly at the boundary between the first portion 23 and the second portion 24, thereby preventing the inner sheath 20 from kinking at the boundary. Furthermore, by making the seventh step dimension H3 larger than the second step dimension H2, the second step dimension H2 can be made smaller while the first step dimension H1 is sufficiently ensured.

[0029] The method for forming the first portion 23 and the second portion 24 on the large diameter portion-constituting tube 36 is not particularly limited, but examples include a method for cutting a portion of the large diameter portion-constituting tube 36 by laser processing or the like, and a method for transferring the irregularities of a mold when molding the large diameter portion-constituting tube 36. Furthermore, the first portion 23 and the second portion 24 may be formed from separate members, and the large diameter portion 22 (large diameter portion-constituting tube 36) may be formed by bonding the member that constitutes the first portion 23 and the member that constitutes the second portion 24 together. In this case, the step 23a described above can be made into an R-chamfered shape by performing chamfering processing at the boundary between the member that constitutes the first portion 23 and the member that constitutes the second portion 24. In the present invention, the stent delivery device 100 does not include the large diameter portion-forming tube 36, and the large diameter portion 22 may be integrally molded with, for example, the inner sheath body 31. In this case, the method for forming the first portion 23 and the second portion 24 is also not particularly limited, but examples include a method for cutting a portion of the inner sheath body 31 by laser processing or the like, and a method for transferring the irregularities of a mold when molding the inner sheath body 31.

[0030] Furthermore, for example, as shown in Figures 3(a) and 3(b), the position of the large diameter portion 22 of the first sheath 45 (in this embodiment, the first large diameter portions 22a, 22b) and the position of the large diameter portion 22 of the second sheath 47 (in this embodiment, the second large diameter portion 22c) are different from each other in the tip-to-base direction. 2(a) and 2(b), when the first sheath 45 and the second sheath 47 are both inserted into the outer sheath 10, the large-diameter portion 22 of the first sheath 45 and the large-diameter portion 22 of the second sheath 47 do not overlap with each other in the distal-proximal direction. This makes it easier to set the outer sheath 10 to a smaller diameter. Furthermore, the frictional resistance when the outer sheath 10 is retracted relative to the inner sheath 20 can be reduced.

[0031] Furthermore, in this embodiment, the number of large diameter portions 22 included in the first sheath 45 (for example, two) is different from the number of large diameter portions 22 included in the second sheath 47 (for example, one). As shown in Figures 2(a) and 2(b), the large diameter portions 22a and 22b (first large diameter portions 22a, 22b) of the first sheath 45 are disposed at different positions in the distal-proximal direction. Furthermore, the position of the large diameter portion 22c (second large diameter portion 22c) of the second sheath 47 is different from the positions of the large diameter portions 22a and 22b (same as above) of the first sheath 45 in the distal-proximal direction. With this configuration, the position of the large diameter portion 22 of the first sheath 45 and the position of the large diameter portion 22 of the second sheath 47 can be different from each other in the tip-to-proximal direction, and a forward force can be transmitted effectively to each of the first branch pipe 220 and the second branch pipe 230 via the large diameter portion 22.

[0032] More specifically, when the stent 200 is attached to the stent mounting section 21, the first large diameter section 22a is located within the distal end of the first branched vessel 220, and the first large diameter section 22b is located within the proximal end of the first branched vessel 220. Furthermore, when the stent 200 is attached to the stent mounting section 21, the second large diameter section 22c is located within the intermediate section of the second branched vessel 230 (the middle in the tip-to-base direction).

[0033] In the present invention, the number of large diameter portions 22 in the first sheath 45 and the number of large diameter portions 22 in the second sheath 47 are not limited to this example and can be set according to the dimensions of the stent 200. Furthermore, the number of large diameter portions 22 in the first sheath 45 and the number of large diameter portions 22 in the second sheath 47 may be equal to each other. In the present embodiment, for example, the large diameter portion 22 of the first sheath 45 and the large diameter portion 22 of the second sheath 47 are set to have the same shape and dimensions. However, the present invention is not limited to this example, and the large diameter portion 22 of the first sheath 45 and the large diameter portion 22 of the second sheath 47 may be set to have different shapes.

[0034] As shown in FIG. 5, the length L2 of the second portion 24 in the tip-to-proximal direction is preferably longer than the length L1 of the first portion 23, for example. According to this configuration, when the inner sheath 20 is bent, stress concentration in the large diameter portion 22 is alleviated, thereby improving kink resistance. However, the present invention is not limited to this example, and in the axial direction, the length dimension L2 of the second portion 24 may be the same as the length dimension L1 of the first portion 23, or may be smaller than the length dimension L1 of the first portion 23.

[0035] The inner sheath body 31 is formed, for example, in a long tubular shape. The inner diameter and outer diameter of the inner sheath body 31 are constant regardless of the position in the axial direction. Therefore, the inner diameter and outer diameter of the distal adjacent section 26 and the proximal adjacent section 27 are also constant regardless of the position in the axial direction. The inner sheath body 31 of the first sheath 45 and the inner sheath body 31 of the second sheath 47 are set to have the same length dimension, and are also set to have the same inner diameter and outer diameter. The inner diameter of the large diameter portion forming tube 36 is constant, for example, regardless of the position in the axial direction. The inner diameter of the large diameter portion forming tube 36 is set, for example, to a dimension slightly larger than the outer diameter of the inner sheath body 31. An adhesive (not shown) is filled between the inner peripheral surface of the large diameter portion forming tube 36 and the outer peripheral surface of the inner sheath body 31.

[0036] Here, in the large-diameter tube 36, for example, the surface roughness of the inner circumferential surface of the portion constituting the second portion 24 is greater than the surface roughness of the outer circumferential surface of the portion constituting the second portion 24. Note that the "surface roughness" referred to here refers to the height, depth, spacing, etc. of the depressions (valleys) and protrusions (mountains) on the inner and outer circumferential surfaces, and "high surface roughness" means that the scale of the depressions and protrusions is relatively large. More specifically, the surface roughness is defined by any of the arithmetic mean height Ra, maximum height Rz, and ten-point mean height Rzjis defined in the JIS standard. In this embodiment, the surface roughness may be expressed using any of these definitions. The "size of surface roughness" referred to in this embodiment refers to the size of the surface roughness value expressed by the above definition. This allows the second portion 24 to be favorably bonded to the outer circumferential surface of the inner sheath body 31 with the adhesive. As described above, the thickness T1 of the portion that constitutes the first portion 23 is smaller than the thickness of the portion that constitutes the second portion 24. This allows the transparency (transmittance of visible light) of the second portion 24 to be increased, and therefore, for example, a light (UV) curing adhesive can be used as the adhesive. Furthermore, adhesive 61 is applied around the step 27a between the proximal end of the large diameter portion-forming tube 36 and the outer peripheral surface of the proximal adjacent portion 27, and the outer peripheral surface tapers slightly in diameter toward the proximal side. This makes it possible to prevent the stent 200 from interfering with the proximal end of the large diameter portion 22 when the inner sheath 20 is pulled out from the stent 200 .

[0037] A distal tip 38 (see FIGS. 2(a) and 3(b), etc.) is provided at the distal end of each of the inner sheath body 31 of the first sheath 45 and the inner sheath body 31 of the second sheath 47. The distal tip 38 is formed, for example, in a cylindrical shape whose diameter gradually decreases toward the distal side and the proximal side. The proximal end of the distal tip 38 is connected to the distal end of the inner sheath body 31, and the inner lumen of the distal tip 38 and the inner lumen of the inner sheath body 31 communicate with each other. When inserting the stent delivery device 100 into a body cavity, the guidewire 300 (see FIG. 8(a) and other figures) that has been inserted into the body cavity in advance is inserted into the lumen of the inner sheath body 31 from the distal opening of the tip 38. This allows the outer sheath 10 and the inner sheath 20 to be inserted into the body cavity along the guidewire 300.

[0038] As shown in Figures 3(a) and 3(b), in this embodiment, a first radiopaque marker 51 is provided in the first sheath 45 of the individual sheath portion 43 at a position corresponding to the stent branch portion 211, and a second radiopaque marker 52 is provided in the second sheath 47 of the individual sheath portion 43 at a position corresponding to the stent branch portion 211. Here, "a position corresponding to the stent branch portion 211" means that when the stent 200 is attached to the inner sheath 20, the formation area of ​​the first radiopaque marker 51 (or the second radiopaque marker 52) straddles the stent branch portion 211 in the tip-to-base direction. This allows the user to easily grasp the positions of the first branch tube 220 and the second branch tube 230 of the stent 200, respectively, under X-ray (radiation) observation by using the positions of the first radiopaque marker 51 and the second radiopaque marker 52 as indicators. Of the first sheath 45 and the second sheath 47, the distal tip 38 of the first sheath 45 is provided with a third radiopaque marker 53. This allows the user to easily distinguish between the first sheath 45 and the second sheath 47, and ultimately the first branch tube 220 and the second branch tube 230 of the stent 200, under X-ray (radiation) observation, using the position of the third radiopaque marker 53 as an indicator. Furthermore, a fourth radiopaque marker 54 is provided at the distal end of the third sheath 49. This allows the user to easily determine the position of the sheath branching portion 42 by using the position of the third radiopaque marker 53 as an index. In Fig. 2(a), Fig. 2(b), Fig. 3(a) and Fig. 3(b), the locations where the first radiopaque marker 51 to the fourth radiopaque marker 54 are formed are shaded with dots.

[0039] The first radiopaque marker 51 to the fourth radiopaque marker 54 are made of an X-ray opaque material, such as platinum or tungsten. However, the present invention is not limited to this example, and the first radiopaque marker 51 to the fourth radiopaque marker 54 may be formed, for example, by applying ink to the outer peripheral surface of the inner sheath body 31. The outer sheath 10 is made of, for example, a transparent resin material (transparent to visible light). Therefore, the user can visually recognize the first to fourth radiopaque markers 51 to 54 through the outer sheath 10.

[0040] Examples of materials that can be used for the inner sheath body 31 include various resin materials such as polyolefins such as polyethylene and polypropylene, polyvinyl chloride, polyurethane, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyamide, polyether polyamide, polyester polyamide, polyether ether ketone, polyetherimide, fluorine-based resins such as polytetrafluoroethylene and tetrafluoroethylene-hexafluoropropylene copolymer, and various thermoplastic elastomers such as polyolefins, polyurethanes, polyesters, polyamides, and polybutadiene. Two or more of these materials can also be used in combination. The material of the large diameter portion forming tube 36 can be, for example, the same type of material as the material of the inner sheath body 31. In particular, the large diameter portion forming tube 36 is preferably made of a transparent (transparent to visible light) resin material.

[0041] The outer diameter of the inner sheath body 31 is not particularly limited, but is preferably 0.1 mm or more and 2.0 mm or less. The inner diameter of the inner sheath body 31 is not particularly limited, but is preferably 0.01 mm or more and 3.0 mm or less. The total length of the inner sheath body 31 is not particularly limited, but is preferably 300 mm or more and 3000 mm or less. The inner diameter of the large-diameter portion-forming tube 36 is not particularly limited, but is preferably 0.5 mm or more and 3.0 mm or less. The outer diameter of the first portion 23 is not particularly limited, but is preferably 0.5 mm or more and 3.0 mm or less. The outer diameter (maximum diameter) of the second portion 24 is not particularly limited, but is preferably 0.5 mm or more and 3.0 mm or less. Furthermore, the overall length of the large-diameter portion-forming tube 36 is not particularly limited, but is preferably 0.5 mm or more and 50 mm or less. The length dimension L1 of the first portion 23 is not particularly limited, but is preferably 0.1 mm or more and 20 mm or less. The length dimension L2 of the second portion 24 is not particularly limited, but is preferably 0.01 mm or more and 3 mm or less. The first step dimension H1 is preferably, for example, 0.01 mm or more and 2.0 mm or less, the second step dimension H2 is preferably, for example, 0.01 mm or more and 2.0 mm or less, and the seventh step dimension H3 is preferably, for example, 0.01 mm or more and 2.0 mm or less. The length L2 of the second portion 24 is preferably, for example, 0.1 to 10 times the length L1 of the first portion 23, and more preferably 0.2 to 5 times the length L1.

[0042] An example of a method of using the stent delivery device 100 of this embodiment will be described below with reference to FIGS. 8(a) to 9(b). As an example, the following will describe a case where the stent delivery device 100 is used in a procedure for placing a stent 200 inside a bile duct 510. The description will be given starting from a state in which the distal end of the insertion section of the endoscope 400 is placed in advance inside the duodenum (not shown) near the duodenal papilla (papilla of Vater), a needle hole is formed in the bile duct, and the distal end of the guidewire 300 is anchored (locked) to the needle hole. More specifically, the first guidewire 300a is anchored to the needle hole in the left hepatic duct 512, and the second guidewire 300b is anchored to the needle hole in the right hepatic duct 513. First, the stent delivery device 100 is introduced along the guidewire 300. More specifically, first, the first sheath 45 is inserted over the first guidewire 300a, and the second sheath 47 is inserted over the second guidewire 300b. Then, while sliding the inner sheath 20 from the proximal side to the distal side along the axial direction of the guidewire 300, the distal end of the inner sheath 20 and the outer sheath 10 are advanced to the bifurcation 511a of the common hepatic duct 511 (see FIG. 8(b)). Next, the outer sheath 10 is retracted proximally, thereby exposing the individual sheath portion 43 of the inner sheath 20 from the outer sheath 10 (see FIG. 9(a)). Then, the first sheath 45 of the individual sheath portion 43 is fed into the left hepatic duct 512 along the first guidewire 300a, and the second sheath 47 of the individual sheath portion 43 is fed into the right hepatic duct 513 along the second guidewire 300b (see FIG. 9(b)). Then, the wire member 250 is withdrawn proximally, thereby releasing the string member 240 from the stent 200. This releases the string member 240 from its restraint on the stent 200, causing the first branch vessel 220 and the second branch vessel 230 of the stent 200 to change from their contracted state to their deployed state. Next, the entire stent mounting portion 21 of the inner sheath 20 is exposed from the outer sheath 10, causing the main vessel 210 of the stent 200 to change from its contracted state to its deployed state. After the entire stent 200 has changed from its contracted state to its deployed state in this way, the inner sheath 20 is withdrawn from the stent 200. Then, the inner sheath 20 and the outer sheath 10 are removed from the body cavity. In this manner, the stent 200 is placed inside the bile duct 510 .

[0043] As described above, in this embodiment, a portion of the stent mounting section 21 is the large diameter section 22 formed with a larger diameter than the other sections. This allows the stent 200 to be well anchored to the large diameter portion 22, thereby restricting the stent 200 from being displaced in the axial direction relative to the stent mounting portion 21 as the inner sheath 20 is retracted or advanced. Therefore, the inner sheath 20 can smoothly transport the stent 200 to a desired site in a body cavity. Furthermore, in the inner sheath 20, the second step dimension H2, which is the step 27a between the proximal end of the large diameter portion 22 and the proximal adjacent portion 27, is smaller than the first step dimension H1, which is the step 26a between the distal adjacent portion 26 and the distal end of the large diameter portion 22. According to this configuration, when the inner sheath 20 is pulled out from the stent 200 after the stent 200 has been placed, it is possible to prevent the large diameter portion 22 from interfering with the stent 200. Furthermore, since the first step dimension H1 can be sufficiently ensured, the stent 200 is well anchored to the distal end of the large diameter portion 22, and the advancing force can be well transmitted to the stent 200 via the large diameter portion 22. In this way, according to this embodiment, the stent 200 can be placed more reliably at the desired site.

[0044] <Variation 1> Next, Modification 1 will be described with reference to Figures 10(a) to 14(b). The stent delivery device 100 according to this modification differs from the stent delivery device 100 according to the above embodiment in the points described below, but is otherwise configured similarly to the stent delivery device 100 according to the above embodiment. Note that Figure 11 is a side view of the inner sheath 20 as viewed in the direction of arrow A shown in Figure 13(b), and Figure 12 is a side view of the inner sheath 20 as viewed in the direction of arrow B shown in Figure 13(b).

[0045] In this modified example, as shown in Fig. 10(a), each of the first sheath 45 and the second sheath 47 has a large diameter portion 22 at least at a position corresponding to the main tube 210 of the stent 200. As shown in Fig. 10(b), the large diameter portion 22 of the first sheath 45 and the large diameter portion 22 of the second sheath 47 (in this modified example, a third large diameter portion 22d, which will be described later) are arranged to overlap each other in the tip-to-proximal direction. Here, "having a large diameter portion 22 at a position corresponding to the main tube 210" means that when the stent 200 is attached to the stent attachment portion 21, the large diameter portion 22 is positioned within the main tube 210. With this configuration, even if the main pipe 210 is formed with a larger diameter than the first branch pipe 220 and the second branch pipe 230 as shown in Figure 10(a), the distal end of the large diameter portion 22 can have a sufficient contact area of ​​the outer surface of the distal end with the main pipe 210, so that the forward force can be transmitted well to the main pipe 210 via the large diameter portion 22.

[0046] In this modification, each of first sheath 45 and second sheath 47 has a plurality of large diameter portions 22. First sheath 45 has, as the plurality of large diameter portions 22, first large diameter portions 22a and 22b which are large diameter portions 22 formed at a position corresponding to first branch pipe 220, and third large diameter portion 22d which is large diameter portion 22 formed at a position corresponding to main pipe 210. Similarly, second sheath 47 has, as the plurality of large diameter portions 22, second large diameter portion 22c which is large diameter portion 22 formed at a position corresponding to second branch pipe 230, and third large diameter portion 22d which is large diameter portion 22 formed at a position corresponding to main pipe 210. According to this configuration, the forward force can be effectively transmitted to the entire stent 200 via the large diameter portions 22 (first large diameter portion 22a to third large diameter portion 22d) in each of the first branch pipe 220, the second branch pipe 230, and the main pipe 210. On the other hand, when the inner sheath 20 is withdrawn proximally from the stent 200 after placement of the stent 200, interference of the corresponding large diameter portions 22 with the first branch pipe 220, the second branch pipe 230, and the main pipe 210 can be suppressed.

[0047] In the present invention, the third large diameter portion 22d of the first sheath 45 and the third large diameter portion 22d of the second sheath 47 may be formed separately from each other, or may be formed integrally as described below (or may be a common third large diameter portion 22d). When the third large diameter portion 22d of the first sheath 45 and the third large diameter portion 22d of the second sheath 47 are formed separately from each other, the phrase "the large diameter portion 22 of the first sheath 45 and the large diameter portion 22 of the second sheath 47 are arranged to overlap each other in the proximal-tip direction" means that at least a portion of the formation region of the third large diameter portion 22d of the first sheath 45 and at least a portion of the formation region of the third large diameter portion 22d of the second sheath 47 overlap each other in the proximal-tip direction, and preferably the entire formation region of the third large diameter portion 22d of the first sheath 45 and the entire formation region of the third large diameter portion 22d of the second sheath 47 overlap each other in the proximal-tip direction. Furthermore, when the third large diameter portion 22d of the first sheath 45 and the third large diameter portion 22d of the second sheath 47 are integrally formed (are a common third large diameter portion 22d), "the large diameter portion 22 of the first sheath 45 and the large diameter portion 22 of the second sheath 47 are arranged to overlap each other in the tip-proximal direction" means that the portion of the third large diameter portion 22d formed in the first sheath 45 and the portion of the third large diameter portion 22d formed in the second sheath 47 are arranged to overlap each other in the tip-proximal direction.

[0048] 11 to 13(b), in this modified example, the inner sheath 20 is fitted over the first sheath 45 and the second sheath 47, and includes a connecting member 37 that connects in parallel partial sections of the first sheath 45 and the second sheath 47. In FIGS. 13(a) and 13(b), the first sheath 45 and the second sheath 47 are each indicated by a two-dot chain line. The connecting member 37 constitutes the large diameter portion 22 (third large diameter portion 22d) common to the first sheath 45 and the second sheath 47. In other words, the large diameter portion 22 of the first sheath 45 and the large diameter portion 22 of the second sheath 47 are integrally formed with each other. Here, the direction in which the first sheath 45 and the second sheath 47 are aligned is defined as the first direction (the direction of arrow X shown in Figure 13(a) etc.), and the direction perpendicular to both the first direction and the central axis of the large diameter portion 22 is defined as the second direction (the direction of arrow Y shown in Figure 13(a) etc.). The dimension in the second direction of the step 26a between the distal adjacent portion 26 and the distal end of the large diameter portion 22 is the third step dimension (dimension H4 shown in Figure 12), and the dimension in the second direction of the step 27a between the proximal end of the large diameter portion 22 and the proximal adjacent portion 27 is the fourth step dimension (dimension H5 shown in Figure 12). As shown in FIG. 12, the fourth step dimension H5 is smaller than the third step dimension H4. With this configuration, it is possible to reduce the contact area between the proximal end of the third large diameter portion 22d and the stent 200, while ensuring a space (dimension in the first direction) in the third large diameter portion 22d (connecting member 37) that allows the first sheath 45 and the second sheath 47 to be inserted in parallel with each other. Therefore, when the inner sheath 20 is pulled out from the stent 200 after the stent 200 has been placed, it is possible to prevent the third large diameter portion 22d (connecting member 37) from interfering with the stent 200.

[0049] More specifically, in this modified example, the first sheath 45 and the second sheath 47 of the individual sheath portion 43 have a third large diameter portion 22d that is common to them, in addition to the first large diameter portion 22a, 22b or the second large diameter portion 22c that are formed individually. As shown in FIG. 10(a), in a state in which the stent 200 is attached, the third large diameter portion 22d is disposed, for example, within the distal end portion of the main vessel 210, that is, in the vicinity of the stent bifurcation portion 211. With this configuration, it is possible to ensure appropriate rigidity of the inner sheath 20 in the section (region where the third large diameter section 22d is formed) corresponding to the vicinity of the stent bifurcation section 211, and to improve the pushability of the inner sheath 20.

[0050] Furthermore, in the first sheath 45 of the individual sheath portion 43, a section distal to the third large diameter section 22d is disposed within the first branch pipe 220 and has first large diameter sections 22a, 22b. Similarly, in the second sheath 47 of the individual sheath portion 43, a section distal to the third large diameter section 22d is disposed within the second branch pipe 230 and has second large diameter section 22c.

[0051] As shown in Figures 11 and 12, the distal adjacent portion 26 of the third large diameter portion 22d is composed of a first distal adjacent portion 45a, which is a portion of the first sheath 45 adjacent to the distal side of the third large diameter portion 22d, and a second distal adjacent portion 47a, which is a portion of the second sheath 47 adjacent to the distal side of the third large diameter portion 22d. The proximal adjacent portion 27 of the third large diameter portion 22d is composed of a first proximal adjacent portion 45b, which is the portion of the first sheath 45 adjacent to the proximal side of the third large diameter portion 22d, and a second proximal adjacent portion 47b, which is the portion of the second sheath 47 adjacent to the proximal side of the third large diameter portion 22d.

[0052] In this modified example, the dimension in the second direction of the step between the first distal adjacent portion 45a and the distal end of the third large diameter portion 22d and the dimension in the second direction of the step between the second distal adjacent portion 47a and the distal end of the third large diameter portion 22d are equal to each other and larger than the above-mentioned fourth step dimension H5. Similarly, the dimension in the second direction of the step between the first proximal adjacent portion 45b and the proximal end of the third large diameter portion 22d and the dimension in the second direction of the step between the second proximal adjacent portion 47b and the proximal end of the third large diameter portion 22d are equal to each other and smaller than the third step dimension H4. In Figure 12, of the dimension in the second direction of the step between the first distal adjacent portion 45a and the distal end of the third large diameter portion 22d and the dimension in the second direction of the step between the second distal adjacent portion 47a and the distal end of the third large diameter portion 22d, the dimension in the second direction of the step between the second distal adjacent portion 47a and the distal end of the third large diameter portion 22d is selectively illustrated as the third step dimension H4. Similarly, in Figure 12, of the dimension in the second direction of the step between the first proximal adjacent portion 45b and the proximal end of the third large diameter portion 22d and the dimension in the second direction of the step between the second proximal adjacent portion 47b and the proximal end of the third large diameter portion 22d, the dimension in the second direction of the step between the second proximal adjacent portion 47b and the proximal end of the third large diameter portion 22d is selectively illustrated as the fourth step dimension H5.

[0053] However, the present invention is not limited to this example, and the dimension in the second direction of the step between the first distal adjacent portion 45a and the distal end of the third large diameter portion 22d and the dimension in the second direction of the step between the second distal adjacent portion 47a and the distal end of the third large diameter portion 22d may be different from each other. In this case, the larger of these dimensions is defined as the third step dimension H4. However, it is preferable that the smaller of these dimensions also satisfy the condition of being larger than the fourth step dimension H5. Similarly, the dimension in the second direction of the step between the first proximal adjacent portion 45b and the proximal end of the third large diameter portion 22d may be different from the dimension in the second direction of the step between the second proximal adjacent portion 47b and the proximal end of the third large diameter portion 22d. In this case, the smaller of these dimensions is defined as the fourth step dimension H5. However, it is preferable that the larger of these dimensions also satisfy the condition of being smaller than the third step dimension H4.

[0054] As shown in Figures 13(a) to 14(b), in this modified example, the connecting member 37 is a tubular member and has a first lumen 37aa through which the first sheath 45 is inserted and a second lumen 37ab through which the second sheath 47 is inserted. Here, the thickness in the second direction at the proximal end of the connecting member 37 (T4 shown in Figure 13(b)) is smaller than the thickness in the second direction at the distal end of the connecting member 37 (T3 shown in Figure 13(a)). This configuration can ensure appropriate rigidity of the distal end portion, in addition to the contact area between the distal end portion of third large diameter portion 22d and stent 200. Therefore, the forward force can be effectively transmitted to main tube 210 and ultimately to the entire stent 200 via third large diameter portion 22d. On the other hand, the contact area between the proximal end of the third large diameter portion 22d and the stent 200 can be reduced, and the rigidity of the proximal end can be appropriately reduced. Therefore, when the inner sheath 20 is pulled out from the stent 200, interference between the stent 200 and the proximal end of the large diameter portion 22 can be more reliably prevented.

[0055] In this modified example, the thickness of one side of the distal end of the connecting member 37 in the second direction and the thickness of the other side of the distal end of the connecting member 37 in the second direction are equal to each other and are greater than the thickness T4 of the proximal end of the connecting member 37 in the second direction. Similarly, the thickness of one side of the proximal end of the connecting member 37 in the second direction and the thickness of the other side of the proximal end of the connecting member 37 in the second direction are equal to each other and smaller than the thickness T3 of the distal end of the connecting member 37 in the second direction. In Figure 13(a), of the thickness of one side of the distal end of the connecting member 37 in the second direction and the thickness of the other side of the distal end of the connecting member 37 in the first direction, the thickness of one side of the distal end of the connecting member 37 in the second direction is selectively illustrated as thickness T3. Similarly, in Figure 13(b), of the thickness of one side of the proximal end of the connecting member 37 in the second direction and the thickness of the other side of the proximal end of the connecting member 37 in the second direction, the thickness of one side of the proximal end of the connecting member 37 in the second direction is selectively illustrated as thickness T4.

[0056] However, the present invention is not limited to this example, and the thickness of one side of the distal end of connecting member 37 in the second direction may be different from the thickness of the other side of the distal end of connecting member 37 in the second direction. In this case, the larger of these thicknesses is defined as thickness T3. However, it is preferable that the smaller of these thicknesses also satisfy the condition of being larger than thickness T4. Similarly, the thickness of one side of the proximal end of connecting member 37 in the second direction may be different from the thickness of the other side of the proximal end of connecting member 37 in the second direction. In this case, the smaller of these thicknesses is defined as thickness T4. However, it is preferable that the larger of these thicknesses also satisfy the condition of being smaller than thickness T3.

[0057] In addition, in this modified example, as shown in Figures 13(b) and 14(a), etc., a pair of grooves 37b are formed on the outer surface of the proximal end of the large diameter portion 22 (third large diameter portion 22d) in the second direction, facing each other on either side of the central axis of the large diameter portion 22. As shown in FIG. 11, each of the pair of grooves 37b extends from the middle portion to the proximal end in the axial direction of the large diameter portion 22 (third large diameter portion 22d). With this configuration, it is easy to reduce the contact area between the proximal end of the third large diameter portion 22d (connecting member 37) and the stent 200, while still ensuring space (dimension in the first direction) in which the first sheath 45 and the second sheath 47 can be inserted in parallel to each other.

[0058] 14(a) and 14(b), in this modification, the dimension W2 in the first direction at the distal end of large diameter portion 22 (third large diameter portion 22d) is equal to the dimension W1 in the second direction at the distal end of large diameter portion 22. On the other hand, the dimension W3 in the second direction at the proximal end of large diameter portion 22 (third large diameter portion 22d) is smaller than the dimension W4 in the first direction at the proximal end of large diameter portion 22. With this configuration, the contact area between the distal end of the third large diameter portion 22d and the stent 200 can be ensured satisfactorily, while the contact area between the proximal end of the third large diameter portion 22d and the stent 200 can be reduced.

[0059] Furthermore, in the present modified example, if the dimension in the first direction of the step 26a between the distal adjacent portion 26 and the distal end of the large diameter portion 22 is defined as the fifth step dimension (dimension H6 shown in Figure 11), and the dimension in the first direction of the step 27a between the proximal end of the large diameter portion 22 and the proximal adjacent portion 27 is defined as the sixth step dimension (dimension H7 shown in Figure 11), the fifth step dimension H6 and the sixth step dimension H7 are equal to each other.

[0060] In this modified example, the thickness T5 in the first direction at the distal end of the connecting member 37 (see FIG. 13(a)) is equal to the thickness T6 in the first direction at the proximal end of the connecting member 37 (see FIG. 13(b)).

[0061] More specifically, in this modified example, the cross-sectional shape of the lumen of the main pipe 210 (the cross-sectional shape along a direction perpendicular to the axial direction of the main pipe 210) is a substantially perfect circle. In contrast, the outer shape of the distal end surface 22da of the third large diameter portion 22d when viewed from the distal side (see FIG. 13(a)) is also a substantially perfect circle. On the other hand, the outer shape of the proximal end surface 22db of the third large diameter portion 22d when viewed from the proximal side (see FIG. 13(b)) is an oval shape that is narrowed in the second direction. With this configuration, the distal end of the third large diameter portion 22d is in circumferential contact with the stent 200, while at least a portion of the proximal end of the third large diameter portion 22d in the circumferential direction (the portion corresponding to the second direction) can be made non-contact with the stent 200.

[0062] In this modified example, as shown in FIGS. 11 to 13(b), the connecting member 37 is, for example, a single tube member that is inserted around the first sheath 45 and the second sheath 47. However, the present invention is not limited to this example, and the connecting member 37 may be, for example, a fixing tape wound around the first sheath 45 and the second sheath 47 so as to bind them together, or may be an S-shaped hook member or the like that is engaged with the first sheath 45 and the second sheath 47. In other words, the third large diameter portion 22d may be formed of a fixing tape, an S-shaped hook member, or the like.

[0063] The connecting member 37 has a first lumen 37aa through which the first sheath 45 is inserted, and a second lumen 37ab through which the second sheath 47 is inserted. As shown in FIGS. 13(a) and 13(b), the first lumen 37aa and the second lumen 37ab are formed symmetrically with respect to the central axis of the connecting member 37. Each of the first lumen 37aa and the second lumen 37ab extends from the distal end to the proximal end of the connecting member 37. The cross-sectional shape of each of the first lumen 37aa and the second lumen 37ab is substantially circular. The inner diameter of each of the first lumen 37aa and the second lumen 37ab is constant, for example, regardless of the position in the axial direction. The inner diameter of the first lumen 37aa is set, for example, to a dimension equal to or slightly larger than the outer diameter of the first sheath 45. The inner diameter of the second lumen 37ab is set, for example, to a dimension equal to or slightly larger than the outer diameter of the second sheath 47.

[0064] In this modified example, as shown in Figures 13(a) and 13(b), the first lumen 37aa and the second lumen 37ab are formed continuously with each other in the first direction (i.e., the direction in which the first sheath 45 and the second sheath 47 are arranged), and are connected to each other via a boundary portion 37ac. More specifically, in the first direction, the end of the first lumen 37aa on the second lumen 37ab side and the end of the second lumen 37ab on the first lumen 37aa side are continuous and communicated with each other. The first lumen 37aa and the second lumen 37ab are defined by the inner circumferential surface 37a of the connecting member 37. With this configuration, it is easier to reduce the outer diameter of the third large diameter portion 22d (connecting member 37), particularly the dimension in the first direction at the proximal end of the third large diameter portion 22d, compared to when the first lumen 37aa and the second lumen 37ab are formed independently of each other. Therefore, when the inner sheath 20 is pulled out from the stent 200 after the stent 200 has been placed, the proximal end of the third large diameter portion 22d can be effectively prevented from interfering with the stent 200. However, the present invention is not limited to this example, and the first lumen 37aa and the second lumen 37ab may be formed independently of each other.

[0065] As shown in FIGS. 11 and 12, the third large diameter portion 22d (connecting member 37) has, for example, a first portion 23b located on the distal side and a second portion 24b located on the proximal side.

[0066] 14(a) and 14(b), the outer diameter (including the dimension in the first direction and the dimension in the second direction) of the first portion 23b of the third large diameter portion 22d is constant, for example, regardless of the position in the axial direction. That is, the thickness (including the thickness in the first direction and the thickness in the second direction) of the first portion 23b of the third large diameter portion 22d is constant, for example, regardless of the position in the axial direction. With this configuration, the entire outer circumferential surface of first portion 23b of third large diameter portion 22d in the axial direction can be brought into contact with main vessel 210 of stent 200. Therefore, a forward force can be effectively transmitted to main vessel 210 via first portion 23b of third large diameter portion 22d.

[0067] The pair of grooves 37b are formed in the outer peripheral surface of the second portion 24a of the third large diameter portion 22. As shown in Fig. 14(a), the depth of each of the pair of grooves 37b gradually decreases toward the distal side. Therefore, the dimension of the second portion 24a in the second direction gradually decreases toward the proximal side. In other words, the thickness of the second portion 24a in the second direction gradually decreases toward the proximal side. The dimension in the second direction at the distal end of second portion 24a (at the boundary with first portion 23b) is approximately equal to the dimension in the second direction of first portion 23b. The thickness in the second direction at the distal end of second portion 24a (at the boundary with first portion 23b) is approximately equal to the thickness in the second direction of first portion 23b. According to this configuration, the fourth step dimension H5 can be made smaller while realizing a configuration in which the outer peripheral surface of the first portion 23b of the third large diameter portion 22d makes good contact with the main tube 210. Therefore, when the inner sheath 20 is pulled out from the stent 200, interference of the second portion 24a with the stent 200 can be more reliably prevented.

[0068] The method for forming a pair of grooves 37b in the third large diameter portion 22 (connecting member 37) is not particularly limited, but examples include a method of cutting a portion of the third large diameter portion 22 (connecting member 37) by laser processing, or a method of transferring the irregularities of a mold when molding the connecting member 37.

[0069] 14(b), the dimension of the second portion 24a in the first direction is constant regardless of the position in the axial direction and is approximately equal to the dimension of the first portion 23b in the first direction. That is, the thickness of the second portion 24a in the first direction is constant regardless of the position in the axial direction and is approximately equal to the thickness of the first portion 23b in the first direction. According to this configuration, it is possible to ensure a space (dimension in the first direction) in the third large diameter portion 22d (connecting member 37) that allows the first sheath 45 and the second sheath 47 to be inserted in parallel with each other.

[0070] However, the present invention is not limited to this example, and for example, in addition to a pair of grooves 37b facing each other so as to sandwich the central axis (central axis (axial center) of the third large diameter portion 22d) in the second direction, a pair of grooves (not shown) facing each other so as to sandwich the central axis (same as above) in the first direction may also be formed on the outer peripheral surface of the second part 24a of the third large diameter portion 22d. With this configuration, the dimension of the second portion 24a in the first direction can be gradually reduced toward the proximal side, and the thickness of the second portion 24a in the second direction can be gradually reduced toward the proximal side.

[0071] The third step dimension H4 is, for example, 1.0 to 100.0 times the fourth step dimension H5, and preferably 1.5 to 25.0 times the fourth step dimension H5. The thickness T3 in the second direction of the distal end of the connecting member 37 is, for example, 1.0 to 100.0 times the thickness T4 in the second direction of the proximal end of the connecting member 37, and preferably 1.5 to 25.0 times the thickness T4.

[0072] In this modified example, as in the above embodiment, the stent 200 is attached to the stent mounting section 21 while being restrained in a reduced diameter state by the string members 240. As shown in FIG. 10(a), the string member 240 is spirally wound in the tip-to-proximal direction with gaps formed between the multiple turns 240a. The distal end of the large diameter portion 22 (third large diameter portion 22d) is adjacent to at least one turn 240a of the plurality of turns 240a. Here, "the distal end of large diameter portion 22 (third large diameter portion 22d) is adjacent to one turn 240a" means that the distance between the distal end of large diameter portion 22 (third large diameter portion 22d) and the one turn 240a in the tip-to-proximal direction is no more than twice the outer diameter of the distal end of large diameter portion 22 (the dimension in the first direction or the dimension in the second direction in the case of third large diameter portion 22d). Preferably, the distance between the distal end of large diameter portion 22 (third large diameter portion 22d) and the one turn 240a in the tip-to-proximal direction is no more than one time the outer diameter (same as above) of the distal end of large diameter portion 22. According to this configuration, when the stent 200 is constrained in a reduced diameter state and attached to the stent attachment section 21, a constriction of the stent 200 can be formed on the distal side of the third large diameter section 22d by the string member 240. Therefore, a sufficient contact area between the distal end of the third large diameter section 22d and the stent 200 can be ensured.

[0073] More specifically, in this variation, either or both of the string member 240 restraining the first branch vessel 220 of the stent 200 and the string member 240 restraining the second branch vessel 230 also restrain the distal end of the main vessel 210. 10(a), third large diameter portion 22d is disposed, for example, in a gap between adjacent turns 240a at the distal end of main pipe 210. In other words, one turn 240a is disposed distal to the distal end of third large diameter portion 22d, and one turn 240a is disposed proximal to the proximal end of third large diameter portion 22d. With this configuration, constrictions can be formed on both the distal and proximal sides of the third large diameter portion 22d of the stent 200. This prevents the main tube 210 from being displaced in the axial direction relative to the inner sheath 20 when the inner sheath 20 (the first sheath 45 and the second sheath 47) is advanced or retracted.

[0074] <Variation 2> Next, Modification 2 will be described using Fig. 15 to Fig. 18(b). The stent delivery device 100 according to this modification differs from the stent delivery device 100 according to Modification 1 described above in the points described below, but is otherwise configured similarly to the stent delivery device 100 according to Modification 1 described above. Fig. 15 is a side view of the inner sheath 20 as viewed from the direction of arrow A shown in Fig. 17(b), and Fig. 16 is a side view of the inner sheath 20 as viewed from the direction of arrow B shown in Fig. 17(b). In Figs. 17(a) and 17(b), the first sheath 45 and the second sheath 47 are each indicated by a two-dot chain line.

[0075] In this modified example, as in the first modified example, the fourth step dimension H5 is smaller than the third step dimension H4, as shown in FIG. Furthermore, in the case of this modified example, if the dimension in the first direction of the step 26a between the distal adjacent portion 26 and the distal end of the large diameter portion 22 is defined as the fifth step dimension (dimension H6 shown in Figure 15), and the dimension in the first direction of the step 27a between the proximal end of the large diameter portion 22 and the proximal adjacent portion 27 is defined as the sixth step dimension (dimension H7 shown in Figure 15), the sixth step dimension H7 is smaller than the fifth step dimension H6. With this configuration, the contact area between the distal end of the third large diameter portion 22d and the stent 200 can be sufficiently secured in both the first and second directions, while the contact area between the proximal end of the third large diameter portion 22d and the stent 200 can be further reduced.

[0076] In this modified example, the dimension in the first direction of the step between the first distal adjacent portion 45a and the distal end of the third large diameter portion 22d and the dimension in the first direction of the step between the second distal adjacent portion 47a and the distal end of the third large diameter portion 22d are equal to each other and larger than the sixth step dimension H7. Similarly, the dimension in the first direction of the step between the first proximal adjacent portion 45b and the proximal end of the third large diameter portion 22d and the dimension in the first direction of the step between the second proximal adjacent portion 47b and the proximal end of the third large diameter portion 22d are equal to each other and smaller than the above-mentioned fifth step dimension H6. In Figure 15, of the dimension in the first direction of the step between the first distal adjacent portion 45a and the distal end of the third large diameter portion 22d and the dimension in the first direction of the step between the second distal adjacent portion 47a and the distal end of the third large diameter portion 22d, the dimension in the first direction of the step between the first distal adjacent portion 45a and the distal end of the third large diameter portion 22d is selectively illustrated as a fifth step dimension H6. Similarly, in Figure 15, of the dimension in the first direction of the step between the first proximal adjacent portion 45b and the proximal end of the third large diameter portion 22d and the dimension in the first direction of the step between the second proximal adjacent portion 47b and the proximal end of the third large diameter portion 22d, the dimension in the first direction of the step between the first proximal adjacent portion 45b and the proximal end of the third large diameter portion 22d is selectively illustrated as the sixth step dimension H7.

[0077] However, the present invention is not limited to this example, and the dimension in the first direction of the step between the first distal adjacent portion 45a and the distal end of the third large diameter portion 22d and the dimension in the first direction of the step between the second distal adjacent portion 47a and the distal end of the third large diameter portion 22d may be different from each other. In this case, the larger of these dimensions is defined as the fifth step dimension H6. However, it is preferable that the smaller of these dimensions also satisfy the condition of being larger than the sixth step dimension H7. Similarly, the dimension in the first direction of the step between the first proximal adjacent portion 45b and the proximal end of the third large diameter portion 22d may be different from the dimension in the first direction of the step between the second proximal adjacent portion 47b and the proximal end of the third large diameter portion 22d. In this case, the smaller of these dimensions is defined as the sixth step dimension H7. However, it is preferable that the larger of these dimensions also satisfy the condition of being smaller than the fifth step dimension H6.

[0078] Also, in this modified example, the thickness T4 in the second direction at the proximal end of the connecting member 37 (see Figure 18(a)) is smaller than the thickness T3 in the second direction at the distal end of the connecting member 37 (see Figure 18(a)). Furthermore, in this modified example, the thickness T6 in the first direction at the proximal end of the connecting member 37 (see Figures 17(b) and 18(b)) is smaller than the thickness T5 in the first direction at the distal end of the connecting member 37 (see Figures 17(a) and 18(b)). With this configuration, it is possible to ensure an appropriate contact area between the distal end of third large diameter portion 22d and stent 200 in both the first and second directions, as well as an appropriate rigidity of the distal end. Furthermore, it is possible to reduce the contact area between the proximal end of third large diameter portion 22d and stent 200 in both the first and second directions, and to appropriately reduce the rigidity of the proximal end.

[0079] In this modified example, the thickness of one side of the distal end of the connecting member 37 in the first direction and the thickness of the other side of the distal end of the connecting member 37 in the first direction are equal to each other and are greater than the thickness T6 of the proximal end of the connecting member 37 in the first direction. Similarly, the thickness of one side of the proximal end of the connecting member 37 in the first direction and the thickness of the other side of the proximal end of the connecting member 37 in the first direction are equal to each other and smaller than the thickness T5 of the distal end of the connecting member 37 in the first direction. In Figure 17(a), the thickness of one side of the distal end of the connecting member 37 in the first direction and the thickness of the other side of the distal end of the connecting member 37 in the first direction are selectively illustrated as thickness T5. Similarly, in Figure 17(b), of the thickness of one side of the proximal end of the connecting member 37 in the first direction and the thickness of the other side of the proximal end of the connecting member 37 in the first direction, the thickness of one side of the proximal end of the connecting member 37 in the first direction is selectively illustrated as thickness T6.

[0080] However, the present invention is not limited to this example, and the thickness of one side of the distal end of connecting member 37 in the first direction may be different from the thickness of the other side of the distal end of connecting member 37 in the first direction. In this case, the larger of these thicknesses is defined as thickness T5. However, it is preferable that the smaller of these thicknesses also satisfy the condition of being larger than thickness T6. Similarly, the thickness of one side of the proximal end of connecting member 37 in the first direction may be different from the thickness of the other side of the proximal end of connecting member 37 in the first direction. In this case, the smaller of these thicknesses is defined as thickness T6. However, it is preferable that the larger of these thicknesses also satisfy the condition of being smaller than thickness T5.

[0081] Also, in this modified example, the dimension in the first direction at the distal end of the large diameter portion 22 (third large diameter portion 22d) is equal to the dimension in the second direction at the distal end of the large diameter portion 22, while the dimension in the second direction at the proximal end of the large diameter portion 22 (third large diameter portion 22d) is smaller than the dimension in the first direction at the proximal end of the large diameter portion 22.

[0082] More specifically, in this modification, as in the first modification, the outer shape of the distal end surface 22da of the third large diameter portion 22d as viewed from the distal side (see FIG. 17(a)) is also a substantially perfect circle. On the other hand, the outer shape of the proximal end surface 22db of the third large diameter portion 22d as viewed from the distal side (see FIG. 17(b)) is a substantially elliptical shape (more specifically, a substantially oval shape) that is elongated in the first direction. That is, the long axis direction of the proximal end surface 22db is the first direction, and the short axis direction of the proximal end surface 22db is the second direction. Even with this configuration, the distal end of the third large diameter portion 22d is in circumferential contact with the stent 200, while at least a portion of the proximal end of the third large diameter portion 22d in the circumferential direction (the portion corresponding to the second direction) is not in contact with the stent 200.

[0083] In this modification, the outer diameter (including the dimensions in the first and second directions) of the first portion 23b of the third large diameter portion 22d is constant, for example, regardless of the position in the axial direction. That is, the thickness (including the thickness in the first and second directions) of the first portion 23b of the third large diameter portion 22d is constant, for example, regardless of the position in the axial direction.

[0084] On the other hand, the outer diameter (including the dimension in the first direction and the dimension in the second direction) of the second portion 24b of the third large diameter portion 22d tapers down toward the proximal side, for example. 18(a), the dimension of the second portion 24a in the second direction gradually decreases toward the proximal side. That is, the thickness of the second portion 24a in the second direction gradually decreases toward the proximal side. The dimension in the second direction at the distal end of second portion 24a (at the boundary with first portion 23b) is approximately equal to the dimension in the second direction of first portion 23b. The thickness in the second direction at the distal end of second portion 24a (at the boundary with first portion 23b) is approximately equal to the thickness in the second direction of first portion 23b. 18(b), the dimension of the second portion 24a in the first direction gradually decreases toward the proximal side. That is, the thickness of the second portion 24a in the first direction gradually decreases toward the proximal side. The dimension in the first direction of the distal end of second portion 24a (at the boundary with first portion 23b) is approximately equal to the dimension in the first direction of first portion 23b. The thickness in the first direction of second portion 24a at the distal end (at the boundary with first portion 23b) is approximately equal to the thickness in the first direction of first portion 23b. With this configuration, it is possible to ensure an appropriate contact area between the distal end of third large diameter portion 22d and stent 200 in both the first and second directions, as well as an appropriate rigidity of the distal end. Furthermore, it is possible to reduce the contact area between the proximal end of third large diameter portion 22d and stent 200 in both the first and second directions, and to appropriately reduce the rigidity of the proximal end.

[0085] The fifth step dimension H6 is, for example, 1.0 to 100.0 times the sixth step dimension H7, and more preferably 1.5 to 25.0 times the sixth step dimension H7. The thickness T5 in the first direction of the distal end of the connecting member 37 is, for example, 1.0 to 100.0 times the thickness T6 in the first direction of the proximal end of the connecting member 37, and more preferably 1.5 to 25.0 times the thickness T6 in the first direction of the proximal end of the connecting member 37.

[0086] The present invention is not limited to the above-described embodiments and modifications, but includes various modifications and improvements as long as the object of the present invention is achieved.

[0087] The present embodiment encompasses the following technical ideas. (1) A stent delivery device for delivering a stent into a body, comprising: a long inner sheath having a stent mounting portion to which the stent is mounted in an exterior state during delivery of the stent; A portion of the stent mounting section is a large diameter section formed to have a larger diameter than the other sections, the inner sheath has a distal adjacent portion which is a portion of the inner sheath adjacent to a distal side of the large diameter portion, and a proximal adjacent portion which is a portion of the inner sheath adjacent to a proximal side of the large diameter portion, a first step dimension is a radial dimension of a step between the distal adjacent portion and the distal end of the large diameter portion; When the dimension in the radial direction of the step between the proximal end of the large diameter portion and the proximal adjacent portion is defined as a second step dimension, a stent delivery device in which the second step dimension is smaller than the first step dimension. (2) The stent delivery device according to (1), wherein the outer diameter of the large diameter portion decreases toward the proximal side. (3) The large diameter portion has a first portion located on the distal side and a second portion located on the proximal side, a step exists at the boundary between the first portion and the second portion, The stent delivery device according to (2), wherein the second portion has a smaller diameter than the first portion. (4) The stent delivery device according to (3), wherein the second portion gradually tapers in diameter toward the proximal side. (5) The inner sheath includes an inner sheath body and a large-diameter portion-constituting tube that is fitted around the inner sheath body and constitutes the large-diameter portion, The stent delivery device according to (3) or (4), wherein the wall thickness of the portion of the large diameter tube constituting the second portion is smaller than the wall thickness of the portion constituting the first portion. (6) The stent delivery device according to (3) or (4), wherein the step at the boundary between the first portion and the second portion is rounded. (7) The inner sheath includes an inner sheath body and a large-diameter portion-constituting tube that is fitted around the inner sheath body and constitutes the large-diameter portion, The stent delivery device according to (3) or (4), wherein the surface roughness of the inner circumferential surface of the portion constituting the second portion in the large diameter portion-constituting tube is greater than the surface roughness of the outer circumferential surface of the portion constituting the second portion. (8) The stent has a main vessel and a first branch vessel and a second branch vessel each branching from a stent bifurcation portion that is a distal end of the main vessel, the inner sheath includes a first sheath inserted through the main pipe and the first branch pipe, and a second sheath inserted through the main pipe and the second branch pipe, each of the first sheath and the second sheath has the large diameter portion; The stent delivery device according to any one of (1) to (7), wherein the position of the large diameter portion of the first sheath and the position of the large diameter portion of the second sheath are different from each other in the proximal-to-proximal direction. (9) The stent has a main vessel and a first branch vessel and a second branch vessel each branching from a stent bifurcation portion that is a distal end of the main vessel, the inner sheath includes a first sheath inserted through the main pipe and the first branch pipe, and a second sheath inserted through the main pipe and the second branch pipe, each of the first sheath and the second sheath has the large diameter portion at least at a position corresponding to the main pipe; A stent delivery device according to any one of (1) to (8), wherein the large diameter portion of the first sheath and the large diameter portion of the second sheath are arranged to overlap each other in the tip-base direction. (9-1) Each of the first sheath and the second sheath has a plurality of the large diameter portions, the first sheath has, as the plurality of large diameter portions, a first large diameter portion which is the large diameter portion formed at a position corresponding to the first branch pipe, and a third large diameter portion which is the large diameter portion formed at a position corresponding to the main pipe, The stent delivery device according to (8) or (9), wherein the second sheath has the plurality of large diameter portions, the second large diameter portion being the large diameter portion formed at a position corresponding to the second branch vessel, and the third large diameter portion being the large diameter portion formed at a position corresponding to the main vessel. (10) The inner sheath has a connecting member that is wrapped around the first sheath and the second sheath and connects partial sections of the first sheath and the second sheath in parallel, the connecting member constitutes the large diameter portion common to the first sheath and the second sheath, a first direction is a direction in which the first sheath and the second sheath are arranged, and a second direction is a direction perpendicular to both the first direction and a central axis of the large diameter portion, a dimension in the second direction of a step between the distal adjacent portion and the distal end of the large diameter portion is a third step dimension; When the dimension in the second direction of the step between the proximal end of the large diameter portion and the proximal adjacent portion is defined as a fourth step dimension, The stent delivery device according to (9), wherein the fourth step dimension is smaller than the third step dimension. (10-1) The large diameter portion has a first portion located on the distal side and a second portion located on the proximal side, a dimension of the first portion in the second direction is constant regardless of a position of the large diameter portion in the axial direction, The stent delivery device according to (10), wherein the dimension of the second portion in the second direction gradually decreases toward the proximal side. (11) A dimension in the first direction of a step between the distal adjacent portion and the distal end of the large diameter portion is a fifth step dimension; When the dimension in the first direction of the step between the proximal end of the large diameter portion and the proximal adjacent portion is defined as a sixth step dimension, The stent delivery device according to (10), wherein the sixth step dimension is smaller than the fifth step dimension. (11-1) The large diameter portion has a first portion located on the distal side and a second portion located on the proximal side, a dimension of the first portion in the first direction is constant regardless of a position in the axial direction of the large diameter portion, The stent delivery device according to (11), wherein the dimension of the second portion in the first direction gradually decreases toward the proximal side. (12) The connecting member is a tubular member and has a first lumen through which the first sheath is inserted and a second lumen through which the second sheath is inserted, The stent delivery device according to (10) or (11), wherein the wall thickness in the second direction at the proximal end of the connecting member is smaller than the wall thickness in the second direction at the distal end of the connecting member. (12-1) The stent delivery device according to (12), wherein the first lumen and the second lumen are formed to be continuous with each other in the first direction. (13) The stent delivery device according to (12), wherein the wall thickness of the connecting member in the first direction at the proximal end is smaller than the wall thickness of the connecting member in the first direction at the distal end. (14) A pair of grooves facing each other in the second direction are formed on the outer circumferential surface of the proximal end of the large diameter portion, with the central axis of the large diameter portion sandwiched therebetween, The stent delivery device according to any one of (10) to (13), wherein each of the pair of grooves extends from a middle portion of the large diameter portion in the axial direction to a proximal end thereof. (15) The dimension of the large diameter portion in the first direction at the distal end is equal to the dimension of the large diameter portion in the second direction at the distal end, A stent delivery device according to any one of (10) to (14), wherein the dimension in the second direction at the proximal end of the large diameter portion is smaller than the dimension in the first direction at the proximal end of the large diameter portion. (15-1) The cross-sectional shape of the lumen of the main pipe is a perfect circle, The outer shape of the distal end surface of the large diameter portion when viewed from the distal side is a perfect circle, The stent delivery device according to (15), wherein the outer shape of the proximal end face of the large diameter portion when viewed from the proximal side is a shape that is narrowed in the second direction. (16) The stent is attached to the stent mounting portion while being restrained in a reduced diameter state by a string member, the string member is wound spirally in the tip-to-proximal direction with gaps formed between a plurality of turns, The stent delivery device according to any one of (1) to (16), wherein the distal end of the large diameter portion is adjacent to at least one of the plurality of turns. (16-1) The stent delivery device according to (16), wherein the large diameter portion is disposed in a gap between adjacent turns in the tip-to-proximal direction. [Explanation of symbols]

[0088] 10 outer sheath 20 Inner sheath 21 Stent attachment part 22 Large diameter section 22a, 22b First large diameter section 22c Second large diameter section 22d Third large diameter section 22da distal end face 22db proximal end face 23, 23b Part 1 23a Step 24, 24b 2nd part 26 Distal adjacent region 26a Step 27 Proximal adjacent region 27a Step 31 Inner sheath body 36 Large diameter tube 37 Connecting member 37a Inner surface 37aa 1st lumen 37ab 2nd lumen 37ac border 37b Groove 38 Tip 41 Sheath main part 42 Sheath branch 43 Individual sheath section 45 First Sheath 45a First distal adjacent segment 45b First proximal adjacent part 46a 4th sheath 46b 5th sheath 47 Second Sheath 47a 2nd distal adjacent segment 47b Second proximal adjacent segment 49 Third Sheath 51 First radiopaque marker 52 Second radiopaque marker 53 Third radiopaque marker 55 Radiopaque marker 61 Adhesive 90 Operation section 91 Shaft Handle 92 Shaft 100 Stent delivery device 200 stents 210 Master 211 Stent bifurcation 220 1st branch pipe 230 2nd branch pipe 240 String members 240a Multiple Turns 250 Wire material 300 Guidewire 300a First guide wire 300b Second guide wire 400 Endoscope 510 Bile duct 511a Branch 512 Left hepatic duct 513 Right hepatic duct

Claims

1. A stent delivery device for delivering a stent into a body, comprising: a long inner sheath having a stent mounting portion to which the stent is mounted in an exterior state during delivery of the stent; A portion of the stent mounting section is a large diameter section formed to have a larger diameter than the other sections, the inner sheath has a distal adjacent portion which is a portion of the inner sheath adjacent to a distal side of the large diameter portion, and a proximal adjacent portion which is a portion of the inner sheath adjacent to a proximal side of the large diameter portion, a first step dimension is a radial dimension of a step between the distal adjacent portion and the distal end of the large diameter portion; When the dimension in the radial direction of the step between the proximal end of the large diameter portion and the proximal adjacent portion is defined as a second step dimension, The stent delivery device wherein the second step dimension is smaller than the first step dimension.

2. 2. The stent delivery device of claim 1, wherein the outer diameter of the larger diameter section tapers proximally.

3. The large diameter portion has a first portion located on a distal side and a second portion located on a proximal side, a step exists at the boundary between the first portion and the second portion, 3. The stent delivery device of claim 2, wherein said second portion has a smaller diameter than said first portion.

4. 4. The stent delivery device of claim 3, wherein the second section tapers proximally.

5. the inner sheath includes an inner sheath body and a large diameter portion-constituting tube that is fitted around the inner sheath body and constitutes the large diameter portion, 5. The stent delivery device according to claim 3, wherein the wall thickness of the portion of the large diameter tube constituting the second portion is smaller than the wall thickness of the portion of the large diameter tube constituting the first portion.

6. 5. The stent delivery device according to claim 3, wherein the step at the boundary between the first portion and the second portion is rounded and chamfered.

7. the inner sheath includes an inner sheath body and a large diameter portion-constituting tube that is fitted around the inner sheath body and constitutes the large diameter portion, 5. The stent delivery device according to claim 3, wherein the surface roughness of the inner circumferential surface of the large diameter portion constituting the second portion is greater than the surface roughness of the outer circumferential surface of the portion constituting the second portion in the large diameter portion constituting the tube.

8. The stent has a main vessel and a first branch vessel and a second branch vessel each branching from a stent bifurcation portion that is a distal end of the main vessel, the inner sheath includes a first sheath inserted through the main pipe and the first branch pipe, and a second sheath inserted through the main pipe and the second branch pipe, each of the first sheath and the second sheath has the large diameter portion; The stent delivery device according to claim 1 , wherein the position of the large diameter portion of the first sheath and the position of the large diameter portion of the second sheath are different from each other in the proximal-to-proximal direction.

9. The stent has a main vessel and a first branch vessel and a second branch vessel each branching from a stent bifurcation portion that is a distal end of the main vessel, the inner sheath includes a first sheath inserted through the main pipe and the first branch pipe, and a second sheath inserted through the main pipe and the second branch pipe, each of the first sheath and the second sheath has the large diameter portion at least at a position corresponding to the main pipe; The stent delivery device according to claim 1 , wherein the large diameter portion of the first sheath and the large diameter portion of the second sheath are arranged to overlap each other in the proximal-to-proximal direction.

10. the inner sheath is fitted over the first sheath and the second sheath and includes a connecting member connecting partial sections of the first sheath and the second sheath in parallel to each other; the connecting member constitutes the large diameter portion common to the first sheath and the second sheath, a direction in which the first sheath and the second sheath are arranged is defined as a first direction, and a direction perpendicular to both the first direction and the central axis of the large diameter portion is defined as a second direction; a dimension in the second direction of a step between the distal adjacent portion and the distal end of the large diameter portion is a third step dimension; When the dimension in the second direction of the step between the proximal end of the large diameter portion and the proximal adjacent portion is defined as a fourth step dimension, 10. The stent delivery device of claim 9, wherein the fourth step dimension is smaller than the third step dimension.

11. a dimension in the first direction of a step between the distal adjacent portion and the distal end of the large diameter portion is a fifth step dimension; When the dimension in the first direction of the step between the proximal end of the large diameter portion and the proximal adjacent portion is defined as a sixth step dimension, 11. The stent delivery device of claim 10, wherein the sixth step dimension is smaller than the fifth step dimension.

12. the connecting member is a tubular member and has a first lumen through which the first sheath is inserted and a second lumen through which the second sheath is inserted, 11. The stent delivery device of claim 10, wherein the wall thickness in the second direction at the proximal end of the connecting member is smaller than the wall thickness in the second direction at the distal end of the connecting member.

13. 13. The stent delivery device of claim 12, wherein the wall thickness of the connecting member in the first direction at the proximal end is smaller than the wall thickness of the connecting member in the first direction at the distal end.

14. a pair of grooves facing each other in the second direction and sandwiching the central axis of the large diameter portion are formed on an outer circumferential surface of the proximal end portion of the large diameter portion; The stent delivery device according to claim 10, wherein each of the pair of grooves extends from an axially intermediate portion of the large diameter portion to a proximal end thereof.

15. a dimension in the first direction at the distal end of the large diameter portion is equal to a dimension in the second direction at the distal end of the large diameter portion; 11. The stent delivery device of claim 10, wherein the dimension of the large diameter section at the proximal end in the second direction is smaller than the dimension of the large diameter section at the proximal end in the first direction.

16. the stent is attached to the stent mounting portion while being restrained in a reduced diameter state by a string member; The string member is wound spirally in the tip-to-proximal direction with gaps formed between a plurality of turns, 10. The stent delivery device of claim 9, wherein the distal end of the larger diameter section is adjacent to at least one of the plurality of turns.

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