Stent

Abstract

Provided is a stent excellent in shape followability and radial compressibility.　A stent 1 comprises: an outer stent body 10 in which a plurality of outer cells 12 surrounded by an outer strut 11 is arranged at least in the central axis direction; and an inner stent body 20 in which a plurality of inner cells 22 surrounded by an inner strut 21 is arranged at least in the central axis direction, the inner stent body 20 being located inside the outer stent body 10 at least in a region for expanding a biological lumen. The inner stent body 20 includes an open cell including free protrusion portions 26, 27 in which the inner strut 21 forms a projection toward the inside of an opening portion of the inner cell 22. In a free state in which the stent 1 is freely radially expanded, a circular cylindrical part 1a, which radially expands into a circular cylindrical shape, of the outer stent body 10 does not include free protrusion portions 26, 27 in which the outer strut 11 forms a projection toward the inside of opening portion of the outer cell 12.

Description

stents

[0001] The present disclosure relates to stents.

[0002] 2. Description of the Related Art Catheter therapy is known in the art, in which a stent is deployed at a lesion site in a blood vessel lumen.

[0003] Furthermore, as a stent with a larger surface area and excellent shape-conforming properties to the vascular structure and diameter reduction properties, a stent comprising an outer stent body and an inner stent body inserted into the outer stent body (hereinafter also referred to as a two-layer structure stent) has been disclosed (see Patent Document 2). In the two-layer structure stent described in Patent Document 2, the outer stent body and the inner stent body have the same stent pattern.

[0004] U.S. Patent No. 10,390,982 International Publication No. 2022 / 085313

[0005] Although bilayer stents have excellent shape conformability and diameter reduction properties, even greater shape conformability and diameter reduction properties are required so that they can be used in smaller blood vessels. The cell structures that make up stents can be broadly classified into open cell and closed cell. Open cell stents have struts with free ends. Closed cell stents do not have struts with free ends. Stents primarily having open cells are generally more flexible, have higher shape conformability, and have superior diameter reduction properties than stents primarily having closed cells. Therefore, it is expected that bilayer stents will also use stents primarily having open cells. However, if a bilayer stent has open cells in the outer stent body, there is a risk that the free ends will get caught when inserted into a catheter.

[0006] An object of the present disclosure is to provide a stent that is excellent in shape conformability and diameter reduction ability.

[0007] The present disclosure solves the above-mentioned problems by the following means: For ease of understanding, the following description will be given with reference numerals corresponding to the embodiments of the present disclosure, but the present disclosure is not limited to these.

[0008] The first disclosure relates to a stent (1) that is inserted into a catheter and removed from the catheter within a biological lumen to be used for expanding the biological lumen, the stent (1) comprising: an outer stent body (10) having a plurality of outer cells (12) surrounded by outer struts (11) arranged at least in the central axis direction; and an inner stent body (20) having a plurality of inner cells (22) surrounded by inner struts (21) arranged at least in the central axis direction, the inner stent body (20) being inserted into the outer stent body (10) at least in the region where the biological lumen is expanded, wherein the inner stent body (20) includes open cells that include free convex portions (26, 27) where the inner struts (21) are convex toward the inside of the openings of the inner cells (22).

[0009] The second disclosure is the stent (1) according to the first disclosure, wherein the free convex portions (26, 27) of the inner cell (22) all protrude distally.

[0010] A third disclosure is a stent (1) according to the first or second disclosure, wherein in a free state in which the outer stent body (10) is freely expanded in diameter, the cylindrical portion (1a) in which the outer struts (11) are expanded in a cylindrical shape does not include free convex portions (26, 27) in which the outer struts (11) are convex toward the inside of the openings of the outer cells (12).

[0011] A fourth disclosure is a stent (1) according to the first or second disclosure, wherein in the cylindrical portion (1a) which expands into a cylindrical shape in a free state in which it is freely expanded in diameter, the free convex portion (26, 27) of at least one of the inner cells (22) is arranged in the opening portion of one of the outer cells (12) for all of the outer cells (12).

[0012] A fifth disclosure is a stent (1) according to the first or second disclosure, wherein the outer stent body (10) does not have the free protrusions (26, 27).

[0013] A sixth disclosure is a stent (1) according to the first or second disclosure, wherein the stent (1) is expanded in diameter and placed in a biological lumen, and then removed.

[0014] The seventh disclosure is a method for expanding a biological organ having a luminal structure using a stent (1), the stent (1) comprising an outer stent body (10) in which a plurality of outer cells (12) surrounded by outer struts (11) are arranged at least in the central axis direction, and an inner stent body (20) in which a plurality of inner cells (22) surrounded by inner struts (21) are arranged at least in the central axis direction and inserted into the outer stent body (10) at least in a region where the biological lumen is to be expanded, the inner stent body (20) being oriented inward of the openings of the inner cells (22). The stent (1, 1B) includes open cells including free convex portions (26, 27) in which the inner struts (21) are convex, and the method includes: delivering the stent (1, 1B) housed in a catheter (50) in a contracted state together with the catheter (50) through the biological organ to a planned position in the biological organ where the stent (1, 1B) is to be expanded; withdrawing the catheter (50) proximally and starting to expand the stent (1, 1B) from the distal side; completing the expansion of the stent (1, 1B); and re-accommodating the expanded stent (1, 1B) into the catheter (50).

[0015] According to the present disclosure, a stent having excellent shape conformability and diameter reduction properties can be provided.

[0016] FIG. 1 is a side view of a stent 1 of a first embodiment. FIG. 2 is a virtual development view of a portion of the cylindrical portion 1a of the outer stent body 10 and the inner stent body 20 of the first embodiment. FIG. 3 is a virtual development view of a portion of the cylindrical portion 1a of the outer stent body 10 of the first embodiment. FIG. 4 is a virtual development view of a portion of the cylindrical portion 1a of the inner stent body 20 of the first embodiment. FIG. 5 is a virtual development view of only one inner cell 22 of the inner stent body 20 of the first embodiment. FIG. 6 is a virtual development view of a portion of the cylindrical portion 1a of the stent 1 in a state in which the relative circumferential positions of the outer stent body 10 and the inner stent body 20 are deviated from the target design positions. FIG. 7 is a diagram illustrating the outer diameter D1 of the outer stent body 10 alone. FIG. 8 is a diagram illustrating the outer diameter D2 of the inner stent body 20 alone. FIG. 9 is a diagram illustrating the process of inserting the inner stent body 20 into the outer stent body 10. FIG. 11 is a virtual development view of a portion of the cylindrical portion 1a of the outer stent body 10 and the inner stent body 20 of a second embodiment. FIG. 10 is a virtual development view of a portion of the cylindrical portion 1a of the outer stent body 10 of the second embodiment. FIG. 11 is a virtual development view of a portion of the cylindrical portion 1a of the inner stent body 20 of the second embodiment. FIG. 12 is a virtual development view of a portion of the cylindrical portion 1a of the outer stent body 10 of the third embodiment. FIG. 13 is a virtual development view of a portion of the cylindrical portion 1a of the inner stent body 20 of the third embodiment. FIG. 14 is a virtual development view of a portion of the cylindrical portion 1a of the outer stent body 10 of the third embodiment. FIG. 15 is a virtual development view of a portion of the cylindrical portion 1a of the inner stent body 20 of the third embodiment. FIG. 16 is a virtual development view of a portion of the cylindrical portion 1a of the outer stent body 10 of the fourth embodiment. FIG. 17 is a virtual development view of a portion of the cylindrical portion 1a of the outer stent body 10 of the fourth embodiment. FIG. 18 is a virtual development view of a portion of the cylindrical portion 1a of the inner stent body 20 of the fourth embodiment. Fig. 10 is a virtual development view of a portion of the cylindrical portion 1a of the outer stent body 10 of the fifth embodiment. Fig. 11 is a virtual development view of a portion of the cylindrical portion 1a of the inner stent body 20 of the fifth embodiment. Fig. 12 is a schematic diagram showing a procedure for dilating a stenotic site in a blood vessel using a stent 1. Fig. 13 is a schematic diagram showing a procedure for dilating a stenotic site in a blood vessel using a stent 1. Fig. 14 is a schematic diagram showing a procedure for dilating a stenotic site in a blood vessel using a stent 1.1A to 1C are schematic diagrams showing a procedure for expanding a stenosed area in a blood vessel using a stent 1.

[0017] Hereinafter, an embodiment of a stent will be described. Note that the drawings attached to this specification are all schematic diagrams, and the shape, scale, aspect ratio, etc. may be modified or exaggerated from the actual product. Furthermore, hatching indicating the cross section of a component may be omitted as appropriate in the drawings.

[0018] In this specification, terms specifying the shape, geometric conditions, and the degree of these, such as "orthogonal" and "direction," include not only the strict meaning of the terms but also the range in which they can be considered to be nearly orthogonal or the range in which they can be considered to be roughly in that direction. In this specification, the axial direction (longitudinal direction) LD refers to the side closer to the practitioner (proximal) as the LD1 side (or proximal LD1 side), and the side farther from the practitioner (distal) as the LD2 side (or distal LD2 side), and the direction orthogonal to the axial direction LD is referred to as the radial direction RD. Also, in this specification, the direction in which the cells are arranged is referred to as the circumferential direction OD.

[0019] (First embodiment) Fig. 1 is a side view of a stent 1 of the first embodiment. Fig. 2A is a virtual development view of a portion of the cylindrical portion 1a of the outer stent body 10 and the inner stent body 20 of the first embodiment. Fig. 2B is a virtual development view of a portion of the cylindrical portion 1a of the outer stent body 10 of the first embodiment. Fig. 2C is a virtual development view of a portion of the cylindrical portion 1a of the inner stent body 20 of the first embodiment. Fig. 2D is a virtual development view of only one inner cell 22 of the inner stent body 20 of the first embodiment.

[0020] In the drawings, to make it easier to distinguish between the outer stent body 10 and the inner stent body 20, the struts of the outer stent body 10 are shown in black, and the struts of the inner stent body 20 are shown in white. Furthermore, in this specification, etc., the term "cell" refers to the portion surrounded by struts that form the stent. The "cells" may have the same shape and size, or may have different shapes and sizes. The term "strut" refers to the portion made of the wire-like material. In this specification, etc., the opening of a cell is referred to as the "opening portion," and the portion where struts of adjacent cells are connected or overlapped is referred to as the "overlapping portion."

[0021] The stent 1 of the first embodiment can be used, for example, to dilate a narrowed or blocked blood vessel by being housed in a catheter and then being removed from the catheter in the lumen of the blood vessel and expanding its diameter. The stent 1 is used in applications where it is temporarily placed in the blood vessel and then retrieved from the body, but it can also be used in applications where it is left in the blood vessel without being retrieved from the body. When used in such applications, it is preferable that the wire 2 and the stent 1 can be separated by an operator's operation.

[0022] The stent 1 includes a cylindrical portion 1a and a converging portion 1b. In a free state where the cylindrical portion 1a is freely expanded, the cylindrical portion 1a is configured to have a cylindrical shape as shown in FIGS. 3A and 3B , and has a mesh pattern structure composed of outer cells 12 and inner cells 22 (described later). The converging portion 1b is a portion where the proximal LD1 side of the cylindrical portion 1a converges to the wire 2. The stent 1 is configured to have a substantially cylindrical shape when extended in a free state after being removed from the catheter (see FIGS. 3A and 3B , described later). Although not shown, the stent 1 has an elongated cylindrical shape in a contracted state. The wire 2 is connected to the end of the proximal LD1 side of the stent 1. Examples of methods for connecting the proximal end of the stent 1 to the wire 2 include welding, UV bonding, and infiltration with silver solder. However, any connection method commonly used in medical devices is not particularly limited.

[0023] The practitioner advances or retreats the stent 1 within the catheter or blood vessel by pushing or pulling the wire 2 via an ex vivo operating unit (not shown) connected to the proximal LD1 side of the wire 2. The practitioner can also extend the stent 1 out of the catheter and expand its diameter, or retract it into the catheter, by pulling (retreating) or pushing (advancing) the catheter without moving the wire 2 (stent 1).

[0024] The stent 1 comprises an outer stent body 10 and an inner stent body 20, which are substantially cylindrical structures. The stent 1 is a two-layer structure (two-layer structure) in which the inner stent body 20 is inserted into the outer stent body 10 at least in the region that dilates the narrowed portion of the biological lumen. Here, the region that dilates the narrowed portion of the biological lumen refers to the region that substantially contributes to dilating the narrowed portion during use, and in the case of the stent 1 of this embodiment, it refers to the region that is expanded into a substantially cylindrical shape in the expanded state shown in Fig. 1 . The above-mentioned "at least" means that the inner stent body 20 must be inserted into the outer stent body 10 in the region that dilates the narrowed portion. The range in which the inner stent body 20 is inserted into the outer stent body 10 is not limited to the region that substantially expands the narrowed area described above (in this embodiment, the region that expands into an approximately cylindrical shape), and in this embodiment, the inner stent body 20 is inserted into the outer stent body 10 up to the point where it is connected to the wire 2.

[0025] Furthermore, the statement that the inner stent body 20 is disposed inside (or inserted inside) the outer stent body 10 does not mean that the inner stent body 20 is completely inside the outer stent body 10 at all positions of the stent. That is, even in a region where the inner stent body 20 is disposed inside (internalized inside) the outer stent body 10, a portion of the inner stent body 20 may be radially outer than the inner surface of the outer stent body 10 or outer than the surface (outer surface) of the outer stent body 10. As will be described later, in this embodiment, a portion of the inner stent body 20 is intentionally configured to be radially outer than the inner surface of the outer stent body 10 or outer than the surface (outer surface) of the outer stent body 10. Note that, similar to the above, a portion of the outer stent body 10 may be radially inner than the surface (outer surface) of the inner stent body 20.

[0026] The outer stent body 10 and the inner stent body 20 are not connected to each other in the radial direction. Specifically, the outer stent body 10 and the inner stent body 20 are indirectly connected via the wire 2, but are not connected in other regions. Therefore, in the stent 1, the outer stent body 10 and the inner stent body 20 can flexibly deform independently. Furthermore, even in the expanded diameter state, the outer stent body 10 and the inner stent body 20 are merely in close contact with each other in the radial direction and are not linked (connected) together in the radial direction. Therefore, the outer stent body 10 and the inner stent body 20 are independently deformable and do not restrict each other's deformation.

[0027] The proximal LD1 side of the outer stent body 10, the proximal LD1 side of the inner stent body 20, and the distal LD2 side of the wire 2 are directly connected. Here, "directly connected" means, for example, that the proximal LD1 side of the outer stent body 10 is connected to the distal LD2 side of the wire 2, and that the proximal LD1 side of the inner stent body 20 is connected to the distal LD2 side of the wire 2. In this case, the position where the proximal LD1 side of the outer stent body 10 is connected to the wire 2 and the position where the proximal LD1 side of the inner stent body 20 is connected to the wire 2 may be the same as or different from each other.

[0028] The proximal LD1 side of the outer stent body 10, the proximal LD1 side of the inner stent body 20, and the distal LD2 side of the wire 2 may be indirectly connected. Here, "indirectly connected" refers to, for example, a configuration in which the proximal LD1 side of the outer stent body 10 is connected to the distal LD2 side of the wire 2, and the proximal LD1 side of the outer stent body 10 is connected to the proximal LD1 side of the inner stent body 20 (or a configuration in which the connections between the two stent bodies are reversed). In this case, the proximal LD1 side of the inner stent body 20 is indirectly connected to the wire 2 via the proximal LD1 side of the outer stent body 10. Alternatively, the proximal LD1 side of the outer stent body 10 and the proximal LD1 side of the inner stent body 20 are connected via a pipe-shaped sleeve (not shown) fitted onto the distal LD2 side of the wire 2. In this case, the proximal LD1 side of the outer stent body 10 and the proximal LD1 side of the inner stent body 20 are indirectly connected to the distal LD2 side of the wire 2 via the sleeve. Thus, in this specification, "indirectly connected" includes a configuration in which one of the proximal LD1 side of the outer stent body 10 or the proximal LD1 side of the inner stent body 20 is directly connected to the wire 2, and the other stent body is indirectly connected to the wire 2 via the directly connected stent body. Methods for connecting the proximal end of each stent body to the wire 2 include, for example, welding, UV bonding, impregnation with silver solder, etc., but are not particularly limited as long as they are connection methods used in general medical devices.

[0029] As will be described later, the stent 1 of the first embodiment is produced by inserting an inner stent body 20, which has an outer diameter larger than that of the outer stent body 10 in its natural state, into the outer stent body 10 in a contracted state. As a result, the inner stent body 20 constantly presses the outer stent body 10 outward in the radial direction RD, thereby firmly adhering the outer stent body 10 to the inner stent body 20. Furthermore, as will be described later, in an expanded diameter state, a portion of the inner stent body 20 can be positioned radially outward of the inner surface of the outer stent body 10.

[0030] 1 , the ends of the outer stent body 10 and the inner stent body 20 on the proximal LD1 side are tapered and gradually converge toward the wire 2, and are connected to the wire 2. This restricts the inner stent body 20 from moving in the axial direction relative to the outer stent body 10.

[0031] The stent 1 is provided with a first wire marker portion 31 and a second wire marker portion 32 as markers. These markers are components that serve as landmarks for confirming the position and state of the stent 1 under radiographic observation within a tubular organ such as a blood vessel, and are made of a material that is highly radiopaque (highly contrast-enhancing). Here, radiopaque refers to a material that is more radiopaque than portions of the stent 1 other than the markers (other portions that do not have radiopaque properties) under radiographic observation during a procedure, and is radiopaque to the extent that the markers can be observed as an image. "Radiopaque" is necessary to obtain "visibility" and "contrast" under radiographic observation.

[0032] Highly radiopaque materials that can be used as markers may be metals or synthetic resins. Examples of metal materials include gold, tantalum, platinum, tungsten, iridium, platinum tungsten, etc., and alloys thereof. Other examples include radiopaque polymer materials to which a radiopaque filler or the like has been added. When the marker is configured as a linear member, for example, a composite wire having a core material made of the aforementioned metal material coaxially within a nickel-titanium wire can be used.

[0033] Furthermore, as a method for attaching the marker to the stent 1, any processing method that has been conventionally used to place a marker on a known stent can be used as appropriate, such as soldering laser welding of gold-tin or silver-tin, mechanical crimping, or adhesive bonding with resin.

[0034] The first wire marker portion 31 is a coil marker formed by coiling a linear member made of a highly radiopaque material, and is fixed by welding in a position covering the end of the outer strut 11 on the proximal LD1 side. The second wire marker portion 32 is a ring marker formed by soldering a marker component made of a highly radiopaque material in a cylindrical shape to the strut, and is fixed by solder in a position covering the end of the inner stent body 20 on the proximal LD1 side. Note that the first wire marker portion 31 and the second wire marker portion 32 in this embodiment are examples of some of the specific forms of markers, and their locations and numbers can be changed as appropriate. For example, markers may also be provided on the stent portion.

[0035] As shown in FIG. 2B , the outer stent body 10 has a plurality of outer cells 12 surrounded by outer struts 11 arranged to surround a region in a generally diamond shape except for the proximal LD1 side, and the outer cells 12 are arranged in the circumferential direction OD. In the outer stent body 10, the outer cells 12 are arranged in the axial direction LD. That is, the outer stent body 10 has a mesh pattern in which the outer cells 12 are arranged in the circumferential direction OD and the axial direction LD. Note that, although the outer stent body 10 of this embodiment has a configuration in which the outer cells 12 are arranged in the circumferential direction OD and the axial direction LD, the configuration is not limited thereto. The outer stent body 10 may have a configuration in which the outer cells 12 surrounded by the outer struts 11 are arranged at least in the axial direction (central axis direction) LD. Here, "arranged in the axial direction (central axis direction) LD" does not necessarily mean that the outer cells 12 are arranged parallel to the axial direction (central axis direction) LD, but also means that the outer cells 12 are arranged non-parallel to the axial direction (central axis direction) LD. Openings 13 are formed in the outer cells 12. Adjacent outer cells 12 in the circumferential direction OD are connected at outer overlapping portions 14. As described above, the proximal LD1 side of the outer stent body 10 gradually converges toward the wire 2 and is connected to the wire 2. In this embodiment, the distal LD2 side of the outer stent body 10 is open and does not converge. The distal LD2 side of the outer stent body 10 may also be configured to converge in the same manner as the proximal LD1 side.

[0036] The outer overlapping portion 14 is a portion where the outer struts 11 of four adjacent outer cells 12 are connected. The outer overlapping portion 14 has a generally rectangular shape that is elongated in the axial direction LD. Each outer strut 11 is connected to one of the four corners of the outer overlapping portion 14. Each outer strut 11 has a curved portion 15 formed at the portion where it is connected to the outer overlapping portion 14. Therefore, when the expanded stent 1 is bent into a generally U-shape, each outer strut 11 connected to the outer overlapping portion 14 can be deformed independently. This allows the outer cells 12 arranged in the circumferential direction OD to bend more flexibly. In this way, the outer stent body 10 allows the outer cells 12 arranged in the circumferential direction OD to bend flexibly, thereby providing excellent shape conformability and diameter reduction properties.

[0037] As shown in Figure 2C, the inner stent body 20 has inner struts 21 arranged in a zigzag (sawtooth) pattern along the circumferential direction OD so that multiple (four in this embodiment) approximately diamond-shaped unit openings 23a are formed continuously in the circumferential direction OD, thereby constituting one inner cell 22. In this embodiment, one inner cell 22 is arranged in the circumferential direction OD. Furthermore, in the inner stent body 20, the inner cells 22 arranged in the circumferential direction OD are arranged in the axial direction LD. That is, the inner stent body 20 has a mesh pattern in which one inner cell 22 is arranged with its longitudinal direction aligned along the circumferential direction OD and is arranged in the axial direction LD. Inner overlapping portions 24 are provided at the portions of one inner cell 22 connected in the circumferential direction OD (both ends in the circumferential direction OD). Although the inner stent body 20 of this embodiment has been shown to have one inner cell 22 arranged in the circumferential direction OD and multiple inner cells 22 arranged in the axial direction LD, this configuration is not limited thereto. For example, multiple inner cells 22 may also be arranged in the circumferential direction OD. The inner stent body 20 may have any configuration in which multiple inner cells 22 surrounded by inner struts 21 are arranged at least in the axial direction (central axis direction) LD. Here, "arranged in the axial direction (central axis direction) LD" does not necessarily mean that the inner cells 22 are arranged parallel to the axial direction (central axis direction) LD, but also includes that the inner cells 22 are arranged non-parallel to the axial direction (central axis direction) LD. As described above, the proximal LD1 side of the inner stent body 20 gradually converges toward the wire 2 and is connected to the wire 2. In this embodiment, the distal LD2 side of the inner stent body 20 is open and does not converge. The distal LD2 side of the inner stent body 20 may be configured to converge in the same manner as the proximal LD1 side.

[0038] The inner overlapping portion 24 is the portion where the inner struts 21 of four adjacent inner cells 22 are connected. The inner overlapping portion 24 has a generally rectangular shape that is elongated in the axial direction LD. Where the inner overlapping portion 24 is provided, each inner strut 21 is connected to one of the four corners of the inner overlapping portion 24. Each inner strut 21 has a curved portion 25 formed at the portion where it is connected to the inner overlapping portion 24. Therefore, when the expanded stent 1 is bent into a generally U-shape, each inner strut 21 connected to the inner overlapping portion 24 can be deformed independently. This allows the inner cells 22 arranged in the circumferential direction OD to bend more flexibly.

[0039] As described above, the opening portion 23 of the inner cell 22 has a shape in which four unit opening portions 23a are connected along the circumferential direction OD. The portions where the unit opening portions 23a are connected in the circumferential direction OD have free protrusions 26, 27 that face each other in the axial direction LD. In each of the free protrusions 26, 27, the inner strut 21 protrudes toward the inside of the opening portion 23 of the inner cell 22, and the tip end of the protrusion is a free end that is not constrained. Therefore, the portion of the inner strut 21 connected to the free protrusions 26, 27 can deform more freely than the portion of the inner strut 21 connected to the inner overlap portion 24. Note that a cell having a free protrusion, such as the free protrusions 26, 27, in which the strut protrudes toward the inside of the cell opening, is referred to as an "open cell," and a cell without a free protrusion is referred to as a "closed cell." The unit opening portion 23a can also be considered to be a virtually defined portion of the opening portion 23 between the opposing free protrusions 26, 27. The distance between the opposing free convex portions 26, 27 is, for example, 0.01 to 1.00 mm. As described above, in this embodiment, the inner stent body 20 includes open cells with free convex portions 26, 27. On the other hand, the outer stent body 10 is composed only of closed cells without free convex portions in which the outer struts 11 convex toward the inside of the openings 13 of the outer cells 12, and does not include open cells. Here, the term "free convex portion" refers to the portion where the struts convex toward the inside of the cell openings, but does not simply include the portion where the struts convex. Therefore, although the distal LD2 end of the outer stent body 10 is formed in a shape similar to a free convex portion, this portion is a portion where the struts do not convex toward the inside of the cell openings, and is not a free convex portion or an open cell.

[0040] 2A , in the cylindrical portion 1a in a free state where the diameter is freely expanded, the outer stent body 10 and the inner stent body 20 are overlapped such that the inner overlapping portions 24 or free convex portions 26, 27 of the inner cells 22 (inner stent body 20) are disposed in the opening portions 13 of all the outer cells 12 (outer stent body 10). Specifically, the inner overlapping portions 24 or free convex portions 26, 27 of the inner cells 22 are disposed in the opening portions 13 of the outer cells 12, and the outer overlapping portions 14 of the outer cells 12 are disposed in the unit opening portions 23a of the inner cells 22. Therefore, the opening portions 13 of the outer cells 12 are complemented by the inner overlapping portions 24 or free convex portions 26, 27, and the unit opening portions 23a of the inner cells 22 are complemented by the outer overlapping portions 14. Four outer struts 11 and four inner struts 21 are gathered in each of the outer overlapping portion 14 and the inner overlapping portion 24, or the free convex portions 26 and 27. This arrangement allows the inner struts 21 and the outer struts 11 to abut against the inner wall of the blood vessel, even in the opening portion 13 and the unit opening portion 23a. This increases the density of the mesh pattern throughout the stent, thereby increasing the surface area of ​​the stent 1.

[0041] The inner stent body 20 has inner cells 22 that have open cells with free convex portions 26, 27, and can be flexibly bent, so that it has even better shape conformability and diameter reduction properties than the outer stent body 10. Therefore, the entire stent 1 also has excellent shape conformability and diameter reduction properties. Furthermore, the outer stent body 10 has outer cells 12 that are all closed cells and do not include open cells, so that the free ends do not get caught when inserted into a catheter, and not only is it easy to insert the stent 1 that has been reduced in diameter into a catheter, but it is also easy to insert the stent 1 that has expanded in a blood vessel back into the catheter.

[0042] If the outer stent body 10 were also configured with open cells, there would be a high risk that the free convex portions of the outer stent body 10 would get caught when the stent 1 was inserted into a catheter. Therefore, in the stent 1 of this embodiment, all of the outer cells 12 are configured as closed cells and do not include any open cells, which facilitates insertion of the stent 1 into a catheter. It is desirable that, in the free state in which the stent 1 is freely radially expanded, the outer stent body 10 has closed cells, at least in the cylindrical portion 1a, that do not include any free convex portions in which the outer struts convex toward the inside of the openings of the outer cells. This is because the outer stent body 10 presses against the free convex portions 26, 27 of the inner stent body 20, facilitating insertion of the stent 1 into a catheter.

[0043] In an ideal deployed state, the relative circumferential positions of the outer stent body 10 and the inner stent body 20 are such that the inner overlapping portion 24 or the free convex portions 26, 26 are positioned approximately at the center of the opening 13 of the outer stent body 10, as shown in Fig. 2A . However, as described above, even in the expanded state, the outer stent body 10 and the inner stent body 20 are merely in close contact with each other in the radial direction and are not linked (connected) in the radial direction. Therefore, the relative circumferential positions of the outer stent body 10 and the inner stent body 20 may deviate from the target position shown in Fig. 2A . Fig. 2E is a virtual planar development view of a portion of the cylindrical portion 1a of the stent 1 when the relative circumferential positions of the outer stent body 10 and the inner stent body 20 are deviated from the target position. For example, it is conceivable that the relative circumferential positions of the outer stent body 10 and the inner stent body 20 may be shifted to a position where the outer overlapping portion 14 and the free protrusions 26, 26 approach each other, as shown in Figure 2E. However, even in such a case, both the outer struts 11 and the inner struts 21 can contact the inner wall of the biological lumen.

[0044] FIG. 3A is a diagram illustrating the outer diameter D1 of the outer stent body 10 alone. FIG. 3B is a diagram illustrating the outer diameter D2 of the inner stent body 20 alone. FIG. 4 is a diagram illustrating the process of inserting the inner stent body 20 into the outer stent body 10. As shown in FIGS. 3A and 3B , in the first embodiment, the relationship between the outer diameter D1 of the outer stent body 10 alone and the outer diameter D2 of the inner stent body 20 alone is D1<D2. Therefore, according to the procedure indicated by the arrows in FIG. 4 , the inner stent body 20, which has an outer diameter larger than that of the outer stent body 10, is reduced in diameter and the inner stent body 20A is inserted into the outer stent body 10. This allows the self-expansion force of the inner stent body 20 to produce a two-layered stent 1 in which the inner stent body 20 is closely attached to the inside of the outer stent body 10 in the radial direction RD. Therefore, it is unlikely that the outer stent body 10 and the inner stent body 20 will be misaligned relative to each other in the direction along the axial direction LD (see Figure 1) of the stent 1. Note that, for ease of understanding, Figure 4 shows only the annular cell rows arranged in the circumferential direction in each stent body, and the number of cells is greater than in other figures and the shape of the cells is simplified to make the tubular form easier to understand.

[0045] By deploying the stent 1 of the first embodiment described above at a lesion site in a blood vessel lumen, the blood vessel lumen is expanded, ensuring patency of the lesion site. By removing (retrieving) the stent from the blood vessel lumen after a predetermined period of time, it is possible to prevent complications such as restenosis, re-occlusion, and thrombosis caused by the indwelling stent in the blood vessel. Furthermore, the stent 1 of the first embodiment has excellent shape-following properties, and therefore is highly protective of the blood vessel. Note that the stent 1 of the first embodiment can be used not only for the treatment of blood vessels, but also for the treatment of luminal structures in general, such as the esophagus and large intestine.

[0046] The stent 1 of the first embodiment can also be used to treat cerebral vasospasm. Note that the stents of other embodiments described below also exhibit the same effects as the stent 1 of the first embodiment.

[0047] The stent 1 of the first embodiment may also be used for applications requiring placement in a blood vessel for a predetermined period of time or permanently. An example of an application requiring placement of a stent in a blood vessel is a stent for treating an aneurysm. The aneurysm treatment stent is deployed at a target location and placed there. The purpose of placing the aneurysm treatment stent at a target location is, for example, to reduce blood flow into an aneurysm present at the target location or to retain an embolic coil placed in the aneurysm. After the aneurysm treatment stent is placed at the target location, an embolic coil (neither of which is shown) can be delivered to the distal LD2 side via a microcatheter inserted into the catheter, allowing the embolic coil to be placed in the aneurysm through the mesh of the aneurysm treatment stent. Furthermore, because the stent 1 has a fine mesh, it can also be used alone without the use of a coil to reduce blood flow into the aneurysm and induce thrombosis within the aneurysm for treatment.

[0048] Furthermore, an application of placing a stent in a blood vessel includes, for example, a stent for placement in a cerebrovascular vessel, and the stent 1 of the first embodiment can be used to treat cerebrovascular disorders. Cerebrovascular disorders are mainly classified into ischemic cerebrovascular disorders and hemorrhagic cerebrovascular disorders. Examples of ischemic cerebrovascular disorders include cerebral infarction such as atherothrombotic cerebral infarction, lacunar infarction, and cardiogenic cerebral embolism, while examples of hemorrhagic cerebrovascular disorders include cerebral hemorrhage and subarachnoid hemorrhage. Furthermore, the stent 1 can be used to treat cerebral vasospasm and the like. Note that a stent placed in a blood vessel or the like is removed after a predetermined period of time has elapsed or after the purpose of placing the stent has been achieved.

[0049] Second Embodiment Fig. 5A is a development view showing a part of the cylindrical portion 1a of the outer stent body 10 and the inner stent body 20 of a second embodiment, which is virtually spread out into a plane. Fig. 5B is a development view showing a part of the cylindrical portion 1a of the outer stent body 10 of the second embodiment, which is virtually spread out into a plane. Fig. 5C is a development view showing a part of the cylindrical portion 1a of the inner stent body 20 of the second embodiment, which is virtually spread out into a plane. The stent 1 of the second embodiment is similar to the stent 1 of the first embodiment, except that the stent patterns of the outer stent body 10 and the inner stent body 20 are different from those of the stent 1 of the first embodiment. Therefore, a description of the same parts as in the first embodiment will be omitted.

[0050] As shown in Fig. 5B, the outer stent body 10 has, as its basic shape, outer cells 12. In the outer stent body 10, a plurality of outer cells 12 are arranged in the circumferential direction OD, each of which is made up of outer struts 11a, 11b arranged to surround an opening 13 except on the proximal LD1 side. In the outer stent body 10, the plurality of outer cells 12 arranged in the circumferential direction OD are also arranged in the axial direction LD. That is, the outer stent body 10 has a mesh pattern in which the plurality of outer cells 12 are arranged in the circumferential direction OD and in the axial direction LD.

[0051] The outer cell 12 is surrounded by outer struts 11a arranged in a zigzag (sawtooth) pattern along the circumferential direction OD and outer struts 11b connecting vertices 16, 17 (outer overlapping portions) where the outer struts 11a turn back. More specifically, the outer struts 11b are arranged periodically in a zigzag pattern along the circumferential direction OD, and the phase of the zigzag period is the same for outer struts 11b aligned in the axial direction LD. The outer cell 12 is formed by outer struts 11b connecting vertex 16, which is convex toward the distal LD2 side, and vertex 17, which is convex toward the proximal LD1 side.

[0052] As shown in Figure 5C, the inner stent body 20 has an inner cell 22 as its basic shape. The inner stent body 20 has a plurality of inner cells 22 arranged in the circumferential direction OD, each of which is made up of inner struts 21a, 21b arranged to surround an opening 23 except on the proximal LD1 side. In the inner stent body 20, the plurality of inner cells 22 arranged in the circumferential direction OD are also arranged in the axial direction LD. In other words, the inner stent body 20 has a mesh pattern in which the plurality of inner cells 22 are arranged in the circumferential direction OD and in the axial direction LD.

[0053] The inner cell 22 is surrounded by inner struts 21a arranged in a zigzag (sawtooth) pattern along the circumferential direction OD and inner struts 21b connecting vertices (inner overlapping portions) 28 where the inner struts 21a turn back. More specifically, the inner struts 21b are periodically arranged in a zigzag pattern along the circumferential direction OD, and the zigzag periodicity of the inner struts 21b aligned in the axial direction LD is the same. The inner cell 22 is formed by connecting vertices 28 that are convex toward the proximal (LD1) side with inner struts 21b arranged along the axial direction LD. Furthermore, among the vertices where the inner struts 21a turn back, the vertices that are convex toward the distal (LD2) side form free convex portions 26. Therefore, the inner cell 22 is an open cell. Furthermore, the inner struts 21b are formed narrower than the inner struts 21a, which is advantageous for improving shape conformability and diameter reduction.

[0054] As shown in Figure 5A, the outer stent body 10 and the inner stent body 20 are overlapped such that the free convex portions 26 and vertices 28 of the inner cells 22 (inner stent body 20) are positioned in the opening portions 13 of the outer cells 12 (outer stent body 10). Specifically, the outer stent body 10 and the inner stent body 20 are overlapped such that one free convex portion 26 and one vertex 28 of the inner cells 22 are positioned in the opening portions 13 of the outer cells 12, and one vertex 17 of the outer cells 12 is positioned in the opening portions 23 of the inner cells 22. Therefore, the free convex portions 26 and vertices 28 complement the opening portions 13 of the outer cells 12, and the vertices 17 complement the opening portions 23 of the inner cells 22. Furthermore, in the axial direction LD, the vertices 17 of the outer cells 12 and the free convex portions 26 of the inner cells 22 face each other, and the vertices 16 of the outer cells 12 and the vertices 28 of the inner cells 22 face each other. The above arrangement allows the inner struts 21 and the outer struts 11 to abut against the inner wall of the blood vessel, respectively, at the openings 13 and 23. This increases the density of the mesh pattern throughout the stent, thereby increasing the surface area of ​​the stent 1.

[0055] Furthermore, in the second embodiment, the free convex portions 26 are provided and the inner cells 22 are configured as open cells, allowing the inner cells 22 to be flexibly bent. Therefore, the inner stent body 20 has even better shape-following and diameter-reducing properties than the outer stent body 10. Therefore, the entire stent 1 also has excellent shape-following and diameter-reducing properties. Furthermore, the outer stent body 10 has closed cells in the outer cells 12 and does not include open cells. This prevents the free ends from getting caught during insertion into the catheter, making it easy to insert the stent 1 into a catheter after its diameter has been reduced. Furthermore, the stent 1 expanded in a blood vessel can be easily reinserted into the catheter. In particular, the free convex portions 26 of the stent 1 of the second embodiment are convex toward the distal LD2 side, and the stent 1 does not have a free end convex toward the proximal LD1 side. Therefore, even if the free convex portions 26 unintentionally deform and protrude outward from the outer stent body 10, the stent 1 expanded in a blood vessel can be easily reinserted into the catheter.

[0056] (Third embodiment) Fig. 6A is a development view showing a part of the cylindrical portion 1a of the outer stent body 10 and the inner stent body 20 of a third embodiment, which is virtually spread out into a plane. Fig. 6B is a development view showing a part of the cylindrical portion 1a of the outer stent body 10 of the third embodiment, which is virtually spread out into a plane. Fig. 6C is a development view showing a part of the cylindrical portion 1a of the inner stent body 20 of the third embodiment, which is virtually spread out into a plane. The stent 1 of the third embodiment is similar to the stent 1 of the second embodiment, except that the stent pattern of the inner stent body 20 is different from that of the stent 1 of the second embodiment. Therefore, a description of the same parts as in the second embodiment will be omitted.

[0057] As shown in Figure 6B, the outer stent body 10 of the third embodiment has a similar configuration to that of the outer stent body 10 of the second embodiment. On the other hand, as shown in Figure 6C, the inner stent body 20 of the third embodiment has a configuration in which the number of inner struts 21b is reduced from that of the inner stent body 20 of the second embodiment. More specifically, as in the second embodiment, inner cells 22 are formed by connecting vertices (inner overlapping portions) 28 that are convex toward the proximal LD1 side with inner struts 21b arranged along the axial direction LD. However, the second embodiment differs from the second embodiment in that the inner strut 21b is provided at only one location in the circumferential direction OD. The vertex that is convex toward the proximal LD1 side, where no inner strut 21b is provided, is a free convex portion 27. Furthermore, as in the second embodiment, the vertex at which the inner struts 21a turn back and that is convex toward the distal LD2 side is a free convex portion 26. 6A , in the axial direction LD, the apex 17 of the outer cell 12 faces the free convex portion 26 of the inner cell 22, the apex 16 of the outer cell 12 faces the free convex portion 27 of the inner cell 22, and the apex 16 faces the apex 28. Therefore, the inner cell 22 of the third embodiment is also an open cell. The inner cell 22 of the third embodiment has a smaller number of inner struts 21b and also includes the free convex portion 27, and therefore has even better shape conformability and diameter reduction properties than the inner cell 22 of the second embodiment. Therefore, the stent 1 as a whole also has excellent shape conformability and diameter reduction properties.

[0058] (Fourth embodiment) Fig. 7A is a development view of a part of the cylindrical portion 1a of the outer stent body 10 and the inner stent body 20 of a fourth embodiment, which is virtually spread out into a plane. Fig. 7B is a development view of a part of the cylindrical portion 1a of the outer stent body 10 of the fourth embodiment, which is virtually spread out into a plane. Fig. 7C is a development view of a part of the cylindrical portion 1a of the inner stent body 20 of the fourth embodiment, which is virtually spread out into a plane. The stent 1 of the fourth embodiment is similar to the stent 1 of the first embodiment except that the stent patterns of the outer stent body 10 and the inner stent body 20 are different from those of the stent 1 of the first embodiment. Therefore, a description of the same parts as in the first embodiment will be omitted.

[0059] 7B , the outer stent body 10 has a plurality of outer cells 12 arranged in the circumferential direction OD, each of which is made up of outer struts 11 arranged to surround an area in a generally diamond shape except on the proximal LD1 side. The shape of the outer cells 12 of the fourth embodiment is basically the same as that of the outer cells 12 of the first embodiment, but the position of the outer overlapping portion 14 has been changed to match the shape of the inner stent body 20 described below, and the length in the axial direction LD has been increased.

[0060] As shown in Figure 7C, the inner stent body 20 has an inner cell 22 as its basic shape. The inner stent body 20 has a plurality of inner cells 22 arranged in the circumferential direction OD, each of which is made up of inner struts 21a, 21b arranged to surround an opening 23 except for the proximal LD1 side. In the inner stent body 20, the plurality of inner cells 22 arranged in the circumferential direction OD are also arranged in the axial direction LD. In other words, the inner stent body 20 has a mesh pattern in which the plurality of inner cells 22 are arranged in the circumferential direction OD and in the axial direction LD.

[0061] The inner cell 22 is surrounded by inner struts 21a arranged in a zigzag (sawtooth) pattern along the circumferential direction OD and inner struts 21b connecting vertices (inner overlapping portions) 28 where the inner struts 21a turn back and midpoints 29 of the inner struts 21a. More specifically, the inner struts 21b are arranged periodically in a zigzag pattern along the circumferential direction OD, and the phase of the zigzag period of inner struts 21b aligned in the axial direction LD is shifted by half a period in the circumferential direction OD. The inner cell 22 is formed by inner struts 21b connecting the vertices 28 that are convex toward the proximal LD1 side with the midpoints 29 of the inner struts 21a. Here, in the fourth embodiment, the midpoints 29 are located on the inner struts 21 that connect to the free protrusions 26 that are arranged facing and immediately adjacent to the vertices 28. Among the vertices at which the inner struts 21a are folded back, the vertices that are convex toward the distal LD2 side form free convex portions 26. Therefore, the inner cells 22 are open cells.

[0062] As shown in Figure 7A, in the cylindrical portion 1a, in a free state where the diameter is freely expanded, the outer stent body 10 and the inner stent body 20 are overlapped such that the free convex portions 26 and vertices 28 of the inner cells 22 (inner stent body 20) are positioned at the opening portions 13 of all the outer cells 12 (outer stent body 10). Specifically, the inner cells 22 are overlapped such that one free convex portion 26 and one vertex 28 are positioned at the opening portions 13 of the outer cells 12, and the outer overlapping portions 14 of the outer cells 12 are positioned at the opening portions 23 of the inner cells 22. Therefore, the free convex portions 26 and vertices 28 complement the opening portions 13 of the outer cells 12, and the outer overlapping portions 14 complement the opening portions 23 of the inner cells 22. This arrangement allows the inner struts 21 and outer struts 11 to abut against the inner wall of the blood vessel at the opening portions 13 and 23, respectively. Therefore, the density of the mesh pattern is increased throughout the stent, allowing the surface area of ​​the stent 1 to be increased.

[0063] Furthermore, in the fourth embodiment, the free convex portions 26 are provided and the inner cells 22 are configured as open cells, allowing the inner cells 22 to be flexibly bent. Therefore, the inner stent body 20 has even better shape-following and diameter-reducing properties than the outer stent body 10. Therefore, the entire stent 1 also has excellent shape-following and diameter-reducing properties. Furthermore, the outer stent body 10 has closed cells in the outer cells 12 and no open cells. This prevents the free ends from getting caught during insertion into the catheter. This not only makes it easy to insert the stent 1 into a catheter after it has been contracted, but also makes it easy to reinsert the stent 1 after it has been expanded in a blood vessel. In particular, the free convex portions 26 of the stent 1 of the fourth embodiment are convex toward the distal LD2 side, and the stent 1 does not have a free end that is convex toward the proximal LD1 side. Therefore, even if the free convex portions 26 unintentionally deform and protrude outward from the outer stent body 10, the stent 1 after it has been expanded in a blood vessel can be easily reinserted into the catheter.

[0064] Fifth Embodiment Fig. 8A is a development view showing a part of the cylindrical portion 1a of the outer stent body 10 and the inner stent body 20 of a fifth embodiment, which is virtually spread out into a plane. Fig. 8B is a development view showing a part of the cylindrical portion 1a of the outer stent body 10 of the fifth embodiment, which is virtually spread out into a plane. Fig. 8C is a development view showing a part of the cylindrical portion 1a of the inner stent body 20 of the fifth embodiment, which is virtually spread out into a plane. The stent 1 of the fifth embodiment is similar to the stent 1 of the fourth embodiment except that the stent pattern of the inner stent body 20 is different from that of the stent 1 of the fourth embodiment. Therefore, a description of the same parts as in the fourth embodiment will be omitted.

[0065] As shown in Figure 8B, the outer stent body 10 of the fifth embodiment has a configuration similar to that of the outer stent body 10 of the fourth embodiment. On the other hand, as shown in Figure 8C, in the inner stent body 20 of the fifth embodiment, the inner struts 21b are periodically arranged in a zigzag pattern along the circumferential direction OD, and the phase of the zigzag pattern between adjacent inner struts 21b in the axial direction LD is shifted by half a period in the circumferential direction OD, similar to the fourth embodiment. Furthermore, inner struts 21b connect vertices 28 (inner overlapping portions) convex toward the proximal LD1 side with midpoints 29b of the inner struts 21a to form inner cells 22. The midpoints 29b in the fifth embodiment are located at different positions from the midpoints 29 in the fourth embodiment. That is, the midpoint 29b in the fifth embodiment is provided on an inner strut 21 that is connected to a free protrusion 26 disposed immediately opposite the apex 28 and that folds back once at the apex 28 on the proximal LD1 side, extending toward the distal LD2 side. Of the apexes at which the inner strut 21a folds back, the apex that is convex toward the distal LD2 side forms a free protrusion 26. Therefore, the stent 1 of the fifth embodiment is similar to the fourth embodiment in that the inner cells 22 are open cells. The stent 1 of the fifth embodiment also has free protrusions 26 and the inner cells 22 are open cells, so that it can achieve the same effects as the fourth embodiment.

[0066] (Method of Use) Next, an example of a method of using the stent 1 of each embodiment will be described. Figures 9A to 9D are schematic diagrams showing the procedure for expanding a stenotic site in a blood vessel using the stent 1. Figures 9C and 9D show a simplified shape of the stent 1. Here, a procedure for widening a stenotic site CS formed in a blood vessel BV to ensure blood flow will be described. Note that the following procedure is performed by identifying the position of the stent, etc., using a visible marker (radiopaque marker).

[0067] First, as shown in Fig. 9A, a guidewire 40 is passed through the stenosis site CS. A catheter 50 is fitted onto the guidewire 40. Next, as shown in Fig. 9B, the tip of the catheter 50 fitted onto the guidewire 40 is inserted into the stenosis site CS along the passed guidewire 40 and passed through until it reaches the distal LD2 side of the stenosis site CS. Next, although not shown, the guidewire 40 is pulled out of the living body and recovered from the catheter 50. Then, a stent 1 is inserted from the proximal LD1 side of the catheter 50. The stent 1 is inserted into the catheter 50 in a contracted state.

[0068] Next, as shown in Figure 9C, the stent 1 is deployed from the tip of the catheter 50 on the distal LD2 side of the stenosis site CS. The tip of the catheter 50 is positioned on the distal LD2 side of the stenosis site CS, and the catheter 50 is retracted toward the proximal LD1 side, thereby deploying the stent 1 from the tip of the catheter 50. When the stent 1 is deployed from the tip of the catheter 50, the stent 1 expands by its own expansion force, thereby pushing open the stenosis site CS from the inside. By pushing open the stenosis site CS from the inside with the expanded stent 1, blood flow in the blood vessel BV can be ensured.

[0069] After it is confirmed that blood flow in the blood vessel BV is ensured, follow-up observation is performed for, for example, about 5 to 60 minutes. After the follow-up observation, as shown in Figure 9D, the tip of the catheter 50 is advanced toward the distal end LD2 of the stent 1, and the entire stent 1 is retracted into the catheter 50. This allows the stent 1 and the catheter 50 to be retrieved outside the body.

[0070] (Modifications) The present disclosure is not limited to the above-described embodiment, and various modifications and variations are possible, and these are also within the scope of the present disclosure.

[0071] In each embodiment, an example has been described in which the inner stent body 20 contains open cells, while the outer stent body 10 contains only closed cells without any open cells. However, this is not limiting, and a configuration in which both the inner stent body 20 and the outer stent body 10 contain open cells is also possible. For example, even if the open cell structure is such that the free convex end is limited to the distal direction as shown in Figures 5C, 7C, and 8C, the free end can be inserted into a catheter without getting caught. Therefore, a configuration in which both the outer stent body 10 and the inner stent body 20 are as shown in Figure 5C is also possible. As with the second embodiment, the inner stent body 20 has open cells, which provides excellent shape conformability and diameter reduction. Furthermore, the outer stent body 10 also has open cells, which provides excellent shape conformability and diameter reduction, even compared to the second embodiment.

[0072] The embodiments and modifications may be used in combination as appropriate, but detailed description thereof will be omitted. The present disclosure is not limited to the embodiments described above.

[0073] DESCRIPTION OF SYMBOLS 1 Stent 1a Cylindrical section 1b Converging section 2 Wire 10 Outer stent body 11 Outer strut 11a Outer strut 11b Outer strut 12 Outer cell 13 Opening section 14 Outer overlapping section 15 Curved section 16 Vertex 17 Vertex 20 Inner stent body 20A Inner stent body 21 Inner strut 21a Inner strut 21b Inner strut 22 Inner cell 23 Opening section 23a Unit opening section 24 Inner overlapping section 25 Curved section 26 Free convex section 27 Free convex section 28 Vertex 29 Midpoint 29b Midpoint 31 First wire marker section 32 Second wire marker section

Claims

1. A stent that is inserted into a catheter and used to be taken out of the catheter in a body lumen to expand the body lumen, comprising: an outer stent body in which a plurality of outer cells surrounded by outer struts are arranged at least in the central axis direction; and an inner stent body in which a plurality of inner cells surrounded by inner struts are arranged at least in the central axis direction and are inserted into the outer stent body at least in a region for expanding the body lumen, wherein the inner stent body includes open cells including free convex portions where the inner struts are convex toward the inside of the opening portions of the inner cells.

2. The stent according to claim 1, wherein the free convex portions of the inner cells all protrude toward the distal side.

3. The stent according to claim 1 or 2, wherein in a freely expanded free state, in a cylindrical portion that expands in a cylindrical shape, the outer stent body does not include free convex portions where the outer struts are convex toward the inside of the opening portions of the outer cells.

4. The stent according to claim 1 or 2, wherein in a freely expanded free state, in a cylindrical portion that expands in a cylindrical shape, for all of the outer cells, the free convex portions of at least one of the inner cells are arranged at the opening portions of one of the outer cells.

5. The stent according to claim 1 or 2, wherein the outer stent body does not include the free convex portions.

6. The stent according to claim 1 or 2, wherein the stent is removed after being expanded and left in the body lumen.

Images