Catheter and method for manufacturing catheter

Abstract

An excision instrument 13 of this DCA catheter includes a tubular coil shaft 21 and a cylindrical cutter 22 provided on a distal end side of the coil shaft 21. The coil shaft 21 includes an outer layer 31 that forms an outer peripheral portion of the coil shaft 21. The outer layer 31 is formed by spirally winding a plurality of wires 32a, arranged in the circumferential direction of the coil shaft 21, along the axial direction. A portion of the distal end side of the coil shaft 21 is a reduced diameter section 41 in which the outer diameter and the inner diameter are smaller than in other sections. In the reduced diameter section 41, the cutter 22 is disposed on the outer peripheral side of the outer layer 31 and is welded and fixed to the outer layer 31.

Description

Catheter and Method for Manufacturing the Same ,

[0006] Cross - Reference to Related Applications

[0001] This application is based on Japanese Patent Application No. 2024 - 229343 filed on December 25, 2024, the content of which is incorporated herein by reference.

[0002] This disclosure relates to a catheter and a method for manufacturing a catheter.

[0003] As a catheter, a DCA catheter used for removing atherosclerotic plaques formed in a human coronary artery is known (see, for example, Patent Document 1). The DCA catheter has a cutting instrument for removing atherosclerotic plaques. The cutting instrument has a tubular coil shaft and a cutter provided at the tip of the coil shaft. A drive unit for rotating the coil shaft around its axis is connected to the proximal end side of the coil shaft. By driving this drive unit, the coil shaft rotates, and thus the cutter rotates. In the DCA catheter, with the cutting instrument inserted into the coronary artery, when the cutter rotates by driving the drive unit, the atherosclerotic plaque in the coronary artery is removed by the cutter.

[0004] The coil shaft of the cutting instrument has a coil layer forming its outer peripheral portion. The coil layer is formed by helically winding a plurality of wire materials (for example, round wires) arranged in the circumferential direction of the coil shaft along the axial direction of the coil shaft. Also, the cutter has a cylindrical shape and is disposed on the outer peripheral side of the coil layer at the tip side of the coil shaft. The cutter is fixed to the coil layer by welding.

[0005] Japanese Unexamined Patent Application Publication No. 2021 - 78814

[0006] In a coil shaft, the outer periphery of the coil layer is made uneven by multiple wires. In this case, the coil layer has concave gaps that open outwards between adjacent wires in the circumferential direction. When welding a cutter to such a coil layer, it is expected that some of the molten cutter will flow into the concave gaps. In this case, the thickness of the cutter will locally decrease due to the flow into the concave gaps, which may cause defects such as holes forming in the cutter.

[0007] Therefore, as a countermeasure, it is conceivable to polish the outer periphery of the coil layer (specifically, each wire) before welding the cutter to the coil layer to reduce the unevenness on the outer periphery of the coil layer. In this case, the concave gaps in the coil layer can be reduced, thereby reducing the amount of cutter that melts and flows into the concave gaps during welding. As a result, the aforementioned welding defects caused by flowing into the concave gaps can be suppressed.

[0008] However, polishing the outer periphery of the coil layer reduces its thickness, which may decrease its strength. This could lead to defects such as damage to the coil layer during welding.

[0009] Furthermore, the aforementioned problem is not limited to welding a cutter to a coil shaft; it can also occur when welding cylindrical members other than cutters to a coil shaft.

[0010] This disclosure has been made in view of the above circumstances, and its primary purpose is to provide a catheter and a method for manufacturing a catheter that can suppress the occurrence of welding defects when welding a cylindrical member to a coil shaft.

[0011] To solve the above problems, the catheter of the first disclosure comprises a coil shaft which is tubular in shape and has two ends in the axial direction which are designated as a first end and a second end, the coil shaft having a coil layer which forms the outer circumference of the coil shaft, the coil layer which is formed by winding a plurality of wires arranged in the circumferential direction of the coil shaft in a spiral manner along the axial direction, a part of the coil shaft on the first end side which is a reduced diameter portion which has a smaller outer and inner diameter than the other part, and a cylindrical member which is provided on the outer circumference side of the coil layer in the reduced diameter portion and welded to the coil layer.

[0012] According to the first disclosure, the coil shaft has a coil layer that forms its outer circumference. A portion of the coil shaft at the first end is a reduced-diameter portion in which the outer and inner diameters are smaller than those of the other portion. The reduced-diameter portion is formed by reducing the diameter of the portion of the coil shaft (for example, by swaging or drawing). A cylindrical member is provided on the outer circumference of the coil layer in the reduced-diameter portion, and the cylindrical member is welded to the coil layer.

[0013] In the reduced diameter section, the circumferential length of the coil layer is shorter than in other sections, resulting in each wire in the coil layer being compressed and deformed in the circumferential direction. Therefore, in the reduced diameter section, the concave gaps between adjacent wires in the circumferential direction, which open outwards, can be narrowed in the circumferential direction. In this case, when welding a cylindrical member to the outer surface of the coil layer in the reduced diameter section, the amount of molten cylindrical member that flows into the concave gaps can be reduced. This helps to suppress welding defects caused by flow into the concave gaps.

[0014] Furthermore, when narrowing the concave gap by diameter reduction processing, it is possible to suppress the reduction in the thickness of the coil layer compared to when the concave gap is reduced by polishing the coil layer. Therefore, it is possible to suppress the decrease in the strength of the coil layer. This makes it possible to suppress welding defects caused by a decrease in the strength of the coil layer.

[0015] Therefore, when welding a cylindrical member to a coil shaft, it is possible to suppress the occurrence of welding defects.

[0016] The catheter of the second disclosure, in the first disclosure, has a concave gap formed between adjacent wires in the circumferential direction in the coil layer, opening to the outer periphery of the coil layer, and the cross-sectional area of ​​the concave gap in the section perpendicular to the axial direction is smaller in the reduced diameter portion than in the other portions.

[0017] As described above, in the reduced diameter section, the concave gap formed between adjacent wires in the coil layer is narrowed in the circumferential direction. As a result, in the second disclosure, the cross-sectional area of ​​the section perpendicular to the axial direction in the concave gap is smaller in the reduced diameter section than in other parts. This makes it possible to reduce the amount of molten cylindrical member that flows into the concave gap during welding.

[0018] The catheter of the third disclosure, in the first or second disclosure, has a concave gap formed between the circumferentially adjacent wires in the coil layer, opening to the outer periphery of the coil layer, and the cylindrical member has a welded portion welded across the circumferentially adjacent wires in the coil layer, a portion of which is an indentation portion that fits into the concave gap, and the indentation portion, when viewed in a cross section perpendicular to the axial direction, fits into the entire concave gap.

[0019] According to the third disclosure, in the cylindrical member, a portion of the welded portion welded to the coil layer is an indented portion that fits into the concave gap. The indented portion is the part of the cylindrical member that molten during welding flowed into the concave gap and solidified. When viewed in a cross section perpendicular to the axial direction, the indented portion fits into the entire concave gap. In this case, it is possible to increase the joint strength between the cylindrical member (more specifically the welded portion) and the coil layer. Furthermore, in the reduced diameter portion, as described above, the concave gap is narrowed in the circumferential direction, which makes it possible to realize a configuration in which the indented portion fits into the entire concave gap when viewed in a cross section perpendicular to the axial direction.

[0020] The catheter of the fourth disclosure, in the first or second disclosure, has a reduced diameter portion in which the inclination of the wire with respect to the axial direction is smaller than in the other portions.

[0021] According to the fourth disclosure, in the reduced-diameter section, the inclination of the wire with respect to the axial direction of the coil shaft is smaller than in other sections. In this case, bending is less likely to occur in the reduced-diameter section than in other sections. Therefore, a cylindrical member can be welded and fixed to the reduced-diameter section in a stable state.

[0022] The catheter of the fifth disclosure, in the first or second disclosure, has an inner coil layer on the inner circumference side of the outer coil layer in addition to the outer coil layer as the coil layer, and the inner coil layer is formed by winding a plurality of wires spirally in the axial direction.

[0023] According to the fifth disclosure, the coil shaft has a multilayer structure having multiple coil layers. In a multilayer coil shaft, the thickness of the coil layers is smaller compared to a single-layer coil shaft. Therefore, when polishing is performed on the outer coil layer in a multilayer coil shaft, there is a risk that the strength of the outer coil layer will be significantly reduced. In this regard, since the first disclosure is applied to a multilayer coil shaft, it is possible to suppress the reduction in the strength of the outer coil layer. Therefore, when welding a cylindrical member to the outer circumference of the outer coil layer, it is possible to suppress welding defects caused by the reduction in the strength of the outer coil layer.

[0024] The catheter of the sixth disclosure, in the fifth disclosure, has a thickness less than the thickness of the inner coil layer.

[0025] In some multi-layered coil shafts, the thickness of the outer coil layer is smaller than the thickness of the inner coil layer. In such coil shafts, if the outer coil layer is polished, the thickness of the outer coil layer may decrease significantly, potentially leading to a significant reduction in the strength of the outer coil layer. For example, polishing may make the wire of the outer coil layer significantly thinner, potentially causing the wire to break during welding. In this regard, the sixth disclosure applies the first disclosure to such a configuration, thus suppressing welding defects caused by a decrease in the strength of the outer coil layer, even when the thickness of the outer coil layer is small.

[0026] The catheter of the seventh disclosure, in the first or second disclosure, has a diameter reduction portion comprising an arrangement region on the outer circumference side of the cylindrical member and a non-arrangement region on the second end side of the cylindrical member, where the cylindrical member is not arranged on the outer circumference side.

[0027] In the reduced-diameter section, the rigidity is considered to be high in the region where the cylindrical member is positioned on the outer circumference. On the other hand, in the coil shaft, the rigidity is considered to be low in the parts other than the reduced-diameter section (i.e., the other parts; hereafter referred to as the non-reduced-diameter section) because the cylindrical member is not positioned on the outer circumference. As a result, there is a large change in rigidity between the positioning region and the non-reduced-diameter section, which may cause stress concentration between the positioning region and the non-reduced-diameter section, for example, when the cylindrical member is rotated via the coil shaft.

[0028] In this regard, the seventh disclosure includes, in addition to the arrangement region where the cylindrical member is placed, a non-arrangement region in the region on the second end side of the cylindrical member (in other words, the non-reduced diameter side) where the cylindrical member is not placed. In this case, the non-arrangement region is interposed between the arrangement region and the non-reduced diameter region. Since the non-arrangement region is part of the reduced diameter region, each wire in the coil layer in the non-arrangement region is compressed in the circumferential direction. Therefore, the stiffness in the non-arrangement region is higher than in the non-reduced diameter region. In this case, the change in stiffness between the arrangement region and the non-reduced diameter region can be made gradual. This makes it possible to suppress stress concentration between the arrangement region and the non-reduced diameter region.

[0029] The catheter of the eighth disclosure, in the first or second disclosure, comprises a drive unit in which the first end is the tip of the coil shaft, the second end is the base end of the coil shaft, and is connected to the base end side of the coil shaft, and rotates the cylindrical member in the circumferential direction via the coil shaft.

[0030] In the eighth disclosure, a portion of the tip of the coil shaft is a reduced-diameter section, and a cylindrical member is welded to the outer circumference of this reduced-diameter section. A drive unit is connected to the base end of the coil shaft, and the drive unit rotates the cylindrical member circumferentially via the coil shaft. In this configuration, the coil shaft functions as a torque shaft that transmits rotational force (torque) to the cylindrical member. Therefore, the joint strength of the cylindrical member to the coil shaft is particularly important. In this respect, since the first disclosure is applied to this configuration, it is possible to suppress welding defects and obtain stable joint strength.

[0031] A method for manufacturing a catheter according to the ninth disclosure is a method for manufacturing a catheter according to the first or second disclosure, comprising: a preparation step of preparing the coil shaft and the cylindrical member before the diameter-reduced portion is formed; a diameter-reducing step of forming the diameter-reduced portion on the coil shaft by reducing the diameter of a part of the first end of the coil shaft prepared in the preparation step; a placement step of arranging the cylindrical member on the outer circumference side of the coil layer in the diameter-reduced portion; and a welding step of welding the cylindrical member arranged in the placement step to the coil layer.

[0032] According to the ninth disclosure, a reduced-diameter portion is formed in the coil shaft by reducing the diameter of a portion of the first end of the coil shaft. In this case, the reduced-diameter processing compresses and deforms each wire in the coil layer in the reduced-diameter portion in the circumferential direction, thereby narrowing the concave gap between adjacent wires in the circumferential direction. Subsequently, a cylindrical member is placed on the outer circumference of the coil layer in the reduced-diameter portion, and the cylindrical member is welded to the coil layer in this position. In this case, the amount of molten cylindrical member that flows into the concave gap during welding can be reduced. Therefore, welding defects caused by flow into the concave gap can be suppressed. Examples of diameter reduction processing include swaging and deep drawing.

[0033] Furthermore, the above method of narrowing the concave gap by diameter reduction processing can suppress the reduction in the thickness of the coil layer compared to the method of reducing the concave gap by polishing. Therefore, it is possible to suppress a decrease in the strength of the coil layer, and as a result, it is possible to suppress welding defects caused by a decrease in the strength of the coil layer. Thus, as described above, it is possible to suppress welding defects when welding cylindrical members to a coil shaft.

[0034] The catheter manufacturing method of the tenth disclosure, in the ninth disclosure, comprises a core insertion step of inserting a core material into the reduced diameter portion and pushing the reduced diameter portion outward, after the placement step and before the welding step.

[0035] It is anticipated that there will be some variation in the outer diameter of the reduced-diameter section formed by the diameter reduction process (in other words, the outer diameter of the coil layer). Therefore, after the diameter reduction process, when the cylindrical member is positioned on the outer circumference side of the coil layer in the reduced-diameter section, it is anticipated that a small gap may occur between the coil layer and the cylindrical member. In that case, it is thought that welding defects are more likely to occur when the cylindrical member is subsequently welded to the coil layer.

[0036] Therefore, in view of these points, the tenth disclosure involves placing a cylindrical member on the outer circumference side of the coil layer in the reduced diameter section, and then inserting a core material into the inside of the reduced diameter section to expand the reduced diameter section outward. This makes it possible to bring the coil layer of the reduced diameter section into contact with the inner surface of the cylindrical member. As a result, when welding the cylindrical member to the coil layer thereafter, the two can be welded in contact. This makes it possible to suppress the occurrence of the welding defects mentioned above.

[0037] The above-mentioned and other purposes, features and advantages of this disclosure will be further clarified by the following detailed description with reference to the attached drawings. A schematic overall side view showing the configuration of the DCA catheter. A side view showing the tip of the resection instrument. A cross-sectional view along line A-A in Figure 2. A cross-sectional view along line B-B in Figure 2. A cross-sectional view along line C-C in Figure 2. A diagram illustrating the manufacturing method of the resection instrument.

[0038] An embodiment of the present disclosure will be described below with reference to the drawings. In this embodiment, the catheter of the present disclosure is embodied as a DCA catheter used in directional coronary artery atherectomy (DCA). Figure 1 is a schematic overall side view showing the configuration of the DCA catheter.

[0039] As shown in Figure 1, the DCA catheter 10 comprises an outer shaft 11, a connector 12 connected to the proximal end of the outer shaft 11, and an excision instrument 13. The outer shaft 11 is formed in a cylindrical shape, and a housing 15 is provided at its tip. The housing 15 is formed in a cylindrical shape, and an opening 15a is formed in its peripheral wall that connects the inside and outside of the housing 15. In addition, a balloon 18 is provided on the outer circumference of the housing 15, on the opposite side of the opening 15a, straddling the axis of the housing 15.

[0040] The cutting instrument 13 has a coil shaft 21 and a cutter 22 connected to the tip of the coil shaft 21 (see also Figure 2). The coil shaft 21 is formed in a cylindrical shape and is inserted inside the outer shaft 11. The coil shaft 21 is drawn out to the base end through the inside of the connector 12. A drive unit 25 that rotates the coil shaft 21 around its axis is connected to the base end of the coil shaft 21. The drive unit 25 includes a motor. The cutter 22 is formed in a cylindrical shape and has an annular blade portion 22a at its tip. The cutter 22 is housed inside the housing 15, and in this housed state, the blade portion 22a is exposed through the opening 15a of the housing 15.

[0041] Next, we will briefly explain how to use the DCA catheter 10. Here, we will explain how to remove atherosclerotic plaque formed inside a blood vessel using the DCA catheter 10.

[0042] First, the DCA catheter 10 is introduced into the blood vessel along a guide wire previously introduced into the blood vessel. At this time, the DCA catheter 10 is introduced into the blood vessel until the opening 15a of the housing 15 reaches the atherosclerotic plaque. When the opening 15a of the housing 15 reaches the atherosclerotic plaque, a compression fluid is sent to the balloon 18 to expand the balloon 18. As a result, the opening 15a is pressed against the atherosclerotic plaque, and the housing 15, and thus the DCA catheter 10, is fixed to the blood vessel. Also, a part of the atherosclerotic plaque is made to enter the housing 15 from the opening 15a.

[0043] Subsequently, by driving the drive unit 25, the coil shaft 21 of the resection instrument 13 is rotated around the axis. As a result, the cutter 22 rotates around the axis (in other words, in the circumferential direction) together with the coil shaft 21, and the atherosclerotic plaque is resected by the blade portion 22a of the rotating cutter 22. In this case, the coil shaft 21 functions as a torque shaft that transmits the rotational force of the drive unit 25 to the cutter 22. More specifically, the cutter 22 can be pushed distally via the coil shaft 21. Then, while pushing the rotating cutter 22, the atherosclerotic plaque is resected.

[0044] After the resection of the atherosclerotic plaque is completed, the balloon 18 is brought into a contracted state, and the DCA catheter 10 is pulled out from the blood vessel. Thereby, a series of operations is completed.

[0045] Subsequently, the configuration of the resection instrument 13 will be described based on FIGS. 2 to 5. FIG. 2 is a side view showing the distal end side of the resection instrument 13. FIG. 3 is a cross-sectional view taken along line A - A of FIG. 2, FIG. 4 is a cross-sectional view taken along line B - B of FIG. 2, and FIG. 5 is a cross-sectional view taken along line C - C of FIG. 2.

[0046] As shown in FIGS. 3 to 5, the coil shaft 21 of the resection instrument 13 has a two-layer structure including an outer layer 31 and an inner layer 32 provided on the inner peripheral side of the outer layer 31. The inner layer 32 and the outer layer 31 are laminated in the radial direction of the coil shaft 21. The outer peripheral portion of the coil shaft 21 is formed by the outer layer 31, and the inner peripheral portion of the coil shaft 21 is formed by the inner layer 32. The outer layer 31 corresponds to the "outer coil layer" and the "coil layer", and the inner layer 32 corresponds to the "inner coil layer".

[0047] The outer layer 31 is formed by winding a plurality of (18 in this embodiment) wire rods 31a arranged in the circumferential direction (hereinafter, also simply referred to as the "circumferential direction") of the coil shaft 21 in a spiral shape along the axial direction (hereinafter, also simply referred to as the "axial direction") of the coil shaft 21. The plurality of wire rods 31a are wound densely so that adjacent wire rods 31a are in contact with each other. Each wire rod 31a is made of a round metal wire, and its cross section (specifically, the cross section orthogonal to the length direction of the wire rod 31a) is circular.

[0048] The inner layer 32 is formed by winding a plurality of (9 in this embodiment) wire rods 32a arranged in the circumferential direction in a spiral shape along the axial direction. The plurality of wire rods 32a are wound densely so that adjacent wire rods 32a are in contact with each other. Each wire rod 32a is made of a round metal wire, and its cross section (specifically, the cross section orthogonal to the length direction of the wire rod 32a) is circular.

[0049] Each wire rod 32a of the inner layer 32 is thicker than each wire rod 31a of the outer layer 31. In other words, each wire rod 31a of the outer layer 31 is thinner than each wire rod 32a of the inner layer 32. For this reason, the thickness t1 of the outer layer 31 is smaller than the thickness t2 of the inner layer 32. Specifically, the thickness t1 of the outer layer 31 is 3 / 4 or less of the thickness t2 of the inner layer 32.

[0050] As shown in FIG. 2, a part of the tip side of the coil shaft 21 is a reduced-diameter portion 41 whose diameter is reduced compared to other parts. The reduced-diameter portion 41 is a portion including the tip of the coil shaft 21 and is reduced in diameter by swaging. The portion of the coil shaft 21 other than the reduced-diameter portion 41 is an unreduced-diameter portion 42 that is not reduced in diameter. In the reduced-diameter portion 41, both the outer diameter and the inner diameter are smaller than those of the unreduced-diameter portion 42. Note that the unreduced-diameter portion 42 corresponds to the "other parts". Also, the tip of the coil shaft 21 corresponds to the "first end", and the base end of the coil shaft 21 corresponds to the "second end".

[0051] In the reduced diameter section 41, the inclination angle α of each wire 31a of the outer layer 31 with respect to the axial direction is smaller than the inclination angle β of each wire 31a with respect to the axial direction in the non-reduced diameter section 42. Similarly, in the reduced diameter section 41, although not shown in the figures, the inclination angle of each wire 32a of the inner layer 32 with respect to the axial direction is smaller than the inclination angle of each wire 32a with respect to the axial direction in the non-reduced diameter section 42. Note that the inclination angles of the wires 31a and 32a include acute angles and obtuse angles, but in this specification, the inclination angles of the wires 31a and 32a refer to the acute angles.

[0052] As shown in Figures 3 and 4, in the reduced diameter section 41, the circumferential length of the outer layer 31 is shorter than the circumferential length of the outer layer 31 in the non-reduced diameter section 42. Therefore, in the reduced diameter section 41, each wire 31a of the outer layer 31 is compressed and deformed in the circumferential direction. As a result, in the reduced diameter section 41, the circumferential length (width) L1 of the wire 31a is shorter than the circumferential length (width) L2 of the wire 31a in the non-reduced diameter section 42. In addition, in the reduced diameter section 41, the contact area where adjacent wires 31a are in close contact in the circumferential direction is larger than in the non-reduced diameter section 42.

[0053] In the outer layer 31, concave gaps 34 and 35 are formed between adjacent wires 31a in the circumferential direction. The concave gaps 34 and 35 include a concave gap 34 that opens toward the outer circumference of the outer layer 31 and a concave gap 35 that opens toward the inner circumference of the outer layer 31. The concave gap 34 corresponds to the "concave gap" described in the claims.

[0054] In the reduced-diameter section 41, as described above, each wire 31a of the outer layer 31 is compressed and deformed in the circumferential direction. Therefore, in the reduced-diameter section 41, the concave gap 34 is narrower in the circumferential direction than in the non-reduced-diameter section 42. Specifically, in the reduced-diameter section 41, the circumferential width W1 (opening width) of the concave gap 34 is smaller than the circumferential width W2 (opening width) of the concave gap 34 in the non-reduced-diameter section 42. As a result, in the reduced-diameter section 41, the cross-sectional area of ​​the cross section perpendicular to the axial direction in the concave gap 34 is smaller than in the non-reduced-diameter section 42.

[0055] Similarly, in the reduced-diameter portion 41, the concave gap 35 is narrower in the circumferential direction than in the non-reduced-diameter portion 42. As a result, in the reduced-diameter portion 41, the cross-sectional area of ​​the cross section perpendicular to the axial direction in the concave gap 35 is smaller than in the non-reduced-diameter portion 42.

[0056] In the inner layer 32, concave gaps 37 and 38 are formed between adjacent wires 32a in the circumferential direction. The concave gaps 37 and 38 include a concave gap 37 that opens toward the outer circumference of the inner layer 32 and a concave gap 38 that opens toward the inner circumference of the inner layer 32. In the reduced diameter section 41, each wire 32a of the inner layer 32 is compressed and deformed in the circumferential direction. Therefore, in the reduced diameter section 41, each concave gap 37 and 38 is narrower in the circumferential direction than in the non-reduced diameter section 42. As a result, in the reduced diameter section 41, the cross-sectional area of ​​the cross-section perpendicular to the axial direction in the concave gaps 37 and 38 is smaller than in the non-reduced diameter section 42.

[0057] As shown in Figures 2 and 5, a cutter 22 is provided in the reduced-diameter portion 41 of the coil shaft 21. The cutter 22 is positioned with the tip end of the reduced-diameter portion 41 inserted inside it. In this case, the cutter 22 is positioned on the outer circumference of the reduced-diameter portion 41, and more specifically, on the outer circumference of the outer layer 31 of the reduced-diameter portion 41. The outer diameter of the cutter 22 is approximately the same as the outer diameter of the non-reduced-diameter portion 42 of the coil shaft 21. The cutter 22 corresponds to a "cylindrical member".

[0058] The cutter 22 is fixed to the outer layer 31 of the diameter-reduced portion 41 by welding. This welding is performed by laser welding. The cutter 22 is welded to the outer layer 31 of the diameter-reduced portion 41 at multiple locations (four locations in this embodiment). Therefore, the cutter 22 has multiple (four) welded joints 45 welded to the outer layer 31 of the diameter-reduced portion 41. Each welded joint 45 is arranged at equal intervals (90° intervals) in the circumferential direction. Therefore, each welded joint 45 is in the same position in the axial direction. In Figures 2 and 5, each welded joint 45 is shown with a dot hatch.

[0059] Each welded joint 45 is welded across multiple circumferentially adjacent wires 31a in the outer layer 31. Each welded joint 45 has an indentation portion 45a that fits into the concave gap 34 between adjacent wires 31a. The indentation portion 45a is the part where a portion of the cutter 22 that melted during welding flowed into the concave gap 34 and solidified. When viewed in a cross section perpendicular to the axial direction, the indentation portion 45a fits into the entire concave gap 34.

[0060] At the same axial position as the welded joint 45, the molten portion 46 has entered the concave gap 35 of the outer layer 31 and the respective concave gaps 37 and 38 of the inner layer 32. The molten portion 46 is, for example, a portion of the wire 32a of the inner layer 32 or a portion of the wire 31a of the outer layer 31 that melted during welding and flowed into the concave gaps 35, 37, and 38 and solidified. The molten portion 46 has entered the concave gaps 35, 37, and 38 that are at the same circumferential position as the welded joint 45. More specifically, when viewed in a cross-section perpendicular to the axial direction, the molten portion 46 has entered the entirety of the concave gaps 35, 37, and 38.

[0061] As shown in Figure 2, the reduced diameter portion 41 has an arrangement region 47 on the outer circumference side where the cutter 22 is located, and a non-arrangement region 48 that is on the base end side of the arrangement region 47 (in other words, on the cutter 22 side) where the cutter 22 is not located on the outer circumference side. The axial length of the non-arrangement region 48 is longer than the axial length of the arrangement region 47. In addition, the outer diameter of the non-arrangement region 48 is slightly smaller than the outer diameter of the arrangement region 47, and the inner diameter of the non-arrangement region 48 is slightly smaller than the inner diameter of the arrangement region 47.

[0062] Next, the manufacturing method of the DCA catheter 10 will be described. In particular, the manufacturing method of the excision instrument 13 will be described based on Figure 6. Figure 6 is a diagram illustrating the manufacturing method of the excision instrument 13.

[0063] First, as shown in Figure 6(a), a preparation step is performed to prepare the coil shaft 21 (hereinafter referred to as the coil shaft 21A) and the cutter 22 before the reduced diameter portion 41 is formed. The coil shaft 21A has a constant outer diameter and inner diameter.

[0064] Next, as shown in Figure 6(b), a diameter reduction process is performed to form a reduced-diameter portion 41 on the coil shaft 21A by reducing the diameter of a portion of the tip side of the coil shaft 21A. In this process, swaging is performed as the diameter reduction process. In swaging, the tip side of the coil shaft 21A is continuously struck with a die to reduce the diameter. As a result, a coil shaft 21 having a reduced-diameter portion 41 is formed.

[0065] In the diameter reduction process (diameter reduction processing) described above, each wire 31a of the outer layer 31 is compressed and deformed in the circumferential direction in the diameter reduction section 41. As a result, in the diameter reduction section 41, the concave gap 34 between adjacent wires 31a in the circumferential direction is narrowed in the circumferential direction (see Figure 4).

[0066] Next, as shown in Figure 6(c), a positioning step is performed in which the cutter 22 is positioned on the outer circumference side of the outer layer 31 in the reduced diameter section 41. Here, it is expected that there will be some variation in the outer diameter of the reduced diameter section 41 (in other words, the outer diameter of the outer layer 31) formed by the previous diameter reduction step. Therefore, when the cutter 22 is positioned on the outer circumference side of the outer layer 31, there is a risk that a small gap will occur between the cutter 22 and the outer layer 31. In that case, there is a risk that welding defects will occur when the cutter 22 is welded to the outer layer 31 afterward. Also, if there is a gap between the cutter 22 and the outer layer 31, there is a risk that welding will be performed with the cutter 22 positioned non-coaxially with respect to the outer layer 31.

[0067] Therefore, in light of these points, after the placement process, a mandrel insertion process is performed, as shown in Figure 6(d), in which a mandrel 53 is inserted into the inside of the reduced diameter portion 41 to push the reduced diameter portion 41 outward. The outer diameter of the mandrel 53 is smaller than the inner diameter of the non-reduced diameter portion 42 and larger than the inner diameter of the reduced diameter portion 41. This process brings the outer layer 31 of the reduced diameter portion 41 into contact with the inner circumferential surface of the cutter 22, or more specifically, the outer layer 31 is tightly fitted to the inner circumferential surface of the cutter 22. The mandrel 53 corresponds to the "core material". The mandrel insertion process corresponds to the "core material insertion process".

[0068] Next, as shown in Figure 6(e), a welding process is performed to weld the cutter 22 to the outer layer 31 of the diameter-reduced portion 41. In this process, the cutter 22 is laser-welded to the diameter-reduced portion 41 using a laser irradiator 55. Furthermore, in the welding process, the mandrel 53 is inserted inside the diameter-reduced portion 41, in other words, the outer layer 31 of the diameter-reduced portion 41 is in close contact with the inner circumferential surface of the cutter 22 when laser welding is performed. In this case, welding can be performed without any gaps between the cutter 22 and the outer layer 31. Therefore, welding defects caused by the gap can be suppressed. Also, in this case, welding can be performed with the cutter 22 coaxially positioned with the outer layer 31. Therefore, torque transmission when rotating the cutter 22 can be improved.

[0069] Furthermore, during the welding process, the concave gap 34 in the outer layer 31 of the reduced diameter portion 41 is narrowed in the circumferential direction by the aforementioned diameter reduction process. As a result, the amount of cutter 22 that melts and flows into the concave gap 34 during the welding process can be reduced. This makes it possible to suppress welding defects caused by flow into the concave gap 34.

[0070] Furthermore, in the method of narrowing the concave gap 34 by a diameter reduction process (diameter reduction processing), it is possible to suppress the reduction in the thickness of the outer layer 31 compared to the method of reducing the concave gap 34 by polishing the outer circumference of the outer layer 31. Therefore, it is possible to suppress a decrease in the strength of the outer layer 31. This makes it possible to suppress welding defects caused by a decrease in the strength of the outer layer 31.

[0071] Based on the above, the above steps make it possible to suppress welding defects when welding the cutter 22 to the coil shaft 21.

[0072] After the welding process, a mandrel extraction process is performed to pull the mandrel 53 out of the reduced diameter section 41. Through this process, the cutting instrument 13 is manufactured.

[0073] As described in detail above, the configuration of this embodiment provides the following excellent effects.

[0074] - In the cutter 22, a portion of the welded portion 45 welded to the outer layer 31 is an indented portion 45a that fits into the concave gap 34. The indented portion 45a is the part of the cutter 22 that melted during welding and flowed into the concave gap 34 and solidified. When viewed in a cross section perpendicular to the axial direction, the indented portion 45a fits into the entire concave gap 34. In this case, it is possible to increase the joint strength between the cutter 22 (more specifically the welded portion 45) and the outer layer 31. Note that in the reduced diameter portion 41, the concave gap 34 is narrowed in the circumferential direction, which makes it possible to achieve a configuration in which the indented portion 45a fits into the entire concave gap 34 when viewed in a cross section perpendicular to the axial direction.

[0075] In the reduced diameter section 41, the inclination of the wire material 31a of the outer layer 31 with respect to the axial direction of the coil shaft 21 is smaller than in the non-reduced diameter section 42. In this case, bending is less likely to occur in the reduced diameter section 41 than in the non-reduced diameter section 42. Therefore, the cutter 22 can be welded and fixed to the reduced diameter section 41 in a stable state.

[0076] In a coil shaft 21 with a two-layer structure consisting of an outer layer 31 and an inner layer 32, the thickness of each layer 31 and 32 is smaller compared to a single-layer coil shaft. Therefore, if the outer layer 31 is polished, there is a risk that the strength of the outer layer 31 will be significantly reduced. In particular, in a configuration where the thickness of the outer layer 31 is smaller than the thickness of the inner layer 32, if the outer layer 31 is polished, the thickness of the outer layer 31 will be significantly reduced, and there is a risk that the strength of the outer layer 31 will be significantly reduced (for example, the wire material 31a of the outer layer 31 may become significantly thinner, and there is a risk that the wire material 31a may break during welding). In this regard, in the above embodiment, instead of polishing, a diameter reduction process is performed on such a coil shaft 21. Therefore, even when the thickness of the outer layer 31 is small, it is possible to suppress a significant reduction in the strength of the outer layer 31, and as a result, it is possible to suppress welding defects caused by a decrease in the strength of the outer layer 31.

[0077] - It is thought that the rigidity is high in the arrangement region 47 where the cutter 22 is positioned in the reduced diameter portion 41. On the other hand, it is thought that the rigidity is low in the non-reduced diameter portion 42 of the coil shaft 21 because the cutter 22 is not positioned there. Therefore, there is a large change in rigidity between the arrangement region 47 and the non-reduced diameter portion 42, which may cause stress concentration between the arrangement region 47 and the non-reduced diameter portion 42 when the cutter 22 is rotated via the coil shaft 21.

[0078] In this respect, in the above embodiment, the diameter-reduced portion 41 has a configuration region 47 where the cutter 22 is positioned, as well as a non-configuration region 48 that is on the base end side of the cutter 22 and where the cutter 22 is not positioned on the outer circumference. In this case, the non-configuration region 48 is interposed between the configuration region 47 and the non-diameter-reduced portion 42. Since the non-configuration region 48 is part of the diameter-reduced portion 41, each wire 31a of the outer layer 31 in the non-configuration region 48 is compressed in the circumferential direction. Therefore, the rigidity in the non-configuration region 48 is higher than that in the non-diameter-reduced portion 42. In this case, the change in rigidity between the configuration region 47 and the non-diameter-reduced portion 42 can be made gradual. This makes it possible to suppress stress concentration between the configuration region 47 and the non-diameter-reduced portion 42.

[0079] As described above, in the reduced-diameter section 41, the concave gap 34 of the outer layer 31 is narrower in the circumferential direction than in the non-reduced-diameter section 42, thus reducing the amount of cutter 22 that melts and flows into the concave gap 34 during welding. On the other hand, in the non-reduced-diameter section 42, the concave gap 34 of the outer layer 31 is wider in the circumferential direction than in the reduced-diameter section 41, thus ensuring flexibility.

[0080] Each welded section 45 is arranged at equal intervals (90° intervals) in the circumferential direction. This allows the center of the coil shaft 21 and the center of the cutter 22 to be aligned, and as a result, the rotational force generated in the drive unit 25 can be efficiently transmitted to the cutter 22 via the coil shaft 21.

[0081] This disclosure is not limited to the embodiments described above, and may be implemented, for example, as follows.

[0082] (1) In the above embodiment, the coil shaft 21 had a two-layer structure consisting of an outer layer 31 and an inner layer 32. However, coil shafts can also have three or more layers, or a single layer structure consisting of only one layer. The present disclosure can also be applied when welding cylindrical members to such coil shafts.

[0083] (2) In the above embodiment, the reduced diameter portion 41 of the coil shaft 21 had a non-arranged region 48 on the outer circumference where the cutter 22 was not arranged. However, the reduced diameter portion 41 may be configured so that it does not have a non-arranged region 48 by arranging the cutter 22 over the entire axial direction of the reduced diameter portion 41.

[0084] (3) In the above embodiment, the mandrel insertion step was performed before the welding step, but the mandrel insertion step may be omitted. However, considering the variation in the outer diameter of the reduced diameter portion formed by the diameter reduction step, it is desirable to perform the mandrel insertion step.

[0085] (4) In the above embodiment, the present disclosure was applied to the DCA catheter 10, but the present disclosure may also be applied to other catheters. For example, the present disclosure may be applied to an imaging diagnostic catheter used for diagnosis of coronary arteries, etc. The imaging diagnostic catheter has a coil shaft and an ultrasonic sensor provided at the tip of the coil shaft. After being introduced into a blood vessel, the imaging diagnostic catheter acquires an image of the blood vessel by ultrasonic waves emitted from the ultrasonic sensor. A drive unit is connected to the proximal end of the coil shaft, and the coil shaft and, consequently the ultrasonic sensor, rotate within the blood vessel by the drive of the drive unit. A cylindrical housing (corresponding to a cylindrical member) that protects the ultrasonic sensor is welded to the tip of the coil shaft. The present disclosure may also be applied when welding this housing to the coil shaft.

[0086] (5) In some cases, a cylindrical member is provided on the proximal end side of the coil shaft. In such cases, the present disclosure may be applied to such a configuration. In this case, a portion of the proximal end side of the coil shaft is made into a reduced diameter portion, and the cylindrical member is welded to the outer circumference of the coil layer in the reduced diameter portion.

[0087] (6) In the above embodiment, four welds 45 were provided at 90° intervals in the circumferential direction, but three welds may be provided at 120° intervals in the circumferential direction, or two welds may be provided at 180° intervals in the circumferential direction. Furthermore, it is not necessary to provide multiple welds; for example, one weld may be provided over the entire circumferential area.

[0088] (7) Swaging is not necessarily required for the diameter reduction process; for example, pressing or drawing may be used instead.

[0089] (8) The mandrel insertion step may be performed so that only a portion of the outer layer 31 of the reduced diameter portion 41 in the circumferential direction comes into contact with the inner surface of the cutter 22. In this case, during the subsequent welding step, the cutter 22 may be welded to the outer layer 31 at the portion that came into contact.

[0090] This disclosure is described in accordance with embodiments, but it is understood that this disclosure is not limited to such embodiments or structures. This disclosure also includes various modifications and variations within the scope of equivalents. In addition, various combinations and forms, as well as other combinations and forms that include only one, more, or fewer of those elements, fall within the scope and idea of ​​this disclosure.

[0091] 10...DCA catheter as a catheter, 13...excision instrument, 21...coil shaft, 22...cutter as a cylindrical member, 31...outer layer as coil layer and outer coil layer, 32...inner layer as inner coil layer, 31a...wire, 34...concave gap, 41...reduced diameter section, 42...non-reduced diameter section as other parts, 45...welded section, 45a...insertion section.

Claims

1. A catheter comprising a coil shaft which is tubular in shape and has two ends in the axial direction designated as a first end and a second end, the coil shaft having a coil layer which forms the outer circumference of the coil shaft, the coil layer which is formed by winding a plurality of wires arranged in the circumferential direction of the coil shaft in a spiral manner along the axial direction, a portion of the coil shaft on the first end side being a reduced diameter portion which has a smaller outer and inner diameter than the other portion, and a cylindrical member which is provided on the outer circumference side of the coil layer in the reduced diameter portion and is welded to the coil layer.

2. The catheter according to claim 1, wherein a concave gap opening to the outer circumference of the coil layer is formed between adjacent wires in the circumferential direction in the coil layer, and the cross-sectional area of ​​the concave gap in a cross section perpendicular to the axial direction is smaller in the reduced diameter portion than in the other portions.

3. The catheter according to claim 1 or 2, wherein a concave gap opening to the outer circumference of the coil layer is formed between adjacent wires in the circumferential direction in the coil layer, the cylindrical member has a welded portion welded across adjacent wires in the circumferential direction in the coil layer, a portion of the welded portion is an indentation portion that fits into the concave gap, and the indentation portion, when viewed in a cross section perpendicular to the axial direction, fits into the entire concave gap.

4. The catheter according to claim 1 or 2, wherein the inclination of the wire with respect to the axial direction is smaller in the reduced diameter portion than in the other portions.

5. The catheter according to claim 1 or 2, wherein the coil shaft has an inner coil layer on the inner circumference side of the outer coil layer in addition to the outer coil layer, and the inner coil layer is formed by winding a plurality of wires spirally in the axial direction.

6. The catheter according to claim 5, wherein the thickness of the outer coil layer is smaller than the thickness of the inner coil layer.

7. The catheter according to claim 1 or 2, wherein the reduced diameter portion has an arrangement region on the outer circumference side in which the cylindrical member is arranged, and a non-arrangement region that is on the second end side of the cylindrical member and in which the cylindrical member is not arranged on the outer circumference side.

8. The catheter according to claim 1 or 2, wherein the first end is the tip of the coil shaft, the second end is the base end of the coil shaft, and the catheter is connected to the base end side of the coil shaft and includes a drive unit that rotates the cylindrical member in the circumferential direction via the coil shaft.

9. A method for manufacturing a catheter according to claim 1 or 2, comprising: a preparation step of preparing the coil shaft and the cylindrical member before the diameter-reduced portion is formed; a diameter-reducing step of forming the diameter-reduced portion on the coil shaft by reducing the diameter of a part of the first end of the coil shaft prepared in the preparation step; a placement step of arranging the cylindrical member on the outer circumference side of the coil layer in the diameter-reduced portion; and a welding step of welding the cylindrical member arranged in the placement step to the coil layer.

10. A method for manufacturing a catheter according to claim 9, comprising a core material insertion step, which occurs after the arrangement step and before the welding step, in which a core material is inserted into the inside of the reduced diameter portion to expand the reduced diameter portion toward the outer circumference.

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