Guidewire and method for manufacturing the guidewire

Abstract

To improve operability and durability in a guide wire.SOLUTION: A guide wire includes: a first core shaft which is arranged on an end side; and a second core shaft which is arranged nearer on a base end side than the first core shaft and has greater rigidity than that of the first core shaft. The first core shaft is provided with a non-linear pseudoelastic region having non-linear pseudoelasticity toward a proximal end side from an end side and a linear pseudoelastic region having linear pseudoelasticity side by side. At the boundary between the non-linear pseudoelastic region and the linear pseudoelastic region, no welded part is formed, and between a base end part of the linear pseudoelastic region and an end part of the second core shaft, a welded part between the first core shaft and the second core shaft is formed.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a guidewire and a method for manufacturing the guidewire. [Background technology]

[0002] Guidewires used for inserting catheters or the like into blood vessels are known. Such guidewires are required to have flexibility and resilience to bending, torque transmission and pushability for transmitting manipulation of the guidewire at the proximal end to the distal end, and kink resistance to deformation due to bending or twisting. Torque transmission and pushability are also collectively referred to as "operability." For example, Patent Documents 1 and 2 each disclose a guidewire in which, in order to improve operability and kink resistance, a first wire, a third wire, and a second wire are arranged from the distal end to the proximal end, and the second wire has a higher elastic modulus than the first wire, and the third wire has a higher elastic modulus than the first wire but lower than the second wire (i.e., the elastic modulus is intermediate between that of the first wire and that of the second wire). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-65797 [Patent Document 2] Patent No. 4455808 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in both of the guidewires described in Patent Documents 1 and 2, the first wire and the third wire are connected by welding, and the third wire and the second wire are also connected by welding. That is, in the guidewires described in Patent Documents 1 and 2, there are at least two portions where different wires are welded together (hereinafter also referred to as "welds"). Here, the welds between the wires are more fragile than the wire base material, and therefore the wire may deform from the welds due to changes in shape during use of the guidewire or the application of force. Therefore, to improve the durability of the guidewire, it is preferable to have fewer welds between the wires. Furthermore, from the viewpoint of reducing the number of manufacturing steps and lowering the manufacturing cost of the guidewire, it is also preferable to have fewer welds between the wires. Note that these issues are not limited to the vascular system, but are common to guidewires inserted into various organs within the human body, such as the lymphatic system, biliary system, urinary system, respiratory system, digestive system, secretory glands, and reproductive organs. Note that the wire is also referred to as a "core shaft."

[0005] The present invention has been made to solve at least part of the above-mentioned problems, and an object of the present invention is to improve the operability and durability of a guidewire. [Means for solving the problem]

[0006] The present invention has been made to solve at least part of the above-mentioned problems, and can be realized in the following aspects.

[0007] (1) According to one aspect of the present invention, there is provided a guidewire comprising: a first core shaft disposed at a distal end; and a second core shaft disposed proximal to the first core shaft and having a harderness greater than that of the first core shaft, wherein the first core shaft is provided with a nonlinear pseudoelastic region having nonlinear pseudoelasticity and a linear pseudoelastic region having linear pseudoelasticity adjacent to each other from the distal end to the proximal end, wherein no weld is formed at the boundary between the nonlinear pseudoelastic region and the linear pseudoelastic region, and a weld between the first core shaft and the second core shaft is formed between a proximal end of the linear pseudoelastic region and a distal end of the second core shaft.

[0008] According to this configuration, the first core shaft is provided with a nonlinear pseudoelastic region having nonlinear pseudoelasticity (also called "superelasticity") and a linear pseudoelastic region having linear pseudoelasticity, which are adjacent to each other from the distal end to the proximal end. Here, the linear pseudoelastic region provided at the proximal end of the first core shaft has a higher hardness than the nonlinear pseudoelastic region. Furthermore, the second core shaft has a higher hardness than the first core shaft (the nonlinear pseudoelastic region and the linear pseudoelastic region). Therefore, according to this configuration, by providing the linear pseudoelastic region at the proximal end of the first core shaft, the hardness gap between the first core shaft and the second core shaft can be reduced. As a result, it is possible to easily form a weld between the proximal end of the linear pseudoelastic region and the distal end of the second core shaft, and the operability of the guidewire can be improved. Furthermore, no weld is formed at the boundary between the nonlinear pseudoelastic region and the linear pseudoelastic region in the first core shaft. Therefore, according to this configuration, the durability of the guidewire can be improved compared to conventional guidewires that have two welds. As a result, a guidewire with improved operability and durability can be provided.

[0009] (2) In the guidewire of the above aspect, in the first core shaft, the nonlinear pseudoelastic region and the linear pseudoelastic region may have substantially the same stoichiometric composition. According to this configuration, in the first core shaft, the nonlinear pseudoelastic region and the linear pseudoelastic region have substantially the same stoichiometric composition, so the nonlinear pseudoelastic region and the linear pseudoelastic region can be formed from the same material, such as a NiTi (nickel titanium) alloy or an alloy of NiTi and another metal.

[0010] (3) In the guidewire of the above aspect, in the first core shaft, the length of the linear pseudoelastic region in the longitudinal direction may be equal to or less than ¼ of the length of the nonlinear pseudoelastic region in the longitudinal direction. According to this configuration, the longitudinal length of the linear pseudoelastic region is less than 1 / 4 of the longitudinal length of the nonlinear pseudoelastic region, thereby improving the blood vessel selectivity, flexibility, and restorability of the guidewire.

[0011] (4) In the guide wire of the above aspect, in the first core shaft, the hardness of the linear pseudoelastic region may be greater than the hardness of the nonlinear pseudoelastic region. According to this configuration, in the first core shaft, the hardness in the linear pseudoelastic region is greater than the hardness in the nonlinear pseudoelastic region, so that the linear pseudoelastic region can reduce the hardness gap between the first core shaft and the second core shaft.

[0012] (5) According to one aspect of the present invention, there is provided a method for manufacturing a guidewire, the method including: a preparation step of preparing a first core shaft having linear pseudoelasticity and a second core shaft having a harderness than the first core shaft, a welding step of welding a distal end of the second core shaft to a proximal end of the first core shaft, and a heat treatment step of heat treating a portion of the distal end of the first core shaft to form a nonlinear pseudoelastic region having nonlinear pseudoelasticity on the distal end of the first core shaft. In general, welding components with large differences in hardness is difficult. In this regard, according to the present manufacturing method (welding process), the distal end of the second core shaft is welded to the proximal end of the first core shaft having linear pseudoelasticity. This facilitates welding compared to welding the second core shaft to the first core shaft having nonlinear pseudoelasticity as a whole. Furthermore, since only one welding is required, the labor hours and costs of the welding process can be reduced compared to conventional guidewires with two welds. Furthermore, according to the present manufacturing method (heat treatment process), a nonlinear pseudoelastic region having nonlinear pseudoelasticity can be formed by heat-treating a portion of the distal end of the first core shaft having linear pseudoelasticity. That is, by changing the linear pseudoelasticity of the first core shaft to nonlinear pseudoelasticity through heat treatment, a nonlinear pseudoelastic region and a linear pseudoelastic region can be easily formed and coexist within a single first core shaft. As a result, a guidewire with improved operability and durability can be manufactured.

[0013] (6) In the method for producing a guidewire according to the above aspect, the welding step may be carried out after the heat treatment step. According to this configuration, the welding step is carried out after the heat treatment step, so that deterioration and damage to the welded portion due to the heat treatment can be suppressed compared to the reverse case.

[0014] The present invention can be realized in various forms, for example, as a guidewire, a core shaft for a guidewire (a joined body of first and second core shafts, or the first core shaft alone), a method for manufacturing a guidewire, etc. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is an explanatory diagram illustrating the configuration of a guide wire according to a first embodiment. [Figure 2] FIG. 10 is an explanatory diagram showing the configuration of a guide wire of a comparative example. [Figure 3] FIG. 10 is a diagram showing a change in hardness of a core shaft in the vicinity of a welded portion. [Figure 4] FIG. 10 is a diagram showing a change in stiffness of a core shaft. [Figure 5] 2A to 2C are diagrams illustrating an example of a method for manufacturing the guide wire shown in FIG. [Figure 6] 1. FIG. 5 is a diagram showing another example of a method for manufacturing the guide wire shown in FIG. [Figure 7] FIG. 10 is an explanatory diagram illustrating the configuration of a guide wire according to a second embodiment. [Figure 8] FIG. 10 is an explanatory diagram illustrating the configuration of a guide wire according to a third embodiment. [Figure 9] 1 is a graph showing SS curves of nonlinear pseudoelasticity and linear pseudoelasticity. DETAILED DESCRIPTION OF THE INVENTION

[0016] First Embodiment 1 is an explanatory diagram illustrating the configuration of a guidewire 1 according to a first embodiment. The guidewire 1 is a medical instrument used when inserting other medical devices (such as a catheter) into blood vessels or digestive organs, and includes a first core shaft 10, a second core shaft 20, a welded portion 30, a coil body 40, a distal end fixing portion 51, a proximal end fixing portion 52, and an intermediate fixing portion 53. The guidewire 1 is configured such that the first core shaft 10 and the second core shaft 20 are connected by a single welded portion 30, and a linear pseudoelastic region A2 is provided on the proximal end side of the first core shaft 10, thereby improving the operability and durability of the guidewire 1. Note that operability is a general term for torque transmission ability and pushability.

[0017] In FIG. 1, the axis passing through the center of the guidewire 1 is represented by axis O (dotted line). In the example of FIG. 1, axis O coincides with the axis passing through the centers of the first core shaft 10, the second core shaft 20, and the coil body 40. However, axis O may differ from the central axis of each of the above-mentioned components. FIG. 1 illustrates mutually orthogonal X, Y, and Z axes. The X axis corresponds to the length direction of the guidewire 1, the Y axis corresponds to the height direction of the guidewire 1, and the Z axis corresponds to the width direction of the guidewire 1. The left side (-X axis direction) of FIG. 1 is referred to as the "distal side" of the guidewire 1 and each component, and the right side (+X axis direction) of FIG. 1 is referred to as the "proximal side" of the guidewire 1 and each component. Furthermore, for the guidewire 1 and each component, the end located on the distal side is referred to as the "distal end," and the distal end and its vicinity are referred to as the "distal portion." Furthermore, the end located on the proximal side is referred to as the "proximal end," and the proximal end and its vicinity are referred to as the "proximal portion." The distal end is inserted into the living body, and the proximal end is operated by a surgeon such as a doctor. These points are the same in the figures from Fig. 1 onwards.

[0018] The first core shaft 10 is disposed on the distal end side of the guidewire 1, in other words, closer to the distal end than the second core shaft 20. The first core shaft 10 is a tapered, long member having a large diameter on the proximal end side and a small diameter on the distal end side. The first core shaft 10 of this embodiment is formed from a NiTi (nickel titanium) alloy or an alloy of NiTi and another metal. The first core shaft 10 has, in order from the distal end side to the proximal end side, a small diameter section 11, a tapered section 12, a first large diameter section 13, and a second large diameter section 14. The outer diameter and length of each section can be determined as desired.

[0019] The thin diameter portion 11 is provided at the tip end of the first core shaft 10. The thin diameter portion 11 is the portion of the first core shaft 10 with the smallest outer diameter, and is a substantially cylindrical portion having a substantially constant outer diameter. The tapered portion 12 is provided between the thin diameter portion 11 and the first large diameter portion 13. The tapered portion 12 is a substantially truncated cone-shaped portion whose outer diameter increases from the tip end to the base end. Note that in this embodiment, "substantially constant" is synonymous with "generally constant" and means that the shape is generally constant while allowing for variations due to manufacturing errors, etc. Similarly, "substantially cylindrical shape / generally truncated cone shape" is synonymous with "approximately cylindrical shape / generally truncated cone shape" and means that the shape is generally the same while allowing for variations due to manufacturing errors, etc.

[0020] The first large diameter portion 13 is provided between the tapered portion 12 and the second large diameter portion 14. The first large diameter portion 13 is a generally cylindrical portion having a generally constant outer diameter larger than that of the small diameter portion 11. The second large diameter portion 14 is provided at the base end of the first core shaft 10. The second large diameter portion 14 is a generally cylindrical portion having an outer diameter larger than that of the small diameter portion 11 and the same as that of the first large diameter portion 13. In this embodiment, "same" and "equal" do not necessarily mean strict agreement, but also mean that differences due to manufacturing errors and the like are allowed.

[0021] Here, the thin diameter section 11, the tapered section 12, and the first thick diameter section 13 have nonlinear pseudoelasticity (also called "superelasticity"). The section of the first core shaft 10 having nonlinear pseudoelasticity is also called the "nonlinear pseudoelastic region A1." The nonlinear pseudoelastic region A1 is a section from the tip of the thin diameter section 11 to the base end of the first thick diameter section 13. The second thick diameter section 14 has linear pseudoelasticity, and the section of the first core shaft 10 having linear pseudoelasticity is also called the "linear pseudoelastic region A2." The linear pseudoelastic region A2 is a section from the tip to the base end of the second thick diameter section 14. The length L1 of the nonlinear pseudoelastic region A1 in the longitudinal direction (X-axis direction) and the length L2 of the linear pseudoelastic region A2 in the longitudinal direction (X-axis direction) can be determined arbitrarily. To improve the blood vessel selectivity, flexibility, and restorability of the guidewire 1, it is preferable that the length L2 be equal to or less than ¼ of the length L1. The difference between nonlinear pseudoelasticity (superelasticity) and linear pseudoelasticity will be described later.

[0022] As shown in FIG. 1 , the first core shaft 10 has a nonlinear pseudoelastic region A1 and a linear pseudoelastic region A2 adjacent to each other from the distal end to the proximal end. The boundary between the nonlinear pseudoelastic region A1 and the linear pseudoelastic region A2 (i.e., the boundary between the first large-diameter portion 13 and the second large-diameter portion 14) is not welded, and no weld is formed. In the first core shaft 10, the nonlinear pseudoelastic region A1 (i.e., any portion of the small-diameter portion 11, the tapered portion 12, and the first large-diameter portion 13) and the linear pseudoelastic region A2 (i.e., any portion of the second large-diameter portion 14) have substantially the same stoichiometric composition when analyzed by ICP optical emission spectroscopy. ICP optical emission spectroscopy uses high-frequency inductively coupled plasma as a light source. Here, "substantially the same" means that the abundance ratio of each atom obtained as a result of analysis has an error of within 0.5%.

[0023] The second core shaft 20 is disposed on the proximal end side of the guidewire 1, in other words, closer to the proximal end than the first core shaft 10. The second core shaft 20 is a tapered, elongated member having a large diameter on the proximal end side and a small diameter on the distal end side. The second core shaft 20 of this embodiment is formed of a material having a higher hardness than the first core shaft 10 (specifically, the nonlinear pseudoelastic region A1 and the linear pseudoelastic region A2 of the first core shaft 10), such as stainless steel such as SUS304 or SUS316, or a CoCr alloy. The second core shaft 20 has, in order from the distal end side to the proximal end side, a small diameter portion 21, a tapered portion 22, and a large diameter portion 23. The outer diameter and length of each portion can be determined arbitrarily.

[0024] The thin diameter portion 21 is provided at the tip end of the second core shaft 20. The thin diameter portion 21 is the portion of the second core shaft 20 with the smallest outer diameter, and has a substantially cylindrical shape with the same and substantially constant outer diameter as the second large diameter portion 14 of the first core shaft 10. The tapered portion 22 is provided between the thin diameter portion 21 and the large diameter portion 23. The tapered portion 22 has a substantially truncated cone shape with an outer diameter increasing from the tip end to the base end. The large diameter portion 23 is provided at the base end of the second core shaft 20. The large diameter portion 23 is the portion of the second core shaft 20 with the largest outer diameter, and has a substantially cylindrical shape with a substantially constant outer diameter. Note that the section of the second core shaft 20 from the tip of the thin diameter portion 21 to the base end of the large diameter portion 23 is also referred to as the "second core shaft region A3" to distinguish it from the nonlinear pseudoelastic region A1 and the linear pseudoelastic region A2 of the first core shaft 10.

[0025] The welded portion 30 is a portion where the first core shaft 10 and the second core shaft 20 are welded together. As shown in FIG. 1, the welded portion 30 is provided between the base end of the linear pseudoelastic region A2 (second large diameter portion 14) of the first core shaft 10 and the tip end of the second core shaft 20. In the example of FIG. 1, the welded portion 30 has a planar shape that is approximately perpendicular to the axis O. The first core shaft 10 and the second core shaft 20 are fixed together by this welded portion 30.

[0026] Of the first core shaft 10, the thin diameter portion 11, the tapered portion 12, and the distal end side of the first large diameter portion 13 are covered by the coil body 40. On the other hand, of the first core shaft 10, the proximal end side of the first large diameter portion 13, the second large diameter portion 14, and portions of the second core shaft 20 are not covered by the coil body 40 and are exposed from the coil body 40. The large diameter portion 23 of the second core shaft 20 is used when the surgeon grasps the guidewire 1.

[0027] The coil body 40 is formed by winding a wire 41 in a spiral shape around the first core shaft 10, and has a substantially cylindrical shape. The coil body 40 may be a single-strand coil formed by winding a single wire, a multi-strand coil formed by winding multiple wires, a single-strand stranded coil formed by winding a single strand of a twisted wire obtained by twisting multiple wires together, or a multi-strand stranded coil formed by using multiple twisted wires obtained by twisting multiple wires together and winding each twisted wire multiple times. The wire diameter of the wire 41 of the coil body 40, the outer diameter and inner diameter of the coil body 40, and the length of the coil body 40 can be determined arbitrarily.

[0028] The wires 41 of the coil body 40 can be formed from, for example, stainless steel alloys such as SUS304 and SUS316, radiolucent alloys such as NiTi alloys, piano wire, nickel-chromium alloys, and cobalt alloys, radiopaque alloys such as gold, platinum, tungsten, and alloys containing these elements (e.g., platinum-nickel alloys), or other known materials.

[0029] The distal fixing portion 51 is provided at the distal end 1d of the guidewire 1 and integrally holds the distal end of the small diameter portion 11 of the first core shaft 10 and the distal end of the coil body 40. The proximal end fixing portion 52 is provided at a portion on the proximal end side of the first large diameter portion 13 of the first core shaft 10 and integrally holds the first large diameter portion 13 of the first core shaft 10 and the proximal end of the coil body 40. The intermediate fixing portion 53 is provided at a portion on the distal end side of the first large diameter portion 13 of the first core shaft 10 and integrally holds the first large diameter portion 13 of the first core shaft 10 and the central portion of the coil body 40. Note that the intermediate fixing portion 53 may be omitted or multiple intermediate fixing portions 53 may be provided. The distal end fixing portion 51, the proximal end fixing portion 52, and the intermediate fixing portion 53 can be formed using any bonding agent, for example, metal solder such as silver solder, gold solder, zinc, Sn-Ag alloy, Au-Sn alloy, or adhesive such as epoxy adhesive. The distal end fixing portion 51, the proximal end fixing portion 52, and the intermediate fixing portion 53 may each use the same bonding agent, or different bonding agents.

[0030] FIG. 2 is an explanatory diagram showing the configuration of a guidewire 1x of a comparative example. Before describing the difference between nonlinear pseudoelasticity (superelasticity) and linear pseudoelasticity, the guidewire 1x of the comparative example will be described. The guidewire 1x has a first core shaft 10x instead of the first core shaft 10, and a welded portion 30x instead of the welded portion 30. The first core shaft 10x does not have the second large diameter portion 14 described in FIG. 1, and the entire first core shaft 10x from the distal end to the proximal end is a nonlinear pseudoelastic region A1 having nonlinear pseudoelasticity. The welded portion 30x is a portion where the first core shaft 10x and the second core shaft 20 are welded. As shown in FIG. 2, the welded portion 30x is provided in the first core shaft 10x between the proximal end of the nonlinear pseudoelastic region A1 (first large diameter portion 13) and the distal end of the second core shaft 20. In the guidewire 1x of the comparative example, the first core shaft 10x and the second core shaft 20 are fixed together by the welded portion 30x.

[0031] Nonlinear pseudoelasticity (hyperelasticity) and linear pseudoelasticity are different in terms of stress (N / mm 2In the SS curves, where the stress (%) is plotted on the vertical axis and the elongation (%) is plotted on the horizontal axis, the behavior differs in the range where the elongation is 2% or more. Figure 9 shows the SS curves for nonlinear pseudoelasticity and linear pseudoelasticity. In nonlinear pseudoelasticity (superelasticity), the stress continues to increase up to a certain level (e.g., about 7-8%) while maintaining a nearly constant stress, after which the stress increases as the elongation increases. On the other hand, in linear pseudoelasticity, the stress does not remain constant and increases as the elongation increases. That is, in the first core shaft 10 of this embodiment, the nonlinear pseudoelastic region A1 and the linear pseudoelastic region A2 have the following characteristics a1 and a2. (a1) Both are formed from NiTi alloys or alloys of NiTi and other metals, and have substantially the same stoichiometric composition. (a2) The behavior, hardness, and rigidity in the SS curve are different from each other.

[0032] Fig. 3 is a diagram showing changes in hardness of the core shaft near the welded portion 30. Fig. 3(A) shows changes in hardness of the first core shaft 10 and the second core shaft 20 near the welded portion 30 in the guide wire 1 of the present embodiment described in Fig. 1. Fig. 3(B) shows changes in hardness of the first core shaft 10x and the second core shaft 20 near the welded portion 30x in the guide wire 1x of the comparative example described in Fig. 2. In Figs. 3(A) and 3(B), the vertical axis represents Vickers hardness (Hv) obtained using a known Vickers hardness tester, and the horizontal axis represents each of the regions A1 to A3 in the guide wires 1 and 1x.

[0033] As shown in FIG. 3A, the hardness of the nonlinear pseudoelastic region A1 is the smallest, the hardness of the second core shaft region A3 is the largest, and the hardness of the linear pseudoelastic region A2 is between that of the nonlinear pseudoelastic region A1 and the second core shaft region A3. In other words, the hardness of the linear pseudoelastic region A2 is greater than that of the nonlinear pseudoelastic region A1. That is, as shown in FIG. 3A, in the first core shaft 10 of this embodiment, by providing the linear pseudoelastic region A2, the hardness can be gradually changed in a stepwise manner along the longitudinal direction of the first core shaft 10 from the nonlinear pseudoelastic region A1 to the linear pseudoelastic region A2 to the second core shaft region A3. On the other hand, as shown in FIG. 3B, in the first core shaft 10x of the comparative example, a large change in hardness occurs from the nonlinear pseudoelastic region A1 to the second core shaft region A3, with the welded portion 30x as the boundary.

[0034] Fig. 4 is a diagram showing changes in stiffness of the core shaft. Fig. 4(A) shows changes in stiffness of the first core shaft 10 and the second core shaft 20 near the welded portion 30 in the guide wire 1 of the present embodiment described in Fig. 1. Fig. 4(B) shows changes in stiffness of the first core shaft 10x and the second core shaft 20 near the welded portion 30x in the guide wire 1x of the comparative example described in Fig. 2. In Figs. 4(A) and 4(B), the vertical axis represents the gradient of stress in a portion of the SS curve obtained by a well-known three-point bending test where the elongation is 2% or more, and the horizontal axis represents each of the regions A1 to A3 in the guide wires 1 and 1x.

[0035] As shown in FIG. 4A, the nonlinear pseudoelastic region A1 has the smallest rigidity, the second core shaft region A3 has the largest rigidity, and the linear pseudoelastic region A2 has a rigidity between the nonlinear pseudoelastic region A1 and the second core shaft region A3. In other words, the linear pseudoelastic region A2 has a greater rigidity than the nonlinear pseudoelastic region A1. That is, as shown in FIG. 4A, in the first core shaft 10 of this embodiment, by providing the linear pseudoelastic region A2, the rigidity can be gradually changed in a stepwise manner along the longitudinal direction of the first core shaft 10 from the nonlinear pseudoelastic region A1 to the linear pseudoelastic region A2 to the second core shaft region A3. On the other hand, as shown in FIG. 4B, in the first core shaft 10x of the comparative example, a large rigidity change occurs from the nonlinear pseudoelastic region A1 to the second core shaft region A3, with the welded portion 30x as the boundary.

[0036] As described above, according to the guidewire 1 of the first embodiment, the first core shaft 10 is provided with a nonlinear pseudoelastic region A1 having nonlinear pseudoelasticity (superelasticity) and a linear pseudoelastic region A2 having linear pseudoelasticity, which are adjacent to each other from the distal end to the proximal end. As described with reference to FIG. 3A , the linear pseudoelastic region A2 provided on the proximal end side of the first core shaft 10 has a higher hardness than the nonlinear pseudoelastic region A1 ( FIG. 3 ). Furthermore, the second core shaft 20 has a higher hardness than the first core shaft 10 (the nonlinear pseudoelastic region A1 and the linear pseudoelastic region A2). Therefore, according to the guidewire 1 of the first embodiment, by providing the linear pseudoelastic region A2 on the proximal end side of the first core shaft 10, the hardness gap between the first core shaft 10 and the second core shaft 20 can be reduced. As a result, it is possible to easily form the weld 30 between the proximal end of the linear pseudoelastic region A2 and the distal end of the second core shaft 20, and the operability of the guidewire 1 can be improved. Furthermore, no welded portion is formed at the boundary between the nonlinear pseudoelastic region A1 and the linear pseudoelastic region A2 in the first core shaft 10. Therefore, the guide wire 1 of the first embodiment can improve the durability of the guide wire 1 compared to conventional guide wires that have welded portions in two locations. As a result, a guide wire 1 with improved operability and durability can be provided.

[0037] Furthermore, according to the guide wire 1 of the first embodiment, in the first core shaft 10, the nonlinear pseudoelastic region A1 and the linear pseudoelastic region A2 have substantially the same stoichiometric composition, so the nonlinear pseudoelastic region A1 and the linear pseudoelastic region A2 can be formed from the same material, such as a NiTi alloy or an alloy of NiTi and another metal.

[0038] Furthermore, according to the guidewire 1 of the first embodiment, the hardness of the linear pseudoelastic region A2 in the first core shaft 10 is greater than the hardness of the nonlinear pseudoelastic region A1, and therefore, as described in Fig. 3(A), the linear pseudoelastic region A2 can reduce the hardness gap between the first core shaft 10 and the second core shaft 20. Furthermore, according to the guidewire 1 of the first embodiment, the stiffness of the linear pseudoelastic region A2 in the first core shaft 10 is greater than the stiffness of the nonlinear pseudoelastic region A1, and therefore, as described in Fig. 4(A), the linear pseudoelastic region A2 can reduce the stiffness gap between the first core shaft 10 and the second core shaft 20.

[0039] Furthermore, according to the guidewire 1 of the first embodiment, a nonlinear pseudoelastic region A1 having nonlinear pseudoelasticity (superelasticity) is provided on the distal end side of the first core shaft 10, and the length L2 in the longitudinal direction of the linear pseudoelastic region A2 is equal to or less than ¼ of the length L1 in the longitudinal direction of the nonlinear pseudoelastic region A1. This allows the distal end portion of the guidewire 1 to be configured to be flexible, and also allows for improved blood vessel selectivity and restorability at the distal end of the guidewire 1.

[0040] <Method of Manufacturing Guidewire 1> Figure 5 shows an example of a method for manufacturing the guide wire 1 shown in Figure 1. Figure 5(A) shows the preparation step and the heat treatment step. Figure 5(B) shows the welding step. Figure 5(C) shows the completed core-shaft assembly 10, 20.

[0041] In this method, first, as shown in FIG. 5(A), a first core shaft 10z having linear pseudoelasticity as a whole and a second core shaft 20 (not shown) having a harder material than the first core shaft 10z are prepared. In FIG. 5(A), the thin-diameter portion 11 and the tapered portion 12 have different properties (i.e., linear pseudoelasticity) from those described in FIG. 1, and therefore are denoted by different reference numerals, such as the thin-diameter portion 11z and the tapered portion 12z, from those in FIG. 1. Next, a portion 10zd on the distal end of the first core shaft 10z (specifically, the portion where the nonlinear pseudoelastic region A1 is to be formed) is heat-treated at 400 to 600 degrees for a predetermined time, thereby converting the linear pseudoelasticity into nonlinear pseudoelasticity. The heat-treatment time can be determined arbitrarily, for example, from 30 seconds to 1 hour. This allows the formation of a first core shaft 10 having a nonlinear pseudoelastic region A1 (Figure 5(B): thin diameter portion 11, tapered portion 12, and first thick diameter portion 13) in a portion 10zd on the tip side and a linear pseudoelastic region A2 (Figure 5(B): second thick diameter portion 14) on the base side.

[0042] 5(B), the tip end 21d of the small diameter portion 11 of the second core shaft 20 is welded to the base end 14p of the second large diameter portion 14 of the first core shaft 10. The welding can be performed by a well-known method.

[0043] 5(C), a core shaft assembly 10, 20 (first core shaft 10 and second core shaft 20) can be obtained, which is joined by a welded portion 30 formed between the base end of the linear pseudoelastic region A2 of the first core shaft 10 and the tip end of the second core shaft 20. Thereafter, a separately formed coil body 40 is fixed to the core shaft assembly 10, 20 by the tip fixing portion 51, the base end fixing portion 52, and the intermediate fixing portion 53, thereby producing the guide wire 1 shown in FIG.

[0044] In general, welding components with large differences in hardness is difficult. In this regard, according to the manufacturing method (welding step) illustrated in FIG. 5, the distal end portion 21d of the second core shaft 20 is welded to the proximal end portion 14p of the second large-diameter portion 14 of the first core shaft 10, which has linear pseudoelasticity. This facilitates welding compared to welding the second core shaft 20 to the first core shaft 10x, which has nonlinear pseudoelasticity as a whole, as in the comparative guidewire 1x illustrated in FIG. 2. Furthermore, since welding is performed in only one location, the labor hours and costs of the welding step can be reduced compared to conventional guidewires with two welds. Furthermore, according to the manufacturing method (heat treatment step) illustrated in FIG. 5, a nonlinear pseudoelastic region A1 having nonlinear pseudoelasticity can be formed by heat-treating a distal portion 10zd of the first core shaft 10z, which has linear pseudoelasticity. That is, by changing the linear pseudoelasticity of the first core shaft 10z to nonlinear pseudoelasticity by heat treatment, it is possible to easily form and allow the nonlinear pseudoelastic region A1 and the linear pseudoelastic region A2 to coexist within a single first core shaft 10. As a result, it is possible to manufacture a guidewire 1 with improved operability and durability. Furthermore, as described in FIG. 1, the guidewire 1 has a nonlinear pseudoelastic region A1 having nonlinear pseudoelasticity (superelasticity) provided on the distal end side of the first core shaft 10, and therefore the distal end is flexible, and the distal end has excellent blood vessel selectivity and restorability.

[0045] Furthermore, according to the manufacturing method described with reference to FIG. 5, the welding step is carried out after the heat treatment step, and therefore deterioration and damage to the welded portion 30 due to the heat treatment can be suppressed compared to the reverse case.

[0046] Figure 6 shows another example of a method for manufacturing the guide wire 1 shown in Figure 1. Figure 6(A) shows the preparation step and the welding step. Figure 6(B) shows the heat treatment step. Figure 6(C) shows the completed core-shaft assembly 10, 20.

[0047] In this method, first, as shown in Fig. 6(A), a first core shaft 10z having linear pseudoelasticity as a whole and a second core shaft 20 having a higher hardness than the first core shaft 10z are prepared. Note that in Fig. 6(A), the thin-diameter portion 11z and the tapered portion 12z are assigned different reference numerals from those in Fig. 1 for the same reason as in Fig. 5(A). Next, the tip end portion 21d of the thin-diameter portion 11 of the second core shaft 20 is welded to the base end portion 14p of the second large-diameter portion 14 of the first core shaft 10z. The welding can be performed by a well-known method.

[0048] Next, a portion 10zd of the first core shaft 10z on the distal end side (specifically, the portion where the nonlinear pseudoelastic region A1 is to be formed) is heat-treated in the same manner as in Fig. 5(A) to change the linear pseudoelasticity to nonlinear pseudoelasticity. This allows the formation of a first core shaft 10 having the nonlinear pseudoelastic region A1 (Fig. 6(C): thin diameter portion 11, tapered portion 12, and first large diameter portion 13) in the distal end portion 10zd and the linear pseudoelastic region A2 (Fig. 6(C): second large diameter portion 14) on the proximal end side.

[0049] As a result, this method also makes it possible to obtain a core-shaft assembly 10, 20 (first core shaft 10 and second core shaft 20) joined by a welded portion 30 formed between the base end of the linear pseudoelastic region A2 of the first core shaft 10 and the tip end of the second core shaft 20, as shown in Fig. 6(C). Thereafter, a separately formed coil body 40 is fixed to the core-shaft assembly 10, 20 by the tip fixing portion 51, the base fixing portion 52, and the intermediate fixing portion 53, thereby producing the guide wire 1 shown in Fig. 1.

[0050] The manufacturing method (welding process) described in Fig. 6 can also manufacture a guidewire with improved operability and durability, similar to the manufacturing method described in Fig. 5. Furthermore, as described in Fig. 1, the guidewire 1 has a nonlinear pseudoelastic region A1 having nonlinear pseudoelasticity (superelasticity) provided on the distal end side of the first core shaft 10, and therefore the distal end is flexible, and the distal end has excellent blood vessel selectivity and restorability.

[0051] Second Embodiment 7 is an explanatory diagram illustrating the configuration of a guidewire 1A of a second embodiment. The guidewire 1A of the second embodiment has the same configuration as the first embodiment, except that it includes a first core shaft 10A instead of the first core shaft 10, a second core shaft 20A instead of the second core shaft 20, and a welded portion 30A instead of the welded portion 30. The second core shaft 20A does not have the small diameter portion 21 and the tapered portion 22 described in the first embodiment, but has a large diameter portion 23A that is generally cylindrical and has a generally constant outer diameter throughout.

[0052] The first core shaft 10A has, in order from the distal end to the proximal end, a thin diameter portion 11, a tapered portion 12, a first large diameter portion 13, a second tapered portion 15, a third large diameter portion 16, and a second large diameter portion 14A. The configurations of the thin diameter portion 11, the tapered portion 12, and the first large diameter portion 13 are the same as those in the first embodiment. The second tapered portion 15 is provided between the first large diameter portion 13 and the third large diameter portion 16. The second tapered portion 15 is a generally truncated cone-shaped portion whose outer diameter increases from the distal end to the proximal end. The third large diameter portion 16 is provided between the second tapered portion 15 and the second large diameter portion 14A. The third large diameter portion 16 is the portion of the first core shaft 10A where the outer diameter is greatest, and is a generally cylindrical portion with a generally constant outer diameter. The second large diameter portion 14A is provided at the proximal end of the first core shaft 10A. The second large diameter portion 14A is a generally cylindrical portion that is larger than the small diameter portion 11 and the first large diameter portion 13 and has the same outer diameter as the third large diameter portion 16.

[0053] In the first core shaft 10A, in addition to the thin diameter portion 11, the tapered portion 12, and the first large diameter portion 13, the second tapered portion 15 and the third large diameter portion 16 also have nonlinear pseudoelasticity (superelasticity). Therefore, in the first core shaft 10A, the section from the tip of the thin diameter portion 11 to the base end of the third large diameter portion 16 corresponds to a "nonlinear pseudoelastic region A1." Furthermore, since the second large diameter portion 14A has linear pseudoelasticity, in the first core shaft 10A, the section from the tip to the base end of the second large diameter portion 14A corresponds to a "linear pseudoelastic region A2."

[0054] The welded portion 30A is a portion where the first core shaft 10A and the second core shaft 20A are welded together. As shown in Fig. 7, the welded portion 30A is provided between the base end of the linear pseudoelastic region A2 (second large diameter portion 14A) of the first core shaft 10A and the tip end of the second core shaft 20A (large diameter portion 23A). The first core shaft 10A and the second core shaft 20A are fixed together by the welded portion 30A.

[0055] As described above, the configuration of the guidewire 1A can be modified in various ways. The first core shaft 10A can have any shape as long as the proximal end welded to the second core shaft 20A is in the linear pseudoelastic region A2. The second core shaft 20 can also have any shape. For example, as described with reference to FIG. 7, the first core shaft 10A may have portions (the third large diameter portion 16 and the second large diameter portion 14A) having substantially the same outer diameter as the large diameter portion 23A of the second core shaft 20A, and may be welded to the second core shaft 20A at these portions. Furthermore, the first core shaft 10A may not have the above-described portions (e.g., the small diameter portion 11 and the tapered portion 12), and may have other portions (e.g., a protruding portion configured to have a diameter larger than the third large diameter portion 16) not described above. The guidewire 1A of this second embodiment can also achieve the same effects as the first embodiment.

[0056] <Third embodiment> 8 is an explanatory diagram illustrating the configuration of a guidewire 1B according to a third embodiment. The guidewire 1B according to the third embodiment has the same configuration as the first embodiment, except that it includes a second core shaft 20B instead of the second core shaft 20, a coil body 40B instead of the coil body 40, and a base end fixing portion 52B instead of the base end fixing portion 52.

[0057] The second core shaft 20B does not have the tapered portion 22 and the large-diameter portion 23 described in the first embodiment, and instead has the small-diameter portion 21 as a whole. The coil body 40B is formed by spirally winding a wire 41 around the first core shaft 10 and the second core shaft 20B. In other words, the coil body 40B covers the entire guidewire 1B from the distal end of the first core shaft 10 to the proximal end of the second core shaft 20B. The proximal-end fixing portion 52B is provided at the proximal end 1p of the guidewire 1B and integrally holds the proximal end of the small-diameter portion 21 of the second core shaft 20B and the proximal end of the coil body 40B. As shown in FIG. 8 , in the guidewire 1B of the third embodiment, the welded portion 30 is covered by the coil body 40B. Covering the welded portion 30 with the coil body 40B can further reduce the rigidity gap that occurs near the welded portion.

[0058] As described above, the configuration of the guidewire 1B can be modified in various ways, and the first core shaft 10 and the second core shaft 20B may be entirely covered by the coil body 40B. Also, the welded portion 30 at which the first core shaft 10 and the second core shaft 20B are welded together may be covered by the coil body 40B. The guidewire 1B of this third embodiment can also achieve the same effects as the first embodiment.

[0059] <Modification of this embodiment> The present invention is not limited to the above-described embodiment, and can be embodied in various forms without departing from the spirit of the invention. For example, the following modifications are also possible.

[0060] [Variation 1] In the first to third embodiments, the configurations of the guidewires 1, 1A, and 1B have been described as examples. However, various modifications to the configuration of the guidewire are possible. For example, in the first core shaft, the boundary surface between the nonlinear pseudoelastic region A1 and the linear pseudoelastic region A2 does not have to be a plane perpendicular to the axis O and can have any shape. Specifically, the boundary surface between the nonlinear pseudoelastic region A1 and the linear pseudoelastic region A2 may be a plane inclined with respect to the axis O, or may have a curved shape in which a portion of the distal end surface of the linear pseudoelastic region A2 protrudes toward the distal end of the guidewire (in other words, a portion of the proximal end surface of the nonlinear pseudoelastic region A1 is recessed toward the distal end), or may have a curved shape in which a portion of the proximal end surface of the nonlinear pseudoelastic region A1 protrudes toward the proximal end of the guidewire (in other words, a portion of the distal end surface of the linear pseudoelastic region A2 is recessed toward the proximal end).

[0061] For example, the welding surface between the first core shaft and the second core shaft does not have to be a plane perpendicular to the axis O, and can have any shape. For example, it may be a plane inclined with respect to the axis O, or a curved surface projecting toward the axial direction (toward the distal end or the proximal end).

[0062] For example, the guidewire may not have a coil body. In this case, the distal fixing portion, proximal fixing portion, and intermediate fixing portion may also be omitted. For example, a portion of the coil body or a portion of the first and second core shafts of the guidewire may be coated with a hydrophilic or hydrophobic coating. For example, the guidewire may be manufactured with a portion of the distal end of the first core shaft pre-bent. For example, the guidewire may have a configuration other than those described above.

[0063] For example, in the first core shaft, the nonlinear pseudoelastic region A1 (thinner diameter portion 11, tapered portion 12, first thicker diameter portion 13) and the linear pseudoelastic region A2 (second thicker diameter portion 14) may have different stoichiometric compositions. For example, in the first core shaft, the length L2 in the longitudinal direction of the linear pseudoelastic region A2 may be greater than ¼ of the length L1 in the longitudinal direction of the nonlinear pseudoelastic region A1. By making the length L2 greater than ¼ of the length L1, the operability of the guidewire 1, 1A-1D can be improved, instead of the blood vessel selectivity, flexibility, and restorability of the guidewire 1, 1A-1D.

[0064] [Variation 2] In the first embodiment, one example (FIG. 5) and another example (FIG. 6) of the method for manufacturing the guidewire 1 are shown. These manufacturing methods are similarly applicable to the guidewires 1A and 1B of the second and third embodiments. Furthermore, various modifications are possible to the method for manufacturing the guidewire. For example, instead of the first core shaft 10z, a first core shaft 10y having nonlinear pseudoelasticity (superelasticity) throughout may be prepared. In this case, prior to the welding step, a portion of the base end of the first core shaft 10y (specifically, a portion where the linear pseudoelastic region A2 is to be formed) may be subjected to plastic processing (e.g., swaging, pressing, die processing, etc.). This changes the nonlinear pseudoelasticity to linear pseudoelasticity, thereby forming a first core shaft 10 having a linear pseudoelastic region A2 in a portion of the base end. This method can also achieve the same effects as the manufacturing method described with reference to FIGS. 5 and 6.

[0065] [Variation 3] The configurations of the guidewires according to the first to third embodiments and the configurations of the guidewires according to the above-described Modifications 1 and 2 may be combined as appropriate. For example, the configurations described in the second and third embodiments may employ the shape of the boundary surface described in Modification 1. For example, the guidewires described in the second and third embodiments may be manufactured by the method described in Modification 2.

[0066] This aspect has been described above based on embodiments and modifications. However, the above-described embodiments are intended to facilitate understanding of this aspect and are not intended to limit this aspect. This aspect may be modified or improved without departing from the spirit and scope of the claims, and equivalents thereof are included in this aspect. Furthermore, if a technical feature is not described as essential in this specification, it may be deleted as appropriate. [Explanation of symbols]

[0067] 1, 1A, 1B...Guidewire 1x...Guidewire (comparison example) 10, 10A, 10B...First core shaft 10x...First core shaft (comparison example) 11...Small diameter section 12...Tapered section 13...First large diameter section 14, 14A...Second large diameter section 15...Second tapered section 16...Third large diameter section 20, 20A, 20B...Second core shaft 21...Small diameter section 22...Tapered section 23,23A…Large diameter part 30, 30A...welded section 30x...Welded section (comparison example) 40, 40B...Coil body 41...Elemental wire 51…Tip fixing part 52,52B…Proximal end fixing part 53...Intermediate fixed part 131...Proximal surface 141…Tip surface A1: Nonlinear pseudoelastic region A2…Linear pseudoelastic region A3: Second core shaft area

Claims

1. A guidewire, a first core shaft disposed on the distal end side; a second core shaft disposed on the proximal side of the first core shaft and made of stainless steel having a higher hardness than the first core shaft; Equipped with The first core shaft is provided with a nonlinear pseudoelastic region having nonlinear pseudoelasticity and a linear pseudoelastic region having linear pseudoelasticity, which are adjacent to each other from a distal end side to a proximal end side, no weld is formed at the boundary between the nonlinear pseudoelastic region and the linear pseudoelastic region; A guide wire, wherein a welded portion between the first core shaft and the second core shaft is formed between the proximal end of the linear pseudoelastic region and the distal end of the second core shaft.

2. 2. The guidewire of claim 1, The guidewire, wherein the nonlinear pseudoelastic region and the linear pseudoelastic region in the first core shaft have substantially the same stoichiometric composition.

3. The guide wire according to claim 1 or 2, A guidewire, wherein the length of the linear pseudoelastic region in the longitudinal direction of the first core shaft is ¼ or less of the length of the nonlinear pseudoelastic region in the longitudinal direction.

4. The guide wire according to any one of claims 1 to 3, A guidewire, wherein in the first core shaft, the hardness of the linear pseudoelastic region is greater than the hardness of the nonlinear pseudoelastic region.

5. A method for manufacturing a guidewire, comprising: a preparation step of preparing a first core shaft having linear pseudoelasticity and a second core shaft made of stainless steel having a harder hardness than the first core shaft; a welding step of welding a tip end portion of the second core shaft to a base end portion of the first core shaft; a heat treatment step of heat-treating a portion of a tip end side of the first core shaft to form a nonlinear pseudoelastic region having nonlinear pseudoelasticity on the tip end side of the first core shaft; Including, By the heat treatment step, the first core shaft is provided with the nonlinear pseudoelastic region and the linear pseudoelastic region having the linear pseudoelasticity, which are adjacent to each other from the distal end side to the proximal end side, a welded portion between the first core shaft and the second core shaft is formed between a base end portion of the linear pseudoelastic region and a distal end portion of the second core shaft by the welding step, The method for manufacturing a guidewire, wherein no weld is formed at the boundary between the nonlinear pseudoelastic region and the linear pseudoelastic region.

6. 6. A method for manufacturing a guidewire according to claim 5, comprising the steps of: The method for manufacturing a guide wire includes carrying out the welding step after carrying out the heat treatment step.

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