guide wire

Abstract

A guide wire has a core shaft including a first shaft having a first tip and a first base end opposite the first tip, and a second shaft having a second tip connected to the first base end and having a higher hardness than the first shaft, the second shaft having a reduced portion disposed near the second tip and having a smaller cross-sectional area than a base end surface of the first shaft, a base portion disposed at a position farther from the first base end than the reduced portion and having a constant cross-sectional area larger than that of the reduced portion, and an intermediate portion disposed between the reduced portion and the base portion and having a cross-sectional area that continuously or stepwise increases from the reduced portion toward the base portion, the cross-sectional area of the reduced portion having a rotational symmetry shape, a sum of a length of the reduced portion and a length of the intermediate portion being L1, and a minimum value of a length of a straight line passing through a rotational center in the cross-sectional area of the reduced portion and connecting two points on an outer periphery being L2, L1 satisfying L1 ≥ L2 × 10.

Description

Technical Field

[0001] The technology disclosed in this specification relates to a guidewire. Background Technology

[0002] The guidewire disclosed in Patent Document 1 includes, for example, a first shaft disposed on the front end side and a second shaft disposed on the base end side of the first shaft and made of a material with an elastic modulus greater than that of the constituent material of the first shaft.

[0003] Existing technical documents Patent documents Patent Document 1: Japanese Patent No. 4138583. Summary of the Invention

[0004] The problem that the invention aims to solve There is room for improvement in the rotational durability of the aforementioned guidewire.

[0005] This specification discloses a technique that can solve the above-mentioned problems.

[0006] Technical means for solving problems The techniques disclosed in this specification can be implemented, for example, in the following forms.

[0007] (1) The guidewire disclosed in this specification has a mandrel, which has: a first shaft having a first front end and a first base end opposite to the first front end; The second shaft has a second front end connected to the first base end and has a higher stiffness than the first shaft. The second shaft has: The reduced portion, which is disposed near the second front end, has a cross-sectional area smaller than that of the base end face of the first shaft; The base, which is located further away from the first base end than the reduced portion, has a constant cross-sectional area that is larger than the cross-sectional area of ​​the reduced portion; The intermediate portion, disposed between the reduced portion and the base portion, has a cross-sectional area larger than that of the reduced portion and smaller than that of the base portion. The cross-section of the narrowed portion has a rotationally symmetric shape. When the sum of the length of the reduced portion and the length of the middle portion is set as L1, and the minimum length of the straight line passing through the center of rotation and connecting two points on the outer periphery in the cross section of the reduced portion is set as L2, the following equation (1) is satisfied: L1≥L2×10…(1).

[0008] Based on the above structure, the rotational durability of the guidewire is improved.

[0009] (2) The guidewire described in (1) above can also satisfy the following equation (2).

[0010] L1 ≥ L2 × 100 … (2) With this structure, the rotational durability of the guidewire is further improved.

[0011] (3) In the guidewire described in (1) or (2) above, the cross-sectional area of ​​the middle part may also increase in stages from the narrowed part to the base part.

[0012] With this structure, the rotational durability of the guidewire is further improved. It can suppress deformation of the bending shape when the mandrel is bent.

[0013] (4) In the guidewire described in (3) above, the middle part may also have a first increasing part, a constant part and a second increasing part arranged sequentially from the second front end side, the cross-sectional area of ​​the first increasing part increases as it approaches the base, the cross-sectional area of ​​the constant part is constant, and the cross-sectional area of ​​the second increasing part increases as it approaches the base.

[0014] This structure improves the rotational durability of the guidewire and simplifies its design.

[0015] (5) In the guidewire described in (1) or (2) above, the cross-sectional area of ​​the middle portion may also increase continuously from the narrowed portion to the base portion.

[0016] With this structure, the rotational durability of the guidewire is further improved. It can suppress deformation of the bending shape when the mandrel is bent.

[0017] The technology disclosed in this specification can be implemented in various forms, such as guidewires and their manufacturing methods. Attached Figure Description

[0018] Figure 1 This is a cross-sectional view of the guidewire according to the first embodiment.

[0019] Figure 2 This is a cross-sectional view of the reduced portion of the first embodiment.

[0020] Figure 3 This is a cross-sectional view of the guidewire according to the second embodiment.

[0021] Figure 4 This is a cross-sectional view of the guidewire according to the third embodiment.

[0022] Figure 5 It is a graph showing the relationship between the value of L1 / L2 and the number of rotations before the mandrel breaks in the rotational durability test using samples S1 to S10.

[0023] Figure 6 It is a graph showing the relationship between the value of L1 / L2 and the number of rotations before the mandrel breaks in the rotational durability test using samples S11 to S16. Detailed Implementation

[0024] A. First implementation method: Reference Figure 1 and Figure 2 The first embodiment will be described. Figure 1 This is an explanatory diagram schematically showing the guide wire 10 of the embodiment. Figure 1 The longitudinal section of guidewire 10 is shown. The longitudinal section is a YZ section. In guidewire 10, the positive Z-axis side is the anterior end side inserted into the body, and the negative Z-axis side is the basal end side operated by the physician or other operator. The anterior end side is the distal side. The basal end side is the proximal side. Sometimes, a portion of guidewire 10 is omitted from the illustrations. Figure 1 The guidewire 10 is shown as a whole in a straight line that is approximately parallel to the Z-axis. The guidewire 10 has a degree of flexibility that allows it to bend. These points are also shown in the following figures.

[0025] In this specification, the end on the front end side of the guidewire 10 and its constituent components is referred to as the "front end", the front end and its vicinity as the "front end", the end on the base end side is referred to as the "base end", and the base end and its vicinity as the "base end".

[0026] The guidewire 10 is a medical device inserted into a biological lumen, for example, to guide a catheter (not shown) to a lesion in a biological lumen such as a blood vessel. The length of the guidewire 10 is, for example, 1500 mm or more and 3000 mm or less.

[0027] like Figure 1 As shown, the guide wire 10 includes a spindle 100, a coil body 200, a front end joint 300, and a base end joint 400.

[0028] like Figure 1 As shown, the mandrel 100 is a long, narrow-diameter mandrel capable of bending. The mandrel 100 includes a first shaft 110 and a second shaft 120 arranged sequentially from its front end. The first shaft 110 and the second shaft 120 are coaxially arranged along the central axis Ax of the mandrel 100. In this specification, the cross-section of the mandrel 100 and its constituent parts refers to the cut plane when the mandrel 100 and its constituent parts are cut perpendicularly to the central axis Ax.

[0029] The material forming the mandrel 100 is, for example, a metallic material, more specifically, stainless steel such as SUS301, SUS302, SUS303, SUS304, SUS305, SUS306, SUS309, SUS310, SUS316, SUS317, SUS321, SUS347, and SUS384, superelastic alloys such as Ni-Ti alloys, piano wire, nickel-chromium alloys, cobalt alloys, tungsten, etc. The hardness of the second shaft 120 is higher than that of the first shaft 110. In this specification, "hardness" refers to Vickers hardness. In this embodiment, the material of the first shaft 110 is a Ni-Ti alloy, and the material of the second shaft 120 is stainless steel. The stainless steel can be, for example, austenitic stainless steel. Because the hardness of the first shaft 110 is relatively low, relatively high flexibility is ensured at the tip of the guidewire 10. Because the hardness of the second shaft 120 is relatively high, relatively high torque transmission is ensured at the base of the guidewire 10.

[0030] The first shaft 110 is a narrow-diameter shaft with a circular cross-section, having a first front end 111 and a first base end 112. The length of the first shaft 110 is, for example, 100 mm or more and 500 mm or less. The first shaft 110 includes a narrow-diameter portion 113, a tapered portion 114, and a wide-diameter portion 115 arranged sequentially from the front end. The narrow-diameter portion 113 includes the first front end 111 and has a constant outer diameter, i.e., a portion with a constant cross-sectional area. The wide-diameter portion 115 includes the first base end 112 and has a constant outer diameter larger than the outer diameter of the narrow-diameter portion 113, i.e., a portion with a constant cross-sectional area larger than the cross-sectional area of ​​the narrow-diameter portion 113. The tapered portion 114 connects the narrow-diameter portion 113 and the wide-diameter portion 115. The outer diameter of the tapered portion 114 continuously decreases from the wide-diameter portion 115 to the narrow-diameter portion 113. That is, the cross-sectional area of ​​the tapered portion 114 decreases continuously from the coarse diameter portion 115 to the fine diameter portion 113. The outer diameter of the fine diameter portion 113 is 0.03 mm or more and 0.085 mm or less, and the outer diameter of the coarse diameter portion 115 is, for example, 0.1 mm or more and 10 mm or less.

[0031] The second shaft 120 is a narrow shaft with a circular cross-section, its front end being a second front end 121 and its base end being a second base end 122. The length of the second shaft 120 is, for example, 1000 mm or more and 2000 mm or less. The second front end 121 is joined to the first base end 112, for example, by welding. The second shaft 120 includes a shaping portion 130, a connecting portion 140, a narrowing portion 150, a middle portion 160, and a base portion 170 arranged sequentially from the front end.

[0032] The shaping portion 130 is a short, narrow diameter portion with a circular cross-section, includes a second front end 121, and has a constant outer diameter equal to the outer diameter of the coarse diameter portion 115, that is, a portion having a constant cross-sectional area equal to the cross-sectional area of ​​the coarse diameter portion 115.

[0033] The connecting portion 140 is disposed between the shaping portion 130 and the reducing portion 150 and connects the two. The connecting portion 140 is short and narrow in diameter with a circular cross-section. The outer diameter of the connecting portion 140 continuously decreases from the shaping portion 130 to the reducing portion 150. That is, the cross-sectional area of ​​the connecting portion 140 continuously decreases from the shaping portion 130 to the reducing portion 150.

[0034] The shaping portion 130 and the connecting portion 140 are preferably as short as possible. This is to allow the tapered portion 150 to be positioned as close as possible to the second front end 121, thereby mitigating stress generated at the junction of the first shaft 110 and the second shaft 120 due to the torsion of the guide wire 10. The length of the shaping portion 130 can be, for example, 0.1 mm to 10 mm or 1 mm to 5 mm. The length of the connecting portion 140 can be, for example, 0.1 mm to 5 mm or 0.1 mm to 3 mm.

[0035] The narrowing portion 150 is a short, narrow-diameter section with a circular cross-section connected to the connecting portion 140. The narrowing portion 150 has a constant outer diameter smaller than that of the thicker diameter portion 115, meaning it has a constant cross-sectional area smaller than that of the thicker diameter portion 115. In other words, the cross-sectional area of ​​the narrowing portion 150 is smaller than the area of ​​the base end face 112S on the base end side of the first shaft 110. The narrowing portion 150 is the section with the smallest cross-sectional area in the second shaft 120.

[0036] The base 170 is a narrow-diameter portion with a circular cross-section, located further away from the first base end 112 than the reduced-diameter portion 150. The base 170 has a constant outer diameter larger than the outer diameter of the reduced-diameter portion 150, i.e., a constant cross-sectional area larger than the cross-sectional area of ​​the reduced-diameter portion 150. More specifically, the base 170 is a portion that includes the second base end 122 and has a constant outer diameter equal to the outer diameter of the thicker-diameter portion 115, i.e., a portion with a constant cross-sectional area equal to the cross-sectional area of ​​the thicker-diameter portion 115. The second shaft 120 is typically obtained by processing a wire having a substantially constant outer diameter and cross-sectional area to form the reduced-diameter portion 150 and the intermediate portion 160. The base 170 has the constant outer diameter and cross-sectional area of ​​the aforementioned wire before processing. Typically, from a production standpoint, the processing of changing the outer diameter and cross-sectional area of ​​the wire, as described above, is carried out for a length of less than 50% of the total length of the second shaft 120. Therefore, the base 170 typically has a constant outer diameter and cross-sectional area occupying more than 50% of the total length of the second shaft 120. The portion near the second base end 122 in the base 170 is a holding part held by an operator such as a doctor.

[0037] The intermediate portion 160 is disposed between the reduced portion 150 and the base portion 170, connecting the two. The cross-sectional area of ​​the intermediate portion 160 is larger than that of the reduced portion 150 and smaller than that of the base portion 170 over its entire length. In this embodiment, the outer diameter of the intermediate portion 160 increases progressively from the reduced portion 150 to the base portion 170. That is, the cross-sectional area of ​​the intermediate portion 160 increases progressively from the reduced portion 150 to the base portion 170. The intermediate portion 160 includes a first increasing portion 161, a constant portion 162, and a second increasing portion 163 arranged sequentially from the second front end 121 side.

[0038] The constant portion 162 is a portion having a constant outer diameter that is larger than that of the reduced portion 150 and smaller than that of the base portion 170. That is, the constant portion 162 has a constant cross-sectional area that is larger than that of the reduced portion 150 and smaller than that of the base portion 170.

[0039] The first increasing portion 161 is disposed between the reducing portion 150 and the constant portion 162 and connects the two. The outer diameter, i.e., the cross-sectional area, of the first increasing portion 161 is larger than that of the reducing portion 150 and smaller than that of the constant portion 162. The cross-sectional area of ​​the first increasing portion 161 increases continuously from the reducing portion 150 to the constant portion 162, i.e., as it approaches the base 170.

[0040] The second extension portion 163 is disposed between the constant portion 162 and the base portion 170 and connects the two. The outer diameter, i.e., the cross-sectional area, of the second extension portion 163 is larger than that of the constant portion 162 and smaller than that of the base portion 170. The cross-sectional area of ​​the second extension portion 163 increases continuously from the constant portion 162 to the base portion 170.

[0041] In this specification, the cross-section of the reduced portion has a rotationally symmetrical shape. In this embodiment, the cross-section 151 of the reduced portion 150 is a perfect circle. In this specification, "perfect circle" includes not only a strictly perfect circle, but also a shape that deviates slightly from a perfect circle due to unavoidable factors such as manufacturing errors. Figure 2 As shown, in this embodiment, the rotation center of the cross section 151 coincides with the central axis Ax of the mandrel 100.

[0042] The sum of the length of the reduced portion 150 and the length of the intermediate portion 160 is defined as L1. The length of the reduced portion 150 is represented by the distance between the front end and the base end of the reduced portion 150, and the length of the intermediate portion 160 is represented by the distance between the front end and the base end of the intermediate portion 160. In the cross-section 151 of the reduced portion 150, the minimum length of the straight line passing through the center of rotation and connecting two points P1 and P2 on the outer periphery is defined as L2. The center of rotation is the central axis Ax. In this embodiment, the minimum length L2 of the straight line passing through the center of rotation of the cross-section 151 and connecting two points P1 and P2 on the outer periphery is the diameter length of the cross-section 151. The center of rotation is the central axis Ax. L1 and L2 satisfy the following equation (1). L1 and L2 can also satisfy the following equation (2).

[0043] L1≥L2×10…(1) L1≥L2×100…(2) like Figure 1 As shown, the coil body 200 is arranged to surround the front end of the mandrel 100. More specifically, the coil body 200 is arranged to surround the portion of the first shaft 110 excluding the first base end 112 and its vicinity. The coil body 200 is a multi-strand coil formed by winding multiple wires into a spiral shape. The overall length of the coil body 200 is, for example, 10 mm to 500 mm, and the outer diameter of the coil body 200 is, for example, 0.2 mm to 0.9 mm.

[0044] The coil body 200 is made of materials such as metals, more specifically, stainless steel such as SUS302, SUS304, and SUS316, super-elastic alloys such as Ni-Ti alloys, piano wire, nickel-chromium alloys, cobalt alloys, tungsten, etc.

[0045] like Figure 1 As shown, the front-end joint 300 is a component that connects the front end of the mandrel 100 to the front end of the coil body 200. The front ends of both the mandrel 100 and the coil body 200 are embedded within the front-end joint 300. The front-end surface of the front-end joint 300 is, for example, a smooth surface such as a roughly hemispherical surface. The material of the front-end joint 300 can be, for example, a metallic solder such as silver solder, gold solder, zinc, Sn-Ag alloy, or Au-Sn alloy, or an adhesive such as an epoxy adhesive. Because the front-end joint 300 is provided at the front end of the mandrel 100, it can prevent the front end of the mandrel 100 from contacting the blood vessel wall or the like, and suppress damage to the mandrel 100.

[0046] The base end joint 400 is a component that joins the base end of the coil body 200 to the mandrel 100. The material of the base end joint 400 is, for example, the same material as that of the front end joint 300 described above.

[0047] The guidewire 10 advances and rotates within the lumen of the organism by the operator rotating the handle. When passing through curved sections of the lumen, the guidewire 10 bends and rotates in accordance with the curvature of the lumen. Rotation of the guidewire 10 generates torsional stress in the mandrel 100. The guidewire 10 is required to have high rotational durability, meaning it is not easily damaged by the stress generated by the rotation of the guidewire 10.

[0048] Because the hardness of the second shaft 120 is higher than that of the first shaft 110, the stress at the joint between the first shaft 110 and the second shaft 120 tends to increase when the mandrel 100 is torn. In this embodiment, the cross-sectional area of ​​the relatively harder second shaft 120 decreases in stages from the base 170 to the second front end 121. That is, the rigidity of the second shaft 120 decreases in stages from the base 170 to the second front end 121. As a result, stress concentration near the second front end 121 is mitigated, and breakage of the mandrel 100 at the joint between the first shaft 110 and the second shaft 120 is suppressed. Furthermore, deformation of the bending shape when the mandrel 100 is bent can be suppressed.

[0049] The cross-sectional area of ​​the intermediate portion 160 increases progressively from the narrowing portion 150 to the base portion 170, with a step between the narrowing portion 150 and the constant portion 162. Therefore, when the mandrel 100 is torn, stress is concentrated to a certain extent in the narrowing portion 150. Consequently, when a large amount of stress caused by torsion accumulates, the mandrel 100 can reliably break at the narrowing portion 150. Based on this structure, the magnitude of the stress that causes the mandrel 100 to break depends on the material of the mandrel 100 and the size of the narrowing portion 150, and is therefore easily predictable. Thus, the design of the guide wire 10 becomes easier.

[0050] From the perspective of improving rotational durability, the value obtained by dividing L1 by L2 (L1 / L2) can be between 10 and 1000, between 30 and 500, between 100 and 300, or between 150 and 250. If the value of L1 / L2 is within the above range, the stress generated by the torsion of the mandrel 100 is appropriately dispersed, and the rotational durability is improved.

[0051] In this embodiment, the ratio of the length LA of the reduced portion 150 to the length LB of the intermediate portion 160, LA:LB, can be in the range of 1:99 to 99:1. From the viewpoint of excellent rotational durability and bending condition, it can be in the range of 1:99 to 50:50, 1:99 to 30:70, 2:98 to 20:80, or 2:98 to 10:90.

[0052] In this embodiment, from the viewpoint of excellent rotational durability and bending condition, the volume of the middle part can be larger than the volume of the reduced part, and the ratio of the volume of the reduced part to the volume of the middle part (volume of the reduced part / volume of the middle part) can be 0.50 or more and 0.01 or less, 0.10 or more and 0.01 or less, or 0.09 or more and 0.02 or less.

[0053] As described above, according to this embodiment, the guidewire 10 includes a mandrel 100. The mandrel 100 includes a first shaft 110 and a second shaft 120. The first shaft 110 has a first front end 111 and a first base end 112 opposite to the first front end 111. The second shaft 120 has a second front end 121 and a second base end 122 opposite to the second front end 121, with the second front end 121 connected to the first base end 112. The second shaft 120 has a higher stiffness than the first shaft 110. The second shaft 120 includes a narrowing portion 150, a base portion 170, and an intermediate portion 160. The narrowing portion 150 is disposed near the second front end 121 and has a smaller cross-sectional area than the area of ​​the base end face 112S of the first shaft 110. The base portion 170 includes the second base end 122 and has a constant cross-sectional area. The intermediate portion 160 is disposed between the reduced portion 150 and the base portion 170, and has a cross-sectional area that is larger than that of the reduced portion 150 and smaller than that of the base portion 170. The cross-section 151 of the reduced portion 150 has a rotationally symmetric shape. When the sum of the length of the reduced portion 150 and the length of the intermediate portion 160 is set as L1, and the minimum length of the straight line passing through the center of rotation and connecting two points P1 and P2 on the outer periphery in the cross-section 151 of the reduced portion 150 is set as L2, the following equation (1) is satisfied.

[0054] L1≥L2×10…(1) Based on the above structure, the rotational durability of the guidewire 10 is improved.

[0055] Guide wire 10 can also satisfy the following equation (2).

[0056] L1≥L2 × 100 … (2) Based on this structure, the rotational durability of the guidewire 10 is further improved.

[0057] The cross-sectional area of ​​the middle portion 160 increases progressively from the narrowed portion 150 to the base portion 170. This structure further improves the rotational durability of the guide wire 10. Furthermore, it can suppress deformation of the bending shape when the mandrel 100 is bent.

[0058] The intermediate portion 160 includes a first increasing portion 161, a constant portion 162, and a second increasing portion 163 arranged sequentially from the second front end 121 side. The cross-sectional area of ​​the first increasing portion 161 increases as it approaches the base 170. The cross-sectional area of ​​the constant portion 162 remains constant. The cross-sectional area of ​​the second increasing portion 163 increases as it approaches the base 170. With this structure, the rotational durability of the guidewire 10 is improved. Furthermore, the design of the guidewire 10 becomes easier.

[0059] B. Second Implementation Method Reference Figure 3 The second embodiment will be described. The shape of the middle portion 160B of the guidewire 10B in this embodiment differs from that in the first embodiment. In this embodiment, the same reference numerals are used to label structures identical to those in the first embodiment, and descriptions are omitted.

[0060] The guide wire 10B has a mandrel 100B that, like the first embodiment, has a first shaft 110 and a second shaft 120B with a higher hardness than the first shaft 110.

[0061] The second shaft 120B is a narrow diameter shaft with a circular cross-section, comprising a narrowed portion 150, an intermediate portion 160B, and a base 170. The intermediate portion 160B is disposed between the narrowed portion 150 and the base 170, connecting the two. The outer diameter of the intermediate portion 160B continuously increases from the narrowed portion 150 to the base 170. That is, the cross-sectional area of ​​the intermediate portion 160B continuously increases from the narrowed portion 150 to the base 170.

[0062] Similar to the first embodiment, when the sum of the length of the reduced portion 150 and the length of the intermediate portion 160B is set as L1, and the minimum length of the straight line passing through the center of rotation and connecting two points P1 and P2 on the outer periphery in the cross section 151 of the reduced portion 150 is set as L2, L1 and L2 satisfy the following equation (1). L1 and L2 can also satisfy the following equation (2).

[0063] L1≥L2×10…(1) L1≥L2×100…(2) According to the guide wire 10B of this embodiment, similarly to the first embodiment, the rotational durability of the guide wire 10 is improved. Furthermore, deformation of the bending shape when the mandrel 100 is bent can be suppressed.

[0064] C. Third Implementation Method Reference Figure 4 The third embodiment will be described. The shapes of the reduced portion 150C and the intermediate portion 160C of the guidewire 10C in this embodiment differ from those in the first embodiment. In this embodiment, the same reference numerals are used to label structures identical to those in the first embodiment, and descriptions are omitted.

[0065] The guide wire 10C has a mandrel 100C that, like in the first embodiment, includes a first shaft 110 and a second shaft 120C with a higher hardness than the first shaft 110. The second shaft 120C is a narrow diameter with a circular cross-section and includes a tapered portion 150C, a middle portion 160C, and a base portion 170.

[0066] The reduced portion 150C is the part with the smallest cross-sectional area in the spindle 100C, which is located at the base end of the connecting portion 140. The reduced portion 150C may have a length of approximately 0.01 mm, or it may be a shape in which the length is practically invisible.

[0067] The intermediate portion 160C is disposed between the reduced portion 150C and the base portion 170 and connects the two. The outer diameter of the intermediate portion 160C increases continuously from the reduced portion 150 to the base portion 170. That is, the cross-sectional area of ​​the intermediate portion 160C increases continuously from the reduced portion 150C to the base portion 170.

[0068] Similar to the first embodiment, the sum of the lengths of the reduced portion 150C and the intermediate portion 160C is set as L1, and the minimum length of the straight line passing through the center of rotation and connecting two points on the outer periphery in the cross-section 151C of the reduced portion 150C, i.e., the diameter of the reduced portion 150C, is set as L2. L1 and L2 satisfy the following equation (1). L1 and L2 can also satisfy the following equation (2).

[0069] L1≥L2×10…(1) L1≥L2×100…(2) In the second embodiment, the ratio of the length LA of the reduced portion to the length LB of the middle portion, LA:LB, can be in the range of 1:99 to 99:1. From the viewpoint of excellent rotational durability and bending condition, it can be in the range of 1:99 to 50:50, 1:99 to 30:70, 2:98 to 20:80, or 2:98 to 10:90.

[0070] In the second embodiment, from the viewpoint of excellent rotational durability and bending condition, the volume of the intermediate part can be larger than the volume of the reduced part, and the ratio of the volume of the reduced part to the volume of the intermediate part (volume of the reduced part / volume of the intermediate part) can be 0.50 or more and 0.01 or less, 0.10 or more and 0.01 or less, or 0.09 or more and 0.02 or less.

[0071] According to the guide wire 10C of this embodiment, similarly to the first embodiment, the rotational durability of the guide wire 10 is improved. Furthermore, deformation of the bending shape when the mandrel 100 is bent can be suppressed.

[0072] D. Performance Evaluation: 1) Performance Evaluation 1 Ten mandrel samples S1 to S10 with the same shape as the second embodiment described above were manufactured, and their rotational durability and bending properties were evaluated.

[0073] The first shaft was formed using a Ni-Ti alloy with an outer diameter of 0.42 mm as the base material. The composition, by mass percent, was Ni: 56.1%, C: 0.032%, O: 0.025%, Ti: balance. The second shaft was formed using stainless steel (SUS304) with an outer diameter of 0.42 mm as the base material. Multiple mandrels were fabricated by joining the first and second shafts. For all mandrels, the first shaft was 100 mm long, the second shaft was 1900 mm long, and the total length was 2000 mm.

[0074] For these mandrels, the front end of the second shaft is ground to form a connecting part, a reduction part, and a middle part. The length of the shaping part is 1 mm, the length of the connecting part is 1 mm, the length of the reduction part is 4 mm, and the length of the middle part is shown in Table 1.

[0075] [Table 1]

[0076] Rotational durability tests were conducted using samples S1 to S10. Each sample was placed inside a U-shaped groove with a semi-circular portion having a radius of curvature of 15 mm. The joint between the first and second shafts was located at the center of the semi-circular portion of the groove, with the front end of the first shaft and the base end of the second shaft extending out of the groove. Next, with the front end of the first shaft fixed, the base end of the second shaft, located 100 mm from the groove outlet, was rotated around the central axis of the mandrel at a speed of 3000 rpm. The number of rotations until fracture was measured. Furthermore, the fracture location was observed.

[0077] As shown in Table 1 and Figure 5 As shown, it was generally confirmed that the larger the L1 / L2 value, the greater the number of rotations until fracture, and the higher the rotational durability. In particular, it was confirmed that compared with samples S1 to S4, whose L1 / L2 values ​​were less than 100, samples S5 to S10, whose L1 / L2 values ​​were greater than 100, had a significantly increased number of rotations until fracture.

[0078] Bending tests were conducted using samples S1 to S10. Two iron plates of varying thickness were prepared and fixed parallel to each other at a 30mm interval. Each sample was bent and then placed between the two iron plates. At this point, the joint between the first and second shafts was positioned at the center of the two iron plates. The bending state of the samples was visually observed. Samples that were approximately linearly symmetrical about a line drawn parallel to the two iron plates at their center were rated as A, while samples that showed slight deformation but did not exhibit a V-shaped bend were rated as B. It should be noted that, as a comparison, a sample with the same outer diameter along its second shaft as the first shaft was also tested.

[0079] In the comparative samples, a V-shaped bend was observed at the junction of the first and second axes. No V-shaped bend was observed in samples S1 to S10, which have a narrowed section and a middle section. In samples S1 to S4, where the L1 / L2 value is 10 or higher but less than 100, a slight deformation of the bend shape was observed, but not to the extent that it would hinder its use as a mandrel. Samples S5 to S10, with an L1 / L2 value of 100 or higher, exhibited approximately linearly symmetrical bending, and the bend shape was observed to be largely unbiased. Thus, without bias in the bend shape of the mandrel, the guidewire can be smoothly bent within the lumen of a biological organism.

[0080] Next, a sample S11 with a mandrel having the same shape as the first embodiment described above was manufactured, and its rotational durability was evaluated.

[0081] 2) Performance Evaluation 2 Samples S11 to S16, having the same shape as the first embodiment described above, were prepared, and their rotational durability and bending properties were evaluated.

[0082] The first shaft was formed using a Ni-Ti alloy with an outer diameter of 0.34 mm as the base material. The composition, by mass percent, was Ni: 56.1%, C: 0.032%, O: 0.025%, Ti: balance. The second shaft was formed using stainless steel with an outer diameter of 0.34 mm as the base material. Multiple mandrels were fabricated by joining the first and second shafts. For all mandrels, the first shaft was 100 mm long, the second shaft was 1900 mm long, and the total length was 2000 mm.

[0083] For these mandrels, the front end of the second shaft is ground to form a connecting portion, a reduction portion, and an intermediate portion having a first increasing portion, a constant portion, and a second increasing portion. The length of the shaping portion is 1 mm, the length of the connecting portion is 1 mm, the length of the reduction portion is 4 mm, the length of the first increasing portion is 5 mm, the length of the second increasing portion is 5 mm, and the length of the constant portion and the overall length of the intermediate portion are shown in Table 2.

[0084] [Table 2]

[0085] Using these samples S11 to S16, rotational durability tests were conducted in the same manner as in performance evaluation 1. See Table 2 and... Figure 6 As shown, it was generally confirmed that the larger the L1 / L2 value, the greater the number of rotations until fracture, and the higher the rotational durability. In particular, it was confirmed that compared with sample S11, which had an L1 / L2 value of less than 100, samples S12 to S16, with an L1 / L2 value of 100 or more, showed a significant increase in the number of rotations until fracture. Furthermore, it was confirmed that samples S11 to S16 all fractured at the narrowed portion, rather than at the joint.

[0086] Using samples S11 to S16, the bendability test was performed in the same manner as in performance evaluation 1. No V-shaped bends were observed in samples S11 to S16. In sample S11, with an L1 / L2 value of 10 or higher but less than 100, a slight deformation of the bend shape was observed. Samples S12 to S16, with an L1 / L2 value of 100 or higher, exhibited approximately linearly symmetrical bends, with virtually no deviation in the bend shape. Thus, without deviation in the mandrel's bend shape, the guidewire can bend smoothly within the lumen of a biological organism.

[0087] E. Variation example: The technology disclosed in this specification is not limited to the above-described embodiments. It can be modified into various forms without departing from its spirit. For example, the following modifications can also be made.

[0088] (1) The cross-section of the reduced part can be rotationally symmetric, such as ellipse, ellipse (flat ellipse), rectangle, rhombus, regular polygon. Regular polygons include equilateral triangle, square, regular pentagon, regular hexagon, regular heptagon, regular octagon, regular nonagon, regular decagon, etc.

[0089] (2) The second shaft may not have a shaping part. The second shaft may not have a connecting part. The second shaft may have neither a shaping part nor a connecting part.

[0090] (3) The middle part may not have the extension part connecting the shrinking part and the constant part, and the constant part may be adjacent to the shrinking part. Alternatively, the middle part may not have the extension part connecting the shrinking part and the base, and the constant part may be adjacent to the base.

[0091] (4) The middle part may also have more than two constant parts. In this case, the cross-sectional area of ​​the constant part closer to the base may be larger than the cross-sectional area of ​​the constant part farther from the base. In addition, two adjacent constant parts may be connected by an increasing part whose cross-sectional area increases as it gets closer to the base.

[0092] (5) The base may not include the base end of the second shaft, and the second shaft may include a portion with a different cross-sectional area than the base between the base and the base end. For example, the base end side of the base may also include a portion with a smaller outer diameter and cross-sectional area than the base.

Claims

1. A guidewire (10, 10B, 10C) comprising a mandrel (100, 100B, 100C), The mandrels (100, 100B, 100C) have: A first shaft (110) has a first front end (111) and a first base end (112) opposite to the first front end (111); The second shaft (120, 120B, 120C) has a second front end (121) connected to the first base end (112) and has a higher hardness than the first shaft (110). The second shaft (120, 120B, 120C) has: The reduced portion (150, 150C), which is disposed near the second front end (121), has a cross-sectional area smaller than that of the base end face (112S) of the first shaft (110); The base (170), which is located further away from the first base end (112) than the reduced portion (150, 150C), has a constant cross-sectional area that is larger than the cross-sectional area of ​​the reduced portion (150, 150C); The intermediate portion (160, 160B, 160C), disposed between the reduced portion (150, 150C) and the base portion (170), has a cross-sectional area larger than that of the reduced portion (150, 150C) and smaller than that of the base portion (170). The cross-sections (151, 151C) of the reduced portion (150, 150C) have a rotationally symmetric shape. When the sum of the lengths of the reduced portion (150, 150C) and the intermediate portion (160, 160B, 160C) is set as L1, and the minimum length of the straight line passing through the center of rotation and connecting two points (P1, P2) on the outer periphery in the cross-section (151, 151C) of the reduced portion (150, 150C) is set as L2, the following equation (1) is satisfied. L1≥L2×10…(1).

2. The guidewire (10, 10B, 10C) according to claim 1 satisfies the following formula (2), L1≥L2×100…(2).

3. The guidewire (10) according to claim 1 or 2, wherein, The cross-sectional area of ​​the middle portion (160) increases in stages from the narrowed portion (150) to the base portion (170).

4. The guidewire (10) according to claim 3, wherein, The middle portion (160) includes a first increasing portion (161), a constant portion (162), and a second increasing portion (163) arranged sequentially from the second front end (121) side. The cross-sectional area of ​​the first increasing portion (161) increases as it approaches the base portion (170). The cross-section of the constant part (162) is constant. The cross-sectional area of ​​the second increasing portion (163) increases as it approaches the base portion (170).

5. The guidewire (10B, 10C) according to claim 1 or 2, wherein, The cross-sectional area of ​​the intermediate portion (160B, 160C) increases continuously from the reduced portion (150, 150C) to the base portion (170).

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