Medical pt alloy and medical member formed from medical pt alloy

Abstract

The present invention relates to a medical Pt alloy formed from a Pt alloy containing Pt as a main component. The Pt alloy according to the present invention is a medical Pt alloy comprising a PtRe alloy containing 6.5-16.64 at% of Re with the balance being Pt and inevitable impurities. The medical Pt alloy of the present invention has biocompatibility and X-ray visibility and also has good mechanical properties and workability. The medical Pt alloy of the present invention is formed into a medical member in the form of a Pt alloy wire rod or another form and then applied to medical devices such as embolization coils, guide wires, stents, and catheters.

Description

Medical-grade Pt alloy and medical components made from said medical-grade Pt alloy

[0001] This invention relates to medical-grade Pt alloys that constitute components of various medical devices. In particular, it relates to medical-grade Pt alloys that have superior mechanical properties compared to conventional medical-grade Pt alloys, as well as good biocompatibility, X-ray visibility, and processability.

[0002] Medical materials that make up medical devices such as embolization coils, guidewires, stents, and catheters require various properties, including mechanical properties such as strength and springiness, chemical stability to ensure biocompatibility, and processability. For example, embolization coils are medical devices that are placed inside blood vessels to prevent the rupture of cerebral aneurysms in the treatment of cerebrovascular disorders such as subarachnoid hemorrhage. Guidewires are medical devices used to guide catheters during catheter treatment, and stents are medical devices that expand tubular parts such as blood vessels from the inside of the lumen. The medical materials that make up these medical devices require high strength (tensile strength) and springiness (elastic limit and elastic elongation limit) so that they can withstand the stress received from pulsating blood vessels and move while repeatedly deforming within curved blood vessels.

[0003] Furthermore, since the medical devices mentioned above come into direct contact with the human body and are sometimes implanted within it, biocompatibility is required for the medical materials used. In addition, since embolization coils and guide wires are manufactured by coiling or twisting extremely thin metal wires, processability must also be considered when selecting their constituent materials.

[0004] As medical materials being considered for application to various medical devices, various alloys such as stainless steel, Ni-Ti alloy, Pt alloy, Pd alloy, etc. are known, and currently stainless steel and Ni-Ti alloy are widely used in actual applications. Also, research on various alloys as medical materials is progressing. For example, Patent Document 1 describes a wire for medical devices made of a Pt alloy of a ternary or higher system of the Pt-Ni system. In this prior art, it is a Pt alloy containing 18 to 27% by mass of Ni in Pt and a total of 2 to 7.0% by mass of additive elements (at least one or more of Ir, Pd, Rh, Ru, Nb, Mo, Re, W, and Ta). Also, Patent Document 2 discloses a medical alloy made of a Pd-based alloy. This prior art clarifies the applicability of a Pd-based multi-component alloy obtained by adding at least one or more of B, Re, Ru, Ir, Pt, W, Au, Zr, Co, Ni, and Ta to Pd to a medical alloy.

[0005] Japanese Patent Application Laid-Open No. 2022-501502, Japanese Patent Application Laid-Open No. 2008-500452

[0006] Among the above-mentioned conventional medical materials, stainless steel and Ni-Ti alloy with usage records have good mechanical properties such as tensile strength and corrosion resistance, but since they are composed of relatively light (low atomic weight) metal elements such as Fe, Cr, Ni, etc., they have insufficient X-ray visibility. In the above-mentioned medical device-based diagnosis and treatment methods, it is usually necessary to confirm the position of the device while performing X-ray imaging. In particular, for medical devices composed of extremely thin wires, a metal material having X-ray visibility is preferable to avoid overlooking.

[0007] On the other hand, the Pt-Ni-based multi-component alloy and Pd-based alloy of Patent Documents 1 and 2 have good X-ray visibility, but there is room for improvement in mechanical properties. Since medical materials are used in the human body, any deviation in behavior or unexpected breakage / fracture during use must be avoided. For that purpose, the pursuit of higher mechanical properties is required. Also, improvement from the perspective of biocompatibility is necessary for medical materials, and it is also required to ensure chemical stability and not contain elements that induce metal allergies.

[0008] Furthermore, wires made from medical alloys are often incorporated into medical devices after processes such as coiling and twisting, and heat treatment is sometimes performed to provide shape stability during incorporation. Therefore, it is desirable that medical alloys not only have excellent mechanical properties as described above, but also maintain their mechanical properties even after undergoing the aforementioned heat treatment.

[0009] This invention was made against the background described above, and provides an alloy for medical devices that possesses biocompatibility and X-ray visibility, while having better mechanical properties than the prior art and also having good processability. Furthermore, it provides medical components to which these improved medical alloys are applied.

[0010] The inventors decided to develop a medical alloy based on a Pt alloy, in which Pt is the main component, as a solution to the above-mentioned problems. Pt is a metallic element with a large atomic weight, has good X-ray visibility, and is also extremely biocompatible. Therefore, by applying an alloy in which Pt is the main component, these properties can be ensured.

[0011] The inventors decided to apply solid solution strengthening as a means to improve the mechanical properties of Pt alloys. A challenge for the inventors is to obtain an alloy that enhances mechanical properties while minimizing the effects of heat treatment. Besides solid solution strengthening, other known strengthening mechanisms for metals and alloys include precipitation strengthening (aging strengthening) and microstructure adjustment such as grain refinement. However, precipitation strengthening can lead to changes in the precipitates and microstructure due to heat treatment. Unlike precipitation strengthening, solid solution strengthening strengthens the matrix itself through alloying, and therefore is considered to have less impact on the microstructure and mechanical properties due to heat treatment.

[0012] However, the strengthening effect due to solid solution strengthening usually increases with increasing content of added elements. As stated above, in the present invention, the Pt content is increased to ensure X-ray visibility, etc. Applying solid solution strengthening as a strengthening mechanism would contradict this policy.

[0013] Therefore, we decided to investigate an additive element suitable for solid solution strengthening of Pt alloys that improves mechanical properties with a small amount of addition. As a result, we determined that Re (rhenium) is the optimal additive element, and by identifying a Re content that can solve the above-mentioned problems, we arrived at the present invention.

[0014] In other words, the present invention is a medical-grade Pt alloy comprising a PtRe alloy containing 6.5 atomic% to 16.64 atomic% of Re, with the remainder being Pt and unavoidable impurities. The composition of the medical-grade Pt alloy according to the present invention, various medical components made from this medical-grade Pt alloy, and their uses will be described in detail below.

[0015] I. Composition and Properties of the Medical Pt Alloy According to the Present Invention As described above, the medical Pt alloy according to the present invention is composed of a Pt alloy to which a predetermined amount of Re is added as an additive element. Furthermore, the Pt alloy according to the present invention has suitable mechanical properties due to solid solution strengthening as its strengthening mechanism.

[0016] A. Composition of the medical-grade Pt alloy according to the present invention The essential constituent elements of the Pt alloy constituting the present invention are Pt and Re. The function of each constituent element and their content are as follows.

[0017] A-1. Re Re, an essential additive element in the Pt alloy of the present invention, is a metallic element with particularly high hardness and high elastic modulus among metallic elements, and contributes to improving the mechanical properties such as hardness and tensile strength of the Pt alloy by solid solution in Pt. In particular, the basic policy of the present invention is to increase the Pt content of the Pt alloy, and Re can impart suitable mechanical properties to the Pt alloy with the addition of a relatively small amount. Furthermore, Re is a metallic element with a relatively high mass, similar to Pt (atomic weight: 186.2). Therefore, it can also contribute to ensuring X-ray visibility when used as a Pt alloy. Moreover, Re does not easily form intermetallic compounds with other metals such as Pt. Therefore, the PtRe alloy can be strengthened by solid solution strengthening without forming different phases that may impair the stability of its mechanical properties.

[0018] The Re content of the PtRe alloy used in the present invention is 6.5 atomic% to 16.64 atomic%. Below 6.5 atomic% the material strengthening by solid solution strengthening is insufficient. On the other hand, as the Re content increases, the tensile strength of the PtRe alloy increases, but PtRe alloys with an Re content exceeding 16.64 atomic% become excessively hard and their workability decreases. This decrease in workability makes it difficult to process the alloy into wires of the dimensions required for various medical devices. The Re content of the Pt alloy of the present invention is preferably 10.43 atomic% to 14.57 atomic%, and more preferably 11.46 atomic% to 13.54 atomic%.

[0019] A-2. Pt In the Pt alloy according to the present invention, Pt is the main constituent metal element of the alloy. As can be seen from the range of Re content described above, the Pt content of the Pt alloy of the present invention is 83.36 atomic percent or more. In the present invention, the X-ray visibility and biocompatibility of the Pt alloy are ensured by increasing the Pt content.

[0020] A-3. Inevitable Impurities The Pt alloy according to the present invention is substantially composed of Pt and Re. However, the inclusion of unavoidable impurities is permitted. Unavoidable impurities may include Mg, Al, Si, Ca, Cr, Fe, Ni, Cu, and Sn. The total amount of these impurities is preferably 0.5% by mass or less, and more preferably 0.2% by mass or less.

[0021] The method for measuring the concentrations of Re and unavoidable impurities in the Pt alloy according to the present invention, as described above, is not particularly limited. Inductively coupled emission spectrometry (ICP) and inductively coupled plasma mass spectrometry (ICP-MS) are preferred methods for measuring the concentrations of each element. In ICP, the Pt alloy is broken into small pieces as needed, and the solution liquefied with hydrofluoric acid is analyzed using an analytical instrument. ICP is a suitable analytical method when the analyte is in the state of wire or medical component before being incorporated into a medical device, or when it is in a state where it can be extracted as an analytical sample even after being incorporated into a medical device. Other analytical methods that can be applied include instrumental analysis methods such as X-ray fluorescence analysis (XRF), energy-dispersive X-ray analysis (EDX), and wavelength-dispersive X-ray analysis (WDX). Instrumental analysis methods are useful when the analyte is incorporated into a medical device and difficult to separate.

[0022] B. Medical components made of medical-grade Pt alloy according to the present invention. The medical-grade Pt alloy according to the present invention has good processability and can be processed into various types of medical components to construct medical devices.

[0023] B-1. Medical-grade Pt alloy wire The Pt alloy according to the present invention can preferably be made into a Pt alloy wire. Pt alloy wire is a particularly effective use of the Pt alloy according to the present invention, and can be used as a constituent material for medical components such as coils, which will be described later, and the wire itself may also be applied to medical devices. In the Pt alloy wire according to the present invention, the wire diameter is preferably 10 μm or more and 100 μm or less. In medical devices such as embolization coils and guide wires, metal wires with wire diameters within the above range are often used. The cross-sectional shape of the wire is not limited to a perfect circle, and may be elliptical or rectangular. When the cross-sectional shape of the wire is other than a perfect circle, the wire diameter shall be the maximum diameter.

[0024] Furthermore, the Pt alloy wire according to the present invention exhibits excellent mechanical properties as a medical material due to the action of Re, the alloying element described above. Mechanical properties required for medical materials include tensile strength (UTS), elongation at break, elastic limit, and elastic limit elongation, which are measured by tensile testing. The mechanical properties of the Pt alloy wire according to the present invention change depending on the heat treatment during the manufacturing process and the resulting wire diameter, and are specifically explained below.

[0025] B-1-1. Tensile Strength Tensile strength is the maximum stress until the material breaks under tensile load, and in this invention, ultimate tensile strength (UTS) is applied. Tensile strength is related to the resistance to breakage when secondary processing such as coiling, stranding, and bending is performed on the Pt alloy wire according to the present invention. Furthermore, improving tensile strength contributes to improving the processing yield during the aforementioned processing. In addition, tensile strength is related to the durability when the Pt alloy wire is applied to various medical devices. For these reasons, tensile strength is a particularly important mechanical property for the Pt alloy wire according to the present invention.

[0026] The tensile strength (UTS) of Pt alloy wire is preferably 1000 MPa or higher. More preferably, the tensile strength of Pt alloy wire is 1500 MPa to 2000 MPa. Furthermore, the upper limit of the tensile strength is preferably 3500 MPa or lower. Wire with excessively high tensile strength may affect its workability.

[0027] B-1-2. Elongation at Break Elongation at break is the elongation rate when material fracture occurs under tensile load, and, like tensile strength, is related to the resistance to fracture and processing yield when processing Pt alloy wire. The Pt alloy wire according to the present invention preferably has an elongation at break of 1.5% or more. Furthermore, the upper limit of the elongation at break is preferably 10% or less. The elongation at break of the Pt alloy wire is more preferably 2% or more and 10% or less.

[0028] B-1-3. Elastic Limit The elastic limit is the stress at which elastic deformation occurs without permanent strain, and is related to springiness. As described above, medical devices such as guide wires are often used under intermittent stress in curved paths, and it is required that their dimensional accuracy does not deviate. Therefore, a high elastic limit and excellent springiness are preferable. The elastic limit of Pt alloy wire is preferably 700 MPa or higher, and more preferably 1000 MPa or higher. However, since wires with excessively high elastic limits may result in devices lacking flexibility, the elastic limit of Pt alloy wire is preferably 2500 MPa or lower.

[0029] B-1-4. Elastic elongation Elastic elongation refers to the amount of deformation that can occur within the elastic deformation range and is a characteristic related to the applicability of wire materials to various medical devices. The higher the elastic elongation, the better it can follow the complex curved shapes of blood vessels, etc., and the larger the amount of deformation that can be returned to its original shape, thus expanding the range of applications to medical devices. The elastic elongation of Pt alloy wire is preferably 0.40% or more, and more preferably 0.5% or more. The upper limit of the elastic elongation is preferably 1.0% or less.

[0030] B-1-5. Young's Modulus In addition to the above, Young's modulus is a general indicator of the mechanical properties of metallic materials. The Young's modulus of the Pt alloy wire according to the present invention is preferably 140 GPa or higher, and more preferably 150 GPa or higher. The upper limit of Young's modulus is preferably 170 GPa or lower. The Young's modulus can also be adjusted within the above range before and after aging heat treatment.

[0031] The various mechanical properties described above can be measured by tensile testing of Pt alloy wire. The tensile testing method can be the same as that used for tensile testing of metal wire (for example, tensile testing in accordance with JIS Z 2241 "Tensile Testing Method for Metallic Materials").

[0032] B-2. Pt alloy coils or Pt alloy stranded wires Coils and stranded wires made by coiling or twisting wires made from wires of medical alloys are important medical components that constitute medical devices. The Pt alloy wire according to the present invention is capable of secondary processing and can be made into Pt alloy coils or Pt alloy stranded wires by coiling or twisting. Specifically, Pt alloy stranded wires that will become medical components can be manufactured by twisting together multiple Pt alloy wires. Furthermore, Pt alloy coils for medical devices can be manufactured by coiling single wires or one or more Pt alloy stranded wires. In addition, in such coiling or twisting processes, coils or stranded wires may be made by combining them with wires of materials other than the Pt alloy wire according to the present invention.

[0033] Coils and stranded wires used as medical components are microscopic components manufactured by processing Pt alloy wires with the minute wire diameters described above, for purposes such as movement within the blood vessels of the human body. Considering the wire diameter of the Pt alloy wires described above, the processing rate of coiling using this coil index can be said to be high. The Pt alloy coils and Pt alloy stranded wires according to the present invention remain in a desirable state without surface cracks, etc., even after undergoing such heavy processing.

[0034] B-3. ​​Other Forms of Medical Components The Pt alloy according to the present invention can be used to form medical components in forms other than the wires, coils, and stranded wires described above. For example, pipes or rods. There are no restrictions on the dimensions and shape (cross-sectional shape) of such medical components. These forms of medical components can also acquire the various mechanical properties described above through appropriate processing and heat treatment.

[0035] B-4. Influence of Heat Treatment on Mechanical Properties The preferred mechanical properties of the medical Pt alloy wire and various medical components according to the present invention remain stable even after heat treatment. Here, "heat-treated" refers to a state in which the processed wire or wire after secondary or subsequent processing, such as a coil, has been heated to a temperature between 300°C and 1000°C. Furthermore, "slight variation in mechanical properties" means that the variation before and after heat treatment is within ±20%.

[0036] C. Medical devices equipped with various medical components according to the present invention The medical components made of Pt alloy according to the present invention described above can be components of various medical devices. For example, Pt alloy coils and Pt alloy strands can constitute part or all of medical devices such as embolization coils, guide wires, catheters, and stents. Embolization coils are generally in the shape of a secondary coil. Embolization coils are formed by further coiling the Pt alloy coil of the present invention. Guide wires (spring wires) are manufactured by joining a hollow member (for example, in the shape of a coil) obtained by processing the Pt alloy wire or Pt alloy strand of the present invention with a core (core material) made of an appropriate material. Alternatively, a guide wire may be formed by joining a guide wire core using the Pt alloy wire or Pt alloy strand of the present invention with a hollow member made of an appropriate material. A catheter may have a tube made of resin or the like, and a marker in which the Pt alloy wire or Pt alloy strand of the present invention is wound around the outer circumference of the tube. The embolization coil and guide wire according to the present invention can function stably without being easily damaged, thanks to the favorable mechanical properties of the Pt alloy wire.

[0037] Furthermore, medical components other than Pt alloy wires, Pt alloy coils, and Pt alloy stranded wires can be used as markers for catheters, etc., or as medical devices such as stents. When using medical components made of Pt alloy according to the present invention as medical devices, they can be combined with medical components made of other materials.

[0038] Furthermore, when the Pt alloy according to the present invention is processed into a coil shape or the like and incorporated into a medical device, it is not easy to measure its tensile strength, etc. Therefore, as a simple method for estimating the tensile strength of the Pt alloy constituting the coil, etc., measurement of Vickers hardness is recommended. Since Vickers hardness can be measured with relatively small samples, it can be applied to coils, etc. incorporated into medical devices. Moreover, although there is no perfect agreement between tensile strength and hardness, there is a certain degree of correlation, so it is possible to estimate whether the Pt alloy has the tensile strength described above by measuring its hardness.

[0039] Herein, the Pt alloy according to the present invention having the tensile strength described above has a Vickers hardness of 300 Hv to 600 Hv. Vickers hardness can generally be measured using a Vickers hardness tester or a micro-Vickers hardness tester under known conditions. For example, it can be measured using a method conforming to JIS Z 2244 "Vickers hardness test - Test method".

[0040] II. Method for Manufacturing Medical Pt Alloy and Various Medical Components According to the Present Invention The Pt alloy according to the present invention can be manufactured by obtaining a Pt alloy ingot by general melting and casting. The Pt alloy ingot can be manufactured by mixing Pt and the additive element Re to the above-mentioned composition and casting it by arc melting, vacuum melting, etc. The shape of this alloy ingot is not particularly limited and can be rod-shaped, plate-shaped, etc.

[0041] And a medical member can be obtained by plastically processing (cold working) a Pt alloy ingot. Hot working may be performed between the production of the Pt alloy ingot and the plastic processing. The hot working process is a process for destroying the cast structure of the alloy ingot. Also, by the hot working process, the cross-sectional area of the alloy ingot can be reduced to a thick wire suitable for cold working. In the hot working process, hot swaging, hot forging, and hot rolling (hot grooving rolling) are performed. These hot working processes may be performed multiple times. The processing temperature in the hot working process is preferably 600°C or higher and 1500°C or lower.

[0042] Also, when performing hot working in the present invention, it is preferable to perform hot working with a cross-sectional reduction rate of 50% or more before and after processing. This is to further homogenize the material structure in addition to destroying the cast structure. The workability in cold working can be improved.

[0043] The Pt alloy ingot that has been hot worked as needed becomes a medical member of a desired size through a cold working process. In the cold working process, cold rolling (cold grooving rolling), cold wire drawing, cold drawing, cold extrusion, etc. are performed. These cold working processes may be combined and cold working may be performed multiple times. The processing temperature in the cold working process is preferably room temperature or higher and 100°C or lower.

[0044] In the processing of the Pt alloy wire, in order to obtain the target wire diameter, the cold working process can be performed multiple times. The processing rate in one cold working process is preferably 5% or more and 25% or less. Also, an annealing treatment may be performed between cold working processes to ensure workability. The temperature of the annealing treatment is preferably 700°C or higher and 1300°C or lower. By going through the above cold working process, a Pt alloy wire of the target wire diameter can be obtained.

[0045] Regarding the production of medical members other than the Pt alloy wire, for the Pt alloy coil and the Pt alloy stranded wire, coiling processing and stranding processing are performed as described above. Also, for other forms of medical members, they are processed until they have the desired shape and dimensions by the above plastic processing, cutting processing, grinding processing, etc.

[0046] As described above, the medical alloy according to the present invention is composed of a Pt alloy having a high Pt content with Re as an additive element, and its mechanical properties are improved. Furthermore, by using a high-Pt alloy, X-ray visibility and biocompatibility are also good. And the medical member made of the Pt alloy according to the present invention exhibits suitable properties as a constituent member of medical instruments such as embolization coils, guide wires, stents, catheters, etc.

[0047] Schematic side view showing one embodiment of the guide wire of the present invention. Schematic side view showing another embodiment of the guide wire of the present invention.

[0048] First Embodiment: Hereinafter, embodiments of the present invention will be described. In this embodiment, PtRe alloys having different Re contents in Pt were produced. Then, the Pt alloy ingot was processed into a Pt alloy wire, and its mechanical properties were measured.

[0049] [Production of Pt Alloy] Prepare Pt ingots (purity 99.98% by mass) and Re ingots (purity 99.9% by mass), weigh and mix them to obtain various compositions, and produce a master alloy by arc melting. This master alloy was vacuum melted to produce round bar-shaped Pt alloy ingots (diameter 10 to 15 mm).

[0050] [Processing into Pt Alloy Wire] The rod-shaped Pt alloy ingot produced above was processed into a thick wire in a hot working process. In the hot working process, the rod-shaped Pt alloy ingot was heated at 900 to 1500°C for 10 to 15 minutes, and then formed into a thick wire with a wire diameter of 5 to 7.5 mm by hot swaging (total reduction ratio of cross-sectional area of 50% or more). The thick wire produced in this hot working process was subjected to cold grooving rolling and cold wire drawing at room temperature and processed to φ1.0 mm. After the wire production, samples of various lengths for measurement and evaluation were cut out.

[0051] For the various Pt alloy wires produced above, the workability evaluation, tensile strength (UTS), elastic limit, elongation at break, and elastic limit elongation were measured. In the workability evaluation, those that could be processed into a wire (wire diameter 1 mm) without breakage and surface cracking during the above-mentioned multiple cold working processes were judged as qualified for workability (○). And when cracks or breakage occurred, it was judged as unqualified for workability (×). For the Pt alloy wires that were unqualified for processing, the subsequent tensile test, which is an evaluation test, was not performed.

[0052] For the tensile test, a 150 mm length of wire was cut as a measurement sample and tested using a tensile testing machine (Autograph AGS-X, Shimadzu Corporation). The test conditions were a gauge length of 100 mm and a crosshead speed of 10 mm / min.

[0053] Table 1 shows the evaluation results of the processability and mechanical properties of the Pt alloy wires manufactured in this embodiment. The composition of each Pt alloy wire listed in Table 1 is based on the amount of each element added when the Pt alloy was melted and cast, and this composition was consistent with the composition obtained by ICP analysis of the Pt alloy wires. In this embodiment, the mechanical properties of metal wires that constitute embolization coils and guide wires currently used in medical settings were referenced, and each Pt alloy wire was evaluated with the following acceptance criteria: tensile strength: 1000 MPa or more, elastic limit: 550 MPa or more, elongation at break: 1% or more, elastic limit elongation: 0.45% or more, and Young's modulus: 110 GPa or more.

[0054]

[0055] Table 1 shows that Pt alloy wires made from PtRe alloy exceed the acceptable standards in tensile strength, elastic limit, elongation at break, and elongation at elastic limit in the processed state when the Re content is 6.5 atomic percent or more (No. 2 to No. 6). Furthermore, the tensile strength and elastic limit of Pt alloy wires made from PtRe alloy increase with increasing Re content. However, excessive addition of Re reduces the processability of the PtRe alloy and causes wire breakage during the processing stage (No. 7 to No. 9). While increasing the Re content contributes to improving the tensile strength of PtRe alloy wires, it was confirmed that there is an upper limit to the amount of Re that can be added from the perspective of processability.

[0056] Furthermore, it can be confirmed that PtRe alloy wires exhibit little change in mechanical properties due to heat treatment. In addition to the small decrease in tensile strength due to heat treatment, the PtRe alloy wires of this embodiment also show a small decrease in the elastic limit (less than 20%). The PtRe alloy wires also maintain favorable properties after heat treatment in terms of elongation at break and elongation at the elastic limit. Looking at elongation at break, the PtRe alloy wires show a significant increase after heat treatment at 300°C. The fact that elongation increases significantly even with relatively low-temperature heat treatment can be said to be a favorable characteristic of PtRe alloy wires.

[0057] Second Embodiment: In this embodiment and the following third embodiment, an embodiment of a guide wire will be described as an example of a medical device to which the medical Pt alloy of the present invention is applied. The guide wire according to the present invention can be composed of a Pt alloy wire or Pt alloy stranded body made by processing a Pt alloy wire and a core (core shaft) made of appropriate constituent materials. In this case, the guide wire has a core shaft, a Pt alloy coil or Pt alloy stranded body provided on the outer circumference of the core shaft, and a tip fixing portion disposed at the tip of the core shaft. The core shaft may be straight or may have a tapered portion. When the core shaft has a tapered portion, the Pt alloy coil may be arranged so as to cover the tapered portion.

[0058] Figure 1 is a schematic side view showing one embodiment of the guide wire of the present invention. The guide wire 10 of this embodiment is composed of a core shaft 11, a Pt alloy coil 12, and a tip fixing portion 13.

[0059] The core shaft 11 has a tapered section 14 that gradually decreases in diameter towards the tip, and equal-diameter sections 15a and 15b. The dimensions of the core shaft 11 in the longitudinal direction are typically 1,800 to 3,000 mm in total length and 1 mm to 3 mm in tapered section 14. The outer diameter of the core shaft 11 is typically 0.25 mm to 0.46 mm. Examples of materials used to construct the core shaft 11 include stainless steel and superelastic alloys such as Ni-Ti alloy. The diameter of the Pt alloy wire that constitutes the Pt alloy coil 12 is typically 0.01 to 0.10 mm.

[0060] The tip fixing portion 13 is the part where the tip of the core shaft 11 and the tip of the Pt alloy coil 12 are fixed together, and is formed from brazing material or the like. The rear end of the Pt alloy coil 12 is fixed to the core shaft 11.

[0061] Third Embodiment: Figure 2 shows a schematic side view illustrating another embodiment of the guide wire of the present invention. The guide wire 20 of this embodiment is composed of a core shaft 21, a Pt alloy coil 22, and a tip fixing portion 23. The core shaft 21 has tapered portions 24a, 24b, 24c, and 24d that gradually decrease in diameter toward the tip, and equal-diameter portions 25a, 25b, and 25c. The guide wire 20 of this embodiment also has a stranded body 26 that covers the equal-diameter portion 25c and a part of the tapered portion 24d. As the stranded body 26, a stranded body made of stainless steel such as SUS316 can be used. Alternatively, a stranded body made of a superelastic alloy such as Ni-Ti alloy, or a radiopaque metal such as platinum or tungsten may be used. Furthermore, a stranded body of Pt alloy according to the present invention may be used.

[0062] The Pt alloy for medical use according to the present invention has desirable mechanical properties and good processability. The Pt alloy for medical use according to the present invention is useful as a component material for various medical devices. Medical components made of the Pt alloy according to the present invention are particularly expected to be applied to medical devices such as embolization coils, guide wires, stents, and catheters. Explanation of symbols

[0063] 10, 20 Guide wire 11, 21 Core shaft 12, 22 Pt alloy coil 13, 23 Tip fixing part 14, 24a, 24b, 24c, 24d Tapered part 15a, 15b, 25a, 25b, 25c Equal diameter part 26 Stranded wire

Claims

1. A medical-grade Pt alloy consisting of a PtRe alloy containing 6.5 atomic% to 16.64 atomic% of Re, with the remainder being Pt and unavoidable impurities.

2. A medical Pt alloy wire made of the medical Pt alloy described in claim 1.

3. A medical component comprising a Pt alloy coil formed by coiling the medical Pt alloy wire described in claim 2, or a Pt alloy stranded wire body formed by twisting the medical Pt alloy wire.

4. A pipe-shaped or rod-shaped medical component made of medical-grade Pt alloy as described in claim 1.

5. A medical device comprising a Pt alloy wire as described in claim 2, or at least one of the medical components described in claim 3 or claim 4, wherein the medical device is an embolization coil, a guide wire, a stent, or a catheter.

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