Medical guide wire

A medical guide wire which has a core wire having a distal end-side small-diameter portion and a proximal end-side large-diameter portion having a larger outside diameter than the outside diameter of the distal end-side small-diameter portion, and a coil spring installed on an outer periphery of the distal end-side small-diameter portion of the core wire along an axial direction and fixed to the core wire at at least the front end portion and rear end portion thereof. The outside diameter of the proximal end-side large-diameter portion of the core wire and the outside diameter of coil of the coil spring are each at most 0.012 inch. The front end portion of the coil spring is fixed to the core wire by gold-containing solder. The length of a distal end portion stiffened by the gold-containing solder is 0.1 to 0.5 mm. The medical guide wire is high in fixing strength of the coil spring to the core wire and can shorten a shaping length compared with a conventional medical guide wire.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a United States national phase application of International Application PCT/JP2010/051859 filed Feb. 9, 2010.

TECHNICAL FIELD

The present invention relates to a medical guide wire having a coil spring installed on an outer periphery of a distal end-side small-diameter portion of a core wire, and more particularly to a medical guide wire which is high in fixing strength of a coil spring to a core wire, can more shorten a shaping length in a shaping operation at a distal end portion than a conventional one and is excellent in operability within a micro-channel of CTO lesion.

BACKGROUND ART

A guide wire for guiding a medical instrument such as a catheter to a predetermined position in a body cavity such as a blood vessel is required to have flexibility at its distal end portion.

Therefore, there is known a guide wire in which the outside diameter of an distal end portion of a core wire is made smaller than that of its proximal end portion, and a coil spring is installed on an outer periphery of the distal end portion (distal end-side small-diameter portion) of the core wire, thereby intending to improve the flexibility of the distal end portion (see, for example, Patent Literature 1).

In order to install the coil spring on the outer periphery of the distal end-side small-diameter portion of the core wire, both front end portion and rear end portion of the coil spring are generally fixed to the core wire by solder.

Here, Ag—Sn solder is used as the solder for fixing both front end portion and rear end portion of the coil spring to the core wire because of its low melting point and easy handling.

The solder penetrated into the interior of the coil at both front end portion and rear end portion of the coil spring comes into contact with the outer peripheral surface of the core wire, whereby the coil spring is fixed to the core wire.

In addition, a distal end tip is formed by any other solder than the solder penetrated into the interior of the coil at the front end portion of the coil spring.

In order to ensure the fixing ability of the coil spring to the core wire, however, it is necessary to sufficiently penetrate the solder into the interior of the coil at the front end portion of the coil spring, which is fixed to a distal end portion of the core wire, which has a minimum outside diameter. Specifically, it is necessary to penetrate the solder (Ag—Sn solder) into the interior of the coil in a range corresponding to about 6 pitches to about 8 pitches of the coil spring.

A portion (including the distal end tip formed by the solder) stiffened by the solder filled into the interior of the coil is formed at the distal end portion of the guide wire produced in this manner.

The length (length correspond to the distal end tip and about 6 pitches to about 8 pitches of the coil) of this distal-end stiff portion is about 0.8 to 1.1 mm.

In order to achieve low invasiveness in a patient, it has been recently desired to miniaturize medical instruments.

With this desire, there has been a demand for making the diameter of a guide wire small, and so the present inventors have come to develop a guide wire having a smaller wire diameter (0.010 inch) than that (0.014 inch) of a conventional one.

The guide wire of 0.010 inch can greatly contribute to the miniaturization of medical instruments such as catheters.

In addition, this guide wire is also good in operability upon accessing, for example, a micro-channel in CTO (chronic total occlusion) lesion.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

The guide wire inserted into the micro-channel in the CTO lesion is required to more improve the operability. For example, it is desired to reduce a frictional resistance upon operation within the micro-channel. However, there is a limit to the reduction of the frictional resistance by making the wire diameter of the guide wire small.

By the way, an operator shapes (shaping) a distal end portion of a guide wire into a bent portion when the guide wire is inserted into the micro-channel.

For example, when the shaping is conducted by bending the guide wire G by 45° at a position 1.0 mm away from the distal end thereof as illustrated inFIG. 5, and rotational torque is applied to the guide wire on its proximal end side, the distal end of the guide wire comes to be rotated on a circumference having a diameter of about 1.4 mm.

This shaping operation greatly affects the operability of the guide wire within the micro-channel.

The diameter (operation area) of a circle drawn by the rotation of the distal end of the guide wire is preferably made small from the viewpoint of, for example, reducing the frictional resistance within the micro-channel. It is thus necessary to make a shaping length (length of the bent portion on the distal end side) as short as possible, specifically, not more than 0.7 mm.

However, the conventional guide wire has the above-described distal-end stiff portion, and so the shaping length cannot be set to 1.0 mm or less, thereby failing to sufficiently reduce the frictional resistance.

Incidentally, if the length of the distal-end stiff portion is shortened by narrowing a range where the solder (Ag—Sn solder) is penetrated, the fixing ability of the coil spring to the core wire cannot be sufficiently ensured, and the core wire in a state inserted into the coil spring is pulled out from the coil spring when tensile force is applied between the core wire and the coil spring.

The present invention has been made on the basis of the foregoing circumstances.

The first object of the present invention is to provide a medical guide wire which is high in fixing strength of a coil spring to a core wire and can shorten a shaping length compared with a conventional one.

The second object of the present invention is to provide a medical guide wire excellent in operability within a micro-channel of CTO lesion.

Solution to Problem

The medical guide wire according to the present invention is a medical guide wire comprising

a core wire having a distal end-side small-diameter portion and a proximal end-side large-diameter portion having a larger outside diameter than the outside diameter of the distal end-side small-diameter portion, and

a coil spring installed on an outer periphery of the distal end-side small-diameter portion of the core wire along an axial direction and fixed to the core wire at least the front end portion and rear end portion thereof, wherein

the outside diameter of the proximal end-side large-diameter portion of the core wire and the outside diameter of coil of the coil spring are each at most 0.012 inch,

the front end portion of the coil spring is fixed to the core wire by gold-containing solder, and

the length of a distal end portion (distal-end stiff portion) stiffened by the gold-containing solder is 0.1 to 0.5 mm.

The medical guide wire according to a preferred embodiment of the present invention is a medical guide wire comprising

a core wire having a distal end-side small-diameter portion and a proximal end-side large-diameter portion having a larger outside diameter than the outside diameter of the distal end-side small-diameter portion, and

a coil spring installed on an outer periphery of the distal end-side small-diameter portion of the core wire along an axial direction and fixed to the core wire at least the front end portion and rear end portion thereof, wherein

the outside diameter of the proximal end-side large-diameter portion of the core wire and the outside diameter of coil of the coil spring are each at most 0.012 inch,

the front end portion of the coil spring is fixed to the core wire by Au—Sn solder, and

the length of a distal end portion (distal-end stiff portion) stiffened by the Au—Sn solder is 0.1 to 0.5 mm.

The medical guide wire according to another preferred embodiment of the present invention is a medical guide wire comprising

a core wire having a distal end-side small-diameter portion and a proximal end-side large-diameter portion having a larger outside diameter than the outside diameter of the distal end-side small-diameter portion, and

a coil spring installed on an outer periphery of the distal end-side small-diameter portion of the core wire along an axial direction and fixed to the core wire at least the front end portion and rear end portion thereof, wherein

the outside diameter of the proximal end-side large-diameter portion of the core wire and the outside diameter of coil of the coil spring are each at most 0.012 inch,

the front end portion of the coil spring is fixed to the core wire by Au—Ge solder, and

the length of a distal end portion (distal-end stiff portion) stiffened by the Au—Ge solder is 0.1 to 0.5 mm.

Here, “the distal-end stiff portion.” means a front (distal) end portion of the coil spring (guide wire), which cannot be freely bent due to the solder penetrated into the interior of the coil. When a distal end tip is formed by the solder, this distal end tip also becomes a part of the distal-end stiff portion.

In addition, “the length of the distal-end stiff portion” means a length of the guide wire from the distal end of the guide wire to the rear end of the solder penetrated into the interior of the coil in an axial direction.

In the medical guide wire according to the present invention, the following embodiments are preferred.

(1) The outside diameter of the proximal end-side large-diameter portion of the core wire and the outside diameter of coil of the coil spring are each at most 0.010 inch, particularly, 0.006 to 0.010 inch.

(2) The coil pitch of the coil spring at its front end portion is 1.0 to 1.8 times as much as the wire diameter of the coil, and the Au—Sn solder or Au—Ge solder penetrates into the interior of the coil in a range (length) corresponding to 1 to 3 pitches of the coil spring.
(3) A resin is filled into the interior (space surrounded by the outer periphery of the distal end-side small-diameter portion of the core wire and the inner periphery of the coil spring) of the coil spring, a resin layer by the resin is formed on the outer periphery of the coil spring, a hydrophilic resin layer is laminated and formed on the surface of the resin layer, and a water-repellent resin layer is formed on the surface of the core wire.
(4) The coil spring is composed of a front end-side densely-coiled portion whose coil pitch is 1.0 to 1.8 times as much as the wire diameter of the coil, and a rear end-side roughly-coiled portion whose coil pitch exceeds 1.8 times as much as the wire diameter of the coil.
(5) An intermediate portion of the coil spring, including the front end-side densely-coiled portion and the rear end-side roughly-coiled portion, is fixed to the core wire by the Au—Sn solder or Au—Ge solder.
(6) The core wire is composed of stainless steel.

Advantageous Effects of Invention

According to the medical guide wires of the present invention, the gold-containing solder, preferably, Au—Sn solder or Au—Ge solder is used as solder for fixing the front end portion of the coil spring to the core wire, so that the fixing strength of the coil spring to the core wire can be made sufficiently high (higher than the breaking strength of the distal end-side small-diameter portion of the core wire) though the length of the distal-end stiff portion is as short (narrow in a region fixed by the solder) as 0.1 to 0.5 mm, and so the core wire is not pulled out from the coil spring when tensile force is applied to the core wire in a state inserted into the coil spring.

In addition, since the length of the distal-end stiff portion is as short as 0.1 to 0.5 mm, the shaping length (length of the bent portion on the distal end side) can be made short (not more than 0.7 mm). As a result, frictional resistance upon operation within the micro-channel can be sufficiently reduced.

Further, a treatment in a narrow region, which has been unable to be conducted by using the conventional guide wire, also becomes feasible.

The medical guide wires according to the present invention are excellent in operability within the micro-channel of CTO lesion because of the wire diameter as fine as 0.012 inch or less, high fixing strength owing to the gold-containing solder and the distal-end stiff portion as short as 0.1 to 0.5 mm.

According to the medical guide wire of the embodiment (3), the resin is filled into the interior of the coil spring, whereby the core wire and the coil spring can be integrated with each other to especially improve the torque transferability and operability of the guide wire.

In addition, since the hydrophilic resin layer is laminated and formed on the outer periphery of the coil spring through a resin layer by the same resin as that filled into the interior of the coil spring, the hydrophilic resin layer can be surely fixed to stably develop the lubricating ability by the hydrophilic resin.

Further, the water-repellent resin layer is formed on the surface of the core wire, whereby a blood of a patient can be prevented from coming into contact with a metal making up the core wire to cause an allergy, and the adhesion of the blood can be surely prevented by the water-repellent resin layer. In addition, lubricating ability to other medical instruments can be developed.

According to the medical guide wire of the embodiment (4), good contrasting characteristic for X-ray (visibility) can be developed at the front end portion (front end-side densely-coiled portion) of the coil spring.

According to the medical guide wire of the embodiment (5), a boundary region between the front end-side densely-coiled portion and the rear end-side roughly-coiled portion, where stress concentration is easy to occur, is fixed by the Au—Sn solder or Au—Ge solder high in fixing ability, so that the fixing strength of the coil spring to the core wire can be more improved.

DESCRIPTION OF EMBODIMENTS

The guide wire illustrated inFIG. 1has a core wire10and a coil spring20.

The core wire10has a distal end-side small-diameter portion11subjected to taper machining so as to expand its diameter towards proximal direction, a tapered portion13whose diameter expands towards proximal direction, and a proximal end-side large-diameter portion14.

The distal end-side small-diameter portion11, the tapered portion13and the proximal end-side large-diameter portion14are integrally formed by the same wire material, for example, a round bar member.

The sectional surfaces (cross sections) of the tapered portion13and the proximal end-side large-diameter portion14are substantially circular.

The sectional surface on a proximal end side of the distal end-side small-diameter portion11is substantially circular. However, the wire material may be compressed into a plate form on a distal end side of the distal end-side small-diameter portion11, and the sectional surface thereof is substantially rectangular in that case.

No particular limitation is imposed on the material of the core wire10. As examples thereof, however, may be mentioned metals such as stainless steel (for example, SUS316 and SUS304), gold, platinum, aluminum, tungsten, tantalum and alloys thereof. In this embodiment, the core wire is composed of stainless steel.

A water-repellent resin layer is formed on the outer periphery of the core wire10.

As a resin forming the water-repellent resin layer, may be used all resins medically used and having water repellency, and fluororesins such as PTFE may be mentioned as preferable resins.

As illustrated inFIG. 2, the overall length (L1) of the guide wire1is, for example, 1,500 to 3,000 mm, and is 1,780 mm as a preferable example.

The outside diameter (D1) of the proximal end-side large-diameter portion14is generally 0.012 inch (0.305 mm) or less, preferably 0.010 inch (0.254 mm) or less, more preferably 0.006 to 0.010 inch, and is 0.010 inch as a preferable example.

The fact that the outside diameter (D1) of the proximal end-side large-diameter portion14is 0.012 inch or less can contribute to the miniaturization of medical instruments such as catheters used together with the guide wire according to the present invention and in turn, to low invasiveness.

No particular limitation is imposed on the maximum outside diameter of the distal end-side small-diameter portion11so far as it is smaller than the inside diameter of the coil spring20. However, the outside diameter is about ⅕ to ⅗ of the outside diameter (D1) of the proximal end-side large-diameter portion14.

The coil spring20making up the guide wire10is installed on an outer periphery of the distal end-side small-diameter portion11of the core wire10along an axial direction.

The coil spring20is formed by one wire material and composed of a front end-side densely-coiled portion21whose coil pitch is 1.0 to 1.8 times as much as the wire diameter of the coil, and a rear end-side roughly-coiled portion22whose coil pitch exceeds 1.8 times as much as the wire diameter of the coil, and a radiopaque region is formed by the front end-side densely-coiled portion21and a distal end tip which will be described subsequently.

The coil pitch at the front end-side densely-coiled portion21is 1.0 to 1.8 times as much as the wire diameter of the coil, and is 1.0 time as a preferable example.

The coil pitch at the rear end-side roughly-coiled portion22is 1.8 to 2.5 times as much as the wire diameter of the coil, and is 2.0 time as a preferable example.

The coil pitch is changed between the front end side and the rear end side as described above, whereby good contrasting characteristic for X-ray (visibility) can be developed at the front end-side densely-coiled portion21.

When the pitch of the coil spring is made equal over the whole region, lowering of the visibility is incurred because the radiopaque region becomes long.

InFIG. 2, the length (L2) of the coil spring20is, for example, 30 to 800 mm, and is 115 mm as a preferable example.

The length (L21) of the front end-side densely-coiled portion21is, for example, 10 to 50 mm, and is 30 mm as a preferable example.

The length (L22) of the rear end-side roughly-coiled portion22is, for example, 20 to 750 mm, and is 85 mm as a preferable example.

The length (L3+L2) from the distal end of the guide wire1to the rear end of the coil spring20is, for example, 30 to 800 mm, and is 115.2 mm as a preferable example.

The length (L3+L21) from the distal end of the guide wire1to the rear end of the front end-side densely-coiled portion21is, for example, 10 to 50 mm, and is 30.2 mm as a preferable example.

The outside diameter (D2) of coil of the coil spring20is generally 0.012 inch (0.305 mm) or less, preferably 0.010 inch (0.254 mm) or less, more preferably 0.006 to 0.010 inch, and is 0.010 inch as a preferable example.

The fact that the outside diameter (D1) of the proximal end-side large-diameter portion14of the core wire10is 0.012 inch or less, and the outside diameter (D2) of coil of the coil spring20is also 0.012 inch or less makes the operability upon accessing a micro-channel (for example, lubricating ability in the micro-channel) excellent.

No particular limitation is imposed on the outside diameter of the wire material forming the coil spring20. However, the outside diameter thereof is preferably 30 to 90 μm, and is 60 μm as a preferable example.

As example of the material of the coil spring20, may be mentioned materials (radiopaque materials) good in contrasting characteristic for X-ray, such as platinum, platinum alloys (for example, Pt/W=92/8), gold, gold-copper alloys, tungsten and tantalum.

In the guide wire according to the present invention, the front end portion, rear end portion and intermediate portion (boundary region between the front end-side densely-coiled portion21and the rear end-side roughly-coiled portion22) of the coil spring20are respectively fixed to the outer periphery of the distal end-side small-diameter portion11of the core wire10by solder.

As illustrated inFIG. 1andFIG. 3(A), the front end portion of the coil spring20is fixed to the core wire10by the Au—Sn solder31.

In short, the Au—Sn solder31penetrates into the interior of the coil spring20and comes into contact with the outer periphery of the core wire10(distal end-side small-diameter portion11), whereby the front end portion of the coil spring20is fixed to the core wire10(distal end-side small-diameter portion11).

As illustrated inFIG. 3(A), the Au—Sn solder31penetrates into the interior of the coil in a range corresponding to 2 pitches of the coil spring20.

In addition, a substantially semispherical distal end tip is formed by any other Au—Sn solder31than the solder penetrated into the interior of the coil spring20at the front end portion of the coil spring20.

A distal-end stiff portion (stiff portion by the front end portion of the coil spring20that has been unable to be freely bent due to the Au—Sn solder31penetrated into the interior of the coil, and the distal end tip formed by the Au—Sn solder31) by the Au—Sn solder31is thereby formed at the distal end portion of the guide wire according to this embodiment.

The length (length from the distal end of the guide wire1to the rear end of the Au—Sn solder31penetrated into the interior of the coil) (L4) of this distal-end stiff portion is about 0.3 to 0.4 mm.

In the guide wire according to the present invention, the length of the distal-end stiff portion is 0.1 to 0.5 mm.

If the length of the distal-end stiff portion is less than 0.1 mm, the fixing ability of the coil spring to the core wire cannot be sufficiently ensured.

If the length of the distal-end stiff portion exceeds 0.5 mm on the other hand, a shaping length (outside length (L52) which will be described subsequently) cannot be set to 0.7 mm or less.

In order to set the length of the distal-end stiff portion to 0.1 to 0.5 mm in the guide wire according to the present invention, it is preferable that the coil, pitch of the front end portion of the coil spring is 1.0 to 1.8 times as much as the wire diameter of the coil, and the Au—Sn solder penetrates into the interior of the coil in a range corresponding to 1 to 3 pitches of the coil spring.

The medical guide wire according to this embodiment has a feature in that the Au—Sn solder is used as the solder for fixing the front end portion of the coil spring to the core wire.

The Au—Sn solder used in the present invention is composed of, for example, an alloy of 75-80% by mass of Au and 25 to 20% by mass of Sn.

Stainless steel is fixed to platinum (alloy) with the Au—Sn solder, whereby about 2.5 times of fixing strength (tensile strength) can be obtained compared with a case where they are fixed with the Ag—Sn solder.

Therefore, even when the length of the distal-end stiff portion is as short as 0.1 to 0.5 mm (even when the penetration range of the solder is 1 to 3 times as much as the coil pitch), the fixing strength of the coil spring20to the core wire10can be made sufficiently high. Specifically, the fixing strength can be made higher than tensile break strength at the distal end-side small-diameter portion11of the core wire10. Therefore, even when tensile force is applied between the coil spring20and the core wire10, the core wire10can be prevented from being pulled out from the coil spring20.

In addition, the Au—Sn solder is excellent in contrasting characteristic for X-ray compared with the Ag—Sn solder.

Further, the Au—Sn solder is also excellent in corrosion resistance to blood and body fluid compared with the Ag—Sn solder.

As illustrated inFIG. 1andFIG. 3(B), an intermediate portion of the coil spring20, including a boundary region between the front end-side densely-coiled portion21and the rear end-side roughly-coiled portion22, is fixed to the core wire10by Au—Sn solder32.

In short, the Au—Sn solder32penetrates into the interior of the coil spring20and comes into contact with the outer periphery of the core wire10(distal end-side small-diameter portion11), whereby the intermediate portion of the coil spring20is fixed to the core wire10(distal end-side small-diameter portion11).

The boundary region between the front end-side densely-coiled portion21and the rear end-side roughly-coiled portion22is easy to cause stress concentration. The intermediate portion including this boundary region is fixed by the Au—Sn solder high in fixing ability, whereby the fixing strength of the coil spring20can be more improved.

As illustrated inFIG. 1andFIG. 3(C), the rear end portion of the coil spring20is fixed to the core wire10by Ag—Sn solder33.

In short, the Ag—Sn solder33penetrates into the interior of the coil spring20and comes into contact with the outer periphery of the core wire10(distal end-side small-diameter portion11), whereby the rear end portion of the coil spring20is fixed to the core wire10(distal end-side small-diameter portion11).

Since the outside diameter of the portion, to which the rear end portion of the coil spring20is fixed, in the distal end-side small-diameter portion11of the core wire10is larger (relatively larger in fixing area) than the outside diameter of the portion (distal end), to which the front end portion of the coil spring20is fixed, the Ag—Sn solder low in fixing ability compared with the Au—Sn solder can be used.

As illustrated inFIG. 1toFIG. 3, in the guide wire according to this embodiment, a cured resin40is filled into the interior of the coil spring20, and the outer periphery of the coil spring20and the distal end tip are covered with a resin layer40A by this cured resin40.

A hydrophilic resin layer50is laminated and formed on the surface of this resin layer40A.

The cured resin40is filled into the interior of the coil spring20, whereby the core wire10is integrated with the coil spring20, and the torque transferability of the guide wire is especially improved to surely transfer rotational torque transferred from the proximal end-side large-diameter portion14of the core wire10to the distal end of the coil spring20integrated with the distal end-side small-diameter portion11.

In addition, the hydrophilic resin layer50is formed on the outer periphery of the coil spring20through the resin layer40A (primer layer), so that this hydrophilic resin layer50can be firmly fixed to stably develop the lubricating ability by the hydrophilic resin.

Here, the cured resin40filled into the interior of the coil spring20and forming the resin layer40A covering the outer periphery of the coil spring20preferably has good adhesive property to both coil spring20and hydrophilic resin, and as specific examples thereof, may be mentioned cured products of photo-setting resins or thermosetting resins such as urethane-acrylate resins, polyurethane resins, silicone resins, epoxy resins, acrylic resins and nylon resins.

The film thickness of the resin layer40A covering the outer periphery of the coil spring20and the distal end tip is, for example, 1 to 100 μm, preferably 3 to 10 μm.

As a resin forming the hydrophilic resin layer laminated and formed on the surface of the resin layer40A, may be used all resins used in the field of medical instruments.

The film thickness of the hydrophilic resin layer50is, for example, 1 to 30 μm, preferably 3 to 19 μm.

As examples of a method for filling the cured resin40and forming the resin layer40A and a method for laminating and forming the hydrophilic resin layer50, may be mentioned a method of immersing the coil spring20installed on the core wire10in a curable resin, thereby filling the curable resin into the interior of the coil spring20and forming a resin layer on the surface of the coil spring20, and thermosetting or photo-setting this resin to form the cured resin40(resin layer40A), and a method of applying a hydrophilic resin to the surface of the resin layer40A by a proper means.

According to the guide wire1of this embodiment, the Au—Sn solder is used as the solder for fixing the front end portion of the coil spring20to the core wire10, so that the fixing strength of the coil spring to the core wire (distal end-side small-diameter portion11) is sufficiently high though the outside diameter of the proximal end-side large-diameter portion14of the core wire10is as fine as 0.012 inch or less, and the length of the distal-end stiff portion is as short as 0.3 to 0.4 mm, and so the core wire10is not pulled out from the coil spring20even when tensile force is applied between the coil spring20and the core wire10.

In addition, the shaping length can be shortened because the length of the distal-end stiff portion is as short as 0.3 to 0.4 mm. As a result, frictional resistance upon operation within a micro-channel can be sufficiently reduced. In addition, a treatment in a narrow region, which has been unable to be conducted by using the conventional guide wire, also becomes feasible.

Further, the cured resin40is filled into the interior of the coil spring20, so that the core wire10can be integrated with the coil spring20, and the torque transferability and operability of the guide wire1can be especially improved.

Furthermore, the hydrophilic resin layer50is laminated and formed on the outer periphery of the coil spring20through the resin layer40A by the cured resin40, so that the lubricating ability by the hydrophilic resin can be stably developed.

In addition, the coil spring20is composed of the front end-side densely-coiled portion21and the rear end-side roughly-coiled portion22, so that good contrasting characteristic for X-ray (visibility) can be developed at the front end-side densely-coiled portion21.

FIG. 4(A)illustrate a state that the distal end portion of the guide wire (outside diameter of the coil spring=0.010 inch) according to the present invention has been shaped. The length of the distal-end stiff portion of this guide wire is 0.35 mm (the penetration range of the Au—Sn solder corresponds to 2 pitches of the coil spring), and the shaping length is 0.32 mm for inside length (L51) and 0.53 mm for outside length (L52).

FIG. 4(B)illustrate a state that the distal end portion of the conventional guide wire (outside diameter of the coil spring=0.010 inch) has been shaped. The length of the distal-end stiff portion of this guide wire is 0.8 mm (the penetration range of the Ag—Sn solder corresponds to 6 pitches of the coil spring), and the shaping length is 0.82 mm for inside length (L51) and 1.01 mm for outside length (L52).

The embodiment that the Au—Sn solder is used as the solder for fixing the front end portion and intermediate portion of the coil spring to the core wire has been described above. However, the same effect as in the case where the Au—Sn solder is used can be exhibited even by using other gold-containing solder in place of the Au—Sn solder.

As examples of other gold-containing solder than the Au—Sn, may be mentioned Au alloy solder such as Au—Ge solder, Au—Si solder, Au—In solder and Au—Sb solder, and Au solder.

EXAMPLES

(1) Preparation of Guide Wire

A coil spring was installed on a distal end-side small-diameter portion of a core wire (core wire composed of stainless steel coated with PTFE) the outside diameter of a proximal end-side large-diameter portion of which was 0.010 inch to prepare 13 guide wires of such a structure as illustrated inFIG. 1toFIG. 3according to the present invention.

Here, the coil springs used were such that the outside diameter (D2) of the coil is 0.010 inch, the length (L2) is 115 mm, the length (L21) of a front end-side densely-coiled portion (the coil pitch is 1.0 time as much as the wire diameter of the coil) is 30 mm, and the length (L22) of a rear end-side roughly-coiled portion (the coil pitch is 2.0 times as much as the wire diameter of the coil) is 85 mm.

A front end portion and an intermediate portion of the coil spring were fixed to the core wire with Au—Sn solder, and a rear end portion of the coil spring was fixed to the core wire with Ag—Sn solder.

In each of the 13 guide wires, the number (in Table 1, abbreviated as “Number of pitches”) of pitches a coil portion corresponding to a region (length) where the solder penetrated into the interior thereof was set to any of 1 to 3. The length of a distal-end stiff portion is thereby as shown in Table 1.

After the coil spring was installed on the core wire, a cured resin (urethane-acrylate resin) was filled into the interior of the coil spring, a resin layer by the cured resin was formed on an outer periphery of the coil spring, and a hydrophilic resin layer composed of polyethylene oxide was laminated and formed on the surface of this resin layer.

(2) Evaluation of Guide Wire

With respect to each of the 13 guide wires obtained in the above item (1), a minimum shaping length (minimum length capable of being bent) was measured.

The measurement of the minimum shaping length was conducted on an inside length (L51) and an outside length (L52) as illustrated inFIG. 4.

Tensile force was applied between the coil spring and the core wire to observe a broken site, thereby evaluating the fixing ability of the coil spring to the core wire. With respect to the evaluation standard, the guide wires were ranked as “A” where breaking occurred at the distal end-side small-diameter portion of the core wire or “B” where separation occurred between the coil spring or the distal end-side small-diameter portion and the solder. When even one guide wire was ranked as “B”, their guide wires cannot be provided as products. The results are shown collectively in Table 1.

Thirteen guide wires of such a structure as illustrated inFIG. 1toFIG. 3according to the present invention were prepared in the same manner as in Example 1 except that Au—Ge solder was used as the solder for fixing the front end portion and intermediate portion of the coil spring to the core wire, and Ag—Sn solder was used as the solder for fixing the rear end portion of the coil spring to the core wire.

In each of the 13 guide wires, the number (in Table 2, abbreviated as “Number of pitches”) of pitches at a coil portion corresponding to a region (length) where the solder penetrated into the interior thereof was set to any of 1 to 3. The length of a distal-end stiff portion is thereby as shown in Table 2.

After the coil spring was installed on the core wire, in the same manner as in Example 1, the cured resin was filled into the interior of the coil spring, the resin layer by the cured resin was formed on an outer periphery of the coil spring, and the hydrophilic resin layer was laminated and formed on the surface of this resin layer.

With respect to each of the 13 guide wires obtained in the above-described manner, a minimum shaping length was measured in the same manner as in Example 1, thereby evaluating the fixing ability. The results are shown collectively in Table 2.

Comparative Example 1

Ag—Sn solder was used as solder for fixing the front end portion, intermediate portion and rear end portion of a coil spring to a core wire to prepare 13 comparative guide wires.

In each of the 13 guide wires, the number (in Table 3, abbreviated as “Number of pitches”) of pitches at a coil portion corresponding to a region (length) where the solder penetrated into the interior thereof was set to any of 1 to 3. The length of a distal-end stiff portion is thereby as shown in Table 3.

After the coil spring was installed on the core wire, in the same manner as in Example 1, the cured resin was filled into the interior of the coil spring, the resin layer by the cured resin was formed on an outer periphery of the coil spring, and the hydrophilic resin layer was laminated and formed on the surface of this resin layer.

With respect to each of the 13 guide wires obtained in the above-described manner, a minimum shaping length was measured in the same manner as in Example 1, thereby evaluating the fixing ability. The results are shown collectively in Table 3.

This Comparative Example 1 is a comparative example where no gold-containing solder was used upon fixing the front end portion of the coil spring to the core wire.

Comparative Examples 2 to 6

Ag—Sn solder was used as solder for fixing the front end portion, intermediate portion and rear end portion of a coil spring to a core wire to prepare comparative guide wires the lengths of distal-end stiff portions of which exceeded 0.5 mm.

In each of the guide wires, the number (in Table 4, abbreviated as “Number of pitches”) of pitches at a coil portion corresponding to a region (length) where the solder penetrated into the interior thereof was set to any of 4 to 8. The length of a distal-end stiff portion is thereby as shown in Table 4.

After the coil spring was installed on the core wire, in the same manner as in Example 1, the cured resin was filled into the interior of the coil spring, the resin layer by the cured resin was formed on an outer periphery of the coil spring, and the hydrophilic resin layer was laminated and formed on the surface of this resin layer.

With respect to each of the guide wires obtained in the above-described manner, a minimum shaping length was measured in the same manner as in Example 1. The results are shown collectively in Table 4.

Examples 3 to 5

Any of Au—Si solder, Au—In solder and Au—Sb solder was used as the solder for fixing the front end portion and intermediate portion of a coil spring to a core wire, and Ag—Sn solder was used as the solder for fixing the rear end portion of the coil spring to the core wire, thereby preparing 9 guide wires (3 guide wires in each Example) according to the present invention. In each of the guide wires thus obtained, the number (in Table 5, abbreviated as “Number of pitches”) of pitches at a coil portion corresponding to a region (length) where the solder penetrated into the interior thereof was set to any of 1 to 3. The length of a distal-end stiff portion is thereby as shown in Table 5.

After the coil spring was installed on the core wire, in the same manner as in Example 1, the cured resin was filled into the interior of the coil spring, the resin layer by the cured resin was formed on an outer periphery of the coil spring, and the hydrophilic resin layer was laminated and formed on the surface of this resin layer.

With respect to each of the 9 guide wires obtained in the above-described manner, a minimum shaping length was measured in the same manner as in Example 1, thereby evaluating the fixing ability. The results are shown collectively in Table 5.

REFERENCE SIGNS LIST