Patent Publication Number: US-2020289795-A1

Title: Guidewire

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation of International Application No. PCT/JP2018/004193 filed Feb. 7, 2018. The entire content of the priority application is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a medical device, and specifically to a medical guidewire. 
     BACKGROUND ART 
     In related art, a variety of guidewires guiding a catheter or the like that is used by being inserted into tubular organs such as a blood vessel, a gastrointestinal tract and a ureter or body tissues for treatment or examination has been developed. For example, Patent Document 1 discloses a guidewire comprising a wire body, a coil body including a distal coil body and a proximal coil body covering a distal end portion of the wire body, and a resin coating layer provided on an outer periphery of the coil body consisting of the distal coil body and the proximal coil body (see  FIG. 1  etc.).
     Patent Document 1: Japanese Patent Application Publication No. 2007-135645 A   

     SUMMARY 
     Technical Problems 
     A resin coating layer covering an outer periphery of a guidewire generally reduces friction of the guidewire and improves operability of the guidewire by improving slidability of the guidewire. That is also described in Patent Document 1 regarding a resin coating layer described therein (see paragraph [0116]). 
     However, an entire coil body has same slidability and flexibility, since the resin coating layer described in Patent Document 1 is formed with a substantially uniform thickness throughout the coil body. In the case of forming the entire coil body with a thick film thickness, there is a problem that flexibility of a distal end of the coil body may be impaired, in the case of forming the entire coil body with a thin film thickness, there is a problem that slidability in a proximal side of the coil body may be impaired. 
     Moreover, it is conceivable to set a good film thickness throughout the coil body, but tolerable range of the good film thickness is very narrow, there is a problem that manufacturing yield of the guidewire is poor. 
     The present disclosure has been made in response to forgoing problems of the related technique and is intended to provide a guidewire capable of being easily manufactured and providing good slidability of the guidewire and good flexibility of a distal end of the guidewire. 
     Solution for Problems 
     It is characterized in that, to solve the foregoing problems, a guidewire according to a first aspect of the present disclosure comprises a core shaft, a coil body covering a distal end portion of the core shaft, and a coating agent covering an outer periphery of the coil body, wherein the coil body includes a distal coil body disposed on a distal side of the coil body, and a proximal coil body disposed on a proximal side of the distal coil body, a surface roughness of the proximal coil body is higher than a surface roughness of the distal coil body. 
     A second aspect of the present disclosure is characterized in that, in the guidewire according to the first aspect, a groove is formed along a longitudinal direction of a wire included in the proximal coil body on a surface of the proximal coil body. 
     A third aspect of the present disclosure is characterized in that, in the guidewire according to the first aspect or the second aspect, the wire included in the proximal coil body is rectangular shape in cross section. 
     Furthermore, a fourth aspect of the present disclosure is characterized in that, in the guidewire according to the third aspect, a wire included in the distal coil body is circular shape in cross section. 
     Advantageous Effects 
     According to the guidewire of the first aspect of the present disclosure, as a guidewire comprises a core shaft, a coil body covering a distal end portion of the core shaft, and a coating agent covering an outer periphery of the coil body, wherein the coil body includes a distal coil body disposed on a distal side of the coil body, and a proximal coil body disposed on a proximal side of the distal coil body, a surface roughness of the proximal coil body is higher than a surface roughness of the distal coil body, when the coating agent is applied to a surface of the coil body, it is capable of improving slidability of the guidewire by forming a thick coating film with high adhesion to the proximal coil body at a proximal side of the coil body, and improving flexibility of a distal end of the guidewire wire by forming a thin coating film to the distal coil body at a distal side of the coil body. 
     According to the second aspect of the present disclosure, in the guidewire according to the first aspect, as a guidewire further comprises a groove formed along a longitudinal direction of a wire included in the proximal coil body on a surface of the proximal coil body, in addition to the effects of the guidewire of the first aspect of the present disclosure, it is capable of easily forming the proximal coil body with high surface roughness only by passing a wire included in the proximal coil body through a die with an uneven inner circumference. And it is capable of easily improving slidability of the guidewire by forming a thick coating film with high adhesion to the proximal coil body at a proximal side of the coil body, and easily improving flexibility of a distal end of the guidewire wire by forming a thin coating film to the distal coil body at a distal side of the coil body. 
     According to the third aspect of the present disclosure, in the guidewire according to the first aspect or the second aspect, as a wire included in the proximal coil body has a rectangular shape in cross section, in addition to the effects of the guidewire of the first aspect or the second aspect of the present disclosure, when an inner surface of the distal coil body is aligned with an inner surface of the proximal coil body, it is capable of increasing a thickness of the coating film of the proximal coil body. 
     According to the fourth aspect of the present disclosure, in the guidewire according to the third aspect, as a wire included in the distal coil body has a circular shape in cross section, in addition to the effects of the guidewire of the third aspect of the present disclosure, wires included in the distal coil body are point contact with each other, it is capable of further improving flexibility of a distal end of the guidewire. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of a guidewire according to a first embodiment of the present disclosure. 
         FIG. 2  is a distal end enlarged view of the guidewire of the first embodiment. 
         FIG. 3  is a distal end enlarged view of a guidewire of a second embodiment. 
         FIG. 4  is a distal end vertical sectional view of the guidewire of the second embodiment. 
         FIG. 5  is a distal end enlarged view of a guidewire of a third embodiment. 
         FIG. 6  is a distal end enlarged view of a guidewire of a fourth embodiment. 
         FIG. 7  is a distal end vertical sectional view of the guidewire of the fourth embodiment. 
         FIG. 8  is a distal end vertical sectional view of a guidewire of a fifth embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. 
     First Embodiment 
     First of all, a first embodiment of the present disclosure will be described.  FIG. 1  is a schematic view of a guidewire according to a first embodiment of the present disclosure, and  FIG. 2  is a distal end enlarged view of the guidewire of the first embodiment. 
     As shown in  FIG. 1 , a guidewire  1  of the present embodiment includes a core shaft  9 , a coil body  3  covering a distal portion of the core shaft  9 , and a coating agent  7  covering an outer periphery of the coil body  3 . 
     The core shaft  9  is a rod-like member of circular cross-section which is reduced in diameter toward a distal end from a proximal end of the core shaft  9 , is an elongate flexible member. Material of the core shaft  9  is not particularly limited as long as it is biocompatible material such as stainless steel, Ni—Ti-based alloys, cobalt based alloys or the like. Stainless steel may be used in the present embodiment. 
     The coil body  3  is a cylindrical hollow coil body formed by winding one or more metal wires, a distal end of the coil body  3  is joined to the core shaft  9  by brazing material  2 , and a proximal end of the coil body  3  is joined to the core shaft  9  by brazing material  4 . 
     The coil body  3  of the present embodiment is formed from two coil bodies consisting of a distal coil body  3   a  disposed on a distal side in the coil body  3  and a proximal coil body  3   b  disposed on a proximal side of the distal coil body  3   a . Incidentally, the distal coil body  3   a  of the present embodiment means a coil body located on a distal side from an intermediate position A of the coil body  3  in the coil body  3 , and the proximal coil body  3   b  of the present embodiment means a coil body located on a proximal side from the intermediate position A of the coil body  3  in the coil body  3 . 
     Further, a surface roughness of the proximal coil body  3   b  is higher than a surface roughness of the distal coil body  3   a  in the present embodiment. Incidentally, an area of the proximal coil body  3   b  is illustrated by hatching in  FIGS. 1 and 2  in order to show that the surface roughness of the proximal coil body  3   b  is higher than the surface roughness of the distal coil body  3   a.    
     Concerning adjustment of the surface roughness, for example, the surface roughness of the proximal coil body  3   b  can be made higher than the surface roughness of the distal coil body  3   a  by performing a known surface treatment such as a blasting throughout the coil body  3  after masking a portion of the distal coil body  3   a  in the coil body  3 . 
     The material of a wire included in the coil body  3  is not particularly limited as long as it is biocompatible material such as tungsten, Ni—Ti-based alloy or the like, and stainless steel may be used in the present embodiment. The material of wires included in the distal coil body  3  and the proximal coil body  3   b  may also be of the same stainless steel. 
     Further, the material of the brazing material  2  and the brazing material  4  is not particularly limited as long as it is biocompatible material such as gold-tin brazing metal, silver-tin brazing material or the like, and silver-tin brazing material may be used in the present embodiment. 
     The coating agent  7  covers the outer periphery of the coil body  3  and the core shaft  9  as described above, and the coating agent  7  of the present embodiment has a feature that the coating thickness of the proximal coil body  3   b  located on a proximal side from an intermediate position A of the coil body  3  is larger than the coating thickness of the distal coil body  3   a  located on a distal side from the intermediate position A of the coil body  3  as shown in  FIGS. 1 and 2 . 
     Incidentally, the difference between the coating thickness of the proximal coil body  3   b  and the coating thickness of the distal coil body  3   a  in the present embodiment may be, for example, about several μm-10 μm, and it is illustrated exaggeratedly to facilitate understanding of the difference in  FIGS. 1 and 2 . 
     Since the surface roughness of the proximal coil body  3   b  is higher than the surface roughness of the distal coil body  3   a , when the coating agent  7  is applied on the surface of the coil body  3 , the coating thickness of the proximal coil body  3   b  automatically becomes larger than the coating thickness of the distal coil body  3   a . That is a reason why the coating thickness of the proximal coil body  3   b  is larger than the coating thickness of the distal coil body  3   a  in the present embodiment. 
     In this case, since the surface roughness of the proximal coil body  3   b  is high, it is capable of improving the adhesion between the proximal coil body  3   b  and the coating agent  7 , and improving slidability of the guidewire  1 . 
     On the other hand, it is capable of securing a good flexibility of the distal end of the guidewire  1  by applying the coating agent  7  in a thin layer on the distal coil body  3   a  at the distal side of the coil body  3 . 
     Incidentally, the coating agent  7  is preferably formed by material such as polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene glycol, polyacrylamide, polyacrylic acid, sodium polyacrylate, poly (2-hydroxyethyl methacrylate), maleic anhydride copolymer, ethylene-vinyl alcohol copolymer, 2-methacryloyloxyethyl phosphorylcholine or a copolymer thereof, (2-hydroxyethyl methacrylate)—styrene block copolymer, various synthetic polypeptides, collagen, hyaluronic acid, cellulose-based polymer, and mixtures thereof. 
     According to the guidewire  1  of the present embodiment, as a guidewire  1  comprises a core shaft  9 , a coil body  3  covering a distal end portion of the core shaft  9 , and a coating agent  7  covering an outer periphery of the coil body  3 , wherein the coil body  3  includes a distal coil body  3   a  disposed on a distal side of the coil body  3 , and a proximal coil body  3   b  disposed on a proximal side of the distal coil body  3   a , a surface roughness of the proximal coil body  3   b  is higher than a surface roughness of the distal coil body  3   a , when the coating agent  7  is applied to a surface of the coil body  3 , it is capable of improving slidability of the guidewire  1  by forming a thick coating film with high adhesion to the proximal coil body  3   b  at a proximal side of the coil body  3 , and improving flexibility of a distal end of the guidewire wire  1  by forming a thin coating film to the distal coil body  3   a  at a distal side of the coil body  3 . 
     Second Embodiment 
     Next, a second embodiment of the present disclosure will be described.  FIG. 3  is a distal end enlarged view of a guidewire of a second embodiment, and  FIG. 4  is a distal end vertical sectional view of the guidewire of the second embodiment. 
     In the present embodiment, portions common to the first embodiment will be denoted by the same reference numerals, and descriptions of the portions will be omitted. 
     As shown in  FIG. 3 , a guidewire  10  of the present embodiment includes a core shaft  9 , a coil body  13  covering a distal portion of the core shaft  9 , and a coating agent  17  covering an outer periphery of the coil body  13 . 
     The coil body  13  is a cylindrical hollow coil body formed by winding one or more metal wires, a distal end of the coil body  13  is joined to the core shaft  9  by brazing material  2 , and a proximal end of the coil body  13  is joined to the core shaft  9  by brazing material  4 . 
     The coil body  13  of the present embodiment is formed from two coil bodies consisting of a distal coil body  13   a  disposed on a distal side in the coil body  13  and a proximal coil body  13   b  disposed on a proximal side of the distal coil body  13   a . Incidentally, a distal end of a wire included in the proximal coil body  13   b  of the present embodiment is joined to a proximal end of a wire included in the distal coil body  13   a . Accordingly, a boundary between the distal coil body  13   a  and the proximal coil body  13   b  inclines obliquely along a twist angle of the coil body  13  as shown in  FIGS. 3 and 4 . 
     Further, a hardness of the distal coil body  13   a  is lower than a hardness of the proximal coil body  13   b  in the present embodiment. Incidentally, an area of the proximal coil body  13   b  is illustrated by hatching in  FIGS. 3 and 4  in order to show that the surface roughness of the proximal coil body  13   b  is higher than the surface roughness of the distal coil body  13   a  as described below. 
     A material similar to that of the coil body  3  of the first embodiment may be used for the material of a wire included in the coil body  13 . Platinum may be used in the distal coil body  13   a  and stainless steel may be used in the proximal coil body  13   b  in the present embodiment. 
     Incidentally, the distal coil body  13   a  is not limited as long as it has a hardness less than a hardness of the proximal coil body  13   b . For example, as described above, they may be of different kinds of metals, such as platinum and stainless steel, or they may be of metals of different hardnesses by wire drawing or heat treatment in the same kind of metals. 
     The coating agent  17  covers the outer periphery of the coil body  13  and the core shaft  9  as described above, and the coating agent  17  of the present embodiment has a feature that the coating thickness of a range of the proximal coil body  13   b  is larger than the coating thickness of a range of the distal coil body  13   a  as shown in  FIGS. 3 and 4 . 
     Incidentally, the difference between the coating thickness of the range of the proximal coil body  13   b  and the coating thickness of the range of the distal coil body  13   a  in the present embodiment may be, for example, about several μm-10 μm, and it is illustrated exaggeratedly to facilitate understanding of the difference in  FIGS. 3 and 4 . 
     Since the surface roughness of the proximal coil body  13   b  is higher than the surface roughness of the distal coil body  13   a , the coating thickness of the proximal coil body  13   b  becomes larger than the coating thickness of the distal coil body  13   a.    
     Also, the following process is performed to the coil body  13  in order to increase the surface roughness of the proximal coil body  13   b  than the surface roughness of the distal coil body  13   a  in the present embodiment. 
     That is, first of all, scratches (unevennesses) are formed on a surface of a wire included in the proximal coil body  13   b  and the distal coil body  13   a  in a process of wire drawing using a die. Then a surface of the distal coil body  13   a  is smoothed by swaging the distal coil body  13   a  having lower hardness than the proximal coil body  13   b . Accordingly, the surface roughness of the proximal coil body  13   b  becomes higher than the surface roughness of the distal coil body  13   a.    
     Accordingly, the proximal coil body  13   b  is illustrated by hatching, but the distal coil body  13   a  is not illustrated by hatching in  FIGS. 3 and 4 . That does not mean that the surface of the distal coil body  13   a  is flat, but means merely that the surface roughness of the distal coil body  13   a  is smaller than the surface roughness of the proximal coil body  13   b.    
     Thereafter when the coating agent  17  is applied on the surface of the coil body  13 , the coating thickness of a range of the proximal coil body  13   b  automatically becomes larger than the coating thickness of a range of the distal coil body  13   a.    
     In this case, since the surface roughness of the proximal coil body  13   b  is high, it is capable of improving the adhesion between the proximal coil body  13   b  and the coating agent  17 , and improving slidability of the guidewire  10 . 
     On the other hand, it is capable of securing a good flexibility of the distal end of the guidewire  10  by applying the coating agent  17  in a thin layer on the distal coil body  13   a  at the distal side of the coil body  13 . 
     Incidentally, the coating agent  17  may use the same material as the coating agent  7  of the first embodiment. 
     According to the guidewire  10  of the present embodiment, as a guidewire  10  comprises a core shaft  9 , a coil body  13  covering a distal end portion of the core shaft  9 , and a coating agent  17  covering an outer periphery of the coil body  13 , wherein the coil body  13  includes a distal coil body  13   a  disposed on a distal side of the coil body  13 , and a proximal coil body  13   b  disposed on a proximal side of the distal coil body  13   a , and a hardness of the distal coil body  13   a  is lower than a hardness of the proximal coil body  13   b , the surface roughness of the proximal coil body  13   b  may be easily higher than the surface roughness of the distal coil body  13   a . Accordingly it is capable of improving slidability of the guidewire  10  by forming easily a thick coating film with high adhesion to the proximal coil body  13   b  at a proximal side of the coil body  13 , and improving flexibility of a distal end of the guidewire wire  10  by forming a thin coating film to the distal coil body  13   a  at a distal side of the coil body  13 . 
     Third Embodiment 
     Next, a third embodiment of the present disclosure will be described.  FIG. 5  is a distal end enlarged view of a guidewire of a third embodiment. 
     In the present embodiment, portions common to the first embodiment will be denoted by the same reference numerals, and descriptions of the portions will be omitted. 
     As shown in  FIG. 5 , a guidewire  20  of the present embodiment includes a core shaft  9 , a coil body  23  covering a distal portion of the core shaft  9 , and a coating agent  27  covering an outer periphery of the coil body  23 . 
     The coil body  23  is a cylindrical hollow coil body formed by winding one or more metal wires, a distal end of the coil body  23  is joined to the core shaft  9  by brazing material  2 , and a proximal end of the coil body  23  is joined to the core shaft  9  by brazing material  4 . 
     The coil body  23  of the present embodiment is formed from two coil bodies consisting of a distal coil body  23   a  disposed on a distal side in the coil body  23  and a proximal coil body  23   b  disposed on a proximal side of the distal coil body  23   a . Incidentally, a distal end of a wire included in the proximal coil body  23   b  of the present embodiment is joined to a proximal end of a wire included in the distal coil body  23   a . Accordingly, a boundary between the distal coil body  23   a  and the proximal coil body  23   b  inclines obliquely along a twist angle of the coil body  23  as shown in  FIG. 5 . 
     Further, a plurality of grooves  25  are formed on the surface of wires included in the proximal coil body  23   b  along the longitudinal direction of the wires as shown in  FIG. 5  in the present embodiment. 
     Incidentally, the grooves  25  are formed on an entire surface of a wire included in the proximal coil body  23   b . The grooves  25  may also be formed on a part of the surface of the wire included in the proximal coil body  23   b . However, if the grooves  25  are formed on the entire surface of the wire included in the proximal coil body  23   b , it may further increase the thickness of a coating agent described later. 
     A material similar to that of the coil body  3  of the first embodiment may be used for the material of a wire included in the coil body  23 . Stainless steel may be used in the distal coil body  23   a  and the proximal coil body  23   b  in the present embodiment. 
     The coating agent  27  covers the outer periphery of the coil body  23  and the core shaft  9  as described above, and the coating agent  27  of the present embodiment has a feature that the coating thickness of a range of the proximal coil body  23   b  is larger than the coating thickness of a range of the distal coil body  23   a  as shown in  FIG. 5 . 
     Incidentally, the difference between the coating thickness of the range of the proximal coil body  23   b  and the coating thickness of the range of the distal coil body  23   a  in the present embodiment may be, for example, about several μm-10 μm, and it is illustrated exaggeratedly to facilitate understanding of the difference in  FIG. 5 . 
     Since a plurality of grooves  25  are formed on the surface of wires included in the proximal coil body  23   b  along the longitudinal direction of the wires in the present embodiment, the surface roughness of the proximal coil body  23   b  is higher than the surface roughness of the distal coil body  23   a , and the coating thickness of the range of the proximal coil body  23   b  becomes larger than the coating thickness of the range of the distal coil body  23   a.    
     Thereafter when the coating agent  27  is applied on the surface of the coil body  23 , the coating thickness of the proximal coil body  23   b  automatically becomes larger than the coating thickness of the distal coil body  23   a.    
     Since a plurality of grooves  25  are formed on the surface of wires included in the proximal coil body  23   b  along the longitudinal direction of the wires, it is capable of improving the adhesion between the proximal coil body  23   b  and the coating agent  27 , and improving slidability of the guidewire  20 . 
     On the other hand, it is capable of securing a good flexibility of the distal end of the guidewire  20  by applying the coating agent  27  in a thin layer on the distal coil body  23   a  at the distal side of the coil body  23 . 
     Incidentally, the coating agent  27  may use the same material as the coating agent  7  of the first embodiment. 
     According to the guidewire  20  of the present embodiment, as a guidewire  20  comprises a core shaft  9 , a coil body  23  covering a distal end portion of the core shaft  9 , and a coating agent  27  covering an outer periphery of the coil body  23 , wherein the coil body  23  includes a distal coil body  23   a  disposed on a distal side of the coil body  23 , and a proximal coil body  23   b  disposed on a proximal side of the distal coil body  23   a , and a plurality of grooves  25  are formed on the surface of wires included in the proximal coil body  23   b  along the longitudinal direction of the wires, it is capable of forming the proximal coil body  23   b  having high surface roughness only by passing a wire included in the proximal coil body  23   b  through a die with an uneven inner circumference. Accordingly it is capable of improving slidability of the guidewire  20  by forming easily a thick coating film with high adhesion to the proximal coil body  23   b  at a proximal side of the coil body  23 , and improving flexibility of a distal end of the guidewire  20  by forming a thin coating film to the distal coil body  23   a  at a distal side of the coil body  23 . 
     The distal coil body  23   a  and the proximal coil body  23   b  in the present embodiments have been described as consisting of the same stainless steel. However, they may be set such that the hardness of the distal coil body  23   a  is lower than the hardness of the proximal coil body  23   b  and grooves  25  may be formed on the surface of wires included in the proximal coil body  23   b  along the longitudinal direction of the wires as described in the second embodiment. Further, they may be made by well-known surface treatment methods such as blasting processing being applied to the entire coil body  23  after masking a portion of the distal coil body  23   a  in the coil body  23  as described in the first embodiment. 
     In that case, in addition to the effect of the guidewire  20  of the present embodiment, the guidewire  20  may achieve effects of the guidewire of the first embodiment and the guidewire of the second embodiment. For example, it is capable of forming easily the proximal coil body  23   b  having high surface roughness only by passing a wire included in the proximal coil body  23   b  through a die with an uneven inner circumference; and in the case of forming the surface roughness of the entire coil body  23  in the same condition, the surface roughness of the proximal coil body  23   b  may be easily made higher than the surface roughness of the distal coil body  23   a.    
     Fourth Embodiment 
     Next, a fourth embodiment of the present disclosure will be described.  FIG. 6  is a distal end enlarged view of a guidewire of a fourth embodiment, and  FIG. 7  is a distal end vertical sectional view of the guidewire of the fourth embodiment. 
     In the present embodiment, portions common to the first embodiment will be denoted by the same reference numerals, and descriptions of the portions will be omitted. 
     As shown in  FIG. 6 , a guidewire  30  of the present embodiment includes a core shaft  9 , a coil body  33  covering a distal portion of the core shaft  9 , and a coating agent  37  covering an outer periphery of the coil body  33 . 
     The coil body  33  is a cylindrical hollow coil body formed by winding one or more metal wires, a distal end of the coil body  33  is joined to the core shaft  9  by brazing material  2 , and a proximal end of the coil body  33  is joined to the core shaft  9  by brazing material  4 . 
     The coil body  33  of the present embodiment is formed from two coil bodies consisting of a distal coil body  33   a  disposed on a distal side in the coil body  33  and a proximal coil body  33   b  disposed on a proximal side of the distal coil body  33   a . Incidentally, a distal end of a wire included in the proximal coil body  33   b  of the present embodiment is joined to a proximal end of a wire included in the distal coil body  33   a . Accordingly, a boundary between the distal coil body  33   a  and the proximal coil body  33   b  inclines obliquely along a twist angle of the coil body  33  as shown in  FIGS. 6 and 7 . 
     Further, a surface roughness of the proximal coil body  33   b  is higher than a surface roughness of the distal coil body  33   a  in the present embodiment. Incidentally, an area of the proximal coil body  33   b  is illustrated by hatching in  FIGS. 6 and 7  in order to show that the surface roughness of the proximal coil body  33   b  is higher than the surface roughness of the distal coil body  33   a.    
     Further, wires included in the distal coil body  33   a  and the proximal coil body  33   b  are rectangular in cross-section. 
     A material similar to that of the coil body  3  of the first embodiment may be used for the material of a wire included in the coil body  33 . Stainless steel may be used in the distal coil body  33   a  and the proximal coil body  33   b  in the present embodiment. 
     The coating agent  37  covers the outer periphery of the coil body  33  and the core shaft  9  as described above, and the coating agent  37  of the present embodiment has a feature that the coating thickness of a range of the proximal coil body  33   b  is larger than the coating thickness of a range of the distal coil body  33   a  as shown in  FIGS. 6 and 7 . 
     Incidentally, the difference between the coating thickness of the range of the proximal coil body  33   b  and the coating thickness of the range of the distal coil body  33   a  in the present embodiment may be, for example, about several μm-10 μm, and it is illustrated exaggeratedly to facilitate understanding of the difference in  FIGS. 6 and 7 . 
     Since the surface roughness of the proximal coil body  33   b  is higher than the surface roughness of the distal coil body  33   a , the coating thickness of the proximal coil body  33   b  becomes larger than the coating thickness of the distal coil body  33   a.    
     Thereafter when the coating agent  37  is applied on the surface of the coil body  33 , the coating thickness of the proximal coil body  33   b  automatically becomes larger than the coating thickness of the distal coil body  33   a.    
     Also, it is capable of improving the adhesion between the proximal coil body  33   b  and the coating agent  37  and improving slidability of the guidewire  30 . 
     On the other hand, it is capable of securing a good flexibility of the distal end of the guidewire  30  by applying the coating agent  37  in a thin layer on the distal coil body  33   a  at the distal side of the coil body  33 . 
     Incidentally, the coating agent  37  may use the same material as the coating agent  7  of the first embodiment. 
     According to the guidewire  30  of the present embodiment, as a guidewire  30  comprises a core shaft  9 , a coil body  33  covering a distal end portion of the core shaft  9 , and a coating agent  37  covering an outer periphery of the coil body  33 , wherein the coil body  33  includes a distal coil body  33   a  disposed on a distal side of the coil body  33 , and a proximal coil body  33   b  disposed on a proximal side of the distal coil body  33   a , and wires included in the distal coil body  33   a  and the proximal coil body  33   b  are rectangular cross-section, it is capable of forming thicker coating film of at least the proximal coil body  33   b  than before. 
     In particular, if the cross-sectional shape of the distal coil body  33   a  is circular, the effect is remarkable when an inner circumference of the distal coil body  33   a  is aligned with an inner circumference of the proximal coil body  33   b.    
     The distal coil body  33   a  and the proximal coil body  33   b  in the present embodiments have been described as consisting of the same stainless steel. However, they may be set such that the hardness of the distal coil body  33   a  is lower than the hardness of the proximal coil body  33   b , or grooves may be formed on the surface of wires included in the proximal coil body  33   b  along the longitudinal direction of the wires as described in the third embodiment, or they may be made by well-known surface treatment methods such as blasting processing being applied to the entire coil body  33  after masking a portion of the distal coil body  33   a  in the coil body  33  as described in the first embodiment. 
     In that case, in addition to the effect of the guidewire  30  of the present embodiment, the guidewire  30  may achieve effects of the guidewire of the first embodiment to the third embodiment. 
     Fifth Embodiment 
     Next, a fifth embodiment of the present disclosure will be described.  FIG. 8  is a distal end vertical sectional view of a guidewire of a fifth embodiment. 
     In the present embodiment, portions common to the first embodiment will be denoted by the same reference numerals, and descriptions of the portions will be omitted. 
     As shown in  FIG. 8 , a guidewire  40  of the present embodiment includes a core shaft  9 , a coil body  43  covering a distal portion of the core shaft  9 , and a coating agent  47  covering an outer periphery of the coil body  43 . 
     The coil body  43  is a cylindrical hollow coil body formed by winding one or more metal wires, a distal end of the coil body  43  is joined to the core shaft  9  by brazing material  2 , and a proximal end of the coil body  43  is joined to the core shaft  9  by brazing material  4 . 
     The coil body  43  of the present embodiment is formed from two coil bodies consisting of a distal coil body  43   a  disposed on a distal side in the coil body  43  and a proximal coil body  43   b  disposed on a proximal side of the distal coil body  43   a . Incidentally, a distal end of a wire included in the proximal coil body  43   b  of the present embodiment is joined to a proximal end of a wire included in the distal coil body  43   a . Accordingly, a boundary between the distal coil body  43   a  and the proximal coil body  43   b  inclines obliquely along a twist angle of the coil body  43  as shown in  FIG. 8 . 
     Further, a surface roughness of the proximal coil body  43   b  is higher than a surface roughness of the distal coil body  43   a  in the present embodiment. Incidentally, an area of the proximal coil body  43   b  is illustrated by hatching in  FIG. 8  in order to show that the surface roughness of the proximal coil body  43   b  is higher than the surface roughness of the distal coil body  43   a.    
     Further, wires included in the distal coil body  43   a  are circular in cross-section, and wires included in the proximal coil body  43   b  are rectangular in cross-section. 
     A material similar to that of the coil body  3  of the first embodiment may be used for the material of a wire included in the coil body  43 . Stainless steel may be used in the distal coil body  43   a  and the proximal coil body  43   b  in the present embodiment. 
     The coating agent  47  covers the outer periphery of the coil body  43  and the core shaft  9  as described above, and the coating agent  47  of the present embodiment has a feature that the coating thickness of a range of the proximal coil body  43   b  is larger than the coating thickness of a range of the distal coil body  43   a  as shown in  FIG. 8 . 
     Incidentally, the difference between the coating thickness of the range of the proximal coil body  43   b  and the coating thickness of the range of the distal coil body  43   a  in the present embodiment may be, for example, about several μm-10 μm, and it is illustrated exaggeratedly to facilitate understanding of the difference in  FIG. 8 . 
     Since the surface roughness of the proximal coil body  43   b  is higher than the surface roughness of the distal coil body  43   a , the coating thickness of the proximal coil body  43   b  becomes larger than the coating thickness of the distal coil body  43   a.    
     Thereafter when the coating agent  47  is applied on the surface of the coil body  43 , the coating thickness of the proximal coil body  43   b  automatically becomes larger than the coating thickness of the distal coil body  43   a.    
     Also, it is capable of improving the adhesion between the proximal coil body  43   b  and the coating agent  47  and improving slidability of the guidewire  40 . 
     On the other hand, it is capable of securing a good flexibility of the distal end of the guidewire  40  by applying the coating agent  47  in a thin layer on the distal coil body  43   a  at the distal side of the coil body  43 . 
     Incidentally, the coating agent  47  may use the same material as the coating agent  7  of the first embodiment. 
     According to the guidewire  40  of the present embodiment, as a guidewire  40  comprises a core shaft  9 , a coil body  43  covering a distal end portion of the core shaft  9 , and a coating agent  47  covering an outer periphery of the coil body  43 , wherein the coil body  43  includes a distal coil body  43   a  disposed on a distal side of the coil body  43 , and a proximal coil body  43   b  disposed on a proximal side of the distal coil body  43   a , and wires included in the distal coil body  33   a  are circular cross-section and wires included in the proximal coil body  33   b  are rectangular cross-section, it is capable of further improving flexibility of a distal end of the guidewire  40 , since wires included in the distal coil body  43   a  tend to be in point contact each other. 
     The distal coil body  43   a  and the proximal coil body  43   b  in the present embodiments have been described as consisting of the same stainless steel. However, they may be set such that the hardness of the distal coil body  43   a  is lower than the hardness of the proximal coil body  43   b , or grooves may be formed on the surface of wires included in the proximal coil body  43   b  along the longitudinal direction of the wires as described in the third embodiment, or they may be made by well-known surface treatment methods such as blasting processing being applied to the entire coil body  43  after masking a portion of the distal coil body  43   a  in the coil body  43  as described in the first embodiment. 
     In that case, in addition to the effect of the guidewire  40  of the present embodiment, the guidewire  40  may achieve effects of the guidewire of the first embodiment to the third embodiment. 
     DESCRIPTION OF THE CODE 
     
         
           1 ,  10 ,  20 ,  30 ,  40  . . . guidewire 
           2 ,  4  . . . brazing material 
           3 ,  13 ,  23 ,  33 ,  43  . . . coil body 
           3   a ,  13   a ,  23   a ,  33   a ,  43   a  . . . distal coil body 
           3   b ,  13   b ,  23   b ,  33   b ,  43   b  . . . proximal coil body 
           7 ,  17 ,  27 ,  37 ,  47  . . . coating agent 
           9  . . . core shaft 
           25  . . . groove