Patent Publication Number: US-2023149662-A1

Title: Catheter

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation application of International Application No. PCT/JP2020/028761 filed Jul. 27, 2020, the entire contents of which is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The disclosed embodiments relate to a catheter. 
     BACKGROUND ART 
     Conventionally, there is known a catheter including a hollow shaft with a curved distal end portion (Patent Literature 1, for example). 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: JP 2001-87389 A 
     SUMMARY 
     Technical Problems 
     However, the above-described prior art still has room for improvement in technology of enhancing the performance (selectivity) for advancing a catheter to a target direction in complicatedly branching internal organs and blood vessels. 
     Disclosed embodiments aim at enhancing the performance (selectivity) for advancing a catheter to a target direction in complicatedly branching internal organs and blood vessels. 
     Solutions to Problems 
     Disclosed embodiments have been made to solve at least a part of the problems described above, and can be realized as the following aspects. 
     (1) According to one aspect of the disclosed embodiments, a catheter is provided. The catheter is a catheter including a hollow shaft, in which a distal end portion of the hollow shaft includes a first section extending substantially linearly, a second section connected to a distal end side of the first section and provided with a first curved portion, and a third section connected to a distal end side of the second section and provided with a second curved portion, the rigidity of the second section is larger than the rigidity of the third section, with a virtual plane set along an axis of the first section, a space area on one side with respect to the virtual plane being a first area, and a space area on the other side being a second area, the first curved portion and a distal end of the catheter are positioned in the first area, the second curved portion is positioned in the second area, and a distance from the distal end of the catheter to the virtual plane is larger than a distance from the first curved portion to the virtual plane. 
     With this configuration, force applied in the axial direction of the catheter, such as the force for pushing in the catheter, is converted to the distal end direction of the catheter through the first curved portion and the second curved portion. Thus, the catheter easily advances toward the distal end direction of the catheter. Moreover, the distance from the distal end of the catheter to the virtual plane is larger than the distance from the first curved portion to the virtual plane. Thus, when the distal end of the catheter reaches a branching portion of a blood vessel, the distal end of the catheter is easily inserted to the branching portion. Furthermore, the rigidity of the second section is larger than the rigidity of the third section. Thus, the possibility that the distal end of the catheter is pushed back to the rear end side of the catheter may be reduced. 
     (2) In the catheter of the above-described aspect, the rigidity of the first section of the hollow shaft may larger than the rigidity of the second section. With this configuration, the force for pushing in the catheter, the force for rotating the catheter, and the like, may be securely transmitted from the rear end side of the catheter to the distal end side of the catheter. 
     (3) In the catheter of the above-described aspect, in a front view of the catheter, a distal end of the first section, a distal end of the first curved portion, and a distal end of the second curved portion in the hollow shaft are arranged on a straight line. 
     In a front view of the catheter, the distal end of the first section, the vertex of the first curved portion, and the vertex of the second curved portion may be arranged on a straight line. With this configuration, as compared with the case where the distal end of the first section, the vertex of the first curved portion, and the vertex of the second curved portion are not arranged on a straight line, the possibility that force in a direction orthogonal to the axial direction of the catheter occurs, is reduced, thereby reducing the possibility that the distal end portion of the catheter rotates in a direction not intended by a user. 
     Note that the disclosed embodiments can be achieved in various aspects, such as a guide wire, a method for producing a guide wire, a method for producing a catheter, an endoscope, and a dilator, for example. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is an explanatory view illustrating the entire configuration of a catheter according to a first embodiment. 
         FIG.  2    is an explanatory view illustrating curved portions of the catheter according to the first embodiment. 
         FIG.  3    is an explanatory view illustrating a front view of the catheter according to the first embodiment. 
         FIG.  4    is a first explanatory view illustrating a use state of the catheter in a blood vessel. 
         FIG.  5    is a second explanatory view illustrating a use state of the catheter in a blood vessel. 
         FIG.  6    is an explanatory view illustrating the entire configuration of a catheter according to a second embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     First Embodiment 
       FIG.  1    is an explanatory view illustrating the entire configuration of a catheter  1  according to the first embodiment. In  FIG.  1   , the relative ratio of the sizes of the components is partially different from the actual ratio, for convenience of description. The same applies to the explanatory views illustrated in  FIG.  2    to  FIG.  6   . 
     In  FIG.  1   , the left side is the distal end side of the catheter  1  and of each component of the catheter  1 , while the right side is the rear end side of the catheter  1  and of each component of the catheter  1 . The distal end side of the catheter  1  is the side (far side) to be inserted into a body, and the proximal end side of the catheter  1  is the side (near side) to be operated by a technician such as a physician. The right and left direction of  FIG.  1    is referred to as an axial direction of the catheter  1  and of each component. The direction orthogonal to the axial direction is referred to as a radial direction of the catheter  1  and of each component. 
     Moreover, an end portion positioned on the distal end side of the catheter  1  and of each component of the catheter  1  is described as a “distal end”, and a region including the “distal end” and extending from the distal end to the midway toward the rear end side is described as a “distal end portion”. Similarly, an end portion positioned on the rear end side of the catheter  1  and of each component of the catheter  1  is described as a “rear end”, and a region including the “rear end” and extending from the rear end to the midway toward the distal end side is described as a “rear end portion”. 
     The catheter  1  is a medical instrument inserted into blood vessels or digestive organs for treatment or examination. The catheter  1  includes a hollow shaft  10 , a distal tip  60 , and a grip portion  70 . 
     The hollow shaft  10  is a long tubular body extending in the axial direction of the catheter  1 . The hollow shaft  10  is formed of flexible resin. The distal end portion of the hollow shaft  10  is curved. The grip portion  70  is connected to the rear end portion of the hollow shaft  10 , while the distal tip  60  is connected to the distal end portion of the hollow shaft  10 . The lumen (inner cavity) of the hollow shaft  10  is communicated to the lumen of the grip portion  70  and the lumen of the distal tip  60 . 
     The distal tip  60  is a tubular body connected to the distal end portion of the hollow shaft  10 . The distal tip  60  is a member forming the most distal end of the catheter  1  to reduce the possibility that the catheter  1  damages an internal body. The distal tip  60  may be formed of a flexible material, e.g., a resin material, e.g., TPU (thermoplastic polyurethane elastomer) or a metal material. 
     The grip portion  70  is a tubular body connected to the rear end portion of the hollow shaft  10 . A user, e.g., a physician, holds the grip portion  70  to operate the catheter  1 . The grip portion  70  includes a protector  71 , a main body  72 , and a connector  73 . The protector  71  has a tapered shape with an outer diameter increasing toward the rear end side of the protector  71 . The main body  72  has a projection on the outer periphery so as to facilitate holding by a tuser. The connector  73  has a screw thread on the inner peripheral side, and is connectable to another medical device such as a syringe, e.g., the grip portion  70  may be formed of a material that is durabile and suitable for sterilization. For example, metal, resin formed by injection molding, or a combination thereof may be used. 
     The hollow shaft  10  includes a first hollow shaft  11 , a second hollow shaft  12 , and a third hollow shaft  13 . The proximal end portion of the first hollow shaft  11  is connected to the grip portion  70 , and the distal end portion thereof is connected to the second hollow shaft  12 . The proximal end portion of the second hollow shaft  12  is connected to the distal end portion of the first hollow shaft  11 , and the distal end portion thereof is connected to the third hollow shaft  13 . The proximal end portion of the third hollow shaft  13  is connected to the distal end portion of the second hollow shaft  12 , and the distal end portion thereof is connected to the distal tip  60 . A connection portion  14  is between the distal end of the first hollow shaft  11  and the rear end of the second hollow shaft  12 . The connection portion  14  is a linear part of the hollow shaft  10 . In other words, the connection portion  14  is on the axis of the first hollow shaft  11 . A connection portion  15  is between the distal end of the second hollow shaft  12  and the rear end of the third hollow shaft  13 . The first hollow shaft  11  is substantially linear, and is substantially parallel to the axial direction of the catheter  1 . At least a part of the second hollow shaft  12  is curved. At least a part of the third hollow shaft  13  is curved. The first hollow shaft  11 , the second hollow shaft  12 , and the third hollow shaft  13  are continuously connected, and have a lumen in communication with each other. The lumen is used to insert other devices, e.g., a guide wire, feed chemical liquid, and the like. 
     In the embodiment, in the hollow shaft  10 , a first section  21  is a substantially linear section that is formed by the first hollow shaft  11 , a second section  22  includes a substantially linear part and a curved portion formed by the second hollow shaft  12 , and a third section  23  includes a curved portion formed by the third hollow shaft  13 . The length of the first section  21  may be longer than a length of either of the second section  22  and the third section  23 . Moreover, the length of the first section  21  may be longer than a total length of the second section  22  and the third section  23  combined. 
     The rigidity of the first section  21  may be larger than the rigidity of the second section  22 . Moreover, the rigidity of the second section  22  may be larger than the rigidity of the third section  23 . In the embodiment, the rigidity of the first hollow shaft  11  is larger than the rigidity of the second hollow shaft  12 , and the rigidity of the second hollow shaft  12  is larger than the rigidity of the third hollow shaft  13 . In other words, the rigidity of the hollow shaft  10  is reduced stepwise from the rear end side toward the distal end side. Thus, the catheter  1  has a configuration in which the flexibility increases toward the distal end direction of the catheter  1 . For example, with the rigidity of the third section  23  being 1, the ratio of rigidity among the sections may be third section  23 : second section  22 : first section  21 =1:10 to 20:30 to 300. In this case, the rigidity value of each section may beset to 0.005 to 0.050 gf cm 2 /cm in the third section  23 , 0.050 to 1.00 gf cm 2 /cm in the second section  22 , and 0.150 to 15.0 gf cm 2 /cm in the first section  21 . With the rigidity of each section designed in this manner, the catheter  1  may have pushability and distal flexibility. That is, the inventors have found that in the hollow shaft  10  having a first curved portion  31  and a second curved portion  32 , which will be described later, and having a first distance D 1 , a second distance D 2 , and a third distance D 3  satisfying a condition described later, both the pushability and the distal flexibility are sufficiently satisfied when the rigidity of the first section, the second section, and the third section are set to the above-described range. 
     A virtual plane  40  is positioned on the axis of the first hollow shaft  11  and extends toward the distal end direction of the catheter  1 . The virtual plane  40  in  FIG.  1    illustrates a longitudinal section thereof. A first space area  51  extends on a first side side of, e.g., above, the virtual plane  40 , while a second space area  52  extends on a second side of, e.g., below, the virtual plane  40  is, the space areas being divided and thus defined by the virtual plane  40 . The first space area  51  and the second space area  52  face each other with the virtual plane  40  as a boundary. 
     A first curved portion  31  is part of the curved shape formed by the second hollow shaft  12  in the first area  51  in the second section  22 . A second curved portion  32  is part of the curved shape formed by the third hollow shaft  12  in the second area  52  in the third section  23 . The connection portion  15  between the second hollow shaft  12  and the third hollow shaft  13  is between the first curved portion  31  and the second curved portion  32 . 
       FIG.  2    is an explanatory view illustrating curved portions of the catheter  1  according to the first embodiment. 
     A part with the largest curvature, in the curved shape formed by the second hollow shaft  12 , is a most curved portion Rmax 1  having a center C 1  of the curvature radius Rc 1 . The range of the first curved portion  31  in the second hollow shaft  12  is a part included inside an arc A 1  with a center angle α 1  of 60°, the arc A 1  symmetrically expanding on both sides of the curvature radius Rc 1  of the most curved portion Rmax 1  as a center line from the center C 1  toward the outside of the curved shape. A part with the largest curvature, in the curved shape formed by the third hollow shaft  13 , is a most curved portion Rmax 2  having a center of the curvature radius Rc 2 . The range of the second curved portion  32  in the third hollow shaft  13  is a part included inside an arc A 2  with a center angle α 2  of 60°, the arc A 2  symmetrically expanding on both sides of the curvature radius Rc 2  of the most curved portion Rmax 2  as a center line from the center C 2  toward the outside of the curved shape. In each figure, the first curved portion  31  and the second curved portion  32  are hatched. 
     In the first curved portion  31 , a vertex p 1  of the first curved portion is the point furtherst from the virtual plane  40 . A distance from the vertex p 1  of the first curved portion to the virtual plane  40  is the first distance D 1 . In the second curved portion  32 , a vertex p 2  of the second curved portion is the furthest from the virtual plane  40 . A distance from the vertex p 2  of the second curved portion to the virtual plane  40  is the second distance D 2 . In the distal end of the catheter  1  (the distal end of the distal tip  60 ), a distance between the point most apart from the virtual plane  40  and the virtual plane  40  is the third distance D 3 . In the catheter  1 , in a free state, i.e., unbent, the second distance D 2  is larger than the first distance D 1 . Thus, as illustrated in  FIG.  4   , in a state where the distal end (distal tip  60 ) of the catheter  1  is bent to the proximal end side of the catheter  1  in a blood vessel, the second distance D 2  is shortened, so that the first distance D 1  and the second distance D 2  become substantially equal. Therefore, force generated when the proximal end side of the catheter  1  is pushed passes the vicinity of the center of gravity on the distal end side of the catheter  1 , thereby improving the pushability. Moreover, if the first distance D 1  is larger than the second distance D 2 , the length of the first curved portion  31  is relatively large at the distal end portion of the catheter  1 . In this case, force generated when the proximal end side of the catheter  1  is pushed is absorbed by the first curved portion  31  when the first curved portion  31  is bent. With the first distance D 1  smaller than the second distance D 2  an attenuation rate of force may be reduced until the force generated when the proximal end side of the catheter  1  is pressed reaches the distal end of the catheter  1 . In the catheter  1 , the third distance D 3  is larger than the first distance D 1 . In this manner, the distal end (distal tip  60 ) of the catheter  1  may be easily bent to the proximal end side of the catheter  1  in a blood vessel as illustrated in  FIG.  4   . Moreover, in the catheter  1 , the third distance D 3  is larger than the second distance D 2 . In this manner, as illustrated in  FIG.  4   , in a state where the distal end (distal tip  60 ) of the catheter  1  is bent to the proximal end side of the catheter  1  in a blood vessel, the reduction amount of the third distance D 3  is larger than the reduction amount of the second distance D 2 , so that the second distance D 2  and the third distance D 3  become substantially equal. Therefore, force generated when the proximal end side of the catheter  1  is pushed passes the vicinity of the center of gravity on the distal end side of the catheter  1 , thereby improving the pushability. Moreover, if the first distance D 1  is larger than the third distance D 3  the length of the first curved portion  31  is relatively large at the distal end portion of the catheter  1 . In this case, force generated when the proximal end side of the catheter  1  is pushed is absorbed by the first curved portion  31  when the first curved portion  31  is bent. With the first distance D 1  smaller than the third distance D 3 , an attenuation rate of force may be reduced until the force generated when the proximal end side of the catheter  1  is pressed reaches the distal end of the catheter  1 . For example, with the rigidity of the first distance D 1  being 1, the ratio of rigidity among the distances may be first distance D 1 : second distance D 2 : third distance D 3 =1:5 to 10:6 to 16. In this case, the first distance D 1  may be set to 0.500 to 3.00 mm, the second distance D 2  may be set to 2.50 to 5.00 mm, and the third distance D 3  may be set to 3.00 to 8.00 mm. 
     The most curved portion Rmax 2  of the second curved portion is provided on the more distal end side in the axial direction of the catheter  1  than the vertex p 2  of the second curved portion. In this manner, the distal end (distal tip  60 ) of the catheter  1  is preliminarily bent slightly to the proximal end side of the catheter  1 . Thus, the distal end of the catheter  1  may more easily bend to the proximal end side of the catheter  1  in a blood vessel as illustrated in  FIG.  4   . 
     The maximal curvature of the second curved portion  32  is larger than the maximum curvature of the first curved portion  31 . In other words, the maximal curvature of the curved portion on the distal end side is larger than the maximum curvature of the curved portion on the rear end side. Thus, the distal end of the catheter  1  has a shape warping to the rear end side of the catheter  1 . 
     The rigidity of the first curved portion  31  is larger than the rigidity of the second curved portion  32 . In other words, the rigidity of the curved portion on the rear end side is larger than the rigidity of the curved portion on the distal end side. In this manner, the distal end of the catheter  1  may be more easily bent to the proximal end side while suppressing deformation of the first curved portion  31  when the distal end (distal tip  60 ) of the catheter  1  is bent to the proximal end side of the catheter  1 . Moreover, an attenuation rate at the first curved portion  31  of force generated when the proximal end side of the catheter  1  is pushed may be reduced. 
       FIG.  3    is an explanatory view illustrating a front view of the catheter according to the first embodiment.  FIG.  3    illustrates, with dotted line, the outline of the transverse section of the distal end portion of the first section  21 , the outline of the transverse section of the first curved portion  31  including the vertex p 1 , and the outline of the transverse section of the second curved portion  32  including the vertex p 2 . 
     The distal end portion of the first section  21  of the first hollow shaft  11 , the vertex p 1  of the first curved portion  31  and the vertex p 2  of the second curved portion  32 , and the distal tip  60  are positioned on one straight virtual line  41 . Note that being straight here includes a case of being completely straight and a case of being substantially straight. For example, in the front view of  FIG.  3   , if an angle formed by a straight line connecting the distal tip  60  and the vertex p 2  of the second curved portion  32  and a straight line connecting the vertex p 2  of the second curved portion  32  and the vertex p 1  of the first curved portion  31  is equal to or smaller than 10°, these are considered to be positioned on a straight line. 
     The hollow shaft  10  preferably has antithrombogenicity, flexibility, and biocompatibility, and may be formed of a resin material, e.g., polyamide resin, polyolefin resin, polyester resin, polyurethane resin, silicone resin, fluororesin, or the like for example. The outer diameter, the inner diameter, and the length of the hollow shaft  10  may be arbitrarily determined. 
       FIG.  4    is a first explanatory view illustrating a use state of the catheter  1  in a blood vessel. 
     In  FIG.  4   , the catheter  1  is inserted in a blood vessel  100 . A user advances the catheter  1  in a blood vessel toward a target region, e.g., a lesion to be treated. In a case where the inner diameter of the blood vessel  100  is smaller than a distance between the first curved portion  31  and the second curved portion  32  of the catheter  1 , as illustrated in  FIG.  4   , both the first curved portion  31  and the second curved portion  32  advance while being in contact with a blood vessel wall  102 . Thus, the catheter  1  advances while applying force in the radial direction of the blood vessel  100  with the first curved portion  31  and the second curved portion  32  as contacts. In other words, the catheter  1  advances in the blood vessel  100  while pushing and widening the blood vessel wall  102 . A user may advance the catheter  1  in a branching blood vessel  101 . In that case, the user pushes or pulls the catheter  1  or rotates the catheter  1  to insert the distal end of the catheter  1  into the branching blood vessel  101 . 
     &lt;Examples of the Effects of the First Embodiment&gt; 
       FIG.  5    is a second explanatory view illustrating a use state of the catheter  1  in a blood vessel. 
       FIG.  5    illustrates the state in which the distal end of the catheter  1  is inserted in the branching blood vessel  101 . When a target lesion is in the branching blood vessel  101 , a technician such as a physician confirms that the distal end of the catheter  1  is inserted in the branching blood vessel  101 , and then advances the catheter  1  into the branching blood vessel  101 . 
     When the catheter  1  is brought to a branching portion of a blood vessel, the distal end of the catheter  1  pressed by the blood vessel wall  102  is released, and the distal end of the catheter  1  tends to restore the original curved shape. Thus, the distal end of the catheter  1  is inserted to the branching blood vessel  101 . Therefore, the use is able to easily advance the catheter  1  into the branching blood vessel  101 . Moreover, force  120  applied in the axial direction of the catheter  1  by the user pushing in the catheter  1 , for example, is transmitted to the distal end of the catheter  1  through the first curved portion  31  and the second curved portion  32 . Here, the first curved portion  31  and the second curved portion  32  are supported by the blood vessel wall  102 . Thus, the force  120  is converted from the force in the axial direction of the catheter  1  to the force in the distal end direction. Thus, the distal end of the catheter  1  is easily advanced into the branching blood vessel  101 . 
     The catheter  1  advances while pushing and widening the blood vessel  100 . In this manner, when force in the opposite direction from the advancing direction of the catheter  1  is applied on the catheter  1 , the resistance force acting to prevent the catheter  1  from being pushed back (backup force of the catheter  1 ) is exerted, thereby reducing the possibility that the catheter  1  is pushed back. Moreover, the rigidity of the first curved portion  31  is larger than the rigidity of the second curved portion  32 . Thus, the backup force of the catheter  1  occurs at the first curved portion  31 . Therefore, the possibility that the catheter  1  is pushed back in the opposite direction from the advancing direction may be reduced. 
     The length of the first section is longer than those of the second section and the third section. In this manner, when chemical liquid is injected to the lumen of the catheter  1 , and the injected chemical liquid is ejected from the distal end of the catheter  1 , the resistance force acting to prevent the catheter  1  from being pushed back (backup performance of the catheter  1 ) is sufficiently exerted, thereby reducing the possibility that the catheter  1  is pushed back. Moreover, the length of the first section is longer than the total length of the second section and the third section. This further improves the backup performance of the catheter  1 . 
     The rigidity of the first section  21  is larger than the rigidity of the second section  22 . Thus, the force for pushing in the catheter  1 , the force for rotating the catheter  1 , and the like, may be securely transmitted from the rear end side of the catheter  1  to the distal end side of the catheter  1 . Therefore, the user may easily operate the catheter  1 . Moreover, the rigidity becomes smaller in the order of the first hollow shaft  11 , the second hollow shaft  12 , and the third hollow shaft  13 . Thus, the flexibility of the catheter  1  increases toward the distal end direction of the catheter  1 . Therefore, the catheter  1  is easily adapted to the shapes of complicatedly curved internal organs and blood vessels. 
     The connection portion  14  between the first hollow shaft  11  and the second hollow shaft  12  is provided at the linear part of the hollow shaft  10 . If the connection portion  14  is provided at a curved portion, smooth deformation of the curved portion may be suppressed. With the connection portion  14  provided at the linear part, the possibility that the deformation of the curved portion is suppressed may be reduced. 
     The connection portion  15  between the second hollow shaft  12  and the third hollow shaft  13  is provided between the first curved portion  31  and the second curved portion  32 . If the connection portion  15  is provided at a curved portion, smooth deformation of the curved portion may be suppressed. With the connection portion  15  provided at the linear part, the possibility that the deformation of the curved portion is suppressed may be reduced. 
     The third distance D 3  may be larger than the first distance D 1 . In other words, the distal end of the catheter  1  is positioned on the outer side in the radial direction of the catheter  1  than the vertex p 1  of the first curved portion  31 . Thus, when the catheter  1  reaches the branching blood vessel  101 , the distal end of the catheter  1  is smoothly inserted to the entrance of the branching blood vessel  101 . 
     The most curved portion Rmax 2  of the second curved portion is provided on the more distal end side in the axial direction of the catheter  1  than the vertex p 2  of the second curved portion. In this manner, when the catheter  1  advances in the blood vessel  100 , the possibility that resistance force occurs against the force applied in the advancing direction of the catheter  1  by a user, is reduced, whereby the catheter  1  easily advances in a blood vessel. 
     The degree of curvature of the second curved portion  32  is larger than the degree of curvature of the first curved portion  31 . Thus, the distal end of the catheter  1  has a shape warping to the rear end side of the catheter  1 . Therefore, it becomes easy to advance the distal end of the catheter  1  into the branching blood vessel  101  extending in the opposite direction from the advancing direction of the catheter  1 , such as the branching blood vessel  101  illustrated in  FIGS.  4  and  5   . 
     As illustrated in  FIG.  3   , the first hollow shaft  11 , the first curved portion  31 , and the second curved portion  32  are positioned on one straight virtual line  41 . In this manner, as compared with the case where the first hollow shaft  11 , the first curved portion  31 , and the second curved portion  32  are not arranged on one axis, the possibility that force in a direction orthogonal to the axial direction of the catheter  1  occurs, is reduced. This reduces the possibility that the distal end portion of the catheter  1  rotates in a direction not intended by a user. 
     Second Embodiment 
       FIG.  6    is an explanatory view illustrating the entire configuration of a catheter according to a second embodiment. 
     A catheter  2  of the second embodiment is different from the catheter  1  of the first embodiment only in the aspect that the first section  21  and the second section  22  are formed by the first hollow shaft  11  and the first hollow shaft  11  is connected to the third hollow shaft  13 . The other parts have the same configurations as the catheter  1 , and thus the description thereof is omitted. 
     In the catheter  2 , the first hollow shaft  11  has a part extending substantially linearly from the rear end portion of the catheter  2  toward the distal end direction of the catheter  2 , and the first curved portion  31 . The distal end portion of the first hollow shaft  11  is connected to the third hollow shaft  13 . The rear end portion of the third hollow shaft  13  is connected to the first hollow shaft  11 . In other words, the distal end portion of the catheter  2  is formed by two hollow shafts. The first section  21  is defined by the linear part of the first hollow shaft  11 . The second section  22  is defined by the linear part of the first hollow shaft  11  and a part including the first curved portion  31 . A connection portion  14   a  is between the distal end of the first hollow shaft  11  and the rear end of the third hollow shaft  13 . 
     &lt;Examples of the Effects of the Second Embodiment&gt; 
     In addition to the effects of the catheter  1  of the first embodiment, the catheter  2  avoids stress concentration at the connection portion of a hollow shaft and a hollow shaft and reduces the possibility of a kink by reducing the number of hollow shafts forming the distal end portion of the catheter  2 . 
     &lt;Modification Examples of the Embodiments&gt; 
     The disclosed embodiments are not limited to the above-described embodiments, and can be implemented in various aspects without departing from the gist thereof. For example, the following modification examples are also possible. 
     Modification Example 1 
     The catheter  1  of the first embodiment may be formed by a multilayer tube in which a plurality of resin tubes are stacked in a radial direction. In this case, the catheter  1  may include, between a plurality of resin layers, a braided body formed by metal wire or a reinforcing body such as a coil body. The catheter  1  may include a plurality of lumens. In that case, one lumen may be used for insertion of a device used together such as a guide wire, and the other lumen may be used for feeding of chemical liquid. Moreover, the catheter  1  may not include the distal tip  60  or the grip portion  70 . 
     Modification Example 2 
     The hollow shaft  10  of the catheter  1  of the first embodiment may be formed by one resin tube. In this case, the rear end side of one resin tube is formed straight, and the first curved portion  31  and the second curved portion  32  are provided on the distal end side. The hollow shaft  10  may be formed by a plurality of unlimited number of resin tubes connected to each other. In this case, in a plurality of resin tubes, a resin tube positioned on the distal end side includes the first curved portion  31  and the second curved portion  32 . 
     Modification Example 3 
     The first section  21  and the second section  22  of the catheter  1  of the first embodiment may include a curved portion on the rear end side than the first curved portion  31 . In other words, the catheter  1  may include three or more curved portions in a range not losing the effects of the disclosed embodiments. 
     The above-described modification examples are applicable not only to the first embodiment but also to the second embodiment. 
     In the above, the present aspects are described on the basis of the embodiments and the modification examples. However, the embodiments of the aforementioned aspects are provided to facilitate understanding of the present aspects, and do not limit the present aspects. The present aspects may be altered or improved without departing from the spirit thereof and claims, and the present aspects include their equivalents. In addition, if the technical features are not described as essential in the present specification, they may be deleted as appropriate. 
     REFERENCE SIGNS LIST 
     
         
           1  catheter 
           10  hollow shaft 
           11  first hollow shaft 
           12  second hollow shaft 
           13  third hollow shaft 
           14  connection portion between first hollow shaft and second hollow shaft 
           15  connection portion between second hollow shaft and third hollow shaft 
           21  first section 
           22  second section 
           23  third section 
           31  first curved portion 
           32  second curved portion 
         p 1  vertex of first curved portion 
         p 2  vertex of second curved portion 
           40  virtual plane 
           41  virtual line 
           51  first area 
           52  second area 
           60  distal tip 
           70  grip portion 
           71  protector 
           72  main body 
           73  connector 
           100  blood vessel 
           101  branching blood vessel 
           102  blood vessel wall 
         D 1  first distance (distance from the vertex of the first curved portion to the virtual plane) 
         D 2  second distance (distance from the vertex of the second curved portion to the virtual plane) 
         D 3  third distance (distance from the distal end of the hollow shaft to the virtual plane) 
         C 1  center of curvature radius Rc 1  of the most curved portion Rmax 1   
         C 2  center of curvature radius Rc 2  of the most curved portion Rmax 2