Abstract:
A stent delivery device includes a stent, a guide member, a pulling member including an engaging portion that is inserted in a gap between an inner cavity of the stent and the guide member and detachably engages the stent, and an insertion portion that passes through an inner cavity of the guide member, the pulling member executing an operation for pulling the stent when the engaging portion engages the stent, and an engagement-releasing member that releases engagement between the engaging portion and the stent.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This is a Continuation Application of PCT Application No. PCT/JP03/05581, filed May 1, 2003, which was published under PCT Article 21(2) in Japanese.  
         [0002]     This application is based upon and claims the benefit of priority from prior Japanese Patent Applications No. 2002-129961, filed May 1, 2002; and No. 2002-133127, May 8, 2002, the entire contents of both of which are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0003]     1. Field of the Invention  
         [0004]     The present invention relates to a stent delivery device that is used at a time of performing an operation for inserting a stent into a body cavity of a patient using an endoscope and positioning it there.  
         [0005]     2. Description of the Related Art  
         [0006]     For example, the following treatment is performed to exhaust bile, etc., which is present in the bile duct. A stent is guided to a stenotic part of the bile duct through a channel of an endoscope. Thus, the stent is positioned in the stenotic part. In this state, the bile in the bile duct is exhausted via an inner cavity of the stent.  
         [0007]     The stent is a relatively soft hollow tube that is formed of a high-polymer compound such as polyethylene or silicone rubber, as disclosed in Jpn. U.M. Appln. KOKAI Publication No. 63-20854 (Patent Document 1). Outer peripheral portions at both ends of the stent are provided with mutually opposed flaps for preventing removal.  
         [0008]     A therapy technique for guiding the stent with the above-described structure into a body cavity through an endoscope and positioning the stent in a stenotic part of the bile duct is performed as follows. As is shown in  FIG. 23A , an elongated guide wire  3  that is formed of a flexible wire is inserted in advance in a forceps channel  2  that is provided in an insertion portion  4  of an endoscope  1 . In this state, the guide wire  3 , together with the insertion portion  4  of endoscope  1 , is guided into a bile duct  5 .  
         [0009]     Next, the guide wire  3  is advanced and passed through the stenotic part  6  by a proximal-side manual operation. Then, as shown in  FIG. 23B , using the guide wire  3 , which has been passed through the stenotic part  6 , as a guide, a stent  7  is pushed by a pusher tube  8  and inserted and positioned in the stenotic part  6 .  
         [0010]     However, the stenotic part  6  is located in a deep region of the body cavity. This disables direct observation of stenotic part  6  by the endoscope  1 . In general, the stenotic part  6  is treated under X-ray imaging. In this case, it is likely that the stent  7  is pushed too deeply into the stenotic part  6  by the pusher tube  8 . However, the stent  7  and pusher tube  8  are not coupled. If the stent  7  is pushed too deeply, the stent  7  cannot be pulled back even if the pusher tube  8  is pulled, as indicated by an arrow in  FIG. 23B .  
         [0011]     To solve this problem, a drainage catheter delivery system, as disclosed in U.S. Pat. No. 5,921,952 (Patent Document 2), has been developed. In this system, a pusher tube and a stent are coupled by a suture. When the stent is pushed too deeply, the stent can be pulled back by means of the suture if the pusher tube is pulled.  
         [0012]     In the system of Patent Document 2, a distal end portion of the pusher tube is provided with an insertion hole for insertion of the suture. The stent is provided with an opening that is made by forming a flap. A suture that is engaged with the guide wire is led out of the opening of the stent. Then, the suture is passed through the insertion hole of the pusher tube and knotted. Thus, the stent and pusher tube are coupled.  
         [0013]     Thus, when the stent is pushed too deeply, if the pusher tube is pulled, the stent can be pulled back by means of the suture. In addition, after the stent is positioned in the stenotic part, the guide wire is pulled back. At this time, if the distal end portion of the guide wire is disengaged from the engagement part with the suture, the suture is removed from the stent. Thereby, the stent and the pusher tube are separated.  
         [0014]     In the system of Patent Document 2, after the stent is stayed in the stenotic part, the guide wire is pulled back. At this time, if the distal end portion of the guide wire is not disengaged from the engagement part with the suture, the stent and the pusher tube are not separated.  
         [0015]     Thus, at the time of the procedure for positioning the stent, the guide wire is pulled off. Consequently, even if a subsequent treatment is to be performed using the guide wire as a guide after the stent is positioned, such a treatment cannot be performed.  
         [0016]     In the system of Patent Document 2, in the setting condition prior to use, the stent is passed over the guide wire, and the distal end portion of the stent is held in contact with the distal end portion of the pusher tube. Since the coupling part between the pusher tube and stent is kept in such a state that the end faces of the pusher tube and stent are merely abutted on each other, the bending strength of the coupling part between the pusher tube and stent is weak. Consequently, when the pusher tube is advanced in the procedure for positioning the stent in the stenotic part, buckling may occur at the coupling part between the pusher tube and the stent, and the stent may not be approached to a target part.  
         [0017]     Moreover, the distal end portion of the pusher tube needs to be provided with the insertion hole for insertion of the suture. Consequently, when a liquid is fed through the pusher tube, the liquid may disadvantageously leak from the insertion hole.  
         [0018]     The present invention has been made in consideration of the above circumstances, and the object of the invention is to provide a stent guide that is configured such that a stent, which is pushed too deeply at a time of a procedure for positioning the stent, can be pulled back, that the stent has a high bending strength and can be advanced to a target position even when the bending angle of a curved part of an endoscope is large, and that there is no liquid leak when a liquid is fed.  
       BRIEF SUMMARY OF THE INVENTION  
       [0019]     According to the present invention, a stent delivery device included a stent, a guide member having an inner cavity, at least a distal end portion of the guide member being insertable in the stent, a pulling member including an engaging portion that is inserted in a gap between the inner cavity of the stent and the guide member and detachably engages the stent, and an insertion portion that passes through at least a part of the inner cavity of the guide member, the pulling member executing an operation for pulling the stent when the engaging portion engages the stent, and an engagement-releasing member that moves the pulling member in an axial direction of the guide member, thereby releasing the engagement between the engaging portion and the stent.  
         [0020]     According to the above structure, since the engaging portion, which is connected to a distal end portion of the pulling member, is positioned in the engaged state between the stent and the guide member, the stent can be approached to a target part and positioned by advancing the guide member. When the stent is pushed too deeply, the stent can be pulled back by pulling the pulling member toward a proximal-end side.  
         [0021]     After the stent is positioned at the target part, the pulling member is pulled toward the proximal-end side while the guide member is being held. Thereby, the engagement between the engaging portion and the stent can be released, and the stent can be positioned at the target part. Furthermore, since the distal end portion of the guide member is inserted through the inner cavity of the stent, the stent can be advanced to the target part in accordance with the curving of the curved part of the endoscope. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
       [0022]      FIG. 1A  is a side view showing the entirety of a stent delivery device according to a first embodiment of the present invention;  
         [0023]      FIG. 1B  is a longitudinal cross-sectional view of a distal end portion of the stent delivery device according to the first embodiment;  
         [0024]      FIG. 2A  is a partially cut-out side view of a stent delivery device according to a second embodiment of the present invention;  
         [0025]      FIG. 2B  is a cross-sectional view taken along line IIB-IIB in  FIG. 2A ;  
         [0026]      FIG. 2C  is a cross-sectional view taken along line IIC-IIC in  FIG. 2A ;  
         [0027]      FIG. 2D  is a side view of the stent delivery device according to the second embodiment;  
         [0028]      FIG. 3A  is a longitudinal cross-sectional view of a distal end portion of a stent delivery device according to a third embodiment of the invention;  
         [0029]      FIG. 3B  is a side view of the distal end portion of the stent delivery device shown in  FIG. 3A ;  
         [0030]      FIG. 4A  is a partially cut-out side view of a stent delivery device according to a fourth embodiment of the present invention;  
         [0031]      FIG. 4B  is a cross-sectional view taken along line IVB-IVB in  FIG. 4A ;  
         [0032]      FIG. 4C  is a cross-sectional view taken along line IVC-IVC in  FIG. 4A ;  
         [0033]      FIG. 4D  is a side view of the stent delivery device according to the fourth embodiment;  
         [0034]      FIG. 5A  is a partially cut-out side view of the stent delivery device according to the fourth embodiment, showing the state in which a flexible wire and a stent are separated;  
         [0035]      FIG. 5B  is a side view of the stent delivery device according to the fourth embodiment, showing the state in which the flexible wire and the stent are separated;  
         [0036]      FIG. 6A  is a longitudinal cross-sectional view of the distal end portion of the stent delivery device according to the fourth embodiment, showing the state in which the stent is positioned in a stenotic part by the stent delivery device;  
         [0037]      FIG. 6B  is a longitudinal cross-sectional view of a main part of a modification of the stent delivery device according to the fourth embodiment;  
         [0038]      FIG. 6C  is a longitudinal cross-sectional view showing the state in which the flexible wire of the stent delivery device shown in  FIG. 6B  is pushed in;  
         [0039]      FIG. 7  is a side view showing a stent delivery device according to a fifth embodiment of the present invention;  
         [0040]      FIG. 8A  is a longitudinal cross-sectional view of a distal end portion of a stent delivery device according to a sixth embodiment of the present invention;  
         [0041]      FIG. 8B  is a longitudinal cross-sectional view of a main part of a first modification of the stent delivery device according to the sixth embodiment;  
         [0042]      FIG. 8C  is a longitudinal cross-sectional view of a main part of a second modification of the stent delivery device according to the sixth embodiment;  
         [0043]      FIG. 8D  is a longitudinal cross-sectional view of a main part of a third modification of the stent delivery device according to the sixth embodiment;  
         [0044]      FIG. 8E  is a longitudinal cross-sectional view of a main part of a fourth modification of the stent delivery device according to the sixth embodiment;  
         [0045]      FIG. 8F  is a longitudinal cross-sectional view of a main part of a fifth modification of the stent delivery device according to the sixth embodiment;  
         [0046]      FIG. 8G  is a longitudinal cross-sectional view of a main part of a sixth modification of the stent delivery device according to the sixth embodiment;  
         [0047]      FIG. 8H  is a longitudinal cross-sectional view of a main part of a seventh modification of the stent delivery device according to the sixth embodiment;  
         [0048]      FIG. 8I  is a longitudinal cross-sectional view of a main part of an eighth modification of the stent delivery device according to the sixth embodiment;  
         [0049]      FIG. 9  is a partially cut-out side view of a stent delivery device according to a seventh embodiment of the present invention;  
         [0050]      FIG. 10  is a plan view showing the state in which the stent and the engaging member of the stent delivery device according to the seventh embodiment are engaged;  
         [0051]      FIG. 11A  is a longitudinal cross-sectional view showing the state in which the engaging member of the stent delivery device according to the seventh embodiment is set in a position of engagement with the stent;  
         [0052]      FIG. 11B  is a longitudinal cross-sectional view showing the state in which the engaging member of the stent delivery device according to the seventh embodiment is pushed forward and disengaged from the stent;  
         [0053]      FIG. 11C  is a longitudinal cross-sectional view showing the state in which the engaging member of the stent delivery device according to the seventh embodiment is pulled to the proximal-end side;  
         [0054]      FIG. 12  is an explanatory view for explaining the operation state of the engaging member of the stent delivery device according to the seventh embodiment;  
         [0055]      FIG. 13A  is a perspective view showing the state in which the stent and pusher tube of a stent delivery device according to an eighth embodiment of the invention are connected;  
         [0056]      FIG. 13B  is a perspective view showing the state in which the stent and pusher tube of the stent delivery device according to the eighth embodiment are separated;  
         [0057]      FIG. 13C  is a longitudinal cross-sectional view of a part A in  FIG. 13A ;  
         [0058]      FIG. 14  is a longitudinal cross-sectional view of a connection part between the stent and pusher tube according to a ninth embodiment of the invention;  
         [0059]      FIG. 15  is a longitudinal cross-sectional view of a connection part between the stent and pusher tube according to a tenth embodiment of the invention;  
         [0060]      FIG. 16A  is a perspective view showing the state in which the stent and pusher tube of a stent delivery device according to an eleventh embodiment of the invention are connected;  
         [0061]      FIG. 16B  is a perspective view showing the state in which the stent and pusher tube of the stent delivery device according to the eleventh embodiment are separated;  
         [0062]      FIG. 16C  is a longitudinal cross-sectional view of a part B in  FIG. 16A ;  
         [0063]      FIG. 17A  is a transverse cross-sectional view showing the state in which a cylindrical member of an apparatus according to a twelfth embodiment of the invention is press-fitted in inner cavities of the stent and pusher tube;  
         [0064]      FIG. 17B  is a transverse cross-sectional view showing a modification of the stent of the twelfth embodiment;  
         [0065]      FIG. 18  is a perspective view showing the state in which the stent and pusher tube of an apparatus according to a 13th embodiment of the invention are connected;  
         [0066]      FIG. 19  is a longitudinal cross-sectional view of a part B in  FIG. 18 ;  
         [0067]      FIG. 20  is a perspective view showing the state in which the stent and pusher tube of the apparatus according to the 13th embodiment are separated;  
         [0068]      FIG. 21A  is a longitudinal cross-sectional view of a main part of an apparatus according to a 14th embodiment of the invention in the state in which the stent and pusher tube are connected;  
         [0069]      FIG. 21B  is a longitudinal cross-sectional view showing a main part of the apparatus according to the 14th embodiment in the state in which the stent and pusher tube are separated;  
         [0070]      FIG. 22A  is a longitudinal cross-sectional view of a main part of a modification of the 14th embodiment in the state in which the stent and pusher tube are connected;  
         [0071]      FIG. 22B  is a longitudinal cross-sectional view showing the main part in the state in which the stent and pusher tube shown in  FIG. 22A  are separated;  
         [0072]      FIG. 23A  is an explanatory view for explaining a therapy technique for guiding a stent into a body cavity through an endoscope; and  
         [0073]      FIG. 23B  is an explanatory view for explaining the state in which the stent is pushed in by a pusher tube, inserted in a stenotic part, and positioned. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0074]     Embodiments of the present invention will now be described with reference to the accompanying drawings.  
         [0075]      FIG. 1A  and  FIG. 1B  show a stent delivery device according to a first embodiment.  
         [0076]     As is shown in  FIG. 1A , the stent delivery device according to the present embodiment is provided with an elongated guide catheter  11  that is insertable in a forceps channel of an endoscope (not shown). The guide catheter  11  is formed of a flexible synthetic resin material such as a fluoro-resin or a nylon resin. An inner cavity  12  is formed in the guide catheter  11  over the entire length thereof. A guide catheter cock  13  is provided near a proximal end portion of the guide catheter  11 .  
         [0077]     As is shown in  FIG. 1B , a single small hole  14  is formed in a side wall of the guide catheter  11  near a distal end portion of the guide catheter  11 . A fixing ring  15 , which is an enlarged part with a large outside diameter, is fitted on the outer peripheral surface of the guide catheter  11  at a position corresponding to the small hole  14 . The fixing ring  15  is disposed so as to close part of the small hole  14 .  
         [0078]     In addition, a hollow-tube-like stent  16 , which serves as a stent, is provided on the outer peripheral surface of the guide catheter  11  on the distal-end side of the fixing ring  15 . In the state in which the stent  16  is engaged with the guide catheter  11 , the small hole  14  of the guide catheter  11  is closed by the fixing ring  15  and the stent  16 .  
         [0079]     The stent  16  is formed of a resin with biocompatibility, such as polyethylene, fluoro-resin, nylon resin, thermoplastic elastomer or silicone rubber. It is desirable that the outer peripheral surface of the stent  16  be coated with a hydrophilic lubricant. Outer peripheral portions at both ends of the stent  16  are provided with mutually opposed flaps  17  for preventing removal.  
         [0080]     A guide wire  18  and a flexible wire  19  serving as a pulling member are passed through the inner cavity  12  of the guide catheter  11 . The flexible wire  19  is formed of an elongated metallic twisted wire. The flexible wire  19  may partly be formed of a fibrous member of, e.g. stainless steel, nickel, a titanium alloy, nylon, liquid crystal polymer, or silk. The flexible wire  19  may have a substantially rectangular cross section or a substantially circular cross section. Further, the flexible wire  19  may be provided with a large-diameter portion at a distal end thereof.  
         [0081]     The guide wire  18  is formed of an elongated metallic linear material, twisted material or coil-shaped material. The guide wire  19  should preferably be formed of a metal with superelastic properties of, in particular, a nickel-titanium alloy. The distal end portion of the guide wire  18  is tapered. Further, the proximal end portion of the guide wire  18  is led out of the guide catheter cock  13 . The distal end side of the flexible wire  19  is led out of the guide catheter  11  from the inner cavity of the guide catheter  11  via the small hole  14 .  
         [0082]     The distal end portion of the flexible wire  19  is press-fitted between the inner peripheral surface of the stent  16  and the outer peripheral surface of the guide catheter  11 . An operation ring  20  is provided at the proximal end of the flexible wire  19 .  
         [0083]     The distal end portion of the flexible wire  19  is not necessarily press-fitted over the entire length of the stent  16 . It should suffice if the distal end portion of the flexible wire  19  is pressed-fitted over such a length that the stent  16  can be moved together with the flexible wire  19  toward the proximal end side when the flexible wire  19  is pulled toward the proximal end side. For example, a portion of the flexible wire  19 , which has an axial length of about 5 mm or more, may be positioned within the stent  16 .  
         [0084]     If the flexible wire  19  is pulled to the proximal end side with a greater force in the state in which the stent  16  abuts on the fixing ring  15 , the engagement between the stent  16  and flexible wire  19  is released and the stent  16  is separated from the flexible wire  19 .  
         [0085]     Next, the operation of the first embodiment is described. When the stent delivery device according to this embodiment is used, the stent delivery device is set as follows.  
         [0086]     To begin with, the flexible wire  19  is inserted in the inner cavity  12  of the guide catheter  11  of the stent delivery device. The distal end portion of the flexible wire  19  is led out of the small hole  14 . Then, the stent  16  is fitted on the guide catheter  11  from the distal end thereof. Further, the distal end portion of the flexible wire  19  is press-fitted between the stent  16  and guide catheter  11 . Thus, as shown in  FIG. 1B , the guide catheter  11 , stent  16  and flexible wire  19  are set in the assembled state.  
         [0087]     The insertion portion of the endoscope is inserted in a body cavity in advance, and a distal-end structural part, which is disposed at the distal end of the insertion portion of the endoscope, is guided to the vicinity of the bile duct.  
         [0088]     Subsequently, the guide wire  18  is passed through the forceps channel of the endoscope that is inserted in the body. At this time, under observation using the endoscope and observation using X-rays, the guide wire  18  is advanced and the distal end portion of the guide wire  18  is guided into a stenotic part of the bile duct.  
         [0089]     Thereafter, as described above, the guide catheter  11 , on which the stent  16  is set, is passed over the guide wire  18 , and the guide catheter  11  is inserted into the forceps while being guided by the guide wire  18 .  
         [0090]     At this time, the guide catheter  11  is advanced by a manual operation on the proximal end side of the guide catheter  11 . The guide catheter  11  is led out of the distal-end structural part of the endoscope, and the guide catheter  11  and stent  16  are inserted into the stenotic part.  
         [0091]     During the operation for inserting the guide catheter  11 , the stent  16  is kept fitted on the guide catheter  11 . Thus, the bending strength of the stent  16  is high, and even if the guide wire  18  is curved with a large angle of bend, the stent  16  is not buckled. The stent  16  can be advanced together with the guide catheter  11  and guided to a target part.  
         [0092]     After the stent  16  is inserted into the stenotic part by means of the guide catheter  11 , X-ray observation is performed. If it is confirmed by the X-ray observation that the stent  16  is pushed too deeply, an operation for pulling back the stent  16  to a position on the proximal end side is performed. In the procedure, the finger is hooked on the operation ring  20  and pulled to the proximal end side. Thereby, the stent  16  can be pulled back by the flexible wire  19 , and the stent  16  can exactly be positioned at the target part.  
         [0093]     Then, an operation for pulling the flexible  19  toward the proximal end side is performed by hooking the finger on the operation ring  20  while holding the guide catheter  11 . In this operation, the distal end portion of the flexible wire  19  is removed from between the guide catheter  11  and stent  16 . As a result, the flexible wire  19  and stent  16  are separated, and the stent  16  is positioned at the stenotic part.  
         [0094]     In this case, the guide wire  18  is kept in the state in which the guide wire  18  is passed through the guide catheter  11 . The distal end portion of the guide wire  18  is left at the position of the stenotic part. Thus, using the guide wire  18  as a guide, a subsequent treatment may be performed.  
         [0095]     In addition, since the guide catheter  11  has the inner cavity  12 , it is possible to feed or suck a liquid from the guide catheter cock  13 .  
         [0096]     The apparatus with the above structure can achieve the following advantageous effects. In the stent delivery device according to the present embodiment, the stent  16  is fitted on the guide catheter  11 , and the distal end portion of the flexible wire  19  is press-fitted between the stent  6  and guide catheter  11 . Thereby, as shown in  FIG. 1B , the guide catheter  11 , stent  16  and flexible wire  19  are set in the integrally assembled state. Therefore, at the time of the procedure for positioning the stent  16  at the stenotic part of the bile duct, the stent  16  can be pulled back to the proximal end side by means of the flexible wire  19  even if the stent  16  is pushed too deeply.  
         [0097]     Moreover, during the work for inserting the guide catheter  11 , the stent  16  is kept fitted on the guide catheter  11 . Thus, the bending strength of the stent  16  is high, and even if the angle of bend of the curved part of the endoscope is large, the stent  16  can be advanced to the target part.  
         [0098]     Furthermore, the small hole  14  in the guide catheter  11  is closed by the fixing ring  15  and stent  16 . Therefore, when a liquid is fed, there is no possibility of liquid leak from the small hole  14 .  
         [0099]      FIGS. 2A  to  2 D show a second embodiment of the present invention. The structural parts common to those in the first embodiment are denoted by like reference numerals, and a description thereof is omitted. The stent  16  is fitted on the distal end portion of the guide catheter  11 .  
         [0100]     In addition, a pusher tube  21  is axially movably fitted on the outer peripheral surface of the guide catheter  11  on the proximal end side of the stent  16 . The pusher tube  21  is formed of a flexible synthetic resin material. A pusher tube cock  22  is provided at the proximal end of the pusher tube  21 .  
         [0101]     A flexible wire  19 , which serves as a pulling member, is axially movably passed between the outer peripheral surface of the guide catheter  11  and the inner peripheral surface of the pusher tube  21 . A distal end portion of the flexible wire  19  is press-fitted between the inner peripheral surface of the stent  16  and the outer peripheral surface of the guide catheter  11 .  
         [0102]     A proximal end portion of the flexible wire  19  is led out of the pusher tube cock  22 . An operation ring  20  is provided at the proximal end of the flexible wire  19 .  
         [0103]     Next, the operation of the stent delivery device according to the second embodiment is described. When the stent delivery device according to this embodiment is used, the stent delivery device is set as follows.  
         [0104]     To begin with, the flexible wire  19  is passed between the guide catheter  11  and the pusher tube  21  of the stent delivery device. Then, the stent  16  is fitted on the distal end portion of the guide catheter  11 . Subsequently, the distal end portion of the flexible wire  19  is press-fitted between the stent  16  and guide catheter  11 . Thus, as shown in  FIG. 2A , the guide catheter  11 , stent  16 , flexible wire  19  and pusher tube  21  are set in the assembled state.  
         [0105]     Thereafter, like the first embodiment, the guide wire  18  is passed through the forceps channel of the endoscope. Then, the operation for guiding the stent  16  to the stenotic part of the bile duct by means of the guide catheter  11  is performed. This method is the same as in the first embodiment. In the present embodiment, the stent  16  is inserted into the stenotic part by advancing the pusher tube  21 .  
         [0106]     After the stent  16  is inserted into the stenotic part by means of the pusher tube  21 , X-ray observation is performed. If it is confirmed by the X-ray observation that the stent  16  is pushed too deeply, an operation for pulling back the stent  16  to a position on the proximal end side is performed. In the procedure, the finger is hooked on the operation ring  20  and pulled to the proximal end side. Thereby, the stent  16  can be pulled back by the flexible wire  19 , and the stent  16  can exactly be positioned at the target part.  
         [0107]     Then, an operation for pulling the flexible  19  toward the proximal end side is performed by hooking he finger on the operation ring  20  while holding the guide catheter  11 . In this operation, the distal end portion of the flexible wire  19  is removed from between the guide catheter  11  and stent  16 . As a result, the flexible wire  19  and stent  16  are separated, and the stent  16  is stayed at the stenotic part.  
         [0108]     In this case, the guide wire  18  is kept in the state in which the guide wire  18  is passed through the guide catheter  11 . The distal end portion of the guide wire  18  is left at the position of the stenotic part. Thus, using the guide wire  18  as a guide, a subsequent treatment may be performed.  
         [0109]     In addition, since the guide catheter  11  has the inner cavity  12 , it is possible to feed or suck a liquid from the guide catheter cock  13 .  
         [0110]     In the apparatus with the above structure, too, at the time of the procedure for positioning the stent  16  at the stenotic part of the bile duct, the stent  16  can be pulled back to the proximal end side by means of the flexible wire  19  even if the stent  16  is pushed too deeply.  
         [0111]     Moreover, during the work for inserting the guide catheter  11 , the stent  16  is kept engaged with the guide catheter  11 . In addition, the distal end portion of the flexible wire  19  is inserted in the inner cavity of the stent  16 . Thus, the bending strength of the stent  16  is high. Even if the angle of bend of the curved part of the endoscope is large, the stent  16  can be advanced to the target part in accordance with the curving of the curved part of the endoscope.  
         [0112]     After the stent  16  is positioned at the target part, the flexible wire  19  is pulled to the proximal end side while the guide catheter  11  is being held. Thereby, the engagement between the distal end portion of the flexible wire  19  and the stent  16  is released. Thus, the stent  16  can be positioned at the target part.  
         [0113]     Furthermore, when a liquid is fed through the guide catheter  11 , there is no possibility of liquid leak.  
         [0114]      FIG. 3A  and  FIG. 3B  show a third embodiment of the present invention. The structural parts common to those in the first embodiment are denoted by like reference numerals, and a description thereof is omitted.  
         [0115]     A stent  23  of this embodiment has a small-diameter portion  23   a  at a distal end thereof. The stent  23  has a large-diameter portion  23   b  at a proximal end thereof. The large-diameter portion  23   b  has the same diameter as the pusher tube  21 .  
         [0116]     The distal end portion of the flexible wire  19  is press-fitted between the inner peripheral surface of the large-diameter portion  23   b  of the stent  23  and the outer peripheral surface of the guide catheter  11 .  
         [0117]     Since the stent  23  of this embodiment has the small-diameter portion  23   a  at its distal end, the stent  23  can easily be inserted into the stenotic part of the bile duct.  
         [0118]      FIG. 4A  to  FIG. 6A  show a fourth embodiment of the present invention. In this embodiment, a pusher tube  24 , which has a structure different from the structure of the pusher tube  21  of the second embodiment (see  FIGS. 2A  to  2 D), is provided. The other structural parts are the same as those in the second embodiment. The structural parts common to those in the second embodiment are denoted by like reference numerals, and a description thereof is omitted.  
         [0119]     As is shown in  FIG. 4A , in this embodiment, the pusher tube  24  includes a small-diameter portion  24   a  at a distal end thereof. The small-diameter portion  24   a  is inserted in the inner cavity of the stent  16 .  
         [0120]     The pusher tube  24  is provided with a stepped portion  24   c  between the small-diameter portion  24   a  and a large-diameter portion  24   b  thereof, which is formed on the proximal end side of the small-diameter portion  24   a . The stepped portion  24   c  has a passage hole  25 .  
         [0121]     The distal end portion of the flexible wire  19 , which is passed through the inner cavity of the pusher tube  24 , is led out of the passage hole  25  to the outside of the small-diameter portion  24   a . The distal end portion of the flexible wire  19  is press-fitted between the inner peripheral surface of the stent  16  and the outer peripheral surface of the small-diameter portion  24   a.    
         [0122]     Further, a side hole  26  is formed in the side wall of the pusher tube  24 . The proximal end portion of the flexible wire  19  is led out of the side hole  26  of the pusher tube  24 .  
         [0123]     Next, the operation of the fourth embodiment is described. When the stent delivery device according to this embodiment is used, the stent delivery device is set as follows.  
         [0124]     To begin with, the flexible wire  19  is inserted in the inner cavity of the pusher tube  24 , and the distal end portion thereof is led out of the passage hole  25  to the outside of the small-diameter portion  24   a . Then, the stent  16  is fitted on the distal-end small-diameter portion  24   a  of the pusher tube  24 . Further, as shown in  FIG. 4B , the distal end portion of the flexible wire  19  is press-fitted between the inner peripheral surface of the stent  16  and the outer peripheral surface of the small-diameter portion  24   a . Thus, as shown in  FIG. 4A , the pusher tube  24 , stent  16  and flexible wire  19  are set in the assembled state.  
         [0125]     The guide wire  18  is passed through the forceps channel of the endoscope, and the stent  16  is guided to the stenotic part of the bile duct by means of the pusher tube  24  in the same manner as in the first embodiment. In the present embodiment, when the pusher tube  24  is advanced, the stepped portion  24   c  abuts on the proximal end of the stent  16 . If the pusher tube  24  is further advanced, the stent  16  is inserted into the stenotic part.  
         [0126]     After the stent  16  is inserted into the stenotic part by means of the pusher tube  24 , X-ray observation is performed. If it is confirmed by the X-ray observation that the stent  16  is pushed too deeply, an operation for pulling back the stent  16  to a position on the proximal end side is performed. In the procedure, the finger is hooked on the operation ring  20  and pulled to the proximal end side. Thereby, the stent  16  can be pulled back by the flexible wire  19 , and the stent  16  can exactly be positioned at the target part.  
         [0127]     Then, an operation for pulling the flexible  19  toward the proximal end side is performed by hooking the finger on the operation ring  20  while holding the pusher tube  24 . In this operation, as shown in  FIG. 5A , the distal end portion of the flexible wire  19  is removed from between the pusher tube  24  and stent  16 . As a result, as shown in  FIG. 6A , the flexible wire  19  and stent  16  are separated. The stent  16  is thus positioned at the stenotic part.  
         [0128]     In this case, the guide wire  18  is kept in the state in which the guide wire  18  is passed through the pusher tube  24 . The distal end portion of the guide wire  18  is left at the position of the stenotic part. Thus, using the guide wire  18  as a guide, a subsequent treatment may be performed.  
         [0129]     In the apparatus with the above structure, too, at the time of the procedure for positioning the stent  16  at the stenotic part of the bile duct, the stent  16  can be pulled back to the proximal end side by means of the flexible wire  19  even if the stent  16  is pushed too deeply.  
         [0130]     In this embodiment, the guide catheter  11  can be dispensed with, so cost reduction is possible. Further, the diameter of the stent  16  and pusher tube  24  can be reduced. In a case where the stenotic part is small in size, the stent  16  can easily be inserted.  
         [0131]      FIG. 6B  and  FIG. 6C  show a modification of the stent delivery device of the fourth embodiment. The guide wire  18  is inserted into the pusher tube  24  via the side hole  26  of the pusher tube  24 .  
         [0132]      FIG. 7  shows a fifth embodiment of the invention. In this embodiment, the stent delivery device of the fourth embodiment (see  FIG. 4A  through  FIG. 6C ) is modified as follows. The parts common to those in the fourth embodiment are denoted by like reference numerals, and a description thereof is omitted.  
         [0133]     In this embodiment, an operation ring  20   a  is axially movably fitted on a proximal end portion of the guide catheter  11 . The proximal end of the flexible wire  19 , which is inserted in the pusher tube  24 , is coupled to the operation ring  20   a.    
         [0134]     According to this embodiment, the flexible wire  19  is pulled by moving the operation ring  20   a  backward. Thereby, the engagement between the flexible wire  19  and stent  16  can be released.  
         [0135]      FIG. 8A  shows a sixth embodiment of the invention. In this embodiment, the parts common to those in the second embodiment (see  FIGS. 2A  to  2 D) are denoted by like reference numerals, and a description thereof is omitted. In this embodiment, the distal end portion of the flexible wire  19  is provided with a bent portion  19   c  that is bent upward. The bent portion  19   c  is put in pressure contact with the inner wall of the stent  16 .  
         [0136]      FIG. 8B  shows a first modification of the stent delivery device according to the sixth embodiment. In this modification, the distal end portion of the flexible wire  19  is provided with a wavy bent portion  27 . The wavy bent portion  27  is put in pressure contact with the inner wall of the stent  16 .  
         [0137]      FIG. 8C  shows a second modification of the stent delivery device according to the sixth embodiment. In this modification, the distal end portion of the flexible wire  19  is provided with an S-shaped bent portion  28 . The S-shaped bent portion  28  is put in pressure contact with the inner wall of the stent  16 .  
         [0138]      FIG. 8D  shows a third modification of the stent delivery device according to the sixth embodiment. In this modification, the distal end portion of the flexible wire  19  is provided with a widened portion  29  with an increased dimension in its width direction. The widened portion  29  is put in pressure contact with the inner wall of the stent  16 .  
         [0139]      FIG. 8E  shows a fourth modification of the stent delivery device according to the sixth embodiment. In this modification, a single flexible wire  19  is folded within the stent  16  and thus provided with a folded portion  30 . The folded portion  30  is put in pressure contact with the inner wall of the stent  16 .  
         [0140]      FIG. 8F  shows a fifth modification of the stent delivery device according to the sixth embodiment. In this modification, the distal end portion of the flexible wire  19  is provided with a meandering portion  31 . The meandering portion  31  is put in pressure contact with the inner wall of the stent  16 .  
         [0141]      FIG. 8G  shows a sixth modification of the stent delivery device according to the sixth embodiment. In this modification, the distal end portion of the flexible wire  19  is provided with a wavy bent portion  32  that is bent in a wavy shape in the width direction. The wavy bent portion  32  is put in pressure contact with the inner wall of the stent  16 .  
         [0142]      FIG. 8H  shows a seventh modification of the stent delivery device according to the sixth embodiment. In this modification, the distal end portion of the flexible wire  19  is provided with a spiral portion  33 . The spiral portion  33  is put in pressure contact with the inner wall of the stent  16 .  
         [0143]      FIG. 8I  shows a first modification of the stent delivery device according to the sixth embodiment. In this modification, two flexible wires  19   a  and  19   b  are provided in parallel. The distal end portions of the two flexible wires  19   a  and  19   b  are put in pressure contact with the inner wall of the stent  16 .  
         [0144]      FIG. 9  to  FIG. 12  show a seventh embodiment of the present invention. In this embodiment, the stent delivery device of the second embodiment (see  FIG. 2A  through  FIG. 2D ) is modified as follows. As regards the stent delivery device of this embodiment, the parts common to those in the second embodiment are denoted by like reference numerals, and a description thereof is omitted.  
         [0145]     As is shown in  FIG. 9 , a stent  16  of the stent delivery device of the present embodiment is provided with an opening  117   a  at a distal end side thereof, which is made by forming a flap  17 .  
         [0146]     A distal end portion of the flexible wire  19 , which serves as a pulling member, is provided with an engaging member  42 . The engaging member  42  is provided with a plate-spring-like engaging plate  43 . The engaging plate  43  has spring characteristics and is formed using a plate-like member that is made of a spring material of, e.g. stainless steel.  
         [0147]     A front end portion of the engaging plate  43  is fixed to a distal end portion of the flexible wire  19  by means of brazing. As is shown in  FIG. 9  and  FIG. 10 , a rear end portion of the engaging plate  43  is inserted in a side hole  17   a  that is made by the flap  17  of the stent  16 , and is detachably hooked.  
         [0148]     As is shown in  FIG. 11A  and  FIG. 12 , the stent delivery device of this embodiment is set in the state in which the rear end portion of the engaging plate  43  is inserted and hooked in the side hole  17   a  of the stent  16 . In this state, like the first embodiment, the guide wire  18  is passed through the forceps channel of the endoscope, and the stent  16  is guided to the stenotic part of the bile duct by means of the guide catheter  11  in the same manner as in the first embodiment. In the present embodiment, the stent  16  is inserted into the stenotic part  16  by advancing the pusher tube  21 .  
         [0149]     After the stent  16  is inserted into the stenotic part by means of the pusher tube  21 , X-ray observation is performed. If it is confirmed by the X-ray observation that the stent  16  is pushed too deeply, an operation for pulling back the stent  16  to a position on the proximal end side is performed. In the procedure, the finger is hooked on the operation ring  20  and pulled to the proximal end side. Thereby, the stent  16  can be pulled back by the flexible wire  19 , and the stent  16  can exactly be positioned at the target part.  
         [0150]     When the flexible wire  19  and stent  16  are to be separated, the operation ring  20  is once pushed. Thereby, the flexible wire  19  is pushed forward. At this time, by the elastic deformation of the engaging member  42 , the engaging plate  43  is disengaged from the side hole  41  of the stent  16 . Further, as shown in  FIG. 11B , the rear end portion of the engaging plate  43  is pulled out of the side hole  41  of the stent  16 . At this time, the engaging plate  43  is restored to its straight original shape. In this state, the flexible wire  19  is pulled backward. Thereby, as shown in  FIG. 11C , the engaging plate  43  is shifted beyond the side hole  41  of the stent  16  and is pulled out backward. Thus, the flexible wire  19  and stent  16  are separated, and the stent  16  is stayed at the stenotic part.  
         [0151]     The apparatus with the above structure can achieve the following advantageous effects. In the present embodiment, the apparatus is set in the state in which the rear end portion of the engaging plate  43  of the engaging member  42  is inserted and hooked in the side hole  17   a  of the stent  16 . Therefore, at the time of the procedure for positioning the stent  16  at the stenotic part of the bile duct, the stent  16  can be pulled back to the proximal end side by means of the flexible wire  19  even if the stent  16  is pushed too deeply.  
         [0152]     When the flexible wire  19  and stent  16  are to be separated, the operation ring  20  is once pushed. Thereby, the flexible wire  19  is pushed forward. By the elastic deformation of the engaging member  42 , the engaging plate  43  is disengaged from the side hole  41  of the stent  16 , and in this state the flexible wire  19  is pulled backward. Thereby, as shown in  FIG. 11C , the engaging plate  43  is shifted beyond the side hole  41  of the stent  16  and is pulled out backward. Thus, the flexible wire  19  and stent  16  are separated, and the stent  16  is positioned at the stenotic part.  
         [0153]     Besides, in the present embodiment, the flexible wire  19  is connected over the stent  16  and pusher tube  21 . Hence, the bending strength at the connection part between the stent  16  and pusher tube  21  is high. Even if the angle of bend of the curved part of the endoscope is large, buckling at the connection part between the stent  16  and pusher tube  21  can be reduced.  
         [0154]      FIG. 13A  to  FIG. 13C  show a stent delivery device according to an eighth embodiment of the present invention. As is shown in  FIG. 13A , the stent delivery device according to the present embodiment is provided with an elongated guide catheter  111  that is insertable in a forceps channel of an endoscope (not shown). The guide catheter  111  is formed of a flexible synthetic resin material such as a fluoro-resin or a nylon resin. An inner cavity  112  is formed in the guide catheter  111  over the entire length thereof. A guide catheter cock  113  is provided near a proximal end portion of the guide catheter  111 .  
         [0155]     A stent  114 , which serves as a stent, is provided on a distal end portion of the guide catheter  111  in the state in which the stent  114  is engaged with the guide catheter  111 . A pusher tube  115  is provided on an outer peripheral surface of the guide catheter  111  on a proximal-end side of the stent  114 . The pusher tube  115  is held in the state in which the pusher tube  115  is engaged with the guide catheter  111 .  
         [0156]     The stent  114  is a relatively soft hollow tube, which is formed of a high-polymer compound with biocompatibility, such as polyethylene or silicone rubber. It is desirable that the outer peripheral surface of the stent  114  be coated with a hydrophilic lubricant. Outer peripheral portions at both ends of the stent  114  are provided with mutually opposed flaps  116  for preventing removal.  
         [0157]     The pusher tube  115  is formed of a flexible synthetic resin material such as a fluoro-resin or a nylon resin. A pusher tube cock  117  is provided at the proximal end of the pusher tube  21 .  
         [0158]     A guide wire  118  is axially passed through the inner cavity of the guide catheter  111 . The guide wire  118  is an elongated metallic twisted wire. The distal end portion of the guide wire  118  is tapered. Further, the proximal end portion of the guide wire  118  is led out of the guide catheter cock  113 .  
         [0159]     As is shown in  FIG. 13C , a cylindrical member  119  that serves as a connection mechanism is press-fitted in both the inner cavity of the stent  114  on the proximal end side thereof and the inner cavity of the pusher tube  115  on the distal end side thereof. The cylindrical member  119  separably connects the stent  114  and pusher tube  115 . The cylindrical member  119  is formed of a synthetic resin material or a metallic material. The guide catheter  111  is passed through the inner cavity of the cylindrical member  119 .  
         [0160]     One end portion of an operation wire  120 , which serves as release means, is connected to a proximal end portion of the cylindrical member  119 . The other end portion of the operation wire  120  extends to the vicinity of the pusher tube cock  117  through the inner cavity of the pusher tube  115 . A side hole  121  is formed in the pusher tube  115  in the vicinity of the pusher tube cock  117 . The operation wire  120  is led out of the side hole  121  and connected to an operation ring  122 .  
         [0161]     The apparatus with the above structure can achieve the following advantageous effects. In the stent delivery device with the above-described structure, the stent  114  and pusher tube  115  are-connected by the cylindrical member  119 . Thus, when the pusher tube  115  is axially moved, the stent  114  is also axially moved as one body. In addition, the cylindrical member  119  is press-fitted in the inner cavities of the stent  114  and pusher tube  115 . Accordingly, the bending strength of the connection part between the stent  114  and pusher tube  115  is high. Hence, even if the angle of bend of the curved part of the endoscope is large, the connection part is not buckled and the stent  114  can be advanced to the target part.  
         [0162]     If the operation wire  120  is pulled to the proximal end side by the operation ring  122  in the state in which the pusher tube  115  is held, the distal end portion of the cylindrical member  119  is removed from the inner cavity of the stent  114  and pulled into the inner cavity of the pusher tube  115 . As a result, the stent  114  and pusher tube  115  are separated.  
         [0163]     The operation of the eighth embodiment is described. When the stent delivery device according to this embodiment is used, the stent delivery device is set as follows.  
         [0164]     To begin with, as shown in  FIG. 13A , the operation wire  120  is inserted into the pusher tube  115 . Then, a proximal end portion of the cylindrical member  119  is press-fitted in the inner cavity of the pusher tube  115  at the distal end portion thereof. The cylindrical member  119  is coupled to the operation wire  120 .  
         [0165]     Further, after the guide catheter  111  is passed through the pusher tube  115 , the stent  114  is passed over the distal end portion of the guide catheter  111 . In this state, the distal end portion of the cylindrical member  119  is press-fitted in the inner cavity of the stent  114 , and the proximal end of the stent  114  is abutted upon the distal end of the pusher tube  115 . Thereby, as shown in  FIG. 13A , the pusher tube  115 , stent  114  and cylindrical member  119  are set in the assembled state.  
         [0166]     Thereafter, the insertion portion of the endoscope is inserted in the body cavity in advance, and a distal-end structural part, which is disposed at the distal end of the insertion portion of the endoscope, is guided to the vicinity of the bile duct.  
         [0167]     Subsequently, the guide wire  118  is passed through the forceps channel of the endoscope that is inserted in the body. At this time, under observation using the endoscope and observation using X-rays, the guide wire  118  is advanced and the distal end portion of the guide wire  118  is guided into a stenotic part of the bile duct.  
         [0168]     After the guide wire  118  is passed through the forceps channel of the endoscope, the guide catheter  111  on which the stent  114  and pusher tube  115  are set is passed over the guide wire  118 . At this time, the guide catheter  111  is inserted into the forceps while being guided by the guide wire  118 .  
         [0169]     Subsequently, the guide catheter  111  and pusher tube  115  are advanced by a manual operation on the proximal end side of the guide catheter  111 , and are led out of the distal-end structural part of the endoscope. In this state, the guide catheter  111  and stent  114  are inserted into the stenotic part. At this time, the stent  114  is engaged with the guide catheter  111 , and the cylindrical member  119  is press-fitted in the inner cavities of the stent  114  and pusher tube  115 . Thus, even if the guide wire  118  is curved with a large angle of bend, the stent  114  is not buckled. The stent  114  can be advanced together with the guide catheter  111  and pusher tube  115  and guided to the target part.  
         [0170]     After the stent  114  is inserted into the stenotic part by means of the guide catheter  111 , X-ray observation is performed. If it is confirmed by the X-ray observation that the stent  114  is pushed too deeply, the pusher tube  115  is pulled back to a position on the proximal end side. Thereby, the stent  114  can be pulled back by the cylindrical member  119 , and the stent  114  can exactly be positioned at the target part.  
         [0171]     Then, in the state in which the guide catheter  111  and guide wire  118  are left as such, the proximal end portion of the pusher tube  115  is held and the operation ring  122  is hooked with the finger and pulled toward the proximal end side. Thereby, the cylindrical member  119  is pulled into the inner cavity of the pusher tube  115  by the operation wire  120 . As is shown in  FIG. 13B , the distal end portion of the cylindrical member  119  is removed from the inner cavity of the stent  114 , and the stent  114  and pusher tube  115  are separated. As a result, the stent  114  is stayed at the stenotic part.  
         [0172]     In this case, the distal end portions of the guide catheter  111  and guide wire  118  are inserted into the stenotic part. Therefore, a contrast medium, etc. may be fed using the guide catheter  111  as a guide, or a subsequent treatment may be performed using the guide wire  118  as a guide.  
         [0173]      FIG. 14  shows a ninth embodiment of the invention. In this embodiment, the stent delivery device of the eighth embodiment (see  FIG. 13A  through  FIG. 13C ) is partly modified as follows. The parts common to those in the eighth embodiment are denoted by like reference numerals, and a description thereof is omitted.  
         [0174]     In this embodiment, the guide catheter  111  of the eighth embodiment is not used. Accordingly, in this embodiment, the structure can be simplified and the cost can be reduced. Further, the stent  114  and pusher tube  115  can be made thinner. In a case where the stenotic part is small in size, the stent  114  can easily be inserted.  
         [0175]     The advantageous effects of the ninth embodiment are the same as those of the eighth embodiment.  
         [0176]      FIG. 15  shows a tenth embodiment of the present invention. In this embodiment, the guide catheter  111  is not used. In addition, a substantially cylindrical member that serves as a connection member is formed of a spiral member  123 . A distal end portion of the spiral member  123  is press-fitted in the inner cavity of the stent  114 , and a proximal end portion thereof is press-fitted in the inner cavity of the pusher tube  115 . By using a spring member as the spiral member  123 , the resilience force for restoring elastic deformation of the connection part becomes excellent and the anti-buckling property of the connection part can be improved.  
         [0177]     The advantageous effects of the tenth embodiment are the same as those of the eighth embodiment.  
         [0178]      FIG. 16A  to  FIG. 16C  show an eleventh embodiment of the present invention. In this embodiment, the guide catheter  111  is not used. A cylindrical member  124  is tightly fitted on the outer peripheral surfaces of the stent  114  and pusher tube  115 .  
         [0179]     A side hole  125  is formed in the side wall of the distal end portion of the pusher tube  115 . The operation wire  120 , which is coupled to the cylindrical member  124 , is introduced into the inner cavity of the pusher tube  115  from the side hole  125 .  
         [0180]     Like the eighth embodiment, after the stent  114  is inserted into the stenotic part, X-ray observation is performed. If it is confirmed by the X-ray observation that the stent  114  is pushed too deeply, the pusher tube  115  is pulled back to a position on the proximal end side. Thereby, the stent  114  can be pulled back by the cylindrical member  124 , and the stent  114  can exactly be positioned at the target part.  
         [0181]     Then, the proximal end portion of the pusher tube  115  is held and the operation ring  122  is hooked with the finger and pulled toward the proximal end side. Thereby, the cylindrical member  124  is pulled onto the outer peripheral surface of the pusher tube  115  by the operation wire  120 . As is shown in  FIG. 16B , the distal end portion of the cylindrical member  124  is removed from the outer peripheral surface of the stent  114 , and the stent  114  and pusher tube  115  are separated. As a result, the stent  114  is positioned at the stenotic part.  
         [0182]     In this embodiment, there is no component in the stent  114  or pusher tube  115 , and therefore the stent  114  and pusher tube  115  can be made thinner.  
         [0183]      FIG. 17A  shows a twelfth embodiment of the present invention. In this embodiment, the cylindrical member  119 , which serves as the connection mechanism of the stent delivery device according to the eighth embodiment, is modified as follows.  
         [0184]     A cylindrical member  126  of the present embodiment has an outer peripheral surface that is provided with a plurality of recess/projection portions  127  arranged in the circumferential direction thereof. Each recess/projection portion  127  extends in the axial direction of the cylindrical member  126 . The cylindrical member  126  of this embodiment is press-fitted in the inner cavities of the stent  114  and pusher tube  115 . In this case, the cylindrical member  126  is firmly press-fitted in the inner cavities of the stent  114  and pusher tube  115 , and these parts are fixed.  
         [0185]      FIG. 17B  shows a modification of the cylindrical member  126  according to the twelfth embodiment. In this modification, as shown in  FIG. 17B , a ridge portion  129  is axially provided on a part of the outer peripheral surface of a cylindrical member  128 . The cylindrical member  128  of this embodiment is press-fitted in the inner cavities of the stent  114  and pusher tube  115 . In this case, the cylindrical member  128  is firmly press-fitted in the inner cavities of the stent  114  and pusher tube  115 .  
         [0186]     FIGS.  18  to  20  show a 13th embodiment of the invention. In this embodiment, the cylindrical member  124  of the eleventh embodiment (see  FIGS. 16A  to  16 C) is formed of a heat-shrinkable tube. Further, as shown in  FIG. 19 , a recess portion  131  is formed at a part of the outer peripheral surface of the stent  114 , which is covered with the cylindrical member  124 . A ball chip  132  is embedded in the recess portion  131 . The ball chip  132  is coupled to a distal end portion of the operation wire  120 .  
         [0187]     The heat-shrinkable tube is fitted in the state in which the ball chip  132  is placed in the recess portion  131  of the stent  114 . Thus, the ball chip  132  is buried between the cylindrical member  124  and the recess portion  131  of the stent  114 .  
         [0188]     Next, the operation of the 13th embodiment is described. When the stent delivery device of this embodiment is to be used, the stent  114  and pressure tube  115  are coupled by the cylindrical member  124 . Thus, when the pusher tube  115  is axially moved, the stent  114  is also axially moved as one body. In addition, the cylindrical member  119  is fitted over the outer peripheral surfaces of the stent  114  and pusher tube  115 . Accordingly, the bending strength of the connection part between the stent  114  and pusher tube  115  is high. Hence, even if the angle of bend of the curved part of the endoscope is large, the connection part is not buckled and the stent  114  can be advanced to the target part.  
         [0189]     If the operation wire  120  is pulled to the proximal end side by the operation ring  122  in the state in which the pusher tube  115  is held, the ball chip  132  is pulled and removed from between the cylindrical member  124  and the recess portion  131  of the stent  114 . With the removal of the ball chip  132 , as shown in  FIG. 20 , the pusher tube  115  is pulled out of the inner cavity of the cylindrical member  124 , and the stent  114  and pusher tube  115  are separated. Thereby, the stent  114  is positioned in the stenotic part.  
         [0190]     With the present embodiment, too, the same advantageous effects as in the eleventh embodiment can be obtained. In addition, in this embodiment, in particular, when the stent  114  and pusher tube  115  are separated, the cylindrical member  124  remains attached to the stent  114  that is separated from the pusher tube  115 . Therefore, when the stent  114  is changed, the part of the cylindrical member  124  attached to the stent  114  can be held, and this facilitates the work for removing the stent  114 .  
         [0191]      FIG. 21A  and  FIG. 21B  show a 14th embodiment of the present invention. In this embodiment, the cylindrical member  119  according to the eighth embodiment (see  FIG. 13A  to  FIG. 13C ) is formed of a shape-memory alloy tube.  
         [0192]     For example, at a normal temperature (reference temperature), the shape-memory alloy tube of the cylindrical member  119  is broadened to have a greater outside diameter than the stent  114 , as shown in  FIG. 21A . At this time, the stent  114  and pusher tube  115  are separably coupled by the cylindrical member  119 .  
         [0193]     On the other hand, for example, when the shape-memory alloy tube of the cylindrical member  119  is heated up to a higher temperature than the reference temperature or cooled down to a lower temperature than the reference temperature, the shape-memory alloy tube deforms to have a less outside diameter than the stent  114 , as shown in  FIG. 21B .  
         [0194]     In the present embodiment, if the shape-memory alloy tube of the cylindrical member  119  is deformed to a reduced shape, the stent  114  and pusher tube  115  can be separated.  
         [0195]     The shape-memory alloy tube of the cylindrical member  119  may be configured to be heated by application of electric power.  
         [0196]      FIG. 22A  and  FIG. 22B  show a modification of the 14th embodiment. In this modification, the shape-memory alloy tube of the cylindrical member  119  according to the 14th embodiment (see  FIG. 21A  and  FIG. 21B ) is replaced with a coil-shaped engaging member  141 . This engaging member  141  is formed of a spiral member of a shape-memory alloy.  
         [0197]     For example, at a normal temperature (reference temperature), the shape-memory alloy of the engaging member  141  is broadened to have a greater outside diameter than the stent  114 , as shown in  FIG. 22A . At this time, the stent  114  and pusher tube  115  are separably coupled by the engaging member  141 .  
         [0198]     On the other hand, for example, when the shape-memory alloy of the engaging member  141  is heated up to a higher temperature than the reference temperature or cooled down to a lower temperature than the reference temperature, the shape-memory alloy deforms to have a less outside diameter than the stent  114 , as shown in  FIG. 22B .  
         [0199]     In the present embodiment, if the shape-memory alloy of the engaging member  141  is deformed to a reduced shape, the stent  114  and pusher tube  115  can be separated.  
         [0200]     As has been described above, the present invention is effective in the technical field of a stent delivery device that is used in performing an operation for inserting and positioning a stent in a body cavity using an endoscope, and in the technical field of the manufacture and use of this stent delivery device.