an embodiment of a stent delivery system 1 of the present invention will be described . fig1 is a plan view of the stent delivery system 1 of the present embodiment . fig2 is a bottom view of the stent delivery system 1 . fig3 is a cross - sectional view in line a - a of fig1 . fig4 is a cross - sectional view in line b - b of fig3 . fig5 is an explanatory view for illustrating the positional relationship between a first passage and a second passage in the stent delivery system . fig6 is a cross - sectional view showing a state after the release of a stent 2 in the stent delivery system 1 . fig7 is a cross - sectional view showing a state after the release of the stent 2 in the stent delivery system 1 and after the stent 2 comes off a connecting member 7 . in the stent delivery system 1 of the present embodiment shown in fig1 , a tubular stent 2 is arranged at a desired position within a living body . the stent 2 , which can be applied to the stent delivery system 1 of the present embodiment , is formed with a through - hole 2 a that allows the inside and outside of the stent 2 to communicate with each other and couples the stent delivery system 1 and the stent 2 . in the present embodiment , the through - hole 2 a is provided in the vicinity of an end portion of the stent 2 . when the stent 2 is inserted into the stent delivery system 1 , the stent 2 is connected to the stent delivery system 1 with the stent 2 being directed to the stent delivery system 1 so that the side of the stent where the through - hole 2 a is formed gets closer to a distal end of the stent delivery system 1 . additionally , the shape of the stent 2 may have flaps formed at both ends or may be a simple tubular shape with no flap . the material of the stent 2 is not particularly limited . for example , the stent 2 may be made of resin having flexibility . as shown in fig1 , the stent delivery system 1 includes a guide catheter 3 , a push catheter 4 , and a connecting member 7 . the guide catheter 3 is an elongated member that is inserted into the stent 2 and inserted into the living body together with the stent 2 . the guide catheter 3 may be solid or tubular . the guide catheter 3 has flexibility . the push catheter 4 is a tubular member provided in order to push the stent 2 along the guide catheter 3 . the push catheter 4 has an internal diameter such that the guide catheter 3 can be freely advanced and retracted within the push catheter . moreover , a gap that the guide catheter 3 can be advanced and retracted with respect to the push catheter 4 is provided between the guide catheter 3 and the push catheter 4 even in a state where both the guide catheter 3 and the connecting member 7 are disposed within the push catheter 4 . the push catheter 4 is inserted into the living body together with the guide catheter 3 after the guide catheter 3 is inserted into the push catheter . additionally , the push catheter 4 has a first passage 5 formed with a through - hole ( first through - hole ) that allows the inside and the outside of the push catheter 4 to communicate with each other , and a second passage 6 formed with a through - hole ( second through - hole ) that allows the inside and the outside of the push catheter 4 to communicate with each other at a position different from the first passage 5 . the first passage 5 and the second passage 6 are passages into which the connecting member 7 is inserted . additionally , the first passage 5 and the second passage 6 are arranged on a line that is parallel to a central axis o 1 of the push catheter 4 and open , in the external surface of the push catheter 4 . there is a space in between the first passage 5 and the second passage 6 . accordingly , compared to a case where the first passage 5 and the second passage 6 are located in parallel along the circumferential direction of the push catheter 4 , the distance of the first passage 5 and the second passage 6 is easily increased , and it is possible to prevent a situation where , when the connecting member 7 is caught in an endoscope or other devices and an external force acts on the push catheter 4 , the push catheter 4 is completely torn and the connecting member 7 comes off the push catheter 4 . additionally , in the present embodiment , a proximal end of the push catheter 4 and a proximal end of the guide catheter 3 are enabled to be coupled to each other . the push catheter 4 and the guide catheter 3 can be integrally advanced and retracted in a state where the proximal end of the push catheter 4 and the proximal end of the guide catheter 3 are coupled to each other . the connecting member 7 is a member for connecting the stent 2 to the push catheter 4 . the connecting member 7 is a flexible thread having a closed loop shape . in the present embodiment , the thread used as the connecting member 7 has a closed loop shape as both ends thereof are tied together by one knot 8 shown in fig2 . the materials of the thread used as the connecting member 7 are not particularly limited if materials that do not affect the living body are provided . for example , the connecting member 7 may be a thin wire made of resin or metal . additionally , the distances of the first passage 5 and the second passage 6 from a distal end of the push catheter 4 are set to optimal distances in correspondence with the structure of an endoscope to which the stent delivery system 1 is applied . for example , as shown in fig5 , when the stent delivery system 1 is applied to a side view type endoscope 100 , it is preferable that the first passage 5 and the second passage 6 be located closer to proximal end side than forceps raising base 102 in the side view type endoscope 100 , in a state where the distal end of the push catheter 4 is delivered from a distal end of a treatment tool channel 101 of the side view type endoscope . additionally , in a case where there is a step in the inner surface of the treatment tool channel 101 on the distal end side due to a connecting portion x 1 or the like between a rigid portion 103 of a distal end of the endoscope and a channel tube 104 , when the distal end of the push catheter 4 is delivered to a position suitable for the indwelling of the stent 2 , it is preferable that the first passage 5 and the second passage 6 be located closer to the proximal end side than this step ( a portion shown by symbol x 1 in fig5 ). more specifically , when the length from an opening portion of the distal end of the treatment tool channel 101 to a proximal end of the forceps raising base 102 is about 10 mm , and the length from the opening portion of the distal end of the treatment tool channel 101 to a proximal end of the stepped portion ( portion shown by symbol x 1 in fig5 ) of the treatment tool channel 101 is about 20 mm , the first passage 5 and the second passage 6 are provided at a position apart from the distal end of the push catheter 4 by about 55 mm . in this case , even if the distal end of the push catheter 4 is made to protrude by about 20 mm from the opening portion of the treatment tool channel when the stent 2 is arranged , the first passage 5 and the second passage 6 are located closer to the proximal end side than the forceps raising base 102 and the stepped portion ( portion shown by symbol x 1 in fig5 ) of the treatment tool channel 101 . by setting the positions of the first passage 5 and the second passage 6 as described above , the effect of preventing a phenomenon in which the connecting member 7 extending from the inside of the push catheter 4 through the first passage 5 and the second passage 6 to the outside is cut or the knot 8 is untied is exhibited . next , a state where the connecting member 7 is attached to the push catheter 4 will be described in detail with reference to fig3 and 4 . only one thread is inserted through the first passage 5 , and only one thread is inserted through the second passage 6 . accordingly , the thread used as the connecting member 7 is configured so as not to come off the push catheter 4 unless either the thread is cut or the push catheter 4 is torn . the connecting member 7 ( thread ) pulled out of the push catheter 4 from the first passage 5 and the second passage 6 is fixed to an external surface of the push catheter 4 . the thread pulled out from the inside of the push catheter 4 through the first passage 5 to the outside and the thread pulled out from the inside of the push catheter 4 through the second passage 6 to the outside extend in opposite directions along the circumferential direction of the push catheter 4 , in the circumferential direction of the push catheter 4 . in the present embodiment , the knot 8 of the connecting member 7 ( thread ) is disposed on the outside of the push catheter 4 , and the knot 8 is fixed by adhesion . additionally , the knot 8 may be adhered and fixed to the outer peripheral surface of the push catheter 4 . additionally , both the connecting member 7 pulled in from the outside of the push catheter 4 via the first passage 5 to the inside of the push catheter and the connecting member 7 pulled in from the outside of the push catheter 4 via the second passage 6 to the inside of the push catheter are able to extend from the distal end of the push catheter 4 through the inside of the push catheter 4 . the connecting member 7 extended from the distal end of the push catheter 4 has a u shape that is folded back in the vicinity of the distal end of the push catheter 4 . the extending length of the connecting member 7 from the distal end of the push catheter 4 is set according to the shape of the stent 2 . next , a state where the connecting member 7 is attached to the stent 2 and the guide catheter 3 will be described in detail . as shown in fig4 , in the use of the stent delivery system 1 , before the release of the stent 2 , the stent 2 is disposed parallel to the push catheter 4 so as to be capable of coming into contact with the distal end of the push catheter 4 , and the guide catheter 3 is inserted through the inside of the stent 2 and the inside of the push catheter 4 . moreover , before the release of the stent 2 , the connecting member 7 ( thread ) is fixed to the push catheter 4 , both the thread extending from the first passage 5 and the thread extending from the second passage 6 are delivered together with the guide catheter 3 from the distal end of the push catheter 4 , and extends to the inside of the stent 2 through the through - hole 2 a of the stent 2 along an external surface of the stent 2 . the connecting member 7 extending to the inside of the stent 2 has a loop shape surrounding the guide catheter 3 inside the stent 2 . in this state , the stent 2 is locked to the connecting member 7 built between the push catheter 4 and the guide catheter 3 , and the stent 2 is held by the thread so that the stent 2 does not fall off the stent delivery system 1 . as shown in fig4 and 6 , in the use of the stent delivery system 1 , when the stent 2 is released at a desired position within the living body , the guide catheter 3 is moved to the proximal end side after the stent 2 is arranged at the desired position . accordingly , the guide catheter 3 slips out from the connecting member 7 ( thread ) having the loop shape surrounding the guide catheter 3 inside the stent 2 . subsequently , the push catheter 4 and the guide catheter 3 are moved to the proximal end side . then , the connecting member 7 ( thread ) fixed to the push catheter 4 is pulled out of the stent 2 through the through - hole 2 a of the stent 2 . then , the thread comes off the stent 2 . the thread that has come off the stent 2 , as shown in fig7 , is pulled back to the proximal end side together with the push catheter 4 in a state where the thread is supported by an opening end portion in the distal end of the push catheter 4 . at this time , a distal end portion of the thread used as the connecting member 7 is in a state where the distal end portion extends in a distal end direction from the opening end portion of the distal end of the push catheter 4 . in the related art , in a stent delivery system that holds a stent using thread , the thread may be entangled in an endoscope or other devices if the thread , which is brought into a state where the thread is delivered from a distal end of a push catheter after the release of the stent , is long . for example , in the case of the thread having folding within the stent as in patent document 1 , the thread is long compared to the thread that is the connecting member of the present embodiment . thus , the thread becomes easily entangled . additionally , when the push catheter is provided with only one passage for allowing the thread to pass through the push catheter , and a closed loop - shaped thread is hung between the passage and a distal end opening of the push catheter , the thread may be deflected so as to spread in a radial direction of the push catheter after the release of the stent . even in this case , the thread becomes easily entangled . in the present embodiment , the thread is shortened by forming the loop surrounding the guide catheter 3 within the stent 2 , and is brought into a state where the thread is supported by the opening end portion in the distal end of the push catheter 4 after the release of the stent 2 . thus , as compared to the above related - art configuration , a probability that the thread may be entangled in the endoscope and other devices in the process of extracting the push catheter 4 from the endoscope after the release of the stent 2 can be lowered . although the embodiment of the present invention has been described above with reference to the drawings , specific configuration is not limited to the embodiment . additions , omissions , substitutions , and other modifications of components can be made as long as there is no departure from the concept of the present invention . accordingly , the present invention is not considered to be limiting from the foregoing description , and is only limited by the scope of the appended claims . for example , in the above - described embodiment , the stent 2 is provided with the through - hole 2 a for allowing the connecting member 7 to pass therethrough . however , if there is the through - hole that allows the inside and the outside of the stent 2 to communicate with each other irrespective of a purpose , the stent 2 can be suitably indwelled through the connecting member 7 similar to the above embodiment . additionally , the through - hole formed in the stent 2 may be machined so that resistance decreases when the thread is pulled out from the through - hole . additionally , in the above - described embodiment , the passages on the push catheter 4 formed in order to allow the connecting member 7 to pass through are two including the first passage 5 and the second passage 6 . however , only one passage may be provided . in that case , two connecting members can be connected outside the push catheter 4 by pulling out the connecting members through one passage similar to the above - described example . additionally , the thread used as the connecting member 7 may have elasticity . if the thread used as the connecting member 7 has elasticity , the thread delivered from the distal end of the push catheter 4 does not hang down easily , and is held in the loop shape that is directed to the distal end direction of the push catheter 4 . thus , the thread is not further easily entangled . although the preferred embodiments of the present invention have been described above , the present invention is not limited to these embodiments . additions , omissions , substitutions , and other modifications of components can be made without departing to the invention as long as there is no departure from the concept of the invention . the invention is not to be considered as being limited by the foregoing description , and is limited only by the scope of the appended claims .
a stent delivery system for delivering a stent , the stent delivery system having a push catheter , a guide member , and an elongated stent securing material having a first portion arranged to a push catheter outer surface , a second portion , a third portion , and a fourth portion arranged to the push catheter outer surface , in that order . the first portion and the fourth portion are arranged to the push catheter outer surface such that only one of the first portion and the fourth portion is present on a cross - section plane orthogonal to the longitudinal axis . the stent delivery system is configured to have a secured configuration in which the guide member is arranged within a push catheter lumen and a stent lumen and through a loop formed by a section between the second portion and the third portion to secure the stent .