now looking first at fig7 , the introducer with a stent graft mounted onto it according to one embodiment of the present invention is shown schematically . the introducer generally shown as 1 has an introducer catheter 3 extending over a guide wire catheter 5 . the guide wire catheter 5 extends from the distal end 7 of the introducer 1 to immediately distal of the nose cone dilator 11 . a branched stent graft 13 is retained at its proximal end by a retention arrangement ( see fig1 and 13 for one example of a proximal retention arrangement ) onto the introducer immediately distal of the nose cone dilator 11 . the branched stent graft 13 is retained at its distal end by another retention arrangement ( see fig1 and 15 for examples of a proximal retention arrangement ) onto the introducer . a sleeve 15 operated by a sleeve manipulator 17 is mounted on the introducer catheter 3 and in the ready to deploy position the sleeve 15 extends over the branched stent graft 13 to the nose cone dilator 11 . as illustrated in fig7 , however , the sleeve 15 is withdrawn so that the branched stent graft is exposed to show detail of the assembly . a handle 19 at the distal end of the introducer catheter 3 enables manipulation of the introducer 1 . an indwelling catheter 21 enters a lumen ( not shown ) of the introducer catheter 3 at the handle 19 and exits from the introducer catheter 3 at the distal end 23 of the branched stent graft 13 . the branched stent graft 13 has a substantially tubular body with a main lumen through the main tubular body and a side lumen through the branch 25 . the indwelling catheter 21 enters the lumen of the branch 25 from its distal end 26 and hence it passes outside the main tubular body of the branched stent graft before it enters the branch lumen . the indwelling catheter then exits from the main body adjacent the nose cone dilator and extends along the side of the nose cone dilator in a groove 27 in the nose cone dilator . within the indwelling catheter 21 , there is a guide wire 29 . this guide wire 29 can be pushed through the indwelling catheter so that it extends beyond the tip 31 of the nose cone dilator so that it can be snared as will be discussed in relation to fig1 to 6 showing one embodiment of the stent graft placement procedure . preferably the tip 32 of the indwelling catheter is tapered around the guide wire 29 to prevent blood loss through the indwelling catheter . now looking at fig1 to 6 , it will be seen that there is schematically illustrated a series of arteries within the human body , although as discussed earlier , the invention is not restricted to this particular application . a descending aorta 40 extends down to an aortic bifurcation 42 from which extend common iliac arteries 44 and 46 . from each of the common iliac arteries an internal iliac artery 48 and 50 , respectively , extends . as discussed earlier , the internal iliac arteries 48 and 50 cannot be practically accessed from their distal ends remote from the junction with the common iliac artery . as shown in fig1 , a guide wire 50 for the deployment device 52 has been extended into a femoral artery via a femoral incision ( not shown ) and extended up beyond the aortic bifurcation 42 to the aorta 40 . the introducer 1 has then been deployed over the guide wire with the nose cone dilator 11 extending nearly up to the aortic bifurcation . at this stage , the sleeve 15 on the deployment device extends up to the nose cone dilator 11 but has been withdrawn slightly to expose the proximal end 32 of the indwelling catheter 21 . as can be seen in fig2 , the guide wire 29 from the indwelling catheter 21 has been extended so that it extends up beyond the aortic bifurcation but only a short distance up the aorta 40 . a snare catheter 52 has been deployed via the contra - lateral iliac artery 46 and by suitable radiographic techniques the loop 54 of the snare catheter 52 is used to catch the guide wire 29 . fig2 a shows an alternative step in the process . i this step the indwelling catheter 21 and the guide wire 29 have been advanced together to the aortic bifurcation 42 and so that the indwelling catheter 21 is beyond the nose cone dilator 11 . the guide wire 29 is then advance so that it can be snared by the loop 54 of the snare catheter . by this alternative step the guide wire 29 is held more firmly and there is less likelihood that it will become entangled with the main guide wire 50 . as shown in fig3 , the guide wire 29 has been withdrawn through the contra - lateral iliac artery 46 and the indwelling catheter 21 has been advanced over the guide wire so that it extends over the aortic bifurcation 42 and down the contra - lateral iliac artery 46 . to assist this process , the sheath 15 has been withdrawn to the distal end 23 of the branched stent graft 13 so that it is just distal of the proximal end of the introducer catheter 3 . at this stage the branched stent graft 13 is partially freed but is still retained by retention arrangements at at least the proximal and distal ends of the branched stent graft and is hence in an unexpanded or not fully expanded condition . fig4 shows the next stage of the process where a sheath 58 of a suitable size has been advanced over the guide wire 29 via the contra - lateral artery and indwelling catheter 21 so that it enters the proximal end 60 of the branched stent graft 13 . at this stage , the indwelling catheter and guide wire 29 still extends down the iliac artery 44 on the introducer 1 so that the sheath 58 can be manipulated to successfully enter the proximal end of the branched stent graft so that it extends towards and into the branch 25 on the stent graft 13 . at this stage , the indwelling catheter 21 and guide wire 19 can be withdrawn either from the contra - lateral iliac artery 46 or from the iliac artery 44 and another guide wire 62 introduced via the sheath 58 . this guide wire 62 can then be manipulated so that it enters the internal iliac artery 48 . as shown in fig5 , a further deployment device 63 can then be introduced via the sheath 58 from the contra - lateral iliac artery 46 to extend out of the distal end of the branch 25 of the branched stent graft 13 so that a leg extension 64 can be deployed to extend from the branch 25 of the branched stent graft 13 . as shown in fig6 , the sheath 58 from the contra - lateral iliac artery 46 can then be withdrawn and the release mechanisms at each end of the stent graft 13 can be released and the leg extension 64 released so that the branched stent graft with leg extension is then deployed in the common iliac artery . the introducer 1 can then be withdrawn although in some situations it may be desirable to leave the sleeve 15 in position so that further deployment of a stent graft into the aorta such as a bifurcated stent graft can be achieved through the sheath 15 . in summary therefore , the steps in the graft placement procedure accordingly using the device of the present invention may be as follows : 1 . deploy an introducer into a femoral artery via a femoral incision and extend the introducer up to the aortic bifurcation . 2 . withdraw the sheath to expose the proximal end of an indwelling catheter associated with the introducer . 3 . advance an indwelling guide wire through the indwelling catheter beyond the nose cone dilator of the introducer . 4 . introduce a snare catheter into the contra - lateral iliac artery via a femoral route and snare the indwelling guide wire . 5 . withdraw the indwelling guide wire through the contra - lateral iliac artery and advance the indwelling catheter around the aortic bifurcation to protect the aortic bifurcation during subsequent steps . 6 . withdraw the main sheath to expose the branched stent graft but still have the branched stent graft retained at each of its ends . 7 . deploy an auxiliary sheath over the indwelling guide wire up the contra - lateral iliac artery and into the branched stent graft via the proximal end of the branched stent graft . 8 . advance the auxiliary sheath into the short leg of the branched stent graft via the indwelling catheter guide wire or another guide wire which has been deployed through the sheath which has been placed via the contra - lateral iliac artery . 9 . remove the indwelling catheter and indwelling guide wire . 10 . advance a guide wire through the auxiliary sheath via the contra - lateral iliac artery and manipulate it into the internal iliac artery . at this stage , it may be necessary to withdraw the deployment device or rotate it slightly to guide the branch of the branched stent graft towards the internal iliac artery . 11 . advance a short leg introducer with a leg stent graft over the guide wire in the contra - lateral iliac artery and through the auxiliary sheath and into the internal iliac artery . 12 . release the proximal distal ends of the branched stent graft 13 . release the leg stent graft from the short leg introducer or balloon expand the leg stent graft . 14 . withdraw the contra - lateral iliac artery auxiliary sheath , introducer and guide wire . 15 . withdraw the main introducer . as discussed earlier it may be necessary or desirable to leave the sheath of the main introducer and / or the main guide wire to enable deployment of further stent grafts within the aorta and aortic bifurcation . now looking at fig8 and 9 , an introducer with a stent graft mounted onto it according to an alternative embodiment of the present invention is shown schematically . the same reference numerals are used for corresponding features to those of fig7 . the introducer generally shown as 1 has an introducer catheter 3 extending over a guide wire catheter 5 . the guide wire catheter 5 extends from the distal end 7 of the introducer 1 to immediately distal of the nose cone dilator 11 which is at the proximal end 9 of the introducer . a fenestrated stent graft 70 is retained by a retention arrangement ( not shown ) onto the introducer immediately distal of the nose cone dilator 11 . a sleeve 15 operated by a sleeve manipulator 17 is mounted on the introducer catheter 3 and in the ready to deploy position the sleeve 15 extends over the stent graft 70 to the nose cone dilator 11 . as illustrated in fig7 , however , the sleeve 15 is withdrawn so that the stent graft is exposed to show detail of the assembly . a handle 19 at the distal end of the introducer catheter 3 enables manipulation of the introducer 1 . an indwelling catheter 21 enters a lumen ( not shown ) of the introducer catheter 3 at the handle 19 and exits from the introducer catheter at the distal end 23 of the stent graft 70 . the stent graft 70 has a substantially tubular body with a main lumen through the main tubular body and a fenestration 71 . the indwelling catheter 21 enters the fenestration 71 from outside the stent graft and hence it passes outside the main tubular body of the stent graft at the distal end thereof , before it enters fenestration . the indwelling catheter then passes through the main lumen of the stent graft to its proximal end and exits from the main body adjacent the nose cone dilator 11 and extends along the side of the nose cone dilator in a groove 27 in the nose cone dilator . within the indwelling catheter 21 , there is a guide wire 29 . this guide wire 29 can be pushed through the indwelling catheter so that it extends beyond the tip 31 of the nose cone dilator so that it can be snared as discussed in relation to fig1 to 6 showing a stent graft placement procedure . preferably the tip 32 of the indwelling catheter is tapered around the guide wire 29 to prevent blood loss through the indwelling catheter . fig1 shows a stage of deployment of the stent graft as shown in fig8 and 9 corresponding to the stage of deployment shown in fig5 above . the same reference numeral are used for corresponding features to those of fig1 to 6 . prior to the stage shown in fig1 a guide wire 50 for the deployment device 52 has been extended into a femoral artery via a femoral incision ( not shown ) and extended up beyond the aortic bifurcation 42 into the aorta 40 . an introducer 1 has then been deployed over the guide wire with the nose cone dilator 11 extending nearly up to the aortic bifurcation . at this stage , the sleeve 15 on the deployment device extends up to the nose cone dilator but has been withdrawn slightly to expose the proximal end of the indwelling catheter 21 . next a guide wire from an indwelling catheter ( not shown in fig1 ) has been extended so that it extends up beyond the aortic bifurcation but only a short distance up the aorta 40 . a snare catheter has been deployed via the contra - lateral iliac artery 46 and by suitable radiographic techniques the loop of the snare catheter has been used to catch the guide wire . the guide wire has then been withdrawn through the contra - lateral iliac artery 46 and the indwelling catheter has been advanced over the guide wire so that it extends over the aortic bifurcation 42 and down the contra - lateral iliac artery 46 . to assist this process , the sheath 15 has been withdrawn to just distal of the fenestration 25 and still covering the distal end 23 of the stent graft 70 . at this stage the stent graft 13 is partially freed but is still retained by a retention arrangements at the proximal end 60 of the stent graft and by the sheath at the distal end . the exposed portion of the stent graft between the proximal end and the fenestration can expand although there may be diameter reducing ties ( not shown ) to restrict the amount of expansion . next a sheath 58 of a suitable size has been advanced over the guide wire 29 and indwelling catheter 21 so that it enters the proximal end 60 of the branched stent graft 70 . at this stage , the indwelling catheter and guide wire 29 still extends down the iliac artery 44 on the introducer 1 so that the sheath 58 can be manipulated to successfully enter the proximal end of the branched stent graft 60 so that it extends towards and into the fenestration 71 on the stent graft 70 . at this stage , the indwelling catheter 21 and guide wire 19 can be withdrawn , either from the contra - lateral iliac artery 46 , or from the iliac artery 44 and another guide wire 62 introduced via the sheath 58 . this guide wire 62 can then be manipulated so that it enters the internal iliac artery 48 . as shown in fig1 , a further deployment device 63 has then been introduced via the sheath 58 from the contra - lateral iliac artery 46 to extend out of the fenestration 71 of the stent graft 70 . the further deployment device 63 carries a leg extension 64 . the leg extension 64 can be deployed to extend from the fenestration 71 of the stent graft 70 . the leg extension 64 can be a covered balloon expandable stent for instance , which is carried on a balloon in the deployment device so that it can be deployed and expanded with its proximal end retained in the fenestration and extending into the internal iliac artery 48 . now looking at fig1 , an introducer with a stent graft mounted onto it according to an alternative embodiment of the present invention is shown schematically . in this embodiment the stent graft 90 has a fenestration 94 in the wall of the stent graft 90 and an internal leg extension 92 extending inwardly and toward the proximal end 74 of the stent graft 90 from the fenestration 94 . the indwelling catheter 80 extends into the fenestration 94 and into the internal leg extension 92 and toward the proximal end 74 of the stent graft 90 . the indwelling catheter 80 then exits from the main body adjacent the nose cone dilator 82 and extends along the side of the nose cone dilator 82 in a groove 81 in the nose cone dilator 82 . fig8 to 11 show various embodiments of the present invention in a stylised manner . it should be noted that the configuration with the main sheath withdrawn completely off the stent graft but with the indwelling catheter and guide wire in its initial position would not occur in practice . fig1 shows a side view of one method of proximal retention suitable for the present invention and fig1 shows a cross sectional view of the arrangement shown in fig1 . the same reference numerals are used for corresponding features to those of fig7 for corresponding items . the guide wire catheter 5 extends to a nose cone dilator 11 and the proximal end of the stent graft 13 is retained onto the guide wire catheter just distal of the nose cone dilator . retention is by means of a pair loops of suture material 101 each of which is engaged with a trigger wire 103 extending from an aperture in the guide wire catheter 5 . the loops are placed so that there is formed a smaller 105 and larger fold 107 of the stent graft 13 at its proximal end . the indwelling catheter passes through the region defined by the larger fold 107 and therefore when the sheath 58 ( see fig4 ) has been advanced over the guide wire then it can more easily enter the lumen of the stent graft . fig1 shows a side view of one method of distal retention suitable for the present invention . the same reference numerals are used for corresponding features to those of fig7 for corresponding items . in this embodiment the distal end 23 of the stent graft 13 is retained onto the guide wire catheter 5 just proximal of the deployment catheter 3 by means of a suture loop 109 engaged into the stent graft 13 and a loop of trigger wire 111 extending from the deployment catheter 3 . removal of the trigger wire 111 when required will release the distal end 23 of the stent graft 13 . fig1 shows a side view of an alternative method of distal retention suitable for the present invention . the same reference numerals are used for corresponding features to those of fig7 for corresponding items . in this embodiment the distal end 23 of the stent graft 13 is retained onto the guide wire catheter 5 just proximal of the deployment catheter 3 by means a loop of trigger wire 113 extending from the deployment catheter 3 and passing through a portion of the stent graft 13 . removal of the trigger wire 113 when required will release the distal end 23 of the stent graft 13 . throughout this specification various indications have been given as to the scope of this invention but the invention is not limited to anyone of these but may reside in two or more of these combined together . the examples are given for illustration only and not for limitation . throughout this specification and the claims that follow , unless the context requires otherwise , the words ‘ comprise ’ and ‘ include ’ and variations such as ‘ comprising ’ and ‘ including ’ will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers .
an introduction arrangement for a fenestrated or branched stent graft intended for deployment into the lumen of a vessel having a blind vessel extending from it . the introducer has a distal end intended to remain outside a patient in use and a proximal end with a nose cone dilator and an arrangement to retain the branched stent graft distally of the nose cone dilator . a sheath on the introducer extends over the branched stent graft to the nose cone dilator . an indwelling catheter extends from the distal end of the introducer and enters the fenestration or side arm and through to the nose cone dilator , the indwelling catheter has a guide wire extending through it . the guide wire can be extended beyond the nose cone dilator in use before the sheath is withdrawn from the branched stent graft so that it can be snared from the contra - lateral artery .