the following detailed description and examples are provided for the limited purpose of illustrating exemplary embodiments of the invention and not for the purpose of exhaustively describing all possible embodiments of the invention . fig1 a through 1e show one example of a method for treating an endoleak that has occurred in a bifurcated aorto - illiac endovascular graft 10 that has been implanted in a human patient to treat an abdominal aortic aneurysm an that involved the infrarenal aorta a and portions of the illiac arteries i . in this example , the endoleak has resulted from less than adequate coaptation or sealing between the graft anchoring device 14 at the end of one of the bifurcated legs of the endovascular graft 10 and the wall of the patient &# 39 ; s left iliac artery i . initially , as shown in fig1 b , a guidewire 18 is inserted into the patient &# 39 ; s right femoral artery and the guidewire 18 is advanced , using well known technique , through the right iliac leg of the graft 10 and into the main aortic portion of the graft 10 . a catheter 20 is advanced over the guidewire to a position where the distal outlet opening 23 of the catheter 20 is directed at the wall of the graft 10 as shown in fig1 c . a hollow penetrator cannula 22 having a sharpened distal tip is then advanced out of the distal end opening 23 of the catheter 20 and through the wall of the graft into the perigraft space pgs , as also shown in fig1 c . thereafter , as shown in fig1 d , the expansile polymeric material 30 is introduced , while in its non - expanded state , through the lumen of the penetrator cannula 22 and into the perigraft space pgs . after being introduced into the perigraft space pgs , the expansile polymeric material 30 expands to its expanded state so as to substantially fill the aneurysmic sac in the manner shown in fig1 e . another example of a method according to the present invention is shown in fig2 a - 2d . in this example , the aneurysm an involves only the infrarenal abdominal aorta a and does not extend into the iliac arteries i . as shown in fig2 a , a catheter 20 is percutaneously inserted into a femoral artery and advanced to a position where the distal end of the catheter 20 is located within the aorta slightly inferior to the aneurysm . a blunt tipped cannula 22 a is then advanced out of the end of the catheter 20 , into the aneurysmic portion of the aorta . as shown in fig2 b , a straight endovascular graft 10 a is then introduced , radially expanded and implanted , in accordance with technique well known in the art . when so implanted , the graft 10 a bridges or extends through the aneurysm a and the graft anchoring devices 14 a are in substantial coaptation with the healthy aortic wall above and below the aneurysm . the blunt tipped cannula 22 a is captured between the inferior end of the graft 10 a and the aorta wall , as shown . preferably , the blunt tipped cannula 22 a will be formed of metal hypotubing or plastic tubing that is sufficiently strong and crush resistant to avoid substantial collapsing or closing of its lumen when it is compressed between the adjacent graft anchoring device 14 a and the aorta wall , as shown in fig2 b . thereafter , as shown in fig2 c , the expansile polymeric material 30 is then injected through the catheter 20 , through the lumen of the cannula 22 a , and into the perigraft space pgs . after being introduced into the perigraft space pgs , the expansile polymeric material 30 expands to its expanded state so as to substantially fill the aneurysm sac . the catheter 20 and cannula 22 are then removed , leaving the graft 10 a and expanded polymeric material 30 in place , in the manner shown in fig2 d . fig3 shows an example of yet another method for carrying out the present invention , wherein the expansile polymeric material is injected into the perigraft space pgs through a cannula 20 b that has been non - transluminally inserted through adjacent tissues and into the aneurysm sac . in this example , an abdominal aortic aneurysm a has been treated by placement of an endovascular graft 10 within the aorta . to treat an existing endoleak or to prevent aneurysm rupture or other complication that could arise from a subsequently occurring endoleak , it is desired to introduce an expansile polymeric material 30 into the perigraft space pgs within the aneurysm a . as shown in fig3 , the cannula 20 b is inserted percutaneously into the patient &# 39 ; s body , typically on the flan or side of the patient &# 39 ; s back , and is advanced through the skin , muscle and other intervening tissues to a position where the distal end of the cannula 20 b is positioned within the perigraft space pgs , within the aneurysm a . in applications where specific guidance of the cannula is desired to avoid damage to organs or critical anatomical structures , or for other reasons , the insertion and advancement of the cannula 20 b may be carried out under radiographic guidance or with the use of steriotaxis as known in the art , examples of such radiographic guidance and / or stereotaxis instruments and methods being found in united states patent nos . described in u . s . pat . nos . 4 , 733 , 661 ; 4 , 930 , 525 and 5 , 196 , 019 , 5 , 053 , 042 and include those commercially available from various sources including the accuplace ™ needle guide ( in - rad corporation , kentwood mich . ), the bard ct guide # 550000 ( c . r . bard , inc ., murray hill , n . j . ), the picker venue ™ ( picker corp ., cleveland , ohio ); and the toshiba aspire ™ ct - fluoroscopy system ( toshiba america medical systems , tustin , calif .). alternatively , the cannula 20 b may be inserted and advanced with the aid of electro - anatomical mapping and / or guidance devices and methods , examples of which are found in u . s . pat . nos . 5 , 647 , 361 ; 5 , 820 , 568 ; 5 , 730 , 128 ; 5 , 722 , 401 ; 5 , 578 , 007 ; 5 , 558 , 073 ; 5 , 465 , 717 ; 5 , 568 , 809 ; 5 , 694 , 945 ; 5 , 713 , 946 ; 5 , 729 , 129 ; 5 , 752 , 513 ; 5 , 833 , 608 ; 5 , 935 , 061 ; 5 , 931 , 818 ; 6 , 171 , 303 ; 5 , 931 , 818 ; 5 , 343 , 865 ; 5 , 425 , 370 ; 5 , 669 , 388 ; 6 , 015 , 414 ; 6 , 148 , 823 and 6 , 176 , 829 and are commercially available as the carto ™ or noga ™ system available from biosense - webster , inc ., a johnson & amp ; johnson company , diamond bar , california and / or other systems available from cardiac pathways corporation , 995 benicia avenue , sunnyvale , calif . and / or stereotaxis , inc ., 4041 forrest park avenue , st . louis , mo ., or modifications thereof . after the distal tip of the cannula 20 b has been positioned within the perigraft space pgs , the expansile polymeric material 30 is injected through the cannula and into the perigraft space pgs , where it expands to substantially fill the aneurysm sac . the expansile polymeric material may comprise a hydrogel . preferable hydrogels include a biocompatible , macroporous , hydrophilic hydrogel foam material as described in u . s . pat . no . 5 , 570 , 585 ( park et al . ), the entirety of which is expressly incorporated herein by reference as well as other hydrogels that undergo controlled volumetric expansion in response to changes in such environmental parameters as ph or temperature . an example of one such hydrogel that undergoes controlled volumetric expansion in response to changes in is environment is described in u . s . patent application ser . no . 09 / 867 , 340 , the entirety of which is expressly incorporated herein by reference . these ph responsive hydrogels are prepared by forming a liquid mixture that contains ( a ) at least one monomer and / or polymer , at least a portion of which is sensitive to changes in an environmental parameter ; ( b ) a cross - linking agent ; and ( c ) a polymerization initiator . if desired , a porosigen ( e . g ., nacl , ice crystals , or sucrose ) may be added to the mixture , and then removed from the resultant solid hydrogel to provide a hydrogel with sufficient porosity to permit cellular ingrowth . the controlled rate of expansion is provided through the incorporation of ethylenically unsaturated monomers with ionizable functional groups ( e . g ., amines , carboxylic acids ). for example , if acrylic acid is incorporated into the crosslinked network , the hydrogel is incubated in a low ph solution to protonate the carboxylic acids . after the excess low ph solution is rinsed away and the hydrogel dried , the hydrogel can be introduced through a microcatheter filled with saline at physiological ph or with blood . the hydrogel cannot expand until the carboxylic acid grous deprotonate . conversely , if an amine containing monomer is incorporated into the crosslinked network , the hydrogel is incubated in a high ph solution to deprotonate amines . after the excess high ph solution is rinsed away and the hydrogel dried , the hydrogel can be introduced through a microcatheter filled with saline at physiological ph or with blood . the hydrogel cannot expand until the amine groups protonate . more specifically , in a preferred formulation of the hydrogel , the monomer solution is comprised of ethylenically unsaturated monomers , an ethylenically unsaturated crosslinking agent , a porosigen , and a solvent . at least a portion , preferably about 10 % to about 50 %, and more preferably about 10 % to about 30 %, of the monomers selected must be ph sensitive . the preferred ph sensitive monomer is acrylic acid . methacrylic acid and derivatives of both acids will also impart ph sensitivity . since the mechanical properties of hydrogels prepared exclusively with these acids are poor , a monomer to provide additional mechanical properties should be selected . a preferred monomer for providing mechanical properties is acrylamide , which may be used in combination with one or more of the above - mentioned ph sensitive monomers to impart additional compressive strength or other mechanical properties . preferred concentrations of the monomers m the solvent range from 20 % w / w to 30 % w / w . the crosslinking agent can be any multifunctional ethylenically unsaturated compound , preferably n , n ′- methylenebisacrylamide . if biodegradation of the hydrogel material is desired , a biodegradable crosslinking agent should be selected . the concentrations of the crosslinking agent in the solvent should be less than about 1 % w / w , and preferably less than about 0 . 1 % w / w . the porosity of the hydrogel material is provided by a supersaturated suspension of a porosigen in the monomer solution . a porosigen that is not soluble in the monomer solution , but is soluble in the washing solution can also be used . sodium chloride is the preferred porosigen , but potassium chloride , ice , sucrose , and sodium bicarbonate can also be used . it is preferred to control the particle size of the porosigen to less than about 25 microns , more preferably less than about 10 microns . the small particle size aids in the suspension of the porosigen in the solvent . preferred concentrations of the porosigen range from about 5 % w / w to about 50 % w / w , more preferably about 10 % w / w to about 20 % w / w , in the monomer solution . alternatively , the porosigen can be omitted and a non - porous hydrogel can be fabricated . the solvent , if necessary , is selected based on the solubilities of the monomers , crosslinking agent , and porosigen . if a liquid monomer ( e . g . 2hydroxyethyl methacrylate ) is used , a solvent is not necessary . a preferred solvent is water , but ethyl alcohol can also be used . preferred concentrations of the solvent range from about 20 % w / w to about 80 % w / w , more preferably about 50 % w / w to about 80 % w / w . the crosslink density substantially affects the mechanical properties of these hydrogel materials . the crosslink density ( and hence the mechanical properties ) can best be manipulated through changes in the monomer concentration , crosslinking agent concentration , and solvent concentration . the crosslinking of the monomer can be achieved through reduction - oxidation , radiation , and heat . radiation crosslinking of the monomer solution can be achieved with ultraviolet light and visible light with suitable initiators or ionizing radiation ( e . g . electron beam or gamma ray ) without initiators . a preferred type of crosslinking initiator is one that acts via reduction - oxidation . specific examples of such red / ox initiators that may be used in this embodiment of the invention are ammonium persulfate and n , n , n ′, n ′- tetramethylethylenediamine . after the polymerization is complete , the hydrogen is washed with water , alcohol or other suitable washing solution ( s ) to remove the porosigen ( s ), any unreacted , residual monomer ( s ) and any unincorporated oligomers . preferably this is accomplished by initially washing the hydrogel in distilled water . as discussed above , the control of the expansion rate of the hydrogel is achieved by protonation / deprotonaton of the ionizable functional groups present on the hydrogel network . once the hydrogel has been prepared and the excess monomer and porosigen have been washed away , the steps to control the rate of expansion can be performed . in embodiments where ph sensitive monomers with carboxylic acid groups have been incorporated into the hydrogel network , the hydrogel is incubated in a low ph solution . the free protons in the solution protonate the carboxylic acid groups on the hydrogel network . the duration and temperature of the incubation and the ph of the solution influence the amount of control on the expansion rate . generally , the duration and temperature of the incubation are directly proportional to the amount of expansion control , while the solution ph is inversely proportional . it has been determined that the water content of the treating solution also affects the expansion control . in this regard , the hydrogel is able to expand more in the treating solution and it is presumed that an increased number of carboxylic acid groups are available for protonation . an optimization of water content and ph is required for maximum control on the expansion rate . after the incubation is concluded , the excess treating solution is washed away and the hydrogel material is dried . the hydrogel treated with the low ph solution has been observed to dry down to a smaller dimension than the untreated hydrogel . this is a desired effect since delivery of these hydrogel materials through a microcatheter is desired . in embodiments where ph sensitive monomers with amine groups were incorporated into the hydrogel network , the hydrogel is incubated in high ph solution . deprotonation then occurs on the amine groups of the hydrogel network at high ph . the duration and temperature of the incubation , and the ph of the solution , influence the amount of control on the expansion rate . generally , the duration , temperature , and solution ph of the incubation are directly proportional to the amount of expansion control . after the incubation is concluded , the excess treating solution is washed away and the hydrogel material is dried . examples of other biodegradable , expansile hydrogels that may be used in this invention include , but are not necessarily limited to those described in u . s . pat . no . 5 , 162 , 430 ( rhee et al . ), u . s . pat . no . 5 , 410 , 016 ( hubbell et al . ), u . s . pat . no . 5 , 990 , 237 ( bentley et al . ), u . s . pat . no . 6 , 177 , 095 ( sawhney et al . ), u . s . pat . no . 6 , 184 , 266 b1 ( ronan et al . ), u . s . pat . no . 6 , 201 , 065 b1 ( pathak et al . ), u . s . pat . no . 6 , 224 , 892 b1 ( searle ), u . s . pat . no . 5 , 980 , 550 ( eder et al .) and pct international patent publication nos . wo 00 / 44306 ( murayama et al . ), wo 00 / 74577 ( wallace et al .). the expansile polymeric material , whether a hydrogel or other type of polymer , may be mixed with a carrier fluid to facilitate delivery into the body . in cases where the expansile polymeric material is in the form of solid pellets or particles , those pellets or particles may be suspended in a liquid carrier , such as saline , polyethylene glycol or a radiographic contrast medium . alternatively , one or more solid pieces of the expansible polymeric material me be formed , mounted on or attached to a carrier member to facilitate introduction of the polymeric material into the aneurysm sac . fig5 through 6 e show examples of embodiments where a solid expansile polymeric material is disposed on a coiled carrier filament to form an implantable embolizing device 100 or 200 that comprises the expansile polymer . in the particular example shown in fig5 - 5b , the embolization device 100 comprises a plurality of embolizing bodies , each configured as a substantially cylindrical pellet 120 , located at spaced intervals along a filamentous carrier 140 . the number of pellets 120 will vary , depending on the length of the carrier 140 , which , turn , will depend on the size of the aneurysm sac to be embolized . the carrier member 140 comprises plurality of highly flexible coil spacers 160 , each of which is disposed between and separates a pair of pellets 12 . the carrier 140 has a distal portion on which is carried a relatively long distal coil segment 18 that is retained in place by a distal retention member 201 . the carrier 140 has a proximal portion on which is carried a relatively long proximal microcoil segment 203 . the proximal end of the device 100 is terminated by a hydrogel linkage element 203 , to be described below . the spacers 160 , the distal coil segment 180 , and the proximal coil segment 205 are all highly flexible , and they are preferably made of platinum or platinum / tungsten wire , which has the advantages of being biocompatible and radiopaque . the pellets 120 are non - releasably carried on the carrier 140 . they may be fixed in place on the filamentous carrier 140 , either mechanically or by a suitable biocompatible , water - insoluble adhesive , or they may be simply strung loosely on the carrier 140 between successive spacers 160 . another suitable material for the pellets 120 is a porous hydrated polyvinyl alcohol ( pva ) foam gel prepared from a polyvinyl alcohol solution in a mixed solvent consisting of water and a water - miscible organic solvent , as described , for example , in u . s . pat . no . 4 , 663 , 358 ( hyon et al . ), the disclosure of which is incorporated herein by reference . other suitable pva structures are described in u . s . pat . no . 5 , 823 , 198 ( jones et al .) and u . s . pat . no . 5 , 258 , 042 ( mehta ), the entireties of which are also expressly incorporated herein by reference . another suitable material is a collagen foam , of the type described in u . s . pat . no . 5 , 456 , 693 ( conston et al . ), the entirety of which is also expressly incorporated herein by reference . still another suitable material is phema , as discussed in the references cited above . see , e . g ., horák et al ., and rao et al ., supra . the preferred foam material , as described in the above - referenced patent to park et al ., has a void ratio of at least about 90 %, and its hydrophilic properties are such that it has a water content of at least about 90 % when fully hydrated . in the preferred embodiment , each of the embolizing micropellets 12 has an initial diameter of not more than about 0 . 5 mm prior to expansion in situ , with an expanded diameter of at least about 3 mm . to achieve such a small size , the micropellets 120 may be compressed to the desired size from a significantly larger initial configuration . the compression is performed by squeezing or crimping the micropellets 120 in a suitable implement or fixture , and then “ setting ” them in the compressed configuration by heating and / or drying . each of the micropellets 120 is swellable or expansible to many times ( at least about 25 times , preferably about 70 times , and up to about 100 times ) its initial ( compressed ) volume , primarily by the hydrophilic absorption of water molecules from an aqueous solution ( e . g ., resident blood plasma and / or injected saline solution ), and secondarily by the filling of its pores with blood . also , the micropellets 120 may be coated with a water - soluble coating ( not shown ), such as a starch , to provide a time - delayed expansion . another alternative is to coat the micropellets 120 with a temperature - sensitive coating that disintegrates in response to normal human body temperature . see , e . g ., u . s . pat . no . 5 , 120 , 349 ( stewart et al .) and u . s . pat . no . 5 , 129 , 180 ( stewart ), the entireties of which are incorporated herein by reference . the foam material of the embolizing pellet 120 may advantageously be modified , or provided with additives , to make the device 100 visible by conventional imaging techniques . for example , the foam can be impregnated with a water - insoluble radiopaque material such as barium sulfate , as described by thanoo et al ., “ radiopaque hydrogel microspheres ”, j . microencapsulation , vol . 6 , no . 2 , pp . 233 - 244 ( 1989 ). alternatively , the hydrogel monomers can be copolymerized with radiopaque materials , as described in horak et al ., “ new radiopaque polyhema - based hydrogel particles ”, j . biomedical materials research , vol . 34 , pp . 183 - 188 ( 1997 ). it will be appreciated that in any embodiment of the invention , the expansile polymeric material may further include , contain , comprise or incorporate a medicament ( e . g ., drug , biological , gene , gene therapy preparation , diagnostic agent , imageable contrast material , growth factor , other biological factor , peptide or other bioactive compound , therapeutic or diagnostic substance ) to cause a desired medicament effect ( a therapeutic , diagnostic , pharmacological or other physiological effect ) in the patient . the filamentous carrier 140 is preferably a length of nickel / titanium wire , such as that marketed under the trade name “ nitinol ”. wire of this alloy is highly flexible , and it has an excellent “ elastic memory ”, whereby it can be formed into a desired shape to which it will return when it is deformed . in a preferred embodiment of the invention , the wire that forms the carrier 140 has a diameter of approximately 0 . 04 mm , and it is heat - treated to form a multi - looped structure that may assume a variety of three - dimensional shapes , such as a helix , a sphere , or an ovoid ( as disclosed , for example , in u . s . pat . no . 5 , 766 , 219 ( horton ), the disclosure of which is incorporated herein by reference ). preferably , the intermediate portion of the carrier 14 ( i . e ., the portion that includes the micropellets 12 ) and the proximal portion ( that carries the proximal microcoil segment 22 ) are formed into loops having a diameter of approximately 6 mm , while the distal portion ( that carries the distal microcoil segment 18 ) may have a somewhat greater diameter ( e . g ., approximately 8 - 10 mm ). the carrier 14 may be formed of a single wire , or it may be formed of a cable or braided structure of several ultra - thin wires . in another embodiment , the carrier 140 may be made of a thin filament of a suitable polymer , such as a pva , that is formed in a looped structure . the polymer may be impregnated with a radiopaque material ( e . g ., barium sulfate or particles of gold , tantalum , or platinum ), or it may enclose a core of nickel / titanium wire . alternatively , the carrier 14 may be constructed as a “ cable ” of thin polymer fibers that includes fibers of an expansile polymer , such as polyvinyl alcohol ( pva ), at spaced intervals to form the micropellets 120 . still another alternative construction for the carrier 140 is a continuous length of microcoil . in such an embodiment , the micropellets 120 would be attached at spaced intervals along the length of the carrier 140 . the hydrogel linkage element 203 may be made of the same material as the pellets 120 . indeed , the most proximal of the micropellets 120 may function as the linkage element 203 . another embodiment of an embolizing device 200 that incorporates the expansile polymeric material is shown in fig6 a - 6e . in this embodiment , the embolization device 200 comprises an elongate , flexible , filamentous carrier 202 which is substantially covered by an embolizing element 204 formed of a suitable expansile polymeric material such as any of those described hereabove . the embolizing element 204 is non - releasably carried on the elongate carrier member 202 . the carrier member 202 is preferably formed from a continuous , hollow coil 106 , made from a suitable metal such as platinum , gold , tungsten , or tantalum , or a metallic alloy , such as stainless steel or nitinol . of these materials , platinum and nitinol are preferred . the coil is formed of tightly packed convolutions , so that there is little or no spacing between adjacent convolutions of the coil . the carrier 202 may also include a filamentous core 208 extending axially through the coil 206 . the core 208 is a thin metal wire , preferably made of a shape memory metal such as nitinol . the device 200 includes a distal portion comprising an outer coil 210 coaxially surrounding the coil 206 , and terminating in a rounded distal tip 212 . a hydrogel linkage element ( not shown ), of the type described in relation to the embodiment shown in fig5 - 5d and described above may advantageously be provided at the proximal end of the carrier member 202 . the carrier 202 may , alternatively , be made of any of the materials described above with respect to the carrier of the first preferred embodiment . while it is preferably in the configuration of a coil , it may also be formed as a single strand of metal wire or polymeric filament , or as a multi - strand braid or cable of metal wire or polymeric filament . the carrier should have a column strength sufficient to allow it to be pushed through a microcatheter , as mentioned above . further description and some possible variations / modifications of this embodiment of the embolization device 200 are shown and described in co - pending u . s . patent application ser . no . 09 / 867 , 340 , the entirety of which is expressly incorporated herein by reference . a device for delivering the expansile polymeric material into the perigraft space within the aneurysm sac : the expansile polymeric material , when in the form of a flowable liquid or suspension of particles or pellets , may be introduced into the perigraft space through any suitable cannula 22 , 22 a , 22 b , including needles , hypotube , catheter or other tubular conduits . when , however , the expansile polymeric material is incorporated into an implantable embolization device such as the devices 100 , 200 described above , it is desirable to use a more specialized delivery cannula for delivering the embolization device into the perigraft space . one example of a delivery device 40 useable for delivering an elongate embolization coil or device ( such as the embolization devices 100 , 200 described above ) is shown in fig4 a - 4 d . this delivery device 40 comprises a catheter 20 that has a delivery cannula 22 coaxially disposed within and slidably advanceable from the lumen of the catheter 20 . a pusher rod 48 is inserted into the proximal portion of the delivery cannula 22 . a handpiece is formed on the proximal end of the cannula . when the handpiece is advanced in the distal direction , the distal end of the delivery cannula 22 advances out of the distal end of the catheter 20 as shown in fig4 c . when the handpeice 42 is retracted in the proximal direction , the distal tip of the delivery cannula 22 is retracted into the lumen of the catheter 20 as shown in fig4 b . a knob 49 is formed on the proximal end pusher member 48 and is advanceable and retractable within a track 43 formed on the handpiece 42 . advancement of the knob 49 in the distal direction will advance the pusher member 48 in the distal direction and retraction of the knob 49 in the proximal direction will cause the pusher member to retract in the proximal direction . notches 45 a , 45 b and 45 c are formed in the track to facilitate stopping and locking of the knob 49 in various partially advanced and fully advanced positions . a series of pieces or pellets 30 a of the expansile polymeric material may be positioned in the lumen of the delivery cannula 22 , distal to the pusher member , as shown in fig4 d . as the pusher member 48 is advanced , the pellets 30 a will be expelled from the distal end of the delivery cannula 22 , into the perigraft space . similarly , an embolization device 100 , 200 that incorporates the expansile polymeric material may be placed in a substantially linear configuration and inserted into the lumen of the delivery cannula 22 distal to the pusher member 48 and advancement of the pusher member in the distal direction will expel the embolization device out of the distal end of the delivery cannula 22 and into the perigraft space . if biased to a coiled configuration , the embolization device 100 , 200 may then assume its coiled configuration after it has been introduced into the perigraft space . in some embodiments , the pellets 30 a or embolization device 100 , 200 may be attached to the pusher member 48 by a disconnectable ( e . g ., severable , separable , releasable or breakable ) linkage so as not to become separated from the pusher member 48 until the linkage is severed . the severable linkage may comprise a tube having a plug member inserted in the distal end of the tube and attached to the embolization device such that , after the embolization device has been implanted in the perigraft space as desired , a fluid may be injected through the tube to propel the plug member out of the tube , thereby separating the embolization device from the tube . examples of this type of disconnectable linkage are found in copending u . s . patent application ser . no . 09 / 692 , 248 ( ferrera et al ), the entirety of which is incorporated herein by reference . alternatively , any other suitable type of disconnectable linkages may be used , including linkages that disconnect by either mechanical means , biodegradation , dissolution , electrolysis or by way of an electro - mechanical disconnection apparatus . as shown in fig7 and 7 a , in some embodiments , a stabilized catheter 20 c may be used . this stabilized catheter has a stabilization member 63 , such as an inflatable balloon or deployable lateral member , located adjacent the outlet port 25 through which the cannula 22 is advanced . this stabilization member 23 is deployed ( e . g ., the balloon is inflated ) prior to and during the advancement of the cannula 22 through the wall of the endovascular graft 10 , thereby preventing the catheter 20 a from recoiling in a recoil direction rd that is generally opposite to the advancement direction ad in which the cannula 22 is advanced through the wall of the graft 10 . this facilitates the desired penetration of the cannula through the wall of the graft 10 and into the perigraft space . it will be appreciated that in any embodiment of the invention , the hydrogel may further include or incorporate a medicament ( e . g ., drug , biological , gene , gene therapy preparation , diagnostic agent , imageable contrast material , growth factor , other biological factor , peptide or other bioactive compound , therapeutic or diagnostic substance ) to cause a desired medicament effect ( a therapeutic , diagnostic , pharmacological or other physiological effect ) in the patient . examples of some of the types of medicaments that may be incorporated into the hydrogels of this invention are described in u . s . pat . no . 5 , 891 , 192 ( murayama , et al . ), u . s . pat . no . 5 , 958 , 428 ( bhatnagar ) and u . s . pat . no . 6 , 187 , 024 ( boock et al .) and in pct international publication wo 01 / 03607 ( slaikeu et al . ), the entireties of each such document being expressly incorporated herein by reference . specifically , byway of example , the pellets 120 may optionally include bioactive or therapeutic agents to promote thrombosis , cellular ingrowth , and / or deposition of granulation tissue , healing , etc . see , e . g , vacanti et al ., “ tissue engineering : the design and fabrication of living replacement devices for surgical reconstruction and transplantation ,” the lancet ( vol . 354 , supplement 1 ), pp . 32 - 34 ( july , 1999 ); langer , “ tissue engineering : a new field and its challenges ,” pharmaceutical research , vol . 14 , no . 7 , pp . 840 - 841 ( july , 1997 ); persidis , “ tissue engineering ,” nature biotechnology , vol . 17 , pp . 508 - 510 ( may , 1999 ). the invention has been described herein with reference to certain examples and embodiments only . no effort has been made to exhaustively describe all possible examples and embodiments of the invention . indeed , those of skill in the art will appreciate that various additions , deletions , modifications and other changes may be made to the above - described examples and embodiments , without departing from the intended spirit and scope of the invention as recited in the following claims . it is intended that all such additions , deletions , modifications and other changes be included within the scope of the following claims .
methods and apparatus for treating or preventing endoleaks after an endovascular graft has been implanted in the vasculature of a human or veterinary patient . an expansile polymeric material , such as a swellable polymer , a flexible or elastomeric polymer foam or a carrier member that carries a quantity of such expansile polymer is delivered into a perigraft space such that the polymeric material expands in situ to substantially fill the perigraft space or a portion thereof . the expansile polymeric material is delivered into he perigraft space through a catheter and / or cannula that is placed prior to , during or after the implantation of the endovascular graft . the invention includes an injector apparatus that is useable to deliver the expansile polymeric material through the wall of a previously implanted graft . after delivery into the perigraft space , the expanded polymeric material expands so as to fill all or an intended portion of the perigraft space in a manner that substantially prevents additional blood from leaking or flowing into such perigraft space . one type of blood - absorbing , porous , expansile polymeric material useable in this invention is a super - expansile hydrogel .