while the support device of the present invention may be used in a range of different vessels , including blood vessels , it has particular application in procedures where an organ or anatomical region is undergoing localized perfusion with a therapeutic , diagnostic or other agent . for simplicity , these agents will be hereinafter referred to as therapeutic agents . however , it is to be understood that the term “ therapeutic ” is not to be construed as limiting , and that it includes , without limitation , therapeutic , diagnostic , prophylactic and other agents not specifically identified herein , but which would be considered by the relevant skilled addressee to be suitable for perfusion to an organ or anatomical region . perfusion may be total perfusion , where the entire organ is totally or substantially isolated from the systemic flow , or partial perfusion where only a portion of the organ is substantially isolated . localized perfusion of this kind presents advantages by improving efficacy and the time exposure of the therapeutic agent to the relevant cells . it also limits exposure and hence toxicity to non - target cells as described in brief above . however , it is to be understood that the present invention may also be used simply to collect or drain fluid from an organ or region . collected fluid may be removed from the subject and re - circulated into the organ , filtered and / or treated , or discarded . in some organs , it may be difficult to achieve total isolation , so partial isolation and perfusion may be performed , for example to the right or left lobe of the liver . despite partial perfusion being capable of delivering therapeutic agent to merely a part of the organ , significant therapeutic benefit may still be achieved . particular benefit may be achieved where perfusate is collected after perfusing the target organ , so as to prevent subsequent circulation of the therapeutic agent to other regions of the body where toxic effects may be observed , or the therapeutic agent wasted . the benefit may be improved further where collected perfusate is re - circulated into the target organ utilizing any therapeutic agent which remains after a first pass through the target organ . this may be achieved using the approach described in published patent application wo2005 / 082440 , the entire contents of which are herein incorporated by reference . as discussed infra , when fluid is collected from vessels draining from a target organ or region , one or more of these vessels may require cannulation with a collection catheter . when fluid is drained through these collection catheters , the vessels in which they are positioned become susceptible to collapse as the pressure inside decreases . while some vessels may be more susceptible to collapse than others , the support device of the present invention can provide advantages by supporting and stabilizing the vessel and even anchoring the collection catheter in position . the support device of the present invention may facilitate or at least improve the performance of perfusion . in some instances , the advantages of the present invention have been found to be essential to maintaining adequate positioning of collection catheters and flow rates within the vessel during perfusion . the right and left lobes of the liver have been identified as possible target regions and in this context , the support device may be deployed in one of the hepatic veins to support and maintain patency of the vein as fluid ( e . g . perfusate ) is collected from the liver . however , it is to be understood that fluid from many other organs or regions may be accessed in this way . deploying the support device may also protect the vessel wall by maintaining the tip of the catheter substantially centrally of the vessel or at least at a distance from the vessel walls to prevent aspiration or cavitation . deployment of the device may refer to partial or complete deployment . in complete deployment , the entire expandable member is released from the catheter and expanded to its full extent . in partial deployment , part of the expandable member is retained within the catheter and the amount of expansion is limited by the diameter of the catheter opening . partial deployment may be useful where , for example , during deployment it is found that the diameter of the expandable member may exceed the vessel diameter by an unsafe amount and complete deployment is likely to damage the vessel wall . limiting expansion of the device by partial deployment may avoid vessel damage . partial deployment may also stabilize the expandable member by limiting its movement relative to the catheter tip . thus by retaining part of the expandable member within the catheter , torsional , axial and lateral movement of the member , relative to the catheter is prevented or at least minimized by the struts of the expandable member being in abutment with the internal surface of the catheter . alternatively , the expandable member may be modified at the proximal end , for example by incorporating a lead , a link or other means to limit the extent of movement possible between the catheter tip and the expandable member once deployed . as a further positioning aid , markings may be provided at the proximal end of the control stem / shaft , outside the patient &# 39 ; s body . as the device is released into the vessel , the markings may be utilized to indicate the distance of device deployment , past the catheter tip . during collection of fluid from the vessel , low pressures may develop at the collection device tip , particularly where a roller / peristaltic pump or the like is used to draw fluid from the target organ out of the vessel . this may be indicated by pressures in a lumen feeding into the pump as low as , for example , − 190 mmhg , although clearly these pressures are variable depending on the vessel type , health and age of the subject , characteristics of the perfusion circuit and the like . in the absence of the inventive support device , these pressures can cause the vessel to collapse . not only would vessel collapse affect the perfusion procedure , vessel collapse can also cause venous pooling in the organ and irreversible tissue damage . the advantages and benefits of the present invention will be expanded upon in the following detailed description presenting some of the preferred embodiments of the invention , and the specific examples which follow . it is to be understood that the embodiments and examples provided herein are intended to indicate how the present invention may be performed and are not intended to be limiting on the scope of protection sought as is defined in the claims appended hereto . fig1 a shows an example of an expandable member , in its expanded condition , suitable for supporting a vessel . expandable member 104 is provided in the form of an expandable framework and is adapted to be percutaneously deliverable to the blood vessel in a collapsed condition . fig1 b shows the expandable member in a collapsed condition within a catheter 110 , in which ends 105 , 107 have been drawn apart to radially reduce the member . when collapsed within catheter 110 , atraumatic tip 101 may protrude from the catheter to assist in guiding the support device into the vessel prior to deployment . when the expandable member has been guided into the target blood vessel , the catheter 110 is retracted ( or the expandable member is pushed out of the catheter ), deploying the device into the vessel where it expands . fig1 c shows the support device fully deployed from the catheter , with the expandable member in its fully expanded condition . a guidewire or stem 106 extends within the catheter 110 and is used to deliver the device from a point of entry through the peripheral vasculature to the target vessel . atraumatic tip 101 coupled to the expandable member 104 , is adapted to make atraumatic contact with vessel walls during placement of the device by deforming or deflecting off the vessel wall on contact . this can be achieved by incorporating flexibility into the tip so that it deforms upon contact with the vessel wall . alternatively or additionally , the tip may be shaped or curved to avoid trauma . the atraumatic tip may take any one of a number of forms . in the examples illustrated in fig1 to 3 , the atraumatic tip 101 , 201 is j - shaped . however , other shapes are considered to be suitable , including but not limited to those illustrated in fig4 . for example , the atraumatic tip may have a cross section which is enlarged relative to the guidewire radius , and have a smooth surface so as to avoid causing perforation when the tip comes into contact with the vessel wall . one such example is shown in fig4 a where the atraumatic tip 401 is tear - shaped . alternatively , the atraumatic tip may include a portion having a pigtail shaped curve 402 ( fig4 b ), or an angled tip ( not shown ). preferably , the expandable member is formed from a biocompatible superelastic material , or alternatively from a shape memory material or a material which exhibits both of these properties , being capable of recovery after deformation for delivery in a collapsed or compressed state within a catheter . devices manufactured using these materials can be collapsed for percutaneous delivery to a deployment site and then resume a known shape on deployment . a range of biocompatible materials may be suitable such as alloys of nickel and titanium ( e . g . nitinol ). other suitable biocompatible materials include but are not limited to polymers and plastics such as hydrophilic plastics , ceramics and the like . fig3 illustrates the support device of fig1 a to 1 c , with an occluding balloon inflated around catheter 110 . the occluding balloon 114 may be utilized during collection of fluid from an organ or region of the body in isolation , where substantially all of the fluid flowing out of the organ or region is collected by the catheter 110 . the occluding means substantially prevents blood , therapeutic agent and / or other fluids entering the vessel from flowing on to other organs or regions , and permits collection of substantially all of the fluid entering the vessel . collected fluid may then be analyzed and / or re - oxygenated and / or perfused through the organ , discarded or handled otherwise . the occlusion means may include an occluding balloon , flange , disc or other means . catheter 110 is delivered to the vessel with the balloon 114 in a deflated condition . the expandable member is delivered , through the catheter , and deployed inside the vessel . the balloon is then inflated around the catheter and substantially all the fluid in the vessel flows through the catheter and into a perfusion set or reservoir to which it is connected . a pump , syringe or other means may be incorporated into the perfusion set to draw fluid out of the vessel , through the catheter , at a rate which substantially maintains the required flow through the organ or region , or through a re - perfusion circuit . as fluid is drawn out of the vessel through the catheter , the expanded support structure supports the vessel walls , preventing collapse or cavitation which might otherwise result from the low pressures or high flow rates generated at the catheter tip , maintaining patency and ensuring flow in the circuit . the expandable member may also anchor the device in position within the vessel , substantially precluding movement of the device and ensuring that the catheter is retained in an optimal location for collection of fluid . the expandable member may take a range of different shapes when in an expanded ( or collapsed ) configuration , and may provide any number of supporting filaments or struts . the design of the expandable member may be based on a range of criteria including but not limited to the size and strength of the vessel wall and the flow rates and pressures likely to be generated near the device . some of these embodiments are illustrated in fig8 a to 8 c although these are examples only and are not intended to limit the scope of the invention as broadly described herein . fig8 a to 8 c illustrate expandable members having elongate portions in the supporting struts adapted for contact with the vessel wall . in the example in fig8 b , the supporting struts are slightly rounded to reduce trauma to the vessel walls . fig8 c provides additional struts when compared with fig8 a , as may be necessitated in particularly flaccid vessels requiring more substantial support . embodiments illustrated herein provide expandable members with a substantially elongate structure adapted for coaxial insertion into and placement within the vessel . the elongate structure supports the vessel over a length on the elongate portions of the struts substantially parallel to and in contact with the vessel wall . these elongate portions may be substantially straight , or may be curved ( e . g . fig8 b ). supporting the vessel wall over a length of the support device , compared with the point of supports of the prior art , improves the capacity of the device to maintain patency , even when very low pressures and high flow rates are generated at the catheter tip , and also reduces the likelihood of the device causing damage to the vessel wall . the elongate portions may have a length which is about the same as or greater than the diameter of the vessel being supported , or some multiple of the vessel diameter , or for example from 1 mm up to 30 mm depending on the vessel size and structure . the length of the elongate portion may be selected according to the vessel being supported , the size of the catheter being used and the flow rates and pressures likely to be generated at the catheter tip . preferably , the elongate portions of the expandable member which contact the vessel wall , are just adjacent the distal tip of the catheter when the device is fully deployed . thus , a proximal end of one or more of the elongate portions may commence , for example , within 0 . 1 to 25 mm of the catheter tip , or at least at a distance which is less than the diameter of the catheter opening . this prevents the vessel wall from being drawn into the space between the catheter tip and the start of the elongate portion of the expandable member which contacts the vessel wall . further , the device may be configured so that when it is in an expanded condition , the distance between adjacent elongate portions is sufficiently small to prevent the vessel wall from being drawn into gaps between them . for example , the distance between adjacent elongate portions may be less than the diameter of the catheter . alternatively , the distance between the adjacent elongate portions may be less than , for example , 3 , 2 . 5 , 2 , 1 . 5 , 1 or 0 . 5 mm , depending on the size and type of the target vessel , and the diameter of the collection catheter being used . preferably , the support device possesses sufficient mechanical strength to maintain patency during collection of fluid , withstanding the deformation forces which may occur in response to suction or low pressures produced at the collection catheter tip . in some embodiments however , it may also be desirable for the device to exhibit some flexibility , and conform to the shape of the vessel when deployed . thus , the support device is capable of providing support and maintaining patency along a length of the vessel , even where there is a curve in the vessel wall . an alternative embodiment of a support device 200 is illustrated in fig2 . proximal end 205 of the expandable member 204 is fixedly attached to a stem or shaft 206 , whereas distal end 203 of the expandable member is movable and able to slide over part of the shaft . this enables the member to collapse radially for delivery inside a delivery catheter , and also facilitates recapture of the device . fig5 illustrates another alternative embodiment of a support device shown at 500 in an expanded condition . in this embodiment , both the proximal end 505 and the distal end 503 of the expandable member are movable along a stem or shaft 506 used to deliver the device to the vessel . stops 508 a , 508 b are provided at fixed locations on a distal portion of the shaft , arranged between ends 503 , 505 of the expandable member . these stops may consist of a small ring , crimp or node of increased diameter , relative to the shaft diameter , and prevent the ends of the expandable member from moving across the stop . this facilitates deployment and retrieval of the expandable member from a catheter . fig1 illustrates a support device 151 consisting of an expandable framework 155 having a woven or braided , basket - like configuration when in the expanded condition . in this arrangement , the support device may also include occluding means in the form of a thin flow - proof coating 156 on the inner and / or outer surface of framework 155 to prevent flow of liquid from the vessel . thus , substantially all fluid in the vessel may be collected by catheter 160 . the flow - proof coating may be made from biocompatible silicon , elastomer or flow - proof polymer . preferably , the support device includes a radiopaque or other marker so that it can be positioned within the target vessel using an imaging system such as those generally known in the art . this enables the physician to position and deploy the expandable member into the blood vessel accurately . the marker may be incorporated into the expandable member and / or into an atraumatic guiding tip which may be incorporated into the support device . preferably , the atraumatic tip is manufactured from , includes or is coated with a lubricant and / or a material having a low coefficient of friction . many materials having low coefficient of friction properties may be used including but not limited to biocompatible high density polyethylene ( hdpe ), teflon ®, polypropylene , polyethylene , microglide ™, low friction chromium and silicon to name a few . this improves the performance of the atraumatic tip , so that it “ slides ” along the vessel wall upon making contact , thereby substantially avoiding trauma . use of an atraumatic guiding tip improves the safety and ability to position the expandable member in the target vessel . moreover , since the atraumatic tip may exhibit greater flexibility than the rest of the device , the device is easier to manipulate into position . the atraumatic tip may be provided at a distance from the distal end of the expandable member which enables a physician to guide the expandable member into position within the target vessel . this distance may be anywhere from , for example , 0 . 25 to 5 centimeters from the distal end of the expandable member when in an expanded condition , although it is to be understood that larger or smaller distances may be utilized , depending on the location of the target vessel and the anatomy surrounding it . referring now to fig6 a and 6 b , another example of a support device 600 is shown . a lumen 602 has a control stem 601 extending therein . four loop portions 603 are provided . each loop portion is attached at a first loop end to a distal end 604 of the lumen , and at a second loop end to the control stem at 605 . the loop portions are controllably expandable by advancing the control stem within the lumen in the direction shown by arrow 606 ( fig6 b ). the support device is percutaneously deliverable with the plurality of loop portions housed substantially within the lumen 602 as illustrated in fig6 a and expandable as illustrated in fig6 b . whilst the embodiment illustrated in fig6 a and 6 b provides 4 loop portions , it is to be understood that any number of loop portions may be used . the number of loop portions incorporated into the device may depend on , for example , the anatomy of the vessel being supported , and / or the size of the catheter used to deliver the device . fig7 a and 7 b illustrate another example of a support device 700 which provides 3 loop portions 703 attached to control stem 701 at juncture 705 . the 3 loop portions are contained during delivery substantially within lumen 702 ( fig7 a ), and are controllably expandable to maintain patency within the blood vessel by advancing control stem 701 in the direction of arrow 706 ( fig7 b ). the rounded edges of the loop portions present a reduced risk of damaging the vessel walls , e . g . by perforation or bruising during delivery . the one or more loop portions may be attached to or near the distal end of the delivery lumen in any suitable manner . the point of attachment may be inside or outside the lumen . the loops may be manufactured from any suitable material such as a metal , metal alloy , plastic , polymer , or other filamentous material or composite . the one or more loop portions may be attached at a second loop end to the control stem by soldering , fusing , an adhesive , or any other suitable means . in another embodiment , the loop portions may be attached to a first and a second loop end to the control stem . the support structure of fig6 a , 6 b , 7 a and 7 b may further include an atraumatic guiding tip of the kind described above to aid in positioning the support structure within the blood vessel . alternatively , parts of the loop portions which may protrude from the lumen when the loop portions are in their collapsed state may be used to guide the support structure into the blood vessel . one or more of the loop portions may be provided with a radiopaque or other marker to assist in this regard . retention means may also be provided with the support structure to retain the expandable member in an expanded condition within the vessel . the retention means may be in the form of a clamp , clip , thumb - slide or the like accessible from outside the patient &# 39 ; s body , and may facilitate adjustment of a deployed expandable member during a procedure . retention means may also impart additional rigidity and strength to the expandable member . thus , the retention member may be used to counteract excessively low pressures which may otherwise cause the expanded member to fail . a support structure of the kind illustrated in the figures may be delivered within a multilumen catheter 900 of the kind illustrated in cross section in fig9 . using this catheter , the support device 910 can be delivered through a first internal lumen 901 without interfering with flow in a second lumen 902 . a third lumen 903 may be provided for monitoring flow rates and pressures , for blood analysis or for delivering other percutaneous tools or devices to the vessel or as an inflation lumen for an occlusion balloon . it is to be understood that in the various embodiments of the present invention , the expanded member does not require constant contact with the vessel walls to provide the required support . for example , the diameter of the expanded member may be less than the diameter of the vessel so that the expanded member only contacts the vessel wall when the vessel begins to collapse . patency is considered to be maintained as long as the support device keeps the vessel open to a degree which is sufficient to maintain continuous flow . to avoid causing turbulence or other undesirable blood flow effects within the vessel , and to optimize flow in the vessel it may be desirable to substantially match the diameter of the expanded member to the diameter of the vessel . alternatively the expandable member may be shaped , e . g . as a coil or helix , to have minimal effect on the flow in the vessel . in one embodiment , the expandable member may have a slightly larger expanded diameter than the relaxed vessel to create an anchoring effect . depending on the size of the outflow vessel from which blood and perfusate is collected from the target region , there may be a natural tendency for the collection catheter tip to move about and contact the vessel , thus increasing the risk of vessel collapse or invagination of the catheter tip into the vessel wall . this can cause pooling of fluid in the isolated target region and may cause serious and permanent damage to the organ or region of the patient being treated . use of a support structure in conjunction with the collection catheter to maintain patency of the outflow vessel , in accordance with embodiments of the present invention can minimize the risk of these complications eventuating . thus , a collection catheter associated with the expanding member can be retained in position during fluid collection . this minimizes movement of the catheter tip , ensures that it is substantially centered relative to the vessel walls and improves withdrawal of fluid out of the vessel . at completion of the procedure , it is desirable that the expanded member is collapsed or compressed and recaptured , preferably in the catheter from which it was deployed . this facilitates removal of the support device from the patient . a reinforcing tip may be provided on the catheter end to strengthen it for recapture . alternatively or additionally , the tip may be coated with a lubricant and / or material having a low coefficient of friction to facilitate smooth recapture of the expandable member . the catheter may also have an internal coating of lubricant and / or a material having a low coefficient of friction to assist translation of support device along its interior during delivery and removal of the device from the patient . although the present invention has been described in terms of the presently preferred embodiments , it is to be understood that the disclosure is not to be interpreted as limiting . various alterations and modifications will no doubt become apparent to those skilled in the art after having read the above disclosure and it is intended that the present disclosure be interpreted as covering all alterations and modifications as fall within the true spirit and scope of the invention . effect of support device on flow rates and pressures achievable during recirculation in sheep right hepatic vein , cephalic vein , coronary sinus and renal vein during recirculation a 0 . 014 ″ diameter superelastic nitinol wire stem of 1 . 35 m length was used , coupled to an expandable member having 6 pre - shaped elliptical loop portions welded to the stem . a 0 . 024 ″ od atraumatic tip of 2 cm length attached to the distal end of the expandable member was used to position the device in the blood vessel . a balloon occlusion catheter was positioned in the vessel and the expandable member deployed at the tip of the catheter . the balloon was inflated to isolate and capture flows in the vessel and the catheter was connected to a standard extracorporeal circuit for blood circulation . negative pressures were observed in perfusion lines draining the coronary sinus , renal vein , right hepatic vein and cephalic vein during recirculation both with and without a support device . these data show that cavitation is prevented at certain pressures in the vessels tested where a support device is used , but is not prevented where the support device is absent in the vessel at those pressures . although cavitation may occur even with the support device , it occurs at higher flows . also , cavitation ceases sooner where the support device was employed allowing flow to return to normal . in the coronary sinus , recovery from cavitation was not possible without the support device , emphasizing the importance of the device in the procedure . the data further demonstrates that vessel collapse can be irreversible in the absence of a support structure . however , where a support structure is present , the vessel collapse may be reversed by increasing pressure in the vessel or by slowing or reversing the flow rate of fluid through the vessel . more specifically , considering the data for the right hepatic vein , flow rates of up to 250 ml per minute may be achieved before cavitation occurs where a support device is present in the vessel . under the same conditions but where there is no support device , flow rates of only up to 180 ml per minute are possible . a more striking example of the advantages of the support device is seen for the cephalic vein where no flow is achievable without the device . when the vessel wall is supported by the device flow rates of up to 200 ml per minute are noted before cavitation occurs . when the vessel wall is supported flow rates of up to 200 ml per minute are noted before cavitation occurs .
the present invention provides devices and methods for use in the perfusion of organs and anatomical regions . in one aspect the present method provides a percutaneously deliverable device for supporting a vessel in a human or animal subject including means for supporting the vessel during delivery of a fluid thereto or collection of a fluid therefrom . in another aspect the invention provides a method for delivery or collection of a fluid to or from an organ or anatomical region in a human or animal subject , the method including the step of supporting a vessel associated with the organ or anatomical region . the devices and methods may be used to deliver , remove or recirculate a therapeutic agent to an organ or anatomical region .