Patent Publication Number: US-2023147735-A1

Title: Clot capture systems and associated methods

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation of U.S. patent application Ser. No. 16/664,671, filed Oct. 25, 2019, which is a Continuation of U.S. patent application Ser. No. 15/204,537, filed Jul. 7, 2016, now U.S. Pat. No. 10,582,939 issued Mar. 10, 2020, which is a Continuation of U.S. patent application Ser. No. 13/662,299 filed Oct. 26, 2012, now U.S. Pat. No. 9,407,707 issued Aug. 2, 2016, which is a Continuation-In-Part of U.S. patent application Ser. No. 12/737,527, filed Jan. 21, 2011, now U.S. Pat. No. 8,777,976 issued Jul. 15, 2014, which is the National Stage of PCT/IE2009/000051, filed Jul. 22, 2009, which claims the benefit of U.S. Provisional Application No. 61/202,612, filed Mar. 18, 2009 and claims the benefit of U.S. Provisional Application No. 61/129,823, filed Jul. 22, 2008. 
     U.S. patent application Ser. No. 13/662,299 filed Oct. 26, 2012, now U.S. Pat. No. 9,407,707 issued Aug. 2, 2016, is a Continuation-In-Part of PCT/IE2011/000026, filed Apr. 28, 2011, which claims the benefit of U.S. Provisional Application No. 61/282,950, filed Apr. 28, 2010. 
     The contents of all of the above-listed applications are herein incorporated by reference. 
    
    
     FIELD OF INVENTION 
     The invention relates to devices, and methods of removing acute blockages from blood vessels. The invention especially relates to removing acute obstructions from blood vessels. Acute obstructions may include clots, misplaced devices, migrated devices, large emboli and the like. More particularly the invention relates to removing clots from cerebral arteries in patients suffering acute ischemic stroke. 
     BACKGROUND 
     Accessing the neurovascular bed is difficult with conventional technology as the target vessels are small in diameter, are remote relative to the site of insertion and are highly tortuous. Despite the fact that there are over 600,000 acute ischemic strokes in the US each year, clot retrieval devices are used to treat patients in less than &lt;1% of cases. The reasons for this are that conventional technology is either too large in profile, lacks the deliverability to navigate tortuous vessels or is not effective at removing clots when delivered to the target site. 
     There are significant challenges associated with designing clot removal devices that can deliver high levels of performance. Firstly there are a number of access challenges that make it difficult to deliver devices. In some patients the configuration of the aortic arch makes it difficult to position a guide catheter in the larger arteries that supply blood to the brain. These difficult arch configurations are classified as either type 2 or type 3 aortic arches with type 3 arches presenting the most difficulty. The tortuosity challenge is even more severe in the arteries approaching the brain. It is not unusual at the distal end of the internal carotid artery that the device will have to navigate a vessel segment with a 180° bend, a 90° bend and a 360° bend in quick succession over a few centimeters of vessel. 
     Secondly, neurovascular vessels are more fragile than similarly sized vessels in other parts of the body and are in a soft tissue bed. This issue is compounded by the fact that in many instances the clot is firmly wedged in the vessel. Typically a few hours have passed before the patient arrives at the hospital, is appropriately screened and arrives at the catheterization lab for treatment. During this time a number of processes are in play that strongly bonds the clot to the vessel wall. Firstly the clot is under the influence of pulsing blood pressure and this pulsing blood pressure progressively force-fits the clot to the vessel. Some additional clot will also be laid down adjacent the occlusion. After the initial occlusion, endothelial cells between the clot and the vessel wall are compromised and bonds are formed between the vessel wall and the clot. All three of these mechanisms play a role in strongly adhering the clot to the vessel wall. Breaking these bonds without damaging these fragile vessels is a significant challenge. The high aspect ratio of the device and the vessel tortuosity make it difficult to transmit forces to the clot and for the user to feel reaction forces from the clot. 
     SUMMARY 
     In accordance with the present invention, devices and methods for removing obstructions are described. The invention provides designs and systems for removing clots and other obstructions from the neurovascular arteries and veins as well as other vascular beds. 
     In one case the invention provides endovascular capture devices which capture obstructive elements and retrieve them from the vessel. The devices of the invention may be used in vessels that are small, tortuous and easily ruptured. 
     The invention provides a means for removing acute blockages or obstructions from blood vessels. Acute obstructions may include clots, misplaced devices, migrated devices, large emboli and such like. The invention is especially directed at removing clot from cerebral arteries in patients suffering acute ischemic stroke. 
     The invention provides a clot retrieval device that can be delivered through a micro catheter. The device has sufficient structure to engage the clot. The device provides a means for debonding the clot from the vessel wall. The device further provides means to prevent the fragmentation of the clot and effectively retrieve the clot from the vessel. 
     There are significant challenges associated with retrieving clots from cerebral vessels including: navigation of the highly tortuous pathways that often exist in the distal internal carotid artery and cerebral arteries, collapsing a device into a profile compatible with the tiny microcatheters typically used in cerebral vessels, disengaging the target clot from the vessel wall without applying painful or harmful forces to the cerebral vessels, and retaining adequate clot retaining scaffolding features in an ultra low profile device to remove the captured clot without fragmentation. 
     This invention provides a therapeutic device which can be collapsed to a very low profile, and which has a flexible configuration suitable for navigation beyond the Petris portion of the internal carotid artery to restore blood flow by the capture and removal of target clots from the cerebral vasculature. Features and methods that enable disengagement and capture of the target clots which are substantially equivalent in size to the target vessel and to the opening of the clot retrieval device itself are also disclosed. 
     The invention further provides a device for removing an obstruction from a vessel comprising: an elongate member, a frame with one or more openings, and a plurality of fiber segments wherein the elongate member has a proximal end, a distal end and an intermediate segment, and in use the proximal end extends exterior of the patient, the intermediate segment extends through the vasculature of the patient to the target vessel, and the distal end is positioned in the target vessel with the frame connected to the elongate member adjacent the distal end. 
     The obstruction to be removed may be a clot, with removal of this clot providing the therapeutic benefit of restoring blood flow to the vessel. 
     The device may comprise a proximal support frame; and a distal fiber net, the support frame having a retracted delivery configuration and an expanded deployed configuration, the proximal support frame in the expanded configuration defining a proximal inlet mouth for engaging or embracing a clot and the net confining the clot; and an elongate member to facilitate capture and/or withdrawal of a clot from a vessel. 
     The frame may comprise a collapsed state for delivery through the vasculature to the vessel and an expanded state for removing the obstruction from the vessel. The expanded state of the frame may comprise a hoop. 
     The frame may be cut from a metallic tube and the cut frame may comprise a one piece construction. This one piece frame may comprise at least one connector element and a hoop element, and may also comprise a collar. 
     The frame may be connected to the elongate member and the point of attachment to the elongate member may be spaced apart from the hoop. 
     The connector element may extend between the points of connection to both the elongate member and the hoop, and may be fixedly connected to the elongate member. 
     One or more connector elements may be fixed to the elongate member so as to allow rotation between the elongate member and the connector element, or said connector elements may be indirectly fixed to the elongate member. 
     One or more connector elements may be coupled to a collar and said collar fixed to said elongate member. 
     The frame may be made of one piece and comprise regions of low strain and regions of high strain, wherein the regions of high strain comprise curved segments to relieve said high strain. 
     The frame may have an “as cut” state and an expanded state wherein in the ‘as cut’ state the frame has a pattern cut through its wall and said pattern defines the collar, one or more connectors, the hoop and the struts that define the hoop. 
     The frame expanded state may be achieved by expanding the hoop and connector elements to the desired shape for clot retrieval and heat setting the frame in the expanded such that the expanded shape is remembered by the frame and the frame is relaxed in the expanded state. 
     The connector element may be parallel to the axis of the tube in the as cut state, or may be at an angle to the axis of the metallic tube. 
     The struts that define the hoop may be parallel to the axis of the tube in the as cut state, or may comprise a helix which traces a pathway around the axis of the tube. Said helix may trace a pathway of not greater than 180 degrees around the axis of the tube. 
     The cross section of the tube may comprise four quadrants and the at least one first strut and the at least one second strut may be situated either in adjacent quadrants or in the same quadrant over at least a portion of their length in the as cut state. 
     The hoop may comprise at least one first strut and at least one second strut and said at least one first strut and said at least one second strut may meet at a junction element and said junction element may be at the end of said at least one first and second struts. The at least one first strut and the at least one second strut may be diametrically opposite when the frame is in the as cut state. 
     The cut pattern of the junction element may comprise a smooth inner curve and a smooth outer curve. 
     The at least one first strut and the at least one second strut and the junction element may comprise a common neutral axis of bending in the as cut configuration. 
     The shape defined by the neutral axis of the at least one first strut and at least one second strut may be substantially linear and the shape defined by the neutral axis of the junction element may be curved. 
     The radius of curvature of the neutral axis of the junction element may be greater when the junction element is in the expanded state than when the junction element is in the as cut state. 
     The frame may comprise a collar, one or more connector elements and a hoop, and said collar may be fixed to the elongate member. Said collar may be slidable relative to the elongate member, and said elongate member may comprise at least one stop to limit the translation of the collar. 
     The distal end of the elongate member may comprise a frame, or the elongate member may comprise a shaped section adjacent its distal end and said shaped section comprises the frame. 
     The elongate member may comprise a tube and the elongate member and the frame may be integral. 
     The elongate member may comprise a guidewire. 
     The bending stiffness of the elongate member may decrease along the length of the elongate member. 
     The elongate member may comprise a plurality of circumferential slots adjacent its distal end, said slots reducing the bending stiffness of the elongate member. The distance between said slots may vary along the length of the elongate member. 
     The elongate member may comprise at least one continuous helical slot adjacent the distal end of the elongate member to reduce the bending stiffness of the elongate member. 
     The bending stiffness of the elongate member may decrease gradually along the length of the distal segment of the elongate member. Also the diameter of the elongate member may be less in the distal segment than in the proximal segment. 
     The elongate member may comprise a solid wire, a wire with a coating, a wire and an outer tube, a wire and an outer coil, a tubular member and an inner core, a tubular member and an inner cable, or a tubular member and an inner tube. 
     The elongate member may be offset relative to the axis of the vessel when the frame is in the expanded configuration, or the elongate member may be substantially concentric with the axis of the vessel when the frame is expanded in the vessel, or the elongate member may be adjacent the wall of the vessel when the frame is in the expanded configuration in the vessel. 
     The frame may comprise a collapsed state for delivery through the vasculature to the vessel and an expanded state for removing the obstruction from the vessel. The expanded state of the frame may comprise a hoop. 
     The wire of the hoop may comprise a round wire, a square wire, a rectangular wire, an elliptical wire, a flattened wire, or a multifilament. 
     The elongate member may comprise a wire and the distal segment of said wire is formed into a hoop. The distal end of said wire may be fixed to the wire in order to close the hoop. The fixing of the wire distal end to the wire may comprise a weld joint, a solder joint, an adhesive joint, a bifilar joint, a coupling, a compression joint, a snap fit, or an interlock. 
     The hoop may comprise a single piece hoop cut from a metallic tube or from a metallic sheet. 
     The distal section of the elongate member may comprise a tube and said hoop may be integral with said tube. 
     The elongate member distal end may comprise a machined section. The elongate member distal end machined section may comprise a hoop. 
     The elongate member cross-section may comprise four quadrants and the hoop may comprise at least two struts, each extending from a separate quadrant. The first strut may extend from said first quadrant and said second strut extend from said third quadrant. The first and second struts may be diametrically opposite. The first strut may extend from said first quadrant and said second strut may extend from said second quadrant. The first strut may extend from said first quadrant and said second strut may extend from said first quadrant. 
     The struts may comprise a plurality of net attachment features. 
     The hoop of the frame may be expanded by inserting a pin between the struts and heat treating the frame to set the shape. This pin diameter may be similar to the diameter of the target vessel. 
     The hoop may be cut from a large diameter tube, the diameter of which is similar to the diameter of the target vessel. Alternatively the hoop may be integral with the elongate member. 
     A plurality of connector elements may be attached to the hoop. This plurality of connector elements may be connected to the hoop at a series of spaced apart junction points around the circumference of the hoop and said spacings may be substantially equal. 
     In its expanded state the hoop may define an opening, and said opening may be elliptical or circular in shape, and may be similar in size to the cross-sectional area of the target vessel. The axis of the elongate member may pass through this opening created in the hoop in its expanded state. 
     The connector element may extend at least partially radially inward from the hoop and be connected to the collar, or the connector element may extend radially inward and proximally from the hoop and be connected to the collar, or the connector element may extend radially inward and distally from the hoop and be connected to the collar. 
     In the collapsed state the hoop may lie substantially parallel the elongate member, or may lie at an angle of approximately 90 degrees to the axis of the elongate member. 
     In the expanded state the hoop may make an angle of greater than 90 degrees to the axis of the elongate member, or may make an angle of less than 90 degrees to the axis of the elongate member. The angle between the hoop and the elongate member may be between 45 degrees and 135 degrees. The angle between the hoop and the elongate member may be between 60 degrees and 120 degrees. The angle between the hoop and the elongate member may be between 80 degrees and 100 degrees. 
     The hoop may comprise a number of struts wherein said struts are rectangular, square or circular in cross-section. The struts may be interconnected. These interconnections may be at the strut ends and said interconnections may comprise curved crown elements. 
     In the collapsed state the curved crown elements may connect strut segments that are substantially parallel, or may connect strut segments that are angled relative to one another. 
     The hoop may comprise a plurality of curved segments. The plurality of curved segments of the hoop may be configured to from a single plane, or may be configured to form two planes with the curved segments interconnecting at a point of intersection of the planes. 
     The plurality of curved segments may comprise a plurality of struts and said plurality of struts may form a substantially circular hoop when viewed along the axis of the elongate member. 
     The frame may comprise at least two openings in the expanded state, each opening defining an opening for the capture of a clot. The two openings may comprise a circular shape. 
     Each opening may be defined by a strut section and a body strut section, wherein the strut section comprises two radially projecting struts and the body strut section comprises a curved strut, and wherein the radius of curvature of said body strut section is substantially similar to the target vessel size for the device. 
     The body strut section may connect the ends of the two projecting radial struts. The two substantially parallel wires may be connected to each other at least one end. 
     The elongate member may extend in use from the target vessel through the vasculature of the patient and further extend exterior of the patient. 
     The elongate member may comprise a distal end, said distal end may terminate adjacent the frame collar, or may terminate at the distal junction of the capture fibers. Or the distal end may terminate distal of said frame and net and comprise a soft atraumatic tip. 
     The elongate member may comprise an inner lumen said inner lumen may extend from the proximal end of the elongate member at least to an area adjacent the frame. 
     The elongate member may comprise an exit port, said exit port located in the distal region of the elongate member. 
     The elongate member may comprise an inner core and an outer tube. Said inner core may comprise a wire and said wire may comprise a tapered distal end. The inner core wire may comprise an atraumatic distal end. 
     The distal end of the inner core wire may be associated with the distal fiber junction. The fiber junction may be adjacent to the core wire. The fiber junction may be tethered to the core wire. 
     The fiber junction may be integral with the distal segment of the inner core, or may be moveable relative to the inner core, or may be moveable by the inner core. 
     The inner core may comprise a coil. This coil may be a radiopaque coil. 
     The frame may comprise at least one collar. The collars may be fixed relative to the elongate member, or the collars may be slidable relative to the elongate member. 
     The frame may comprise a first collar and a second collar. Said first collar may be fixed relative to the elongate member and said second collar may be slidable relative to said elongate member. 
     The collar may be integral with at least one first strut and the collar and first strut may comprise a collapsed state for delivery through the vasculature and an expanded state for capturing and removing said occlusive material. 
     The at least one integral collar strut may define an area of bending and said area of bending may comprise a relaxed state and a strained state, wherein in the frame expanded state the area of bending is in the relaxed state, and in the frame collapsed state the area of bending is in the strained state. 
     The frame may comprise at least one proximal connector strut and at least one distal connector strut, where said at least one proximal connector strut is connected to the hoop at a point which is spaced apart from the point of connection of the at least one distal connector strut. 
     The cross-sectional dimensions of the connector struts may be different to the cross-sectional dimensions of the hoop struts. 
     The device may further comprise a third collar distal of previously mentioned first and second collars. 
     The frame may further comprise a formed collar wherein the collar comprises a C shaped section. This C shaped section may be formed by cutting a segment of the large diameter tube, and forming the tube section such that its radius of curvature is greatly reduced, and heat treating the section so as to permanently set the formed shape. 
     Any or all of these collars may comprise at least one longitudinal slot extending along at least a portion of the length of the collar, and/or at least one circumferential slot extending partially around the circumference of the collar. 
     The plurality of fibers may constitute a capture net, said net comprising a series of fiber segments arranged to create a three dimensional clot capture net. The net may be connected to the frame at a plurality of points or engagement features around the circumference of the frame. 
     The capture net may comprise a knitted, braided or crocheted structure, or may comprise a series of longitudinal fiber segments. This structure may comprise a tube. This tube may be cylindrical or conical in shape. 
     The net comprises an inner layer and an outer layer. The inner layer and the net outer layer may be integral. 
     The net may be connected to the frame with a fiber. The net may partially encircle the frame. 
     The net may comprise a fiber junction, wherein a plurality of fiber segments are connected. The capture net may comprise a series of fiber segments extending between the frame and this fiber junction. The fiber junction may be spaced apart from the frame and the fiber segments may define a basket for restraining clot that has been debonded from the vessel. 
     The clot capture system may have a capture net wherein the net comprises a proximal end and a distal end, the proximal end of the net being attached to the frame. The capture net may have a low density structure where the area ratio of the fibers to the capture net pores is &lt;20%. 
     At least one of the plurality of high tensile fibers may have an ultimate tensile strength of at least 1500 MPa, or at least 2000 MPa, or at least 2500 MPa, or 3000 MPa or greater. 
     At least one of the plurality of high tensile fibers may comprise polymer fibers such as Ultra High Molecular Weight Polyethylene or Kevlar, or metal fibers such as 302 stainless steel, 304 stainless steel, other stainless steels, MP35N, L604, 35N LT, or Nitinol. 
     Wherein a metal fiber is used it may be cold worked to at least 50%. 
     An Ultra High Molecular Weight Polyethylene (UHMWPE) fiber may comprise a Dyneema, Celanese, Spectra or a Tekmilon fiber. 
     The frame may comprise a plurality of attachment points around its circumference, and the capture net may be secured to the frame at a plurality of points around the circumference of the frame. 
     The attachment features may be integral with the frame struts and comprise localized changes to the cross section of the struts. The localized change in cross section may comprise a hole in the strut wherein the hole is circular, oblong, elliptical, curved and the hole may be in the center of the strut or is offset. The hole may extend through the wall of the frame. 
     The localized change in cross section may comprise a notch, a recess, a depression, or a groove in the outer surface of the strut of the frame. The attachment points may comprise a plurality of such localized changes in cross section. The plurality of attachment points may be spaced equally around the circumference of the frame. 
     The plurality of attachment points may comprise holes in the struts and said holes may be less than 50 microns in diameter, or less than 30 microns in diameter, or less than 25 microns in diameter, or less than 20 microns in diameter. 
     The holes may not be fully cylindrical, but may be less than 50 microns in one dimension, or less than 30 microns in one dimension, or less than 25 microns in one dimension, or less than 20 microns in one dimension. 
     The frame and holes may be polished by a polishing process selected from sand blasting or electropolishing or chemical etching. 
     The device may further comprise a fiber junction where a plurality of fiber segment ends are connected. This fiber junction may comprise a knot, a weld, an adhesive joint, a site of attachment, a laminated junction, a coupling, a bonded joint, or an assembly joint. 
     The device may further comprise a distal collar and said distal collar may comprise a junction for a number of fibers of the fiber net. 
     The distal collar may comprise a reception space and said reception space may be configured to restrain the ends of said fiber segments. 
     The distal collar reception space may comprise an annular space, said annular space sized to allow fibers to be received in the space. 
     The distal collar reception space may comprise at least one hole, wherein said hole is sized to receive at least one fiber. The distal collar reception space may also comprise a plurality of holes, said plurality of holes being sized to receive one or more fibers. 
     The distal collar reception space may comprise a feature such as a hole, a groove or an annular space in the wall of the collar, wherein said feature is sized to receive at least one fiber. This feature may also be located between the collar and the elongate member. 
     The device may comprise an expansion cable which may be connected to the frame and extend in use exterior of the patient. 
     The expansion cable may comprise a relaxed state and a tensioned state, wherein in the relaxed state the expansion cable exerts no force on the frame and in the tensioned state the expansion cable exerts an expansion force on the frame. This expansion force may assist in the expansion of the frame. 
     The expansion cable in use may extend from exterior of the patient through a lumen in the elongate member, through an exit port located in the distal region of the elongate member and terminate at a point of connection with the frame. 
     The expansion cable may comprise a polymeric or metallic cable, and may be a monofilament or multifilament. The material of the expansion cable may be a polymer, such as a polyester, Ultra high molecular weight polyethylene, a fluoropolymer, a nylon, or Kevlar, or may be metallic such as a stainless steel or nitinol, or may be a mixture of the above or may possess similar properties to the above. 
     The frame may comprise an expanded configuration and a collapsed configuration and may be naturally biased towards the collapsed configuration and may further comprise a restraining system, which allows the frame to be stored in the collapsed state (during delivery) by interconnecting elements of the frame to one another. 
     The restraining system may comprise restraining one or more struts to each other. 
     The restraining system may comprise restraining a frame hoop in a collapsed state substantially parallel with the axis of the elongate member. 
     The elongate member may comprise an inner core extending distal of the collar of the frame, and the restraining system may comprise fixing the hoop to the inner core in a collapsed state. 
     The frame may comprise a supporting strut extending distally from the collar and substantially parallel to the axis of the collar, and the restraining system may comprise fixing the hoop to the supporting strut in a collapsed state. 
     The supporting strut may comprise an engagement feature allowing the supporting strut and the hoop and/or a connector element to be fastened to the supporting strut. 
     The device may further comprise a micro-delivery catheter comprising a reception space and a shaft. This reception space may extend proximally wherein the frame and net are configured to be received in the reception space in the collapsed state for delivery to the site of occlusion. The reception space may comprise a tubular element. 
     The collar or collars of the frame may be mounted on a tubular member and the tubular member may be moveable relative to the guidewire. The tubular member may be connected to a control wire and said control wire may extend proximally to the user, allowing the user to move the frame relative to the guidewire, or the tubular member may extend proximally to the user, allowing the user to move the frame relative to the guidewire. 
     The frame of this invention may also compromise hinges and may comprise a plurality of struts with one or more hinges connecting at least a pair of said struts. The expansion of the frame from its collapsed state to its expanded state may comprise an articulation of one or more of these hinges. Said hinges may be configured to articulate without significant resistance. 
     The at least one pair of struts may comprise a first strut and a second strut and the first strut may comprise a first point wherein said first point is spaced apart from the hinge. The at least one hinge may be configured such that said first point is restricted to move through a segment of a substantially circular arc when said hinge is articulated. The at least one hinge may be configured such that said first point is restricted to move through a set of points defining a substantially spherical surface when said hinge is articulated. 
     The at least one hinge may each comprise a first strut and a second strut, the first and second struts comprising hinge attachment features and said first and second struts being coupled by a hinge coupling element. 
     The hinge attachment features may comprise a hole, a mounting, a loop, a cut profile or a formed shape. 
     The hinge coupling may comprise a monofilament fiber, a multifilament fiber, a pin, a loop, a C section, a ring, a tether, or an articulating coupling. 
     The hinge attachment feature may comprise a hole and the hinge coupling may comprise a fiber wherein said fiber is looped through the hole in said first and second struts so as to fix said struts to one another while allowing said struts to articulate in at least one direction. 
     The frame may comprise a hoop and at least one connector strut. This hoop may comprise a plurality of hoop struts. The at least one hinge may comprise a pair of hoop struts. The at least one hinge may comprise a hoop strut and a connector strut. 
     The frame may comprise a compound hinge wherein more than two struts are hinged relative to each other. The compound hinge may comprise three struts. The compound hinge may comprise two hoop struts and a connector strut. 
     The at least one connector strut may be connected to the elongate member. The connection between the connector strut and the elongate member may comprise a hinge. The connection between the connector strut and the elongate member may comprise a collar wherein said collar connects the connector strut to the elongate member. 
     The frame may comprise an arrangement of hinges and said hinges may comprise movement freedoms and movement constraints and said movement freedoms and movement constraints may be arranged such that the frame moves progressively between a collapsed state and an expanded state when activated and between an expanded state and a collapsed state when deactivated. 
     The frame may be expanded by advancing or retracting at least a part of the elongate member. The elongate member may be connected to at least one strut and advancing or retracting a portion of the elongate member may cause the articulation of the at least one hinge and the frame expands. 
     The elongate member may comprise a first portion and a second portion and the elongate member first portion may be connected to an at least one first strut and the elongate member second portion may be connected to at least one second strut and relative movement between the elongate member first portion and the elongate member second portion may cause expansion or collapse of the frame depending on the direction of relative motion. 
     The elongate member may comprise an inner shaft and an outer tubular member and said outer member may be slidable relative to said inner shaft. Movement of the outer tubular member relative to the inner shaft may cause the frame to expand and/or collapse. 
     Any of the frames disclosed herein may be expanded by the release of stored energy. Said stored energy may comprise the release of stored elastic energy wherein at least one element of the frame comprises an elastic component and said elastic component is restrained in a strained state during delivery. Upon removal of said constraint, said elastic component relaxes to its unstrained state and in so doing the frame is expanded. 
     The elastic component may comprise a nitinol component, a shape memory component, an elastic component or a super-elastic component. 
     The elastic component may comprise a hoop strut, a connector strut, a connector or a combination of these elements or a junction between these elements. 
     This invention also comprises a clot debonding device (also referred to herein as a clot debonder or clot debonding element) which may be used in conjunction with the clot retrieval designs described herein. The clot debonding device is designed to assist in the removal of obstructions from a vessel by providing an abutment surface which may be used to appose one side of the obstruction so that a force may be applied to the other side of the obstruction without said force being transmitted to the vessel in which the obstruction is placed. It therefore enables a clot retrieval device or other similar device to more effectively engage and capture clot or other such vessel obstructions. 
     It will be appreciated that such a device also has applications beyond its use with the clot retrieval device described herein. Such a clot debonder may be effectively used to aid the disengagement and removal of vessel obstructions in conjunction with other clot retrieval devices or thrombectomy devices or aspiration devices. 
     The invention further provides a clot capture system for disengaging a clot from a vessel wall and removing the clot from the vessel, the clot capture system comprising: a clot capture device for placement on a distal side of a clot, the clot capture device having a retracted delivery configuration and an expanded deployed configuration; and a clot debonding device for placement on a proximal side of a clot, the clot debonding device having a retracted delivery configuration and an expanded deployed configuration and comprising a clot engagement element which defines a distal abutment in the deployed configuration for urging a clot into the clot capture device. 
     It will be understood that the above mentioned clot capture device may be any of the clot retrieval device embodiments previously described herein, and the clot capture system may comprise any combination of the permutations described below with those of the clot retrieval devices described above. 
     The abutment area of the clot debonding device may be configured to engage with the clot in its expanded configuration. The engagement of the abutment area with the clot may comprise a relative movement between the abutment area and the clot and said relative movement may at least partially disengage the clot from the vessel. The relative movement between the abutment area and the clot may comprise an axial movement or a rotational movement or a combination of both movements of the abutment area. 
     The clot retrieval device may be configured to engage the clot from a distal end and the clot debonding device may be configured to engage the clot from a proximal end. The clot debonding device may thus be configured to apply a debonding force to the clot to disengage the clot from the vessel, and the clot retrieval device may be configured to apply a reaction force to the clot wherein the reaction force is applied substantially in the opposite direction to the debonding force and the combination of said forces disengages the clot from the vessel wall. 
     The clot retrieval device may comprise an engagement element and a reception space, wherein said engagement element may be configured to engage the clot from a distal end and said reception space may be configured to receive said disengaged clot and to allow the removal of said clot from the vasculature. 
     The clot debonding device may be configured to at least partially protect the blood vessel from the forces of clot debonding. 
     The clot engagement element may extend substantially the width of the mouth of the capture device in the deployed configuration. 
     The clot debonding device is movable relative to the clot capture device in the deployed configuration. 
     The clot engagement element may have a longitudinal axis and the distal abutment may extend radially of the longitudinal axis. The longitudinal axis may be a substantially central axis and the distal abutment may extend radially outwardly of the substantially central axis, or the longitudinal axis may be an offset axis and the distal abutment may extend radially outwardly of the offset axis. 
     The clot engagement element may comprise an axially extending region and a radially extending region. The clot engagement element may further comprise a circumferential region extending from the radial region. The clot engagement element may also comprise a transition region between the axial region and the radial region. 
     The clot debonding device may comprise an axially extending collar. 
     The clot capture device may define an inlet mouth in the deployed configuration and the clot engagement element may extend substantially the width of the inlet mouth of the clot capture device. 
     The clot debonding device may be slidable relative to the clot capture device. 
     The clot debonding device may be rotatable relative to the clot capture device. 
     In the deployed configuration, the clot capture device may be located distal of the clot debonding device. 
     The clot capture device and the clot debonding device may be independently movable. 
     The clot capture system may comprise an elongate member. The clot capture system may comprise a first elongate member associated with the clot capture device. The clot capture system may comprise a second elongate member associated with the clot debonding device. The first elongate member may comprise a guidewire, and said guidewire may comprise a stop. This stop may comprise a distal stop. 
     The second elongate member may comprise a proximal shaft. The clot debonding device may be mounted to the proximal shaft. The clot bonding device may be fixedly mounted to the proximal shaft. 
     The clot capture system may comprise a delivery catheter for the clot capture device. 
     The system may further comprise a first access catheter and a second access catheter, the distal end of said first access catheter being placed in a proximal vessel and the distal end of said second access catheter being placed in a distal vessel wherein the second access catheter is delivered to said distal vessel through the lumen of said first access catheter. Said first access catheter may comprise a guide catheter or a guide sheath and said second access catheter may comprise a delivery catheter or a microcatheter, wherein the clot retrieval device is configured to be delivered through the second access catheter. 
     The clot debonding device may comprise a lumen extending from its distal end and a proximal shaft connected either directly or by a collar to the expandable engagement element. The clot debonding device may be configured as a rapid exchange catheter. 
     The distal end of the clot debonding device may comprise an abutment surface in the collapsed state for advancement of the clot retrieval basket through a catheter lumen. 
     The expandable engagement element may expand radially outward from a central axis and may comprise an inflatable element, a self expanding element, a shape memory element, a super elastic element, a remotely activated element, a coil, or spring element. 
     The expandable engagement element may comprise a balloon, an inflatable cuff, a plurality of struts, a slotted section, a cell structure, a plurality of wire segments, a helical coil, a flare, a ring, a braided section, or a hoop. 
     The expandable engagement element may comprise a slotted tubular member, or a number of overlapping coaxial slotted tubular members. The slotted tubular members may be self expanding or may be expanded by retraction of an actuation element connected to their distal end. 
     The expandable engagement element may comprise elements which expand into a generally helical configuration, such as a coiled element which at least partially uncoils to expand from one diameter to a second larger diameter. 
     The expandable engagement element may comprise a number of curved wire struts or segments, which may have points of inflection, and/or which may be configured to create closed or open cells, or a mixture of both. 
     The expandable engagement element of the clot debonder may be made from a shape memory alloy or a super elastic alloy such as Nitinol, or from another metal such as stainless steel, or from a polymer such as PEEK, Nylon, PE or Polyimide. 
     The expandable engagement element may comprise a plurality of struts or segments cut from a tube. Said struts or segments may be cut from a tube with slots that run substantially parallel to the longitudinal axis of the tube, or with slots that are not parallel to the longitudinal axis of the tube. 
     Said struts or segments may overlap or may be non-overlapping. 
     The engagement element may comprise a collapsed state, wherein the engagement struts are aligned with the axis of the clot debonder and said plurality of struts comprise a tubular structure. 
     Said plurality of struts may be close packed in the delivery configuration. 
     In the expanded state, the engagement element is preferably configured to transmit axial force of the user to the clot. The engagement element may comprise an engagement surface and said engagement surface may comprise a distally facing surface. In one embodiment the engagement surface comprises an annular surface. With this embodiment the engagement surface may have an outer diameter and an inner diameter. The outer diameter may be substantially the same or smaller than the diameter of the vessel. The outer diameter may be substantially the same or smaller than the diameter of the clot. The inner diameter may be substantially the same or larger than the diameter of the guidewire. 
     In one embodiment the engagement surface comprises a flared surface. In another embodiment the engagement surface comprises a plurality of struts, said struts configured to apply pressure to the clot over a substantial portion of the cross-section of the vessel. In one embodiment the engagement surface is configured to apply an axial displacement to the entire body of the clot. The engagement surface of the clot debonding device may be configured to prevent clot fragmentation during debonding and capture. 
     In one embodiment the engagement element comprises a plurality of elongate struts. In the delivery configuration, the elongate struts may be substantially aligned with the axis of the vessel. In the expanded configuration, the struts may project radially outward from the axis of the clot debonder. In one embodiment the struts are interconnected. The struts may comprise regions of bending. 
     In one embodiment the struts of the engagement element comprise an outer ring member and a plurality of radial struts connected to said outer ring member. In another embodiment the strut arrangement of the engagement element comprises a plurality of cells. Each cell boundary may be defined by a strut. In another embodiment the engagement element comprises an outer ring member. The outer ring may comprise a plurality of struts configured in a circumferential ring. The engagement element may comprise an inner ring member. The inner ring member may be connected to or separate of the outer ring member. In one embodiment the outer ring member is connected to the collar by a plurality of radial struts. In one embodiment the outer ring member comprises a plurality of zig zag strut elements. 
     In one embodiment the struts are cut from a nitinol tube. The tube may comprise a cut pattern. The cut pattern may comprise a plurality of longitudinal slots and a plurality of struts. In one embodiment the cut pattern comprises a plurality of curved segments interconnecting said struts. 
     In another embodiment the engagement element comprises a plurality of wires. The wires may comprise a collapsed state and an expanded state. In the collapsed delivery state, the wires may be substantially aligned with the axis of the vessel. In the expanded state, the wires may project radially outwardly of the axis of the clot debonding device. 
     In the fully expanded state, the engagement element may comprise an outer rim. The outer rim may comprise a plurality of curved segments. 
     In another embodiment the engagement element comprises a plurality of shaped wires. Each shaped wire may comprise a first wire end and a second wire end. The first wire ends and second wire ends may be fixed to a tubular member. The wire segment may comprise a first radial curve adjacent the collar and a second circumferential curve. The circumferential curve in the wire may comprise an atraumatic vessel interface. 
     In one embodiment the engagement element comprises an axial strut segment, a curved strut segment, and a radial strut segment. With this embodiment the engagement element may be connected to a tubular member at the proximal end of the axial strut section. The struts of the axial segment may be oriented substantially parallel to the axis of the clot debonding device. The engagement element may comprise an immediate segment distal of the axial segment. The intermediate segment may comprise the radial curve. The intermediate section may comprise most of the engagement surface. The intermediate section may provide a high area surface for the transmission of force to the clot. 
     The clot debonding element may be designed to transmit force over the entire surface of the clot. The clot debonding element may be configured to debond the clot in one piece. The clot debonder may be configured such that the clot does not snag on its surface. The clot debonder may be configured to push the clot into the opening of the clot capture basket. 
     The clot debonder engagement element may be configured such that upon withdrawal it disengages from the clot without snagging, or fragmenting the clot and without removing the clot from the capture basket. 
     The connection between the wire and the collar may be configured so as to orient the wire parallel to the axis of the clot debonding device. The connection between the collar and the wire may comprise a hole in the collar. Immediately distal of the collar the wire may comprise a curve. The wire may be radially curved so as to create an abutment surface. The body of the wire may be substantially radial relative to the axis of the clot debonder. The clot engagement element may comprise a plurality of radial wire segments configured to deliver and distribute pressure to one face of the clot. The wires may comprise a second curved segment. This second curved segment may define an outer rim of the clot engagement element. The curved segment may also present an atraumatic surface to the vessel. This second curved segment may be curved in the circumferential direction. 
     The clot engagement element may comprise radial and circumferential engagement elements and may transmit force to the clot in a manner similar to that of a piston. 
     In another embodiment the struts or wires of the engagement element comprise an articulation region. The engagement element may assume the expanded state by an articulation of the struts or wires about the articulation region. 
     The invention also provides a method for removing a clot from a vessel involving a clot capture device that comprises a frame, a net and an elongate member such as a wire and is capable of being advanced through a microcatheter comprising the steps of: advancing a crossing guidewire through the vasculature and across the clot, advancing a microcatheter over the guidewire such that the tip of the microcatheter is across the clot, removing the crossing guidewire from the microcatheter, advancing through the lumen of the microcatheter a collapsed clot capture device, deploying the clot capture device distal of the tip of the microcatheter, expanding the clot capture device distal of the microcatheter, retracting the clot capture device and engaging with the clot, applying a force to the clot over at least a portion of the outer circumference of the clot, applying shearing forces to the clot, disengaging the clot from the wall of the vessel, capturing the clot within the clot capture basket, removing the clot capture basket and the clot from the patient and taking a final angiogram of the recanalized vessel. 
     The step of removing the clot capture basket may comprise at least partially collapsing the basket and/or applying compressive forces to the clot. 
     The clot capture device may comprise a frame, a wire and a net wherein the frame is expandable and the net is attached to the frame and the frame is at least partially fixed to the guidewire. 
     The invention provides a further method for removing a clot from a vessel involving a clot capture device that comprises a frame and a net and is capable of being advanced through a microcatheter and is further advanceable relative to a guidewire comprising the steps of: advancing a guidewire through the vasculature and across the clot, advancing a microcatheter over the guidewire such that the tip of the microcatheter is across the clot, advancing the frame and net in a collapsed state over the guidewire, deploying the frame and net from the distal end of the microcatheter, expanding the frame and net distal of the clot, retracting the frame and net and engaging with the clot, applying a force to the clot over at least a portion of the outer circumference of the clot, applying shearing forces to the clot, disengaging the clot from the wall of the vessel, encircling at least a portion of the clot with the frame, restraining fragments of the clot with the net, removing the frame and net from the patient and taking a final angiogram of the recanalized vessel. 
     The clot capture device may comprise an advancement element and the step of advancing the frame and net over the guidewire may comprise advancing the advancement element parallel of and relative to the guidewire. 
     The invention provides a further method for removing a clot from a vessel involving a clot capture device that comprises a frame, a net and an elongate wire and is capable of being advanced through a guide catheter comprising the steps of: advancing a guidewire through the vasculature and across the clot, advancing a guide catheter into the target vessel and positioning the tip of the guide catheter proximal of the clot, advancing the clot capture device in a collapsed state through the guide catheter, advancing the frame and net and the distal portion of the elongate wire across the clot, deploying the frame and net distal of the clot, expanding the frame and net distal of the clot, retracting the elongate wire with the frame and net attached, applying a force to the clot over at least a portion of the outer circumference of the clot, disengaging the clot from the wall of the vessel, encircling at least a portion of the clot with the frame, restraining fragments of the clot with the net, removing the frame and net from the patient, taking a final angiogram of the recanalized vessel. 
     The invention also provides a further method for removing a clot from a vessel involving a clot capture device that comprises a capture basket and a clot debonding element, the capture basket comprising a collapsed state for delivery through the vasculature and an expanded state for the capture of clot, the clot debonding element comprising a collapsed delivery state and an expanded state the method comprising the steps of: advancing a guidewire through the vasculature and across the clot, advancing a microcatheter over the guidewire such that the tip of the microcatheter is across the clot, advancing the capture basket through the microcatheter, deploying the capture basket from the distal end of the microcatheter, expanding the basket distal of the clot, retracting the microcatheter until the tip of the microcatheter is proximal of the clot, retracting the capture basket and engaging with the clot, advancing the clot debonder through the microcatheter, deploying the clot debonder proximal of the clot, advancing the clot debonder to engage with the clot from the proximal side, retracting the capture basket while holding the clot debonder steadfast, disengaging the clot from the wall of the vessel without applying force to the vessel wall distal of the occlusion, disengaging the clot from the wall of the vessel, encircling at least a portion of the clot with the frame, retracting the clot debonder, collapsing the clot debonder inside the lumen of the microcatheter, restraining fragments of the clot with the capture basket, removing the capture basket and the clot from the patient and taking a final angiogram of the recanalized vessel. 
     The above methods may include applying a force to the clot over at least a portion of the outer circumference of the clot, and/or applying shearing forces to the clot and/or collapsing the clot debonder inside the lumen of the guide catheter and/or expanding the clot debonder at the distal end of the microcatheter. 
     The step of expanding the clot debonder may comprise inflating the clot debonder, or inflating a sac at the distal end of the clot debonder. 
     The step of expanding the clot debonder may comprise removing an outer restraint from clot debonder and allowing the clot debonder to self-expand. The step of removing this restraint may comprise removing a pod from over the clot debonder. 
     The step of removing the restraint may comprise retracting the distal end of the microcatheter from over the clot debonder. 
     The invention further discloses a method for removing a clot from a vessel comprising the steps of: providing a clot capture device comprising a capture basket and a debonding element, the capture basket comprising a collapsed state for delivery through the vasculature and an expanded state for the capture of the clot, the clot debonding element comprising a collapsed delivery state and an expanded state; advancing the capture basket through the vasculature in the collapsed state; deploying the capture basket distal of the clot; advancing the clot debonder through the vasculature; deploying the clot debonder proximal of the clot; engaging the capture basket and/or the clot debonder with the clot; disengaging the clot from the wall of the vessel; capturing the clot in the capture basket; and removing the clot from the vasculature. 
     A number of embodiments of the invention are disclosed herein. In the statements above and below the main embodiments are firstly described as a whole, with a list of further embodiments relating to variants of specific features or uses appended the main embodiments. It will be appreciated that these further embodiments/feature variants may also be applicable to any of the main embodiments. 
     A device is disclosed for the removal of an occlusive clot from a vessel wherein the occlusion has substantially cut off blood supply to a distal vascular bed, the device comprising a basket and a clot holding assembly, the basket comprising a frame, a net and an elongate member, the frame comprising a first ring member and having a collapsed delivery configuration, a deployed configuration and an expanded configuration for dislodging the occlusive clot from a vessel wall, the first ring member configured to be expanded distal of the occlusive clot, the basket further comprising a cable extending through the lumen of the elongate member, the cable attached to the first ring member, the cable comprising an activated state and a deactivated state, in the activated state the cable transmitting a force from the user to the frame, said force causing the deployed frame to assume the expanded state. 
     In other embodiments, this invention may further include one or more of the following: The expansion of the frame may comprise an articulation of at least a portion of the frame. 
     The frame may further comprise a connector element and a collar arrangement. 
     The expansion of the frame may comprise an articulation of the first ring member. 
     The frame articulation may comprise an angular displacement of the frame. 
     The frame articulation may comprise a change in the shape of the frame. 
     The expansion of the frame may comprise an articulation of the connector member. 
     The deployed state may comprise a partially expanded state. 
     The frame may be biased towards the deployed state. 
     The frame may return to the deployed state when the cable is deactivated. 
     The frame may comprise a cable attachment to which the distal end of the cable is fixed. 
     The frame may comprise at least one cable guide. 
     The cable guide may at least partially encapsulate the cable. 
     The cable guide may comprise a channel which restrains the cable. 
     The channel of the cable guide may be configured such that the cable can slide in the channel. 
     The channel may comprise an eyelet. 
     The channel may comprise a restraining feature. 
     The axis of a portion of the cable may run substantially parallel to the neutral axis of the first ring along at least a portion of the circumference of the first ring. 
     In the expanded configuration, the diameter of the frame may be substantially the same as the diameter of the vessel in a region of occlusion. 
     In the expanded configuration, the diameter of the frame may be substantially the same as a diameter of the clot. 
     The elongate member may comprise a tubular member. 
     The elongate member may extend in use from the region of the occlusion through the vasculature to a user interface external of the patient. 
     The elongate member may comprise a spring, or a polymer tube, or a hypo tube over at least a portion of its length. 
     The elongate member may comprise a plurality of wire filaments, wherein said filaments are arranged so as to define an inner lumen. 
     The wire filaments may be wound in a spiral arrangement. 
     The wire filaments may be packed tightly together and define an inner lumen. 
     The basket and the clot holding assembly may be configured to be delivered through the lumen of a microcatheter. 
     The basket and the clot holding assembly may be restrained in the collapsed state during delivery through the microcatheter. 
     The frame may be restrained in the collapsed state during delivery by a restraining element. 
     The restraining element may comprise a tether, or a tube, or a core to which the frame is fixed. 
     The restraining element may be removed distal of the clot and the frame deployed. 
     The restraining element may comprise the inner wall of the microcatheter. 
     The first ring member may be configured in the expanded state to engage with the occlusive clot at the interface between the clot and the vessel wall. 
     The clot holding assembly may be configured to provide an abutment. 
     The basket may be moveable relative to the clot holding assembly. 
     The clot holding assembly may be configured to provide a clot engaging surface. 
     The basket may not be moveable relative to the clot holding assembly. 
     The clot holding assembly may comprise an engagement frame and an elongate tube. 
     The clot holding assembly may be configured to be expanded proximal of the basket frame. 
     The clot holding assembly may be configured to transmit a holding force from the user to the proximal face of the clot. 
     The clot holding assembly may hold the clot in a fixed position while the first ring member of the basket is retracted over the clot. 
     The clot holding assembly may hold the vessel in a fixed position while the first ring member of the basket is retracted over the clot. 
     The basket may be held in a fixed position while the clot holding assembly is retracted with the clot. 
     The basket and clot holding assembly may be retracted together with the clot. 
     The first ring member of the basket may apply an action force to the clot to dislodge the clot from the vessel wall. 
     The clot holding assembly may apply a reaction force to the proximal end of the clot. 
     The reaction force may reduce the portion of the action force that is transmitted to the vessel wall. 
     The clot holding assembly may be configured to allow the user to apply a greater action force to the clot distal end. 
     The clot holding assembly may protect the vessel from force applied to the clot by the basket. 
     The abutment may comprise an abutment surface. 
     The abutment surface may comprise a plurality of tether segments. 
     The abutment surface may comprise a plurality of tethers lased to the second ring element. 
     The abutment surface may comprise a plurality of strut elements. 
     The abutment surface may comprise a plurality of strut elements and a plurality of tether segments. 
     The abutment surface may be configured to hold the clot stationary while the first ring dislodges the clot from the vessel wall. 
     The abutment surface may be configured to distribute the engagement force over the proximal surface of the clot. 
     The engagement frame may comprise a second ring element. 
     The plurality of tether segments may be lased to the second ring. 
     At least one of the plurality of tether segments may be taut when the engagement frame is in the expanded configuration. 
     The abutment may be configured to distribute force across a surface of the clot. 
     In the expanded configuration, the second ring element may comprise a hoop. 
     The hoop may comprise a flat hoop. 
     The hoop may comprise a zig-zag hoop. 
     The abutment surface may comprise a flat surface. 
     The abutment surface may comprise an undulating surface. 
     The abutment surface may comprise two or more interpenetrating flat surfaces. 
     The abutment surface may comprise a complex 3 dimensional surface. 
     The abutment surface may be configured to grip the clot. 
     The abutment surface may be configured to engage with the clot on multiple planes. 
     The engagement frame may comprise a wire. 
     The engagement frame may comprise at least a pair of wire segments. 
     The wire may comprise a hoop in the expanded state and the wire may comprise a pair of substantially parallel wire segments in the collapsed configuration. 
     The engagement frame may comprise at least a pair of struts. 
     In one embodiment the pair of struts may comprise a first end and a second end. 
     The struts may be connected to one another at the first end. 
     The engagement frame may be connected to the tubular member adjacent the strut first end. 
     The struts may be connected to each other at the second end. 
     In the collapsed configuration, the engagement frame may comprise a pair of substantially parallel struts. 
     In the collapsed configuration, the pair of struts may lie along the surface of the elongate member of the basket assembly. 
     In the expanded configuration, the struts may move apart between the first and second ends to form a hoop. 
     The basket may comprise a connector member which connects the first ring member of the basket to the elongate member. 
     The frame may comprise a collar arrangement. 
     The collar arrangement may be configured to allow the elongate member to rotate relative to the frame. 
     The collar arrangement may comprise a frame collar and a proximal and distal stop. 
     The frame collar may be disposed over the elongate member and may be rotatable relative to the elongate member. 
     The proximal and distal stops may be fixed to the elongate member. 
     Axial movement of the frame collar may be restricted by said proximal and distal stops. 
     The frame collar may be connected to the connector member. 
     The connector member may comprise an articulating member. 
     The net may comprise a braided, knitted or filament wound net and the net may be tubular with an open end and a closed end. 
     The open end of the net may be attached to the ring member. 
     The net may be configured to capture dislodged clot. 
     The net may be configured to capture clot fragments. 
     The net may comprise a high tensile fiber. 
     The net may comprise a para-aramid, meta-aramid, a UHMWPE, a polyethylene naphthalate (PEN), a stainless steel, a nitinol, a tungsten alloy or a mixture of these. 
     The first ring may comprise a plurality of net attachments. 
     The net attachments may comprise eyelets, notches, contoured surface. 
     The cable may comprise a plurality of filaments. 
     The distal end of the cable may be branched and each branch may be fixed to the frame at a separate attachment point. 
     In one embodiment one of the cable branches may be attached to the net. 
     The elongate member may comprise an inner lumen. 
     The inner lumen of the elongate member may comprise a smooth undulating surface. 
     The device may comprise a user interface and said user interface may be configured to allow the user to control the frame assembly and the holding assembly. 
     The user interface may comprise a handle attached to the proximal end of the elongate member. 
     The handle may comprise a control mechanism. 
     The proximal end of the cable may be fixed to the control mechanism. 
     The control mechanism may be configured to apply or remove tension on the cable. 
     The control mechanism may be activated by a thumbwheel on the handle. 
     In another embodiment the device comprises a device for the removal of a thrombotic or embolic occlusion of a blood vessel, the device comprising: a basket, a clot engagement element, a pull cable, and a user interface, wherein the basket comprises a frame and a net, the frame configured to engage generally with the outer rim of the clot, the frame having a collapsed configuration and an expanded configuration, the clot engagement element being disposed proximal of the basket and configured to engage with the clot, the pull cable extending proximally from the basket to the user interface, the pull cable comprising a relaxed configuration and a tensioned configuration, such that tensioning of the pull cable at least partially causing the frame to assume the expanded configuration. 
     In another embodiment the device comprises a device for the removal of a clot obstructing the flow of blood through an arterial vessel, the device comprising an elongate member, a clot engaging element and a capture basket; the elongate member extending in use from a point adjacent the target treatment site interior of the patient to a point exterior of the patient; the capture basket comprising a frame and a net, and having an expanded and a collapsed configuration; the clot engaging element comprising a plurality of struts having an expanded and a collapsed configuration, the plurality of struts forming a first section and a second section, said first section tapering outward and distally from the elongate member and connected to the second section, said second section comprising a plurality of cells defined by a plurality of struts and arranged around at least a portion of the circumference of an axis substantially parallel to that of the elongate member; the clot engaging element and the capture basket being restrained in the collapsed configuration for delivery to the target site; and the clot engaging element being located adjacent the distal end of the elongate member and proximal of the capture basket and configured to engage with and dislodge the clot from the vessel. 
     The capture basket frame may be self expanding. 
     The clot engaging element may be self expanding. 
     The elongate member may comprise a proximal section adjacent its proximal end and a distal section adjacent its distal end, said proximal section having a flexural stiffness greater than four times that of said distal section. The clot engaging element may comprise a central axis and a contact surface, said central axis being substantially parallel to the elongate member, said contact surface engaging with the clot and extending around at least a portion of the central axis. 
     The contact surface may extend around the entire circumference of the central axis. 
     The plurality of cells of the second section of the clot engaging element may be arranged around the entire circumference of an axis substantially parallel to that of the elongate member. 
     The elongate member may comprise an outer tubular element and an inner operating element. 
     The inner operating element may be movable relative to the outer tubular element and may extend both proximally and distally of the outer tubular element. 
     The clot engaging element may be attached to the distal section of the outer tubular element and the capture basket attached to the distal section of the inner operating element. 
     The capture basket frame may be expandable to conform to the inner diameter of the vessel in which it is deployed. 
     The elongate member may contain an operating cable which may be connected to an element of the capture net frame and which can be advanced or retracted relative to the elongate member to control the degree of expansion of the frame. 
     The clot engaging element may be expandable to conform to the inner diameter of the vessel in which it is deployed. 
     The net may comprise a braided, knitted or filament wound net and may have an open end and a closed end. 
     The clot engaging element may comprise one or more tether segments which extend between some or all of the plurality of struts. 
     The clot engaging element may be laser cut from a tube or sheet. 
     The clot engaging element and the capture basket may be restrained in the collapsed configuration by the inner lumen of a microcatheter during delivery. 
     The capture basket frame may be self adjusting, and/or the expansion of the capture basket frame may be adjustable by the user. 
     In another embodiment a device for the removal of a thrombotic or embolic occlusion of a blood vessel comprises a self expanding frame for use in the treatment of embolic or thrombotic disease of a blood vessel, the frame comprising a collapsed state for delivery, a partially expanded state, and a fully expanded state, wherein in the fully expanded state the frame comprises an unrestricted opening of substantially the same size as the cross-section of the target vessel, the frame further comprising at least one cable attachment point and at least one cable guide, wherein the cable guide restrains the cable in a path substantially parallel to the path of the strut but spaced apart from the neutral axis of the strut and allows the cable to slide relative to the cable guide. 
     In another embodiment a device for the dislodgement and removal of an occlusive clot in a blood vessel comprises a self expanding frame, the frame comprising a collapsed state for delivery, a partially expanded state, and a fully expanded state, wherein in the fully expanded state, the frame comprises a first hoop and a second hoop, the first hoop and the second hoop are connected at an articulating junction, the angle of the first and second hoops with respect to each other being variable. 
     The articulating junction may comprise a strut. 
     The first hoop, the second hoop, and the articulating junction may be integral 
     The first hoop, the second hoop, and the articulating junction may be cut from a self expanding tube. 
     The first hoop, the second hoop, and the articulating junction may be cut from a self expanding sheet. 
     The first hoop, the second hoop, and the articulating junction may comprise a shaped wire. 
     The device further may comprise an elongate member and the elongate member is connected to the frame adjacent the distal end of the elongate member. 
     In use, the elongate member may extend from the region of the occlusion through the vasculature to the exterior of the patient. 
     The elongate member may comprise an inner lumen. 
     The device may comprise a cable, said cable fixed to an attachment point on the frame and extending through the vasculature to the exterior of the patient. 
     The cable may comprise an activated state wherein tension is applied to the cable by the user and a deactivated state wherein the cable is substantially free of tension. 
     In the cable activated state the frame may articulate. 
     The cable may comprise a plurality of activated states. 
     The frame may comprise a plurality of fully expanded states. 
     The frame may comprise two pairs of struts connected by the articulating junction in the collapsed state. 
     The frame may comprise a pair of elliptical rings in the deployed state. 
     The pair of elliptical rings may comprise a major axis and a minor axis. 
     The major axis of the pair of elliptical rings may be substantially aligned with the central axis of the vessel in the deployed state. 
     The cable attachment point may be adjacent the distal end of the distal ring when the distal ring is in the deployed state. 
     Activation of the cable may cause both rings to rotate relative to the axis of the vessel. 
     Activation of the cable may cause the rings to rotate in opposite directions. 
     Activation of the cable may cause the distal end of the distal ring moves towards the proximal end of the proximal ring. 
     The center of the frame may comprise the crossing point of the major axis and the minor axis and the center of the frame may be substantially coaxial with the central axis of the elongate member. 
     The center of the frame may be spaced apart from the axis of the elongate member. 
     The frame may comprise a connector member, the connector member configured to connect the proximal hoop of the frame to the elongate member. 
     The net may be attached to the frame. 
     The net may be attached to the distal hoop of the frame. 
     The net may be attached to the proximal hoop of the frame. 
     The net may pass over the distal hoop of the frame. 
     The net may pass through the opening defined by the distal hoop of the frame. 
     The distal hoop may be slidable relative to the net. 
     The articulating junction may comprise an area where the thickness of the frame is reduced. 
     The articulating junction may comprise an area where the width of the frame is reduced. 
     The articulating junction may comprise a strut or a wire connecting the first and second hoops. 
     The articulating junction may comprise a pair of struts or wires connecting the first and second hoops. 
     The pair of struts or wires may be connected to each other. 
     The articulating junction may comprise a tether connecting the first and second hoops. 
     The articulating junction may comprise a weakened section. 
     The articulating junction may comprise a stress distributing region. 
     The frame may be fixed to the elongate member. 
     The frame may be rotatable relative to the elongate member. 
     The cable may extend parallel with the elongate member. 
     The cable may extend through the lumen of the elongate member. 
     Another embodiment of this device is for use in the dislodgement of an occlusive clot in a vessel, the device comprising an expandable distal section and an elongate tubular member, wherein the expandable distal section comprises a collapsed configuration for delivery and an expanded configuration for dislodgement of the occlusive clot, the self expanding distal section comprising a plurality of self expanding members, said self expanding members projecting radially outward from the distal section of the elongate tube, each self expanding member comprising an atraumatic end, an engagement section and an attachment, the engagement section projecting substantially radially outwardly relative to the elongate tube and the attachment fixed to the elongate tube. 
     The elongate tube may comprise a lumen and said lumen may be configured to slidably receive a clot removal assembly, wherein the clot removal assembly comprises a shaft and a clot removal element and the shaft extends through the lumen of the tubular member and the clot removal element is distal of the expandable distal section of the device. 
     The clot removal element may comprise a basket. 
     The clot removal element may comprise a clot engagement device. 
     The expandable distal section may comprise a clot engagement device. 
     The atraumatic end of the at least one self expanding member may comprise a curved surface. 
     The atraumatic end of the at least one self expanding member may comprise an eyelet. 
     The atraumatic end of the at least one self expanding member may comprise a soft material. 
     The atraumatic end of the at least one self expanding member may comprise a curved member. 
     The self expanding distal section may comprise an abutment surface. 
     The abutment surface may comprise an annular surface. 
     The abutment surface may comprise a tapered surface. 
     The abutment surface may be concentric with the lumen of the elongate tube. 
     The abutment surface may be offset relative to the lumen of the elongate tube. 
     The abutment surface may comprise a plurality of tether segments. 
     At least one of the tether segments may comprise at least a partially circumferential segment. 
     At least one of the tether segments may comprise at least a partially radial segment. 
     At least two of the self expanding members may be connected. 
     In another embodiment a device for the dislodgement and removal of an occlusive clot in a blood vessel comprises a basket assembly, the basket assembly comprising a self expanding frame, a net and an elongate member, wherein the frame comprises a hoop and a support ring segment, the hoop is connected to the elongate member and configured to appose a vessel circumference, the support ring segment is fixed to the hoop and the support segment is configured to appose a portion of a circumference of the vessel, the support segment providing an engagement support to the hoop. 
     The hoop may comprise a collapsed delivery configuration and an expanded configuration for engagement and dislodgement of the occlusive clot. 
     The hoop may be biased towards the expanded configuration. 
     The hoop may comprise a first strut and a second strut and each strut may be configured to form one half of the hoop. 
     The support ring segment may comprise a first end and a second end and the first and second ends may be attached to the first and second struts. 
     The center of the hoop may be substantially coaxial with the axis of the elongate member. 
     The center of the hoop may be spaced apart from the axis of the elongate member. 
     The elongate member of the basket assembly may be sized such that it can be interfaced with a clot debonding device. 
     In another embodiment a device for the dislodgement and removal of an occlusive clot in a blood vessel comprises a basket assembly, the basket assembly comprising a frame, a net, a cable and a tubular member, the frame comprising a self expanding hoop and a support, the support comprising a curved strut wherein the curve is configured to interact with the surface of the vessel, the ends of curved strut articulating with respect to the hoop and being fixedly connected to the hoop. 
     The curved strut may be integral with the hoop. 
     The frame may comprise a one piece self expanding structure cut from a tube. 
     The structure may comprise an articulation region connecting the curved strut to the hoop. 
     The articulation region may comprise a region wherein the wall of the tube is reduced. 
     The articulation region may comprise a region wherein the width of the section is reduced. 
     The curved strut may comprise a hinge at each of its ends. 
     The net may be attached to the hoop. 
     The frame may comprise a collapsed configuration, a deployed configuration, and an expanded configuration. 
     The expanded configuration may comprise the clot dislodgement configuration. 
     The collapsed configuration may comprise the delivery configuration. 
     The deployed configuration may comprise the clot removal configuration. 
     In the collapsed configuration, the struts that form the hoop may be compressed together to facilitate delivery. 
     In the collapsed configuration, the curved strut may be collapsed to facilitate of the frame through a microcatheter. 
     In the deployed configuration, the hoop may expand. 
     The cable may comprise an activated state and a deactivated state. 
     In the activated state, the cable may be in tension and may cause the curved strut to articulate relative to the hoop. 
     In the activated state, the cable may be in tension and may cause the expanded hoop to articulate relative to the elongate member. 
     In the deactivated state, the cable may not be in tension and the frame may return to its deployed state. 
     The tubular member may comprise an abutment surface at its distal end. 
     The abutment surface may engage with the frame when the cable is activated. 
     The tubular member may be integral with the frame. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be more clearly understood from the following description of some embodiments thereof, given by way of example only, with reference to the accompanying drawings, in which:— 
         FIG.  1    shows a patient catheterized via femoral access with a clot retrieval device positioned in a cerebral vessel using the arterial system for its delivery; 
         FIG.  2    shows some of the anatomy of arteries above the aortic arch leading to the brain; 
         FIG.  3   a    shows part of the cerebral circulation with an obstructive clot positioned in the Anterior Cerebral Artery, distal of the Middle Cerebral Artery branch; 
         FIG.  3   b    shows a guidewire being placed across the obstructive clot; 
         FIG.  3   c    shows a micro-catheter with the clot retrieval device of the invention crossing the obstructive clot; 
         FIG.  3   d    shows the micro-catheter removed with the clot retrieval device placed distal of the obstructive clot; 
         FIG.  3   e    shows the clot retrieval device being advanced proximally and capturing the obstructive clot with a removal catheter advanced from the proximal side; 
         FIG.  3   f    shows the clot retrieval device, the captured occlusive clot and the removal catheter being removed from the vessel; 
         FIG.  3   g    shows the target vessel with the obstructive clot and devices completely removed; 
         FIG.  4   a    shows a target vessel with an occlusive clot; 
         FIG.  4   b    shows a guidewire with its distal tip across the obstructive clot; 
         FIG.  4   c    shows a micro-catheter advanced over the guidewire until its distal end is across the obstructive clot; 
         FIG.  4   d    shows the preplaced micro-catheter with its distal end across the occlusive clot and a clot retrieval device being advanced through its inner lumen; 
         FIG.  4   e    shows clot retrieval device deployed distal of the occlusive clot with the micro-catheter being withdrawn, the clot retrieval device being connected to a wire and the proximal end of the wire exiting the patient and being controlled by a physician; 
         FIG.  4   f    shows the clot retrieval device deployed distal of the occlusive clot; 
         FIG.  4   g    shows the clot retrieval device being advanced proximally and capturing the obstructive clot with a removal catheter advanced from the proximal side; 
         FIG.  4   h    shows the clot retrieval device, the captured occlusive clot and the removal catheter being removed from the vessel; 
         FIG.  4   i    shows the target vessel with the obstructive clot and devices completely removed; 
         FIG.  5   a    shows a target vessel with an occlusive clot; 
         FIG.  5   b    shows a micro delivery catheter with a clot retrieval device collapsed within a distal lumen of the micro delivery catheter, the micro delivery catheter being advanced across the occlusive thrombus, the clot retrieval device having a guidewire that extends proximally and distally; 
         FIG.  5   c    shows the micro delivery catheter being removed with the clot retrieval device deployed in the target vessel distal of the occlusive clot with the guidewire extending across the lesion and proximal to the user; 
         FIG.  5   d    shows the clot retrieval device deployed in the target vessel distal of the occlusive clot with the guidewire extending across the lesion and proximal to the user; 
         FIG.  5   e    shows the clot retrieval device being advanced proximally and capturing the obstructive clot with a removal catheter advanced from the proximal side; 
         FIG.  5   f    shows the clot retrieval device, the captured occlusive clot and the removal catheter being removed from the vessel; 
         FIG.  5   g    shows the target vessel with the obstructive clot and devices completely removed; 
         FIG.  6    is a detailed view of the distal end of a clot retrieval device in its expanded clot capture state; 
         FIG.  7   a    shows a clot retrieval device in its expanded capture state; 
         FIG.  7   b    shows the clot retrieval device of  FIG.  7   a    inside a micro delivery catheter in its collapsed delivery state; 
         FIG.  8   a    shows a clot retrieval device frame constructed from a guidewire; 
         FIG.  8   b    shows a clot retrieval device frame attached to a guidewire; 
         FIG.  8   c    shows a clot retrieval device frame mounted between stops on a guidewire; 
         FIG.  8   d    shows a clot retrieval device frame connected to a tubular element mounted proximal to a stop on a guidewire; 
         FIG.  8   e    shows a clot retrieval device frame connected to a tubular element mounted a guidewire; 
         FIG.  8   f    shows a clot retrieval device frame connected to a tubular element with an exit port and proximal shaft, mounted on a rapid exchange guidewire; 
         FIG.  9   a    shows the frame of a clot retrieval device in the expanded state; 
         FIG.  9   b    shows the frame of a clot retrieval device in the expanded state; 
         FIG.  9   c    shows the frame of a clot retrieval device in the expanded state; 
         FIG.  9   d    shows the frame of a clot retrieval device in the expanded state; 
         FIG.  9   e    shows the frame of a clot retrieval device in the expanded state; 
         FIG.  9   f    shows the frame of a clot retrieval device in the expanded state; 
         FIG.  9   g    shows the frame of a clot retrieval device in the expanded state; 
         FIG.  9   h    shows the frame of a clot retrieval device in the expanded state; 
         FIG.  9   i    shows the frame of a clot retrieval device in the expanded state; 
         FIG.  10   a    shows a clot retrieval device in its expanded state; 
         FIG.  10   b    is a view of a clot retrieval device in which a proximal collar support struts and frame are cut from a single piece of tubing; 
         FIG.  10   c    is an elevational view of one piece frame component of  FIG.  10   b    in a collapsed configuration; 
         FIG.  10   d    is an end view of a collar end of the device of  FIG.  1 . 0     c;    
         FIG.  10   e    is a cross sectional view on the line a-a in  FIG.  10     c;    
         FIG.  11   a    shows a clot retrieval device in its expanded capture state; 
         FIG.  11   b    shows the clot retrieval device of  FIG.  11   a    inside a micro delivery catheter in its collapsed delivery state with the capture fibers removed (for illustration); 
         FIG.  11   c    shows the clot retrieval device of  FIG.  11   a    inside a micro delivery catheter in its collapsed delivery state; 
         FIG.  12   a    shows a clot retrieval device in its expanded capture state without capture fibers being shown (for illustrative purposes); 
         FIG.  12   b    shows a clot retrieval device of  FIG.  12   a    inside a micro delivery catheter in its collapsed delivery state with the capture fibers removed (for illustration); 
         FIG.  13   a    shows a clot retrieval device in its expanded state; 
         FIG.  13   b    shows a view of a collar and strut arrangement for use with a number of frame designs of the invention; 
         FIG.  13   c    shows another view of a collar and strut arrangement for use with a number of frame designs on the invention; 
         FIG.  13   d    shows an end view of a collar and strut arrangement for use with a number of frame designs of the invention with the strut in its collapsed state; 
         FIG.  13   e    shows an end view of a collar and strut arrangement for use with a number of frame designs on the invention with the strut in its expanded state; 
         FIG.  14    shows a distal collar mounted on a guidewire with eyelets for fiber alignment and/or attachment; 
         FIG.  15    shows a distal collar with eyelets for fiber alignment and/or attachment; 
         FIG.  16    shows a distal collar mounted on a guidewire with eyelets for fiber alignment and/or attachment; 
         FIG.  17    shows a distal collar mounted on a guidewire with eyelets for fiber alignment and/or attachment; 
         FIG.  18    shows a clot retrieval device in the deployed configuration distal of an occlusive clot; 
         FIG.  19    shows a clot retrieval device being withdrawn proximally to capture a clot; 
         FIG.  20   a    shows a first side view of a strut of the hinged frame of a clot retrieval device; 
         FIG.  20   b    shows a second side view of a strut of the hinged frame of a clot retrieval device; 
         FIG.  20   c    shows a strut of the hinged frame of a clot retrieval device. The strut has a preset curved shape; 
         FIG.  20   d    shows the joining of the ends of two struts in the construction of a hinged frame; 
         FIG.  20   e    shows a hinged frame with four struts forming a ring and four support elements supporting the frame; 
         FIG.  20   f    shows four struts of a hinged support frame configured into a ring; 
         FIG.  20   g    shows how the hinged support frame can collapse about the X axis; 
         FIG.  20   h    shows how the hinged support frame can collapse about the Y axis; 
         FIG.  20   i    shows how the hinges allow the support frame to collapse; 
         FIG.  20   j    shows the hinges in the collapsed state; 
         FIG.  20   k    is another view of a hinged support frame; 
         FIG.  21   a    shows an enlarged view of a hinged support frame with eyelets for fiber attachment; 
         FIG.  21   b    shows the frame of  FIG.  20   j    integrated with proximal and distal frame supports; 
         FIG.  21   c    shows a clot retrieval device assembled and in a collapsed configuration with capture fibers included; 
         FIG.  22    shows a clot retrieval device with a hinged frame in the expanded configuration; 
         FIG.  23   a    shows a clot retrieval device with a hinged frame in the expanded configuration; 
         FIG.  23   b    shows a clot retrieval device with a hinged frame in the partially collapsed configuration; 
         FIG.  23   c    shows a clot retrieval device with a hinged frame in the fully collapsed configuration; 
         FIG.  24   a    shows a clot retrieval device with a hinged frame in the fully expanded configuration; 
         FIG.  24   b    shows a clot retrieval device with a hinged frame in the partially collapsed configuration; 
         FIG.  24   c    shows a clot retrieval device with a hinged frame in the fully collapsed configuration; 
         FIG.  25   a    shows a section of a strut of a clot retrieval device; 
         FIG.  25   b    shows a section of a strut of a clot retrieval device; 
         FIG.  25   c    shows a section of a strut of a clot retrieval device; 
         FIG.  25   d    shows two sections of two adjacent struts of a clot retrieval device nesting together; 
         FIG.  26   a    shows an eyelet for capture fiber attachment to a strut; 
         FIG.  26   b    shows an eyelet for capture fiber attachment to a strut; 
         FIG.  26   c    shows an eyelet for capture fiber attachment to a strut; 
         FIG.  26   d    shows an eyelet in a strut section with a capture fiber in situ; 
         FIG.  26   e    shows an eyelet in a strut section with a capture fiber in situ; 
         FIG.  26   f    shows an eyelet in a strut section with a capture fiber in situ; 
         FIG.  27   a    shows a cross section of a strut with a capture fiber threaded through an eyelet; 
         FIG.  27   b    shows a strut with a capture fiber threaded through an eyelet; 
         FIG.  27   c    shows a cross section of a strut with a capture fiber threaded through an eyelet; 
         FIG.  27   d    shows a strut with a capture fiber threaded through an eyelet; 
         FIG.  28   a    shows a segment of a strut of a clot retrieval device; 
         FIG.  28   b    shows a cross section of a strut; 
         FIG.  28   c    shows a fixture for assembling capture fibers to struts; 
         FIG.  29   a    shows two eyelets for capture fiber attachment to a strut; 
         FIG.  29   b    shows an eyelet for capture fiber attachment to a strut; 
         FIG.  29   c    shows an eyelet for capture fiber attachment to a strut; 
         FIG.  29   d    shows a strut with curvature to define a capture fiber attachment location; 
         FIG.  29   e    shows a strut with raised features to define a capture fiber attachment location; 
         FIG.  29   f    shows a strut with recessed features to define a capture fiber attachment location; 
         FIG.  29   g    shows a strut with recessed features to define a capture fiber attachment location; 
         FIG.  29   h    shows a strut with bands to define a capture fiber attachment location; 
         FIG.  29   i    shows a strut with coils to define a capture fiber attachment location; 
         FIG.  30   a    shows a strut with a sleeve to create a capture fiber attachment location; 
         FIG.  30   b    shows a strut with a coating to create a capture fiber attachment location; 
         FIG.  30   c    shows a strut and a capture net with a connecting fiber joining the two; 
         FIG.  30   d    shows a strut and a capture net with connecting rings joining the two; 
         FIG.  30   e    shows a strut and a capture net with a connecting fiber joining the two; 
         FIG.  31   a    shows a capture net of a woven or braided construction; 
         FIG.  31   b    shows a capture net of a knitted construction; 
         FIG.  31   c    shows a sectional side view of the capture net of  FIG.  31   a    or  FIG.  31   b    inverted and mounted on a frame; 
         FIG.  32   a    shows a monofilament capture fiber; 
         FIG.  32   b    shows a multifilament twisted capture fiber; 
         FIG.  32   c    shows a multifilament braided capture fiber; 
         FIG.  32   d    shows a multifilament capture fiber with a cover sleeve; 
         FIG.  32   e    shows a multilayer capture fiber; 
         FIG.  33   a    shows a frame with a capture net with a porosity gradient; 
         FIG.  33   b    shows a frame with a capture net with a porosity gradient; 
         FIG.  33   c    shows a frame with capture fibers with a porosity gradient; 
         FIG.  33   d    shows a frame with capture fibers with a stiffening fiber; 
         FIG.  34   a    shows a clot retrieval device in the fully expanded configuration; 
         FIG.  34   b    shows a clot retrieval device in the collapsed configuration inside a catheter; 
         FIG.  34   c    shows a ring and guidewire of a clot retrieval device; 
         FIG.  34   d    shows a ring and guidewire of a clot retrieval device; 
         FIG.  34   e    shows a portion of a guidewire of a clot retrieval device; 
         FIG.  34   f    shows a portion of a guidewire of a clot retrieval device; 
         FIG.  35   a    shows a vessel with an obstructive clot; 
         FIG.  35   b    shows a clot retrieval device crossing an obstructive clot; 
         FIG.  35   c    shows a clot retrieval device being deployed in a vessel; 
         FIG.  35   d    shows a clot retrieval device deployed in a vessel; 
         FIG.  35   e    shows a clot retrieval device fully expanded in a vessel; 
         FIG.  35   f    shows a clot retrieval device capturing an obstructive clot; 
         FIG.  35   g    shows a clot retrieval device being collapsed; 
         FIG.  35   h    shows a clot retrieval device partially collapsed; 
         FIG.  35   i    shows a clot retrieval device being removed from a vessel; 
         FIG.  36   a    shows a clot retrieval device in the expanded configuration; 
         FIG.  36   b    shows a clot retrieval device in the collapsed delivery configuration; 
         FIG.  37   a    shows a conventional guidewire; 
         FIG.  37   b    shows a portion of a guidewire modified to create a clot retrieval device; 
         FIG.  37   c    shows a clot retrieval device in the expanded state; 
         FIG.  37   d    shows a clot retrieval device in the collapsed delivery configuration; 
         FIG.  37   e    shows an end view of a clot retrieval device; 
         FIG.  38   a    shows a portion of a guidewire modified to create a clot retrieval device; 
         FIG.  38   b    shows a portion of a guidewire modified to create a clot retrieval device; 
         FIG.  38   c    shows a cross sectional view of a guidewire modified to create a clot retrieval device; 
         FIG.  39   a    shows an end view of a clot retrieval device; 
         FIG.  39   b    shows a clot retrieval device in the expanded configuration; 
         FIG.  39   c    shows a clot retrieval device in the collapsed delivery configuration; 
         FIG.  40   a    shows an end view of a clot retrieval device; 
         FIG.  40   b    shows a clot retrieval device in the expanded configuration; 
         FIG.  41   a    shows an end view of a clot retrieval device; 
         FIG.  41   b    shows a clot retrieval device in the expanded configuration; 
         FIG.  42   a    shows an end view of a clot retrieval device; 
         FIG.  42   b    shows a clot retrieval device in the expanded configuration; 
         FIG.  43    shows a clot retrieval device in the expanded configuration; 
         FIG.  44   a    shows an end view of a frame design of a clot retrieval device; 
         FIG.  44   b    shows a view of a portion of frame of a clot retrieval device; 
         FIG.  44   c    shows a clot retrieval device in the expanded configuration; 
         FIG.  44   d    shows a clot retrieval device in the delivery configuration; 
         FIG.  45   a    shows an end view of a frame design of clot retrieval device; 
         FIG.  45   b    shows a view of a portion of frame of a clot retrieval device; 
         FIG.  45   c    shows a clot retrieval device in the expanded configuration; 
         FIG.  46    shows a clot retrieval device in the expanded configuration; 
         FIG.  47   a    shows a clot retrieval device in the expanded configuration; 
         FIG.  47   b    shows a clot retrieval device in the partially collapsed configuration; 
         FIG.  47   c    shows a clot retrieval device in the delivery configuration; 
         FIG.  47   d    shows a view of a portion of frame section of a clot retrieval device; 
         FIG.  48   a    shows a clot retrieval frame mounted on a guidewire; 
         FIG.  48   b    shows the device of  FIG.  48   a    and a delivery device housed in a microcatheter; 
         FIG.  49   a    shows a clot retrieval device and a delivery catheter; 
         FIG.  49   b    shows the device of  FIG.  49   a    loaded within its delivery catheter; 
         FIG.  50   a    shows a clot retrieval device; 
         FIG.  50   b    shows the device of  FIG.  50   a    loaded within a catheter; 
         FIG.  50   c    shows the device of  FIG.  50   a    partially withdrawn into a retrieval catheter; 
         FIG.  51   a    shows a clot retrieval device positioned over a full length guidewire; 
         FIG.  516    shows a clot retrieval device positioned over a rapid exchange length guidewire; 
         FIG.  52   a    shows a clot retrieval device; 
         FIG.  52   b    shows a guidewire of the clot retrieval device of  FIG.  52     a;    
         FIG.  53    shows another clot retrieval device; 
         FIG.  54    shows a frame cut from a hypotube for use as the frame of a clot retrieval device; 
         FIG.  55   a    shows another clot retrieval device delivered through a microcatheter; 
         FIG.  55   b    shows another clot retrieval device delivered through a microcatheter; 
         FIG.  56    shows a detailed view of the distal end of a clot retrieval device and a microcatheter delivery system; 
         FIG.  57    shows a detailed view of the distal end of another clot retrieval device and a microcatheter delivery and retrieval system; 
         FIG.  58   a    shows a detailed view of the distal end of another clot retrieval device and a microcatheter delivery and retrieval system; 
         FIG.  58   b    shows a detailed view of the clot retrieval device of  FIG.  58   a    in another configuration; 
         FIG.  59   a    shows a guidewire with a step at the distal, the tip of the guidewire is placed in a vessel (not shown); 
         FIG.  59   b    shows a microcatheter being advanced over the guidewire; 
         FIG.  59   c    shows the clot retrieval device being delivered through the microcatheter and over the wire, a clot debonding device is also being advanced through the microcatheter; 
         FIG.  59   d    shows the clot retrieval device deployed from the distal end of the microcatheter and expanded in the vessel (not shown); 
         FIG.  59   e    shows the clot retrieval device deployed from the distal end of the microcatheter and the microcatheter advanced proximally; 
         FIG.  59   f    shows the clot debonding element deployed from the microcatheter; 
         FIG.  59   g    shows the clot debonding element retrieved back into the distal end of the microcatheter; 
         FIG.  59   h    shows the clot retrieval device collapsed back into the pod of the microcatheter; 
         FIG.  60   a    shows an end view of a clot debonding element; 
         FIG.  60   b    shows an end view of another clot debonding element; 
         FIG.  61   a    shows a side view of an unexpanded clot debonding element; 
         FIG.  61   b    shows a side view of the expanded clot debonding element from  FIG.  61     a;    
         FIG.  61   c    shows an end view of the expanded clot debonding element from  FIG.  61     a;    
         FIG.  62   a    shows an end view of another clot debonding element; 
         FIG.  62   b    shows a side view of a clot debonding device; 
         FIG.  62   c    shows a side view of another clot debonding device; 
         FIG.  62   d    shows a side view of yet another clot debonding device; 
         FIG.  62   e    shows a side view of an alternative clot debonding device; 
         FIG.  63   a    shows a side view of the end of an unexpanded clot debonding catheter; 
         FIG.  63   b    shows a side view of the end of an expanded clot debonding catheter from  FIG.  63     a;    
         FIG.  64   a    shows a side view of the end of an unexpanded clot debonding catheter; 
         FIG.  64   b    shows a side view of the end of an expanded clot debonding catheter from  FIG.  64     a;    
         FIG.  65   a    shows a side view of the end of an unexpanded clot debonding catheter; 
         FIG.  65   b    shows a side view of the end of an expanded clot debonding catheter from  FIG.  65     a;    
         FIG.  66   a    shows a side view of the end of an unexpanded clot debonding catheter; 
         FIG.  66   b    shows a side view of the end of a partially expanded clot debonding catheter from  FIG.  66     a;    
         FIG.  66   c    shows an end view of the expanded clot debonding catheter from  FIG.  66     a;    
         FIG.  67   a    shows a side view of the end of an unexpanded clot debonding catheter; 
         FIG.  67   b    shows an end view of the expanded clot debonding catheter from  FIG.  67     a;    
         FIG.  68   a    shows a side view of the end of an unexpanded clot debonding catheter; 
         FIG.  68   b    shows a side view of the end of a partially expanded clot debonding catheter from  FIG.  68     a;    
         FIG.  68   c    shows an end view of the expanded clot debonding catheter from  FIG.  68     a;    
         FIG.  69   a    shows the clot debonding catheter from  FIG.  68   a    mounted over a microcatheter prior to deployment proximal to a clot and clot retrieval device; 
         FIG.  69   b    shows the clot debonding catheter from  FIG.  69   a    post deployment; 
         FIG.  70    shows a clot retrieval device in the deployed configuration distal of an occlusive clot; 
         FIG.  71    shows a collector device being used with a clot retrieval device; 
         FIG.  72    shows a collector device with deployed elements being used to advance clot into a clot retrieval device; 
         FIG.  73    shows the collector device in an advanced position with most of the clot inside the clot retrieval device; 
         FIG.  74    shows an alternative clot advancement device; 
         FIG.  75    shows a clot advancement device with two coil elements; 
         FIG.  76   a    shows a side view of another clot advancement device; 
         FIG.  76   b    shows an end view of the clot advancement device of  FIG.  76     a;    
         FIG.  77    shows another clot retrieval device with an integral clot debonding element; 
         FIG.  78   a    shows an artery or vein with an occlusive clot acutely lodged in the vessel, the occlusive clot reduces or prevents distal blood flow; 
         FIG.  78   b    shows the occlusive clot of  FIG.  78   a    with platelets being activated at the site of occlusion; 
         FIG.  78   c    shows bonds formed between the occlusive clot and the vessel wall; 
         FIG.  79   a    shows a vein or artery with an occlusive clot lodged therein; 
         FIG.  79   b    shows an occlusive clot with the tip of a guidewire advanced across the occlusive clot; 
         FIG.  79   c    shows a microcatheter advanced over the guidewire such that its tip is distal of the occlusive clot; 
         FIG.  79   d    shows the microcatheter tip distal of the occlusive clot with the guidewire removed; 
         FIG.  79   e    shows a clot retrieval device being advanced through the lumen of the microcatheter; 
         FIG.  79   f    shows the clot retrieval device expanded with the microcatheter partially withdrawn; 
         FIG.  79   g    shows a clot debonding element advanced through the microcatheter and in the deployed state; 
         FIG.  79   h    shows the clot being engaged by both the clot retrieval device and the clot debonding element; 
         FIG.  79   i    shows the clot captured in the net of the clot retrieval device with the clot debonding element removed through the lumen of the microcatheter; 
         FIG.  79   j    shows the clot retrieval device with the frame partially collapsed and the clot captured in the net; 
         FIG.  79   k    shows the clot retrieval device, the microcatheter and the captured clot being removed from the vessel; 
         FIG.  79   l    shows the vessel recanalized; 
         FIG.  80   a    shows a vein or artery with an occlusive clot lodged therein; 
         FIG.  80   b    shows an occlusive clot with the tip of a guidewire advanced across the occlusive clot; 
         FIG.  80   c    shows a microcatheter advanced over the guidewire such that its tip is distal of the occlusive clot; 
         FIG.  80   d    shows the microcatheter tip distal of the occlusive clot with the guidewire removed; 
         FIG.  80   e    shows a stepped guidewire advanced through the lumen of the microcatheter; 
         FIG.  80   f    shows a clot retrieval device being advanced through the lumen of the microcatheter and over the guidewire; 
         FIG.  80   g    shows the clot retrieval device expanded with the microcatheter partially withdrawn; 
         FIG.  80   h    shows a clot debonding element advanced through the microcatheter and in the deployed state; 
         FIG.  80   i    shows the clot being engaged by both the clot retrieval device and the clot debonding element; 
         FIG.  80   j    shows the clot captured in the net of the clot retrieval device with the clot debonding element removed through the lumen of the microcatheter; 
         FIG.  80   k    shows the clot retrieval device with the frame partially collapsed and the clot captured in the net; 
         FIG.  80   l    shows the clot retrieval device, the microcatheter and the captured clot being removed from the vessel; 
         FIG.  80   m    shows the vessel recanalized; 
         FIGS.  81   a  and  81   b    are isometric views of a device for removing an obstruction to a vessel, 
         FIG.  81   a    is the device in an expanded configuration and  FIG.  81   b    is the device in a collapsed configuration; 
         FIG.  82   a    is an isometric view of another device of the invention; 
         FIGS.  82   b  to  82   e    are side views of the distal end of the device of  FIG.  82     a;    
         FIG.  82   f    is an isometric view of the proximal end of a device of the invention; 
         FIG.  82   g    shows a portion of a frame support tube; 
         FIG.  82   h    is a cross section of a frame support tube; 
         FIG.  83   a    is an isometric view of another device of the invention; 
         FIGS.  83   b  to  83   f    are close up views of the basket frame of  FIG.  83     a;    
         FIGS.  83   g  to  83   h    are isometric views of basket constructions; 
         FIG.  84   a    is an isometric view of a basket frame; 
         FIG.  84   b    is a partial cross section of a basket in a microcatheter; 
         FIG.  84   c    is an isometric view of a debonder; 
         FIG.  84   d    is an isometric view of the device; 
         FIG.  84   e    is a partial cross section view of the device inside a vessel; 
         FIG.  85   a    is an isometric view of a basket frame; 
         FIG.  85   b    is an end view of the basket frame of  FIG.  85     a;    
         FIG.  86   a    is an isometric view of a basket frame; 
         FIG.  86   b    is an end view of the basket frame of  FIG.  86     a;    
         FIG.  87   a    is an isometric view of a basket frame; 
         FIG.  87   b    is an end view of the basket frame of  FIG.  87     a;    
         FIG.  88   a    is an isometric view of a basket frame; 
         FIG.  88   b    is an end view of the basket frame of  FIG.  88     a;    
         FIG.  88   c    is an illustration of a basket frame in a collapsed configuration; 
         FIG.  89   a    is an isometric view of a basket frame; 
         FIG.  89   b    is an end view of the basket frame of  FIG.  89     a;    
         FIG.  90   a    is an isometric view of a basket frame 
         FIG.  90   b    is an end view of the basket frame of  FIG.  90     a;    
         FIG.  91   a    is an isometric view of a basket frame; 
         FIG.  91   b    is an end view of the basket frame of  FIG.  91     a;    
         FIG.  92    and  FIG.  93    illustrate two basket frames of this invention; 
         FIGS.  94   a  to  94   g    are isometric views of another device of this invention; 
         FIGS.  95  to  97    are isometric views of other devices of this invention; 
         FIG.  98   a    is an isometric view of another device of the invention in an expanded configuration; 
         FIG.  98   b    is an isometric view of the device of  FIG.  98   a    in a collapsed configuration; 
         FIGS.  99   a  to  99   i    illustrate a method of use for the devices described in  FIGS.  95 - 98   ; 
         FIGS.  100   a  to  100   d    are isometric views of a basket assembly; 
         FIGS.  100   e  and  100   f    are close up views of  FIG.  100     d;    
         FIG.  101   a    is an isometric view of another device of the invention in a collapsed configuration; 
         FIG.  101   b    is an isometric view of the device of  FIG.  101   a    in an expanded configuration; 
         FIG.  101   c    is a top-view of an activation mechanism of the device of  FIG.  101     a;    
         FIGS.  102  to  105    are partial cut away views of a debonding assembly; 
         FIG.  106   a    to  FIG.  106   c    are views of another the device of the invention; 
         FIGS.  107 ,  108 ,  109     a ,  109   b , and  110  are isometric views of a device of the invention in various configurations; 
         FIG.  111   a    is an isometric view of a device of the invention; 
         FIG.  111   b    is an elevation view of the device of  FIG.  111   a    in a collapsed configuration; 
         FIG.  111   c    is an elevation view of the device of  FIG.  111   a    in an expanded configuration; 
         FIG.  111   d    to  FIG.  111   f    illustrate the device of  FIG.  111   a    in use; 
         FIG.  112   a    is an isometric view of another device of the invention; 
         FIG.  112   b    and  FIG.  112   c    illustrate the device of  FIG.  112   a    in use; 
         FIG.  113   a    is an isometric view of another device of the invention with a debonder in a delivery configuration; 
         FIG.  113   b    is the device of  FIG.  113   a    with the debonder assembly in an expanded configuration; 
         FIGS.  114  and  115    are close up views of two debonders; 
         FIGS.  116   a  to  116   i    show a device of the invention in use; 
         FIG.  117   a    is an isometric view of another device of the invention; 
         FIG.  117   b    is a plan view of the untensioned basket frame of  FIG.  117     a;    
         FIG.  117   c    is a side view of the untensioned basket frame of  FIG.  117     a;    
         FIG.  117   d    shows the basket of  FIG.  117   a    in a collapsed configuration; 
         FIG.  117   e    shows the debonder of  FIG.  117   a    in a collapsed configuration; 
         FIG.  118   a    is an isometric view of a debonder assembly; 
         FIG.  118   b    is and end view of the debonder of  FIG.  118     a;    
         FIG.  119   a    is a close up view a basket frame; 
         FIG.  119   b    is an isometric view of a basket frame; 
         FIG.  120   a    is an isometric view of a basket frame; 
         FIGS.  120   b  to  120   d    are close up views of a basket frame of  FIG.  120   a   ; and 
         FIGS.  121   a ,  121   b ,  122   a ,  122   b ,  123   a , and  123   b    are isometric views of basket frames according to the invention. 
     
    
    
     Sheet  92  of drawings: Eccentric Basket &amp; Debonder. Hoop type debonder (self expanding). Basket frame with tether guides. Net connection eyelets. Hoop debonder. Slotted tube type debonder. 
     Sheet  93  of drawings: Eccentric Basket &amp; Debonder. Hoop type debonder with strings. Swivel hoop basket with net and activation tethers. Control handle to tension tethers 
     Sheet  95  of drawings: Eccentric Basket and Debonder. Hoop type debonder (self expanding). Double hoop basket with tether activation 
     Sheet  97  of drawings: Double Hoop Eccentric Basket with radially projecting strut type debonder. Method of use. 
     Sheet  99  of drawings: Basket Frames. Tether activated. Eccentric with support strut. 
     Sheet  102  of drawings: Tether Activated Baskets. Collapsed and expanded. Structural elements. Self expanding/hinged. 
     Sheet  104  of drawings: Tether Activated Baskets. Tether connected centrally to frame. Tether guided along frame and connected to distal end of hoop. 
     Sheet  105  of drawings: Tether Activated Baskets. With hoop type debonder. 
     Sheet  106  of drawings: Tether Activated Baskets. With hoop type debonder. Method of use. 
     Sheet  107  of drawings: Tether Activated Baskets. With hoop type debonder. Method of use. 
     Sheet  108  of drawings: Tether Activated Baskets. With hoop type debonder. Method of use. 
     Sheet  109  of drawings: Tether Activated Baskets. Flat hoop frame Frame. articulated by tether. Distal end of wire articulated by tether. 
     Sheet  110  of drawings: Tether Activated Baskets. Detailed construction of articulating end of frame wire. 
     Sheet  112  of drawings: Debonder. Hoop style debonder. Tether activated. Constructions. 
     Sheet  113  of drawings: Debonder. Hoop style debonder. Configuration when used with basket. 
     Sheet  114  of drawings: Debonder. Hoop style debonder. Configuration when used with basket. 
     Sheet  115  of drawings: Debonder. Hoop style debonder. Configuration when used with basket 
     Sheet  116  of drawings: Basket and Debonder. Slotted tube debonder. Slotted tube basket frame. 
     Sheet  119  of drawings: Double Hoop Basket. Eccentric basket. Eccentric clot debonder. Delivery and deployment. 
     Sheet  120  of drawings: Double Hoop Basket. Method of use. 
     DETAILED DESCRIPTION 
     The present invention is related to an apparatus and methods for the removal of obstructions in vessels. More particularly the present invention relates to devices and methods for the removal of obstructive clot from cerebral vessels. 
     With reference to  FIG.  1    there is shown a schematic representation of the catheterization of a patient with a clot retrieval device  1  according to the invention. The patient is catheterized via the femoral artery with a catheter  2  in accordance with standard interventional technique. 
       FIG.  2    shows a schematic representation of some of the arteries supplying blood to the brain. The arteries shown are on the anterior circulation. Vessel  400  is the Aorta. Vessel  401  is the brachio-cephalic artery. Vessel  402  is the subclavian artery. Vessel  403  is the common carotid artery. 
     Vessel  404  is the internal carotid artery. Vessel  405  is the external carotid artery. Vessel  406  is the middle cerebral artery. Vessel  407  is the anterio-cerebral artery. A catheter  2  is shown with its distal end in the common carotid artery. In the more detailed drawings of the invention the details of the access site will not be shown but in general access and delivery is in accordance with  FIG.  1    and/or  FIG.  2   . It will be appreciated that the devices and methods disclosed in this invention relate to all of femoral access, radial access, direct stick access, carotid access even where only one variation is shown or described 
     Now with reference to  FIG.  3   a    to  FIG.  3   g    a first method of using the devices of the invention is highlighted.  FIG.  3   a    shows an obstructive clot  3  located on a cerebral vessel  4 . The first step in treating this obstruction is to cross the obstruction  3  with a guidewire  5 . The guidewire  5  is inserted into the arterial system through conventional techniques and is advanced to the obstruction. The tip of the guidewire  5  is advanced across the obstruction  3 ,  FIG.  3   b   . A micro delivery catheter  6  can then be advanced over the guidewire  5  and across the obstructive clot  3 . The clot retrieval device  1  is expanded in the target vessel distal of the clot  4 . The micro delivery catheter is withdrawn until its tip is proximal of the occlusive clot. Alternatively it can be completely removed from the patient. The clot retrieval device is positioned at the distal end of guidewire  5  and is fixed thereto. The obstructive clot  3  is captured in the device by advancing the device proximally ( FIG.  3   e   ). A removal catheter  7  is advanced over the guidewire  5  to assist in the removal of the clot  3 . The removal catheter  7  may be a micro-catheter, a guide catheter, a sheath or a special recovery catheter. Aspiration may be employed through the lumen of the recovery catheter to assist in clot removal.  FIG.  3   g    shows the target vessel recanalized after the removal of the obstructive clot  3 . 
       FIG.  3   a    shows part of the cerebral circulation with an obstructive clot  3  positioned in the Anterior Cerebral Artery  4 , distal of the Middle Cerebral Artery branch. 
       FIG.  3   b    shows a Guidewire  5  being placed across the obstructive clot  3 . 
       FIG.  3   c    shows a micro-catheter  6  with the clot retrieval device  1  of the invention crossing the obstructive clot  3 . 
       FIG.  3   d    shows the micro-catheter removed with the clot retrieval device  1  placed distal of the obstructive clot  3 . 
       FIG.  3   e    shows the clot retrieval device  1  being advanced proximally and capturing the obstructive clot  3  with a removal catheter  7  advanced from the proximal side. 
       FIG.  3   f    shows the clot retrieval device  1 , the captured occlusive clot  3  and the removal catheter  7  being removed from the vessel. 
       FIG.  3   g    shows the target vessel  4  with the obstructive clot and devices completely removed. 
     With reference to  FIG.  4   a    to  FIG.  4   i    another method of employing the clot retrieval devices of this invention is described. With this method an access guidewire  15  is used to cross the obstructive clot  13 . A micro catheter  16  is advanced over the access guidewire  15  and across the clot  13 . The access guidewire  15  is removed from the lumen of the micro-catheter  16 . A clot retrieval device  11  is advanced through the lumen of the micro-catheter  16  in a collapsed state. It will be appreciated that the clot retrieval device was collapsed in order to access the proximal end of the lumen of the micro-catheter  16 . The clot retrieval device  11  expands distal of the tip of the micro-catheter  16  and clot  13 . The micro-catheter  16  is advanced proximally until its tip is proximal of the clot. Alternatively the micro-catheter  16  can be removed from the patient (as shown  FIG.  4   d   ). The clot retrieval device  11  is advanced proximally with the aid of guidewire  18  to capture the obstructive clot  13 . The guidewire  18  of the clot retrieval device  11  extends proximally of the expanded section of the device  11  and allows the physician to control the clot retrieval device  11 . A removal catheter  17  is advanced over the guidewire  18  to assist in the removal of the clot  13 . The removal catheter  17  may be the same micro-catheter that was used to deliver the clot removal device or it may be different size micro-catheter, or a guide catheter, or a sheath or a balloon catheter or a special recovery catheter. The recovery catheter  17  may also be used by the physician to assist with the clot capture by preventing the clot  13  from migrating proximally. Aspiration may be employed through the lumen of the recovery catheter to assist in clot removal.  FIG.  4   i    shows the target vessel recanalized after the removal of the obstructive clot  13 . 
       FIG.  4   a    shows a target vessel  14  with an occlusive clot  13 . 
       FIG.  4   b    shows a guidewire  15  with its distal tip across the obstructive clot  13 . 
       FIG.  4   c    shows a micro-catheter  16  advanced over the access guidewire  15  until its distal end is across the obstructive clot  13 . 
       FIG.  4   c    shows the preplaced micro-catheter  16  with its distal end across occlusive clot  13  and a clot retrieval device  11  being advanced through its inner lumen. 
       FIG.  4   d    shows clot retrieval device  11  deployed distal of occlusive clot  13  with the micro-catheter  16  being withdrawn and access guidewire  15  having been removed from the micro-catheter  16 . Clot retrieval device is connected to guidewire  18  and proximal end of guidewire  18  exits the patient and is controlled by the physician. 
       FIG.  4   e    shows the clot retrieval device  11  deployed distal of occlusive clot  13  with the micro-catheter  16  being removed. 
       FIG.  4   f    shows the clot retrieval device  11  deployed distal of occlusive clot  13 . 
       FIG.  4   g    shows the clot retrieval device  11  being advanced proximally and capturing the obstructive clot  13  with a removal catheter  17  advanced from the proximal side. 
       FIG.  4   h    shows the clot retrieval device  11 , the captured occlusive clot  13  and the removal catheter  17  being removed from the vessel. 
       FIG.  4   i    shows the target vessel  14  with the obstructive clot  13  and devices completely removed. 
     Referring now to  FIG.  5   a    to  FIG.  5   g   , another method of employing the clot retrieval devices of this invention is described. With this method the obstructive clot  23  in target vessel  24  is crossed directly with a clot retrieval micro-delivery catheter  26 . The clot retrieval micro delivery catheter  26  has a reception space at its distal end and the collapsed capture device  21  resides in this reception space during delivery. In one embodiment the distal end of the guidewire  28  of the clot retrieval device  21  extends distally of the micro-delivery catheter  26  and assists the device in crossing the occlusive clot  23 . When the distal end of the micro-delivery catheter is across the clot  23 , the clot retrieval device  21  is deployed and the micro-delivery catheter  26  advanced proximally. 
     The clot retrieval device  21  is advanced proximally with the aid of guidewire  28  to capture the obstructive clot  23 . The guidewire  28  of the clot retrieval device  21  extends proximally of the expanded section of the device  21  and allows the physician to control the clot retrieval device  21 . A removal catheter  27  is advanced over the guidewire  28  to assist in the removal of the clot  23 . The removal removes the clot and capture device as described above. 
       FIG.  5   a    shows a target vessel  24  with an occlusive clot  23 . 
       FIG.  5   b    shows a micro-delivery catheter  26  with a clot retrieval device  21  collapsed within a distal lumen of the micro-delivery catheter. The micro-delivery catheter is advanced across the occlusive thrombus  23 . The clot retrieval device  21  has a guidewire  28  that extends proximally and distally. 
       FIG.  5   c    shows micro-delivery catheter  26  being removed with the clot retrieval device  21  deployed in the target vessel  24  distal of the occlusive clot  23  with guidewire  28  extending across the lesion and proximal to the user. 
       FIG.  5   d    shows the clot retrieval device  21  deployed in the target vessel  24  distal of the occlusive clot  23  with guidewire  28  extending across the lesion and proximal to the user. 
       FIG.  5   e    shows the clot retrieval device  21  being advanced proximally and capturing the obstructive clot  33  with a removal catheter  27  advanced from the proximal side. 
       FIG.  5   f    shows the clot retrieval device  21 , the captured occlusive clot  23  and the removal catheter  27  being removed from the vessel. 
       FIG.  5   g    shows the target vessel  24  with the obstructive clot  23  and devices completely removed. 
     In one embodiment (not shown) the removal catheter comprises a balloon catheter, wherein the guidewire lumen of the balloon catheter is larger than the guidewire diameter. The distal end of the balloon catheter lumen provides a reception space for a portion of the collapsed clot capture device. The balloon may be inflated during the clot capture step to prevent the clot from migrating proximally. 
     With reference to  FIG.  6   , an example of the clot retrieval device of this invention is shown. The device  31  comprises a frame  34 , a proximal collar  33 , a distal collar  36 , capture fibers  35 , and a guidewire  32  with tip  37 . Frame  34  comprises a metallic elliptical hoop. The hoop  34  is subtended at an acute angle relative to the guidewire  32  in the expanded configuration. In the collapsed state the hoop  34  sits substantially parallel to the guidewire  32 . The frame  34  further comprises eyelets  38  that allow for a low profile interconnection between the capture fibers  35  and the frame  34 . The eyelets  38  are shown as circular eyelets positioned substantially in the center of the struts. Multiple eyelets are located around the frame. Corresponding eyelets  38  are located on distal collar  36 . The capture fibers are looped through the eyelets either in a simple single loop or using multiple loops. Where two or more loops are employed, the loops act like a knot and prevent fiber slippage. In the embodiment shown the capture fibers  35  are not interconnected with each other but form straight line connections between the frame and the distal collar. This configuration means that there are no knots or fiber overlaps in the entire capture net which improves the wrapping profile of the device. In one embodiment the fibers are looped through the eyelets of the collar and the eyelets of the frame and this avoids the need for knots thus reducing the profile. The eyelets  38  of the distal collar  36  are arranged around the circumference of the distal collar  36 . In one embodiment the distal collar is fixed to the guidewire  32 . In another embodiment the distal collar  36  is slidable relative to the guidewire  32 . In another embodiment the distal collar is rotatable relative to the guidewire. The proximal collar and the frame are preferably connected. In one embodiment the proximal collar and the frame are integral. In another embodiment both the frame and collar are machined from a hypotube. In this embodiment the hypotube diameter corresponds to that of the collar and the frame is laser cut in a configuration that corresponds closely to the shape of the frame when it is collapsed for delivery. The proximal hypotube is mechanically connected to the wire. This mechanical connection allows the memory in the metal to act to generate an angle between the frame and the guidewire in its expanded state. In one embodiment the mechanical connection comprises a closely tolerance fit between the collar inner diameter and the wire. In another embodiment the collar is fixed to the wire. It may be fixed by gluing, welding, or other well known means. The tip  37  of guidewire  32  is soft and flexible to allow the delivery system (not shown) to steer through the anatomy. 
     With reference to  FIG.  7   a   , another clot capture device  41  of the invention is shown. This device employs a similar arrangement to the device of  FIG.  6   , however in this instance the capture fibers  45  are interconnected. It will be noted that the fibers  45  are connected in a series of interconnecting loops  49 . These loops  49  can be crafted by hand and have the advantage of avoiding the need for knots, bonds or other features that will significantly impact the profile of the device in the delivery configuration. The loops mean that the interconnected fibers can slide relative to one another and this allows the net to change its shape in response to an irregularly shaped clot. Alternatively the net may be knitted or braided so as to create a regular net structure. With both knitting and braiding it is also possible to create fiber interconnections without rigidly fixing the fibers at the cross over points. Attachment fibers are used to connect the net to the frame. In one case the proximal collar  43 , distal collar  46 , guidewire  42 , and tip  47  have similar features to those of  FIG.  6   . 
     The clot capture device of  FIG.  7   a    is shown in the delivery configuration in  FIG.  7   b   . The frame  44  lies substantially parallel to the guidewire  42  inside the lumen of delivery catheter  50 . The delivery catheter  50  comprises a proximal shaft  51 , a distal shaft  52  and a distal tip  53 . The clot retrieval device sits inside a reception space at the distal end of the delivery catheter  50 . The distal tip  53  of the delivery catheter is preferably a soft tip material. The proximal shaft  51  of the delivery catheter  50  extends back to the user. In one embodiment the delivery catheter is a rapid exchange catheter. 
     In another embodiment the shaft  50  comprises a loading system. The distal tip  53  of the shaft  50  is engaged with the proximal end of a micro-catheter. The micro-catheter has had its distal end preplaced at a target treatment site. With the distal tip  53  engaged with the proximal end of the micro-catheter, the clot retrieval element  41  is advanced into the lumen of the micro-catheter. When the proximal collar  43  has entered the micro-catheter, the shaft  50  can be removed and the clot retrieval device  41  advanced through the micro-catheter to the target location. It will be appreciated that the features of the loading system described with respect to the clot retrieval device  41  could be applied to other clot retrieval devices of the invention. It will also be appreciated that the method steps described can be applied with the methods described in  FIGS.  3  to  5   . 
       FIGS.  8   a - f    show a variety of frame mounting constructions that could be employed in the creation of a device similar to that described in  FIG.  6   .  FIG.  8   a    shows a frame  501  constructed from a guidewire  502 .  FIG.  8   b    shows a frame  503  fixedly attached to guidewire  504  at proximal collar  505 .  FIG.  8   c    shows a frame  506  connected to a guidewire  507  in such a way that the collar  508  of the frame can translate and rotate along and around the guidewire between the two stops  509 , which are fixedly attached to the guidewire, or an integral part of the guidewire.  FIG.  8   d    shows a frame  510  whose proximal end is attached to tube  511 , which is slideably mounted on guidewire  513  proximal to stop  512 .  FIG.  8   e    shows a frame  514  which is attached to tube  516 , which is slideably mounted on guidewire  515  such that the tube and frame can be advanced or retracted over the guidewire and the guidewire can be moved or exchanged through the tube.  FIG.  8   f    shows a variant of the design shown in  FIG.  8   e   , in which frame  517  is attached to tube  518  and tube  518  is connected to a proximal shaft  519  at the guidewire exit port  520 . Such a design would facilitate the deployment of the device over a shorter “rapid exchange” guidewire 
     In other embodiments alternative stop configurations to those shown in  FIG.  8   c    may be employed, in order to facilitate and control movement of the clot retrieval device relative to the guidewire, and/or in order to control the manner in which force may be transmitted to the device during delivery, retrieval and general use. Some of these alternative configurations are shown in various figures throughout this document. It will also be understood that the many other frame designs disclosed in previous and subsequent figures, although illustrated in a certain configuration, may be configured in any of the other configurations depicted in  FIGS.  8   a   - f.    
       FIGS.  9   a - i    show a variety of frame designs that could be employed in the creation of a clot capture device. Frame  550  in  FIG.  9   a    has a generally circular perimeter with which to appose the vessel wall, and two proximal arms which taper outward distally from a proximal terminus. Such a design could be constructed from wire or from a cut tube or by other means, and could be made from any of the materials described later as suitable for the manufacture of frame  64  in  FIG.  10   a   . Frame  551  in  FIG.  9   b    is similar to frame  550  except that the inner terminus of the proximal arms is positioned distal to the outer circumferential portion of the frame. Frame  552  in  FIG.  9   c    is similar to frame  550  except that the frame arms are of unequal lengths and/or angles, such that an offset is created between the centerline of the vessel and the proximal neck of the frame. Frame  553  in  FIG.  9   d    is similar to frame  550  except that the frame arms are of unequal lengths and/or angles, such that the circumferential portion of the frame is inclined at an angle relative to the centerline of the vessel. Frame  554  in  FIG.  9   e    is similar to frame  553  except that the frame has only one proximal arm. Frame  555  in  FIG.  9   f    is similar to frame  550  except that the frame has three proximal arms. Frame  556  in  FIG.  9   g    is similar to frame  550  except that the frame has four proximal arms. Frame  557  in  FIG.  9   h    is similar to frame  554  except that the frame has an additional arm that tapers distally inwards from the outer circumferential portion. Frame  558  in  FIG.  9   i    is similar to frame  501  of  FIG.  8   a    except that the frame is not constructed directly from the guidewire itself, but from a separate material. 
     Another clot retrieval device  61  is shown in  FIG.  10   a - e   . The clot retrieval device  61  shown in  FIG.  10   a    comprises a frame  64 , a guidewire  62 , proximal collar  63 , distal collar  66 , support struts  60  and capture fibers  65 . With this embodiment the frame  64  forms a three dimensional shape in its expanded configuration. The three dimensional shape is such that the outer surface of the frame in its expanded configuration can oppose the wall of a generally cylindrical vessel. The frame is preferably cut from a hypotube and is preferably metallic. Preferably the frame is nitinol, stainless steel, tantalum, MP35N, L604, a memory material, spring steel, or another high strength alloy. The frame comprises a number of segments  67 . In a preferred embodiment the frame comprises pairs of segments. Each pair of segments are arranged at an angle and the angle of arrangement gets smaller as the frame is collapsed and increases as the frame is expanded. The pairs of segments are interconnected to from a 3D structure. In the embodiment two pairs of segments are shown. Three pairs of segments or more is also possible. The frame  64  is connected to the guidewire with support struts  60 . In the embodiment shown the support struts  60  are attached to the frame  64  at its proximal end. The support struts  60  however are positioned underneath the frame  64  in the expanded configuration. This ensures that the frame  64  has maximum support when the guidewire  62  is being advanced proximally as the support struts  60  act generally to expand the frame. With this embodiment the frame is advanced proximally with a push force transmitted from the distal side. The force is transmitted along support struts  60  and has two components. One component acts to push the frame in the proximal direction while the other force acts to push the frame against the wall of the vessel. This makes it difficult for a clot to escape around the outside of the frame  64 . The support struts  60  are connected to the guidewire  62  through proximal collar  63 . The support struts  60  may be connected to the frame in a number of ways. The support struts  60  may be laser cut from the same tube as the frame  67  and as such would be integral with the frame  67 . 
       FIG.  10   b - e    show a clot retrieval device  61  where the proximal collar  63 , the support struts  60 , and the frame are cut from a single piece of tubing which may be a hypotube.  FIG.  10   b    is similar to  FIG.  10   a    except that the proximal collar, the support struts, and the frame are a single component. In order to manufacture such a complex component, the metal used may be elastic. In one embodiment spring steel or a nitinol alloy is used. Preferably nitinol is used to make the frame. 
       FIG.  10   c    shows an elevation of the one piece frame component  64  in the collapsed (as cut) configuration. The proximal collar  63  is simply a segment of the original hypotube and should be kept as short as possible. A pair of support struts  60  extends from proximal collar  63  and connects the proximal collar  63  with the struts  67  of the frame  64 . The support struts  60  are positioned diametrically opposite (thus only one is visible in the elevation view). The interface  87  between the support struts  60  and the collar  63  is an area of high strain when the device is expanded. The wall thickness of the support struts  60  may be locally thinned to reduce strain in this area. At the distal end each support strut  60  bifurcates to form two struts  67  of frame  64 . The two struts are of the same length and reconnect at their distal end. The bifurcation  85  is also an area of high strain during expansion and the stress is relieved in this area by reducing locally the width of the struts. The junction  86  at the distal end is another area of high stress during expansion and the stress is relieved in this area by locally reducing the width of the strut in the region of the junction  86 .  FIG.  10   d    shows an end-view looking at the collar  63  end.  FIG.  10   e    shows a sectional view at a-a. This sectional view shows the arrangement of the four struts  67 , and the cut gap  88  between the struts. The construction of junction area  86  where neighboring struts  67  are connected is further highlighted. 
     In another embodiment the support struts  60  may be separate components that are joined to the frame  67 . The support struts  60  may be connected to the frame by a hinge. The resistance of the hinge to movement is much less than the resistance of the frame or support struts to bending movements. The hinge may be formed by an interconnection between the support strut  60  and the frame  64 . In another embodiment a suture or fiber(s) is used to create the hinge. With this embodiment the flexibility of the suture/fiber allows the strut to move relative to the frame while their points of connection are relatively constrained. 
     The capture fibers  65  of this embodiment are of similar size to those described earlier. The capture fibers  65  are attached to the frame  64  and the distal collar  66  through eyelets  68 . Preferably the fibers are highly oriented fibers. This high orientation results in fibers that are anisotropic and these fibers are particularly preferred. These fibers are very strong along the axis of the fiber and less strong in other directions. The distal collar  66  contains eyelets  68  through which the capture fibers are threaded. In one embodiment the distal collar  66  is fixed to the guidewire. In another embodiment the distal collar  66  is integral with the guidewire. In yet another embodiment the guidewire is a hypotube and the eyelet holes are made in the guidewire hypotube, thus eliminating the need for a separate distal collar. In yet other embodiments the fibers are attached to a collar or directly to the guidewire or to each other by bonding, welding or other methods. 
     Yet another embodiment of the invention is shown in  FIG.  11   a - 11   c   . The clot retrieval device  71  comprises a frame  74 , a guidewire  72  with tip  77 , proximal collar  73 , intermediate collar  70 , a distal collar  76 , support struts  79  and capture fibers  75 . With this embodiment the frame comprises a hoop subtended at an angle relative to the guidewire  72 . The hoop is held relative to the wire by two support struts  79 , a proximal collar  73 , and an intermediate collar  70 . In one embodiment the proximal collar is fixed and the distal collar slides on the guidewire  72 . In another embodiment the distal collar is fixed and the proximal collar slides on the guidewire  72 . In yet another embodiment both collars are slidable on the guidewire  72  and a stop or stops are used to enable a force to be applied through the guidewire  72  to either collar, such as illustrated in  FIGS.  7 ,  48  and  50   .  FIG.  11   b    shows the clot retrieval device  71  in the collapsed crossing configuration. In this illustration the capture fibers  75  are not shown (for clarity). The support struts  79  are positioned distal and proximal of the frame in the collapsed configuration. The crossing catheter  80  is preferably a micro-catheter. Preferably the crossing catheter  80  is 2.3 French or less in its distal diameter  82 . Preferably the crossing catheter  80  has a distal diameter  82  of 1.9 French or less. More preferably the crossing catheter  80  has a distal diameter  82  of 1.6 French or less. The tip  83  of the crossing catheter is preferably made of a soft material and has a smooth transition.  FIG.  11   c    shows the clot retrieval device  71  and the crossing catheter  80  of  FIG.  11   b   , with the exception that the capture fibers  75  are also shown. The diameter of the capture fibers  75  is so small as they exert only a minor influence on the profile. 
       FIG.  12   a    and  FIG.  12   b    show another embodiment of the invention. This embodiment is similar to that of  FIG.  11   a - 11   c    except that the frame  94  is circular rather than elliptical and the support struts  99  make an angle with the guidewire that is closer to a right angle. In the expanded position the proximal collar  93  and the intermediate collar  90  are adjacent each other. The support struts  99  are connected to the frame in a hinged configuration. This hinged configuration is important as the support strut moves through a large angle during device expansion. In one embodiment the support strut moves through an angle of greater than 60′. Preferably the support strut moves through an angle of at least 80′. More preferably the support strut moves through an angle of at least 90′. This large angle of movement has the effect of reducing the length of the device in the collapsed configuration and this shorter device is more deliverable. 
     For example: For a device with an expanded diameter of 3 mm, changing the strut angle from 45′ to 90′ has the effect of shortening the device by 1.24 mm. In the neurovascular territory where vessel diameters are small and vessel tortuosity is high this is a very significant reduction. In one embodiment the hinge comprises three elements, a strut element  99 , a frame element  94 , and a hinge element  104 . The frame element  94  and the strut element  99  are connected with the hinge element  104 . The hinge element allows the frame element  94  and strut element  99  to change angle relative to each other with little resistance. In one embodiment the hinge element is a pin. In another the hinge element  104  is a fiber, a filament, a multifilament or a suture. In another embodiment the strut element  99  and the frame element  94  are connected and the hinge is integral of the connection. In another embodiment the hinge comprises a weakness in the structure at the area where the strut element  99  and frame element  94  meet. In another embodiment the hinge between the strut element  99  and frame element  94  is adjacent a hinge in the frame. 
     In one embodiment the intermediate collar is fixed to the wire. With this embodiment the intermediate collar  90  provides a movement stop to the proximal collar  93 . This configuration provides a particularly stiff frame construction even for a low profile device. In another embodiment the proximal collar is fixed and the intermediate collar  90  can move axially. In one embodiment the proximal collar  93 , intermediate collar  90  and distal collar  96  are radiopaque. With this embodiment the collars are made from or coated with a material that absorbs X-Rays. Typically this involves using materials that have a high atomic mass. Materials with a concentration of gold, platinum, iridium, tungsten, and tantalum are especially suited. It will be appreciated that a variety of other metals, alloys or compounds could be employed. Such radiopaque features may be used in any of the devices described herein. 
       FIG.  12   b    shows the clot retrieval device  91  in the delivery configuration. A crossing catheter  100  is used to constrain the device  91  in the collapsed state during delivery and crossing of the obstruction. The catheter has a proximal end  101  and a distal end  102 . The guidewire extends proximally through a lumen of the crossing catheter  100  and exits at either the proximal end of the crossing catheter  100  or through an exit port in the wall of the crossing catheter  100 . The capture fibers are arranged as previously described although they are not shown in  FIG.  12   a    or  12   b.    
       FIG.  13   a    shows the clot retrieval device of  FIG.  12    except that the capture fibers  95  are shown.  FIG.  13    also shows the collar arrangement whereby the intermediate collar  90  is fixed relative to guidewire  92  and the proximal collar  93  is slidable relative to guidewire  92 . In another embodiment the proximal collar  93  and intermediate collar  90  are rotatable relative to guidewire  92 .  FIG.  13   b    to  FIG.  13   e    show views of the proximal collar, intermediate collar and support struts of  FIG.  12    and  FIG.  13   . The collar  105  could be either a proximal collar or an intermediate collar. In the embodiments shown the strut  106  and collar  105  are integral. In one embodiment they are formed from a single piece of hypotube. Preferably the tube is nitinol and the shape of the strut  106  is set by heat treatment.  FIG.  13   b    and  FIG.  13   d    show an arrangement where the strut is in the delivery configuration. This is also the pre-heat treatment configuration. The lumen  108  is sized to fit over the guidewire of the earlier embodiments.  FIG.  13   d    and  FIG.  13   e    show the collar  105  and strut  106  in the expanded configuration. The hole  107  allows for the creation of a hinge feature with the frame of earlier embodiments. 
     Some examples of intermediate or distal collars  131  associated with the clot retrieval devices of the invention are shown in  FIG.  14    to  FIG.  17   .  FIG.  14   ,  FIG.  16    and  FIG.  17    shows collar  131  with lumen  109  mounted on guidewire  112 . The collar comprises eyelets  130  for attachment of capture fibers  115 . In  FIG.  14    the capture fibers form a knitted structure and are connected to the collar in a series of loops through the eyelets  130 . In  FIG.  16    the capture fibers  115  are arranged in a weaved configuration and are attached to the eyelets through a series of loops. The capture fiber may be looped between one eyelet  130  and a neighboring eyelet or it may be looped through the eyelet and the body of the collar  131 . 
       FIG.  18    and  FIG.  19    show the clot retrieval device  91  of  FIG.  12    and  FIG.  13    in use. The device  91  is shown deployed distal of obstructive clot  103 . The device is advanced proximally in order to capture the clot as shown in  FIG.  19   . 
     Now with reference to  FIG.  20    through to  FIG.  23    there is shown another clot retrieval device of the invention. This device is constructed from a series of sub-elements that work together through a series of hinge elements. For the purpose of describing the hinge features of this invention, hinges will be classified in terms of the number of axis of freedom available to the hinge. One axis of freedom shall mean that the hinge movement is limited to a single plane of movement. An example of a hinge with one axis of freedom is the human knee joint. Two axis of freedom shall mean that the hinge movement is limited to a two planes of movement and the two planes are normal to each other (X,Y). An example of a hinge with two axis of freedom is the human hip joint. 
     With reference to  FIG.  20   a - h    there is shown a number of sub-elements to the frames of the clot retrieval devices of the invention.  FIG.  20   a    and  FIG.  20   b    show a strut element  150  with curved ends  152  and a hinge hole  151  located concentric with curved ends. Curved ends  152  may be curved in one axis or two axes depending on whether the hinge has one axis of freedom or two axis of freedom.  FIG.  20   c    shows the strut  150  in a curved configuration.  FIG.  20   d    shows a schematic of the construction of a hinge between two struts  150 . The end curves  152  of two struts are brought into contact and a hinge element  153  secures the strut ends  152  relative to each other. Since both ends are curved in two planes this configuration creates a hinge with two axis of freedom. In one embodiment the hinge element  153  is a ring element. In another embodiment the hinge element  153  is a fiber, monofilament, multifilament, a wire or a suture.  FIG.  20   d    also shows eyelets  154  on the strut for attachment of capture fibers. 
       FIG.  20   e    shows another hinge configuration of the clot retrieval devices of the invention whereby two struts or a strut and a support member are joined in a hinged configuration. The strut  150  has two curved ends  152  and each curved end  152  has two hinge holes  151 . Each hinge hole is fastened to its neighboring hinge hole to create a hinge that has one axis of freedom. A frame  164  for a clot retrieval device is shown in  FIG.  20   f    and  FIG.  20   g   . The frame comprises four struts  150  configured in a circular arrangement. Each strut comprises curved ends  152  and hinge holes  151  adjacent said curved ends  152 . The frame  164  is supported by support members. In one embodiment proximal support members  157  and distal support members  156  are employed. Proximal support members  157  are connected to the guidewire proximally. Distal support members  156  are connected to the guidewire distally. In one embodiment the proximal support member  157  and/or the distal support member  156  is connected to the guidewire  172  via a collar  155 . In one embodiment the support member  156 / 157  is integral with the collar  155 . In another embodiment the support member  156 / 157  is connected to the collar with a hinge arrangement. Preferably the hinge arrangement comprises a hinge with one axis of freedom. In one embodiment the support member  156 / 157  and the collar are integral and the hinge is made by thinning out the wall of the support member in the plane of bending adjacent the collar. Thinning the wall reduces plastic strain in the wall during hinging and allows large angles of movement. In one embodiment the support member  156 / 157  contacts the frame on its inner surface. In another embodiment the support member  157  contacts the frame intermediate the inner and outer surfaces. 
       FIG.  20   h    shows the arrangement of a frame support  165 . The frame support comprises a collar  155  and support members  157 . The collar comprises an inner lumen  166  and an outer surface. The support members  157  comprise a curved end  158  and a hinge hole  151 . 
       FIG.  20   h    and  FIG.  20   i    show how the hinges  167 / 168  allow the support frame to collapse. It will be noted that pairs of hinges facilitate most efficient collapse of the frame of the clot retrieval device. In the delivery configuration the curve of the struts  150  is straightened. This is illustrated in  FIG.  20   j - k    where all of the hinges  168 / 167  are in the collapsed state and the struts  150  are straightened and lie substantially parallel to the axis of the guidewire  172 . 
       FIG.  21   a - c    shows the frame elements of  FIG.  20   a - k    assembled and mounted on a guidewire.  FIG.  21   a    shows the frame  164  of  FIG.  20   j    integrated with proximal and distal frame supports  165  of  FIG.  20   h   .  FIG.  21   b    shows the frame  164  of  FIG.  20   j    integrated with proximal and distal frame supports  165  of  FIG.  20   h    and all of this mounted on guidewire  172  with tip  170 .  FIG.  21   c    shows the clot retrieval device  175  assembled and in the collapsed configuration with capture fibers  171  included. 
     The hinges  167 / 168  associated with the body of frame  164  provide no bias for the frame. The hinges  167 / 168  thus provide no significant resistance to either expansion or collapse. The frame can thus be expanded from a collapsed state in one of the following ways. 
     In one embodiment the frame  164  is expanded and collapsed by movement of the more proximally located collar  155   a  relative to the more distal collar  155   b . In one embodiment either the more proximally located collar  155   a  or the more distally located collar  155   b  is fixed to the guidewire  172 . If the more distally located collar  155   b  is fixed longitudinally, then, advancing the more proximally located collar  155   a  distally expands the frame  164 . In one embodiment movement of the collar  155   a  is achieved using a bumper catheter  173  as shown in  FIG.  21   c   . The bumper catheter  173  has an outside diameter, a lumen, and a distal face. The bumper catheter  173  is advanced over the guidewire  172  until its distal face is adjacent the proximal end of collar  155   a . The bumper catheter is further advanced and engages with the collar  155   a  and causes collar  155   a  to advance distally. As collar  155   a  advances distally, the frame  164  expands. With the frame  164  in the expanded state, and the bumper catheter  173  held in position, the clot retrieval device  175  and bumper catheter  173  are advanced proximally to capture the clot. When the clot is captured, the bumper catheter  173  is disengaged from the collar  155   a . The clot retrieval device  175  is retrieved. This may be achieved using a retrieval catheter, a micro-catheter, a sheath or guide catheter or the lumen of another catheter. Alternatively the clot retrieval device  175  can be withdrawn proximally into the procedural catheter. 
     In another embodiment the bumper catheter is connected to the collar  155   a . In this way, advancing the bumper catheter distally causes the frame  164  of the clot retrieval device  175  to expand, while advancing the bumper catheter proximally causes the frame  164  to collapse. In another embodiment the bumper catheter  173  is detachably coupled to the clot retrieval device  175  through collar  155   a.    
     In another embodiment the support members  157 / 156  of frame support  165  are biased to the expanded state. For delivery the frame  164  is stored inside the pod of a delivery catheter. Upon deployment distal and proximal frame supports  165  acts on hinge points  167 / 168  and cause these hinge points  167 / 168  to move radially outward. As these hinge points  167 / 168  move outward, the frame  164  of the clot retrieval device expands. On full expansion, the frame  164  assumes a 3 dimensional ring-like configuration. With this embodiment, when the clot retrieval device  175  is deployed and the frame  164  is expanded, the clot is captured by proximally advancing the clot retrieval device  175 . After the clot is captured, the clot retrieval device  175  is retrieved using a retrieval catheter, a micro-catheter, a sheath or guide catheter, or the lumen of another catheter. Alternatively the clot retrieval device  175  can be withdrawn proximally into the procedural catheter. 
     A capture fiber collar  169  is located distal of the collars  155   a / 155   b  and this collar  169  provides an anchor site for the capture fibers distally. The capture fiber collar  169  may be fixed on the wire  172  or may be slidable and/or rotatable on the wire  172 . In a preferred embodiment the capture fiber collar  169  has a limited range of movement. The movement may be limited proximally by abutment with the collar  155   b  of the frame support  165 , or it may be limited by a stop (not shown) on the guidewire  172 . The movement of the capture fiber collar  169  may be limited distally by the capture fibers or by a stop on the guidewire  172 . In yet another embodiment the distal tip  170  of the guidewire  172  ends proximal of collar  169 , and collar  169  is therefore not engaged with the guidewire  172 , but still acts as a distal terminus for the capture fibers. 
       FIG.  22    shows the frame  164  of the invention when viewed from the proximal end in its expanded configuration. The struts  150 , the support members  157 / 156  and the collars  155   a / 155   b / 169  are preferably manufactured from a metal. Preferably the material is nitinol, stainless steel, MP35N, L604, Tantalum, a mixture of the above or another alloy with similar mechanical attributes. The optimum choice of materials is dependent on the design and operating mechanism of the frame. In the case of a self expanding frame as illustrated in  FIGS.  10   a - d   , it will be advantageous to select a material which can recover from the high strains that may be induced in collapsing the frame for delivery through a small diameter catheter. Such strains will be design dependent, but selection of a superelastic material such as nitinol, which can recover from strains as high as 8%, will enable more compact geometries for areas  85  and  86  to be adopted. In the case of a frame that is expanded by an external force as described in relation to  FIG.  21   c   , greater flexibility in material choice is made possible. In the case of hinged designs, as for example is shown in  FIG.  22   , still greater material choice is afforded, as significant strains are not induced in the hinged areas. 
     A frame  164  of a clot retrieval device of the invention is shown in  FIG.  23   a - 23   c    at various levels of expansion. In  FIG.  23   a    the frame  164  is shown in the fully expanded configuration. Struts  150  form a circular ring and these are supported by support members  157 / 156 . The proximal collar  155   a  and support member  157  support the frame  164  at two opposing hinge points  168 . The more distally located collar  155   b  and support members  156  support the frame at the two remaining opposing hinge points  167 . The frame  164  is shown in the partially collapsed state in  FIG.  28   b   . The proximal collar  155   a  has moved proximally relative to the more distally located collar  155   b . In the partially collapsed (or expanded) configuration, the struts form a zigzag pattern in three dimensions. The zigzag pattern is defined on a cylindrical surface in 3D space. 
     The frame  164  is shown in the fully collapsed state in  FIG.  23   c   . The collar  155   a  has moved even more proximally and the strut  150  is substantially parallel to the axis of the guidewire  172  with tip  170 . 
       FIG.  24   a - 24   c    shows the device of  FIG.  23    with the capture fibers  171  in place. It will be appreciated that other capture fiber arrangements described in this invention could be used with the frames  164  and clot retrieval devices of  FIG.  20 - 28   . 
       FIG.  25   a - d    and  FIG.  26   a - f    show more detailed views of aspects of the struts  150  of the frames  164 . In one embodiment the struts are rectangular in cross-section  180 . In another the cross-section  181  of the struts  150  is circular. In another embodiment the strut  150  comprises a number of eyelets  154  and the strut  150  comprises a thickened section  185  adjacent the eyelet  154 . The eyelets  154  and thickened sections  185  are staggered on neighboring struts such that the struts stack more efficiently in the collapsed configuration. In one embodiment the eyelets  154  are circular. In another embodiment the eyelets  154  are centered on the neutral axis  195  of the strut  150 . The neutral axis  195  of the strut  150  is defined as the portion of the strut that undergoes zero strain when the strut is loaded in bending. In another embodiment the eyelets  190  are elliptically shaped and the major axis of the elliptical eyelets  190  is substantially parallel with the neutral axis  195  of the strut  150 . In another embodiment the eyelet  191  is elongated and the axis of elongation is approximately parallel to the neutral axis  195  of the strut  150 . Capture fibers  192  are looped through eyelets  150 . In one embodiment the capture fiber  192  makes a single loop through the eyelets  150 . In another embodiment the capture fiber  193  makes a double loop through the eyelet  190 . In another embodiment multiple capture fibers are looped through eyelets  191  or a single capture fiber  194  is looped multiple times. 
     The eyelets of this invention could be configured in a variety of shapes including elliptical, square, oblong, rectangular, polyhedral, or combinations or variations of the above. The eyelets are typically very small in diameter and are preferably processed by laser machining. The eyelets have a minor axis and a major axis. For the purpose of this invention, the dimension of the minor axis is defined as the largest diameter of cylindrical pin gauge (gage) that will fit into the eyelet without deforming the eyelet. Per this invention it is desired that the eyelet dimension be as small as possible. Preferably the eyelet has a minor axis that is less than 100 micrometers. More preferably the eyelet has a minor axis that is less than 50 micrometers. More preferably the eyelet has a minor axis that is less than 30 micrometers. Most preferably the eyelet has a minor axis that is less than 20 micrometers. When the major axis of the eyelet is positioned on the neutral axis of the strut then it is the size of the minor axis that dictates the loss of mechanical properties of the strut. It is therefore an object of this invention to minimize the loss of mechanical integrity of the struts while allowing high strength fibers to be secured to the frame. In another embodiment the capture fiber has a flattened aspect. The fiber may be elliptical or flattened in cross section or the fiber may be multifilament fiber. 
     The capture fibers used with the clot capture devices of this invention have special properties. In order to deliver the capture device through a micro catheter the capture fibers are exceedingly small. Fibers with a diameter of less than 100 micrometers are desired. More preferably the diameter of the fibers is less than 50 micrometers. Even more preferably the diameter of the fiber is less than 30 micrometers. Most preferably the diameter of the fiber is less than 20 micrometers. 
     The capture fibers  35  of this invention are exceptionally strong in order to achieve the really low delivery profiles of the invention. Suitable fibers include Ultra High molecular weight polyethylene fibers, PET fibers, stainless steel fibers, MP35N fibers, PTFE fibers, Polypropylene fibers, nylon fibers, Kevlar fibers and PEEK fibers. More preferably the fibers are polymeric fibers. More preferably the fibers are Nylon, PET, Kevlar or UHMWPE. Most preferably the fibers are made from ultra high molecular weight polyethylene (UHMWPE) or Kevlar. UHMWPE has a very long molecular chain and can therefore have molecular weights from 3 million to as high as 10 million atomic units, as opposed to approximately 500,000 atomic units for standard HDPE. This gives it excellent abrasion resistance as well as strength, making it an excellent choice for a capture net fiber. An exemplary UHMWPE capture fiber is supplied by DSM Dyneema BV, Urmond, The Netherlands. 
     Tables 1 and 2 below compare the properties of a range of material fibers. The strength of a specific fiber strand is proportional to ultimate tensile strength of its material and to the square of the fiber diameter. Therefore a big reduction in strength is caused by a relatively small reduction in diameter. For example with reference to Table 1, reducing the diameter of a Dyneema UHMWPE fiber from 30 microns to 15 microns results in a four-fold decrease in fiber strength from 1.86N to 0.46N. For this reason while it is desirable for profile reasons to use a low fiber diameter, it is also desirable to use a fiber with a high ultimate tensile strength. The fibers used are sufficiently strong to withstand the loads that will be experienced during device delivery and clot retrieval, and also to facilitate device manufacturability. Inadequate fiber strength in manual, automated or semi-automated assembly processes is likely to result in frequent breakages and low yields. Preferably an individual fiber strength will be greater than 0.25N. More preferably an individual fiber strength will be greater than 0.35N. Most preferably an individual fiber strength will be greater than 0.5N. While PET is generally considered a high strength polymer, particularly when highly oriented, it can be seen from Table 2 that to achieve a 0.5N fiber strength a PET fiber diameter of over 25 microns is required, while the same strength can be achieved with UHMWPE or Kevlar fibers in diameters of less than 20 microns. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Fiber Strengths (in Newtons) for specific fiber diameters 
               
            
           
           
               
               
               
            
               
                   
                 Fiber strength required (N) 
                 UTS 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Fiber material 
                 0.20 
                 0.50 
                 1.00 
                 5.00 
                 10.00 
                 (Mpa) 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 UHMWPE - 
                 0.46 
                 0.82 
                 1.29 
                 1.85 
                 5.14 
                 2620 
               
               
                 Dyneema 
               
               
                 UHMWPE - Celanese 
                 0.23 
                 0.41 
                 0.64 
                 0.92 
                 2.55 
                 1300 
               
               
                 UHMWPE - 
                 0.51 
                 0.90 
                 1.41 
                 2.03 
                 5.64 
                 2870 
               
               
                 Spectra 1000 
               
               
                 UHMWPE - Tekmilon 
                 0.43 
                 0.77 
                 1.20 
                 1.73 
                 4.81 
                 2450 
               
               
                 PET 
                 0.18 
                 0.31 
                 0.49 
                 0.71 
                 1.96 
                 1000 
               
               
                 Nylon 
                 0.14 
                 0.25 
                 0.39 
                 0.57 
                 1.57 
                 800 
               
               
                 Kevlar 
                 0.53 
                 0.94 
                 1.47 
                 2.12 
                 5.89 
                 3000 
               
               
                 302 SS (50% CW) 
                 0.27 
                 0.48 
                 0.74 
                 1.07 
                 2.98 
                 1516 
               
               
                 302 SS (90% CW) 
                 0.42 
                 0.75 
                 1.17 
                 1.68 
                 4.67 
                 2378 
               
               
                 MP35N (95% CW) 
                 0.44 
                 0.78 
                 1.22 
                 1.76 
                 4.90 
                 2495 
               
               
                 35NLT (90% CW) 
                 0.45 
                 0.80 
                 1.25 
                 1.80 
                 5.01 
                 2551 
               
               
                 L604(50% CW) 
                 0.40 
                 0.70 
                 1.10 
                 1.59 
                 4.40 
                 2241 
               
               
                 Nitinol 
                 0.26 
                 0.45 
                 0.71 
                 1.02 
                 2.84 
                 1448 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Fiber diameters (in microns) for specific fiber strengths 
               
            
           
           
               
               
               
            
               
                   
                 Fiber strength required (N) 
                 UTS 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Fiber material 
                 0.20 
                 0.50 
                 1.00 
                 5.00 
                 10.00 
                 (Mpa) 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 UHMWPE - 
                 9.86 
                 15.59 
                 22.04 
                 49.29 
                 69.71 
                 2620 
               
               
                 Dyneema 
               
               
                 UHMWPE - Celanese 
                 14.00 
                 22.13 
                 31.30 
                 69.98 
                 98.97 
                 1800 
               
               
                 UHMWPE - 
                 9.42 
                 14.89 
                 21.06 
                 47.10 
                 66.61 
                 2870 
               
               
                 Spectra 1000 
               
               
                 UHMWPE - Tekmilon 
                 10.19 
                 16.12 
                 22.80 
                 50.97 
                 72.09 
                 2450 
               
               
                 PET 
                 15.96 
                 25.23 
                 35.68 
                 79.79 
                 112.84 
                 1000 
               
               
                 Nylon 
                 17.84 
                 28.21 
                 39.89 
                 89.21 
                 126.16 
                 800 
               
               
                 Kevlar 
                 9.21 
                 14.57 
                 20.60 
                 46.07 
                 65.15 
                 3000 
               
               
                 302 SS (50% CW) 
                 12.96 
                 20.49 
                 28.98 
                 64.80 
                 91.64 
                 1516 
               
               
                 302 SS (90% CW) 
                 10.35 
                 16.36 
                 23.14 
                 51.74 
                 73.17 
                 2378 
               
               
                 MP35N (95% CW) 
                 10.10 
                 15.97 
                 22.59 
                 50.51 
                 71.44 
                 2495 
               
               
                 35NLT (90% CW) 
                 9.99 
                 15.80 
                 22.34 
                 49.96 
                 70.65 
                 2551 
               
               
                 L604(50% CW) 
                 10.66 
                 16.85 
                 23.84 
                 53.30 
                 75.38 
                 2241 
               
               
                 Nitinol 
                 13.26 
                 20.97 
                 29.65 
                 66.31 
                 93.77 
                 1448 
               
               
                   
               
            
           
         
       
     
     While UHMWPE fibers are extremely strong, they are difficult to bond. The present invention overcomes these difficulties by allowing one single fiber to be used to manufacture the entire capture net. Furthermore, the arrangement of the frame eyelets and collar eyelets allows a single fiber to be threaded over and over. Single loops can be made through the eyelets or multiple loops can be made. Multiple loops can be used to terminate a fiber. A small drop of adhesive can be used to fix the end of the fibers in the eyelets. Even though it is difficult to bond to the surface of UHMWPE fibers the adhesive acts as a mechanical constraint that prevents the loops from unraveling. Further since the load is carried by multiple fibers and multiple loops it is dispersed. 
     In another embodiment the capture fiber is a multifilament fiber. In yet another embodiment the fiber is a flat fiber or an oblong fiber. 
     In one embodiment the eyelets are positioned on the neutral axis of the strut of the frame. The neutral axis is generally at the center of the strut and corresponds to the line or plane in the strut that sees zero strain when the strut is loaded in bending. The advantage of putting the eyelet on the neutral axis is that it reduced the weakening effect of the eyelet. Where the eyelet has a major and a minor axis it is preferred that the major axis is as close to the neutral axis of the strut as possible. 
       FIG.  27   a    shows a cross-sectional view of a strut  150 . The cross section shows an eyelet  197  and a capture fiber threaded through the eyelet.  FIG.  27   b    shows a plan view of the same strut  150 , eyelet  197  and capture fiber  196  arrangement. 
       FIG.  27   c    shows another arrangement of strut  150 , eyelet  198  and capture fibers  199 . This time the eyelet is offset relative to the neutral axis of the strut  150 . The eyelet is positioned close to one wall of the strut. A relief section  200  is also shown. This relief section  200  is created by partially machining material in the area where the capture fiber lies. In the embodiment shown the relief section  200  is created on the outer surface of the device. This ensures that the capture fibers do not add to the profile of the device as they loop about the frame. A plan view of the strut  150 , eyelet  198 , capture fiber  199  and relief section  200  is shown in  FIG.  27   d   . It will be noted that the capture fiber  199  loops around the strut section twice in this schematic. 
     It will be appreciated that the capture fibers of this invention and the eyelets of the invention are both very small and assembling both presents a challenge.  FIG.  28   a    shows a view of a segment of a strut  150  with eyelet  154 .  FIG.  28   b    shows a cross sectional view of the strut  150  taken through eyelet  154  along section line a-a.  FIG.  28   c    shows a representation of a fixture device that allows the assembly of the capture fibers 
     In another embodiment the eyelet is positioned close to the edge of the strut. With this embodiment the strut may be thickened on the side opposite the eyelet to compensate for any weakening. 
       FIGS.  29   a - i    show additional eyelets and fiber path defining features to those previously described in  FIGS.  25 - 28   . The purpose of these features is to provide points or areas of engagement between the frame and the fibers that help to define the configuration of the fiber or fibers. Frame  600  in  FIG.  29   a    has eyelets  601  and  602  similar to those described in frames  26   a  and  26   b . Frame  603  in  FIG.  29   b    has a circular offset eyelet  604 . Frame  605  in  FIG.  29   c    has an asymmetrical offset eyelet  606 . Frame  607  in  FIG.  29   d    has an inflexion  608  which creates a feature to provide a preferential seat for fiber attachment.  FIG.  29   e    shows two variations of raised features  610  and  611 , pairs of which may be used to define a fiber attachment point to the frame  609 .  FIG.  29   f    shows recessed features  613  which may be used to define fiber attachment points to the frame  612 .  FIG.  29   g    shows recessed features  615  which may be used to define fiber attachment points to the round wire of frame  614 . Frame  616  in  FIG.  29   h    is similar to frame  614 , except that its raised features  617  are separate components, which in one embodiment are radiopaque marker bands, and in another embodiment are of other metallic or polymeric materials. Element  619  in  FIG.  29   i    is wrapped around frame  618  in such a way as to leave defined spaces  620  in which to attach fibers to the frame. In one embodiment element  619  is a radiopaque platinum wire, but in other embodiments may also be of other materials or in the shape of a coil. The recesses and raised areas illustrated may be created by a laser machining process, or by other mechanical, electrical or chemical means. 
     Now with reference to  FIGS.  30   a - e    there are shown various frame features which may assist the attachment of a distal fiber or fiber structure to a frame structure.  FIG.  30   a    illustrates a frame  650  with an external sleeve  651 , which provides an attachment surface to which fibers may be more easily bonded or a higher friction surface on which fibers will slip less easily if tied in place. Attachment surface  651  may be a polymer sleeve, which may be placed prior to forming the frame shape and may also be bonded or heat shrunk into position. Alternatively the attachment surface may be a coating  652 , as shown in  FIG.  30   b   .  FIGS.  30   c - e    describe variants in which connection elements are used to join distal fibers to a frame. These connection elements may be fibers also, and may be used with any of the frame designs disclosed elsewhere, particularly those with features as shown in  FIGS.  25 - 30   . Fiber  655  in  FIG.  30   c    is connected to frame  653  by connection element  654 , which is itself wrapped around frame  653 . Fiber  655  is shown connected to the eyelets of frame  656  by discrete connection elements  657  in  FIG.  30   d   , and by a continuous connection element  658  in  FIG.  30     e.    
       FIGS.  31   a  and  31   c    show two fiber configurations that may be employed to reduce the size of embolus that can pass through the fiber net. The weave or braid configuration  700  shown in  FIG.  31   a    is constructed from multiple fibers, which is advantageous in that if one fiber breaks the integrity of the entire structure is not significantly affected; however this structure leaves multiple loose fiber ends  701  at each end.  FIG.  31   b    shows a design which deals with this challenge by folding the woven net around the frame  703  and joining the loose ends together at a distal junction  704 . In another embodiment the woven net may be folded around a connecting element which is in turn connected to the frame, or may be connected to the frame in a similar fashion to that described in  FIGS.  30   c - e   .  FIG.  31   c    shows a knitted net  705 , which can be formed from a single fiber, and thus does not have the disadvantage of multiple loose ends. Such a net may be joined to the frame in a multitude of ways, many of which have been previously described in  FIGS.  25 - 30   . 
       FIG.  32   a - e    illustrates a number of fiber types that may be employed in the construction of a fiber net. A monofilament fiber  750  is shown in  FIG.  32   a   . A multifilament twisted fiber  751  is shown in  FIG.  32   b   . A multifilament braided fiber  752  is shown in  FIG.  32   c   . A multifilament fiber with an outer sleeve  753  is shown in  FIG.  32   d   . A multilayer fiber  754  is shown in  FIG.  32   e   . Any of these fibers may be used to construct the net designs shown in  FIGS.  33   a - d   .  FIGS.  33   a  and  33   b    show how a porosity gradient may be created with either a knitted  756  or braided  757  design, which may be advantageous in efficiently balancing wrapped profile and effective particle retention.  FIGS.  33   c  and  33   d    show a clot retrieval device constructed with axial fibers  758 , which also create a similar porosity gradient.  FIG.  33   d    illustrates a similar design to  FIG.  33   c   , except that a stiffening element  759  is provided, which serves to control the wrapped configuration of the net during delivery and retrieval. 
     Now with reference to  FIG.  34   a - f   , there is shown a clot retrieval device  218  which comprises a frame assembly  225  and a catheter  211 . The frame assembly  225  further comprises strut section  214  with eyelets  212 , capture fibers  215 , a fiber junction  217 , an expansion cable  213 , and a guidewire  210 . The frame assembly  225  is shown in its expanded state in  FIG.  34   a    and in its delivery state in  FIG.  34   b   . The strut section  214  lies substantially parallel to the axis of the catheter  211  in the delivery configuration. The strut section  214  expands to a ring shape when it is not constrained. The strut section  214  is deployed from the catheter  211  by advancing the guidewire  210  relative to the catheter  211 . In order to deliver the device  218  into very small vessels it is necessary that the profile (diameter) of the device is very small. In retrieving obstructive clots from the brain it is desired that the device can be delivered through a micro-catheter. Typical commercially available micro catheters have profiles of 1.2 F to 1.9 F (1F=0.333 mm=0.013″). The inner lumen of a 1.9 F micro-catheter is approximately 0.016″ (0.41 mm). In order for the clot retrieval device to fit into this space the cross-sectional area of the strut section needs to be very small. However in order to capture clot effectively larger strut sections are desired. The strut section  214  of  FIG.  34    has a cross sectional area that can fit into a micro-catheter. The expansion cable  213  is a flexible yet strong cable and it is fastened to the strut section  214  at anchor point  223 . The anchor point  223  is at the distal most portion of strut section  214 . The other end of expansion cable  213  is fastened to the distal end  216  of catheter  211 . The expansion cable is strong, flexible and very small in diameter. The cable may be manufactured from polymeric or metallic cable materials. Preferably the cable is made from polyester, nylon, olefin, fluoropolymer, stainless steel or other similar cables. The expansion cable may be monofilament or multifilament. PET, Nylon, UHMWPE, Kevlar and PEN fibers are especially preferred. When the strut section  214  is deployed, it expands to form a ring. The strut section  214  is connected to the guidewire section  210  at the distal end  229  of guidewire. The strut section  214  and distal end  229  of guidewire are adapted such that the strut section  214  sits at an angle transverse to the axis of the vessel. In one embodiment the strut section  214  and/or/not the distal section of guidewire  210  have a preset shape that causes the strut section  214  to sit transverse to the axis of the vessel. In another embodiment the expansion cable  213  is tensioned by advancing the catheter  211  proximally relative to frame assembly  225 . When the expansion cable is tensioned it causes the strut section  214  to move more transversely in the vessel. It will be appreciated that this mechanism allows the user to modify the shape of the strut section  214  as well as controlling the resistance of the strut section to collapse during clot capture. It will also be appreciated that this allows the device to be delivered through micro-catheters as the cross sectional area of the strut section can be reduced significantly. In another embodiment more than one expansion cable  213  is employed. With this embodiment the expansion cables are preferably attached to opposite sides of the strut section  214 . Both cables are attached to the distal end of catheter  211  and both cables are tensioned by a proximal advancement of the catheter  211  relative to the frame assembly  225 . With two cables, the position of attachment  223  to the strut section can be varied. However some displacement relative to distal end  229  of guidewire is desired as this reduces the force required to bias the strut section  214 . 
     In another embodiment the tensioning of the expansion cable  213  is controlled by a handle at the user end. The handle comprises means for locking to the guidewire, means for locking to the catheter  211  and a mechanism to control fine axial motion of the catheter  211  and guidewire  210 . 
     In one embodiment the fine axial motion is controlled by a helical mechanism such as a thread or coil. In another embodiment the fine axial motion is achieved with a gear arrangement such as a rack and pinion. In one embodiment the guidewire locking mechanism comprises a pin vice. In another embodiment the expansion cable is fastened to the proximal end of catheter  211 . In another embodiment the expansion cable is releasably attached to the proximal end of catheter. 
     In yet another embodiment the expansion cable  213  can be released from catheter  211  and catheter  211  can be removed from the guidewire  210 , leaving the frame assembly and the expansion cable behind. With this embodiment the strut section can be activated directly by the user by tensioning the expansion cable. In another embodiment the expansion cable has a grip section attached to its proximal end. 
     In the embodiment shown in  FIG.  34   a - b    the strut section  214  is shown delivered inside the distal end  216  of catheter  211 . The catheter  211  with strut section  214  collapsed are delivered to the target location through a procedural catheter. The lumen at the distal end  216  of catheter  211  is sized to accommodate the frame assembly  225  in its collapsed state. 
     With reference to  FIG.  34   c - f    there is shown some detailed embodiments of the frame assembly  225  of the invention.  FIG.  34   c    shows a frame assemble  225  comprising a strut section  214  and guidewire  210 . The strut section  214  is ring shaped and is integral with the distal section  228  of guidewire  210 . The guidewire  210  comprises a proximal section  226  and a distal section  228 . The proximal and distal segments are joined at junction section  227 . In one embodiment the proximal section at least partially comprises a tube and said tube engages with junction section  227  to connect the proximal  226  and distal  228  sections of the guidewire  210 . The joint between the proximal  226  and distal  228  sections of the guidewire may be further reinforced by any of a variety of conventional joining techniques including screw joint, welding, soldering brazing, adhesive bonding, crimping, swaging or combinations of the above. The guidewire  210  extends from the strut section  214  back to the user in use and is thus much longer than depicted. The strut section  214  may be any of a variety of cross-sectional shapes including circular, elliptical, rectangular, square, polyhedral, and multifilament. Circular or rectangular are preferred. The strut section further comprises eyelets  212 . The eyelets  212  are as described earlier in  FIG.  30 - 33   . The expansion cable  213  is connected to the strut section  214  at its distal end. An eyelet  223  may be used to effect cable attachment. The cross sectional area of the distal end of the guidewire  210  may be locally modified to improve the shaping of the frame by the expansion cables. The guidewire  210  may be flattened so as to create a directional bias for strut section  214  when expansion cable  213  is activated. A flattened cross section in this area has the effect of keeping the strut section  214  in plane during expansion. The strut section  214  of  FIG.  34   c    may be cut from a hypotube. The shape may be cut from a small diameter tube and expanded or it may be cut directly from a large diameter tube. 
       FIG.  34   d    shows an alternative construction of the frame assembly  225 . The guidewire  210  and frame assembly  214  are manufactured from a single piece of wire. The strut section  214  forms a ring shape and comprises eyelets  212  and an expansion cable  213  attachment eyelet  223 . The strut section  214  is made from a wire that is looped and joined to itself. The joint area  219  is at the distal end of guidewire  210 . A smooth transition  224  is effected between the joint area  219  and the distal end of the guidewire  210 . The distal end  229  of the joint area  219  may be locally thinned or flattened to create a bias for strut section expansion.  FIG.  34   e   -f show segments of strut sections  214  of the invention wherein the strut sections  214  have either a circular or rectangular cross section. 
     The method of use of clot retrieval device  218  of  FIG.  34   a - f    is highlighted in  FIG.  35   a - i   .  FIG.  35   a    shows a vessel  220  and an obstructive clot  221 . The clot retrieval device  218  is shown in its collapsed state crossing the obstructive clot  221 . The distal tip  216  of catheter  211  is advanced across obstructive clot  221  with strut section  214  collapsed inside the lumen of the catheter distal tip  216 . The guidewire extends proximally and is operably moveable relative to catheter  211  to deploy the strut section  214 . The strut section  214  is deployed by advancing catheter  211  proximally while holding the guidewire  210  fixed ( FIG.  35   c - d   ). The strut section  214  assumes its remembered ring shape in the vessel. The clot retrieval device  218  is advanced proximally until its strut section  214  is adjacent the obstructive clot  221 . At this point the catheter  211  is advanced proximally relative to the guidewire  210  until the expansion cable  213  is tensioned ( FIG.  35   e   ). This step can be controlled with a handle mechanism at the proximal end as described elsewhere. Increasing the tension in expansion cable  213  changes the angle that the strut frame  214  makes relative to the axis of the vessel  220 . This in effect changes the size of the capture opening of the clot retrieval device  218 . As the capture opening increases, the strut frame  214  achieves better apposition with the walls of the vessel  220 . It will be appreciated that these features allow the user to achieve very efficient clot capture. However overly tensioning the expansion cable  213  is not desirable as this will induce trauma to the vessel. Rather the expansion cable  213  is tightened to the point where the strut section  214  has achieved apposition with the vessel and the catheter  211  is then locked relative to the guidewire  210  at the user end. The clot retrieval device  218  is now advanced proximally to capture the obstructive clot  221  ( FIG.  35   f   ). With the obstructive clot captured, the lock between catheter  211  and guidewire  210  is released. The guidewire  210  is advanced proximally relative to catheter  211  and at least the proximal portion of strut section  214  is drawn into the lumen at the distal end  216  of catheter  211  ( FIG.  35   g - h   ). This step reduces the diameter of the strut section  214  and makes removal of the clot  221  and clot retrieval device  218  easier. The clot retrieval device  218  and clot  221  are removed from the body ( FIG.  35   i   ). 
     In another embodiment the lumen at the distal end  216  of catheter  211  is sized only to accommodate guidewire  210 . With this embodiment the strut section  214  cannot be collapsed inside catheter  211 . Instead, the frame assembly  225  and catheter  211  are delivered through the lumen of a micro catheter. The tip of the micro-catheter is placed across the obstructive clot. The strut section  214  is collapsed and while restrained in the collapsed state the frame assembly  225  and catheter  211  are advanced into the proximal lumen of the micro-catheter. The clot retrieval device is advanced through the lumen of the micro-catheter and deployed distal of the tip of the micro-catheter. When the device is deployed the micro-catheter is advanced proximally. Subsequently the clot retrieval device is advanced until the strut section is adjacent the obstructive clot. The catheter  211  is advanced proximally and expansion cable  213  is activated. When the frame section is expanded to the desired shape, the expansion cable  213  and catheter  211  are locked relative to guidewire  210 . The clot retrieval device  218  is advanced proximally to capture the clot. The micro-catheter is again advanced until its distal tip engages with the strut section  214  of the clot retrieval device  218 . The micro catheter is advanced further and partially collapses the strut section. The micro-catheter and clot retrieval device  218  are withdrawn from the vessel together. 
     Yet another embodiment is shown in  FIG.  36   a - b   . The clot retrieval device  218  is the same as the clot retrieval device of  FIG.  35   . However in the embodiment shown in  FIG.  36    the lumen of catheter  211  accommodates a separate crossing guidewire  222 . The crossing guidewire  222  runs parallel the guidewire  210  of the clot retrieval device. The crossing guidewire  222  may sit side by side with the collapsed clot retrieval device. Alternatively catheter  211  has a separate lumen for crossing guidewire  222 . The crossing guidewire  222  is free to move axially and rotationally relative to the clot retrieval device. The crossing guidewire  222  is preferably a conventional guidewire and its tip can be shaped to access target vessels. This allows the crossing guidewire  222  to be used in conjunction with catheter  211  to access difficult to reach locations by advancing the crossing guidewire  222  relative to the catheter  211  and torquing it as necessary to achieve access. When the tip section of crossing guidewire  222  has accessed a side branch, the catheter  211  can be advanced over the crossing guidewire  222 . When the clot retrieval device  218  is delivered to the target location the crossing guidewire  222  may be removed. Alternatively the crossing guidewire  222  may be left in the target vessel. 
       FIG.  36   a    shows a crossing guidewire  222  with its distal tip across the capture fibers  215  of clot retrieval device  218 . The capture fibers are arranged in a fashion that a small diameter device can be pushed through the gaps in the capture fibers  215 . The ability of low profile devices to cross the capture fibers allows other devices to be used with the clot retrieval device. 
     Another embodiment of the invention is shown in  FIG.  37   a - e   .  FIG.  37   a    shows a conventional guidewire  230 . The guidewire  230  comprises a proximal end  231 , a distal end  232  and a tip  234 . The tip  234  is flexible and atraumatic to vessels. Many of the features of the clot retrieval device  250  of this embodiment are achieved by modifying the area  233  adjacent the tip  234  of conventional guidewire  230 . With reference to  FIG.  37   b    there is shown a guidewire  233  which has been modified proximal of the tip in order to create clot retrieval device  250 . The guidewire  233  comprises an inner shaft  235  and an outer shaft  236 . The inner shaft and the outer shaft are fixed together. Proximal of the tip of the guidewire  230 , the outer shaft  236  has substantially longitudinal cuts  238  so as to create strut elements  237 . The strut elements  237  are cut so as to create ring elements  247 . One or more ring elements may be created with strut elements  237 . In the embodiment shown two ring elements  247  are created by cutting two pairs of strut elements  237  and connecting the strut elements  237  at their distal ends. In one embodiment the segment of the outer shaft  236  adjacent the tip  234  is made from an elastic, a super elastic or a shape memory material. Preferably said elastic material is nitinol or a spring steel. Most preferably the outer shaft  236  is made from nitinol.  FIG.  37   c    shows the clot retrieval device  250  in its expanded state. It can be seen that a number of elements have been added to the modified guidewire of  FIG.  37   b    to create the clot retrieval device  250 . The strut elements  237  have a collapsed state and an expanded state.  FIG.  37   b    shows the strut section  237  in its as machined (laser cut) state. The strut section  237  is shown in its expanded state in  FIG.  37   c   . In the expanded state the strut sections  237  form a capture frame  247 . In the embodiment shown the capture frame  247  comprises two D-shaped elements. The capture frame comprises radial strut sections  246  and body strut sections  248 . The body strut sections  248  interface with the vessel wall in the expanded state and provide a line of apposition around the circumference of the vessel. The radial strut section  246  connects the body strut section to guidewire shaft  236 . Eyelets  244  are provided on at least the body strut section  248  and capture fibers  241  are fixed to the capture frame  247  using said eyelets  244 . The capture fibers  241  are fixed to collar  243  distally. Collar  243  is fixed to the distal portion of the guidewire. In another embodiment the distal eyelets are cut into the outer shaft  236  of the guidewire  230 . This eliminates the need for collar  243  and reduces the distal profile of the device. When the strut section  237  is in the expanded state, a recess area  240  is created in the wall of the guidewire. The integrity of the guidewire is maintained by the presence of connector elements  242 . The connector element  242  is a portion of the outer shaft  236  that lies adjacent the recess area and connects the distal part  232  of the outer tube  236  with the proximal part  231  of the outer shaft  236 . The connection between the proximal portion  231  and the distal portion  232  of the guidewire  230  is further reinforced with the inner shaft  235 . In one embodiment the inner shaft  235  is fixed to the outer shaft  236 . In one embodiment the connector element  242  is fixed to the inner shaft  235 . When the strut section  237  is in the collapsed state, it packs into the recess area  240 . This keeps the delivery profile of the clot retrieval device  250  extremely low. Since the capture fibers are made from a highly oriented fiber such as Dyneema (UHMWPE), and since the recess space  240  is larger than the strut section, the attachment of the capture fibers to the strut section  237  will not adversely impact the profile of the strut section  237  of the clot retrieval device  250  in the collapsed configuration. 
     The clot retrieval device  250  is shown in the delivery configuration in  FIG.  37   d   . The delivery catheter  245  is of an extremely low profile. Preferably the delivery catheter is less than 2 F (0.66 mm). More preferably the delivery catheter profile is less than 1.9 F. Even more preferably the delivery catheter is less than 1.6 F. 
       FIG.  37   e    shows an end view of the device  250  in the expanded state. The view is as seen from distal of the expanded strut section  237 . The inner core  235  is visible with two connector elements  242  diagonally opposite. The strut section  237  is shown expanded to form capture frame  247 . The capture frame  247  comprises a double-D shape. The capture frame  247  further comprises radial strut sections  246  and body strut sections  248 . The strut sections  237  are provided with eyelets  238  for capture fiber attachment. 
     In yet another embodiment the clot retrieval device  250  is delivered to the target site without the need for a delivery catheter. With this embodiment the inner shaft  235  and the outer shaft  236  are moveable relative to each other. The strut section  237  is connected to the inner shaft  235  in the delivery configuration and said connection restrains the strut section  237  in the collapsed state. Upon reaching the target site relative movement of the inner shaft relative to the outer shaft releases the connection and allows the strut section  237  to expand. In one embodiment the connection comprises a tether that is attached to both the strut section  237  and the inner shaft  235 . In the collapsed configuration the tether is under tension as it restrains the strut section  237 . The inner shaft  235  is either advanced or rotated to relax the tension in the tether and this allows the strut section  237  to expand. In another embodiment an engagement between the inner shaft  235  and the strut section  237  retains the strut section  237  in the collapsed state. The inner shaft  235  is either rotated or advanced to disengage with the strut section  237  and this allows the strut section  237  to expand. The engagement may be a frictional engagement, a snap engagement, a clip engagement feature, a hook engagement or other similar engagements. 
     Now with reference to  FIGS.  38 - 39    there is shown another low profile clot retrieval device  280 .  FIG.  38   a - b    shows modifications to guidewire  260  necessary to create clot retrieval device  280  of  FIG.  39   a - b   . The modified guidewire  260  comprises a tubular shaft  261  which has approximal end  266  and a distal end, an outer surface and an inner lumen. The distal end of tubular shaft  261  comprises a strut section  267  and an expansion cable  265 . The strut section is shown in the “as cut” state in  FIG.  38   a - b   . The strut section  267  comprises at least one pair of generally longitudinal struts  264  and a strut connection  268  at the distal end of longitudinal struts  264 . Where the strut segment  267  comprises a single pair of longitudinal struts  264 , then in the expanded configuration the axis of the outer shaft adjacent the strut section  267  will be offset relative to the axis of the vessel (as shown in  FIG.  39   a - b   ). However, where the strut segment  267  comprises two pairs (or more) of longitudinal struts  264 , then in the expanded configuration the axis of the outer shaft adjacent the strut section  267  will he generally coaxial with the axis of the vessel. In one embodiment the strut connection is a short strut like element. In a preferred embodiment the strut connection  268  has a curved aspect. The curved aspect helps to distribute stress as the strut section is expanded to from a ring. Preferably the strut connection has an inner curve and an outer curve wherein the inner curve has a smaller radius than the outer curve. Preferably the difference in radius of the inner curve versus the outer curve is less than the width of the strut sections  267 . Preferably the strut connection comprises a strain relief feature. In another embodiment the strut connection  268  comprises an element that is curved in at least two dimensions. 
     The expansion cable is attached to the frame section  267  at attachment point  269  and extends proximally to the user. The expansion cable  265  enters the lumen of the tubular shaft  261  at port  262  and extends through the lumen back to the user. The expansion cable can be tensioned by the user at the proximal end of the guidewire shaft  261 . In one embodiment the expansion cable is attached to a fine adjustment mechanism at the user end. This allows the user to control the level of tension in the expansion cable  265  and thus the resistance of the strut section  267  to collapse during clot capture. The port  262  position along the tubular shaft  261  may be varied. In one embodiment the distal opening of the lumen of the tubular shaft  261  is used as the port  262 . 
     In the embodiment shown in  FIG.  38    the eyelets  270  are shown along the length of strut section  267 . Eyelets may also be placed at the distal end of the tubular shaft  261 . The eyelets  270  may be created in a variety of configurations as previously described. Likewise, the attachment of the capture fibers  279  is as described earlier. 
     In another embodiment the width of struts  264  is sufficiently great that an expansion cable is not needed in order for the strut section  267  to effectively capture the obstructive clot. 
     The clot retrieval device  280  is shown assembled and in the expanded state in  FIG.  39   a - b   . The capture fibers and the distal collar  282  have been added to  FIG.  38    and the strut section  267  has been expanded. The strut section  267  is preferably made from an elastic material, a super elastic material or a shape memory material. The strut section  267  forms a ring in the expanded state, and the ring shaped strut section  267  apposes the vessel in the expanded state. In use, the expanded strut section  267  is advanced proximally to capture the clot. The expansion fiber  265  is used to add stiffness to the frame and prevent its partial collapse during clot capture. The large open mouth of the strut section in the expanded state makes this embodiment an effective clot capture device. The capture fibers  279  are terminated at a distal junction  281  with a collar as previously described. The distal collar comprises eyelets  270  for capture fiber  279  attachment. In another embodiment the distal junction  281  is formed by the joining of the distal ends of the capture fibers  280  to each other. In one embodiment a knot arrangement is used, in another embodiment the capture fibers are bonded or welded together. 
     In the embodiment shown in  FIG.  39    the distal junction  281  is free to move proximally as it is not constrained relative to the guidewire  261 . In another embodiment at least one of the capture fibers has a bias. Preferably said bias generally pushes the distal junction  281  distal of the strut section. Preferably the biased capture fiber is elastic, super elastic, or shape memory. Preferably said biased capture fiber is metallic. Preferably said capture fiber is nitinol, or stainless steel. 
       FIG.  39   c    shows the clot retrieval device  280  in the delivery configuration. The strut section  267  is shown in the collapsed configuration inside a pod  285  of delivery catheter  284 . The guidewire shaft  261  extends proximally through the lumen of catheter  284 . In one embodiment the catheter  284  and guidewire  261  are arranged in an over the wire fashion. In another embodiment the catheter  284  and guidewire  261  are arranged in a rapid exchange fashion. The catheter shaft is preferably made from a thin walled flexible material. Preferably the catheter is made from an olefin, nylon, a PEBAX, polyester, polyurethane or a fluoropolymer. The delivery catheter may be made from a combination of these materials. The catheter may be made with two or more layers and at least one of these layers comprise at least one of the above list of materials. 
       FIG.  40   a - b    shows a clot retrieval device  290  that is very similar to the clot retrieval device  280  of  FIG.  39   . The clot retrieval device  290  has a first difference in that the distal junction is connected to strut tip  287 . The strut tip is created during the machining of the strut section  267 . The strut tip is formed from a portion of the wall of the tubular shaft  261  that lies between longitudinal struts  264 . The strut tip is designed to be mechanically similar to the core of a guidewire tip. The strut tip tapers distally and has an atraumatic element  287  at its distal end. The strut tip  287  provides a site upon which the distal junction  281  can be connected. In the embodiment a collar  268  is used as the distal junction  281  and the collar has limited movement relative to the strut tip  287 . In one embodiment the collar is fixed relative to the strut tip. A second difference between the clot retrieval device  280  of  FIG.  39    and clot retrieval device  290  of  FIG.  40    is that the distal end of the tubular shaft  261  has machined slots  286  to improve the trackability of the device. In one embodiment the slots run transverse to the axis of the tubular shaft and run only part of the circumference. In another embodiment pairs of transverse slots  286  are arranged on opposite sides of the tubular shaft  261 . In another embodiment the slots  286  are arranged in a continuous helix along a portion of the distal end of the tubular shaft  261 . In another embodiment the clot retrieval device comprises a supporting strut  288 . The supporting strut  288  extends distally and substantially parallel of the axis of the tubular shaft  261  and comprises a restraining feature. The supporting strut  288  is configured to restrain the strut section  267  in the collapsed state during delivery. The restraining feature may comprise a tether arrangement, an interconnection between the supporting strut and the strut section  267 , an interlock between the supporting strut and the strut section  267 , or a coupling between the supporting strut  288  and the strut section  267 . The restraining feature may be deactivated when the clot retrieval device  290  is at the site of the occlusion causing the strut section  267  to expand to its remembered expanded state. The deactivation may be brought about by means of a release cable, use of an inner core which may be advanced or retracted to free the strut section, or advancement or retraction of an outer tubular member, or a combination of these mechanisms. In another variant, the restraining feature may be configured such that the strut section is firstly restrained to itself and secondly restrained to the supporting strut and that both restraints are decoupled either simultaneously or in series when the clot retrieval device  290  is at the site of occlusion. The clot retrieval device  290  is otherwise the same as clot retrieval device  280  and similar numbers shall have the same meaning for both devices. 
     The clot retrieval devices of  FIG.  41 - 43    are very similar to the clot retrieval devices shown in  FIG.  39    and  FIG.  40   . With  FIG.  41    the strut tip is cut substantially parallel to the longitudinal struts  264  of strut section  267 . The longitudinal strut extends distal of the strut section and connects the tubular shaft proximally  261  with a distal segment of tubular shaft  291 . The distal segment of the tubular shaft  291  is modified to make it atraumatic to vessels. The modification may comprise a spiral cut or slots as described previously. The distal tip  293  of the tubular shaft  291  is smooth soft and atraumatic. The distal junction  268  is connected to the distal shaft  291  as previously described. 
       FIG.  42   a - b    shows an inner core  301  adapted to from a guidewire like tip to the clot retrieval device  300 . The inner core  301  has a proximal diameter that allows it to fit inside the lumen of the tubular shaft  261 . The inner core  301  may be fixed relative to outer shaft  261  or it may be moveable relative to outer shaft  261 . The distal portion of the inner core  301  tapers distally and has an atraumatic tip  302 . The atraumatic tip  302  comprises a rounded tip  304  and a coil segment  303 . The rounded tip  304 , the distal tip of the inner core  301  and the coils  303  are preferably fastened together. The distal junction  268  is positioned proximal of the distal end of the core wire. In one embodiment the distal junction  268  comprises a collar with eyelets for capture fiber attachment. The proximal end of inner core  301  may be terminated distal of port  262 . Alternatively the inner core extends proximally but provides clearance for the expansion cable  265 . In yet another embodiment the inner core  301  and the expansion cable  265  are connected proximal of port  262  and the inner core  301  movement is used to tension the expansion cable  265 . In another embodiment the inner core  301  distal end is shapeable. 
     In another embodiment the clot retrieval devices of this invention are adopted for use as embolic protection devices. With this embodiment the delivery catheter is removed after deployment and the guidewire is employed to deliver treatment devices. A greater number of capture fibers are employed and the capture fibers are arranged so as to create distal pores of less than 200 microns. 
     Another embodiment of the invention is shown in  FIG.  44 - 46    wherein the clot retrieval device comprises a guidewire  330 , a clot capture ring  320 , and capture fibers  333 . With reference to  FIG.  44   a    there is shown a clot capture ring  320  of clot retrieval device  350 . The clot capture ring is characterized in that it is cut from a tube and formed. The strut section  321  is shown in its as cut configuration and provides strong vessel apposition. The strut section  321  is attached to the guidewire with a collar element  322 . The collar element  322  is cut from the same tube as the strut section  321  but it is formed into a collar after cutting. The collar element  322  comprises at least one finger element  323 . The finger element  323  is formed into a tubular segment such that it can be attached to the guidewire. Preferably one or more finger elements  323  wrap around the guidewire diameter and make a secure attachment. Multiple finger elements are preferred over one wide finger element to ensure the device is trackable while distributing forces to the guidewire. The collar element  322  may be welded or bonded to the guidewire. Alternatively the collar element  322  may be a force fit with the guidewire.  FIG.  44   b    shows a view of the collar element  322  and a portion of the strut section  321  in the as cut configuration. In this embodiment pairs of finger elements  323  are located on either side of member  326 . The collar element  322  is connected to the strut section by a connector element  325 . The connector element  325  has a curved interface with the strut section  321 . The connector element  325  is designed such that it distributes strain loads it has to endure during collapse and delivery. The curved interface helps to distribute the loads. Preferably the connector element comprises strain distributing features as described. The eyelets  327  are shown on the strut section and these function as previously described. 
       FIG.  44   c    shows the clot retrieval device  350  in the expanded configuration mounted on guidewire  330 . The guidewire comprises a shaft, a proximal end  331 , a distal end  332  and a tip  329 . The capture ring  320  is connected to the guidewire adjacent the distal end  332 . The capture ring is secured to the guidewire  330  using collar element  322 . Capture fibers  333  are attached to the strut section using eyelets  327  and are attached to the distal end of the guidewire  332  at distal attachment point  328 . Distal attachment point  328  comprises at least one eyelet in the guidewire  330 . The guidewire  330  may be tubular in this area or at least one micro-hole may be drilled through the wall of the guidewire  330  to create an attachment. Alternatively the capture fibers may be bonded or mechanically fastened to the guidewire  330 . 
     The clot retrieval device  350  is shown in the collapsed configuration inside the distal lumen of delivery catheter  335  in  FIG.  44   d   . The clot retrieval device is deployed by advancing the guidewire  330  relative to the delivery catheter  335 . 
       FIG.  45   a - c    shows a variation in the embodiments shown in  FIG.  44   . This time the connector element  340  is longer than previously described. This allows better strain relief to be achieved in the area of bending during collapse and it also allows the offset of the guidewire position to be controlled. In the embodiment shown the guidewire position is close to the strut frame but there is still a gap between the guidewire and the wall. This partial offset feature allows for a large capture opening. 
     Another variation of the embodiments described in  FIG.  44 - 45    is shown in  FIG.  46   . This time an expansion cable  341  is employed to help frame expansion. The device is shown with the expansion cable  341  in the tensioned configuration with the frame expanded into a ring. The expansion cable  341  allows the angle of the ring to the vessel to be controlled by the user. In the embodiment shown the angle is greater than 90′. This makes the resistance of the frame to collapse very difficult during clot capture. The guidewire shaft has a port  342  and an inner lumen  343  through which the expansion cable runs. The proximal end of the expansion cable  341  exits the lumen  343  at the proximal end of the guidewire  331 . 
     With reference to  FIG.  47   a - d    there is shown another clot retrieval device  360  which is constructed from a guidewire  364 , capture fibers  365  and a fiber anchor  367 . The guidewire comprises a proximal end  363 , a distal end  368 , a distal tip  369  and a frame section  361 . The proximal end of the guidewire  363 , comprises a tube section with an expansion cable  362  extending from the frame section  361  to a point proximal and external of the guidewire  364 . The proximal end of the guidewire  363 , in use, is external of the patient. The expansion cable  362  is attached to the distal end of the distal frame section  371 . The distal tip  369  has an atraumatic tip to prevent vessel injury. The frame section  361  further comprises a distal frame section  371  and a proximal frame section  370 . The frame section  361  has an expanded configuration and a collapsed configuration. In the collapsed configuration, the frame section comprises an elongate element. In the expanded configuration, the proximal frame section  370  and distal frame section  371  forms a ring that orients transverse to the axis of the vessel. 
     In a first embodiment the frame section  361  is a substantially elongate element in its relaxed state. When the expansion cable  362  is tensioned, the shape of frame section  361  changes from its relaxed elongate state to its expanded ring configuration. This shape change is controlled by compression slots  375  in the tubular wall of the guidewire shaft  364 . The compression slots  375  allow the shaft  364  to compress preferentially on one side and this allows the shaft to adopt a curved configuration. Where all the slots are on one side of the tube, then the tube will bend into a simple curve when loaded in compression. Complex curves can be achieved by using multiple slots and moving the position of the slots around the axis of the tube.  FIG.  47   d    shows a section  364  of a guidewire shaft with slots designed to create both simple and complex curves. In the center of the slotted section, all the slots  375  are in a line and this construction will allow for a simple curve when the shaft is compressed. At both the proximal and distal end of the section, the slot position changes as we move along the shaft. This creates a curve in two dimensions (Y &amp; Z). In order to create the ring shown in  FIG.  47   a    two complex curves (“a” in  FIG.  47   d   ) at either end of a simple curve (“b” in  FIG.  47   d   ) are required. 
     In another embodiment the frame section  361  is ring shaped in its relaxed state. In this configuration the device is collapsed for delivery using a delivery catheter  372 . The collapsed device is stored in the lumen of the delivery catheter and advanced across the obstruction. It is deployed distal of the obstruction and opposes the vessel wall. The expansion cable may be employed in order to improve the stiffness of the device in the expanded configuration. Since the expansion cable effectively locks the distal end of the distal frame section  371  to the proximal end of the proximal frame section, it greatly increases the resistance of the frame section to collapse. 
     In another embodiment two or more expansion cables are used. The first expansion cable is used as described above. The second expansion cable is attached to the frame section  361  between the distal frame section  371  and the proximal frame section  370 . The expansion cable extends proximally until it enters the lumen of the guidewire  364  proximal of the frame section through a port in the wall. This second expansion cable when tensioned prevents the frame from collapsing distally when capturing clot. 
     With each of these embodiments the capture fibers  365  are attached to the frame section  361  at the proximal end and to the fiber anchor  367  at the distal end. Preferably the capture fibers  365  are slidably attached to the fiber anchor  367 . In one embodiment the capture fibers  365  are connected to the compression slots  375 . In another embodiment the frame section  361  comprises eyelets as previously described and the capture fibers are attached to the eyelets. In either scenario the attachment points of the capture fibers  365  are spaced apart along the length of the frame section  361 . Preferably the capture fibers  365  are evenly spaced apart along the frame section  361 . The fiber anchor  367  at the distal end provides for secure fiber attachment to the distal shaft  368  while allowing the capture fibers  365  to slide at the fiber anchor. The ability of the fibers to slide is important in allowing the frame section to collapse efficiently. Fibers attached to the distal part of distal frame section  371  require very little slack in order to allow that portion of the frame to move from an expanded state to a collapsed state. However, fibers at the proximal end of the proximal section of the frame  370  require considerable slack in order to allow that portion of the frame to collapse unconstrained. In order to minimize the amount of capture fiber  365  slack, it is preferred that fibers connected to the distal section of the distal frame section  371  be looped through the fiber anchor and connected back to the proximal end of the proximal frame section  370 . By taking this approach throughout the frame, the level of capture fiber slack can be minimized. It will be appreciated that in order to allow for this fiber slack to be distributed the fibers need to slide through the fiber anchor with ease. Preferably the size of the opening on the distal anchor for fiber attachment is a clearance fit for the capture fibers. In one embodiment the anchor  367  comprises a ring with an inner diameter. The inner diameter is larger than the diameter of the guidewire and one or more attachment legs  376  fix the ring relative to the guidewire. 
       FIG.  48   a    shows a clot retrieval device  800  in the expanded state.  FIG.  48   b    shows the same device loaded into a microcatheter  812  for delivery to the target site. Frame  804  is similar to frame  361  in  FIG.  47   a   , but in this case is not formed from the guidewire. Frame  804  expands to a generally circular shape in end view, but elongates and twists into a longitudinal element when collapsed for delivery and retrieval as shown in  FIG.  48   b   . The proximal  807  and distal  806  ends of the frame  804 , are mounted to tubular elements  808  and  805  respectively. These elements are mounted on the guidewire  809 , allowing rotation and translation of the frame relative to the guidewire. Stops  801 ,  802  and  803  are positioned on the guidewire  809  to allow the user to apply a push or pull force to appropriate elements of the device to facilitate its advancement or withdrawal. Stop  803  prevents the frame from elongating during clot retrieval, and together with stop  802  acts against the frame during clot capture and retrieval. Stop  802  apposes element  805  during device advancement through and from a delivery microcatheter  812  as shown in  FIG.  48   b   . Apposing the distal end of the frame in this way keeps the frame  804  in tension rather than compression, as would be the case if force were applied to element  807  to facilitate advancement. Keeping the frame in tension reduces the lateral forces applied to the lumen of the microcatheter, and thus reduces the force required to advance the clot retrieval device through the microcatheter. In one embodiment of this design a delivery assist catheter  811 , with proximal element  810 , may be used to transmit a push force to stop  801 , which in turn transmits a push force through the guidewire to stop  802  and thus to the distal end of the frame. This method of advancement eliminates the need for that element of the guidewire proximal of stop  801  to transmit push force, and therefore permits the use of a more flexible wire. In another embodiment (not shown) stop  801  is not present and delivery assist catheter  811  is not required as push force can be transmitted through the guidewire to stop  802  and thus to the frame. 
       FIGS.  49   a - b    illustrate another clot retrieval device  850  similar to device  360  shown in  FIG.  47   a   , but employing an additional tether element  853 . Frame  851  is configured to tend to adopt a curved profile and appose the vessel wall when released from the constraints of the delivery microcatheter  854  shown in  FIG.  49   b   . When placed in tension the tether element  853  provides additional integrity to the frame, and acts against the tendency of the frame to elongate when meeting resistance, such as during clot capture. Once the target clot has been successfully captured, the tether element may be relaxed so as to allow the frame to elongate again for ease of retrieval. Alternatively the tether element may be kept in tension to maintain the frame and capture net  852  in a more preferential configuration for retention of captured clot during retrieval from the body. 
       FIGS.  50   a - c    show another clot retrieval device  870 .  FIG.  50   a    shows the device in its deployed state. Frame  871  is connected to guidewire  875  by element  873 , which allows the frame to rotate and translate relative to the guidewire. Distal capture net  872  is connected to frame  871  and is also connected at its distal end to collar  874 .  FIG.  50   b    shows the device encapsulated in microcatheter  878  just prior to deployment from the microcatheter. To effect deployment, the guidewire  875  on which the device is mounted is fitted with a stop  877 , which apposes collar  874  when the microcatheter is retracted, preventing the clot retrieval device from retracting with the catheter as shown in  FIG.  50   c   . This configuration also holds the capture net in tension, with the associated benefits described previously in relation to  FIGS.  48   a  and  b   . In the embodiment shown a second guidewire stop  876  is provided, which apposes proximal frame element  873  during retraction and retrieval of the device. Such a design allows the length of guidewire protruding distal to stop  877  to be limited or eliminated. In another embodiment (not shown) only one guidewire stop is provided which acts in both deployment and retrieval. 
       FIG.  51   a    shows a clot retrieval device  890  configured in such a way that it may be used in conjunction with a variety of suitably sized guidewires  891 . The device  890  has a shaft  892  which is sized to be able to advance or retract over guidewire  890 .  FIG.  51   b    shows a similar device  894  mounted on a shaft  895  which has a guidewire exit port  896 , so that the device may be used with any suitably sized short length guidewires. 
       FIG.  52   a    shows a clot retrieval device  2010 . The clot retrieval device  2010  comprises guidewire  2020  and a clot capture basket  2011 . The clot capture basket comprises a frame  2012 , and a net  2015 . The clot retrieval device  2010  has an expanded state for engagement and capture of clots and a collapsed state for delivery through the vasculature. The frame  2012  comprises a collar  2023  for mounting the frame  2012  on the guidewire  2020 , a hoop  2014  composed of struts  2009  and at least one connector element  2013  to connect the collar  2023  and the hoop  2014 . Preferably the frame  2012  is made from a superelastic or shape memory material. The frame further comprises a bifurcation point  2022  where the connector  2013  splits to form two struts  2009 . In this embodiment the connector  2013  has greater width than the struts  2009 . In another embodiment the connector  2013  has greater width over most of its length than the strut  2009  except in the region just proximal to the bifurcation. In this area, the width of the connector  2013  is significantly reduced. This allows the connector  2013  to hinge at this point and so respond to vessel asymmetry or asymmetry in the guidewire access.  FIG.  52   b    shows stop  2017  at the distal end  2018  of guidewire  2020 . 
     In one embodiment the clot capture basket  2011  is fixed to the guidewire  2020 . In another embodiment the clot capture basket  2011  is slidable on the guidewire  2020 . 
       FIG.  53    shows another clot retrieval device  2010  which is almost identical to the clot retrieval device of  FIG.  52   a - b    except that the connector comprises a pair of parallel struts  2025 . The pair of parallel struts  2025  allows the connector to contribute strongly to the engagement force of the device while providing greater lateral flexibility. The capture basket  2011  further comprises a basket mounting tube  2019 . The basket mounting tube  2019  extends from the proximal end of the basket  2011  to the distal end of the net  2015 . The net  2015  is attached to the mounting tube  2019 . The mounting tube  2019  may be fixed relative to the collar  2023  or it may slide relative to the collar  2023 . The distal end of mounting tube  2019  is configured to engage with the stop  2017  at the distal end  2018  of the guidewire  2020 . 
       FIG.  54    shows a frame  2012  of  FIG.  52    as a sub-component. The frame  2014  comprises three segments; the proximal segment comprises a collar  2023  which is a short tube for mounting on the guidewire  2020 , the intermediate segment comprises two connectors  2013  which split at bifurcation point  2022  and the distal segment comprises a plurality of struts that form a hoop  2014 . Ideally there are four struts that each form a quadrant of the hoop. The frame  2014  is preferably made from a super elastic or a shape memory alloy. 
       FIG.  55   a - b    shows another clot retrieval device  2030 , which is similar to the clot retrieval devices of  FIG.  52 - 54   , and similar numerals are used to describe similar elements. The clot retrieval device  2030  is shown with a microcatheter  2031 . The clot retrieval device  2030  is delivered through the lumen of a microcatheter and is moveable relative to the microcatheter  2031 . The movement of the clot retrieval device  2030  relative to the microcatheter is effected by the movement element  2019 . In one embodiment movement element  2019  comprises a tubular element which is slidable over the guidewire. The tubular element may be fixed to the collar  2023  of the capture basket  2011  and can thus control movement of the capture basket  2011  in both directions relative to the guidewire or the microcatheter. Alternatively the tubular element  2019  is separate from the capture basket and advances the capture basket as a bumper tube. With this embodiment the bumper tube can advance the clot capture basket  2011  but cannot withdraw the basket. In this embodiment the capture basket is withdrawn by engaging the stop  2020  at the distal end of the guidewire. 
     Alternatively the movement element  2019  is a guidewire. With this embodiment the capture basket  2011  is fixed to the guidewire  2019  and thus movement of the capture basket  2011  is controlled by the guidewire  2019 . Forward and backward movement of the capture basket  2011  are controlled by the guidewire  2019 . 
       FIG.  56    shows another clot retrieval device  2040 , which is similar to the clot retrieval devices of  FIG.  52 - 55   , and similar numerals are used to describe similar elements. With this embodiment the capture basket  2011  is deployed from a reception space  2046  at the distal end  2047  of the microcatheter  2041 . The guidewire  2020  is moveable relative to the capture basket  2011 . The microcatheter is connected to the capture basket  2011  by a telescoping tube  2048  with lumen  2045  which is fixed to the collar  2023 . The telescoping tube  2048  further comprises a stop  2043  which engages with a microcatheter stop  2044  to prevent complete separation of the basket  2011  and the microcatheter  2041 . A bumper tube (not shown) is used to deploy the capture basket  2011  from the reception space  2046 . The capture basket  2011  is removed at the end of the procedure by withdrawing the guidewire  2020  so as to engage the guidewire distal stop  2017  with the body tube  2021 . This forces the telescoping tube  2048  and the capture basket back into the reception space for removal. 
       FIG.  57    shows another clot retrieval device  2060 , which is similar to the clot retrieval devices of  FIG.  52 - 56   , and similar numerals are used to describe similar elements. With this embodiment a bumper tube  2048  is used to advance the clot capture basket  2011  over the guidewire. The bumper tube further comprises a rapid exchange feature. The bumper tube comprises a lumen  2045  with a proximal exit port  2061  from which the guidewire exits. A control element  2063  is connected to the proximal end of bumper tube  2048 . The control element  2063  extends proximal of the microcatheter  2041  and out of the patient. The user controls the position of the clot capture basket  2011  using a control handle  2065  at the proximal end  2064  of the control element  2063 . 
       FIG.  58    shows another clot retrieval device  2080 , which is similar to the clot retrieval devices of  FIG.  52 - 57   , and similar numerals are used to describe similar elements. With this embodiment a tether  2042  extends between the collar  2023  of the capture basket  2011  and the distal end  2082  of microcatheter  2041 . The tether  2042  has a relaxed configuration as shown in  FIG.  58   a    and a taut configuration as shown in  FIG.  58   b   . The proximal end of the tether  2042  extends proximally. In one embodiment the tether  2042  is controlled by the user. In another embodiment the proximal end of the tether  2042  is connected to the microcatheter. The tether  2042  allows the capture basket  2011  to move relative to the microcatheter within a certain limit. 
       FIG.  59   a - h    shows the devices as described in  FIG.  52 - 58    and similar numerals are used to describe similar elements.  FIG.  59   a - h    also shows some of the methods of use of the clot retrieval devices described in the earlier drawings. These figures also disclose a clot debonding device  2091 , which may be used in conjunction with the clot retrieval designs described herein. The clot debonding device is designed to assist in the removal of obstructions from a vessel by providing an abutment surface which may be used to appose one side of the obstruction so that a force may be applied to the other side of the obstruction without said force being transmitted to the vessel in which the obstruction is placed. It therefore enables a clot retrieval device or other similar device to more effectively engage and capture clot or other such vessel obstructions. 
     It will be appreciated that such a device also has applications beyond its use with the clot retrieval device described herein. Such a clot debonder may be effectively used to aid the disengagement and removal of vessel obstructions in conjunction with other clot retrieval devices or with thrombectomy devices or aspiration devices. 
       FIG.  59   a    shows a guidewire  2020  with a step  2017  at its distal end. The tip of the guidewire is placed in a vessel (not shown) distal of an occlusive clot (not shown). In  FIG.  59   b    a microcatheter  2041  is advanced over the guidewire  2020  until its tip is also distal of the occlusive clot. A clot retrieval basket  2011  is advanced through the lumen of the microcatheter  2041  in  FIG.  59   c   . In  FIG.  59   c    the clot capture basket  2011  is being advanced using the distal end of a clot debonding device  2091 . The clot debonding device  2091  comprises an expandable engagement element  2093  at its distal end. The expandable engagement element  2093  has an expanded configuration for engaging with a clot and debonding the clot and a collapsed state for delivery through a microcatheter. The expandable engagement element  2093  comprises a number of struts or wire segments  2094 . In one embodiment the clot debonding element is cut from a hypo tube and the struts are expanded to the desired expanded shape and heat treated to remember that shape. Preferably the expandable engagement element  2093  is made from a shape memory alloy, a super elastic alloy. In one embodiment the expandable engagement element  2093  is made of Nitinol. The clot debonding device  2091  comprises a lumen extending from its distal end. The expandable engagement element  2093  comprises a channel or a lumen in both the expanded and collapsed states. In one embodiment the struts or wires of the expandable engagement element  2093  assume a collapsed state which maintains a channel (or lumen) over the distal end of the expandable engagement element  2093 . In another embodiment the expandable engagement element  2093  comprises a collar  2095  and said collar comprises a lumen. 
     The clot debonding device  2091  further comprises a proximal shaft  2096 . The proximal shaft  2096  is connected to the expandable engagement element  2093  and facilitates advancing and withdrawing the expandable engagement element  2091 . In one embodiment the proximal shaft is connected directly to the expandable engagement element  2093 . In another embodiment the proximal shaft  2096  is connected to the collar  2095  which in turn is connected to the expandable engagement element  2093 . In one embodiment the expandable engagement element is integral with the collar  2095 . In another embodiment the expandable engagement element is integral with the proximal shaft  2096 . The proximal shaft  2096  comprises a lumen  2099  which is connected with the lumen or channel of the expandable engagement element and extends proximally to an exit port  2100 . In  FIG.  59    the exit port is shown at the proximal end of the shaft  2096 . However, it will be appreciated that the exit port could be distal of the proximal end of the shaft  2096 . The exit port may be towards the distal end of the shaft  2096 . In one embodiment the exit port comprises an opening in the sidewall of the shaft. In another embodiment the shaft  2096  comprises a construction of at least two elements. The distal element comprises a tubing with a lumen and the proximal end comprises a connector element to connect the user with the distal lumen. 
     In one embodiment (not shown) the clot capture basket is advanced with a bumper tube which is removed upon deployment. When the clot capture basket  2090  is deployed distal of the occlusive clot, then the clot debonding device is advanced over the proximal section of the guidewire  2020  and through the lumen of the microcatheter  2041  and it is deployed proximal of the occlusive clot. With this embodiment the rest of the procedure is as described in  FIG.  59   a   - 59   h.    
     The clot debonding device  2091  comprises an engagement surface. The engagement surface is configured to engage with a clot and comprises an expanded state and a collapsed state. The engagement surface is configured to achieve a low profile in the collapsed state and it is further configured to be highly trackable such that it can easily navigate the pathway to tortuous neurovascular vessels. In one embodiment the engagement surface comprises a substantially tubular structure for advancement through the vasculature in the collapsed state. Preferably in the collapsed state the tubular structure comprises a short tubular structure. The engagement surface in one embodiment comprises a cylindrical surface in the collapsed state. 
     In the expanded state the engagement surface is preferably configured for the transmission of force or pressure to the clot. The engagement surface may comprise an annular surface. With this embodiment the engagement surface has an outer diameter and an inner diameter. In one embodiment the outer diameter is sized to be similar to the diameter of the vessel or to the diameter of the clot and the inner diameter is similar in diameter to the dimensions of the guidewire  2020 . 
     In one embodiment the engagement surface comprises a flared surface. In another embodiment the engagement surface comprises a plurality of struts said struts configured to apply pressure to the clot over a substantial portion of the cross-section of the vessel. In one embodiment the engagement surface of the clot debonding device is configured to apply an axial displacement to the entire body of the clot. Preferably the engagement surface of the clot debonding device is configured to displace the clot without fragmenting the clot. 
     In one embodiment the engagement surface comprises a plurality of elongate struts. In the delivery configuration, the elongate struts are substantially aligned with the axis of the vessel, while in the expanded configuration the struts project radially outward from the axis of the vessel. In one embodiment the struts are connected to each other. In one embodiment the struts of the engagement surface comprises an outer ring member and a plurality of radial struts connected to said outer ring member. In another embodiment the strut arrangement of the engagement surface comprises a plurality of cells. In another embodiment the engagement surface comprises an outer ring member and an inner ring member. 
     The inner ring member may be connected to or separate of the outer ring member. In one embodiment the outer ring member is connected to the collar  2095  by a plurality of radial struts. In one embodiment the outer ring member comprises a plurality of zig zag strut elements. In one embodiment the struts are cut from a tube and the tube comprises an “as cut” configuration and an expanded configuration 
     In another embodiment the engagement surface comprises a plurality of wires. The wires comprise a collapsed state and an expanded state, and in the collapsed delivery state the wires are substantially aligned with the axis of the vessel. In the expanded state, the wires project radially outwardly of the axis of the clot debonding device. In this or in any of the other embodiments the engagement surface may expand concentrically about its axis, or may take up an eccentric configuration. 
       FIG.  59   d    shows the clot capture basket  2090  in its deployed state distal of the occlusive clot. The deployment is effected by advancing the clot debonding device  2091 . The expandable engagement element  2093  abuts the collar  2023  of the basket  2090  and deploys the basket  2090 . The expandable engagement element  2093  remains in the collapsed state at the distal end of the microcatheter  2041 . The microcatheter  2041  is withdrawn until its distal end is proximal of the occlusive clot. 
     With reference to  FIG.  59   e   , the system further comprises a tether  2092  which limits the movement of the clot retrieval basket relative to either the microcatheter  2041  or the clot debonding device  2091 . In the embodiment shown the tether  2092  is attached to the clot debonding device  2091 . As the microcatheter  2041  is withdrawn, the distance between the clot engagement device and the microcatheter  2041  increases until all the slack in the tether  2092  is removed. 
     With reference to  FIG.  59   f   , the tip of the microcatheter is proximal of the occlusive clot, the basket  2090  is deployed distal of the clot and the expandable engagement element  2093  is deployed. This is achieved by advancing the proximal shaft  2096  relative to the microcatheter  2041 . Upon deployment, the struts or wires  2094  of the expandable engagement element  2093  expanded to their remembered expanded state. The guidewire is now moved proximally until the step engages with the clot capture basket  2090  and then both the basket  2090  and guidewire  2020  move proximally until the basket frame  2012  engages with the distal side of the occlusive clot. At this point, the clot debonding device is advanced until the expanded struts  2094  engage with the proximal side of the occlusive clot. With the occlusive clot engaged at both ends, the clot debonding device is advanced while holding the capture basket  2090  steadfast. This breaks the bonds between the clot and the vessel without applying any force to the distal vessels. This arrangement ensures that most of the forces of clot debonding are contained in the segment of the vessel where the clot is adherent. This is usually a segment of a few millimeters and the forces applied are shear forces rather than tensile forces. It may be necessary to adjust the position of the basket  2090  during the debonding step to continue to keep vessel tensile forces very low. 
     It will be appreciated that in order to remove an occlusive clot from a vessel that two sets of forces need to be dealt with. Firstly there is a blood pressure drop that lodges the clot in the vessel. More importantly, the presence of an initial clot results in platelet activation and inflammation at the site. During the inflammatory response, a complex series of reactions are occurring, including the cross linking of blood soluble fibrinogen into fibrin (a blood insoluble macromolecule that is the main component of clot) and the formation of platelet bridges. These reactions result in the progressive formation of chemical bonds between the clot and the vessel wall. Over time the clot becomes more rigidly fixed or bonded at the site of occlusion. In order to break these bonds, a force needs to be applied and as the inflammation process progresses, these bonds become more difficult to break. Furthermore, where a mechanical force is applied to the clot there is automatically a reaction force which is equal in size but acting in the opposite direction. With conventional devices, this force is absorbed by the vessel. It is an object of this invention to prevent significant force being applied to the vessel during clot debonding. 
     In another embodiment the clot debonding device  2091  is deployed in the clot and a first portion of the clot is debonded from the vessel wall. It will be appreciated that this step could be repeated until all the clot has been debonded and captured in the clot capture basket  2090 . 
     In an alternative method, both the clot capture basket  2090  and the clot debonding device  2091  are both engaged with the occlusive clot as described above. Then the clot capture basket  2090  is pulled proximally while the clot debonding device is held steadfast. Whichever method is employed, one element (either the clot debonding device, or the clot capture basket) is held steadfast and this element absorbs the reaction forces of clot debonding and thus prevents force being transmitted to the vessel. 
     With reference to  FIG.  59   g   , after the clot has been debonded and captured in the clot capture basket  2090 , the clot debonding device  2091  can be collapsed. This is achieved by pulling the device proximally such that the microcatheter tip collapses the struts  2094  of the expandable engagement element  2093 . As the clot debonding device  2091  is pulled proximally, the tether  2092  becomes taut and the clot capture basket is also drawn proximally. 
     In  FIG.  59   h    the clot debonding device is withdrawn to the point where at least a portion of the frame  2012  of the clot capture basket  2090  is inside the distal end of the microcatheter  2041 . The clot debonding device  2091  and the clot capture basket  2090  can be withdrawn from the patient at this point. Because of the tether between the clot debonding device  2091  and the capture basket  2090 , the clot capture basket  2090  can be removed without removing the guidewire  2020 . The guidewire  2020  is left behind (not shown) for a final angiogram before also being removed if no further intervention is required. 
       FIGS.  60   a - b    show end views of the clot debonding devices of this invention. The clot debonding element  2110  of  FIG.  60   a    comprises a lumen  2113  sized to accommodate a guidewire, a plurality of struts or wires  2111  which have an expanded state and a collapsed state, and a tubular element  2095 . In the expanded state, the struts or wires  2095  project at least partially radially outward with respect to the tubular member. In the collapsed state, the struts or wires  2095  assume a somewhat tubular configuration when collapsed inside a microcatheter. In the collapsed state, the struts or wires are substantially aligned with the longitudinal axis of the microcatheter and comprise a channel or lumen that can accommodate a guidewire. The pattern of the expandable portion  2112  can be varied greatly. In the figures, shown two patterns are shown. However it will be appreciated that a myriad of other patterns are possible. These patterns may comprise some of the following elements: Single struts, bifurcated struts, bifurcated wires, struts or wires with curved segments, curved struts or wires with points of inflection, struts or wires connected with tethers, struts or wires that are configured to create a closed cell, a combination of at least one open and one closed cell, closed cells with multiple curved segments, struts or wires configured to create a cell with multiple curved segments, struts or wires configured to create a planar cell, and/or struts or wires configured to create a non-planar cell. 
     The pattern of the clot debonding element  2110  of  FIG.  60   a    has overlapping wires. The use of crossing wires provides for better engagement with the clot. In this case, the wires overlap to achieve the cross. However where the struts are cut from a hypotube, junctions can be created without the need to cross the wires, as shown in the pattern in  FIGS.  62   a   - c.    
       FIG.  60   b    shows a pattern with no cross overs. This pattern may be manufactured from a hypotube. In the fully expanded state, the clot debonder may comprise an outer rim  2116 . With the embodiment shown in  FIGS.  60   a  and  60   b   , the outer rim  2116  comprises a plurality of curved segments. Each pair of radially projecting struts  2095  meet at their distal end and this region is characterized in that it comprises a curved atraumatic region. This curved region is preferably curved in the circumferential direction. 
       FIGS.  61     a - c  show another clot debonder pattern  900  which features multiple longitudinal slots  902  which enable the distal end of tubular element  901  to expand radially outward to create an abutment surface as shown in side view in  FIG.  61   b    and in end view in  FIG.  61   c   . Tubular element  901  is preferentially cylindrical, and may be made from either a metallic or polymeric material, but preferentially metallic, and most preferentially nitinol. 
     In one embodiment the engagement surface comprises an axial strut segment  903 , a curved strut segment  904  and a radial strut segment  905 . With this embodiment the engagement surface  906  is connected to a tubular member  901  at its proximal end. The axial strut section  903  defines the expanded configuration the struts of the axial segment  903  are oriented substantially parallel to the axis of the clot debonding device. However the axial segment  903  is preferably extremely short. Immediately distal of the axial segment  903  comprises the curved segment  904 . In the expanded state, this segment is curved such that the struts assume a radial configuration. The radial section  905  preferably comprises most of the engagement surface  906  and provides a high area surface for the transmission of force to the clot. 
     It will be appreciated that the clot debonding element is designed to transmit force over the entire surface of the clot and this ensures that the clot is debonded in one piece. The clot debonder is further configured such that the clot does not snag on its surface and it is further configured to push the clot into the opening of the clot capture basket. 
     The clot debonder engagement surface is configured such that upon withdrawal it disengages from the clot without snagging, or fragmenting the clot and without removing the clot from the capture basket. 
     In another embodiment the engagement surface  906  of  FIG.  61   a - c    comprises a plurality of wires. With this embodiment the engagement surface  906  comprises an axial wire segment  903  which is connected to the collar  2095 . Preferably the connection between the wire and the collar is configured so as to orient the wire parallel to the axis of the clot debonding device. While the connection point with the collar is aligned with the axis of the vessel, the segment of the wire immediately distal of the collar (curved wire segment) comprises a curve in the expanded configuration. The wire is curved so as to orient the wire radially and create an abutment surface. The intermediate segment of the wire is distal of the curved segment and is characterized in that the wire is substantially radial relative to the axis of the clot debonder. This plurality of radial wire segments is configured to deliver and distribute pressure to one face of the clot. The distal segment of the wires comprises a second curved segment  908 . This second curved segment  908  defines an outer rim  2116  of the clot engagement surface  906 . The curved segment  908  also presents an atraumatic surface to the vessel. This second curved segment  908  is curved in the circumferential direction. 
     In one variation the engagement surface  906  comprises a plurality of first wires and a plurality of second wires and said first and second wires are connected at the distal most point. In the embodiment described above said first and second wires may be integral and may comprise a single formed wire. With this embodiment the wire engagement surface comprises a plurality of petal like engagement elements. Each petal comprises a radial clot engagement element and a circumferential clot engagement element. Because the engagement surface  906  comprises radial and circumferential engagement elements force is transmitted to the surface in a manner similar to that of a piston. 
     In another embodiment the struts or wires of the engagement surface  906  comprise an articulation region. With this embodiment the engagement surface  906  assumes the expanded state by an articulation of the struts or wires about the articulation region. 
       FIG.  62   a - e    shows side views of a number of clot debonding devices. These devices could be employed with any of the clot retrieval devices described in  FIG.  52 - 59    or  FIG.  79 - 80   .  FIG.  62   a    shows a colt debonding device  2126  wherein the device comprises an expandable portion  2112 , and a collar  2095  connecting said expandable portion  2112  with the tubular member  2114 . In use, the tubular member  2114  extends from the site of occlusion proximally through the vasculature and extends outside the patient such that it can be manipulated by the user. The tubular member  2114  comprises a lumen  2113  extending over its entire length. 
       FIG.  62   b    shows an alternative configuration of the clot debonding device  2115 . This device also comprises an expandable section  2112 , struts or wires  2111 , a connecting collar  2095  and a tubular member  2114  with exit port  2120 . In this case, the tubular member  2114  is shorter than in  FIG.  62   a   . In use, the tubular member extends from the site of occlusion only partially through the vasculature. In this case, the user controls clot engagement using the connector element  2117  and control element  2118 . The connector element  2117  is fixed to the tubular member  2114  at an attachment point  2119 . The lumen  2113  of the tubular member  2114  is sized to accommodate a guidewire. This embodiment has the advantage of providing single user wire exchange (a rapid exchange feature). 
       FIG.  62   c    shows an alternative configuration which is similar to that of  FIG.  62   b    except that no collar is employed. The tubular member  2114  is connected directly with the expandable section  2112 . The proximal end of tubular member  2114  comprises an exit port  2120  to facilitate rapid exchange delivery.  FIG.  62   d    shows an alternative configuration which is similar to that of  FIG.  62   b    except that no tubular member is employed. In this case the connector element  2117  is connected directly with the collar  2095  at connection point  2136 . 
       FIG.  62   e    shows yet another configuration which is similar to that of  FIG.  62   d    except that no collar is employed. The connector element  2117  is connected directly with the expandable section  2112  at connection point  2136 . 
       FIGS.  63 ,  64  and  65    show three designs of clot debonders that can alter the shape of their distal ends to create an abutment surface to facilitate capture of clot into a clot retrieval device.  FIG.  63   a    shows device  910  with an inflatable distal cuff  911 , which is shown in the inflated state in  FIG.  63   b   . Inflation may be with a liquid, such as saline or contrast media or a mix of the two, or may be with a gas such as carbon dioxide. The inflating media is injected from the proximal end of the device through a lumen (not shown) in the wall of tube  912 . 
       FIG.  64   a    shows device  920  with an expandable section  924 , which is shown in the expanded state in  FIG.  64   b   . The expandable section  924  is formed from wound or braided elements, which form a structure which tends to increase in diameter when compressed, and reduce in diameter when elongated. Expansion of this cuff is effected by advancement of outer member  921  relative to inner member  922 , which is connected to the distal end of the expandable section by means of distal cuff  923 . Retraction of outer member  921  reverses the effect by elongating the expandable section and reducing it to its original diameter. 
       FIG.  65   a - b    show a clot debonder  915  with an expansile distal cuff  916  and inner surface  917  of a similar design to that of device  920 , but in which no actuation is required to effect the expansion. The expansile distal cuff is configured to preferentially adopt the expansile state depicted in  FIG.  65   b   , and is held in the unexpanded state by the constraint provided by the lumen of the catheter  918  (not shown) through which it is advanced to the target site. 
       FIGS.  66  and  67    show two examples of self-expanding clot debonders that expand upon advancement past the end of an outer constraining surface such as that of the lumen of a microcatheter  926 . Debonder  925  is shown in the constrained state in  FIG.  66   a   , in the partially expanded state in  FIG.  66   b   , and in the fully expanded state in end view in  FIG.  66     c.    
       FIGS.  67   a  and  b    show a similar design to  FIG.  66   , wherein an additional element is employed to create a greater abutment surface area and perimeter. 
       FIGS.  68   a - c    show views of another clot debonding device, which could be employed with any of the clot retrieval devices described herein.  FIG.  68   a    shows a side view of the debonder  950  in its unexpanded state.  FIG.  68   b    shows a side view of the debonder in a partially expanded state.  FIG.  68   c    shows an end view of the debonder in its fully expanded state. Device  950  contains multiple expandable portions  952 , created by the addition of a plurality of longitudinal slots  953  to tubular member  954 . An actuating element  951  is attached to the distal end of member  954 , and runs within member  954  from the distal to the proximal end of the device. Retraction of the actuating element applies a compressive force to expandable portions  952  defined by slots  953 . 
     Controlled buckling of areas is facilitated by the presence of crease lines  956 . Tubular member  954  may be configured in a similar manner to member  954  in  FIG.  62   a    or  FIG.  62   c   , such that the debonder is used as an “over the wire” or “rapid exchange” device. In one embodiment the clot debonder lumen  955  is sized so that it may be advanced through a preplaced access microcatheter to the target site. In another embodiment the clot debonder lumen  955  is sized so that it may be backloaded onto a microcatheter prior to insertion of the microcatheter, and can then be advanced over the microcatheter to the target site. 
       FIGS.  69   a  and  69   b    show the clot debonder  950  depicted in  FIG.  68    in use in conjunction with a clot retrieval device  961  and microcatheter  963 .  FIG.  69   b    shows the clot debonder advanced past the end of the microcatheter  963  and the actuator  951  retracted to expand the expandable distal area  952 , which is shown in abutment with clot  962  just prior to retrieval of the clot into the clot retrieval device  961 . 
       FIGS.  70 - 73    show the clot retrieval device of  FIGS.  12  and  13    being used in conjunction with clot retrieval assist device  119 . With this embodiment the clot retrieval device  91  is delivered across the obstructive clot  103  and deployed as previously described. The clot retrieval assist device  119  is delivered over the proximal section of the guidewire  92  until its distal tip is proximal of the obstructive clot  103 . The clot retrieval assist device  119  comprises a catheter  116  with a lumen, an expandable element(s)  117 , wherein the expandable element  117  comprises a wire frame  118  that defines an inner space  132 . The wire frame  118  has a remembered expanded configuration and a collapsed delivery configuration. In one embodiment the wire frame  118  defines an inner space  132  that has a paddle like expanded shape. In another embodiment the wire frame defines a circular inner space  132 . In another embodiment the wire frame  118  defines a kidney shaped inner space  132 . With the clot retrieval assist device  91  proximal of the occlusive clot  103 , the expandable element  117  is deployed. The size of the expanded element  117  is controlled by the degree of deployment. When the expandable element  117  is at least partially deployed, it is advanced against the occlusive clot  103  and forces the clot  103  into the clot retrieval device  91 . In another embodiment the clot retrieval assist device  119  is held stationary with its expandable element  117  in the at least partially expanded state and clot retrieval device  91  is advanced proximally to capture the occlusive clot  103 . 
     In another embodiment the clot retrieval device comprises a frame  94 , a proximal collar  93 , and a distal collar  90 , and two connector elements  99 . The proximal  93  and distal  90  collars are associated with the guidewire  92 , and the connector elements  99  connect the proximal and distal collars to the guidewire  92 . At least one of said proximal and distal collars is slidable relative to the guidewire  92 . 
       FIG.  74    shows an alternative clot retrieval assist device  110 . With this device  110  the expandable element  113  comprises a helical element and is attached to inner shaft  112 . In the delivery configuration, inner shaft  112  is retracted and both the inner shaft and expandable element  113  are housed inside the lumen of delivery catheter  111 . With this embodiment advancement of the clot may be achieved by pushing as described with  FIG.  19    or alternatively by rotation. With the rotation embodiment, the expandable element  113  is either deployed in the body of the occlusive clot  103  or it is advanced in its expanded state until it is in the body of the occlusive clot. The inner shaft is rotated and the helical frame acts like an auger to move the occlusive clot into the clot retrieval device  91 . 
     An alternative clot retrieval assist device  110  is shown in  FIG.  75   . With this device, the expandable element  113  comprises multiple coil elements. An inner helical element  115  and outer element  114  are both connected to inner shaft  112  and rotation of inner shaft  112  rotates both coil elements. 
     Yet another clot retrieval assist device  120  is shown in  FIG.  76   a    and  FIG.  76   b   . The clot retrieval device is delivered over the proximal end  127  of guidewire  92 . The clot retrieval assist device comprises an inner shaft  122 , an expandable element  123  and a delivery catheter (not shown). The expandable element  123  comprises a wire formed into a spiral  124 . The spiral  124  has a gradually increasing diameter. An inner coil of the spiral  124  has a smaller diameter than outer coil  125 . In the expanded configuration, the clot retrieval assist device  120  is advanced distally over the guidewire  92  and the expandable element  113  engages the obstructive clot and forces the clot  100  into the clot retrieval device  91 . Alternatively the clot retrieval device  91  may be advanced proximally while the clot retrieval assist device  120  remains stationary and limits the proximal movement of the clot and thus forces the clot into the clot retrieval device  91 . 
     An alternative clot retrieval system is shown in  FIG.  77   a - b   . The clot retrieval system  2160  comprises a clot capture basket  2154  mounted on a guidewire  2162 . The clot retrieval system  2160  further comprises a clot debonding element  2161  mounted on the guidewire  2162 . The clot capture basket  2163  comprises a frame  2167 , a collar  2168  mounted on the guidewire  2162 , and at least one connector  2180  connecting the collar  2168  with the frame  2164 . The frame  2164  comprises one or more pairs of struts  2166 . In one embodiment the struts comprise a series of net attachment points  2175 . The attachment points  2175  comprise a change in the cross section of the strut  2166  and provide a location for the attachment of a fiber of the net  2163  to the frame  2164 . In one embodiment the attachment point  2175  comprises an eyelet. In another the point of attachment comprises a recess or a nick, or a reduction in the strut dimension. 
     The collar  2168  may be fixedly mounted on the guidewire  2162 . In the embodiment shown the collar  2168  is rotationally mounted on the guidewire  2162 . This is achieved by the use of a proximal stop  2170  and distal stop  2172  mounted on either side of the collar  2168 . The capture net  2163  is connected to the guidewire distal of the collar  2168 . In one embodiment a distal collar  2169  is employed to provide an attachment point between the net  2163  and the guidewire  2162 . 
     The frame  2164  has a collapsed state and an expanded state and in the expanded state (shown) comprises a hoop  2165 . The hoop  2165  allows the frame to effectively engage with the outer bonded surface of the clot. The hoop  2165  is created by constructing that portion of the frame with at least one pairs of struts  2166 . The pairs of struts form segments of a hoop  2165  in the expanded state but lay adjacent each other and parallel to the guidewire in the collapsed state. 
     The clot debonding element  2161  comprises at least one strut  2173 , and it also has an expanded configuration (shown) and a collapsed configuration. In the collapsed state, the struts  2173  of the clot debonding element  2161  lie adjacent and substantially parallel to the guidewire  2162 . The at least one strut  2173  comprises a strut distal end  2178  and a strut proximal end  2177 . At least one of said distal  2178  and proximal  2177  strut ends is slidable relative to the guidewire  2162 . Furthermore, at least one of said distal strut ends  2178  or proximal strut ends  2177  are restricted from rotational motion relative to the guidewire  2162 . The ability of at least one strut end to slide relative to the guidewire provides a first means of allowing the clot debonding element to assume an expanded configuration when not constrained. On the other hand, preventing at least one strut end from rotating relative to the guidewire  2162  allows torque transmitted from the proximal end of the guidewire to be applied to the occlusive clot  2001  and debond said clot from the vessel wall  2002 . 
     In the collapsed state both the basket and the clot debonding element collapse inside a microcatheter  2041  (not shown) in a fashion similar to that described earlier. 
     It will be appreciated that the clot debonding element as described with reference to  FIG.  77    could equally be employed with any of the baskets described in any of the other clot capture basket devices of the invention. 
     With reference to  FIG.  78    there is shown a schematic representation of a vessel with an acute occlusion with a piece of thrombus (clot). The clot may be embolic in origin or it may be thrombotic. Embolic occlusions of cerebral vessels are responsible for between 20% and 35% of all strokes. Embolic strokes are most frequently of cardiogenic origin with carotid and aortic disease also being major contributors. Thrombotic occlusions occur when thrombus forms in the vessel usually in response to underlying vascular disease. Thrombotic occlusions are responsible for between 45% and 50% of all strokes. The acute occlusion  2001  of  FIG.  78   a    is fixed in the vessel  2002  primarily by the forces of blood pressure acting on the proximal side and force fitting it in a tapered vessel  2002  with proximal end  2005  and distal end  2006 . 
     However, the presence of the clot causes an inflammatory response at the site and platelets  2003  in the area are activated ( FIG.  78   b   ). The inflammatory response results in the formation of more thrombus and bonds  2004  start to form between the occlusive thrombus  2001  and the vessel wall  2002 . Over time, the bonding forces between the clot and the vessel wall become more significant and make removal of the clot more difficult.  FIG.  78   c    shows a schematic representation of the occlusive clot  2001  after a time has passed with further thrombus deposited at the site and bonds  2004  formed between the clot  2001  and the vessel wall  2002 . 
       FIG.  79   a   - 1  shows a method of using the devices of this invention.  FIG.  79   a    shows a vessel  2002  with an occlusive clot  2001 . The vessel  2002  has a proximal end  2005  and a distal end. The procedure to treat the occlusion per this invention comprises firstly gaining access to the vasculature. This is carried out by conventional means (the Seldenger technique). A guide catheter is placed in a large vessel proximal of the occlusion (not shown). A procedural guidewire  2020  is advanced through the guide catheter or sheath and is advanced across the occlusive clot  2001  as in  FIG.  79   b   . When the procedural guidewire  2020  is in place, a microcatheter is advanced over the guidewire until the tip of the microcatheter is across the occlusion ( FIG.  79   c   ). As can be seen with reference to  FIG.  79   d   , the procedural guidewire  2020  is now removed thus leaving the microcatheter  2041  in place with its tip  2047  across the occlusion  2001  and an empty lumen prepared for device advancement. With reference to FIG.  79   e , the clot retrieval device  2130  is advanced in its collapsed state through the lumen of the microcatheter  2041  until it is deployed out of the distal end of the microcatheter  2041  along with guidewire  2018 . Upon deployment, the frame  2012  of the clot retrieval device  2130  causes the basket to expand. In the embodiment described in  FIG.  79   e   , the frame  2012  is attached to the guidewire  2018 . The frame  2012  may be fixedly attached to the guidewire  2018  or it may be rotationally attached to the guidewire  2018  or it may be attached such that it has at least some rotational and/or some translational freedom. 
     With reference to  FIG.  79   f   , the microcatheter is withdrawn to the proximal side of the occlusion  2001  when the clot capture device  2130  is deployed. The clot capture device  2130  is manipulated to ensure that it is fully engaged with the vessel wall. The clot debonding device  2091  is now advanced through the lumen of the microcatheter and its distal end is advanced distal of the microcatheter tip  2047 . When the distal portion  2095  of the clot debonding device  2091  exits the microcatheter  2041 , the expandable segment  2112  expands to its remembered expanded state. In the expanded state, the clot debonding device  2091  is advanced until it engages with the proximal portion of the clot  2001  ( FIG.  79   h   ). At this point, the clot capture basket of clot retrieval device  2130  is advanced proximally while the clot debonding device  2091  is held steadfast. This action breaks the bonds between the clot and the vessel and the clot  2001  is forced into the clot capture basket of clot retrieval device  2130 . The clot debonding device  2091  can now be removed. This is achieved by withdrawing it back into the lumen of the microcatheter  2041 . In its expanded state, the clot debonding device has a conical aspect and this facilitates the retrieval of the device  2091  into the microcatheter  2041  ( FIG.  79   i   ). The clot debonding device  2091  can be fully withdrawn through the lumen of the microcatheter or it can be advanced a sufficient distance proximally to allow recovery of the clot capture basket of clot retrieval device  2130 . 
     The clot capture basket recovery steps are described with reference to  FIGS.  79   j  and  79   k   . The microcatheter distal end  2047  is engaged with the frame  2012  of the capture basket  2130 . The guidewire is pulled proximally to force the proximal section of the frame  2012  into the lumen of the microcatheter. As the proximal section of the frame enters the microcatheter the frame struts  2009  collapse and the mouth of the basket closes. This allows the basket to be withdrawn from the vessel without the frame engaging with the vessel wall. The capture basket  2130 , the microcatheter  2041 , and the guidewire  2020  are removed together. The capture basket  2130  scaffolds the clot during removal and prevents fragments from embolizing. The capture basket  2130 , the microcatheter  2041  and the guidewire  2020  are withdrawn through the lumen of the guide catheter or sheath and removed from the patient. The capture basket  2130  allows the clot to deform and change shape as it is pulled into the guide catheter or sheath without allowing particles or fragments to embolize.  FIG.  79   l    shows the vessel  2002  free of the clot and devices. 
       FIG.  80   a - m    shows another method of using the devices of this invention.  FIG.  80   a    shows a vessel  2002  with an occlusive clot  2001 . The vessel  2002  has a proximal end  2005  and a distal end. The procedure to treat the occlusion per this invention comprises firstly gaining access to the vasculature. This is carried out by conventional means (the Seldenger technique). A guide catheter is placed in a large vessel proximal of the occlusion (not shown). A procedural guidewire  2020  is advanced through the guide catheter or sheath and is advanced across the occlusive clot  2001  as in  FIG.  80   b   . When the guidewire  2020  is in place, a microcatheter is advanced over the guidewire until the tip of the microcatheter is across the occlusion ( FIG.  80   c   ). As can be seen with reference to  FIG.  80   d   , the guidewire  2020  is removed, thus leaving the microcatheter  2041  in place with its tip  2047  across the occlusion  2001  and an empty lumen prepared for device advancement. With reference to  FIG.  80   e   , a special clot retrieval guidewire  2142  is advanced through the microcatheter until its distal tip is distal of the microcatheter  2041 . The clot retrieval guidewire  2142  has a stop  2144  at its distal end. The stop  2144  limits the movement of the clot capture basket of clot retrieval device  2140  on the wire and prevents the clot capture device  2140  from sliding off the distal end of the guidewire  2142 . 
     The clot retrieval device  2140  is advanced over the guidewire  2142  in its collapsed state through the lumen of the microcatheter  2041  until it is deployed out of the distal end of the microcatheter  2041 . Upon deployment, the frame  2012  of the clot retrieval device  2140  causes the capture basket to expand. In the embodiment described in  FIG.  80   f   , the capture basket of clot retrieval device  2140  is slidable on the clot capture guidewire  2142 . 
     With reference to  FIG.  80   g   , the microcatheter  2041  is withdrawn to the proximal side of the occlusion  2001  when the clot capture device  2140  is deployed. The clot capture device  2140  may be manipulated to ensure that it is fully engaged with the vessel wall  2002 . The clot debonding device  2091  is now advanced through the lumen of the microcatheter  2041  and its distal end  2095  is advanced distal of the microcatheter tip  2047 . When the distal end  2095  of the clot debonding device  2091  exits the microcatheter  2041 , the expandable segment  2112  expands to its remembered expanded state. In the expanded state, the clot debonding device  2091  is advanced until it engages with the proximal portion of the clot  2001  ( FIG.  80   i   ). At this point, the clot capture guidewire  2142  is advanced proximally until the stop  2144  engages with the capture basket of clot retrieval device  2140 . In one embodiment the stop  2144  engages with either the collar  2023  or the capture basket of clot retrieval device  2140 . In another embodiment the stop  2144  engages with a tube extending from the proximal end of the basket of clot retrieval device  2140 . Further withdrawal of the guidewire  2142  causes the clot capture basket  2140  to advance proximally. The guidewire  2142  is advanced proximally until the capture basket of clot retrieval device  2140  engages with the distal end of the occlusive clot  2001 . With the clot debonding device  2091  held steadfast, the basket is withdrawn proximally until the clot is debonded and enters the basket of clot retrieval device  2140 . 
     The clot debonding device  2091  can now be removed. This is achieved by withdrawing it back into the lumen of the microcatheter  2041 . In its expanded state the clot debonding device has a conical aspect and this facilitates the retrieval of the device  2091  into the microcatheter  2041  ( FIG.  80   j   ). The clot debonding device  2091  can be fully withdrawn through the lumen of the microcatheter or it can be advanced a sufficient distance proximally to allow recovery of the clot capture device  2140 . 
     The clot capture device recovery steps are described with reference to  FIGS.  80   k  to  80   m   . The microcatheter distal end  2047  is engaged with the frame  2012  of the capture basket of clot retrieval device  2140 . The guidewire is pulled proximally to force the proximal section of the frame  2012  into the lumen of the microcatheter  2041 . As the proximal section of the frame enters the microcatheter the frame struts  2009  collapse and the mouth of the basket closes. This allows the basket of clot retrieval device  2140  to be withdrawn from the vessel without the frame  2012  engaging with the vessel wall  2002 . In this embodiment the capture basket of clot retrieval device  2140  and the microcatheter  2041  are removed together. The guidewire  2142  is left in the vessel until the very end of the procedure. This has the advantage of allowing the physician carry out final imaging steps prior to loosing access to the vessel. The capture net  2015  scaffolds the clot during removal and prevents fragments from embolizing. The capture basket of clot retrieval device  2140 , the microcatheter  2041  and the clot  2001  are withdrawn through the lumen of the guide catheter or sheath and removed from the patient. The net allows the clot  2001  to deform and change shape as it is pulled into the guide catheter or sheath without allowing particles or fragments to embolize. 
     It will be appreciated that the various features illustrated and/or described herein may be used as appropriate with any of the devices, methods or systems described. 
     The invention is not limited to the embodiments hereinbefore described which may be varied in detail. 
     The present invention is related to an apparatus and methods for the removal of obstructions in vessels. The present invention is directed towards the treatment of occlusions to blood vessels, especially arterial vessels and more particularly the removal of occlusive clots from cerebral arterial vessels. 
     Accessing cerebral vessels involves the use of a number of commercially available products and conventional procedural steps. Access products such as guidewires, guide catheters and microcatheters are described elsewhere and are regularly used in procedures carried out in cerebral vessels. It is assumed in the descriptions below that these products and methods are employed in conjunction with the device and methods of this invention and do not need to be described in detail. 
     With reference to  FIG.  81   a - b    there is shown a schematic representation of a device  1  for the removal of an obstruction  40  to a vessel  41 . The device  1  comprises a clot debonder device  2  and a clot engagement and capture basket  3 . The clot engagement and capture basket  3  comprises a collapsed configuration for delivery and an expanded configuration for clot engagement and capture. The clot engagement and capture basket  3  is biased towards the expanded configuration. The clot debonder  2  comprises a collapsed state for delivery through the vasculature and an expanded state for engagement with the clot and for disengaging the clot from the vessel wall. 
     The capture basket  3  further comprises a frame  4  and a capture net  5  (as shown in  FIG.  82   a   ). The frame  4  comprises rigid strut members  30  configured to form a hoop. The frame  4  comprises a capture opening  31 . The capture opening  31  comprises a hoop shaped opening, or an elliptical shaped opening, or a circular shaped opening. In one embodiment the frame  4  comprises a metallic frame manufactured from either a wire or a tube. In one embodiment the frame is manufactured from nitinol. The frame  4  may be manufactured from a hypotube. This allows the struts  30  of the frame  4  to be shaped and profiled, including drilling the eyelets  6  in the frame. 
     In one embodiment the frame comprises eyelets  6  for the attachment of a capture net  5 . The eyelets are preferably machined in the frame. Eyelets may be laser drilled in the frame  4 . The frame  4  may be a profiled frame. The frame  4  comprises cable guides  7 . The cable guides  7  comprise holes or guiding features in the frame through which a small high tension cable  21  passes. The cable guides  7  are configured such that the cable  21  (not shown) can slide through the cable guide  7 . 
     The cable guides  7  are configured so as to guide the cable  21  substantially parallel to the axis of the strut  30  over at least a portion of its length. The cable guide  7  is further configured so as to ensure that when the cable  21  is under tension that it is spaced apart from the neutral axis of the strut  30  of the frame  4  over at least a portion of its length. In spacing the cable  21  from the neutral axis the cable  21  imparts a bending moment to the strut  30  when tensioned. This bending moment has the effect of changing the shape of the frame  4 . The bending moment may be used to change the angle of articulation of the frame  4  relative to the axis of the frame support tube  13 . To do this the cable  21  is axially spaced apart from the neutral axis of the frame  4 , with the cable  21  positioned axially proximal of the frame  4 . 
     In another embodiment the bending moment associated with tensioning the cable  21  is used to change the shape of the capture opening  31  of the frame  4 . To do this the cable is spaced apart radially relative to the neutral axis of the frame  4 . It will be appreciated that the cable  21  may be guided so as to articulate the frame over one portion of its length and to change the shape of the frame over another portion of its length. 
     In another embodiment two cables are employed. The first cable is used to control the articulation of the frame  4  with respect to a support element and the second cable is employed to change the shape of the capture opening  31  of the frame  4 . In one embodiment the support element comprises a tubular support  13  extending proximally of the basket  3 . 
     The basket  3  further comprises a connector member  9  that connects the hoop shaped portion of the frame  4  to the support  13 . The connector member  9  may comprise a strut element and in one embodiment the connector member is integral with the hoop shaped portion of the frame  4 . The connector is mounted to the support tube  13  with frame collar  10 . The frame collar  10  is configured to swivel or rotate around support tube  13 . This is achieved by providing proximal and distal abutment surfaces for the collar  10  to engage with. In the embodiment shown the abutment surfaces comprise first fixed collar  11  and second fixed collar  12 . It will be appreciated that other abutment surface configurations are possible including: a flare on the tubular support  13 , a step on the support  13 , a recess on the support  13 , one or more projecting tabs on the support  13  or combinations of these. 
     The connector member  9  is configured to lie substantially parallel to the support tube  13  in the delivery configuration and to lie at an angle to the support tube in the expanded configuration (shown). Where the angle between the connector element  9  and the support tube  13  is shallow, then the axis of the support tube  13  shall be spaced apart from the center of the capture opening  31  and the support tube  13  will be biased towards the wall of the vessel adjacent the clot  40 . In one embodiment the length and angle of the connector element  9  are configured such that the axis of the support tube  13  and the center of the capture opening  31  are substantially coaxial. In another embodiment the length and angle of the connector element  9  are configured such that the axis of the support tube  13  and the center of the capture opening  31  are spaced apart. In another embodiment the length and angle of the connector member  9  are configured such that the axis of the support tube  13  lies between the center of the capture opening  31  and the rim of the capture opening  31 . The rim of the capture opening  31  is defined as the inner most surface of the struts  30  of the capture opening  31 . 
     The net  5  is configured to be highly soft and flexible and is made from a yarn that is exceptionally fine. The fineness of a yarn is defined by its linear density. 
     The linear density, (or linear mass) is a measure of mass per unit of length, and is used to characterize yarns, strings and other similar one-dimensional objects. The SI unit of linear density is the kilogram per meter (kg/m). The linear density, .mu. (sometimes denoted by .λ.), of an object is defined as: 
     
       
         
           
             μ 
             = 
             
               
                 ∂ 
                 m 
               
               
                 ∂ 
                 x 
               
             
           
         
       
     
     where m is the mass, and x is a coordinate along the (one dimensional) object. 
     A common unit of measure of the linear density of a yarn is Dtex. Dtex is defined as the number of decigrams in one kilometer of the yarn. Thus 1 Dtex=1 dg/km=0.1 mg/m. 
     The net is preferably made from an Ultra High Molecular Weight Polyethylene yarn, an aramid yarn, a liquid crystal polymer yarn, an aromatic yarn, a Zylon yarn, a nitinol yarn, a stainless steel yarn, a stainless steel alloy yarn, or a tungsten yarn. It will be appreciated that these yarns may be used in conjunction with any of the baskets and debonders of this invention. The net may also be constructed from a monofilament of any of the above materials. 
     Commercially available UHMWPE yarns include Dyneema by DSM and Spectra BY Honeywell. The aramid yarn is preferably a para-aramid yarn. Commercially available aramid yarns include Kevlar by DuPont, Twaron, and Technora both supplied by Teijin. Commercially available LCPs include Vectra by Ticona, Vectran by Kuraray, and Zydar by Solvay Advanced Polymers. Zylon is commercially available from Toyoba. 
     The Table below outlines the suitable linear densities, preferred linear densities and most preferred linear density for each of the polymer yarns described above. 
     
       
         
           
               
               
               
               
               
             
               
                   
               
               
                 Yarn 
                 Suitable linear 
                 Preferred Linear 
                 More preferred 
                 Most preferred 
               
               
                 Material 
                 density 
                 density 
                 linear density 
                 linear density 
               
               
                   
               
             
            
               
                 UHMWPE 
                 Less than 19 Dtex 
                 Less than 10 Dtex 
                 Less than 7 Dtex 
                 Less than 3 Dtex 
               
               
                   
                   
                   
                 and greater than 
                 and greater than 
               
               
                   
                   
                   
                 1 Dtex 
                 1 Dtex 
               
               
                 Aramid 
                 Less than 22 Dtex 
                 Less than 12 Dtex 
                 Less than 8 Dtex 
                 Less than 4 Dtex 
               
               
                   
                   
                   
                 and greater than 
                 and greater than 
               
               
                   
                   
                   
                 1 Dtex 
                 1 Dtex 
               
               
                 Zylon 
                 Less than 28 Dtex 
                 Less than 15 Dtex 
                 Less than 12 Dtex 
                 Less than 5 Dtex 
               
               
                   
                   
                   
                 and greater than 
                 and greater than 
               
               
                   
                   
                   
                 1 Dtex 
                 1 Dtex 
               
               
                 LCP 
                 Less than 25 Dtex 
                 Less than 14 Dtex 
                 Less than 9 Dtex 
                 Less than 5 Dtex 
               
               
                   
                   
                   
                 and greater than 
                 and greater than 
               
               
                   
                   
                   
                 1 Dtex 
                 1 Dtex 
               
               
                   
               
            
           
         
       
     
     The device shaft is an elongate member that extends in use from a point exterior of the patient to a point adjacent the target clot to be retrieved. Various shaft constructions are disclosed and described herein, including means by which the shaft may be rendered flexible for ease of delivery through tortuous vasculature. It is, however, also desirable that the shaft is not made so flexible that it becomes difficult to deliver a sufficient push force to advance it to the target site. To deal with this apparent conflict, it is desirable that the shaft have a stiffness gradient along its length, with the flexural stiffness of the proximal region of the shaft being greater than that of the distal region. Specifically, it is desirable that the flexural stiffness of the proximal region of the shaft be more than four times greater than that of the region adjacent the clot engaging portions at the distal end of the device. For the purposes of this specification, flexural stiffness is defined as the stiffness measured by a 5% deflection in a three point bend test such as described by ASTM D790. 
     In one embodiment as shown in  FIG.  81   a   , the shaft comprises an assembly of tubular members and an inner cable. The support tube  13  extends in use from the region of the occlusion through the vasculature to the user. The support tube  13  allows the user to advance or retract the basket  3 . The support tube comprises an inner lumen  33  and an exit port  14 . The inner lumen  33  guides the cable  21  from the user interface  70  (not shown) which is exterior of the patient to a region adjacent the frame  4  where the cable  21  exits the lumen  33  via exit port  14 . The exit port  14  is shown at the end of the tube  13 . It will be appreciated that the exit port  14  may also be placed proximal of the distal end of the support tube  13 . In this case the exit port  14  comprises a hole or a slot or a skive in the wall of the support tube  13 . The support tube  13  is required to track through tortuous anatomy and deliver excellent mechanical force transmission to the treatment region. It is also required to facilitate relative motion between its inner lumen  33  and the pull cable  21 . 
     It is generally recognized that providing good surface finish to metal tubes whose inner diameter is less than 0.010″ is very difficult. Normally metal tubes are formed in a cold drawing process. In order to provide for a smooth and dimensionally accurate inner lumen an inner plug is used during the drawing step. However, with very small inner diameter tubes it is not possible to support a floating plug inside the ID during drawing which results in a less accurate tolerance on the ID and a rougher surface. 
     In one embodiment of the invention the inner surface of the support tube  13  comprises a polished surface. The surface may be polished by injecting polishing slurry through the lumen of the support tube  13  at high pressure. In another embodiment the inner surface of the support tube  13  comprises a low friction liner. In one embodiment the liner is at least partially composed of a fluoropolymer or a polyolefin (PTFE or HDPE or UHMWPE). 
       FIG.  81   b    shows another embodiment of the support tube  13  where the tube comprises a plurality of helical wires  34 . With this embodiment a plurality of small diameter wires  34  are twisted to form a tube  13 . The wires  34  are preferably sized greater than 30 microns and less than 80 microns. More preferably the wires  34  are between 30 microns and 60 microns. Even more preferably the wires  34  are sized between 30 and 60 micrometers. The number of wires  34  and the twist angle can be varied but which ever configuration is used the wires  34  are arranged such that a line of force contact exists between each pair of adjacent wires. This contact force keeps the wires in a tubular configuration and prevents collapse of the structure. It also ensures that the interface between the wires  34  is substantially sealed. 
     In another embodiment, support tube  13  comprises an inner layer of wires and an outer layer of wires  34 . In one embodiment the inner layer and the outer layer have different wire diameters. 
     In another embodiment, support tube  13  comprises a plurality of helical wires  34  comprising non-circular cross-sections. In one embodiment the wires  34  comprise at least one substantially flat surface. In another embodiment the wires  34  comprise an elliptical cross-section. 
     Support tubes comprised of helical wires provide a number of important advantages that are not possible with other technologies. Firstly the inside surface of the tube is as smooth as the outer surface even at diameters of 0.010″ or less. This in combination with the undulating inner surface provides an excellent interface for relative motion between the tube and an inner member such as a core wire or a pull cable or a tether. The mechanical properties of the construction are also excellent since the twisted wire tubes have excellent push properties and good trackability features. 
     The construction of the elongate tube  19  may comprise a plurality of helical wires as described for the support tube  13  above. Although the inner diameter and outer diameter of the elongate tube  19  are larger than the support tube  13  the descriptions, construction details and embodiments of the elongate tube  19  are the same as for the support tube and will not be repeated. 
     The clot debonder  2  comprises an abutment surface  36  and an elongate tube  19 . The abutment surface  36  comprises an engagement frame  16  and engagement yarn  17 . The abutment surface  36  comprises a collapsed state for delivery and an expanded state for abutment with the occlusion. The distal end of the elongate tube  19  comprises a mounting section  18 . The frame  16  and the elongate tube  19  are connected in the mounting section  18 . In one embodiment the mounting section and the frame  16  are integral. This may be achieved by cutting the frame  16  from a metallic tube, such as nitinol, and heat treating it such that the frame is biased towards the expanded configuration. In another embodiment the mounting section  18  comprises a frame attachment  28 . In one embodiment the frame attachment comprises a slot or a recess in the mounting section. The frame  16  comprises at least one projecting strut and said strut is engaged with said slot or recess. The at least one projecting strut may further be welded, glued, laminated or bonded to the mounting section  18 . 
     The clot engagement yarn  17  of the abutment surface  36  comprises very fine yarn that is attached to the frame  16  at fixing points  15  along the frame  16 . The fixing points  15  facilitate the yarn  17  being laced over and back across the opening of the frame  16  so as to create a clot engagement surface (like a tennis racquet). Preferably the yarn  17  has a slight tension in the laced configuration when expanded. This ensures that all segments of the yarn  17  engage with the proximal end of the clot  40  at the same time. It will be appreciated that the yarns will not be tensioned in the collapsed configuration. In one embodiment the fixing points  15  comprise eyelets. The frame  16  is sized such that it is the same size or smaller than the proximal lumen of the vessel. Since the primary function of the debonding element  2  is to provide an abutment surface  36  it is not necessary that the debonding frame  16  be precisely sized to the vessel. The abutment surface  36  needs to be configured to engage with at least a portion of the proximal surface of the clot  40  and provide a reaction force to the forces associated with retracting the basket  3  over the clot  40 . 
     In another embodiment the basket  3  comprises a collapsed state for delivery, a deployed partially expanded state and an activated fully expanded state. In the collapsed state, the two struts  30  of the frame  4  lie parallel to each other and substantially parallel to the axis of the micro-catheter  20  through which they are delivered. In the deployed partially expanded state, the two struts move apart to form a hoop shaped frame. However, the engagement force of the frame  4  is low and the hoop frame  4  makes a shallow angle with the axis of the support tube  13 . When the cable  21  is activated by the user, the hoop frame is articulated to a steeper angle relative to the axis of the support tube and the hoop comes into contact with the wall of the vessel. In this configuration with the cable  21  tensioned, the frame  4  can engage strongly with the clot  40 . The fact that the device is configured to have three configurations as opposed to two brings significant advantages. Firstly it is desired that the device strongly engage the clot such that the vessel van be recanalized rapidly without the basket pulling through the clot, a common problem with current technology. However, where the physician judges that the clot is too firmly bonded to the wall and the risks of debonding the clot are too high it is desirable that the device can be disengaged from the clot and removed. In this situation, a low engagement force deployed configuration is a big advantage as otherwise removal without debonding would be problematic. 
     The basket of  FIG.  81   a    can be used with the following procedural steps: 
     A guide catheter or sheath of between 6 F to 9 F is advanced through the vasculature until the tip of the catheter or sheath is in the carotid artery. 
     A guidewire and microcatheter  20  are advanced through the lumen of the guide catheter and further advanced through the internal carotid and cerebral vasculature until the tip of the microcatheter  20  is adjacent the occlusion  40 . 
     The distal tip of the guidewire is advanced across the occlusion  40 . 
     The microcatheter  20  is advanced over the guidewire until the tip of the microcatheter  20  is across the occlusion  40 . 
     The guidewire is removed from the patient. 
     The device  1  is advanced through the lumen of the microcatheter  20  until the basket  3  emerges from the distal end of the microcatheter  20 . 
     The basket  3  self expands to the partially expanded state. 
     The user activates the cable  21  at the user interface  70  and the basket  3  assumes the fully expanded state. 
     The microcatheter  20  is withdrawn until the tip of the microcatheter  20  is proximal of the occlusion  40 . 
     The debonder  2  is advanced until the debonding frame  16  is distal of the tip of the microcatheter  20 . 
     The debonding frame  16  self expands. 
     The support tube  13  is retracted by the user until the frame  4  of the basket  3  engages with the clot  40 . 
     The debonder  2  is advanced over the support tube  13  until the debonder abutment surface  36  engages with the clot  40 . 
     The basket  3  is retracted while holding the debonder  2  steadfast and the clot  40  is disengaged from the vessel wall. 
     The basket  3  is retracted further and captures the clot. 
     The tether is deactivated and the frame partially collapses. 
     The microcatheter  20 , the device  1  and the clot  40  are removed from the vasculature through the lumen of the guide catheter. 
     In one embodiment the method involves the steps of; disengaging the basket from the occlusion, deactivating the cable, at least partially collapsing the basket, and retracting the basket across the occlusion in the partially collapsed state. 
     It will be noted that the use of an expansion cable allows the frame to be made with finer struts. These finer struts in general provide reduced radial force. However, since the basket is relaxed in the partially expanded state, there is a reduction in the strain required to collapse it fully and this feature further reduces the radial force of the frame when fully collapsed. Both of these features make it possible to deliver a high clot engagement force frame through a small microcatheter. It also makes it easier to retract the partially collapsed frame through an occlusion without causing a vessel dissection. 
       FIG.  82   a    shows another embodiment of the invention. The device  60  is similar to the device of  FIG.  81   a    and  FIG.  81   b    and similar elements carry the same numbers. The device  60  comprises a basket  61  and a clot debonder  2 . The basket  61  comprises a frame  4 , which is metallic and comprises a pair of struts  30  which in the expanded configuration comprise a clot capture opening  63 . Unlike the frame of  FIG.  81   a    and  FIG.  81   b    which was a planar hoop, the frame  4  of basket  61  is a curved hoop. When viewed in end-view, the frame  4  of basket  61  comprises a hoop and said hoop is sized to appose the wall of the vessel in the region of the occlusion. In a side elevation view, the frame comprises a C shaped element with the connector member  9  extending between the frame  4  and the support tube. 
       FIG.  82   a    shows a portion of the net  5  attached to the frame  4 . The net may be a knitted net, a braided net or a weaved net. A pair of cables  21  extend from the user interface  70  through the lumen of the support tube  13  and are attached to the frame at cable attachment points  8 . It will be noted that the cable attachment points  8  are fashioned in the frame  4  between the center of the clot capture opening and the point where the connector member  9  is connected to the frame  4 . With this embodiment the cables  21  pull the frame  4  towards the exit port  14  of the support tube  13 . In so doing, the cables  21  pull the frame  4  into a fully expanded configuration. The cables  21 , when tensioned, add significantly to the force with which the frame  4  engages with the occlusion. However, this increase in engagement force (or engagement resistance) is directional. The frame  4  provides strong engagement when being retracted towards the clot  40  but has reduced resistance when being advanced away from the clot  40 . 
     As with the previous design, the frame  4  may be partially collapsed by deactivating the cable  21 . The frame  4  of basket  61  may be cut from a flat sheet. With this embodiment the frame and connector element may be easily cut in a single pattern. With this method of manufacture no expansion steps are required and the connector is subsequently attached to the collar  10 . 
     In another embodiment of the processing method, the collar  10  is also cut from a flat sheet. With this embodiment the collar  10  is cut as a flat rectangle where the width of the rectangle is equal to the circumference of the collar. The rectangle is then rolled or formed into a collar  10 . The formed or rolled collar  10  may then be welded to itself or heat set to permanently assume the shape of a collar  10 . 
     The flat sheet frame  4  of basket  61  has a collapsed configuration, a partially expanded configuration, and a fully expanded configuration. The collapsed configuration of the frame  4  is as described for  FIG.  81   a    and  FIG.  81   b   . The frame  4  comprises a Nitinol frame and can be heat set to a remembered shape or a biased shape. The partially expanded configuration is the biased shape of the frame  4  of basket  61 . The partially expanded state requires some compressive deformation in order to fully collapse the frame and some expansive deformation in order to fully expand the frame. 
       FIG.  82   b    to  FIG.  82   e    shows a schematic side view of the frame  4  of basket  61  in the partially expanded state and in the fully expanded state. The frame comprises a distal segment  62  and a proximal segment  64 . The cable attachment point  8  separates the distal and proximal segments. When the cable  21  is activated, the proximal frame segment  64  and the connector  9  change shape. The distal segment  62  of the frame  4  does not undergo significant shape change when the cable is activated. However, this segment is displaced by the movement of the proximal segment  64 . 
       FIG.  82   d    shows the frame  4  in the partially expanded state. The frame has a gentle C shaped curve when viewed in side elevation. If viewed in plan view, the capture opening  31  would be generally elliptical or oval in shape. In  FIG.  82   e   , the frame  4  of  FIG.  82   b    is shown in the fully expanded state (with the cable activated). The distal segment  62  of the frame  4  still comprises a gentle C shaped curve in side elevation while the proximal segment  64  and the connector  9  have a smaller radius of curvature.  FIG.  82   c    shows another partially expanded frame  4  where the distal segment has a smaller radius of curvature than the proximal segment. In the fully expanded configuration as shown in  FIG.  82   e   , the radius of curvature of the proximal segment is now similar to that of the distal segment due to the activation of the cable  21 . 
     In another embodiment the proximal segment  64  of the frame  4  and/or the connector  9  comprise areas of articulation. These areas are configured to bend more readily than neighboring segments, and these articulation areas facilitate the shape change in the proximal segment  64  and connector  9  when the cable  21  is tensioned. 
     In one embodiment the cable attachment point is adjacent the neutral axis of the strut  30  of the frame  4 . In another embodiment the cable attachment point is spaced apart from the neutral axis of the strut. With this embodiment, the tension in the pull cable  21  sets up a torque in the strut  30  to which the attachment point  8  is fixed and this assists in changing the shape of the frame  4 . 
     The frame  4  of  FIGS.  82   a  to  82   e    is attached to the support tube  13  as described in  FIG.  81   a    to  FIG.  81   b    and the features of the debonder  2  are also the same as described in  FIG.  81   a    to  FIG.  81     b.    
     The user interface  70  is shown in  FIG.  82   f   . The user interface  70  comprises a handle  24  for control of the basket and a control element  23  to control the position and orientation of the debonder  2 . The user interface  70  of device  60  could be applied to any of the devices of this invention which employ a cable activated basket and a debonder. The handle  24  comprises a thumb wheel  25  and a hand grip  26 . The handle further comprises graduations  65  to guide the user in expanding the basket. The handle  24  is fixed to the proximal end of the support tube  13 . The cable  21  extends from the proximal end of the support tube  13  into the handle  24  where it is mounted to a tension mechanism  66 . The tension mechanism  66  comprises a cable wheel  67  or drum onto which the cable can be wound when being tensioned. The cable wheel  67  is rotated by activating the thumb wheel  25 . The cable  21  can thus be tensioned or relaxed by rotation of the thumb wheel  25  in either a clockwise direction or an anticlockwise direction. It will be appreciated that the cable wheel  67  could also be activated with a sliding mechanism. 
     The control element  23  is fixed to the proximal end  27  of the elongate tube  19  and is configured to allow the user to advance or retract the debonder  2  relative to the basket  61 . The control element is also configured to allow rotation of the elongate tube  19 . It will be appreciated that the elongate tube  19  is moveable and rotatable relative to the support tube  13 . 
     The control element  23  is comprises a locking element such that the control element  23  and the elongate tube  19  can be locked to the support tube  13 . This allows the basket  61  and the clot debonder  2  to be fixed together and can thus advanced together or retracted together or rotated together. In one embodiment the control element  23  comprises a touhy-borst arrangement. In another embodiment the control element  23  comprises a clamp. In either case, the control element  23  can be locked to the support tube  13  by the user and can subsequently be unlocked from the support tube  13  by the user. 
     In another embodiment the control element  23  comprises a luer fitting such that the annular space between the support tube  13  and the elongate tube  19  can be flushed by a physiological fluid like saline. The construction of the support tube  13  and the elongate tube  19  are as described in  FIGS.  82   f   - h.    
     The proximal end of the microcatheter  20  is shown in  FIG.  82   f    with the elongate tube extending through the lumen of the microcatheter. A guide catheter is not shown but it will be appreciated that the microcatheter is inserted through the lumen of the guide catheter and the proximal end of the microcatheter  20  extends out of the proximal hub of the guide catheter (or sheath). The microcatheter hub  22  is shown and allows flushing with standard syringes and luer connectors. 
       FIG.  82   g    shows a close-up view of the support tube  13 , and  FIG.  82   h    shows a longitudinal cross-section of the same tube  13  in which the undulating inner surface  35  can be observed. The combination of the helix angle and the curved cross-section of the wire  13  ensures that the inside surface of the lumen is a smooth undulating surface  35 . The undulating surface  35  provides for an excellent frictional interface with pull cables  21 . In a curved vessel, the pull cable  21  slides over the high points of the undulating surface  35 . The cable therefore has a reduced amount of contact with the surface over its length. Furthermore, because the wires  34  are drawn before being fashioned into a tube, they have a smooth outer surface which also improves the frictional interface. A portion of the outer surface of the wires  34  makes up the inner surface of the tube  13 . The undulating surface reduces the frictional drag and this allows for better control of the articulation of the frame  4  with the cable  21 . 
       FIG.  83   a    shows another device  50  of the invention. The device  50  is similar to devices of  FIG.  81   a - b    and  FIG.  82   a - h    in that the debonder  2  and user interface  70  are the same. In this embodiment the basket  51  comprises a double hoop frame  52 . The double hoop frame comprises a distal hoop  53 , a proximal hoop  54 , an articulating bridge  55  and a connector member  9 . The distal hoop  53  and the proximal hoop  54  are constructed from struts  30  wherein each hoop comprises at least one pair of struts  30 . The distal hoop  53  and the proximal hoop  54  are connected to each other by articulating bridge  55 . The connector member  9  is connected to the support tube  13  as described in  FIG.  81   a - b    and  FIG.  82   a - h   . The cable  21  is attached to an attachment point on the distal hoop  53 . The attachment point  8  is radially opposite the point where the articulating bridge  55  is connected to the distal hoop  53 . The cable  21  extends from the attachment point through the opening of the proximal hoop  54  and through the lumen  33  of the support tube  13  to the cable wheel  57  of the handle  24 . The construction of the attachment point is shown more clearly in  FIG.  83   e   . The cable  21  is attached at attachment point  8 . The attachment point  8  may comprise an eyelet as shown in  FIG.  83   e   . The area adjacent the attachment point  8  is an area that undergoes significant strain in moving to the collapsed configuration.  FIG.  83   e    shows a strain relieving feature adjacent attachment point  8  which is designed to allow the struts  30  of the hoop frame to collapse to a configuration whereby they are substantially parallel while distributing the strains associated with said collapse. 
     In another embodiment the proximal hoop  54  comprises a cable guide  7  (as described previously) and said cable guide directs the path of the cable  21  between the attachment point  8  and the exit port  14  of the support tube  13 . In one embodiment the cable guide  7  is positioned at the base of the proximal hoop  54  diametrically opposite the bridge  55 . In yet another embodiment the cable guide  7  is associated with the connector. 
     The double hoop frame  52  comprises a collapsed delivery configuration, a deployed partially expanded configuration, and a fully expanded configuration. In the collapsed state, the single strut of the connector member  9  and the pair of struts of the proximal hoop  54  and the pair of struts of the distal hoop  53  are connected in series and all lie substantially parallel to the axis of the microcatheter within which they are housed. When deployed from the microcatheter  20 , the pair of struts  30  of the proximal hoop  54  move apart in the center to form an elliptical or hoop shape. Likewise, the struts of the distal hoop move apart to form an ellipse of hoop shaped frame. The connector member  9  expands such that it forms an angle with the axis of the support tube. 
     In the fully expanded configuration, the cable  21  is tensioned and this draws the cable attachment point  8  proximally which causes the articulating bridge  55  to articulate and the frame  52  moves to the expanded configuration (as shown in  FIG.  83   a   ). 
     The bridge  55  connects the proximal hoop  54  and the distal hoop  53  and allows them to articulate with respect to one another. A number of bridge configurations are possible and some variants are shown in  FIG.  83   b    to  FIGS.  83   d  and  83   f   . In  FIG.  83   b   , the bridge  55  comprises a connector strut  56 . The connector strut is sized so as to be a point of flexure as the proximal and distal hoops are articulated relative to each other. The wall thickness of the connector strut may be thinner than that of the struts  30  over at least a portion of its length. The cross sectional area of the connector may be less than the cross-sectional area of a strut  30  of the fame  52 .  FIG.  83   c    shows another variant where by the bridge  55  comprises a pair of strut connectors. With this embodiment the proximal frame hoop and the distal frame hoop are not fully closed as a slight gap exists in the region of the bridge. The two open hoops are connected by two connector struts  56 . The two connector struts are free to move relative to each other.  FIG.  83   d    shows another variant which is almost identical to that described in  FIG.  83   c    except that the two connector struts are tethered together. The tether  57  reduces the movement between the two connectors  56  and this ensures that the hoop shape is always preserved irrespective of the forces of clot engagement and capture. 
       FIGS.  83   g  and  83   h    show two alternative net attachment configurations. In  FIG.  83   g   , the net is attached to distal hoop  53 , while in  FIG.  83   h   , the net is attached to proximal hoop  54 . 
       FIG.  84   a    through to  FIG.  84   e    show another device  100  of the invention. The device  100  comprises a basket  101  and a clot debonder  102 . The basket  101  comprises a frame  103  with a large unobstructed capture opening  113  and a support member  104  connected directly to the rim of the capture opening  113 . The debonder  102  is slidable over the support member  104  and comprises a clot engagement surface  106 . The clot engagement surface  106  comprises radially projecting elements  107  and circumferential filaments  108 . The circumferential filaments  108  are configured to distribute the clot engagement forces between the radially projecting elements. In one embodiment the radially projecting elements  107  comprise struts. In one embodiment the radially projecting struts  107  comprise metal struts. Preferably the metal struts  107  are made from spring steel, a shape memory metal or a super elastic metal such as nitinol. The circumferential filaments  108  may comprise a thin strut, a wire, a fiber, a yarn or a multi-filament yarn. In the embodiment shown in  FIG.  84   c    the filament  108  interconnects the radially projecting struts at the outer diameter. It will be appreciated that the circumferential filaments  108  may interconnect the radially projecting struts  107  at multiple diameters. In so doing, an engagement surface  106  is created that is comprised of a plurality of spaced apart radial elements and a plurality of spaced apart circumferential filaments. The net result is an engagement surface  106  with a spiders web pattern. 
     With reference to  FIG.  84   a   , the basket  101  of the clot removal device  100  is shown. The basket  101  is shown with the net  105  removed. The basket  101  comprises a double hoop frame  103  which is similar to the frame  52  of  FIG.  83   . However, in this case, the frame  103  does not employ a cable to effect deployment. The frame  103  has an enlarged deployment configuration for engagement with and removal of occlusions, and a collapsed configuration for delivery through the vasculature, and the frame is biased towards the deployed configuration. 
     The frame  103  is shown in the collapsed configuration in  FIG.  84   b   . In this case the frame  103  is collapsed inside the lumen of a microcatheter  112 . The two struts  117  of the proximal hoop  116  lie substantially parallel to one another in the collapsed state. Likewise the two struts  117  of the distal hoop  115  lie substantially parallel to one another in the collapsed state. 
     The frame  103  further comprises a bridge section  114  which interconnects the two hoops of the frame  103 . The bridge section  114  is configured to articulate as the frame  103  moves between the collapsed configuration and the expanded configuration. In this case the bridge  114  needs to be sufficiently strong to expand the frame  103  and thus the bridge is preferably a strut or a plurality of struts. 
       FIG.  84   c    shows the debonder  102  separated from the basket  101 . The debonder  102  comprises a collapsed configuration for delivery through a microcatheter  112  and an expanded configuration for engagement with an occlusion  40 . The debonder is shown in the expanded configuration with the struts  107  projecting radially outward over a portion of their length. The proximal portion of the struts  107  lie substantially parallel to the axis of the debonder tube  110 . In the collapsed configuration, the radially projecting section of the struts  107  are collapsed such that they lie substantially parallel to the axis of the debonder tube  110 . In this collapsed state, the debonder  102  may be advanced through the lumen of a low profile microcatheter. 
       FIG.  84   d    shows the debonder mounted on the support member with both the basket  101  and the engagement surface  106  of the debonder  102  in the expanded configuration. The device  100  is shown projecting from the lumen of a microcatheter  112 . This configuration corresponds to the device configuration just prior to the step of debonding the clot from the vessel wall.  FIG.  84   e    shows the device  100  in the same configuration but this time in a vessel with the basket  101  and debonder  102  deployed either side of clot  40 . 
     A number of different frame designs are shown in  FIGS.  85   a  to  94   g   . It will be appreciated that these frames could be employed with any of the baskets in this invention. 
       FIG.  85   a    shows an isometric view and  FIG.  85   b    shows an end view of frame  150 . Frame  150  comprises a clot engagement ring  156 , a pair of connector elements  152  and a collar  151 . The clot engagement ring  156  is shown in the expanded state and comprises four struts  153 . The four struts  153  are arranged to form a hoop  156  in the expanded state. The hoop is configured to engage with an occlusive clot and to disengage the clot from the wall of the vessel. The clot engagement ring  156  further comprises articulation points  154  at the intersections of the four struts  153 . These articulation points  154  allow the frame  150  to move between the collapsed and expanded states. The connector elements  152  ensure the frame is stable in the expanded state. 
       FIG.  86   a    shows an isometric view and  FIG.  86   b    shows an end view of frame  210 . Frame  210  comprises a hoop section  165 , and a collar  151 . The hoop section  165  of the frame  210  comprises struts  164  and the hoop section  165  is sized such that it is in contact with substantially the entire circumference of the vessel when deployed. The hoop section  165  of the frame  210  is sized so it will engage the clot at or adjacent to the interface between the clot and the vessel wall. In so doing the hoop section  165  of the frame  210  will be effective in peeling or delaminating the clot from the vessel wall. The hoop section  165  of the frame  210  comprises a large unobstructed capture opening  161  which allows disengaged obstruction to enter the basket without resistance. The frame  160  further comprises a collar  151 . The collar  151  facilitates the mounting of the frame  160  on an elongate member such as a support member  104  or a support tube  13  of a basket assembly. 
       FIG.  87   a    shows an isometric view and  FIG.  87   b    shows an end view of frame  160 . This frame  160  is similar to the frame  210  in  FIG.  86   , except that it has an articulating support. The frame comprises a hoop section  165 , an articulating support  162  that is attached to hoop section  165  at hinge  163 , and a collar  151 . The articulating support  162  is integral with the hoop section  165  of frame  160  and provides support to the hoop section  165  of frame  160 . In the expanded state, the articulating support  162  engages with the wall of the vessel and prevents the collapse of the hoop section  165  as it engages with the obstruction. 
       FIGS.  88   a  and  88   b    shows another frame  170  which is similar to the frame  160  of  FIG.  87   a - b   . In this case, the frame comprises a hoop section  165 , an articulating support  162 , and a support wire  171 . The hoop section  165  and the articulating support are as described in  FIG.  87   . The support wire  171  may be integral with the hoop section  165  of the frame  170 . In this case, the support wire  171  is configured in the same way as support members or support tubes described with other baskets of the invention. In another embodiment the support wire  171  is fixed to a support member at its proximal end.  FIG.  88   c    shows the frame  170  in the collapsed configuration, with the struts of both the hoop section  165  and the articulating support  162  being substantially parallel. 
       FIG.  89   a    shows an isometric view and  FIG.  89   b    an end view of frame assembly  180  which is composed of a frame  181 , an expansion cable  184  and a bumper tube  183 . The frame  181  comprises a proximal hoop  190  and a distal hoop  191  and a bridge element  187  connecting the two hoops. The frame further comprises a cable attachment  188  on the distal hoop  191  and a cable guide  189  on the proximal hoop  190 . The cable guide  189  comprises an abutment surface  192  on its proximal side. In one embodiment the frame  181  has a collapsed state for delivery and an expanded state for clot engagement, and the frame  181  is biased towards the expanded configuration. With this embodiment the cable  184  serves to purpose of reinforcing the frame  181  in the expanded configuration, such that it provides strong resistance to collapse and thus good clot engagement. With this embodiment the bridge  187  comprises an articulating element. While the bridge  187  is configured to allow the proximal hoop  190  and distal hoop  191  to articulate through a large angle of displacement, it is a relatively stiff element so as to provide good radial strength to the frame  181  in the expanded state. 
     In another embodiment the bridge  187  comprises a flexible hinge. With this embodiment the frame has three configurations. In the collapsed delivery configuration, the frame sits within the microcatheter. The two struts  185  of the proximal hoop  190  lie substantially parallel to one another in the collapsed state. Likewise, the two struts  185  of the distal hoop  191  lie substantially parallel to one another in the collapsed state. In the deployed configuration, the proximal hoop  190  and the distal hoop  191  expand into a hoop shape but do not articulate. The deployed frame assumes a planar configuration along the axis of the vessel. When the cable  184  is activated, the abutment surface  192  of the cable guide  189  engages with the distal abutment  182  of the bumper tube  183 . Further activation of the tether causes the cable attachment point  188  to move towards the cable guide  189  and this is facilitated by the hinge  187  connecting the proximal hoop  190  to the distal hoop  191 . By controlling the displacement of the cable, the size of the expanded frame can be adjusted by the user. The frame can be expanded such that it is in interference with the walls of the vessel, or it can be expanded such that it is closely sized to the lumen of the vessel or it can be undersized relative to the vessel. This one size fits all feature is a significant advantage of this embodiment. 
     In the final device configuration, the frame assembly has a net attached to the frame and a debonder mounted over the bumper tube  183 . The net may be attached to either the proximal hoop  190  or the distal hoop  191 . Where the net is attached to the proximal hoop  190  the net must pass the struts of the distal hoop  191 . In one embodiment the net passes over the distal hoop  191  and is attached to the proximal hoop  190 . With this embodiment the collapsing and expanding of the frame requires the distal hoop to slide inside the net. 
     In another embodiment the net passes through the opening of the distal hoop  191  and is attached to the proximal hoop  190 . With this embodiment the net slides through the mouth of the distal frame  191  during deployment or collapse of the frame  181 . 
     It will be appreciated that any of the clot debonders disclosed in this invention could be employed in conjunction with the frames or frame assemblies described in  FIG.  85    to  FIG.  94   . 
       FIG.  90   a    shows an isometric view and  FIG.  90   b    an end view of another frame assembly  200 , which is similar to the frame assembly  180  in  FIGS.  89   a  and  89   b   . In this case, the frame assembly  200  is composed of a frame  201 , an expansion cable  203 , and a support member  202 . The frame  201  comprises a proximal hoop  208 , a distal hoop  209 , and a bridge element  207  connecting the two hoops. The frame  201  further comprises a cable attachment  206  on the distal hoop  209 . The cable  203  extends from the cable attachment  206  parallel to the support member  202  back to the user interface (not shown). The support member  202  comprises an elongate member and is fixed to the frame  201  at its distal end. In one embodiment the frame  201  has a collapsed state for delivery and an expanded state for clot engagement, and the frame  201  is biased towards the expanded configuration. With this embodiment the cable  203  serves to purpose of reinforcing the frame  201  in the expanded configuration such that it provides strong resistance to collapse and thus good clot engagement. With this embodiment the bridge  207  comprises an articulating element. While the bridge  207  is configured to allow the proximal hoop  208  and distal hoop  209  to articulate through a large angle of displacement, it is a relatively stiff element so as to provide good radial strength to the frame  201  in the expanded state. 
     In another embodiment the bridge  207  comprises a flexible hinge. In one embodiment the flexible hinge comprise a tether. With the flexible hinge embodiment the frame has three configurations as were described in  FIG.  89    above. 
       FIG.  91   a    shows an isometric view and  FIG.  91   b    an end view of another frame assembly  220 . In this case the frame assembly comprises a hoop frame  221 , an expansion strut  222 , a cable  223  and a support member  224 . The hoop frame  221  comprises a pair of struts  225  and a capture opening  226 . The expansion strut  222  is connected to the frame  221  at one end  228  and comprises a vessel wall engagement section  227  at the other end. The vessel wall engagement  227  engages the vessel wall and provides support to the frame  221  in the expanded state. In order to avoid trauma to the vessel, the vessel wall engagement  227  comprises an engagement surface. Preferably the engagement surface is soft. Preferably the engagement surface engages the vessel wall over a segment of the vessel wall. The expansion strut  222  further comprises a cable attachment  229  where expansion cable  223  is attached. Expansion cable  223  and support member  224  extend proximally to the user interface (which is described elsewhere in this specification). 
     Another frame assembly  240  is shown in  FIG.  92   , which could be incorporated into any of the baskets of the devices of the invention. The frame assembly  240  is similar to the frame assembly described in  FIG.  81    and  FIG.  82    and it will be appreciated that the frame assembly  240  could be incorporated with the clot debonder  2  and user interface  70  of  FIG.  81    and  FIG.  82   . The frame assembly  240  comprises an elastic, a shape memory or a super elastic frame and has a remembered at least partially expanded state and a deformed state. In the deformed state, the frame assembly is strained by an external restraining element. In one embodiment the deformed state comprises a collapsed delivery state. In one embodiment the restraining element comprises a microcatheter. In another embodiment the restraining element comprises a tether which ties the frame assembly  240  in the restrained delivery configuration. The frame assembly  240  comprises a frame  241 , a vessel engagement strut  242 , a support member  246  and a pull tether  245 . The frame  241  comprises a capture ring  247 . The capture ring  247  comprises a vessel opposing ring in its expanded state. Said capture ring  247  comprises a first ring segment  248  and a second ring segment  249 . Said first ring segment  248  and said second ring  249  are connected by two articulation regions  243  and  244 . Said first ring segment  248  is articulated relative to said second ring segment  249  by activation of the pull tether  245 . 
     In one embodiment the frame assembly  240  comprises cable guides  7  as described in  FIG.  81   . In one embodiment the pull tether  245  runs substantially parallel to capture ring  247  over at least a portion of its length. The pull tether  245  is spaced apart from the neutral axis of the capture ring  247  of the frame  241  over at least a portion of its length. The spacing of the pull tether from the neutral axis of the capture ring  247  imparts a bending moment to the capture ring  247  when the pull tether  245  is tensioned. This bending moment causes the first ring segment  248  to articulate relative to the second ring segment  249  about articulation region  243  and  244 . In another embodiment the pull tether  245  causes the capture ring  247  to articulate relative to the support member  246 . The vessel engagement strut  242  comprises a curved segment and the ends of said segment are connected to the capture ring  247 . Preferably the vessel engagement strut  242  is integral with the capture ring  247 . The vessel engagement strut  242  engages with the vessel wall and prevents the capture ring  247  from collapsing under the forces of clot engagement. The support member  246  is connected to the frame  241  and extends proximally to the user interface  70 . The pull tether  245  extends proximally from the frame to the user interface  70  from where it is activated or deactivated as previously described. In one embodiment the pull tether  245  extends parallel to the support member  246  over a substantial portion of its length. In another embodiment the support member comprises a tubular member over at least a portion of its length. In one embodiment the tubular segment of the support member comprises exit port and the tether extends through the lumen of the tubular segment and exits the tubular segment via said exit port. 
       FIG.  93    shows another frame assembly  260  which is similar to the frame assembly of  FIG.  81   . However in this case the frame assembly comprises a frame  261  and a support member  262 . The frame  261  comprises a one piece frame which comprises a capture ring  263 , a support strut  264 , a connector strut  265  and a collar  266 . The frame  261  is preferably cut from a tube. In one embodiment the frame  261  is laser cut from a hypo tube. The engagement of the support strut  264  with the wall of the vessel prevents the collapse of the frame when the clot engagement ring  263  engages with the occlusion  40 . The support strut  264  is connected to the engagement ring  263  at connection points  267 . The connection points  267  comprise regions of bending when the frame  261  is collapsed for delivery. The engagement ring  263  must collapse in concert with the support strut  264  and the strains of collapse are absorbed in the bending regions  268 . The frame  261  further comprises net attachment points  269  on both the ring  263  and the support strut  264 . In one embodiment the attachment points  269  comprise eyelets in the struts of the frame  261 . The connector strut  265  is configured to connect the engagement ring  263  to the support member  262 . The connector strut  265  may flex such that the axis of the support member  262  may move apart from or towards the axis of the vessel while the ring  263  is engaged with the wall of the vessel. The collar  266  is fixed to the support member  262  and holds the frame  261  steadfast relative to the support member  262 . 
     With reference to  FIG.  94   a    to  FIG.  94   f    there is shown basket assembly  300  including frame assembly  280 . The basket assembly  300  has a collapsed state for delivery as shown in  FIG.  94   g   , a partially expanded unconstrained configuration as shown in  FIG.  94   a    and  FIG.  94   b    and a fully expanded state as shown in  FIG.  94   c    and  FIG.  94   f   . The basket assembly  300  comprises a frame assembly  280  and a net  287 . The basket assembly may be integrated with any of the clot debonder assemblies and user interfaces of the invention to create a device for the recanalization of vascular occlusions especially acute stroke occlusions. 
     The frame assembly comprises a frame  281 , a control tube  282 , and a pull cable  288 . The frame  281  comprises an engagement ring  283 , and a hinged support  284 . The hinged support  284  is connected to the engagement ring  283  with hinges  285 . The pull cable is attached to the hinged support  284  at an attachment junction  289 . The attachment junction lies substantially midway between the hinges  285 . The pull cable  288  extends from the attachment junction through cable guide  290  and further extends through the lumen of control tube  282 . Preferably the cable  288  is activated with the assistance of a control mechanism at the user interface  70 . 
     With reference to  FIG.  94   a    and  FIG.  94   b   , the frame assembly  280  is shown in the partially expanded state. The frame assembly  280  assumes the partially expanded state when the frame assembly is deployed from the microcatheter  293  with the pull cable  288  is deactivated. The pull cable  288  is deactivated when the distal abutment surface  292  of the control tube  282  is not engaged with the cable guide abutment  291 . In this configuration, the engagement ring  283  is expanded as is the hinged support  284  with the hinged support  284  being substantially parallel to engagement ring  283 . In one embodiment the engagement ring  283  and the support  284  lie substantially parallel to the axis of the vessel in the partially expanded state. In another embodiment the engagement ring  283  and the support  284  lie substantially parallel to the axis of the control tube  282  in the partially expanded state.  FIG.  94   c    shows the frame assembly  280  in the expanded configuration. In this configuration, the pull cable  288  is activated and this causes the abutment  292  of the control tube  282  to engage with the cable guide abutment  291  of the cable guide  290 . Activation of the pull cable  288  further causes the hinged support  284  to articulate relative to the engagement ring  283 . The articulation of the support  284  causes the ring to articulate relative to the control tube  282  and the user may control the degree of articulation by the displacement of the pull cable  288 . In this way the user may size the mouth of the engagement ring to the size of the occlusion that is to be disengaged and captured. 
     In one embodiment the hinge  285  comprises a pin and eyelet arrangement. In another embodiment the hinge  285  comprises a tether. In another embodiment the hinge  285  comprises an integral hinge. One embodiment of an integral hinge is shown in  FIG.  94   d    and  FIG.  94   e    where the hinge  285  comprises a relief section  286 . The relief section  286  comprises a thinned section of the wall of the support  284 . The relief section  286  allows the support  284  to articulate relative to the engagement ring  283 .  FIG.  94   d    shows a close up view of the hinge  285  when the frame  281  is in the expanded configuration.  FIG.  94   e    shows a close up of the hinge  285  when the frame  281  is in the collapsed or the partially deployed state. 
     In one embodiment the integral hinge  285  is made from an elastic, a super elastic, or a shape memory material and said hinge comprises a biased configuration. In one embodiment the biased configuration comprises the collapsed state. In another embodiment the biased configuration comprises the expanded state. 
       FIG.  94   f    shows a basket assembly incorporating the frame assembly  280  as described above. The basket assembly  300  is shown with the frame  281  in the fully expanded configuration. In the expanded configuration, the hinged support  284  is subtended at an angle relative to the engagement ring  283 . 
       FIG.  94   g    shows the frame assembly  280  in the fully collapsed configuration inside microcatheter  293 . In this configuration, the struts  294  of the engagement ring  283  and the hinged support  284  all lie substantially parallel to the axis of the microcatheter  293 . 
       FIG.  95    shows another basket assembly  320  according to the invention. The basket assembly comprises a frame  321 , a net  322 , an expansion cable  343 , a support member  325 , and an expansion member  328 . The frame comprises an engagement hoop  324 , and a collar  327  connecting said hoop  324  with elongate support member  325 . The frame  321  further comprises cable attachment  326  which facilitates fixing of the cable  343  to the frame  321 . The net  322  comprises a closed end net with openings of 500 micrometers or less configured to prevent captured clot from fragment during removal. The net  322  is attached to the frame  324  at a plurality of connection points around the circumference of the frame  321 . The frame comprises a collapsed configuration for delivery, a first expanded state, and a second expanded state. In the first expanded state, the frame  321  self expands such that the hoop frame  324  comprises a substantially elliptical opening and said hoop frame  324  is at least partially engaged with the vessel wall. In the second expanded state, the expansion member  328  is moved proximally relative to the support member  325  and this brings the cable  343  into a state of tension. The cable  343  provides additional support to the frame  321 . In one embodiment the resistance of the frame to collapse is greater in the second expanded state than the first expanded state. In another embodiment the radial force of the frame is greater in the second expanded state when compared to the first expanded state. 
     The expansion member  328  is slidable relative to the support member  325 . In one embodiment the expansion member is configured such that a debonding assembly can be mounted on its outside diameter. 
       FIG.  96    shows another basket assembly  340  according to the invention. The basket assembly comprises a frame  341 , a net  342 , an expansion cable  343 , and a support member  345 . The frame  341  comprises an engagement hoop  344 , and a collar  347  connecting said hoop  324  with elongate support member  345 . The support member  345  comprises an elongate tube and the pull cable  343  extends from the attachment point  346  through the lumen of said tube to the user interface  70 . The collar  347  is fixed to the support member  345 . In one embodiment the support member  345  comprises a tube and the collar  347  is integral with said tube. The frame  341  further comprises cable attachment  346  which facilitates fixing of the cable  343  to the frame  341 . The net  342  comprises a closed end net with openings of 500 micrometers or less configured to prevent captured clot from fragment during removal. The net  342  is attached to the frame  344  at a plurality of connection points around the circumference of the frame  341 . The frame comprises a collapsed configuration for delivery, a first expanded state and a second expanded state. In the first expanded state, the frame  341  self expands such that the hoop frame  344  comprises a substantially elliptical opening and said hoop frame  344  is at least partially engaged with the vessel wall. In the second expanded state, the cable  343  is pulled proximally relative to the support member  345  and this brings the cable  343  into a state of tension. The cable  343  provides additional support to the frame  341 . In one embodiment the resistance of the frame to collapse is greater in the second expanded state than the first expanded state. In another embodiment the radial force of the frame  341  is greater in the second expanded state when compared to the first expanded state. 
       FIG.  97    shows another basket assembly  360  according to the invention. The basket assembly  360  comprises a frame  361 , a net  362 , an expansion cable  363 , and a support member  365 . The frame  361  comprises an engagement hoop  364 , and a collar  347  connecting said hoop  364  with elongate support member  365 . The support member  365  comprises an elongate tube and the pull cable  363  extends from the attachment point  366  through the lumen of said tube to the user interface  70 . The collar  367  is fixed to the support member  365 . In one embodiment the support member  365  comprises a tube and the collar  347  is integral with said tube. The frame  361  further comprises cable attachment  366  which facilitates fixing of the cable  363  to the frame  361 . The frame  361  further comprises a plurality of cable guides  368 . The cable guides  368  comprise guide elements through which the cables  363  can slide. The cable guides are configured such that the path of the cable is parallel to the neutral axis of the hoop frame  364  over at least a portion of the length of the hoop frame  364 . The support member  365  comprises a lumen and the expansion cable  363  extends through the lumen of the support member  365  to the user interface  70  (not shown). 
     The net  362  comprises a closed end net with openings of 500 micrometers or less configured to prevent captured clot from fragment during removal. The net  362  is attached to the frame  364  at a plurality of connection points around the circumference of the frame  361 . The frame  361  comprises a collapsed configuration for delivery, a first expanded state and a second expanded state. In the first expanded state, the frame  361  self expands such that the hoop frame  364  comprises a substantially elliptical opening and said hoop frame  364  is at least partially engaged with the vessel wall. In the second expanded state, the cable  363  is pulled proximally relative to the support member  365  and this brings the cable  363  into a state of tension. The cable  363  provides additional support to the frame  361 . In one embodiment the resistance of the frame to collapse is greater in the second expanded state than the first expanded state. In another embodiment the radial force of the frame  361  is greater in the second expanded state when compared to the first expanded state. 
       FIGS.  98   a  and  98   b    show a device  400  comprised of a basket assembly  380  and a debonder assembly  401 . The basket assembly  380  is very similar to the basket assembly  360  of  FIG.  97    with the exception that the support member is directly connected to the hoop frame. This eliminates the collar element  347  shown in the previous drawing. The basket assembly  380  functions in exactly the same way as that of basket assembly  360  of  FIG.  97   . The debonder  401  comprises a ring member  402 , a clot engaging surface  403 , and an outer member  404 . The ring member  402  comprises a collapsed delivery configuration as shown in  FIG.  98   b    and an expanded engagement configuration as shown in  FIG.  98   a   . The outer member  404  comprises an elongate tube and is sized to facilitate relative movement with the support member  365  of the basket assembly  380 . In the deployed configuration, the ring member  402  engages with the proximal end of the clot and the ring member  402  comprises an abutment against which the basket is retracted so as to disengage the clot from the wall of the vessel without applying significant tensile forces to the wall of the vessel. 
     The method use of the devices described in  FIG.  95    through to  FIG.  98   b    will be described below with reference to  FIG.  99   a - i   .  FIG.  99   a    shows an occlusive clot  421  in a vessel  420 . The occlusive clot  421  is fixed strongly to the vessel wall  422  of the vessel  420 . A guide catheter is advanced into an upstream vessel of larger diameter. In the case of an occlusion of an anterior vessel of the cerebral circulation, the guide catheter  425  is placed in a carotid artery. The guide catheter  425  is preferably 8 F in diameter or less. More preferably the guide catheter  425  is 7 F in diameter or less. Even more preferably the guide catheter  425  is 6 F in diameter or less. In one embodiment the procedure comprises the step of advancing a transition catheter  426  through the lumen of the guide catheter  425  such that the tip of the transition catheter  426  extends from the distal tip of the guide catheter  425  and the transition catheter  426  is advanced to into a smaller bore vessel than is possible with the guide catheter. In the example above the transition catheter  426  may be advanced into the internal carotid vessel. The tip of the transition catheter  426  may be placed in the cervical section of the internal carotid artery. Catheters  425  and  426  are not shown in  FIGS.  99   a - i   . For the purposes of the remaining descriptions associated with  FIG.  99   a - i    reference to the guide catheter  425  may be interpreted to include the transition catheter  426  or not since the procedure may be conducted with or without the transition catheter  426 . 
     With the guide catheter  425  in place (not shown) a microcatheter  424  is advanced through the lumen of the guide catheter  425  until its distal end is advanced distal of the tip of the microcatheter. The microcatheter  424  is advanced further with the assistance of a guidewire  423  within the lumen of the microcatheter  424  and both instruments are manipulated until the tip of the microcatheter is across the occlusive clot. At this point the guidewire  423  is withdrawn. 
     Referring now to  FIG.  99   b   , the device  430  is advanced through the lumen of the microcatheter  424  with the basket  431  and the debonder  432  in the collapsed configuration until the basket  431  is advanced distal of the tip of the microcatheter  424  with the debonder still restrained in the collapsed configuration. The basket  431  is partially expanded. 
     Referring to  FIG.  99   c   , the microcatheter  424  is withdrawn while holding the basket  431  stationary until the tip of the microcatheter  424  is proximal of the occlusion  421 . The debonder  432  and outer member  438  are deployed proximal of the occlusion  421 . In one embodiment the debonder  432  is deployed by withdrawing the microcatheter proximally while holding the debonder hub  442  (shown in  FIG.  99   d   ) stationary. In another embodiment the debonder  432  is deployed by holding the microcatheter  424  stationary while advancing the debonder assembly  432 . 
     Referring to  FIG.  99   d   , the basket  431  is fully expanded by activating the pull cable  436  with the activator  441  of the handle  440  (shown in  FIG.  99   e   ). In one embodiment the activator  441  comprises a thumbscrew. In another embodiment the cable activator  441  comprises a slider. In yet another embodiment the activator comprises a lever. The cable  436  is tensioned by the user activating the activator  441 . The tension may be transmitted to the cable via a number of mechanisms. In one embodiment the mechanism comprises a rack and pinion mechanism. In another embodiment the mechanism comprises a circular drum onto which the cable  436  is wound. The fully expanded basket is withdrawn proximally until the frame  434  engages with the distal end of the clot. In one embodiment the frame comprises radiopaque elements to facilitate visualization under fluoroscopy. The step of engaging the basket with the distal end of the clot involves sizing the vessel  420  in the region distal of the clot  421 , moving the activator  441  so as to expand the frame  434 , and monitoring the expansion of the frame  434  on fluoroscopy. The debonder  432  is advanced distally until the ring member contacts the proximal end of the clot  421 . The debonder is advanced further to ensure the ring member  437  is fully engaged with the clot. In one embodiment the ring member  437  is deployed in a partially expanded state with the ring member deployed at an angle relative to the support member  435 . With this embodiment when the ring member  437  is further advanced, engagement with the clot causes it to expand to a fully deployed configuration. Preferably the relative angle is greater than 40°. 
       FIG.  99   e    shows the basket  431  and debonder  432  fully engaged with the clot. The basket is withdrawn proximally while holding the debonder steadfast and this action breaks the bonds between the vessel wall and the clot. The debonder forces the clot into the open mouth of the basket as the basket is withdrawn. In another embodiment, as shown in  FIG.  99   f   , the step of debonding the clot  421  from the vessel wall  420  and the step of forcing the clot  421  into the open mouth of the basket  431  comprise advancing the debonder  432  while holding the basket  431  steadfast.  FIG.  99   f    shows the clot  421  almost completely enveloped by the net  433 . The debonder  432  is advanced until the clot  421  is completely enveloped by the basket  431 . In one embodiment the debonder  432  is advanced until the outer member  438  of the debonder  432  abuts the frame  434 . In another embodiment the debonder  432  is configured such that at least a portion of the debonder  432  may enter the mouth of the basket  431 . 
     In one embodiment the basket  431  and clot  421  are removed with the ring member  437  of the debonder  432  occluding the mouth of the basket  431 . With this embodiment the removal steps comprise: 
     Slightly disengaging the debonder  432  from the proximal end of the clot  421  so as to reduce applied pressure. 
     Deactivating the frame  434  and partially collapsing the basket  431  by deactivating the pull cable  436 . 
     Locking the debonder  432  to the support member  435  (thus, locking the debonder  432  to the basket  431 ). 
     Retracting the device  430  and withdrawing the basket  431  and clot  421  through the lumen of the guide catheter  425 . 
     Referring to  FIG.  99   g    to  FIG.  99   i    another embodiment of the steps of removing the basket and clot comprises: 
     Disengaging the ring member  437  from the proximal end of the clot  421 . 
     Retracting the debonder from the vessel segment. 
     Deactivating the activator  441  so as to remove the tension in the cable  436  and at least partially collapsing the basket  431 . 
     Retracting the basket  431  proximally and removing the basket from the vessel segment. 
     Removing the basket  431  through the lumen of the guide catheter  425 . 
     In one embodiment the microcatheter  424 , debonder  432  and basket  431  are removed through the lumen of the guide catheter  425  together. 
     Referring now to  FIG.  100   a    to  FIG.  100   c   , there is shown yet another embodiment of the invention. In this case, a basket assembly  450  comprises a support member  451 , an engagement ring  452 , a pull cable  454 , and a net  455 . The support ring  452  comprises two struts  458  and the net  455  is attached to said struts  458 . The support member  451  comprises a lumen and the pull cable  454  extends through the lumen of the support member  451 . The basket assembly  450  comprises a collapsed delivery configuration as shown in  FIG.  100   a   , an expanded configuration, and an expanded articulated configuration as shown in  FIG.  100   c   . The ring member is comprised of Nitinol and has a remembered expanded configuration. The remembered expanded configuration of the engagement ring  452  comprises a substantially planar hoop and the plane of the hoop is aligned with the axis of the support member  451 . The basket assembly  450  further comprises a junction  456  where the support member  451  and the engagement ring  452  are interconnected. 
     With reference to  FIG.  100   c   , the basket assembly further comprises an articulation region  457  adjacent to the junction  456 . Pulling the pull cable  454  relative to the support member  451  causes the ring member to articulate relative to the support member, and the ring member  452  makes an angle with the support member  451 . In one embodiment the angle is less than 90°. In another embodiment the angle is equal to or greater than 90°. In one embodiment the articulation region  457  is adjacent the junction  456 . In one embodiment the articulation region forms part of the engagement ring  452  adjacent the junction  456 . In another embodiment the junction  456  comprises the articulation region  457 . 
     Yet another embodiment is shown in  FIG.  100   d    to  FIG.  100   f   , where the articulation region  457  forms part of the distal end  459  of the support member  451  adjacent the junction  456 . With this embodiment, activation of the pull cable  454  causes the distal end  459  of the support member  451  to change shape and this results in the engagement ring  452  articulating relative to the proximal end  460  of the support member  451 . The shape change of the distal end  459  of the support member  451  comprises a change from a straight configuration to a curved configuration. The curved segment at the distal end  459  of the support member  451  has the effect of displacing and angulating the ring member  452  relative to the proximal end of the support member  451  and this allows the basket to reach around curved segments. This feature is especially useful at bifurcations where the occlusion needs to be removed from two branches simultaneously. 
       FIG.  100   e    and  FIG.  100   f    show close up views of one embodiment of articulating basket assembly described in  FIG.  100   d   . With this embodiment, the support member  451  comprises a tube and the distal end  459  of said tube comprises a slotted section. The slots  461  in the slotted section are partial slots that extend around a portion of the diameter. In the embodiment the slots  461  are all shown on one side of the tubular member  451 . The side of the tubular member  451  with the slots  461  is more compressible than the side of the tube that possesses no slots. The pull cable is connected to the tubular member distal of the slotted section. In one embodiment the cable  454  is fixed to the support member  451 . In another embodiment the cable  454  is fixed to the junction  456 . In another embodiment the cable  454  is fixed to the ring member  452 . In yet another embodiment the slotted section  459  of the support member  451  comprises an exit port and the cable  454  extends through the exit port and is fixed to the engagement ring  452 . 
     When the pull cable  454  is activated (tensioned), it applies a compressive force on the support member  451 . Since the distal end  459  of the support member  451  has a compressible section, this section compresses under the force. The compression of the distal end  459  comprises the closing of the slots  461  in the tubing and this is shown in  FIG.  100   f   . The compression of the slots  461  causes the distal section of the support member to change shape. In the embodiment shown in  FIG.  100   f   , the deformed shape comprises a curved segment at the distal end  459  of the support member  451 . It will be appreciated that curves of tighter radius can be achieved by increasing the number of slots in the support member. 
     With reference to  FIG.  101   a    and  FIG.  101   b   , another device  480  of the invention is described. The device  480  comprises a basket assembly  481 , and a debonder assembly  482 . The basket assembly  481  comprises a frame  483 , a support member  484 , and a handle  485 . The support member  484  comprises an elongate tube and the frame  483  is fixed to the distal end of the support member  484 . The frame  483  comprises a collapsed configuration for delivery through the vasculature and an expanded configuration. The frame  483  further comprises a clot engagement opening  505 , and in the expanded configuration, the clot engagement opening is sized such that the frame  483  can engage the outer circumference of the clot and such that the clot can be forced through the opening and into the capture net  499 . In the collapsed state, the engagement opening  505  is substantially closed as is shown in  FIG.  101   a   . The frame in the expanded state further comprises an angulation of the frame  483  with respect to the support member  484 . In the collapsed state, the axis of the frame lies substantially parallel to the axis of the support member  484 . For the purposes of  FIG.  101   a - b   , the axis of the frame  483  shall mean a line drawn between the exit port  496  at the distal end of the support member  484  and the attachment point  494  on the frame  483 . In the expanded state, the axis of the frame is subtended at an angle to the axis of the support member. In one embodiment the axis of the frame  483  makes an angle of 30° or greater with the axis of the support member  484 . In another embodiment the axis of the frame  483  makes an angle of 45° or greater with the axis of the support member  484 . In yet another embodiment the axis of the frame  483  makes an angle of 60° or greater with the axis of the support member  484 . In yet another embodiment the axis of the frame  483  makes an angle of 90° or greater with the axis of the support member  484 . 
     The basket assembly  481  further comprises a first cable  492  extending from the handle  485  through the lumen of the support member  484 , exiting the support member  484  at first exit port  496  and attaching to the frame  483  at first cable attachment  494 . The first cable  492 , when tensioned, is responsible for expanding the ring member  490  comprising struts  491 . It will be appreciated that the strut  491  width and thickness dimensions can be adjusted along the length of the strut  491  so as to assist in opening the ring member  490 . The proximal end of the first cable  492  is fixed to an activation mechanism in the handle  485 . In one embodiment the activation mechanism comprises a thumb wheel  486 , and a first spool  487  fixed to the thumbwheel  486 . A portion of the thumbwheel  486  extends through the wall of the handle  485  and allows the user to rotate the thumbwheel  486 . The spool  487  is configured such that rotation of the thumbwheel  486  causes the first cable  492  to be wound onto the spool  487 . The diameter of the first spool  487  controls the rate at which the first cable  492  is wound and thus the rate at which the engagement opening  505  of the ring member  490  is expanded. 
     The basket assembly  481  further comprises a second cable  493  extending from the handle  485  through the lumen of the support member  484 , exiting the support member  484  at the second exit port  497  and attaching to the frame  483  at second cable attachment points  495 . In one embodiment the second cable comprises two cables and the second attachment point comprises two attachment points. The second cable  493 , when tensioned, is responsible for angulating the ring member  490  with respect to the distal end of the support member  484 . The basket assembly  481  comprises an articulation region adjacent the end of the support member  484 . In one embodiment the frame  483  comprises an articulation region adjacent the junction  498  between the frame  483  and the support member  484 . In another embodiment the distal end of the support member  484  comprises an articulation region. The proximal end of the second cable  493  is also fixed to an activation mechanism in the handle  485 . In one embodiment the activation mechanism comprises the thumb wheel  486 , and a second spool  488  fixed to the thumbwheel  486 . The second spool  488  is configured such that rotation of the thumbwheel  486  causes the second cable  493  to be wound onto the spool  488 . The diameter of the second spool  488  controls the rate at which the second cable  493  is wound and thus the rate at which the angulation of the engagement ring  490  is changed with respect to the support member  484 .  FIG.  101   c    shows a representation of the thumbwheel  486  wherein the first spool  487  and the second spool  488  are integral with the thumbwheel. The diameter of the first spool  487  and the second spool  488  can be independently adjusted so as to balance the rate of ring member  490  opening with the rate of angulation of the frame  483 . It will also be appreciated that the first spool  487  and the second spool  488  may be mounted on separate thumbwheels. In this case the handle  485  would comprise two thumbwheels. 
     The device further comprises a net  499  mounted to the ring member as previously described. In one embodiment the device comprises a clot debonder  482 . The clot debonder is as shown in  FIG.  101   b    and comprises a debonding ring  500 , a connector strut  501 , an elongate tube  503  and a hub  504 . The debonding ring  500  further comprises a lased surface  502  and said lased surface  502  comprises filaments lased across the opening defined by the debonder ring  500 . The debonding ring  500  is connected to the tubular member  503  and the tubular member  503  extends proximally to control hub  504 . The tubular member  503  is configured to slide over the support member  484  such that the lased surface  502  can be advanced to engage with the occlusion. 
     A significant advantage of the device  480  of this invention is that the frame  483  assumes the collapsed configuration when not activated. This means that it can be advanced through the lumen of a microcatheter without any restraint and that it applies no radial force to the wall of the microcatheter. This allows the device to be constructed with a very low profile and allows the frame  483  to be advanced through the lumen of a microcatheter with ease. Neurovascular vessels are highly tortuous and ease of advancement is key to delivering the device to the target vessel segment. 
     Another aspect of the invention is shown in  FIG.  102    through to  FIG.  110    where a variety of debonder assemblies are disclosed. These debonder assemblies generally comprise a distal section wherein said distal section comprises an elongate member in the delivery configuration and the elongate member undergoes a shape change to form a ring member under the influence of a pull cable and said ring member is employed in conjunction with baskets to break the bonds that exist between occlusive clot and the wall of a vessel. 
       FIG.  102    shows a debonder assembly  520  comprising an elongate tube  521  and a pull cable  524 . The elongate tube further comprises a distal section  522 , an exit port  523 , a distal cable attachment  525 , and an articulation region  527 . The pull cable  524  and the elongate tube extend proximally to a handle  528 . The pull cable  524  is connected to an activator  529  in the handle  528  and said activator  529  is configured to allow the user to tension the pull cable  524 . 
     In one embodiment the activator  529  comprises a slider. In another embodiment the activator  529  comprises a thumbscrew. In one embodiment the proximal end of the elongate tube  521  is fixed to the distal end of the handle  528  and the pull cable exits the elongate tube via its proximal lumen. In another embodiment the elongate tubing extends through the handle and provides a continuous lumen through the handle such that the assembly can be interfaced with other devices. With this embodiment the proximal end of the elongate tube  521  comprises a proximal exit port  531  (not shown) and the cable  524  exits the lumen of the elongate tube  521  through the proximal exit port. The proximal exit port  531  is preferably distal of the activator  529 . The distal end of the cable  524  is fixed at attachment point  525  at the distal end of the distal section  522 . The assembly is delivered to the treatment site in the collapsed configuration as shown in  FIG.  102    with the pull cable relaxed. In a preferred embodiment the pull cable  524  encircles the distal section  522  once between the exit port  523  and the attachment point  525 . At the treatment site the distal section is transformed into a ring member  600  as shown in  FIG.  105   . The ring member comprises a generally circular or elliptical hoop and is configured to abut a vessel occlusion. The ring member  600  preferably engages the occlusion adjacent the interface between the occlusion and the vessel wall. In this way, the ring member  600  delivers an abutment force to the interface between the clot and the vessel wall and this is the region where clot separation is most desired. The device further comprises an articulation region  527  adjacent the exit port  523 . In one embodiment the articulation region comprises a local weakening of the tube in that region. In another embodiment the articulation region comprises at least one cut or slot in the wall of the tube in the articulation region. In another embodiment the cut comprises a spiral cut. In another embodiment the cut comprises a circular cut. In another embodiment the cut comprises at least one helical cut. In another embodiment the cut comprises a cut thickness. In another the cut thickness comprises at least two cut thicknesses. In yet another embodiment the articulation region comprises a plurality of patterned slots. 
       FIG.  103    shows a debonder assembly  540  which is similar to the assembly shown in  FIG.  102    and comprises an elongate tube  541  and a pull cable  544 . The elongate tube  541  further comprises a distal section  542 , a lumen  546 , a lumen distal end  543 , a distal cable attachment  545 , and an articulation region  547 . The pull cable  544  and the elongate tube  541  extend proximally to a handle  528 . The construction and functions of the handle  528  are the same as was described in  FIG.  102   . 
     The lumen  546  extends from its distal end  543  to the proximal end of the handle  528  and is sized so as to accommodate the pull cable  544  and another elongate assembly such as a basket assembly. The debonder assembly  540  is delivered to the treatment site in the collapsed configuration as shown in  FIG.  103    with the pull cable  544  relaxed. At the treatment site, the distal section  542  is transformed into a ring member  600  as shown in  FIG.  105   . The distal section  542  comprises a strut  548 . The strut  548  preferably comprises a spiral member. In one embodiment the strut  548  is cut from a hypotube and the spiral extends the entire length of the strut. In one embodiment the spiral comprises a 360° spiral. The pull cable  544  extends from the lumen distal end  543  and is attached at attachment point  545 . In a preferred embodiment the pull cable  544  encircles the distal section  542  once between the lumen distal end  543  and the attachment point  545 . When the pull cable is activated, the distal attachment point  545  moves towards the lumen distal end  543 . The strut progressively forms into a hoop and articulates about the articulation region  547 . 
     The ring member  600  when formed comprises a generally circular or elliptical hoop and is configured to abut a vessel occlusion. The ring member  600  preferably engages the occlusion adjacent the interface between the occlusion and the vessel wall. The assembly  540  further comprises an articulation region  547  adjacent the distal end  543  of lumen  546 . In one embodiment the articulation region  547  comprises a local weakening of the strut  548  in that region. In another embodiment the articulation region  547  comprises at least one cut or slot in the wall of the strut in the distal section  542 . 
       FIG.  104    shows a debonder assembly  560  which is similar to the debonder assembly  520  shown in  FIG.  102    and comprises an elongate tube  561  and a pull cable  564 . The only difference between the debonder assembly  520  of  FIG.  102    and the debonder assembly  560  of  FIG.  104    lies in the construction of the distal section  562 . The distal section  562  comprises a plurality of slots  568  arranged along the substantially the entire length of the distal section. The plurality of slots  568  are arranged in a helical pattern. Each slot has a significant circumferential component, and each slot comprises a width. In one embodiment the circumferential component of the slot comprises at least one quadrant. The width of the slot  568  is configured so as to facilitate compression of the slot  568  by the pull cable  564 . Preferably the sum of the widths of all the slots  568  in the distal section  562  should add up to a dimension that is less than the difference between the inner and outer circumference of the ring member  600  when the ring member  600  sized to the diameter of the target vessel. In a preferred embodiment the pull cable  564  encircles the distal section  562  once between the exit port  563  and the attachment point  565 . The construction and functions of the handle  528  are the same as was described in  FIG.  102   . 
       FIG.  105    shows a debonder assembly  580  with the distal section formed into a hoop shaped ring member  600 . The debonder assembly  580  represents the expanded configuration of the debonder assemblies  520 ,  540 , and  560  of  FIG.  102 - 104   . The assembly comprises a ring member  600 , a support member  601 , a support member lumen  606 , a distal section  602 , a cable exit (port/lumen)  603 , a pull cable  604 , a handle assembly  528  (as shown in  FIG.  102   ), and a distal attachment point  605 . 
       FIG.  106   a    to  FIG.  106   c    shows the arrangement of a device  620  wherein a debonder assembly  580  as described in  FIG.  102 - 105    is being used in conjunction with a basket assembly  621 . The basket assembly  621  comprises a hoop frame  622 , a net  623  and a support member  624 . The frame  622  is similar to the frame construction employed in  FIG.  86   . The support member  624  of the basket assembly  621  extends parallel to the support member  601  of the debonder assembly  580 . The support member  624  extends between the pull cable  604  and the distal section  602  of the debonder assembly  580 . In one embodiment both the support member and the elongate tube extend through the lumen of a microcatheter. In another embodiment the support member extends through the lumen of the elongate tube and the elongate tube is configured to be advanced or retracted relative to the support member. In  FIG.  106   a   , the basket assembly  621  is shown in the expanded configuration with the debonder assembly in the collapsed configuration. In  FIG.  106   b   , the pull cable  604  is activated and the distal section  602  is being reshaped into an engagement ring  600 . In  FIG.  106   c   , the pull cable  604  is activated further through the handle  528  (not shown) and the reshaping of the distal section  602  is almost complete. It will be appreciated that the engagement ring  600  engages the occlusion in an area adjacent the wall of the vessel and that some clot may project through the opening in the engagement ring  600 . However, the primary purpose of the engagement ring  600  is to provide a reaction force to the action of the basket assembly  621 . This reaction force allows the basket assembly to be retracted strongly without fear of vessel rupture or dissection. 
     Using the device  620  of the invention comprises at least some of the following steps: 
     Advancing a guide catheter into a large diameter vessel proximal of the cerebral vasculature (the CCA or the ICA). 
     Advancing a microcatheter through the lumen of the guide catheter until its distal end is advanced distal of the tip of the guide catheter. 
     Further advancing the microcatheter with the assistance of a guidewire within the lumen of the microcatheter. 
     Manipulating both the microcatheter and the guidewire until the tip of the microcatheter is across the occlusive clot. 
     Withdrawing the guidewire  423  from the lumen of the microcatheter. 
     Advancing the device  620  through the lumen of the microcatheter with both the basket and the clot debonder in the collapsed configuration. 
     Deploying the basket from the microcatheter distal of the occlusion. 
     Expanding the fame of the basket distal of the occlusion. 
     Retracting the microcatheter and exposing the distal section  602  of the debonder assembly  580 . 
     Activating the cable such that the distal section  602  of the debonder assembly changes shape and forms an engagement ring. 
     Engaging the engagement ring with the proximal end of the clot. 
     Engaging the hoop frame  622  of the basket assembly  621  with the distal face of the clot. 
     Retracting the basket assembly while holding the debonder assembly  580  stationary. 
     Disengaging the clot from the vessel wall. 
     Applying a capture force to the clot. 
     Forcing the clot into the capture opening of the basket. 
     Disengaging the engagement ring  600  from the proximal face of the occlusion. 
     The step of disengaging the engagement ring  600  comprises at least removing some of the tension in the cable such that the engagement ring  600  at least partially reverts to its original configuration. 
       FIG.  107    shows a device  640  which comprises a basket assembly  621  and a debonder assembly  650 . The basket assembly  621  is as described in  FIG.  106   a - c   . The debonder assembly  650  comprises an elongate tube  651 , a distal section  652 , a cable  654 , a cable exit port  653 , and a cable attachment  655 . The distal section  652  comprises a tube and the tube comprises a spiral cut. The spiral cut allows the distal section  652  to deform into a ring member for clot abutment when the cable  654  is tensioned. The distal section  652  further comprises a cable loop  656 . The cable loop  656  comprises a loop of yarn wherein both ends of the yarn are fixed to the distal section  652 . The loop  656  is sized to accommodate the support member  624  of the basket assembly  621  and the loop  656  holds at least a portion of the support member  624  adjacent the distal section  652 . When the distal section  652  is expanded and assumes its expanded configuration as a ring member, the loop  656  guides the ring member along the support member  624  as it is advanced and retracted. 
       FIG.  108    shows a device  660  which comprises a basket assembly  621  (as described in  FIG.  106   a - c   ) and a debonder assembly  670 . The debonder assembly  670  is very similar to the debonder assembly  650  of  FIG.  107   . The debonder assembly  670  comprises an elongate tube  671 , a distal section  672 , a cable  674 , a cable exit port  673 , and a cable attachment  675 . The distal section  672  comprises a tube and the tube comprises a plurality of slots  677 . The plurality of slots  677  controls the bending of the distal section  652  when the cable  654  is tensioned. The slots  677  are arranged such that the distal section deforms into a hoop and said hoop is articulated so as to create a distal abutment ring for clot engagement. The distal section  672  further comprises a cable loop  676  and the cable loop  676  functions in the same manner as cable loop  656  of  FIG.  107   . 
     The device  680  of  FIG.  109   a    and  FIG.  109   b    comprises a basket assembly  621  (as described in  FIG.  106   a - c   ) and a debonder assembly  690 . The debonder assembly  690  comprises an elongate tube  671 , a distal section  672 , a cable  674 , a cable exit port  673 , and a cable attachment  675 . The distal section  672  comprises a tube and the tube comprises a plurality of slots  677 . The plurality of slots  677  controls the bending of the distal section  652  when the cable  654  is tensioned. The slots  677  are arranged such that the distal section deforms into a hoop and said hoop is articulated so as to create a distal abutment ring for clot engagement. The distal section  672  further comprises a cable loop  676  and the cable loop  676  functions in the same manner as cable loop  656  of  FIG.  107   . The elongate tube  671  comprises an inner lumen  691  and said inner lumen is sized to accommodate the support member  624  over at least a portion of the length of the elongate tube  671 . The elongate tube  671  further comprises an inlet  691  and said inlet  691  is sized to allow the support member  624  access to the lumen of the catheter. In one embodiment the inlet  691  is located proximal of the cable exit port  673 . In another embodiment the inlet  691  is distal of the cable exit port  673 . In another embodiment the inlet  691  is adjacent the cable exit port  673 . In yet another embodiment the cable exit port  673  comprises the inlet  691 . 
     In yet another embodiment the shape change of the distal section  672  is achieved using two cables. The first cable is attached to the distal section at the distal end of the distal section. This cable, when activated, pulls the cable attachment  675  towards the exit port  673  and thus forms an engagement ring  678  as shown in  FIG.  109   b   . The second cable is attached to the distal section  672  proximal of the distal end and causes the ring to articulate such that the ring  678  comprises a distally facing abutment ring. In one embodiment the first and second cables are activated with a single activator  529  (not shown). In another embodiment the first and second thumbwheels are activated by two separate thumbwheels. 
     The device  700  of  FIG.  110    comprises the basket assembly  621  and the debonder assembly  540  both of which have been described previously. The figure shows the two assemblies configured as a device for use in treating acute occlusions. The strut  548  of the distal section  542  is wrapped around the support member  651  of the basket assembly  621  in the delivery configuration. 
       FIG.  111   a - 111   c    show another device  720  of the invention. The device comprises a debonder assembly  722  and a basket assembly  721 . The basket assembly  721  comprises support struts  723 , a frame  733 , and a net  724 . The support struts  723  are connected to the user end at the basket proximal hub  727  via a plurality of pull cables  726 . The pull cables  726  are spaced apart from the support member  725 . The pull cables are assembled through cable guides  732  of the struts  731  in the debonder assembly  722 . In this embodiment the debonder assembly  722  and basket assembly  721  move relative to each other in order to retrieve a vessel obstruction while the pull cables  726  remain adjacent the vessel wall. 
       FIG.  111   b    is an elevation view of the device of  FIG.  111   a    in the collapsed configuration and  FIG.  111   c    shows the device of  FIG.  111   a    in an expanded configuration. The support member  725  is assembled inside elongate tube  728 . The support struts  731  are connected to elongate tube  728 . The elongate tube  728  contains a plurality of exit ports  730 . In this embodiment the pull cables are fixed to the support struts  723  at the distal end and the basket proximal hub  727 , and are moveable through the cable guides  732  and exit ports  730 . 
       FIG.  111   c    shows the device in a partially activated state with the support struts  723  and struts  731  expanded. The device may be partially actuated by moving the proximal basket hub  727  proximally relative to the debonder hub  735 . 
       FIG.  111   d   - FIG.  111   f    shows the device of  FIG.  111   a    inside a vessel removing an occlusive clot  421 .  FIG.  111   d    shows the device with the basket assembly  721  distal of a clot and the debonder assembly  722  proximal of the clot.  FIG.  111   e    shows the device  720  in a partially actuated state with the struts  731  and support struts  723  in an expanded configuration. In  FIG.  111   f   , the basket assembly  721  is located adjacent the occlusive clot and the pull cables  726  are in tension. This draws the basket assembly  721  and the debonder assembly  722  together. The engagement segment  729  of the debonder assembly provides a support surface for the clot as the basket assembly  721  engulfs the occlusive clot. 
       FIG.  112   a   - FIG.  112   c    show another device  750  of the invention. In  FIG.  112   a   , the debonder assembly  722  (similar to debonder assembly  722  of  FIGS.  111   a - f   ) is fixed to an elongate tube  728  similar to the device of  FIG.  111   a   , but in this device the basket assembly  751  is slidable relative to a guidewire  753 . Basket assembly  751  includes frame  733 , support struts  723 , and net  724  as in  FIGS.  111   a - f   .  FIG.  112   b    shows the device  750  in a vessel with an occlusive clot  421  with the basket assembly deployed distal of the occlusive clot. In  FIG.  112   c   , the control hub  734  is moved relative to the debonder hub  735  to draw the basket assembly  751  over the clot. The guidewire  753  is movable relative to the debonder assembly  722  and the basket assembly  751 . With this device, the user may leave the guidewire  753  in place after removing the basket assembly  751  containing the occlusive clot  421 . 
       FIG.  113   a    and  FIG.  113   b    show another device  800  of the invention. In this case, the device  800  comprises an eccentric basket  801  and an eccentric debonder  802 . The eccentric basket  801  comprises a frame  803 , a net  804 , and a support member  805 . The frame comprises a proximal hoop  806 , a distal hoop  807 , and an expansion member  809 . The frame expansion comprises of two components. Firstly, the proximal and distal hoops  806  and  807  form. The proximal and distal hoops  806  and  807  comprise pairs of struts in the collapsed configuration. The struts move apart to form a hoop when the external restraint is removed. Secondly the proximal and distal hoops  806  and  807  undergo an angular displacement with respect to each other. This angular displacement is driven by elastic energy stored in the expansion member  809 . The expansion member  809  also interconnects the proximal hoop  806  to the distal hoop  807 . When the frame  803  is in the expanded configuration, the expansion member  809  provides the frame  803  with a significant portion of its resistance to collapse. 
     Thus, the expansion member  809  is configured to withstand significant strain and provide good resistance to collapse. Preferably the expansion member  809  comprises a metal. More preferably the metal comprises a nitinol. Preferably the expansion member  809  and the frame  803  comprise the same material and preferably the expansion member  809  and the frame  803  are integral. In one embodiment the expansion member  809  comprises a strut connecting the proximal hoop  806  to the distal hoop  807 . In one embodiment the strut comprises a width and a thickness and the ratio of the width and the thickness comprises the aspect ratio of the strut. Preferably the aspect ratio of the strut is greater than 1. More preferably the aspect ratio is 1.5 or greater. 
     The frame  803  is mounted to the support member  805  at attachment  808 . Preferably the attachment  808  comprises an attachment between the proximal hoop  806  and the support member  805 . In one embodiment the net  804  is attached to the distal hoop  807 . In another embodiment the net  804  is attached to the proximal hoop  806 . 
     The debonder  802  comprises an elongate tube  812 , a control handle  816  (not shown) and a debonding element  815 . The debonding element  815  comprises a plurality of engagement struts  814  and the engagement struts are configured so as to create the clot engagement face  813  when expanded. 
     In one embodiment the debonding element or clot engager  815  comprises a plurality of struts forming a first section and a second section, with the first section tapering outward and distally from elongate member  812  and connected to the second section, and the second section comprising a plurality of cells defined by a plurality of struts and arranged around at least a portion of the circumference of an axis substantially parallel to that of the elongate member. In another embodiment these cells are arranged around the entire circumference of said axis. 
     The debonding element  815  comprises a plurality of cells  817 , wherein each cell is defined by a plurality of boundary struts  814 . It will be appreciated that a number of cell  817  and strut  814  arrangements are possible in creating a clot engagement surface  813 . 
     The debonding element  815  is connected to the elongate tube  812  and the debonding element  815  is advanced or retracted using the control handle  816  (not shown) at the user interface (not shown). The user interface comprises the proximal hub  818  of the guide catheter  811 , the proximal hub  819  of the microcatheter  810 , the control handle  816  of the debonder  802  and the proximal end of the support member  805 . The guide catheter hub  818  and the microcatheter hub  819  both comprise luer connectors and both facilitate the addition of accessories such as Y-connectors, Touhy Borsts and syringes. These accessories facilitate flushing as well as locking the guide catheter to the microcatheter  810  or locking the microcatheter  810  to the elongate tube  812 . In one embodiment the control handle  816  comprises a luer fitting. In another embodiment the control handle  816  comprises a locking element for locking the control handle to the support member  805 . 
       FIG.  114    shows a blown up view of one embodiment of the clot debonding element  815  of  FIG.  113   . In the embodiment shown, the struts  814  are integral with the distal end of the elongate tube  812  and form cells  817 . In another embodiment the clot debonding or clot engaging element  815  may be a separate component to elongate tube  812 . 
       FIG.  115    shows an end view of another eccentric debonding element  830 . The debonding element  830  comprises a plurality of cells  833  defined by a plurality of struts  831 . The plurality of cells  833  are configured such that in the expanded state the debonding element  830  will engage with a substantial portion of a vessel with a substantially circular cross-section. The struts  831  are connected to an elongate tube  832 . 
     Now with reference to  FIG.  116   a    to  FIG.  116   i   , there is shown another device  850  which is very similar to the devices described in  FIG.  113    to  FIG.  115    and similar numerals will be employed to describe similar elements.  FIG.  116   a    to  FIG.  116   i    show the procedural steps associated with using the device  850 . The device  850  comprises a basket  801  and a debonder  851 . The debonder  851  is an eccentric debonder and is similar to the debonder  802  described with reference to  FIG.  113   a - b   . The basket  801  is an eccentric basket and is similar to the basket  801  described with reference to  FIG.  113   a - b   . The debonder  851  comprises a debonding element  852  and an elongate tube  812 . The elongate tube  812  comprises a lumen sized to accommodate the support member  805  of the basket  801 . The debonding element  852  is fixed to the distal end of the elongate tube  812  and comprises a collapsed state for delivery, a deployed partially expanded state, and a fully deployed state. The debonder element  852  comprises a plurality of struts  814 , and said struts  814  are configured to expand on deployment. The engagement struts  814  are configured so as to create a clot engagement surface  813  when expanded. The debonding element  852  comprises a plurality of cells  817 , wherein each cell is defined by a plurality of boundary struts  814 , as shown in  FIG.  114   . It will be appreciated that a number of arrangements of cells  817  and struts  814  are possible in creating a clot engagement surface  813 . 
     The debonding element  852  deployed state comprises an intermediate diameter when expanded in an unconstrained fashion. Preferably the debonding element  852  comprises a nitinol, a shape memory or a super elastic material. The debonding element  852  comprises an engagement surface  813  in the deployed state. The engagement surface  813  is a distally facing surface and is configured to engage with the occlusion  840 . The engagement surface  813  comprises a tapered surface, and when the tapered surface engages with the clot  840 , the reaction force of the clot  840  causes the debonding element  852  to expand further. In one embodiment the further expansion of the debonding element  852  comprises an articulation of at least a portion of the engagement surface  813 . In another embodiment the further expansion comprises a change in shape of the cells  817  of the debonding element  852 . Conversely, when the debonding element  852  is disengaged from the occlusion  840 , the debonding element  852  partially collapses, returning to its biased partially expanded configuration. Furthermore, when the debonding element is withdrawn through an occlusion  840  or a partial occlusion, the outer side of the tapered surface engages with the clot and the debonding element  852  is further collapsed by the reaction force of the occlusion  840  on its outer surface. Thus, the debonding element  852  spontaneously engages when advanced against an occlusion  840  and collapses when retracted through a restriction or occlusion  840 . 
       FIG.  116   a    shows the start of the procedure and the steps for gaining access to the distal side of the occlusion. The steps comprise: 
     Advancing a guide catheter  811  into a large supra aortic vessel  841 . 
     Advancing a guidewire  843  and a microcatheter  810  through the lumen of the guide catheter  811 . 
     Manipulating the guidewire  843  and the microcatheter in concert so as to access the target vessel. 
     Passing the guidewire  843  and the tip of the microcatheter  810  across the occlusion  840 . 
     Removing the guidewire  843  from the lumen of the microcatheter. 
     With reference to  FIG.  116   b   , the device  850  is advanced through the lumen of the microcatheter  810 . The procedural steps involved in delivering and deploying the basket  801  and the support member  805  comprise: 
     Providing the device with the basket  801  and the debonder  851  in the collapsed configuration. 
     Inserting the distal end of the device  850  into the lumen of the microcatheter  810 . 
     Advancing the device  850  through the lumen of the microcatheter  810  until the basket frame  803  exits the microcatheter  810 . 
     Expanding the frame to the deployed clot engagement configuration. 
     With reference to  FIG.  116   c    and  FIG.  116   d   , the microcatheter  810  is withdrawn and unsheathes the debonding element  852  which expands towards its intermediate diameter. The expansion of the debonding element  852  occurs adjacent the distal end of the occlusion  840 . The orientation of the debonding element  852  is checked and, if necessary, the orientation of the debonding element  852  adjusted. The debonder  851  is withdrawn into the distal body of the occlusion  840 . The basket  801  is retracted and engaged with the clot  840 . The debonder  851  is advanced slightly and the debonding element  852  engages with the clot  840 , expands under the reaction force of the clot  840  and in so doing sets up a shearing force on the body of the clot  840 . The procedural steps comprise: 
     Deploying the debonding element  852  within the target vessel. 
     Orienting the debonding element  852 . 
     Retracting the debonding element  852  into the body of the occlusion  840 , wherein the retraction step comprises an incremental collapse of the debonding element  852 . 
     Engaging the basket  801  with the distal end of the clot  840 . 
     Engaging the debonding element  852  with the clot  840 , said engagement comprising a spontaneous incremental expansion of the debonding element  852 . 
     With reference to  FIG.  116   e   , the device  850  is shown with a distal portion  854  of the clot  840  sheared from the main body of the clot  840  and being forced into the mouth of the basket  801 . 
     The spontaneous expansion of the debonding element  852  when engaged with the clot  840  helps the debonder  851  to shear away a portion  854  of the clot  840 . This approach is particularly advantageous where the occlusion is an especially long occlusion. Occlusions of 30 mm are not unusual in cerebral vessels. Breaking the occlusion into segments reduces the stress applied to the vessel wall and this reduces complications. It will be appreciated that the device  850  can be used to debond and capture short length occlusions without breaking up the clot. The steps associated with the shearing off and capture of the first segment  854  of the occlusion  840  comprise: 
     Shearing off a segment  854  of the clot  840 . 
     Advancing the debonder with the sheared segment  854  distal while holding the basket  801  steadfast and forcing the sheared segment  854  into the basket  801 . 
     Disengaging the debonding element  852  from the clot segment  854 . 
     With reference to  FIG.  116   f    and  FIG.  116   g   , the device is shown engaging with and capturing a second segment  855  of the clot  840 . The debonder  851  is withdrawn proximally and the debonding element  852  is withdrawn into the remaining clot. When the user is satisfied with the size of the second clot segment  855 , the debonder  851  is advanced slightly such that the debonding element  852  engages with the clot. The basket  801  is withdrawn proximally while holding the debonder  851  stationary and the basket  801  is engaged with the distal end of the clot segment  855 . The debonder  851  is advanced while holding the basket  801  steadfast and the second clot segment  855  is sheared off and captured in the basket  801 . The steps associated with capturing the second clot segment comprise: 
     Retracting the debonding element  852  into the body of the remaining occlusion  840 , wherein the retraction step comprises an incremental collapse of the debonding element  852  as it engages with the occlusive material. 
     Engaging the basket  801  with the distal end of the remaining clot  840 . 
     Engaging the debonding element  852  with the clot  840 , in the body of the remaining clot, said engagement comprising a spontaneous incremental expansion of the debonding element  852 . 
     Shearing off a second segment  855  of the clot  840 . 
     Advancing the debonder with the sheared segment  855  distal while holding the basket  801  steadfast and forcing the sheared segment  855  into the basket  801 . 
     In one embodiment the second segment comprises all of the remaining clot  840 . In this case the method comprises the steps of: 
     Retracting the debonding element  852  through the remaining occlusion  840 , wherein the retraction step comprises an incremental collapse of the debonding element  852  as it engages with the occlusive material, the debonding element  852  spontaneously expanding when the debonding element  852  emerges on the proximal side of the occlusion. 
     Engaging the basket  801  with the distal end of the remaining clot  840 . 
     Engaging the debonding element  852  with the proximal face of the clot  840 , said engagement comprising a spontaneous incremental expansion of the debonding element  852 . 
     Shearing the remaining clot  840  from the wall of the vessel  841 . 
     Advancing the debonder with the remaining clot  840  distal while holding the basket  801  steadfast and forcing the remaining clot  840  into the basket  801 . 
     The remaining steps in the procedure are described in  FIG.  116   h    and  FIG.  116   i   . The debonder is withdrawn from the vessel segment. The basket is then withdrawn from the vessel segment and a final angiogram is completed. In one embodiment the steps comprise: 
     Retracting the debonding element  852  from the vessel segment. 
     Retracting the basket  801  with the captured clot from the vessel segment. 
     Removing the device  850  and the clot from the vasculature through the lumen of the guide catheter  811 . 
     In another embodiment the device  850  and the microcatheter  810  are removed in concert. This approach allows the lumen of the microcatheter  810  to protect the vessel wall from the some of the frictional forces of the elongate tube  812  and the support member  805  during removal. The method comprises the steps of:
         1. Retracting the debonder  851  until the expanded section of the debonding element  852  engages with the distal end of the microcatheter  810 .   2. Locking the debonder  851  and the microcatheter  810  together.   3. Retracting the basket  801  until the frame  803  is adjacent the debonding element  852 .   4. Retracting the microcatheter  810  and debonder  851  through another segment of vessel.   5. Repeat steps 3 and 4 until the debonder element is adjacent the tip of the guide catheter  811 .   6. Retract the microcatheter  810 , the debonder  851  and the basket through the lumen of the Guide catheter  811  and remove from the patient.   7. Conduct a final angiogram by flushing contrast media through the lumen of the guide catheter  811 .       

     The debonder and the microcatheter can be easily locked together where a Touhy Borst fitting is connected to the proximal luer of the microcatheter. 
     Another device  870  of the invention is described with reference to  FIGS.  117   a - e   .  FIG.  117   a    shows device  870  which comprises a basket assembly  871  and a debonding assembly  872  (similar to debonding assembly  482 ). The basket assembly  871  comprises a frame  875 , a net  876 , a support member  877 , pull cable  878 , and a handle assembly  883 . The support member  877  comprises a tubular member and the support member is connected to the frame at junction  881 . The support member  877  comprises an inner lumen and an exit port  879 . The pull cable  878  extends from attachment point(s)  880  through the exit port  879  through the lumen of the support member  877  to the handle  883 . In one embodiment the pull cable  878  is interfaced with a slider  884  such that activation of the slider  884  causes the pull cable  878  to undergo tension and deactivation of the slider  884  reduces or removes tension from the pull cable  878 . Tensioning the pull cable  878  causes the frame  875  to articulate about a region adjacent the junction  881 .  FIG.  117   b    and  FIG.  117   c    show a top and side view respectively of the basket  871  with pull cable  878  in the untensioned state.  FIG.  117   d    shows a top view of the basket  871  constrained in a vessel with pull cable  878  in the untensioned state.  FIG.  117   e    shows a close-up of the debonding assembly  872  in the collapsed state for delivery. 
     In one embodiment the region of articulation is distal of the junction  881 . In another embodiment the region of articulation is proximal of the junction  881 . In another embodiment the region of articulation includes the junction. In one embodiment at least a portion of the region of articulation comprises a reduced section. In one embodiment the reduced section comprises a reduction in the width of the section. In another embodiment the reduced section comprises a reduction in the thickness of the section. In another embodiment the reduced section comprises a reduction in the cross sectional area of the section. In another embodiment the reduced section comprises a reduction in the stiffness of the material of the section. 
       FIG.  118   a    shows another debonder  900  which may be used in conjunction with previous devices disclosed in the invention. The debonder is connected to an elongate tube  901  and has an engagement surface  902  for abutment with an occlusive clot. The engagement struts  903  in  FIG.  118   b    have a radial section  904 , a curved segment  905 , and a termination section  906 . This debonder configuration provides a large abutment surface area for an occlusive clot. It will be appreciated that tethers may be attached to the termination sections  906  of the engagement struts to provide additional engagement for the struts.  FIG.  118   b    shows an end view of the same debonder  900 . 
       FIGS.  119   a  and  119   b    show another basket frame  911  according to the invention. The basket frame has a tether connection  912  at the distal end. The frame may be constructed from a cut sheet of material. The frame may be constructed from cut tubular material. The frame may be constructed of wire material. The frame may be constructed of ribbon material. The material may be Nitinol. In the frame of  FIGS.  119   a  and  119   b   , the pull tether  21  is integrally attached to the frame. It will be appreciated that the pull tether may be attached by other means such as welding, laser welding, bonding, or tied to the basket frame. The frame in  FIG.  119    has eyelets  6  as net attachment points. 
       FIG.  120    shows another basket assembly  921  according to the invention. This basket frame has a proximal hoop  922  and a distal hoop  923 . The frame may be constructed from a cut sheet of material. The frame may be constructed from cut tubular material. The frame may be constructed of wire material. The frame may be constructed of ribbon material. The material may be Nitinol. The struts of the proximal hoop and distal hoop are adjacent at a frame cross over  924 . The struts of the proximal hoop and distal hoop may remain unconnected.  FIG.  120   a    shows eyelets  6  of the proximal hoop struts and distal hoop struts may align at the frame cross over  924 .  FIG.  120   b    shows the frame cross over  924  wherein a pin  925  is inserted through eyelets  6 .  FIG.  120   c    shows the frame cross over  924  attached with a connecting wire  926 . It will be appreciated that the means of connecting the struts shown in  FIGS.  120   b  and  120   c    maintain the struts adjacent in the expanded configuration and in the collapsed configuration. The struts may move relative to each other in a scissors-like manner to move from an expanded configuration to a collapsed configuration. 
       FIGS.  121   a  and  121   b    illustrate another basket assembly  931  of the invention in an expanded configuration. This basket assembly has a proximal loop  932 , a middle loop  933 , and a distal loop  934 . In  FIG.  121   a   , a cable or pull tether  21  is connected at tether connection point  935  adjacent the middle loop  933  and distal loop  934  cross over point. In  FIG.  122   b   , the tether connection  936  is on the distal loop  934 . The frame comprises three loops substantially the same circumference in  FIG.  121   . It will be appreciated that the plurality of loops can be incorporated in order to provide additional support to the basket assembly, and further loops can be incorporated. 
       FIGS.  122   a  and  122   b    illustrate another basket assembly  941  of the invention with a proximal loop  942 , a middle loop  943 , and a distal loop  944 . In basket assembly  941 , the distal loop  944  has a circumference smaller than that of the proximal or middle loops.  FIG.  122   a    shows the frame without a tether and  FIG.  122   b    shows a basket assembly  941  with a cable or pull tether  21 . The bending stiffness of the smaller distal loop  944  gives the basket assembly rigidity in the axial direction to facilitate encapsulation of an occlusive clot. 
       FIGS.  123   a  and  123   b    show another basket assembly  951  of the invention with a proximal loop  952  and a distal loop  953 .  FIG.  123   b    has a cable or pull tether  21  connected to the distal loop  953  for actuation. The distal loop  953  has a larger circumference than proximal loop  952 , but in end view each loop will have substantially circular shapes to appose a vessel wall. 
     In  FIGS.  121 - 123    it will be appreciated that basket assemblies may comprise cut sheet material, cut tube material, ribbon material or wire material. 
     Modifications and additions can be made to the embodiments of the invention described herein without departing from the scope of the invention. For example, while the embodiments described herein refer to particular features, the invention includes embodiments having different combinations of features. The invention also includes embodiments that do not include all of the specific features described. 
     The invention is not limited to the embodiments hereinbefore described, with reference to the accompanying drawings, which may be varied in construction and detail.