Patent Publication Number: US-8114115-B2

Title: Support frame for an embolic protection device

Description:
This application is a continuation of U.S. application Ser. No. 11/332,485 filed Jan. 17, 2006, which is a continuation of U.S. application Ser. No. 10/325,954, filed Dec. 23, 2002, now U.S. Pat. No. 7,037,320, and claims benefit under 35 U.S.C. §119 to U.S. Provisional Application 60/341,836 filed Dec. 21, 2001, U.S. Provisional Application No. 60/341,805 filed Dec. 21, 2001, U.S. Provisional Application No. 60/373,640 filed Apr. 19, 2002, U.S. Provisional Application No. 60/373,641 filed Apr. 19, 2002 and U.S. Provisional Application No. 60/377,248 filed May 3, 2002, all of the disclosures of which are hereby incorporated by reference in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to an embolic protection device. 
     In particular, it relates to an embolic protection device of the type comprising a collapsible filter body to capture embolic material, and a support to maintain the filter body in an expanded position when the embolic protection device is deployed in a vasculature. 
     2. Description of the Related Art 
     Embolic protection devices of this general type are known. 
     However, there exist a number of problems with some of the known devices. In particular, upon collapse of the filter support, prior to delivery of the embolic protection device into and/or retrieval from a vasculature, large, localized stresses may be induced in the support. Solutions to this problem heretofore may result in features which inhibit the optimum performance of the device. In some systems flow paths for the blood can develop between the filter body and the interior wall of the vasculature. In general conventional devices are not highly trackable because of their length in the wrapped delivery configuration. 
     There is therefore a need for an embolic protection device which overcomes at least some of the disadvantages that exist with some of the known devices. 
     SUMMARY OF THE INVENTION 
     According to the invention there is provided an embolic protection device comprising:
         a collapsible filter element for delivery through a vascular system of a patient;   the filter element comprising a collapsible filter body and a filter support for the filter body;   the filter body having an inlet end and an outlet end, the inlet end of the filter body having one or more inlet openings sized to allow blood and embolic material enter the filter body, the outlet end of the filter body having a plurality of outlet openings sized to allow through passage of blood but to retain undesired embolic material within the filter body;   the filter support being movable between a collapsed position for movement through the vascular system, and an extended outwardly projecting position to support the filter body in an expanded position;   the filter support comprising a number of segments at least some of which are interconnected by a strain distributing linking element.       

     In one embodiment at least some of the segments are of wire. 
     The linking element may be of wire. The linking element may be of the same wire as that of the support segments. 
     In one embodiment the linking element extends normally of adjacent segments. The linking element may extend longitudinally of the axis of the filter and/or the linking element extends radially inwardly of the adjacent segments. 
     In a preferred embodiment the linking element comprises a loop. The loop may be of generally omega shape. 
     In one embodiment at least portion of the linking element is radiopaque. Alternatively or additionally at least portion of at least some of the support segments are radiopaque. 
     In one embodiment the linking element is of multifilament construction. Alternatively or additionally at least one of the support segments is of multifilament construction. 
     In one embodiment the support frame is defined by at least two wire segments terminating distally, the distal terminations of adjacent segments being fixed relative to one another and extending generally parallel. 
     The support frame may be defined by at least two wire segments terminating proximally, the proximal terminations of adjacent segments being fixed relative to one another and extending generally parallel. 
     In one embodiment the support frame comprises a support arm for one end of the filter body which extends towards on opposite end of the filter body in the deployed configuration. 
     In one embodiment the device comprises a carrier extending longitudinally of the frame. The carrier may be a tubular member, sleeve or sleeves or may comprise a guidewire. 
     A flexible tether may extend between the carrier and the support frame. 
     In one embodiment the support frame comprises a support loop or hoop. 
     In another aspect the invention provides an embolic protection device comprising:
         a collapsible filter element for delivery through a vascular system of a patient;   the filter element comprising a collapsible filter body and a filter support for the filter body;   the filter body having an inlet end and an outlet end, the inlet end of the filter body having one or more inlet openings sized to allow blood and embolic material enter the filter body, the outlet end of the filler body having a plurality of outlet openings sized to allow through passage of blood but to retain undesired embolic material within the filter body;   the filter support being movable between a collapsed position for movement through the vascular system, and an extended outwardly projecting position to support the filter body in an expanded position;   the filter support comprising a support frame having at least two longitudinally spaced-apart segments which are interconnected by at least one flexible linking element.       

     The support frame segments may be of wire. 
     In a further aspect the invention provides an embolic protection device comprising:
         a collapsible filter element for delivery through a vascular system of a patient;   the filter element comprising a collapsible filter body and a filter support for the filter body;   the filter body having an inlet end and an outlet end, the inlet end of the filter body having one or more inlet openings sized to allow blood and embolic material enter the filter body, the outlet end of the filter body having a plurality of outlet openings sized to allow through passage of blood but to retain undesired embolic material within the filter body;   the filter support being movable between a collapsed position for movement through the vascular system, and an extended outwardly projecting position to support the filter body in an expanded position;   the filter support comprising a support frame defined by at least two wire segments having terminations, the terminations of adjacent segments being fixed relative to one another and extending generally parallel.       

     The wire segments may terminate distally, the distal terminations of adjacent segments being fixed relative to one another and extending generally parallel. Alternatively or additionally the wire segments terminate proximally, the proximal terminations of adjacent segments being fixed relative to one another and extending generally parallel. 
     The terminations may extend axially in relation to the filter. The distal terminations may be free to move axially. Alternatively or additionally the proximal terminations are free to move axially. 
     In one embodiment the proximal terminations of adjacent wire segments are configured to meet in a loop formation. The distal terminations of adjacent wire segments may be configured to meet in a loop formation. 
     In one embodiment the wire segments are of substantially the same length. 
     The wire segments may be fixed relative to one another by soldering, or welding, or bonding the wire segments to one another. Alternatively or additionally the device comprises a clamp around the wire segments to fix the wire segments relative to one another. The clamp may comprise a tubular sleeve. The clamp may comprise a clamp wire wound around the wire segments. The clamp may be at least partially of radiopaque material. 
     In one embodiment the wire segments are provided by a single wire bent back on itself. 
     Terminations may be located on an outer circumference of the filter frame. Alternatively or additionally terminations are located on an axis of the filter. 
     One of the proximal or distal terminations may be located on an outer circumference of the filter frame and the other of the proximal or distal terminations located on an axis of the filter. 
     In one embodiment each wire element has a circumferentially extending portion, and together the circumferentially extending portions of the wire elements define a cell which forms a substantially complete loop. 
     The wire elements may together define a number of cells axially spaced-apart. The support frame may have a connector between a first cell and a second cell. 
     The wire element may extend in an irregular path such as in a substantially wave-like pattern. 
     In one embodiment the wire element extends in an arcuate path. 
     In one embodiment the filter support comprises at least one support leg extending radially inwardly from the support frame, the leg being defined by at least one wire. The cross-sectional area of the support leg may decrease radially inwardly. 
     In one embodiment at least part of the support leg is integral with at least part of the support frame. The support leg may be provided as an extension of one wire element and/or the support leg is provided as an extension of two or more adjacent wire elements. 
     In one embodiment the support leg extends at least partially distally inwardly from the support frame. 
     The wire element may have a round cross-section. 
     Alternatively, the wire element has an elongate cross-section with a long dimension and a short dimension. The short dimension of the wire element cross-section may be aligned substantially along the radial direction of the filter support. The wire element may be rectangular in cross-section. 
     In one embodiment the filter body comprises a flap wrappable around a wire element of the filter support to fix the filter body to the filter support. 
     In another aspect the invention provides a method of collapsing an embolic protection device for delivery and/or retrieval of the device through a vascular system, the method comprising the steps of:
         providing an embolic protection device comprising a collapsible filter body and a filter support for the filter body; and   collapsing the filter support to a low-profile configuration with an associated torqueing of at least part of the filter support upon elongation of the filter support.       

     In another aspect the invention, an embolic protection device, comprises:
         a collapsible filter element for delivery through a vascular system of a patient; the filter element comprising a collapsible filter body and a filter support for the filter body;   the filter body having an inlet end and an outlet end, the inlet end of the filter body having one or more inlet openings sized to allow blood and embolic material enter the filter body, the outlet end of the filter body having a plurality of outlet openings sized to allow through passage of blood but to retain undesired embolic material within the filter body;   the filter support being movable between a collapsed position for movement through the vascular system, and an extended outwardly projecting position to support the filter body in an expanded position; the filter support comprising a support frame, a carrier, and   a flexible tether extending between the carrier and the support frame.       

     In one embodiment the carrier extends longitudinally of the frame. The carrier may be a tubular member or sleeve(s). Alternatively the carrier is a guidewire. The filter support may comprise a number of segments, at least some of which are interconnected by a strain distributing element. 
     The filter support may comprise a loop. 
     In one embodiment at least some of the segments are of wire. The linking element may be of wire. The linking element may be of the same wire as that of the support segments. The linking element may extend normally of adjacent segments, for example longitudinally of the axis of the filter and/or radially inwardly of the adjacent segments. 
     In one embodiment the linking element comprises a loop which may be of generally omega shape. 
     At least portion of the linking element may be radiopaque. At least some of the support segments may be radiopaque. 
     In one embodiment the linking element is of multifilament construction. 
     In another embodiment at least one of the support segments is of multifilament construction. 
     In one embodiment the support frame is defined by at least two wire segments having terminations, the terminations of adjacent segments being fixed relative to one another and extending generally parallel. The support frame may be defined by at least two wire segments terminating distally, the distal terminations of adjacent segments being fixed relative to one another and extending generally parallel. The support frame may be defined by at least two wire segments terminating proximally. the proximal terminations of adjacent segments being fixed relative to one another and extending generally parallel. 
     In one embodiment the support frame comprises a support arm for one end of the filler body which extends towards on opposite end of the filter body in the deployed configuration. 
     In one embodiment the device comprises a carrier extending longitudinally of the frame. A flexible tether may extend between the carrier and the support frame. 
     In one embodiment the support frame comprises a support loop. 
     In another aspect the invention provides an embolic protection device comprising:
         a collapsible filter element for delivery through a vascular system of a patient;   the filter element comprising a collapsible filter body and a filter support for the filter body;   the filter body having an inlet end and an outlet end. the inlet end of the filter body having one or more inlet openings sized to allow blood and embolic material enter the filter body, the outlet end of the filter body having a plurality of outlet openings sized to allow through passage of blood but to retain undesired embolic material within the filter body;   the filter support being movable between a collapsed position for movement through the vascular system, and an extended outwardly projecting position to support the filter body in an expanded position;   the filter support comprising a support frame,   a support arm for one end of the filter body which extends towards an opposite end of the filter body in the deployed configuration.       

     The support arm may be a proximal support arm that extends distally in the deployed configuration. Alternatively or additionally the support arm is a distal support arm that extends proximally in the deployed configuration. 
     In a further aspect the invention provides an embolic protection device comprising:
         a collapsible filter element for delivery through a vascular system of a patient;   the filter element comprising a collapsible filter body and a filter support for the filter body;   the filter body having an inlet end and an outlet end, the inlet end of the filter body having one or more inlet openings sized to allow blood and embolic material enter the filter body, the outlet end of the filter body having a plurality of outlet openings sized to allow through passage of blood but to retain undesired embolic material within the filter body;   the filter support being movable between a collapsed position for movement through the vascular system, and an extended outwardly projecting position to support the filter body in an expanded position;   the filter support comprising a generally tubular support frame defined by at least one wire.       

     The at least one wire of the tubular support frame becomes torqued during collapse of the filter support. This torque induced upon collapse is evenly distributed along the wire without resulting in stress concentrations on the filter support. ‘thus, the wires may be of a small cross-sectional area which advantageously collapse down to a very low profile. 
     In addition, small wires enable greater flexibility for the filter element, which allow for ease of advancement through the vascular system. 
     The frame may comprise a number of cells, at least one of the cells defining a segment of a tube. Each cell may define a segment of a tube. 
     In one embodiment at least portion of an element of one cell is connected to an element of another cell. The connection means may be provided by an extension wire between the cells. At least portion of an element of one cell may be directly fixed to an element of another cell. 
     The or each cell may be defined by two wire elements. The two wire elements may be of substantially the same length. The or each wire element may have a proximal termination and a distal termination, and the proximal terminations of adjacent wire elements are fixed relative to one another, and/or the distal terminations of adjacent wire elements are fixed relative to one another. 
     The terminations of adjacent wire elements may extend generally axially and parallel. The proximal terminations may be circumferentially aligned with the distal terminations. Alternatively the proximal terminations are circumferentially offset from the distal terminations. 
     In one embodiment each wire element has an axially extending portion and a circumferentially extending portion. 
     In one embodiment at least one wire element has an S-shaped portion for distributed filter body support. 
     The wire elements may be provided by a single wire bent back on itself. The single wire may have a strain relief means at the bend in the wire. The wire may be treated to minimize stress at the bend in the wire. 
     In one embodiment the filter support comprises at least one support leg extending radially inwardly from the tubular support frame, the leg being defined by at least one wire. At least part of the support leg is integral with at least part of the tubular support frame. The support leg may extend distally inwardly from the support frame. 
     According to a further aspect of the invention, there is provided an embolic protection device comprising:
         a collapsible filter element for delivery through a vascular system of a patient;   the filter element comprising a collapsible filter body and a filter support for the filter body;   the filter body having an inlet end and an outlet end, the inlet end of the filter body having one or more inlet openings sized to allow blood and embolic material enter the filter body, the outlet end of the filter body having a plurality of outlet openings sized to allow through passage of blood but to retain undesired embolic material within the filter body;   the filter support being movable between a collapsed position for movement through the vascular system, and an extended outwardly projecting position to support the filter body in an expanded position;   the filter support comprising a support frame defined by at least two wire elements, each wire element having a proximal termination and a distal termination, the terminations of adjacent elements extending generally axially and parallel.       

     According to the invention, there is provided a medical device having a collapsed configuration for transport through a body passageway, and an expanded configuration for deployment in a body; 
     the medical device comprising a support movable from the collapsed configuration to the expanded configuration to support the medical device in the expanded configuration; 
     the support comprising a radiopaque core. 
     The second moment of area of the radiopaque material is proportional to the fourth power of its diameter. Therefore because the radiopaque material is provided as the core of the support, this greatly reduces the diameter and thus the second moment of area of the radiopaque material. Correspondingly the forces required to facilitate deployment of the medical device are also greatly reduced. 
     In this manner the invention minimizes the dampening effect of the radiopaque material on the medical device. 
     By locating the radiopaque material as the core of the support, this also results in a low-profile medical device. 
     In one embodiment of the invention the core is located substantially along the neutral axis of bending of the support. 
     Preferably the support comprises at least one support element. The support element may be of a superelastic material. Ideally the radiopaque core is provided as a core embedded within at least one support element. In one case the radiopaque core is in powder form. In another case the radiopaque core is in liquid form. 
     In a preferred embodiment the radiopaque core comprises a radiopaque element amongst a plurality of support elements. The element may comprise a wire. Ideally the elements are wound together. 
     The radiopaque core may be of mercury, or gold, or platinum. 
     In another aspect. the invention provides a medical device having a collapsed configuration for transport through a body passageway, and an expanded configuration for deployment in a body; 
     the medical device comprising a support movable from the collapsed configuration to the expanded configuration to support the medical device in the expanded configuration; 
     the support comprising a reservoir enclosing a fluid, the fluid being expandable upon an increase in temperature to bias the support to the expanded configuration. 
     According to a further aspect of the invention, there is provided a medical device having a collapsed configuration for transport through a body passageway. and an expanded configuration for deployment in a body; 
     the medical device comprising a support movable from the collapsed configuration to the expanded configuration to support the medical device in the expanded configuration; 
     the support comprising a reservoir enclosing a fluid, the fluid being pressurized to bias the support to the expanded configuration upon release of a constraint. 
     In one case the reservoir comprises an enclosed tube. The tube may extend at least partially circumferentially around the device. Ideally the ends of the tube meet to form an enclosed loop. 
     The fluid may be of a radiopaque material. Preferably the fluid is liquid mercury. 
     In a preferred embodiment of the invention the device is an intravascular medical device for transport through a vasculature and deployment in a vasculature. Most preferably the device is an embolic protection filter. Ideally the filter comprises a filter body supported by the support, the filter body having an inlet end and an outlet end, the inlet end of the filter body having one or more inlet openings sized to allow blood and embolic material enter the filter body, and the outlet end of the filter body having a plurality of outlet openings sized to allow through passage of blood but to retain undesired embolic material within the filter body. 
     According to the invention, there is provided a medical device having a collapsed configuration for transport through a body passageway, and an expanded configuration for deployment in a body; 
     the medical device comprising a support movable from the collapsed configuration to the expanded configuration to support the medical device in the expanded configuration; 
     at least part of the support being of a multifilament wire construction. 
     In the multifilament wire construction of the invention, each filament bends independently of the other filaments. Correspondingly, the overall force required to bend the support is a summation of the forces required to bend each filament. Because the force required to bend a wire is proportional to the fourth power of the diameter of the wire, the overall force required to bend the multifilament support is much less than the force which would be required to bend a single wire with the same overall diameter as the multifilament support. 
     In this manner, the medical device of the invention achieves enhanced trackability during transport through even tortuous body passageways, while ensuring the medical device is moved by the support from the collapsed configuration to the expanded configuration upon deployment in the body. 
     The multifilament wire construction also provides the medical device with greater deformability in the expanded configuration. This enables the medical device to adapt to the particular characteristics of the body passageway in which it is deployed. 
     In one embodiment of the invention at least one filament is wound around at least one other filament. By winding the filament, the bending stress induced in the filament is reduced. Preferably at least some of the filaments arc braided together. 
     In a particularly preferred embodiment at least one filament is of a radiopaque material. The radiopaque nature of the filament provides visualization of the medical device during transport through and deployment in a body. The radiopaque filament is ideally located substantially along the neutral axis of bending of the support. 
     In another case at least one filament may comprise a radiopaque core embedded within the filament. 
     In a further embodiment of the invention the support comprises a jacket around the filaments. The jacket helps to maintain the structure of the multifilament wire construction intact and ensure the filaments move in a coordinated manner. Preferably the filaments are embedded within the jacket. Ideally the jacket is at least partially of a radiopaque material. The jacket may be at least partially of a polymeric material. 
     Desirably the support is of the multifilament wire construction at a point of high curvature in the expanded support. 
     The device is preferably an intravascular medical device for transport through a vasculature and deployment in a vasculature. Ideally the device is an embolic protection filter. Most preferably the filter has an inlet end and an outlet end, the inlet end having one or more inlet openings sized to allow blood and embolic material enter the filter, and the outlet end having a plurality of outlet openings sized to allow through passage of blood but to retain undesired embolic material within the filter. 
     In a preferred case the filter comprises a filter body supported by the support, and the inlet openings and the outlet openings are provided in the filter body to retain undesired embolic material within the filter body. The filaments may define a mesh. Ideally the inlet openings and the outlet openings are provided by openings through the mesh. 
    
    
     
       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  is a perspective view of an embolic protection device according to the invention; 
         FIGS. 2 and 3  are perspective views of a filter support of the embolic protection device of  FIG. 1 ; 
         FIG. 4  is an end view of the filter support of  FIGS. 2 and 3 ; 
         FIGS. 5 to 7  are perspective views illustrating collapse of the filter support of  FIGS. 1 to 4 ; 
         FIG. 8A  is an enlarged view of part of the filter support of  FIG. 5 ; 
         FIG. 8B  is an enlarged view of part of the filter support of  FIG. 6 ; 
         FIG. 9  is a perspective view of the filter support of  FIGS. 1 to 7 ; 
         FIGS. 10 to 20  are views of various alternative strain distributing linkage elements; 
         FIG. 21  is a perspective view of another filter support; 
         FIG. 22  is an end view of the filter support of  FIG. 21 ; 
         FIGS. 23 to 25  are perspective views of part of other filter supports: 
         FIG. 26  is a perspective view of a further filter support; 
         FIG. 27  is a perspective view of part of the filter support of  FIG. 26  in use; 
         FIG. 28  is a view along line A-A in  FIG. 27 ; 
         FIGS. 29 and 30  are enlarged perspective views of part of other filter supports; 
         FIG. 31  is a perspective view of another device of invention; 
         FIG. 32  is a perspective view of the device of  FIG. 31 , in use; 
         FIG. 33  is a cross sectional view on the line A-A in  FIG. 31 ; 
         FIG. 34  is a cross sectional view on the line B-B in  FIG. 31 ; 
         FIG. 35  is a cross sectional view similar to  FIG. 34  of an alternative embolic protection device. 
         FIGS. 36 and 37  are perspective views of other embolic protection devices according to the invention; 
         FIG. 38  is a perspective view of another embolic protection device; 
         FIG. 39  is a perspective view of an embolic protection device; 
         FIG. 40  is a perspective view of a further embolic protection device; 
         FIG. 41  is a perspective view of another embolic protection device; 
         FIG. 42  is a longitudinal cross-sectional view of the device of  FIG. 41 ; 
         FIG. 43  is a cross-sectional view on the line A-A in  FIG. 41 ; 
         FIG. 44  is a perspective view of another embolic protection device; 
         FIG. 45  is a cross-sectional view of the device of  FIG. 44 ; 
         FIG. 46  is a perspective view of a support frame of the invention; 
         FIG. 47  is an end view in the direction of the arrow A in  FIG. 46 ; 
         FIGS. 48 to 51  are views similar to  FIGS. 46 and 47  of further support frames; 
         FIGS. 52 to 62  are various views of linkage elements rendered radiopaque; 
         FIG. 63  is a perspective view of a portion of a frame element or a linkage element; 
         FIG. 64  is a perspective view of the element of  FIG. 63 , in use; 
         FIGS. 65 and 66  are perspective views of alternative frame elements or linkage elements; 
         FIG. 67  is a perspective view of a portion of another frame element or linkage element of the invention; 
         FIG. 68  is a perspective view of the element of  FIG. 67 , in use; 
         FIGS. 69 to 77  are perspective views of portions of frame elements or linkage elements; 
         FIGS. 78 to 81  are perspective views of portions of other frame elements or linkage elements; 
         FIG. 82  is a perspective view of a support frame of the invention; 
         FIG. 83  is a perspective view of another support frame of the invention; 
         FIGS. 84 to 86  are perspective views of portions of other frame elements or linkage elements; 
         FIGS. 87 to 99  are perspective views of various support frames of the invention. most of which include tether elements; 
         FIGS. 100A to 100D  are perspective views illustrating one attachment of a tether to a support frame; 
         FIG. 101  is a perspective view of another support frame including tethers; 
         FIG. 102  is a perspective view of portion of a further support frame; 
         FIG. 103  is a perspective view of another embolic protection device of the invention; 
         FIG. 104  is a perspective view of another support frame; 
         FIG. 105  is a perspective view of a further support frame; 
         FIG. 106  is a perspective view of another embolic protection device; 
         FIG. 107  is a perspective view of another support; 
         FIG. 108  is a perspective view of a further support 
         FIG. 109  is a perspective view illustrating the wrapping down of the frame of  FIG. 108 ; 
         FIGS. 110 and 111  are views similar to  FIGS. 108 and 109  of another support frame; 
         FIGS. 112 to 115  are perspective views illustrating termination details; 
         FIG. 116  is a perspective view of another support frame; 
         FIG. 117  is a perspective view of another embolic protection device; 
         FIG. 118  is a perspective view of a further embolic protection device; 
         FIGS. 119 to 125  are perspective views of various terminations; 
         FIG. 126  is a perspective view of another embolic protection device of the invention; 
         FIG. 127  is a perspective view of the support frame of  FIG. 126 ; 
         FIGS. 128 and 129  are perspective views illustrating the wrap-down of the frame of  FIG. 127 ; 
         FIG. 130  is a perspective view of another embolic protection device; 
         FIG. 131  is a perspective view of a further embolic protection device; 
         FIGS. 132 to 134  illustrate steps in the method for forming embolic protection devices of  FIG. 131 ; 
         FIG. 135  is a perspective view of another embolic protection device; 
         FIG. 136  is a perspective view of an embolic protection device; 
         FIG. 137  is a perspective view of another embolic protection device; 
         FIG. 138  is a perspective view of a further embolic protection device; 
         FIG. 139  is a perspective view of another embolic protection device; 
         FIG. 140  is a perspective view of another support frame of the invention; 
         FIG. 141  is a perspective view of another embolic protection device; 
         FIG. 142  is a perspective view of a support frame of the device of  FIG. 141 ; 
         FIG. 142A  is a detail view of portion of the support frame of  FIG. 142B ; 
         FIG. 142B  is a plan view of an offset variant of the support frame of  FIG. 142 ; 
         FIG. 143  is a perspective view of an alternative support frame; 
         FIG. 144  is a perspective view of an embolic protection device with a single loop support frame; 
         FIG. 145  is a perspective view of another embolic protection device; 
         FIGS. 146 to 148  are perspective views of support frames of the invention; 
         FIG. 149  is a perspective view of another support frame; 
         FIG. 150  is a view of a detail of the frame of  FIG. 149 ; 
         FIG. 151  is a view of an alternative detail of the frame of  FIG. 149 ; 
         FIG. 152  and  FIG. 153  are views of the frame of  FIG. 149  being wrapped down; 
         FIG. 154  is a perspective view of another embolic protection device; 
         FIG. 155  is a perspective view of a support frame of the device of  FIG. 154 ; 
         FIGS. 156-165  are views of further embodiments of support frames of the invention. 
         FIG. 166  is a perspective view of the filter support of  FIG. 164 ; 
         FIG. 167  is a schematic side view illustrating collapse of the embolic protection device of  FIG. 162 ; 
         FIG. 168  is a schematic plan view illustrating collapse of the embolic protection device of  FIG. 162 ; 
         FIGS. 169A to 169C  are perspective views illustrating collapse of the embolic protection device of  FIG. 162 ; 
         FIG. 170  is a perspective view of another filter support and the inner tube of  FIG. 164 ; 
         FIGS. 171 to 173  are plan, side and perspective views respectively of a further filter support; 
         FIGS. 174 and 175  are side and perspective views respectively of another filter support; 
         FIGS. 176 to 178  are plan, side and perspective views of a further filter support; 
         FIG. 179  is a perspective view of another embolic protection device according to the invention; 
         FIG. 180  is a schematic view of another filter support; 
         FIG. 181  is a development view of the filter support of  FIG. 180 ; 
         FIG. 182  is an enlarged view of part of the filter support of  FIG. 181 ; 
         FIG. 183  is a perspective view of another filter support and inner tube; and 
         FIG. 184  is a perspective view of the filter support of  FIG. 183 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to the drawings, there are illustrated several embolic protection devices according to the invention. In general the embolic protection devices comprise a collapsible filter element for delivery through a vascular system of a patient. The filter element comprises a collapsible filter body  102  and a filter support  103  for the filter body  102 , and a carrier which may comprise a tubular member  108  to which the filter support  103  may be mounted. 
     The filter body  102  has an inlet end  104  and an outlet end  105 . The inlet end  104  has one or more large inlet openings  106  which are sized to allow blood and embolic material enter the filter body  102 . The outlet end  104  has a plurality of small outlet openings  107  which are size to allow through passage of blood but to retain undesired embolic material within the filter body  102 . In this way, the filter element captures and safely retains any undesired embolic material in the blood stream within the filter body  102  while facilitating continued flow of blood through the vascular system. Emboli are thus prevented from flowing further downstream through the vascular system, which could otherwise have potentially catastrophic results. 
     The filter body  102  may be of an oriented polymeric material, as described in WO O1/97714A and US 2002/0042627A, the relevant contents of which are incorporated herein by reference. 
     The filter support  103  is movable between a low-profile, collapsed position for movement through the vascular system, and an extended outwardly projecting position. In this outwardly projecting position, the filter body  102  is supported in an expanded position by the filter support  103 , so as to maximize the internal volume of the filter body  102  to capture and safely retain as much embolic material as possible. The inner tube  108  has a guidewire lumen  112  there through, through which a guidewire may pass for exchange of the filter element  1  over the guidewire. Alternatively, in all embodiments the carrier may comprise a guidewire. 
     One embolic protection device  100  according to the invention is illustrated in  FIGS. 1 to 9 . A proximal end of the filter support  103  may be fixed to the inner tube  108 . Upon collapse of the filter element, the proximal end of the filter support  103  may remain fixed relative to the inner tube  8 , and the filter support  103  collapses distally against the inner tube  108 . In this collapsed position, the filter support  103  is axially elongated relative to the expanded position. 
     The filter support  103  in this case comprises two round wires  116  which extend from the proximal end  109 . The wires  116  extend together axially and radially outwardly in a leg  118  from the proximal end  109 , where the wires  116  are fixed to the inner tube  108 . The junction of the leg  118  with the support hoop is referred to in this specification as the proximal termination point  119 . 
     At a proximal termination point  119 , the wires  116  separate, and extend circumferentially around to form support hoops. 
     This arrangement of the circumferential hoop formed by the wires  116  ensures that in the expanded position, the filter body  102  will be supported by the support frame  103  in circumferential apposition with the interior wall of the vasculature. 
     The length of each wire  116  around the hoop is equal. At the proximal termination point  19 , the wires  116  are fixed to each other, and extend generally axially and parallel in a bi-filar arrangement. 
     As the filter support  103  collapses down against the inner tube  108 , the wires  116  become torqued. This torqueing action is similar to the process of elongation of a coiled spring. Because the support frame  103  is defined by round wires  116 , the torque developed in each wire  116  will be evenly distributed along the length of each wire  116 . In addition, the bi-filar connection of the wires  116  to each other at the termination point  19 , further assists in torque distribution along the wires  116 . Thus, collapse of the filter support  103  does not induce high, localized stresses in the filter support  103 . In this way, the filter support  103  may be constructed of wires  116  of a small cross-sectional area which will collapse down to a very low profile. Furthermore, the collapsed filter element with small wires  116  has greater flexibility for ease of advancement of the filter element  1  through the vascular system. 
     The wires  116  are preferably of a self-expanding material, such as Nitinol™. 
     The wires  116  may have a strain distributing linkage element. In this case, the linkage element comprises a loop  120  in each wire. The loop  120  in this case extends axially and distally of the wire hoop. The loop  120  is of generally omega shape as illustrated and is formed integrally in a wire  116 . The loop  120  acts as a strain reliever or distributor when the wires  116  are wrapped down as illustrated in  FIGS. 6 ,  7  and  8 B. The loop  120  has a relatively large radius resulting in highly efficient strain distribution. Radii R 1 , R 2 , R 3  are provided at key points in the support frame to relieve strain as illustrated in  FIG. 9 . In addition, the loop  120  allows the support frame to accommodate varying vessel contours and sizes. In effect the loop  120  acts as a diameter or circumference adjuster allowing an embolic protection device to adapt to difference vessel contours and sizes whilst maintaining apposition with the vessel wall. The strain relieving geometry of the loops enhances the compliance of the bend points without creating a weakened hinge point, thus ensuring that there is no discontinuity in the circumferential seal against the vessel wall. 
     The loops  120  can also be regarded as distal termination points which have a pair of arms which extend axially and generally parallel. The looped terminations  120  enhance the ability of the filter support  103  to be wrapped down to a low profile. 
     In addition, the looped configuration of the distal termination  120  spreads the force exerted by the filter support  103  on the filter body  102  over a greater area. In this way, the local pressures applied by the filter support  103  on the filter body  102  and the walls of a vasculature are more evenly distributed, this minimizing the possibility of vessel trauma. 
     Another important advantage of the strain distributing features such as loops  120  is that they provide an anchor to which connecting elements such as tethers may be readily attached as described in more detail below. 
     In use, the filter element is collapsed down and loaded into a delivery catheter with an associated torqueing of the wires  116  around the hoop. The filter element is then delivered through a vasculature fixed to or over a guidewire using the delivery catheter until the filter element is located at a desired site in the vasculature. 
     By moving the delivery catheter proximally relative to the filter element  1 , the element is deployed out of the delivery catheter at the desired site in the vasculature. The filter support  103  expands radially outwardly to support the filter body  102  in circumferential apposition with the interior wall of the vasculature. In the fully expanded position, the wires  116  of the support frame  103  are substantially free of torque. 
     The site of deployment of the filter element in the vasculature is typically downstream of a treatment site, such as a region of stenosis in the vasculature. During the performance of a treatment procedure, the filter element captures and safely retains any embolic material in the blood stream within the filter body  102 . 
     The delivery, deployment and retrieval of the embolic protection device of the invention, as described above, is similar to the described in our W099/23976, WO 01/80776A (US 2002-0052626A) and WO 01/80773A (US 2002-0049467A), the relevant contents of which are incorporated herein by reference. The filter element may be slidably exchanged over the guidewire without any attachment means between the filter element and the guidewire. A distal stop on the guidewire assists in retrieval of the filter element. The guidewire may remain in the vasculature after retrieval of the filter element. 
     The support comprises a segmented ring structure which may have two circumferential wire segments. The wire segments may be connected by a strain distributing linkage element at one end and by a bifilar joint at the other end. The bifilar joint may be coupled to the carrier by a single or multiple struts and/or tethers. In one case the strut is attached to the carrier. The connection may permit rotation relative to the carrier either longitudinally distal or proximal to the point of attachment to the segmented ring. 
     In some cases the attachment to the carrier is rigid, in other cases a flexible joint is provided using a tether, a loop, a thinned wire section or the like. A focal tether may be utilized. A focal tether implies that the strut has tensile and compressive integrity but the joint is not rigid. The joint can thus flex in all directions but it cannot translate. 
     Individual wires may taper towards the proximal or distal end. 
     The support frames may have distal, proximal and/or intermediate anchors. One anchor may be fixed and another translatable and/or rotatable relative to the carrier. For example a proximal anchor may be translatable or in arrangements in which both proximal and distal anchors are provided both may be translatable. 
     The support frame may comprise a segmented ring or hoop which may have an elliptical cross-section in the free expanded state. The support ring may be angulated relative to the axis of the inner member. 
     Various strain distributing linkage elements are illustrated in  FIGS. 10 to 20 . In  FIG. 10  the strain distribution is provided by a zig zag linkage element  103 . The omega shape of the preferred loop  120  will be apparent in  FIG. 11  however the loop may approximate to a curved V shape  131  as illustrated in  FIG. 12 . Various arrangements in which a strain distributing element is provided by a separate component defining a loop  135  are illustrated in  FIGS. 13 to 19 . The loops  135  may be attached or formed in a number of ways, as illustrated. Another strain distributing diameter/adjusting feature  136  is illustrated in  FIG. 20 . 
     Referring to  FIGS. 21 and 22 , there is illustrated a further filter support  140 , which is similar to the filter support of  FIGS. 1 to 9 , and similar elements in  FIGS. 21 and 22  are assigned the same reference numerals. In this case the filter support  140  comprises two wires  141  which have an elongate cross-section, in this case a rectangular cross-section, along their proximal section  118 . The wires  141  are arranged such that the shorter dimension of the rectangle is aligned along the radial direction of the filter support, as illustrated in  FIG. 22 . 
     This flattened wire configuration provides for a filter support  140  with enhanced flexibility. This is achieved because the second moment of area of the wires  118  is reduced in the flattened configuration. 
     In addition, the flattened wires  141  minimize the influence of the support leg  118  on the outward radial force R 1  exerted by the support frame. This results in a filter support  140  which exerts a relatively constant outward radial force R 1  around the circumference of the filter support ( FIG. 22 ). 
     In  FIG. 24 , there is illustrated a filter support  145  in which the cross-sectional area of the round wire  141  decreases radially inwardly along the support leg  118  from the proximal termination point  119  to the proximal end of the filter support  145 . This tapered support leg  118  also achieves the enhanced flexibility, and the relatively constant outward radial force R 1  around the circumference of the filter support  145 , similar to that discussed previously with reference to  FIGS. 21 and 22 . 
     As illustrated in  FIG. 23 , the support leg  118  may be provided by only one of the two round wires  116 , with the other round wire  116  terminating at the proximal termination point  119  where the wires  16  are fixed together. Another arrangement of this type is illustrated in  FIG. 25 . 
     The configuration of a single wire support leg  118  also achieves the enhanced flexibility, and the relatively constant outward radial force R 1  around the circumference of the filter support  340 , similar to that discussed previously with reference to  FIGS. 21 and 22 . 
       FIGS. 26 to 28  illustrate another filter support  150 , which is similar to the filter support described above, and similar elements are assigned the same reference numerals. In the filter support  150 , the round wires  116  extend circumferentially around the support frame in an irregular, wave-like pattern. This configuration increases the area of contact between the wires  116  and the filter body  102 . As illustrated in  FIG. 28  this increased area of contact assists in more evenly distributing the radial forces R 1  from the support wires  116  to the filter body  102  and hence to the vessel wall. In this way, the risk of vessel trauma due to the forces exerted by the filter support  150  is minimized. 
     The radial forces exerted by the filter support on the filter body  102  and the walls of a vasculature depend on a number of factors, such as the diameter of the round wires  116 , the material chosen for the wire  116  and the properties of that material, the number of wires  116  in the filter support, the angle of inclination a of the support leg  118  ( FIG. 9 ), and the radii R 1 , R 2 , R 3  of the bends in the filter support. By suitably varying these factors, the radial force exerted by the filter support  301  may be accurately controlled. 
     Another important influencing factor on the radial force exerted by the filter support is the fixing of the wires  116  relative to one another at the proximal termination points  119  and/or at the distal termination points  120 . It may be advantageous to securely fix the wires  116  relative to one another at the proximal termination point  119  to achieve the required radial force perpendicular to the proximal termination point  119 . 
     One means of fixing the two wires  116  of the filter support relative to one another at the proximal termination point  119  is to clamp the wire  116  together using a tubular polymeric sleeve  151 , as illustrated in  FIG. 29 . The sleeve  151  provides a durable means of fixing the wires  116  together which will effectively resist peeling of the wires  116  apart, thus resulting in a highly robust filter element. 
     The sleeve  151  may be partially of a radiopaque material, such as platinum, or iridium, to provide visualization of the filter element during use. 
     Alternatively the wires  116  may be clamped together by winding a wire  152  around the support wires  16 , and then bonding or soldering the wire  152  in place around the clamped support wires  16 , as illustrated in  FIG. 30 . The wire  152  may be radiopaque. 
     Another suitable means of fixing the two wires  116  together is to directly solder, weld or bond the tow wires  116  together. 
     It will be appreciated that a variety of different means may be used to effectively fix the wires  116  relative to one another at the proximal termination point  119  and/or at the distal termination point  120 . 
     As illustrated in  FIG. 32 , the looped termination  120  may be configured to fold radially inwardly upon collapse of the filter  160 , so that the looped termination  120  will engage emboli  161  which have collected in the filter body  102 . In this manner, the looped terminations  120  will assist in holding the emboli  161  in place within the filter body  2  and in preventing extrusion of the emboli  161  out of the filter body  102  during retrieval of the filter  160 . Thus the filter  160  will safely retain the emboli  161  for removal from the vasculature. 
     Furthermore, as illustrated in  FIGS. 31 to 35 , the looped termination  120  may be folded radially inwardly to engage against the inner tube  108 . This arrangement provides enhanced radial support for the filter body  102 . 
     Upon collapse of the filter  162 , the looped terminations  120  slide over the inner tube  108  until the filter support is in the fully collapsed, elongated configuration. 
     The loops  120  may be attached at  163  to constrain their freedom of movement to the axis of the tube  108  ( FIG. 35 ). 
     Another filter  170 , is illustrated in  FIG. 36 , and similar elements to those in previous drawing are assigned the same reference numerals. The filter support comprises a single round wire  116  which extends axially and radially outwardly in a single leg  118  to the proximal termination point  119 . The wire  116  extends circumferentially around the support frame, looping at the distal termination  120 . 
     The filter body  102 , has a single, large inlet opening  106  defined at the inlet end  104 . This arrangement further minimizes the possibility of any embolic material becoming caught or hung-up on any parts of the filter at the inlet end  104 . This arrangement also further reduces the overall longitudinal length of the filter  170 . 
     In this case the filter body  102  is fixed directly to the filter support at the inlet end  104  by wrapping two flaps  171  of the filter body  102  around the support wires  116  and then fixing the flaps  171  to the filter body  102  in this wrapped position ( FIG. 36 ). 
     In the filter element  175  of  FIG. 37 , the support leg  118  is fixed to the inner tube  108  at an inner foot section  176 . The inner section  176  is inverted to extend distally along the inner tube  108 . In addition, the filter body  102  is configured to slide distally over the timer tube  108  upon collapse by means of a sleeve  177  fixed to the filter body  102  at the distal end  105 . The sleeve  117  is also inverted to extend proximally along the inner tube  108 . 
     In this way, by inverting the inner section  176  of the leg  118  and the sleeve  177 , the overall longitudinal length of the filter support is minimized. This results in less “parking space” in a vasculature being required to deploy the filter. 
     Furthermore, by extending the inner section  176  of the leg  118 . distally, the possibility of embolic material becoming caught or hung-up at the inlet end  104  of the filter element is reduced. 
     Referring to  FIG. 38  another filter  180  which has a more enhanced transition to the foot  176  is illustrated. 
     The filter  185  of  FIG. 39  has a proximal support leg  118  that extends distally to minimize the length and hence the parking space of the filter. A support foot  176  is again provided for load distribution. 
     The filter  190  of  FIG. 140  has two proximal support legs  191 ,  192  which are axially offset. 
     Referring to  FIGS. 41 to 43  another filter  195  has a single proximal support arm  196  which terminates in an open collar  197  which is slidably engagable with the tubular member  108 . This arrangement provides a large single inlet opening on deployment. The support frame is held in a lip  198  of the filter body/membrane  102 . 
     Another filter  200  is illustrated in  FIGS. 44 and 45  which has a construction similar to that of  FIG. 40  but with the support frame having neither proximal nor distal support arms. The frame design provides a very short wrapped length for superior trackability. The stepped filter arms provide a large inlet opening on deployment. 
     Various alternative support frames are illustrated in  FIGS. 46 to 51 . In each case, the support hoop is of generally elliptical shape. 
     In the support  205  of  FIGS. 46 and 47  the hoop is biased towards an elliptical shape in its unconstrained state. When constrained within a vessel the major axis of the ellipse will be compressed, which will tend to expand the minor axis. This action may assist in the even distribution of radial force to the vessel wall in the case where the support frame is inherently more flexible at the loops than at the top of its proximal arms. 
     In the support  215  of  FIGS. 48 and 49  the proximal arms of the support frame are staggered so that the hoop is inclined at an angle to the axis of the filter in side view. 
     Thus although the hoop is actually elliptical it appears circular in end view as shown in  FIG. 51 . 
     In the support  210  of  FIGS. 50 and 51  the loops of the support frame are offset so that the hoop is inclined at an angle to the axis of the filter in top view. Thus although the hoop is actually elliptical it appears circular in end view as shown in  FIG. 51 . 
     To enhance visualization of the filter the wire segments and/or the linkage elements may be rendered radiopaque. Referring to  FIG. 52  a section  250  is of a different material or has different properties than that of the wire or linkage element  251 . The section  250  is ductile and radiopaque. In  FIG. 53  the section  250  is formed by straight wires  252  some or all of which may be radiopaque. In  FIG. 54  the section  250  is of braided construction, some or all of which may be radiopaque. A radiopaque coil  260  is provided in  FIG. 55 . In  FIG. 56  a linkage element  120  is rendered radiopaque by using a radiopaque braid. The linkage element  120  may be of different material and/or have a similar radiopacifying arrangement as shown in  FIGS. 52 to 55 . 
     Methods of rendering terminations and/or linkage element radiopaque are illustrated in  FIGS. 57 to 62 . In  FIG. 57  a radiopaque band or cup  270  may be used. A radiopaque solder  271  may also be used ( FIG. 58 ). Similarly a radiopaque band  275  may be crimped around the heck of a loop  120  as illustrated in  FIG. 59 . A coil  280  of radiopaque material may be wound around the loop  120  as illustrated in  FIG. 60  or across the loop as illustrated in  FIGS. 61 and 62 . 
     As illustrated in  FIG. 63 , at least part of the support may be of a multifilament wire construction. In this case seven Nitinol™ wires  300  are wound in a spiral around a single radiopaque wire  301 , the radiopaque wire  301  being located substantially along the axis of bending of the support. The support may have the multifilament wire construction along the entire length of the support in this instance. 
     During bending of the support ( FIG. 64 ), for example upon movement of the support to the expanded configuration, each wire  300 ,  301  bends independently of the other wires. As a result, the force required to bend the multifilament support is minimized, and thus the filter achieves enhanced trackability during transport through a tortuous vasculature, such as in coronary applications. 
     Because the Nitinol™ wires  300  are wound in a spiral around the radiopaque wire  301 . This configuration acts to decrease the bending stresses induced in each wire  300 ,  301  upon bending ( FIG. 64 ). 
     The radiopaque wire  301  provides visualization for a clinician during transport of the filter  1  through a vasculature and deployment of the filter in the vasculature. Because the radiopaque wire  301  is located along the neutral axis of the support, the forces required to plastically deform the radiopaque wire  301  as the support moves from the collapsed configuration to the expanded configuration, upon deployment of the filter  1 , are minimized. In this way the dampening effect of the radiopaque material is minimized. 
       FIG. 65  illustrates portion of a support  310  of another embolic protection filter according to the invention. In this case, the support comprises two radiopaque wires  311  around which are wound in a spiral a plurality of Nitinol™ wires  312 . 
     A support  315  of a further embolic protection filter according to the invention is illustrated in  FIG. 65 . The Nitinol™ wires  318  and the radiopaque wire  317  are braided together to form the multifilament wire support  35 . 
     Referring to  FIGS. 67 and 68  there is illustrated a support  320  of another embolic protection filter according to the invention. The support comprises a single radiopaque wire  321  which extends substantially longitudinally, and a single Nitinol™ wire  322  which is wrapped around the radiopaque wire  321  in a coil. As illustrated in  FIG. 68 , the bending stress induced in the Nitinol™ wire  322  upon bending is substantially less than the bending stresses induced in a solid wire bent through the same angle. 
     A portion of a wire support  330  of another embolic protection filter is illustrated in  FIG. 69 . In this case, a single Nitinol™ wire  331  extends substantially longitudinally, and a single radiopaque wire  332  is wrapped around the Nitinol™ wire  331  in a coil. 
       FIG. 70  illustrated part of a support  340  of another embolic protection filter according to the invention. The support  340  does not have any radiopaque wire filaments, instead radiopacity is achieved by a radiopaque core  341  embedded within at least one of the wires  342 . The radiopaque core  341  is located substantially along the neutral axis of the Nitinol™ wire  342 , and thus the force required to plastically deform the radiopaque core during movement of the support from the collapsed configuration to the expanded configuration is minimized, and the dampening effect of the radiopaque material is minimized. 
     Referring to  FIGS. 71 to 72  a linking element loop  120  may be provided with radiopacity in a similar manner. 
     Referring to  FIG. 73  or  74  a radiopaque material  345  may be sandwiched between two outer layers. Such a frame could be constructed by laser machining an entire frame (or portion thereof) from a large diameter bi-metal or tri-metal tube. The frame cross section could thus be square or rectangular as shown in  FIG. 73 , or could be electropolished to create an elliptical or round wire shape as shown in  FIG. 74 . 
     The support wire(s) may be of any suitable superelastic material, or alternatively of a high strength material, such as stainless steel. 
     Referring to  FIG. 75 , there is illustrated portion of a support  350  of another embolic protection filter according to the invention. In this case, the support  350  comprises a jacket  351  of a polymeric material around multifilament wires  352 ,  353 . The Nitinol™ wires  352  and the radiopaque wire  353  are embedded within the polymeric jacket  351 . A variety of manufacturing procedures, such as ovenmoulding, heat-shrinking, dipping, spraying, painting, depositing may be used to fabricate the wires embedded within the jacket  351 . The jacket  351  acts to maintain the structure of the multifilament wire construction intact, and ensures that the wires move in a coordinated manner. 
       FIG. 76  illustrates a support  360  of another embolic protection filter which comprises five Nitinol™ wires  361  wound together in a spiral without any radiopaque wire filaments. A radiopaque material, such as tungsten, bismuth subcarbonate, barium sulphate, may be loaded into the polymeric jacket  362  to achieve visualization. 
     It will be appreciated that a jacket may be used with any of support structure described previously. For example,  FIG. 77  illustrated a support  370  of a further embolic protection filter in which the Nitinol™ wires  371  and the radiopaque wire  372  are braided together and embedded in the polymeric jacket  373 . 
     Various ways of rendering a wire, linkage element or tubular member of the embolic protection devices of the invention radiopaque are illustrated in  FIGS. 78 to 83 . In general a radiopaque material  390  is provided around the element or may itself define the element such as in the case of the tubular member of  FIG. 83 . 
     Referring to  FIG. 84  a portion of a support  400  may be in the form of one or more wires  401  of superelastic material, such as Nitinol™. A core of radiopaque material is embedded within at least portion of at least one of the support wires  401 . In this case, the core is also in the form of a wire  402  of a suitable radiopaque material, such as gold, or platinum, or mercury and extends along the length of a support wire. The radiopaque wire  402  is located substantially along the neutral axis of bending of the support wire  401 . The radiopaque wire  402  provides visualization for a clinician during transport of the filter through a vasculature and deployment of the filter in the vasculature. By providing the radiopaque wire  402  as the core of the support wire  401 , this minimizes the diameter of the radiopaque wire  402  and its distance from the neutral axis. Because the second moment of area of the radiopaque wire  402  is proportional to the fourth power of its diameter, the second moment of area of the radiopaque wire  402  is also minimized. Correspondingly, the forces required to plastically deform the radiopaque wire  402  as the support wire  401  moves from the collapsed configuration to the expanded configuration. upon deployment of the filter, are also minimized. In this manner, the radiopaque core configuration of the invention acts to minimize the dampening effect of the radiopaque material, which is necessary to achieve visualization of the filter. 
     The radiopaque material may also be provided in powder form  405 , as illustrated in  FIG. 85 , or in liquid form  406 , as illustrated in  FIG. 86 . Because the radiopaque core  405 ,  406  is embedded within the support wire  401 , the radiopaque powder or radiopaque liquid  26  will be safely retained and controlled within the support wire  401 . 
     By using a powder or liquid for the radiopaque material, the yield stress of the radiopaque material is reduced. Thus the forces required to move the support wire  401  from the collapsed configuration to the expanded configuration are further reduced. 
     The support may comprise a reservoir for enclosing a fluid, the reservoir being provided, which extends circumferentially around the filter at the inlet end  104  to form an enclosed loop around the inlet opening. 
     The tube may enclose a fluid such as mercury. The temperature of the fluid increases towards body temperature upon deployment of the filter in a vasculature, which causes the fluid to expand. This expansion of the fluid forces the support tube towards the expanded configuration until the support tube is fully expanded and the filter is supported in the expanded configuration. 
     It will be appreciated that the expansible fluid may be of any suitable material. By using a radiopaque material, such as mercury, this provides the additional advantage that visualization of the filter will be possible during transport of the filter through a vasculature and deployment of the filter in a vasculature. 
     In another embolic protection filter according to the invention, the fluid enclosed in the reservoir may be pressurized. In this case, upon release of a constraint on the filter, such as upon deployment of the filter out of the pod of the delivery catheter, the pressurized fluid in the support reservoir forces the support towards the expanded configuration until the filter is supported in the fully expanded configuration. 
     It will be appreciated that the radiopaque core aspect of the invention, and/or the temperature expansible fluid aspect of the invention, and/or the pressurized fluid aspect of the invention may be used in any suitable manner or combination with any appropriate medical device. 
     It will further be appreciated that aspects of the invention may be applied with any medical device for transport through a body passageway and deployment in a body. 
     Referring to  FIGS. 87 to 105  there are illustrated various alternative support frames incorporating tethering features for connecting the support frame distally and/or proximally and/or intermediately to a carrier. Tethers may also be used additionally or alternatively for connecting various elements of a support frame. 
     In all cases the tethers may be of any suitable material such as fine gauge wire, for example Nitinol™ wire, fiber or polymers. The tethers may be of solid or braided construction, for example. 
     Referring to  FIGS. 87 to 89  two distal tethers  500 ,  501  are used to connect a support hoop  503  to a tubular member  504 . The distal tethers provide added safety and stability to the frame without any increase in the length of the device when wrapped down as illustrated in  FIG. 89 . 
       FIG. 90  illustrates an alternative arrangement of distal tethers  505 . 
     The tethers may be connected to the support frame and carrier in any suitable fashion. For example, the distal tethers may be double stranded and looped around the support frame as shown in  FIG. 87 . 
     Referring to  FIGS. 91 to 96  there are illustrated various constructions with proximal tethers, with  FIG. 90  illustrating a basic construction of two tethers  520  and a simple hoop support frame. 
       FIG. 92  illustrates a similar frame to that shown in  FIG. 9  previously, but with the proximal frame arms replaced with tethers  520 . Additional strain relieving loops are provided at the tether connection points to assist in the wrap down of the device as discussed previously in relation to the distal loops. The use of flexible tethers in place of wire arms enables the length and stiffness of the wrapped down frame to be reduced, enhancing the trackability of the device. The flexibility of the tethers also enables an even radial force to be provided around the circumference of the frame without interference from the proximal arms. 
     In  FIG. 97  there are proximal tethers  530  and distal tethers  531 . This construction provides the benefits described in relation to  FIG. 92  with the added benefit of the safety and stability provided by the distal tethers. Again the tethers provide a means of anchoring the support frame to the carrier without affecting the stiffness or profile of the wrapped device. 
     In  FIG. 98  an offset loop support  540  has a distal tether  541  to prevent the support frame from moving too far proximally and outside the filter body. 
     In  FIG. 99  another offset loop  550  has a proximal tether  551  to restrain the movement of the loop section of the frame and thus reduce the overall length of the wrapped device. 
     Referring now to  FIGS. 100A to 100D  there is illustrated one type of knot  600  in a tether  605  being tied to a linkage element loop  601  of a support hoop  602 . 
     Referring to  FIG. 101  there is illustrated a support frame with circumferentially extending tethers  610  which allows the frame to move circumferentially to accommodate a broad vessel size range. The tethers  610  also assist in providing added support to a filter body, especially in large vessels. There is also an axially extending tether  615  interconnecting elements of the support frame. 
     Referring to  FIG. 102 , there is illustrated a filter support  620  comprising a hollow tube  605  which extends circumferentially around the support frame to define a hoop. A tether  626  is looped through the tube  605 , passing out of the tube  605  at the proximal termination point  119 . The tether  626  extends proximally and radially inwardly from the proximal termination point  119  to the inner tube  108  to which the ends  627  of the wire  626  are fixed. The tether  626  could be of wire and/or of a radiopaque material. 
     Torqueing of the tether  626  within the tube  605  is possible during collapsing and expanding of the filter. In the filter support, the tube  605  exerts the outward radial force to support the filter body  102  in the extended outwardly projecting position, and the element  626  acts as a flexible tether to maintain safe, reliable control over the support tube  605 . 
     The support tube  605  may be of any suitable material, such as polyamide or a superelastic material, for example Nitinol™. The tube  605  may be flexible or rigid. The tube  605  strengthens the proximal termination point  119  while permitting a degree of flexibility at the proximal termination point  119 . 
     One end of the tether  626  may terminate at the proximal termination point  119  where the end is attached to the other side of the looped tether  626 , with the other end of the tether  626  fixed to the inner tube  605 . 
     The invention incorporates circumferential wire angulation into support structure design to give maximum circumferential support to the filter membrane. 
     Referring now to  FIG. 103  a filter  650  with a proximal tether  651  extending from the support hoop is illustrated. Other details of this filter are as described with reference of  FIGS. 36 and 41 . 
     Referring to  FIG. 104  there is illustrated an alternative support frame in which axially adjacent frame elements  660  are interconnected by tethers  661  which provide additional support for the filter body. The tethers  661  may be of light gauge thread or wire to facilitate ease of wrapping down. 
     Referring to  FIG. 105  there is illustrated another filter support frame comprising two axially spaced-apart support hoops  670  interconnected by axially extending tethers  671 . The tethers  671  provide membrane support but are of light and flexible material which will add very little to the wrapped profile or stiffness of the support frame. Referring next to  FIG. 106 , there is illustrated another filter element  700 . In this case, the filter support comprises four round wires  116  which extend axially and radially outwardly in two legs  118  from the proximal end to two opposed proximal termination points  119 . 
     The wires  116  separate at the proximal termination points  119  and extend circumferentially around the support frame  115  until two opposed distal termination points  120  are reached. The wires  116  then regroup into legs  121  at the distal termination points  120 . the legs  121  extending axially and radially inwardly to the sleeve  111  to which the wires  116  are fixed. 
     In this case, the proximal termination points  119  are 90° offset from the distal termination points  120 . 
       FIG. 107  illustrates a support frame  710  of simpler construction that than of  FIG. 106 . 
       FIGS. 108 and 109  illustrate the wrapping down of the support frame of the filter of  FIG. 106 . 
       FIGS. 110 and 111  illustrate another support frame  720  in which the sleeve  111  is located proximally resulting in a shorter wrapped down configuration. 
       FIGS. 112 to 115  illustrate various terminations for the wires in the wire frames of the invention which could be employed to connect a single proximal or distal frame arm to the circumferential hoop portion of the frame. A construction such as that shown in  FIG. 114  allows rotation of the hoop relative to the arm, reducing the stresses induced during wrapping. 
     Referring to  FIG. 116  there is illustrated another support frame comprising a single hoop  800  with two strain distributing loops  801 . One of the loops  801  has an arm or tether  802  connecting the hoop  800  to a tubular member  803 . This arrangement provides a support frame with a very short parking space in use. Thus, it can be deployed even if only a short segment of vessel is available downstream of a treatment location. The support can wrap down in either direction for loading and/or retrieval. 
     It will be appreciated that the wires  116  may be slidably mounted to the inner tube  108  at both the proximal support leg  118  and the distal support leg  121 . 
     It will be further appreciated that by increasing the number of wires  116  which define the complete looped cell  117  of the support frame  115 , the elongation of the overall filter support, when collapsed down, will be reduced. For example, the filter support of  FIG. 117  comprises eight round wires  116  which extend axially and radially outwardly in four legs  118 . In this manner, the space required in a vasculature to deploy and retrieve the embolic protection device is correspondingly reduced. 
     Depending on the configuration of the filter element, the inner tube may or may not be present. In this case the filter support may be mounted directly onto a guidewire for exchange of the filter element over the guidewire. 
     It will also be appreciated that the shape of one wire  116  of a cell  117  does not have to be symmetrical or similar to the shape of the other wire  116  of the cell  117 , provided that the length of each wire  116  is equal. 
     Furthermore it will be appreciated that a single wire  116 , bent back on itself, may be used to define the support frame, in which case the cells  117  of the support frame are defined by elements of the single wire, as illustrated in  FIG. 118 . 
       FIGS. 119 to 121  illustrate possible means by which the single wire  116  may be bent back on itself and wrapped around the inner tube  108 . This single wire arrangement enables case of attachment to the inner tube  108  without stress concentration points occurring at the regions of looping of the wire  116  around the inner tube  108 . 
     The fixing of two separate wires  116  to each other in a bi-filar arrangement is illustrated in  FIG. 122 . The fixing means may be provided by, for example, welding, brazing, soldering, or an adhesive joint at the point of fixation  820 . In the case of a single wire  116  bent back on itself to define the support frame, a 180° U-bend at the end of the wire  116  may be formed in multiple strain-temperature stages to prevent plastic deformation of the wire  116  ( FIG. 123 ). A strain relief means  821 , such as solder, braze or adhesive, may be provided at the base of the U-bend, as illustrated in  FIG. 124 . Alternatively, a strain relief tube  822  may be provided at the end of the single wire  116  ( FIG. 125 ). 
     Referring to  FIGS. 126 to 129  there is illustrated another embolic protection filter  830 . The wires  116  of the filter support  830  are connected to the inner tube  108  by two legs  121 , in this case, which are fixed directly to the inner tube  108 . The four round wires  116  of the filter support extend axially proximally and radially outwardly in the two legs  121  to the two opposed distal termination points  120 . The wires  116  then separate and extend circumferentially around the support frame until the two opposed proximal termination points  119  are reached. Upon collapse of the filter element, the support frame flips distally over the legs  121  until the filter support is fully collapsed against the inner tube  108  with the legs  121  at the proximal end of the filter support. 
     By locating the support legs  121  distally of the inlet end  104  of the filter body  102 , this arrangement minimizes the possibility of embolic material becoming caught or hung-up at the inlet openings  106 . In this manner, substantially all of the embolic material is retained safely with the filter body  102  for subsequent retrieval from the vascular system using a retrieval catheter  832  as illustrated in  FIGS. 128 and 129 . 
     As illustrated with the filter  840  of  FIGS. 130 and 131 , a proximal neck  841  of the filter body may be inverted to extend distally rather than proximally, as is the case with the filter element of  FIG. 129 . This arrangement reduces the overall longitudinal length of the filter element, and thus the filter element may be deployed and retrieved with a shorter “parking space” in the vasculature. 
       FIGS. 132 to 134  illustrate the process of inverting the proximal neck  841 . The neck  841  is split along each side  842  ( FIG. 133 ), and the neck  841  is then pushed distally into the interior of the filter body ( FIG. 134 ). 
     In addition, the longitudinal length of the filter element of  FIG. 130  is further shortened by providing a hemi-spherically shaped proximal nose  845  instead of a conical nose, as is the case with the filter element of  FIG. 129 . Furthermore, the overall crossing profile of the filter element is reduced by means of the hemi-spherical nose  845 . 
     Referring to  FIG. 135  there is illustrated a filter with a proximally extending neck  847  which is split into two parts  847 . 
     Referring to  FIGS. 136 and 137  there is illustrated a filter  870  in which the filter body is connected directly to the frame by means of folded filter seams. 
       FIG. 137  shows a variant filter  875  in which a second frame provides additional body support to the filter. 
     Referring to  FIG. 138 , there is illustrated another filter element  880 , with a filter body which, in this case, has a single, large inlet opening  881  defined at the inlet end  104 . This arrangement further minimizes the possibility of any embolic material becoming caught or hung-up on any parts of the filter element at the inlet end  104 . This arrangement also further reduces the overall longitudinal length of the filter element. 
       FIGS. 139 and 140  illustrate a further filter element  885 , in which the proximal end  9  of the filter support is fixed to the inner tube  108 , while the distal end  110  of the filler support remains unconnected to the inner tube  108 . The filter support comprises four round wires  116  which extend axially and radially outwardly in two legs  118  from the proximal end  109  to the proximal termination points  119 . At the proximal termination points  119 , the wires  116  separate and extend circumferentially around the support frame until the two distal termination points  120  are reached. The proximal termination points  119  are circumferentially offset by 90° from the distal termination points  120 . 
     The proximal end  109  of the filter support  103  is fixed to the inner tube  108 , and the distal end  110  of the filter support  103  is fixed to a sleeve  111  which is slidable over the inner tube  108 . Upon collapse of the filter element, the proximal end  109  of the filter support  103  remains fixed relative to the inner tube  108 , and the distal sleeve  111  slides over the tube  108 , until the filter support  103  is fully collapsed against the inner tube  108 . In this collapsed position, the filter support  103  is axially elongated relative to the expanded position. 
     The filter support  103  is illustrated in  FIG. 142 . The filter support  103  comprises two round wires  116  which extend from the proximal end  109  to the distal end  110 . The wires  116  extend together axially and radially outwardly in a leg  118  from the proximal end  109 , where the wires  116  are fixed to the inner tube  108 , to a central support hoop  115 . The junction of the leg  118  with the support hoop  115  is referred to in this specification as the proximal termination point  119 . 
     At the proximal termination point  119 , the wires  116  separate, and extend circumferentially around the support hoop  115  until a symmetrical distal termination point  120  is reached. In this way, the two wires  116  define the support hoop  115 . 
     At the distal termination point  120 , the wires  116  regroup into a leg  121  which extends axially, and then axially and radially inwardly to the sleeve  111  to which the wires  116  are fixed. 
     The path of the two wires  116  around the support hoop  115  together define a cell  116  which forms a complete loop, as illustrated in  FIG. 142 . This arrangement of the circumferential looped cell  117  ensures that in the expanded position, the filter body  102  will be supported by the support hoop  115  in circumferential apposition with the interior wall of the vasculature. 
     The length of each wire  116  around the cell  117  is equal. At the proximal and distal termination points  119 ,  120 , the wires  116  are fixed to each other, and extend generally axially and parallel in a bi-filar arrangement. 
     As the filter support  103  collapses down against the inner tube  108 , the wires  116  around the cell  117  become torqued. This torqueing action is similar to the process of elongation of a coiled spring. 
     Because the support frame  115  is defined by round wires  116 , the torque developed in each wire  116  will be evenly distributed along the length of each wire  116 . In addition, the bi-filar connection of the wires  116  to each other at the termination points  119 ,  120  further assists in torque distribution along the wires  116 . 
     Thus, collapse of the filter support  103  does not induce high, localized stresses in the filter support  103 . In this way, the filter support  103  may be constructed of wires  116  of a small cross-sectional area which will collapse down to a very low profile. 
     Furthermore the collapsed filter element with small wires  116  has greater flexibility for ease of advancement of the filter element through the vascular system. 
     As illustrated in  FIG. 142 , the proximal termination point  119  is circumferentially offset by 180° from the distal termination point  120 . 
     The wires  116  are preferably of a self-expanding material, such as Nitinol™, and the inner tube  108  is preferably of gold. This arrangement provides for radiopacity. 
     In use, the filter element is collapsed down and loaded into a delivery catheter with an associated torqueing of the wires  116  around the cell  117 . The filter element is then delivered through a vasculature fixed to or over a guidewire using the delivery catheter until the filter element is located at a desired site in the vasculature. 
     By moving the delivery catheter proximally relative to the filter element, the filter element is deployed out of the delivery catheter at the desired site in the vasculature. The filter support  103  expands radially outwardly to support the filter body  102  in circumferential apposition with the interior wall of the vasculature. In the fully expanded position, the wires  116  of the support frame  115  are substantially free of torque. 
     The site of deployment of the filter element in the vasculature is typically downstream of a treatment site, such as a region of stenosis in the vasculature. During the performance of a treatment procedure, the filter element captures and safely retains any embolic material in the blood stream within the filter body  102 . 
     After completion of the treatment procedure, the filter element is collapsed down and retrieved into a retrieval catheter with any retained embolic material within the filter body  102 . The wires  116  around the support frame  115  are again torqued during collapse. 
     The retrieval catheter is then withdrawn from the vasculature with the filter element within the retrieval catheter. 
     Referring to  FIGS. 142A and 142B  there is illustrated a lower portion and a top view of a modified support frame similar to  FIG. 142  in which the loops defined by the wires  115  are offset at point  120 . This offset could also be applied to point  119 . Such a design may be of benefit in broadening the area of circumferential apposition and sealing provided by the filter. 
     Referring to  FIG. 143  there is illustrated a support frame.  910  similar to that of  FIG. 142  except that in this case the distal and proximal legs  121 ,  118  are defined by a single wire, the second wire extending only a short distance distally or proximally from the distal and proximal termination points respectively. 
     Referring to  FIG. 144  there is illustrated another embolic protection filter  920  which comprises a single hoop support frame  921  with additional wire support anus  922 ,  923 . In this case the distal support leg is connected to the proximal end of the carrier. Thus additional support is provided to the hoop without any impact on the wrapped length of the device. 
     Referring to  FIG. 145  there is illustrated a further embolic protection filter  930  comprising support hoops  931 ,  932  which are offset. 
     Referring to  FIGS. 146 to 148  there are illustrated various filter frames comprising a wire support hoops which may have strain distribution features and/or tethers as described above. 
     The frame  935  of  FIG. 146  comprises a single wire offset hoop  936 . The frame  938  of  FIG. 147  is preferred because parking space is minimized while facilitating wrapdown. It will be noted the support comprises an offset wire support hoop  939  with an axially extending proximally extending wire section  940  and an inwardly extending support arm  941 . The frame  945  of  FIG. 148  is similar to that of  FIG. 147  except that there are two oppositely directed offset hoops  946 ,  947  similar to the frame used in the filter of  FIG. 145 . 
     Another support frame  950  is illustrated in  FIGS. 149 to 150  which is again of wire and includes strain distributing loop features  951  which may be of any suitable type as described above and exemplified in  FIGS. 150 and 151 . 
     The support frame  960  of  FIGS. 152 and 153  again has an offset hoop  961  which can wrap down as illustrated in  FIG. 153 . 
     Referring to  FIGS. 154 and 155 , there is illustrated another filter element  970 , in which the filter support  972  comprises four round wires  116 . At the proximal termination point  119 , two of the wires  116  extend circumferentially around the support frame  115  to define a first call  117 , and the other two wires  116  extend axially and then extend circumferentially around the support frame to define a second cell  1   117 . 
     In this manner, the wires  116  define two axially spaced-apart cells  117 , each cell  117  forming a complete loop, as illustrated in  FIG. 155 . This arrangement ensures that in the expanded position, the filter body  102  will be supported by the support frame in tubular apposition with the interior wall of the vasculature. The tubular apposition further minimizes the possibility of any flow path for blood occurring between the filter body  102  and the vasculature wall to bypass the filter element. At the distal termination point  120 , all four wires  116  regroup into leg  121 . 
     It will be appreciated that as the wires  116  extend circumferentially around the support frame  115 , the wires  116  may also extend partially axially, so that the defined cell  117  partially slopes axially. Furthermore, the wires  116  may be at least partially of an arcuate shape, as illustrated in the support frame  973  of  FIG. 156 . In either case, the sloping or arcuate configuration of the wires  116  increases the contact area between the wires  116  and the filter body  102 , and in this way, the supporting force exerted by the wires  116  on the filter body  102  is more evenly distributed. This arrangement minimizes any trauma experienced by the vasculature due to the apposition of the filter element with the vasculature. 
       FIG. 157  illustrates another filter support  975 , which is similar to the filter support of  FIGS. 154 and 155 , and similar elements in  FIG. 157  are assigned the same reference numerals. In this case, the filter support comprises six round wires  116 . The wires  116  extend axially and radially outwardly in two legs  118  from the proximal end  109  to two opposed proximal termination points  119 . As illustrated in  FIG. 157 , the wires  116  are arranged to define two axially spaced-apart, complete loop cells  117 . In addition, two of the wires  116  act as axial bridges to connect the two cells  117 . At the distal termination points  120 , the wires  116  regroup into two legs  121 . The proximal termination points  119  are circumferentially aligned with the distal termination points  120 , in this case. 
     The support frame  980  of  FIG. 158  is similar to that of  FIG. 157  except that in this case there are no proximal support arms with consequential reduced filter length. 
     Referring to  FIGS. 159 to 161 , there is illustrated another filter support  990 , which is similar to the filter support of  FIGS. 154 and 155 , and similar elements are assigned the same reference numerals. In this case, the filter support  990  comprises only two round wires  116 . The wires  116  extend together axially and radially outwardly in a single leg  118  from the proximal end  109  to the proximal termination point  119 . The wires  116  then separate and extend circumferentially around the support frame  115  to define the first cell  117 . The wires  116  extend axially, and then circumferentially around the support frame  115  to define the second cell  117 . At the distal termination point  120 , the wires  116  regroup into a single leg  121 . 
     As illustrated in  FIG. 161 , the proximal termination point  119  is circumferentially aligned with the distal termination point  120 . 
     Referring to the drawings, and initially to  FIGS. 162 to 169  thereof, there is illustrated an embolic protection device according to the invention. The embolic protection device comprises a collapsible filter element  1  for delivery through a vascular system of a patient. 
     The filter element  1  comprises a collapsible filter body  2  and a filter support  3  for the filter body  2 , and an inner tube  8 , around which the filter support  3  is mounted. 
     The filter body  2  has an inlet end  4  and an outlet end  5 . The inlet end  4  has one or more, and in this case two, large inlet openings  6  which are sized to allow blood and embolic material enter the filter body  2 . The outlet end  5  has a plurality of small outlet openings  7  which are sized to allow through passage of blood but to retain undesired embolic material within the filter body  2 . In this way, the filter element  1  captures and safely retains any undesired embolic material in the blood stream within the filter body  2  while facilitating continued flow of blood through the vascular system. Emboli are thus prevented from flowing further downstream through the vascular system, which could otherwise have potentially catastrophic results. The filter body  2  may be of an oriented polymeric material. as described in our WO 01/97714A and US 2002/0042627A, the relevant contents of which are incorporated herein by reference. 
     The filter support  3  is movable between a low profile, collapsed position ( FIG. 169C ) for movement through the vascular system, and an extended outwardly projecting position ( FIG. 169A ). As particularly illustrated in  FIG. 2 , in this outwardly projecting position, the filer body  2  is supported in an expanded position by the filter support  3  so as to maximize the internal volume of the filter body  2  to capture and safely retain as much embolic material as possible. 
     The inner tube  8  has a guidewire lumen  12  there through, through which a guidewire may pass for exchange of the filter element  1  over the guidewire. 
     The proximal end  9  of the filter support  3  is fixed to the inner tube  8 , and the distal end  10  of the filter support  3  is fixed to a sleeve  11  which is slidable over the inner tube  8 , as illustrated in  FIG. 164 . As illustrated in  FIGS. 167 to 169C , upon collapse of the filter element  1 , the proximal end  9  of the filter support  3  remains fixed relative to the inner tube  8 , and the distal sleeve  11  slides over the tube  8  ( FIG. 169B ), until the filter support  3  is fully collapsed against the inner tube  8  ( FIG. 169C ). The partially and fully collapsed positions of the filter support  3  are illustrated by dashed lines in  FIGS. 167 and 168 . In the fully collapsed position of ( FIG. 169C ), the filter support  3  is axially elongated relative to the expanded position. 
     The filter support  3  is illustrated in detail in  FIGS. 164 to 166 . The filter support  3  comprises eight round wires  16  which extend from the proximal end  9  to the distal end  10 . The wires  16  extend axially and radially outwardly in two legs  18  from the proximal end  9 , where the wires  16  are fixed to the inner tube  8 , to a central tubular support frame portion  15 . The junction points of the legs  18  with the tubular frame  15  are referred to in this specification as the proximal termination points  19 . 
     At each proximal termination point  19 , the wires  16  separate, and then extend axially along and circumferentially around the tubular frame  15  until symmetrical distal termination points  20  are reached. At these distal termination points  20 , the wires  16  regroup into two legs  21  which extend axially and radially inwardly to the sleeve  1 , to which the wires  16  are fixed. In this way, the wires  16  define the central tubular frame portion  15 . 
     The path of the wires  16  around and along the tubular frame portion  15  defines four cells  17 , with each cell  17  forming a segment of the tubular frame  15  ( FIG. 166 ). Together the four cells  17  extend circumferentially around the tubular frame  15  in a complete loop. 
     This arrangement of the tubular frame  15  ensures that in the expanded position, the filter body  2  will be supported by the tubular frame  15  in tubular apposition with the interior wall of the vasculature. The tubular apposition further minimizes the possibility of any flow path for blood occurring between the filter body  2  and the vasculature wall to bypass the filter element  1 . 
     Each cell  17  is defined by two of the wires  16  which are arranged, in the expanded position. in a generally parallelogram, “hysteresis loop” shape. The length of each wire  16  around the cell  17  is equal. At the proximal and distal termination points  19 ,  20 , adjacent wires  16  are fixed to each other, and extend generally axially and parallel in a bi-filar arrangement. Adjacent cells  17  within the tubular frame  15  are also connected together by fixing a wire  16  in one cell  17  to a wire  16  in an adjacent cell  17 . 
     As the filter support  3  collapses down against the inner tube  8 , the wires  16  around each cell  17  become torqued. This torqueing action is similar to the process of elongation of a coiled spring. 
     Because the tubular support frame  15  is defined by round wires  16 , the torque developed in each wire  16  will be evenly distributed along the length of each wire  16 . In addition, the bi-filar connection of the wires  16  to each other at the termination points  19 ,  20  further assists in torque distribution along the wires  16 . 
     Thus, collapse of the filter support  3  does not induce high, localized stresses in the filter support  3 . In this way, the filter support  3  may be constructed of wires  16  of a small cross-sectional area which will collapse down to a very low-profile. Furthermore the collapsed filter element  1  with small wires  16  has greater flexibility for ease of advancement of the filter element  1  through the vascular system. 
     As illustrated in  FIGS. 165 and 166 , the proximal termination points  19  are circumferentially offset by 90° from the distal termination points  20 . 
     In use, the filter element  1  is collapsed down and loaded into a delivery catheter with an associated torqueing of the wires  16  around the cells  17 . The filter element  1  is then delivered through a vasculature fixed to or over a guidewire using the delivery catheter until the filter element  1  is located at a desired site in the vasculature. 
     By moving the delivery catheter proximally relative to the filter element  1 , the filter element  1  is deployed out of the delivery catheter at the desired site in the vasculature. The filter support  3  expands radially outwardly to support the filter body  2  in tubular apposition with the interior wall of the vasculature. In the fully expanded position, the wires  16  of the tubular support frame  15  are substantially free of torque. 
     The site of deployment of the filter element  1  in the vasculature is typically downstream of a treatment site, such as a region of stenosis in the vasculature. During the performance of a treatment procedure, the filter element  1  captures and safely retains any embolic material in the blood stream within the filter body  2 . 
     After completion of the treatment procedure, the filter element  1  is collapsed down and retrieved into a retrieval catheter with any retained embolic material within the filter body  2 . The wires  16  around the tubular wire support frame  15  are again torqued during collapse. 
     The retrieval catheter is then withdrawn from the vasculature with the filter element  1  within the retrieval catheter. 
     The delivery, deployment and retrieval of the embolic protection device of the invention, as described above, is similar to that described in our WO 99/23976A; WO 01/80776A (US 2002-0052676A) and WO 01/80773A (US 2002-0049467A), the relevant contents of which are incorporated herein by reference. The filter element  1  may be slidably exchanged over the guidewire without any attachment means between the filter element  1  and the guidewire. A distal stop on the guidewire assists in retrieval of the filter element  1 . The guidewire may remain in the vasculature after retrieval of the filter element  1 . 
       FIG. 170  illustrates another filter support  30 , which is similar to the filter support  3  of  FIGS. 162 to 168 , and similar elements in  FIG. 170  are assigned the same reference numerals. 
     In this case, the filter support  30  comprises only six wires  16 , which define only three tubular segment cells  17  as the wires  16  extend axially along and circumferentially around the tubular frame  15 . The three cells  17  do not form a complete 360° loop around the tubular frame  15 . An extension wire  31  is provided, in this case, to provide support to the filter body  2  between the two circumferentially spaced-apart cells  17 . The linkage element  31  may provide a diameter adjusting feature. 
     Referring to  FIGS. 171 to 173 , there is illustrated another filter support  35 , which is similar to the filter support  3  of  FIGS. 162 to 169 , and similar elements in  FIGS. 171 to 173  are assigned the same reference numerals. 
     The wires  16  extend, in this case, circumferentially around the tubular frame  15  in an “S-shape”. The S-shape increases the contact area between the wires  16  and the filter body  2 , and in this way, the supporting force exerted by the wires  16  on the filter body  2  is more evenly distributed. This arrangement minimizes any trauma experienced by the vasculature due to the apposition of the filter element  1  with the vasculature. 
     An alternative filter support  40  having wires  16  with a more exaggerated S-shaped portion  41  is illustrated in  FIGS. 174 and 175 . 
     It will be appreciated that the shape of one wire  16  of a cell  17  does not have to be symmetrical or similar to the shape of the other wire  16  of the cell  17 , provided that the length of each wire  16  is equal. 
     Referring to  FIGS. 176 to 178 , there is illustrated another filter support  45 , which is similar to the filter support  3  of  FIGS. 162 to 169 , and similar elements in  FIGS. 176 to 178  are assigned the same reference numerals. 
     In this case, the filter support  45  comprises only four wires  16 , which extend circumferentially around and axially along the tubular support frame  15  to define two cells. The two cells have a hexagonal, hysteresis loop shape, and together the two cells  17  extend circumferentially around the tubular frame  15  in a complete loop. 
     The proximal termination points  19  are circumferentially aligned with the distal termination points  20 . 
     Another support frame  50 , illustrated in  FIG. 179 , is similar to the support frame  3  of  FIGS. 161 to 169 , and similar elements if  FIG. 179  are assigned the same reference numerals. 
     In this case, the wires  16  are fixed to inner tube  8  at a point  51  distally of the tubular support frame portion  15 . The wires  16  extend from the fixation point  51  axially proximally and radially outwardly in a single leg  52  to the tubular support frame portion  15 . 
     By providing a single proximal support leg  52 , and by locating this leg  52  distally of the inlet end  4  of the filter body  2 . this arrangement minimizes the possibility of embolic material becoming caught or hung-up on the leg  18  at the inlet openings  6 . In this manner, substantially all of the embolic material is retained safely within the filter body  2  for subsequent retrieval from the vascular system. 
     The wires  16  are preferably of a self-expanding material, such as Nitinol™, and the inner tube  8  is preferably of gold. This arrangement provides for radiopacity. 
     It will be appreciated that a plurality of cells  17  may be defined by the wires  16  around the tubular support frame  15 , as illustrated in  FIG. 18 . Each wire  16  may be fixed to a wire  16  in an adjacent cell  17  ( FIG. 181 ) by welding, or by adhesive means  57  ( FIG. 182 ), or by any other suitable means. 
     The wires  16  may be slidably mounted to the inner tube  8  at both the proximal support leg  18  and the distal support leg  21 . 
     By increasing the number of wires  16  which define the cells  17  of the tubular support frame  15 , the elongation of the overall filter support, when collapsed down, is reduced. In this way, the space required in a vasculature to deploy and retrieve the embolic protection device is also reduced. 
     Depending on the configuration of the filter element, the inner tube may not be present. In this case the filter support will be mounted directly onto the guidewire for exchange of the filter element over the guidewire. 
     It will be appreciated that a single wire  16 , bent back on itself, may be used to define the tubular support frame  15 , in which case the cells  17  of the tubular support frame  15  are defined by elements of the single wire  16 , as illustrated in  FIGS. 21 and 22 . The support frame  90  of  FIGS. 183 and 184  is similar to the support frame  3  above, with the exception that the support frame is defined by a single wire  16  bent back on itself. 
     A proximal neck of the filter body may be inverted to extend distally rather than proximally. This arrangement reduces the overall longitudinal length of the embolic protection device, and thus the embolic protection device may be deployed and retrieved with a shorter “parking space” in the vasculature. To invert the proximal neck, the neck may be split along each side, and then the pushed distally into the interior of the filter body. 
     In addition, the longitudinal length of the embolic protection device may be further shortened by providing a hemi-spherically shaped proximal nose instead of a conical nose. Furthermore, the overall crossing profile of the embolic protection device may be reduced by means of the hemi-spherical nose. 
     The invention incorporates circumferential wire angulation into support structure design to give maximum circumferential support to the filter membrane. 
     The angulated hysteresis structure/cell configurations of the invention are particularly suitable as support structures because the strain energy is distributed over long lengths of the wire structure. The wrapping/loading mechanisms of these hysteresis structures are both a bending/straightening of the constituent wires as well as a twisting/torsion of the wires. The energy applied/introduced during the loading process is both bending and torsional strain energy. These energies due to their nature and the method by which the support structure folds/loads are distributed over long lengths of the wire as opposed to concentrated focal points so that the level of energy within the wire at any point does not exceed the elastic strain energy limits. Hysteresis designs optimize the strain distribution along the wire lengths. With these designs there is distributed bending and torsional strain along the wires. The component of radial force is converted to torque strain energy. The corollary of this principle. that the torsional strain energy provides radial stiffness, also applies. 
     Angulated hysteresis structures also enable large radial forces to be achieved from structures with small wire diameters. The reason for this is that these designs use a greater proportion of the wires&#39; torsional strain resistance. The wires offer far greater resistance to torsional strain than to bending strain and therefore these designs optimize this feature. The angulated hysteresis structure design arranges the wires so that the load induces torsional strain and therefore delivers far higher performance with small wire diameters than those designs that rely on the bending strain/resistance. 
     The hysteresis support structure of the invention has sections of wire curvature that can be defined in 3D planes. These sections of wire have geometrical properties such as a radius of curvature and a centre of radius of curvature. As the hysteresis structure designs are loaded and deployed, the geometrical properties of these sections change that is the radius of curvature changes and the center for the radius of curvature moves in a path that can only be defined within a 3D plane. 
     Even relatively simple hysteresis designs are made up of numerous sections of curvature with their corresponding radius of curvature joined end to end to form a complete hysteresis loop. These sections of curvature depending on the complexity of the design may be combinations of concave and convex elements/segments. The hysteresis loops themselves can be various shapes and there are multitudes of hysteresis loop/cell geometries. 
     A wire or laser cut support structure design based on a hysteresis cell type design typically may have four arms acting to provide uniform radial force to give good vessel apposition In attempting to provide support over the complete body length structure designs tend to have multiple arms/cells providing the support. The problems with many of these designs is the excessive elongation associated with them during loading. The advantage with the invention in suit is that it only extends the same length whether one/two or multiple arms are used. The invention also lends itself to low wrapping profiles, because during loading it contracts both radially and circumferentially leaving parallel straight wires which often prove to be the easiest for loading. 
     Further advantages of the round wire arrangements include: 
     Using a round wire allows for substantially more of the strain energy induced during loading/wrapping down into a low profile to be stored as torque along the wire lengths. This means that the strain energy is more evenly distributed within the wires than with conventional section designs, in which the strain energy generally becomes concentrated around the bend points which can cause problems such as exceeding the elastic strain energy limit at these locations. 
     The invention also has the advantage of being more trackable and flexible. This design achieves this by allowing the structure to hinge at points. Planes through these points demonstrate that bending at these hinge points is very easy. 
     Furthermore. the radial force may be altered by: 
     a) changing the wire diameter; 
     b) changing the proximal and distal cone angles. 
     Points of stress concentration can become strained plastically and result in poor support structure performance. 
     Conventional approaches to dealing with these issues involve designing in strain distributing geometric features to spread these strains over a greater area of the structure. Another approach involves the use of thinning out sections in the area of high strain. At a given radius of curvature the strain in a thin section is less than that of a thick section. Thinning however compromises the overall support provided by the structure. 
     The filter support of the invention provides for torsional strain and thus eliminates the need to use section thinning or thickening to distribute strain. 
     When collapse strains are evenly distributed, it is possible that the overall level of strain in the system can be increased without inducing plastic deformation. This makes it possible to achieve a high level of radial support from small diameter support members. 
     Designs that induce torque-strain into the support structure during collapse are particularly advantageous. Bending strains tend very often to have a strong cantilever effect with the strain becoming localized at points of stress concentration. 
     The torque strain in the wire can be released in a variety of expansion pathways. This means that the release of the torque is not inhibited when uniaxial resistance is encountered. This feature helps the support structure deliver good apposition to eccentric vessels. This is an important aspect of the invention, especially when the filter is placed in diseased vessel segments. 
     The geometric configuration of the filter support aligns the wires of the cell in a substantially circumferential direction in the expanded state. This ensures that radial pressure applied by the vessel is initially transmitted as compressive hoop stress to the structure. 
     The compressive component of applied stress decreases as the system collapses, however the torsional resistance increases resulting in a relatively flatter loading stress curve. 
     It will be appreciated that the body maybe attached to or independent of the support frame. 
     The invention is not limited to the embodiments hereinbefore described which may be varied in detail.