Patent Publication Number: US-8968382-B2

Title: Method and apparatus for restricting flow through an opening in the side wall

Description:
REFERENCE TO PENDING PRIOR PATENT APPLICATIONS 
     This patent application: 
     (i) is a continuation-in-part of prior U.S. patent application Ser. No. 12/657,598, filed Jan. 22, 2010 by Howard Riina et al. for METHOD AND APPARATUS FOR RESTRICTING FLOW THROUGH AN OPENING IN THE SIDE WALL OF A BODY LUMEN, AND/OR FOR REINFORCING A WEAKNESS IN THE SIDE WALL OF A BODY LUMEN, WHILE STILL MAINTAINING SUBSTANTIALLY NORMAL FLOW THROUGH THE BODY LUMEN, which patent application: (a) is a continuation-in-part of prior U.S. patent application Ser. No. 12/332,727, filed Dec. 11, 2008 by Howard Riina et al. for METHOD AND APPARATUS FOR SEALING AN OPENING IN THE SIDE WALL OF A BODY LUMEN, AND/OR FOR REINFORCING A WEAKNESS IN THE SIDE WALL OF A BODY LUMEN, WHILE MAINTAINING SUBSTANTIALLY NORMAL FLOW THROUGH THE BODY LUMEN, which in turn claims benefit of prior U.S. Provisional Patent Application Ser. No. 61/007,189, filed Dec. 11, 2007 by Howard Riina et al. for DEPLOYABLE BLOCKING SPHERE; (b) claims benefit of prior U.S. Provisional Patent Application Ser. No. 61/205,683, filed Jan. 22, 2009 by Jeffrey Milsom et al. for METHOD AND APPARATUS FOR SEALING AN OPENING IN THE SIDE WALL OF A BODY LUMEN, AND/OR FOR REINFORCING A WEAKNESS IN THE SIDE WALL OF A BODY LUMEN, WHILE MAINTAINING SUBSTANTIALLY NORMAL FLOW THROUGH THE BODY LUMEN; and (c) claims benefit of prior U.S. Provisional Patent Application Ser. No. 61/277,415, filed Sep. 24, 2009 by Howard Riina et al. for METHOD AND APPARATUS FOR RESTRICTING AN OPENING IN THE SIDE WALL OF A BODY LUMEN, AND/OR FOR REINFORCING A WEAKNESS IN THE SIDE WALL OF A BODY LUMEN, WHILE MAINTAINING SUBSTANTIALLY NORMAL FLOW THROUGH THE BODY LUMEN; 
     (ii) claims benefit of prior U.S. Provisional Patent Application Ser. No. 61/544,372, filed Oct. 7, 2011 by J. Frederick Cornhill et al. for METHOD AND APPARATUS FOR RESTRICTING FLOW THROUGH AN OPENING IN THE SIDE WALL OF A BODY LUMEN, AND/OR FOR REINFORCING A WEAKNESS IN THE SIDE WALL OF A BODY LUMEN, WHILE STILL MAINTAINING SUBSTANTIALLY NORMAL FLOW THROUGH THE BODY LUMEN; and 
     (iii) claims benefit of prior U.S. Provisional Patent Application Ser. No. 61/639,711, filed Apr. 27, 2012 by Howard Riina et al. for BIFURCATION FLOW DIVERTERS AND DEPLOYMENT SYSTEMS. 
     The seven (7) above-identified patent applications are hereby incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to medical procedures and apparatus in general, and more particularly to medical procedures and apparatus for restricting flow through an opening in the side wall of a body lumen, and/or for reinforcing a weakness in the side wall of a body lumen, while still maintaining substantially normal flow through the body lumen. 
     BACKGROUND OF THE INVENTION 
     The human body consists of many different anatomical structures. Among these anatomical structures are the blood vessels which circulate blood throughout the body, i.e., the arteries which deliver oxygenated blood to the end tissues and the veins which return oxygen-depleted blood from the end tissues. 
     In some cases, a blood vessel can become weakened, thereby causing the side wall of the blood vessel to balloon outwardly so as to create an aneurysm. See, for example,  FIGS. 1-3 , which show various types of aneurysms, e.g., a fusiform aneurysm ( FIG. 1 ), where the aneurysm extends around a substantial portion of the circumference of a blood vessel; a lateral aneurysm ( FIG. 2 ), where the aneurysm extends out of a limited portion of the side wall of a blood vessel, with a well-defined neck; and a bifurcation aneurysm ( FIG. 3 ), where the aneurysm extends out of the apex of a bifurcation of a blood vessel. For purposes of the present invention, all of these aneurysms (e.g., fusiform aneurysms, lateral aneurysms and/or bifurcations aneurysms) are considered to extend out of the side wall of a blood vessel. 
     Aneurysms can present a serious threat to the patient, since they may enlarge to the point of rupture, thereby resulting in a rapid and uncontrolled loss of blood. Depending upon the size and location of the aneurysm, the aneurysm can be life-threatening. 
     By way of example but not limitation, an intracranial aneurysm can be fatal if rupture occurs. Given the life-threatening nature of such intracranial aneurysms, these aneurysms have traditionally been treated with an open craniotomy and microsurgical clipping. This procedure generally involves placing a small titanium clip across the neck of the aneurysm, thus isolating the aneurysm from blood flow and inhibiting subsequent rupture (or re-rupture). This clipping procedure is typically done under direct visualization, using an operating microscope. 
     More recently, minimally-invasive techniques have also been used to treat both ruptured and un-ruptured brain aneurysms. These minimally-invasive techniques generally employ interventional neuroradiological procedures utilizing digital fluoroscopy. More particularly, these interventional neuroradiological procedures generally use X-ray visualization to allow the surgeon to place a microcatheter within the dome of the aneurysm. With the microcatheter in place, detachable coils are then deployed within the dome of the aneurysm, thereby reducing blood velocity within the dome of the aneurysm and causing thrombosis of the aneurysm so as to prevent subsequent rupture (or re-rupture). However, this coil-depositing procedure has a number of drawbacks, including the risk of coil herniation into the lumen of the blood vessel; the risk of coil migration out of the aneurysm and into the blood vessel, with subsequent downstream migration; the risk of aneurysm rupture; etc. 
     As a result, a primary object of the present invention is to provide a new and improved device, adapted for minimally-invasive, endoluminal delivery, which may be used to restrict blood flow to an aneurysm while still maintaining substantially normal blood flow through the blood vessel. 
     Another object of the present invention is to provide a new and improved device, adapted for minimally-invasive, endoluminal delivery, which may be used to reinforce a weakness in a side wall of a blood vessel while still maintaining substantially normal blood flow through the blood vessel. 
     And another object of the present invention is to provide a new and improved device, adapted for minimally-invasive, endoluminal delivery, which may be used to facilitate the retention of detachable coils and/or other embolic material deployed within the interior of an aneurysm while still maintaining substantially normal flow through the blood vessel. 
     SUMMARY OF THE INVENTION 
     These and other objects of the present invention are addressed through the provision and use of a new and improved device which is adapted for minimally-invasive, endoluminal delivery. 
     In one form of the invention, there is provided a device for positioning within the lumen of a blood vessel, adjacent to the mouth of an aneurysm extending from the lumen of the blood vessel, for causing thrombosis of the aneurysm while maintaining substantially normal blood flow through the blood vessel, the device comprising: 
     a single closed loop of elastic filament configurable between: 
     (i) a first longitudinally-expanded, radially and laterally-contracted configuration for movement along a blood vessel, the first configuration providing two parallel lengths of the closed loop of elastic filament; and 
     (ii) a second longitudinally-contracted, radially and laterally-expanded configuration for lodging within a blood vessel, the second configuration providing (a) a single flow-restricting face sized and configured so as to cover the mouth of the aneurysm and obstruct blood flow to the aneurysm while permitting substantially normal blood flow through the blood vessel when the flow-restricting face is positioned over the mouth of the aneurysm, with the degree of obstruction at the mouth of the aneurysm being such that the aneurysm thromboses when the flow-restricting face is positioned over the mouth of the aneurysm, the single, flow-restricting face comprising a plurality of lengths of the closed loop of elastic filament disposed in close proximity to one another in a switchback configuration, and (b) at least one leg for holding the single flow-restricting face adjacent the mouth of the aneurysm, the at least one leg configured so as to maintain substantially normal blood flow through the blood vessel. 
     In another form of the invention, there is provided a method for causing thrombosis of an aneurysm extending from the lumen of a blood vessel while maintaining substantially normal blood flow through the lumen of the blood vessel, the method comprising: 
     providing a device comprising:
         a single closed loop of elastic filament configurable between:   (i) a first longitudinally-expanded, radially and laterally-contracted configuration for movement along a blood vessel, the first configuration providing two parallel lengths of the closed loop of elastic filament; and   (ii) a second longitudinally-contracted, radially and laterally-expanded configuration for lodging within a blood vessel, the second configuration providing (a) a single flow-restricting face sized and configured so as to cover the mouth of the aneurysm and obstruct blood flow to the aneurysm while permitting substantially normal blood flow through the blood vessel when the flow-restricting face is positioned over the mouth of the aneurysm, with the degree of obstruction at the mouth of the aneurysm being such that the aneurysm thromboses when the flow-restricting face is positioned over the mouth of the aneurysm, the single flow-restricting face comprising a plurality of lengths of the closed loop of elastic filament disposed in close proximity to one another in a switchback configuration, and (b) at least one leg for holding the single flow-restricting face adjacent the mouth of the aneurysm, the at least one leg configured so as to maintain substantially normal blood flow through the blood vessel;       

     delivering the single closed loop of elastic filament to the aneurysm site while the single closed loop of elastic filament is configured in its first configuration; and 
     transforming the single closed loop of elastic filament to its second configuration so that the single closed loop of elastic filament is lodged adjacent the mouth of the aneurysm, with the single flow-restricting face being positioned over the mouth of the aneurysm so as to obstruct blood flow to the aneurysm while permitting substantially normal blood flow through the blood vessel and with the at least one leg maintaining substantially normal blood flow through the blood vessel. 
     In another form of the invention, there is provided a system for treating a patient, comprising: 
     a device for positioning within the lumen of a blood vessel, adjacent to the mouth of an aneurysm extending from the lumen of the blood vessel, for causing thrombosis of the aneurysm while maintaining substantially normal blood flow through the blood vessel, the device comprising:
         a single closed loop of elastic filament configurable between:   (i) a first longitudinally-expanded, radially and laterally-contracted configuration for movement along a blood vessel, the first configuration providing two parallel lengths of the closed loop of elastic filament; and   (ii) a second longitudinally-contracted, radially and laterally-expanded configuration for lodging within a blood vessel, the second configuration providing (a) a single flow-restricting face sized and configured so as to cover the mouth of the aneurysm and obstruct blood flow to the aneurysm while permitting substantially normal blood flow through the blood vessel when the flow-restricting face is positioned over the mouth of the aneurysm, with the degree of obstruction at the mouth of the aneurysm being such that the aneurysm thromboses when the flow-restricting face is positioned over the mouth of the aneurysm, the single, flow-restricting face comprising a plurality of lengths of the closed loop of elastic filament disposed in close proximity to one another in a switchback configuration, and (b) at least one leg for holding the single flow-restricting face adjacent the mouth of the aneurysm, the at least one leg configured so as to maintain substantially normal blood flow through the blood vessel; and       

     an inserter for carrying the device to a deployment site, wherein the installation tool comprises:
         an elongated structure having a first mount for seating a first portion of the closed loop and a second mount for seating a second portion of the closed loop, the first mount and the second mount being movable relative to one another between a first position and a second position so that (i) when the first portion of the closed loop is seated in the first mount and the second portion of the closed loop is seated in the second mount and the first mount and second mount are in their first position, the open frame is in its second configuration, and (ii) when the first portion of the closed loop is seated in the first mount and the second portion of the closed loop is seated in the second mount and the first mount and second mount are in their second position, the open frame is in its first configuration.       

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other objects and features of the present invention will be more fully disclosed or rendered obvious by the following detailed description of the preferred embodiments of the invention, which is to be considered together with the accompanying drawings wherein like numbers refer to like parts, and further wherein: 
         FIGS. 1-3  are schematic views showing various types of aneurysms; 
         FIGS. 4-8  are schematic views showing a novel expandable spherical structure formed in accordance with the present invention, wherein the expandable spherical structure comprises an open frame with a flow-restricting face (i.e., a closed face in this particular embodiment), and wherein the expandable spherical structure is shown being used to close off a lateral aneurysm in a blood vessel; 
         FIGS. 9-13  are schematic views showing another novel expandable spherical structure formed in accordance with the present invention, wherein the expandable spherical structure comprises an open frame with a flow-restricting face (i.e., a closed face in this particular embodiment), wherein the open frame is formed out of an absorbable material and the closed face is formed out of a non-absorbable material, and wherein the expandable spherical structure is shown being used to close off a lateral aneurysm in a blood vessel; 
         FIGS. 14-18  are schematic views showing the expandable spherical structure of  FIGS. 4-8  being used to close off a bifurcation aneurysm; 
         FIGS. 19-23  are schematic views showing the expandable spherical structure of  FIGS. 9-13  being used to close off a bifurcation aneurysm; 
         FIG. 24  is a schematic view showing another novel expandable spherical structure formed in accordance with the present invention, wherein the expandable spherical structure comprises an open frame with a flow-restricting face (i.e., a closed face in this particular embodiment), and wherein the open frame of the expandable spherical structure comprises a plurality of struts arranged in a rectangular pattern; 
         FIG. 25  is a schematic view showing another novel expandable spherical structure formed in accordance with the present invention, wherein the open frame comprises a plurality of struts arranged in a hexagonal pattern; 
         FIG. 26  is a schematic view showing another novel expandable spherical structure formed in accordance with the present invention, wherein the expandable spherical structure comprises an open frame with a flow-restricting face (i.e., a closed face in this particular embodiment), and wherein the open frame of the expandable spherical structure comprises a spherical spiral; 
         FIG. 27  is a schematic view showing another novel expandable spherical structure formed in accordance with the present invention, wherein the expandable spherical structure comprises an open frame with a flow-restricting face (i.e., a closed face in this particular embodiment), and wherein the open frame of the expandable spherical structure comprises a spherical cage; 
         FIGS. 28-37  are schematic views showing other novel expandable spherical structures formed in accordance with the present invention, wherein the expandable spherical structures comprise spherical cages; 
         FIGS. 38-43  are schematic views showing other novel expandable spherical structures formed in accordance with the present invention, wherein the expandable spherical structure comprises an open frame with a flow-restricting face (i.e., a closed face in this particular embodiment), and wherein the flow-restricting face is disposed to one side of the axis of approach; 
         FIGS. 44 and 45  are schematic views showing the expandable spherical structure of  FIG. 27  being deployed with a syringe-type (e.g., an outer sleeve with an internal pusher) installation tool; 
         FIG. 46  is a schematic view showing the expandable spherical structure of  FIG. 27  being deployed with a syringe-type installation tool equipped with a gripper mechanism; 
         FIGS. 47-49  are schematic views showing the expandable spherical structure of  FIG. 27  being deployed with a syringe-type installation tool equipped with an expansion balloon; 
         FIGS. 50-54  are schematic views showing another novel expandable spherical structure formed in accordance with the present invention, wherein the expandable spherical structure comprises an open frame with a flow-restricting face (i.e., a face having a high strut density in this particular embodiment), and wherein the expandable spherical structure is shown being used to restrict flow to a lateral aneurysm in a blood vessel; 
         FIGS. 55-63  are schematic views showing other expandable spherical structures formed in accordance with the present invention, wherein the expandable spherical structures comprise open frames with flow-restricting faces (i.e., faces having high strut densities in these particular embodiments); 
         FIGS. 64-66  are schematic views showing the expandable spherical structure of  FIGS. 4-8  being deployed within the interior of a lateral aneurysm so as to close off the aneurysm; 
         FIGS. 67-71  are schematic views showing the expandable spherical structure of  FIGS. 9-13  being deployed within the interior of a lateral aneurysm so as to close off the aneurysm; 
         FIGS. 72-76  are schematic views showing the expandable spherical structure of  FIGS. 4-8  being deployed within the interior of a bifurcation aneurysm so as to close off the aneurysm; 
         FIGS. 77-81  are schematic views showing the expandable spherical structure of  FIGS. 9-13  being deployed within the interior of a bifurcation aneurysm so as to close off the aneurysm; 
         FIGS. 82 and 83  are schematic views showing an expandable spherical structure having stabilizing legs extending therefrom so as to form a “comet-shaped” structure, with the structure being configured to restrict flow to a lateral aneurysm in a blood vessel; 
         FIGS. 84-97  are schematic views showing various constructions for the “comet-shaped” structure of  FIGS. 82 and 83 , but with the flow-restricting face of the expandable spherical structure being omitted in  FIGS. 84-91  for clarity of viewing; 
         FIG. 98  is a schematic view showing another comet-shaped structure, but with this structure being configured to restrict flow to a bifurcation aneurysm; 
         FIGS. 99 and 100  show an expandable spherical structure restricting flow into a bifurcation aneurysm, where the expandable spherical structure is formed out of a “closed loop” of filament, and where the expandable spherical structure is deployed in the patient so that the face having a high strut density is positioned over the mouth/neck of the aneurysm in order to restrict flow into the aneurysm; 
         FIGS. 101 and 102  are schematic views of an inserter which may be used with an expandable spherical structure formed out of a “closed loop” of filament; 
         FIGS. 103-107  are schematic views showing how an expandable spherical structure formed out of a “closed loop” of filament may be deployed using the inserter of  FIGS. 101 and 102 ; 
         FIG. 108  is a schematic view showing an endoluminal device formed in accordance with the present invention; 
         FIGS. 109-111  are schematic views showing another endoluminal device formed in accordance with the present invention; 
         FIGS. 112-115  are schematic views showing the endoluminal device of  FIGS. 109-111  deployed adjacent an aneurysm; 
         FIGS. 116-118  are schematic views showing the endoluminal device of  FIGS. 109-111  mounted to the inserter of  FIGS. 101-107 ; 
         FIGS. 119 and 120  are schematic views showing an alternative form of inserter; 
         FIGS. 121 and 122  are schematic views showing another alternative form of inserter; 
         FIGS. 123 and 124  are schematic views showing still another alternative form of inserter; 
         FIGS. 125 and 126  are schematic views showing yet another alternative form of inserter; 
         FIGS. 127-132  are schematic views showing another endoluminal device formed in accordance with the present invention; 
         FIGS. 133-136  are schematic views showing the endoluminal device of  FIGS. 127-132  deployed adjacent an aneurysm; 
         FIGS. 137-140  are schematic views showing another endoluminal device formed in accordance with the present invention; 
         FIGS. 141-144  are schematic views showing still another endoluminal device formed in accordance with the present invention; and 
         FIG. 145  is a schematic views showing yet another endoluminal device formed in accordance with the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The Novel Expandable Spherical Structure in General 
     Looking now at  FIGS. 4-8 , there is shown a novel expandable spherical structure  5  formed in accordance with the present invention. Expandable spherical structure  5  is adapted for minimally-invasive, endoluminal delivery into a blood vessel or other body lumen, for restricting flow through an opening in the side wall of the blood vessel or other body lumen, and/or for reinforcing a weakness in the side wall of the blood vessel or other body lumen, while still maintaining substantially normal flow through the blood vessel or other body lumen. 
     Expandable spherical structure  5  generally comprises a spherical body comprising an open frame  10  with a flow-restricting face  15  (i.e., a closed face or a face having a high strut density). Preferably open frame  10  and flow-restricting face  15  together define the entire exterior shape of the spherical body, with open frame  10  making up the majority of the exterior shape of the spherical body. 
     In one preferred form of the invention, open frame  10  defines approximately 90% of the exterior shape of the spherical body and flow-restricting face  15  defines approximately 10% of the exterior shape of the spherical body. In another preferred form of the invention, open frame  10  defines approximately 80% of the exterior shape of the spherical body and flow-restricting face  15  defines approximately 20% of the exterior shape of the spherical body. In yet another preferred form of the invention, open frame  10  comprises approximately 70% of the exterior shape of the spherical body and flow-restricting face  15  defines approximately 30% of the exterior shape of the spherical body. And in yet another preferred form of the invention, open frame  10  comprises approximately 60% of the exterior shape of the spherical body and flow-restricting face  15  comprises approximately 40% of the exterior shape of the spherical body. 
     Expandable spherical structure  5  is constructed so that it may be deployed in a blood vessel or other body lumen, by (i) collapsing the expandable spherical structure into a configuration of reduced dimension, (ii) moving the collapsed structure through the blood vessel or other body lumen to a therapy site, and (iii) expanding the collapsed structure to an enlarged dimension at the therapy site, whereby to secure the expandable spherical structure in the blood vessel or body lumen so that its flow-restricting face  15  is presented to a side wall of the blood vessel or other body lumen while open frame  10  spans the blood vessel or other body lumen and bears against opposing anatomy so as to support flow-restricting face  15  in position, whereby to restrict flow to an aneurysm or other opening in the side wall of the blood vessel or other body lumen, or to otherwise reinforce a weakness in the side wall of the blood vessel or other body lumen, without significantly impeding normal flow through the blood vessel or other body lumen. 
     Significantly, by forming expandable spherical structure  5  in the shape of a spherical body, the endoluminal device is readily centered on the neck of an aneurysm or other opening in a body lumen, with flow-restricting face  15  projecting into the neck of the aneurysm or other opening in a body lumen and reliably restricting flow into the aneurysm or other opening in a body lumen. 
     Furthermore, by forming expandable spherical structure  5  so that it can expand at the therapy site and lodge itself in the blood vessel or other body lumen with its flow-restricting face  15  presented to a side wall of the blood vessel or other body lumen while open frame  10  spans the blood vessel or other body lumen and bears against opposing anatomy so as to support flow-restricting face  15  in position, expandable spherical structure  5  is effectively self-sizing, since it can be expanded to the degree necessary to span the blood vessel or other body lumen. 
     More particularly, expandable spherical structure  5  generally comprises an open frame  10  which has a flow restricting face  15  (i.e., a closed face or a face having a high strut density) carried thereon. Open frame  10  is formed so that it can assume a first, collapsed configuration of reduced dimension ( FIG. 4 ) so as to facilitate moving expandable spherical structure  5  endoluminally through the blood vessel or other body lumen to the therapy site. Open frame  10  is also formed so that it can thereafter be re-configured to a second, expanded configuration of enlarged dimension ( FIGS. 5 and 6 ), whereby expandable spherical structure  5  can be lodged in the blood vessel or other body lumen at the therapy site, with its flow-restricting face  15  pressed securely against a side wall of the blood vessel or other body lumen while open frame  10  spans the blood vessel or other body lumen and bears against opposing anatomy so as to support flow-restricting face  15  in position. In this position, flow-restricting face  15  of expandable spherical structure  5  can restrict flow to an aneurysm in the blood vessel (such as the lateral aneurysm shown in  FIGS. 4-8 , or a bifurcation aneurysm as will hereinafter be discussed below), or restrict flow to an opening in the side wall of the blood vessel or other body lumen, or reinforce a weakness in the side wall of the blood vessel or other body lumen, etc. 
     Significantly, by forming the endoluminal device as an expandable spherical structure, the device can be collapsed to a reduced dimension for minimally-invasive, endoluminal delivery into a blood vessel or other body lumen, yet can thereafter be expanded to the required dimension for secure lodgement at the therapy site, whereby to restrict flow to an opening in a body lumen and/or to reinforce a weakness in the side wall of the body lumen. Furthermore, by forming expandable spherical structure  5  in the shape of a spherical body, the endoluminal device is readily centered on the neck of an aneurysm or other opening in a body lumen, with flow-restricting face  15  projecting into the neck of the aneurysm or other opening in a body lumen and reliably restricting flow into the aneurysm or other opening in a body lumen. And by forming expandable spherical structure  5  so that it can expand at the therapy site and lodge itself in the blood vessel or other body lumen with its flow-restricting face  15  presented to a side wall of the blood vessel or other body lumen while open frame  10  spans the blood vessel or other body lumen and bears against opposing anatomy so as to support flow-restricting face  15  in position, expandable spherical structure  5  is effectively self-sizing, since it expands to the degree necessary to span the blood vessel or other body lumen. Additionally, by forming open frame  10  as an open structure, expandable spherical structure  5  can be disposed in the blood vessel or other body lumen and extend across the lumen of the blood vessel or other body lumen without significantly impeding normal flow through the blood vessel or other body lumen ( FIGS. 6-8 ). 
     Expandable Open Frame  10   
     As noted above, (i) expandable spherical structure  5  generally comprises a spherical body comprising an open frame  10  with a flow-restricting face  15  (i.e., a closed face or a face having a high strut density); (ii) open frame  10  and flow-restricting face  15  together preferably define the entire exterior shape of the spherical body, with open frame  10  making up the majority of the exterior shape of the spherical body; (iii) open frame  10  is capable of being collapsed in dimension for easy delivery of expandable spherical structure  5  to the therapy site and thereafter expanded in dimension at the therapy site so as to hold flow-restricting face  15  against a side wall of a blood vessel or other body lumen; and (iv) open frame  10  is configured so that it does not significantly impede normal flow through the blood vessel or other body lumen within which it is deployed. 
     To this end, open frame  10  is preferably formed with an expandable strut construction, so that it can (i) first assume a configuration of reduced dimension, so that expandable spherical body  5  can move easily through the body to the therapy site, and (ii) thereafter assume a configuration of expanded dimension, so that it can be securely retained at the desired location in the blood vessel or other body lumen and press flow-restricting face  15  securely against the side wall of the blood vessel or body lumen, whereby to restrict flow to an aneurysm or other opening in the blood vessel or other body lumen, or to otherwise reinforce the side wall of the blood vessel or other body lumen. And by forming open frame  10  with an expandable strut construction, open frame  10  is effectively self-sizing, since it expands to the degree necessary to span the blood vessel or other body lumen. 
     Significantly, by forming open frame  10  with an expandable strut construction, open frame  10  does not significantly impede normal flow through the blood vessel or other body lumen when open frame  10  is in its expanded configuration within the blood vessel or other body lumen. 
     Thus, for example, in the configuration shown in  FIGS. 4-8 , open frame  10  comprises a plurality of struts arranged in a polygonal configuration, with the struts being sized so that the struts present minimal obstruction to normal flow through the lumen. 
     In one preferred construction, open frame  10  may be formed out of a shape memory alloy (SMA) such as Nitinol, and a temperature transition may be used to change the configuration of open frame  10 . By way of example but not limitation, open frame  10  can be formed so that when it is cooled to a temperature below body temperature, the open frame assumes a collapsed configuration ( FIG. 4 ), and when it is thereafter warmed to body temperature, the open frame assumes an expanded configuration ( FIG. 6 ). If desired, open frame  10  can be warmed to body temperature simply by deploying expandable spherical structure  5  in the body. Alternatively, an electrical current may be applied to open frame  10  so as to heat open frame  10  to its expansion temperature, e.g., via resistance heating. Or, a warm or cold saline solution can be flushed through open frame  10  so as to appropriately modulate the temperature of the open frame, whereby to cause the open frame to assume a desired configuration. 
     Alternatively, open frame  10  can be formed out of a resilient material which can be forcibly compressed into a collapsed configuration, restrained in this collapsed configuration, and thereafter released so that it elastically returns to its expanded configuration. By way of example but not limitation, in this form of the invention, expandable spherical structure  5  might be compressed into a configuration of a reduced dimension, restrained within a sleeve, delivered to the therapy site within the sleeve, and then released from the sleeve so that it elastically returns to an expanded configuration at the therapy site, whereby to lodge itself in the blood vessel or other body lumen, with its flow-restricting face pressed against the side wall of the blood vessel or other body lumen while open frame  10  spans the blood vessel or other body lumen and bears against opposing anatomy so as to support flow-restricting face  15  in position. By way of further example but not limitation, open frame  10  can be formed out of a shape memory alloy (SMA) engineered to form stress-induced martensite (SIM) and thereby exhibit superelastic properties, whereby to permit large shape deformations with elastic return. By way of still further example but not limitation, open frame  10  can be formed out of a suitable polymer which exhibits the desired elastic properties. 
     In another preferred form of the present invention, open frame  10  is formed with a structure which can be collapsed for delivery to the deployment site and thereafter enlarged to an expanded configuration through the use of an expansion device, e.g., an internal balloon, where the balloon is inflated at the therapy site so as to reconfigure open frame  10  to an expanded condition. This arrangement can be advantageous, since it does not require the open frame to rely on temperature transition or elasticity to expand to its fully expanded configuration (or to any desired expanded configuration less than its fully expanded configuration). Thus, a wide range of well known biocompatible materials (e.g., medical grade stainless steel) may be used to form open frame  10 . 
     Flow-Restricting Face  15   
     Flow-restricting face  15  is carried by (e.g., mounted on, formed integral with, or otherwise connected to) open frame  10  so that flow-restricting face  15  can be pressed securely against the side wall of the blood vessel or other body lumen within which expandable spherical structure  5  is deployed. 
     Flow-restricting face  15  may comprise a closed face, in the sense that it comprises a substantially complete surface or barrier which is capable of closing off an aneurysm or other opening in side wall of a blood vessel or other body lumen, and/or for reinforcing a weakness in the side wall of the blood vessel or other body lumen. See  FIGS. 4-8 , where flow-restricting face  15  is depicted as a closed face. 
     Alternatively, and as will be discussed in detail below, flow-restricting face  15  may comprise a face having a high strut density which is capable of restricting flow to an aneurysm or other opening in a side wall of a blood vessel or other body lumen, and/or for reinforcing a weakness in the side wall of the blood vessel or other body lumen. In this case, flow-restricting face  15  may not constitute a substantially complete surface, or flow-restricting face  15  may not constitute a substantially fluid-impervious surface, but flow-restricting face  15  will have a strut density sufficiently high to restrict flow through that face, e.g., so as to cause an aneurysm to thrombose. 
     Flow-restricting face  15  may be formed so as to be substantially rigid or it may be formed so as to be flexible. 
     Flow-restricting face  15  preferably has the convex configuration shown in  FIGS. 4-8 , so that it can form a regular portion of the spherical body of expandable structure  5 . However it should be appreciated that flow-restricting face  15  may also be formed with a planar configuration, or some other configuration, if desired. 
     Use Of Absorbable Materials 
     If desired, expandable spherical structure  5  can have some or all of its elements formed out of an absorbable material, so that some or all of the elements are removed from the therapy site after some period of time has elapsed. 
     By way of example but not limitation, open frame  10  can be formed out of an absorbable material, and flow-restricting face  15  can be formed out of a non-absorbable material, so that only flow-restricting face  15  is retained at the therapy site after some period of time has passed. See  FIGS. 9-13 . This type of construction can be advantageous where flow-restricting face  15  integrates into the side wall of the blood vessel or other body lumen after some period of time has elapsed, so that a supporting frame is no longer necessary to hold flow-restricting face  15  in position against the side wall of the blood vessel or other body lumen. 
     It is also possible for the entire expandable spherical structure  5  to be formed out of absorbable material(s), i.e., with both open frame  10  and flow-restricting face  15  being formed out of absorbable materials. This type of construction can be advantageous where flow-restricting face  15  only needs to be held against the side wall of the blood vessel or other body lumen for a limited period of time, e.g., until aneurysm thrombosis/scarring is complete, or to reinforce the side wall of the blood vessel or other body lumen while healing occurs, etc. 
     It should also be appreciated that, where both open frame  10  and flow-restricting face  15  are absorbable, they may be engineered so as to have different absorption rates, so that they are removed from the therapy site at different times. This may be done by making the various elements out of different materials, or by making the various elements out of different blends of the same materials, etc. 
     Application to Different Types of Aneurysms 
     As noted above, expandable spherical structure  5  can be used to restrict flow to various types of aneurysms. 
     Thus, for example,  FIGS. 4-8  and  9 - 13  show expandable spherical structure  5  being used to restrict flow to a lateral aneurysm (i.e., in these particular embodiments, to close off the lateral aneurysm). 
     However, it should also be appreciated that expandable spherical structure  5  may be used to restrict flow to a bifurcation aneurysm as well. Thus, for example,  FIGS. 14-18  show the expandable spherical structure  5  of  FIGS. 4-8  being used restrict flow to a bifurcation aneurysm, and  FIGS. 19-23  show the expandable spherical structure  5  of  FIGS. 9-13  being used to restrict flow to a bifurcation aneurysm (i.e., in these particular embodiments, to close off the bifurcation aneurysm). In this respect it should be appreciated that the spherical shape of expandable spherical structure  5  is particularly well suited for use in treating bifurcation aneurysms, since it may be seated securely at the bifurcation, pressing flow-restricting face  15  securely against the bifurcation aneurysm, with open frame  10  spanning the blood vessel or other body lumen and bearing against opposing anatomy so as to support flow-restricting face  15  in position, while still allowing blood to flow substantially unobstructed through the blood vessels. 
     It is also anticipated that expandable spherical structure  5  may be used to restrict flow to other types of aneurysms as well, e.g., certain forms of fusiform aneurysms. Where expandable spherical structure  5  is to be used to restrict flow to a fusiform aneurysm, flow-restricting face  15  may comprise a significantly enlarged surface area, or flow-restricting face  15  may comprise two or more separated segments disposed about the lateral portions of open frame  10 , etc. 
     Structure Of Open Frame  10   
     It should be appreciated that open frame  10  can be formed with a variety of different configurations without departing from the scope of the present invention. 
     In one form of the invention, open frame  10  may be formed out of a plurality of struts arranged in a polygonal array. See, for example,  FIGS. 4-8 ,  9 - 13 ,  14 - 18  and  19 - 23 , where open frame  10  is shown formed out of a plurality of struts arranged as triangular polygons. See also  FIG. 24 , where open frame  10  is formed out of a plurality of struts arranged as rectangular polygons, and  FIG. 25 , where open frame  10  is formed out of a plurality of struts arranged as hexagons. 
     It is also possible to form open frame  10  with a non-polygonal structure. 
     Thus, for example, open frame  10  may be formed with a spherical spiral structure, e.g., such as is shown in  FIG. 26 , where a spiral strut forms the open frame  10 . 
       FIG. 27  shows an open frame  10  having a spherical cage structure. More particularly, in this construction, open frame  10  comprises a plurality of axially-aligned struts  20  which extend between flow-restricting face  15  and an annular ring  25 . Struts  20  preferably bow outwardly when open frame  10  is in its expanded configuration, but may be bent inwardly (e.g., to a straight or inwardly-bowed configuration) or otherwise deformed so as to permit open frame  10  to assume a reduced configuration. By way of example but not limitation, struts  20  may be bent inwardly (e.g., so as to extend substantially parallel to one another) when open frame  10  is in its reduced configuration. 
       FIGS. 28-37  show other spherical cage constructions wherein various struts  20  form open frame  10 . 
     It will be appreciated that, with the construction shown in  FIG. 27 , flow-restricting face  15  sits at one end of the plurality of axially-aligned struts  20  and annular ring  25  sits at the opposing end of the plurality of axially-aligned struts  20 . Since struts  20  are intended to be bowed inwardly so that the expandable spherical structure can assume a reduced configuration, the spherical cage structure of  FIG. 27  is generally intended to be delivered axially, with flow-restricting face  15  leading. Thus, this construction is particularly well suited for use with bifurcation aneurysms, where the neck of the aneurysm is typically axially-aligned with the direction of approach (see, for example,  FIGS. 14-18  and  19 - 23 ). Accordingly, where the spherical cage structure is intended to be used with lateral aneurysms, it may be desirable to use the spherical cage configuration shown in  FIG. 38 , where flow-restricting face  15  is disposed to one side of the axis of approach, i.e., to one side of the axis  27  shown in  FIG. 38 . In other words, where the spherical cage structure is intended to be used with a bifurcation aneurysm, flow-restricting face  15  is intended to be aligned with the axis of approach, and where the spherical cage structure is intended to be used with a lateral aneurysm, flow-restricting face  15  is intended to be disposed to one side of the axis of approach. In this way, expandable spherical structure  5  can be endoluminally advanced to the therapy site and flow-restricting face  15  properly positioned relative to the anatomy. 
       FIGS. 39-43  show other spherical cage constructions wherein various struts  20  form open frame  10  and flow-restricting face  15  is disposed to one side of the axis of approach. 
     Installation Tools 
     Various installation tools may be provided to deploy expandable spherical structure  5  within a blood vessel or other body lumen. 
     Thus, for example, in  FIG. 44 , there is shown a syringe-type (e.g., an outer sleeve with an internal pusher) installation tool  100  for deploying the expandable spherical structure  5  shown in  FIG. 45 . Installation tool  100  generally comprises a hollow sleeve  105  having a lumen  110  therein, and a pusher  115  slidably disposed within lumen  110 . Lumen  110  is sized so that it can accommodate expandable spherical structure  5  when the expandable spherical structure is in its reduced configuration ( FIG. 44 ), but not when it is in its enlarged configuration ( FIG. 45 ). As a result of this construction, expandable spherical structure  5  may be positioned within lumen  110  (distal to pusher  115 ) when expandable spherical structure  5  is in its reduced configuration, advanced to the therapy site while within sleeve  105 , and then installed at the therapy site by advancing pusher  115  so that expandable spherical structure  5  is ejected from the interior of sleeve  105 . Once expandable spherical structure  5  has been ejected from sleeve  105 , expandable spherical structure  5  can return to an expanded configuration ( FIG. 45 ) so as to be securely engaged in the blood vessel or other body lumen in the manner previously described, with flow-restricting face  15  pressed against a side wall of the blood vessel or other body lumen. It will be appreciated that the syringe-type installation tool  100  is particularly advantageous where expandable spherical structure  5  is elastically deformable, such that sleeve  105  can serve to mechanically restrain the expandable spherical structure in its reduced configuration while the expandable spherical structure is within sleeve  105 , and release that mechanical constraint when the expandable spherical structure is ejected from sleeve  105 . 
     As noted above, expandable spherical structure  5  of  FIGS. 27 ,  44  and  45  is well suited for use with bifurcation aneurysms, where the neck of the aneurysm is typically axially-aligned with the direction of approach (see, for example,  FIGS. 14-18  and  19 - 23 ). Where the spherical cage structure is intended to be used with lateral aneurysms, it may be desirable to use the spherical cage configuration shown in  FIG. 38 , where flow-restricting face  15  is disposed to one side of the axis of approach. 
     If desired, installation tool  100  can be provided with a gripper mechanism to releasably secure expandable spherical structure  5  to installation tool  100 , e.g., so as to releasably secure expandable spherical structure  5  to installation tool  100  until after expandable spherical structure  5  has been advanced to the therapy site and has returned to its enlarged configuration, so that it is ready to be left at the therapy site. This gripper mechanism ensures complete control of expandable spherical structure  5  as it is moved out of the installation tool and erected within the body, and also facilitates more precise positioning (e.g., with proper rotation, etc.) of the expandable structure against the side wall of the body lumen. 
     More particularly, and looking now at  FIG. 46 , installation tool  100  may be provided with a plurality of spring grippers  125 . Spring grippers  125  are disposed within lumen  110  of sleeve  105 , exterior to pusher  115 . Each spring gripper  125  is formed so that when a bowed portion  130  of the spring gripper is restrained within lumen  110 , a hook portion  135  of that spring gripper holds annular ring  25  of expandable spherical structure  5  to the distal end of pusher  115 . However, when pusher  115  is advanced to the point where bowed portion  130  of spring gripper  125  is no longer restrained within lumen  110 , hook portion  135  of spring gripper  125  moves outboard so as to release annular ring  25  of expandable spherical structure  5  from the distal end of pusher  115 . Thus it will be seen that spring grippers may be used to releasably secure expandable spherical structure  5  to installation tool  100  until after the expandable spherical structure has been advanced out of the distal end of the installation tool and returned to its enlarged configuration. This arrangement can provide the clinician with increased control as expandable spherical structure  5  is deployed within the blood vessel. 
     As noted above, expandable spherical structure  5  of FIGS.  27  and  44 - 46  is well suited for use with bifurcation aneurysms, where the neck of the aneurysm is typically axially-aligned with the direction of approach (see, for example,  FIGS. 14-18  and  19 - 23 ). Where the spherical cage structure is intended to be used with lateral aneurysms, it may be desirable to use the spherical cage configuration shown in  FIG. 38 , where closed face  15  is disposed to one side of the axis of approach. 
     If desired, installation tool  100  can be provided with an expansion balloon for expanding the expandable spherical structure from its reduced configuration to its enlarged configuration. More particularly, and looking now at  FIGS. 47-49 , installation tool  100  may be provided with sleeve  105  and pusher  115  as discussed above. In addition, installation tool  100  may be provided with an expansion balloon  140 . Expansion balloon  140  is supported on an inflation rod  145  which is movably disposed within pusher  115 . Expansion balloon  140  is (in its deflated condition) disposed internal to open frame  10  of expandable spherical structure  5 . As a result of this construction, installation tool  100  may receive expandable spherical structure  5  while the expandable spherical structure is in its reduced configuration, carry the expandable spherical structure to the desired therapy site, position the expandable spherical structure at the desired location, and then expand expansion balloon  140  so as to open the expandable spherical structure to its enlarged configuration. Expansion balloon  140  may then be deflated and withdrawn from the interior of expandable spherical structure  5 . It will be appreciated that providing installation tool  100  with an expansion balloon may be advantageous where expandable spherical structure  5  does not self-erect within the body lumen. 
     Expandable Spherical Structure Having a Flow-Restricting Face Formed with a High Strut Density 
     In  FIGS. 1-49 , flow-restricting face  15  of expandable spherical structure  5  is depicted as a closed face, in the sense that flow-restricting face  15  comprises a substantially complete surface or barrier which is capable of closing off (and/or very significantly reducing flow to) an aneurysm or other opening in the side wall of a blood vessel or other body lumen, and/or for reinforcing a weakness in the side wall of the blood vessel or other body lumen. However, it should be appreciated that for many applications, flow-restricting face  15  need not comprise a substantially complete surface or barrier, i.e., flow-restricting face  15  may be formed with a face having a sufficiently high strut density to form an effectively closed face or to otherwise achieve a desired purpose. Thus, for example, in  FIGS. 50-54 , there is shown an expandable spherical structure  5  comprising an open frame  10  having a flow-restricting face  15  formed with a high strut density such that blood flow to the aneurysm will be restricted and the aneurysm will thrombose. In this circumstance, flow-restricting face  15  may be considered to be effectively closed. Furthermore, where flow-restricting face  15  is being used to reinforce a weakness in a side wall (as opposed to being used to restrict flow to an opening in a side wall), closed face  15  may have a somewhat lower strut density, since it does not need to significantly restrict the flow of a fluid. 
       FIGS. 55-63  show other expandable spherical structures  5  wherein flow-restricting face  15  is formed with a sufficiently high strut density to achieve a desired purpose. In this respect it will be appreciated that, as used herein, the term strut is intended to mean substantially any element spaced from an adjacent element or in contact with an adjacent element. Thus, where flow-restricting face  15  is formed by a face having a high strut density, the struts may be in the form of a screen, a mesh, a lattice, a series of parallel or concentric interlaced or otherwise patterned struts, etc. 
     It should also be appreciated that it is possible to form the entire expandable spherical structure  5  out of a single superelastic wire, e.g., a shape memory alloy constructed so as to form stress-induced martensite at body temperatures. By way of example but not limitation, an appropriately blended and treated Nitinol wire may be used. In this form of the invention, the expandable spherical structure  5  can be (i) deformed into a collapsed configuration wherein a single path of the wire is constrained within a restraining cannula, and (ii) thereafter reformed in situ by simply pushing the wire out of the distal end of the restraining cannula, whereupon expandable spherical structure  5  reforms in the blood vessel or other body lumen. This form of the invention is particularly well suited to constructions where flow-restricting face  15  is formed with a single, patterned strut arranged to have a high strut density, e.g., with a strut density sufficiently high to restrict flow to the mouth of an aneurysm, and/or a strut density sufficiently high to reinforce the side wall of a blood vessel or other body lumen, and/or a strut density sufficiently high to achieve some other desired purpose. See, for example,  FIGS. 59-63 , which show flow-restricting face  15  formed out of a single, patterned strut, where the strut pattern may comprise one or more of a variety of configurations, e.g., with parallel paths, concentric paths, switchback paths, serpentine paths, etc. 
     Utilizing the Expandable Spherical Structure in Conjunction with Thrombosis-Inducing Coils 
     As noted above, conventional minimally-invasive techniques for treating brain aneurysms generally involve depositing thrombosis-inducing coils within the dome of the aneurysm. If desired, the expandable spherical structure  5  of the present invention may be used in conjunction with thrombosis-inducing coils, i.e., the thrombosis-inducing coils may be deposited within the dome of an aneurysm after positioning the expandable spherical structure against the mouth of the aneurysm so as to restrict flow into the aneurysm, i.e., by introducing the thrombosis-inducing coils through the face having a high strut density and into the dome of the aneurysm. Alternatively, the thrombosis-inducing coils may be deposited within the dome of the aneurysm before positioning the expandable spherical struture against the mouth of the aneurysm so as to restrict flow into the aneurysm. Significantly, it is believed that this approach will both facilitate thrombosis formation and also prevent coil migration out of the aneurysm. 
     Deploying the Expandable Spherical Structure within an Aneurysm 
     It should also be appreciated that expandable spherical structure  5  may be deployed within the body of an aneurysm so that its flow-restricting face  15  confronts the lumen, rather than being within the lumen so that its flow-restricting face confronts the body of the aneurysm. See, for example,  FIGS. 64-66 , which show the expandable spherical structure  5  of  FIGS. 4-8  deployed within the body of the aneurysm. See also, for example,  FIGS. 67-71 , which show the expandable spherical structure  5  of  FIGS. 9-13  being disposed within the body of the aneurysm. 
     Again, the expandable spherical structure  5  may be positioned within the interior of a lateral aneurysm ( FIGS. 64-66  and  67 - 71 ) or it may be disposed within a bifurcated aneurysm ( FIGS. 72-76  and  77 - 81 ). 
     Expandable Spherical Structure with Stabilizing Legs—“Comet-Shaped Structure” 
     It is also possible to provide expandable spherical structure  5  with stabilizing legs. Such a construction may be adapted for use with both lateral aneurysms and with bifurcation aneurysms. 
     More particularly, and looking now at  FIGS. 82 and 83 , there is shown an expandable spherical structure  5  which comprises an open frame  10  with a flow-restricting face  15 . Extending out of open frame  10  are one or more stabilizing legs  30 . Stabilizing legs  30  are formed so that, when flow-restricting face  15  is positioned against the side wall of a blood vessel or other body lumen, stabilizing legs  30  extend endoluminally through the blood vessel or other body lumen. Thus it will be appreciated that the expandable spherical structure  5  shown in  FIGS. 82 and 83  is generally intended to be used with a lateral aneurysm, since the center axis  35  of stabilizing legs  30  is set at a right angle to the center axis  40  of flow-restricting face  15  (see  FIG. 83 ). 
     Preferably, and as seen in  FIGS. 82 and 83 , stabilizing legs  30  together form a somewhat cone-shaped structure, so that the overall shape of open frame  10  (with flow-restricting face  15 ) and stabilizing legs  30  is a generally comet-shaped structure. 
     As seen in  FIG. 84 , this comet-shaped structure may be compressed within a containment sheath  200 , with stabilizing legs  30  leading and with open frame  10  (with flow-restricting face  15 ) trailing, and with a push catheter  205  and tension wire  210  engaging open frame  10  of expandable spherical structure  5 . At the aneurysm site, push catheter  205  ejects the comet-shaped structure, “legs first”, so that closed face  15  restricts access to the mouth of the aneurysm while stabilizing legs  30  help maintain the position of open frame  10  (and flow-restricting face  15 ) within the blood vessel. This deployment procedure is preferably conducted over a guidewire  215 . 
     If the comet-shaped structure subsequently needs to be repositioned or removed from a deployment site, tension wire  210  may be used to pull the comet-shaped structure retrograde, e.g., within the blood vessel or all the way back into containment sheath  200 . To this end, and looking now at  FIGS. 85-87 , open frame  10  of expandable spherical structure  5  may comprise a proximal end ring  220 , and tension wire  210  may comprise an expandable head  225  adapted to extend through proximal end ring  220  and then expand, whereupon the comet-shaped structure may be moved retrograde. Alternatively, open frame  10  of expandable spherical structure  5  may comprise an apex  230  of converging wires which can be gripped by a J-hook  235  formed on the distal end of tension wire  210  ( FIG. 88 ) or by C-fingers  240  formed on the distal end of tension wire  210  ( FIG. 89 ). 
     If desired, and looking now at  FIGS. 85-87 , the distal ends of stabilizing legs  30  may be turned into eyelets  245 , so as to minimize trauma (during both placement and repositioning) to the side wall of the body lumen (e.g., blood vessel) in which they are disposed. 
     It will be appreciated that, where flow-restricting face  15  covers only a portion of the circumference of open frame  10 , it can be important for the clinician to ensure the rotational disposition of the comet-shaped structure so that flow-restricting face  15  is properly aligned with the mouth of the lateral aneurysm. For this reason, and looking now at  FIG. 90 , push catheter  205  may include a plurality of slits  250  on its distal end which receive the constituent wires of open frame  10 , whereby to permit the clinician to adjust the rotational disposition of the comet-shaped structure (and hence the rotational disposition of flow-restricting face  15  of open frame  10 ). Alternatively, and looking now at  FIG. 91 , push catheter  205  may be formed with an obround shape (or any other appropriate non-circular shape) so as to permit the clinician to specify the rotational disposition of the comet-shaped structure (and hence the rotational disposition of flow-restricting face  15  of open frame  10 ). 
     Looking now at  FIGS. 92 and 93 , flow-restricting face  15  of open frame  10  can be formed by wrapping a membrane  255  over the wire skeleton making up open frame  10  and securing it in position. Thus,  FIGS. 94 and 95  show membrane  255  covering only a portion of the circumference of frame  10 , and  FIGS. 96 and 97  show membrane  255  covering the complete circumference of frame  10 . 
     In the foregoing description, the expandable spherical structure  5  of  FIGS. 82 and 83  is discussed in the context of a “legs-first” deployment into the blood vessel or other body lumen. However, it should also be appreciated that the expandable spherical structure  5  of  FIGS. 82 and 83  may be deployed “head-first” into the blood vessel or other body lumen (i.e., with stabilizing legs  30  trailing open frame  10 ). 
     Looking next at  FIG. 98 , it is also possible to provide a comet-shaped structure which can be used with a bifurcation aneurysm. More particularly, in this form of the invention, expandable spherical structure  5  is formed so that center axis  40  of flow-restricting face  15  is aligned with center axis  35  of stabilizing legs  30 . It will be appreciated that where the comet-shaped structure is to be used with to treat a bifurcation aneurysm, it is generally desirable that the “head” of the comet (which comprises flow-restricting face  15 ) be ejected out of containment sheath  200  first, with stabilizing legs  30  trailing, whereby to easily place flow-restricting face  15  against the mouth of the aneurysm. 
     Expandable Spherical Structure Formed Out of a “Closed Loop” of Filament 
     In the preceding description, expandable spherical structure  5  is described as comprising an open frame  10  having a flow-restricting face  15  carried thereon. More particularly, in some embodiments of the invention, flow-restricting face  15  comprises a substantially complete surface or barrier. See, for example,  FIGS. 4-49 . However, in other embodiments of the invention, flow-restricting face  15  need not comprise a substantially complete surface or barrier, i.e., flow-restricting face  15  may be formed with a face having a sufficiently high strut density to form an effectively closed face or to otherwise achieve a desired purpose. Thus, for example, in  FIGS. 50-58 , there is shown an expandable spherical structure  5  comprising an open frame  10  having a flow-restricting face  15  formed with a high strut density such that blood flow to the aneurysm will be restricted and the aneurysm will thrombose. In this circumstance, flow-restricting face  15  may be considered to be effectively closed, in the sense that flow-restricting face  15  is sufficiently closed to decrease flow velocity in the aneurysm and result in thrombosis within the aneurysm. Furthermore, where flow-restricting face  15  is being used to reinforce a weakness in a side wall (as opposed to being used to close off an opening in a side wall or to otherwise restrict flow through that opening), flow-restricting face  15  may have a somewhat lower strut density. In any case, however, flow-restricting face  15  will still have a significantly higher strut density than that of open frame  10 . 
     By way of example but not limitation, where flow-restricting face  15  is to be used to thrombose an aneurysm, flow-restricting face  15  preferably has a strut density (i.e., a filament density) sufficient to cover at least 30% of the total surface area of the flow-restricting face, and more preferably about 50% of the total surface area of the flow-restricting face. 
     In the preceding description, it was noted that it is possible to form the entire expandable spherical structure  5  out of a single superelastic wire, e.g., a shape-memory alloy constructed so as to form stress-induced martensite at body temperatures. It was also noted that, in this form of the invention, the expandable spherical structure  5  can be (i) deformed into a collapsed configuration wherein a single path of the wire is constrained within a constraining cannula, and (ii) thereafter reformed in situ by simply pushing the wire out of the distal end of the restraining cannula, whereupon expandable spherical structure  5  reforms in the blood vessel or other body lumen. It was further noted that this form of the invention is particularly well suited to constructions wherein flow-restricting face  15  is formed with a single, patterned strut arranged to have a high strut density, e.g., with a strut density sufficiently high to restrict the flow of blood through the mouth of an aneurysm (i.e., to cause thrombosis of the aneurysm), and/or a strut density sufficiently high to reinforce the side wall of a blood vessel or other body lumen, and/or a strut density sufficiently high to achieve some other desired purpose. Again, however, flow-restricting face  15  will still have a significantly higher strut density than that of open frame  10 . See, for example,  FIGS. 59-63 , which show flow-restricting face  15  formed out of a single, patterned strut, where the strut pattern may comprise one or more of a variety of configurations, e.g., with parallel paths, concentric paths, switchback patterns, serpentine paths, etc. 
     In accordance with the present invention, there is now disclosed a further construction wherein expandable spherical structure  5  is formed out of a single closed loop of filament, such as a single closed loop of highly flexible wire (e.g., Nitinol) which has been worked (e.g., on a mandrel) so that its numerous turns approximate the shape of a sphere or ellipsoid when the single closed loop of filament is in its relaxed (i.e., unconstrained) condition. One face of the sphere (i.e., flow-restricting face  15 ) has a higher turn density than the remainder of the sphere (i.e., open frame  10 ) so that the high density face can restrict blood flow while the remainder of the sphere easily passes blood flow. The single closed loop of filament may be transformed from its unconstrained spherical shape into another shape by applying physical forces (e.g., tension) to the single closed loop of filament. Thus, the single closed loop of filament may be transformed from its three-dimensional substantially spherical configuration into a substantially two-dimensional “elongated loop” configuration (e.g., by applying two opposing forces to the interior of the loop) in order that the single closed loop of filament may be advanced endoluminally through a blood vessel to the site of an aneurysm. Once at the site of the aneurysm, the tension on the elongated loop of filament may be released so that the single closed loop of filament returns to its spherical configuration, whereby to lodge in the blood vessel with the high density face (i.e., flow-restricting face  15 ) diverting the flow of blood away from the aneurysm (i.e., so as to cause thrombosis within the aneurysm) while the remainder of the sphere (i.e., open frame  10 ) spans the blood vessel or other body lumen and bears against opposing anatomy so as to support flow-restricting face  15  in position while easily passing the blood flowing through the parent vessel. If the sphere subsequently needs to be re-positioned within the blood vessel, the tension is re-applied to the sphere so as to transform it part or all the way back to its elongated loop configuration, the position of the device is adjusted, and then the foregoing process is repeated so as to set the sphere at a new position within the blood vessel. Furthermore, if the sphere needs to be removed from the blood vessel, the tension is re-applied to the sphere so as to transform it back to its elongated loop configuration, and then the loop is removed from the patient. Significantly, this construction has the advantages of (i) ease of positioning, (ii) reliably maintaining its deployed position within the vessel, (iii) ease of re-positioning within the body, and (iv) where necessary, removal from the body. 
     By way of example but not limitation,  FIG. 63  shows a expandable spherical structure  5  which is formed out of a single closed loop of highly flexible wire. As can be seen in  FIG. 63 , expandable spherical structure  5  approximates the shape of a sphere or ellipsoid when the loop is in its relaxed condition.  FIG. 63  shows expandable spherical structure  5  being used to restrict blood flow to a lateral aneurysm.  FIGS. 99 and 100  show expandable spherical structure  5  being used to restrict blood flow to a bifurcation aneurysm. 
       FIGS. 101 and 102  shows an inserter  300  which can be used to reconfigure such a “closed loop” expandable spherical structure  5  from its relaxed spherical (or ellipsoidal) configuration into a tensioned elongated loop configuration. To this end, inserter  300  preferably comprises an inner catheter  305  which includes a bifurcated distal end  310  which can seat a segment of the closed loop of filament. Inserter  300  preferably also comprises an outer catheter  315  which includes a mount  320  which can seat another segment of the closed loop of filament. 
     In use, and as shown in  FIGS. 103-107 , inserter  300  is set so that its outer catheter  315  is adjacent to bifurcated distal end  310 , and then a segment of the closed loop expandable spherical structure  5  is seated in bifurcated distal end  310  and another segment of the closed loop expandable spherical structure is seated in mount  320  of outer catheter  315 . Then outer catheter  315  is moved proximally so that the closed loop of filament is reconfigured from its relaxed spherical (or ellipsoidal) configuration into an elongated loop configuration, e.g., in the manner of a tensioned elastic band. With the closed loop of filament held in this elongated condition on inserter  300 , a transport sheath  325  is (optionally) placed over the assembly so as to facilitate atraumatic movement through a blood vessel or other body lumen. Inserter  300  (with its passenger closed loop of filament and with its overlying transport sheath  325 ) is moved through the patient&#39;s anatomy until it is located at the surgical site. Then transport sheath  325  is removed and outer catheter  315  is moved distally on inner catheter  305 . As outer catheter  315  is moved distally on inner catheter  305 , tension on the closed loop of filament is released so that the closed loop of filament can re-assume its spherical or ellipsoidal shape and engage the adjacent anatomy. Then expandable spherical structure  5  is disengaged from inserter  300 , and inserter  300  is removed from the surgical site. 
     If, after deployment, the closed loop expandable spherical structure  5  needs to be re-positioned within the blood vessel, inserter  300  is used to re-apply tension to the spherical structure so as to transform the spherical structure part or all the way back to its elongated loop configuration, the position of the device is adjusted, and then the foregoing process is repeated so as to set the spherical structure at a new position within the blood vessel. 
     Furthermore, if, after deployment, the closed loop expandable spherical structure  5  needs to be removed from the blood vessel, inserter  300  is used to re-apply tension to the spherical structure so as to transform it back to its elongated loop configuration, and then the elongated loop is removed from the patient. 
     Significantly, this construction has the advantages of (i) ease of positioning, (ii) reliably maintaining its deployed position within the vessel, (iii) ease of re-positioning within the body, and (iv) where necessary, removal from the body. 
     TERMINOLOGY 
     In the foregoing disclosure, expandable spherical structure  5  is described as comprising a spherical body. In this regard, it should be appreciated that the term “spherical” is intended to mean a true spherical shape, and/or a substantially spherical shape, and/or a near spherical shape (including but not limited to an ellipsoid shape or a substantially ellipsoid shape or a near ellipsoid shape), and/or an effectively spherical shape, and/or a generally spherical shape, and/or a polyhedron which approximates a sphere, and/or a shape which approximates a sphere, and/or a structure comprising a substantial portion of any of the foregoing, and/or a structure comprising a combination of any of the foregoing, etc. 
     Thus, for example, expandable spherical structure  5  may include a first section that constitutes a portion of a sphere and a second section which roughly approximates the remaining portion of a sphere. 
     Endoluminal Device with “Switchback” Face for Restricting Blood Flow to an Aneurysm while Still Maintaining Substantially Normal Blood Flow Through the Blood Vessel 
     Looking now at  FIG. 108 , there is shown an endoluminal device  405  which is similar to the expandable spherical structure  5  shown in  FIGS. 60-63 . Endoluminal device  405  is formed from a single closed loop of filament (e.g., superelastic wire) which is capable of assuming (i) a substantially elongated shape to facilitate delivery through the vascular system of a patient to an aneurysm located at a remote vascular site, and (ii) an expanded shape to present a flow-restricting face against the mouth of the aneurysm, whereby to restrict blood flow to the aneurysm while maintaining substantially normal blood flow through the lumen of the blood vessel. As noted above, the flow-restricting face of endoluminal device  405  can be formed by patterning the filament in a variety of configurations in the region of the flow-restricting face, e.g., parallel paths, concentric paths, switchback patterns, serpentine paths, etc. One such filament pattern is disclosed in  FIG. 108 . 
     It has been discovered that, as the size of the endoluminal device is decreased (e.g., for use in small diameter vessels, such as to treat brain aneurysms), the diameter of the filament (e.g., the superelastic wire) must generally also be reduced, and this can lead to several problems. 
     First, as the diameter of the filament is reduced, the ability of the filament to reliably re-form to a desired pre-determined pattern is also generally reduced, since the resilient force of the filament is at least partly a function of the diameter of the filament. 
     Second, as the diameter of the filament is reduced, the ability of the filament to maintain its desired pre-determined pattern in a turbulent blood flow is also generally reduced, since the rigidity of the filament is at least partly a function of the diameter of the filament. For purposes of the present invention, a turbulent blood flow may be considered to be any blood flow which is disturbed, or non-laminar, or irregular, or disordered, or agitated, etc., i.e., any blood flow which would tend to disrupt the patterned flow-restricting face of the endoluminal device when the endoluminal device is disposed in a blood vessel. 
     Thus, as the diameter of the filament is reduced, it generally becomes increasingly more difficult to ensure that the endoluminal device will reliably re-form to its desired pre-configured pattern, and it generally becomes increasingly more difficult to ensure that the endoluminal device will maintain its desired pre-determined pattern in a turbulent blood flow. In practice, this reduction of filament diameter can result in the creation of gaps in the density of the flow-restricting face, which can permit high-velocity blood (e.g., “jets” of blood) to enter the aneurysm through those gaps. These jets of blood can inhibit the desired thrombosis of the aneurysm and, if the jets of blood are of sufficient velocity and/or volume flow, can impose dangerous stresses on the aneurysm wall and potentially lead to aneurysm rupture. 
     In addition to the foregoing, when the filament is reconfigured from its elongated, substantially two-dimensional configuration to its expanded, substantially three-dimensional configuration, the elastic filament can become entangled, sometimes preventing the elastic filament from reliably re-forming to its desired pre-determined pattern. By way of example but not limitation, more complex filament patterns can be susceptible to the aforementioned entangling problems. 
     After substantial efforts, it has been discovered that certain filament patterns perform significantly better than other filament patterns, i.e., they more reliably re-form to a desired pre-determined pattern, and they more reliably maintain their desired pre-determined pattern in a turbulent blood flow, and they better resist the aforementioned entangling issues during pattern reformation. 
     More particularly, and looking now at  FIGS. 109-115 , in one preferred form of the invention, there is provided an endoluminal device  410  which is formed out of a single closed loop of elastic filament  415  and which is configured so as to form a flow-restricting face  420  for positioning against the mouth of an aneurysm, and an open frame  422  for spanning the blood vessel and bearing against opposing anatomy so as to support flow-restricting face  15  in position. In this form of the invention, open frame  422  comprises at least one leg  425 , and preferably two legs  425 , for supporting the flow-restricting face  420  in position within the blood vessel. 
     In this form of the invention, flow-restricting face  420  and open frame  422  may combine so as to together form a generally spherical or ellipsoidal structure, or flow-restricting face  420  and open frame  422  may combine so as to together form only a segment of a generally spherical or ellipsoidal structure. Alternatively, only one of the components (e.g., flow-restricting face  420 ) may form only a segment of a generally spherical or ellipsoidal structure. Or flow-restricting face  420  and/or open frame  422  may form, collectively or alone, all or part of other, non-spherical or non-ellipsoidal shapes. 
     Preferably elastic filament  415  is formed out of a single closed loop of superelastic material (e.g., a shape memory alloy such as Nitinol) so that endoluminal device  410  can be (i) deformed into a substantially elongated shape to facilitate delivery through the vascular system of a patient to an aneurysm located at a remote vascular site, and (ii) re-formed in situ so as to present its flow-restricting face  420  against the mouth of the aneurysm, with the flow-restricting face  420  being supported in position by the legs  425 , whereby to restrict blood flow to the aneurysm while maintaining substantially normal blood flow through the blood vessel (i.e., in the case of a lateral aneurysm, the lumen of the blood vessel, or in the case of a bifurcated aneurysm, the parent and daughter blood vessels). 
     Thus, in accordance with the present invention, the single closed loop of elastic filament is configurable between (i) a first longitudinally-expanded, radially and laterally-contracted configuration for movement along a blood vessel, and 
     (ii) a second longitudinally-contracted, radially and laterally-expanded configuration for lodging within the blood vessel, the second configuration providing (a) a single flow-restricting face sized and configured so as to cover the mouth of the aneurysm and obstruct blood flow to the aneurysm, and (b) at least one leg for holding the single flow-restricting face adjacent the mouth of the aneurysm, the at least one leg configured so as to maintain substantially normal blood flow through the blood vessel. 
     In this form of the invention, flow-restricting face  420  is formed by patterning elastic filament  415  in a switchback pattern. More particularly, this switchback pattern is formed by causing elastic filament  415  to assume a plurality of parallel lengths  430 , with adjacent parallel lengths  430  being connected by end returns  435 . For the purposes of the present invention, lengths  430  are considered to be parallel where they are literally parallel, substantially parallel, near parallel, etc. In one preferred form of the invention, flow-restricting face  420  is formed by two symmetric halves  420 A,  420 B separated by a midline  440 , wherein the internal end returns  435 I of each half  420 A,  420 B abut midline  440 , and further wherein the external end returns  435 E define the perimeter of flow-restricting face  420  (i.e., the outer perimeters of halves  420 A,  420 B). If desired, the internal end returns  435 I of one half  420 A of flow-restricting face  420  may be aligned with the internal end returns  435 I of the other half  420 B of flow-restricting face  420  (see  FIGS. 109-111 ). Alternatively, the internal end returns  435 I of one half  420 A of flow-restricting face  420  may be offset (i.e., staggered) with the internal end returns  435 I of the other half of flow-restricting face  420  (not shown in  FIGS. 109-111 ). 
     See also  FIGS. 112-115 , which show the endoluminal device  410  of  FIGS. 109-111  disposed adjacent a bifurcated aneurysm. In this respect it should be appreciated that the endoluminal device  410  shown in  FIGS. 109-111  may also be used to thrombose a lateral aneurysm. 
     It has been found that, by patterning elastic filament  415  in this switchback pattern, endoluminal device  410  more reliably re-forms to a desired pre-determined pattern, and more reliably maintains its desired pre-determined pattern in a turbulent blood flow, and better resists the aforementioned entangling issues during pattern reformation. 
     As seen in  FIGS. 116-118 , endoluminal device  410  may be deployed by the aforementioned inserter  300 . More particularly, the single closed loop of filament forming endoluminal device  410  may be mounted to inserter  300  by mounting one portion of endoluminal device  410  to inner catheter  305  of inserter  300 , and mounting another portion of endoluminal device  410  to outer catheter  315  of inserter  300 . As a result, proximal movement of outer catheter  315  relative to inner catheter  305  (or distal movement of inner catheter  305  relative to outer catheter  315 ) will stretch endoluminal device  410  into an elongated configuration ( FIG. 117 ) so as to facilitate delivery of the endoluminal device through the vascular system of a patient, and distal movement of outer catheter  315  relative to inner catheter  305  (or proximal movement of inner catheter  305  relative to outer catheter  315 ) will restore endoluminal device  410  into its original configuration ( FIG. 118 ) so as to present its flow-restricting face  420  against the mouth of the aneurysm, with the flow-restricting face  420  being supported in position by legs  425 . 
     If desired, one or both of the legs  425  may include a projection  445  (see  FIGS. 109 ,  110 ,  113  and  114 ) adjacent its end so as to facilitate mounting endoluminal device  410  to an inserter (e.g., to the aforementioned inserter  300 ). 
       FIGS. 119-126  show alternative inserters for deploying endoluminal device  410  in the vascular system of a patient. 
     More particularly, and looking first at  FIGS. 119 and 120 , there is shown a modified form of the aforementioned inserter  300  (see  FIGS. 101-107  and  116 - 118 ). In this form of the invention, outer catheter  315  has diametrically-opposed mounts  320  and inner catheter  305  has a bifurcated distal end  310 . Furthermore, in this form of the invention, endoluminal device  410  is transformed from its expanded condition ( FIG. 120 ) to its elongated condition ( FIG. 119 ) by securing the legs  425  of endoluminal device  410  to the diametrically-opposed mounts  410 , and then projecting inner catheter  305  distally (or withdrawing outer catheter  315  proximally) so that an intermediate portion of the endoluminal device  410  is captured by the bifurcated distal end  310  and driven distally ( FIG. 119 ). Endoluminal device  410  is returned to its expanded condition ( FIG. 120 ) by withdrawing inner catheter  305  proximally (or moving outer catheter  315  distally). The form of the invention shown in  FIGS. 119 and 120  is particularly well suited for deploying the endoluminal device  410  adjacent a bifurcation aneurysm. 
     Looking next at  FIGS. 121 and 122 , there is shown an inserter  460  which comprises an inner shaft  465  and an outer shaft  467 . Inner shaft  465  has a pair of parallel lumens  470 ,  475 . A pair of rods  480 ,  485  are telescopically disposed within lumens  470 ,  475 , respectively. Each of the rods  480 ,  485  includes a filament gripping mechanism  490  at its distal end. On account of the foregoing construction, endoluminal device  410  may be mounted to inserter  460  by mounting one portion of endoluminal device  410  to the filament gripping mechanism  490  of rod  480 , and mounting another portion of endoluminal device  410  to the filament gripping mechanism  490  of rod  485 . When endoluminal device  410  is mounted in this manner to inserter  460 , distal movement of rod  480  relative to rod  485  will stretch endoluminal device  410  into an elongated configuration ( FIG. 121 ) which may be housed within outer shaft  467 , e.g., so as to facilitate delivery of the endoluminal device through the vascular system of a patient. When inserter  460  is located adjacent to the aneurysm, outer shaft  467  is retracted proximally, and then proximal movement of rod  480  relative to rod  485  will restore endoluminal device  410  to its original configuration ( FIG. 122 ) so as to present its flow-restricting face  420  against the mouth of the aneurysm, with the flow-restricting face  420  being supported in position by at least one leg  425 . 
       FIGS. 123 and 124  show another inserter  495  which may be used where endoluminal device  410  is formed out of a thermally-activated shape memory alloy. Inserter  495  comprises an inner shaft  500  and an outer shaft  502 . Inner shaft  500  has a pair of rods  505 ,  510  extending distally therefrom. Each of the rods  505 ,  510  includes a filament gripping mechanism  515  at its distal end. On account of the foregoing construction, endoluminal device  410  may be mounted to inserter  495  by mounting one portion of endoluminal device  410  to the filament gripping mechanism  490  of rod  480 , and mounting another portion of endoluminal device  410  to the filament gripping mechanism  490  of rod  485 . Endoluminal device  410  may then be temperature transitioned to its elongated configuration and withdrawn into the interior of outer shaft  502  ( FIG. 123 ). When endoluminal device  410  is mounted in this manner to inserter  495 , the endoluminal device  410  may be advanced through the vascular system of a patient. When endoluminal device  410  has been advanced to an appropriate position adjacent the mouth of the aneurysm, outer shaft  502  may be withdrawn proximally the endoluminal device  410  temperature-activated so as to assume its expanded configuration ( FIG. 124 ), whereby to position flow-restricting face  420  adjacent the mouth of the aneurysm. 
       FIGS. 125 and 126  show still another inserter  520  which may be used to deploy endoluminal device  410 . Inserter  520  is generally similar to the inserter  300  described above, in the sense that it comprises an inner catheter  525  and an outer catheter  530 . A delivery catheter  532  may telescopically surround outer catheter  530 . In this form of the invention, inner catheter  525  comprises a mount  535 , and outer catheter  530  comprises a mount  540 . Mount  540  is preferably formed out of an atraumatic silicone material. Endoluminal device  410  may be mounted to inserter  520  by mounting one portion of endoluminal device  410  to mount  535  of inner catheter  525  and mounting another portion of endoluminal device  410  to mount  540  of outer catheter  530 . As a result, proximal movement of outer catheter  530  relative to inner catheter  525  will stretch endoluminal device  410  into an elongated configuration ( FIG. 125 ), and then delivery catheter  532  advanced distally so as surround endoluminal device  410  whereby to facilitate delivery of the endoluminal device through the vascular system of a patient. When endoluminal device  410  is disposed adjacent to the aneurysm, delivery catheter  532  is withdrawn proximally, and distal movement of outer catheter  530  relative to inner catheter  525  will restore endoluminal device  410  into its original configuration ( FIG. 126 ) so as to present its flow-restricting face  420  against the mouth of the aneurysm, with the flow-restricting face  420  being supported in position by the at least one leg  425 . 
     In the endoluminal device  410  shown in  FIG. 109-126 , the endoluminal device is shown having two equal-sized legs  425 . However, it is possible to form endoluminal device  410  with more than two equal-sized legs (e.g., in a manner analogous to that shown in  FIG. 108 ), or to form endoluminal device  410  with two or more unequal-sized legs, or to form endoluminal device  410  with a single leg, etc. 
     Thus, for example, and looking now at  FIGS. 127-136 , there is shown an endoluminal device  410  which is formed out of a single closed loop of elastic filament  415  and which is configured so as to form a flow-restricting face  420  for positioning against the mouth of an aneurysm, and a single leg  425  for supporting the flow restricting face  420  in position within the blood vessel. Preferably elastic filament  415  is formed out of a single closed loop of superelastic material (e.g., a shape memory alloy such as Nitinol) so that endoluminal device  410  can be (i) deformed into a substantially elongated shape to facilitate delivery through the vascular system of a patient to an aneurysm located at a remote vascular site, and (ii) re-formed in situ so as to present its flow-restricting face  420  against the mouth of the aneurysm, with the flow-restricting face  420  being supported in position by the single leg  425 , whereby to restrict blood flow to the aneurysm while maintaining substantially normal blood flow through the blood vessel. 
     Thus, in accordance with the present invention, the single closed loop of elastic filament is configurable between (i) a first longitudinally-expanded, radially and laterally-contracted configuration for movement along a blood vessel, and (ii) a second longitudinally-contracted, radially and laterally-expanded configuration for lodging within the blood vessel, the second configuration providing (a) a single flow-restricting face sized and configured so as to cover the mouth of the aneurysm and obstruct blood flow to the aneurysm, and (b) a leg for holding the single flow-restricting face adjacent the mouth of the aneurysm, the leg configured so as to maintain substantially normal blood flow through the blood vessel. 
     In this form of the invention, flow-restricting face  420  is formed by patterning elastic filament  415  in a switchback pattern. More particularly, this switchback pattern is formed by causing elastic filament  415  to assume a plurality of parallel lengths  430 , with adjacent parallel lengths  430  being connected by end returns  435 . In one preferred form of the invention, flow-restricting face  420  is formed by two symmetric halves  420 A,  420 B separated by a midline  440 , wherein the internal end returns  435 I of each half  420 A,  420 B abut midline  440 , and further wherein the external end returns  435 E define the perimeter of flow-restricting face  420  (i.e., the outer perimeters of halves  420 A,  420 B). If desired, the internal end returns  435 I of one half  420 A of flow-restricting face  420  may be aligned with the internal end returns  435 I of the other half  420 B of flow-restricting face  420  (see  FIGS. 127-136 ). Alternatively, the internal end returns  435 I of one half  420 A of flow-restricting face  420  may be offset (i.e., staggered) with the internal end returns  435 I of the other half  420 B of flow-restricting face  420  (not shown in  FIGS. 127-136 ). 
     In the endoluminal devices shown in  FIGS. 109-126 , flow-restricting face  420  is formed by two symmetric halves  420 A,  420 B separated by a midline  440 , wherein the internal end returns  435 I of each half  420 A,  420 B abut midline  440  and further wherein the external end returns  435 E define the perimeter of flow-restricting face  420  (i.e., the outer perimeters of halves  420 A,  420 B). 
     However, if desired, and looking now at  FIGS. 137-140 , the two halves  420 A,  420 B of flow-restricting face  420  may overlap one another, so that, for each of them, their internal end returns  435 I reside on the far side of midline  440 . In this form of the invention, adjacent parallel lengths  430  and internal end returns  435 I cooperate with one another so as to define a series of enclosures  545 , with those enclosures  545  being aligned along midline  440 . This construction has been found to have greater strength in situ so that it more reliably maintains its desired pre-determined pattern in a turbulent blood flow. 
       FIGS. 141-144  show an endoluminal device  410  which is similar to the endoluminal device  410  shown in  FIGS. 137-140 , except that enclosures  545  are offset from midline  440 , in an alternating pattern. This construction has been found to have even greater strength in situ so that it more reliably maintains its desired pre-determined pattern in a turbulent blood flow. 
       FIG. 145  shows still another form of endoluminal device  410  formed in accordance with the present invention. In this form of the invention, the endoluminal device is formed out of a single closed loop of a flexible filament (e.g., a continuous loop of superelastic wire), and comprises a flow-restricting face  420  which is supported in position by two legs  425 , i.e., by one leg  425 A which is similar to the legs  425  shown in the endoluminal device of  FIGS. 109-126 , and by one leg  425 B which comprises a generally cylindrical structure. This form of the invention may hold flow-restricting face  420  in position with greater stability, since generally cylindrical leg  425 B may make a more secure fixation to the lumen of a blood vessel. In this respect it should be appreciated that while  FIG. 145  shows endoluminal device  410  deployed adjacent a bifurcation aneurysm, the endoluminal device  410  shown in  FIG. 145  may also be used to thrombose a lateral aneurysm. 
     In the foregoing discussion, endoluminal device  410  is discussed in the context of presenting a flow-restricting face against the mouth of the aneurysm, whereby to thrombose the aneurysm. However, it should also be appreciated that endoluminal device  410  may be used to reinforce a side wall of a blood vessel, or to retain detachable coils or other embolic material within the body of an aneurysm, etc. Furthermore, while endoluminal device  410  is shown in the context of  FIGS. 112-115 ,  123  and  124 ,  127 ,  133 - 136  and  145  as being applied to a bifurcation aneurysm, it should also be appreciated that these endoluminal devices  410  may be equally well applied to a lateral aneurysm. 
     Modifications 
     It will be appreciated that still further embodiments of the present invention will be apparent to those skilled in the art in view of the present disclosure. It is to be understood that the present invention is by no means limited to the particular constructions herein disclosed and/or shown in the drawings, but also comprises any modifications or equivalents within the scope of the invention.