Patent Publication Number: US-2023132550-A1

Title: Stent and Stent Delivery Device

Description:
RELATED APPLICATIONS 
     This application is a continuation of and claims priority to U.S. patent application Ser. No. 16/988,546 filed Aug. 7, 2020 entitled Stent And Stent Delivery Device, which is a continuation of and claims priority to U.S. patent application Ser. No. 16/414,689 filed May 16, 2019 entitled Stent And Stent Delivery Device (now U.S. Pat. No. 10,65,540 issued Sep. 8, 2020), which is a continuation of U.S. patent application Ser. No. 15/247,714 filed Aug. 25, 2016 entitled Stent And Stent Delivery Device (now U.S. Pat. No. 10,335,297 issued Jan. 28, 2020), which is a continuation of U.S. patent application Ser. No. 13/843,342 filed Mar. 15, 2013 entitled Stent And Stent Delivery Device (now U.S. Pat. No. 9,439,791 issued Sep. 13, 2016), which claims benefit of and priority to U.S. Provisional Application Ser. No. 61/667,895 filed Jul. 3, 2012 entitled Stent, U.S. Provisional Application Ser. No. 61/618,375 filed Mar. 30, 2012 entitled Stent Deployment Device, and U.S. Provisional Application Ser. No. 61/612,158 filed Mar. 16, 2012 entitled Stent Deployment System, all of which are hereby incorporated herein by reference in their entireties. 
    
    
     BACKGROUND OF THE INVENTION 
     All of the following applications are hereby incorporated by reference in their entireties: U.S. Provisional Patent Application Ser. No. 61/422,604 filed Dec. 13, 2010 entitled Stent; U.S. Provisional Patent Application Ser. No. 61/425,175 filed Dec. 20, 2010 entitled Polymer Stent And Method Of Manufacture; International Patent Application No. PCT/US2010/061627, International Filing Date 21 Dec. 2010, entitled Stent; U.S. Provisional Patent Application Ser. No. 61/427,773 filed Dec. 28, 2010 entitled Polymer Stent And Method Of Manufacture 2; and U.S. Nonprovisional patent application Ser. No. 13/003,277 filed Jan. 7, 2011 entitled Stent. 
     The present invention relates to devices for the treatment of body cavities, such as the embolization of vascular aneurysms and the like, and methods for making and using such devices. 
     The occlusion of body cavities, blood vessels, and other lumina by embolization is desired in a number of clinical situations. For example, the occlusion of fallopian tubes for the purposes of sterilization, and the occlusive repair of cardiac defects, such as a patent foramen ovale, patent ductus arteriosis, and left atrial appendage, and atrial septal defects. The function of an occlusion device in such situations is to substantially block or inhibit the flow of bodily fluids into or through the cavity, lumen, vessel, space, or defect for the therapeutic benefit of the patient. 
     The embolization of blood vessels is also desired to repair a number of vascular abnormalities. For example, vascular embolization has been used to control vascular bleeding, to occlude the blood supply to tumors, and to occlude vascular aneurysms, particularly intracranial aneurysms. 
     In recent years, vascular embolization for the treatment of aneurysms has received much attention. Several different treatment modalities have been shown in the prior art. One approach that has shown promise is the use of thrombogenic microcoils. These microcoils may be made of biocompatible metal alloy(s) (typically a radio-opaque material such as platinum or tungsten) or a suitable polymer. Examples of microcoils are disclosed in the following patents: U.S. Pat. No. 4,994,069—Ritchart et al.; U.S. Pat. No. 5,133,731—Butler et al.; U.S. Pat. No. 5,226,911—Chee et al.; U.S. Pat. No. 5,312,415—Palermo; U.S. Pat. No. 5,382,259—Phelps et al.; U.S. Pat. No. 5,382,260—Dormandy, Jr. et al.; U.S. Pat. No. 5,476,472—Dormandy, Jr. et al.; U.S. Pat. No. 5,578,074—Mirigian; U.S. Pat. No. 5,582,619—Ken; U.S. Pat. No. 5,624,461—Mariant; U.S. Pat. No. 5,645,558—Horton; U.S. Pat. No. 5,658,308—Snyder; and U.S. Pat. No. 5,718,711—Berenstein et al.; all of which are hereby incorporated by reference. 
     Stents have also been recently used to treat aneurysms. For example, as seen in U.S. Pat. No. 5,951,599—McCrory and U.S. Pub. No. 2002/0169473—Sepetka et al., the contents of which are incorporated by reference, a stent can be used to reinforce the vessel wall around the aneurysm while microcoils or other embolic material are advanced into the aneurysm. In another example seen in U.S. Pub. No. 2006/0206201—Garcia et al. and also incorporated by reference, a densely woven stent is placed over the mouth of the aneurysm which reduces blood flow through the aneurysm&#39;s interior and ultimately results in thrombosis. 
     In addition to flow diversion and occlusion, the present invention can also be used in applications where high coverage or low porosity is desirable. For example, when treating carotid artery stenosis with a stent, emboli or particulates may be dislodged during stent deployment or post-deployment dilatation. Since these emboli can become lodged in the brain and cause a stroke, it is desirable to provide a stent with low porosity to entrap the particulates. Another application of a high coverage stent is in areas of the body prone to thrombus formation such as in coronary bypass grafts (also called saphenous vein grafts or SVG) and arteries and veins in the lower extremities. Since the thrombus can dislodge and occlude downstream tissues, it is desirable to deploy a high coverage device of the instant invention to cover and/or entrap the thrombus to prevent it from migrating. 
     SUMMARY OF THE INVENTION 
     In one embodiment according to the present invention, a stent is described having a generally cylindrical body formed from a single woven nitinol wire. The distal and proximal ends of the stent include a plurality of loops, some of which include marker members used for visualizing the position of the stent. 
     In another embodiment according to the present invention, a delivery device is described, having an outer catheter member and an inner pusher member disposed in a passage of the catheter. The distal end of the pusher member includes a distal and proximal marker band that is raised above the adjacent portions of the pusher member body. The previously described stent can be compressed over the distal marker band such that the stent&#39;s proximal loops and proximal marker members are disposed between the distal and proximal marker bands on the pusher member. 
     In one example, the delivery device can be used to deliver the previously described stent over an opening of an aneurysm. The aneurysm is preferably first filled with microcoils or embolic material either before or after delivery of the stent. 
     In another embodiment according to the present invention, a dual layer stent is described having an outer anchoring stent similar to the previously described stent and a discrete inner mesh layer formed from a plurality of woven members. The proximal end of the outer stent and the inner stent are connected together by connecting members or crimping, allowing the remaining portions of the outer anchoring stent and inner mesh layer to independently change in length as each begins to expand in diameter. Alternately, the inner mesh layer may only extend along a portion of the length of outer stent and may be symmetrically or asymmetrically positioned between the out stent&#39;s distal and proximal ends. 
     In one example, the dual layer stent can be delivered over the opening of an aneurysm to modify the flow of blood that enters the aneurysm. As the blood flow into the aneurysm becomes stagnant, a thrombosis forms to block up the interior aneurysm space. 
     In another embodiment according to the present invention, a single or dual layer stent can be created by polymerizing a prepolymer liquid inside a tube, syringe or similar structure. Patterns can be created in the polymer structure via a pre-patterned mandrel on which the polymer structure is polymerized or by cutting the polymer structure after polymerization. 
     In another embodiment according to the present invention, a dual-layer stent is connected at multiple locations along its length. For example, a tantalum wire can be woven between both layers, maintaining the layers in close proximity to each other. Both layers of the stent may be braided or woven at the same braid angle (i.e., picks per inch) which allows both layers to contract in length by the same amount and rate during expansion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other aspects, features and advantages of which embodiments of the invention are capable of will be apparent and elucidated from the following description of embodiments of the present invention, reference being made to the accompanying drawings, in which: 
         FIG.  1    illustrates a side view of a stent according to a preferred embodiment of the present invention; 
         FIG.  2    illustrates a front view of the stent of  FIG.  1   ; 
         FIG.  3    illustrates a magnified view of area  3  in  FIG.  1   ; 
         FIG.  4    illustrates a magnified view of area  4  in  FIG.  1   ; 
         FIG.  5    illustrates a magnified view of area  5  in  FIG.  1   ; 
         FIG.  6    illustrates a magnified view of area  6  in  FIG.  1   ; 
         FIG.  6 A  illustrates an alternate view of area  6  in  FIG.  1    have two coils formed by different strands of wire; 
         FIG.  7    illustrates a side view of a pusher member according to a preferred embodiment of the present invention; 
         FIG.  8    illustrates a partial cross sectional view of the pusher member of  FIG.  7    having the stent of  FIG.  1    compressed over its distal end and being positioned in a catheter; 
         FIG.  9    illustrates the stent of  FIG.  1    positioned over the opening of an aneurysm; 
         FIG.  10    illustrates a side view of a mandrel according to the present invention that can be used to create the stent of  FIG.  1   ; 
         FIG.  11    illustrates a side view of a stent according to a preferred embodiment of the present invention; 
         FIGS.  12 - 14    illustrate various views of a dual layer stent according to a preferred embodiment of the present invention; 
         FIG.  15    illustrates a cross sectional view of a delivery system for the dual layer stent of  FIGS.  12 - 14   ; 
         FIG.  16    illustrates a perspective view of dual layer stent having an outer stent layer formed from a tube or sheet of material; 
         FIG.  17    illustrates a cross sectional view of the dual layer stent of  FIG.  15    showing various optional attachment points of both layers of the dual layer stent; 
         FIG.  18    illustrates another preferred embodiment of a dual layer stent according to the present invention; 
         FIG.  19    illustrates a stent according to the present invention composed of a flow-diverting layer; 
         FIG.  20    illustrates a dual layer stent according to the present invention having a shortened flow-diverting layer; 
         FIG.  21    illustrates a dual layer stent according to the present invention having an elongated flow-diverting layer; 
         FIG.  22    illustrates a dual layer stent according to the present invention having an asymmetrically positioned flow-diverting layer; 
         FIGS.  23  and  24    illustrate an expansile wire for use with a flow-diverting layer according to the present invention; 
         FIG.  25    illustrates a portion of a flow-diverting layer having an expansile wire incorporated into its structure; 
         FIG.  26 - 29    illustrate a process according to the present invention for creating a polymer stent or stent layer; 
         FIG.  30    illustrates another process according to the present invention for creating a polymer stent or stent layer; 
         FIGS.  31 - 36    illustrate another process according to the present invention for creating a polymer stent or stent layer; 
         FIGS.  37 - 39    illustrate various aspects of a stent delivery pusher according to the present invention; 
         FIGS.  40 - 50    illustrates various embodiments of stent delivery pushers having different distal end shapes according to the present invention; 
         FIGS.  51 - 59    illustrate various embodiments of a rapid exchange stent delivery system according to the present invention; 
         FIG.  60    illustrates another embodiment of a stent delivery pusher according to the present invention; 
         FIG.  61    illustrates another embodiment of a stent delivery pusher according to the present invention; 
         FIGS.  62 - 66    illustrate another embodiment of a dual layer stent according to the present invention; and, 
         FIG.  67    illustrates another embodiment of a single layer stent having different sized wires according to the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Specific embodiments of the invention will now be described with reference to the accompanying drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. The terminology used in the detailed description of the embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention. In the drawings, like numbers refer to like elements. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
       FIG.  1    illustrates a stent  100  according to a preferred embodiment of the present invention. The stent  100  is woven or braided together from a single wire  102  to form a generally cylindrical shape with a plurality of loops  104  around the perimeter of both ends of the stent  100 . 
     As seen in area  5  in  FIG.  1    and in  FIG.  5   , the ends of the single wire  102  can be connected to each other via welding (see welded region  116 ), bonding agents or a similar adhesive mechanism. Once the ends are welded or bonded, the wire  102  has no “free” ends. 
     Each of the loops  104  may contain one or more coil members  106 . Preferably, the coil members  106  are disposed around the wire  102  of the loops  104  which, as discussed in greater detail below, denote the proximal and distal ends of the stent  100 . Additionally, these coil members  106  may provide additional anchoring force within a delivery device as described in greater detail below. 
     In one example, a distal end of the stent  100  includes at least two loops  104  with two coil members  106  each and a proximal end of the stent  100  includes at least two loops  104  with one coil member  106  each. However, it should be understood that the stent  100  can include any number of coil members  106  on any number of loops  104 . 
     Preferably, these coil members  106  are positioned near a center area of the loop  104 , such that when the stent  100  is in a collapsed state, the coil members  106  are positioned near the very distal or very proximal end of the stent  100 . 
     Preferably, each coil member  106  is composed of a wire  105  wound around a portion of the loop  104 . Each coil member  106  can be composed of a discrete wire  105  (as seen in  FIG.  3   ) or a single wire  105  can form multiple coil members  106  (as seen in  FIGS.  1 ,  3  and  6   ). In the present preferred embodiment, some coil members  106  are composed of discrete sections of wire  105  while other coil members  106  on either end are formed from the same, continuous wire  105 . As seen in  FIG.  1   , the wire  105  can connected to coil members  106  on each end of the stent  100  by being located within the inner portion or lumen of the stent  100 . Alternately, the wire  105  may be woven into the wires  102  of the stent  100 . 
     In another embodiment, wire  105  can be composed of two or more constituent wire elements which are wound together to produce wire  105 . Utilizing two or more twisted wires to create element  105  can increase the flexibility of wire  105 , by lowering the bend radius and thus increasing the overall curvature/flexibility. Increased flexibility may aid in collapsibility and trackability of the device. 
     When multiple wires are wound together to produce wire  105 , each constituent wire element may individually wind at the proximal and distal ends of the stent to produce coils  106  in series. Thus one of the constituent wire elements can be wound to form one coil  106 , followed by another one of the constituent wire elements wound into a subsequent coil  106 . 
     Preferably, the wire  105  of the coil members  106  is composed of a radiopaque material such as tantalum or platinum. The wire  105  preferably has a diameter of about 0.00225″. 
     Alternately, the coil members  106  may be a radiopaque sleeve that is disposed on and adhered to the loop  104 . 
     In one embodiment, the loops  104  on the proximal end of the stent  100  have one coil  106  on each side of the loop  104  (as seen in  FIG.  3   ) while the distal end of the stent  100  includes only one coil  106  on one side of each loop  104  (as seen in  FIG.  6   ). 
     Preferably, the weaving pattern of the stent  100  prevents the distal coils  106  from being exposed or “sticking up” from an outer diameter of the stent  100  during retraction. Hence, if the user decides to retract the stent  100  back into the catheter for repositioning and redeployment, the distal coils  106  will not catch or contact the distal edge of the catheter, thereby minimizing damage to the stent  100  that might otherwise occur during retraction. 
     One specific technique for minimizing the exposure of the distal coils  106  during retraction is to weave the stent  100  such that portions of the wire  102  overlap (i.e., are positioned at a greater outer diameter position) than the side of the loop  104  with coil  106 . As seen in  FIG.  6   , some smaller, minor loops  107  are woven to overlap a first side  104 A of the loop  104  that includes the coil  106  (see location  109 ) while other minor loops  107  are woven underneath a second side  1048  of the loop  104  (see location  111 ). 
     As a user retracts the stent  100  back into the catheter, the minor loops  107  move inward (i.e., towards the center of the stent&#39;s passage) as the stent  100  compresses in diameter, thereby inwardly pressing on the first side  104 A of the loop  104 . In this respect, the minor loops  107  exert inward or compressive force on the first side  104 A of the loop  104 . This configuration ensures that the first side  104 A of the loop  104  and therefore the coil  106  is not positioned at an outermost diameter of the stent  100  during retraction and therefore reduces the likelihood of the coils  106  of catching or hooking on to the distal end of the deployment catheter. 
     As seen best in  FIG.  1    and  FIG.  2   , the loops  104  are flared or biased to an outer diameter  114  when fully expanded relative to the diameter of the main body of stent  100 . These loops  104  can also expand to a diameter that is even with or smaller than that of the main body. 
     The stent  100  preferably has a diameter  110  sized for a vessel  152  in the human body, as seen in  FIG.  9   . More preferably, the diameter  110  is between about 2 mm and 10 mm. The length of the stent  100  is preferably sized to extend beyond the mouth of an aneurysm  150  as also seen in  FIG.  9   . More preferably, the length of the stent  100  is between about 5 mm and 100 mm. 
       FIGS.  7  and  8    illustrate a delivery system  135  according to the present invention which can be used to deliver the stent  100 . A catheter or sheath  133  is positioned over a delivery pusher  130 , maintaining the stent  100  in its compressed position. Once the distal end of the sheath  133  has achieved a desired target location (i.e., adjacent an aneurysm  150 ), the sheath  133  can be retracted to release the stent  100 . 
     The delivery pusher  130  is preferably composed of a core member  132 , which tapers in diameter near its distal end (made from nitinol). A proximal area of the tapered end of the core member  132  includes a larger diameter first wire coil  134  that is preferably made from stainless steel and welded or soldered in place on the core member  132 . Distal to the coiled wire is a first marker band  136  that is fixed to the core member  132  and preferably made from a radiopaque material such as platinum. 
     A smaller diameter second wire coil  138  is located distal to the marker band  136  and is preferably made from stainless steel or plastic sleeve. A second marker band  140  is located distal to the second wire coil  138  and is also preferably made from a radiopaque material such as platinum. Distal to the second marker band  140  is a narrow, exposed section  142  of the core member  132 . Finally, a coiled distal tip member  144  is disposed on the distal end of the core member  132  and is preferably composed of a radiopaque material such as platinum or tantalum. 
     In one example, the inner diameter of the sheath  133  is about 0.027″ and about 1 meter in length. The delivery pusher  130  is also about 2 meters in length. The sections of the delivery pusher  130  preferably have the following diameters: the proximal region of the core member  132  is about 0.0180 inch, the first wire coil  134  is about 0.0180 inch, the first marker band  136  is about 0.0175 inch, the second wire coil  138  is about 0.0050 inch, the second marker band  140  is about 0.0140 inch, the distal core member section  142  is about 0.003 inch, and the distal tip member  144  is about 0.0100 inch. The sections of the delivery pusher  130  preferably have the following lengths: the proximal region of the core member  132  is about 1 meter, the first wire coil  134  is about 45 cm, the first marker band  136  is about 0.020 inch, the second wire coil  138  is about 0.065 inch, the second marker band  140  is about 0.020 inch the distal core member section  142  is about 10 cm, and the distal tip member  144  is about 1 cm. 
     As seen in  FIG.  8   , the stent  100  is compressed over the distal end of the delivery pusher  130  such that the coil members  106  on the proximal end of the stent  100  are positioned between the first marker band  136  and the second marker band  140 . Preferably, the proximal coil members  106  are not in contact with either marker band  136  or  140  and are maintained via frictional forces between the sheath  133  and the second coiled area  138 . 
     When the distal end of the delivery pusher has reached an area adjacent a desired target location (e.g., near an aneurysm), the sheath  133  is retracted proximally relative to the delivery pusher  130 . As the sheath  133  exposes the stent  100 , the stent  100  expands against the walls of the vessel  152 , as seen in  FIG.  9   . 
     The stent  100  can also be retracted (if it was not fully deployed/released) by retracting the pusher  130  in a proximal direction, thereby causing the marker band  140  to contact the proximal marker bands  106 , pulling the stent  100  back into the sheath  133 . 
     In one example use, the stent  100  can be delivered over the opening of an aneurysm  150  after embolic devices or material, such as embolic coils, have been delivered within the aneurysm  150 . In this respect, the stent  100  helps prevent the treatment devices from pushing out of the aneurysm  150  and causing complications or reducing efficacy of the treatment. 
     In one example, the wire  102  is composed of a shape-memory elastic material such as nitinol between about 0.001 inch and 0.010 inch in diameter. 
     The wire  102  may also vary in diameter over the length of the stent  100 . For example, the diameter of the wire  102  near the proximal and distal ends may be thicker than that of the middle portion of the stent  100 . In another example, the proximal and distal ends may be thinner than the middle portion. In another example, the diameter of the wire  102  may alternate between larger and smaller diameters along the length of the stent  100 . In yet another example, the diameter of the wire  102  may gradually increase or decrease along the length of the stent  100 . In yet another example, the loops  104  may be composed of wire  102  having a larger or smaller diameter than that of the wire  102  comprising the main body of the stent  100 . In a more detailed example, the diameter of the wire  102  of the loops  104  may be about 0.003 inch while the wire  102  of the body of the stent  100  may be about 0.002 inch. 
     In yet another example, select areas of the wire  102  may have a reduced thickness where the wire  102  may cross over another section in a compressed and/or expanded configuration of the stent  100 . In this respect, the thickness of the stent  100  can be effectively reduced in certain configurations. For example, if sections of the wire  102  were reduced at areas where the wire  102  overlapped when in a compressed configuration, the overall profile or thickness of the stent  100  can be reduced, allowing the stent  100  to potentially fit into a smaller delivery catheter. 
     This variation in diameter of the wire  102  can be achieved by electropolishing, etching or otherwise reducing portions of the assembled stent  100  to cause a diameter reduction. Alternately, regions of the wire  102  can be reduced prior to being wound or woven into the shape of the stent  100 . In this respect, a desired weaving pattern can be determined, the desired post-weaving, reduced-diameter regions can be calculated and reduced, and finally the stent  100  can be woven with the modified wire  102 . 
     In another variation, the pre-woven wire  102  can be tapered along a single direction and woven together to form the stent  100 . 
     In one example preparation, a 0.0035 inch diameter nitinol wire is wound or woven over a mandrel  160 . As seen in  FIG.  10   , the mandrel  160  may have three pins  162 ,  164 ,  166  extending through each end, such that a portion of each end of each pin extends out from the body of the mandrel  160 . The wire  102  begins at one pin, and then is wound 3.0625 revolutions clockwise around the body of the mandrel  160 . The wire  102  is bent around a nearby pin, then wound 3.0625 revolutions clockwise back towards the other side of the mandrel  160 , passing over and under the previously wound section of wire  102 . This process is repeated until eight loops are formed on each end. 
     In another example, the mandrel  160  may have 8 pins and the wire  102  is wound 2.375 revolutions. In another example, the mandrel  160  may have 16 pins and the wire  102  is wound 3.0625 revolutions. In yet another example, the mandrel may have between 8 and 16 pins and is wound between 2.375 and 3.0625 revolutions. 
     Once wound, the stent  100  is heat-set on the mandrel  160 , for example, at about 500° C. for about 10 minutes. The two free ends of the nitinol wire can be laser welded together and electro-polished such that the final wire diameter is about 0.0023 inch. 
     Finally, the radiopaque wire  105  of about 0.00225 inch in diameter is wound onto different areas of the stent loops  104 , forming coil members  106 . Preferably, the wire  105  is wound for about 0.04 inch in length to create each coil member  106 . 
     In another embodiment, the stent  100  can be formed from a plurality of discrete wires instead of a single wire  102 . The ends of this plurality of wires can be left free or can be welded, adhered or fused together for form loops  104 . In another embodiment, the stent  100  can be formed by laser cutting, etching, machining or any other known fabrications methods. 
     The wire  102  is preferably composed of a shape memory metal such as Nitinol. Optionally, this shape memory metal can include a variety of different therapeutic coatings or a hydrogel coating that swells or expands when exposed to blood. The wire  102  can also be composed of a biocompatible polymer material (e.g., PET) or from a hydrogel material. 
       FIG.  11    illustrates an embodiment of a stent  190  that is similar to the previously described stent  100 , except that each end of the stent  190  includes three loops  104  instead of the four loops  104  of the previous stent  100 . Additionally, the radiopaque wire  105  that form each of the coils  106  is also preferably woven into the stent  190 , connecting at least some of the coils  104  on each end of the stent  190 . Finally, the wire  102  is woven back and forth about 12 times along the length of the stent  190 . 
       FIG.  12    illustrates a preferred embodiment of a dual layer stent  200  according to the present invention. Generally, the dual layer stent  200  includes an outer anchoring stent  100  that is similar to the previously described stent  100  seen in  FIGS.  1 - 9   . The dual layer stent  200  also includes an inner flow-diverting layer  202  that is disposed within the inner lumen or passage of the anchoring stent  100 . 
     Often, stents with relatively small wires do not provide adequate expansile forces and therefore do not reliably maintain their position at a target location. Additionally, prior art woven stents created with many wires can have free ends that can poke or damage a patient&#39;s vessel. In contrast, larger wires are difficult to weave tightly enough (i.e., large spaces between adjacent wires) to modify blood flow at a desired location. The stent  200  seeks to overcome these disadvantages by including both the larger wire braid anchoring stent  100  to provide a desired anchoring force and the smaller wire braid flow-diverting layer  202  to divert blood. 
     In one example, the flow-diverting layer  202  is composed of at least 32 wires  204  that are between about 0.0005 to about 0.002 inch in diameter and made from a memory elastic material such as nitinol. These wires  204  are woven or braided together in a tubular shape having a pore size less than 0.010 inch. Preferably, this braiding is achieved with a braiding machine, which is known in the art and can braid the wires  204  in a regular pattern such as a diamond shaped pattern. 
     The flow-diverting layer  202  can have areas of its wire  204  that have a reduced diameter, similar to the patterns and techniques previously described with regard to the wire  102  of the stent  100 . Additionally, the flow-diverting layer  202  can be formed by laser cutting or etching a thin tube. 
     In the present example, the distal and proximal ends of the flow-diverting layer  202  are perpendicular relative to the length of the layer  202 . However, these ends may also be angled relatively to the length of layer  202  in a matching, opposite or irregular angular configuration. 
     As best seen in  FIGS.  13  and  14   , the proximal end of the dual layer stent  200  includes a plurality of attachment members  206  that connect the anchoring stent  100  with the flow-diverting layer  202 . The attachment members  206  can be composed of tantanlum wire (in this case is 0.001″ dia.) and can be attached to portions of wire  102  and wire  202 . In another embodiment, the proximal end of the flow-diverting layer  202  can be crimped on to the wires  102  of the anchoring stent  100 . In another embodiment, portions of the stent  100  and flow-diverting layer can be woven through each other for attachment purposes. In yet another embodiment, the stent  100  can be formed with eye-loops (e.g., formed via laser cutting or etching) or similar features sized to allow wires  202  to be woven through for attachment purposes. 
     Since the anchoring stent  100  and the flow-diverting layer  202  may have different weave patterns or weave densities, both will shorten in length at different rates as their diameter expands. In this respect, the attachment members  206  are preferably located at or near the proximal end of the anchoring stent  100  and the flow-diverting layer  202  as oriented in the delivery device (i.e., on the end opposite the distal tip member  144 ). Hence, as the stent  200  is deployed, both the anchoring stent  100  and the flow-diverting layer  202  can decrease in length (or increase if retracting the stent  200  back into a delivery device), yet remain attached to each other. Alternately, attachment members  206  can be positioned at one or more locations along the length of the dual layer stent  200  (e.g., at the distal end, both ends, the middle, or at both ends and the middle region). 
     In one example embodiment of the stent  200 , a flow-diverting layer  202  comprises 48 wires with a density of about 145 ppi and fully expands to a diameter of about 3.9 mm. An outer stent  100  comprises a single wire wound in a 2.5 revolution winding pattern and fully expands to a diameter of about 4.5 mm. When both layers  100  and  202  are fully expanded, the lengths are about 17 mm and 13 mm respectively. When both layers  100  and  202  are compressed on a 0.027 inch region of a delivery device, their lengths are about 44 mm and 37 mm respectively. When both layers  100  and  202  are expanded within a 3.75 mm vessel, their lengths are about 33 mm and 21 mm respectively. 
     In one preferred embodiment of the dual layer stent  200 , the flow-diverting layer  202  is composed of wires  204  having a diameter between about 0.0005 inch and about 0.0018 inch and the wires  102  of the stent  100  have a diameter between about 0.0018 inch and about 0.0050 inch. Therefore, the minimum preferred ratio between the diameter of the wire  102  and wire  204  is about 0.0018 to 0.0018 inch respectively (or about a 1:1 ratio) and the maximum preferred ratio is about 0.0050/0.0005 inch (or about a 10:1). 
     It should be noted that the dual layer stent  200  can produce a larger amount of radial force (defined as the radial force exerted at about 50% radial compression of a stent) than either the stent  100  or flow diverting layer  200  alone. This higher radial force allows the dual layer stent  200  to have improved deployment and anchoring characteristics. In one example test of a dual layer stent embodiment, the outer stent  100  alone had an average radial force of about 0.13 N, the flow diverting layer  202  alone had an average radial force of about 0.05 N and the dual layer stent  200  had an average radial force of about 0.26 N. In other words, the average radial force of the stent  200  was greater than or equal to that of the flow diverting layer  202  and the stent  100  combined. 
     It should be noted that the porosity (i.e., the percentage of open space to non-open space) in the flow-diverting layer  202  changes as it radially expands. In this respect, a desired porosity or pore size can be controlled by selecting different sized stents  200  (i.e., stents that fully expand to different diameters). Table 1 below illustrates different example porosities that the flow-diverting layer  202  can achieve by varying the size of the stent  200  (i.e., its fully expanded diameter) in a particular target vessel. It should be understood that modifying other aspects of the flow-diverting layer  202 , such as the number of wires used, picks per inch (PPI), or wire size may also modify porosity. Preferably, the flow-diverting layer  202  has a porosity between about 45-70% when expanded. 
     Similar techniques are also possible with regard to the porosity of the stent  100 . Preferably, the stent  100  has a porosity when expanded that is between about 75% and 95% and more preferably a range between about 80% and 88%. Put a different way, the stent  100  preferably has a metal surface area or percentage of metal between about 5% and 25% and more preferably between 12% and 20%. 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                 Fully 
                 Expansion 
                 Porosity of 
               
               
                 No. of 
                   
                 Expanded 
                 Size in Target 
                 Flow-Diverting 
               
               
                 Wires 
                 PPI 
                 Stent OD (mm) 
                 Vessel (mm) 
                 Layer 202 
               
               
                   
               
             
            
               
                 48 
                 145 
                 2.9 mm 
                 Fully 
                 50% 
               
               
                   
                   
                   
                 Expanded 
               
               
                 48 
                 145 
                 2.9 mm 
                 2.75 mm 
                 56% 
               
               
                 48 
                 145 
                 2.9 mm 
                 2.50 mm 
                 61% 
               
               
                 48 
                 145 
                 3.4 mm 
                 Fully 
                 51% 
               
               
                   
                   
                   
                 Expanded 
               
               
                 48 
                 145 
                 3.4 mm 
                 3.25 mm 
                 59% 
               
               
                 48 
                 145 
                 3.4 mm 
                 3.00 mm 
                 64% 
               
               
                 48 
                 145 
                 3.9 mm 
                 Fully 
                 52% 
               
               
                   
                   
                   
                 Expanded 
               
               
                 48 
                 145 
                 3.9 mm 
                 3.75 mm 
                 61% 
               
               
                 48 
                 145 
                 3.9 mm 
                 3.50 mm 
                 67% 
               
               
                   
               
            
           
         
       
     
     The stent  100  can be “oversized” or have a larger internal diameter relative to the outer diameter of the flow-diverting layer  202  when in a fully expanded position or a target vessel (having a target diameter). Preferably, the difference between the inner surface of the stent  100  and the outer surface of the flow-diverting layer  202  is between about 0.1 mm and about 0.6 mm (e.g., a gap between about 0.05 mm and about 0.3 mm between the two). Generally, the dual layer stent  200  can be slightly oversized for a patient&#39;s target vessel. In this respect, the outer stent  100  can slightly push into the tissue of the target vessel, allowing the “undersized” flow-diverting layer  202  to maintain a profile that is relatively close to or even touching the tissue of the vessel. This sizing can allow the stent  100  to better anchor within the vessel and closer contact between the flow-diverting layer  202  and vessel tissue. It should be further noted that this “oversizing” of the dual layer stent  200  can result in about a 10-15% increase in the porosity of the flow-diverting layer  202  relative to the fully expanded (and unobstructed) position of the flow-diverting layer  202 , as seen in the example data in Table 1. 
     The dual layer stent  200  can provide improved tracking and deployment performance, especially when compared to a stent of similar size and thickness to the flow-diverting layer  202 . For example, tests have shown that a reduced amount of force is needed during deployment or retraction of the dual layer stent  200  from the delivery device in comparison to a stent similar to the flow-diverting layer alone. The inclusion of the outer stent  100  as part of the dual layer stent  200  reduces friction in the delivery system relative to the radial force and porosity of the stent  200 . 
     Preferably, the dual layer stent  200  can be deployed or retracted with between about 0.2 lbs and about 0.6 lbs of force. By including the stent  100  on the outside of the flow diverting layer  202 , the deployment force can be reduced between about 10-50% as compared with the deploying/retracting the flow diverting layer  202  alone (i.e., a standalone layer  202  used by itself as seen in  FIG.  19   ). Since less deployment force is required for the dual layer stent  200  as compared with a bare flow diverting layer  202 , more desirable delivery characteristics can be achieved from a deployment device. 
     One example deployment and retraction force test was performed on an example dual layer stent  200  as seen in  FIGS.  12 - 14    and a flow-diverting layer  202  alone, as shown in  FIG.  19   . The dual layer stent  200  required an average maximum deployment force of about 0.3 lbs and an average maximum retraction force of about 0.4 lbs. The stent of only a flow-diverting layer  202  had an average deployment force of about 0.7 lbs. Note that retraction of the flow-diverting layer  202  stent was not possible in the tests due to a lack of a locking or release mechanism (e.g., no coils  106  to contact marker band  140 , as seen in  FIG.  15   ). Preferably, the dual layer stent  200  includes differences in the diameter of the wire  102  of the outer stent  100 , similar to those described for the embodiment of  FIGS.  1 - 10   . Specifically, the wire  102  making up the middle region of the stent  100  have a reduced diameter while the wire  102  at the ends (e.g., at loops  104 ) have a larger diameter than the middle region. For example, the middle region can be electropolished to reduce the diameter of wire  102  while the ends of the stent  100  can be protected from electropolishing, maintaining their original diameter. Put another way, the thickness of the stent  100  is thinner at a middle region. Note that this reduced thickness in the middle region is also applicable to embodiments of the outer stent that do not use wire (e.g., laser cut tube stent seen in  FIG.  16   ). In test trials of an example embodiment of the dual layer stent  200  with this diameter difference, relatively low deployment and retraction forces were demonstrated. These lower deployment and retraction forces can provide desirable tracking, deployment and retraction characteristics. Preferably, the wires  102  of the middle region are between about 0.0003 inch and about 0.001 inch smaller in diameter or thickness than the distal and/or proximal regions of the stent  100 . Preferably, the wires  102  of the middle region are between about 10% to about 40% smaller in diameter or thickness than the distal and/or proximal regions of the stent  100  and most preferably about 25% smaller. 
     For example, one embodiment included ends composed of wire  102  having a diameter of about 0.0025 inch and a middle region composed of wire  102  having a diameter of about 0.0021 inch. This embodiment averaged a maximum average deployment force of about 0.3 lbs within a range of about 0.2-0.4 lbs and a maximum average retraction force of about 0.4 lbs within a range of about 0.3-0.4 lbs. 
     Another embodiment included ends composed of wire  102  having a diameter of about 0.0020 inch and a middle region composed of wire  102  having a diameter of about 0.0028 inch. This embodiment averaged a maximum average deployment force of about 0.2 lbs within a range of about 0.2-0.3 lbs and a maximum average retraction force of about 0.3 lbs in a range of about 0.3-0.4 lbs. 
     Another embodiment included ends composed of wire  102  having a diameter of about 0.0021 inch and a middle region composed of wire  102  having a diameter of about 0.0028 inch. This embodiment averaged a maximum average deployment force of about 0.4 lbs within a range of about 0.3-0.4 lbs and a maximum average retraction force of about 0.6 lbs in a range of about 0.5-0.6 inch. 
     Turning to  FIG.  15   , a delivery device  210  is shown according to the present invention for deploying the stent  200  within a patient. The delivery device  210  is generally similar to the previously described delivery device  135 , including a sheath  133  disposed over a delivery pusher  130  to maintain the stent  200  in a compressed position over marker band  140 . 
     As with the previous device, a proximal end  201  of the stent  200  is disposed over distal marker band  140  and proximal coil members  106  are positioned between marker bands  136  and  140 . The stent  200  can be deployed by proximally retracting the sheath  201  relative to the pusher  130 . The stent  200  can also be retracted (if it was not fully deployed/released) by retracting the pusher  130  in a proximal direction, thereby causing the marker band  140  to contact the proximal coil members  106 , pulling the stent  200  back into the sheath  133 . 
     As previously described, the proximal end  201  of the stent  200  includes attachment members  206  (not shown in  FIG.  15   ) which connect the stent  100  with the flow-diverting layer  202 . In this respect, as the sheath  133  is proximally retracted during deployment and a distal portion  203  of the dual layer stent  200  begins to radially expand, the stent  100  and the flow-diverting layer  202  can decrease in length at different rates. 
     A portion of the wire  105  can be woven along the length of the stent  100  in a distinctive pattern. This length can correspond to the length and position of the inner flow diverting layer  202 , thereby indicating the length and position of the inner flow diverting layer  202  to the user during a procedure. 
     In another preferred embodiment according to the present invention, the flow-diverting layer  202  may be woven into the anchoring stent  100 . 
       FIG.  16    illustrates another embodiment according to the present invention of a dual layer stent  300  comprising an inner flow-diverting layer  202  and an outer stent  302 . Preferably, the outer stent  302  is formed by cutting a pattern (e.g., laser cutting or etching) in a sheet or tube composed of a shape memory material (e.g. Nitinol).  FIG.  16    illustrates a pattern of a plurality of diamonds along the length of the outer stent  302 . However, it should be understood that any cut pattern is possible, such as a plurality of connected bands, zig-zag patterns, or wave patterns. 
     The cross sectional view of the dual layer stent  300  illustrates a plurality of example positions for attachment member  206  to connect the outer stent  302  and inner flow-diverting layer  202 . As with any of the previously described embodiments, the attachment members  206  (or other methods of attachment such as welding or adhesive) can be located at one or more of the example locations shown. For example, attachment members  206  may be located at the proximal end, distal end, or the middle. In another example, attachment members  206  can be located at both the proximal and distal ends. Alternately, no attachment members  206  or attachment mechanism are used to attach the inner flow-diverting layer  202  with the outer stent  302 . 
       FIG.  18    illustrates another embodiment of a dual layer stent  400  according to the present invention. The stent  400  comprises an inner flow-diverting layer  202  attached to an outer stent  402 . The outer stent  402  comprises a plurality of radial, zigzag bands  404  that are bridged or connected via longitudinal members  406 . Preferably, the stent  402  can be created by welding a plurality of members together, laser cutting or etching this pattern into a sheet or tube, or using vapor deposition techniques. As with previous embodiments, the flow-diverting layer  202  can be attached to the outer stent  402  near the distal end, proximal end, middle region, or any combination of these locations. 
     As best seen in  FIGS.  12  and  13   , the flow-diverting layer  202  preferably has a length that extends near the ends of the main body portion of stent  100  and stops near the formation of the loops  104 . However, the flow-diverting layer  202  can alternately include any range of lengths and positions relative to the stent  100 . For example,  FIG.  20    illustrates a dual layer stent  200 A in which the flow-diverting layer  202  is shorter in length than the stent  100  and longitudinally centered or symmetrically positioned. 
     In another example,  FIG.  21    illustrates a dual layer stent  200 B in which the flow-diverting layer  202  is longer in length than the stent  100 . While the flow-diverting layer  202  is shown as being longitudinally centered within the stent  100 , asymmetrical positioning of the flow-diverting layer  202  is also contemplated. 
     In yet another example,  FIG.  22    illustrates a dual layer stent  200 C in which a flow-diverting layer  202  is shorter in length than the stent  100  and asymmetrically positioned within the stent  100 . In this example, the flow-diverting layer  202  is positioned along the proximal half of the stent  100 , however, the flow-diverting layer  202  may also be positioned along the distal half of the stent  100 . While the flow-diverting layer  202  is shown extending about one half of the length of the stent  100 , the flow-diverting layer  202  may also span one third, one quarter or any fractional portion of the stent  100 . 
     Turning to  FIGS.  23 - 25   , the flow-diverting layer  202  can be composed of one or more expansile wires  500  or filaments. Preferably, the expansile wires  500  are composed of the previously described wires  204  that are coated with a hydrogel coating  502  that expands in a patient&#39;s vessel. The wires  204  may be composed of a shape memory metal (e.g., nitinol), a shape memory polymer, nylon, PET or even entirely of hydrogel. As seen in  FIG.  25   , the hydrogel wires  500  can be woven amongst wires  204  which are not coated with hydrogel. Alternately, partial lengths of the wires can be coated with hydrogel so as to coat only a specific region of the flow-diverting layer  202  (e.g., the center region). 
     In any of the previous embodiments, one or more of the stent layers (e.g., stent  100  or flow diverting layer  202 ) can be mostly composed of a polymer (e.g., a hydrogel, PET (Dacron), nylon, polyurethane, Teflon, and PGA/PGLA). Generally, a polymer stent can be manufactured by the free radical polymerization of a liquid prepolymer solution within a container of a desired shape. 
     One example polymer stent manufacturing technique can be seen in  FIGS.  26 - 29   . Starting with  FIG.  26   , a generally cylindrical mandrel  602  is placed within a tube  600 . Preferably, the mandrel  602  can create a fluid-tight seal on at least one end of the tube  600  and preferably the opposing end of the tube  600  is also closed. 
     In  FIG.  27   , a liquid prepolymer is injected into the space between the mandrel  602  and the tube  600 . Polymerization is induced in the prepolymer solution (e.g., heating at 40-80° C. for 12 hours). Once polymerized, the tube  600  and mandrel  602  are removed from the solid polymer tube  606 , shown in  FIG.  28   . This tube  606  can be washed to eliminate residual monomers and dried over a mandrel to maintain shape. 
     Finally, the polymer tube  606  can be laser cut, CNC machined, etched or otherwise shaped into a desired pattern, as seen in  FIG.  29   . The length and thickness of the final stent can also be modified during the manufacturing process by changing the diameter or length of the tube  606  or the mandrel  602 . 
     In another example stent manufacturing process seen in  FIG.  30   , centrifugal force is used to disperse the prepolymer solution along the inside of a syringe tube  605 . Specifically, a plunger  603  is positioned in the tube  605  and a predetermined amount of prepolymer solution  604  is taken into the syringe tube  605 . The syringe tube  605  is connected to a mechanism that causes the tube  605  to spin in a horizontal orientation along a longitudinal axis of the tube  605  (e.g., an overhead stirrer positioned horizontally with its rotating member connected to the tube  605 ). 
     Once the tube  605  achieves a sufficient rotational speed (e.g., about 1500 rpm), the syringe plunger  603  is pulled toward the end of the tube  605 , taking in a gas such as air. Since the prepolymer solution now has more space to spread out, the centrifugal force causes an even coating to form on the wall of the tube  605 . Polymerization can be initialed using a heat source (e.g., a heat gun) and then heated (e.g., 40-80° C. for 12 hours). The solid polymer tube can then be removed from the tube  605 , washed to eliminate residual monomers, dried on a mandrel, and then laser cut, CNC machined, etched or otherwise shaped into a desired pattern. 
       FIGS.  31 - 36    illustrate yet another example process for creating a polymer stent according to the present invention. Turning first to  FIG.  31   , a plastic or degradable rod  608  is placed in tube  600  and luer adapters  610  are connected to each opening of the tube  600 . The rod  608  has an engraved or depressed pattern (e.g., created by laser machining, CNC machining or other suitable method) on its outer surface in the patter desired for the final stent. When the rod  608  is placed in the tube  600 , these patterns form channels that are later filled by the prepolymer  604 . In other words, the outer diameter of the rod  608  and the inner diameter of the tube  600  are such that the prepolymer  604  is prevented from moving outside the channels or patterned area. 
     As seen  FIG.  32   , a syringe  612  is inserted into a luer adapter  610  and prepolymer solution  604  is injected into the tube  600  as seen in  FIG.  33   . The prepolymer solution  604  fills into the pattern on the surface of the rod  608 . The syringe  612  is removed from the luer adapter  610  and polymerization is completed by heating the prepolymer solution  604  (e.g., 40-80° C. for about 12 hours). 
     The rod  608  is removed from the tube  600  as seen in  FIG.  34    and placed in an organic solvent bath  622  as seen in  FIG.  35   . The organic solvent bath  622  dissolves the rod  608 , leaving only the polymer stent  622  ( FIG.  36   ) having the same pattern as the surface of the rod  608 . 
     It should be noted that different aspects of the stent  622  can be controlled by changing the pattern on the surface of the rod  608 , the diameter of the rod  608  and the tube  600 , the length of the rod  608  and tube  600  and similar dimensions. Additional modification is also possible by laser cutting, CNC machining, etching, or similar processes. 
       FIGS.  37 - 50    illustrate various modifications of delivery pusher  130  which have been previously described in this embodiment. Some of the embodiments include a friction region of larger diameter near a distal end of the pusher to prevent the stent from over compressing and creates friction between the stent and pusher to help push the stent out of the catheter sheath. Additionally, when the friction region is in contact with the inner surface of the stent, it allows the physician to pull the stent out of the delivery sheath rather than pushing on the stent from its proximal end. Hence, the stent may require less rigidity. Furthermore, the friction region distributes the deployment force from the pusher over a greater surface area of the stent, thereby reducing stress on the stent that can result from pushing or pulling on the stent at a single location. This distribution of force makes the delivery system more reliable since the strength of the bond between the delivery pusher and the friction region can be lower than would be otherwise required if the stent was pushed or pulled from a single location. Including the friction region with pushing or pulling features of the marker bands also creates a redundancy for both advancing the stent our of the catheter or retracting the stent back into the catheter, since if one mechanism fails, the other would allow the physician to complete the procedure. 
     In  FIGS.  37 - 39   , the pusher  700  includes several tapered or conical regions between the marker bands  136  and  140 . Specifically, the pusher  700  includes two regions of UV adhesive: a distal region  708  at the distal end of the coiled distal tip member  144  and a tapered or conical region  704  at the proximal end of the tip member  144 . The second marker band  140  includes a distal tapered region  702  composed of epoxy (e.g., EPOTEK 353). The proximal face of marker band  140  and the distal face of marker band  136  include a small amount of epoxy  706  that is shaped to a slight taper or conical shape. The marker bands  136  and  140  and coiled tip member  144  are preferably composed of platinum. The core wire  132  is preferably composed of Nitinol and the coil  134  is preferably composed of stainless steel. In one example, the distance between markers  136  and  140  is about 0.065, the distance between marker  140  and conical region  704  is about 0.035 cm, and the coiled tip is about 0.100 cm in length. 
     In the pusher embodiment  710  of  FIG.  40   , an elongated polymer region  712  (e.g., PET, Teflon, Pebax, nylon, PTFE) is located on section  142  of the core member  132  between the distal marker band  140  and the distal tip  144 . This polymer region  712  can be formed from a shrink tube having a thickness of about 0.00025 inches or from braided polymer strands. One advantage of the polymer region is that it adds some thickness to the core wire and thereby prevents the stent (which is compressed on top) from over-compressing or collapsing when advanced through highly tortuous vessels of a patient. 
       FIG.  41    illustrates a pusher embodiment  714  having a plurality of spaced apart sections  716  having a diameter that is larger than that of the core wire. These sections can be composed of polymer (e.g., shrink tube or braiding) or from a non-polymer material. A portion of the core wire  718  can be pre-shaped to have a plurality of curves or a wave shape. The wave region and material sections may prevent the stent from over-compressing during tortuous passage through a vessel. Additionally, the wave shapes may help force open a stent as it is delivered from the catheter. More specifically, the wave shape may be relatively straight when a stent is compressed over the wave shape in the delivery device, but expands as it exits the catheter, forcing the stent open. This stent expansion may be especially important when delivering the stent to a curved or bent vessel where the physician would typically push the delivery system forward to assist in causing the stent to open. In this respect, the delivery system would be less operator-dependent since the delivery system would pushed open automatically by the pusher  714 . By including multiple material sections  716 , the curves of the wave region may be better retained when expanded as compared to a single elongated polymer section (e.g.,  FIG.  41   ). 
       FIG.  42    illustrates a pusher embodiment  720  having an elongated polymer region  712  similar to the embodiment of  FIG.  40    and a wave region  718  similar to the embodiment of  FIG.  41   .  FIG.  43    illustrates a pusher embodiment  722  having multiple polymer areas  716  similar to the embodiment of  FIG.  41    and a generally straight core wire  142  at the distal end of the pusher, similar to that of  FIG.  40   . 
       FIG.  44    illustrates a pusher embodiment  724  having an elongated straight region with a polymer region similar to the embodiment of  FIG.  40   . However, this polymer region extends the entire length between the distal marker band  140  and the distal tip  144 . 
       FIG.  45    illustrates a pusher embodiment  726  forming a closed loop between the distal marker band  140  and the distal tip  144  of the pusher  726  (i.e., an aperture in region  142  of the core member). This loop may prevent the stent from collapsing or over-compressing on the pusher, especially when advanced through tortuous vessels. Preferably, this loop is formed by welding both ends of a Nitinol wire  728  to an area  730  of the pusher&#39;s core wire. Both the attached wire  728  and the area of the core wire  730  can be bent or angled at each end to form an elongated loop shape of varying sizes. In this regard, the core member forms two opposing, branching shapes who&#39;s arms connect together to form an aperture or loop. 
       FIG.  46 A  illustrates a pusher embodiment  732  having a generally straight distal end  142  that terminates in a pigtail shape  734 . The pigtail shape  734  can be created by bending the core wire  142  in several different orientations, as seen in  FIG.  46 A . For example, the pigtail shape  734 B can be symmetrically positioned on the core wire ( FIG.  46 C ) or asymmetrically offset  734 A in one direction ( FIG.  46 B ). This pigtailed shape helps to resist the stent from collapsing or over-compressing, thus aiding in the deployment and retrieval of the device. 
       FIG.  47    illustrates a pusher  736  with a spiral or coil region  738  formed from a plurality of loops  739  near its distal end. The spiral region may encompass all exposed areas of the core wire or a fractional length. The pusher  740  of  FIG.  48    illustrates a coil region  142  in which some loops  744 A are relatively close together, while other loops  744 B have a larger spacing from each other. Additionally, the spiral region  748  of pusher  746  in  FIG.  49    may include a continuous or segmented coating or jacket  750  along its length or adjacent to the spiral region (e.g., PET, Teflon, Pebax, nylon, PTFE). Similar to previous embodiments, the spiral region increases the diameter of the pusher&#39;s distal end and thereby prevents the stent from collapsing or over compressing. However, since the spiral region&#39;s effective diameter increase of the pusher can be achieved without necessarily increasing the diameter of the core wire, flexibility of the pusher is generally similar to embodiments with straight distal core wires. The spiral region  754  of pusher  752  may also vary in diameter or pitch (e.g., increasing pitch, decreasing pitch, or discrete sections of different diameters) as seen in  FIG.  50    and is preferably selected based on based on the shape, size and properties of the stent. 
       FIGS.  51 - 59    disclose an embodiment of a rapid exchange delivery device  770  for delivering a stent  793 . While this delivery device  770  may be used for a variety of locations, it may be particularly useful for delivering stents in the carotid arteries for treatment of peripheral artery disease. 
     Turning first to  FIG.  51   , the device  770  includes a pusher member  772  having an elongated core member  776  that slides within a catheter  774 , through proximal catheter port  780 . Preferably, the proximal end of the core wire includes a handle  778  for facilitating movement of the pusher member  772  relative to the catheter  774 . 
     Instead of providing a guide wire passage that extends throughout the entire length of the catheter  774 , the catheter  774  preferably includes a shortened “rapid exchange” passage in which the guide wire  786  only passes through a relatively short, distal portion of the catheter  774  (e.g., 5-10 inches). Once a distal end of the guide wire  786  is positioned near a target location, the proximal end of the guide wire  786  is inserted into a rapid exchange port  794 A of a distal guide wire tube  794 , as seen in  FIG.  58   . As seen best in  FIGS.  55 - 57   , the proximal end of the guide wire  786  passes through the distal guide wire tube  794  and into catheter tube  788 . Finally, as best seen in  FIG.  53   , the guide wire  786  exits tube  788 , passes through a remaining portion of the outer catheter tube  782 , and exits the catheter at rapid exchange port  784 . 
     Returning to  FIGS.  55 - 57   , the distal guide wire tube  794  extends into catheter tube  788  in a telescoping arrangement. Preferably, the distal guide wire tube  794  extend into the catheter tube  788  by at least the same distance the catheter  774  is retracted relative to the pusher  772 . In this respect, the distal guide wire tube  794  and the catheter tube  788  maintain a continuous passage for the guide wire  786 , even as the catheter  774  is retracted relative to the pusher  772  to release the stent  793 . 
     As best seen in  FIGS.  54 - 57   , a distal end of the core member  776  includes an anchor member  792  for anchoring and retracting the stent  793  during deployment. The anchor member  792  includes a body  792 A that forms a backstop surface  792 D against which the stent  793  can be pushed. 
     The stent  793  preferably includes a plurality of proximal loops that fit over a plurality of radially oriented posts  792 C when the stent  793  is compressed on the pusher as seen in  FIG.  54   . For example, the stent  793  may have three loops and the anchor member  792  may have three posts  792 C fixed at equidistant radial intervals from each other. During stent deployment, a physician may wish to retract the stent  793  so that it can be repositioned. As the pusher  772  is retracted or the catheter  774  is advanced, the posts  792 C pull or anchor the end of the loops, causing the stent  793  to be pulled back into the outer tube  782  of the catheter  774 . 
     In one embodiment, the posts  792 C each have a generally flat distal surface and two angled or rounded proximal surfaces. In another embodiment seen in  FIG.  59   , the anchor  793  includes posts  793 C having both distal and proximal surfaces that are angled toward each other (i.e., similar to a pyramid with a flat top surface). 
     Returning to  FIGS.  54 - 57   , the anchor  792  includes an elongated depression  792 B that is sized to contain the core member  776 . A distal end of the core member  776  is fixed in the depression  792 B via known methods, such as welding or adhesives. As previously discussed, the core member passes through a core member passage  787  in the catheter  774 , exits out of proximal port  780  and terminates with handle  778  on its proximal end. Hence, the core member  776  directly connects the anchor  792  and therefore the stent  793  to the handle  778 , providing direct, positive, tactile feedback to the physician. Preferably, the anchor  792  is composed of metal to further enhance the tactile feedback felt by the physician. 
       FIG.  60    illustrates another embodiment of a delivery pusher  130  that is generally similar to the delivery pusher  130  in  FIGS.  7  and  8   . However, delivery pusher  800  includes a third, middle marker band  137  located between marker bands  136  and  140 . Preferably, the marker band  137  has a diameter similar to that of marker band  140  and is somewhat smaller in diameter than marker band  136 . The stent  100  is preferable compressed over both markers  137  and  140  such that the proximal coils  106  of the stent  100  are positioned between and closely associated with the two markers  137  and  140 . During deployment of the stent  100 , a physician may wish to advance the pusher  800  relative to the outer catheter sheath  133 . In this regard, the marker  137  distally pushes on the coils  106  at a location that may reduce the tendency of the stent  100  to buckle. 
       FIG.  61    illustrates another embodiment of a delivery pusher  802  that is similar to the previously described pusher  800 . However, the pusher  802  also includes a marker  139  positioned near the coiled distal tip member  144 . Preferably, the marker  139  is spaced proximally from the distal tip member  144  so as to allow space for the distal coils  106  of the stent  100 . During stent deployment, the marker  139  may contact the distal coils  106  if the pusher  802  is advanced relative to the catheter sheath  133 . In this regard, the marker  139  may be configured to initially push on the distal coils  106  until the distal end of the stent  100  exits the catheter sheath  133  and expands. From there, the marker  137  may push on proximal coils  106  until the remaining portion of the stent  100  has been pushed out of the catheter sheath  133 . 
     In yet another embodiment similar to  FIG.  61   , the pusher may include markers  139 ,  140  and  136 . In this respect, advancing the pusher relative to the sheath  133  may push the distal coils  106  and distal end of the stent  100  out of the catheter sheath  133 . 
     It should be noted that one or more of any of the markers  136 ,  137 ,  139 , and  140  from the previously described embodiments may alternately be composed of a non-radiopaque material. Additionally, one or more of any of the markers  136 ,  137 ,  139 , and  140  from the previously described embodiments may be removed. 
       FIG.  62    illustrates an embodiment of a flow diverting stent  810  which is similar to the stent  200  shown in  FIGS.  12 - 14   , including an outer anchoring stent layer  100  having six loops  104  on each of its distal and proximal ends, and a flow-diverting layer  202  that is located within the inner lumen or passage of the anchoring stent layer  100 . However, the outer anchoring stent layer  100  and inner flow-diverting layer  202  are woven or braided so that their wires  102  and  204  have substantially the same pitch. 
     Woven stent layers tend to increase in length as they compress and decrease in length as they expand. When two woven stent layers have different pitches of braiding, the layer with the higher pitch typically elongates further and faster than a similarly sized layer having a relatively lower pitch braid. Therefore, to expand correctly, stent layers with different braid pitches can typically be attached at only one end of the stent. 
     In contrast, the layers  100 ,  202  of stent  810  have the same braid pitch which allows each layer to radially compress to the same increased length at the same rate, from similar expanded shapes, or radially expand to the same decreased length at the same rate. In other words, the layers  100 ,  202  maintain similar positions relative to each other as they simultaneously expand or contract. Since the layers  100 ,  202  remain in relatively the same positions in relation to each other, the layers can be constructed such that they have substantially no clearance between each other. This lack of clearance between layers may reduce or even prevent collapsing or buckling of the inner flow-diverting layer  202  within tortuous vessels. In one example, both the outer anchoring layer  100  and inner flow-diverting layer  202  may have a woven pitch of 40, 45, or 50 picks per inch. 
     As previously discussed, the layers  100 ,  202  of the stent  810  can be constructed to have substantially no clearance or gap between them. In addition to matching the pitch of the layers  100 ,  202 , this close association of layers can be achieved by braiding and heat-setting the inner flow-diverting layer  202  on a rod or mandrel to have an outer diameter that is equal to the inner diameter of the inner diameter of the outer anchoring layer  100 . This sizing provides a line to line fit of both layers, which can prevent physiological reactions like thrombosis. 
     The close association of the layers  100 ,  202  can be further maintained by including one or more additional support wires  814  that are woven through both layers. For example, each end of a tantalum support wire  814  can be coiled around wire  102  near a distal and proximal end of the stent  810  and woven between the layers, as seen in  FIG.  62    and the magnified areas of  FIGS.  63  and  64   . 
     In the present example embodiment, three different support wires  814  are woven in a generally helical pattern through both layers  100 ,  202 . For example, starting at one of the coils  816 , the support wire  814  generally follows the curvature and position of each wire  102 . As seen in  FIG.  65   , at areas where the wire  102  crosses over another portion of itself (i.e., radially outward), the support wire  814  follows a similar path over the crossing portion of wire  102 , as well as over wires  204  (e.g., the area at  820 ). As seen in  FIG.  66   , at areas where the wire  102  passes underneath another portion of itself (i.e., radially inward), the support wire  814  also passes underneath the intersecting region of wire  102 , but also further passes underneath the next intersecting wire  204 , shown at area  822 . Preferably, the pattern of  FIG.  65    followed by  FIG.  66    alternate with each other along the length of the stent  810 . In this respect, the support wire  814  creates a radial shape that passes underneath wires  202  at regular intervals, thereby maintaining the two layers  100  and  202  against each other. By providing this additional support to maintain the layers, the stent  810  may particularly maintain the close association of layers  100  and  202  when deployed an a curved or tortuous vessel, such as a carotid artery. 
     In the present example embodiment, three support wires  814  extend substantially the entire length of the stent  810  and have equal radial spacing from each other. However, any number of support wires  814  can be used, such as 1, 2, 3, 4, 5, 6, 7, 8, 9. In another example embodiment, each support wire may extend from a location substantially near an end of the stent to a middle region of a stent, forming two sets of support wires  814  on each side of the stent  810 . In another example embodiment, each support wire  814  may extend between each end of the stent  810 , but may also include additional areas where the support wire  814  is coiled, such as at a middle region of the stent  810 . 
       FIG.  67    illustrates another embodiment of a stent  830  having a single layer braided from larger wires  102  and smaller wires  204  that can have different sizes as described elsewhere in this specification. The wires  102  and  204  are preferably braided at the same braid angle, allowing them to expand and contract as similar rates and lengths. Preferably, all wires  102 ,  204  are woven according to the same braid pattern and the larger wire  102  is preferably separate by several wires  204  (e.g., each wire  102  is followed and preceded by 3 or 6 wires  204 ). 
     One advantage of this single layer stent  830  is that is can be braided on a braiding machine, rather than having portions or layers that are braided by hand. Unlike the previously described embodiments that utilize the single-wire stent layer  100 , the single layer stent  830  may include multiple free ends of wires  102  after an initial braiding. Since these larger wires may have a tendency to curl and/or unravel, the free ends are preferably fixed together via welding, coils, tubes, adhesives, or similar methods. The free ends of wires  204  can be left free since they may not curl or unravel to the same extent as wires  102 , or the ends of wires  204  can be similarly fixed or welded together. The stent  830  can be cylindrical or can be braided or heat-set to have a tapered shape. 
     It should be noted that any of the aspects of each stent or delivery system embodiment described in this specification can be combined with other aspects of other stent or delivery system embodiments described in this application. Therefore, while specific stent and delivery system embodiments have been shown, other combinations are contemplated in accordance with the present invention. 
     Although the invention has been described in terms of particular embodiments and applications, one of ordinary skill in the art, in light of this teaching, can generate additional embodiments and modifications without departing from the spirit of or exceeding the scope of the claimed invention. Accordingly, it is to be understood that the drawings and descriptions herein are proffered by way of example to facilitate comprehension of the invention and should not be construed to limit the scope thereof.