|
|
Home | Alpha Telephone | Domain Names | Web Hosting | Get Traffic | xrEvidence | xrSoccer United States Patent
Woven intravascular devices and methods for making the same and apparatus for delivery of the same Self-expandable, woven intravascular devices for use as stents (both straight and tapered), filters (both temporary and permanent) and occluders for insertion and implantation into a variety of anatomical structures. The devices may be formed from shape memory metals such as nitinol. The devices may also be formed from biodegradable materials. Delivery systems for the devices include two hollow tubes that operate coaxially. A device is secured to the tubes prior to the implantation and delivery of the device by securing one end of the device to the outside of the inner tube and by securing the other end of the device to the outside of the outer tube. The stents may be partially or completely covered by graft materials, but may also be bare. The devices may be formed from a single wire. The devices may be formed by either hand or machine weaving. The devices may be created by bending shape memory wires around tabs projecting from a template, and weaving the ends of the wires to create the body of the device such that the wires cross each other to form a plurality of angles, at least one of the angles being obtuse. The value of the obtuse angle may be increased by axially compressing the body.
Primary Examiner: Thaler; Michael Attorney, Agent or Firm: The present application claims priority to U.S. Provisional Patent Application Ser. No. 60/118,211 filed Feb. 1, 1999 and U.S. Provisional Patent Application Ser. No. 60/125,191 filed Mar. 18, 1999. The entire texts of the above-referenced disclosures are specifically incorporated by reference herein without disclaimer. The invention claimed is: 1. A device comprising: a plurality of shape memory wires woven together to form a body suitable for implantation into an anatomical structure, the body having first and second ends, the shape memory wires crossing each other to form a plurality of cells and a plurality of angles, at least one of the angles being obtuse, at least one of the cells being defined by only four sides, and both ends of at least one shape memory wire being located proximate one end of the body, wherein the value of the at least one obtuse angle may be increased by axially compressing the body. 2. The device of claim 1, wherein the shape memory wires comprise nitinol. 3. The device of claim 1, wherein the shape memory wires comprise FePt, FePd or FeNiCoTi. 4. The device of claim 1, wherein the shape memory wires comprise FeNiC, FeMnSi or FeMnSiCrNi. 5. The device of claim 1, wherein the shape memory wires each have a diameter ranging in size from about 0.006 inches to about 0.012 inches. 6. The device of claim 1, wherein the plurality of shape memory wires includes at least 6 shape memory wires. 7. The device of claim 1, wherein the body has a tubular shape with a substantially uniform diameter. 8. The device of claim 1, wherein the body has a tapered shape with a diameter that decreases from one end of the body to the other end of the body. 9. The device of claim 1, wherein the body has a generally hourglass shape. 10. The device of claim 1, wherein the body is hand woven. 11. The device of claim 1, wherein the body is machine woven. 12. The device of claim 1, further comprising a graft material attached to the body. 13. The device of claim 12, wherein the graft material comprises woven polyester. 14. The device of claim 12, wherein the graft material comprises Dacron. 15. The device of claim 12, wherein the graft material comprises polyurethane. 16. The device of claim 12, wherein the graft material comprises PTFE. 17. The device of claim 12, wherein the graft material partially covers the body. 18. The device of claim 1, further comprising: a first tube configured to accept a guide wire; and a second tube configured to fit over the first tube. 19. The device of claim 18, wherein the second tube is placed over the first tube, one end of the body is secured to the first tube and the other end of the body is secured to the second tube. 20. A device comprising: a body suitable for implantation into an anatomical structure, the body having a first end, a second end and being defined by at least n shape memory wires, wherein n is greater than one, the n shape memory wires being arranged such that the body comprises a first portion, the first portion comprising a first woven portion and at least one strut, the shape memory wires of the first woven portion crossing each other to form a plurality of cells and a plurality of angles, at least one of the angles being obtuse, at least one of the cells being defined by only four sides, and both ends of at least one shape memory wire being located proximate one end of the body; wherein the value of the at least one obtuse angle may be increased by axially compressing the body. 21. The device of claim 20, wherein the shape memory wires comprise nitinol. 22. The device of claim 20, wherein the shape memory wires comprise FePt, FePd or FeNiCoTi. 23. The device of claim 20, wherein the shape memory wires comprise FeNiC, FeMnSi or FeMnSiCrNi. 24. The device of claim 20, wherein the body further comprises a second portion adjacent the first portion, the second portion comprising a second woven portion, and the second portion having n+x shape memory wires, wherein x is at least one. 25. The device of claim 20, wherein the first portion comprises a first woven portion separated from a second woven portion by multiple first struts. 26. The device of claim 25, wherein the first portion has a generally domed shape. 27. The device of claim 25, wherein the first woven portion has a generally domed shape and the multiple first struts are bent slightly so as to increase the self-anchoring capability of the body in an anatomical structure. 28. The device of claim 25, wherein the first portion further comprises a third woven portion separated from the second woven portion by multiple second struts, and wherein the first and third woven portions have generally domed shapes. 29. The device of claim 20, further comprising a graft material attached to the body. 30. The device of claim 29, wherein the graft material comprises woven polyester. 31. The device of claim 29, wherein the graft material comprises Dacron. 32. The device of claim 29, wherein the graft material comprises polyurethane. 33. The device of claim 29, wherein the graft material comprises PTFE. 34. The device of claim 29, wherein the graft material partially covers the body. 35. The device of claim 20, further comprising: a first tube configured to accept a guide wire; and a second tube configured to fit over the first tube. 36. The device of claim 35, wherein the second tube is placed over the first tube, one end of the body is secured to the first tube and the other end of the body is secured to the second tube. 37. An occluding system comprising: a plurality of shape memory wires woven together to form a body useful for occluding an anatomical structure, the body having first and second ends, both ends of at least one shape memory wire being located proximate one end of the body, the shape memory wires crossing each other to form a plurality of cells and a plurality of angles, at least one of the angles being obtuse, and at least one of the cells being defined by only four sides; wherein the value of the at least one obtuse angle may be increased by axially compressing the body. 38. A device comprising: a body suitable for implantation into an anatomical structure, the body having a first end and a second end, wherein the body comprises a shape memory wire having a first segment and a second segment, the segments being separated by a bend in the wire located proximate one end of the body, the first segment and second segments being arranged to form loops and twisted segments such that at least two contiguous substantially closed loops are separated from another loop by a twisted segment. 39. A device comprising: a body suitable for implantation into an anatomical structure, the body having two ends and comprising a shape memory wire having a first segment and a second segment, the segments being separated by a bend in the wire located proximate one end of the body, the segments being secured to each other in loop-defining locations, the segments also extending between the loop-defining locations in spaced relation to each other so as form at least two loops, at least one of the at least two loops having a compressed shape. 40. A device comprising: a plurality of shape memory wires woven together to form a body suitable for implantation into an anatomical structure, the body having a first end, a second end, and an intersection of two shape memory wires crossed in non-interlocking fashion; where both ends of at least one shape memory wire are located proximate one end of the body, and the two crossed wires form an obtuse angle that may be increased by axially compressing the body. 41. The device of claim 40, where the shape memory wires comprise nitinol. 42. The device of claim 40, where the shape memory wires comprise FePt, FePd or FeNiCoTi. 43. The device of claim 40, where the shape memory wires comprise FeNiC, FeMnSi or FeMnSiCrNi. 44. The device of claim 40, where the shape memory wires each have a diameter ranging in size from about 0.006 inches to about 0.012 inches. 45. The device of claim 40, where the plurality of shape memory wires includes at least 6 shape memory wires. 46. The device of claim 40, where the body has a tubular shape with a substantially uniform diameter. 47. The device of claim 40, where the body has a tapered shape with a diameter that decreases from one end of the body to the other end of the body. 48. The device of claim 40, where the body has a generally hourglass shape. 49. The device of claim 40, where the body is hand woven. 50. The device of claim 40, where the body is machine woven. 51. The device of claim 40, further comprising a graft material attached to the body. 52. The device of claim 51, where the graft material comprises woven polyester. 53. The device of claim 51, where the graft material comprises Dacron. 54. The device of claim 51, where the graft material comprises polyurethane. 55. The device of claim 51, where the graft material comprises PTFE. 56. The device of claim 51, where the graft material partially covers the body. 57. The device of claim 40, further comprising: a first tube configured to accept a guide wire; and a second tube configured to fit over the first tube. 58. The device of claim 57, where the second tube is placed over the first tube, one end of the body is secured to the first tube and the other end of the body is secured to the second tube. 59. A device comprising: a plurality of shape memory wires woven together to form a body suitable for implantation into an anatomical structure, the body having a first end, a second end, a middle, and an intersection of two shape memory wires crossed in non-interlocking fashion; where both ends of at least one shape memory wire are located nearer one end of the body than the middle, and the two crossed wires form an obtuse angle that may be increased by axially compressing the body. 60. The device of claim 59, where the shape memory wires comprise nitinol. 61. The device of claim 59, where the shape memory wires comprise FePt, FePd or FeNiCoTi. 62. The device of claim 59, where the shape memory wires comprise FeNiC, FeMnSi or FeMnSiCrNi. 63. The device of claim 59, where the shape memory wires each have a diameter ranging in size from about 0.006 inches to about 0.012 inches. 64. The device of claim 59, where the plurality of shape memory wires includes at least 6 shape memory wires. 65. The device of claim 59, where the body has a tubular shape with a substantially uniform diameter. 66. The device of claim 59, where the body has a tapered shape with a diameter that decreases from one end of the body to the other end of the body. 67. The device of claim 59, where the body has a generally hourglass shape. 68. The device of claim 59, where the body is hand woven. 69. The device of claim 59, where the body is machine woven. 70. The device of claim 59, further comprising a graft material attached to the body. 71. The device of claim 70, where the graft material comprises woven polyester. 72. The device of claim 70, where the graft material comprises Dacron. 73. The device of claim 70, where the graft material comprises polyurethane. 74. The device of claim 70, where the graft material comprises PTFE. 75. The device of claim 70, where the graft material partially covers the body. 76. The device of claim 59, further comprising: a first tube configured to accept a guide wire; and a second tube configured to fit over the first tube. 77. The device of claim 76, where the second tube is placed over the first tube, one end of the body is secured to the first tube and the other end of the body is secured to the second tube. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to intravascular devices. More particularly, it concerns self-expandable woven intravascular devices for use as stents, occluders or filters, the methods of making the same, and the apparatus and methods for delivery of the same into a living creature. 2. Description of Related Art Intravascular devices that serve as stents or filters constructed using a plain weave, such as the stent disclosed in U.S. Pat. No. 4,655,771 to Wallsten (hereinafter, the WALLSTENT), have a propensity to show a high-degree of elongation axially with diameter reduction. This is especially significant, when the angle of the crossing wires is close to the largest possible. The closer that the angle between the wires is to 180.degree., the more the corresponding elongation of the stent is at a given percentage of decrease in diameter. Any discrepancy between the diameters of the stent and the vessel can result in a considerable elongation of the stent. Simultaneously, the woven type stent has the largest expansile force and hence the biggest resistance to outer compression when the angle between the crossing wires is close to 180.degree.. In some applications, such as outer compression by a space occupying lesion, the increased radial force may be advantageous. The disadvantage of a propensity for elongation is that great care must be taken when delivering such a stent in a vessel or non-vascular tubular structure in order to properly position it. A further disadvantage of intravascular devices formed using a plain weave, is that they are often incapable of maintaining their shape when bent. For example, when such a stent is being delivered through a tortuous passageway with many turns, upon being bent, the weave of the stent tightens (e.g., the angle of the crossing wires approaches 180.degree.). As a result of this tightening, the diameter of the stent increases and the length of the stent decreases. Consequently, the diameter of the stent may exceed the diameter of the vessel or structure through which it is traveling, impeding the delivery of the stent or causing the stent to lodge in the vessel. This problem may be due in part to the use of weave materials such as stainless steel, which exhibit poor shape memory. This problem may also be due to the free, unclosed wires used to form the stent. The free sharp ends can create potential complications by penetrating, or perforating the wall of the tubular structure where such a stent is placed. Further, steps that have been taken to eliminate the free, sharp ends, such as connection with U-shaped members using welding, glue or the like (Wallsten, 1987) are time-consuming and expensive. The delivery systems for such devices have also suffered from problems relating to the repositionability of the devices as they are delivered into position in the living creature. In stenting long arterial segments, the contiguously decreasing diameter of the arterial system from the center to the periphery may pose problems. Woven stents with a uniform diameter will exert a substantial expansile force to the vessel wall along the tapered portion. Additionally, the stent may remain more elongated in the tapered portion. In a study where WALLSTENTs with a uniform diameter were used to bridge central venous obstruction in hemodialysis patients, it was found that the stents which were selected according to the size of the larger diameter central vein exerted considerably higher force to the wall of the smaller caliber subclavian vein (Vesely, 1997). Simultaneously, the length of the stents in the smaller caliber vein was longer than expected. In the prior art, most of the filter designs except for the Bird's Nest filter (Cook Inc., Bloomington, Ind.) have a conical shape and are anchored with multiple legs in the wall of the cava. The conical design is used because the main stream of the blood carries the thrombi from the lower part of the body through the center of the inferior vena cava. Therefore, all these devices are designed to have good filtration capacity at the center of the cava. The situation is quite different after some thrombi have been successfully captured. The center of the cava will no longer be patent and as a result, the blood will be diverted from the center to the periphery of the cava. The aforementioned designs, however, are not capable of catching thrombi effectively at the periphery of the lumen so the patients will practically be unprotected against subsequent peripheral embolization (Xian, 1995; Jaeger, 1998). Further, most of filters tend to be tilted in the cava which can deter their thrombus-capturing efficacy. Additionally, except for the Simon nitinol filter (C.R. Bard, New Jersey, N.J.) the aforementioned designs require a fairly large invasive delivery system of 10-F or larger. The uniform caliber of cylindrical stents in the prior art used in the ureter, as well as the peristalsis arrested at the proximal end of the stent, has resulted in severe hyperlasia of the urothelium and eventually occlusion of the ureter. Turning to occluders, percutaneous occlusion techniques have become indispensable tools in minimally invasive management of a wide range of pathological conditions. Use of permanent mechanical occlusion devices has been shown to be equivalent to that of surgical ligation. The Gianturco-Wallace stainless steel coil (Cook Inc., Bloomington, Ind.) has been the most widely used permanent, expandable intravascular occlusion device for transcatheter delivery (Gianturco et al., 1975). Percutaneous coil embolization has been shown to be advantageous over traditional surgical procedures in treatment of life threatening hemorrhage due to trauma or obstetric emergencies (Schwartz et al., 1993; Teitelbaum et al., 1993; Selby Jr., 1992; Levey et al., 1991; Ben-Menachem et al., 1991; Vedantham et al., 1997). Furthermore, coils have been used alone or in combination with microvascular embolic agents for the treatment of vascular fistulas and malformations, tumors, and varices (Wallace et al., 1979; Hendrickx et al., 1995; Furuse et al., 1997; White et al., 1996; Sagara et al., 1998; Punekar et al., 1996). During the last few years, the transcatheter closure of the patent ductus arteriosus (PDA) with coils has become a frequently used technique (Hijazi and Geggel, 1994; Hijazi and Geggl, 1997). Although coil type occlusion devices have shown at least a degree of utility, they have a number of drawbacks that could be significant in some applications. Intravascular stability of the coils has been shown to be highly dependent on proper matching of coil diameter with the diameter of the target vessel (Nancarrow et al., 1987), and with the exception of small vessels, a single coil rarely results in a stable occlusive thrombus (Hijazi and Geggel, 1994). Moreover, a long vascular segment is often obliterated because of the frequent need for multiple coils and the coils often remain elongated within the vessel because their unconstrained diameter is larger than the vascular lumen. Furthermore, delayed recanalization rates of 37% 57% have been reported in humans within 1 3 months after initially successful coil embolization (Sagara et al., 1998; O'Halpin et al., 1984; Schild et al., 1994). These and other drawbacks have inspired modifications in the design and technique of coil embolization. Recently, detachable microcoils and macrocoils with controlled delivery have been designed to achieve a more compact conglomerate of the coil and to prevent migration by allowing optimal positioning of the coil before release (Zubillaga et al., 1994; Guglielmi et al., 1995; Marks et al., 1994; Reidy and Qureshi, 1996; Uzun et al., 1996; Tometzki et al., 1996; Dutton et al., 1995). However, since optimal arrangement of the coil alone may not prevent migration in some cases, such as high flow conditions or venous placement, a coil anchoring system has been devised (Konya et al., 1998). Although an anchoring system may stabilize a coil conglomerate within the vasculature, significantly reducing or eliminating the possibility of coil migration, such a system may render the coil non-repositionable. Several different non-coil devices have been designed to achieve a more stable, limited size plug with higher hemostatic efficiency particularly for transcatheter closure of larger vessels (Schmitz-Rode et al., 1993; Kato et al., 1997; Konya et al., 1999) and PDAs (Pozza et al., 1995; Magal et al., 1989; Grifka et al., 1996). Recently, initial clinical experiences with a new self-expanding nitinol-mesh PDA occluder have been reported (Sharafuddin et al., 1996; Masura et al., 1998). A similar self-expanding, repositionable quadruple-disc device constructed of a braided nitinol mesh and polyester fibers has been reported to be superior to standard Gianturco coils in experimental occlusion of mid-size arteries (Sharaffuddin et al., 1996). Although such non-coil devices may be repositionable, they too exhibit drawbacks. For instance, the quadruple-disc device is several centimeters long in an elongated fashion, making difficult to keep the superselective position of the catheter tip during deployment. The multiple rigid connections between the layers and the relative long and rigid connection between the occluder and the delivery cable further increase this drawback. Although the nitinol mesh-PDA occluder has demonstrated utility, its proper placement requires a proper match both in size and shape between the occluder and the lesion to be occluded. The type and quality of the connection between the occluder and the delivery cable is the same as in the quadruple-disc design. A common disadvantage of both designs is that they lack guidewire compatibility. As a result, a delivery catheter must often be navigated to the site of occlusion first before an occluder may be loaded into the catheter and delivered through it. Another relative disadvantage of both devices is their cost of manufacturing. Percutaneous catheter technique for permanent closure of isolated persistently patent ductus arteriosus (PDA) is now a treatment of choice among doctors, obviating open surgery. The configuration of the PDA varies considerably. A majority of PDAs tend to have a funnel or conical shape due to ductal smooth muscle constriction at the pulmonary artery insertion, although narrowings in the middle or aortic ends can be observed (Krichenko, 1989). That is the reason why not only the size, but also the configuration, of the lesion plays a significant role in selecting an appropriate occluding device. Except from the small caliber lesions (with a maximum diameter of 2.5 mm or 3.3 mm, respectively), where some authors have achieved successful closure of the PDA with Gianturco coils (Cambier, 1992; Lloyd, 1993; Sommer, 1994), Rashkind's "double umbrella" occluder is the most often used device for this purpose (Rashkind, 1987; Hosking, 1991; Latson, 1991; Wessel, 1988; Report of the European Registry, 1992). It is available in two sizes (with a diameter of 12 mm and 17 mm) which require a 8-F and 11-F delivery system, respectively. In the majority of cases, the deployment of the traditional PDA device is performed from a femoral vein access (Report of the European Registry, 1992). Because of the size of the delivery sheath, such a device is not suitable for the treatment of patients with a body weight of less than 8 kg. Using even a larger umbrella, this procedure is not recommended for the treatment of the lesions with a diameter of 8 mm or above (Latson, 1991). About 80% of unselected patients with isolated PDA are candidates for the Rashkind device using the aforementioned criteria (Latson, 1991). With the Rashkind device, the proportion of patients with residual flow through the lesion fell from 76% immediately after implantation to 47% by the day after implantation and to 17% by a year after implantation (Report of the European Registry, 1992). According to some authors the residual flow carries a potential risk of infective endocarditis and should be avoided if possible. Its abolishment can be achieved by implantation of another device or surgery. One of the main drawbacks of the Rashkind umbrella is that it is not suitable for occlusion of all types of PDA. Preferably, it is used to occlude short PDAs with relatively wide end-openings. Its two discs cover both the pulmonary and the aortic opening of the PDA. Longer PDA may hinder the discs to be positioned in the proper way, that is, parallel to each other, thereby deteriorating its self-anchoring. Another disadvantage of the umbrella is that the occluding capacity of the design depends exclusively on the thrombogenicity of the porous Dacron material, frequently resulting in partial and lengthy occlusion. For the majority of patients with urinary leakage and/or fistulas (mainly due to tumor propagation to their ureters), the diversion of urine is currently performed by a percutaneous transrenal approach together with ureteral occlusion. Formerly, detachable and non detachable balloons were used for this purpose, but they did not cause satisfactory ureteral occlusion. Migration as well as deflation of the balloons occurred relatively frequently (Gunter, 1984; Papanicolau, 1985) leading to recurrence of the urine leakage. A silicone ureteral occluder was developed and used with only limited success because of device migration (Sanchez, 1988). This resulted in repositioning and consequent incomplete ureteral occlusion. It appears that the best results have been accomplished with Gianturco coils and Gelfoam embolization (Gaylord, 1989; Bing, 1992 a; Farrel, 1996). Even with multiple coil placements, together with Gelfoam plugs, the ureteral occlusion may sometimes be achieved for only weeks or months, and was attributed mostly to the induced urothelial hyperplasia (Bing, 1992 b). Coil migration was frequently encountered in these studies. The lack of appropriate self-anchoring results in coil migration which eventually deteriorates the occlusive effect. Problems pointed out in the foregoing are not intended to be exhaustive but rather are among many that tend to impair the effectiveness of previously known stents, occluders and filters. Other noteworthy problems may also exist; however, those presented above should be sufficient to demonstrate that previous techniques appearing in the art have not been altogether satisfactory, particularly in providing flexible, self-expanding, repositionable stents, occluders and filters. SUMMARY OF THE INVENTION The present invention overcomes the problems inherent in the prior art by providing a self-expandable, repositionable device for use as a stent, an occluder, or a filter which may be formed using a plain weave, and may have closed structures at both its ends. In one respect, the invention is a device that includes, but is not limited to, a plurality of shape memory wires woven together to form a body suitable for implantation into an anatomical structure. The body has first and second ends. The shape memory wires cross each other to form a plurality of angles, at least one of the angles being obtuse. Both ends of at least one shape memory wire are located proximate one end of the body. The value of the obtuse angle is increased when the body is axially compressed. The shape memory wires may be made of nitinol. The shape memory wires may be made of FePt, FePd or FeNiCoTi. The shape memory wires may be made of FeNiC, FeMnSi or FeMnSiCrNi. The shape memory wires may each have a diameter ranging in size from about 0.006 inches to about 0.012 inches. The plurality of shape memory wires may include at least 6 shape memory wires. The body may have a tubular shape with a substantially uniform diameter. The body may have a tapered shape with a diameter that decreases from one end of the body to the other end of the body. The body may have a generally hourglass shape. As used herein, "a generally hourglass" shape is a shape that resembles a body having two ends that are larger in terms of cross-sectional area than a mid-portion located therebetween. Such shapes include those resembling traditional hourglasses or dumbbells, for example. The body may be woven by hand. The body may be woven by a machine, such as a braiding machine. The device may also include, but is not limited to, a graft material attached to the body. The graft material may be made from woven polyester. The graft material may be made from Dacron. The graft material may be made from polyurethane. The graft material may be made from PTFE. The graft material may partially cover the body. As used herein, a graft material that "partially covers" a body is attached to the body such that a portion of the wire or wires forming the body are left bare or exposed. As a result of only partially covering a body, blood or other bodily fluids may flow through the bare portion of the body relatively unimpeded by the graft material. The device may also include, but is not limited to, a first tube that is configured to accept a guide wire and a second tube that is configured to fit over the first tube. Prior to delivering the body into an anatomical structure, the second tube is placed over the first tube, one end of the body is secured to the first tube and the other end of the body is secured to the second tube. In another respect, the invention is a device that includes, but is not limited to, a body suitable for implantation into an anatomical structure. The body has a first end, a second end and is defined by at least n shape memory wires, wherein n is greater than one. The n shape memory wires are arranged such that the body includes a first portion. The first portion includes a first woven portion and at least one strut. The shape memory wires of the first woven portion cross each other to form a plurality of angles, at least one of the angles being obtuse. Both ends of at least one shape memory wire are located proximate one end of the body. The value of the obtuse angle is increased when the body is axially compressed. The shape memory wires may be made from nitinol. The shape memory wires may be made from FePt, FePd or FeNiCoTi. The shape memory wires may be made of FeNiC, FeMnSi or FeMnSiCrNi. The first portion may include a first woven portion separated from a second woven portion by multiple first struts. The body may also include, but is not limited to, a second portion located adjacent to the first portion. The second portion includes a second woven portion. The second portion has n+x shape memory wires, and x is at least one. The first portion may have a generally domed shape. The first woven portion may have a generally domed shape and the multiple first struts may be bent slightly so as to increase the self-anchoring capability of the body in an anatomical structure. The first portion may also include a third woven portion separated from the second woven portion by multiple second struts. The first and third woven portions may have generally domed shapes. The device may also include, but is not limited to, a graft material attached to the body. The graft material comprises may be made from woven polyester. The graft material may be made from Dacron. The graft material may be made from polyurethane. The graft material may be made from PTFE. The graft material may partially cover the body. The device may also include, but is not limited to, a first tube that is configured to accept a guide wire and a second tube that is configured to fit over the first tube. Prior to delivering the body into an anatomical structure, the second tube is placed over the first tube, one end of the body is secured to the first tube and the other end of the body is secured to the second tube. In another respect, the invention is a device that includes, but is not limited to, a plurality of biodegradable filaments woven together to form a self-expanding body suitable for implantation into an anatomical structure. The self-expanding body has a first end and a second end. The biodegradable filaments cross each other to form a plurality of angles, at least one which is obtuse. The value of the obtuse angle is increased when the body is axially compressed. The biodegradable filaments may be made from polyglycolic acid. The biodegradable filaments may be made from poly-L-lactic acid. The biodegradable filaments may be made from a polyorthoester. The biodegradable filaments may be made from a polyanhydride. The biodegradable filaments may be made from a polyiminocarbonate. The biodegradable filaments may be made from an inorganic calcium phosphate. The biodegradable filaments may include about 0.05 to 0.25 percent by weight of calcium oxide, calcium hydroxide, calcium carbonate, calcium phosphate, magnesium oxide, magnesium hydroxide, magnesium carbonate, magnesium phosphate, sodium phosphate or potassium sulfate. The biodegradable filaments may be made from a polymer having about 15 to about 30 mole percent glycolide. At least one of the biodegradable filaments may be made from paclitaxel, docetaxel or heparin. Both ends of at least one biodegradable filament may be located proximate the first end of the self-expanding body. Each end of the self-expanding body may include at least one closed structure. The device may also include, but is not limited to, at least one shape memory wire secured to the self-expanding body. Both ends of the one shape memory wire may be located proximate one end of the self-expanding body. In another respect, the invention is a method of creating a body suitable for implantation into an anatomical structure. The body has two end ends. The method includes, but is not limited to, bending the shape memory wires in a plurality of shape memory wires to create bent portions in the shape memory wires. The bent portions are arranged to define one end of the body. Each shape memory wire has two ends. The method also includes, but is not limited to, weaving the ends of the shape memory wires to create the body such that the shape memory wires cross each other to form a plurality of angles, at least one of the angles being obtuse. The value of the obtuse angle is increased when the body is axially compressed. The bent portions may be bends or loops. The shape memory wires may be made from nitinol. The shape memory wires may be made of FePt, FePd or FeNiCoTi. The shape memory wires may be made of FeNiC, FeMnSi or FeMnSiCrNi. The shape memory wires may each have a diameter ranging in size from about 0.006 inches to about 0.012 inches. The plurality of shape memory wires may include at least 6 shape memory wires. The body may have a tubular shape with a substantially uniform diameter. The body may have a tapered shape with a diameter that decreases from one end of the body to the other end of the body. The body may have a generally hourglass shape. The body may be woven by hand. The body may be woven by a machine, such as a braiding machine. In another respect, the invention is a method of creating a body suitable for implantation into an anatomical structure. The body has two ends. The method includes, but is not limited to, providing a weaving system that includes a template having first template projections. The method also includes, but is not limited to, bending shape memory wires around the first template projections to create bent portions in the shape memory wires. The bent portions are arranged to define one end of the body. Each shape memory wire has two ends. The method also includes, but is not limited to, weaving the ends of the shape memory wires around the template to create the body such that the shape memory wires cross each other to form a plurality of angles, at least one of the angles being obtuse. The value of the obtuse angle is increased when the body is axially compressed. The first template projections may be tabs. The first template projections may be pins. The pins may be attached to a ring engaged with the template. The weaving system may also include, but is not limited to, a first weaving plate configured to rotate in a first direction during the weaving. The weaving system may also include, but is not limited to, first bobbins arranged on the first weaving plate, and one end of each shape memory wire is attached to each first bobbin prior to the weaving. The weaving system may also include, but is not limited to, a second weaving plate configured to rotate in a second direction during the weaving, and the second weaving plate is spaced apart from the first weaving plate. The weaving system may also include, but is not limited to, second bobbins arranged on the second weaving plate, and one end of each shape memory wire is attached to each second bobbin prior to the weaving. The method may also include, but is not limited to, securing the shape memory wires to the template. The method may also include, but is not limited to, forming closed structures with the ends of the shape memory wires. The closed structures may be arranged to define the other end of the body. The method may also include, but is not limited to, heating the body and the template. In another respect, the invention is a device for delivering an axially and radially expandable woven body having two ends into an anatomical structure. The device includes, but is not limited to, a first tube configured to accept a guide wire, and a second tube configured to fit over the first tube. When the tubes are used for delivering the axially and radially expandable woven body, one end of the axially and radially expandable woven body is secured to the outside of the first tube and the other end of the axially and radially expandable woven body is secured to the outside of the second tube. The first tube may be made from NYLON or TEFLON. The second tube may be made from NYLON or TEFLON. The device may also include, but is not limited to, a guide wire configured to be placed within the first tube. The outer diameter of the first tube may range in size from 3 French to 7 French. The outer diameter of the second tube may range in size from 5 French to 9 French. The device may also include, but is not limited to, a push-button release/lock mechanism configured to secure the first tube to the second tube. The device may also include, but is not limited to, an end fitting having a side arm. The end fitting is configured to be secured to the first tube. The first tube may be provided with at least one pair of first tube holes through which a first securing wire may be threaded. The pair of first tube holes may be positioned proximate one end of the first tube. The second tube may be provided with at least one pair of second tube holes through which a second securing wire may be threaded. The pair of second tube holes may be positioned proximate one end of the second tube. In another respect, the invention is a device for delivering an axially and radially expandable woven body having two ends into an anatomical structure. The device includes, but is not limited to, a first tube configured to accept a guide wire. The first tube has at least one pair of first tube holes that are positioned proximate one end of the first tube. The device also includes, but is not limited to, a second tube configured to fit over the first tube. The second tube has at least one pair of second tube holes that are positioned proximate one end of the second tube. The device also includes, but is not limited to, a first securing wire configured to be threaded through the pair of first tube holes. The device also includes, but is not limited to, a second securing wire configured to be threaded through the pair of second tube holes. When the tubes are used for delivering the axially and radially expandable woven body, one end of the axially and radially expandable woven body is secured to the outside of the first tube with the first securing wire and the other end of the axially and radially expandable woven body is secured to the outside of the second tube with the second securing wire. In another respect, the invention is an occluding system that includes, but is not limited to, a plurality of shape memory wires woven together to form a body useful for occluding an anatomical structure. The body has first and second ends. Both ends of at least one shape memory wire are located proximate one end of the body. The shape memory wires cross each other to form a plurality of angles, at least one of the angles being obtuse. The value of the obtuse angle is increased when the body is axially compressed. The shape memory wires may be made from nitinol. The occluding system may also include, but is not limited to, an occluding agent enclosed within the body. The occluding agent may include one or more threads of polyester. The occluding agent may also include, but is not limited to, one or more threads of DACRON. The occluding system may also include a jacket coupled to the body. The jacket may be made from silicone. The jacket may be made from polyurethane. The occluding system may also include, but is not limited to, a first tube configured to accept a guide wire, and a second tube configured to fit over the first tube. Prior to delivering the body into an anatomical structure, one end of the body is secured to the outside of the first tube and the other end of the body is secured to the outside of the second tube. In another respect, the invention is a device that includes, but is not limited to, a body suitable for implantation into an anatomical structure. The body has an axis, a first end and a second end. The body is made from a shape memory wire that has a first segment and a second segment. The segments are separated by a bend in the shape memory wire that is located proximate one end of the body. The first segment extends helically in a first direction around the axis toward the other end of the body. The second segment extends helically in a second direction around the axis toward the other end of the body. The first and second segments cross each other in a plurality of locations. The first segment may be positioned farther from the axis than the second segment at at least one location. The first segment may be positioned farther from the axis than the second segment at each location. The shape memory wire may be made from nitinol. The device may also include a first tube configured to accept a guide wire, and a second tube configured to fit over the first tube. Prior to delivering the body into an anatomical structure, one end of the body is secured to the outside of the first tube and the other end of the body is secured to the outside of the second tube. In another respect, the invention is a device that includes, but is not limited to, a body suitable for implantation into an anatomical structure. The body has a first end and a second end. The body is formed from a shape memory wire that has a first segment and a second segment. The segments are separated by a bend in the wire that is located proximate one end of the body. The first segment and second segments are arranged to form loops and twisted segments such that at least two contiguous loops are separated from another loop by a twisted segment. The definition of "contiguous" is set forth below with reference to the figures herein for the sake of clarity. At least three contiguous loops may be separated from another loop by a twisted segment. At least four contiguous loops may be separated from another loop by a twisted segment. At least two contiguous loops may be separated from two other contiguous loops by a twisted segment. The shape memory wire may be made from nitinol. The device may also include, but is not limited to, a first tube configured to accept a guide wire, and a second tube configured to fit over the first tube. Prior to delivering the body into an anatomical structure, one end of the body is secured to the outside of the first tube and the other end of the body is secured to the outside of the second tube. In another respect, the invention is a device that includes a body suitable for implantation into an anatomical structure. The body has, but is not limited to, two ends and is formed from a shape memory wire that has a first segment and a second segment. The segments are separated by a bend in the wire that is located proximate one end of the body. The segments are positioned adjacent to each other in loop-defining locations. The segments also extend between the loop-defining locations in spaced relation to each other so as form at least two loops. At least one of the at least two loops has a compressed shape. The definition of a "compressed" shape is set forth below with reference to the figures herein for the sake of clarity. The shape memory wire may be made from nitinol. The segments may be secured together using welds at the loop-defining locations. The segments may be secured together with collars at the loop-defining locations. The body may also include, but is not limited to, at least one coil placed over at least a portion of one of the segments, and, as a result, the body may be used as an occluder. The body may also include at least one fiber attached to the coil. The device may also include, but is not limited to, a first tube configured to accept a guide wire, and a second tube configured to fit over the first tube. Prior to delivering the body into an anatomical structure, one end of the body is secured to the outside of the first tube and the other end of the body is secured to the outside of the second tube. The present invention also provides a delivery system that may secure both the proximal and distal ends of the stent, occluder or filter. Advantageously, this delivery system allows the stent, occluder or filter to be easily repositioned as it is being delivered into place. As a result, the stent, occluder or filter may be more precisely positioned within the living creature. One advantage of the present invention is the unique fixation method of the tapered stent. The tapered shape of the stent allows the stent to be fixed in a tapered vessel or tubular structure with less radial or expansile force than a straight stent might exhibit, thus potentially resulting in a less hyperplastic intimal reaction. The straight stent of the present invention exhibits a high expansile force and thus a large capability of withstanding outer compression. This may be especially advantageous in tumorous stenoses, or fibrous strictures (including radiation-induced stenoses) where stents with inadequate expansile forces can be easily compressed and/or are incapable of assuming their nominal shape and diameter. In some cases, even the stenoses of arteriosclerotic origin can be so calcified (e.g., iliac or renal artery stenoses) that extra radial force is required from the stent to hold the patency of the vessel. Furthermore, the woven intravascular devices of the present invention are also able to return to their original, unconstrained shape after being bent, even maximally. Advantageously, the stents, occluders and filters of the present invention do not possess free, sharp wire ends. Thus, many potential complications are eliminated (Prahlow, 1997). Additionally, the tight mesh of the stents of the present invention coupled with the use of nitinol wires, for example, makes them easy to monitor under fluoroscopy. The present invention also includes a group of self-expanding, self-centering cava filters woven from materials as described above such that a coherent element is formed that without the use of a joint or attachment between the portions of the filters. The cava filters of the present invention provide increased filtrating efficiency not only at the center but also at the periphery of the cava. Additionally, the hourglass filter of the present invention utilizes multiple filtration levels. The cava filters of the present invention are able to self-center due to the symmetrical nature of their design and their potentially flared base. The cava filters of the present invention may utilize a relatively small, 7 French delivery catheter or sheath. Additionally, the superb flexibility of the cava filters makes it possible to deliver them via any of the possible access sites of the human body (femoral, jugular, antecubital veins). The present invention also includes a bi-iliac filter ("BI filter") that is a low-profile, self-expanding, flexible, temporary filter which may be woven from a number of superelastic or shape memory alloys. The BI filter is a type of temporary filter that can be deployed from either femoral vein, and it can filtrate the blood at the iliac veins/inferior cava junction. The BI filter of the present invention typically works at a low level of venous circulation. Advantageously, the BI filter simultaneously filters all the blood coming from both iliac veins, achieving almost 100% filtration. Further, the use of the BI filter is particularly beneficial in perioperative and posttraumatic cases. The inverse U-shape of the BI filter together with the expansile force of the tubular weave ensures firm position along the iliac/cava junction. A further advantage of the present invention is that the BI filter may utilize a relatively small, 7 French delivery catheter or sheath. Further, due to the flexibility of the mesh of the BI filter, the delivery system thereof may be advanced from ipsi- to contralateral iliac vein. As with the cava filters, the BI filter may possess a non-ferromagnetic character making it MRI compatible. The BI filter is suitable for temporary filtration. The BI filter allows for removal of the entrapped thrombi safely and successfully before removal of the filter. Using an adequately sized sheath, the small thrombus fragments entrapped within the mesh could also be removed together with the filter. The stents of the present invention can be advantageously covered with materials such as silicone, polyurethane, and/or an anticancer coating agent that allow the stents to reduce the possibility of restenosis after delivery, and which also allow the stents to be used in stenting malignant stenoses, for example. The filters of the present invention may also be covered with anticoagulant coating agents. Ureter strictures/compression/occlusion may be stented with these uncovered and/or covered stents; in particular, the use of a long tapered stent may advantageously match the special conditions posed by the different caliber and distensibility of the different segments of the ureter as well as the constant peristalsis. The stents of the present invention can also be used in some non-vascular applications including biliary tree and tracheo-bronchial system if the lesion does not require a bifurcated stent. The stents, occluders and filters of the present invention may be used in many different applications. They provide the advantages of superb flexibility, repositionability/removability, and precise positionability. BRIEF DESCRIPTION OF THE DRAWINGS The following drawings form part of the present specification and are included to further demonstrate certain aspects of the present invention. The invention may be better understood by reference to one or more of these drawings in combination with the description of illustrative embodiments presented herein. FIG. 1A is a perspective view of a stent according to one embodiment of the present invention. FIG. 1B is a front view of a stent end defined by bends according to one embodiment of the present invention. FIG. 1C is a perspective view of one wire of a stent according to one embodiment of the present invention. FIG. 2 is a side view of the arrangement of wires in a plain weave according to one embodiment of the present invention. FIG. 3 is a perspective view of a delivery system according to one embodiment of the present invention. FIG. 4 is a side view of a delivery system according to one embodiment of the present invention. FIGS. 5A E sequentially illustrative steps in a delivery method according to one embodiment of the present invention. FIG. 6 is a front view of a conical filter having bends or loops in the proximal (rear) end thereof according to one embodiment of the present invention. FIG. 7 is a front view of a conical filter having bends or loops in the distal (front) end thereof according to one embodiment of the present invention. FIG. 8 is a front view of a dome filter having bends or loops in the distal end thereof according to one embodiment of the present invention. FIG. 9 is a front view of an hourglass filter according to one embodiment of the present invention. FIG. 10 is a front view of an hourglass filter according to one embodiment of the present invention placed in the Inferior Vena Cava. FIG. 11 is a front view of a bi-iliac filter according to one embodiment of the present invention placed in the iliac veins. FIG. 12 is a front view of a bi-iliac filter having a retrieval loop according to one embodiment of the present invention placed in the iliac veins. FIG. 13 is a front view of a bi-iliac filter having a retrieval loop and a stabilizing wire according to one embodiment of the present invention placed in the iliac veins. FIG. 14 is a perspective view of a tapered stent according to one embodiment of the present invention. FIG. 15 is a perspective view of a single wire embodiment filter according to one embodiment of the present invention. FIGS. 16 24 show stages in a hand weaving method according to one embodiment of the present invention. FIG. 25 is a front view of the proximal portion of a delivery system according to one embodiment of the present invention. FIG. 26 is a front view of a delivery system for a temporary filter according to one embodiment of the present invention. FIGS. 27A and B illustrate stages in the removal of a filter from a vessel according to one embodiment of the present invention. FIG. 28 is a front view of a conical filter in a fully stretched position according to one embodiment of the present invention. FIG. 29 is a projected cross section of an hourglass filters taken across the middle portion of the filter according to one embodiment of the present invention. FIG. 30A is a front view of two wires coupled together for use in a hand weaving method according to one embodiment of the present invention. FIG. 30B is a perspective view of the placement of two wires each coupled to a pin for use in a hand weaving method according to one embodiment of the present invention. FIG. 31 is a perspective view of a biodegradable stent with a reinforcing wire according to one embodiment of the present invention. FIG. 32 is a perspective view of a biodegradable stent with a reinforcing wire according to a second embodiment of the present invention. FIGS. 33A G are front views of various configurations of an occluder according to the present invention. FIG. 34 is a front view of an occluder having a jacket according to one embodiment of the present invention. FIG. 35 is a front view of an occluder having clips according to one embodiment of the present invention. FIG. 36 is a front view of an aneurysm being treated by transcatheter embolization according to one embodiment of the present invention. FIG. 37 is perspective view of a template with longitudinal tabs around which wires are bent according to one embodiment of the present invention. FIG. 38A is an enlarged perspective view of the longitudinal tab and bent wire depicted in FIG. 37 according to one embodiment of the present invention. FIG. 38B is an enlarged perspective view of a longitudinal tab depicted in FIG. 37 around which a wire is bent to form a loop according to one embodiment of the present invention. FIG. 39 is a perspective view of a wire bent around a longitudinal tab and wrapped around a pair of bobbins according to one embodiment of the present invention. FIG. 40 is a top view of inner and outer weaving plates provided with bobbins according to one embodiment of the present invention. FIG. 41 is a perspective view depicting an upper weaving plate provided with bobbins and wires, a partial cross-sectional view of a lower weaving plate provided with bobbins and wires, and a partial cross-sectional view of a template around which both plates are arranged according to one embodiment of the present invention. FIG. 42A is a top view of upper and lower weaving plates provided with bobbins and wires and arranged around a template, and illustrates the first crossing of the wires according to one embodiment of the present invention. FIG. 42B is a front view of a small caliber loop formed by bending a wire according to one embodiment of the present invention. FIG. 43A is a top view of upper and lower weaving plates provided with bobbins and wires and arranged around a template, and illustrates the first crossing of the wires according to another embodiment of the present invention. FIG. 43B is a front view of a bend formed by bending a wire according to one embodiment of the present invention. FIG. 44 is a perspective view of upper and lower weaving plates provided with bobbins and arranged around a template such that the surfaces of the weaving plates from which the bobbin rods extend face each other according to one embodiment of the present invention. FIG. 45 is a perspective view of upper and lower weaving plates provided with bobbins and wires and arranged around a template such that the surfaces of the weaving plates from which the bobbin rods extend face each other according to one embodiment of the present invention. FIG. 46A is a perspective, partial cross-sectional view of a tool for twisting the wire ends of a woven body according to one embodiment of the present invention. FIG. 46B is a cross-sectional view of the jaws and outer housing of the tool illustrated in FIG. 46A. FIG. 47A is a perspective view of a body woven around a template having longitudinal and transverse tabs according to one embodiment of the present invention. FIG. 47B is an enlarged perspective view of one of the transverse tabs and twisted wire ends depicted in FIG. 47A according to one embodiment of the present invention. FIG. 48 is a perspective view of a template around which a ring having finish pins has been threadably engaged according to one embodiment of the present invention. FIG. 49 is a perspective view of a template having finish holes through which finish pins may be placed according to one embodiment of the present invention. FIG. 50A is a front view of a stent formed from a single wire according to one embodiment of the present invention. FIG. 50B is a front view of a stent formed from a single wire according to a second embodiment of the present invention. FIG. 50C is a front view of a stent formed from a single wire according to a third embodiment of the present invention. FIG. 50D is a perspective view of the stent depicted in FIG. 50B positioned on a template according to one embodiment of the present invention. FIG. 51 is a perspective view of a barbless stent filter according to one embodiment of the present invention. FIG. 52 is a perspective view of a barbless stent filter having bent longitudinal segments according to one embodiment of the present invention. FIG. 53 is a perspective view of a barbless stent filter having two filtrating levels according to one embodiment of the present invention. FIG. 54 is a front view of two stents placed in side-by-side relationship with each other in the aorta according to one embodiment of the present invention. FIG. 55 is a perspective view of two partially-covered stents placed in side-by-side relationship with each other in the aorta according to one embodiment of the present invention. FIG. 56 is a perspective view of a stent having struts placed in side-by-side relationship with another stent in the aorta according to one embodiment of the present invention. FIG. 57A is a front view of an occluder formed from a single wire around a template according to one embodiment of the present invention. FIG. 57B is a perspective view of an occluder formed from a single wire that includes collars placed around the wire segments at loop-defining locations according to one embodiment of the present invention. FIG. 57C is a top view of an occluder formed from a single wire that has coil pieces placed over portions of the wire segments located between collars according to one embodiment of the present invention. FIG. 57D is a top view of an occluder formed from a single wire that has coil pieces placed over portions of the wire segments located between collars and also has thrombogenic filaments attached to the coil pieces according to one embodiment of the present invention. FIGS. 58A D show stages in the delivery of one stent of a pair of stents in the aorto-renal junction according to one embodiment of the present invention. FIG. 59 is a front view of a barb (of a filter) that is penetrating a vessel wall according to one embodiment of the present invention. FIG. 60 is a perspective view of a single wire embodiment filter according to another embodiment of the present invention. FIG. 61 is a front view of upper and lower weaving plates supported by a weaving plate supporter according to one embodiment of the present invention. DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 1. Stents Straight Stents With reference to the illustrative embodiment shown in FIG. 1A, there is shown a stent for insertion and delivery into an anatomical structure. The stent includes a plurality of wires 5 which may be arranged in a plain weave so as to define an elastically deformable body 10. As used herein, "elastically deformable" means that the deformation of such a body is non-permanent and an original or initial shape may be substantially recovered, or regained, upon the release of a force (which may be mechanical, electromagnetic, or any other type of force). As used herein, "substantially recovered" means that recovery need not be such that the exact, original shape be regained. Rather, it means that some degree of plastic deformation may occur. In other words, recovery need not be total. Such elastic deformability may be achieved by utilizing the superelastic properties of suitable shape memory wires, which are discussed below. U.S. Pat. No. 4,655,771 to Wallsten (1987), which is hereby expressly incorporated by reference, displays the manner in which wires cross each other using plain weave as shown in FIG. 1a therein. FIG. 2 also illustrates the manner in which the wires 5 of the present intravascular devices may be arranged utilizing a plain weave. Body 10 is both radially and axially expandable. Body 10 includes front or distal end 12 and rear or proximal end 2. As shown in FIG. 1A, end 12 has a plurality of closed structures. These closed structures may be small closed loops 6 or bends 8 (FIG. 1B). Both bends 8 and small closed loops 6 may be formed by bending a wire 5 at a selected point located between the ends 7 of wire 5 (FIG. 1C shows small closed loops 6). For most applications, the selected point of the bend or small closed loop may be close to the midpoint of wire 5, as shown in FIG. 1C with respect to small closed loop 6. FIG. 1C also shows both ends of wire 5 being located proximate end 2 of body 10 (although the remainder of body 10 is not shown). Body 10 is formed by plain weaving wires 5, as will be discussed below in greater detail. Loops 6 and bends 8 provide significant advantages, some of which are unexpected, over woven devices such as the WALLSTENT that have free wire ends. For instance, the Wallsten patent recognizes that the free wire ends of the WALLSTENT should be protected, implicitly acknowledging the potential tissue-damaging dangers such free, sharp wire ends pose. The Wallsten patent suggests methods by which one can attempt to lessen these dangers, such as connecting the free wire ends to each other by attaching U-shaped members to them through heat welding, gluing or the like. These suggested methods can be time-consuming and, as a result, expensive. No such steps need to be taken in creating either loops 6 or bends 8 of the present woven devices as will be discussed below in greater detail. Further, the connections resulting from the methods disclosed in the Wallsten patent are likely more prone to mechanical failure than are loops 6 or bends 8 of the present woven devices. For example, welding can introduce anomalies such as cracks (which may result from the non-uniform solidification, uneven boundaries, etc.); voids or other irregularities resulting from porosity; inclusions (which include slag, oxides, etc.); etc., into the welded metal that create stress concentrations and dramatically increases the propensity for the welded connection to fail at those locations. In contrast, the gentle curves and bends resulting in loops 6 and bends 8 are virtually free of any such induced stresses and, as a result, are much less likely to fail. The Wallsten patent also suggests gluing the free wire ends, a method that provides even less structural integrity than can welding, because the resulting bond between the joined wire ends is only as strong as the surface tension between the glue and the metal used. Consequently, the joint created is more prone to failure than a welded joint suffering from the anomalies just discussed. Similarly, the Wallsten patent discloses first utilizing electric resistance heating to weld together the points of crossing of the free wire ends in a ring around the stent and then folding the free wire ends extending beyond the welded ring inwardly with light plastic deformation through controlled heating. This method involves not only the likely introduction of the anomalies discussed above that can result from welding, it also involves an additional stress on the joints created as the free wire ends are folded inwardly while being heated. Thus, this proferred joint is similar to the glued joint in that it is likely even more prone to failure than one involving only welding. In sum, the gentle curves and bends that may be used to create loops 6 and bends 8 of the present woven devices provide devices with safer ends: no free wire ends exist that may unintentionally penetrate and damage the wall of the structure into which they are delivered; the bends 8 or loops 6 are much less likely to mechanically fail than are the free wire ends that are connected together using welding or glue; and the likely time-consuming task of creating multiple welded or glued joints does not exist. Further, while the closed structures 4 (discussed below in greater detail) may be reinforced using methods similar to those suggested by the Wallsten patent (i.e., such as by welding), the present woven devices have, at most, only half as many potential locations for using such methods (and most likely less than half considering fewer wires are generally needed for making the present stents than are needed for making comparably-sized WALLSTENTS, even equating one of the present wires to two wires as those are used in the WALLSTENT). As a result, the potential for mechanical failure of the present woven devices is reduced accordingly. In addition to the foregoing benefits, loops 6 and bends 8 also provide advantages over the modified free wire ends disclosed in the Wallsten patent discussed above that are unexpected. For example, the inventors have found that the mesh of one of the present woven stents may be formed from fewer wires than can the mesh of a comparably-sized WALLSTENT (even equating one of the present wires to two wires as those are used in the WALLSTENT). Accordingly, the expansile force of one of the present woven stents of a given size may be maintained with fewer wires than would be needed to maintain the same expansile force of a WALLSTENT of the same size by simply increasing the mesh tightness (i.e., by increasing angle a--FIG. 1A--discussed below in greater detail). Similarly, the inventors have found that the same result may be achieved by increasing the diameter of the present wires with or without adjusting the mesh tightness. As a result, the amount of metal needed for the present woven stents may be less than what is needed in another comparably-sized woven stent, such as the WALLSTENT. This reduction in necessary metal translates to a cost savings, and, as described above, also means that patients are less likely to experience thrombosis and/or restenosis. As a further result, the variety of sizes that may be created for the present stents and the variety in the tightness of the weave of each is virtually unlimited, thereby facilitating virtually all potential applications. Further, the inventors also discovered that virtually no shortening occurs while bending the present woven stents, nor do the diameters of the present woven stents increase during bending. Thus, it is easier to accurately and predictably position the present stents in a tortuous anatomy than it is to position other woven stents that shorten more or suffer larger increases in diameter when bent, such as the WALLSTENT. For example, a tightly-woven present stent, 2.5 cm long, 10 mm in diameter, formed from 10 0.006-inch wires may be maximally bent by simply holding the two ends thereof between two fingers and bringing those ends together, and no shortening or diameter increase occurs during maximal bending. In contrast, for a WALLSTENT formed from 24 0.005-inch wires to behave similarly, the inventors found that it should be 6 cm long and 9 mm in diameter; although, when manipulated in a similar manner, the WALLSTENT experienced a 10% increase in diameter and some shortening. Thus, the length-to-diameter ratios of the foregoing stents were 2.5 and 6.6, respectively. As few as five wires, and an unlimited maximum number of wires may be used to form body 10 for any given application. As used herein, "wires" will mean a strand formed of any material, such as metal, plastic, fiber, etc. In an exemplary embodiment of the present invention, 6 to 12 wires are typically used to form body 10 in most applications. The number of wires that may be used depends on the application, and specifically on the desired expansile force of the stent. The expansile force of the stent is the radial force necessary to reduce the diameter of the stent. Factors affecting the expansile force of the stent include: the tightness of the weave (which is determined by the number of wires used and the angle formed by the crossed wires--the more wires or the closer the angle is to 180.degree., the tighter the weave), the number of wires used to form the woven stent, and the diameter of the wires used. When body 10 is used in the coronary artery, for example, it may be desirable to use the smallest possible amount of wire material to prevent thrombosis and reduce the possibility of restenosis in the vessel with a relatively slow circulation. In FIG. 1A, when body 10 is in its initial, unconstrained shape, angle a may range from about 90.degree. up to, but not including, 180.degree.. The expansile force of body 10 increases as angle a approaches 180.degree.. It is to be understood that angles less than 90.degree. may be utilized for angle a. In an exemplary embodiment, angle a is preferably obtuse, i.e., more than 90.degree., and most preferably about 150.degree.. In certain applications, however, a larger expansile force may be desirable, and, thus, angle a may be closer to 180.degree., such as in the case of a tumorous stricture or the like. In this regard, in an in vitro comparative study, a stent according to the present invention exhibited a higher expansile force and thus a larger capability of withstanding outer compression than both a Z-stent and a WALLSTENT of the same diameter, as revealed in Table 1, below. In Table 1, the designation .DELTA. in the leftmost column represents the circumferential displacement (in mm) of the stent in question. For example, a .DELTA. of 2 mm indicates that the circumference of the stent in question was reduced by 2 mm, and the force necessary to effect that displacement was then recorded. The designation "W" refers to the WALLSTENT. TABLE-US-00001 TABLE 1 Comparison of Expansile Forces of a Z-Stent, a WALLSTENT and a Nitinol Woven Stent W Z Side Z Z Side by W W by Woven .DELTA. Center Between Side Center Overlap Side Stent (mm) (g) (g) (g) (g) (g) (g) (g) 2 16 13 19 15 35 18 44 4 36 28 31 25 59 22 91 6 51 44 42 42 80 35 126 8 63 61 56 50 108 42 158 10 81 79 62 60 126 48 167 12 100 98 76 74 149 54 175 14 115 119 90 84 170 63 184 16 127 133 101 100 197 73 202 18 146 192 122 111 220 84 20 165 unmeasur. 142 129 248 96 With respect to Table 1, the unit "g" for "grams" is used as a measure of force. Although the correct unit of force is the "dyne", which is equal to the mass in grams multiplied by the gravitational constant, the inventors believe that the average reader will have a better idea about the size of force when the associated mass unit (grams) is specified. When one uses, e.g., a WALLSTENT or other commercially available stent for stenting, the manufacturer usually recommends to use a stent one mm larger than the diameter of the vessel, after precise determination of the size of the vessel, to eliminate the magnification factor caused by the fluoroscopy/radiography. This minimal "overstenting" is used to achieve good contact between the stent and the vessel wall. The manufacturer also typically provides exact data regarding the relationship between the stent's diameter and length to facilitate precise positioning thereof. The woven nitinol design of the present invention has significantly greater expansile force than that of the WALLSTENT if a comparable number of wires are used to form the same caliber stent (understanding that one wire as used herein and shown in FIG. 1C would require the use of two wires in the WALLSTENT, given the free, unclosed wires thereof). Compared to the WALLSTENT, the closed structures of the stents of the present invention and the better shape memory of the wires that may be used may result in a considerable reduction in the size of the wires used, in the number of wires used, as well as in the angles between the wires. For instance, in small vessel applications (e.g., coronary artery) it is advantageous to use the minimum amount of wire (metal) to reduce the possibility of thrombosis and/or restenosis. Furthermore, in preferred embodiments, angle a may be reduced below 90 degrees without losing the necessary expansile force for self anchoring. For the same vascular application, the same or even greater expansile force can be achieved with a loosely-woven nitinol design of the present invention compared to the WALLSTENT and other available stents. A stent of the present invention may also be chosen so as to have a diameter approximately ten percent larger than the diameter of the tubular structure to be stented. Body 10 may also be formed from a single wire ("the single wire embodiment"). The single wire embodiment is illustrated in FIG. 1C, wherein wire ends 7 have not yet been twisted or coupled together to form a closed structure 4, as described below in greater detail. One version of the single wire embodiment is illustrated in FIG. 50A. As illustrated in FIG. 50A, body 10 of the stent has an axis 810, distal end 12 and proximal end 2. First segment 812 of wire 5 is separated from second segment 814 by either bend 8 (not shown) or closed loop 6. As shown in FIG. 50A, first segment 812 extends helically in a first direction around axis 810 toward end 2, and second segment 814 extends helically in a second direction around axis 810 toward end 2. First segment 812 crosses second segment 814 in a number of locations 816. As shown in FIG. 50A, locations 816 define loops 818, which touch each other such that the loops are contiguous. Loops 818 are "contiguous" because, with the exception of the first and last loops, each loop shares a point--location 816--with two other loops. Segments 812 and 814 may be arranged in two different ways with respect to each other. As shown in FIG. 50A, segment 812 is positioned farther from axis 810 than segment 814 at each location 816, while in FIG. 50B, segments 812 and 814 alternate being further from axis 810 at each location 816. It will be understood to those of skill in the art, with the benefit of this disclosure, that segment 812 may be positioned farther from axis 810 than segment 814 at one or more locations 816. In the single wire embodiment of the stents in FIGS. 50A and 50B, loops 818 reside in a series of planes that includes two groups of planes (not shown), one of which includes the planes passing through the first, third, fifth, etc. loops 818, and the other of which includes the planes passing through the second, fourth, sixth, etc. loops 818. The planes in each group are roughly parallel to each other. When body 10 is in its unconstrained state, the planes in one of the groups intersect the planes in the other group at acute angles falling within the range of slightly greater than 0.degree. to about 45.degree.. Axis 810 passes generally through the center of each of loops 818. As shown in FIG. 50C, certain of loops 818 of the single wire embodiment of body 10 of the stent may be separated by longitudinal segments in which segments 812 and 814 are twisted together. As shown, pairs of contiguous loops 818--with the exception of the loop located after closed loop 6--are separated by twisted segments 820. Although not shown, it will be understood to those of skill in the art, with the benefit of this disclosure, that as many contiguous loops as are desired may be separated by a twisted segment 820 from another loop or any other number of contiguous loops to suit a particular application. For example, three contiguous loops may be separated from another loop or two or more other contiguous loops by a twisted segment in the same manner that the pairs of contiguous loops are separated by twisted segments as illustrated in FIG. 50C. Similarly, four contiguous loops may be separated from another loop or two or more other contiguous loops by a twisted segment. As yet another example, a single wire embodiment stent may have only one twisted segment separating two groups of five contiguous loops. In contrast to the "hoop stent" disclosed in U.S. Pat. No. 5,830,229 to Konya et al. ("the hoop stent"), which is incorporated herein by reference, the single wire embodiment of the stent that has twisted segments 820, depicted in FIG. 50C for example, possesses multiple contiguous loops 818. As a result, the single wire embodiment stents with such twisted segments are more resistant to forces compressing loops 818 in a lateral manner. The directions of such lateral forces are indicated by the large arrows in FIG. 50C. As a result, if the single wire embodiment of the stent having multiple contiguous loops, such as the stent depicted in FIG. 50C, is placed in a vessel or other structure that is sometimes bent or flexed, that vessel or structure will more likely remain patent when bent or flexed than it would were it supported by the hoop stent. Body 10 of a stent according to the present invention may be formed by various methods of plain weave including hand weaving and machine weaving. The following process is an exemplary embodiment of plain weaving according to the present invention. As shown in FIG. 16, a template 300 having a diameter corresponding to the chosen diameter of body 10 is provided. The top of the template is equipped with holes 302 around its circumference. Pins 304 are placed through the holes such that they extend beyond the outer surface of the template on opposing sides. As shown in FIG. 16, wires 5 are bent at about their midpoint around the pins. This bending may result in the formation of bend 8 as shown, or wires 5 may be wrapped around the pins to form small loops 6 (not shown). In one embodiment of body 10, angle b of small closed loop 6 or bend 8 (FIG. 1A) may be less than 90.degree.. In a more typical embodiment of body 10, angle b may be equal to or greater than 90.degree., and may approach, but not include, 180.degree.. In an even more typical embodiment, angle b may be about 140 160.degree.. As discussed above, bends 8 and loops 6 are created in a manner that makes them likely more mechanically sound than the joints disclosed in the Wallsten patent created by connecting two wire ends together through welding or gluing. In one embodiment of the present plain weaving process, the ends of two wires 5 may be coupled together and placed around pin 304, instead of bending a single wire 5 as above described. This coupling may be achieved by using any suitable means capable of preventing the wires from returning to their straight, unbent configuration. As shown in FIG. 30A, such means include bending and crimping a metal clip around the wires. In another embodiment of the present plain weaving process, as shown in FIG. 30B, two wires 5 may each be wrapped around pin 304 separately and secured using any suitable means, such as those just described, in further contrast to bending one wire around pin 304. After annealing (i.e., heating and cooling) wires 5 shown in FIG. 30B as described below, the two wires may be coupled to each other using any suitable means such as twisting, crimping or tying as further below described. Although only two pins are shown in FIG. 16, it is to be understood that this is done for illustrative purposes only, and not to indicate the appropriate number of wires to use in any given application. In an exemplary embodiment, template 300 is typically formed of brass or copper, but may be formed of any suitable material capable of withstanding the cure temperature below discussed, such as stainless steel. Similarly, in an exemplary embodiment, pins 304 are typically formed of stainless steel, but may be formed of any similarly suitable material. It is to be understood that the pins may be supported by the template by any suitable means capable of withstanding the cure temperature, including preforming, attachment by welding, threading, or the like. As shown in FIG. 17, after the wires have been bent around the pins, the wires are secured to the template to prevent them from returning to their original, straight, unbent position. This may be necessary given the superelastic nature of wires such as nitinol and the like (discussed below). As shown in FIG. 17, wires 5 are secured by securing wire 306 around the outside of wires 5 so as to secure wires 5 against the outside of the template. In an exemplary embodiment, copper is typically used for securing wire 306, but it is to be understood that any suitable wire capable of withstanding the annealing temperature of about 500.degree. C. discussed below may be used. After the wires are secured, small weights 360 (shown in FIG. 20) are attached to the free ends of the wires using any suitable means such as tying, or the like. In an exemplary embodiment, weights with masses of approximately 50 100 grams may typically be used with wires having diameters of between about 0.005 inches and about 0.011 inches. However, it is to be understood that weights of different masses may be chosen so long as the wires are kept under tension (i.e. straight) during plain weaving (as described below), and properly balance the central weight (described below). As shown in FIG. 18, a stand 330 with a circular plate 320 is provided with an opening 325. The diameter of the opening may depend on the diameter of the template. In an exemplary embodiment, an opening with a diameter of about 4.5 cm may be typically utilized in conjunction with a template of about 1.0 cm. It is to be understood, however, that an opening with a diameter more closely corresponding to the diameter of the template may be utilized. As shown in FIG. 19, before or after the weights are attached to the ends of wires 5, the template is inverted. In an exemplary embodiment, the weights may be typically attached to the free ends of the wires prior to inversion of the template such that the wires are kept under tension and may be prevented from returning to their unbent, nominal state. A central weight 340 may then be attached to the end of the template. In an exemplary embodiment, the central weight may be typically hung from the pins. However, it is to be understood that the central weight may be attached to the template's end in any suitable manner, such as hanging from holes in the template itself, etc. Before or after central weight 340 is attached to the end of the template, the inverted template is placed through opening 325, as shown in FIG. 20. In an exemplary embodiment, the central weight may typically be attached to the inverted template after the inverted template is placed through opening 325. As shown in FIG. 20, the wires 5 may be arranged fairly evenly around the circumference of the circular plate. As shown in FIG. 21, in an exemplary embodiment o |