Abstract:
Prosthesis delivery devices and methods are provided that enable precise control of prosthesis position during deployment. The prosthesis delivery devices may carry multiple prostheses and include deployment mechanisms for delivery of a selectable number of prostheses. Control mechanisms are provided in the prosthesis delivery devices that control either or both of the axial and rotational positions of the prostheses during deployment. This enables the deployment of multiple prostheses at a target site with precision and predictability, eliminating excessive spacing or overlap between prostheses. In particular embodiments, the prostheses of the invention are deployed in stenotic lesions in coronary or peripheral arteries, or in other vascular locations.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is a continuation of U.S. patent application Ser. No. 10/957,079 (Attorney Docket No. 021629-002710US) filed Sep. 30, 2004 which is a continuation-in-part of U.S. patent application Ser. No. 10/879,949 (Attorney Docket No. 021629-002700US), filed Jun. 28, 2004, the full disclosures of which are hereby incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    Stents are tubular prostheses designed for implantation in a vessel to maintain patency of the vessel lumen. Stents are used in various vessels throughout the body, including the coronary arteries, femoral arteries, iliac arteries, renal artery, carotid artery, vascular grafts, biliary ducts, trachea, and urethra, to name some examples. Stents are typically implanted by means of long and flexible delivery catheters that carry the stents in a compact, collapsed shape to the treatment site and then deploy the stents into the vessel. In some applications, balloon expandable stents are used. These stents are made of a malleable metal such as stainless steel or cobalt chromium and are expanded by means of a balloon on the tip of the delivery catheter to plastically deform the stent into contact with the vessel wall. In other applications, self-expanding stents are used. These are made of a resilient material that can be collapsed into a compact shape for delivery via catheter and that will self-expand into contact with the vessel when deployed from the catheter. Materials commonly used for self-expanding stents include stainless steel and elastic or superelastic alloys such as nickel titanium (Nitinol™). 
         [0003]    While self-expanding stents have demonstrated promise in various applications, such stents face a number of challenges. One such challenge is that in some cases the disease in a vessel may be so extensive that a stent of very long length, e.g. 30-200 mm, is called for. Currently available stents are typically less than 30 mm in length, and suffer from excessive stiffness if made longer. Such stiffness is particularly problematic in peripheral vessels such as the femoral arteries, where limb movement requires a high degree of flexibility in any stent implanted in such vessels. 
         [0004]    To overcome the stiffness problem, the idea of deploying multiple shorter stents end-to-end has been proposed. However, this approach has suffered from several drawbacks. First, currently available delivery catheters are capable of delivering only a single stent per catheter. In order to place multiple stents, multiple catheters must be inserted, removed and exchanged, heightening risks, lengthening procedure time, raising costs, and causing excessive material waste. In addition, the deployment of multiple stents end-to-end suffers from the inability to accurately control stent placement and the spacing between stents. This results in overlap of adjacent stents and/or excessive space between stents, which is thought to lead to complications such as restenosis, the renarrowing of a vessel following stent placement. With self-expanding stents the problem is particularly acute because as the stent is released from the catheter, its resiliency tends to cause it to eject or “watermelon seed” distally from the catheter tip by an unpredictable distance. During such deployment, the stent may displace not only axially but rotationally relative to the delivery catheter resulting in inaccurate, uncontrollable, and unpredictable stent placement. 
         [0005]    Interleaving stents or stent segments such as those disclosed in co-pending application Ser. No. 10/738,666, filed Dec. 16, 2003, which is incorporated herein by reference, present even greater challenges to conventional delivery systems. Interleaving stents have axially extending elements on each end of the stent that interleave with similar structures on an adjacent stent. Such interleaving minimizes the gap between adjacent stents and increases vessel wall coverage to ensure adequate scaffolding and minimize protrusion of plaque from the vessel wall. However, such interleaving requires that the relative rotational as well as axial positions of the adjacent stents be maintained during deployment to avoid metal overlap and excessive gaps between stents. Conventional delivery systems suffer from the inability to control both the axial and rotational positions of self-expanding stents as they are deployed. 
         [0006]    What are needed, therefore, are stents and stent delivery system that overcome the foregoing problems. In particular, the stents and stent delivery systems should facilitate stenting of long vascular regions of various lengths without requiring the use of multiple catheters. Such stents and delivery systems should also provide sufficient flexibility for use in peripheral vessels and other regions where long and highly flexible stents might be required. In addition, the stents and stent delivery systems should enable the delivery of multiple stents of various lengths to one or more treatment sites using a single catheter without requiring catheter exchanges. Further, the stents and stent delivery systems should facilitate accurate and repeatable control of stent placement and inter-stent spacing to enable deployment of multiple self-expanding stents end-to-end in a vessel at generally constant spacing and without overlap. Moreover, the stents and delivery systems should enable the deployment of interleaving stents or stent segments with precision and control over both the axial spacing and rotational position of each stent or segment. 
       BRIEF SUMMARY OF THE INVENTION 
       [0007]    The present invention provides prostheses, prosthesis delivery systems, and methods of prosthesis deployment that enable the precise and controllable delivery of multiple prostheses using a single delivery catheter. The prostheses, delivery systems, and methods of the invention provide for the precise control of prosthesis placement so that inter-prosthesis spacing is maintained at a constant and optimum distance. In some embodiments, both axial and rotational displacement of the prostheses relative to the delivery catheter is controlled during deployment, enabling the delivery of multiple prostheses that interleave with one another without overlap. The prostheses, prosthesis delivery systems, and methods of the invention further enable the length of prostheses to be customized in situ to match the length of the site to be treated. The invention is particularly useful for delivery of self-expanding prostheses, but balloon expandable prostheses are also contemplated within the scope of the invention. The invention is well-suited to delivery of stents to the coronary arteries and to peripheral vessels such as the popliteal, femoral, tibial, iliac, renal, and carotid arteries. The invention is further useful for delivery of prostheses to other vessels including biliary, neurologic, urinary, reproductive, intestinal, pulmonary, and others, as well as for delivery of other types of prostheses to various anatomical regions, wherever precise control of prosthesis deployment is desirable. 
         [0008]    In a first aspect of the present invention, a prosthesis delivery catheter includes an outer shaft forming a first lumen, a plurality of self-expanding tubular prostheses carried within the first lumen, and a movable coil member interactive with the prostheses to control expansion of the prostheses when the prostheses are deployed from the first lumen. The prostheses are generally adapted to radially expand upon deployment from the first lumen. 
         [0009]    In some embodiments, the coil member is removable from the deployed prostheses by rotating the coil member. In some embodiments, the prostheses have sidewalls with a plurality of openings, the coil member being threaded through the openings. Alternatively, the prostheses may include a plurality of struts, at least one of the struts being bent inwardly, with the coil member being threaded through the inwardly bent struts. Optionally, the coil member may be radially expandable to allow controlled expansion of the prostheses. In some embodiments, a distal portion of the coil member is retractable into the outer shaft following deployment of the selected number of prostheses. In some embodiments, the prostheses are disposed within the coil member. 
         [0010]    In various embodiments, the coil member may include a plurality of loops forming a helix. For example, in some embodiments between 2 and 6 loops are disposed in each prosthesis. In other embodiments, more than 6 loops are disposed in each prosthesis. In some embodiments, the coil member comprises a plurality of loops contacting each other to form a continuous tube. 
         [0011]    Optionally, the delivery catheter may also include a deployment mechanism for deploying a selected number of prostheses from the inner lumen. In some embodiments, for example, the deployment mechanism includes a pushing element slidably disposed in the first lumen, the pushing element being in engagement with at least one of the prostheses to advance the prostheses distally relative to the outer shaft. Optionally, adjacent ends of adjacent prostheses may be interleaved to resist rotation of the prostheses relative to each other. In one embodiment, a distal end of the pushing element is interleaved with a proximal end of a proximal-most prosthesis to resist rotation of the prostheses. In these or other embodiments, the coil member may optionally be configured to maintain rotational position of the prostheses relative to each other. 
         [0012]    In another aspect of the present invention, a prosthesis delivery catheter for delivering prostheses into a vessel lumen includes an outer shaft forming a first lumen, an inner shaft slidably disposed within the first lumen, an evertible tube having a first end coupled with a distal end of the outer shaft and a second end coupled with a distal end of the inner shaft, and a plurality of self-expanding tubular prostheses carried within the evertible tube. Again, the prostheses are generally adapted to radially expand upon deployment from the evertible tube. Moving the outer shaft proximally relative to the inner shaft everts a distal portion of the evertible tube so as to deploy one or more of the prostheses. 
         [0013]    In some embodiments, an inner surface of the inner shaft comprises at least one adherent element for releasably holding the prostheses to the inner surface. For example, in one embodiment, the adherent element comprises a tacky surface coating. Alternatively, the adherent element may comprise a softenable material into which the prostheses are removably embedded. In other embodiments, the adherent element comprises a plurality of inwardly-facing protrusions positioned to extend through openings in the prostheses. Such protrusions may have any of a number of shapes in various embodiments, such as but not limited to mushroom-shaped, L-shaped, T-shaped, hook-shaped, rounded, spiked, pyramidal, barbed, arrow-shaped or linear. In yet other embodiments, the adherent element may comprise a structure such as but not limited to bumps, bristles, spines, ridges ribs, waves, grooves, pits, channels, detents or random surface irregularities. 
         [0014]    In another aspect of the present invention, a method of delivering one or more prostheses to a treatment site in a vessel involves: positioning a delivery catheter at the treatment site, the delivery catheter carrying a plurality of self-expanding prostheses; selecting a desired number of the prostheses to deploy; deploying the desired number of prostheses from the delivery catheter into the vessel, each prosthesis expanding into contact with the vessel upon deployment; controlling axial displacement of each of the selected number of prostheses relative to the delivery catheter during deployment of the prostheses with an expandable coil member coupled with the prostheses; and removing the expandable coil member from the deployed prostheses. 
         [0015]    In some embodiments, removing the coil member involves rotating the coil member. For example, the coil member may be helically threaded through the prostheses such that rotating the coil member unthreads the coil member from one or more prostheses. In some embodiments, the method also involves controlling the rotational displacement of the selected number of prostheses relative to the delivery catheter during deployment of the prostheses. In one embodiment, for example, the rotational displacement is controlled by interleaving adjacent ends of adjacent prostheses and interleaving a proximal end of a proximal-most prosthesis with a portion of the catheter device. In some embodiments, a distal portion of the coil member expands with the selected number of prostheses. 
         [0016]    In yet another aspect of the present invention, a method of delivering one or more prostheses to a treatment site in a vessel involves: positioning a delivery catheter at the treatment site, the delivery catheter carrying a plurality of self-expanding prostheses within an evertible tube; selecting a desired number of the prostheses to deploy; and everting a distal portion of the evertible tube to deploy the desired number of prostheses from the delivery catheter into the vessel, each prosthesis expanding into contact with the vessel upon deployment. In some embodiments, the distal portion of the evertible tube is everted by sliding an outer shaft of the catheter device relative to an inner shaft of the catheter device. For example, in some embodiments, a distal end of the outer shaft is coupled with a distal end of the evertible tube such that sliding the outer shaft proximally relative to the inner shaft causes the distal end of the evertible tube to bend outward and fold over on itself. 
         [0017]    Optionally, the method may further involve controlling axial displacement of each of the selected number of prostheses relative to the delivery catheter during deployment of the prostheses by contacting an adherent inner surface of the evertible tube with the prostheses. In one embodiment, for example, the adherent surface maintains engagement with the prostheses until the distal portion of the evertible tube is peeled away from the prostheses. In some embodiments, the adherent surface comprises a friction-inducing coating or friction-inducing surface feature. In some embodiments, contacting the adherent surface with the prostheses involves releasably coupling one or more retention structures on the inner surface with the prostheses. Alternatively, contacting the adherent surface with the prostheses may involve embedding the prostheses in a deformable material on the adherent inner surface. 
         [0018]    In a further aspect of the invention, a prosthesis delivery catheter comprises an outer shaft having a distal end and a first lumen, a plurality of self-expanding tubular prostheses carried within the first lumen, the prostheses being adapted to radially expand upon deployment from the first lumen, and a control member extending distally from the distal end of the outer shaft and defining an interior communicating with the first lumen for receiving one or more of the prostheses. The control member has an undeflected shape when not engaged by one of the prostheses and is configured to deflect radially outwardly when engaged by a prosthesis during expansion thereof. The control member is also configured to resiliently return to the undeflected shape when the prosthesis is removed from the interior. In one embodiment, the control member generally includes a plurality of deflectable tines having free distal ends received within an aperture on the nose cone or nose piece of the catheter. Optionally, the control member may further include a plurality of webs between the tines. In an alternative embodiment, the control member may comprise a distensible tubular structure. 
         [0019]    Further aspects of the nature and advantages of the invention will be apparent from the following detailed description of various embodiments of the invention taken in conjunction with the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]      FIG. 1  is a side cut-away view of a prosthesis delivery catheter according to the invention. 
           [0021]      FIG. 2A  is a side cross-sectional view of a distal portion of a prosthesis delivery catheter according to the invention in a further embodiment thereof. 
           [0022]      FIG. 2B  is a side cross-sectional view of the prosthesis delivery catheter of  FIG. 2A  showing the deployment of prostheses in a vessel. 
           [0023]      FIGS. 3A-3C  are perspective, side, and end views respectively of a prosthesis coupled to control wires according to further embodiments of the invention. 
           [0024]      FIG. 4A  is a side cross-section of a distal portion of a prosthesis delivery catheter according to the invention in a further embodiment thereof. 
           [0025]      FIG. 4B  is a side cross-section of the prosthesis delivery catheter of  FIG. 4A  showing the deployment of prostheses in a vessel. 
           [0026]      FIG. 5  A is a side cross-section of a distal portion of a prosthesis delivery catheter according to the invention in a further embodiment thereof. 
           [0027]      FIG. 5B  is an oblique view of a distal portion of a prosthesis delivery catheter according to the invention in yet another embodiment thereof. 
           [0028]      FIGS. 6A-6C  are side cross-sectional views of a distal portion of a prosthesis delivery catheter according to the invention in still another embodiment thereof, showing the outer shaft unretracted, outer shaft retracted with sleeve unexpanded, and sleeve with stents expanded, respectively. 
           [0029]      FIGS. 7A-7B  are side cross-sectional views of a distal portion of a prosthesis delivery catheter according to the invention in another embodiment thereof, showing outer shaft retracted with sleeve unexpanded, and outer shaft retracted with sleeve and stents expanded, respectively. 
           [0030]      FIGS. 8A-8C  are side cross-sectional views of a distal portion of a prosthesis delivery catheter according to the invention in a further embodiment thereof, showing the outer shaft unretracted, outer shaft retracted with sleeve unexpanded, and sleeve with stents expanded, respectively. 
           [0031]      FIGS. 9A-9B  are side cross-sectional views of a distal portion of a prosthesis delivery catheter in a vessel according to the invention in another embodiment thereof, showing outer shaft retracted with prosthesis partially deployed, and prosthesis fully deployed, respectively. 
           [0032]      FIGS. 10A-10B  are side cross-sectional views of a distal portion of a prosthesis delivery catheter in a vessel according to the invention in yet another embodiment thereof, showing outer shaft retracted with prosthesis partially deployed, and prosthesis fully deployed, respectively. 
           [0033]      FIGS. 11A-11C  are side cross-sectional views of a distal portion of a prosthesis delivery catheter in a vessel according to the invention in yet another embodiment thereof, showing a first prosthesis deployed, an expandable member expanded within the first prosthesis, and a second stent deployed with expandable member expanded in the first prosthesis, respectively. 
           [0034]      FIGS. 11D-11F  are side cross-sectional views of a distal portion of a prosthesis delivery catheter according to another embodiment of the invention, showing the delivery catheter prior to stent deployment, the deployment of a first prosthesis in a vessel, and a deployed prosthesis in the vessel, respectively. 
           [0035]      FIG. 12  is a side cross-sectional view of a distal portion of a prosthesis delivery catheter in a vessel according to the invention in still another embodiment thereof, showing a first prosthesis deployed in a lesion. 
           [0036]      FIGS. 13A-13C  are side cross-sectional views of a distal portion of a prosthesis delivery catheter according to another embodiment of the invention, demonstrating a method for delivering prostheses in a vessel. 
           [0037]      FIG. 14  is a side view of a prosthesis coupled with a coil member according to one embodiment of the invention. 
           [0038]      FIG. 15  is an end-on view of a prosthesis coupled with a coil member according to one embodiment of the invention. 
           [0039]      FIG. 16  is an end-on view of a prosthesis coupled with a coil member according to another embodiment of the invention. 
           [0040]      FIG. 17  is a cross-sectional side view of a distal end of a prosthesis delivery catheter having an evertible tube according to one embodiment of the present invention. 
           [0041]      FIG. 18  is a cross-sectional side view of a portion of an evertible tube of a prosthesis delivery catheter according to one embodiment of the present invention. 
           [0042]      FIG. 19  is a cross-sectional side view of a portion of an evertible tube of a prosthesis delivery catheter according to another embodiment of the present invention. 
           [0043]      FIGS. 20A-20B  are oblique views a prosthesis delivery catheter according to the invention in a further embodiment thereof, before and during deployment of a prosthesis, respectively. 
           [0044]      FIGS. 21A-21E  are side cross-sectional views of the prosthesis delivery catheter of  FIGS. 20A-B , illustrating the steps of deploying a prosthesis according to the invention. 
           [0045]      FIG. 22  is an oblique view of a distal end of a prosthesis delivery catheter according to the invention in a further embodiment thereof. 
           [0046]      FIG. 23  is an oblique view of a distal end of a prosthesis delivery catheter according to the invention in still another embodiment thereof. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0047]    Referring to  FIG. 1 , a first embodiment of a prosthesis delivery catheter according to the invention is illustrated. Delivery catheter  20  may have any of various constructions, including that described in co-pending application Ser. No. 10/637,713, filed Aug. 8, 2003 (Attorney Docket No. 21629-000340), which is incorporated herein by reference. Delivery catheter  20  has a handle assembly  21  and an elongated catheter body  22  that includes three concentric tubular shafts all axially slidable relative to one another: an outer shaft  24 , a pusher  26 , and an inner shaft  28 . Pusher  26  has a distal extension  27  to which a pusher ring  29  is fixed. In a distal region of the catheter body  22 , a guidewire tube  30  extends slidably through a port  32  in outer shaft  24  and through pusher ring  29  and has a distal end  34 , to which is mounted a nosecone  36  and a stop member  38 . 
         [0048]    Delivery catheter  20  further includes one or more stent expansion control members, which in the illustrated embodiment comprise a plurality of control wires  40 . Preferably, one or more pairs of control wires  40  are mounted on opposing sides of delivery catheter  20 , e.g. four control wires  40  offset 90° from each other. Control wires  40  are fixed at their proximal ends  42  to inner shaft  28 , and have free distal ends  44 . 
         [0049]    Outer shaft  24  has a distal extremity  46  defining a first lumen  48 . A plurality of stents  50  are disposed in a collapsed configuration within first lumen  48 . Stents  50  are preferably composed of a resilient material such as stainless steel or Nitinol so as to self-expand from the collapsed configuration to a radially expanded configuration when deployed from first lumen  48 . While stents  50  as illustrated have a wave-like or undulating pattern in a plurality of interconnected circumferential members, the pattern illustrated is merely exemplary and the stents of the invention may have any of a variety of strut shapes, patterns, and geometries. From 2 up to 10 or more stents may be carried by outer shaft  24 . Optionally, a valve member  49  is mounted within first lumen  48  to facilitate separating those stents  50  to be deployed from those to remain within outer shaft  24 , as described in co-pending application Ser. No. 10/412,714, filed Apr. 10, 2003, which is incorporated herein by reference. 
         [0050]    Control wires  40  run along the outside of stents  50  or through the interior of stents  50 , are threaded through openings in the walls of stents  50  or are otherwise coupled with stents  50  to control the deployment thereof, as described more fully below. Control wires  40  are composed of a resilient material such as stainless steel, Nitinol, or a suitable polymer, and are preferably generally straight and biased inwardly against guidewire tube  32  or to a position generally parallel to the axial direction. In  FIG. 1 , outer shaft  24  has been retracted to expose a plurality of stents  50  which are partially expanded and remain coupled to or restrained by control wires  40 , as explained in greater detail below. 
         [0051]    Handle assembly  21  has a rotatable retraction knob  52  coupled to a shaft housing  53 , to which outer shaft  24  is fixed. By rotating retraction knob  52 , outer shaft  24  may be retracted proximally relative to pusher  26  and inner shaft  28 . A pull ring  54  is coupled to inner shaft  28 , allowing inner shaft  28 , and hence control wires  40 , to be retracted proximally relative to outer shaft  24 . A switch  56  engages and disengages pusher  26  with outer shaft  28 , so that pusher  26  either moves with outer shaft  24  or remains stationary as outer shaft  24  is retracted. Indicia  58  on shaft housing  53  indicate the extent of retraction of outer shaft  28  by distance, number of stents, or other suitable measure. Other aspects of handle assembly  21  are described in co-pending application Ser. No. 10/746,466, filed Dec. 23, 2003 (Attorney Docket No. 21629-002200), which is incorporated herein by reference. Except as stated otherwise, any of the embodiments of the stent delivery catheter described below may incorporate the features and be otherwise constructed as just described. 
         [0052]      FIGS. 2A-2B  illustrate a distal extremity of a stent delivery catheter  60  according to the invention in a further embodiment thereof. In this embodiment, stents  62  have a series of diamond shaped openings  64  in the walls thereof through which a plurality of control wires  66  are threaded. Stents  62  have a plurality of axially-extending V-shaped points  63  on their distal and proximal ends. These points  63  are configured to interleave or nest with the points  63  on the adjacent stent  62 , preferably both in the collapsed and expanded configurations. Various suitable interleaving stent geometries are described in co-pending application Ser. No. 10/736,666, filed Dec. 16, 2003, which is incorporated herein by reference. In order to maintain this interleaving, it is important to maintain the relative rotational and axial positions of the adjacent stents  62  both before and during deployment. By extending through the openings  64  in each stent, control wires  66  keep adjacent stents  62  in rotational alignment as they are advanced forward through the catheter and during deployment. Preferably, each control wire  66  is threaded through at least two openings  64  in each stent  62 , one opening  64   a  near the distal end of each stent  62  and one opening  64   b  near the proximal end of each stent  62 . Alternatively, control wires  66  may be threaded through only a single opening  64  or through three or more openings  64  on each stent  62 . Preferably, however, control wires  66  are threaded so that the distal and proximal ends of stents  64  will expand at a generally uniform rate when released, as described below. 
         [0053]    Control wires  66  are constructed of a resilient and flexible metal or polymer with sufficient stiffness to provide controlled resistance to the expansion of stents  62 . This stiffness may be selected to allow the desired expansion behavior of stents  62  such that “watermelon seeding” is avoided, inter-stent spacing is maintained, and sufficient stent expansion occurs. Control wires  66  may have various cross-sectional geometries, and may be a flat ribbons or blades, round or oval wires, I-beams, or other suitable structures to control stent expansion, maintain spacing and rotational position, and facilitate withdrawal from stents  62  without interference. Control wires  66  may be composed of or coated with a lubricious material such as PTFE to reduce friction during removal from stents  62 . In other embodiments, control wires  66  may have surface features, be wrapped with wire windings, or be coated with “sticky” material to increase friction with stents  62 . Coatings or surface structures such as scales with one-way frictional effects may also be applied to control wires  66 . 
         [0054]    As a further alternative, control wires  66  may comprise flexible hollow tubes which are pneumatically or hydraulically controllable to vary their rigidity or stiffness. For example, control wires  66  may comprise polymeric tubes that radially contract or flatten and are very flexible when evacuated of fluid, but which become more rigid when filled with pressurized fluid, such as saline, air, or other liquid or gas. In such an embodiment, control wires  66  are fluidly connected to a pump, syringe, or other suitable fluid delivery mechanism at the proximal end of the delivery catheter. In this way, control wires  66  may be pressurized to increase stiffness as stents  62  are deployed, then evacuated of fluid to reduce their profile and stiffness during withdrawal from the deployed stents. 
         [0055]    Stents  62  are slidably positioned over an inner shaft  68 , to which is attached a nosecone  70  at the distal end of the device. An outer shaft  72  is slidably disposed over inner shaft  68  and surrounds stents  62 , maintaining them in a collapsed configuration, as shown in  FIG. 2A . A pusher shaft  74  is slidably disposed over inner shaft  68  and is configured to engage the proximal end of the proximal-most stent  62 . Outer shaft  72  is retractable relative to inner shaft  68  in order to expose a desired number of stents  62  as shown in  FIG. 2B . When outer shaft  72  is retracted, the exposed stents  62  self-expand to a larger-diameter expanded shape in engagement with lesion L in vessel V. Preferably, at least the distal end of the distal-most stent  62 , and more preferably a substantial portion of all stents  62  being deployed, is allowed to expand into engagement with lesion L while control wires  66  remain threaded through openings  64 . Control wires  66  are then withdrawn from openings  62 , preferably by holding catheter  60  in position and pulling control wires  66  proximally using a suitable mechanism such as that described above with reference to  FIG. 1 . Alternatively, the entire catheter  60  may be retracted proximally relative to stents  62  to withdraw control wires  66  from openings  62 . Because at least a portion of stents  62  is in engagement with lesion L, stents  62  are held in position in the vessel as control wires  66  are withdrawn. 
         [0056]    Optionally, inner shaft  68  may have a balloon  76  mounted thereto near its distal end to enable pre- or post-dilatation of lesion L. In this embodiment, inner shaft  68  has an inflation lumen through which inflation fluid may be delivered to balloon  76 . Balloon  76  is preferably as long as the longest lesion that might be treated using catheter  60 . To dilate lesion L prior to stent deployment, or to further expand stents  62  after deployment, outer shaft  72  and those of stents  62  remaining therein are retracted relative to inner shaft  68  to expose a desired length of balloon  76 . The exposed portion of balloon  76  may then be inflated within the lesion L and/or the deployed stents  62 . 
         [0057]    Following deployment and any post-dilatation, inner shaft  68  is retracted into outer shaft  72  while maintaining pressure against pusher shaft  74 . This slides stents  62  distally along control wires  66  and repositions stents  62  to the distal end of inner shaft  68  so as to be ready for deployment. Catheter  60  may then be repositioned to another vascular location for deployment of additional stents  62 . 
         [0058]    Control wires  66  may be coupled to stents  62  in various ways, some of which depend upon the configuration of stents  62 . For example, as shown in  FIGS. 3A-B , the points  63  at the ends of each stent  62  may be bent inwardly such that a portion of the openings  64 ′ are oriented axially. Control wires  66  may then be threaded through these axially-oriented openings  64 ′. Preferably, upon deployment, points  63  are adapted to  30  deform with stent expansion so as to be more parallel to the axial direction, thereby providing a smooth and open flow path through the stent. 
         [0059]    In another embodiment, shown in  FIG. 3C , stents  80  have axially-aligned eyelets  82  through which control wires  84  are threaded. These eyelets  82  may be in the interior of stents  82  as shown in  FIG. 3C , or such eyelets may be on the exterior surface of stents  82 , or could be drilled through one or more of the struts of stents  82 . Various other structures may also be used for coupling the stents of the invention to control wires, including hooks, channels, holes, sleeves, and others, disposed on the interior, exterior or end surfaces of the stent, or through the struts themselves. Such structures may by integral with stent struts and of the same material, may be attached to the stent struts and be of same or different material, or may be a biodegradable material that erodes and eventually is absorbed into the body following deployment. 
         [0060]    Referring now to  FIGS. 4A-4B , in a further embodiment, a stent delivery catheter  90  has an outer shaft  92  slidably disposed over an inner shaft  94 , and at least one stent  96  (shown schematically in  FIG. 4A ) in a collapsed shape within outer shaft  92 . A plurality of control wires  97  have an outer extremity  98  outside of inner shaft  94  and an inner extremity  100  extending through one or more lumens  102  and distal ports  103  in inner shaft  94 . Both outer portion  98  and inner portion  100  extend proximally to the proximal end of delivery catheter  90 . Outer extremities  98  are threaded through openings in the wall of stent  96  or are otherwise coupled thereto as described above so as to resist expansion of stent  96  upon deployment. Control wires  97  thus form a continuous loop from the proximal end of stent delivery catheter  90 , through stent  96  and back to the proximal end of the catheter. 
         [0061]      FIG. 4B  illustrates this embodiment of delivery catheter  90  positioned in a vessel V and carrying plurality of stents  96 ′. Stents  96 ′ have axial projections  104  at their distal and proximal ends configured to interleave when stents  96 ′ are collapsed within outer shaft  92  and when deployed in vessel V. When outer shaft  92  is retracted to expose one or more stents  96 ′, the expansion of stents  96 ′ can be resisted and controlled by maintaining tension on control wires  97 . Tension may be controllably relaxed to allow stents  96 ′ to expand into contact with lesion L, as shown in  FIG. 4B . By controlling the expansion in this way, the axial spacing and rotational positions of adjacent stents  96 ′ may be maintained so that gaps and overlaps are minimized and the interleaving of axial projections  104  is maintained. When stents  96 ′ are fully expanded, one end of each control wire  97  may be released at the proximal end of delivery catheter  90  while the other end is pulled to retract the control wires from stents  96 ′. 
         [0062]    In a further embodiment, illustrated schematically in  FIGS. 5A-B , delivery catheter  108  is constructed as described above except that control wires  110  are releasably coupled to the distal end of an inner shaft  112  or to nose cone  114 . In an exemplary embodiment, control wires  110  have balls  116  at their distal ends configured to be received within slots  118  on the outer surface of nosecone  114  ( FIG. 5A ) or on the proximal face of nosecone  114  ( FIG. 5B ; outer shaft not shown for clarity). Slots  118  have an enlarged portion  120  of sufficient size to receive ball  116  and a narrow portion  122  through which balls  116  may not pass. Inner shaft  112  is axially rotatable relative to control wires  110 . As in the embodiment of  FIGS. 4A-B , with balls  116  held within slots  118 , tension may be maintained on control wires  110  to resist expansion of stent  124 . Stent  124  may be allowed to expand by gradually relaxing tension on control wires  110 . Once stent  124  is fully expanded tension on control wires  110  may be fully relaxed and nosecone  114  then rotated by rotating inner shaft  112 , thereby allowing balls  116  to pass through enlarged portions  120 . Control wires  110  may then be withdrawn from the deployed stent  124 . Nosecone  114  is then retracted or control wires  110  advanced so as to reinsert balls  116  into slots  118 . Nosecone  114  is then rotated to align balls  116  with narrow portions  122 , again securing the control wires to nosecone  114 . Delivery catheter  108  may then be repositioned to deploy additional stents. 
         [0063]    Optionally, delivery catheter  108  may include a middle shaft or balloon  126  over which stents  124  are positioned, as shown in  FIG. 5A . In this case, inner shaft  112  is slidably and rotatably disposed in an inner lumen though middle shaft or balloon  126 . If a balloon is included, it may be used for pre-dilatation of lesions prior to stent deployment, or for further expansion of stent  124  following deployment. 
         [0064]    In the foregoing embodiment, control wires  110  will be constructed to have sufficient stiffness to resist rotation, twisting or bending as nosecone  114  is rotated to release control wires  110 . Maintaining some tension on control wires  110  as nosecone  114  is rotated may facilitate the release process. In addition, control wires  110  will have sufficient column strength to facilitate reinsertion into slots  118  following deployment of stents  124 . Thus the size, material and geometry of control wires  110  will be selected to enable these actions while providing the desired level of control of stent expansion. 
         [0065]    In a further embodiment of a stent delivery catheter according to the invention, an expandable sleeve  130  is slidably positioned within outer shaft  132  and carries stents  134  as shown in  FIGS. 6A-C . A pusher shaft  136  is slidable within sleeve  130  and engages the proximal-most stent  134 . An inner shaft  138  extends through pusher shaft  136  and has a nosecone  140  fixed to its distal end. Sleeve  130 , or at least a distal extremity thereof, may be a tube constructed of a resilient deformable material such as urethane or other medical grade elastomer, or may be a tubular mesh, cage, grating, or other suitable structure of flexible and resilient polymer or metal such as stainless steel or Nitinol. The elasticity and stiffness of sleeve  130  are selected to allow stents  134  to expand at the desired rate when deployed from outer shaft  132  without excessive axial or rotational displacement relative to each other or to outer shaft  132 . Sleeve  130  is resiliently biased toward an unexpanded shape so that following stent deployment, sleeve  130  returns to a generally tubular shape. Outer shaft  132  is constructed of a material with sufficient radial strength and stiffness to resist expansion of stents  134  and sleeve  130 , and may include a metallic or polymeric braid, ribs, rings or other structural reinforcement near its distal end for such purpose. 
         [0066]    The interior surface of sleeve  130  optionally may have surface features such as bumps, scales, bristles, ribs, or roughness to enhance friction with stents  134 . These features may be configured to have a grain such that they provide more friction against movement in the distal direction than in the proximal direction, or vice versa. Further, such features may be adapted to provide more friction when sleeve  130  is in an unexpanded shape than when it is expanded by stents  134 . For example, bristles may be provided that point more in the proximal direction when sleeve  130  is in its unexpanded cylindrical shape, but which point more distally or radially (perpendicular to the surface of sleeve  130 ) when sleeve  130  is expanded. This allows sleeve  130  to be more easily withdrawn from stents  134  when stents  134  are deployed. 
         [0067]    In order to deploy stents  134 , delivery catheter  129  is positioned across a vascular lesion so that nosecone  140  is disposed just distally of the distal end of the lesion. Outer shaft  132  is then retracted to expose the desired number of stents  134  (and the associated length of sleeve  130 ) which will cover the length of the lesion, as shown in  FIG. 6B . As outer shaft  132  is retracted, stents  134  are allowed to expand into contact with the lesion as shown in  FIG. 6C . Sleeve  130  controls the rate of expansion and maintains the positions of stents  134  so they are deployed precisely at the intended location. Once stents  134  are fully expanded, sleeve  130  may be retracted from between the stents and the lesion until sleeve  130  is again disposed in outer shaft  132 . Pressure is maintained on pusher shaft  136  during this process so that the stents  134  remaining in delivery catheter  129  are advanced to the distal end of sleeve  130  and outer shaft  132 . Delivery catheter  129  may then be repositioned for deployment of additional stents at other locations. 
         [0068]    Referring now to  FIGS. 7A-B , in a further embodiment, a delivery catheter  142  may be constructed largely as described in connection with  FIGS. 6A-C , including an outer shaft  144 , an expandable sleeve  146  slidably disposed therein, a pusher shaft  148 , and inner shaft  150 . A plurality of stents  152  are carried in expandable sleeve  146  (shown in  FIG. 7B ). In order to facilitate expansion, expandable sleeve  146  includes a longitudinal slit  154  in at least a distal extremity thereof. When outer shaft  144  is retracted relative to sleeve  146 , sleeve  146  may be controllably expanded by axially twisting sleeve  146  such that the opposing edges  156  along longitudinal slit  154  pivot away from one another, forming a cone shape ( FIG. 7B ). In this way, the expansion of stents  152  is further controllable after retraction of outer shaft  144  by controlling the rate of twisting of sleeve  146 . An actuator may be provided at the proximal end of delivery catheter  142  to control such twisting. Optionally, sleeve  146  may have a helical thread on its outer surface that mates with a complementary thread on the interior of outer shaft  144  such that sleeve  146  is automatically twisted as outer shaft  144  is retracted. As in the embodiment of  FIGS. 6A-C , following stent deployment, sleeve  146  is retracted from the space between the deployed stents and the vessel wall and returned within outer shaft  144 . Sleeve  146  may be resiliently biased to return to its unexpanded configuration, or may be manually twisted back to an unexpanded shape by the operator. 
         [0069]    In another embodiment, shown in  FIGS. 8A-C , delivery catheter  160  is again constructed much like delivery catheter  129  of  FIGS. 6A-C , including an outer shaft  162 , a slidable expandable sleeve  164  carrying stents  166 , a pusher shaft  168 , and an inner shaft  170 . A nosecone  172  is attached to the distal end of inner shaft  170  and has a concavity  174  at its proximal end configured to receive the distal end of sleeve  164 . A distal extremity of sleeve  164  includes a plurality of axial slits  176  defining separate deflectable longitudinal beams  178 . Sleeve  164  includes at least two, preferably four, and as many as six, eight, or more slits  176  to provide a corresponding number of longitudinal beams  178 . Longitudinal beams  178  are resiliently biased into an axial orientation wherein sleeve  164  is generally cylindrical. Longitudinal beams  178  have sufficient stiffness against lateral deflection to resist and control the expansion of stents  166 . 
         [0070]    Advantageously, by containing the distal ends of longitudinal beams  178  in concavity  174 , outer shaft  162  may be retracted to expose the desired number of stents to cover a target lesion without immediate expansion of stents  166 , as shown in  FIG. 8B . When the desired number of stents  166  is exposed, inner shaft  170  may be advanced distally relative to sleeve  164 , releasing longitudinal beams  178  from concavity  174 . This permits longitudinal beams  178  to laterally deflect, allowing stents  166  to expand, as shown in  FIG. 8C . When full expansion is achieved, longitudinal beams  178  may be retracted from between stents  166  and the vessel wall. Longitudinal beams  178  then return to their undeflected axial orientation, allowing inner shaft  170  to be retracted so as to return the distal ends of longitudinal beams  178  into concavity  174 . Inner shaft  170  and sleeve  164  may then be retracted into outer shaft  162  while maintaining pressure on pusher shaft  168 , thereby advancing additional stents  166  toward the distal end of sleeve  164  for additional deployments. 
         [0071]    In some embodiments of the stent delivery catheter of the invention, the stents themselves are configured to provide greater control and precision in stent deployment. For example,  FIGS. 9A-9B  illustrates a delivery catheter  180  having a plurality of stents  182  disposed in an outer shaft  184 . An inner shaft  186  with optional balloon  188  and nosecone  190  extends through outer shaft  184  and stents  182  and is axially movable relative thereto. A pusher shaft (not shown) is slidably disposed over inner shaft  186  and engages stents  182  for purposes of deploying stents  182  from outer shaft  186  and repositioning the remaining stents  182  within outer shaft  186 , as in earlier embodiments. In this embodiment, stents  182  comprise a plurality of struts  191  forming a series of rings  192  interconnected at joints  193 . Each ring  192  has a series of closed cells  194  interconnected circumferentially and having an “I” shape in the unexpanded configuration. 
         [0072]    As outer shaft  184  is retracted to deploy one or more stents  182 , at least a distal ring  192 ′ is configured to expand into engagement with the vessel wall before the entire length of the stent  182  is deployed from outer shaft  184  ( FIG. 9A ). Once in engagement with the lesion L in vessel V, distal ring  192 ′ anchors stent  182  in position as the remainder of the stent is deployed ( FIG. 9B ), preventing “watermelon seeding” of the stent from the catheter. The axial length of stent  182 , the length of each ring  192 , the number of rings, the stiffness of struts  191 , and the flexibility of joints  193  are all selected to optimize this deployment behavior. Each stent  182  has at least two, and preferably four or more rings  192 , each ring being about 2-5 mm in length, giving stent  182  an overall length of at least about 8-20 mm. Of course, stents of shorter or longer length are also contemplated within the scope of the invention. Lesions longer than each stent  182  may be treated by deploying multiple stents  182  end-to-end. Advantageously, each stent  182  can be deployed precisely at a desired spacing from a previously-deployed stent  182  because the distal ring  192 ′ of each stent  182  can be first allowed to expand into engagement with the vessel at the target location, anchoring the stent in position as the remainder is deployed. 
         [0073]    Rings  192  are preferably formed from a common piece of material and are integrally interconnected at joints  193 , making joints  193  relatively rigid. In this embodiment, the majority of flexibility between rings  192  is provided by struts  191  rather than by joints  193 . Alternatively, joints  193  may comprise welded connections between rings  192  which are also fairly rigid. As a further alternative, joints  193  may comprise hinge or spring structures to allow greater deflection between adjacent rings  192 , as exemplified in  FIGS. 10A-10B , described below. 
         [0074]    In the embodiment of  FIG. 10A-10B , stents  200  are constructed similarly to stents  182  of  FIGS. 9A-9B , including a plurality of interconnected rings  202  having I-shaped cells  204 . However, in this embodiment, some of rings  202  are interconnected by spring members  206  that may be elongated to increase the distance between rings  202  and that are resiliently biased into a shortened configuration to draw rings  202  toward each other. In one embodiment, spring members  206  have a wave-like shape and extend from the tip of an axial projection  208  on one ring  202  to a concave portion  210  between axial projections  208  on the adjacent ring  202 . Of course a variety of spring configurations and connection locations are possible, including zig-zags, coils, spirals, accordion or telescoping structures, and the like. Further, resilient elongatable elastomeric elements may link the adjacent rings  202 . In the illustrated embodiment, stent  200  comprises two pairs of rings  202 , with the rings of each pair interconnected by integral joints  212  as in  FIGS. 9A-B  and the pairs of rings  202  being connected to each other by spring members  206 . Stents  200  may alternatively include two, three, five, six or more rings  202 , and spring members  206  may interconnect all or only a portion of rings  202 . 
         [0075]    Spring members  206  may be formed of the same or different material as that of rings  202 , depending upon the desired performance characteristics. In addition, spring members  206  may be biodegradable so as to erode and eventually disappear, leaving the adjacent pairs of rings  202  unconnected. 
         [0076]    During deployment, as outer shaft  184  is retracted to expose a stent  200 , the distal pair of rings  202 ′ first expands into engagement with lesion L in vessel V ( FIG. 10A ). Spring members  206  elongate to allow rings  202 ′ to fully expand without pulling the second pair of rings  202 ″ from outer shaft  184 . As retraction of outer shaft  184  continues, the second pair of rings  202 ″ expands and simultaneously is drawn toward distal ring pair  182 ′ by contraction of spring members  206  ( FIG. 10B ). This results in a predictable and constant axial spacing between the adjacent pairs of rings  202 . In addition, spring members  206  maintain rotational alignment of rings  202  to maintain the interleaving of axial projections  208  without overlap. As in previous embodiments, multiple stents  200  may be deployed sequentially from delivery catheter  180  to cover longer lesions. The ability to precisely deploy each stent permits the relative axial spacing and rotational position of such stents to be controlled to avoid excessive space or overlap. 
         [0077]    In a further embodiment, shown schematically in  FIGS. 11A-11C , a delivery catheter  216  has an outer shaft  218  carrying a plurality of stents  220 . An inner shaft  222  extends through outer shaft  218  to a nosecone  224 , and a pusher shaft  226  is slidably disposed over inner shaft  222 . An anchoring balloon  228  is mounted to inner shaft  222  proximal to nosecone  224 . Anchoring balloon  228  has an axial length sufficient to frictionally engage the wall of vessel V and remain stable so as to anchor delivery catheter  216  in place as further described below. Preferably, anchoring balloon  228  has a length about equal to the length of one of stents  220 . 
         [0078]    In use, outer shaft  218  is retracted so that a first stent  220 ′ is released therefrom and expands into engagement with lesion L ( FIG. 11A ). Anchoring balloon  228  is then inflated until it engages the interior of stent  220 ′ ( FIG. 11B ). This not only stabilizes delivery catheter  216 , but may be used to further expand stent  220 ′ and/or dilate lesion L to firmly implant stent  220 ′. While keeping anchoring balloon inflated within stent  220 ′, outer shaft  218  is further retracted to release a second stent  220 ″, which expands into engagement with lesion L ( FIG. 11C ). Advantageously, anchoring balloon  228  stabilizes delivery catheter  216  and anchors it in position relative to first stent  220 ′ as second stent  220 ″ is deployed. Second stent  220 ″ is thus deployable precisely at the intended spacing and rotational position relative to first stent  220 ′. Anchoring balloon  228  may then be deflated and retracted into outer shaft  218 , with pressure maintained upon pusher shaft  226  to reposition remaining stents  220  at the distal end of inner shaft  222 . 
         [0079]    In  FIG. 13A , delivery catheter  260  is positioned adjacent a lesion L in a vessel V. Outer shaft  262  may then be retracted (solid-tipped arrows) to begin deployment of stents  268 . In  FIG. 13B , outer shaft  262  has been retracted to expose two stents  268 ′, thus allowing them to expand within the vessel V. Coil  266  expands along with expanding stents  268 ′ and remains coupled with them, thus helping prevent axial displacement (“watermelon seeding”) and in some cases rotation of stents  268 ′ relative to one another. Once stents  268 ′ have been exposed, and stents  268 ′ and coil  266  have expanded so that at least a distal portion of the distal-most stent  268 ′ is contacting the vessel wall, coil  266  is withdrawn from expanded stents  268 ′. This may be accomplished, in one embodiment, by rotating coil  266  (as shown by the solid-tipped arrow) to unscrew coil  266  from stents  268 ′. Alternatively, coil  266  may be configured to be simply pulled proximally without rotation to decouple it from stents  268 ′. Preferably, coil  266  has a radiopaque marker at its distal tip and/or at other suitable locations along its length to allow visualization via fluoroscopy. To facilitate retraction of coil  266  from stents  268 ′, coil  266  may be coated or covered with a lubricious or other friction-reducing coating or sleeve. Rotation is continued to retract coil  266  back into outer shaft  262  and the remaining unexpanded stents  268 . In  FIG. 13C , coil  266  has been retracted out of expanded stents  268 ′, thus allowing them to fully expand into contact with the inner surface of the vessel V. The process just described may be repeated as many times as desired to treat a long lesion L and/or multiple lesions L. 
         [0080]    Optionally, balloon  223  may have surface features or coatings on its periphery that enhance retention of stents  221  thereon. Such features may include structures such as scales or protuberances that are activated by pressurization of the balloon so that retention is lessened when the balloon is deflated, but heightened when the balloon is pressurized. Following stent deployment, pressure can optionally be increased in balloon  223  for post-dilation of stents  221  and the target lesion L. Balloon  223  is then deflated and retracted within sheath  229  as distal pressure is maintained against pusher  225 , repositioning stents  221  near the distal end of balloon  223  within sheath  229  for deployment at another location, as shown in  FIG. 11C . 
         [0081]    In a further embodiment, the stents in the delivery catheter of the invention may releasably interconnect with one another and/or with the pusher shaft to enable greater control and precision during deployment. As illustrated in  FIG. 12 , delivery catheter  230  carries a plurality of stents  232  having a structure much like that described above in connection with  FIGS. 9A-9B . However, in this embodiment, the axial projections  234  extending distally and proximally from stents  232  are configured to interconnect with concavities  236  on adjacent stents  232  until expanded. In one embodiment, axial projections  234  have enlarged heads  246  and concavities  236  have necks  248  that retain heads  246  within concavities  236  in the unexpanded configuration. Pusher shaft  250  has a distal end  252  having projections  254  and concavities  256  like those of stents  232 , thus being able to interconnect with the proximal-most stent  232 ′. When a stent  232 ″ expands, the interconnecting structures thereon are configured to separate from the adjacent stent or pusher shaft, thus releasing the deployed stent  232 ″ from delivery catheter  230 . In the example shown, as stent  232 ″ expands, heads  246 ″ contract in size while necks  248 ″ enlarge, thereby allowing heads  246 ″ on the expanded stent to be released from concavities  236  in the adjacent unexpanded stent, and vice versa. By exerting traction on pusher shaft  250  during the deployment process, the line of stents  232  is kept from moving distally relative to outer shaft  231 , thus preventing the deployed stent  232 ″ from “watermelon seeding” as it expands. 
         [0082]    Various types of interconnecting structures between adjacent stents and between the stents and the pusher shaft are possible within the scope of the invention, including those described in co-pending application Ser. No. 10/738,666, filed Dec. 16, 2003, which is incorporated herein by reference. Such interconnecting structures may also be breakable or frangible to facilitate separation as the stent expands. In addition, a mechanism such as an expandable balloon or cutting device may be disposed at the distal end of delivery catheter  230  to assist in separating stents  232  upon deployment. Further, the interconnections between stents may be different than the interconnection between the proximal-most stent and the pusher shaft. For example, the pusher shaft may have hooks, magnets, or other mechanisms suitable for releasably holding and maintaining traction on the proximal end of a stent until it is deployed. 
         [0083]    In another embodiment, as shown in  FIGS. 13A-13C , a delivery catheter  260  includes an outer shaft  262  (or sheath), a pusher shaft  264  slidably disposed within outer shaft  262 , a plurality of stents  268  slidably disposed within outer shaft  262 , and a coil  266  extending through catheter  260  and coupled with stents  268 . In various embodiments, coil  266  may extend through pusher shaft  264  (as shown) or be disposed around pusher shaft  264 . Coil  268  is constructed of a resilient material, such as but not limited to Nitinol™, spring stainless steel, resilient polymers, or other shape memory or super-elastic materials. Coil  266  may have various pitches, depending upon the desired spacing between adjacent loops. Coil  266  may have a relatively high pitch (individual loops spread relatively far apart), e.g., between about 2 and 6 loops disposed in each stent  268 . In other embodiments, coil  266  may have a lower pitch (individual loops closer together), e.g., greater than 6 loops, or even greater than 10 loops disposed in each stent  268 . Of course, the number of loops will vary according to the length of each stent  268 , the thickness, diameter, and flexibility of coil  266 , and other factors. Adjacent loops in coil  266  may also be in contact with each other to form a tube having a substantially continuous wall without openings. Coupling of coil  266  with stents  268  is described further below with reference to  FIGS. 14-16 . 
         [0084]    In  FIG. 13A , delivery catheter  260  is positioned adjacent a lesion L in a vessel V. Outer shaft  262  may then be retracted (solid-tipped arrows) to begin deployment of stents  268 . In  FIG. 13B , outer shaft  262  has been retracted to expose two stents  268 ′, thus allowing them to expand within the vessel V. Coil  266  expands along with expanding stents  268 ′ and remains coupled with them, thus helping prevent axial displacement (“watermelon seeding”) and in some cases rotation of stents  268 ′ relative to one another. Once stents  268 ′ have been exposed, and stents  268 ′ and coil  266  have expanded so that at least a distal portion of the distal-most stent  268 ′ is contacting the vessel wall, coil  266  is withdrawn from expanded stents  268 ′. This may be accomplished, in one embodiment, by rotating coil  266  (as shown by the solid-tipped arrow) to unscrew coil  266  from stents  268 ′. To facilitate retraction of coil  266  from stents  268 ′, coil  266  may be coated or covered with a lubricious or other friction-reducing coating or sleeve. Rotation is continued to retract coil  266  back into outer shaft  262  and the remaining unexpanded stents  268 . In  FIG. 13C , coil  266  has been retracted out of expanded stents  268 ′, thus allowing them to fully expand into contact with the inner surface of the vessel V. The process just described may be repeated as many times as desired to treat a long lesion L and/or multiple lesions L. 
         [0085]    In a preferred embodiment, adjacent stents are “keyed,” or “interleaved,” to each other, meaning that fingers or other protrusions on each end of one stent interleave with complementary fingers/protrusions on immediately adjacent stents, as described above in reference to  FIGS. 2A-B ,  4 B,  9 A-B,  10 A-B and  12 . This feature helps prevent stents from rotating relative to one another during deployment. Optionally, the distal end of the pusher shaft may also include fingers/protrusions to interleave with the proximal end of the proximal-most stent, as shown in  FIG. 12  above. Interleaving the stents with the pusher shaft helps prevent rotation of the stents relative to the outer shaft. 
         [0086]    Referring to  FIG. 14 , a stent  270  is shown in side view with a portion of a coil  272  coupled therewith. In some embodiments, coil  272  is threaded though openings  274  between struts  275  in stent  270 . This is shown in end-on cross section, in  FIG. 15 . As described above, coil  272  may be made of any of a number of resilient materials and may have a variety of different configurations in various embodiments. For example, coil  272  is shown having four loops for one stent  270 , whereas in alternative embodiments fewer or more loops per stent may be used. In an alternative embodiment (not shown), coil  272  may be disposed around the outside stents  270 , with stents  270  being capable of sliding axially through coil  272  or being helically (screw) driven by rotating coil  272 . 
         [0087]      FIG. 16  shows and end-on view of another embodiment of a stent  280  coupled with a coil  282 . In this embodiment, stent  280  includes multiple, inwardly-bent struts  284 , through which coil  282  is threaded. Thus, coil  282  is disposed entirely within the inner diameter of stent  280 . Such struts  284  may be adapted to remain in the inwardly-bent configuration only when stent  280  is collapsed in the catheter, such that struts  284  return to a position even with the cylindrical surface of stent  280  when stent  280  expands. Alternatively, struts  284  may remain in the inwardly bent configuration even when stents  280  expand. Or struts  284  may be merely elastically deflected to the inwardly bent configuration to facilitate threading coil  282  therethrough, with struts  284  being biased to return to a position along the cylindrical surface of stent  280  when coil  282  is removed. 
         [0088]    In another embodiment, illustrated in  FIG. 17 , a delivery catheter  290  includes a tubular outer shaft  292  and a tubular inner shaft  294  slidably disposed in outer shaft  202 . An evertible tube  295  is attached to the distal end of inner shaft  294  and extends distally therefrom. Evertible tube  295  has a flexible distal portion  295 ′ configured to evert (fold over on itself), and a distal end  297  attached to the distal end of outer shaft  292 . To provide flexibility, at least the flexible distal portion  295 ′ of evertible tube  295  (and optionally all of evertible tube  295 ) may be made of a flexible polymer or other bendable material and may, in some embodiments, have thinner walls than inner shaft  294  or outer shaft  292 . A pusher shaft  300  is slidably disposed in inner shaft  294 , and a plurality of stents  302  are slidably disposed within inner shaft  294  distally of pusher shaft  300 . When outer shaft  292  is retracted (slid proximally) relative to inner shaft  294 , the flexible distal portion  295 ′ of evertible tube  295  everts (i.e., bends outward and folds back on itself) and thus follows outer shaft  292  proximally. This process of sliding outer shaft  292  proximally to evert and pull flexible distal portion  295 ′ proximally causes stents  302 ′ to deploy out of the distal end  299  of the delivery catheter  290 . 
         [0089]    Axial displacement of each stent  302 ′ is controlled (and watermelon seeding is avoided) due to frictional engagement with the inner surface  296  of evertible tube  295 . To enhance retention of stents  302  in evertible tube  295 , inner surface  296  may include adherent coatings or other surface features adapted to engage and retain stents  302 . For example, inner surface  296  may comprise a layer or coating of sticky, tacky or otherwise high-friction material. Alternatively, inner surface  296  may include friction-inducing features such as roughened areas, bumps, spines, bristles, ridges, ribs, channels, grooves, or random surface irregularities. As flexible distal portion  294 ′ everts and moves proximally, stents  302 ′ peel off of adherent surface  296  in a controlled fashion. 
         [0090]    In an alternative embodiment, shown in  FIG. 18 , stents  308  are partially embedded in an inner surface  306  of an evertible tube  304 . For example, evertible tube  304  may have an inner surface  306  that softens and/or becomes malleable when heated. When stents  308  are loaded in evertible tube  304 , inner surface  306  is heated so that stents  308  are partially and releasably embedded in inner surface  306 , with portions of the softened surface material extending through the openings  307  between struts  309  in stent  308 . To deploy stents  308 , the distal end of evertible tube  304  is everted as described above, peeling inner surface  306  away from each stent  308  to release it into the vessel. Because stents  308  are embedded in inner surface  306 , they are not fully released from the catheter until evertible tube  304  is peeled completely off of stent  308 , at which time the distal end of stent  308  has expanded into contact with the vessel. Uncontrolled axial displacement of stent  308  is thus avoided. 
         [0091]    In the embodiment shown in  FIG. 19 , an evertible tube  314  includes multiple retention structures  316  on an inner surface  319 , which extend through openings  317  between struts  315  in a stent  318  to releasably hold stent  318 . Retention structures  316  are preferably adapted to extend through openings  317  and abut the inner surfaces of struts  315  to provide secure but releasable engagement with stents  318 . When the distal end of evertible tube  314  is peeled back to deploy stents  318 , retention structures  316  are adapted to be pulled out of openings  317  to release stent  318 . Retention structures  316  may comprise, for example, multiple mushroom-shaped protrusions (as shown) or alternatively, or alternatively, L-shaped, T-shaped, barbed, pyramidal, arrow-shaped, linear or hook-shaped protrusions. 
         [0092]    Retention structures  316  may be integrally formed with evertible tube  314  and made of the same flexible polymer, or alternatively may be separate structures of polymer, metal wire or other flexible material attached to evertible tube  314 . Such retention structures may be positioned to engage stent  318  at various locations along its length, e.g. at several locations along the entire length of the stent, e.g. near the proximal and distal ends (as shown), only near the proximal end, only near the distal end, only at the middle, or at another discreet location. 
         [0093]    Referring now to  FIGS. 20-23 , a further embodiment of a prosthesis delivery catheter according to the invention will be described. In this embodiment, delivery catheter  400  has a tubular outer shaft  402 , a pusher shaft  404  slidably disposed within outer shaft  402 , and an inner shaft  406  slidably disposed within pusher shaft  402 . Inner shaft  406  has a guidewire lumen extending axially therethrough for receiving a guidewire GW. A plurality of self-expanding stents  420  (not shown in  FIG. 20A ) are slidably disposed within outer shaft  402  distally of pusher shaft  404 , which can be used to exert a distal force against such stents for the deployment thereof, as described further below. A nosecone  407  is fixed to the distal end of inner shaft  406  and has a proximally-facing aperture  409  in its proximal end. Outer shaft  402  has a distal end  408  to which is attached a control member  410  defining an interior  411  in which a stent  420  may be received. Control member  410  has a plurality of flexible tines  412  extending distally and having free distal ends  414  removably received within aperture  409 . A wall  416  extending circumferentially around aperture  409  retains flexible tines  412  within aperture  409 . Nosecone  407  is movable distally relative to control member  410  to release tines  412  from aperture  409 . 
         [0094]    Control member  410  may be constructed of a polymer, metal, or other flexible and resilient material. Tines  412  are deflectable outwardly under the expansion force of stents  420 . Tines  412  are preferably biased inwardly into general alignment with the longitudinal axis of delivery catheter  400  such that free distal ends  414  remain positioned inwardly near inner shaft  406  even after release from aperture  409 . Tines  412  may include a friction-enhancing coating, texture, cover, or other surface features on their inwardly-facing surfaces to create more friction with stents  420 . Alternatively, a lubricious coating may be provided on the inner or outer surfaces of tines  412  for greater slidability. Tines  412  may have an axial length which is less than or equal to the length of one stent  420 , a length greater than the length of one stent  420 , or a length as long as the length of 2, 3 or more stents  420 . Aperture  409  may be relatively shallow, as shown, so as to receive only the free distal ends  414  of tines  412 , or may be somewhat deeper so that a portion or substantially all of the length of tines  412  is disposed within aperture  409 . 
         [0095]    As shown in  FIGS. 21A-21E , in use, delivery catheter  400  is positioned in a vessel at the treatment site with tines  412  disposed within aperture  409  on nosecone  407 . Nosecone  407  is then advanced distally relative to control member  410  (or outer shaft  402  is retracted proximally relative to nosecone  407 ) to release tines  412  from aperture  409  as shown in  FIG. 21B . Outer shaft  402  is then retracted relative to pusher shaft  404  (or pusher shaft  404  may be pushed distally) to advance one or more stents  420  out of outer shaft  402  into control member  410 , as shown in  FIG. 21C . Tines  412  exert an inward force on stents  420  to resist, but not prevent, the expansion thereof. This slows down the rate of stent expansion and also provides frictional resistance between tines  412  and the outer surface of stent  420 , thereby reducing the tendency of the stent to jump distally as it expands. As shown in  FIG. 21D , tines  412  preferably have a length selected so that before a first stent  420 A is fully expanded and released from control member  410 , a second stent  420 B is at least partially contained within control member  410 . In this way multiple stents  420  may be deployed end-to-end with a desired degree of inter-stent spacing and without overlaps or excessive gaps. Outer shaft  402  is retracted until the desired number of stents  420  has been deployed at the treatment site. Outer shaft  402  and pusher shaft  404  are then retracted together to slidably decouple tines  412  from the deployed stents  420 , as shown in  FIG. 21E . Nosecone  407  may then be retracted through the deployed stents until tines  412  are positioned in aperture  409 . The device can then be repositioned at a new treatment site for additional deployments. 
         [0096]      FIG. 22  illustrates an alternative embodiment of control member  410 , in which multiple webs  422  are disposed between tines  412 . Webs  422  are preferably made of a flexible, resilient and distensible elastomer configured to radially expand or stretch under the expansion force of a stent  420 . Webs  422  may comprise a substantially continuous, non-porous sheet, or may have openings, or may be comprised of a plurality of woven strands. Optionally, webs  422  may extend over the outer and/or inner surfaces of tines  412 , and may connect to form a continuous tubular structure. Webs  422  may serve to provide additional resistance to stent expansion, may provide a protective surface around stent  420  and/or tines  412 , and may also have lubricity on their outer and/or inner surfaces to facilitate withdrawal of tines  412  from stents  420  following deployment. 
         [0097]      FIG. 23  illustrates a further embodiment in which control member  410  comprises a single distensible tubular member  424  rather than having tines  412 . Tubular member  424  is preferably a flexible, resilient, and distensible elastomer configured to stretch or expand radially under the expansion force of a stent  420 . Tubular member  424  is normally in a radially contracted, generally cylindrical shape without stents  420  positioned therein, with its distal end  426  adapted for positioning in aperture  409  in nosecone  407 . As with web  422 , tubular member  424  may be a substantially continuous, non-porous sheet, or it may have openings, or it may be comprised of a plurality of woven strands. In addition, tubular member  424  may have a lubricious outer or inner surface to facilitate withdrawal from stents  420  following deployment. The inner surface of tubular member  424  may also include friction enhancing coatings, textures, or features to enhance retention of stents  420  therein. 
         [0098]    While the above is a complete description of the preferred embodiments of the invention, various alternatives, modifications, improvements and additions are possible without departing from the scope thereof, which is defined by the claims.