Abstract:
A stent delivery device for deploying a low column strength stent may include an inner member having a distal region and a stent receiving area disposed therein. A low column strength stent convertible between a compressed configuration and an expanded configuration may be disposed on the stent receiving area. The stent receiving area may include a soft durometer polymer configured to permit the low column strength stent to sink into the soft durometer polymer when the low column strength stent is in the compressed configuration. An outer member may be moveable between an extended position in which the outer member extends over the stent and a retracted position in which the outer member is proximal of the stent.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application Ser. No. 62/318,283 filed on Apr. 5, 2016, the disclosure of which is incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention pertains to medical devices and methods for making and using medical devices. More particularly, the present invention pertains to stent delivery systems. 
       BACKGROUND 
       [0003]    A wide variety of intracorporeal medical devices have been developed for medical use, for example, intravascular use. Some of these devices include stent delivery systems. These devices are manufactured by any one of a variety of different manufacturing methods and may be used according to any one of a variety of methods. Of the known stent delivery devices and methods for making and using the same, each has certain advantages and disadvantages. There is an ongoing need to provide alternative stent delivery devices as well as alternative methods for making and using stent delivery devices. 
       SUMMARY 
       [0004]    The disclosure is directed to several alternative designs, materials and methods of manufacturing medical device structures and assemblies, and uses thereof. A stent delivery device for deploying a low column strength stent is disclosed. 
         [0005]    One exemplary stent delivery device includes an inner member including a distal region, and a stent receiving area disposed within the distal region of the inner member. The device also includes a low column strength stent disposed on the stent receiving area and convertible between a compressed configuration and an expanded configuration. The stent receiving area includes a soft durometer polymer configured to permit the low column strength stent to sink into the soft durometer polymer when the low column strength stent is in the compressed configuration. The device also includes an outer member movable between an extended position in which the outer member extends over the low column strength stent and maintains the low column strength stent in the compressed configuration and a retracted position in which the outer member is proximal of the low column strength stent, permitting the low column strength stent to expand into the expanded configuration. 
         [0006]    Alternatively or additionally to any of the embodiments above, the low column strength stent is at least partially embedded into the soft durometer polymer when the low column strength stent is in the compressed configuration. 
         [0007]    Alternatively or additionally to any of the embodiments above, the low column strength stent comprises an esophageal stent. 
         [0008]    Alternatively or additionally to any of the embodiments above, the low column strength stent comprises a woven stent. 
         [0009]    Alternatively or additionally to any of the embodiments above, the low column strength stent comprises a laser cut stent. 
         [0010]    Alternatively or additionally to any of the embodiments above, the low durometer polymer has a Shore D hardness value ranging from about 10 to about 80. 
         [0011]    Alternatively or additionally to any of the embodiments above, the low durometer polymer includes at least one of a polyolefin, a vinyl, a silicone and a fluoropolymer. 
         [0012]    Alternatively or additionally to any of the embodiments above, the outer member has an inner diameter and the stent receiving region of the inner member has an outer diameter, and a difference between the inner diameter of the outer member and the outer diameter of the stent receiving region of the inner member is less than a wall thickness of the low column strength stent. 
         [0013]    A stent delivery device that is configured to laterally constrain a stent during deployment in order to help maintain a three dimensional shape of the stent is disclosed. The stent delivery device includes an inner member including a distal region, and a stent receiving area disposed within the distal region of the inner member. The stent receiving area includes a soft durometer polymer configured to laterally constrain a stent during delivery by allowing the stent to at least partially embed itself in the soft durometer polymer when the stent is in a compressed configuration. The device also includes an outer member movable between an extended position in which the outer member extends over the stent receiving area and a retracted position in which the outer member is proximal of the stent receiving area. The stent is able to maintain its three dimensional shape during deployment by virtue of the stent being at least partially embedded in the soft durometer polymer as the outer member is withdrawn proximally in order to allow the stent to expand into an expanded configuration. 
         [0014]    Alternatively or additionally to any of the embodiments above, the soft durometer polymer permits a partially deployed stent to be recaptured by extending the outer member back over the partially deployed stent, compressing the partially deployed stent back into its compressed configuration in which the stent is at least partially embedded in the soft durometer polymer. 
         [0015]    Alternatively or additionally to any of the embodiments above, the stent delivery device further comprises a woven stent disposed within the stent receiving area. 
         [0016]    Alternatively or additionally to any of the embodiments above, the stent delivery device further comprises a laser cut stent disposed within the stent receiving area. 
         [0017]    Alternatively or additionally to any of the embodiments above, the low durometer polymer has a Shore D hardness value ranging from about 10 to about 80. 
         [0018]    Alternatively or additionally to any of the embodiments above, the low durometer polymer includes at least one of a polyolefin, a vinyl, a silicone and a fluoropolymer. 
         [0019]    A method of delivering a low column strength stent using a stent delivery device having a compliant stent-receiving area and a deployment sheath deployable over the stent-receiving area is disclosed. The method includes advancing the stent delivery device to a stent deploying position with a low column strength stent disposed within the compliant stent receiving area, the stent in a compressed configuration in which the stent is at least partially embedded within the compliant stent receiving area. The method further includes starting to deploy the stent by withdrawing the deployment sheath proximally, allowing a portion of the stent to expand from the compressed configuration to an expanded deployment configuration. The method further includes continuing to deploy the stent by further withdrawing the deployment sheath proximally, allowing a further portion of the stent to expand from the compressed configuration to the expanded deployment configuration. The method further includes recapturing the partially deployed stent by advancing the deployment sheath distally over the partially deployed stent to compress the partially deployed stent back into the compressed configuration in which the stent is at least partially embedded within the compliant stent receiving area. 
         [0020]    Alternatively or additionally to any of the embodiments above, the compliant stent receiving area is configured such that as the deployment sheath is advanced distally over the partially deployed stent to compressed the partially deployed stent back into the compressed configuration, the compliant stent receiving area provides a holding force on the stent that exceeds a frictional force applied to the stent via the deployment sheath. 
         [0021]    Alternatively or additionally to any of the embodiments above, the deployment sheath is dimensioned such that as the deployment sheath is advanced distally over the partially deployed stent, the deployment sheath applies a compressive force to embed the partially deployed stent into the compliant stent receiving area. 
         [0022]    Alternatively or additionally to any of the embodiments above, the method further comprises deploying the recaptured stent by withdrawing the deployment sheath proximally. 
         [0023]    Alternatively or additionally to any of the embodiments above, the compliant stent receiving area comprises a polymer having a Shore D hardness value of about 10 to about 80. 
         [0024]    Alternatively or additionally to any of the embodiments above, the low column strength stent comprises a stent that is easily distorted from its native three dimensional shape. 
         [0025]    The above summary of some embodiments is not intended to describe each disclosed embodiment or every implementation of the present disclosure. The Figures, and Detailed Description, which follow, more particularly exemplify these embodiments. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0026]    The aspects of the disclosure may be further understood in consideration of the following detailed description of various embodiments in connection with the accompanying drawings, in which: 
           [0027]      FIG. 1  is a side view of an example stent delivery system; 
           [0028]      FIG. 2  is a partial cross-sectional view of a distal portion of the stent delivery system of  FIG. 1 ; 
           [0029]      FIG. 3  is a partial cross-sectional view of a distal portion of the stent delivery system of  FIG. 1 ; 
           [0030]      FIG. 4  is a partial cross-sectional view of a distal portion of the stent delivery system of  FIG. 1 , shown with a stent being partially deployed; 
           [0031]      FIG. 5A  is a side view of an inner member forming part of the distal portion of  FIGS. 3 and 4 ; 
           [0032]      FIG. 5B  is a side view of an inner member illustrating another polymer layer configuration; 
           [0033]      FIG. 5C  is a side view of an inner member illustrating another polymer layer configuration; 
           [0034]      FIG. 5D  is a side view of an inner member illustrating another polymer layer configuration; 
           [0035]      FIG. 6A  is an enlarged cross-sectional view of the inner member shown in  FIG. 5 , in combination with a stent; 
           [0036]      FIG. 6B  is a schematic enlarged view of a portion of  FIG. 6A , illustrating a relative embedding depth of the stent; 
           [0037]      FIG. 6C  is a schematic enlarged view of a portion of  FIG. 6A , illustrating another relative embedding depth of the stent; 
           [0038]      FIGS. 7A through 7C  provide an illustrative but non-limiting example of deploying a low column strength stent; and 
           [0039]      FIGS. 8A through 8C  provide an illustrative but non-limiting example of recapturing a low column strength stent that has been partially deployed. 
       
    
    
       [0040]    While the disclosure is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure. 
       DESCRIPTION 
       [0041]    For the following defined terms, these definitions shall be applied, unless a different definition is given in the claims or elsewhere in this specification. 
         [0042]    Definitions of certain terms are provided below and shall be applied, unless a different definition is given in the claims or elsewhere in this specification. 
         [0043]    All numeric values are herein assumed to be modified by the term “about”, whether or not explicitly indicated. The term “about” generally refers to a range of numbers that one of skill in the art would consider equivalent to the recited value (i.e., having the same function or result). In many instances, the term “about” may be indicative as including numbers that are rounded to the nearest significant figure. 
         [0044]    The recitation of numerical ranges by endpoints includes all numbers within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5). 
         [0045]    Although some suitable dimensions, ranges and/or values pertaining to various components, features and/or specifications are disclosed, one of skill in the art, incited by the present disclosure, would understand desired dimensions, ranges and/or values may deviate from those expressly disclosed. 
         [0046]    As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include or otherwise refer to singular as well as plural referents, unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term “or” is generally employed to include “and/or,” unless the content clearly dictates otherwise. 
         [0047]    The following detailed description should be read with reference to the drawings in which similar elements in different drawings are numbered the same. The detailed description and the drawings, which are not necessarily to scale, depict illustrative embodiments and are not intended to limit the scope of the disclosure. The illustrative embodiments depicted are intended only as exemplary. Selected features of any illustrative embodiment may be incorporated into an additional embodiment unless clearly stated to the contrary. 
         [0048]      FIG. 1  illustrates an example stent delivery system  10 . The delivery system  10  may include an elongate shaft  12  and a handle  14  coupled to shaft  12 . In general, system  10  may be used to deliver a suitable stent, graft, endoprosthesis or the like to an area of interest within a body lumen of a patient. The body lumen may be a blood vessel located near the heart (e.g., within or near a cardiac vessel), within a peripheral vessel, within a neurological vessel, or at any other suitable location. Deployment of the stent may include the proximal retraction of an outer member or deployment sheath (not seen in this Figure), which overlies the stent. In some cases, the outer member or deployment sheath may be moved either distally or proximally by actuating an actuation member such as an actuation member  18  or an actuation member  20 , both of which are generally disposed within the handle  14 . In the example illustrated in  FIG. 1 , actuation member  18  is a thumb wheel that can be rotated by a clinician in order actuate the outer the outer member or deployment sheath relative to the stent. The elongate shaft  12  may include a distal region  22 , shown in greater detail in  FIG. 2 . 
         [0049]      FIG. 2  may be considered as being an enlarged partial cross-sectional view of the distal region  22  (of the elongate shaft  12 ). In some cases, as illustrated, the distal region  22  includes an outer member or deployment sheath  24  that is slidingly disposed over an inner member  26 , which is shown in phantom extending through the lumen of the outer member or deployment sheath  24 . In some cases, a stent to be deployed may be secured about the inner member  26  and constrained in a compressed configuration within the lumen of the deployment sheath  24  for delivery via the deployment sheath  24 . In some instances, the inner member  26  may include an atraumatic tip  25  at a distal end of the inner member  26  located distal of the distal end of the outer member  24 . In some cases, while not illustrated, a distal end  23  of the deployment sheath  24  may include an atraumatic tip. In some instances, the inner member  26  may be a tubular member including a lumen  29 , such as a guidewire lumen, extending therethrough. A stent  28 , which may for example be a braided stent, a knitted stent, a woven stent or a laser cut stent, is shown in phantom in  FIG. 3 . In some cases, the stent  28  may be an esophageal stent, but this is not required. 
         [0050]    Turning to  FIG. 4 , the stent  28  has been partially deployed by moving the deployment sheath  24  in a proximal direction relative to the stent  28  and the inner member  26 . The stent  28  may be considered as being a self-expanding stent, meaning that once unconstrained, the stent  28  will automatically expand from a compressed configuration to an expanded configuration. As can be seen, a distal end region of the stent  28  begins to expand as soon as the distal end region of the stent  28  is no longer constrained by the deployment sheath  24 . While shown partially deployed, it will be appreciated that as the deployment sheath  24  is moved further in a proximal direction as indicated by an arrow  30 , more and more of the stent  28  will regain its expanded configuration, until the entire stent  28  has been exposed, and thus unconstrained by the deployment sheath  24 . 
         [0051]    In some cases, the stent  28  may be configured such that it has a low column strength, meaning for example that it is easily deformed or otherwise altered from a native three dimensional shape of the stent  28 , or that the stent  28  contains certain sections, individual components (e.g., filaments), or regions that are permitted to slide or move relative to adjacent sections, individual components (e.g., filaments), or regions at least partially along the longitudinal length of the stent  28  when the stent  28  is deployed. In some instances, for example, the frictional forces between the deployment sheath  24  and the stent  28 , caused by pulling the deployment sheath  24  proximally to release the stent  28  can itself stretch or pull individual components (e.g., filaments) of the stent  28 , such as individual windings and/or filaments, relative to other individual components (e.g., filaments) of the stent  28 , thereby causing the stent  28  to stretch or otherwise deform from a native or otherwise intended three dimensional shape of the stent  28 . In some cases, the forces applied to the stent  28  by moving the deployment sheath  24  in a distal direction as indicated by an arrow  32 , such as for example if there is a desire to recapture the stent  28  after partial deployments in order to move it prior to redeployment, can cause further deformation of the stent  28 . In some instances, the frictional force between the stent  28  and the deployment sheath  24  may be about 8.9 N to about 17.8 N (2 lbf to about 4 lbf), for example, whereas, the column strength of the stent  28  in its constrained configuration may be less than 17.8 N (4 lbf), less than 13.3 N (3 lbf), or less than 8.9 N (2 lbf). In other words, the column strength of the stent  28  in the constrained configuration may be sufficiently low such that the length of the stent  28  will be longitudinally stretched (e.g., filament segments move longitudinally relative to adjacent filament segments) when subjected to an axial force of greater than 8.9 N (2 lbf), greater than 13.3 N (3 lbf), or greater than 17.8 N (4 lbf) caused by frictional forces between the stent  28  and the deployment sheath  24  as the deployment sheath  24  is pulled proximally off of the stent  28  to deploy the stent  28  and/or the length of the stent  28  will be longitudinally collapsed (e.g., filament segments move longitudinally relative to adjacent filament segments) when subjected to an axial force of greater than 8.9 N (2 lbf), greater than 13.3 N (3 lbf), or greater than 17.8 N (4 lbf) caused by frictional forces between the stent  28  and the deployment sheath  24  as the deployment sheath  24  is pushed distally over the stent  28  to recapture the stent  28 . 
         [0052]    Accordingly, in some cases the inner member  26  may be configured to help maintain the three dimensional shape of the stent  28  during deployment, recapturing and/or redeployment. In some cases, for example, maintaining the three dimensional shape of the stent  28  may be defined in terms of percent elongation (stretching), referring to a change in length relative to a nominal length during deployment, recapture and/or redeployment. For example, it may be reasonable to define a percent of elongation that is less than about ten percent, or in some cases less than about five percent. In some cases, maintaining the three dimensional shape of the stent  28  may be defined in terms of percent compression, referring to a change in length relative to a nominal length during deployment, recapture and/or deployment. For example, it may be reasonable to define a percent of compression that is less than about ten percent, or in some cases less than about five percent. Another way to consider maintaining the three dimensional shape of the stent  28  may be to state that the stent  28  retains about 95% to about 105% of its length during deployment, recapture and/or deployment. It will be appreciated that as the stent  28  changes in length, it may also change in radius. As the stent  28  elongates, the radius of the stent  28  may correspondingly decrease. Conversely, if the stent  28  shortens, the radius of the stent  28  may correspondingly increase. 
         [0053]    As seen in  FIG. 5A , which is a cross-sectional view of the inner member  26 , the inner member  26  may include a shaft  34  and a polymeric coating or layer  36   a . The inner member  26  may be considered as including a stent receiving area  38 . In some cases, the stent receiving area  38  may include a portion of the polymeric layer  36   a . In some instances, the polymeric layer  36  may essentially form the stent receiving area  38 . In  FIG. 5A , the polymeric layer  36   a  is shown as having a smooth outer surface, with a relatively constant outer diameter. In some cases, the polymeric layer  36   a  may have other configurations. For example, in  FIG. 5B , a polymeric layer  36   b  has an undulating or wave-like outer surface configuration. In some cases, individual windings or filaments  40  of the stent  28  may, for example, fit into valleys or low spots in the undulating polymeric layer  36   b  between adjacent peaks or high spots in the undulating polymeric layer  36   b .  FIG. 5C  shows a polymeric layer  36   c  that includes a plurality of fingers  37  that extend outward from the polymeric layer  36   c . In some cases, individual windings or filaments  40  of the stent  28  may fit between adjacent fingers  37 . While  FIG. 5C  is a cross-sectional view, it will be appreciated that the polymeric layer  36   c  may include a plurality of fingers  37  that are axially spaced along the shaft  34  as well as being radially spaced about the shaft  34 .  FIG. 5D  illustrates another configuration in which the polymer layer is divided into distinct strips  39 . While two strips  39  are illustrated, it will be appreciated that any number of individual strips  39  may be used. While the strips  39  are illustrated as being axially aligned, in some cases the strips  39  may be radially aligned, helically aligned, and the like. 
         [0054]    In some cases, the polymeric layer  36   a ,  36   b ,  36   c  may be a soft durometer polymer such as a polyolefin, a vinyl, a fluoropolymer or a silicone. In some instances, the polymeric layer  36   a ,  36   b ,  36   c  may be formed of a polymer having a Shore D hardness value in the range of about 10 to about 80, or a range of about 20 to about 70, or a range of about 30 to about 60, or a range of about 40 to about 50, where the Shore D hardness value is determined using known testing procedures. While the polymer layer  36   a ,  36   b ,  36   c  is shown in  FIGS. 5A, 5B, 5C and 5D  as being applied to an outer surface of the shaft  34 , it will be appreciated that in some cases the polymeric layer  36   a ,  36   b ,  36   c  may be inset into an outer surface of the shaft  34 . In some cases, the inner member  26  may itself be formed of the soft durometer polymer. 
         [0055]    In some cases, the polymeric layer  36   a ,  36   b ,  36   c  may be soft enough to enable the stent  28  to be at least partially embedded within the polymeric layer  36   a ,  36   b ,  36   c  when the stent  28  is in its compressed configuration. In some instances, the deployment sheath  24  may be dimensioned, relative to the inner member  26 , such that the deployment sheath  24  pushes the stent  28  into the polymeric layer  36   a ,  36   b ,  36   c . For example, in some cases, a difference between an inner diameter of the deployment sheath  24  and an outer diameter of the polymer layer  36   a ,  36   b ,  36   c  of the inner member  26  may be less than a wall thickness of the stent  28 . Accordingly, when the stent  28  is positioned within the lumen of the deployment sheath  24  and surrounding the polymer layer  36   a ,  36   b ,  36   c  of the inner member  26 , the stent  28  may be pressed into the polymer layer  36   a ,  36   b ,  36   c , thereby deforming and/or displacing a portion of the polymer layer  36 . 
         [0056]    It will be appreciated that embedding the stent  28  at least partially into the polymeric layer  36   a ,  36   b ,  36   c  will be beneficial both in helping to hold the stent  28  in place as the deployment sheath  24  is moved proximally or distally relative to the inner member  26  (and thus relative to the stent  28 ) as well as helping the stent  28  to resist applied forces that would otherwise tend to longitudinally stretch, longitudinally compress or otherwise deform the stent  28 . In some cases, this may be considered as laterally constraining the stent  28  in order to maintain its three dimensional shape.  FIG. 6A  is a cross-sectional view of a portion of the stent receiving area  38 , showing individual filaments, windings, struts or other stent components  40  partially embedded into the polymeric layer  36   a ,  36   b ,  36   c.    
         [0057]    It will be appreciated that in some cases the stent  28  may be farther embedded into the polymeric layer  36   a ,  36   b ,  36   c  while in other cases the stent  28  may be relatively less embedded into the polymeric layer  36   a ,  36   b ,  36   c .  FIGS. 6B and 6C  are enlarged views of a single stent component  40  embedded into a polymeric layer generically identified as polymeric layer  36 . A dimension D 1  may be considered as being a radial thickness (e.g., diameter) of the stent component  40  measured from an radially inner surface of the stent component  40  to a radially outer surface of the stent component  40  while a dimension D 2  may be considered as indicating a distance that the stent component  40  has been embedded into the polymeric layer  36 . A ratio between D 1  and D 2 , such as D 2 /D 1 , may define a level of embedding. In  FIG. 6B , the stent component  40  is not as deeply embedded as in  FIG. 6C . This may, for example, be a result in a different durometer polymer being used for the polymeric layer  36 . This may also result, at least in part, from a different sized stent and thus a different value for D 1 . Accordingly, the ratio D 2 /D 1  will be relatively smaller in the situation shown in  FIG. 6B  and relatively larger in the situation shown in  FIG. 6C . In some cases, the ratio D 2 /D 1  may vary from about 0.1, indicating a relatively small level of embedding, to about 1.0, indicating that the stent  28  is completely embedded. In some cases, the ratio D 2 /D 1  may vary from about 0.2 to about 0.8, or about 0.3 to about 0.7, or about 0.4 to about 0.5. In some cases it may be desirable to have the stent component  30  embedded into the polymer layer  36  at least one-half or greater than one-half of the radial thickness (e.g., diameter) of the stent component  40  measured from an radially inner surface of the stent component  40  to a radially outer surface of the stent component  40  (i.e., D 2 ≧D 1 /2). The degree that the stent component  40  is embedded in the polymer layer  36  may prevent the stent component  40  from moving axially relative to the polymer layer  36  during deployment, recapturing, and/or redeployment of the stent  28 . 
         [0058]      FIGS. 7A through 7C  provide an illustrative but non-limiting example of deploying a low column strength stent such as the stent  28 . In  FIG. 7A , the stent  28  is seen disposed over the inner member  26 , in a compressed configuration, with the deployment sheath  24  (for simplicity shown as being transparent) disposed over the stent  28 , thereby holding the stent  28  in the compressed configuration. While not clearly shown, it is anticipated that the stent  28  is at least partially embedded into the soft durometer polymer that, as discussed for example with respect to  FIG. 5 , forms at least an outer surface of the inner member  26 . Moving to  FIG. 7B , the deployment sheath  24  has been moved proximally, in the direction indicated by the arrow  30 . As can be seen, a portion of the stent  28 , freed from constrainment by the deployment sheath  24 , has begun to expand into its expanded configuration. A portion of the polymeric layer  36  can be seen under the expanded portion of the stent  28 . Moving to  FIG. 7C , it can be seen that the stent  28  has been almost completely deployed as the deployment sheath  24  has been withdrawn further proximally relative to the stent  28 . 
         [0059]      FIGS. 8A through 8C  provide an illustrative but non-limiting example of recapturing a low column strength stent such as the stent  28 . In some cases, there may be a desire to recapture a partially deployed stent in order to move the stent axially and/or rotationally prior to fully and finally deploying the stent  28 .  FIG. 8A  is similar to  FIG. 7C , and shows the stent  28  as being substantially (but not completely) deployed. Moving to  FIG. 8B , it can be seen that the deployment sheath  24  has been moved distally relative to the stent  28 , in the direction indicated by the arrow  32 . As the deployment sheath  24  moves distally relative to the stent  28 , the deployment sheath  24  compresses the stent  28  back down into its compressed configuration, and at least partially embeds the stent  28  into the polymer layer  36 . As a result, the polymer layer  36  helps maintain the native three dimensional shape of the stent  28 , and the holding forces provided by the embedded elements of the stent  28  are at least as strong if not stronger than any frictional forces created between the moving deployment sheath  24  and the stent  28 . Moving to  FIG. 8C , the stent  28  has been almost completely recaptured, so that it can be repositioned and redeployed, or perhaps completely removed if, for example, a decision is made that a different size or type of stent is more appropriate for a particular physiology. 
         [0060]    Various components of the stent deployment system  10 , as well as the stent  28 , may be made from a metal, metal alloy, polymer (some examples of which are disclosed below), a metal-polymer composite, combinations thereof, and the like, or any other suitable material. Some examples of suitable metals and metal alloys include stainless steel, such as 304V, 304L, and 316LV stainless steel; mild steel; nickel-titanium alloy such as linear-elastic and/or super-elastic nitinol; other nickel alloys such as nickel-chromium-molybdenum alloys (e.g., UNS: N06625 such as INCONEL® 625, UNS: N06022 such as HASTELLOY® C-22®, UNS: N10276 such as HASTELLOY® C276®, other HASTELLOY® alloys, and the like), nickel-copper alloys (e.g., UNS: N04400 such as MONEL® 400, NICKELVAC® 400, NICORROS® 400, and the like), nickel-cobalt-chromium-molybdenum alloys (e.g., UNS: R30035 such as MP35-N® and the like), nickel-molybdenum alloys (e.g., UNS: N10665 such as HASTELLOY® ALLOY B2®), other nickel-chromium alloys, other nickel-molybdenum alloys, other nickel-cobalt alloys, other nickel-iron alloys, other nickel-copper alloys, other nickel-tungsten or tungsten alloys, and the like; cobalt-chromium alloys; cobalt-chromium-molybdenum alloys (e.g., UNS: R30003 such as ELGILOY®, PHYNOX®, and the like); platinum enriched stainless steel; titanium; combinations thereof; and the like; or any other suitable material. 
         [0061]    As alluded to above, within the family of commercially available nickel-titanium or nitinol alloys, is a category designated “linear elastic” or “non-super-elastic” which, although may be similar in chemistry to conventional shape memory and super elastic varieties, may exhibit distinct and useful mechanical properties. Linear elastic and/or non-super-elastic nitinol may be distinguished from super elastic nitinol in that the linear elastic and/or non-super-elastic nitinol does not display a substantial “superelastic plateau” or “flag region” in its stress/strain curve like super elastic nitinol does. Instead, in the linear elastic and/or non-super-elastic nitinol, as recoverable strain increases, the stress continues to increase in a substantially linear, or a somewhat, but not necessarily entirely linear relationship until plastic deformation begins or at least in a relationship that is more linear that the super elastic plateau and/or flag region that may be seen with super elastic nitinol. Thus, for the purposes of this disclosure linear elastic and/or non-super-elastic nitinol may also be termed “substantially” linear elastic and/or non-super-elastic nitinol. 
         [0062]    In at least some embodiments, portions or all the stent deployment system  10  may also be doped with, made of, or otherwise include a radiopaque material including those listed herein or other suitable radiopaque materials. 
         [0063]    In some embodiments, a degree of MRI compatibility is imparted into system  10 . For example, to enhance compatibility with Magnetic Resonance Imaging (MRI) machines, it may be desirable to make part or all of the stent deployment system  10  in a manner that would impart a degree of MRI compatibility, such as by using materials that do not substantially distort the image and create substantial artifacts (artifacts are gaps in the image). Certain ferromagnetic materials, for example, may not be suitable because they may create artifacts in an MRI image. Portions of the stent deployment system  10  may also be made from a material that the MRI machine can image. Some materials that exhibit these characteristics include, for example, tungsten, cobalt-chromium-molybdenum alloys (e.g., UNS: R30003 such as ELGILOY®, PHYNOX®, and the like), nickel-cobalt-chromium-molybdenum alloys (e.g., UNS: R30035 such as MP35-N® and the like), nitinol, and the like, and others. 
         [0064]    Some examples of suitable polymers that may be used include polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene (ETFE), fluorinated ethylene propylene (FEP), polyoxymethylene (POM, for example, DELRIN® available from DuPont), polyether block ester, polyurethane (for example, Polyurethane 85A), polypropylene (PP), polyvinylchloride (PVC), polyether-ester (for example, ARNITEL® available from DSM Engineering Plastics), ether or ester based copolymers (for example, butylene/poly(alkylene ether) phthalate and/or other polyester elastomers such as HYTREL® available from DuPont), polyamide (for example, DURETHAN® available from Bayer or CRISTAMID® available from Elf Atochem), elastomeric polyamides, block polyamide/ethers, polyether block amide (PEBA, for example available under the trade name PEBAX®), ethylene vinyl acetate copolymers (EVA), silicones, polyethylene (PE), Marlex high-density polyethylene, Marlex low-density polyethylene, linear low density polyethylene (for example REXELL®), polyester, polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polytrimethylene terephthalate, polyethylene naphthalate (PEN), polyetheretherketone (PEEK), polyimide (PI), polyetherimide (PEI), polyphenylene sulfide (PPS), polyphenylene oxide (PPO), poly paraphenylene terephthalamide (for example, KEVLAR®), polysulfone, nylon, nylon-12 (such as GRILAMID® available from EMS American Grilon), perfluoro(propyl vinyl ether) (PFA), ethylene vinyl alcohol, polyolefin, polystyrene, epoxy, polyvinylidene chloride (PVdC), poly(styrene-b-isobutylene-b-styrene) (for example, SIBS and/or SIBS 50A), polycarbonates, ionomers, biocompatible polymers, other suitable materials, or mixtures, combinations, copolymers thereof, polymer/metal composites, and the like. In some embodiments the sheath can be blended with a liquid crystal polymer (LCP). For example, the mixture can contain up to about 6% LCP. 
         [0065]    In some embodiments, the exterior surface of the system  10  may include a coating, for example a lubricious, a hydrophilic, a protective, or other type of coating. Hydrophobic coatings such as fluoropolymers provide a dry lubricity which improves device handling and exchanges. Lubricious coatings improve steerability and improve lesion crossing capability. Suitable lubricious polymers may include silicone and the like, polymers such as high-density polyethylene (HDPE), polytetrafluoroethylene (PTFE), polyarylene oxides, polyvinylpyrolidones, polyvinylalcohols, hydroxy alkyl cellulosics, algins, saccharides, caprolactones, and the like, and mixtures and combinations thereof. Hydrophilic polymers may be blended among themselves or with formulated amounts of water insoluble compounds (including some polymers) to yield coatings with suitable lubricity, bonding, and solubility. Some other examples of such coatings and materials and methods used to create such coatings can be found in U.S. Pat. Nos. 6,139,510 and 5,772,609, the entire disclosures of which are incorporated herein by reference. 
         [0066]    It should be understood that this disclosure is, in many respects, only illustrative. Changes may be made in details, particularly in matters of shape, size, and arrangement of steps without exceeding the scope of the invention. The invention&#39;s scope is, of course, defined in the language in which the appended claims are expressed.