Abstract:
Medical devices and methods for making and using medical devices are disclosed. An example medical device may include an elongate shaft including a first tubular member and a second tubular member. A balloon may be coupled to the shaft. A first member may be coupled to the first tubular member and positioned within the balloon. A second member may be coupled to the first tubular member and positioned within the balloon. A medical implant may be coupled to the shaft and positioned adjacent to the balloon.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of U.S. Ser. No. 12/715,016, filed Mar. 1, 2010; which is a continuation of U.S. Ser. No. 10/737,497, filed Dec. 16, 2003 and issued as U.S. Pat. No. 7,670,364; which is a continuation of U.S. Ser. No. 09/794,648, filed Feb. 27, 2001 and issued as U.S. Pat. No. 6,663,660; which is a continuation of U.S. Ser. No. 09/418,277, filed Oct. 14, 1999 and issued as U.S. Pat. No. 6,203,558; which is a continuation of U.S. Ser. No. 08/916,554, filed Aug. 22, 1997 and issued as U.S. Pat. No. 5,968,069; which is a Continuation-in part application based on U.S. Ser. No. 08/807,791, filed Feb. 28, 1997 and issued as U.S. Pat. No. 6,077,273, U.S. Ser. No. 08/701,979, filed Aug. 23, 1996 and issued as U.S. Pat. No. 6,395,008, U.S. Ser. No. 08/697,453, filed Aug. 23, 1996 abandoned, and U.S. Ser. No. 08/702,150, filed Aug. 23, 1996 and issued as U.S. Pat. No. 6,007,543; all of which are incorporated by reference in their entirety. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to an assembly and method for delivering and deploying an inflation expandable stent, particularly within a lumen of a body vessel. More specifically, this invention relates to stent securement devices most notably positioned between the balloon and the inner shaft of the catheter. 
     BACKGROUND OF THE INVENTION 
     Stents and stent delivery assemblies are utilized in a number of medical procedures and situations, and as such their structure and function are well-known. A stent is a general cylindrical prosthesis introduced via a catheter into a lumen of a body vessel in a configuration having a generally reduced diameter and then expanded to the diameter of the vessel. In its expanded configuration, the stent supports and reinforces the vessel walls while maintaining the vessel in an open, unobstructed condition. 
     Both self-expanding and inflation expandable stents are well-known and widely available. Self-expanding stents must be maintained under positive external pressure in order to maintain their reduced diameter configuration during delivery of the stent to its deployment site. Inflation expandable stents (also known as balloon expandable stents) are crimped to their reduced diameter about the delivery catheter, positioned at the deployment site, and then expanded to the vessel by diameter by fluid inflation of the balloon positioned between the stent and the delivery catheter. The present invention is particularly concerned with enhanced stent securement and safer stent loading in the delivery and deployment of balloon expandable stents. 
     In angioplasty procedure, there may be restenosis of the artery, which either necessitates another angioplasty procedure, a surgical bi-pass procedure, or some method of repairing or strengthening the area. To prevent restenosis and strengthen the area, a physician can implant an intravascular prosthesis for maintaining vascular patency, i.e. a stent, inside the artery at the lesion. The stent is expanded to a larger diameter for placement in the vasculature, often by the balloon portion of the catheter. Stents delivered to a restricted coronary artery, expanded to a larger diameter as by a balloon catheter, and left in place in the artery at the site of a dilated lesion are shown in U.S. Pat. No. 4,740,207 to Kreamer; U.S. Pat. No. 5,007,926 to Derbyshire; U.S. Pat. No. 4,733,665 to Palmaz; U.S. Pat. No. 5,026,377 to Burton et al; U.S. Pat. No. 5,158,548 to Lau et al; U.S. Pat. No. 5,242,399 to Lau et al; U.S. Pat. No. 5,344,426 to Lau et al; U.S. Pat. No. 5,415,664 to Pinchuck; U.S. Pat. No. 5,453,090 to Martinez et al; U.S. Pat. No. 4,950,227 to Savin; U.S. Pat. No. 5,403,341 to Solar; U.S. Pat. No. 5,108,416 to Ryan et al; and European Patent Application No. 707837A1 to Scheiban, all of which are incorporated herein by reference. A stent particularly preferred for use with this invention is described in PCT Application No. 96/03092-A1, published 8 Feb. 1996, the content of which is incorporated herein by reference. 
     In advancing a balloon expandable stent through a body vessel to the deployment site, there are a number of important considerations. The stent must be able to securely maintain its axial position on the delivery catheter. The stent, particularly its distal and proximal ends, are sometimes protected to prevent distortion of the stent, and minimize trauma to the vessel walls. Balloon expandable stent delivery and deployment assemblies are known which utilize restraining means that overlay the stent during delivery. U.S. Pat. No. 4,950,227 to Savin et al, relates to a balloon expandable stent delivery system in which a sleeve overlaps the distal or proximal margin (or both) of the stent during delivery. During inflation of the stent at the deployment site, the stent margins are freed of the protective sleeve(s) and the sleeves then collapse toward the delivery catheter for removal. A number of balloon expandable stent delivery and deployment assemblies do not use overlaying restraining members, such as the Savin sleeves, to position the stent for delivery. European Patent Application No. EP 055 3960A1 to Lau et al, uses an elastic sheath interspaced between the balloon and the stent. The sheath is said to act as a barrier to protect the balloon from the stent, allow uniform stent expansion, decrease balloon deflation time, prevent undesirable balloon flattening upon deflation and provide a friction substrate for the stent. The Lau sheath can be positioned on the inside or outside of the balloon. U.S. Pat. No. 5,409,495 to Osborne, similarly uses an elastic sleeve or sheath surrounding and in contact with the balloon for controlling the balloon radial expansion. In addition, Osborne is said to use restraining bands or a pair of balloons to achieve controllable stent expansion characteristics. U.S. Pat. No. 5,403,341 to Solar, relates to stent delivery and deployment assembly which uses a retaining sheath positioned about opposite ends of the compressed state. The retaining sheaths of Solar are adapted to tear under pressure as the stent is radially expanded, thus releasing the steno for engagement with the sheaths. U.S. Pat. No. 5,108,416 to Ryan et al. describes a stent introducer system which uses one or two flexible end caps and annular socket surrounding the balloon to position the stent during introduction to the deployment site. The content of all of these patents is incorporated herein by reference. 
     In positioning a balloon expandable stent on the delivery catheter over the fluid expandable balloon, the stent must be smoothly and evenly crimped to closely conform to the overall profile of the catheter and the unexpanded balloon. It has been noted that, due to physical properties of the material used in manufacturing the stent (typically a shaped memory metal, such as stainless steel or Nitinol™) there is a certain amount of “recoil” of the stent despite the most careful and firm crimping. That is the stent evidences a tendency to slightly open up from the fully crimped position and once the crimping force has been released. For example, in the typical stent delivery and deployment assembly, if the stent has been fully crimped to a diameter of approximately 0.0035″, the stent has been observed to open up or recoil to approximately 0.0037″. This phenomenon has been characterized as “recoil crimping”. Due to recoil crimping to this slightly enlarged diameter, it can be understood that the stent tends to evidence a certain amount of looseness from its desired close adherence to the overall profile of the underlying catheter and balloon. That is, the stent tends to have a perceptible relatively slack fit in its mounted and crimped position. During delivery, the stent can thus tend to slip and dislocate from its desired position on the catheter or even become separate from the catheter, requiring further intervention by the physician. 
     According to the present invention, a securement device is secured over the inner catheter beneath the balloon to compensate for the undesired looseness or slack that due to recoil crimping and to aid in securing the stent to the balloon, as well as protecting the balloon material from being sandwiched between the stent and any metal or protruding item which may be mounted on the inner shaft/guide wire lumen, for delivery of the stent. The securement devices secure the stent during tracking and delivery and provide a good friction fit to the stent and insure good contact between the stent and underlying balloon and catheter, instead of merely crimping the stent onto the balloon and the underlying catheter and relying on the bulk of the flaccid balloon to hold the stent on. 
     The art referred to and/or described above is not intended to constitute an admission that any patent, publication or other information referred to herein is “prior art” with respect to this invention. In addition, this section should not be construed to mean that a search has been made or that no other pertinent information as defined in 37 C.F.R. §1.56(a) exists. 
     SUMMARY OF THE INVENTION 
     This invention concerns a catheter apparatus suitable for performing angioplasty and for delivery of stents to body cavities. In general, stents are prosthetic devices which can be positioned within a body cavity, for example, a blood vessel or in some other difficultly accessible place of the body of a living human or animal. The stent prosthesis is formed of a generally tubular body, the diameter of which can be decreased or increased. Stents are particularly useful for permanently widening a vessel which is either in a narrowed state, or internally supporting a vessel damaged by an aneurysm. Such stents are typically introduced into the body cavity by use of a catheter. The catheter is usually of the balloon catheter type in which the balloon is utilized to expand the stent, which is positioned over the balloon for delivery, to place it in a selected location in the body cavity. The present invention is particularly directed to improved arrangements for releasably attaching and securing the stent to the catheter to facilitate delivery thereof, specifically having a securement device within the balloon. The below identified embodiments all disclose improved means for securing the stent to the catheter during the delivery procedure. 
     In certain embodiments the stent is held in place on the catheter by means of an enlarged mounting body carried within the balloon by the catheter shaft to which the stent and balloon are fitted. The stent is fitted over the balloon, as by crimping. According to the invention in some embodiments, the enlarged body is axially movable on the inner shaft of the catheter so that it can be retracted from the stent mounting area to provide a small profile for performing angioplasty. The catheter can then be withdrawn; the enlarged body can be moved into the stent mounting area; the stent can be mounted and the catheter can be re-inserted to implant the stent. In other embodiments, the enlarged body can be arranged to be reducible and enlargeable in size rather than being movable. Alternatively, the movable mounting body may be carried outside the balloon. A catheter of this type makes possible a method in which, before stent loading with the associated mounting body arranged to provide reduced diameter in the balloon region, the catheter may be used to dilate a lesion or the like. The catheter may be withdrawn and the mounting body may then be selectively manipulated to provide an enlarged diameter in the stent mounting region and a stent may be loaded onto the catheter. The catheter may be re-inserted to implant the stent. The catheter may be withdrawn or left in situ and the mounting body may be manipulated to provide reduced diameter again and the catheter may be used for any post-dilation desired. Also, the catheter may be used multiple times in the procedure for dilation and stent implantation. 
     Another embodiment of the present invention is also an assembly for delivery and deployment of an inflation expandable stent within a vessel. The assembly comprises a catheter, an expandable tube component mounted on the catheter, an expandable balloon mounted on the catheter and encompassing the tube component, and a stent mounted on the balloon. The catheter has proximal and distal ends. The stent is inflation expandable from a delivery diameter to a deployment diameter. The delivery diameter is reduced from the deployment diameter for conforming the stent to the catheter. The stent, in its delivery diameter, is coaxially mounted on the catheter near the catheter distal end. The expandable balloon is coaxially mounted on the catheter axially within the stent. The balloon is designed and adapted for expansion of the stent from the delivery diameter to the deployment diameter upon application of fluid deployment pressure to the balloon. The expandable tube component is coaxially mounted on the catheter, axially within the expandable balloon. The tube components is designed and adapted for fluid expansion to provide a securement pressure to the stent in the delivery diameter to maintain the stent in position on the catheter during delivery to the deployment site. The expandable tube component is sized and constructed to be fluid expandable to no more than the delivery diameter. The tube component is essentially equal in length to the stent and the stent is positioned on the assembly essentially coextensive with the tube component. 
     In another embodiment, this invention is a method for delivering and deploying a stent using an assembly as just described. A catheter is provided having proximal and distal ends. An expandable balloon is coaxially mounted on the catheter. An expandable tube component is coaxially mounted on the catheter, axially within the expandable balloon. The balloon and the tube component are each in an unexpanded condition. A stent is provided which is expandable from a delivery diameter to a deployment diameter. The stent, in a diameter greater than the delivery diameter, is mounted on the balloon. The stent is collapsed to the delivery diameter to conform to an overall profile of the catheter, the tube component and the balloon. The tube component is inflated to provide to the stent a securement pressure, to retain the stent on the assembly in the delivery diameter. The assembly is delivered to a deployment site. The balloon is inflated to expand the stent to its deployment diameter. 
     An alternative embodiment of present invention is also an assembly for delivery and deployment of an inflation expandable stent within a vessel. The assembly comprises a catheter, an expandable balloon mounted on the catheter, a corrugated tubing mounted on the catheter beneath or within the balloon, and a stent mounted on the balloon. The catheter has proximal and distal ends. The stent is inflation expandable from a delivery diameter to a deployment diameter. The delivery diameter is reduced from the deployment diameter for conforming the stent to the catheter. The stent, in its delivery diameter, is coaxially mounted on the catheter near the catheter distal end. The expandable balloon is coaxially mounted on the catheter axially within the stent. The balloon is designed and adapted for expansion of the stent from the delivery diameter to the deployment diameter upon application of fluid deployment pressure to the balloon. The corrugated tubing is mounted and adhered coaxially onto the catheter and is situated between the balloon and the catheter itself. When the stent is crimped and loaded onto the balloon, the balloon is situated therefore between the stent and the corrugated tubing. The tubing is preferably essentially equal to the length of the stent and the stent is positioned on the assembly essentially co-extensive with the tube component. The tubing on the catheter effectively holds the stent in place, takes up the slack due to recoil and protects the balloon material from being damaged during crimping. 
     Still another embodiment of the present invention comprises an assembly for delivery and deployment of an inflation expandable stent. The assembly comprises a catheter having proximal and distal ends. An annular collar or the like is coaxially located on the catheter distal end. A fluid expandable balloon is coaxially mounted over the collar at the catheter distal end. The balloon is expandable from a contracted to an expanded state. A stent is coaxially mounted on the balloon. The stent is inflation expandable from a reduced to an enlarged condition, the reduced condition conforming the stent to the balloon, collar and catheter in the preferred embodiment. The stent has at least an end portion overlying the balloon. At least one cup is coaxially mounted on the catheter distal end. The cup has a first end portion which may overlie the stent end portion. The cup and collar are cooperatively constructed and arranged to retain the stent end portion on the catheter in the stent reduced condition when the balloon is in the contracted state. The balloon and catheter are cooperatively constructed and arranged to cause expansion of the balloon from the contracted to the expanded state to cause enlargement of the stent, including the stent end portion, from the reduced to the enlarged condition, and thereby release the stent end portion from the cup end portion. The cup may be axially spaced from the collar but preferably they are relatively close together. The second end portion of the cup may be fixed to the catheter. The cup may overlie at least a portion of the collar. The collar can be shaped as a single member with the catheter, that is integral with it or the collar may be a separate body mounted axially and positioned on the catheter. The collar may be a mounting ring or cylinder axially positioned between stent end portions under the stent and balloon. The collar may be a sheath under the stent and balloon. 
     A further embodiment is also directed to improved arrangements for releasably attaching the stent to the catheter to facilitate delivery thereof. The stent is held in place on the catheter by means of an enlarged body carried by the catheter shaft within the balloon to which the stent and balloon are fitted, as by crimping in combination with one or more sleeves releasably overlying an end portion or portions of a stent and balloon. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is an isometric view, a portion of which is enlarged and in longitudinal section, of a balloon catheter having a mounting body in a retracted position; 
         FIG. 2  is an even more enlarged view in longitudinal cross-section of the distal end portion of the catheter of  FIG. 1 ; 
         FIG. 3  is similar to  FIG. 2  but showing the mounting body advanced to receive a stent mounted on the balloon; 
         FIG. 4  is an enlarged cross-sectional view of the distal end portion of the catheter of  FIG. 1  similar to that of enlarged view  FIG. 3  but showing the balloon in an expanded condition along with the expanded stent; 
         FIG. 5  is a schematic showing of a preferred mounting body carried by the catheter shaft within the balloon, the body being spirally cut to improve flexibility; 
         FIG. 6  is a schematic showing in cross-section of another embodiment of the invention with a mounting body positioned to receive a stent but with a stent not yet mounted; 
         FIG. 7  is a schematic showing of another embodiment of the invention; 
         FIG. 8  is a schematic showing of a means for conveniently crimping the stent on the embodiment shown in  FIG. 5 ; 
         FIG. 9  is a schematic showing of yet another embodiment of the invention; 
         FIG. 10  is a showing of another embodiment of a mounting body according to the invention; 
         FIG. 11  is a schematic of an enlargeable mounting body which is not axially movable; 
         FIG. 12  is a schematic of an alternate enlargeable mounting arrangement which is not axially movable; 
         FIGS. 13 and 14  are schematic showings of yet another embodiment in which the axially movable mounting body is carried outside the balloon; 
         FIGS. 15 and 16  are schematic showings of still yet another embodiment of the invention, and 
         FIGS. 17 and 18  are modified versions of the embodiment shown in  FIG. 11 . 
         FIGS. 19-21  are modified versions of the securement means of the present invention. 
         FIG. 22  is a side profile section showing a balloon expandable stent delivery and deployment assembly, with the stent crimped to delivery diameter onto the balloon, the underlying inflating component and the catheter and with the inflating tube component inflated to securement pressure. 
         FIG. 23  is a side profile section, similar to  FIG. 22 , with the balloon and the stent fully inflated to deployment diameter. 
         FIG. 24  is a side profile section showing an alternative embodiment of a balloon expandable stent delivery and deployment assembly, having a tube component formed in several sections. 
         FIGS. 25 ,  26  and  27  are cross-sectional views taken along lines  4 - 4 ,  5 - 5  and  6 - 6  of  FIG. 24 , respectively. 
         FIG. 28  is a side profile section showing a balloon expandable stent delivery and deployment assembly, with the stent crimped to delivery diameter onto the balloon, the underlying tube component and the catheter. 
         FIG. 29  is a side profile section, similar to  FIG. 28 , with the balloon and the stent fully inflated to deployment diameter. 
         FIG. 30  is a perspective view of the corrugated tubing of the present invention. 
         FIGS. 31-33  are side profile sections showing alternative embodiments of balloon expandable stent delivery and deployment assemblies, having the tubing component formed in a plurality of sections. 
         FIGS. 34-35  are side profile sections showing alternative embodiments of the balloon expandable stent delivery and deployment assemblies, the tube component inflatable to add securement pressure. 
         FIG. 36  is a side profile section showing a balloon expandable stent delivery and deployment assembly, with the stent crimped to delivery diameter onto the balloon, the underlying tube component and the catheter, and also having containment sleeves covering the ends of the stent. 
         FIG. 37  is a side profile section showing a balloon expandable stent delivery and deployment assembly, with the stent crimped to delivery diameter onto the balloon, the underlying tube component and the catheter, and also having a pull-back wire attached to the tube component. 
         FIG. 38  is a longitudinal cross-section of a stent delivery and deployment assembly of this invention showing a catheter with a collar mounted at the catheter distal end, an uninflated balloon mounted on the catheter over the collar, an unexpanded stent mounted on the balloon abutting the collar and a cup overlying the stent proximal end portion. 
         FIG. 39  is a longitudinal cross-section of another stent delivery and deployment assembly of this invention showing a catheter with a collar mounted as a mounting ring at the catheter distal end, an uninflated balloon mounted on the catheter over the mounting ring, an unexpanded stent mounted on the balloon overlying the mounting ring and a cup overlying the stent proximal end portion; note that the collar is positioned closer to the cup than in  FIG. 38 . 
         FIG. 40  is a longitudinal profile in partial cross-section of an assembly similar to that of  FIG. 38 , with a bulge formed under the uninflated balloon at the catheter distal end. 
         FIG. 41  is a longitudinal profile in partial cross-section of the assembly shown in  FIG. 38  with the balloon inflated and the stent expanded, showing the cup end portion flared to release the stent. 
         FIG. 42  is a longitudinal profile, similar to  FIG. 41 , showing the cup end portion rolled proximally to release the stent. 
         FIG. 43  is a longitudinal profile of yet another stent delivery and deployment assembly of this invention, with the balloon mounted on the catheter, which has a collar formed as a tapered single enlarged piece on the catheter, an unexpanded stent mounted on the unexpanded balloon abutting the collar and a cylindrical sleeve overlying the stent proximal end portion. 
         FIG. 44  is a longitudinal profile of the assembly of  FIG. 43  with the balloon inflated and the stent expanded, showing the sleeve moved proximally to release the stent. 
         FIG. 45  is a side profile of still another stent delivery and deployment assembly of this invention with the uninflated balloon mounted on the catheter which has two collars formed integrally with the catheter, an unexpanded stent mounted on the balloon abutting the collar and a cylindrical cup overlying the stent proximal end portion and the underlying collar. 
         FIG. 46  is a longitudinal profile of another stent delivery and deployment assembly of this invention with the uninflated balloon mounted on the catheter, an unexpanded stent mounted on the balloon, mounting a cylinder on the catheter and a pair of cups overlying the stent ends. 
         FIG. 47  is an isometric view, a portion of which is enlarged and in longitudinal section, of a balloon catheter having a stent fixed to the catheter over the balloon; 
         FIG. 48  is an even more enlarged view in longitudinal cross-section of the distal end portion of the catheter of  FIG. 47 ; 
         FIG. 49  is a schematic showing of one form of retraction of the releasable sleeve upon expansion of the balloon; 
         FIG. 50  is a schematic showing of another form of retraction of the releasable sleeve upon expansion of the balloon; 
         FIG. 51  is yet another form of retraction of the releasable sleeve upon expansion of the balloon; 
         FIG. 52  is a schematic showing of yet another form of retraction of the releasable sleeve upon expansion of the balloon; 
         FIG. 53  is a schematic showing of a modified shape for the releasable sleeve; 
         FIG. 54  is a schematic showing in cross-section of another embodiment of the invention with a stent not yet mounted; 
         FIG. 55  is a schematic showing of another embodiment of the invention; and 
         FIG. 56  is a schematic showing of yet another embodiment of the invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention relates to stent securement devices, most notably positioned between the balloon and the inner shaft of the catheter. Individual elements of the below disclosed embodiments are generally interchangeable if desired. Referring to  FIGS. 1-4  an angioplasty and stent delivery catheter system generally indicated at  10  includes a balloon catheter  12  having a balloon  14  on a distal end portion generally indicated at  16 .  FIG. 1  shows a proximal portion of the catheter at  12   a  and a distal portion  12   b  in enlarged view.  FIGS. 2 and 3  show the distal end portion  16  in an even more enlarged view. The illustrative catheter  12  is of the type known as a rapid exchange or single operator catheter. However, other types of catheters may be used, such as over the wire and fixed wire types. The balloon  14  is fixed to the catheter  12  by standard means. The balloon is shown in its contracted state in. A stent  18  is fixed about the balloon by crimping thereto. The stent has a larger expanded diameter which is obtained when the balloon is expanded in the known manner. In  FIGS. 1 and 2  catheter is shown prepared for performing angioplasty and in  FIG. 3  it is prepared for stent implantation. 
     In  FIGS. 1 and 2 , an axially movable mounting body  30  is shown in a position proximal to the end portion  16  of the catheter where a stent may be mounted. The catheter includes at its proximal end a manifold, generally designated  13 , as is known in the art. The manifold includes an inflation port  15  as is known in the art. A wire  31  is attached to body  30  to enable remote (from the proximal catheter end) advancement and retraction of it axially on inner lumen  26  over which it slides. In the retracted position shown in  FIGS. 1 and 2 , the catheter has a low profile for performing angioplasty. 
     This position is a refracted position and is selected by operation of a pull wire  31 . The retracted position of the mounting body may vary. To maximize the low profile of the distal end  16  of the catheter, the retracted position may be within the outer member  24 . 
     After such a procedure, the balloon is deflated, the catheter is withdrawn and the mounting body is advanced by means of wire  31  to the stent mounting position shown in  FIG. 3 . A stent  18  may then be fixed about the deflated balloon by crimping it thereto. The stent has a larger expanded diameter which is obtained when the balloon is again expanded in the known manner. That is, the stent is released from the catheter upon expansion of the balloon as shown in  FIG. 4  to be placed in a vessel at the desired location. When the balloon is then again deflated, removal of the balloon and catheter may be accomplished, leaving the stent in place. Exemplary dimensions for the inner  26  is a diameter of ½ mm and for body  30  a diameter of ¾ mm. 
     As is known in the art the balloon is either bonded at its ends by adhesive  20  and  22 , respectively to the outer member  24  of the catheter and to the inner member  26  of the catheter in the manner as shown, or is made one-piece with the outer member as is known in the art. The catheter balloon may be inflated by fluid (gas or liquid) from an inflation port extending from a lumen  28  (seen in  FIGS. 2 and 3 ) contained in the catheter shaft and opening into the balloon as shown, or by other known arrangements, depending on the design of the catheter. The details and mechanics of balloon inflation and specific overall catheter construction will vary according to the particular design involved in any given instance, and are known in the art per se. Such details are only shown schematically herein. All variations are acceptable for use with this invention. 
     Any balloon expandable stent may be used with this invention. Many are known in the art including plastic and metal stents. Some are more well known such as the stainless steel stent shown in U.S. Pat. No. 4,735,665; the wire stent shown in U.S. Pat. No. 4,950,227; another metal stent shown in European Patent Application EPO 707 837 A1 and that shown in U.S. Pat. No. 5,445,646, or U.S. Pat. No. 5,242,451. All of these patents are incorporated herein by reference. Also, shape memory metal stents may be used. As already indicated the stent of PCT Application 960 3092 A1 is particularly preferred. 
     The stent is typically for example about 16 mm long, while the balloon may be 20 mm long for example. These dimensions, however, are merely representative for illustrative purposes only and are not meant to be limiting. The stent is positioned over the balloon portion of the dilatation catheter and gently crimped onto the balloon either by hand or with a tool such as a pliers or the like to be mounted for delivery as shown in  FIG. 3 . The crimping may be readily accomplished by the physician during the procedure. 
     In accordance with this invention, mounting body  30 , best seen in  FIGS. 2 and 3 , is included inside balloon  14  to provide a cushion and/or substrate of enlarged diameter relative to the stent to support and hold the stent and secure it during crimping and the delivery procedure. The mounting body may be axially movable proximally or distally from the position shown in  FIG. 3 , proximally being preferred. 
     In the embodiment shown in  FIGS. 1-3 , mounting body  30  is cylindrical in form and takes the shape of a sleeve axially and slidably carried on inner lumen  26 , providing an enlarged area or portion for receiving the balloon and stent when the latter is crimped to the balloon. Marker band  34  may also be included on inner  26  as shown. Any radiopaque material such as gold is useful for this purpose. A stop member  36  of generally conical shape or any other shape may also be included on the marker band  34  as shown to provide additional resistance to stent movement during delivery and to protect the leading edge of the stent during delivery. Polyethylene or the like is suitable for the stop member. Other marker arrangements and stop arrangements may be used as well. 
     Although, the material of the mounting body may be hard, it is preferably of any deformable thermoplastic material, preferably an elastomer material and more preferably of a relatively resilient elastomer material, e.g., lower durometer silicone. A preferred deformable thermoplastic material is high density polyethylene (HDPE). A preferred lower durometer silicone is in the form of tubing. The deformation of the resilient material of the mounting body when the stent/balloon is crimped to it causes a radial outward force on the stent/balloon increasing the friction therebetween despite any recoil of the stent. 
     During stent delivery, the balloon catheter is advanced through and positioned in a patient&#39;s vasculature so that the stent is adjacent to the portion of the vessel where treatment is to take place. The balloon is inflated to expand the stent to an enlarged diameter. When the stent has reached the desired diameter, the balloon is deflated so that the catheter may be removed leaving the stent in place. 
     Another embodiment of the invention is shown in  FIG. 5 . In this embodiment mounting body  30  is a spiral cut elastomer or other suitable material, such as a rigid or flexible plastic, to provide separation for flexibility in that portion of the catheter, allowing more easy movement or tracking around bends. The spiral cut may be only partly through the mounting body or may be all the way through as shown in  FIG. 5 . Also, while stop member  36  is shown at the distal end portion of the catheter in this embodiment, no stop member may be used. 
     Another similar version is shown in  FIG. 6  which includes a cylindrical mounting body  30  made up of a plurality of separate adjacent rings  30   a  held together by wire  31  which extends therethrough as shown with stops  29  to secure the rings together. Rings  30   a  may be individual bodies carried on the sheath or bodies cut from a cylinder to partially separate them or fully separate them. Suitable arrangements may be made to wire  31  at each end of the body  30  to hold the rings together, as shown. 
     The embodiment shown in  FIG. 7  includes another feature based on the geometry of the mounting body for further securing the stent upon crimping. This feature is referred to herein as “interlocking” That is, the stent may be interlocked to the mount so that the stent cannot slide proximally or distally on the balloon unless it is deformed, such as by expansion. This can be seen by perusing the structure shown in  FIG. 7  which includes the inner  26  having a two-piece mounting body made up of spaced mounting bodies  30   a  and  30   b . These bodies are connected to each other by connection means  33  which may be a separate or integral cylindrical body of lesser diameter or may be one or two or more relatively rigid wire members as shown. The spacing between bodies  30   a  and  30   b  allows portions of the stent  18  and balloon  14  to be depressed or inserted between the bodies upon crimping of the stent thus forming an interlock against sliding of the stent axially or longitudinally before the stent is released. 
     The interlock formation or crimping is readily accomplished by any suitable means such as a two-piece die  40  shown in  FIG. 8  or the like. 
       FIG. 9  demonstrates that more than a two-piece mounting body arrangement may be used if desired. In this embodiment, the mounting body is comprised of three spaced interconnected bodies  30   a ,  30   b  and  30   c  on the inner  26 . Preferably in the embodiments of  FIGS. 7 and 9 , the mounting bodies will be ring-like in shape or cylindrical in shape although other configurations will be readily apparent to those familiar with this art. 
     Referring now to  FIG. 10 , another embodiment of a movable mounting body  30  is shown in the form of a rigid coil of plastic, metal or the like having a control wire  31 , preferably integral therewith. When in the metal form, the coil may be coated with a polymer such as polyethylene or PTFE or enclosed in a polymeric sheath of similar material. The coil may be slidably received on the inner  26  similar in arrangement to that shown in the preceding Figures. 
     As already indicated, an alternate arrangement may be used in which the mounting body, instead of being movable, is designed to be enlargeable and reducible or collapsible, while remaining in a fixed position in the stent mounting area of the catheter.  FIGS. 11 and 12  are directed to such an arrangement. 
     In  FIG. 11 , an inner balloon  50  of smaller diameter than outer balloon  14  is mounted on the inner  26 . Balloon  50  may have a separate inflation conduit  52  inside inner  26 , preferably including a valving arrangement  54 . Valve  54  may be a one-way valve allowing only inflation of balloon  50  if desired. However, inner  26  may serve as the inflation conduit as well. In addition to fully inflating the balloon, inner balloon  50  may also be partially inflated. 
       FIG. 19  shows a modification to  FIG. 11  in which two inner balloons  50   a  and  50   b  are included.  FIG. 20  shows a modification in which two inflation valves  54   a  and  54   b  are included. 
       FIG. 21  shows a full arrangement of inner balloon  50  in which a syringe  120  is inserted into the distal end of the liner  26  of the catheter. The syringe has at its ends blocks  122  and  124  to enable local pressurization of inner  26  to inflate balloon  50 . 
       FIGS. 17 and 18  show an inner balloon  50  similar to the arrangement of  FIG. 11  but the balloon  50  in  FIG. 17  has a narrow center portion and wide ends to provide a mounting shape similar to that of  FIG. 7 . In  FIG. 17 , balloon  50  is inflated and balloon  14  is partially inflated. In  FIG. 18 , balloon  50  is inflated and balloon  14  is uninflated ready for stent loading. Balloon material is preferably a polyethylene or urethane elastomer such as Tecoflex or Tecothane from Thermedics. 
     Referring to  FIG. 12 , an alternate embodiment is shown in which the proximal portion of the inner  26  is axially movable while the distal portion  26   b  is fixed with respect to the catheter. In between portion  26   a  and portion  26   b  is a coil spring  60  inside a flexible sheath  62  of PTFE or the like. Portion  26   b  of the inner is attached to balloon  14  at the very distal end portion of the catheter. Portion  26   a  is movable axially within the outer  22 . Thus, if  26   a  is pushed in the distal direction and held to compress coil  60 , the coil will enlarge in diameter to provide an enlarged mounting area for a stent. Twisting the inner to twist the coil will enhance enlargement. Alternatively, coil spring  60  may be replaced by a braided element. 
     Also, by providing different pitch over the length of the coil it can be made to enlarge more in some regions than in others. For example, if the coil windings are closer together in the center portions than in the end portions, when the coil undergoes compressing, the two end portions will enlarge in diameter more than the center portion to provide a mount similar to that of  FIG. 7 . 
     Referring now to  FIGS. 13 and 14 , another embodiment is shown which is alternative to the earlier described embodiments which are inside the balloon on the catheter. In this embodiment a sheath  80  is carried on the outside of the catheter. Sheath  80  is elastomeric and is axially movable from a stent mounting position as shown in  FIG. 14  to a position remote from the stent mounting position, such as the retracted position as shown in  FIG. 13 . In the position shown in  FIG. 13 , balloon  14  may be inflated and deflated. In the position shown in  FIG. 14 , balloon  14  will be deflated for low profile. Sheath  80  when over the balloon as in  FIG. 14  acts to increase the profile of the catheter to facilitate crimping a stent thereto during deployment of the stent, sheath  80  will expand with balloon  14  to facilitate inflation and during deflation the elastomer sheath will return to its original dimension. An elastomer material which is presently preferred is Tecothane, a trade name for a thermoplastic polyurethane available from Thermedics, Inc., of Woburn, Mass. It may be about 0.003 inches thick, for example. 
     With respect to  FIGS. 15 and 16 , a further embodiment of the invention is shown in which inner  26  carries a mounting body  30 , the distal end  100  of which is secured or fixably attached to inner  26 , as by any suitable adhesive. The remainder of body  30  is slidable over inner  26  as by the application of compression in the distal direction at the proximal end  102 . This may be accomplished by push wire  104  which extends to the proximal end of the catheter for remote manipulation as is known in the art. 
     Mounting body  30  is accordion folded with more widely spaced folds at the end portions  106 , than at the central portion  108 . Thus, as can be seen in  FIG. 15 , a relatively low profile is provided without compression for normal angioplasty use. When a stent is to be mounted (not shown), compression by means of push wire  104  will result in a configuration of enlarged diameter of body  30  as shown in  FIG. 16  to provide a mount similar to that of  FIG. 7  in general configuration. If the spring is uniform over the body, it will enlarge uniformly, similar to the inner balloon of  FIG. 11 . The Figures are schematic in form but the concept can be readily appreciated. 
     As an alternative to a folded construction, the body may be of braided construction to achieve the same operation. 
     Also, this form of body  30  may be inserted into a two piece inner  26  similar to the arrangement shown in  FIG. 12 . In all of these arrangements, the accordion folded body material may be of any suitable polymer, such as polyethylene. For example, tubing having a wall thickness of about 0.002 inches may be used. The accordion folds or pleats may be readily formed in such tubing by means of a pressure mold containing spaced blades placed in a heated chamber. 
       FIGS. 22-27  show embodiments wherein the inner securement device comprises an inner balloon beneath the outer catheter balloon, similar to above.  FIGS. 22 and 23  illustrate a side profile section showing an inflation expandable stent delivery and deployment assembly generally designated  110 . Assembly  110  includes a catheter comprised of inner shafts  112  and  113  and an outer shaft  115  of the coaxial type, an inflation expandable balloon  114 , an inflation tube component  116  such as an inner balloon and inflation expandable stent  118 . Any conventional type of catheter may be used, such as a catheter of the type generally used for PTA or PTCA angioplasty procedures, for prostate therapy, and TTS endoscopic catheters for gastrointestinal use. However, coaxial types as shown are most preferred. The particular catheter  112  shown is formed of a biocompatible and hydrophilic compatible material, such as a lubricous polyimide or polyethylene. Other suitable materials for the catheter  112  include nylons, urethanes, and polypropylene materials compatible with coatings such as silicone and/or hydrophilic coatings. In addition to hydrophilic compatible materials, any biocompatible material may be used. For example, polyethylene or polypropylene can be coated with a hydrophilic material to render them hydrophilic compatible suitable catheters for use according to the present invention include a number of catheters available from SciMed Life Systems, Inc., Maple Grove, Minn., the assignee of the present invention, such as BANDI™, COBRA™, VIVA™, and VIVA PRIMO™ catheters. 
     Inflatable tube component  116  is fixed at its distal and proximal end to inner shaft  112  and at its proximal end to inner shaft  113  at a position to be encompassed within the distal and proximal ends of the outer balloon  114 . According to art-recognized convention, the length L-B of the balloon  114  is defined as the length of the body portion of the balloon  114 , excluding the terminal cone sections  120 . As seen in  FIG. 23 , the body portion of the balloon  114  is generally cylindrical when in its deployed or inflated condition. Tube component  116  is illustrated as having terminal sections  122  which are more relatively vertical than the cone sections  120  illustrated for the balloon  114 . However, it is to be understood that, according to the present invention, either of the terminal sections  120 ,  122  may be relatively cone shaped, relatively vertical or of any other configuration known to those of skill in this art. A preferred length L-T of the tube component  116  is illustrated in  FIGS. 22 and 23  as substantially equal to the length L-B of balloon  114 , and substantially equal to the length L-S of stent  118 . However, according to the present invention, stent  118  should be supported by the underlying tube component  116  for a length sufficient to permit accomplishment of the stated purpose of the tube component  116 , when inflated, to provide-securement pressure for stent  118  to maintain stent  118  in position with assembly  110  during delivery. It is also within the present invention for tube component  116  to be slightly shorter than stent  118 , for example, the distal end  119  of stent  118  may extend distally beyond the distal end  121  of tube component  116  (not shown), so that the distal end  119  of stent  121  can be crimped over the distal end  121  of tube component  116  to prevent the distal end  119  of stent  118  from catching and tending to further open as it is maneuvered within a body vessel. As has been explained above, tube component  116  is designed and constructed to be inflatable to no more than is necessary to compensate for recoil crimping of stent  118  and to closely accommodate (or even slightly over-stress) the delivery diameter of stent  118 , taking into consideration the thickness of the intervening uninflated balloon  114 . Tube component  116  is inflated through the opening(s)  117  of inner shaft  112 . Typically, tube component  116  will have a wall thickness of about 0.0002-0.0007 inch and will be inflatable to no more than about 0.035.-0.045 inches. 
     Inflating tube component  116  may be formed of either compliant or non-compliant balloon materials. Compliant materials include low pressure, relatively soft or flexible polymeric materials, such as thermoplastic polymers, thermoplastic elastomers, polyethylene (high density, low density, intermediate density, linear low density), various co-polymers and blends of polyethylene, ionomers, polyesters, polyurethanes, polycarbonates, polyamides, poly-vinyl chloride, acrylonitrile-butadiene-styrene copolymers, polyether-polyester copolymers, and polyetherpolyamide copolymers. Suitable materials include a copolymer polyolefin material available from E.I. DuPont de Nemours and Co. (Wilmington, Del.), under the trade name Surlyn™ Ionomer and a polyether block amide available under the trade name PEBAX. Non-compliant materials include relatively rigid of stiff high pressure polymeric materials, such as thermoplastic polymers and thermoset polymeric materials, poly(ethylene terephthalate) (commonly referred to as PET), polyimide, thermoplastic polyimide, polyamides, polyesters, polycarbonates, polyphenylene sulfides, polypropylene and rigid polyurethanes. 
     A balloon  114  for use according to the present invention may be any conventional balloon for catheter delivery, such as a balloon of the type generally used for PTA and PTCA procedures. Typically, balloon  114  is fixed at its distal end to inner shaft  112  near the catheter-distal end and at its proximal end to outer shaft  115 . Balloon  114  is larger in diameter than tube component  116 , because balloon  114  must be able to expand to a larger diameter than tube component  116 . Balloon  114  is inflatable through an inflation conduit  123 , i.e., the space between coaxial inner shaft  113  and outer shaft  115  of the catheter. The distal and proximal ends of balloon  114  are shown in  FIGS. 22 and 23  positioned exterior to the distal and proximal ends of tube component  116 , respectively, and of a length L-B generally equal to the length L-T of the tube component  116 . To be compatible with tube component  116  illustrated in  FIGS. 22 and 23  and described above, balloon  114  is inflatable at deployment to about the diameter of the body vessel in which the stent  118  is to be deployed. Balloon  114  may be formed of a compliant or non-compliant material, of the types of compliant materials described herein above, such as polyethylene or any standard balloon material. Balloon  114  typically has a wall thickness of about 0.0007-0.004 inch for example. 
     A stent for use according to the present invention may be any conventional type of balloon expandable stent, including stents of the type used for PTA and PTCA angioplasty procedures, for prostate therapy, and TTS endoscopic catheters for gastrointestinal use. Suitable stent material is biocompatible stainless steel in the form of sheet metal, tube component wire or Nitinol. A preferred stent is described in PCT Application No. 960 3072 A1, published 8 Feb. 1996, the content of which is incorporated herein by reference. All such stents are well known in this art generally and additional examples are described in U.S. Pat. No. 5,507,768 to Lau et al; in U.S. Pat. No. 5,458,615 to Klemm et al; in U.S. Pat. No. 5,226,889 to Sheiban; in U.S. Pat. No. 4,875,480 to Imbert; in U.S. Pat. No. 4,848,343 to Wallsten et al, and in U.S. Pat. No. 4,733,665 to Palmaz. Stent  18  as shown in  FIGS. 22 and 23  is positioned on balloon  114 , the underlying inflatable tube component  116  and the distal end of the catheter. The length L-S of stent  118  is shown as essentially equal or slightly smaller than the length L-T of tube component  116  and is positioned on assembly  110  to be co-extensive with tube component  116 . In this position, stent  118  is shown in  FIG. 22  crimped to its delivery diameter D 1 , which is about 0.035-0.045 inch for example. 
     As discussed above, despite the most careful and firm crimping of stent  118  to closely conform to the overall profile of the catheter unexpanded balloon  114  and underlying inflatable tube component  116 , there is a certain amount of “recoil” of stent  118  or a tendency of stent  118  to slightly open from a desired hypothetical minimum crimped diameter. The actual minimum diameter achievable for fully crimped stent  118  on assembly  110  is referred to as the stent  118  delivery diameter D 1 . This tendency of stent  118  to open or recoil slightly when crimped on assembly  10  has been characterized as “recoil crimping”. In  FIG. 22 , inflatable tube component  116  is shown inflated to a diameter which is generally sufficient to compensate for any slack or looseness between crimped stent  118  and the overall profile of the catheter, the unexpanded balloon  114  and the underlying inflatable tube component  116  due to recoil crimping. 
       FIG. 23  illustrates a side profile section showing a stent delivery and deployment assembly  110  of this invention with balloon  114  fluid inflated to its fully expanded position. As a result of the fluid inflation of the balloon  114 , stent  118  has also been fully expanded to its deployment diameter D 2  in which it can be deployed against the walls of a body vessel in which it is situated. 
     Tube component  116  may have a shape other than the cylindrical shape described and illustrated with regard to the embodiment shown in  FIGS. 22 and 23 . Further, the tube component may be comprised of more than one separately inflatable pouch. For example, as illustrated with regard to  FIG. 24 , the tube component of an alternative stent delivery and deployment assembly generally designated  130  can be comprised of three separately inflatable pouches  136 ,  138 ,  140 . The pouches  136 ,  138 ,  140  are each separately inflatable through their respective inflation conduits  137 ,  139   141 , and each of the pouches  136 ,  138 ,  140  can be inflatable to a different extent. The conduits are formed in the wall of shaft  132  as can be seen in  FIGS. 25-27 . The stent delivery and deployment assembly  130  of  FIG. 24  is also comprised of a catheter having inner shaft  132  and outer shaft  135 , a balloon  134 , with its balloon inflation conduit  139  and the balloon terminal cone sections  144 , and a stent  142 . As has been explained above with reference to  FIGS. 22 and 23 , stent  142  is crimped to closely conform to the overall profile of the catheter the unexpanded balloon  134  and the underlying inflatable pouches  136 ,  138 ,  140 . Even with the most careful and firm crimping, there is a certain amount of “recoil” of the stent  142  or a tendency of stent  142  to slightly open from a desired hypothetical minimum diameter. In  FIG. 24 , the first  136  and third  140  pouches are inflated to a slightly larger size than the second pouch  138 . As discussed above, the inflation of the pouches  136 ,  138 ,  140  to this configuration is generally sufficient to compensate for any slack or looseness between the crimped stent  142  and the overall profile of the catheter, the unexpanded balloon  134  and the underlying inflatable pouches  136 ,  138 ,  140  due to recoil crimping. Once pouches  136 ,  138   140  have been inflated to the configuration shown in  FIG. 24 , stent  142  is firmly secured against axial movement with regard to assembly  130 . The distal  146  and proximal  148  ends of stent  142  are protected from any possible unwanted contact with vessel walls during maneuvering, which helps to protect the vessel walls from abrasion and also helps to protect the ends  146 ,  148  of stent  142  from distortion. Additionally, stent  142  may be of a length such that it fits over pouch  140  and pouch  136  as well as over pouch  138 . 
     The method of using the stent delivery and deployment assembly  110  of this invention, as shown in  FIGS. 22 and 23 , is described as follows. The assembly  110  is constructed as described above. Stent  118  is compressed or crimped onto balloon  114 , inflatable tube component  116  and the catheter to a delivery diameter D 1 . This crimping can be done manually or with the aid of tooling specially designed for the purpose either by the physician or the manufacturer. In the crimped position, stent we closely conforms to the overall profile of balloon  114 , inflatable tube component  116  and the catheter except for the slight slack or looseness due to recoil crimping. Tube component  116  is fluid inflated to the extent necessary to compensate for this slack or looseness due to recoil crimping. The pressure of force required to inflate tube component  116  to this extent is also referred to as securement pressure, i.e., the force or pressure needed to secure stent  118  in this position. It is to be noted that, since tube component  116  is designed and constructed to be capable of fully expanding to no more than the size necessary to compensate for recoil crimping, there is no possibility of stent  118  expanding or beginning to open to a larger diameter. Thus, there is no hazard of stent  118  moving out of its position on the catheter during delivery or of becoming separated from the catheter within a body vessel. The catheter distal end is delivered by standard techniques to the deployment site within the body vessel of interest. At this point, stent  118  is positioned as required by the physician and balloon  114  is fluid inflated by standard technique to expand stent  121  to its deployment diameter D 2 . During this expansion, stent  118  is expanded to fill the body vessel. Following deployment of stent  118 , balloon  114  and optionally, tube component  116  are deflated and the assembly  110  is retracted proximally and withdrawn from the body. If required by the procedure, the site of entry to the body is appropriately closed. 
     The method of using the stent delivery and deployment assembly  130  of this invention, as shown in  FIG. 24 , is similarly described. The assembly  130  is constructed as described above. Stent  142  is compressed or crimped to closely conform to the overall profile of balloon  134 , inflatable pouches  136 ,  138 ,  140  and the catheter except for the slight slack or looseness due to recoil crimping. Pouches  136 ,  138 ,  140  are each fluid inflated to the profile shown in  FIG. 24  through separate fluid inflation conduits (not shown) to securement pressure to compensate for this slack or looseness and to secure stent  142  in this position. The overall configuration of pouches  136 ,  138   140  further serves to position stent  142  against axial dislocation during delivery. The catheter is delivered by standard techniques to the deployment site within the body vessel of interest. At this point, stent  142  is positioned as required by the physician and balloon  134  is fluid inflated by standard technique to expand and deploy stent  142 . Following deployment of stent  142 , balloon  134  and, optionally, pouches  136 ,  138   140  are deflated and the assembly  130  is retracted proximally and withdrawn from the body. If required by the procedure, the site of entry to the body is appropriately closed. 
     The inflation tube component provided by this invention maximizes stent securement force by optimizing the frictional force between the inflating tube component, the balloon wall and the internal diameter of the stent in its reduced crimped delivery diameter. The inflation tube component is more flexible than a solid sheath under the expandable balloon, and thus the entire assembly has greater flexibility. This invention has particular advantages for assemblies in which the stent is provided for use as pre-crimped to the balloon and underlying catheter, by increasing the shelf life of the pre-crimped assembly. The features and principles described for this invention are suitable for use with fixed wire, over-the-wire and single operator exchange assemblies. 
       FIGS. 28-37  disclose still further embodiments of the securement device.  FIGS. 28 and 29  illustrate a side profile section showing an inflation expandable stent delivery and deployment assembly, generally designated  210 . Assembly  210  includes a catheter comprised of inner shaft  212  and outer shaft  213  of the coaxial type and an optional retractable delivery shaft  211  (typically called a guide catheter, shown refracted in  FIG. 29 , an inflation expandable balloon  214 , a corrugated/ribbed stent securement device  216 , optional marker bands  217  and an inflation expandable stent  218 . Any conventional type of catheter may be used, such as a catheter of the type generally used for PTA or PTCA angioplasty procedures, for prostate therapy, and TTS endoscopic catheters for gastrointestinal use. However, coaxial types as show are most preferred. The particular catheters  212  and  213  shown are formed of a biocompatible and hydrophilic compatible material, such as a lubricous polyimide or poly ethylene. Other suitable materials for the catheters  212  and  213  include nylons, urethanes, and polypropylene materials compatible with coatings such as silicone and/or hydrophilic coatings. In addition to hydrophilic compatible materials, any biocompatible material may be used. For example, polyethylene or polypropylene can be coated with a hydrophilic material to render them hydrophilic compatible. Suitable catheters for use according to the present invention include a number of catheters available from SciMed Life Systems, Inc., Maple Grove, Minn., the assignee of the present invention, such as BANDIT™, COBRA™, VIVA™, VIVA PRIMOT™, MAXXUM™, MAXXUM ENERGY™ and RANGER™ catheters. 
     Securement device  216  is fixed at its distal and/or proximal ends to inner shaft  212  at a position to be encompassed within the distal and proximal ends of the outer balloon  214 . According to art-recognized convention, the length L-B of the balloon  214  is defined as the length of the body portion of the balloon  214 , excluding the terminal cone sections  220 . As seen in  FIG. 29 , the body portion of the balloon  214  is generally cylindrical when in its deployed or inflated condition. Securement device/tube component  216  is illustrated as having terminal sections  221 , 222 . It is to be understood that, according to the present invention, either of the terminal sections  220 ,  222  may be relatively cone shaped, relatively vertical, relatively flat or of any other configuration known to those of skill in this art. A preferred length L-T of the tubing  216  is illustrated in  FIGS. 28 and 29  as substantially equal to the length L-B of balloon  214 , and substantially equal to the length L-S of stent  218 . However, according to the present invention, stent  218  should be supported by the underlying tube component  216  for a length sufficient to permit accomplishment of the stated purpose of the tube component  216 , to provide a superior securement and protective surface for stent  218  to maintain stent  218  in position with assembly  210  and to protect the balloon material during loading/crimping. It is also within the present invention for the tube component  216  to be slightly shorter than stent  218 , for example, the distal end  219  of stent  218  may extend distally beyond the distal end  222  of tube component  216  (not shown), so that the distal end  219  of stent  218  can be crimped over the distal end  222  of tube component  216  to prevent the distal end  219  of stent  218  from catching and tending to snag or further open as it is maneuvered within a body vessel. As has been explained above, tube component  216  is designed and constricted to have enough flexibility and have enough volume to no more than is necessary to compensate for recoil crimping of stent  218  and to closely accommodate (or even slightly over stress) the delivery diameter of stent  218 , taking into consideration the thickness of the intervening uninflated balloon  214 . Typically, the tube component  216  will have a consistent frequency of ribs, but may also vary by having intermittent groups of ribs along the tubing. 
     The balloon and the crimped stent slightly conform to the undulations of the tube component for greater securement, but this conformation is not illustrated. 
     Tube component  216  may be formed from a thermoplastic material, preferably a low modulus polymer, such as Surlyn™, Pebax and urethane. The device such as polypropylene, low density polyethylene (LDPE), high density polyethylene (HDPE), ethylene vinyl acetate (EVA), nylon, polyester and polyethylene terephthalate (“PET”), may be prepared through free blowing in a mold or inside a coil. Tubing is extruded with relatively thin walls and then free-blown in a mold, coil or other fixture to form the ribs/corrugation. 
     A balloon  214  for use according to the present invention may be any conventional balloon for catheter delivery, such as a balloon of the type generally used for PTA and PTCA procedures. Typically, balloon  214  is fixed at its distal end to inner shaft  212  near the catheter distal end and at its proximal end to inner shaft  212 , near the distal end of the outer shaft  213 . Balloon  214 . is inflatable through an inflation conduit  223 , i.e., the space between coaxial inner shaft  213  and outer shaft  213  of the catheter. The distal and proximal ends of balloon  214  are shown in  FIGS. 28 and 29  positioned exterior to the distal and proximal ends of tube component  216 , respectively, and of a length L-B generally equal to the length L-T of the tube component  216 . To be compatible with the tube component  216  illustrated in  FIGS. 28 and 29  and described above, balloon  214  is inflatable at deployment to about the diameter of the body vessel in which the stent  218  is to be deployed. Balloon  214  may be formed of a compliant or non-compliant material, such as polyethylene or any standard balloon material. Compliant materials include low pressure, relatively soft or flexible polymeric materials, such as thermoplastic polymers, thermoplastic elastomers, polyethylene (high density, low density, intermediate density, linear low density), various co-polymers and blends of polyethylene, ionomers, polyesters, polyurethanes, polycarbonates, polyamides, poly-vinyl chloride, acrylonitrile-butadiene-styrene copolymers, polyether-polyester, copolymers, and polyetherpolyamide copolymers. Suitable materials include a copolymer polyolefin material available from E.I. DuPont de Nemours and Co. (Wilmington, Del.), under the trade name Surlyn™ Ionomer and a polyether block amide available under the trade name PEBAX™. Non-compliant materials include relatively rigid stiff high pressure polymeric materials, such as thermoplastic polymers and thermoset polymeric materials, poly(ethylene terephthalate) (commonly referred to as PET), polyimide, thermoplastic polyimide, polyamides, polyesters, polycarbonates, polyphenylene sulfides, polypropylene and rigid polyurethanes, or combinations thereof. The balloon  214  typically has a wall thickness of about 0.0007-0.004 inch for example. 
     A stent for use according to the present invention may be any conventional type of balloon expandable stent, including stents of the type used for PTA and PTCA angioplasty procedures, for prostate therapy, and TTS endoscopic catheters for gastrointestinal use. Suitable stent material is biocompatible stainless steel in the form of sheet metal, tube component wire or Nitinol. A preferred stent is described in PCT Application No. 960 3072 A1, published 8 Feb. 1996, the content of which is incorporated herein by reference. All such stents are well known in this art generally and additional examples are described in U.S. Pat. No. 5,507,768 to Lau et al; in U.S. Pat. No. 5,458,615 to Klemm et al; in U.S. Pat. No. 5,226,899 to Sheiban; in U.S. Pat. No. 4,875,480 to Imbert; in U.S. Pat. No. 4,848,343 to Wallsten et al; and in U.S. Pat. No. 4,733,665 to Palmaz. Stent  218  as shown in  FIGS. 28 and 29  is positioned on balloon  214 , which is over the underlying tube component  216 , at the distal end of the catheter. The length L-S of stent  218  is shown as essentially equal or slightly smaller than the length L-T of tube component  216  and is positioned on assembly  210  to be coextensive with tube component  216 . In this position, stent  218  is shown in  FIG. 28  crimped to its delivery diameter D 1 , which is about 0.035-0.45 inch for example. 
     As discussed above, despite the most careful and firm crimping of stent  218  to closely conform to the overall profile of the catheter unexpanded balloon  214  and underlying tube component  216 , there is a certain amount of “recoil” of stent  218  or a tendency of stent  218  to slightly open from a desired hypothetical minimum crimped diameter. The actual minimum diameter achievable for fully crimped stent  218  on assembly  210  is referred to as stent  218  delivery diameter D 1 . This tendency of stent  218  to open or recoil slightly when crimped on assembly  210  has been characterized as “recoil crimping”. In  FIG. 28 , tube component  216  is shown inflated to a diameter which is generally sufficient to compensate for any slack or looseness between crimped stent  218  and the overall profile of the catheter, the unexpanded balloon  214  and the underlying tube component  216  due to recoil crimping. 
       FIG. 29  illustrates a side profile section showing a stent delivery and deployment assembly  210  of this invention with balloon  214  fluid inflated to its fully expanded position. As a result of the fluid inflation of the balloon  214 , stent  218  has also been fully expanded to its deployment diameter D 2  in which it can be deployed against the walls of a body vessel in which it is situated. 
       FIG. 30  illustrates the preferred configuration of the tube component  216 . The tube component has a plurality of ribs  230  and is configured in a corrugated or accordion fashion. The ends of the tube component  216 ,  222  and  221 , are substantially rib-free so as to provide a flat surface to receive an adhesive and thereby bond to the inner shaft  212 . Preferable adhesives include cyanoacrylates such as Loctite 4061/4011 or urethanes, such as H.B. Fuller 3507/3506. The tube component may also be heat bonded to the inner shaft. The ribs may vary in frequency and spacing. 
     Tube component  216  may have different configurations in other embodiments, as shown in  FIGS. 31-33 . The tube component  216  may be comprised of more than one piece of corrugated tubing ( FIG. 31 ), a smaller single piece ( FIG. 32 ) or one single piece of tubing sectioned into a plurality of ribbed sections, wherein the tubing is adhered to the inner shaft  212  in more than two locations ( FIG. 33 ). 
       FIG. 31  shows two pieces of tubing component  216   a ,  216   b . Both pieces are adhered to inner shaft  212  at adhesion points  232 .  FIG. 32  discloses an embodiment which comprises one smaller piece of tube component  216  which is adhered to inner shaft  212  at adhesion points  232 .  FIG. 33  discloses an embodiment which comprises one tube component  216  which has interrupted ribbed sections  234  adhered to the inner shaft  212 . 
       FIGS. 34 and 35  illustrate an alternative embodiment in which the tubing component is inflatable to increase the securement pressure on the inside of balloon  214  when the stent is crimped onto the balloon so as to negate additional recoiling. The full expansion of the tube component  216  should only be slightly greater than the diameter of the inside of the balloon  214  when the stent  218  is fully crimped onto the balloon  214 . 
     In  FIG. 34 , the inflating fluid comes through the guide wire lumen  212  under pressure from the proximal end or the distal end of the guide wire lumen  212 , preferably via a syringe, and fills the tubing component  216  through a one-way valve  247  (preferably resisting up to about 4 atm) in the inner catheter  212 . 
     In  FIG. 35 , the tubing component  216  is inflated via an additional lumen  242  which extends from the proximal end of the catheter along the guide wire lumen  240 , much the same as any inflating lumen incorporated to inflate a balloon. 
     In an alternative embodiment, as shown in  FIG. 36 , socks or sleeves  251  may be incorporated to stretch over the ends of the stent to prevent snagging and to secure the stent onto the balloon. Such sleeves are demonstrated in U.S. application Ser. No. 08/702,149, filed Aug. 23, 1996, and Ser. No. 08/701,979, filed Aug. 23, 1996, which are incorporated in their entirety herein by reference. 
     In still another embodiment, as shown in  FIG. 37 , the tubing component  216  is slidable axially along the inner shaft  212  and is connected to a retracting wire  250  such that the tubing component may be retracted into the outer shaft  213  after the balloon has been inflated to reduce the profile of the balloon  214  when the catheter is removed. The tubing component, since it is not adhered to the inner shaft  212  in this embodiment, should fit tightly enough on the inner shaft to stay in place, but not too tightly so that it may be retracted by pulling on the retracting wire  250 . 
     The method of using the stent delivery and deployment assembly  210  of this invention, as shown in  FIGS. 1 and 2 , is described as follows. The assembly  210  is constructed as described above. Stent  218  is compressed or crimped onto balloon  214 , tube component  216  and the catheter to a delivery diameter D 1 . This crimping can be done manually or with the aid of tooling specifically designed for the purpose either by the physician or the manufacturer. In the crimped position, stent  218  closely conforms to the overall profile of balloon  214 , tube component  216  and the catheter except for the slight slack or looseness due to recoil crimping. Tube component  216  is flexible enough to slightly collapse during crimping and rebound to the extent necessary to compensate for the slack or looseness due to recoil crimping, thus securing the stent. As a result, the stent does not move out of its position on the catheter during delivery or become separated from the catheter within a body vessel. The catheter distal end is delivered by standard techniques to the deployment site within the body vessel of interest. At this point, stent  218  is positioned as required by the physician and balloon  214  is fluid inflated by standard technique to expand stent  218  to its deployment diameter D 2 . During this expansion, stent  218  is expanded to fill the body vessel. Following deployment of stent  218 , balloon  214  is deflated and the assembly is retracted proximally and withdrawn from the body. If required by the procedure, the site of entry to the body is appropriately closed. 
     The tube component provided by this invention increases stent securement force by increasing the frictional force between the tube component, the balloon wall and the internal diameter of the stent in its reduced crimped delivery diameter. The tube component is more flexible than a solid sheath under the expandable balloon, and thus the entire assembly has greater flexibility. This invention has particular advantages for assemblies in which the stent is provided for use as pre-crimped to the balloon and underlying catheter, by increasing the shelf life of the pre-crimped assembly. The tube component also protects the balloon material during crimping by acting as a buffer between the balloon material and whatever may be mounted on the inner shaft, such as marker bands  217 . The features and principles described for this invention are suitable for use with fixed wire, over-the-wire and single operator exchange assemblies. 
       FIGS. 38-46  disclose alternative embodiments of the securement device.  FIG. 38  shows a stent delivery and deployment assembly generally designated  310 . A catheter  312  has a collar  314  coaxially mounted at the catheter distal end portion  316 . An uninflated balloon  318  is coaxially mounted on catheter  312  over collar  314 . An unexpanded stent  320  is coaxially mounted on the balloon  318  abutting but not overlying collar  314 . A cup  322  coaxially overlies the stent proximal end portion  324 . Cup  322  may be elastomeric or rigid, preferably elastomeric. Cup  322  is over-expanded over the stent  320 , so that recoil of the cup  322  is sufficient to secure stent  320  in place and prevent it from being pulled off of the assembly  310  distally or proximally as assembly  310  is delivered to a deployment site in a body vessel. Cup  322  also protects the proximal end of stent  324  from inadvertently catching on anatomical structures or other things during maneuvering within the body or during loading and other handling. The ends of the stent may axially protrude and should be protected during maneuvering of stent  320  to keep stent  18  on assembly  310  in its contracted configuration and to maintain the structural integrity of stent  320 . Collar  314  abuts the stent distal end  326  without underlying stent  320 . The position of cup  322  overlying stent  320  and containing stent  320  against collar  314  increases the securement force maintaining stent  320  in its axial and radial position on catheter  12 .  FIG. 40  is similar to  FIG. 38 , showing a bulge  28  beneath the uninflated balloon  318  at catheter distal end  316 . 
     Any of the various types of known stents may be used in the delivery system of this invention, even self-expanding stents which are partly balloon-expandable may be used, the balloon initiating release of the stent and/or finally seating the stent after self-expansion. However, ordinary balloon expandable stents are preferred and aforenoted. 
       FIG. 39  shows another stent delivery and deployment assembly generally designated  330 . A catheter  332  has a collar coaxially mounted as a mounting ring  334  on the catheter. An uninflated balloon  338  is coaxially mounted on catheter  332  over mounting ring  334 . An unexpanded stent  340  is coaxially mounted on balloon  338  overlying the mounting ring  34 . A cup  342  overlies the stent proximal end portion  344  to secure the stent  340  in place and prevent it from being pulled off of assembly  330  distally or proximally, as assembly  330  is delivered to a deployment site in a body vessel. Cup  342  also protects the proximal end of stent  40  from inadvertently catching on anatomical structures during maneuvering within the body. The position of cup  342  overlying stent  340  together with the closer positioning of mounting ring  334  as compared to  FIG. 38  increases the securement force maintaining stent  340  in its axial and radial position on catheter  332 . The closer the mounting ring  334  is positioned to cup  342  the more securely the stent is held in place and interlocked between this cup and ring. When used in conjunction with mounting ring  334 , cup  342  will also prevent the stent proximal segment  344  from opening up, i.e., increasing its diameter, and will keep the stent  340  locked onto the mounting ring  334 . This will prevent stent  340  from moving on the catheter distally as well as proximally. This cup does not have to be an elastomer, but may be sufficiently rigid to prevent the stent  340  from expanding. 
     Cups  322 ,  342  of  FIGS. 38-40  release stents  320 ,  340  when balloons  318 , 338  are inflated during deployment. Cups  322 , 342  can, for example, flare radially outward as illustrated with reference to  FIG. 41 , roll axially away from stents  320 ,  340  as illustrated with reference to  FIG. 42 , or slide axially away from stents  320 ,  340  as illustrated with reference to  FIGS. 43 and 44 . Also, the cups may be formed with axial areas of weakness which split on balloon inflation, as described in the aforenoted Savin patent. 
       FIG. 41  shows an assembly generally designated  310  as shown in  FIGS. 38 and 36  with balloon  318  inflated and stent  320  expanded, showing the cup  322  end portion flared to release stent  320 . As noted above, cup  322  may be elastomeric or rigid. The dimension L is short enough and the material of cup  322  is sufficiently elastic so that cup  322  flares out and is no longer in contact with stent  320  when balloon  318  is inflated and the stent  320  expanded for deployment. 
       FIG. 42  shows an assembly generally designated  310 , as shown in  FIGS. 38 and 36 , with balloon  318  inflated and stent  320  expanded, showing cup  322  end portion rolled proximally to release the stent  320 . As noted above, the cup  322  may be elastomeric to facilitate rolling. The cup may also accordion or bunch up on itself to release the stent. 
       FIGS. 43 and 44  show yet another stent delivery and deployment assembly generally designated  350 . The catheter  352  has a coaxial collar  354  formed integrally with catheter  352  at the catheter distal end  356 . A balloon  358  is coaxially mounted on catheter  352 , overlying collar  354 . In  FIG. 43 , balloon  358  is coaxially mounted on catheter  352 , overlying collar  354 . In  FIG. 43 , balloon  358  is shown as uninflated, with an unexpanded stent  360  mounted on balloon  358  abutting collar  354 , and a cylindrical cup in the form of sleeve  362  overlying the stent proximal end portion  364 .  FIG. 44  shows the assembly  350  of  FIG. 43  with balloon  358  inflated and stent  360  released and expanded. Sleeve  362  is designed, constructed and adapted so that, as balloon  358  and stent  360  are enlarged, the sleeve portion  366  gathers or moves proximally to release stent  360 . The increasing angle of the balloon  358  cone (the tapered end sections of balloon  358 ) during inflation push sleeve  362  axially away from stent  360 . This can be done by shaping sleeve  362  with preformed accordion pleats  368 . Sleeve  362  may also be formed so that the portion detaining (that is, abutting or overlying) stent  360  is of thicker or more rigid material than the portion of sleeve  362  axially distant from stent  360 . Materials which may be used to provide the foregoing function are silicones, urethanes and the like as well as other elastomers, for example. A rigid sleeve carried on the catheter for sliding movement may also be used. Sleeves may be included at the proximal and distal end of the stent. 
       FIG. 45  shows still another stent delivery and deployment assembly generally designated  370 . A catheter  372  has two collars  374  formed integrally with catheter  372  and spaced from each other on the catheter distal end portion. A balloon  378  is coaxially mounted on the catheter  372 , overlying the collars  374 . The balloon  378  is shown as uninflated with an unexpanded stent  380  mounted on balloon  378  abutting both of the collars  374 . It can be seen that the distance between the collars  374  is to be chosen to closely accommodate stent  380  in its fully contracted position about the balloon  378  and underlying catheter  372 . A cup  382  overlies the stent proximal end portion  384  and the underlying proximal collar  374 . Cup  382  will deploy during balloon  378  inflation in the manner described above with reference to  FIGS. 41-44 . 
       FIG. 46  shows even another stent delivery and deployment assembly generally designated  390 . The uninflated balloon  398  is shown coaxially mounted on a catheter  392  at the catheter distal end portion. An unexpanded stent  400  is coaxially mounted on balloon  398 . A pair of cups  402  overlap the ends of the stent  400  ends. A mounting cylinder  404  is carried by the catheter shaft  392 . 
     The Figure also illustrates cups at both ends of the stent, an arrangement which may be used in all the foregoing embodiments. 
     The cups or sleeves used in the various embodiments of this invention can be of elastomeric or rigid material to contain one or both ends of the stent. In preferred embodiments of this invention the cups are used in conjunction with one or more stent collars positioned under the balloon. The collar may be formed as a ring, to abut the end of the stent, to lie under the stent and the intervening balloon, or as a cylinder, to lie under essentially the entire length of the stent and the intervening balloon. The stent detainment according to the present invention offers increased stent securement, particularly on pre-mounted delivery systems. The cups and sleeves illustrated in the various embodiments of this invention can be secured to the catheter, as by adhesive or thermal bonding, or they may be sliding cups or sleeves. When the cups are freely sliding on the catheter, they should always be used directly over a collar so that there is a friction fit between the cup and the stent. 
     A method for delivering and deploying a stent using an assembly according to the present invention is described as follows: A catheter is provided as described above with reference to any of  FIGS. 38-40 ,  43  and  45 . At least one collar is coaxially mounted at the catheter distal end. As discussed above, the collar may be a separate element affixed to the catheter or the collar and catheter may be formed together as a single element. The collar may be positioned abutting an end of the stent. The collar may be a mounting ring, may be positioned under the stent or underlying the balloon. The collar may be a cylinder essentially coextensive in length with the stent and underlying the balloon. A fluid expandable balloon is coaxially mounted over the collar on the catheter distal end. A stent is provided which is inflation expandable from a reduced to an enlarged condition. The stent, in its reduced condition, is coaxially mounted on the balloon so that at least an end portion of the stent overlies the balloon. A cup is provided which has first and second end portions. The cup is in an expanded form and also has a retracted form. The expanded cup is coaxially mounted on the catheter at the distal end portion so that the cup first end portion detains the stent end portion. The cup first end portion detains the stent end portion by overlying the stent end portion, or by closely accommodating the stent against the collar without overlying the stent end portion. The cup is then contracted about the catheter and the stent end portion to fix the stent to the catheter. The cup and collar cooperate to retain the stent on the catheter in its reduced condition. The assembly is then maneuvered by the physician through a body vessel by methods known per se to reach a pre-selected deployment site. The surgeon can determine when the assembly has reached the deployment site by means which are themselves known per se. For example, the assembly may be provided with radiopaque marking bands at either end of the stent, or the cups or the collars or both may be made of radiopaque material. Once the surgeon determines that the stent has been correctly positioned at the desired site, the balloon is inflated to expand the stent to its enlarged condition. Inflation of the balloon expands the stent and the stent is released from the cup or cups. As has been discussed above, the cups may deploy to release the stent in a number of ways, dependent on the construction and materials of the cup or cups. The cup may flare or enlarge radially following the increasing angle of the balloon cones. The cup may roll axially away from the stent. The portion of the cup axially distant from the stent may accordion back on itself. The cup may slide axially. The cup may accordion or buckle. If the cup is not fixed to the catheter, but is freely slidable on the catheter, the cup may slide axially away from the stent. After deployment of the stent, the balloon, according to previously known procedures, is deflated and the assembly is withdrawn proximally from the body vessel. Any incision made to allow access from the assembly is appropriately closed. 
       FIGS. 47-56  illustrated alternative embodiments of securement devices. Referring to  FIGS. 47 and 48  a stent delivery system generally indicated at  410  includes a balloon catheter  412  having a balloon  414  on a distal end portion generally indicated at  416 .  FIG. 47  shows a proximal portion of the catheter at  412   a  and a distal portion  412   b  in enlarged view.  FIG. 48  shows the distal end portion  416  in an even more enlarged view. The illustrative catheter  412  is of the type known as an over the wire catheter. However, other types of catheters may be used, such as rapid exchange/single operator exchange and fixed wire types. The balloon  414  is fixed to the catheter  412  by standard means. The balloon is shown in its contracted state in  FIGS. 47 and 48 . A stent  418  is fixed about the balloon by crimping it thereto. The stent has a larger expanded diameter which is obtained when the balloon is expanded in the known manner. That is, the stent is released from the catheter upon expansion of the balloon when placed in a vessel. When the balloon is then deflated, removal of the balloon and catheter may be accomplished while leaving the stent in place. 
     As is known in the art the balloon is either bonded at its ends by adhesive  420  and  422 , respectively to the outer member  424  of the catheter and to the inner member  426  of the catheter in the manner as shown, or is made one-piece with the outer member as is known in the art. The catheter balloon may be inflated by fluid (gas or liquid) from an inflation port extending from a lumen  428  contained in the catheter shaft and opening into the balloon as shown, or by other known arrangements, depending on the design of the catheter. The details and mechanics of balloon inflation and specific overall catheter construction will vary according to the particular design involved in any given instance, and are known in the art per se. All variations are acceptable for use with this invention. 
     Any balloon expandable stent may be used with this invention. Many are known in the art including plastic and metal stents. Some are more well known such as the stainless steel stent shown in U.S. Pat. No. 4,735,665; the wire stent shown in U.S. Pat. No. 4,950,227; another metal stent shown in European Patent Application No. EPO 707 837 A1 and that shown in U.S. Pat. No. 5,445,646. All of these patents are incorporated herein by reference. Also, shape memory metal stents may be used. As already indicated the stent of PCT Application 960 3092 A1 is particularly preferred. 
     The stent is typically about 16 mm long, while the balloon may be 20 mm long. These dimensions, however, are merely representative for illustrative purposes only and are not meant to be limiting. The stent is positioned over the balloon portion of the dilatation catheter and gently crimped onto the balloon either by hand or with a tool such as a pliers or the like to be mounted for delivery as shown in  FIGS. 47 and 48 . The crimping may be accomplished by either the manufacturer or the physician. 
     In accordance with one embodiment of this invention, a mounting bodies  430 , seen in  FIGS. 47 and 48  are included inside balloon  414  to provide a cushion and/or substrate of enlarged diameter relative to the shaft to support and hold the stent and secure it during crimping and the delivery procedure. The mounting bodies are preferably located in the body portion of the balloon. 
     In the embodiment shown, mounting bodies  430  are ring-like in form and are mounted on inner lumen  426 , providing an enlarged area or portion for receiving the balloon and stent when the latter is crimped. Marker bands  432  and  434  may also be included on inner  426  as shown. Any radiopaque material such as gold is useful for this purpose. Although, the material of the mounting bodies may be hard, it is preferably of any thermoplastic elastomer having elastic or deformable properties, more preferably of a relatively resilient elastomer material, e.g., silicone, preferably a lower durometer silicone, or polyurethane, such as Tecothane 1055D. A deformable thermoplastic material such as high density polyethylene (HDPE) may be used. Any deformation of resilient material of the mounting body when the stent/balloon is crimped to it causes a radial outward force on the stent/balloon increasing the friction therebetween despite a recoil of the stent. 
     The stent is also fixed in position by two overlying retaining sleeves  436  and  438 . Sleeves  436  and  438  are formed of polyurethane, preferably Tecothane 1055D, and are axially fixed on catheter  412  by adhesive plugs  440  and  442  of urethane adhesive. The plugs of adhesive may be tapered to the catheter as shown to facilitate movement of the catheter in a vessel. The sleeves overlap the marginal end portions of stent  418  as shown. 
     A lubricating solution such as silicone fluid may be used between balloon  414  and sleeves  436  and  438  and thereon to facilitate release of stent  418  from the sleeves. 
     During delivery, the balloon catheter is advanced through and positioned in a patient&#39;s vasculature so that the stent is adjacent to the portion of the vessel where treatment is to take place. The balloon is inflated to expand the stent to an enlarged diameter. At this time, expansion of the balloon causes the end margin of the sleeves to slide axially from over the stent thereby releasing the ends of the stent from the catheter. Various forms of retraction of sleeves  436  and  438  are shown in  FIGS. 49-52 . These figures illustrate the configuration of the sleeves  436  and  438  in their retracted state after the balloon  414  has been fully expanded. Only the distal sleeve  438  is shown.  FIG. 49  illustrates the preferably refraction configuration. To promote easier retraction sleeves are coated with silicone. The sleeves are preferably adhered to the outer shaft  424  and the inner shaft  426  at point  440 ,  442 , but may be adhered further up the waste  441  of the balloon. The refraction configurations may be controlled by either pre-creasing the sleeves or adhering the sleeve to a point further up on the waist of the balloon. The sleeves have a tendency of folding at a pre-fold crease or at the point of adherence. A preferred cone angle of 45.degree, for the balloon is shown in  FIG. 52 , which shows an expanded balloon  414  and retracted sleeves  436 , 438 . When the stent has reached the desired diameter, the balloon is deflated so that the catheter may be removed leaving the stent in place. 
     A modified  439  sleeve configuration is shown in  FIG. 53  in stepped form  43  having a large diameter at  444  in one section  446  and a small diameter  445  in a second section  450 . 
       FIGS. 54-56  show alternative embodiments of the invention. Specifically, alternative positioning and number of mounting bodies  430 . These figures show an unexpanded balloon having the mounted bodies  430  within the balloon. They are meant to illustrate essentially the same structure as shown in  FIG. 448  differing only in the number and positioning of the mounted bodies  430 . In the embodiment shown in  FIG. 54 , the ring-like mounting body  430  is singular. Another similar version is shown in  FIG. 55  which includes three ring-like mounting bodies  430 . The embodiment shown in  FIG. 56  includes four ring-like mounting bodies  430 . 
     It should be understood that the various elements and materials of all embodiments could be utilized in each of the other embodiments, if desired. 
     The above Examples and disclosure are intended to be illustrative and not exhaustive. These examples and description will suggest many variations and alternatives to one of ordinary skill in this art. All these alternatives and variations are intended to be included within the scope of the attached claims. Those familiar with the art may recognize other equivalents to the specific embodiments described herein which equivalents are also intended to be encompassed by the claims attached hereto.