Abstract:
A balloon catheter in which its distal tip is precisely positionable in order to control movement of the catheter through tortuous vasculature and especially through the lumen of a deployed stent is disclosed. The distal tip of the catheter is rendered radiopaque, at least at its distal-most end, to enable visualization of the position of the catheter and to facilitate placing the catheter in the desired position.

Description:
TECHNICAL FIELD 
     This invention relates to the field of intravascular medical devices and more particularly to balloon dilatation and stent delivery catheters which are readily trackable within vasculature in which they are used. 
     BACKGROUND OF THE INVENTION 
     Intravascular diseases are commonly treated by relatively non-invasive techniques such as percutaneous transluminal angioplasty (PTA) and percutaneous transluminal coronary angioplasty (PTCA). These therapeutic techniques are well known in the art and typically involve the use of a balloon catheter with a guidewire, possibly in combination with other intravascular devices such as stents. A typical balloon catheter has an elongate shaft with a balloon attached proximate the distal end and a manifold attached to the proximal end. In use, the balloon catheter is advanced over the guidewire such that the balloon is positioned adjacent a restriction in a diseased vessel. The balloon is then inflated and the restriction in the vessel is opened. 
     There are three basic types of intravascular catheters for use in such procedures, including fixed-wire (FW) catheters, over-the-wire (OTW) catheters and single-operator-exchange (SOE) catheters. The general construction and use of FW, OTW and SOE catheters are all well known in the art. An example of an OTW catheter may be found in commonly assigned U.S. Pat. No. 5,047,045 to Arney et al. An example of an SOE balloon catheter is disclosed in commonly assigned U.S. Pat. No. 5,156,594 to Keith. 
     Several characteristics that are important in intravascular catheters include pushability, trackability and crossability. Pushability refers to the ability to transmit force from the proximal end of the catheter to the distal end of the catheter. Trackability refers to the ability to navigate tortuous vasculature. Crossability refers to the ability to navigate the balloon catheter across narrow restrictions in the vasculature, such as stenosed vessels or fully and partially deployed stents. 
     To maximize pushability, some prior art catheters incorporate a stainless steel outer tube (also referred to as a hypotube) on the proximal shaft section and a polymeric distal shaft section. One limitation of such a construction is that hypotubing is often prone to kinking. To reduce the likelihood of kinking, some prior art catheters use a relatively stiff polymer (e.g., composite) or reinforced polymer in the proximal shaft section. 
     The trackability of a particular catheter design is analyzed in terms of the trackability of the distal portion of the catheter, as this portion must track the guidewire through small tortuous vessels to reach the area to be treated. A more flexible distal portion has been found to improve trackability. Therefore, to maximize pushability, the catheter should have a relatively stiff proximal section. To maximize trackability, the catheter should have a relatively flexible distal section. To maximize crossability, in addition to the characteristics needed for pushability and trackability, the catheter should have a distal tip, the location of which within the vessel can be readily determined so that the progress of the catheter through the vessel can be followed. 
     One limitation of the basic structure of catheters described above is that kinking can occur at the joint between the relatively stiff proximal shaft section and the relatively flexible distal shaft section. To reduce the likelihood of kinking, some prior art catheters use one or more tubular sections of intermediate flexibility between the relatively stiff proximal section and the relatively flexible distal section to provide a more gradual transition in flexibility theretween. While this approach provides some benefit, the resulting transition in flexibility is often step-wise, and can still be susceptible to kinking at the junctions of the various intermediate sections. In order to overcome this deficiency, an intravascular catheter that has a more gradual transition in flexibility along its length has been needed. A catheter satisfying this need is described in commonly assigned U.S. Pat. No. 5,891,110 to Larson et al., which is incorporated herein by reference. 
     However, while overcoming some of the problems with regard to flexibility, comparatively little effort has been directed toward facilitating control of the direction of the catheter tip with respect to a deployed stent or a stenosis. Recrossing a deployed self-expanding or balloon-expandable stent with a post-dilation balloon catheter or additional stent delivery catheter, for example, can prove to be a difficult procedure. Inability of the catheter to cross the stent might be due to failing to direct the distal tip of the catheter into the stent lumen. Instead, the distal tip could be directed into the vessel wall or could get hung up in the struts of the stent. It is also possible for the guidewire to be misdirected by threading it between the stent and the wall of the vessel instead of through the stent lumen. The end result would be that the balloon catheter would get stuck in the vessel and could not be easily removed. 
     Previous attempts to provide catheters that are more readily visualized within the vessel have involved the utilization of radiopaque markers in catheters. For example, it has been proposed to track the balloon of a balloon catheter by placing radiopaque bands inside the balloon. Such bands, however, are of little assistance in positioning the distal-most end of the catheter tip, which may be separated from the balloon by a distance of several centimeters. 
     It would be desirable, therefore, to provide a catheter having improved crossability. It would also be desirable to provide a catheter in which the precise position of the distal tip relative to a deployed balloon, stent or stenosis could be readily ascertained. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes many of the disadvantages of the prior art by providing a balloon catheter having a distal tip which can be readily located and its position closely followed within vasculature in which it is deployed. The balloon catheter of the present invention is rendered radiopaque proximate the distal-most tip thereof, enabling the physician to observe the position of the tip of the catheter within the body of the patient. Precise placement of the catheter tip by the physician is thereby facilitated. 
     Radiopacity can be imparted proximate the distal-most tip of the catheter in any of various ways. These include, among others, (1) embedding the catheter tip with radiopaque powder or particles, (2) applying a radiopaque pigment, such as a paint or ink, to the surface of the tip of the catheter, (3) using a radiopaque contrast media to coat the interior surface of a balloon immediately adjacent the distal-most end of the catheter tip, (4) providing bands of radiopaque material proximate the distal-most end of the catheter tip, (5) providing a coil of radiopaque material encircling the distal-most end of the catheter tip, (6) covering at least part of the catheter tip adjacent the distal-most end thereof with a radiopaque mesh or braid, (7) incorporating radiopaque wires in the wall of at least part of the catheter tip adjacent the distal-most end thereof, (8) capping the distal-most end of the catheter tip with a radiopaque cap, and (9) using an arc of a radiopaque hypotube or similar tubing to encircle at least that part of the catheter tip adjacent the distal-most end thereof. Other ways of imparting radiopacity to at least that part of the catheter tip adjacent or proximate the distal-most end thereof are within the scope of the present invention. 
     Rendering the catheter tip radiopaque proximate its distal-most end is especially important in balloon catheters, because guiding the catheter tip within stenosed vasculature and particularly through stents deployed therein requires knowledge of the precise position of the catheter tip. A radiopaque catheter tip of the present invention can be viewed within body vasculature from outside the body to enable precise maneuvering and placement of the catheter with respect to the stenosed area or to facilitate passage through deployed stents and the like. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects of the present invention and many of the attendant advantages thereof will be readily appreciated as the same become better understood by reference to the following detailed description when considered in connection with the accompanying drawings, in which like reference numerals designate like parts throughout the figures thereof and wherein: 
     FIG. 1 is a cross-sectional view of a representative prior art catheter of the type used with the present invention; 
     FIG. 2 is a partial cross-sectional view of a prior art distal tip area of a catheter as in FIG. 1; 
     FIG. 3 is a partial cross-sectional view of another prior art design of the distal tip area of the catheter of FIG. 1; 
     FIG. 4 is a plan view of the distal end of a balloon catheter showing one preferred embodiment of the present invention; 
     FIG. 5 is a plan view of another preferred embodiment of the present invention; 
     FIG. 6A is a plan view of another preferred embodiment of the present invention; 
     FIG. 6B is a cross-section of the embodiment of FIG. 6A along the line  6 B— 6 B; 
     FIG. 7 is a plan view of another preferred embodiment of the present invention; 
     FIG. 8A is a plan view of another preferred embodiment of the present invention; 
     FIG. 8B is a cross-section of the embodiment of FIG. 8A along the line  8 B— 8 B; 
     FIG. 9 is a plan view of another preferred embodiment of the present invention; 
     FIG. 10 is a plan view of another preferred embodiment of the present invention; 
     FIG. 11 is a plan view of another preferred embodiment of the present invention; and 
     FIG. 12 is a partial cross-sectional view of another preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following detailed description should be read with reference to the drawings in which like elements in different drawings are numbered identically. The drawings, which are not necessarily to scale, depict selected embodiments and are not intended to limit the scope of the invention. 
     Examples of constructions, materials, dimensions and manufacturing processes are provided for selected elements. All other elements employ that which is known to those skilled in the field of the invention. Those skilled in the art will recognize that many of the examples provided have suitable alternatives which may also be utilized. 
     Referring now to the drawings, FIG. 1 is a cross-sectional view of an over-the-wire (OTW) balloon catheter, which is representative of one type of catheter that can incorporate the present invention. Other intravascular catheter embodiments are additionally suitable without deviating from the spirit and scope of the present invention. For example, intravascular catheters suitable for incorporating the present invention include fixed-wire (FW) catheters and single-operator-exchange (SOE) catheters. 
     The balloon catheter  20  includes a shaft assembly  22  and a balloon assembly  24  connected proximate the distal end of shaft assembly  22 . A conventional OTW-type manifold assembly  26  is connected to the proximal end of the shaft assembly  22 . The shaft assembly  22  includes an inner tube  28  having a proximal end  30  and a distal end  32 . The proximal end of the shaft assembly  21  extends into a manifold assembly  26  adhesively bonded to the shaft assembly  22 . A polyurethane strain relief  23  is snap-fit to the manifold assembly  26 , and the shaft assembly  22  extends into the manifold assembly  26  through the polyurethane strain relief  23 . An outer tube  34  is co-axially disposed about the inner tube  28  to define an annular inflation lumen  37  therebetween. 
     The balloon assembly  24  includes a balloon body portion  36  with a proximal balloon waist  38  and a distal balloon waist  40 . The proximal balloon waist  38  is connected to the outer tube  34  near its distal end  42  by means of an adhesive  44 , or alternatively, is thermally bonded. The distal balloon waist  40  is connected to the inner tube  28  near its distal end  32  by means of an adhesive bond  48  or a thermal bond such that the interior of the balloon  46  is in fluid communication with the annular inflation lumen  37 . 
     A radiopaque marker band  50  may be adhesively secured with cyanoacrylate to the inner tube  28  at a point underneath the balloon body  36 . Alternatively, the marker band may be swaged onto the outer surface of the inner tube  28  within the balloon. 
     The inner tube  28  defines a guidewire lumen  54 , which provides a passage for a guidewire (not shown). The outer tube  34  defines an annular inflation lumen  37 , which is in fluid communication with the interior of the balloon  46 . 
     As previously stated, the catheter of the present invention includes an outer tube  34  which may have multiple segments including a relatively stiff proximal outer section, a mid-shaft section of lesser stiffness, and a tapering distal outer section of the least stiffness. The progressive arrangement of more flexible materials as the catheter proceeds distally provides an optimal level of pushability and trackability to navigate tortuous vasculature. The flexibility of the sections of the outer tubular member were tested utilizing a Gurley bending resistance tester, Part No. 4171-DT, as manufactured by Precision Instruments, Troy, N.Y. The apparatus consists of a balanced pendulum or pointer which is center-pivoted and can be weighted at three points below its center. The pointer moves freely in both the left and right directions. A sample of specific size is attached to a clamp, which in turn is located in one of several positions on a motorized arm which also moves left and right. During the test, the sample is moved against the top edge of the vane, moving the pendulum until a sample bends and releases it. The test is run in two steps, first to the left and then to the right. The scale reading is measured in each direction and the results are averaged. The instrument provides a relative flexibility measurement between the components of the outer tubular member as detailed below to achieve improved trackability and pushability. 
     The outer tube  34  has a relatively stiff, proximal outer section  56  with a proximal end  60  and a distal end  62 . The proximal outer tube may be made of nylon, a polyamide, such as DURETHAN available from Bayer, GRILAMID available from EMS-American Grilon, Inc., a DURETHAN, GRILAMID, CRISTAMID or CRISTAMID/VESTAMID blend braid or polyetheretherketone (PEEK) braid. The preferred embodiment of PEEK braid is a variable PIC tube, wherein said PIC varies from about 30 to 100 PIC to give varying flexibility over the length of the proximal outer tube. The PIC preferably varies from about 50 to about 80. The braiding material in the PEEK or DURETHAN (polymer) braid may be made from stainless steel, or Nitinol (nickel titanium alloy). This proximal outer section  56  will have an outside diameter ranging from 0.040 inches to 0.065 inches with a wall thickness ranging from 0.0026 inches to 0.0056 inches. The proximal outer section has a preferred Gurley value of about 700 to about 1300 over its length. A preferred range is about 800 to about 1200. 
     A midshaft section  58  with a proximal end  64  and a distal end  66  extends distally from the distal end  62  of the proximal outer section  56 . The midshaft section  58  has a stiffness less than that of the proximal outer section  56 . The midshaft section  58  is preferably made from a polyamide, such as CRISTAMID available from Elf Atochem, having a durometer of about 81D. A preferred Gurley value for the midsection is about 350 to about 500, with a range of 400 to 450 preferred. This midshaft section  58  will have an outside diameter ranging from 0.040 inches to 0.045 inches with a wall thickness ranging from 0.0028 inches to 0.0044 inches. 
     The distal end of the proximal outer section  62  is joined to the proximal end of the midshaft section  64  with a urethane adhesive bond or a thermal weld. A distal outer section  68  having a proximal end  70  and a distal end  72  extends distally from the distal end of the midshaft section  66  to the distal end of the outer tube  44 . This distal outer section  68  is more flexible or has less stiffness than both the proximal outer section  56  and the midshaft section  58 . The outer diameter of the distal outer section  68  will taper from about 0.045 inches at the proximal end  70  to 0.030 inches at the distal end  72 . This distal outer section  68  is made of polyether block amide (PEBAX) with a durometer of 70D. The tapered distal outer section preferably has a Gurley value of about 70 to about 90 at its proximal end and about 15 to about 40 at its distal end. Thus, the distal end of the distal outer section  72  will exhibit less stiffness than the proximal end of the distal outer section  70 . The distal end of the midshaft section  66  is joined to the proximal end of the distal outer section  70  with a urethane adhesive bond or a thermal weld. 
     A Nitinol braid insert  74  with a length of about 1.0 inches is placed within the proximal end of the distal outer section  70  to provide strain relief and reduce kinkability at the midshaft/distal outer section junction. This Nitinol braid  74  has a 0.001 inches×0.005 inches ribbon. 
     The inner tube  28  is made of polyethylene such as Marlex HDPE or a multilayer co-extrusion with Marlex interior layer and PEBAX outer layer. At the proximal end of the inner tube  30 , the inner tube  28  has an outside diameter ranging from 0.022 inches to 0.028 inches and preferably about 0.025 inches, with the inner tube  28  having an inside diameter ranging from 0.016 inches to 0.021 inches for a 0.014 inch guidewire with which this lumen is designed to be compatible. The inner tube  28  has a wall thickness ranging from 0.0024 inches to 0.005 inches and preferably about 0.0032 inches. The outside diameter-to-wall thickness ratio must be sufficiently small to minimize the propensity of kinking. 
     As the inner tube  28  extends distally through the junction area between the distal end of the proximal outer section  62  and the proximal end of the midshaft section  64  of the outer tube  28 , both the inner and outer diameters of the inner tube  28  will taper from wider diameters to narrower diameters. Likewise, at the distal end of the inner tube  32 , both the inner and outer diameters of the inner tube  28  will once again taper from wider diameters to narrower diameters as the tube extends distally. 
     As illustrated in FIG. 2, which shows details of the catheter assembly of FIG. 1, a distal tip  76  having a distal-most end  78  is formed on the distal end of the inner tube  32 , where the inner tube  28  distally tapers from a larger outer diameter to a smaller outer diameter. The distal balloon waist  40  is attached to the distal tip  76  through a urethane adhesive bond or thermal bond at a bonding area. The area just distal of the distal waist bond is backfilled with adhesive  43  to provide a smooth transition. The adhesive coating provides for improved adhesion between dissimilar substrates. 
     The proximal catheter shaft portion is preferably about 35 to 45 inches in length with a preferred length of 42 inches. The midshaft section, if included, can be about 1 to about 3 inches in length with a preferred length of 2 inches. The distal outer section having the most flexibility is preferably about 8 to about 12 inches in length with a preferred length of about 10 inches. 
     In another embodiment of the catheter assembly of FIG. 1, as shown in FIG. 3, a polyethylene, polyamide, or block copolymer such as PEBAX distal tip  80  having a durometer between about 50D and 70D, preferably about 63D is heat welded or bonded to the distal end of the inner tube  32  with a durometer of about 63-65D, and the distal balloon waist  40  of the balloon is adhesively or thermally bonded to both the inner tube and the tip extending therefrom. As shown in FIG. 3, the joint  41  between the inner tube and the tip is located under the distal waist of the balloon. The outer diameter of the polyethylene distal tip  80  distally tapers from a larger outer diameter to a smaller outer diameter. 
     In another embodiment also shown in FIG. 3, the last ½ to 1 mm of the tip at its distal end is made of a different material from the tip material to form a tip extension. In particular, the last ½ to 1 mm is made from a material which is more durable relative to the softer tip material. In particular, the more durable material will resist deforming or tearing when in use, such as in tracking tortuous anatomy or in moving through a deployed stent. For example, this last ½ mm to 1 mm may be manufactured from Marlex high-density polyethylene having a 63D durometer which improves the integrity of the tip portion at its distal-most end  81 . 
     FIG. 4 shows a preferred embodiment of a tip assembly which can be included in catheters such as that in FIGS. 1 and 3. In the embodiment, radiopacity is provided to the tip assembly proximate its distal-most end by a radiopaque coil. Distal tip  76  is positioned distally from the distal balloon waist  40  of balloon  36 . In particular, the distal tip is illustrated as having a coil  90  encircling the distal-most end  78 . Coil  90  may be comprised of any radiopaque material. Preferable materials forming coil  90  include any metals or plastics being radiopaque, or capable of being impregnated with radiopaque materials. In particular, tungsten, tantalum, platinum, gold, and the like are examples of preferred materials forming coil  90 . 
     Coil  90  is preferably wire-shaped. Various shaped wires, however, may be used to form coil  90 . As such, coil  90  may be manufactured as a round wire, a wire ribbon, a cable wire, or a machined hypotube. The wire is wound about the distal tip  76 , imparting a helical configuration to coil  90 . Coil  90  may additionally encircle distal tip  76  through a series of connected spirals or concentric rings. In preferred embodiments, the windings of coil  90  terminate prior to reaching the distal-most end  78  of distal tip  76 . 
     The longitudinal spacing and tensile strength of the windings may vary from catheter to catheter. By varying the longitudinal spacing and tensile strength, the physical characteristics of the distal tip  76  may be altered. For example, close spacing and elevated tensile strength often result in an increase in the stiffness of the distal tip  76 , and more particularly, causing the distal-most end  78  to become less supple. Larger spacing and lower tensile strength, on the other hand, while still decreasing the flexibility of the distal tip  76  alone, retain a sufficiently supple distal-most end  78 . 
     FIG. 5 shows another preferred embodiment of a tip assembly in which radiopacity is contributed by a radiopaque mesh material. A radiopaque mesh  92  extends generally from distal balloon waist  40  of balloon  36  proximate distal-most end  78  of distal tip  76 . Depending upon the flexibility desired for the catheter tip, the mesh can either encircle distal tip  76  entirely, or only a portion thereof. Alternatively, distal tip  76  can itself be fabricated of the radiopaque mesh material  92 . 
     When radiopaque mesh  92  is attached to the distal tip  76 , the attachment generally occurs through the use of a urethane adhesive or thermal bond at the desired bonding location. A thermal bond permits embedding the radiopaque mesh  92  into the surrounding polymeric material forming distal tip  76 . Embedding the mesh affords a manufacturer the option of eliminating the need to backfill the area just distal of the distal balloon waist  40 . The embedding procedure itself provides a smooth transition along the distal tip  76 . Backfilling, when desired, is generally accomplished using an adhesive or other suitable polymeric material. Backfilling may additionally occur toward the distal-most end  78 , or over the radiopaque mesh  92 , to insure a smooth transition throughout the distal tip  76 . 
     In an alternative embodiment, a radiopaque braid can be used in place of the radiopaque mesh material. A further embodiment provides that a polymeric material may be extruded over the radiopaque mesh or braid  92  forming a distal tip  76  having a lumen  54  extending longitudinally therein. 
     FIGS. 6A and 6B show another preferred embodiment of a tip assembly in which the radiopacity is provided by a radiopaque member or wire incorporated into the wall of the catheter tip. A radiopaque wire  94 , shown in phantom in FIG. 6A, is embedded in distal tip  76 . Various shaped wires may be used to form wire  94 . As such, radiopaque wire  94  may be manufactured as a round wire, a wire ribbon, a cable wire, or a machined hypotube. Radiopaque wire  94  may be comprised of any radiopaque material. Materials forming radiopaque wire  94  include any metals or plastics being radiopaque or capable of being impregnated with radiopaque materials. In particular, tungsten, tantalum, platinum, gold, and the like, are examples of preferred materials forming radiopaque wire  94 . 
     Radiopaque wire  94  may originate anywhere within balloon distal waist  40  and extend longitudinally until terminating at or proximate the distal-most end  78  of distal tip  76 . Preferably, radiopaque wire  94  generally extends longitudinally from the proximal-most end of distal tip  76  and terminates prior to the distal-most end  78  thereof. The radiopaque wire  94  is preferably straight, however, the wire may additionally assume alternative configurations that follow a general longitudinal progression (e.g., a sinusoidal curve). 
     FIG. 6B shows a cross-section of the distal tip of FIG. 6A having radiopaque wire  94  embedded therein. Lumen  50  is defined by an inner diameter and an outer diameter at the distal tip  76 . The inner diameter defines a pathway for the passage of a guidewire. The outer diameter defines the surface of distal tip  76 . Radiopaque wire  94  is positioned between the inner and outer diameters. Preferably, radiopaque wire  94  is entirely encapsulated between the inner and outer diameter. 
     FIG. 7 shows a radiopaque cap over the distal tip of the catheter. A radiopaque cap  96  surrounds distal tip  76 , shown in phantom. Radiopaque cap  96  may be comprised of any radiopaque material. Materials forming radiopaque cap  96  include any metals or plastics being radiopaque or capable of being impregnated with radiopaque materials. In a preferred embodiment, radiopaque cap  96  is made of a high durometer polymeric material. Radiopaque caps of high durometer allow the distal tip region to remain supple, minimizing trauma associated with the catheter&#39;s advancement through the surrounding vessel walls. 
     Since radiopaque cap  96  is formed independent from distal tip  76 , the cap may be molded to redefine the original shape of the distal tip  76  of a catheter. For instance, radiopaque cap  96  may form a gradually decreasing taper from where cap  96  seats against balloon waist  40  to the cap&#39;s distal-most end. This cap configuration allows for a smooth transition between the distal tip region to the balloon region of a catheter. Alternatively, cap  96  may mimic the shape of a typical distal tip  76  having a straight tubular shape, as illustrated in FIG.  7 . Once the cap design is chosen and slid over the distal tip  76 , the radiopaque cap  96  is preferably attached to distal tip  76  through a urethane adhesive or by thermal bonding. 
     FIG. 8A shows a half arc hypotube providing radiopacity to the distal-most end of the distal tip. Half arc hypotube  98  is securely attached to distal tip  76 . The hypotube  98  may be attached anywhere along the length of distal tip  76 . To aid a physician in pinpointing the distal-most end of the catheter, however, it is believed that the hypotube should be placed close to the distal-most end  78  of distal tip  76 . Once positioned, hypotube  98  is attached to the outer diameter of the distal tip  76  through a urethane adhesive or by thermal bonding. 
     Thermal bonding hypotube  98  to distal tip  76  permits the embedding of hypotube  98  into the polymeric material forming distal tip  76 . The depth of the subsequent embedding may be varied. In one embodiment, hypotube  98  is embedded into distal tip  76  until the outer diameter of hypotube  98  is flush with the outer diameter of distal tip  76 . Alternatively, hypotube  98  may be partially embedded into the polymeric material forming distal tip  76 . If desired, backfill of polymeric material may be added to smooth the transition around the exposed portions of hypotube  98 . 
     FIG. 8B shows a cross-section of the distal tip  76  of FIG. 8A having half arc hypotube  98  attached thereto. Lumen  54  is defined by an inner diameter and an outer diameter. The inner diameter defines a pathway for the passage of a guidewire. The outer diameter defines the outer surface of distal tip  76 . As illustrated in FIG. 8B, hypotube  98  is attached directly upon the outer surface of distal tip  76 . With this configuration, the edges of half arc hypotube  98  are exposed. Exposed edges may cause trauma to the surrounding vessel walls as the catheter is advanced. To alleviate this possibility for trauma, polymeric material may be added along these exposed edges to smooth the profile of distal tip  76 . 
     FIG. 9 shows the distal tip embedded with radiopaque particles. Distal tip  76  is fabricated using a polymeric material impregnated with radiopaque particles  100 . Radiopaque particles  100  may be in powder or particulate form. Any radiopaque material may be used that may be readily blended and extruded. Radiopaque particles  100  are preferably blended with a polymeric material capable of forming a soft distal tip  76 . The blended material is then extruded to form an elongate distal tip  76  having a lumen  54  extending longitudinally therein. The resultant distal tip  76  may be either extruded simultaneously with the portions of the lumen forming the guidewire lumen, or the extruded distal tip  76  may be attached to the body of the catheter at a later time. If distal tip  76  is extruded independent of the main body of the catheter, the later attachment is preferably accomplished through a urethane adhesive or by thermal bonding. The distal tip may be assembled as described with reference to FIG.  3 . 
     FIG. 10 shows the use of a radiopaque pigment which is painted upon the distal tip. Radiopaque pigment  102  painted upon the distal tip allows identification of relevant portions on the catheter&#39;s body while within a vasculature. In particular, radiopaque pigment may be applied anywhere between the distal-most end  78  and balloon waist  40  of distal tip  76 . 
     Physicians may easily navigate and align a catheter across a stenosis or a stent when the physician accurately knows the location of the catheter&#39;s distal-most end  78 . Additionally, when radiopaque pigment is applied to balloon waist  40 , a physician may easily align the balloon within a stent. When a balloon is accurately positioned within a stent, on expansion, the stent opens with uniformity and with reduced trauma to the surrounding vasculature. 
     In an alternative embodiment, radiopaque pigment  102  may be incorporated into a polymeric backfill. Backfill having radiopaque pigment  102  may be added to portions of distal tip  76 . In particular, backfill may be added upon distal-most end  78  to readily identify the terminal point of the catheter. 
     FIG. 11 shows alternating bands of radiopaque material  104  incorporated within distal tip  76 . Alternating hard radiopaque material with softer non-radiopaque material is possible. Bands  104  of radiopaque material may also alternate with bands  106  of non-radiopaque material throughout the length of distal tip  76 . In an alternative embodiment, the radiopaque material is soft and the non-radiopaque material is hard. The alternating band configuration may additionally be applied to only a portion of distal tip  76 , preferably, to the distal-most end. 
     Alternating bands of different durometers affects the flexibility of distal tip  76 . This embodiment provides a more flexible and supple distal tip  76 . During catheter advancement, this distal tip design permits aggressive navigation without traumatizing the surrounding vasculature. 
     In a preferred embodiment, distal tip  76  is comprised wholly of a soft non-radiopaque material. Bands of material are then removed from the distal tip through an abrasion process. Specifically, the band of material is removed by bringing distal tip  76  into contact with a grinding wheel. The distal tip  76  is then rotated  360  degrees to remove the material circumferentially around the tip. The grinding wheel is slowly advanced to increase the depth of the cut. Although abrasion is the preferred method of processing, the band can be created using many different processes, some of which include alternate extrusion methods, cutting, and thermal processing. Material differing in durometer and radiopacity than the one removed from distal tip  76  is then backfilled into the exposed bands. Therefore, backfill material comprising of a hard radiopaque material is filled into the exposed bands of the soft non-radiopaque distal tip  76 . 
     As illustrated in FIG. 12, the distal region of the catheter includes a balloon with a distal balloon waist  110  connected to the inner tube near its distal-most end. In preferred embodiments, the distal-most end of the distal balloon waist  112  is connected to the inner tube by means of an adhesive bond or thermal bond. Adhesive or thermal bonding permits the interior of the balloon  36  to be in fluid communication with an annular inflation lumen. The distal balloon waist  110  extends proximally from the distal-most end along and slightly above the inner tube forming a narrow channel  114 . The proximal end of the narrow channel  114  extends outwardly forming the distal end of balloon  36 . As a result, the narrow channel  114  remains in fluid communication with balloon  36 . In a preferred embodiment, the portion of distal balloon waist  110  forming the narrow channel  114  comprises a non-compliant balloon material. 
     A reservoir of contrast media  108  is fluidly connected to balloon  36 . The reservoir may dispense contrasting media  108  to balloon  36  when balloon  36  is either in an inflated or deflated state. When balloon  36  is supplied with contrasting media  108 , the contrasting media  108  fills both the balloon  36  and the narrow channel  114  under the distal balloon waist  110 . Visualization of the distal-most end of the narrow channel  114  is generally a close approximation of the distal-most end  78  of distal tip  76 . A physician, therefore, may accurately identify the catheter&#39;s positioning within the vasculature by adjusting for the known discrepancy between the distal-most end of the narrow channel  114  and the distal-most end  78  of distal tip  76 . 
     Having thus described the preferred embodiments of the present invention, those of skill in the art will readily appreciate that yet other embodiments may be made and used within the scope of the claims hereto attached.