Abstract:
Catheters such as guide catheters can be configured to provide distal occlusion, while still providing sufficient interior lumen space for device delivery. Such catheters can also provide a desired level of flexibility, yet can include sufficient column support. A catheter can include an elongate shaft having a distal region, a proximal region and a lumen extending therebetween. Distal occlusion means can be disposed over a portion of the distal region of the elongate shaft and occlusion activating means can be disposed over the elongate shaft.

Description:
TECHNICAL FIELD  
       [0001]     The invention relates generally to catheters and more specifically to catheters that include distal occlusion means.  
       BACKGROUND OF THE INVENTION  
       [0002]     Catheters such as guide catheters can be subject to a number of often conflicting performance requirements such as flexibility, strength, minimized exterior diameter, maximized interior diameter, and the like. In particular, there can be a balance between a need for flexibility and a need for strength or column support. If a catheter is sufficiently flexible to reach and pass through tortuous vasculature, the catheter may lack sufficient column strength to remain in position while, for example, subsequent treatment devices are advanced through the catheter.  
         [0003]     Some medical procedures require a method of occluding blood flow distally of a treatment site, while other procedures benefit from occluding blood flow proximally of a treatment site. While a balloon catheter can be used to occlude blood flow, inclusion of a balloon catheter requires either a separate lumen through a guide catheter or a substantial amount of the lumen space within the guide catheter.  
         [0004]     A need remains for a catheter such as a guide catheter that can provide desired strength versus flexibility characteristics. A need remains for a catheter such as a guide catheter that can occlude blood flow without sacrificing the interior lumen space otherwise required by a balloon catheter.  
       SUMMARY OF THE INVENTION  
       [0005]     The invention is directed to catheters such as guide catheters configured for providing distal occlusion, while still providing sufficient interior lumen space for device delivery. The invention is directed to catheters such as guide catheters that also provide a desired level of flexibility, yet can include sufficient column support.  
         [0006]     Accordingly, an example embodiment of the invention can be found in a catheter that includes an elongate shaft having a distal region, a proximal region and a lumen extending therebetween. Distal occlusion means are disposed over a portion of the distal region of the elongate shaft and occlusion activating means are disposed over the elongate shaft.  
         [0007]     Another example embodiment of the invention can be found in a guide catheter assembly having a distal region and a proximal region. An elongate shaft extends from the distal region to the proximal region and defines a lumen extending therebetween. An outer member is slidably disposed over an outer surface of the elongate shaft. An expandable member is disposed over the outer surface of the elongate shaft such that a distal end of the outer member is proximate a proximal end of the expandable member. A stop is disposed on the elongate shaft in order to limit distal travel of the expandable member. A distal end of the expandable member contacts the stop.  
         [0008]     Another example embodiment of the invention can be found in a method of deploying a treatment device within a patient&#39;s vasculature. A distal occlusion device is provided that has a distal region, a proximal region and a lumen extending therebetween. The distal occlusion device includes an elongate shaft extending between the distal region and the proximal region, an outer tube disposed over a portion of the elongate shaft, and an expandable member disposed over the elongate shaft.  
         [0009]     The distal occlusion device is advanced through the vasculature, and the outer tube is advanced distally to expand the expandable member to engage the expandable ember and to transform the expandable member from an initial collapsed configuration to an expanded or engaged configuration. The treatment device is advanced through the lumen. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]     The invention may be more completely understood in consideration of the following detailed description of various embodiments of the invention in connection with the accompanying drawings, in which:  
         [0011]      FIG. 1  is a side elevation view of an intravascular catheter in accordance with an embodiment of the invention;  
         [0012]      FIG. 2  is a cross-sectional view taken along line  2 - 2  of  FIG. 1 ;  
         [0013]      FIG. 3  is a partially sectioned view of a portion of a catheter assembly including the intravascular catheter of  FIG. 1  with an outer member and an expandable member positioned over the intravascular catheter;  
         [0014]      FIG. 4  is a cross-sectional view of the catheter of  FIG. 3  at line  4 - 4 ;  
         [0015]      FIG. 5  is a partially-sectioned view of  FIG. 3 , showing the expandable member in an expanded configuration;  
         [0016]      FIG. 6  is a partially-sectioned view of a portion of  FIG. 3 , showing the expandable member in greater detail;  
         [0017]      FIG. 7  is a side elevation view of a cylinder in accordance with an embodiment of the invention, seen in a collapsed configuration;  
         [0018]      FIG. 8  is a side elevation view of the cylinder of  FIG. 7 , shown in an expanded configuration;  
         [0019]      FIG. 9  is a side elevation view of a cylinder in accordance with another embodiment of the invention, seen in a collapsed configuration;  
         [0020]      FIG. 10  is a side elevation view of the cylinder of  FIG. 9 , shown in an expanded configuration;  
         [0021]      FIG. 11  is a partially-sectioned view of the catheter of  FIG. 3 , shown advanced into a patient&#39;s vasculature, the expandable member shown in its collapsed configuration;  
         [0022]      FIG. 12  is a partially-sectioned view of the catheter of  FIG. 3 , shown advanced into a patient&#39;s vasculature, the expandable member shown in its expanded configuration; and  
         [0023]      FIG. 13  is a partially-sectioned view of the catheter of  FIG. 3 , shown advanced into a patient&#39;s vasculature, the expandable member shown in its expanded configuration, with a treatment device deployed through the catheter and extending distally of the occlusion. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0024]     For the following defined terms, these definitions shall be applied, unless a different definition is given in the claims or elsewhere in this specification.  
         [0025]     All numeric values are herein assumed to be modified by the term “about”, whether or not explicitly indicated. The term “about” generally refers to a range of numbers that one of skill in the art would consider equivalent to the recited value (i.e., having the same function or result). In many instances, the terms “about” may include numbers that are rounded to the nearest significant figure.  
         [0026]     The recitation of numerical ranges by endpoints includes all numbers within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5).  
         [0027]     As used in this specification and the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.  
         [0028]     The following description should be read with reference to the drawings wherein like reference numerals indicate like elements throughout the several views. The drawings, which are not necessarily to scale, depict illustrative embodiments of the claimed invention.  
         [0029]      FIG. 1  is a plan view of a catheter  10  in accordance with an embodiment of the invention. The catheter  10  can be one of a variety of different catheters, but is preferably an intravascular catheter. Examples of intravascular catheters include balloon catheters, atherectomy catheters, drug delivery catheters, diagnostic catheters and guide catheters. As illustrated,  FIG. 1  portrays a guide catheter, but the invention is not limited to such. Except as described herein, the intravascular catheter  10  can be manufactured using conventional techniques and materials.  
         [0030]     The intravascular catheter  10  can be sized in accordance with its intended use. The catheter  10  can have a length that is in the range of about 50 centimeters to about 100 centimeters and can have a diameter that is in the range of about 4 F (French) to about 9 F.  
         [0031]     In the illustrated embodiment, the intravascular catheter  10  includes an elongate shaft  12  that has a proximal region  14 , a distal region  16  and a distal end  18 . A hub and strain relief assembly  20  can be connected to the proximal region  14  of the elongate shaft  12 . The hub and strain relief assembly  20  includes a main body portion  22 , a pair of flanges  24  designed to improve gripping, and a strain relief  26  that is intended to reduce kinking. The hub and strain relief assembly  20  can be of conventional design and can be attached using conventional techniques.  
         [0032]      FIG. 2  is a cross-sectional view of the elongate shaft  12 , taken along line  2 - 2  of  FIG. 1 . The elongate shaft  12  includes an outer layer  28  and an inner layer  30 . Each of the outer layer  28  and the inner layer  30  can extend from the proximal region  14  of the elongate shaft  12  to the distal region  16  of the elongate shaft  12 . The inner layer  30  defines a lumen  32  that extends through the elongate shaft  12 .  
         [0033]     In some embodiments, the elongate shaft  12  can optionally include a reinforcing braid or ribbon layer to increase particular properties such as kink resistance. If a reinforcing braid or ribbon layer is included, it can be positioned between the outer layer  28  and the inner layer  30 .  
         [0034]     In some embodiments (not illustrated), the elongate shaft  12  can include one or more shaft segments having varying degrees of flexibility. For example, the elongate shaft  12  can include a proximal segment, an intermediate segment and a distal segment. In some embodiments, the elongate shaft  12  can also include a distal tip segment that can be formed from a softer, more flexible polymer. The elongate shaft  12  can include more than three segments, or the elongate shaft  12  can include fewer than three segments.  
         [0035]     If the elongate shaft  12  has, for example, three segments, such as a proximal segment, an intermediate segment and a distal segment, each segment can include an inner layer  30  that is the same for each segment and an outer layer that becomes increasingly more flexible with proximity to the distal end  18  of the elongate shaft  12 . For example, the proximal segment can have an outer layer that is formed from a polymer having a hardness of 72 D (Durometer), the intermediate segment can have an outer layer that is formed from a polymer having a hardness of 68 D and the distal segment can be formed from a polymer having a hardness of 46 D.  
         [0036]     If the elongate shaft  12  has three segments, each of the segments can be sized in accordance with the intended function of the resulting catheter  10 . For example, the proximal segment can have a length of about 35 inches, the intermediate segment can have a length that is in the range of about 2 inches to about 3 inches, and the distal segment can have a length that is in the range of about 1 inch to about 1.25 inches.  
         [0037]     The inner layer  30  can be a uniform material and can define a lumen  32  that can run the entire length of the elongate shaft  12  and that is in fluid communication with a lumen (not illustrated) extending through the hub assembly  20 . The lumen  32  defined by the inner layer  30  can provide passage to a variety of different medical devices, and thus, the inner layer  30  can include, be formed from or coated with a lubricious material to reduce friction within the lumen  32 . An exemplary material is polytetrafluoroethylene (PTFE), better known as TEFLON®. The inner layer  30  can be dimensioned to define a lumen  32  having an appropriate inner diameter to accommodate its intended use. In some embodiments, the inner layer  30  can define a lumen  32  having a diameter of about 0.058 inches and the inner layer  30  can have a wall thickness of about 0.001 inches.  
         [0038]     The outer layer  28  can be formed from any suitable polymer that will provide the desired strength, flexibility or other desired characteristics. Polymers with low durometer or hardness can provide increased flexibility, while polymers with high durometer or hardness can provide increased stiffness. In some embodiments, the polymer material used is a thermoplastic polymer material. Some examples of some suitable materials include polyurethane, elastomeric polyamides, block polyamide/ethers (such as PEBAX®), silicones, and co-polymers. The outer layer  28  can be a single polymer, multiple layers, or a blend of polymers. By employing careful selection of materials and processing techniques, thermoplastic, solvent soluble, and thermosetting variants of these materials can be employed to achieve the desired results.  
         [0039]     In particular embodiments, a thermoplastic polymer such as a co-polyester thermoplastic elastomer such as that available commercially under the ARNITEL® name can be used. The outer layer  28  can have an inner diameter that is about equal to the outer diameter of the inner layer  30 . The outer layer  28  defines an outer surface  34 .  
         [0040]     In some embodiments, the outer layer  28  can have an inner diameter in the range of about 0.0600 inches to about 0.0618 inches and an outer diameter in the range of about 0.0675 inches to about 0.0690 inches. Part or all of the outer layer  28  can include materials added to increase the radiopacity of the outer layer  28 , such as 50% bismuth subcarbonate.  
         [0041]     Turning to  FIG. 3 , a portion of the elongate shaft  12  is illustrated with additional elements disposed over the outer surface  34  of the elongate shaft  12 . An outer member  36  having a distal end  38  is slidingly disposed over the elongate shaft  12 . An expandable member  40  having a proximal end  42  and a distal end  44  is also disposed over the elongate shaft  12 . A distal stop  46  is secured to the outer surface  34  of the elongate shaft  12 . In combination, the elongate shaft  12 , outer member  36 , expandable member  40  and distal stop  46  form a catheter assembly  200 .  
         [0042]     In some embodiments, the outer member  36  can be positioned such that its distal end  38  is close to or even in contact with the proximal end  42  of the expandable member  40 . In some embodiments, the distal stop  46  limits distal travel of the expandable member  40  and is positioned within the distal region  16  of the elongate shaft  12 .  
         [0043]     As illustrated, for example, in  FIG. 4 , which is a cross-section taken along line  4 - 4  of  FIG. 3 , the outer member  36  can be a single layer  50  having a lumen therethrough that is sized to accommodate the outer surface  34  of the elongate shaft  12 . In some embodiments, the outer member  36  can have an outer diameter that is in the range of about 0.065 inches to about 0.13 inches and an inner diameter that is in the range of about 0.050 inches to about 0.12 inches. The outer member  36  can have an overall length that is in the range of about 50 cm to about 150 cm.  
         [0044]     The single layer  50  has an outer surface  52  and an inner surface  54 . The outer member  36  can be formed of any suitable material such as a polymeric material. Polymers with low durometer or hardness can provide increased flexibility, while polymers with high durometer or hardness can provide increased stiffness. In some embodiments, the outer member  36  can be formed of a material that will provide the outer member  36  with characteristics useful in providing column support to the elongate shaft  12  when the outer member  36  is deployed thereon.  
         [0045]     In some embodiments, the polymer material used is a thermoplastic polymer material. Some examples of some suitable materials include those discussed previously with respect to the outer layer  28  of the elongate shaft  12 . By employing careful selection of materials and processing techniques, thermoplastic, solvent soluble, and thermosetting variants of these materials can be employed to achieve the desired results.  
         [0046]     In the illustrated embodiment in which the outer member  36  is a single layer  50 , he inner surface  54  of the outer member  36  can be coated with a lubricious material to reduce friction between the inner surface  54  of the outer member  36  and the outer surface  34  of the elongate shaft  12 . An exemplary material is polytetrafluoroethylene (PTFE), better known as TEFLON®.  
         [0047]     In some embodiments (not illustrated), the outer member  36  can be formed having two or more layers. In such embodiments, the outer member  36  can have an inner layer that includes, is coated with, or formed from TEFLON®. The outer layer can be formed of any suitable polymer such as those discussed with respect to the outer layer  28  of the elongate shaft  12 .  
         [0048]     The expandable member  40  is moveable between a collapsed configuration, as seen in  FIG. 3 , and an expanded configuration as seen in  FIG. 5 . In the collapsed configuration, the expandable member  40  has a first length and a first diameter. In the expanded configuration, the expandable member  40  has a second length and a second diameter. By comparing  FIG. 3  to  FIG. 5 , it is clear that the first length of the expandable member is greater than the second length, while the second diameter is greater than the first diameter.  
         [0049]     The expandable member  40  can be sized as appropriate to fit over the outer surface  34  of the elongate shaft  12 , as well as to nearly or completely occlude a particular vasculature in which the expandable member  40  will be used. In some embodiments, the expandable member  40  can have a first length (collapsed configuration) that is in the range of about 1 cm to about 2 cm and a second length (expanded configuration) that is in the range of about 0.5 cm to about 1.0 cm. The expandable member  40  can have a first diameter (collapsed configuration) that is in the range of about 0.065 inches to about 0.13 inches and a second diameter (expanded configuration) that is in the range of about 1 mm to about 1.5 cm.  
         [0050]     The distal stop  46  can be removably or permanently secured to the outer surface  34  of the elongate shaft  12 . The distal stop  46  can be formed from any suitable material that can be adhered or otherwise secured to the outer surface  34  of the elongate shaft and the distal stop  46  can have any suitable configuration or structure that is adapted to limit distal travel of the expandable member  40 .  
         [0051]     In some embodiments, the distal stop  46  can include a metallic or polymeric ring that is bonded to the outer surface  34  of the elongate shaft  12 . In other embodiments, the distal stop  46  can be formed by creating a narrow band of molten or nearly molten material at least partway around the circumference of the outer surface  34  of the elongate shaft  12 . In some embodiments, the distal stop  46  can be a metal clamp secured to the outer surface  34  of the elongate shaft  12 .  
         [0052]     With respect to  FIG. 5 , in some embodiments, moving the outer member  36  distally, as evidenced by an arrow  48 , causes the proximal end  42  of the expandable member  40  to move distally. As the distal end  44  of the expandable member  40  is held in place by the distal stop  46 , moving the outer member  36  distally causes the proximal end  42  of the expandable member  40  to move closer to the distal end  44  thereof.  
         [0053]     The expandable member  40  can be considered as having a proximal portion  56 , a distal portion  58  and an intermediate portion  60 . As the distal end  44  of the expandable member  40  moves distally and closer to the proximal end  42  thereof, at least the intermediate portion  60  moves radially outward.  
         [0054]      FIGS. 6 through 10  describe the expandable member  40  in greater detail.  FIG. 6  is a partially-sectioned view of a portion of  FIG. 3  in which expandable member  40  is depicted as a cylindrical member  62  having an overlaying polymer sheath  64 . The expandable member  40  has a proximal end  66  and a distal end  68 . In some embodiments, as illustrated, the polymer sheath  64  can extend proximally a slight distance beyond the proximal end  66  and can extend distally a slight distance beyond the distal end  68  of the expandable member  40 . In other embodiments, the polymer sheath  64  can extend only to or approximately to the proximal end  66  and the distal end  68  of the expandable member  40 . The polymer sheath  64  can have a length that is in the range of about 1 cm to about 2 cm and an average thickness that is in the range of about 0.001 inches to about 0.002 inches.  
         [0055]     The polymer sheath  64  can be formed of any suitable polymer that is sufficiently elastic to move with the cylindrical member  62  as the expandable member  40  moves between its collapsed and expanded configurations. In some embodiments, the polymer sheath  64  can be formed of a urethane polymer or a Chronoprene™ thermoplastic rubber elastomer available from Carditech International, Inc.  
         [0056]     The cylindrical member  62  can be formed of materials such as metals, metal alloys, polymers, metal-polymer composites, or other suitable materials, and the like. Some examples of some suitable materials can include stainless steels (e.g., 304v stainless steel), nickel-titanium alloys (e.g., nitinol such as super elastic or linear elastic nitinol), nickel-chromium alloys, nickel-chromium-iron alloys, cobalt alloys, nickel, titanium, platinum, or alternatively, a polymer material such as a high performance polymer, or other suitable materials, and the like.  
         [0057]     In some embodiments, the cylindrical member  62  can be formed of a shape memory material such as a nickel-titanium alloy. Nitinol is an exemplary shape memory material.  
         [0058]     Within the family of commercially available nitinol alloy, is a category designated “linear elastic” which, although similar in chemistry to conventional shape memory and superelastic varieties, exhibits distinct and useful mechanical properties. By skilled applications of cold work, directional stress, and heat treatment, the tube is fabricated in such a way that it does not display a substantial “superelastic plateau” or “flag region” in its stress/strain curve. Instead, as recoverable strain increases, the stress continues to increase in an essentially linear relationship until plastic deformation begins. In some embodiments, the linear elastic nickel-titanium alloy is an alloy that does not show any martensite/austenite phase changes that are detectable by DSC and DMTA analysis over a large temperature range.  
         [0059]     For example, in some embodiments, there is no martensite/austenite phase changes detectable by DSC and DMTA analysis in the range of about −60° C. to about 120° C. The mechanical bending properties of such material are, therefore, generally inert to the effect of temperature over this very broad range of temperature. In some particular embodiments, the mechanical properties of the alloy at ambient or room temperature are substantially the same as the mechanical properties at body temperature.  
         [0060]     In some embodiments, the linear elastic nickel-titanium alloy is in the range of about 50 to about 60 weight percent nickel, with the remainder being essentially titanium. In some particular embodiments, the composition is in the range of about 54 to about 57 weight percent nickel. One example of a suitable nickel-titanium alloy is FHP-NT alloy commercially available from Furukawa Techno Material Co., of Kanagawa, Japan. Some examples of nickel-titanium alloys include those disclosed in U.S. Pat. Nos. 5,238,004 and 6,508,803, which are incorporated herein by reference.  
         [0061]      FIGS. 7 through 10  illustrate particular embodiments of cylindrical members.  FIG. 7  illustrates a cylindrical member  70  having a proximal region  72 , a proximal end  74 , a distal region  76  and a distal end  78 . A plurality of spirally aligned cuts  80  extend at least from the proximal region  72  to the distal region  76 . In some embodiments, the spirally aligned cuts  80  extend from the proximal end  74  to the distal end  78 . The spirally aligned cuts  80  can be formed in any suitable manner, such as by laser cutting. Each of the spirally aligned cuts  80  can extend completely through the cylindrical member  70  in a radial direction and can have a width that is in the range of about 0.0005 inches to about 0.1 inches.  
         [0062]     In  FIG. 8 , the cylindrical member  70  of  FIG. 7  has been moved into its engaged configuration. As the outer member  36  moves distally and forces the proximal end  74  of the cylindrical member  70  to move distally toward the distal end  78  thereof, the spirally aligned cuts  80  can cause the proximal region  72  of the cylindrical member  70  to rotate with respect to the distal region  76 . As the cylindrical member  70  opens up, a plurality of struts  82  representing the portions of the cylindrical member  70  positioned between adjacent spirally aligned cuts  80  will move radially outward.  
         [0063]     Turning to  FIG. 9 , another embodiment of a cylindrical member is shown.  FIG. 9  illustrates a cylindrical member  84  having a proximal region  86 , a proximal end  88 , a distal region  90  and a distal end  92 . A plurality of axially aligned cuts  94  extend at least from the proximal region  86  to the distal region  90 . In some embodiments, the axially aligned cuts  94  extend from the proximal end  88  to the distal end  92 . The axially aligned cuts  94  can be formed in any suitable manner, such as by laser cutting. Each of the axially aligned cuts  94  can extend completely through the cylindrical member  84  in a radial direction and can have a width that is in the range of about 0.0005 inches to about 0.1 inches.  
         [0064]     In  FIG. 10 , the cylindrical member  84  of  FIG. 9  has been moved into its engaged configuration. As the outer member  36  moves distally and forces the proximal end  88  of the cylindrical member  84  to move distally toward the distal end  92  thereof, the axially aligned cuts  94  permit the proximal region  86  of the cylindrical member  84  to remain rotationally stationary with respect to the distal region  90 . As the cylindrical member  70  opens Up, a plurality of struts  96  representing the portions of the cylindrical member  84  positioned between adjacent axially aligned cuts  94  will move radially outward.  
         [0065]      FIGS. 11-13  demonstrate an intended use of the catheter assembly  200 . In  FIG. 11 , an introducer sheath  98  having a distal end  100  and a proximal end  102  has been extended through a patient&#39;s tissue  104  into the patient&#39;s vasculature  106  as is well known in the art. In  FIG. 11 , the catheter assembly  200  has been inserted into the proximal end  102  of the introducer sheath  98  and has been advanced toward a desired treatment site.  
         [0066]     As discussed previously, the catheter assembly  200  includes an elongate shaft  12  which extends through the outer member  36  and expandable member  40 . As illustrated, the outer member  36  can include a proximal hub  108  that can be configured to easily permit insertion of the elongate shaft  12  therethrough, as well as allowing a physician or other medical professional using the catheter assembly  200  to easily grasp and manipulate the outer member  36 .  
         [0067]      FIG. 11  shows the catheter assembly  200  with the expandable member  40  in its collapsed configuration. In  FIG. 12 , however, the expandable member  40  has been moved into its expanded configuration. By comparing  FIG. 11  to  FIG. 12 , it can be seen that in  FIG. 12 , the outer member  36  has been moved distally relative to its starting position in  FIG. 11 . As discussed previously with respect to  FIG. 5 , at least the intermediate portion  60  of the expandable member  40  has moved radially outward and is in at least partial contact with the vasculature  106 .  
         [0068]     At this point, the catheter assembly  200  is configured for passage of a treatment device such as a balloon catheter, stent delivery catheter, atherectomy device or the like.  FIG. 13  illustrates placement of a treatment device  108  having a distal region  110  that extends distally beyond the distal end  18  of the elongate shaft  12  and a proximal region  112  that extends proximally beyond the hub  20  of the elongate shaft  12 .  
         [0069]     In some embodiments, the treatment device  108  can be positioned within the catheter assembly  200  after moving the expandable member  40  into its expanded configuration, as illustrated. In other embodiments, it can be advantageous to position the treatment device  108  within the catheter assembly  200  prior to expanding the expandable member  40  in order to minimize the amount of time over which blood flow is occluded.  
         [0070]     In some embodiments, parts of the catheter assembly  200  can be made of, include, be doped with, include a layer of, or otherwise include a radiopaque material. Radiopaque materials are understood to be materials capable of producing a relatively bright image on a fluoroscopy screen or another imaging technique during a medical procedure. This relatively bright image aids the user of device in determining its location. Some examples of radiopaque materials can include, but are not limited to, gold, platinum, palladium, tantalum, tungsten alloy, plastic material loaded with a radiopaque filler, and the like.  
         [0071]     In some embodiments, a degree of MRI compatibility can be imparted. For example, to enhance compatibility with Magnetic Resonance Imaging (MRI) machines, it may be desirable to make any metallic parts such as the cylindrical member  62  in a manner that would impart a degree of MRI compatibility. For example, the cylindrical member  62  can be made of a material that does not substantially distort the image and create substantial artifacts (artifacts are gaps in the image). Certain ferromagnetic materials, for example, may not be suitable because they may create artifacts in an MRI image. The cylindrical member  62  can also be made from a material that the MRI machine can image. Some materials that exhibit these characteristics include, for example, tungsten, Elgiloy, MP35N, nitinol, and the like, and others.  
         [0072]     In some embodiments, part or all of the catheter assembly  200  can include a lubricious coating. Lubricious coatings can improve steerability and improve lesion crossing capability. Examples of suitable lubricious polymers include hydrophilic polymers such as polyarylene oxides, polyvinylpyrolidones, polyvinylalcohols, hydroxy alkyl cellulosics, algins, saccharides, caprolactones, and the like, and mixtures and combinations thereof. Hydrophilic polymers can be blended among themselves or with formulated amounts of water insoluble compounds (including some polymers) to yield coatings with suitable lubricity, bonding and solubility. In some embodiments, a distal portion of the catheter can be coated with a hydrophilic polymer, while the more proximal portions can be coated with a fluoropolymer.  
         [0073]     It should be understood that this disclosure is, in many respects, only illustrative. Changes may be made in details, particularly in matters of shape, size and arrangement of steps, without exceeding the scope of the invention. The invention&#39;s scope is, of course, defined in the language in which the appended claims are expressed.