Abstract:
A method of making a remotely imagable balloon for use with a balloon catheter, such as might be used for angioplasty procedures. Adhesive and imagable material may be coated onto an inner surface of the balloon before assembly into a balloon catheter and the adhesive may be allowed to cure and fix the imagable material within the balloon. A powder injector for inserting imagable material within a balloon. A curing station for curing light cured adhesive coated along an inner surface of a balloon.

Description:
FIELD  
       [0001]     The present invention relates generally to methods and apparatus for making imagable angioplasty balloons.  
       BACKGROUND  
       [0002]     Stenosis of vascular elements in humans can pose a severe health risk, particularly when coronary vessels are involved. A variety of methods of addressing and resolving stenosis problems have been implemented to varying degrees of success. Once of the more acceptable and at least moderately successful methods of addressing stenosis of coronary vessels has been the use of angioplasty. Angioplasty generally refers to a method of compressing the material occluding the coronary vessel to reopen the vessel, permitting increased blood flow past the occlusion.  
         [0003]     Angioplasty is conventionally carried out with a catheter inserted at a site distant from the occlusion, where the catheter includes an expandable distal end portion, generally referred to as a balloon. At the time of insertion, the balloon is preferably in a collapsed or unexpanded compact shape. The catheter is advanced from the insertion site to the site of the occlusion so that the balloon is inserted through the occlusion. The balloon is then expanded, either mechanically or by the injection of a fluid through a lumen of the catheter which inflates the balloon. As the balloon expands, the material forming the occlusion is compressed against the walls of the vessel. After the balloon is deflated or recompacted, the material forming the occlusion remains at least partially in a compressed state against the vessel wall, providing a larger opening through the vessel at the site of the occlusion.  
         [0004]     While a variety of approaches exist for identifying the location and extent of occlusion within the vasculature of a patient, one of the keys to successful angioplasty is the correct positioning of the distal end of the catheter with respect to the occlusion to be addressed. One of the approaches that may be used to locate occlusions and catheters within a patient&#39;s vasculature involves the use of radio imaging. Unfortunately, many of the materials used to construct angioplasty catheters and balloons are generally radiotransparent, meaning that the distal end of the catheter may not be generally visible to an operator of a radio imaging system.  
         [0005]     It is also desirable to have the balloon or distal end of the angioplasty catheter be radiopaque so that the extent to which the occlusion is opened and blockage removed can be verified. Conventional approaches to this desire for visibility of the inflated balloon were addressed by the use of a radiopaque fluid to inflate the balloon during compression of the occlusion. However, such radiopaque fluids can be quite viscous and require a relatively large lumen be included in the catheter to permit injection of the fluid through the catheter to inflate the balloon. The need for large lumens within the catheter can lead to the overall external diameter of the angioplasty being undesirable large, and may limit the size of the vessels within which occlusions can be treated.  
         [0006]     Conventional methods have provided a variety of constructions of catheters and balloons to insert or include radiopaque material in or around the distal end of angioplasty catheters. One of these approaches is described in commonly owned and invented U.S. Pat. No. 6,884,234, where radiopaque material is added to an inner surface of the balloon, without hindering the expansion or contraction of the balloon. Constructing catheters and balloons which include such radiopaque materials may be difficult to accomplish and therefore may result in a higher cost of manufacture.  
         [0007]     Improvements to conventional methods of manufacturing radiopaque balloons are desirable.  
       SUMMARY  
       [0008]     The present invention relates generally to a method of making a remotely imagable balloon for use with a balloon catheter, such as might be used for angioplasty procedures. Adhesive and imagable material may be coated onto an inner surface of the balloon before assembly into a balloon catheter and the adhesive may be allowed to cure and fix the imagable material within the balloon. The present invention also relates to a powder injector for inserting imagable material within a balloon. The present invention further relates to a curing station for curing light cured adhesive coated along an inner surface of a balloon. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]     The accompanying drawings, which are incorporated in and constitute a part of the description, illustrate several aspects of the invention and together with the description, serve to explain the principles of the invention. A brief description of the drawings is as follows:  
         [0010]      FIG. 1  is a diagrammatic view of a balloon coating apparatus according to the present invention.  
         [0011]      FIG. 2  is a closer view of the powder injector of  FIG. 1 .  
         [0012]      FIG. 3  is a view of a portion of an electrostatic charging element that may be incorporated into the coating apparatus of  FIG. 1 .  
         [0013]      FIG. 4  is a diagrammatic view of a balloon curing apparatus according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0014]     Reference will now be made in detail to exemplary aspects of the present invention which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.  
         [0015]     Conventional balloon catheters used in angioplasty have used a variety of approaches and methods to provide a radiopaque or other imagable quality to aid in the positioning of the balloon. One such approach is disclosed in commonly owned and invented U.S. Pat. No. 6,884,234, the disclosure of which is incorporated herein by reference. While the approach of the catheter according to the invention of this patent does permit a uniform coating of an interior surface of the balloon, the process and approach to including the radiopaque material within the balloon could be improved. Particularly, the coating within the balloon may be segmented to aid in compaction of the balloon for insertion. Such segmenting of the radiopaque or imagable coating permits the desirably small compacted size to be achieved but may require a complex manufacturing process.  
         [0016]     The present invention relates to an apparatus and a method of manufacturing and assembling of balloon catheters that include a uniform radiopaque interior coating and are compactable for insertion through desirably sized guide catheters into a patient&#39;s vascular system. An apparatus  10  for coating balloons with radiopaque material according to the present invention is shown diagrammatically in  FIG. 1 , with a open ended balloon  12  positioned to receive the powder coating. Prior to being positioned within apparatus  10 , balloon  12  may be coated along an inner surface  14  with an adhesive to adhere the radiopaque material to the inner surface. Adhesives commonly used for this sort of application tend to be relatively viscous and may need to be thinned prior to application within balloon  12 . Methods and devices for coating inner surface  14  are conventionally known and may involve the use an adhesive thinned with a volatile solvent to a desired low viscosity. This adhesive and solvent combination may be injected within balloon  12  while balloon  12  is rotated or otherwise manipulated to ensure that adhesive is applied to inner surface  14  as desired. Once the adhesive has been applied to the desired portions or all of inner surface  14 , the solvent used to dilute the adhesive may be allowed to evaporate, leaving a desired coating of adhesive on inner surface  14  and preparing balloon  12  for insertion within coating apparatus  10 .  
         [0017]     The adhesive may preferably require a separate curing process so that maximum flexibility in the positioning of radiopaque material within balloon  12  is retained, although self curing or air curing adhesives may also be used. Suitable adhesives may include but are not limited to epoxy, urethane, silicone, acrylic, or cyanoacrylate adhesives and corresponding solvents for each adhesive. Corresponding solvents may include but are not limited to acetone, alcohol, freon, or a combination of these solvents.  
         [0018]     In the illustrated embodiment, radiopaque material is preferably a powder when injected within balloon  12 , and apparatus  10  is configured for injecting and positioning a dry powder within balloon  12 . When inserted within apparatus  10 , balloon  12  may be engaged by a powder injector  16  at a first open end  20  and a back pressure device  18  at a second opposite open end  22 . Connected to each of injector  16  and back pressure device  18  are a gas source  24  and a pressure regulator  26  which are configured to deliver gas at a desired pressure and flow rate. One or more valves  28  are situated between pressure regulator  26  and injector  16  and back pressure device  18  to control flow of gas. Valves  28  may be connected to and actuated by a timer  30 . It is preferable that a gas supply line  32  between valves  28  and powder injector  16  be controllable separately from a gas supply line  34  between valves  28  and back pressure device  18 , such as through separate valves.  
         [0019]     With the adhesive coated and uncured on inner surface  14  of balloon  12  positioned as shown within apparatus  10 , a process for positioning radiopaque material within balloon  12  can be carried out. To position the radiopaque material throughout inner surface  14  of balloon  12 , pulses of gas through injector  16  and back pressure device  18  may be directed into balloon  12 . The gas used for these pulses or bursts is preferably a dry gas, so that the characteristics of the powder in injector  16  may be controlled and maintained without unwanted humidity. These bursts of gas directed by valves  28  through injector  16  and back pressure device  18  are preferably controlled by solenoid-actuated valves. Such valves may permit precise control of the time and duration of gas supplied to injector  16  and back pressure device  18  to ensure uniform and complete coating of inner surface  14 . In place of the back pressure device and the injection of gas through second end  22  of balloon  12 , a second injector  16  could be positioned at second end  22  and radiopaque material could be injected into both ends of balloon  12 . In this way, the gas carrying the radiopaque material into balloon  12  from one end can serve as the back pressure for the radiopaque material being injected through the opposite end.  
         [0020]     It is preferable that a powdered form of a desired radiopaque material  38  be held within a powder vessel  36  of injector  16 , as shown in  FIG. 2 . Connected to gas supply line  32  in  FIG. 1  is a gas inlet  40  with an inner end  42  releasing gas into vessel  36  preferably located near a top end of vessel  36  with powdered material  38  typically adjacent a bottom end of vessel  36 . A gas outlet  44  provides a path for material  38  to exit vessel  36  through an inner end  46 . An outer end  48  of gas outlet  44  may have a needle  50  or some other appropriate nozzle arrangement for injecting material  38  into balloon  12 . An outer end  52  of needle  50  may be positioned at one location within balloon  12  while material  38  is being injected or may be longitudinally moved within balloon  12  to provide a more uniform coating of inner surface  14 . The size of needle  50  may be selected based on the size of balloon  12  and the characteristics of radiopaque material. Preferably, needle  50  will range in size from 18 to 25 gauge.  
         [0021]     It is desirable that the physical properties of material  38  be maintained as consistent as possible to ensure uniformity of injection and coating. Powdered material  38  may have better flow characteristics when keep as dry as possible, so a heater  53  may be positioned on an exterior of vessel  36  to heat powder  38  and dry off as much water or other moisture as possible prior to injection. It is anticipated that material  38  may have flow characteristics which do not require such preheating or may not be susceptible to atmospheric moisture, so that a heater is not required as part of injector  16 . To improve flow of material  38  through injector  16 , injector  16  may also be physically agitated before material  38  is injected into balloon  12  to aerate material  38 . Injector  16  may also include an integral mechanism such as a vibrator or other physical agitation device to promote aeration of material  38  prior to injection into balloon  12 .  
         [0022]     Other arrangements of inner ends  42  and  46  may be provided which are tailored to the physical characteristics of the specific material  38  used and may not necessarily be arranged as shown in  FIG. 2 . The disposition of material  38  within balloon  12  may be aided by the injection of gas through back pressure device  18  as gas and material  38  are injected through nozzle end  52 . Back pressure within balloon  12  may assist in dispersing material  38  more uniformly about inner surface  14  so that the adhesive coating within balloon  12  is consistently coated with material  38 . The timing of gas flow through injector  16  and back pressure device  18  may coordinated as required by the characteristics of the material being injected, the nature of the adhesive coating, and the size and shape of balloon  12  to ensure such uniform coating. Balloon  12  may also be rotated within apparatus  10  to aid in the uniform distribution of material  38  on inner surface  14 .  
         [0023]     It is anticipated that some materials  38  may require more than mere physical agitation and the use of back pressure to uniformly coat inner surface  14 . It may be desirable to provide corresponding electrostatic charges to the powder and to balloon  12  to aid in the positioning of material  38  within balloon  12 . Such as arrangement is shown in  FIG. 3 , including a direct current power supply  54  with a positive electrical connection  56  being applied about balloon  12  and a negative electrical connection  58  being applied about material  38  at outer end  50  of injector  16 . In this electrostatic configuration, a charge is not applied directly balloon  12  but to a metal cylinder  60  positioned about balloon  12 . In addition, a second glass cylinder  62  is positioned between balloon  12  and metal cylinder  60 . Positive connection  56  is electrically connected to metal cylinder  60  which will in turn provide an appropriate charge within balloon  12 . Material  38  passes through outer end  50  which is electrically connected by negative connection  58  and is oppositely charged prior to injection into balloon  12 . Once charged material  38  is injected within balloon  12 , the opposite charges applied to material  38  and about balloon  12  will attract material  38  to inner surface  14 .  
         [0024]     Uniform coating of inner surface  14  with material  38  may be accomplished by any or a combination of the above described approaches, including injecting gas to provide back pressure through an opposite end of balloon  12 , movement of nozzle  52  within balloon  12  as material  38  is injected, rotation of balloon  12  as material is injected, and electrostatic charges applied to material  38  and about balloon  12 . The extent and nature of the approaches or combinations of approaches used or required may vary with the characteristics of the balloon and radiopaque coating material used. Any combination of approaches or sole use of any of the approaches is anticipated within the scope of the present disclosure.  
         [0025]     Once inner surface  14  of balloon  12  has been coated as desired by apparatus  10 , areas of inner surface  14  may be cleaned of material  38  adjacent to ends  20  and  22 . Balloon  12  will eventually be sealed to provide an expandable arrangement for an angioplasty catheter. Such sealing may be carried out by heat sealing, ultrasonic welding, or any other appropriate sealing technique. It may be desirable that the portions of inner surface  14  that will be sealed are free of any material  38  or adhesive coating to ensure a good seal. So, after balloon  12  is removed from apparatus  10 , ends  20  and  22  may be dipped into a bath of solvent to remove any adhesive coating or material  38  prior to curing the adhesive and securing material  38  to inner surface  14 . It is also desirable that excess material  38  be removed from balloon  12  prior to curing, such as by blowing or washing.  
         [0026]     A curing device  100  is shown in  FIG. 4 , for curing the adhesive coating on inner surface  14  to fix radiopaque material  38  within balloon  12 . As shown, curing device  100  includes a UV light source  102  and would thus be appropriate for use with a UV or light cured adhesive. It is anticipated that adhesives which are sensitive to and cured by other sources of energy, such as heat, may also be used on balloon  12 , and that curing device  100  may be adapted to provide the appropriate energy source to cure these adhesives as well. It is also anticipated that coating apparatus  10  may be used with air curing or other self curing adhesives, so that a separate curing device is not required to fix material  38  to inner surface  14 .  
         [0027]     Curing device  100  includes a light pipe  104 , such as an optical fiber pathway or other light transmission conduit from light source  102  to a head  105 . Head  105  directs light from light source  102  against balloon  12  mounted to curing device  100 . A specific filter  106  may be provided in head  105  to ensure that the light which will be most effective at curing the adhesive within balloon  12  is used. Different adhesives which may be used with balloon  12  may be sensitive to different portions of the spectrum of light generated by light source  102  and other portions of the spectrum may be filtered out. As shown, the adhesive in balloon  12  is a UV-sensitive adhesive and a UV specific light source  102  and filter  106  are included in curing device  100 . If light source  102  is adapted to provide a very precisely tailored light to head  105 , or the adhesive is sensitive to a broader range of the spectrum generated by light source  102 , filter  106  may be not needed or included in curing device  100 .  
         [0028]     As shown, head  105  is mounted to a movable arm  108  which is in turn connected to a motor  110 . Motor  110  is shown as a step motor but other motors or actuators may be used to move head  105  along a length of balloon  12 . Balloon  12  is mounted about a spindle or shaft  112 . Shaft  112  is in turn connected to a motor  114  and a platen or base  115 . Motor  114  is shown as a step motor but other motors or actuators may be used to rotate shaft  112  so that all portions of a circumference of balloon  12  are exposed to light from head  105 . Alternatively, motor  110  could be connected to base  115 , with head  105  fixed in position within curing device  100 . Motor  110  could then move balloon  12  back and forth under a fixed head  105  to expose balloon  12  to light from head  105 .  
         [0029]     Each of motors  110  and  114  are connected to a motor control  116 , which is connected to and controlled by a computer  118 . Computer  118  may signal motor control  116  to actuate motors  110  and  114  as needed to ensure that all of balloon  12  is adequately exposed to light or other energy from head  105  to sufficiently cure the adhesive along inner surface  14 . Curing the adhesive will fix radiopaque material  38  to inner surface  14 . A rate of rotation of spindle  112  and balloon  12 , and a rate of movement of head  105  longitudinally along balloon  12  are selected according to the amount of light needed to cure the amount of adhesive within balloon  12  and are selected to ensure that excessive energy is not applied to balloon  12  to avoid damaging the balloon during curing. Balloon  12  may be made of a material which is sensitive to the light or energy used to cure the adhesive. Computer  118  will preferably control the time of exposure over all portions of balloon  12  to light or energy from head  105  to avoid any deleterious effects to balloon  12  while still ensuring curing of the adhesive within balloon  12 . After curing, any remaining loose powder within balloon  12  can be washed away prior to sealing balloon  12  for use with an angioplasty catheter.  
         [0030]     It is desirable that material  38  be applied along inner surface  14  of balloon  12 , rather than on an external surface of balloon  12 . While such coating could be more easily affected on an outer surface of balloon  12 , such exterior coating may be susceptible to peeling off in the patient&#39;s blood stream, possibly causing a stroke or an infarct.  
         [0031]     Providing a balloon  12  with a radiopaque coating permits fluids other than radiopaque fluids to be used to inflate or expand balloon  12  within a patient&#39;s bloodstream to perform angioplasty. Typically, liquids are used as the fluid as liquids are generally less compressible than air or other gases that might be used, and accidental releases of air from an angioplasty catheter could have devastating consequences for a patient. As balloon  12  is radiopaque by itself, without any injection of a radiopaque fluid, a neutral fluid such as common saline solution may be used to inflate the balloon. Saline is much less viscous that known or common radiopaque fluids which have been used in conventional balloon catheters permitting a smaller diameter fluid injection lumen to be used. Smaller fluid injection lumens mean that smaller diameter catheters may used for angioplasty. Smaller diameter catheters may mean less trauma to the patient being treated and may allow smaller vessels within a patient&#39;s vasculature to be treated.  
         [0032]     While the above description has focused on securing a radiopaque material within a balloon, other imagable materials may be coated within the balloon, according to the present disclosure. Such alternative imagable materials might be visible using other known or to be developed corpal imaging techniques or apparatus, such as MRI, CAT Scans, PET Scans, or other approaches to imaging patients during a medical procedure. For radiopaque materials, metallic elements or alloys may be used to make the coating radiopaque. Also, while the above description is directed to production of a balloon for angioplasty, balloon catheters for other uses within a patient are also anticipated according to the present disclosure.  
         [0033]     The embodiments of the inventions disclosed herein have been discussed for the purpose of familiarizing the reader with novel aspects of the present invention. Although preferred embodiments have been shown and described, many changes, modifications, and substitutions may be made by one having skill in the art without unnecessarily departing from the spirit and scope of the present invention. Having described preferred aspects and embodiments of the present invention, modifications and equivalents of the disclosed concepts may readily occur to one skilled in the art. However, it is intended that such modifications and equivalents be included within the scope of the claims which are appended hereto.