Abstract:
A catheter system suitable for the retrieval of debris and other solid or liquid matter from body passages, and the removal of said matter from the body. More particularly, a catheter system including two or more concentrically-arranged conduits and an inflatable element connected therebetween, wherein the inflatable element is arranged such that it may entrap solid or liquid matter in an internal annular cavity.

Description:
This application claims the benefit of priority to U.S. Patent Application Nos. 60/695,868 filed on Jul. 5, 2005 and 60/726,160 filed on Oct. 14, 2005, the entire contents of each of which are hereby incorporated by reference into this disclosure. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a catheter system suitable for the retrieval of debris and other solid or liquid matter from body passages, and the removal of said matter from the body. More particularly, the invention relates to catheter systems comprising two or more concentrically-arranged conduits and an inflatable element connected therebetween, wherein said inflatable element is arranged such that it may entrap solid or liquid matter in an internal annular cavity. 
     BACKGROUND OF THE INVENTION 
     Catheters are used in various interventional procedures for delivering therapeutic means to a treated site (e.g., body organ or passageway such as blood vessels). In many cases, a catheter with a small distal inflatable balloon is guided to the treated site. Once the balloon is in place it is inflated by the operator for affixing it in place, for expanding a blocked vessel, for placing treatment means (e.g., stent) and/or for delivering surgical tools (e.g. knives, drills etc.) to a desired site. In addition, catheter systems have also been designed and used for retrieval of objects such as stents from body passageways. 
     Two basic types of catheter have been developed for intravascular use: other-the-wire (OTW) catheters and rapid-exchange catheters. 
     OTW catheter systems are characterized by the presence of a full-length guide wire, such that when the catheter is in its in situ working position, said guide wire passes through the entire length of a lumen formed in, or externally attached to, the catheter. OTW systems have several operational advantages which are related to the use of a full length guide wire, including good stiffness and pushability, features which are important when maneuvering balloon catheters along tortuous and/or partially occluded blood vessels. 
     U.S. Pat. No. 6,039,721 describes a balloon catheter system comprising two concentrically-arranged conduits, with a balloon connected between the distal regions thereof. The catheter system permits both expansion/deflation of the balloon and alteration in the length of the balloon when in situ, such that the balloon may be moved between extended and intussuscepted conformations. The catheter system is constructed in order that it may be use for two main purposes: firstly, treatment (i.e. expansion) of different-length stenosed portions of blood vessels with a single balloon and secondly, the delivery of either stents or medication to intravascular lesions, wherein the stent or medication is contained within the distally-intussuscepted portion of the balloon. When used for multiple, differing-length lesion expansion, the balloon is inserted into blood vessel in a collapsed, shortened, intussuscepted conformation, and is advanced until it comes to rest in the region of the shortest lesion to be treated. The balloon is then inflated and the lesion treated (i.e. expanded). Following deflation of the balloon, the distal end of the catheter system is moved such that the balloon becomes positioned in the region of the next—shortest lesion to be treated. The effective length of the balloon is then increased by moving the inner conduit in relation to the proximal conduit, following which the balloon is again inflated and the lesion treated. In this way, a series of different length stenoses—in order from the shortest to the longest—may be treated using a single balloon. When used for stent delivery, the stent is pre-loaded into a proximal annular space formed as a result of balloon intussusception. The balloon is then moved to the desired site and the stent delivered by means of moving the inner conduit distally (in relation to the outer tube), thereby “unpeeling” the stent from the catheter. 
     WO 00/38776 discloses a dual-conduit balloon catheter system similar in basic design to that described above in relation to U.S. Pat. No. 6,039,721. This catheter system is intended for use in a vibratory mode in order to break through total occlusions of the vascular lumen. In order to fulfill this aim, the outer conduit has a variable stiffness along its length, while the inner conduit. In addition, the inner conduit while being intrinsically relatively flexible is stiffened by the presence of axial tensioning wires. These conduit design features are used in order to permit optimal translation of vibratory movements of the proximal end of the inner conduit into corresponding vibration of the distal tip thereof. 
     Rapid exchange (“monorail”) catheters typically comprise a relatively short guide wire lumen provided in a distal section thereof, and a proximal guide wire exit port located between the catheter&#39;s distal and proximal ends. This arrangement allows exchange of the catheter over a relatively short guide wire, in a manner which is simple to perform and which can be carried out by a single operator. Rapid exchange catheters have been extensively described in the art, for example, U.S. Pat. Nos. 4,762,129, 4,748,982 and EP0380873. 
     Rapid exchange catheters are commonly used in Percutaneous Transluminal Coronary Angioplasty (PTCA) procedures, in which obstructed blood vessels are typically dilated by a distal balloon mounted on the catheter&#39;s distal end. A stent is often placed at the vessel&#39;s dilation zone to prevent reoccurrences of obstruction therein. The dilation balloon is typically inflated via an inflation lumen which extends longitudinally inside the catheter&#39;s shaft between the dilation balloon and the catheter&#39;s proximal end. 
     The guide wire lumen passes within a smaller section of the catheter&#39;s shaft length and it is accessed via a lateral port situated on the catheter&#39;s shaft. This arrangement, wherein the guidewire tube is affixed to the catheter&#39;s shaft at the location of its lateral port, usually prevents designers from developing new rapid exchange catheter implementations which requires manipulating its inner shaft. For example, extending or shortening the catheter&#39;s length during procedures may be advantageously exploited by physicians to distally extend the length of the catheter into a new site after or during its placement in the patient&#39;s artery, for example in order to assist with the passage of tortuous vessels or small diameter stenoses, or to allow in-situ manipulation of an inflated balloon at the distal end of the catheter. 
     The rapid exchange catheters of the prior art are therefore usually designed for carrying out a particular procedure and their implementations are relatively restricted as a consequence of the need for at least one catheter shaft to exit the catheter system laterally, between the proximal and distal ends of said system. Consequently, a need exists for a rapid exchange catheter that overcomes the above mentioned problems and which allows expanding the range of applications of such catheters. 
     Despite the large number of different balloon catheter systems currently available, a need still exists for a system that can efficiently and safely collect plaque debris and other particulate matter from the lumen of internal body passages such as pathologically-involved blood vessels. 
     The primary object of the present invention is, therefore, to provide a balloon catheter system capable of collecting samples and/or debris from the body treated site and reducing the risk of distal embolization of any material that may be dislodged during inflation of the balloon at the treated site. 
     Another aim is to provide such a system in which the balloon length may be substantially shortened during use without unduly increasing internal pressure. 
     A further aim is to provide such a system in which the catheter tubing is of a construction suitable for withstanding the forces generated during balloon folding and unfolding. 
     Yet another aim is to provide such a system in which the balloon is of a shape and constructions that permits both optimal debris entrapment and low-profile folding within the passages to be treated. 
     A further object of the present invention is to provide balloon catheter systems having the advantages outlined hereinabove, wherein said catheter systems are OTW systems. 
     A further object of the present invention to provide a rapid exchange catheter having an adjustable balloon length and shape which may be modified during a procedure. 
     Yet another object of the present invention to provide a rapid exchange balloon catheter wherein the shape and/or volume of a standard inflated balloon may be adjusted during a procedure. 
     A still further object of the present invention to provide a rapid exchange balloon catheter capable of collecting samples and/or debris from the body treated site and reducing the risk of distal embolization of any material that may be dislodged during inflation of the balloon at the treated site. 
     Other objects and advantages of the invention will become apparent as the description proceeds. 
     SUMMARY OF THE INVENTION 
     The present invention is therefore primarily directed to a balloon catheter system comprising at least one inner conduit and one outer conduit mutually disposed one inside the other, such that their longitudinal axes either coincide or are substantially parallel to each other, said inner tube being movably disposed along a longitudinal (i.e. distal-proximal) axis wherein an inflatable element such as a balloon is attached between the distal regions of said conduits, the distal end of the balloon being attached to the distal region of the inner conduit, and the proximal end of the balloon being attached to the distal region of said outer conduit. The catheter system is constructed such that the longitudinal position of the inner conduit in relation to the outer conduit may be altered by means of moving the proximal end of the inner conduit (i.e. the end closest to the operator). In this way, the distal-proximal length of the outer surface of the balloon may be altered, such that the balloon may be caused to progressively move between an elongated, extended conformation and a shortened, terminally-intussuscepted conformation, wherein in the latter conformation, an open-ended inner cavity is created in the terminally-intussuscepted region of the balloon. In use, this inner cavity may be employed to entrap particulate debris, liquids and other objects and substances and safely remove same from the body passage in which the balloon catheter system is inserted. The inflatable element used in the presently-disclosed and described catheter system is of a shape that permits said element to meet the dual requirements of effective debris collection and low-profile delivery and retrieval. Thus, in one preferred embodiment the inflatable element is provided in the form of a balloon having, in its inflated state, a tapered shape with a rounded distal extremity. A further feature of the presently-disclosed system is the presence of means for preventing internal pressure changes that occur as a consequence of changing the length and conformation of the balloon. 
     Thus, in one aspect, the present invention provides an OTW balloon catheter system comprising an outer conduit; an inner conduit disposed within the lumen of said outer conduit such that the longitudinal axes of said inner and outer conduits are substantially parallel, and positioned such that the distal tip of said inner conduit extends beyond the distal tip of said outer conduit, wherein said inner conduit is capable of being moved along its longitudinal axis in relation to said outer conduit, and wherein the lumen of said inner conduit is suitable for allowing the passage of a guidewire therethrough; an angioplastic balloon whose proximal margin is attached to the outer surface of the distal tip of said outer conduit, and whose distal margin is attached to the outer surface of the portion of the inner conduit that extends beyond the distal tip of said outer conduit, and wherein the distal portion of said balloon is capable of intussusception upon proximal movement of said inner conduit in relation to said outer conduit; means for the introduction of an expansion fluid into the annular space formed between the inner surface of the outer conduit and the outer surface of the inner conduit and therefrom into the lumen of said balloon, and for the removal thereof, and means for preventing pressure changes within said annular space upon axial movement of said inner conduit in relation to said outer conduit. 
     In one preferred embodiment of the OTW balloon catheter system of the present invention, the inner and outer conduits are characterized by their ability to withstand axially directed forces in the range of between 2 and 20 Newton without undergoing significant deformation. In the context of the present invention, the term “significant deformation” refers to changes in conduit length in excess of 5% of the total length of said conduit. While these conduits may be constructed of any suitable material capable of withstanding the aforementioned forces, in a preferred embodiment, the inner and outer conduits are constructed either from a biocompatible polymer (which in a preferred embodiment is selected from the group consisting of braided nylon thread and nylon thread that has undergone orientation treatment) or from flexible stainless steel tube. 
     In one preferred embodiment of the present invention, the balloon is characterized by having, in its inflated state, a pre-folding profile, i.e. it has shape which is capable of assisting and guiding the intussusception of the distal portion thereof upon proximal movement of the inner conduit in relation to the outer conduit. 
     In one particularly preferred embodiment of the catheter system, the aforementioned balloon pre-folding profile is achieved by manufacturing the balloon such that it has (in its inflated state) a tapered shape with a rounded distal extremity. 
     Preferably, the balloon is constructed from Nylon 12, Pevax or mixtures thereof. It is to be recognized, however, that the balloon may also be constructed of any other suitable materials as are well known in the art, without deviating from the scope of the present invention as defined in the claims. 
     In one preferred embodiment, the aforementioned means for preventing pressure changes comprises a syringe-like structure positioned at the proximal end of the catheter system, wherein the barrel of said syringe-like structure is formed by an expanded portion of the outer conduit, and wherein the plunger of said structure co-axially surrounds the proximal end of the inner conduit, and is affixed thereto. 
     In another aspect, the present invention also provides a method for collecting debris from an internal passage of a mammalian subject comprising the steps of:
     a) inserting an OTW balloon catheter system as defined hereinabove over a guidewire into said internal passage, and advancing said catheter until the distal tip thereof has reached the site, at which it is desired to collect debris;   b) inflating the balloon with expansion fluid;   c) pulling the inner conduit of said balloon catheter in a proximal direction, such that the distal and/or proximal end(s) of said balloon intussuscept(s);   d) deflating the balloon, thereby forming a cavity into which debris is collected and entrapped; and   e) removing the balloon catheter from the internal passage of the subject, together with the entrapped debris.   

     In one preferred embodiment of the presently-disclosed method, the aforementioned internal passage is a vein or artery. 
     In another aspect, the present invention further encompasses rapid exchange (RE) catheter implementations in which the length of a distal section of the catheter and the shape and/or volume of its distal balloon may be manipulated during procedures carried out therewith. Such implementations are ideally suited for use in debris collection applications, as described in connection with the OTW device of the present invention, hereinabove. However, the RE solutions of the present invention may also be used in any other RE application wherein it is necessary to alter the length of a distally-placed balloon element. 
     Consequently, the present invention is also directed to a rapid exchange catheter that permits axial movement of an inner conduit within an outer conduit comprising:
         a) an outer conduit;   b) an inner conduit, suitable for total or partial passage over a guide wire, wherein said inner conduit is disposed within the lumen of said outer conduit such that the longitudinal axes of said inner and outer conduits are substantially parallel, wherein said inner conduit is capable of being moved along its longitudinal axis in relation to said outer conduit and wherein the proximal end of said inner conduit is angled such that it pierces the wall of said outer conduit;   c) means for permitting said axial movement of said inner conduit within said outer conduit, such that said movement is not hindered by the passage of the angled proximal part of the inner conduit through said outer conduit; and   d) means, situated at the proximal end of the outer conduit, for causing axial pushing-pulling movements of said inner conduit.       

     In one preferred embodiment of the above-defined rapid exchange catheter, the means for permitting unhindered axial movement of the inner conduit is provided by a sealing sleeve that is slidably fitted around the external conduit, such that the angled proximal portion of said inner conduit passes firstly through an elongated aperture in the wall of the external conduit, and secondly through a tightly sealed aperture in said sealing sleeve, such that upon axial movement of the inner conduit, said sealing sleeve is capable of preventing the transfer of fluid through said elongated aperture. 
     In another preferred embodiment, the above means for permitting unhindered axial movement of the inner conduit is provided by a two-part inner conduit construction, whereby the first, proximal part of said construction is non-movable, and wherein the second, distal part is slidably disposed within said proximal part. 
     In a further preferred embodiment, the abovementioned means for permitting unhindered axial movement of the inner conduit is provided by a two-part inner conduit construction, whereby the first, proximal part of said construction is non-movable, and wherein the second, distal part is slidably disposed over said proximal part. 
     In a still further preferred embodiment, the aforementioned means for permitting unhindered axial movement of the inner conduit is provided by a three-part inner conduit construction, whereby the first, proximal part of said construction is non-movable, and wherein the second, intermediate part is non-movably disposed within said proximal part, and wherein the third, distal part is slidably disposed within said intermediate part. 
     In another preferred embodiment of the rapid exchange catheter of the present invention, the means for causing axial movements of the inner conduit mentioned hereinabove comprise one or more wires, the distal end(s) thereof being attached to the inner conduit, and the proximal end(s) thereof extending beyond the proximal end of the outer conduit. 
     In another aspect, the present invention also provides a rapid exchange balloon catheter system comprising:
         a) an outer conduit;   b) an inner conduit, suitable for total or partial passage over a guide wire, wherein said inner conduit is disposed within the lumen of said outer conduit such that the longitudinal axes of said inner and outer conduits are substantially parallel, wherein said inner conduit is capable of being moved along its longitudinal axis in relation to said outer conduit, wherein the proximal end of said inner conduit is angled such that it pierces the wall of said outer conduit, and wherein the distal tip of said inner conduit extends beyond the distal tip of said outer conduit;   c) an angioplastic balloon whose proximal margin is attached to the outer surface of the distal tip of said outer conduit, and whose distal margin is attached to the outer surface of the portion of the inner conduit that extends beyond the distal tip of said outer conduit, and wherein the distal and/or proximal end portion(s) of said balloon are capable of intussusception upon proximal movement of said inner conduit in relation to said outer conduit;   d) means, situated at the proximal end of the outer conduit, for causing axial pushing-pulling movements of said inner conduit;   e) means for the introduction of an expansion fluid into the annular space formed between the inner surface of the outer conduit and the outer surface of the inner conduit and therefrom into the lumen of said balloon, and for the removal thereof;   f) means for preventing pressure changes within said annular space upon axial movement of said inner conduit in relation to said outer conduit; and   g) means for permitting axial movement of said inner conduit within said outer conduit, such that said movement is not hindered by the passage of the angled proximal part of the inner conduit through said outer conduit.       

     In one preferred embodiment of the rapid exchange balloon catheter system defined hereinabove, said system is constructed such that the distal portion of the balloon is capable of intussusception upon proximal movement of the inner tube in relation to the outer tube. 
     In one preferred embodiment of this aspect of the invention, the means for causing axial movements of the inner conduit comprise one or more wires, the distal end(s) thereof being attached to the inner conduit, and the proximal end(s) thereof extending beyond the proximal end of the outer conduit. 
     In another preferred embodiment of this aspect of the invention, the means for preventing pressure changes comprises a plunger slidably disposed within the proximal end of the outer conduit, wherein said plunger is connected to the axial pushing-pulling means, such that upon operation of said pushing-pulling means, said plunger is caused to slide either distally or proximally, thereby changing the volume of the outer conduit. 
     Any suitable means may be employed for permitting unhindered axial movement of the inner conduit in the above-defined rapid exchange balloon catheter system. Preferably, however, these means are as defined in any one of the preferred embodiments disclosed hereinabove and claimed hereinafter. 
     In particularly preferred embodiments of the RE catheter system of the present invention, the balloon shape and force resistance characteristics of the catheter tubing are as described hereinabove in connection with the OTW systems, and as exemplified in the Examples provided hereinbelow. 
     It should be noted that in each of the embodiments of the catheter systems of the present invention disclosed and described hereinabove, a lubricant (such as silicone oil or mineral oil) may be present in order to facilitate the mutual sliding of the various conduits. 
     In another aspect, the present invention also provides a method for collecting debris from an internal passage of a mammalian subject comprising the steps of:
     a) inserting a rapid exchange balloon catheter system as defined hereinabove into said internal passage, and advancing said catheter until the distal tip thereof has reached the site, at which it is desired to collect debris;   b) inflating the balloon with expansion fluid;   c) pulling the inner conduit of said balloon catheter in a proximal direction, such that the distal and/or proximal end(s) of said balloon intussuscept(s);   d) deflating the balloon, thereby forming a cavity into which debris is collected and entrapped; and   e) removing the balloon catheter from the internal passage of the subject, together with the entrapped debris.   

     In one preferred embodiment of the presently-disclosed method, the aforementioned internal passage is a vein or artery. 
     All the above and other characteristics and advantages of the present invention will be further understood from the following illustrative and non-limitative examples of preferred embodiments thereof. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is illustrated by way of example in the figures of the accompanying drawings, in which like references indicate similar elements and in which: 
         FIG. 1A  schematically illustrates over-the-wire insertion of the balloon catheter of the invention; 
         FIG. 1B  shows a cross sectional side view of the balloon catheter of the invention; 
         FIG. 1C  schematically illustrates one embodiment of the syringe-like pressure-compensating device situated at the proximal end of the catheter system; 
         FIG. 2  schematically illustrates the balloon catheter of the invention when inflated at a treatment site; 
         FIGS. 3 and 4  schematically illustrate debris collection carried out by the balloon catheter of the invention by folding the inflated balloon and deflating it thereafter; and 
         FIG. 5  is a flowchart demonstrating the steps of an interventional procedure performed with the balloon catheter of the invention that may involve sample collection; 
         FIG. 6  schematically illustrates the four balloon designs that were analyzed and compared in the finite element analysis study: a. Standard 20° tapering; b. 20° tapering with smooth round ending; c. Round ending; d. Round ending with initial retracting; 
         FIG. 7  graphically depicts the displacement vs. retracting force for the four balloon shapes, compared at an inflation pressure of 6 atmospheres. 
         FIG. 8  graphically depicts the maximum force generated in the catheter tubes following balloon folding, measured for different balloon inflation pressures; 
         FIGS. 9A to 9C  show longitudinal section views of a rapid exchange catheter according to one preferred embodiment of the invention wherein the distal section of the inner tube comprise an internal slidable tube; 
         FIGS. 9D and 9E  demonstrate utilizing different balloons for different manipulations thereof; 
         FIG. 9F  demonstrates a piston-like construction for preventing pressure accumulation within the catheter during retraction; 
         FIGS. 10A to 10C  show longitudinal section views of a rapid exchange catheter according to a second preferred embodiment of the invention wherein the diameter of the distal section of the inner tube is adapted to receive an internal slidable tube; 
         FIG. 11  shows a longitudinal section view of a rapid exchange catheter according to a third preferred embodiment of the invention wherein the distal section of the inner tube comprise an external slidable tube; 
         FIG. 12  shows a longitudinal section view of a rapid exchange catheter according to a fourth preferred embodiment of the invention wherein the diameter of the distal section of the inner tube is adapted to be received in an external slidable tube; 
         FIG. 13  shows a longitudinal section view of a rapid exchange catheter according to a fifth preferred embodiment of the invention wherein the distal section of the inner tube comprises a fixed inner tube on which an external slidable tube is mounted; 
         FIGS. 14A to 14C  show longitudinal section views of a rapid exchange catheter according to a sixth preferred embodiment of the invention wherein the inner tube of the catheter is encompassed in a slidable intermediate tube; and 
         FIGS. 15A to 15C  show longitudinal section views of a rapid exchange catheter according to a seventh preferred embodiment of the invention comprising a movable inner tube affixed to a slidable sealing sleeve. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The present invention is directed to a method and apparatus for removing objects (such as atheromatous plaque debris) or collecting samples from a body passageway such as a blood vessel. The presently-disclosed method and apparatus may also be used to expand a region of a body passageway (such as an atheromatous narrowing or occlusion of a blood vessel) in addition to removing debris or other matter or objects therefrom. In a preferred embodiment of the invention, a balloon catheter that is suitable for carrying out common interventional procedures is adapted to enable the expansion of a region of a body passageway and collection of objects or samples from the treated site utilizing a unique design of catheter and balloon. 
     In the following description, the terms “conduit” and “tube” are used interchangeably. 
     Referring to  FIG. 1A  which illustrates the insertion of an OTW balloon catheter  10  of the invention to a treatment site, for example body passage  20 . As shown, balloon catheter  10  comprises an inner tube  17  slidably positioned inside outer tube  18 . The proximal (i.e., trailing) end of inner tube  17  comprises an entry port  12 , which extends outwardly through orifice  29  provided at the proximal end of outer tube  18 . Orifice  29  tightly fits around the outer surface of inner tube  17  without gripping it, thereby allowing proximal and distal movements of inner tube  17  while sealing the inner lumen of outer tube  18 . Graduated scale  19  may optionally be provided on the outer surface of inner tube  17 . 
     The proximal end of outer tube  18  further comprises a fluid port  11  for injecting/removing inflation fluids to/from inner lumen of outer tube  18 , an over-pressure valve outlet  15  for discharging inflation fluids whenever over-pressure conditions develop in the inner lumen of outer tube  18 , and an inner tube safety lock  14  adapted for gripping the outer surface of inner tube  17 , thereby preventing proximal-distal movements thereof relative to outer tube  18 . 
     Over-pressure valve outlet  15  may include an over-pressure valve  16  for sealing the opening of over-pressure valve outlet  15  and for discharging portions of inflating fluids therethrough whenever over-pressure conditions are reached in inner lumen of outer tube  18 . It should be realized however that such over-pressure conditions may be resolved by other means. For example, an inflatable member (not shown) may be attached to the opening of over-pressure valve outlet  15 , and in such an implementation over-pressure valve  16  may be eliminated. Moreover, outer tube  18 , or portions thereof, may be inflatable such that over-pressure conditions may be resolved by its expansion. 
     Inner tube safety lock  14  contacts the outer surface of inner tube  17  via a tight orifice provided on the outer surface at the proximal end of outer tube  18 . As shown in the cross sectional view of  FIG. 1B , a “U”-shaped gripping clip  24  may be attached to inner tube safety lock  14  for gripping inner tube  17  therewith by pushing inner tube safety lock  14  inwardly and fitting the arms of gripping clip  24  around the outer surface of inner tube  17 . 
     As seen in  FIG. 1A  distal (leading) end of inner tube  17  extends outwardly via the distal opening of outer tube  18 , into the body passage  20 . An inflatable member, for example non-compliant balloon  5 , is attached to the distal ends of outer tube  18  and inner tube  17 . Balloon  5  is preferably made from a flexible resilient sleeve having conical ends having gradually decreasing diameters towards the tips of the sleeve. Balloon  5  is attached at circumferential attachment point  7  to the outer surface near the distal tip of outer tube  18 , and at circumferential attachment point  6  to the outer surface near the distal tip of inner tube  17 , such that it seals the distal opening of outer tube  18 . 
     As mentioned hereinabove, in one preferred embodiment of this aspect of the invention, the means for preventing pressure changes in the inflation fluid space comprises a syringe-like structure positioned at the proximal end of the catheter system, wherein the barrel of said syringe-like structure is formed by an expanded portion of the outer conduit, and wherein the plunger of said structure co-axially surrounds the proximal end of the inner conduit. Referring now to  FIG. 1C , the mechanism in this preferred embodiment consists of a barrel portion  26  and plunger  17   a  movably disposed therein and affixed to outer surface of inner tube  17 . Plunger  17   a  seals the inflation lumen of balloon catheter  10 , such that proximal movements thereof, responsive to proximal movements of inner tube  17 , generate suction of inflation media into barrel portion  26 . 
     With reference to the flowchart of  FIG. 5 , demonstrating the steps of an interventional procedure performed with an OTW balloon catheter of the invention. The procedure starts in step  50  wherein the balloon catheter  10  is guided to the treatment site (e.g., over the wire).  FIG. 1A  demonstrates over-the-wire insertion, wherein the insertion of balloon catheter  10  is performed over guide wire  13 . It should be clear, however, that the invention is not limited to one specific insertion method and that other appropriate and practicable insertion methods (e.g., using a guiding catheter) may also be used. 
     Next, in step  51 , the operator inflates balloon  5  by injecting inflation fluids via fluid port  11  and the inner lumen of outer tube  18 , as demonstrated by fluid inflation arrows  8   a  in  FIG. 1A . When carrying out procedures in body passage  20  as demonstrated in the  FIGS. 1-4  inflation fluids are preferably injected into balloon  5  such that its circumferential sides are expanded and pressed against the inner wall  21  of body passage  20 , as demonstrated in  FIG. 2 . The pressure inside balloon  5  in such conditions may be in general about 1-25 Atmospheres, preferably about 6 Atmospheres. 
     In this state in which the balloon catheter  10  is anchored, the inner lumen of inner tube  17  may now be utilized for operating in the treated site with different interventional tools (not shown), as may be required. Step  52  indicates the possibility of performing procedures if needed, however, some procedures (for example angioplasty) may be completed, or be near completion, once balloon  5  reaches its inflated state. 
     If it is determined in step  53  that a sample or other liquid or solid matter should be collected from the treatment site, for example fluids, secretions, and/or debris  25 , then in step  54  inner tube safety lock  14  is pulled thereby releasing its grip from inner tube  17 , as demonstrated by arrow  27   a  in  FIG. 2 . In step  55  the inner tube  17  is retracted outwardly (proximally) by the operator as shown by arrow  28 . During retraction of inner tube  17  the distal tip of balloon  5  collapses and the outer surface portions are folded inwardly over the distal tip of inner tube  17  and thereafter over itself as further portions of the balloon collapse, as illustrated in  FIG. 3 . 
     Retraction of inner tube  17  and the resulting inward folding of balloon  5  shorten the overall length of inflated balloon  5  which actually reduces the volume of inflated balloon  5 . Consequently, the pressure exerted by the inflating fluids increases, resulting in a considerable pressure increase in balloon  5  and inner lumen of outer tube  18 . Whenever the pressure in balloon  5  and inner lumen of outer tube  18  reaches a certain set-point, inflation fluids are discharged via over-pressure valve outlet  15 , as shown by arrows  8   b  in  FIG. 3 , such that the pressure in balloon  5  and inner lumen of outer tube  18  remains within a predetermined pressure range (e.g., 1-25 atmospheres). During this step the operator can determine via graduated scale  19  the amount of length of inner tube  17  that has been retracted and in this way determine when to stop the retraction and prevent further axial movement of inner tube  17  (step  58 ) by pushing down inner tube safety lock  14 , as indicated by arrow  27   b.    
     Next, in step  56 , balloon  5  is deflated by retracting inflation fluids via fluid port  11 , as indicated by arrows  8   c  in  FIG. 4 . In result, the pressure inside balloon  5  and inner lumen of outer tube  18  is substantially decreased, and balloon  5  is deflated. The reduction in the volume of balloon  5  results in the formation of an inner cavity  40  defined by the outer surface of the folded balloon section, as shown in  FIG. 4 . In step  57  the operator retracts balloon catheter  10  proximally such that portion of fluid/secretion and debris  25  confined within inner cavity  40  are withdrawn with the balloon catheter  10  (not shown in the figures). The debris, objects or samples collected may be easily collected when the entire length of balloon catheter  10  is ejected from the body of the treated subject, by pushing the inner tube  17  distally and unfolding the folded portions of balloon  5 , thus restoring the deflated state of balloon  5  (shown in  FIG. 1A ). 
     In view of the axially-directed stretching and buckling forces exerted on the inner and outer tubes during elongation and shortening of the balloon, said tubes need to be constructed such that they are able to withstand axially-directed forces in the range of between 2 and 20 Newton without undergoing deformation. In order to achieve this aim, the conduits may be constructed of a braided material or of materials having a defined molecular orientation. The approximate maximum forces that the inner and outer tubes need to withstand (for two difference size ranges of balloon) are as follows:
         2.5-4 mm balloons: the tubing should withstand up to 500 g; polymer tubing made of nylon or pevax reinforced during the manufacturing process can be used.   4-5 mm (or larger) balloons: the tubing should withstand forces up to 2 kg. In this case it will be necessary to use a braided tube (polymer tube with metal mesh reinforcement).       

     Results for a representative study of the forces generated during balloon folding are presented in Example 2, hereinbelow. 
     Outer tube  18  is preferably made from a biocompatible polymer type of material, such as polyurethane or nylon or PET, and may be manufactured utilizing conventional methods, such as extrusion. The diameter of inner lumen of outer tube  18  is generally in the range of 0.5-2.0 mm (millimeters), preferably about 0.7 mm, and the diameter of fluid port  11  is generally in the range of 2-6 mm, preferably about 4 mm. The diameter of over-pressure valve outlet  15  is generally in the range of 1-6 mm, preferably about 4 mm, and the entire length of outer tube  18  is generally in the range of 100-2000 mm, preferably about 1400 mm. 
     Inner tube  17  is preferably made from a biocompatible polymer type of material, such as polyurethane or nylon or PET, and it may be manufactured utilizing conventional methods, such as extrusion. The diameter of inner lumen of inner tube  17  is generally in the range of 0.2-2.0 mm, preferably about 0.5 mm, and its entire length is generally in the range of 100-2000 mm, preferably about 1500 mm. 
     While the diameter of orifice  29  provided at the proximal tip of outer tube  18  should be adapted to provide appropriate sealing of inner lumen of outer tube  18  it should also close over the outer surface of inner tube  17  such that inner tube  17  may be displaced therethrough with relatively low frictional forces. For example, if the diameter of inner tube  17  is 0.7 mm, then the diameter of orifice  29  should be 1.0 mm. 
     Balloon  5  is preferably a non-compliant or semi-compliant balloon such as manufactured by Advanced Polymers (Salem, USA) and by Interface Associates (CA). It may be manufactured utilizing conventional methods known in the balloon catheter industry from a non-compliance type of material such as Pebax or Nylon (preferably Nylon 12). Its length is generally in the range of 10-60 mm, preferably about 20 mm. The body diameter can vary from 2.0 mm to 5 mm for coronary artery applications, and be significantly larger for use in larger blood vessels. Preferably, the balloon should have a burst pressure within the range of 12-20 atmospheres. The proximal and distal edges of balloon  5  are preferably adhered to the outer surfaces of outer tube  18  and inner tube  17  respectively, at circumferential attachment points  7  and  6  respectively, by utilizing a UV or thermobonding type of adhesive such as commonly used in the art. 
     The shape of balloon  5  has been found by the present inventors to be critical in order for said balloon to fulfill its intended functions in the presently-disclosed and claimed catheter system, namely:
         i. to facilitate folding in such a way that the desired annular space is formed at the distal end of the intussuscepted balloon, by the application of the lowest possible retracting force;   ii. to present a low profile that will facilitate introduction and withdrawal of the deflated balloon into and out of the catheter system and body passage.       

     The materials and design of the balloon, especially the shape of the distal taper and the relationship between the distal and the proximal taper, thus allow the balloon to fold smoothly and with relatively low pulling forces. This also insures that the balloon will fold only its distal side. 
     It appears, from modeling studies performed by the inventors, that a tapered balloon with a smooth round ending folds best and has a relatively low retracting force, when compared to standard tapered balloon or a balloon with a round ending. In a particularly preferred embodiment, the balloon has a proximal taper cone shaped with a 15-17 degree angle, and a 15 degree round cone distal taper, having a radius of about 0.5 mm at the junction of the taper and the neck. The results of the aforementioned modeling studies are presented in Example 2, hereinbelow. 
     Inner tube safety lock  14  is preferably made from a biocompatible polymer such as Tecoflex; its length is generally in the-range of 1-15 mm, preferably about 5 mm. If, for example, the cross-sectional diameter of inner tube safety lock  14  is about 2 mm, then the orifice provided on the outer surface of outer tube  18  through which inner tube safety lock  14  accesses inner lumen of outer tube  18  is preferably about 2.4 mm for providing suitable sealing of inner lumen of outer tube  18 . 
     In another aspect, the present invention aims to provide rapid exchange (RE) catheter implementations in which the length of a distal section of the catheter and the shape and/or volume of its distal balloon may be manipulated during procedures carried out therewith. Such implementations are ideally suited for use in debris collection applications, as described in connection with the OTW device of the present invention, hereinabove. However, the RE solutions of the present invention may also be used in any other RE application wherein it is necessary to alter the length of a distally-placed balloon element. 
     In general, the RE catheter of the invention comprises an outer catheter shaft and an inner tube provided therein, wherein the lumen of said inner tube may be accessed via a lateral port provided on the catheter&#39;s shaft. In some of the preferred embodiments of the present invention described herein the inner tube of the catheter is affixed to the catheter&#39;s outer shaft and the catheter&#39;s length and its balloon are manipulated by a unique construction of the inner tube. In these constructions the catheter&#39;s inner tube may comprise a slidable distal tube that may be moved by the operator, distally or proximally relative to the catheter&#39;s outer shaft, via a displacement rod attached thereto. Alternatively, the inner tube may be encompassed in a slidable intermediate tube which may be moved by the operator distally or proximally relative to the catheter&#39;s shaft. 
     In further embodiments of the invention a unique catheter construction is developed in order to provide a movable inner tube affixed to a slidable sealing sleeve which allows the operator to move the inner tube distally or proximally relative to the catheter&#39;s outer shaft and thereby manipulate its length and balloon. 
       FIG. 9  shows longitudinal section views of a first embodiment of the rapid exchange catheter  610  of the invention wherein the distal end of the catheter&#39;s inner tube  614  comprises a slidable internal tube  613 . Catheter  610  comprises a hollow outer shaft  66  comprising inner tube  614  installed therein, and a slidable internal tube  613  placed in inner tube  614  such that it protrudes distally via a distal opening thereof. In this construction the inner lumens of inner tube  614  and slidable internal tube  613  are linked, thereby providing a continuous inner lumen ending at a distal opening of slidable internal tube  613 . Proximal end of balloon  611   a  is attached to hollow outer shaft  66  at proximal attachment points  62   b  provided around the outer surface of a distal section thereof, and the distal end of said balloon is attached to the slidable internal tube  613  at distal attachment points  62   a  provided around the outer surface of a distal section of said slidable internal tube. 
     The lumen of inner tube  614  may be accessed via a lateral port  612  provided on hollow outer shaft  66 , between a distal and proximal ends thereof. Guide wire  65  (or other suitable accessories) may be inserted via lateral port  612 , advanced along the inner lumens of inner tube  614  and slidable internal tube  613 , and exit the inner lumen of slidable internal tube  613  through a distal opening thereof. 
     Slidable concentric member  613  is adapted to fit into inner tube  614  and its diameter is preferably smaller than the diameter of inner tube  614  such that it seals its distal opening while comfortably permitting distal or proximal sliding of slidable internal tube  613  therethrough. Distal end portion of displacement rod  618  is attached to slidable internal tube  613  thereby allowing the operator to move slidable internal tube  613  distally or proximally relative to the catheter&#39;s outer shaft by pushing or pulling the proximal tip of displacement rod  618 . 
     Further sealing of the distal opening of inner tube  614  may be achieved by an annular gasket  64  attached to the surface of distal tip of inner tube  614  such that a distal portion thereof is pressed against an annular portion of the outer surface of slidable internal tube  613 . 
     The proximal portion of hollow shaft  66  comprises a fluid port  617  used for inflating or deflating balloon  611   a  by an inflation fluid pressurized therethrough, an optional discharge valve  616  installed in discharge valve outlet  615 , and rod aperture  619  for moving displacement rod  618  distally or proximally therethrough. 
     During a typical procedure RE catheter  10  is inserted into a body treatment site in which balloon  611   a  may be inflated by an inflation fluid (designated by arrows  67   a  in  FIG. 9A ) pressurized through inflation fluid port  617 , for effecting dilation or other procedures in said treatment site and/or for anchoring said balloon therein. The pressurized fluids pass via the hollow interior of hollow shaft  66  and reach the interior of balloon  611   a  via a distal opening thereof. In its inflated state, shown in  FIG. 9B , the hollow interior of hollow shaft  66  and the internal space of balloon  611   a  are filled with pressurized inflation fluid. Distal opening of inner tube  614  is sealed by slidable internal tube  613  and (optionally) by gasket  64 , thereby preventing leakage of pressurized inflation fluid thereinto. The pressure of the inflation fluid inside the system presses the gasket and improves the sealing provided by gasket  64 . On the other hand, when the pressure of the inflation fluid is reduced the gasket&#39;s grip on the outer surface of inner tube  614  is diminished which makes it easier for the gasket to slide over it. 
     The requisite procedure is typically carried out in the inflated state of the balloon. By using the catheter of the invention for such procedures the operator may manipulate the catheter length and the shape and volume of balloon  611   a  by pulling displacement rod  618   b , thereby moving slidable internal tube  613  proximally further into inner tube  614 , as demonstrated by arrows  68   a . In result, the distal end of balloon  611   a  collapses and folds internally, as shown in  FIG. 9C , which increases the pressure of the inflation fluid. Whenever the pressure of the inflation fluid inside the hollow interior of hollow outer shaft  66  and in balloon  611   a  is above a predetermined threshold value a slender passage of discharge valve is expanded to allow portions of inflation fluid to exit via discharge valve outlet  615  and thereby reduce the pressure of inflation fluid below said threshold value. 
     It should be noted that the use of pressure discharge elements  615  and  616  constitutes merely one possible means of pressure reduction. 
     Hollow outer shaft  66  is preferably made from a polymer or metal material, such as stainless steel (e.g. stainless steel 316), nitinol, or nylon, and it may be manufactured utilizing conventional methods, such as extrusion and laser cutting. The diameter of the hollow interior of hollow shaft  66  is generally in the range of 1-2 mm (millimeters), preferably about 1.2 mm, and the diameter of inflation fluid port  617  is generally in the range of 2-6 mm, preferably about 3 mm. The diameter of discharge valve outlet  615  is generally in the range of 2-6 mm, preferably about 3 mm, and the entire length of hollow shaft  66  is generally in the range of 500-2000 mm, preferably about 1400 mm. 
     Inner tube  614  is preferably made from a flexible polymer or metal material, such as pevax, nylon, stainless or nitinol and it may be manufactured utilizing conventional methods, such as extrusion and laser cutting. The diameter of inner lumen of inner tube  614  is generally in the range of 0.3-1 mm, preferably about 0.8 mm, and its entire length is generally in the range of 100-300 mm, preferably about 120 mm. Slidable internal tube  613  is preferably made from a flexible polymer or metal type of material, such as pevax, nylon, stainless or nitinol, and it may be manufactured utilizing conventional methods (e.g. extrusion). The diameter of inner lumen of slidable internal tube  613  is generally in the range of 0.3-1 mm, preferably about 0.5 mm, and its entire length is generally in the range of 30-150 mm, preferably about 70 mm. 
     Balloon  611   a  is preferably a type of non-compliant or semi-compliant or low-compliant balloon such as manufactured by Interface Associates. It may be manufactured utilizing conventional methods known in the balloon catheter industry from a biocompatible polymer type of material such as nylon 12. Its length is generally in the range of 5-50 mm, preferably about 20 mm, and its diameter is generally in the range of 2 to 12 mm, preferably about 3 to 5 mm. The proximal and distal edges of balloon  611   a  are preferably adhered to the outer surfaces of hollow shaft  66  and slidable internal tube  613 , at circumferential attachment points  62   b  and  62   a  respectively, by utilizing a low profile type of adhesion such as thermo bonding, UV adhesives or acrylic manufactured by Locktight. 
     Displacement rod  618  may be manufactured from a metal wire or tube, such as Stainless steel, Nitinol (Nickel Titanium) and polymers, having a diameter generally in the range of 0.2-2 mm, preferably about 0.5 mm, and length generally in the range of 500-2000 mm, preferably about 1600 mm. Distal portion of displacement rod  618  may be adhered to the distal section of slidable internal tube  613 . Most preferably, distal portion of displacement rod  618  may be combined into the wall of internal tube  613  thereby enhancing its rigidity and the grip provided therewith. Rod aperture  619  is adapted to allow conveniently moving displacement rod  618  therethrough while providing suitable sealing of the hollow interior of hollow shaft  66 , thereby preventing leakage of inflation fluid therefrom. 
     The inflation fluid is preferably a saline or a saline mixed with radio-opaque solution in different ratios. A syringe pump, or other suitable inflation pumps, as commonly used in the field, may be used for introducing the inflation fluid into the system. The pressure in the system in its various states is typically in the range of 1 to 25 atmospheres. 
     While different discharge valves may be employed, discharge valve  616  is preferably implemented by an annular element having an axial slender passage passing therein. In such implementation discharge valve  616  is manufactured from an elastomer type of material, such as PVC by an injection molding process. Its outer diameter is generally in the range of 2-6 mm, preferably about 4 mm, and its slender passage is designed to expand whenever a pressure gradient of about 4 atmospheres evolves between its ends. 
     Optionally, a proximal part  618   c  of rod  618  is made to be wide enough to occupy a volume of space within a proximal portion  66   b  of hollow shaft  66 , as sown in  FIG. 9F . This piston-like construction  618   c  allows for a syringe like action of rod  618  when retracted proximally, causing it to evacuate enough space in the proximal portion  66   b  of the lumen of hollow shaft  66 . This extra space will then be filled by inflation fluid, thereby preventing pressure build-up within the catheter during retraction of the rod  618 . 
     As shown in  FIG. 9C  in its folded state distal cavity  63   a  is obtained by the inwardly folded distal sections of balloon  611   a . The volume encompassed by cavity  63   a  may be enlarged by (partially or entirely) deflating the balloon in this folded state, thereby filling the enlarged cavity with samples and/or debris from the treatment site. Different distal balloons may be designed to provide various balloon manipulations as exemplified in  FIGS. 9D and 9E . 
     For example, in balloon  611   b  shown in  FIG. 9E  a proximal section of the balloon collapses and folds inwardly in response to movement of slidable internal tube  613  proximally, thereby forming a proximal cavity  63   b . Such a result may be achieved by using a balloon which has higher resistance to folding at its proximal tapered end relative to its distal tapered end This can be achieved by using a balloon having different angles at its distal and proximal tapers, wherein a steeper taper facilitates its folding. 
     As another example, in balloon  611   ab  shown in  FIG. 9D  both, proximal and distal, sections of the balloon are folded in response to movement of slidable internal tube  613  proximally, thereby forming a proximal cavity  63   b  and a distal cavity  63   a . This result may be obtained for example by using a balloon  611   ab  with a symmetric shape—namely, the balloon having the same taper at its distal and proximal sides. 
     The procedure for using the RE balloon catheter of the present invention may be briefly described as follows:
         1) Insertion of catheter into the body via peripheral blood vessel by use of standard rapid exchange method, as is well known in the art;   2) Inflation of the balloon by injecting inflation fluids via fluid port  617  and the inner lumen of outer shaft  66 , as demonstrated by fluid inflation arrows  67   a  in  FIG. 9A ; the pressure inside balloon  611  may be in general about 1-25 Atmospheres, preferably about 6 Atmospheres.   3) If required, a sample or other liquid or solid matter (for example fluids, secretions, and/or debris) may be collected from the treatment site. Firstly, the safety lock mechanism fitted to the proximal end of proximal displacement rod  618  is pulled, thereby releasing its grip on said proximal displacement rod. (The safety lock is not shown in  FIG. 9A ; a suitable type of safety mechanism is, however, depicted in  FIG. 1B  and described—in relation to the OTW device of the present invention—hereinabove.) Displacement rod  618  is then pulled proximally, thereby releasing retracting slidable internal tube  613  proximally, as demonstrated by arrow  68   a  in  FIG. 9B . During retraction of slidable internal tube  613  by the operator the distal tip of balloon  611  collapses and its outer surface portions are folded inwardly over the distal tip of slidable internal tube  613  and thereafter over itself as further portions of the balloon collapse, as illustrated in  FIG. 9C .   4) Retraction of slidable internal tube  613  and the resulting inward folding of balloon  611  shortens the overall length of inflated balloon  611  which actually reduces the volume of inflated balloon  611 . Consequently, the pressure exerted by the inflating fluids increases, resulting in a considerable pressure increase in balloon  611  and inner lumen of outer shaft  66 . Whenever the pressure in balloon  611  and inner lumen of outer shaft  66  reaches a certain set-point inflation fluids can be discharged via discharge valve  616 , as shown by arrows  67   b  in  FIG. 9B , such that the pressure in balloon  611  and inner lumen of outer shaft  66  remains within a predetermined pressure range (e.g., 1-25 atmospheres). Another exemplary option for discharging pressure is by widening the proximal section  618   c  of rod  618  so it can act similar to a syringe action, as shown in  FIG. 9F . During this step the operator can determine via graduated scale (not shown) provided on rod  618  the amount of length of inner tube  614  that has been retracted and in this way determine when to stop the retraction of inner tube  614 . The aforementioned safety lock is then returned to its locked state, thereby preventing any further movement of displacement rod  618  and inner tube  614 .   5) Subsequently, balloon  611  is deflated by retracting inflation fluids via fluid port  617 . As a result, the pressure inside balloon  611  and inner lumen of outer tube  66  is substantially decreased, and balloon  611  is deflated. The reduction in the volume of balloon  611  results in enlargement of distal cavity  63   a.      6) The operator then retracts balloon catheter  610  proximally such that portion of fluid/secretion and debris confined within proximal cavity  63   a  are withdrawn with the balloon catheter  610  (not shown in the figures). The debris, objects or samples collected may be easily collected when the entire length of balloon catheter  610  is ejected from the body of the treated subject, by pushing the inner tube  614  distally and unfolding the folded portions of balloon  611 , thus restoring the deflated state of balloon  611  (shown in  FIG. 9A ).       

       FIGS. 10A to 10C  show longitudinal section views of a rapid exchange catheter  620  according to a second preferred embodiment of the invention wherein the diameter of a distal section  624   b  of the inner tube  624   a  is adapted to receive internal slidable tube  613 . In this preferred embodiment the diameter of distal section  624   b  of inner tube  624   a  is made relatively greater than the diameter of the proximal section thereof. Internal slidable tube  613  is designed to tightly fit into proximal section  624   b  and thereby seal its distal opening and prevent leakage of inflation fluid thereinto. Alternatively or additionally, sealing may be achieved by gasket  64  attached to the distal section  624   b  of inner tube  624   a  such that a distal portion thereof is pressed against an annular portion of the outer surface of slidable internal tube  613 . Internal slidable tube  613  and the proximal section of inner tube  624   a  may be manufactured to have the same inner diameter, thereby forming a substantially homogenous inner lumen therebetween, particularly when internal slidable tube  613  is advanced all the way into distal section  624   b.    
     The structure and geometrical dimensions of elements of catheter  620  are much the same as those elements designated by the same numerals which were described above with reference to  FIGS. 9A to 9C . Similarly, balloon  611   a  may be inflated by inflation fluid ( 67   a ) pressurized via inflation fluid port  617 , and catheter&#39;s  620  length and the shape and volume of balloon  611   a  may be manipulated by moving displacement rod  618  distally or proximally, as exemplified in  FIGS. 10A to 10C . Different balloons may be designed to provide various balloon folding configurations as exemplified in  FIGS. 9D and 9E . 
     Inner tube  624   a  may be manufactured by an extrusion and laser cutting process from a plastomeric or metallic type of material, preferably from nylon, PET or stainless steel. The diameter of the distal section of inner tube  624   a  is generally in the range of 0.3-2 mm, preferably about 0.5 mm, and the diameter of slidable internal tube  613  is adapted to provide tight fitting and the necessary sealing of distal opening of inner tube  624   a  when said internal tube is inserted thereinside. 
       FIG. 11  shows a longitudinal section view of catheter  630  according to a third preferred embodiment of the invention wherein the distal section of the inner tube  614  comprises an external slidable tube  613   a . In this preferred embodiment the distal end of balloon  611   a  is attached to the slidable external tube  613   a  at distal attachment points  62   a  provided around the outer surface of a distal section of said slidable external tube. The diameter of external slidable tube  613   a  is made relatively greater than the diameter of inner tube  614 . External slidable tube  613   a  is designed to tightly fit over the outer surface of the proximal section of inner tube  614  and to thereby seal its distal opening and prevent leakage of inflation fluid thereinto. Alternatively or additionally, sealing may be achieved by gasket  64  attached to the proximal end portion of external slidable tube  613   a  such that a proximal portion thereof is pressed against an annular portion of the outer surface of inner tube  614 . 
     Using such external slidable tube  613   a  in catheter  630  allows attaching a relatively shorter displacement rod  618   a  to the proximal section of said slidable tube  613   a . Alternatively or additionally, the distal portion of displacement rod  618   a  may be combined into the wall of external slidable tube  613   a  along its longitudinal length, thereby enhancing its rigidity and the grip provided therewith. 
     The structure, geometrical dimensions of elements of catheter  630  designated by the same numerals, and the method of manipulating its length and balloon&#39;s volume and shape, are much the same as those elements and manipulating method which were previously described hereinabove and therefore, for the sake of brevity, said elements will not be further discussed at this point. External slidable tube  613   a  may be manufactured by an extrusion and laser cutting process from a plastomeric or metallic type of material, preferably from nylon or stainless steel. The diameter of external slidable tube  613   a  is adapted to provide tight fitting and the necessary sealing of distal opening of inner tube  614  when said external slidable tube is mounted thereover. For example, the diameter of external slidable tube  613   a  may be in the range of 0.3-2 mm, preferably about 0.8 mm. 
     A fourth preferred embodiment ( 640 ) of the invention is demonstrated in the longitudinal section view shown in  FIG. 12 , wherein the diameter of the distal section  644   b  of inner tube  644   a  is adapted to be received in an external slidable tube  613   a . In this preferred embodiment the distal end of balloon  611   a  is attached to the slidable external tube  613   a  at distal attachment points  62   a  provided around the outer surface of a distal section of said slidable external tube. The diameter of distal section  644   b  of inner tube  644   a  is made relatively smaller than the diameter of the proximal section thereof. External slidable tube  613   a  is designed to tightly fit over proximal section  644   b  and thereby seal its distal opening and prevent leakage of inflation fluid thereinto. Alternatively or additionally, sealing may be achieved by gasket  64  attached to the proximal end of External slidable tube  613   a  such that a proximal portion thereof is pressed against an annular portion of the distal section  644   b  of inner tube  644   a.    
     The external slidable tube  613   a  of catheter  640  allows attachment of a relatively shorter displacement rod  618   a  to the proximal section of said slidable tube  613   a . Alternatively or additionally, the distal portion of displacement rod  618   a  may be combined into the wall of external slidable tube  613   a  along its longitudinal length, thereby enhancing its rigidity and the grip provided therewith. 
     The structure, geometrical dimensions of elements of catheter  640  designated by the same numerals, and the method of manipulating of its length and balloon&#39;s volume and shape, are much the same as those elements and the manipulating method which were previously described hereinabove and therefore will not be further discussed here. Inner tube  644   a  may be manufactured by an extrusion and laser cutting process from a plastomeric or metallic type of material, preferably from nylon or stainless steel. The diameter of the distal section  644   b  of inner tube  644   a  is generally in the range of 0.3-2 mm, preferably about 0.5 mm, and the diameter of external slidable tube  613   a  is adapted to provide tight fitting and the necessary sealing of distal opening of inner tube  644   a  when said external tube is mounted thereover. 
     In a fifth preferred embodiment of the invention, illustrated in the longitudinal section view shown in  FIG. 13 , an external slidable tube  613   a  is mounted over a inner tube  654   b  protruding distally through a distal opening of fixed inner tube  654   a  of catheter  650 . In this preferred embodiment the distal end of balloon  611   a  is attached to the slidable external tube  613   a  at distal attachment points  62   a  provided around the outer surface of a distal section of said slidable external tube. A proximal end portion of fixed inner tube  654   b  is fitted into a distal opening of inner tube  654   a , such that it seals said distal opening and most of its longitudinal length protrudes distally therefrom into the hollow interior of hollow shaft  66 . The diameter of external slidable tube  613   a  is adapted to tightly fit over the external surface of fixed inner tube  654   b , thereby sealing its distal opening while allowing it to be easily moved distally or proximally thereon by the operator. 
     Sealant  64   c  may be applied to the proximal end of fixed inner tube  654   b  in order to provide enhanced sealing of the distal opening of inner tube  654   a . Sealing of the distal opening of fixed inner tube  654   b  may be achieved by an annular gasket  64  attached to the proximal tip of external slidable tube  613   a  such that a proximal portion thereof is pressed against an annular portion of the outer surface of fixed inner tube  654   b.    
     Gaskets  64  can be made of a flexible material such as silicone or polyurethane. Alternatively, gaskets  64  may be implemented by an added lubricant such as mineral oil or silicone oil which improves the sliding between the tubes. The sealing may be further increased by increasing the pressure in the balloon. 
     It should be noted that tubes  613   a  and  654   a  may be fixed tubes such that tube  654   a  is fixed to the shaft  663  and tube  613   a  is fixed to the distal neck of balloon  611   a , such that tube  654   b  can slide into both tubes. 
     The structure, geometrical dimensions of elements of catheter  650  designated by the same numerals, and the method of manipulating of its length and balloon&#39;s volume and shape, are much the same to those elements and manipulating method which were previously described hereinabove and therefore will not be discussed here, for the sake of brevity. Fixed inner tube  654   a  and external slidable tube  613   a  may be manufactured by an extrusion and laser cutting process from a plastomeric or metallic type of material, preferably from nylon or flexible metal. Their diameters are adapted to provide tight fitting and the necessary sealing of distal openings of inner tube  654   a  and of fixed inner tube  654   b.    
       FIGS. 14A to 14C  show longitudinal section views of a sixth preferred embodiment of the invention in which the inner tube  64  of catheter  660  is encompassed in a slidable intermediate tube  633   b . In this preferred embodiment the distal end of balloon  611   a  is attached to the slidable intermediate tube  633   b  at distal attachment points  62   a  provided around the outer surface of a distal section of said slidable intermediate tube. Horizontal opening  638  is provided on an upper side of slidable intermediate tube  633   b . Tube  64  protrudes upwardly through horizontal opening  638  towards the upper side of hollow shaft  66  at the location in which it is affixed thereto and provide an access to its lumen via lateral port  612 . 
     During a procedure balloon  611   a  may be inflated by pressurized fluid (designated by arrows  67   a  in  FIG. 14A ) provided via inflation fluid port  617 . As illustrated in  FIG. 14B , pressurized fluid passes through the hollow interior of hollow shaft  663  into the internal space of balloon  611   a . The catheter and its balloon in the inflated state are illustrated in  FIG. 14B . The proximal section of intermediate tube  633   b  between horizontal opening  638  and the proximal end of intermediate tube  633   b  may be sealed by a sealant  666  in order to prevent entry of inflation fluids thereinto. Whenever the pressure in balloon  611   a  and hollow interior of hollow shaft  663  is greater than a predetermined threshold value, a portion of inflation fluids are discharged via discharge valve  616  installed in discharge valve outlet  615 . 
     The proximal section of intermediate tube  633   b  protrudes proximally via proximal opening  665  provided at the proximal end of shaft  663 . Proximal opening  665  is designed to conveniently allow the sliding of intermediate tube  633   b  therethrough while providing suitable sealing thereof and preventing leakage of inflation fluid therefrom. Manipulation of the catheter&#39;s length and its balloon&#39;s shape and volume are performed by sliding the intermediate tube  633   b  proximally or distally relative to the catheter&#39;s shaft. 
     For example, after inflating balloon  611   a  the operator may pull the proximal section of intermediate tube  633   b  (designated by arrow  68   a  in  FIG. 14B ) thereby causing distal section of balloon  611   a  to collapse and fold inwardly and deform cavity  63   a , as illustrated in  FIG. 14C . Horizontal opening  638  is adjusted to allow sliding intermediate tube  633   b  proximally into a state in which attachment point  62   a  reaches proximal end of shaft  663 , and on the other hand, to allow sliding intermediate tube  633   b  sufficiently distally and enable stretching the full length of balloon  611   a.    
     Intermediate tube  633   b  may be manufactured by extrusion or laser cutting processes, from a plastomer or metallic type of material such as nylon, Teflon, or flexible stainless steel. The diameters of inner tube  664  and of intermediate tube  633   b  are adapted to allow insertion of inner tube into the lumen of intermediate tube  633   b  while providing suitable sealing thereof and preventing leakage of inflation fluids thereinto. For example intermediate tube  633   b  may have an inner diameter of about 0.8 mm and the outer diameter of inner tube  664  may be of about 0.78 mm. 
     Intermediate tube  633   b  can be manufactured by an extrusion process in which the ID (internal diameter) has an appropriate tolerance to fit over the outer diameter of inner tube  664 . Inner tube  664  and intermediate tube  633   b  are assembled together such that lateral port  612  is located in the horizontal opening  638  of intermediate tube  633   b . Thereafter the tubes  664  and  633   b  are inserted into the hollow shaft  663  and lateral port  612  can be attached to hollow shaft  663 . 
     It should be noted that intermediate tube  633   b  is not necessarily a complete tube. While the distal portion of intermediate tube  633   b  should be of a tubular shape, its proximal portion may have other cross-sectional shapes such as a semilunar shape. Alternatively, proximal portion of intermediate tube  633   b  may be implemented by a wire attached to its distal portion and exiting catheter  660  via proximal opening  665 . 
       FIGS. 15A to 15C  show longitudinal section views of a catheter  670  according to a seventh preferred embodiment of the invention wherein the inner tube  674  is made movable by affixing it to a slidable sealing sleeve  679 . In this preferred embodiment the distal end of balloon  611   a  is attached to the inner tube  674  at distal attachment points  62   a  provided around the outer surface of a distal section of said inner tube. 
     The structure, geometrical dimensions of elements of catheter  670  designated by the same numerals, and the method of manipulating its length and balloon&#39;s volume and shape, are much the same as those elements and manipulating method which were previously described hereinabove and therefore will not be further discussed herein, for the sake of brevity. 
     As with previous embodiments of the invention the inner tube is disposed in the hollow interior of the catheter&#39;s hollow outer shaft  676  and a curved section  637  thereof comprising lateral port  612  protrudes outwardly therefrom. A lateral opening  69  is provided on hollow outer shaft  676  from which said curved section  637  of inner tube  674  is protruding outwardly from hollow shaft  676 . Lateral opening  69  is sealed by sealing sleeve  679  mounted over an outer surface of hollow outer shaft  676 . Sealing sleeve  679  is designed to tightly fit over the outer surface of hollow outer shaft  676 , and to seal lateral opening  69  and the attachment area between sealing sleeve  679  and the curved section  637  of inner tube  674  protruding therefrom. Moreover, sealing sleeve is also made slidable to allow its movement distally or proximally within the limits imposed by lateral opening  69 . 
     In this way a movable inner tube  674  is obtained. The operator may inflate (designated by arrows  67   a  in  FIG. 15A ) balloon  611   a  and move inner tube distally or proximally by sliding sealing sleeve  679  over hollow shaft  676 . Additionally or alternatively, a displacement rod  648  may be employed for this purpose. Displacement rod  648  may be attached to a proximal section of inner tube  674  and a proximal section thereof can be made available to the operator via a proximal opening  675  provided at the proximal end of hollow shaft  676 . Proximal opening  675  is designed to allow conveniently sliding displacement rod  648  therethrough while providing suitable sealing thereof and preventing leakage of inflation fluid therefrom. 
     Lateral opening  69  is adjusted to allow moving inner tube  674  proximally into a state in which attachment point  62   a  reaches the proximal end of hollow shaft  676 , and on the other hand, to allow moving inner tube  674  sufficiently distally and enable stretching balloon  611   a  to its fullest length. 
     Sealing sleeve  679  can be manufactured by an extrusion and laser cutting process from a plastomer or metallic type of material, preferably from nylon or flexible stainless steel. The sealing and attachment of sealing sleeve  679  and the curved section  637  of inner tube  674  is preferably obtained by bonding these parts together by thermo-bonding or any other adhesive method such that they can slide together. The diameter of sealing sleeve  679  is adjusted according to the geometrical dimensions of hollow shaft  676 . For example, if the diameter of hollow shaft is about OD (outer diameter) 1.2 mm then the diameter of sealing sleeve is made about ID 1.22 mm. 
       FIG. 15C  demonstrates an implementation of catheter  670   a , similar to catheter  670 , wherein an inner sealing sleeve  677  is adapted to be installed in the hollow interior of hollow shaft  676 . In this implementation inner sealing sleeve  677  is adapted to be pressed against the inner wall of hollow shaft  676  about the area of lateral opening  69  and thereby to provide suitable sealing thereof. As in catheter  670  illustrated in  FIG. 15A , vertical section of inner tube  674  protrudes outwardly via inner sealing sleeve  677  and may be accessed by the operator via lateral port  612 . The sealing and attachment of inner sealing sleeve  677  and vertical section of inner tube  674  may be obtained using the same means described above with reference to catheter  670 . 
     Inner sealing sleeve  677  can be manufactured by an extrusion and laser cutting process from a plastomeric or metallic type of material, preferably from nylon or flexible stainless steel. The sealing and attachment of inner sealing sleeve  677  and the vertical section of inner tube  674  is preferably obtained in a similar manner as was explained hereinabove. The diameter of sealing sleeve  677  is adjusted according to the geometrical dimensions of hollow shaft  676 . For example, if the diameter of hollow shaft is about ID 1 mm then the diameter of inner sealing sleeve is made about OD 0.98 mm. 
     All of the abovementioned parameters are given by way of example only, and may be changed in accordance with the differing requirements of the various embodiments of the present invention. Thus, the abovementioned parameters should not be construed as limiting the scope of the present invention in any way. In addition, it is to be appreciated that the different tubes, balloons, shafts, and other members, described hereinabove may be constructed in different shapes (e.g. having oval, square etc. form in plan view) and sizes from those exemplified in the preceding description. 
     It should be noted that the different balloon catheter embodiments of the invention which were described hereinabove may be implemented with different types of balloon enabling folding of the proximal section of the balloon, the distal section of the balloon, or both proximal and distal sections of the balloon, as was exemplified hereinabove with reference to  FIGS. 9D and 9E . 
     In particularly preferred embodiments of the RE catheter system of the present invention, the balloon shape and force resistance characteristics of the catheter tubing are as described hereinabove in connection with the OTW systems, and exemplified in the following two Examples. 
     EXAMPLES 
     Example 1 
     Finite Element Analysis (FEA) of a Debris-Collecting Balloon for Use in the Present Invention 
     FEA is a computerized tool which was used to optimize the balloon design in order to improve its ability to fold in the desired way. The FE model describes an inflated balloon which its edge is retracted, resulting in folding of the balloon. The simulation was performed on different balloon designs and at varied inflation pressures, taking into account the mechanical properties of the balloon material, which was chosen to be nylon 12 or pebax. 
     Assumptions: 
     
         
         i. The balloon is made of a homogenous and isotropic material. 
         ii. The balloon&#39;s shape is symmetrical around its longitudinal axis. 
         iii. The balloon&#39;s shape is symmetrical around its mid transverse axis. 
         iv. The folding results in flexural stresses in the balloon material. Thus the mechanical properties (Modulus and Poisson Ratio) of the substance when flexed are taken into account in the FE analyses.
 
Methods:
 
         a) The analyses were performed using a nonlinear Finite Elements Analysis (FEA) program MSC.MARC. This software allows assessment of the structural integrity and performance of parts undergoing large deformations as a result of thermal or structural load (www.mscsoftware.com). 
         b) The analyses were nonlinear, assuming large displacements and taking into account stiffness change due to geometry update and sequential forces. 
         c) The model was 2D axisymmetric. 
         d) The model consisted of about 1000 nodes and 1000 2D solid elements. 
         e) Constant pressure was applied from within the balloon on its walls, reflecting the inflation pressure. Simultaneously, gradually increased axial force was exerted to the edge of the balloon, results in its folding. The displacement of the balloon wall in the horizontal (longitudinal) axis was measured versus the applied force. 
         f) The longitudinal axis of the balloon was kept fixed, while the balloon walls were free to move/fold as a result of the axial load. 
         g) The balloon&#39;s specifications are listed in the following table: 
       
    
     
       
         
               
             
               
               
               
             
               
             
               
               
               
             
           
               
                   
               
             
             
               
                 Balloon Specifications 
               
             
          
           
               
                   
                 Balloon length [mm] 
                 20 
               
               
                   
                 Balloon Outer Diameter [mm] 
                 3 
               
               
                   
                 Tube Outer Diameter [mm] 
                 0.4 
               
               
                   
                 Balloon Body Wall Thickness [μm] 
                 10 
               
               
                   
                 Neck Wall Thickness [μm] 
                 50 
               
               
                   
                 Tube Wall Thickness [μm] 
                 100 
               
               
                   
                 Tapering 
                 varying 
               
               
                   
                 Material 
                 PET (Polyethylene 
               
               
                   
                   
                 Terephthalate) 
               
             
          
           
               
                 Mechanical Properties 
               
             
          
           
               
                   
                 Flexural Modulus [Kg/mm 2 ] 
                 100 
               
               
                   
                 Flexural Yield Strength 
                 8.15 
               
               
                   
                 [Kg/mm 2 ] 
               
               
                   
                 Poisson Ratio 
                 0.4 
               
               
                   
                   
               
             
          
         
       
         
         h) Four balloon designs were analyzed, wherein the differences reside in the design of their tapering (see  FIG. 6 ):
       Standard 20° tapering   20° tapering with smooth round ending   Round ending   Round ending with initial retracting   
     
         i) The simulations were performed at five different inflation pressures: 1, 3, 6, 9 and 12 atmospheres.
 
Results:
 
       
    
       FIG. 7  shows the displacement vs. retracting force for the four balloon shapes at an inflation pressure of 6 atmospheres. Considering the maximal force required for collapse of the balloon, the Tapered-Round Ending Balloon required the lowest force, whereas the Round Ending Balloons need the greatest force to collapse. The Tapered Ending Balloon is somewhere between them. The slope of the Tapered Ending Balloon in the initial phase seems to be relatively moderate compared to the other balloon configurations. The moderate slope indicates higher stiffness. In other words, higher force is required to induce a given displacement. The slope of the Tapered-Round Ending Balloon is the steepest one, and suggests relatively high compliance to folding. 
     The balloon retracted shape vs. the original shape, at different inflation pressures was also studied (results not shown). The results demonstrated that the Tapered Ending Balloon is barely retracted, compared to the Round Ending Balloons which are retracted in a more smooth and continuous fashion. This is in spite of the higher force required to fold them. 
     Conclusion: 
     From the above analyses it was concluded that the inflation pressure and the balloon geometry have an important role in determining of the required folding force and the folding style. It appears that a tapered balloon with a smooth round ending folds best and has a relatively low retracting force, when compared to standard tapered balloon or a balloon with a round ending. 
     Example 2 
     Determination of the Force that is Required in Order to Fold the Balloon at Different Inflation Pressure 
     Equipment and Materials: 
     
         
         3.0 mm Nylon 12 Vestamid L2101F Balloon (Interface Associates 316079-1) 
         Glass tube with inner diameter of 3 mm. 
         Guidant HI-TORQUE CROSS-IT 200XT 0.014″ Guidewire. 
         Hounsfield Test Equipment Model TX0927, 50-N load cell. This computer controlled testing machine enables determining tension, compression, shear, flexure and other mechanical and physical properties of materials. The machine provides selection of test speeds and direction of travel. It can measure the force and displacement values and can also graphically display the test. 
         Assouline Compressor type 1.5 HP. 
         Fluid dispensing system Model 1500XL.
 
Procedure:
 
       
    
     The balloon was inserted into a 3-mm glass tube, at straight position or inclined to 45°. A guidewire was inserted into the inner tube in order to stabilize the folding motion. The balloon was inflated using a compressor and the inflation pressure was controlled by a dispenser. The procedure was performed at pressures ranging between 3-7 atm, with increments of 1 atm. The balloon was folded using the Hounsfield Test machine, by pulling the inner tube at speed of 100 mm/min up to 20 mm, and then pushing back at the same speed until the balloon was completely unfolded. 
     Four tests were conducted at each pressure, to confirm that the results could be replicated. 
     Results: 
     The maximal force required for folding the balloon at each pressure is presented in  FIG. 8  The maximal force increases with the inflation pressure for both positions (straight and inclined) and ranges between 2-3.5 N (200-350 gr) with increments vary between 0.2-0.4 N (20-40 gr) per step of 1 atm in pressure. Higher inflation pressure requires greater force to fold the balloon. The relationship is approximately linear (R 2 =0.98). The maximal forces are slightly lower for the inclined position; however, repeated tests at the straight position revealed that the lesser forces result from the material fatigue. To support this assumption, visual examination of the balloon after 40 repeats showed that the balloon material lost its flexibility and looked crumpled. 
     The above examples and description have of course been provided only for the purpose of illustration, and are not intended to limit the invention in any way. As will be appreciated by the skilled person, the invention can be carried out in a great variety of ways, employing more than one technique from those described above, all without exceeding the scope of the invention.