Abstract:
A catheter for delivering an agent to an area of treatment is presented. The catheter includes a catheter body, a balloon assembly coupled to the catheter body, a first lumen, and a second lumen. The balloon assembly has spaced-apart balloons that define an area between the balloons. The first lumen extends along the catheter body to pass an inflation material to the balloons to control an inflation level of the balloons. The second lumen extends along the catheter body and having an outlet in the area between the balloons. There may be a third lumen for bypassing a biological fluid such as blood while the catheter is being used. The method of using this catheter is also presented. The method entails simultaneously inflating the balloons to isolate a treatment area and adding an agent to the treatment area through one of the lumens.

Description:
RELATED APPLICATION  
       [0001]     This application is a Continuation-in-Part application of U.S. Ser. No. 10/355,017 filed on Jan. 31, 2003, which claims the benefit of U.S. Provisional Application Nos. 60/353,305 filed on Feb. 1, 2002 and 60/387,260 filed on Jun. 7, 2002. 
     
    
     TECHNICAL FIELD  
       [0002]     The present invention relates to medical devices and procedures for medical treatment. In particular, this invention relates to using a catheter to apply an agent in a targeted manner.  
       BACKGROUND  
       [0003]     Catheters have been widely used to access the vascular system and other anatomical spaces in medical procedures. Catheters may be used for infusion of therapeutics and for the insertion or placement of substances or apparatuses for treating various disorders. Catheters may also be modified, for example, by the addition of balloon systems, for the treatment of arterial plaques and aneurisms.  
         [0004]     Arterial plaques grow on arterial walls as cholesterol circulates in the blood, and as the plaques enlarge the arteries become narrow and stiffened. This process is called atherosclerosis, commonly known as “hardening of the arteries” because the plaque buildup thickens the walls of the arteries, narrowing the space through which blood flows. The narrowing or blockage of the vessel is also referred to as “stenosis.” 
         [0005]     One of the common methods for treating arterial plaques is balloon angioplasty. As an established procedure in the management of a variety of obstructive disorders of the vascular system, balloon angioplasty has been applied to obstructive lesions of the iliac, femoral, renal, coronary and cerebral vascular systems. Typically, a small flexible guide wire is advanced through a guiding catheter into the vessel and across the stenosis. A balloon catheter is then advanced over the wire and positioned across the stenosis. The balloon is usually inflated for a short period of time to dilate the vessel and is then deflated. Alternatively, stenosis may be treated by chemical means. For example, U.S. Pat. No. 4,636,195 to Harvey Wolinsky describes a catheter with distal and proximate balloon segments expandable to produce a chamber around an arterial plaque and a conduit for delivering a solubilizing liquid into the chamber to dissolve the plaque. U.S. Pat. No. 6,056,721 to John Shulze also describes a balloon catheter device for treating an obstructing material within a vascular conduit. The device comprises an elongate catheter body extending between a proximal end and a distal end. A balloon is attached at the distal end to block the flow of a body fluid and a drug is released from the catheter body to treat the obstructing material. Other methods for treating stenosis include ionizing radiation and laser evaporation.  
         [0006]     All these procedures usually cause some degree of biological reaction of the vessel wall and often result in new growth and significant reduction of the vessel lumen (restenosis) at the treatment site. Therefore, it is a common procedure to place a stent at the treatment site after balloon angioplasty to prevent restenosis. The stent is usually introduced to the target area in a compressed form by an insertion catheter and then expanded in situ by means of a special balloon catheter. The stent will remain in position in its expanded state, supporting the wall of the vessel in a manner that essentially restores the original form of the vessel. The stent may also be formed in situ. For example, U.S. Pat. No. 6,039,757 to Stuart Edwards et al. generally describes a device for forming a fenestrated stent in situ in a body lumen. Briefly, the body lumen and the stent-forming device form a mold space within which a fluent composition is provided and transformed into a non-fluent composition in the shape of a stent with a series of fenestrations.  
         [0007]     The term “aneurysm” refers to the abnormal enlargement or bulging of an artery caused by damage to or weakness in the blood vessel wall. Although aneurysms can occur in any type of the body&#39;s blood vessels, they almost always form in an artery. A ruptured aneurysm can lead to internal bleeding that often results in severe impairment of body functions and even death. Traditional treatment for aneurysms is surgical clipping which requires major surgery and cannot be performed on aneurysms inside vital organs, such as the brain. A much less-invasive technique, endovascular coiling, has been developed as a viable alternative to surgery for many patients whose aneurysms might otherwise go untreated. In an endovascular coiling procedure, a microcatheter is inserted into the femoral artery in a patient&#39;s groin area. The microcatheter is tracked through the patient&#39;s blood vessels (arteries), from the femoral artery up to the site of the aneurysm. Matrix coils are fed through the catheter and into the aneurysm, filling it and sealing it off from the artery. In animal studies, the coils were found to promote the development of connective (scar) tissue inside the aneurysm. The connective tissue excluded the aneurysm from arterial blood flow. An aneurysm occluded from blood circulation may have a decreased risk of rupture.  
         [0008]     In order to treat an aneurysm effectively with an endovascular coil system, the coil must be inserted into the aneurysm and positioned inside the aneurysm in a proper configuration. The process, however, is often time-consuming and requires experienced operators.  
         [0009]     Another illness that is currently not treated effectively is cancer. Most current efforts to eliminate tumors include systematic approaches such as chemotherapy, radiation, and surgical removal of tissues. When a tumor is vascular, chemotherapy and radiation treatments are less effective than desired because it is difficult to target the tumor with an effective level of specificity and only a small percentage of the chemotherapy and radiation get “pushed” into the capillaries that feed the tumor. With only a small percentage of the chemotherapy and radiation actually getting to the tumor, more of the chemotherapy and radiation end up reaching the healthy tissues instead of the tumor. A treatment method that allows a more targeted approach to kill the tumor is desirable.  
         [0010]     Most catheters are specialized and can only be used for a specific medical procedure. For example, an angioplasty catheter cannot be used for treating aneurysms and, vice versa, catheters designed for treating aneurysms cannot be used for stenosis. In the case of balloon angioplasty, the angioplasty and stent installation typically require two different disposable, low profile guiding catheters. The insertion and removal of the catheters are time-consuming processes and the catheters are expensive.  
         [0011]     In order to reduce costs and improve efficiency, it would be desirable to have one catheter that could be used to treat multiple illnesses such as stenosis, aneurysm, and vascular cancer.  
       SUMMARY OF INVENTION  
       [0012]     In one aspect, the invention is a catheter for delivering an agent to an area of treatment. The catheter includes a catheter body, a balloon assembly coupled to the catheter body, a first lumen, and a second lumen. The balloon assembly has spaced-apart balloons that define an area between the balloons. The first lumen extends along the catheter body to pass an inflation material to the balloons to control an inflation level of the balloons. The second lumen extends along the catheter body and having an outlet in the area between the balloons. The balloon assembly may have two balloon elements, although the number is balloon elements is not so limited.  
         [0013]     In another aspect, the invention is a method of delivering an agent to a treatment area. The method includes providing a catheter that is attached to inflatable balloons and positioning the catheter so that the area of treatment is between the balloons. The catheter has a first lumen and a second lumen extending along the catheter. The inflation level of the balloons is simultaneously controlled to create the treatment area between the balloons. The inflation level is controlled by passing an inflation material through the first lumen that has an opening into each of the balloons. The agent is passed into the treatment area through a second lumen. This method may be used with two inflatable balloons, although the invention is not so limited.  
         [0014]     In yet another aspect, the invention is a catheter for cancer treatment. The catheter includes a catheter body having a proximal end and a distal end, a first balloon positioned to inflate around the proximal end of the flexible catheter body, and a second balloon positioned to inflate around the distal end of the flexible catheter body. The flexible catheter body has a first lumen for allowing a fluid to pass across the first and the second balloons, a second lumen for inflating the first balloon and the second balloon, and a third lumen for passing an agent to an outlet between the first balloon and the second balloon. 
     
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0015]     The inventions of this application are better understood in conjunction with the following drawings, in which:  
         [0016]      FIGS. 1A, 1B  and  1 C illustrate side views of various embodiments of a multi-function catheter with an uninflated balloon in accordance with the teachings of the present invention;  
         [0017]      FIGS. 2A and 2B  illustrate a side-sectional view of an embodiment of a multi-function catheter with an inflated balloon, and a cross-sectional view of the proximal end of the multi-function catheter, respectively;  
         [0018]      FIG. 3  is a flow diagram showing a method for treating arterial plaque using a multi-function catheter pursuant to the principles of the present invention;  
         [0019]      FIGS. 4A-4E  generally depict a procedure for plaque removal and stent installation using a multi-function catheter as set forth in the present invention;  
         [0020]      FIG. 5  is a flow diagram showing a method for treating aneurysms using a multi-function catheter pursuant to the principles of the present invention;  
         [0021]      FIGS. 6A-6D  generally depict a treatment process for aneurysms using a multi-function catheter as set forth in the present invention;  
         [0022]      FIG. 7  is a flow diagram showing a method for treating tumors using a multi-function catheter pursuant to the principles of the present invention;  
         [0023]      FIGS. 8A-8D  generally depict a process of oncology treatment using a multi-function catheter as set forth in the present invention;  
         [0024]      FIG. 9  illustrates an alternative embodiment of the multi-function catheter; and  
         [0025]      FIG. 10  is a flow diagram showing a method of treatment using the alternative catheter of  FIG. 9 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0026]     The following detailed description is presented to enable any person skilled in the art to make and use the invention. For purposes of explanation, specific nomenclature is set forth to provide a thorough understanding of the present invention. However, it will be apparent to one skilled in the art that the specific nomenclature and details are not required to practice the invention. Descriptions of specific applications are provided only as representative examples. Various modifications to the preferred embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be applied to other embodiments and applications without departing from the scope of the invention. The present invention is not intended to be limited to the embodiments shown, but is to be accorded the widest possible scope consistent with the principles and features disclosed herein.  
         [0027]     With reference now to  FIGS. 1A-1C , various embodiments of the multi-function catheter of the present invention will be described. As will be described in more detail below, the multi-function catheter may be used for removal of arterial plaques; installation of a stent, infusion of drugs; sealing off an aneurysm or a branch of a vessel; dilation of a biological path; and other usages.  
         [0028]     As shown in  FIG. 1A , a multi-function catheter, generally designated by the reference number  100 , has a flexible tubular catheter body  102  having an inner lumen  104 , a proximal end  105 , and a distal end  106 ; an inflatable balloon assembly  108  that is capable of multi-stage inflation at the distal end  106  of the catheter body  102 ; at least one fluid delivery conduit  110  that is adapted to permit a biological fluid (e.g., blood) flow through a path; and at least one balloon control conduit  112  that inflates and deflates the balloon assembly  108 . The multi-function catheter  100  may further include a pre-manufactured stent  114  on the outer periphery of the balloon assembly  108 , as illustrated in  FIG. 1B , and/or a magnetized metal  116  at the distal end  106  of the catheter body  102 , as illustrated in  FIG. 1C . The magnetized metal  116  allows an operator of the multi-function catheter  100  to move the catheter  100  through a biological path to a target site by a magnetic field, e.g., in conjunction with 3D imaging. The biological path includes, but is not limited to, blood vessels, respiratory tracts, urinary tracts, gastrointestinal tracts, reproductive tracts, and biliary ducts. In a preferred embodiment, the multi-function catheter  100  is approximately 0.03 to 0.07 inches in diameter. The absolute dimensions of the multi-function catheter  100  chosen for a particular procedure depend on the location of the target site and the size of the biological path used to access the target site, as is well understood to those skilled in the art.  
         [0029]     With reference now to the sectional views in  FIGS. 2A and 2B , the catheter body lumen  104  allows a guide wire  202  to enter at the proximal end  105  and exit at the distal end  106 . The body lumen  202  also allows blood to flow through the catheter  100  during a procedure. Typically, the guide wire  202  is placed into a biological path and advanced beyond a treatment site. Then the catheter  100  is placed over the guide wire  202  and advanced to the treatment site, guided thereto using the trajectory of the prelaid guide wire  202 . Various types of guide wires may be used. For example, a metal wire generally made of nickel, preferably of 0.018 inch diameter or smaller, may be used. Guide wire  202  may be removed and replaced during a treatment procedure.  
         [0030]     With further reference to  FIG. 2A , the balloon assembly  108 , when inflated, has at least three balloon elements: a proximal balloon element  124 , a central balloon element  126 , and a distal balloon element  128 . The central balloon element  126  can be inflated to at least two different stages. In one embodiment, the three balloon elements  124 ,  126  and  128  are integrated parts of the balloon assembly  108  and are controlled collectively by the balloon control conduit  112 . In another embodiment, the central balloon element  126  can be individually controlled by the balloon control conduit  112 . In yet another embodiment, each of the three balloon elements can be individually controlled by the balloon control conduit  112 . The individualized control allows one balloon element to be inflated or deflated without affecting the inflation status of the other balloon elements in the balloon assembly  108 . As shown in  FIG. 2A , the proximal balloon element  124  and the distal balloon element  128 , when inflated, form a chamber  204  between the balloon assembly  108  and an arterial wall  206  around a plaque  208 . The volume of the chamber  204  may be adjusted by inflating the central balloon  126  to different stages.  
         [0031]     The catheter body  102  can be prepared from any of a number of readily available, non-toxic, flexible polymers including, for example, polyolefins such as polyethylene or polypropylene and polyvinyl halides such as polyvinyl chloride or polyvinylidene chloride. The balloon assembly  108  can be fabricated from similar materials manufactured so as to be expansible under pressure and with sufficient elasticity to contract when the pressure is released. The dimensions of the balloon elements will be such that they will reach the desired diameters at preset pressures. In a preferred embodiment, the proximal and the distal balloon elements  124  and  128  will reach the desired diameter at a first preset pressure of about 75 mm to 150 mm Hg and hold the dimensions even if the pressure is increased to as high as 15 atmospheres, while the central balloon element  126  will reach a first diameter at the first preset pressure and other diameters at other preset pressures.  
         [0032]     The absolute dimensions selected for the balloons will depend upon the diameter of the vessel involved in the treatment. In one embodiment, the proximal and the distal balloon elements  124  and  128  are from about 0.3 mm to about 10 mm in length and their expanded diameters may be in approximately the same range. The shape of the inflated balloons may be conical, spherical, square, or any shape that is convenient for the particular application. The central balloon  126  is inflatable to the same diameter range as the proximal and the distal balloons  124  and  128 , but the length is preferably from about 0.4 to 2 inches.  
         [0033]     With reference again to  FIGS. 2A and 2B , the fluid delivery conduit  110  and the balloon control conduit  112  are formed within the catheter body  102 . The fluid delivery conduit  110  includes one or more fluid delivery channels for allowing fluids and/or gases (hereinafter referred to as fluids) to flow into and/or out of the chamber  204 . As is understood by one skilled in the art, more than one fluid delivery conduit  110  may be formed within the catheter body  102 . The balloon control conduit  112  also includes one or more channels for allowing the inflation material to flow into or out of the inflatable balloon assembly  108  for the inflation/deflation of the balloon assembly  108 . The inflation material may be any liquid or gas that would be safe for the treatment subject even if there is a leakage, such as a saline solution. The fluid delivery conduit  110  and the balloon control conduit  112  may be formed using Teflon, polyurethane, polyethylene, or other similar materials.  
         [0034]     With reference now to  FIG. 3  of the drawings, there is illustrated a method, generally designated by the reference number  300 , for treating arterial plaque using the multi-function catheter of the present invention. First, the multi-function catheter  100  is advanced to the plaque site (step  302 ). Second, the balloon assembly  108  is inflated to create a perfusion chamber around the plaque (step  304 ). Third, a plaque removal agent is perfused into the perfusion chamber to dissolve or digest the plaque (step  306 ). Fourth, a stent is placed at the treatment site to prevent restenosis (step  308 ). In one embodiment, the stent is formed using a fluent composition that is transformed into a non-fluent composition in situ at the treatment site. In another embodiment, the stent is pre-manufactured and is part of the multi-function catheter  100 , as shown in  FIG. 1B . Finally, the multi-function catheter  100  is withdrawn and the stent is left behind to assist the cell wall in healing at the treatment site (step  310 ).  
         [0035]     The treatment process is further illustrated in  FIGS. 4A-4E . As shown in  FIG. 4A , the multi-function catheter  100  is advanced to the treatment site so that the balloon assembly  108  is located right inside the area of the plaque  208 . The balloon assembly  108  is then inflated to a first stage to form a chamber  204  around the plaque  208  ( FIG. 4B ). A plaque removal agent is then delivered within the chamber  204 . The plaque removal agent can be forced into the plaque by the application of pressure through the fluid delivery conduit  110  (shown in  FIG. 2A ) or by the expansion of the central balloon element  126 , as discussed in more details hereinabove. The plaque removal agent can also be recirculated into the chamber  204  until the plaque (mostly cholesterol) is dissolved. After the desired effect is obtained, the chamber  204  is then washed with a washing solution such as saline in order to remove any traces of the plaque removal agent. In the next step, the balloon assembly  108  is inflated to a second stage ( FIG. 4C ). At this stage, most of the space vacated by the plaque  208  is taken up by the further inflated balloon assembly  108 . The much smaller chamber, designated by the reference number  204 ′, now serves as a mold for the formation of a customized stent. As shown in  FIG. 4D , the chamber  204 ′ is filled with a fluent pre-stent composition delivered through the fluid delivery conduit  110  (shown in  FIG. 2A ). The pre-stent composition solidifies in the chamber  204 ′ to form a stent  210 . The balloon assembly  108  is then deflated and the multi-function catheter  100  is withdrawn, leaving behind the stent  210  at the treatment site ( FIG. 4E ). In a preferred embodiment, the stent  210  may contain or be coated with a material to reduce the occurrence of restenosis and clotting. In another preferred embodiment, the chamber  204 ′ defines a streamlined shape for the stent  210  so that the risk of blood clot over the stent  210  is reduced.  
         [0036]     With regard to the plaque removal process of  FIG. 4B , various types of plaque removing agents may be used with the multi-function catheter  100 . In general, the plaque removing agent should be non-toxic and should not cause clotting of the blood. Because of the low volumes involved, e.g. about 0.1 to about 0.5 ml, a number of polar organic solvents can be employed to dissolve cholesterol and its esters, even though this would normally be considered too toxic for internal use. These organic solvents include, for example, acetone, ether, ethanol, and mixtures thereof.  
         [0037]     The plaque removing agent may also include isotonic aqueous buffers containing phospholipids. Phospholipids are naturally available compounds which on hydrolysis yield fatty acids; phosphoric acid; an alcohol, usually glycerol; and a nitrogenous base such as choline or ethanolamine. Examples of phospholipids include lecithins, cephalins and sphingomyelins. The efficiency of the plaque removing agent containing lecithin or other phospholipid can be improved by the addition of bile acids such as cholic, deoxycholic, chenodeoxycholic, lithocholic, glycocholic and taurocholic acid.  
         [0038]     The plaque removing agent may also include an enzyme or a mixture of enzymes. In one embodiment, the enzyme is a pancreatic cholesterol esterase that hydrolyzes cholesterol into sterol and fatty acids. In another embodiment, the enzyme is a collagenase. The collagenase cleaves collagen which is the main supportive structure of the plaque. The plaque body then collapses. Other enzymes such as papain, chymotrypsin, chondroitinase and hyaluronidase may also be employed together with the collagenase or as an alternative thereto. The enzymes may be used either with or without bile acid or phospholipid. The enzyme may be solubilized in a number of physiologically acceptable buffers including phosphate buffered saline, tris buffer, Ringer&#39;s lactate buffer and the like.  
         [0039]     In a preferred embodiment, a fluid delivery system, preferably with multiple fluid delivery channels, is used. Usually, an automatic machine is used to perfuse the chamber  204  with the plaque removing agent through the fluid delivery conduits  110 . Similarly, the inflation and deflation of the balloon assembly  108  can be controlled by an automatic machine connected to the balloon control conduit  112 .  
         [0040]     Various fluent materials may be used to form the stent  210  in situ. The fluent pre-stent composition can be formulated from any one or more components which have the necessary biocompatible properties and which can be converted in situ to a solid stent composition. Typically, the liquid-to-solid phase transformation is triggered by the introduction of a chemical catalyst and/or energy, such as RF energy or microwave energy. Materials capable of this phase transformation are discussed in detail in U.S. Pat. No. 5,899,917, which is hereby incorporated by reference.  
         [0041]     The pre-stent composition may also contain a protein and/or a polysaccharide. Examples of the protein/polysaccharide component include, but are not limited to, collagen, fibrin, elastin, fibronectin, vironectin, aglin, albumin, laminin, gelatin, cellulose, modified cellulose, starch, modified starch, synthetic polypeptide; acetylated, sulfonated and phosphorylated collagen, and glycosaminoglycans (heparin, heparan, dermatan, chrondoin sulfate).  
         [0042]     The pre-stent composition may contain an aqueous electrolyte solution with sufficient ionic strength to conduct electric current or RF energy. The pre-stent composition may also contain a reinforcement agents and adjuvants to promote wound healing. Examples of the reinforcement agent include, but are not limited to, poly(lactide), poly (glycolide), poly (lactide)-co-(glycolide), poly (caprolactone), poly (betahydroxtbutylate), a poly (anhydride), and a poly (orthoester).  
         [0043]     The pre-stent compositions may also contain materials that have a high susceptibility and absorbance for microwave energy. Such materials include, but are not limited to, metal oxides, such as ferric oxide, and carboniferous materials, such as acetylene black and graphite, or hydroxyl containing materials, such as alcohols or water.  
         [0044]     If the pre-stent composition solidifies by forming covalent bonds mediated by free radical species, a thermally-activated free radical initiator and/or an accelerator may be included in the composition. Such thermal initiation materials include, but are not limited to, a peroxide material like benzoyl peroxide or lauroyl peroxide or ammonium persulfate, or an azo material, such as azo bis(isobutylnitrile) (AIBN, Vazo 64). Accelerator materials include, but are not limited to, reductants such as amines, like triethanol amine (TEOA), alpha hydroxy ketones, like benzoin and acetoin, and ascorbic acid and derivatives.  
         [0045]     The pre-stent material can be mixed with therapeutic agents to promote healing and prevent restenosis. Examples of the therapeutic agents include, but are not limited to, immunosuppressant agents such as cycloporin, adriamycin, and equivalents; anticoagulants such as heparin, anti-platelet agents, fibrinolytic and thrombolytic agents; anti-inflammatory agents; and growth factors. Alternatively, the stent  210  may be coated with a material to reduce restenosis and clotting.  
         [0046]     The stent composition may also be formed of a bioresorbable material and itself be bioreabsorbed into the surrounding tissue.  
         [0047]     The multi-function catheter  100  of the present invention can also be used to treat aneurysms. As described earlier, treatment using an endovascular coil system is often time-consuming and requires experienced operators. The multi-function catheter of the present invention offers an relatively simple and quick alternative treatment for aneurysms, which is particularly useful in an emergency setting.  
         [0048]     With reference now to  FIG. 5 , there is illustrated a flow diagram of a method, generally designated by the reference number  500 , for treating aneurysms using the multi-function catheter  100  of the present invention. First, the multi-function catheter  100  is advanced to the aneurysm site (step  502 ). The balloon assembly  108  is then inflated to create a chamber around the area weakened by the aneurysm (step  504 ). The blood in the aneurysm can be removed through the fluid delivery conduit  110  (shown in  FIG. 2A ) to prevent vasospasms and hydrocephalus (step  506 ). A stent is then placed around the weakened area to seal off the aneurysm (step  508 ) and the multi-function catheter is withdrawn (step  510 ). As described earlier, the stent may be a pre-manufactured stent or be formed in situ.  
         [0049]     The treatment process set forth hereinabove in connection with  FIG. 5  is further illustrated in  FIGS. 6A-6D . As shown in  FIG. 6A , the multi-function catheter  100  is advanced to the treatment site so that the balloon assembly  108  is placed in the area weakened by the aneurysm  602 . The balloon assembly  108  is then inflated to form a chamber  204  adjacent to the aneurysm  602  ( FIG. 6B ). A negative pressure may be created inside the chamber  204  by the fluid delivery conduit  110  in order to remove the blood from the aneurysm  602 . A stent  604  is then formed at the area weakened by the aneurysm  602  ( FIGS. 6C and 6D ). In an emergency, a pre-manufactured stent may be installed to quickly seal off the aneurysm  602 . As readily realized by one skilled in the art, the method  500  can be used for almost any aneurysm in the body.  
         [0050]     The multi-function catheter  100  of the present invention can also be used for oncology purposes. Using the endovascular catheter of the invention results in a treatment that is effectively targeted to a vascular tumor because the catheter is able to get very close to the tumor without impairing the blood supply to other organs. The endovascular catheter is placed within the one of the principal vessels feeding the tumor. The tumor is connected to the principal vessel via one or more branch vessels, and the bloodflow through the branch vessels keep the tumor sustained (e.g., by delivering oxygen and nutrients to the tumor cells). The endovascular catheter of the invention causes necrosis of the tumor by pumping an anti-tumor agent or saline solution through the branch vessels, killing the tumor either chemically or through hypoxia.  
         [0051]     With reference to  FIG. 7 , there is illustrated a flow diagram of a method, generally designated by the reference number  700 , for treating tumors using the multi-function catheter  100  of the present invention. In this procedure, the multi-function catheter is advanced to the opening of a branch vessel that provides blood supply to a tumor (step  702 ). The balloon assembly is then inflated to create a chamber around the opening of the branch vessel (step  704 ) and the tumor is perfused with an agent via the branch vessel to induce necrosis (step  706 ). Optionally, a stent is formed at the opening of the branch vessel to cut off the blood supply to the tumor after the perfusion (steps  708  and  710 ). The method  700  thus allows direct targeting of the tumor with an anti-tumor agent and minimizes side effects.  
         [0052]     The treatment process set forth hereinabove in connection with  FIG. 7  is further illustrated in  FIGS. 8A-8D . As shown in  FIG. 8A , the multi-function catheter  100  is advanced to the treatment site so that the balloon assembly  108  is placed near the vessel opening  802  of a branch artery that provides blood to a tumor  804  or other deleterious tissue. The balloon assembly  108  is then inflated to form a chamber  204  around the vessel opening  802  ( FIG. 8B ). The tumor  804  is then perfused with an agent through the branch artery to induce necrosis of tumor cells. In one embodiment, the agent is a saline solution. The replacement of blood with saline induces ischemic necrosis of tumor cells. In another embodiment, the agent is an anti-tumor agent that is toxic to tumor cells. After the infusion, a stent  806  may be formed at the vessel opening  802  to seal off the branch artery and cuts off the blood supply to the tumor  804  ( FIGS. 8C and 8D ).  
         [0053]      FIG. 9  is an alternative embodiment of the multi-function catheter, shown as a catheter  920 . This multi-function catheter  920  has a proximal balloon element  922  and a distal balloon element  924  but no central balloon element (it could be there but just not inflated). As shown in  FIG. 9 , the proximal and distal balloon elements  922 ,  924  are inflated in a blood vessel  101 . The blood vessel  101  has openings  802  through which the tumor  804  draws blood and receives oxygen. The balloon elements  922 ,  924  are positioned so that they stop the blood from circulating to the vessel openings  802 .  
         [0054]     The catheter  920  includes a catheter body  930 , which is similar to the flexible catheter body  102  shown in  FIG. 2B . The catheter body  930  may be made of aliphatic polyurethane such as the commercially available Tecoflex EG68D. Like the flexible catheter body, the catheter body  930  is preferably flexible and has lumens extending through it. For example, since it is undesirable to cut off the circulation of a biological fluid (e.g., blood), there is a fluid bypass lumen that provides a bypass for the biological fluid. Although not shown, the inlet and outlet of the fluid bypass lumen are somewhere on the catheter body  930  outside the region defined by the balloon elements  922 ,  924 . For example, there is a first opening that is proximal to the balloon assembly and a second opening that is distal to the balloon assembly. In addition, there is a fluid delivery conduit for delivering the agent to the chamber formed by the balloon elements  922 ,  924 , and a balloon control conduit for controlling the inflation levels of the balloon elements  922 ,  924 . The balloon control conduit extends from its inlet to a proximal outlet in the balloon element  922  and a distal outlet in the balloon element  924  so that both balloons are inflated and deflated through the same lumen. The fluid delivery conduit extends from its inlet to an outlet  934  that is positioned between the two balloon elements  922 ,  924 . There may be one or more outlets  934  for the fluid delivery conduit. The shape of the outlet  934  may be varied. For example, the outlet  934  may be rectangular (as shown), round, oval, trapezoidal, etc.  
         [0055]     As the balloon elements  922 ,  924  are inflated, a treatment area including the tumor  804  becomes isolated. A chemotherapy agent and an imaging agent are added to the isolated area between the balloon elements  922 ,  924 . To achieve the isolation, the imaging agent is added to the space between the balloon elements  922 ,  924  while the balloon elements  922 ,  924  are being simultaneously inflated. This way, a user knows that the inflation should be stopped when no more imaging agent leaks out of the isolated area. The imaging agent and a chemotherapy agent is then added to the isolated area and forced into the tumor  804 . The chemotherapy agent is held in contact with the tumor  804  as long as necessary. An embolic material (e.g., polyvinyl alcohol) in the form of gels or foams may be added so that they are pushed into the tumor to help cut off blood flow to the tumor  804 .  
         [0056]     As more agent is added to the chamber between the balloon elements  922 ,  924 , more of it will be delivered to the tumor  804 , as shown by the arrows from the outlet  934 . The agent enters the tumor instead of the blood, but does not carry oxygen like the blood. Thus, as the agent flows through the tumor, the tumor experiences hypoxia. The agent that is fed to the tumor  804  circulates through the tumor  804  and exits the tumor  804  through another vessel opening  802 . The amount of the agent that is fed to the tumor  804  is insignificant enough that the addition of the circulated agent to the blood stream does not cause any adverse side effects.  
         [0057]     The multi-purpose catheter  920  has markers  936  on its outer surface and a radiopaque tip  938 . The markers  936  and the radiopaque tip  938 , which may be made of the same material (e.g., platinum iridium), can be seen with an imaging device, and are useful for proper placement of the catheter  920 .  
         [0058]     When inflated, the balloon elements  922 ,  924  have a maximum diameter of about 4-8 mm, the actual diameter being adjusted to the size of the blood vessel  101 . The balloon elements  922 ,  924  may be made of polyurethane or silicon urethane of about 0.001-inch thickness, or of polyisoprene. The balloon elements  922 ,  924  may be manufactured as components that are separate from the flexible catheter body  930  but designed to slip over the flexible catheter body  930 . The markers  936 , which protrude relative to the catheter body  930 , indicate the positions of the balloon elements  922 ,  924  (which varies depending on the specific application) and holds the balloon elements  922 ,  924  in place. In the embodiment shown, the markers  934  are between the balloon elements  922 ,  924  and in the balloon elements  922 ,  924 . However, the number of markers and their positions may be adjusted to the application.  
         [0059]      FIG. 9  depicts the balloon elements  922 ,  924  in their inflated state. When not inflated, the balloons are positioned around the catheter body  102  in fixed locations. When the balloon elements  922 ,  924  are inflated, the center portion becomes larger while the end portions remain adhered to the catheter body  102  to hold the inflated portion in place.  
         [0060]      FIG. 10  is a flow diagram of a method  900  for treating an area (e.g., a tumor) using an embodiment of the multi-function catheter of the invention, such as the catheter shown in  FIG. 10  below. The catheter  100  is placed at an area of treatment (step  902 ), for example by using the radiopaque tip and markers through an imaging device. Once the catheter is properly positioned, the balloon assembly on the catheter is inflated to create a space between the balloon elements  922 ,  924  (step  904 ). Then, an agent (e.g., an anti-tumor agent, saline solution) is delivered to this space through a lumen extending through the catheter (step  906 ). After the agent has been delivered for a desired period of time, the agent delivery is stopped and the balloon elements  922 ,  924  are deflated (step  908 ). The catheter  100  is then withdrawn from the area of treatment (step  910 ).  
         [0061]     The use of saline solution to kill the tumor through hypoxia is described above. In methods  700  and  900 , a variety of anti-tumor agent may be used instead of saline solutions to chemically kill the tumor. The anti-tumor agent can be any commonly used chemotherapy agent, such as alkylating agents, vinca alkaloids, anthracycline antibiotics, glucocorticoids, and inhibitors of protein/DNA/RNA synthesis. A lower concentration of the chemotherapy agent can be used in this invention than in the conventional chemotherapy treatments without compromising the effectiveness because in this method, the agent is provided to the tumor in a targeted manner. The exact concentration of the chemotherapy agent that is used depends on the type of chemotherapy agent. The saline solution or the anti-tumor agent may be combined with an imaging agent (e.g., barium sulfate) so that the infusion of the saline or the anti-tumor agent into the tumor can be observed and carefully controlled. The imaging technology that may be used with the multi-function catheter  100  is well known.  
         [0062]     The multi-function catheter of the present invention may also be used in a number of other procedures. For example, the multi-function catheter can be used to permanently open a constricted vessel passage, such as constricted tracheobronchial or a partially blocked fallopian tube, by dilating the constructed vessel passage and installing a stent in the constricted area. The multi-function catheter can also be used for the treatment of trauma patient. Specifically, the multi-function catheter may be used to stop bleeding or to remove blockage in vessels in a wounded tissue.  
         [0063]     Having described the preferred embodiments of the multi-function catheter of the present invention and use thereof (which are intended to be illustrative and not limiting), it is noted that modifications and variations can be made by persons skilled in the art in light of the above teachings. For example, although the embodiments depicted herein show two balloon elements in a balloon assembly, the balloon assembly is not so limited. Therefore, it is understood that changes may be made in the particular embodiments disclosed which are within the scope and spirit of what is described as defined by the appended claims.