Abstract:
An apparatus is provided that is useful in an embolization procedure and enables substantially unrestricted forward flow of blood in a vessel and reduces or stops reflux (regurgitation or backward flow) of embolization agents which are introduced into the blood. A method of using the apparatus is also provided.

Description:
RELATED APPLICATIONS 
       [0001]    The present application claims priority from U.S. Ser. No. 61/266,068 filed Dec. 2, 2009 entitled “Anti-Reflux Protection Device” which is hereby incorporated by reference herein in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of Invention 
         [0003]    The present invention relates generally to a medical embolizing treatment system. More particularly, the present invention relates to an embolizing treatment system utilizing a protection device which reduces the reflux of a treatment agent in a blood vessel during an embolization therapy procedure, where the embolization agent is delivered through a catheter to provide therapy to tissue distal via a delivery orifice of the catheter. 
         [0004]    2. State of the Art 
         [0005]    Embolization, chemo-embolization, and radio-embolization therapy are often clinically used to treat a range of diseases, such as hypervascular liver tumors, uterine fibroids, secondary cancer metastasis in the liver, pre-operative treatment of hypervascular menangiomas in the brain and bronchial artery embolization for hemoptysis. An embolizing agent may be embodied in different forms, such as beads, liquid, foam, or glue placed into an arterial vasculature. The beads may be uncoated or coated. Where the beads are coated, the coating may be a chemotherapy agent, a radiation agent or other therapeutic agent. When it is desirable to embolize a small blood vessel, small bead sizes (e.g., 40 μm-100 μm) are utilized. When a larger vessel is to be embolized a larger bead size (e.g., 100 μm-900 μm) is typically chosen. 
         [0006]    While embolizing agent therapies which are considered minimally or limited invasive therapies have often provided good results, they have a small incidence of non-targeted embolization which can lead to adverse events and morbidity. One cause of non-targeted delivery of embolizing agents is reflux in the artery. Reflux occurs where the embolic agent exits the distal end of the catheter and then backflows around the outside of the catheter. This backflow can end up in a healthy organ and damage it. 
         [0007]    Reflux can also occur during the administration of the embolization agent, while the artery is still patent. Reflux may also occur when the artery becomes static and injected embolizing agents flow backward. 
         [0008]    Additionally, reflux can be a time-sensitive phenomenon. Sometimes, reflux occurs as a response to an injection of the embolic agent, where the reflux occurs rapidly (e.g., in the time-scale of milliseconds) in a manner which is too fast for a human operator to respond. Also, reflux can happen momentarily, followed by a temporary resumption of forward flow in the blood vessel, only to be followed by additional reflux. 
         [0009]      FIG. 1  shows a conventional (prior art) embolization treatment in the hepatic artery  106 . Catheter  101  delivers embolization agents (beads)  102  in a hepatic artery  106 , with a goal of embolizing a target organ  103 . It is important that the forward flow (direction arrow  107 ) of blood is maintained during an infusion of embolization agents  102  because the forward flow is used to carry embolization agents  102  deep into the vascular bed of target organ  103 . 
         [0010]    Embolization agents  102  are continuously injected until reflux of contrast agent is visualized in the distal area of the hepatic artery. Generally, since embolization agents  102  can rarely be visualized directly, a contrast agent may be added to embolization agents  102 . The addition of the contrast agent allows for a visualization of the reflux of the contrast agent (shown by arrow  108 ), which is indicative of the reflux of embolization agents  102 . The reflux may, undesirably, cause embolization agents  102  to be delivered into a collateral artery  105 , which is proximal to the tip of catheter  101 . The presence of embolization agents  102  in collateral artery  105  leads to non-target embolization in a non-target organ  104 , which may be the other lobe of the liver, the stomach, small intestine, pancreas, gall bladder, or other organ. 
         [0011]    Non-targeted delivery of the embolic agent may have significant unwanted effects on the human body. For example, in liver treatment, non-targeted delivery of the embolic agent may have undesirable impacts on other organs including the stomach and small intestine. In uterine fibroid treatment, the non-targeted delivery of the embolic agent may embolize one or both ovaries leading to loss of menstrual cycle, subtle ovarian damage that may reduce fertility, early onset of menopause and in some cases substantial damage to the ovaries. Other unintended adverse events include unilateral deep buttock pain, buttock necrosis, and uterine necrosis. 
         [0012]    Often, interventional radiologists try to reduce the amount and impact of reflux by slowly releasing the embolizing agent and/or by delivering a reduced dosage. The added time, complexity, increased x-ray dose to the patient and physician (longer monitoring of the patient) and potential for reduced efficacy make the slow delivery of embolization agents suboptimal. Also, reducing the dosage often leads to the need for multiple follow-up treatments. Even when the physician tries to reduce the amount of reflux, the local flow conditions at the tip of the catheter change too fast to be controlled by the physician, and therefore rapid momentary reflux conditions can happen throughout infusion. 
       SUMMARY OF THE INVENTION 
       [0013]    According to one aspect of the invention, an apparatus is provided that is useful in an embolization procedure and which enables substantially unrestricted forward flow of blood in a vessel and reduces or stops reflux (regurgitation or backward flow) of embolization agents which are introduced into the blood. 
         [0014]    In one embodiment, the apparatus which enables substantially unrestricted forward flow in a vessel and which reduces or stops reflux of embolization agents allows the reflux of blood or contrast agent. In another embodiment, the apparatus which enables substantially unrestricted forward flow in a vessel and which reduces or stops reflux of embolization agents and also reduces or stops backward flow of blood. 
         [0015]    In a preferred embodiment, the deployable apparatus includes a delivery catheter having a valve coupled to the distal end thereof. The valve includes a plurality of filaments which cross over each other (i.e., are braided) and which have a spring bias to assume a preferred crossing angle relative to each other. In a first state, the valve is preferably kept in a cylindrical arrangement with a diameter substantially equal to the diameter of the delivery catheter. In a second state, the valve is free to open due to the spring bias in the filaments. In the second state, with the proximal end of the valve attached to the delivery catheter, in the bloodstream, if the blood is not flowing distally past the valve, the valve assumes a substantially frustoconical shape. The distal end of the valve is intended to make contact with the walls of the vessel in which it is deployed when blood is not flowing distally past the valve. 
         [0016]    According to one aspect of the invention, the valve has a radial force of expansion when in the undeployed state of less than 40 mN. 
         [0017]    According to another aspect of the invention, the valve has a time constant of expansion from the cylindrical arrangement to the fully-open position when in a static fluid having a viscosity of approximately 3.2 cP of between 1.0 and 0.01 seconds, and more preferably between 0.50 and 0.05 seconds. 
         [0018]    According to a further aspect of the invention, the valve has a Young&#39;s modulus of elasticity that is greater than 100 MPa. 
         [0019]    According to yet another aspect of the invention, the preferred crossing angle of the valve filaments is approximately 110 degrees. 
         [0020]    According to even another aspect of the invention, the filaments of the valve are selected to be of a desired number and diameter such that in an open position, they are capable of trapping embolization agents. By way of example only, the filaments of the valve are selected so that in an open position they present a pore size of 500 μm and are thus capable of preventing reflux of embolizing agent such as beads having a size larger than 500 μm. As another example, the filaments of the valve are selected so that in an open position they present a pore size of 250 μm and are thus capable of preventing reflux of embolizing agent having a size larger than 250 μm. 
         [0021]    In one embodiment, the valve filaments are coated with a filter which is formed and attached to the filaments according to any desired manner, such as by spraying, spinning, electrospinning, bonding with an adhesive, thermally fusing, melt bonding, or other method. The filter is preferably arranged to have a desired pore size, although it will be appreciated that the pore size may be non-uniform depending upon the technique in which the filter is formed and attached. By way of example, the pore size of the filter may be approximately 40 μm such that embolizing agents having a characteristic size of more than 40 μm are prevented from refluxing past the valve. By way of another example, the pore size of the filter may be approximately 20 μm such that embolizing agents having a characteristic size of more than 20 μm are prevented from refluxing past the valve. In both cases, blood cells (which have a characteristic size smaller than 20 μm), and contrast agent which has a molecular size smaller than 20 μm will pass through the filter and valve. 
         [0022]    According to an additional aspect of the invention, when in a fully-open position where the filaments assume the preferred crossing angle, the valve is adapted to have a distal diameter which is at least twice the diameter of the delivery catheter, and preferably at least five times the diameter of the delivery catheter. 
         [0023]    In one embodiment, the filaments are all formed from a polymer. In another embodiment, one or more of the filaments is formed from platinum or platinum-iridium. 
         [0024]    In an embodiment where one or more filaments are formed from a polymer, the filaments that are formed from the polymer are melted at their proximal end into the delivery catheter. 
         [0025]    According to one aspect of the invention, the valve, which is preferably coupled to the distal end of the delivery catheter, may deployed in any of several manners. Thus, by way of example only, an outer catheter or sleeve extending over the delivery catheter may be used to keep the valve in an undeployed state, and the outer catheter or sleeve may be pulled backward relative to the delivery catheter in order to deploy the valve. Where an outer catheter or sleeve is utilized, the valve may be captured and returned to its undeployed position by moving the delivery catheter proximally relative to the outer catheter or sleeve. 
         [0026]    As another example, the distal end of the valve may be provided with loops which are adapted to engage a guidewire which extends through and distal the distal end of the delivery catheter and through the distal loops of the valve. When the guidewire is withdrawn proximally, the valve deploys. 
         [0027]    As another example, a knitted sleeve with a control thread can be provided to cover the valve. The control thread, when pulled, causes the knitted sleeve to unravel, thereby releasing the valve. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0028]    Prior art  FIG. 1  shows a conventional embolizing catheter in a hepatic artery with embolizing agent refluxing into a non-targeted organ. 
           [0029]      FIGS. 2A-2C  are schematic diagrams of a first exemplary embodiment of an apparatus of the invention respectively in an undeployed state, a deployed partially open state with blood passing in the distal direction, and a deployed fully open state where the blood flow is static. 
           [0030]      FIGS. 3A and 3B  are schematic diagrams of an exemplary embodiment of a valve having a braid component that is covered by a filter component in respectively an undeployed state and a deployed state. 
           [0031]      FIGS. 4A-4C  are schematic diagrams of the exemplary embodiment of a valve of  FIGS. 3A and 3B  covered by a weft knit respectively in an undeployed state, a partially deployed state, and a more fully deployed state. 
           [0032]      FIGS. 5A-5B  are schematic diagrams showing an exemplary embodiment of a valve that can be deployed by movement of a guidewire. 
           [0033]      FIGS. 6A-6D  show two exemplary methods of attaching the mesh component of the valve to a catheter; and 
           [0034]      FIGS. 7A-7B  show an exemplary embodiment of a valve composed of a single shape memory filament and a filter. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0035]    A first exemplary embodiment of the invention is seen in  FIGS. 2A-2C . It is noted that  FIGS. 2A-2C  are not shown to relative size but rather are shown for purposes of explanation. In  FIGS. 2A-2C  a delivery catheter  201  having a proximal end (not shown) and a distal end  205  is shown positioned within an artery  204 . The delivery catheter  201  is adapted for delivery of an embolizing agent from outside the body of the patient (not shown) to a target vessel (artery or vein) in the patient. Attached to the distal end  205  of the catheter  201  is an exemplary embodiment of a valve  203  shown having multiple filaments  203   a ,  203   b ,  203   c , . . . which are preferably braided and can move relative to each other. As discussed hereinafter, the filaments are spring biased (i.e., they have “shape memory”) to assume a desired crossing angle relative to each other so that the valve can assume a substantially frustoconical shape (it being noted that for purposes herein the term “substantially frustoconical” should be understood to include not only a truncated cone, but a truncated hyperboloid, a truncated paraboloid, and any other shape which starts from a circular proximal end and diverges therefrom). Around the catheter  201  is an outer catheter or sleeve  202  which is movable over the delivery catheter  201  and valve  203 . If desired, the outer catheter or sleeve  202  can extend the entire length of the delivery catheter. Where the outer catheter or sleeve  202  extends along the entire length of the delivery catheter, it has a proximal end (not shown) which extends proximally and which can be controlled by a practitioner from outside the body of the patient. Alternatively, the outer catheter or sleeve  202  extends only over the distal end of the delivery catheter  201  and valve  203 , but is controlled by a control element which extends proximally and which can be controlled by a practitioner from outside the body of the patient. 
         [0036]    As seen in  FIG. 2A , when the outer catheter or sleeve  202  extends over the valve  203 , the multiple filaments are forced into a cylindrical shape. Thus,  FIG. 2A  shows the braid valve in a retracted or undeployed cylindrical state, with the braid filaments  203   a ,  203   b ,  203   c  . . . attached to a distal end of a catheter  205  and covered by the sleeve  202 . Catheter  201  is positioned within an artery  204  that has forward blood flow in the direction of arrows  220 . As seen in  FIG. 2B , upon retraction of the sleeve  202  in the direction of arrow  210 , the non-constrained portion of the valve  203  is freed to expand radially (and retract longitudinally) towards its shape memory position. However, the distally flowing blood (indicated by arrows  220 ) generates a force that prevents the valve from opening more completely, and prevents the valve from touching the walls of vessel  204 . As a result, the valve  203  is maintained in a condition where it is not sufficiently open to block blood flow in the distal or proximal directions. In other words, the forward blood flow causes the braid to lengthen and simultaneously decrease its diameter (relative to a fully open position) to allow fluid to pass between the braid and the vessel wall. 
         [0037]      FIG. 2C  shows the valve  203  where the bloodstream is in slow forward flow  221 , static flow, or reverse flow  222  which might occur after delivery of embolic agents through catheter  201  and past the valve  203 . In slow forward flow  221 , the force applied by the blood against the filaments of the braided valve is not sufficient to prevent the valve from opening until the valve  203  reaches the wall of the vessel  204 . In static flow (no significant movement of blood in either direction), the blood does not apply any forward force. During reverse flow  222 , the blood applies a force which helps the valve open. In the fully deployed arrangement of  FIG. 2C , the braid valve acts as a filter to stop embolic agents from flowing proximal the valve. However, as discussed in more detail hereinafter, depending upon the pore size of the braid valve  203 , blood and contrast agent may be permitted to flow backward through the valve and around the catheter  201  while stopping or significantly reducing the flow of embolic agents. 
         [0038]    It should be appreciated by those skilled in the art that the catheter  201  can be any catheter known in the art. Typically, the catheter will be between two and eight feet long, have an outer diameter of between 0.67 mm and 3 mm (corresponding to catheter sizes 2 French to 9 French), and will be made from a liner made of fluorinated polymer such as PTFE or FEP, a braid made of metal such as stainless steel or titanium, or a polymer such as PET or liquid crystal polymer, and a outer coating made of polyurethane, polyamide, copolymers of polyamide, polyester, copolymers of polyester, fluorinated polymers, such as PTFE, FEP, polyimides, polycarbonate or any other suitable material, or any other standard or specialty material used in making catheters used in the bloodstream. Sleeve or outer catheter  202  is comprised of a material capable of holding valve braid  203  in a cylindrical configuration and capable of sliding over the valve braid  203  and the catheter  201 . Sleeve or outer catheter  202  can be comprised of polyurethane, polyamide, copolymers of polyamide, polyester, copolymers of polyester, fluorinated polymers, such as PTFE, FEP, polyimides, polycarbonate or any other suitable material. The sleeve or outer catheter may also contain a braid composed of metal such as stainless steel or titanium, or a polymer such as PET or liquid crystal polymer, or any other suitable material. The wall thickness of sleeve or outer catheter  202  is preferably in the range of 0.002″ to 0.010″ with a more preferred thickness of 0.004″-0.006″. 
         [0039]    The valve  203  is composed of one, two, or more metal (e.g., stainless steel or nitinol) or polymer filaments, which form a substantially frustoconical shape when not subject to outside forces. Where polymeric filaments are utilized, the filaments may be composed of PET, polyethylene-napthalate (PEN), liquid crystal polymer, fluorinated polymers, nylon, polyamide or any other suitable polymer. If desired, when polymeric filaments are utilized, one or more metal filaments may be utilized in conjunction with the polymeric filaments. According to one aspect of the invention, where a metal filament is utilized, it may be of radio-opaque material such that it may be tracked in the body. The valve is capable of expanding in diameter while reducing in length, and reducing in diameter while expanding in length. The valve is preferably composed of shape memory material that is formed and set in a large diameter orientation. As previously mentioned, the valve is preferably held in a small diameter orientation until it is released, and when released by removing the sleeve or other restricting component  202 , the distal end of the valve expands to a larger diameter. Where the valve is comprised of multiple filaments, it is preferred that the filaments not to be bonded to each other or at their distal ends so to enable the valve to rapidly open and close in response to dynamic flow conditions. 
         [0040]    In the preferred embodiment, the valve is constrained only at its proximal end where it is coupled to the catheter body, while the remainder of the valve can either be constrained (retracted state) by a sleeve or catheter, or partially unconstrained (partially deployed state) or completely unconstrained (completely deployed state). When in the partially or completely unconstrained conditions, depending upon the flow conditions in the vessel, the valve may either reach the walls of the vessel or it may not. 
         [0041]    As previously mentioned, the valve diameter should change in response to local flow conditions so as to enable forward flow, but capture embolic agents in brief or prolonged periods of reverse flow. For simplicity, the valve can be considered to exist in two conditions. In a “closed” condition, the valve is not sealed against the vessel wall and blood may flow around the valve in either direction. In an “open” condition, the valve is sealed against the vessel wall and blood must pass through the valve if it is to flow past the valve in either direction. 
         [0042]    Three parameters help define the performance and novel nature of the valve: the radial (outward) force of the valve, the time constant over which the valve changes condition from closed to open, and the pore size of the valve. 
         [0043]    In a preferred embodiment, the valve expands fully to the vessel wall (i.e., reaches an open condition) when any part of the flow around the braid nears stasis and remains in a closed condition when blood is flowing distally with regular force in the distal direction. More particularly, when the radial force of expansion of the valve is greater than the force from forward blood flow, the valve expands to the vessel wall. However, according to one aspect of the invention, the radial force of expansion of the valve is chosen to be low (as described in more detail below) so that blood flow in the distal direction will prevent the valve from reaching the open condition. This low expansion force is different than the expansion forces of prior art stents, stent grafts, distal protection filters and other vascular devices, which have a sufficiently high radial force to fully expand to the vessel wall in all flow conditions. 
         [0044]    The radial force of expansion of a braid is described by Jedwab and Clerc ( Journal of Applied Biomaterials , Vol. 4, 77-85, 1993) and later updated by DeBeule (De Beule et al.  Computer Methods in Biomechanics and Biomedical Engineering,  2005) as: 
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         [0000]    and I and I p  are the surface and polar moments of inertia of the braid filaments, E is the Young&#39;s modulus of elasticity of the filament, and G is the shear modulus of the filament. These material properties along with the braid angle (β), stent diameter (D 0 ), wire thickness (d), and number of filaments (n) impact the radial force of the braided valve. 
         [0045]    In one embodiment, with a valve arrangement as shown in  FIGS. 2A-2C , the valve  203  is composed of twenty-four polyethylene terephthalate (PET) filaments  203   a ,  203   b , . . . , each having a diameter of 0.004″ and pre-formed to an 8 mm diameter mandrel and a braid angle of 110° (i.e., the filaments are spring-biased or have a shape memory to assume an angle of 110° relative to each other). The filaments preferably have a Young&#39;s modulus greater than 200 MPa, and the valve preferably has a radial force of less than 40 mN in the fully deployed position (i.e., where the filaments assume their shape memory). More preferably, the valve has a radial force in the fully deployed position of less than 20 mN, and even more preferably the valve has a radial force of approximately 10 mN (where the term “approximately” as used herein is defined to mean±20%) in the deployed position. Where the valve includes a filter as well as the braided filaments (as will be discussed hereinafter with respect to  FIGS. 3A and 3B ), the braid component preferably has a radial force of less than 20 mN in the fully deployed position, and more preferably a radial force of less than 10 mN, and even more preferably a radial force of approximately 5 mN. This compares to prior art embolic capture devices such as the ANGIOGUARD (a trademark of Cordis Corporation), and prior art Nitinol stents and stent-grafts which typically have radial forces of between 40 mN and 100 mN in their fully deployed positions. 
         [0046]    According to one aspect of the invention, the valve opens and closes sufficiently quickly to achieve high capture efficiency of embolic agents in the presence of rapidly changing flow direction. In one embodiment, the valve moves from a fully closed (undeployed) position to a fully open position in a static fluid (e.g., glycerin) having a viscosity approximately equal to the viscosity of blood (i.e., approximately 3.2 cP) in 1/15 second. For purposes herein, the time it takes to move from the fully closed position to the fully open position in a static fluid is called the “time constant”. According to another aspect of the invention, the valve is arranged such that the time constant of the valve in a fluid having the viscosity of blood is between 0.01 seconds and 1.00 seconds. More preferably, the valve is arranged such that the time constant of the valve in a fluid having the viscosity of blood is between 0.05 and 0.50 seconds. The time constant of the valve may be adjusted by changing one or more of the parameters described above (e.g., the number of filaments, the modulus of elasticity of the filaments, the diameter of the filaments, etc.). 
         [0047]    As will be appreciated by those skilled in the art, the braid geometry and material properties are intimately related to the radial force and time constant of the valve. Since, according to one aspect of the invention, the valve is useful in a variety of arteries of different diameters and flow conditions, each implementation can have a unique optimization. By way of example only, in one embodiment, the valve has ten filaments, whereas in another embodiment, the valve has forty filaments. Preferably, the filament diameter is chosen in the range of 0.001″ to 0.005″, although other diameters may be utilized. Preferably, the pitch angle (i.e., the crossing angle assumed by the filaments in the fully open position—the shape memory position) is chosen in the range of 90° to 145°, although other pitch angles may be used. Preferably, the Young&#39;s modulus of the filament is at least 100 MPa, and more preferably at least 200 MPa. 
         [0048]    According to another aspect of the invention, the valve is chosen to have a pore size which is small enough to capture (filter) embolic agents in the blood stream as the blood passes through the valve. Where large embolic agents (e.g., 500 μm) are utilized, it may be possible for the filaments of the valve to act directly as a filter to prevent embolic agents from passing through the valve (provided the filaments present pores of less than, e.g., 500 μm). Alternatively, a filter may be added to the filament structure. Such a separate filter is particularly useful where smaller embolic agents are utilized. 
         [0049]      FIG. 3A  shows a braid valve  203  at the distal end of a catheter  201  and having a filter  301  that is added to the braid structure  203 . The filter can be placed onto the braid by spraying, spinning, electrospinning, bonding with an adhesive, thermally fusing, mechanically capturing the braid, melt bonding, or any other desired method. The filter can either be a material with pores such as ePTFE, a solid material that has pores added such as polyurethane with laser drilled holes, or the filter can be a web of very thin filaments that are laid onto the braid. Where the filter  301  is a web of thin filaments, the characteristic pore size of the filter can be tested determined by attempting to pass beads of different diameters through the filter and finding which diameter beads are capable of passing through the filter in large quantities. The very thin filaments can be spun onto a rotating mandrel according to U.S. Pat. No. 4,738,740 with the aid of an electrostatic field or in the absence of an electrostatic field or both. The filter thus formed can be adhered to the braid structure with an adhesive or the braid can be placed on the mandrel and the filter spun over it, or under it, or both over and under the braid to essentially capture it. The filter can have some pores formed from spraying or electrospinning and then a secondary step where pores are laser drilled or formed by a secondary operation. In the preferred embodiment a material capable of being electrostatically deposited or spun is used to form a filter on the braid, with the preferred material being capable of bonding to itself. The filter may be made of polyurethane, polyolefin, polyester, fluorpolymers, acrylic polymers, acrylates, polycarbonates, or other suitable material. The polymer is spun onto the braid in a wet state, and therefore it is desirable that the polymer be soluble in a solvent. In the preferred embodiment, the filter is formed from polyurethane which is soluble in dimethylacetamide. The polymer material is spun onto the braid in a liquid state, with a preferred concentration of 5-10% solids for an electrostatic spin process and 15-25% solids for a wet spin process.  FIG. 3B  shows the valve in the deployed state, with outer catheter  202  retracted proximally (as indicated by the arrow) where the braid  203  and the filter  301  are expanded. 
         [0050]    According to one aspect of the invention, the filter  301  has a characteristic pore size between 10 μm and 500 μm. More preferably, the filter  301  has a characteristic pore size between 15 μm and 100 μm. Even more preferably, the filter  301  has a characteristic pore size of less than 40 μm and more preferably between 20 μm and 40 μm. Most desirably, the filter  301  is provided with a characteristic pore size that will permit blood and contrast agent to pass therethrough while blocking passage of embolizing agent therethrough. By allowing regurgitating blood and contrast agent to pass through the filter in a direction from distal the valve toward the proximal end of the valve, the contrast agent may be used to indicate when the target site is fully embolized and can serve to identify a clinical endpoint of the embolization procedure. Therefore, according to one aspect of the invention, the valve allows the reflux of the contrast agent as an indicator of the clinical endpoint while preventing the reflux of the embolization agents at the same time. 
         [0051]    According to one aspect of the method of the invention, the valve is capable of endovascular deployment. The valve is preferably coupled to the distal end of a catheter. When the distal end of the catheter is in the correct location for treatment, the valve is deployed. Preferably, with the valve deployed, embolization agents are delivered distally through the catheter into the vessel. Delivery of the embolization agents will tend to result in the slowing or stoppage of blood flow in the distal direction and a resultant expansion of the valve from an initial diameter which is smaller or equal to the outer diameter of the catheter (i.e., its undeployed position) to a final diameter (its open position) which is preferably at least twice, and more typically four to ten times the outer diameter of the catheter. In its open position, the valve stops embolization agents from traveling past the valve (between the catheter wall and the vessel wall) in a proximal direction. According to one aspect of the invention, the valve is preferably capable of being refracted into its closed position after the embolization treatment procedure is completed. 
         [0052]    It is important to note that the valve is a dynamic element that opens and closes based on local flow conditions. In normal flow conditions, the flow pressure is sufficient to overcome the weak biasing force, thereby forcing the valve into a closed position such that it does not contact the vascular wall. In static or reverse flow, the biasing force of the valve filaments causes the valve to an open position where it preferably is in full contact with the vascular wall, thereby restricting reflux of embolizing agents, while preferably permitting reflux of blood and contrast agents. 
         [0053]    According to one aspect of the invention, deployment of the valve is controlled from the proximal end of the catheter. In some embodiments, a control wire or a set of two or more control wires extending from the proximal end of the catheter to the distal end of the catheter may be used and controlled by the practitioner to deploy and optionally retract the valve. In some embodiments, a control thread extending from the proximal end of the catheter to the distal end of the catheter is used to unravel fabric covering the valve in order to deploy the valve. In some embodiments, an outer catheter that extends the length of the catheter to which the valve is coupled, covers the valve and during deployment is pulled backward to allow the valve to expand. In some embodiments, an outer sleeve that is coupled to a control element that extends the length of the catheter, covers the valve and during deployment is pulled backward by the control element to allow the valve to expand. In some embodiments, the valve is coupled to a guidewire, and removal of the catheter guidewire initiates deployment of the valve. The control wires, threads, sleeves, etc. may be of standard length, ranging, for example, from 2 to 8 feet long. 
         [0054]    As previously mentioned, the deployment of the valve can be achieved in a variety of manners. As was described in  FIG. 2 , the valve can be deployed by moving an outer catheter or sleeve that covers the valve. In that embodiment, the valve can be recaptured by the outer catheter or sleeve by moving the catheter or sleeve distally or the delivery catheter and valve proximally. In another embodiment, and as seen in  FIGS. 4A-4C , the valve is released by irreversibly removing (unraveling) a knitted sleeve (weft knit)  402  that covers the valve  203  (shown with filter  301 ). More particularly, as seen in  FIG. 4A , the valve  203  is attached to the distal end of the catheter  201 . On top of the valve is a weft knit sleeve  402 . A control thread  401  is attached to the weft knit and extends to the proximal end of the catheter. In one embodiment the unravelable knit is composed of polyester of a thickness between 10 μm and 60 μm. The knit can be a textile sheath that is held under tension.  FIG. 4B  shows the deployment of the valve by pulling on the control thread  401 . In one embodiment the thread  401  is connected to the distal end of the knit sleeve  402  and releases the valve by first removing material from the distal end of the sleeve  402 . As the control thread  401  is pulled back and the sleeve is reduced in size, the distal end of the valve  203  having filter  301  is free to open. The weft knit sleeve  402  may be partially or fully removed to allow the physician control of the diameter or length of the valve. In  FIG. 4C  the weft knit is more fully removed enabling more of the length of the valve  203  and filter  301  to be free. In another embodiment the thread is attached to the middle or proximal end of the sleeve, and releases the valve by first removing material from the proximal end or from the middle of the sleeve. 
         [0055]    Turning now to  FIGS. 5A and 5B , in another embodiment, a guidewire  501  can be used to deploy the valve  503 . More particularly, valve  503  is provided with loops  502 , which are attached at or near the distal end of the filaments of the valve  503 . The loops  502  may be integral with the filaments or may be made of a separate material and attached to the filaments. As seen in  FIG. 5A , the loops  502  are looped over the distal end of the guidewire  501  which extends through the lumen of the catheter  201 . The loops at the end of the valve  502  are looped around the guidewire  501  while the catheter  201  and guidewire  501  are advanced through the vasculature. In this manner, the distal end of the valve is maintained in a closed position. When the guidewire  501  is withdrawn proximally as denoted by the arrow in  FIG. 5B , the distal loops  502  are released, and the valve  503  is deployed. 
         [0056]    According to one aspect of the invention, the valve of any embodiment of the invention is attached to the distal end of the catheter in any of several manners. As seen in FIG.  6 A, the valve  203  is attached to the catheter  201  by a sleeve  601  which overlies the proximal end of the valve  203  and extends proximal the proximal end of the valve  203  over the catheter  201 .  FIG. 6B  shows a cross-sectional view of the catheter  201 , valve  203 , and sleeve  601 . The sleeve  601  is bonded or mechanically held by a heat shrink process or other mechanical process to the catheter  201 , and thus holds the distal end of the valve  203  on the catheter  201  by trapping the distal end of the valve between the catheter  201  and the sleeve  601 . 
         [0057]    In one preferred embodiment, the valve is fused into the catheter. More particularly, as seen in  FIG. 6C  the valve  203  fused into the catheter  201  such that at the region  602  where the valve and catheter are fused, there is at most a minimal change to the inner or outer diameter of the catheter  201 .  FIG. 6D  shows a cross-sectional view of the fused valve, where the catheter  201 , valve  203  and fused region  602  are all of the same diameter. Fusion of the catheter and valve can be achieved by thermally melting the valve, melting the catheter, melting both the valve and the catheter, or by a chemical process. 
         [0058]    Turning now to  FIGS. 7A and 7B , a valve  702  composed of a single filament coil is seen. The coil may be made of metal or polymer, and preferably the filament is a shape memory polymer.  FIG. 7A  shows a coil valve  701  in the retracted state on a catheter  201 . The coil valve is provided with a filter  702  on its distal end.  FIG. 7B  shows the coil valve in the deployed state, where the valve  701  and the filter  702  are expanded at the distal end. Any of a variety of methods as previously disclosed can be used in deploying the valve. 
         [0059]    In any of the embodiments described herein the valve may include textured portions that extend into or engage with the artery wall to reduce or inhibit proximal or distal movement of the valve relative to the vessel wall. 
         [0060]    In any of the embodiments described herein the components of the valve may be coated to reduce friction in deployment and retraction. The components may also be coated to reduce thrombus formation along the valve or to be compatible with therapeutics, biologics, or embolics. The components may be coated to increase binding of embolization agents so that they are removed from the vessel during retraction. 
         [0061]    According to one aspect of the invention, the catheter body and mesh may be separately labeled for easy visualization under fluoroscopy. The catheter body can be labeled by use of any means shown in the art; for example, compounding a radio-opaque material into the catheter tubing. The radio-opaque material can be barium sulfate, bismuth subcarbonate or other material. Alternatively or additionally, radio-opaque rings can be placed or crimped onto the catheter, where the rings are made of platinum, platinum iridium, gold, tantalum, and the like. The valve may be labeled by crimping a small radio-opaque ring on one or a plurality of filaments. Alternatively or additionally, radio-opaque medium can be compounded into the materials of the braid and the filter. Or, as previously described, one or more of the filaments may be chosen to be made of a radio-opaque material such as platinum iridium. 
         [0062]    In the preferred embodiment, the valve is attached to a catheter which may be a single lumen or a multi-lumen catheter. Preferably, the catheter has at least one lumen used to deliver the embolization agents. According to other embodiments, however, the catheter may provided with a lumen which either serves to store the valve before deployment or through which the valve can be delivered. Where control wires are utilized to control the valve, an additional lumen may be provided, if desired, to contain the control wires for deployment and retraction. An additional lumen may also be used to administer fluids, e.g., for flushing the artery after the administration of embolization agents, or for controlling a balloon which could be used in conjunction with the valve. 
         [0063]    There have been described and illustrated herein multiple embodiments of devices and methods for reducing or preventing reflux of embolization agents in a vessel. While particular embodiments of the invention have been described, it is not intended that the invention be limited thereto, as it is intended that the invention be as broad in scope as the art will allow and that the specification be read likewise. Thus while particular deployment means for the protection valve have been described, such as a catheter, a sleeve and control element, a fabric sleeve with a control thread, etc., it will be appreciated that other deployment mechanisms such as balloons, absorbable sleeves, or combinations of elements could be utilized. Likewise, while various materials have been listed for the valve filaments, the valve filter, the catheter, and the deployment means, it will be appreciated that other materials can be utilized for each of them. Also, while the invention has been described with respect to particular arteries of humans, it will be appreciated that the invention can have application to any blood vessel of humans and animals. Further, the embodiments have been described with respect to their distal ends because their proximal ends can take any of various forms, including forms well known in the art. By way of example only, the proximal end can include two handles with one handle connected to the inner (delivery) catheter, and another handle connected to an outer catheter or sleeve or actuation wire or string. Movement of one handle in a first direction relative to the other handle can be used to deploy the valve, and where applicable, movement of that handle in an opposite second direction can be used to recapture the valve. Depending upon the handle arrangement, valve deployment can occur when the handles are moved away from each other or towards each other. As is well known, the handles can be arranged to provide for linear movement relative to each other or rotational movement. If desired, the proximal end of the inner catheter can be provided with hash-marks or other indications at intervals along the catheter so that movement of the handles relative to each other can be visually calibrated and give an indication of the extent to which the valve is opened. It will therefore be appreciated by those skilled in the art that yet other modifications could be made to the provided invention without deviating from its spirit and scope as claimed.