Patent Publication Number: US-2020297351-A1

Title: Devices and methods for low pressure tumor embolization

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 15/844,389, filed Dec. 15, 2017, which is a continuation of U.S. application Ser. No. 15/202,391, filed Jul. 5, 2016, now U.S. Pat. No. 9,844,383, which is a continuation-in-part of U.S. application Ser. No. 14/954,699, filed Nov. 30, 2015, now U.S. Pat. No. 10,130,762, which is a divisional of U.S. application Ser. No. 14/273,445, filed May 8, 2014, now U.S. Pat. No. 9,205,226, which claims the benefit of U.S. Provisional Application No. 61/821,058, filed May 8, 2013, U.S. Provisional Application No. 61/915,425, filed Dec. 12, 2013, and U.S. Provisional Application No. 61/917,131, filed Dec. 17, 2013, each of which is herein incorporated by reference in its entirety. 
    
    
     GOVERNMENT RIGHTS 
     This invention was made with Government support under Grant No. 1417279 awarded by the National Science Foundation. The Government has certain rights in this invention. 
    
    
     INCORPORATION BY REFERENCE 
     All publications and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference. 
     FIELD 
     This application relates generally to medical methods and devices. More specifically, the present application discloses various embodiments of occlusion devices adapted to a catheter, and methods for their use in delivering fluids, embolic materials and other therapeutic agents to sites within the body. 
     BACKGROUND 
     There are over one million cases of cancer diagnosed each year in the United States and numerous approaches of therapy including systemic chemotherapy, radiation and surgical resection. Given that systemic chemotherapy and radiation interact with healthy tissue, complications and toxicity often result. Targeted drugs are now being used and produce a lower rate of complications. Ablative approaches, including microwave, radiofrequency and cryogenic therapies have been used; however, these methods are often not selective and tissues and organs surrounding or below the tumor can be affected. 
     According to the National Institute of Health, 30,640 people were diagnosed with primary liver cancer (hepatocellular carcinoma, HCC) and 142,820 people were diagnosed with colorectal cancer in the U.S. in 2013. Seventy-five percent of these will metastasize to the liver. Liver resection and transplant are the only curative means; however, only small numbers of patients are eligible. Systemic chemotherapy for primary and metastatic tumors in the liver is ineffective, having a response rate of about 20% and a survival benefit of 10.7 months vs. 7.9 months over symptomatic care. 
     Catheters are commonly used in medicine for delivery of fluids, therapeutics, and implants, and in sampling tissues and bodily fluids. Catheters can be constructed with balloons or other tools to dilate tissue, block fluid flow or isolate segments of the anatomy, such as in treatment of the cancers described above. 
     Transvascular fluid delivery via arteries or veins is typically used to distribute materials throughout the body and without consideration of a specific target tissue or organ. One notable exception to this is the use of compounds, such as anti-cancer agents that are conjugated to antibodies that target a specific binding site. Anti-tumor agents can also be fashioned to bind to specific cell receptors and block cellular functions of cancer cells. In this way, cytotoxic therapies seek out cancer cells and avoid healthy tissues, reducing systemic toxicity. 
     However, most drugs are not conjugated or otherwise contrived to seek out a target and drugs that are injected are distributed throughout the body, even though the beneficial effect is limited to one or several target sites. Delivery of drug to non-target sites can cause complications and result in considerable morbidity. 
     Trans-Arterial Embolization therapy is the transvascular injection of drug and/or embolic agents directly into the tumor vasculature using a microcatheter. Embolization therapy causes a shutdown of blood flow and, when drug or radioactivity is present, simultaneous release of high concentrations of drug or radioactivity. The technique is also noted for its very low level of toxicity. 
     In the early 1980&#39;s, transarterial chemoembolization (TACE) began to be used as a selective cancer therapy. In this method, chemotherapeutic and embolic agents are injected directly into the vasculature of the tumor, a technique that is most common for the treatment of hepatocellular carcinoma. More recently, transarterial radioembolization (TARE) has been used clinically. In this method, radioactive embolic particles, typically yttrium-90 (y90), are injected rather than chemotherapeutic agents. Although the liver is a common target for TACE and TARE, other organs, including, but not limited to, the pancreas, lung, kidney, prostate, stomach, colon and head and neck have been treated using these methods. Chemoembolization was established as a standard of care for intermediate stage hepatocellular carcinoma in 2006. 
     Numerous studies have demonstrated transarterial embolization to be effective on a number of primary cancers and to have better performance than chemotherapy for both HCC and metastatic colorectal cancers in the liver; however, studies show inconsistent outcomes with reported tumor responses from 15% to 85%. Although anatomical and individual differences are clearly of significance in between-patient variation, clinical studies, each of which include numerous patients, show very different outcomes, indicating that the procedure is not reproducible and that there is little procedural optimization or standardization. 
     The above procedures are accomplished by inserting a small catheter into the femoral artery at the groin or radial artery of the forearm and navigating it into the liver vasculature, typically the hepatic artery, then into the right or left lobe of the liver or more selectively into particular segments of the liver or super-selectively directly into or adjacent to the tumor. Typically, the tip of the microcatheter is positioned in a supply artery that is proximal to the tumor feeder artery and collateral arteries that branch from the supply artery and flow toward healthy tissues. In this instance, blood flows over the catheter tip and into the tumor and collateral arteries that feed healthy tissues. Injection of embolic agents will follow blood flow and deposit into both the tumor and healthy tissues (non-target embolization). Presently, standard microcatheters, typically at or about 3 Fr, are used to inject antitumor agents into the target vasculature. These standard microcatheters rely on normal blood flow as the means by which the embolic agent moves into the tumor and systolic and/or mean arterial pressure as the packing force. However, as the tumor begins to become embolized, it cannot accept the normal rate of blood flow and intra-tumor pressure rises to a point where the tumor can no longer accept the blood flow and the blood begins to reflux into the tumor feeder and supply artery. At this point tumor embolization can no longer proceed since embolization agents are refluxing out of the tumor along with the blood, even though the tumor is only partially filled with embolic agents. Under these conditions, further injection of embolic agents results in high pressures in the supply artery and a concomitant increase in non-target flow of embolic agents to healthy tissues and reflux backwards over the catheter. This situation also results in loss of an unknown amount of drug which, at least in part, explains the irreproducibility of the technique. 
     The endpoint of the above procedures is determined by physicians&#39; visual observation of contrast flow and therefore the amount of dose delivered is highly variable. Reflux, non-target embolization in antegrade and retrograde directions, distribution of embolic agents, packing and quantity of dose delivered are variables that can be highly dependent on the rate and pressure of injection, the selection of the type of endpoint, the patient&#39;s systolic and/or mean arterial pressure, anatomy and the operator. As such, clinical trials using TACE to treat hepatocellular carcinoma have demonstrated wide variations in tumor response. The most significant clinical problems that occur with the current means of delivery and methods of embolization therapy include inconsistent efficacy and complications from non-target embolization. 
     Using standard straight-tip catheters, non-target embolization in the retrograde and antegrade directions can be caused when the pressure of injection exceeds the mean arterial blood pressure whereby embolic agents flow into healthy tissues causing complications. Antegrade 
     When therapeutic agents are delivered into the vasculature of a target structure using the normal antegrade blood flow to carry the therapy to the target, antegrade non-target flow is unavoidable and injection rate of therapeutic agents must be carefully controlled in relation to the then present flow volume and pressure of blood to avoid an increased amount of antegrade non-target flow and reflux of drug backward over the catheter and into healthy tissues. In particular, when injecting embolic agents into the vasculature of a tumor, pressure distal to the catheter tip continues to increase as embolization progresses, causing a resistance that prevents embolic agents from filling the target vasculature and the possibility of reflux and non-target flow and embolization. It would be desirable to eliminate this antegrade non-target flow and reflux, and the inconsistent dosages that are delivered to targets with current state of the art procedures. It would be further desirable to eliminate the low levels of particle distribution and density throughout the target vasculature. It would be still further desirable to replace current delivery devices that are not always capable of fully isolating the target vasculature and often do not allow the operator to control pressure, flow rate and other parameters associated with therapeutic delivery. 
     The present state-of-the-art embolization therapy using standard straight-tip microcathetes for tumors in the liver relies on high volume forward flow from the hepatic artery (supply artery) to deliver embolization agents into the tumor. However; as tumor embolization proceeds, larger arterioles and capillaries are filled first, this substantially stopping flow in these vessels which causes: (1) high intra-tumor vascular pressure, (2) high pressure in arteries feeding the tumor, (3) high pressure in the supply artery, (4) reflux over the delivery catheter, (4) increased antegrade non-target flow into hepatoenteric arteries and (5) poor filling and distribution of embolic agents in the tumor. This situation results in an uncontrollable and irreproducible number of particles entering the tumor and high procedural variability. 
     Problems with the current method of embolization therapy that cause inconsistent outcomes include: high flow rates into the tumor, variable procedural endpoints, unknown quantity of dose delivered, reflux of embolization agents, antegrade non-target flow of embolization particles into branch arteries, rising intra-tumor arterial pressures during the initial stages of embolization, catheter movement during injection, catheter tip position and the catheter not being centered in the blood vessel. The current delivery catheters are unable to control many of the above mentioned variables, producing inconsistent outcomes and making any standardization of the current procedures difficult or impossible to achieve. 
     The following patents and published patent applications provide some examples of the current state of this art. U.S. Pat. No. 5,647,198 describes a catheter with a pair of spaced apart balloons that define an intra-balloon space. A lumen passes through the catheter and exits within the intra-balloon space allowing injection of drugs, emulsions, fluids and fluid/solid mixtures. A perfusion lumen or bypass extends from a location proximal to the proximal balloon and to the distal tip to allow shunting of blood past the inflated balloons. U.S. Pat. No. 5,674,198 describes a two balloon catheter that is designed for treating a solid tumor. The balloons are positioned to isolate the blood flow into the tumor and allow injection of a vaso-occlusive collagen material to block the tumor blood supply. Clifton et al. (1963) Cancer 16:444-452 describes a two balloon catheter for the treatment of lung carcinoma. The four lumen catheter includes a lumen for independent injection in the space between the balloons. Rousselot et al. (1965) JAMA 191:707-710 describes a balloon catheter device for delivering anticancer drugs into the Liver. See also U.S. Pat. Nos. 6,780,181; 6,835,189; 7,144,407; 7,412,285; 7,481,800; 7,645,259; 7,742,811; U.S. App. No. 2001/008451; U.S. App. No. 2001/0041862; U.S. App. No. 2003/008726; U.S. App. No. 2003/0114878; U.S. App. No. 2005/0267407; U.S. App. No. 2007/0137651; U.S. App. No. 2008/0208118; U.S. App. No. 2009/0182227 and U.S. App. No. 2010/0114021. 
     What is needed, and not provided by the prior art, are delivery devices and methods that enable exclusive delivery of drug to a target area of the anatomy and elimination or reduction of the flow of drug outside of the target area. 
     SUMMARY OF THE DISCLOSURE 
     According to aspects of the present disclosure, devices and methods are provided for full or partial occlusion that are designed to be adapted to a catheter for delivery of therapeutic agents to a target site within the body. Such delivery devices may be intended for any medical purpose, but the embodiments described herein are focused on devices intended for performing transarterial delivery of therapeutic agents to a target site within the body. The entry point for the delivery catheter can be any arterial access point, typically the femoral artery located at the groin or the radial artery in the forearm. The target can be any structure; however, of particular interest are tumors, primary or metastatic, of any organ or tissue that is accessible by a microcatheter through the arterial system. Cancers of particular interest include, but are not limited to, primary and metastatic cancers in the liver, pancreas, colon, rectum, kidney, stomach, lung, bladder, head and neck, prostate and uterus. Procedures that can benefit from the access and delivery methods and devices of the present disclosure include, but are not limited to, transarterial chemoembolization using drug eluting beads (DEB TACE), transarterial chemoembolization using Lipiodol (Lipiodol TACE), transarterial radioembolization (TARE) and transarterial embolization (TAE). Other procedures which can benefit from methods and devices of the present disclosure include direct delivery of chemotherapy or targeted drugs to the site of the cancer, the general delivery of drugs, venous or arterial embolization or other substances to specific regions of the body and drainage or aspiration of fluid or tissue. Of particular interest are embolization of the prostate, as a therapy for benign prostatic hyperplasia (BPH), and embolization of the uterus, as a therapy for uterine fibroids. 
     The occlusion device of the present disclosure causes an immediate pressure drop in the vascular area distal to the occlusion, creating a low pressure zone in the distal artery and surrounding tissue. Since fluid will flow from high pressure to low pressure, blood flow will redistribute in favor of the low pressure zone. When a tumor or other structure with terminal capillary beds is within, or in the vicinity of, the low pressure zone, the blood will flow toward the terminal capillaries since they empty in to veins that have very low pressure. In this instance, the anatomical structure with terminal capillaries acts as a sump that accepts blood flow from surrounding area. By way of example, embolization of tumors in the right lobe of the liver are accessed by a catheter advanced through the right hepatic artery (RHA) and to the vicinity of the tumor. Typically, the catheter tip does not enter the tumor vasculature and remains proximal to the tumor and within the right hepatic artery or branch thereof. In this example, the artery feeding the tumor is typically a branch of the RHA. However, there other distal hepatoenteric arteries that branch from the RHA and flow away from the RHA and to the liver and gastrointestinal tract. In this instance, when using a standard straight catheter, injection of embolic agents from the distal tip of the catheter results in flow of embolic agents into both the tumor and collateral arteries causing antegrade non-target embolization of the liver and gastrointestinal tract, a situation that causes toxicity and complications. The device and method of the present disclosure causes a flow redistribution whereby collateral arteries reverse flow in favor of the tumor, minimizing non-target flow and increasing the number of embolic particles that enter the tumor. 
     In some embodiments, the methods and devices disclosed herein include a balloon or other structure that can be expanded or activated to create a full occlusion of the target blood vessel with a concomitant reduction in pressure and flow rate in the anatomical zone distal to the full occlusion that can: (1) eliminate reflux, (2) reduce or eliminate antegrade non-target flow, (3) reduce or eliminate non-target embolization, (4) reduce flow rate and volume moving into the tumor, (5) slow the increase of intra-tumor pressure, (6) slow the onset of blood reflux from the tumor, (7) increase the time that embolic agents can enter the tumor, (8) increase the amount and distribution of embolic agents that are deposited in the tumor, (9) isolate the vascular area distal to the occlusion from the general circulation, (10) create a low pressure zone in the vicinity of the tumor and (11) cause a general inflow of blood toward the low pressure area created by the occlusion. 
     In other embodiments, the microcatheter methods and devices disclosed herein, include a balloon or other structure that can be expanded or activated to create a partial occlusion of the target blood vessel such as by creating channels from the proximal end of the occlusion structure to the distal end of the occlusion structure. When in the expanded configuration there is a concomitant reduction in pressure and flow rate in the anatomical zone distal to the occlusion. The device of this embodiment can: (1) provide a distal directed bypass (forward flow) of blood, (2) eliminate reflux, (2) reduce or eliminate antegrade non-target flow, (4) reduce or eliminate non-target embolization, (5) reduce flow rate and volume moving into the tumor, (6) slow the increase of intra-tumor pressure, (7) slow the onset of blood reflux from the tumor, (8) increase the time that embolic agents can enter the tumor, (9) increase the amount and distribution of embolic agents that are deposited in the tumor, (10) isolate the vascular area distal to the occlusion from the general circulation, (11) create a low pressure zone in the vicinity of the tumor and (12) cause a general inflow of blood toward the low pressure area created by the occlusion. 
     In some embodiments, a catheter assembly may be provided with a catheter body and an inflatable balloon. The catheter body has a proximal end, a distal end and a balloon inflation lumen. The inflatable balloon is attachable to the distal end of the catheter body. The balloon has an inner surface that at least partially defines an interior volume. The balloon is configured such that the interior volume can be in fluid communication with the inflation lumen of the catheter body to inflate the balloon. The balloon also has a proximal surface and a distal surface. The balloon is provided with a channel that extends through the balloon as in partial occlusion or the balloon is without channels as in full occlusion. If present, the channel may be configured to provide fluid communication between the proximal surface of the balloon and the distal surface of the balloon. 
     In some embodiments, a device for delivering a therapeutic agent to a target site within a body is provided. The device comprises a catheter body having a proximal end, a distal end, a first axial lumen and a second axial lumen. The first axial lumen extends from the proximal end of the catheter body to the distal end of the catheter body and provides fluid communication therebetween. The second axial lumen extends from the proximal end of the catheter body to a more distal location on the catheter body. The device further comprises a balloon radially disposed near the distal end of the catheter body. The balloon has a proximal balloon surface, a distal balloon surface, a radially constrained configuration and a radially expanded configuration. The balloon is in fluid communication with the second axial lumen and is a full occlusion balloon or has at least one channel, said channel extending from the proximal balloon surface to the distal balloon surface, thereby providing fluid communication therebetween. 
     In some embodiments, a method of embolization of a tumor is provided. The method comprises advancing a device including a catheter body and a partial occlusion structure to a supply artery in the vicinity of a target tumor site within the body, and allowing an antegrade blood flow past the partial occlusion structure. The allowed antegrade blood flow is less than a blood flow that would normally be present if the partial occlusion structure were not in place. The partial occlusion produces a pressure drop in the anatomic zone distal to the occlusion, flow redistribution of collateral arteries and capillaries associated with the supply artery and flow being directed into and through the tumor into the venous system. The method further comprises injecting an embolic substance from the device to allow the antegrade blood flow to carry the embolic substance into a vasculature of the tumor and withdrawing the device from the body. 
     By isolating the distal arterial space that is adjacent to the tumor from the arterial blood supply, the device of the present disclosure enables pressure measurement to be used to signal a procedural endpoint at a predetermined pressure or pressures. By way of example, the endpoint of the procedure can occur at a point when systolic pressure (120 mmHg) is first reached or at a point when systolic pressure and/or mean arterial pressure is stabilized, however any pressure, pressure profile or algorithm can be used to determine an endpoint of the procedure. Such a measurable endpoint can contribute to standardization of the procedure and improved efficacy. 
     The occlusion structure of the device of the present disclosure may be held within a pocket within the catheter such that the outer diameter of the radially constrained occlusion structure is approximately equal to or less than the outer diameter of the catheter as described in co-pending U.S. patent application Ser. No. 15/044,864 and issued U.S. Pat. No. 9,205,226. The pocket can be a longitudinal space in the catheter and can be formed as a reduction in the catheter diameter of a defined length and a depth equal to or greater than the thickness of the occlusion structure in a radially constrained configuration. Alternately, a pocket can be formed using an extension projecting distally beyond the catheter body, the distal extension having a diameter smaller than the catheter body. In this instance, the distal end of the catheter pocket is defined by the proximal end of a nose-piece. In some embodiments, the nose-piece has a diameter equal to or less than the diameter of the catheter body and is positioned over the distal extension at a defined distance from the distal end of the catheter body. 
     The occlusion structure of devices of the present disclosure can be advanced in a radially constrained configuration, to at least the proximity of a target within the body and then placed in its radially expanded configuration. Alternately, the device can be pre-formed in a fully expanded configuration, adapted to the distal end of a catheter and delivered to the target site. Antegrade. 
     According to aspects of the present disclosure, methods of transarterial embolization agent delivery at a low pressure are provided. In some embodiments, the method comprises advancing a delivery device with an occlusion structure in a retracted non-occlusive configuration, through a supply artery having a plurality of collateral vessels that branch therefrom and being in fluid communication with a target anatomical structure, to a vascular position in the supply artery that is in the vicinity of the target anatomical structure. The target structure has terminal capillary beds. The method further comprises expanding the occlusion structure from the retracted non-occlusive configuration to an expanded occlusive configuration, lowering a mean arterial pressure in a vascular space distal to the expanded occlusion structure, and redirecting fluid flow from the collateral vessels toward the lowered pressure vascular space and into the target anatomical structure. The method further comprises injecting an embolization agent through the delivery device and into the lowered pressure vascular space, and delivering the embolization agent from the lowered pressure vascular space into the target anatomical structure. 
     In some embodiments, the mean arterial pressure in the lowered pressure vascular space is lowered during the lowering step to between 10% and 60% of a normal mean arterial pressure. The lowering step may comprise measuring a pressure in the vascular space after expanding the occlusion structure. The lowering step may further comprise ensuring the measured pressure is within a predetermined range before proceeding with the injecting step. In some embodiments, the lowering step comprises waiting a predetermined period of time before proceeding with the injecting step to ensure that a sufficient pressure drop has occurred. 
     In some embodiments, the mean arterial pressure of the lowered pressure vascular space is kept below an un-occluded starting pressure by at least 10% of the difference between the un-occluded starting pressure and a stabilized occluded pressure during the injecting step. In some embodiments, the mean arterial pressure of the lowered pressure vascular space is kept below an un-occluded starting pressure by at least 30% of the difference between the un-occluded starting pressure and a stabilized occluded pressure during the injecting step. 
     In some embodiments the fluid is predominantly blood or interstitial fluid. The embolization agent may be injected with a flow rate in the range of 0.25 to 6 ml/minute. The delivery device may comprise a catheter, a needle, or a cannula. In some embodiments, the occlusion structure allows a fluid flow of 5 to 25% of normal to bypass the occlusion structure after it has been expanded into the occlusive configuration. In some embodiments, the occlusion structure creates a substantially full occlusion having less than 2% bypass blood flow. 
     In some embodiments, the occlusion structure comprises a balloon. The balloon may be provided with a generally v-shaped channel extending along a least a portion of its length, thereby providing a fluid bypass channel when the balloon is inflated. The balloon may be provided with a spiral channel extending from a proximal end of the balloon to a distal end, thereby providing a fluid bypass channel when the balloon is inflated. In some embodiments, the delivery device is provided with a pressure transducer located distal to the occlusion structure and configured to sense fluid pressure when located in the supply artery. 
     In some embodiments, the target anatomical structure is a tumor, a prostate, or a uterus. 
     While aspects of the present disclosure will be described with particular reference to delivery of chemotherapeutic agents, radiotherapeutic agents, embolic agents or combinations thereof into the vasculature that supplies blood to a tumor, the same principles apply to the delivery or aspiration of a variety of materials into or from other locations, and through other luminal structures in the body. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The novel features of the disclosure are set forth with particularity in the claims that follow. A better understanding of the features and advantages of the present disclosure will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the disclosure are utilized, and the accompanying drawings of which: 
         FIGS. 1A, 1B and 1C  illustrate embodiments of the disclosure herein; 
         FIG. 2  illustrates a distal cross sectional view of a bidirectional embodiment; 
         FIG. 3  illustrates a unidirectional embodiment; 
         FIG. 4  illustrates a unidirectional embodiment with balloon inflation and guidewire/injection lumens; 
         FIG. 5  illustrates an embodiment of the present disclosure including a distal tip and adapter; 
         FIG. 6  illustrates an embodiment of the present disclosure with a bidirectional channel within the catheter; 
         FIG. 7  illustrates an embodiment of the present disclosure with a unidirectional channel; 
         FIG. 8  illustrates a device of the present disclosure with a distal tip; 
         FIG. 9A  shows a linear cross section through the catheter and balloon; 
         FIG. 9B  shows a linear cross section through the catheter and balloon and two circular bidirectional channels; 
         FIG. 9C  shows a linear cross section through the catheter and balloon and three circular bidirectional channels; 
         FIG. 9D  shows a linear cross section through the catheter and balloon and two circular unidirectional bypass channels with individual valves on each channel; 
         FIG. 9E  shows a linear cross section through the catheter and balloon and three circular unidirectional bypass channels with individual valves on each channel; 
         FIG. 9F  shows a linear cross section through the catheter and balloon and two circular unidirectional channels with a one-piece valve covering both channels; 
         FIG. 9G  shows a linear cross section through the catheter and balloon and two circular unidirectional channels with a one-piece valve covering three channels; 
         FIG. 9H  shows a linear cross section through the catheter and balloon and four bidirectional bypass channels formed from pleats in the balloon; 
         FIG. 9I  shows a linear cross section through the catheter and balloon and four unidirectional bypass channels formed from pleats in the balloon and a one-piece valve covering all 4 channels; 
         FIG. 9J  shows a linear cross section through the catheter and balloon and four bidirectional channels which radiate outward from the catheter; 
         FIG. 9K  shows a linear cross section through the catheter and balloon and four unidirectional channels which radiate outward from the catheter and a one-piece valve covering all four valves; 
         FIG. 9L  shows a linear cross section through the catheter and balloon and four unidirectional channels which radiate outward from the catheter outward and a single cross shaped valve covering all four channels; 
         FIG. 10  shows a tumor and associated vasculature; 
         FIG. 11  shows an expanded view of a tumor and its vasculature including blood flow direction; 
         FIG. 12  illustrates a standard micro-catheter over a guidewire inside the tumor vasculature with injection; 
         FIG. 13  illustrates a catheter of the present disclosure over a guidewire and inside a main artery; 
         FIG. 14  illustrates a catheter of the present disclosure over a guidewire and inside the branch artery; 
         FIG. 15  illustrates a catheter of the present disclosure with inflated balloon and closed valves; 
         FIG. 16  illustrates a catheter of the present disclosure with inflated balloon and open valves; 
         FIG. 17  illustrates a catheter of the present disclosure with inflated balloons, open valves and initiation of fluid injection; 
         FIG. 18  illustrates a catheter of the present disclosure during injection with inflated balloons and valves closed; 
         FIG. 19  illustrates a catheter of the present disclosure at a period of time following the completion of injection with inflated balloon and open valves; 
         FIG. 20  shows the deflation of the balloon; 
         FIG. 21  shows the withdrawal of the catheter into a main artery; 
         FIG. 22  shows an embodiment of the present disclosure with a channel within the catheter and closed valve; 
         FIG. 23  shows an embodiment of the present disclosure with a channel within the catheter and open valve; 
         FIG. 24A  illustrates a standard microcatheter; 
         FIGS. 24B, 24C, 24D and 24E  illustrate a cross sectional view of a sequential construction of an embodiment of the present disclosure; 
         FIGS. 25A and 25B  illustrate a cross sectional view of the distal portion of one embodiment of the device according to the present disclosure; 
         FIGS. 26A and 26B  illustrate a view of an embodiment including an occlusion balloon concealed within pocket formed between proximal and distal surfaces; 
         FIGS. 27A and 27B  illustrate a distal catheter with and occlusion balloon unexpanded and expanded; 
         FIGS. 28A, 28B, 28C, and 28D  illustrate an embodiment of the present disclosure including a two layer catheter; 
         FIG. 29  gives examples of balloons used in various embodiments of the present disclosure; 
         FIG. 30  shows a front view of a balloon with one-way bypass channels and valves; 
         FIG. 31  shows a cross section through the balloon of  FIG. 30 ; 
         FIGS. 32A, 32B, 32C, 32D, 32E and 32F  illustrate a cross sectional view of a sequential construction of an embodiment of the present disclosure including a balloon pocket and integral nose cone; 
         FIGS. 33A, 33B, 33C, 33D and 33E  illustrate a cross sectional view of a sequential construction of an embodiment of the present disclosure including a balloon pocket and separate nose cone; 
         FIG. 34  illustrates an embodiment of the present disclosure with two balloons; 
         FIG. 35  illustrates an embodiment of the present disclosure including a balloon with valves; 
         FIG. 36  illustrates an embodiment of the present disclosure with pressure sensors; 
         FIGS. 37A, 37B, 37C and 37D  illustrate an embodiment of the present disclosure with a balloon or balloons placed on the circumference of the catheter; 
         FIGS. 38A and 38B  illustrate a tumor with vascular anatomy and embolization using a standard straight nose catheter; 
         FIGS. 39A and 39B  illustrate a tumor with vascular anatomy and embolization using a balloon including channels and valves; 
         FIGS. 40A, 40B, 40C and 40D  illustrate a tumor with vascular anatomy and embolization using an occlusion balloon; 
         FIGS. 41A, 41B, 41C, 41D, 41E, 41F and 41G  illustrate constructions of embodiments of the present disclosure; 
         FIGS. 42A, 42B, 42C and 42D  illustrate a two layer occlusion structure with unidirectional flow; 
         FIG. 43  illustrates a prototype of the occlusion structure of  FIG. 42 ; 
         FIGS. 44A and 44B  illustrate an embodiment of the present disclosure including a catheter with a pocket; 
         FIGS. 45A and 45B  illustrate embodiments of the present disclosure for complete occlusion; 
         FIGS. 46A and 46B  illustrate an embodiment with bidirectional and unidirectional channels; 
         FIGS. 47A and 47B  illustrate valve constructions of an embodiment of a unidirectional occlusion structure of the present disclosure; 
         FIGS. 48A and 48B  show a prototype micro-valve; 
         FIGS. 49A and 49B  show an alternate embodiment of an occlusion structure; 
         FIGS. 50A, 50B and 50C  illustrate a method of operation of one embodiment of a unidirectional occlusion structure of the present disclosure; 
         FIGS. 51A, 51B, 51C, 51D, 51E and 51F  illustrate a method for delivery of embolic particles using a device of the present disclosure; 
         FIG. 52  illustrates a partial occlusion balloon with channel and valve; 
         FIG. 53  illustrates a side view of constrained occlusion balloon in catheter pocket; 
         FIGS. 54A, 54B and 54C  illustrate a distal end construction including pocket, constrained balloon and expanded partial occlusion balloon with channels and valves in closed position; 
         FIGS. 55A, 55B and 55C  illustrate a serial construction of a full length catheter device; 
         FIG. 56  illustrates liver vasculature and associated tumor vasculature; 
         FIGS. 57A, 57B, 57C, 57D, 57E, 57F, 57G and 57H  illustrate a tumor embolization method for a standard catheter; 
         FIGS. 58A, 58B, 58C, 58D and 58E  illustrate a tumor embolization method for the catheter of the present disclosure; 
         FIGS. 59A, 59B, 59C and 59D  illustrate fabrication steps of the distal end of an occlusion catheter according to aspects of the present disclosure; 
         FIG. 60  illustrates the completed distal end of the occlusion catheter of  FIGS. 59A-59D  being introduced into small branches of a vascular system; 
         FIG. 61A  shows an entire occlusion catheter constructed according to principles of the present disclosure; 
         FIG. 61B  shows details of construction features on the distal end of the occlusion catheter of  FIG. 61A ; 
         FIG. 62  shows a representative arterial system located adjacent to target tissue, before occlusion; 
         FIG. 63  shows the representative arterial system of  FIG. 62  after a temporary occlusion is introduced; 
         FIG. 64  shows target tissue and immediately adjacent arteries and capillaries, before occlusion; 
         FIG. 65  shows the target tissue and immediately adjacent arteries and capillaries of  FIG. 64  after a temporary occlusion is introduced into the target artery; 
         FIG. 66  is a chart showing pressure vs. time for an exemplary low pressure embolization method according to aspects of the present disclosure compared with a standard embolization procedure; 
         FIG. 67  is an axial cross-section showing an alternative catheter balloon design; 
         FIG. 68  shows an embodiment of a catheter balloon having spiral channels, shown in a deflated configuration; 
         FIG. 69  shows the balloon of  FIG. 68  in an inflated configuration; 
         FIG. 70  shows an in-vivo tumor flow model developed in Phase 1B of animal testing, in particular illustrating a normal blood flow pattern; 
         FIG. 71  shows the in-vivo tumor flow model of  FIG. 70 , with a standard embolization catheter maintaining a normal blood flow pattern; 
         FIG. 72  shows the in-vivo tumor flow model of  FIG. 70 , with an inventive embolization catheter creating blood flow redirection; and 
         FIG. 73  is a table summarizing bead collection results of the animal testing. 
     
    
    
     DETAILED DESCRIPTION 
     The device of the present disclosure allows improved distribution of anti-cancer agents into target tumor vasculature by reducing arterial flow and pressure during drug and/or embolic agent injection. The present device reduces toxicity and complications by eliminating reflux of embolic materials and/or anti-cancer agents into proximal arterial branches and reduces or eliminates antegrade bypass of embolic materials and/or anticancer agents into distal arterial branches. Further, the present disclosure enables pressure measurement as a means to a quantitative endpoint of the procedure. Such a device can improve efficacy and reproducibility of the technique and reduce complications. 
     Referring to  FIG. 1A , a longitudinal cross section of device  2  of the present disclosure is shown with catheter body  4 , distal tip  6 , balloon  8  (unexpanded configuration), balloon inflation tube  10 , guidewire and injection tube  12  and fittings  14 . Catheter body  4  can have a length of 10 cm to 400 cm, typically 60 cm to 250 cm and a diameter of 0.25 mm to 5 mm, typically 0.5 mm to 1.5 mm. Device  2  may or may not include a distal tip  6 , the distal tip having a length of 1 mm to 50 mm, more typically from 5 mm to 30 mm. The balloon inflation tube  10 , positioned at the proximal end of catheter body  4 , is connected to, and in fluid communication with a balloon inflation lumen that runs longitudinally through the length of catheter body  4  and terminates at, and is in fluid communication with balloon  8 . The guidewire and injection tube  12 , positioned at the proximal end of catheter body  4 , is connected to, and in fluid communication with a lumen that runs longitudinally through the length of catheter body  4  and terminates at the distal end or distal tip of catheter body  4 , thereby allowing a guidewire to enter through fitting  14  and exit through the distal end of device  2  through catheter body  4 . Fittings  14  are connected to each of balloon inflation tube  10  and guidewire and injection tube  12  and can connect to a syringe, inflation device or any other device or means to inject air, gas, fluid, suspensions, emulsions, contrast, therapeutic agents, embolic agents or any other material capable of being injected through balloon tube  10  or guidewire tube  12  and longitudinal lumens that run to the balloon or distal end of device  2 . 
     Referring to  FIG. 1B , a longitudinal cross section of a first embodiment of the present disclosure is shown, with device  2 , balloon  8  (in the expanded configuration) having valve  16  in the open position and valve  18 , in the closed position. In this embodiment flow channels  20  and  22  are constructed through balloon  8 . Valves  16  and  18  allow fluid to flow in only one direction. Balloon  8  has a proximal side  9  and a distal side  11 . By way of example, if fluid pressure is higher on the proximal side of balloon  8  and lower on the distal side of balloon  8 , both valves  16  &amp;  18  will open in response to the pressure difference and allow fluid to flow distally through the valves. If the pressure is higher on the distal side of balloon  8 , valves  16  and  18  will close and prevent fluid from flowing proximally. Alternately, the valves can be position or constructed so that fluid can pass proximally and be prevented from flowing in the distal direction. Valves  16  and  18  are shown as a simple “flap” type valve, however, they can be any type of valve, such as a diaphragm that open and close in response to a pressure differential. Balloon  8  is shown with two channels and two valves; however there can be 1, 2, 3 or more channels and/or valves. Device  2  of this embodiment may include channels and may or may not include valves. If valves are not included, a bidirectional flow will result. 
     Referring to  FIG. 1C , a longitudinal cross section of another embodiment of the present disclosure is shown with device  24  and channel  26  running through and within catheter body  28 . Balloon  30  has a proximal side  13  and a distal side  15 . Channel  26  extends from the proximal side of balloon  30  to the distal side of balloon  30 . A valve  32  is illustrated over channel  26  on the distal side of balloon  30 , however, if desired the valve can be positioned on the proximal side of channel  26  and balloon  30 . The function and operation of valve  32  of this embodiment of the present disclosure is identical to that presented in  FIG. 1A  and  FIG. 1B . As in this embodiment, if valve  32  is not included, a bidirectional flow will result. 
       FIG. 2  illustrates an exemplary embodiment of a longitudinal cross section of the distal end of device  2  with catheter body  4 , balloon inflation lumen  34 , balloon  8 , and channel  38 . Balloon inflation lumen  34  extends from the proximal end of catheter body  4  and exits at balloon  8 . In this case, a valve in balloon  8  is not included and a bidirectional flow will result. The optimal balloon inflation lumen diameter is 0.1 mm to 0.5 mm; however this lumen can be in the range of 0.25 mm to 1 mm. 
       FIG. 3  illustrates an example of a longitudinal cross section of the distal end of device  2  with catheter body  4 , balloon inflation lumen  34 , balloon  8 , channel  38  and valve  16 . Valve  16  is shown over the distal opening of channel  38  in the closed position, however if pressure is applied to the proximal valve surface through channel  38 , the valve will allow fluid to pass distally. The valve  16  will prevent proximal flow. The valve can be positioned at the proximal or distal opening or anywhere within the cannel. Location and configuration of the valve will determine flow direction. 
     Referring to  FIG. 4 , a longitudinal cross section of the distal end of device  2  is shown with catheter body  4 , balloon inflation lumen  34 , balloon  8 , channel  38  and guidewire/injection lumen  40 . Guidewire/injection lumen  40  extends from the proximal end of catheter body  4  and exits at the distal end of catheter body  4  or distal tip  6 . The optimal guidewire/injection lumen diameter is 0.1 to 1.0 mm; however, this lumen can be in the range form 0.025 mm to 2 mm. 
     Referring to  FIG. 5 , an example of a longitudinal cross section of the distal end of device  2  is shown with catheter body  4 , balloon inflation lumen  34 , balloon  8 , channel  38 , guidewire/injection lumen  40 , adapter  42 , balloon pocket  44  and distal tip  6 . Distal tip  6  has an optimal diameter of 0.3 mm to 1.3 mm; however, distal tip  6  can range from 0.1 mm to 4 mm. Adapter  42  is adapted to create a smooth transition from the distal tip  6  to the catheter body  4 . By way of example, if the distal tip  6  is 1 mm in diameter and the catheter body  4  is 2 mm in diameter, the adapter will taper from a diameter of 1 mm at its distal most point to 2 mm at its proximal most point to create a smooth transition from the smaller diameter distal tip to the larger diameter catheter body. As shown in  FIG. 5 , adapter  42  is positioned on the distal tip  6  at a location that is distal to distal end of catheter body  4 , such that a balloon pocket  44  is formed between the distal end of catheter body  4  and the proximal end of adapter  42 . Balloon pocket  44  holds unexpanded balloon  8  such that its unexpanded profile is minimized. Optimally balloon  8  would conform to an outer diameter that is equal to the diameter of the catheter body  4 . By way of example, if the distal tip diameter is 1 mm and the catheter body is 2 mm, a balloon pocket is formed that is 0.5 mm deep. If balloon  8  is no more than 0.5 mm thick when unexpanded, it will lie equal to or below the surface of catheter body  4 . This allows facilitation of the movement of the caterer within the artery or vein. 
     Referring to  FIG. 6 , a longitudinal cross section of the distal end of device  24  is shown with catheter body  28 , balloon inflation lumen  50 , guidewire/injection lumen  52 , balloon  30 , and channel  26  with proximal port  54  and distal port  56 . Channel  26  passes through and within catheter body  28  and extends from the proximal side of balloon  30  to the distal side of balloon  30 . Port  54 , at the proximal end of channel  26  is in fluid communication with the outside of the catheter body that is proximal to balloon  30  and port  56 , at the distal end of channel  26 , is in fluid communication with the area outside of catheter body  28  that is distal to the balloon  30 . In this case, the flow through channel  26  is bidirectional. The optimal channel diameter is 0.1 mm to 1 mm; however this channel can be in the range of 0.05 mm to 2 mm. 
       FIG. 7  illustrates an exemplary embodiment of a longitudinal cross section of the distal end of device  24  with catheter body  28 , balloon inflation lumen  50 , guidewire/injection lumen  52 , balloon  30 , valve  32  and channel  26  with proximal port  54  and distal port  56 . Channel  26  passes through and within catheter body  28  and extends from the proximal side of balloon  30  to the distal side of balloon  30 . Port  54 , at the proximal end of channel  26  is in fluid communication with the outside of the catheter body that is proximal to balloon  30  and port  56 , at the distal end of channel  26 , is in fluid communication with the area outside of catheter body  28  that is distal to the balloon  30 . Valve  32 , is shown at the opening of port  56  of channel  26 . Valve  32  allows flow in the distal direction and prevents flow in the proximal direction. In this case, the flow through channel  26  is unidirectional. The optimal channel diameter is 0.1 mm to 1 mm; however this channel can be in the range of 0.05 mm to 2 mm. The valve can be positioned at the proximal or distal opening or anywhere within the channel. Location and configuration of the valve will determine flow direction. 
     Referring to  FIG. 8 , a longitudinal cross section of the distal end of device  24  is shown with catheter body  28 , balloon inflation lumen  50 , guidewire/injection lumen  52 , balloon  30 , valve  32 , channel  26  and distal tip  6 . 
     Referring to  FIG. 9 , linear cross sections through catheter body  4  and balloon  8  are shown.  FIG. 9  illustrates examples of flow channels through a balloon positioned on a catheter, however, various alternatives, modifications, and equivalents may be used.  FIG. 9A  shows catheter  4  and balloon  8  without a channel.  FIG. 9B  shows catheter  4  and balloon  8  with two channels  38  through balloon  8 . In this case the flow is bidirectional.  FIG. 9C  shows a catheter and balloon with three bidirectional cannels.  FIG. 9D  shows a catheter  4  with a balloon  8  with two channels, each with a one-way valve. In this case the channel flow in each channel is unidirectional.  FIG. 9E  shows catheter  4  with balloon  8  and three channels  38 , each with an independent valve  38 . The flow is unidirectional.  FIG. 9F  is a catheter and balloon with two channels and a single circumferential valve  33  that covers both channels  38  and allows flow in only 1 direction.  FIG. 9G  shows a catheter  4  and balloon  8  with three channels and a single circumferential valve  33  that covers all three channels.  FIG. 9H  shows a catheter  5 , and four bidirectional channels  39  that are formed by pleating balloon  36  from the outer circumference of the expanded balloon, inward toward the central catheter and securing the inner apex of the balloon to the catheter, thereby forming triangular channels which radiate outward from the central catheter, forming a “V” shape. The lower point of the ‘V” is positioned at the catheter surface and the open end of the “V” is positioned at the outer circumference of the circle defined by the largest diameter of the inflated balloon.  FIG. 9I  shows four channels  39 , with a single circumferential valve  35  covering all four triangular channels. Although the figure shows four channels, the device of this disclosure can have one, two, three, four or any number of channels.  FIG. 9J  shows a catheter  7  and a balloon  39  with four channels  37  that are formed by pleating the balloon  39  from the inner catheter  7  toward the outer circumference of the expanded balloon  39 .  FIG. 9K  shows four channels  37  as in  FIG. 9J  with a single circumferential valve  39  that covers all four channels  37 .  FIG. 9L  shows four channels  37  as in  FIG. 9J  with a one piece cross-shaped flap valve  41 . 
     While the above is a complete description of exemplary embodiments of the present disclosure, various alternatives, modifications, and equivalents may be used. Therefore, the above description should not be taken as limiting the scope of the disclosure, which is defined by the appended claims and the claims in any subsequent applications claiming priority hereto. 
       FIG. 10  illustrates a tumor and its associated vasculature with tumor  60 , main artery  62 , side branch artery  64 , tumor artery  66 , tumor capillary  68  and antegrade arterial flow direction illustrated by arrows  70 . 
       FIG. 11  is an expanded view of  FIG. 10  with tumor  60 , main artery  62 , side branch artery  64 , tumor artery  66  and antegrade arterial flow direction illustrated by arrows  70 . 
       FIG. 12  illustrates injection of fluid  76  using a standard micro-catheter  72  with tumor  60 , main artery  62 , side branch artery  64 , tumor artery  66 , guidewire  74  and retrograde arterial flow direction illustrated by arrows  70 . In this instance, injection pressure and flow volume of the fluid  76  that may contain anti-cancer drugs, radioembolic substances, chemoembolic substances, embolic agents or the like, through microcatheter  72  is higher than the tumor vasculature can accept causing a reversal of fluid flow and blood flow in tumor artery  66 , side branch artery  64  and main artery  62 . This retrograde flow causes the injected fluid  76  to enter the main artery, flowing in both directions and into the general circulation resulting in the injected fluid traveling to non-target tissues and organs. This unintended delivery of fluid  76  to non-target sites is undesirable and must be avoided since it can cause serious complications. The present disclosure solves this problem by preventing reflux and associated non-target delivery of fluid  76 . 
       FIG. 13  illustrates catheter  4  of the present disclosure entering the main artery with balloon  8  and distal tip  6 . Although the entry point from outside the body is typically through the femoral artery at the groin, any artery or vein from any location on the body can be used for access provided that it creates a pathway to the target vasculature. 
       FIG. 14  illustrates catheter  4  with balloon  8 , of the present disclosure, following guidewire  74  into side branch artery  64 . 
       FIG. 15  illustrates catheter  4 , inside the branch artery  64  with balloon  8  in the expanded configuration, channels  38  and valves  16 . Valves  16  are illustrated in the closed position immediately following the inflation of balloon  8 . 
       FIG. 16  illustrates catheter  4 , inside the branch artery  64  with balloon  8  in the expanded configuration, channels  38  and valves  16 . Valves  16  are illustrated in the open position since antegrade blood flow as indicated by arrows  70  and associated blood pressure causes these valves to open and allow the blood to continue to flow in the antegrade direction and into the tumor vasculature. 
       FIG. 17  illustrates the initial injection of fluid  76  into side branch artery  64  through catheter  4 , channels  38  and open valves  16 . When the injection is initiated, the antegrade blood flow carries the injection fluid  76  into the tumor vasculature including tumor arteries  66 , and capillaries  68 . 
       FIG. 18  illustrates injection of fluid  76  at a point when fluid pressure increases within the tumor vasculature and concomitant retrograde arterial blood flow and injection fluid flow in the direction as illustrated by arrows  70 . Shown in this figure are catheter  4  of the present disclosure with tumor  60 , main artery  62 , side branch artery  64 , tumor artery  66 , and guidewire  74 . Injection fluid  76 , may contain anti-cancer drugs, radioembolic substances, chemoembolic substances, embolic agents or the like, which can cause serious complications if delivered to non-target sites. In this case, the retrograde pressure causes valves  16  to close and prevents the reflux of injection fluid into the general circulation, thereby preventing complications associated with delivery of injection fluid to non-target sites. 
       FIG. 19  illustrates a point in time following the completion of fluid injection. At this point, the pressure in the vasculature that is the distal to balloon  8 , including side branch  64  and tumor artery  66 , is reduced below normal blood pressure due to the gradual uptake of the injected fluid into the tumor vasculature. The blood pressure on the proximal surface of balloon  8  and valves  16  cause them to open allowing antegrade blood flow to be reestablished. When this occurs, the excess fluid  76  distal to balloon  8  and within the side branch artery  64  and tumor vasculature, including tumor artery  66  and tumor capillaries  68 , is flushed forward and up into the tumor vasculature, thereby enabling delivery of the entire fluid dose and eliminating fluid reflux and associated complications. 
       FIG. 20  illustrates the deflation of balloon  8  on catheter  4 . 
       FIG. 21  illustrates the withdrawal of catheter  4  into the main artery  62 . 
       FIG. 22  illustrates another embodiment of the present disclosure as described in  FIGS. 6, 7 and 8 . In this case valve  32  on the distal end of channel  26  of catheter  28  is in the closed position. 
       FIG. 23  illustrates an embodiment of  FIG. 22  with valve  32  in the open position. 
     A Method, according to the present disclosure is illustrated by  FIGS. 13 through 21 ; the method applies to both the embodiment illustrated in  FIGS. 1B, 2, 3, 4 and 5  and the embodiment illustrated in  FIGS. 1C, 6, 7, 8, 22 and 23 . 
     Referring to  FIG. 24A , a longitudinal cross section of a standard single lumen straight tip catheter  101 , having a proximal and distal end, is shown with catheter body  102 , and hub  105 . Hub  105 , positioned at the proximal end, further comprises guidewire/injection lumen  110 , in fluid communication with a catheter lumen longitudinally oriented and extending from hub  105  and exiting at the distal end of the catheter body  102 . The proximal hub connects to a syringe or other means to inject fluids via a luer fitting, thereby allowing injection of a fluid through the longitudinal lumen and exit at the distal end of catheter body  102 . 
     Referring to  FIG. 24B through 24E , longitudinal cross-sections of a sequential assembly of a preferred embodiment of the present disclosure is shown. Referring to  FIG. 24B , device  103  is shown, having a proximal and a distal end, catheter body  102 , catheter extension  104  and hub  106 . Hub  106  further comprises handle  109 , guidewire/injection luer fitting  110  and balloon fill luer fitting  112 . Luer fitting  110  is in fluid communication with a first longitudinal guidewire/injection lumen of catheter body  102 , extending to the distal end of catheter extension  104 , and luer fitting  112 , in fluid communication with a second longitudinal balloon fill lumen of catheter body  102 , extending to a balloon fill port located near the distal end of catheter body  102 .  FIG. 24C  further comprises nose cone  114 , positioned on catheter extension  104 , forming balloon pocket  116  disposed between the distal end of catheter body  102  and nose cone  114 . Further, a portion of catheter extension  104  can, if desired, extend distal to nose cone  114 , thereby forming distal tip  118 .  FIG. 24C , further illustrates occlusion balloon  120  in a radially compressed configuration and  FIG. 24E  illustrating balloon  120  in a radially expanded configuration. Hubs  106  can be constructed from styrene, polyurethane, polypropylene, lipid resistant polycarbonate, polycarbonate, Pebax (polyether block amide), of any durometer, or any convenient material and can have any configuration, including, but not limited to, a solid structure comprising two lumens or tubular extensions of the lumens of catheter body  102 , provided that they are in fluid communication as described above. Catheter body  102  can be formed from any plastic or thermoplastic material including polyurethane, PTFE, polyimide, polypropylene, Pebax or the like, and can comprise a single section or multiple sections of different diameter, durometer, braid or coil reinforcement or any convenient construction with a diameter of between 1 Fr and 10 Fr more typically of 2 Fr to 5 Fr. Catheter extension  104  can have a diameter of 0.5 Fr to 5 Fr, more typically of 1 Fr to 3 Fr and can be absent or can be of any length, typically 2 mm to 30 mm, more typically from 5 mm to 20 mm. If the catheter extension  104  extends beyond nose cone  114 , the section distal to the nose cone forms the distal tip  118 . Distal tip  118  is advantageous when injecting deep into the tumor vasculature is desired and will also help tracking of device  103  over a guidewire around sharp corners and through a tortuous vasculature path. Nose cone  114  can be made from any polymer or metal or can be formed from a radiopaque marker band. Balloon pocket  116  can be of any length between 2 mm and 50 mm, more typically between 5 mm and 20 mm. Occlusion balloon  120  has a longitudinal length of 1 mm to 30 mm, more typically of 2 mm to 10 mm and a diameter of 1 mm to 50 mm, typically from 2 mm to 10 mm and can be composed of silicone, polyurethane, polyethylene, PET (polyethylene terephthalate), nylon or the like and can be of any configuration or of any length or shape and can be glued, chemically bonded, heat bonded, RF welded, sonically fused, compressed or crimped under a collar to catheter  102  or catheter extension  104 . 
     Referring to  FIG. 25A , a distal section of a device  128  of a preferred embodiment of the present disclosure is shown and includes catheter body  102 , catheter extension  104 , nose cone  114 , balloon pocket  116 , balloon fill lumen  124 , guidewire/injection lumen  126  and radially compressed balloon  120 . Referring to  FIG. 25B , balloon  120  is shown in its radially expanded configuration. Balloon fill lumen  124  can be of any convenient shape including but not limited to round, semicircular, or crescent or any shape, typically optimized to provide maximum area and flow rate. Guidewire/injection lumen  126  is typically round, having a diameter of 0.005″ to 0.1″, more typically from 0.01″ to 0.05″; however, it can be of any desirable shape. 
     Referring to  FIG. 26A , the distal end  133  of an embodiment of the present disclosure is shown with catheter body  102 , catheter extension  104 , nose cone  114 , balloon pocket  116 , balloon fill lumen  124 , guidewire/injection lumen  126  and radially compressed balloon  120 . In this instance, the balloon pocket  116  is formed between a proximal collar  130  and a distal collar  114 , tapered forward thereby forming a nose cone. The balloon bonding tails  115  can be bonded within the pocket or compressed or bonded under collars  114  and  130 . Distal collar  130  can comprise a metal, such as a radiopaque marker band or a plastic such as heat shrink tubing and can be 1 mm to 20 mm in length, more typically from 2 mm to 10 mm. Balloon fill lumen  124  is shown traveling under balloon pocket  116  and ending at its distal end. Guidewire/injection lumen  126  is shown traveling longitudinally through catheter  102  and catheter extension  104 , ending at the distal end of the catheter. Balloon  120  is shown tucked into pocket  116  with outer diameter substantially no larger than the outer diameter of catheter body  102 .  FIG. 26B  shows the same construction as  FIG. 26A  with balloon  120  in its radially expanded configuration. 
     Referring to  FIG. 27A , a view of distal section  133  is shown and further illustrates that the profile of a preferred embodiment of the present disclosure, including the radially compressed balloon  120 , the distal collar  114  and the proximal band  130 , have an outer diameter equal to or less than that of catheter body  102 .  FIG. 27B  shows the same construction as  FIG. 27A  with balloon  120  expanded from pocket  116  and between collars  114  and  130 . 
     Referring to  FIG. 28A , a distal section of an alternate embodiment  135  of the present disclosure is shown with outer catheter  119 , inner catheter  127 , nose cone  125 , radially constrained balloon  131  and catheter channels  123 . The outer catheter  119  is adapted over inner catheter  121 , the catheters configured to provide a radially distributed space between inner and outer catheters extending longitudinally along the length of device  135 . Outer and inner catheters can have a length of 10 cm to 250 cm, more typically 550 cm to 150 cm and a diameter of between 0.5 Fr and 10 Fr more typically of 1 Fr to 5 Fr. Inner catheter  127  can have a length less than, equal to, or longer than the outer catheter  119 , however in the present figure, inner catheter  127  is shown to be longer than outer catheter  119 , its distal end forming the catheter extension  127 . Nose cone  125  is disposed along the distal extension of inner catheter  127  at some distance from the distal end of outer catheter  119 , the distance being 2 mm to 50 mm, more typically between 5 mm and 20 mm. The balloon pocket is formed between the distal end of catheter  119  and the proximal end of nose cone  125 .  FIG. 28B  shows an end view of outer catheter  119 , disposed over inner catheter  127 , with radially configured channels  123  and stand-offs  127  disposed between outer catheter  119  and inner catheter  127 . Four channels are illustrated, however device  135  can have 0, 1, 2, 3, 4 or any number of channels and stand-offs, the stand-offs defining the outer edges of the channels  123  and can be formed on either the inner or outer catheter with a height limited only by the diameter of the inner and outer catheters and space there between. Although stand-offs are shown, they are not required, provided that the inner catheter OD is smaller than the outer catheter ID, thereby forming a space between the inner and outer catheters which allow fluid to flow longitudinally along device  135 . Device  135  can comprise single layer inner and outer catheters or one or both can have multiple layers. In a preferred embodiment, outer catheter  19  is a three layer construction with an outer Pebax layer, a central polyimide layer including reinforcement such as a coil or braid and an inner Teflon layer. Inner catheter  127  is a single layer of low friction tubing, or tubing of similar construction to that described for the outer catheter  119 .  FIG. 28C  shows a longitudinal view of device  135  with outer catheter  119 , unexpanded balloon  131 , nose cone  125  and a catheter extension of inner catheter  127 . Balloon  131  is shown tucked within a pocket formed between the distal end of catheter  119  and the proximal end of nosecone  125 .  FIG. 28D  shows a longitudinal cross section of device  135 , showing balloon inflation channel  123  disposed between outer catheter  119  and inner catheter  121 . In this instance, the distal end of balloon  131  is shown inserted into the proximal end of nose cone  125 ; however both proximal and distal balloon tails can be bonded directly to inner catheter  127 , reflowed into catheter  119  or nose cone  125  or by any means, provided that the balloon tails are positioned approximately below the outer diameter of catheter  119 . 
     Referring to  FIG. 29A  though  FIG. 29E , examples of balloon configurations that may be used in the device of the present disclosure are shown which can be compliant or noncompliant, dilation or occlusion and can be made from any material including, but not limited to, silicone, polyurethane, polyethylene, PET (polyethylene terephthalate) and nylon. 
     Referring to  FIG. 30 , a surface view of balloon  160  is shown with one-way bypass channels  162  and valves  164 , the balloon is described in detail in co-pending patent application No. 61/821,058. 
     Balloon  160  and valves  164  allow flow from the compartment proximal to the proximal surface of balloon  160  to the compartment distal to the distal surface of balloon  160  (antegrade flow) and prevents flow from the compartment distal to the distal surface of balloon  160  to the compartment proximal to the proximal surface of balloon  160  (retrograde flow). Balloon  160  can be disposed on the catheter of the present disclosure and held within a balloon pocket as illustrated in  FIGS. 24-29  and enable antegrade injection of therapeutic agents from within an artery and into a target while maintaining normal (antegrade) blood flow through channels  162  of balloon  160  and prevent retrograde flow (reflux) of therapeutic agents backward over the catheter, even when pressure distal to balloon  160  is elevated above systolic and/or mean arterial pressure. 
     Referring to  FIG. 31 , a cross section of balloon  160  is shown with channels  162  and microvalves  164 , positioned within channels  162 . 
       FIG. 32  shows an example of a sequential assembly of an embodiment of the present disclosure. Referring to  FIG. 32A , catheter  170  of device  168  is shown.  FIG. 32B  illustrates a first step in the construction of device  168  whereby a balloon pocket  172  is formed about a distal section of catheter  170  and a second step, as in  FIG. 32C , whereby a rounded distal end  174  of catheter  170  is formed and a third step as in  FIG. 32D  whereby a balloon  176 , with bonding tails  178  is disposed within pocket  172  of catheter  170  and a fourth optional step whereby catheter  170  or other material is reflowed at position  180  over balloon tails  178 .  FIG. 32F  illustrates balloon  176  in its radially expanded configuration with balloon pocket  172  and tails  178  bonded in pocket  172  without being covered by reflow or other means. 
     Referring to  FIG. 33 , three alternate embodiments of the present disclosure are illustrated.  FIG. 10A  shows device  173  with catheter  181 , balloon pocket  177 , radially constrained balloon  178 , catheter extension  171  and nose cone  182 .  FIG. 33B  shows device  173  with radially expanded balloon  178  and bonding tails  183  bonded within balloon pocket  177 .  FIG. 33C  illustrates device  175  with nosecone  182  and proximal bonding tail  191  reflowed into catheter  181  at position  179  and the distal balloon bonding tail  193  reflowed into or under nose cone  182  to catheter extension  171  at location  184 .  FIG. 33D  illustrates device  179  with catheter  181 , balloon  178 , nose cone  182  and collar  186 . Balloon  178  has a proximal tail  191  positioned under collar  186  and distal balloon tail  193  reflowed or bonded to catheter extension  171 and under nose cone  182  or into nose cone  182 .  FIG. 33E  shows device  179  with balloon  178  expanded from within the balloon pocket formed between collar  186  and nose cone  182 . 
       FIG. 34  shows yet another embodiment of the present disclosure with two balloons  188  and  189 , catheter  183 , balloon pockets  194  and  190 , reflow areas  192  and nose cone  189 . Although the example of  FIG. 34  shows both balloon  188  and  189  positioned within pockets  194  and  190 , only one balloon need be positioned within a pocket. 
       FIG. 35  shows still another embodiment of the present disclosure with balloon  196  containing channels  195  and  197 , valve  198  in the closed orientation, valve  199  in the open orientation, collar  183 , nose cone  1102  and reflow area  1100 . Although valve  198  is shown closed and valve  199  is shown open, they will typically act in unison and all either be simultaneously open or closed. 
       FIG. 36  shows still another embodiment of the present disclosure which includes two pressure sensors, positioned distal and proximal to balloon  1110 , although a single pressure sensor positioned either distal or proximal to the balloon can be used. These pressure sensors can be used to monitor and, in conjunction with a syringe, control injection pressure either manually of by an automated means. Alternately pressure proximal or distal to the occlusion balloon can be measured through the catheter using an external pressure gauge ( 1113 ), the distal pressure being measured via the guidewire/injection lumen  1105  or any other catheter lumen or other tube. The pressure gauge can be connected to a pump, via a processor, allowing the pump to achieve a defined pressure or be programed to a specific set of pressures, volumes and/or flow rate as a function of time. 
     Referring to  FIG. 37 , four embodiments of balloon configurations are shown.  FIG. 37A , shows device  1115  with balloon  1117  and catheter  1116 . Balloon  117  in a radially expanded configuration, occupies only part of the circumference of catheter  1116 .  FIG. 37B  illustrates device  1118  with catheter  1119  and balloons  1121  whereby the four balloons  1121 , in radially expanded configurations are arranged circumferentially about catheter  1119 , each occupying a part of the overall outer circumference of catheter  1119 .  FIG. 37C  illustrates device  1123 , with catheter  1125  and balloon  1127  in a radially expanded configuration, whereby balloon  1127 , in a radially constrained configuration is positioned within a pocket of catheter  1125  and the radially outermost part of balloons  1127  is positioned approximately at or below the outer diameter of catheter  1125 .  FIG. 37D  illustrates device  1131  with catheter  1135  and balloons  1137  in a radially expanded configuration, whereby balloons  1137 , in a radially constrained configuration are positioned within a pocket of catheter  1135  and the radially outermost part of balloons  1137  are approximately positioned at or below the outer diameter of catheter  1135 . 
     Referring to  FIG. 38 , an anatomical structure  1120  is shown with main artery  1122 , right artery  1124 , left artery  1126 , right capillaries  1128 , left capillary  1129 , arterial side branch  1136 , vein  1130 , arteriovenus shunt  1132 , tumor  1133 , blood flow directional arrows  1134 , standard straight tip catheter  1138 , and embolization particles  1125 .  FIG. 38A  illustrates the beginning of a transarterial embolization (TAE) procedure wherein the embolization particles  1125  are exiting the distal end of catheter  1138  and are carried by forward (antegrade) blood flow into tumor  1133  in a delivery method that is completely mediated by blood flow and normal blood pressure (flow mediated delivery). Capillary beds  1128  and  1129  of tumor  1133  begin to fill with embolic particles  1125  and arteriovenus shunt  1132  carries particles into vein  1130  causing antegrade reflux and non-target embolization. The flow through the arteriovenous shunt  1132  is rapid since the arterial pressure is significantly higher than venous pressure. Referring to  FIG. 38B , continued injection of particles  1125  from the distal end of standard straight tip catheter  1138  results in the packing of particles and embolization of the distal ends of capillary beds  1128  and  1129 . Distal capillary embolization causes the flow through arteriovenous shunt  1132  to stop and pressure to build in left artery  1126 . As embolization progresses, the back pressure in artery  1126  continues to rise until embolic particles reflux in the retrograde direction  1142  causing non-target embolization of the right artery  1124 , arterial side branch  1136  and main artery  1122 . This situation can cause non-target embolization, loss of an unknown amount of particles, delivery of an unknown and irreproducible dose and non-optimal distribution of embolic particles in the tumor vasculature. In this instance, both antegrade and retrograded reflux can occur. 
     Referring to  FIG. 39 , anatomical structure  1120  is shown as in  FIG. 38 . In this instance, a balloon  1141 , with channels  1143  and one-way valves ( FIGS. 30 and 31 ) is positioned about the distal end of catheter  1139 . Balloon  1141 , so constructed, will allow only antegrade (normal) flow and prohibit retrograde flow. Referring to  FIG. 39A , balloon  1141  is shown in its radially expanded configuration and blood is flowing through balloon channels  1143  as indicated by blood flow arrow  1134  and into the vasculature of tumor  1133 . Embolic particles  1125  are released from the distal end of catheter  1139  and carried forward by blood flow into capillaries  1128  and  1129 . Capillary beds  1128  and  1129  of tumor  1133  begin to fill with embolic particles  1125  and arteriovenus shunt  1132  carries particles into vein  1130  causing antegrade reflux and non-target embolization. The flow through the arteriovenous shunt  1132  is rapid since the arterial pressure is significantly higher than venous pressure. Referring to  FIG. 39B , continued injection of particles  1125  from the distal end of balloon catheter  1139  results in the packing of particles and embolization of the distal ends of capillary beds  1128  and  1129 . Distal capillary embolization causes the flow through arteriovenous shunt  1132  to stop and pressure to build in left artery  1126 . As embolization progresses, the pressure in artery  1126  continues to rise, however the valves of balloon  1141  close and prohibit retrograde reflux. In this instance, continued injection will increase the packing pressure of particles  1125  and can increase packing density and increase flow into distal locations in the margins of a tumor or other structure thereby improving particle distribution throughout the target vasculature. As part of the present method, pressure distal to the balloon can be regulated between systolic and/or mean arterial pressure and any pressure above that pressure, provided that it is within a range that is safe for the patient. By way of example, injection pressure can be low at the onset of the embolization procedure and increased at some point thereafter to a pressure greater than systolic and/or mean arterial pressure. Such a point may, for example, be chosen to coincide with the stoppage of flow through arteriovenous shunt  1132 . This method may improve particle distribution and packing. Alternately, the injection pressure through catheter  1139  can be high at the onset, thereby forcing particles rapidly into the distal section of capillaries  1128  and  1129  and hasten embolization of arteriovenous shunt  1132 , thereby reducing antegrade reflux. Alternately, according to this method, a low to high pressure gradient or a high to low pressure gradient can be used. The aim for the use of a pressure mediated delivery of particles is to optimize for a low level of antegrade reflux, substantial elimination of retrograde reflux, high particle distribution and high particle density. A pressure sensor as in  FIG. 36  can be used on the proximal and/or distal side of balloon  1142  to monitor pressure and enable a selection of a procedural end point based on a definitive pressure reading. 
     Referring to  FIG. 40 , anatomical structure  1120  is shown as in  FIG. 38 . In this instance, an occlusion balloon  1142  is positioned about the distal end of catheter  1140 . Referring to  FIG. 40A , balloon  1142  of catheter  1140  is shown in a radially expanded configuration. Since expanded balloon  1142  completely occludes artery  1126 , all arteries and capillaries distal to the balloon are isolated from the main artery  1122 , right artery  1124  and side branch artery  1136  thereby causing blood pressure distal to the balloon to drop from approximately normal arterial pressure of about 80 mmHg to a pressure in the range of 0-50 mmHg. When this happens, blood flow through the arteriovenous shunt  1132  can reverse as shown by blood flow arrow  1135 , or the antegrade flow slowed or stopped. Referring to  FIG. 40B , initial injection of particles  1125  will be against a pressure, with a minimal antegrade flow or into a flow stasis. Retrograde pressure flow against the particle injection can result from the flow of venous blood from vein  1130 , through arteriovenus shunt  1135  and into the arterial capillary  1129  or from arteriovenous capillary beds associated with capillaries  1128 . As particles  1125  are injected, they fill capillaries  1128  and  1129 ; however, particles cannot easily flow through arteriovenous shunt  1132  because of the reversal or slowing of flow and pressure. Continued injection can result in embolization of the distal portion of capillary  1129  and blockage of arteriovenous shunt  1132  with concomitant reduction or elimination of antegrade reflux. Increasing injection pressure through catheter  1140  following embolization of arteriovenous shunt  1132 , can result in a high levels of particle density and distribution. Alternately, according to this method, a gradient can be used. The profile of the pressure gradient can be any function of time and pressure including, but not limited to, a linear or step function from low to high, high to low, alternating high to low and low to high or any other function and can be administered manually, in a semi-automated manner or using a programmable delivery means. Alternately according to this method, a pressure sensor as in  FIG. 36  can be used on the proximal and/or distal side of balloon  1142  to monitor pressure and select a procedural end point based on a definitive pressure reading. Referring now to  FIG. 40D , the injection through catheter  1140  into tumor  1133  can be accomplished using an automated pump/pressure monitor system whereby the pressure distal to occlusion balloon  1142  is measured on gauge  1152 , the pressure reading transferred through connection  1154  to pump  1150  which controls the injection of anti-tumor agents from syringe  1156 . Pump  1150  can be controlled manually or programed to any function of flow rate, time and/or pressure. The endpoint can be selected at any desirable pressure. 
     The aim of the present method is to eliminate retrograde reflux, reduce or eliminate antegrade reflux, control the particle density and distribution, deliver an optimal dose, enable a defined pressure endpoint, improve efficacy and reduce toxicity. 
     Referring to  FIG. 41A , a longitudinal cross section of a catheter is shown with proximal and distal ends, catheter body  204 , distal tip  203  and proximally disposed hub  206 . Catheter body  204  has two lumens that are in fluid communication with hub  206 , a first lumen extending from port  208  of hub  6  to the distal tip  203  of catheter  204  whereby fluid can be injected from the proximal hub  206  and exit at the distal tip  203  of catheter  204  and a second lumen extending from port  210  of hub  206  to an intermediate location at some distance from the distal tip  203  of catheter  204 , the second lumen adapted to communicate with a balloon for inflation and deflation. 
     Referring to  FIG. 41B , a longitudinal cross section of a first embodiment of the present disclosure is shown with proximal and distal ends, catheter body  204 , distal tip  203 , and two layered occlusion balloon  214  with channels  205  and valves  207  and proximally located hub  206 . Although balloon  214  is shown with two channels, each with a valve, balloon  214  can have 1, 2, 3, 4 or any number of channels and any number of valves or be without valves. In this instance, the valve configuration allows fluid to flow from the proximal side of balloon  214  to the distal side of balloon  214  and to restrict flow from the distal side of balloon  214  to the proximal side of balloon  214 ; however, the opposite valve orientation and flow direction is also part of the present disclosure. Catheter body  204  can have a diameter of between 1 Fr and 10 Fr, more typically 2 Fr to 5 Fr and a length of 10 cm to 250 cm, more typically 550 cm to 150 cm. Two layered occlusion balloon  214  can be from 1 mm to 30 mm in diameter, more typically 2 mm to 10 mm in diameter, in its radially expanded configuration. 
     Referring to  FIG. 41C , an alternate embodiment of the device of the present disclosure is shown, having catheter body  218 , distal tip  209 , hub  206  and umbrella shaped occlusion structure  220 . When in its radially expanded configuration, the occlusion structure will completely occlude the flow of the vessel. The umbrella shaped occlusion structure  220  is positioned at some distance from the distal end of catheter  216  and forms an umbrella shaped structure disposed circumferentially about catheter  216  with its outer diameter in contact with the vessel. Umbrella shaped occlusion structure  220  can be from 1 mm to 30 mm in diameter more typically 2 mm to 10 mm in diameter when in its radially expanded configuration and a longitudinal thickness of 0.25 mm to 10 mm, more typically 0.5 mm to 2 mm. Umbrella shaped occlusion structure  220  is shown with its closed end attached to the catheter distal to the open end of the V shape; however, it can be positioned in the opposite orientation or it can be positioned at a 90 degree angle with respect to catheter body  18 . 
     Referring to  FIG. 41D , device  222  of the present disclosure is shown having catheter  218 , distal tip  209 , hub  206 , and a unidirectional umbrella occlusion structure  224  with channels  230  and valves  228 . Occlusion structure  224  will allow proximal to distal flow and prevent distal to proximal flow. 
     Referring to  FIG. 41E , device  232  is shown with catheter body  234 , catheter distal extensions  235  and distal tip  211 . Catheter extension  235  can have a diameter of 0.5 Fr to 5 Fr, more typically of 1 Fr to 3 Fr and can be absent or can be of any length, typically 2 mm to 30 mm, more typically from 5 mm to 20 mm. 
     Referring to  FIG. 41F , a preferred embodiment of the present disclosure is shown with catheter body  237 , catheter extension  235 , distal tip  211 , nose-piece  241  and two layered occlusion balloon  243  in its radially expanded configuration. In this instance, two layered occlusion balloon  243  is disposed within a pocket formed on distal catheter extension  235  and between the distal end of catheter body  237  and the proximal end of nose-piece  241 . The nose piece can be a tapered nose cone, a distally rounded piece of tubing or catheter, a blunt tube or any structure with a diameter equal to less than the catheter body. When in the radially constrained configuration, the outer diameter of the two layered occlusion balloon  243  has an outside diameter that is about equal to the outer diameter of the catheter body  237 . 
     Referring to  FIG. 41G , yet another embodiment of device  245  of the present disclosure is shown, having catheter body  247 , distal tip  234 , nose-piece  241 , proximal hub  206  and unidirectional umbrella shaped occlusion structure  224  with channels  230  and valves  228 . In this instance, unidirectional umbrella occlusion structure  224  with channels  230  and valves  228  is disposed within a pocket formed on distal catheter extension  234  and between the distal end of catheter body  247  and the proximal end of nose-piece  241 . The nose piece  241  can be a tapered nose cone, a radiopaque marker band, a distally rounded piece of tubing or catheter, a blunt tube or any structure of about equal diameter to the catheter body. When in the radially constrained configuration, the unidirectional umbrella shaped occlusion structure  224  has an outside diameter that is about equal to the outer diameter of the catheter body  247 . 
     Referring to  FIG. 42 , four views of a preferred embodiment of the unidirectional occlusion structure of present disclosure is shown.  FIG. 42A  illustrates a two layered unidirectional occlusion structure  236  in its radially expanded configuration (also seen in  FIGS. 41B and 41F ), having a proximal end  238 , a distal end  240 , balloon  242 , balloon sheath  244 , channel  246 , valve structure  250 , outer balloon sheath tail  254 , balloon tail  256 , flow direction arrow  252  and flow exit  248 . When occlusion structure  236  is disposed on a catheter as in  FIG. 41F , fluid flows in the proximal to distal direction (antegrade) as indicated by arrow  252  through channel  246  and valve  250  and exits out the distal flow exit  248 . The antegrade fluid pressure on the inner surface of balloon sheath  244  at the distal end of channel  246 , causes distally directed displacement or deflection of the inner surface of balloon sheath  244  at valve  250 , thus allowing fluid to pass through flow exit  248 . When flow is reversed, fluid pressure on the outer distal surface of balloon sheath  244  at valve  250  causes the balloon sheath  244  to press against the distal surface of balloon  242 , closing valve  250  and preventing retrograde flow. Placing the unidirectional occlusion structure  236  in the opposite direction on the catheter will result in distal to proximal flow and prohibit proximal to distal flow. Although the occlusion structure of  FIG. 42A  is shown with two layers including an inner balloon and an outer sheath, it is understood that the sheath need not be present and a balloon with channels from the proximal surface to the distal surface is considered part of the present disclosure. Balloon  242 , including channels  246  can be formed by molding, extruding, vacuum forming or otherwise shaping a material to include the desired number and configuration of channels. Alternately, a standard balloon, including but not limited to, round or oval, can be modified to achieve proximal to distal channels. One method to modify a balloon is by forming longitudinal pleats circumferentially oriented, thereby forming V shaped channels that extend from the proximal surface of the balloon to the distal surface of the balloon. Placing a sheath over such a modified balloon in the same manner as described above would give the same result as the balloon shown in  FIGS. 42A through 42D . 
     Referring to  FIG. 42B , a side view of the unidirectional occlusion structure  236  of this disclosure is shown with proximal end  238  distal end  240 , balloon  242 , balloon sheath  244  and flow direction arrow  252 . 
     Referring to  FIG. 42C , a proximal view of the unidirectional occlusion structure  236  is shown with proximal end  238 , distal end  240  and channels  246 . 
     Referring to  FIG. 42D , a distal surface view of the unidirectional occlusion structure  236  is shown with proximal end  238 , distal end  240  and flow exit  248 . Flow exit  248  is formed as a space between balloon tail  256  and balloon sheath  254 . It is also possible to terminate balloon sheath  244  immediately below channels  246  forming a valve  250  that does not include balloon sheath tail  254 . 
     Referring to  FIG. 43 , an illustration of a prototype of the unidirectional occlusion structure  236  is shown in its radially expanded configuration with proximal end  238 , distal end  240 , balloon sheath  244 , balloon  242  (positioned inside balloon sheath  244 ), and channel  246 . This device was tested and will withstand at least 220 mmHg against its distal surface without retrograde flow. 
     Referring to  FIG. 44 , device  60  illustrates the unidirectional occlusion structure  272  in a radially constrained configuration adapted to the distal extension  267  of a catheter  265  with distal end  262 , proximal end  264 , proximal collar  266 , distal collar  268  (formed into a nose cone) and device pocket  270 . Proximal collar  266  and distal collar  268  can comprise a metal, such as a radiopaque marker band, heat shrink tubing or any plastic material such as polyurethane, polyethylene, polystyrene, acetal, PTFE, nylon or the like, and can be 1 mm to 20 mm in length, more typically from 2 mm to 10 mm in length. In this instance, circumferentially oriented occlusion structure  272  is held within pocket  270  of catheter  265 , with an outer diameter approximately equal to the outer diameter of catheter  265 . 
     Referring to  FIG. 44B , device  260  is shown with unidirectional occlusion structure  272  in its radially expanded configuration with proximal end  264 , distal end  262 , balloon  242 , balloon sheath  244 , valve  250 , flow exit  248 , channel  246 , flow arrow  252 , proximal collar  266 , distal collar  268 , catheter  274 , balloon fill lumen  270  and guidewire/injection lumen  276 . In this instance, there is no distal balloon sheath tail, the balloon sheath terminating on the balloon surface just below channel  246  and above the perimeter of catheter extension  267 , thereby positioning the flow exit between the termination of the balloon sheath and the catheter. 
     Referring to  FIG. 45A , device  280  is shown with catheter  282  and an umbrella shaped structure occlusion structure  2284  in its radially expanded configuration, whereby the umbrella shaped occlusion structure  284  is oriented circumferentially about catheter  282  such that its outer circumference is 360 degrees about catheter  282 . When device  280  is placed in an artery or vein and umbrella shaped occlusion structure  284  is placed in its radially expanded configuration, the outer perimeter of occlusion device  284  will be at least in contact with the interior of the vessel wall and substantially occlude flow.  FIG. 45A  shows occlusion structure  284  in forward V orientation and  FIG. 45B  shows device  282  with the umbrella shaped occlusion device  288  in a reverse V configuration. The occlusion structure of the present disclosure can also have a  90  degree orientation with respect to the catheter when in its radially expanded configuration. 
     Referring to  FIG. 46A , device  290  is shown with proximal end  292 , distal end  294 , catheter  296 , two-way occlusion structure  299  in its radially expanded configuration, frame  298  and channels  2100 , whereby fluid can flow from proximal to distal or distal to proximal through channels  2100 . Although two channels are shown, two-way occlusion structure  298  can have 1, 2, 3 or any number of channels. 
     Referring to  FIG. 46B , device  2102  is shown with proximal end  2104 , distal end  2106 , catheter  2108 , and unidirectional umbrella shaped occlusion device  2110  comprising, frame  2111 , channels  2112  and radial valve  2114 , whereby fluid will flow from proximal to distal (antegrade) only, retrograde flow being prohibited by radial valve  2114 . Although device  2102  will allow only antegrade flow, if desired, device  2110  of apparatus  2102  can be configured to allow only retrograde flow and/or have a forward V configuration as shown, or, if desired, a reverse V configuration or an orientation 90 degrees with respect to catheter  2108 . 
     The frames  298  and  2111  of occlusion structure  2110  can be made of metal, such as shape memory metals nitinol or elgiloy, or plastic such as polyethylene, polyurethane, polystyrene, PTFE, acetal and nylon or elastic materials such as silicone or fabrics such as cotton and rayon and can include a mesh, a wire frame, a diaphragm and can be pleated or otherwise folded or can be any other convenient structure or material provided that it is of sufficient strength and porosity to occlude elevated vascular pressures and capable of integrating channels and valves. Valve  114  can be made from flexible or rigid plastics including polypropylene and polyurethane, elastomeric materials such as silicone and can have a configuration including a flap, sock, cone, duck bill and diaphragm or the like with a thickness of 1 mil to 50 mil, more typically 2 mil to 10 mil. 
     Referring to  FIG. 47A , a distal surface view of a unidirectional occlusion structure  2120  of the present disclosure is illustrated with the catheter  2122  (extending forward), device frame  2124 , radial valve  2125  and channels  2126  disposed under radial valve  2125 . As shown, radial valve  2125  extends radially outward from catheter  290  and covers all four valves. Four channels are shown in this example; however, any number of channels can be used. This configuration allows flow from the proximal surface to the distal surface of unidirectional umbrella shaped occlusion structure  2120 ; however, the reverse flow is also possible. 
       FIG. 47B  illustrates another embodiment of the present disclosure comprising unidirectional umbrella shaped occlusion structure  2128  with catheter  2130  (extending forward), device frame  2132 , valves  2136  and channels  2134  disposed under valves  2136 . In this instance, each channel has a separate valve and although four channels and valves are shown, the device of this disclosure can have any number of channels and valves limited only by the size of the valve and channel and the area of the frames  2124  and  2132 . This unidirectional configuration allows flow from the proximal surface to the distal surface of umbrella shaped occlusion structure  2128 ; however, the opposite flow can be easily achieved by changing the flow direction of the valves or rotating the unidirectional occlusion device 180 degrees on catheters  2122  and  2130 . 
       FIGS. 48A and 48B  illustrate a prototype micro-valve  2140  configured from 5 mil polyurethane material. This device was tested and will restrain a fluid pressure of at least 220 mmHg applied against its distal surface. 
     Referring to  FIG. 49A , device  2142  is shown with triangular shaped occlusion structure  2145  in its radially expanded configuration and adapted to catheter  2144  whereby the occlusion structure  2145  has frame  2146  oriented circumferentially about catheter  2144  such that its outer circumference comprises 360 degrees. When device  2142  is placed in an artery or vein, frame  2146  is placed in its radially expanded configuration and the outer perimeter of device frame  2146  will be at least in contact with the interior of the vessel wall and at least substantially occlude flow. 
     Referring to  FIG. 49B , device  2148  is shown with catheter  2150  and a unidirectional triangular shaped occlusion structure  2151  comprising frame  2152 , channels  2154  and radial valve  2158 . Although reference has been made to a unidirectional occlusion valve with an umbrella shape or a triangular shape, it is understood that any shape including, but not limited to, rectangular, oval, conical, and round can be used. Yet another construction of a unidirectional occlusion structure is a dilation or occlusion balloon or any other medical balloon disposed with channels and valves, the valves extending from a proximal surface to a distal surface. 
     Referring now to  FIG. 50A to 50C , a method of deploying an occlusion structure  2191  from a radially constrained configuration to a radially expanded configuration and then returning it to the constrained configuration is shown.  FIG. 50A  shows a longitudinal cross section of device  2180  with a proximal end  2182 , a distal end  2184 , outer catheter  2186 , inner catheter  2188 , nose cone  2190  and radially constrained unidirectional occlusion structure  2191  with frame  2192 , valve  2194 , and frame attachment point  2196 . Unidirectional occlusion structure  2191  is attached to inner catheter  2188  at attachment point  2196  whereby occlusion device  2191  is preloaded with a force which encourages its distal end to pivot proximally outward at attachment point  2196 . In this instance, the outer catheter  2186  constrains occlusion structure  2191  against the preloaded force. Device  2180  is first positioned in the vasculature at or in the vicinity of a target structure. 
     Referring to  FIG. 50B , outer catheter  2186  is retracted proximally as shown by arrow  2200  while the inner catheter  2188  is held stationary, thereby removing the constraint on occlusion structure  2191 , allowing it to pivot outward and in a proximal direction at attachment point  2196  and into its radially expanded configuration. Frame  2192  can be made from a memory metal such as nitinol or elgiloy and pre-formed at attachment point  2196  to the radially expanded configuration thereby pre-loading an outward force on occlusion structure  2191  as it is moved to its radially constrained configuration. If a braided nitinol tube is used, it can be pre-formed into a radially expanded configuration whereby occlusion structure  2191  is oriented circumferentially about catheter  2144  with an outer circumference of 360 degrees. As in this example, the mesh can be coated with polyurethane, PTFE, silicone or the like and channels formed through the mesh and valves placed over the channels. 
     Referring to  FIG. 50C , outer catheter  2186  is retracted distally while holding inner catheter  2188  stationary thereby pivoting frame  2192  distally at attachment point  2198  and placing occlusion structure  2191  in its radially constrained configuration. 
     Referring to  FIG. 51 , an anatomical structure  2200  is shown with main artery  2202 , right artery  2204 , left artery  2206 , capillaries  2208 , tumor  2209  and blood flow directional arrows  2212 .  FIGS. 51A-51E  illustrates a method of the present disclosure wherein a tumor is embolized with drug eluting beads as in Transarterial Chemoembolization (TACE). 
     In a first step, device  2211 , comprising a two lumen catheter  2214  and a radially constrained unidirectional balloon occlusion structure  2216  (also in  FIG. 42 ), is advanced over a guidewire  2213  using lumen one (guidewire/injection lumen) of catheter  2214  from an entry point on the surface of the body, usually the femoral artery at the groin, and positioned at, or in the vicinity of, an artery feeding a tumor as in  FIG. 51A . As indicated by arrows  2212 , the blood flows in an antegrade direction over device  2211  and into capillaries  2208  of tumor  2209 . 
     In a second step, the unidirectional balloon occlusion structure  2216  is placed in a radially expanded configuration by inflating the inner balloon of the two layered device of  FIG. 42  using the second lumen of catheter  2214  (balloon inflation lumen) as seen in anatomical  FIG. 51B . When placed in a radially expanded configuration, normal blood pressure between about 80 mmHg and 130 mmHg urges valves  2217  of occlusion structure  2216  to the open position, thereby allowing antegrade blood flow through channels  2219  and into the capillaries  2208  of tumor  2209 . 
       FIG. 51C  illustrates a third step whereby chemoembolization particles  2218  are beginning to be injected into left artery  2206  and capillaries  2208  of tumor  209 . At this point, valves  2217  of unidirectional occlusion structure  2216  are in the open position and blood is flowing in the antegrade direction through channels  2219  which continues to carry chemoembolization particles  2218  into the vasculature of tumor  2209 . 
     Referring to  FIG. 51D , a fourth step is illustrated whereby chemoembolization particles  2218  begin to embolize the distal ends of capillaries  2208 , increasing pressure in the proximal section of capillaries  2208  and left artery  2206 . This back pressure causes blood flow and chemoembolization particles  2218  to flow in a retrograde direction; however, the back-pressure in left artery  2206  urges valves  2217  to close, thereby maintaining particles  2218  in the vascular compartment distal to occlusion device  2217 . Using currently available straight tip catheters, the chemoembolization procedure would be terminated at this point since particles would reflux backward over the catheter and into the general circulation causing non-target embolization and associated complications. 
       FIG. 51E  illustrates a fifth step, not possible using present catheters, whereby embolization particles continue to be injected, without retrograde reflux, and further fill the vasculature of the tumor with particles  2218 . This method can both prevent the complications associated with retrograde reflux and allow more particles to enter the tumor. 
       FIG. 51F  is a final step in the present method whereby occlusion structure  2216  is placed in a radially constrained configuration and device  2211  is withdrawn from the body over guidewire  2213 . 
     Although particular mention has been given to a device that is capable of transitioning from a radially constrained configuration to a radially expanded configuration, such a transition is not required. A unidirectional occlusion structure of the present disclosure can be configured in a permanently expanded configuration. In this instance, the occlusion structure may be a highly flexible material such as a low durometer plastic or rubber or a flexible mesh or any material or construction that provides sufficient strength and flexibility to navigate through vasculature and to a target and provide unidirectional occlusion. 
     Referring to  FIG. 52 , distal section  302  of a device is shown with distal end  303 , proximal end  304 , catheter body  306 , distal tip  308 , nose cone  310 , partial occlusion balloon  312  in a fully expanded configuration, channel  314  and one-way valve  316 . In this embodiment, flow is permitted in the proximal to distal direction through channel  314  and restricted, by one-way valve  316  to flow proximally. Partial occlusion balloon  312  can be any shape and diameters from 1 mm to 30 mm more typically from 2 mm to 10 mm. 
     Referring to  FIG. 53 , a longitudinal section  320  of a distal section of the device of the present disclosure is shown with catheter body  306  distal tip  308 , nose cone  310 , radially constrained balloon  322 , proximal balloon pocket boundary  324  and distal balloon pocket boundary  326 . Radially constrained balloon  322  sits within the pocket defined by the distal end of catheter  306  at boundary  324  and the proximal end of nosecone  310  at boundary  326 . The outer diameter of the constrained balloon is approximately equal to the outer diameter of catheter body  306 . This allows the balloon to sit within the pocket and maintain the catheter at a desirable minimal diameter. 
     Referring to  FIG. 54A , a distal section  330  of the device of the present disclosure is shown with catheter body  306 , catheter extension  307 , distal tip  308 , nose cone  310 , balloon pocket  332 , guidewire and injection lumen  334  and balloon inflation lumen  336 . The catheter body  306  has a diameter of 0.25 mm to 5 mm, more typically from 0.5 mm to 1.5 mm and a length of 10 cm to 240 cm more typically from 75 cm to 150 cm. The catheter extension  307  has a diameter of 0.25 mm to 3 mm more typically from 0.4 mm to 1 mm and a length of 5 mm to 100 mm more typically from 5 mm to 40 mm. The balloon pocket  332  has a depth equal to the difference in diameter of the catheter body  306  and the catheter extension  307  and a length of 1 mm to 50 mm more typically from 5 mm to 15 mm. The balloon wall thickness and inner diameter are selected, extruded or molded to fit into balloon pocket  332  with minimal balloon extending above of balloon pocket  332 . 
     Referring to  FIG. 54B , distal section  330  includes a balloon  338  in a radially constrained configuration held within balloon pocket  332  and having an outer diameter approximately equal to the outer diameter of catheter body  306 . 
     Referring to  FIG. 54C , distal section  330  includes balloon  338  in a radially expanded configuration with channels  314  and one-way valves  316  in a closed orientation. Partial occlusion balloon  338  can be any shape and diameters from 1 mm to 30 mm more typically from 2 mm to 10 mm and a length of 1 mm to 50 mm more typically from 5 mm to 15 mm. Channels  314  can be of any shape and configuration and an opening that is calibrated to the desired flow therethrough. In a preferred embodiment, the balloon will have a diameter of 6 mm and a channel diameter of 0.5 mm to 1.5 mm. Balloon  338 , including channels  314  can be formed by molding, extruding, vacuum forming or otherwise shaping a material to include the desired number and configuration of channels. Alternately, a standard balloon, including but not limited to, round or oval, can be modified to achieve proximal to distal channels. One method to modify a balloon is by forming longitudinal pleats circumferentially oriented; thereby forming V shaped channels that extend from the proximal end of the balloon to the distal end of the balloon. Placing a sheath or film over such a modified balloon results in longitudinal channels and a one way valve as described in co-pending application 61/917,131. 
     Referring to  FIG. 55A through 55C , a serial construction of the device of the present disclosure is illustrated. 
     Referring to  FIG. 55A , a longitudinal view of device construction  350  with catheter body  306 , distally located catheter extension  307  and proximally located hub  352  comprising guidewire and injection port  354  and balloon inflation/deflation port  356 . 
     Referring to  FIG. 55B , a longitudinal view of a device construction  350  is shown with added nose cone  310  and balloon pocket positioned between the distal end of catheter body  306  and the proximal end of nose cone  310 . 
     Referring to  FIG. 55C , a longitudinal view of the device  358  of the present disclosure is shown with catheter body  306 , balloon  340  and hub  352 . Balloon  340  is shown in a radially expanded configuration with channels  314  and valves  316  in the open position. 
     Referring to  FIG. 56 , an anatomical structure  360  is shown with tumor  362 , main artery  366 , distal main artery  367 , side branch arteries  370  and  374 , tumor capillaries  373 ,  375 ,  377  and  379  and blood flow direction arrows  368 ,  372 ,  376  and  378 . In the case of a tumor in the right liver lobe, artery  366  is the right hepatic artery and  367  is the distal right hepatic artery which flow toward the tumor as seen by flow direction arrow  368  and  378 . In this instance, artery  370  is the gastroduodenal artery and artery  374  is a hepatoenteric artery such as the superduodenal artery, the normal flow of both is away from the hepatic artery, as shown by flow direction arrows  372  and  376 , and into arterial networks which supply both the liver and gastrointestinal tract. Blood from the hepatic artery  366  also flows into the tumor capillaries  373 ,  375 ,  377 , and  379 . Normal blood flow through the right hepatic artery is in the range of 4 ml/sec. 
     Referring to  FIG. 57A through 57H , a tumor embolization method according to current medial practice is shown. At least some of the steps shown are used in current catheter based embolization therapy in tumors of the liver 
     The first step of the procedure is to advance guidewire  382  from the femoral artery at the groin, through the iliac artery, aorta, celiac artery, hepatic artery and into the right hepatic artery  366  as in anatomical structure  380  of  FIG. 57A . The diameter of guidewire  382  is typically from about 0.25 mm to 1.25 mm more typically from 0.4 mm to 1 mm. 
     In the second step of the procedure, illustrated in  FIG. 57B , guide-catheter  392  is advanced over guidewire  382  and along the same arterial path as for guidewire  382 . Typically, the guide catheter has an outer diameter of about 1.5 mm to 2.5 mm and has a central lumen that can accept a microcatheter with an outer diameter of 0.5 mm to 1.5 mm. The guide catheter is too large to access the vasculature in the vicinity of the tumor and is typically advanced as far along the vascular path toward the tumor as possible. The blood flow follows the same normal pattern as in  FIG. 56  and flows around the sides of guide catheter  392 . 
     In the third step shown in  FIG. 57C , guidewire  382  is optionally removed and replaced with a smaller diameter guidewire  398  that can fit in the central lumen of a microcatheter. Guidewire  398  typically has a diameter of 0.2 mm to 0.75 mm, more typically in the range of 0.25 mm to 0.6 mm. 
     The fourth step of the procedure, microcatheter  3104  is advanced over guidewire  398  to a position beyond the distal end of guide catheter  392  and into the vasculature within or in the vicinity of the tumor as shown in anatomical structure  3102  of  FIG. 57D . Microcatheter  3104  is advanced as close as is practical to the tumor and, if the anatomy allows, into the vasculature of the tumor as in superselective embolization. Microcatheter  3104  typically has a diameter of 0.75 mm to 1.5 mm, more typically at about 1 mm and a total length of 550 cm to 200 cm, more typically from 75 cm to 150 cm. The central lumen microcatheter  3104  is optimized to have an inner diameter as large as possible; however it is usually in the range of about 0.5 mm. 
     In a fifth step, guidewire  398  is removed from microcatheter  3104  as illustrated in anatomical structure  3200  of  FIG. 57E . Removal of guidewire  398  allows the central lumen of microcatheter  3104  to be used to inject drug and/or embolic materials into the target site within the right hepatic artery and tumor. Blood continues to flow around guide catheter  392  and microcatheter  3104  and into capillaries  373 ,  375 ,  377 , and  379  of tumor  362 , gastroduodenal branch  370  and hepatoenteric branch  374  according to the normal flow pattern shown by arrows  368 ,  372 ,  376 , and  378 . 
     In a sixth step illustrated in anatomical structure  3208  of  FIG. 57F , drug and or embolization agents are injected using a syringe or other means from the proximal end of microcatheter  3104  through guidewire/injection port  354  of hub  52  ( FIG. 55 ), longitudinally through guidewire injection lumen  334  ( FIG. 54 ), and out the distal end of catheter extension  307 . In this instance, embolic particles  3210  are carried by normal blood flow into distal right hepatic artery  3214 , tumor capillaries  373 ,  375 ,  377  and  379 , as illustrated by flow arrow  3212 , and into hepatoenteric artery  374  in the direction indicated by flow arrow  376 . Drug and/or embolization agents that travel through gastroenteric branch artery  374  or any other arterial branch distal to the distal tip of microcatheter  3104 , by normal forward flow, are deposited at non-target sites, including parts of the liver and intestine. This antegrade (to the catheter tip) bypass into distal hepatoenteric arteries can cause serious complications including damage or death to sections of the liver or intestine, gastric ulcers or even the death of the patient. Further, drug and/or embolic agents that travel to non-target sites, fail to enter the tumor; this resulting in a lower than optimal dose to be delivered to the tumor and a lower efficacy than desired. However, to avoid the aforementioned serious complications, physicians often under-embolize the tumor vasculature. 
     Referring to  FIG. 57G , as forward flow mediated embolization progresses, the distal ends of capillaries  373 ,  375 ,  377  and  379  fill with particles  3210  and become embolized. This process dramatically slows the blood flow moving through the tumor and causes a sharp rise in pressure within the tumor vasculature and concomitant retrograde deflection of the high volume blood flow from the hepatic artery. Further, backpres sure develops in the distal hepatic artery  3214 , resulting in particles to flow in a retrograde direction as in flow direction arrow  3234 . This can result in: (1) increased antegrade bypass into hepatoenteric branch  374 , reflux over the catheter and into gastrodudenal artery  370  and (3) a signal to the physician that particle injection should stop, even though the tumor is only partially embolized. In this instance, it is possible that larger capillaries become embolized first, due to a larger blood flow while smaller capillaries remain un-embolized. The rapid rise in pressure is in part caused by distal capillary embolization and in part caused by the high volume blood flow from the hepatic artery. Given that embolization is the desired endpoint, it appears that slowing the forward flow of blood from the hepatic artery would allow the tumor to accept the blood and drug and/or embolic agent flow for a longer period of time and allow more embolization to occur and an improved distribution of particles in the tumor vasculature. 
     Referring to  FIG. 57H , injection of drug and/or embolic agents is complete, microcatheter  3104  and guide catheter  392  are removed and the final embolization distribution in tumor capillaries  373 ,  375 ,  377  and  379  is shown where, in this example, lager capillary  379  is embolized to the greatest extent, smaller capillary  377  is embolized to a lesser extent and small capillary  373  remains un-embolized. 
     Referring to  FIG. 58 , a method of tumor embolization, according to the device of the present disclosure is shown. Steps 1 through step 5, shown in  FIGS. 57A through 57E , are the same for both a standard catheter as shown in  FIG. 57  and the device of the present disclosure and are not further illustrated. 
     Referring to  FIG. 58A , the device of the present disclosure is positioned in the distal right hepatic artery  3214 , with partial occlusion balloon  3256  in its radially expanded configuration comprising channels  3258  and  3260 , and one-way valves  3262  and  3264  that are in the open position.  FIG. 58A  shows two channels, however, one, two, three or any number of channels can be used. With or without valves. The maximum channel size is limited by balloon diameter, but can be as small as is practical. Valves  3262  and  3264  can be flap, duck bill, diaphragm, or any type of valve provided that it permits flow only in one direction. Optional pressure sensors  3266 , which provides real time pressure measurement in the vascular space distal to partial occlusion balloon  3256  and pressure sensor  3265  which provides real time pressure monitoring in the vascular space proximal to the partial occlusion balloon  3256  are shown. Pressure sensor  3266  which measures pressure in the distal vascular space can be used to signal a procedural endpoint based on a predetermined or non-predetermined pressure reading. This will, for the first time, allow a quantitative and definitive pressure mediated endpoint rather than the present subjective flow mediated endpoint and will enable the procedure to be reproducible and able to be standardized allowing center to center and physician to physician consistency. This is possible only because the vascular space distal to the partial occlusion balloon  3256  is isolated from the vascular space proximal to partial occlusion balloon  3256 , thereby allowing that the arterial pressure in the distal space to be closely related to the intra-tumor arterial blood pressure. Blood flow direction through hepatic artery  368 , distal hepatic artery  3214  and proximal artery  370  are normal as seen in flow direction arrows  368 ,  372  and  378  as is the blood flow in tumor capillaries  373 ,  375 ,  377  and  379  and illustrated by flow direction arrows  3212 . However, partial occlusion balloon  3256  causes a significant reduction in blood flow in distal right hepatic artery  214  and in tumor capillaries  373 ,  375 ,  377  and  379 . Blood flow can be regulated by the partial occlusion balloon of the present disclosure such that total flow can range from near 100% (unconcluded flow) to near 0% as in full occlusion. Of most interest is partial occlusion that results in 1% to 25% flow as compared to the un-occluded artery. Therefore, channels  3258  and  3220  allow only a fraction of normal blood flow to pass distally. Blood pressure distal to partial occlusion balloon  3256  is also dramatically reduced by anywhere from about 5 mmHg reduction to 100 mmHg reduction, depending on the nature of the occlusion. This pressure drop causes branch artery  374  to reverse direction as seen by flow direction arrow  376  and now flow toward the distal main artery  3214  and tumor capillaries  373 ,  374 ,  377  and  379 . The flow reduction and pressure reduction caused by partial occlusion balloon  256  also reduces the flow and pressure within the tumor capillaries  373 ,  374 ,  377  and  379 . This is of significance because it allows more drug/embolization agents to enter the tumor before backpressure causes flow stasis and retrograde flow. 
     Referring now to anatomical structure  3280  of  FIG. 58B , injection of drug and/or embolic agents is initiated. Blood flow from the proximal main artery  366  is attenuated as it passes through channels  3258  and  3260  and into distal main artery  3214 . The anti-cancer agents are carried by the attenuated forward blood flow through distal main artery  3214  and into tumor capillaries  373 ,  375 ,  377  and  379 . Valves  3262  and  3264  are in the open position as pressure in the distal vascular space is lower than the blood pressure in the vascular space proximal to partial occlusion balloon  3256 . Branch artery  374  continues to flow in the reverse direction as indicated by flow direction arrow  376  since blood pressure in the distal right hepatic artery is lower than that of the arterial network connected to the distal end of branch artery  374 . In this instance, antegrade drug/embolic agents are prevented from flowing into branch artery  374  and antegrade bypass and non-target delivery does not occur. Optional pressure sensors  3266  and  3265  or pressure measurement through guidewire/injection lumen  334  of catheter  6  ( FIG. 54A ) can be used to monitor real-time pressure. 
     Referring to  FIG. 58C , and looking at anatomical structure  3290 , a slower rate of blood flow and lower pressure through distal hepatic artery  3214  allows tumor capillaries  373 ,  375 ,  377  and  379  to fill at a slower pace and to a greater distribution than in the current method of full unregulated forward flow. At some point, however, the embolization of tumor capillaries will cause retrograde deflection of blood and anti-tumor agents and a pressure build up in distal hepatic artery  3214  as in  FIG. 58D . At this point, the increased pressure in distal right hepatic artery  3214  causes valves  3262  and  3264  to close, preventing retrograde flow and non-target embolization through branch artery  370  or any other arteries proximal to partial occlusion balloon  3256 . This retrograde deflection and pressure build up will progress at a slower rate as compared to the current standard method of  FIG. 57 . The slower buildup of pressure and retrograde flow allows a larger time window for the physician to terminate the procedure. If pressure monitoring is done, a defined pressure can be used to terminate the procedure. If the back pressure in distal hepatic artery  3214  exceeds about systolic pressure and/or mean arterial pressure, branch artery  374  will again follow in the normal flow pattern as illustrated in the flow direction arrow  376  of  FIG. 56 . This situation will allow antegrade drug and/or embolic agents to flow in branch artery  374  and to non-target sites. However, visual observation of contrast movement in branch artery  374  or a defined pressure measurement at or below the flow reversal pressure of branch artery  374  can be used as a procedural endpoint signal. 
     Referring now to anatomical structure  3300  of  FIG. 58E , the procedure is complete and catheter  3254 , of the present disclosure, and guide catheter  3252  are removed. The distribution and filling of tumor capillaries  373 ,  375 ,  377  and  379 , using the device of the present disclosure, are improved as compared to the distribution and filling associated with the current microcatheter  3104  of  FIG. 57H . 
     In some embodiments, a pressure feedback loop is implemented to control the rate of fluid introduction (e.g. the rate of embolic bead injection). In such embodiments, a blood pressure sensor may be located at the distal tip of the catheter to monitor the pressure of the vasculature distal to the occlusion or partial occlusion structure. In some embodiments, a predetermined pressure set point may be used. The set point may be an absolute pressure, or a percentage of systolic and/or mean arterial pressure (such as about 100% of systolic and/or mean arterial pressure). Such systems can be programmed to maintain the distal vasculature at or below the set point by automatically controlling the infusion rate (e.g. the rate or pressure of an injection pump.) By ensuring that the pressure of the distal vasculature does not exceed systolic and/or mean arterial pressure, retrograde and/or other undesirable blood flows can be prevented. 
     In some embodiments, a rate of pressure change can be used instead of or in addition to a preset pressure in the pressure feedback loop. For example, if the distal vasculature pressure begins to rise faster than a predetermined rate, the rate of embolic substance injection can be slowed, temporarily stopped, or a procedural endpoint may be signaled. The endpoint signal may be an audible, visual, tactile or other signal to persons involved in the procedure, and/or may be a signal that automatically shuts off or changes the state of medical equipment used in the procedure. 
       FIGS. 59A-59D  show the fabrication steps of the distal end of an occlusion catheter  400  according to aspects of the present disclosure. 
       FIG. 60  shows the completed distal end  402  of the occlusion catheter  400  of  FIGS. 59A-59D  being introduced into small branches of a vascular system  404 . The two enlarged contact points  406  and  408  of this design allow the catheter  400  to be navigated into smaller vasculature than can be navigated by conventional catheter tips. 
       FIG. 61A  shows an entire occlusion catheter constructed according to principles of the present disclosure.  FIG. 61B  shows details of construction features on the distal end  402  of the occlusion catheter  400  of  FIG. 61A . These details include a catheter extension  410  (which may comprise a coaxial inner catheter) extending from the distal end  412  of the catheter body  414 , which includes a balloon pocket section  416  and a distal tip section  418 . A nose cone radio-opaque marker  408  is located at the proximal end of the distal tip section  418 , and a radio-opaque marker  406  is located at the distal end of the distal tip section  418 . As previously mentioned, both markers  406  and  408  have enlarged diameters as compared with the diameter of the adjacent distal tip section  418 . 
     Referring now to  FIG. 62 , an axial cross-section of an alternative catheter balloon design is shown. In this design, a single balloon  560  is concentrically aligned over inner catheter  562 . During manufacture, balloon  560  is longitudinally bonded to inner catheter  562  in two locations  564  and  566 , circumferentially spaced 180 degrees apart. This arrangement provides two generally V-shaped channels  568  and  570  when balloon  560  is inflated, as shown. These longitudinal V-shaped channels keep balloon  560  from fully occluding a blood vessel by allowing a portion of the normal blood flow to bypass the balloon through the channels. By specifying and controlling the dimensions of this construction, predetermined bypass flow rates may be obtained. 
     The longitudinal bonds  564  and  566  may be formed by ultrasonic welding, heat staking, adhesive, fasteners, or other suitable arrangements. Inner catheter  562  many include flat portions or grooves where the bonds are located, as shown, or may have an entirely round circumference. In other embodiments (not shown), a single channel or more than two channels may be formed. The channel(s) may run the entire length of the balloon or less than the entire length. In some embodiments the balloon segments when inflated may be more rounded than those shown in  FIG. 62 . 
     Referring now to  FIGS. 63 and 64 , a catheter balloon having spiral channels is shown.  FIG. 63  shows one embodiment in a deflated configuration while  FIG. 64  shows the balloon in an inflated configuration. The balloon can be slender and elongated, and wrapped around the inner catheter in a spiral fashion leaving a spiral channel formed between windings. In this arrangement, the balloon can be inflated from its proximal or distal end. Alternatively, a larger balloon can be placed coaxially over the inner catheter and secured in place by a spiral wound wire. When the balloon is inflated, only the portions between the wire winding will inflate, leaving a spiral channel having a wire running along its inner diameter. In some embodiments, the coaxial balloon can be bonded to the inner catheter, as previously described but in a spiral rather than a straight fashion. Two or more wires or bonds can be placed in parallel, forming two or more separate but interlaced spiral channels. With any of these configurations, the spiral channels can be sized to provide the desired range of bypass flows across the occlusion balloon. 
     Referring now to  FIGS. 65-73 , additional embodiments are shown and described, as well as animal testing results and refined understandings of flow models for previously described embodiments. In conjunction with the following descriptions the following definitions are used: 
     A “Drug” includes, but is not limited to, embolic agents, therapeutic agents, anticancer agents, fillers, glue, foam, ablative agents, sclerotherapy agents, contrast agents, nutrients, and any fluid or material that can be delivered through the lumen of a catheter. 
     “Mean arterial pressure” is the mean blood pressure at a particular point or points in the arterial vessel system during a particular time period as the blood pressure varies between the systolic pressure and the diastolic pressure with each pulse. 
     “Normal mean arterial pressure” is the mean arterial pressure at a particular point or points in the arterial vessel system when no temporary occlusions are in place. 
     A “Target” is a tissue, organ, defined space within a tissue, part of an organ, tumor, or any other anatomical structure, in whole or in part, such as primary and metastatic tumors, prostate, uterus, pancreas, spleen, bladder, stomach, kidney, liver, gallbladder, thyroid, eye and bone and any other tissue or organ system in the human body. 
     A “Supply Artery” is one that delivers blood to the target and is in fluid communication with one or more collateral vessels, arteries, arterioles, capillaries, and/or anastomotic vessels. 
     A “Collateral” includes, but is not limited to, an artery, arteriole or capillary that branches from or anastomoses to and is in fluid communication, either directly or through interstitial flow, with the supply artery. Collateral Arteries supply normal tissues. 
     An “Anatomical Zone” is an area surrounding that portion of the supply artery that is distal to an occlusion. In some embodiments of the present disclosure, the supply artery distal to an occlusion has a pressure substantially lower than normal mean arterial pressure. 
     A “Normal Gradient” comprises arterial pressures that define normal flow circulation in the human body. 
     A “Redistribution Gradient” comprises arterial pressures that result from an occlusion in a Supply Artery which causes flow to redistribute and move toward a low pressure, into a target, and away from healthy tissues. 
     Blood flow follows pressure gradients. Normal (un-occluded) blood pressure in the supply artery is higher than that of the collaterals and the collaterals may have a pressure higher than that of the target. 
     In general, the normal pressure gradient (Normal Gradient) is as follows: Supply Artery&gt;Collaterals&gt;Target. The supply artery may have a pressure at or near the mean arterial pressure of the heart which is patient dependent, however, typically has a pressure in the range of 60 mmHg to 110 mmHg. According to aspects of the disclosure, the area of the supply artery distal to an occlusion of the supply artery is typically 10% to 60% below the normal mean arterial pressure at that area. 
     Under normal physiological conditions and due to the aforementioned normal pressure gradient, the supply artery flows into both the collateral arteries and into the target and is associated with interstitial flow in the surrounding Anatomical Zone. Thereby blood flow in a collateral vessel typically travels away from the supply artery and into healthy tissues. 
     Collaterals are arteries that branch from the supply artery and are connected to capillary beds that have more than one blood supply and inherently have pressure that may be attenuated below the mean arterial pressure of the supply arteries. When a temporary occlusion is introduced in the supply artery according to the present disclosure, a new pressure gradient (Redistribution Gradient) and related flow redistribution results. 
     A temporary occlusion is created using a balloon catheter or any other occlusive device or a partially occlusive device. In some embodiments, a partial occlusion device is configured to allow a bypass flow volume in the order of 5% to 25%. To ensure a large pressure gradient, in some embodiments the bypass flow volume is between 5% and 10%, inclusive. The occlusion device can be positioned on a catheter, needle, cannula or the like and can be delivered percutaneously, intravenously or surgically. 
     As a result of the occlusion, the area distal to the occlusion of the supply artery has a lower pressure than the Normal Mean Arterial Pressure of the Anatomical Zone. The occlusion causes the flow in the supply artery to stop, or be substantially reduced, and new pressure gradient is Collaterals&gt;Supply Artery&gt;Target. In this instance, flow redistribution moves blood from the collaterals and into the target through the supply artery (Redistribution Gradient). 
     Targets that have terminal capillary beds will continue to accept flow from collateral arteries and the Anatomical Zone, whereby inward blood flow exits through the target into veins that have a very low pressure at about 10 mmHg. Targets can have sump like properties that “drain” the inflow of blood that moves toward the low pressure zone. Due to the terminal capillary beds, targets can have a lower pressure than collateral arteries and associated capillaries. 
     In this instance, mass flow of capillaries, arterioles and arteries of the Anatomical Zone will be directed toward the low pressure zone of the Target. This includes capillaries distal to the occlusion and in the vicinity of the Target. When drug is injected through the catheter, redistributed blood flow will carry the drug exclusively into the Target, and flow of the drug through the collaterals and into healthy tissue will not occur. During the time that the occlusion of the supply artery is in place, the area surrounding the low pressure anatomical zone will flush into the low pressure zone through the capillary beds that are normally fed by both the Supply Artery and other source arteries. To create this reverse flow from the capillary beds, a low pressure anatomical zone is maintained by the temporary occlusion. 
     In the case of tumor embolization, tumors have terminal capillaries and the aforementioned method will create flow into the tumor. In the case of prostate artery embolization (PAE), the prostate has terminal capillaries and the aforementioned method will create redistributed flow into the prostate. By performing the method on both of the main arteries feeding the prostate, ischemia in the entire prostate can be achieved, shrinking it by at least  10 %. 
     In the case of embolization therapy, such as in tumor embolization, pressure measured in the vessels distal to the occlusion can be used to quantitatively detect embolization endpoint as previously described, since pressure will rise as embolization of the target progresses. An automated injection system can control embolization agent injection pressure to maintain a favorable pressure gradient. 
     Referring now to  FIGS. 65 and 66 , a representative arterial system located adjacent to target tissue is shown.  FIG. 65  depicts the representative arterial system before occlusion, and  FIG. 66  depicts the same arterial system after a temporary occlusion is introduced. Blood flow direction is shown by arrows  503 . Before occlusion ( FIG. 65 ), blood flows from supply artery  501  into target artery  525  feeding target tissue  527 . Eventually blood makes its way into the terminal capillaries of target  527 . The terminal capillaries include the arterial side  531 , the venous side  533 , and the arterial venous interface  535  therebetween. 
     In addition to feeding target  527 , supply artery  501  feeds a first capillary bed  509  through a first collateral artery  505 , and a second capillary bed  511  through a second collateral artery  507 . Capillary beds  509  and  511  each contain hundreds of capillaries. Supply artery  501  typically will feed more than two capillary beds but only two are shown for ease of understanding. Reference numerals  517  and  519  depict the position of healthy tissue fed by first capillary bed  509 , and reference numerals  521  and  523  depict the position of healthy tissue fed by second capillary bed  511 . In addition to being fed by first collateral artery  505 , first capillary bed  509  is also fed by a secondary arterial supply  513 . Similarly, in addition to being fed by second collateral artery  507 , second capillary bed  511  is also fed by a secondary arterial supply  515 . Capillary beds  509  and  511  may each be fed by more than two arteries but only two are shown for ease of understanding. 
     Under a normal pressure gradient, the mean arterial pressure at each point along a blood flow path typically goes down as blood flows from supply artery  501 , through collateral artery  505 ,  507 , and target artery  525 , through arterial side capillaries  531  and into venous side capillaries  533 . This reducing pressure is what causes the blood to continue flowing through the arterial system. In some patients, a typical pressure gradient would include a mean arterial blood pressure of 90 mm Hg in supply artery  501 , a pressure of 60 mm Hg in collateral and target arteries  505 ,  507  and  525 , and a pressure of 20 mm Hg in terminal capillaries  529 . Typical flow rates could be about 3 to 5 ml/sec in the artery that feeds supply artery  501 , 2 to 3 ml/sec in supply artery  501 , and 0.5 to 1.0 ml/sec in collateral and target arteries  505 ,  507  and  525 . 
     As shown in  FIG. 66 , a balloon catheter  537  may be introduced into the arterial system of  FIG. 65 , such as through a femoral or radial artery. Once in place, balloon  539  may be inflated to partially or fully occlude a proximal portion of supply artery  501 . The target  527  continues to draw blood into it, acting as a sump. According to some aspects of the present disclosure, the mean arterial blood pressure in supply artery  501  drops 10 to 60% below its normal, un-occluded state in the vascular space distal to the occlusion. In some embodiments, the drop in pressure is between 5 and 90% below normal. In some embodiments, the drop in pressure is between 20 and 40% below normal. This drop in pressure causes a redistribution pressure gradient and redistributed blood flow, which includes blood flowing in an opposite direction in some vessels distal to the occlusion. In particular, blood flows in a reverse direction in collateral arteries  505  and  507 , and in the distal end of supply artery  501 , as shown by flow direction arrows  503 . Instead of blood flowing from supply artery  501  to capillary beds  509  and  511 , blood instead flows in a reverse direction from capillary beds  509  and  511 , through supply artery  501  and into target  527 . During this redistributed flow, capillary beds  509  and  511  are not adversely affected since they continue to be fed by at least secondary arterial supplies  513  and  515 , respectively. This redistributed flow ensures that embolization agents and/or other drugs emanating from balloon catheter  537  are carried toward target  527  and do not migrate into healthy tissue such as  517 ,  519 ,  521  and  523 . Partial blood flow past occlusion balloon  539  may be used to carry drugs from a region of supply artery  501  just distal to balloon  539  towards and into target  527 . 
     During the redistributed blood flow described above, and as a result of a lower pressure in the Anatomical Zone, it is believed that there is a general flushing of fluids toward the low pressure zone which protects healthy tissue from non-target drug flow. Initial testing indicates that lower pressure gradients and lower blood flows result in better tumor filling with embolization agents. 
     Referring now to  FIGS. 67 and 68 , a modified method will be described that is similar to the method previously described in relation to  FIGS. 65 and 66 . In  FIGS. 67 and 68  the catheter is moved up into target artery  651 , which is analogous to target artery  525  shown in  FIGS. 65 and 66 .  FIG. 67  shows the target anatomy un-occluded while  FIG. 68  shows an occlusion balloon  673  in place and inflated, causing a redistribution pressure gradient. 
     In this instance, target  663  can be an organ, tissue, tumor or any other anatomical structure that has a terminal capillary bed (i.e. empties directly into the venous system) such as a prostate, pancreas, liver, kidney or other organ, in whole or in part. The arteries, arterioles and capillaries of the target can have collaterals which feed networks that can be within another organ or tissue and have an arterial supply  675 . The target capillary bed  665  (having arterial side  667  and venous side  669 ) may have similar pressures to the capillary beds  659  and  661  which can be within an organ or tissue. Thereby flow may travel in either direction as seen by arrow  653  of  FIG. 67 . In  FIG. 68 , the occlusion balloon  673  of catheter  671  blocks the flow of target artery  651  and causes a pressure drop in the target  663 . When the pressure of target  663  drops, collateral arteries  655  and  657  flow only into target  663  as indicated by arrow  653  of  FIG. 68 . In this manner, drug delivery into an anatomical structure such as target  663  can be enhanced by occluding the artery or arteries that feed the target. The pressure in an anatomical structure can be lowered and blood and fluid flow will be directed exclusively toward the target anatomical structure. 
     Referring now to  FIG. 69 , a chart is provided showing pressure vs. time for an exemplary low pressure embolization method according to aspects of the present disclosure compared with a standard embolization procedure. The low pressure method is depicted by line  550  and the standard method is depicted by line  552 . For both methods the horizontal axis represents time (in minutes) elapsed since the pressure measurements started and the vertical axis represents the mean arterial pressure (in mm Hg) in the vascular space distal to the tip of the embolization catheter. At times 1 minute to 4 minutes, the line of the standard method ( 552 ) and the low pressure method ( 550 ) overlap at the normal mean arterial pressure which is, in this case 120 mmHg. In the standard procedure  552 , release of the embolization agent begins around 4 minutes. Because an occlusion device is not used, as the embolization agent is injected and the embolization progresses, the pressure increases above the mean arterial pressure to 150 mmHg at minute 7. Once the injection stops at 7 minutes, the pressure will no longer increase and over a time may return to the mean arterial pressure at minute 11 as the collateral arteries are able to accept the normal blood flow. In contrast to the standard embolization procedure, at minute 4 in the exemplary low pressure procedure  550  an occlusion structure, such as a balloon, is expanded into an occlusion configuration in the supply artery, as previously described. Since blood flow into the supply artery is partially or fully occluded by the structure, the pressure drops (sometimes to zero, or close thereto) and stabilizes at 80 mmHg, which is 40 mmHg below normal mean arterial pressure. The pressure drop is stable until embolization injection starts at minute 8. In this instance the pressure drops from 120 to 80 mm Hg, or about 33%. At minute 8 injection of embolization agent is begun through the balloon catheter into the supply artery. The injection is done at a low pressure and at a slow flow rate to ensure that the redistribution pressure gradient is maintained. In some embodiments, the embolization flow rate is maintained between 0.25 to 6 ml/minute and/or a flow rate that keeps the pressure rising slowly, such as in the example shown in  FIG. 69 . Between minutes 8 and 16, the tumor is progressively filling with more embolization agent and therefore accepting less blood from the supply artery, thereby allowing the pressure to rise. In this example, the tumor is embolized around minute 16, causing the pressure to level off at 100 mm Hg. The pressure leveling off or reaching a predetermined point may be used to signal the endpoint of the procedure. By using this low pressure and slow flow approach, the tumor can be filled more completely than with the standard procedure, and embolization agent can be kept away from healthy tissue adjacent the tumor. In initial testing, the methods disclosed herein allow a tumor to fill with 2.4 times as many microbeads of embolization agent compared with standard procedures. Initial testing indicates that the mean arterial pressure just distal of the occlusion should be kept below the starting pressure by at least 10 to 30% of the difference between the un-occluded starting pressure and the stabilized occluded pressure to maintain the Redistribution Gradient and optimal tumor filling. In the example of  FIG. 69 , the starting pressure is 120 mmHg and the stabilized occluded pressure is 80 mmHg, yielding a difference of 40 mmHg. 10 to 30% of this difference is 4 to 12 mmHg, so the pressure during tumor filling should be kept below 116 to 108 mmHg for optimal filling. The lowered pressure may be maintained by limiting the pressure and/or flow rate of the embolization agent. It should be noted that this pressure ceiling range also applies to dispensing other drugs in other procedures targeting certain target tissue and is not limited to dispensing embolization agent. 
     The following is a summary of an animal study conducted during the development of the methods and devices disclosed herein. 
     Animal Study Approach 
       FIGS. 70-72  show the in-vivo tumor flow model developed in Phase 1B of the testing. A capillary is inserted into a hepatic artery that has at least one or several branch hepatoenteric arteries, arterioles, anastomotic vessels and/or capillaries that normally flow away from the hepatic artery. The proximal end of the capillary is open producing a low pressure “pseudo-tumor”. When particles are injected as in  FIGS. 70-72 , the blood and particles can be collected.  FIG. 70  also illustrates a normal blood flow pattern in a patient with a tumor as indicated by arrows. Blood will flow away from higher pressure and toward lower pressure. Systolic pressure is higher than that of branch arteries, capillaries, and tumor, thereby blood flows both into the branch arteries toward healthy tissue and into the tumor. 
     Current Method: Presently, standard delivery catheters are used for tumor embolization. Typically, the catheter tip is positioned in an artery proximal to both the tumor and one or several branch arteries and capillaries that flow away from the tumor as shown in  FIG. 71 . When embolic agents are injected, the flow pattern remains normal as in  FIGS. 70 and 71  such that particles are distributed between the tumor feeder artery(s) and branch arteries that feed healthy tissues and organs. In addition, the right hepatic artery of  FIG. 71  is flowing at about 2-4 ml/sec. The extensive capillary beds of the tumor can normally accept this high rate of flow. However, at the onset of embolization, larger tumor capillaries become blocked, high intra-tumor pressure causes tumor flow to be progressively and sharply reduced; this limiting the extent of embolization (analogous to filling a tea cup with a fire hose). For these reasons, efficacy and reproducibility of present embolization therapy are far from optimal. 
     Occlusive Method: According to the method developed in Phase I and illustrated in  FIG. 72 , an occlusion balloon is expanded in the right hepatic artery to temporarily occlude flow. Immediately following the balloon inflation, the blood pressure distal to the balloon drops significantly and in the order of 10-50 mmHg. When the pressure is reduced distal to the occlusion, branch arteries and capillaries reverse flow, following the pressure gradient as in  FIG. 72 . Because the tumor has the lowest pressure, all blood flow is directed into the tumor whereby non-target flow into branch arteries no longer can occur. The tumor has extensive terminal capillary beds that exit into low pressure veins, thereby creating a sump-like effect that accepts the flow from the reversed side branches which have a much slower flow rate as compared to the unobstructed right hepatic artery. The net result is that all embolic agents are directed into the tumor at a reduced flow rate, whereby the tumor filling is improved while the surrounding non-cancerous tissue is protected. 
     Animal Study Protocol (Used for Phase IB and Phase II) 
     Using contrast injected through a guide catheter placed into the celiac artery and with fluoroscopic imaging, select locations for placement of the Inventive Occlusion Balloon Catheter and the AccuStick (Boston Scientific) Catheter as in  FIG. 70 . 
     Under fluoroscopic guidance, advance the Inventive Occlusion Balloon Catheter within hepatic artery to a position that is 2 to 6 cm proximal to the location selected for the AccuStick, making sure that there are branch arteries between the distal tip of the Inventive Catheter and the AccuStick. 
     Perform a laparotomy and use visual examination (with ultrasound assist), of the liver and associated arteries and identify the tip of the Inventive Catheter in the hepatic artery and the distal artery selected for insertion of the AccuStick. 
     Make a small incision in the arterial wall and insert the AccuStick into the artery. Secure with suture. 
     Connect the proximal end of the AccuStick to ⅛″ tubing, including an adjustable stopcock, and extend the tubing to a blood collection vessel as in  FIGS. 70-72 . 
     Using a Pendotech in-line pressure transducer connected to the proximal injection lumen of the Inventive Occlusion Balloon Catheter ( FIG. 76 ) measure blood pressure through the catheter with the balloon in the unexpanded configuration (P 0 , Standard Pressure). 
     Inflate the occlusion balloon and measure the pressure (P 1 ) at the tip of the catheter, noting flow of branch arteries via contrast injection. 
     While measuring blood pressure, begin to open stopcock of AccuStick (or 19 gauge needle) until the pressure reading at the tip of the catheter is 10-30 mmHg lower than Standard Pressure while collecting blood in a flask as seen in  FIGS. 70-72 , noting flow of branch arteries via contrast injection. Measure blood pressure (P 2 ). 
     Inject microparticles through the Inventive Occlusion Balloon Catheter while collecting blood. 
     Following the completion of microparticle injection, allow the blood to flow for an additional several minutes, and then close the stopcock. 
     Measure blood pressure (P 3 ). 
     Repeat the microparticle injection 2 more times with the balloon in its expanded configuration, collecting blood in a new vessel for each replicate. 
     Repeat the microparticle injection 3 times with the balloon in its unexpanded configuration, collecting the blood in a new centrifuge tube each time. 
     Repeat steps 1 through 10 on a second pig. 
     Isolate the microparticles using filtration and suspend in 250 μL of saline. Determine yield by weight (Phase 1B) or particle count. 
     Compare results from inflated balloon and uninflated balloon. Improved particle recovery from the balloon up condition as compared to the balloon down condition is considered to be a validation of the theory. 
     Discussion 
     As in the Phase IB Project Description, 2 animals will be used to test the in-vivo tumor model design that is illustrated in  FIGS. 70-72 . 
     The Phase 1B pig study has been completed and the results shown in FIGS. A, B and C (not adequately reproducible for patent application) which are contrast enhanced fluorographic images taken during the animal procedure. 
     Figure A (not in patent application) shows an angiogram of the vascular structure in the pig&#39;s liver showing artery  2  which is the right hepatic artery, artery  1 , a branch off the right hepatic and arteries  3 - 5  which are other hepatic and hepatoenteric arteries. The marker bands of the Inventive Catheter are seen in the common hepatic artery. In this figure the, contrast was injected through the guide catheter with its [balloon] positioned proximal to the Inventive Catheter tip. The tip of the guide catheter is positioned in the celiac artery as it exits the aorta. This positioning is the reason that the entire vascular tree is visualized. Since the guide catheter used in this study had a 5 Fr inner diameter, contrast was injected at a high flow and the vascular tree is relatively dark. 
     Also noted in FIG B (not shown) is the placement site of the “pseudo-tumor” catheter in distal artery  3 . The blood from the catheter placed in artery  3  was collected in a test tube as shown. 
     FIG B (not shown) is a fluorographic image of the Inventive Device placed in the common hepatic artery as evidenced by the marker bands. In this instance, the Inventive Balloon was down which is equivalent to a standard catheter that is currently used for tumor embolization. This time, contrast was injected through the Inventive Catheter and the angiogram (lighter because the slower contrast flow rate through a microcatheter) shows the same arterial tree as in FIG A (not shown) with arteries  1 ,  2 ,  3 ,  5  &amp;  6  visible. Artery  4  could not be seen because the contrast concentration was insufficient to visualize this artery. Figure C (not shown) illustrates what happens when the balloon is inflated. In this case only the tumor feeder artery  3  is visible. When contrast was injected using a power injector at about 3 ml/sec, contrast was forced up branch arteries  1 ,  2 ,  4  &amp;  5 , however once the contrast injection stopped, contrast in the branch arteries flushed back into the tumor feeder artery  3 , this demonstrating flow reversal of these non-tumor arteries. 
     Particle Injection: Embolic particles (100-300μ, Merit Medical) were injected under the conditions seen in both FIG B (not shown—standard condition) and FIG C (not shown—inventive condition). 
     According to the method as stated above, blood pressure would drop immediately following balloon occlusion and stabilize in the vascular compartment distal to the occlusion. In fact, it is this pressure reduction that causes flow reversal of branch arteries and blood flow directed exclusively into the tumor. Pressure was measured through the catheter using an in-line pressure transducer located at the proximal end of the catheter. According to the Phase 1 theory, the pressure in the vascular compartment distal to the balloon occlusion would immediately drop to a pressure lower than systolic, but not to zero. The pressure is non-zero because of the flow reversal of branch arteries and capillaries which are part of arterial networks. These networks inherently have a pressure due to the multiple sources that are feeding the network. In this instance, the blood pressure in the networks is attenuated given the multitude of vessels in the network. As a point of interest, when the Inventive Catheter Balloon is up, the blood pressure that is measured is that of the arterial networks and inward flow of other vessels. In one experiment, the initial blood pressure is about 67 mmHg which rapidly drops when the balloon is inflated to below 35 mmHg, then stabilizes at about 48 mmHg, a pressure drop of 19 mmHg. During particle injection, the pressure reading is not attainable using this in-line sensor. Following injection, the pressure returns to about systolic. This data again meets the Phase 1 expectations. 
     The occlusion microcatheter of Phase 1 has been successfully developed and tested and is, at this point, clinically capable. In addition, it appears that the new animal study design is feasible and has already provided quantitative results that are consistent with the Phase 1 theory. 
     Phase IB Animal Study (For Set Up) 
     This study was used to test and optimize the proposed protocol prior to use in the final Phase I animal study. This study included 2 pigs and followed the protocol outlined above. For each animal there are 3 balloon up replicates and 3 balloon down replicates or 6 data points per animal. Following collection of the beads, the following table shows the data points from each animal averaged in the balloon up and balloon down cases: 
     
       
         
           
               
               
               
               
               
             
               
                   
               
               
                 Animal  
                 Balloon  
                 Balloon  
                 Delta 
                 Fold increase in 
               
               
                 # 
                 Down 
                 Up 
                 (g) 
                 bead capture 
               
               
                   
               
             
            
               
                 1 
                 0.45 g 
                 0.92 g 
                 0.47 g 
                 2.04 
               
               
                 2 
                 0.15 g 
                 0.22 g 
                 0.07 g 
                 1.46 
               
               
                   
               
            
           
         
       
     
     Discussion: The animal study of Phase IB showed a significant increase in particles collected when the balloon was up. This is consistent with the expected results and the theory set forth in the present project. However, as in FIGS. B and C (not shown), the difference between the balloon up and balloon down conditions appears to be visually greater than 2× and it was noted that weight differences are difficult to measure accurately since the cell strainer has a mass many times that of the beads. The total mass of beads that were injected was 1.0 g. It is noted that the total recovery in animal #1 is reasonable while that of animal #2 is low. It is believed that the tumor catheter leaked at the entry to the tumor artery due to an incomplete seal. 
     Conclusions: The animal protocol as in the Phase IB is shown to be quantitative and far better than that initially described. As such this new protocol will be used for the final Phase 1 study. The following improvements will be made: 
     Use particle count as a means to measure each condition rather than mass 
     Suture the tumor catheter in place and make sure there are no leaks throughout the study 
     Phase 1 Animal Study (Aim #3 of the Phase I Project Description) 
     The Animal Study Protocol of Phase IB, will be used. 
     Materials and Methods 
     Animals used: American Yorkshire Pigs, 75 Kg+15 Kg 
     Microbeads: CeloNova Embozene® Microsphere 
     400 μm—blue; REF 14020-S1 
     250 μm—yellow; REF 12020-S1 
     2 ml syringe reconstituted to 8 ml total with 100% contrast 
     Excess fluid removed after beads settle in syringe 
     Contrast (100%) added to help maintain bead constitution in fluid 
     2 ml beads+6 ml contrast=8 ml total volume 
     Split to (2) 1 ml samples of 4 ml each 
     Injected via stopcock using 1 ml injection syringe 
     Study Algorithm 
     24 data sets (12 pairs) Analyzed 
     First test date: 
     Pig 1: data rejected, abnormal vascular anatomy 
     Pig 2: 8 data sets (4 pairs) 3 pair analyzed
         250 μm &amp; 400 μm balloon up &amp; down (×2)
           2nd 250 μm data set not analyzed—clot blocked blood flow proximal to catheter   
               

     Pig 3: 6 data sets (3 pair) 3 pair analyzed
         250 μm balloon up &amp; down (×2)   400 μm balloon up &amp; down (×2)       

     Second test date:
         Pig 1: 6 data sets (3 pair) 1 pair analyzed
           250 μm balloon up &amp; down (×2)
               1st 250 μm data set not analyzed—placement too close to tumor model; no branch arteries between catheters   
               400 μm balloon up &amp; down (×1)
               Note: 400 μm would not reconstitute after collection—data not analyzed   
               
           Pig 2: 6 data sets (3 pair) 3 pair analyzed
           250 μm balloon up &amp; down (×2)   400 μm balloon up &amp; down (×1)   
           Pig 3: 4 data sets (2 pair) 2 pair analyzed
           Anatomy limited testing to 1 catheter location   250 μm balloon up &amp; down (×1)   
           400 μm balloon up &amp; down (×1)       

     Bead Count Methodology 
     Beads collected in cell filter
         Falcon, 70 μm filter   Cleaned with water       

     Beads mixed with 25 ml water 
     Magnetic mixer homogenizes beads 
     250 μm analysis:
         100 μl pipette placed on slide       

     400 μm analysis:
         250 μl pipette placed on slide       

     3 samples taken for each collection
         Min/Mid/Max   Counted under microscope       

     Extrapolate to full 25 ml mix
         Ex: bead count/pipette volume*25 ml solution=beads collected       

     Discussion 
     The in-vivo model described herein is intended to emulate anatomical structure and flow dynamic properties associated with a tumor in the human liver. The low pressure pseudo-tumor described herein is characteristic of a tumor which functionally behaves like a sump since the vast capillary bed within a tumor empties directly into veins that have near zero pressure. Examination of contrast flow with the balloon down (straight tip catheter) and the balloon up (occlusive condition) demonstrate flow redistribution in favor of the pseudo-tumor when the balloon is occlusive. It is therefore not surprising that injection with the balloon up always resulted in a much higher (average 2.4 times) amount of beads collected. Furthermore, it is evident that when the balloon is down, fewer beads are collected and the balance of the beads are randomly distributed among the branch arteries and healthy tissues. The bead collection results of this study are summarized in the table of  FIG. 73 . 
     It is noted that Bead recovery may be impacted by multiple sequential bead injections in the same animal due to embolization of branch arteries. We believe that this favors the balloon down condition since non-target flow into occluded arteries cannot occur. In order to minimize this effect, the first injection was done at a location closest to the low pressure zone and the second injection furthest from the low pressure zone. It is likewise noted that the pseudo-tumor is never embolized and remains as a “sump”. This too will impact the relative bead collection between the balloon up and balloon down conditions. Further study is needed to elucidate a broader understanding of embolization at a low pressure. 
     Conclusions of Animal Study 
     The in-vivo flow simulation of a liver tumor shows that balloon occlusion consistently results in a sizable increase in the quantity of embolic particles delivered to a “pseudo tumor”. The explanation for this phenomenon is clearly a function of pressure gradients that result from blockage of the high pressure supply artery and redistribution of blood flow in favor of the tumor. Normal unoccluded flow is driven by the supply hepatic artery that has the highest pressure and flow rate. Thereby the normal flow is characterized by the following pressure gradient: hepatic artery pressure is greater than branch arterial network pressure which is greater than tumor pressure. In contrast, when the hepatic artery flow is stopped, the ΔP between the branch arterial networks and the tumor creates a flow from the capillary networks into the tumor. It follows that balloon occlusion produces a favorable flow pattern that directs injected agents exclusively into the tumor and an absence of embolic agent flow toward healthy tissues. It is also speculated that occlusion of the high flow supply artery and subsequent redirection of branch arteries results in a substantial reduction in the rate of flow into the tumor, this allowing an improvement in tumor filling. We conclude that the mechanism behind the observed improvement in tumor filling is directly related to a low distal pressure that results from balloon occlusion. Low Pressure Embolization will enable a new era of tumor embolization with improvements in both safety and efficacy. The method should also make tumor embolization to be less technique dependent and provide improved center to center reproducibility. 
     It is important to note that in some embodiments of the present disclosure the devices regulate flow and pressure in the arterial space distal to the partial occlusion balloon, significantly reducing flow rate and pressure in tumor capillaries and cause flow reversal of distal branch arteries. These devices and methods thereby enable substantial elimination of retrograde and antegrade flow to non-target sites and a more complete filling of the tumor vasculature with drug and or embolic agents and should improve efficacy and reduce complications over standard devices and methods.