Patent Publication Number: US-2018042628-A1

Title: Methods And Devices To Remove Thromboembolic Material From Blood Vessels

Description:
FIELD OF THE INVENTION 
       
     
       
         
           
               
             
               
                   
               
               
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     The present invention relates to methods and devices for removing thromboembolic materials from blood vessels, including cerebral arteries, and for the treatment of Acute Ischemic Stroke. 
     DESCRIPTION OF THE PRIOR ART 
     Stroke is a leading cause of death and disability in the US with over 700,000 people suffering a major stroke and over 150,000 deaths each year. This tragic situation is expected to get worse as the “baby boomer” population reaches advanced age, and with increasing population obesity, which are two main contributing factors leading to stroke. Of those who survive a stroke, approximately 90% will suffer deficit including long-term impairment of movement, sensation, memory or reasoning, ranging from mild to severe. The total cost to the US healthcare system is estimated to be over $60 billion per year. Strokes may be caused by a rupture of a cerebral artery (“hemorrhagic stroke”) or a blockage in a cerebral artery due to a thromboembolism (“ischemic stroke”). A thromboembolism is a detached blood clot that travels through the bloodstream and lodges so as to obstruct or occlude a blood vessel. Between the two types of strokes, ischemic stroke comprises the larger problem, with over 600,000 people in the US suffering from ischemic stroke per year. 
     Ischemic stroke may be treated using a pharmacological elimination of the thromboembolism and/or by mechanical removal of the thromboembolism. Pharmacological elimination may be accomplished via the administration of thombolytics (e.g. streptokinase, urokinase, tissue plasminogen activator (TPA)), and/or anticoagulant drugs (e.g., heparin, warfarin) designed to dissolve and prevent further growth of the thromboembolism. Pharmacologic treatment is non-invasive and generally effective in dissolving the thromboembolism. However, significant drawbacks exist with the use of pharmacologic treatment. One such drawback is the relatively long amount of time required for the thrombolytics and/or anticoagulants to take effect and restore blood flow. Given the time-critical nature of treating ischemic stroke, any added time is potentially devastating. Another significant drawback is the increased risk of potential bleeding or hemorrhage elsewhere in the body due to the thombolytics and/or anticoagulants. 
     Mechanical removal of thromboembolic material for the treatment of ischemic stroke has been attempted using a variety of catheter-based transluminal interventional techniques. Most of such interventional techniques involve deploying a helical member into a thromboembolism in an effort to ensnare or envelope the thromboembolism so it can be removed from the patient. Although an improvement over pharmacologic treatments for ischemic stroke, such clot retrieval systems have only slightly increased clot removal success due to thromboembolic material slipping past or becoming dislodged by the removal devices. The dislodgement of thromboembolic material may lead to an additional stroke in the same artery or a connecting artery. 
     Another interventional technique involves deploying a basket or net structure distally (or downstream) from the thromboembolism in an effort to ensnare or envelope the thromboembolism so it can be removed from the patient. While such an approach overcomes the drawbacks of pharmacologic treatment, it requires extended manipulations of the basket or net and increases the danger of damaging the vessel and the potential of dislodging clot mass that also may lead to distal flow of thromboembolic material. 
     Latest interventional techniques for treating ischemic stroke involve advancing a suction catheter to the thromboembolism with the goal of removing it via aspiration (i.e. negative pressure Although generally safe, removal via aspiration is only effective with relatively soft thromboembolic material. When facing a more organized clot mass, such aspiration catheters tend to get clogged and require removal of the catheter, catheter cleaning, and repeating aspiration of remaining clots. Such techniques also carry clot dislodgement and additional stroke risk. 
     Interventional techniques described in the prior art are sub-optimal for treating ischemic stroke. The present invention is intended for improvement of the weaknesses of the prior art by providing blood clot removal devices and methods capable of efficient removal of the blood clots from large and small cerebral vessels. Particularly, the present invention provides methods and devices to remove emboli from cerebral vessels that minimize separation of the blood clot mass to be removed, which could escape and travel distally. 
     SUMMARY OF THE INVENTION 
     The devices and methods of the present invention are suitable for shielding and removal of thromboembolic material from the human cerebral arteries and treatment of Acute Ischemic Stroke. The devices may also be deployed and used in other endovascular locations and ducts throughout the body. 
     The clot or thromboembolic material removal devices of the present invention typically comprise a guard assembly device having a placement catheter, a shielding device including a pusher wire and at least one expandable braid attached to the pusher wire and deliverable through the placement catheter, and an aspiration catheter and aspiration pump with clot collecting accessories. 
     When the expandable braid is released outside of the placement catheter beyond the location of the thromboembolic material, it expands outwardly against the blood vessel wall forming a shield that prevents thromboembolic mass or any of its parts from distal flow. Then, the aspiration catheter is activated to remove thromboembolic material. 
     In a preferred embodiment of the present invention, a guard device for thromboembolic material removal from a blood vessel is provided and comprises a placement catheter having at least one axial lumen, and a shield device comprising a pusher wire with an expandable braid assembly attached to its distal end and deliverable through the lumen of the placement catheter. The expandable braid assembly is movable during deployment from a first delivery position to a second placement position, where in the first delivery position the expandable braid assembly is in an unexpanded position inside the placement catheter having a nominal first diameter, and where in the second position the expandable braid assembly is in a radially expanded position having a second nominal diameter greater than the first nominal diameter when deployed within the vasculature of a patient. 
     In another embodiment, the shield device with expandable braid assembly traverses concomitant bends as the placement catheter when delivered through the placement catheter to the thromboembolic material location. 
     In another embodiment, the expandable braid assembly has a distal end/tip that prevents a very distal end of the expandable braid from fully expanding when deployed from the placement catheter. The tip may be made of one of the following materials: metal, polymer, rubber, adhesive or any combination thereof. 
     In yet another embodiment, the expandable braid assembly has a preset expanded transverse shape including: circular, non-circular or a combination of both, and has a distal end/tip and a proximal end/tip that prevents both ends from fully expanding when deployed from the placement catheter. 
     In another embodiment, the proximal end of the expandable braid assembly expands to a cylindrical shape with a fully open proximal end. 
     In yet another embodiment the expandable braid assembly includes at least one radiopaque marker positioned on the distal end, on the proximal end, or on both ends. Such radiopaque marker may be positioned inside the expandable braid assembly on the outside surface of the expandable braid assembly, or on both locations. The radiopaque marker may be included in a radiopaque solder. A radiopaque component may also be included within the expandable braid assembly. 
     In another embodiment, the expandable braid assembly is at least as large as the treatment area and has a diameter that is at least 1.5 times larger in its expanded configuration versus its collapsed configuration when inside the placement catheter. Such braid may be formed from a plurality of strands of Nitinol wire having an outside diameter between 0.0005 inches and 0.002 inches and a pore size formed between strands in the expanded configuration of less than about 0.5 square mm. 
     In yet another embodiment the expandable braid assembly may be formed from a plurality of strands of Nitinol wire having multiple wire strands of equal dimensions, or of different dimensions, braided into the tubular shape using circular wire, oval wire, flat wire or any other suitable wire configuration or combinations. 
     In another embodiment, the expandable braid assembly may be also made of Nitinol/Platinum composite. 
     In another embodiment, the expanded braid assembly is configured to have a pre-set expanded diameter of the cross-sectional shape including one of the following configurations: circular shape, non-circular shape or a combination of both. 
     In another embodiment, the expandable braid assembly comprises between 8-72 strands made of a monofilament wire having a braid angle of 40 degrees or less in the collapsed configuration inside the placement catheter, the expandable braid assembly is configured to have an expanded braid angle between about 90-150 degrees and the expanded braid assembly outside diameter is between about 1 mm to about 8.0 mm. 
     In yet another embodiment, a friction reduction means is located on the surface of the expandable braid assembly to improve ease of deployment and retrieval out of and into the placement catheter. 
     In yet another embodiment, the expandable braid assembly is made of a monofilament wire having a closed pitch of about 5-50 picks per inch in the collapsed configuration inside the placement catheter and 20-100 picks per inch in the expanded configuration. 
     In another embodiment the expandable braid assembly has dimensional and material characteristics that result in higher radial forces on the proximal end of the braid. The expandable braid has the radial force exerted by the expandable braid assembly being close to zero when the expandable braid assembly is expanded. 
     In yet another embodiment the expandable braid assembly comprises one or more undulations including but not limited to twists, bends, folds, waves, changes in cross sectional profile, or other. 
     In another embodiment at least one elongate constraining member is extended at least partially through the expandable braid assembly. Such constraining member may enhance the radiopacity of the expandable braid assembly by having a radiopaque composition. 
     In another preferred embodiment, a guard device for thromboembolic material removal from a blood vessel is provided which comprises a placement catheter having at least one lumen extended longitudinally, and a shield device comprising a pusher wire with expandable braid assembly having at least two subsequent braids attached to its distal end of the pusher wire and slidable in the lumen of the placement catheter. The expandable braid assembly is movable during deployment from a first delivery position to a second placement position, where in the first delivery position the expandable braid assembly is in an unexpanded position inside the placement catheter having a nominal first diameter, and where in the second position the expandable braid assembly is in a radially expanded position having a second nominal diameter greater than the first nominal diameter when deployed within the vasculature of a patient. 
     In another embodiment, the shield device with the expandable braid assembly traverses concomitant bends as the placement catheter when delivered through the placement catheter to the thromboembolic material location. 
     In another embodiment, the dual expandable braid assembly comprises the following configurations: a larger distal expandable braid and smaller proximal expandable braid connected together, or one continuous braid having two different dimensions. 
     In yet another preferred embodiment, a guard device for thromboembolic material removal from a blood vessel is provided which comprises a placement catheter having at least one lumen extended longitudinally, and a shield device comprising a pusher wire with an expandable braid assembly having an inner expandable braid and an outer expandable braid attached to the pusher wire and deliverable through the lumen of the placement catheter. The expandable braid assembly is movable during deployment from a first delivery position to a second placement position, where in the first delivery position the expandable braid assembly is in an unexpanded position inside the placement catheter having a nominal first diameter, and where in the second position the expandable braid assembly is in a radially expanded position having a second nominal diameter greater than the first nominal diameter when deployed within the vasculature of a patient. 
     In another embodiment, the shield device with the expandable braid assembly traverses concomitant bends as the placement catheter when delivered through the placement catheter to the thromboembolic material location. 
     In another embodiment, the expandable braid assembly is configured with the proximal end of the outer expandable braid open-ended, the inner expandable braid located inside the outer expandable braid, the distal end of the inner expandable braid attached to the distal end of the outer expendable braid, and the pusher wire attached to the proximal end of the inner expandable braid. 
     In another embodiment, the inner expandable braid and the outer expandable braid are configured with the proximal end of the outer expandable braid open-ended, the distal end of the outer expandable braid having a tip, the inner expandable braid having a distal tip connected to the distal tip of the outer expandable braid, and a proximal tip attached to the pushing member. 
     In yet another embodiment, the outer larger expandable braid and smaller inner expandable braids are configured with the inner and outer expandable braids about the same length in the expanded configuration, the inner expandable braid being shorter than the outer expandable braid in the expanded configuration, or the inner expandable braid being longer than the outer expandable braid in the expanded configuration. 
     In another preferred embodiment of the present invention, a method for removing a thromboembolic material from a blood vessel is provided. The method provides a guard device including a placement catheter having an axial lumen and a shield device having a pusher wire attached to an expandable braid assembly and deliverable through the lumen of the placement catheter. The distal end of the placement catheter is passed through the thromboembolic material in the blood vessel, then the shield device is advanced through the placement catheter. The expandable braid is deployed such that the expandable braid is located distally beyond the thromboembolic material. Next, the placement catheter is withdrawn outside the blood vessel, and an aspiration catheter is introduced over the pusher wire to the proximal end of the thromboembolic material. The thromboembolic material is aspirated outside the blood vessel, the guard device and the aspiration catheter are removed outside the blood vessel. 
     In yet another embodiment, the expandable braid assembly is movable during deployment from a first delivery position to a second placement position. In the first delivery position, the expandable braid assembly is in an unexpanded position inside the placement catheter having a nominal first diameter. In the second position, the expandable braid assembly is in a radially expanded position having a second nominal diameter greater than the first nominal diameter when deployed within the vasculature of a patient. 
     In another embodiment, the proximal end of the expandable braid assembly expands inside the vessel to a cylindrical shape with a fully open proximal end and wherein the proximal open end of the expanded braid has one of the following dimensions: smaller than the size of the vessel, equal to the vessel size, or larger than the vessel size. In each case, a deployed expandable braid assembly provides distal protection to prevent thromboembolic material from moving distally. 
     In yet another embodiment, the expandable braid assembly exerts radial forces to the vessel wall when expanded to a conforming shape as the blood vessel, or a larger size than the vessel size. 
     In another embodiment, the placement catheter is positioned inside the blood vessel using a guidewire. 
     In yet another embodiment, the expandable braid assembly may be repositioned after deployment. 
     In another embodiment, the placement catheter is introduced to the treatment area through the aspiration catheter. 
     In yet another embodiment, the expandable braid assembly expanded inside the vessel is configured to have a pre-set expanded shape, including one of the following configurations: circular shape, non-circular shape or a combination of both. 
     In another embodiment the placement catheter has a sufficient flexibility to navigate the vasculature of the patient. The placement catheter comprises a proximal end, a distal end and an inner lumen, with the inner lumen having a diameter sufficient to receive the expandable braid in its unexpanded position and for advancing the unexpanded braid from the proximal end to the distal end of the placement catheter, and the expandable braid is configured to permit proximal retraction of the braid into the lumen of the placement catheter when the braid is partially or fully deployed outside the distal end of the placement catheter. 
     In yet another embodiment, the expandable braid assembly is retrieved inside the aspiration catheter to exert pressure against the thromboembolic material in a radially inward direction to facilitate removal of the thromboembolic material and to prevent the aspiration catheter from clogging. 
     In another embodiment, the aspiration catheter is pushed against the proximal end of the expanded braid assembly to exert pressure against the thromboembolic material in a radially forward direction to facilitate removal of the thromboembolic material and to prevent the aspiration catheter from clogging. 
     In yet another embodiment, the aspiration catheter and/or the shield device are repositioned during removal of thromboembolic material. 
     In another embodiment, the shield device is retracted into the aspiration catheter and removed from the blood vessel upon removal of thromboembolic material. 
     In yet another embodiment, a method for removing thromboembolic material from a blood vessel includes inserting a placement catheter through the thromboembolic material, and introducing a shield device having a pusher wire attached to an expandable braid assembly having at least two expandable braids into the placement catheter, wherein the proximal expandable braid is smaller and distal expandable braid is larger when in expanded position. The method also includes deploying the expandable braid assembly from the placement catheter distally to the thromboembolic material location, wherein the deployed dual expandable braid assembly provides distal protection to prevent embolic material from moving distally. The method also includes removing the placement catheter, introducing an aspiration catheter, aspirating thromboembolic material outside the body, and removing the aspiration catheter and shield device outside the body. 
     In another embodiment, the dual in line expandable braid assembly is retracted at least partially into the aspiration catheter when the aspiration catheter clogs. 
     In accordance with another embodiment of the present invention, the shield device comprises a pusher wire and an expandable braid assembly having at least two expandable braid sections: a larger distal braid section attached to the distal end of the pusher wire and a smaller proximal braid section movable at least partially along the pusher wire. When the shield device is in the expanded configuration, the distal braid provides distal protection to prevent embolic material from moving distally, while the proximal braid provides a separator or plunger that can be moved inside the aspiration catheter in case when the aspiration catheter is clogged. 
     In accordance with a further embodiment, the shield device comprises an internal stopper that prevents the proximal braid from collapsing when retrieved into the aspiration catheter when it is being unclogged. 
     In yet another embodiment, a distal portion of the aspiration catheter is advanced against the proximal expandable braid to exert pressure against the thromboembolic material in a radially forward direction to facilitate clot removal. 
     In another embodiment of the present invention, a method for removing thromboembolic material from a blood vessel includes inserting a placement catheter through the thromboembolic material, introducing a shield device into the placement catheter, deploying the shield device expandable braid at least partially from the placement catheter distally beyond the thromboembolic material location, wherein deployed shield device provides distal protection to prevent embolic material from moving distally, removing the placement catheter, introducing an aspiration catheter, aspirating thromboembolic material outside the body, and removing the aspiration catheter and shield device outside the body. A variety of shield devices may be used as described in the present invention disclosure. 
     In yet another embodiment, the shield device may be rotated during blood clot removal to cause the blood clot to wobble, shake or be disrupted to further expedite clot removal. The shield device may be rotated clockwise and/or anti-clockwise while pulling back the shield device into the aspiration catheter. 
     In another embodiment, maximum aspiration pressure is applied instantaneously to clots to avoid clogging of the aspiration catheter. 
     In yet another embodiment, the shield device engages into the clot material to be removed. When the shield device is rotated the clot material rotates as well. Also, when the shield device is repositioned longitudinally, the clot material moves too. 
     In another embodiment, the shield device comprises the expandable braid and an expandable separator. The expandable separator provides means to unplug a clogged aspiration catheter, while the expandable braid prevents particles or emboli from moving distally. 
     Several alternative shield devices are described in the present invention describing methods and devices to remove thromboembolic material from blood vessels. All shield devices of the present invention are designated to perform two fundamental functions: (i) distal protection and separation, or (ii) plunger function to facilitate unclogging aspiration catheters. Both these functions are performed by shield device regardless of its structure, such as a single device, assembly device, or combined device. Furthermore, other structures of the shield device may include but are not limited to: non-braids, expandable clot pullers and distal protection devices, and dual balloon device, among others 
    
    
     
       DRAWINGS DESCRIPTION 
         FIG. 1 —Illustrates a schematic view of a guard device for the removal of thromboembolic material from a blood vessel with a shield device inside the placement catheter (expandable braid assembly in a collapsed configuration). 
         FIG. 2 —Illustrates a schematic view of the same guard device as in  FIG. 1  with a shield device having dual inner and outer braids deployed outside the placement catheter (expandable braid assembly in expanded/released configuration). 
         FIG. 3 —Illustrates a schematic view of an alternative guard device with the shield device having dual in line expandable braids deployed outside the placement catheter (expandable braid in expanded/released configuration). 
         FIG. 4 —Shows another alternative version of the guard device with a shield device made of a single expandable braid assembly with tips located on both ends in an expanded configuration. 
         FIG. 5 —Shows another alternative guard device with a shield device comprising a pusher wire and a pusher tube attached to the shield device. 
         FIGS. 6A, 6B, 6C —Show alternative versions of the guard device that includes a retrieval sleeve. 
         FIG. 7 —Shows another alternative version of the guard device having a shield device comprising an expandable braid and an expandable separator. 
         FIG. 8 —Shows the placement catheter positioned proximally at the thromboembolic material location and the guidewire across the thromboembolic material. 
         FIG. 9 —Shows the placement catheter positioned across the thromboembolic material location with the shield device inside the placement catheter. 
         FIG. 10 —Shows the shield device deployed distally to the thromboembolic material location and the placement catheter removed. 
         FIG. 11 —Shows the aspiration catheter placed over the pusher wire of the shield device at the location of the thromboembolic material. 
         FIG. 12 —Shows the aspiration catheter clogged and the shield device pulled back into the aspiration catheter to unclog the aspiration catheter. 
         FIG. 13 —Shows the shield device pulled back into the aspiration catheter after successful aspiration/removal of thromboembolic material and ready for retrieval from the body. 
         FIGS. 14A &amp; 14B —Show alternative versions of the shield device. 
     
    
    
     DETAILED DRAWINGS DESCRIPTION 
       FIG. 1  illustrates a schematic view of the guard device  100  for removal of thromboembolic material from a blood vessel. The guard device  100  comprises the placement catheter  101  having an axial inner lumen  102  and a shield device  103 . The shield device  103  comprises a pusher wire  104  and a braid assembly  105 . The braid assembly  105  includes an inner expandable braid  106  having a proximal end  107  and an outer expandable braid  108  with an open proximal end  109  and a distal tip  110 . The pusher wire  104  is attached to the proximal end  107  of the inner expandable braid  106  using any suitable methods, including but not limited to bonding, gluing, welding, soldering, crimping or other applicable means. The shield device  103  is deliverable through the lumen  102  of the placement catheter  101 . The expandable braid assembly  105  is movable during deployment from a first delivery position as shown in  FIG. 1  (compressed position) to a second placement position as shown in  FIG. 2 . In the first delivery position, the expandable braid assembly  105  is in an unexpanded position inside the placement catheter  101  and has a nominal first diameter. In the second position, the braid assembly  105  is in a radially expanded position and has a second nominal diameter which is greater than the first nominal diameter when both the inner expandable braid  106  and the outer expandable braid  108  are deployed within the vasculature of a patient. For better visibility, radiopaque markers may be located on the distal end  110  and on the proximal end  107  of the inner braid  106  (not shown). 
     The proximal tip  107  of the expandable inner braid  106  connects with the pusher wire  104  and prevents a very proximal end of the inner expandable braid  106  from fully expanding when deployed from the placement catheter  101 . The distal tip  110  of the outer expandable braid  108  connects the inner expandable braid  106  and prevents the very distal end of the outer expandable braid  108  and inner expandable braid  106  from fully expanding when deployed from the placement catheter  101 . Such distal and/or proximal tips may be made from, but are not limited to, the following materials: metal, polymer, rubber, adhesive or any combination thereof. 
     During delivery of the guard device  100  to the treatment zones where thromboembolic material is located, the placement catheter  101  is navigated through bends and curves. In such situations, the shield device  103  traverses concomitant bends as the placement catheter  101  when delivered through the placement catheter  101  to the location of the thromboembolic material. 
     The outer surface of the expandable braid  108  may be covered with any suitable friction reduction polymer, including but not limited to Parylene (poly paraxylylene) or any other suitable polymers, to reduce the friction coefficient to improve ease of deployment and retrieval of the expandable braid assembly  105  into/out of the delivery catheter  101 . 
       FIG. 2  illustrates a schematic view of the guard device  200  (the same guard device  100  is shown in  FIG. 1  in unexpanded/compressed configuration) outside the placement catheter  101  with the expanded braid assembly  201  having the inner expandable braid  202  and the outer expandable braid  203  and deployed outside the placement catheter  101 . The inner expanded braid  202  (shown in compressed configuration  104  in  FIG. 1 ) and the outer expandable braid  203  (shown in compressed configuration  108  in  FIG. 1 ) may have a preset expanded transverse shape including one of the following configurations: circular, non-circular or a combination of both. The proximal end  109  of the outer expanded braid  203  is free and open, preferably opposed to a blood vessel wall (not shown) to cover a full cross-sectional area of the vessel wall to better capture any dislodged part of the thromboembolic material. 
     Radiopaque markers may be positioned outside of the braid assembly  201 , inside of the braid assembly  201 , or in both locations (not shown). Radiopaque markers may also include a radiopaque solder. Alternatively, the expandable braid assembly  105  may include radiopaque components within the expandable braid structure, or braid wires may be made of Nitinol/Platinum composite. 
     The expanded braid assembly  201  may should have at least 1.5 times larger diameter in its expanded configuration versus its collapsed configuration when inside the placement catheter  101  as shown in  FIG. 1 . The most common material to make the expandable braid assembly  105 / 201  is Nitinol or Nickel/Titanium alloy. The expandable braid assembly  105 / 201  may be formed from a plurality of strands of Nitinol wire having an outside diameter between 0.0005 inches and 0.002 inches, and having a pore size formed between strands in the expanded configuration of less than about 0.5 square mm. The strands of Nitinol wire may have the same diameter or different diameters, and may be formed using circular wire, oval wire, flat wire or any other suitable wire configuration or combinations thereof. 
       FIG. 3  illustrates a schematic view of an alternative guard device  300  for removal of thromboembolic material from a blood vessel. The guard device  300  comprises the placement catheter  101  having the axial inner lumen  102  and a shield device  301 . The shield device  301  comprises the pusher wire  104  and a braid assembly  302  attached together at an attachment area  309 . The braid assembly  302  includes a distal tubular larger braid  303  and a smaller proximal braid  304  attached together at an attachment area  307 . The braid assembly  302  may be made of one continuous braid shaped accordingly, or it may be made of two different braids attached together. The braid assembly  302  may have a radiopaque marker  306  located on the distal end  305  of the larger braid  303 . Another radiopaque marker  308  may be located within the attachment area  307  between the larger braid  303  and the smaller braid  304 , and yet another radiopaque marker  310  may be located proximally at the attachment area  309 . 
     The expandable braid assembly  302  attached to the distal end of the pusher wire  104  is deliverable through the inner lumen  102  of the placement catheter  101 . The expandable braid assembly  302  is movable during deployment from a first delivery position to a second placement position. The first delivery position of the expandable braid assembly  302  is in an unexpanded position inside the placement catheter  101  and has a nominal first diameter (not shown). The second position of the expandable braid assembly  302  is in a radially expanded position having a second nominal diameter greater than the first nominal diameter when deployed outside the placement catheter  101  and within the vasculature of a patient. The shield device  302  traverses concomitant bends as the placement catheter  101  when delivered through the placement catheter  101  to the treatment location. 
     The expandable braid assembly  302  may comprise between 8-72 strands made of a monofilament wire having a braid angle of 40 degrees or less in the collapsed configuration inside the placement catheter, and configured to have an expanded braid angle between about 90-150 degrees, and wherein the outside diameter of the expanded braid is between about 1 mm to about 30 mm. The braid assembly  302  may be formed from a plurality of strands having a pore size formed between strands in the expanded configuration of less than about 0.5 square mm. 
     The expandable braid assembly  302  may comprise between 8-72 strands made of a monofilament wire having a closed pitch of about 5-50 picks per inch in the collapsed configuration inside the placement catheter  101 , and when expanded to have 20-100 picks per inch. The expandable braid assembly  302  may have dimensional and material characteristics that result in radial forces on the distal braid  303  when expanded within the vessel. The expandable braid assembly  302  may also have radial force exerted by the expandable proximal braid  304  being close to zero when fully expanded. 
     An elongate constraining member  311  may be extended at least partially through the expandable braid assembly  302 . Such constraining member  311  may connect the distal end  305  of the braid  303  with the proximal end  309  of braid  304  and can be made of material that enhances the radiopacity of the braid assembly  302  by virtue of its composition. Examples of such constraining members include but are not limited to, a wavy platinum coil with inner metal core, radiopaque cable, or any other suitable structure. While the expandable braid assembly  302  shown in  FIG. 3  has a tubular shape, other embodiments of the expandable braid assembly  302  may include the distal braid  303  having a tapered configuration to fit vascular configurations that are either tapered distally or tapered proximally (not shown). The expandable braid assembly  302  may have one or more undulations, either partial or along the whole braid configuration (not shown). 
       FIG. 4  shows another alternative version of the guard device  400  having a shield device  401  comprising a single expandable braid  402  attached to the pusher wire  104  at the proximal end  403  of the expandable braid  402 . The radiopaque marker  405  is located on the distal end  404  of the expandable braid  402 . Another radiopaque marker  406  is located on the proximal end  403 . 
     The expandable braid  402  is movable during deployment from a first delivery position to a second placement position. The first delivery position of the expandable braid  402  is in an unexpanded position inside the placement catheter  101 , and has a nominal first diameter. The second position of the expandable braid  402  is in a radially expanded position having a second nominal diameter greater than the first nominal diameter when deployed outside the placement catheter  101  and within the treatment area or vasculature of a patient. The shield device  401  traverses concomitant bends as the placement catheter  101  when delivered through the placement catheter  101  to the treatment area. 
     The shield device  401  can be rotated, either through clockwise rotation as shown by arrow  407 , anti-clockwise rotation as shown by arrow  408 , or a combination of both. Rotation of the shield device  402  may be accomplished by rotating the distal portion  409  of the pusher wire  104 . The shield device  401  may also be moved back and forth (as shown by arrow  410 ) within the treatment area or into and outside the aspiration catheter  101  (not shown). While rotation and back-and-forth movement of the shield device  401  is described in reference to  FIG. 4 , such rotations and motions may be applied to all shield devices and embodiments of the present invention. 
       FIG. 5  shows a guard device  500  with a shield device  501  having an expandable braid  502 . A pusher wire  504  is attached to the distal end  503  of the expandable braid  502 . A pusher tube  506  is attached to the proximal end  505  of the expandable braid  502 . The pusher wire  504  is extended within the inner lumen  507  of the pusher tube  506 . The pusher tube  506  may be made of polymer, metal or metal alloy in such a way that allows free movement of the pusher wire  504  within the inside lumen  507  of the pusher tube  506 . The proximal end  508  of the pusher wire  504  allows the distal end  503  of the expandable braid  502  to be moved distally when the proximal end  508  of the pusher wire  504  is pushed in the distal direction. Thus, while holding the pusher tube  506 , the entire expandable braid  502  can be stretched to reduce its outside diameter. This feature may be helpful to ease placement, movement and delivery of the expandable braid  502  through the placement catheter  101  to the treatment location since the inner diameter  102  of the placement catheter  101  is much smaller than the size of the expandable braid  502 . The distal end  509  of the pusher tube  506  allows for longitudinal back and forth movement of the proximal end  505  of the expandable braid  502 . This feature may be helpful during removal of the expandable braid  502  outside the treatment location. By pushing the proximal end  508  of the pusher wire  504  distally and pulling the proximal end  509  of the pusher tube  506  proximally, the expandable braid  502  will undergo extensive stretching that may be helpful during the deployment of the expandable braid  502  though the placement catheter  101  and its retrieval into the aspiration catheter (not shown). 
     The shield device  501  with expandable braid  502 , attached pusher wire  504  and attached pusher tube  506  are movable during deployment from a first delivery position to a second placement position. The first delivery position of the expandable braid  502  is in an unexpanded position inside the placement catheter  101  and has a nominal first diameter, and the second position of the expandable braid  502  is in a radially expanded position having a second nominal diameter greater than the first nominal diameter when deployed within the treatment area of a patient. The shield device  501  traverses concomitant bends as the placement catheter  101  when delivered through the placement catheter  101  to the treatment location. The shield device  501  is movable distally during deployment using the distally attached pusher wire  502 , and retracted proximally using the pusher tube  506 . A radiopaque marker  510  may be positioned on the distal end  503  of the expandable braid  502 . Another radiopaque marker  511  is positioned on the proximal end  505  of the expandable braid  502 . 
     The shield device  501  may be rotated and repositioned back and forth within the treatment area as desired. By pulling/pushing the pusher tube  506  and pulling/pushing the pusher wire  504 , the size of the expandable braid  502  may be adjusted according to clinical need. The proximal portion  505  of the expandable braid  502  when retrieved back into the aspiration catheter (not shown) may provide a plunger or a separator to move blood clots proximally into the aspiration catheter in case the aspiration catheter becomes clogged (not shown). 
       FIG. 6A  illustrates a schematic view of an alternative version of the guard device  600  comprising a shield device  601 , a placement catheter  609  and Touhy Borst  606 . The shield device  601  includes a coaxial retrieval open-ended sleeve  602 , an open-ended expandable braid  603 , a pusher wire  604  attached to the distal end  610  of the retrieval sleeve  602 , and a pusher tube  605  attached to the distal end  611  of the expandable braid  603 . The pusher wire  604  attached to the distal end  610  of the retrieval sleeve  602  extends coaxially through a pusher tube  605  that is attached to the distal end  611  of the expandable braid  603 . The proximal end of the pusher tube  605  is secured to a double-sided Touhy Borst valve  606 . The proximal end of the pusher wire  604  passes through the double-sided Touhy Borst valve  606 , and may be selectively clamped down with the distal part  607  of the Touchy Borst  606  holding the pusher tube  605 , and the proximal part  608  of the Touhy Borst  606  holding the pusher wire  604 . Such a double-sided Touhy Borst connection allows for the pusher wire  604  and the pusher tube  605  to either be manipulated in conjunction with or independently from one another. The double-sided Touhy Borst valve  606  may also be entirely removed from the pusher tube  605  and the pusher wire  604  to facilitate removal of the placement catheter  609 . 
       FIG. 6B  shows the guard device  600  with the expandable braid  603  in the collapsed configuration and the attached retrieval sleeve  602  delivered through the placement catheter  609  in a serial fashion. The expanded braid  603  and retrieval sleeve  602  may be further advanced in this manner to the treatment site and through the thromboembolic material. 
     Alternatively,  FIG. 6C  shows the guard device  600  with the expandable braid  603  in the collapsed configuration inside the retrieval sleeve  602  delivered through the delivery placement catheter  609  in a parallel overlapping fashion. The system may be further advanced in this manner to the treatment location and through the thromboembolic material. 
     The expandable braid  603  is movable during deployment from a first delivery position to a second placement position. The first delivery position of the expandable braid  603  is in an unexpanded position inside the placement catheter  609  having a nominal first diameter, and wherein in the second position of the expandable braid  603  is in a radially expanded position having a second nominal diameter greater than the first nominal diameter when deployed outside the placement catheter  609  and within the vasculature of a patient. 
     The retrieval sleeve  602  incorporates a pusher wire  604  attached to its distal end  610 , the pusher wire  604  extends coaxially through the pusher tube  605  that is attached to the distal end  611  of the expandable braid  603  and moves independently. When pulling the pusher wire  604 , the expandable braid  603  collapses distally into the proximal open end of the retrieval sleeve  602 . The shield device  601  ( FIG. 6A ) traverses concomitant bends as the placement catheter  609  when delivered through the placement catheter  609  to the treatment location. 
       FIG. 7  shows an alternative version of the guard device  700  comprising a shield device  701  and the placement catheter  101 . The shield device  701  comprises an expandable braid  702  having a distal tip  707  and an expandable plunger or separator  703  attached to the proximal end  705  of the expandable braid  702 . The expandable braid  702  has a distal end/tip  707  to prevent the very distal end of the expandable braid  702  from fully expanding when deployed from the placement catheter  101 . 
     The pusher wire  704  is attached to the proximal end  706  of the expandable separator  703 . The pusher wire  704  and the expandable separator  703  may be made of two or more components attached together, or may be made from one pre-formed component. When an aspiration catheter (not shown) becomes plugged by clots and is unable to continue aspiration of thromboembolic material, the expandable separator  703  is designated to unplug the aspiration catheter by pulling, pushing and/or rotating the shield device  701  and clots outside and inside of the aspiration catheter. The expandable separator  703  may be rotated to macerate clots inside the plugged aspiration catheter (not shown) and may also engage clots to rotate and further push back and forth, or move inside the aspiration catheter (not shown). The expandable separator  703  shown in  FIG. 7  has a helical configuration to illustrate in general a plunger feature or plunger means that can be used to facilitate unclogging of the aspiration catheter when needed. Any suitable configuration of the expandable separator  703  may be considered, including but not limited to a circular structure, a non-circular structure, wire formed wing, looped wires, sinusoidal shape, basket shape, crossing wire shape, and/or a variety of bends. The shield device  701  may have several radiopaque markers  708 ,  709  placed along the shield device  701  for better visibility. The expandable separator  703  may be made of metal, metal alloys including Nickel-Titanium alloys, polymers or any combination thereof. 
     While the expandable separator  703  provides a means to un-plug the aspiration catheter in case such clogging of the aspiration catheter occurs, the expandable distal braid  702  provides a distal shield or protection to prevent clot particles or other emboli from moving distally. 
     The expandable braid  702  and expandable separator  703  are movable during deployment from a first delivery position to a second placement position. The first delivery position of the expandable braid and expandable separator are in an unexpanded position inside the placement catheter  101  having a first nominal diameter. In the second position, the expandable braid  702  and expandable separator  703  are in a radially expanded position having a second nominal diameter greater than the first nominal diameter when deployed from the placement catheter  101  and into the vasculature of a patient. The shield device  701  traverses concomitant bends as the placement catheter  101  when delivered through the placement catheter  101  to the thromboembolic material location. 
       FIGS. 8-13  illustrate how thromboembolic material is removed from a blood vessel according to different methods of the present invention.  FIG. 8  shows thromboembolic material or blood clots  800  located inside the blood vessel  801 . The placement catheter  101  having the axial lumen  102  is positioned in the vicinity of the blood clot  800 . A conventional guide wire  802  is introduced through the placement catheter  101  and crossed though the blood clot  800 . If blood clots are soft, a conventional guidewire  802  will easily cross the blood clot  800  as shown. However, if blood clots are older and well organized, the guidewire  802  may go around the blood clot  800  and between blood clots  800  and the vessel wall  801  (not shown). In either case, the distal portion of the guidewire  802  will be placed distally to the location of the blood clot  800 . Once the guidewire  802  is positioned beyond the blood clot  800 , the placement catheter  101  is pushed through blood clot  800  as shown in  FIG. 9 . If the guidewire  802  is placed around the blood clot  800 , the placement catheter  101  follows the same path (not shown). The placement catheter  101  is a part of the guard device described in the following figures. 
     Once the placement catheter  101  is positioned across the blood clot  800 , the guidewire  802  is removed and the shield device  900  is introduced into the placement catheter  101  as shown in  FIG. 9 . The shield device  900  can be one of several shield devices described in the present invention, and comprises the expandable braid  901  attached to the expandable separator  902 . The expandable braid  901  and the expandable separator  902  are attached proximal to the pusher wire  903 . The shield device  900  is pushed through the placement catheter  101  and is intended to be deployed distally beyond the blood clot  800 . The placement catheter  101  may be introduced to the treatment area, and location of the blood clot  800 , through the aspiration catheter (not shown). 
     The placement catheter  101  has a sufficient flexibility to navigate the vasculature of the patient and may comprise a proximal end, a distal end and an inner lumen, wherein the inner lumen  102  has a diameter sufficient to receive the expandable braid  900  and the expandable separator  901  in a collapsed unexpanded state, and for advancing the unexpanded braid  901  and unexpanded separator  902  from the proximal end to the distal end of the placement catheter  101 . The expandable braid  901  and expandable separator  902  are configured to permit proximal retraction of the braid  901  and the separator  902  into the distal end of the lumen  102  of the placement catheter  101  when the braid  901  and/or separator  902  are partially or fully deployed outside the distal end of the placement catheter  101 . 
     The shield device  1000  shown in  FIG. 10  is deployed across the blood clot  800 . The expandable braid  1001  is transformed from the unexpanded configuration  901  as shown in  FIG. 9  to fully expanded configuration  1001  shown in  FIG. 10 . Also, the expandable separator  1002  is transformed from the unexpanded configuration  902  shown in  FIG. 9  to the fully expanded configuration  1002  shown in  FIG. 10 . 
     The expandable braid  1001  and the expandable separator  1002  are movable during deployment from a first delivery position inside the placement catheter  101  to a second placement position outside the placement catheter  101 . In the first delivery position, the expandable braid  1001  and the expandable separator  1002  are in an unexpanded position inside the placement catheter  101  having a nominal first diameter. In the second position the expandable braid  1001  and the expandable separator  1002  are in a radially expanded position having a second nominal diameter greater than the first nominal diameter when deployed outside the placement catheter  101 . 
     The expandable braid  1001  may be configured to have a pre-set expanded shape including one of the following configurations: circular shape, non-circular shape or a combination of both. The expanded braid  1001  is configured to assume a radial configuration that opposes the blood vessel wall to prevent the expanded braid  1001  from moving freely along the vessel wall. 
     In  FIG. 11 , the aspiration catheter  1100  is introduced over the pusher wire  903  to the location of the blood clot  800 . The aspiration catheter  1100  traverses concomitant bends as the pusher wire  903  when delivered to the location of the blood clot  800 . The aspiration catheter  1100  may also be positioned over the placement catheter  101  during introduction of the shield device (not shown). When the aspiration catheter  1100  is positioned against the blood clot  800 , the aspiration pump (system) is activated as shown by arrows  1101 . Aspiration may be provided by any suitable vacuum source including but not limited to: any reusable aspiration pump(s) with suction containers, aspiration wall line in the hospital, or by manual, small disposable liquid vacuum pumps (not shown). 
       FIG. 12  shows the aspiration catheter  1100  clogged with a portion of the blood clot  1200  partially aspirated in to the aspiration catheter  1100  and too organized or hard to be further aspirated outside the patient. To ease and facilitate blood clot removal and move the portion of blood clot  1200  that blocks the aspiration catheter  1100  distally, the shield device  1000  may be pulled back into the aspiration catheter  1100 . When the shield device  1000  is pulled back into the aspiration catheter  1100 , the expanded separator  1002  will be first to enter into the aspiration catheter  1100  and force a portion of the blood clot  1200  that is clogging the aspiration catheter  1100  to move proximally. Such pulling of the shield device  1000  is done under aspiration, so the separator  1002  action will disrupt and separate the clogging blood clots  1200  and continue its aspiration outside the patient. 
     To achieve the same effect of unclogging the aspiration catheter  1100 , the aspiration catheter  1100  may be pushed over the pusher wire  903  distally causing the separator  1002  to enter the distal end of the aspiration catheter  1100  and moving the blood clots  1200  proximally. To further facilitate un-clogging of the aspiration catheter  1100 , the shield device  1000  may be moved back and forth as desired and rotated clockwise, anticlockwise or both. Such rotations may be done manually, in motorized fashion, or a combination of both. 
     When the shield device  1000  (pusher wire  903 , expandable separator  1002  and expandable braid  1001 ) is rotated as shown by arrows  1201 , the expandable separator  1002  engages the clot material  1200 / 800  and rotates it inside and/or outside the vessel  801 , thereby further unclogging the aspiration catheter  1200 , and removing the blood clot or thromboembolic material outside the patient. Longitudinally repositioning of the shield device  1000  as shown by arrows  1202  may provide additional help in moving clot material. 
     The expandable separator  1002  when retrieved inside the aspiration catheter  1100  exerts pressure against the thromboembolic material  1200 / 800  in a radially inward direction to facilitate proximal movement of thromboembolic material, thereby preventing the aspiration catheter  1100  from clogging. 
     The deployed expandable braid  1001  provides distal protection to prevent thromboembolic material from moving distally either after deployment of the shield device  1000  distally beyond the blood clots  800 , during the introduction of the aspiration catheter  1200  to the location of the blood clot  800 , or during manipulation (rotations and/or forth and back movement) of the shield device  1000  or aspiration catheter  1200  to unclog the aspiration catheter  1200 . 
     The expandable braid  1001  expands inside the vessel  801  to a generally cylindrical shape and may have a size smaller than size of the vessel  801 , equal to the size of the vessel, or larger than the size of the vessel. The expandable braid  1001  exerts radial forces on to the vessel wall when expanded to a larger size than the size of the vessel. The expanded braid  1001  expands to a conforming shape as the blood vessel  801  with or without exerting radial forces on to the vessel wall. 
     To make the blood clot removal process effective and to avoid clogging of the aspiration catheter  1200 , the highest possible aspiration pressure should be applied. The clot removal process will be most effective if the process of aspiration pressure build-up time is reduced and/or the maximum aspiration is applied instantaneously. 
     In the case where the shield device is used without a separator as shown in  FIG. 4 , the proximal end  403  of the expandable braid  402  provides an identical function as the expanded separator  1002 . The aspiration catheter (not shown in  FIG. 4 ) may be advanced against the proximal end  403  of the expanded braid  402  to exert pressure against the thromboembolic material in a radially forward direction to facilitate removal of thromboembolic material and to prevent the aspiration catheter from clogging. 
     Rotation of the shield device  1000  when the expandable separator  1002  and the expandable braid  1001  are outside the aspiration catheter  1100 , or when the expandable separator  1002  is partially inside the aspiration catheter  1100  as shown in  FIG. 12 , may initiate rotation of the blood clot  800  inside the vessel  801 . Such rotation of the blood clot  800  inside the vessel  801  may cause separation of the blood clot mass, and fragmentation and creation of small particles. While the distal flow of small particles will be prevented by the expandable braid  1001 , motions of the blood clot  800  within the vessel  800  and/or within the aspiration catheter  1100  may further dismember the blood clot and facilitate its removal outside the patient. 
       FIG. 13  shows the shield device  1000  (pusher wire  903 , expandable separator  1002  and expandable braid  1001 ) pulled back into the aspiration catheter  1100  after successful aspiration of thromboembolic material from the blood vessel  801 . 
       FIGS. 8-13  illustrate methods and steps to remove thromboembolic material from the blood vessel. While the shield device having the expandable braid  1001  and the expandable separator  1002  was shown in  FIGS. 8-13 , other shield devices as described in  FIGS. 2, 3, 4, 5, 6  can also be used deployed using the same steps and methods. The shield devices used in  FIG. 5  and  FIG. 6  differ from other shield devices. The shield device shown in  FIG. 5  includes the pusher wire  504  attached to the distal end of the expandable braid  502  and the pusher tube  506  attached to the proximal end of the expandable braid  502 . This unique shield device structure provides additional attributes with much expanded potential for distal protection and for un-clogging aspiration catheters. The expandable braid  502  may be pushed longitudinally during the introduction of the shield through the placement catheter  101  to the treatment area using the pusher wire  504 . The expandable braid  502  may be repositioned and retrieved into the aspiration catheter using the pusher tube  506 . The shield device shown in  FIG. 6  comprises a pusher tube  605  attached to the distal end of the expandable braid  603 . The pusher wire  604  is attached to the distal end of the retrieval sleeve  602 . The pusher wire  604  extends coaxially through the pusher tube  605  and moves independently. Pulling the pusher wire  604  proximally collapses the expandable braid  603  into the retrieval sleeve  602 . 
       FIG. 14A  shows an alternative version of the shield device  1400  deployed from the placement catheter  101  inside the vessel  801  and positioned distal to the clots  800 . The shield device  1400  comprises a braid  1401 , a pusher wire  1402  and a stopper  1403  positioned on the pusher wire  1402 . The larger distal braid  1404  has a tip  1407  with the radiopaque marker  1408 . The puller wire  1402  is attached to the distal braid  1404  at the tip  1407 . The braid  1401  comprises a larger distal braid portion  1404  and a smaller proximal braid portion  1405 . The proximal braid portion  1405  has a very distal end  1406  that is movable along the pusher wire  1402 . The stopper  1403  serves as a stopper preventing the very proximal end  1406  of the proximal braid  1405  from moving distally towards the distal braid  1404  (also known as braid squeezing) when the proximal end  1406  reaches the stopper  1403 . The stopper  1403  may be made of polymer, metal or a combination of both and is affixed to the pusher wire  1402  using any suitable attachment methods, including but not limited to gluing, welding, fusing and others. The braid  1401  may be stretched out to fit the inner lumen  102  of the placement catheter  101  when the shield device  1400  is delivered to the treatment site. 
       FIG. 14B  shows the same shield device  1400  as in  FIG. 14A . The proximal end  1406  of the braid  1405  is partially retrieved inside the aspiration catheter  1410 . During aspiration of the clots  800  into the aspiration catheter  1410  as shown by arrows  1411 , a portion  1419  of the clots  800  enters the aspiration catheter  1410  and often clogs the aspiration catheter  1410 , preventing clots from being aspirated. To un-clog the aspiration catheter  1410 , the braid  1401  is pulled into the aspiration catheter  1410  using the puller wire  1402  such that the proximal end  1406  and the portion  1405  of the braid  1401  enter inside the aspiration catheter  1410 . The proximal end  1406  and the proximal braid  1405  exerts pressure against the thromboembolic material  1419  that is clogging the aspiration catheter  1410  in a radially inward direction and facilitates proximal movement of the thromboembolic material outside the patient. The shield device  1400  may be moved back and forth and/or rotated to facilitate movement of the clots  1419  and un-clogging of the aspiration catheter  1410 . The stopper  1403  prevents squeezing of the proximal braid  1405  while it is pulled inside the aspiration catheter  1410 . Squeezing of the braid  1401 , particularly the proximal braid  1405 , may result in an increase in its predetermined outside diameter, and present an obstacle towards pulling the proximal braid  1405  inside the aspiration catheter  1410 . 
     To unclog the aspiration catheter  1410  and to move clots  1419  more proximally into the aspiration catheter  1410 , the aspiration catheter  1410  may alternatively be pushed distally over the pusher wire  1402  such that the proximal end  1406  and the braid  1405  will enter the aspiration catheter and move the clots  1419  proximally. 
     The braid  1401  of the shield device  1400  shown in  FIG. 14A  is deployed distally beyond the clots  800 . In an alternative embodiment, the proximal braid  1405  may be at least partially deployed within the clots  800  while the distal braid  1404  is fully deployed distally inside the vessel  801  (not shown). 
     The device and methods of un-clogging the aspiration catheter shown in  FIG. 14A  and  FIG. 14B  have similar functions and operational principles as other devices described: the proximal portion of the shield device serves as a plunger or separator for unclogging the aspiration catheter when needed, while the distal part of the shield device provides distal protection to prevent thromboembolic material from moving distally. 
     As shown in  FIGS. 10-14 , the expandable braids of the present invention have a diameter that is at least the same as the diameter of the treatment area, thus providing a proper distal protection function. Preferably, the radial forces of the expandable braid at the treatment area should be at least partially larger than zero. Sizes of the expandable braid may vary, but to facilitate the other function of declogging the placement catheter, the expandable braid should preferably have a diameter that is at least 1.5 times larger in its expanded configuration versus its collapsed configuration when inside the placement catheter. 
     The present invention is not limited to expandable braids having a uniform number of picks per inch (PPI) of braid or any particular dimensional characteristics. In one embodiment, the braid structure is uniform along the braid length with the same PPI. In alternative embodiments, the braid PPI of the proximal and/or distal end portions are either higher or lower than the PPI in the main body portion of the braid. In one embodiment, the PPI in the proximal portion is higher than those in the main body portion and the distal end of the braid, so that the radial forces exerted in the proximal portion are higher than the radial forces exerted in the main body portion and the distal end of the braid. 
     The radial strength along the length of the expandable braid may be varied in a few ways. One method is to vary the mass (wire size) along the length of the expandable braid. Another method is to vary the PPI along the length of the expandable braid. The use of higher a PPI will generally provide higher radial forces than those that have lower PPI. Varying the radial force exerted along the length of the expandable braid can be advantageous for use in guarding embolic obstruction so small dislodged particles will not flow distally around the expanded proximal portion of the braid and vessel wall. 
     Also, the radial force exerted by the expandable braid will reach zero value when the expandable braid is at its designed maximum expandable diameter. The radial forces of the expandable braid at the treatment area should be at least partially larger than zero. Sizes of the expandable braid may be varied, and preferably should have a diameter that is at least 1.5 times larger in its expanded configuration versus its collapsed configuration when inside the placement catheter. 
     Although the invention has been described above with respect to certain embodiments, it will be appreciated that various changes, modifications, deletions and alterations may be made to such above-described embodiments without departing from the spirit and scope of the invention. Accordingly, it is intended that all such changes, modifications, additions and deletions be incorporated into the scope of the following claims. Drawings and descriptions have been provided that relate to devices and methods for thrombotic material removal from blood vessels with focus on detailed method descriptions related to the expandable separator and expandable braid assembly attached to the pusher wire. However, the scope of the invention includes equally the application of devices and methods that are included in this specification.