Patent Document

RELATED APPLICATIONS 
   The present application is a US National Phase of PCT Application No. PCT/IL2003/000144, filed on Feb. 25, 2003, published as WO 2004/012628. This application also claims the benefit under 35 USC §119(e) of U.S. provisional application 60/400,801, filed on Aug. 05, 2002, the disclosure of which is incorporated herein by reference. 

   FIELD OF THE INVENTION 
   The present invention relates to devices for filtering embolitic material from circulating blood. 
   BACKGROUND OF THE INVENTION 
   Embolitic material comprising calcium, intimal debris, pieces of an artheromatous plaque and/or thrombi, has the potential of migrating and causing distal tissue damage, for example, stroke and/or myocardial infarction. (See Topol, E. J. and Yadov, J. S., “Recognition of the Importance of Embolization in Athereosclerotic Vascular Disease”,  Circulation  2000, 101:570.) Embolic material with the potential of distal tissue damage is often released during vascular interventional procedures, for example, stenting of an artheromatous region. 
   In response to the risk posed by released emboli during vascular intervention procedures, a mesh filter mounted on a specially adapted guidewire may be introduced into a blood vessel to strain released embolitic material from the circulation, thereby reducing the risk of distal tissue damage. To deploy such a mesh filter, a specially designed guidewire, for example having a built-in stop, may be placed in the blood vessel so that the stop is just distal to the target area. A collapsed filter is advanced along the guidewire until it is prevented from further advancement by the stop and opened so that it catches debris released from the target area. 
   Unfortunately, the specially designed guidewire is bulky and hard to manipulate due, in part, to the incorporated stop and accurate positioning of the filter is difficult once it has reached the guidewire stop. In addition, the use of a non-standard guidewire may require replacement or stocking of new catheterization sets. 
   Tsugita et al. in U.S. Pat. No. 6,361,971 B1 and US Applications 2002/0095174 and 2002/0183782, the disclosure of which is incorporated hereby in its entirety by reference, demonstrate filters and locking mechanisms. 
   SUMMARY OF THE INVENTION 
   An aspect of some embodiments of the invention relates to an embolism filter stop and method for its deployment, comprising a filter with one or more self-deploying stops attached thereto that stop the filter at substantially any desired location along a length of guidewire. 
   According to an exemplary embodiment of the present invention, the filter with its self-deploying stops can be deployed on guide wires in a variety of lengths and/or a variety of diameters. Alternatively or additionally, different stop designs and/or materials may be used for specific guidewires with specific properties, for example a flexible and/or small gage wire that may be used in fetal surgery. It is a particular feature of some embodiments of the invention, that the filter can be deployed on a substantially smooth guide wire, with no projections (where the filter is deployed) and/or with a uniform diameter in such a section. However, the filter can also be deployed with non-standard guide wires, for example, with a stepped or tapered diameter or with stops, ignoring or utilizing these stops, depending on the filter geometry. 
   In an exemplary embodiment, the at least one stop comprises is self-expanding, for example comprising a spring. Alternatively or additionally, the at least one self-expanding stop comprises a cushion made of, for example, a flexible rubber material. Additionally or alternatively, the at least one self-expanding stop comprises a fluid-filled flexible compartment containing compressed fluid, for example a gas that expands upon removal of a restrainer. 
   In an exemplary embodiment, a restrainer prevents the one or more stops from prematurely contacting and locking to the guidewire. Upon reaching the target tissue, the restrainer is pulled free and the stop self-deploys, fixing the filter in place. Optionally, the at least one stop comprises at least two stops that are, for example, symmetrically disposed around said wire and/or apply symmetric and/or equivalent force around the wire. Alternatively or additionally, the stops provide equal amounts of motion (e.g., while expanding) on opposing sides of the guide wire and/or on axially spaced locations on the guidewire, so that the placement of the filter is parallel to the guide wire, in some embodiments, an intentionally skewed placement of the filter may be desirable. 
   In an alternative embodiment of the invention, the stop is not self-deploying but is integral to and mechanically coupled to the filter and is activated other than by the guidewire. In one example, the stop is a deforming and/or expandable element, such as an inflatable balloon having an inflation port to which an inflation hose is attached. In an exemplary embodiment, the port self-seals following inflation of the balloon and removal of the hose. If the balloon is elastic, it can also be restrained after inflation. 
   Optionally, the filter defines a front and rear boundary and the at least one stop is connected to at least one of said boundaries. In an exemplary embodiment, the at least one stop is substantially contained between said boundaries, for example, so the overall length of the filter is conserved, allowing the filter to be easily maneuvered in the vasculature. Alternatively or additionally, said at least one stop projects beyond one or more of said boundaries. 
   An aspect of some embodiments of the invention relates to a filter that has some axial freedom of motion relative to a guidewire, after it is locked in place on a guidewire. In an exemplary embodiment of the invention, the filter deploys around a sleeve that travels along a guidewire, said sleeve having one or more stops shiftably attached thereto. In an exemplary embodiment, the shiftable stops allow the open filter to remain stationary in relation to the vascular environment even if the guidewire is moved a small amount. In this manner, a shiftable stop limits movement of the open filter that may cause trauma to the surrounding tissue, during for example, positional adjustments of a guidewire. 
   In an exemplary embodiment, the filter comprises one or more support members, for example struts that support the filter membrane and/or slide along the sleeve during deployment and/or collapse of the filter. 
   In an exemplary embodiment, a sleeve capable of traveling along a guidewire, comprising one or more self-deploying stops, is used in conjunction with one or more devices deployed in the vasculature or in other hollow organs of the body, for example an arthroscopic fiber optic cable, brachytherapy device and/or a laser, using these devices as its guidewire. 
   There is thus provided in accordance with an exemplary embodiment of the invention, an embolism filter adapted to selectively stop an embolism filter along a length of guidewire, said filter comprising: 
   a) a filter adapted to encircle a guidewire; and 
   b) at least one self-deploying stop attached to said filter and adapted to selectively stop movement of said filter. Optionally, said at least one stop comprises a spring. Optionally, said spring expands during deployment. 
   Alternatively or additionally, at least a portion of said stop is removably attached to said filter. 
   In an exemplary embodiment of the invention, said at least one stop comprises a cushion. Alternatively or additionally, said at least one stop comprises a chamber containing an expandable fluid. Optionally, said filter comprises a fluid release mechanism adapted to cause the release of said expandable fluid. 
   In an exemplary embodiment of the invention, said at least one stop is adapted to be restrained from contacting said guidewire by at least one stop restrainer. Optionally, said at least one stop is adapted to self-deploy upon removal of said restrainer. Alternatively or additionally, said restrainer comprises a material that changes configuration in response to contact with blood tissue. 
   In an exemplary embodiment of the invention, said at least one stop comprises at least one inflatable member. 
   In an exemplary embodiment of the invention, said at least one stop comprises at least two stops. Optionally, said at least two stops are radially disposed around said wire. Alternatively or additionally, said at least two stops are adapted to apply substantially equivalent force to said wire. 
   In an exemplary embodiment of the invention, said filter is adapted to collapse within a restrictive cavity. Alternatively or additionally, said filter is adapted to self-expand upon exiting a restrictive cavity. Alternatively or additionally, said restrictive cavity comprises a delivery sheath. Optionally, said delivery sheath is removably coupled to said filter. 
   In an exemplary embodiment of the invention, at least one of said one or more stops are adapted to move a limited distance along said filter. 
   In an exemplary embodiment of the invention, said filter comprises a sleeve surrounding said one or more stops. Optionally, said stops do not extend beyond at least one end of said sleeve. Alternatively or additionally, said filter is mounted on said sleeve and does not extend axially beyond said sleeve. 
   There is also provided in accordance with an exemplary embodiment of the invention, a method for stopping motion of a filter along a guidewire comprising: 
   a) positioning a guidewire in a blood vessel; 
   b) advancing along said guidewire a filter having at least one stop attached thereto; and 
   c) allowing said stop to self-deploy and engage said guidewire, thereby securing said filter along said guidewire. Optionally, the method comprises expanding said filter. Alternatively or additionally, the method comprises, collecting particulate matter in the filter. Optionally, the method comprises collapsing said filter with said collected particulate matter. Optionally, the method comprises removing said filter with said collected particulate matter from said blood vessel. Optionally, removing said filter comprises not removing said guidewire. 
   There is also provided in accordance with an exemplary embodiment of the invention, a guidewire stop, comprising: 
   a) a sleeve that slideably engages a guidewire; and 
   b) at least one self-deploying stop attached to said sleeve that selectively stops movement of said sleeve along said guidewire. Optionally, the stop includes a vascular filter having front and rear boundaries wherein said sleeve is attached to at least one of said boundaries. Optionally, said sleeve is extends beyond at least one of said boundaries. Alternatively, said sleeve is substantially contained between said boundaries. 
   There is also provide din accordance with an exemplary embodiment of the invention, an embolism filter adapted to selectively stop an embolism filter along a length of guidewire, said filter comprising: 
   a) a filter adapted to encircle a guidewire; and 
   b) at least one deformable stop attached to said filter and adapted to selectively stop movement of said filter. Optionally, said stop comprises an inflatable stop. Optionally, the filter comprises a removal sheath adapted to puncture said stop. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Exemplary non-limiting embodiments of the invention are described in the following description, read with reference to the figures attached hereto. In the figures, identical and similar structures, elements or parts thereof that appear in more than one figure are generally labeled with the same or similar references in the figures in which they appear. Dimensions of components and features shown in the figures are chosen primarily for convenience and clarity of presentation and are not necessarily to scale. The attached figures are: 
       FIGS. 1-3  are cross sectional schematic views showing the operation of an embolism filter and its self-deploying stops, in accordance with an exemplary embodiment of the invention; 
       FIGS. 4-6  are cross sectional schematic views of various embodiments of guidewire sleeves with stops, in accordance with an exemplary embodiment of the invention; 
       FIG. 7  is a schematic view of a sleeve and guidewire stop in combination with a filter, in accordance with an exemplary embodiment of the invention; 
       FIGS. 8A and 8B  are schematic views of a shiftable filter stop, in accordance with an exemplary embodiment of the invention; 
       FIG. 9  is a detailed cross sectional view of a filter during delivery in a blood vessel, in accordance with an exemplary embodiment of the invention; 
       FIG. 10A  is a detailed cross sectional view of a filter following deployment in a blood vessel, in accordance with an exemplary embodiment of the invention; 
       FIG. 10B  is a partial detailed cross sectional view of the filter shown in  FIG. 10A , in accordance with an exemplary embodiment of the invention; 
       FIG. 10C  is a head on view of the filter of  FIG. 10A , in accordance with an exemplary embodiment of the invention; and 
       FIG. 11  is a detailed cross sectional view of a filter during removal from a blood vessel, in accordance with an exemplary embodiment of the invention. 
   

   DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
   Filter with Spring Stops 
     FIG. 1  is a cross sectional view of a filter  100  contained within a delivery sheath  150 , in accordance with an exemplary embodiment of the invention. In an exemplary embodiment, filter  100  comprises stops  180  and  182  that are restrained from contacting a guidewire  102  by a restrainer  132 . During positioning of filter  100 , optional stabilizers  152  that project from a sheath wall  120  press against filter  100  to advance filter  100  along guidewire  102 . 
   Filter  100  and/or stops  180  and  182  may be designed in a variety of materials and shapes for example a range of guidewire diameters, for example a range of 1:1.5, 1:2 or 1:4 or any smaller, intermediate or larger ratio of diameters. Alternatively or additionally, in any specific design, filter  100  and/or stops  180  and  182  may be manufactured to encompass a guidewire of a specific diameter. Guidewire diameters for which filter  100  and/or stops  180  and  182  can be designed include, for example: 
   i) small gage flexible guidewires for use in peripheral vasculature, for example having a diameter of 0.014, 0.018, 0.032 or 0.035 inches; 
   ii) guidewires designed for coronary surgery, for example having a diameter of 0.014. 
   iii) specially designed guidewires designed for coronary interventions and/or fetal surgery, having diameters smaller than 0.014, greater than 0.035 and/or having non-standard diameters between 0.014 and 0.035 inches. 
   In an exemplary embodiment, restrainer  132  has a passage  134  that rides along wire  102  and permits movement of filter  100  distal to the target tissue location. 
   In an exemplary embodiment, a front boundary  122  of delivery sheath may be tapered to facilitate easy movement through the vasculature. Additionally or alternatively, front boundary  122  may be curved in towards wire  102 . Optionally, front boundary  122  comprises a flexible material so that it allows filter  100  to exit in spite of being unvaccinated. 
   In an exemplary embodiment, front boundary  124  of a sleeve wall  184  is tapered to ease advancement of filter  100  through the vasculature. Additionally or alternatively, a rear boundary  126  is tapered to facilitate retreat of filter  100  through the vasculature. 
   Optionally, stops  180  and/or  182  are contained internal to wall  184 , for example near or at front boundary  124  and/or rear boundary  126  of filter  100 , so the overall length of filter  100  is conserved. Having a shorter profile associated with internally contained stops  180  and/or  182 , may assist filter  100  in maneuvering in the vasculature. Alternatively or additionally, stops  180  and/or  182 , within wall  184 , project beyond front boundary  124  and/or rear boundary  126  of filter  100 . In an exemplary embodiment, stops  180  and/or  182  comprises springs, for example a spring steel, or resilient plastic. 
   Deployment of stops  180  and  182  may be actuated, for example, by using restrainer  132  that is remotely controlled, for example using an RF signal to cause its displacement and/or dissolution. Alternatively, other methods of actuation of stops  180  and  182  are contemplated, for example, restrainer  132  may dissolve or fall apart in the presence of blood or under the action of RF radiation or ultrasonic radiation. 
   In  FIG. 2 , delivery sheath  150  remains around filter  100  and stabilizers  152  press against filter  100  while restrainer  132  is pulled away from stops  180  and  182 , using a restrainer cable  130  to pull restrainer  132  in a direction  140 . In an exemplary embodiment, restrainer  132  has a length of between 1-4 centimeters. Optionally restrainer  132  is less than 1 or 0.5 centimeter in length when used, for example, with small stops  180  and/or  182 , designed for fetal and/or pediatric procedures. Optionally, restrainer  132  has a length of greater than 4 centimeters when used, for example, with stops  180  and/or  182 , for example, that are 3 or 4 centimeters or more in length for use when filter  100  is larger, for example where large amounts of particulate matter is anticipated that cannot be contained by a smaller filter. Restrainer  132  is optionally flexible in bending, even if it is not compressible, for example it may be segmented into narrow rings that are interconnected by a soft material. 
   Optionally, restrainer  132  is removed from contact with stops  180  and/or  182  by pulling restrainer cable  130  so that restrainer  132  shifts approximately 1 centimeter with respect to stops  180  and/or  182 . In pediatric and/or large vessel use, when smaller or larger stops  180  and/or  182  are used, restrainer  132  may require less than 1 centimeter or greater than 1 centimeter of movement to allow stops  180  and/or  182  to expand. 
   With restrainer  132  removed, stops  180  and  182  expand to contact guidewire  102  thereby fixing filter  100  in place along guidewire  102 . With filter  100  fixed in place, stops  180  and  182  stabilize filter  100  so that sheath  150  can be pulled away from filter  100  as seen, for example, in  FIG. 3 . 
   With delivery sheath  150  removed from filter  100 , a porous filter membrane  190  expands, for example as a result of blood flow pressure against it, to act as a filter, serving to strain particulate matter from the blood. Alternatively or additionally, filter  190  is made of resilient material that self-expands as it is freed of delivery sheath  150 . 
   Optionally, delivery sheath  150  is moved in a direction  142  against filter membrane  190 , thereby causing filter membrane  190  to collapse. With membrane  190  collapsed, filter  100 , guide wire  102  and sheath  150  are removed from the blood vessel. Using a guidewire of uniform diameter and/or without projections to aid in positioning filter  100 , is potentially advantageous as any number of additional devices, for example stents, can be interchangeably used with any guidewire  102  and any filter  100 . Stents of a variety of diameters, for example, can be stocked separately of guidewires  102  and/or filters  100  of different diameters. This reduces inventory costs associated with packaging each diameter of stent in multiple packages, each package containing a different diameter and/or design of guidewire  102  and/or filter  100 . 
   Sleeve with Inflatable Stops 
   In an alternative stop mechanism to spring stops  180  and  182 ,  FIG. 4  shows a cross sectional view of a sleeve stop  400  having an outer wall  402  from which one or more inflatable balloon stops  480  and  482  project. In an exemplary embodiment, sleeve is delivered to a target site and an inflation hose  484  connected to one or more inflatable balloon stops  480  and/or  482  is used to transfer fluid into balloons  480  and/or  482  thereby causing their expansion. Balloons  480  and/or  482  expand until they contact wire  102 , thereby preventing further movement of sleeve stop  400 . In an exemplary embodiment, a hose attachment port  486 , self-seals following inflation of balloons  480  and/or  482  and removal of hose  484 . 
   In an exemplary embodiment, fluid contained in balloons  480  and  482  is biologically inert so that its introduction into the blood stream will not cause any untoward sequella. In an exemplary embodiment, sleeve stop  400  may be removed from the blood vessel without removing guide wire  102 , for example using the following technique: 
   1. A sheath having one or more sharp projections at its leading edge, for example, is fed along guidewire  102  until its leading edge contacts balloons  480  and/or  482 . 
   2. The sheath is pressed against sleeve stop  400  so that the one or more sharp projections puncture balloon  480  and/or  482 , allowing the biologically inert fluid within to escape harmlessly into the blood stream. 
   3. A retrieval sheath is introduced along guide wire  102  and sleeve stop  400  is pulled into the retrieval sheath, using methods well known in the art, for example; Optionally, the retrieval sheath includes one or more retractable hooks that engage and pull back the filter portion, so that it collapses. Alternatively or additionally, the retrieval sheath includes a cooling material, which when applied to a filter made of a suitable shape memory material causes the filter to change its shape to a collapsed filter. The retrieval sheath containing sleeve stop  400  is removed from the blood vessel while guidewire  102  is optionally left in place. The retrieval sheath may be provided before balloons  480  and  482  are deflated. 
   Alternatively or additionally, inflation hose  484  is coupled to balloons  480  and/or  482  so that removal of hose  484  leaves an opening in balloons  480  and/or  482 . Hose  484  is left in place following expansion of balloons  480  and/or  482  until, for example, sleeve stop  400  requires removal. 
   To remove sleeve stop  400  without removing guidewire  102 , the following procedure is optionally followed: 
   1. Inflation hose  484  is pulled so that it disconnects from inflatable balloon stops  480  and/or  482 . Disconnection of hose  484  allows the biologically inert fluid to escape harmlessly into the blood stream and balloons  480  and/or  482  deflate. 
   2. Sleeve stop  400  is pulled into a retrieval sheath and removed as noted above in previous step  3 . 
   Sleeve with Expanding Cushion Stops 
   In another alternative stop mechanism to spring stops  180  and  182 ,  FIG. 5  shows a cross sectional view of a sleeve stop  400 . Sleeve stop  400  has outer wall  402  from which one or more self-expanding cushions,  580  and/or  582  are restrained from contacting wire  102  by restrainer  132 . In an exemplary embodiment, after sleeve stop  400  reaches its target area, restrainer  132  is pulled away from sleeve  400  using restrainer cable  130 , thereby allowing cushions  580  and/or  582  to deploy and fix sleeve  400  in place. These cushions may be formed, for example, out of silicone polymers. 
   Alternatively or additionally, cushions  580  and/or  582  comprise expanding absorbent materials that, for example, absorb intravascular fluid and expand. Restrainer  132 , for example, compresses cushions  580  and/or  582  so they are prevented from absorbing fluid until they are freed from restrainer  132 . 
   With cushions  580  and/or  582  comprising fluid-absorbing embodiments, restrainer  132 , for example, may comprise a layer of materials  544  and/or  546  that interfaces with cushions  580  and/or  582  to prevent fluid from being absorbed. Upon displacement of materials  544  and/or  546 , for example with removal of restrainer  132 , fluid absorption by cushions  580  and/or  582  subsequently takes place. 
   Compressed Gas Stops 
     FIG. 6  is an alternative embodiment of self-deploying sleeve stop  400  having outer wall  402  from which project one or more flexible compartments  680  and/or  682  containing compressed gas. In an exemplary embodiment, restrainer  132  is removed from flexible compartments  680  and/or  682 , so that the compressed gas within expands, causing flexible compartments  680  and/or  682  to expand and contact guidewire  102 . 
   Optionally, compartments  680  and/or  682  contain compressed gas canisters  690  and  692  respectively that are restrained from expanding by restrainer  132 . Upon removal of restrainer  132 , for example, the compressed gas breaks through a weak spot  694  in canister  690  and/or a weak spot  696  in canister  692 , allowing compressed gas to escape and expand compartments  680  and/or  682 . 
   Alternatively or additionally,  694  and  696  comprise openings in canisters  690  and  692  respectively. In an exemplary embodiment, restrainer  132  press the walls of compartments  680  and/or  682  compress against openings  694  and  696  so they remain sealed. Upon removal of restrainer  132 , walls of compartments  680  and/or  682  remove from openings  694  and  696 , allowing gas to expand into compartments  680  and/or  682 . 
   Membranous Filter with Guide Stop Sleeve 
     FIG. 7  is a sleeved guidewire stop and filter  700 , in accordance with an exemplary embodiment of the invention, comprising outer wall  402  with stops  180  and  182 , in accordance with an exemplary embodiment of the invention. 
   In an exemplary embodiment, porous membrane filter  190  has one or more living (or other type) hinge attachments  720  to outer wall  402 , allowing filter  190  to pivot open or closed in relation to wall  402 , during expansion and/or collapse. The hinge attachment of porous filter  190  to wall  402  may comprise a variety of materials, for example, different formulations of resilient plastics. Alternatively or additionally, attachment of porous filter  190  to wall  402  may comprise alternative designs, for example, one or more hooks passing through one or more eyes. 
   In an exemplary embodiment, porous membrane  190  has one or more struts  710  and/or  712  attached to a circumferential ring  722 . Struts  710  and/or  712  support porous membrane  190  and circumferential ring  722  slides along outer wall  402  during deployment and/or collapse of struts  710  and/or  712 . For example, as a filter surface  740  moves in a direction  732 , strut  710  and/or circumferential ring  722  move in a direction  730 , so that filter  700  assumes the deployed-configuration shown. 
   In an exemplary embodiment, movement of strut  710  in direction  730  and/or movement of filter surface  740  in direction  732  is automatic when they exit from sheath  150 . Alternatively or additionally, an operator-controlled mechanism, for example a membrane filter deployer cable  750  is pulled in a direction  752  so that struts  710  and/or  712  move radially outward from guidewire  102  until membrane  190  is in the deployed position. 
   In an exemplary embodiment, following expansion, filter  190  serves to trap particulate matter, for example, one or more of pieces of an artheromatous plaque, thrombi, and/or gas. Following completion of the procedure, filter  190  is collapsed and removed, along with the particulate matter, for example, with guide wire  102 . 
   In an exemplary embodiment, porous membrane  190  and/or struts  710  and/or  712  contact the inner surface of blood vessel  864  to form a seal and/or substantially span blood vessel  864  so that at least a substantial amount, if not all, blood passing through blood vessel  864 , is filtered by membrane  190 . 
   Blood vessel size may be from 2-8 millimeters in diameter, and even less than 2 millimeters or greater than 8 millimeters in certain areas and/or individuals. Optionally, to accommodate this range in blood vessels, different embodiments of porous membrane  190  and/or struts  710  and/or  712  may exhibit different degrees of radial expansion or may be partially deployed. 
   For example, in vessels  864  with a smaller diameter, struts  710  and/or  712  may deploy so they are not maximally expanded with respect to guidewire  102 , while in larger blood vessels, struts  710  and/or  712 , for example, may approach their maximal expansion configuration. 
   Filter with Shiftable Stops 
     FIG. 8A  is a filter  800  with shiftable guidewire stop  180 , mounted on a shift platform  810  and guidewire stop  182 , mounted on a shift platform  812 . Shiftable stops  180  and/or  182  shiftably secure sleeve wall  184  in relation to guidewire  102 . In this and other embodiments it should be noted that platforms  810  and  812  may be a single tubular platform and that stops  180  and  182  maybe a single tubular stop. Use of separate elements, however, especially in this embodiment, may allow some extra freedom in accommodation of shifting and/or other movement (e.g., bending) of guide wire  102 . 
     FIG. 8B  shows filter  800  remaining stationary relative to blood vessel  864 , while platform  812  and guidewire  102  move a small amount in a direction  824 . 
   The degree of allowed shifting may depend, for example, on an inner geometry of wall  184 , for example, if rails are provided for the platforms and/or if stops are provided for the platforms, for example at the ends of wall  184 . 
   In an exemplary embodiment, shift platform  810  shifts in relation to sleeve wall  184 , for example one centimeter in direction  824 , or one centimeter in direction  820 . Greater or smaller amounts of shifting may be allowed, for example, between 2 and 5 mm, or greater or smaller amounts. Filter  800  is optionally designed to shift in a symmetrical manner, once deployed. 
   Alternatively or additionally, filter  800  may be used in an environment where shifting in direction  820  is anticipated to be different than shifting in direction  824 . For example where multiple stents are being placed one after the other, filter  800  may need to shift more in direction  820  than in direction  824 . Alternatively or additionally to axial shifting, rotational shifting may be allowed, for example by providing rotational freedom (optionally with one or more stops) between platform  810  and sleeve  184 . 
   In an exemplary embodiment, shiftable stops  180  and/or  182  are confined in their movement, for example, within a rear sleeve boundary  830  and/or a front sleeve boundary  834 . Changing the distance between boundaries  830  and  834 , increases or decreases the excursion available to stops  180  and  182  in relation to wall  184 . 
   Optionally filter  800  may be designed so that sleeve wall  184  has a greater excursion than plus or minus one centimeter in relation to platforms  810  and  812 , for example in large diameter blood vessels. Alternatively or additionally filter  800  may be designed so that sleeve wall  184  has a smaller excursion in relation to platforms  810  and  812 , for example in small diameter blood vessels in fetal applications. In an exemplary embodiment, platforms  810  and  812 , for example, comprise a ring that is shiftably mounted against sleeve wall  184 . 
   Alternatively or additionally to free shifting, platforms  810  and  812  are elastically attached to sleeve wall  184 , for example to absorb shock caused by sudden movement of guidewire  102  (and then optionally realign the filter in accordance with the new guidewire position), or to encourage smaller amounts of shifting. 
   Referring back to  FIG. 7 , to show a potential advantage of using a shiftable filter, upon deployment of shiftable filter  700 , filter membrane  190 , for example, contacts a blood vessel wall  864 , for example, around its perimeter. Pressure on filter  700  in directions  824  and/or  820 , for example due to movement of guidewire  102 , may cause movement of filter  700 , so that filter membrane  190  scrapes blood vessel wall  864 , possibly causing damage to blood vessel. Alternatively, distortion of the filter may occur, which may also be undesirable. 
   By allowing movement of shiftable filter  800  as sleeve  184  moves in relation to shift platforms  810  and  812 , shiftable filter  800  remains stationary with respect to blood vessel wall  864  even when there is movement pressure in directions  820  and/or  824 . By limiting movement of shiftable filter  800  with respect to blood vessel wall  864 , trauma to wall  864  is possibly reduced and/or eliminated. 
   Filter Structure Detail 
     FIG. 9  is a detailed cross sectional view of a filter  900  and stops  180  and  182  during delivery in a blood vessel  864 , in accordance with an exemplary embodiment of the invention. In an exemplary embodiment, stops  180  and/or  182  are limited in movement by a forward limiter  932  and a rear limiter  942 . Stops  180  and/or  182 , for example, are attached to limiters  932  and  942 . Limiters  932  and/or  942  may be fixed to wall  402 , slideably attached to wall  402  and/or slideably attached to wall  402  for example so that limiters  932  and/or  942  move only under a relatively large displacement force. 
   In an exemplary embodiment, delivery sheath  150  has an opening  948  that allows filter  900  to be deployed on a guidewire  902  using a rapid exchange and/or a monorail technique. In a monorail technique, guidewire  902  does not require excursion along the length of delivery sheath  150 , for example two meters or more. 
   In an exemplary embodiment, to facilitate rapid deployment, sleeve  150 , for example has curved section  922  that curves toward guide wire  902 . Curved section  922 , for example, may be advantageous in that it aids sheath  150  in passing easily through blood vessel  864  without scraping walls of blood vessel  864 . 
   Alternatively or additionally, curved section  922  edges may be beveled along the front boundary. Beveling the edges of curved section  922  may be advantageous in that it aids in placement of filter  900  without causing trauma to surrounding tissue. Outer wall  402  optionally contains curved tip  920  to additionally aid in placement of filter  900  without causing tissue trauma. Section  922  and/or tip  920  optionally seal against guidewire  902 , to prevent blood flow between them. 
   In an exemplary embodiment, filter  900  has a curved section  920  that allows movement of filter  900  against blood vessel  864  without causing trauma during a rapid exchange technique. 
   In an exemplary embodiment, struts  910  are collapsed within deployment sheath  150 , along with filter  190  that is attached to circumferential ring  722 . 
     FIG. 10A  is a detailed cross sectional view of filter  900  following expansion of stops  180  and  182  and removal of delivery sheath  150 . Upon removal of delivery sheath  150 , for example, struts  910  and/or filter membrane  190  have expanded radially outwardly in accordance with an exemplary embodiment of the invention. 
   In an exemplary embodiment, rings  932  and  942  are fixed in place along wall  402 , while ring stops  180  and  182 , for example, deform under pressure from restrainer  132  ( FIG. 9 ). Deformation of stops  180  and  182 , for example, may comprise undulations along stops  180  and  182 . Upon removal of restrainer  132 , stops  180  and  182  expand to a final state shown schematically in  FIG. 10A . 
     FIG. 10B  is an alternative embodiment of stops  180  and  182  shown in  FIG. 10A  Filter  900  comprises ring  942  that is fixed in place along wall  402  and ring  932  that is slideably connected to wall  402 . In an exemplary embodiment, upon removal of restrainer  132 , spring stops  180  and  182  change their profile. To accommodate this change in profile, ring  932  slides along wall  402 , for example leaving gaps  1010  and  1012  respectively. 
   Porous membrane  190 , for example, is made of materials having pores of 200 microns in diameter, though it could have pores of between 20 and 250 microns, depending upon anticipated type and size of debris. 
   In delicate fetal procedures, for example fetal hydrocephalic shunt placement, pore size may be below 20 microns, while in retrieval of embolitic material from the lungs pores may be above 250 microns in diameter. 
   In an exemplary embodiment, porous membrane has an internal volume of 0.3 cubic centimeters or greater, for example within the area defined between porous filter  190  and wall  402 , allowing filter  900  to trap significant amounts of particulate debris. Alternatively or additionally, porous membrane has an internal volume of 0.3 cubic centimeters or less, for example, when used in blood vessels of smaller size, and/or in procedures where less debris is generated. 
     FIG. 10C  is a detailed head on view of  900  filter of  FIG. 10A , in accordance with an exemplary embodiment of the invention, showing stops  1080  and  1082  in addition to stops  180  and  182  so that guidewire  902  is surrounded by stops  180 ,  182 ,  1080  and  1082 . 
     FIG. 11  is a detailed cross sectional view of filter  900  during removal from blood vessel  846  following deployment of a stent  1140 , in accordance with an exemplary embodiment of the invention. 
   Removal sheath  1110  is placed on guidewire  902 , for example through opening  1048 , and moved along guidewire  902 , through guide catheter  940  until its front boundary contacts strut  910 . As sheath  1110  contacts strut  910 , strut  910  moves radially toward guidewire  902  while circumferential ring  722  moves toward and/or past curved tip  920 . 
   In an exemplary embodiment, space  1124  maintains a volume suitable for transporting the particulate and/or gaseous debris during removal of filter  900  from blood vessel. With filter  900  collapsed and partially or totally contained within sheath  150 , filter  900  and/or sheath  150 , and/or guidewire  902  are pulled through stent  1140 , and out of blood vessel  846 . Filter  900  is optionally designed to resist deformity during removal so that it fully removes any particulate it captured during its deployment in vessel  864 . 
   An Exemplary Surgical Procedure 
   In an exemplary embodiment, filter  900  is deployed in and removed from a blood vessel in the following manner: 
   1. An entry portal is made into an accessible blood vessel  846 , for example the femoral artery. 
   2. A guide catheter and/or dedicated sheath  940  is fed from the femoral artery to the target area. 
   3. Guide wire  902  is fed through guide catheter  940  into blood vessel  864  past, for example, an artheromatous plaque  916  ( FIG. 9 ). 
   4. Sheath  150 , containing filter  900  in the collapsed state, is threaded onto guidewire  902  and moved along blood vessel  864  using sheath  150  to push it forward. 
   5. Upon reaching or passing the target site, restrainer  132  is removed so that stops  180  and/or  182  deploy to lock filter  900  on guide wire  902 . 
   6. Sheath  150  is removed from filter  900  and filter  900  expands so that membrane  190  spans all or part of the cross sectional diameter of blood vessel  864  and sheath  150  is pulled out of vessel  846 , as seen in  FIG. 10A . 
   7. When filter  900  is used in conjunction with a stenting procedure, for example, guide catheter and/or dedicated sheath  940  is fed over guidewire  902  until it reaches the target area and stent  1140  is deployed and anchored in blood vessel  864  while embolitic material is caught by open filter  900  as seen in  FIG. 10C , for example downstream of stent  1140 . 
   8. As seen in  FIG. 11 , following completion of the procedure, removal sheath  1110  is optionally fed onto guidewire  902  and pushed forward in blood vessel  846  until its front boundary contacts struts  910 . 
   9. Sheath  1110  is pressed against struts  910  to cause them to collapse radially and sheath  1110  along with filter  900  and guide wire  902  are removed from blood vessel  864 . 
   Exemplary Specifications 
   Referring to  FIG. 9 , rapid exchange guidewire  902  used in a rapid exchange technique, for example, may be flexible anywhere along its length, for example at a flexed section  952  as filter  900  moves along guidewire  902 . 
   To secure filter  100  in place, stops  180  and  182  are designed to each deliver, for example, 100 to 500 grams of force against guide wire  102 . However, stops  180  and  182  may be designed to deliver a force less than 100 grams for used in special situations, for example where the displacement force is extremely low, for example in peripheral veins. Alternatively or additionally, stops  180  and  182  may be designed to deliver a force greater than 500 grams, for example, in patients with high blood flow speed, where released emboli are likely to have large mass and/or when a more slippery guide wire is anticipated. Alternatively or additionally, a force greater than 500 grams may be required when guidewire  102  comprises smooth materials that do not provide a friction finish to which stops  180  and  182  secure under lower pressure. 
   Stops  180  and  182 , for example, may be manufactured from resilient material such as surgical grade spring steel. For example, the whole wall  184  including the stops may be cut (e.g., using a laser or other means known in the at) from a sheet of steel or other biocompatible metal, such as titanium, or a nickel titanium alloys. Depending on the implementation, it may be desirable that the filter, body and/or stops be formed of plastic, elastic and/or super elastic materials. 
   Stops  480  and  482  ( FIG. 4 ),  580  and  582  ( FIG. 5 ), and  680  and  682  ( FIG. 6 ), may be, for example, manufactured from surgical grade polyethylene, nylon and/or terephthalate and/or other flexible, surgical-grade materials suitable for use in the vasculature. 
   Two stops,  180  and  182  are shown, but filter  100  may comprise less or more stops, for example, depending upon the diameter of guidewire  102 , the material from which guidewire  102  is manufactured and/or the design of filter  100 . 
   In an exemplary embodiment, stops  180  and  182  are radially disposed around wire  102 , for example so they apply equivalent radial pressure, that will not cause deformation to filter  100 . Applying even pressure allows stops  180  and  182  to be positioned between boundaries  122  and  124  ( FIGS. 1-3 ) without distorting the architecture of filter  100  and/or wall  184 . Optionally, two or more axially displaced stops (relative to the guidewire) or sets of stops may be used. 
   In an exemplary embodiment of the present invention, sleeve stop  400  ( FIGS. 4-6 ) is used in conjunction with any number of devices that are delivered into the vasculature. Such devices, for example, may include ablation lasers and/or catheter balloons that are used to ablate intravascular plaques, stents for restoring and/or maintaining patency of blood vessels. 
   Alternatively or additionally, such devices may include a variety of instrumentation including an arthroscopic tip, laparoscopic tools, and/or artheromatous shavers that are often used in vascular procedures. 
   While the invention has been described with respect to a limited number of embodiments, it will be appreciated that many variations, modifications and other applications of the invention may be made. In particular, features from one embodiment may be combined with features of another embodiment, in accordance with some embodiments of the present invention. 
   A variety of values have been utilized to describe the invention including, diameters, lengths and types of materials for the various filters, sleeves and/or stops. Although a variety of values and/or materials have been provided, it should be understood that these could vary even further based upon a variety of engineering principles, materials, intended use and designs incorporated into the invention. 
   It should be appreciated that different features may be combined in different ways. In particular, stop sleeve may be utilized with other instruments and/or devices used in the vasculature and may be modified in shape, size and/or materials to be ergonomically and engineeringly compatible with the specific usage. 
   Hence, not all the features, shapes and/or dimensions shown above in a particular embodiment may be necessary in every similar exemplary embodiment of the invention. The particular geometric forms and measurements used to illustrate the invention should not be considered limiting the invention in its broadest aspect to only those forms. Although some limitations are described only as method or apparatus limitations, the scope of the invention also includes apparatus designed to carry out the methods of using the apparatus. 
   Also within the scope of the invention are surgical kits, for example, kits that include sets of delivery systems, guidewires, filters and/or self-deploying stops. Optionally, such kits also include instructions for use. Measurements are provided to serve only as exemplary measurements for particular cases, the exact measurements applied will vary depending on the application. When used in the disclosure and/or claims, the terms “comprises”, “comprising”, “includes”, “including” or the like mean “including but not limited to”. 
   A person skilled in the art will appreciate that the present invention is not limited by what has thus far been described. Rather, the scope of the present invention is limited only by the following claims.

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