Abstract:
Disclosed is a thrombus filter comprising a sheath ( 1 ), a thrombus intercepting net ( 2 ) with an intercepting port, a first pushing piece ( 4 ) and a control handle. The thrombus filter is also provided with prevention umbrella ( 3 ), wherein the direction of the opening of the overfill prevention umbrella ( 3 ) is identical to that of the intercepting port. The overfill prevention umbrella ( 3 ) is provided outside the thrombus intercepting net ( 2 ). A second pushing piece ( 5 ) is located in the sheath ( 1 ) to push and pull the overfill prevention umbrella ( 3 ). The overfill prevention umbrella ( 3 ) comprises an umbrella surface ( 32 ) and an umbrella stand ( 31 ) connected between the second pushing piece ( 5 ) and the umbrella surface ( 32 ), and the open end of the umbrella surface ( 32 ) is a closed shape memory. When filtering thrombi in blood vessels, the overfill prevention umbrella ( 3 ) is opened by the thrombus intercepting net ( 2 ); after completion of the filtration, the thrombus intercepting net ( 2 ) returns into the overfill prevention umbrella ( 3 ) and the umbrella surface ( 32 ) of the overfill prevention umbrella ( 3 ) will be drawn into the centre of the intercepting port, in order to fully cover the intercepting port, thus preventing overflow of patches; the sheath ( 1 ) is pushed forward to retract the thrombus intercepting net ( 2 ); and the overfill prevention umbrella ( 3 ) is pulled into the sheath ( 1 ). The thrombus filter can effectively recover calcified patches in blood vessels through the thrombus intercepting net ( 2 ) and the overfill prevention umbrella ( 3 ) can effectively prevent overflow of thrombi when being retracted after capturing thrombi.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a blood vessel filter and utilization method thereof, in particular to a thrombus filter and utilization method thereof. 
       BACKGROUND 
       [0002]    With the wide application of interventional operation in the world, the complications resulted therefrom are also increasingly occurred. For example, in the interventional aortic valve replacement operation, due to the severe stenosis and calcification in aorta, there is a need to support and replace the original aortic valve via the aortic valve, but most of the severely stenosed and calcified aortas will bring about a reduced inner diameter of the blood flow channel, at this time, in general, the original calcified valve is firstly pre-expanded with a balloon, during this process, part of the calcified clots will be shed off during the expansion process, or the thrombus generated during the operation will enter coronary artery, brain and lower limb vessels, etc., with the blood flow, thus leading to vascular embolism, and finally resulting in the patient&#39;s death or paralysis. 
         [0003]    In order to solve the above problems, the Chinese Patent Publication No. CN1515326A, published on Jul. 28, 2004, entitled “thrombus filter”, discloses a thrombus filter, comprising a thrombus intercepting net, a guide wire, a distal connecting piece and a proximal connecting piece, wherein the thrombus intercepting net is in a funnel-shaped network structure made from nickel titanium shape memory alloy wire, with a coating film with filtration pores, the retracting line of the nickel titanium memory alloy wire is wound through the mesh pores of the opening portion of the thrombus intercepting net, then connected to the proximal connecting piece, the rear portion of the network structure of the thrombus intercepting net is connected to the distal connecting piece, and the front end of the distal connecting piece is provided with a guiding head. The opening portion of the thrombus interceptor is connected to the nickel titanium memory alloy wire to make the thrombus interceptor tightly fitted to the inner wall of the blood vessel under the restoring force of the nickel titanium memory alloy wire, so as to effectively filtrate the thrombus; when the thrombus interceptor is retracted, the retracting line firstly tightens the opening of the funnel-shaped thrombus intercepting net, and can effectively prevent the thrombus from overflow, therefore the thrombus interceptor can improve the recovery rate of thrombus, reduce the risks of embolism in coronary artery, brain and lower limb blood vessels, etc., and has the advantages of simple structure, convenient operation, good filtrability, high safety and reliability, and can be widely used in a variety of angioplasty and thrombolysis as a overfill prevention umbrella for the thrombus or the shed clot, so as to reduce the operation risk and improve the success ratio of operation 
         [0004]    The above thrombus filter only discloses the case that the opening portion of the intercepting net faces toward the proximal end (control end), and does not describe the thrombus intercepting means where the opening portion of the intercepting net faces toward the distal end (away from the control end), and such technology has not been effectively solved. At the same time, in the stenosed blood vessel channel, how the thrombosis filter not only can capture the thrombus or the shed clot, but also does not cause interference to the implantation process, is a problem to be solved. 
       SUMMARY 
       [0005]    In order to overcome the defects in the prior art, the present invention provides a thrombus filter which not only can effectively prevent the thrombus from leakage when it is retracted after capturing thrombus, but also has a simple structure, and convenient operation. 
         [0006]    The technical solution of the present invention is a thrombus filter, comprising a sheath, a thrombus intercepting net with an intercepting port, a first pushing piece for driving the thrombus intercepting net in and out of the sheath, and a control handle for controlling the first pushing piece, 
         [0007]    also provided with an overfill prevention umbrella, wherein the direction of the opening of the overfill prevention umbrella is identical to that of the intercepting port, and the overfill prevention umbrella is sleevedly provided outside the thrombus intercepting net; 
         [0008]    a second pushing piece, which is located in the sheath to push and pull the overfill prevention umbrella; 
         [0009]    the overfill prevention umbrella comprises an umbrella stand and an umbrella surface, the umbrella stand has one end connected to the second pushing piece, and the other end connected to the umbrella surface, and the open end of the umbrella surface is in a constricted memory shape; 
         [0010]    when the thrombus intercepting net is released, the opening of the overfill prevention umbrella is pushed open by the intercepting port of the thrombus intercepting net; and 
         [0011]    when the thrombus intercepting net is returned, the umbrella surface of the overfill prevention umbrella covers the intercepting port of thrombus intercepting net, and the open end of the umbrella surface is constricted to prevent the thrombus from leakage. 
         [0012]    Preferably, both the thrombus intercepting net and the overfill prevention umbrella are in a network structure, and the network structure is made from a memory alloy. 
         [0013]    Preferably, the thrombus intercepting net is in a network structure, the overfill prevention umbrella is consisted of an umbrella stand and a coating film with filtration pores coated on the umbrella stand, and the umbrella stand is made from a memory alloy. 
         [0014]    Preferably, the thrombus intercepting net is in a network structure, the umbrella surface of the overfill prevention umbrella is in a network form, the umbrella stand is a support rod connected to the umbrella surface, and the umbrella surface is made from a memory alloy. 
         [0015]    Preferably, thrombus intercepting net is consisted of a framework and a coating film with filtration pores coated on the framework, the umbrella surface of the overfill prevention umbrella is in a network form, the umbrella stand is a support rod connected to the umbrella surface, and the umbrella surface is made from a memory alloy. 
         [0016]    Preferably, the second pushing piece is in a tubular shape, the second pushing piece is slidingly sleevedly provided on the first pushing piece, and is coaxially located with the first pushing piece. 
         [0017]    Preferably, the first pushing piece is in a tubular shape, and the hollow portion inside the tubular first pushing piece forms a transport channel. 
         [0018]    Preferably, the umbrella surface is in an annular shape, the outer edge of the annular shape is connected to the umbrella stand. 
         [0019]    Preferably, one end of the thrombus intercepting net is an intercepting port, the other end of the same is a net bottom, the net bottom part is extended into the sheath and connected to the first pushing piece. 
         [0020]    The present invention has the beneficial effects as follows: the overall structure is sample, the operation is convenient, when the thrombus intercepting net and the overfill prevention umbrella are released, the thrombus generated during the operation process can be effectively recovered, and when the overfill prevention net is retracted after capturing thrombus, the thrombus leakage can be effectively prevented. 
         [0021]    The present invention provides a method for utilizing the thrombus filter according to claim  1 , comprising the steps of: 
         [0022]    (1) a sheath loaded with a thrombus intercepting net and an overfill prevention umbrella is transported to a position in blood vessel required to capture thrombus; 
         [0023]    (2) the sheath is retracted to expose the intercepting net and the overfill prevention umbrella outside the sheath and release them together, the intercepting port of the thrombus intercepting net is opened, at the same time the opening of the overfill prevention umbrella is pushed open, and the thrombus is captured reverse the blood flow by the thrombus intercepting net; 
         [0024]    (3) upon the capture of thrombus is finished, the thrombus intercepting net is returned via the first pushing piece, the umbrella surface of the overfill prevention umbrella is moved forward with respect to the thrombus intercepting net, and covers the intercepting port, and the open end of the umbrella surface is constricted under the constriction force of memory shape so as to prevent the thrombus from leakage; 
         [0025]    (4) upon the opening of the overfill prevention umbrella is completely constricted, the sheath is pushed forward to retract the overfill prevention umbrella back into the sheath; 
         [0026]    (5) the sheath loaded with the thrombus intercepting net and the overfill prevention umbrella is withdrawn from the blood vessel. 
         [0027]    As compared with the prior art, the present invention has the beneficial effects as follows, the thrombus filter has a simple utilization method and operation procedure, is convenient to use, and not only has a good filtering effect on the thrombus generated during the operation process, but also can effectively prevent the thrombus from leakage when it is extracted after capturing thrombus. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0028]      FIG. 1  is a structural schematic diagram of example 1 of the present invention. 
           [0029]      FIG. 2  is a structural schematic diagram of example 2 of the present invention. 
           [0030]      FIG. 3  is a structural schematic diagram of example 3 of the present invention. 
           [0031]      FIG. 4  is a structural schematic diagram of example 4 of the present invention. 
           [0032]      FIG. 5  is a structural schematic diagram of example 5 of the present invention, when the thrombus filter is placed into the blood vessel. 
           [0033]      FIG. 6  is a structural schematic diagram of example 5 of the present invention, when the thrombus is captured by the thrombus filter. 
           [0034]      FIG. 7  is a structural schematic diagram of example 5 of the present invention, when the intercepting net of the thrombus filter is returned. 
           [0035]      FIG. 8  is a structural schematic diagram in example 5 of the present invention, when the thrombus filter is retracted. 
           [0036]      FIG. 9  is a local structural schematic diagram of the example of the present invention. 
           [0037]      FIG. 10  is a section view of  FIG. 9 . 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0038]    The technical solutions of the present invention will be further illustrated below in combination with drawings of the description and the particular examples. It should be understood that the particular examples described herein are only used to explain the present invention, but not intended to make any limitation. 
         [0039]    As shown in  FIG. 1-10 , the thrombus filter of the present invention comprises a sheath  1  and a control handle (not shown), in the initial state, a thrombus intercepting net  2  and a overfill prevention umbrella  3 , and a first pushing piece  4  and a second pushing piece  5  connected to the thrombus intercepting net  2  and the overfill prevention umbrella  3 , respectively, and controlled by the control handle are accommodated in the sheath  1 . Among them, the first pushing piece  4  and the second pushing piece  5  are in a tubular shape, the second pushing piece  5  has a bigger diameter and coaxially sleevedly provided outside the first pushing piece  4 ; the thrombus intercepting net  2  is in a funnel shape, wherein one end of the thrombus intercepting net  2  is an intercepting port, the other end of the same is a net bottom, the net bottom part is connected to the first pushing piece  4  which is located inside the sheath  1 ; the net bottom part also has a vent corresponding to the pipe orifice of the first pushing piece  4 , the vent can be used as a channel for balloon, interventional device, etc., when they are in the same path with the thrombus filter. Therefore, when there is a need for importing the balloon and interventional device, etc., into the blood vessel, there is unnecessary to make an additional opening on the blood vessel I, thus facilitating to reduce the harm to human body. Of course, the first pushing piece  4  and the second pushing piece  5  can also employ a fitting between a cylindrical shape and a tubular shape, or other structures which can realize the pushing function, all of these embodiments fall in the scope of protection of the present invention. 
         [0040]    The overfill prevention umbrella  3  is sleevedly provided on the peripheral wall of the converged thrombus intercepting net  2 , and the overfill prevention umbrella  3  can be divided into two parts, the umbrella stand  31  and the umbrella surface  32 , the umbrella stand  31  is sleevedly provided on the peripheral wall of the thrombus intercepting net  2 . In the present invention, the first pushing piece  4 , the second pushing piece  5 , the umbrella stand  31  and the umbrella surface  32 , have the ends adjacent to the control handle, as the proximal ends, and the ends away from the control handle, as the distal ends, the proximal end of the umbrella stand  31  is connected to the distal end of the second pushing piece  5 ; the proximal end of the umbrella surface  32  is connected to the distal end of the umbrella stand  31 , the direction of the open end of the umbrella surface  32  is identical to that of the intercepting port of the thrombus intercepting net  2 , the opening on the open end of umbrella surface  32  is in an actively constricted state, which is used to cover the intercepting port of the thrombus intercepting net  2 . 
         [0041]    Memory alloy material is a new material which has the advantages of nonmagnetic, wear resistance, corrosion resistance, non-toxicity, etc., when it is cooled, in the austenite phase state, it is soft and can be easily compressed into the bridge pipe, and when it is released in body, it turns into a martensite phase, and restore the design shape. 
         [0042]    In order to facilitate the implementation of the process, the umbrella stand  31  and the umbrella surface  32  can be in a one-piece structure, both of them are made from a memory alloy material, and the production for the one-piece structure is simple. In addition, the umbrella stand  31  and the umbrella surface  32  can also be in a composite structure, both of them are connected together by means of a suture or connecting piece, so as to further reduce the consumptive materials and the overall size. 
         [0043]    The materials for the umbrella stand  31  and the umbrella surface  32  can be different, the umbrella stand  31  can be made from a material which is contracted toward the axial direction of the sheath in the original state, and is flexible; the umbrella stand  31  is moved with the expansion and convergence of the thrombus intercepting net  2 , particularly, after the thrombus intercepting net  2  is opened, the umbrella stand  31  will also be pushed open. 
         [0044]    The control handle can make a pull and push operation on the first pushing piece  4 , at the same time the control handle can be an intrinsic part on the proximal end of the first pushing piece  4 , and can also be separately constructed with the first pushing piece  4  and assembled and arranged. The control hand not only can control the pushing motion of the thrombus intercepting net  2 , but also can control the pushing motion of the sheath  1  and the overfill prevention umbrella  3 , when the displacement of the overfill prevention umbrella  3  is controlled and supported via the second pushing piece  5  and the sheath  1  is retracted, the movement of the overfill prevention umbrella  3  is limited by the second pushing piece  5 , and the backward friction force is overcome, based on the same reasoning, the first pushing piece  4  are linked with the thrombus intercepting net  2  to make the forward and backward movements in the sheath  1 . After the sheath  1  loaded with the thrombus intercepting net  2  and the overfill prevention umbrella  3  is transported to the designated position in the blood vessel I, the sheath  1  is retracted, the overfill prevention umbrella  3  and thrombus intercepting net  2  are maintained a relative still by the relatively fixed second pushing piece  5  and first pushing piece  4 , and placed in the blood vessel. 
         [0045]    According to the characteristics of the thrombus intercepting net  2  and the overfill prevention umbrella  3 , the present invention comprises at least the following four examples, but not limited thereto. 
       Example 1 
       [0046]    As shown in  FIG. 1 , both the thrombus intercepting net  2  (bold black line) and the overfill prevention umbrella  3  are in a network structure, the network structure is weaved from a memory alloy, wherein the thrombus intercepting net  2  is in a open state at the body temperature, and the overfill prevention umbrella  3  is in a constricted state at the body temperature, and the expansion force produced in the thrombus intercepting net  2  under the expansion tendency is higher than the constriction force in the overfill prevention umbrella  3  under the constricted state, that is, if the thrombus intercepting net  2  is opened at the body temperature, the overfill prevention umbrella  3  will be subjected to a force and pushed open by the thrombus intercepting net  2 . The open end of the umbrella surface  32  of the overfill prevention umbrella  3  is in a constricted memory shape, the open end of the umbrella surface  32  can be always maintained to converge toward the center, that is, the coverage on the intercepting port of the thrombus intercepting net  2  is achieved. The position distal from the intercepting port on the thrombus intercepting net  2  is connected to the first pushing piece  4 , and the thrombus intercepting net  2  can be freely pushed in the sheath  1  via the first pushing piece  4 ; the umbrella stand  31  of the overfill prevention umbrella  3  is connected to the second pushing piece  5 , and the overfill prevention umbrella  3  can be freely pushed in the sheath  1  via the second pushing piece  5 . 
       Example 2 
       [0047]    As shown in  FIG. 2 , the thrombus intercepting net  2  is in a network structure, the network structure is weaved from a memory alloy, the thrombus intercepting net  2  is in a open state at the body temperature. The umbrella surface  32  of the overfill prevention umbrella  3  is a coating film with filtration pores, the umbrella stand  31  (bold black line) is made from a memory alloy strip, the umbrella stand  31  is axially arranged around the sheath  1 , and the longitudinal direction of the umbrella stand  31  is identical to the direction of the sheath  1 , the memory shape for the distal end of the umbrella stand  31  is an arc bending toward the axial center, the proximal end of the umbrella stand  31  is connected to the second pushing piece  5 , at the body temperature, the distal end of the umbrella stand  31  is converged toward the axial direction of the sheath  1 , wherein the umbrella surface  32  is coated on the peripheral wall of the umbrella stand  31 , and moved with the expansion and convergence of the umbrella stand  31 . 
       Example 3 
       [0048]    As shown in  FIG. 3 , the thrombus intercepting net  2  (bold black line) is in a network structure, the network structure is weaved by a memory alloy, and the thrombus intercepting net  2  is in an open state under the body temperature. The umbrella surface  32  of the overfill prevention umbrella  3  is in a network structure weaved from a memory alloy wire, wherein the memory state of the opening of the umbrella surface  32  is a converged state; the umbrella stand  31  (bold black line, which is more bold than that of the thrombus intercepting net  2 ) is a support rod connected to umbrella surface  32 , the two ends of the support rod are connected to the second pushing piece  5  and the umbrella surface  32  respectively. 
         [0049]    The thrombus intercepting nets  2  in examples 1, 2 and 3 are weaved from a metal wire having a support force, it is pushed open by a balloon and shaped; and can also be made from memory alloy materials, and at the body temperature, it is actively expanded by restoring the expanded memory shape. 
       Example 4 
       [0050]    As shown in  FIG. 4 , the thrombus intercepting net  2  is consisted of a framework  21  (bold black line) and a coating film  22  with filtration pores, wherein the coating film  22  is coated on the peripheral wall of the framework  21 , the framework  21  is made from a memory alloy strip, one end of the framework  21  is connected to the first pushing piece  4 , and at the body temperature, the part away from the first pushing piece  4  on the framework  21  will be up-wrapped toward the direction away from the axis of the sheath  1 , wherein the coating film  22  is coated on the peripheral wall of the framework  21 , and moved with the expansion and convergence of the framework  21 . The umbrella surface  32  of the overfill prevention umbrella  3  is in a network structure weaved by a memory alloy wire, wherein the memory state of the umbrella surface  32  is a converged state; the umbrella stand  31  (bold black line, which is more bold than that of framework  21 ) is a support rod connected to umbrella surface  32 , the two ends of the support rod are connected to the second pushing piece  5  and the umbrella surface  32 , respectively. 
         [0051]    The framework of the thrombus intercepting net  2  in example 4 is a metal rod with a support force, it is pushed open by a balloon and shaped; and can also be made from a memory alloy material, and at the body temperature, it is actively expanded by restoring the expanded memory shape. 
       Example 5 
       [0052]    As shown in  FIGS. 5-8 , the thrombus intercepting net  2  is consisted of a framework  21  and a coating film  22  with filtering holes, wherein the coating, film  22  is coated on the peripheral wall of the framework  21 , the framework  21  is made from a memory alloy strip, one end of the framework  21  is connected to the first pushing piece  4 , at the body temperature, the part away from the first pushing piece  4  on the framework  21  will be up-wrapped toward the direction away from the axis of the sheath  1 , wherein the coating film  22  is coated on the peripheral wall of the framework  21 , and moved with the expansion and convergence of the framework  21 . The open end of the umbrella surface  32  of the overfill prevention umbrella  3  is in a constricted memory shape, and the open end of the umbrella surface  32  can be always maintained to converge toward the center, that is, the coverage on the intercepting port of the thrombus intercepting net  2  can be achieved. 
         [0053]    The coating films in the above examples are thin films of polymeric material, the thin films of polymeric material generally refer to the thin films of medical polymeric material, such as medical polytetrafluoroethylene film, medical polyurethane film, medical silicon gel film, etc. In addition, the thrombus intercepting net  2  and the overfill prevention umbrella  3  can also have other claimed structures other than the abovementioned structure combinations, without limiting to the 5 cases in the examples. 
         [0054]    In the present invention, although there are various examples, the operation procedure and principle in each of the examples are the same, and the utilization method of the thrombus filter is described in detail in example 5 below. 
         [0055]    Step  1 : As shown in  FIG. 5  (in this Figure, the thrombus intercepting net  2  and the overfill prevention umbrella  3  are in an overlapped state and located in the sheath  1 ), the thrombus filter is placed into the blood vessel I. The sheath  1  loaded with the thrombus intercepting net  2  and the overfill prevention umbrella  3  is transported into the designated position in the blood vessel I. The arrow direction shows the flow direction of the blood mixed with the thrombus  6 . 
         [0056]    Step  2 : As shown in  FIG. 6  (the thrombus intercepting net  2  and the overfill prevention umbrella  3  are in an overlapped state, and parts of them are exposed outside the sheath  1 , at this time, the thrombus intercepting net  2  and the overfill prevention umbrella  3  are the same part in the figure, without significant difference), the thrombus  6  is captured by the thrombus filter. When the sheath  1  loaded with the thrombus intercepting net  2  and the overfill prevention umbrella  3  is moved to the designated position in the blood vessel I, then the sheath  1  is pulled to make it returned, at the same time, the overfill prevention umbrella  3  and the thrombus intercepting net  2  are pushed via the first pushing piece  4  and the second pushing piece  5 , to make the overfill prevention umbrella  3  and the thrombus intercepting net  2  overcame the backward force (such force mainly refers to friction force) and hold still in situ, that is, the overfill prevention umbrella  3  and the thrombus intercepting net  2  are maintained to hold a relative still with respect to the blood vessel I by the pushing of the first pushing piece  4  and the second pushing piece  5 . 
         [0057]    At this point, if the thrombus intercepting net  2  is made from a memory alloy material, and the original state of the thrombus intercepting net  2  is an open state, the net opening of the thrombus intercepting net  2  in the blood vessel is extended actively; if the thrombus intercepting net  2  is made from a stainless steel metal, at first, the thrombus intercepting net  2  is expanded to a suitable size by a balloon; at the same time the overfill prevention umbrella  3  which is sleevedly provided on the peripheral wall of the thrombus intercepting net  2  is also pushed open. 
         [0058]    As required, after the thrombus intercepting net  2  and the overfill prevention umbrella  3  are released, the steps of transportation, placement, and retraction of the surgical instruments are carried out via the channel II in the core of the second pushing piece  5 , all of the processes are carried out under a protected state. 
         [0059]    Step  3 : As shown in  FIG. 7 , the intercepting net of the thrombus filter is retracted. After the device implantation process is finished, and when the conjugated capture work of thrombus  6  is finished, the thrombus intercepting net  2  is pulled to return back into the sheath  1  via the first pushing piece  4 , during this process, the thrombus intercepting net  2  and the overfill prevention umbrella  3  are staggered each other at the intercepting port of the thrombus intercepting net  2 , that is, the thrombus intercepting net  2  is moved backward and returned back into the overfill prevention umbrella  3 , and the overfill prevention umbrella  3  is maintained to hold still with respect to the blood vessel I, so as to avoid making an injury on the blood vessel I during the thrombus intercepting net  2  is returned, and the overfill prevention umbrella  3  is moved forward with respect to the thrombus intercepting net  2 , and the umbrella surface  32  covers above the intercepting port of the thrombus intercepting net  2  under the constricted memory shape. According to the staggered distance, there will appears a gradual or even complete separation of the overlapped parts between the umbrella surface  32  of the overfill prevention umbrella  3  and the thrombus intercepting net  2 , at this time the umbrella surface  32  will gradually or even completely cover above the intercepting port of the thrombus intercepting net  2 . That is, the umbrella surface  32  of the overfill prevention umbrella  3  will exceed the intercepting port of the thrombus intercepting net  2  and converge toward the center of the intercepting port, so as to achieve the coverage on the intercepting port, which is equivalent to that the diameter of the intercepting port is reduced under the effect of umbrella surface  32 , so that a lid-like structure is formed and covers the intercepting port, thereby avoiding the easy overflow of thrombus  6  from the intercepting port. When the open end of the opening of the overfill prevention umbrella  3  is completely closed due to itself constricted memory shape (incomplete close is possible, as the converged opening under the constriction is very small, there will not occur the situation that the thrombus  6  is overflowed, it is approximately understood in a state that the open end is completely closed), the thrombus  6  obtained by filtrating from the blood vessel I is encapsulated in the thrombus intercepting net  2  by the overfill prevention umbrella  3 . In  FIG. 7 , the thrombus intercepting net  2  is not completely in place, that is, the overfill prevention net  3  does not completely cover the intercepting port of the thrombus intercepting net  2 , at this time, it is necessary for the thrombus intercepting net  2  to be returned, until the overfill prevention net  3  completely covers the intercepting port of the thrombus intercepting net  2 , then the sheath  1  is pushed forward to retract the overfill prevention net  3  and the thrombus intercepting net  2 . 
         [0060]    In the present invention, there are no explicit definition on the distinguished boundaries between the umbrella surface  32  and umbrella stand  31  on the overfill prevention umbrella  3 , as long as in the above situations, the umbrella surface  32  can cover the intercepting port. Among them, upon the umbrella surface  32  of the overfill prevention umbrella  3  and the intercepting port of the thrombus intercepting net  2  are staggered each other, all of the parts hanging outside the intercepting port will cover toward the center of the intercepting port under the constriction force, and the diameter of the intercepting port is reduced, so as to avoid the overflow of thrombus  6  from the intercepting port when the thrombus intercepting net  3  and the overfill prevention umbrella  3  are retracted into the sheath  1 . The first pushing piece  4  continuously pulls the thrombus intercepting net  2  until the opening of the overfill prevention umbrella  3  is completely constricted, at this time, the overfill prevention umbrella  3  can completely avoid the overflow of thrombus  6  from the thrombus intercepting net  2 . 
         [0061]    Step  4 : As shown in  FIG. 8 , the thrombus filter is retracted. Upon the opening of the overfill prevention umbrella  3  is completed constricted, the sheath  1  is pushed to make it moved forward, the overfill prevention umbrella  3  is completely accommodated into the sheath  1  gradually from the rear of the overfill prevention umbrella  3 , so that the thrombus filter can realize the filtration of the blood in the blood vessel I, and at the same time can solve the overflow of thrombus  6  when the thrombus intercepting net  2  is retracted, and ensure the stability and safety of the environments in the blood vessel I. As the mucous membrane of the inner wall of the blood vessel I to be protected is frail, when the overfill prevention umbrella  3  is located outside the sheath  1  and inside the blood vessel I, there should not presents a relative movement between the overfill prevention umbrella  3  and the blood vessel I, if not, the outer wall of the overfill prevention umbrella  3  will easily scrape the inner wall of the blood vessel I, so as to cause an injury or even lesion on the blood vessel I, therefore, when the thrombus intercepting net  2  and the overfill prevention umbrella  3  are released and retracted, it can be achieved mainly by the relative backward and forward movement of the sheath  1 . In addition, in order to make a further protection on the inner wall of the blood vessel I, the bending part of the overfill prevention umbrella  3  and the thrombus intercepting net  2 , in a memory state, is in an arc structure. 
         [0062]    Step  5 : The sheath  1  loaded with the thrombus intercepting net  2  and the overfill prevention umbrella  3  is withdrawn from the blood vessel I. 
         [0063]    In the present invention the umbrella surface  32  has at least the following three states: before the thrombus intercepting net  2  is released, the umbrella surface  32  is located inside the sheath  1  and is sleevedly provided on the peripheral wall of the thrombus intercepting net  2 ; when the thrombus intercepting net  2  is released, the umbrella surface  32  is located in the periphery of the thrombus intercepting net  2  and expanded by the support of the thrombus intercepting net  2 ; and when the thrombus intercepting net  2  is retracted, the umbrella surface  32  is converged from the periphery of the intercepting port of the thrombus intercepting net  2  towards the center of the intercepting port, forming a coverage on the intercepting port. The present invention has the advantages as follows: the overall structure is simple, the operation is convenient, and after the thrombus intercepting net  2  and the overfill prevention umbrella  3  are released, the thrombus  6  generated during the operation process can be effectively recovered, and when the overfill prevention net  3  is retracted, the leakage of thrombus  6  can effectively prevented.