Abstract:
A system and method of integrating electromagnetic microsensors into interventional endovascular devices such as guidewires for tracking guidewires within vessels of a body with the use of a surgical navigation system.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This disclosure relates generally to guidewires, and more particularly, to a system and method of integrating trackable devices into guidewires for tracking the guidewires within vasculature of a body. 
         [0002]    A guidewire typically includes a flexible wire to be positioned in an organ, vessel, or duct of a body for the purpose of directing passage of a larger device threaded over or along the length of the guidewire to a desired location in the vasculature of a body. A wide variety of guidewires have been developed for various applications including medical applications. Generally, guidewires are used to aid in the insertion of catheters or other devices into a body. During endovascular interventions, a guidewire is inserted into a body system such as the vascular system at a point of entry, which is usually a small percutaneous incision in the arm, leg or groin, and advanced to a desired location, typically under fluoroscopic guidance. Accurate positioning of the guidewire with respect to the vasculature is generally required for a successful procedure. 
         [0003]    In some applications, a generally hollow cylindrical catheter is slipped over the guidewire and directed to the desired location by following the guidewire. The catheter doesn&#39;t have the stiffness or rigidity of the guidewire. The guidewire and catheter must be precisely and efficiently positioned at the desired location in order to most effectively treat the underlying medical condition. 
         [0004]    There are clinical benefits to tracking the tip, a portion or entire length of a guidewire that is used in endovascular interventional applications. One benefit is that a user can more efficiently navigate a guidewire to a target site with the aid of a surgical navigation tracking system. Another benefit is that the tracking system will provide real-time location data of the guidewire to the user, requiring a lower radiation dose from the imaging apparatus. 
         [0005]    Guidewires have been developed to include one or more trackable devices, such as microsensors, integrated within the guidewire. Surgical navigation systems may then be employed to track the tip, a portion or entire length of the guidewire by tracking the position and orientation of integrated microsensors, for example. A clinician may use the position and orientation information associated with the integrated microsensors in the guidewire to efficiently navigate the guidewire to a desired location within a body. 
         [0006]    It is very difficult to incorporate trackable microsensors of high signal strength into devices of the sizes provided by typical guidewires having a diameter of less than a 1 mm. Additionally, trackable microsensors may require a shielded type of electrical connection (e.g., coax or twisted pair) with the surgical navigation tracking system to reduce the introduction of noise into the tracking signals. The microsensors must efficiently occupy the volume available to maximize signal strength without affecting the clinical and mechanical performance of the guidewire. The guidewire must be robust for the clinical applications contemplated and the trackable microsensors must have minimal impact on the mechanical performance of the guidewire, especially with regards to pushability and steerability. 
         [0007]    Therefore, it is desirable to provide a guidewire with the ability of coupling at least one trackable device into the guidewire for systematically navigating the guidewire to a desired location within a body and having minimal impact on the performance of the guidewire during clinical applications. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0008]    In accordance with an aspect of the disclosure, a guidewire assembly comprising a substantially flexible flat member having a plurality of projections extending thereform; and at least one electromagnetic microsensor attached to each of the plurality of projections; wherein the substantially flexible flat member with the at least one electromagnetic microsensor attached to each of the plurality of projections is wound around a mandrel to form a spring-like flexible tip member. 
         [0009]    In accordance with an aspect of the disclosure, a guidewire assembly comprising a substantially tubular member having a plurality of projections extending outwardly therefrom and a plurality of openings extending therethrough; and at least one electromagnetic microsensor attached to each of the plurality of projections; wherein the at least one electromagnetic microsensor attached to each of the plurality of projections are positioned within the tubular member to form a flexible tip member. 
         [0010]    In accordance with an aspect of the disclosure, a method for making a trackable guidewire assembly comprising providing a substantially flexible flat member having a plurality of projections extending therefrom; attaching at least one electromagnetic microsensor to each of the plurality of projections; winding the substantially flexible flat member with the electromagnetic microsensors attached thereto around a mandrel to create a flexible tip member; and attaching a strengthening member to a proximal end of the flexible tip member to create a guidewire assembly. 
         [0011]    In accordance with an aspect of the disclosure, a method for making a trackable guidewire assembly comprising providing a substantially tubular member having a plurality of projections extending outwardly therefrom and a plurality of openings extending therefrom; attaching at least one electromagnetic microsensor to each of the plurality of projections; positioning the plurality of projections with the electromagnetic microsensors attached thereto within the substantially tubular member to create a flexible tip member; and attaching a strengthening member to a proximal end of the flexible tip member to create a guidewire assembly. 
         [0012]    Various other features, aspects, and advantages will be made apparent to those skilled in the art from the accompanying drawings and detailed description thereof. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a top view of an exemplary embodiment of a portion of a substantially flexible flat member with a plurality of projections extending outwardly at an angle from one side thereof; 
           [0014]      FIG. 2  is a top view of the substantially flexible flat member of  FIG. 1  with the plurality of projections extending substantially perpendicular with respect to the substantially flexible flat member; 
           [0015]      FIG. 3  is a top view of the substantially flexible flat member of  FIG. 2  with at least one electromagnetic microsensor attached to each of the plurality of projections; 
           [0016]      FIG. 4  is a top view of a portion of the substantially flexible flat member of  FIG. 3  with the plurality of projections with the at least one electromagnetic microsensor attached thereto extending substantially parallel to and spaced apart from the substantially flexible flat member; 
           [0017]      FIG. 5  is a perspective view of a portion of an exemplary embodiment of a mandrel used for making a flexible tip for a guidewire out of the substantially flexible flat member with the plurality of electromagnetic microsensors attached thereto; 
           [0018]      FIG. 6  is a perspective view of an exemplary embodiment of a spring-like flexible tip member for a guidewire after winding the substantially flexible flat member around the mandrel; 
           [0019]      FIG. 7  is a perspective view of an exemplary embodiment of the spring-like flexible tip member of  FIG. 6  attached to a strengthening member of a guidewire; 
           [0020]      FIG. 8  is an enlarged perspective view of a distal end of the strengthening member of the guidewire of  FIG. 7 ; 
           [0021]      FIG. 9  is a perspective view of a portion of an exemplary embodiment of a guidewire assembly; 
           [0022]      FIG. 10  is a perspective view of a tip portion of a guidewire with at least one electromagnetic microsensor attached to each of a plurality of projections of the tip portion; 
           [0023]      FIG. 11  is a perspective view of the tip portion of the guidewire of  FIG. 10  with the plurality of electromagnetic microsensors positioned within the center of the tip portion; 
           [0024]      FIG. 12  is a flow diagram of an exemplary embodiment of a method for making a trackable guidewire assembly; and 
           [0025]      FIG. 13  is a flow diagram of an exemplary embodiment of a method for making a trackable guidewire assembly. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0026]    Referring to the drawings,  FIGS. 1-9  illustrate a structure and method of forming a spring-like flexible tip member  40  for a trackable guidewire assembly  60  made out of a substantially flexible flat member  10  that may be formed into the spring-like flexible tip member  40  with a plurality of electromagnetic microsensors  24  incorporated into the center of the spring-like flexible tip member  40  to function as the spring-like flexible tip member  40  of the guidewire assembly  60 . 
         [0027]      FIG. 1  illustrates a top view of an exemplary embodiment of a portion of a substantially flexible flat member  10  with a plurality of projections  12  extending outwardly at an angle from one side  14  thereof for use in making a flexible tip for a guidewire. The substantially flexible flat member  10  may be cut from a stock of flat flexible material. The substantially flexible flat member  10  may be made up of a flat flexible material that may be easily formed into a spring-like structure. In an exemplary embodiment, the substantially flexible flat member  10  may comprise materials selected from the group of stainless steel, nickel, titanium, alloys of these materials, e.g., nickel-titanium alloy (nitonal), plastics, and composite materials. 
         [0028]    In an exemplary embodiment, the substantially flexible flat member  11  may be 2 to 3 meters long that tapers to an end at one end thereof. In an exemplary embodiment, the angle at which each of the plurality of projections  12  extends from one side  14  of the substantially flexible flat member  10  may be any angle from approximately 20 to 70 degrees. 
         [0029]    The substantially flexible flat member  10  includes at least two plated electrical feedthrough contacts  16  located at a base  20  of each projection  12  with a plated electrical conductor lead or trace  18  extending from one side of each feedthrough contact  16  along the length of the substantially flexible flat member  10  for connection to an electromagnetic microsensor that is attached to each projection  12 . 
         [0030]    In an exemplary embodiment, the feedthrough contacts  16  and traces  18  comprise conductive material such as copper, silver, gold, or any other conductive material. The feedthrough contacts  16  are designed for connection to electrical components, such as electromagnetic microsensors. The traces  18  are designed for transmitting or receiving electrical power or electronic signals from the feedthrough contacts  16  to what ever is connected to the end of the traces  18  at the end of the substantially flexible flat member  10 . In an exemplary embodiment, there may be additional feedthrough contacts at the end of the traces  18  at opposite end of the substantially flexible flat member  10 , opposite the feedthrough contacts  16 . 
         [0031]    In preparation for attachment of an electromagnetic microsensor to each of the plurality of projections  12  of the substantially flexible flat member  10 , each of the projections  12  are bent upwardly at their base  20  so that they are substantially perpendicular to a horizontal plane  22  of the substantially flexible flat member  10 .  FIG. 2  illustrates a top view of the substantially flexible flat member  10  with the plurality of projections  12  extending substantially perpendicular with respect to the horizontal plane  22  of the substantially flexible flat member  10 . 
         [0032]      FIG. 3  illustrates the substantially flexible flat member  10  with at least one electromagnetic microsensor  24  attached to each of the plurality of projections  12 . In an exemplary embodiment, the electromagnetic microsensor  24  may be built with various electromagnetic microsensor architectures, including, but not limited to electromagnetic microcoils, flux gate magnetometer sensors, squid magnetometer sensors, Hall-effect sensors, anisotropic magneto-resistance (AMR) sensors, giant magneto-resistance (GMR) sensors, and extraordinary magneto-resistance (EMR) sensors. 
         [0033]    In an exemplary embodiment, the electromagnetic microsensor  24  may be an electromagnetic microcoil that may be built with various electromagnetic microcoil architectures. In an exemplary embodiment, the electromagnetic microsensor  24  may include a ferrite core with wire wound around the ferrite core. In an exemplary embodiment, the electromagnetic microsensor  24  may include a ferrite material, such as a ferrite paste, that is applied to each of the plurality of projections  12  with wire wound around the ferrite material. In an exemplary embodiment, each electromagnetic microsensor  24  may be sealed within a shrink wrap sleeve or coating on the outside of the microsensor  24  with a shrinkable material. 
         [0034]    In preparation for winding the substantially flexible flat member  10  around a mandrel  30  for making a spring-like flexible tip member for a guidewire, each of the plurality of projections  12  with the at least one electromagnetic microsensor  24  attached thereto are bent downwardly at the bottom  26  of the electromagnetic microsensor  24  so that the plurality of projections  12  with the at least one electromagnetic microsensor  24  attached thereto are substantially parallel to the horizontal plane  22  of the substantially flexible flat member  10 .  FIG. 4  illustrates a top view of a portion of the substantially flexible flat member  10  with the plurality of projections  12  with the at least one electromagnetic microsensor  24  attached to each of the plurality of projections  12  extending substantially parallel to and spaced apart from the substantially flexible flat member  10 . 
         [0035]    In an exemplary embodiment, each of the electromagnetic microsensors  24  include fine electrical conductor leads or conductors  28  that are brazed, soldered, or welded to the feedthrough contacts  16 . In an exemplary embodiment, having three electromagnetic microsensors  24 , there may be six traces, three traces, two traces or one trace. The electromagnetic microsensors  24  may each include at least one electrical return. The electrical return from each electromagnetic microsensor  24  may be combined together. In an exemplary embodiment, the electrical return from the electromagnetic microsensor  24  may be the substantially flexible flat member  10 . In this embodiment, the substantially flexible flat member  10  must be treated to be isolated from traces. In an exemplary embodiment, the electrical return from an electromagnetic microcoil may be the microcoil itself. 
         [0036]      FIG. 5  illustrates a perspective view of a portion of an exemplary embodiment of a mandrel  30  used for making a spring-like flexible tip member  40  for a guidewire out of the substantially flexible flat member  10  with the plurality of electromagnetic microsensors  24  attached thereto. In an exemplary embodiment, the mandrel  30  is a hollow cylindrical rod around which the substantially flexible flat member  10  may be wound for forming the spring-like flexible tip member  40  for a guidewire. The mandrel  30  includes a plurality of openings  32  extending thereto for accepting the plurality of electromagnetic microsensors  24  therein. The openings  32  should be large enough to clearly accept the electromagnetic microsensors  24  therein. The substantially flexible flat member  10  is wound around the mandrel  30  to form a spring-like flexible tip member  40  for a guidewire with a plurality of electromagnetic microsensors  24  positioned within the center of the spring-like flexible tip member  40 , as shown in  FIG. 6 . 
         [0037]      FIG. 6  illustrates a perspective view of an exemplary embodiment of a spring-like flexible tip member  40  for a guidewire after winding the substantially flexible flat member  10  around the mandrel  30 . The spring-like flexible tip member  40  includes a distal end  42  and a proximate end  44 . The spring-like flexible tip member  40  further includes the plurality of electromagnetic microsensors  24  that are attached to and positioned within the center of the spring-like flexible tip member  40 . Each of the electromagnetic microsensors  24  include at least one electrical signal line and an electrical return that extend from the plurality of electromagnetic microsensors  24  through the feedthrough contacts  16  and traces  18  to the end of the guidewire. 
         [0038]    In an exemplary embodiment, the mandrel  30  may be left inside the spring-like flexible tip member  40  to function as a guidewire core or may be removed from the spring-like flexible tip member  40  after winding. In an exemplary embodiment, the spring-like flexible tip member  40  may be a relatively short distal portion of the guidewire or continue to the proximal end with a guidewire core inside the spring-like flexible tip member  40 . 
         [0039]    In an exemplary embodiment, the spring-like flexible tip member  40  may be laser cut from a hollow cylindrical tube of material having a plurality of electromagnetic microsensors  24  that are attached to and positioned within the center of the spring-like flexible tip member  40 . 
         [0040]      FIG. 7  illustrates a perspective view of an exemplary embodiment of the spring-like flexible tip member  40  of  FIG. 6  attached to a strengthening member  50  of a guidewire.  FIG. 8  illustrates an enlarged perspective view of the distal end  52  of the strengthening member  50  of the guidewire. The strengthening member  50  may be a solid wire or a hollow cylindrical tube with a plurality of plated electrical conductor leads or traces  56  extending along the length of the strengthening member  50  of the guidewire. The strengthening member  50  includes a distal end  52  and a proximal end  54 . The distal end  52  of the strengthening member  50  may be brazed, soldered, or welded to the proximal end  44  of the spring-like flexible tip member  40 . In an exemplary embodiment, strengthening member  50  may comprise materials selected from the group of stainless steel, nickel, titanium, alloys of these materials, e.g., nickel-titanium alloy (nitonal), plastics, and composite materials. 
         [0041]      FIG. 9  illustrates a perspective view of a portion of an exemplary embodiment of a guidewire assembly  60 . In an exemplary embodiment, the spring-like flexible tip member  40  may be sealed within an outer member  46  forming an outer covering around the outside of the spring-like flexible tip member  40  or around the outside of the guidewire assembly  60  with a shrinkable protective material. 
         [0042]      FIGS. 10 and 11  illustrate a flexible tip member  70  for a trackable guidewire assembly  80  made out of a substantially tubular member  90  with a plurality of electromagnetic microsensors  24  incorporated into the center of the substantially tubular member  90  to function as the flexible tip member  70  of the guidewire assembly  80 . 
         [0043]      FIG. 10  illustrates a perspective view of an exemplary embodiment of a flexible tip member  70  of a guidewire assembly  80  with at least one electromagnetic microsensor  24  attached to each of a plurality of projections  72  of the flexible tip member  70 . The flexible tip member  70  is made from a substantially tubular member  90  with a plurality of projections  72  attached to and extending upwardly from the substantially tubular member  90  at one end  74  thereof The substantially tubular member  90  farther includes a plurality of openings  76  extending therethrough and positioned adjacent to the end  74  of the plurality of projections  72  that is attached to the substantially tubular member  90  for accepting the plurality of electromagnetic microsensors  24  therein. The openings  76  should be large enough to clearly accept the electromagnetic microsensors  24  therein. 
         [0044]    The substantially tubular member  90  further includes a plurality of plated electrical conductor leads or traces  78  extending along the length of the substantially tubular member  90  for connection to the at least one electromagnetic microsensor  24  attached to each of the plurality of projections  72 . 
         [0045]    In an exemplary embodiment, the traces  78  comprise conductive material such as copper, silver, gold, or any other conductive material. The traces  78  are designed for transmitting or receiving electrical power or electronic signals from the plurality of electromagnetic microsensors  24  to what ever is connected to the end of the traces  78  at the end of the substantially tubular member  90 . Each of the electromagnetic microsensors  24  include at least one electrical signal line and an electrical return that are coupled to the traces  78  that extend along the length of the guidewire assembly  80 . 
         [0046]    In an exemplary embodiment, the electromagnetic microsensors  24  may be built with various electromagnetic microsensor architectures, including, but not limited to electromagnetic microcoils, flux gate magnetometer sensors, squid magnetometer sensors, Hall-effect sensors, anisotropic magneto-resistance (AMR) sensors, giant magneto-resistance (GMR) sensors, and extraordinary magneto-resistance (EMR) sensors. 
         [0047]    In an exemplary embodiment, the electromagnetic microsensors  24  may be electromagnetic microcoils that may be built with various electromagnetic microcoil architectures. In an exemplary embodiment, the electromagnetic microsensors  24  may each include a ferrite core with wire wound around the ferrite core. In an exemplary embodiment, the electromagnetic microsensors  24  may each include a ferrite material, such as a ferrite paste, that is applied to each of the plurality of projections  72  with wire wound around the ferrite material. In an exemplary embodiment, each electromagnetic microsensor  24  may be sealed within a shrink wrap sleeve or coating on the outside of the microsensor  24  with a shrinkable material. 
         [0048]    In an exemplary embodiment, the substantially tubular member  90  may comprise materials selected from the group of stainless steel, nickel, titanium, alloys of these materials, e.g., nickel-titanium alloy (nitonal), plastics, and composite materials. 
         [0049]      FIG. 11  illustrates a perspective view of the flexible tip member  70  of the guidewire assembly  80  of  FIG. 10  with the plurality of electromagnetic microsensors  24  positioned within the center of the flexible tip member  70 . The plurality of projections  72  with the at least one electromagnetic microsensor attached thereto are pushed inside of the flexible tip member  70 , such that the plurality of electromagnetic microsensors  24  positioned within the center of the substantially tubular member  90 . 
         [0050]    In an exemplary embodiment, the flexible tip member  70  may be sealed within an outer member  82  forming an outer covering around the outside of the flexible tip member  70  or around the outside of the guidewire assembly  80  with a shrinkable protective material. 
         [0051]      FIG. 12  illustrates a flow diagram of an exemplary embodiment of a method  100  for making a trackable guidewire assembly. The method  100  includes providing a substantially flexible flat member having a plurality of projections extending therefrom  102 . Another step in the method is attaching at least one electromagnetic microsensor to each of the plurality of projections  104 . The electromagnetic microsensors are properly positioned relative to the substantially flexible flat member for winding the substantially flexible flat member on a mandrel. This step includes winding the substantially flexible flat member with the electromagnetic microsensors attached thereto around the mandrel to create a spring-like flexible tip member for a guidewire  106 . The next step is attaching a strengthening member to a proximal end of the spring-like flexible tip member to create a guidewire assembly  108 . A sleeve or coating may be provided around the outside of the spring-like flexible tip member or the entire guidewire assembly  110 . 
         [0052]      FIG. 13  illustrates a flow diagram of an exemplary embodiment of a method  120  for making a trackable guidewire assembly. The method  120  includes providing a substantially tubular member having a plurality of projections extending outwardly therefrom and a plurality of openings extending therethrough for accepting a plurality electromagnetic microsensors therein  122 . Another step in the method is attaching at least one electromagnetic microsensor to each of the plurality of projections  124 . The plurality of projections with electromagnetic microsensors attached thereto within the substantially tubular member to create a flexible tip member for a guidewire  126 . The next step is attaching a strengthening member to a proximal end of the flexible tip member to create a guidewire assembly  128 . A sleeve or coating may be provided around the outside of the flexible tip member or the entire guidewire assembly  130 . 
         [0053]    Several embodiments are described above with reference to drawings. These drawings illustrate certain details of exemplary embodiments that implement the apparatus, assemblies, systems, and methods of this disclosure. However, the drawings should not be construed as imposing any limitations associated with features shown in the drawings. 
         [0054]    The exemplary embodiments described herein provide specific, feasible apparatus, systems, and methods of integrating electromagnetically trackable microsensors into guidewires that do not currently exist. By integrating microsensors into guidewires in a robust and clinically effective way, minimally invasive surgical techniques and interventional procedures, can utilize electromagnetic tracking technology to provide more efficient treatments, less radiation dose, and faster procedures. 
         [0055]    The exemplary embodiments of guidewires described herein may be used as part of a surgical navigation system employing electromagnetic tracking technology that may be used in an interventional surgical suite. The surgical navigation system may be integrated into a fixed C-arm system, a portable C-arm system, or a stand-alone tracking (electromagnetic-based navigation) system. 
         [0056]    The foregoing description of exemplary embodiments has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the disclosure. The embodiments were chosen and described in order to explain the principles of the disclosure and its practical application to enable one skilled in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. 
         [0057]    While the disclosure has been described with reference to various embodiments, those skilled in the art will appreciate that certain substitutions, alterations and omissions may be made to the embodiments without departing from the spirit of the disclosure. Accordingly, the foregoing description is meant to be exemplary only, and should not limit the scope of the disclosure as set forth in the following claims.