Patent Publication Number: US-2015074995-A1

Title: Guidewire assembly methods and apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of International Application No. PCT/US2013/038147 filed Apr. 25, 2013, which claims the benefit of priority to U.S. Provisional Application No. 61/644,326 filed May 8, 2012, which is incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to methods and apparatus for the assembly of guidewires having multiple sensors incorporated within or along the body of the guidewire. In particular, the present invention relates to methods and apparatus for the assembly of guidewires incorporating pressure sensors and one or more electrodes within or along the body of the guidewire. 
     BACKGROUND OF THE INVENTION 
     Guidewires may have a number of sensors or sensor assemblies integrated directly into the guidewire. Such sensor-equipped guidewires may be adapted for measuring various physiological parameters within a patient&#39;s body. For instance, sensors typically have one or more cables passed through the guidewire for electrically coupling the sensor element to an electronic assembly. 
     Guidewires are generally comprised of a hypotube and coiled segment about a core wire which may extend through the length or a partial length of the guidewire. The core wire may be fabricated from stainless steel or Nitinol with the coiled segment fabricated from a wire or braid which provide for flexibility, pushability, and kink resistance to the guidewire. Nitinol wire, used by itself or braided with stainless steel, may further help to increase flexibility and allow the wire to spring back into shape. 
     Moreover, guidewires have a standard diameter of 0.014 in. and consequently accommodating certain types of sensors or having multiple sensors may be limited by the relatively small space provided by the guidewire. Moreover, guidewires are typically used for insertion into and advancement through the vasculature which can present an extremely tortuous pathway. Thus, the guidewire and any sensors or electrodes along the guidewire may experience relatively large stresses as the guidewire is pushed, pulled, or torqued over a passageway having numerous curves and bends. 
     Guidewires incorporating one or more electrodes along their length may present additional challenges to guidewire construction and use. For instance, the presence of a plurality of electrodes along the guidewire may require additional conductive wiring passed through the length of the guidewire. Because of the limited space and flexibility required from guidewires, any sensors and/or electrodes positioned along their length are desirably correspondingly constructed. 
     Consequently, there is a need for guidewire designs which provide for effective construction of a guidewire incorporating one or more electrodes and/or sensors along the length. 
     SUMMARY OF THE INVENTION 
     Guidewires may incorporate a number of different sensors within or along the body of the guidewire. One particular variation may incorporate a pressure sensor with one or more electrodes along the body of the guidewire or at the distal end of the guidewire. A guidewire having one or more electrodes integrated directly along the guidewire body may have a proximal coil attached to an electrode assembly having one or more electrodes and a distal coil attached to a distal end of the electrode assembly. The electrode assembly may further have insulative spacing segments positioned between each of the electrodes to provide for electrical insulation and both the electrodes and spacing segments may be positioned along an electrode assembly or substrate fabricated from insulative polymers, e.g., polyimide. A core wire may extend through the length of the guidewire assembly and may extend partially or entirely through the electrode assembly. 
     One variation for assembling the guidewire assembly may generally comprise providing a core wire having a tapered distal section, securing a sensor package having one or more conductive wires to the core wire by passing the core wire through a wire receiving channel defined through or along the sensor package, securing the one or more conductive wires to the core wire, and then encasing the one or more conductive wires and the core wire. 
     Another variation for assembling the guidewire assembly and integrating an electrode assembly may have the proximal end of a truncated core wire and the distal end of core wire or hypotube coupled, joined, or otherwise attached to one another. The electrode assembly may then be advanced over the core wire or hypotube into contact against the proximal end of the distal coil where the electrodes may be electrically coupled to a corresponding conducting wire. The proximal coil may be advanced over the core wire or hypotube into contact against the proximal end of the electrode assembly and the two may be coupled or otherwise attached to one another. 
     In yet another variation for manufacturing the guidewire, a relatively shortened core wire, e.g., less than 3 cm, may be used or in another variation, a core wire having a length greater than 3 cm, e.g., 20 cm or longer, may be used instead. 
     In yet another method of attachment to a core wire, the hypotube may have a distal section initially reduced in diameter. The reduced annular portion may then be further processed to remove an arcuate or skived portion which extends from a shoulder of the annular portion down to the distal end of the hypotube such that a tapered distal section is formed. The narrowed end of the distal section may be coupled directly to one another. With the core wire positioned within the distal coil, the electrode assembly may be connected to the proximal end of distal coil while the proximal coil may be connected to the proximal end of the electrode assembly. The various attachments may be achieved through any number of attachment methods, e.g., solder joint, adhesively joined, etc. The attachment may also alternatively use a clip or collar which may be placed over or upon the respective terminal ends. 
     In yet another variation for manufacturing the guidewire assembly, a core wire may be joined directly to a tapered portion of the hypotube utilizing any number of attachment methods described herein. With the core wire and hypotube coupled, the electrode assembly may be placed along the core wire and the wires passed through the hypotube lumen. The proximal and distal coils may also be attached proximally and distally of the electrode assembly. 
     Aside from the integration of an electrode assembly along the guidewire, the guidewire assembly may also optionally incorporate one or more sensors along its length. Although any number of sensors for detecting physiological parameters may be integrated, one particular sensor may include a pressure sensor for detecting intravascular fluid pressure. Because of the sensitive nature of the sensor, the pressure sensor diaphragm may be generally insulated from stress, e.g., by omitting coatings or epoxy from areas beneath and/or over the diaphragms. Hence, the regions around the wirebonding connecting the sensor to a substrate or conducting wires are ideal areas for maintaining low stress regions. One example for assembling a pressure sensor having low stress attachment may utilize a platform either formed directly along the core wire or along a separate platform integrated along the core wire or guidewire body used as a floor for attaching the various components of a pressure sensor. 
     In mounting or attaching the conductive wires along the sensor assembly, various methods may be used for electrically and mechanically bonding the wires along the sensor assembly to maintain a low profile configuration for integrating along the guidewire assembly. One example may be to form a surface mount configuration where an assembly jig may be used. The assembly jig may define a surface having a recess which is sized to receive the substrate or die to be mounted in a secure fitting. One or more channels may be defined along the jig extending from one or more openings directly to the recess. The number of channels may correspond to the number of conductive wires to be surface mounted along the substrate or die. Moreover, the channels may be angled and/or tapered to facilitate guidance of the wires directly to the recess. 
     The wires may be inserted through a respective opening and placed into proximity to, e.g., a pressure sensor die, positioned within the recess, where the exposed terminal ends may then be soldered or otherwise attached directly to the pressure sensor die. Additionally and/or alternatively, rather than directly attaching the wires to the die surface, an optional endcap fabricated from a metal or plastic may be used to alleviate any stresses which may be imparted between the attachment of wires to the sensor die. 
     In yet another example for integrating a pressure sensor assembly into a guidewire while maintaining a low profile configuration, the pressure sensor die may be electrically connected directly to one or more conductive wires through attachment via conductive pads utilizing a flip chip type mounting configuration. In the arrangement shown, the one or more conductive wires may be routed through the guidewire and into proximity to the pressure sensor mounting region defined along the guidewire. Within the mounting region, a platform or floor formed along the region may further form recessed region which may be formed as a recess within the platform. With the pressure sensor die inverted relative to the platform, the conductive wires may be electrically connected directly to the respective conductive pads located along the surface of the pressure sensor die. Another example for mounting the pressure sensor die along the guidewire in a low profile may have the pressure sensor die mounted directly to the platform or floor thus allowing for the direct surface mounting of the once or more wires to the respective conductive pads along the surface of the sensor die. This variation also allows for the direct exposure of the diaphragm for sensing physiological parameters. Additionally, this variation may also present the shortest overall height of the pressure sensor relative to the platform thus allowing for a low profile and may also accommodate a relatively wider die. 
     To electrically couple each of the electrodes and the pressure sensor, multiple conductive wires may be routed through the length of the guidewire but to ensure that the multiple wires are ordered and remain untangled, the wires may be bundled relative to one another. With the conductive wires accordingly stacked and aligned, a first row of wires may be assigned for electrical coupling to the corresponding number of electrodes while the second row of wires may be assigned for electrical coupling to the pressure sensor assembly. 
     Another example may have the wires processed to have exposed selective regions through the insulative covering at uniform or staggered longitudinal locations for electrically coupling to electrodes or sensors. Alternatively, the terminal ends of the wires may be cut such that the exposed terminal portions are positioned at staggered lengths relative to one another. 
     In yet another variation for mounting a pressure sensor die having a diaphragm and one or more conductive pads, an electrode assembly may be formed as a composite assembly to which the sensor die may be mounted directly upon. The electrode assembly may be formed to have one or more electrode segments alternated with one or more corresponding insulating segments. Each of the electrode segments may be patterned and removed from a sheet or layer of conductive material such that the electrode segments are individually formed from the sheet or layer or stacked upon one another to form the composite structure. 
     The electrode assembly may define a core wire receiving channel through the length of the assembly and the outer surfaces of the assembly may define a sensor receiving slot along a length of the assembly as well as an optional slot, e.g., for wiring, etc., along the length of the assembly opposite to the sensor receiving slot. The pressure sensor die may be placed directly within the receiving slot and electrically coupled via respective wirebonds to conductive wires which may be passed through the slot. 
     Another variation may involve a core wire configured to have a reduced section along its length to provide a sensor mounting section. The reduced section may have a cross-sectional area which is shaped into various configurations to facilitate the mounting or securement of the electrode assembly or other sensors along the section. The conductive segment may define a core wire receiving channel which may be optionally narrowed to provide for a snap fit over the reduced section. Similarly, the insulating segment may also define one or more wire receiving channels as well as a core wire receiving channel. With the desired number of conductive segments formed and the corresponding number of insulating segments also formed, each of the segments may be secured upon the reduced section in an alternating manner as well as secured to one another through various securement methods, e.g., adhesives, mechanical, etc. While the reduced section may be formed to have a cross-sectional area which is shaped into various configurations, the receiving channels defined by the segments may be correspondingly configured as well. 
     In yet another variation, a discontinuous core wire may be separately attached to the sensor housing. A proximal core wire section and a distal core wire section may each be attached at their respective locations via any number of attachments. Such an arrangement may allow for maintaining adequate space for securement of the sensor along the housing while maintaining a low profile guidewire assembly. Yet another variation may have a portion of the sensor die having the diaphragm extend proximally or distally from the electrode assembly in a cantilevered manner remaining unattached beneath the die. Another variation may incorporate an adjacently secured barrier segment which defines a sensor opening and core wire receiving channel. The sensor opening may be configured as a passage, e.g., rectangular, which is sized to fit the pressure sensor through without necessarily contacting the pressure sensor so as to limit any transfer of stresses. 
     Yet another variation may be formed from a conductive tube fabricated from a metallic material and attached or otherwise connected over an insulative tube which may provide structural support to the electrode assembly by holding and maintaining a position of each of the conductive segments as well as providing electrical insulation. The insulative tube may define a core wire channel through which the core wire may be positioned. With the conductive tube, portions of the tubing may be removed to provide for space into which the pressure sensor die may be positioned. A structure with similar functional attributes may also be achieved using different manufacturing techniques, e.g., molding the body along with the core wire hole with plastic (non-conductive such as PEEK) and then selectively metalizing the surfaces (e.g., using photo chemical etching) to obtain the conducting pattern to dimensionally align with the conductive pads on the corresponding sensor die. 
     With the respective channels formed, segments may be formed by the conductive tube by removing selective portions of the material. The formed gaps between each of the conductive segments may have a width to provide for the placement of electrically insulative materials within. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a cross-sectional side view of one variation of a guidewire illustrating one or more electrodes positioned along the guidewire body near or at the distal end. 
         FIG. 2  shows a perspective view of the distal end electrode spacing. 
         FIG. 3  shows a side view of an electrode assembly having one or more electrodes spaced apart from one another with insulative material positioned between. 
         FIGS. 4A to 4C  illustrate one variation for assembling an electrode assembly along a guidewire. 
         FIG. 5  shows a cross-sectional side view of another variation for assembling a guidewire having one or more electrodes positioned therealong. 
         FIG. 6  shows a cross-sectional side view of yet another variation for assembling a guidewire having one or more electrodes. 
         FIGS. 7A and 7B  show side views of a hypotube which may be configured for attachment to a core wire. 
         FIGS. 7C and 7D  show top views of a hypotube attached to a core wire and integrally forming a guidewire having one or more electrodes integrated therealong. 
         FIG. 7E  shows a cross-sectional side view of a core wire to hypotube attachment using a clip or collar for coupling the two portions. 
         FIGS. 8A to 8D  show perspective views of another variation for assembling a guidewire having one or more electrodes positioned therealong. 
         FIG. 9  shows a detail perspective view for coupling a hypotube to a second tubular member for forming a guidewire. 
         FIG. 10  shows a partial cross-sectional side view of one method for placing one or more radio-opaque bands on the guidewire. 
         FIG. 11  shows a partial cross-sectional side view of a guidewire incorporating a continuous core wire through a pressure sensor housing. 
         FIGS. 12A and 12B  show top and side views of a pressure sensor die positioned directly upon a floor of the sensor housing. 
         FIGS. 13A and 13B  illustrate a top view of an assembly jig which may be used to attach one or more conductive wires to a pressure sensor die. 
         FIGS. 14A and 14B  show side and end views of one or more conductive wires and an end cap which may be used to position and maintain the wires relative to a pressure sensor die. 
         FIGS. 15A to 15D  illustrate partial cross-sectional side views of another variation for attaching one or more wires through an endcap and onto a pressure sensor die. 
         FIGS. 16A to 16C  show respective end, side, and top views of a flip-chip assembly method for attaching a pressure sensor die directly to a sensor housing. 
         FIGS. 17A to 17C  show respective end, side, and top views of another method for attaching the pressure sensor die directly to the sensor housing. 
         FIG. 18  shows a perspective view of a guidewire having the one or more electrodes and a pressure sensor integrated directly into the guidewire. 
         FIG. 19A  shows a cross-sectional end view of one variation for aligning multiple conductive wires through the guidewire. 
         FIG. 19B  shows a cross-sectional end view of another variation of aligned multiple conductive wires having an optional metallization layer coated over the assembly. 
         FIG. 20A  shows one variation for terminating a first set of conductive wires at the one or more electrodes and a second set of conductive wires at the pressure sensor assembly. 
         FIG. 20B  shows a top view of conductive wires which may have offset exposed portions for electrical coupling. 
         FIG. 20C  shows a top view of conductive wires illustrating how the terminal ends may be offset for electrical coupling. 
         FIG. 21  show a perspective view of a pressure sensor die to be secured to an electrode assembly along a guidewire. 
         FIGS. 22A and 22B  show perspective and end views of another variation of a guidewire having a defined channel for positioning of the pressure sensor. 
         FIG. 23A  shows a side view of a core wire having a reduced section for securing an electrode assembly. 
         FIGS. 23B and 23C  show end views of one variation of conductive and insulative segments for securement to the core wire. 
         FIGS. 23D and 23E  show end views of another variation of conductive segments which may be configured to the core wire having a predetermined cross-sectional shape. 
         FIG. 24  shows a side view of another variation of a core wire which may be attached as separate portions to a pressure sensor housing. 
         FIGS. 25A to 25C  show side and end views of a pressure sensor die which may be cantilevered to reduce or eliminate any stresses imparted to the sensing diaphragm. 
         FIGS. 26A to 26C  show side, end, and perspective views of another variation of a barrier segment which may be integrated into the guidewire. 
         FIGS. 27A and 27B  show perspective and end views of another variation of a core wire having a tubular pressure sensor housing secured around the core wire. 
         FIGS. 28A and 28B  show end views illustrating an example of how material from the tubular pressure sensor housing may be removed for forming a pressure sensor receiving channel. 
         FIG. 29  shows a side view of the conductive segments and tubular pressure sensor housing secured upon the core wire. 
         FIG. 30  shows an end view illustrating a pressure sensor die and conductive wires positioned upon the respective receiving slots. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Guidewires may incorporate a number of different sensors within or along the body of the guidewire. One particular variation may incorporate a pressure sensor with one or more electrodes along the body of the guidewire or at the distal end of the guidewire. To achieve the combination of the pressure sensor and one or more electrodes, various assembly methods and apparatus may be utilized as described in further detail herein. 
     Examples of guidewires which may incorporate one or more electrodes for assessing various anatomical parameters, such as lumen dimension in vivo, and which may also integrate one or more sensors such as pressure sensors, are shown and described in further detail in the following: U.S. Prov. 61/383,744 filed Sep. 17, 2010; U.S. application Ser. No. 13/159,298 filed Jun. 13, 2011 (U.S. Pub. 2011/0306867); Ser. No. 13/305,610 filed Nov. 28, 2011 (U.S. Pub. 2012/101355); Ser. No. 13/305,674 filed Nov. 28, 20111 (U.S. Pub. 2012/0101369); Ser. No. 13/305,630 filed Nov. 28, 2011 (U.S. Pub. 2012/0071782); Ser. No. 13/709,311 filed Dec. 10, 2012; and Ser. No. 13/764,462 filed Feb. 11, 2013. Each of the applications is incorporated herein by reference in its entirety and is provided for any purpose herein. 
     Additional examples are also shown and described for the assembly and use of the combination of one or more pressure sensors and one or more electrodes within or along a guidewire in PCT/US2012/034557 filed Apr. 20, 2012 (published as WO 2012/173697 and designating the U.S.) which is also incorporated herein by reference in its entirety for any purpose herein. It is intended that any of these guidewires and other guidewires may utilize any of the methods and apparatus described herein in various combinations as practicable. 
     Turning now to  FIG. 1 , an example of a guidewire  10 , e.g., 0.014 in. diameter guidewire, having one or more electrodes integrated directly along the guidewire body is shown in the partial cross-sectional side view. As shown, a hypotube  12 , e.g., Nitinol, stainless steel, etc., may have a proximal coil  20 . e.g., fabricated from stainless steel, attached to an electrode assembly  14  having one or more electrodes  18  (in this variation four electrodes spaced apart from one another) and a distal coil  22  attached to a distal end of the electrode assembly  14  and terminating in an atraumatic distal tip  26 . 
     The electrode assembly  14  may further have insulative spacing segments  28  positioned between each of the electrodes  18  to provide for electrical insulation and both the electrodes  18  and spacing segments  28  may be positioned along an electrode assembly or substrate  16  fabricated from, e.g., polyimide. One or both of the proximal coil  20  and/or distal coil  22  may be fabricated from a variety of biocompatible materials which also provide sufficient structural strength, e.g., platinum (Pt), platinum-iridium alloys (Pt/Ir), etc. A core wire  24  may extend through the length of the guidewire assembly  10  and may extend partially or entirely through the electrode assembly  14 . The core wire  24  may be fabricated from, e.g., stainless steel, Nitinol, etc., and may also be tapered into a relatively smaller diameter the further distal the core wire  24  extends. 
     Another view of the guidewire assembly  10  is shown in the perspective view of  FIG. 2 , which illustrates the spacing of the electrodes  18  with the adjacent insulative spacing segments  28  between each of the electrodes  18 . Also shown are the proximal and distal coils  20 ,  22 , respectively, and the smooth outer surface presented by the assembly  10 .  FIG. 3  shows a side view of the electrode assembly  16  removed from the guidewire body to illustrate the positioning of the electrodes  18  relative to the spacing segments  28  and how the one or more conducting wires  30  electrically coupled to each of the respective electrodes  18  may extend proximally from the assembly  16 . 
       FIGS. 4A to 4C  illustrate one variation for assembling the guidewire assembly  10  and integrating an electrode assembly  16 . As shown in  FIG. 4A , core wire  24  may be secured within a portion of the distal coil  22  where the core wire  24  having an outer diameter of, e.g., 0.005 in., may be tapered to an outer diameter of, e.g., 0.002 in., over a length of, e.g., 3 cm. A core wire or hypotube  12  separate from the core wire  24  may have one or more conducting wires  30  for attachment to the electrodes twisted, spooled, or otherwise wrapped around the core wire or hypotube  12 . With this assembly, the proximal end of the core wire  24  and the distal end of core wire or hypotube  12  may be coupled, joined, or otherwise attached at an attachment  40 , e.g., laser welded joint, to one another, as shown in the side view of  FIG. 48 . In this embodiment two different core wires are described since the materials of the core wires can be different (e.g. Nitinol for the distal core wire and stainless steel for the proximal core wire) to take advantage of the material properties and satisfy different performance requirements of the wire (e.g., high kink resistance offered by a Nitinol distal core versus high stiffness along the proximal shaft which may be derived using a stainless steel core). However, it should be noted that a single continuous core wire material (e.g., stainless steel) may be used for the wire construction. 
     The electrode assembly having the electrodes  18  and insulative spacing segments  28  may then be advanced over the core wire or hypotube  12  and conducting wires  30  into contact against the proximal end of the distal coil  22  where the electrodes  18  may be electrically coupled to a corresponding conducting wire  30 . The proximal coil  20  may be advanced over the core wire or hypotube  12  into contact against the proximal end of the electrode assembly and the two may be coupled or otherwise attached to one another, as shown in the side view of  FIG. 4C . It should be noted that in place of a coil  20  a suitable polymer (e.g., polyimide or nylon) can be used to encapsulate the core and the conducting wires through the length of the guidewire. 
     In yet another variation for manufacturing the guidewire,  FIG. 5  shows a partial cross-sectional side view of a guidewire assembly having a relatively shortened core wire  24 , e.g., less than 3 cm, such that the proximal end of the core wire  24  is positioned within the distal coil  22 . The distal end of core wire or hypotube  12  is correspondingly longer and may extend distally through the electrode assembly and at least partially into and through the proximal end of the distal coil  22 . The addition of a hypotube  42 , e.g., laser cut, may be attached or coupled to a proximal end of the proximal coil  20 . 
       FIG. 6  shows yet another variation where the core wire  24  may be relatively lengthened such that the core wire  24  has a length greater than 3 cm, e.g., 20 cm or longer, and may extend proximally such that the terminal end is positioned proximally of the electrode assembly and within the proximal coil  20 . The attachment  40  between the proximal end of the lengthened core wire  24  and the distal end of the core wire or hypotube  12  may be accordingly positioned proximal to the electrode assembly and within the proximal coil  20  or within the hypotube  42 . 
       FIGS. 7A to 7D  illustrate yet another method of attachment to a core wire  24  through an electrode assembly and directly to a hypotube  42 . In this variation, the hypotube  42  may have a distal section initially reduced in diameter from an outer diameter of, e.g., 0.014 in., down to an outer diameter of, e.g., 0.012 in., along a length of less than, e.g., 1.0 in., as shown by the reduced annular portion  50  in the side view of  FIG. 7A . The reduced annular portion  50  may then be further processed to remove an arcuate or skived portion  54  which extends from a shoulder  58  of the annular portion  50  (e.g., forming a length of 0.315 in.) down to the distal end  52  of the hypotube  42  such that a tapered distal section  56  is formed, as shown in the side view of  FIG. 7B . 
     As seen in the top view of  FIG. 7C , the resulting tapered distal section  56  may be narrowed down to a width of, e.g., 0.005 in., which may correspond to a diameter of the core wire  24 . The narrowed end of the distal section  56  may be coupled directly to one another via attachment  40  (using any of the attachment methods herein) such that the core wire  24  and connected distal section  56  form a direct and integrated structure. With core wire  24  positioned within the distal coil  22 , the electrode assembly may be connected to the proximal end of distal coil  22  via attachment  64  while proximal coil  20  may be connected to the proximal end of the electrode assembly via attachment  62  and to the shoulder  58  of hypotube  42  via attachment  60 , as shown in the partial cross-sectional side view of  FIG. 7D . The various attachments may be achieved through any number of attachment methods, e.g., solder joint, adhesively joined, etc. 
     While the attachment  40  between the core wire  24  and the tapered distal section  56  may be achieved via any of the attachment methods described above, the attachment may also alternatively use a clip or collar  70  (e.g., platinum tube, etc.) which may be placed over or upon the respective terminal ends. The terminal end of the core wire  24  may alternatively define a reduced section  66  (e.g., having a diameter of 0.012 in.) while the terminal end of the distal section  56  may similarly define a reduced section  68  (also having a similarly reduced diameter of 0.012 in.). The clip or collar  70  may be placed over each of the reduced sections  66 ,  68  and crimped or attached accordingly, e.g., laser or spot welded to respective reduced sections  66 ,  68 , as shown in the detail side view of  FIG. 7E . 
     In yet another variation for manufacturing the guidewire assembly,  FIGS. 8A to 8D  show perspective views illustrating another example of how an electrode assembly  14  having one or more corresponding conductive wires  30 , as shown in  FIG. 8A , may be assembled with a core wire  24  joined directly to a tapered portion  56  of the hypotube  42 , as shown in  FIG. 8B . A proximal section of the core wire  24  may be joined along an attachment region  70  to a distal section  56  of the tapered hypotube  42 . The core wire  24  may be attached utilizing any number of attachment methods described herein. With the core wire  24  and hypotube  42  coupled, the electrode assembly  14  may be placed along the core wire  24  and the wires  30  passed through the hypotube lumen  72 , as shown in  FIG. 8C . The proximal and distal coils  20 ,  22  may also be attached proximally and distally of the electrode assembly  14 , as shown in  FIG. 8D  and as described herein. 
     Additionally and/or optionally, in the event that a second hypotube  80  is joined to the hypotube  42 , a reduced section  82  of second hypotube  80  and a reduced section  84  of hypotube  42  may be coupled to one another via a clip or collar  86 , e.g., platinum tube, which may be laser or spot welded to the respective reduced sections  82 ,  84 , as shown in the detail perspective view of  FIG. 9 . 
     In the event that any of the guidewire assemblies described herein require one or more radio-opaque markers to be integrated along its length, any number of crimping or attachment methods may be utilized. One additional and/or optional variation is shown in the partial cross-sectional side view of  FIG. 10  which shows a guidewire assembly having one or more radio-opaque markers  90  attached. Such markers  90  may be attached, e.g., by gold solder formed upon the respective coiled sections. By omitting any metal components for the markers  90 , the number of steps may be reduced in manufacturing the guidewire and may further avoid any increase in guidewire profile. 
     Aside from the integration of an electrode assembly along the guidewire, the guidewire assembly may also optionally incorporate one or more sensors along its length. Although any number of sensors for detecting physiological parameters may be integrated, one particular sensor may include a pressure sensor for detecting intravascular fluid pressure. A partial cross-sectional side view is shown in  FIG. 11  to illustrate an example of the relative positioning of the pressure sensor within or along the guidewire. As shown, the pressure sensing guidewire assembly  100  may have the pressure sensor housing  102  secured along the guidewire body at or near the terminal end  26  of the guidewire such that the diaphragm  106  of substrate  108  is exposed through slot  110  for contact with the surrounding fluid. The guidewire assembly  100  may further include the core wire  24  passing through the guidewire and sensor housing  102 . The distal coiled body  22  of the guidewire assembly  100  may extend distally from the sensor housing  102  while the leads  112  connecting the diaphragm  106  and substrate  108  may pass proximally through the guidewire body  104  that is encapsulated in one or more polymers along its length may also be seen for connection to another module, e.g., a processor, monitor, etc., located outside the patient&#39;s body in use. 
     Because of the sensitive nature of the sensor, the pressure sensor diaphragm may be generally insulated from stress, e.g., by omitting coatings or epoxy from areas beneath and/or over the diaphragms. Hence, the regions around the wirebonding connecting the sensor to a substrate or conducting wires are ideal areas for maintaining low stress regions. One example for assembling a pressure sensor having low stress attachment may be seen in the top and side views of  FIGS. 12A and 12B  which show pressure sensor assembly  120  which may be integrated along the guidewire assembly. As shown in  FIG. 12A , a platform  122  either formed directly along the core wire or along a separate platform integrated along the core wire or guidewire body may be used as a floor for attaching the various components of a pressure sensor. The platform  122  may be secured between apposed cylindrical walls  136  and the walls  136  and platform  122  may be secured to the core wire or a distal and proximal portion of a core wire may be attached at respective distal and proximal locations along the cylindrical walls  136 . 
     As shown, the pressure sensor die  124  and substrate  126  (e.g., PCB substrate, flex circuit, etc.) may be attached directly to the floor  122  between the walls  136 . One or more conductive wires  134  may be secured through the proximal cylindrical wall  136  such that the exposed terminal ends of the wires  134  may be electrically attached to the substrate  126 . Electrical connections between the pressure sensor die  124  and substrate  126  may be made by wirebonds  132  coupling respective conductive pads  128 ,  130  which are also electrically coupled to the one or more conductive wires  134 . The wirebonds  132  may have a loop height generally about, e.g., 0.001 to 0.002 in., above the surface of the substrate  126  with a wirebond outer diameter of about, e.g., 0.001 in., as shown in the side view of  FIG. 12B . With this configuration of the pressure sensor die  124  and substrate  126  placed directly upon the floor  122 , the assembly may maintain a low profile for integration along the guidewire body. Aside from utilizing wirebonds, flip chip methods of bonding using stud bumps can also be utilized to save space (as described in further detail herein). 
     In mounting or attaching the conductive wires along the sensor assembly, such as the substrate  126  or pressure sensor die  124 , various methods may be used for electrically and mechanically bonding the wires along the sensor assembly to maintain a low profile configuration for integrating along the guidewire assembly. One example may be to form a surface mount configuration where an assembly jig  140  such as the one shown in the top view of  FIG. 13A  may be used. The assembly jig  140  may define a surface having a recess  142  which is sized to receive the substrate or die to be mounted in a secure fitting. One or more channels  144  may be defined along the jig  140  extending from one or more openings  146 A,  146 B,  146 C directly to the recess  142 . The number of channels  144  may correspond to the number of conductive wires  148  to be surface mounted along the substrate or die. Moreover, the channels  144  may be angled and/or tapered to facilitate guidance of the wires  148  directly to the recess  142 . 
     The conductive wires  150 A,  150 B,  150 C, shown in this example as three wires although fewer or greater number of wires may be used, may each have their terminal ends  152 A,  152 B,  152 C exposed for attachment, as shown in  FIG. 13A . The wires  150 A,  150 B,  150 C may be inserted through a respective opening  146 A,  146 B.  146 C and placed into proximity to, e.g., a pressure sensor die  154 , positioned within the recess  142 , where the exposed terminal ends  152 A,  152 B,  152 C may then be soldered or otherwise attached directly to the pressure sensor die  154 , in this example although other substrates may also be used, and as shown in  FIG. 13B . 
     Additionally and/or alternatively, rather than directly attaching the wires  148  to the die surface, an optional endcap  160  fabricated from a metal or plastic may be used to alleviate any stresses which may be imparted between the attachment of wires  148  to the sensor die  154 . An example is shown in the end and side views of  FIGS. 14A and 14B  which illustrate a cylindrical endcap  160  (also shown as the cylindrical wall  136  in  FIGS. 12A and 12B ). The endcap  160  may have a diameter consistent with the diameter of the guidewire and may further define one or more wire receiving openings  162 A,  162 B,  162 C each having a diameter of, e.g., 0.0015 to 0.003 in, for receiving a corresponding wire. Fewer than three or more than three openings may be utilized depending upon the number of wires used. Alternatively, the openings may be sized to accommodate two or more wires and the openings may be sized in different configurations depending upon the number of wires passed through the openings. An additional core wire opening  164  having a diameter of, e.g., 0.003 to 0.006 in., may also be defined through the endcap  160 . The position of the core wire opening  164  can either be concentric or off-centered depending on space availability and performance requirements. 
       FIGS. 15A to 15D  show partial cross-sectional side views of another variation for surface mounting or attaching conductive wires to a substrate or pressure sensor die using the endcap  160 . As shown in  FIG. 15A , the assembly jig  170  may similarly define a recess  172  sized to receive a substrate or sensor die upon which the wires are to be connected. The jig  170  may further define an endcap channel or recess  174  at a location adjacent to where the wire channels  178  are defined through a wire guide  176 . The endcap channel or recess  174  may extend into the jig  170  at a depth sufficient to accommodate the diameter of the endcap  160  such that the openings  162 B through the endcap  160  align with the wire channels  178  and substrate or die when positioned within the recess  172 , as shown in the partial cross-sectional side view of  FIG. 15B . 
     With the one or more wires  150 B inserted through the corresponding wire channel  178  and endcap opening  162 B, the exposed terminal end  152 B may be placed upon the conductive pad along the pressure sensor die  180  positioned adjacent to the endcap  160  and within the recess  172 . The terminal end  152 B may then be attached or appropriately surface-mounted upon the sensor  180  through any number of attachment methods such as solder, conductive epoxy, etc. optionally followed by an additional overcoat  182 , as shown in  FIG. 15C . The wire guide  176  may be slidably attached to the remainder of the jig  170  such that the guide  176  may be retracted to expose the endcap  160 . The junction formed between the entry location of the wire  150 B and endcap  160  may also be attached relative to one another using any number of attachment methods described above. The attachment may be followed by an optional overcoat  184 , as shown in  FIG. 15D . Once the attachment has been completed, the sensor  180 , endcap  160 , and wire  152 B assembly may be removed from the jig  170  for assembly into the guidewire. 
     In yet another example for integrating a pressure sensor assembly  190  into a guidewire while maintaining a low profile configuration,  FIGS. 16A to 16C  show another variation in the end, side, and top views where the pressure sensor die  180  may be electrically connected directly to one or more conductive wires  148  through attachment via conductive pads  192  utilizing a flip chip type mounting configuration. In the arrangement shown, the one or more conductive wires  148  may be muted through the guidewire and into proximity to the pressure sensor mounting region  200  defined along the guidewire. Within the mounting region  200 , a platform or floor  202  formed along the region may be further form recessed region  204  which may be formed as a recess within the platform  202 . With the pressure sensor die  180  inverted relative to the platform  202 , the conductive wires  148  may be electrically connected directly to the respective conductive pads  192  located along the surface of the pressure sensor die  180 . Moreover, by inverting the pressure sensor die  180  the location of the diaphragm  106  may also be inverted to become placed in apposition to the platform  202 , as shown in the side view of  FIG. 16B , directly over the recessed region  204 , as further shown in the top view of  FIG. 16C . Hence, the diaphragm  106  may remain exposed over the region  204  and uninhibited so as to allow for the sensing of physiological parameters such as fluid pressure. It is also possible to make the diaphragm  106  and the conductive pads on the sensor die  192  on the opposite surfaces of the pressure sensor by a technique referred to as Through Silicone Via (TSV). In such a case, the same technique of using the flip chip method described above can be utilized with or without having any recess in the platform  202 . 
     Another example for mounting the pressure sensor die  180  along the guidewire in a low profile is further shown in the end, side, and top views of  FIGS. 17A to 17C . In this variation, the pressure sensor die  180  may be mounted directly to the platform or floor  202  thus allowing for the direct surface mounting of the once or more wires  148  to the respective conductive pads  192  along the surface of the sensor die  180 . This variation also allows for the direct exposure of the diaphragm  106  for sensing physiological parameters. Additionally, this variation may also present the shortest overall height of the pressure sensor relative to the platform  202  thus allowing for a low profile and may also accommodate a relatively wider die. 
       FIG. 18  illustrates a perspective view of an electrode and pressure sensing assembly integrated along a single guidewire  210 . Although the electrode assembly  14  is shown proximal to the pressure sensing housing  102  along the guidewire body, the pressure sensing housing  102  may alternatively be located proximal to the electrode assembly  14  instead. To electrically couple each of the electrodes and the pressure sensor, multiple conductive wires may be routed through the length of the guidewire but to ensure that the multiple wires are ordered and remain untangled, the wires may be bundled relative to one another. 
       FIG. 19A  shows a cross-sectional end view illustrating how multiple conductive wires  212 A,  212 B,  212 C,  212 D and conductive wires  214 A.  214 B,  214 C,  214 D may be positioned relative to one another. While shown in this example with eight wires, this is intended to be illustrative and fewer than eight or greater than eight wires may be utilized in practice. Nonetheless, each of the wires may have a base coating  216 , e.g., polyimide, and a further polymer matrix  218 , e.g., pellathane matrix, surrounding each of the wires and forming an attachment to adjacent wires such that the wires form an ordered and stacked ribbon. Another variation to the conductor configuration may include an additional layer of metallization  219  over the coated polymer matrix  218 , as shown in the end view of  FIG. 19B . Such a metallization layer  219  may have a thickness of, e.g., 2 to 5 microns, and can be added by processes well known in the art such as chemical vapor deposition where metals such as copper, gold, aluminum, etc., are commonly deposited on a substrate (such as polyimide or other polymers). In this case, the metallization layer  219  may be deposited over the polymer matrix  218 . The metallization layer  219  can serve several functions such as electrically isolating the conducting wires from Electro Magnetic (EM) Coupling thus providing an EM shield. This may be desirable in many sensor applications where external noise coupling needs to be avoided. 
     With the conductive wires accordingly stacked and aligned, a first row of wires, e.g., wires  212 A,  212 B,  212 C,  212 D, may be assigned for electrical coupling to the corresponding number of electrodes while the second row of wires, e.g., wires  214 A,  214 B,  214 C,  214 D, may be assigned for electrical coupling to the pressure sensor assembly  102 .  FIG. 20A  shows an example of how the first row of wires may terminate at the electrode assembly  14  through the guidewire while the second row of wires may continue on through the guidewire for coupling to the pressure sensor assembly  102 . 
     Another example is illustrated in the top view of  FIG. 20B  which shows how portions of the conductive wires may be processed to have exposed selective regions  220 A,  220 B,  220 C,  220 D through the insulative covering at uniform or staggered longitudinal locations for electrically coupling to electrodes or sensors. Alternatively, the terminal ends of the wires may be cut such that the exposed terminal portions  222 A,  222 B,  222 C,  222 D are positioned at staggered lengths relative to one another, as shown in the top view of  FIG. 20C . 
     In yet another variation for mounting a pressure sensor die  238  having a diaphragm  240  and one or more conductive pads  242 , as shown in the perspective view of  FIG. 21 ,  FIG. 22A  shows a perspective view of an electrode assembly  230  which may be formed as a composite assembly to which the sensor die  238  may be mounted directly upon. The electrode assembly  230  may be formed to have one or more electrode segments  246  (e.g., fabricated from a conductive material such as gold or other metallic) alternated with one or more corresponding insulating segments  248  (e.g., fabricated from polyimide or other polymeric material or another electrically insulative material). Each of the electrode segments  246  may be patterned and removed (e.g., EDM, laser cut, etc.) from a sheet or layer of conductive material such that the electrode segments  246  are individually formed from the sheet or layer or stacked upon one another to form the composite structure. 
     The electrode assembly  230  may define a core wire receiving channel  236  through the length of the assembly and the outer surfaces of the assembly may define a sensor receiving slot  232  along a length of the assembly as well as an optional slot  234 , e.g., for wiring, etc., along the length of the assembly opposite to the sensor receiving slot  232 . The pressure sensor die  238  may be placed directly within the receiving slot  232  and electrically coupled via respective wirebonds  244  to conductive wires which may be passed through slot  234 , as shown in the partial cross-sectional end view of  FIG. 22B . Once the sensor die  238  has been wirebonded, the assembly may be potted using an appropriate material to provide for further mechanical strength and structural stability. The potting may be restricted to the conductive pads while remaining free from the sensor diaphragm  240 . While wirebonding is shown as the attachment method from the sensor conductive pads to the conducting elements  246 , other methods such as flip chip as described above can be utilized to attach the sensor die directly on the base of the channel  232 . In this case the sensor dies may be fabricated such that the conducting pads  242  and the diaphragm  240  are on opposite faces of the sensor die  238 . This can be achieved by sensor die fabrication methods know in the art such as TSV. Using such a method may yield a desirable profile to package the sensor along a 0.014 in. guidewire. 
       FIG. 23A  illustrates a side view of a core wire  250  which may be configured to have a reduced section  252  along its length to provide a sensor mounting section. The reduced section  252  may have a cross-sectional area which is shaped into various configurations to facilitate the mounting or securement of the electrode assembly or other sensors along the section. One variation is illustrated in the end view of  FIG. 23B  which illustrates a conductive segment  254  and  FIG. 23C  which illustrates an insulating segment  260  which may be attached to the core wire  250  adjacent to the conductive segment  254 . The conductive segment  254  may be formed to have one or more wire receiving channels  258  for passage of the conducting wires and the segment  254  may further define a core wire receiving channel  256  which may be optionally narrowed to provide for a snap fit over the reduced section  252 . Similarly, the insulating segment  260  may also define one or more wire receiving channels  264  as well as a core wire receiving channel  262 . The receiving channel  262  defined by the segment  260  may further define narrowed receiving members  266  which allow for the segment  260  to be snapped into place upon the reduced section  252 . With the desired number of conductive segments  254  formed and the corresponding number of insulating segments  260  also formed, each of the segments  254 ,  260  may be secured upon the reduced section  252  in an alternating manner as well as secured to one another through various securement methods, e.g., adhesives, mechanical, etc. 
     While the reduced section  252  may be formed to have a cross-sectional area which is shaped into various configurations, the receiving channels defined by the segments may be correspondingly configured as well. An example is shown in the end view of  FIG. 23D  which illustrates a conductive segment  270  defining a core wire receiving channel  272  which is formed into a receiving section  274  correspondingly shaped for placement upon a keyed core wire section  252 ′, e.g., elliptical, rectangular, etc. Another variation is shown in the end view of  FIG. 23E  which also shows a conductive segment  276  having a configured receiving section  278  for securement to a correspondingly keyed core wire section  252 ″, e.g., semi-spherical, etc. In this variation, the pressure sensor die may also be placed directly upon the reduced section  242 ″. Other configurations of the reduced section  252  as well as the corresponding shapes defined by the segments may be utilized in other variations. 
     In yet another variation,  FIG. 24  shows a side view of an assembly having a discontinuous core wire  280  which may be separately attached to the sensor housing  102 . A proximal core wire section  282  and a distal core wire section  284  may each be attached at their respective locations via any number of attachments  286 ,  288 . e.g., welded joint, adhered attachment, etc. Such an arrangement may allow for maintaining adequate space for securement of the sensor along the housing  102  while maintaining a low profile guidewire assembly. 
       FIG. 25A  shows a side view of yet another variation where the exposed diaphragm  292  of the pressure sensor die  290  may be isolated from any stresses which may be imparted by the guidewire or sensor die. The pressure sensor die  290  may be attached through the electrode assembly  14  such that the portion of the die  290  having the diaphragm  292  may extend proximally or distally from the electrode assembly  14  in a cantilevered manner remaining unattached beneath the die. A polymeric housing  294  defining a core wire receiving channel  296  may also extend through the electrode assembly  14  adjacent to the cantilevered sensor die  290 , as shown in the end views of  FIGS. 25B and 25C . 
     Another variation is shown in the side, end, and perspective views of  FIGS. 26A to 26C  which illustrates an electrode assembly  14  having an adjacently secured barrier segment  300 , e.g., insulative disc, which defines a sensor opening  302  and core wire receiving channel  296 . The sensor opening  302  may be configured as a passage, e.g., rectangular, which is sized to fit the pressure sensor through without necessarily contacting the pressure sensor so as to limit any transfer of stresses. The sensor opening  302  may also be scaled in size once the sensor has been placed to allow for its uninhibited passage 
     Yet another variation is illustrated in the perspective and end views of  FIGS. 27A and 27B  which show an electrode assembly  310  which may be formed from a conductive tube  312  having a length of, e.g., 0.050 to 0.060 in., and a diameter of, e.g., 0.007 in., fabricated from a metallic material, e.g., stainless steel, platinum-iridium, etc. The conductive tube  312  may be attached or otherwise connected over an insulative tube  314 , e.g., polyimide, etc., having a diameter of, e.g., 0.005 in., which may provide structural support to the electrode assembly  310  by holding and maintaining a position of each of the conductive segments as well as providing electrical insulation. The insulative tube  314  may define a core wire channel through which the core wire may be positioned. 
     With the conductive tube  312 , portions of the tubing may be removed to provide for space into which the pressure sensor die may be positioned. One example is shown in the end views of  FIGS. 28A and 28B  which illustrate how portions of the conductive tube  312  as well as portions of the insulative tube  314  may be removed as indicated by the removed section  318 . The removed section  318  may have a width of, e.g., 0.007 in., and a height of, e.g., 0.0035 in., while an optionally removed section  320  may have a width of, e.g., 0.009 in., as shown in  FIG. 28A . The dimensions of the removed sections  318 ,  320  may be varied depending upon the size of the pressure sensor die used as well as the number of conducting wires.  FIG. 28B  illustrates the end view of the assembly having the sections  318 ,  320  removed to provide for a sensor channel  322  as well as an optional channel  324 , e.g., for passage of wires. 
     With the respective channels formed, segments may be formed by the conductive tube  312  by removing selective portions of the material. An example is shown in the side view of  FIG. 29  which illustrates portions of the conductive tube  312  removed to form conductive segments  326 . The formed gaps  328  between each of the conductive segments  326  where material has been removed may have a width of, e.g., 0.001 to 0.002 in., to provide for the placement of electrically insulative materials within.  FIG. 30  illustrates an end view of the conductive segments  326  having a pressure sensor die  238  positioned along the sensor channel  322  and one or more conductive wires  148  positioned along the optional channel  324 . It should be noted that while a method of obtaining the metal pattern on a insulative material is described, other methods such as selectively metalizing a 3D polymer surface (such as a cylinder or a rectangle with required features such as a core wire hole) via vapor deposition and photo masking it is feasible to create similar patterns and achieve the desired function. 
     It is intended that any of the various manufacturing and assembly processes described herein for the sensor die and/or electrode assembly may be combined in any combination as practicable. For instance, any of the assembly methods and apparatus for integrating the electrode assembly along a guidewire may be applied in combination with any of the assembly methods and apparatus for integrating the sensor along the guidewire as well. Hence, each of the variations described may be utilized alone or in any number of combinations as well. 
     The applications of the devices and methods discussed above are not limited but may include any number of further applications. Moreover, modification of the above-described assemblies and methods for carrying out the invention, combinations between different variations as practicable, and variations of aspects of the invention that are obvious to those of skill in the art are intended to be within the scope of the claims.