Patent Publication Number: US-2021163284-A1

Title: Capacitive intravascular pressure-sensing devices and associated systems and methods

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of U.S. patent application Ser. No. 16/447,635, filed Jun. 20, 2019, which is a continuation of U.S. patent application Ser. No. 15/489,622, filed Apr. 17, 2017, now U.S. Pat. No. 10,329,145, which is a continuation of U.S. patent application Ser. No. 14/133,312, filed Dec. 18, 2013, now U.S. Pat. No. 9,624,095, which claims priority to and the benefit of U.S. Provisional Patent Application No. 61/747,019, filed Dec. 28, 2012, each of which is hereby incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to intravascular devices, systems, and methods. In some embodiments, the intravascular devices are guide wires that include a capacitive pressure-sensing component. 
     BACKGROUND 
     Heart disease is very serious and often requires emergency operations to save lives. A main cause of heart disease is the accumulation of plaque inside the blood vessels, which eventually occludes the blood vessels. Common treatment options available to open up the occluded vessel include balloon angioplasty, rotational atherectomy, and intravascular stents. Traditionally, surgeons have relied on X-ray fluoroscopic images that are planar images showing the external shape of the silhouette of the lumen of blood vessels to guide treatment. Unfortunately, with X-ray fluoroscopic images, there is a great deal of uncertainty about the exact extent and orientation of the stenosis responsible for the occlusion, making it difficult to find the exact location of the stenosis. In addition, though it is known that restenosis can occur at the same place, it is difficult to check the condition inside the vessels after surgery with X-ray. 
     A currently accepted technique for assessing the severity of a stenosis in a blood vessel, including ischemia causing lesions, is fractional flow reserve (FFR). FFR is a calculation of the ratio of a distal pressure measurement (taken on the distal side of the stenosis) relative to a proximal pressure measurement (taken on the proximal side of the stenosis). FFR provides an index of stenosis severity that allows determination as to whether the blockage limits blood flow within the vessel to an extent that treatment is required. The normal value of FFR in a healthy vessel is 1.00, while values less than about 0.80 are generally deemed significant and require treatment. 
     Often intravascular catheters and guide wires are utilized to measure the pressure within the blood vessel, visualize the inner lumen of the blood vessel, and/or otherwise obtain data related to the blood vessel. To date, guide wires containing pressure sensors, imaging elements, and/or other electronic, optical, or electro-optical components have suffered from reduced performance characteristics compared to standard guide wires that do not contain such components. For example, the handling performance of previous guide wires containing electronic components have been hampered, in some instances, by the need to physically couple the proximal end of the device to a communication line in order to obtain data from the guide wire, the limited space available for the core wire after accounting for the space needed for the conductors or communication lines of the electronic component(s), the stiffness and size of the rigid housing containing the electronic component(s), and/or other limitations associated with providing the functionality of the electronic components in the limited space available within a guide wire. 
     Accordingly, there remains a need for improved intravascular devices, systems, and methods that include pressure-sensing components. 
     SUMMARY 
     Embodiments of the present disclosure are directed to intravascular devices, systems, and methods. 
     In one embodiment, a guide wire is provided. The guide wire comprises a first elongate flexible element having a proximal portion and a distal portion, the first elongate flexible element being formed of a conductive material; a second elongate flexible element positioned around the first elongate flexible element, the second elongate flexible element being formed of a conductive material and having an outer diameter of 0.018″, 0.014″, or less; a radial capacitive pressure sensing structure coupled to the distal portion of the first elongate flexible element, the radial capacitive pressure sensing structure having a flexible membrane positioned around at least a portion of a cavity and a conductive member positioned around at least a portion of the flexible membrane such that the conductive member is displaced by changes in ambient pressure relative to a pressure in the cavity; and an application-specific integrated circuit (ASIC) coupled to the distal portion of the elongate flexible element, the ASIC in electrical communication with the conductive member of the radial capacitive pressure sensing component and the first and second flexible elongate elements. 
     In some instances, a section of the proximal portion of the first elongate flexible element is electrically coupled to a first conductive band. Further, in some instances a section of a proximal portion of the second elongate flexible element defines a second conductive band, such that the first conductive band is positioned proximal of the second conductive band. In some embodiments, the guide wire further includes an insulating member positioned between the first and second conductive bands, the insulating member being positioned around the first elongate flexible element. In some implementations, a majority of the second elongate flexible element is electrically isolated from the first elongate flexible element by a non-conductive layer covering the first elongate flexible element. The cavity of the radial capacitive pressure sensing structure includes a lumen of housing in some instances. In some embodiments, the housing includes a plurality of openings in a sidewall of the housing that are in communication with the lumen. In some instances, the plurality of openings are formed radially around a circumference of the housing where the housing has a cylindrical profile. 
     In another embodiment, an intravascular pressure-sensing system is provided. The system comprises a pressure-sensing guide wire having features similar to those described above; a processing system configured to process the data obtained by the pressure-sensing guide wire; and an interface configured to communicatively couple the pressure-sensing guide wire to the processing system. 
     In another embodiment, method of making a pressure-sensing apparatus is provided. The method includes: providing a first conductive tubular member, the first conductive tubular member having a lumen extending along its length; forming a plurality of openings through a sidewall of the first conductive tubular member, the plurality of openings in communication with the lumen of the first conductive tubular member; filling a portion of the lumen of the first conductive tubular member and the plurality of openings with a temporary material; forming a band of the temporary material around an outer surface of the first conductive tubular member, the band of the temporary material formed over the plurality of openings; forming a layer of flexible material over the first conductive tubular member such that the layer of flexible material covers the band of the temporary material; removing the temporary material filling the portion of the lumen and the plurality of openings; and removing the band of temporary material such that a space is created between an inner surface of the layer of flexible material and the outer surface of the first conductive member adjacent each of the plurality of openings such that the layer of flexible material is responsive to changes in ambient pressure relative to a pressure in the lumen of the first conductive tubular member. 
     Additional aspects, features, and advantages of the present disclosure will become apparent from the following detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Illustrative embodiments of the present disclosure will be described with reference to the accompanying drawings, of which: 
         FIG. 1  is a diagrammatic, schematic side view of an intravascular device according to an embodiment of the present disclosure. 
       Collectively,  FIGS. 2-27  illustrate various aspects of manufacturing and/or assembling the intravascular device of  FIG. 1  according to embodiments of the present disclosure. 
         FIG. 2  is a diagrammatic perspective view of a distal core portion of the intravascular device according to an embodiment of the present disclosure. 
         FIG. 3  is a diagrammatic perspective view of an expander coupled to the distal core portion of  FIG. 2  according to an embodiment of the present disclosure. 
         FIG. 4  is a diagrammatic perspective view of a tubular member coupled to the expander of  FIG. 3  according to an embodiment of the present disclosure. 
         FIG. 5  is a diagrammatic perspective view of the tubular member coupled to the expander, similar to that of  FIG. 4 , but showing removal of portions of the tubular member and/or expander according to an embodiment of the present disclosure. 
         FIG. 6  is a diagrammatic perspective view of the tubular member coupled to the expander, similar to that of  FIGS. 4 and 5 , but showing the tubular member and expander in phantom with a temporary structure filling open space within the tubular member according to an embodiment of the present disclosure. 
         FIG. 7  is a diagrammatic perspective view of the tubular member coupled to the expander similar to that of  FIG. 6 , but with a temporary annular band formed around a portion of the tubular member according to an embodiment of the present disclosure. 
         FIG. 8  is a diagrammatic perspective view of the tubular member, expander, and distal core portion coated with a material layer according to an embodiment of the present disclosure. 
         FIG. 9  is a diagrammatic perspective view of the tubular member coupled to the expander after formation of the material layer of  FIG. 8 , where a section of the material layer surrounding the tubular member is shown in phantom to allow the temporary structure and temporary annular band to be visualized according to an embodiment of the present disclosure. 
         FIG. 10  is a diagrammatic perspective, side view of the tubular member coupled to the expander after removal of the temporary structure and the temporary annular band according to an embodiment of the present disclosure. 
         FIG. 11  is a diagrammatic perspective, cross-sectional side view of the tubular member coupled to the expander after removal of the temporary structure and the temporary annular band according to an embodiment of the present disclosure. 
         FIG. 12  is a close up of a portion of the diagrammatic perspective, cross-sectional side view of the tubular member coupled to the expander of  FIG. 11 . 
         FIG. 13  is a diagrammatic, schematic cross-sectional side view of a section of the tubular member and a section of the material layer after removal of the temporary structure and the temporary annular band according to an embodiment of the present disclosure. 
         FIG. 14  is a diagrammatic perspective view of the tubular member coupled to the expander with an electrode formed on a portion of the material layer surrounding the tubular member according to an embodiment of the present disclosure. 
         FIG. 15  is a diagrammatic perspective view of the tubular member coupled to the expander, but showing removal of a section of the material layer and coupling of a flexible elongate member to the tubular member according to an embodiment of the present disclosure. 
         FIG. 16  is a diagrammatic perspective view of the tubular member coupled to the flexible elongate member of  FIG. 15 , but showing application of a dielectric to a portion of the tubular member according to an embodiment of the present disclosure. 
         FIG. 17  is a diagrammatic perspective view of the tubular member coupled to the flexible elongate member similar to that of  FIG. 16 , but showing another electrode formed on a portion of the material layer surrounding the tubular member according to an embodiment of the present disclosure 
         FIG. 18  is a diagrammatic perspective view a portion of the tubular member showing a plurality of conductive pads formed thereon according to an embodiment of the present disclosure. 
         FIG. 19  is a diagrammatic perspective view a portion of the tubular member showing an application-specific integrated circuit (ASIC) mounted to the plurality of conductive pads of  FIG. 18  according to an embodiment of the present disclosure. 
         FIG. 20  is a diagrammatic perspective view of the flexible elongate member and the tubular member showing formation of a conductive layer over an insulating layer surrounding a majority of the flexible elongate member according to an embodiment of the present disclosure. 
         FIG. 21  is a diagrammatic perspective view of a distal portion of the flexible elongate member and the tubular member showing a conductive spacer being positioned around the distal portion of the flexible elongate member adjacent to the tubular member according to an embodiment of the present disclosure. 
         FIG. 22  is a diagrammatic perspective view of the flexible elongate member and the tubular member showing a flexible element being positioned around the distal portion of the flexible elongate member adjacent to the conductive spacer of  FIG. 21  and the tubular member and the conductive spacer coated with an insulating material layer according to an embodiment of the present disclosure. 
         FIG. 23  is a diagrammatic perspective view of the flexible elongate member and the tubular member showing a conductive tubular member positioned around a majority of the flexible elongate member and adjacent the flexible element of  FIG. 22  according to an embodiment of the present disclosure. 
         FIG. 24  is a diagrammatic perspective view of the flexible elongate member and the conductive tubular member of  FIG. 23  with an insulating material layer formed around a portion of the conductive tubular member according to an embodiment of the present disclosure. 
         FIG. 25  is a diagrammatic perspective view of the flexible elongate member and the conductive tubular member similar to that of  FIG. 24 , but showing an insulating spacer positioned around the flexible elongate member proximal of a proximal end of the conductive tubular member according to an embodiment of the present disclosure. 
         FIG. 26  is a diagrammatic perspective view of the flexible elongate member and the conductive tubular member similar to that of  FIG. 25 , but showing a conductive sleeve positioned around the flexible elongate member proximal of a proximal end of the insulating spacer according to an embodiment of the present disclosure. 
         FIG. 27  is a diagrammatic perspective end view of the conductive sleeve positioned around the flexible elongate member according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     For the purposes of promoting an understanding of the principles of the present disclosure, reference will now be made to the embodiments illustrated in the drawings, and specific language will be used to describe the same. It is nevertheless understood that no limitation to the scope of the disclosure is intended. Any alterations and further modifications to the described devices, systems, and methods, and any further application of the principles of the present disclosure are fully contemplated and included within the present disclosure as would normally occur to one skilled in the art to which the disclosure relates. In particular, it is fully contemplated that the features, components, and/or steps described with respect to one embodiment may be combined with the features, components, and/or steps described with respect to other embodiments of the present disclosure. For the sake of brevity, however, the numerous iterations of these combinations will not be described separately. 
     As used herein, “flexible elongate member” or “elongate flexible member” includes at least any thin, long, flexible structure that can be inserted into the vasculature of a patient. While the illustrated embodiments of the “flexible elongate members” of the present disclosure have a cylindrical profile with a circular cross-sectional profile that defines an outer diameter of the flexible elongate member, in other instances all or a portion of the flexible elongate members may have other geometric cross-sectional profiles (e.g., oval, rectangular, square, elliptical, etc.) or non-geometric cross-sectional profiles. Flexible elongate members include, for example, guide wires and catheters. In that regard, catheters may or may not include a lumen extending along its length for receiving and/or guiding other instruments. If the catheter includes a lumen, the lumen may be centered or offset with respect to the cross-sectional profile of the device. 
     In most embodiments, the flexible elongate members of the present disclosure include one or more electronic, optical, or electro-optical components. For example, without limitation, a flexible elongate member may include one or more of the following types of components: a pressure sensor, a temperature sensor, an imaging element, an optical fiber, an ultrasound transducer, a reflector, a mirror, a prism, an ablation element, an RF electrode, a conductor, and/or combinations thereof. Generally, these components are configured to obtain data related to a vessel or other portion of the anatomy in which the flexible elongate member is disposed. Often the components are also configured to communicate the data to an external device for processing and/or display. In some aspects, embodiments of the present disclosure include imaging devices for imaging within the lumen of a vessel, including both medical and non-medical applications. However, some embodiments of the present disclosure are particularly suited for use in the context of human vasculature. Imaging of the intravascular space, particularly the interior walls of human vasculature can be accomplished by a number of different techniques, including ultrasound (often referred to as intravascular ultrasound (“IVUS”) and intracardiac echocardiography (“ICE”)) and optical coherence tomography (“OCT”). In other instances, infrared, thermal, or other imaging modalities are utilized. 
     The electronic, optical, and/or electro-optical components of the present disclosure are often disposed within a distal portion of the flexible elongate member. As used herein, “distal portion” of the flexible elongate member includes any portion of the flexible elongate member from the mid-point to the distal tip. As flexible elongate members can be solid, some embodiments of the present disclosure will include a housing portion at the distal portion for receiving the electronic components. Such housing portions can be tubular structures attached to the distal portion of the elongate member. Some flexible elongate members are tubular and have one or more lumens in which the electronic components can be positioned within the distal portion. 
     The electronic, optical, and/or electro-optical components and the associated communication lines are sized and shaped to allow for the diameter of the flexible elongate member to be very small. For example, the outside diameter of the elongate member, such as a guide wire or catheter, containing one or more electronic, optical, and/or electro-optical components as described herein are between about 0.0007″ (0.0178 mm) and about 0.118″ (3.0 mm), with some particular embodiments having outer diameters of approximately 0.014″ (0.3556 mm) and approximately 0.018″ (0.4572 mm)). As such, the flexible elongate members incorporating the electronic, optical, and/or electro-optical component(s) of the present application are suitable for use in a wide variety of lumens within a human patient besides those that are part or immediately surround the heart, including veins and arteries of the extremities, renal arteries, blood vessels in and around the brain, and other lumens. 
     “Connected”, “coupled”, and variations thereof as used herein includes direct connections, such as being glued or otherwise fastened directly to, on, within, etc. another element, as well as indirect connections where one or more elements are disposed between the connected elements. 
     “Secured” and variations thereof as used herein includes methods by which an element is directly secured to another element, such as being glued or otherwise fastened directly to, on, within, etc. another element, as well as indirect techniques of securing two elements together where one or more elements are disposed between the secured elements. 
     Referring now to  FIG. 1 , shown therein is a portion of an intravascular device  100  according to an embodiment of the present disclosure. In that regard, the intravascular device  100  includes a flexible elongate member  102 , a distal portion  104  adjacent a distal end  105 , and a proximal portion  106  adjacent a proximal end  107 . A component  108  is defined within the distal portion  104  of the flexible elongate member  102  proximal of the distal tip  105 . Generally, the component  108  is representative of one or more electronic, optical, or electro-optical components. In that regard, the component  108  may be a pressure sensor, a temperature sensor, an imaging element, an optical fiber, an ultrasound transducer, a reflector, a mirror, a prism, an ablation element, an RF electrode, a conductor, and/or combinations thereof. The specific type of component or combination of components can be selected based on an intended use of the intravascular device. As described below, in some particular embodiments of the present disclosure, the component  108  is a capacitive pressure sensor and associated components. In some instances, the component  108  is positioned less than 10 cm, less than 5, or less than 3 cm from the distal tip  105 . 
     In the illustrated embodiment, the component  108  is positioned between a proximal flexible element  109  and a distal flexible element  110 . The proximal flexible elements  109 ,  110  typically have an increased flexibility relative to the flexible elongate member  102 . To that end, in some embodiments one or both of the flexible elements is a coil, a polymer tubing, a polymer tubing embedded with a coil, and/or combinations thereof. In that regard, the coils may take on any suitable form including round wire, flat wire, round and flat wire, constant gauge wire, variable gauge wire, constant pitch, variable pitch, single coil, multiple coils, overlapping coils, threading coils, and/or combinations thereof. In some instances, the component  108  is positioned within a housing. In that regard, the housing is a separate component secured to the proximal and distal flexible element  109 ,  110  in some instances. In other instances, the housing is integrally formed as a part of at least one of the flexible elements  109 ,  110 . To that end, in some instances the proximal and distal flexible element  109 ,  110  are formed of a single, continuous flexible element with the component  108  secured thereto. 
     The intravascular device  100  also includes a connector  111  adjacent the proximal portion  106  of the device. In the illustrated embodiment, the proximal-most portion of the connector  111  is extends to the proximal end  107  of the intravascular device  100 . In other instances, the proximal-most portion of the connector  111  is spaced from the proximal end  107  of the flexible elongate member  102 . Generally, the spacing of the connector from the proximal end  107  is between 0% and 50% of the total length of the intravascular device  100 . While the total length of the intravascular device can be any length, in some embodiments the total length is between about 1300 mm and about 4000 mm, with some specific embodiments have a length of 1400 mm, 1900 mm, and 3000 mm. Accordingly, in some instances the connector  111  is spaced from the proximal end  107  between about 0 mm and about 1400 mm. In some specific embodiments, the connector  111  is spaced from the proximal end by a distance of 0 mm, 300 mm, and 1400 mm. 
     The connector  111  is configured to facilitate communication between the intravascular device  100  and another device. More specifically, in some embodiments the connector  111  is configured to facilitate communication of data obtained by the component  108  to another device, such as a computing device or processor. Accordingly, in some embodiments the connector  111  is an electrical connector. In such instances, the connector  111  provides an electrical connection to one or more electrical conductors that extend along the length of the flexible elongate member  102  and are electrically coupled to the component  108 . In other embodiments, the connector  111  is an optical connector. In such instances, the connector  111  provides an optical connection to one or more optical communication pathways (e.g., fiber optic cable) that extend along the length of the flexible elongate member  102  and are optically coupled to the component  108 . Further, in some embodiments the connector  111  provides both electrical and optical connections to both electrical conductor(s) and optical communication pathway(s) coupled to the component  108 . In that regard, it should again be noted that component  108  is comprised of a plurality of elements in some instances. In some instances, the connector  111  is configured to provide a physical connection to another device, either directly or indirectly. In other instances, the connector  111  is configured to facilitate wireless communication between the intravascular device  100  and another device. Generally, any current or future developed wireless protocol(s) may be utilized. In yet other instances, the connector  111  facilitates both physical and wireless connection to another device. 
     As noted above, in some instances the connector  111  provides a connection between the component  108  of the intravascular device  100  and an external device. Accordingly, in some embodiments one or more electrical conductors, one or more optical pathways, and/or combinations thereof extend along the length of the flexible elongate member  102  between the connector  111  and the component  108  to facilitate communication between the connector  111  and the component  108 . Generally, any number of electrical conductors, optical pathways, and/or combinations thereof can extend along the length of the flexible elongate member  102  between the connector  111  and the component  108 . In some instances, between one and ten electrical conductors and/or optical pathways extend along the length of the flexible elongate member  102  between the connector  111  and the component  108 . For the sake of clarity and simplicity, the embodiments of the present disclosure described below and shown in  FIG. 1 , include two electrically conductive bands  112 ,  114  that are each coupled to an electrically conductive element extending the length of the flexible elongate member  102  to component  108 . In that regard, two electrically conductive bands  112 ,  114  and associated conductive elements is particularly suited for use with the capacitive pressure sensing system of the present disclosure. However, it is understood that the total number of communication pathways and/or the number of electrical conductors and/or optical pathways is different in other embodiments. More specifically, the number of communication pathways and the number of electrical conductors and optical pathways extending along the length of the flexible elongate member  102  is determined by the desired functionality of the component  108  and the corresponding elements that define component  108  to provide such functionality. 
     Referring now to  FIGS. 2-27 , shown therein are various steps and/or aspects of manufacturing and/or assembling the intravascular device of  FIG. 1  according to embodiments of the present disclosure. In that regard, the  FIGS. 2-27  will be described in the context of steps associated with manufacturing and/or assembling the intravascular device. It is understood that the described steps are exemplary in nature and that one or more of the steps may be omitted, one or more additional steps may be added, and/or the order of the steps may be changed without departing from the scope of the present disclosure. Further, one skilled in the art will recognize that there are alternative ways or manners of achieving the same results as the steps described below and that such alternative techniques are included within the scope of the present disclosure. 
     Referring initially to  FIG. 2 , shown therein is a distal core  120  of the intravascular device according to an embodiment of the present disclosure. As shown, the distal core  120  includes a proximal portion  122  having a generally cylindrical profile and a distal portion  124  having a generally rectangular profile. In some instances, the distal portion  124  is formed by flattening a portion of the distal core  120  that initially has a cylindrical profile. Generally, the distal portion  124  is configured to extend to a distal tip or end of the intravascular device. In some instances, a flexible element is positioned around the distal portion  124  of the distal core  120 , such as flexible element  110  described with respect to  FIG. 1 . The distal core  120  may be formed of any suitable material, including without limitation stainless-steel, nitinol, optical fiber, and/or other suitable material or combination of materials. In the illustrated embodiment, the distal core  120  is formed of stainless-steel. 
     Referring now to  FIG. 3 , an expander  126  is shown positioned around the proximal portion  122  of the distal core  120 . In particular, the expander  126  is positioned around the proximal portion  122  of the distal core  120  such that distal ends of the expander  126  and the proximal portion  122  are aligned along the length of the distal core  120 . However, such alignment is not required and, in other embodiments, the distal ends are offset along the longitudinal axis of the distal core  120 . The expander has a generally cylindrical profile and, serves to expand the radial diameter of the proximal portion  122  of the distal core  120 . To that end, in some instances the proximal portion  122  has a diameter between about 0.05 mm and about 0.15 mm, while the expander  126  has an inner-diameter slightly larger than proximal portion  122  and an outer-diameter between about 0.15 mm and about 0.35 mm. Further, the expander  126  has an axial length  128 . In some implementations, the axial length  128  of the expander  126  is between about 0.5 mm and about 6.0 mm. In some instances, the axial length  128  of the expander  126  is equal to the axial length of the proximal portion  122 . In other instances, the axial length  128  of the expander  126  is shorter or longer than the axial length of the proximal portion  122 . In some instances, the inner-diameter of the expander  126  extends the entire axial length  128 , while in other instances, the inner-diameter of the expander  126  does not extend the entire axial length  128 . The expander  126  may be formed of any suitable material, including without limitation stainless-steel, nitinol, optical fiber, and/or other suitable material or combination of materials. In some implementations, the expander  126  is formed, at least partially, of conductive material. The expander  126  is fixedly secured and sealed against pressure loss to the proximal portion  122  of the distal core  120  utilizing suitable techniques for the selected materials of the expander  126  and the proximal portion  122  of the distal core  120 . Accordingly, in some instances the expander  126  is fixedly secured to the proximal portion  122  of the distal core  120  by solder, weld, adhesive, swaging, and/or combinations thereof. In the illustrated embodiment, the expander  126  is formed of stainless-steel and is laser welded to the proximal portion  122  of the distal core  120 . 
     Referring now to  FIG. 4 , a tubular member  130  is shown positioned around the expander  126 . In that regard, the expander has a generally cylindrical profile and, therefore, further expands the radial diameter of the expander. To that end, in some instances the tubular member  130  has an inner-diameter slightly larger than the outer-diameter of expander  126  and an outer-diameter between about 0.15 mm and about 0.35 mm. In the illustrated embodiment, the tubular member  130  is positioned around the expander  126  such that distal ends of the tubular member  130  and the expander  126  are aligned along the length of the proximal portion  122 . However, such alignment is not required and, in other embodiments, the distal ends are offset along the longitudinal axis of the proximal portion  122 . Further, the tubular member  130  has an axial length  132  that may be greater than, equal to, or less than the axial length  128  of the expander  126 . In the illustrated embodiment, the axial length  132  of the tubular member  130  is greater than the axial length  128  of the expander  126 . In some implementations, the axial length  132  of the tubular member  130  is between about 0.5 mm and about 6.0 mm. As will be discussed in greater detail below, the increased length or axial offset of the tubular member  130  relative to the expander  126  allows a central lumen of the tubular member  130  to be only partially occupied by the expander  126  (and proximal portion  122  of the distal core  120 ). In the illustrated embodiment, with the distal ends of the tubular member  130  and the expander  126  aligned and a tubular member  130  with an axial length  132  greater than the axial length  128  of expander  126 , a cavity is created in the central lumen equal to the difference between the axial length  132  and the axial length  128 . This open space in the lumen of the tubular member  130  is utilized to facilitate capacitive pressure measurements in some implementations of the present disclosure. 
     The tubular member  130  may be formed of any suitable material, including without limitation stainless-steel, nitinol, optical fiber, polymer, copper, gold, and/or other suitable material or combination of materials. In some implementations, the tubular member  130  is formed, at least partially, of conductive material. For example, in some instances the tubular member is formed first of a non-conductive material, then coated with a conductive material. In such instances, all or only portions of the tubular member may be coated with the conductive material. The tubular member  130  is fixedly secured to the expander  126  utilizing suitable techniques for the selected materials of the tubular member  130  and the expander  126 . Accordingly, in some instances the tubular member  130  is fixedly secured to the expander  126  by solder, weld, adhesive, pressed, swaged, and/or combinations thereof. In the illustrated embodiment, the tubular member  130  is formed of stainless-steel and is laser welded to the extender  126 . Thus, in the illustrated embodiment the tubular member  130  is electrically coupled to the extender  126 . In other embodiments, the tubular member  130  and the extender  126  are micro-molded as one device then welded, glued, soldered, pressed, swaged, and/or otherwise coupled to proximal portion  122  of the distal core  120 . Similarly, in some implementations a shape corresponding to the shape resulting from the tubular member  130  and the extender  126  is over-molded directly onto the proximal portion  122  of the distal core  120 . The over-molded materials can be conductive or non-conductive. If a non-conductive material is utilized, then a conductive coating could be applied as described above. Generally speaking, the assembly consisting of the distal core  120 , the expander  126 , and the tubular member  130  may be thought of as the substrate of an electrical device (like a printed-circuit board or flex-circuit) or an “anode” or static member of a capacitive sensor. 
     Referring now to  FIG. 5 , portions of the tubular member  130  and the expander  126  have been removed according to an embodiment of the present disclosure. In particular, a mounting structure  134  has been defined by removal of portions of the tubular member  130  and the expander  126 . The mounting structure  134  is sized and shaped to facilitate mounting and interconnection of one or more electrical, optical, and/or electro-optical components. Accordingly, the mounting structure  134  can take on virtually any shape desirable for mounting such components. In the illustrated embodiment, the mounting structure  134  has a generally rectangular profile with a planar bottom surface  136  bounded by a proximal wall  138  and distal wall opposite the proximal wall. As will be described below, the mounting structure  134  of the illustrated embodiment is sized and shaped to facilitate the mounting of an application-specific integrated circuit (ASIC), including electrical coupling of the ASIC to associated components of the intravascular device. Further, a plurality of openings  140  are formed in the tubular member  130  to provide access to the central lumen of the tubular member. Generally, any number of openings may be utilized, but in some instances between 1 and 20 openings are formed. In the illustrated embodiment, the openings  140  are formed annularly around the circumference of the tubular member  130 . In that regard, the openings may be equally spaced about the circumference, symmetrically spaced about the circumference, or irregularly spaced about the circumference. Further, in the illustrated embodiment the openings  140  have circular cross-sectional profiles. However, it is understood that the openings may have virtually any geometric (e.g., triangle, rectangle, square, circle, oval, ellipse, trapezoid, pentagon, hexagon, etc.) or non-geometric cross-sectional profile. 
     Generally, the portions of the tubular member  130  and the expander  126  may be removed using any suitable technique for the applicable material. For example, in some instances the portions of the tubular member  130  and the expander  126  are removed using laser, EDM, micro-drill, grinding, CNC, other suitable techniques, and/or combinations thereof. Further, it is understood that in some instances that portions of the tubular member  130  and/or the expander  126  are removed prior to assembly of the tubular member  130  onto the expander  126  and/or prior to assembly of the expander  126  onto the proximal portion  122  of the distal core  120 . Further still, in some instances a plurality of tubular members  130  are formed from a single elongated hypotube. In that regard, the single elongated hypotube may be cut into a plurality of sections, each having the axial length  132 . Also, the portions of tubular member  130  shown as being removed in  FIG. 5  may likewise be removed while in the form of the single elongated hypotube (e.g., by repeatedly removing the requisite portions along the length of the elongated hypotube at spacings necessary to form the plurality of tubular members) or after formation of the individual tubular member components. Likewise, a plurality of expanders  126  are formed from a single elongated hypotube in some instances. In that regard, the single elongated hypotube may be cut into a plurality of sections, each having the axial length  128 . Also, the portions of expander  126  shown as being removed in  FIG. 5  in the context of mounting structure  134  may likewise be removed while in the form of the single elongated hypotube (e.g., by repeatedly removing the requisite portions along the length of the elongated hypotube at spacings necessary to form the plurality of expanders) or after formation of the individual expander components. 
     Referring now to  FIG. 6 , a material  142  has been introduced into the lumen of the tubular member  130  to fill the open space within the tubular member  130 , including the central lumen and openings  140 . The material  142  forms a temporary structure that will be removed subsequently. Accordingly, the material  142  is formed of a material that can be chemically removed without damaging the tubular member  130 , expander  126 , and/or the proximal portion  122  of the distal core  120  in some instances. For example, in some instances the material  142  could be copper (Cu). 
     In some instances, the surface of tubular member  130  is precision center-ground and polished. Further, in some instances a precision groove is optionally cut or ground into the tubular member  130 . In that regard, the groove is sized and shaped to receive an annular band  144  described in greater detail below. Accordingly, in some instances the groove is formed prior to the introduction of material  142  such that the material  142  fills the groove. In some instances, the groove filled with the material  142  is precision center-ground and polished to be smooth such that it has the same outer diameter as the remaining portions of tubular member  130 . 
     Referring now to  FIG. 7 , an annular band  144  is formed around a portion of the tubular member  130  according to an embodiment of the present disclosure. In that regard, the annular band  144  extends annularly around the tubular member  130  in alignment with the openings  140 . In some embodiments, the annular band  144  is formed in a groove formed in the outer surface of the tubular member as discussed above. The annular band  144  is also a temporary structure that will be removed subsequently. Accordingly, the annular band  144  is formed of a material that can be chemically removed without damaging the tubular member  130 , expander  126 , and/or the proximal portion  122  of the distal core  120  in some instances. To that end, in some implementations the annular band  144  is formed of the same material as the temporary structure defined by material  142 . For example, in some instances the annular band  144  could be formed of copper. 
     Referring now to  FIG. 8 , a material layer  146  is formed over the tubular member  130 , expander  126 , and proximal portion  122  of the distal core  120  according to an embodiment of the present disclosure. Generally, the material layer  146  is formed of a flexible material suitable to act as a membrane for a capacitive pressure sensing arrangement as will described in further detail below. Accordingly, in some instances the material layer  146  is formed of a flexible, non-conductive polymer material. In some embodiments, the material layer  146  is formed of parylene, PDMS (Polydimethylsiloxane), and/or combinations thereof. Further, the material layer  146  has a thickness between about 0.001 mm and about 0.003 mm in some instances. In the illustrated embodiment, the material layer  146  is parylene having a thickness of approximately 0.0013 mm. In some instances, the material layer  146  extends over the distal portion  124  of the distal core  120 . In other instances, the distal portion  124  of the distal core  120  is masked and/or otherwise treated, protected, or avoided such that material layer  146  does not extend over the distal portion  124 . 
     Referring now to  FIG. 9 , a section of the material layer  146  extending around the tubular member  130  and portions of the tubular member  130  are shown in phantom to reveal the presence of the temporary structure  142  and the temporary annular band  144  after formation of the material layer  146 . With the material layer  146  formed, the temporary structure  142  and the temporary annular band  144  are chemically removed. In some embodiments, the temporary structure  142  and the temporary annular band  144  are removed immediately following formation of the material layer  146 . In other embodiments, one or more additional steps are performed after formation of the material layer  146  before the temporary structure  142  and the temporary annular band  144  are removed. For example, in some instances the formation of the electrode described in the context of  FIG. 14  is performed prior to removal of the temporary structure  142  and the temporary annular band  144 . 
     Referring now to  FIGS. 10-12 , the material layer  146 , the tubular member  130 , the expander  126 , and the proximal portion  122  of the distal core  120  are shown after removal of the temporary structure  142  and the temporary annular band  144  according to an embodiment of the present disclosure. As best shown in  FIGS. 11 and 12 , with the temporary structure  142  and the temporary annular band  144  removed, the flexible material layer  146  is in communication with the central lumen  148  of the tubular member  130  via openings  140 . Further, the sections of the material layer  146  positioned adjacent to the openings  140  are spaced from the outer wall of the tubular member  130  by a distance equal to the thickness of the temporary annular band  144  that was removed. This spacing allows the material layer  146  to flex in response to pressure changes. 
     Referring to  FIG. 13 , a more detailed cross-sectional profile of the arrangement of the material layer  146  and tubular member  130  adjacent an opening  140  is shown. As illustrated, space  150  is provided between a lower surface  152  of the material layer  146  and the outer wall of the tubular member  130  adjacent the opening  140 . As noted above, the space  150  is defined by the thickness of the annular band  144 . In the illustrated embodiment, the annular band  144  had a width  154  that is greater than the diameter  156  of the opening  140 . In some instances, the width  154  is between about 0.1 mm and about 0.2 mm, while the diameter  156  is between about 0.1 mm and about 0.2 mm. The space  150  facilitates flexing of the material layer  146  in response to pressure changes and, in particular, relative changes in pressure between the environmental pressure surrounding material layer  146  and an ambient (if vented) or sealed central lumen  148  of the tubular member  130 . In some instances, the pressure within the central lumen  148  of the tubular member  130  is an atmospheric pressure. For example, in some instances the central lumen  148  is in communication with one or more additional lumens associated with the intravascular device that extend from the lumen  148  to an atmospheric pressure source. In other instances, the lumen  148  is sealed with a known and/or fixed pressure value. 
     Referring now to  FIG. 14 , an electrode  158  has been formed over a portion of the material layer  146 , and over the cavity formed by  144 . The width of electrode  158  may be greater than groove width  154 , equal to groove width  154 , or less than groove width  154 . In the illustrated embodiment, the width of  158  is greater than groove width  154 . Electrode  158  is formed of a conductive material, such as gold (Au), titanium/gold alloy (Ti/Au), and/or other suitable conductive material, and may consist of one or multiple layers of identical or varied materials. The electrode  158  may be formed by additive or subtractive methods. These methods include, but are not limited to: aerosol jet printing, ink-jet printing, powder-metal fabrication, laser-direct sintering, plating-etching, plating-laser ablation, and/or other suitable technique. In the illustrated embodiment, the electrode  158  includes and is in electrical communication with, an annular portion  160  that extends around the tubular member  130 , an axial portion  162  that extends along the major axis of the tubular member  130 , and a pad portion  164  that extends across the distal-most region of mounting structure  134 . 
     The annular portion  160  of the electrode  158  is fixedly attached to the outer surface of material layer  146  directly above the cavity formed by  144 . In some embodiments, the annular portion  160  is centered on the cavity formed by  144 , while in other embodiments, annular portion  160  is not centered on the cavity formed by  144 . A capacitor is formed from the annular portion  160  (cathode), the material layer  146  (dielectric), and the structure formed from  120 ,  126 , and  130  (anode). With sufficient difference between the pressure surrounding the cavity formed by  144  and the ambient or sealed cavity pressure, the suspended material layer  146  and annular portion  160  will deflect—creating a variable capacitor. To facilitate this capacitive pressure sensing operation, in some embodiments the annular portion  160  of electrode  158  is centered upon the openings  140  and extends around the circumference of the tubular member  130  between about 25% and about 100% of the total circumference of the tubular member. As shown in  FIGS. 15-18 , in the illustrated embodiment the annular portion  160  of electrode  158  extends around a majority of the circumference of the tubular member  130 , but not completely around, such that a non-conductive section  166  of material layer  146  remains between the extents of annular portion  160 . In other instances, annular portion  160  of electrode  158  extends completely around the circumference of the tubular member  130 . In such instances, a dielectric patch or layer may be formed over a section of the annular portion  160  to define a non-conductive area similar to section  166 . 
     The axial portion  162  of the electrode  158  extends between annular portion  160  and pad portion  164 . In the illustrated embodiment, axial portion  162  of the electrode  158  is positioned on a side of the tubular member  130  substantially opposite section  166 . The pad portion  164  of the electrode  158  defines a pad site for an ASIC component that will be subsequently mounted within the mounting structure  134 . Accordingly, the axial portion  162  of the electrode  158  provides a conductive path between the annular portion  160  and the pad portion  164  such that changes in capacitance of the annular portion  160  can be conveyed to the ASIC component. 
     Referring now to  FIG. 15 , a section  167  of the material layer  146  within the mounting structure  134  has been removed (e.g., using laser ablation or other suitable technique) to expose a ground pad  168  on the expander  126  and proximal portion  122  of distal core  120 . Section  168  defines a bond pad for the ASIC component that will be subsequently mounted within the mounting structure  134 . Further, a flexible elongate member  170  is coupled to a proximal portion of the tubular member  130 . In the illustrated embodiment, a distal portion of the flexible elongate member  170  is positioned within the lumen  148  of the tubular member  130 . However, the distal portion of the flexible elongate member  170  is positioned within the lumen such that it is spaced proximally from the openings  140  in the tubular member  130  so as to not block the material layer  146  and annular portion  160  of the electrode  158  from having access to the lumen pressure through the openings  140 . In some implementations, the lumen  148  of the tubular member  130  includes a counter bore, shoulder(s), and/or other suitable engagement structures to ensure that the distal portion of the flexible elongate member  170  is properly positioned within the tubular member  130  without blocking the openings  140 . 
     In some implementations, the flexible elongate member  170  is a tubular member having a lumen extending along its length. To that end, the lumen of the flexible elongate member  170  is in communication with the lumen  148  of the tubular member  130  such that the lumen of the flexible elongate member  170 , alone or in combination with other elements, can be used to expose the lumen  148  to a reference pressure source, such as atmospheric pressure and/or a known pressure value. In some embodiments, the flexible elongate member  170  is a solid wire and therefore does not reference atmospheric pressure. The flexible elongate member  170  may be formed of any suitable material, including without limitation stainless-steel, nitinol, optical fiber, ceramic, and/or other suitable material or combinations thereof. In some implementations, the flexible elongate member  170  is formed, at least partially, of conductive material. For example, in some instances the tubular member is formed of a non-conductive material coated with a conductive material. In such instances, all or only portions of the tubular member may be coated with the conductive material. The flexible elongate member  170  is fixedly secured to the tubular member  170  utilizing suitable techniques for the selected materials of the flexible elongate member  170  and the tubular member  130 . Accordingly, in some instances the flexible elongate member  170  is fixedly secured to the tubular member  130  by solder, weld, adhesive, pressing, swaging, and/or combinations thereof. In the illustrated embodiment, the flexible elongate member  170  is formed of stainless-steel and is laser welded to tubular member  130  as indicated by weld line  172 . In the illustrated embodiment the flexible elongate member  170  is electrically coupled to the tubular member  130 . In some implementations, the elongate member  170 , tubular member  130 , and associated electrically coupled portions of the device carry a ground signal. 
     In some instances, the flexible elongate member  170  includes an outer insulating coating (e.g., a parylene layer or other suitable insulating material) along a majority of its length. In some instances, the insulating coating is applied after the flexible elongate member  170  is coupled to the tubular member  130 . In other instances, the insulating coating is applied prior to the flexible elongate member  170  being coupled to the tubular member  130 . To that end, in some instances one or more sections of the flexible elongate member  170  are masked, treated, and/or avoided to prevent application of the insulating coating. For example, the section of the flexible elongate member  170  that is welded to the tubular member  130  may not include an insulating coating after the procedure, and/or a proximal section of the flexible elongate member  170  that is used to define an electrical connector (or be coupled to an electrical connector) may not include an insulating coating. Alternatively, in some instances an insulating coating is applied to the entire flexible elongate member  170  and then sections of the insulating coating are removed, as necessary, to expose underlying portions of the flexible elongate member  170 . 
     Referring now to  FIG. 16 , a dielectric patch  174  is formed over the weld line  172 . As shown, the dielectric patch  174  is generally aligned with the section  166  of material layer  146  separating the ends of the annular portion  160  of the electrode  158 . For embodiments where the annular portion  160  of the electrode  158  extends completely around the tubular member  130 , the dielectric patch  174  can extend across both the weld line  172  and the annular portion  160 . Alternatively, two different dielectric patches could be formed across the weld line  172  and the annular portion  160 , respectively, for embodiments where the annular portion  160  of the electrode  158  extends completely around the tubular member  130 . The dielectric patch can be formed of any suitable dielectric material such as Parylene, PDMS, or other suitable dielectric material. The dielectric patch  174  and section  166  serve to electrically isolate an electrode  176  (See,  FIG. 17 ) from the electrode  158  and the tubular member  130 . 
     Referring now to  FIG. 17 , an electrode  176  has been formed over a portion of the material layer  146  surrounding the tubular member  130  according to an embodiment of the present disclosure. The electrode  176  is formed of a conductive material, such as gold (Au), titanium/gold alloy (Ti/Au), and/or other suitable conductive material, and may consist of one or multiple layers of identical or varied materials. The electrode  176  may be formed by additive or subtractive methods. These methods include, but are not limited to: aerosol jet printing, ink-jet printing, powder-metal fabrication, laser-direct sintering, plating-etching, plating-laser ablation, etc. In the illustrated embodiment, the electrode  176  includes and is in electrical communication with, a ring pad  178  that is formed on the proximal end of tubular member  130 , an axial portion  180  that extends along the major axis of the tubular member  130 , and a pad portion  182  that extends across the proximal-most region of mounting structure  134 . 
     The ring pad  178  of the electrode  176  extends around the circumference of the tubular member  130  between about 25% and about 100% of the total circumference of the flexible elongate member  170 . In the illustrated embodiment, the ring pad  178  of electrode  176  extends completely around the circumference of the flexible elongate member  170 . The axial portion  180  of the electrode  176  extends between ring pad  178  and pad portion  182 . In the illustrated embodiment, axial portion  180  of the electrode  176  is positioned on a side of the tubular member  130  substantially opposite axial portion  162  of electrode  158 . To that end, the axial portion  180  extends across dielectric patch  174  and section  166  of the material layer  146  such that the electrode  176  is electrically isolated from the electrode  158  and the tubular member  130 . The pad portion  182  of the electrode  176  defines a further pad site for the ASIC component that will be subsequently mounted within the mounting structure  134 . Accordingly, the pad portion  182  of the electrode  176  provides a conductive path between the ring pad  178  and the pad portion  182 . 
     Referring now to  FIG. 18 , a conductive material (e. g. conductive adhesive, conductive film, solder paste, solder balls, etc.) is applied to the pad sites on mounting structure  134 . In the illustrated embodiment, conductive adhesive is applied to pad portion  164  of electrode  158 , ground pad  168  on expander  126 , and pad portion  182  of electrode  176  to facilitate mounting of an ASIC within the mounting structure  134  such that the ASIC is electrically coupled to the pad sites. As shown, adhesive  184  is applied to pad portion  164  of electrode  158 , adhesive  186  is applied to ground pad  168  on expander  126 , and adhesive  188  is applied to pad portion  182  of electrode  176 . Generally, any suitable conductive adhesive may be utilized. In some instances, the adhesive is silver-epoxy. 
     Referring now to  FIG. 19 , an ASIC module  190  has been mounted within the mounting structure  134  and electrically coupled to pad portion  164  of electrode  158 , ground pad  168  on expander  126 , and pad portion  182  of electrode  176  by the conductive adhesives  184 ,  186 ,  188 , respectively. In some instances, the ASIC module  190  may be one or more components and may include one, several, or all of the capabilities related to memory storage, signal conditioning, wireless communication interface, etc. The memory element may store information about the characteristics and use of the sensor. In some instances, the memory element stores device-specific information such as: device ID, usage limit, sensor ID, temperature coefficient, zero offset, scale factor, sensitivity, manufacture date, manufacture time, and manufacture location. In addition, the memory element may store information related to one or more specific periods of device activation or use, such as: count, date, time, location, system ID, pressure minimum, pressure maximum, velocity minimum, velocity maximum, temperature minimum, temperature maximum, and centered (y/n). The ASIC module  190  is energized via VCC from pad portion  164  and ground from ground pad  168 . With the ASIC module  190  mounted within the mounting structure  134 , the spacing around the ASIC module  190  can be filled in using under-filling and/or over-molding to further secure the ASIC module  190  in place and/or return the outer profile of the device to a cylindrical form such that it has generally constant outer profile along the length of the tubular member  130 . 
     Referring now to  FIG. 20 , a conductive layer  192  is formed over the material layer  146  such that the conductive layer covers all but an insulating band portion  194  at the proximal-most portion of insulating material layer  146 . As shown, the proximal-most portion of insulating material layer  146  defining insulating band portion  194  is spaced from the proximal-most portion of flexible elongate member  170  such that a conductive band  196  is defined. As discussed above, in some instances the flexible elongate member  170  serves as a ground source such that the conductive band  196  is a ground band.  FIG. 20  also illustrates an opening to the lumen  198  of the flexible elongate member  170  at the proximal end of the flexible elongate member  170 . In some instances, the material layer  146  defining insulating band portion  194  and/or the conductive layer  192  of the flexible elongate member  170  are formed prior to the assembly of the flexible elongate member with any other components of the intravascular device. In this manner, the flexible elongate member  170  may be a separate sub-assembly to streamline manufacturing procedures. 
     Referring now to  FIG. 21 , a conductive spacer  200  is positioned around the distal portion of the flexible elongate member  170  adjacent to the proximal end of the tubular member  130 . In that regard, the conductive spacer includes a conductive material on at least its distal end surface to electrically couple to the ring pad  178  of electrode  176  and its inner surface to electrically couple to the conductive layer  192 . An electrically conductive adhesive (such as silver-epoxy) is utilized in some instances to secure the conductive spacer  200  to the electrode  176  and/or the conductive layer  192 . In other instances, the conductive spacer  200  is electrically coupled and secured to the electrode  176  and/or the conductive layer  192  using conductive film. In an alternate embodiment, ring pad  178  and conductive layer  192  are direct-printed as one continuous, and electrically connected structure. 
     Referring now to  FIG. 22 , a flexible element  204  is positioned around a distal portion of the flexible elongate member  170  adjacent to the conductive spacer  200 . In particular, a distal end of the flexible element  204  abuts a proximal end of the conductive spacer  200 . In some embodiments, the outer-diameter of the conductive spacer  200  is smaller than the inner-diameter of the flexible element  204  or contains external threads or protrusions that allow the flexible element  204  to slide or thread onto the conductive spacer  200 . The flexible element  200  is fixed to the conductive spacer  200  with a suitable adhesive. The flexible element  204  is similar to the proximal flexible element  109  discussed in the context of  FIG. 1 . Further, the flexible element  204  has a generally cylindrical outer profile and, therefore, further expands the radial diameter of the flexible elongate member  170 . To that end, in some instances the flexible element  204  has an outer diameter generally equal to the sensor region  202  (about 0.36 mm). 
     Similarly, in a previous or subsequent step, another flexible element is positioned around the distal portion  124  of the distal core  120  in a manner similar to the distal flexible element  110  discussed in the context of  FIG. 1 . This distal flexible element also has a generally cylindrical outer profile and, therefore, further expands the radial diameter of the distal portion  124  of the distal core  120 . To that end, in some instances the distal flexible element  110  has an outer diameter generally equal to the sensor region  202  (about 0.36 mm). In the illustrated embodiment, the distal-most tip  105  of the distal flexible element  110  is radiopaque. The radiopaque tip is generally round to facilitate navigation while minimizing tissue damage while manipulating the intravascular device through the vasculature. 
     Referring now to  FIG. 23 , a conductive tubular member  206  is positioned over the conductive layer  192  of the flexible elongate member  170 . As shown, a distal end of the conductive tubular member  206  abuts a proximal end of the flexible element  204 , while a proximal end of the conductive tubular member  206  terminates adjacent to the insulating band portion  194  of the flexible elongate member  170 . Further, the conductive tubular member  206  has a generally cylindrical outer profile and, therefore, further expands the radial diameter of the flexible elongate member  170 . To that end, in some instances the conductive tubular member  206  has an outer generally equal to the sensor region  202  (about 0.36 mm). 
     The conductive tubular member  206  may be formed of any suitable conductive material, including without limitation stainless-steel, nitinol, and/or other suitable conductive material. In some implementations, conductive tubular member  206  is formed of a non-conductive material, then coated/plated with a conductive material. In such instances, all or only portions of the tubular member may be coated with the conductive material. The conductive tubular member  206  is fixedly secured and electrically coupled to the conductive layer  192  of the flexible elongate member  170  utilizing suitable techniques for the selected materials of the conductive tubular member  206  and the conductive layer  192 . Accordingly, in some instances the conductive tubular member  206  is fixedly secured to the flexible elongate member  170  by conductive adhesive, swaging and/or combinations thereof. In the illustrated embodiment, the conductive tubular member  206  is formed of stainless-steel and is coupled to the flexible elongate member  170  by conductive adhesive. Thus, in the illustrated embodiment the conductive tubular member  206  is electrically coupled to the conductive layer  192 , the conductive spacer  200 , and the electrode  176 . 
     Referring now to  FIG. 24 , an insulating layer  208  is formed over the conductive tubular member  206  along a majority of the length of the conductive tubular member. In some instances, the insulating coating is applied after the conductive tubular member  206  is coupled to the conductive layer  192  of flexible elongate member  170 . In other instances, the insulating layer  208  is applied prior to the conductive tubular member  206  being coupled to the flexible elongate member  170 . To that end, in some instances one or more sections of the conductive tubular member  206  are masked, treated, and/or avoided to prevent application of the insulating coating. For example, in the illustrated embodiment the insulating layer  208  does not extend over a section  210  at the proximal end of the conductive tubular member  206 . In that regard, in some implementations the section  210  defines an electrical connector similar to conductive band  114  of connector  111  discussed in the context of  FIG. 1 . Alternatively, in some instances the insulating coating is applied to the entire conductive tubular member  206  and then sections of the insulating coating are removed, as necessary, to expose underlying portions of the conductive tubular member  206 . 
     Referring now to  FIG. 25 , an insulating spacer  212  is positioned over insulating band portion  194  of the flexible elongate member  170  according to an embodiment of the present disclosure. As shown, a distal end of the insulating spacer  212  abuts a proximal end of the conductive tubular member  206 , while a proximal end of the insulating spacer  212  terminates adjacent to the distal extent of ground band  196  of the flexible elongate member  170 . The insulating spacer  212  has a generally cylindrical outer profile and, therefore, further expands the radial diameter of the flexible elongate member  170 . To that end, in some instances the insulating spacer  212  has an outer diameter generally equal to the sensor region  202  (about 0.36 mm). The insulating spacer  212  may be formed of any suitable insulating material, including without limitation PP/PE/PA/PC/ABS. The insulating spacer  212  is fixedly secured to the flexible elongate member  170  utilizing suitable techniques for the selected materials of the insulating spacer  212  and the insulating material of insulating band portion  194  of the flexible elongate member  170 . Accordingly, in some instances the insulating spacer  212  is fixedly secured to the flexible elongate member  170  by an adhesive. In other instances, the insulating spacer  212  is not itself fixedly secured to the flexible elongate member, but is positioned between components that are fixedly secured, such as conductive tubular member  206  and conductive sleeve  214  (See,  FIG. 26 ). In the illustrated embodiment, the insulating spacer  212  is formed of PP and is not fixedly coupled to insulating band portion  194  on the flexible elongate member  170 . 
     Referring now to  FIGS. 26 and 27 , a conductive sleeve  214  is positioned over ground band  196  at the proximal extent of flexible elongate member  170 . As shown, a distal end of the conductive sleeve  214  abuts a proximal end of the insulating spacer  212 , while a proximal end of the conductive sleeve  214  terminates adjacent to proximal end of the flexible elongate member  170 . Further, the conductive sleeve  214  has a generally cylindrical outer profile and, therefore, further expands the radial diameter of the flexible elongate member  170 . To that end, in some instances the conductive sleeve  214  has an outer diameter generally equal to the sensor region  202  (about 0.36 mm). 
     The conductive sleeve  214  may be formed of any suitable conductive material, including without limitation gold (Au), titanium-gold (Ti/Au), platinum-iridium (PtIr), and/or other suitable conductive material. In some implementations, conductive sleeve  214  is formed of a non-conductive material then coated with a conductive material. In such instances, all or only portions of the tubular member may be coated with the conductive material. The conductive sleeve  214  is fixedly secured and electrically coupled to the conductive ground band  196  of the flexible elongate member  170  utilizing suitable techniques for the selected materials of the conductive sleeve  214  and the conductive ground band  196  of the flexible elongate member  170 . Accordingly, in some instances the conductive sleeve  214  is fixedly secured to the flexible elongate member  170  by solder, weld, conductive adhesive, pressing, swaging, and/or combinations thereof. In the illustrated embodiment, the conductive sleeve  214  is formed of PtIr and is coupled to ground band  196  of the flexible elongate member  170  by swaging. Thus, in the illustrated embodiment the conductive sleeve  214  is electrically coupled to the flexible elongate member  170 , tubular member  130 , and extender  126 , which is electrically coupled to the ASIC module  190  via ground pad  168 . 
     Persons skilled in the art will also recognize that the apparatus, systems, and methods described above can be modified in various ways. Accordingly, persons of ordinary skill in the art will appreciate that the embodiments encompassed by the present disclosure are not limited to the particular exemplary embodiments described above. In that regard, although illustrative embodiments have been shown and described, a wide range of modification, change, and substitution is contemplated in the foregoing disclosure. It is understood that such variations may be made to the foregoing without departing from the scope of the present disclosure. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the present disclosure.