Patent Publication Number: US-2019192322-A1

Title: Vascular flow diversion

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a divisional of U.S. application Ser. No. 15/469,324, filed Mar. 24, 2017, which claims the benefit of and priority to U.S. Provisional Patent Application No. 62/313,055, filed Mar. 24, 2016, both of which are incorporated herein by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     The subject technology relates generally to methods and devices for diverting blood flow in a blood vessel, and particularly to inhibiting blood flow into an aneurysm. Some embodiments of the subject technology relate to flow-diverting devices including a plurality of interconnected struts. 
     BACKGROUND 
     Aneurysms are an abnormal bulging or ballooning of a blood vessel that can result from the vessel wall being weakened by disease, injury, or a congenital abnormality. Aneurysms have thin, weak walls and have a tendency to rupture, which can lead to stroke, death, disability, etc. One method of treating aneurysms includes inserting a flow-diverting stent or braid into a parent vessel that includes the aneurysm to be treated. Such stents or braids can be inserted into a vessel in a collapsed state, positioned next to the neck of the aneurysm, and expanded into apposition with the vessel wall. If the stent or braid has a sufficiently low porosity, it can function to block the flow of blood through the device and into the aneurysm to induce embolization of the aneurysm. 
     However, some aneurysms—and especially cerebral aneurysms—are located in small and tortuous portions of the vasculature. Current designs for flow-diverting stents or braids have difficulty achieving a snug fit across the neck of the aneurysm if the parent vessel is curved, twisted, or forked. For example, current designs generally suffer from crimping or kinking when positioned in such tortuous vessels. This can make it more difficult to position a flow-diverting device and can cause the device to have an inadequate porosity as the device is expanded within the vessel. Also, current designs often undesirably block blood flow to branching or secondary vessels that are close to the aneurysm. Accordingly, there exists a need for improved flow-diverting devices for treating aneurysms. 
     SUMMARY 
     Expandable devices can be delivered into vascular system to divert flow. According to some embodiments, expandable devices are provided for treating aneurysms by diverting flow. A flow-diverting expandable device can comprise a plurality of struts and/or bridges and configured to be implanted in a blood vessel. The expandable device can be expandable to an expanded state at an aneurysm. The expandable device can have at least a section for spanning the neck of the aneurysm and a plurality of pores or openings located between the struts/bridges. The expandable device can have a sidewall and a plurality of pores/openings in the sidewall that are sized to inhibit flow of blood through the sidewall into an aneurysm to a degree sufficient to lead to thrombosis and healing of the aneurysm when the expandable device is positioned in a blood vessel and adjacent to the aneurysm. The subject technology is illustrated, for example, according to various aspects described below. 
     Further, some embodiments can provide a delivery system for treating an aneurysm. The system can comprise a microcatheter configured to be implanted into a blood vessel, a core member, extending within the microcatheter, having a distal segment, and the device extending along the core member distal segment. 
     The subject technology is illustrated, for example, according to various aspects described below. Various examples of aspects of the subject technology are described as numbered clauses (1, 2, 3, etc.) for convenience. These are provided as examples and do not limit the subject technology. 
     Clause 1. An expandable device comprising:
         a plurality of connector sections, each of the connector sections extending circumferentially about the expandable device and comprising a plurality of connector struts; and   a plurality of bridge sections, each of the bridge sections attached to and extending between two of the connector sections and comprising a plurality of parallel, non-branching, helical bridge members.       

     Clause 2. The expandable device of clause 1, wherein a first one of the bridge sections comprises first bridge members winding in a first helical direction about an axis of the expandable device and a second one of the bridge sections comprises second bridge members winding in a second helical direction about the axis of the expandable device, the first helical direction being opposite the second helical direction. 
     Clause 3. The expandable device of clause 1, wherein each of the connector struts is coupled to another connector strut at an apex. 
     Clause 4. The expandable device of clause 3, wherein each apex is coupled to one of the bridge members. 
     Clause 5. The expandable device of clause 3, wherein some of the apices are not coupled to any of the bridge members. 
     Clause 6. The expandable device of clause 3, wherein each bridge member is coupled to a connector strut at a location other than the apex. 
     Clause 7. The expandable device of clause 1, wherein each bridge member is coupled to a connector strut with a region of the bridge member that is tangent to the connector strut. 
     Clause 8. The expandable device of clause 1, wherein at least a portion of each of the connector struts of a connector section are parallel to each other. 
     Clause 9. The expandable device of clause 1, wherein some of the bridge members extend entirely through one of the connector sections without being coupled to a connector strut of the one of the connector sections. 
     Clause 10. The expandable device of clause 1, further comprising anchor sections at longitudinal ends of the expandable device, each of the anchor sections comprising a plurality of closed cells. 
     Clause 11. The expandable device of clause 1 wherein the expandable device is a mesh. 
     Clause 12. The expandable device of clause 11 wherein the expandable device is a laser cut sheet. 
     Clause 13. The expandable device of clause 11 wherein the mesh is non-braided. 
     Clause 14. The expandable device of clause 1 wherein the device is non-braided. 
     Clause 15. A device for treating an aneurysm, the device comprising:
         a plurality of connector sections, each of the connector sections extending circumferentially about the mesh structure and comprising a plurality of connector struts; and   a plurality of bridge sections, each of the bridge sections attached to and extending between two of the connector sections and comprising a plurality of parallel, non-branching, helical bridge struts coupled to adjacent connector struts,   wherein the connector sections and bridge sections together define a monolithic, self-expanding mesh structure.       

     Clause 16. The device of clause 15, wherein a first one of the bridge sections comprises first bridge struts winding in a first helical direction about an axis of the mesh structure and a second one of the bridge sections comprises second bridge struts winding in a second helical direction about the axis of the mesh structure, the first helical direction being opposite the second helical direction. 
     Clause 17. The device of clause 15, wherein each of the connector struts is coupled to another connector strut at an apex. 
     Clause 18. The device of clause 17, wherein each apex is coupled to one of the bridge struts. 
     Clause 19. The device of clause 17, wherein some of the apices are not coupled to any of the bridge struts. 
     Clause 20. The device of clause 17, wherein each bridge strut is coupled to a connector strut at a location other than the apex. 
     Clause 21. The device of clause 15, wherein each bridge strut is coupled to a connector strut with a region of the bridge strut that is tangent to the connector strut. 
     Clause 22. The device of clause 15, wherein at least a portion of each of the connector struts of a connector section are parallel to each other. 
     Clause 23. The device of clause 15, wherein some of the bridge struts extend entirely through one of the connector sections without being coupled to a connector strut of the one of the connector sections. 
     Clause 24. The device of clause 15, further comprising anchor sections at longitudinal ends of the expandable device, each of the anchor sections comprising a plurality of closed cells. 
     Clause 25. The device of clause 15 wherein the mesh structure is a laser cut sheet. 
     Clause 26. The device of clause 15 wherein the mesh structure is non-braided. 
     Clause 27. The device of clause 15 wherein the mesh structure is made of a superelastic material. 
     Additional features and advantages of the subject technology will be set forth in the description below, and in part will be apparent from the description, or may be learned by practice of the subject technology. The advantages of the subject technology will be realized and attained by the structure particularly pointed out in the written description and clauses hereof as well as the appended drawings. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the subject technology. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide further understanding of the subject technology and are incorporated in and constitute a part of this description, illustrate aspects of the subject technology and, together with the specification, serve to explain principles of the subject technology. 
         FIG. 1A  shows a plan view of an expandable device with a strut pattern, according to some embodiments of the subject technology. 
         FIG. 1B  shows an enlarged plan view of a portion of the expandable device of  FIG. 1A , according to some embodiments of the subject technology. 
         FIG. 2A  shows a perspective view of struts, according to some embodiments of the subject technology. 
         FIG. 2B  shows a cross-sectional view of a strut, according to some embodiments of the subject technology. 
         FIG. 3A  shows a plan view of an expandable device with a strut pattern, according to some embodiments of the subject technology. 
         FIG. 3B  shows an enlarged plan view of a portion of the expandable device of  FIG. 3A , according to some embodiments of the subject technology. 
         FIG. 4A  shows a plan view of an expandable device with a strut pattern, according to some embodiments of the subject technology. 
         FIG. 4B  shows an enlarged plan view of a portion of the expandable device of  FIG. 4A , according to some embodiments of the subject technology. 
         FIG. 5A  shows a plan view of an expandable device with a strut pattern, according to some embodiments of the subject technology. 
         FIG. 5B  shows an enlarged plan view of a portion of the expandable device of  FIG. 5A , according to some embodiments of the subject technology. 
         FIG. 6A  shows a plan view of an expandable device with a strut pattern, according to some embodiments of the subject technology. 
         FIG. 6B  shows an enlarged plan view of a portion of the expandable device of  FIG. 6A , according to some embodiments of the subject technology. 
         FIG. 7A  shows a plan view of an expandable device with a strut pattern, according to some embodiments of the subject technology. 
         FIG. 7B  shows an enlarged plan view of a portion of the expandable device of  FIG. 7A , according to some embodiments of the subject technology. 
         FIG. 8A  shows a plan view of an expandable device with a strut pattern, according to some embodiments of the subject technology. 
         FIG. 8B  shows an enlarged plan view of a portion of the expandable device of  FIG. 8A , according to some embodiments of the subject technology. 
         FIG. 9A  shows a plan view of an expandable device with a strut pattern, according to some embodiments of the subject technology. 
         FIG. 9B  shows an enlarged plan view of a portion of the expandable device of  FIG. 9A , according to some embodiments of the subject technology. 
         FIG. 10A  shows a plan view of an expandable device with a strut pattern, according to some embodiments of the subject technology. 
         FIG. 10B  shows an enlarged plan view of a portion of the expandable device of  FIG. 10A , according to some embodiments of the subject technology. 
         FIG. 11A  shows a plan view of an expandable device with a strut pattern, according to some embodiments of the subject technology. 
         FIG. 11B  shows an enlarged plan view of a portion of the expandable device of  FIG. 11A , according to some embodiments of the subject technology. 
         FIG. 12A  shows a plan view of an expandable device with a strut pattern, according to some embodiments of the subject technology. 
         FIG. 12B  shows an enlarged plan view of a portion of the expandable device of  FIG. 12A , according to some embodiments of the subject technology. 
         FIG. 13A  shows a plan view of an expandable device with a strut pattern, according to some embodiments of the subject technology. 
         FIG. 13B  shows an enlarged plan view of a portion of the expandable device of  FIG. 13A , according to some embodiments of the subject technology. 
         FIG. 14A  shows a plan view of an expandable device with a strut pattern, according to some embodiments of the subject technology. 
         FIG. 14B  shows an enlarged plan view of a portion of the expandable device of  FIG. 14A , according to some embodiments of the subject technology. 
         FIGS. 15A-15D  shows a side view of an expandable device in various curved states of different curvatures, according to some embodiments of the subject technology. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, specific details are set forth to provide an understanding of the subject technology. However, the subject technology may be practiced without some of these specific details. In some instances, well-known structures and techniques have not been shown in detail so as not to obscure the subject technology. 
     An expandable device comprising a thin film forming a mesh can be used to treat an aneurysm. The expandable device can impede blood flow along an aneurysmal flow path between the prevailing direction of arterial flow and the interior of the aneurysm via, e.g., high pore density, small pore size and/or high material coverage across the aneurysmal flow path, and facilitate endothelial growth across the neck of the aneurysm or otherwise across the aneurysmal flow path. The expandable device can comprise a single component, low profile, high pore density flow diverter of a single material and/or of monolithic construction. The expandable device can facilitate accurate placement by requiring less foreshortening as compared to other commercially available devices, including braided devices. The expandable device can have a thickness that is small enough to enable placement in smaller blood vessels, thereby opening new areas of treatment for flow diversion. 
     According to some embodiments, an expandable device, such as a stent, can have a flow diverting section or other portion of the device that provides embolic properties so as to interfere with blood flow in (or into) the body space (e.g., an aneurysm) in (or across) which the device is deployed. The sidewall material coverage, porosity, and/or pore size of one or more sections of the device can be selected to interfere with blood flow to a degree sufficient to lead to thrombosis of the aneurysm or other body space. 
     According to some embodiments, the expandable device can be configured to interfere with blood flow to generally reduce the exchange of blood between the parent vessel and an aneurysm, which can induce thrombosis of the aneurysm. A device (or a device component, such as a sidewall of a stent or a section of such a sidewall) that interferes with blood flow can be said to have a “flow diverting” property. 
     According to some embodiments, a porosity of the expandable device is equal to a ratio of an open surf ace area of the expandable device to a total surface area of the expandable device. The expandable device may comprise a plurality of struts, which form pores or cells as open areas between the struts. 
     The device can exhibit a porosity configured to reduce haemodynamic flow into and/or induce thrombosis within an aneurysm. The device can simultaneously allow perfusion to an adjacent branch vessel whose ostium is crossed by a portion of the device. The device can exhibit a high degree of flexibility due to the materials used, the density (i.e., the porosity) of the struts, and the arrangement of struts. 
     The device can be self-expanding to a relaxed state or an expanded state. As used herein, the relaxed state is one to which the expandable device will self-expand in the absence of any containment or external forces. As used herein, expanded state is one to which the expandable device is capable of self-expanding, ignoring any containment, such by as a blood vessel. For example and simplicity of measurement, this expanded state can be one to which the expandable device will self-expand within a straight, non-tapering cylindrical tube with an inside diameter that is slightly smaller than the maximum diameter of the expandable device in the relaxed state. 
     The struts and bridge configuration of the expandable device may be formed, for example, by laser cutting a pre-formed tube or sheet, by interconnecting components (e.g., by laser welding), by vapor deposition techniques, or combinations thereof. A more detailed description of methods by which an expandable device may be formed is provided further herein. 
     According to some embodiments, the expandable device may include a plurality of individual struts and individual cells, as well as a first longitudinal edge and a second longitudinal edge. The first longitudinal edge and the second longitudinal edge may be connected to each other to form a substantially cylindrical shape or a circumferentially continuous cylindrical shape by welding, soldering, or otherwise joining the struts or edges. 
     According to some embodiments in which the device is not a circumferentially continuous cylinder, the first edge and second edge may be formed, for example, by cutting a preformed, etched or laser-cut tube longitudinally along the length of the tube. Regardless of the manner of forming, the expandable device may be rolled or curled such that the first and second longitudinal edges overlap one another when the expandable device is in a compressed state and/or an expanded state. Upon release from a constraint (e.g. upon exiting a catheter), the expandable device (when configured to be self-expanding) may spring open and attempt to assume an expanded state. 
     While the views provided in several of the figures (e.g.,  FIGS. 1A, 1B, 3A-8A, 9A , and  10 A- 14 B) show expandable devices laid flat for ease of explanation and understanding, it will be understood that the devices can possess a tubular shape (e.g.,  FIGS. 8B, 9B and 15A-15D ), and the laid-flat drawings presented herein depict the configuration of a sidewall of the tube. While in the tubular shape, the expandable devices can have open ends of a lumen extending through the expandable device. 
     Many embodiments of the subject technology are directed to expandable, flow-diverting mesh devices formed of a non-braided, thin-film mesh structure that includes a plurality of helical bridge struts (described in greater detail below). The mesh devices of the subject technology provide several advantages over conventional, braided flow-diverting devices, especially braided devices. For example, because the mesh devices disclosed herein are non-braided, they foreshorten significantly less than braided devices and thus may be more accurately deployed and positioned within the parent vessel. Moreover, many of the mesh devices disclosed herein are formed of a monolithic piece of metal and thus may have a very small wall thickness (e.g., about 15-20 microns), thereby enabling placement in smaller blood vessels and allowing new anatomical areas of treatment for flow diversion. Finally, because of the density, shape and arrangement of struts, the mesh devices of the subject technology are more flexible than conventional stents and may be positioned around tight corners or bends without kinking. 
     According to some embodiments, for example as shown in  FIGS. 1A and 1B , an expandable device  100  can comprise a plurality of connector struts  120  within a plurality of connector sections  110  and a plurality of bridge members  160  within a plurality of bridge sections  150 . Some or all of the bridge sections  150  can be disposed longitudinally between a pair of connector sections  110 . Some or all of the connector sections  110  and the bridge sections  150  can extend along some or all of a circumference of the expandable device  100  when the expandable device  100  forms a tubular shape. Some or all of the connector sections  110  can be connected to bridge sections  150  on opposing longitudinal sides of the connector section  110 . Some or all of the bridge sections  150  can be connected to connector sections  110  on opposing longitudinal sides of the bridge section  150 . 
     According to some embodiments, for example as shown in  FIG. 1B , the connector struts  120  of the connector section  110  can be connected to each other within the connector section  110 . As depicted, the connector struts  120  can be arranged in a “zigzag” pattern and the connector section  110  formed thereby can be in the form of a circumferential band, or a V-strut band. An end of one connector strut  120  can be connected to an end of another connector strut  120 . One or more connector struts  120  can be connected at an apex  130 . Some or all of the apices  130  can be formed at longitudinal ends of the connector section  110 , such that each of the apices  130  faces an adjoining bridge section  150 . Each connector section  110  can have 28-108 connector struts  120 . 
     According to some embodiments, for example as shown in  FIG. 1B , the bridge members  160  of the bridge section  150  can be connected to connector struts  120  of adjacent connector sections  110 . Each of the bridge members  160  can connect to a connector strut  120  (e.g., at an apex  130 ) of one connector section  110  with one end of the bridge member  160  and to a connector strut  120  (e.g., at an apex  130 ) of another connector section  110  with an opposite end of the bridge member  160 . Between the ends of the bridge member  160 , the bridge member  160  can be non-branching. Between the ends of the bridge member  160 , the bridge member  160  can be unconnected to any other bridge member  160 . Each bridge section  150  can have, e.g., 28-108 bridge members  160 . Each bridge member  160  can span a circumferential distance of the expandable device  100  while the expandable device  100  is in a tubular shape. For example, each bridge member  160  can span 30° to 180° about the longitudinal axis, for example 120°. By further example, each bridge member  160  can span a distance of 3 to 54 apices  130  between terminal ends of the bridge member  160 . At least a portion of a bridge member  160  can be parallel to some or all of the other bridge members  160  of the same bridge section  150  when the expandable device  100  is represented in a laid-flat view such as in  FIGS. 1A-1B , etc. At least a portion of a bridge member  160  in a helical shape can be parallel to some or all of the other bridge members  160  in a helical shape of the same bridge section  150  when the expandable device  100  is considered in its tubular form. As used herein, two helical shapes are considered “parallel” if they wind about the same axis, at the same distance (i.e., radius) from the axis, with the same pitch angle or helix angle with respect to the axis, and in the same rotational direction (dextrorotatory or levorotatory) with respect to the axis. 
     According to some embodiments, a helical winding direction of the bridge members  160  of one bridge section  150  can be different than a helical winding direction of the bridge members  160  of a different bridge section  150 . For example, the helical winding direction of some bridge members  160  of one bridge section  150  can be dextrorotatory and the helical winding direction of the bridge members  160  of a different bridge section  150  can be levorotatory. The helical winding direction within any given bridge section  150  can be different than the helical winding direction of any adjacent bridge section  150 . For example, alternating bridge sections  150  along a longitudinal length of the expandable device  100  can have alternating helical winding directions relative to each other. When the expandable device  100  is extended longitudinally, the bridge members  160  of the bridge sections  150  can straighten relative to the longitudinal axis, causing the connector sections  110  to rotate about the axis in different directions. This allows the extreme ends of the expandable device  100  to rotate relative to each other less than they would if the bridge members  160  of every bridge section  150  were wound in the same helical direction, or not at all. 
     According to some embodiments, a bridge gap  162  is a distance between a pair of adjacent bridge members  160 . The bridge gap  162  can be measured across parallel portions of pairs of adjacent bridge members  160 . The bridge gap  162  can be the same (e.g., uniform) or different among different pairs of bridge members  160  within a single bridge section  150 . The bridge gap  162  can be the same/uniform or different among different bridge sections  150  of a single device  100 . The bridge gap  162  can be 1 to 250 for example greater than 100 μm. 
     According to some embodiments, the bridge members  160  form a pitch angle  164  with respect to a line that is orthogonal to the longitudinal axis of the expandable device  100 . The pitch angle  164  can be the same/uniform or different for different bridge members  160  within a single bridge section  150 . The pitch angle  164  can be the same/uniform or different among different bridge sections  150  of a single device  100 . The pitch angle  164  can be 10° to 60°, for example 19°. 
     According to some embodiments, an apex gap  132  is a distance between a pair of adjacent apices  130  on a same longitudinal side of a connector section  110 . The apex gap  132  can be measured as orthogonal to a longitudinal axis of the expandable device  100 . The apex gap  132  can be the same/uniform or different among different pairs of apices  130  within a single connector section  110 . The apex gap  132  can be the same/uniform or different among different connector sections  110  of a single device  100 . The apex gap  132  can be 10 to 450 μm, for example 300 μm. 
     According to some embodiments, a connector section length  112  is a longitudinal distance between opposing longitudinal sides of a connector section  110  (e.g., between a pair of bridge sections  150 ). The connector section length  112  can be measured as parallel to a longitudinal axis of the expandable device  100 . The connector section length  112  can be the same/uniform or different among different connector sections  110  of a single device  100 . The connector section length  112  can be 10 to 450 μm, for example 300 μm. 
     According to some embodiments, a bridge section length  152  is a longitudinal distance between opposing longitudinal sides of a bridge section  150  (e.g., between a pair of connector sections  110 ). The bridge section length  152  can be measured as parallel to a longitudinal axis of the expandable device  100 . The bridge section length  152  can be the same/uniform or different among different bridge sections  150  of a single device  100 . The bridge section length  152  can be 500 to 4500 μm, for example 1,100 μm. 
     According to some embodiments, some or all of the bridge members  160  and/or some or all of the connector struts  120  can comprise a radiopaque marker. The radiopaque marker can be disposed on a substantially straight section of a bridge member  160  and/or a connector strut  120 , so the radiopaque marker is predominantly not subject to bending or flexing. For example, the radiopaque marker(s) can be disposed a distance away from an apex  130 . The radiopaque marker(s) can be formed on the bridge members  160  and/or the connector struts  120  by a process that is the same or different than a process used to form the bridge members  160  and/or the connector struts  120 , which are discussed further herein. 
     According to some embodiments, the expandable device  100  can provide a porosity that is the range of 5%-95%. The cells of the expandable device  100  can provide a pore size that is between 5 and 450 μm. A pore size can be measured via a maximum inscribed circle technique. 
       FIG. 2A  depicts a perspective view of a connector strut  120  according to some embodiments of the subject technology.  FIG. 2B  depicts a cross-sectional view of the connector strut  120  according to one aspect of the subject technology. As shown, the connector strut  120  has a length, a width, and a thickness. The thickness can be measured as a dimension that is orthogonal to a central axis when the expandable device  100  is considered in a tubular shape or as a dimension that is orthogonal to a plane of the expandable device  100  when represented as laid-flat. The length can be measured as a distance extending between ends of a strut, where the ends connect to another structure. The width can be measured as the distance that is generally orthogonal to the length and thickness. The width and length of a strut can contribute to a surface coverage and porosity of the expandable device  100 . According to some embodiments, the connector strut  120  can have a square cross-section. According to some embodiments, the bridge member  160  can have a similar square cross-section. However, the connector strut  120  and/or the bridge member  160  may have other suitable cross-sectional shapes, such as rectangular, polygonal, round, ovoid, elliptical, or combinations thereof. 
     According to some embodiments, a thickness of the connector struts  120  and/or the bridge members  160  can be 5 to 50 μm, for example 50 μm. According to some embodiments, a width of the connector struts  120  and/or the bridge members  160  can be 5 to 50 μm, for example 50 μm. 
     According to some embodiments, for example as shown in  FIGS. 3A and 3B , an expandable device can have a number of apices that is greater than a number of bridge members, such that at least some of the apices do not connect directly to a bridge member. 
     According to some embodiments, for example as shown in  FIGS. 3A and 3B , an expandable device  300  can comprise a plurality of connector struts  320  and apices  330  within a plurality of connector sections  310  and a plurality of bridge members  360  within a plurality of bridge sections  350 . Features of the expandable device  300  that are identified with reference numerals that differ from the reference numerals for the expandable device  100  by a multiple of 100 can have the same aspects as the corresponding features in the expandable device  100 , unless noted otherwise. 
     According to some embodiments, for example as shown in  FIGS. 3A and 3B , at least some of the apices  330  do not connect directly to a bridge member  360 . For example, a number of apices  330  or connector struts  320  can be greater than a number of bridge members  360 . Accordingly, at least some of the connector struts  320  terminate at an apex  330  that does not connect to a bridge member  360 . For example, a given connector section  310  can form a number of apices  330  that face an adjacent bridge section  350 , and the bridge section  350  can comprise fewer (for example, one-half or one-third) bridges than such adjacent, facing apices. Accordingly, every other (or every third, fourth, fifth, etc.) adjacent, facing apex  330  can be connected to a bridge of the adjacent bridge section  350 , and the remaining apices can be unconnected to a bridge. 
     According to some embodiments, for example as shown in  FIGS. 4A and 4B , an expandable device  400  can comprise a plurality of connector struts  420  and apices  430  within a plurality of connector sections  410  and a plurality of bridge members  460  within a plurality of bridge sections  450 . Features of the expandable device  400  that are identified with reference numerals that differ from the reference numerals for the expandable device  100  by a multiple of 100 can have the same aspects as the corresponding features in the expandable device  100 , unless noted otherwise. 
     According to some embodiments, for example as shown in  FIGS. 4A and 4B , at least some of the apices  430  do not connect directly to a bridge member  460 . For example, a number of apices  430  or connector struts  420  can be greater than a number of bridge members  460 . Accordingly, at least some of the connector struts  420  terminate at an apex  430  that does not connect to a bridge member  460 . For example, a given connector section  410  can form a number of apices  430  that face an adjacent bridge section  450 , and the bridge section  450  can comprise fewer (for example, one-half or one-third) bridges than such adjacent, facing apices. Accordingly, every other (or every third, fourth, fifth, etc.) adjacent, facing apex  430  can be connected to a bridge of the adjacent bridge section  450 , and the remaining apices can be unconnected to a bridge. 
     According to some embodiments, for example as shown in  FIGS. 5A and 5B , bridge members of an expandable device can connect to connector struts at a location other than at an apex where two connector struts are coupled together. 
     According to some embodiments, for example as shown in  FIGS. 5A and 5B , an expandable device  500  can comprise a plurality of connector struts  520  and apices  530  within a plurality of connector sections  510  and a plurality of bridge members  560  within a plurality of bridge sections  550 . Features of the expandable device  500  that are identified with reference numerals that differ from the reference numerals for the expandable device  100  by a multiple of 100 can have the same aspects as the corresponding features in the expandable device  100 , unless noted otherwise. 
     According to some embodiments, for example as shown in  FIGS. 5A and 5B , some or all of the bridge members  560  connect to a connector section  510  at a location that is not, or is slightly offset from a centerline of, an apex  530  of two connector struts  520 . Instead, some or all of the bridge members  560  connect more closely to one connector strut  520  than to the other connector strut  520  with which it forms an apex  530 . In this configuration, the connection to the bridge member  560  is less likely to interfere with the flexing of the apex  530 . 
     According to some embodiments, for example as shown in  FIGS. 6A and 6B , each and every bridge member of an expandable device can extend in the same helical winding direction. 
     According to some embodiments, for example as shown in  FIGS. 6A and 6B , an expandable device  600  can comprise a plurality of connector struts  620  and apices  630  within a plurality of connector sections  610  and a plurality of bridge members  660  within a plurality of bridge sections  650 . Features of the expandable device  600  that are identified with reference numerals that differ from the reference numerals for the expandable device  100  by a multiple of 100 can have the same aspects as the corresponding features in the expandable device  100 , unless noted otherwise. 
     According to some embodiments, for example as shown in  FIGS. 6A and 6B , a helical winding direction of the bridge members  660  of one bridge section  650  can be the same as a helical winding direction of the bridge members  660  of a different bridge section  650 . For example, the helical winding direction of all bridge members  660  of all bridge sections  650  can be dextrorotatory or levorotatory. When the expandable device  600  is extended longitudinally, the bridge members  660  of the bridge sections  650  can straighten relative to the longitudinal axis, causing the connector sections  610  to rotate about the axis in the same direction. This allows the extreme ends of the expandable device  600  to rotate relative to each other in the same way throughout the expansion of the expandable device  600 . 
     According to some embodiments, for example as shown in  FIGS. 7  A and  7 B, an expandable device can incorporate (1) the connection of struts as described with respect to the expandable device  500  and (2) the helical winding direction as described with respect to the expandable device  600 . 
     According to some embodiments, for example as shown in  FIGS. 7  A and  7 B, an expandable device  700  can comprise a plurality of connector struts  720  and apices  730  within a plurality of connector sections  710  and a plurality of bridge members  760  within a plurality of bridge sections  750 . Features of the expandable device  700  that are identified with reference numerals that differ from the reference numerals for the expandable device  100  by a multiple of 100 can have the same aspects as the corresponding features in the expandable device  100 , unless noted otherwise. 
     According to some embodiments, for example as shown in  FIGS. 7  A and  7 B, a helical winding direction of the bridge members  760  of one bridge section  750  can be the same as a helical winding direction of the bridge members  760  of a different bridge section  750 . According to some embodiments, some or all of the bridge members  760  connect to a connector section  710  at a location that is not at, or is slightly offset from, a centerline of an apex  730  of two connector struts  720 . Instead, some or all of the bridge members  760  connect more closely to one connector strut  720  than to the other connector strut  720  with which it forms an apex  730 . According to some embodiments, at least some of the apices  730  do not connect directly to a bridge member  760 . 
     According to some embodiments, for example as shown in  FIGS. 8A and 8B , an expandable device can incorporate (1) the unconnected apices described with respect to the expandable device  300  and (2) the connection of struts as described with respect to the expandable device  500 . 
     According to some embodiments, for example as shown in  FIGS. 8A and 8B , an expandable device  800  can comprise a plurality of connector struts  820  and apices  830  within a plurality of connector sections  810  and a plurality of bridge members  860  within a plurality of bridge sections  850 . Features of the expandable device  800  that are identified with reference numerals that differ from the reference numerals for the expandable device  100  by a multiple of 100 can have the same aspects as the corresponding features in the expandable device  100 , unless noted otherwise. 
     According to some embodiments, for example as shown in  FIGS. 8A and 8B , a helical winding direction of the bridge members  860  of one bridge section  850  can be different than a helical winding direction of the bridge members  860  of a different bridge section  850 . According to some embodiments, some or all of the bridge members  860  connect to a connector section  810  at a location that is not at, or is slightly offset from, a centerline of an apex  830  of two connector struts  820 . Instead, some or all of the bridge members  860  connect more closely to one connector strut  820  than to the other connector strut  820  with which it forms an apex  830 . According to some embodiments, at least some of the apices  830  do not connect directly to a bridge member  860 . 
     According to some embodiments, for example as shown in  FIGS. 9A and 9B , an expandable device can incorporate (1) the unconnected apices described with respect to the expandable device  300 , (2) the connection of struts as described with respect to the expandable device  500 , and (3) the helical winding direction as described with respect to the expandable device  600 . 
     According to some embodiments, for example as shown in  FIGS. 9A and 9B , an expandable device  900  can comprise a plurality of connector struts  920  and apices  930  within a plurality of connector sections  910  and a plurality of bridge members  960  within a plurality of bridge sections  950 . Features of the expandable device  900  that are identified with reference numerals that differ from the reference numerals for the expandable device  100  by a multiple of 100 can have the same aspects as the corresponding features in the expandable device  100 , unless noted otherwise. 
     According to some embodiments, for example as shown in  FIGS. 9A and 9B , a helical winding direction of the bridge members  960  of one bridge section  950  can be the same a helical winding direction of the bridge members  960  of a different bridge section  950 . According to some embodiments, some or all of the bridge members  960  connect to a connector section  910  at a location that is not at, or is slightly offset from, a centerline of an apex  930  of two connector struts  920 . Instead, some or all of the bridge members  960  connect more closely to one connector strut  920  than to the other connector strut  920  with which it forms an apex  930 . According to some embodiments, at least some of the apices  930  do not connect directly to a bridge member  960 . 
     According to some embodiments, for example as shown in  FIGS. 10A and 10B , an expandable device can incorporate (1) the connection of struts as described with respect to the expandable device  500  and (2) the helical winding direction as described with respect to the expandable device  600 . 
     According to some embodiments, for example as shown in  FIGS. 10A and 10B , an expandable device  1000  can comprise a plurality of connector struts  1020  and apices  1030  within a plurality of connector sections  1010  and a plurality of bridge members  1060  within a plurality of bridge sections  1050 . Features of the expandable device  1000  that are identified with reference numerals that differ from the reference numerals for the expandable device  100  by a multiple of 100 can have the same aspects as the corresponding features in the expandable device  100 , unless noted otherwise. 
     According to some embodiments, for example as shown in  FIGS. 10A and 10B , a helical winding direction of the bridge members  1060  of one bridge section  1050  can be the same as a helical winding direction of the bridge members  1060  of a different bridge section  1050 . According to some embodiments, some or all of the bridge members  1060  connect to a connector section  1010  at a location that is not at, or is slightly offset from, a centerline of an apex  1030  of two connector struts  1020 . 
     According to some embodiments, for example as shown in  FIGS. 11A and 11B , an expandable device can comprise some connector struts that are curved between apices, wherein the connector struts are parallel to each in a helical winding direction. For example, at least a portion of each of the connector struts  1120  that are joined at a given apex  1130  (or at some or all apices  1130  of one, some or all connector sections  1110 ) are parallel to each other. In a given connector section every other connector strut  1120  can have a curved section near each end, and a straight midsection between the two curved sections. Such a configuration can shift some of the strain of device compression or expansion from the apices  1130  to the curved sections to avoid over-straining or distorting the apices, and/or to allow a greater degree of device compression or expansion. 
     According to some embodiments, for example as shown in  FIGS. 11A and 11B , an expandable device  1100  can comprise a plurality of connector struts  1120  and apices  1130  within a plurality of connector sections  1110  and a plurality of bridge members  1160  within a plurality of bridge sections  1150 . Features of the expandable device  1100  that are identified with reference numerals that differ from the reference numerals for the expandable device  100  by a multiple of 100 can have the same aspects as the corresponding features in the expandable device  100 , unless noted otherwise. 
     According to some embodiments, for example as shown in  FIGS. 11A and 11B , a helical winding direction of the bridge members  1160  of one bridge section  1150  can be the same as a helical winding direction of the bridge members  1160  of a different bridge section  1150 . According to some embodiments, some or all of the bridge members  1160  connect to a connector section  1110  at a location that is not at, or is slightly offset from, a centerline of an apex  1130  of two connector struts  1120 . Optionally, the connector section  1110  located at one or both longitudinal terminal ends of the device  1100  can comprise a V-strut band such as the connector section  110  of  FIGS. 1A-1B . 
     According to some embodiments, for example as shown in  FIGS. 12A and 12B , an expandable device can have connector struts that are coupled together at an apices that have a curve that is configured to reduce a bend radius at each apex. 
     According to some embodiments, for example as shown in  FIGS. 12A and 12B , the apices  1230  can have a shape that is configured to reduce a bend radius at each apex  1230  while preserving the size and relative orientation of the connector struts  1220 . For example, some or all of the connector struts  1220  can be curved so that as a pair of struts  1220  approach an apex  1230 , the struts  1220  turn away from each other forming generally parallel terminal portions that extend to the apex  1230 . This allows for a smaller bend radius at the apex  1230  while preserving the size and angle of the V formed by the struts  1220 . During compression or expansion of the device  1200 , this tends to concentrate bending of each V at the apex  1230  rather than along the struts  1220  which can cause undesirable distortion or out-of-plane movement of the struts  1220 . The inside edge of the apex  1230  can be made semicircular. When the expandable device  1200  is compressed radially, the connector struts  1220  move closer to each other by bending about the apices  1230 . The connector struts  1220  at terminal ends of the expandable device  1200  can have a different shape (e.g., the shape of the connector struts  120  of the expandable device  100 ). 
     According to some embodiments, for example as shown in  FIGS. 12A and 12B , an expandable device  1200  can comprise a plurality of connector struts  1220  and apices  1230  within a plurality of connector sections  1210  and a plurality of bridge members  1260  within a plurality of bridge sections  1250 . Features of the expandable device  1200  that are identified with reference numerals that differ from the reference numerals for the expandable device  100  by a multiple of 100 can have the same aspects as the corresponding features in the expandable device  100 , unless noted otherwise. 
     According to some embodiments, for example as shown in  FIGS. 12A and 12B , a helical winding direction of the bridge members  1260  of one bridge section  1250  can be the same as a helical winding direction of the bridge members  1260  of a different bridge section  1250 . According to some embodiments, some or all of the bridge members  1260  connect to a connector section  1210  at a location that is not an apex  1230  of two connector struts  1220 . 
     According to some embodiments, for example as shown in  FIGS. 13A and 13B , an expandable device can have some bridge members that terminate at a pass-through strut  1370  that extends through a connector section  1310  without contacting or being connected to any connector struts or apex. 
     According to some embodiments, for example as shown in  FIGS. 13A and 13B , an expandable device  1300  can comprise a plurality of connector struts  1320  and apices  1330  within a plurality of connector sections  1310  and a plurality of bridge members  1360  within a plurality of bridge sections  1350 . Features of the expandable device  1300  that are identified with reference numerals that differ from the reference numerals for the expandable device  100  by a multiple of 100 can have the same aspects as the corresponding features in the expandable device  100 , unless noted otherwise. 
     According to some embodiments, for example as shown in  FIGS. 13A and 13B , a helical winding direction of the bridge members  1360  of one bridge section  1350  can be the same as a helical winding direction of the bridge members  1360  of a different bridge section  1350 . According to some embodiments, some or all of the bridge members  1360  connect to a connector section  1310  at a location that is not an apex  1330  of two connector struts  1320 . 
     According to some embodiments, for example as shown in  FIGS. 13A and 13B , some of the bridge members  1360  can terminate at a pass-through strut  1370  that extends through the connector section  1310  without contacting or being connected to any connector struts  1320  or apex  1330 . The pass-through struts  1370  can extend from one bridge section  1350  to another bridge section  1350  on an opposing side of the connector section  1310 . Only some (e.g., ⅓) of the bridge members  1360  that connect to a given connector section  1310  connect to a pass-through strut  1370  at that connector section  1310 . The remainder of the bridge members  1360  can connect to a connector strut  1320  or apex  1330  at that connector section  1310 . Each bridge member  1360  that connects to a pass-through strut  1370  on one terminal end of the bridge member  1360  can connect to a connector strut  1320  and/or an apex  1330  at the opposite terminal end of the bridge member  1360 . Optionally, the connector section  1310  located at one or both longitudinal terminal ends of the device  1300  can comprise a V-strut band such as the connector section  110  of  FIGS. 1A-1B . 
     According to some embodiments, for example as shown in  FIGS. 14A and 14B , an expandable device can have an end section at one or both of its longitudinally terminal ends to provide securement of the expandable device within a body vessel. 
     According to some embodiments, for example as shown in  FIGS. 14A and 14B , an expandable device  1400  can comprise a plurality of connector struts  1420  and apices  1430  within a plurality of connector sections  1410  and a plurality of bridge members  1460  within a plurality of bridge sections  1450 . Features of the expandable device  1400  that are identified with reference numerals that differ from the reference numerals for the expandable device  100  by a multiple of 100 can have the same aspects as the corresponding features in the expandable device  140 , unless noted otherwise. 
     According to some embodiments, for example as shown in  FIGS. 14A and 14B  a helical winding direction of the bridge members  1460  of one bridge section  1450  can be the same as a helical winding direction of the bridge members  1460  of a different bridge section  1450 . According to some embodiments, some or all of the bridge members  1460  connect to a connector section  1410  at a location that is not an apex  1430  of two connector struts  1420 . 
     According to some embodiments, for example as shown in  FIGS. 14A and 14B  the expandable device  1400  can comprise an end section  1480  at one or both of its longitudinally terminal ends. The end sections  1480  can be generally stiffer than the bridge sections  1450 . Each of the end sections  1480  can comprise end struts  1490 . The end struts  1490  can be interconnected at apices  1495 . The end struts  1490  can form a series of undulations (e.g., sinusoidal or “S-curves”) that extend longitudinally across the some or all of the end section  1480 . The end struts  1490  can be connected to each other at or near peaks or troughs thereof. The end struts  1490  can be arranged to form a series of cells that are similar in size and shape. For example, the cells can be approximately diamond shaped. The end struts  1490  can be shorter than the bridge members  1460 . For example, the end struts  1490  can be approximately the same length as the connector struts  1420 . The end struts  1490  can comprise a series of longitudinally adjacent V-strut bands like that employed as the connector sections  1410 . In such a configuration, every other band can be inverted longitudinally and the bands connected apex-to-apex as shown in  FIG. 14B . 
     According to some embodiments, as shown in  FIGS. 15A-D , when an expandable device  1500  is bent to conform to a body vessel with tortuous curvature, the connector sections  1510  can move closer to each other on the “inside-curving” side of the expandable device  1500  when the bridge members  1560  collapse longitudinally and move closer to each other on that side. The thinness and arrangement of struts provides enhanced longitudinal flexibility and better arching capability. When deployed in a tortuous body vessel, the device of the subject technology will readily bend at a bridge section, thus providing improved wall apposition at a curve. For example, referring to  FIGS. 15A-D , the device  1500  is disposed in a body vessel with tortuous curvature. At an apex of a curve in the body vessel, the bridge members  1560  adjacent the apex move toward each other to facilitate contact with an inner surface of the vessel, thereby providing improved wall apposition near the apex. A distance between bridge members  1560  adjacent to the apex of the curve is less than a distance between bridge members  1560  disposed away from the apex. By allowing the bridge members  1560  to move near each other, the bridge members  1560  may better conform to the shape of the curve. This helps avoid issues that may occur in other devices, such as tendencies to ovalize, kink, or fish mouth when placed in a body vessel with tortuous curvature. 
     An expandable device may be formed, for example, by laser cutting a preformed tube or sheet, by interconnecting components (e.g., by laser welding), by vapor deposition techniques, or combinations thereof. The expandable device can be formed using known flexible materials such as nitinol, stainless steel, cobalt-chromium alloys, Elgiloy, magnesium alloys, tungsten, tantalum, platinum, or combinations thereof. 
     According to some embodiments, an expandable device can be formed by a photolithography process. A substrate can be provided with a base for supporting the formation of the expandable device. The base (e.g., copper) can be used temporarily as a buffer between the substrate and a primary material used to form the expandable device. After the base is provided on the substrate, the primary material is provided thereon, for example by vapor deposition. The primary material can be provided as a thin film of substantially uniform thickness. Portions of the primary material can be removed to form the structure of the expandable device. For example, a photomask, based on a strut pattern, can be used to selectively expose portions of the primary material to light and etch the primary material into the desired shape for the expandable device. Alternatively or in combination, a chemical agent can be used to remove the portions of the primary material that are not protected by a photoresist. The base can then be eroded to separate the expandable device from the substrate. The expandable device can be further treated to form a desired shape (e.g., tubular) and have the desired heat set and/or shape memory properties. 
     According to some embodiments, an expandable device can be formed by a laser cutting process. The expandable device may be formed by cutting a pattern of struts on a tube or on a flat sheet and then rolling the flat sheet into a generally tube-like or coiled shape. The expandable device in a generally tube-like or coiled shape can be circumferentially continuous or discontinuous. Where the expandable device is circumferentially discontinuous, portions of the expandable device can overlap in certain states. 
     As mentioned elsewhere herein, the present disclosure also includes methods of treating a vascular condition, such as an aneurysm, with any of the embodiments of the expandable devices disclosed herein. The expandable device could be deployed across the neck of an aneurysm and its flow-diverting properties employed to impede blood flow between the aneurysm and the parent vessel, cause the blood inside the aneurysm to thrombose, and lead to healing of the aneurysm. 
     In order to implant any of the expandable devices disclosed herein, the expandable device can be mounted in a delivery system. Generally, the delivery system can comprise an elongate core member that supports or contains the expandable device, and both components can be slidably received in a lumen of a microcatheter or other elongate sheath for delivery to any region to which the distal opening of the microcatheter can be advanced. The core member is employed to advance the expandable device through the microcatheter and out the distal end of the microcatheter so that the expandable device is allowed to self-expand into place in the blood vessel, across an aneurysm or other treatment location. Accordingly, a vascular treatment apparatus can comprise a delivery system, such as any of the delivery systems described herein, and an expandable device, such as any of the expandable devices described herein, mounted in the delivery system. 
     A treatment procedure can begin with obtaining percutaneous access to the patient&#39;s arterial system, typically via a major blood vessel in a leg or arm. A guidewire can be placed through the percutaneous access point and advanced to the treatment location, which can be in an intracranial artery, or any neurovascular artery, peripheral artery or coronary artery. (As configured for neurovascular use, any of the expandable devices disclosed herein can have a diameter of 2-8 mm in the relaxed state or the expanded state; expandable devices used in the peripheral or coronary vasculature can have a diameter of 1-20 mm in the relaxed state or the expanded state.) The microcatheter is then advanced over the guidewire to the treatment location and situated so that a distal open end of the guidewire is adjacent to the treatment location. The guidewire can then be withdrawn from the microcatheter and the core member, together with the expandable device mounted thereon or supported thereby, can be advanced through the microcatheter and out the distal end thereof. The expandable device can then self-expand into apposition with the inner wall of the blood vessel. Where an aneurysm is being treated, the expandable device is placed across the neck of the aneurysm so that a sidewall of the expandable device separates the interior of the aneurysm from the lumen of the parent artery. Once the expandable device has been placed, the core member and microcatheter are removed from the patient. The expandable device sidewall can now perform a flow-diverting function on the aneurysm, thrombosing the blood in the aneurysm and leading to healing of the aneurysm. 
     The foregoing description is provided to enable a person skilled in the art to practice the various configurations described herein. While the subject technology has been particularly described with reference to the various figures and configurations, it should be understood that these are for illustration purposes only and should not be taken as limiting the scope of the subject technology. 
     There may be many other ways to implement the subject technology. Various functions and elements described herein may be partitioned differently from those shown without departing from the scope of the subject technology. Various modifications to these configurations will be readily apparent to those skilled in the art, and generic principles defined herein may be applied to other configurations. Thus, many changes and modifications may be made to the subject technology, by one having ordinary skill in the art, without departing from the scope of the subject technology. 
     A phrase such as “an aspect” does not imply that such aspect is essential to the subject technology or that such aspect applies to all configurations of the subject technology. A disclosure relating to an aspect may apply to all configurations, or one or more configurations. An aspect may provide one or more examples of the disclosure. A phrase such as “an aspect” may refer to one or more aspects and vice versa. A phrase such as “an embodiment” does not imply that such embodiment is essential to the subject technology or that such embodiment applies to all configurations of the subject technology. A disclosure relating to an embodiment may apply to all embodiments, or one or more embodiments. An embodiment may provide one or more examples of the disclosure. A phrase such “an embodiment” may refer to one or more embodiments and vice versa. A phrase such as “a configuration” does not imply that such configuration is essential to the subject technology or that such configuration applies to all configurations of the subject technology. A disclosure relating to a configuration may apply to all configurations, or one or more configurations. A configuration may provide one or more examples of the disclosure. A phrase such as “a configuration” may refer to one or more configurations and vice versa. 
     It is understood that the specific order or hierarchy of steps in the processes disclosed is an illustration of exemplifying approaches. Based upon design preferences, it is understood that the specific order or hierarchy of steps in the processes may be rearranged. Some of the steps may be performed simultaneously. Various methods are disclosed presenting elements of the various steps in a sample order, and are not meant to be limited to the specific order or hierarchy presented. 
     Furthermore, to the extent that the term “include,” “have,” or the like is used herein, such term is intended to be inclusive in a manner similar to the term “comprise” as “comprise” is interpreted when employed as a transitional word in a claim. 
     A reference to an element in the singular is not intended to mean “one and only one” unless specifically stated, but rather “one or more.” The term “some” refers to one or more. All structural and functional equivalents to the elements of the various configurations described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and intended to be encompassed by the subject technology. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the above description. 
     While certain aspects and embodiments of the subject technology have been described, these have been presented by way of example only, and are not intended to limit the scope of the subject technology. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms without departing from the spirit thereof. The numbered clauses and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the subject technology.