Patent Publication Number: US-2021169499-A1

Title: Systems And Methods For Embolization Of Body Structures

Description:
RELATED APPLICATIONS 
     This application is a continuation of and claims priority to patent application Ser. No. 15/923,266, filed Mar. 16, 2018, entitled Systems And Methods For Embolization Of Body Structures, which claims benefit of and priority to U.S. Provisional Application Ser. No. 62/476,104 filed Mar. 24, 2017 entitled Systems And Methods For Embolization Of Body Structures, both of which are hereby incorporated herein by reference in their entireties. 
    
    
     FIELD OF THE INVENTION 
     Embodiments of devices and methods herein are directed to blocking a flow of fluid through a tubular vessel or into a small interior chamber of a saccular cavity or vascular defect within a mammalian body. More specifically, embodiments herein are directed to devices and methods for treatment of a vascular defect of a patient including some embodiments directed specifically to the treatment of cerebral aneurysms of patients. 
     BACKGROUND 
     The mammalian circulatory system is comprised of a heart, which acts as a pump, and a system of blood vessels that transport the blood to various points in the body. Due to the force exerted by the flowing blood on the blood vessel the blood vessels may develop a variety of vascular defects. One common vascular defect known as an aneurysm results from the abnormal widening of the blood vessel. Typically, vascular aneurysms are formed as a result of the weakening of the wall of a blood vessel and subsequent ballooning and expansion of the vessel wall. If, for example, an aneurysm is present within an artery of the brain, and the aneurysm should burst with resulting cranial hemorrhaging, death could occur. 
     Surgical techniques for the treatment of cerebral aneurysms typically involve a craniotomy requiring creation of an opening in the skull of the patient through which the surgeon can insert instruments to operate directly on the patient&#39;s brain. For some surgical approaches, the brain must be retracted to expose the parent blood vessel from which the aneurysm arises. Once access to the aneurysm is gained, the surgeon places a clip across the neck of the aneurysm thereby preventing arterial blood from entering the aneurysm. Upon correct placement of the clip the aneurysm will be obliterated in a matter of minutes. Surgical techniques may be effective treatment for many aneurysms. Unfortunately, surgical techniques for treating these types of conditions include major invasive surgical procedures that often require extended periods of time under anesthesia involving high risk to the patient. Such procedures thus require that the patient be in generally good physical condition in order to be a candidate for such procedures. 
     Various alternative and less invasive procedures have been used to treat cerebral aneurysms without resorting to major surgery. Some such procedures involve the delivery of embolic or filling materials into an aneurysm. The delivery of such vaso-occlusion devices or materials may be used to promote hemostasis or fill an aneurysm cavity entirely. Vaso-occlusion devices may be placed within the vasculature of the human body, typically via a catheter, either to block the flow of blood through a vessel with an aneurysm through the formation of an embolus or to form such an embolus within an aneurysm stemming from the vessel. A variety of implantable, coil-type vaso-occlusion devices are known. The coils of such devices may themselves be formed into a secondary coil shape, or any of a variety of more complex secondary shapes. Vaso-occlusive coils are commonly used to treat cerebral aneurysms but suffer from several limitations including poor packing density, compaction due to hydrodynamic pressure from blood flow, poor stability in wide-necked aneurysms and complexity and difficulty in the deployment thereof as most aneurysm treatments with this approach require the deployment of multiple coils. 
     Another approach to treating aneurysms without the need for invasive surgery involves the placement of sleeves or stents into the vessel and across the region where the aneurysm occurs. Such devices maintain blood flow through the vessel while reducing blood pressure applied to the interior of the aneurysm. Certain types of stents are expanded to the proper size by inflating a balloon catheter, referred to as balloon expandable stents, while other stents are designed to elastically expand in a self-expanding manner. Some stents are covered typically with a sleeve of polymeric material called a graft to form a stent-graft. Stents and stent-grafts are generally delivered to a preselected position adjacent a vascular defect through a delivery catheter. In the treatment of cerebral aneurysms, covered stents or stent-grafts have seen very limited use due to the likelihood of inadvertent occlusion of small perforator vessels that may be near the vascular defect being treated. 
     In addition, current uncovered stents are generally not sufficient as a stand-alone treatment. In order for stents to fit through the microcatheters used in small cerebral blood vessels, their density is usually reduced such that when expanded there is only a small amount of stent structure bridging the aneurysm neck. Thus, they do not block enough flow to cause clotting of the blood in the aneurysm and are thus generally used in combination with vaso-occlusive devices, such as the coils discussed above, to achieve aneurysm occlusion. 
     A number of aneurysm neck bridging devices with defect spanning portions or regions have been attempted; however, none of these devices has had a significant measure of clinical success or usage. A major limitation in their adoption and clinical usefulness is the inability to position the defect spanning portion to assure coverage of the neck. Existing stent delivery systems that are neurovascular compatible (i.e., deliverable through a microcatheter and highly flexible) do not have the necessary rotational positioning capability. Another limitation of many aneurysm bridging devices described in the prior art is the poor flexibility. Cerebral blood vessels are tortuous and a high degree of flexibility is required for effective delivery to most aneurysm locations in the brain. 
     Recently, devices and methods have been developed for delivery and use in small and tortuous blood vessels that can substantially block the flow of blood into an aneurysm, such as a cerebral aneurysm. In some cases, these devices achieve short term results, but may be prone to compression or other changes in shape or orientation, which may result in recanalization of the aneurysm. New methods and devices are desired which are suitable for blocking blood flow in cerebral aneurysms over an extended period of time without a significant risk of deformation, compaction or dislocation. 
     SUMMARY OF THE INVENTION 
     In an embodiment of the present disclosure, a device for treatment of a vascular defect within a patient&#39;s vasculature includes a self-expanding permeable shell having a proximal end, a distal end, and a longitudinal axis, the shell comprising a plurality of elongate resilient filaments having a braided structure, wherein the filaments are secured at at least one of the proximal end or the distal end of the permeable shell, wherein the permeable shell has a radially constrained elongated state configured for delivery within a microcatheter and has an expanded state with an axially shortened configuration relative to the radially constrained state, the permeable shell having a plurality of openings formed between the braided filaments, wherein the permeable shell in its expanded state comprises a plurality of circumferentially-arrayed lobes. 
     In another embodiment of the present disclosure, a device for treatment of a vascular defect within a patient&#39;s vasculature includes a self-expanding permeable shell having a proximal end, a distal end, and a longitudinal axis, the shell comprising a plurality of elongate resilient filaments having a braided structure, wherein the filaments are secured at at least one of the proximal end or the distal end of the permeable shell, wherein the permeable shell has a radially constrained elongated state configured for delivery within a microcatheter and has an expanded state with an axially shortened configuration relative to the radially constrained state, the permeable shell having a plurality of openings formed between the braided filaments, wherein the permeable shell in its expanded state comprises at least one recess extending circumferentially around at least a portion of a perimeter of the permeable shell. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of a patient being accessed by an introducer sheath, a microcatheter and a device for treatment of a patient&#39;s vasculature releasably secured to a distal end of a delivery device or actuator. 
         FIG. 2  shows a deployment sequence of a device for treatment of a patient&#39;s vasculature. 
         FIG. 3  shows a deployment sequence of a device for treatment of a patient&#39;s vasculature. 
         FIG. 4  shows a deployment sequence of a device for treatment of a patient&#39;s vasculature. 
         FIG. 5  shows a deployment sequence of a device for treatment of a patient&#39;s vasculature. 
         FIG. 6  is a perspective view of a device for treatment of vascular deformities according to an embodiment of the present disclosure. 
         FIG. 7  is a first cross-sectional view of the device of  FIG. 6  deployed within an aneurysm. 
         FIG. 8  is a second cross-sectional view of the device of  FIG. 6  deployed within an aneurysm. 
         FIG. 9  is a perspective view of a device for treatment of vascular deformities according to an embodiment of the present disclosure. 
         FIG. 10  is a perspective view of a device for treatment of vascular deformities according to an embodiment of the present disclosure. 
         FIG. 11  is a perspective view of a device for treatment of vascular deformities according to an embodiment of the present disclosure. 
         FIG. 12  is a perspective view of a device for treatment of vascular deformities according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Discussed herein are devices and methods for the treatment of vascular defects that are suitable for minimally invasive deployment within a patient&#39;s vasculature, and particularly, within the cerebral vasculature of a patient. For such embodiments to be safely and effectively delivered to a desired treatment site and effectively deployed, some device embodiments may be configured for collapse to a low profile constrained state with a transverse dimension suitable for delivery through an inner lumen of a microcatheter and deployment from a distal end thereof. Embodiments of these devices may also maintain a clinically effective configuration with sufficient mechanical integrity once deployed so as to withstand dynamic forces within a patient&#39;s vasculature over time that may otherwise result in compaction of a deployed device. Unless otherwise stated, one or more of the features, dimensions, or materials of the various embodiments may be used in other similar embodiments discussed herein. 
     Some embodiments are particularly useful for the treatment of cerebral aneurysms by reconstructing a vascular wall so as to wholly or partially isolate a vascular defect from a patient&#39;s blood flow. Some embodiments may be configured to be deployed within a vascular defect to facilitate reconstruction, bridging of a vessel wall or both in order to treat the vascular defect. For some of these embodiments, a permeable shell of the device may be configured to anchor or fix the permeable shell in a clinically beneficial position. For some embodiments, the device may be disposed in whole or in part within the vascular defect in order to anchor or fix the device with respect to the vascular structure or defect. The permeable shell may be configured to span an opening, neck or other portion of a vascular defect in order to isolate the vascular defect, or a portion thereof, from the patient&#39;s nominal vascular system in order allow the defect to heal or to otherwise minimize the risk of the defect to the patient&#39;s health. 
     For some or all of the embodiments of devices for treatment of a patient&#39;s vasculature discussed herein, the permeable shell may be configured to allow some initial perfusion of blood through the permeable shell. The porosity of the permeable shell may be configured to sufficiently isolate the vascular defect so as to promote healing and isolation of the defect, but allow sufficient initial flow through the permeable shell so as to reduce or otherwise minimize the mechanical force exerted on the membrane the dynamic flow of blood or other fluids within the vasculature against the device. For some embodiments of devices for treatment of a patient&#39;s vasculature, only a portion of the permeable shell that spans the opening or neck of the vascular defect, sometimes referred to as a defect spanning portion, need be permeable and/or conducive to thrombus formation in a patient&#39;s bloodstream. For such embodiments, that portion of the device that does not span an opening or neck of the vascular defect may be substantially non-permeable or completely permeable with a pore or opening configuration that is too large to effectively promote thrombus formation. 
     In general, it may be desirable in some cases to use a hollow, thin walled device with a permeable shell of resilient material that may be constrained to a low profile for delivery within a patient. Such a device may also be configured to expand radially outward upon removal of the constraint such that the shell of the device assumes a larger volume and fills or otherwise occludes a vascular defect within which it is deployed. The outward radial expansion of the shell may serve to engage some or all of an inner surface of the vascular defect whereby mechanical friction between an outer surface of the permeable shell of the device and the inside surface of the vascular defect effectively anchors the device within the vascular defect. Some embodiments of such a device may also be partially or wholly mechanically captured within a cavity of a vascular defect, particularly where the defect has a narrow neck portion with a larger interior volume. In order to achieve a low profile and volume for delivery and be capable of a high ratio of expansion by volume, some device embodiments include a matrix of woven or braided filaments that are coupled together by the interwoven structure so as to form a self-expanding permeable shell having a pore or opening pattern between couplings or intersections of the filaments that is substantially regularly spaced and stable, while still allowing for conformity and volumetric constraint. 
     As used herein, the terms woven and braided are used interchangeably to mean any form of interlacing of filaments to form a mesh structure. In the textile and other industries, these terms may have different or more specific meanings depending on the product or application such as whether an article is made in a sheet or cylindrical form. For purposes of the present disclosure, these terms are used interchangeably. 
     Some embodiments for devices and methods for the treatment of vascular defects having permeable shells are described in U.S. Pat. No. 9,078,658, issued Jul. 14, 2015, and titled “Filamentary Devices for Treatment of Vascular Defects,” which is incorporated herein by reference in its entirety for all purposes. Further embodiments for devices and methods for the treatment of vascular defects having permeable shells are described in co-owned U.S. Patent Application Publication No. 2016/02409934, published Sep. 1, 2016, and titled “Filamentary Devices for Treatment of Vascular Defects,” which is incorporated herein by reference in its entirety for all purposes. 
     Embodiments for devices and methods for forming tubular braids to for creating permeable shells such as those described herein are described in U.S. Pat. No. 9,528,205, issued Dec. 27, 2016, and titled “Braiding Mechanism and Methods of Use,” which is incorporated herein by reference in its entirety for all purposes. Devices for the treatment of vascular defects having permeable shells may be attached to delivery devices and delivered to vascular defects using embodiments of devices and methods such as those described in U.S. Pat. No. 8,876,855, issued Nov. 4, 2014, and titled “Delivery and Detachment Systems and Methods for Vascular Implants,” which is incorporated herein by reference in its entirety for all purposes. 
     Embodiments of a delivery apparatus  110  may generally have a length greater than the overall length of a microcatheter  61  to be used for a delivery system  112 . This relationship allows the delivery apparatus  110  to extend, along with an implantable device secured to the distal end thereof, from the distal port of the inner lumen  111  of the microcatheter  61  ( FIG. 3 ) while having sufficient length extending from a proximal end  150  of the microcatheter  61 , shown in  FIG. 1 , to enable manipulation thereof by a physician. For some embodiments, the length of the delivery apparatus  110  may be about 170 cm to about 200 cm. A patient  158  is shown in  FIG. 1  undergoing treatment of a vascular defect  160 , which may be a cerebral aneurysm. An access sheath  162  is shown disposed within either a radial artery  164  or femoral artery  166  of the body  156  of the patient  158  with the delivery system  112  that includes a microcatheter  61  and delivery apparatus  110  disposed within the access sheath  162 . The delivery system  112  is shown extending distally into the vasculature of the patient&#39;s brain adjacent a vascular defect  160  in the patient&#39;s brain. 
     Access to a variety of blood vessels of a patient may be established, including arteries such as the femoral artery  166 , radial artery  164 , or other blood vessels, in order to achieve percutaneous access to a vascular defect  160 . In general, the access artery may be exposed via a small surgical incision  152  and access to the lumen of the blood vessel is gained using the Seldinger technique where an introducing needle is used to place a wire over which a dilator or series of dilators dilates a vessel allowing an introducer sheath  162  to be inserted into the vessel. This would allow the device to be used percutaneously. With an introducer sheath  162  in place, a guiding catheter  168  is then used to provide a safe passageway from the entry site to a region near the target site  154  to be treated. For example, in treating a site in the human brain, a guiding catheter  168  would be chosen which would extend from the entry site  152  at the femoral artery up through the large arteries extending around the heart through the aortic arch, and downstream through one of the arteries extending from the upper side of the aorta such as the carotid artery  170 . Typically, a guidewire  159  and microcatheter  61  are then placed through the guiding catheter  168  and advanced through the patient&#39;s vasculature, until a distal end of the microcatheter  61  is disposed adjacent or within the target vascular defect  160 , such as an aneurysm. 
     Once a properly sized device  10  ( FIGS. 2-5 ) has been selected, the delivery and deployment process may then proceed. It should also be noted also that the properties of the device embodiments  10  and delivery system embodiments  112  discussed herein generally allow for retraction of a device  10  after initial deployment into a defect  160 , but before detachment of the device  10 . Therefore, it may also be possible and desirable to withdraw or retrieve an initially deployed device  10  after the fit within the defect  160  has been evaluated in favor of a differently sized device  10 . An example of a terminal aneurysm  160  is shown in  FIG. 2  in section. The tip  151  of a catheter, such as a microcatheter  61  may be advanced into or adjacent the vascular site or defect  160  (e.g., aneurysm) as shown in  FIG. 3 . For some embodiments, an embolic coil or other vaso-occlusive device or material may optionally be placed within the aneurysm  160  to provide a framework for receiving the device  10 . In addition, a stent may be placed within a parent vessel of some aneurysms substantially crossing the aneurysm neck prior to or during delivery of devices for treatment of a patient&#39;s vasculature discussed herein. 
     Detachment of the device  10  from the delivery apparatus  110  may be controlled by a control switch disposed at a proximal end of the delivery system  112  ( FIG. 1 ), which may also be coupled to an energy source, which severs a tether  72  that secures the device  10  to the delivery apparatus  110 . Once the device  10  is pushed out of the distal port of the microcatheter  61 , or the radial constraint is otherwise removed, a distal end  66  of the device  10  may then axially move towards a proximal end  67  so as to assume the globular everted configuration within the vascular defect  160  as shown in  FIGS. 4-5 . 
     The device  10  may be inserted through the microcatheter  61  such that the catheter lumen  111  restrains radial expansion of the device  10  during delivery. Once the distal tip or deployment port of the delivery system  112  is positioned in a desirable location adjacent or within a vascular defect  160 , the device  10  may be deployed out the distal end of the catheter  61  thus allowing the device to begin to radially expand as shown in  FIG. 4 . As the device  10  emerges from the distal end of the delivery system  112 , the device  10  expands to an expanded state within the vascular defect  160 , as shown in  FIG. 5 , but may be at least partially constrained by an interior surface of the vascular defect  160 . 
     Upon complete deployment, radial expansion of the device  10  may serve to secure the device  10  within the vascular defect  160  and also deploy the permeable shell  40  across at least a portion of an opening  190  (e.g., aneurysm neck) so as to at least partially isolate the vascular defect  160  from flow, pressure or both of the patient&#39;s vasculature adjacent the vascular defect  160  as shown in  FIG. 5 . The conformability of the device  10 , particularly in the neck region  190  may provide for improved sealing. For some embodiments, once deployed, the permeable shell  40  may substantially slow flow of fluids, impede flow into the vascular site, and thus reduce pressure within the vascular defect  160 . For some embodiments, the device  10  may be implanted substantially within the vascular defect  160 , however, in some embodiments, a portion of the device  10  may extend into the defect opening or neck  190  or into branch vessels. The longitudinal axis  46  of the permeable shell  40  is shown in  FIG. 5  extending along a maximum projection of the vascular defect  160  (e.g., from the neck  190  to the dome  191 ). In other cases, the device  10  may be placed so that the permeable shell  40  has a different orientation in regard to the vascular defect  160 , such that the longitudinal axis  46  of the permeable shell extends transversely or obliquely in relation to the neck  190  and dome  191 . 
       FIG. 6  illustrates device for treatment of a vascular defect  200  comprising a permeable shell  202  which is woven or braided from a plurality of resilient elongate filaments  204 . The resilient elongate filaments  204  are only partially shown to simplify the depiction, but in actuality make up generally the entire structure of the permeable shell  202 . The permeable shell  202  has a first end  206 , a second end  208 , and a longitudinal axis  210 . In some embodiments, the elongate resilient filaments  204  of the permeable shell  202  may have a transverse cross section that is substantially round in shape and be made from a superelastic material that may also be a shape memory metal. The filaments  204  are bonded, welded, or otherwise secured together at the first end  206 . In the embodiment of  FIG. 6 , a collar  216  is fastened around ends  218  of the filaments  204 , by crimping, welding, adhesive or epoxy bonding, or even soldering or brazing. In this particular embodiment, the first end  206  is configured to be the proximal end, adjacent to a delivery device, however, in other embodiments, the filaments  204  may be held together at the second end  208  instead of the first end  206 . In still other embodiments, the filaments  204  may be held together at both ends  206 ,  208 . The shape memory metal of the filaments of the permeable shell  202  may be heat set in the globular configuration of the relaxed expanded state. Suitable superelastic shape memory metals may include alloys such as NiTi alloy and the like. The superelastic properties of such alloys may be useful in providing the resilient properties to the elongate filaments  204  so that they can be heat set in the form shown, fully constrained for delivery within an inner lumen of a microcatheter  61  and then released to self-expand back to substantially the original heat set shape of the globular configuration upon deployment within a patient&#39;s body. Further embodiments for devices and methods for heat setting permeable shells are described in co-owned U.S. Patent Application Publication No. 2009/0275974, published Nov. 5, 2009, and titled “Filamentary Devices for Treatment of Vascular Defects,” which is incorporated herein by reference in its entirety for all purposes. 
     The permeable shell  202  is heat set into a secondary shape  214  that comprises six lobes  212   a - f  (or ribs, ears, projections, protuberances) that are circumferentially arrayed with respect to the longitudinal axis  210  of the permeable shell  202 . A braided wall  220  of the permeable shell  202  has different mechanical characteristics than a wall of a permeable shell having a simple cylindrical shape (e.g., circular cross-section). Instead of a single radius of curvature being heat formed into the braided wall around the entire circumference, the braided wall  220  of the permeable shell  202  comprising the secondary shape  214  has a more complex contouring, and contains multiple radii of curvature, which can be seen in more detail in  FIGS. 7 and 8 . 
       FIGS. 7 and 8  show cross-sectional views of the device for treatment of a vascular defect  200  deployed within a vascular defect  160 , which in this particular case is an aneurysm. As shown in  FIG. 7 , the lobes  212   a - f  are evenly distributed around the longitudinal axis  210 , and may be separated from each other by about 60°. In alternative embodiments, an uneven distribution may be desired, and may be achieved by using a different forming fixture during the heat setting operation. As shown in both  FIGS. 6 and 7 , between each of the lobes  212   a - f  is a longitudinally-extending channel  222   a - f . The lobes  212   a - f  are shown in  FIG. 6  extending substantially between the first end  206  and the second end  208  of the permeable shell  202 . The channels  222   a - f  may extend substantially between the first end  206  and the second end  208  of the permeable shell  202 . In other embodiments, distal ends of adjacent lobes may blend into one another and/or proximal ends of adjacent lobes may blend into one another such that the channels  222   a - f  do not extend completely between the first end  206  and the second end  208  of the permeable shell,  202 , but instead are present only in a central portion of the permeable shell  202 . The channels  222   a - f  may be configured to provide a fold or a pleat to allow the permeable shell  202  to selectively collapse into a desired constricted or compressed shape, for placement through the lumen  111  of a microcatheter  61 . 
     As best seen in  FIG. 7 , each lobe  212   a - f  has a first side  224  having a first radius of curvature r 1  and a second side  226  having a second radius of curvature r 2 . In the embodiment of  FIG. 7 , the first radius of curvature r 1  is about equal to the second radius of curvature r 2 , but in other embodiments, they may differ. Each lobe  212   a - f  may also include a central section  228 , between the first side  224  and the second side  226 , the central section  228  having a third radius of curvature r 3 . In some embodiments, the third radius r 3 , is larger than the first radius of curvature r 1  and larger than the second radius of curvature r 2 , and in other embodiments, the third radius r 3  is smaller than the first radius of curvature r 1  and smaller than the second radius of curvature r 2 . Each channel  222   a - f  may have a fourth radius of curvature r 4 . By heat setting the braided wall  220  into several smaller radii of curvature, for example, radii of curvature r 1 , r 2 , and r 4 , an expanded state of the permeable shell  202  may be produced that resists compression over time, for example, radial compression by repetitive blood pressure cycling when the device for treatment of a vascular defect  200  resides within a vascular defect  160  after implantation. The adjacent and opposing radii of curvature in the braided wall  220 , for example, r 1  and r 4 , create a bolstered structure that causes the lobe  212   b  (in this particular example) of the permeable shell  202  in its expanded state to resist compressive forces that would otherwise tend to crush, collapse or compress a single, larger-radiused portion of a purely circular braided wall, such as in a permeable shell having a circular cross-section of diameter D. The heat set smaller radii may increase the bending stiffness of the braided wall  220  in comparison to a purely circular cross-section braided wall having a diameter D. The permeable shell  202 , in contrast, has a major diameter D and a minor diameter d. In some embodiments, a ratio (D/d) between the major diameter D and the minor diameter d is between about 1.05 and about 1.35, or between about 1.15 and about 1.25, or about 1.20. The generally wavy outer perimeter of the radial cross-section of the braided wall  220  shown in  FIG. 7  may in some cases have larger dimension than a purely circular cross-section braided wall having a diameter D, for example, 0.5% to 10% larger. 
     In some embodiments, the major diameter D is between about two millimeters and about fourteen millimeters, or between about three millimeters and about twelve millimeters, or between about four millimeters and about eleven millimeters. In some embodiments, the length of the permeable shell  202  (e.g., measured along the longitudinal axis  210  between the first end  206  and second end  208 ) is between about two millimeters and about ten millimeters, or between about four millimeters and about eight millimeters. 
     In some embodiments, the third radius of curvature r 3  is about equal to one-half the major diameter D of the permeable shell  202 , thus the central sections  228  of the lobes  212   a - f  would each more or less follow the contours of a circle having a diameter D. 
     Returning to  FIG. 6 , a tether  272  is connected to the device for treatment of a vascular defect  200  at a first tether end  274 . A second tether end  276  is configured to couple to a delivery or “pusher” device. In  FIG. 8 , the tether  272  has been cut, melted or otherwise severed during a detachment procedure, with only a small remnant  278  remaining. Also in  FIG. 8 , the second end  208  of the permeable shell  202  includes a closed end portion  209 . Embodiments for devices and methods for producing devices for the treatment of vascular defects having closed end portions are described in U.S. Patent Application Publication No. 2016/02409934. The filaments  204  of the permeable shell  202  each have first ends  218   a  and second ends  218   b  which are secured at the first end  206  of the permeable shell  202 . The filaments  204  also each have a central section  211  between the first end  218   a  and second end  218   b  which passes through or is incorporated into the closed end portion  209  of the second end  208  of the permeable shell  202 . 
     In the longitudinal cross-section of the device for treatment of a vascular defect  200  in its expanded state in  FIG. 8 , other heat formed radii of curvature in the braided wall  220  serve to resist axial/longitudinal compression from factors such as repetitive blood pressure cycling. A fifth radius of curvature r 5  is adjacent a generally opposed sixth radius of curvature r 6 . In some embodiments, the fifth radius of curvature r 5  is larger than the sixth radius of curvature r 6 . 
     Representative ranges for the various radii of curvature, though non-limiting, are as follows. Radius of curvature r 1  may range from about 0.29 millimeters to about 2.10 millimeters, or about 0.36 millimeters to about 1.10 millimeters. Radius of curvature r 2  may range from about 0.29 millimeters to about 2.10 millimeters, or about 0.36 millimeters to about 1.10 millimeters. Radius of curvature r 3  may range from about 0.29 millimeters to about 7.28 millimeters, or about 0.89 millimeters to about 2.69 millimeters. Radius of curvature r 4  may range from about 0.16 millimeters to about 1.21 millimeters, or about 0.20 millimeters to about 0.63 millimeters. Radius of curvature r 5  may range from about 0.28 millimeters to about 2.06 millimeters, or about 0.36 millimeters to about 1.09 millimeters. Radius of curvature r 6  may range from about 0.16 millimeters to about 1.27 millimeters, or about 0.21 millimeters to about 0.65 millimeters. 
     Representative ranges for the ratios between different radii of curvature, though non-limiting, are as follows. The ratio r 1 /r 3  may range from about 0.04 to about 2.49, or about 0.16 to about 0.48, or about 0.28 to about 0.36. The ratio r 3 /r 4  may range from about 0.68 to about 44.18, or about 1.71 to about 6.42, or about 2.14 to about 6.31. The ratio r 1 /r 4  may range from about 0.87 to about 12.39, or about 1.50 to about 2.61, or about 1.71 to about 1.77. The ratio r 6 /r 5  may range from about 0.08 to about 4.08, or about 0.58 to about 0.90, or about 0.29 to about 0.63. The range of the ratio r 2 /r 3  is expected to be similar to the range of the ratio r 1 /r 3 . The range of the ratio r 2 /r 4  is expected to be similar to the range of the ratio r 1 /r 4 . 
     Though the device for treatment of a vascular defect  200  is depicted having six lobes  212   a - f , other embodiments are possible which have a different number of lobes, for example, between two lobes and sixteen lobes, or even as many as thirty-two lobes or more. 
       FIG. 9  illustrates a device for treatment of a vascular defect  300  comprising a permeable shell  302  which is woven or braided from a plurality of resilient elongate filaments  304 . The permeable shell  302  has a first end  306 , a second end  308 , and a longitudinal axis  310 . Any of the materials and construction techniques described in relation to the device for treatment of a vascular defect  200  of  FIG. 6 , may also be used in constructing the device for treatment of a vascular defect  300 . The permeable shell  302  is heat set into a secondary shape  314  that comprises four lobes  312   a - d  (or ribs, ears, projections, protuberances) that are circumferentially arrayed with respect to the longitudinal axis  310  of the permeable shell  302 . Between each of the lobes  312   a - d  is a longitudinally-extending channel  322   a - d . Also in  FIG. 9 , the first end  306  of the permeable shell  302  includes a closed end portion  309 , which may be formed in the same manner as the closed end portion  209  of the device for treatment of a vascular defect  200  of  FIG. 8 . 
       FIG. 10  illustrates a device for treatment of a vascular defect  400  comprising a permeable shell  402  which is woven or braided from a plurality of resilient elongate filaments  404 . The permeable shell  402  has a first end  406 , a second end  408 , and a longitudinal axis  410 . Any of the materials and construction techniques described in relation to the device for treatment of a vascular defect  200  of  FIG. 6  or the device for treatment of a vascular defect  300  of  FIG. 9  may also be used in constructing the device for treatment of a vascular defect  400 . The permeable shell  402  is heat set into a secondary shape  414  that comprises eight lobes  412   a - h  (or ribs, ears, projections, protuberances) that are circumferentially arrayed with respect to the longitudinal axis  410  of the permeable shell  402 . Between each of the lobes  412   a - h  is a longitudinally-extending channel  422   a - h . Each of the lobes  412   a - h  extends longitudinally with a generally semi-cylindrical shape arrayed around the outer periphery of the permeable shell  402 . In this particular embodiment, each of the lobes  412   a - h  has an outer radius which is less than the one-half of the major diameter of the permeable shell  402 . 
     It should be noted that the lobes  412   a - h  of the permeable shell  402  of  FIG. 10 , when cross-sectioned in a plane parallel to the longitudinal axis  410  in a midpoint along the longitudinal axis  410 , do not have the multiple radii of curvature (e.g., where r 1  is not equal to r 3 ) that are displayed in the cross-section of the permeable shell  202  of  FIG. 7 . Instead a single radius of curvature (such that curvature r 1 , r 2 , and r 3  are all equal to each other) exists between each adjacent and generally opposite radius of curvature r 4 . Thus, the eight lobes  412   a - h  each have a generally cylindrical outer contour at their outer extents. 
       FIG. 11  illustrates a device for treatment of a vascular defect  500  comprising a permeable shell  502  which is woven or braided from a plurality of resilient elongate filaments  504 . The permeable shell  502  has a first end  506 , a second end  508 , and a longitudinal axis  510 . Any of the materials and construction techniques described in relation to the device for treatment of a vascular defect  200  of  FIG. 6 , the device for treatment of a vascular defect  300  of  FIG. 9 , or the device for treatment of a vascular defect  400  of  FIG. 10  may also be used in constructing the device for treatment of a vascular defect  500 . The permeable shell  502  is heat set into a secondary shape  514  that comprises eight lobes  512   a - h  (or ribs, ears, projections, protuberances). Lobes  512   a - d  are circumferentially arrayed with respect to the longitudinal axis  510  of the permeable shell  502 . Lobes  512   e - h  are also circumferentially arrayed with respect to the longitudinal axis  510  of the permeable shell  502 . Between lobes  512   a - d  and lobes  512   e - h  is a circumferentially-extending channel  516  (groove, indentation, recess). The lobes  512   a - h  are also separated by longitudinally-extending channels  522   a - h . The circumferentially-extending channel  516  may be heat formed in the braided wall  520  and has a cross-section having a semicircular shape with a radius of curvature rc. The radius of curvature rc serves to resist axial and even radial compression from factors such as repetitive blood pressure cycling, as described herein. In other embodiments, the cross-section of the circumferentially-extending channel  516  may have a substantially triangular shape. In other embodiments, the cross-section of the circumferentially-extending channel  516  may comprise two or more channels, each at a different longitudinal location along the longitudinal axis  510 . For example, a first channel may be located closer to the first end  506  and a second channel may be located closer to the second end  508 . Though the channel  516  is shown in  FIG. 11  extending 360° around the longitudinal axis  510 , in other embodiments, the channel may extend only partially around the longitudinal axis  510 . In some embodiments, there may be two or more channels, each at about the same longitudinal location along the longitudinal axis  510 , but each extending less than about 180° around the longitudinal axis. In one example, four different circumferentially-extending channels, each having comprising arc of about 80° are separated from each other by about 10°. 
       FIG. 12  illustrates a device for treatment of a vascular defect  600  comprising a permeable shell  602  which is woven or braided from a plurality of resilient elongate filaments  604 . The permeable shell  602  has a first end  606 , a second end  608 , and a longitudinal axis  610 . Any of the materials and construction techniques described in relation to the device for treatment of a vascular defect  200  of  FIG. 6 , the device for treatment of a vascular defect  300  of  FIG. 9 , the device for treatment of a vascular defect  400  of  FIG. 10 , or the device for treatment of a vascular defect  500  of  FIG. 11  may also be used in constructing the device for treatment of a vascular defect  600 . The permeable shell  602  is heat set into a secondary shape  614  that comprises two lobes  612   a - b . Between lobes  612   a  and  612   b  is a circumferentially-extending channel  616  (groove, indentation, recess). The circumferentially-extending channel  616  may be heat formed in the braided wall  620  and has a cross-section having a substantially triangular shape. The channel  616  serves to resist axial and even radial compression from factors such as repetitive blood pressure cycling, as described herein. In other embodiments, the cross-section of the circumferentially-extending channel  616  may have a semi-circular shape. In other embodiments, the cross-section of the circumferentially-extending channel  616  may comprise two or more channels. 
     In any of the embodiments described herein, the filaments  204 ,  304 ,  404  may include filaments of different transverse dimensions. For example, one sub-group of filaments may have an outer diameter of about 0.00075 inches and another sub-group of filaments may have an outer diameter of about 0.001 inches. There may even be three or more different sub-groups of filaments, each group having a particular transverse dimension and/or material composition. In some embodiments, one or more of the filaments may contain a radiopaque material such as platinum, platinum iridium, gold, or other materials, in order to increase the radiopacity of the permeable shell  202 ,  302 ,  402 . In order to provide both superelastic and/or shape memory characteristics and radiopacity within each filament, a composite filament, such as a filament comprising a drawn filled tube (DFT) may be used. Some embodiments for composite and/or DFT filaments are described in U.S. Pat. No. 9,078,658. 
     Embodiments are contemplated which utilize filaments having transverse dimensions of between about 0.0005 inches and about 0.002 inches, or between about 0.00075 inches and about 0.00125 inches. 
     It can be appreciated that the multi-lobe geometry of the permeable shell  202 ,  302 ,  402  with a heat-formed secondary shape  214 ,  314 ,  414  having multiple radii or curvature resists in vivo compression of the permeable shell  202 ,  302 ,  402 , both radial and axial/longitudinal compression, when the permeable shell  202 ,  302 ,  402  is in its expanded state or condition. However, some elongation of the permeable shell  202 ,  302 ,  402  occurs when the permeable shell  202 ,  302 ,  402  is being compressed into is compressed, radially constrained state or condition, and is aided by some sliding which is able to occur between the filaments  204 ,  304 ,  404 . This makes the desired forced collapse on the permeable shell  202 ,  302 ,  402  for delivery through a catheter lumen simple and efficient, even though the device is able to resist compression while implanted in its expanded state over a significant length of time in a vascular defect. 
     While embodiments have been shown and described, various modifications may be made without departing from the scope of the inventive concepts disclosed herein. In additional to cerebral aneurysms, other types of aneurysms may be treated with devices described herein, including, but not limited to aortic aneurysms. Other vascular defects which may be treated with devices described herein include structural heart deformities, including, but not limited to left atrial appendages.