Patent Publication Number: US-2023140095-A1

Title: Detachment mechanism with a tab for delivering intravascular implants

Description:
BACKGROUND 
     A number of vascular disorders are treated by an intravascular delivery of an implant that is either positioned or deployed within a vessel of a body of an individual. For example, an intravascular stent used for treating peripheral artery disease may be deployed in a stenotic region of a blood vessel in order to improve blood flow past the stenosis in the vessel. For further example, an embolic coil may be placed or deployed within an intracerebral aneurysm in order to occlude the aneurysm thus preventing blood flow into the aneurysm and thus preventing a rupture of the aneurysm. 
     SUMMARY 
     Described herein are systems and methods for delivering an intravascular implant. The systems and methods described herein use an intravascular approach for delivering an implant into the intravascular system of a patient. In some embodiments of the systems and methods described herein, the systems and methods comprise a mechanical detachment system that is configured to deploy an intravascular implant, such as an embolic coil, at a target location within the vascular system of a patient when a user manually deploys the implant. 
     In some embodiments of the systems and methods described herein, the systems and methods are used for the delivery of an embolic coil to an intracranial aneurysm and are configured to provide manually triggered deployment of an embolic coil within the intracranial aneurysm. 
     The systems and methods described herein improve upon traditional implant detachment systems, such as, for example, embolic coil detachment systems, in a number of ways: 
     Prevention of Undesired Thrombotic Events 
     One example of how the systems and methods described herein improve on traditional systems and methods for delivering embolic coils is by preventing undesired thrombotic events. 
     Many traditional systems and methods for delivering embolic coils to cerebral aneurysms employ electrolytic detachment mechanisms, which have been shown to cause generation of gas bubbles at the detachment zone. The formation of gas bubbles intravascularly leads to the formation of blood clots, which may lead to thromboembolic complications. Furthermore, if the clot remains attached to a micro-catheter tip or to the end of an embolic coil, there is a risk that the clot will grow in size and/or embolize during repeated embolic coil detachment procedures. This presents an increased risk of the generation of blood clots that can travel to small vessels and occlude these vessels, leading to anoxic injury. 
     Decrease in Detachment Time 
     Another example of how the systems and methods described herein improve on traditional systems and methods of delivering embolic coils is by decreasing the time to detach the total number of embolic coils. 
     The systems and methods described herein take significantly less time to detach and deploy an embolic coil as compared to traditional electrolytic systems. The systems and methods described herein comprise mechanical components that actuate rapid deployment whereas electrolytic systems require time to heat an embolic coil system in order to detach and deploy a coil. As, in most cases, delivery of multiple embolic coils into one cerebral aneurysm is often necessary, the reduction in procedure time by the systems and methods described herein presents a significant advantage. 
     Prevention of Detachment Failure 
     Yet another example of how the systems and methods described herein improve on traditional systems and methods of delivering embolic coils is by preventing a failed detachment of an embolic coil. 
     Traditional electrolytic detachment systems and methods have been shown to have a significant detachment failure rate. Detachment failure may occur due to electrical equipment failure and/or failure to properly induce a current through the device and the patient. Because the systems and methods described herein employ mechanical components rather than electrical components, the failure rate is significantly lower than that of the traditional electrolytic deployment systems. 
     Described herein is an embolic coil delivery system for delivering and deploying an embolic coil at an aneurysm comprising:
     i. an embolic coil with an anchoring element disposed at a proximal end of the embolic coil;   ii. a conduit having a deployment location from which the embolic coil is deployed, and a first radiopaque marker:   iii. a detachment system configured to fit within the conduit and to be easily advanced and withdrawn within the conduit, the detachment system comprising:
   a. a detachment mechanism comprising: 
   1) a housing that defines a tab with a first end coupled to a proximal end of the housing and a free end that extends toward a distal end of the housing, the tab comprising a shape memory material wherein the tab is configured to move from a first position to a second position, wherein when the tab is in the first position, the fee end of the tab is deflected toward an interior of the housing, wherein the tab comprises a passthrough clearance aperture; and   2) a primary member configured and positioned to engage with the tab (extends through the passthrough clearance aperture) so that the tab is in the first position when engaged with the primary member and is moved to the second position by the memory material when the primary member is no longer engaged with the tab,   3) wherein the anchoring element of the embolic coil is configured and positioned to engage with the tab (and extends through the passthrough clearance aperture of the tab) in the first position so that the embolic coil is coupled to the detachment system when the tab is in the first position, and wherein the anchoring mechanism is configured and positioned to not engage with the tab in the second position so that the embolic coil is deployed when the tab is in the second position;   4) a radiopaque marker coupler; and   
   b. a second radiopaque marker that is mechanically coupled with the radiopaque marker coupler and is positioned to align with the first radiopaque marker when the detachment mechanism is positioned at the deployment location.   
   

     In some embodiments of the delivery system, the detachment system comprises a flexible tube that surrounds the detachment system and fixedly couples the radiopaque marker coupler and the radiopaque marker. In some embodiments of the delivery system, the first radiopaque marker partially surrounds the conduit so that when the detachment mechanism is advanced within the conduit and the first radiopaque marker aligns with the second radiopaque marker, the second radiopaque marker is radiographically visible under fluoroscopy. In some embodiments of the delivery system, the tab comprises a shape memory metal material. In some embodiments of the delivery system, the detachment mechanism further comprises a primary member that detachably couples with the tab so that when the primary member and the tab are coupled, the tab is in the first position and when the primary member and the tab are decoupled, the tab moves to the second position. In some embodiments of the delivery system, the tab moves to the second position when the primary member is drawn away from the tab. In some embodiments of the delivery system, the detachment system includes a segment that is configured to manually detach from the detachment system, and wherein the primary member is coupled to the segment so that when the segment is manually detached and withdrawn away from the detachment system, the primary member is drawn away from the tab so that the tab moves to the second position and deploys the coil. In some embodiments of the delivery system, the segment comprises oblong cuts around its outer diameter that are configured to fracture the segment when a bending force is applied to the segment. 
     Also described herein is a method for deploying an embolic coil in an intracranial aneurysm comprising: directing a conduit through one or more blood vessels of the patient to the aneurysm, the conduit comprising a first radiopaque marker and a deployment location; advancing a detachment system through the conduit while the conduit is within the blood vessel, the detachment system comprising a radiopaque marker coupler, a second radiopaque marker, and a detachment mechanism comprising a tab having a first position and a second position; deploying the embolic coil within the aneurysm using the detachment system; wherein the radiopaque marker coupler and the second radiopaque marker couple mechanically; wherein when the detachment mechanism is positioned at the deployment location, the first radiopaque marker and the second radiopaque marker align; wherein the embolic coil is coupled to an anchoring element; wherein when the tab is in the first position, the anchoring element engages the tab thus coupling the embolic coil to the detachment system; and wherein the anchoring element does not engage the tab in the second position thus decoupling the embolic coil from the detachment system and thus deploying the embolic coil in the intracranial aneurysm. In some embodiments of the method, the detachment system comprises a flexible tube that surrounds the detachment system and fixedly couples the radiopaque marker coupler and the radiopaque marker. In some embodiments of the method, the first radiopaque marker partially surrounds the conduit so that when the detachment system is advanced within the conduit and the first radiopaque marker aligns with the second radiopaque marker, the second radiopaque marker is radiographically visible. In some embodiments of the method, the tab comprises a memory metal material. In some embodiments of the method, the detachment mechanism further comprises a primary member that detachably couples with the tab so that when the primary member and the tab are coupled, the tab is in the first position, and when the primary member and the tab are decoupled, the tab moves to the second position. In some embodiments of the method, the step of deploying comprises decoupling the primary member from the tab by drawing the primary member away from the tab. In some embodiments of the method, the conduit includes a segment that is configured to manually detach from the conduit, and wherein the primary member is coupled to the segment so that when the segment is manually detached and withdrawn away from the conduit, the primary member is drawn away from the tab so that the tab moves to the second position and deploys the embolic coil. In some embodiments of the method, the segment comprises oblong cuts around its outer diameter that are configured to fracture the segment when a bending force is applied to the segment. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The novel features of the subject matter disclosed herein are set forth with particularity in the appended claims. A better understanding of the features and advantages of the subj ect matter disclosed herein will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the subject matter disclosed herein are utilized, and the accompanying drawings of which: 
         FIG.  1    shows an illustration of the anatomical path of travel for a delivery system according to one embodiment of the present disclosure. 
         FIG.  2    shows an illustration of an exemplary embodiment of a delivery system for delivering and deploying an intravascular implant such as an embolic coil. 
         FIG.  3    shows an illustration of an exemplary embodiment of a detachment system that comprises an embolic coil that is detachably coupled to the detachment system of  FIG.  2   . 
         FIG.  4    shows a perspective view of the detachment system of  FIG.  3    in a locked configuration. 
         FIG.  5    shows a perspective view of an embodiment of a distal end of the detachment system of  FIG.  3    in an unlocked configuration as the embolic coil is deployed from the detachment system. 
         FIG.  6    shows an illustration of an exemplary embodiment of a detachment system with a cover covering the detachment system. 
         FIG.  7    shows an exemplary illustration of an embodiment of an expansion tube of a delivery system. 
     
    
    
     DETAILED DESCRIPTION 
     Described herein are systems and methods for delivering and deploying an intravascular implant to an intravascular target such as, for example, delivering one or more embolic coils to an intracranial aneurysm and deploying the one or more embolic coils within the aneurysm. 
     A delivery system as described herein comprises a conduit such as a traditional catheter or micro-catheter and a detachment system that is configured to be slideably advanced within the catheter. The catheter of the delivery system described herein is configured to be advanced through a blood vessel of a patient to a target location. For example,  FIG.  1    shows an illustration of the anatomical path of travel of a catheter  1014 . The catheter  1014  may be inserted into a femoral artery of a patient (using, for example, Seldinger technique) and advanced up through the aorta  1050  of the patient. From there, the catheter  1014  may be advanced up through a carotid artery  1060  to an intracranial target location such as an intracranial aneurysm where an intravascular implant may be deployed in order to, for example, occlude the aneurysm thus preventing aneurysm rupture. The conduit of the delivery system is thus configured to deliver the detachment system described herein to a target location. In some embodiments, the delivery system as described herein does not include a conduit, but rather the detachment system is delivered directly to a target location. 
     Delivery System 
       FIG.  2    shows an illustration of an exemplary embodiment of a delivery system  2000  for delivering and deploying an intravascular implant (not shown) such as an embolic coil. Other non-limiting examples of implants suitable for use with the systems, devices, and methods described herein include, for example, occluding coils and intravascular stents. 
     The delivery system  2000  comprises a conduit such as a standard catheter  2014  or micro-catheter (or other conduit) and a detachment system  2004 . The detachment system  2004  comprises an elongate body that is configured to be slideably positioned (i.e., advanced and withdrawn) within the catheter  2014  and, in some embodiments, the detachment system  2004  is delivered via the catheter  2014  to a target location such as, for example, an intracranial aneurysm. That is, in embodiments of the delivery system  2000  that include the catheter  2014 , the catheter  2014  with the detachment system  2004  within the catheter  2014  is typically delivered to a target location by a user, wherein a target location may comprise, for example, an intracranial aneurysm or, for example, an atherosclerotic lesion. In some embodiments, the detachment system  2004  may be delivered directly to a target location without the catheter  2014 . 
     Detachment System 
     The detachment system  2004  comprises a proximal end  2017  and a distal end  2016 , which are each configured to include different functional elements of the detachment system  2004 . In general, the proximal end  2017  of the detachment system  2004  remains outside of the patient during the use of the delivery system  2000 , and the proximal end  2017  of the detachment system  2004  generally includes features that allow a user to manually direct the detachment system  2004  and control the deployment of an implant, such as an embolic coil. The proximal end  2017  of the detachment system  2004  is configured to provide a mechanism for manually deploying an implant at a target location by the user of the delivery system  2000 . In general, the distal end  2016  includes a detachment mechanism  2005  that is configured to release or deploy an intravascular implant at a target location and a radiopaque marker  2006  that is positioned to align with a radiopaque marker on the distal end of the catheter  2014  when the detachment system  2004  is within a proper position relative to the catheter  2014  for implant deployment. 
     The detachment mechanism  2005  is disposed at a distal end  2016  of the detachment system  2004 . In some embodiments of the delivery system  2000 , the detachment system  2004  comprises an elongate body including a series of respectively optional interconnected tubes comprising an optional shrink tube  2002 , an optional connecting tube  2010 , an optional expansion tube  2026 , and an optional grip tube  2012 . The optional interconnected tubes  2002 ,  2010 ,  2026 , and  2012  are each respectively configured to provide different qualities or features to the detachment system  2004 . 
     The shrink tube  2002  comprises a flexible material such as a polymer, and is configured to cover and/or surround at least a portion of the distal end  2016  of the delivery system  2000  while providing flexibility to maneuver through bends in the vasculature system. The shrink tube  2002  also maintains a protective covering over the detachment mechanism  2005  to encapsulate a primary member  2018 , discussed in more detail below. The shrink tube  2002  also maintains a tight coupling between the radiopaque marker  2006  and the detachment mechanism  2005  via mechanical coupling between the radiopaque marker  2006  and a radiopaque marker coupler  2008 . 
     The connecting tube  2010  may optionally be connected to the shrink tube  2002  and comprises a relatively rigid material (as compared to the shrink tube  2002 ) that provides rigidity to portions of the distal end  2016  and/or proximal end  2017  so that the detachment system  2004  is more easily advanced and withdrawn within the catheter  2014 . 
     The expansion tube  2026  is optionally connected to the connecting tube  2010  and provides a segment with an expanded diameter (as compared to the optional shrink tube  2002  and connecting tube  2010 ), providing ease of handling relative to the relatively small diameter optional shrink tube  2002  and connecting tube  2010 . In some embodiments of the detachment system  2004 , the expansion tube  2026  facilitates deployment of an implant from the detachment mechanism  2005  by facilitating manual withdrawal of the primary member  2018 . A connecting wire  2011  connects the distal portion of the detachment system  2004 . 
     In some embodiments of the delivery system  2000 , the detachment mechanism  2005  is formed entirely from a memory metal material. In some embodiments, the memory metal material of the detachment mechanism  2005  is nitinol. In some embodiments of the detachment mechanism  2005 , the detachment mechanism  2005 , not including the primary member  2018  (which comprises a different material), comprises a memory material such as nitinol. In some embodiments of the detachment mechanism  2005 , the detachment mechanism  2005 , not including the radiopaque marker  2006  (which comprises a different material), comprises a memory material such as nitinol. In some embodiments of the detachment mechanism  2005 , the detachment mechanism  2005 , not including the primary member  2018  and the radiopaque marker  2006  (which comprise a different material), comprises a memory material such as nitinol. 
     The distal end  2016  of the detachment system  2004  includes the radiopaque marker  2006 , and the distal end of the catheter  2014  includes a radiopaque marker (not shown). Non-limiting examples of metals suitable for use as either the radiopaque marker  2006  of the detachment system  2004  or the radiopaque marker on the catheter  2014  include noble metals or alloys such as platinum, platinum-tungsten, platinum iridium, silver, or gold. In some embodiments of the delivery system  2000 , the radiopaque marker  2006  of the detachment system  2004  and the radiopaque marker on the catheter  2014  are positioned so that they align with one another when the detachment mechanism  2005  is positioned at a deployment location  2013 . In some embodiments of the delivery system  2000 , the radiopaque marker  2006  of the detachment system  2004  and the radiopaque marker of the catheter  2014  are positioned so that they align at a location about 30 mm proximal to the deployment location  2013 . 
     In some embodiments of the delivery system  2000 , the detachment system  2004  includes the radiopaque marker coupler  2008  at a radiopaque marker location. The radiopaque marker coupler  2008  is a portion of the detachment system  2004  that is configured to couple with the radiopaque marker  2006 . That is, the radiopaque marker coupler  2008  of the detachment system  2004  typically comprises a metal such as, for example, platinum, platinum-tungsten, platinum iridium, silver, or gold. Because the remaining portions of the detachment mechanism  2005  (except in some embodiments the primary member  2018  is not present) comprise a memory material such as nitinol, coupling the radiopaque marker coupler  2008  to the detachment mechanism  2005  is not easily achievable with typical methods such as welding due to differences between the materials (i.e., between the radiopaque marker coupler  2008  and the memory material of the detachment mechanism  2005 ). As such, the radiopaque marker coupler  2008  is configured to couple with the radiopaque marker  2006  mechanically without the need for the two elements to be welded or similarly fused. In some embodiments of the detachment system  2004 , the radiopaque marker coupler  2008  and the radiopaque marker  2006  have complimentary shapes that are configured so that the two components couple together by fitting together as shown in  FIG.  2   . That is, in some embodiments of the detachment system  2004 , the radiopaque marker coupler  2008  is a component of the detachment mechanism  2005  that has an alternating tooth pattern (as shown) with elevations and indentations or, alternatively, for example, a sawtooth pattern, and likewise the radiopaque marker  2006  has a complimentary alternating tooth pattern (as shown) with elevations and indentations or, alternatively, for example, a sawtooth pattern so that the two components—the radiopaque marker coupler  2008  and the radiopaque marker  2006 —fit together wherein an elevation of one component fits an indentation of the complementary component. In some embodiments of the detachment system  2004 , the flexible shrink tube  2002  tightly surrounds these two coupled components—the radiopaque marker coupler  2008  and the radiopaque marker  2006 —so that they are fixedly coupled together. 
     In order for the detachment system  2004  to properly deploy an implant such as an embolic coil within an aneurysm (i.e., the target), the detachment mechanism  2005  must be advanced to the deployment location  2013  along the catheter  2014 . The deployment location  2013  may be a different location along the catheter  2014  depending on the type of implant deployed. For example, in some embodiments of the delivery system  2000 , for proper deployment of an embolic coil or other implant within an aneurysm or other target location, the embolic coil or other implant is advanced entirely out of an aperture  2009  of the catheter  2014 . For example, in some embodiments of the delivery system  2000 , for proper deployment of an embolic coil or other implant within an aneurysm or other target location, the embolic coil is advanced partially out of the aperture  2009  of the catheter  2014 . For example, in some embodiments of the delivery system  2000 , for proper deployment of an embolic coil or other implant within an aneurysm or other target location, the detachment mechanism  2005  is advanced entirely out of the aperture  2009  of the catheter  2014 . In some embodiments of the delivery system  2000 , for proper deployment of an embolic coil or other implant within an aneurysm or other target location, the detachment mechanism  2005  is advanced partially out of the aperture  2009  of the catheter  2014 . As shown in the exemplary embodiment shown in  FIG.  2   , a detachment mechanism  2005  in the illustrated embodiment is positioned within the distal portion of the catheter  2014  for proper deployment of an implant and as such the deployment location  2013  in the embodiment shown in  FIG.  2    is located at the distal end of the catheter  2014 . 
     That is, as shown in  FIG.  2   , the distal end  2016  of the catheter  2014  defines the deployment location  2013 , which is a position or zone to where the detachment system  2004  (and thus the detachment mechanism  2005  at the distal end  2016  of the detachment system  2004 ) must be advanced in order to achieve successful deployment of an implant. For example, in embodiments of the delivery system  2000  wherein the detachment system  2004  remains entirely within the distal end of the catheter  2014  in order to achieve proper deployment of an implant, the deployment location  2013  is located where the detachment system  2004  is positioned within the distal end  2016  of the catheter  2014 . For example, in embodiments of the delivery system  2000  wherein the detachment system  2004  is partially out of the aperture  2009  at the distal end  2016  of the catheter  2014  and partially within the distal end  2016  of the catheter  2014  in order to achieve proper deployment of an implant, the deployment location  2013  is located partially outside of the aperture  2009  and partially within the catheter  2014  where the detachment system  2004  is positioned. For example, in embodiments of the delivery system  2000  wherein the detachment system  2004  is completely out of the aperture  2009  in order to achieve proper deployment of an implant, the deployment location  2013  is located where the detachment system  2004  is positioned outside of the catheter  2014 . 
     In general, the proximal end  2017  of the catheter  2014  is coupled to one or more features that provide a user with manual control over the advance of the implant to the target and deployment of the implant at or in the target. In some embodiments of the delivery system  2000 , the proximal end  2017  of the catheter  2014  is coupled with the expansion tube  2026 . The expansion tube  2026  is configured to have a larger diameter than the relatively small diameter of the shrink tube  2002 . The expansion tube  2026  is generally configured so that it may couple the delivery system  2000  to other elements. For example, in some embodiments of the delivery system  2000 , the expansion tube  2026  couples to the grip tube  2012  at the most proximal end  2017  of the delivery system  2000 . The grip tube  2012  provides a user with a manual grip to advance and/or withdraw the detachment system  2004  in order to guide the detachment system through the vasculature of a patient. In some embodiments of the delivery system  2000 , the expansion tube  2026  includes one or more oblong cuts or breaks within its material in order to facilitate a manual fracturing of the expansion tube  2026  so that the expansion tube  2026  is divided. Manually dividing the expansion tube  2026  provides a mechanism for withdrawing the fractured portion of the expansion tube  2026  away from the detachment system in a proximal direction, which is used in some embodiments of the delivery system  2000  to manually trigger deployment of an implant. In some embodiments of the delivery system  2000 , the expansion tube  2026  couples with an external detachment device that is configured to manually trigger deployment of an implant using the detachment system  2004   
     Detachment Mechanism 
     In some embodiments of the systems, devices, and methods described herein, the detachment mechanism  2005  is positioned at the distal end  2016  of the detachment system  2004 , and the detachment system  2004  along with the catheter  2014  form the delivery system  2000 . 
     In some embodiments, the detachment mechanism  2005  comprises a housing with a tab and a primary member  2018  that are configured to engage with an anchoring member of the intravascular implant. The user may position to actuate the detachment mechanism  2005 , causing the detachment mechanism  2005  to release the anchoring member and deploy the intravascular implant. 
     The primary member  2018  as shown in  FIG.  2    is sized to be long enough to extend the length of the delivery system  2000  when the detachment mechanism  2005  is at the deployment location  2013 . 
     A number of additional features of embodiments of the detachment mechanism  2005  are now described with additional reference to  FIG.  3    as well as further reference to  FIG.  2   . 
       FIGS.  3 - 5    show an illustration of an exemplary embodiment of a detachment mechanism  3005  that is detachably coupled to an embolic coil  3022  (or another implant). The embolic coil  3022  is coupled to the detachment mechanism  3005  and is disposed distal to the detachment mechanism  3005  in the catheter  3014 . When the embolic coil  3022  is disposed within the catheter  3014 , the embolic coil  3022  is in a linear configuration and the configuration of the coil  3022  may change when the coil  3022  is placed in the desired location. The embolic coil is configured to be slideably positioned (i.e., advanced and withdrawn) within the catheter  3014  along with the elongate body of detachment system  2004 . The embolic coil  3022  may include an anchoring element  3020  that is detachably coupled to the detachment mechanism  3005 . The anchoring element  3020  may be integral with the embolic coil  3022  or be coupled to the embolic coil  3022  at a proximal end of the embolic coil  3022 . 
     The detachment mechanism  3005  comprises elements that are configured to cause the deployment of the embolic coil  3022 . In some embodiments, the detachment mechanism  3005  includes a housing  3010  with a tab  3016  and a primary member  3018  that are engageable with the anchoring element  3020  of the embolic coil  3022 . 
     In some embodiments, the housing  3010  with a distal end  3011  and a proximal end  3012 . The housing  3010  defines the tab  3016  in a body of the housing  3010 . The tab  3016  may have a proximal end  3017  that is coupled to or integral with a proximal end  3012  of the housing  3010  and a free end  3015 . The free end  3015  of the tab  3016  is not coupled to the housing  3010  and extends toward the distal end  3011  of the housing  3010 . The connection between the proximal end  3017  of the tab  3016  and the housing  3010  may form a hinge  3019  that the tab  3016  may rotate about. In other words, the hinge  3019  acts as an axis of rotation to enable the tab  3016  to rotate. 
     In some embodiments, the tab  3016  defines a substantially rectangular shape in which three edges of the tab  3016  are separated from the housing  3010  and the proximal end  3017  couples to the housing  3010 . In other words, there is a gap between the tab  3016  and the housing  3010  on all three edges of the tab  3016  except the proximal end  3017  of the tab  3016 . In some embodiments, the tab  3016  further includes an aperture  3013  as seen in  FIG.  4   . The aperture  3013  may comprise a substantially rectangular shape and have a width that is slightly greater than a width of the primary member  3018 . The aperture  3013  is configured to receive the primary member  3018  so that the primary member  3018  may extend through the aperture  3013 . In the illustrated embodiment, a distal end of the primary member  3018  may extend beyond the distal end  3011  housing  3010  of the detachment mechanism  3005  such that the distal end of the primary member is disposed outside the housing  3010 . 
     In some embodiments, the tab  3016  is configured to have at least two configurations or positions: a first configuration or position and a second configuration or position.  FIGS.  3  and  4    illustrate the tab  3016  in the first configuration or position. In the first configuration, the free end  3015  of the tab  3016  is deflected towards an interior of the housing  3010 . The first configuration may be achieved when the primary member  3018  extends through the aperture  3013  to deflect the free end  3015  towards an interior of the housing  3010 . When the tab  3016  is deflected towards the interior of the housing  3010  in its first position, it is positioned to couple directly with either the embolic coil  3022  that is at least partially within the housing  3010  or, in some embodiments, couple indirectly with the embolic coil  3022  by coupling with an anchoring element  3020  of the embolic coil  3022  that in some embodiments is coupled with the embolic coil  3022 . When the primary member  3018  is engaged with the tab  3016 , the tab  3016  may be deflected along the hinge  3019  and extend into the interior of the housing  3010 . The hinge  3019  is perpendicular with an axis of the housing  3010  and the catheter  3014 . By virtue of coupling to the tab  3016  in its first position, the embolic coil  3022  is held within the housing  3010  of the detachment mechanism  3005 . 
     In some embodiments of the detachment mechanism  3005 , the embolic coil  3022  (or other intravascular implant) is coupled with the anchoring element  3020  that is configured to couple with the tab  3016 . In these embodiments, the anchoring element  3020  is configured to releasably couple with the tab  3016  when the tab  3016  is in the first position and deflected towards the interior of the housing  3010 . For example, in some embodiments of the delivery system  3000 , as shown in  FIG.  3   , the anchoring element  3020  comprises a sphere or ball and when the tab  3016  is in its first position, it hooks or latches the ball so that the ball is held within the housing  3010  and thus the embolic coil  3022  is held by the detachment mechanism  3005 . In some embodiments, the ball is spherical and solid. As discussed above, in the first configuration, the primary member  3018  may extend through the aperture  3013  of the tab  3016  to deflect the tab  3016  toward the interior of the housing  3010 . The primary member  3018  may further extend beyond the distal end  3011  of the housing  3010 . 
     In embodiments of the detachment mechanism  3005  that include the primary member  3018 , when the primary member  3018  is coupled with the tab  3016  it holds the tab  3016  in the first position of the tab  3016  so that the tab  3016  is deflected towards the interior of the housing  3010 . When the primary member  3018 , in these embodiments, is decoupled from the tab  3016  by being, for example, withdrawn in a proximal direction, the tab  3016  moves away from the interior of the housing  3010  to move to a second position as shown in  FIG.  5   . In embodiments where the tab  3016  comprises a memory material, the material of the tab  3016  facilitates its movement away from the interior of the housing  3010  when decoupled from the primary member  3018 . In some embodiments of the delivery system  3000 , the primary member  3018  is withdrawn proximally by a user when the detachment mechanism  3005  is positioned near a target location such as, for example, an intracranial aneurysm. The primary member  3018  may, for example, comprise a wire that extends out of the proximal end  3017  of the catheter  3014  to a location where the wire may be pulled proximally by a user thus decoupling the primary member  3018  and the tab  3016 . The ability of the primary member  3018  to extend beyond the aperture  3013  of the tab  3016  provides some leeway so that slight proximal movement of the primary member  3018  does not dislodge the primary member  3018  from the aperture  3013 . In other words, slight proximal movement of the primary member  3018  does not transition the tab  3016  from the first configuration. Instead, only a deliberate proximal pull on the primary member  3018  would dislodge the primary members from the tab  3016  to transition the tab  3016  from the first configuration to deploy the embolic coil  3022 . 
     In some embodiments of the detachment system  3004 , an expansion tube  3026  (not shown but similar to  2026 ) is configured to fracture so that at least a portion of the expansion tube  3026  may be withdrawn in a proximal direction away from the rest of the detachment system  3004 . In some of these embodiments, the primary member  3018  is coupled with the expansion tube  3026  so that when the expansion tube  3026  is fractured and withdrawn in a proximal direction, the primary member  3018  is decoupled from the tab  3016  so that the tab  3016  moves from the first position to the second position and causes the release of the embolic coil  3022 . In some embodiments of the delivery system  3000 , the primary member  3018  comprises a wire that spans the length of the detachment system  3004  and extends out through the hole of the tab,  3016 . 
       FIG.  5    shows an illustration of an embodiment of a distal end of the detachment mechanism  3005  showing how the anchoring element  3020  of the embolic coil  3022  is deployed from the detachment mechanism  3005 . As described with reference to  FIGS.  3  and  4   , the tab  3016  has at least a first position and a second position. In the second position of the tab  3016 , the tab  3016 , as shown in  FIG.  5   , is positioned so that it is not deflected towards the interior of the housing  3010  but rather is positioned away from the interior of the housing  3010 . The primary member  3018  is shown being withdrawn away from and thus decoupled from the tab  3016 . As such, the anchoring element  3020  is no longer held by the detachment mechanism  3005  and the embolic coil  3022  (not shown in  FIG.  5   ) is released or deployed at a target location. 
       FIG.  6    illustrates another exemplary embodiment of a detachment mechanism  4005  that is detachably coupled to an embolic coil  4022  via an anchoring mechanism  4020 . As discussed above, a tab  4016  in a first configuration secures the anchoring mechanism  4020  to prevent deployment of the embolic coil  4022  until a primary member  4018  is removed from the tab  4016  enabling the tab  4016  to go to a second position to release the embolic coil  4022 . A covering  4002  encompasses a housing  4010  of the detachment mechanism  4005 , a proximal end  4021  of the embolic coil  4022 , and a distal end  4019  of the primary member  4018 . While the covering encompasses the housing  4010  of the detachment mechanism  4005 , a proximal end  4021  of the embolic coil  4022 , and a distal end  4019  of the primary member  4018 , for ease of illustration, the covering  4022  is shown in broken lines so that the underlining components may be seen. The covering  4002  may be a polymer that is heat shrunk to seal the detachment mechanism  4005  from bodily fluid during the implantation process. 
     Expansion Tube 
       FIG.  7    shows an exemplary illustration of an embodiment of an expansion tube  5026 . As described with reference to  FIGS.  1  and  2   , some embodiments of a detachment system  5004  include an expansion tube  5026  at a proximal end  5017  of the detachment system  5004 . In some of these embodiments, the expansion tube  5026  includes one or more cuts  5030  at least partially surrounding the diameter of the expansion tube  5026  so that the cuts  5030  are positioned and/or configured to facilitate a fracture of the expansion tube  5026  when a bend is applied to the expansion tube  5026  by a user. Also shown in  FIG.  5    is a primary member  5018  within the expansion tube  5026 . As described with reference to  FIGS.  1 - 2   , a primary member  5018 , in some embodiments of the detachment system  5004 , is connected to the expansion tube  5026 . When the expansion tube  5026  is fractured, the fractured portion of the expansion tube  5026  is able to be withdrawn away from the catheter in a proximal direction. In some embodiments of the detachment system  5004 , when the expansion tube  5026  is fractured so that detachment system  5004  separates into a distal piece and a proximal piece that are able to be withdrawn from one another, the primary member  5018  is no longer held against the tab , so that the tab moves to a second position (facilitated by the memory material), which exerts a force on the primary member  5018  driving it proximally. 
     Any methods disclosed herein include one or more steps or actions for performing the described method. The method steps and/or actions may be interchanged with one another. In other words, unless a specific order of steps or actions is required for proper operation of the embodiment, the order and/or use of specific steps and/or actions may be modified. Moreover, sub-routines or only a portion of a method described herein may be a separate method within the scope of this disclosure. Stated otherwise, some methods may include only a portion of the steps described in a more detailed method. 
     Reference throughout this specification to “an embodiment” or “the embodiment” means that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment. Thus, the quoted phrases, or variations thereof, as recited throughout this specification are not necessarily all referring to the same embodiment. 
     Similarly, it should be appreciated by one of skill in the art with the benefit of this disclosure that in the above description of embodiments, various features are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure. This method of disclosure, however, is not to be interpreted as reflecting an intention that any claim requires more features than those expressly recited in that claim. Rather, as the following claims reflect, inventive aspects lie in a combination of fewer than all features of any single foregoing disclosed embodiment. Thus, the claims following this Detailed Description are hereby expressly incorporated into this Detailed Description, with each claim standing on its own as a separate embodiment. This disclosure includes all permutations of the independent claims with their dependent claims. 
     Recitation in the claims of the term “first” with respect to a feature or element does not necessarily imply the existence of a second or additional such feature or element. It will be apparent to those having skill in the art that changes may be made to the details of the above-described embodiments without departing from the underlying principles of the present disclosure.