Patent Publication Number: US-2019192275-A1

Title: Radiopaque markers on a medical device

Description:
PRIORITY CLAIM 
     This invention claims the benefit of priority of U.S. Provisional Application Ser. No. 62/609,917, entitled “Radiopaque Markers on a Medical Device,” filed Dec. 22, 2017, the disclosure of which is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     The present disclosure relates generally to medical devices, systems, and methods, and particularly, to systems and techniques for positioning radiopaque markings on medical stent devices. Stent devices may be comprised of a metal or alloy material shaped into a tube form, that are inserted into vessels or passageways for various repair purposes. For example, once inserted into a vessel, the stent device may be used to expand the vessel in an angioplasty procedure to restore increased blood flow through a previously narrowed vessel. Stent devices may also be used to strengthen and stabilize weakened vessel walls to prevent the vessel from rupturing. Stent devices may also be used as part of a procedure to treat aortic dissections, where the stent device is expanded within either a true lumen or a false lumen of the aorta to re-attach an aortic wall dissection. 
     Imaging techniques that utilize the attachment of radiopaque markings on the stent device are used to identify the positioning and location of the stent device as the stent device traverses through a vessel. Understanding the positioning and location of the stent device is helpful to an administrator controlling the insertion of the stent device to guide the stent device to a desired location and in a desired orientation. However, with the existing simple radiopaque marking techniques, there may be a limit to the amount of helpful information the radiopaque markings can convey back to the administrator. 
     The present disclosure looks to address the shortcomings of the existing simple radiopaque marking techniques. 
     SUMMARY 
     Radiopaque marking systems and methods of implementing the different radiopaque marking combinations made available by the radiopaque marking system are disclosed. In one example, a stent device is disclosed comprised of a strut wire, a coil threaded onto the strut wire, and a ring marker threaded onto the strut wire and positioned adjacent to the coil, wherein the coil and the ring marker are positioned on the stent device to represent feedback information related to the stent device. 
     In another example, a method of producing a stent device is disclosed comprising threading a coil around a strut, threading a ring marker around the strut to be adjacent to the coil, attaching a rod strut to the stent device, attaching a ring strut to the stent device, and wherein the coil, the ring marker, the rod strut, and the ring strut are positioned on the stent device to represent feedback information related to the stent device. According to some embodiments, the rod strut and the ring struts are formed to be a single continuous structure, whereas in other embodiments the rod strut and the ring struts are separate and distinct structures. 
     Other systems, methods, features and advantages of the disclosed features will be, or will become, apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be within the scope of this disclosure, and be encompassed by the following claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosed features may be better understood with reference to the following drawings and description. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the disclosed features. Moreover, in the figures, like referenced numerals designate corresponding parts throughout the different views. 
         FIG. 1  shows a side view of an exemplary first embodiment for a radiopaque marking system. 
         FIG. 2  shows a side view of an exemplary second embodiment for the radiopaque marking system. 
         FIG. 3  shows a cross sectional side view and a corresponding front view from a distal end of exemplary radiopaque markers. 
         FIG. 4  shows a top view of exemplary radiopaque marking configurations according to the first embodiment of the radiopaque marking system. 
         FIG. 5  shows a top view of exemplary radiopaque marking configurations according to the first embodiment of the radiopaque marking system. 
         FIG. 6  shows a top view of an exemplary radiopaque marking configuration according to the second embodiment of the radiopaque marking system. 
         FIG. 7  shows a top view and a rotated view of an exemplary radiopaque marking configuration. 
         FIG. 8  shows a graph depicting brightness gains under fluoroscopy imaging for a ring marker only configuration, coil only configuration, and a threaded combination of a ring marker and coil. 
         FIGS. 9A-9B  show perspective views of exemplary configurations for radiopaque marking configurations of a side branch of a stent-graft. 
     
    
    
     DETAILED DESCRIPTION 
     Radiography, fluoroscopy, and X-ray computed tomography (X-ray CT) are examples of X-ray based imaging techniques for viewing the internal workings of an object, often times a human body. The X-ray is a form of electromagnetic radiation generated by an X-ray generator and projected towards the object. As the X-rays pass through the object, some of the X-rays are absorbed to varying degrees by the different materials within the object based on various factors such as density and composition. The X-rays that make it through the object without being absorbed are detected by an X-ray detector and used to create X-ray images. Fluoroscopy is an X-ray based imaging technique that produces live, moving, images of the object that are comprised of a plurality of static X-ray images. X-ray CT is an X-ray based imaging technique that utilizes image processing techniques on X-ray images to produce a 3-dimensional image of the object. 
     When applying X-ray imaging techniques to monitor the insertion of a medical device into a human body, understanding the location and orientation of the medical device is desired. To provide the feedback information on the location and orientation of the medical device as it is being inserted, radiopaque markers may be included at strategic locations on the medical device. For exemplary purposes, this disclosure will reference the monitoring of a stent type of medical device into the human body during a fluoroscopy imaging procedure, although the radiopaque marking monitoring features disclosed herein may be applicable to other types of medical devices that are inserted into the human body and other types of X-ray based imaging. The stent device may be, for example, a stent-graft or endograft. 
     Radiopaque markers are made from a material (e.g., platinum or gold) that prevents X-rays from passing through. This results in the radiopaque markers standing out in a bright contrast in the resulting X-ray image. Radiopaque markers may be placed at specific locations on an endograft to identify specific features of the endograft. For example, radiopaque markers may be positioned along a side branch on the endograft to more easily identify these features on the resulting X-ray image. 
     As the number of radiopaque markers that are included on the endograft increases, the ability of an administrator to differentiate the intended feedback information from the radiopaque markers may become more difficult. As a solution to this problem, a radiopaque marking strategy is provided that combines the use of coil, ring, and/or other radiopaque markers at strategic locations on an endograft to represent specific information to be read by an administrator of the endograft during an X-ray imaging process. The radiopaque markers are threaded onto the endograft strut directly to provide both intuitive pseudo-3D information of the side branch portions on the endograft, while also reducing a sewing time for threading the radiopaque markers onto the endograft strut, and also reducing a diameter profile of the resulting endograft. The radiopaque marking strategy includes embodiments where different types of radiopaque markers (e.g., coils and ring markers) are positioned adjacent to each other in specific combinations representing specific predetermined feedback information, as well as embodiments where different types of radiopaque markers are positioned overlapping each other in specific combinations representing specific predetermined feedback information. The placement of the radiopaque markers in the specific combinations are highlighted visual accent points viewable in the resulting X-ray images. The feedback information are representative of labeling specific endograft portions, as well as indicating orientation of the specific endograft portions. 
       FIG. 1  shows a side view of four exemplary combinations of radiopaque coils and radiopaque ring markers under an exemplary first embodiment. The side view shown in  FIG. 1  is a close up view on a single strut wire on an endograft, where ring markers are shown as cross sectional views to expose the strut wire around which the ring markers are secured, including but not limited using knots, glue, frictional fits, clamps, or other securing members. 
     A first combination  110 , a second combination  120 , a third combination  130 , and a fourth combination  140  are all shown in  FIG. 1  to include specific combinations of radiopaque coils and radiopaque ring markers, that are secured onto the individual strut wires. The radiopaque coils and radiopaque ring markers are made from a composite material that inhibits X-rays from passing through, such as platinum or gold.  FIG. 1  also shows a resulting exemplary image under fluoroscopy for each of the first combination  110 , the second combination  120 , the third combination  130 , and the fourth combination  140 . 
     The first combination  110  includes a coil  112  and a ring marker  113  installed adjacent to each other along a strut wire  111  of the endograft. A resulting image of the first combination  110  under fluoroscopy shows how the coil  112  and the ring marker  113  are visibly highlighted to clearly show the coil  112  adjacent to the ring marker  113 . Although the strut wire  111  is illustrated to be non-visible in the resulting image under fluoroscopy, according to some embodiments the strut wire  111  may be visible to varying degrees in the resulting image under fluoroscopy based on the fluoroscopy imaging technique being used. The space between the coil  112  and ring marker  113  may be an empty space, or occupied by a non-radiopaque marker, to better distinguish between the individual coil  112  and ring marker  113  that combines to form the distinct first combination  110  under the resulting fluoroscopy image. Alternatively, according to some embodiments the space between the coil  112  and the ring marker  113  may be removed so that the coil  112  and the ring marker  113  are adjacent to each other. By removing the space, the first combination  110  is modified into another unique form under the resulting fluoroscopy image. 
     The second combination  120  includes a coil  122 , a ring marker  123 , and a ring marker  124  that are installed adjacent to each other along a strut wire  121  of the endograft. A resulting image of the second combination  120  under fluoroscopy shows how the coil  122  and the two ring markers  123 ,  124  are visibly highlighted to clearly show the coil  122  adjacent to the ring marker  123 , and the ring marker  123  adjacent to the ring marker  124 . 
     Although the strut wire  121  is illustrated to be non-visible in the resulting image under fluoroscopy, according to some embodiments the strut wire  121  may be visible to varying degrees in the resulting image under fluoroscopy based on the fluoroscopy imaging technique being used. The space between the coil  122  and the ring marker  123 , and/or the space between the ring marker  123  and the ring marker  124 , may be an empty space, or occupied by a non-radiopaque marker, to better distinguish between the individual radiopaque members that comprise the second combination  120  (e.g., coil  122 , ring marker  123 , ring marker  124 ) under the resulting fluoroscopy image. Alternatively, according to some embodiments a space between the individual radiopaque members that comprise the second combination  120  (e.g., coil  122 , ring marker  123 , ring marker  124 ) may be removed so that one or more of the individual radiopaque members that comprise the second combination  120  (e.g., coil  122 , ring marker  123 , ring marker  124 ) are adjacent to each other. By removing a space, the second combination  120  is modified into another unique form under the resulting fluoroscopy image. 
     The third combination  130  includes a coil  132 , a ring marker  133 , a ring marker  134 , and a ring marker  135 , that are installed adjacent to each other along a strut wire  131  of the endograft. A resulting image of the third combination  130  under fluoroscopy shows how the coil  132  and the three ring markers  133 ,  134 ,  135  are visibly highlighted to clearly show the coil  132  adjacent to the ring marker  133 , the ring marker  133  adjacent to the ring marker  134 , and the ring marker  134  adjacent to the ring marker  135 . 
     Although the strut wire  131  is illustrated to be non-visible in the resulting image under fluoroscopy, according to some embodiments the strut wire  131  may be visible to varying degrees in the resulting image under fluoroscopy based on the fluoroscopy imaging technique being used. The space between the coil  132  and the ring marker  133 , and/or the space between the ring marker  133  and the ring marker  134 , and/or the space between the ring marker  134  and the ring marker  135 , may be an empty space, or occupied by a non-radiopaque marker, to better distinguish between the individual radiopaque members that comprise the third combination  130  (e.g., coil  132 , ring marker  133 , ring marker  134 , ring marker  135 ) under the resulting fluoroscopy image. Alternatively, according to some embodiments a space between the individual radiopaque members that comprise the third combination  130  (e.g., coil  132 , ring marker  133 , ring marker  134 , ring marker  135 ) may be removed so that one or more of the individual radiopaque members that comprise the third combination  130  (e.g., coil  132 , ring marker  133 , ring marker  134 , ring marker  135 ) are adjacent to each other. By removing a space, the third combination  130  is modified into another unique form under the resulting fluoroscopy image. 
     The fourth combination  140  includes a coil  142 , a ring marker  143 , and a ring marker  144  that are installed adjacent to each other along a strut wire  141  of the endograft. A resulting image of the fourth combination  140  under fluoroscopy shows how the coil  142  and the two ring markers  143 ,  144  are visibly highlighted to clearly show the ring marker  143  installed on one end of the coil  142 , and the ring marker  144  installed on the opposite end of the coil  142 . 
     Although the strut wire  141  is illustrated to be non-visible in the resulting image under fluoroscopy, according to some embodiments the strut wire  141  may be visible to varying degrees in the resulting image under fluoroscopy based on the fluoroscopy imaging technique being used. The space between the ring marker  143  and the coil  142 , and/or the space between the coil  142  and the ring marker  144 , may be an empty space, or occupied by a non-radiopaque marker, to better distinguish between the individual radiopaque members that comprise the fourth combination  140  (e.g., coil  142 , ring marker  143 , ring marker  144 ) under the resulting fluoroscopy image. Alternatively, according to some embodiments a space between the individual radiopaque members that comprise the fourth combination  140  (e.g., coil  142 , ring marker  143 , ring marker  144 ) may be removed so that one or more of the individual radiopaque members that comprise the fourth combination  140  (e.g., coil  142 , ring marker  143 , ring marker  144 ) are adjacent to each other. By removing a space, the fourth combination  140  is modified into another unique form under the resulting fluoroscopy image. 
     The combinations illustrated in  FIG. 1  are not limiting, and any number of combinations of ring markers, coils, spaces, and/or non-radiopaque members are within the scope of this disclosure. 
     Each combination of adjacent radiopaque coils and radiopaque ring markers shown in  FIG. 1  may represent feedback information such as a specific endograft feature (e.g., a side arm) or an outline of the endograft itself for orientation purposes. Other combinations of adjacent radiopaque coils and radiopaque ring markers are also within the scope of the first embodiment for representing feedback information not specifically discussed. The radiopaque coils may be made from a same or different material as the radiopaque ring markers. The radiopaque coils provide a different density/composition due to its coiled shape as the radiopaque markers, and therefore result in a different overall brightness compared to the solid radiopaque ring markers on the resulting fluoroscope image. 
       FIG. 2  shows a side view of three exemplary combinations of radiopaque coils and radiopaque ring markers under an exemplary second embodiment. The side view shown in  FIG. 2  is a close up view on a single strut wire on an endograft, where ring markers are shown as cross sectional views to expose the coils around which the ring markers are installed over. 
     A first combination  210 , a second combination  220 , and a third combination  230  are all shown in  FIG. 2  to include specific combinations of radiopaque coils and radiopaque ring markers, that are secured onto the individual strut wires. The radiopaque coils and radiopaque ring markers are made from a composite material that inhibits X-rays from passing through, such as platinum or gold.  FIG. 2  also shows a resulting image under fluoroscopy for each of the first combination  210 , the second combination  220 , and the third combination  230 . 
     The first combination  210  includes a coil  212  and a ring marker  213 , where the coil is installed along a strut wire  211  of the endograft, and the ring marker  213  is installed over the coil  212 . A resulting image of the first combination  210  under fluoroscopy shows how the coil  212  and the ring marker  213  are visibly highlighted to clearly show the ring marker  213  installed to overlap with the coil  212 . Under a magnified view of the fluoroscopy image of the first combination  210 , the density of the ring marker  213  overlapping the coil  212  is shown as being darker on the fluoroscopy image than either the coil  212  or the ring marker  213  alone. 
     Although the strut wire  211  is illustrated to be non-visible in the resulting image under fluoroscopy, according to some embodiments the strut wire  211  may be visible to varying degrees in the resulting image under fluoroscopy based on the fluoroscopy imaging technique being used. 
     The second combination  220  includes a coil  222 , a ring marker  223 , and a ring marker  224 . The coil  222  is installed on a strut wire  221  of the endograft, and the ring markers  223 ,  224  are installed to overlap with the coil  222 . A resulting image of the second combination  220  under fluoroscopy shows how the coil  222  and the two ring markers  223 ,  224  are visibly highlighted to clearly show the two ring markers  223 ,  224  installed to overlap the coil  222 , where the overlapping portions in the fluoroscopy image are shown to be darker than either the coil  222  or the ring markers  223 ,  224  alone. 
     Although the strut wire  221  is illustrated to be non-visible in the resulting image under fluoroscopy, according to some embodiments the strut wire  221  may be visible to varying degrees in the resulting image under fluoroscopy based on the fluoroscopy imaging technique being used. The space between the ring marker  223  and the ring marker  224 , may be an empty space, or occupied by a non-radiopaque marker, to better distinguish between the ring marker  223  and the ring marker  224  that overlap the coil  222 , under the resulting fluoroscopy image. Alternatively, according to some embodiments the space between the ring marker  223  and the ring marker  224  may be removed so that they are adjacent to each other. By removing the space, the second combination  220  is modified into another unique form under the resulting fluoroscopy image. 
     The third combination  230  includes a coil  232 , a ring marker  233 , a ring marker  234 , and a ring marker  235 . The coil  232  is installed on a strut wire  231  of the endograft, and the ring markers  233 ,  234 ,  235  are installed to overlap with the coil  231 . A resulting image of the third combination  230  under fluoroscopy shows how the coil  232  and the three ring markers  233 ,  234 ,  235  are visibly highlighted to clearly show the three ring markers  233 ,  234 ,  235  installed to overlap the coil  232 , where the overlapping portions in the fluoroscopy image are shown to be darker than either the coil  232  or the ring markers  233 ,  234 ,  235  alone. 
     Although the strut wire  231  is illustrated to be non-visible in the resulting image under fluoroscopy, according to some embodiments the strut wire  231  may be visible to varying degrees in the resulting image under fluoroscopy based on the fluoroscopy imaging technique being used. The space between the ring marker  233  and the ring marker  234 , and/or the space between the ring marker  234  and the ring marker  235 , may be an empty space, or occupied by a non-radiopaque marker, to better distinguish between the ring marker  233 , the ring marker  234 , and the ring marker  235  that overlap the coil  232 , under the resulting fluoroscopy image. Alternatively, according to some embodiments the space between the ring marker  233 , the ring marker  234 , and the ring marker  235  may be removed so that they are adjacent to each other. By removing the space, the third combination  230  is modified into another unique form under the resulting fluoroscopy image. 
     The combinations illustrated in  FIG. 2  are not limiting, and any number of combinations of ring markers, coils, spaces, and/or non-radiopaque members are within the scope of this disclosure. 
     Each combination of overlapping radiopaque ring markers and radiopaque rings shown in  FIG. 2  may represent feedback information such as a specific endograft feature (e.g., a side arm) or an outline of the endograft itself for orientation purposes. Other combinations of overlapping radiopaque coils and radiopaque ring markers are also within the scope of the second embodiment for representing feedback information not specifically discussed. For example, a fourth combination (shown under fluoroscopy only) includes a coil  241  and ring marker  242 , where the ring marker  242  is installed over a strut wire (not illustrated) while being within the coil  241 . 
     The radiopaque coils may be made from a same or different material as the radiopaque ring markers. The radiopaque coils may provide a different level of fluoroscopic brightness from that of the radiopaque markers due to its coiled shape configuration versus the solid band of the radiopaque marker even if both radiopaque coil and radiopaque markers are made from the same material with a similar path length of x-ray transmission. For example, when brightness profile sampling is performed across the ring marker only, the coil only, and the combination of overlapping ring marker and coil, the overall gain from the combination of the threaded ring marker and coil is about a 20% increase in both a maximum and an average in the “brightness” over the ring marker only or coil only. This gain is illustrated by graph  800  shown in  FIG. 8 . 
       FIG. 3  shows a cross sectional view of three exemplary designs for a radiopaque ring marker. A first ring marker  310  is shown to have perpendicular, or substantially perpendicular, edges. Looking into the first ring marker  310  from a distal end taken along the A-A line, shows a cross sectional view of the first ring marker  310 . The cross sectional view of the first ring marker  310  shows a hollow section in the middle of the first ring marker  310  through which the first ring marker  310  is secured onto a strut wire of an endograft. 
     A second ring marker  320  is shown to have beveled, or substantially beveled, edges. Looking into the second ring marker  320  from a distal end taken along the B-B line, shows a cross sectional view of the second ring marker  320 . The cross sectional view of the second ring marker  320  shows a hollow section in the middle of the second ring marker  320  through which the second ring marker  320  is secured onto a strut wire of an endograft. 
     A third ring marker  330  is shown to have a rounded bead-like shape with no edges. Looking into the third ring marker  330  from a distal end taken along the C-C line, shows a cross sectional view of the third ring marker  330 . The cross sectional view of the third ring marker  330  shows a hollow section in the middle of the third ring marker  330  through which the third ring marker  330  is secured onto a strut wire of an endograft. 
     Other embodiments may use ring markers having different shapes. Ring marker shapes having rounded edges may be more easily secured onto the strut wires, and/or may prevent damaging inner linings of vessels through which the endografts travel along or the medical device itself. 
       FIG. 4  shows a top view and resulting fluoroscopy image for two different patterns of adjacent radiopaque markers according to the first embodiment. Each pattern may further be comprised of one or more sub-combination of adjacent radiopaque markers. 
     A first pattern  410  includes a first sub-combination  411  comprised of three ring markers secured onto different locations of a z-strut wire of an endograft. The first pattern  410  further includes a second sub-combination  412  comprised of two sets of markers in a “check mark” configuration secured onto a z-strut, where each set is comprised of ring markers of different sizes (e.g., different diameters) secured one behind the other (i.e., one is secured to the front (anterior) of the endograft and the other is secured to the back (posterior) of the endograft). The use of two sets of markers in the check mark configuration gives an operator even more precise control over orientation of the medical device as it is being inserted and moved within the subject. This is because having the two sets of markers in the check mark configuration is able to show a displacement between the two check mark markers during slight rotations of the medical device, thus giving the operator the ability to have finer ability to discern exactly what the correct orientation should be as compared to just a single check mark. In contrast, under some circumstances when the medical device is slightly rotated one way or the other with only the single check mark, the resulting image may be displayed as the same single check mark without as much discernment as to how the rotation translated to the endograft. 
     The first pattern  410  further includes a single check mark configuration  417  positioned above a third sub-combination  413 . The third sub-combination  413  includes four branch configurations  416 , where each branch configuration  416  includes a strut rod  416   a,  a strut ring  416   b  at each end of the strut rod  416   a,  and two ring markers  416   c  attached around the strut rod  416   a.  Each branch configuration  416  represents feedback information identifying a branch structure, where the branch configuration  416  promotes the ability to see each branch structure in the endograft individually by providing an outline of an entire branch (minus, for example, a side due to two-dimensional imaging). The two strut rings  416   b  together with the strut rod  416   a  may be a single continuous piece, and work together to identify an end (e.g., distal or proximal) of the branch structure. The strut rod  416   a  further provides added visibility of one side and distal end of a branch by utilizing the ring markers  416   c  to be threaded along the strut rod  416   a  to be closer to one of the ends of the strut rod  416   a.  The combination and relative positioning of the components that comprise the branch configuration  416  further provides an operator to view a relative length, width, and orientation of the branches in space. 
     The first pattern  410  further includes another single check mark configuration  414  secured onto a z-strut at a position below the third sub-combination  413 , where the single check mark configuration  414  is comprised of ring markers of different sizes (e.g., different diameters) secured adjacent to each other. The first pattern  410  further includes a fourth sub-combination  415  comprised of three ring markers secured onto different locations on a z-strut wire of the endograft. In  410 , the use of the second sub-combination  412  positioned on the top of the endograft, the set of branch markers in the third sub-combination  413  in the middle of the endograft, and the single check mark configuration  414  positioned at the bottom of the endograft allows the user to see the relative rotational orientation of the endograft throughout the entire length of the device. The resulting fluoroscopy image of the first pattern  410  is shown below the top view, and shows the contrasting display of the radiopaque coil and radiopaque ring markers. 
     A second pattern  420  includes a first sub-combination  421  comprised of three ring markers secured onto different locations of a z-strut wire of an endograft. The second pattern  420  further includes a single check mark configuration  425  positioned above a second sub-combination  422 . The second sub-combination  422  includes four branch configurations  424 , where each branch configuration  424  includes a single strut ring  424   a  at one distal end, and two ring markers  424   b  attached at an opposite end from the ring marker  424   a.  Each branch configuration  424  represents feedback information identifying a branch structure, where the branch configuration  424  promotes the ability to see each branch structure in the endograft individually by providing an outline of an entire branch (minus, for example, a side due to two-dimensional imaging). Compared to the first pattern  410 , the second pattern  420  includes fewer components. Even so, although the branch configuration  424  does not include distinct strut rods, the combination and relative positioning of the strut rings  424   a  and ring markers  424   b  still offer feedback information to identify, for example, a proximal and/or distal end of a branch as well as a relative length, width, and orientation of a branch in space. 
     The second pattern  420  further includes a third sub-combination  423  comprised of three ring markers secured onto different locations on a z-strut wire of the endograft. In the second pattern  420 , the use of the single check mark configuration  425  at the top of the endograft and second sub-combination  422  in the middle of the endograft, allows the user to see the relative rotational orientation of the endograft throughout the part of the length of the device. The resulting fluoroscopy image of the second pattern  420  is shown below the top view, and shows the contrasting display of the radiopaque coil and radiopaque ring markers. 
     The location and design of the radiopaque coils, radiopaque ring markers, spaces between radiopaque markers (e.g., empty space or non-radiopaque materials such as glue or other solid materials), as well as the strut rods and strut rings, serve to provide feedback information by identifying specific features and/or orientation of the endograft. 
       FIG. 5  shows a top view and resulting fluoroscopy image for three different patterns of adjacent radiopaque markers according to the first embodiment. Each pattern may further be comprised of one or more sub-combination of adjacent radiopaque markers. 
     A first pattern  510  includes a single ring marker  511  secured onto a z-strut wire of an endograft at a distal end. The first pattern  510  further includes a single check mark configuration  512  comprised of ring markers of different sizes installed adjacent to each other, where the check mark configuration  512  is positioned above a first sub-combination  513 . The first sub-combination  513  comprises four branch configurations  514 , where each branch configuration  514  includes a strut ring  514   a  at each distal end. Each branch configuration  514  represents feedback information identifying a branch structure, where the branch configuration  514  promotes the ability to see each branch structure in the endograft individually by providing an outline of an entire branch (minus, for example, a side due to two-dimensional imaging). With the ring struts  514   a  positioned at the distal ends of the branch configurations  514 , feedback information to identify, for example, a proximal and/or distal end of a branch as well as a relative length, width, and orientation of a branch in space is provided. 
     The first pattern  510  further includes another single ring marker  515  secured onto a z-strut wire of the endograft at a distal end. The resulting fluoroscopy image of the first pattern  510  is shown below the top view, and shows the contrasting display of the radiopaque coil and radiopaque ring markers. 
     A second pattern  520  includes a first sub-combination  521  comprised of three ring markers secured onto different locations of a z-strut wire of an endograft at a distal end. The second pattern  520  further includes a single check mark configuration  522  comprised of ring markers of different sizes installed adjacent to each other, where the check mark configuration  522  is positioned above a second sub-combination  523 . The second sub-combination  523  comprises four branch configurations  524 , where each branch configuration  524  includes some combination of a strut ring  524   a,  a strut rod  524   b,  and ring markers  524   c,  where the ring markers  524   c  are threaded onto the strut rod  524   b.  Each branch configuration  524  represents feedback information identifying a branch structure, where the branch configuration  524  promotes the ability to see each branch structure in the endograft individually by providing an outline of an entire branch (minus, for example, a side due to two-dimensional imaging). With the combination and relative positioning of the strut ring  524   a  positioned at a proximal end of the branch configurations  524 , the strut rod  524   b,  and the combination of ring markers  524   c , feedback information to identify, for example, a proximal and/or distal end of a branch as well as a relative length, width, and orientation of a branch in space is provided. Having the ring markers  524   c  at the edges of some but not other branch configurations  524 , provides a way of having better distinguishing between the branch structures. 
     The second pattern  520  further includes another single check mark configuration  525  comprised of ring markers of different sizes installed adjacent to each other, where the check mark configuration  525  is positioned below the second sub-combination  523 . The second pattern  520  further includes a third sub-combination  526  comprised of three ring markers secured onto different locations on a z-strut wire of the endograft. The resulting fluoroscopy image of the second pattern  520  is shown below the top view, and shows the contrasting display of the radiopaque coil and radiopaque ring markers. 
     A third pattern  530  includes a single ring marker  531  secured onto a z-strut wire of an endograft. The third pattern  530  further includes a single check mark configuration  532  comprised of ring markers of different sizes installed adjacent to each other, where the check mark configuration  532  is positioned above a first sub-combination  533 . The first sub-combination comprises four branch configurations  534 , where each branch configuration  534  includes some combination of a strut ring  534   a  and ring markers  534   b.  Each branch configuration  534  represents feedback information identifying a branch structure, where the branch configuration  534  promotes the ability to see each branch structure in the endograft individually by providing an outline of an entire branch (minus, for example, a side due to two-dimensional imaging). With the combination and relative positioning of the strut ring  534   a  positioned at a proximal end of the branch configurations  534 , and the combination of ring markers  534   b,  feedback information to identify, for example, a proximal and/or distal end of a branch as well as a relative length, width, and orientation of a branch in space is provided. Having the ring markers  534   b  at the edges of some but not other branch configurations  534 , provides a way of having better distinguishing between the branch structures. The ring markers  534   b  also provides a user with important features, such as identifying a proximal end of a branch structure so that a path to inserting the endograft into the branch structure is shown. 
     The third pattern  530  further includes another single check mark configuration  535  comprised of ring markers of different sizes installed adjacent to each other, where the check mark configuration  535  is positioned below the first sub-combination  533 . The third pattern  530  further includes another single ring marker  536  secured onto a z-strut wire of an endograft. The resulting fluoroscopy image of the third pattern  530  is shown below the top view, and shows the contrasting display of the radiopaque coil and radiopaque ring markers. 
     The location and design of the radiopaque coils, radiopaque ring markers, spaces between radiopaque markers (e.g., empty space or non-radiopaque materials such as glue or other solid materials), as well as the rods and rings, serve to provide feedback information by identifying specific features and/or orientation of the endograft. 
       FIG. 6  shows a top view and resulting fluoroscopy image for a first pattern  610  of adjacent radiopaque markers according to the second embodiment. Each pattern may further be comprised of one or more sub-combination of adjacent radiopaque markers, and further including overlapping radiopaque markers. 
     The first pattern  610  according to the second embodiment is similar to the first pattern  410  according to the first embodiment. In addition, the first pattern  610  according to the second embodiment includes a first sub-combination  611  comprised of a coil and two overlapping ring markers placed over a middle section of the coil. The first pattern  610  provides the ability to see each branch structure individually. The first pattern  610  provides an outline of a branch structure (except for one side). The first pattern  610  also provides added visibility of one side and distal end of the branch structure where the two ring markers are located on a branch configuration. The first pattern  610  also provides the ability to see the relative length, width, and orientation of the branch structures in space. 
       FIG. 7  shows an exemplary endograft  700  having an exemplary radiopaque marking configuration. The endograft  700  is shown under both a top view  710  and a rotated view  720 , where the rotated view  720  is a view taken of the endograft  700  that has been rotated (e.g., rotated 90 degrees) from the top view  710 .  FIG. 7  further shows the endograft in an unconstrained view and a constrained view under the top view  710 , and an unconstrained view and a constrained view under the rotated view  720 . The unconstrained views of the endograft  700  illustrate the endograft  700  in an expanded state (e.g., for when expanded within a vessel), and the constrained views of the endograft  700  illustrate the endograft in a constricted state (e.g., for when traveling through a vessel). The comparison provided by the constrained and unconstrained views exemplify how the radiopaque marking system on the endograft  700  is configured to achieve the advantages of the feedback information by patterning the radiopaque markers in the adjacent and overlapping patterns, while still maintaining a low profile that will not adversely affect the ability of the endograft traveling within vessels. The check mark radiopaque marker  711  shown in exemplary pattern  710  is comprised of a single coil made of a radiopaque material. 
     Patterns that include overlapping radiopaque markers may be applied in different combinations with adjacent radiopaque markers. The combinations may include combinations of different radiopaque marker types (e.g., coils, ring markers, strut rods, strut rings), combination of different radiopaque markers that are spaced apart by empty space or non-radiopaque materials (e.g., glue, suture, or other materials with low radiopacity), combination of different radiopaque marker materials (e.g., platinum, gold, non-radiopaque materials, materials with low radiopacity, nitinol), and/or different radiopaque marker dimensions (e.g., larger radiopaque markers positioned next to smaller radiopaque markers to distinguish a unique pattern of different radiopaque markers) to achieve specific patterns of shapes and brightness on a resulting fluoroscopy image. 
     As noted above,  FIG. 8  shows a graph depicting brightness gains under fluoroscopy imaging for a ring marker only configuration, coil only configuration, and a threaded combination of a ring marker and coil. The numerical values represent relative brightness under experimental imaging modalities. When brightness profile sampling is performed across the marker and coil, the overall gain from the threading coil into a marker is about 20% increase in the “brightness,” including both maximum and average. 
       FIGS. 9A-9B  show perspective views of exemplary configurations for radiopaque marking configurations of a side branch of an endograft. The components in  FIGS. 9A-9B  collectively form a two-part frame, including a first segment  910  and a second segment  930 , which together provide support for a single side branch. This two-part frame shown in  FIGS. 9A-9B  may be an alternative structural support system to any of the side branch support structures that are depicted in the endografts shown in  FIGS. 4-7 , i.e., any individual side branch represented in  FIGS. 4-7  may instead comprise the two-part frame of  FIGS. 9A-9B . 
     In  FIG. 9A , the first segment  910  comprises a wire  912  having a first end  912   a  and a second end  912   b.  The wire  912  spans from the first end  912   a  to form a first loop  913 , and then continues as a relatively straight strut segment  914 . The strut segment  914  extends from a first region  914   a,  which may be the exit location of the first loop  913 , to a second region  914   b.  From the second region  914   b,  the wire  912  transitions into a ring  915 , and further continues to form a second loop  916 . The second loop  916  transitions to the second end  912   b  of the wire  912 . 
     The ring  915  of the first segment  910  is dimensioned to encircle a fenestration in the main endograft body. Accordingly, the ring  915  and adjacent second loop  916  are disposed proximal (upstream) relative to the first loop  913 . The first and second loops  913  and  916  may allow suture coupling locations for the first segment  910  to graft material of the side branch. 
     In the embodiment of FIG.  FIG. 9A , the first segment  910  comprises a coil  920  that is wound about a portion, and preferably a majority, of the strut segment  914 . In one non-limiting embodiment, the coil  920  comprises a radiopaque material such as platinum, although other materials may be used. 
     The first segment  910  further comprises at least one ring marker, such as ring markers  922   a  and  922   b,  which are disposed proximal to the coil  920 . In one non-limiting embodiment, the ring markers  922   a  and  922   b  comprise a radiopaque material such as gold, although other materials may be used. In this embodiment, a plurality of spacers  924   a  and  924   b  are also used, such that the length of the strut segment  914  comprises the following sequence in a distal to proximal direction between first region  914   a  and second region  914   b : coil  920 , spacer  924   a,  ring marker  922   a,  spacer  924   b,  and ring marker  922   b.    
     Advantageously, by having components arranged in this sequence, enhanced imaging of a side branch may be achieved, particularly along a longitudinal length of the side branch. As a further advantage, the spaced-apart ring markers  922   a  and  922   b  may provide a visual indication just distal to a fenestration in the main endograft when the ring  915  encircles the fenestration. 
     In  FIG. 9B , the second segment  930  comprises a wire  932  having a first end  932   a  and a second end  932   b.  The wire  932  spans from the first end  932   a  to form a first loop  933 , and then transitions into a ring  935 , which in this non-limiting example comprises a “D-shape.” From the ring  935 , the wire  932  transitions to a relatively straight strut segment  934 . The strut segment  934  extends from a first region  934   a , which is generally at the end of the ring  935 , to a second region  934   b.  From the second region  934   b,  the wire continues to form a second loop  936 . The second loop  936  transitions to the second end  932   b  of the wire  932 . 
     The ring  935  of the second segment  930  is dimensioned to encircle an open distal end of the side branch of the endograft. Accordingly, the ring  935  and adjacent first loop  933  are disposed distal to the second loop  936 . The first and second loops  933  and  936  may allow suture coupling locations for the second segment  930  to graft material of the side branch. 
     In the embodiment of  FIG. 9B , the second segment  930  comprises a coil  940  that is wound about the wire  932  in the location of both the ring  935  and the strut segment  934 . The coil  940  has a distal region  940   a  that is disposed near the end of the loop  933  and a proximal region  940   b  that is disposed near the second region  934   b  of the strut segment  934  In one non-limiting embodiment, the coil  940  comprises a radiopaque material such as platinum, although other materials may be used. 
     Advantageously, by having a coil  940  encircle the wire  932  along a substantial part of its length, e.g., around all or substantially all of the ring  935  and strut segment  934 , enhanced imaging of the side branch may be achieved, particularly at the distal opening of the side branch and along the longitudinal length of the side branch. In some embodiments, the coil  940  may comprise multiple coils, which may be spaced apart slightly from one another, e.g., to help negotiate turns of the wire  932 , while still achieving the same benefits. As will be appreciated, in alternative embodiments, one or more ring markers may be disposed adjacent to the coil  940  (in a manner similar to  FIG. 9A  and other embodiments above). Further, in either of the embodiments of  FIGS. 9A-9B , one or more ring markers may be disposed over the coils  920  or  940  as explained, for example, with respect to  FIG. 2  above. 
     Advantageously, the two-part frame comprising the first segment  910  and the second segment  930  cooperate to provide excellent structural support for a single side branch, while also integrating radiopaque markers in the form of coils and ring markers. The coil and ring markers are beneficially arranged in specific patterns around the wires  912  and  932  of the first and second segments  910  and  930  to provide optimal visualization of the location of the side branch, its distal opening, and the fenestation in the main body of the endograft. 
     While various embodiments have been described, the disclosed features are not to be restricted except in light of the attached claims and their equivalents. Moreover, the advantages described herein are not necessarily the only advantages and it is not necessarily expected that every embodiment will achieve all of the advantages described. Some embodiments may also include a fewer, or greater, number of components or steps than those specifically described and still remain within the scope of this disclosure.