Patent Publication Number: US-2021178139-A1

Title: Fiducial deployment mechanisms, and related methods of use

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of priority of U.S. Provisional Application No. 61/834,235, filed Jun. 12, 2013, the entirety of which is incorporated by reference herein. 
    
    
     TECHNICAL FIELD 
     Various embodiments of the present disclosure relate generally to medical devices and related systems and methods. More specifically, the present disclosure relates to devices, systems, and methods for deploying fiducials. 
     BACKGROUND 
     Endosonographers use Endoscopic Ultrasound Fine Needle Aspiration (EUS FNA) for diagnosis and staging of disease. EUS FNA is a highly effective diagnostic procedure. An ultrasound image generated by EUS FNA allows a physician to visualize the position of a needle in relation to a target and surrounding tissue structures. This aids in ensuring that the correct tissue is sampled and that the risk to the patient is minimized. 
     However, therapeutic tools and procedures for endosonographers are less well established. Current industry trends and research are focusing on development of devices that would enable endosonographers to treat specific conditions once diagnosis has been established. 
     One area currently being explored for EUS guided therapy is the placement of fiducials. Fiducials act as markers so diseased tissue can be targeted for more effective delivery of radiation or other treatments. Currently, the fiducial placement is a very time consuming procedure for the endosonographers. It generally requires the physician to load and place the markers one at a time. 
     SUMMARY 
     The present disclosure includes devices, systems, and methods for deploying fiducials, for example, during an EUS FNA procedure. 
     In accordance with an embodiment, the present disclosure is directed to a medical device. The medical device may include an elongate member having a proximal end and a distal end, and a lumen disposed through the elongate member. The medical device may also include an opening disposed at the distal end of the elongate member in communication with the lumen, and a pushing element disposed with the lumen. The medical device may also include at least one fiducial disposed within the lumen and distal to the pushing element, and a separating mechanism disposed at the distal end of the elongate member. The separating mechanism may be configured to apply a separating force to deploy the at least one fiducial. 
     Various embodiments of the disclosure may include one or more of the following aspects: wherein the at least one fiducial may be one of a plurality of fiducials disposed within the lumen and connected to each other by a linkage; wherein the separating mechanism may be configured to direct the separating force to a distal portion of the linkage to deploy a distalmost fiducial; wherein the at least one fiducial may be one of a plurality of fiducials disposed within the lumen, and adjacent fiducials may be disposed within compartments separated by spacers; and wherein the separating mechanism may be configured to apply the separating force to a distalmost spacer to deploy a distalmost fiducial. 
     In accordance with an embodiment, the present disclosure is directed to a method of deploying multiple fiducials within a patient. The method may include advancing a medical device into a body lumen of the patient, and applying a distally-directed force to direct at least one fiducial toward an opening at a distal end of the medical device. The method may also include applying a separating force, distinct from the distally-directed force, to deploy the fiducial. 
     Various embodiments of the disclosure may include one or more of the following aspects: wherein the distally-directed force may be applied by a pushing element disposed within a lumen of the medical device; wherein the separating force may be one of an electric charge, heat, or a mechanical force; wherein the at least one fiducial may be one of a plurality of fiducials connected to each other by a linkage, and the method may further include applying the separating force to a distal portion of the linkage to deploy a distal fiducial; wherein the at least one fiducial may be one of a plurality of fiducials disposed within the lumen, and adjacent fiducials may be disposed within compartments separated by spacers, and the method may further include applying the separating force to a distalmost spacer to deploy a distalmost fiducial; and applying the separating force to a distal end of a continuous length of fiducial material to form a plurality of fiducials. 
     In accordance with an embodiment, the present disclosure is directed toward a medical device. The medical device may include an elongate member having a proximal end and a distal end, and a first lumen disposed through the elongate member. The method device may also include an opening disposed at the distal end of the elongate member in communication with the lumen, and a plurality of fiducials disposed within the first lumen. The medical device may also include at least one biasing element disposed within the first lumen proximal to the plurality of fiducials. The biasing element may be configured to urge the plurality of fiducials toward the opening after deployment of a distalmost fiducial. 
     Various embodiments of the disclosure may include one or more of the following aspects: a distal opening mechanism disposed at the distal end of the elongate member, the distal opening mechanism configured to rotate about a joint to eject a distalmost fiducial from the first lumen; and a second lumen may be disposed in the elongate member parallel to the first lumen, and a pushing element may be disposed through the second lumen, the pushing element being configured to reciprocally move between a proximal loading position and a distal deployment position, wherein when the pushing element is in the proximal loading position and no fiducial is in the second lumen, a distalmost fiducial disposed within the first lumen is urged toward the second lumen. 
     In accordance with an embodiment, the present disclosure is directed toward a medical device. The medical device may include an elongate member having a proximal end and a distal end, and a lumen disposed through the elongate member. The medical device may also include an opening disposed at the distal end of the elongate member in communication with the lumen, and a plurality of fiducials disposed distal to the pushing element. The medical device may also include a pull wire having a distal protrusion being disposed distal to a distalmost fiducial of the plurality of fiducials and configured to retain the plurality of fiducials within the lumen. 
     In accordance with an embodiment, the present disclosure is directed toward a medical device. The medical device may include an elongate member having a proximal end and a distal end, and a lumen disposed through the elongate member. The medical device may also include an opening disposed at the distal end of the elongate member in communication with the lumen, and a plurality of fiducials disposed distal to the pushing element, each of the plurality of fiducials having a protrusion. The medical device may also include a groove disposed on a side surface of the elongate member that receives the protrusion of each of the plurality of fiducials. 
     In accordance with an embodiment, the present disclosure is directed toward a medical device. The medical device may include an elongate member having a proximal end and a distal end, and a lumen disposed through the elongate member. The medical device may also include an opening disposed at the distal end of the elongate member in communication with the lumen, and a plurality of fiducials disposed within the lumen. The medical device may also include a pushing element configured to direct the plurality of fiducials through the opening, and a liquid disposed between adjacent fiducials. 
     In accordance with an embodiment, the present disclosure is directed toward a medical device. The medical device may include an elongate member having a proximal end and a distal end, and a lumen disposed through the elongate member. The medical device may also include an opening disposed at the distal end of the elongate member in communication with the lumen, and a cartridge disposed at the distal end of the elongate member distal to the pushing element. The cartridge may have a plurality of chambers disposed radially about the cartridge. The medical device may also include a plurality of fiducials disposed within the plurality of chambers. 
     In accordance with an embodiment, the present disclosure is directed toward a medical device. The medical device may include an elongate member having a proximal end and a distal end, and a lumen disposed through the elongate member. The medical device may also include an opening disposed at the distal end of the elongate member in communication with the lumen, and a plurality of fiducials disposed within the lumen. The medical device may also include an actuator disposed at a proximal end of the elongate member. The actuator may include a cap having a distal projection. The medical device may also include a plurality of seats configured to couple with the distal projection. Adjacent seats of the plurality of seats may be transposed about the longitudinal axis of the elongate member, and the longitudinal distance between adjacent seats may correspond to the longitudinal distance moved by the actuator to deploy a single fiducial of the plurality of fiducials. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate various exemplary embodiments and together with the description, serve to explain the principles of the disclosed embodiments. 
         FIG. 1  is a side perspective view of a medical device in accordance with an embodiment of the present disclosure. 
         FIGS. 2-6  are partial side cross-sectional views of deployment mechanisms in accordance with various embodiments of the present disclosure. 
         FIG. 7  is a side perspective view of a medical device in accordance with an embodiment of the present disclosure. 
         FIGS. 8-9  are partial side cross-sectional views of deployment mechanisms in accordance with various embodiments of the present disclosure. 
         FIGS. 10-11  are partial side cross-sectional views of a deployment mechanism in accordance with an embodiment of the present disclosure. 
         FIG. 12  is a partial side cross-sectional view of a deployment mechanism in accordance with an embodiment of the present disclosure. 
         FIG. 13  is a top plan view of a cartridge used in conjunction with the deployment mechanism of  FIG. 12 . 
         FIGS. 14-15  are partial side perspective views of exemplary actuators in accordance with various embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
     As shown in  FIG. 1 , a medical device  100  according to an exemplary embodiment of the present disclosure may include a first needle  102  and a second needle  104  connectable to one another. A further example of a suitable medical device includes that described in U.S. Patent Application Publication 2011/0196258, published on Aug. 11, 2011, the entire disclosure of which is incorporated by reference herein. First needle  102  may include a first longitudinal element  106  defining a lumen (not shown). First longitudinal element  106  may be flexible such that first longitudinal element  106  may be inserted into the body along a tortuous path (e.g., within a body lumen) to reach a target area within the body. 
     A proximal end of first longitudinal element  106  may be coupled to a first handle  116  sized to slidably receive first longitudinal element  106 . First handle  116  may further include a luer fitting  122  for coupling to the second needle  104 . Second longitudinal element  108  may extend longitudinally from a proximal end to a distal end and include a lumen (not shown). An outer diameter of second longitudinal element  108  may be smaller than an inner diameter of the first lumen of first longitudinal element  106  such that second longitudinal element  108  may be slidably inserted through the first lumen. For example, in one embodiment, first longitudinal element  106  may be a 19 gauge needle while second longitudinal element  108  may be a 22 gauge needle. Alternatively, first longitudinal element  106  may be a 22 gauge needle while second longitudinal element  108  may be a 25 gauge needle. 
     A length of second longitudinal element  108  may be longer than a length of first longitudinal element  106  such that when the second longitudinal element  108  is inserted into the first lumen, the distal end of the second longitudinal element  108  may be extended distally past the distal end of the first longitudinal element  106 . The proximal end of the second longitudinal element  108  may include an actuator  140 . 
     A second handle  130  may be attached to the proximal end of second longitudinal element  108 . The distal end of the second handle  130  may include a coupling element  138  adapted and configured to mate with the luer fitting  122  of first needle  102  such that first and second needles  102 ,  104  may be connected to one another. 
     Second longitudinal element  108  of second needle  104  may be inserted through the lumen of first longitudinal element  106  of first needle  102  such that second longitudinal element  108  is “nested” within first longitudinal element  106 . Second longitudinal element  108  may be slid through the lumen of first longitudinal element  106  until coupling element  138  of second needle  104  comes into contact with luer fitting  122  of first needle  102 . 
       FIG. 2  shows a partial side cross-sectional view of a medical device  200  for deploying fiducials in accordance with an embodiment of the present disclosure. Medical device  200  may include an elongate member  202  having a proximal end  204  and a distal end  206 . The elongate member  202  may be inserted into a lumen of a patient&#39;s body to access a target site whereupon a medical or diagnostic procedure, such as EUS FNA, is performed. The proximal end  204  may be coupled to an actuating mechanism, such as actuator  140  (referring to  FIG. 1 ), for operating the medical device  200 . In some embodiments, medical device  200  may represent the distal end of second longitudinal element  108  (referring to  FIG. 1 ). 
     A pushing element  208  may be disposed within a lumen  210  defined by elongate member  202 . Pushing element  208  may be coupled to actuator  140  in any suitable manner. Pushing element  208  may be advanced distally by actuator  140  and may contact a fiducial  212  disposed within lumen  210 . A plurality of fiducials  212  may be disposed along a longitudinal axis of lumen  210  and may be connected to each other by a linkage  214 . Linkage  214  may extend within and between the plurality of fiducials  212 . Linkage  214  may be a wire, suture, or other suitable linkage. Fiducials  212  may include a generally radiopaque material so that targeted regions of a patient&#39;s body may be located by ultrasound or other suitable imaging techniques. Fiducials  212  may likewise include a porous, pitted, angled, rough, or irregular surface in order to improve visibility under ultrasound or other suitable imaging techniques, including by providing structures on the surface(s) of the fiducial  212 . Fiducials  212  may include gold or another suitable metal. In some embodiments, fiducials  212  may further include compliant materials. In one embodiment, fiducials  212  may be spherical, although any other suitable shape also may be utilized, including shapes selected to improve visibility under ultrasound, e.g. polygonal. In an alternative embodiment, fiducials  212  may include substance-eluting (e.g., drug-eluting) materials. Fiducials  212  may likewise be configured for placement at a desired region of a patient&#39;s body, including by implantation on, within, or underneath tissue at a targeted region of a patient&#39;s body by piercing, cutting, or separating tissue at the desired region, or by adhering the fiducial  212  to the tissue by, e.g., providing an adhesive coating or pattern on the surface of fiducial  212 . 
     A separating mechanism  216  may be disposed at distal end  206  of medical device  200 . Separating mechanism  216  may be configured to disintegrate or otherwise sever linkage  214  between consecutive fiducials  212 . In one exemplary embodiment, as pushing element  208  is moved distally (e.g., by actuator  140 ), a distalmost fiducial  212  may extend distally out of lumen  210  via an opening  218 . In an alternative embodiment, elongate member  202  may be moved proximally (while pushing member  208  is held in place) to eject the distalmost fiducial  212  out of lumen  210 . In yet another alternative embodiment, pushing element  208  may be coupled to linkage  214 , and both pushing element  208  and linkage  214  may be moved proximally such that a distalmost end of linkage  214  is removed from the distalmost fiducial  212 , releasing the distalmost fiducial  212 . 
     In one embodiment, once a distalmost linkage  214  is within an effective range of separating mechanism  216 , separating mechanism  216  may generate a separating force to deploy a distalmost fiducial  212 . In one embodiment, separating mechanism  216  may emit an electrical charge that disintegrates or severs a distalmost portion of linkage  214 . Current carrying wires (not shown) may extend through medical device  200  to proximal end  204 , where they may be coupled to, e.g., an RF generator or other suitable mechanism. An actuator (not shown) may be disposed at proximal end  204  that may be activated to cause current to flow along the current carrying wires and across opening  218  to separate fiducials  212 . In an alternative embodiment, separating mechanism  216  may direct heat toward linkage  214 , thereby melting linkage  214  and releasing the distalmost fiducial  212 . It should be noted, however, that other alternative separating mechanisms utilizing electrical, mechanical, and/or chemical mechanism are also contemplated. 
       FIG. 3  is a partial side cross-sectional view of a deployment mechanism in accordance with an embodiment of the present disclosure. A medical device  300  may include an elongate member  302  having a proximal end  304  and a distal end  306 . Similar to elongate member  202 , elongate member  302  may be inserted into a lumen of a patient&#39;s body to access a target site whereupon a medical or diagnostic procedure, such as EUS FNA, is performed. The proximal end  304  may be coupled to an actuating mechanism, such as actuator  140  (referring to  FIG. 1 ), for operating the medical device  300 . In some embodiments, medical device  300  may represent the distal end of second longitudinal element  108  (referring to  FIG. 1 ). 
     Elongate member  302  may be a needle defined by a first lumen  308  and a second lumen  310  that are parallel to each other and separated by a wall  312 . Elongate member  302  may include a tapered section  314  disposed partway around the circumference of elongate member  302  that extends from an intermediate portion of elongate member  302  toward an opening  316  disposed at distal end  306 . A biasing element  318  may be disposed in first lumen  308  and may be located proximally to a loading zone  320  configured to hold a plurality of fiducials  322 . Loading zone  320  may thus be defined by biasing element  318 , wall  312 , tapered section  314 , and an inner portion of elongate member  302 . In one embodiment, biasing element  318  may be a coiled spring. Alternatively, biasing element  318  may be any suitable structure capable of providing a biasing force including, but not limited to, other compressible materials. 
     A pushing element  324  may be disposed within second lumen  310  and may be capable of reciprocal movement to load and eject fiducials  322  one at a time from elongate member  302 . As shown in  FIG. 3 , pushing element  324  may be in an intermediate position, where a fiducial  322  is in a loaded position distal to the distal end of pushing element  324 . Pushing element  324  may be moved distally toward opening  316  to eject a loaded fiducial out of elongate member  302 . In a fully extended position, the distal end of pushing element  324  may be coplanar with opening  316  or proximal to opening  316 . Alternatively, the distal end of pushing element  324  may extend through opening  316  to deploy fiducials  322 . After deployment of a fiducial  322 , pushing element  324  may be retracted to a loading position represented by reference axis A-A (i.e., a location that is proximal to a distalmost fiducial  322  within first lumen  308 ). That is, pushing element  324  may be retracted so that its distal end is located generally along axis A-A, and a distalmost fiducial  322  located in loading zone  320  may be laterally urged by biasing element  318  and tapered section  314  toward second lumen  310  and the distal end of pushing element  324 . After loading of a fiducial  322 , pushing element  324  may be returned to the intermediate position. 
       FIG. 4  is a partial side cross-sectional view of a deployment mechanism in accordance with an embodiment of the present disclosure. A medical device  400  may include an elongate member  402  having a proximal end  404  and a distal end  406 . Similar to elongate member  202 , elongate member  402  may be inserted into a lumen of a patient&#39;s body to access a target site whereupon a medical or diagnostic procedure, such as EUS FNA, is performed. The proximal end  404  may be coupled to an actuating mechanism, such as actuator  140  (referring to  FIG. 2 ), for operating the medical device  400 . In some embodiments, medical device  400  may represent the distal end of second longitudinal element  108  (referring to  FIG. 1 ). 
     A pushing element  408  may be disposed within a lumen  410  defined by elongate member  402 . Pushing element  408  may be coupled to actuator  140  in any suitable manner. Pushing element  408  may be advanced distally by actuator  140  and may contact a fiducial  412  disposed within lumen  410 . A plurality of fiducials  412  may be disposed along a longitudinal axis of lumen  410 . Fiducials  412  may be substantially similar to fiducials  212  (referring to  FIG. 2 ), but may be shaped such that fiducials  412  are retained in lumen  410  absent a compressing force applied to them. In one embodiment, at least one diameter of fiducials  412  is greater than the diameters of both a tapered section  413  and an opening  414  disposed at distal end  406  of elongate member  402 . Fiducials  412  may be conical, though any other suitable shape is also contemplated including, but not limited to spherical, ovular, rectangular, asymmetrical, or the like. Tapered section  413  may be an interference fit taper section that extends entirely around a circumference of elongate member  402  that defines opening  414 . In an alternative embodiment, instead of having a smaller diameter than a remaining portion of elongate member  402 , tapered section  413  may have substantially the same diameter as the remaining portion of elongate member  402  but also include inward protrusions that reduce an effective diameter of lumen  410  at tapered section  413 . Fiducials  412  may include a compliant material such that fiducials  412  are contained within lumen  410 . That is, a compressing force may be applied to fiducials  412 , reducing the effective diameter of fiducials  412  to enable them to eject from elongate member  402  via tapered section  413  and opening  414  (i.e., fiducials  412  may snap through tapered section  413  and opening  414  when a sufficient compressive and distally-directed force is applied). In an alternative embodiment, elongate member  402  may be moved proximally (while pushing member  408  is held in place) to apply the compressing force to a distalmost fiducial  412 , enabling it to eject out of lumen  410 . 
       FIG. 5  is a partial side cross-sectional view of a deployment mechanism in accordance with an embodiment of the present disclosure. A medical device  500  may include an elongate member  502  having a proximal end  504  and a distal end  506 . Similar to elongate member  202 , elongate member  502  may be inserted into a lumen of a patient&#39;s body to access a target site whereupon a medical or diagnostic procedure, such as EUS FNA, is performed. The proximal end  504  may be coupled to an actuating mechanism, such as actuator  140  (referring to  FIG. 1 ), for operating the medical device  500 . In some embodiments, medical device  500  may represent the distal end of second longitudinal element  108  (referring to  FIG. 1 ). 
     A pushing element  508  may be disposed within a lumen  510  defined by elongate member  502 . Pushing element  508  may be coupled to actuator  140  in any suitable manner. Pushing element  508  may be advanced distally by actuator  140  and may contact a fiducial  512  disposed within lumen  510 . A plurality of fiducials  512  may be disposed along a longitudinal axis of lumen  510 . Fiducials  512  may be substantially similar to fiducials  412  (referring to  FIG. 4 ), but may be shaped such that fiducials  512  are contained by a projection  514  extending from a pull wire  516  disposed within lumen  510 . Similar to pushing element  508 , pull wire  516  may be coupled to actuator  140  or a similar mechanism. In one embodiment, fiducials  512  may be conical, though any other suitable shape is also contemplated including, but not limited to spherical, ovular, rectangular, asymmetrical, or the like. Fiducials  512  may include a compliant material and may be contained within lumen  510  by projection  514  unless a sufficient compressing force is applied. That is, projection  514  may be sized to inhibit the distal movement of fiducials  512 . To deploy a distalmost fiducial  512 , pull wire  516  may be retracted proximally so that projection  514  is proximal to the distalmost fiducial  512 . Then, pushing element  508  may be directed distally to eject distalmost fiducial  512  out of lumen  510  via an opening  518 . In an alternative embodiment, elongate member  502  may be moved proximally (while pushing member  508  is held in place) to eject the distalmost fiducial  512  out of lumen  510 . It should also be noted that as projection  514  is moved proximal to the distalmost fiducial  512 , projection  514  may secure (inhibit the distal movement of) a proximally adjacent fiducial  512  in place for a subsequent deployment. 
       FIG. 6  is a partial side cross-sectional view of a deployment mechanism in accordance with an embodiment of the present disclosure. A medical device  600  may include an elongate member  602  having a proximal end  604  and a distal end  606 . Similar to elongate member  202 , elongate member  602  may be inserted into a lumen of a patient&#39;s body to access a target site whereupon a medical or diagnostic procedure, such as EUS FNA, is performed. The proximal end  604  may be coupled to an actuating mechanism, such as actuator  140  (referring to  FIG. 1 ), for operating the medical device  600 . In some embodiments, medical device  600  may represent the distal end of second longitudinal element  108  (referring to  FIG. 1 ). 
     A pushing element  608  may be disposed within a lumen  610  defined by elongate member  602 . Pushing element  608  may be coupled to actuator  140  in any suitable manner. Pushing element  608  may be advanced distally by actuator  140  and may contact a fiducial  612  disposed within lumen  610 . A plurality of fiducials  612  may be disposed along a longitudinal axis of lumen  610 . Fiducials  612  may be substantially similar to fiducials  212  (referring to  FIG. 2 ), but also include a first seal  614  and a second seal  616 . Both first seal  614  and second seal  616  may be disposed around a periphery of fiducials  612 . Adjacent fiducials  612  may be separated by a liquid volume  617  (e.g., saline) to promote separation and ease of deployment. Further, the presence of liquid volume  617  between adjacent fiducials  612  may reduce the formation of air pockets within a patient&#39;s body during deployment of fiducials  612 , improving the clarity of images generated by ultrasound and other imaging techniques. In one exemplary embodiment, as pushing element  608  is moved distally (e.g., by actuator  140  of  FIG. 1 ), a distalmost fiducial  612  may extend distally out of lumen  610  via an opening  618 . In an alternative embodiment, elongate member  602  may be moved proximally (while pushing member  608  is held in place) to eject a distalmost fiducial  612  out of lumen  610 . First and second seals  614 ,  616  may be O-rings or similar structures, and may have material properties that permit them to “roll” along the inside of lumen  610  with its corresponding fiducial  612 . Thus, as fiducials  612  are moved distally, liquid volume  617  may be maintained between adjacent fiducials  612 . 
       FIG. 7  is a partial side perspective view of a deployment mechanism in accordance with an embodiment of the present disclosure. A medical device  700  may include an elongate member  702  having a proximal end  704  and a distal end  706 . Similar to elongate member  202 , elongate member  702  may be inserted into a lumen of a patient&#39;s body to access a target site whereupon a medical or diagnostic procedure, such as EUS FNA, is performed. The proximal end  704  may be coupled to an actuating mechanism, such as actuator  140  (referring to  FIG. 1 ), for operating the medical device  700 . In some embodiments, medical device  700  may represent the distal end of second longitudinal element  108  (referring to  FIG. 1 ). 
     A pushing element  708  may be disposed within a lumen  710  defined by elongate member  702 . Pushing element  708  may be coupled to actuator  140  in any suitable manner. Pushing element  708  may be advanced distally by actuator  140  and may contact a fiducial  712  disposed within lumen  710 . A plurality of fiducials  712  may be disposed along a longitudinal axis of lumen  710 . Fiducials  712  may be substantially similar to fiducials  212  (referring to  FIG. 2 ), but also include a protrusion  714  extending from a longitudinal surface of each fiducial  712 . Protrusions  714  may be arranged within lumen  710  such that protrusions  714  are disposed within a groove  716  disposed within a longitudinal surface of elongate member  702 . That is, as fiducials  712  move distally through lumen  710 , protrusions  714  may promote proper orientation and deployment of fiducials  712  via its interaction with groove  716 . Further, protrusions  714  may act as retention elements, preventing deployment of fiducials  712  unless a sufficient compressing and distally-directed force is applied by pushing element  708 . Protrusions  714  and/or fiducials  712  may be compressible to facilitate deployment of fiducials  712 . Groove  716  may extend from a first longitudinal point to a second longitudinal point along the longitudinal axis of elongate member  702 , though other suitable configurations are also contemplated. For example, in one alternative embodiment, groove  716  may extend to proximal end  704  and/or distal end  706  of elongate member  702 . In one exemplary embodiment, as pushing element  708  is moved distally (e.g., by actuator  140  of  FIG. 1 ), a distalmost fiducial  712  may extend distally out of lumen  710  via an opening  718 . In an alternative embodiment, elongate member  702  may be moved proximally (while pushing member  708  is held in place) to eject the distalmost fiducial  712  out of lumen  710 . It is also contemplated that elongate member  702  may include a tapered section to retain fiducials  712  within lumen  710 . 
       FIG. 8  is a partial side cross-sectional view of a deployment mechanism in accordance with an embodiment of the present disclosure. A medical device  800  may include an elongate member  802  having a proximal end  804  and a distal end  806 . Similar to elongate member  202 , elongate member  802  may be inserted into a lumen of a patient&#39;s body to access a target site whereupon a medical or diagnostic procedure, such as EUS FNA, is performed. The proximal end  804  may be coupled to an actuating mechanism, such as actuator  140  (referring to  FIG. 1 ), for operating the medical device  800 . In some embodiments, medical device  800  may represent the distal end of second longitudinal element  108  (referring to  FIG. 1 ). 
     A pushing element  808  may be disposed within a lumen  810  defined by elongate member  802 . Pushing element  808  may be coupled to actuator  140  in any suitable manner. Pushing element  808  may be advanced distally by actuator  140  and may contact a spacer  811  disposed within lumen  810 . A plurality of fiducials  812  may be disposed in compartments along a longitudinal axis of lumen  810  between adjacent spacers  811 . Fiducials  812  may be substantially similar to fiducials  212  (referring to  FIG. 2 ). 
     A separating mechanism  816  may be disposed at distal end  806  of medical device  800 . Separating mechanism  816  may be substantially similar to separating mechanism  216  (referring to  FIG. 2 ) and may be configured to disintegrate or otherwise sever spacers  811  between consecutive fiducials  812 . In one exemplary embodiment, as pushing element  808  is moved distally (e.g., by actuator  140  of  FIG. 1 ), a distalmost spacer  811  may extend distally toward an opening  818  disposed at distal end  806  of elongate member  802 . In an alternative embodiment, elongate member  802  may be moved proximally (while pushing member  808  is held in place) to direct the distalmost spacer  811  toward distal end  806 . 
     In one embodiment, once a distalmost spacer  811  is within an effective range of separating mechanism  816 , separating mechanism  816  may generate a separating force to deploy a distalmost fiducial  812 . In one embodiment, separating mechanism  816  may emit an electrical charge that severs spacer  811 . In an alternative embodiment, separating mechanism  816  may direct heat toward spacer  811 , thereby melting spacer  811  and releasing the distalmost fiducial  812 . It should be noted, however, that other alternative separating mechanisms utilizing electrical, mechanical, and/or chemical mechanism are also contemplated. 
       FIG. 9  is a partial side cross-sectional view of a deployment mechanism in accordance with an embodiment of the present disclosure. A medical device  900  may include an elongate member  902  having a proximal end  904  and a distal end  906 . Similar to elongate member  202 , elongate member  902  may be inserted into a lumen of a patient&#39;s body to access a target site whereupon a medical or diagnostic procedure, such as EUS FNA, is performed. The proximal end  904  may be coupled to an actuating mechanism, such as actuator  140  (referring to  FIG. 1 ), for operating the medical device  900 . In some embodiments, medical device  900  may represent the distal end of second longitudinal element  108  (referring to  FIG. 1 ). 
     A pushing element  908  may be disposed within a lumen  910  defined by elongate member  902 . Pushing element  908  may be coupled to actuator  140  in any suitable manner. Pushing element  908  may be advanced distally by actuator  140  and may contact a fiducial source  911  disposed within lumen  910 . Fiducial source  911  may be a continuous length of fiducial material configured to be formed into a plurality of individual fiducials  912 . Fiducials  912  may be substantially similar to fiducials  212  (referring to  FIG. 2 ). 
     A separating mechanism  916  may be disposed at distal end  906  of medical device  900 . Separating mechanism  916  may be substantially similar to separating mechanism  216  (referring to  FIG. 2 ) and may be configured to form individual fiducials  912  from fiducial source  911 , e.g., by the application of an electric charge, heat, or mechanical force. In one exemplary embodiment, as pushing element  908  is moved distally (e.g., by actuator  140  of  FIG. 1 ), a distal end of fiducial source  911  may extend distally toward an opening  918  disposed at distal end  906  of elongate member  902 . In an alternative embodiment, elongate member  902  may be moved proximally (while pushing member  908  is held in place) to direct a distal end of fiducial source  911  toward distal end  906 . 
     In one embodiment, once fiducial source  911  has been distally advanced a sufficient amount, separating mechanism  916  may generate a separating force to form a distalmost fiducial  912 . The distal advancement can be measured at the proximal end by movement of pushing member  908 . In one embodiment, an actuator may also be a ratchet or other like mechanism at the proximal end to permit incremental advancement of pushing member  908 . That is, in each increment, the actuator may move pushing member  908  a predetermined amount to deploy one or more fiducials  912 . In one embodiment, separating mechanism  916  may emit an electrical charge that severs fiducial source  911  at a distal region to generate an individual fiducial  912 . In an alternative embodiment, separating mechanism  916  may direct heat toward fiducial source  911 , thereby generating and releasing a newly formed distalmost fiducial  912 . It should be noted, however, that other alternative separating mechanisms utilizing electrical, mechanical, and/or chemical mechanisms are also contemplated. 
       FIGS. 10-11  are partial side cross-sectional views of a deployment mechanism in accordance with an embodiment of the present disclosure. A medical device  1000  may include an elongate member  1002  having a proximal end  1004  and a distal end  1006 . Similar to elongate member  202 , elongate member  1002  may be inserted into a lumen of a patient&#39;s body to access a target site whereupon a medical or diagnostic procedure, such as EUS FNA, is performed. The proximal end  1004  may be coupled to an actuating mechanism, such as actuator  140  (referring to  FIG. 1 ), for operating the medical device  1000 . In some embodiments, medical device  1000  may represent the distal end of second longitudinal element  108  (referring to  FIG. 1 ). 
     A biasing element  1008  may be disposed within a lumen  1010  defined by elongate member  1002 . Biasing element  1008  may be coupled to a plurality of stacked fiducials  1012  disposed within lumen  1010 . A distal opening mechanism  1013  may include a cap  1014  coupled to an arm  1016  via a joint/pivot pin  1018 . Fiducials  1012  may be substantially similar to fiducials  212  (referring to  FIG. 2 ). In one embodiment, biasing element  1008  may be a coiled spring. Alternatively, biasing element  1008  may be any suitable structure capable of providing a biasing force including, but not limited to, other compressible materials. 
     To deploy a distalmost fiducial  1012 , cap  1014  may be rotated about joint  1018  such that arm  1016  ejects the distalmost fiducial  1012  from lumen  1010  via an opening  1020 . After a fiducial  1012  has been ejected, biasing element  1008  may urge a next distalmost fiducial  1012  to the distalmost position. Cap  1014  may be actuated at the proximal end via a pull wire (not shown) that couples cap  1013  to actuator  140  (referring to  FIG. 1 ). 
       FIGS. 12-13  depict a deployment mechanism in accordance with an embodiment of the present disclosure. A medical device  1200  may include an elongate member  1202  having a proximal end  1204  and a distal end  1206 . Similar to elongate member  202 , elongate member  1202  may be inserted into a lumen of a patient&#39;s body to access a target site whereupon a medical or diagnostic procedure, such as EUS FNA, is performed. The proximal end  1204  may be coupled to an actuating mechanism, such as actuator  140  (referring to  FIG. 1 ), for operating the medical device  1200 . In some embodiments, medical device  1200  may represent the distal end of second longitudinal element  108  (referring to  FIG. 1 ). 
     A pushing element  1208  may be disposed within a lumen  1210  defined by elongate member  1202 . Pushing element  1208  may be coupled to actuator  140  in any suitable manner. Pushing element  1208  may be advanced distally by actuator  140  and may contact a fiducial  1212  disposed within a cartridge  1214 . Cartridge  1214  may be disposed distal to pushing element  1208  within lumen  1210  and may be configured to hold fiducials  1212  in a plurality of chambers  1216  disposed in a radial arrangement about cartridge  1214 . In one embodiment, cartridge  1214  may include six chambers  1216 , though any other suitable number of chambers may be utilized, if desired. Fiducials  1212  may be substantially similar to fiducials  212  (referring to  FIG. 2 ). Each fiducial  1212  may stay in a chamber  1216  via, e.g., a friction fit, until a sufficient force is applied by pushing member  1208 . 
     In one exemplary embodiment, pushing element  1208  may be aligned with a first chamber  1216 . As pushing element  1208  is moved distally through the first chamber  1216  (e.g., by actuator  140  of  FIG. 1 ), a first fiducial  1212  disposed within first chamber  1216  may extend distally toward an opening  1218  disposed at distal end  1206  of elongate member  1202 . In an alternative embodiment, cartridge  1214  may be moved proximally (while pushing member  1208  is held in place) to eject fiducials  1212  from chambers  1216 . 
     Cartridge  1214  may then be rotated so that pushing element  1208  is aligned with a second chamber  1216 . In an alternative embodiment, pushing element  1208  may be rotated to align with second chamber  1216 . 
     In yet another alternative embodiment, a plurality of pushing elements  1208  may be aligned with an equal number of chambers  1216 , such that each pushing element  1208  is aligned with a corresponding chamber  1216 . In this embodiment, each pushing element  1208  may be aligned with a corresponding actuating mechanism. 
       FIG. 14  depicts an actuating mechanism in accordance with an embodiment of the present disclosure. Medical device  1400  may include a proximal cap  1402 , an elongate member  1404 , and a plurality of threads  1406  disposed along the length of elongate member  1404 . This particular embodiment may allow for precision in the deployment of fiducials in accordance with other embodiments of the present disclosure. In some embodiments, the length and geometry of threads  1406  may be configured such that, e.g., one full rotation of proximal cap  1402  may deploy one fiducial from a distal end of a medical device. In some embodiments, medical device  1400  may represent actuator  140  of  FIG. 1 . In some embodiments, proximal cap  1402  may be moved distally to deploy fiducials into a patient&#39;s body, while in other embodiments, proximal cap  1402  may be moved proximally to deploy the fiducials. 
       FIG. 15  depicts an actuating mechanism in accordance with an embodiment of the present disclosure. Medical device  1500  may include a proximal cap  1502 , an elongate member  1504 , and a protrusion  1506  extending distally from proximal cap  1502 . Medical device  1500  may also include a plurality of seats configured to cooperate with protrusion  1506 . This particular embodiment may also allow for precision in the deployment of fiducials in accordance with other embodiments of the present disclosure. In one embodiment, medical device  1500  includes three seats  1508 ,  1510 , and  1512 . In some embodiments, a distally adjacent seat may be transposed about the longitudinal axis of medical device  1500  with respect to a proximally adjacent seat. For example, seat  1510  may be distal to seat  1508  and may be transposed about the longitudinal axis of medical device  1500  in either a clockwise or counterclockwise direction. To deploy a first fiducial (not shown in  FIG. 15 ), a user may rotate cap  1502  so that protrusion  1506  is aligned with seat  1510 , and then apply a distal force to cap  1502  so that protrusion  1506  and seat  1510  contact each other or are otherwise coupled. The distance d traveled by protrusion  1506  may be configured to deploy a precise number of fiducials (e.g., one fiducial). In some embodiments, medical device  1500  may represent actuator  140  of  FIG. 1 . To deploy a second fiducial (not shown in  FIG. 15 ), the user may rotate cap  1502  so that protrusion  1506  is aligned with seat  1512 , and then apply a distal force to cap  1502  so that protrusion  1506  and seat  1512  are coupled. While three seats are depicted in the embodiment of  FIG. 15 , any suitable number of seats may alternatively be utilized. 
     Any aspect set forth in any embodiment may be used with any other embodiment set forth herein. Every device and apparatus set forth herein may be used in any suitable medical procedure, may be advanced through any suitable body lumen and body cavity, and may be used to access tissue from any suitable body portion. For example, the apparatuses and methods described herein may be used through any natural body lumen or tract, including those accessed orally, vaginally, rectally, nasally, urethrally, or through incisions in any suitable tissue. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the disclosed systems and processes without departing from the scope of the invention. Other embodiments of the disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure disclosed herein. It is intended that the specification and examples be considered as exemplary only. The following disclosure identifies some other exemplary embodiments.