Patent Publication Number: US-2019183602-A1

Title: Marker delivery device for tissue marker placement

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to medical devices, and, more particularly, to a marker delivery device for percutaneous tissue marker placement. 
     2. Description of the Related Art 
     Tissue biopsies are commonly performed on many areas and organs of the human body where it is desirable to ascertain whether or not a lesion or other tissue to be biopsied is cancerous. Often, the lesion or other tissue to be biopsied is identified through use of an imaging technique, such as a computerized axial tomography (CAT) scan, ultrasonography, and mammography. 
     In breast biopsies, for example, the lesion typically is so small that the biopsy reduces its size to the extent that it is no longer visible by the imaging method employed. In such circumstances, it is desirable to place a tissue marker at the site of the biopsy to enable the medical practitioner subsequently to locate the lesion quickly and accurately in the event complete removal of the affected tissue is indicated. The tissue marker is placed at the biopsy site, for example, by a marker delivery device having a needle cannula that houses the tissue marker. 
     In some marker delivery devices, the marker may not be completely ejected from the cannula, or may be drawn back into or toward the cannula by the vacuum created upon the withdrawal of the cannula, which results in the marker being moved from the intended site, leading to inaccurate identification of the location of the biopsy area. Another issue is the safe disposal of the marker delivery device after use, particularly the safe disposal of the cannula portion of the marker delivery device that is inserted into the tissue of the patient, which typically has a sharp point. 
     SUMMARY OF THE INVENTION 
     The invention provides, according to one aspect thereof, a marker delivery device configured to fully deliver the tissue marker at a delivery site in the patient where the tissue marker is less likely to migrate, which is achieved by delivering the tissue marker via a rigid cannula having a flexible portion for directing the distal end of the cannula, for example, into tissue adjacent a biopsy site. The invention provides, according to another aspect thereof, a marker delivery device configured to facilitate the safe disposal of the marker delivery device after use. The marker delivery device may be used, for example, in association with various imaging systems, such as X-ray, ultrasound, MRI etc. 
     The invention, in one form thereof, is directed to a marker delivery device configured for deploying a tissue marker. The marker delivery device includes a handle having a chamber. A cannula is configured for holding the tissue marker for deployment. The cannula has a side wall surrounding a lumen that extends along a lengthwise extent of the cannula. The cannula has a flexible portion formed by a slot arrangement having of a plurality of peripheral slots extending through the side wall of the cannula to the lumen. The plurality of peripheral slots is spaced apart to be substantially parallel along the lengthwise extent of the cannula to facilitate a flexure at the flexible portion of the cannula. A marker introducer rod is movably disposed in the lumen of the cannula. The marker introducer rod has a flexible region that corresponds to the flexible portion of the cannula. A deployment mechanism is mounted to the handle and configured to displace the marker introducer rod for deploying the tissue marker upon an actuation of the deployment mechanism. A retraction mechanism is mounted to the handle and is configured to facilitate a complete retraction of both the cannula and the marker introducer rod into the chamber of the housing of the handle upon an actuation of the retraction mechanism. 
     The invention, in another form thereof, is directed to a marker delivery device configured for deploying a tissue marker. The marker delivery device includes a handle configured to be grasped by a user. A cannula has a proximal end and a distal end, the proximal end being coupled to the handle. The cannula is substantially rigid and has a side wall surrounding a lumen that extends along a lengthwise extent of the cannula. The cannula has a flexible portion formed by a slot arrangement having of a plurality of peripheral slots extending through the side wall of the cannula to the lumen. The slots of the plurality of peripheral slots are spaced apart to be substantially parallel along the lengthwise extent of the cannula to facilitate a flexure at the flexible portion of the cannula. A marker introducer rod is movably disposed in the lumen of the cannula to effect a deployment of the tissue marker from the distal end of the cannula. The marker introducer rod has an actuation end and a marker deployment end, and a flexible region that corresponds to the flexible portion of the cannula. 
     The invention, in another form thereof, is directed to a marker delivery device configured for deploying a tissue marker. The marker delivery device includes a handle configured to be to be grasped by a user. The handle includes a housing having a front end and a back end, with a chamber located between the front end and the back end, and having a hole leading from the chamber to the exterior of the handle. A cannula has a proximal end, a distal end, and a lumen extending along a lengthwise extent of the cannula between the proximal end and the distal end. The cannula is positioned in the handle such that the cannula retractably extends through the hole beyond the front end of the housing. A marker introducer rod is movably disposed in the lumen of the cannula to effect a deployment of the tissue marker from the distal end of the cannula. The marker introducer rod has an actuation end and a marker deployment end. A deployment mechanism is mounted to the housing. The deployment mechanism is coupled to the actuation end of the marker introducer rod. The deployment mechanism is configured to displace the marker introducer rod for deploying the tissue marker upon an actuation of the deployment mechanism. A retraction mechanism is mounted to the housing, and is coupled to the proximal end of the cannula. The retraction mechanism is configured to facilitate a complete retraction of both the cannula and the marker introducer rod into the chamber of the housing of the handle upon an actuation of the retraction mechanism. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein: 
         FIG. 1  is a perspective view of a marker delivery device configured for deploying a tissue marker in accordance with an embodiment of the present invention; 
         FIG. 2  is a section view of a portion of the marker delivery device of  FIG. 1  taken along plane  2 - 2 ; 
         FIG. 3  is a section view of a portion of the marker delivery device of  FIG. 1  taken along plane  3 - 3 ; 
         FIG. 4A  is a top view of a portion of the cannula of the marker delivery device of  FIG. 1  depicting a flexible portion of the cannula; 
         FIG. 4B  is a side view of the flexible portion of the cannula of  FIG. 4A , showing in phantom lines the flexure of the flexible portion of the cannula relative to non-flexure; 
         FIG. 4C  is an end view of the cannula of  FIG. 4A  from the perspective of looking into the lumen of the cannula from the distal end of the cannula, also showing in phantom lines the flexure of the flexible portion of the cannula relative to non-flexure; 
         FIG. 5  is a top view of an alternative configuration of the flexible portion of the marker delivery device of  FIG. 1 ; 
         FIG. 6  is a top view of another alternative configuration of the flexible portion of the cannula of the marker delivery device of  FIG. 1 ; 
         FIG. 7  is a side view of a portion of the marker introducer rod of the marker delivery device of  FIG. 1 , showing the actuation end, the marker deployment end, and the flexible region; 
         FIG. 8  is a perspective view of the marker delivery device of  FIG. 1  used in conjunction with a biopsy device, showing a flexure of flexible portion of the cannula; 
         FIG. 9  is a perspective view of the marker delivery device of  FIG. 1  following complete retraction of the cannula and marker introducer rod into the longitudinal chamber of the housing of the handle; 
         FIG. 10  is a perspective view of a marker delivery device configured for deploying a tissue marker in accordance with another embodiment of the present invention; 
         FIG. 11  is a section view of the marker delivery device of  FIG. 10  taken along plane  11 - 11 , showing the deployment mechanism in an initial position; 
         FIG. 12  is a section view of the marker delivery device of  FIG. 10 , showing the deployment mechanism in a marker deployed position; 
         FIG. 13  is a section view of the marker delivery device of  FIG. 10 , showing the deployment mechanism in a marker introducer rod initial retraction position; 
         FIG. 14  is a section view of the marker delivery device of  FIG. 10 , showing the deployment mechanism in a marker introducer rod post-initial retraction position; and 
         FIG. 15  is a section view of a portion of the marker delivery device of  FIG. 10  taken along plane  15 - 15 , depicting the cannula retraction mechanism. 
     
    
    
     Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate embodiments of the invention, and such exemplifications are not to be construed as limiting the scope of the invention in any manner. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings, and more particularly to  FIGS. 1-3 , there is shown a marker delivery device  10  configured for deploying a tissue marker  12 , in accordance with an embodiment of the present invention. 
     Marker delivery device  10  includes a handle  14 , a cannula  16 , a marker introducer rod  18 , a deployment mechanism  20  and a retraction mechanism  22 . 
     Handle  14  is configured to be grasped by a user, i.e., is of an appropriate size and shape to be grasped by the hand of the user of marker delivery device  10 . Handle  14  includes a housing  24  having a front end  24 - 1 , a back end  24 - 2  and a side wall  24 - 3 , with a longitudinal chamber  26  located between front end  24 - 1  and back end  24 - 2  that is surrounded by side wall  24 - 3 . A hole  24 - 4  leads from chamber  26  through front end  24 - 1  of housing  24  to the exterior of handle  14 . A trigger slot  24 - 5  extends through side wall  24 - 3  of housing  24 . 
     Cannula  16  is configured for holding tissue marker  12  for deployment into a tissue mass of a patient, and may be in the form of a hollow needle. Cannula  16  is positioned in handle  14  such that cannula  16  extends through the hole  24 - 4  beyond the front end  24 - 1  of housing  24  prior to marker deployment. Cannula  16  has a proximal end  16 - 1  and a distal end  16 - 2 , with the proximal end  16 - 1  being coupled to handle  14 . Cannula  16  has a side wall  16 - 3  that surrounds a lumen  16 - 4  that extends along a lengthwise extent  28  along a longitudinal axis  16 - 5  of cannula  16 . Cannula  16  is substantially rigid, and may be made, for example, from a metallic material, such as for example, stainless steel, nitinol, a nickel-chromium alloy, titanium, etc. 
     Referring also to  FIGS. 4A-4C , cannula  16  has a flexible portion  30  formed by a slot arrangement  32  having of a plurality of peripheral slots  34  arranged circumferentially around cannula  16 . Slot arrangement  32  may be formed in cannula  16 , for example, by making cuts in cannula  16 , such as through the use of a cutting laser. In the present embodiment, flexible portion  30  of cannula  16  is located closer to the distal end  16 - 2  of cannula  16  than to proximal end  16 - 1  of cannula  16 . The plurality of peripheral slots  34  extends through the side wall  16 - 2  of cannula  16  to lumen  16 - 4 . Also, as illustrated in  FIG. 4C , in the present embodiment a circumferential extent  34 - 1  of each of the slots of the plurality of peripheral slots  34  of slot arrangement  32  is approximately two-thirds of the total circumference of cannula  16 . 
     As illustrated in  FIGS. 4A and 4B , in the present embodiment the plurality of peripheral slots  34  are spaced apart from one another to be substantially parallel along the lengthwise extent  28  of cannula  16  to facilitate a flexure at flexible portion  30  of cannula  16 .  FIG. 4B  shows in phantom lines the flexure of the flexible portion  30  of cannula  16  relative to a non-flexure of cannula  16 . As illustrated in  FIGS. 4B and 4C , the configuration of the plurality of peripheral slots  34  (e.g., the circumferential placement of the slots along cannula  16 ) may be selected so that the flexure occurs along a single predetermined plane  36 . In the present embodiment, for example, each of the substantially parallel plurality of peripheral slots  34  is arranged to be orthogonal to the longitudinal axis  16 - 5  of cannula  16 . 
     The configuration of the plurality of peripheral slots  34  and the material forming cannula  16  may be selected such that the flexure does not result in a permanent deformation of cannula  16 . For example, a slot width  34 - 2  relative to longitudinal axis  16 - 5  of the slots, the circumferential extent  34 - 1  of the slots, the axial placement of the slots along cannula  16 , and the material used to form cannula  16  may be selected, through empirical studies and/or through materials analysis, so that flexible portion  30  formed by slot arrangement  32  will flex (e.g., bend at an acute angle with respect to longitudinal axis  16 - 5 ) when the distal end  16 - 2  of cannula  16  is acted on by an external force (F), and then return to the pre-deflected state, e.g., straight along longitudinal axis  16 - 5 , when the external force (F) is removed. 
       FIG. 5  shows another slot arrangement  38  that may be used as an alternative to slot arrangement  32  shown in  FIGS. 4A-4C . Slot arrangement  38  may be formed in cannula  16 , for example, by making cuts in cannula  16 , such as through the use of a cutting laser. Slot arrangement  38  includes of a plurality of peripheral slots  40  arranged circumferentially around cannula  16 . The plurality of peripheral slots  40  include a first set of peripheral slots  42 - 1  having a first circumferential extent  44 - 1  and a second set of peripheral slots  42 - 2  having a second circumferential extent  44 - 2 . The first circumferential extent  44 - 1  of the first set of peripheral slots  42 - 1  is circumferentially staggered with respect to the second circumferential extent  44 - 2  of the second set of peripheral slots  42 - 2 . 
       FIG. 6  shows another slot arrangement  46  that may be used as a further alternative to slot arrangement  32  shown in  FIGS. 4A-4C , and includes the plurality of peripheral slots  34  arranged circumferentially around cannula  16 , but in addition includes an axial slot  48  that extends along the lengthwise extent  28  of cannula  16  to link at least a portion, or all, of the plurality of peripheral slots  34  in a continuous slot arrangement. Slot arrangement  46  may be formed in cannula  16 , for example, by making cuts in cannula  16 , such as through the use of a cutting laser. 
     Referring again to  FIGS. 2 and 3 , marker introducer rod  18  is movably disposed in lumen  16 - 4  of cannula  16  to effect a deployment of tissue marker  12  from the distal end  16 - 2  of cannula  16 . Referring also to  FIG. 7 , marker introducer rod  18  has an actuation end  18 - 1  and a marker deployment end  18 - 2 , and has a flexible region  50  that corresponds to the flexible portion  30  of cannula  16 . Accordingly, as flexible portion  30  of cannula  16  flexes, the flexible region  50  also flexes, while retaining the ability of marker introducer rod  18  to move longitudinally along lumen  16 - 4  to effect a deployment of tissue marker  12 . 
     The flexible region  50  of marker introducer rod  18  may be formed as a flexible metallic element or a flexible plastic element, which in the present embodiment may be of reduced diameter with respect to a diameter of the remainder of marker introducer rod  18 . Also, the remainder of marker introducer rod  18  may be formed from metal or plastic. 
       FIG. 8  illustrates an exemplary implementation of marker delivery device  10  with respect to the flexible portion  30  of cannula  16 , and more particularly shows a portion of an exemplary breast biopsy device  52  having the driver removed (not shown) that drives a cutter and vacuum unit in harvesting a tissue sample via a biopsy needle  54 . Thereafter, cannula  16  of marker delivery device  10  is inserted through the lumen of biopsy needle  54  for placing tissue marker  12  in the tissue of the patient. 
     Biopsy needle  54  has a side sample notch  56  leading to a sample chamber  58  located at the lumen of biopsy needle  54 . As cannula  16  is advanced in the lumen of biopsy needle  54  to the end of sample chamber  58 , a ramped surface  58 - 1  at the end of sample chamber  58  exerts force (F) to deflect the distal end  16 - 2  of cannula  16  resulting in a flexure of flexible portion  30  of cannula (see also  FIGS. 4A-4C ), thereby exposing the distal end  16 - 2  of cannula  16  to sample notch  56 . With a further advancement of cannula  16  in the lumen of biopsy needle  54 , as shown in  FIG. 8 , the distal end  16 - 2  of cannula  16  extends through sample notch  56  to penetrate tissue adjacent the biopsy site. 
     Thereafter, an advancement of marker introducer rod  18  in lumen  16 - 4  of cannula  16  (see, e.g.,  FIG. 3 ) causes tissue marker  12  to be deployed into the tissue surrounding the biopsy site. Flexible region  50  of marker introducer rod  18  (see, e.g.,  FIG. 7 ) conforms to the shape of flexible portion  30  of cannula  16 , before, during and after the flexure of flexible portion  30  of cannula  16 . 
     Alternatively, the distal end  16 - 2  of cannula  16  may be exposed to sample notch  56  without extending though sample notch  56 , and tissue marker  12  may be deployed though sample notch  56  of biopsy needle  54  into the biopsy cavity. 
     Referring again to  FIGS. 1-3 , deployment mechanism  20  is mounted to housing  24  of handle  14  and is configured to displace marker introducer rod  18  for deploying tissue marker  12  upon an actuation of deployment mechanism  20  by the user. In general, deployment mechanism  20  is configured to limit marker delivery device  10  to a single use for marker deployment.  FIGS. 1 and 2  show deployment mechanism  20  in an initial position  60  (marker not deployed) and  FIG. 3  shows deployment mechanism  20  in a marker deployed position  62 . 
     More particularly, deployment mechanism  20  includes an introducer rod guide block  64 , a marker deployment trigger  66 , and a first shear member  68 . Introducer rod guide block  64  is fixedly attached to the actuation end  18 - 1  of marker introducer rod  18 , such as by molding a portion of marker introducer rod  18  into introducer rod guide block  64 , and is slidably disposed in chamber  26  of housing  24 . Marker deployment trigger  66  is accessible at an exterior of housing  24  of handle  14 . Marker deployment trigger  66  is mounted to housing  24  for siding movement along trigger slot  24 - 5  of housing  24  from the initial position  60  shown in  FIGS. 1 and 2  toward the front end  24 - 1  of housing  24  to position deployment mechanism  20  at the marker deployed position  62 . 
     In the present embodiment, marker deployment trigger  66  and introducer rod guide block  64  are linked by first shear member  68 . First shear member  68  extends from marker deployment trigger  66  and resides in a recess  70  located in introducer rod guide block  64 . Thus, an actuation of marker deployment trigger  66  causes first shear member  68  to displace introducer rod guide block  64 , which in turn displaces marker introducer rod  18  along the lengthwise extent  28  of cannula  16  to deploy tissue marker  12  from lumen  16 - 4  of cannula  16 . First shear member  68  has a region of reduced cross section dimension  68 - 1 , e.g., an annular groove, to provide a shear location. 
     An outer contour of introducer rod guide block  64  may be selected to be slidably received in a like-inner contour of longitudinal chamber  26  of housing  24  of handle  14 . Accordingly, in embodiments where the outer contour of introducer rod guide block  64  and the like-inner contour of longitudinal chamber  26  are non-circular, introducer rod guide block  64  prevents rotation of marker introducer rod  18  with respect to housing  24  of handle  14 , thus maintaining a constant orientation of marker introducer rod  18  relative to handle  14 . 
     Also, in embodiments where the outer contour of introducer rod guide block  64  and the like-inner contour of longitudinal chamber  26  are circular, recess  70  of introducer rod guide block  64  may be in the form of a circumferential groove to facilitate a change in angular position, i.e., rotation, of marker introducer rod  18  with respect to housing  24  of handle  14 . In such case, a rotator, e.g., knob, (not shown) positioned external to handle  14  may be coupled to introducer rod guide block  64  to effect a change in orientation of marker introducer rod  18  relative to handle  14 . 
     As best shown in  FIG. 2 , deployment mechanism  20  may further include a lock mechanism  72  to lock marker deployment trigger  66  in the marker deployed position  62  after tissue marker  12  has been deployed. In the present embodiment, lock mechanism  72  includes a first lock member  72 - 1  formed on, or attached to, marker deployment trigger  66  and includes a second lock member  72 - 2  formed on, or attached to, housing  24 . In operation, first lock member  72 - 1  permanently engages second lock member  72 - 2  when marker deployment trigger  66  is positioned in the marker deployed position  62 , thereby limiting marker delivery device  10  to a single marker deployment operation. 
     One of first lock member  72 - 1  and second lock member  72 - 1  may be, for example, a lock channel and the other of first lock member  72 - 1  and second lock member  72 - 2  may be a spring-loaded insert member that engages the lock channel when marker deployment trigger  66 , and in turn marker introducer rod  18 , is positioned in marker deployed position  62 . In the present embodiment shown in  FIG. 2 , for example, first lock member  72 - 1  is formed as a lock channel in marker deployment trigger  66 , and second lock member  72 - 2  is in the form of a spring-loaded pin that engages the lock channel when marker deployment trigger  66  is slid toward the front end  24 - 1  of housing  24  to position deployment mechanism  20 , and in turn marker introducer rod  18 , in marker deployed position  62 . As a further example, when second lock member  72 - 2  is formed as a lock channel in housing  24 , the lock channel may be formed by, or integral with, trigger slot  24 - 5 , and first lock member  72 - 1  as a spring-loaded insert member may be a cantilevered arm having a protrusion that engages the lock channel when marker deployment trigger  66  is positioned in marker deployed position  62 . 
     Again referring to  FIGS. 1-3 , retraction mechanism  22  is mounted to housing  24  of handle  14  and is configured to facilitate a complete retraction of both cannula  16  and marker introducer rod  18  into chamber  26  of housing  24  of handle  14  upon an actuation of retraction mechanism  22  by the user, which most likely will occur following deployment of tissue marker  12 . Retraction mechanism  22  is configured to prevent cannula  16  and marker introducer rod  18  from extending outside chamber  26  of housing  24  of handle  14  after the complete retraction of cannula  16  and marker introducer rod  18  into chamber  26 , thus facilitating the safe disposal of marker delivery device  10 , and alleviating concern about the accidental puncturing of medical personnel, or the patient, following the use of marker delivery device  10 . 
     More particularly, retraction mechanism  22  includes a retraction trigger  74 , a cannula guide block  76 , a second shear member  78 , and a spring  80 . Retraction trigger  74  may be in the form of a push button that is accessible at the exterior of the housing  24 , e.g., through a hole  24 - 7  in side wall  24 - 3 . Cannula guide block  76  is fixedly attached to the proximal end  16 - 1  of cannula  16 , such as by molding a portion of cannula  16  into cannula guide block  76 . Cannula guide block  76  is slidably disposed in longitudinal chamber  26  of housing  24 . In the present embodiment, second shear member  78  is formed as an extension of retraction trigger  74 . 
     As best shown in  FIG. 3 , retraction trigger  74  and cannula guide block  76  are linked by second shear member  78  that is resident in a recess  82  located in cannula guide block  76 , thus holding cannula guide block  76  stationary, e.g., axially stationary, relative to housing  24  of handle  14 . Spring  80  is located between the front end  24 - 1  of housing  24  and cannula guide block  76 , with spring  80  being in a compressed state prior to actuation of retraction trigger  74 , thus providing a preload on cannula guide block  76 . 
     An outer contour of cannula guide block  76  may be selected to be slidably received in an inner like-contour of longitudinal chamber  26  of housing  24  of handle  14 . Accordingly, in embodiments where the outer contour of cannula guide block  76  and the inner like-contour of longitudinal chamber  26  are non-circular, cannula guide block  76  prevents rotation of cannula  16  with respect to housing  24  of handle  14 , thus maintaining a constant orientation of cannula  16  relative to handle  14 . 
     However, in embodiments where the outer contour of cannula guide block  76  and the inner like-contour of longitudinal chamber  26  are circular, recess  82  of cannula guide block  76  may be in the form of a circumferential groove to facilitate a change in angular position, i.e., rotation, of cannula  16  with respect to housing  24  of handle  14 , thus facilitating a changeable orientation of cannula  16  relative to handle  14 . In such case, cannula  16  may be manually rotated by grasping cannula  16  and turning. Alternatively, a rotator, e.g., knob, (not shown) positioned external to handle  14  may be coupled to guide block  76  to effect a change in orientation of cannula  16  relative to handle  14 . 
     An actuation of retraction trigger  74  causes a complete retraction of both cannula  16  and marker introducer rod  18  into chamber  26  of housing  24  of handle  14 . More particularly, as shown in  FIG. 3 , second shear member  78  has a region of reduced cross section dimension  78 - 1 , e.g., an annular groove, to provide a shear location. Initially, the region of reduced cross section dimension  78 - 1  of second shear member  78  is contained within the hole  24 - 7  formed in side wall  24 - 3 , thereby providing additional support at the region of reduced cross section dimension  78 - 1 . 
     In the present embodiment, an actuation (depressing) of retraction trigger  74  radially displaces second shear member  78  causing second shear member  78  to shear. More particularly, by depressing retraction trigger  74 , the region of reduced cross section dimension  78 - 1  of second shear member  78  enters longitudinal chamber  26  through side wall  24 - 3  of housing  24 , such that the region of reduced cross section dimension  78 - 1  of second shear member  78  is no longer supported by side wall  24 - 3 , and whereby the spring force exerted by spring  80  overcomes the shear resistance of the region of reduced cross section dimension  78 - 1  of second shear member  78 . The shearing of second shear member  78  results in a release of spring  80  from the compressed state shown in  FIGS. 1-3  to force cannula guide block  76  to move toward the back end  24 - 2  of housing  24  to begin an initial retraction of cannula  16 , and wherein a continued decompression of spring  80  causes cannula guide block  76  to impact introducer rod guide block  64  to shear first shear member  68 , whereby beginning a simultaneous retraction of both cannula  16  and marker introducer rod  18  into chamber  26  of housing  24  of handle  14 . The simultaneous retraction of both cannula  16  and marker introducer rod  18  into handle  14  terminates after both cannula  16  and marker introducer rod  18  are completely contained in longitudinal chamber  26  of housing  24  of handle  14 , as illustrated in  FIG. 9 . 
     Alternatively, a spacing device  84  (see  FIG. 1 ) may be positioned between introducer rod guide block  64  and cannula guide block  76 . Spacing device  84  has a length along the lengthwise extent  28  such that cannula guide block  76  is in operable contact with introducer rod guide block  64  when introducer rod guide block  64  is positioned in the marker deployed position  62 , such that first shear member  68  and second shear member  78  are sheared substantially simultaneously when retraction trigger  74  displaced, resulting in a complete simultaneous retraction of both cannula  16  and marker introducer rod  18  into chamber  26  of housing  24 . 
       FIGS. 10-15  depict another embodiment of the invention, depicting a marker delivery device  110  that includes a handle  112 , cannula  16 , marker introducer rod  18 , a deployment mechanism  114  and a cannula retraction mechanism  116 . Cannula  16  and marker introducer rod  18  may be configured as previously described, and thus for brevity the full details of their operation will not be repeated here. Marker delivery device  110  functionally differs from the embodiment of marker delivery device  10 , in that deployment mechanism  114  of marker delivery device  110  may be configured to facilitate a full retraction of marker introducer rod  18  prior to beginning the retraction of cannula  16  effected by cannula retraction mechanism  116 . 
     Handle  112  is configured of an appropriate size and shape to be grasped by the hand of the user of marker delivery device  110 . Handle  112  includes a housing  118  having a front end  118 - 1 , a back end  118 - 2  and a side wall  118 - 3 , with a longitudinal chamber  120  located between front end  118 - 1  and back end  118 - 2  that is surrounded by side wall  118 - 3 . A hole  118 - 4  leads from longitudinal chamber  120  through the front end  118 - 1  of housing  118  to the exterior of handle  112 . Cannula  16  is positioned in handle  112  such that cannula  16  initially extends through hole  118 - 4  beyond the front end  118 - 1  of housing  118  prior to marker deployment. A trigger slot  118 - 5  extends through side wall  118 - 3  of housing  118 . 
     Deployment mechanism  114  is mounted to housing  118  of handle  112  and is configured to displace marker introducer rod  18  for deploying tissue marker  12  upon an actuation of deployment mechanism  114  by the user.  FIGS. 10 and 11  show deployment mechanism  114  in an initial position  121  (unused, marker not deployed),  FIG. 12  shows deployment mechanism  114  in a marker deployed position  122 ,  FIG. 13  shows deployment mechanism  114  in a marker introducer rod initial retraction position  124 , and  FIG. 14  shows deployment mechanism  114  in a marker introducer rod post-initial retraction position  126 . 
     Deployment mechanism  114  includes an introducer rod guide block  128 , a multi-stage marker deployment trigger  130 , a first shear member  132 , and an introducer rod retraction spring  133 . First shear member  132  has a region of reduced cross section dimension  132 - 1 , e.g., an annular groove, to provide a shear location. Introducer rod guide block  128  is attached to the actuation end  18 - 1  of marker introducer rod  18 , and is slidably disposed in longitudinal chamber  120  of housing  118 . Marker deployment trigger  130  is accessible at an exterior of housing  118  of handle  112 . Marker deployment trigger  130  includes an inner sleeve  130 - 1  and an outer actuator  130 - 2 . Marker deployment trigger  130  is mounted to housing  118  for siding movement along trigger slot  118 - 5 . 
       FIGS. 11-14  show various stages of movement of inner sleeve  130 - 1  and an outer actuator  130 - 2  of marker deployment trigger  130 . In the present embodiment, marker deployment trigger  130  and introducer rod guide block  128  are linked by first shear member  132 . First shear member  132  extends from inner sleeve  130 - 1  of marker deployment trigger  130  and resides in a recess  134  located in introducer rod guide block  128 . 
     Initially, as shown in  FIG. 11 , inner sleeve  130 - 1  and outer actuator  130 - 2  of marker deployment trigger  130  are linked by a drive tab  136  mounted to inner sleeve  130 - 1  that engages a drive slot  138  formed in outer actuator  130 - 2 , so that inner sleeve  130 - 1  and outer actuator  130 - 2  initially move concurrently. Drive slot  138  is defined by a downward facing lip  140  that separates drive slot  138  from an elongate introducer rod retraction slot  142 . Drive tab  136  may be hinge-mounted, e.g., by a linking membrane, to inner sleeve  130 - 1 . Drive tab  136  includes an upwardly extending protrusion  136 - 1  that is initially engaged with lip  140  in drive slot  138 . Introducer rod retraction spring  133  is positioned between cannula retraction mechanism  116  and introducer rod guide block  128  under slight compression, and more particularly, between introducer rod guide block  128  and cannula guide block  156 . 
     Referring to  FIG. 12 , an actuation of marker deployment trigger  130  by sliding outer actuator  130 - 2  of marker deployment trigger  130  toward the front end  118 - 1  of housing  118  of handle  112  causes inner sleeve  130 - 1  to move first shear member  132  longitudinally along longitudinal chamber  120  to displace introducer rod guide block  128 , which in turn displaces marker introducer rod  18  along the lengthwise extent  28  of cannula  16  to deploy tissue marker  12  from lumen  16 - 4  of cannula  16  when the marker deployed position  122  depicted in  FIG. 12  is reached. At this stage, introducer rod retraction spring  133  is being compressed. Housing  118  includes an indicator line  144 , such that when a leading edge  146  of inner sleeve  130 - 1  aligns with indicator line  144  to indicate that the marker deployed position  122  has been reached, the user is assured of a complete deployment of tissue marker  12  out of the distal end  16 - 2  of cannula  16 . 
     Also, as depicted in  FIG. 12 , when marker deployment trigger  130  is positioned at marker deployed position  122 , drive tab  136  is positioned over a retraction channel  148  in housing  118 . A further sliding of outer actuator  130 - 2  of marker deployment trigger  130  toward the front end  118 - 1  of housing  118  of handle  112  causes lip  140  forming a trailing edge of drive slot  138  to force protrusion  136 - 1  of drive tab  136  to twist forward into a deformation downward into a retraction channel  148  formed in housing  118  of handle  112 , thereby allowing lip  140  to begin to pass over protrusion  136 - 1  of drive tab  136 . At this stage, introducer rod retraction spring  133  has reached maximum compression. 
     As depicted in  FIG. 13 , the further sliding of outer actuator  130 - 2  of marker deployment trigger  130  toward the front end  118 - 1  of housing  118  of handle  112  causes lip  140  to pass over the upward protrusion  136 - 1  of drive tab  136 , thereby allowing drive tab  136  to regain its original geometry with respect inner sleeve  130 - 1 , thereby moving upwardly out of retraction channel  148 . This action occurs when the leading edge  150  of outer actuator  130 - 2  aligns with indicator line  152  of inner sleeve  130 - 1 . At this stage, introducer rod retraction spring  133  starts to decompress. Accordingly, a portion of deployment mechanism  114 , e.g., inner sleeve  130 - 1 , outer actuator  130 - 2 , drive tab  136 , lip  140 , and retraction channel  148  of deployment mechanism  114 , also functions as an introducer rod retraction mechanism  153  for marker introducer rod  18 . 
     As depicted in  FIG. 14 , with upward protrusion  136 - 1  of drive tab  136  fully released from retraction channel  148  and upward protrusion  136 - 1  of drive tab  136  being positioned in introducer rod retraction slot  142 , the decompression of introducer rod retraction spring  133  forces introducer rod guide block  128  toward the back end  118 - 2  of housing  118  (see  FIG. 10 ), and in turn marker introducer rod  18  and inner sleeve  130 - 1  are returned toward their initial positions as depicted in  FIGS. 10 and 11 . The spring force provided by introducer rod retraction spring  133  may be selected, for example, such that the impact of inner sleeve  130 - 1  with end wall  118 - 6  of housing  118  causes first shear member  132  to shear at the region of reduced cross section dimension  132 - 1 , thereby facilitating a complete retraction of marker introducer rod  18  into longitudinal chamber  120 , prior to initiating retraction of cannula  16 . 
     Alternatively, the spring force provided by introducer rod retraction spring  133  may be selected, for example, such that the impact of inner sleeve  130 - 1  with end wall  118 - 6  of housing  118  stops the retraction of marker introducer rod  18  into longitudinal chamber  120  after a partial retraction of marker introducer rod  18 , prior to initiating retraction of cannula  16 . 
     Also, as depicted in  FIG. 14 , at this stage outer actuator  130 - 2  of marker deployment trigger  130  is no longer linked to inner sleeve  130 - 1 . Thus, a subsequent extension of marker introducer rod  18  by actuation of outer actuator  130 - 2  of marker deployment trigger  130  is prevented, thereby rendering marker delivery device  110  usable for only a single tissue marker deployment. 
     Referring again also to  FIG. 10  in relation to  FIGS. 14 and 15 , cannula retraction mechanism  116  is mounted to housing  118  of handle  112  and is configured to facilitate a complete retraction of cannula  16  into longitudinal chamber  120  of housing  118  of handle  112  upon an actuation of cannula retraction mechanism  116  by the user, which most likely will occur following deployment of tissue marker  12 .  FIG. 15  shows cannula retraction mechanism  116 , with marker introducer rod  18  in marker deployed position  122 . Cannula retraction mechanism  116  is configured to prevent cannula  16  and marker introducer rod  18  from extending outside longitudinal chamber  120  of housing  118  of handle  112  after the complete retraction of cannula  16  and marker introducer rod  18  into longitudinal chamber  120 , thus facilitating the safe disposal of marker delivery device  110 , and alleviating concern about the accidental puncturing of medical personnel, or the patient, following the use of marker delivery device  110 . 
     Cannula retraction mechanism  116  includes a retraction trigger  154 , a cannula guide block  156 , a second shear member  158 , and a cannula retraction spring  160 . Retraction trigger  154  may be in the form of a push button that is accessible at the exterior of housing  118 , e.g., through a hole  118 - 7  in side wall  118 - 3 . Cannula guide block  156  is attached to the proximal end  16 - 1  of cannula  16 . Cannula guide block  156  is slidably disposed in longitudinal chamber  120  of housing  118 . In the present embodiment, second shear member  158  is formed as an extension of retraction trigger  154 . 
     Retraction trigger  154  and cannula guide block  156  are linked by second shear member  158  that is resident in a recess  162  located in cannula guide block  156 , thus holding cannula guide block  156  stationary relative to housing  118  of handle  112 . Cannula retraction spring  160  is located between the front end  118 - 1  of housing  118  and cannula guide block  156 , with cannula retraction spring  160  being in a compressed state prior to actuation of retraction trigger  154 , thus providing a preload on cannula guide block  156 . 
     An actuation of retraction trigger  154  causes a complete retraction of cannula  16  into longitudinal chamber  120  of housing  118  of handle  112 . More particularly, as shown in  FIG. 15 , initially, the region of reduced cross section dimension  158 - 1  of second shear member  158  is supported by side wall  118 - 3 , thereby providing additional support at the region of reduced cross section dimension  158 - 1 . An actuation (depressing) of retraction trigger  154  radially displaces second shear member  158  causing the region of reduced cross section dimension  158 - 1  of second shear member  158  to enter longitudinal chamber  120  through side wall  118 - 3  of housing  118 , such that the region of reduced cross section dimension  158 - 1  of second shear member  158  is no longer supported by the side wall  118 - 3 , and whereby the spring force exerted by cannula retraction spring  160  overcomes the shear resistance of the region of reduced cross section dimension  158 - 1  of second shear member  158 . The shearing of second shear member  158  results in a release of cannula retraction spring  160  from the compressed state shown to force cannula guide block  156  to move toward the back end  118 - 2  of housing  118  to complete a full retraction of cannula  16  into longitudinal chamber  120  of housing  118  of handle  112 . 
     In the event of a partial retraction of marker introducer rod  18 , or in the event that the user does not perform the previously described retraction of marker reducer rod, into longitudinal chamber  120  of housing  118  of handle  112  prior to actuation of retraction trigger  154  (as depicted in  FIG. 15 ), the continued decompression of cannula retraction spring  160  causes cannula guide block  156  to impact introducer rod guide block  128  to shear first shear member  132 , whereby facilitating a full simultaneous retraction of both cannula  16  and marker introducer rod  18  into longitudinal chamber  120  of housing  118  of handle  112 . 
     The retraction process is completed when both cannula  16  and marker introducer rod  18  are completely contained in longitudinal chamber  120  of housing  118  of handle  112 . 
     While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.