fig1 to 4 illustrate a biopsy marking apparatus 10 according to the invention , which is capable of the percutaneous placement of a radiopaque marker at the location of a tissue biopsy . the biopsy marking apparatus 10 comprises an introducer 12 and a radiopaque marker 14 ( fig2 ) contained within the introducer 12 . the introducer 12 includes a handle 16 having a hollow interior 18 . the handle 16 comprises a grip portion 20 from which extends a tapered nose portion 22 . the grip portion 20 defines a rear opening 24 that provides access to the hollow interior 18 . a pair of detents 26 are formed in the grip portion 20 near the rear opening 24 . channels 28 are formed on the interior surface of the grip portion 20 and extend from the rear opening 24 to the detents 26 . the nose portion 22 comprises a guide passage 30 extending from the tip of the nose portion 22 to the hollow interior 18 of the handle 16 . the guide passage 30 decreases in diameter inwardly from the tip of the nose portion to form a cannula seat 32 . alternatively , the diameter of the guide passage 30 may be substantially equal to or slightly smaller than the outer diameter of a cannula 34 , which in any case is press - fit within the cannula seat 32 . as is customary , the cannula is formed with a hollow interior 36 and a sharpened tip 38 . a stylet 40 comprising a shaft 42 and a base 44 is received within the hollow interior 18 of the handle 16 in a manner such that the shaft 42 extends through the guide passage 30 and into the cannula interior 36 and the stylet base lies within the hollow interior 18 . a plunger 50 comprises a cylindrical body 52 from which extend a pair of catches 54 at diametrically opposed positions . the cylindrical body 52 is sized so that it is slidably received within the rear opening 24 of the handle 16 , where it is so oriented with respect to the handle that the catches 54 are aligned with the guide channels 28 . it will be recognized that the foregoing construction provides a biopsy marking apparatus which may be preassembled as a unit and prepackaged , all under sterile conditions , thereby affording the practitioner substantially greater convenience and reliability . such a construction also permits use of a narrower cannula , which may be of 14 gauge or smaller . in operation , the introducer 12 begins in the ready condition shown in fig4 . in this condition , the stylet shaft is received within the cannula but does not extend to the cannula tip 38 , thereby forming a marker recess 46 within the cannula 34 , the radiopaque marker 14 is disposed within the marker recess 46 , and the plunger 50 is in a position relative to the handle 20 in which the catches are outside the handle ; that is , they are not received within the detents 26 . however , the plunger 50 is so oriented with respect to the handle that the catches 54 are aligned with the guide channels 28 . with the introducer in the ready condition , the cannula is positioned so that its tip is at or near the location of a tissue mass where a biopsy has been taken . preferably , the cannula tip is positioned by using imaging systems . the cannula tip 38 can be designed for enhanced visibility using common imaging systems , such as cat scan , ultrasonography and mammography . suitable cannula tips are disclosed in u . s . pat . no . 5 , 490 , 521 , issued feb . 13 , 1996 to r . e . davis and g . l . mclellan , which is incorporated by reference . ultrasound enhancement technology is also disclosed in u . s . pat . no . 4 , 401 , 124 , issued aug . 30 , 1983 to j . f . guess , d . r . dietz , and c . f . hottinger ; and u . s . pat . no . 4 , 582 , 061 , issued apr . 15 , 1986 to f . j . fry . once the cannula is positioned at the desired location , the plunger 50 is moved from its first or ready condition as illustrated in fig1 to 4 to a second or discharged condition in which the catches 54 are received within the detents 26 to lock the plunger 50 in the discharged condition and the stylet shaft extends beyond the cannula tip 38 . the catches 50 and detents combine to function as a latch for locking the plunger in the discharged condition . as the plunger 50 is moved from the ready condition to the discharged condition , the plunger 50 drives the stylet base 44 forward to advance the stylet shaft 42 within the cannula interior 36 . as the stylet shaft 42 is advanced , the radiopaque marker 14 is ejected from the marker recess 46 through the cannula tip 38 and into the tissue at the biopsy location . it is preferred that the stylet shaft 42 be sized in a manner such that when the plunger 50 is in the discharged condition the stylet shaft 42 extends beyond the cannula tip 38 to ensure the complete ejection of the radiopaque marker 14 from the marker recess 46 . the extension of the stylet shaft 42 beyond the cannula tip 38 also prevents the radiopaque marker 14 from being drawn back into the marker recess upon the removal of the introducer 12 from the tissue mass , which can occur as the tissue mass collapses and is drawn towards and into the cannula by the resilient nature of the tissue mass and the creation of a vacuum by the cannula as it is withdrawn from the tissue . the rate at which the plunger 50 is moved from the ready condition to the discharged condition is preferably manually controlled by the user to control the rate at which the marker 14 is ejected into the tissue mass . manual control of the ejection rate of the radiopaque marker provides the user with the ability to adjust the position of the cannula tip as the marker is being ejected and thereby permits additional control of the final location of the marker within the tissue mass . in other words , “ on - the - fly ” adjustment of the cannula tip during positioning of the marker 14 enables a more accurate placement of the marker . the biopsy marking apparatus 12 may be placed in a safety condition ( not shown ) before packaging or use by rotationally orienting the plunger 50 with respect to the handle 16 so that the catches 54 are out of alignment with the guide channels 28 , whereby the plunger cannot be depressed or advanced within the handle . it will be apparent that the marking apparatus can be placed in the ready condition previously described simply by rotating the plunger relative to the handle until the catches 54 are aligned with the guide channels 28 . it will also be apparent that the biopsy marking apparatus 10 may incorporate or be fitted with any one of several known trigger devices , some of them spring - loaded , for advancement of the plunger 50 . such a trigger device is disclosed , for example , in u . s . pat . no . 5 , 125 , 413 , issued jun . 30 , 1992 to g . w . baran . it should be noted that as a variation of the foregoing procedure the cannula employed during the biopsy procedure might be left in place with its tip remaining at the site of the lesion . the introducer 12 of the present invention would then be directed to the site through the biopsy cannula or , alternatively , the marker 14 of the present invention would be introduced to the biopsy cannula and ejected from its tip into the tissue mass by fitting the biopsy cannula to the introducer 12 in place of the cannula 34 . the radiopaque marker 14 used in combination with the introducer 12 to mark the location of the tissue biopsy should not only be readily visible using contemporary imaging techniques but it should not migrate within the tissue from the position in which it is initially placed . fig6 to 15 disclose various embodiments of radiopaque markers 14 that are highly visible using contemporary imaging techniques and are resistant to migration in the tissue . fig6 illustrates a first embodiment 60 of a radiopaque marker comprising a coil spring 62 from which extend radiopaque fibers 64 . the coil spring 62 is preferably made from platinum or any other material not rejected by the body . the coil spring 62 is wound to effectively form a hollow interior comprising one or more air pockets , which are highly visible using contemporary ultrasound imaging techniques . the radiopaque fibers 64 are preferably made from dacron , which is also highly visible using current imaging techniques . the radiopaque marker 60 is highly visible using any of the commonly employed contemporary imagining techniques because of the combination of reflective surfaces formed by the coils , the hollow interior and the air pockets of the coil spring 62 , as well as the radiopaque fibers 64 . the coil spring 62 is pre - shaped prior to being loaded into the marker recess 46 so that it tends to form a circular shape as shown in fig6 after it is ejected from the marker recess 46 . the circular shape tends to resist migration within the tissue . fig7 illustrates a second embodiment 70 of a radiopaque marker having a star - burst configuration comprising a core 72 with multiple fingers 74 extending from the core . fig8 illustrates a third embodiment 80 of a radiopaque marker that is similar to the star - burst marker 70 in that it comprises a core 82 from which extend three fingers 84 . each of the fingers includes radiopaque fibers 86 , which are preferably made from dacron or a similar material . fig9 illustrates a fourth embodiment 90 of a radiopaque marker having a generally y - shaped configuration comprising an arm 92 from which extend diverging fingers 94 . the arm and fingers 92 , 94 are preferably made from a suitable resilient metal such that the fingers can be compressed towards each other and the entire radiopaque marker 90 stored within the marker recess 46 of the cannula . upon ejection of the marker 90 from the marker recess 46 into the tissue mass , the fingers 94 will spring outwardly to provide the marker 90 with an effectively greater cross - sectional area . in addition to providing the marker 90 with an effectively greater cross - sectional area , the tips of the fingers 94 , together with the free end of the arm 92 , effectively form points of contact with the surrounding tissue mass that help to anchor the marker 90 in its release condition to prevent migration through the tissue mass . fig1 illustrates a fifth embodiment 100 of a radiopaque marker having a wire - form body in a horseshoe - like configuration comprising a rounded bight portion 102 from which extend inwardly tapering legs 104 , each of which terminate in curved tips 106 . the entire marker 100 preferably has a circular cross section defining a hollow interior 108 . the hollow interior provides for the trapping of air within the marker 100 to improve the ultrasound characteristics of the marker 100 . the curved bight portion 102 and legs 104 preferably lie in a common plane . however , the tips 106 extend away from the legs 104 and out of the common plane so that the tips 106 will better function as anchors for the tissue that prolapses about the tips 106 once the marker 100 is ejected from the marker recess 46 and the introducer 12 is withdrawn from the tissue mass . fig1 illustrates a sixth embodiment 110 of a radiopaque marker that is similar to the horseshoe - like fifth embodiment marker 100 in that it comprises a bight portion 112 from which extend legs 114 , which terminate in tips 116 . the legs 114 of the marker 110 are crossed relative to each other , unlike the legs of the marker 100 , providing the marker 110 with an effectively larger cross - sectional diameter . the tips 116 are oriented at approximately 90 ° relative to the legs 114 to form anchors . the marker 110 also has a hollow interior 118 for enhanced radiopaque characteristics . though , as illustrated in fig1 , the tips 116 of the marker 110 are oriented at approximately 90 ° with respect to the legs 114 , it is within the scope of the invention for the tips 116 to extend at substantially any angle with respect to the legs 114 . the tips 116 also need not extend away from the legs in the same direction . for example , the tips 116 could extend in opposite directions from the legs 114 . fig1 illustrates a seventh embodiment 120 of a radiopaque marker having a generally helical configuration comprising multiple coils 122 of continuously decreasing radius . the helical marker 120 is preferably made from a radiopaque material and has a hollow interior 124 to enhance its radiopaque characteristics . the decreasing radius of the coils 122 provides the marker 120 with multiple anchor points created by the change in the effective cross - sectional diameter along the axis of the helix . in other words , since the effective cross - sectional diameter of each coil is different from the next and each coil is effectively spaced from adjacent coils at the same diametric location on the helix , the tissue surrounding the marker 120 can prolapse between the spaced coils and each coil effectively provides an anchor point against the tissue to hold the marker 120 in position and prevent its migration through the tissue mass . fig1 illustrates an eighth embodiment 130 of a radiopaque marker comprising a cylindrical body 132 in which are formed a series of axially spaced circumferential grooves 134 . the spaced grooves 134 form a series of ridges 136 therebetween on the outer surface of the cylindrical body 132 . the cylindrical body 132 preferably includes a hollow interior 138 . the alternating and spaced ridges 136 and grooves 134 provide the marker 130 with a repeating diameter change along the longitudinal axis of the cylindrical body 132 . as with the helical marker 120 , the grooves 134 between the ridges 136 provide an area in which the tissue surrounding the marker 130 can prolapse thereby enveloping the ridges 136 , which function as anchors for preventing the migration of the marker 130 in the tissue mass . fig1 illustrates a ninth embodiment 140 of a radiopaque marker comprising a cylindrical body 142 having an axial series of circumferential grooves 144 whose intersections with adjacent grooves form ridges 146 . the cylindrical body 142 preferably includes a hollow interior 148 . an anchor 150 extends from the cylindrical body 142 . the anchor 150 comprises a plate 152 connected to the cylindrical body 142 by a wire 154 . the grooves 144 and ridges 146 of the maker 140 provide anchors in the same manner as the grooves 134 and ridges 136 of the marker 130 . the anchor 150 further enhances the non - migrating characteristics of the marker 140 by permitting a large portion of the surrounding tissue mass to prolapse between the plate 150 and the cylindrical body 142 . the fifth through the ninth embodiments all preferably have a wire - form body . the various wire - form body shapes can be formed by stamping the shape from metal stock or the bending of a wire . it should be noted that virtually all of the embodiments of the radiopaque marker described as being hollow can be made without a hollow interior . similarly , those without a hollow interior can be made with a hollow interior . the hollow interior improves the ultrasound characteristics of the particular marker beyond the inherent radiopaque and ultrasound characteristics attributable to the marker shape and material . in practice , the use of the hollow interior is limited more by manufacturing and cost considerations rather than by performance . also , the shape of each marker can be altered to improve or enhance its non - migrating characteristics by adding an express anchor such as that disclosed in connection with the marker 140 or by modifying the marker to provide more anchor points as may be compatible with the basic configuration of the marker . the combination of the enhanced radiopaque characteristics of the markers and the enhanced non - migrating features result in markers that are superior in use for identifying biopsy location after completion of the biopsy . the ability to accurately locate the biopsy site greatly reduces the amount of tissue that must be removed in a subsequent surgical procedure if the biopsy is cancerous . additionally , the marker further enhances the ability to use percutaneous methods for removing the entire lesion , reducing the trauma associated with more radical surgical techniques . the radiopaque markers described and illustrated herein are smaller than the staple - type clip and embolization coil used heretofore , thereby permitting a cannula of 14 gauge or less . while the invention has been specifically described in connection with certain specific embodiments thereof , it is to be understood that this is by way of illustration and not of limitation , and the scope of the appended claims should be construed as broadly as the prior art will permit .
a biopsy marking apparatus for placing a radiopaque marker at the location of a percutaneous biopsy . the biopsy marking apparatus comprises an introducer in combination with a radiopaque marker . the introducer ejects the radiopaque marker at the location of the biopsy . the introducer is configured to completely eject the radiopaque marker and prevent it from being subsequently drawn into the introducer as the introducer is removed from the biopsied tissue mass . the radiopaque marker has enhanced radiopaque characteristics and enhanced non - migration characteristics .