the following detailed description , and the accompanying drawings to which it refers are provided for purposes of exemplifying and illustrating representative examples and embodiments of the invention only , and are not intended to limit the scope of the invention in any way , and do not exhaustively illustrate and describe all possible embodiments and configurations in which one or more features of the present invention may take physical form . all patents and patent applications cited in this specification are herein incorporated by reference as if each individual patent or patent application were specifically and individually indicated to be incorporated by reference . fig1 shows the use and insertion into a biopsy site of any one of the biopsy site marker embodiments of the invention described herein . fig1 is a perspective view of a human breast 2 having a lesion 3 from which a biopsy specimen has been removed , thereby forming a biopsy cavity 4 within the lesion 3 , into which a biopsy site marker 10 of the of the present invention is implanted . the figure shows an outer cannula 12 with the distal end thereof operatively positioned within the biopsy site 4 . the outer cannula 12 has been inserted percutaneously into the lesion 3 and a biopsy needle ( not shown ) has been passed through the outer cannula 12 and used to remove a biopsy specimen from the center of the lesion . syringe - like marker application device 13 includes a marker introduction tube or inner cannula 14 . after removal of the biopsy needle ( not shown ), the marker introduction cannula 14 has been passed through the outer cannula 12 such that inner cannula distal end 14 d is located within the biopsy cavity 4 , the marker 10 being housed within cannula 14 . piston 15 of marker applicator 13 has an extension 16 which passes through the interior of inner cannula 14 . upon depressing piston 15 , extenuation 16 pushes marker 10 outward through an opening 17 in the tip 14 d of inner cannula 14 into the cavity 4 . the outer cannula 12 may be an outer tube element of a conventional vacuum assisted large core biopsy device , which has been left in place to assist in site marker application following biopsy sample recovery . one example of a applicator syringe device 13 is described in further detail below with respect to fig5 . fig2 a , 2 b , 2 c , 2 d and 2 e show exemplary internal conformations and shapes of the sintered or porous site marker embodiments of the invention 20 a - 20 e respectively . fig2 a and 2b show schematic cross sections of a alternative porous or sintered marker body embodiments . fig2 a is a cross section of a sintered site marker embodiment 20 a . the matrix or base material 21 encloses a plurality of irregular shaped pores 22 distributed within the body 20 a , preferably throughout the body volume . the term “ sintered ” will be used to describe the porous body conformation , it being noted that conventional methods of production other than sintering may be employed to produce a material containing internal voids , pores , discontinuities , inclusions , bubbles and the like . the pores 22 may be open celled , in which the pores 22 generally intersect or communicate with one another and the marker body exterior , which may give the body surface 23 a pitted texture on the scale of the pore size . alternatively , the pores may be closed celled , in which the pores 22 generally do not intersect one another or the exterior . in the event that the pores 22 communicate with the marker exterior 23 , the matrix material 21 is preferably hydrophobic ( or treated to have hydrophobic surfaces ) to resist displacement of air entrained in pores 22 . the base or matrix composition 21 has may be of high acoustic impedance relative to the surrounding tissue ( not shown ). sintered metal material may be shaped and sintered from commercially available metallic powders comprising a metal or mixtures of : metals , using conventional sintering and forming techniques to produce body of selected shaped , and selected pore size and surface texture , so as to enhance acoustic reflectivity . the porosity of the sintered metal provides an irregular surface texture as well as internal voids . a suitable bio - compatible material is sintered 316l stainless steel , and suitable sintered stainless steel stock is commercially available in various forms , for example from the mott corporation . the sintered stock may be economically cut and shaped by conventional methods . sintered stainless steel stock is commercially available with controlled pore size , selectable over a range of pore sizes . the pores 22 of the sintered body 20 a may vary over a range of pore sizes , and is typically from about 1 micrometer to 100 micrometers and preferably from about 5 micrometers to 40 micrometers . in addition to sintered metal , alternative bio - compatible , impedance materials may be included or substituted , such as ceramics , metal oxides , polymers or composites / mixtures of these materials , which may be configured to have a generally distributed internal porosity and porous surface texture . thus , the marker body 20 a may comprise a matrix or base composition 21 which has an acoustic impedance close to that of the tissue at the marked body site , since the air or other gas within the pores or internal spaces 22 provides a dramatic contrast to the matrix material 21 . suitable bio - compatible materials include polyethylene , polytetrafluoroethylene , pebax ( made by autochem corp . ), and the like . such porous materials may be formed by conventional methods , such as heat bonding of polymer powders , extrusion and the like . fig2 b is a schematic cross section of an alternative site marker embodiment 20 b . the matrix or base material 24 encloses a plurality of inclusions , suspended particles or bubbles 25 distributed within the body 20 b , preferably throughout the body volume . the inclusions 25 may be low - density or gas - filled particles , such as foamed - in - place bubbles , micro - beads , expanded beads , and the like , which have an acoustic impedance substantially lower than the matrix material 24 . the matrix material 24 may as in the example of fig2 a . fig2 c and 2d show exemplary shapes of the sintered or porous site marker embodiments of the invention 20 c and 20 d respectively . fig2 c shows schematically a cylindrical sintered marker 20 c . the marker 20 c comprises a generally cylindrical body having a diameter d and length 1 . the body may have diameter d of from 0 . 5 to 5 mm , and preferably about 1 . 5 mm . the length i may be from about 1 diameters to about 10 diameters , and preferably from about 5 to 7 diameters . this biopsy site marker produces a distinct , recognizable , marker image of artificial appearance when implanted at a depth of about 2 to 4 cm in human breast tissue , and visualized by a commercially available accuson 128 us imaging system with an l7 transducer . fig2 d illustrates a marker body 20 d having a polyhedral form of multiple intersecting flat surfaces 26 , 27 and 28 . fig2 e shows a cruciform shaped marker 20 e having cruciform cross - section having four longitudinal fin - like portions 29 , which may be aligned at right angles to one another and joined at the longitudinal central axis 30 providing a selectable number of side facets ( e . g ., hexagonal cross - section ). optionally , medial web portions 31 may span laterally and join between adjacent fins 29 , the webs 31 preferably being aligned perpendicularly to the fins 29 . in the example shown , there are four such web portions 31 positioned at about mid - length of the body 20 e , so that each fin 29 is joined by a pair of webs 31 , one on each side , to each adjacent fin . thus , the planes of the intersecting fins and webs form a pattern of eight mutually - perpendicular “ corner reflectors ” 32 . the length i and characteristic cross - section dimension c may be as described with respect to the embodiments of fig2 c and 2d . fig3 illustrates yet another alternative where the marker body is shaped to have the form , under ultrasound or radiological visualization , preferably both , of a familiar symbol or letter , to by easily recognizable as an artificial shape which is the lower - case greek letter gamma ( γ ), which when visualized in a biopsy site bears a resemblance to a familiar breast - cancer - awareness symbol . fig4 shows schematically an alternative coil marker 30 of the invention . the marker 30 comprises a generally helical coil - like body formed from one or more lengths of fine wire and / or fiber 31 . the coil 30 has a generally cylindrical overall form . as with the other biopsy site marker embodiments of the invention , the optimum dimensions of the coil shaped marker embodiment will depend on such factors as the type of visualization system used , its imaging resolution , and the physical nature of the biopsy tissue region . the coil length i and diameter d may be of a range of sizes , selected so as to be large enough to provide a distinct , recognizable ultrasound marker image within the tissue biopsy site , and small enough to avoid masking or obscuring diagnostically important tissue features . for example , the coil diameter d may be from 0 . 5 to 5 mm , and preferably about 1 . 5 mm . the coil length i is typically from about 1 coil diameters to about 10 coil diameters , and preferably from about 5 to 7 coil diameters . the helical turns of the coil provide a body surface contour including a outer helical groove 32 and inner helical groove 33 on the coil surfaces ( more than one such groove for a multiple helix ). the grooved coil body surface includes a plurality of lobes and crevices on the exterior of the coil which enhance acoustic reflectivity . in addition the similarly lobed internal surfaces of the coil provide additional reflectivity . optionally , the coil may be given a “ frosted ” or textured surface , such as by particle blasting in the manner of the spheroid marker described above . a uniform coil embodiment has a shape which is markedly artificial in appearance under conventional visualization methods , and is not easily confused tissue features of biological origin . the coil may comprise a fine wire 31 of a material of high acoustic impedance relative to the tissue of the site , and may optionally be radio - opaque . suitable materials are biologically compatible metals , such as stainless steel , titanium , platinum , palladium , alloys thereof and the like . the coil may alternatively comprise a composite of different materials , such as a composite of metal and polymeric materials . the coil may be wound about a central core of the same or different composition . coil stock of suitable material , helical form and diameter is available commercially , and may be cut to a selected length by conventional means . a suitable material is 316 l stainless steel surgical embolization coil currently used in arterial embolism repair procedures , e . g ., cook 4 mm diameter embolization coil mwce - 25 - 2 . 5 - 4 of 316l stainless steel and dacron . other suitable embolization coil stock is available in a range of coil diameters . this biopsy site marker produces a distinct , recognizable marker image as implanted at a depth of about 2 to 4 cm in human breast tissue , when visualized by a commercially available accuson 128 us imaging system with an l7 transducer . fig5 shows schematically the alternative spheroid marker 40 of the invention having a generally spherical body 40 . note that the porous or sintered marker embodiments of fig2 a - 2d may be spherical also . however , the embodiment of fig5 is a non - porous example , and the biopsy site marker 40 comprises a high acoustic impedance , biologically compatible material , such as 316 l stainless steel and titanium , or radiopaque metals such as platinum , palladium , or the like . non - spherical shaped bodies may be used , however , metallic spheres of suitable materials are readily commercially available , and have a shape which is markedly artificial in appearance under conventional visualization methods , i . e ., not easily confused tissue features of biological origin . the generally spherical body may have a diameter d selected so as to be large enough to provide a distinct , recognizable ultrasound marker image within the tissue biopsy site , and small enough to avoid obscuring tissue features . as with the other biopsy site marker embodiments of the invention , the optimum size of the sphere will depend on such factors as the type of visualization system used , its imaging resolution , and the physical nature of the biopsy tissue region . for example , the sphere diameter d is typically be from about 1 mm to about 4 mm , and preferably from about 1 . 5 mm . the spherical body 40 may include a pitted , matte , peened or frosted surface texture 41 , which may be produced by conventional particle blasting or peening techniques . for example , the sphere may be blasted with glass beads of about 100 micrometer diameter to produce a frosted surface . in another example , the sphere may be blasted with aluminum oxide abrasive particles of about 25 micrometer diameter to produce a frosted surface . the frosted surface 41 thus produced provides enhanced acoustic reflectivity in comparison to the untreated , smooth sphere . other conventional texturing , pitting or faceting methods may alternatively be used to produce a frosted or irregular surface texture . this biopsy site marker produces a distinct , recognizable marker image of artificial appearance when implanted at a depth of about 2 to 4 cm in human breast tissue , and visualized by a commercially available acuson 128 us imaging system with an l7 transducer . fig6 shows schematically in cut - away section an exemplary marker applicator device 50 configured to be operated in association with a conventional vacuum assisted large core biopsy device 6 . the dimensional size of the applicator device ( particularly the inside diameter ) may be adjusted to correspond to the selected diameter or characteristic dimension of the biopsy site marker to be deposited . in this connection it should be understood that the biopsy markers of the invention can be used without this applicator , and can be deposited in accordance with the various methods and techniques utilized in the state of the art . the applicator 50 comprises an elongated cylindrical body 52 which has an outer diameter selected so that it fits , and may be inserted through , the outer cannula 7 of vacuum assisted large core biopsy device 6 . as shown in fig6 the outer cannula 7 is inserted through the biopsy incision into the biopsy cavity 4 previously formed in the patient &# 39 ; s tissue site 8 , e . g ., a human breast in the case of a breast biopsy . the cylindrical body 52 has an interior cavity and a piston 54 that fits and slides back and forth in the elongated cylindrical body 52 . the proximal end of the outer cannula 7 may be provided with rectangularly shaped handle 56 the orientation of which indicates to the operator the orientation of the opening 9 provided in the distal end of the cannula 7 . the cylindrical body 52 may have an enlarged finger disk or handle 57 at its outer ( exterior to the patient ) end which permits a user ( not shown ) to operate or move the piston 54 within the cylinder 52 of applicator 50 . the orientation of the elongated finger disk 57 indicates the orientation of the opening 58 of body 53 adjacent its other , closed end 59 ( internal within biopsy cavity ). the opening 58 is configured to form a ramp in the side of the tube 52 . in this connection it should be understood that the selected dimensions of the tube 52 are coordinated with the dimensions of the piston 54 and with the cannula 7 of the vacuum assisted large core biopsy device 6 , thus permitting the tube 52 to both fit within cannula 7 and to contain one or more markers of the invention 10 within the inside diameter of cylinder 52 . the cylinder or tube 52 and the piston 54 may be made from any appropriate medical grade plastic material , such as high density polyethylene or pebax , made by the autochem corporation . in one method of implanting the biopsy markers 10 of the present invention , the tube 52 is loaded with one or more of markers 10 . the markers 10 may be any of the embodiments of the invention described above , and is shown schematically as a cylindrical object . optionally , in addition to the markers 10 , pellets composed of various other materials may be inserted along with one of the embodiments of the biopsy markers of the present invention described herein . for example , gelatin pellets of the type disclosed in our above referenced co - pending application ser . no . 09 / 343 , 975 may be inserted in conjunction with the biopsy markers 10 of the present invention . with the markers 10 in the tube 52 and the tube 52 and cannula 7 inserted into the biopsy site 4 , the opening 58 in the cylinder 52 is moved into alignment with the opening or port 9 of the in the internal end of cannula 7 of biopsy sampler 6 . the piston 54 is pressed inward by the operator so that the marker or markers 10 are expelled from the tube 52 through the ramp shaped opening 58 as the piston 54 is pushed into the cylinder or tube 52 . the markers 10 are thereby extruded through opening 59 and port 9 into the biopsy cavity 4 . the applicator 50 and biopsy device 6 are subsequently withdrawn . fig7 shows schematically an alternative marker 60 of the invention including one or more optional tissue - engaging or haptic elements 62 for resisting migration of the marker from the biopsy site . an exemplary cylindrical marker body 10 is shown , although each embodiment of the biopsy site marker of the invention described above may optionally comprises one or more such tissue engaging structures . the haptic elements 62 may comprise an wire - like material fixed to the marker body 10 at the proximal haptic end 64 and extending outward from the marker body 10 . the haptic 62 may be looped back at its hook - like terminal end 66 . the haptic 62 assists in resisting , migration of the marker from the biopsy cavity , during initial placement , i . e ., it engages the adjacent tissue to resist being sucked back towards the applicator when the applicator is withdrawn . the haptic also resists migration during later movement , flexure or manipulation of the tissue surrounding the biopsy site ; such as when a patient &# 39 ; s breast is decompressed upon removal from a mammography device . optionally , the marker body 10 may include an adhesive component 68 coated onto its surface to cause the marker body to adhere to adjacent tissue within the biopsy site . fig8 shows schematically the alternative marker 70 of the invention including an encapsulating element 72 and optional adhesive layer or component 74 , for resisting migration of the marker within the tissue . an exemplary cylindrical marker body 10 is shown , although each of the biopsy site marker of the invention described above may optionally comprise a pellet - shaped encapsulating element . the pellet - shaped encapsulating element 72 is disposed surrounding the marker body 10 and may fully or partially enclose the marker body . the encapsulating element 72 may be of lower impedance than the metallic marker body 10 . suitable materials are gelatin or reconstituted collagen material , polymers , or mixtures or composites thereof . an optional adhesive component 74 is shown coating the external surface of the encapsulating element , but may be included within the composition the encapsulating element 72 . fig9 a illustrates an alternative device 80 for delivering markers to a biopsy site which includes an elongated tube 81 , a handle 82 on the tubes proximal end and a closed distal end having a plurality of leafs or petals 83 as shown in more detail in fig9 b . as shown in fig9 c , the petals 83 open up to allow a marker 84 to be discharged into the biopsy site 85 as shown in fig9 c . the device 80 has an elongated plunger or piston 86 slidably disposed within the tube 81 for pushing one or more markers 84 through the petalled distal end by pressing on the knob 87 on the proximal end of the shaft 86 . the orientation of the body 88 on the shaft 86 gives the operator an indication of the orientation of the shaped distal end 89 . fig1 illustrates an alternative marker 90 which has an elongated cylindrically shaped body of gel 91 surrounded with a metallic band 92 which is preferably formed of radiopaque material . the band 92 may conpletely or only partially surround the body of gel 91 . in any of the above - described embodiments of the invention , the marker body ( and / or the optional encapsulating element ) may include an adhesive component to cause the marker body ( or encapsulating element ) to adhere to adjacent tissue within the biopsy site . the adhesive component may comprise a biocompatible adhesive , such as a polyurethane , polyacrylic compound , polyhydroxymethacrylate , fibrin glue ( e . g ., tisseal ™), collagen adhesive , or mixtures thereof . while particular forms of the invention have been illustrated and described , it will be apparent that various modifications can be made without departing from the spirit and scope of the invention . accordingly , it is not intended that the invention be limited to the specific embodiments illustrated . it is therefore intended that this invention to be defined by the scope of the appended claims as broadly as the prior art will permit , and in view of the specification if need be .
the invention is directed biopsy site markers and methods of marking a biopsy site , so that the location of the biopsy cavity is readily visible by conventional imaging methods , particularly by ultrasonic imaging . the biopsy site markers of the invention have high ultrasound reflectivity , presenting a substantial acoustic signature from a small marker , so as to avoid obscuring diagnostic tissue features in subsequent imaging studies , and can be readily distinguished from biological features . the several disclosed embodiments of the biopsy site marker of the invention have a high contrast of acoustic impedance as placed in a tissue site , so as to efficiently reflect and scatter ultrasonic energy , and preferably include gas - filled internal pores . the markers may have a non - uniform surface contour to enhance the acoustic signature . the markers have a characteristic form which is recognizably artificial during medical imaging . the biopsy site marker may be accurately fixed to the biopsy site so as to resist migration from the biopsy cavity when a placement instrument is withdrawn , and when the marked tissue is subsequently moved or manipulated .