Abstract:
A needle core biopsy instrument/extractor for extracting a tissue sample via needle aspiration is disclosed. The extractor comprises a first cannula having a sharpened, beveled cutting tip and biopsy reservoir formed on it distal end. The proximal end of the first cannula is in fluid communication with a conventional syringe such that when the plunger of the syringe is retracted via manipulation o the extractor, a vacuum is created within the biopsy reservoir of the first cannula Axially mounted about the first cannula is a second cutting cannula which is designed and configured to selectively cover and uncover the distal end of the first cannula. A biasing member, preferably a spring, is provided to urge the second cannula forward about the distal end of the first cannula. The syringe, coaxially positioned first and second cannulas, and biasing member are contained within an introducer which is preferably designed and configured to be manipulated by one hand. The handle slide and lever of the device are oriented in such a way as to allow the retention of tissue via vacuum and the severing of the specimen by the second cannula to be exactly timed by cam operation.

Description:
RELATED APPLICATIONS 
     This patent application is a continuation-in-part patent application of U.S. Ser. No. 08/331,283, filed Oct. 27, 1994 now U.S. Pat. No. 5,469,860, which is a continuation-in-part of U.S. Ser. No. 08/225,594, filed on Apr. 11, 1994, now U.S. Pat. No. 5,511,556, both of which are hereby incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to tissue extraction devices, and more particularly to a hand-held device for extracting tissue samples by needle aspiration which utilizes a disposable cannula assembly. 
     BACKGROUND OF THE INVENTION 
     Biopsy devices utilizing needle aspiration to extract tissue samples are well known to those skilled in the art. Such devices are extremely useful to obtain samples of tissue suspected of being cancerous so that such tissue may be examined in order to confirm such suspected diagnosis. Such devices are frequently used when sampling suspected cancerous tissue in the lungs, breasts, and prostate, as well as other body organs. Numerous other applications have also been found for these devices. 
     Generally, such biopsy instruments extract a sample of tissue from a tissue mass by either drawing a tissue sample into a hollow needle via an external vacuum force or by severing and containing a tissue sample within a notch formed on a stylet. Typical of such devices utilizing a vacuum force are U.S. Pat. No. 5,246,011 issued to Cailouette and U.S. Pat. No. 5,183,052 issued to Terwilliger. Such devices contemplate the use of advancing a hollow needle into a tissue mass and applying a vacuum force to draw a sample into the needle and hold the same therein while the tissue is extracted. Such devices, however, fail to adequately sever and contain such tissue samples as the vacuum force may not be sufficiently strong enough to sever and hold the sample within the biopsy needle. 
     Alternatively, other prior art biopsy instruments alternatively utilize a biopsy needle with a tissue sample recovery notch formed thereon to extract a specimen, such as described in U.S. Pat. No. 3,477,423 issued to Griffith, often referred to as the TRU-CUT needle and U.S. Pat. No. 4,776,346 issued to Beraha et al. Such devices, however, have the drawback of not effectively drawing a tissue sample of sufficient size into the biopsy notch on the cannula. Accordingly, such samples extracted by such biopsy needles may not provide sufficient tissue to perform an examination and thus require additional biopsies to be taken. Additionally, such needles have the disadvantage of having to be advanced into the desired tissue site such that the needle may possibly extend beyond the tissue site, thus resulting in the recovery of an inaccurate or non-usable tissue sample or injury to adjacent organs or structures by over-penetration. 
     Further attempts in the art have tried using specially designed cannulas to enhance the cutting and recovery of tissue samples as well as combining the application of a vacuum force to draw in a tissue sample into a biopsy cavity and then cutting the tissue contained therein. U.S. Pat. No. 4,708,147 issued to Haaga discloses a cannula for a biopsy needle designed to cut a sample of tissue and then applying a vacuum to the cannula such that the tissue is drawn into the cannula and thus retained therein for recovery. Additionally, U.S. Pat. No. 3,844,272 issued to Banko discloses a biopsy device wherein a suction force, created by a vacuum, draws a sample of tissue into a receiving compartment whereby two coaxial members are rotated relative to each other so that the members essentially coact to cut off the specimen and place it into a compartment. Such combination devices, however, fail to either sufficiently isolate a sample or fail to draw in a sample of sufficient size into a biopsy compartment. Additionally, such instruments typically are difficult to maneuver and manipulate and are not necessarily accurate or effective enough to achieve their desired purpose. 
     Accordingly, there exists a substantial need in the art to provide a tissue sample extractor capable of effectively and efficiently drawing in a suitable sample of tissue and isolating the tissue sample within the biopsy instrument. Additionally, there is a need for a biopsy device that is easy to use and can effectively be manipulated by one hand in light of the fact that it is advantageous to perform such biopsy procedures wherein the physician user is allowed to have an additional free hand. Furthermore, there is need in the art to provide a tissue sample extractor that not-only provides tissue samples of sufficient size, but allows the user to take multiple tissue samples without having to repeatedly puncture and penetrate the tissue mass. Further, it would be of even greater advantage to provide a tissue sample extractor having the above-mentioned features and also utilizing a disposable cannula assembly. 
     SUMMARY OF THE INVENTION 
     The present invention specifically addresses and alleviates the above-mentioned deficiencies associated with the art. More particularly, the present invention comprises a tissue sample needle core biopsy needle specifically designed to allow the physician user to extract a sample of tissue in an effective and efficient manner while only requiring the user to use one hand to operate the device. The device comprises a first cannula having a specifically configured, sharpened, and beveled cutting tip and biopsy reservoir formed at its distal end wherein the biopsy reservoir is formed proximal to the cutting tip. The first cannula is attachable to a conventional syringe such that the biopsy reservoir is in fluid communication with the barrel piston of the syringe. Axially mounted about the first cannula is a second cutting cannula, preferably having a sharpened cutting edge formed about its distal end and a shoulder attached to its proximal end. The second cannula is designed and configured to axially telescope relative the first cannula such that the second cannula selectively covers and uncovers the distal end of the first cannula. Disposed between the proximal ends of the first cannula and second cannula is a biasing member, preferably a spring, which urges the second cutting cannula to advance axially toward the distal end of the first cannula. 
     The syringe, the coaxially positioned first and second cannulas, and biasing member are preferably mountable within a hand-held introducer. Preferably, the introducer is comprised of two parts, namely a handle and syringe retainer as well as a plunger retractor member. The handle, syringe retainer, and plunger retractor member preferably cooperate to form a gun-like structure that is easy to grasp and manipulate with one hand. The handle and syringe retainer portion includes a grippable handle and means for retaining the syringe on the syringe retainer. The plunger retractor member includes a C-shaped member designed and configured to engage the plunger of the syringe. Additionally, the plunger retractor member includes a trigger-shaped member depending therefrom to enhance the grippability and function of the extractor. Furthermore, the plunger retractor member includes a cam bar that is pivotally attached to a tip portion of the C-shaped member. The cam bar is preferably provided with a first cam slot and a second cam abutment surface sized and configured to selectively control the axial position of the second cannula about the first cannula. The second cannula is preferably attached to a shoulder at its proximal end that is specifically designed and configured to engage the first cam slot and second cam abutment surface. When the shoulder is engaged with the first cam slot, the distal end of the second cannula is maintained in a distal axial position wherein the second cannula covers the biopsy reservoir formed on the first cannula but leaves the cutting tip of the first cannula exposed. When the shoulder is allowed to advance to the second cam abutment surface, the second cannula is maintained in a distal axial position wherein the distal end of the second cannula extends just beyond the biopsy channnel of the first cannula. Additionally, the shoulder may be released altogether from the cam bar whereby the first cannula may be withdrawn from the second cannula while maintaining the second cannula resident in the patient. Such selective withdrawal of the first cannula enables multiple biopsies to be effectuated without multiple punctures of the patient&#39;s tissue mass to enhance the ability to remove multiple samples with one puncture. The cannula assembly may be rotated to position the biopsy channel a full range of 360 degrees without the need to rotate the handle. 
     In order to facilitate the selective axial positioning of the second cannula relative the first cannula, the introducer is preferably provided with a spring-activated detent or locking member and a plurality of locking apertures. Preferably, the locking member is disposed upon the handle and syringe retainer while the locking apertures are formed upon the plunger retractor member. Accordingly, the interconnection between the locking member and a respective aperture advantageously maintains the desired axial positions of the second cannula relative the first cannula whereby the second cannula is controllably axially telescoped about the first cannula. Importantly, this interconnection detachably maintains the second cannula in a distal and a proximal axial position wherein the second cannula is axially retracted about the biopsy reservoir of the first cannula. Such exposure of the biopsy reservoir via reciprocation of the second cannula from a distal position covering the biopsy channel to a proximal position and back to distal position coupled with vacuum ultimately enables a sample to be extracted by the extractor of the present invention. 
     Optionally, the shoulder moves along a guide which restricts lateral movement thereof so as to ensure that the shoulder, and consequently the second cannula, move only longitudinally, i.e., directly toward the patient, during actuation of the device. The guide thus prevents bending of the cannula assembly, particularly in an upward direction, as has been found to be common during use of such devices. 
     The guide preferably comprises an elongate member having a channel formed therein such that the shoulder slides along the channel in a manner which prevents undesirable bending of the cannula assembly. Thus, the guide effectively prevents side-to-side and upward bending of the first biopsy cannula and the second cutting cannula. 
     According to the preferred embodiment of the present invention the shoulder is configured as a disk, but may be of various other configurations, and the guide comprises a complimentary channel along which the shoulder moves as the shoulder urges the second cutting cannula to distally advance about the first biopsy cannula. 
     The beveled cutting tip of the first biopsy cannula preferably comprises a solid plug having a scalloped portion defining the sharpened bevel thereof. The scalloped portion is preferably, but not necessarily, formed via electron discharge machining, e.g., either standard or wire electron discharge machining. 
     The diameter of the solid plug of the beveled cutting tip of the first cannula is preferably either approximately equal to the outer diameter of the first biopsy cannula or it is approximately equal to the outer diameter of the second cutting cannula. Thus, the beveled cutting tip is configured to facilitate easy insertion of the cannula assembly into tissue. 
     The solid plug is preferably attached to the first biopsy cannula prior to forming the scalloped portion therein so as to provide a convenient means for handling the solid plug. Alternatively, the solid plug may be formed at the end of an elongate solid bar member and subsequently cut therefrom prior to insertion into the first biopsy cannula. 
     The beveled cutting tip is preferably attached to the first biopsy cannula via at least one of press fitting and crimping. Those skilled-in the art will appreciate that various other different means for attaching the beveled cutting tip to the first biopsy cannula are likewise suitable. For example, thermal or electrical welding, adhesive bonding, or the use of various different mechanical fasteners may be utilized. 
     The biopsy reservoir preferably comprises an obstructing member for preventing the vacuum from pulling a tissue sample from the biopsy reservoir. The obstructing member preferably comprises an inwardly bent tab formed from the first biopsy cannula at a proximal portion of the periphery of the biopsy reservoir. 
     The obstructor is preferably formed in the biopsy reservoir by forming an undercut tab at a proximal end of the biopsy reservoir and then bending the under cut tab inwardly so as to prevent tissue samples from being pulled proximally through the lumen of the first biopsy cannula by the vacuum of the syringe, but still allows vacuum to be applied to the biopsy channel. 
     An optional seal is configured to mitigate vacuum leakage intermediate the first biopsy cannula and the second biopsy cannula. The seal preferably comprises an annular member formed of a resilient material disposed about the first biopsy cannula. The annular member is preferably biased in position via the biasing member or spring. 
     Optionally, the sharpened cutting edge of the second cutting cannula comprises a beveled or slanted surface so as to afford more efficient cutting of the biopsy tissue sample. 
     The cannula assembly, comprised of the first biopsy cannula and the second biopsy cannula, and preferably further comprised of the biasing means and shoulder, preferably define an assembly which is removable from the introducer and which is disposable. Thus, after each procedure, the entire cannula assembly is easily removed from the introducer and is disposed of. A new cannula assembly is attached to the introducer prior to a subsequent use thereof. 
     In use, the introducer is initially maintained in an operable orientation wherein the second cannula is disposed in its distal axial position covering the biopsy reservoir but leaving the cutting tip of the first cannula exposed In this position, the physician user grips the introducer and forces the coaxially positioned cannulas into the tissue mass. As the coaxially positioned cannulas advance into the tissue, the cutting tip of the first cannula selectively cuts and positions the tissue over and about the biopsy reservoir covered by the second cannula. Once positioned within the target mass, the plunger retractor member of the introducer is manually withdrawn rearwardly with respect to the handle and syringe retainer portion such that the second cannula is axially retracted to its proximal axial position wherein the biopsy reservoir of the first cannula becomes exposed to the tissue mass. Simultaneously, by such retracting or withdrawing of the plunger retractor member, the plunger of the syringe is retracted, thus creating a vacuum within the syringe that is communicated via the axial lumen of the first cannula into the biopsy reservoir. Due to the created vacuum, the cut tissue is drawn into the biopsy reservoir. Having contained the tissue therein, the cam bar of the introducer may be released from the shoulder attached to the second cannula whereupon, due to the action of the biasing member, the second cannula rapidly axially advances from the first cam slot to contact the second cam abutment surfaces of the cam bar, thus causing the second cannula to axially advance to its distal axial position. During this rapid axial advancement to the distal axial position, the cutting edge of the second cannula severs the tissue sample adjacent the biopsy reservoir and captures the same within the biopsy reservoir of the first cannula. Having thus captured the tissue sample, the introducer may then be removed and the tissue sample may be examined. Alternatively, the cam bar may be completely released from the shoulder of the second cannula thereby allowing the second cannula to remain resident within the tissue mass while withdrawing the first cannula therefrom. In such arrangement, the second cannula may subsequently be used as a passageway through which other multiple tissue samples may be extracted without the need for further puncture of the patient. 
     It is therefore an object of the present invention to provide a tissue sample extractor that will effectively and efficiently remove a portion of tissue from a tissue mass. 
     Another object of the present invention is to provide a tissue sample extractor that extracts a sample of tissue by simultaneously drawing a sample of tissue into a biopsy reservoir, via a vacuum, and severing and containing the sample within the biopsy reservoir. 
     Another object of the present invention is to biopsy tissue without the need for axial advancement of a stylet into the tissue but rather, to biopsy tissue by exact placement of the covered biopsy reservoir within the tissue and eliminating any further axial movement of the same. 
     Another object of the present invention is to provide a tissue sample extractor that may be easily held and manipulated by one hand. 
     Another object of the present invention is to provide a tissue sample extractor that allows a user to take repeated tissue samples from a tissue mass without having to repeatedly puncture the tissue mass. 
     Another object of the present invention is to provide a tissue sample extractor which may be easily adapted for ultrasound, C.T. guided and/or stereotactic biopsy techniques. 
     Yet another object of the present invention is to provide a tissue sample extractor that is of simple construction, inexpensive to manufacture, and easy to use. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a tissue sample extractor according to a preferred embodiment of the present invention; 
     FIG. 2 is a perspective view of the tissue sample extractor as shown in use; 
     FIG. 3 is a perspective view of the distal end of the first biopsy cannula of the tissue sample extractor; 
     FIG. 4 is a cross-sectional view taken along line 4-4 of FIG. 3; 
     FIG. 5 is a cross-sectional view taken along line 5--5 of FIG. 3; 
     FIG. 6 is a perspective view of the distal end of the second cutting cannula of the tissue sample extractor; 
     FIG. 7 is a perspective view of the distal ends of the first biopsy cannula and the second cutting cannula wherein the first biopsy cannula is telescoped within the second cutting cannula; 
     FIG. 8 is a perspective view of the first and second cannulas wherein the second cannula selectively c overs a portion of the distal end of the first cannula; 
     FIG. 9 is a perspective view of the distal ends of the first cannula and second cannula wherein the second cannula substantially covers the distal end of the first cannula; 
     FIG. 10 is an exploded view of the tissue sample extractor; 
     FIG. 11 is a side view of the tissue sample extractor wherein the extractor is maintained in a configuration suitable for insertion into a tissue mass; 
     FIG. 11a is a cross-sectional view of the first and second cannulas corresponding to the position of the extractor as depicted in FIG. 11; 
     FIG. 12 is a side view of the extractor while positioned to obtain a sample from a tissue mass; 
     FIG. 12a is a cross-sectional view depicting the first ad second cannulas corresponding to the position of the extractor as depicted in FIG. 12 wherein the first cannula is advanced into a tissue mass; 
     FIG. 13 is a side view of the extractor being maintained in a position suitable for recovery of the tissue sample; 
     FIG. 13a is a cross-sectional view of the first and second cannulas corresponding to the configuration maintained by the extractor in FIG. 13; 
     FIG. 14 is a side view of the extractor wherein the introducer has been disengaged from the second cannula and the first cannula and introducer may be removed therefrom; 
     FIG. 14a is a cross-sectional view of the first and second cannulas corresponding to the configuration of the extractor as depicted in FIG. 14 wherein the second cannula is maintained stationery in the patient and the first cannula may be withdrawn therefrom; 
     FIG. 15 is an end view of the disk guide assembly showing the second shoulder and cam bar in phantom; 
     FIG. 16 is a perspective view of the disk guide assembly mounted to the tissue sample extractor of the present invention; 
     FIG. 17 is a side view of the disk guide assembly of FIGS. 15 and 16; 
     FIG. 18 is an enlarged side view of a seal disposed about the first biopsy cannula and urged into abutment with the second shoulder via the spring so as to prevent vacuum leakage intermediate the first biopsy cannula and the second cutting cannula; 
     FIG. 19 is an enlarged prospective view of the distal end of the first biopsy cannula and second cutting cannula showing the solid plug having a scooped out portion so as to define a sharp point, and also showing the biopsy reservoir formed in the first biopsy cannula so as to prevent biopsy tissue samples from being pulled into the lumen of the first biopsy cannula by the vacuum formed by the syringe, and also showing the slanted or beveled tip of the second cutting cannula; and 
     FIG. 20, is a side view, partially in cross-section, of the first biopsy cannula and solid plug of FIG. 19. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the drawings, and more particularly to FIG. 1, there is shown the needle core biopsy instrument or tissue sample extractor 10 embodying the principles of the present invention. The instrument/extractor 10 comprises a first biopsy cannula 12 that is shaped and configured to be coaxially mounted within second cutting cannula 14. Both first biopsy cannula 12 and second cutting cannula 14 have proximal and distal ends, wherein the proximal end of the first biopsy cannula 12 and second cutting cannula 14 have proximal and distal ends, wherein the proximal end of the first biopsy cannula 12 is attached to the first shoulder 16 and the proximal end of the second cutting cannula 14 is attached to second shoulder 18. 
     The distal ends of first cannula 12 and second cannula 14 are more clearly depicted in FIGS. 3 and 6, respectively. The distal end of first cannula 12 includes a sharpened, beveled cutting tip 44 preferably having a gradual, upwardly extending slope that forms a shovel-type scooped shape. Such scoop-like shape advantageously allows for more efficient and less traumatic tissue penetration than other cannula cutting tips currently in use. Additionally, first cannula 12 has a hollowed-out biopsy reservoir 46, also shown in FIG. 5, formed proximal the beveled cutting tip 44. The biopsy reservoir 46 preferably is formed having a semi-circular shape that advantageously allows for relatively large, generally cylindrically-shaped tissue samples to be extracted from the tissue mass. As will be discussed in more detail infra, the distal ends of the first and second cannulas 12, 14 cooperate via relative axial movement to cut and contain a tissue sample within the biopsy reservoir 46. 
     At the rear portion of biopsy reservoir 46 is a lumen or channel 13 which runs the length of first cannula 12 and allows the biopsy reservoir 46 to establish fluid communication with a conventional syringe 22 via connector 76, as shown in FIG. 1. Such fluid communication between biopsy reservoir 46 and syringe 22 enhances the ability of the extractor 10 to draw in and isolate a tissue sample due to the generation of a vacuum force by the syringe 22, which shall be discussed below. The distal end of second cannula 14 is preferably formed having a hollow, frusto-conical shape that is designed and configured to allow first cannula 12 to axially pass therethrough. The distal rim 48a of the frusto-conical portion 48 is sharpened so that distal rim 48a may cut and contain a tissue sample disposed within biopsy reservoir 46 when the rim 48a is axially passed across the biopsy reservoir 46 of the first cannula 12. 
     As shown in FIG. 7, the distal end of first cannula 12 freely passes, via axial movement, through the distal end 48 of second cannula 14. Second cannula 14 also preferably includes a barrel section 50 that serves as a sleeve to protect and contain a biopsy sample contained within a biopsy reservoir 46 when such sample is extracted from a tissue mass. The first and second cannulas may be formed in differing lengths and diameters to be utilized for a wide variety of tissue sampling applications such as beast, prostate, deep body, lung and other soft tissue biopsies. 
     In addition to being coaxially positioned relative to one another, first cannula 12 and second cannula 14 are maintained in an arrangement whereby the second cannula is constantly urged forward by biasing member 20, more clearly depicted in FIG. 1. Preferably, biasing member 20 comprises a spring that is interposed between the first shoulder 16 formed on the first cannula 12 and second shoulder 18 formed on the second cannula 14. The distally urging biasing force exerted by spring 20 forces the second shoulder 18, and hence second cannula 14, to axially advance upon the first cannula 12. 
     In order to selectively control the position of the second cannula 14 relative to first cannula 12, the extractor 10 of the present invention advantageously incorporates the use of introducer 26. In the preferred embodiment, the introducer 26 is fabricated from polymer and/or metal materials that may be sterilized or disposed of, such materials being well known to those skilled in the art. Preferably, the introducer 26 is comprised of two parts, namely a handle and syringe retainer 28 and a plunger retractor member 30, more clearly depicted in FIG. 10. The handle and syringe retainer 28 comprises a handle portion as well as structure sized and configured for detachably interconnecting with the conventional syringe 22. More specifically, the syringe retainer 28 preferably includes first and second syringe support members 58, 60 and syringe support collar 62 which engage the syringe 22 and firmly hold the syringe 22 in position. Additionally, there is provided slot 56 that is designed and configured to detachably engage with rim 22a on syringe 22 so as to further provide secure attachment with syringe retainer 28. 
     The plunger retractor member 30 of introducer 26 comprises a generally C-shaped member having a trigger member 32 depending therefrom. The rear portion of the plunger retractor member 30 has a slot 52 to receive plunger 24 on syringe 22. As will be discussed, slot 52 provides means for retracting the plunger 24 such that a vacuum is created in syringe 22 and ultimately in biopsy reservoir 46 via lumen 13 shown in FIG. 3. 
     Mounted adjacent the top portion of the retractor member 30 is a cam bar 34, which is preferably pivotally mounted 36 thereon. As more clearly illustrated in FIG. 10, the cam bar 34 includes a first can slot 38 and a second cam abutment shoulder or surface 40. Additionally, cam bar 34 has a groove 42 which allows the coaxially positioned first cannula 12 and second cannula 14 to pass therethrough. As will be discussed, the first cam slot 38 and second cam abutment surface 40 provide means for adjusting the relative axial position of second cannula 14 with respect to first cannula 12. 
     The handle and syringe retainer 28 and plunger retractor member 30 are preferably connected to one another via a sliding-type engagement. More specifically, the plunger retractor member 30 is removably mounted onto the rear portion of syringe retainer 28 such that surface 30a is received upon upper guideway 64 and flanked by elongate guide members 66 and 68. Additionally, surface 30b is received within lower guideway slot 70 such that trigger member 32 protrudes from the handle and syringe retainer 28 to form a gun-type configuration. In addition, the handle and syringe retainer 28 further include a spring-activated detent or locking member 72 to engage apertures formed on surface 30c of the plunger retractor member 30, said apertures being more clearly depicted as 74a,b in FIGS. 11, 12, 13, and 14. Such spring-activated locking member 72, when aligned with locking apertures 74a,b, provide means for positioning the handle and syringe retainer 28 with respect to the plunger retractor member 30 such that desired depths and axial positioning of the cannulas 12, 14 may be more easily attained when using the extractor 10. Importantly, spring-activated locking member 72, when aligned with locking aperture 74b, maintains the introducer 26 in an orientation that causes second cannula 14 to axially retract about biopsy reservoir 46 in a proximal axial position. 
     Having thus described the structure of the biopsy instrument/extractor 10 of the present invention, the operation of the same shall now be described with specific reference to FIGS. 11 through 14. Preparatory for use, the first and second cannulas 12 and 14 are coaxially positioned with biasing member 20 interposed between the shoulders 16 and 18. The proximal end 76 of the first cannula 12 may then be attached to the distal end of the syringe 22. As shown in FIG. 11, the syringe 22 is mounted within handle and syringe retainer 28 with plunger 24 being received in slot 52 of the plunger retractor member 30. Additionally, cam bar 34 is positioned such that second shoulder 18 is received within first cam slot 38. Additionally, the spring-activated locking member 72 is received within locking aperture 74a in such a manner that relative orientation or position of the handle 28 and plunger retractor member 30 is maintained unless otherwise manually adjusted. FIG. 11a depicts the corresponding axial position (i.e., the distal axial position) between first cannula 12 and second cannula 14 while the introducer 26 is maintained in the initial orientation depicted in FIG. 11. As illustrated, the second cannula 14 is selectively covers biopsy reservoir 46 while beveled cutting tip 44 axially protrudes or extend therebeyond. 
     While the introducer 26 and first and second cannulas 12, 14 are maintained in the orientation and relative axial position depicted in FIG. 11 and FIG. 11a, the introducer 26 is then gripped, as shown in FIG. 2, and the first and second cannulas are manually pressed or inserted into a tissue mass from which a sample is to be extracted. As mentioned above, the introducer 26, namely the combination of handle and syringe retainer 28 and plunger retractor member 30, is formed to have a gun-like shape that allows the user to manually insert the coaxially positioned cannulas 12, 14 while maintained in this distal axial position and ultimately extract a sample of tissue using only one hand. Such design advantageously allows the physician user to utilize their other hand so as to manipulate the tissue or perform some other function as may be required. 
     During insertion of the first and second cannulas 12, 14 through the tissue, the user forces both interconnected portions 28, 30 of the introducer 26 into the tissue in a direction indicated by the arrows &#34;A&#34; in FIG. 11. As should be noted, locking member 72 is engaged within aperture 74a during such insertion to prevent any relative axial movement between the handle 28 and plunger retractor member 30. Additionally, during such insertion the introducer 26 forces the cannulas 12, 14 into the tissue whereby the sharpened beveled cutting tip 44 is forced directly into the tissue, and the cutting tip 44 of the first cannula simultaneously cuts the tissue and positions the cut tissue adjacent its periphery so as to overlie the second cannula 14 adjacent the biopsy reservoir 46. 
     Once embedded within the tissue and having cut the tissue sample, the introducer 26 is manipulated such that the handle and syringe retainer 28 of the introducer 26 remains stationary while the plunger retractor member 30 is rearwardly retracted in the direction indicated by &#34;B&#34;. The plunger retractor member 30 is retracted, via manipulation of trigger member 32, such that spring-activated locking member 72 is released (i.e., overcome) from locking aperture 74a and subsequently engage with locking aperture 74b as shown in FIG. 12. Due to the engagement of the second shoulder 18 with the cam slot 30 of the cam bar 34, during such rearward movement, the second cannula 14 axially retracts relative the first cannula 12 and is disposed in its proximal axial position wherein the biopsy reservoir 46 is exposed to the tissue mass 82, as depicted in FIG. 12a. Accordingly, the axial retraction of the frusto-conical end portion 48 of second cannula 14 allows such cut tissue mass 82 to be received within the biopsy reservoir 46. Advantageously, during such retraction of the plunger retractor member 30 relative to handle and syringe retainer 23, a vacuum is generated in syringe 22 such that the previously cut tissue mass 82 is drawn downwardly into the biopsy reservoir 46 as depicted in FIG. 12a. 
     Having effectively drawn the mass of tissue 82 to be extracted into the biopsy reservoir 46, the cam bar 34 is manually raised in the direction indicated by the letter &#34;D&#34; in FIG. 13 such that the second shoulder 18 is released from first cam slot 38. Spring member 20 preferably provides sufficient force such that upon release from first cam slot 38 the second cannula 14 rapidly axially advances with sufficient force to cause the sharpened distal end 48a of the second cannula 14 to sever and retain the tissue sample 82a to be extracted within biopsy reservoir 46. Such forward axial movement of the second cannula 12 continues until the second shoulder 18 abuts the second cam abutment surface 40. The cross-sectional view depicting this distal axial position of the second cannula 14 depicted in FIG. 13a, which corresponds with the abutment between second shoulder 18 and second cam abutment surface 40, as shown in FIG. 13. As shown, in this distal axial position, the second cannula 14 securely captures the cut tissue mass 82a within the biopsy reservoir. 
     Having thus isolated the tissue sample 82a from tissue mass 82, the extractor 10, and hence first and second cannulas 12, 14, may both be removed from the tissue mass by withdrawal of the extractor 10 where the tissue sample 82a may be recovered from the biopsy reservoir 46 and subsequently examined. Alternatively, as illustrated in FIG. 14, the present invention provides that cam bar 34 may be raised even further about pivot 36 to allow second shoulder 18, and thus second cannula 14, to remain in place while introducer 26, syringe 22, and first cannula 12 may be manually withdrawn in the direction indicated by the arrow &#34;E&#34;. Advantageously, by allowing the second cannula 14 to remain stationary within tissue mass 82, the user, if desired, may make further tissue sample extractions through second cannula 14 in the manner described above. Advantageously, by using the extractor 10 of the present invention, the user will not have to make repeated punctures into the tissue which will thus facilitate the extraction of multiple samples while subjecting the subject to a less traumatic experience as compared to other devices known in the art. 
     Referring now to FIGS. 15-17, a disk guide assembly 98 comprises first 100 and second 102 disk guides having a circular channel 103 formed therein so as to slidably receive the second shoulder 18. Second shoulder 18 is thus prevented from moving side-to-side and upward by the disk guide assembly 98, particularly during the insertion process. This disk guide assembly allows rotation of the cannula assembly through 360 degrees. 
     As those skilled in the art will appreciate, it is common to exert pressure upon the tissue sample extractor of the present invention during the insertion process which tends to bend the first biopsy cannula 12 and the second cutting cannula 14 upward with respect to the device. Such bending of the first biopsy cannula 12 and second cutting cannula 14 is undesirable because it interferes with proper operation of the device. Thus, the optional disk guide assembly 98 assures reliable operation of the present invention. 
     The disk guide assembly 98 may either be formed as an integral part of the device or, optionally, may comprise an add-on assembly. Those skilled in the art will appreciate that various different configurations of the disk guide assembly 98 are likewise suitable for limiting movement of the second shoulder 18 in a longitudinal direction with respect to the first biopsy cannula 12 and second cutting cannula 14. 
     Referring now to FIG. 18, an optional seal 110 is disposed about the first biopsy cannula 12 and urged into abutment with the second shoulder 18 such that it prevents vacuum leakage intermediate the first biopsy cannula 12 and the second cutting cannula 14. The seal 110 preferably has shoulder 112 formed thereon so as to receive the distal end of the spring 120. Those skilled in the art will appreciate that various other configurations of the optional seal 110 are likewise suitable. 
     Referring now to FIGS. 19 and 20, the second cutting cannula 14 is preferably formed to have a slanted or beveled cutting tip 135 formed thereon so as to facilitate reliable cutting of the biopsy tissue samples. 
     The biopsy reservoir 46 is preferably formed to have an obstructor 128 disposed at the proximal end thereof so as to prevent vacuum from pulling the cut tissue sample into the lumen 13 of the first biopsy cannula 12. The obstructor 128 is preferably formed by forming an undercut 126 at the proximal end of the biopsy reservoir 46 and then bending the proximal protruding portion or tab 128 formed thereby in the wall of the first biopsy cannula 12 inward so as to partially obscure the lumen 13 of the first biopsy cannula 12. The tab 128 is bent sufficiently to assure that the biopsy tissue sample remains within the biopsy reservoir, yet still allows the vacuum to draw the tissue sample into the biopsy reservoir. Optionally, similar but shallower undercut 122 may be formed at the distal end of the biopsy reservoir 46 to define distal tab 124. 
     The tip 120 of the first biopsy cannula 12 is preferably formed by machining a solid plug 132, preferably via electron discharge machining, i.e., either standard or wire electron discharge machining, so as to form a scooped out portion 134 which defines a sharp point 136. 
     The solid plug 132 may either first be attached to the first biopsy cannula 12, so as to facilitate handling thereof during the machining process, or alternatively, may be formed at the end of an elongate bar and then cut therefrom prior to insertion into the first biopsy cannula 12. 
     The solid plug 132 is preferably attached to the first biopsy cannula 12 via forming at least one crimp 123 in the first biopsy cannula 12, which is pressed into a corresponding cut-out or dimple formed in the solid plug 132 or by being press fit into the first biopsy cannula 12. Alternatively, those skilled in the art will appreciate that various other different means, as discussed above, may be utilized to attached the solid plug 132 to the first biopsy cannula 12. Further, various different combinations of such means may be utilized. 
     The cross-sectional area or profile defined by the scooped out portion 134 of the solid plug 132 facilitates easy insertion into tissue, while maintaining sufficient strength to prevent premature dulling or deformation of the sharp point 136. 
     The diameter of the solid plug 132 may either be approximately equal to the outer diameter of the first biopsy cannula 12, so as to provide a substantially flush fit therewith, or alternatively may similarly be approximately equal to the outer diameter of the second cutting cannula 14. 
     According to the preferred embodiment of the present invention, the cannula assembly, comprised of the first biopsy cannula 12, the second cutting cannula 14, and preferably the spring 20, seal 110, and second shoulder 18 as well, may be formed so as to be disposable. Thus, these items are preferably formed of comparatively inexpensive materials, which is made possible due to their limited expected life. By making the cannula assembly disposable, a high degree of convenience is achieved. Thus, the cannulas do not need to be sterilized between uses, rather a new cannula assembly is installed for each use. 
     There has thus been disclosed a tissue sample extractor, with various preferred embodiments thereof, having been described in detail with the various advantages being set forth. It is understood, however, that equivalents are possible and that variations in structure may be made that fall within the underlying principles of the present invention.