Abstract:
A surgical apparatus for removing tissue, which includes a housing, an elongated body which extends from the housing and forms an opening at a distal end, the elongated body further forming a tissue receiving cavity in communication with the opening, a cutting member operatively associated with the housing and movable transverse to the elongated body in proximity to the opening, and a tissue retaining member positioned in proximity to the opening and the cutting member, the retaining member being selectively movable from a retracted position to a deployed position, wherein when positioned in the deployed position, the tissue retaining member obstructs at least a portion of the opening at the distal end of the elongated body. A method is also provided for surgically removing tissue including the steps of positioning a tissue removing instrument including an elongated housing having a tissue receiving cavity at a distal end, a first tissue cutting surface longitudinally movable relative to the elongated housing distal end, an obturator having a sharpened distal end portion such that the sharpened end portion is positioned adjacent the tissue to be removed and a second tissue cutting surface transversely movable relative to the elongated housing, removing the obturator from the elongated housing, coring the tissue to be removed, severing the cored tissue from the surrounding tissue with the second cutting surface, and removing the severed tissue from the patient.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]    This application is a Continuation of U.S. patent application Ser. No. 09/495,113 filed Feb. 1, 2000 which is a Continuation of U.S. patent application Ser. No. 09/178,730 filed Oct. 26, 1998 which is a Continuation of U.S. patent application Ser. No. 08/525,450 filed Sep. 8, 1995, now U.S. Pat. No. 5,857,982.  
     
    
     
       BACKGROUND  
         [0002]    1. Technical Field  
           [0003]    The present disclosure relates to apparatus and method for biopsy/removal of tissue from within a patient&#39;s body. More particularly, the present disclosure relates to apparatus and method for breast tissue biopsy/removal.  
           [0004]    2. Background of Related Art  
           [0005]    Numerous surgical instruments have been developed for performing minimally invasive surgical procedures. Such procedures greatly reduce recovery time for the patients in comparison to conventional open surgical procedures. Minimally invasive instruments also reduce damage to tissue surrounding the operative site. The enormous success of such instruments in procedures such as gall bladder removal and hernia repair has led to increased development of minimally invasive instruments for other operative procedures as well.  
           [0006]    One area where minimally invasive instruments have been utilized is in performing biopsies of target breast tissue to determine whether the tissue is malignant or benign. As is quite often the case, lesions within the breast are non-palpable, therefore, making cancerous lesions more difficult to diagnose. Early diagnosis of suspect lesions in a patient&#39;s breast, however, has been greatly enhanced through the development of imaging machines, for example, stereotactic mammography imaging systems (hereafter referred to as “stereotactic machines”). In such machines, an elongated prone supporting examining table for x-ray mammography is provided with a central breast receiving aperture, through which the patient&#39;s pendulant breast is exposed to a horizontal beam of x-rays from a source which is angularly movable through an arc centered on the patient&#39;s breast. Thus, x-ray projection through more than 360 degrees around the patient&#39;s body is possible. An example of such a stereotactic machine is disclosed in U.S. Pat. No. 5,289,520 which issued on Feb. 22, 1994 to Pellegrino et al., the contents of which are hereby incorporated by reference.  
           [0007]    Fine needle biopsy is also facilitated by stereotactic machines. In such procedures, doctors can take advantage of the precision instrument positioning and suspect tissue position locating capabilities of the machine&#39;s imaging systems, to precisely insert a biopsy needle and retrieve a tissue sample.  
           [0008]    However, minimally invasive instrumentation to efficiently and efficaciously biopsy and/or remove tissue so as to potentially avoid open surgical techniques are not readily available. The present disclosure provides minimally invasive apparatus which are relatively easy to use and inexpensive to reliably manufacture and use. The present disclosure also provides apparatus and method(s) for removing breast tissue using minimally invasive techniques.  
         SUMMARY  
         [0009]    The present disclosure provides a surgical apparatus for removing tissue, which includes a housing, an elongated body which extends from the housing and forms an opening at a distal end, the elongated body further forming a tissue receiving cavity in communication with the opening, a cutting member operatively associated with the housing and configured to cut tissue in proximity to the opening in a direction transverse to the elongated body, and a tissue retaining member positioned in proximity to the opening and the cutting member, the retaining member being selectively movable from a retracted position to a deployed position, wherein when positioned in the deployed position, the tissue retaining member obstructs at least a portion of the opening at the distal end of the elongated body.  
           [0010]    Preferably, the tissue retaining member is operatively connected to the cutting member such that movement of the cutting member across (or transverse to) the elongated body causes movement of the tissue retaining member from the retracted position to the deployed position. In one embodiment, the tissue retaining member is a strap. Also, in one embodiment, the cutting member is a filament and preferably a wire. The cutting member may also be adapted to cooperate with a source of electrocautery current (e.g., by way of a conventional cautery adapter on the housing) so as to cauterize tissue while making a cut therethrough.  
           [0011]    In another embodiment of the present disclosure a surgical apparatus for removing tissue is provided which includes an elongated body defining an opening at a distal end, the elongated body further forming a tissue receiving cavity in communication with the opening, a tubular member movable relative to the elongated body, the tubular member having a tissue cutting surface formed at a distal end thereof, and a tissue cutting member disposed adjacent the tubular member, at least a portion of the tissue cutting member being movable in a direction transverse to the elongated body in proximity to the opening, the tissue cutting member and the tubular member being movable independently of each other.  
           [0012]    The tubular member is preferably rotatably movable relative to the housing and longitudinally movable relative to the housing.  
           [0013]    Additionally, a locking mechanism to prevent longitudinal movement of the tubular member and a penetrating member having a sharpened distal end portion may be provided.  
           [0014]    As a further feature, a lockout disposed on the housing may be provided which, when engaged, interacts with a portion of the penetrating member to prevent rotation of the penetrating member with respect to the housing. The tubular member is preferably adapted to interact with the lockout and the portion of the penetrating member to prevent rotation of the tubular member when the lockout is engaged.  
           [0015]    The penetrating member may be removable from the housing and may interact with a lockout disposed on the housing which, when engaged, prevents removal of the penetrating member from the housing.  
           [0016]    A further embodiment of the present disclosure provides a surgical apparatus for removing tissue which includes an elongated body defining an opening at a distal end, the elongated body further forming a tissue receiving cavity in communication with the opening, a tubular member movable relative to the elongated body, the tubular member having a tissue cutting surface formed at a distal end thereof, a tissue cutting member disposed adjacent the tubular member, at least a portion of the tissue cutting member being movable in a direction transverse to the elongated body in proximity to the opening, the tissue cutting member and the tubular member being movable independently of each other, and an actuator operatively connected to the tissue cutting member, wherein the at least a portion of the tissue cutting member is moved transverse to the elongated body upon movement of the actuator from a first position to a second position.  
           [0017]    An additional feature of this embodiment is a safety lockout movable from at least a first position wherein the actuator is prevented from moving, to a second position wherein the actuator is movable relative to the housing. This embodiment may also include a penetrating member removably disposed within the housing, the penetrating member having a sharpened distal end portion. With the penetrating member positioned in the housing, the lockout is prevented from moving to the second position.  
           [0018]    Additionally, a safety lockout may be included which is movable from at least a first position wherein the tubular member is prevented from moving, to a second position wherein the tubular member is not prevented from moving. Alternatively, the safety lockout may be positionable in a first position wherein both the tubular member and the actuator are prevented from moving, a second position wherein the tubular member is movable and the actuator is prevented from moving, and a third position wherein the tubular member is prevented from moving and the actuator is movable relative to the housing to permit the user to effect cutting with the cutting member.  
           [0019]    The lockout may be prevented from moving to at least one of the second or third positions when a penetrating member is positioned within the housing.  
           [0020]    As an additional feature, a control member may be provided which is operatively associated with the tubular member to facilitate longitudinal movement of the tubular member relative to the housing. A safety lockout may be operatively associated with the control member and movable from at least a first position wherein the control member is prevented from moving to a second position wherein the control member is movable relative to the housing.  
           [0021]    The present disclosure also provides a method for surgically removing tissue which includes the steps of positioning a tissue removing instrument including an elongated housing having a tissue receiving cavity at a distal end, a first tissue cutting surface longitudinally movable relative to the elongated housing distal end, an obturator having a tissue-contacting distal end portion such that the tissue-contacting end portion is positioned adjacent the tissue to be removed and a tissue cutting surface transversely movable relative to the elongated housing, removing the obturator from the elongated housing, coring the tissue to be removed, severing the cored tissue from the surrounding tissue with the cutting surface, and removing the severed tissue from the patient.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]    Various embodiments are described herein with reference to the drawings, wherein:  
         [0023]    [0023]FIG. 1 is a perspective view of one embodiment of a tissue removing instrument constructed in accordance with the present disclosure;  
         [0024]    [0024]FIG. 2 is a perspective view with parts separated, of the embodiment of FIG. 1;  
         [0025]    [0025]FIG. 3 is a partial view of the interior distal end of one handle half-section of the embodiment of FIG. 1;  
         [0026]    [0026]FIG. 4 is an enlarged view of the area of detail indicated in FIG. 2;  
         [0027]    [0027]FIG. 5 is a perspective view, with parts separated, of the concentrically disposed tool mechanisms of the embodiment of FIG. 1;  
         [0028]    [0028]FIG. 6 is a perspective view, with parts separated, of the obturator of the embodiment of FIG. 1;  
         [0029]    [0029]FIG. 7 is an enlarged view of the area of detail indicated in FIG. 6;  
         [0030]    [0030]FIG. 8 is a perspective view, with parts separated, of the elongated tissue coring tube of the embodiment of FIG. 1;  
         [0031]    [0031]FIG. 9 is a perspective view of the tissue coring tube of FIG. 8, which shows the reverse side of the distal end of the tube;  
         [0032]    [0032]FIG. 10 is a perspective view, with parts separated, of the cutting wire and support tube of the embodiment of FIG. 1;  
         [0033]    [0033]FIG. 11 is an enlarged perspective view of the distal end of the cutting wire positioned on the support tube;  
         [0034]    [0034]FIG. 12 is a horizontal cross-sectional view of the embodiment of FIG. 1;  
         [0035]    [0035]FIG. 13 is an enlarged view of the indicated area of detail of the distal end of the instrument shown in FIG. 12;  
         [0036]    [0036]FIG. 14 is an initial view showing the embodiment of FIG. 1 in use;  
         [0037]    [0037]FIG. 15 is a further view, similar to FIG. 14, showing the embodiment of FIG. 1 in use;  
         [0038]    [0038]FIG. 16 is a horizontal cross-sectional view of the embodiment FIG. 1 with the obturator removed therefrom;  
         [0039]    [0039]FIG. 17 is an enlarged view of the area of detail indicated in FIG. 16;  
         [0040]    [0040]FIG. 18 is a cross-sectional view taken along section line  18 - 18  of FIG. 16;  
         [0041]    [0041]FIG. 19 is a view, similar to FIG. 18, showing operational features of the instrument;  
         [0042]    [0042]FIG. 20 is a cross-sectional view of the proximal end of the embodiment of FIG. 1, showing the lockout lever in the locked position;  
         [0043]    [0043]FIG. 21 is a view, similar to FIG. 20, showing the lockout lever in the released position;  
         [0044]    [0044]FIG. 22 is a view, similar to FIG. 17, showing the movement of the central elongated tube;  
         [0045]    [0045]FIG. 23 is a further view, similar to FIG. 14, showing the embodiment of FIG. 1 in use;  
         [0046]    [0046]FIG. 24 is a view of the distal end of the embodiment of FIG. 1 inserted around target tissue;  
         [0047]    [0047]FIG. 25 is a view, similar to FIG. 24, showing deployment of the cutting loop of wire and retaining strap;  
         [0048]    [0048]FIG. 26 is a horizontal cross-sectional view showing the proximal end of the instrument during operation of the trigger;  
         [0049]    [0049]FIG. 27 is a view, similar to FIGS. 24 and 25, showing complete deployment of the cutting loop of wire and retaining strap;  
         [0050]    [0050]FIG. 28 is a perspective view of a further embodiment constructed in accordance with the present disclosure and mounted on a cooperative portion of a stereotactic imaging machine;  
         [0051]    [0051]FIG. 29 is a longitudinal cross-sectional view from the top of the embodiment of FIG. 28;  
         [0052]    [0052]FIG. 30 is a perspective view, with parts separated, of the components contained in the housing or handle portion of the embodiment of FIG. 28;  
         [0053]    [0053]FIG. 31 is a cross-sectional view taken along section line  31 - 31  of FIG. 29;  
         [0054]    [0054]FIG. 32 is a cross-sectional top view of the proximal end of the embodiment of FIG. 28;  
         [0055]    [0055]FIG. 33 is a cross-sectional view taken along section line  33 - 33  of FIG. 32;  
         [0056]    [0056]FIG. 34 is a view, similar to FIG. 32, showing the operation of various elements of the embodiment of FIG. 28;  
         [0057]    [0057]FIG. 35 is a cross-sectional view taken along section line  35 - 35  of FIG. 34;  
         [0058]    [0058]FIG. 36 is a view demonstrating a sequence of operation of the embodiment of FIG. 28 as mounted on a cooperative portion of a stereotactic imaging machine;  
         [0059]    [0059]FIG. 37 is a view, similar to FIG. 36, demonstrating a further sequence of operation of the embodiment of FIG. 28;  
         [0060]    [0060]FIG. 38 is a view, similar to FIG. 36, demonstrating a further sequence of operation of the embodiment of FIG. 28;  
         [0061]    [0061]FIG. 39 is a view, similar to FIG. 36, demonstrating a further sequence of operation of the embodiment of FIG. 28;  
         [0062]    [0062]FIG. 40 is a view, similar to FIG. 36, demonstrating a further sequence of operation of the embodiment of FIG. 28; and  
         [0063]    [0063]FIG. 41 is a perspective view of a further embodiment of a tissue removing apparatus constructed in accordance with the present disclosure.  
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0064]    Referring initially to FIGS.  1 - 5 , one embodiment of an instrument for removing and/or taking a biopsy of tissue in accordance with the present disclosure is designated by reference numeral  100  throughout the several views. The instrument  100  is particularly adapted for minimally invasive insertion into tissue immediately adjacent the target tissue, and then for coring out and removing the target tissue from the patient. It will be understood by those skilled in the art, however, that the embodiments of the tissue removing instrument described herein, although generally directed to removal of breast tissue, may also be utilized for removal and/or biopsy of target tissue from other areas of a patient&#39;s body as well.  
         [0065]    Generally, instrument  100  includes a housing such as body portion  110  (formed from handle half-sections  112  and  114 ), and an elongated tubular body portion  116 . A penetrating member, such as obturator  118  extends through a longitudinal passageway of instrument  100  and extends out the distal end. An actuator, for example trigger  120  is preferably pivotally mounted in an opening formed between handle half-sections  112  and  114 . Except where noted otherwise, the materials utilized in the components of the instrument generally include such materials as polycarbonate for housing sections and related components, and stainless steel for components which transmit forces. One preferred polycarbonate material is available from General Electric under the tradename LEXAN. It is also preferred that radiolucent materials be utilized for appropriate instrument components, e.g., elongated tubular portions, so as not to interfere with imaging of tissue positioned adjacent thereto.  
         [0066]    The relative assembly of the various structural components of instrument  100  can be readily appreciated with reference to FIGS.  2 - 13 . Referring initially to FIGS. 1 and 2, handle half-sections  112  and  114  are preferably molded to have predetermined contoured regions for housing the various components as well as facilitating the instrument&#39;s operation. Each of the handle half-sections  112  and  114  has a grip portion  122 , in the shape of a pistol grip, which extends generally transversely away from a longitudinal axis “L” of a barrel portion formed when handle half-sections  112  and  114  are joined. Opposed semi-cylindrical walls  128  and  130  form a generally cylindrical passageway with adjacent semi-cylindrical portions, i.e., raised wall portion  136  and semi-annular groove  144 , from the proximal end of body  110  to the distal end thereof. Handle half-sections  112  and  114  may be joined together by any suitable means, for example, by sonic welding, snap fit, securing screw(s), adhesive bonding or the like.  
         [0067]    Referring to FIGS. 4 and 5 in conjunction with FIGS. 1 and 2, elongated tubular portion  116  includes a series of elongated components which are preferably concentrically disposed with respect to each other. An outer tubular sheath  132  has a proximal end held securely between semi-cylindrical walls  128  and  130  and a distal end which is covered by a collar  133  securely attached thereto. A pair of transversely extending tab portions  134  are formed at the proximal end of outer tubular sheath  132  and fit into slots  135  formed at the juncture of semi-cylindrical walls  128 ,  130  and raised portions  135 . Tab portions  134  bias against raised portions  136  to prevent proximal movement of outer tubular sheath  132  when the instrument  100  is inserted into the body tissue.  
         [0068]    A tubular member, such as central tubular shaft  138 , is axially and rotatably movable within outer tubular sheath  132 . The rotation of central tubular shaft  138 , however, may be selectively prevented by a mechanism described in detail below. Additionally, central tubular shaft  138  may be temporarily and selectively maintained in a fixed axial position relative to barrel portion  126  of body  110 . This fixed axial relationship may be accomplished, for example, by a cylindrical protrusion  140  (FIG. 9) formed near the proximal end of central tubular shaft  138  being positioned in an annular groove formed by closing semi-annular groove portions  142  and  144  formed in handle half-sections  112  and  114 , respectively. In this manner, central tubular shaft  138  may remain fixed axially within body  110  so as to freely rotate therein but not be removed therefrom.  
         [0069]    Obturator  118  is slidably positioned within central tubular shaft  138  and is preferably designed to cooperate with central tubular shaft  138  so as to prevent rotation of both central tubular shaft  138  and obturator  118  during the initial insertion of instrument  100  into the patient. A preferred manner in which to accomplish this selective fixing of the rotational movement of both central tubular shaft  138  and obturator  118  as well as to prevent relative axial movement of those components with respect to each other as well as body  110  is best shown in FIGS. 2, 3 and  5 .  
         [0070]    In particular, a pin  146  is transversely secured in elongated shaft  148  of obturator  118  near its proximal end. Upon insertion of obturator  118  in central tubular shaft  138 , pin  146  is received in a slot  150  formed in a collar  152 , which is secured to the proximal end of central tubular shaft  138 . This relationship between obturator  118  and central tubular shaft  138  prevents relative rotational movement between the two components. To prevent relative rotational movement between either obturator  118  or central tubular shaft  138  and body  110 , the subassembly of obturator  118  and central tubular shaft  138  is secured in body  110  by a bayonet-type mount, FIG. 3, created by the interaction of pin  146  and a lockout groove, such as L-shaped groove  154  formed along the inner wall of handle half-section  112 . L-shaped groove  154  is preferably provided with a lip  156  which serves to maintain pin  146  in the locked-out position.  
         [0071]    Referring once again to FIGS. 2 and 4, another locking mechanism is shown provided on instrument  100  to facilitate selective axial movement of central tubular shaft  138  once the instrument is inserted around the target tissue. Lockout lever  158  is pivotably mounted to body  110  and is temporarily maintained in the locked-out position by raised portions  160  extending laterally from the side surfaces of lockout lever  158  near a proximal end thereof being seated in detents  162  formed along the inner surface of handle portions of  112  and  114 , respectively, at a position proximal of the groove formed by semi-annular groove portions  142  and  144 . The operational aspects of lever lockout  158  will be explained in further detail herein.  
         [0072]    Trigger  120  is preferably pivotably attached to body  110  in recessed portions  164  and  166  formed in the handle half-sections  112  and  114 . Trigger  120  is connected to a tissue cutting member, e.g., a filament or wire, such as wire  168 , by a pin extending through a throughbore formed near the top of trigger  120  (FIG. 16). Wire  168  is maintained in a preferred orientation by an elongated tubular sheath  170  which is preferably concentrically disposed within outer tubular sheath  132  such that laterally extending tab portions  172  are situated adjacent tab portions  134  and maintained between housing handle half-sections  112  and  114  as described above for outer tubular sheath  132 . A longitudinal slot  174  is formed beginning at the proximal end of outer tubular sheath  132  and is disposed between laterally extending tab portions  134  so as to receive wire  168  and permit movement of the wire loop with respect to outer tubular sheath  132 .  
         [0073]    Referring now to FIGS.  6 - 13 , the various structural subassemblies will now be described individually. As shown in FIGS. 6 and 7, obturator  118  includes elongated shaft  148 , a cutting head  176  secured to a distal end of the shaft and a knob  178  attached to a proximal end of the shaft to facilitate insertion and removal of the obturator  118  from the instrument  100 . Cutting head  176  is preferably provided with slots  180  and  182 , formed orthogonally with respect to each other and which are dimensioned to receive individual blades  184  such that a cutting edge  186  formed on each blade  184  is angled to correspond to the angled distal surfaces  188  of the cutting head  176 .  
         [0074]    To facilitate assembly of the cutting head  176 , individual blades  134  are each provided with a transversely extending slot  188  having a series of individual tooth members  190  extending from the side wall of the slot. Teeth  190  are preferably formed in the shape of a ramp-shaped camming surface to interlock with complimentary surfaces (not shown) formed within orthogonally disposed slots  180  and  182 . Cutting head  176  is in the shape of a plug member having a proximally extending portion  192  of reduced diameter which is inserted into a bore  194  formed at the distal end of obturator  118  so as to be fixedly secured thereto. Any suitable known techniques for mounting may be utilized, such as friction fitting, bonding, adhesives or the like.  
         [0075]    As shown in FIGS. 8 and 9, central tubular shaft  138  has a tissue cutting surface, such as annular cutting edge  196  formed at the distal end to facilitate coring of the tissue surrounding and including the target tissue within the patient. The shaft is preferably formed of a material suitable for forming a sharpened edge, such as, for example, stainless steel. A knob  198  is secured to the proximal end of central tubular shaft  138 , for example, by locking tabs  200  engaging cut out portions  202  formed in cylindrical section  152  of knob  198 . Knob  198  is preferably further provided with a knurled gripping surface  206  to facilitate rotation of the shaft during the coring action of the tissue. Such rotational movement is facilitated by the disposition of pin  140  within the annular groove formed by semi-annular groove portions  142  and  144 , as noted above.  
         [0076]    In FIGS. 10 and 11, the cutting assembly including wire  168  and elongated tubular sheath  170  are shown in detail. As will be described later herein, wire  168  facilitates the severing of the tissue core to permit removal of the targeted tissue from the patient and, optionally, delivers electrocautery current to the tissue as cutting is accomplished. Wire  168  is preferably formed of a single length of thin gauge, stainless steel wire which is bent to an initial configuration or pre-fired condition contained within instrument  100 , as shown in FIG. 10.  
         [0077]    Initially, wire  168  is folded in half such that free ends  208  and  210  are positioned at the proximal end and are formed into a U-shaped bend to hook around pin  212  disposed at the top of trigger  120  (FIGS. 2 and 17). Wire  168  extends longitudinally along the outer surface of elongated tubular sheath  170  to the distal end thereof. A circular loop  213  is formed at the distal end of wire  168  and is positioned adjacent a flange  214  formed at the distal end of the tubular sheath  170 . Flange  214  is provided with radially extending leg portions  218  which form diametrically opposed passageways which hold wire  168  in a position substantially aligned with the distal end of tubular sheath  170 . A tissue retaining member, such as strap  216 , is wrapped around circular loop  213  and is provided with a tabbed end portion  220  to maintain the positioning of the strap across the distal opening of elongated tubular sheath upon cutting of the tissue core, which will explained in greater detail herein.  
         [0078]    The relative positioning of the various structural subassemblies in the initial configuration of instrument  100  is shown in the longitudinal cross-sectional view of FIG. 12. In particular, obturator  118  is shown inserted in instrument  100  with lockout lever  158  preventing proximal movement of central tubular shaft  138 . As best seen in the greatly enlarged view of FIG. 13, wire  168  is maintained in position by central tubular shaft  138  and obturator  118  on the interior side and by collar  133  on the exterior side. Wire  168  cannot be deployed to cut tissue until both obturator  118  and central tubular shaft  138  are moved distally of loop  213  (FIG. 10).  
         [0079]    A preferred method of using instrument  100  is illustrated in FIGS.  14 - 27 . Instrument  100  is inserted into the breast tissue along a predetermined path toward the target tissue  222 . The location of the target tissue can be specifically determined through the use of known localization techniques, such as for example, the insertion of a localization needle and/or the use of a stereotactic mammography device. Thus, for example, the target tissue may be tagged with a tagging device and instrument  100  moved adjacent the tagged location under conventional imaging guidance, or instrument  100  may be adapted to move along a target tissue locating device, such as a conventional K-wire, which was pre-positioned adjacent or across the target tissue. Instrument  100  may cooperate with a target tissue locating device in a variety of manners such as sliding coaxially along such locating device.  
         [0080]    Once instrument  100  is inserted to a position immediately adjacent the target tissue, obturator  118  is first rotated in a counterclockwise fashion as indicated by arrow “A” in FIG. 14, by the user gripping knob  178  and rotating the knob in a counterclockwise fashion. This rotational movement disengages pin  146  from L-shaped groove  154  (FIGS. 3 and 6) to permit axial movement of obturator  118  relative to the instrument  100 . In particular, obturator  118  may be removed from the instrument  100  by pulling on knob  178  in a proximal direction as indicated by arrow “B” in FIG. 14.  
         [0081]    With the obturator  118  removed, the target tissue is cored out from the surrounding tissue by urging instrument  100  in a proximal direction as indicated by arrow “C” in FIG. 15, while simultaneously turning knob  198  of central tubular shaft  138  to cause rotation of annular cutting edge  196  at the distal end of the central tubular shaft  138 . Rotation of the elongated central tubular shaft  138  may be in either a clockwise or counterclockwise direction or both depending on the preference of the user, as indicated by arrow “D” in FIG. 15.  
         [0082]    When the target tissue is completely within the distal end of instrument  100 , central tubular shaft  138  is moved proximally to allow for deployment of wire loop  168  to sever the tissue core from the patient. Electrocautery current is optionally delivered to the tissue by wire loop  168  as severing is accomplished. As shown in FIGS. 16 and 17, elongated central tubular shaft  138  is shown extending distally from the distal end of instrument  100  and preventing wire loop  168  from moving out of alignment with the circumferential alignment with the distal end of elongated tubular sheath  170 .  
         [0083]    [0083]FIG. 18 shows the relative positioning of pin  140  within annular groove  141  to facilitate the rotation of elongated central tubular shaft  138  therein. Such rotation is possible when the obturator  118  is removed from instrument  100 . When the tissue core is of sufficient depth, knob  198  is rotated, as indicated by arrow “E” in FIG. 19, to align pin  140  with a keyway  224  formed in handle half-sections  112  and  114 . This alignment permits proximal movement of central tubular shaft  138  when lever lockout  158  is pushed down, as indicated by arrow “F” in FIG. 21, to release protrusion  160  from detent  162  (FIGS. 2 and 4). Knob  198  is pulled proximally as indicated by arrow “G” in FIG. 21 to move the distal end of central tubular shaft  138  proximal of wire loop  213 .  
         [0084]    With central tubular shaft moved proximal of wire loop  213 , transverse movement of the wire loop across the distal open end of elongated tubular sheath  170  is effected by squeezing trigger  120 , as indicated by arrow “H” in FIG. 25. Upon transverse movement of wire loop  168 , strap  216  is pulled distally in the direction indicated by arrow “I” in FIG. 25. With further squeezing of trigger  120 , strap  214  is pulled completely across the opening at the distal end of elongated tubular sheath  170  so that tab portion  220  is prevented from further distal movement by leg portions  218  and strap  214  is pulled taut across the distal end opening of elongated tubular sheath  170 . Instrument  100  may thus be removed from the patient&#39;s breast. Due to the partial obstruction of the distal end opening of elongated tubular sheath  170  by strap  214 , the severed tissue core will be removed from the patient with instrument  100 . To the extent necessary, the puncture wound left by instrument  100  may be closed by any suitable known suturing techniques.  
         [0085]    Another embodiment of the presently disclosed instrument for removing and/or taking a biopsy of target tissue and a method of its use are illustrated in FIGS.  28 - 40 . Referring initially to FIGS.  28 - 30 , instrument  300  is particularly adapted for use on a precision instrument positioning machine, for example, a stereotactic imaging machine. Such devices are commercially available, for example, from Lorad Corporation of Danbury, Conn. An example of such a machine is disclosed in U.S. Pat. No. 5,289,520 which issued Feb. 22, 1994 to Pellegrino et al., the contents of which are hereby incorporated by reference.  
         [0086]    Briefly, stereotactic machines facilitate stereo x-ray imaging of a patient&#39;s breast using a three dimensional coordinate system, while the patient is in a prone position on a specially designed table. An opening is provided on the table to permit the patient&#39;s breast to be pendulantly disposed therethrough and a clamp is used to fix the exact location of the patient&#39;s pendulant breast relative to the operational components of the machine which facilitate precision interaction of instrumentation with the breast, i.e. for biopsy or tissue removal.  
         [0087]    The overall structural and operational features of instrument  300  are very similar to those described above for instrument  100 . Accordingly, the following description will focus on those features which are either unique to instrument  300  or are substantially different than corresponding elements of instrument  100 . In FIG. 28, instrument  300  is shown mounted in place on the instrument positioning control mechanism of a stereotactic machine, generally designated by reference numeral  302 . Stereotactic machine  302  has an instrument mount  304 , the movement of which is coordinated with the imaging capabilities of the machine. The instrument mount  304  is provided with a standardized instrument or tool mounting bracket  305  to facilitate mounting of various surgical instruments which can take advantage of the precision positioning features of the stereotactic machine. This is particularly beneficial in procedures where the target tissue is not palpable. As will be readily apparent based on the disclosure herein, the cooperative structures on instrument  300  and stereotactic machine  302  may be reconfigured so that more structure is included on instrument  300  and less on machine  302 , or vice versa. All that is required is that stereotactic machine  302  and instrument  300  cooperate so as to position instrument  300  as desired with respect to the target tissue.  
         [0088]    Instrument  300  is provided with four slide mounts  306 , two of which are formed on each side of housing half-sections  312  and  314  so that instrument  300  can be mounted on either side. Thus, the mechanical operational controls of instrument  300 , all of which are positioned on the same side of the instrument, may be oriented to suit the preference of the personnel using the instrument during the particular procedure. It is envisioned that some of the control actuators of instrument  300  may be reconfigured so that they would be operable from a different side than the remaining control actuators. Housing half-sections  312  and  314  are preferably molded to conform to the dimensions of the stereotactic machine tool mounting bracket  305 , for example, a rectangular base dimension.  
         [0089]    Obturator  318  has a pair of resiliently formed retaining members  319  each of which include a shoulder portion  321  which engages a cut-out portion of the proximal end wall of housing half-section  314  to maintain obturator  318  in place during insertion of instrument  300 .  
         [0090]    As shown in FIGS.  29 - 31 , a firing lockout mechanism is provided to prevent premature movement of the cutting wire before obturator  318  and central tubular shaft  338  are properly positioned relative to the wire loop positioned at the distal end of wire  368  (similar to loop  213  of wire  168 ). The firing lockout mechanism includes a safety lockout member  323  and a control member, such as slide bar member  341 . Lockout member  323  is slidably received in a cutout  325  formed in a sidewall of housing half-section  314  and has a pair of slotted keyways  327  and  329  formed thereon. Also provided on lockout member  323  are raised portions  331  which provide tactile indication to the user of the relative positioning of lockout member  323  during a two-stage lockout release process described below.  
         [0091]    Trigger  320  is provided with a retaining pin  333  which has a pair of bores formed therethrough to receive and frictionally retain wire loop  368 . A latch portion  335  is formed extending from the distal side of trigger  320  which is configured and dimensioned to interact with lockout member  323  and specifically to slide in keyway  327 .  
         [0092]    Central tubular shaft  338  is fitted at a proximal end with gear collar  337 , the teeth of which are designed to mesh with the teeth of gear  339  which is manually driven by a drive mechanism. Alternatively, a powered drive mechanism may be provided on stereotactic machine  302 . A slide bar  341  cradles gear collar  337  to permit rotational movement thereof while controlling the axial alignment of central tubular shaft  338  within housing half-sections  312  and  314 . Slide bar  341  is provided with a latch portion  343  formed at a proximal end thereof. At the distal end, slide bar  341  has actuator button  345  to facilitate proximal movement of slide bar  341  by the user. Another feature of slide bar  341  is a diagonal groove  347  which is formed in the side surface adjacent the proximal end of the slide bar to permit wire loop  368  to slidably pass therethrough, as best seen in FIG. 29.  
         [0093]    The two stage lockout process of lockout member  323  is best shown in FIGS.  31 - 35  in conjunction with FIGS.  36 - 40 . Upon the insertion of the instrument into the patient, FIGS. 36 and 37, it is desirable to maintain the relative axial positioning of central tubular shaft  338  with respect to outer tubular sheath  332  as well as to prevent firing of trigger  320 . Both of these preventive goals are accomplished when obturator  318  is positioned within the instrument and lockout member  323  is maintained in its initial position as shown in FIG. 29 by obturator member  318  and shoulder portion  349  of lockout member  323  biasing against the outer wall of housing half-section  314 . In this position, keyways  327  and  329  of lockout member  323  are maintained out of alignment with slide bar  341  and latch portion  335  of trigger  320 , respectively.  
         [0094]    After insertion of instrument  300  into the patient as shown in FIG. 37, preferably by automated movement of instrument mount  304  by a drive mechanism on stereotactic machine  300 , obturator  318  is removed (FIGS. 29 and 38) by pressing radially inwardly on retaining members  319  to disengage the retaining members from shoulder portions  321  from the proximal end wall of housing half-section  314 . With obturator  318  removed from the instrument, as shown in FIG. 32, lockout member  323  is free to move transversely toward the central longitudinal axis of instrument  300 .  
         [0095]    The first stage of releasing lockout member  323 , illustrated in FIG. 32, is accomplished when the user pushes lockout member  323  inwardly toward the center of the instrument. A tactile indication is felt by the user when the first raised portion  331  passes over the side wall of housing half-section  314 . Actuator button  345  is moved proximally, as indicated by arrow “J” in FIG. 32, to effect proximal movement of central tubular shaft  138 . This proximal movement is limited by partition  351  formed transversely across housing half-section  314 . During proximal movement of slide bar  341 , latch portion passes through keyway  327  and prevents further transverse movement of lockout member  323  until latch portion  343  passes completely through keyway  327 .  
         [0096]    After proximal movement of central tubular shaft  38 , lockout member  323  is again pushed transversely inward (see FIGS. 32 and 33) until the user feels another tactile indication, resulting from the second raised portion  331  crossing over the side wall of housing half-section  314 . In this position, as shown in FIGS. 34 and 35, latch  335  of trigger  320  is aligned with keyway  329 . Trigger  320  is moved proximally in the direction of arrow “K”. Also when lockout member  323  is in the orientation shown in FIG. 34, latch portion  343  of slide bar  341  is in engagement with lockout member  323  to prevent distal movement of slide bar  341  and, therefore, central tubular shaft  338 , during firing of trigger  320 .  
         [0097]    A further embodiment of a tissue removing instrument is shown in FIG. 41. Instrument  400  is similar to the embodiment of FIGS.  28 - 40  and is designed to be inserted and used manually by a surgeon, rather than in conjunction with a stereotactic machine. The handle of instrument  400  includes handle half-sections  412  and  414  which are molded to a dimension suitable for being held in the palm of either the user&#39;s left or right hands. The control mechanisms of instrument  400  may be the same as those for instrument  300  or lockout member  323  may be eliminated as shown in FIG. 41. The basic manner of usage of instrument is the same as that for instrument  300 .  
         [0098]    It will be understood that various modifications may be made to the embodiments disclosed herein. Therefore, the above description should not be construed as limiting, but merely as exemplifications of preferred embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.