Abstract:
A breast biopsy lateral arm system includes a removable gun mount which attaches to a carriage that traverses along an X-axis defined by a lateral arm in order to position a biopsy needle relative to a patient. The carriage rides along the lateral arm on self-adjusting rollers which are loaded against the lateral arm by spring members. A cam-actuated carriage slide lock can be used to secure the carriage in a desired position relative to the lateral arm. A cam-actuated removable gun mount lock allows the gun mount to be quickly changed and offset orthogonally with respect to the X-axis. An X-axis stop can be used to establish a position to which the carriage can be returned with accuracy.

Description:
BACKGROUND 
       [0001]    The subject matter of this application is generally related to the medical field. Medical imaging technologies such as stereotactic x-ray, fluoroscopy, computer tomography, ultrasound, nuclear medicine and magnetic resonance imaging enable detection of small abnormalities in the body of a patient. The discovery of certain abnormalities may prompt performance of a biopsy procedure to obtain a tissue sample for lab analysis to help diagnose and treat patients suspected of having cancerous tumors, pre-malignant conditions or other diseases or disorders. A stereotactic guided percutaneous breast biopsy is often preferable to an open surgical breast biopsy in the case of small abnormalities located deep within the body because a percutaneous biopsy removes a relatively small amount of tissue. For example, a needle can be used to remove individual cells or clusters of cells in the case of fine needle aspiration (FNA), and a core or fragment of tissue in the case of a core biopsy. One difficulty associated with such procedures is that it is necessary to locate the biopsy needle with considerable precision in order to obtain a suitable sample of a small abnormality, particularly if it is located deep within the body. Moreover, it would be advantageous if the medical equipment for performing such procedures were practical to manufacture at a reasonable cost and usable by medical personnel without extensive training. 
       SUMMARY 
       [0002]    In accordance with an aspect, an apparatus comprises: a lateral arm; a carriage assembly which traverses along the lateral arm in a predefined axis, the carriage assembly including a carriage and self-adjusting rollers which are loaded against the lateral arm by spring members; and a gun mount configured to support a biopsy gun, the gun mount being connected to the carriage. The self-adjusting rollers may include a set of fixed guide rollers on a first side of the lateral arm and a movable set of guide rollers on a second side of the lateral arm. One or more spring members may be used to load the movable set of guide rollers against the lateral arm. The spring member may include a resilient beam. A cam-actuated X-axis stop may be removably secured to the lateral arm to limit an extent of traverse of the carriage. 
         [0003]    In accordance with another aspect, an apparatus comprises: a lateral arm; a carriage which traverses along the lateral arm in a predefined axis; a cam-actuated lock assembly which secures the carriage to the lateral arm in an engaged state; and a gun mount configured to support a biopsy gun, the gun mount being connected to the carriage. Movement of the carriage relative to the lateral arm may be controlled by a lead screw associated with the lateral arm and carriage nut attached to the carriage, and the lock assembly may include a clamp which applies frictional force to the lead screw in response to actuation of a camshaft, thereby inhibiting rotation of the lead screw. A clamp bushing may be disposed between the clamp and the lead screw. A cam-actuated X-axis stop may be removably secured to the lateral arm to limit an extent of traverse of the carriage. 
         [0004]    In accordance with another aspect, an apparatus comprises: a lateral arm; a carriage which traverses along the lateral member in a predefined axis; a gun mount configured to support a biopsy gun, the gun mount being connected to the carriage; and a cam-actuated locking mechanism for securing the gun mount to the carriage. A positional offset feature may be provided which repositions the gun mount along a secondary axis which is orthogonal to the predefined axis. The locking mechanism may include a tee nut associated with the carriage and a corresponding tee slot associated with the gun mount. A camshaft can be used to actuate the tee nut to apply frictional force against the tee slot in an engaged state. The camshaft may actuate the tee nut in the engaged state by allowing a spring to apply force directly to the tee nut, such that the camshaft does not apply force against the tee slot via the tee nut. A camshaft may actuate a locking pilot pin associated with the carriage, the pin applying force against the gun mount. The camshaft may actuate the locking pilot pin in an engaged state by allowing a spring to apply force directly to the locking pilot pin, such that the camshaft does not apply force against the gun mount via the locking pilot pin. The carriage may include at least one stop pin and the gun mount may include at least one stop pin seat, such that the gun mount is aligned in a predetermined relationship with the carriage when the stop pin is fully inserted into the stop pin seat. First and second sets of stop pin seats may be provided such that the first set of stop pin seats align the gun mount in a position offset by 180 degrees from an alignment position determined by the second set of stop pin seats. 
         [0005]    In accordance with another aspect, a method comprises: securing a biopsy needle to a gun mount associated with a carriage; and positioning the biopsy needle for a procedure by traversing the carriage along a lateral arm in a predefined axis, including the carriage riding on self-adjusting rollers which are loaded against the lateral arm by spring members. The self-adjusting rollers may include a set of fixed guide rollers on a first side of the lateral arm and a movable set of guide rollers on a second side of the lateral arm. At least one spring member may be used to load the movable set of guide rollers against the lateral arm. The spring member may include a resilient beam. A cam-actuated X-axis stop may be secured to the lateral arm to limit an extent of traverse of the carriage. 
         [0006]    In accordance with another aspect, a method comprises: securing a biopsy needle to a gun mount associated with a carriage; and positioning the biopsy needle for a procedure by traversing the carriage along the lateral arm in a predefined axis; and securing the carriage to the lateral arm via a cam-actuated lock assembly. Movement of the carriage relative to the lateral arm may be controlled by a lead screw associated with the lateral arm and carriage nut attached to the carriage, and the lock assembly may include a clamp which applies frictional force to the lead screw in response to actuation of a camshaft, thereby inhibiting rotation of the lead screw. A clamp bushing may be disposed between the clamp and the lead screw. A cam-actuated X-axis stop may be secured to the lateral arm to limit an extent of traverse of the carriage. 
         [0007]    In accordance with another aspect, a method comprises: securing a biopsy needle to a gun mount via a cam-actuated locking mechanism, the gun mount associated with a carriage; and positioning the biopsy needle for a procedure by traversing the carriage along the lateral arm in a predefined axis. A positional offset feature may be provided to reposition the gun mount along a secondary axis which is orthogonal to the predefined axis. The locking mechanism may include a tee nut associated with the carriage and a corresponding tee slot associated with the gun mount. A camshaft can be used to actuate the tee nut to apply frictional force against the tee slot in an engaged state. For example, the camshaft may actuate the tee nut in the engaged state by allowing a spring to apply force directly to the tee nut, such that the camshaft does not apply force against the tee slot via the tee nut. A camshaft can be used to actuate a locking pilot pin associated with the carriage, the pilot pin applying force against the gun mount. The camshaft may actuate the locking pilot pin in an engaged state by allowing a spring to apply force directly to the locking pilot pin, such that the camshaft does not apply force against the gun mount via the locking pilot pin. The carriage may include at least one stop pin and the gun mount may include at least one stop pin seat, such that the gun mount is aligned in a predetermined relationship with the carriage when the stop pin is fully inserted into the stop pin seat. First and second sets of stop pin seats may be provided such that the first set of stop pin seats align the gun mount in a position offset by 180 degrees from an alignment position determined by the second set of stop pin seats. 
         [0008]    Unless specifically stated otherwise, the features described herein can be used in any combination, and the aspects can include any one or more of the embodiments. Moreover, other features and advantages will become apparent to those of ordinary skill in the art in view of the figures and detailed description. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0009]      FIGS. 1 and 2  are isometric and side views, respectively, of one embodiment of a breast biopsy station according to the present invention, the breast biopsy station being shown in  FIG. 2  together with a breast; 
           [0010]      FIG. 3  is an isometric view of the integrated biopsy needle guidance system of the breast biopsy station of  FIG. 1 ; 
           [0011]      FIG. 4  is a cross-sectional view taken along line K-K of  FIG. 5A , illustrating the roller guide wheels of the carriage assembly and the generally V-shaped grooves of the lateral arm of the needle guide system in greater detail: 
           [0012]      FIG. 5A  is a side view of certain components of the integrated biopsy needle guidance system shown in  FIG. 3 ; 
           [0013]      FIG. 5B  is a bottom view of certain components of the integrated biopsy needle guidance system shown in  FIG. 3 ; 
           [0014]      FIG. 6A  is a partly exploded perspective view of the combination of the carriage slide locking assembly and the carriage assembly shown in  FIG. 5B ; 
           [0015]      FIG. 6B  is a section view taken along line P-P of  FIG. 5A ; 
           [0016]      FIG. 7A  is an end view of the combination of the gun mount and the carriage assembly of  FIG. 3 , the roller guide wheels of the carriage assembly not being shown, the locking knob of the carriage assembly being shown in an unlocked or disengaged position; 
           [0017]      FIG. 7B  is a top view of the carriage assembly of  FIG. 7A , the roller guide wheels of the carriage assembly not being shown, the locking knob of the carriage assembly being shown in an unlocked or disengaged position; 
           [0018]      FIG. 7C  is a top view of the gun mount shown in  FIG. 7A , together with the needle guide; 
           [0019]      FIGS. 7D and 7E  are cross-sectional views corresponding to  FIGS. 7B and 7C , respectively, taken along section lines B 1 -B 1  and B 1 . 1 - 1 . 1 ; 
           [0020]      FIG. 7F  is a cross-sectional view of the carriage assembly of  FIG. 7B  taken along section line B 2 -B 2 ; 
           [0021]      FIG. 8A  is an end view of the combination of the gun mount and the carriage assembly of  FIG. 3 , the roller guide wheels of the carriage assembly not being shown, the locking knob of the carriage assembly being shown in a locked or engaged position; 
           [0022]      FIG. 8B  is a top view of the combination of the gun mount and the carriage assembly shown in  FIG. 8A ; 
           [0023]      FIG. 8C  is a cross-sectional view of the combination of the gun mount and the carriage assembly shown in  FIG. 8B  taken along section line C 1 -C 1 ; 
           [0024]      FIG. 8D  is a cross-sectional view of the combination of the gun mount and the carriage assembly shown in  FIG. 8B  taken along line section C 2 -C 2 ; 
           [0025]      FIG. 9  is an isometric view of the X-axis stop shown in  FIG. 3 ; 
           [0026]      FIG. 10A  is a top view of the X-axis stop of  FIG. 9  shown in the unlocked position; 
           [0027]      FIG. 10B  is a cross-sectional view of the X-axis stop of  FIG. 10A  taken along section line D 1 -D 1 ; 
           [0028]      FIG. 10C  is a side view of the X-axis stop of  FIG. 9  in the unlocked position; 
           [0029]      FIG. 10D  is a top view of the X-axis stop of  FIG. 9  in the locked position. 
           [0030]      FIG. 10E  is a cross-sectional view of the X-axis stop of  FIG. 10D  taken along section line D 2 -D 2 ; 
           [0031]      FIG. 10F  is a side view of the X-axis stop of  FIG. 9  in the locked position; 
           [0032]      FIG. 10G  is a section view showing the X-axis stop of  FIG. 9  mounted on the lateral arm of  FIG. 3 ; and 
           [0033]      FIGS. 11 through 18  illustrate various configurations of the lateral arm needle guide and assembly steps of various components. 
       
    
    
     DETAILED DESCRIPTION 
       [0034]    Referring to  FIGS. 1 and 2 , there is shown one embodiment of a breast biopsy station according to the present invention, the breast biopsy station being represented generally by reference numeral  1000 . Breast biopsy station  1000  may comprise a breast platform  1004 , a compression paddle  1006 , a radiographic imaging system  1008 , and an integrated biopsy needle guidance system  1010 . As seen best in  FIG. 2 , breast platform  1004  and compression paddle  1006  may be arranged so that the chest wall  1002  of a patient may be pressed against breast platform  1004  and compression paddle  1006 , with the patient&#39;s breast being positioned on top of breast platform  1004  and under compression paddle  1006 , i.e., the breast may be compressed between breast platform  1004  and compression paddle  1006 . Radiographic imaging system  1008  may be used to produce an image of the breast that is compressed between breast platform  1004  and compression paddle  1006  in order to locate a feature of interest, e.g., a lesion, located within the breast. Integrated biopsy needle guidance system  1010  may be used to obtain a tissue sample of the feature of interest. More particularly, integrated biopsy needle guidance system  1010  may display information about the relative locations of the targeted feature and a biopsy gun  101  in order to help position biopsy gun  101  and to guide its path of travel such that a needle on biopsy gun  101  may intersect with the target feature. 
         [0035]    Referring now to  FIG. 3 , there is shown integrated biopsy needle guidance system  1010  in greater detail. Integrated biopsy needle guidance system  1010  may comprise a gun mount  100 , a carriage assembly  110 , a lateral arm  102 , and a biopsy guidance module  105 . Biopsy gun  101  may be connected to gun mount  100 . Gun mount  100  may be connected to carriage assembly  110 . Carriage assembly  110  may be connected to lateral arm  102 . Lateral arm  102  may be connected to biopsy guidance module  105 . Biopsy guidance module  105  may include interface features which help calculate, utilize and display useful information. Reconfiguration features may be provided to allow secure repositioning of the selected biopsy gun, and sensing features such as described in U.S. patent application Ser. No. 13/611,502, inventors Girgenti et al., filed Sep. 12, 2012, titled Breast Biopsy Lateral Arm System, which is incorporated herein by reference in its entirety, may be provided to detect certain reconfiguration and repositioning data in order to facilitate the biopsy procedure, e.g., by providing the data to the biopsy guidance module in order to automate calculation of offsets, adjustments and other information that helps to obtain tissue cores from a specific location. Moreover, the data can be used to verify that a configuration entered by an operator matches the actual configuration of the needle guidance system. 
         [0036]    A selected biopsy gun  101  may be positioned and secured by gun mount  100 . More particularly, an operator can securely mount and remove any of various biopsy guns that might be selected, so different biopsy guns may be utilized as needed. Indexing features may help assure that the biopsy gun can be predictably and repeatedly mounted in a particular position with respect to the gun mount when mounted. Biopsy gun  101  may be operative in response to information from an embedded computer, information provided by an operator via biopsy guidance module  105 , and sensor input to locate a biopsy needle of biopsy gun  101  to obtain a tissue sample, e.g., by inserting an outer cannula into a predetermined location of interest within the patient, extracting a tissue core sample by moving an inner cannula relative to the outer cannula, and removing the needle from the patient. A needle guide  103  may help to guide the outer cannula of the biopsy gun, e.g., by inhibiting deflection. Various types of biopsy guns and needles are known, and the functioning of biopsy guns and needles in obtaining tissue cores is well understood in the art. Therefore, these features will not be described in greater detail. 
         [0037]    One aspect of positioning biopsy gun  101  relative to the patient may be via movement of lateral arm  102 . Biopsy guidance module  105  may include a post member  106 . Lateral arm  102  may include a clamp member  150  which can be slidably moved along and secured to post member  106  at any of various locations along the length of post member  106 . As a result, biopsy gun  101  may be repositionable via movement of lateral arm  102  with respect to post member  106 . 
         [0038]    Another aspect of positioning the biopsy gun  101  relative to the patient may be via movement of biopsy gun  101  relative to lateral arm  102 . Carriage assembly  110  may be selectively movable (e.g., slidably) along an X-axis defined by lateral arm  102 , to which carriage assembly  110  may be connected. When biopsy gun  101  is secured to gun mount  100 , and gun mount  100  is secured to carriage assembly  110 , biopsy gun  101  may be positioned at any of various points along the X-axis by moving carriage assembly  110  with respect to lateral arm  102 . A carriage slide locking feature may enable an operator to secure carriage assembly  110  to lateral arm  102  when a desired X-axis position is attained, thereby securing biopsy gun  101  in a desired X-axis position relative to the patient. Moreover, an X-axis stop  152  may be used to reliably return biopsy gun  101  to a particular X-axis position. 
         [0039]    Referring now to  FIGS. 4 ,  5 A and  5 B, lateral arm  102  may comprise an elongated member that may be generally H-shaped in transverse cross-section. Lateral arm  102  may be shaped to include a first side surface  102 - 1 , a second side surface  102 - 2 , a top surface  102 - 3 , and a bottom surface  102 - 4 . A first generally V-shaped groove  400 - 1  with a rounded vertex may be provided in first side surface  102 - 1  of lateral arm  102 , and a second generally V-shaped groove  400 - 2  with a rounded vertex may be provided in second side surface  102 - 2  of lateral arm  102 . First and second generally V-shaped grooves  400 - 1  and  400 - 2  may extend for at least a portion of the length of lateral arm  102 , with first and second generally V-shaped grooves  400 - 1  and  400 - 2  extending parallel to one another along the X-axis of lateral arm  102 . A top channel  401 - 1  may be provided in top surface  102 - 3  of lateral arm  102 , and a bottom channel  401 - 2 , the purpose of which will become apparent below, may be provided in bottom surface  102 - 4  of lateral arm  102 . 
         [0040]    Carriage assembly  110  may comprise a carriage  412 . Carriage  412 , in turn, may comprise a structure, optionally a unitary structure, shaped to include a central body  413 , a set of fixed guide roller mounts  410  positioned on a first side of central body  413 , and a set of self-adjusting guide roller mounts  414  positioned on a second side of central body  413 . As will be discussed further below, fixed guide roller mounts  410  and self-adjusting guide roller mounts  414  may be used to mount guide rollers  301  that, in turn, may engage lateral arm  102  by seating against generally V-shaped grooves  400 - 1  and  400 - 2 . More specifically, self-adjusting guide roller mounts  414  may be positioned proximate to first side surface  102 - 1  of lateral arm  102 , with its associated guide rollers  301  seated against generally V-shaped groove  400 - 1 , and fixed guide roller mounts  410  may be positioned proximate to second side surface  102 - 2  of lateral arm  102 , with its associated guide rollers  301  seated against generally V-shaped groove  400 - 2 . Self-adjusting guide roller mounts  414  may be connected to one another by deflecting beams  416 . Deflecting beams  416  may allow self-adjusting guide roller mounts  414  to flex laterally relative to central body  413  whereas fixed guide roller mounts  410  may not move relative to central body  413 . Deflecting beams  416  may be resilient and/or may serve to apply a spring force to help keep guide rollers  301  seated against generally V-shaped grooves  400 - 1  and  400 - 2 , thereby compensating for dimensional variations associated with the machining processes of related parts. Deflecting beams  416  may be formed by machining carriage  412  in a manner that leaves two thin beams of aluminum or other suitable material which are designed to deflect to a pre-determined position and apply a pre-determined force when deflected. The deflection creates a preload force that helps keep guide rollers  301  engaged against generally V-shaped grooves  400 - 1  and  400 - 2 . However, a wide variety of means of applying spring force might also be utilized. 
         [0041]    As noted above, guide rollers  301  may allow carriage  412  to travel along the X-axis of lateral arm  102  while inhibiting movement of carriage  412  outside the X-axis. Each guide roller  301  may include a bearing  402  and a wheel  404 . Wheel  404  may be appropriately shaped to contact its respective generally V-shaped groove  400 - 1  or  400 - 2  and to center guide roller  301  therewithin. Wheel  404  may be shaped to include a central groove, which may be generally V-shaped, generally U-shaped, or any other of a wide variety of shapes. The outer edges of wheel  404  may be chamfered so that contact with generally V-shaped groove  400 - 1  or  400 - 2  does not prevent wheel  404  from centering within the generally V-shaped groove. Wheel  404  may be connected to carriage  412  via bearing  402 , which may enable wheel  404  to turn as carriage assembly  110  is moved along the X-axis of lateral arm  102 . 
         [0042]    Referring now to  FIG. 6A , there is shown the combination of a carriage slide locking assembly  599  and carriage assembly  110 . As will become apparent from the discussion below, carriage slide locking assembly  599  may be constructed so that, when in an unlocked state, carriage locking assembly  599  allows carriage assembly  110  to move freely along the x-axis of lateral arm  102 , and so that, when in a locked state, carriage locking assembly  599  secures carriage assembly  110  to lateral arm  102  at a desired position along the x-axis of lateral arm  102 . Carriage locking assembly  599  may comprise a carriage nut  600 , a lead screw  602 , lead screw bearings  603 - 1  and  603 - 2 , a clamp bushing  604 , a clamp  606 , a camshaft  608 , and a carriage locking knob  610 . Carriage nut  600  may be fixed to the top of central body  413  of carriage  412  and may be appropriately dimensioned to slide longitudinally back and forth within channel  401 - 2  of lateral arm  102 . Lead screw  602  may be coupled to lateral arm  102  via lead screw bearings  603 - 1  and  603 - 2  in such a way that lead screw  602  may rotate about its longitudinal axis while otherwise being fixed to lateral arm  102 . Lead screw  602  may extend through a longitudinal bore in carriage nut  600 . Carriage nut  600  and lead screw  602  may have complementary internal and external threads (not shown) so that, as lead screw  602  is rotated, carriage nut  600  is caused to move along the x-axis of lead screw  602 , the direction of X-axis movement being a function of the direction of rotation of lead screw  602 . 
         [0043]    Once carriage nut  600  has been positioned at a desired location along the x-axis of lead screw  602 , further rotation of lead screw  602  may be limited by the combination of clamp bushing  604 , clamp  606 , camshaft  608 , and carriage locking knob  610 . More specifically, clamp bushing  604  may be positioned coaxially around an unthreaded clamping portion  612  of lead screw  602  that is located between lead screw bearings  603 - 1  and  603 - 2 . One end of clamp  606  may be positioned proximate to clamp bushing  604 , and the opposite end of clamp  606  may be coupled to camshaft  608 . Camshaft  608 , which may be mechanically coupled to and actuated by rotation of carriage locking knob  610 , may include a machined section which may be asymmetrical with respect to the axis about which camshaft  608  rotates. In the unlocked state, camshaft  608  does not apply any force to clamp  606  due to the asymmetry of the machined section. As a result, clamp  606  does not cause clamp bushing  604  to grip lead screw  602  at clamping surface  612 ; consequently, lead screw  602  is free to rotate, and carriage assembly  110  may move along the x-axis of lateral arm  102 . By contrast, in the locked state (see  FIG. 6B ), the asymmetrical cam section on camshaft  608  bears down on clamp  606 , causing clamp  606  to compress clamp bushing  604  against lead screw  602 , thereby preventing lead screw  602  from rotating due to frictional force between bushing  604  and clamping surface  612 . Such a lack of rotation of lead screw  602  keeps carriage nut  600  from moving and, thereby, prevents carriage assembly  110  from moving along the x-axis of lateral arm  102 . 
         [0044]    Referring now to  FIGS. 7A through 7F  and to  FIGS. 8A through 8D , the manner in which carriage assembly  110  and gun mount  100  may be reversibly and lockably interconnected is made apparent. In particular,  FIG. 7A  shows carriage assembly  110  and gun mount  100  interconnected in an unlocked state, and  FIGS. 8A through 8D  show carriage assembly  110  and gun mount  100  interconnected in a locked state. 
         [0045]    As can be seen, for example, in  FIG. 7D , carriage assembly  110  may further comprise a camshaft  700 . Camshaft  700  may be rotatably mounted within a cavity  701  that may be provided in carriage  412 . A locking knob  702 , which may be disposed outside of carriage  412 , may be mechanically coupled to camshaft  700  and may be used to rotate camshaft  700 . Carriage assembly  110  may further comprise a tee nut  706 . Tee nut  706  may be movably mounted in a vertical direction relative to a cavity  703  that may be provided in carriage  412 . Vertical movement of tee nut  706  relative to cavity  703  may be controlled by camshaft  700 , a tee nut cam follower  704 , and tee nut springs  712 . More specifically, camshaft  700  and tee nut cam follower  704  may be sized and shaped so that, when camshaft  700  is in an unlocked or disengaged position (i.e., locking knob  702  horizontal), camshaft  700  causes tee nut cam follower  704  to cause tee nut springs  712  to be compressed, thereby lowering tee nut  706  to its lowest operating position (see, for example,  FIG. 7F ). By contrast, when camshaft  700  is in a locked or engaged position (i.e., locking knob  702  vertical), camshaft  700  causes tee nut cam follower  704  to cause tee nut springs  712  not to be compressed, thereby raising tee nut  706  to its highest operating position (see, for example,  FIG. 8C ). 
         [0046]    Carriage assembly  110  may further comprise a locking pilot pin  710 . Locking pilot pin  710  may be movably mounted in a vertical direction into and partially out of a cavity  705  that may be provided in carriage  412 . Vertical movement of locking pilot pin  710  may be controlled by a secondary cam  714  on camshaft  700 , a secondary lock cam follower  708 , and a secondary lock spring  802 . More specifically, secondary cam  714  and secondary lock cam follower  708  may be sized and shaped so that, when camshaft  700  is an unlocked or disengaged position (i.e., locking knob  702  horizontal), locking pilot pin  710  is raised to a position that is entirely within cavity  705  (see, for example,  FIG. 7D ). By contrast, when camshaft  700  is in a locked or engaged position (i.e., locking knob  702  vertical), locking pilot pin  710  is driven down to a position that extends partially out of cavity  705  (see, for example,  FIG. 8C ). 
         [0047]    Carriage assembly  110  may further comprise one or more X-axis stop pins  716  fixedly mounted on the bottom of carriage  412 . X-axis stop pins  716  may be used to mate with X-axis stop pin seats  718  provided in gun mount  100  in such a way that gun mount  100  may be properly aligned with carriage  412  only when stop pins  716  are disposed in stop pin seats  718 . Such positioning facilitates calculations associated with biopsy needle positioning relative to the patient. An additional set of X-axis stop pin seats  720  may be provided in gun mount  100  to allow gun mount  100  to be mounted in a 180 degree offset position. 
         [0048]    To couple gun mount  100  to carriage assembly  110 , locking knob  702  may be placed in a horizontal position (toward either side). Placement of locking knob  702  in such a horizontal position orients camshaft  700  so that tee nut cam follower  704  compresses tee nut springs  712 , thereby lowering tee nut  706  to its lowest operating position. In addition, placement of locking knob  702  in such a horizontal position also causes locking pilot pin  710  to be raised into cavity  705  of carriage  412 . With tee nut  706  thus lowered and locking pilot pin  710  thus raised, carriage assembly  110  may then be coupled to gun mount by sliding the bottom end of carriage  412 , as well as tee nut  706 , into one of the two tee slots  800  provided in gun mount  100  until stop pins  716  are seated within their corresponding stop pin seats  718 . Locking knob  702  may then be turned to its vertical position (i.e., an approximately 90 degree rotation) in order to lock gun mount  100  to carriage assembly  110 . The rotation of camshaft  700  in response to the rotation of locking knob  702  enables tee nut cam follower  704  to be raised by tee nut springs  712 . This, in turn, causes tee nut  706  to be raised. Tree nut  706 , in turn, grabs the flanges  801  of gun mount  100  and clamps flanges  801  against the bottom of carriage  412 , thereby locking gun mount  100  against carriage  412 . The rotation of camshaft  700  in response to moving locking knob  702  to a vertical position also allows secondary cam  714  (now driven down by secondary lock spring  802 ) and, thus, locking pilot pin  710  to lower down and engage gun mount  100 , preventing gun mount  100  from being removed from carriage assembly  110 . 
         [0049]    To decouple gun mount and carriage assembly  110 , locking knob  702  is moved from a vertical position to a horizontal position. Such movement causes locking pilot pin  710  to be raised, so that locking pilot pin  710  no longer engages gun mount  100 . In addition, such movement also causes tee nut  706  to be lowered, thereby releasing the grip of tee nut  706  on gun mount  100 . As a result of the foregoing, carriage assembly  110  can be slid away from gun mount  100 . 
         [0050]      FIGS. 7A ,  7 C,  8 A,  8 B and  8 D illustrate a Y-axis offset feature. More specifically, gun mount  100  can be attached to carriage  412  via either of two tee slots  800  which are offset in the Y-axis. The two mounting positions defined by the Y-axis offset allow a biopsy needle to be positioned farther back from the chest wall of the patient. This advantageously accommodates a wider range of breast sizes, e.g., the offset position for larger breasts. 
         [0051]    Referring now to  FIGS. 9 ,  10 A,  10 B,  10 C,  10 D,  10 E and  10 F, X-axis stop  152  is shown in greater detail. X-axis stop  152  may be removably mounted in bottom channel  401 - 2  of lateral arm  102  (see  FIG. 10G ) to provide a hard stop for delimiting x-axis movement of carriage assembly  110  relative to lateral arm  102 . Corresponding locking knobs  900  are connected via a locking cam  902  which is disposed in an opening machined through the x-axis stop body  904 . In the unlocked state specifically shown in  FIGS. 10A ,  10 B and  10 C, the locking knobs  900  are in the upper vertical position. In this position, the locking cam  902  exerts force against the locking cam follower  906 , thereby lifting the tee nut  908  and compressing the locking springs  910 . This is the highest operating position of the tee nut  908 , which creates enough clearance between flanges of the tee nut and the X-axis stop body so that the assembly can be installed onto and move freely within a tee slot of the lateral arm  102 . In the locked state specifically shown in  FIGS. 10D ,  10 E and  10 F, the locking knobs  900  are in the lower vertical position (rotated 180 degrees relative to the unlocked position). In this position, the locking cam  902  is no longer applying force against the locking cam follower  906  so the locking springs  910  are free to retract the tee nut  908  toward the X-axis stop body  904 , thereby clamping against lateral arm  102 . Note that the likelihood of premature wear due to excess clamping force is mitigated by use of the locking springs rather than direct pressure from the knobs. 
         [0052]      FIGS. 11 through 18  illustrate various configurations of the lateral arm needle guide and assembly steps of various components.  FIG. 11  shows lateral arm  102  being secured to post member  106 .  FIG. 12  shows needle guide  103  being attached to gun mount  100 .  FIG. 13  shows biopsy needle gun  101  being attached to gun mount  100 .  FIG. 14  shows gun mount locking knob  702  being positioned in the disengaged state.  FIG. 15  shows gun mount  100  being slid into a mounted position with respect to carriage  412 .  FIG. 16  shows gun mount locking knob  702  being positioned in the engaged state, thereby securing gun mount  100  to carriage  412 .  FIG. 17  shows X-axis stop  152  being positioned in the disengaged state and mounted onto lateral arm  102 .  FIG. 18  shows X-axis stop  152  being positioned in the engaged state, thereby securing it in position relative to the lateral arm  102 . 
         [0053]    While the invention has been described through the above examples and features, it will be understood by those of ordinary skill in the art that a wide variety of modifications, combinations and variations of the examples and features may be made without departing from the inventive concepts herein disclosed. Moreover, the invention should not be viewed as being limited to any specific purposes described herein, but rather should be viewed as being applicable to accomplish a wide variety of purposes beyond those described herein.