CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of and claims the benefit of priority under 35 U.S.C. §120 to U.S. application Ser. No. 11/392,088, filed Mar. 29, 2006, which is a continuation of U.S. application Ser. No. 10/300,249, filed Nov. 20, 2002, the entire contents of both of which are being hereby fully incorporated by reference. 
    
    
     TECHNICAL FIELD 
     The invention relates to medical instruments. 
     BACKGROUND 
     A biopsy needle instrument can be used to obtain a tissue specimen for microscopic examination, e.g., to determine malignancy, while preferably subjecting the patient to the least trauma. In some embodiments, the instrument has of a long, thin probe, called a stylet, within a close-fitting hollow needle, called a cannula. The stylet has a notch into which tissue can prolapse when the stylet enters the tissue. 
     During use, a firing device first projects the stylet into tissue, followed immediately by the cannula. As the cannula slides over the stylet, the cannula severs from the surrounding mass tissue that has prolapsed into the notch of the stylet, and captures the prolapsed tissue as a specimen within the notch. The instrument can then be withdrawn and the piece of tissue removed from the stylet. 
     SUMMARY 
     The invention relates to medical instruments. 
     In one aspect, the invention features a medical instrument including a housing, a stylet, a cannula, and a lever. The stylet has a portion in the housing and is movable between an extended position and a retracted position. The cannula coaxially receives the stylet and has a portion in the housing. The cannula is movable between an extended position and a retracted position. The lever is coupled, for example, pivotally, to the housing. The lever is configured to move, for example, sequentially, the stylet from the extended position to the retracted position, and to move the cannula from the extended position to the retracted position. 
     Embodiments may include one or more of the following features. The engaging element engages with the housing when the cannula is in the retracted position. The instrument further includes a linkage attached to the lever, the linkage being engageable with the cannula block to move the cannula to the retracted position. The instrument further includes a stylet block attached to a proximal end of the stylet, and a latch in the housing, the latch and the stylet block engaging when the stylet is in the retracted position. The instrument further includes a linkage attached to the lever, the linkage being engageable with the stylet block to move the stylet to the retracted position. The instrument further includes a first trigger engageable with the latch to release the stylet from the retracted position. The first trigger pivotally moves the latch to disengage the latch from the stylet block. The instrument further includes a second trigger engageable with the latch to release the stylet from the retracted position. 
     The instrument can further include a cannula block attached to a proximal end of the cannula, the cannula block having an engaging element capable of releasably holding the cannula in the retracted position. 
     The instrument can further include a stylet block attached to a proximal end of the stylet, a cannula block attached to a proximal end of the cannula, and a linkage attached to the lever, the linkage capable of being in a first position in which the linkage is engageable with the cannula block to move the cannula to the retracted position without moving the stylet block, and in a second position in which the linkage is engageable with the stylet block to move the stylet to the retracted position. 
     Embodiments may include one or more of the following features. The instrument further includes a first trigger configured to release the stylet from the retracted position. The first trigger is located at a proximal end of the housing. The first trigger and the lever are located on opposing surfaces of the housing. The instrument further includes a second trigger configured to release the stylet from the retracted position. The instrument further includes a lock engageable with the lever when the stylet block is in the retracted position. The instrument further includes an indicator capable of being in a condition representative of when the stylet is in the second retracted position. 
     The instrument can further include a first trigger configured to hold the stylet in the retracted position, and a second trigger engageable with the first trigger, wherein the first and second triggers are configured to release the stylet from the retracted position. The first trigger can be pivotally attached to the housing. In some embodiments, the first trigger has a proximal end, and the second trigger has a distal end configured to engage with the proximal end of the first trigger. The proximal and distal ends can be angled. 
     In another aspect, the invention features a medical instrument including a housing, a stylet, a cannula, a lever, and a linkage. The\a stylet has a portion in the housing and is movable between an extended position and a retracted position. The cannula coaxially receives the stylet and has a portion in the housing. The cannula is movable between an extended position and a retracted position. The lever is pivotally coupled to the housing. The linkage is attached to the lever. The linkage is capable of being in a first position in which the linkage is capable of moving the cannula to the retracted position without moving the stylet, and in a second position in which the linkage is capable of moving the stylet to the retracted position. The instrument can further include two triggers configured to release the stylet from the retracted position. 
     In another aspect, the invention features a medical instrument including a housing, a stylet attached to the housing, the stylet being movable between an extended position and a retracted position, and an indicator associated with the housing, the indicator providing a visual indication of the position the stylet by a change in color. 
     In another aspect, the invention features a medical instrument including a housing, a stylet attached to the housing, the stylet being movable between an extended position and a retracted position, and an indicator associated with the housing, the indicator providing a visual indication of the position the stylet by a change in symbol. 
     In another aspect, the invention features a method including actuating a lever to move a stylet from a first extended position to a second retracted position, and actuating the lever to move a cannula from a third extended position to a fourth retracted position. 
     Embodiments may include one or more of the following features. The method further includes releasing the lever after the stylet is moved to the second retracted position. The method further includes locking the lever after the cannula is moved. The method further includes sliding a trigger to release the stylet from the second retracted position. The method further includes pushing a trigger to release the stylet from the second retracted position. The stylet is moved without moving the cannula. The method further includes pushing a first trigger or a second trigger to release the stylet from the retracted position. Pushing the second trigger can move the first trigger out of engagement with the stylet. 
     In another aspect, the invention features a method including pivotally actuating a lever to move a stylet from an extended position to a retracted position. 
     In another aspect, the invention features a method including pivotally actuating a lever to move a cannula from an extended position to a retracted position. 
     In another aspect, the invention features a medical instrument including a housing, a stylet attached to the housing, the stylet being movable between an extended position and a retracted position, and two triggers associated with the housing, wherein the triggers are capable of releasing the stylet from the retracted position. 
     One of the triggers can be at a proximal end of the housing. One of the triggers can be slidably associated with the housing. 
     In another aspect, the invention features a medical instrument including a housing, a stylet having a portion in the housing, the stylet being movable between an extended position and a retracted position, a cannula coaxially receiving the stylet and having a portion in the housing, the cannula being movable between an extended position and a retracted position, and a member coupled to the housing, the member being capable of moving the stylet from the extended position to the retracted position, and when separately engaged, moving the cannula from the extended position to the retracted position. The member can include a lever. The member can be engaged by a user&#39;s hand, e.g., palm and/or fingers. Embodiments of the aspect of the invention may include one or more of the features described above and below, in any combination. 
     Embodiments may have one or more of the following advantages. The instrument can be relatively easy to load prior to firing the instrument. The lever of the instrument provides good mechanical advantage and is used to load the stylet and the cannula with the same motion. The instrument includes two trigger mechanisms, which enhances the versatility and convenience of the instrument. For example, depending on a target site and/or preference of a user, a radiologist can prefer to use a side trigger, while a urologist can prefer the rear trigger. 
     Other aspects, features, and advantages of the invention will be apparent from the description of the preferred embodiments thereof and from the claims. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view of an embodiment of a biopsy instrument. 
         FIGS. 2A and 2B  are exploded, perspective views of the biopsy instrument of  FIG. 1 , at different angles. 
         FIGS. 3A ,  3 B,  3 C,  3 D, and  3 E illustrate the biopsy instrument of  FIG. 1  at various stages of operation. 
         FIG. 4A  is a schematic diagram of an embodiment of a biopsy instrument in a rest position; and  FIG. 4B  is a schematic diagram of the instrument of  FIG. 4A  in a cocked position. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1 ,  2 A,  2 B, and  3 A, a biopsy instrument  20  includes a housing  22 , a stylet  24 , a cannula  26 , a lever  28  pivotally attached to the housing, a side trigger  36 , and a rear trigger  38 . Housing  22  includes a left shell  30  and a right shell  32  (as shown in Figures) that are bonded together. Stylet  24  and cannula  26  have portions located within housing  22  and are configured to be axially movable relatively to each other, between retracted positions and extended positions. As shown in  FIG. 3A , stylet  24  and cannula  26  are in their extended positions. During use, stylet  24  and cannula  26  are loaded or cocked to their retracted positions, ready to be triggered. When stylet  24  and cannula  26  are triggered, they rapidly move distally to their extended positions, e.g., to collect a tissue specimen that has prolapsed into a notch  40  of the stylet. Lever  28  is connected to a linkage  44  configured to move stylet  24  and cannula  26  from their extended positions to their retracted or loaded positions. In particular, lever  28  is part of a mechanism that is used to load both stylet  24  and cannula  26  to their retracted positions. After stylet  24  and cannula  26  are loaded, either side trigger  36  or rear trigger  38  can be used to release the stylet and the cannula to their extended positions. 
     Referring to  FIGS. 2A ,  2 B, and  3 A, cannula  26  is generally a hollow sheath, e.g., made of stainless steel, that receives stylet  24 . At its distal end  27 , cannula  26  is configured to sever tissue that has prolapsed into notch  40 . From distal end  27 , cannula  26  extends into housing  22  where the cannula is attached to an axially movable (arrow A) cannula block  42 . Cannula block  42  includes a raised portion  46  that engages with linkage  44  during use (described below), and two deflectable tabs  48  that can engage with notches or lips (not shown) integrally formed on housing  22  to hold cannula  26  and cannula block  42  in their retracted positions. A compression spring  50  engages cannula block  42  and biases the cannula block distally. Spring  50  can be, e.g., a stainless steel spring having a spring rate of 9.77 lb/in. 
     Stylet  24  is slidably and coaxially located in cannula  26 . Stylet  24  has a distal end  34  configured to penetrate tissue and notch  40  for collecting a tissue sample. Examples of suitable stylet  24  and cannula  26  configurations are exemplified by the ASAPTM Automated Biopsy System having a Delta Cut® needle or a Channel Cut®) needle (available from Boston Scientific Corp., Natick, Mass.), and described in Chu, U.S. Pat. No. 5,989,196, hereby incorporated by reference. From distal end  34 , stylet  24  extends into housing  22  where stylet is attached to an axially movable stylet block  52 . At its distal portion, stylet block  52  includes a distal post  54  and a distal wall  56 , both of which engage with linkage  44  when stylet  24  is moved to its retracted position. At its proximal portion, stylet block  52  includes a proximal wall  58  that is used to hold stylet block  52  in its retracted position, and a proximal post  60 . Proximal post  60  can engage with an axially movable lever lock  62 , which is used to lock lever  28  in a closed position before stylet  24  and cannula  26  are released to their extended positions. Stylet block  52  further includes two deflectable tabs  64  configured to engage with tabs  48  of cannula block  42  to disengage tabs  48  from housing  22 . A compression spring  65  engages stylet block  52  and biases the stylet block distally. 
     Lever  28  is configured to load cannula  26  and stylet  24  to their retracted positions. Lever  28  is connected to housing  22  by a link  66  having a pin  68 , which serves as an axis about which the lever rotates (arrow B). In some embodiments, a torsion spring (not shown) is attached to pin  68  to bias lever  28  toward an open position ( FIG. 3A ). Lever  28  is connected to a linkage  44  via a pin  45 , and a hook  70  ( FIG. 2A ). A torsion spring (not shown) is attached to pin  45  to bias linkage  44  toward stylet block  52 . As described below, during use, linkage  44  engages with cannula block  42  and stylet block  52 . Linkage  44  further includes a curved portion  72  that engages with distal post  54  of stylet block  52 . Hook  70  engages with protrusions  74  of lever lock  62  to hold lever  28  in a closed position. 
     Instrument  20  further includes a mechanism  76  to hold stylet block  52  and to release the stylet block from its retracted position. Mechanism  76  includes a rear latch  78 , side trigger  36 , and rear trigger  38 . Rear latch  78  includes a pin  80  and is mounted in housing  22  such that the rear latch can pivot about the length of the pin (arrow C). Rear latch  78  further includes a hook portion  82 , two side members  84  having curved ends  86 , and a rear plate  87 . Hook portion  82  is configured to engage with, e.g., hook on to, proximal wall  58  of stylet block  52  to hold the stylet block in its retracted position. 
     Side trigger  36  and rear trigger  38  are configured to move rear latch  78  such that hook portion  82  can disengage from proximal wall  58 . Side trigger  36 , which is axially slidable (arrow A), includes a side button  85 , an end member  88  having a ramped surface  90 , and an elongate member  92  connecting the side button and the end member. Ramped surface  90  contacts and engages with curved ends  86  of side members  84 . When side button  85  is pulled proximally, end member  88  also moves proximally. As a result, ramped surface  90  engages with curved ends  86  and pivots rear latch  78  such that hook portion  82  can lift and disengage from proximal wall  58 . Rear trigger  38  is movably mounted to housing  22  and is configured to engage with rear plate  87 . In particular, when depressed, rear trigger  38  pushes against rear plate  87 . As a result, rear latch  78  pivots about pin  80 , and hook portion  82  can disengage from proximal wall  58 . 
     In some embodiments, instrument  20  also includes a visual indicator that shows when stylet  24  has been loaded to its retracted position. The indicator includes one or more windows  94  formed in housing  22  that allow a user to detect a change in the position of stylet block  52 . For example, window(s)  94  can be formed on housing  22  such that tabs  64  of stylet block  52  cover the window(s) when the stylet block is in its extended position. When stylet block  52  is retracted, tabs  64  slide away from window(s)  94  and uncover interior portions of instrument  20 . The interior portions can be colored, e.g., red, for enhanced visibility. In other embodiments, window(s)  94  can be aligned with the proximal portion of stylet block  52  having a first color, e.g., green, and the distal portion of the stylet block can have a second color, e.g., red. When stylet block  52  is moved from its extended position to its retracted position, the color visible through window(s) changes from the first color to the second color to indicate that instrument  20  is loaded. Alternatively or in addition, instrument  20  can include window(s) aligned with cannula block  42  to indicate the position of the cannula block. For example, cannula block  42  can be formed with portions with different colors as described above. 
       FIGS. 3A-3E  illustrate a sequence of the operation of instrument  20 . Referring to  FIG. 3A , instrument  20  is in its rest position, e.g., as taken out of its packaging. Cannula block  42  and stylet block  52  are at their most distal, extended positions. Lever  28  is in its open position, and linkage  44  is adjacent to raised portion  46  of cannula block  42 . Lever lock  62  is shown in a distal position. 
     To load or move cannula block  42  and stylet block  52  to their retracted positions, lever  28  is actuated, e.g., closed, two times. Referring to  FIG. 3B , when lever  28  is actuated the first time, linkage  44  pivots and engages with raised portion  46  of cannula block  42 . As a result, cannula block  42  and cannula  26  are pushed proximally until tabs  48  engage with housing  22 , thereby holding the cannula block and the cannula in their retracted positions ( FIG. 3B ). Cannula block  42  compresses against spring  50 . Lever  28  is then released to its open position, e.g., aided by the torsional spring (not shown) attached to pin  68 . 
     Referring to  FIG. 3C , when lever  28  is returned to its open position, linkage  44  engages with distal wall  56  of stylet block  52 . The torsion spring (not shown) attached to pin  45  of linkage  44  helps bias the tip of the linkage toward stylet block  52 . Lever  28  is then actuated to load stylet block  52  and stylet  24  to their loaded, retracted positions. When lever  28  is actuated, linkage  44  pushes against distal wall  56  and moves stylet block  52  and stylet  24  proximally. Referring to  FIG. 3D , as stylet block  52  is pushed further proximally, distal post  54  engages, e.g., contacts, with curved portion  72  of linkage  44 . As stylet block  52  is pushed to its retracted position, distal post  54  pushes linkage  44  out of engagement with distal wall  56  and stylet block  52 . When stylet block  52  is at its retracted position, hook portion  82  of rear latch  78  engages with proximal wall  58  of the stylet block and holds the stylet block in its retracted position. At the same time, when stylet block  52  is in its retracted position, proximal post  60  pushes lever lock  62  proximally ( FIG. 3D ). As a result, hook  70  of lever  28  can engage with protrusions  74  of lever lock  62  to hold the lever in a closed position ( FIG. 3E ). Stylet block  52  compresses against spring  65 . Instrument  20  is ready to be triggered or fired. 
     To fire instrument  20 , distal end  34  of stylet  24  is placed adjacent to a target area, and either side trigger  36  or rear trigger  38  can be actuated. To actuate side trigger  36 , side button  85  is pulled proximally, e.g., using an index finger, which causes end member  88  to move proximally. As a result, curved ends  86  of side members  84  are advanced over ramped surface  90 , which causes rear latch  78  to pivot about pin  80 , thereby lifting hook portion  82  out of engagement with proximal wall  58  of stylet block  52 . Upon disengagement, stylet block  52  and stylet  24  are propelled distally by the spring force of spring  65 , which allows the stylet to penetrate the targeted area. Stylet block  52  then strikes cannula block  42 , which disengages tabs  48  of the cannula block from housing  22 . In particular, the ramped configuration of the tips of tabs  64  help to wedge tabs  64  between tabs  48  and housing  22  to disengage tabs  48  and cannula block  42  from the housing. Upon disengagement, cannula block  42  and cannula  26  are propelled distally by the spring force of spring  50 , which allows the cannula to slide over stylet  24  and to sever a specimen that has prolapsed into notch  40  of the stylet. 
     Instrument  20  can then be withdrawn. Lever  28  can be returned to its open position by slightly depressing the lever to allow lever lock  62  to move (e.g., distally) and to disengage from hook  70 , e.g., similar to the operation of a lockable grip vise. The specimen can be removed from notch  40  by actuating lever  28  once to retract cannula  26 . The specimen can be placed on a slide or in a preservative solution. If desired, lever  28  can be actuated to retract and load stylet  24  to collect another specimen. 
     Rear trigger  38  is actuated by distally pushing the rear trigger, which pushes against rear plate  87 . As a result, rear latch  78  pivots about pin  80 , and hook portion  82  is lifted out of engagement with proximal wall  58  of stylet block  52 . Upon disengagement, stylet  24  and cannula  26  are propelled distally as described above. 
     In other embodiments, mechanism  76  used to hold stylet block  52  and to release the stylet block from its retracted position can be modified. Referring to  FIGS. 4A and 4B , instrument  100  (generally the same as instrument  20  except as described below) includes a mechanism  102  having a side trigger  104  and a rear trigger  106 . Side trigger  104  includes an elongated body  108  having a side button  110 , a distal portion  112 , and a proximal portion  114 . Body  108  is pivotally attached to housing  22  at pivot  116 . Distal portion  112  is a generally elongated, curved member that engages portions of housing  22  to bias side button  110  out of the housing (or downward as shown in  FIG. 4A ). Distal portion  112  also biases proximal portion  114  upward (as shown in  FIG. 4A ) via pivot  116 . Proximal portion  114  includes a projection  118  configured to engage with stylet block  52 , specifically, a notch  120  defined by the stylet block. Proximal portion  114  terminates with an angled surface  122 . Rear trigger  106  includes a rear button  124  integrally form with a proximal portion  126  that terminates with an angled surface  128 . Angled surface  128  contacts angled surface  122 , but for clarity, the surfaces are shown spaced from each other. 
     Operation of instrument  100  is similar to operation of instrument  20 . The user retracts cannula block  42  by actuating lever  28  once. When the user actuates lever  28  again, stylet block  52  is moved proximally until projection  118  engages notch  120 , thereby holding the stylet block in its retracted position ( FIG. 4B ). Projection  118  is biased upward (as shown in  FIG. 4A ) by distal portion  112  and pivot  116  to facilitate engagement with notch  120 . 
     To fire instrument  100 , either side trigger  104  or rear trigger  106  can be actuated. To actuate side trigger  104 , side button  108  is pushed into housing  22 , which overcomes biasing force of distal portion  112  and causes projection  118  to move down (arrow X, as shown in  FIG. 4B ) via pivot  116 . As a result, projection  118  disengages from notch  120 , and stylet block  52  and cannula block  42  can be propelled distally as described above. 
     Rear trigger  106  is actuated by pushing rear button  124  distally (arrow Y). As a result, angled surface  128  contacts, e.g., slides over, angled surface  122 , thereby moving proximal portion  114  and projection  118  downward (arrow X) and out of engagement with notch  120 . Stylet block  52  and cannula block  42  are propelled distally as described above. 
     In some embodiments, housing  22  and/or lever  28  can each be made of different materials, e.g., to enhance the grip or “feel” of instrument  20 . For example, housing  22  and/or lever  28  can be formed of materials with different hardness, e.g., a core of relatively hard material and an outer layer of relatively soft material. The outer layer can be a foamy material, such as a urethane, to enhance the grip and/or to absorb vibrations from the firing of instrument  20 . Each of lever  28  and/or housing  22  can be formed with two or more different materials. 
     The components of instrument  20  described above can be formed by conventional injection molding techniques, e.g., of polycarbonate and/or ABS. Stylet  24 , cannula  26 , springs  50  and  65 , and the torsion springs can be formed of stainless steel. 
     Terms, such as “left”, “right”, and “rear”, are used to describe the embodiment as shown in the orientation of the figures, and not intended to be limiting. 
     Other embodiments are within the claims.
A method includes actuating a lever to move a cannula of a medical instrument from a first extended position to second retracted position; and actuating the lever to move a stylet of the medical instrument from a third extended position to a fourth retracted position. Actuating the lever comprises moving the lever from a first lever position spaced apart from a housing of the medical instrument to a second lever position closer to the housing.