WO2002024077A1

WO2002024077A1 - Automated core biopsy instrument and methods

Info

Publication number: WO2002024077A1
Application number: PCT/US2001/042240
Authority: WO
Inventors: Erik S. Kass; Carter Van Waes
Original assignee: The Government Of The United States Of America, As Represented By The Secretary Of The Department Of Health And Human Services
Priority date: 2000-09-20
Filing date: 2001-09-20
Publication date: 2002-03-28
Also published as: AU2001293300A1

Abstract

A tissue sampling device according to one disclosed embodiment includes a cannula (304) and a stylet (306) slidably received in the cannula. The stylet has a distal end with at least one tissue receiving recess (308, 310). First (354) and second (334) biasing mechanisms are configured to urge the stylet and the cannula, respectively, from respective retracted positions to respective extended positions. First (340) and second (336) latch mechanisms are configured to releasably hold the stylet and the cannula, respectively, in their retracted positions. A trigger mechanism (120) is configured to be selectively positionable at a plurality of positions so that when the trigger mechanism is moved from a first position to a second position, the trigger mechanism causes the first latch mechanism to release the stylet, and when the trigger mechanism is moved from the second position to a third position, the trigger mechanism causes the second latch mechanism to release the cannula.

Description

AUTOMATED CORE BIOPSY INSTRUMENT AND METHODS

FIELD

The present invention relates to surgical instruments for obtaining tissue samples.

BACKGROUND In the field of medicine, before effective treatment can be prescribed, physicians normally perform a series of tests to determine the nature of the illness, infection, or disease. Such tests, in many cases, are performed on diseased tissue. This, in fact, requires the physician to obtain a specimen of the infected or diseased tissue in the most efficient manner with the least discomfort to the patient. Various biopsy methods are known for obtaining tissue samples.

Biopsies typically are performed using an open or a closed technique. Open biopsy removes the entire mass (excision biopsy) or a part of the mass (incision biopsy). Closed biopsy is usually performed with a needle-like instrument and may be either an aspiration or a core biopsy. In needle aspiration biopsy, individual cells or clusters of cells are obtained for cytologic examination and may be prepared such as in a Papanicolaou smear. In core biopsy, a core or filament of tissue is obtained for histologic examination. The type of biopsy that is performed depends on the circumstances; however, core biopsy is extremely useful in a number of conditions and is the most widely used type ofbiopsy. Minimally invasive biopsy instruments are commonly used to obtain tissue specimens for examination to aid in the diagnosis of disease. These types of instruments are used to rmnimize trauma and reduce the risk of serious injury to the patient. Typically, these instruments consist of an outer hollow needle, referred to as a "cutting cannula," and a coaxial inner needle, referred to as a "stylet." The stylet has a notch proximate the end thereof so that when the stylet is advanced into the targeted tissue of interest, a tissue sample is received in the notch.

The stylet and cannula usually are contained within, and extend from, one end of a housing. In order to obtain a tissue specimen, the entire instrument is moved forward and the needles are advanced through the tissue. Once the desired location is reached, the stylet is advanced into the adjacent tissue of interest, followed by the cutting cannula. As the cutting cannula advances forward over the stylet, prolapsed tissue is severed and trapped within the notch of the stylet. The instrument is then withdrawn and the tissue sample removed from the notch for analysis.

One example of a biopsy instrument is disclosed in U.S. Patent No. 4,699,154 to Lindgren. The Lindgren patent is understood to disclose a biopsy needle instrument that automatically projects the cannula immediately after the stylet is fired. However, this arrangement is disadvantageous in that it does not allow the physician to first determine whether the stylet has been deployed into the targeted tissue of interest (e.g., a tumor) before the cutting cannula is fired.

U.S. Patent No. 4,958,625 to Bates et al. is understood to disclose a biopsy needle instrument that, in part, attempts to address the problem of the device disclosed in the Lindgren patent by providing a locking mechanism in one embodiment for preventing automatic deployment of the cannula upon deployment of the stylet. Thus, if it is determined that the stylet missed the targeted area, unnecessary damage to healthy tissue by projection of the cannula can be avoided. To activate the cannula, the locking mechanism is moved to an unlocked position and pressure is applied to a slide switch. The Bates device suffers from the disadvantage that the switch for firing the cannula is separate from the button used to fire the stylet. Thus, pressure must be applied at separate locations on the device for firing the stylet and the cannula, which may make the device difficult to operate. Thus, a need exists for a new and improved biopsy instrument.

SUMMARY According to one aspect, an automated core biopsy instrument is configured to be operated with one hand and has an activation element that will cause both the inner stylet of a needle system to advance into the tissue of interest that is to be biopsied, and the outer cannula of the same needle system to advance over the stylet to cut tissue in the specimen notches of the stylet from surrounding tissue. According to one representative embodiment, a tissue sampling device includes a housing having a first opening. A needle assembly includes a hollow first needle extending outwardly through the first opening so that a distal end of the first needle is positioned outside the housing. A second needle of the needle assembly is at least partially received in the first needle and has a distal end with at least one tissue receiving recess. A first biasing mechanism is configured to urge the first needle distally in a first direction from a retracted position to an extended position. A second biasing mechanism is configured to urge the second needle distally in the first direction from a retracted position to an extended position. A first latch mechanism is configured to releasably hold the first needle in its retracted position. A second latch mechanism is configured to releasably hold the second needle in its retracted position.

A firing mechanism is provided for actuating both the first and second needles. The firing mechanism is configured to be selectively positionable at a plurality of positions. When the firing mechanism is moved from a first position to a second position, a first surface of the firing mechanism engages the second latch mechanism to cause the second latch mechanism to release the second needle and thus allow the second needle to move to its extended position. In its fully extended position, the distal end of the second needle extends beyond the distal end of the first needle at least enough to fully expose the tissue receiving recess to the tissue of interest. When the firing mechanism is moved from the second position to a third position, a second surface of the firing mechanism engages the first latch mechanism to cause the first latch mechanism to release the first needle and thus allow the first needle to move to its extended position over the second needle. As the first needle is driven over the second needle, tissue in the tissue receiving recess is sheared off from any surrounding tissue by the distal end of the first needle.

Since a single firing mechanism is configured to deploy both the first and second needles, the instrument may be operated while maintaining hand position on the instrument. It is therefore possible to operate the instrument with only one hand. Unlike conventional biopsy instruments, the physician (or other health care professional) is not required to adjust the settings of a selector switch or apply pressure at multiple locations on the instrument to deploy the first and second needles. In addition, because the firing mechanism provides for independent firing of the first and second needle, the physician can first determine whether the second needle has been properly deployed into the tissue of interest before activating the first needle.

The instrument may also include a cocking mechanism configured to retract the first needle and the second needle from their extended positions to their retracted positions after the first needle and the second needle have been deployed to retrieve a tissue sample. In a specific implementation, the cocking mechanism is supported for movement relative to the housing. Movement of the cocking mechanism over a first distance causes the first needle to move to its retracted position and further movement of the cocking mechanism over a second distance beyond the first distance causes the second needle to move to its retracted position.

The instrument desirably has a locking mechanism or safety switch to prevent inadvertent firing of the first needle. The locking mechanism is adapted for movement between a first locking position and a second release position. When the locking mechanism is in the first locking position, the locking mechanism is in position to oppose the release of the first latch mechanism. When the locking mechanism is in the second release position, the locking mechanism is removed from opposing the release of the first latch mechanism. According to a second representative embodiment, a tissue sampling device includes a housing having a first opening. The housing also has first and second ends and a longitudinal axis extending therebetween. A cannula assembly has a cannula extending outwardly through the first opening of the housing. The cannula assembly is supported in the housing for movement along the longitudinal axis relative to the housing. A stylet assembly has a stylet slidably received in the cannula. The stylet assembly is supported in the housing for movement along the longitudinal axis relative to the housing and the cannula assembly. The stylet has a distal end portion extending outwardly through the first opening. The distal end of the stylet has a least one tissue receiving member.

A stylet moving mechanism is disposed in the housing and is configured to bias the stylet in

I a first direction along the longitudinal axis. A cannula moving mechanism is disposed in the housing and is configured to bias the cannula in the first direction along the longitudinal axis. A stylet retaining member is disposed in the housing for preventing movement of the stylet against the stylet moving mechanism. A cannula retaining member is disposed in the housing for preventing movement of the cannula against the cannula moving mechanism. A trigger mechanism is provided for controllably releasing the stylet fcom. the stylet retaining member and the cannula from the cannula retaining member. The trigger mechanism is selectively movable from a first position to a stylet triggering position and from the stylet triggering position to a cannula triggering position. When the trigger mechanism is moved to the stylet triggering position, the trigger mechanism removes the stylet retaining member from preventing movement of the stylet to allow the stylet moving mechanism to move the stylet in the first direction for obtaining a tissue sample in the tissue receiving member. When the trigger mechanism is moved to the cannula triggering position, the trigger mechanism removes the cannula retaining member from preventing movement of the cannula in the first direction to allow the cannula moving mechanism to move the cannula in the first direction over the stylet to separate the tissue sample in the tissue receiving member from surrounding tissue.

According to yet another representative embodiment, a tissue sampling device includes a housing. A hollow first needle extends from the housing and is supported for movement relative to the housing between a retracted position and an extended position. A second needle, which is at least partially disposed in the first needle, is supported for movement relative to the first needle and the housing between a retracted position and an extended position. The second needle has a distal end with at least one tissue receiving notch.

A first biasing means urges the first needle distally from the retracted position to the extended position. A second biasing means urges the second needle distally from the retracted position to the extended position. A first latch means is provided for releasably latching the first needle in the retracted position against the first biasing means. A second latch means is provided for releasably latching the second needle in the retracted position against the second biasing means.

An activation means is provided for separately activating the first needle and the second needle. The activation means is supported for movement relative to the housing in a first direction. When the activation means is moved over a first distance in the first direction, the activation means unlatches the second latch means to allow the second biasing means to move the second needle to its extended position. When the activation means is moved over a second distance in the first direction beyond the first distance, the activation means unlatches the first latch means to allow the first biasing mechanism to move the first needle to its extended position. The foregoing and other objects, features and advantages of the invention will become more apparent from the following detailed description of several embodiments, which proceeds with reference to the accompanying figures. BRIEF DESCRIPTION OF THE DRA WINGS

FIG. 1 is a side elevation view of an automated core biopsy instrument according to one embodiment.

FIG. 1A is a top plan view of the biopsy instrument shown in FIG. 1. FIG. 2A is a front elevation view of the biopsy instrument taken along line 2-2 of FIG. 1.

FIG. 2B is a back elevation view of the biopsy instrument of FIG. 1.

FIG. 3 is a vertical cross-sectional view of the biopsy instrument taken along lines 3-3 of FIGS. 1A and 2A.

FIG. 4 is a vertical cross-sectional view of the biopsy instrument taken along lines 4-4 of FIGS. 1A and 2B.

FIG. 5 is a horizontal cross-sectional view of the biopsy instrument taken along line 5-5 of FIG. 1.

FIG. 6 is a horizontal cross-sectional view of the biopsy instrument taken along line 6-6 of FIG. 1. FIG. 7 is a horizontal cross-sectional view of the biopsy instrument taken along line 7-7 of

FIG. 1.

FIG. 8 is a horizontal cross-sectional view of the biopsy instrument taken along line 8-8 of FIG. 1.

DETAILED DESCRIPTION

According to one aspect, an automated core biopsy instrument is configured to be operated with one hand. A single activation element (also referred to herein as a trigger mechanism or firing mechanism) selectively actuates a stylet assembly and a cutting cannula assembly of a needle system to obtain a tissue sample from the tissue of interest. In other words, when activated (e.g., by depressing a button), the activation element deploys the stylet assembly, but not the cannula assembly. After the stylet assembly is deployed, the cannula assembly may be deployed upon further activation of the activation element. In one embodiment, for example, movement of the activation element from a first position to a second position causes a stylet of the stylet assembly to advance into the targeted tissue. Further movement of the activation element from the second position to a third position causes a cutting cannula of the cannula assembly to advance over the specimen notches of the stylet to shear off the tissue in the notches from surrounding tissue. The instrument can then be removed from the patient for testing of the tissue sample.

Referring first to FIGS. 1 and 1A, there is shown side and top views respectively, of an automated core biopsy instrument 100 according to one embodiment. The biopsy instrument 100 has an elongated housing or body 102, which has a top wall 111, a bottom wall 113, side walls 115 and 117, a front end wall 104, and a rear end wall 108. A longitudinal axis L extends between the front end wall 104 and the rear end wall 108. The housing 102 in the illustrated form has a rectangular cross-sectional shape. However, the housing 102 may have other cross-sectional shapes. For example, the cross-sectional shape of the housing 102 may be circular, elliptical, or any of various other shapes. In addition, the housing 102 is shown as being straight longitudinally, although the housing 102 may have other longitudinal shapes. One example is that the longitudinal shape may be curved. Other longitudinal shapes are also possible for the purpose of facilitating the use of the instrument 100. Referring to FIGS. 3, 6 and 7, a cutting cannula assembly 119 and a stylet assembly 305 are supported in the housing 102. Both the cannula assembly 119 and the stylet assembly 305 are longitudinally moveable fore and aft (as represented by arrows A and B, respectively) relative to each other and the housing 102. When the cannula assembly 119 and the stylet assembly 305 are activated to retrieve a tissue sample, they are caused to move forwardly in the A direction from a retracted position, such as shown in FIG. 3, to an extended position. After firing, the cannula assembly 119 and the stylet assembly 305 may be moved rearwardly in the direction of arrow B from their extended positions to their retracted positions for reloading. The operation of the cannula assembly 119 and the stylet assembly 305 is described in further detail below.

The cannula assembly 119 includes a hollow, elongate cannula 304 that extends outwardly through an opening 302 defined in the front end wall 104 of the housing 102. The cannula 304 has a tapered or beveled distal end 309, as generally known in the art. The proximal end of the cannula 304 (i.e., the end opposite the distal end 309) is connected to the forward end of a cannula latch member 328, the rear portion of which forms an enlarged flanged portion 330. A cannula moving mechanism, such as a biasing mechanism or other resilient member, is provided to urge the cannula assembly 119 to its extended position. In the illustrated embodiment, for example, a compression spring 334 is disposed around a spring guide 332. The spring guide 332 is connected to and desirably extends from the rear end of flanged portion 330 through an opening in a support member 324, which extends perpendicularly from the side wall 115 of the housing 102 (as best shown in FIG. 7). In an alternative embodiment, the spring guide 332 extends from the rear end of the flanged portion 330 toward the support member 324, but does not extend through the support member 324. In either case, one end of the spring 334 abuts against the rear end of the flanged portion 330 and the other end of spring 334 abuts against the support member 324. In this manner, the biasing force of the compression spring 334 provides the motive force to drive the cannula 304 forwardly to its extended position when activated. The support member 324 maintains the axial alignment of the cannula assembly 119 and serves as a bearing surface for the spring guide 332 as the cannula assembly 119 is moved fore and aft.

The stylet assembly 305 has an elongate stylet 306 that is slidably received in the cannula 304 and corresponding axial bores extending through the cannula latch member 328 and the spring guide 334. Like the cannula 304, the stylet 305 also has a tapered or beveled distal end 311. When the stylet 305 is in its retracted, or cocked, position (such as shown in FIG. 3), the tapered end 311 desirably is aligned with the tapered end 309 of the cannula 304. When activated, the stylet 305 and the cannula 306 move outwardly from the housing 102 an equal distance so that the tapered ends 309, 311 of the cannula and stylet 304, 306, respectively, align with each other in their extended positions. The stylet 306 has at least one tissue-receiving member for receiving a tissue sample when the stylet 306 is advanced into the tissue of interest. As shown in FIG. 3, for example, elongated specimen notches or recesses 308 and 310 are formed in the distal end portion of the stylet 306. The notches 308, 310 extend longitudinally of the stylet 306. Although the stylet 306 in the illustrated embodiment is shown as having two tissue receiving notches, more or fewer notches may be used. Moreover, in other configurations, the tissue receiving notches may have other shapes, such as an annular groove.

The proximal end of stylet 306 is connected to a stylet latch member 350 (FIGS. 3, 6 and 7). A stylet moving mechanism provides the motive force for moving the stylet assembly 305 to its extended position. The stylet moving mechanism may be a conventional biasing mechanism or other resilient member. In the present embodiment, for example, a compression spring 354 is disposed around a spring guide 352. The spring guide 352 is connected to the rear surface of the stylet latch member 350. Desirably, but not necessarily, the spring guide 352 extends through an opening in a support member 326, which extends perpendicularly from the side wall 115 of the housing 102.

Alternatively, the spring guide 352 may extend to a position in front of the support member 326. In either configuration, one end of the spring 354 abuts against the rear surface of the stylet latch member 350 and the other end abuts against the support member 326. Thus, the biasing force of the spring 354 urges the stylet 306 forwardly to its extended position. The support member 326 maintains the axial alignment of the stylet assembly 305 and serves as a bearing surface for the spring guide 352 as the stylet assembly 305 is move fore and aft.

The cannula assembly 119 and the stylet assembly 305 desirably are retained in their retracted positions by respective latch mechanisms or retaining members. In the illustrated embodiment, for example, a cannula latch mechanism 336 is pivotally mounted on a pivot pin 116, which is connected at each end to a respective side wall 115, 117 (as best shown in FIG. 5). As best shown in FIG. 3, the cannula latch mechanism 336 has a distal end 338 configured to engage the flanged portion 330 of the cannula latch member 328. The cannula latch mechanism 336 is pivotable about pin 116, in the directions indicated by arrows E and F, between a latched position (such as shown in FIG. 3) and an unlatched position. In the latched position, a vertical surface 136 of the distal end portion 338 engages the vertical leading edge 138 of the flanged portion 330 (as best shown in FIG. 6) to retain the cannula assembly 119 in its retracted position against the biasing force of the compression spring 334. The leading edge 138 therefore serves as a latch surface for the cannula latch mechanism 336. In the unlatched position, the vertical surface 136 of the distal end portion 338 is disengaged from the leading edge 138 of the flanged portion 330 to allow the cannula assembly 119 to project forwardly under the biasing force of the spring 334.

As best shown in FIG. 4, the cannula latch mechanism 336 also has a downwardly projecting trigger engaging portion 404. The trigger engaging portion 404 has an angled trigger engaging surface 407 that is adapted to engage a corresponding inclined trigger surface 411 of a trigger or firing mechanism 120. As discussed in greater detail below, translational movement of the trigger mechanism 120 in the A direction causes the inclined surface 411 to engage the trigger engaging surface 407, thereby causing pivoting of the cannula latch mechanism 336 in the F direction for releasing the cannula assembly 119.

The cannula latch mechanism 336 may be biased with an optional biasing mechanism or other resilient member to urge the distal end 338 toward the flanged portion 330 in the direction of arrow E. For example, in the illustrated embodiment, a leaf spring 130 is interposed between the top surface of the cannula latch mechanism 336 and the inner surface of the top wall 111 (FIG. 3). The biasing force of the leaf spring 130 facilitates cocking or reloading of the cannula assembly 119, as will be appreciated with reference to the description of the operation of the instrument 100 provided in greater detail below. A stop member (not shown) may be disposed within the housing 102 to prevent the cannula latch mechamsm 336 from rotating under the biasing force of the leaf spring 130 in the E direction past the substantially parallel position (as shown in FIG. 3) after the cannula assembly 119 is activated. By maintaining the latch mechanism 336 in a substantially parallel position after firing, the cannula assembly 119 can be moved back to its retracted position for reloading. Such a stop member may extend perpendicularly from the side wall 115 and have an end portion disposed at a position underneath the lower surface of the latch mechanism 336.

If a biasing mechanism, such as the leaf spring 130, is not provided to urge the distal end portion 338 of the cannula latch mechanism 336 toward the flanged portion 330, the proximal end of the compression spring 334 may be situated to at least partially contact the downwardly extending proximal portion of the cannula latch mechanism 336. In this configuration, when the cannula assembly is moved rearwardly for reloading, compression of the spring 334 against the proximal portion of the cannula latch mechanism 336 causes the distal end portion 338 to pivot downwardly toward the flanged portion 330.

A stylet latch mechanism 340, the construction of which is similar to the cannula latch mechanism 336, is provided for retaining the stylet assembly 305 in its retracted position. The stylet latch mechanism 340 is pivotably disposed on a pivot pin 118 that is connected at each end to a respective side wall 115, 117 (as best shown in FIG. 5). The stylet latch mechamsm 340 has a distal end 342 configured to engage the stylet latch member 350 (FIG. 3). The stylet latch mechanism 340 is pivotable about pin 118, as indicated by arrows E and F, between a latched position (such as shown in FIG. 3) and an unlatched position. In the latched position, a vertical surface 140 of the distal end portion 342 engages the vertical leading edge 142 of the stylet latch member 350 (as best shown in FIG. 6) to retain the stylet assembly 305 in its retracted position against the biasing force of the compression spring 354. The leading edge 142 therefore serves as a latch surface for the stylet latch mechanism 340. In the unlatched position, the vertical surface 140 of the distal end portion 342 is disengaged from the leading edge 142 of the stylet latch member 350 to allow the stylet assembly 305 to project forwardly under the biasing force of the spring 354.

The stylet latch mechanism 340 also has a downwardly projecting trigger engaging portion 406 (FIG. 4). The trigger engaging portion 406 has an angled trigger engaging surface 403 that is adapted to engage a corresponding inclined trigger surface 412 of the trigger mechanism 120. The inclined surface 412 of the trigger mechanism 120 is configured to engage the trigger engaging surface 405 upon translational movement of the trigger mechanism, thereby causing pivoting of the stylet latch mechamsm 340 in the F direction for releasing the stylet assembly 305.

An optional leaf spring 132 may be interposed between the top surface of the stylet latch mechanism 342 and the inner surface of the top wall 111 for urging the stylet latch mechamsm to its latched position. A stop member (not shown) may be disposed within the housing 102 to prevent the stylet latch mechanism 342 from rotating under the biasing force of the leaf spring 132 in the E direction past the substantially parallel position (shown in FIG. 3) after the stylet assembly 305 is activated. If the leaf spring 132 is not provided, the compression spring 354 may be situated with its proximal end in contact with the downwardly extending proximal end portion of the stylet latch mechanism 340 to urge the distal end portion 342 toward the stylet latch member 350 when the stylet assembly is moved rearwardly for reloading.

The trigger mechanism 120 is configured to selectively activate the stylet assembly 305 and the cannula assembly 119. In other words, the trigger mechanism 120 is operable to cause deployment of the stylet 306 into the targeted tissue without also deploying the cannula assembly

119. Once it is determined that the stylet 306 has been properly deployed into the targeted tissue, the cannula 304 may be activated by the trigger mechanism for deployment over the stylet 306.

Referring to FIGS. 4, 5 and 6, the trigger mechanism 120 in the illustrated form includes an elongated trigger shaft 124. The trigger shaft 124 extends outwardly through an opening 402 defined in the back end wall 108 of the housing 102. The proximal end of the trigger shaft 124 forms a thumb or finger engageable trigger button 122. The trigger shaft 124 is supported within the housing 102 on a recessed portion 420b of a trigger pad 420 (as best shown in FIG. 4). The trigger mechanism 120 is slidable longitudinally fore and aft relative to the trigger pad 420. A vertical ledge 422 extending between the upper surface of the recessed portion 420b and the upper surface of a distal end portion 420a of the trigger pad 420 limits the forward movement of the trigger mechanism 120.

The distal end portion of the trigger shaft 124 defines the inclined trigger surface 411 for engaging the angled trigger engaging surface 407 of the cannula latch mechamsm 336. The trigger shaft 124 also has a recessed portion 413 disposed in the housing 102. The proximal end portion of the recessed portion 413 defines the inclined trigger surface 412 for engaging the angled trigger engaging surface 403 of the stylet mechanism 340.

A trigger stop member 416 extends perpendicularly outward from the side wall 117 at a position over the recessed area 413 of the trigger shaft 124. As can be seen, the stop member 416 is positioned to engage a vertical ledge 414 at the distal end of the recessed portion 413 and therefore limit backward movement of the trigger shaft 124. A trigger guide 418 also extends perpendicularly outward from the side wall 117 at a position over the recessed portion 413 of trigger shaft 124. The trigger guide 418 and the stop member 416 prevent upward displacement of the trigger shaft 124 (arrow C in FIG. 4) as the trigger mechanism is moved fore and aft. The trigger surfaces 411, 412 are spaced on the trigger shaft 124 such that when the trigger mechanism 120 is moved forwardly over a first distance, the trigger surface 412 engages the trigger engaging surface 403 of the stylet latch mechanism 340 to cause pivoting of the stylet latch mechanism 340 against the biasing force of the leaf spring 132. The stylet latch mechanism 340 is pivoted in the F direction to a point where the distal end 342 clears the latch member 350, at which point the stylet 306 is automatically deployed to its extended position by the compression spring 354. As the trigger mechanism 120 is moved through the first distance to deploy the stylet 306, the trigger surface 411 remains separated from its corresponding trigger engaging surface 407 of the cannula latch mechanism 336. Upon further forward movement of the trigger mechanism 120 over a second distance beyond the first distance, the trigger surface 411 engages the trigger engaging surface 407 to cause pivoting of the cannula latch mechanism 336. When the distal end 338 clears the flanged portion 330, the cannula 304 is automatically deployed to its extended position by the compression spring 334.

An optional safety switch or locking mechanism 109 may be provided to prevent inadvertent firing of the cannula assembly 119. The safety switch 109, as best shown in FIG. 3, includes a horizontal slide member 126 and an upright thumb or finger engaging tab 114. The tab 114 extends through an opening 202 defined in the top wall 111 of the housing 102. The safety switch 109 is operable to slide fore and aft between a locked position (as shown in FIG. 3) and an unlocked position. . In the locked position, the slide member 126 is disposed between the top surface of the cannula latch mechanism 336 and the inner surface of the top wall 111 to oppose upward pivoting of the cannula latch mechanism 336, and thereby prevent deployment of the caimula 304. To unlock the cannula latch mechamsm 336, the safety switch 109 is slid forwardly in the A direction until the slide member 126 is no longer in a position over the cannula latch mechamsm 336 to oppose its upward pivoting movement. A cocking mechanism 315 is configured to return the cannula assembly 119 and the stylet assembly 305 to their retracted positions after being deployed. The cocking mechanism 315 is mounted for fore and aft movement along the inner surface of the bottom wall 113. As best shown in FIG. 3, the cocking mechanism 315 has a longitudinally extending base 316 and an upright front-end member 317. The front-end member 317 defines an opening 134 through which the cannula 304 and stylet 306 extend (FIGS. 5, 6 and 7). The opening 134 is dimensioned to permit fore and aft longitudinal movement of the cannula 304 but restrict the forward movement of the cannula latch member 328 into or through the opening 134. In this manner, the front-end member 317 serves as a stop for limiting the forward movement of the cannula assembly 119. In addition, when the cocking mechanism 315 is moved rearwardly, the front end member 317 engages the front end of the cannula latch member 328 to return the cannula assembly 119 to its retracted position.

A cocking knob 112 extends perpendicularly from one side of the front end member 317 through a longitudinal slot or opening 110 defined in the side wall 115 (FIGS. 1 and 7). The cocking knob 112 is moveable longitudinally fore and aft in the slot 110 to cause fore and aft longitudinal movement of the cocking mechanism 315 inside the housing 102. As can be seen in FIG. 1, fore and aft movement of the cocking knob 112 is limited by the ends of the slot 110. The cocking knob 112 extends through the slot 110 a sufficient amount to permit mampulation of the knob 112 with a thumb or finger.

The base 316 also has a vertically upright rear-end member 318 and a vertically upright recocker 320 positioned intermediate the front-end member 317 and the rear-end member 318 (as best shown in FIG. 3). The recocker 320, when moved rearwardly by movement of the cocking knob 112, engages the front end of the stylet latch member 350 to return the stylet assembly 305 to its retracted position. The rear-end member 318 prevents the stylet latch member 350 from moving rearwardly past the end of base 316. As best shown in FIG. 8, a trigger engaging post 322 projects perpendicularly from one side of the base 316 toward the side wall 117. The post 322 is positioned to engage the distal end 410 of the trigger shaft 124 when the cocking mechamsm 315 is moved rearwardly in the B direction for returning the trigger mechanism 120 to its pre-firing position.

Having described one specific implementation of the automated core biopsy instrument in the foregoing, operation of the instrument will now be described.

The biopsy instrument 100 is shown in a cocked or ready-to-fire position in FIGS. 1-8. In this position, the trigger member 120 is moved to its farthest extent in the B direction (as best shown in FIG. 4) and the cannula latch mechanism 336 and the stylet latch mechanism 340 are in their latched positions for releasably holding the cannula assembly 119 and the stylet assembly 305, respectively (as best shown in FIG. 3). In addition, the stylet 306 is in a retracted position in which the tapered end 311 of the stylet 306 desirably does not extend beyond the tapered end 309 of the cannula 304. Desirably, the beveled end 311 of the stylet 306 is aligned with the beveled end 309 of the cutting cannula 304. As is shown in FIG. 3, the specimen notches 308 and 310 are positioned within the cannula 304. To obtain a tissue sample for the purpose, among other things, of testing such tissue, the tapered ends 309, 311 of the cannula and the stylet 304, 306, respectively, are positioned adjacent to, or within, the tissue of interest in a conventional manner. Once the instrument 100 is properly positioned, the trigger button 122 of the trigger mechanism 120 may be depressed to deploy the stylet 306. As the trigger button 122 is depressed, the trigger mechanism 120 is moved to a stylet triggering position where the trigger surface 412 of the trigger shaft 124 engages the trigger engaging surface 403 to cause pivoting of the stylet latch mechanism 340 (in the direction of arrow F) against the biasing force of the leaf spring 132. When the latch mechamsm 340 has pivoted to the point at which the vertical surface 140 of the distal end portion 342 clears the leading edge 142 of the latch member 350, the biasing force of the compression spring 354 drives the stylet assembly 305 forwardly into the adjacent tissue. In this extended position, the tapered end 311 of the stylet 306 extends past the tapered end 309 of the cannula 304. Desirably, the extent to which the tapered end 311 of the stylet 306 is driven beyond the tapered end 309 of the cannula 304 is at least enough to fully expose the specimen notches 308 and 310 to the tissue of interest for receiving a tissue sample therein. The firing of the stylet assembly 305 also will cause the stylet latch member 350 to engage the recocker 320 and move the cocking mechanism 315 forwardly over a first distance.

At this point, the physician (or other health care professional) operating the instrument 100 may now examine the tissue into which the stylet 306 has been deployed to determine whether the stylet 306 has been properly deployed into the tissue of interest. If the stylet 306 missed the targeted tissue and is instead embedded in adjacent healthy tissue, the stylet 306 may be removed without further damage to the healthy tissue. If, on the other hand, the stylet 306 has been properly deployed into the targeted tissue, the safety switch 109 can be moved to its unlocked position to permit firing of the cannula assembly 119.

To fire the cannula assembly 119, the trigger button 122 of the trigger mechanism 120 is further depressed to move the trigger mechanism 120 to a cannula triggering position where the trigger surface 411 of the trigger shaft 124 engages the trigger engaging surface 407 to cause pivoting of the cannula latcher 336 (in the F direction). When the cannula latch mechamsm 336 has pivoted to the point at which the vertical surface 136 of the distal end portion 338 clears the leading edge 138 of the flanged portion 330, the biasing force of the compression spring 334 fires the cannula assembly 119 forwardly to its fully extended position. In its fully extended position, the tapered end 309 of the cannula 304 is again aligned with the tapered end 311 of the stylet 306. As the cannula 304 is driven over the stylet 306, the tissue in specimen notches 308, 310 is sheared off from any surrounding tissue by the cannula 304. After firing the cannula assembly 119, the instrument 100 may be removed from the patient. To remove the tissue sample from the specimen notches 308, 310 the cocking knob 112 of the cocking mechanism 315 is moved rearwardly to move the cannula assembly 119 toward its retracted position, thereby exposing the tissue sample in the specimen notches 308, 310. As the cannula assembly 119 is moved to its retracted position, the flanged portion 330 of the latch member 328 slides back under the distal end portion 338. When the leading edge 138 of the flanged portion 330 is at a position behind the vertical surface 136 of the distal end portion 338, the biasing force of the leaf spring 130 returns the cannula latch mechanism 336 to its latched position for retaining the cannula , assembly 119. Movement of the cocking knob 112 in the B direction also causes the post 322 of cocking member 315 to engage the front end 410 of the trigger shaft 124, thereby moving the trigger mechanism 120 in the same direction. In addition, the recocker 320 of the cocking mechanism 315 engages the stylet latch member 350 to move the stylet assembly 305 toward its retracted position. However, without further retraction of the cocking knob 112 beyond the position where cannula latch mechamsm 336 latches onto the cannula latch member 328, the stylet latch member 350 remains unlatched from the stylet latching mechanism 340. Thus, the cocking knob 112 may be released with the cannula assembly 119 being held in its retracted position and the stylet assembly 305 still in its extended position under the biasing force of the compression spring 354 to expose the tissue sample for removal. The safety switch 109 may be returned to its locked position (FIG. 3) to prevent inadvertent firing of the cannula assembly 119.

Following removal of the tissue sample, the exposed distal end portion of the stylet 306, including the specimen notches 308, 310, may be cleaned in a convention manner. The stylet assembly 305 may then be returned to its cocked position in which the stylet assembly 305 is retained by the stylet latch mechamsm 340. This may be accomplished by retracting the cocking knob 112 beyond the position at which the cannula latch mechanism 328 latches onto the cannula latch member 328 until the leading edge 142 of the stylet latch member 350 is at a position behind the vertical surface 140 of the distal end portion 342 of the stylet latch mechanism 340. At this point, the biasing force of the leaf spring 132 returns the stylet latch mechanism 340 to its latched position for retaining the stylet assembly 305. Before the instrument 100 is reused, it may be sterilized in a conventional manner. In an alternative embodiment, a biopsy instrument is adapted to receive a removable, disposable needle system. In this configuration, a needle system may be removed and replaced with a new needle system after each use. The present invention has been shown in the described embodiments for illustrative purposes only. The present invention may be subject to many modifications and changes without departing from the spirit or essential characteristics thereof. We therefore claim as our invention all such modifications as come within the spirit and scope of the following claims.

Claims

WE CLAIM:

1. A tissue sampling device comprising: a housing having a first opening; a needle assembly supported in the housing, the needle assembly having a hollow first needle extending outwardly through the first opening so that a distal end of the first needle is positioned outside the housing, and a second needle at least partially received in the first needle and having at least one tissue receiving recess in a distal end portion thereof; first and second biasing mechanisms, the first biasing mechanism configured to urge the first needle distally in a first direction from a retracted position to an extended position, the second biasing mechanism configured to urge the second needle distally in the first direction from a retracted position to an extended position; first and second latch mechanisms, the first latch mechanism configured to releasably hold the first needle in its retracted position, the second latch mechanism configured to releasably hold the second needle in its retracted position; and a firing mechanism for actuating the first and second needles, the firing mechanism defining first and second surfaces, the firing mechanism configured to be selectively positionable at a plurality of positions so that when the firing mechanism is moved from a first position to a second position, the first surface engages the second latch mechanism to cause the second latch mechanism to release the second needle and thus allow the second needle to move to its extended position, and when the firing mechanism is moved from the second position to a third position, the second surface engages the first latch mechanism to cause the first latch mechanism to release the first needle and thus allow the first needle to move to its extended position.

2. The device of claim 1, wherein the housing includes a first end defining the first opening and a second end opposite the first end so as to define a longitudinal axis extending between the first and second ends of the housing, and wherein the firing mechanism is supported for longitudinal movement, and the first, second and third positions are spaced along the longitudinal axis.

3. The device of claim 2, wherein the housing includes a second opening and the firing mechanism includes a first portion and a second portion, the first portion being disposed in the housing and defining the first and second drive surfaces, the second portion of the firing mechanism extending outwardly through the second opening of the housing and forming a thumb or finger engaging surface upon which force may be applied to move the firing mechanism longitudinally to the plurality of positions.

4. The device of claim 1, further comprising a third biasing mechanism positioned to urge the first latch mechanism to a latched position for retaining the first needle in its retracted position.

5. The device of claim 1, further comprising a forth biasing mechanism positioned to urge the second latch mechanism to a latched position for retaining the second needle in its retracted position.

6. The device of claim 1, further comprising a cocking mechanism configured to retract the first needle from its extended position to its retracted position and to retract the second needle from its extended position to its retracted position.

7. The device of claim 6, wherein the first latch mechanism is normally biased toward a latch surface of the first needle such that when the cocking mechanism is activated to move the first needle to its retracted position, the first latch mechanism automatically engages the latch surface to retain the first needle in its retracted position against the first biasing mechanism.

8. The device of claim 6, wherein the second latch mechanism is normally biased toward a latch surface of the second needle such that when the cocking mechanism is activated to move the second needle to its retracted position, the second latch mechanism automatically engages the latch surface to retain the second needle in its retracted position against the second biasing mechanism.

9. The device of claim 1, further comprising a locking mechanism adapted for movement between a first locking position and a second release position, wherein when the locking mechanism is in the first locking position, the locking mechanism is in position to oppose the release of the first latching mechanism, and when the locking mechanism is in the second release position, the locking mechanism is removed from opposing the release of the first latching mechanism.

10. The device of claim 1, wherein the first latch mechanism comprises a first rocker arm and a first pin, the first rocker arm being mounted on the first pin for pivoting between a latched position and an unlatched position, wherein when the first rocker arm is in the latched position, the first rocker arm engages a latch surface of the first needle to retain the first needle in its retracted position, and when the first rocker arm is in the unlatched position, the first rocker arm is disengaged from the latch surface of the first needle.

11. The device of claim 1, wherein the second latch mechanism comprises a second rocker arm and a second pin, the second rocker arm being mounted on the second pin for pivoting between a latched position and an unlatched position, wherein when the second rocker arm is in the latched position, the second rocker arm engages a latch surface of the second needle to retain the second needle in its retracted position, and when the second rocker arm is in the unlatched position, the second rocker arm is disengaged from the latch surface of the second needle.

12. A tissue sampling device comprising: a housing having a first opening, the housing having first and second ends and defining a longitudinal axis extending between said first and second ends; a cannula assembly supported in the housing, the cannula assembly having a cannula extending outwardly through the first opening of the housing, the cannula assembly being supported for movement along the longitudinal axis relative to the housing; a stylet assembly supported in the housing, the stylet assembly having a stylet slidably received in the cannula and having a distal end portion extending outwardly through the first opening, the stylet having a distal end portion with a least one tissue receiving member, the stylet assembly being supported for movement along the longitudinal axis relative to the housing and the cannula assembly; a stylet moving mechanism disposed in the housing and configured to bias the stylet in a first direction along the longitudinal axis; a cannula moving mechanism disposed in the housing and configured to bias the cannula in the first direction along the longitudinal axis; a stylet retaining member disposed in the housing for preventing movement of the stylet against the stylet moving mechanism; a cannula retaining member disposed in the housing for preventing movement of the cannula against the cannula moving mechanism; and a trigger mechanism for controllably releasing the stylet from the stylet retaining member and the cannula from the cannula retaining member, the trigger mechanism being selectively movable from a first position to a stylet triggering position and from the stylet triggering position to a cannula triggering position, wherein when the trigger mechanism is moved to the stylet triggering position, the trigger mechanism removes the stylet retaining member from preventing movement of the stylet to allow the stylet moving mechanism to move the stylet in the first direction for obtaining a tissue sample hi the tissue receiving member, and when the trigger mechanism is moved to the cannula triggering position, the trigger mechanism removes the cannula retaining member from preventing movement of the cannula in the first direction to allow the cannula moving mechanism to move the cannula in the first direction over the stylet to separate the tissue sample in the tissue receiving member from surrounding tissue.

13. The device of claim 12, wherein the cannula moving mechanism comprises a first compression spring carried by the cannula and the stylet moving mechanism comprises a second compression spring carried by the stylet.

14. The device of claim 12, wherein the stylet retaining member is movable between a latched position wherein the stylet retaining member prevents movement of the stylet in the first direction and an unlatched position wherein the stylet retaining member is removed from opposing movement of the stylet in the first direction, and the device further comprises a first biasing member configured to urge the stylet retaining member to the latched position.

15. The device of claim 12, wherein the cannula retaining member is movable between a latched position wherein the cannula retaining member prevents movement of the cannula in the first direction and an unlatched position wherein the cannula retaining member is removed from opposing movement of the cannula in the first direction, and the device further comprises a second biasing member configured to urge the stylet retaining member to the latched position.

16. The device of claim 12, wherein the trigger mechanism includes a first trigger surface and a second trigger surface, the first trigger surface being spaced longitudinally from the second trigger surface, wherein when the trigger mechanism is moved to the stylet trigger position, the first trigger surface engages the stylet retaining member to remove the stylet retaining member from preventing movement of the stylet in the first direction, and when the trigger mechanism is moved to the cannula trigger position, the second trigger surface engages the cannula retaining member to remove the cannula retaining member from preventing movement of the cannula in the first direction.

17. The device of claim 12, further comprising a cocking mechanism configured to move the stylet in a second direction opposite the first direction after the stylet is released from the stylet retaining member and to move the cannula in the second direction after the cannula is released from the cannula retaining member.

18. The device of claim 12, wherein the stylet assembly includes a latch member coupled to the stylet, the latch member having a latch surface and the stylet retaining member comprises a first rocker arm and a first pin, the first rocker arm being mounted on the first pin for pivoting between a latched position and an unlatched position, wherein when the first rocker arm is in the latched position, the first rocker arm engages the latch surface to prevent movement of the stylet, and when the first rocker arm is in the unlatched position, the first rocker arm is disengaged from the latch surface of the stylet to permit movement of the stylet.

19. The device of claim 12, wherein the cannula assembly includes a latch member coupled to the cannula, the latch member having a latch surface and the cannula retaining member comprises a second rocker arm and a second pin, the second rocker arm being mounted on the second pin for pivoting between a latched position and an unlatched position, wherein when the second rocker arm is in the latched position, the second rocker arm engages the latch surface to prevent movement of the cannula, and when the second rocker arm is in the unlatched position, the second rocker arm is disengaged from the latch surface of the cannula to pennit movement of the cannula.

20. A tissue sampling device comprising: a housing; a hollow first needle extending from the housing, the first needle supported for movement between a retracted position and an extended position; a second needle at least partially disposed in the first needle, the second needle supported for movement relative to the first needle and the housing between a retracted position and an extended position, the second needle having a distal end with at least one tissue receiving notch; a first biasing means for urging the first needle distally from the retracted position to the extended position; a second biasing means for urging the second needle distally from the retracted position to the extended position; a first latch-means for releasably latching the first needle in the retracted position against the first biasing means; a second latch means for releasably latching the second needle in the retracted position against the second biasing means; and an activation means for separately activating the first needle and the second needle, the activation means being supported for movement relative to the housing in a first direction, wherein when the activation means is moved over a first distance in the first direction, the activation means unlatches the second latch means to allow the second biasing means to move the second needle to its extended position, and when the activation means is moved over a second distance in the first direction beyond the first distance, the activation means unlatches the first needle to allow the first biasing mechanism to move the first needle to its extended position.

21. The device of claim 20, further comprising a cocking mechanism for returning the first and the second needles to their retracted positions, the cocking mechanism being supported for movement relative to the housing in a second direction, wherein movement of the cocking mechanism over a first distance in the second direction causes the first needle to move to its retracted position and movement of the cocking mechanism over a second distance in the second direction beyond the first distance causes the second needle to move to its retracted position.

22. The device of claim 21, wherein the cocking mechanism further comprises a first needle engaging portion and a second needle engaging portion, wherein when the cocking mechanism is moved over the first distance in the second direction, the first needle engaging portion engages the first needle to move the first needle to its retracted position, and when the cocking mechanism is moved over the second distance in the second direction, the second needle engaging portion engages the second needle to move the second needle to its retracted position.

23. The device of claim 20, wherein the first biasing means comprises a first compression spring carried by the first needle and the second biasing means comprises a second compression spring carried by the second needle.

24. The device of claim 20, wherein the second latch means is movable between a latched position wherein the second latch means prevents movement of the second needle to its extended position and an unlatched position wherein the second latch means is removed from opposing movement of the second needle to its extended position, and the device further comprises a forth biasing means configured to urge the second latch means to the latched position.

25. The device of claim 20, wherein the first latch means is movable between a latched position wherein the first latch means prevents movement of the first needle to its extended position and an unlatched position wherein the first latch means is removed from opposing movement of the first needle to its extended position, and the device further comprises a third biasing means configured to urge the first latch means to the latched position.

26. The device of claim 20, wherein the activation means includes a needle engaging first surface and a needle engaging second surface, the needle engaging first surface being spaced longitudinally from the needle engaging second surface, wherein when the activation means is moved over the first distance in the first direction, the needle engaging first surface engages the second latch means to unlatch the second latch means, and when activation means is moved over the second distance in the first direction, the needle engaging second surface engages the first latch means to unlatch the first latch means.

27. The device of claim 20, wherein the second needle includes a latch member having a latch surface and the second latch means comprises a first rocker arm mounted for pivotal movement between a latched position and an unlatched position, wherein when the first rocker arm is in the latched position, the first rocker arm engages the latch surface of the second needle to prevent the second needle from moving to its extended position, and when the first rocker arm is in the unlatched position, the first rocker arm is disengaged from the latch surface of the second needle to permit the second needle to move to its extended position.

28. The device of claim 27, wherein the first needle includes a latch member having a latch surface and the first latch means comprises a second rocker arm mounted for pivotal movement between a latched position and an unlatched position, wherein when the second rocker arm is in the latched position, the second rocker arm engages the latch surface of the first needle to prevent the first needle from moving to its extended position, and when the first rocker arm is in the unlatched position, the first rocker arm is disengaged from the latch surface of the first needle to permit the first needle to move to its extended position.

29. A tissue sampling device comprising: a housing having a first opening; an outer cannula supported in the housing and extending outwardly through the first opening, the cannula being movable between a retracted position and an extended position; an inner stylet slidably received in the cannula, the stylet being movable between a retracted position and an extended position; and an activation element for selectively deploying the stylet and the cannula to their respective extended positions, wherein activating the activation element a first time causes the stylet but not the cannula to deploy to its extended position and activating the same activation element a second time causes the cannula to deploy to its extended position.

30. The device of claim 29, wherein depressing the activation element a first time causes the stylet but not the cannula to deploy to its extended position and depressing the same activation element a second time causes the cannula to deploy to its extended position.

31. The device of claim 29, further comprising a stylet moving mechanism for moving the stylet from its retracted position to its extended position when the activation element is activated for the first time to deploy the stylet.

32. The device of claim 31 , further comprising a stylet latch mechanism for releasably holding the stylet in its retracted position against the stylet moving mechanism and wherein the activation element is configured to unlatch the stylet latch mechanism for releasing the stylet when the activation element is activated for the first time to deploy the stylet.

33. The device of claim 29, further comprising a cannula moving mechanism for moving the cannula from its retracted position to its extended position when the activation element is activated for the second time to deploy the cannula.

34. The device of claim 33, further comprising a cannula latch mechanism for releasably holding the cannula in its retracted position against the cannula moving mechanism and wherein the activation element is configured to unlatch the cannula latch mechanism for releasing the cannula when the activation element is activated for the second time to deploy the cannula.

35. The device of claim 29, wherein the activation element is configured to be selectively movable from a first position to a second position and from the second position to a third position, wherein when the activation element is moved from the first position to the second position, the activation element causes the stylet to deploy to its extended position, and when the activation element is moved from the second position to the third position, the activation element causes the cannula to deploy to its extended position.

36. A tissue sampling device comprising: a housing having a first opening; an outer cannula supported in the housing and extending outwardly through the first opening, the cannula being configured to project in a first direction relative to the housing; an inner stylet slidably received in the cannula, the stylet being configured to project in the first direction relative to the housing and the cannula; and an activation element configured to cause the stylet and the cannula to successively project in the first direction, wherein activation of the activation element causes the stylet but not the cannula to project in the first direction and further activation of the same activation element causes the cannula to project in the first direction over the stylet.

37. The device of claim 36, wherein depressing the activation element causes the stylet but not the cannula to project in the first direction and further depressing the same activation element causes the cannula to project in the first direction over the stylet.

38. The device of claim 36, further comprising a first biasing mechanism configured to urge the stylet in the first direction and a stylet latch mechanism configured to releasably retain the stylet from moving in the first direction against the first biasing mechanism, and wherein the activation element is configured to engage the stylet latch mechanism for releasing the stylet.

39. The device of claim 36, further comprising a second biasing mechanism configured to urge the cannula in the first direction and a cannula latch mechanism configured to releasably retain the cannula from moving in the first direction against the second biasing mechanism, and wherein the activation element is configured to engage the cannula latch mechanism for releasing the cannula.

40. The device of claim 36, further comprising a cocking mechanism configured to move the stylet and the cannula in a second direction opposite the first direction after the stylet and the cannula are projected in the first direction.

41. A method for obtaining a tissue sample from tissue of interest with a tissue sampling device comprising an outer cannula, an inner stylet slidably disposed in the cannula and an activation element for projecting the cannula and the stylet, the method comprising: activating the activation element to cause the stylet but not the cannula to project into the tissue of interest; and activating the same activation element a second time to cause the cannula to project over the stylet.

42. The method of claim 41 , further comprising examining the tissue into which the stylet is projected before activating the activation element a second time to cause the cannula to project over the stylet.

43. The method of claim 41 , wherein activating the activation element to cause the stylet, but not the cannula to project into the tissue of interest further comprises unlatching a stylet latch mechanism with the activation element to allow the stylet to project to the tissue of interest.

44. The method of claim 41 , wherein activating the activation element a second time to cause the cannula to project over the stylet further comprises unlatching a cannula latch mechanism with the activation element to allow the cannula to project over the stylet.

45. The method of claim 41 , wherein the act of activating the activation element to cause the stylet but not the cannula to project into the tissue of interest comprises depressing the activation element to cause the stylet but not the cannula to project into the tissue of interest and the act of activating the same activation element a second time to cause the cannula to project over the stylet comprises depressmg the same activation element a second time to cause the cannula to project over the stylet.

46. The method of claim 45, further comprising depressing the activation element over a first distance to cause the stylet but not the cannula to project into the tissue of interest and depressing the same activation element over a second distance to cause the cannula to project over the stylet.