referring now more particularly to fig1 , there is shown the distal end 12 of a first preferred embodiment of an inventive tissue retrieval or biopsy instrument 10 . the distal end 12 preferably comprises a disposable wand portion , including a distal tip 14 . the tip 14 may comprise a conventional trocar tip , or , preferably , may include an electrosurgical ( rf ) element or wire 16 which may be energized by a conventional electrosurgical generator ( not shown ) in order to facilitate tissue cutting and consequent advancement of the instrument 10 to a predetermined tissue site in the patient &# 39 ; s body . proximally of the tip 14 is a shaft 18 , preferably lying along an axis 19 ( fig1 ) of the instrument , on which is disposed a cutting element or wire 20 . this wire 20 is disposed axially along the length of the shaft 18 in its retracted position ( not shown ), but may be deployed radially outwardly , as shown in fig1 . the element 20 is preferably comprised of a wire or rectangular band fabricated of memory metal such as nitinol , though stainless steel , tungsten , or other biocompatible materials could also be employed , if desired . the cutting element 20 acts as an electrosurgical cutter , energizable by means of rf energy provided by the electrosurgical generator discussed supra . the instrument 10 may be monopolar , as illustrated in fig2 , with the cutting element 20 comprising the active electrode and a return electrode spaced from the instrument 10 and most typically being disposed on the patient &# 39 ; s skin in the form of a patch electrode on the thigh or back . alternatively , the instrument 10 may preferably be bipolar , as illustrated in fig3 , with the cutting element comprising the active electrode and a return electrode 22 being disposed on the instrument in close proximity to the active electrode , such as along the shaft 18 . with such an arrangement , a layer of insulation 23 is disposed between the return electrode ( comprising a major portion of the surface area of the shaft 18 ) and the portion of the shaft adjacent to the active electrode , which receives the cutting element 20 in its retracted position . the bipolar embodiment is generally preferred because of a greater safety factor and lower power requirements . a plurality of cutting wires 20 may be employed if desired , preferably spaced circumferentially about the shaft 18 . in some embodiments , it may be preferably to have webs between the cutting elements , to create a “ sail ” rather than entire distinct separate cutting elements . referring now more particularly to fig4 - 7 , a proximal reusable driver portion 24 for the distal end or disposable wand portion 12 is shown . the driver portion 24 is preferably disposed on a stereotactic rail 26 , in known fashion , for guidance of the instrument 10 to a predetermined tissue site using known imaging techniques . such stereotactic imaging systems are available , for example , from fischer , inc . or lorad , inc . alternative imaging systems , such as mammographic , ultrasonic , ct , mri guidance systems may be used in place of a stereotactic system , if desired . additionally , the instrument may be guided to the lesion site using an articulating arm system or manually , rather than on a stereotactic rail . the reusable driver portion 24 comprises a housing 28 within which is disposed a coaxial arrangement comprising an outer sheath 30 , the shaft 18 , and a rod 32 which is attached at its distal end to the cutter element 20 . a knob 34 is rotatably attached to the shaft 18 through a gearing system 35 to rotate the shaft 18 as desired , for the purpose of circumferentially orienting and rotating the cutting element 20 . three levers 36 , 38 , and 40 extend outwardly through slots 42 , 44 , and 46 , respectively , in the side of the housing 28 . the first lever 36 is actuatable to slide the sheath 30 axially both proximally and distally , for a purpose to be described hereinbelow . the second lever 38 is actuatable to move the shaft 18 axially in distal and proximal directions , as desired . the third lever 40 is actuatable to move the rod 32 axially in distal and proximal directions , as desired . since the rod 32 is attached at its distal end to the proximal end of the wire cutter 20 , movement of the rod 32 in an axial direction also causes the proximal end of the wire cutter 20 to move in an axial direction . since the distal end of the cutter 20 is anchored to the shaft 18 , movement of the proximal end of the cutter element 20 in a distal direction causes the midportion of the cutting element 20 to bow radially outwardly to a radially expanded position , as shown in any of fig1 - 3 , while movement of the proximal end of the cutter element 20 in a proximal direction causes the midportion of the cutter element 20 to retract radially to its stowed position , disposed linearly along the axial length of the shaft 18 , preferably within a recess 48 ( fig1 ). an advantageous feature of the invention is the employment of a series of stops 50 in the second slot 44 , and a series of stops 52 in the third slot 46 , as illustrated in fig5 - 7 . the stops 50 enable the second lever 38 to be actuated to a plurality of discrete axial positions , which in turn permits the shaft 18 to be actuated to a corresponding plurality of discrete axial positions for fine tuning the axial position of the electrosurgical cutting element 20 . similarly , the stops 52 enable the third lever 40 to be actuated to a plurality of discrete axial positions , which in turn permits the electrosurgical cutting element 20 to be radially extended to a corresponding plurality of radially extended positions , for a purpose to be described more fully hereinbelow . with reference now more particularly to fig8 - 10 , the operation of the first preferred embodiment of the inventive device will be explained . initially , when it is determined that either a diagnostic or therapeutic biopsy procedure is indicated , the distal disposable wand portion 12 of the instrument 10 will be moved axially to a position wherein the distal tip is adjacent to and preferably within a target lesion 54 , using the stereotactic rail 26 and associated imaging system . during this process step , wherein gross linear movement of the wand 12 is controlled by the rail system 26 , the electrosurgical cutting element 16 on the distal tip 14 is energized to pierce and cut through the patient &# 39 ; s body tissue 56 to permit distal advancement of the wand 12 to the region surrounding the lesion 54 . once the distal tip 14 is generally in the desired position adjacent to or within the target lesion 54 , using the stereotactic rail 26 , the second lever 38 is actuated to provide fine tuning of the axial position of the distal tip 14 relative to the lesion 54 , by moving the shaft 18 axially to a desired position , and securing the lever 38 in an appropriate stop 50 to maintain the desired axial position . this fine axial adjustment of the axial movement of the shaft 18 is performed using appropriate imaging equipment . the objective of this process step is to ensure that the distal end of the cutting wire 20 is disposed distally of the distal peripheral edge of the lesion 54 , while at the same time the proximal end of the cutting wire 20 is disposed proximally of the proximal peripheral edge of the lesion 54 . this will ensure the ability to isolate the entire lesion 54 during the cutting procedure , with sufficient margins to minimize the chance that any portion of the lesion inadvertently remains behind in the patient &# 39 ; s body following removal thereof . when the distal tip 14 is in the precise position desired by the practitioner , first lever 36 , which is normally disposed in a first detent 58 ( fig5 and 6 ) in the first slot 42 , is actuated proximally until it rests in a second detent 60 ( fig5 ) in the first slot 42 . this action retracts the sheath 30 proximally a sufficient distance to partially uncover the cutting element 20 . it should be noted , however , that in some circumstances it may be desirable to fully retract the sheath , so that the entire cutting element 20 is released , in order to create a different cutting geometry . in such an instance , a detent 61 ( fig7 ) is provided within the slot 42 to accommodate the lever 36 in the fully proximal position necessary to achieve full axial retraction of the sheath . additional intermediate detents 60 ( not shown ) may be provided to retract the sheath to intermediate positions corresponding to various partial radial extension positions of the cutting element . after the sheath 30 is retracted as desired , the third lever 40 may then be actuated distally along the third slot 46 to an intermediate stop 52 , thereby causing the rod 32 , and therefore the proximal end of the cutting element 20 , to move axially a distance equivalent to that traversed by the lever 40 . this , of course , results in the partial radial expansion of the cutting element 20 to an arched or bowed configuration as shown in fig8 . the extended configuration of the cutting element 20 may define , when rotated about the instrument axis , a spherical cutting volume , as shown , or it may be configured to define an elliptical or toroidal cutting volume when the cutting element is rotated about the instrument axis 19 , rather than a spherical volume . of course many other mechanisms for radially expanding the cutting element 20 may be utilized as well , within the scope of the invention . for example , since the wire 20 is preferably fabricated of a shaped memory or superelastic material , the proximal retraction of the sheath 30 , and resultant release of the wire 20 , may be sufficient to cause the cutting wire 20 to radially expand to its desired position . once the cutting element 20 is partially radially expanded as described supra , an inner portion of the target lesion 54 is isolated from surrounding tissue . to complete this step , the cutting element 20 is energized by the electrosurgical generator ( not shown ), after which the knob 34 is rotated , either manually or via a motorized drive mechanism , to rotate the cutting element 20 through a 360 degree arc . this rotational cutting action functions to completely sever the inner portion of the tissue sample from the surrounding tissue , thereby cutting off all blood supply to the inner tissue sample . alternatively , if desired , the cutting element 20 may be simultaneously rotated and moved axially , by moving the shaft 18 axially , in order to create a “ corkscrew ”- shaped tissue segment . once this initial isolation step is completed , the cutting element or wire 20 is preferably further radially extended to the position shown in fig9 . this is accomplished by sliding the lever 36 proximally to another detent 60 to further proximally retract the sheath 30 . then , the third lever 40 may be axially slid distally to another stop or detent 52 to further radially extend the cutting wire 20 . once radially positioned , the cutting element 20 is energized by the electrosurgical generator , after which the knob 34 is rotated to rotate the cutting element 20 through a 360 degree arc . this rotational cutting action functions to completely sever a second segment of the tissue sample from the surrounding tissue , thereby cutting off all blood supply to this segment as well . these steps may be repeated as many times as desired , in order to ensure that the tissue sample is segmented for efficient removal from the patient &# 39 ; s body . ultimately , however , a final cut is preferably made , by fully retracting the outer sheath 30 , using the slide lever 36 , and fully extending the cutting wire 20 , using the slide lever 40 , so that the cutting element 20 extends radially beyond the periphery of the target lesion 54 , as illustrated in fig1 . the cutting element is then energized with rf energy , in the same manner as previously , after which the knob 34 is rotated to rotate the cutting wire 20 through a complete arc about the axis 19 . at this point , the entire lesion 54 should be completely isolated from surrounding tissue , with a sufficient margin about the outer periphery thereof to ensure successful removal of the entire lesion . during the foregoing segmentation process , if the cutting element 20 remains charged by rf energy during the stepwise radial extension process , the outer tissue rings will be further segmented radially . other segmentation approaches may be advantageously utilized as well , if desired . for example , rather than segmenting the tissue sample circumferentially , from the inside out , the tissue sample may be segmented circumferentially from the outside in , i . e . by making an outer circumferential cut ( fig1 ), then partially retracting the cutting element 20 and cutting additional layers , as shown in fig8 and 9 . alternatively , the tissue may be sectioned by extending and retracting the cutting element 20 radially , akin to “ sectioning an orange ”. additional radially oriented cutting elements could be employed as well to further segment the tissue . an alternative approach to segmenting the tissue specimen to be retrieved is illustrated in the embodiment shown in fig1 - 19 . in this embodiment , wherein like elements to those in the embodiment of fig1 are designated by like reference numerals , succeeded by the letter a , there is shown a tissue retrieval or biopsy instrument 10 a , having a distal tip 14 a with an electrosurgical element or wire 16 a for cutting tissue and thereby permitting advancement of the instrument into a patient &# 39 ; s body . a shaft or cannula 18 a is disposed along an axis 19 a of the instrument . a longitudinal slot 66 is disposed axially along a portion of the length of the cannula 18 a . a cutting element or wire 20 a , which is preferably an electrosurgical cutting element , is disposed so as to be extendable from and retractable into the slot . the cutting element is shown in a retracted position in fig1 , and in an extended position in fig1 and 19 . in operation , once the instrument 10 a has been positioned so that the distal tip is adjacent to a lesion to be removed , in the manner described supra with respect to the embodiment of fig1 , the cutting element 20 a is charged with rf energy from a proximally disposed electrosurgical generator ( not shown ). then , the cutting element 20 a is radially extended by the practitioner , using a proximal control mechanism ( not shown ), to a position as shown , for example , in fig1 . once extended , the cutting element is moved axially in a proximal direction along the slot 66 , as illustrated by the arrow 68 and the phantom images of the cutting element 20 a , in order to isolate a generally cylindrical tissue segment , as the cannula 18 a is rotated about its axis 19 a simultaneously . fig1 illustrates a procedure similar to that illustrated in fig1 , except that while the cutting element 20 a is being axially moved in a proximal direction as shown by arrows 70 , it is also deployed to various radial heights , in order to create a variable height cut . once segmentation of the tissue sample has been completed , whichever embodiment has been employed , each tissue segment can be withdrawn using a suitable retrieval apparatus . preferably , the tissue segments are withdrawn through a cannula , such as the sheath 30 , using such means as a suction grasper , flexible mechanical grassers , an auger conveyor , a prickly bristle or brush grasper , a wire retrieval basket , or the like . the foregoing procedure and apparatus may be used for either a diagnostic or a therapeutic purpose . it is particularly advantageous for a diagnostic procedure because the resultant incision from the procedure will not substantially exceed in length the diameter of the cannula . on the other hand , a second preferred embodiment , illustrated in fig1 - 16 , is particularly suited to a therapeutic procedure , wherein it is highly desired to ensure that the entire lesion of interest is removed in one step , without segmenting that lesion within the body . this approach emphasizes maximum safety , in that only a single procedure is necessary , assuming the tissue sample margins are clean , and the incision necessary to remove the intact tissue sample is of the minimum size necessary to remove the sample . with this procedure , there is also a somewhat reduced risk of cell migration from the specimen to the surrounding tissue , since as described below , the specimen is encapsulated as soon as it is isolated and then promptly removed . no segmentation of the specimen occurs within the patient &# 39 ; s body . referring now to fig1 - 14 , wherein like elements to those in the first embodiment are identified by like reference numerals , followed by the letter “ b ”, there is shown the distal end or disposable wand portion 12 b of an instrument 10 b . the portion 12 b includes a distal tip 14 b , which may be constructed in a manner similar to that of tip 14 in fig1 , a shaft 18 b , and a sleeve 30 b . disposed in a radially retracted orientation in a recess 48 b of the shaft 18 b are a plurality of encapsulation elements or bands 72 , one of which also comprises a single electrosurgical cutting element 20 b . for the purposes of the invention it is unimportant which of the encapsulation elements 72 may be charged by means of rf energy to form an electrosurgical cutter , and in certain instances it may be advantageous to employ a plurality of cutting elements . each of the encapsulation elements 72 and the cutting element 20 b are attached at their distal ends to the distal end of the shaft 18 b , at its connection with the distal tip 14 b of the instrument 10 b , which connection is preferably accomplished by means of a keyway 74 . the proximal end of the instrument 10 b may be substantially the same as that for the instrument 10 , illustrated in fig4 - 7 , comprising a reusable driver portion having an actuator for axially moving the sheath 30 b between proximal and distal positions , a linear actuator for axially moving the shaft 18 b , an actuator for rotationally moving the shaft 18 b , and an actuator for axially moving the proximal ends of the encapsulation elements 72 and cutting element 20 b , in order to radially extend and retract each of the elements 72 and 20 b , as illustrated in fig1 - 16 . in operation , as with the first embodiment of fig1 , when it is determined that either a diagnostic or therapeutic biopsy procedure is indicated , the distal disposable wand portion 12 b of the instrument 10 b will be moved axially to a position wherein the distal tip is adjacent to and distally of a target lesion , using the stereotactic rail 26 and associated imaging system . during this process step , wherein gross linear movement of the wand 12 b is controlled by the rail system 26 , the electrosurgical cutting element ( not shown ) on the distal tip 14 b is energized to pierce and cut through the patient &# 39 ; s body tissue to permit distal advancement of the wand 12 b to the region surrounding the lesion . once the distal tip 14 b is generally in the desired position adjacent to the target lesion , using the stereotactic rail 26 , the second lever 38 is actuated to provide fine tuning of the axial position of the distal tip 14 b relative to the lesion , by moving the shaft 18 b axially to a desired position , and securing the lever 38 in an appropriate stop 50 to maintain the desired axial position . this fine axial adjustment of the axial movement of the shaft 18 b is performed using appropriate imaging equipment . the objective of this process step is to ensure that the distal end of the cutting wire 20 b is disposed distally of the distal peripheral edge of the lesion , while at the same time the proximal end of the cutting wire 20 b is disposed proximally of the proximal peripheral edge of the lesion . this will ensure the ability to isolate the entire lesion during the cutting procedure , with sufficient margins to minimize the chance that any portion of the lesion inadvertently remains behind in the patient &# 39 ; s body following removal thereof . when the distal tip 14 b is in the precise position desired by the practitioner , first lever 36 , which is normally disposed in a first detent 58 ( fig5 and 6 ) in the first slot 42 , is actuated proximally until it rests in a second detent 60 ( fig7 ) in the first slot 42 . this action retracts the sheath 30 b proximally a sufficient distance to completely uncover the cutting element 20 b and associated encapsulation elements 72 . the third lever 40 may then be actuated distally along the third slot 46 to the distal - most stop 52 , thereby causing the rod 32 , and therefore the proximal ends of the cutting element 20 a and encapsulation elements 72 , to move axially a distance equivalent to that traversed by the lever 40 . this , of course , results in the radial expansion of the cutting element 20 b and encapsulation elements 72 to an arched or bowed configuration as shown in fig1 , wherein the cutting element 20 b defines a peripheral boundary which lies radially beyond the peripheral boundary of the lesion , as in the case of the first embodiment shown in fig8 . again , it should be noted that the cutting element and encapsulation elements need not be fully extended , especially if an ellipsoidal or toroidal cutting geometry is desired , in which case intermediate stop 61 is utilized . once the cutting element 20 b and associated encapsulation elements 72 are radially expanded as described supra , it is time to isolate the target lesion from surrounding tissue . advantageously , a spherical or toroidal tissue sample having a radius of at least 15 mm may be defined and isolated by rotating the cutting element 20 b about the axis of the shaft 18 b . the encapsulation elements 72 will also be rotated during this process , but their function is not yet important . to complete the isolation step , the cutting element 20 b is energized by the electrosurgical generator ( not shown ), after which the knob 34 is rotated , either manually or via a motorized drive mechanism , to rotate the shaft 18 b , and thus the cutting element 20 b through a 360 degree arc . this rotational cutting action functions to completely sever the tissue sample from the surrounding tissue , thereby cutting off all blood supply to the tissue sample ( and thus from the lesion , which should be completely contained within the tissue sample ). after the isolation step is completed , the isolated tissue sample may be retrieved from the patient &# 39 ; s body 56 . this retrieval step may be accomplished in a number of ways , but it is the objective in connection with the illustrated embodiment to encapsulate and remove the isolated tissue sample in one piece . accordingly , as is illustrated in fig1 and 16 , continued rotation of the shaft 18 b , once the isolation step has been completed , preferably with the cutting element 20 b de - energized , will twist and tighten the encapsulating elements 72 and the cutting element 20 b about the tissue sample ( not shown ). as the shaft 18 b is rotated , and the encapsulating elements 72 radially retracted and twisted , they will function to deform the tissue sample radially so that it is more compact and more securely retained within the spaced defined by the encapsulating elements 72 . once the tissue sample has been fully encapsulated , the tissue sample may be removed from the patient &# 39 ; s body . advantageously , since the tissue sample is larger in cross - section than the cross - section of the sheath 30 b , the inventors have developed an inventive approach for removal thereof which results in minimum trauma and incision size for the patient while still permitting the removal of an intact specimen . to remove the specimen , the sheath 30 b is retracted proximally , following which the cutting element 20 b is again energized by the electrosurgical generator . the shaft 18 b , with the tissue specimen encapsulated thereabout , is then proximally withdrawn by the practitioner , with the cutting element 20 b functioning to cut through the tissue necessary to create a passage for exit of the sample . once the unit , including the shaft and encapsulated tissue mass , is completely withdrawn from the body , the incision created by the cutting element 20 b upon withdrawal from the body may be adhesively closed , with minimal required follow - up care and scarring . many alternative embodiments may be used to accomplish the method outlined supra , which essentially involves isolating the tissue mass from surrounding tissue , encapsulating the tissue mass in place about a shaft , then removing the encapsulated tissue mass and shaft from the body by energizing an rf electrosurgical cutter to cut its way out , without the need for a cannula or pre - existing incision . for example , a plurality of cutting elements could be employed , or a separate cutting element could be disposed on the shaft . an important aspect of the invention , of course , is a relatively high likelihood of acquiring the entire lesion of interest in a single therapeutic procedure , without the need for follow - up surgery . while this invention has been described with respect to various specific examples and embodiments , it is to be understood that the invention is not limited thereto and that it can be variously practiced within the scope of the following claims .
an apparatus and method are provided for precisely isolating a target lesion in a patient &# 39 ; s body tissue , resulting in a high likelihood of “ clean ” margins about the lesion when it is removed for diagnosis and / or therapy . this approach advantageously will often result in the ability to both diagnose and treat a malignant lesion with only a single percutaneous procedure , with no follow - up percutaneous or surgical procedure required , while minimizing the risk of migration of possibly cancerous cells from the lesion to surrounding tissue or the bloodstream . in particular , the apparatus comprises a biopsy instrument having a distal end adapted for entry into the patient &# 39 ; s body , a longitudinal shaft , and a cutting element disposed along the shaft . the cutting element is actuatable between a radially retracted position and a radially extended position . advantageously , the instrument is rotatable about its axis in the radially extended position to isolate a desired tissue specimen from surrounding tissue by defining a peripheral margin about the tissue specimen . the specimen may be encapsulated and removed as an intact piece .