Patent Publication Number: US-2021177387-A1

Title: Single insertion multiple sample biopsy apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. provisional patent application Ser. No. 62/425,974 filed Nov. 23, 2016, which is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to biopsy devices, and, more particularly, to a single insertion multiple sample biopsy apparatus. 
     BACKGROUND ART 
     A biopsy may be performed on a patient to help in determining whether the tissue in a region of interest includes cancerous cells. One biopsy technique used to evaluate breast tissue, for example, involves inserting a biopsy probe into the breast tissue region of interest to capture one or more tissue samples from the region. Such a biopsy technique often utilizes a vacuum to pull the tissue to be sampled into a sample notch of the biopsy probe, after which the tissue is severed and collected. Efforts continue in the art to improve the ability of the biopsy device to sever a tissue sample, and to transport the severed tissue sample to a sample collection container. 
     What is needed in the art is a biopsy device that has the ability to promote effective severing of a tissue sample and effective transport of the tissue sample to a sample collection container. 
     SUMMARY OF INVENTION 
     The present invention provides a biopsy device that has the ability to promote effective severing of a tissue sample and effective transport of the tissue sample to a sample collection container. 
     The invention in one form is directed to a biopsy apparatus that includes a driver assembly and a biopsy probe assembly. The driver assembly has an electromechanical power source and a vacuum source. The biopsy probe assembly is releasably attached to the driver assembly. The biopsy probe assembly has a vacuum cannula and a stylet cannula coaxially arranged along a longitudinal axis, with the vacuum cannula being positioned inside the stylet cannula. The vacuum cannula is coupled in fluid communication with the vacuum source. The vacuum cannula has an elongate portion and a flared portion that extends distally from the elongate portion. The stylet cannula is coupled in driving communication with the electromechanical power source. The stylet cannula is movable relative to the vacuum cannula between a first extended position and a first retracted position. The stylet cannula has a proximal portion and a distal portion. The distal portion has a sample notch and a protrusion member that extends proximally in a lumen of the stylet cannula along a portion of a longitudinal extent of the sample notch, wherein when the stylet cannula is in the first retracted position, the protrusion member is received within the flared portion of the vacuum cannula. 
     The biopsy apparatus may further include a controller circuit that has a virtual energy reservoir, and the controller circuit executes program instructions to control current to motors when engaging dense tissue. 
     The invention in another form is directed to a biopsy apparatus that includes a driver assembly and a biopsy probe assembly. The driver assembly has an electromechanical power source, a vacuum source, and a controller circuit. The controller circuit is electrically and communicatively coupled to the electromechanical power source and to the vacuum source. The biopsy probe assembly is releasably attached to the driver assembly. The biopsy probe assembly has a vacuum cannula, a stylet cannula, and a cutter cannula coaxially arranged along a longitudinal axis. The vacuum cannula is positioned inside the stylet cannula, and the stylet cannula is positioned inside the cutter cannula. The vacuum cannula is coupled in fluid communication with the vacuum source. The vacuum cannula has an elongate portion and a flared portion that extends distally from the elongate portion. The stylet cannula is coupled in driving communication with the electromechanical power source. The stylet cannula is movable relative to the vacuum cannula between a first extended position and a first retracted position. The stylet cannula has a proximal portion and a distal portion. The distal portion has a sample notch and a protrusion member that extends proximally in a lumen of the stylet cannula along a portion of a longitudinal extent of the sample notch. When the stylet cannula is in the retracted position, the protrusion member of the stylet cannula is received within the flared portion of the vacuum cannula. The cutter cannula is coupled in driving communication with the electromechanical power source. The cutter cannula is movable relative to the stylet cannula between a second extended position to cover the sample notch and a second retracted position to expose the sample notch when the stylet cannula is in the first extended position. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein: 
         FIG. 1  is a perspective view of a biopsy apparatus configured in accordance with an embodiment of the present invention, with a biopsy probe assembly attached to a driver assembly; 
         FIG. 2  is a perspective view of the biopsy apparatus of  FIG. 1 , with the biopsy probe assembly detached from the driver assembly and with the driver assembly inverted to expose the drive features of the driver assembly; 
         FIG. 3  is a block representation of the driver assembly of  FIG. 1 ; 
         FIG. 4  is an exploded view of the biopsy probe assembly of  FIG. 1 ; 
         FIG. 5A  is a section view of the biopsy probe assembly of  FIG. 1 , taken along line  5 A- 5 A of  FIG. 2 ; 
         FIG. 5B  is an enlarged portion of the vacuum cannula depicted in  FIG. 5A ; 
         FIG. 5C  is an enlarged portion of the stylet cannula depicted in  FIG. 5A ; 
         FIG. 6A  shows the relative positions of the vacuum cannula, the stylet cannula, and the cutter cannula before, during, and immediately after a piercing shot; 
         FIG. 6B  shows the relative positions of the vacuum cannula, the stylet cannula, and the cutter cannula, and with the cutter cannula retracted to expose the sample notch of the stylet cannula; 
         FIG. 6C  shows the relative positions of the vacuum cannula, the stylet cannula, and the cutter cannula, depicting a shaking of the sample notch by alternatingly moving the stylet cannula in the proximal direction and in the distal direction for a short distance; 
         FIG. 6D  shows the relative positions of the vacuum cannula, the stylet cannula, and the cutter cannula, wherein the cutter cannula is rotated and translated in the distal direction to sever a tissue sample from the tissue received in the sample notch; 
         FIG. 6E  shows the relative positions of the vacuum cannula, the stylet cannula, and the cutter cannula, wherein the stylet cannula is moved within the cutter cannula in the proximal direction to mechanically aid in moving the tissue sample into the flared portion of the vacuum cannula; 
         FIG. 6F  shows the relative positions of the vacuum cannula, the stylet cannula, and the cutter cannula, wherein the stylet cannula is moved within the cutter cannula in the distal direction to disengage the protrusion member from the flared portion of the vacuum cannula; 
         FIG. 6G  shows the relative positions of the vacuum cannula, the stylet cannula, and the cutter cannula, wherein the stylet cannula is again moved within the cutter cannula in the proximal direction, such that the protrusion member re-engages the flared portion of the vacuum cannula; 
         FIG. 6H  shows the relative positions of the vacuum cannula, the stylet cannula, and the cutter cannula, wherein the stylet cannula is again moved within the cutter cannula in the distal direction to disengage the protrusion member from the flared portion of vacuum cannula and return to the extended position; 
         FIG. 7  is a vacuum/time graph depicting a baseline vacuum pressure at several different positions during a tissue sample cutting and transport sequence as depicted in  FIGS. 6A-6H ; 
         FIG. 8A  is a graph of actual motor winding current (I) of a motor of the driver assembly of  FIG. 1 , to be viewed in conjunction with the graph of  FIG. 8B ; and 
         FIG. 8B  is a graph of the energy status of a virtual energy reservoir established in a memory circuit of the driver assembly of  FIG. 1 , to be viewed in conjunction with the graph of  FIG. 8A . 
     
    
    
     Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate at least one embodiment of the invention, and such exemplifications are not to be construed as limiting the scope of the invention in any manner. 
     DESCRIPTION OF EMBODIMENTS 
     Referring now to the drawings, and more particularly to  FIGS. 1 and 2 , there is shown a biopsy apparatus  10  which generally includes a non-invasive, e.g., non-disposable, driver assembly  12  and an invasive, e.g., disposable, biopsy probe assembly  14 . As used herein, the term “non-disposable” is used to refer to a device that is intended for use on multiple patients during the lifetime of the device, and the term “disposable” is used to refer to a device that is intended to be disposed of after use on a single patient. Driver assembly  12  includes a driver housing  16  that is configured and ergonomically designed to be grasped by a user. 
     Referring to  FIGS. 2 and 3 , driver assembly  12  includes within driver housing  16  a controller circuit  18 , an electromechanical power source  20 , a vacuum source  22 , a vacuum sensor  24 , and a battery  26  (or alternatively an AC adapter). A user interface  28  (see  FIG. 1 ), such as a keypad, is located to be mounted to driver housing  16 , and externally accessible by the user with respect to driver housing  16 . Battery  26  may be, for example, a rechargeable battery, which may be charged by an inductive charging device coupled to inductive coil  29 , or alternatively, by an electrical connection to an electrical power supply. Battery  26  is electrically coupled to controller circuit  18 , electromechanical power source  20 , vacuum source  22 , and user interface  28 . 
     Referring to  FIG. 3 , user interface  28  may include control buttons and visual/aural indicators, with the control buttons providing user control over various functions of biopsy apparatus  10 , and with the visual/aural indicators providing visual/aural feedback of the status of one or more conditions and/or positions of components of biopsy apparatus  10 . The control buttons may include a sample button  28 - 1  and a prime/pierce button  28 - 2 . The visual indicators may include a display screen  28 - 3  and/or one or more light emitting diodes (LED)  28 - 4 . The aural indicator may include a buzzer  28 - 5 . The control buttons may include tactile feedback to the user when activated. 
     Controller circuit  18  is electrically and communicatively coupled to electromechanical power source  20 , vacuum source  22 , vacuum sensor  24 , and user interface  28 , such as by one or more wires or circuit traces. Controller circuit  18  may be assembled on an electrical circuit board, and includes, for example, a processor circuit  18 - 1  and a memory circuit  18 - 2 . 
     Processor circuit  18 - 1  has one or more programmable microprocessors and associated circuitry, such as an input/output interface, clock, buffers, memory, etc. Memory circuit  18 - 2  is communicatively coupled to processor circuit  18 - 1 , e.g., via a bus circuit, and is a non-transitory electronic memory that may include volatile memory circuits, such as random access memory (RAM), and non-volatile memory circuits, such as read only memory (ROM), electronically erasable programmable ROM (EEPROM), NOR flash memory, NAND flash memory, etc. Controller circuit  18  may be formed as one or more Application Specific Integrated Circuits (ASIC). 
     Controller circuit  18  is configured via software and/or firmware residing in memory circuit  18 - 2  to execute program instructions to perform functions associated with the retrieval of biopsy tissue samples, such as that of controlling and/or monitoring one or more components of electromechanical power source  20 , vacuum source  22 , and vacuum sensor  24 . 
     Electromechanical power source  20  may include, for example, a cutter module  30 , a transport module  32 , and a piercing module  34 , each being respectively electrically coupled to battery  26 . Each of cutter module  30 , transport module  32 , and piercing module  34  is electrically and controllably coupled to controller circuit  18  by one or more electrical conductors, e.g., wires or circuit traces. 
     Cutter module  30  may include an electrical motor  30 - 1  having a shaft to which a drive gear  30 - 2  is attached. Transport module  32  may include an electrical motor  32 - 1  having a shaft to which a drive gear  32 - 2  is attached. Piercing module  34  may include an electrical motor  34 - 1 , a drive spindle  34 - 2 , and a piercing shot drive  34 - 3 . Each electrical motor  30 - 1 ,  32 - 1 ,  34 - 1  may be, for example, a direct current (DC) motor or stepper motor. As an alternative to the arrangement described above, each of cutter module  30 , transport module  32 , and piercing module  34  may include one or more of a gear, gear train, belt/pulley arrangement, etc., interposed between the respective motor and drive gear or drive spindle. 
     Piercing module  34  is configured such that an activation of electrical motor  34 - 1  and a drive spindle  34 - 2  causes a piercing shot drive  34 - 3  to move in a proximal direction  36 - 1  to compress a firing spring, e.g., one or more coil springs, and to latch piercing shot drive  34 - 3  in a ready position. Upon actuation of prime/pierce button  28 - 2  of user interface  28 , piercing shot drive  34 - 3  is propelled, i.e., fired, in a distal direction  36 - 2  (see  FIG. 2 ). 
     Vacuum source  22  is electrically and controllably coupled to battery  26  by one or more electrical conductors, e.g., wires or circuit traces. Vacuum source  22  may include, for example, an electric motor  22 - 1  that drives a vacuum pump  22 - 2 . Vacuum source  22  has a vacuum source port  22 - 3  coupled to vacuum pump  22 - 2  for establishing vacuum in biopsy probe assembly  14 . Electric motor  22 - 1  may be, for example, a rotary, linear or vibratory DC motor. Vacuum pump  22 - 2  may be, for example, a peristaltic pump or a diaphragm pump, or one or more of each connected in series or parallel. 
     Vacuum sensor  24  is electrically coupled to controller circuit  18  by one or more electrical conductors, e.g., wires or circuit traces. Vacuum sensor  24  may be a pressure differential sensor that provides vacuum (negative pressure) feedback signals to controller circuit  18 . In some implementations, vacuum sensor  24  may be incorporated into vacuum source  22 . 
     Referring to  FIGS. 1 and 2 , biopsy probe assembly  14  is configured for releasable attachment to driver assembly  12 . As used herein, the term “releasable attachment” means a configuration that facilitates an intended temporary connection followed by selective detachment involving a manipulation of disposable biopsy probe assembly  14  relative to driver assembly  12 , without the need for tools. 
     Referring to the exploded view of  FIG. 4 , biopsy probe assembly  14  includes a probe housing  40 , a probe sub-housing  42 , a vacuum cannula  44 , a stylet cannula  46 , a stylet gear-spindle set  48  for linear stylet translation, a cutter cannula  50 , a cutter gear-spindle set  52  for rotary and linear cutter translation, a sample manifold  54 , and a sample cup  56 . 
     Referring to  FIGS. 2, 4, and 5A , probe housing  40  is formed as an L-shaped structure having an elongate portion  40 - 1  and a front plate  40 - 2 . When biopsy probe assembly  14  is attached to driver assembly  12 , front plate  40 - 2  is positioned distally adjacent to an entirety of front surface  16 - 1  of driver housing  16 , i.e., so as to shield the entirety of front surface  16 - 1  of the non-disposable driver assembly from contact with a patient. 
     Vacuum cannula  44 , stylet cannula  46 , and cutter cannula  50  are coaxially arranged along a longitudinal axis  58  in a nested tube arrangement, with vacuum cannula  44  being the innermost tube, cutter cannula  50  being the outermost tube, and stylet cannula  46  being the intermediate tube that is interposed between vacuum cannula  44  and cutter cannula  50 . In other words, vacuum cannula  44  is positioned inside stylet cannula  46 , and stylet cannula  46  is positioned inside cutter cannula  50 . 
     Vacuum cannula  44  is mounted to be stationary relative to probe sub-housing  42 . Vacuum cannula  44  is coupled in fluid communication with vacuum source  22  via sample manifold  54 . 
     Referring to  FIGS. 4, 5A, and 5B , vacuum cannula  44  includes an elongate portion  44 - 1  and a flared portion  44 - 2  that extends distally from elongate portion  44 - 1 . Elongate portion  44 - 1  has a first outside diameter D 1 . Flared portion  44 - 2  flares from elongate portion  44 - 1  in two stages, namely, a first flared stage  45 - 1  and a second flared stage  45 - 2 . First flared stage  45 - 1  diverges from elongate portion  44 - 1  at a first acute angle A 1 , and second flared stage  45 - 2  diverges from first flared stage  45 - 1  at a second acute angle A 2  relative to elongate portion  44 - 1 , with acute angle A 2  being larger than acute angle A 1 . A distal outside diameter D 2  of second flared stage  45 - 2  is selected to be accommodated within, and in sliding contact with, lumen  46 - 4  of stylet cannula  46 . Each of first flared stage  45 - 1  and second flared stage  45 - 2  of flared portion  44 - 2  has a distally and gradually increasing diameter, which is larger than the diameter D 1  of elongate portion  44 - 1 . 
     Referring again to  FIG. 4 , stylet cannula  46  includes a proximal portion  46 - 1  and a distal portion  46 - 2 . Distal portion  46 - 2  includes a sample notch  60 . Attached to distal portion  46 - 2  is a piercing tip  62 , which in turn forms part of stylet cannula  46 . Stylet gear-spindle set  48  threadably engages a transport spindle  42 - 3  is fixedly attached (e.g., glued, welded or staked) to proximal portion  46 - 1  of stylet cannula  46 . Stylet gear-spindle set  48  is a unitary gear having a driven gear  48 - 1  fixedly attached to a threaded spindle  48 - 2 , and may be formed as a single molded component. Stylet cannula  46  is retracted or extended along longitudinal axis  58  by activation of transport module  32  of biopsy probe assembly  14 , with drive gear  32 - 2  of transport module  32  of driver assembly  12  being engaged with driven gear  48 - 1  of stylet gear-spindle set  48 . 
     Referring also to  FIG. 5C, 6A, and 6B , sample notch  60  is formed as an elongate opening in a side wall  46 - 3  of stylet cannula  46  to facilitate a reception of tissue  66  into a lumen  46 - 4  of stylet cannula  46 . Sample notch  60  has a longitudinal extent  60 - 1  that extends along longitudinal axis longitudinal axis  58 . Sample notch  60  does not extend in side wall  46 - 3  below a centerline of the diameter of stylet cannula  46 , and may include cutting edges around the perimeter of the opening formed by sample notch  60 , wherein the cutting edges of the elongate (linear) portions of sample notch  60  each have a cutting edge  46 - 5  that diverges from a cutting edge along the side wall  46 - 3  to the centerline at a diameter of stylet cannula  46 . 
     Piercing tip  62  has a tip portion  62 - 1 , a mounting portion  62 - 2 , and a protrusion member  62 - 3 . Piercing tip  62  is inserted into lumen  46 - 4  of stylet cannula  46  at distal portion  46 - 2 , with mounting portion  62 - 2  being attached to distal portion  46 - 2  of stylet cannula  46 , such as an adhesive or weld. As such, tip portion  62 - 1  extends distally from distal portion  46 - 2  of stylet cannula  46 , and protrusion member  62 - 3  extends proximally (i.e., in proximal direction  36 - 1 ) in lumen  46 - 4  along a portion of the longitudinal extent  60 - 1  of sample notch  60 . Accordingly, as depicted in  FIGS. 6E and 6G , when stylet cannula  46  is fully retraced in the proximal direction  36 - 1 , protrusion member  62 - 3  is received into flared portion  44 - 2  of vacuum cannula  44 . At least the proximal tip portion of protrusion member  62 - 3  has a proximally decreasing diameter. 
     Referring again to  FIG. 4 , cutter cannula  50  includes a proximal portion  50 - 1  and a distal portion  50 - 2 . Distal portion  50 - 2  includes an annular cutting edge  64 . Cutter gear-spindle set  52  is fixedly attached (e.g., glued, welded or staked) to proximal portion  50 - 1  of cutter cannula  50 . Cutter gear-spindle set  52  is a unitary gear having a driven gear  52 - 1  fixedly attached to a threaded spindle  52 - 2 , and may be formed as a single molded component. Cutter cannula  50  is retracted or extended along longitudinal axis  58  by activation of cutter module  30  of biopsy probe assembly  14 , with drive gear  30 - 2  of cutter module  30  of driver assembly  12  being engaged with driven gear  52 - 1  of cutter gear-spindle set  52 . Thus, cutter cannula  50  has a rotational cutting motion and is translated axially along longitudinal axis  58 . The pitch of the threads of threaded spindle  52 - 2  determines the number of revolutions per axial distance (in millimeters (mm)) that cutter cannula  50  moves axially. 
     Referring to  FIGS. 4 and 5A , sample manifold  54  is configured as an L-shaped structure having a vacuum chamber portion  54 - 1  and a collection chamber portion  54 - 2 . Vacuum chamber portion  54 - 1  includes a vacuum input port  54 - 3  that is arranged to sealably engage vacuum source port  22 - 3  of vacuum source  22  of driver assembly  12  when biopsy probe assembly  14  is attached to driver assembly  12 . Vacuum chamber portion  54 - 1  is connected in fluid communication with collection chamber portion  54 - 2 . Proximal end of elongate portion  44 - 1  of vacuum cannula  44  passes through vacuum chamber portion  54 - 1  and is in direct fluid communication with collection chamber portion  54 - 2 . Collection chamber portion  54 - 2  has a cavity sized and arranged to removably receive sample cup  56 , such that sample cup  56  is in direct fluid communication with elongate portion  44 - 1  of vacuum cannula  44 , and sample cup  56  also is in direct fluid communication with vacuum input port  54 - 3  of vacuum chamber portion  54 - 1 . Blotting papers are placed in vacuum chamber portion  54 - 1  in a region between vacuum input port  54 - 3  and collection chamber portion  54 - 2 . 
     Accordingly, a tissue sample severed by cutter cannula  50  at sample notch  60  of stylet cannula  46  may be transported by vacuum applied by vacuum source  22  at sample cup  56 , through vacuum cannula  44 , and into sample cup  56 . 
     Referring again to  FIGS. 2, 4 and 5A , probe sub-housing  42  is a sub-housing that is slidably coupled to probe housing  40 , e.g., using a rail/slot arrangement. Probe sub-housing  42  includes a proximal threaded portion  42 - 1  and a distal threaded portion  42 - 2 . 
     Proximal threaded portion  42 - 1  in probe sub-housing  42  has a threaded hole that threadably receives threaded spindle  48 - 2  of stylet gear-spindle set  48 , such that rotation of driven gear  48 - 1  of stylet gear-spindle set  48  results in a linear translation of stylet cannula  46  along longitudinal axis  58 , with a direction of rotation correlating to a direction of translation of stylet cannula  46  in one of proximal direction  36 - 1  and distal direction  36 - 2 . Driven gear  48 - 1  of stylet gear-spindle set  48  engages drive gear  32 - 2  of transport module  32  when biopsy probe assembly  14  is attached to driver assembly  12  (see  FIG. 1 ). 
     Likewise, distal threaded portion  42 - 2  of probe sub-housing  42  has a threaded hole that threadably receives threaded spindle  52 - 2  of cutter gear-spindle set  52 , such that rotation of driven gear  52 - 1  of cutter gear-spindle set  52  results in a combined rotation and linear translation of cutter cannula  50  along longitudinal axis  58 , with a direction of rotation correlating to a direction of translation of cutter cannula  50 . Driven gear  52 - 1  of cutter gear-spindle set  52  engages drive gear  30 - 2  of cutter module  30  when biopsy probe assembly  14  is attached to driver assembly  12  (see  FIG. 1 ). 
     Also, when biopsy probe assembly  14  is attached to driver assembly  12 , referring also to  FIGS. 2 and 3 , probe sub-housing  42  is connected to piercing shot drive  34 - 3  of piercing module  34 . As such, upon a first actuation of prime/pierce button  28 - 2 , probe sub-housing  42  and piercing shot drive  34 - 3  are translated in unison in proximal direction  36 - 1  to position piercing shot drive  34 - 3  and probe sub-housing  42  carrying stylet cannula  46  and cutter cannula  50  in the ready, i.e., cocked position, and upon a second actuation of prime/pierce button  28 - 2  to effect a piercing shot, probe sub-housing  42  and piercing shot drive  34 - 3  are rapidly propelled in unison in distal direction  36 - 2  to position stylet cannula  46  and cutter cannula  50  at the distal most position of the combined elements, e.g., within the patient. 
       FIGS. 6A-6H  collectively represent a tissue sample severing and transport sequence.  FIGS. 6E and 6G  show stylet cannula  46  in its retracted position  68 - 1 .  FIGS. 6A, 6B, and 6H  show stylet cannula  46  in its extended position  68 - 2 , sometimes also referred to as a zero position.  FIGS. 6C, 6D, and 6F  show stylet cannula  46  in various positions intermediate to retracted position  68 - 1  and extended position  68 - 2 .  FIGS. 6B and 6C  show cutter cannula  50  in its retracted position  70 - 1 , which exposes sample notch  60  of stylet cannula  46  when stylet cannula  46  is in or near its extended position  68 - 2 .  FIGS. 6A and 6D-6H  show cutter cannula  50  in its extended position  70 - 2 , sometimes also referred to as a zero position, wherein cutter cannula  50  covers the sample notch  60  of stylet cannula  46 . 
     To effect the described movements of stylet cannula  46 , controller circuit  18  executes program instructions and sends respective control signals to transport module  32  of driver assembly  12 , which in turn transfers the motion to stylet gear-spindle set  48  of biopsy probe assembly  14  Likewise, to effect the described movements of cutter cannula  50 , controller circuit  18  executes program instructions and sends respective control signals to cutter module  30  of driver assembly  12 , which in turn transfers the motion to cutter gear-spindle set  52  of biopsy probe assembly  14 . Controller circuit  18  may determine an axial position of each of stylet cannula  46  and cutter cannula  50 , relative to the respective zero position, by counting the respective number of motor drive pulses, or alternatively, the respective number of motor shaft revolutions. 
       FIG. 6A  shows the relative positions of vacuum cannula  44 , stylet cannula  46 , and cutter cannula  50  before, during, and immediately after the piercing shot effected by piercing module  34 . As shown, distal portion  50 - 2  of cutter cannula  50  is extended over sample notch  60 . 
     In the sequence step illustrated in  FIG. 6B , vacuum source  22  is actuated to deliver a vacuum via vacuum cannula  44  to lumen  46 - 4  of stylet cannula  46  at sample notch  60 , and cutter cannula  50  is retracted by actuation of cutter module  30  to expose sample notch  60 , thereby permitting tissue  66  to be drawn into lumen  46 - 4  of stylet cannula  46  through sample notch  60 . In the present embodiment, in order to expose sample notch  60 , cutter cannula  50  rotates counterclockwise to effect a linear translation of cutter cannula  50  in proximal direction  36 - 1  for a distance of approximately 23 millimeters (mm) to define the open length of sample notch  60 . As used herein, the relative term “approximately” means the base value in the indicated units (if any) plus or minus five percent, unless stated otherwise. The actual aperture size at sample notch  60 , corresponding to a desired sample size, may be user-selected at user interface  28 , wherein a distance that cutter cannula  50  is retracted toward retracted position  70 - 1  from extended position  70 - 2  is controlled by controller circuit  18  to correspond to the sample size selected by the user. 
       FIGS. 6C and 6D  illustrate a cutting sequence. 
     In the sequence step illustrated in  FIG. 6C , in order to increase the size of tissue sample to be collected, stylet cannula  46  may be moved alternatingly in proximal direction  36 - 1  and distal direction  36 - 2  a short distance e.g., 2 to 5 mm, so as to shake sample notch  60 , thereby increasing the amount of tissue  66  that passes through sample notch  60  and into lumen  46 - 4  of stylet cannula  46 . The last move of the shake is defined to keep sample notch  60  in a 1 mm retracted position (see  FIG. 6C ) compared to the zero position of stylet cannula  46  as depicted in  FIG. 6A . This is to ensure that cutter cannula  50  closes sample notch  60  during the cutting sequence (see  FIG. 6D ) and will cut 1 mm further, to thus ensure that connective tissue or strings are completely cut during the cutting sequence step illustrated in  FIG. 6D . 
     In the cutting sequence step illustrated in  FIG. 6D , cutter cannula  50  is rotated and translated in distal direction  36 - 2  to sever a tissue sample  66 - 1  from tissue  66 . In the present embodiment, cutter cannula  50  rotates clockwise to effect a linear translation of cutter cannula in distal direction  36 - 2  for a distance of approximately 23 mm in order to cut the tissue and return to the zero position. 
       FIGS. 6E-6H  illustrate a tissue sample transport sequence. 
     In the sequence step illustrated in  FIG. 6E , vacuum is applied by vacuum cannula  44 , and stylet cannula  46  is moved within cutter cannula  50  in proximal direction  36 - 1  to mechanically aid in moving tissue sample  66 - 1  into flared portion  44 - 2  of vacuum cannula  44 . More particularly, as stylet cannula  46  is moved within cutter cannula  50  in proximal direction  36 - 1 , protrusion member  62 - 3  of piercing tip  62  engages tissue sample  66 - 1  to assist tissue sample  66 - 1  into vacuum cannula  44 . Protrusion member  62 - 3  then engages flared portion  44 - 2  of vacuum cannula  44  to close off an air inflow into flared portion  44 - 2  of vacuum cannula  44 . 
     In the sequence step illustrated in  FIG. 6F , with vacuum being applied by vacuum cannula  44 , stylet cannula  46  is moved within cutter cannula  50  in distal direction  36 - 2  to disengage protrusion member  62 - 3  from the flared portion  44 - 2  of vacuum cannula  44  to cause an abrupt change in air flow into vacuum cannula  44 , thereby helping the vacuum transport of tissue sample  66 - 1  through vacuum cannula  44 . 
     The sequence steps illustrated in  FIGS. 6G and 6H  are essentially a repeat of sequence steps  6 E and  6 F. 
     In the sequence step illustrated in  FIG. 6G , with vacuum applied to vacuum cannula  44  by vacuum source  22 , stylet cannula  46  is again moved within cutter cannula  50  in proximal direction  36 - 1 , such that protrusion member  62 - 3  of piercing tip  62  re-engages flared portion  44 - 2  of vacuum cannula  44  to again close off an air inflow into flared portion  44 - 2  of vacuum cannula  44 . 
     In the sequence step illustrated in  FIG. 6H , with vacuum being applied to vacuum cannula  44  by vacuum source  22 , stylet cannula  46  is moved within cutter cannula  50  in distal direction  36 - 2  to again disengage protrusion member  62 - 3  from flared portion  44 - 2  of vacuum cannula  44  to cause an abrupt change in air flow into vacuum cannula  44 , thereby helping the vacuum transport of tissue sample  66 - 1  (if not already delivered by sequence steps of  FIGS. 6E and 6F ) through vacuum cannula  44 . At the end of the sequence of  FIG. 6H , stylet cannula  46  is re-positioned at the tissue receiving position i.e., extended position  68 - 2 , also referred to as the zero position, and is ready to receive tissue for a next tissue sample, in which the sequence steps of  FIGS. 6A-6H  would be repeated. 
     It is noted that the sample transport sequence illustrated in  FIGS. 6E and 6F  may be repeated as many times as necessary to complete the vacuum transport of tissue sample  66 - 1  through vacuum cannula  44 . Also, the backward motion of protrusion member  62 - 3  of piercing tip  62  of stylet cannula  46  in proximal direction  36 - 1  may be implemented as incremental steps, alternating between a backward motion and then a forward motion (the forward distance being less than the backward distance) until the final position (retracted position  68 - 1 ) is reached, as depicted in  FIGS. 6E and 6G . 
       FIG. 7  is a vacuum graph depicting a baseline vacuum pressure at different positions during the tissue sample cutting and transport sequence depicted in  FIGS. 6A-6H . 
     Referring to the vacuum graph of  FIG. 7 , it is noted that vacuum is applied throughout the entire sequence depicted in  FIGS. 6A-6H . At time TO, vacuum source  22  is activated, and vacuum (negative pressure) builds in vacuum cannula  44 . At time T 1 , maximum vacuum is achieved, which corresponds to the end of the cutting sequence step depicted in  FIG. 6D . At time T 2 , the tissue stuffing sequence of  FIGS. 6E-6F  begins, and vacuum pressure abruptly drops due to a moment in which vent holes  80  in stylet cannula  46  are not restricted. Vacuum begins to build prior to time T 3  as protrusion member  62 - 3  of piercing tip  62  approaches flared portion  44 - 2  of vacuum cannula  44 , and maximizes, representing the end of the first stuffing sequence depicted in  FIG. 6E . At time T 3 , vacuum pressure abruptly drops due to protrusion member  62 - 3  of piercing tip  62  being moved away from flared portion  44 - 2  as depicted in  FIG. 6F . In some instances, tissue sample  66 - 1  may have been delivered to sample cup  56 . At time T 4 , the second stuffing sequence depicted in  FIGS. 6G and 6H  begins. Time T 5  corresponds to the end of the second stuffing sequence depicted in  FIG. 6G . At time T 6 , vacuum pressure drops due to protrusion member  62 - 3  of piercing tip  62  again being moved away from flared portion  44 - 2  as depicted in  FIG. 6H , and back to the tissue receiving (zero) position. 
     By comparing an actual vacuum pressure to the baseline vacuum graph depicted in  FIG. 7  at different stages of the tissue cutting and transport sequence depicted in  FIGS. 6A-6H , cutting or tissue transport anomalies can be identified and corrective action can be attempted. 
     In accordance with an aspect of the invention, vacuum sensor  24  provides vacuum pressure feedback signals to controller circuit  18 , and controller circuit  18  executes program instructions to determine whether the actual vacuum pressure provided by vacuum sensor  24  deviates by more than a predetermined amount from the baseline pressure of the vacuum graph of  FIG. 7  at a corresponding point in the tissue cutting and transport sequence. The predetermined amount may be, for example, the baseline vacuum pressure plus or minus 10 percent. If the deviation is outside the acceptable range of deviation, then corrective action may be taken depending upon when in the tissue cutting and transport sequence the anomaly occurred. 
     For example, if the vacuum pressure falls below the baseline by more than the allowable deviation during the time period between times T 1  and T 2 , this may be an indication of an incomplete cut, and thus controller circuit  18  may repeat the cutting sequence depicted in  FIGS. 6C and 6D  without user intervention, rather than immediately going into an error state. Similarly, if the vacuum pressure rises above the baseline by more than the allowable deviation between the times T 3  to T 5 , this may be an indication of an incomplete tissue transport through vacuum cannula  44 , and thus controller circuit  18  may increase the number of iterations of sequence steps  6 E and  6 F without user intervention. 
     Referring again to  FIG. 5A , vacuum is maintained in biopsy probe assembly  14  by a series of seals. A seal  72 , e.g., a sleeve-type seal or O-ring arrangement, is located to provide a seal between cutter cannula  50  and stylet cannula  46 . A seal  74 , e.g., an O-ring, is located to provide a seal between stylet cannula  46  and vacuum cannula  44 . A seal  76 , e.g., a sleeve-type seal or O-ring arrangement, is located to provide a seal between vacuum cannula  44  and vacuum chamber portion  54 - 1  of sample manifold  54 . Also, a seal  78  may be located in collection chamber portion  54 - 2  of sample manifold  54  and sample cup  56 . Finally, a seal is placed at vacuum input port  54 - 3  at the vacuum interface between biopsy probe assembly  14  and driver assembly  12   
     During operation, vacuum pump  22 - 2  of vacuum source  22  will build up vacuum (negative pressure) in the vacuum reservoir formed by sample manifold  54  and sample cup  56 . More particularly, the volume of sample cup  56  and sample manifold  54  will define the strength of a “vacuum boost”, and also defines the cycle time for vacuum pump  22 - 2  of vacuum source  22 . In the present embodiment, for example, the volume is approximately 10 milliliters. 
     Regarding the “vacuum boost”, stylet cannula  46  has one or more vent openings  80 , e.g., annularly arranged, at a predetermined distance proximal from tip portion  62 - 1 , and these vent openings  80  (see  FIG. 4 ) will be exposed to the atmosphere when the stylet cannula  46  is retracted to retracted position  68 - 1  (see  FIGS. 6E and 6G ), wherein vent openings  80  slide under seal  72  between cutter cannula  50  and stylet cannula  46 . Once these vent openings  80  are exposed to the atmosphere, the system is ‘open’ and the build-up vacuum pressure will be equalized with the surrounding pressure so as to create the vacuum boost effect, in addition to the continuous flow delivered by vacuum pump  22 - 2  of vacuum source  22 . 
     Referring again to  FIG. 3 , when activating the cutter motor  30 - 1  for cutting tissue by moving cutter cannula  50  or activating transport motor  32 - 1  for transporting tissue by moving stylet cannula  46 , each motor pulls current from battery  26 . This current will linearly increase with load on the respective motor. Thus, the amount of current consumed can be translated into load. When working with dense tissue, the load may increase, and this is detected by monitoring the current using a current monitoring program executed by controller circuit  18 . 
     Each of cutter motor  30 - 1  and transport motor  32 - 1  has a maximum continuous current rating (load) at which the motor can run indefinitely, and when the respective motor exceeds this continuous current (load), the motor can only run for a limited time before the motor is damaged (e.g., the windings burn in the motor), wherein the higher the load the shorter the time. The current monitoring program executed by controller circuit  18  monitors the current for each motor, and when the current exceeds the maximum continuous level for a respective motor, then it is determined that the motor has entered dense tissue, and driver assembly will go into a dense tissue mode. 
     When dense tissue is encountered, controller circuit  18  controls the current supplied to the respective motor to provide motor protection and to permit the motor current to exceed the maximum continuous current rating for short periods of time, based on the status (virtual energy level) of a virtual energy reservoir that is established in memory circuit  18 - 2  of controller circuit  18 . 
     The idea is to exert as much strength of the motor as possible without damaging the motor windings, when such challenging dense tissue is encountered. Once the motor, e.g., cutter motor  30 - 1  and/or transport motor  32 - 1 , starts running in any of the phases, the motor speed (revolutions per minute (rpm)) is set as 100% based on the voltage being set in controller circuit  18 , e.g., to e.g. 6 volts, and then an increase in load (torque) will increase the current consumption and potentially slow down the motor until it stalls. Controller circuit  18  has the option of increasing the voltage from 6 volts to, e.g., 9 volts and by that increase the speed (rpm) and stall torque, and thus overcome more dense tissue. In the present example, it is assumed that each motor has three separate windings, or phases. It was recognized, however, that some very dense tissue could potentially stall the motor from rotating, and meanwhile only one of the motor phases or windings is in conduction, which will lead a dramatic temperature increase in this single phase and lead to burn-out of the motor. The virtual energy reservoir is used for monitoring the heat when running between continues torque level and stall torque level, where there is a risk to burn the motor windings. 
     In accordance with an aspect of the invention, it is possible to exceed the continuous current level, e.g., when encountering dense tissue, and still protect the motor without sacrificing motor performance. 
     It is assumed that each of the motor is initialized at rest, and the ambient temperature is the normal room temperature. By keep tracking of the instant current consumption over the operation time, a corresponding increment of motor winding temperature can be predicted. Thus, for dense tissue detection/motor protection, a virtual energy reservoir is established in memory circuit  18 - 2  for each motor cutter motor  30 - 1  and transport motor  32 - 1 . The virtual energy reservoir can be filled up or drained at runtime based on integrating the difference of the actual motor winding current and the nominal motor winding current (maximum continuous current) over time. The motor winding temperature starts to increase when the actual motor winding current is higher than the nominal motor winding current (maximum continuous current), and vice versa. 
     Controller circuit  18  thus executes program instructions to predict when the winding temperature is above its thermal limit, and if so determined, controller circuit  18  will send control signals to the respective cutter module  30  or transport module  32  to lower the motor torque before the respective motor gets too hot. The algorithm executed as program instructions by controller circuit  18  is as follows: 
       ∫(I 2 −In 2 )t wherein: “I” represents the actual motor winding current;
 
     “In” represents the nominal current of the motor windings; and 
     “t” represent time. 
       FIG. 8A  is a graph of actual motor winding current (I), and  FIG. 8B  is a graph of the energy status of the virtual energy reservoir established in memory circuit  18 - 2 . In the graph of  FIG. 8B , STH represents the upper threshold and STL represents the lower threshold of the virtual energy reservoir. 
     Referring to  FIGS. 8A and 8B  in combination, when the motor starts running from t 0 , there is a huge current spike for the motor to accelerate, at the same time, the virtual energy reservoir starts to be filled though it has not exceeded the upper threshold. The virtual energy reservoir is empty at t 1 , and the virtual energy reservoir continues being zero until the current abruptly increases again at t 2 . When the energy accumulation in the virtual energy reservoir is over the upper threshold STH for the first time at t 3 , then controller circuit  18  takes immediate action to reduce the current supplied to the respective motor to a safe level (predefined). The virtual energy reservoir level begins to drop from then on, even though the virtual energy reservoir level has been experienced with a very short overshooting. When the energy accumulation of the virtual energy reservoir level drops below the lower threshold STL at t 4 , then controller circuit  18  takes immediate action to increase, i.e., boost, the current again. The same process may be repeated three times before controller circuit  18  designates the condition as an error condition, meaning that the tissue is significantly dense, i.e., too dense to be cut. The three repeated times before error is predefined in the software executed by controller circuit  18 . The number of repetitions may be varied, if desired, based at least in part on the length of the cycle time (e.g., the time of t 5 -t 3 ). 
     In the present embodiment, the dense tissue mode is entered automatically when driver assembly  12  is powered on, and runs all the time after driver assembly  12  has been powered. 
     The following items also relate to the invention: 
     In one form, the invention relates to a biopsy apparatus that includes a driver assembly and a biopsy probe. The driver assembly has an electromechanical power source and a vacuum source. The biopsy probe assembly is releasably attached to the driver assembly. The biopsy probe assembly has a vacuum cannula and a stylet cannula coaxially arranged along a longitudinal axis. The vacuum cannula is positioned inside the stylet cannula. The vacuum cannula is coupled in fluid communication with the vacuum source. The vacuum cannula has an elongate portion and a flared portion that extends distally from the elongate portion. The stylet cannula is coupled in driving communication with the electromechanical power source. The stylet cannula is movable relative to the vacuum cannula between a first extended position and a first retracted position. The stylet cannula has a proximal portion and a distal portion. The distal portion has a sample notch and a protrusion member that extends proximally in a lumen of the stylet cannula along a portion of a longitudinal extent of the sample notch. When the stylet cannula is in the first retracted position, the protrusion member is received within the flared portion of the vacuum cannula. 
     The flared portion of the vacuum cannula may have a first flared stage that diverges from the elongate portion at a first acute angle relative to the elongate portion, and a second flared stage that diverges from the first flared stage at a second acute angle relative to the elongate portion. Optionally, the second acute angle is larger than the first acute angle. 
     The biopsy probe assembly may further include a cutter cannula coaxial with the stylet cannula and the vacuum cannula, wherein the stylet cannula is positioned within the cutter cannula. The cutter cannula is movable relative to the stylet cannula between a second extended position to cover the sample notch and a second retracted position to expose the sample notch when the stylet cannula is in the first extended position. 
     In any of the embodiments, the driver assembly optionally includes a driver housing that has a front surface. The biopsy probe assembly has a probe housing with an elongate portion, and in any of the embodiments, may include a front plate. When the biopsy probe assembly is attached to the driver assembly, the front plate is positioned distally adjacent to an entirety of the front surface of the driver housing so as to shield the entirety of the front surface of the driver assembly from contact with a patient. 
     In any of the embodiments, the driver assembly may include a controller circuit and an electromechanical power source. The controller circuit is electrically and communicatively coupled to the electromechanical power source. The electromechanical power source has a cutter module and a transport module. The cutter module has a first motor and the transport module has a second motor. When the biopsy probe assembly is attached to the driver assembly, the cutter module is drivably coupled to the cutter cannula and the transport module is drivably coupled to the stylet cannula. Each of the first motor and the second motor has a maximum continuous current rating at which the respective motor can run indefinitely. The controller circuit is configured to execute program instructions to control the current for each of the first motor and the second motor. The controller circuit is configured to determine that the motor has entered dense tissue, when the current exceeds the maximum continuous level for a respective motor. 
     In any of the embodiments having a controller circuit, the controller circuit may include a processor circuit and memory circuit, and may have a virtual energy reservoir established in the memory circuit for each of the first motor and the second motor. The processor is configured to execute program instructions to control the current supplied to a respective motor to provide motor protection and to permit the respective motor current to exceed the maximum continuous current rating for short periods of time, based on the status of the virtual energy reservoir. 
     In any of the embodiments having at least one virtual energy reservoir, each virtual energy reservoir can be filled up or drained. The controller circuit may be configured to integrate a difference between an actual motor winding current for a respective motor and the maximum continuous current rating over time. The controller circuit may be configured to take action to reduce the current supplied to the respective motor, when an energy accumulation level in the virtual energy reservoir is over an upper threshold. The controller circuit may be configured to take action to increase the current supplied to the respective motor, when the energy accumulation level of the virtual energy reservoir level drops below a lower threshold. The apparatus may be controlled such that when an energy accumulation level in the virtual energy reservoir is over an upper threshold, the controller circuit then takes action to reduce the current supplied to the respective motor. The apparatus may be controlled such that when the energy accumulation level of the virtual energy reservoir level drops below a lower threshold, the controller circuit then takes action to increase the current supplied to the respective motor. 
     In any of the embodiments having a controller circuit, the controller circuit may be configured to execute program instructions to repeatedly move the protrusion member of the stylet cannula into and away from the flared portion of the vacuum cannula to aid in delivering a tissue sample into the flared portion of the vacuum cannula. The apparatus may be controlled such that vacuum may be continuously applied to the vacuum cannula during the time that the protrusion member of the stylet cannula is repeatedly moved into and away from the flared portion of the vacuum cannula. 
     In another form, the invention relates to a biopsy apparatus having a driver assembly that has an electromechanical power source, a vacuum source, and a controller circuit electrically and communicatively coupled to the electromechanical power source and to the vacuum source. A biopsy probe assembly is releasably attached to the driver assembly. The biopsy probe assembly has a vacuum cannula, a stylet cannula, and a cutter cannula coaxially arranged along a longitudinal axis. The vacuum cannula is positioned inside the stylet cannula. The stylet cannula is positioned inside the cutter cannula. The vacuum cannula is coupled in fluid communication with the vacuum source. The vacuum cannula has an elongate portion and a flared portion that extends distally from the elongate portion. The stylet cannula is coupled in driving communication with the electromechanical power source. The stylet cannula is movable relative to the vacuum cannula between a first extended position and a first retracted position. The stylet cannula has a proximal portion and a distal portion. The distal portion has a sample notch and a protrusion member that extends proximally in a lumen of the stylet cannula along a portion of a longitudinal extent of the sample notch. When the stylet cannula is in the retracted position, the protrusion member is received within the flared portion of the vacuum cannula. The cutter cannula is coupled in driving communication with the electromechanical power source. The cutter cannula is movable relative to the stylet cannula between a second extended position to cover the sample notch and a second retracted position to expose the sample notch when the stylet cannula is in the first extended position. 
     The controller circuit may be configured to execute program instructions to control the apparatus such that the protrusion member of the stylet cannula is repeatedly moved into and away from the flared portion of the vacuum cannula to aid in delivering a tissue sample into the flared portion of the vacuum cannula. The apparatus may be controlled such that vacuum is continuously applied to the vacuum cannula during the time that the protrusion member of the stylet cannula is repeatedly moved into and away from the flared portion of the vacuum cannula. 
     The electromechanical power source may include a cutter module and a transport module. The cutter module has a first motor and the transport module has a second motor. When the biopsy probe assembly is attached to the driver assembly, the cutter module is drivably coupled to the cutter cannula and the transport module is drivably coupled to the stylet cannula. 
     Each of the first motor and the second motor has a maximum continuous current rating at which the respective motor can run indefinitely. The controller circuit is configured to execute program instructions to control the current for each of the first motor and the second motor. The controller circuit may be configured to determine that the motor has entered dense tissue, when the current exceeds the maximum continuous level for a respective motor. 
     The controller circuit may include a processor circuit and memory circuit. The controller circuit may have a virtual energy reservoir established in the memory circuit for each of the first motor and the second motor. The processor may be configured to execute program instructions to control the current supplied to a respective motor to provide motor protection and to permit the respective motor current to exceed the maximum continuous current rating for short periods of time, based on the status of the virtual energy reservoir. 
     In any of the embodiments having at least one virtual energy reservoir, each virtual energy reservoir can be filled up or drained. The controller circuit is configured to integrate a difference between an actual motor winding current for a respective motor and the maximum continuous current rating over time. The controller circuit may be configured to reduce the current supplied to the respective motor, when an energy accumulation level in the virtual energy reservoir is over an upper threshold. The controller circuit may be configured to increase the current supplied to the respective motor, when the energy accumulation level of the virtual energy reservoir level drops below a lower threshold. The apparatus may be controlled such that when an energy accumulation level in the virtual energy reservoir is over an upper threshold, the controller circuit then takes action to reduce the current supplied to the respective motor. The apparatus may be controlled such that when the energy accumulation level of the virtual energy reservoir level drops below a lower threshold, the controller circuit then takes action to increase the current supplied to the respective motor. 
     The flared portion of the vacuum cannula may have a first flared stage that diverges from the elongate portion at a first acute angle relative to the elongate portion, and a second flared stage that diverges from the first flared stage at a second acute angle relative to the elongate portion. Optionally, the second acute angle is larger than the first acute angle. 
     While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.