Abstract:
A tissue acquisition system includes electrodes that are energized by a radio frequency (RF) energy source. Retractable electrodes are energized and extended from a cannula and the cannula is advanced in the tissue to position the cannula near the target tissue site in a patient. The retractable electrodes are then retracted and a distal electrode cuts a tissue sample from the tissue site when the cannula is further advanced into the tissue. The retractable electrodes are then energized and extended from the cannula and the cannula is rotated to separate the tissue sample from the tissue site. The tissue sample is ejected through the cannula for collection by advancing a dilator.

Description:
RELATED APPLICATIONS 
     This application claims priority from and is a continuation of U.S. application Ser. No. 09/618,685, filed Jul. 18, 2000, by Homet et al. now abandoned, which is a continuation-in-part of U.S. application Ser. No. 09/159,467, filed Sep. 23, 1998, by Burbank et al. now U.S. Pat. No. 6,261,241 and co-pending U.S. application Ser. No. 09/196,125, filed Nov. 20, 1998, by Burbank et al., and U.S. application Ser. No. 09/057,303, filed Apr. 8, 1998, by Burbank et al. now U.S. Pat. No. 6,331,166, which claims priority from U.S. Provisional Application Serial No. 60/076,973, filed Mar. 3, 1998 by Burbank et al. All of the aforementioned applications are hereby incorporated by reference in their entirety. 
    
    
     BACKGROUND 
     At times it is necessary to sample or remove a portion of tissue from humans or animals in the diagnosis and treatment of patients with suspicious lesions or areas of tissue, whether they are cancerous or malignant. If the patient has cancer, such as cancer of the breast, there is an advantage for early detection and diagnosis through the use of screening techniques, such as physical examination, or mammography. Mammography is capable of detecting small abnormalities, which are often not palpable during physical examination. A physician determines through mammography, ultrasound or other screening techniques when a biopsy must be performed. A biopsy may be performed by an open or percutaneous technique. Open biopsy is an invasive surgical procedure involving cutting into the suspicious tissue and directly visualizing the target area to remove the entire mass or a part of the mass. Percutaneous biopsy is usually done with a needle-like instrument through a small incision performed with the aid of an imaging device such as X-ray, ultrasound, MRI or the like, and may utilize either a fine needle aspiration or a core biopsy. Core biopsy is extremely useful in a number of conditions and is being used more frequently by the medical profession. 
     To arrive at a definitive tissue diagnosis, intact tissue is needed from an organ or lesion within the body. In most instances, only part of the organ or lesion need be sampled. However, the portions of tissue obtained must be representative of the organ or lesion as a whole. In the past, to obtain tissue from organs or lesions within the body, surgery had to be performed to locate, identify and remove the tissue. With the advent of medical imaging equipment (X-rays and fluoroscopy, computed tomography, ultrasound, nuclear medicine, and magnetic resonance imaging) it became possible to identify small abnormalities even deep within the body. However, definitive tissue characterization still requires obtaining adequate tissue samples to characterize the histology of the organ or lesion. 
     For example, mammography can identify non-palpable (not perceptible by touch) breast abnormalities earlier than they can be diagnosed by physical examination. Most non-palpable breast abnormalities are benign; some of them are malignant. When breast cancer is diagnosed before it becomes palpable, breast cancer mortality can be reduced. However, it is often difficult to determine if pre-palpable breast abnormalities are malignant, as some benign lesions have mammographic features which mimic malignant lesions and some malignant lesions have mammographic features which mimic benign lesions. Thus, mammography has its limitations. To reach a definitive diagnosis, tissue from within the breast must be removed and examined under a microscope. Prior to the late 1980&#39;s, reaching a definitive tissue diagnosis for non-palpable breast disease required a mammographically guided localization, either with a wire device, visible dye, or carbon particles, followed by an open, surgical biopsy utilizing one of these guidance methods to lead the surgeon to the non-palpable lesion within the breast. 
     One type of image-guided breast biopsy instrument currently available is a vacuum-assisted automatic core biopsy device. One such successful biopsy device is shown and disclosed in U.S. Pat. No. 5,526,822 to Burbank et al, which is expressly incorporated by reference herein. This device, known commercially as the MAMMOTOME™ Biopsy System, which is available from Ethicon Endo-Surgery, Inc., a division of Johnson &amp; Johnson, has the capability to actively capture tissue prior to cutting the tissue. Active capture allows for sampling through non-homogeneous tissues. The device is comprised of a disposable probe, a motorized drive unit, and an integrated vacuum source. The probe is made of stainless steel and molded plastic and is designed for collection of multiple tissue samples with a single insertion of the probe into the breast. The tip of the probe is configured with a laterally-disposed sampling notch for capturing tissue samples. Orientation of the sample notch is directed by the physician, who uses a thumbwheel to direct tissue sampling in any direction about the circumference of the probe. A hollow cylindrical cutter severs and transports the tissue samples to a tissue collection chamber for later testing. 
     Co-pending U.S. patent application Ser. No. 09/057,303, which is expressly incorporated by reference herein, discloses apparatuses and methods for precisely isolating a target lesion, resulting in a high likelihood of “clean” margins about the lesion. This 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. Various tissue acquisition instrument embodiments are disclosed for segmenting the target tissue, including embodiments wherein the instrument comprises a cutting element which is extendable radially outwardly and movable circumferentially to define a peripheral margin about a tissue sample, and other embodiments wherein the cutting element is extendable radially outwardly and movable axially to define peripheral margins about the tissue sample. 
     Co-pending U.S. patent application Ser. No. 09/196,125, which is expressly incorporated by reference herein, discloses tissue acquisition systems and methods that include radio frequency (RF) cutter loops which are extendable out of a cannula to cut cylindrical tissue samples from a tissue of interest in a patient. The cannula includes inner and outer cannulae which are mutually rotatable and include cutouts through which the cutting loop can be rotated and longitudinally extended to perform the cuts. The tissue samples are then aspirated proximally through the cannula for collection. 
     SUMMARY 
     According to a first exemplary embodiment of the present invention a tissue acquisition device useful in retrieving tissue samples from a patient comprises a cannula that has a longitudinal axis and a lumen extending along the longitudinal axis and a distally located electrode that has a lumen that is coaxially aligned with the cannula lumen, the electrode is fixedly attached to and is located adjacent to the cannula. 
     According to a second exemplary embodiment of the present invention, a system for sampling tissue from a patient comprises a RF energy generator capable of generating RF energy and a tissue acquisition device that includes a cannula that has a longitudinal axis and a lumen extending along the longitudinal axis and a distally located electrode that has a lumen that is coaxially aligned with the cannula lumen, the electrode is fixedly attached to and is located adjacent to the cannula and is in electrical communication with the RF energy generator. 
     According to the third exemplary embodiment of the present invention, a method of sampling tissue from a patient comprises the steps of inserting a cannula into tissue of a patient, the cannula includes an electrode coaxially aligned with and fixedly attached to the cannula, and separating the tissue by advancing the cannula through the tissue of a patient. 
     Still other objects, features, and attendant advantages of the present invention will become apparent to those skilled in the art from a reading of the following detailed description of embodiments constructed in accordance therewith, taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention of the present application will now be described in more detail with reference to specific embodiments of the apparatus and method, given only by way of example, and with reference to the accompanying drawings. 
     FIG. 1 is a schematic illustration of a tissue acquisition system according to the present invention. 
     FIG. 2 is a perspective view of a cannula assembly according to the present invention with a dilator retracted. 
     FIG. 3 is an elevational distal end view taken at arrow  3  in FIG. 2 of the cannula assembly illustrated in FIG.  2 . 
     FIG. 4 is a cross-sectional view taken at line  4 — 4  in FIG. 2 of the cannula assembly illustrated in FIG.  2 . 
     FIG. 5 is a cross-sectional view taken at line  5 — 5  in FIG. 2 of the cannula assembly illustrated in FIG. 2, showing a pair of opposing retractable electrodes in a retracted position. 
     FIG. 6 is a cross-sectional view of the cannula assembly illustrated in FIG. 2, showing the pair of opposing retractable electrodes in a partially extended position. 
     FIG. 6A shows an elevational view in partial longitudinal section of the cannula assembly. 
     FIG. 6B is an end view of the cannula assembly taken at arrow  6 B shown in FIG.  6 A. 
     FIG. 7 is a cross-sectional view of the cannula assembly illustrated in FIG. 2, showing the dilator distally positioned and a pair of opposing retractable electrodes in a fully extended position and positioned in a skin incision and in the tissue of a patient. 
     FIG. 8 is a cross-sectional view of the cannula assembly illustrated in FIG. 7, showing the pair of opposing retractable electrodes in the extended position and the cannula assembly positioned further inside of the tissue of the patient. 
     FIG. 9 is a cross-sectional view of the cannula assembly illustrated in FIG. 2, showing the pair of opposing retractable electrodes in the retracted position and the cannula assembly positioned inside of the tissue of the patient with a tissue sample located in the cannula assembly adjacent to the dilator. 
     FIG. 10 is a cross-sectional view of the cannula assembly illustrated in FIG. 2, showing the pair of opposing retractable electrodes in the extended position and the cannula assembly positioned inside of the tissue of the patient with a tissue sample located in the cannula assembly. 
     FIG. 10A shows the cannula assembly of FIG. 10 taken along lines  10 A— 10 A illustrating rotation of the cannula assembly about the longitudinal axis of the cannula in order to separate the tissue sample contained within the cannula. 
     FIG. 11 is a cross-sectional view of the cannula assembly illustrated in FIG. 2, showing the pair of opposing retractable electrodes in the retracted position with a tissue sample ejected from the cannula assembly by a dilator. 
     FIG. 12 is an illustration of an exemplary process according to the present invention. 
    
    
     DETAILED DESCRIPTION 
     Referring to the drawing figures, like reference numerals designate identical or corresponding elements throughout the several figures. In FIG. 1, a system  100  for sampling or removing tissue from a patient (not illustrated), includes a cannula assembly  102 , which is preferably constructed of materials so that it can economically be disposable. System  100  further includes an actuator  104  to which cannula assembly  102  is removably attached. Actuator  104  is preferably non-disposable or constructed of materials and includes components which are intended to be reused. Actuator  104  is the interface between cannula assembly  102  and an RF generator  106  and an optional vacuum source  108 . The actuator  104  also includes at least one motor (not illustrated), which extends and retracts a pair of retractable electrodes (see FIGS. 5 and 6) from the cannula assembly  102 . Additionally, actuator  104  includes switches and proximity sensors which provide control signals for controlling the motor, RF generator  106 , and vacuum source  108 . 
     Actuator  104  is connected to and in electrical communication with RF generator  106 , which is connected to and in electrical communication with a patient return pad  110  for the RF cutting, or tissue separating system, described in greater detail below. The switches in actuator  104  (not illustrated) control the application of RF energy to the cannula assembly  102 , as described in greater detail below. The RF generator  106  can be activated by a footswitch or other means and typically operates at about 200 to about 1000 KHz, specifically, about 300 to about 900 KHz, and more specifically about 330 to about 500 KHz. Power output for the RF generator  106  can be about 50 to about 150 Watts, more specifically, about 80 to about 100 Watts. However, it will be realized that an RF generator  106  exhibiting a wide variety of output parameters would be suitable. A motor driver  112  is also connected to actuator  104 , and provides power to the motors in actuator  104 . Motor driver  112  receives signals from the switches and proximity sensors in actuator  104 , which are used as feedback control signals to control the states of the motors. Vacuum source  108  is optional and includes a vacuum pump or other suitable source of vacuum (not illustrated), and is controllable to at least two vacuum pressure levels. The vacuum pump can also be controllable over a continuum of pressure levels. 
     As shown in FIGS. 2-7, the cannula assembly  102  includes a cannula  116 , a pair of opposing retractable electrodes  118  and  120  that generally extend along the length of the cannula  116 , a distally located electrode  122  (a distal electrode that is supported by a pair of distal electrode supports  124  and  126  that generally extend the length of the cannula  116 ), an electrical input block  128 , and an electrically nonconductive sheath  130 . The sheath  130  extends from a cannula proximal end  132  to a cannula distal end  134  and compressively covers and holds the pair of retractable electrodes  118  and  120  and the pair of distal electrode supports  124  and  126  against the cannula  116 . Although a pair of distal electrode supports are shown, a single distal electrode support may be utilized. 
     The cannula  116  is generally tubular and has a longitudinal axis  136  that extends between the proximal end  132  and the opposite distal end  134 . The cannula  116  has a tissue lumen  138  that extends longitudinally from the proximal end  132  to the distal end  134 . The cannula  116  is preferably formed of a relatively rigid, electrically non-conductive, and biocompatible material. The cannula  116  is optionally provided with a lubricious coating on the inner surface and the outer surface of the cannula  116 , which allows a tissue sample to be more easily drawn along the tissue lumen  138 . The cannula  116  can be formed of an electrically insulating biocompatible material, such as a medical grade polymer like polycarbonate. The cannula  116  can have a length of about 3 to about 15 cm, more specifically, about 5 to about 13 cm, and even more specifically, about 8 to about 9 cm. In one embodiment, the cannula  116  can have an inside transverse dimension or diameter of about 3 to about 10 mm, more specifically, about 5 to about 7 mm. 
     The distal electrode  122  is fixedly attached to and is located distally of the cannula  116  approximate to the cannula distal end  134  to define a gap  140  between the distal electrode  122  and the cannula  116 . The distal electrode  122  has a lumen  142  that has the same geometric cross sectional shape as the tissue lumen  138  and is coaxially aligned with the tissue lumen  138  so as to have the same longitudinal axis  136 . In the example shown, the lumen  142  and the tissue lumen  138  each have a generally circular cross sectional shape when taken perpendicular to the longitudinal axis  136 . The distal electrode  122  is supported by the first distal electrode support  124  and the opposing second distal electrode support  126 . The electrode supports  124  and  126  extend from the proximal end  132  to the distal end  134  and are located externally of the cannula  116  approximately 180 degrees apart from each other. The electrode supports  124  and  126 , as well as the distal electrode  122 , are electrically connected to the electrical input block  128  for the input of RF energy. 
     A dilator  144  is movably positioned in the tissue lumen  138  for ejecting a tissue sample  162 , once obtained, from the cannula  116 . The distal end of the dilator  144  is generally convex, so that it bulges out from the dilator  144  to help push the tissue sample  162  out of the tissue lumen  138 . The dilator  144 , as explained below, is positioned distally while inserting the cannula assembly to the tissue sample location, which provides a separating traction force to the tissue while it is being separated. 
     The retractable electrodes  118  and  120  generally extend from the proximal end  132  to the distal end  134  and are located externally of the cannula  116  approximately 180 degrees apart from each other and approximately 90 degrees apart from the electrode supports  124  and  126 . The first retractable electrode  118  is housed in a first housing  146  and likewise, the second retractable electrode  120  is housed in a second housing  148 . The housings  146  and  148  are generally tubular in shape to accommodate the retractable electrodes  118  and  120 , which are slidably positioned in the respective housings. The retractable electrodes  118  and  120  are electrically connected to the electrical input block  128  for the input of RF energy. The housings  146  and  148  extend from the proximal end  132  to the distal end  134 , but do not extend beyond the gap  140 . When the retractable electrodes  118  and  120  are retracted into the housings  146  and  148  respectively, the retractable electrodes  118  and  120  do not extend distally beyond the housings and are generally parallel to the longitudinal axis  136 . 
     The retractable electrodes  118  and  120  each are pre-stressed, or pre-bent so that as the retractable electrodes  118  and  120  have a first configuration when retracted in the housings and a second configuration when extended from the housings. When the retractable electrodes  118  and  120  are extended from the electrode housings  146  and  148  respectively, the retractable electrodes  118  and  120  follow a desired path. 
     As shown in FIGS. 5-7, the first retractable electrode  118  has an outwardly biased first apex  150  and a first distally located portion  152 . Likewise, the second retractable electrode  120  is a mirror image of the first retractable electrode  118  with an outwardly biased second apex  154  and a second distally located portion  156 . As the retractable electrodes  118  and  120  are extended from the respective housings  146  and  148 , the distally located portions  152  and  156  approach the longitudinal axis  136 . When the retractable electrodes  118  and  120  are fully extended from the respective housings  146  and  148 , the distally located portions  152  and  156  intersect and overlap or cross the longitudinal axis  136  and each other. In addition, when the retractable electrodes  118  and  120  are fully extended from the respective housings  146  and  148 , the apexes  150  and  154  extend radially beyond the outer surfaces of the cannula  116  and the cannula assembly  102  by a dimension D so that the cannula assembly  102  may be inserted into an incision made or augmented by the retractable electrodes  118  and  120 . The extension of the retractable electrodes  118  and  120  to dimension D can compensate for the circumference of the cannula assembly  102  so that the transverse dimension of the retractable electrodes  118  and  120  in their extended position can be about one half the circumference of the cannula  116 . Generally, the greater the magnitude of dimension D, the more easily the cannula assembly  102  will follow an incision or channel made by activated or energized retractable electrodes  118  and  120  when inserted into tissue. 
     The distal electrode  122  and the retractable electrodes  118  and  120  are formed of a conductive material so that the electrodes can be used as a RF energy cutting, or separating electrode. Preferably, the electrodes are formed of stainless steel, tungsten, platinum, or titanium alloy wire. The electrodes  118 ,  120  and  122  can be made from wire having a transverse dimension or diameter of about 0.002 to about 0.015 inch, more specifically, about 0.004 to about 0.01 inch, and even more specifically, about 0.006 to about 0.008 inch. 
     In use, an optional incision is made in the skin of the patient at the body surface  160  with a scalpel or similar instrument. The retractable electrodes  118  and  120  are fully extended, as shown in FIG. 7, and positioned within the incision made with the scalpel. RF energy is applied to the retractable electrodes, and the cannula assembly  102  is advanced into the patient&#39;s tissue by pressing the cannula assembly  102  into the body surface  160  and into the tissue  158 . Optionally, RF energy from RF generator  106  can pass through the first and second distal electrode supports  124  and  126 , which act as electrical conductors, to the distal electrode  122  during penetration of the cannula assembly into the patient&#39;s tissue. 
     The dilator  144  can be positioned through the lumen  142  and extends distally out of the cannula assembly  102  during penetration into the tissue. The dilator  144  provides traction to the tissue and helps to separate the tissue during the insertion step. The dilator  144  is retracted during or prior to the tissue sampling step. The distal electrode  122  is advanced into the incision and into the tissue, which allows the cannula assembly  102  to advance into the tissue  158  and to a site at which a tissue sample is desired with a minimum amount of trauma to the patient. 
     The use of the retractable electrodes  118  and  120  to get to the site and use of the distal electrode  122  is also advantageous because the RF cutting, or separating which is provided therewith allows entry of the cannula assembly  102  into the target tissue with much less pushing force than prior devices, and in particular than prior devices which rely on a sharpened or pointed cannula for entry into the target tissue. In addition, there is less deflection of the cannula assembly  102  when compared to prior devices since the distal electrode  122  easily separates different tissue that is adjacent to each other. For example, adjacent fatty, glandular, and lesion tissue would typically cause the prior devices to deflect as the device passes from one tissue to the next; however, the distal electrode  122  of the present invention easily separates adjacent varying tissue with the RF energized electrode  122 . 
     A method of operating the above-described apparatus for collecting tissue samples will now be described with reference to FIGS. 7-12. The region of the tissue from which the sample is to be drawn is located. The retractable electrodes  118  and  120  are then extended and energized with RF energy. The cannula assembly  102  is then positioned adjacent to the tissue region of interest. With the aid of ultrasound, palpation, MRI, stereotactic X-ray equipment or other imaging devices, the cannula assembly  102  is advanced through the body surface  160  and through the tissue  158  to the lesion  161 , as shown in FIGS. 7 and 8. The retractable electrodes  118  and  120  are then de-energized and retracted. As shown in FIG. 9, the distal electrode  122  is then energized with RF energy, which allows the cannula assembly  102  to be easily advanced into the tissue  158  to the target site  161 . The dilator  144  is pushed back by the tissue or is retracted from the cannula  116  while the cannula assembly  102  is advanced to create a vacuum in the cannula  116 . 
     As the cannula assembly  102  is advanced a tissue channel is created and a tissue sample  162  is captured in the tissue lumen  138  of the cannula  116 . Before the advancement of the cannula assembly  102  into the tissue, the optional vacuum source is activated to begin drawing tissue close to the tissue lumen  138 . If it is necessary to draw the tissue closer to the tissue lumen  138 , the vacuum source  108  can be adjusted to increase the negative pressure applied through tissue lumen  138 . As the vacuum source is applied to the tissue lumen  138 , the tissue sample  162  is drawn into the tissue lumen  138  of the cannula  116 , beginning with the proximal end thereof. At this point, the tissue sample  162  is still connected to the tissue mass. 
     When an adequate tissue sample  162  is located in the tissue lumen  138 , the cannula assembly  102  is stopped and the RF energy to the distal electrode  122  is turned off as well as the optional vacuum source  108 . The retractable electrodes  118  and  120  are then energized with RF energy and are extended. As shown in FIG. 10, the cannula assembly  102  is rotated approximately 180 to 270 degrees to separate the tissue sample  162  from the body of the patient. Preferably, the cannula assembly  102  is rotated approximately 180 to 225 degrees. More preferably, the cannula assembly  102  is rotated approximately 180 to 210 degrees. The retractable electrodes  118  and  120  are then de-energized. The cannula assembly  102  is then removed from the tissue  158  with the retractable electrodes  118  and  120  being fully extended to help secure the tissue sample  162  in the tissue lumen  138 . The retractable electrodes  118  and  120  are then retracted and the dilator  144  is advanced through the tissue lumen  138  to eject the tissue sample  162  from the cannula  116 . The tissue sample is then placed in a container. The retractable electrodes  118  and  120  are then extended and positioned for another biopsy if another tissue sample is required. If tissue sampling is complete, post-procedural bandaging is performed. 
     The process described above may be assisted by computer logic that may be implemented in controlling the vacuum source  108 , motor driver  112 , and RF generator  106  by a programmable logic controller (not illustrated), a general purpose digital computer in communication with a memory element containing computer readable instructions which embody the control logic (not illustrated), application specific integrated circuit (ASIC) (not illustrated), or discrete digital signal processing (DDSP) (not illustrated). 
     While the invention has been described in detail with reference to preferred embodiments thereof, it will be apparent to one skilled in the art that various changes can be made, and equivalents employed, without departing from the scope of the invention.