Abstract:
A method and apparatus for reducing bleeding in biopsy procedures provides a cauterizing electrical current through an introducer needle as the needle is withdrawn. A majority of the length of the introducer needle may be insulated to concentrate the cauterization at its tip, and a field smoothing cauterizing stylet may be used in conjunction with the tube to provide more even cauterization and/or instrumentation to monitor cauterization. Cauterization may be controlled by the speed of withdrawal of the introducer needle as guided manually or automatically by the instrumentation.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to biopsy systems, and in particular, to a biopsy apparatus and method providing reduced bleeding after the biopsy needle is retracted.  
           [0002]    Biopsy is the removal of a small piece of tissue from the body in order to determine the presence of disease. A special biopsy needle may be used to penetrate the organ where the disease is suspected and to extract the tissue sample, which can then, for example, be examined under a microscope.  
           [0003]    Current biopsy procedures may employ a special biopsy needle having a laterally opening tray into which tissue will expand. Once the needle is in position within the tissue to be sampled, the physician releases a spring-loaded sheath, which slides over the tray cutting the tissue sample free and trapping the tissue sample inside the tray. The biopsy needle is withdrawn from the patient.  
           [0004]    When multiple biopsy samples are to be taken or when it is difficult to accurately locate the biopsy needle, a guide may be employed for the biopsy needle comprising a sharp rod (stylet) that is housed inside a hollow cylindrical tube (introducer needle). The introducer needle and stylet are inserted through the skin and into the organ of interest and then the stylet is removed from the introducer needle and replaced with the biopsy needle. The biopsy needle is longer than the introducer needle to extend outward therefrom allowing multiple samples to be taken.  
           [0005]    The primary risk associated with liver biopsy is bleeding after the removal of the needle from the patient. Although this occurs in less than 1% of the patients, complications due to this bleeding are severe and can lead to death. One method of reducing bleeding in biopsies is described in the article  Electrocautery of the Track after Needle Biopsy of the Liver to Reduce Blood Loss,  by Edwin H. Kim et al., published in Investigative Radiology, Vol. 28, No. 3, pgs. 28-230 (1993).  
           [0006]    According to this method, the outside of the biopsy needle is coated with a thin layer of electrical insulation except for the last two centimeters. A source of radio frequency electrical power is then connected to the biopsy needle as it is withdrawn from the body to provide an electrocauterization of the needle track.  
           [0007]    A significant drawback to this approach is the need to severely limit the power of the electrocauterizing source. The investigators noted that at higher cauterizing power, there was visible thermal damage to portions of the biopsy specimen. A significant question remains as to whether biopsy specimens using even lower power are not subtly altered by this process.  
           [0008]    A secondary risk of biopsies of cancerous tissue is the risk of the biopsy needle “seeding” cancer cells into other tissues and bloodstream as the needle is withdrawn.  
         BRIEF SUMMARY OF THE INVENTION  
         [0009]    The present invention allows the use of electrocauterization in biopsies without risk of thermal damage to the biopsy specimen. The invention thus allows the use of higher power to cauterize the track of the biopsy needle. Higher cauterizing power may provide the benefits of superior cauterization, faster procedures producing less discomfort to the patient, and has the potential of reduced risk of tumor seeding.  
           [0010]    Generally, the invention eliminates thermal damage to the biopsy specimen by using an introducer needle as the cauterizing tool. In this way, the biopsy needle and specimen can be fully withdrawn from the patient before cauterization is initiated. Higher cauterizing power promotes greater temperature gradients in the tissue, resulting in a sharper boundary between living and cauterized tissue. Insulating the needle allows the power to be concentrated at a relatively small (few millimeter) region at the end of the introducer needle. The smaller cauterizing region may reduce charred tissue adhering to the needle such as may further promote bleeding and hinder retraction of the introducer needle.  
           [0011]    The introducer needle may be more easily instrumented with thermocouples and the like, than the biopsy needle, to allow monitoring of the cauterizing process. The introducer needle may be further fitted with a cauterizing stylet particularly designed for cauterizing.  
           [0012]    Thus, it is one feature of the invention that it provides for electrocauterization of a biopsy needle track without risk of heat damage to the biopsy tissue.  
           [0013]    Another feature of the invention is that it reduces the contact area between the cauterizing probe and the tissue track. This may reduce the risk of adhesion of tissue to the cauterizing probe or tearing of tissue, and promotes higher cauterization power and greater current densities in the tissue that may produce improved and/or faster cauterization.  
           [0014]    Yet another feature of the invention is that it allows greater control of the cauterizing probe including shaping of the cauterization area to provide more uniform cauterization currents and instrumentation of the cauterization area with temperature probes and the like.  
           [0015]    In this respect, the invention better allows quantitative feedback with respect to the cauterization process to control the speed of withdrawal of the biopsy needle ensuring proper cauterization.  
           [0016]    The foregoing features and advantages may not apply to all embodiments of the inventions and are not intended to define the scope of the invention, for which purpose claims are provided.  
           [0017]    In the following description, reference is made to the accompanying drawings, which form a part of this application, and in which there is shown by way of illustration, a preferred embodiment of the invention. Such embodiment also does not define the scope of the invention and reference must be made therefore to the claims for this purpose.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]    [0018]FIG. 1 is a side elevational view of the introducer needle of the present invention showing an insulated section separating uninsulated distal and proximal ends of the needle, the former of which is connected to a cauterizing electrical source;  
         [0019]    [0019]FIG. 2 is a fragmentary cross sectional view of the proximal end of the needle of FIG. 1 when fitted with an introducer stylet for insertion into the patient;  
         [0020]    [0020]FIG. 3 is a figure similar to that of FIG. 2 showing the introduction of a biopsy needle into the introducer needle of FIG. 1 after removal of the introducer stylet and with the tray of the biopsy needle open for receiving biopsy specimens;  
         [0021]    [0021]FIG. 4 is a figure similar to that of FIG. 4 showing extension of a biopsy needle sheath to cut and trap tissue within the tray of the biopsy needle;  
         [0022]    [0022]FIG. 5 is a figure similar to that of FIG. 2 showing the introducer needle of FIG. 1 after the biopsy needle and introducer stylet are removed, during withdrawal of the introducer needle as cauterizing electrical power is applied;  
         [0023]    [0023]FIG. 6 is a figure similar to that of FIG. 5 showing an alternative embodiment of the invention in which the cauterizing electrical power is applied through a specially shaped cauterizing stylet inserted into the introducer needle and showing two alternative locations of thermocouple placement;  
         [0024]    [0024]FIG. 7 is a schematic representation of the introducer needle after insertion into the patient as connected to an external cauterizing power supply and monitoring equipment;  
         [0025]    [0025]FIG. 8 is a fragmentary perspective view of the distal end of the introducer needle of FIG. 1 showing an alternative embodiment having a combination power clamp and display, the latter providing guidance for how fast to withdraw the introducer needle; and  
         [0026]    [0026]FIG. 9 is a simplified schematic diagram of a mechanism to provide for automated withdrawal of the introducer needle using feedback signals obtained from the introducer needle during the cauterization.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0027]    Referring now to FIG. 1, the biopsy system  10  of the present invention includes an introducer needle  12  comprised of a tube  14  of an electrically conductive biocompatible metal, for example, stainless steel. In an example embodiment, the tube  14  may have an outer diameter of approximately 1.2 mm. and be 15 centimeters in length. Introducer needles having tubes  14  of this type are well known in the art and commercially available from a number of sources.  
         [0028]    The introducer needle  12  of the present invention differs from those that are commercially available by the application of an outer electrically insulating coating  30  that produces a circumferentially continuous insulated section  18  extending along the tube  14  less than the fall length of the tube  14  so as to expose a proximal end  20  of the tube  14  and a distal end  22  of the tube  14 . The exposed portion of the proximal end  20  in a preferred embodiment extends 4 mm.  
         [0029]    The insulated section  18  may comprise any biocompatible insulator, however, the present invention uses a layer of Parylene C vapor deposited to a thickness of approximately 0.001 inches. Parylene C is commercially available from the Vitek Research Corporation of Derby, Connecticut and has a lubricity approaching that of Teflon to present a coefficient of friction approximately equal to 0.29. Other insulating materials may also be used.  
         [0030]    The distal end  22  of the tube  14  is partially received by a handle  24  that may be grasped during insertion or removal of the introducer needle  12  into or out of the patient. The handle  24  is of electrically insulating material such as a moldable thermoplastic. An exposed portion of the distal end  22  before the handle  24  may accept an electrical clamp  26  to conduct radio frequency electrical power through the tube  14  beneath the insulating section  18  to the proximal end  20  as will be described.  
         [0031]    Printed on or visible through the insulated section  18  are graduation marks  28  allowing the physician to determine the insertion depth of the introducer needle  12 . A proximal zone  31  of distinct marking or color preceding the proximal end  20  is provided to indicate to the physician that the proximal end  20  is about to pass out of the patient so that the radio frequency electrical power may be turned off.  
         [0032]    Referring now to FIG. 2, before the biopsy, a rod-shaped stylet  32  is fit snugly within the bore of the tube  14  having a sharpened end protruding from the proximal end  20  of the tube  14  to ease the insertion of the introducer needle  12  into the body tissue  34 . The proximal end  20  of the introducer needle  12  is positioned within tissue  34  near the site where a biopsy will be taken using ultrasound or radiographic imaging.  
         [0033]    Referring to FIG. 3, after the introducer needle  12  is correctly positioned, the stylet  32  of FIG. 2 is removed and replaced with a biopsy needle  35  providing a central shaft  36  and an outer concentric tubular sheath  38  drawn back from the proximal end to expose a laterally opening tray  40  in the shaft  36 . The proximal end of the central shaft  36  of the biopsy needle  35  is sharpened like the stylet  32  allowing the biopsy needle  35  to extend easily beyond the proximal end  20  of the tube  14  so that tissue  34  may enter the tray  40 . Biopsy needles suitable for use with the present invention are commercially available from a number of sources including Cook Urological of Spenser, Ind., and C. R. Bard, Inc. of Covington, Ga.  
         [0034]    Referring now to FIG. 4, once the central shaft  36  of the biopsy needle  35  is in place, the sheath  38  may be driven forward by a spring mechanism over the tissue  42  within the tray  40  to sever the tissue  42  from the remaining tissue  34  and hold it within the tray  40 .  
         [0035]    Referring now to FIG. 5, the biopsy needle  35  is now withdrawn and the biopsy tissue  42  removed. The biopsy needle  35  may be reinserted into the introducer needle  12  and additional biopsy samples taken. Upon conclusion of the sampling as shown in FIG. 5, the biopsy needle  35  is removed leaving only the introducer needle  12 .  
         [0036]    Referring now to FIGS. 1, 5 and  7 , at this time, the clamp  26  shown in FIG. 1 may be attached to the distal end  22  of the introducer tube to provide, via a power lead  46 , a connection to a radio frequency electrical power source  50 . This power source may be a standard cauterizing electrical generator such as the RITA Model 1500 RF Generator available from Rita Medical Systems, Inc. of Mountain View, Calif. whose specifications include an adjustable power of from 0 to 150 watts at a frequency of 460 kHz. A return lead  52  of the power source  50  is connected to a large area conducted pad  55  of a type well known in the art to allow for complete circuit through the patient without the concentration of current flow that would produce cauterization temperatures occurring anywhere except at the introducer needle  12 .  
         [0037]    Referring still to FIG. 5, as cauterizing electrical power is applied to the tube  14 , it is transferred to the tissue  34  through the exposed conductive surface of the proximal end  20  of the tube  14 . For a moment after connection of the cauterizing electrical power to the introducer needle  12 , the introducer needle is held in place to allow the adjacent tissue  34  to rise to cauterizing temperatures. Then the introducer needle  12  is withdrawn, producing a cauterization region  54  along the biopsy track  56 . In the preferred embodiment, a wattage setting of between 100 and 150 watts may be used. While the Applicants do not wish to be bound by a particular theory, it is believed that higher wattages focused in the limited area of the proximal end  20  produce higher current densities and greater temperature gradients resulting in a sharper boundary between the cauterization region  54  and living tissue  34 .  
         [0038]    Referring now to FIG. 6, in an alternative embodiment, an electrically conductive cauterizing stylet  58  may be introduced into the introducer needle  12  before the cauterization procedure. The cauterizing stylet  58  may be connected directly to the cauterizing power source in lieu of a connection to the distal end  22  of the tube  14 , or may receive electrical power through its intimate contact with the interior conductive portion of the tube  14 . In an alternative embodiment, the insulation of the tube  14  may be eliminated or supplemented with an insulating outer coating  63  positioned between the tube  14  and the cauterizing stylet  58 .  
         [0039]    The proximal end of the cauterizing stylet  58  is rounded to provide more even field lines than those produced by the sharp edges of the tube  14 , limiting hot spots that may lead to uneven cauterization or burning.  
         [0040]    The cauterizing stylet  58  may include an internal thermocouple  60  so as to allow monitoring of the temperature at the cauterizing region with instrumentation leads  61  passing through a central bore of the cauterizing stylet  58 . Alternatively, a thermocouple  62  may be placed directly on the proximal end  20  of the introducer needle  12  to measure temperature at this location, with instrumentation leads  61  passing between the insulating material  30  and the outer wall of tube  14 . In yet a further embodiment, a thermocouple is placed down the middle of the introducer needle  12  without the cauterizing stylet  58 . A suitable thermocouple is the Endocare CRYOcare™ thermocouple commercially available from Endocare, Inc. of Irvine, Calif.  
         [0041]    Referring again to FIG. 7, the thermocouple  60  or  62  may communicate via instrumentation leads  61  to instrument readout  64  providing, for example, an LCD display of the cauterizing temperature or a synthesized voice temperature readout. Ideally, the temperature will be monitored to be within 65 to 80 degrees Celsius. Alternatively, the read out may indicate a desired speed of retraction of the introducer needle  12  based on these temperature ranges. As mentioned above, the present inventors have determined that before withdrawal of the introducer needle  12 , a cauterizing holding time should be observed until the temperature rises to within this range. At that time, the introducer needle  12  is retracted at a speed adjusted to maintain a cauterizing temperature within this range. In an alternative embodiment, power dissipation or electrical resistance may be measured to guide in the cauterization process.  
         [0042]    Referring now to FIG. 8, in order to provide the attending physician with guidance as to the retraction speed of the introducer needle  12 , the instrument readout  64  may be moved to the distal end  22  of the introducer needle  12  to provide a display thereupon. For example, the display may provide for three light emitting diodes (LEDs)  66  of different colors: a red LED lighting to indicate a temperature below 65 Celsius, a yellow LED to indicate a temperature between 65 and 80 degrees Celsius and a green LED indicating a temperature above 80 degrees Celsius. The colors also indicating generally to the physician how speed of retraction of the introducer needle  12  should be adjusted with red indicating a slowing or stopping of the retraction; green indicating a speeding or starting of the retraction; and yellow indicating that the proper retraction speed has been obtained.  
         [0043]    The instrument readout  64  may also provide the connection between the power lead  46  and the tube  14  (not visible in FIG. 8), replacing electrical clamp  26  shown in FIG. 1. A unified cable  68  may be provided carrying both the power lead  46  of FIG. 7 and the instrumentation leads  61  to the radio frequency electrical power source  50  and instrument readout circuitry driving the LEDs  66  according to techniques well known in the art.  
         [0044]    Referring now to FIG. 9, the ability to monitor the temperature or other properties of the cauterization region  54  raises the possibility of automatic retraction of the introducer needle  12  during the cauterization procedure using an automated retracting device  70 . In one embodiment of such a device, the retracting device  70  may include a collet  72  receiving the handle  24  of the introducer needle  12 . The collet may attach to a motor driven retracting rack  74  controlled by motor  76  such as a DC servo or stepper motor. Thermocouple signals through instrumentation leads  61  may be provided to a servo amplifier  78  operating through well known techniques to receive a reference temperature  80  to provide a control signal  82  to the motor adjusting its speed according to the thermocouple measurement. In this case, low temperatures cause a slowing of the motor; higher temperatures cause a speeding or stopping of the motor.  
         [0045]    The motor  76  may also provide a position output signal  84  to be received by a comparator  86  detecting, by means of a reference voltage  88 , that the proximal end  20  of the introducer needle  12  is about to pass out of the skin and providing a disable signal  88  to the power source  50  to stop power at this time. This corresponds to the physician ceasing radio frequency electrical power when the proximal zone  31  shown in FIG. 1 of the introducer needle  12  is exposed. In practice, the retracting device  70  might be attached to the handle  24  only upon completion of the biopsy for automated withdrawal of the retracting.  
         [0046]    Preliminary use of this device indicates that an average time of withdrawal from 10 to 15 seconds provides an even cauterization.  
         [0047]    It is specifically intended that the present invention not be limited to the embodiments and illustrations contained herein, but that modified forms of those embodiments including portions of the embodiments and combinations of elements of different embodiments also be included as come within the scope of the following claims.