Abstract:
Disclosed is a method and an apparatus for ablating biological tissues, in which a cannula is configured to affect biological tissue and a heat transmitting end-effecter is coupled to the cannula. A source of electromagnetic energy is provided via an electro-magnetic energy emitter and a wall of the heat transmitting end-effecter is made of an electromagnetic-energy-absorbing material that absorbs electromagnetic waves.

Description:
PRIORITY 
       [0001]    This application claims priority to U.S. patent application Ser. NoS. 61/020,194, filed with the U.S. Patent and Trademark Office Jan. 10, 2008, and 61/143,623, filed with the U.S. Patent and Trademark Office Jan. 9, 2009, the disclosure of each of which is incorporated herein by reference. 
     
    
     BACKGROUND OF INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates to an electromagnetic energy based apparatus for thermal treatment of biological tissues. 
         [0004]    2. Description of the Related Art 
         [0005]    Conventional devices utilize electromagnetic energy to thermally treat biological tissue. For example, see, e.g. U.S. Pat. Nos. 6,325,796, 6,836,688, 5,697,925, 5,800,493, 5,653,692, 6,443,947, 4,869,248, 5,571,088, 5,474,530 and 5,575,772, the contents of which are incorporated herein by reference. Conventional devices apply electromagnetic energy in microwave or radio frequency range directly to the treated tissue. However, such devices do not allow for fully limiting of the depth of energy penetration into a tissue. As a result, a layer of healthy tissue located behind the treated tissue may be negatively affected. Moreover, these devices do not allow direct control of the temperature in the treated area, and, as a result, the temperature may be higher than required by the procedure and, thus damaging the tissue, or lower than required by the procedure and, thus making the procedure ineffective. 
         [0006]    It is, therefore, desirable to provide an apparatus for thermally treating a biological tissue that allows for a relatively brief treatment in a safe and target-oriented manner. 
       SUMMARY OF THE INVENTION 
       [0007]    An aspect of the present invention addresses at least the problems and/or disadvantages and provides at least the advantages described below. Accordingly, an aspect of the present invention is to provide a method and apparatus powered by an electromagnetic energy source to transmit energy, which is then transformed into heat energy that thermally treats a biological tissue, to minimize a period of time necessary to reach a desired temperature. 
         [0008]    The present invention also provides an apparatus for thermally treating a biological tissue that has a heat transmitting end-effecter configured with selective electromagnetically-energy-absorbing areas to target diseased tissues while minimizing heat exposure of healthy tissues. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The above and other features and advantages of exemplary embodiments of the present invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which: 
           [0010]      FIG. 1  is a view of a thermal treatment apparatus in accordance with a preferred embodiment of the invention; 
           [0011]      FIG. 2  is a close-up view of an end-effecter of the thermal treatment apparatus of  FIG. 1 ; 
           [0012]      FIG. 3  through  FIG. 7  are cross-sectional views along line A-A on  FIG. 2  of different embodiments of the end-effecter; and 
           [0013]      FIG. 8  is a schematic view of power supply and control systems. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0014]    Reference will now be made in detail to several views of the invention that are illustrated in the accompanying drawings. Wherever possible, same or similar reference numerals are used in the drawings and the description to refer to the same or like parts or steps. The drawings are in simplified form and are not to precise scale. For purposes of convenience and clarity, directional terms, such as rear and front may be used with respect to the drawings. These and similar directional terms should not be construed to limit the scope of the invention in any manner. The term “microwave frequency range” refers herein to frequencies between 30 MHz and 30,000 MHz inclusive, where MHz is one million Hertz, and the term “radio-frequency range” refers herein to frequencies between 30 kHz and 30 MHz, where kHz is one thousand Hertz. Although the following description operates via a microwave energy emitter, the present invention is operable by various electromagnetic energy sources and is not limited to microwave energy. 
         [0015]      FIG. 1  provides an overall view of an electromagnetic apparatus for ablation configured in accordance with a preferred embodiment of the invention and operative to perform a thermal treatment of biological tissues. As shown in  FIG. 1 , cannula  10  includes a heat transmitting end-effecter  12 . An electromagnetic generator  106  is coupled to an antenna  24  located within heat transmitting end-effecter  12  via conductive elements or wires  14 . In a preferred embodiment, generator  106  is an oscillator that provides a sinusoidal voltage signal. Oscillator  106  is preferably a microwave or radio frequency oscillator. 
         [0016]    As shown in  FIGS. 1 and 3 , the temperature of the end-effecter  12  is monitored by a control unit  104  through cable  16  connected to a temperature sensor  17 . When excited, antenna  24  emits energy waves that are selectively absorbed by the wall of heat transmitting end-effecter  12 , causing the wave absorbing wall regions to heat. In a preferred embodiment in which the energy is transmitted through a layer of air, as shown on  FIG. 4  though  FIG. 6 , oscillator  106  provides for rapid heating of the wave absorbing regions of heat transmitting end-effecter  12 , effectively heating diseased tissue in a time-effective, safe operation. 
         [0017]    Referring to  FIG. 2  through  FIG. 7 , the wires  14  are coupled to a wall element  26  and antenna  24 . Wall element  26  is constructed as an outer coaxial cable conductor, preferably coated or covered by electrical and heat insulators such as nylon, polypropylene or Teflon®. The antenna  24  and wall element  26  are electrically isolated relative to one another by an insulator  32 . In certain preferred embodiments, wall element  26 , insulator  32 , and antenna  24  may be a coaxial cable having an inner conductor thereof extended beyond the wall element  26  and insulator  32 . 
         [0018]    The antenna  24  is located within a heat transmitting outer shell  28 . The antenna  24  propagates energy waves within heat transmitting end-effecter  12 . For certain medical procedures, such as where the end-effecter is inserted into a blood vessel and forced to follow the path of the blood vessel to a treatment area, outer shell  28  is preferably constructed of substantially flexible material. In alternative embodiments utilized for medical procedures in which the end-effecter is directly inserted in the treated tissue, outer shell  28  is constructed from a substantially rigid material. 
         [0019]    In a preferred embodiment, the material of the outer shell  28  is substantially flexible, silicone impregnated with silver (Ag) and glass fillers, which are generally unaffected by exposure to temperatures reaching 500° F. Glass fillers can be regular glass in form of small beads and other fillers include nickel (Ni), cupper (Cu), Aluminum (Al), which can each be used as a single filler or combined with other materials, for example combinations of Ag/Cu; Ag/Al; Ag/Ni; Ag/Glass. Silicone is a preferred material due to compatibility to the human body, and other materials that can be used include fluorosilicone, fluorocarbon, thermoplastic rubber and ethyline propylene diene monomer. When used for a substantially rigid outer shell, thermoplastic materials, such as rigid urethane impregnated with polyamide and thermoplastic urethane impregnated with carbonyl iron powder, iron silicide and ferrites fillers are utilized, in view of advantageous microwave absorbing properties. 
         [0020]    In a preferred embodiment, heated regions on the wall of the outer shell  28  are provided by filling the regions with electromagnetic energy absorption particles, wherein the particles include nickel, nickel-plated graphite, silver-plated aluminum, silver-plated copper, silver-plated nickel, silver-plated glass and pure silver. 
         [0021]    In the embodiments shown in  FIG. 3  through  FIG. 7  the particles are distributed over the entire wall of the outer shell  28 . Thus, electromagnetic waves emitted by antenna  24  propagating through the layer of air, as shown in  FIG. 4  through  FIG. 6 , or the layer of isolating material as shown by the embodiment presented on  FIG. 3 , or directly to the walls of the outer shell  28 , as shown by the embodiment presented on  FIG. 7 . When impinging upon the particles, electromagnetic energy is transferred into heat energy manifested at the particles. In  FIG. 5 , a biologically inert insulator  34  forms a cap on the end of heat-transmitting end-effecter  12 . 
         [0022]    In another preferred embodiment, the wave-absorption particles may be coated on a surface of outer shell  28 , which is made out a regular elastomer such as silicone. The wave-absorption particles in one embodiment cover the entire surface of outer shell  28  and in other embodiments are coated in a pattern. Preferable coating patterns include longitudinal stripes, latitudinal stripes, mesh and series of dots, with the distance between the stripes or dots preferably arranged to place the dots at a distance smaller that a length of the wave emitted by the antenna, to preclude wave energy escaping from the endeffecter. Dots are a preferred embodiment for maintaining flexibility, with an aperture between dots being sized smaller than the emitted wavelength. 
         [0023]    As shown, the outer shell  28  can be formed into various shapes and dimensioned to address specific needs of any given anatomical site or patient. Selective shaping provides a further benefit of reducing the impact of reflection. 
         [0024]    Referring to  FIGS. 1 and 8 , the operation of the apparatus is described in treating a patient. The electromagnetic generator  106  excites antenna  24  through wires  14 . The antenna  24  produces waves in a pre-selected range of frequencies that are absorbed by the electromagnetic energy absorption particles of the elastomeric material in the heat transmitting outer shell  28 . The electromagnetic energy absorbed by the electromagnetic energy absorption particles is transformed into heat energy, which thermally treats the tissue by exposure to elevated temperature. 
         [0025]    The temperature elevation sufficient to cause the required thermal effect is provided via electromagnetic energy from the electromagnetic generator, preferably absorbed by the electromagnetic energy-absorption particles of the conductive elastomeric material. Generally, the level of the generated electromagnetic energy is selected to reach the maximum ablation temperature in a shortest period of time, in order to reduce treatment time and minimize undesirable heat transfer to neighboring healthy tissue. See, e.g., patent application Ser. No. 11/603,866 filed Nov. 24, 2006, and U.S. Pat. Nos. 5,843,144, 5,902,251, 6,041,260, 6,366,818 and 6,447,505, the contents of each of which is incorporated by reference herein. As shown in  FIG. 3 , temperature sensor  17  is coupled to controller  104  and is utilized to monitor the temperature of the heat transmitting end-effecter periphery. Controller  104  controls power source  106  to maintain the desired temperature. 
         [0026]    While the invention has been shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention, as defined by the following claims.