Microwave applicator

Abstract

A microwave applicator comprising a coaxial electrical input ( 4 ) and a waveguide ( 1 ) filled with dielectric ( 2 ), an inner conductor ( 7 ) of the coaxial input extending longitudinally within one end of the waveguide to launch microwaves in the TM 01 mode to travel to the distal end face ( 8 ) of the waveguide so that microwaves are transmitted when the distal end face is contacted by the biological tissue to be treated.

1 . A microwave applicator comprising a coaxial electrical input ( 4 ) and a waveguide ( 1 ) filled with dielectric ( 2 ), an inner conductor ( 7 ) of the coaxial input ( 4 ) extending longitudinally within one end of the waveguide ( 1 ) to launch microwaves mode to travel to the distal end face ( 8 ) of the waveguide ( 1 ) so that microwaves are transmitted when the distal end face ( 8 ) is contacted by biological tissue to be treated.  
     
     
         2 . A microwave applicator as claimed in  claim 1  in which the inner conductor ( 7 ) is axially aligned with the waveguide ( 1 ).  
     
     
         3 . A microwave applicator as claimed in  claim 1  or  2  in which the waveguide ( 1 ) is a circular waveguide.  
     
     
         4 . A microwave applicator as claimed in any one of the preceding claims in which the distal end face ( 8 ) is substantially flat and normal to the axis of the waveguide ( 1 ).  
     
     
         5 . A microwave applicator as claimed in any one of  claims 1  to  3  in which the distal end face ( 8 ) is flat or slightly domed and centred on the axis of the waveguide ( 1 ).  
     
     
         6 . A microwave applicator as claimed in any one of the preceding claims in which the distal end face ( 8 ) has a polymer coating ( 22 ).  
     
     
         7 . A microwave applicator as claimed in any one of the preceding claims in which the length and diameter of the waveguide ( 1 ), the length of the inner conductor ( 7 ) within the waveguide, and the permittivity of the dielectric material ( 2 ) are selected so that at the designed operating frequency, the waveguide is in resonance.  
     
     
         8 . A microwave applicator as claimed in any one of the preceding claims in which the waveguide ( 1 ) is adapted so that in operation, when the distal end face ( 8 ) is in contact with biological tissue to be treated, forwards transmission from the distal end face is enhanced by the relative phase of reflections from the distal end face ( 8 ) and the input ( 4 ) to the waveguide; and when the distal end face ( 8 ) is in air or gas, reflections to the input ( 4 ) are enhanced by the relative phase of reflections from the distal end face ( 8 ) and the input ( 4 ) to the waveguide.  
     
     
         9 . A microwave applicator comprising a waveguide ( 1 ), a coaxial electrical input ( 4 ) with an inner conductor ( 7 ) extending longitudinally within one end of the waveguide to launch microwaves in the TM 01  mode that travel to the distal end ( 8 ) of the waveguide and are transmitted into biological tissue to be treated, a diaphragm ( 20 ) of low loss dielectric material being provided within the waveguide ( 1 ) so as to extend laterally of the waveguide to reflect the microwaves travelling along it, the longitudinal location of the diaphragm ( 20 ) being selected in relation to the ends of the waveguide ( 1 ) so that the phase of reflections from the diaphragm ( 20 ) and said ends serve to reduce or cancel rearward reflections in the coaxial input ( 4 ).  
     
     
         10 . A microwave applicator as claimed in  claim 9  in which the thickness of the diaphragm ( 20 ), and the permittivity of the dielectric material from which it is made are selected to determine the magnitude of the rearward reflection of microwaves from the diaphragm ( 20 ) for optimum cancellation of the rearward reflection in the coaxial input.  
     
     
         11 . A microwave applicator as claimed in  claim 9  or  10  which is air-filled.  
     
     
         12 . A microwave applicator as claimed in any one of the preceding claims in which the waveguide launches microwaves in the TM 01  mode.  
     
     
         13 . A method of heat treating surface tissue using the microwave applicator of any one of  claims 1  to  12  in which the end face ( 8 ) of the waveguide ( 1 ) is brought into contact with the surface tissue.  
     
     
         14 . A method as claimed in  claim 13  in which the surface tissue is internal tissue and the applicator is inserted into a body for treatment.  
     
     
         15 . A method as claimed in  claim 14  in which the insertion of the applicator is via a Trocar.  
     
     
         16 . A method as claimed in  claim 13  in which the surface tissue is the external skin of the body.  
     
     
         17 . A method of treating a liver in a body comprising providing a microwave applicator having a treatment head at one end capable of emitting microwave radiation from an emitting face, inserting the microwave applicator through an incision into the body positioning the head of the microwave applicator in contact with a surface of the liver with the emitting face adjacent to a region to be treated, and powering the microwave applicator so that the emitting face emits microwave radiation that heats said region to be treated.  
     
     
         18 . A method of treating biological tissue to stop bleeding comprising providing a microwave applicator having a treatment head at one end capable of emitting microwave radiation from an emitting face, positioning the head of the microwave applicator in contact with a surface of the biological tissue to be treated with the emitting face adjacent to bleeding tissue to be treated, and powering the microwave applicator so that the emitting face emits radiation that heats the bleeding tissue to be treated.  
     
     
         19 . A method of treating a skin condition such as psoriasis using a microwave applicator having a microwave emitting window which is brought into contact with, or into close proximity of, skin to be treated and is powered so as to emit microwave radiation and irradiate the skin to be treated.