Dynamically matched microwave antenna for tissue ablation

Abstract

A microwave ablation probe for providing microwave energy to tissue includes a feedline having an inner conductor, a secondary inner conductor, and insulating spacer, and an outer conductor. The inner conductor is slidably disposed within the secondary inner conductor. The feedline also includes a radiating portion having an extruded portion of the inner conductor centrally disposed therein, wherein longitudinal movement of the inner conductor relative to the feedline tunes the radiating portion.

1 . (canceled) 
     
     
         2 . A microwave ablation system, comprising:
 a microwave generator configured to generate microwave energy; and   a probe coupled to the microwave generator, the probe including:
 a feedline including an inner conductor, an outer conductor, and an insulating spacer disposed between the inner and outer conductors, the inner conductor including a tubular conductor and a slidable conductor disposed within the tubular conductor, the slidable conductor being longitudinally movable relative to the tubular conductor while maintaining electro-mechanical contact with the tubular conductor during use; and 
 a radiating portion coupled to the feedline and including at least a portion of the slidable conductor disposed therein. 
   
     
     
         3 . The microwave ablation system according to  claim 2 , further comprising:
 a choke disposed around at least a portion of the feedline and configured to confine the microwave energy to the radiating portion.   
     
     
         4 . The microwave ablation system according to  claim 3 , wherein the choke includes a conductive housing having a chamber configured to store a cooling dielectric liquid. 
     
     
         5 . The microwave ablation system according to  claim 4 , wherein the choke includes at least one inlet tube and at least one outlet tube configured to supply the cooling dielectric liquid into the chamber. 
     
     
         6 . The microwave ablation system according to  claim 4 , wherein the choke includes a seal member slidably disposed within the chamber, such that when the cooling dielectric liquid is supplied thereto the seal member is moved in the distal direction. 
     
     
         7 . The microwave ablation probe according to  claim 4 , wherein the cooling dielectric liquid is selected from the group consisting of water and saline solution. 
     
     
         8 . The microwave ablation probe according to  claim 2 , further including a tapered tip disposed at a distal end of the radiating portion. 
     
     
         9 . A microwave ablation system, comprising:
 a microwave generator configured to generate microwave energy; and   a feedline including an inner conductor and an outer conductor, and an insulating spacer disposed between the inner and outer conductors, the inner conductor including a tubular conductor and a slidable conductor disposed within the tubular conductor, the slidable conductor being longitudinally movable relative to the tubular conductor while maintaining electro-mechanical contact with the tubular conductor during use;   a radiating portion coupled to the feedline and including at least a portion of the slidable conductor disposed therein; and   at least one loading including a direct current (DC) electric field-dependent dielectric material, wherein at least one dielectric property of the DC electric field-dependent dielectric material varies in response to a DC electric field supplied thereto.   
     
     
         10 . The microwave ablation system according to  claim 9 , further including:
 a tapered tip disposed at a distal end of the radiating portion.   
     
     
         11 . The microwave ablation system according to  claim 9 , wherein the DC electric field-dependent dielectric material is a ferroelectric material selected from the group consisting of lead zirconate, lead titanate and barium titanate. 
     
     
         12 . The microwave ablation system according to  claim 9 , further comprising:
 an internal loading disposed at a distal portion of the feedline; and   an external loading disposed at a distal portion of the inner conductor.   
     
     
         13 . The microwave ablation system according to  claim 12 , wherein the internal loading is a dynamic quarter-wave transformer. 
     
     
         14 . The microwave ablation system according to  claim 12 , wherein the internal loading is of first polarity and the external loading is of second polarity. 
     
     
         15 . A method of performing surgery, comprising:
 advancing a microwave ablation probe into target tissue, the microwave ablation probe including a feedline having an inner conductor, an outer conductor, and an insulating spacer disposed between the inner and outer conductors;   sliding a slidable conductor of the inner conductor relative to a tubular conductor of the inner conductor to tune the inner conductor to a desired operational frequency,   wherein the inner conductor maintains electromechanical contact with the tubular conductor during use; and   emitting microwave energy from a radiating portion of the microwave ablation probe to treat tissue, the radiating portion including at least a portion of the inner conductor disposed therein.   
     
     
         16 . The method according to  claim 15 , further including supplying cooling dielectric liquid into a chamber defined within a conductive housing of a choke disposed over at least a portion of the feedline. 
     
     
         17 . The method according to  claim 16 , further including moving a seal member slidably disposed within the chamber when the cooling dielectric liquid is supplied thereto. 
     
     
         18 . The method according to  claim 15 , wherein advancing a microwave ablation probe into target tissue includes advancing a tapered distal tip disposed at a distal end of the radiating portion into target tissue. 
     
     
         19 . The method according to  claim 15 , further including sliding a choke disposed over at least a portion of the feedline to adjust the length of the radiating portion. 
     
     
         20 . The method according to  claim 19 , further including sliding the choke and the inner conductor relative to the tubular conductor.