Adjustable tuning of a dielectrically loaded loop antenna

Abstract

A microwave antenna assembly is disclosed. The antenna assembly includes an elongated member defining a longitudinal axis and having proximal and distal ends. The antenna assembly also includes an outer conductor and an inner conductor each disposed within the elongated member and extending along the longitudinal axis. A portion of the inner conductor is deployable relative to the outer conductor such that the antenna assembly may transition from a first configuration to a second configuration. The antenna assembly also includes an expandable sheath at least partially disposed about a distal portion of the inner conductor and defining at one or more lumens configured to couple to a supply of dielectric material used to regulate the expansion of the expandable sheath.

1 - 19 . (canceled) 
     
     
         20 . A microwave antenna assembly comprising:
 a feedline including an inner conductor, an outer conductor, and an insulator disposed between the inner and outer conductors, the inner conductor configured to at least partially encircle target tissue; and   an expandable sheath defining a lumen configured to receive a dielectric material to expand the expandable sheath, at least a portion of the inner conductor disposed off-center within the lumen, the inner conductor in contact with a first portion of the expandable sheath and defining a dielectric gap between the inner conductor and a second portion of the expandable sheath, the dielectric gap configured to face the target tissue when the inner conductor at least partially encircles target tissue.   
     
     
         21 . The microwave antenna assembly according to  claim 20 , wherein the expandable sheath is disposed about a distal portion of the inner conductor. 
     
     
         22 . The microwave antenna assembly according to  claim 20 , wherein a distal end of the expandable sheath is disposed proximal to a distal end of the inner conductor. 
     
     
         23 . The microwave antenna assembly according to  claim 20 , wherein the expandable sheath is formed of a material selected from the group consisting of polytetrafluoroethylene and tetrafluorethylene-perfluorpropylene. 
     
     
         24 . A microwave ablation system, comprising:
 a microwave antenna assembly including:
 a feedline including an inner conductor, an outer conductor, and an insulator disposed between the inner and outer conductors; 
 an elongated member disposed about the feedline, the inner conductor configured to deploy from a distal end portion of the elongated member to at least partially encircle target tissue; and 
 an expandable sheath defining a lumen, the inner conductor disposed off-center within the lumen to define a dielectric gap between the inner conductor and the expandable sheath, the dielectric gap configured to face the target tissue when the inner conductor is deployed from the distal end portion of the elongated member; and 
   a fill source coupled to the lumen and configured to deliver dielectric material to the lumen.   
     
     
         25 . The microwave ablation system according to  claim 24 , wherein the fill source includes a pump configured to circulate the dielectric material through the lumen. 
     
     
         26 . The microwave ablation system according to  claim 24 , where at least a portion of the inner conductor is in contact with the expandable sheath. 
     
     
         27 . The microwave ablation system according to  claim 24 , wherein the expandable sheath is disposed about a distal portion of the inner conductor. 
     
     
         28 . The microwave ablation system according to  claim 24 , wherein a distal end of the expandable sheath is disposed proximal to a distal end of the inner conductor. 
     
     
         29 . The microwave ablation system according to  claim 24 , wherein the expandable sheath is formed of a material selected from the group consisting of polytetrafluoroethylene and tetrafluorethylene-perfluorpropylene. 
     
     
         30 . A method for performing microwave ablation, the method comprising:
 inserting a microwave antenna assembly into tissue, the microwave antenna assembly including an expandable sheath defining a lumen and an inner conductor disposed off-center within the lumen;   at least partially encircling target tissue with the inner conductor;   delivering a dielectric material to the lumen to expand the expandable sheath; and   energizing the microwave antenna assembly to ablate the at least partially encircled target tissue.   
     
     
         31 . A method according to  claim 30 , further comprising withdrawing the dielectric material from the lumen to contract the expandable sheath. 
     
     
         32 . The method according to  claim 30 , wherein delivering the dielectric material to the lumen creates a dielectric gap between the inner conductor and the expandable sheath.