Tunable microwave ablation probe

Abstract

An electromagnetic surgical ablation probe having a tunable helical antenna element includes a coaxial feedline having an inner conductor coaxially disposed within a dielectric, and an outer conductor coaxially disposed around the dielectric. The inner conductor and dielectric extend distally beyond a distal end of the outer conductor. A helical antenna element is operably coupled to a distal end of the inner conductor. During use, the antenna may be tuned by changing at least one dimension of the helical antenna element. Embodiments are presented wherein a dimension of the helical antenna element is changed by state change of a shape memory alloy, by a change in temperature, by activation of a piston by fluidic pressure, by linear motion of a conical tip, and by a manual screw-type adjustment.

1 .- 19 . (canceled) 
     
     
         20 . A method for tuning an ablation probe, the method comprising:
 applying microwave energy through an ablation probe, the ablation probe including an inner conductor and an outer conductor;   adjusting a dimension of a helical antenna, the helical antenna having a distal end coupled to a distal end portion of the inner conductor; and   tuning the ablation probe during application of the microwave energy to match a change in tissue impedance.   
     
     
         21 . The method according to  claim 20 , wherein adjusting the dimension of the helical antenna includes moving at least a portion of the helical antenna longitudinally relative to the inner conductor. 
     
     
         22 . The method according to  claim 20 , wherein the dimension of the helical antenna that is adjusted is selected from the group consisting of a diameter of the helical antenna, a length of the helical antenna, a pitch of the helical antenna, and a distance between coils of the helical antenna. 
     
     
         23 . The method according to  claim 20 , further comprising:
 adjusting a helical antenna temperature of the helical antenna to adjust the dimension of the helical antenna.   
     
     
         24 . The method according to  claim 23 , wherein adjusting the helical antenna temperature includes heating the helical antenna, and the helical antenna is formed from a shape memory alloy. 
     
     
         25 . The method according to  claim 24 , wherein heating the helical antenna includes transitioning the helical antenna from a martensite configuration to an austenite configuration. 
     
     
         26 . The method according to  claim 25 , wherein heating the helical antenna decreases a diameter of the helical antenna. 
     
     
         27 . The method according to  claim 25 , wherein heating the helical antenna increases a length of the helical antenna. 
     
     
         28 . The method according to  claim 23 , wherein adjusting the helical antenna temperature of the helical antenna includes supplying a fluid having a fluid temperature different from the helical antenna temperature to adjust the dimension of the helical antenna. 
     
     
         29 . The method according to  claim 28 , wherein the fluid is supplied into a fluid chamber disposed within the ablation probe, the fluid chamber being adjacent the helical antenna. 
     
     
         30 . The method according to  claim 20 , wherein adjusting the dimension of the helical antenna includes moving a piston in a longitudinal direction, the piston being slidably disposed within the ablation probe and coupled to the helical antenna. 
     
     
         31 . The method according to  claim 20 , wherein adjusting the dimension of the helical antenna includes moving an adjustment collar in a longitudinal direction, the adjustment collar being coaxially disposed over the outer conductor and coupled to the helical antenna. 
     
     
         32 . A method for tuning an ablation probe, the method comprising:
 applying microwave energy through an ablation probe, the ablation probe including an inner conductor, an outer conductor, a fluid chamber, and a helical antenna formed from a memory alloy, the helical antenna having a distal end coupled to a distal end portion of the inner conductor;   supplying a fluid into the fluid chamber, the fluid chamber having a fluid temperature that is different from an antenna temperature of the helical antenna,   adjusting a dimension of the helical antenna; and   tuning the ablation probe during application of the microwave energy to match a change in tissue impedance.   
     
     
         33 . The method according to  claim 32 , wherein supplying the fluid include circulating the fluid through the fluid chamber coupled to an inflow conduit and an outflow conduit. 
     
     
         34 . The method according to  claim 32 , wherein supplying the fluid includes supplying at least one of water or saline. 
     
     
         35 . The method according to  claim 32 , wherein supplying the fluid is based on a surgical parameter selected from the group consisting of tissue temperature and tissue impedance.