Wide band microwave tissue ablation probe with variable length antenna parameters

Abstract

A variable-length microwave ablation probe is provided. The probe is configured to have a range of resonant frequencies. The probe includes a microwave antenna, an outer conductor, and a cap. The probe further includes a radiation window that is at least partially transparent to microwave energy. The distal boundary of the outer conductor or the proximal boundary of the cap varies in distance from the probe distal end. The probe can have a choke length, an arm length, a radiating portion length, and a cap length. The lengths can each affect the resonant frequency of the antenna. Some examples provide a variable choke length, a variable arm length, a variable radiating portion length, and/or a variable cap length.

1 - 20 . (canceled) 
     
     
         21 . A microwave ablation probe comprising:
 a probe body comprising a shielded portion and a radiation window that is at least partially transparent to microwave energy;   a coaxial cable within the probe body comprising a radiating portion configured for emission of microwave energy, wherein the radiating portion is aligned with the radiation window, the radiating portion comprising:
 a first section having a first length, the first section configured for emission of the microwave energy at a first resonant frequency; and 
 a second section having a second length, the second section configured for emission of the microwave energy at a second resonant frequency that is different from the first resonant frequency. 
   
     
     
         22 . The probe of  claim 21 , wherein a length of the radiating portion varies around a circumference of the coaxial cable. 
     
     
         23 . The probe of  claim 21 , the coaxial cable comprising a cap located at a probe distal end, the cap comprising a cap proximal boundary. 
     
     
         24 . The probe of  claim 23  wherein the cap proximal boundary is uniform in distance from a distal end of the probe around a circumference of the coaxial cable. 
     
     
         25 . The probe of  claim 23  wherein the cap further comprises a cap tip configured to pierce tissue at a cap distal end. 
     
     
         26 . The probe of  claim 23  wherein a radiating portion distal boundary and the cap proximal boundary vary in distance from the probe distal end around a circumference of the coaxial cable. 
     
     
         27 . The probe of  claim 21  wherein the radiating portion comprises a plurality of discrete sections, wherein adjacent discrete sections are at different distances from a probe distal end around a circumference of the coaxial cable. 
     
     
         28 . The probe of  claim 21  wherein the radiating portion comprises a wave shape around a circumference of the coaxial cable or a saw tooth shape around the circumference of the coaxial cable. 
     
     
         29 . The probe of  claim 21  wherein the radiating portion is configured to emit the microwave energy at the first resonant frequency and the second resonant frequency in parallel. 
     
     
         30 . The probe of  claim 29  wherein the radiating portion is configured to emit the microwave energy at the first resonant frequency and the second resonant frequency at the same time. 
     
     
         31 . The probe of  claim 21  further comprising a choke. 
     
     
         32 . The probe of  claim 21  wherein the shielded portion of the probe body comprises a metal cannula. 
     
     
         33 . The probe of  claim 32  further comprising a dielectric layer in between the metal cannula and the coaxial cable. 
     
     
         34 . The probe of  claim 32  further comprising a choke comprising:
 a choke contact between the metal cannula and the coaxial cable; and 
 a choke length extending between the choke contact and a distal end of the metal cannula. 
 
     
     
         35 . The probe of  claim 34  wherein the choke contact or the distal end of the cannula varies in its distance from a probe distal end. 
     
     
         36 . The probe of  claim 33  wherein the radiation window comprises a portion of the dielectric material of the coaxial cable surrounding the radiating portion of the coaxial cable. 
     
     
         37 . A microwave ablation system comprising a microwave energy source and a microwave ablation probe, the microwave ablation probe comprising:
 a probe body comprising:
 a shielded portion and a radiation window that is at least partially transparent to microwave energy; 
 a metal cannula; and 
 a coaxial cable within the probe body connected to a microwave energy source, the coaxial cable comprising a radiating portion configured for emission of microwave energy, wherein the radiating portion is aligned with the radiation window, the radiating portion comprising: 
 a first section having a first length, the first section configured for emission of the microwave energy at a first resonant frequency; and 
 a second section having a second length, the second section configured for emission of the microwave energy at a second resonant frequency that is different from the first resonant frequency. 
   
     
     
         38 . The microwave ablation probe of  claim 37  wherein a radiating portion distal boundary varies in distance from a probe distal end around a circumference of the coaxial cable. 
     
     
         39 . A method of microwave ablation comprising:
 providing a microwave ablation probe comprising:
 a probe body comprising a shielded portion and a radiation window that is at least partially transparent to microwave energy;
 a radiating portion configured for emission of microwave energy, wherein the radiating portion is aligned with the radiation window, 
 
 the radiating portion comprising:
 a first section having a first length, the first section configured for emission of the microwave energy at a first resonant frequency; and 
 a second section having a second length, the second section configured for emission of the microwave energy at a second resonant frequency that is different from the first resonant frequency; and 
 
   delivering microwave energy to the radiating portion.   
     
     
         40 . The method of  claim 39  wherein the microwave ablation probe produces microwave energy at three or more resonant frequencies in parallel.