Electrosurgical devices having dielectric loaded coaxial aperture with distally positioned resonant structure

1. An electrosurgical device for directing energy to a target volume of tissue, comprising:

a coaxial feedline having an inner conductor, an outer conductor coaxially disposed around the inner conductor, and a dielectric material disposed therebetween; and

an antenna assembly, including:

an extension of the inner conductor that extends distally beyond the outer conductor and the dielectric material at a distal end of the coaxial feedline into the antenna assembly;

a first arcuate dielectric segment;

a second arcuate dielectric segment, the first and second arcuate dielectric segments coupled one to the other along a longitudinal axis of the antenna assembly, surrounding a portion of the extension of the inner conductor that extends distally beyond the outer conductor and the dielectric material at the distal end of the coaxial feedline; and

an elongated shaft overlying at least a portion of the second arcuate dielectric segment, the elongated shaft having an opening defined therethrough for passage of energy therethrough, the opening at least partially aligned with the first arcuate dielectric segment.

2. The electrosurgical device of claim 1 , wherein the first arcuate dielectric segment defines a longitudinally-extending channel configured to receive at least a portion of the extension of the inner conductor that extends distally beyond the outer conductor and the dielectric material at the distal end of the coaxial feedline.

3. The electrosurgical device of claim 1 , wherein the first and second arcuate dielectric segments each include at least one flat planar surface and an arcuate surface.

4. The electrosurgical device of claim 3 , wherein, when the first and second arcuate dielectric segments are coupled one to the other, the at least one flat planar surface of the first arcuate dielectric segment is disposed in contact with the at least one flat planar surface of the second arcuate dielectric segment.

5. The electrosurgical device of claim 1 , wherein the opening in the elongated shaft is filled with a RF transparent material.

6. The electrosurgical device of claim 1 , wherein the first arcuate dielectric segment is configured to fill the opening in the elongated shaft.

7. The electrosurgical device of claim 1 , wherein the elongated shaft is electrically coupled to the outer conductor of the coaxial feedline.

8. The electrosurgical device of claim 1 , wherein a dielectric constant of the first arcuate dielectric segment is higher than a dielectric constant of the second arcuate dielectric segment.

9. An electrosurgical device for directing energy to a target volume of tissue, comprising:

a coaxial feedline having an inner conductor, an outer conductor coaxially disposed around the inner conductor, and a dielectric material disposed therebetween; and

an antenna assembly, including:

an extension of the inner conductor that extends distally beyond the outer conductor and the dielectric material at a distal end of the coaxial feedline into the antenna assembly;

a proximal cylindrical dielectric sleeve, disposed at the distal end of the coaxial feedline, surrounding a proximal portion of the extension of the inner conductor that extends distally beyond the outer conductor and the dielectric material at the distal end of the coaxial feedline;

a distal cylindrical dielectric sleeve disposed distal to the proximal cylindrical dielectric sleeve;

a first arcuate dielectric segment; a second arcuate dielectric segment, the first and second arcuate dielectric segments coupled one to the other along a longitudinal axis of the antenna assembly, wherein a dielectric constant of the first arcuate dielectric segment is higher than a dielectric constant of the second arcuate dielectric segment;

wherein the first and second arcuate dielectric segments are disposed between the proximal cylindrical dielectric sleeve and the distal cylindrical dielectric sleeve;

an elongated shaft overlying the proximal cylindrical dielectric sleeve, the first arcuate dielectric segment, the second arcuate dielectric segment and the distal cylindrical dielectric sleeve, the elongated shaft having an opening defined therethrough for passage of energy therethrough, the opening at least partially aligned with the first arcuate dielectric segment; and

a balun structure disposed on the elongated shaft, the balun structure at least partially overlying the opening in the elongated shaft.

10. The electrosurgical device of claim 9 , wherein at least one of the proximal cylindrical dielectric sleeve and the distal cylindrical dielectric sleeve includes a central channel extending longitudinally therethrough configured to accommodate a portion of the extension of the inner conductor.

11. The electrosurgical device of claim 9 , wherein the balun structure includes a first balun outer conductor and a second balun outer conductor, each of the first and second balun outer conductors disposed at least partially overlying the opening in the elongated shaft.

12. The electrosurgical device of claim 9 , wherein the opening in the elongated shaft is filled with a RF transparent material.

13. The electrosurgical device of claim 9 , wherein the first arcuate dielectric segment is configured to fill the opening in the elongated shaft.

14. The electrosurgical device of claim 9 , further comprising a tapered portion, disposed distal to the distal cylindrical dielectric sleeve, having a tip configured to penetrate tissue.

15. The electrosurgical device of claim 9 , wherein the first and second dielectric segments each include at least one flat planar surface and an arcuate surface.