Electrosurgical devices with balun structure for air exposure of antenna radiating section and method of directing energy to tissue using same
An energy applicator for directing energy to tissue includes a feedline having an inner conductor, an outer conductor and a dielectric material disposed therebetween, and an antenna assembly having a radiating section operably coupled to the feedline. The energy applicator also includes a first balun structure configured to substantially confine energy to the radiating section when the energy applicator is energized and disposed in tissue, and a second balun structure configured to substantially prevent energy emitted from the radiating section from propagating proximal to the second balun structure along the feedline when the energy applicator is energized but not disposed in tissue.
1. An energy applicator for directing energy to tissue, comprising:
a feedline having:
an inner conductor;
an outer conductor coaxially disposed around the inner conductor; and
a dielectric material disposed between the inner conductor and the outer conductor;
an antenna assembly having a radiating section operably coupled to the feedline;
a first balun portion configured to confine energy to the radiating section, the first balun portion including:
a single balun insulator disposed around a distal portion of the outer conductor of the feedline; and
a single balun outer conductor disposed around an outer peripheral surface of at least a portion of the single balun insulator, the single balun insulator extending distally beyond a distal-most end of the single balun outer conductor; and
a second balun portion configured to prevent energy emitted from the radiating section from propagating proximal to the second balun portion along the feedline, the second balun portion including:
a balun insulator disposed around the single balun outer conductor of the first balun portion and including a proximal portion in contact with the outer conductor of the feedline; and
a balun outer conductor disposed around the balun insulator of the second balun portion.
2. The energy applicator of claim 1 , further comprising at least one conductive disk disposed within the radiating section.
3. The energy applicator of claim 2 , wherein the at least one conductive disk includes a first conductive disk and a second conductive disk disposed proximal to the first conductive disk.
4. The energy applicator of claim 1 , wherein at least a portion of the inner conductor of the feedline extends distally beyond the outer conductor and the dielectric material.
5. The energy applicator of claim 1 , wherein the first balun portion has a length of a quarter of a wavelength of microwave energy.
6. The energy applicator of claim 1 , wherein the antenna assembly includes a tapered portion having a tip configured to penetrate tissue.
7. The energy applicator of claim 1 , wherein the single balun outer conductor is in direct contact with the single balun insulator.
8. The energy applicator of claim 1 , wherein the balun insulator of the second balun portion extends distally beyond a distal-most end of the balun outer conductor of the second balun portion.
9. The energy applicator of claim 1 , wherein the second balun portion consists of:
the balun insulator of the second balun portion; and
the balun outer conductor of the second balun portion.
10. The energy applicator of claim 1 , wherein the single balun insulator is disposed within a slot defined between an inner surface of the single balun outer conductor and an outer surface of the outer conductor of the feedline.
11. The energy applicator of claim 1 , wherein the single balun insulator has a proximal portion in contact with a proximal portion of the single balun outer conductor.
12. The energy applicator of claim 1 , wherein the single balun outer conductor has a distal portion that extends transversely relative to a proximal portion of the single balun outer conductor.
13. The energy applicator of claim 12 , wherein the distal portion of the single balun outer conductor is in contact with the single balun insulator.
14. The energy applicator of claim 1 , wherein the distal-most end of the balun outer conductor of the second balun portion terminates proximally of a distal-most end of the balun insulator of the second balun portion such that the distal-most end of the balun insulator of the second balun portion is uncovered.
15. The energy applicator of claim 1 , wherein the balun insulator of the second balun portion includes:
a distal portion disposed between and in contact with the single balun outer conductor and the balun outer conductor of the second balun portion; and
an intermediate portion interconnecting the proximal and distal portions of the balun insulator of the second balun portion.
16. The energy applicator of claim 15 , wherein the proximal and distal portions of the balun insulator of the second balun portion are parallel to one another, and the intermediate portion of the balun insulator of the second balun portion is perpendicular to the proximal and distal portions of the balun insulator of the second balun portion.
17. The energy applicator of claim 1 , wherein the balun outer conductor of the second balun portion has a proximal portion in contact with the outer conductor.