Hollow conductive coaxial cable for radio frequency based tissue ablation system
A hollow coaxial cable adapted for conduction of radio frequency (RF) energy, particularly microwave energy, has a proximal end and a distal end and comprises coaxial inner and outer conductors extending substantially the entire length of the cable from the proximal end to a distal end portion of the cable with a dielectric medium disposed between the inner and outer conductors. The inner conductor comprises an elongated electrically conductive tubular member having a hollow, axially extending lumen, and the outer conductor comprises an elongated electrically conductive tubular member disposed in a substantially coaxial relationship over at least a portion of the inner conductor. An ablating member which delivers radio frequency energy, particularly microwave energy, to body tissue is disposed at a distal end portion of the cable.
1. A hollow coaxial cable device adapted for transmission of radio frequency (RF) energy for the ablation of biological tissue, comprising:
an elongate cable adapted for placement adjacent to or within biological tissues and vessels, the elongate cable having a proximal end and a distal end and comprising inner and outer conductors extending substantially the entire length of the elongate cable from the proximal end to a distal end portion of the elongate cable;
the inner conductor comprising a first elongated electrically conductive tubular member having a hollow, axially extending lumen and an outer surface;
the outer conductor comprising a second elongated electrically conductive tubular member disposed in a substantially coaxial relationship over at least a portion of the inner conductor and having an inner surface spaced from the outer surface of the inner conductor to define an annular space between the inner and outer conductors;
a dielectric medium disposed in the annular space and extending between the inner surface of the outer conductor and the outer surface of the inner conductor;
a radio frequency (RF) antenna connected to distal end portions of the inner and outer conductors and projecting forwardly from a distal end of the outer conductor, the RF antenna being configured to deliver radio frequency energy to body tissue disposed at the distal end portion of the elongate cable;
a pre-shaped deflection member located within the distal end portion of the elongate cable and movable for changing a configuration of the distal end portion of the elongate cable between straight and curved configurations, the pre-shaped deflection member extending through the hollow, axially extending lumen to the distal end portion of the elongate cable; and
a temperature sensor located at the distal end portion of the elongate cable within the hollow, axially extending lumen, the hollow, axially extending lumen having a central longitudinal axis, the deflection member extending along the central longitudinal axis, and the temperature sensor being offset from the central axis and having signal wires extending from the temperature sensor alongside the deflection member and up to the proximal end of the elongate cable.
2. The device of claim 1 , wherein the pre-shaped deflection member is extendible between a retracted position spaced from the distal end of the cable and an extended position in which a forward end portion of the deflection member extends up to a location adjacent the distal end of the cable and past the temperature sensor, the deflection member being straight in the retracted position and the forward end portion being curved in the extended position.
3. The device of claim 1 , wherein
the dielectric medium comprises a dielectric layer between the inner and outer conductors having a projecting forward end portion which projects forwardly from the distal end of the outer conductor; and
the RF antenna comprising a helical coil wound circumferentially around an outer surface of the projecting forward end portion of the dielectric layer and.
4. The coaxial cable device of claim 1 , further comprising at least one electrode disposed at the distal end portion of the cable.
5. The device of claim 4 , further comprising a conductive wire extending from the at least one electrode through the hollow, axially extending lumen to the proximal end of the cable.
6. The device of claim 4 , wherein the at least one electrode is an electrocardiogram (“ECG”) electrode.
7. The device of claim 4 , wherein the at least one electrode is comprised of an electrode material that an at least substantially non-metallic material.
8. The device of claim 7 , wherein the at least one electrode is comprised of an electrode material that a flexible conductive polymer material.
9. The device of claim 1 , further comprising an RF signal generator connected to the RF antenna which generates a train of RF energy pulses which is transmitted to the RF antenna, a detector which detects a reflected signal and a forward signal of the train of RF energy pulses when the RF antenna is adjacent to a biological tissue site to be ablated, a controller which communicates with the detector and RF signal generator, the controller having a processing module which determines a voltage standing wave ratio (VSWR) based on the reflected signal and forward signal, and an RF signal adjustment module which adjusts a frequency of the train of RF energy pulses based on the VSWR to effect a substantial match of a coaxial cable impedance with the RF antenna and a biological tissue load impedance.
10. The device of claim 9 , further comprising an interface unit coupled to the distal end portion of the cable, and an electrical conductor having a first end connected to the interface unit and a second end connected to the RF signal generator, the interface unit having an impedance matching electrical interface device connected to a distal end of the inner conductor and the distal end of the outer conductor of the elongate cable and to the first end of the electrical conductor.
11. The device of claim 10 , wherein the interface device comprises a microstrip.
12. The device of claim 1 , wherein the frequency comprises that of the microwave frequency range from approximately 300 MHz and up.
13. The device of claim 1 , further comprising a shape control mechanism connected to the proximal end of the cable which controls the configuration of the distal end portion of the cable.
14. The device of claim 1 , wherein a distal end of the hollow, axially extending lumen is closed.
15. The device of claim 1 , wherein at least one of the first and second electrically conductive tubular members is formed of an electrically conductive wire mesh.
16. The device of claim 1 , wherein at least one of the first and second electrically conductive tubular members is formed of an electrically conductive braided material.
17. The device of claim 1 , wherein at least one of the first and second electrically conductive tubular members is formed of an electrically conductive thin-film material.
18. The device of claim 1 , further comprising an outer layer of non-conductive material extending over the outer conductor.
19. The device of claim 1 , further comprising an inner sleeve of non-conductive material extending inside the inner conductor, the hollow, axially extending lumen extending through the inner sleeve.