Air-core microwave ablation antennas

• US 20060276780A1
• Filed: 09/28/2005
• Published: 12/07/2006
• Est. Priority Date: 04/29/2004
• Status: Active Grant

• Current Assignee: Neuwave Medical, Inc. (Johnson & Johnson)
• Original Assignee: Neuwave Medical, Inc. (Johnson & Johnson)
• Inventors: van der Weide, Daniel Warren, Laeseke, Paul F., Brace, Christopher L., Lee, Fred T. Jr.
• Granted Patent: US 7,244,254 B2
• Time in Patent Office: Days
• US Class Current: 606/33
• CPC Class Codes: A61B 18/18 by applying electromagnetic radiation, e.g. microwaves radiation therapy A61N5/00
• CPC Class Codes: A61B 18/1815 using microwaves
• CPC Class Codes: A61B 2018/00017 with gas
• CPC Class Codes: A61B 2018/00023 closed, i.e. without wound contact by the fluid
• CPC Class Codes: A61N 1/06 for high-frequency therapy

Abstract

A method and device delivers microwave power to an antenna through a coaxial cable utilizing air or other gases as its dielectric core. The cable includes supports made of low-loss materials to keep the inner conductor centered in the cable, and defining spaces therebetween for the air or gas. Channels in the supports allow the air or gas to circulate in the cable. The gas may be chilled or cooled to provide an addition level of heat dissipation. The device enables delivery of large amounts of power to tissue without undue heating of the feed cable or peripheral tissues, and without increasing the diameter of the feeding cable or antenna, keeping the antenna safe for percutaneous use.

Claims

1. A device for delivery of microwave power to an antenna, comprising:

a coaxial cable having an outer conductor and an inner conductor; and

a plurality of supports in the cable for holding and centering the inner conductor relative to the outer conductor, wherein a space is defined in the cable between adjacent supports; and

a gas dielectric filling the space between adjacent supports such that the cable utilizes air or other gas as a dielectric core;

wherein the plurality of supports each have at least one flow channel allowing for the passage of gas through each support.

8. The device of claim 1, wherein each support defines a length, and wherein the length of each support is sufficiently short to be much less than a wavelength inside the cable.

9. The device of claim 1, wherein each support defines a length, and wherein the length of each support is approximately 1 mm.

10. The device of claim 8, wherein the space between adjacent supports defines a distance, and wherein the distance of the space between adjacent supports is approximately 5 to 10 cm.

11. The device of claim 9, wherein the space between adjacent supports defines a distance, and wherein the distance of the space between adjacent supports is approximately 5 to 10 cm.

12. The device of claim 1, wherein the at least one flow channel comprises six channels generally equally spaced around the inner conductor.

13. The device of claim 1, further comprising a pump operatively connected with the coaxial cable, wherein the pump circulates the gas through the coaxial cable.

14. The device of claim 13, wherein the gas is chilled or cooled during circulation.

2. (canceled)

3. A device for combined delivery of microwave power to an antenna and cooling of the device, comprising:

a co-axial cable having an outer conductor and an inner conductor; and

a plurality of supports in the cable for holding and centering the inner conductor relative to the outer conductor, wherein a space is defined in the cable between adjacent supports; and

a gas dielectric filling the space between adjacent supports such that the cable utilizes air or other gas as a dielectric core;

wherein at least a portion of the inner conductor comprises a hollow center allowing for the passage of gas through the hollow center.

4. The device of claim 3, wherein the plurality of supports each have one or more flow channels allowing for the passage of gas through each support.

15. The device of claim 3, wherein the at least a portion of the inner conductor which comprises a hollow center further comprises at least one entrance port and at least one exit port for the gas.

16. The device of claim 15, wherein the at least a portion of the inner conductor which comprises a hollow center forms a joint at one end with a solid center portion of the inner conductor, and forms a joint at an opposite end with the antenna.

17. The device of claim 16, wherein a non-conducting plug supports the center conductor at the joints.

18. The device of claim 17, wherein the non-conducting plug supporting the joint at the end proximate the solid center portion includes a port in fluid communication with the at least one entrance port, and wherein the outer conductor has a port proximate the at least a portion of the inner conductor which comprises a hollow center.

19. The device of claim 18, further comprising a pump operatively connected with the coaxial cable, wherein the pump circulates gas through the hollow center.

20. The device of claim 19, wherein the gas is chilled or cooled during circulation.

5. (canceled)

6. A method for delivery of microwave power to an antenna, comprising the steps of:

defining spaces in a co-axial cable attached to the antenna, between an inner conductor and an outer conductor of the co-axial cable;

holding and centering the inner conductor relative to the outer conductor with a plurality of supports each having at least one flow channel allowing for the passage of gas through each support

circulating cooling gas between the spaces in the co-axial cable; and

supplying power to the co-axial cable.

7. The method of claim 6 wherein the co-axial cable has a hollow tube center conductor portion proximate the antenna, and wherein the method further comprises the step of circulating cooling gas through the hollow tube center conductor portion.