Microwave applicator for transurethral hyperthermia

• US 5,301,687 A
• Filed: 06/06/1991
• Issued: 04/12/1994
• Est. Priority Date: 06/06/1991
• Status: Expired due to Term

• Current Assignee: The Trustees of Dartmounth College (Dartmouth College)
• Original Assignee: The Trustees of Dartmounth College (Dartmouth College)
• Inventors: Wong, Terence Z., Trembly, B. Stuart
• Primary Examiner(s): Pellegrino, Stephen C.
• Assistant Examiner(s): SCHMIDT, JEFFREY
• Application Number:
  US07/711,290
• Time in Patent Office: 1,041 Days
• Field of Search: 128/399, 128/401, 128/783, 128/786, 128/794, 128/804, 606/27, 606/33, 606/41, 600/2, 600/3, 600/6
• US Class Current: 607/116
• 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

Abstract

A radiant heating apparatus for deployment within an animal body to radiate heat-producing electromagnetic energy into the body includes an antenna mounted on a catheter element and connected to an electrical transmission line having first and second conductors for feeding electrical current from a source to the antenna. The apparatus has the improvement in which the antenna comprises a first radiating element carried on the catheter element and extending from an antenna feed junction in a first direction along a first elongation axis. The first radiating element is connected to the first transmission line conductor at the feed junction and presents a first selected impedance to the feed junction. A second radiating element is carried on the catheter element and extends from the feed junction in a second direction opposite to the first direction along the first axis. The second radiating element is connected to the second transmission line conductor and presents a second selected impedance to the feed junction. The first and second radiating elements radiate electromagnetic energy outwardly from the feed junction upon being excited from the transmission line with alternating electrical current within a selected frequency range. The first and second radiating elements are arranged for presenting the first and second impedances and for providing the radiation substantially independently of the length of the catheter element inserted within the animal body beyond the full insertion of the first or second radiating elements within the animal body.

This invention was made in part with government support under contract number NIH/NC1 R01 CA23549 awarded by the National Institute of Health. The government has certain limited rights in the invention.

Claims

1. Radiant heating apparatus for deployment within an animal body to radiate heat-producing electromagnetic energy into the body, said apparatus having an antenna mounted on a catheter element and connected to an electrical transmission line having first and second conductors for feeding electrical current form a source to the antenna, said apparatus having the improvement in which

A. the antenna comprises a first radiating element carried on said catheter element and extending from an antenna food junction in a first direction along a first elongation axis,

(i) said first radiating element being an electrical choke at a frequency within said antenna operating range and being connected to said first transmission line conductor at said feed junction and presenting a first selected impedance to said feed junction,

(ii) said first radiating element forming said electrical choke with a conductive element connected to said transmission line conductor and with a dielectric having a dielectric constant substantially less than that of said animal body,

(iii) said first radiating element having a first length along said first direction that is substantially a quarter wavelength within said animal body at said operating frequency and said choke having a length which in said lesser dielectric constant is substantially less than a quarter wavelength at said same operating frequency,

B. a second radiating element carried on said catheter element and extending form said feed junction in a second direction opposite to said first direction along said first axis,

(i) said second radiating element being connected to said second transmission line conductor and presenting a second selected impedance to said feed junction,

C. said first and second radiating elements radiating electromagnetic energy outwardly form said feed junction upon being excited from said transmission line with alternating electrical current within a selected frequency range, and

D. said first and second radiating elements being axially disposed along said first axis for presenting said first and second impedances to said transmission feed line for providing said radiation substantially independently of the length of said catheter element inserted within the animal body beyond the full insertion of said first or second radiating elements within the animal body.

2. Radiant heating apparatus according to claim 1 having the further improvement wherein said first and second impedances are substantially equal.

3. Radiant heating apparatus according to claim 1, having the further improvement wherein the lengths of said first and second radiating elements along said first axis are substantially equal.

4. Radiant heating apparatus according to claim 1 further comprising a first radiating element being a tubular conductor coaxially seated outwardly over said outer conductor of said transmission feed line and having

(i) a first end proximal to said feed junction and connected to said outer conductor at said first end thereof,

(ii) a second end distal from said feed junction and extending opposite to said first end along said outer conductor wherein said tubular conductor forms part of said electrical choke, and

(iii) said second end of said first radiating element presents to said feed junction a high impedance.

5. Radiant heating apparatus for deployment within an animal body to radiate heat-producing electromagnetic energy into the body, said apparatus having an antenna mounted on a catheter element and connected to an electrical transmission line having inner and outer coaxial conductors for feeding electrical current from a source to the antenna, said apparatus having the improvement in which

A. the antenna comprises a first radiating element carried on said catheter element and extending form an antenna feed junction in a first direction along a first elongation axis,

(i) said first radiating element being an electrical choke at a frequency within said antenna operating range and being a tubular conductor coaxially seated outwardly over said outer conductor to form, in cooperation with said inner conductor, a substantially triaxial geometry, said first radiating element being connected to said outer conductor at said feed junction and presenting a first selected impedance to said feed junction,

(ii) said first radiating element forming said electrical choke with a conductive element connected to said first transmission line conductor and with a dielectric element having a dielectric constant substantially less than that of said animal body,

(iii) said first radiating element having a first length along said first direction that is substantially a quarter wavelength within said animal body at said operating frequency and said choke having a length which is said lesser dielectric constant is substantially less than a quarter wavelength at said same operating frequency,

B. a second radiating element carried on said catheter element and extending from said feed junction in a second direction opposite to said first direction along said first axis, said second radiating element being connected to said inner conductor and presenting a second selected impedance to said feed junction,

C. said first and second radiating elements radiating electromagnetic energy outwardly from said feed junction upon being excited from said transmission line with alternating electrical current within a selected frequency range, and

D. said first and second radiating elements being axially disposed along a first elongation axis for presenting said first and second impedances to said transmission feed lien for providing said radiation substantially independently of the length of said catheter element inserted within the animal body beyond the full insertion of said first or second radiating elements within the animal body.

6. Radiant heating apparatus according to claim 5 having the further improvement wherein said first and second impedances are substantially equal.

7. Radiant heating apparatus according to claim 5, having the further improvement wherein the lengths of said first and second radiating elements along said first axis are substantially equal.

8. Radiant heating apparatus according to claim 5 further comprising a first radiating element being a tubular conductor coaxially seated outwardly over said outer conductor of said transmission feed lien and having

(i) a first end proximal to said feed junction and connected to said outer conductor at said first end thereof,

(ii) a second end distal from said feed junction and extending opposite to said first end along said outer conductor wherein said tubular conductor forms part of said electrical choke, and

(iii) said second end of said first radiating element presents to said feed junction a high impedance.