Single integrated structural unit for catheter incorporating a microwave antenna

• US 6,230,060 B1
• Filed: 10/22/1999
• Issued: 05/08/2001
• Est. Priority Date: 10/22/1999
• Status: Expired due to Fees

• Current Assignee: MMTC Limited (Government of India)
• Original Assignee: MMTC Limited (Government of India)
• Inventors: Mawhinney, Daniel D.
• Primary Examiner(s): Cohen, Lee
• Assistant Examiner(s): GIBSON, ROY DEAN
• Application Number:
  US09/422,181
• Time in Patent Office: 564 Days
• Field of Search: 607/96, 607/98, 607/101-102, 607/154, 607/156, 606/33
• US Class Current: 607/101
• 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 2017/00292 mounted on or guided by flexible, e.g. catheter-like, means
• CPC Class Codes: A61B 2018/00023 closed, i.e. without wound contact by the fluid
• CPC Class Codes: A61B 2018/00166 Multiple lumina
• CPC Class Codes: A61B 2018/00255 arranged one inside another
• CPC Class Codes: A61B 2018/00517 Urinary bladder or urethra
• CPC Class Codes: A61B 2018/1861 with an instrument inserted into a body lumen or cavity, e.g. a catheter

Abstract

The catheter constitutes a single integrated structural unit comprising a first tubular balloon-supporting structure having a given outer diameter and a second structure inserted therein comprising an antenna and a coaxial cable for energizing the antenna. This permits both the antenna and the longitudinal cable to be wider, without any increase in the given outer diameter, than would be the case if the catheter were a prior-art non-integrated structure in which the tubular first structure and the second structure are separate detached units and, therefore, require clearance therebetween to permit insertion. In both basic and preferred embodiments, the single integrated structural is achieved by an electrically conductive shield attached by spacers to an outer conductor of the coaxial cable. In the basic embodiment, the shield is spaced from both the outer cable conductor and first structure to form inner and outer channels for exiting and entering the circulating balloon-inflating liquid. In the preferred embodiment, the shield is bonded to the inner surface of the first structure to form the entering channel, while the exiting channel is formed by the interior of a tubular inner cable conductor which may also house a thin tube for air inflating a Foley balloon. The inner channels of both embodiments include a ¼ wavelength choke structure at the distal end of the coaxial cable. A modification divides the circumference of the channels into separate angular sectors for independently circulating inflating liquid to any of a plural number of differently-sized balloons.

Claims

1. In a urethral balloon catheter incorporating an antenna suitable for use in therapeutically heating a diseased prostate of a male patient with energy radiated from said antenna, wherein said urethral catheter comprises (1) a tubular catheter first structure longitudinally extending from a proximate end thereof to a distal end thereof that includes an attached inflatable balloon situated near the distal end thereof together with input and output channels for use in circulating a balloon-inflating fluid, said tubular catheter first structure having a given outer diameter sufficiently small to permit it to be inserted inside of the urethra of said male patient with said balloon in its deflated state, and (2) a second structure inserted within said tubular catheter first structure that comprises said antenna situated toward said distal end of said tubular catheter first structure and a longitudinal coaxial cable comprising an inner conductor having a first given diameter, an outer conductor having a second given diameter and a dielectric having a given dielectric constant situated between said inner and outer conductors, said coaxial cable extending from the proximate end of said tubular catheter first structure to said antenna for use in energizing said antenna;

the improvement wherein;

said tubular catheter first structure and said second structure of said urethral balloon catheter are constructed to comprise a single integrated structural unit that includes interface structure comprising a longitudinal electrically conductive shield physically attached to both said outer conductor and an inner surface of said tubular catheter first structure;

whereby both said antenna and said longitudinal cable may be wider, without any increase in said given outer diameter, than would be the case if said urethral balloon catheter were a non-integrated structure in which said tubular catheter first structure and said second structure constitute separate units that are detached from one another and, therefore, would require clearance between the second structure and the tubular catheter first structure sufficient for a non-permanent insertion of the second structure within the tubular catheter first structure.

2. The urethral balloon catheter defined in claim 1, wherein said interface structure further comprises:

a first set of spacing means positioned to maintain said shield in spaced relationship with respect to said outer conductor of said coaxial cable and form at least one inner channel therebetween; and

a second set of spacing means positioned to maintain said shield in spaced relationship with respect to said inner surface of said tubular catheter first structure and form at least one outer channel therebetween;

whereby an inner channel may be selectively employed as a certain one of either said input channels or, alternatively, said output channels for use in circulating said balloon-inflating fluid, while an outer channel then is employed as the remaining one of either said output channels or, alternatively, said input channels for use in circulating said balloon-inflating fluid.

3. The urethral balloon catheter defined in claim 2, wherein:

said inner channel is employed as an output channel for use in circulating said balloon-inflating fluid and said outer channel is employed as an input channel for use in circulating said balloon-inflating fluid.

4. The urethral balloon catheter defined in claim 2, wherein:

said electrically conductive shield comprises a metal shield;

said first set of spacing means comprises longitudinally and circumferentially distributed springy plastic spacers situated between said metal shield and said outer conductor of said coaxial cable to form a single inner channel therebetween; and

said second set of spacing means comprises longitudinally and circumferentially distributed springy plastic spacers situated between said metal shield and said inner surface of said tubular catheter first structure to form a single outer channel therebetween.

5. The urethral balloon catheter defined in claim 2, wherein:

said electrically conductive shield comprises a metal shield;

said first set of spacing means comprises a given plural number of circumferentially-distributed longitudinal plastic ribs situated between said metal shield and said outer conductor of said coaxial cable which are angularly spaced in position to form a number of separate inner channels therebetween equal in number to said given number; and

said second set of spacing means comprises said given plural number of circumferentially-distributed longitudinal plastic ribs situated between said metal shield and said inner surface of said tubular catheter first structure which are angularly spaced in position to form a number of separate outer channels therebetween equal in number to said given number.

6. The urethral balloon catheter defined in claim 5, wherein:

said tubular catheter first structure comprises attached different-size inflatable balloons equal in number to said given plural number that individually correspond to a different pair of inner and outer channels of said given plural number of separate inner and outer channels;

whereby each separate one of said given plural number of inflatable balloons is independently inflatable by circulating a balloon-inflating fluid through that pair of inner and outer channels with which that inflatable balloon corresponds.

7. The urethral balloon catheter defined in claim 2, wherein:

said circulating balloon-inflating fluid comprises a given liquid exhibiting a predetermined dielectric constant that flows in said outer channel;

said antenna attached to the distal end of said coaxial cable is energized through said coaxial cable by energy of a given wavelength to be radiated by said antenna;

the distal end of said coaxial cable is open-circuited; and

said interface structure further comprises electrically conductive means for short-circuiting said electrically conductive shield to said outer conductor of said coaxial cable at a certain distance from the distal end of said coaxial cable, which certain distance has a value, as a function of the value of said predetermined dielectric constant of said given liquid, which substantially provides a ¼

wavelength choke at said given wavelength;

whereby the presence of said ¼

wavelength choke considerably reduces the backward flow of reflected given-wavelength energy.

8. The urethral balloon catheter defined in claim 7, wherein:

said a given liquid is deionized water having a predetermined dielectric constant of approximately 75 in value.

9. The urethral balloon catheter defined in claim 1, wherein:

said shield is contiguous with said inner surface of said tubular catheter first structure;

said interface structure further comprising a set of spacing means positioned to maintain said shield in spaced relationship with respect to said outer conductor of said coaxial cable and form at least one outer channel therebetween; and

said inner conductor comprises a tubular inner conductor having an interior that forms at least one inner channel;

whereby an inner channel may be selectively employed as a certain one of either said input channels or, alternatively, said output channels for use in circulating said balloon-inflating fluid, while an outer channel then is employed as the remaining one of either said output channels or, alternatively, said input channels for use in circulating said balloon-inflating fluid.

10. The urethral balloon catheter defined in claim 9, wherein:

each of said set of spacing means comprises a solid ring that includes a plurality of holes through which said circulating balloon-inflating fluid can flow.

11. The urethral balloon catheter defined in claim 9, wherein:

said inner channel is employed as an output channel for use in circulating said balloon-inflating fluid and said outer channel is employed as an input channel for use in circulating said balloon-inflating fluid.

12. The urethral balloon catheter defined in claim 9, wherein:

said circulating balloon-inflating fluid comprises a given liquid exhibiting a predetermined dielectric constant that flows in said outer channel;

said antenna attached to the distal end of said coaxial cable is a gap antenna that is energized through said distal end of said coaxial cable by energy of a given wavelength to be radiated by said antenna;

wherein said gap antenna is formed by a gap in said outer conductor that effectively open-circuits said distal end of said coaxial cable; and

said interface structure further comprises electrically conductive means for short-circuiting said electrically conductive shield to said outer conductor of said coaxial cable at a certain distance from the distal end of said coaxial cable, which certain distance has a value, as a function of the value of said predetermined dielectric constant of said given liquid, which substantially provides a ¼

wavelength choke at said given wavelength;

whereby the presence of said ¼

wavelength choke considerably reduces the backward flow of reflected given-wavelength energy.

13. The urethral balloon catheter defined in claim 12, wherein:

said electrically conductive means for short-circuiting said electrically conductive shield to said outer conductor of said coaxial cable comprises a solid metal ring that includes a plurality of holes through which said circulating balloon-inflating fluid can flow.

14. The urethral balloon catheter defined in claim 12, further comprising:

a solid insulating material exhibiting a given dielectric constant situated between said gap antenna and said inner surface of said tubular catheter first structure.

15. The urethral balloon catheter defined in claim 14, wherein:

said given dielectric constant exhibited by said solid insulating material a given dielectric constant is in the vicinity of the dielectric constant of muscle tissue.

16. The urethral balloon catheter defined in claim 15, wherein:

said solid insulating material is titania.

17. The urethral balloon catheter defined in claim 12, wherein:

said a given liquid is deionized water having a predetermined dielectric constant of approximately 75 in value.

18. In a catheter incorporating an antenna, wherein said catheter comprises (1) a tubular catheter first structure longitudinally extending from a proximate end thereof to a distal end thereof and (2) a second structure inserted within said tubular catheter first structure that comprises said antenna situated toward said distal end of said tubular catheter first structure and a longitudinal coaxial cable comprising an inner conductor having a first given diameter, an outer conductor having a second given diameter and a dielectric having a given dielectric constant situated between said inner and outer conductors, said coaxial cable extending from the proximate end of said tubular catheter first structure to said antenna for use in energizing said antenna;

the improvement wherein;

said tubular catheter first structure and said second structure of said catheter are constructed to comprise a single integrated structural unit that includes a longitudinal electrically conductive shield physically attached to both said outer conductor and an inner surface of said tubular catheter first structure.