In vivo simulator for microwave treatment

• US 6,175,768 B1
• Filed: 09/16/1998
• Issued: 01/16/2001
• Est. Priority Date: 04/17/1996
• Status: Expired due to Fees

• Current Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Original Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Inventors: Karasack, Vincent G., Pieper, Carl F., Arndt, G. Dickey, Carl, James R., Raffoul, George W., Pacifico, Antonio
• Primary Examiner(s): Dvorak, Linda C. M.
• Assistant Examiner(s): Kearney, R.
• Application Number:
  US09/154,622
• Time in Patent Office: 853 Days
• Field of Search: 607/101, 607/102, 607/154-156, 607/115, 422/22, 623/2, 606/33, 606/34, 128/898
• US Class Current: 607/101
• CPC Class Codes: A61B 18/1206 Generators therefor
• CPC Class Codes: A61B 18/1492 having a flexible, catheter-like structure, e.g. for heart ablation A61B18/1477 takes precedence
• 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 2018/00351 Heart
• CPC Class Codes: A61B 2018/00577 Ablation
• CPC Class Codes: A61B 2018/00732 Frequency
• CPC Class Codes: A61B 2018/00791 Temperature
• CPC Class Codes: A61B 2018/1861 with an instrument inserted into a body lumen or cavity, e.g. a catheter
• CPC Class Codes: A61B 2018/1892 Details of electrical isolations of the antenna
• CPC Class Codes: A61F 2/00 Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents as cosmetic articles, see the relevant subclasses, e.g. wigs, hair pieces, A41G3/00, A41G5/00; artificial nails A45D31/00; dental prostheses A61C13/00; materials for prostheses A61L27/00; artificial hearts A61M60/00; artificial kidneys A61M1/14
• CPC Class Codes: A61N 1/06 for high-frequency therapy

Abstract

Method and apparatus are provided for propagating microwave energy into heart tissues to produce a desired temperature profile therein at tissue depths sufficient for thermally ablating arrhythmogenic cardiac tissue to treat ventricular tachycardia and other arrhythmias while preventing excessive heating of surrounding tissues, organs, and blood. A wide bandwidth double-disk antenna (700) is effective for this purpose over a bandwidth of about six gigahertz. A computer simulation provides initial screening capabilities for an antenna such as antenna, frequency, power level, and power application duration. The simulation also allows optimization of techniques for specific patients or conditions. In operation, microwave energy between about 1 Gigahertz and 12 Gigahertz is applied to monopole microwave radiator (600) having a surface wave limiter (606). A test setup provides physical testing of microwave radiators (854) to determine the temperature profile created in actual heart tissue or ersatz heart tissue (841). Saline solution (872) pumped over the heart tissue (841) with a peristaltic pump (862) simulates blood flow. Optical temperature sensors (838) disposed at various tissue depths within the heart tissue (841) detect the temperature profile without creating any electromagnetic interference. The method may be used to produce a desired temperature profile in other body tissues reachable by catheter (510) such as tumors and the like.

Claims

1. An in vivo simulator for measuring a temperature profile in a sample material induced by electromagnetic transmission, comprising:

a biological tissue receptacle containing therein a sample material, said receptacle being substantially water tight;

a pump for pumping fluid past said sample material in said receptacle;

one or more temperature sensors for placement within said sample material in said receptacle;

for sensing said temperature profile;

a supply cable having an electromagnetic antenna disposed at one end thereof for inducing electromagnetic energy into said sample material; and

a power source to apply power to said electromagnetic antenna through said supply cable.

2. The apparatus of claim 1, wherein:

said one or more temperature sensors are substantially unaffected by electromagnetic transmission.

3. The apparatus of claim 1, wherein:

said one or more temperature sensors are optical temperature sensors.

4. The apparatus of claim 3, further comprising:

an optical temperature sensor data transmitters for relaying temperature data from said optical temperature sensors.

5. The apparatus of claim 3, further comprising:

an optical scanner for receiving data from said optical temperature sensors.

6. The apparatus of claim 1, further comprising:

at least one temperature sensor transmission line, said line extending through a wall of said biological tissue receptacle, and

at least one temperature sensor support member for securing said sensor transmission line is a selected position, said at least one temperature sensor member being movable to a second selected position.

7. The apparatus of claim 1, wherein:

said pump is operable for producing peristaltic pumping action.

8. The apparatus of claim 1, further comprising:

a monitor for measuring a standing wave ratio along said catheter.

9. The apparatus of claim 1, wherein:

said sample material is comprised of ersatz heart tissue.

10. The apparatus of claim 1, further comprising:

input and output ports in said biological tissue receptacle for said fluid.

11. The apparatus of claim 1, wherein:

said fluid has electrical properties similar to those of blood.

12. The apparatus of claim 1, wherein:

said sample material has electrical properties similar to those of heart tissue.

13. An in vivo simulator method for measuring a temperature profile in a sample material induced by electromagnetic transmission, comprising:

providing said sample material to have electrical properties similar to those of biological tissues;

providing a microwave antenna for transmitting electromagnetic waves into said sample material;

providing one or more temperature sensors in said sample material for measuring said temperature profile; and

providing fluid adjacent said sample material suitable for modeling effects of in vivo blood flow.

14. The in vivo simulator method of claim 13, further comprising:

measuring temperature changes at a depth in said sample material versus time.

15. The in vivo simulator method of claim 13, wherein providing one or more temperature sensors further comprises:

providing a plurality of optical sensors at different depths from a surface of said sample material for measuring said temperature profile versus depth over a sample time in said sample material.

16. The method of claim 13, wherein said providing fluid further comprises:

providing a volume of fluid flow similar to that of in vivo fluid flow.

17. The method of claim 13, further comprising:

using actual heart tissue for said sample material.

18. The method of claim 13, wherein said providing fluid further comprises:

pumping fluid by said sample material.

19. The method of claim 13, wherein said step of providing a microwave antenna further comprises:

comparing the heating characteristics of different microwave antennas.

20. An in vivo simulator method for measuring a temperature profile in a sample material induced by electromagnetic transmission, comprising:

providing said sample material to have electrical properties similar to those of biological tissues for the frequency of said electromagnetic transmission;

providing a microwave antenna for transmitting electromagnetic waves into said sample material;

providing a plurality of optical temperature sensors at different depths in said sample material for measuring said temperature profile; and

recording said temperature at said different depths in said sample material to provide a temperature profile at different depths in said sample material over time.