Radio-frequency based catheter system and method for ablating biological tissues

• US 20040106917A1
• Filed: 08/08/2003
• Published: 06/03/2004
• Est. Priority Date: 12/14/1998
• Status: Active Grant

• Current Assignee: MedWaves, Inc.
• Original Assignee: MedWaves, Inc.
• Inventors: Leung, George L., Ormsby, Theodore C., Law, Ming-Fan
• Granted Patent: US 7,070,595 B2
• Time in Patent Office: Days
• US Class Current: 606/33
• 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 2017/003 Steerable
• CPC Class Codes: A61B 2018/00214 Expandable means emitting energy, e.g. by elements carried thereon
• CPC Class Codes: A61B 2018/00839 Bioelectrical parameters, e.g. ECG, EEG
• CPC Class Codes: A61B 2018/00875 Resistance or impedance
• CPC Class Codes: A61B 2018/1407 Loop
• CPC Class Codes: A61B 2018/1437 whereby the windings of the spiral touch each other such as to create a continuous surface
• CPC Class Codes: A61B 90/39 Markers, e.g. radio-opaque or breast lesions markers

Abstract

An improved radio-frequency based catheter system and method for ablating biological tissues within the body vessel of a patient comprises a radio-frequency (“RF”) generator for selectively generating high frequency energy in a deployable catheter having a RF co-axial transmission line with a hollow lumen, a RF antenna mounted on the distal portion of the catheter, and steering control lines in the lumen of the transmission line for steering catheter while being inserted into the body vessel and for deflecting the RF antenna to accommodate the contour of the body vessel where tissue ablation is needed. The RF generator having variable output frequency is adapted to generate and communicate RF energy to the RF antenna that minimizes reflected energy from the antenna-tissue interface. In application, the RF antenna establishes line of contact with the body vessel conformable to its internal contour to prescribe the precise tissue ablation pathway despite body vessel movements. The RF antenna is steered by the steering control lines to establish its body vessel conformation. The catheter system is energized and system senses the reflected RF power relative to its output power and adjusts the frequency of the power output to effect impedance match between the transmission line of the system and the tissue ablation load.

Claims

1. A method for biological tissue ablation, comprising:

generating a train of radio frequency (RF) energy pulses at an output frequency for transmission in a transmission line to a RF antenna deployable adjacent to a biological tissue load;

sensing the reflected signal and the forward signal of the RF energy pulses when the RF antenna is placed adjacent to the biological tissue; and

adjusting the output frequency of the RF energy pulses to effect a substantial match of the transmission line impedance with the load impedance.

2. The method of claim 1, wherein the substantial match of the transmission line impedance with the load impedance is characterized by minimum signal reflection.

3. The method of claim 2, wherein minimum signal reflection is characterized by a measurement of the voltage standing wave ratio (VSWR).

4. The method of claim 3, wherein the output frequency is adjusted such that the VSWR is below a preset threshold value.

5. The method of claim 1, further comprising amplifying the train of radio frequency (RF) energy pulses.

6. The method of claim 1, further comprising sampling the forward signal and the reflected signal using a bidirectional coupler.

7. The method of claim 1, further comprising using a catheter to deploy the RF antenna to the biological tissue load.

8. The method of claim 1, further comprising accepting user inputs from a user.

9. The method of claim 1, further comprising setting alarm conditions and outputting alarms to a user.

10. The method of claim 1, further comprising displaying inputs and outputs on a display.

11. A system for biological tissue ablation comprising:

means for generating a train of radio frequency (RF) energy pulses at an output frequency for transmission in a transmission line to a RF antenna deployable adjacent to a biological tissue load;

means for sensing the reflected signal and the forward signal of the RF energy pulses when the RF antenna is placed adjacent to the biological tissue to be ablated; and

means for adjusting the output frequency of the RF energy pulses to effect a substantial match of the transmission line impedance with the load impedance.

12. The system of claim 11, wherein the substantial match of the transmission line impedance with the load impedance is characterized by minimum signal reflection.

13. The system of claim 12, wherein minimum signal reflection is characterized by a measurement of the voltage standing wave ratio (VSWR).

14. The system of claim 13, wherein the output frequency is adjusted such that the VSWR is below a preset threshold value.

15. The system of claim 11, further comprising means for amplifying the train of radio frequency (RF) energy pulses.

16. The system of claim 11, further comprising means for sampling the forward signal and the reflected signal.

17. The system of claim 11, further comprising means for deploying the RF antenna to the biological tissue load.

18. The system of claim 11, further comprising means for accepting user inputs from a user.

19. The system of claim 11, further comprising means for setting alarm conditions and means for outputting alarms to a user.

20. The system of claim 11, further comprising means for displaying inputs and outputs.

21. A system for biological tissue ablation comprising:

an oscillator for generating a train of radio frequency (RF) energy pulses at an output frequency for transmission in a transmission line to a RF antenna deployable adjacent to a biological tissue load;

a bidirectional coupler for sensing the reflected signal and the forward signal of the RF energy pulses when the RF antenna is placed adjacent to the biological tissue to be ablated; and

a microcontroller for adjusting the output frequency of the RF energy pulses to effect a substantial match of the transmission line impedance with the load impedance.

22. The system of claim 21, further comprising a power amplifier for amplifying the train of RF energy pulses.

23. The system of claim 21, further comprising a pre-amplifier for pre-amplifying the RF frequency pulses prior to being amplified by the power amplifier.

24. The system of claim 21, further comprising a display coupled to the microcontroller.

25. The system of claim 21, further comprising an input control coupled to the microcontroller.

26. The system of claim 21, further comprising an alarm output coupled to the microcontroller.

27. The system of claim 21, wherein the RF antenna is deflectable.

28. The system of claim 21, wherein the RF antenna is shapeable.

29. The system of claim 21, further comprising a catheter to deploy the RF antenna to the biological tissue load.