Flow Rate Monitor for Fluid Cooled Microwave Ablation Probe

• US 20110077637A1
• Filed: 09/29/2009
• Published: 03/31/2011
• Est. Priority Date: 09/29/2009
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Vivant Medical, Inc. (Johnson Controls International plc)
• Inventors: Brannan, Joseph D.
• Granted Patent: US 8,556,889 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: A61B 2018/00136 with polymer
• CPC Class Codes: A61B 2018/00178 Electrical connectors
• CPC Class Codes: A61B 2018/00577 Ablation
• CPC Class Codes: A61B 2018/00636 Sensing and controlling the application of energy
• CPC Class Codes: A61B 2018/00642 with feedback, i.e. closed loop control
• CPC Class Codes: A61B 2018/00684 using lookup tables
• CPC Class Codes: A61B 2018/00702 Power or energy
• CPC Class Codes: A61B 2018/00744 Fluid flow
• CPC Class Codes: A61B 2018/00863 Fluid flow
• CPC Class Codes: A61B 2018/0094 Types of switches or controllers
• CPC Class Codes: A61B 2018/00988 Means for storing information, e.g. calibration constants, or for preventing excessive use, e.g. usage, service life counter
• CPC Class Codes: A61B 2018/1823 Generators therefor
• CPC Class Codes: A61B 2018/1838 Dipole antennas
• CPC Class Codes: A61B 2018/1853 Monopole antennas
• CPC Class Codes: A61B 2018/1869 with an instrument interstitially inserted into the body, e.g. needles
• CPC Class Codes: A61B 2090/062 penetration depth
• CPC Class Codes: A61B 2090/064 : for measuring force, pressure or mechanical tension
• CPC Class Codes: A61B 90/06 : Measuring instruments not otherwise provided for

Abstract

A microwave ablation system includes an antenna assembly configured to deliver microwave energy from a power source to tissue and a coolant source operably coupled to the power source and configured to selectively provide fluid to the antenna assembly via a fluid path. The system also includes a controller operably coupled to the power source and a sensor operably coupled to the fluid path and the controller. The sensor is configured to detect fluid flow through the fluid path and the controller is configured to control the energy source based on the detected fluid flow.

Claims

1. A microwave ablation system, comprising:

an antenna assembly configured to deliver microwave energy from a power source to tissue;

a coolant source operably coupled to the power source and configured to selectively provide fluid to the antenna assembly via a fluid path;

a controller operably coupled to the power source; and

at least one sensor operably coupled to the fluid path and the controller, the at least one sensor configured to detect fluid flow through the fluid path, wherein the controller is configured to control the energy source based on the detected fluid flow.

2. A microwave ablation system according to claim 1, wherein the controller is configured to modify the energy source output based on the detected fluid flow.

3. A microwave ablation system according to claim 1, wherein the at least one sensor includes a capacitive device configured to detect fluid flow through the fluid path based on a capacitance of the capacitive device.

4. A microwave ablation system according to claim 3, wherein fluid flow through the fluid path is detected based on a comparison between the capacitance of the capacitive device and a predetermined range.

5. A microwave ablation system according to claim 3, wherein the capacitance of the capacitive device is based on a change of permittivity of fluid flow through the fluid path.

6. A microwave ablation system according to claim 3, wherein the capacitive device is a parallel plate capacitor including a pair of capacitive plates.

7. A microwave ablation system according to claim 6, wherein at least a portion of the fluid path is disposed between the capacitive plates of the parallel plate capacitor.

8. A microwave ablation system according to claim 7, wherein the fluid flow through the fluid path operates as a dielectric between the capacitive plates.

9. A microwave ablation system according to claim 7, wherein capacitance of the capacitive device is calculated based on at least one of a distance between the capacitive plates, an area of the capacitive plates, and a permittivity of the dielectric between the capacitive plates.

10. A microwave ablation system according to claim 1, wherein the at least one sensor is disposed in a resonant feedback loop with an amplifier configured to generate output to a band pass filter centered on a resonant frequency consistent with fluid flow through the fluid path.

11. A microwave ablation system according to claim 10, wherein output of the band pass filter is sampled to indicate fluid flow through the fluid path to the controller.

12. A microwave ablation system according to claim 1, wherein the fluid path comprises a conduit having at least one of an inflow lumen and an outflow lumen.

13. A microwave ablation system according to claim 1, wherein fluid flow through the fluid path is indicative of the presence of at least one of fluid, air, air bubbles, and steam within the fluid path.

14. A microwave ablation system, comprising:

an antenna assembly configured to deliver microwave energy from a power source to tissue;

a coolant source operably coupled to the power source and configured to selectively provide fluid to the antenna assembly via a fluid path;

a controller operably coupled to the power source; and

a capacitive device operably coupled to the fluid path and the controller, the capacitive device configured to detect fluid flow through the fluid path based on a capacitance of the capacitive device, wherein the controller is configured to control the energy source based on the detected fluid flow.

15. A microwave ablation system according to claim 14, wherein the controller is configured to control the energy source based on a comparison between the capacitance of the capacitive device and a predetermined range.

16. A microwave ablation system according to claim 14, wherein the capacitance of the capacitive device is based on a change of permittivity of the fluid flow through the fluid path.

17. A microwave ablation system according to claim 14, wherein the capacitive device is a parallel plate capacitor including a pair of capacitive plates.

18. A method of detecting fluid flow through a microwave ablation system, the method comprising the steps of:

delivering microwave energy from a power source to tissue via an antenna assembly;

supplying fluid from a coolant source to the antenna assembly via a fluid path;

detecting a capacitance of a capacitive device operably coupled to the fluid path;

comparing the detected capacitance to a predetermined range; and

modifying output of energy from the energy source based on the comparison between the detected capacitance and the predetermined range.

19. The method according to claim 18, wherein the capacitive device comprises a dielectric disposed between a pair of parallel capacitive plates.

20. The method according to claim 19, wherein the capacitance of the capacitive device is based on a permittivity of the dielectric disposed between the capacitive plates.