Microwave thermometry for microwave ablation systems

• US 10,363,095 B2
• Filed: 08/21/2015
• Issued: 07/30/2019
• Est. Priority Date: 06/22/2012
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Covidien LP (Medtronic Plc)
• Inventors: Brannan, Joseph D.
• Primary Examiner(s): Stoklosa, Joseph A
• Assistant Examiner(s): Vierra, Rachel A.
• Application Number:
  US14/832,027
• Publication Number:
  US 20150351839A1
• Time in Patent Office: 1,439 Days
• CPC Class Codes: A61B 18/1815 using microwaves
• CPC Class Codes: A61B 2018/00577 Ablation
• CPC Class Codes: A61B 2018/00642 with feedback, i.e. closed loop control
• CPC Class Codes: A61B 2018/00666 using a threshold value
• CPC Class Codes: A61B 2018/00702 Power or energy
• CPC Class Codes: A61B 2018/00791 Temperature
• CPC Class Codes: A61B 2018/00821 measured by a thermocouple
• 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 2018/183 characterised by the type of antenna
• CPC Class Codes: A61B 5/01 Measuring temperature of body parts ; Diagnostic temperature sensing, e.g. for malignant or inflamed tissue clinical contact thermometers G01K13/20
• CPC Class Codes: A61B 5/0507 using microwaves or terahertz waves
• CPC Class Codes: G01J 5/0837 Microantennas, e.g. bow-tie
• CPC Class Codes: G01K 11/006 using measurement of the effect of a material on microwaves or longer electromagnetic waves, e.g. measuring temperature via microwaves emitted by the object G01K17/003, G01J5/00 take precedence; measuring the effect of a material on X-, gamma- or particle radiation G01K11/30
• CPC Class Codes: G01K 13/00 Thermometers specially adapted for specific purposes
• CPC Class Codes: G01K 7/02 using thermoelectric elements, e.g. thermocouples
• CPC Class Codes: H01R 13/66 Structural association with built-in electrical component coupling devices having concentrically or coaxially-arranged contacts H01R24/38

Abstract

A microwave ablation system incorporates a microwave thermometer that couples to a microwave transmission network connecting a microwave generator to a microwave applicator to measure noise temperature. The noise temperature is processed to separate out components the noise temperature including the noise temperature of the tissue being treated and the noise temperature of the microwave transmission network. The noise temperature may be measured by a radiometer while the microwave generator is generating the microwave signal or during a period when the microwave signal is turned off. The microwave ablation system may be configured as a modular system having one or more thermometry network modules that are connectable between a microwave applicator and a microwave generator. Alternatively, the modular system includes a microwave generator, a microwave applicator, and a microwave cable that incorporate a microwave thermometry network module.

Claims

1. A microwave ablation system comprising:

a microwave applicator including an antenna configured to deliver microwave energy to ablate tissue;

a microwave generator coupled to the microwave applicator via a transmission network and configured to generate a microwave signal and transmit the microwave signal to the antenna;

a radiometer configured to measure a noise temperature from a signal propagating through the transmission network;

a controller configured to turn off the microwave signal generated by the microwave generator for a predetermined period and to control the radiometer to measure the noise temperature during the predetermined period; and

at a first thermocouple configured to measure a first temperature of a cooling fluid and a second thermocouple configured to measure a second temperature of the cooling fluid, the radiometer configured to measure the noise temperature when the first temperature is substantially the same as the second temperature.

2. The microwave ablation system according to claim 1, wherein the controller is configured to control the microwave generator to generate a pulse-width modulated (PWM) microwave signal and to control the radiometer to measure the noise temperature during the off periods of the PWM microwave signal.

3. The microwave ablation system according to claim 1, wherein the controller is configured to control the radiometer to measure a noise temperature curve during the predetermined period.

4. The microwave ablation system according to claim 1,

wherein the second thermocouple is in thermal communication with the transmission network and measures, as the second temperature, a temperature of the transmission network.

5. The microwave ablation system according to claim 1, further comprising:

a fluid cooling system including an inlet for receiving the cooling fluid to cool the transmission network and an outlet for returning the cooling fluid from cooling the transmission network;

wherein the first thermocouple is in thermal communication with the cooling fluid flowing into the inlet and measures, as the first temperature, a temperature of the cooling fluid flowing into the inlet, and

wherein the second thermocouple is in thermal communication with the cooling fluid flowing out of the outlet and measures, as the second temperature, a temperature of the cooling fluid flowing out of the outlet.

6. The microwave ablation system according to claim 1, wherein to obtain the noise temperature of the transmission network, the controller is further configured to:

record a first noise temperature measured by the radiometer at the time that the microwave signal turns off;

record a second noise temperature measured by the radiometer at the time that the transmission network temperature reaches a predetermined temperature; and

calculate the difference between the first noise temperature and the second noise temperature to obtain the noise temperature of the transmission network.

7. The microwave ablation system according to claim 6, wherein the controller is further configured to control the microwave signal generated by the microwave generator based on the noise temperature of the transmission network.

8. A microwave ablation system comprising:

a microwave applicator including an antenna configured to deliver microwave energy to ablate tissue;

a microwave generator coupled to the microwave applicator via a transmission network and configured to generate a pulse-width modulated (PWM) microwave signal and transmit the PWM microwave signal to the antenna;

a radiometer configured to measure a noise temperature propagating through the transmission network; and

a controller configured to;

control the radiometer to measure the noise temperature during each of the off times of the PWM microwave signal;

determine a slope of magnitude of the noise temperature measurements;

record a noise temperature measurement when the slope of magnitude of the noise temperature measurements represents solely the temperature of the tissue;

determine whether the noise temperature measurements are greater than a predetermined noise temperature value; and

shut off the PWM microwave signal or reduce the duty cycle of the PWM microwave signal if it is determined that any one or more of the noise temperature measurements is greater than the predetermined noise temperature value.

9. The microwave ablation system according to claim 8, wherein to obtain the noise temperature of the transmission network, the controller is further configured to:

record a first slope of magnitude of the noise temperature measurements by the radiometer at a predetermined time;

record a second slope of magnitude of the noise temperature measurements by the radiometer at the time that a transmission network temperature reaches a predetermined temperature; and

calculate the difference between a first noise temperature and a second noise temperature based on the first slope of magnitude of the noise temperature measurements and the second slope of magnitude of the noise temperature measurements to obtain the noise temperature of the transmission network.

10. The microwave ablation system according to claim 8, wherein the controller is further configured to control the microwave signal generated by the microwave generator based on the noise temperature of the transmission network.

11. A microwave ablation system comprising:

a microwave applicator including an antenna configured to deliver microwave energy to ablate tissue;

a microwave generator coupled to the microwave applicator via a transmission network and configured to generate a microwave signal and transmit the microwave signal to the antenna;

a radiometer configured to measure noise temperature from a signal propagating through the transmission network;

a controller configured to turn off the microwave signal generated by the microwave generator for a predetermined period and to control the radiometer to measure noise temperature during the predetermined period; and

a thermocouple configured to measure a temperature of the transmission network;

wherein to obtain the noise temperature of the transmission network, the controller is configured to;

record a first noise temperature measured by the radiometer at a time that the microwave signal turns off,

record a second noise temperature measured by the radiometer at a time that the transmission network temperature reaches a predetermined temperature; and

calculate the difference between the first noise temperature and the second noise temperature to obtain the noise temperature of the transmission network.