System for controlling tissue ablation using temperature sensors

• US 10,729,485 B2
• Filed: 02/15/2019
• Issued: 08/04/2020
• Est. Priority Date: 12/16/2010
• Status: Active Grant

• Current Assignee: Biosense Webster Incorporated (Johnson & Johnson)
• Original Assignee: Biosense Webster Incorporated (Johnson & Johnson)
• Inventors: Govari, Assaf, Ephrath, Yaron, Altmann, Andres Claudio
• Primary Examiner(s): Layno, Carl H
• Assistant Examiner(s): Pahakis, Manolis
• Application Number:
  US16/277,809
• Publication Number:
  US 20190175247A1
• Time in Patent Office: 536 Days
• Field of Search: None
• CPC Class Codes: A61B 18/08 by means of electrically-heated probes
• CPC Class Codes: A61B 18/1206 Generators therefor
• CPC Class Codes: A61B 18/1233 with circuits for assuring patient safety
• CPC Class Codes: A61B 18/14 Probes or electrodes 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 18/20 using laser
• CPC Class Codes: A61B 18/24 with a catheter A61B18/26, A61B18/28 take precedence
• CPC Class Codes: A61B 2017/00088 using thermistors
• CPC Class Codes: A61B 2017/00092 using thermocouples
• CPC Class Codes: A61B 2017/00243 cardiac
• CPC Class Codes: A61B 2018/00023 closed, i.e. without wound contact by the fluid
• CPC Class Codes: A61B 2018/00351 Heart
• CPC Class Codes: A61B 2018/00577 Ablation
• CPC Class Codes: A61B 2018/00648 using more than one sensed parameter
• CPC Class Codes: A61B 2018/00702 Power or energy
• CPC Class Codes: A61B 2018/00779 Power or energy
• CPC Class Codes: A61B 2018/00791 Temperature
• CPC Class Codes: A61B 2034/2053 Tracking an applied voltage gradient
• CPC Class Codes: A61B 2034/2072 Reference field transducer attached to an instrument or patient
• CPC Class Codes: A61B 2090/374 NMR or MRI
• CPC Class Codes: A61B 2090/378 : using ultrasound
• CPC Class Codes: A61B 2090/3782 : transmitter or receiver in catheter or minimal invasive instrument
• 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 5/055 : involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
• CPC Class Codes: A61N 7/022 : intracavitary

Abstract

Body tissue ablation is carried out by inserting a probe into a body of a living subject, urging the probe into contact with a tissue in the body, generating energy at a power output level, and transmitting the generated energy into the tissue via the probe. While transmitting the generated energy the ablation is further carried out by determining a measured temperature of the tissue and a measured power level of the transmitted energy, and controlling the power output level responsively to a function of the measured temperature and the measured power level. Related apparatus for carrying out the ablation is also described.

Claims

1. A method for ablating body tissue, comprising:

inserting a probe into a body of a subject, the probe having one or more ablation electrodes;

urging the probe into the body such that the one or more ablation electrodes contact with a tissue in the body;

generating ablative energy using one or more ablation power generators at a power output level at a level of current;

transmitting the generated ablative energy into the tissue via the one or more ablation electrodes of the probe;

determining a measured temperature of the tissue by performing magnetic resonance imaging (MRI) concurrently with the transmitting of the generated ablative energy, the MRI comprising acquiring MRI signals from one or more field magnets, enhancing the MRI signals using a reconstruction processor to yield enhanced MRI signals, and determining the measured temperature from the enhanced MRI signals using the reconstruction processor;

determining a measured power level of the generated ablative energy during the transmitting of the generated ablative energy into the tissue;

determining a power deviation by comparing a difference between the measured power level and a predetermined target power level;

determining a temperature deviation by comparing a difference between the measured temperature of the tissue and a predetermined target temperature;

calculating a target current value from a control function, wherein the control function is;

2. The method according to claim 1, wherein the generated energy is radiofrequency energy.

3. The method according to claim 1, wherein the controlling the power output level further comprises restricting or terminating the generation of ablative energy when a predetermined ablation condition is met, the predetermined condition comprising:

power required for generating ablative energy exceeds available power;

or

a change in impedance that exceeds a predetermined impedance value;

or

a change in temperature that exceeds a predetermined maximum temperature;

or

failure to exceed a predetermined minimum temperature;

or

power output exceeding the target power level;

or

elapsed ablation time exceeding a predetermined maximum ablation time;

or

violating a predetermined minimum flow rate.

4. The method according to claim 1, wherein the controlling the power output level further comprises terminating the generation of ablative energy when a predetermined ablation condition is met, the predetermined ablation condition comprising:

a change in impedance that exceeds a predetermined impedance value;

or

a change in temperature that exceeds a predetermined maximum temperature;

or

failure to exceed a predetermined minimum temperature;

power output exceeding the target power level;

or

elapsed ablation time exceeding a predetermined maximum ablation time;

or

violating a predetermined minimum flow rate.

5. The method according to claim 1, wherein the controlling the power output level further comprises terminating the generation of ablative energy when a predetermined ablation condition is met, the predetermined ablation condition comprising:

power required for generating ablative energy exceeds available power

the MRI comprising acquiring MRI signals from one or more field magnets, enhancing the MRI signals using a reconstruction processor to yield enhanced MRI signals, and determining the measured temperature from the enhanced MRI signals using the reconstruction processor.

6. The method according to claim 1, wherein the reconstruction processor comprises a peak calculation module and a temperature analyzer module, wherein:

the enhancing the MRI signals to yield enhanced MRI signals comprises using the peak calculation module; and

the determining the measured temperature from the enhanced MRI signals comprises analyzing the enhanced MRI signals using the temperature analyzer module to yield one or more thermometry signals indicative of the measured temperature.

7. The method according to claim 1, wherein the measured temperature is an electrode temperature.

8. The method according to claim 1, wherein the determining the power deviation, determining the temperature deviation, calculating the target current value, and controlling the power output level are performed iteratively.

9. The method according to claim 8, wherein the determining the power deviation, determining the temperature deviation, calculating the target current value, and controlling the power output level are iterated 10 times per second.

10. The method according to claim 8, wherein the determining the power deviation, determining the temperature deviation, calculating the target current value, and controlling the power output level are iterated 5-50 times per second.

11. The method according to claim 1, wherein the controlling the power output level is performed by limiting an increment or decrement thereof so as not to exceed a predetermined limiting condition, wherein the limiting condition is selected from the group consisting of a maximum current, a minimum electrode temperature, a maximum electrode temperature, a maximum temperature of the tissue, and a maximum power demand.

12. An ablation system, comprising:

a catheter having a distal portion for insertion into a body and configured to bring the distal portion into contact with a tissue in the body;

one or more power generators for generating ablative energy at a power output level having a level of current;

an ablation element disposed on the distal portion of the catheter, configured to accept the ablative energy from the one or more power generators via the catheter and to conduct the ablative energy to the tissue for ablation of the tissue;

one or more magnetic resonance imaging (MRI) field magnets configured to generate MRI signals;

a reconstruction processor operative for determining a measured temperature of the tissue from the MRI signals, the reconstruction processor comprising;

a peak calculation module configured to enhance MRI signals received from the field magnets to yield enhanced MRI signals, and

a temperature analyzer configured to analyze the enhanced MRI signals and generate thermometry signals indicative of the measured temperature;

a system controller comprising;

an ablation module configured to receive the thermometry signals from the reconstruction processor and to receive power level signals from the one or more power generators, and

a processing unit operative to determine a measured power level of the ablative energy conducted through the one or more ablation elements, the processing unit configured to;

determine a power deviation by comparing a difference between the measured power level and a predetermined target power level;

determine a temperature deviation by comparing a difference between the measured temperature of the tissue and a predetermined target temperature;

calculate a target current value from a control function, wherein the control function is;

13. The ablation system according to claim 12, wherein the ablation element comprises one or more ablation electrodes.

14. The ablation system according to claim 12, wherein the measured temperature is a temperature of the ablation element.

15. The ablation system according to claim 12, wherein the ablation module comprises a respective port for each of the one or more power generators, and the ablation module is configured to measure the power level signals from each of the one or more ablation power generators via the respective ports.

16. The ablation system according to claim 12, wherein the determining the power deviation, determining the temperature deviation, calculating the target current value, and controlling the power output level are performed iteratively.

17. The ablation system according to claim 16, wherein the determining the power deviation, determining the temperature deviation, calculating the target current value, and controlling the power output level are iterated 10 times per second.

18. The ablation system according to claim 12, wherein the determining the power deviation, determining the temperature deviation, calculating the target current value, and controlling the power output level are iterated 5-50 times per second.

19. The ablation system according to claim 12, wherein the controlling the power output level is performed by limiting an increment or decrement thereof so as not to exceed a predetermined limiting condition, wherein the limiting condition is selected from the group consisting of a maximum current, a minimum electrode temperature, a maximum electrode temperature, a maximum temperature of the tissue, and a maximum power demand.