ZERO-DRIFT DETECTION AND CORRECTION IN CONTACT FORCE MEASUREMENTS

• US 20120108988A1
• Filed: 11/03/2010
• Published: 05/03/2012
• Est. Priority Date: 11/03/2010
• Status: Active Grant

• Current Assignee: Biosense Webster Incorporated (Johnson & Johnson)
• Original Assignee: Biosense Webster Incorporated (Johnson & Johnson)
• Inventors: Turgeman, Aharon, Katz, Natan, Ludwin, Doron Moshe, Givaty, Galia
• Granted Patent: US 8,979,772 B2
• Time in Patent Office: Days
• US Class Current: 600/508
• 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 2018/00357 Endocardium
• CPC Class Codes: A61B 2034/2051 Electromagnetic tracking systems
• CPC Class Codes: A61B 2090/064 for measuring force, pressure or mechanical tension
• CPC Class Codes: A61B 2090/065 for measuring contact or contact pressure

Abstract

A method, consisting of inserting a probe having a force sensor into a body cavity of a patient, and receiving from the force sensor a plurality of measurements, each of the measurements indicative of a force applied to the force sensor. The method further includes detecting that the measurements received over a period of time of at least a specified duration have not varied by more than a predefined amount, and setting a baseline of the force sensor, for use in further measurements, to a value based on the measurements received during the period.

Claims

1. A method, comprising:

inserting a probe having a force sensor into a body cavity of a patient;

receiving from the force sensor a plurality of measurements, each of the measurements indicative of a force applied to the force sensor;

detecting that the measurements received over a period of time of at least a specified duration have not varied by more than a predefined amount; and

setting a baseline of the force sensor, for use in further measurements, to a value based on the measurements received during the period.

2. The method according to claim 1, wherein the probe comprises a cardiac catheter.

3. The method according to claim 1, wherein the body cavity comprises a chamber of a heart.

4. The method according to claim 1, and comprising:

applying a filter to the measurements upon detecting that the measurements have not varied by more than the predefined amount, the filter being configured to isolate filtered measurements within a specific frequency range; and

setting the baseline upon detecting that the filtered measurements do not indicate contact between the probe and the body cavity tissue.

5. The method according to claim 1, wherein setting the baseline comprises calculating a function based on the received measurements.

6. The method according to claim 5, wherein the function comprises an average of the received measurements.

7. The method according to claim 1, wherein the specified duration comprises at least a single cardiac cycle.

8. The method according to claim 1, wherein the predefined amount is greater than a noise variation of the force sensor.

9. The method according to claim 1, and comprising evaluating the force applied by a distal tip of the probe to a surface of the body cavity by subtracting the baseline from the received measurements, upon detecting that the received measurements vary by more than the predefined amount.

10. Apparatus, comprising:

a probe, configured for insertion into a body cavity of a patient and comprising a force sensor for measuring a force applied to the force sensor; and

a processor, which is configured to receive a plurality of measurements from the force sensor, each of the measurements indicative of the force, to detect that the measurements received over a period of time of at least a specified duration have not varied by more than a predefined amount, and to set a baseline of the force sensor, for use in further measurements, to a value based on the measurements received during the period.

11. The apparatus according to claim 10, wherein the probe comprises a cardiac catheter.

12. The apparatus according to claim 10, wherein the body cavity comprises a chamber of a heart.

13. The apparatus according to claim 10, wherein the processor is configured to apply a filter to the measurements upon detecting that the measurements have not varied by more than the predefined amount, the filter being configured to isolate filtered measurements within a specific frequency range, and to set the baseline upon detecting that the filtered measurements do not indicate contact between the probe and the body cavity tissue.

14. The apparatus according to claim 13, wherein the filter comprises a band-pass filter.

15. The apparatus according to claim 10, wherein the processor is configured to set the baseline by calculating a function based on the received measurements.

16. The apparatus according to claim 15, wherein the function comprises an average of the received measurements.

17. The apparatus according to claim 10, wherein the specified duration comprises at least a single cardiac cycle.

18. The apparatus according to claim 10, wherein the predefined amount is greater than a noise variation of the force sensor.

19. The apparatus according to claim 10, wherein the processor is configured to evaluate the force applied by a distal tip of the probe to a surface of the body cavity by subtracting the baseline from the received measurements, upon detecting that the received measurements vary by more than the predefined amount.

20. A computer software product, operated in conjunction with a medical probe that includes a force sensor for measuring a force applied to the force sensor, the product comprising a non-transitory computer-readable medium, in which program instructions are stored, which instructions, when read by a computer, cause the computer to receive a plurality of measurements from the force sensor, each of the measurements indicative of the force, to detect that the measurements received over a period of time of at least a specified duration have not varied by more than a predefined amount, and to set a baseline of the force sensor, for use in further measurements, to a value based on the measurements received during the period.