Determining absence of contact for a catheter

• US 9,974,608 B2
• Filed: 08/27/2013
• Issued: 05/22/2018
• Est. Priority Date: 08/27/2013
• Status: Active Grant

• Current Assignee: Biosense Webster Incorporated (Johnson & Johnson)
• Original Assignee: Biosense Webster Incorporated (Johnson & Johnson)
• Inventors: Gliner, Vadim, Govari, Assaf
• Primary Examiner(s): DVORAK, LINDA C
• Assistant Examiner(s): Ouyang, Bo
• Application Number:
  US14/010,679
• Publication Number:
  US 20150066021A1
• Time in Patent Office: 1,729 Days
• 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 2017/00725 Calibration or performance testing
• CPC Class Codes: A61B 2018/00577 Ablation
• CPC Class Codes: A61B 2018/00869 Phase
• CPC Class Codes: A61B 2018/00892 Voltage
• CPC Class Codes: A61B 2018/00904 Automatic detection of target tissue
• CPC Class Codes: A61B 2018/00964 Features of probes
• CPC Class Codes: A61B 2090/065 for measuring contact or contact pressure
• CPC Class Codes: A61B 2560/0223 of calibration, e.g. protocols for calibrating sensors
• CPC Class Codes: A61B 5/0538 invasively, e.g. using a catheter
• CPC Class Codes: A61B 5/6885 Monitoring or controlling sensor contact pressure

Abstract

A method, including injecting a current between an electrode of a catheter and tissue in proximity to the catheter, the catheter having a force sensor configured to measure a force between the catheter and the tissue. The method further includes measuring a succession of phase shifts of the current relative to a fixed reference and verifying that a cardinality of the measured phase shifts falling below a predetermined threshold increases over a predetermined time period. A zero-force point for the force sensor is calibrated according to the force measured by the force sensor during the predetermined time period.

Claims

1. A method for measuring force while compensating for drift, comprising:

injecting a current between an electrode of a catheter and tissue in proximity to the catheter, the catheter comprising a force sensor configured to measure a force between the catheter and the tissue;

measuring in succession, a plurality of phase shifts of the current relative to a fixed reference;

populating one or more bins of a histogram of the phase shifts;

determining a condition for zeroing by verifying that a cardinality of the measured phase shifts in a particular bin falling below a predetermined threshold increases over a predetermined time period; and

compensating for drift during the condition for zeroing by calibrating a zero-force point for the force sensor according to the force measured by the force sensor during the predetermined time period.

2. The method according to claim 1, wherein the cardinality is a strictly increasing function over the predetermined time period.

3. The method according to claim 1, wherein the succession of phase shifts comprises a preset number of the measured phase shifts.

4. The method according to claim 1, wherein the measured phase shifts falling below a predetermined threshold comprise phase shifts within a preset interval of possible values of the phase shifts.

5. The method according to claim 4, and comprising, prior to verifying the cardinality of the measured phase shifts, determining values for the preset interval in a learning phase of the method.

6. The method according to claim 1, and comprising determining the fixed reference from a current versus time waveform generated by the current.

7. The method according to claim 6, wherein measuring the succession of phase shifts comprises comparing the current versus time waveform with a voltage versus time waveform generated by the current.

8. The method according to claim 1, wherein calibrating the zero-force point comprises automatically setting the zero-force point as the force measured by the force sensor.

9. The method according to claim 1, wherein calibrating the zero-force point comprises manually setting the zero-force point as the force measured by the force sensor.

10. Apparatus for measuring force while compensating for drift, comprising:

a catheter comprising an electrode and a force sensor configured to measure a force between the catheter and tissue in proximity to the catheter; and

a processor configured to;

inject a current between the electrode and the tissue,

measure, in succession, a plurality of phase shifts of the current relative to a fixed reference,

populate one or more bins of a histogram of the plurality of phase shifts,

determine a condition for zeroing by verifying that a cardinality of the measured phase shifts falling below a predetermined threshold increases over a predetermined time period, and

compensate for drift during the condition for zeroing by calibrating a zero-force point for the force sensor according to the force measured by the force sensor during the predetermined time period.

11. The apparatus according to claim 10, wherein the cardinality is a strictly increasing function over the predetermined time period.

12. The apparatus according to claim 10, wherein the succession of phase shifts comprises a preset number of the measured phase shifts.

13. The apparatus according to claim 10, wherein the measured phase shifts falling below a predetermined threshold comprise phase shifts within a preset interval of possible values of the phase shifts.

14. The apparatus according to claim 13, wherein the processor is further configured to determine values for the preset interval in a learning phase of the method prior to verifying the cardinality of the measured phase shifts.

15. The apparatus according to claim 10, wherein the processor is configured to determine the fixed reference from a current versus time waveform generated by the current.

16. The apparatus according to claim 15, wherein the processor is further configured to measure the succession of phase shifts comparing the current versus time waveform with a voltage versus time waveform generated by the current.

17. The apparatus according to claim 10, wherein the processor is further configured to calibrate the zero-force point the processor automatically setting the zero-force point as the force measured by the force sensor.

18. The apparatus according to claim 10, wherein the processor is further configured to calibrate the zero-force point upon an operator of the apparatus manually setting the zero-force point as the force measured by the force sensor.