DETERMINING ABSENCE OF CONTACT FOR A CATHETER

• US 20150066021A1
• Filed: 08/27/2013
• Published: 03/05/2015
• Est. Priority Date: 08/27/2013
• Status: Active Grant

• Current Assignee: Biosense Webster Israel Ltd. (Johnson & Johnson)
• Original Assignee: Biosense Webster Israel Ltd. (Johnson & Johnson)
• Inventors: Gliner, Vadim, Govari, Assaf
• Granted Patent: US 9,974,608 B2
• Time in Patent Office: Days
• US Class Current: 606/41
• 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, 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 a succession of phase shifts of the current relative to a fixed reference;

verifying that a cardinality of the measured phase shifts failing below a predetermined threshold increases over a predetermined time period; and

calibrating a zero-force point for the force sensor according to the force measured by the force sensor during 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.

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

10. Apparatus, 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 a succession of phase shifts of the current relative to a fixed reference,

verify that a cardinality of the measured phase shifts falling below a predetermined threshold increases over a predetermined time period, and

calibrate 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, 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.

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 measuring the succession or phase shifts comprises comparing the current versus time waveform with a voltage versus time waveform generated by the current.

17. The apparatus according to claim 10, wherein calibrating the zero-force point comprises the processor automatically setting the zero-force point as the force measured by the force sensor.

18. The apparatus according claim 10, wherein calibrating the zero-force point comprises an operator of the apparatus manually setting the zero-force point as the force measured by the force sensor.