# US 10,441,192 B2 · Impedance shift detection

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- Number: US 10,441,192 B2
- Document ID: US10441192B2
- Status: Granted
- Kind: B2
- Application number: 15/649,839
- Filed: 2017-07-14
- Published: 2018-01-18
- Granted: 2019-10-15
- Earliest claimed: 2016-07-15
- Assignees: St. Jude Medical, Cardiology Division, Inc.
- Applicants: St. Jude Medical, Cardiology Division, Inc.
- Inventors: Cable Thompson; Anthony D. Hill
- Web page: https://patentgrep.com/patent/US10441192B2

## CPC

- A61B 5/061: {Determining position of a probe within the body employing means separate from the probe, e.g. sensing internal probe position employing impedance electrodes on the surface of the body (A61B1/00158 takes precedence)}
- A61B 5/062: {using magnetic field}
- A61B 5/063: {using impedance measurements}
- A61B 5/064: {using markers (A61B5/062 takes precedence)}
- A61B 5/066: {Superposing sensor position on an image of the patient, e.g. obtained by ultrasound or x-ray imaging}
- A61B 2017/00694: {with means correcting for movement of or for synchronisation with the body}
- A61B 2017/00725: {Calibration or performance testing}
- A61B 2034/2051: {Electromagnetic tracking systems}
- A61B 2034/2053: {Tracking an applied voltage gradient}
- A61B 2090/0807: {Indication means}
- A61B 2090/0812: {indicating loosening or shifting of parts of an instrument, signaling maladjustment of parts}
- A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D)

## Abstract

A pre-shift set of fiducials each including a pre-shift fiducial impedance location and a pre-shift fiducial magnetic location can be determined. The pre-shift fiducial impedance locations and the pre-shift fiducial magnetic location are associated with a medical device. A post-shift set of fiducials each including a post-shift fiducial impedance location and a post-shift fiducial magnetic location can be determined. The post-shift fiducial impedance locations and the post-shift fiducial magnetic locations are associated with the medical device. A pre-shift transformation can be fit to the pre-shift set of fiducials and a post-shift transformation can be fit to the post-shift set of fiducials. A determination can be made whether the pre-shift transformation differs from the post-shift transformation. An indication that an impedance shift has occurred between the pre-shift set of fiducials and the post-shift set of fiducials can be generated based on the difference between the pre-shift transformation and the post-shift transformation.

## Claims

### Claim 1

A computer implemented method for detection of an impedance shift, comprising:
determining a pre-shift set of fiducials that includes for each fiducial a pre-shift fiducial impedance location and a pre-shift fiducial magnetic location, the pre-shift fiducial impedance locations and the pre-shift fiducial magnetic locations being associated with a medical device;
determining a post-shift set of fiducials that includes for each fiducial a post-shift fiducial impedance location and a post-shift fiducial magnetic location, the post-shift fiducial impedance locations and the post-shift fiducial magnetic locations being associated with the medical device;
fitting a pre-shift transformation to the pre-shift set of fiducials and a post-shift transformation to the post-shift set of fiducials;
determining that a distance, at a current location of the medical device, between the pre-shift transformation and the post-shift transformation exceeds a threshold distance;
determining a statistical confidence that the distance exceeds the threshold distance;
determining that the statistical confidence exceeds a threshold confidence;
determining that the impedance shift has occurred based on the distance exceeding the threshold distance and the statistical confidence exceeding the threshold confidence; and
generating an indication that the impedance shift has occurred.

### Claim 2 (depends on 1)

The method of claim 1, wherein the particular statistical confidence is user configurable.

### Claim 3 (depends on 1)

The method of claim 1, wherein the threshold distance is user configurable.

### Claim 4 (depends on 1)

The method of claim 1, wherein the pre-shift set of fiducials is collected during a pre-shift time period.

### Claim 5 (depends on 4)

The method of claim 4, wherein the pre-shift time period excludes a most recent time period.

### Claim 6 (depends on 1)

The method of claim 1, wherein the post-shift set of fiducials is collected during a post-shift time period.

### Claim 7 (depends on 6)

The method of claim 6, wherein the post-shift time period includes a time period that abuts a current time.

### Claim 8 (depends on 1)

The method of claim 1, wherein the pre-shift set of fiducials is filtered for bad status bits.

### Claim 9 (depends on 1)

The method of claim 1, wherein the pre-shift set of fiducials is gated for a particular respiratory phase.

### Claim 10 (depends on 1)

The method of claim 1, further comprising providing a notification of the impedance shift to a user via a user interface.

### Claim 11 (depends on 1)

The method of claim 1, further comprising determining a time at which the impedance shift has occurred.

### Claim 12 (depends on 11)

The method of claim 11, further comprising preventing an additional impedance shift from being reported within a defined time after the time at which the impedance shift has occurred.

### Claim 13

A system for determining a detection of an impedance shift, comprising:
a computing device comprising processor resources and memory resources, the memory resources storing computer-readable instructions that, when executed by the processor resources, cause the processor resources to:
determine a pre-shift set of fiducials that includes for each fiducial a pre-shift fiducial impedance location and a pre-shift fiducial magnetic location, the pre-shift fiducial impedance locations and the pre-shift fiducial magnetic locations being associated with a medical device;
determine a post-shift set of fiducials that includes for each fiducial a post-shift fiducial impedance location and a post-shift fiducial magnetic location, the post-shift fiducial impedance locations and the post-shift fiducial magnetic locations being associated with the medical device;
fit a pre-shift transformation to the pre-shift set of fiducials and a post-shift transformation to the post-shift set of fiducials;
determine that a distance, at a current location of the medical device, between the pre-shift transformation and the post-shift transformation exceeds a threshold distance;
determine a statistical confidence that the distance exceeds the threshold distance;
determine that the statistical confidence exceeds a threshold confidence;
determine that an impedance shift has occurred, based on the distance exceeding the threshold distance and the statistical confidence exceeding the threshold confidence; and
generate the indication that the impedance shift has occurred.

### Claim 14 (depends on 13)

The system of claim 13, wherein the pre-shift set of fiducials associated with the medical device include a pre-shift fiducial impedance location and a pre-shift fiducial magnetic location.

### Claim 15 (depends on 13)

The system of claim 13, wherein the post-shift set of fiducials associated with the medical device include a post-shift fiducial impedance location and a post-shift fiducial magnetic location.

### Claim 16 (depends on 13)

The system of claim 13, wherein the current location of the medical device is determined based on a signal from a magnetic position sensor disposed on the medical device.