Navigational reference dislodgement detection method and system

Patent metadata

Field	Value
Publication number	US-9585586-B2
Application number	US-97225310-A
Country	US
Kind code	B2
Filing date	Dec 17, 2010
Priority date	Dec 29, 2006
Publication date	Mar 7, 2017
Grant date	Mar 7, 2017

Abstract

A method of detecting dislodgement of a navigational reference for a localization system includes securing a reference catheter, including at least one reference localization element, at an initial reference location within a localization field. The positions of one or more of the reference localization elements are monitored for a perceived displacement that suggests that the reference catheter has become dislodged from the initial reference location (e.g., a displacement above a certain threshold, such as about 4 mm). The direction of this perceived displacement may then be further analyzed (e.g., compared to a predicted or most likely direction of displacement) to determine whether there has been an actual dislodgement of the reference catheter, and, if so, an appropriate signal (e.g., an audible or visual warning) may be generated. Upon dislodgement, guidance may be provided to aid the practitioner in restoring the reference catheter to its initial location.

First claim

What is claimed is:

1. A method of detecting dislodgement of a navigational reference within a localization field, the method comprising:
placing a reference catheter including at least one reference localization element within a localization field;
securing the reference catheter at an initial reference location within the localization field;
computing a slow-moving average location of the at least one reference localization element;
computing a fast-moving average location of the at least one reference localization element;
computing a distance between the slow- and fast-moving average locations of the at least one reference localization element;
comparing the computed distance to a dislodgement threshold; and
determining that a dislodgement of the reference catheter from the initial reference location has occurred; and
generating a signal indicative of the dislodgement of the reference catheter from the initial reference location.

2. The method according to claim 1 , wherein the dislodgement threshold is about 4 mm.

3. The method according to claim 1 , further comprising, if the computed distance exceeds the dislodgement threshold:
for the at least one reference localization element:
computing a vector connecting the slow- and fast-moving average locations of the respective reference localization element at a point in time when the computed distance between the slow- and fast-moving average locations of the respective reference localization element exceeded the dislodgement threshold;
determining an axis of the reference catheter proximate the respective reference localization element at the point in time when the computed distance between the slow- and fast-moving average locations of the respective reference localization element exceeded the dislodgement threshold; and
computing an angle between the computed vector and the axis of the reference catheter proximate the respective reference localization element,

thereby computing at least one angle associated with the at least one reference localization element; and
analyzing the at least one angle for an indication that the reference catheter has dislodged from the initial reference location.

4. The method according to claim 3 , wherein the step of analyzing the at least one angle for an indication that the reference catheter has dislodged from the initial reference location comprises:
determining a count of angles exceeding a sharp angle threshold; and
comparing the count of angles to a count threshold.

5. The method according to claim 3 , wherein the axis of the reference catheter proximate the respective reference localization element is defined by a line segment connecting the respective reference localization element to a neighboring reference localization element.

6. The method according to claim 1 , wherein the fast-moving average location of the at least one reference localization element is computed with a filter time constant of about 12 seconds.

7. The method according to claim 1 , wherein at least one of the slow- and fast-moving average locations of the at least one reference localization element is computed using a filter selected from the group consisting of: exponential moving average filters, moving average filters, infinite impulse response filters, finite impulse response filters, and any combinations thereof.

8. The method according to claim 1 , further comprising providing guidance to a user to help re-position and secure the reference catheter proximate the initial reference location.

9. The method according to claim 1 , further comprising:
defining a new stable location of the reference catheter;
calculating a reference adjustment to compensate for any change in position of the reference catheter between the initial reference location and the new stable location; and
using the reference adjustment to adjust localization element position measurements made after the dislodgement from the initial reference location.

10. A method of detecting dislodgement of a navigational reference within a non-ionizing localization field, the method comprising:
securing a reference catheter including a plurality of reference localization elements at an initial reference location within the localization field;
detecting a perceived displacement of the reference catheter from the initial reference location;
analyzing a direction of the perceived displacement to determine whether there has been a dislodgement of the reference catheter from the initial reference location; and
generating a signal indicating the dislodgement of the reference catheter from the initial reference location.

11. The method according to claim 10 , further comprising:
calculating a reference adjustment to compensate for any change in position of the reference catheter after the dislodgement from the initial reference location; and
using the reference adjustment to adjust localization element position measurements made after the dislodgement from the initial reference location.

12. The method according to claim 10 , wherein the detecting step comprises comparing a magnitude of a perceived displacement of at least some of the plurality of reference localization elements to a dislodgement threshold.

13. The method according to claim 10 , wherein the analyzing step comprises comparing a direction of a perceived displacement of at least some of the plurality of reference localization elements to an anticipated dislodgement direction.

14. The method according to claim 10 , further comprising providing guidance to a user to help re-position and secure the reference catheter proximate the initial reference location.

15. A localization system, comprising:
a plurality of localization field generators;
a reference catheter including a plurality of reference localization elements; and
a reference catheter dislodgement processor that monitors for a dislodgement of the reference catheter from an initial reference location based, at least in part, on a difference between a slow-moving average location and a fast-moving average location of at least one of the plurality of reference localization elements on the reference catheter.

16. The localization system according to claim 15 , wherein the reference catheter dislodgement processor:
compares the difference between the slow-moving average location and the fast-moving average location of at least some of the plurality of reference localization elements to a dislodgement threshold, and, if the difference exceeds the dislodgement threshold:
computes, for at least some of the plurality of reference localization elements, an angle between a vector connecting the slow- and fast-moving average locations of the reference localization element and an axis of the reference catheter proximate the reference localization element, thereby computing a plurality of angles;
determines a count of angles exceeding a sharp angle threshold; and
compares the count of angles to a count threshold to determine whether the reference catheter has dislodged from the initial reference location.

17. The localization system according to claim 15 , further comprising a reference adjustment processor that:
calculates a reference adjustment to compensate for any change in position of the reference catheter after the dislodgement from the initial reference location; and
uses the reference adjustment to adjust localization element position measurements made after the dislodgement from the initial reference location.

18. The localization system according to claim 15 , wherein the ref

Assignees

• Koyrakh Lev A
• Schweitzer Jeffrey A
• Starks Daniel R
• Carbonera Carlos
• St Jude Medical Atrial Fibrillation Div Inc

Inventors

• Koyrakh Lev A
• Schweitzer Jeffrey A
• Starks Daniel R
• Carbonera Carlos

Classifications

• A61B34/20

  Surgical navigation systems; Devices for tracking or guiding surgical instruments, e.g. for frameless stereotaxis · CPC title

• A61B2034/2053

  Tracking an applied voltage gradient · CPC title

• A61B2034/2072

  Reference field transducer attached to an instrument or patient · CPC title

• A61B5/06 Primary

  Devices, other than using radiation, for detecting or locating foreign bodies {; Determining position of diagnostic devices within or on the body of the patient} · CPC title

• A61B5/063

  using impedance measurements · CPC title