# US 10,945,632 B2 · Navigational reference dislodgement detection method and system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,945,632 B2 - Document ID: US10945632B2 - Status: Granted - Kind: B2 - Application number: 15/412,097 - Filed: 2017-01-23 - Published: 2017-06-15 - Granted: 2021-03-16 - Earliest claimed: 2010-12-17 - Assignees: St. Jude Medical, Atrial Fibrillation Division, Inc. - Applicants: St. Jude Medical, Atrial Fibrillation Division, Inc. - Inventors: Lev A. Koyrakh; Jeffrey A. Schweitzer; Daniel R. Starks; Carlos Carbonera - Web page: https://patentgrep.com/patent/US10945632B2 ## CPC - A61B 5/06: Devices, other than using radiation, for detecting or locating foreign bodies {; Determining position of diagnostic devices within or on the body of the patient} - A61B 5/05: Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves (measuring movement of the entire body or parts thereof A61B5/11; detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof A61B5/24) - A61B 5/063: {using impedance measurements} - A61B 5/283: Invasive - A61B 5/7221: {Determining signal validity, reliability or quality (preventing, reducing or removing noise induced by motion artefacts A61B5/7207; noise originating from a therapeutic or surgical apparatus A61B5/7217)} - A61B 34/20: Surgical navigation systems; Devices for tracking or guiding surgical instruments, e.g. for frameless stereotaxis - A61B 5/062: {using magnetic field} - A61B 5/7207: {of noise induced by motion artifacts} - A61B 2034/2051: {Electromagnetic tracking systems} - A61B 2034/2053: {Tracking an applied voltage gradient} - A61B 2034/2072: {Reference field transducer attached to an instrument or patient} - A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D) ## 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. ## Claims ### Claim 1 A method of detecting dislodgement of a navigational reference for a localization system, the method comprising: establishing a non-ionizing localization field using the localization system; establishing an initial reference location for a navigational reference catheter relative to a coordinate system defined by the non-ionizing localization field of the localization system; detecting a perceived dislodgement of the navigational reference catheter from the initial reference location based upon a magnitude of a perceived distance moved by the navigational reference catheter from the initial reference location; confirming that the perceived dislodgement of the navigational reference catheter from the initial reference location is an actual dislodgement of the navigational reference catheter from the initial reference location when a direction of the perceived dislodgement of the navigational reference catheter from the initial reference location is sufficiently coincident with an anticipated direction of dislodgement, wherein the anticipated direction of dislodgement is parallel to a longitudinal axis of the navigational reference catheter; and generating a signal indicating the actual dislodgement of the navigational reference catheter. ### Claim 2 (depends on 1) The method according to claim 1, wherein the detecting step comprises comparing the magnitude of the perceived distance moved to a dislodgement threshold. ### Claim 3 (depends on 2) The method according to claim 2, wherein the dislodgement threshold is 4 mm. ### Claim 4 (depends on 1) The method according to claim 1, wherein confirming that the perceived dislodgement of the navigational reference catheter from the initial reference location is an actual dislodgement of the navigational reference catheter from the initial reference location comprises comparing an angle between the direction of the perceived dislodgement and the anticipated direction of dislodgement to a sharp angle threshold. ### Claim 5 (depends on 1) The method according to claim 1, wherein confirming that the perceived dislodgement of the navigational reference catheter from the initial reference location is an actual dislodgement of the navigational reference catheter from the initial reference location comprises: for each reference localization element of a plurality of reference localization elements carried by the navigational reference catheter: computing an angle between a direction of perceived dislodgement for the reference localization element and an anticipated direction of dislodgement for the reference localization element; and comparing the angle to a sharp angle threshold; computing a count of angles that exceed the sharp angle threshold; and comparing the count of angles to a count threshold. ### Claim 6 (depends on 5) The method according to claim 5, wherein the anticipated direction of dislodgement for the reference localization element is determined by a direction of a longitudinal axis of the navigational reference catheter proximate the reference localization element. ### Claim 7 (depends on 5) The method according to claim 5, wherein the anticipated direction of dislodgement for the reference localization element is determined by a line segment connecting the reference localization element to a neighboring reference localization element. ### Claim 8 (depends on 1) The method according to claim 1, further comprising providing guidance to a user to help re-position and re-secure the navigational reference catheter proximate the initial reference location. ### Claim 9 (depends on 1) The method according to claim 1, further comprising: defining a new stable location of the navigational reference catheter as an updated reference location; calculating a reference adjustment to compensate for a displacement between the initial reference location and the updated reference location; and using the reference adjustment to adjust position measurements made after the dislodgement from the initial reference location. ### Claim 10 A navigational reference catheter dislodgement detection system, comprising: a navigational reference catheter dislodgement detection processor incorporated into a localization system, wherein the navigational reference catheter dislodgement detection processor is configured to: receive as input a signal related to a magnitude and direction of a perceived distance moved by a navigational reference catheter relative to an initial reference location for the navigational reference catheter, wherein the initial reference location is measured relative to a coordinate system defined by a non-ionizing localization field established by the localization system; detect a perceived dislodgement of the navigational reference catheter from the initial reference location based upon the magnitude of the perceived distance moved; confirm an actual dislodgement of the navigational reference catheter from the initial reference location when the direction of the perceived distance moved is sufficiently coincident with an anticipated direction of dislodgement, wherein the anticipated direction of dislodgement is parallel to a longitudinal axis of the navigational reference catheter; and generate a signal indicating the actual dislodgement of the navigational reference catheter from the initial reference location. ### Claim 11 (depends on 10) The system according to claim 10, wherein the navigational reference catheter dislodgement detection processor is configured to compute the perceived distance moved using a difference between a slow-moving average location of the navigational reference catheter and a fast-moving average location of the navigational reference catheter. ### Claim 12 (depends on 10) The system according to claim 10, wherein the navigational reference dislodgement detection processor is configured to compute the direction of the perceived distance moved using an angle between the direction of the perceived distance moved and the anticipated direction of dislodgement.