Catheter navigation using impedance and magnetic field measurements

Patent metadata

Field	Value
Publication number	US-10918307-B2
Application number	US-201113231284-A
Country	US
Kind code	B2
Filing date	Sep 13, 2011
Priority date	Sep 13, 2011
Publication date	Feb 16, 2021
Grant date	Feb 16, 2021

Abstract

A method of operating a positioning system by registering a first coordinate system of a first positioning system in a second coordinate system of a second positioning system includes determining an interpolation function configured to register the first, non-orthonormal coordinate system in the second, orthonormal coordinate system. Fiducial pairs are collected by the respective positioning systems, each of which contain a respective coordinate in the respective coordinate system, both of which refer to the same physical point in three dimensional space. Establishing a working interpolation function involves an analysis of the fiducial pairs using a thin-plate spline algorithm. The method further includes repeatedly obtaining a first coordinate in the first coordinate system and determining a corresponding second coordinate in the second coordinate system in accordance with the interpolation function.

First claim

What is claimed is:

1. A method of operating a computer system for locating a medical device within a body, the computer system comprising an electrical-based positioning system and a magnetic-based positioning system, the method comprising the steps of:
determining, by an electronic control unit (ECU) comprising a processor, an interpolation function configured to register a first, non-orthonormal coordinate system of the electrical-based positioning system in a second, orthonormal coordinate system of the magnetic-based positioning system, wherein said first and second coordinate systems are independent, wherein said determining an interpolation function comprises:
receiving a first signal from the electrical-based positioning system for tracking a location of an electrode coupled to the medical device;
receiving a second signal from the magnetic-based positioning system for tracking a location of a magnetic sensor coupled to the medical device;
collecting, by the ECU based on the second signal, a plurality of fiducial pairs in three-dimensional (3D) space distributed throughout a region of interest, each fiducial pair including (1) a first coordinate in said first coordinate system measured by the electrical-based positioning system and (2) a second coordinate in said second coordinate system measured by the magnetic-based positioning system, each fiducial pair corresponding to a physical point in 3D space in the region of interest based on the second signal;
discarding any fiducial pairs that are degenerate; and
applying, by the ECU, an interpolation algorithm to said plurality of fiducial pairs to yield said interpolation function, wherein the interpolation algorithm determines one or more coefficients for modifying coordinates of the plurality of fiducial pairs;

obtaining, by the ECU, a first coordinate in said first coordinate system within said region of interest;
determining, by the ECU, a corresponding second coordinate in said second coordinate system in accordance with said interpolation function and the one or more coefficients; and
displaying a location of the medical device based on the second coordinate, determined in accordance with said interpolation function, for each of the plurality of fiducial pairs.

2. The method of claim 1 , wherein said interpolation algorithm is a thin-plate spline algorithm.

3. The method of claim 2 , wherein said thin-plate spline algorithm includes Euclidean distance basis functions.

4. The method of claim 2 , wherein said thin-plate spline algorithm includes a smoothing parameter corresponding to a nonzero amount by which the second coordinate determined in accordance with said interpolation function corresponding to the obtained first coordinate can differ from the measured second coordinate in a fiducial pair with the measured first coordinate that is equivalent to said obtained first coordinate.

5. The method of claim 1 , wherein said collecting step includes discarding a fiducial pair when a distance to a nearest fiducial point is less than a pre-determined minimum distance.

6. The method of claim 5 , wherein said pre-determined minimum distance is at least 4 millimeters.

7. The method of claim 1 , wherein said first coordinate is compensated for patient body movement.

8. The method of claim 1 , wherein said obtaining step includes compensating for patient body movement in said first non-orthonormal coordinate system.

9. A method of relating a real-time first coordinate in a first coordinate system of an electrical-based positioning system into a second coordinate system of a magnetic-based positioning system for locating a medical device within a body, comprising:
establishing an interpolation function configured to receive as input said real-time first coordinate from a first electrode electrically coupled with the electrical-based positioning system for tracking a location of the first electrode coupled to the medical device and to output a second coordinate from the magnetic-based positioning system for tracking a location of a first magnetic sensor coupled to the medical device in said second coordinate system, wherein the electrical-based positioning system and the magnetic-based positioning system are independent, said establishing step comprising:
collecting a plurality of fiducial pairs in three-dimensional (3D) space, each fiducial pair including (1) a non-real-time first coordinate in said first coordinate system and (2) a non-real-time second coordinate in said second coordinate system,
discarding any fiducial pairs that are degenerate, and
applying an interpolation algorithm to said plurality of fiducial pairs to yield said interpolation function, wherein said fiducial pairs are input to said interpolation algorithm and wherein said interpolation algorithm determines one or more coefficients for modifying coordinates of said plurality of fiducial pairs, and wherein the interpolation algorithm uses a smoothing parameter that corresponds to an amount by which the second coordinate, determined in accordance with said interpolation function corresponds to an obtained first coordinate, differs from a measured second coordinate in a fiducial pair with a measured first coordinate that is equivalent to the obtained first coordinate;

applying said interpolation function to said real-time first coordinate, by a computer processor associated with a positioning system, to relate said real-time first coordinate into said second coordinate system; and
displaying a location of the medical device based on the second coordinate, determined in accordance with said interpolation function, for each of the plurality of fiducial pairs.

10. The method of claim 9 , wherein said interpolation algorithm is a thin-plate spline algorithm.

11. The method of claim 9 , wherein said thin-plate spline algorithm includes a nonzero smoothing parameter.

Assignees

• Olson Eric S
• Carbonera Carlos
• Koyrakh Lev A
• Starks Daniel R
• St Jude Medical Atrial Fibrillation Div Inc

Inventors

• Olson Eric S
• Carbonera Carlos
• Koyrakh Lev A
• Starks Daniel R

Classifications

• A61B5/063 Primary

  using impedance measurements · CPC title

• A61B5/0538

  invasively, e.g. using a catheter · CPC title

• A61B2090/0818

  Redundant systems, e.g. using two independent measuring systems and comparing the signals · CPC title

• A61B5/6852

  Catheters · CPC title

• A61B5/7207

  of noise induced by motion artifacts · CPC title