Catheter navigation using impedance and magnetic field measurements

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.

What is claimed is: 
     
         1 . A system for determining the position of a medical device, comprising:
 an electronic control unit (ECU);   a magnetic-based positioning system for tracking a magnetic sensor coupled to the medical device;   an electrical-based positioning system for tracking an electrode coupled to the medical device;   a computer-readable memory coupled to said ECU; and   logic stored in said memory configured to be executed by said ECU, said logic configured to establish, by said ECU, an interpolation function and apply said interpolation function to a first coordinate in a region of interest in a first non-orthonormal coordinate system of the electrical-based positioning system to determine a corresponding second coordinate in a second orthonormal coordinate system of the magnetic-based-positioning system;   wherein said logic is configured to determine, by said ECU, said interpolation function by applying, by said ECU, an interpolation algorithm to a plurality of fiducial pairs distributed throughout the region of interest to yield said interpolation function, each fiducial pair including (1) a first coordinate in said first coordinate system measured by the electrical-based positioning system using data from the electrode and (2) a second coordinate in said second coordinate system measured by the magnetic-based positioning system using data from the magnetic sensor, each fiducial pair corresponding to a physical point in three-dimensional (3D) space in the region of interest,   wherein the interpolation function determines one or more coefficients for modifying coordinates of said plurality of fiducial pairs.   
     
     
         2 . The system of  claim 1 , wherein said logic is further configured to determine said interpolation function by using a smoothing parameter, wherein said smoothing parameter corresponds to an amount by which the second coordinate determined in accordance with said interpolation function corresponding to an obtained first coordinate can differ from a measured second coordinate in a fiducial pair with a measured first coordinate that is equivalent to the obtained first coordinate. 
     
     
         3 . The system of  claim 2 , wherein said logic is configured to apply said smoothing parameter to fiducial pairs comprising (1) said first coordinate in said first coordinate system, compensated for patient body movement by said first positioning system, and (2) said second coordinate in said second coordinate system, compensated for patient body movement by said second positioning system. 
     
     
         4 . The system of  claim 1 , wherein said logic is further configured to store reference coordinates in said memory comprising each first coordinate of said plurality of fiducial pairs for use in said interpolation function. 
     
     
         5 . The system of  claim 1 , further comprising a medical device comprising a first sensor configured to output a first signal indicative of a first position in said first non-orthonormal coordinate system and a second sensor configured to output a second signal indicative of a second position in said second orthonormal coordinate system. 
     
     
         6 . The system of  claim 5 , wherein said first sensor and said second sensor are fixed on said medical device at a known physical relationship to each other. 
     
     
         7 . The system of  claim 5 , wherein said medical device is a first medical device and said logic is configured to establish said interpolation function by applying a thin-plate spline algorithm to a plurality of fiducial pairs collected with said first medical device, said system further comprising:
 a second medical device comprising a first sensor configured to output a first signal indicative of a first position in said first non-orthonormal coordinate system and a second sensor configured to output a second signal indicative of a second position in said second orthonormal coordinate system;   wherein said logic is configured to test said interpolation function according to said first and second signals from said second medical device.   
     
     
         8 . The system of  claim 1 , further comprising said first positioning system associated with said first non-orthonormal coordinate system. 
     
     
         9 . The system of  claim 1 , further comprising said second positioning system associated with said second orthonormal coordinate system. 
     
     
         10 . The system of  claim 1 , wherein said logic is further configured to display a location of the medical device based on the second coordinate for each of the plurality of fiducial pairs.