Patent ID: 8000772
Filing Date: 2011-08-16
Classification: A61B

Abstract:
1. A method for tracking a metal tool, for use during a medical procedure, comprising: providing a map of distortion of a position-indicative magnetic field caused by a metal tool in a frame of reference of the tool by applying a calibration procedure to generate a map of the distortion associated with the metal tool, wherein the calibration procedure comprises measuring the distorted field, measuring an undistorted field, and subtracting the distorted field from the undistorted field so as to derive the map of the distortion; providing a metal tool having a transmitter for transmitting a position-indicative magnetic field; fixing at least one field sensor within a frame of reference of a medical procedure; tracking the metal tool as the metal tool moves within the frame of reference of the medical procedure; sensing a first distorted magnetic field transmitted from the metal tool, the first distorted magnetic field comprising the position-indicative magnetic field subject to the distortion caused by the metal tool within the frame of reference of the medical procedure; determining estimated coordinates of the metal tool based on the first distorted magnetic field; estimating the distortion component present in the magnetic field caused by the metal tool being tracked using the map and the estimated coordinates; determining a second distorted magnetic field by subtracting the estimated distortion component from the first distorted magnetic field; and computing corrected coordinates of the metal tool based on the second distorted magnetic field.