Patent ID: 6373240
Filing Date: 2002-04-16
Classification: A61B,G01D

Abstract:
A method for tracking an object, comprising:producing an unperturbed energy field at a plurality of predetermined frequencies in the vicinity of the object; measuring a baseline phase value &phgr;&ohgr; of each of the plurality of resultant signals at the respective plurality of predetermined frequencies before introduction of the article; determining a characteristic of a perturbing energy field induced responsive to the unperturbed field, due to introduction of an article responsive to the unperturbed field into the vicinity of the object; receiving a plurality of resultant signals responsive to the unperturbed and perturbing energy fields generated at a location of the object after introduction of the article; measuring a phase shift &phgr;&ohgr;total at the respective plurality of predetermined frequencies after introduction of the article, so that the parameter comprises a term |&phgr;&ohgr;totalâˆ’&phgr;&ohgr;| for each of the plurality of predetermined frequencies; determining an optimal frequency for the unperturbed energy field from amongst the plurality of predetermined frequencies responsive to a parameter of the resultant signals by determining a frequency &ohgr; at which |&phgr;&ohgr;totalâˆ’&phgr;&ohgr;| a is a minimum; and determining spatial coordinates of the object responsive to the resultant signal at the optimal frequency.