ELECTROMAGNETIC TRACKER CHARACTERIZATION AND OPTIMAL TOOL DESIGN (WITH APPLICATIONS TO ENT SURGERY)

Abstract

Electromagnetic tracking systems prove to have great potential for serving as the tracking component of image guided surgery (IGS) systems. However, despite their major advantage over other trackers in that they do not require line-of-sight to the sensors, their use has been limited primarily due to their inherent measurement distortion problem. Presented here are methods of mapping the measurement field distortion and results describing the distortion present in various environments. Further, a framework for calibration and characterization of the tracking system’s systematic error is presented. The error maps are used to generate polynomial models of the distortion that can be used to dynamically compensate for measurement errors. The other core theme of this work is related to optimal design of electromagnetically tracked tools; presented here are mathematical tools for analytically predicting error propagation and optimally configuring sensors on a tool. A software simulator, using a model of the magnetic field distortion, is used to further design and test these tools in a simulation of actual measurement environments before ever even being built. These tools are used to design and test a set of electromagnetically tracked instruments, specifically for ENT surgical applications.