Magnetic Marker Localization System Using a Super-Low-Frequency Signal

In this paper, a magnetic marker localization system using a super-low-frequency signal-around 100 Hz-is proposed for a surgical navigation system. This method avoids the effect of eddy currents flowing inside metallic surgical tools. The frequency dependence of the magnetic field distortion and localization error due to eddy currents were simulated to determine the optimum signal frequency. From the results of the simulation, the influence of eddy currents on the magnetic marker localization can be insignificant below 1 kHz. The prototype system used marker signals at 94 and 143 Hz and comprised 16-channel fluxgate magnetometers. Markers were successfully localized and the developed system was operational even though metal tools were present in the observation area.