Reducing Effect of Magnetic Field Noise on Sensor Position Estimation in Surgical EM Tracking

Surgery navigation techniques aim to support surgeons during operations, resulting in improved accuracy and patient safety. In this context, electromagnetic tracking systems (EMTSs) are mainly used since they enable real-time tracking of small EM sensors included in surgical tools without line-of- sight restrictions. On the other hand, these systems are very sensible to magnetic field variations that can affect sensor position estimation performance. In this paper we analyze how magnetic field variations caused by the noise of transmitting coils’ excitation currents affect system performance, and we propose a technique to reduce its undesirable effect. This method includes, in the position estimation algorithm, the measurement of excitation currents, thus compensating errors in sensor signal caused by current noise. Different simulation tests were performed to assess the proposed method which is based on modeling the magnetic field produced by the field generator (FG). Finally, it is validated by using experimental data provided by a novel EMTS prototype, obtaining noise peaks reduction and an overall mean position error of 3 mm at a distance of 600 mm from the FG.