Induction sensor characterisation for electromagnetic tracking systems

Induction coil sensors are key components in electromagnetic tracking systems. Sensors can be embedded within a wide variety of tools enabling their position and orientation to be tracked in real-time. The technology is seeing increased adoption within medical devices where medical professionals can localize sensor-enabled devices within a patient without line-of-sight or x-ray imaging. While methods exist for characterising magnetic sensing devices, few implementations provide sufficient dynamic range to effectively simulate the magnetic field conditions present in an electromagnetic tracking system. This work presents a novel printed circuit Helmholtz coil capable of generating low frequency magnetic fields across four orders of magnitude from 10 nanotesla to 100 microtesla. A selection of induction coil sensors are tested and electrical responses measured to calculate individual sensitivity and non-linearity metrics. Results are favourable for existing commercially available electromagnetic sensor designs which exhibit harmonic distortion of as little 0.01 percent. The proposed method is significant as it provides a systematic characterization of induction sensors used in the design of tracked medical instruments.