Analysis and optimization of surgical electromagnetic tracking systems by using magnetic field gradients

Background: Electromagnetic tracking systems (EMTSs) are widely used in surgical navigation, allowing to improve the outcome of diagnosis and surgical interventions, by providing the surgeon with real-time position of surgical instruments during medical procedures. Objective: the main goal is to improve the limited range of current commercial systems, which strongly affects the freedom of movement of the medical team. Studies are currently being conducted to optimize the magnetic field generator (FG) configuration (both geometrical arrangements and electrical properties) since it affects tracking accuracy. Methods: In this paper, we discuss experimental data from an EMTS based on a developed 5-coils FG prototype, and we show the correlation between position tracking accuracy and the gradients of the magnetic field. Therefore, we optimize the configuration of the FG by employing two different metrics based on i) the maximization of the amplitude of the magnetic field as reported in literature, and ii) the maximization of its gradients. Results: The two optimized configurations are compared in terms of position tracking accuracy, showing that choosing the magnetic field gradients as objective function for optimization leads to higher position tracking accuracy than maximizing the magnetic field amplitude.