A buyer's guide to electromagnetic tracking systems for clinical applications

When choosing an Electromagnetic Tracking System (EMTS) for image-guided procedures, it is desirable for the system to be usable for different procedures and environments. Several factors influence this choice. To date, the only factors that have been studied extensively, are the accuracy and the susceptibility of electromagnetic tracking systems to distortions caused by ferromagnetic materials. In this paper we provide a holistic overview of the factors that should be taken into account when choosing an EMTS. These factors include: the system's refresh rate, the number of sensors that need to be tracked, the size of the navigated region, system interaction with the environment, can the sensors be embedded into the tools and provide the desired transformation data, and tracking accuracy and robustness. We evaluate the Aurora EMTS (Northern Digital Inc., Waterloo, Ontario, Canada) and the 3D Guidance EMTS with the flat-panel and the short-range field generators (Ascension Technology Corp., Burlington, Vermont, USA) in three clinical environments. We show that these systems are applicable to specific procedures or in specific environments, but that, no single system is currently optimal for all environments and procedures we evaluated.