Electromagnetic tracking systems are affected by the presence of metal or more general conductive objects. In this paper results of two protocols are presented, which will access the amount of distortions caused by certain type of metals. One of the main application areas of electromagnetic tracking systems is the medical field. Therefore this paper concentrates on types of metals, which are common in a medical environment, like typical tool and implant materials and OR table steel. Results are obtained and compared for the first generation of Aurora systems (Aurora 1), released in September 2003 and for the new Aurora system (Aurora 2), which was released in September 2005.
Magnetic tracking systems can be considered an enabling technology for
many image guided medical interventions, since they are not limited by
line-of-sight requirements. This can allow a much deeper immersion of the technology into a particular medical navigation application. We demonstrate in this paper new prototype sensor and field generator form factors. Miniaturized sensors as small as 0.5 x 5 mm can allow integration of magnetic tracking systems into such instruments as biopsy needles, endoscopes, catheters, and guide wires. Sensors with hollow cores can surround instruments without taking up the space needed for other functions of the instrument. Such an approach shows that sensor miniaturization is not the only way to overcome space limitations in medical instruments. Flat field generators can simplify the setup of the tracking system and better optimize the location of the working volume relative to the field generator.
For example, flat field generators could be built into surgical beds or into head rests. For the prototype systems considered in this paper, we discuss performance attributes such as their trueness,
repeatability, and confidence limits in comparison to the standard field generator and sensors of the Aurora system of Northern Digital.