Downsizing of LC markers for a wireless magnetic position detection system

We have investigated downsizing of the LC resonant magnetic marker of the wireless magnetic position detection system for medical applications. Two shapes of ferrite cores, which are a needletype and a plate-type, were examined for use in the core of the LC marker. The system was capable of wirelessly detecting the position of downsized small LC markers (except for the ferrite core of 1 mm in diameter and 5 mm in length) with an accuracy on the order of less than 90 mm from the pick-up coil array. Comparison of the prepared cores and the large ferrite core (of 3 mm in diameter and 10 mm in length) as the LC marker revealed that the S/N ratio of the LC marker signal was decreased due to core volume reduction. However, the effect of the demagnetizing factors related to core shape was greater than that of the volume reduction that reduced the S/N ratio and the position accuracy of the system.