Optical sensor position indicator for neonatal MEG.

We have developed an inexpensive PC camera-based system to measure sensor position and to track head motion during magnetoencephalography recordings. The system employs mirrors to triangulate the position of markers using a single camera. Sensor position measurement and head tracking can be performed without the need to manually digitize markers or fiducial points. The system is capable of measuring relative 3-D position within the required volume of interest with an accuracy of ~450 μm and can be constructed for approximately $150.