Management of head motion during MEG recordings with Flying Triangulation

We use the Flying-Triangulation principle for the motion tracking of a human head, while recording MEG (magneto-encephalogram-) data. Due to inevitable head motion during a recording (~30 min), tracking is necessary to maintain the correspondence between brain and sensor with high accuracy. A crucial constraint of the task is that MEG recordings are extremely sensitive against magnetic perturbations. Inside an MEG chamber no magnetic sources are allowed. Commonly, two tracking methods are used: Either 2D images are taken or some coils attached to the patient’s head are localized, both before and after the MEG measurement and compared. The problem of both methods is that the motion during an MEG measurement is not captured. The principle “Flying Triangulation” (S. Ettl et al., Appl Opt 51 (2012) 281-289) enables such tracking tasks. Its property to capture 3D data in real time with on-board alignment allows for a continuous motion tracking. Further, the employed light-sectioning sensor can be used in an MEG environment. We present a Flying-Triangulation sensor to continuously track head motion during an MEG recording which satisfies the given constraint.