title: Feasibility of clinical magnetoencephalography (MEG) functional mapping in the presence of dental artefacts.
abstract: OBJECTIVE
  To evaluate the viability of MEG source reconstruction in the presence of large interference due to orthodontic material.
  
  
  METHODS
  We recorded the magnetic fields following a simple hand movement and following electrical stimulation of the median nerve (somatosensory evoked field -SEF). These two tasks were performed twice, once with and once without artificial dental artefacts. Temporal Signal Space Separation (tSSS) was applied to spatially filter the data and source reconstruction was performed according to standard procedures for pre-surgical mapping of eloquent cortex, applying dipole fitting to the SEF data and beamforming to the hand movement data.
  
  
  RESULTS
  Comparing the data with braces to the data without braces, the observed distances between the activations following hand movement in the two conditions were on average 6.4 and 4.5 mm for the left and right hand, respectively, whereas the dipole localisation errors for the SEF were 4.1 and 5.4 mm, respectively. Without tSSS it was generally not possible to obtain reliable dipole fit or beamforming results when wearing braces.
  
  
  CONCLUSIONS
  We confirm that tSSS is a required and effective pre-processing step for data recorded with the Elekta-MEG system. Moreover, we have shown that even the presence of large interference from orthodontic material does not significantly alter the results from dipole localisation or beamformer analysis, provided the data are spatially filtered by tSSS.
  
  
  CONCLUSIONS
  State-of-the-art signal processing techniques enable the use of MEG for pre-surgical evaluation in a much larger clinical population than previously thought possible.
authors: VU University Medical Center, Department of Clinical Neurophysiology and Magnetoencephalography Center, Amsterdam, The Netherlands.
authors: A
authors: A
authors: Hillebrand
authors: P
authors: P
authors: Fazio
authors: J C
authors: JC
authors: de Munck
authors: B W
authors: BW
authors: van Dijk
mesh_terms: D000328:Adult; D000465:Algorithms; D016477:Artifacts; D001931:Brain Mapping / Q000379:methods; D004558:Electric Stimulation; D005073:Evoked Potentials, Somatosensory / Q000502:physiology; D005240:Feasibility Studies; D005260:Female; D006225:Hand / Q000502:physiology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods; D015225:Magnetoencephalography / Q000379:methods; D008297:Male; D008475:Median Nerve / Q000502:physiology; D008670:Metals; D008875:Middle Aged; D009010:Monte Carlo Method; D009068:Movement / Q000502:physiology; D009967:Orthodontic Appliances
chemical_list: D008670:Metals