ResearchArticle Canonical Decomposition of Ictal Scalp EEG and Accurate Source Localisation: Principles and Simulation Study

Correspondence should be addressed to Maarten De Vos, maarten.devos@esat.kuleuven.beReceived 16 February 2007; Revised 13 June 2007; Accepted 2 October 2007Recommended by Andrzej CichockiLong-term electroencephalographic (EEG) recordings are important in the presurgical evaluation of refractory partial epilepsy forthe delineation of the ictal onset zones. In this paper, we introduce a new concept for an automatic, fast, and objective localisationof the ictal onset zone in ictal EEG recordings. Canonical decomposition of ictal EEG decomposes the EEG in atoms. One or moreatoms are related to the seizure activity. A single dipole was then fitted to model the potential distribution of each epileptic atom.In this study, we performed a simulation study in order to estimate the dipole localisation error. Ictal dipole localisation was veryaccurate, even at low signal-to-noise ratios, was not affected by seizure activity frequency or frequency changes, and was minimallyaffected by the waveform and depth of the ictal onset zone location. Ictal dipole localisation error using 21 electrodes was around10.0mm and improved more than tenfold in the range of 0.5–1.0mm using 148 channels. In conclusion, our simulation study ofcanonical decomposition of ictal scalp EEG allowed a robust and accurate localisation of the ictal onset zone.Copyright © 2007 Maarten De Vos et al. This is an open access article distributed under the Creative Commons AttributionLicense, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properlycited.

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