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Journal of Sensors
Volume 2015, Article ID 341208, 9 pages
http://dx.doi.org/10.1155/2015/341208
Research Article

EEG Signal Quality of a Subcutaneous Recording System Compared to Standard Surface Electrodes

1Hypo-Safe A/S, Diplomvej 381, 2800 Kongens Lyngby, Denmark
2Department of Neurology, Roskilde Sygehus, Køgevej 7-13, 4000 Roskilde, Denmark
3Department of Electronic and Electrical Engineering, Imperial College London, London SW7 2BT, UK
4Department of Plastic Surgery, Odense University Hospital, Sdr. Boulevard 29, 5000 Odense, Denmark
5Department of Endocrinology, Sydvestjysk Sygehus, Haraldsgade 7A, 6700 Esbjerg, Denmark

Received 15 October 2014; Revised 25 March 2015; Accepted 1 April 2015

Academic Editor: Chenzhong Li

Copyright © 2015 Jonas Duun-Henriksen et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Purpose. We provide a comprehensive verification of a new subcutaneous EEG recording device which promises robust and unobtrusive measurements over ultra-long time periods. The approach is evaluated against a state-of-the-art surface EEG electrode technology. Materials and Methods. An electrode powered by an inductive link was subcutaneously implanted on five subjects. Surface electrodes were placed at sites corresponding to the subcutaneous electrodes, and the EEG signals were evaluated with both quantitative (power spectral density and coherence analysis) and qualitative (blinded subjective scoring by neurophysiologists) analysis. Results. The power spectral density and coherence analysis were very similar during measurements of resting EEG. The scoring by neurophysiologists showed a higher EEG quality for the implanted system for different subject states (eyes open and eyes closed). This was most likely due to higher amplitude of the subcutaneous signals. During periods with artifacts, such as chewing, blinking, and eye movement, the two systems performed equally well. Conclusions. Subcutaneous measurements of EEG with the test device showed high quality as measured by both quantitative and more subjective qualitative methods. The signal might be superior to surface EEG in some aspects and provides a method of ultra-long term EEG recording in situations where this is required and where a small number of EEG electrodes are sufficient.