Abstracts

Rationale: It has been reported in the literature that chirp-like spectrographic structures are often associated with seizures and are highly precise as markers of seizures [1]. In our previous works, we have shown that electroencephalogram (EEG) signals recorded using the tripolar concentric ring electrode configuration (TCRE) (tEEG signals) has significantly better spatial selectivity and signal-to-noise ratio than conventional EEG from disc electrodes [2-3]. In this study, Wigner-Ville distribution (WVD) with the Hough Transform (HT) was proposed for the observation of chirps in EEG and tEEG signals recorded on human patients.Methods: Electrographic activity was recorded from four patients with epilepsy by placing a set of TCREs in the prime 10-10 system locations in addition to the standard 10-20 system electrode locations used in the hospital. The conventional disc EEG and tEEG were both recorded at 200 S/s (hardware filter: 1-100 Hz). First, the WVD was executed on the selected seizure segment from EEG and tEEG, then the HT was performed on the obtained two-dimensional time-frequency representation. Finally, the maximum value of the HT corresponds to the position of the chirp-like events characterized as a line on the HT plane.Results: Fig.1 (A and C) represent tEEG and EEG signals, respectively. Visual comparison of the WVD-HT shown in Figs. (1B and 1D) illustrates that the HT peak representing the chirp-like signal has larger amplitude (tEEG has a maximum value of 1.9027e+013 compared to EEG with a maximum value of 2.1461e+011) with lower side-lobes for tEEG than EEG. These results confirm our previous results that tEEG signals have better signal to noise ratio (SNR) compared to EEG signals.Conclusions: The advantage of the WVD-HT method is the accuracy in global observation of chirp-like signals during seizure periods using EEG and tEEG signals. In conclusion the WVD-HT made seizure detection more obvious in the tEEG than the EEG signals.