Reduction of the dimensionality of the EEG channels during scoliosis correction surgeries using a wavelet decomposition technique.

Mahmoud Al-Kadi,Mohd Ali,Mamun Reaz,Chian Liu

doi:10.3390/s140713046

Abstract

This paper presents a comparison between the electroencephalogram (EEG) channels during scoliosis correction surgeries. Surgeons use many hand tools and electronic devices that directly affect the EEG channels. These noises do not affect the EEG channels uniformly. This research provides a complete system to find the least affected channel by the noise. The presented system consists of five stages: filtering, wavelet decomposing (Level 4), processing the signal bands using four different criteria (mean, energy, entropy and standard deviation), finding the useful channel according to the criteria's value and, finally, generating a combinational signal from Channels 1 and 2. Experimentally, two channels of EEG data were recorded from six patients who underwent scoliosis correction surgeries in the Pusat Perubatan Universiti Kebangsaan Malaysia (PPUKM) (the Medical center of National University of Malaysia). The combinational signal was tested by power spectral density, cross-correlation function and wavelet coherence. The experimental results show that the system-outputted EEG signals are neatly switched without any substantial changes in the consistency of EEG components. This paper provides an efficient procedure for analyzing EEG signals in order to avoid averaging the channels that lead to redistribution of the noise on both channels, reducing the dimensionality of the EEG features and preparing the best EEG stream for the classification and monitoring stage.

Highlights

The electroencephalogram (EEG) is a device used to determine the brain activity by electrodes placed in different places on the scalp
Any channel having fewer components indicates that the effect of the noise on this channel is less than the others
If we compare among these three criteria (PSD, cross-correlation function (CCF) and wavelet coherence (WC)), we find that the combinational signal reduces the dimensionality of the recorded signal without changing the signal properties, because it is completely derived from the original signal

Summary

Introduction

The electroencephalogram (EEG) is a device used to determine the brain activity by electrodes placed in different places on the scalp. Unconsciousness is defined as lack of movement and unresponsiveness to painful stimuli, whereas the strength of operative stimulation depends on the duration and type of surgery [2] Inappropriate general anesthesia, such as underdosage or overdosage, leads to intraoperative awareness or prolonged anesthesia. Scoliosis correction surgery is one of the most complicated operations that requires a long time under the influence of the anesthetic drugs (more than three hours) During these types of surgeries, surgeons use a lot of electronic devices and hand tools that increase the errors and noise level for the events of the EEG signal, such as neuromuscular monitoring, suction, cautery and X-ray.

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