Avaliação quantitativa do EEG em diferentes ambientes com análise do ruído

Abstract

This study aimed to perform a quantitative analysis of electroencephalography (EEG) signals in different environments, including the frequency range corresponding to electromagnetic noise, as well as those related to clinical and high-frequency brain rhythms. Four EEG signal collections were performed on the same healthy volunteer in the following locations: a shielded room without a notch filter located at the University of São Paulo (USP), an outdoor environment with a notch filter, the Intensive Care Unit (ICU) of the Hospital de Clínicas of the Federal University of Uberlândia (HC-UFU), and the electroencephalography unit located in the basement of the hospital. Quantitative analysis of the EEG signal was performed using two quantifiers: Power Contribution Percentage (PCP) and Coherence. The results showed that the environment significantly influences signal quality, with emphasis on differences in alpha, beta, and supergamma rhythms, in addition to the noise component. In the PCP, electrodes T3 and T4 showed the greatest differences, especially when comparing the basement and indoor environments without a notch. Regarding Coherence, the FP1–FP2 pairs showed greater variation, with the ICU and Indoor comparison without notch being the most critical. The Percentage Variation (PV) analysis indicated that most electrodes remained in intermediate variation ranges, although higher oscillations were observed in some conditions. Overall, it can be concluded that the shielded room presents a cleaner signal, eliminating unwanted bands, while hospital environments were more susceptible to noise and external interference.