Abstract
This paper investigates finite element method-based modeling in the context of neonatal electroencephalography (EEG). In particular, the focus lies on electrode boundary conditions. We compare the complete electrode model (CEM) with the point electrode model (PEM), which is the current standard in EEG. In the CEM, the voltage experienced by an electrode is modeled more realistically as the integral average of the potential distribution over its contact surface, whereas the PEM relies on a point value. Consequently, the CEM takes into account the subelectrode shunting currents, which are absent in the PEM. In this study, we aim to find out how the electrode voltage predicted by these two models differ, if standard size electrodes are attached to a head of a neonate. Additionally, we study voltages and voltage variation on electrode surfaces with two source locations: 1) next to the C6 electrode and 2) directly under the Fz electrode and the frontal fontanel. A realistic model of a neonatal head, including a skull with fontanels and sutures, is used. Based on the results, the forward simulation differences between CEM and PEM are in general small, but significant outliers can occur in the vicinity of the electrodes. The CEM can be considered as an integral part of the outer head model. The outcome of this study helps understanding volume conduction of neonatal EEG, since it enlightens the role of advanced skull and electrode modeling in forward and inverse computations.NEW & NOTEWORTHY The effect of the complete electrode model on electroencephalography forward and inverse computations is explored. A realistic neonatal head model, including a skull structure with fontanels and sutures, is used. The electrode and skull modeling differences are analyzed and compared with each other. The results suggest that the complete electrode model can be considered as an integral part of the outer head model. To achieve optimal source localization results, accurate electrode modeling might be necessary.
Highlights
NEW & NOTEWORTHY The effect of the complete electrode model on electroencephalography forward and inverse computations is explored
In the complete electrode model (CEM), the voltage experienced by an electrode is the integral average of the potential distribution below its contact surface, whereas the point electrode model (PEM) relies on a single mesh node
Our numerical experiments focused on forward simulation differences between the CEM and the PEM boundary conditions with a realistic neonatal head model as the target domain
Summary
NEW & NOTEWORTHY The effect of the complete electrode model on electroencephalography forward and inverse computations is explored. THIS PAPER EXPLORES THE MATHEMATICAL complete electrode model (CEM) (Cheng et al 1989; Ollikainen et al 2000; Pursiainen 2012; Somersalo et al 1992; Vallaghé et al 2009; Vauhkonen 1997) in neonatal electroencephalography (EEG) forward simulation (Baillet et al 2001; de Munck et al 2012; Gargiulo et al 2015; Lew et al 2013; Niedermeyer and da Silva 2004). Subelectrode surface currents due to potential variation, exist These shunting effects consume a small part of the electric field energy, leading to lower voltage amplitudes than what is predicted by a mathematical model not including the skin-electrode interaction. Because of the significant differences between a newborn and a normal adult skull, this study uses a realistic neonatal head model including a skull with fontanels and sutures (Darbas M, Diallo El Badia AM, Lohrengel S, unpublished observations; Lew et al 2013). As the primary forward simulation method, we use the finite element method (FEM)
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