Accurate pediatric head models for {EEG} source localization

Abstract

Children differ from adults in head size, skull morphology, and tissue conductivity. We conducted a simulation to examine the error of source localization when a rescaled adult head model and different skull conductivities are used for EEG source localization in children. We have proven by simulation that source localization accuracy is the best with an infant specific head model including the age specific skull structure and conductivity. 1. Introduction Dense array electroencephalography (dEEG) is an important noninvasive imaging modality for elucidating normal cognitive development in children and brain monitoring in neonates intensive care units. At present, the use and validation of dEEG and Electromagnetic Source Localization (ESL) in infants and children is hindered by the lack of pediatric head models. To generate an ESL solution, two independently specified problems must be solved: (1) the forward problem which specifies how currents move from their site of generation in cortex to the scalp, and (2) the inverse problem which is highly underspecified, and works from the recorded scalp potentials to the source of those signals. While many studies have shown that properly constrained realistic head models based on the high resolution MRI generate more accurate ESL solutions, the computability and necessity of additional variables such as tissue inhomogeneity and anisotropy are less well understood. While this is true of the current head models for normal adult populations, it is even more critical for pediatric populations where both the shape and density of the skull and the volume and composition of the brain are changing rapidly during first few years of life. Therefore, accurate ESL requires an accurate lead field matrix (LFM), specifying the forward lead fields, from each cortical source to each head surface electrode. Children differ from adults in head geometry, skull thickness, and tissue conductivity. We conducted a simulation to examine the error when an adult skull model and different skull conductivities are used in pediatric ESL. Specifically, we analyze three pediatric head models based on 1) a 7 months old infant MRI coregistered with the same subject CT, 2) the same MRI with warped adult CT atlas skull and adjusted thickness, and 3) an adult head rescaled to the 7 month old infant size.