The Influence of Tissue Conductivity and Head Geometry on EEG Measurement Sensitivity Distributions

Abstract

Electrical neuroimaging is a contemporary functional imaging method that evolves electroencephalography (EEG) beyond traditional signal analysis. It exploits the millisecond temporal resolution of EEG and integrates it with its spatial resolution, which is mapped according to the measurement sensitivity distribution of the measurement leads. This thesis assesses the EEG measurement sensitivity distribution according to the influence of tissue conductivities, electrode placement, electrode type, and geometries upon volume conductor head models.

The conductivity of the skull is correlated with the age of the patient, recognizing that juveniles have higher spatial resolution than adults. Surface electrodes are compared with subdermal electrodes and are found to be non-interchangeable because the subdermal electrodes measure electric activity from one-eighth the volume of their surface-electrode counterparts. More accurate geometrical definitions naturally yield more precise forward and inverse calculations; however, a stochastically deformable generic head model based on anthropometric data addresses the void in imaged and segmented heads of different ages, genders and head shapes. Comprehensively, the investigation of these three key areas improves the knowledge of the EEG measurement sensitivity distributions, which will conceivably translate into clinical improvements in the diagnostics of brain functionality.