3D simulation of EIT for monitoring impedance variations within the human head

A preliminary analysis is presented concerning the use of EIT for detecting impedance inhomogeneities within the human brain. The work to date is cent red around the monitoring of two distinct impedance variations: those assoc iated with the application of a carotid clamp during surgery and changes ca used by the redistribution of blood flow during auditory stimuli. Using the commercially available Ansoft Maxwell package, a 3D finite element model o f the human head has been developed to solve the forward problem. The model is hemispherical in shape and comprises regions of brain, cerebrospinal fl uid, skull and skin and includes 16 scalp electrodes each of area 1 cm(2). Results from simulations using the model suggest that an EIT system, incorp orating diametric current excitation, would require a voltage measurement s ensitivity of 100-120 dB in order to detect the impedance variations in the above cases.