System front-end design for concurrent acquisition of electroencephalograms and EIT data

There is recently considerable interest in medical imaging to combine recording of bioelectrical signals with imaging procedures. For example, electroencephalograms (EEGs) recorded during functional magnetic resonance imaging are increasingly being used for neurological and behavioural research. Concurrent acquisition of EEGs and electrical impedance tomography (EIT) data have been suggested as a non invasive technique that could help localize the area of the brain responsible for seizures in epileptic patients awaiting resective surgery. Despite reasonably distinct spectra, EEGs and EIT signals are difficult to record simultaneously because of their very different amplitudes. In this paper, we describe the front-end of a 24-channel system designed to acquire both signals from the same set of scalp electrodes using time-division multiplexing. We have developped a 10-layer 20×15 cm printed circuit board of the front-end and are currently performing circuit characterization tests. System performance parameters and in vivo images will be presented at the conference.