Influence of Electrode Placement Error and Contact Impedance Error to Scalp Voltage in Electrical Impedance Tomography Application

Electrical Impedance Tomography (EIT) is an imaging technique which relies on the accuracy of boundary voltage measurement. In application to the head of EIT, the scalp voltage is very small and sensitive to noise and error. Electrode placement error is an error which is difficult to avoid in practice. Furthermore, the exact value of electrode contact impedance is difficult to know. In this study, the influence of electrode placement error and inaccurate electrode contact impedance were investigated by simulation. The result shows that the scalp voltage error due to the placement error was between 0.003 mV and 4.670 mV. Comparing to the scalp voltage response obtained from brain stimulation, which has been reported less than 90 μV, the most of the error values were much larger. The voltage errors due to inaccurate contact impedance were less than 1.2 μV which is very small and ignorable. This indicates the importance of the attachment procedure of electrodes that needs to be very careful.