Electric impedance tomography (EIT) device with adjustable current feed-in frequency to improve signal to noise ratio

摘要

An electroimpedance tomography (EIT) device having a plurality of electrodes, automatically adjusts the frequency of the current fed into a pair of the electrodes in order to reduce the sensitivity of the device to electromagnetic interference. The frequency spectrum of the background noise is detected by measuring voltage signals from the electrodes over a period of time and transforming the resulting voltage time series into a frequency spectrum. This background noise frequency spectrum is searched for a frequency which when used as the current feed-in frequency would give a signal to noise ratio (SNR) above a predetermined threshold value. This frequency is then selected as the feed-in current frequency.