A high frequency, high frame rate front end for electrical impedance tomography

Electrical impedance tomography (EIT) is an imaging modality that takes spectral images of the tissue under study. The EIT imaging approach, compared to the other imaging techniques such as X-ray, offers an affordable, non-ionizing portable device for home health monitoring. A front-end with high frame rate that covers a wide range of frequencies is essential for such applications. This paper presents the circuit design and implementation of a high frequency, high frame rate front-end for electrical impedance tomography system. The proposed front-end comprises a wide bandwidth programmable gain instrumentation amplifier, a mega-sample per second analog-to-digital converter (ADC), and an ADC driver. The readout channel is designed and fabricated in a 0.18 μm CMOS technology. The measurement results show that the proposed front-end covers the wide frequency range of 100 Hz to 10 MHz, with a frame rate of 30 frames per second for a 16-electrode system, with an average signal-to-noise ratio of more than 60 dB. The entire read-out channel consumes between 6.9 mW and 21.8 mW based on its operation frequency.