Design and implementation of a high-precision electrical impedance tomography data acquisition system for brain imaging

摘要

In this study, a serial EIT data acquisition system was constructed. It is consisted by a digital synthesis based programmable current source, a shield guard and sink current feedback based electrode interface subsystem, a programmable gain amplifier based voltmeter, and an orthogonal sequential digital demodulation based impedance demodulation method. The system has a bandwidth of 1-190 kHz with an imaging speed of 1 fps. It can produce the programmable driving current with a SNR of higher than 89 dB, and measure voltage difference with a CMRR of higher than 75 dB in this bandwidth. The measured results on a calibration model show that it has the high SNR of 83 dB (0.007% in precision) and lower reciprocity error of 0.0036%. Most of these results have been reached or exceed similar systems. Imaging results on brain physical phantom and healthy volunteers also shows that it could detect the small disturbance 0.36% in volume and 17% in resistivity of the phantom and reflect the variations in brain caused by temporary occlusion and reperfusion of unilateral carotid artery. So, the system is competency for brain imaging.