Low-noise current excitation sub-system for medical EIT.
Electrical impedance tomography (EIT) has many potential applications in medicine. The sensitivity and spatial resolution of EIT can be enhanced significantly by increasing the measurement signal-to-noise ratio (SNR), to which a significant contribution is made by the SNR of the current excitation sub-system. In this paper we present a prototype EIT current excitation sub-system with 80 dB SNR, exploiting both digital and analogue techniques. It uses digital waveform synthesis, a 16-bit DAC and subsequent reconstruction filter, to drive an enhanced Howland current source. Detailed analysis and testing of the current sub-system are presented. Its output impedance is 10 MOmega for different load impedances, varying slowly over the frequency range from 10 kHz up to 4 MHz.
School of Electrical and Electronic Engineering, University of Manchester, UK. m.rafiei-naeini@postgrad.manchester.ac.uk
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Rafiei-Naeini
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McCann
D016477:Artifacts; D025802:Electric Capacitance; D017097:Electric Impedance; D014054:Tomography / Q000379:methods*