Audio Codec and Digital Signal Processor for an Electrical Impedance Tomography System

Electrical Impedance Tomography (EIT) can esti- mate thorax fluid/air content and distribution. Its use in crit- ically ill patients is promising and may prove clinically use- ful. Currents are injected and voltages measured in the tho- rax boundary. The measurements are used to reconstruct to- mographic images. An EIT system was implemented based on evaluation board OMAP-L137 (Spectrum Digital) and How- land current source. The board main components are the OMAP-L137 processor with DSP C6747 and AIC 3106 audio codec (Texas Instrument). Fewer than 5% difference in volt- ages against the oscilloscope was measured in the range between 42mV and 1.5V. The entire system showed 8.53% difference when measuring the real part of impedance.