A 16-Channel Electrical Impedance Tomography System Using the Red Pitaya
Electrical Impedance Tomography (EIT) seeks to provide a new modality by which to image portions of the body and tissues which provide differences in conductivity, depending on their state. Unlike bulky, expensive, and hard-to-access traditional medical imaging equipment, such as those used in magnetic resonance imaging and computed tomography, EIT is potentially capable of being contained to small, portable, inexpensive hardware. Here, a Red Pitaya (RP) device is used to provide and process signals that can be generated and multiplexed into 16 channels, all while data is gathered from a set of electrodes embedded into a tank containing electrically conductive simulated tissue. A voltage-controlled current source provides a known value of current to be introduced with each new set of measured signals, which are then amplified and filtered to preprocess the signals. The data is then gathered together by the RP and communicated to a MATLAB program running on a nearby PC through a Standard Commands for Programmable Instrumentation interface, where the data is reconstructed using regularization with EIDORS, a MATLAB toolkit. Precision and accuracy were measured by evaluating the signal-to-noise-ratio (SNR) and a 2D Pearson correlation coefficient to the ideal images of the tank. The first tank design used electrodes of a small, pointed design, while the second used 1 cm2 copper plates for electrodes. The first had a mean system SNR of 31.616 dB (11.347) before filtering and 34.176dB (11.9803) after, and a correlation coefficient of r = 0.702 (0.055), while the second tank showed negative results.