Current Sources for Electrical Impedance Tomography IMPETOM

Reliable current sources are imperative in Electrical Impedance Tomography (EIT) as it requires signals with minimum distortion and relatively broad bandwidth. In this work four current sources are compared, Howland modified amongst them, to select one for IMPETOM, our clinical EIT system. Bandwidth analysis (0.5 Hz–10 MHz), total harmonic distortion (up to 1.5%) and output current (1 mA to 5 mA) are studied for four current source designs. All configurations gave good results with bandwidths between 0.5 MHz and 3 MHz, driving loads of between 2 kΩ and 12 kΩ with up to 5 mA peak output currents and 1% maximum total harmonic distortion (THD). Among the options, we found the Negative Feedback current source (NFCS) to have the best performance for IMPETOM.