Voltage Controlled Current Source (VCCS) for Electrical Impedance Tomography (EIT) Measurements in the alpha and beta Dispersion Frequency Ranges

Electrical Impedance Tomography (EIT) measurements normally use a VCCS (Voltage Controlled Current Source) to excite the object/media to be studied. In general a multiplexer array is used for selecting the excitation and measurement electrodes which limits the maximum current excitation frequency. In particular for breast cancer diagnosis, there are indications that tumors have impedance characteristics that can be identified in the β-dispersion frequency range. Therefore, it is of great importance that the VCCS, and subsequent instrumentation, do not contribute any signal attenuation and phase shift over a wide bandwidth. This paper describes the design of a 25 mA, VCCS current excitation system with <;1 dB attenuation and <;3° phase shift, at 20 MHz, using Debye-like passive network models, that operates without a multiplexer array. The results suggest that it could be used in biomedical EIT for non-invasive breast cancer diagnosis, by increasing the measurement bandwidth compared with previous EIT systems.