A New Symmetric Semi-Parallel Electrical Impedance Tomography (Eit) System - I: The Design

Electrical Impedance Tomography (EIT) is a kind of functional imaging technology which has great potential for tumor diagnosis, and physiological process monitoring. This article introduces a prototype design of a semi-parallel EIT data acquisition system with the purpose of ease of hardware upgrades and scalability. The system consists of one control module and an expandable number of independent front-end modules. Compared with most of the existing data acquisition systems, the newly developed data acquisition system features symmetric and parallel signal conditional circuits. All front-end modules closely and symmetrically connected to electrodes to minimize the length of the signal traces for better measurement accuracy at high frequency. There is only one pair of exciting sources to reduce circuit cost and maximize the agreement among all exciting conditions. Compound electrode interface has been implemented for flexible measurement strategy. For safety purpose, the amplitude of the excitation current is controlled to be less than 0.4 mA and abnormal current alarm are independently controlled by every front-end module. Besides, isolation units have been implemented in the front-end modules to isolate the human body from the control circuits of the system. The developed EIT data acquisition system is suitable for medical applications.