PRELIMINARY RESEARCH ON THE HARDWARE SYSTEM OF ELECTRICAL IMPEDANCE TOMOGRAPHY

The slowly blooding of the vital organs is one of the important factors to cause death or disabled. The common used imaging techniques, such as CT、MRI、PET and ultra sound imaging etc., can not continuously probe or monitor the blooding process for a long term on bedside. Electrical impedance tomography is a new imaging modality. Its aim is to image the conductivity distribution or changes inside the body. The advantage of such a technique over other imaging modalities is that it is harmless, relative low cost, easier to be operated, non-invasive and non-ionizing radiation. So it抯 suitable as a novel long term and continuous image monitoring equipment. In this paper, an image system of electrical impedance tomography (EIT) based on physical phantom is presented(FMMU V3). The hardware system includes a physical phantom with 32 compounded silver electrodes, a constant current source designed by Direct Digital Synthesis (DDS) technique, high accuracy measurement block, driving-mode and measuring-mode program-control block, data acquisition and digital I/O card, and high ccuracy multi-channel power supply units. Based on physical phantom after 100 times data iteration, the measurement accuracy of this system for small and large signal is 1.0% and 0.1%.Acquiring a set of measurement data (32X31) for imaging by external triggered DMA mode, the measurement time is less than one second. It satisfies the need of dynamic imaging based on physical phantom,and some preliminary dynamic images produced by the system based on physical phantom are given.