Electrical Impedance Tomography System-driven Research

The Electrical Impedance Tomography (EIT) is a new medicine imaging technique, which has been developed since twenty years ago. In EIT an array of the electrodes is attached around the aim object, and a small alternating current is injected, at the same time the electrical current field is engendered. Through the surrounding electrical current of the aim object measured by the electrodes, with the injected alternating electrical current signal, the measured voltage data and some appending information, the distributing of the conductance (resistivity) in the cross section (space) of the aim object is reconstructed. Thus the conductance tomography which reflect the characteristic of the aim object interior tissue is recived.In this paper, started with the hardware design of the Electrical Impedance Tomography, the design process of the whole circuitry is analyzed, which included the collectivity structure design and the interior structure design of the modules, and a electrical hardware system with 16 electrodes is designed. At the driver pattern, the injected driver pattern is studied, the two methods of the adjacent driver and the subtend driver are contrastively analyzed, and based on the concept of the equipotential node, the distributing of the sensitivity field through the electrodes is analyzed. At the source part, the constant-current source module of the hardware system is designed through the direct digital synthesis technique, with the direct digital synthesis integration CMOS chip AD9851 as the source, the output of the high accurate and steady sinusoid signal, whose frequency is 50KHz, is realized. And based on the development trend of the Electrical Impedance Tomography in the multi-frequency, the design of the multi-frequency output engendered with the direct digital synthesis is brought forward.