Research On Hardware System Of Electrical Impedance Tomography

Electrical impedance tomography (BIT) is a technique that produces images of the tissues by means of impedance distribution in a body. It is a new imaging technology, which is characteristic of non-invasiveness, cheap, basing on electrical characteristic, succeed other imaging technology. The present study is supported by the project of National Science Foundation of China, "3D Dynamic Imaging of Brain Electrical Activity" and by the project of Science Foundation of Hebei, "Noninvasive Measurement and Functional Imaging of Braintissue"We design a primary hardware system of 16 electrodes on the base of the model. The main work is as follows:(1) We design a source current module, a pattern-setting module, a measure module and a acquire module. Work frequency of the source current module is 50KHz, and peak-peak value is 1mA. The pattern-setting module can set the measure mode of EIT system basing 16 electrodes arbitrarily, and then fit any imaging algorithm. The measure module has bigger Signal-to-Noise Ratio because adopting instrumentation amplifier, Programmable gain amplifier and accumulate measurement. The system has stable quality, high precision and simply operation.(2) We design a model based on compound electrodes, imaged the different object in diameter, conductance by means of back-project algorithm to imaging the physics model and getting actual poison, clear profile.(3) Following the multi-frequency EIT system, we optimize the current source using DDS (direct digital synthesis) technology then can adjust the frequency of the current source dynamically in the range of 2MHz. It have established the basement of the development.