Electrical Impedance Tomography Research And Application

Electrical impedance tomography （EIT） is a new non-destructive functional imagingtechnique developed in recently three decades. Inject excitation current（voltage） in theboundary of object, measure surface voltage （current）, obtain the electrical impedancedistribution of measured internal object using the image algorithm, and then reconstructionthe image that reflect the different internal tissue properties of the measured object. EIT wasmainly applied in the biomedical fields. In this paper, EIT technology was be used for foreignbody detection in the food and detection in situ of plant roots, achieve detection iron or plasticforeign body in fluid food, faster, cheaper and non-polluting and detection plant roots.Electrical impedance tomography system includes hardware and software systems,hardware system acquire data, software system applied this data reconstruct image, thedetection results was finally showed by image. The main contents and results were as follows:(1) The EIT system was built. line connection was achieved based on EIT technicaladjacent excitation measurement mode, the control command was written in matlab softwareenvironment, The instruments was controlled by program and get imaging data. Solveddomain was subdivided into finite element mesh, and finite element mesh topologyinformation was got by number the nodes and elements, in order to calculate the resistivity forimage reconstruction. EIT system achieved the reconstruction image and display;(2) COMSOL simulation software was used for solve the EIT forward problem andimaging data was obtained by simulation. The image quality was better when the electrodewidth is7.5mm through the study of different widths of electrode. Simulation method avoidedwaste money and resources，improve the efficiency of research for EIT parameters. optimumparameters of EIT hardware and software was obtained to prepare for follow-up experiments;(3) The effects of imaging quality by EIT system parameters was studied combinedsimulation and experiment, and quantitative evaluation of the reconstructed image. There wasan optimal regularization parameter for an EIT system, the displayed of foreign body area wassmaller when iterations calculate inadequately, this compensated the error of foreign bodyarea diffusion after fully iterative calculation, so the reconstructed image quality was betterwith little iterative calculation. The reconstructed image quality was also effected by the sizeand frequency of the excitation current. The two evaluation criterion, can objectively and accurately evaluate the reconstructed image quality, and avoided the influence of humanfactors;(4) EIT was applied to detection different materials （plastic and iron） foreign bodies inyogurt and situ detection canola roots in soil. The results show that this EIT experimentalsystem can detection imaging foreign body in food, reconstruction image can reflectimpedance characteristic of foreign body (a conductor or an insulator) the size and position ofthe foreign body，could detection the foreign body, but it is unable to accurately reflect theshape of the actual foreign body; this method is sensitive to the size of the foreign body, andcan only detect the foreign body within a certain range. In situ detection of canola roots, somephysiological information of rhizomes was be reflected by reconstructed image.