Research On Open Electrical Impedance Tomography Based On Newton-Raphson Algorithm With Regularization

Electrical Impedance Tomography (EIT), which is one of the significant research projects in current biomedicine engineering, is an effective noninvasive imaging technique following the techniques of shape imaging and structure imaging. EIT is a relatively new medical imaging modality that produces images by computing electrical properties within the human body. Sinusoidal electrical currents are applied to a subject's body using electrodes attached to the skin, and the voltages that are developed on the electrodes are measured. Reconstruction algorithms use the applied electrical current and the measured electrode voltages to compute the electrical conductivity (or receptivity) distributions in the body. The reconstructed images can give not only the anatomy structure, but also the functional image. The X-CT, MRI and other imaging techniques can't compare this with EIT.This dissertation aims at EIT technology, by realizing the finite element method based on the complete electrode model to compute forward problem and studying the static and dynamic reconstruction method, principle, modeling and application of open EIT. The platform of open EIT imaging system which was built to take experiment and validate the simulation results conveniently has multi-functions such as displaying model, real-time measuring, outputting images etc..The main work of this dissertation is as follows:â‘ As for the forward problem of EIT, the characteristics of four different mathematical models were studied and the difference between the measured data and the voltage data computed by complete electrode model was computed. The result demonstrated that the data computed by the complete electrode model can best approximate the measured data. The sparse matrix was used to generate FEM equation so that the boundary voltage can be computed once.â‘¡The theory of Newton-Raphson algorithm was demonstrated to investigate the reconstruction problem of EIT. The performance of Tikhonov regularization and the variation regularization were compared by simulation. The mixed regularization method was proposed to integrate the advantages of the two methods and the realization and performance of the algorithm was given.â‘¢The open EIT model was proposed to solve the problem of the inaccuracy of the electrode positioning in clinical application. The field and driven strategy were defined by simulations. Use the dynamic mixed regularization method to reconstruct the open EIT image, the results of simulation and the water tank experiment showed that it can obtain good resolution and is valuable for the local area detecting in clinical use.â‘£The open EIT software platform was built under MATLAB environment, which has multi-functions including display of FEM, data and image, serial communication, computation of forward and inverse problem, etc.Finally, this paper summarizes the major research achievements, as well as the existing problems and deficiencies. At the end of this paper, the further researches on this topic are previewed.