QUADRANT-SEARCHING: A NEW TECHNIQUE TO REDUCE THE SEARCH SPACE OF THE INVERSE PROBLEM OF EIT USING THE INVERSE PROBLEM OF EIT USING

摘要

The image reconstruction using the EIT (Electrical Impedance Tomography) technique is annonlinear and ill-posed inverse problem which demands a powerful direct or iterative method.nA typical approach for solving the problem is to minimize an error functional using an iterativenmethod. In this case, an initial solution close enough to the global minimum is mandatory tonensure the convergence to the correct minimum in an appropriate time interval. The aim of thisnpaper is to present a new, simple and low cost technique (quadrant-searching) to reduce thensearch space and consequently to obtain an initial solution of the inverse problem of EIT. Thisntechnique calculates the error functional for four different contrast distributions placing a largenprospective inclusion in the four quadrants of the domain. Comparing the four values of thenerror functional it is possible to get conclusions about the internal electric contrast. For thisnpurpose, initially we performed tests to assess the accuracy of the BEM (Boundary ElementnMethod) when applied to the direct problem of the EIT and to verify the behavior of errornfunctional surface in the search space. Finally, numerical tests have been performed to verifynthe new technique.