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Abstract
In this paper, a spatial-domain method for the reconstruction of the complex permittivity profile of two-dimensional large sizelow contrast objects is presented. The unknown dielectric scatterer is described as a superposition of step functions placed on a rectangular grid with unknown weighting coefficients. Furthermore, an improved Rytov approximation is developed for the description of the unknown internal field in the scattering integral equation. The inverse scattering problem is then solved by minimizing the squared error between measured and predicted values for the scattering amplitude. The efficiency of the direct and inverse scattering technique is validated by using synthetic scattering amplitude data, and a study of noise effects is undertaken. It is shown that significant improvement over conventional diffraction tomography methods based on the first-order Rytov approximation is possible with the proposed technique, and it can be efficiently used for soft tissue imaging in biomedical engineering applications.