3-term optimization criterion for faster inversion in microwave tomography

The problem of microwave tomography consists of finding the electrical characteristics (permittivity and conductivity) of a medium using scattered fields measured under various conditions of illumination. Such inversion can be achieved with a variety of techniques based upon the minimization of an appropriate criterion. The popular current source inversion (CSI) technique is one of those. In this paper, the CSI technique is presented and its main limitations are underlined. Then, in order to overcome these limitations, a generalized form of CSI is developed. An analysis of the time consuming operations of this new algorithm is done, and a new technique is proposed; it proves to be faster than the other two methods, the speed increase ranging between factors of 2 and 5. Performance of the algorithms is illustrated with examples based on synthetic data.