  In this paper, we investigate a non-iterative imaging algorithm based on the
topological derivative in order to retrieve the shape of penetrable
electromagnetic inclusions when their dielectric permittivity and/or magnetic
permeability differ from those in the embedding (homogeneous) space. The main
objective is the imaging of crack-like thin inclusions, but the algorithm can
be applied to arbitrarily shaped inclusions. For this purpose, we apply
multiple time-harmonic frequencies and normalize the topological derivative
imaging function by its maximum value. In order to verify its validity, we
apply it for the imaging of two-dimensional crack-like thin electromagnetic
inhomogeneities completely hidden in a homogeneous material. Corresponding
numerical simulations with noisy data are performed for showing the efficacy of
the proposed algorithm.
