  In this paper, we show that using measurements for different frequencies, and
using ultrasound localized perturbations it is possible to extend the method of
the imaging by elastic deformation developed by Ammari and al. [Electrical
Impedance Tomography by Elastic Deformation SIAM J. Appl. Math., 68(6), (2008),
1557-1573.] to problems for the Helmholtz equations with Neumann boundary
conditions, and to reconstruct by a perturbation method both the conductivity
and the permittivity, provided that the conductivity function is coercive and
the wave number in the Helmholtz equation is not a resonant frequency.
