  This paper proposes a novel approach to reconstruct changes in a target
conductivity from electrical impedance tomography measurements. As in the
conventional difference imaging, the reconstruction of the conductivity change
is based on electrical potential measurements from the exterior boundary of the
target before and after the change. In this paper, however, images of the
conductivity before and after the change are reconstructed simultaneously based
on the two data sets. The key feature of the approach is that the conductivity
after the change is parameterized as a linear combination of the initial state
and the change. This allows for modeling independently the spatial
characteristics of the background conductivity and the change of the
conductivity - by separate regularization functionals. The approach also allows
in a straightforward way the restriction of the conductivity change to a
localized region of interest inside the domain. While conventional difference
imaging reconstruction is based on a global linearization of the observation
model, the proposed approach amounts to solving a non-linear inverse problem.
The feasibility of the proposed reconstruction method is tested experimentally
and with a simulation which demonstrates a potential new medical application of
electrical impedance tomography: imaging of vocal folds in voice loading
studies.

Computational Physics;Medical Physics