  This letter announces and summarizes results obtained in arXiv:1111.5051 and
considers several natural extensions. The aforementioned paper proposes a
procedure to reconstruct coefficients in a second-order, scalar, elliptic
equation from knowledge of a sufficiently large number of its solutions. We
present this derivation and extend it to show which parameters may or may not
be reconstructed for several hybrid (also called coupled physics) imaging
modalities including photo-acoustic tomography, thermo-acoustic tomography,
transient elastography, and magnetic resonance elastography. Stability
estimates are also proposed.
