Nonuniqueness in optical tomography: relevance of the P1 approximation

The question of whether a unique distribution of the absorption coefficient, the scattering coefficient, and the refractive index of a turbid medium can be reconstructed by optical tomography is considered. A recent publication [Opt. Lett. 23, 882 (1998)] established that such reconstruction is not possible when photon transport is well modeled by the diffusion equation. A simple proof is offered that, when measurements at high modulation frequencies are included, the more exact P1 model of light transport suggests that this reconstruction may be possible. (C) 1999 Optical Society of America.