We present a review of methods for the forward and inverse problems in opti
cal tomography. We limit ourselves to the highly scattering case found in a
pplications in medical imaging, and to the problem of absorption and scatte
ring reconstruction. We discuss the derivation of the diffusion approximati
on and other simplifications of the full transport problem. We develop sens
itivity relations in both the continuous and discrete case with special con
centration on the use of the finite element method. A classification of alg
orithms is presented, and some suggestions for open problems to be addresse
d in future research are made.