  When the inverse problem of diffuse optical tomography (DOT) is solved with
the Born or Rytov approximation, the size of the matrix of the linear inverse
problem becomes large if the volume (or area) of the domain in biological
tissue used for reconstruction is large. The number of unknown parameters in
DOT is reduced when constraints about the shape of a target are imposed for the
inverse problem. Due to such constraints, the inverse problem becomes nonlinear
even when the (first) Born or Rytov approximation is employed. We solve this
nonlinear inverse problem by the simulated annealing, which is not trapped by
local minima of the cost function.
