  An inverse scattering problem is formulated for reconstructing optical
properties of biological tissues. A recursive linearization algorithm is used
to solve the inverse scattering problem. We employed the idea of finite element
boundary integral method and added suitable boundary conditions on the surface
of the domain. The initial guess is obtained by Born approximation based on the
fact of weak scattering. The reconstruction is then improved each time by an
increment on wave number. Finite element method is used for the interior domain
containing inhomogeneity. Nystr\"om method is used for setting up the boundary
conditions and jump conditions. Two numerical examples are presented.
