ECE532 Biomedical Optics © 1998 Steven L. Jacques, Scott A. Prahl Oregon Graduate Institute |

The **reduced scattering coefficient** is a lumped property
incorporating the **scattering coefficient µ _{s}** and
the

µ_{s}' = µ_{s}(1 - g) [cm^{-1}]

The purpose of µ_{s}' is to describe the diffusion of
photons in a random walk of step size of 1/µ_{s}' [cm]
where each step involves isotropic scattering. Such a description is
equivalent to description of photon movement using many small steps
1/µ_{s} that each involve only a partial deflection angle
θ if there are many scattering events before an absorption event,
i.e., µ_{a} << µ_{s}'. This situation
of scattering-dominated light transport is called the diffusion regime
and µ_{s}'is useful in the diffusion regime which is
commonly encountered when treating how visible and near-infrared light
propagates through biological tissues.

The following figure shows the equivalence of taking 10 smaller steps
of "mean free path" mfp = 1/µ_{s} with anisotropic
deflection angles and one big step with a "reduced mean free path" mfp'
= 1/µ_{s}'.

The following figure shows how many such big steps involving isotropic scattering are equivalent to many small anisotropic steps: