Fig. 6.

Percentage relative errors for theoretical mean partial pathlengths compared with MC-simulated ones, as a function of $\rho$ , for the two-layered medium (left column), three-layered medium (middle column) and four-layered medium (right column). (a) to (c): ${\mu }_{a,1}=$ 0.0067 ${\mathrm{mm}}^{-1}<{\mu }_{a,3}=$ 0.0125 ${\mathrm{mm}}^{-1}$ . (d) to (f): ${\mu }_{a,1}=$ 0.0125 ${\mathrm{mm}}^{-1}>{\mu }_{a,3}=$ 0.0067 ${\mathrm{mm}}^{-1}$ .