Fig. 4.

Monte Carlo comparisons between the time-resolved transmittance contrast due to a realistic absorption change $\mathrm{\Delta }{\mu }_a$ within a volume of $1000{\mathrm{mm}}^3$ (dotted curves) and that of an equivalent black sphere $V_{\text{black}}$ (solid curves). A slab 40 mm thick with ${\mu }_s^{\prime }=1{\mathrm{mm}}^{-1}$ and refractive index equal to 1.33 is considered. Four realistic inhomogeneities with different values of $\mathrm{\Delta }{\mu }_a$ (rows) are set at decreasing depths $z_i/\mathrm{mm}=30$, 25, 20 (columns) and compared to the equivalent black inclusions. The plots display the relative contrast $|C(t)|$ for three different arrangements of the inclusion, namely transmittance measurements on-axis ($x_i=y_i=0$) and off-axis, with an $x$-offset of 10 mm and of 20 mm, with the source placed at (0,0,0) and the detector placed at (0,0,40) mm. The results are independent of ${\mu }_a$.