Fig. 1
Schematic of the diffusive medium used, featuring one pencil beam source (S) and three detectors at the distance \(\rho =15, 25, 35 \text{ mm}\). In all the figures (except Figs. 7,8) the medium was homogeneous. For the Figs. 7,8 the medium contained a high-absorbing 1 mm thick layer. Two regions of interest were used: (1) a cube having a side of 6 mm (for the Figs. 2, 3, 9, 10); (2) a cube having a side of 1 mm (for the Figs. 4,5,6,7,8). For the calculation of Jacobians (Figs. 2, 3, 4,5,6,7, 8) the region of interest had the same optical properties of the bulk medium. For the forward problem calculations (Figs. 9, 10), the region of interest had a different absorption coefficient than the bulk medium. The outer and inner refractive indices are \({n}_{o}=1\) and \({n}_{i}=1\).4, respectively.
