FIG. 3.

Two 3D phantom configurations that were used in our Monte Carlo simulations. (a) Nine spheres were imaged without (first phantom) and with warm background (second phantom). (b) Derenzo phantom with spheres ranging from 2 to 3 mm diameter (third phantom). In this case, the distances between the spheres were equal to two times their radii. No attenuating medium was simulated in any of these experiments.