Fig. 3

Delineation methods for anthropomorphic phantoms. In methods a 1 and b 2, the inner VOI (green or blue) represents the sphere VOI, while the outer thick ring delineates the surrounding background VOI. In method 2 (b), the thin middle ring is used to separate both VOIs to prevent spill in/out from sphere to background. With method 3 (c), random background spherical VOIs are placed around the sphere VOI