Figure 1

Lung phantom. Cross sections through the CT scan of the lung phantom which consisted of a low density cork cube surrounding a homogeneous plastic sphere of variable diameter (here: 4.2 cm). The cork cube densities ranged from ρ _min = 0.001 to ρ _max = 1.09 with an average density of ρ _mean = 0.12 , while the plastic sphere had a density of ρ = 1.1 . A film could be positioned through the phantom as marked with a dashed line in A and B. The cork cube, plastic sphere and film were fixed relatively to the high density positioning markers (indicated by arrows on A) on the surface of the plastic container by a plastic plate and four plastic screws as shown in B.