Figure 7: The mean reconstructed attenuation coefficient in Al tubes of different diameters, scanned (a) in water (20 mm) or (b) air, with 0.5 mm Al filter and 12 um pixel size. The in-air scans were repeated at a high resolution (4 um pixel) to minimize partial volume effects (c). With 0.5mm Al filter, divergent attenuation linked to thickness is partly correctable with scans in air, but not in water.