Figure 1
Curves of X-ray absorption versus photon energy. (a) X-ray attenuation length in μm. Color codes used were: red for paraffin (Ap), black for paraffin-embedded soft tissue (Apt), blue for water (Aw), green for hydrated soft tissue (Aht), and orange for dehydrated (dry) soft tissue (Adt). Gain in the medium:sample ratio of attenuation length upon the medium replacement from water to paraffin can be calculated as (Ap/Adt)/(Aw/Adt) = Ap/Aw when Aw ≥ Adt, or (Ap/Adt)/(Adt/Aw) when Aw < Adt. Water content by weight, volumetric mass density, and elemental composition for the hydrated soft-tissue (without adipose tissue) were taken from literature37 as 70%, 1.06, and H10.2C14.3N3.4O70.8Na0.2P0.3S0.3Cl0.2K0.3, respectively, which were used to calculate density and elemental composition for the dehydrated soft-tissue as 1.23 and H8.1C47.6N11.3O28.6Na0.7P1S1Cl0.7K1, respectively. Similarly, density and elemental composition for the paraffin-embedded soft-tissue were calculated as 0.99 (0.986) and H5.3C80.4N3.7O9.3Na0.2P0.3S0.3Cl0.2K0.3, respectively. Attenuation length was calculated from density and elemental composition using a web tool (https://henke.lbl.gov/optical_constants/atten2.html)38; densities for paraffin (H1C2) and water (H2O1) were set as 0.90 and 1.00, respectively. (b) 1% Contrast length in μm. Length giving 1% difference in X-ray transmission between paraffin and dehydrated soft tissue was calculated as Ap × Adt × ln(0.99)/(Adt-Ap).
