Studies on mass attenuation coefficients, effective atomic numbers and electron densities for some biomolecules

Mass attenuation coefficients (μ/ρ) for total photon interaction have been determined by using Geant4 package in the energy region 1 keV-1000 MeV for biomolecules such as creatinine hydrochloride, methionine, glycoprotein, glycine, proline and lactose. Such data were then used to calculate the effective atomic numbers (Zeff) and effective electron densities (Neff) for the biomolecules by using the interpolation method. The simulated μ/ρ values were compared with theoretical XCOM results, and good agreement was observed in intermediate and high energy regions while significant discrepancies up to 20 % were observed in energy region 10-150 keV. Also, it is noted that the variations occur in Zeff for a given biomolecule depending on photon energy and chemical compositions where the K-absorption edge of medium-Z element may affect sharply the energy dependence of Zeff. The μ/ρ and Zeff values are found to be in good agreement with the available experimental data.