Mass attenuation coefficients and effective atomic numbers of biological compounds for gamma ray interactions

The mass attenuation coefficients (μ/ρ) for some enzymes, proteins, amino acids and fatty acids were measured at 122, 356, 511, 662, 1170, 1275 and 1330 keV photon energies, by performing transmission experiments using ⁵⁷Co, ¹³³Ba, ¹³⁷Cs, ⁶⁰Co and ²²Na sources collimated to produce 0.52 cm diameter beams. A NaI (Tl) scintillation detector with energy resolution 8.2% at 663 keV was used for detection. The experimental values of (μ/ρ) were then used to determine the atomic cross section (σ_a), electronic cross section (σ_e), effective atomic number (Z_eff) and electron density (N_eff). It was observed that (μ/ρ), σ_a and σ_e decrease initially and then tends to be almost constant at higher energies. Values of Z_eff and N_eff were observed roughly constant with energy. The deviations in experimental results of radiological parameters were believed to be affected by physical and chemical environments. Experimental results of radiological parameters were observed in good agreement with WinXCom values. - Highlights: • Mass attenuation coefficients of twelve biological compounds were measured. • Measured gamma rays energy is 122–1330 keV. • The results of ε, σa, σe, Zeff, Neff were determined and compared with WinXCom. • Investigated results of organic compounds are useful for medical applications.