Effective atomic number and electron density of some biologically important lipids for electron, proton, alpha particle and photon interactions

Abstract

X-ray, γ-ray and charged particle interaction parameters of biomolecules are useful in medical diagnosis and radiation therapy as exposure to radiations can cause energy of photons and charged particles to be deposited in body through various interaction processes. With this in view, the effective atomic number (Z_eff) and electron density (N_eff) of some biologically important lipids for X-ray, γ-ray and charged particle interactions were studied in the energy range 10 keV-500 MeV using logarithmic interpolation method. A non-monotonic variation in Z_eff values was observed for protons and alpha particles in low and intermediate energy regions respectively whereas a sudden increase in Z_eff was observed for electron interaction in higher energy region. Z_eff values were maximum in higher energy region for total electron interactions whereas maximum values of Z_eff for total alpha particle interactions were at relatively lower energies. Highest Z_eff values were found at lower energy region of photoelectric absorption dominance for photon interactions. Variation in N_eff seems to be similar to variation in Z_eff as they are inter-related.

Keywords: Alpha particles; Effective atomic number; Electron density; Electrons; Lipids; Photons; Protons.