Target biological tissue and energy influence on dose enhancement factor produced by gold nanoparticles and its relevant radiological properties

Understanding the radiation dose enhancement factor (DEF) influencing parameter and relevant radiological properties is important for the accurate estimation of absorbed dose in nanoparticle enhanced X-ray therapy (NEXT). In this present study, target tumor tissue influence on DEF produced by 18 mg/g gold nanoparticle (GNP) in ten various biological samples and relevant radiological properties were studied over 15KeV-15MeV energies. The DEF was calculated with the help of mass energy-absorption coefficients (mu(en)/rho) values. Mass attenuation coefficient (mu/rho), (mu(en)/rho), photoelectric absorption coefficients were computed with the help of the XCOM program. Energy absorption buildup factor (EABF), exposure buildup factor (EBF) and effective atomic number (Z(eff)) were calculated by EXABCAL and auto Z(eff) computer program respectively. DEF were significantly varied according to target biological tissue elemental composition and incident photon energies. Among the ten various biological samples, adipose tissue target produces higher DEF which have the lower Z(eff) and bone produce lower DEF which possess higher Z(eff). Optimal energy for the maximum DEF is 40 KeV and 100 KeV for soft tissues and bone respectively. EABF and EBF of GNP doped tissues were discussed as the function of energy and elemental composition and mean free path up 40 mfp. Energy and inhomogeneity correction factors are necessary for the accurate estimation of DEF. These results are helpful for developing the treatment planning algorithms and dosimetry for NEXT. Age and calcification dependent variation of the elemental composition of the target tissue and its effect on DEF need to account for the future work.