Bioactive glasses and the impact of Si3N4 doping on the photon attenuation up to radiotherapy energies

Bioactive glass-ceramic is a promising candidate for medical implants. The impact of Si3N4 doping on the photon attenuation properties of a newly designed bioactive glass system with the chemical composition of (55-3 x )SiO2 -13.5CaO-29Na2O-2.5P205-xSi3N4, where x = 0, 1.76, 3.56, 5.35, and 7.17 mol%, is studied. Mass attenuation coefficient (mu/rho) of these samples is calculated by Geant4 toolkit at photon energies ranging from 0.015 MeV up to radiotherapy energy limit namely: 10 MeV. The generated data of mu/rho are verified using the calculated values of XCOM software. Half value layer (HVL), electron density (Neff), and effective atomic number (Zeff) are obtained for each bioactive glass involved. It is noted that HVL of these bioactive glasses increases by increasing Si3N4 content. Consequently, GP4 bioactive glass possesses the highest HVL values among the studied samples. The photon attenuation properties of GP4 glass are compared with different types of bioactive glasses and commercial glasses in terms of mean free path (MFP). Moreover, exposure and energy absorption buildup factors (EBF and EABF) are calculated for the GP4 bioactive glass at different penetration depths such as 1, 5, 10, 15, 20, 30, and 40 mfp. Additionally, removal cross section (Sigma R) of the present bioactive glasses is calculated. It can be concluded that GP bioactive glasses have equivalent photon attenuation properties to those of the standard bioactive glasses. Therefore, they can be safely used as an international alternative in various applications even if the exposure to gamma-ray is possible.