Investigation of photon interaction properties for thyroid tissue equivalent materials by geant4

Photon – material interaction occurs with different physical processes as Compton scattering, photoelectric effect, and pair production. As a result of these processes, photon may scatter in different directions or absorb in a material and it may pass through material. The information of radiation absorption can be investigated via photon attenuation coefficient, CT number or effective atomic number etc. These parameters, which are also needed for dose calculation in medical applications, can be determined by theoretical calculations and Monte Carlo simulations as well as experimental methods. In this study, photon interaction processes have been investigated for thyroid tissue that is defined in ICRU report and compared with eight different tissue equivalent materials. It has been determined by calculating mass attenuation coefficients, CT numbers and effective atomic numbers in the energy range of 15 keV – 5 MeV by Geant4 simulation program and compared with ICRU data.