Abstract
The photoneutron production from different elements in major body organs using an anthropomorphic voxel-based phantom irradiated with 15, 18 and 25 MV photon beam spectra from Medical Linear Accelerator were estimated by the mean of MCNPX Monte Carlo code. The soft tissue composition recommended by ICRU44 was used in the simulations. Other elements present, less than 0.005% by weight collectively were neglected. The results of this initial simulation will provide the basis for further simulation to estimate the changes in the elemental concentration in the irradiated volume.