The calculation of dose for nuclear radiation dosimetric targets using monte carlo method

The main goal of this study is experimentally calculating the dose released by photons within the media that they proceed that are emitted as a result of pair annihilation of positrons of radioactive isotope used in positron emission tomography and compare them with the results achieved by Monte-Carlo method. Brain was selected as the target organ in our study. The dose released by photons during the course of their progress in brain during PET imaging with brain protocol was determined empirically by placing TLD in jaszczak phantom at certain intervals and placing F-18 FDG source with different activities to the centre of phantom and then making TLD readings after PET scanning. Modeling was performed for sources of photon and positron to be point and cylindrical in MNCP by Monte-Carlo method in line with experimental study geometry and estimated diagnostic doses were compared with the results of experimental PET scans. Moreover, doses acquired with brain protocol during CT and PET/CT scans with TLDs placed at phantoms were determined by TLD readings. Stopping power calculations were made with brain and LiF materials by using analytical forms used by Gümüş (2008). Stopping powers were calculated from the dose and flux values obtained by modeling with point positron source at MNCP by using Monte Carlo method and these were compared with analytical results and ICRU 37 data.