Because of more sensitive organs due to high growth rates, evaluating the absorbed dose is essential for children to prevent irreparable damage. Therefore, to this aim, a one-year-old child's whole-body effective dose and organ absorbed dose were evaluated for various PET imaging Radiopharmaceuticals such as:18F-DOPA, 18F-FDG, 18F-FLT, 18F-FET, and 68Ga-EDTA. For this aim, one-year-old child reference voxel phantoms and GATE Monte Carlo simulation were used, and the results were compared with the ICRP128 report (for stylized phantom). The highest absorbed dose was related to bladder wall (for 18F-DOPA, 18F-FET, and 68Ga-EDTA), heart wall (for 18F-FDG), and liver (for 18F-FLT) between 30 organs that have been studied. Comparing the results with the ICRP128 report values for a one-year-old child show a significant difference in some organs. Comparison of the effective dose with the ICRP128 report shows a relative difference of 22%, 12.5%, 11.8%, 10.8% and 8.6% for 18F-DOPA, 68Ga-EDTA, 18F-FDG, 18F-FET, 18F-FLT, respectively. In conclusion, using new one-year-old voxel phantoms could provide a better estimate of organs absorbed dose and whole-body effective dose due to its exact structure.

Today, with the advancement of nanotechnology, nanomaterials with high atomic number such as gold and titania nanoparticles can be specifically concentrated in tumor cells in various way and benefited from the advantage of increasing the dose due to the proximity of these element next to cancer cells as a radiation sensitizer. In this research, parameters such as radiation energy (in the range of kilo voltage), nanoparticles concentration and tumor depth were investigated in the compressed breast phantom by using the MCNPX code to investigate the effect of radio sensitivity. The tumor in the form of a cube with sides of 0.5 cm was labeled with spherical nanoparticles of titania and gold with a radius of 70 nm with different concentrations.
The results showed that exposure the range of kilo voltage causes photoelectric absorption to accur with a high probability and a relatively large dose is delivered to the tumor. The energy that can cause the most damage to the tumor was obtained 65 keV in the presence of gold nanoparticles and in the range of 40 to 45 keV in the presence of titania nanoparticles. Also, with increasing concentration the dose enhancement factor increases, but with increasing depth, for dose enhancement factor does not change.