effect of gold nanoparticle on percentage depth dose enhancement on megavoltage energy in magica polymer gel dosimeter

background: radiation-sensitive polymer gels are among the most promising three-dimensional dose verification tools and tissue-like phantom developed to date. objective: the aim of this study is an investigating of percentage depth dose enhancement within the gel medium with used of conformal distribution gold nanoparticle as contrast agents by high atomic number material. methods: in this work the normoxic polymer gel dosimeter magica tissue- equivalence was first theoretically verified using mcnpx monte carlo code and experimentally by percentage depth dose curves within the gel medium. then gold nanoparticles (gnps) of 50nm diameter with different concentrations of 0.1mm, 0.2mm, and 0.4mm were embedded in magica gel and irradiated by 18mv photon beam. results: experimental results have shown dose increase of 10%, 2% and 4% in 0.1mm, 0.2mm and 0.4mm concentrations, respectively. simulation results had good agreement in the optimum concentration of 0.1mm. the largest error between experi- mental and simulation results was equal to 9.28% stood for 0.4mm concentration. conclusion: the results showed that the optimum concentration of gold nanoparticles to achieve maximum absorbed dose in both experimental and simula- tion was 0.1 mm and so it can be used for clinical studies.