Effect of Gold Nanoparticles on Prostate Dose Distribution under Ir-۱۹۲ Internal and ۱۸ MV External Radiotherapy Procedures Using Gel Dosimetry and Monte Carlo Method

Background: Gel polymers are considered as new dosimeters for determining radiotherapy dose distribution in three dimensions.Objective: The ability of a new formulation of MAGIC-f polymer gel was assessed by experimental measurement and Monte Carlo (MC) method for studying the effect of gold nanoparticles (GNPs) in prostate dose distributions under the internal Ir-۱۹۲ and external ۱۸MV radiotherapy practices.Method: A Plexiglas phantom was made representing human pelvis. The GNP shaving ۱۵ nm in diameter and ۰.۱ mM concentration were synthesized using chemical reduction method. Then, a new formulation of MAGIC-f gel was synthesized. The fabricated gel was poured in the tubes located at the prostate (with and without the GNPs) and bladder locations of the phantom. The phantom was irradiated to an Ir-۱۹۲ source and ۱۸ MV beam of a Varian linac separately based on common radiotherapy procedures used for prostate cancer. After ۲۴ hours, the irradiated gels were read using a Siemens ۱.۵ Tesla MRI scanner. The absolute doses at the reference points and isodose curves resulted from the experimental measurement of the gels and MC simulations following the internal and external radiotherapy practices were compared. Results: The mean absorbed doses measured with the gel in the presence of the GNPs in prostate were ۱۵% and ۸ % higher than the corresponding values without the GNPs under the internal and external radiation therapies, respectively. MC simulations also indicated a dose increase of ۱۴ % and ۷ % due to presence of the GNPs, for the same experimental internal and external radiotherapy practices, respectively. Conclusion: There was a good agreement between the dose enhancement factors (DEFs) estimated with MC simulations and experiment gel measurements due to the GNPs. The results indicated that the polymer gel dosimetry method as developed and used in this study, can be recommended as a reliable method for investigating the DEF of GNPs in internal and external radiotherapy practices.  Â