Evaluating the effect of Zinc Oxide nanoparticles doped with Gadolinium on dose enhancement factor by PRESAGE dosimeter

Background: New treatment modalities are developed with the aim of escalating tumor absorbed dose and simultaneously sparing the normal structures. The use of nanotechnology in cancer treatment offers some possibilities including destroying cancer tumors with minimal damage to healthy tissues. Zinc Oxide nanoparticles [ZnO NPs] are wide band gap semiconductors and seem to have a good effect on increasing the absorbed dose of target volume especially when doped with a high Z element. The aim of this study was to evaluate the effect of ZnO NPs doped with Gadolinium [Gd] on dose enhancement factor by 6MV photon beam irradiation. Materials and Methods: Various concentrations of ZnO NPs doped with 5% Gd were incorporated into PRESAGE composition, the 3D chemical dosimeter. Then by using a UV-Vis spectrophotometer optical density changes and also dose enhancement factor [DEF] were determined. Results: The results of this study showed that by incorporating 500, 1000, 3000 and 4000 micro g/ml ZnO NPs doped with Gd into PRESAGE structure the dose enhancement factor of about 1.57, 1.69, 1.78 and 1.82 in a 15 ×15 cm[2] field size could be found, respectively. Conclusion: The results of this study showed that ZnO NPs doped with Gd could be considered as new compound for increasing the absorbed dose

Dose measurement outside of radiotherapy treatment field [Peripheral dose] using thermoluminesent dosimeters

In radiation therapy, peripheral dose or the dose outside the radiotherapy field, is important when anatomical structures with very low dose tolerances are involved. One of these critical organs in pelvic irradiation is testis. The amount of radiation delivered to the testes in radiotherapy must be kept as small as possible, consistent with the limit dose of this organ. The threshold doses for temporary and permanent sterility are 0.15 Gy and 6-8 Gy, respectively. Therefore, in pelvic irradiation, protecting testis from these doses and also scattered radiation which could escalate testis dose should be considered. In order to determine the possibility of using testicular shield for high and low energies, TLD dosimetry was done on phantom and 27 patients involved with bladder, rectum and prostate cancers. Dosimetric results showed that the ability of testicular shield in reducing testes absorbed dose is approximately the same [about 7 cGy] for low and high energy photon beams. a testicular shield with a fixed thickness of 1.27cm can be used as testis protection for either high and low energies