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The main aims of this research was to employ alanine doped with gold-nanoparticles “AuNPs” to determine the levels of dose enhancement caused by these particles when irradiated with proton beams, low and high energy X-rays and electrons. dl -alanine was impregnated with 5 nm gold-nanoparticles (3% by weight) and added as a uniform layer within a wax pellet of dimensions 10 × 5 × 5 mm. Control pellets, containing dl -Alanine were also produced, and placed within a phantom, and exposed to various types of radiations: low energy (kV ranges) X-rays were obtained from a superficial machine, high energy (MV) X-rays and electrons derived from a linear accelerator, and protons were produced by the Hyogo Ion Beam Centre in Japan. Nominal doses received ranged from 2 to 20 Gy (within clinical range). The Electron Paramagnetic Resonance (EPR) spectra of the irradiated samples were recorded on a BRUKER Elexsys 9.5 MHz. The dose enhancement caused by gold nanoparticles for 80 kV x-rays was found to be more than 60% at about 5 Gy. Smaller dose enhancements (under the same measurement conditions) were observed for megavoltage x-ray beams (up to 10%). Dose enhancement caused by charged particles indicated minimal values for 6 MeV electrons (approximately 5%) whilst less than that is obtained with protons of 150 MeV. The proton results validate the latest simulation results based on Monte Carlo calculations but the dose enhancement is significantly less than that reported in cell and animal model systems, (about 20%). We attribute this difference to the fact that alanine only measures the levels of free radicals generated by the inclusion of nanoparticles and not the redox type radicals (such as reactive oxygen species) generated from aqueous media in cells. Dose enhancement caused by 5 nm gold-nanoparticles with radiotherapy type proton beams has been found to be less than 5% as determined when using alanine/wax as both a phantom and dosimeter. This agrees well with the latest Monte Carlo simulation results for similar sized gold-nanoparticles. Furthermore, our results for both low and high energy x-rays are validated against published data for in vitro studies.

This paper aims to assess the dose-response characteristics of delaminated GAFCHROMIC™ EBT3 films for radiotherapy beams. Delaminated EBT3 films were produced by peeling off the top polyester substrate of original EBT3 using surgical precision forceps. The films were irradiated to 500 cGy with photon beams of 6 MV and 10 MV, while proton and 192Ir exposures were conducted at nominal energies of 150 MeV and 0.38 MeV respectively. Digitisations were made using a flatbed scanner in Red-channel for optimum sensitivity. Analyses of data fitting, reading reproducibility, film integrity and energy dependency were then implemented for comparison with original EBT3 films. Results of R2 in each curve suggested that the selected non-linear function appropriately fits the data with low reduced chi-square. However, the delaminated films experience integrity degradation of up to 13% due to active layer distress, affecting the reading reproducibility with values extending to 1.0%. Plus, the mean relative response ratio of energy dependency for delaminated EBT3 in photon irradiations was observed at 0.97, which is inferior to their original counterpart. In summary, the delaminated EBT3 yields comparable dose-response behaviour despite integrity deterioration. It is important to factor film delamination uncertainties into existing uncertainty budget as it is instrumental in reading dose-response deviations. Accurate evaluation together with reliable fabrication processes could make delaminated EBT3 attractive in specific applications including α-particles dosimetry and ultraviolet radiation monitoring.