Response of a nanoDot OSLD system in megavoltage photon beams

Purpose: The aim of this study was to investigate the response of a nanoDot optically stimulated luminescence dosimeter (OSLD) system in megavoltage photon beams. Methods: The nanoDot response was compared with the ionization chamber measurements for 4-18-MV photons in a plastic water phantom. The response was also calculated by the Monte Carlo method. In addition, the perturbation correction factor, P-Q, in the nanoDot cavity was calculated according to the Burlin's cavity theory. The angular dependence of the nanoDot was evaluated using a spherical phantom. Results: The calculated and measured nanoDot responses at a 10-cm depth and 10 x 10-cm(2) field were in agreement within 1% for 4-18-MV. The response increased by 3% at a 20 x 20-cm(2) field for the lower energy of 4 MV; however, it was constant within +/- 1% for 6-18 MV. The response was in a range from 1.0 to 0.99 for mean photon energy of more than 1.0 MeV but it increased with less than the 1.0 MeV. P-Q for the nanoDot cavity was approximately constant at 0.96-0.97 for greater than and equal to 10 MV. The angular dependence decreased by 5% and 3% for 6 and 15 MV, respectively. Conclusions: The nanoDot was energy-independent in megavoltage photon beams.