(Sunday, 7/29/2018) 3:00 PM - 6:00 PM
Room: Exhibit Hall
Purpose: To investigate the response of a commercial nanoDot optically stimulated luminescent dosimeter (OSLD) system in megavoltage photon and electron beams.
Methods: The nanoDot response was estimated by comparing with ionization chamber measurements for 4-18 MV photons and 6-20 MeV electrons in a solid water phantom. The photon and electron beams were obtained from a Varian Clinac iX linear accelerator (Varian Oncology Systems). The measured response was compared with that calculated using the BEAMnrc, egs_chamber, and cavity codes in the EGSnrc Monte Carlo (MC) code. The nanoDot response was analyzed as a function of energies, field sizes, depths, and angles. In addition, the response of the nanoDot cavity was analyzed according to Burlin’s cavity theory. The perturbation correction factor, PQ, in the nanoDot cavity was also estimated from MC simulations.
Results: The nanoDot response was almost independent in the range of 4-18 MV photons at a 10 cm depth for a 10 x 10 cm² field. The nanoDot response for 4 MV increased by 1.8% at a 15 cm depth for a 20 x 20 cm² field. The angular response for 6 and 15 MV decreased by 5% and 3% at a parallel incident beam to the dosimeter plane, respectively. According to Burlin’s cavity theory, the dose contributions from photon interactions (1-d) in the nanoDot cavity decreased by less than 0.05 as the mean photon energy increases. Values of PQ were almost constant between 0.96 and 0.97 at 10 MV or more. For 6-20 MeV electrons, the nanoDot response at a reference depth, dref, was constant within 0.9% relative to that of 6 MV photons.
Conclusion: The variation in energy response of the nanoDot was within 2% for 4-18 MV photons. The response at dref for 6-20 MeV electrons was an insignificant difference from that for 6 MV photons.
Funding Support, Disclosures, and Conflict of Interest: The measurement devices used in this study were provided by Nagase Landauer Ltd., Ibaraki, Japan
Keywords
Monte Carlo, Dosimetry, Dose Response
Taxonomy
TH- Radiation dose measurement devices: OSL
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