Angular dependence of optical fibre thermoluminescent dosimeters irradiated using kilo- and megavoltage X-rays

作者：Moradi F^*; Ung N M^*; Mandiraji G A; Khandaker M U; Entezam A; See M H; Taib N A; Amin Y M; Bradley D A

来源：Radiation Physics and Chemistry, 2017, 135: 4-10.

DOI：10.1016/j.radphyschem.2017.03.014

• Optical fibre
• Thermoluminescence
• Angular dependence
• Monte Carlo simulation

Prior investigation of the suitability of optical fibres as thermoluminescent dosimeters for diagnostic and therapeutic radiation beams has not included detailed study of the effect of beam angulation. Present study of such response has made use of optical fibre of cylindrical shape, exposed to 30 kVp photons from an X-ray tube and a 6 MV photon beam from a linear accelerator. The effect of the irradiation medium was also studied, comparing response free-in-air against on-surface and in-depth irradiations through use of solid-water(TM) phantom. Standard optical fibre ((sic) =125 mu m) shows non-uniform response to beams delivered at different incident angles. Monte Carlo simulation provided support for the experimental results, also obtaining absorbed dose in the fibres. The results of free-in-air condition simulated with mono-energy beam show angle independent response for photons within the energy range 100-500 key, while dependency has been observed for beam energies of < 100 keV and > 500 keV. Experimentally, the angular dependency up to 35% is observed in 30 kVp free-in-air, while in 6 MeV beam, this is reduced to 20%, 10%, and 3% in free-in-air, on phantom surface, and in-depth conditions, respectively. The observations have been justified by considering the range of secondary electrons in the dosimeter and the effect of scattered radiation.

• 出版日期2017-6