Abstract
Study focuses on characterisation of diverse concentrations of Ge-doped SiO2 fibre as a potential thermoluminescence (TL) system for radiotherapy dosimetry. Irradiations were made using a linear accelerator providing 6 MV and 10 MV photon beams. Investigation has been done on various doped core diameter Ge-doped SiO2 glass fibres such as commercial telecommunication fibres of 8 mu m and 9 mu m (CorActive High Tech, Canada), tailor-made fibres of 23 and 50 mu m produced by the Central Glass and Ceramic Research Institute Kolkata, and tailor-made fibres of 11 mu m produced by the University of Malaya Photonics Research Centre. The fibres have been characterised for TL sensitivity, reproducibility, dose- and energy-dependence. The area under the TL glow curve increases with increasing core diameter. For repeat irradiations at a fixed dose the dosimeter produces a flat response better than 4% (1SD) of the mean of the TL distribution. Minimal TL signal fading was found, less than 0.5% per day post irradiation. Linearity of TL has been observed with a correlation coefficient (r(2)) of better than 0.980 (at 95% confidence level). For particular dopant concentrations, the least square fits show the change in TL yield, in counts per second per unit mass, obtained from 50 mu m core diameter fibres irradiated at 6 MV of photon to be 8 times greater than that of 8 mu m core diameter fibre. With respect to energy response, the TL yield at 10 MV decreases by similar to 5% compared to that at 6 MV, primarily due to the lower mass energy absorption coefficient at higher photon energy. These early results indicate that selectively screened fibres can be developed into a promising TL system, offering high spatial resolution capability and, with this, verification of complex radiotherapy dose distributions. (C) 2014 Elsevier Ltd. All rights reserved.