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Influence of phantom materials on the energy dependence of LiF:Mg,Ti exposed to low-energy x-rays

Published

Author(s)

Ronaldo Minniti, G. Massillon, Christopher G. Soares

Abstract

Thermoluminescent (TL) dosimeters, particularly LiF:Mg,Ti (commercially known as TLD-100), are widely used to estimate the absorbed dose received by patients during diagnostic and/or treatment processes and for convenience, measurements are usually made in plastic phantom materials. However, at very low photon energies, secondary electrons generated in these materials during the interaction process tend to be emitted predominately backward, which can contribute to the absorbed dose deposited within the dosimeter. Thus, besides the TLD-100 energy dependence, any perturbation produced by the phantom material must be taken into account. Because of this, we have investigated the influence of plastic phantom materials on the energy dependence of TLD-100 exposed to 20-300 kV narrow x-ray spectra, 137Cs and 60Co photons under different experimental irradiation conditions. The TL energy response per air kerma unit, R, relative to 60Co gamma, as well as the relative efficiency, RE, was evaluated as a function of the effective energy. The results suggest that R increases, reaching a maximum value between 1.55 and 1.65 for an effective energy of 25 keV , depending on the phantom material, and then R decreases from 25 keV to 662 keV (137Cs gamma ray line) to a value of 1.033. Instead, RE steadily decreases from a maximum average value of 1.415 at 15 keV down to 1.027 for the 137Cs gamma ray line.
Citation
Physics of Medicine and Biology
Volume
59

Keywords

thermoluminescent, dosimeter, phantom, air kerma, x-rays, gamma-rays, TLD

Citation

Minniti, R. , Massillon, G. and Soares, C. (2014), Influence of phantom materials on the energy dependence of LiF:Mg,Ti exposed to low-energy x-rays, Physics of Medicine and Biology, [online], https://doi.org/10.1088/0031-9155/59/15/4149 (Accessed July 21, 2024)

Issues

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Created July 8, 2014, Updated November 10, 2018