Commercial glass beads as TLDs in radiotherapy produced by different manufacturers

Abstract

While commercial jewellery glass beads offer the basis of novel radiotherapy TL dosimetry (Jafari et al. 2014a,b,c, 2015a,b), detailed study of TL variation is required for the products from various manufacturers. Investigation is made for glass beads from four manufacturers from four countries: China (Rocaille), Japan (Mill Hill), Indonesia (TOHO™) and Czech Republic (Czech). Sample composition was determined using an energy-dispersive X-ray unit coupled to a scanning electron microscope. Values of mass attenuation coefficient, μ/ρ, as a function of photon energy were then calculated for photons of energy 1keV to 10MeV, using the National Institute of Standards and Technology XCOM program. Radiation and energy response were determined using X-rays generated at accelerating potentials from 80kVp to 6MV (TPR20/10=0.670).All bead types showed TL to be linear with dose (R2>0.999). Glow curve dosimetric peaks reached a maximum value at 300°C for the Toho and 290°C for the Czech and Mill Hill products but was between 200–250°C for the Rocaille product. Radiation sensitivity following mass normalisation varied within an order of magnitude; Toho samples showed the greatest and Rocaille the least sensitivity. For the Toho, Czech, Rocaille and Mill Hill samples the energy responses at 80kVp were 5.0, 4.0, 3.6 and 3.3 times that obtained at 6MV. All four glass bead types offer potential use as TL dosimeters over doses commonly applied in radiotherapy. Energy response variation was <1% at 6MV but significant variation was found for photon beam energies covering the kV range; careful characterisation is required if use at this range is intended.