Optimizing the sensitivity and radiological properties of the PRESAGE® dosimeter using metal compounds

The aim of this study is to investigate the radiation-modifying effects of incorporating commercially available bismuth-, tin- and zinc-based compounds in the composition of the PRESAGE (R) dosimeter, and the feasibility of employing such compounds for radiation dose enhancement. Furthermore, we demonstrate that metal compounds can be included in the formulation to yield water-equivalent PRESAGE (R) dosimeters with enhanced dose response. Various concentrations of the metal compounds were added to a newly developed PRESAGE (R) formulation and the resulting dosimeters were irradiated with 100 kV and 6 MV photon beams. A comparison between sensitivity and radiological properties of the PRESAGE (R) dosimeters with and without the addition of metal compounds was carried out. Optical density changes of the dosimeters before and after irradiation were measured using a spectro-photometer. In general, when metal compounds were incorporated in the composition of the PRESAGE (R) dosimeter, the sensitivity of the dosimeters to radiation dose increased depending on the type and concentration of the metal compound, with the bismuth compound showing the highest dose enhancement factor. In addition, these metal compounds were also shown to improve the retention of the post-response absorption value of the PRESAGE (R) dosimeter over a period of 2 weeks. Thus, incorporating 1-3 mM (ca. 0.2 wt%) of any of the three investigated metal compounds in the composition of the PRESAGE (R) dosimeter is found to be an efficient way to enhance the sensitivity of the dosimeter to radiation dose and stabilize its post-response for longer times. Furthermore, the addition of small amounts of the metal compounds also accelerates the polymerization of the PRESAGE (R) dosimeter precursors, significantly reducing the fabrication time. Finally, a novel water-equivalent PRESAGE (R) dosimeter formula optimized with metal compounds is proposed for clinical use in both kilovoltage and megavoltage radiotherapy dosimetry. (C) 2012 Elsevier Ltd. All rights reserved.