Experimental determination of the influence of oxygen on the PRESAGE^®dosimeter

Abstract

It is generally accepted that the PRESAGE(®) radiochromic dosimeter is not sensitive to oxygen, however, this claim has not been supported or verified experimentally. Therefore, the aim of this study was to experimentally determine the potential influence of oxygen on dose sensitivity of the PRESAGE(®) dosimeter and its reporting system. Batches of PRESAGE(®) and its radical initiator-leuco dye reporting system were prepared in aerobic and anaerobic conditions. The anaerobic batches were deoxygenated by bubbling nitrogen through the dosimeter precursors or reporting system for 10 min. The dosimeters and reporting systems were prepared in spectrophotometric cuvettes and glass vials, respectively, and were irradiated with 6 MV photons to various radiation doses. Changes in optical density of the dosimeters and reporting system before and after irradiation were measured using a spectrophotometer. The overall results show that oxygen has some influence on the dosimetric characteristics of PRESAGE(®), although the radical initiator does appear to oxidize the leucomalachite green even in the presence of oxygen. Deoxygenation of the reporting system leads to an increase in sensitivity to radiation dose by ~30% when compared to the non-deoxygenated system. A minor increase in sensitivity (~5%) was also achieved by deoxygenating the PRESAGE(®) precursor prior to casting. In addition, dissolved oxygen measurements revealed low levels of dissolved oxygen (0.40 ± 0.04 mg l(-1)) in the polyurethane precursor used to fabricate the PRESAGE(®) dosimeters, as compared to water (8.60 ± 0.03 mg l(-1)) and the reporting system alone (1.30 ± 0.10 mg l(-1)). The results suggest that the presence of oxygen does not inhibit the radiochromic properties of the PRESAGE(®) system. However, deoxygenation of the dosimeter precursors prior to casting improves the dosimeters dose sensitivity by ~5%, which might be particularly useful for measuring low radiation doses. Nevertheless, we believe this is not sufficient enough to recommend the deoxygenation of commercial PRESAGE(®) precursor prior to casting. In addition, there were no observed changes in the dose linearity, absorption spectrum and post-response photofading characteristics of the PRESAGE(®) under the conditions investigated.

Radiation Dosimetry by Use of Radiosensitive Hydrogels and Polymers: Mechanisms, State-of-the-Art and Perspective from 3D to 4D

“…PRESAGE ® dosimeters also demonstrate a temperature dependence during radiation and storage [ 177 ] and some temporal instability [ 178 ] making it difficult to use the dosimeter with absolute calibration. Some dependence of the dose sensitivity on oxygen content in PRESAGE ® was also found [ 179 ]. Despite these unfavorable properties, the relative dose distribution was found to be reproducible within a 2% dose difference for an allowable distance-to-agreement of 2 mm [ 178 ], and PRESAGE ® was applied in some clinical dosimetric validation studies including IMRT [ 180 , 181 ], VMAT [ 182 , 183 ] in the determination of output factors of gamma knife radiosurgery [ 184 ] and in brachytherapy [ 185 , 186 , 187 ].…”

A Review of PRESAGE Radiochromic Polymer and the Compositions for Application in Radiotherapy Dosimetry

“…The investigation of the oxygen influence on PRESAGE demonstrated that PRESAGE was capable of maintaining good linearity (R 2 > 0.99), with or without the presence of oxygen [ 73 , 104 ]. Although good linearity was obtained by PRESAGE with the presence of a catalyst (DBTDL), the catalyst reduced the linearity by 2% [ 75 ].…”

“…PRESAGE (LMG) [100] 0 Gy-30 Gy 0.9946 PRESAGE (MeO-LMG) [100] 0 Gy-30 Gy 0.9963 PRESAGE (Cl-LMG) [100] 0 Gy-30 Gy 0.9985 PRESAGE (Br-LMG) [100] 0 Gy-30 Gy 0.9997 PRESAGE (Bi Neo) [91] 0 Gy-30 Gy 0.9999 PRESAGE (DBTDL) [91] 0 Gy-30 Gy 0.9999 PRESAGE (Zn OCT) [91] 0 Gy-30 Gy 0.9999 PRESAGE (Iodoform) [93] 0 Gy-30 Gy 0.9988 PRESAGE (Bromoform) [93] 0 Gy-30 Gy 0.9996 PRESAGE (Chloroform) [93] 0 Gy-30 Gy 0.9980 PRESAGE (Organometallic catalyst) [75] 0 Gy-20 Gy 0.9700 PRESAGE (MOD 1) [92] 0 Gy-50 Gy 0.9984 PRESAGE (MOD 2) [92] 0 Gy-50 Gy 0.9993 PRESAGE (MOD 3) [92] 0 Gy-50 Gy 0.9989 PRESAGE (deoxygenation) [104] 0 Gy-30 Gy 0.9981 PRESAGE (no deoxygenation) [104] 0 Gy-30 Gy 0.9972…”

Detection of therapeutic radiation in three-dimensions

“…In contrast the para -substituent DTBs have demonstrated the most facile color fading [ 39 ]. A combination of singlet oxygen and light is thought to be the cause of bleaching of DTBs [ 54 ] even though for these dosimeters the effect is minimal [ 55 ].…”