Comparison between Two Bromine Containing Free Radical Initiators in PRESAGE®

PRESAGE® is an optically clear 3-D polyurethane dosimeter which contains a halogenated carbon as a free radical initiator and leucomalachite dye. The change of the optical density is known to be linear with respect to the absorbed dose and the sensitivity is related to the carbon–halogen bond dissociation energy of the free radical initiator. Although there are some studies regarding free radical initiators and dye materials, there's a lack of reports about the effect of other elements like LMG solvent which can be added when there's a difficulty mixing materials. Also, there are some studies about comparison between free radicals with different kind of halogen atoms but there's a lack of studies of comparison between initiators with the same halogen atom. In this experiments, two kinds of halocarbon free radical initiator with the same halogen atom (bromine) as well as the effect of the LMG solvent were studied to use the dosimeter as a therapeutic purpose. Effective atomic numbers were also calculated. The initiators with the same halogen atom, CBr₄ and C₂H₂Br₄, reacted totally differently. CBr₄ was more sensitive to the radiation and emitted maximum 4 times more free radicals upon irradiation with no additional effective atomic number but the absorbance after irradiation was highly variable with time. For stable measurement, C₂H₂Br₄ would be more appropriate as a free radical initiator