A comparison of three Fe³⁺ chelating agents used in Fricke gel dosimetry

"Fricke solutions" have been used for ionizing radiation dosimetry since 1927. The system consists of an acidic solution of Fe2+ ions, which oxidize to Fe3+ upon irradiation. The addition of the Fricke solution to a tissue-equivalent hydrogel matrix allows 3D dose-mapping, that is the basis of Fricke gel dosimetry. Fricke gel dosimeters still have some drawbacks that hinder its practical usage for 3D mapping, namely signal diffusion effects and spontaneous color changes due to auto-oxidation. To limit these effects, the use of ferric ion ligands has been introduced. In this study, we compared the dosimetric optical response of Fricke gels made with xylenol orange and two alternative ligands suck us methylthymol blue and 5-sulfosalicylic acid.