8 and 10 MeV Electron Beams Small Field-Size Dosimetric Parameters Through the Fricke Xylenol Gel Dosimeter

When small field sizes are recommended in radiotherapy, the dosimeter must have an adequate spatial resolution in order to determine the absorbed dose at the region of interest. The study of electron small field size is important since its dosimetry is not commonly performed in the clinical routine. It was verified that the Fricke Xylenol Gel (FXG) chemical dosimeter, with an effective atomic number of 7.75 and density of 1.05 g/cm³, presents adequate spatial resolution for absorbed dose distribution measurements, when small field sizes (square and circular) for 8 and 10 MeV electron beams are considered. The absorbed dose values are proportional to the absorbance spectrophotometric measurements that are proportional to the concentration of Fe⁺³ and the xylenol orange (XO) dye complex produced in the gel. The FXG behavior, for small field sizes irradiated with electron beams, was compared with those obtained using a small ionization chamber (IC). In this study, dosimetric parameters, such as beam profile, output factor, and percentage depth dose were evaluated. Since the dosimeter results showed no significant differences and the IC is considered the standard reference dosimeter by radiotherapy protocols, the FXG was validated for dosimetric parameter measurements to small field-size electron-beam irradiations.