Dose sensitivity of novel Fricke methyl thymol blue radio-chromic gel dosimeter with different acids and hydrogel matrices
摘要
In this work, the Fricke Methyl Thymol blue (MTB) radiochromic gel dosimeter was studied optically with different acids of sulfuric (H2SO4) as a conventional acidic medium and hydrochloric (HCL) as an alternative acidic medium, different gel matrices with poly vinyl alcohol (PVA) and gelatin, with different cross-linkers of chemical glutaraldehyde (GTA) and physical gellan gum (GG). The optical dosimetry properties of the Fricke MTB dosimeters of H2SO4-GTA-PVA, HCL-GTA-PVA, HCL-GG-PVA, and HCL-gelatin formulations was investigated using ultraviolet–visible (UV–VIS) spectrophotometer. The dosimeters were irradiated using a linear accelerator (LINAC) with 6 MV photon beam and 200 cGy/min dose rate at doses up to 20 Gy. The irradiated cuvette Fricke samples were scanned to determine the degree of oxidation of the Fricke gels accordance to the conversion of ferrous ions (Fe2+) to ferric ions (Fe3+) and absorbance at wavelength of 621 nm (the main peak in the absorbance spectrum). The dose-response increased with absorbed dose up to 20 Gy, while a clear linear calibration region was observed from 0 to 10 Gy for all investigated formulations. Among the investigated formulations, the Fricke HCl-GG-PVA gel demonstrated the highest sensitivity, with a value of 0.096 a.u. Gy−1. Additionally, the effect of different dose rates and photon beams were investigated for selected Fricke formulations (HCL-GG-PVA and HCL-gelatin) and found that the dose response was identical for each formulation. The stability of the Fricke MTB dosimeters (HCL-GG-PVA and HCL-gelatin) for three days after radiation exposure was also studied. It was observed that the Fricke formulation of HCL-GG-PVA is more stable (no absorbance change) after three days of the irradiation. According to these data, the Fricke HCL-GG-PVA gel dosimeters studied are useful tools to validate complex dose distributions in radiation dosimetry.