Improvement on the performance of chemically cross-linked fricke methylthymol-blue radiochromic gel dosimeter by addition of dimethyl sulfoxide

Abstract

The effect of free radical scavenger dimethyl sulfoxide (DMSO) on the performance of transparent Fricke methylthymol blue dye (MTB)-polyvinyl alcohol (PVA)-chemical cross-linking agent glutaraldehyde (GTA) dosimeter (MTB-PVA-GTA) was studied and evaluated using two optical detection methods. By adding different concentrations of DMSO, the properties of the dosimeter were analyzed by ultraviolet–visible (UV–Vis) spectrometry and using 2-D optical imaging system based on a charge-coupled-device (CCD) camera with a diffusing red-light surface. The gel dosimeters were irradiated using 6, 10, and 15 MV photon beams of a medical linear accelerator at various dose rates. Linear absorbance-dose relationships was obtained in the range 0–10 Gy with DMSO ranging from 0 to 3000 mM. No significant changes to the dependence of the response on the dose rate (150, 300, and 600 cGy/min) and the photon energy (6, 10, and 15 MV photon beams) were observed by adding DMSO to the dosimeter. In general, increasing DMSO concentration reduced sensitivity, reduced diffusion coefficient, and enhanced the stability of the dosimeter. The addition of DMSO to the Fricke MTB-PVA-GTA dosimeter showed a good measured sensitivity and a significant low diffusion coefficient when compared with the values measured for other Fricke radiochromic dosimeters reported previously. This improved composition shows a lower diffusion coefficient with respect to those reported so far for a Fricke dosimeter with PVA and gelatin gel. The total uncertainty of the Fricke dosimeter were 4.6%.