Attenuation images of optical CT using Fricke xylenol orange gel for dose mapping in radiotherapy

Abstract

The Fricke gel dosimeter, a gel-based solution containing ferrous ions, can be used for three-dimensional dosimetry by adding xylenol orange to the solution. This changes the optical properties, affecting radiation absorption. These gel dosimeters are recommended for clinical use, and 3D dosimetry uses optical computed tomography (OCT) to analyze reconstructed images. Advancements in radiotherapy focus on accurate irradiation while reducing doses to nearby tissues. This study uses modified FXO gel for 3D dosimetry, utilizing non-toxic, easy-to-handle reagents and optical CT Vista 16 equipment. The experiment aims to characterize the system's practicality and evaluate the impact of lead filters on attenuation values. The study also examines trends in attenuation values for different thicknesses of lead shields, enhancing our understanding of the relationship between attenuation and dose using optical CT. To prevent artifacts, a modified FXO gel was created by introducing a variation of XO in the preparation. The ideal concentration of XO is 0.01 mM to prevent distortions within the dose range of 1 Gy–10 Gy. A calibration system using FXO gel can be developed by comparing the maximum irradiation dose with the attenuation observed in the gel. The modified gel showed a sensitivity of 5.5·10−3 ± 2.6·10−4 cm−1/Gy and a starting dose of 4.2 Gy. Two samples were tested using different configurations of lead filters, with the central holes showing dose peaks of 4.72 Gy, 4.57 Gy, and 4.32 Gy, respectively. The results suggest the feasibility of producing modified FXO gels for examination in optical CT systems and their potential application in radiotherapy systems. Future research is being conducted in clinical irradiation to facilitate comparison with system designs.