Characterization of ferrous-agarose-xylenol gel dosimeter at 60Co γ-rays beam therapy unit

Preparation of polymer gel dosimeters for low gamma irradiation dose

In this study, two separate hydrogel dosimeters were prepared for low-dose measurement. The first system is based on Congo Red (CR) dye and a blend of natural polymers (gelatin/CMC) while the second system is based on 2,6-dichlorophenol indophenol (DCP) blue dye and a hybrid polymer blend (PVA/gelatin/CMC). The sensitivity of Congo red (CR)–(gelatin/CMC) gel dosimeter and 2, 6 – di choro phenol indophenols(DCP)-(PVA/gelatin/CMC) gel dosimetry systems were examined by studying the comparative results between the two different systems through the change in optical properties upon exposure to different gamma radiation doses, which showed the sensitivity of the second system (DCP)-(PVA/gelatin/CMC) to radiation is more than the first system(CR)–(gelatin/CMC) (CR) and (DCP)dyes have absorbance crest at 492 and 622 nm respectively. With the increase of the radiation dose, the decomposition of the dyes increases, and thus the color of the prepared hydrogel changes from orange to colorless in the case of (CR) dye at the dose (0–3.5 kGy) and from blue to colorless in the case (DCP) dye at the absorbed doses ranged from (0–1000 Gy). Dose-response curves, sensitivity, FTIR analysis, and the relative stability of the prepared hydrogel before and after irradiation were studied.

Low-Diffusion Fricke Gel Dosimeters with Core-Shell Structure Based on Spatial Confinement

The diffusion of ferric ions is an important challenge to limit the application of Fricke gel dosimeters in accurate three-dimensional dose verification of modern radiotherapy. In this work, low-diffusion Fricke gel dosimeters, with a core-shell structure based on spatial confinement, were constructed by utilizing microdroplet ultrarapid freezing and coating technology. Polydimethylsiloxane (PDMS), with its excellent hydrophobicity, was coated on the surface of the pellets. The concentration gradient of the ferric ion was realized through shielding half of a Co-60 photon beam field size, and ion diffusion was measured by both ultraviolet-visible spectrophotometry and magnetic resonance imaging. No diffusion occurred between the core-shell pellets, even at 96 h after irradiation, and the diffusion length at the irradiation boundary was limited to the diameter (2-3 mm) of the pellets. Furthermore, Monte Carlo calculations were conducted to study dosimetric properties of the core-shell dosimeter, which indicated that a PDMS shell hardly affected the performance of the dosimeter.