Optical characterization of a new composition of acrylic acid hydrogel dosimeter for quality assurance in radiotherapy treatment

A new polymer hyrogel dosimeter based on acrylic acid in polyvinyl alcohol hydrogel matrix was prepared to be used in radiation measurments for radiotherapy treatment. The hydrogel dosimeters were exposed to ionizing radiation using a medical linear accelerator. The hydrogel samples were irradiated at 6 MV beam energy, 600 cGy min⁻¹ dose rate, and various doses up to 50 Gy. UV–VIS Spectrophotometry was used to readout the dose response of non-irradiated and irradiated hydrogel samples at absorbance of 630 nm. The results show the dose response increases strongly with increasing abosrbed doses, with a large linear dose range (2–30 Gy) and dose sensitivity of 0.013 Gy⁻¹ s⁻¹. Moreover, no significant variation in dose response was obseved when the gel samples are irridiated under different dose-rates as well as radiation beam energies. A noticeble change in the stability of the irradiated hydrogel samples was found within the first three days of irradiation, followed by a high post-irradiation stability, for the next 14 days. The non-irridiated samples were stable, up to 10 weeks.