Dosimetric impact of iodine content in a polyvinyl alcohol-iodide radiochromic gel dosimeter

摘要

Recently, we developed a radiochmmic gel dosimeter based on a polyvinyl alcohol-iodide (PVA-I) complexes that can be reused after annealing. Although, the dosimeter is composed of water mostly, iodine was partially added. In the present study, the dosimeteric impact of iodine content in a PVA-I gel dosimeter was investigated through percentage depth dose (PDD) measurements using a flatbed scanner and Monte Carlo (MC) simulations. In addition, the PDD measurement was repeated 5 times by means of repeated annealing to evaluate repeatability of the dosimeter. In the gel dosimetry study, a good agreement was observed between the PDDs measured with the gel dosimeters with various iodine content, which were read out using a flatbed scanner, and the PDDs calculated with MC simulations in the dosimeters. Furthermore, a good repeatability of PDD(10) at 10 cm depth obtained from the repeated PDD measurements with the gel dosimeters was observed with less than 1% of standard deviation regardless of the iodine content. In the MC simulations, a good agreement was observed between the calculated PDDs in the gel dosimeters and the calculated PDDs in water. The photon fluence was significantly decreased as the iodine content was increased in the low-energy region unlike with the high-energy region. These results enabled us to conclude that the dose response with iodine content can be ignored in high-energy X-rays used in the field of radiotherapy. However, it might not be ignored in low-energy X-rays. Therefore, a small iodine content might be desirable for water-equivalent gel dosimeters.