Development of organic dosimeters based on fluorescence of radiation reaction products of coumarin-3-carboxylic acid

We developed organic materials that can be used as tissue-equivalent dosimeters. We focused on radiation-induced reactions of a water-soluble coumarin derivative, coumarin-3-carboxyl acid (C3CA). C3CA was added to polyvinyl chloride (PVC), polymethyl methacrylate (PMMA), and polyvinyl alcohol (PVA); the photoluminescence spectra of each polymer containing C3CA before and after X-ray irradiation were measured; their sensitivities to X-rays were compared based on changes in their fluorescence intensity. The fluorescent molecules were produced from C3CA upon X-ray irradiation of the three types of polymers. The materials based on PVC, PMMA, and PVA were sensitive to X-rays for doses up to 400 Gy, 8 kGy, and 1 kGy, respectively. These results suggest that the radicals produced from the polymers upon irradiation were added to coumarin. Furthermore, the addition of trichloroacetic acid enhanced the dose sensitivity of the PMMA-based samples. These results indicate that radiation-induced reactions of C3CA can be utilized as tissue-equivalent dosimeters and PVC is the best polymer for this material because of its high dose sensitivity. The difference in the G values and the reactivity of radicals produced in the polymers contributes to the difference in dose sensitivities.