SU‐GG‐T‐308: Polymer Cross‐Linking and Sensitivity Enhancement in Normoxic Polymer Gels Used for Three‐Dimensional Dosimetry

Purpose: To discuss the relation between cross‐linking and sensitivity enhancement in normoxic polymergels in a dose range suitable for intensity modulated radiotherapy, based on considerations related to actual sensor preparation methods and a theoretical description of the optical behavior of irradiated polymergel when dose maps are obtained through optical CT.Method and Materials: Two set of samples of MAGIC gel (9% in weight of methacrylic acid) were prepared at 37°C and 45°C and irradiated with a 60 Co and 6 MV photon beams to doses in the range from 0.1 to 5 Gy. The samples were scanned in an optical CT. Non‐irradiated samples were also scan. A theory based on the number of sites for water solvation, which takes into account polymer cross‐linking, is introduced in order to explain the observed changes in the optical density. The slope of the polymergel response to dose is a measurement of sensitivity and it is analyzed for the actual experimental conditions as well as those for the optimum in connection to cross‐linking phenomena. Conclusion: The analysis showed a proper monotonic behavior for the polymergel response and maximum sensitivity when cross‐linking occurs in an important fraction in the preparation process.