The starting point of this project was a serendipitous observation made within the ERC project SPICE, together with the innovative measurement methodologies developed therein. Building on this finding, we systematically investigated the reaction mechanisms of the nitroxide (NO*) system under irradiation
The influence of concentration, dissolved gases, and various additives was examined by means of EPR spectroscopy.
A comprehensive EPR data set documenting the influence of all relevant parameters is available.
Complementary analytical investigations using LC–MS, watergate NMR, and deuterated compounds revealed a large variety of reaction products.
Despite the fact that the molecular mechanism could not be resolved in full detail, we were able to systematically optimize the chemical properties of the dosimeter system with respect to sensitivity, long-term signal stability, and minimization of dose uncertainty.
We evaluated the dosimeter response under a range of conditions relevant for clinical application. The irradiation experiments were performed in collaboration with the LINAC radiation facility of METAS (Bern). The influence of cumulative irradiation of the same dosimeter was also investigated, which is of particular relevance for long-term patient treatments. A systematic data set characterizing the dosimeter response as a function of the relevant parameters is available.
A systematic investigation of the EPR readout parameters—including temperature, microwave (MW) power, modulation amplitude, sweep time, and number of scans—was performed to further optimize the readout of the liquid dosimeter.
Rapid-scan (RS) EPR spectroscopy was evaluated in comparison to conventional continuous-wave (CW) EPR with respect to sensitivity and readout speed.
A robust measurement protocol was developed to ensure reproducible data acquisition across different users by minimizing handling-related errors and simplifying application. The protocol was validated in multi-user tests.
