ESTRO 2025 - Abstract Book

S2579

Physics - Detectors, dose measurement and phantoms

ESTRO 2025

damage was evaluated through optical, chemical, mechanical and electrical tests to quantify change in color, structural integrity, and important electrical properties such as conductivity and dielectric constant that can affect ionization chambers performance. Results: External appearance of samples after irradiation can be seen in Figure 2. All transparent materials exhibited change in color post-irradiation. Chemical analyses conducted shortly after irradiation and repeated two years later indicated partial recovery in some materials. No significant difference in damage was observed between proton and electron irradiation, suggesting comparable radiation damage mechanisms. Dose rate alone did not exacerbate damage beyond total dose effects; however, extended irradiation at high dose rates resulted in thermal damage in some experiments. Mechanical testing revealed increased fragility and hardness in general, while some materials experienced significant changes in dielectric constant and conductivity.

Conclusion: Materials such as PMMA, PC, POM, and its conductive variant POM ELS, are unsuitable for UHDR applications due to significant structural degradation. For see-through phantom construction, CPS offers a more durable alternative to PMMA. For ionization chamber construction, PEEK and graphite demonstrated promising durability, making them preferable choices under high dose and UHDR conditions.

Keywords: Ultra high dose rate, materials

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Digital Poster A novel phantom design and adaptation of TG-218 statistical process for patient-specific quality assurance for Vertebra SABR Adam Yeo 1,2,3 , Kemal Berk 1 1 Department of Physical Sciences, Peter MacCallum Cancer Centre, Melbourne, Australia. 2 Sir Peter MacCallum Department of Oncology, Peter MacCallum Cancer Centre, Melbourne, Australia. 3 School of Sciences, RMIT University, Melbourne, Australia