Speaker
Description
Abstract
Polytetrafluoroethylene (PTFE) is a chemically stable, biocompatible polymer with near tissue-equivalent properties, making it a candidate material for passive radiation detection in medical applications. In this work, the radiation-induced optical response of ultra-thin (~75 µm) PTFE sheets is investigated under clinical linear accelerator irradiation, with emphasis on comparative behavior under megavoltage photon and electron beams. PTFE samples were irradiated using medical linac 6 MV photon beams over a clinically relevant dose range (0.1-10 Gy), with post-irradiation optical readout using photoluminescence (PL) / absorbance spectroscopy. The results demonstrate a clear dose-dependent increase in absorbance signal under photon irradiation, showing a sublinear response characterized by an approximately linear region at low doses (0.1-4 Gy) followed by a saturation at higher doses. This behavior is consistent with defect formation and recombination mechanisms in polymer systems. In contrast, irradiation under 6 MeV electron beams resulted in significantly weaker and less reproducible changes in optical response. The measured signal variations were found to be comparable to experimental uncertainty, preventing the establishment of a reliable dose–response relationship. This reduced sensitivity is likely attributed to differences in microscopic energy deposition, where localized electron track structures enhance recombination processes within the polymer matrix and reduce the efficiency of stable defect formation. The findings indicate that ultra-thin PTFE shows a stable and measurable response under therapeutic photon irradiation, while its application under electron beams is limited by low signal-to-noise ratio and radiation quality dependent effects. The results highlight the importance of energy deposition characteristics (e.g. LET), and radiation-induced molecular processes within polymer chains in the development of polymer-based radiation detectors, supporting further optimization of PTFE systems for radiation dosimetry applications.
Keywords: PTFE, photoluminescence, linac, photon irradiation, electron irradiation, sublinear response, polymer dosimetry