S2577
Radiobiology – Normal tissue radiobiology
ESTRO 2026
affected by Cherenkov light due to electron beam pulses were identified and removed from the oximetry analysis.To evaluate the biological response, hypoxic and normoxic mice were irradiated with FLASH or CONV. Acute skin reactions were scored from day 7–28 post-irradiation to generate dose–response curves (n = 245 mice). Results: Time-resolved phosphorescence-lifetime oximetry revealed distinct oxygen dynamics during FLASH irradiation under normoxic and hypoxic conditions. In hypoxic mouse legs, the median pre-irradiation pO ₂ was 3.3 mmHg, whereas normoxic tissue exhibited a median pre-irradiation pO ₂ of 24.3 mmHg.During FLASH irradiation normoxic tissue showed a median decrease in pO ₂ of 12.5 mmHg while hypoxic legs exhibited a transient increase in pO ₂ , with median rises of 0.53 mmHg.Dose–response analysis revealed FLASH sparing with a dose-modifying factor of 1.43 under normoxia and significantly reversed FLASH sparing with a dose-modifying factor of 0.96 under hypoxia. The dose to induce acute skin damage in 50% of animals was linearly correlated with pO2 (Figure 2). Conclusion: FLASH irradiation under hypoxic conditions was associated with a reversal of the normal-tissue sparing effect and a transient rise in pO ₂ . These findings indicate that both oxygen dynamics and FLASH sparing differ fundamentally between normoxic and hypoxic environments.
Keywords: FLASH, Oxygen Depletion, Murine model
Digital Poster 3446 Characterization of incidental preclinical radiation- induced chronic nephropathy in an orthotopic pancreatic tumor model Sophie Dobiasch 1,2 , Leona Arps 3,4 , Severin Kampfer 1,5 , Christopher Kessler 1 , Janne Schoening 6 , Daniela Schilling 1,2 , Robert Klopfleisch 7 , Carolin Mogler 3,8 , Jan Jakob Wilkens 1,5 , Katja Steiger 3,8 , Stephanie Elisabeth Combs 1,2 1 Department of Radiation Oncology, TUM School of Medicine and Health, TUM Klinikum Rechts der Isar, Munich, Germany. 2 Institute of Radiation Medicine (IRM), Helmholtz Zentrum München, Neuherberg, Germany. 3 Institute of Pathology, TUM School of Medicine and Health, Technical University of Munich (TUM), Munich, Germany. 4 Comparative Experimental Pathology, TUM School of Medicine and Health, Technical University of Munich (TUM), Munich, Munich, Germany. 5 Department of Physics, TUM School of Natural Sciences, Technical University of Munich (TUM), Garching, Germany. 6 independent, consultant, Hamburg, Germany. 7 Institute of Veterinary Pathology, Freie Universität Berlin, Berlin, Germany. 8 Comparative Experimental Pathology, TUM School of Medicine and Health, Technical University of Munich (TUM), Munich, Germany Purpose/Objective: High-precision irradiation (RT) devices for preclinical tumor models enable simulation of clinical treatment
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