https://doi.org/10.1140/epjp/s13360-025-06391-0
Regular Article
Importance of track density for radiolytic reactions: changes in yields of OH radical molecular probe under protons around the Bragg peak
1
National Institutes for Quantum Science and Technology, 4-9-1 Anagawa, Inage-ku, 263-8555, Chiba, Japan
2
Graduate School of Advanced Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, 169-8555, Tokyo, Japan
3
Graduate School of Science, Rikkyo (St. Paul’s) University, 3-34-1 Nishi-Ikebukuro, Toshima-ku, 171-8501, Tokyo, Japan
Received:
19
November
2024
Accepted:
1
May
2025
Published online:
26
May
2025
The aim of the present study is to elucidate the mechanisms of sparing effects of tissues observed under ultra-high-dose rate (UHDR: > 40 Gy/s) irradiations. To do so, under Bragg peak energy protons, we evaluate changes in OH radicals, that efficiently react with DNA and proteins, consequently, they govern the indirect action, by varying the spatial distribution of proton tracks, while maintaining absorbed dose rate. By applying beam with 2 μm × 2 μm (“micro” beam), yields of OH radicals decrease by − 38 ± 7%, compared to that with 100 μm × 100 μm (“macro beam). The present results show that radical–radical reactions between neighboring tracks occur by UHDR irradiations even around the Bragg peak energy. Additionally, radical–radical reactions, leading the reduction of yields of OH radicals, are one of the mechanisms of sparing effects seen by UHDR irradiations.
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© The Author(s), under exclusive licence to Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature 2025
Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.
