Study on the radical kinetics driven by the beam time profile under different oxygen contents in FLASH radiotherapy
10.3760/cma.j.cn112271-20250624-00213
- VernacularTitle:FLASH放疗中不同氧含量下束流时间结构驱动的自由基动力学研究
- Author:
Jianhan SUN
1
;
Xianghui KONG
;
Jianfeng LYU
;
Jinghui WANG
;
Xiaodong LIU
;
Chen LIN
;
Tian LI
;
Yibao ZHANG
;
Senlin HUANG
Author Information
1. 北京大学核物理与核技术国家重点实验室 北京大学物理学院，北京 100871
- Publication Type:Journal Article
- Keywords:
FLASH radiotherapy;
Free radicals;
Monte Carlo simulation;
Beam physics
- From:
Chinese Journal of Radiological Medicine and Protection
2025;45(11):1061-1068
- CountryChina
- Language:Chinese
-
Abstract:
Objective:To reveal the coupling mechanism of beam temporal profile and tissue oxygen content on radical kinetics, further explain the potential biological basis of the FLASH effect, and provide a reference for beam optimization and treatment planning design of FLASH radiotherapy (FLASH-RT).Methods:TOPAS-nBio v3.0 was used to simulate the physical and chemical processes of electron beams in water, and a full-scale kinetic model was established covering the generation, diffusion, reaction, and quenching of free radicals such as hydroxyl radical (·OH) and hydrated electrons (e aq-). Under different beam temporal profiles (single pulse, multi-pulses, continuous wave irradiation) and different oxygen concentration conditions, the evolution dynamics of free radicals were systematically simulated. At the same time, the data on e aq- content were obtained by experimental measurement of laser absorption spectroscopy to verify the accuracy of the model prediction. Results:The changing trend of e aq- concentration measured in the experiment was highly consistent with the simulation result, verifying the reliability of the constructed model. The beam time structure had a significant impact on the peak value and duration of free radical concentration. The single-pulse structure can cause the free radicals to rapidly increase and then quickly quench in a short time, while the continuous or long-pulse structure can cause the radical concentration to remain at a high level for a long time. The evolution of ·OH was not sensitive to the oxygen environment, while e aq- are greatly affected by the oxygen environment. The scavenging efficiency of free radicals in a hypoxic environment was significantly decreased, leading to an enhanced accumulation of oxidative damage to biological macromolecules. The lifespan of e aq- in an oxygen-rich environment decreased rapidly. Conclusions:Radical kinetics are regulated by both the beam temporal profile and oxygen content. FLASH-RT can utilize single-pulse or multi-pulses intervals to form periodic windows, reducing normal tissue damage by efficiently scavenging free radicals through antioxidants, while free radicals in tumor tissues continuously accumulate and amplify damage, thus generating a selective protective effect.
