Publication: Radical Production with Pulsed Beams: Understanding the Transition to FLASH
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Publication Date
2022-11
Authors
Antonio Vera Sánchez, Juan
Mazal, Alejandro
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MDPI
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Abstract
Ultra-high dose rate (UHDR) irradiation regimes have the potential to spare normal tissue while keeping equivalent tumoricidal capacity than conventional dose rate radiotherapy (CONV-RT). This has been called the FLASH effect. In this work, we present a new simulation framework aiming to study the production of radical species in water and biological media under different irradiation patterns. The chemical stage (heterogeneous phase) is based on a nonlinear reaction-diffusion model, implemented in GPU. After the first 1 mu s, no further radical diffusion is assumed, and radical evolution may be simulated over long periods of hundreds of seconds. Our approach was first validated against previous results in the literature and then employed to assess the influence of different temporal microstructures of dose deposition in the expected biological damage. The variation of the Normal Tissue Complication Probability (NTCP), assuming the model of Labarbe et al., where the integral of the peroxyl radical concentration over time (AUC-ROO) is taken as surrogate for biological damage, is presented for different intra-pulse dose rate and pulse frequency configurations, relevant in the clinical scenario. These simulations yield that overall, mean dose rate and the dose per pulse are the best predictors of biological effects at UHDR.
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This work was funded by the Comunidad de Madrid under project B2017/BMD-3888 PRONTO-CM "Protontherapy and nuclear techniques for oncology" and by the Spanish Government and EU Regional Funds (RTI2018-098868-B-I00, RTC-2015-3772-1). A. Espinosa Rodríguez was funded by an FPU predoctoral fellowship of the Spanish Ministerio de Educación, Cultura y Deporte (FPU18/02551). This is a contribution for the Moncloa Campus of International Excellence, "Grupo de Física Nuclear-UCM", Ref. 910059. Part of the calculations of this work were performed in the "Cluster de Cálculo para Técnicas Físicas", funded in part by UCM and in part by EU Regional Funds.