Abstract Body

FLASH radiation therapy has been shown to reduce normal tissue side effects in multiple animal models. At the same time, other studies observed no or very limited sparing effects. This suggests that the onset of the FLASH tissue sparing effect depends on multiple parameters, including physics parameters such as average dose rate, instantaneous (per pulse) dose rate and dose, but also on the microenvironment, e.g. oxygen concentrations, and the tissue being irradiated. So far, the experimental results still paint a heterogeneous picture and the exact mechanisms why extremely high dose rates cause less tissue damage is still not fully understood.

I will discuss several of the models that have been proposed to explain the mechanisms of FLASH tissue sparing. Common aspects and potential interplay effects will be discussed, starting with track structure Monte Carlo simulations, resulting chemical reactions, effects of oxygen and other reactants, up to potential impacts of blood supply.