Abstract
The Microdosimetric Kinetic Model (MKM) to predict the effects of ionizing radiation on cell colonies is studied and reformulated for the case of high-linear energy transfer (LET) radiations with a low dose. When the number of radiation events happening in a subnuclear domain follows a Poisson distribution, the MKM predicts a linear-quadratic (LQ) survival curve. We show that when few events occur, as for high-LET radiations at doses lower than the mean specific energy imparted to the nucleus, , a Poisson distribution can no longer be assumed and an initial pure linear relationship between dose and survival fraction should be observed. Predictions of survival curves for combinations of high-LET and low-LET radiations are produced under two assumptions for their comparison: independent and combined action. Survival curves from previously published articles of V79 cell colonies exposed to X-rays, α particles, Ar-ions, Fe-ions, Ne-ions and mixtures of X-rays and each one of the ions are predicted according to the modified MKM. We conclude that mixtures of high-LET and low-LET radiations may enhance the effect of individual actions due to the increase of events in domains provided by the low-LET radiation. This hypothesis is only partially validated by the analyzed experiments.
Highlights
Ionizing radiations are capable of compromising the viability of live organisms and the functionality of organs and tissues
We explore the principles of the Microdosimetric Kinetic Model (MKM) to determine under what conditions survival curves after expositions to radiation tend to be linear, in particular when the number of radiation tracks involved in the dose deposition is low, excluding non-targeted effects [20,26]
The MKM relies on the concept of domain, which is intended to represent a structure in which two sublethal lesions can combine in pairs to produce a lethal lesion
Summary
Ionizing radiations are capable of compromising the viability of live organisms and the functionality of organs and tissues. Their effect is largely related to the absorbed dose, which is defined as the energy per unit mass imparted to a certain volume. Not all radiations have the same pattern of local energy deposition, meaning that different radiations do not produce equal effects for the same dose. Heavy ions tend to locally concentrate their interactions in reduced volumes, leading to clustered damage to the DNA [3]. X-rays generally transfer energy in a more spread way, producing more isolated damages to the DNA, which are more repairable [4]
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