Incorporation of microdosimetric concepts into a biologically-based model of radiation carcinogenesis.

The generalised state-vector model of radiation carcinogenesis (SVM) simulates radiation induced biological effects by expressing the transition rates between the various initiation and promotion stages in terms of dose rate for low and high linear energy transfer (LET) particles. In the present work, the SVM has been reformulated to incorporate single track characteristics of particles with varying LET. Transition rates of the initiation phase were expressed as functions of LET by describing the complexity and clustering of DNA double strand breaks (DSBs) and its effect on repair kinetics, while the promotion phase was reformulated based on a multi-target single-hit hypothesis. Such an approach allows the consideration of hit frequencies and the variability of the specific energy and LET spectra of radon progeny alpha particles in bronchial target cells for different exposure conditions.