Mechanistic and phenomenological models for the estimate of radiation-induced biological damage

Different techniques for modelling the radiation action on biological targets are analysed, focussing the attention on phenomenological and mechanistic approaches. Phenomenological models allow practical applications (typically in radioprotection and radiotherapy) and are characterised by descriptive features aimed to organise the experimental observations within a formal structure. Mechanistic models are used in basic research and are aimed to reach a better understanding of the physical, chemical and biological processes that, from the initial energy depositions, lead to biological damage. Many different orders of magnitude are involved, both at a spatial level (from atomic dimensions to cellular and organ dimensions) and at a temporal level (from the 10(-15) s of the physical interactions to the hours, and possibly years, of the biological processes). The following aspects are treated: track structure; DNA damage; chromosome aberrations; cell inactivation; low doses and mixed fields. The attention focuses on the comparison between simulations and experiments, the comparison between mechanistic and phenomenological approaches, the determination of the model parameters (in particular on the uncertainties and correlations) and the role of the models in radioprotection and radiotherapy applications.