Radiation-Induced Cellular Injury and Repair Mechanisms: A Theoretical Review of Cellular Resilience and Survival Modelling

Radiation interaction with biological systems involves coupled physical, chemical, and biological processes that determine cellular fate after exposure. This study presents a theoretical review combined with analytical modelling of radiation-induced cellular injury and repair, using established radiobiological principles with emphasis on the linear-quadratic (LQ) model. Peer-reviewed literature and standard radiobiological datasets for mammalian cell lines exposed to low-LET radiation were selected using defined inclusion criteria (published survival curves, reported α and β parameters, low-LET radiation, mammalian cell lines). The LQ model, S(D) = exp(-αD - βD²), was applied across 0.1–10 Gy using representative parameter values (α = 0.30 Gy⁻¹,β = 0.03 Gy⁻²; α/β = 10 Gy) consistent with previously reported experimental studies. Survival fractions were computed and the linear (αD) and quadratic (βD²) contributions were decomposed as functions of dose. Calculated survival decreased non-linearly with dose, from S = 0.970 at 0.1 Gy to S = 0.055 at 6 Gy and S = 0.0025 at 10 Gy, with a pronounced shoulder below approximately 2 Gy. The linear component dominated at low doses, whereas the quadratic term became comparable to the linear term at approximately 10 Gy (D = α/β), indicating increasing interaction between independent damage events at higher doses. The width of the shoulder region, interpreted as a quantitative index of repair capacity, varied systematically with the assumed α/β ratio. The LQ model provides a reliable and widely applicable framework for describing radiation-induced cell survival, although it is empirical and does not explicitly resolve DNA repair kinetics.