Analysis of High-LET Radiation Effects in Terms of Local Energy Deposition

There is now an emerging consensus amongst most biophysical models of radiation action that at low doses damage to mammalian cells is determined predominantly by very local properties of radiation interaction over distances of 1–100nm. Development and testing of models has been hampered by lack of detailed experimental data on the microscopic patterns of energy deposition over such small distances. More precise analysis has now become possible with the development of Monte Carlo techniques to simulate the tracks of charged particles interaction by interaction. To date, when such methods have been applied they have tended to confirm and emphasise further the importance of very local properties of energy deposition over 1–10 nm. Calculations of energy deposition in sub-cellular structures containing DNA by a particles, reveal the large amount of physical damage which mammalian cells can survive. Further identification is required of the critical stochastic physical and biological damage which is primarily responsible for altered cellular function.