Computer simulation of the dynamics of ion induced radiation damage in cells

The biophysical simulation code PARTRAC has been used in many studies of DNA damage induced by various radiation qualities including photons, electrons, protons, alphas and, recently, ions heavier than alpha particles. Calculated initial DNA damage due to irradiation of human fibroblast cells by B-, N- and Ne-ions was compared to corresponding experimental data. The calculated total DSB yield per dose showed saturation behaviour with an RBE of about 2, unlike the decreasing tendency with increasing LET to RBE values below 1 in the experimental data. However, the experimentalists data analysis method for DSB yield determination applied to simulated data resulted in good agreement. Calculated and measured fluence dependent DNA yields in certain size intervals as well as DNA fragment size distributions were also in accord. A new DSB repair model has been developed and applied to experimental data on DSB rejoining after ion irradiation. Simulated data on correct and incorrect rejoining, DNA fragment distributions and movement of breakpoints are presented and compared to experimental findings