Track structure and the calculation of biological effects of heavy charged particles.

A new approach for the calculation of biological effects of heavy charged particles is discussed. In contrast to other models, the biological effect is determined locally as a function of the local dose deposited by the charged particle tracks. Based on measurable quantities like the X-ray survival curve, the radial dose profile within a track and a geometrical description of the cell nucleus, the model is able to predict several high LET specific properties of charge particle beams, like: (1) the relationship of inactivation cross sections vs. LET and vs. specific energy; (2) the RBE as a function of energy and atomic number of the particles, including the Z-dependent shift of RBE-maxima from 30 keV/micrometer for protons to 300 keV/micrometer for carbon ions; (3) the transition from exponential to shouldered survival curves, depending on the size of the biological object and the corresponding particle fluences.