Theory of Intertrack Pairwise Lesion Interaction

Abstract

Abstract Experimentally observed heavy ion inactivation cross sections of mammalian cells exhibit the superposition of three effects, namely the 'hooks' due to delta ray range, the 'plateau' due to the multiplicity of lethal products per incident particle, and the underlying restricted LET dependence of the yield µ of lethal products per particle traversal. After elimination of the first two effects, the latter has been observed to follow the fitting function µ = uL? + v2L2 ?, which means that yield µ does not show saturation characteristics as a function of L?. Based on this formula it is shown that the RBE maximum for mammalian cell inactivation is always obtained at that position of the LET scale where a particle traversal through the cell nucleus produces about one lethal product. The quadratic term is derived from first principles under consideration of the reaction kinetics holding for pairwise lesion interaction in molecular 'interaction r egions' and of the proper statistical averaging procedures.