THE EFFECTS OF DELTA-RAYS ON THE NUMBER OF PARTICLE-TRACK TRAVERSALS PER CELL IN LABORATORY AND SPACE EXPOSURES

It is a common practice to estimate the number of particle-track trave rsals per cell or cell nucleus as the product of the ion's linear ener gy transfer (LET) and cell area. This practice ignores the effects of track width due to the lateral extension of delta rays. We make estima tes of the number of particle-track traversals per cell, which include s the effects of delta rays using radial cutoffs in the ionization den sity about an ion's track of 1 mGy and 1 cGy. Calculations for laborat ory and space radiation exposures are discussed, and show that the LET approximation provides a large underestimate of the actual number of particle track traversals per cell from high-charge and energy (HZE) i ons. In light of the current interest in the mechanisms of radiation a ction, including signal transduction and cytoplasmic damage, these res ults should be of interest for radiobiology studies with HZE ions. (C) 1998 by Radiation Research Society.