Cell inactivation by ionizing particles and the shapes of survival curves

Recent experiments concerning the survival of monolayer cells irradiated by different parts of ion Bragg peaks opened a way to a deeper mechanistic un derstanding of cell inactivation. A new theoretical formula for survival cu rves has been derived reflecting two basic phases of the given mechanism, i .e. energy transfer to a cell nucleus and subsequent biological effect (dep ending on the amount of imparted energy). The survival ratio for a given do se has been expressed as a function of inactivation probabilities of indivi dual cells after different numbers of nucleus hits (a given amount of energ y being transferred to a cell nucleus in each ion traversal). Having used t he experimental data for V79 cells irradiated by protons, deuterons and hel ium ions in different parts of Bragg peaks preliminary values of these inac tivation probabilities for individual cells at different LET values have be en established. (C) 2001 Academic Press.