Irradiation of cells by single and double pulses of high intensity radiation: oxygen sensitization and diffusion kinetics.

The biological effects of ionizing radiation in living cells are the ultimate result of a long chain of events with the initial step being the local absorption of radiation. Whereas such physical abosrption is probably over within 10(-16) s after dose delivery, the biological consequences of radiation do not manifest themselves until very much later times. Between these two extremes of time, events occur relatively early at the molecular level which are undoubtedly critically related to the still unknown basic mechanisms of cellular radiation damage. These events may include not only the interaction of highly reactive species produced within the cell but also the diffusion of molecules such as oxygen or other chemical radiosensitizers.