The application of a mathematical model of synergism in describing the consecutive combined actions of ionizing radiation and other physical agents has been considered. Using various cell systems it has been shown that the model permits to predict the highest dose modifying factor and conditions in which it can be achieved.
The dependence of dose modifying factor after the consecutive thermoradiation actions on dose rate and dose of ionizing radiation as well as on temperature and duration of its application was studied for yeast cells. The results obtained were described and interpreted by means of the mathematical model of synergism in accordance with which the synergism is expected to result from the additional lethal damage arising from the interaction of sublesions induced by both agents.
A previously proposed mathematical model for the description of the effects of simultaneous action of hyperthermia and ionizing radiation was used to predict the successive treatment of these agents. The model suggests that the synergistic effect of combined action of ionizing radiation and hyperthermia is caused by additional lethal damages arising from the interaction of sublesions induced by both agents. These sublesions are not lethal after the action of these modalities, each taken alone. The model was tested against experimental data reported by other authors. The applicability of the proposed model was demonstrated to predict the dose modifying factor and the limited modification of mammalian cell radiosensitivity by hyperthermia as well as to reveal a more effective sequence of these agents.
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