A Study Of Radiation-Induced Transformation And Tumor Prevalence Model Based On Binary Damage Processes

In the process of long-term space exploration missions,space radiation is generally considered to be one of the most important risk factors for astronaut health.Therefore,it is very important to assess the risk of space radiation before carrying out long-term space missions.However,there exist many uncertainties in the traditional method to assess the space radiation risk.Especially in the modeling of tumor incidence induced by ionizing radiation at low doses,that the use of radiation biophysical models has been controversial.At low doses of radiation,the dose-response curves of these models usually do not fit the observed non-target effects(NTEs).This may lead to deviations in the estimation of relative biological effects(RBEs),which can affect the reliability of radiation risk assessments and the effectiveness of radiation protection strategies developed.In this thesis,a new radiation biophysical model is established based on the initial pattern of chromatin domain aggregation and subsequent incorrect repair of two types of DNA double-strand breaks(DSBs)induced by ionizing radiation.Representative experimental data were used for fitting,and the adjusted determination coefficient(Adj.R2)and Akaike information criterion(AIC)were used as two indicators to evaluate the fitting effect of the model.The results show that the fitting effect of the current model is better than that of the target effect(TE)model and NTE model on the experimental data of chromosome aberration and tumor prevalence induced by different types of particle radiation.This indicates that the model can well describe the dose-response curves of chromosome aberration and tumor prevalence,two carcinogenic related endpoints,within the same theoretical framework.In addition,the model can describe dose-response curves of NTE-induced chromosomal aberration and tumor prevalence in low-dose regions without the introduction of the NTE term.What’s more,based on the fitting parameters of the model,we calculated the linear energy transfer(LET)dependent RBE values of chromosome aberration and tumor prevalence at three low doses,respectively and compared the calculated RBEs with those of other models.These results indicate that the model established in this thesis can effectively estimate the RBE in low-dose regions.Using this model as a basis,this thesis further considers the lethality upper limit.That is,when the number of DSBs exceeds a certain value,the cell will directly die.In this case,Euler-gamma function can be introduced into the model,the value of the upper limit of the lethal event is be assumed,and the survival fraction data and cell transformation data induced low LET radiation can be fitted and analyzed.The results show that the expanded model also has a good fitting effect for radiation-induced cell transformation.