Cell survival prediction in carbon-ion radiotherapy based on DNA radiation damage characterization of mixed beam
Objective To develop a prediction model for cell survival under radiation of mixed carbon ion beam based on DNA radiation damage simulation,and to assess the impacts of secondary particles on the cell survival prediction for regions beyond the Bragg peak.Methods First,the Monte Carlo Damage Simulation(MCDS)code was employed to construct a database of DNA double-strand break(DSB)damage induced by carbon ions and their primary secondary particles for Chinese hamster ovary(CHO)cells.Subsequently,models for cell survival under irradiation of single type of particles were established through fitting and were validated based on the DSB damage database and the Particle Irradiation Data Ensemble(PIDE)experimental database of radiation biology for cells in vitro.Then,the TOPAS Monte Carlo code was used to simulate the depth-dose and energy spectrum distributions of 290 MeV/u clinical carbon ion beam.A dose-weighting method based on a precomputed DSB damage database for monoenergetic particles was proposed,and the impacts of secondary particles on cell survival prediction beyond the Bragg peak were assessed.Results The model established in this study accurately predicted the survival rates of CHO cells under different irradiation conditions.Concurrently,the dose-weighting method employed accurately characterized the radiation damage properties of mixed beams of carbon ions and their secondary particles.The root mean square errors(RMSE)of parameter α between the experimental values and model-derived predictions after irradiation using the H+,He2+,C6+,and Ne10+beams were 0.139 2,0.203 9,0.192 0,and 0.516 9 Gy-1,respectively,while the RMSEs of parameterβwere 0.020 5,0.059 8,0.040 5,and 0.060 5 Gy-2,respectively.The discrepancies between model-derived predictions and experimentally measured values of the survival rates of CHO cells at and beyond the Bragg peak after irradiation using 290 MeV/u carbon ion beam were 0.3％±0.24％and 2.3％±0.24％,respectively.Conclusions A prediction model for cell survival under irradiation of carbon ion beam based on DNA radiation damage simulation is developed in this study.By further considering the dose distributions of various secondary particles,the model can more accurately predict cell survival rates beyond the Bragg peak.This study is expected to provide a reference for accurately assessing the equivalent biological dose beyond the Bragg peak in carbon ion clinical radiotherapy.
Carbon ion radiotherapyCell survival predictionMonte Carlo simulation
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