Influence of dose inhomogeneity on cell survival fraction

Sato, Tatsuhiko   

Radiation doses are inhomogeneously distributed through microscopic sites such as DNA and cell nuclei. Although this inhomogeneity has been regarded as an important factor to determine the relative biological effectiveness (RBE) over 50 years, it had not been frequently used in the quantitative analyses of radiation research because of the difficulty of evaluating the probability density function of dose in microscopic sites. We therefore developed a computational method for calculating the probability density functions in any radiation field and target size by means of combining a multi-scale particle transport simulation code with several mathematical models. Utilizing this method, we established a model for estimating cell-survival fractions in any radiation field. This model employs the probability density functions of domain and cell-nucleus doses as the indexes for characterizing the radiation fields.