Calculation of the relative biological efficiency (RBE) of neutron radiation

The Relative Biological Effectiveness (RBE) of radiation with different LET has to be recognized in the planning of radiation therapy especially if one type of radiation should be replaced by another type or if both should be used within the same irradiation course. In radiation therapy it is suitable to consider the RBE in connection with dose dependent cell survival rates. These rates can be described by means of corresponding mathematical models. A simple way to calculate the RBE on the basis of the modern LQ-model is demonstrated. In that procedure the alpha/beta-ratios which are known at least approximatively for many organs and tissues can be used. The proposed method is demonstrated for the human skin and lung. For these organs we obtained RBE ranges from 3.4 to 1.2 and from 3.8 to 0.8, respectively, considering increasing doses. Thereby, for the lung it can be observed that the dose dependency of the RBE for small doses is especially strong. The obtained results are in good coincidence with experiences in clinical practice.