The use of the D versus dD plot to estimate the alpha/beta ratio from iso-effect radiation damage data

In studies of radiation damage, the parameter alpha/beta of the linear-quadratic (LQ) model is usually estimated from iso-effect data by plotting the iso-effect doses in a so-called Fe-plot, which is a plot of the inverse total dose versus dose per fraction. This method, however, is statistically not well founded. A better, but relatively complex technique to estimate the alpha/beta ratio was described by Tucker. The present contribution shows that results, virtually identical to the ones of Tucker can be obtained in a very simple way if the iso-effect doses are plotted as total dose Dn versus the product of dose per fraction and total dose, Dndn. A reliable estimator of the alpha/beta ratio consists then of the negative inverse slope of the linear-regression line in this plot. The presentation of iso-effect data in such a D-dD plot highlights deviations from the LQ model more clearly than does the Fe-plot. It is therefore suggested to use the D-dD plot as a quick and easy graphical scheme to obtain an estimate of alpha/beta.