A Nonparametric Method for the Derivation of α/β Ratios from the Effect of Fractionated Irradiations

Multifractionation isoeffect data are commonly analysed under the
assumption that cell survival determines the observed tissue or
tumour response, and that it follows a linear-quadratic dose
dependence. The analysis is employed to derive the α/β ratios of
the linear-quadratic dose dependence, and different methods have
been developed for this purpose. A common method uses the so-called
Fe plot. A more complex but also more rigorous method has been
introduced by Lam et al. (1979). Their method, which is based on
numerical optimization procedures, is generalized and somewhat
simplified in the present study. Tumour-regrowth data are used to
explain the nonparametric procedure which provides α/β ratios
without the need to postulate analytical expressions for the
relationship between cell survival and regrowth delay.