A New Concept in Microdosimetry to Evaluate the Quality Factor for Neutrons and Photons

Abstract

Abstract Microdosimetry is potentially a powerful technique for determining radiation quality. Examination of its use has led to the development of a new method by which the effective quality factor Q can be based on the microdosimetric parameter - and the number of ionisations in the DNA double strand diameter (2 nm). Two formulae to evaluate Q have been derived for cell inactivation and other end points of high RBE (e.g. lens opacification). Q values using the first formula were: 1.13, ~4.5, 3.5, 6, 61, and 24, for 60Co(?), 270 eV X rays, 250 KV X rays, 3H(ß), 0.4 MeV and 15 MeV neutrons, respectively. For lens opacification Q values were 1.14, 4.5, 4.4, 9, 230, and 66, respectively, for the above radiations. The above values of Q agree well with published experimental values of RBE, at low doses. The advantage of the present method is that it can predict Q for two radiations of the same -D.