A new concept of cumulative biological effect

The basis of the NSD concept is systematically reviewed and compared with that used in derivation of a new factor describing a cumulative biological effect (CBE) at the end of a fractionated irradiation. It is shown that some basic assumptions used in derivation of NSD and TDF factors cannot be fulfilled. The new CBE factor is free of this deficiency; it can be useful especially for studying biological effects of different irradiation beams.