I. The Dose-time Relationship in Radiotherapy and the Validity of Cell Survival Curve Models

The use of fractionated doses in clinical radiotherapy is discussed, and the literature reviewed. An attempt is made to interpret some of the well-known facts in terms of cellular radiobiology. Assuming cell survival curves to apply to organised tissues, and assuming values for the mitotic cycle times of normal and tumour cells, the efficiency of common treatment plans involving fractionated doses are compared.