Dose-rate Effects: Some Theoretical and Practical Considerations

This is the authors' abstract. We don't add key points for this paper.

In radiotherapy, it is well known that the physical dose required has to be increased with the amount of dose fractionation. Such a relationship may be explained either on the basis of recovery, or on the basis of the theory that the biological effect of a single dose depends on a term proportional to the dose together with a second term proportional to the dose squared. The manner in which dose magnitude and fractionation are related has been determined on the basis of the latter theory, and this relationship has been found to be consistent with collected clinical data. On these assumptions, recovery factors for the first and last fractions are not significantly different. Radiosensitivity factors for doses of differing magnitudes have been determined. Some applications are discussed.