A relationship between microdosimetric spectra and cell survival for high-LET irradiation

A method of calculating cell survival from microdosimetric spectra for high-LET radiations and exponential cell survival is discussed. The basis of the calculation is that a cell nucleus receiving a specific dose D has a probability of survival of exp(-D/Do), where Do, the specific lethal dose, is assumed to be independent of cell size and shape. A relationship between specific lethal dose and mean lethal dose is derived. This approach gives the result that mean lethal dose is sensitive to both cell size and shape (cells with disc-shaped and spherical nuclei are treated) and therefore its uses as an indicator of cell sensitivity at high LET must be viewed with caution.