Module 6 Survival curves

D m , D 0 , D q• The mean lethal dose, D m , is defined as that amount of radiationrequired to reduce the survival by 37%. It is equal to D 37 in the linearportion of the curve. A large D m indicates a radioresistant line ofcells, whereas a small D m is characteristic of cells with a highradiosensitivity.• The D 0 is the slope of the exponential portion of the curve, whichis the nonlethal dose. The threshold dose, D q , is a measure of howmuch damage occurs before it is lethal. The D q is a measure of thewidth of the shoulder. A large D q indicates that a cell can readilyrecover.• The D 0 value is the measure of intrinsic radiosensitivity of a cell type,whereas the clinical radiosensitivity depends upon the size of theshoulder and the cellular environment.