Module 6 Survival curves

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<strong>Survival</strong> Curves• The survival <strong>curves</strong> of mammalian cells can be used toobtain direct information on their response to radiation.• When the logarithm of a typical cell survival is plottedversus dose on a linear scale, several features becomeevident. At larger doses of radiation, the graph becomesa straight line on this scale. At low doses, a shoulder onthe curve is found, which is quantified by the thresholddose. The width of shoulder of the survival curveindicates the degree of sublethal damage, which is morereadily repaired in the S phase.
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.
Page 1: Module 6Survival curves• This les
Page 7 and 8: Quasithreshold, D q• The shoulder
Page 9 and 10: Delay in doseA = ContinuousB = 30 m
Page 11: Cell Cycle Effects• During the ce
Page 15 and 16: Chemical Effects on Dammage
Page 17 and 18: Calculation of OxygenEnhancement Ra
Page 19: Difference of Tract Properties
Page 23: Relative Biological EffectivenessDe
Page 28: Dose Rate—Fractionation• The go
Page 31: Summary• The survival curves, whi

Module 6 Survival curves

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