Module 6 Survival curves

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Types of Radiation Damage• Non-lethal damage involves a lesion which does not prevent proliferation, but itaffects the rate of such proliferation.• Lethal damage is damage which is irreparable, irreversible, and leads irrevocablyto cell death.• Sublethal damage is damage which is repaired in hours unless additional sublethaldamage is added, with which it interacts to form lethal damage. Basically,sublethal damage, which is chiefly evident at low dose levels, is shed after thepassage of a relatively short period of time. It has been shown that the repair ofsublethal damage reflects the repair and the rejoining interval of double strandbreaks before they can interact to form lethal lesions.• Potentially lethal damage is the damage that can be modified by postirradiationenvironmental conditions. This type of damage is manifest in those cellpopulations which are proliferating and are well nourished. This type of damage isonly lethal if cells are stimulated to divide before repair occurs. Therefore, ifmitosis can be delayed by suboptimal growth conditions, the DNA damage can berepaired. Potentially lethal damage limits the effectiveness of radiotherapy ontumors. There is no potentially lethal damage repair following exposure to highlinear energy transfer radiations.
Cell Cycle Effects• During the cell cycle the radiation sensitivity ofthe cells can change dramatically. Studies usingcells which have their cell cycles synchronizedhave shown the results.• The mitosis phase, where the cell divides, isalways the most sensitive, while late in the Sphase, where DNA synthesis occurs, is the leastsensitive. This knowledge is useful in theplanning of cancer treatments.
Page 1: Module 6Survival curves• This les
Page 4 and 5: Survival Curves• The survival cur
Page 7 and 8: Quasithreshold, D q• The shoulder
Page 9: Delay in doseA = ContinuousB = 30 m
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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