Module 6 Survival curves

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Four R’s of Radiobiology• In radiotherapy, these types of cellular damage are regulated by thefour R’s of radiotherapy. The four Rs of radiobiology—repair,reassortment, repopulation, and reoxygenation—are affected by thetype of radiation dose.• There is a prompt repair of sublethal repair damage.• There is a progression of cells through the cell cycle during theinterval between the split doses, called reassortment.• There is an increase of surviving fraction due to cell division, orrepopulation. When the time interval between two dose fractionsexceeds the cell cycle, there will be an increase in the number ofcells surviving due to cell proliferation.• The fractionation of the dose allows greater affect throughreoxygenation of the tumour, which increases the radiosensitivity.
Summary• The survival <strong>curves</strong>, which illustrate the survival of a population ofcells, can show the effects of factors such as sex, age, and doserate.• Graphing a survival curve gives a great deal of pertinent informationsuch as threshold dose and mean lethal dose.• Oxygen has an important influence on the effects of radiation due todestruction of the cell by a free radical.• The effects of radiation are influenced by cell cycle position, water,linear energy transfer, age, sex, chemicals, and temperature.• The effects of dose rate on radiation is important for therapeuticradiation use.• Radiosensitizers and radioprotectors are limited in their use due totoxicity.
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 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

Module 6 Survival curves

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