Dose fractionation

A typical fractionation scheme divides the dose into 30 units delivered every weekday over six weeks.

They have also found that if the radiation is fractionated into smaller doses, with one or more rest periods in between, fewer cells die.

[3][4] The DNA self repair processes in some organisms is exceptionally good; for instance, the bacterium Deinococcus radiodurans can tolerate a 15 000 Gy (1.5 MRad) dose.

[7][8] Hypofractionation is a treatment regimen that delivers higher doses of radiation in fewer visits.

The logic behind this treatment is that applying greater amounts of radiation works to lower the effects of accelerated tumor growth that typically occurs during the later stages of radiotherapy.

This is a graph showing the effect of fractionation on the ability of gamma rays to cause cell death. The blue line is for cells which were not given a chance to recover; the red line is for cells which were allowed to stand for a time and recover.