IGRT 2016 Madrid

2.5 S + 0.7 s is a simplification

• Dose gradients (‘penumbra’ = s p ) shallower in lung  smaller margins for random errors

s s 64.1) ( 64.1 5.2 2 2  + +S = s

M

p

p

• Number of fractions is small in hypofractionation • BUT: beam on time is very long  respiration only causes dose blurring

• Dose prescription at 80% instead of 95%

s s 84.0 ) ( 84.0 5.2 2 2  + +S = s

M

p

p