Physics Bucharest 2017

Assumptions/simplifications in derivation of M PTV,i

= 2.5Σ i

+0.7σ i

:

- large number of fractions - spherical tumor - ideal conformality: - 95% isodose is a spherical surface coinciding with PTV surface (ICRU-50: 100% of PTV should get dose ≥ 95%) - only translational set-up errors: - no tumor rotations - no deformations (derived margin often has to be considered as lower limit)