SBRT2015

Why do we use margins?

 Target / tumor  To a-priori compensate for (unknown) deviations between the intended target position and the real target position during dose delivery  Deviations are estimated from population-based measurements of geometrical errors (can be patient specific, e.g. respiratory motion)

 Healthy tissue  To avoid unintended dose to critical organs after aligning the beam to the displaced target (in case of differential motion between target and OAR)