IMRT

Reliability 4D CT

è Repeated 4D CT before treatment planning: l Four 4D CT in ten minutes interval (Guckenberger IJROBP ‘07)

Ø No systematic changes of motion pattern Ø Increased variability for lower lobe tumors

l Two successive 4D CT (van der Geld radiat oncol ‘06) Ø Volume of the PTV not systematically different Ø Motion range variability < 2mm in 81 % Ø Coverage not compromised

No benefit of repeated 4D CT in one session