IMRT 2018

IGRT frequency

Off-line correction protocol: NAL (No Action Level) • Mean error at N fractions • Correct after N fractions • No additional corrections • Only systematic errors On-line correction protocol: Correct error at each fraction • Both systematic and random errors • Still recidual errors

Red: CT Turquoise: CBCT Grey: perfect match

De Boer et al IJROBP, 50, 350–1365, 2001