IMRT

Reliability 4D CT

è Repeated 4D CT during treatment course: l Second 4D CT after > 2 fractions (Haasbeck IJROBP ‘07) Ø No systematic changes of motion pattern and PTV Ø Target coverage compromised in one patient (atelectasis) l Repeated 4D CBCT scans during RT (Sonke IJROBP ‘08) Ø Stable trajectory with variability (1SD) less than 1mm Ø Significant base-line shifts l Tumor tracking in EPID images (Richter IJROBP ’10) Ø Stable tumor trajectory, both intra- and inter fractional No benefit of replanning because of motion variability