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Reliability 4D CT
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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