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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