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Wrong CT for matching: 4D-CT
•
4D-CT used to generate
Midvent plan.
•
CTV delineation at Midvent
position used to generate
PTV and position isocenter
•
(Plan calculated on average
CT)
•
CBCT should be matched
on midvent CT
•
However, average CT was
used, introducing
systematic shift! (planned
CTV position <> CTV
position on reference CT)