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At the start of treatment
•
Single CT introduces systematic
errors*:
▪
Delineation errors
▪
Organ position and shape at time of
localization
▪
Phantom transfer errors
o
Geometric imaging error
o
Treatment planning system error
o
Linear accelerator geometry error
o
Set-up error at time of localization
▪
TPS beam algorithm error
▪
Breathing positional error
*McKenzie et al., BIR 2003
Image courtesy: Marcel van Herk