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Systematic deviations
Σ
•
Treatment
preparation
errors,
random
between “patients”,
systematic
per “patient”
(“patient”=planning image set)
•
Remains equal for all fractions based on the planning image set
•
Sources:
−
CTV delineated from a snapshot (movements)
−
Delineation errors
−
Systematic positioning/alignment errors of devices
Type of deviations
Random errors
σ
•
Treatment
execution
errors
•
Different and uncorrelated between fractions
•
Sources:
−
Positioning deviations
−
Field uncertainties