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Target volumes - PTV
•
PTV is a geometric concept designed to ensure that the prescription
dose is actually delivered to the CTV
•
In a sense, it is a volume in space, rather than in the patient
•
PTV may extend beyond bony margins, and even outside the
patient
•
Systematic
and
random
errors need to be
quantified to produce the PTV margin
•
PTV = 2.5
S
+ 0.7
s