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Planning Target Volume
PTV
The PTV surrounds the CTV with
a margin to compensate for the different
types of variations and uncertainties of treatment delivery
to the CTV.
The PTV is a geometrical concept, introduced for treatment planning.
A margin must be added to the CTV
•
to compensate for expected physiological movements and variations in size,
shape and position of the CTV during therapy (internal margin)
•
for uncertainties (inaccuracies and lack of reproducibility) in patient
irradiation.