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CTV
→
PTV (Planning Target Volume)
OAR
→
PRV
(Planning Organs at Risk Volume)
The recommended CTV margin to create PTV is at least 5 mm.
But, PTV outside skin can
’
t be used for dosimetric calculations
(air, outside the body ...). Typical solutions:
1. To crop PTV by 3 mm (without reaching the skin) but treatment
planning carried out with 2-3 cm
2. To create PTV outside the body (margin for breathing) without
croping
→
An additional
“
cropped
”
PTV volume will then be
needed for normalization purposes and DVH analysis
5 mm