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CTV to PTV (Planning Target Volume)
OAR to 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 in free breath treatments:
• To crop PTV by 3 mm (without reaching the skin) but treatment planning carried out with 2-
3 cm
• 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