Target volumes – OARs + PRVs
•
Uncertainties apply to the OAR … so a ‘PTV margin’ can be
added around it ‐ to give the Planning organ at Risk Volume
(PRV)
•
But … the use of this technique will substantially increase the
l
f
l
vo ume o norma structures
•
May be smaller than PTV margin
Component for systematic error can often be smaller