ATP 2016

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 Σ + 0.7 σ