Dose 2016

CTV2PTV margin algorithm design concepts

Van Herk etal , IJROBP, 2000 pp. 1121–1135:

“ The PTV is the volume, defined in treatment room coordinates , to which the prescribed dose a must be delivered in order to obtain a clinically acceptable and specified probability that the prescribed dose is actually received by the CTV, which has an uncertain location b ”

a 95% delivered dose, including delivery ( random per patient&fraction)

uncertainties σ 2 = σ 2

+ σ 2

mov … and dose profile “penumbra” σ p

pos

b considering CTV preparation uncertainties Σ 2 = Σ 2 CTpos + Σ 2 … (random but for each patient systematic ) so that for 90% of the patients the entire CTV is inside the ITV delineation

Margin:

(

)

M

2.5 f Σ σ σ = ⋅ + ,

p

ITV

PTV