Target Volume Determination 2015

Margins for random errors

PTV margin* ( ψ = 3.2 mm)

Dose level

PTV margin

80% 85% 90% 95%

0.84 √ (σ ² + ψ ² ) − 0.84 ψ 1.03 √ (σ ² + ψ ² ) − 1.03 ψ 1.28 √ (σ ² + ψ ² ) − 1.28 ψ 1.64 √ (σ ² + ψ ² ) − 1.64 ψ

0.4 σ 0.5 σ 0.6 σ 0.7 σ

σ = SD of random errors, ψ = σ of Gaussian penumbra

*linear approximation