2017_SBRT_Course Book

Margin definition DT patients

Prediction error tolerance level of 3 mm

σ = 1.5 mm (dose blurring) Σ= 1.5 mm (shift)

3 mm

3 mm

1.5 mm

R=3 mm

rebuild CM

Penumbra: σ p =4.05mm β=0.73 (for 95% isodose)

Mechanical tracking errors

marker-TV surrogate uncertainty

Gimbals systematic error

+

σ = 0.5 mm

Σ=CT-slice/2=1 mm

Σ= 0.4 mm

-surrogate vs TV relative rotation in relative ITV -no patient specific tracking error yet M=2.5*√(( 1mm ) 2 +( 1.5mm ) 2 +( 0.4mm ) 2 )+0.73*√(( 1.5mm ) 2 +( 0.5mm ) 2 +(1mm) 2 +(4.05mm) 2 )-0.73*4.05mm =4.9 mm => 5 mm SBRT 2017 - D. Verellen