Course book Advanced Treatment Planning 2018
2.5 S + 0.7 s is a simplification
• Dose gradients (‘penumbra’ = s p
) very shallow in
lung → smaller margins for random errors
s ) ( 64.1 5.2 2 2 s
M
+S =
s − + 64 .1
p
p
• Number of fractions is small in hypofractionation
• Residual mean of random error gives systematic error • Beam on time long → respiration causes dose blurring
• If dose prescription is at 80% instead of 95%:
p 2
2
M
=
+S
s ( 84.0 5.2 +
s
)
−
.0
84
s
p
( van Herk et al, IJROBP 47: 1121-1135, 2000)
Made with FlippingBook - Online Brochure Maker