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planning
isoc
x
y
CTV
2.5Σ
planned (static)
95% isodose
blurred 95% isodose
“seen by” CTV
Probability of CTV underdose > 10%
PTV
95%
planned dose
blurred dose
CTV
2.5Σ
Add random errors
M
PTV
= 2.5Σ + 0.7σ
Solution:
M
PTV
= 2.5Σ + ….