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PTV in practice: oesophagus
Systematic uncertainty
(confidence level)
Σ
(mm)
Σ
2
Snapshot CT
1.32
Delineation (intra observer)
Random uncertainty
(dose blurring)
σ
(mm)
σ
2
Intrafraction organ mobility 1.00
Interfraction setup (laser)
Interfraction setup (laser)
Interfraction setup (IGRT)
(intra observer registration)
End2end IGRT
(eg PentaCheck)
…
QUADRATIC SUM
Intrafraction patient motion
σ
p
3.2
…
QUADRATIC SUM
σ
The PTV 2017 - D. Verellen
Σ
σ
p
3.2
PTV margin (mm)
M
=
a
S +
b s
2
+
s
p
2
-
bs
p
α=2.5
β=1.64