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Margins and number of fractions
•
If the number of fractions decreases (eg
HYPOFRACTIONATION
)
the “random” component becomes more “systematic” (ie a “shift”)
•
Effective systematic uncertainty (shift)
•
Effective random uncertainty (blur)
S
eff
= S
2
+
1
N
s
2
N
®
1
The PTV 2017 - D. Verellen
s
eff
=
1
-
1
N
æ
èç
ö
ø÷
s
2