712 / 1578
•
Low dose spillage:
Ø
Maximal dose at 2cm from PTV must be between 50-77% of
ID
•
Volume low dose spillage:
Ø
Ratio of volume receiving 50% of
PD
over PTV volume must between
5.9 and 2.9
SBRT 2017 - D. Verellen
D
max
donut PTV
+
2.2
cm
[
]
−
PTV
+
2
cm
[
]
(
)
=
32.6
Gy
=
52%(
ID
)
(
50-77%
)
Volume sphere
, 50%
PD
(
)
VolumePTV
=
Volume
24
Gy
(
)
Volume PTV
(
)
=
191.7
cm
3
39.8
cm
3
=
4.8
(
2.9-5.9
)
PTV &
tissue heterogeneity &
dose prescription