420-421 / 3107
IMRT – the tongue and groove effects
03/01/13
Depth [cm]
I/I
0
[%]
Attenuation in Tungsten, 2 MeV photons
I
0
I
T
I
L
I
G
!
"
!
#
= %
&'.')).*+
,- ./ - 0
*.1)
0 ./ 2
4 56
= 0.8427
!
<
!
#
= %
&'.')).*+
,- ./ - 0
*.1)
0 ./ 2
' 56
= 0.7102
100 − ?
@
?
+
+ ?
B
?
+
= 0.8675 < ?
+
= 1
Loss by tongue+Gain by groove
“Only primary component of radiation accounted for”
(monoenergetic)
Nominal
leaf edges