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A Ahnesjö et al (1992)
Med Phys
19, 263-273
( )
2
2
2
,
1
e
z
z
z
z
a r
b r
z
z
r
a r
z
z
A e
B e
p
r z
r
r
A e
r
−
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Penumbra effects:
• electron transport effects – automatically by the kernel
• collimator transmission and finite source occlusion effects
• should be considered during fluence modelling (dosimetric leaf gap
addition not sufficient)
• can also be approximated with a field edge blurring convolution of the
primary part, example (in dose domain,
direct blurring of idealized collimated
fluence also possible
):
calculation techniques:
projected Gaussian
source distribution