618 / 1359
-2
-1
1
2
TPR
20/10
=0.80
20%->80%=0.52 cm
TPR
20/10
=0.68
20%->80%=0.23 cm
g/cm
2
0
Energy fluence profile: finite source size 0.70 cm
Energy fluence profile: finite source size 0.35 cm
Penumbra width influenced by source size
Only at very high beam energies (or in low density
regions) lateral electron transport alone
dominates penumbra shaping
Modelling of source size & electron transport
Nyholm
et al
Rad. Onc. 78, pp 347-51 and PMB 51 pp 6245-62
(Anders Ahnesjö)
energy fluence profile for an ideal point source
38