285 / 1224
The problem …
Energy
[keV]
CSDA-range
electrons [g/cm
2
]
[cm]
30
1.8E-03
2.5
100
1.2E-02
5.6
350
1.1E-01
8.9
1000
4.4E-01
14
1
For brachytherapy photons:
•
secondary e- ranges are small relative to photon
m.f.p.
•
e- radiative energy loss is negligible
•
CPE can be assumed to exist at all points (except
close to a source or high Z materials)
Table from: Venselaar, Baltas, Meigooni, Hoskin (Eds), Comprehensive Brachytehrapy:
physical and clinical aspects. CRC Press, Taylor & Francis, © 2013
Dose to a point can be approximated by collision KERMA throughout a geometry
of mm sized voxel elements
In short, to know the dose distribution one needs to know the energy distribution
of fluence, Φ
Ε
, at all points of a geometry: