Advanced Brachytherapy Physics - Vienna 2016

The problem …

For brachytherapy photons:

1

Energ

y

CSDA range - electrons [g/cm 2 ]

d • secon ary e- ranges are sma re at ve to p oton m.f.p. • e- radiative energy loss is negligible ll l i h



[keV]

[cm]

30

1.8E-03 1.2E-02 1 1E 01 . - 4.4E-01

2.5 5.6 8 9 .

100 350

1000 • CPE can be assumed to exist at all points (except close to a source or high Z materials) Dose to a point can be approximated by collision KERMA throughout a geometry of mm sized voxel elements 14

In short, to know the dose distribution one needs to know the energy distribution of fluence Φ at all points of a geometry: , Ε ,

Table from: Venselaar, Baltas, Meigooni, Hoskin (Eds), Comprehensive Brachytehrapy: physical and clinical aspects. CRC Press, Taylor & Francis, © 2013