ESTRO course Dose Modelling and Verification 2017

Spectral changes from off axis filtration

Lateral variation of the spectrum, such as off axis softening can be modelled by varying coefficients of attenuation and energy release. Off axis HVL values can therefore be modelled without explicit knowledge of the spectrum change causing it!

ln 2

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Tailor, R.C., et al. Med.Phys., 1998. 25(5): p. 662-667

m

direct beam

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HVL

(for water)

Monte Carlo data Sheikh-Bagheri priv. com.

BEAM (EGS4) Elekta SL 25, 25 MV BEAM (EGS4) Elekta SL 25, 6 MV

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