ESTRO course Dose Modelling and Verification 2017

Flattening filter scatter, semi-analytical approach





c c 



 

0 1



   C 

f

k k 

A



d





2





z

z



0

area as

calc

filt

viewed backward through the aperture

Assumptions (Med. Phys. 21 p 1227-1235): • Predominantly first order scatter • Triangular source distribution over the *visible* filter area - Fit parameters c 0 and c 1 from measured output factors. • Correction factors for: - Energy loss in Compton scattering. - Klein-Nishina cross section angular variation. • Modulate the resultant fluence if modulators are present



dA

( X,Y )



( x,y )

35





 

, X Y



i 

i

i

i