Dose Course 2018_Flipping book

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