Advanced Physics for Brachytherapy 2018

The method

Let us take a closer look at q scat :

 







Ed d Er ˆ )ˆ, ,( )ˆ ˆ,  

q

Er scat

E Ers

 = 04 )ˆ, ,( 



,(

   →

The probability of a photon scattering from Ω’ to Ω (for a given energy) depends only on cosθ [-1,1], where θ is the scattering angle and the number of photons scattered in a given direction (for a given energy) depends on the solid angle element around the direction: sinθdθdφ or the area on the unit sphere defined by the solid angle around the direction 

Hence, I can expand q

scat in an infinite series of spherical harmonics.