Advanced Physics for Brachytherapy 2018

Linear attenuation coefficient

Describes attenuation of a photon beam Torikoshi et al :

(

) ) , ( ZEG Z

4

) , ( EF Z E



(

)

= 

+

e

ρ

= ρZ/A*N

A = electron density

• •

e

Z = effective atomic number

• F ( E,Z ) and G ( E,Z ) are the photoelectric absorption and scattering terms (Rayleigh and Compton) of μ

For polychromatic x-rays:



 ) , ( ) , ZEG ZEFZ ji

4

 



=



(

+

j

e

ji

ji

i

x-ray spectra represented by weights ω i

at E

i

Torikoshi et al, Phys. Med. Biol. 2003; 48: 673-685. Tsunoo T, et al , NSS Conference Record, IEEE, 2004; 6: 3764-3768