Physics Bucharest 2017

Shape of a MV photon beam PDD

D max

simplified depth dose formalism

• e -( m • d)

/f+d) 2

DD(d) %

=D max • (f+d m

• K s

distanc e

attenuationscatte r

f distance from source to surface d m or depth to D max d is depth in tissue K s is the scatter Dose build-up region DD(d) % =D max • (f+d m

• e -( m • d)

/f+d) 2

• K s

Exit Dose D ex

Surface Dose D S

A

B

C