Dose Course 2018_Flipping book

Factor-based dose calculations basic dosimetric quantities

Phantom scatter factor, S p

(

)

;

dc D

total

ref

(

)

;

dc D

( )

primary

ref

cS =

(

)

p

;

z c D

total

ref

ref

(

)

;

d c D

primary

ref

ref

SAD

S p is the ratio of scatter factors between the actual field size c in the phantom and that of the reference field size c ref , both at the reference depth d ref :

z

z R

ref

c

c

S

p describes the effects of photon scattering in the phantom only

AAPM TG 74 report, Med Phys 36 (11), 2009