Dose Course 2018_Flipping book

pencil kernel determination:

Radial differentiation of measured dose for (equivalent) circular fields

D

p r z

1

(

)

( ) meas , r z

,

=

r dr



2





since

r

2



p

p

(

)

(

) ( 

)

( ) ,  r z r r  

 

, x x y y z x y − − , d d   



, , D x y z

, x y

=



=





d d





0 0  





constant

cylindrical geometry integrator

Field

within

field radius

Dashed line :MC Solid line: from measurements

p

( ) , r z



z

2 r

C Ceberg, et al (1996) Med Phys 23 , 505-11.

6 MV

Absolute normalization is a problem, can be circumvented by phantom scatter normalized measured dose, and do renormalization via a reference field size of the calculated dose