Dose Course 2018_Flipping book

Summary of Point Kernel model properties

• Heterogeneities are considered through scaling of the rectilinear transport along all lines, hence it models: – loss of CPE for small fields and in lung – penumbra broadening in lung – rebuildup after low density media • Major limitations: – rectilinear scaling coarse approximation for multiple scattering – angular discretization effects • Use of media specific  en in primary raytrace yield dose to medium in medium (not water in medium) but is implementation dependent! • The dose calculation time for N 3 voxels is with the Collapsed Cone approach reduced from being proportional to N 7 operations to to M . N 3 where M is the number of transport directions • Core calculation loops only a few hundred lines of code, much less complex than a multisource beam modelling code

26