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Some TPS’s require CT calibration tables in terms of
relative mass density
e.g. in point kernel dose calculation engines it is TERMA and point kernels that are
scaled
( )
( )
(
)
( )
(
)
−
r
dr r r
medium rMV
o
e
r
medium
rMV
rT
0
'
'
'
,' ,
, ,
Effective (spectrum averaged) mass attenuation
coefficient at radiological distance r for the
medium with certain density
Primary energy fluence at the surface
•
Mass attenuation coefficients usually pre-stored as weighted averages for an
energy spectrum and for media with different composition and mass density
•
N
CT
relative mass density and material composition
mass attenuation coefficient and linear attenuation coefficient
e.g. in Pinnacle, TomoTherapy PS