486 / 1224
2. inhomogeneities
Medium can be of varying material
(different elemental composition
and Zeff)
ACE scales attenuation and absorption
voxel-wise according to:
sc b
m
w
sc en
w
m BmB
sc b
m
w
sc
w
m bmb
1
, 1
1
, 1
=
=
=
=
The same recursive equation applies
BUT:
•
additional input is required to calculate
η
1sc
, χ
1sc
: the energy spectrum of 1sc
photons generated at each point.
This is taken from calculations in water so:
•
the scaling is APPROXIMATE and its
accuracy deteriorates as materials yield
different 1sc spectrum from water (as Z
increases due to coherent & photoelectric
phenomena-x ray fluorescence and S(x,Z))