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The basic equation is the LBTE
Let
be the angular fluence (dΦ/dΩdE=dN/dAdΩdE) denoting the number
of photons in phase space element i e passing through a voxel of area dA
)ˆ, ,( ,
ErE
)ˆ
(
Er
, . .
normal to located at
,
with wιthin Ω and Ω+dΩ and E between E and E+dE.
, ,
ˆ
r
ˆ
h fl
f h
h h
At any part of this “phase space”, conservation of E dictates particle density balance.
)ˆ, ,( ,
ˆ
ErE
T e net ow o p otons t roug a
phase space cell equals:
ˆ
h
d i i
p otons scattere n t
from all others (E’, Ω’)
)ˆ, ,(
Er scat q
h
i d b
ˆ
+ p otons em tte y a source
in it
)
(
4
) , (
pr r
Epq
h b b d
-
p otons a sor e or
scattered out of it
)ˆ, ,( ,
) ,(
ErE Ert
L B T E . . . .