
324 Handbook of Biomedical Optics
EB step method for the FD discretization yields the following
discretized RTE (Figures 16.1 and 16.2):
Ψ Ψ
Δ
Ω
Ψ Ψ
Δ
Ω
Ψ Ψ
ijlk
t
ijlk
t
xk
ijlk
t
i jlk
t
yk
ijlk
t
i
c t x
+ +
−
+ +
−
+
−
+
−
1 1
1
1 1
jj lk
t
zk
ijlk
t
ijl k
t
ijl ijlk
t
i
y
z
Q
−
+
+
−
+
+
+
−
+ +
=
1
1
1
1
1
1
Δ
Ω
Ψ Ψ
Δ
Ψ[ ]μ μ
s a
jjlk
t
ijl k kk ijlk
t
k
w p
+
ʹ ʹ ʹ
+
∑
1
[ ]
’
μ
s
Ψ
(16.20)
16.3.3 Finite-Difference Methods
for Irregular Geometries
Extra steps have to be taken if the FD methods are to be employed
in a domain with non-rectangular surfaces. Such irregular
geometries can be treated with the FD methods on unstruc-
tured as well as on structured grids (ompson et al. 1985, 1999,
Farrashkhalvat ...