Biomedical Engineering Reference
In-Depth Information
1.2
I(r,0)
1
I(0,z)
0.8
radial profile
0.6
0.4
0.2
axial profile
0
0.00
1.00
2.00
3.00
4.00
5.00
Distance [r or z] (mm)
100
Q(r,0)
Q(0,z)
10
1
0.1
0.01
0.001
0
0.00
1.00
2.00
3.00
4.00
5.00
Distance [r or z] (mm)
Methods for Scattering and Absorbing Media
The fundamental quantity in the transport theory approach is the total specific intensity,
r
L
, which is a function of position
for light in the direction given by a unit vector
s
and its
cm
2
s
1
. The equation of transfer satisfied by
units are
W
.
.
L
can be written as
m
s
ð
dL
ð
~
r,
s
^
Þ
s
0
Þ
L
ð~
s
0
Þ
d
o
0
þ
¼ð
m
a
þ
m
s
Þ
L
ð~
r,
s
Þþ
4p
p
ð
^
s,
r,
S
ð~
r,
s
Þ
ð
17
:
34
Þ
^
^
^
^
ds
Equation (17.34) shows the decrease in
L
due to scattering m
s
and absorption m
a
and the in-
s
0
(Figure 17.7). The sum
crease in
L
due to scattering from
L
coming from another direction
