Biomedical Engineering Reference
In-Depth Information
a higher probability of continuing to propagate in this direction. To validate the distinction between
these tissues,
t
-tests were performed at 10 micron depth intervals, and the differences were statistically
significant (
p
< 0.01 in all cases).
As in the OI case, we utilized Monte Carlo simulations of these plots using the measured bulk opti-
cal parameters as inputs to decouple the initial emission directionality (i.e.,
F
SHG
/B
SHG
) from the SHG
propagation (based on μ
s
and
g
). Representative simulations for the normal and malignant biopsies
are shown in Figures 6.11a and 6.11b, respectively. We then fit to the initial directionality by squaring
and summing the residuals between the series of simulations and the experimental data. Taking the
minimum of the
R
2
function yielded %
F
SHG
of 93% and 77%, for the normal and cancer, respectively,
where the uncertainty in each case is approximately ±3%. The corresponding Monte Carlo simulation
generated from the best fit for each tissue type (open squares = normal and open circles = cancer) is
overlapped with the experimental SHG data in Figure 6.11c. The chi-squared test between the experi-
mental and simulated data resulted in values of 0.40 and 0.30 for the normal and cancer, respectively,
indicating that, for both tissues at the α = 0.05 level, the data and corresponding simulation are not
significantly different. This good fit between the simulated and measured data thus gives us confidence
in the extracted %
F
SHG
values, as was the case for the OI tissues.
(a)
(b)
13
13
100%
100%
11
11
97%
9
9
95%
7
7
90%
5
5
75%
65%
50%
3
3
50%
1
1
0
20
40
60
80
100
0
20
40
60
80
100
Depth (microns)
Depth (microns)
(c)
8.0
Normal, measured
Normal, simulated
Cancer, measured
Cancer, simulated
7.0
6.0
5.0
4.0
3.0
2.0
1.0
0
20
40
60
80
100
120
Depth (microns)
FIgurE 6.11
Monte Carlo Simulations of the measured
F/B
response, where (a) and (b) show the results for
normal (a) and malignant (b) ovaries using the bulk optical parameters in Table 6.1 over a range of initial emission
distributions. The best-fit simulation to the data in each case is overlapped with the experimental data in (c), where
the %
F
SHG
was determined to be 77% and 93% for the malignant and normal tissues, respectively. (Reproduced from
Nadiarnykh, O. et al. 2010.
BMC Cancer
10:94.)
