Biomedical Engineering Reference
In-Depth Information
Ta b l e 6 .
Mean path number, mean path depth and mean path length for photons, using the skin
model
Wavelength Fibre distance <Path number> <Path depth> <Path length>
(nm)
(mm)
(mm)
(mm)
(mm)
0.00
3.16
0.02
0.23
0.14
6.20
0.08
0.78
635
0.25
7.99
0.11
1.16
1.20
19.77
0.27
4.11
0.00
3.08
0.02
0.23
0.14
5.98
0.09
0.86
785
0.25
7.46
0.12
1.26
1.20
14.71
0.26
3.65
0.00
3.77
0.04
0.34
0.14
6.93
0.12
1.12
830
0.25
8.34
0.16
1.57
1.20
14.86
0.28
4.01
Ta b l e 7 .
Perfusion median (first quartile - third quartile) values obtained in baseline, biological
zero, and PORH in the ventral forearm
Wavelength Fibre distance
Baseline
Biological Zero
PORH
(nm)
(mm)
(PU)
(PU)
(PU)
0.14
5.2 (3.5-11.5)
4.5 (2.9-8.8)
19.7 (13.6-52.7)
635
0.25
13.7 (9.2-23.1)
13.5 (8.6-20.3)
37.4 (23.3-57.2)
1.20
55.8 (37.5-100.0) 49.0 (33.8-88.1) 116.8 (98.0-198.6)
0.14
7.8 (5.3-10.3)
5.1 (4.2-7.7)
39.6 (29.4-66.0)
785
0.25
14.1 (10.6-17.9)
8.8 (6.8-12.4)
91.9 (48.0-140.0)
1.20
38.2 (27.9-47.8) 22.6 (16.3-24.9) 227.5 (144.7-304.9)
0.14
17.2 (3.0-58.3)
13.3 (2.0-31.8)
80.0 (12.7-246.2)
830
0.25
25.8 (3.2-62.3)
15.2 (2.0-30.7)
81.5 (20.4-303.8)
1.20
31.7 (7.2-90.3)
13.5 (1.8-43.0)
187.5 (63.0-371.4)
the 1.2 mm emitting-receiving fibre distance. This may be related with the distribution
of the Doppler events percentage in each layer (
cf.
table 4) as discussed later when the
percentage of Doppler shifted detected photons is analyzed.
Skin Measurements.
The median perfusion values measured in baseline, biological
zero and PORH are presented in table 7. For all parameters, the perfusion increases
with the fibre distance for each wavelength, except in the biological zero for 830 nm
wavelength. This reflects the larger volume of tissue sampled by the higher fibre dis-
tances. A significant difference between different fibre distances for the same wave-
length was obtained in baseline (p < 0.03) and in PORH (p < 0.023), for all wavelengths.
In biological zero a significant difference was also obtained (p < 0.003), except for 830
nm wavelength.
When different wavelengths are compared at baseline, for the same fibre distance,
the perfusion increases with the wavelength for F0.14 and F0.25 but decreases for
F1.20. In PORH, the perfusion decreases between 785 and 830 nm for F0.25 and F1.20.
These nonlinearities may be the result of the multiple scattering that occurs when the
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