effect of external mechanical compression on optical properties of the human skin in vivo inara a....
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Effect of external mechanical compression onoptical properties of the human skin in vivo
Inara A. Nakhaeva, Mohammod R. Mohammod,
Olga A. Zyuryukina,Yury P. SinichkinSaratov State University
Abstract
This work presents the results of theoretical and experimental studies of the
effect of the nonlocalized external mechanical pressure on human skin diffuse
reflectance spectra in vivo. It was found that spectral changes are a result of
absorption and scattering properties of the human skin decreasing during
compression. The time of stabilization of the human skin optical parameters
during external pressure (~ some minutes) significantly smaller the time of
relaxation of the skin tissue in normal state after compression (~ one hour).
Also blood content and the degree of hemoglobin oxygenation significantly
increase in initial moment after compression.
Experiment
Method: reflectance spectroscopyObject: the inner forearm human skin in vivo
Experimental setup
Fiber-optic probe
Reflectance spectra: 400-1000 nm USB4000 (Ocean Optics, USA)
Results of experiment
Dynamics of human skin reflectance under the external mechanical compression (m = 0.5 kg; p = 13.9 kPa)
400 500 600 700 800 9005
10
15
20
25
30
35
40R
efle
ctan
ce,
%
Wavelength, nm
0
205 s392 s
52 s
Dynamics of human skin reflectance after the external mechanical compression (m = 0.5 kg; p = 13.9 kPa)
400 500 600 700 800 900
5
10
15
20
25
30
35R
efle
ctan
ce,
%
Wavelength, nm
under pressue
22 s
134 s
Results of experiment
Results of experiment
Dynamics of human skin reflectance under the external mechanical compression (m = 4.0 kg; p = 110 kPa)
500 600 700 800 900
28
30
32
34
36
38
40
42
44R
efle
ctan
ce,
%
Wavelength, nm
15 s
105 s200 s290 s
Withoutpressue
Results of experiment
Dynamics of human skin reflectance after the external mechanical compression (m = 4.0 kg; p = 110 kPa)
500 600 700 800 900
20
24
28
32
36
40
44R
efle
ctan
ce,
%
Wavelength, nm
40 minWithoutpressue
0 s150 s
10 s
Results of experiment
Temporal changes of the human skin reflectance coefficients at two wavelengths in the conditions of the external
mechanical compression
0 100 200 300 400 500 600 700 800 90010
15
20
25
30
35
40
Ref
lect
ance
,%
Time, sec
700 nm
450 nm
m=1 kg
m=1 kg
m=2 kg
m=2 kg
m = 8 kg; p = 111 kPa0-225 sec ‑ under compression,
225 sec – 50 min ‑ after compression
Results of experiment
Erythema index
– apparent optical density.
575560 545 510 610E =100× OD +1.5× OD + OD - 2.0× OD + OD
, [nm]
Dynamics of the human skin eryhema index under (0-290 s) and after (290 s -40 min) the external mechanical compression; m = 4 kg (p = 111 kPa)
Results of experiment
Hemoglobin oxygenation degree,
= 31, = 1
0 100 200 300 400 500 600-20
0
20
40
60
80
100
Oxy
gena
tion
degr
ee
Time, s
TheoryThe human skin diffuse reflectance spectrum in the case of diffusion approximation of
radiation transfer theory: source - spot, medium - homogeneous, semi-infinite
(Farrell T.J., Patterson M.S., and Wilson B. A diffuse theory model of spatially resolved, steady-state diffuse reflectance for the noninvasive determination of tissue optical properties in vivo // Med. Phys. 1992. Vol. 19. P. 879-888).
' 4 1'1 exp A 3 12 3 '1 3 1
aR aa
, A = 2.79
Absorption ( ) ( ) ( )C C C C
a hem oxy oxy deoxy deoxy mel mel
2.303 150 ( ),, ( )66500
oxy deoxyoxy deoxya
, (Prahl S. http://omlc.ogi.edu)
( ) 544.936 exp106.207mel
. (Prahl S. http://omlc.ogi.edu)
Scattering12 4 0.22' ( ) 0.55 10 36.85s
(Bashkatov A.N., Genina E.A., Kochubey V.I., Tuchin V.V. Optical properties of human skin, subcutaneous and mucous tissues in the
wavelength range from 400 to 2000 nm // J. Phys. D: Appl. Phys. 2005. Vol. 38. P. 2543-2555).
Results of modellingEffect of hemoglobin absorption Effect of the scattering
Effect of hemoglobin absorption and scattering
1- normal; 2- absorption was decreased 10 times, scattering was decreased in 1.5 times
Effect of the transport scattering coefficient on the skin reflectance
10 9 8 7 6 5 4 3
0,52
0,56
0,60
0,64
0,68
Ref
lect
ance
'S ,cm-1
λ
Decreasing of reflection on 15% is result of decreasing of transport scattering coefficient in 2 times
1. The external mechanical compression decreases the blood content and scattering properties of the human skin.2. The time of blood content stabilization (about 3 minutes) is less than the time of the scattering properties stabilization (about 5 minutes).3. Decreasing of blood content is accompanied with decreasing of hemoglobin oxygenation degree.4. The blood content in the skin sharply increases (about 2.4 times as compared with normal skin) after removing of compression.5. The hemoglobin oxygenation degree also increases (about 2.7 times as compared with normal skin) after removing of compression.6. The time of relaxation of the human skin to normal state after compression ~ one hour.
Conclusions
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