Transcript Слайд 1 - Eventry

Saratov
State University
______________________________________________
Department of Optics
& Biophotonics
Optical properties of human
tonsils in the spectral range from
350 to 2500 nm
Ekaterina A. Kolesnikova, Aliya A. Muldasheva, Julia P. Ireneva,
Darya N. Zmeeva, Alexey N. Bashkatov, Elina A. Genina,
Vyacheslav I. Kochubey, Anatoly B. Knyazev,
Valery V. Tuchin
Saratov State University, Saratov State Medical University
e-mail: [email protected]
Saratov Fall Meeting 2012
Motivation
Saratov
State University
______________________________________________
Department of Optics
& Biophotonics
Development of optical method in modern medicine in the areas
of diagnostics, therapy and surgery has stimulated the investigation of
optical properties of various biological tissues, since the efficacy of
laser treatment depends on the photon propagation and fluence rate
distribution within irradiated tissues.
The knowledge of tissue optical properties is necessary for the
development of the novel optical technologies of photodynamic and
photothermal therapy, optical tomography, optical biopsy, and etc.
Numerous investigations related to determination of tissue optical
properties are available however the optical properties of many
tissues have not been studied in a wide wavelength range.
Goal of the study is to investigate optical properties of
human tonsils in the wavelength range from 350 to 2500 nm
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Materials and methods
Saratov
State University
______________________________________________
Department of Optics
& Biophotonics
 For this study twenty samples of human tonsils have been used. The
samples were kept in saline during 48 hours at temperature 4-5°C
until spectrophotometric measurements. The size of the samples was
approximately 20×25 mm, the average thickness was 2.0±0.5 mm.
For mechanical support, the tissue samples have been sandwiched
between two glass slides
 Measurement of the total reflectance, total and collimated
transmittance have been performed using a commercially available
spectrophotometer LAMBDA 950 (PerkinElmer, USA) in the spectral
range 350-2500 nm
 All measurements were performed at room temperature (about 20°C)
 Inverse Monte Carlo technique has been used for processing the
experimentally measured spectra of the tissue samples
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Saratov Fall Meeting 2012
Materials and methods

Experimental setup
Saratov
State University
______________________________________________
Department of Optics
& Biophotonics
The geometry of the measurements in A)
transmittance mode, B) reflectance mode
1 - the incident beam (diameter 1-4 mm);
2 - the tissue sample; 3 - the entrance
port (square 2516 mm); 4 - the
transmitted (or diffuse reflected) radiation;
5 - the integrating sphere (IS) (inner
diameter is 150 mm); 6 - the exit port
(diameter 28 mm)
The geometry of the collimated
transmittance measurements
Diameter of the incident beam is
2 mm
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Saratov Fall Meeting 2012
Inverse Monte Carlo (IMC)
Saratov
State University
______________________________________________
Department of Optics
& Biophotonics
The computer program package for determination of absorption and
scattering tissue properties has been developed. This inverse Monte Carlo
method based on the solution of direct problem by Monte Carlo simulation
and minimization of the target function
F  a , s , g    Rtexp  Rtcalc  a , s , g    Tcexp  Tccalc  a , s , g    Tt exp  Tt calc  a , s , g  
2
2
2
with the boundary condition 0  g  0.98
To minimize the target function the Simplex method described in detail by
Press W.H., et al. (Numerical recipes in C: the art of scientific computing /
Cambridge: Cambridge University Press, 1992.) has been used. Iteration
procedure repeats until experimental and calculated data are matched within
a defined error limit (<0.1%). Here Rtexp, Ttexp, Tcexp, Rtcalc, Ttcalc, Tccalc are
measured and calculated values of total reflectance and transmittance and
collimated transmittance, respectively.
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Saratov Fall Meeting 2012
Inverse Monte Carlo
Saratov
State University
______________________________________________
Department of Optics
& Biophotonics
This method includes inverse adding-doubling (IAD) method developed by Prahl et al (Prahl S.A.,
et al. // Appl. Opt., 1993, Vol. 32(4), P. 559-568) and inverse Monte Carlo simulations. The IAD
method is widely used in tissue optics for processing the experimental data of spectrophotometry
with integrating spheres. This method allows one to determine the absorption and the reduced
scattering coefficients of a turbid media from the measured values of the total transmittance and the
diffuse reflectance. In these calculations the anisotropy factor can be fixed as 0.9, since this value
is typical for tissues in the visible and NIR spectral ranges.
Based on the obtained values of the tissue absorption and reduced scattering coefficients the
inverse Monte Carlo calculations have been performed. The inverse method includes direct
problem, i.e. Monte Carlo simulation, which takes into account the geometric and optical conditions
(sample geometry, sphere parameters, refractive index mismatch, etc.), and solution of inverse
problem, i.e. minimization of target function by an iteration method. In this study, we used Monte
Carlo algorithm developed by L. Wang et al (Wang L., et al. // Computer Methods and Programs in
Biomedicine, Vol. 47, P. 131-146, 1995). The stochastic numerical MC method is widely used to
model optical radiation propagation in complex randomly inhomogeneous highly scattering and
absorbing media such as biological tissues.
Usually the inverse Monte Carlo technique requires very extensive calculations since all sample
optical parameters (absorption and scattering coefficients and anisotropy factor) unknown. To avoid
the long time calculations as a guest values we used values of absorption and reduced scattering
coefficients obtained from calculations performed by IAD method. For final determination of the
tissue absorption and scattering coefficients, and the tissue anisotropy factor minimization of the
target function has been performed.
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Saratov Fall Meeting 2012
Inverse Monte Carlo
Saratov
State University
______________________________________________
Department of Optics
& Biophotonics
The flow-chart of the inverse Monte Carlo method
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Saratov
State University
Results
______________________________________________
Department of Optics
& Biophotonics
The typical spectra of a human tonsil sample. Rt is total reflectance; Tt is
total transmittance and Tc is collimated transmittance
Rt
Tt
0,1
Tc
0,01
1E-3
1E-4
1E-5
1E-6
0
500
1000
1500
2000
2500
Wavelength, nm
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Saratov Fall Meeting 2012
Saratov
State University
Results
______________________________________________
Department of Optics
& Biophotonics
The absorption spectrum of human tonsils
IS, IMC, data averaged for 20 samples
Absorption coefficient, 1/cm
60
50
40
30
20
10
0
0
500
1000
1500
2000
2500
Wavelength, nm
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Saratov Fall Meeting 2012
Saratov
State University
Results
______________________________________________
Department of Optics
& Biophotonics
The scattering coefficient spectrum of human tonsils
IS, IMC, data averaged for 20 samples
Scattering coefficient, 1/cm
400
350
300
250
200
150
100
50
0
0
500
1000
1500
2000
2500
Wavelength, nm
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Saratov Fall Meeting 2012
Saratov
State University
Results
______________________________________________
Department of Optics
& Biophotonics
Reduced scattering coefficient, 1/cm
The reduced scattering coefficient spectrum of human tonsils
IS, IMC, data averaged for 20 samples
120
100
80
60
40
20
0
0
500
1000
1500
2000
2500
Wavelength, nm
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Saratov Fall Meeting 2012
Saratov
State University
Results
______________________________________________
Department of Optics
& Biophotonics
The wavelength dependence of scattering anisotropy factor of
human tonsils
IS, IMC, data averaged for 20 samples
Anisotropy factor
1,0
0,8
0,6
0,4
0,2
0,0
0
500
1000
1500
2000
2500
Wavelength, nm
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Saratov Fall Meeting 2012
Saratov
State University
Results
______________________________________________
Department of Optics
& Biophotonics
The wavelength dependence of penetration depth
of human tonsils
IS, IMC, data averaged for 20 samples
Penetration depth, cm
0,16
0,14
0,12
0,10
0,08
0,06
0,04
0,02
0,00
0
500
1000
1500
2000
2500
Wavelength, nm
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Saratov Fall Meeting 2012
Summary
Saratov
State University
______________________________________________
Department of Optics
& Biophotonics
 The
analysis of the results has shown that
investigated spectra depend on scattering
coefficient of collagen fibers and absorption
bands of interstitial matrix water. The absorption
bands of oxyhemoglobin at the wavelengths
415, 540 and 570 nm are well seen
 Our
results can be used for the development of
new methods and optimization of the existing
ones of therapy of rhinologic diseases
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Saratov Fall Meeting 2012
Acknowledgements
Saratov
State University
______________________________________________
Department of Optics
& Biophotonics
Grant #224014 Network of Excellence for
Biophotonics (PHOTONICS4LIFE) of the Seventh
Framework Programme of Commission of the
European Communities
Grants # 11-02-00560 and 12-02-92610-КО of Russian
Foundation of Basis Research
Russian Federation governmental contacts
02.740.11.0770, 02.740.11.0879, 11.519.11.2035, and
14.B37.21.0728
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Saratov Fall Meeting 2012