optical properties of parietal peritoneum in the spectral range 350-2500 nm

Optical properties of parietal Optical properties of parietal peritoneum in the spectral range peritoneum in the spectral range 350-2500 nm350-2500 nm

Marina D. Kozintseva1, Alexey N. Bashkatov1, Elina A. Genina1, Vyacheslav I. Kochubey1, Sergey Yu. Gorodkov2, Dmitry A. Morozov3, Valery V. Tuchin1

1 Department of Optics and Biophotonics of N.G. Chernyshevsky Saratov State University, Saratov, Russia 2 Saratov State Medical University named after V.I. Razumovsky3 Moscow State Scientific-Research Institute of Pediatrics and Children Surgery

Saratov State UniversitySaratov State UniversityDepartment of Optics & Department of Optics &

BiophotonicsBiophotonics

Motivation:Motivation: The wide application of optical methods in modern medicine

in the areas of diagnostics, therapy and surgery has stimulated the investigation of optical properties of various biological 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 the optical properties of Goal of the study is to investigate the optical properties of parietal peritoneumparietal peritoneum in the wavelength range 350-2500 nm in the wavelength range 350-2500 nm

Materials and Methods:Materials and Methods: For this study 13 samples of the parietal peritoneum mucous membrane , 10

samples of the parietal peritoneum muscle membrane and 14 samples of the entire parietal peritoneum (mucous membrane + muscle membrane) have been used. The samples keep in saline during 3-4 hour until spectrophotometric measurements at temperature 4-5°C. All the tissue samples has been cut into pieces with the area about 8.4 0.99 cm2. For mechanical support, the tissue samples have been sandwiched between two glass slides. The average thickness of the samples was 0.77 0.2 mm for parietal peritoneum mucous membrane, 2.3 0.8 mm for parietal peritoneum muscle membrane and 3.13 0.15 mm for entire parietal peritoneum (mucous membrane + muscle membrane).

Measurement of the diffuse reflectance, total and collimated transmittance have been performed using a commercially available spectrophotometer PerkinElmer LAMBDA 950 in the spectral range 350-2500 nm. All measurements were performed at room temperature (about 20°C)

For estimation of absorption and scattering coefficients, and anisotropy factor of the tissue the inverse Monte Carlo method was used.



Experimental setupExperimental setup



The geometry of the measurements in A) transmittance mode, B) reflectance mode. 1 ‑ the incident beam (diameter 1-10 mm); 2 ‑ the tissue sample; 3 ‑ the entrance port (square 2516 mm); 4 ‑ the transmitted (or diffuse reflected) radiation; 5 ‑ the integrating sphere (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.

Inverse Monte CarloInverse Monte Carlo

2 2 2exp calc exp calc exp calc, , , , , , , ,a s d d a s c c a s t t a sF g R R g T T g T T g

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

with the boundary condition 0 0.98g

To minimize the target function the Simplex method described in detail by Press

et al (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 Rdexp, Tt

exp, Tcexp, Rd

calc, Ttcalc, Tc

calc are measured

and calculated values of diffuse reflectance and total and collimated

transmittance, respectively.



Inverse Monte CarloInverse Monte CarloThis 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.



Inverse Monte CarloInverse Monte Carlo

The flow-chart of the inverse Monte Carlo method



Results:

500 1000 1500 2000 2500

0

10

20

30

40

50

Abs

orbt

ion

coef

ficie

nt,

1/сm

Wavelenght, nm

425 nm

555 nm

1194 nm

1450 nm1740 nm

1938 nm

0 500 1000 1500 2000 2500

0

20

40

60

80

Re

du

ced

sca

tteri

ng

co

effi

cie

nt,

1/c

m

Wavelenght, nm

The absorption spectrum of the parietal peritoneum mucous

membrane IS, IMC, data averaged for 13

samples

The reduced scattering coefficient spectrum of the parietal

peritoneum mucous membrane IS, IMC, data averaged for 13

samples



Results:

500 1000 1500 2000 2500

0

100

200

300

400

500

Sca

tter

ing

coef

ficie

nt,

1/cm

Wavelenght, nm



500 1000 1500 2000 2500

0,2

0,4

0,6

0,8

1,0

Ani

sotr

opy

fact

or

Wavelenght, nm

The scattering coefficient spectrum of the parietal

peritoneum mucous membrane IS, IMC, data averaged for 13

samples

The wavelength dependence of scattering anisotropy factor of the

parietal peritoneum mucous membrane

IS, IMC, data averaged for 13 samples

Results:

500 1000 1500 2000 25000

2

4

6

8

10

12

Abs

orbt

ion

coef

ficie

nt,

1/сm

Wavelenght, nm

430 нм555 нм

980 нм1183 нм

1450 нм

1950 нм



500 1000 1500 2000 25000

2

4

6

8

10

12

14

16

Re

duce

d sc

atte

ring

co

effic

ien

t, 1/

cm

Wavelenght, nm

The absorption spectrum of the parietal peritoneum muscle

membrane IS, IMC, data averaged for 10

samples

The reduced scattering coefficient spectrum of the parietal

peritoneum muscle membrane IS, IMC, data averaged for 10

samples

Results:

500 1000 1500 2000 25000

2

4

6

8

10

Abs

orbt

ion

coef

ficie

nt,

1/сm

Wavelenght, nm

425 нм

555 нм

970 нм

1194 нм

1450 нм

1740 нм

1935 нм

2343 нм2451 нм



500 1000 1500 2000 25000

5

10

15

20

25

30

35

Red

uced

sca

tterin

g co

effic

ient

, 1/c

m

Wavelenght, nm

The absorption spectrum of the entire parietal peritoneum

(mucous membrane + muscle membrane)


The reduced scattering coefficient spectrum of the entire parietal

peritoneum (mucous membrane + muscle membrane)


Results:



0 500 1000 1500 2000 2500

0,5

1,0

1,5

2,0

2,5

3,0

3,5

Dep

th o

f pe

netr

atio

n, m

m

Wavelenght, nm

The depth of penetration spectrum of the entire parietal peritoneum (mucous membrane + muscle membrane)


Results:

From the last figure we can se, that the penetration depth of the probe radiation is depend on its wavelength. The maximum effect is seen in the spectral range of 700 – 900 nm, where the depth of penetration of the probe radiation is approximately 3 mm, that corresponds to the total depth of mucous membrane of parietal peritoneum and muscle membrane parietal peritoneum. In the spectral range from 900 nm and more in the absorption band of water with increasing wavelength we can see the decreasing of the depth of penetration of the probe radiation up to 0.6 mm.



Acknowledgements:Acknowledgements:

The work was carried out under the partial support from the Russian Foundation for Basic Research (grant 13-02-91176); RF Governmental contract 14.B37.21.0728; project № 1.4.09; 224014 Photonics4life-FP7-ICT-2007-2; RF President’s grant 1177.2012.2 “Scientific Schools”

optical properties of parietal peritoneum in the spectral range 350-2500 nm

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