6.6 Spectrum of Action of Laser Radiation on the Hemoglobin Derivatives
125
from 0.5 to 0.38. However, in [26] the inverse Fahraeus effect was observed, when
the values of the hematocrit in a capillary were higher than in great vessels.
2. Insufficient deformation of erythrocytes prevents their flow into a narrow capillary.
Thus, according to [20, 26], the value of the hematocrit can be chosen as 0.4.
6.7 Numerical Calculations for a Model Medium
and Conclusions
Let us consider a model medium with the following characteristics. Typical layer
thicknesses are equal to d 2 = 65 · 10
−6 , d 3 = 565 · 10
−6 , d 4 = 90 · 10
−6 , n
◦
1 = 1,
χ 1 = 0, χ 2 = χ 3 = χ 4 = χ 5 = 10
−5 , refractive indices of the layers are n
◦
2 = 1.50,
n
◦
3 = 1.40, n
◦
4 = 1.35, n
◦
5 = 1.40 and the following values of parameters are a 1 =
−0.0024, b 1 = 0.020, a 2 = 0.021, b 2 = 0.030, a 3 = 0.041, b 3 = 0.051, c 1 = c 2 =
c 3 = 10
−2 . The values of parameters for the interfaces between the layers are chosen
so that the shape of the surface is maximally close to the shape of the boundary of the
corresponding layer in the structure of the normal human dermis, and wavelength is
λ = 0.63 µm (center of the line of a He−Ne laser).
Since the erythrocyte contains no cell organelles, its cellular membrane is very thin
and does not noticeably affect the scattering of light; consequently, the erythrocyte
can be treated as a homogeneous scatterer. Thus, our computations were performed
for monolayer spherulated particles simulating erythrocytes; the number of particles
in the layer being simulated was assumed to be ten for the following parameters: the
relative refractive index for the first five spherulated erythrocytes was assumed to
be 1.035 + 10
−5 i; for the remaining erythrocytes, it was set as 1.033 + 10
−5 i, for
a particle radius of 4.3 µm, H = 0.4, f = 0.08, S = 0.75, C v = 0.0595 [27]. All
computations were performed up to 32 decimal places.
Figure 6.3a, b illustrates the distribution of radiation intensity for multilayer
medium absorbing and scattering light, which simulates human dermis for specific
electrophysical and geometrical characteristics of the biological structure being simulated. The dependences of the laser radiation intensity on the refractive index and
absorption coefficient of the epidermis for various electrophysical parameters of the
biotissue under investigation are shown in Fig. 6.4a, b.
It should be noted that the model constructed here is quite sensitive to variations of the refractive index of the biological structure being simulated; the model
also permits the variation of electrophysical parameters of the biological sample
under investigation, its geometrical parameters, and the establishment of the relation
between these parameters and the biological properties of the biotissue being simulated. Thus, this model can be used for measuring in vivo the spectral differences
between the normal and pathological tissues for determining pathological changes
in the biosamples under investigation, which are associated with a variation of electrophysical properties of epidermis and blood corpuscles in the upper layer of the
dermis.
125
from 0.5 to 0.38. However, in [26] the inverse Fahraeus effect was observed, when
the values of the hematocrit in a capillary were higher than in great vessels.
2. Insufficient deformation of erythrocytes prevents their flow into a narrow capillary.
Thus, according to [20, 26], the value of the hematocrit can be chosen as 0.4.
6.7 Numerical Calculations for a Model Medium
and Conclusions
Let us consider a model medium with the following characteristics. Typical layer
thicknesses are equal to d 2 = 65 · 10
−6 , d 3 = 565 · 10
−6 , d 4 = 90 · 10
−6 , n
◦
1 = 1,
χ 1 = 0, χ 2 = χ 3 = χ 4 = χ 5 = 10
−5 , refractive indices of the layers are n
◦
2 = 1.50,
n
◦
3 = 1.40, n
◦
4 = 1.35, n
◦
5 = 1.40 and the following values of parameters are a 1 =
−0.0024, b 1 = 0.020, a 2 = 0.021, b 2 = 0.030, a 3 = 0.041, b 3 = 0.051, c 1 = c 2 =
c 3 = 10
−2 . The values of parameters for the interfaces between the layers are chosen
so that the shape of the surface is maximally close to the shape of the boundary of the
corresponding layer in the structure of the normal human dermis, and wavelength is
λ = 0.63 µm (center of the line of a He−Ne laser).
Since the erythrocyte contains no cell organelles, its cellular membrane is very thin
and does not noticeably affect the scattering of light; consequently, the erythrocyte
can be treated as a homogeneous scatterer. Thus, our computations were performed
for monolayer spherulated particles simulating erythrocytes; the number of particles
in the layer being simulated was assumed to be ten for the following parameters: the
relative refractive index for the first five spherulated erythrocytes was assumed to
be 1.035 + 10
−5 i; for the remaining erythrocytes, it was set as 1.033 + 10
−5 i, for
a particle radius of 4.3 µm, H = 0.4, f = 0.08, S = 0.75, C v = 0.0595 [27]. All
computations were performed up to 32 decimal places.
Figure 6.3a, b illustrates the distribution of radiation intensity for multilayer
medium absorbing and scattering light, which simulates human dermis for specific
electrophysical and geometrical characteristics of the biological structure being simulated. The dependences of the laser radiation intensity on the refractive index and
absorption coefficient of the epidermis for various electrophysical parameters of the
biotissue under investigation are shown in Fig. 6.4a, b.
It should be noted that the model constructed here is quite sensitive to variations of the refractive index of the biological structure being simulated; the model
also permits the variation of electrophysical parameters of the biological sample
under investigation, its geometrical parameters, and the establishment of the relation
between these parameters and the biological properties of the biotissue being simulated. Thus, this model can be used for measuring in vivo the spectral differences
between the normal and pathological tissues for determining pathological changes
in the biosamples under investigation, which are associated with a variation of electrophysical properties of epidermis and blood corpuscles in the upper layer of the
dermis.