22 research outputs found
Numerical study of the effect of methemoglobin concentration in the blood on the absorption of light by human skin
Lasers are widely used in dermatology to remove telangiectasias. Increasing the efficiency of sclerosis of deep-lying and
large telangiectasias with laser radiation is possible by changing the optical transmission of the skin when it is heated
and converting the hemoglobin of the blood contained in it into methemoglobin. The influence of the concentration
of methemoglobin in the blood on the absorption of light in human skin is poorly understood, which determines the
relevance of this study in the context of finding ways to improve the efficiency of laser removal of telangiectasias.
Seven-layer optical models of human skin without telangiectasia and with it for numerical simulation were developed.
The extinction coefficients and the degree of change in the optical transmission of whole blood and skin layers were
calculated in the range of wavelength from 400 to 1600 nm for skin model without and with arteriolar and venular
telangiectasias at various concentrations of methemoglobin in the blood. Based on the analysis of these data, the
wavelengths with the biggest change in the optical transmission of whole blood and skin layers occurred during the
transformation of hemoglobin to methemoglobin were selected. At the selected wavelengths, the Monte Carlo method
was used in optical modelling to get the distribution of the absorbed optical power in each layer of the skin model
without and with telangiectasia at various concentrations of methemoglobin. It has been shown that the spectra of
extinction coefficients for arteriolar and venular telangiectasias do not differ significantly. During the transformation
of hemoglobin to methemoglobin, the largest decrease in the degree of change in the optical transmission of whole
blood occurs at wavelengths of 629 nm and 1105 nm, and the largest increase occurs at wavelengths of 447 nm and
578 nm. The part of absorbed optical power in the layer of superficial vascular plexus without and with telangiectasia
at wavelengths of 629 nm and 1105 nm increases, and at wavelengths of 441 nm and 574 nm it decreases with a
growth of the methemoglobin concentration from 0 to 100 % in the skin model. At the same time, in the layer of deep
vascular plexus the value of part of absorbed optical power increases at wavelengths of 441 nm, 574 nm and 1105 nm,
but at a wavelength of 629 nm first increases with a growth of the methemoglobin concentration up to 25 %, and then
decreases, but to values exceeding the value of part of absorbed optical power without methemoglobin. The change in
optical transmission associated with the replacement of blood hemoglobin with methemoglobin is more pronounced
for the superficial vascular plexus layer, which is associated with high blood content in it and a limited contribution of
the overlying skin layers to the deformation of the spectrum of light incident on this layer. In skin with telangiectasia,
a change in the concentration of methemoglobin changes the proportion of absorbed optical power by a greater amount
than in skin without telangiectasia, which can be associated with an increase in the volume concentration of blood in
skin layers with telangiectasia and an increase in their thickness. The obtained results can be applied in the development
of laser systems and technologies for the treatment of skin diseases, including laser sclerosis of telangiectasias