Discussão sobre propriedades ópticas e histologia de pele de rato sadia e queimada

Abstract

Background: The interaction between light and biological tissue occurs through reflection, refraction, absorption, scattering, and transmission. Determining such properties is important for optical devices to be properly designed, diagnostic signals to be well interpreted, and for photonic therapy protocols to be safe once the optical properties of tissue affect the light's behavior. Diffuse optical spectroscopy has advanced as a promising tool for non-invasive determination of reflectance and transmittance. Once this data is collected, the Kubelka-Munk function for the indirect acquisition of the other parameters can be used to determine absorption coefficient, reduced scattering coefficient, reduced attenuation coefficient, and penetration depth. Since the skin is the major physical barrier during photonic therapies and that injured tissue behaves differently compared to healthy tissue, it is important that the optical properties of the skin be known in both physiological states. Objective: The aim of this study was to analyze the optical and histological differences between healthy rat skin and rat skin after burn induction. Methods: Wistar rats underwent scalding burn induction under general anesthesia and were euthanized after 3, 7 and 14 days. Through spectroscopic analysis, skin biopsies had their transmittance and reflectance values collected between 350 and 1400 nm wavelengths. Data was then processed by the Kubelka-Munk function to obtain the absorption coefficient, reduced scattering coefficient, and reduced attenuation coefficient. Histological analysis of the biopsies was performed so that the comparison between the optical and histological properties could be evaluated. Results: 3 days after burn induction the absorption coefficient, reduced scattering coefficient, and reduced attenuation coefficient was higher in healthy skin; histologically, an intense inflammatory infiltrate with loss of epithelium and part of the dermis was observed. 7 days after burn induction all the coefficients studied was higher in burned skin; histologically, the biopsies showed dermal remodeling and reepithelization below the lesion area. 14 days after burn induction, the absorption and reduced attenuation coefficients remained higher in burned skin, while the reduced scattering coefficient was higher in healthy skin; histologically, it’s seen complete epidermal repair and absence of skin appendages. Conclusion: From the results obtained in the present study it can be concluded that the condition in which the skin is found influences the behavior of the light that falls on this tissue, as well as the repair phase in which it is found. There are indications that irradiation parameters should be altered according to the specific condition of the skin.