Caracterização óptica de amostras altamente espalhadoras na região do visível e infravermelho próximo
Year: 2023
Type: dissertation
Abstract: High melanin concentrations in dark skins can negatively affect results in light-based diagnostics and treatments. The optical properties of dark skins are known in the literature, but until now, there has not been a correlation between optical properties and skin phototype through a reliable and reproducible classification. The individual typology angle (ITA) was developed in the 90\'s to classify the skin phenotype by using colorimetric measurements with calibrated equipment. ITA is directly related to the chemical constitutive skin pigmentation and can be used as a reliable method of skin categorization. In this study, different ex-vivo skin phototypes were optically characterized, evaluating the absorption, scattering and effective attenuation coefficient, optical depth penetration and albedo. Each of these optical parameters has relevance in biophotonics applications in health sciences. To measure these properties, 3D-printed integrating spheres system was manufactured, characterized and validated. The optical results indicate the existence of a high correlation between ITA and the optical properties of skins with different phototypes. The absorption coefficient and effective attenuation increase with the decrease of ITA, that is, dark skin absorbs more light. On the other hand, optical penetration and albedo is higher for high ITA values. The scattering coefficient had lower dependence on the skin phototypes. With the experimental data of the absorption coefficient, it was possible to determine an experimental model to estimate the absorption coefficient using only the ITA colorimetric parameters, opening new opportunities for corrections in optical devices such as pulse oximeters, smartwatches, photoacoustic oximetry, and others. Finally, a work developed during the exchange in the Institut für Lasertechnologien in der Medizin an der Universität Ulm - Germany is presented, where an innovative method of carrying out VIS-NIR reflectance spectroscopy measurements regardless of distance is presented.
Author: Cruz Junior, Luismar Barbosa da
Language: English
Subfield: Radiology, Nuclear Medicine and Imaging
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W7120284044