Quantified mapping of skin oxygenation and melanin density

• Grant number: 19/27107-6
• Support type: Scholarships in Brazil - Scientific Initiation
• Effective date (Start): August 01, 2020
• Effective date (End): July 31, 2021
• Field of knowledge: Health Sciences - Medicine
• Principal researcher: George Cunha Cardoso
• Grantee: Murilo Sanches Sampaio
• Home Institution: Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto (FFCLRP). Universidade de São Paulo (USP). Ribeirão Preto , SP, Brazil

Abstract

In this project, we seek an alternative way to measure the blood oxygenation present in the skin (SpO2), in a remote, noninvasive way. Oxygenation is a vital parameter for understanding the functioning of the human organism, being an indicator of several parameters that enable people's health. Conventional ways to estimate tissue oxygenation levels are limited to specific regions of the human body and depend on direct skin contact, which is undesirable in some patients. With the use of cameras, we can perform RGB spectroscopy, which allows the separation of the main chromophores present in the skin through the knowledge of light-tissue interaction physics and optical properties of the tissue. The method is based on the Beer-Lambert optical absorption law and uses RGB (three-channel/three-color) images with polarized visible light. From the absorption spectrum of the oxyhemoglobin (HbO2), deoxyhemoglobin (Hb), and melanin (Mel) chromophores, we can determine, using physical modeling, the concentration of each of the chromophores, and calculate the oxygenation of the skin surface. The amount of melanin is one of the variables found as a response in the proposed method. For this reason, we will carry out experiments on a population sample with skin color diversity. We will seek volunteers to perform forearm images, in whom we will study the sensitivity limits of the proposed technique, comparing results with conventional oximetry techniques. It is possible that a large amount of melanin in a volunteer generates uncertainty in determining its oxygenation levels of the skin because we will use only visible light. We will quantify the effect of melanin on the uncertainty of oxygenation measurement and verify if it is significant (p = 0.05). The objectives of this project include understanding and overcoming the limitations of the proposed technique for measuring tissue oxygenation and skin melanin density. (AU)