Research on Skin Light Absorption Spurs Innovations in Medical Diagnostics
Around the world, scientists have demonstrated how skin pigmentation influences the action of light-based health diagnoses and treatments, adopted, for example, in physiotherapy and dentistry. This effort includes researchers and professors from the Department of Physics at the Faculty of Philosophy, Letters and Sciences of Ribeirão Preto (FCLRP) at USP, who are researching not only the influence of the pigment melanin, present in human skin, on the absorption of light emitted by optical equipment, as well as proposed algorithms to carry out this measurement, aiming for use in applications to evaluate the circulation and oxygenation of blood and tissues, among other functions.
“Not only imaging techniques, but diagnostic and therapeutic procedures involving optical radiation or ultrasound, in dark-skinned patients, need to be better studied”, says professor George Cardoso to Jornal da USP , who supervised work that uses images of the skin to improve the verification of blood microcirculation.
Cardoso highlights that the different behavior of optical techniques depending on skin color occurs due to a characteristic of light. “After all, the role of melanin is to reduce the penetration of light into the skin, especially blue light”, he explains. “Health professionals should be aware of the limitations or adaptations needed for people with high amounts of melanin.”
“Therefore, the development of technologies sensitive to the entire range of phototypes is of utmost importance, especially in a country like ours, characterized by a high diversity of skin tones”, reinforces the FFCLRP professor. “Skin color must be taken into account as an important variable whenever optical techniques are involved. Therefore, our studies are essential to find ways to minimize the influence of melanin.”
Absorption
Laser facial therapy; researchers study the influence of the pigment melanin, present in human skin, on the absorption of light emitted by optical equipment and propose algorithms to carry out this measurement, aiming for use in applications – Photo: Kolobetsoo/wikipedia/CC4.0
Researcher Luismar Barbosa da Cruz Junior, responsible for investigating an algorithm designed to estimate light absorption by the skin based on its tone, highlights that, in 2020, oxygen saturation in patients hospitalized with covid-19 was widely assessed using of pulse oximeters. In these devices, oxygen assessment is carried out using light beams, the action of which can change and compromise the results of tests in people with more pigmented skin. Cruz Junior notes that this device has started to be adopted by an increasing number of people, including outside the hospital environment, as versions of the oximeter are available for purchase in pharmacies. “For healthcare professionals, the oximeter plays a fundamental role in monitoring serious cases of Covid-19, enabling the identification of the need for supplementary oxygenation or, in more extreme cases, intubation”, he tells Jornal da USP .
Luismar Barbosa – Photo: Personal archive
“However, in December 2020, a study of more than 10,000 patients, published in The New England Journal of Medicine , reported that pulse oximeters were not completely reliable for assessing blood oxygen saturation in black patients, who, as a result, they could be at greater risk of not receiving supplementation and, potentially, of death”, emphasizes the researcher. “This problem has been mentioned by several health bodies in the United States, such as the Food and Drug Administration (FDA) and the American Medical Association (AMA). The alerts indicate the importance of studying the influence of color and pigmentation on this type of equipment.”
Professor Theo Pavan, from USP, who supervised a study on image reconstruction techniques to minimize the influence of skin tone on diagnoses, clarifies that the studies do not indicate that optical biomedical techniques, in general, are less effective on skin with a greater amount of melanin. “It is true that light, in the range of colors we work with, interacts with the skin,” he highlights. “However, the studies under discussion here are focused on basic science methods that aim to advance our understanding of this interaction, as well as practical solutions to ensure that these interactions do not cause significant bias in expected outcomes, whether in the context of therapy or diagnosis.”