CS Colloquium, co-sponsored with Biomedical Engineering
Steven L. Jacques
Title: The optics of skin: why skin looks pink instead of orange
Refreshments available at 3:45 outside AKW 000.
Host: Alex Doronin
The skin is an optically turbid medium with embedded absorbers (blood, melanin, water) and scatterers (collagen, lipid membranes). The scattering greatly affects the observed color of the skin. A homogeneous mixture of scatterers and blood will yield an orange color, since absorption by blood scales as blue > green > red. But the architecture of the skin has a superficial layer of relatively low blood content: the epidermis and superficial papillary dermis. Hence, blue light can reflect from this superficial layer before seeing any blood while green and red light penetrate more deeply and see the deeper blood. This moves the skin color from orange to pink. Of course, melanin offers an additional absorption filter that strongly attenuates blue light, but subsurface melanin yields the blue coloring of Nevus of Ota. IN SUMMARY, skin architecture plays a key role in the appearance of skin color.
Steven L. Jacques, Ph.D., received a B.S. degree in Biology at MIT, and an MS degree in Electrical Engineering and Computer Science as well as a PhD in Biophysics and Medical Physics from the University of California-Berkeley (1984), where he used dielectric microwave measurements to explore the in vivo distribution of water in the stratum corneum of human skin. In 1983, he joined the Wellman Laboratory for Photomedicine at Massachusetts General Hospital, rising to a Lecturer in Dermatology/Bioengineering, Harvard Medical School. His team developed the use of Monte Carlo computer simulations to study optical transport in biological tissues, which is now widely used in the field of biophotonics. In 1988, he joined the University of Texas M.D. Anderson Cancer Institute as an Assistant Professor of Urology/Biophysics and established a laboratory developing novel laser and optical methods for medicine, later achieving a tenured position as Associate Professor. He developed a hand-held spectrometer and the analysis software to noninvasively measure hyperbilirubinemia in newborns. This device was patented, licensed and FDA approves to replace heel stick tests, and is now in practice in neonatal care. As of 2009, over 20 million newborns have been tested with the device. In 1996, he moved to Oregon as Professor of Biomedical Engineering and Dermatology at Oregon Health and Science University. In September 2017, he joined Tufts University in Biomedical Engineering.