Biology subjects

Shmuylovich, L.

Publications and source records attributed to Shmuylovich, L..

3 recordsLinked to original sources

bioRxiv2026

The optical origin of the human skin color 'banana' in CIELAB space

Human skin colors occupy a characteristic banana-shaped region in CIE L*a*b* space, but why skin color coordinates are restricted to this region and how they relate to melanin and blood remain incompletely understood. We developed a physics-based framework linking skin chromophore content to colorimeter-derived skin color coordinates using two complementary three-layer light transport models. Across physiologic ranges of epidermal melanosome volume fraction and dermal blood volume fraction, simulated reflectance spectra were converted to CIE L*a*b* coordinates and compared with human skin color measurements from the International Skin Spectra Archive. Physiologic variation in melanin and blood reproduced the observed banana-shaped locus and revealed distinct chromophore-specific trajectories. Iso-melanin trajectories became progressively more linear as melanin increased, whereas iso-blood trajectories retained the curvature of the skin color locus. As melanin increased, perceptible color differences from blood volume changes were reduced, providing a mechanistic explanation for reduced erythema visibility in highly pigmented skin. These relationships were stable across plausible variations in layer thickness and tissue oxygenation and agreed with external validation data. The framework also identified when the Individual Typology Angle is confounded by blood or distorted by dermal melanin. Together, these findings establish a mechanistic optical basis for interpreting colorimeter-derived skin color coordinates.

bioengineering↗

bioRxiv2023

Development and evaluation of a wearable peripheral vascular compensation sensor in a swine model of hemorrhage

Postpartum hemorrhage (PPH) is both the leading and most preventable cause of maternal mortality. PPH is currently diagnosed through visual estimation of blood loss or vital sign analysis of shock index (ratio of heart rate to systolic blood pressure). Visual assessment underestimates blood loss, particularly in the setting of internal bleeding, and compensatory mechanisms stabilize hemodynamics until hemorrhage is massive, beyond the point of pharmaceutical intervention. Quantitative monitoring of hemorrhage-induced compensatory processes, such as the constriction of peripheral vessels to shunt blood to the central organs, may provide an early alert for PPH. To this end, we developed a low-cost, wearable optical device that continuously monitors peripheral perfusion via laser speckle flow index (LSFI) to detect hemorrhage-induced peripheral vasoconstriction. The device was first tested using flow phantoms across a range of physiologically relevant flow rates and demonstrated a linear response. Subsequent testing occurred in swine hemorrhage studies (n=6) by placing the device on the posterior side of the swines front hock and withdrawing blood from the femoral vein at a constant rate. Resuscitation with intravenous crystalloids followed the induced hemorrhage. The mean LSFI vs. percent estimated blood volume loss had an average correlation coefficient of -0.95 during the hemorrhage phase and 0.79 during resuscitation, both of which were superior to the performance of the shock index. With continued development, this noninvasive, low-cost, and reusable device has global potential to provide an early alert of PPH when low-cost and accessible management strategies are most effective, helping to reduce maternal morbidity and mortality from this largely preventable problem.

bioengineering↗

bioRxiv2022

Global health open-source goggles for fluorescence-guided surgery

Fluorescence-guided surgery (FGS), coupled with novel near infrared (NIR) fluorescent contrast agents, has significant potential to improve health but in current practice is less suitable for low resource settings. Although there are efforts to simplify FGS systems, technical, economic, and logistic challenges have hampered its global adoption. To overcome these impediments, we developed a low-cost, open-source, battery-powered and fully wearable FGS system called the fluorescence imaging augmented reality Raspberry Pi-based goggle system (FAR-Pi). Compared to current technologies that are expensive, bulky, and wall-powered, FAR-Pi has higher spatial resolution, depth of focus and fluorescence sensitivity. The FAR-Pi system has broad appeal by detecting the diverse fluorescence of NIR contrast agents undergoing clinical trials, as demonstrated by the successful identification of tumors in vivo with LS301, a tumor-targeting NIR contrast agent. As an open-source, inexpensive, and modifiable system, FAR-Pi promises to broaden access to FGS, thereby improving health worldwide.

bioengineering↗