On the Effective Differentiation and Monitoring of Variable Degrees of Hyperbilirubinemia Severity Through Noninvasive Screening Protocols

In Silico Assessment of Tanning Masking Effects on Skin Chromatic Attributes Elicited by Anemia and Hyperbilirubinemia

Changes in skin appearance are among the most recognizable symptoms of a number of medical conditions. The interpretation of such changes, however, may be inadvertently biased by normal physiological processes affecting skin optical properties. In this paper, we assess the impact of one of the most common of these processes, tanning, on variations in skin chromatic attributes elicited by two ubiquitous and serious medical conditions, anemia and hyperbilirubinemia. We employ a first-principles investigation approach centered on the use of predictive computer simulations of light and skin interactions, and on well-established colorimetry methods. In our in silico experiments, we considered skin chromatic attributes resulting from distinct anemia severity levels and hyperbilirubinemia tox-icity stages. Our findings highlight qualitative and quantitative aspects that need to be considered in the visual screening and monitoring of these conditions, notably when they occur with the concomitant presence of tanning-induced changes in the cutaneous tissues' melanin pigmentation and thickness.

Tanning-Elicited Variations in the Ultraviolet Absorption Spectra of the Cutaneous Tissues: Skin Photobiology and Photomedicine Implications

When ultraviolet radiation is absorbed within the cutaneous tissues, it can trigger a number of phenomena that can have detrimental or beneficial consequences to an individual's health. Tanning is among the most visually noticeable of these phenomena. It may result in significant changes in skin pigmentation and thickness. These spectrally-dependent physiological responses, in turn, can elicit variations in the ultraviolet absorption profiles of the cutaneous tissues and, consequently, alter the occurrence of other ultraviolet-induced photobiological processes such as the breaking of DNA strands and the synthesis of previtamin D3. These tanning-elicited variations in the cutaneous tissues' absorption profiles is often tied to the increased presence of melanin throughout these tissues. However, during the tanning, shifts in the relative content of this pigment within certain skin layers can also be observed. In particular, the stratum basale, the innermost epidermal layer where melanogenesis takes place, can have its relative melanin content significantly reduced in comparison with other epidermal layers. Since the aforementioned photobiological phenomena are preferentially brought about within this layer, such pigmentation shifts may have a more pivotal role in skin photobiology than has been assumed to date. Accordingly, in this work, we investigate the impact of spectrally-dependent tanning-elicited physiological responses, with a particular focus on the inter-layer melanin distribution patterns, on the absorption profiles of the main cutaneous tissues. We also examine how variations in these absorption profiles may alter the outcomes of photo-triggered phenomena associated with the onset of different medical conditions. Our findings are expected to contribute to the advance of the current understanding about skin photobiology, which is indispensable for the success of photomedicine initiatives involving this highly complex organ.

On the Sensitivity of Skin Spectral Responses to Variations in the Thickness of the Cutaneous Tissues

A wide range of devices are being routinely used in the noninvasive screening and monitoring of medical conditions through the analysis of skin spectral responses. The correct interpretation of these responses often depends on the availability of high-fidelity characterization datasets for the selected specimens. More specifically, the higher their fidelity, the more effective the quantification of changes observed in a given biophysical variable of interest. Skin thickness is among the most relevant of these parameters since it plays a pivotal role in the attenuation (scattering and absorption) of light traversing the cutaneous tissues. Transient and permanent physiological processes, such as tanning and ageing, can result in significant time-dependent thickness variations. These, in turn, can introduce biases in the comparison of skin spectral responses obtained at different time instances. In this paper, we investigate the impact of thickness variations on skin reflectance with respect to different regions of light spectrum. Our findings are expected to contribute to the mitigation of interpretation errors and, thus, to the enhancement of noninvasive screening and monitoring procedures based on skin spectral responses.