On Skin Cyanotic Appearances and Spectral Responses Elicited by Methemoglobinemia and Sulfhemoglobinemia

Methemoglobinemia and sulfhemoglobinemia are potentially life-threatening blood disorders characterized by similar symptoms and markedly distinct treatment procedures. In this thesis, we investigate the causal relationship between these disorders and the onset of cyanosis (purple or bluish skin coloration). More specifically, we perform controlled experiments to elicit cyanotic appearances resulting from different severity levels of these disorders and varying physiological conditions. We note that such experiments cannot be induced in living subjects without posing risks to their health. Accordingly, we have resorted to an in silico experimental approach supported by biophysical data reported in the biomedical literature. Besides bringing new insights about cyanotic chromatic variations elicited by methemoglobinemia and sulfhemoglobinemia, our investigation provides the basis for the proposition of a cost-effective protocol for the noninvasive detection and differentiation of these disorders. Our experimental results indicate that its sensitivity range exceeds the range of similar technologies, which are in general associated with high operational costs. We believe that these aspects make the proposed protocol particularly suitable for incorporation into noninvasive disease screening/diagnostic systems, particularly those deployed at the point of care of medical settings with limited access to laboratory resources

On the Bluish Appearance of Veins

The bluish appearance of veins located immediately beneath the skin has long been a topic of interest for biomedical optics researchers. Despite this interest, a thorough identification of the specific optical processes responsible for this phenomenon remains to be achieved. In this paper, we employ controlled in silico experiments to address this enduring open problem. Our experiments, which are supported by measured data available in the scientific literature, are performed using first-principles models of light interaction with human skin and blood. Using this investigation approach, we quantitatively demonstrate that Rayleigh scattering caused by collagen fibrils present in the papillary dermis, a sublayer of the skin, can play a pivotal role in the bluish appearance of veins as suggested by previous works in this area. Moreover, taking colour perception aspects also into account, we systematically assess the effects of variations in fibril radius and papillary dermis thickness on the coloration of veins under different illuminants. Notably, this assessment indicates that Rayleigh scattering elicited by reticulin fibrils, another type of fibril found in the papillary dermis, is unlikely to significantly contribute to the bluish appearance of veins. By strengthening the current understanding about light attenuation mechanisms affecting the appearance of skin and blood, our investigation contributes for the development of more effective technologies aimed at the noninvasive measurement of the physiological properties of these tissues

In Vivo Transcutaneous Monitoring of Hemoglobin Derivatives Using a Red-Green-Blue Camera-Based Spectral Imaging Technique

Cyanosis is a pathological condition that is characterized by a bluish discoloration of the skin or mucous membranes. It may result from a number of medical conditions, including disorders of the respiratory system and central nervous system, cardiovascular diseases, peripheral vascular diseases, deep vein thrombosis, and regional ischemia. Cyanosis can also be elicited from methemoglobin. Therefore, a simple, rapid, and simultaneous monitoring of changes in oxygenated hemoglobin and deoxygenated hemoglobin is useful for protective strategies against organ ischemic injury. We previously developed a red-green-blue camera-based spectral imaging method for the measurements of melanin concentration, oxygenated hemoglobin concentration (C-HbO), deoxygenated hemoglobin concentration (C-Hb(R)), total hemoglobin concentration (C-HbT) and tissue oxygen saturation (StO(2)) in skin tissues. We leveraged this approach in this study and extended it to the simultaneous quantifications of methemoglobin concentration (C-metHb), C-HbO, C-Hb(R), and StO(2). The aim of the study was to confirm the feasibility of the method to monitor C-metHb, C-HbO, C-Hb(R), C-HbT, and StO(2). We performed in vivo experiments using rat dorsal skin during methemoglobinemia induced by the administration of sodium nitrite (NaNO2) and changing the fraction of inspired oxygen (FiO(2)), including normoxia, hypoxia, and anoxia. Spectral diffuse reflectance images were estimated from an RGB image by the Wiener estimation method. Multiple regression analysis based on Monte Carlo simulations of light transport was used to estimate C-HbO, C-HbR, C-metHb, C-HbT, and StO(2). C-metHb rapidly increased with a half-maximum time of less than 30 min and reached maximal values nearly 60 min after the administration of NaNO2, whereas StO(2) dramatically dropped after the administration of NaNO2, indicating the temporary production of methemoglobin and severe hypoxemia during methemoglobinemia. Time courses of C-HbT and StO(2), while changing the FiO(2), coincided with well-known physiological responses to hyperoxia, normoxia, and hypoxia. The results indicated the potential of this method to evaluate changes in skin hemodynamics due to loss of tissue viability and vitality

Appearance Modeling of Living Human Tissues

This is the peer reviewed version of the following article: Nunes, A.L.P., Maciel, A., Meyer, G.W., John, N.W., Baranoski, G.V.G., & Walter, M. (2019). Appearance Modeling of Living Human Tissues, Computer Graphics Forum, which has been published in final form at https://doi.org/10.1111/cgf.13604. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-ArchivingThe visual fidelity of realistic renderings in Computer Graphics depends fundamentally upon how we model the appearance of objects resulting from the interaction between light and matter reaching the eye. In this paper, we survey the research addressing appearance modeling of living human tissue. Among the many classes of natural materials already researched in Computer Graphics, living human tissues such as blood and skin have recently seen an increase in attention from graphics research. There is already an incipient but substantial body of literature on this topic, but we also lack a structured review as presented here. We introduce a classification for the approaches using the four types of human tissues as classifiers. We show a growing trend of solutions that use first principles from Physics and Biology as fundamental knowledge upon which the models are built. The organic quality of visual results provided by these Biophysical approaches is mainly determined by the optical properties of biophysical components interacting with light. Beyond just picture making, these models can be used in predictive simulations, with the potential for impact in many other areas

Modelagem de aparência baseada em biofísica para tecidos do fígado humano

A representação gráfica de tecidos humanos é uma importante demanda para aplicações de áreas como ensino, entretenimento e treinamento médico. Frequentemente, a simulação de tais materiais envolve considerar características dinâmicas vinculadas as suas funções no corpo humano e que influenciam diretamente também em sua aparência. O fígado humano, apesar de um órgão interno, portanto, de difícil acesso, possui diferentes modelos de representação apresentados na literatura da Computação Gráfica (CG). Entretanto, tais modelos desconsideram as influências das propriedades ópticas dos elementos biofísicos que compõem os tecidos hepáticos, fornecendo assim, aproximações cuja parametrização controla apenas um estado específico do material orgânico, em geral, avaliando visualmente o resultado. O presente trabalho apresenta a modelagem dos tecidos do fígado humano através da descrição dos elementos biofísicos que compõem suas camadas estruturais: o parênquima e a cápsula de Glisson. Além disso, tal modelo implementa a interação luz-matéria em termos de eventos como a absorção, dispersão, reflexão e transmissão de luz, como processos biológicos que produzem a coloração específica do material, ou seja, sua resposta espectral. A abordagem matemática do modelo é definida como numérica e estocástica, para a qual é apresentada uma solução para garantir sua convergência. Reunindo recentes descrições sobre a estrutura dos tecidos hepáticos e sua interação com a luz apresentadas na literatura biomédica, o modelo desenvolvido representa a primeira solução baseada em biofísica para um órgão interno do corpo humano. Os resultados de imagens geradas através do modelo são apresentados junto a fotografias de tecidos análogos, assim como, curvas de respostas espectrais e espaciais disponíveis na literatura biomédica são comparadas com as produzidas pelo modelo desenvolvido, evidenciando a capacidade deste na representação gráfica do tecido hepático

Aerospace medicine and biology, an annotated bibliography. volume xi- 1962-1963 literature

Aerospace medicine and biology - annotated bibliography for 1962 and 196

Diversity of brain size in fishes: preliminary analysis of a database including 1174 species in 45 orders

Absolule and relative values of brain weight are now available for 1174 species of fishes, representing 45 taxonomic orders. The original FishBase "Brains" data was assembled by the research team of Bauchot and colleagues, to which the present report adds data for species representing several additional major taxonomic groups. This database is part of the FíshBase 97 package which provides researchers with a tool to explore lhe functional meaning of absolute and relative brain size díversily, in comparison with phylogenetic position, life history mode, locomotion, habitat, and other behavioral parameters. Several results are provided as an example of the use of these data. Galeomorph sharks and batoid rays possess the largest brains among fishes. and elongate forms with anguilliform locomotion (e.g.. hagfishes. lampreys, lrue eels, carapids, zoarcids) possess the smallest relative brain sizes. Among teleost fishes, Osteoglossomorphs possess the largest relative brain sizes. Brain size correlations with oxygen consumption suggest that larger brains consume proportionately more oxygen, or that active fish with higher metabolic rates have larger brain