Deep skin homogeneity and light diffusion: An accelerated Monte Carlo model for in vivo skin characterization and consumer perception.

The appearance of healthy and youthful skin is related to many factors of the skin optical properties as perceived by our visual sense. The optics of light travelling through human tissues has been extensively investigated in the field of biomedical applications, including the experimental characterization and modelling of skin optics and the propagation of light such as lasers through the layers. This work presents an innovative approach to probe deep skin by means of spectrally and spatially resolved light diffusion in the different layers of skin. Dual hyperspectral measurements of the panellist's skin are performed in vivo on subjects to obtain reflectance and light diffusion spectra. Both are simultaneously fitted by a GPU-accelerated Monte Carlo model to obtain skin optical parameters as a function of depth. The results show a clear correlation between deep skin light diffusion at wavelengths above 590 nm and the subject age, which indicates a progressive degradation of skin homogeneity with age. The effect of this orange-red light diffusion background is to alter the colour tone of the skin. A skincare product is used to show that the warmer skin colour tone is clearly perceivable to consumers when evaluating facial images with and without the product. The product effect also correlates well with hyperspectral measurements. Lastly, this innovative approach demonstrates a first step in real-time skin characterization for consumers and opens the door to customized cosmetic solutions for individual needs.

L'aspect jeune et en bonne santé de la peau est lié à de nombreux facteurs des propriétés de la peau perçues par notre sens visuel. L'optique de la lumière qui traverse les tissus humains a fait l'objet de recherches approfondies dans le domaine des applications biomédicales, notamment la caractérisation expérimentale, la modélisation de l'optique cutanée et la propagation de la lumière telle que les lasers à travers ses couches. Ce travail présente une approche innovante permettant de sonder la peau profonde au moyen d'une diffusion de la lumière résolue spectralement et spatialement dans les différentes couches de la peau. Des mesures hyperspectrales doubles de la peau du panéliste sont effectuées in vivo sur des sujets pour obtenir des spectres de réflectance et de diffusion de la lumière. Les deux sont simultanément ajustés par un modèle Monte Carlo accéléré par processeur graphique afin d'obtenir les paramètres optiques de la peau comme fonction de sa profondeur. Les résultats montrent une corrélation claire entre la diffusion de la lumière de la peau profonde à des longueurs d'onde supérieures à 590 nm et l'âge du sujet, ce qui indique une dégradation progressive de l'homogénéité de la peau avec l'âge. L'effet de ce fond de diffusion de la lumière rouge­orangée est l'altération de la couleur de la peau. Un produit de soin de la peau a été utilisé pour montrer que le teint plus chaud de la peau était clairement perceptible par les consommateurs évaluant des images du visage avec ou sans produit. L'effet du produit est aussi bien corrélé avec les mesures hyperspectrales. Cette approche innovante démontre enfin une première étape dans la caractérisation de la peau en temps réel pour les consommateurs et ouvre la voie à une solution cosmétique personnalisée selon les besoins individuels.

Hair surface quality: Laser scattering as a tool for characterizing the surface condition and deposits from shampoos and conditioners.

OBJECTIVES: The hair surface condition underlies many visually perceived attributes such as shine, colour and the 3D perception of a curly hair style. Many factors can alter the hair surface such as cumulated cleansing/styling regimens or chemical treatments which can lead to degradation of the cuticle edges and surface. Similarly, pollutants, sebum, and shampoo/conditioners can build up on the hair surface which are also perceivable to an observer. METHODS: The highly directive light of a laser is reflected and scattered by the surface of hair fibres into a circular pattern. The angular and spatial characteristics of this pattern reflect the hair geometry and the quality of the hair surface, i.e. the outer cuticle layer. Dark flat hair tresses were used to measure the impact of artificial sebum and shampoo/conditioner regimens on the cuticle surfaces. Also, longer single hair fibres from 4 volunteers were characterized for their surface changes from roots to tips, i.e. over the chronological age of the hair. RESULTS: The laser scattering shows clear changes in specular reflection characteristics from treatments and allows for the extraction of the cuticle inclination angle with respect to the hair axis. Deep cleansing or clarifying shampoos do partially restore the cuticle angle by removing residues on the hair surface whereas more conditioning systems can lead to changes in specular reflection angle and scattering, especially for multiple cycles of shampoo + conditioner treatments. Lastly, changes in hair surface can be traced over time of hair age by this approach and are consistent with frequency and nature of hair treatments. CONCLUSIONS: The method shows great potential for characterizing cleansing regimens in terms of their impact on the hair surface, either as single or multiple washes. Coverage or damage to the hair cuticles appears readily as an angle shift of the specular reflection whereas the quality of the surface topology has a direct impact on the angular width of the specular reflection thus affecting the shine band on a person's head. Hair ageing from root to tip can be quantified by laser scattering and correlates well with treatment events in time.

OBJECTIFS: L'état de la surface du cheveu est à la base de nombreuses propriétés optiques d'une coiffure: brillance, rendu couleur, perception d'un style dans l'espace 3D. Beaucoup de facteurs peuvent affecter et dégrader la qualité de surface du cheveu, notamment les régimes de shampoing/conditionneurs qui peuvent laisser des résidus. Les polluants, l'accumulation de sébum peuvent également affecter la perception du cheveu par un observateur. METHODES: La Lumière directionnelle d'un laser est réfléchie et diffusée par le cheveu en un arc de cercle. Les caractéristiques angulaires de cet arc reflètent les caractéristiques de la surface du cheveu. Des tresses de cheveu noir ont été utilisées pour évaluer le pouvoir nettoyant de shampoings sur du sébum artificiel. De plus, différents régimes shampooing + conditionneur ont été évalués en terme d'impact sur la qualité de surface du cheveu. Finalement, des fibres de cheveux longs de 4 volontaires ont été caractérisées grâce aux changements de leur surface entre les racines et les pointes en fonction de l'âge chronologique des cheveux. RESULTATS: La réflexion laser démontre clairement des changements caractéristiques de la réflexion spéculaire pour diffèrent traitements et permet même l'extraction de l'angle d'inclinaison des cuticules par rapport à l'axe du cheveu. L'efficacité nettoyante de shampoings est clairement mesurée par l'élimination de sébum sur la surface du cheveu. L'accumulation de résidus suite à des lavages avec différents régimes shampoing + conditionneur est également mesurée, après 1 et 3 cycles de lavage. Finalement, des changements de la surface du cheveu ont pu être mesurés sur les cheveux de 4 volontaires ce qui corrèlent bien avec les routines et traitements chimiques utilisées dans le temps passé. CONCLUSIONS: La méthode de réflexion et diffusion laser a démontré être très prometteuse pour mesurer les changements de la qualité optique de la surface du cheveu, que celle-ci soit le résultat de dégradation ou d'accumulation de produits. Les effets sont clairement visibles par les changements de l'angle de la réflexion spéculaire ainsi que la largeur angulaire de cette réflexion. Des résidus à la surface peuvent réduire l'angle moyen d'inclinaison des cuticules ce qui décale l'angle de réflexion spéculaire tandis que l'irrégularité de la surface des cuticules affecte la largeur angulaire de cette réflexion. Finalement le vieillissement des cheveux de la racine aux pointes peut être quantifié par diffusion laser et est bien corrélé aux traitements subis par le cheveu a un moment dans son passé.

Effects of hair sprays on colour perception: a hyperspectral imaging approach to shine and chroma on heads.

OBJECTIVES: Hair sprays apply fixative ingredients to provide hold to a hair style as well as weather resistance and optical properties such as shine. Generally, sprays distribute fine particles containing polymeric ingredients to form a thin film on the surface of hair. Different hair types require different strengths of the formed deposit on the hair surface. The present study shows how sprays also alter the visibility of the hair colour by altering the surface topology of the hair fibres. METHODS: Hyperspectral imaging is used to map spectral characteristics of hair on mannequins and panelists over the curvature of heads. Spectral and spatial characteristics are measured before and after hair spray applications. The hair surface is imaged by SEM to visualize the degree of cuticle coverage. Finally, the perception of hair colour was evaluated on red-coloured mannequins by consumer questionnaire. RESULTS: Hair sprays deposit different degrees of fixatives, which lead to a progressive leveling of the cuticle natural tilt angle with respect to the fibre axis. As a result, shine is progressively shifting towards the region of hair colour visibility and decreases the perceived colour of hair seen by consumers. Lighter sprays show thinner film formation on the hair surface and less of a shine shift than strong hold hair sprays. CONCLUSIONS: Hair sprays are generally employed for hair style hold and weather resistance and considered without effect on hair colour. Our approach shows that spray-deposited films can affect colour perception by altering the microstructure of the hair surface. Thin films deposited on the hair fibre surface can partially fill gaps between cuticles, which reduces the cuticle natural angle. This partial erasure results in a angle shift of the shine regions towards the angle of internal reflection, thus decreasing the perceived hair colour regions as experienced by a group of consumers.

Water-resistant sunscreens for skin protection: an in vivo approach to the two sources of sunscreen failure to maintain UV protection on consumer skin.

OBJECTIVES: The water resistance of sunscreen products has taken more importance for the UV protection of consumers involved in water activities and sports. The present work introduces a new in vivo approach to measure the water resistance of sunscreens on the actual skin of subjects, which can be easily applied to salt, chlorine and tap waters. The stress sources of sunscreen films on skin originate from two phenomena: high surface tension stress as the skin transits through the air/water interface and water diffusion into the film immersed in bulk water. METHODS: The water resistance of sunscreen products is measured on the forearms of subjects by means of a new layered water bath approach that physically separates both stresses. Tape strips are subsequently taken and analysed for UV-A and UV-B optical densities via (1) imaging for remaining filters and (2) in vitro SPF absorption spectra. RESULTS: Water-resistant sunscreens generally perform well when immersed in bulk water even subjected to agitation, but they show a wide range of performances when considering their behaviour at the air/water interface. The differences are more pronounced in salt water than tap water. CONCLUSIONS: The results confirm 2 stress origins in sunscreen exposure to water: interfacial surface tension and bulk water diffusion. Polymers bring improvements to the resistance of sunscreens to bulk water but show wide latitude in performances when subject to the water surface tension stress. Globally, a higher loss of filters is observed in the UV-A than in the UV-B, which is attributed to more UV-A filter loss or degradation and thus resulting in a decreased protection in the UV-A.

A new approach for evaluating the water resistance of sunscreens on consumers: tap water vs. salt water vs. chlorine water.

OBJECTIVE: An efficient sunscreen product needs to offer broad spectrum photostable UV protection during consumer use. Water resistance has become an additional criterion requested by consumers spending time near water or outdoors. Polymers generally provide water resistance to formulations and are critical to the formation and stability of a sunscreen film on skin when exposed to water. The present work introduces a new in vivo screening approach to measure water resistance using UVA-induced fluorescence imaging. METHODS: The approach has been applied to several formulations containing different polymers and compared to commercial products, for the three main water types: tap, salt and chlorinated water. All testing has been performed on the forearms of 10 subjects using UVA imaging. In addition, the skin whitening has been measured for all formulations on five subjects when exposed to water by visible light imaging. RESULTS: Our approach showed clear differences in water resistance values among the formulations tested, reflecting the importance of the formulation and the polymers used. The method proved capable of discriminating not only sunscreen performances with different water proofing ingredients but also water specific sunscreens such as a beach dedicated product showing a 20% higher resistance to salt water vs. tap and chlorine waters. CONCLUSION: The use of UVA-induced fluorescence imaging on skin proved a useful in vivo approach for measuring the water resistance performances for various sunscreen lotions with a wide range of skin whitening effects in water. Our method showed how high water resistance can be combined in a Wet skin(®) sunscreen with superior non whitening effect on the skin.

A sunscreen-tanning compromise: 3D visualization of the actions of titanium dioxide particles and dihydroxyacetone on human epiderm.

The self-tanning agent dihydroxyacetone (DHA) was applied to human skin samples, and its effect on light absorption was followed in time to study the DHA influence inside the different layers of skin. Application of DHA shows increased light absorption in the visible light region, as evidenced by skin tanning. The tanning effect is enhanced by UV irradiation and appears localized in the near-stratum corneum layer as revealed by depth analysis of the time signal. As a reference, application of an emulsion containing titanium dioxide particles shows clear surface stability and a screening of light penetration beyond the stratum corneum.

Visualization of Surface Gelation Processes in a Doped Sol-Gel Glass.

Pulsed photoacoustic spectroscopy has enabled depth-resolved, in situ measurements of the chemical changes that occur in a sol-gel process to be examined. By use of beta-carotene as a probe to determine the efficiency of heat transfer to the immediate molecular environment in thin and thick samples, separate surface and bulk gelation processes in a sol-gel material have been observed.

Pulsed photoacoustic spectroscopy applied to the diffusion of sunscreen chromophores in human skin: the weakly absorbent regime.

Pulsed photoacoustic spectroscopy was used to study the penetration of sunscreen chromophores into human skin. This study focuses on basic solutions containing single typical filter molecules, as used in current sunscreens, dissolved in mineral oil. The pulsed form of the photoacoustic technique was preferred because it provides more detailed information on the filter distribution within the different layers of human skin. A new methodology provides better insight into the diffusion process through signal analysis in the time and frequency domains, allowing for global and depth-related characterization. The penetration of the chromophore influences the response signal by inducing changes in the optical and thermal properties at different depths within the medium. The light scattering effect of titanium dioxide was demonstrated by the same technique.

Pulsed photoacoustic study of the diffusion of chromophores in human skin.

The technique of pulsed photoacoustic spectroscopy was used to investigate the diffusion of chromophores in human skin. The kinetic of diffusion has been studied for five solutions at different concentrations in a mixture of chromophores, as used in commercial sunscreens. In addition to the classical macroscopic interpretation of the diffusion process, a new method is shown to give more detailed information on chromophore presence at different depths in skin. For the first time, results are expressed in the frequency domain by means of the Fourier transform applied to the photoacoustic signal. The spectra are discussed versus the depth in skin samples and the time of diffusion kinetics. This new method of data analysis is shown to be very useful for understanding the influence of the internal structure of a medium on the penetration rate of chromophores into skin.

"Rubral" tremor after thalamic haemorrhage.

Tremors in association with thalamic haemorrhage have been infrequently reported, and delayed rubral tremor as a complication of such an event is quite rare. We describe a patient with a combined resting-postural-kinetic tremor due a thalamic haemorrhage. Magnetic resonance imaging showed evidence of a subthalamic involvement but failed to reveal any mesencephalic lesion. Five years after the original stroke there was rapid and almost complete suppression of her abnormal movements, probably related to an ischaemic capsular lesion. Involuntary movements, which resemble rubral tremor, can be due to lesions upstream of the rubral and nigral outflow system.

[Iontophoresis of tenoxicam in the therapy of osteoarthrosis]. / Ionoforesi con tenoxicam nella terapia dell'osteoartrosi.

After a brief physiopathological research about iontophoresis applications, the authors examine this treatment by two drugs (Tenoxicam and acetylsalicylic acid) in a group of patients suffering from painful osteoarthritis. They came to the conclusion that the treatment is efficacious with both substances though realising a quicker analgesic result in the group treated with tenoxicam.

[Estimate of the dose of chlorinated pesticides consumed daily by the Italian population (1978-1984)]. / Una stima della dose di pesticidi clorurati assunta quotidianamente dalla popolazione italiana (1978-84).

This work reports an estimate of the doses of chlorinated pesticides taken with a total diet by the Italian population in the period 1978-84. Previous researches, carried out in 1971-72, had regarded both uncooked and cooked diets, ready for the consumption. It was found that the amount of the considered pesticides taken in total (HCB, gamma-BHC and total-BHC, Aldrin/Dieldrin, Heptachlor/Heptachlor-epoxide and DDT total-equivalent) calculated as a sum of the percentage of each acceptable daily intake (A.D.I.), at that time recommended was near the limit of acceptability (98.5% for cooked diets and 107.0% for uncooked diets). In addition it was found that nearly the 40% of the dose assumed in all came from milk and its derivates (butter, cheese). Then considering the contribution of milk and derivates to the amount of pollutants assumed with a total diet, a new evaluation has been done, with regard to the period 1978-84, i.e. after the prohibition of the use of these pesticides in Italy and in other industrialized countries. Then the data have been processed, with regard to 211 samples of foods (90 of milk, 45 of cheese, 76 butter) coming from determinations carried out by the Multizonal Laboratory of Hygiene and Prevention of Ferrara, Milano, Udine, Bolzano, Trento, Pescara and from the Institute of Hygiene of Rome University "La Sapienza" in the period mentioned. Furthermore, alimentary consumptions of milk, butter and cheese in 1978-84 have been evaluated, and amounts of chlorinated pesticides taken with these foods have been calculated. Finally the dose taken with these foods has been extrapolated to a total diet. It has come out that the doses (estimated) taken with the total diet have notably decreased between 1971-72 and 1978-84. An anomaly is yet represented by HCB: while the quantity taken with food has decreased from 1971-72 to 1978-84 (from 3.7 to 1.3 micrograms/man/day), the concentrations in human adipose tissues have increased (from 1.02 to 1.99 mg/Kg). It can reasonably mean that assumption of HCB is not prevalently alimentary, but that it is due to other factors of environmental contamination. The data of the doses of chlorinated pesticides taken have also been compared with the respective ADI indicated in 1971-72 and in 1978-84.

PCB and other organochlorine compounds in blood of women with or without miscarriage: a hypothesis of correlation.

Polychlorobiphenyls (PCBs) have been shown to affect reproduction in experimental animals and in human beings following intoxication. The concentrations of PCBs and other organochlorine compounds were determined in blood samples from 120 women hospitalized for miscarriages and 120 full-term pregnancy controls. The average PCB hematic level (reported as Fenclor 54) was higher in women with miscarriages than in control women. No differences were detected as far as the hematic concentrations of hexachlorobenzene and DDT compounds were concerned. The reproductive history of each woman was assessed together with confounding variables on the phenomenon of miscarriage and the factors regarding environmental exposure and food intake. Food consumption did not indicate diet as the main source of PCB intake.

Spontaneous abortion in relation to the presence of hexachlorobenzene in the Italian environment.

This study determined hexachlorobenzene (HCB) levels in the blood of women who had suffered spontaneous abortions (120 cases) and women with healthy reproductive functions (120 controls). Samples were collected in 1984 during an epidemiological investigation into the relation between polychlorobiphenyl levels in the blood and spontaneous abortion in the women. Evaluation of the HCB data showed no significant differences between the groups, the blood of the group with spontaneous abortion containing 1.6 +/- 1.6 ppb HCB compared with 1.5 +/- 1.1 ppb for the control group.