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Unique journeys into the depths of the skin
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For great many years, no specific imagery techniques were dedicated to the skin. Physicists at l'Oréal have made major contributions in developing non-invasive methods to travel deep into the skin.
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After sun exposure, visualization of dermis alteration, a dark band showing up between dermis (D) and epidermis (E).
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Ultrasound echography has long been used in medical imagery, especially in obstetrics and cardiology. However, the skin, despite being the body's outermost organ, has long remained "inaccessible" to this technique. The reason was that the skin is only 1 mm thick on average ultrasound-echography resolution was too poor to be able to analyse the structures. A new system of imagery therefore had to be designed, taking into account these constraints of high spatial resolution. L'Oréal was a pioneer in the development of these new devices, to study epidermis and dermis, directly in vivo. L'Oréal laboratories now have various ultrasound sensors, operating at between 25 and 150 MHz, delivering a spatial resolution ranging from 15 to 70 µm. A band, opaque to ultrasound, was identified by this technique. It grows larger with advancing age, and the development of solar elastosis. We are now able to monitor the effects of ageing on the outermost part of the dermis in vivo.
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3D hypodermis Reconstitution by MRI
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Magnetic resonance imagery is a more recent imagery technique also used in medical diagnosis. The MRI
device is equipped with a powerful magnet (over 100,000 times stronger than the earth's natural magnetism). Obtaining an image involves accurately locating the magnetisation of each point in the volume to be scanned. But here again, the spatial coding system installed on these conventional machines was not sharpe enough to obtain sufficient details within the skin. Although developing an ultrasound device specifically for this application was a possibility, the technical and financial constraints involved were too high. No alternative was left, but the development of an accessory connected to a standard MRI machine, enabling it to obtain in vivo images of the skin. This is the way followed by L'Oréal laboratories. In association with the MRI laboratory at the Orsay Institute of Fundamental Electronics, a specific device was developed and patented, including an asymmetric magnetic field gradient coil, which can deliver detailed views of the skin in vivo. The resolution of the device is now 18 µm, 50 times higher than that of a regular MRI. This technique therefore appears as a benchmark method for obtaining a better analysis of the state of the water in these various layers of skin. At such high magnification, a better description and quantification of the three dimensional organisation of the hypodermis was obtained, leading to a better knowledge of the hypodermis in general and of cellulite in particular.
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Confocal microscopy skin observation.
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Confocal microscopy
had been used in vitro
for several years when, in 1991, in association with an American ophthalmology team, L'Oréal researchers managed to adapt it for observing the skin in vivo. Compared with conventional optical microscopy, confocality can deliver a representative image of the volume to be explored at a pre-selected depth. With spatial resolution of 1 µm in three directions, we are able to penetrate the skin outermost, horny layer, µm by µm. Confocal microscopy gives a clear view - with unprecedented accuracy - of keratinocytes in each epidermis layer, or it can track red blood cells in a microcapillary. This technique is the most recent of the major non-invasive observation methods, used in vivo. Resolution is so high, that in addition to measuring tissue thickness (horny layer, epidermis), cells can be counted, and melanosome appearance and distribution in the epidermis monitored after sun exposure.
Confocal microscopy is the method of imagery best suited to examining the horny layer and the epidermis. It therefore complements ultrasound echography and MRI, which are better suited to studying the dermis and hypodermis.
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Synchroton radiation is a highly intense source of X-rays obtained in a particle accelerator such as the one at Orsay (LURE) or Grenoble (ESRF). This technique, like X-ray diffraction, gives structural information concerning the spacial distribution of atoms. L'Oréal researchers used Sychrotron radiation to study the architecture and nature of the intercellular lipids in the horny layer. Their highly organised layout contributes to the efficiency of the cutaneous barrier. Their chemical structure has inspired chemists to synthesise molecules capable of playing the same role (i.e. reinforce the cutaneous barrier), and incorporate them into cosmetic formulae.
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