Opto-thermal measurements for the non-invasive, non-occlusive monitoring of in vivo skin condition |
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Authors: | RMS BINDRA RE IMHOF JJ ANDREW PG CUMMINS GM ECCLESTON |
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Affiliation: | Photophysics Research, School of EE &IE, South Bank University, 103 Borough Rd, London SE1 0AA, England, UK;Unilever Research, Port Sunlight Laboratory, Quarry Rd East, Bebington, Wirral L63 3JW, England, UK;Department of Pharmaceutical Science, Strathclyde University, Glasgow G1 1XW, Scotland, UK |
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Abstract: | Opto-thermal transient radiometry (OTTER) is a non-invasive measurement technique, well suited for in vivo skin research. Its excitation and detection wavelengths can be selected to give a high sensitivity to stratum corneum hydration. This is demonstrated with measurements of hydration changes resulting from occlusion with a neoprene cover and with a topical application of an occlusive preparation. In the former case, the hydration was found to recover to normal levels upon exposure to atmospheric conditions in a characteristic time of 15 min. In the latter case, a topical application of petroleum jelly was found to lead to a doubling of stratum corneum hydration over 2h. This ability to measure hydration changes in the presence of topical hydrating agents is thought to be a particularly valuable property of the OTTER technique. With a different choice of excitation and detection wavelengths, OTTER can be used to measure skin thickness, from the surface down to the vascular bed. This technique was used to measure a skin thickness map of the ventral surface of the forearm of a volunteer, showing distinct thickening near the wrist and ulna. Another use of this technique is the study of changes in subcutaneous blood distribution associated with erythema. As a demonstration of this, blood distribution changes brought about by the topical application of a salicylate/nicotinate preparation were studied. The main finding is that the subcutaneous blood spreads towards the surface, with the mean depth decreasing from 63 μm to 55μm. |
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Keywords: | opto-thermal stratum corneum hydration blood petroleum jelly methyl nicotinate |
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