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This report involves two human volunteers with bruises acquired incidentally at a known time point. DRS spectra in visible spectral range are obtained from laterally uniform lesion sites using an integrating sphere. PPTR measurements involve irradiation with a millisecond laser pulse at 532 nm and recording the resulting transient change of mid-infrared emission with a fast infrared camera. Data from both measurements are analyzed simultaneously by fitting with predictions from a dedicated numerical simulation of light and heat transport in a multi-layer model of human skin. The results show a prominent increase of the dermal hemoglobin content and reduction of its oxygenation level relative to a nearby intact site (resulting from blood extravasation), followed by a rise of the bilirubin content. The parameters of a simple dynamical model of a self-healing bruise are then assessed by fitting together a set of experimental data acquired at different times post injury. The results indicate a rise and subsequent decrease of the hemoglobin decomposition rate, as the inflammatory response first kicks in and then gradually subsides. |
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