Examination of wound healing after curettage by multiphoton tomography of human skin in vivo

Background: The multiphoton tomography (MPT) has evolved into a useful tool for the non-invasive investigation of morphological and biophysical characteristics of human skin in vivo. Until now, changes of the skin have been evaluated mainly by using clinical and histological techniques. In this study, the progress of wound healing was investigated by MPT over 3weeks with a final examination after 24 months. Especially, the collagen degradation, reepithelization and tissue formation were examined. As specific parameter for wound healing and its course the second-harmonic generation-to-autofluorescence aging index of dermis (SAAID) was used. Methods: About 10 volunteers aged between 25 and 58y ears were examined. Acute wounds were scanned with three Z-stacks taken per visit. The stacks were taken up to a depth of 225 mu m at increments of 5 mu m and a scan time for 3 seconds per scan. Subsequently, the SAAID was evaluated as an indicator for wound healing. Furthermore, single scans were taken for morphological investigations. Results: The evaluation revealed a distinct difference in the SAAID behavior between the Z-stacks taken at each visit. Furthermore, the degradation of collagen and cells and their reappearance could be shown in the course of the visits. Conclusions: Clear differences in the curve behavior of the SAAID at every visit were shown in this study. The SAAID curves and morphological images could be correlated with findings of the clinical examination of different wound healing phases. Therefore, SAAID curves and morphological MPT imaging could provide a non-invasive tool for the determination of wound healing phases in patients in vivo.