In-vivo non-linear imaging of collagen before and after laser micro-ablative fractional resurfacing treatment

Second-harmonic generation and two-photon excited fluorescence microscopy were used in combination in the same optical system for in-vivo imaging. This work aimed at detecting collagen remodeling and reorganization in living subjects following laser micro-ablative fractional rejuvenation treatment. Treated regions in the forearm of volunteers covering a wide age range were imaged with two-photon microscopy before and after the treatment. A strong age-dependence of the treatment effectiveness was found, demonstrating a negligible effect in very young subjects (age < 30 years) face to a significant synthesis of new collagen in the most aged subjects ( age > 60 years). The amount of newly synthesized collagen as well as its organization were evaluated by means of both visual examination and an image analysis methods, based on second-harmonic to autofluorescence ageing index of dermis (SAAID) scoring. The obtained results demonstrate the performance of laser fractional micro ablative rejuvenation without the need of an invasive biopsy as well as the wide applicability range of applications for multiphoton microscopy in clinical dermatology.