Nonlinear Microscopy Measures Effects of Laser Skin Surgery

The effects of laser-based skin-tightening plastic surgery can be obvious to the naked eye, but harder to examine below the surface and at the microscale without a biopsy.

A team from the University of Florence and other Italian institutions has developed an in vivo solution using combined two-photon fluorescence (TPF) and second harmonic generation (SHG).

TPF enabled deep optical imaging of tissues, while SHG provides additional morphological information, the researchers said. The two techniques are already used to assess skin cancers. Both examinations can be carried out using the same laser source.

A 3-D projection of a stack of 20 SHG images acquired within the dermis of a healthy subject. The volume shown is 400 × 400 × 100 µm³.

To test their method, the researchers examined the forearms of patients before and 40 days after undergoing a skin-tightening procedure called microablative fractional laser resurfacing.

Skin irradiation with high-power pulsed laser light induces a thermal shock, which stimulates fibroblasts to produce new collagen and reduce wrinkles. Microablative fractional laser resurfacing enables faster healing than earlier techniques by ablating skin only on raster scanned points.

The researchers found stronger collagen synthesis and remodeling on older subjects, whereas the modifications were minimal on younger subjects.

The age-dependent effectiveness of the treatment was confirmed by quantitative spectral analysis, based on the second harmonic to autofluorescence aging index of dermis (SAAID), which the researchers said is a recognized scoring method for skin aging assessment by means of nonlinear microscopy.

The research was published in the Journal of Biophotonics (doi: 10.1002/jbio.201300124).