Development of minimally invasive laser skin treatment applying Selective Photothermolysis: Quantitative evaluation of collagen density in rat dermis.

To develop a minimally invasive laser skin therapy, we studied how the collagen density change by near-infrared pulsed laser irradiation on a rat dermis. We have proposed to apply Selective Photothermolysis using the laser where the absorption coefficient of collagen exceeds that of water can realize the selective heating of the collagen with less heating of water. In this experiment, a CO2 laser, and near-infrared pulsed lasers of 1480, 1550, and 1690 nm wavelengths were irradiated on the ventral skin of a rat. The rat skin was extracted three days after the laser irradiation and Masson trichrome-stained specimen was prepared. To quantify collagen density, image analysis was performed using the average luminance of the blue component of the dermal region as an index. We obtained that 1550 nm wavelength irradiation exceeds the collagen density effectiveness of a CO2 laser without any damage to the skin surface. [ABSTRACT FROM AUTHOR]