Med Lasers.  2020 Dec;9(2):142-149. 10.25289/ML.2020.9.2.142.

In Vivo and Ex Vivo Skin Reactions after Multiple Pulses of 1,064-nm, Microlens Array-type, Picosecond Laser Treatment

• Lyu H
• Park J
• Lee HC
• Lee SJ
• Kim YK
• Cho SB

• KMID: 2533480
• DOI: http://doi.org/10.25289/ML.2020.9.2.142

Abstract

Background and Objectives
A picosecond-domain laser treatment using a microlens array (MLA) or a diffractive optical element elicits therapeutic micro-injury zones in the skin. This study examined the patterns of tissue reactions after delivering multiple pulses of 1,064-nm, MLA-type, picosecond neodymium:yttriumaluminum-garnet laser treatment.
Materials and Methods
Multiple pulses of picosecond laser treatment were delivered to ex vivo human or brown micropig skin and analyzed histopathologically. A highspeed cinematographic study was performed to visualize the multiple pulses of picosecond laser energy-induced skin reactions in in vivo human skin.
Results
In the ex vivo human skin, a picosecond laser treatment at a fluence of 0.3 J/cm² over 100 non-stacking passes generated multiple lesions of thermally-initiated laser-induced optical breakdown (TI-LIOB) in the epidermis and dermis. In the ex vivo micropig skin, stacking pulses of 20, 40, 60, 80, and 100 at a fluence of 0.3 J/cm² generated distinct round to oval zones of tissue coagulation in the mid to lower dermis. High-speed cinemato­graphy captured various patterns of twinkling, micro-spot reactions on the skin surface over 100 stacked pulses of a picosecond laser treatment.
Conclusion
Multiple pulses of 1,064-nm, MLA-type, picosecond laser treatment elicit marked TI-LIOB reactions in the epidermis and areas of round to oval thermal coagulation in the mid to deep dermis.

Keyword

Laser; Neodymium-doped yttrium aluminum garnet; Picosecond; Human skin; Thermally-induced laser-induced optical breakdown; Scar