New protocol for the R134a cryogen spray cooling assisted 1064-nm laser lipolysis.

Laser lipolysis is a promising body contouring technology. However, the skin tissue could be thermally damaged owing to the laser energy absorption by water, which limits the lipolysis efficiency. To protect skin tissue and improve the lipolysis effect, cryogen spray cooling is introduced and synergized with the pulsed laser irradiation aiming to propose a new therapy protocol. By simulating heat conduction in the skin after spray cooling assisted laser lipolysis, the temperature distribution in the skin tissue was obtained to analyze the tissue damage by the Arrhenius integral. After parameter optimization according to the damage threshold of skin and adipose tissue, a new protocol with high laser intensity and short time was proposed including 150-ms R134a spray cooling with spray distance of 30 mm, and 100 ms 1064 nm laser irradiation with energy density of 20 J/cm 2 , with a relaxation for 9.75 s. This cycle of 10 s can be repeated 90 to 150 times for a total of 15 to 25 min. Compared with previous treatment procedure, new protocol can increase the fat dissolution depth from 2 to 4.5 mm beneath the dermis with same order laser fluence.