Histologic and photonic evaluation of a pulsed Nd:YAG laser for ablation of subcutaneous adipose tissue.

Although various lasers are available, few of them are applicable in liposculpture. Laser interaction with fat tissue has not also been well documented. The aim of our study was to gather basic data on laser absorption in fat tissue and to analyze the relationship between laser energy and lipolysis for development of a more effective laser system. The transmittance rate in human fat specimens was measured by a spectrophotometer to determine the optimum wavelength. The absorption coefficient was used to evaluate laser absorption at a wavelength of 1064 nm. Areas of heat degeneration and evaporation were measured by scanning electron microscopy. The relation between laser energy and the areas was analyzed statistically among low-power and high-power groups and controls. Energy dispersion at the fiber tip was investigated and analyzed statistically using the far field pattern. A graph of the absorption rate at wavelengths from 400 to 2400 nm showed a peak near 1700 nm and increases at wavelengths over 2000 nm. The formula gave as an absorption coefficient of 0.4 cm(-1), and involvement of the photo-acoustic effect and non-linear effect with short-pulse and high-peak energy was suggested. Findings of tissue evaporation, destruction, heat coagulation, and rupture of cell membrane were more frequently seen in irradiated specimens than in controls in scanning electron microscopy. The destroyed area in the low-power irradiated groups was significantly larger than that of controls in the statistical analysis. The affected area in the high-power irradiated groups was significantly larger than that of low-power specimens. Energy was concentrated at the tip with laser coherency. Energy at the oblique-cut tip was statistically lower than that at the normal tip, revealing that durability and maintenance of the fiber tip is essential to maintain energy levels in clinical practice. This study is the first to demonstrate the histologic and photonic relationship of energy absorption and lipolysis using a pulsed Nd:YAG laser. The results will be useful for research and development of a more effective laser system for liposculpture.