The Effects of 1064 nm Nd:YAG Laser Irradiation Under the Different Treatment Conditions for Skin Rejuvenation: Quantitative and Histologic Analyses

Abstract

Objective: The aim of this study was to estimate heat distributions and evaluate degrees of tissue damages histologically after transmitting therapeutic lasers to find optimum ranges for skin rejuvenation. Background data: To treat skin aging, many researchers attempted to evaluate treatment effects for the different approaches. The noninvasive skin rejuvenation method was mostly employed to optimize the therapeutic effects by quantifying the laser conditions. However, current approaches produced low reliability for predicting tissue damage. Methods: We transmitted the 1064nm Nd:YAG laser into a skin-mimicking phantom and pig skin samples according to the different fluences and spot diameters, and analyzed its internal-external temperatures. For histologic analyses, we also stained pig skin samples with hematoxylin and eosin (H&E) and compared degrees of tissue damage. The spot diameter conditions were classified into 5, 8, and 10mm, and the fluence conditions were divided into 26, 30, and 36 J/cm(2). In addition, the pulse duration was set to 30 ms. Results: In our experiments, the conditions of a spot diameter of 5mm with a fluence of 36 J/cm(2) and a spot diameter of 10mm with a fluence of 26 J/cm(2) yielded the maximum surface temperatures >40 degrees C. Regarding histologic evaluations, we also found that the degrees of internal thermal injuries are worsened as spot diameters and fluences increased. Conclusions: We selected the optimum treatment conditions for skin rejuvenation as being the laser condition of a spot diameter of 5mm with a fluence of 36 J/cm(2) and a spot diameter of 10mm with a fluence of 26 J/cm(2).