A thermal model was used to calculate the skin temperature rise in porcine skin and predict the damage thresholds in terms of laser power for various wavelengths, pulse durations, skin parameters and laser spot sizes. Laser exposures of 1.54 μm, 0.60 ms in duration and using a 0.7 mm spot size were applied to the porcine skin. The damage thresholds were determined at 1-hour and 24-hour post exposures using probit analysis. Only one subject was exposed giving adequate fiducial limits at the 95% confidence level. The ED50 for these 72 exposures was determined to be 58 mJ, giving a radiant exposure of 15 Jcm-2. The damage threshold is compared with model predictions, with work previously published in the literature and with the ANSI Standard’s MPE for 1540 nm lasers at 0.60 ms.
The current laser safety standard for skin exposures, ANSI Z136.1, was based on a limited number of data points for various beam sizes at a few specific wavelengths. To help refine this standard, we explore the existence of a relationship between beam spot size and the ED50 lesion threshold values. In the first phase of this study we analyzed the spot size dependence of the skin lesion thresholds from previously documented experiments. We utilized the thermal skin model to predict damage thresholds and compared these with those presented in this paper. We report the results of this analysis , which we used to design an experiment to determine the true spot-size dependency of skin laser damage thresholds. The data collected in this first phase is discussed and compared to the existing ANSI Z136.1 (2000) laser safety standard.
The use of lasers in the infrared region between 1200-1400 nm has steadily increased in various industrial and commercial applications. However, there are few studies documenting damage thresholds for the skin in this region, and current laser safety standards are based on limited data. This study has determined preliminary skin damage thresholds for the Effective Dose for 50% probability (ED50) of a Minimum Visible Lesion (MVL) with laser exposure at 1314nm and 0.35 ms pulse width. An in-vivo pigmented animal model, Yucatan mini-pig (Sus scrofa domestica), was used in this study. The type and extent of tissue damage in the porcine skin was determined through histopathologic examination, and the findings are discussed. Finally, the results of this study were compared to other literature as well as to the existing ANSI Z136.1 (2000) standard for safe use of lasers.