Porcine skin damage thresholds for multiple-pulse laser exposure at 1940 nm

Advances in fiber laser technology have resulted in the increased use and availability of several high-power laser systems operating in the mid-infrared band with short switching times and high modulation rates. The current American National Standard for the Safe Use of Lasers (ANSI Z136.1-2014) defines the calculation of the maximum permissible exposure (MPE) on the skin in terms of the exposure duration a single pulse or the total exposure time limit, and is based on continuous-wave laser skin exposure minimum visible lesion (MVL) data. This study determined the MVL data thresholds in Yucatan miniature pig skin for multiple-pulse 1940-nm laser exposures with pulse repetition frequencies (PRFs) of 100, 200, and 1000 Hz, and trains of 300, 1000, or 3000 pulses. The individual pulse duration in each exposure train was 500 µs. We report the MVL thresholds as the median effective dose (ED50) based on varying individual pulse energy. The results highlight the effect of PRF on the thresholds for multiple-pulse cases. Comparison with the existing ANSI Z136.1 MPE limits provides a calculation of the safety margin for each parameter case.

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