ED 50 determination and histological characterization of porcine dermal lesions produced by 1540-nm laser radiation pulses

Abstract

The military and industry are using 1540 nm laser systems for which current consensus safety standards are misleading.Threshold, ED50, exposure data, along with mechanisms oflaser-tissue interaction need to be more accurately determined.Recent studies within our group indicate the Yucatan mini-pig is a more applicable animal model for laser induced skin injury investigators. Laser delivery is accomplished using an Er:Glass system producing 1540 nm oflight at millisecond exposure times and in the range of 17 to 77 J/cm2. Dermal lesion development is evaluated for acute, 1 hour, and 24 hour post exposure presentation. Preliminary data obtained from dermal exposures indicate a difference in ED50 for Yorkshire and Yucatan pigs. In the Yucatan mini-pig erythematous lesions are formed acutely while in the Yorkshire, lesions are seen at 24 hrs. Preliminary data indicates that lesion development occurs at or near the basal layer of the epidermis causing nuclear pyknosis, cellular swelling and loss ofcellular detail. Contrary to the theory that water absorption is the primary mechanism ofdermal tissue damage observed from 1540 nm laser exposures, skin chromophores appears to play a role in lesion development.

Visible lesion thresholds with pulse duration, spot size dependency, and model predictions for 1.54-μm, near-infrared laser pulses penetrating porcine skin

“…We note that the chi-square distribution calculated for the 1.0-mm spot diameter was 1.00, and flashes of light normally associated with laser-induced breakdown ͑LIB͒ production were not observed at this spot diameter. We again hypothesize that the threshold reported by Rico et al, 16 also had LIBs and plasmas generated due to its very high threshold and conclude that more data points below 1 mm in diameter should help to clarify this ambiguity.…”

“…We also report on Q-switched, nanosecond pulses for a spot size of 5 mm and make the same comparison with reported values. Laser-induced damage to porcine skin has been reported by Rico et al 15,16 for the 1.54-m wavelength and a small spot size ͑0.57-mm diameter͒ and they used two pig models ͑Yorkshire and the Yucatan mini-pigs͒ for their threshold measurements. They used a smaller spot size ͑0.57 mm͒ than the one used in this study because they were limited in the available pulse energies from their laser.…”

“…They used an absorption coefficient of ␣ =10 cm −1 , while we used 8 cm −1 in our model. 16 We can also compare the preceding thresholds with those measured for ablation using nanosecond laser pulses at other wavelengths. Hu et al 19 studied the ablation thresholds for different wavelengths from 213 to 1064 nm for 14-ns pulses and reported that the thresholds varied from 1.6 J cm −2 at 213 nm to 129 J cm −2 at 1064 nm.…”

Porcine dermal lesions produced by 1.3um laser pulses

“…The spot size was 1 × 10 -3 cm 2 +/-2 × 10 -4 cm 2 as measured at the 1/e 2 diameter. The exposure arrangement was generally as described in Rico et al 3 The exposure sites were examined immediately post exposure, at 1 hour and 24 hours post exposure. Data from each exposure evaluation was immediately input into EZ-Probit (v. 1.0, TASC, San Antonio, TX) and later evaluated using SAS (v. 8.2 SAS Institute, Cary, SC).…”

TUNEL Assay for Histopathologic Evaluation of Irreversible Chromosomal Damage following Nonablative Fractional Photothermolysis

“…is a nonablative laser that is capable of deep tissue penetration. [7][8][9][10][11] The Fr1540 uses fractional methodology and distributes microarrays of energy at distinct foci throughout the treated region. The near-infrared wavelength, which is preferentially absorbed by water, allows for the option of treating superficial photo-induced wrinkles or focusing on deeper rhytides extending up to 1 to 2 mm from the skin surface.…”