Objective: To test the hypothesis that picosecond laser pulses are more effective than nanosecond domain pulses in clearing of tattoos.Design: Intratattoo comparison trial of 2 laser treatment modalities.Setting: A large interdisciplinary biomedical laser laboratory on the campus of a tertiary medical center.Patients: Consecutive patients with black tattoos were enrolled; all 16 patients completed the study.Intervention: We treated designated parts of the same tattoo with 35-picosecond and 10-nanosecond pulses from 2 neodymium:YAG lasers. Patients received a total of 4 treatments at 4-week intervals. All laser pulse parameters were held constant except pulse duration. Radiation exposure was 0.65 J/cm 2 at the skin surface. Biopsies were performed for routine microscopic and electron microscopic analysis at the initial treatment session and 4 weeks after the final treatment in 8 consenting patients. Also, ink samples were irradiated in vitro. Main Outcome Measures:In vivo, on the completion of treatment, a panel of dermatologists not associ-
Background: Depending on wavelength and pigmentation, human skin can reflect up to 70% of incident laser light. Aims: We tested the hypothesis that returning ("recycling") this diffusely reflected light to the site of laser exposure would increase cutaneous response. Materials and Methods: Thirteen adult volunteers with Fitzpatrick skin types I-IV participated in this IRB-approved study. Matched contralateral test sites on the volar forearms were exposed to a pulsed dye laser operated at 585 nm, 450 microseconds pulse duration in a uniform 5 mm circular exposure spot without skin cooling. On one arm, the laser handpiece was fitted with an aluminized hemispherical mirror with a reflectance of 67%. The minimum fluence causing skin purpura, and the purpura lesion diameter were measured. Results: The mean purpura threshold fluence with the reflector was 3.1 J/cm 2 (0.5 SD), and 3.7 J/cm 2 without the reflector (0.36 SD) (p < 0.001). The mean laser-induced purpura lesion diameter was approximately 5.3 mm with the reflector and 5.0 mm without the reflector. Conclusion: Consistent with a theoretical model and in vitro measurements, this human study confirms that "recycling" reflected laser light can increase skin response. Potentially, the therapeutic response can also be improved with "photon recycling."
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