COMPARISON OF RESPONSES OF TATTOOS TO PICOSECOND AND NANOSECOND Q-SWITCHED NEODYMIUM-YAG LASERS

Objective: To test the hypothesis that picosecond laser pulses are mor e effective than nanosecond domain pulses in clearing of tattoos. Desi gn: Intratattoo comparison trial of 2 laser treatment modalities. Sett ing: A large interdisciplinary biomedical laser laboratory on the camp us of a tertiary medical center. Patients: Consecutive patients with b lack tattoos were enrolled; all 16 patients completed the study. Inter vention: We treated designated parts of the same tattoo with 35-picose cond and 10-nanosecond pulses from 2 neodymium:YAG lasers. Patients re ceived a total of 4 treatments at 4-week intervals. All laser pulse pa rameters were held constant except pulse duration. Radiation exposure was 0.65 J/cm(2) at the skin surface. Biopsies were performed for rout ine microscopic and electron microscopic analysis at the initial treat ment session and 4 weeks after the final treatment in 8 consenting pat ients. Also, ink samples were irradiated in vitro. Main Outcome Measur es: In vivo, on the completion of treatment, a panel of dermatologists not associated with the study (and blinded to the treatment type) eva luated photographs to assess tattoo lightening. Formalin-fixed specime ns were examined for qualitative epidermal and dermal changes as well as depth of pigment alteration. Electron micrographs were examined for particle electron density and size changes (in vivo and in vitro). Th e gross in vitro optical density changes were measured. Results: In 12 of 16 tattoos, there was significant lightening in the picosecond-tre ated areas compared with those treated with nanosecond pulses. Mean de pth of pigment alteration was greater for picosecond pulses, but the d ifference was not significant. In vitro biopsy specimens showed simila r electron-lucent changes for both pulse durations. In vitro results w ere similar for both pulse durations, showing increases in particle si zes and decreased electron density as well as gross ink lightening. Co nclusions: Picosecond pulses are more efficient than nanosecond pulses in clearing black tattoos. Black tattoos clear principally by laser-i nduced changes in the intrinsic optical properties of the ink.