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-

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In order to quantify the energy deposition at a dielectric-tissue interface, a simple optical temperature probe to measure the transient temperature rise of the laser-heated layer at this interface is presented. The optical temperature probe (1) is noninvasive, so as not to alter the optical, thermal, and mechanical properties of the sample, (2) has a fast time response (nanoseconds), in order to measure the temperature increase during a short laser pulse, and (3) has high spatial resolution (micrometers), in order to probe only the heated layer. The probe is also capable of detecting ablation at the optic-tissue interface.