Background: Optimal selective photothermolysis of a pigment particle requires pulse durations equal to or less than the particle's thermal relaxation time (t(1/2)). Since tattoo particles in skin range in diameter from 40 to 300 nm, picosecond pulses would approximate t(1/2) more closely and, therefore, might be more effective at tattoo particle fragmentation.
Materials and methods: India Ink (carbon) or iron oxide tattoos were placed on the back of a Yorkshire pig. Six weeks later, each tattoo was treated with either a 758 nm 500 picosecond laser (Cynosure), a 755 nm 30-50 nanoseconds laser, or left untreated. After 4 weeks, clinical responses were evaluated by three dermatologists based on pre- and post-treatment photographs; histopathologic findings were evaluated by a dermatopathologist; and electron microscopic findings were analyzed for treated and non-treated carbon tattoos.
Results: After a single treatment, picosecond-domain pulses at 758 nm produced a significantly greater degree of carbon tattoo clearance compared to nanosecond-domain pulses at 755 nm. For iron oxide tattoos, both modalities produced minimal-to-poor clearance that was generally comparable. Neither modality resulted in scarring, textural changes, or hypopigmentation, and there was no histopathologic evidence of scarring. Electron micrographs revealed the presence of amorphous material (treated pigment) in picosecond and nanosecond laser-treated tattoos, consistent with effective targeting of India Ink pigment.
Conclusions: The 758 nm 500 picosecond laser is more effective at carbon tattoo clearance after one session in a porcine model than the 30-50 nanosecond laser emitting at a similar wavelength. Both lasers cleared carbon tattoos more effectively than iron oxide tattoos. Both lasers have a comparable safety profile, and neither produced clinical or histopathologic scarring. Further studies in humans are necessary to evaluate whether repeated treatments with picosecond versus nanosecond domain modalities might yield superior tattoo pigment clearance with a comparable safety profile.
2010 Wiley-Liss, Inc.