In Vitro and In Vivo Laser Treatments of Tattoos

Abstract

To analyze the absorption of tattoo inks related to their in vivo and in vitro behavior under laser irradiation to improve laser-assisted tattoo removal. The absorption of 21 tattoo inks in a wavelength range from 300 to 800 nm was characterized by reflection spectroscopy from samples consisting of inks mixed in gelatin. Tattoo inks were removed in vitro using pulsed laser radiation with different variables, and morphologic analysis of the irradiated areas was performed. An interdisciplinary laser laboratory with a common industrial project with the Spanish company Milesman S.A. One person was voluntarily tattooed with 2 of the studied inks. (1) First approach to the optimum dose for pigment removal in in vitro models. (2) Correlation between the in vitro and in vivo situations at the optimum dose. Reflection spectroscopy facilitated selection of the most adequate laser wavelengths for tattoo removal. Red, orange, and rose inks were successfully lightened at 532 nm with 0.6 J/cm2; brown at 1064 nm with 0.3 J/cm2; yellow and green at 448 nm with 2.6 J/cm2; and blue at 600 nm with 0.9 J/cm2. Similar colors in in vitro and in vivo tattoos responded with the same efficiency to the laser variables. High efficiency is reached in the removal of in vivo tattoos by using an irradiation wavelength at which the percentage of reflection from the pigment is minimal. Under this condition, laser pulses can be used with a low fluence, minimizing adverse effects and clinical time.