Tunable ps laser for side-effect-free colored tattoo removal – PARACETAMOL

Tattooing is a practice dating back from the Neolithic. Several bodies, discovered in the permafrost or well-conserved mummies were bearing tattoos. Permanent body painting has therefore found its way through the ages and civilizations. Nowadays, 45 millions of US citizens are tattooed. In France, statistics reveal 6.3 millions people in constant increase. Polls have reported that between 11 and 20 % of the adults who have a tattoo regret getting one and consider removal. Early removal techniques were based on dermabrasion with trichloroacetic acid aimed at peeling the first few layers of skin containing the pigments. Other techniques would scrub the skin with salt or even excise the painted skin sometimes with cryosurgery. Needless to say that these techniques generate clear visible scars. In this context laser tattoo removal has been a revolution. The treatment of pigmentary disorders and tattoos by lasers is based on selective photothermolysis and photoablation. After absorption by the pigment molecules, the energy from the laser beam is converted into heat and breaks the chemical bonds above a given temperature. The laser irradiation modifies the shape and decreases the size of the pigment particles abruptly for further elimination by the body. The lasers that are used for tattoos are Q-switched and deliver pulses with 5 to 100 ns allowing to target most of the exogenous pigments. With new advances in Q-switched laser technology, tattoo removal can be achieved with reduced risk of scarring and permanent pigmentary alteration because of the shorter pulse duration (few ns). The treatment with the Q-switched lasers is relatively painful and often requires anesthesia. Ten to 20 sessions are required for removing professional tattoos with sessions made every other months leading to several years of treatment before complete removal. Because of the large amount of energy deposited, adverse effects following treatment with the Q-switched laser still include textural change, scarring, and hypo- or hyperpigmentation. Since many wavelengths are needed to treat multicolored tattoos, not one laser system can be used alone to remove all the available inks and combination of inks. More recently, picosecond lasers have been developed. Treating with such lasers aims at reducing the pigment into smaller fragments through photo-disruption for easier elimination by the organism. Also, the use of shorter pulses reduces the total energy required for tattoo clearing and therefore lowers the thermal diffusion preventing unnecessary damages. Preliminary investigations provide encouraging results but so far, no study has compared, in a prospective randomized intra-individual trial, the efficacy of these picosecond lasers to the Q-switched lasers. Importantly, these so-called picosecond lasers have pulse duration between 500 and 800 ps and are finally not so different from Q-switched lasers. A technology that would provide a genuine picosecond pulse duration to disrupt pigments in smaller parts facilitating their quick removal and a tunable wavelength to target different pigment colors would thus be of major interest. Here, we offer to move one step forward and propose a novel solution that allows removing any colored tattoo without pain and treating various skin pigmentation disorders. The project proposes to demonstrate a novel technique using a laser system delivering (i) true picosecond pulses (few tens of ps) and (ii) with tunable wavelength covering the visible range and elaborate the protocols for tattoo removal and some medical treatments through ex-vivo and in-vivo experiments. We expect the process to induce a significantly reduced pain avoiding anesthesia and mitigate all secondary detrimental effects, as lower energies are required. Due to the fragmentation in significantly smaller fragments, tattoo removal is expected with very few sessions. Last but not least, the process will make use of one single (tunable) laser for all colors.