A Tattoo is a permanent mark or design made on the body by the introduction of pigment through ruptures in the skin. Currently the tattoos market is growing at a phenomenal rate. This has led in growth of tattoo removal procedure as well. Methods of tattoo removal include dermabrasion, skin grafts or plastic surgery, and laser surgery. The most appealing form is the Q-switched nanosecond domain lasers, that up until recently were the gold standard in the field. Complex and multicolor pigment induced tattoos are a challenge to remove and promising results are seen in the published data regarding the use of shorter - picosecond domain lasers [1]. The reason behind that being that for picosecond domain pulses a lower fluence is needed during the treatment sessions due to the higher peak power and greater photoacoustic effect, which can offer less side-effects and a better pigment clearance [2].
When stating the term "tattoo removal" it is necessary to explain, that the "removal” is the fragmentation of the targeted particle into smaller fragments. Thermal and stress confined laser-energy deposition in the targeted particle is needed, to generate an internal pressure wave or acoustic wave. Fracture can occur when the tensile force of the acoustic wave exceeds the corresponding limit of the particle. That can be affected by the influence of the used laser pulse length, as with shorter length can be noted an increase of particle fracture. This relationship has its limits when the acoustic wave confinement time is longer than the pulse length [3].
Most commercially available lasers excel at 300-600 ps. In our study, we aimed to investigate the laser-tissue interactions of a picosecond domain Nd:YAG laser, that can generate 150 ps pulses and energies ranging up to 250 mJ and 120 mJ for 1064 and 532 nm wavelength, respectively. Thus, providing insight in shorter pulse efficacy and safety in the use for tattoo pigment fragmentation. The effects of 150 ps ultrashort pulses were not currently described, and the area was absent of in vivo animal studies that could offer great translational value, when interpreting study results from animal to human. For that reason, this study was performed on a in vivo porcine model.
As excessive energy delivered to the superficial skin can lead to blistering, prolonged healing, scurrying and change in pigmentation [4] it is important to optimize the fluence of the laser energy. Impact of different fluencies for side-effect development and pigment fragmentation efficacy were investigated on different color tattoos of known pigment composition. This has been carried out by changing the wavelength, spot size and pulse energy of the laser. The tattoo removal was analyzed using clinical macroscopic examination (siascopy) and histochemistry.