Optimization of laser technology for removing tatuage pigment

Abstract

Purpose: To study the effectiveness of tattoo pigment removal with laser light depending on the wavelength and depth of penetration into tissues in order to optimize a technique of laser selective photocavitation. Material and methods. 127 male white mongrel rats, aged 8 weeks, were intradermally injected with pigment particles into their backs looking like 2 rows of spots 0.5 cm in diameter. In 6 weeks, 367 skin samples with tattoo pigment were taken. Each sample was a patch of epidermis with pigment crystals surrounded by connective tissue capsules not less than 2.5 mm of thickness. Before the experiment, the epidermal stratum corneum – 10–15 mkm in depth and about 1 mm in diameter- was removed with spray-coagulation (apparatus EHVCH-50-MEDSI). The rest of skin flap surface remained intact. Thus, each skin sample had two areas on the surface – one with removed stratum corneum (experimental) and the other one intact (control). To register changes in the luminous flux, the authors placed an emitter (IPL xenon lamp 7.65.130), tissue sample and photomultiplier (PMT-62) on one and the same axis. To cut off light waves, the authors used a set of light filters – 315, 364, 400, 440, 490, 540, 590, 670, 750, 870, 980 nm. Results. Destruction of skin surface layers was not statistically significant under wavelengths up to 450 nm and after 1000 nm. The epidermal stratum corneum prevents laser light penetration with wavelengths 450–694 nm by 27%, in average, and with wavelengths 700–1000 nm by 33%, in average. Conclusion. Epidermal stratum corneum destruction statistically significantly increases light density in deep tissue layers and increases the depth of penetration of laser light into biological tissues.