Pattern analysis of laser-tattoo interactions for picosecond- and nanosecond-domain 1,064-nm neodymium-doped yttrium-aluminum-garnet lasers in tissue-mimicking phantom

The Picosecond Laser Effects on Tattoo Removal and Metabolic Pathways

Objective

We aimed to investigate picosecond laser effects regarding rat tattoo removals. We systematically detected the metabolic pathways considering tattoo pigment particles in rat models.

Materials and Methods

We employed fluorescein to mark the tattoo dye and utilized a pattern needle to prepare tattoo on rat so as to establish the tattoo removal effects of picosecond laser methods employing animal models. We applied a picosecond laser to process the tattoo and observed the effects along with metabolic pathways for tattoo removal via pathology and imaging approaches.

Results

Based on the results of characterization, pathology and fluorescence, we discovered that the picosecond laser could effectively remove the pigment particles on rat skin, part of which would be metabolized out of the body through the circulatory system. After picosecond laser treatment, the fluorescence intensity of the rat skin engraved part was gradually weakened. At 8 h after the treatment, the metabolic organs had weak fluorescence, and there was no fluorescence in the metabolic organs at 12 h and 24 h after the treatment.

Conclusion

The picosecond laser had perfect tattoo removal effects, which could be utilized as a reference for clinical tattoo removal.

A Systematic Review of Picosecond Laser in Dermatology: Evidence and Recommendations

BACKGROUND AND OBJECTIVES

The use of picosecond laser in dermatology was originally focused on optimizing the removal of unwanted tattoos. Subsequent advances in this technology have broadened its clinical indications to include treatment of benign pigmented lesions, photodamage, melasma, and scar revision. In this systematic review, evidence-based recommendations are developed for the use of picosecond laser in dermatology.

STUDY DESIGN/MATERIALS AND METHODS

A comprehensive search of the English language literature was performed up to and including November 2019. Relevant citations were individually evaluated, synthesized, and categorized based on the Level of Evidence. With the addition of the authors' combined clinical experience, clinical recommendations were developed.

RESULTS

After application of inclusion and exclusion criteria, a total of 77 unique studies were evaluated. Treatment of benign pigmented lesions was associated with level I-IV evidence; rejuvenation was associated with level II evidence; melasma was associated with level II evidence; scar revision was associated with level II-III evidence; tattoo removal was associated with level I evidence.

CONCLUSION

Picosecond laser is a safe and effective treatment modality for an increasing range of dermatologic indications. Further development of this technology is warranted. Lasers Surg. Med. © 2020 Wiley Periodicals, Inc.

Sequential delivery of long-pulsed 755-nm alexandrite laser and long-pulsed 1,064-nm neodymium:yttrium-aluminum-garnet laser treatment for pigmented disorders

BACKGROUND

Long-pulsed (LP) lasers at pulse durations of 1-300 ms have been used to destroy nests of nevi cells by selectively targeting pigment chromophores.

OBJECTIVE

To evaluate dual-wavelength LP laser-induced tissue reactions.

METHODS

The patterns of LP 755-nm alexandrite (Alex) and/or 1064-nm neodymium (Nd):yttrium-aluminum-garnet (YAG) laser-induced tissue reactions were macroscopically evaluated using a tattoo-embedded phantom. Additionally, a pilot in vivo human study was performed for common acquired melanocytic nevus, of which dermoscopic images and high-speed cinematographs were obtained.

RESULTS

Combinations of Nd:YAG and Alex laser treatments at interpulse intervals of 10 or 20 ms generated round to oval zones of photothermal and photoacoustic injury in two distinctive areas containing disintegrated tattoo particles. Treatment at interpulse intervals of 10 or 20 ms between Alex and Nd:YAG pulses elicited lesser degrees of thermal damage to surrounding tissues, compared to treatment at 100 or 200 ms. Immediately after combined LP laser treatment of human nevus lesions in vivo, Nd:YAG-Alex treatment at a 20-ms interpulse interval exhibited more remarkable crusting and erosive appearances than Alex-Nd:YAG treatment.

CONCLUSION

For treating pigmented disorders, sequential delivery of LP Nd:YAG and Alex pulses at short interpulse intervals of 10-20 ms can effectively destroy nests of pigment chromophores.

Pattern analysis of 532- and 1,064-nm picosecond-domain laser-induced immediate tissue reactions in ex vivo pigmented micropig skin

Optical pulses from picosecond lasers can be delivered to the skin as single, flat-top beams or fractionated beams using a beam splitter or microlens array (MLA). In this study, picosecond neodymium:yttrium aluminum garnet laser treatment using a single flat-top beam and an MLA-type beam at the wavelengths of 532 nm and 1,064 nm were delivered on ex vivo genotype-regulated, pigmented micropig skin. Skin specimens were obtained immediately after treatment and microscopically analyzed. Single flat-top beam treatment at a wavelength of 532 nm and a fluence of 0.05-J/cm² reduced melanin pigments in epidermal keratinocytes and melanocytes, compared to untreated controls. Additionally, 0.1 J/cm²- and 1.3 J/cm²-fluenced laser treatment at 532 nm elicited noticeable vacuolation of keratinocytes and melanocytes within all epidermal layers. Single flat-top beam picosecond laser treatment at a wavelength of 1,064 nm and a fluence of 0.18 J/cm² also reduced melanin pigments in keratinocytes and melanocytes. Treatment at 1,064-nm and fluences of 1.4 J/cm² and 2.8 J/cm² generated increasing degrees of vacuolated keratinocytes and melanocytes. Meanwhile, 532- and 1,064-nm MLA-type, picosecond laser treatment elicited fractionated zones of laser-induced micro-vacuolization in the epidermis and dermis. Therein, the sizes and degrees of tissue reactions differed according to wavelength, fluence, and distance between the microlens and skin.