Picosecond Laser Treatment Research Articles

Patchy Dermal Melanocytosis: Differential Diagnosis and Management.

Nevus of Ito and Mongolian spots are distinct clinical presentations of patchy dermal melanocytosis, characterized by similar dermatological manifestations that can pose diagnostic difficulties for clinicians. This review aims to consolidate current understanding and research advancements on these conditions to facilitate clinical diagnosis, differential diagnosis, and management. A comprehensive search of databases including PubMed and Google Scholar was conducted, along with an analysis of pertinent literature retrieved from reference lists spanning nearly four decades. Epidemiological, clinical, and pathological profiles exhibit nuanced differences between the two conditions, with unique expressions under electron microscopy and the regression possibility. It is noteworthy that most Mongolian spots naturally fade with advancing age, in contrast to nevus of Ito, which persist and may potentially evolve into malignant lesions. While picosecond laser treatment has shown greater efficacy than nanosecond lasers, the lower-energy approach holds particular promise in pediatric cases. The therapeutic landscape for patchy dermal melanocytosis is evolving, shifting from selective photothermal action to photomechanical or subcellular photothermal modalities. This review underscores the importance of meticulous clinical assessment and the potential of innovative therapeutic approaches in managing these conditions.

Modulation of Melanocyte in Melasma Patients After Picosecond Laser Treatment.

Melasma is a therapeutically challenging hyperpigmented skin condition. Currently, there is a lack of invivo observation regarding changes in melanin and dendritic melanocytes after laser treatment. To investigate alterations in melanin and melanocytes in melasma before and after laser treatment using optical coherence tomography (OCT). Eight female melasma patients were enrolled in Taiwan. Based on the baseline OCT scans, the patients were categorized into either epidermal-type or mixed-type melasma and were assigned different treatment protocols accordingly. Sequential OCT images were collected from melasma lesions and normal skin at baseline, Week 4 and Week 8. After 8 weeks of laser treatment, the mean Melasma Area Severity Index (MASI) score improved from 10.92 to 6.30. Results from OCT showed no significant changes in the normalized density, area, or intensity of melanin in both lesional and normal skin. At baseline, the mean length of dendritic melanocytes in the affected skin was 15% longer than those in normal skin; at Week 8, the mean length of lesional dendritic melanocytes became the same as those in normal skin. Additionally, the mean width of dendritic melanocytes decreased from being 4% wider to only 2% wider than those in normal skin. After 8 weeks of treatment, an improvement of MASI score was noted, mainly attributable to a reduction in lesional area. OCT showed no notable change regarding melanin, but a decrease in length and width of dendritic melanocytes was noted in the lesional skin of melasma patients.

1064-nm Picosecond Laser Treatment for Hydroxychloroquine-Induced Hyperpigmentation of the Lower Extremities.

1064-nm Picosecond Laser Treatment for Hydroxychloroquine-Induced Hyperpigmentation of the Lower Extremities.

Fractional picosecond laser treatment of non-acne atrophic scars and scar erythema in Chinese patients.

Fractional picosecond lasers (FPL) are reported to be effective and safe for atrophic acne scars and post-acne erythema. However, there is no evidence regarding the effectiveness and safety of FPL treatment for non-acne atrophic scars and scar erythema among Chinese patients. In this retrospective study, 12 Chinese patients with non-acne atrophic scars, including nine with scar erythema, were treated with one to three sessions of 1064nm FPL treatment. Clinical improvement was objectively assessed through blinded evaluations by external physicians. A modified Manchester Scar Scale (mMSS) and the Clinician Erythema Assessment Scale (CEAS) were individually used to evaluate atrophic scars and scar erythema based on photographs. Physician-assessed and subject-assessed Global Aesthetic Improvement Scale (GAIS) were used to assess changes before and after FPL treatment. Patient satisfaction and adverse events were also documented. Total mMSS scores, as well as three parameters (color, distortion, and texture), were significantly decreased after FPL treatment, with a mean reduction of 3.18±1.60 in total scores (p<0.05). The CEAS scores were significantly reduced from 2.41±0.98 before treatment to 0.41±0.40 at the final visit (p<0.05). Based on physician-assessed and subject-assessed GAIS scores, 11 (91.7%) patients were improved after FPL treatment. 33.3% of patients were very satisfied, and 41.7% were satisfied. No serious, prolonged (>3weeks) adverse events were observed. Our study suggests that 1064nm FPL treatment may be a promising option for non-acne atrophic scars, especially with scar erythema. Further studies are needed to confirm our results.

Laser surface texturing of Ti-cp and Ti6Al4V alloy for the improvement of fibroblast adhesion and alignment and the reduction of bacterial adhesion

Surface texturing is widely investigated for the modulation of the surface properties and biological response of implantable materials. Laser is a green technology for the obtainment of specific patterns without the employment of toxic chemicals. In the present research, a picosecond laser treatment was applied to commercially pure titanium and Ti6Al4V alloy for the obtainment of aligned grooves characterized by micrometric width and spacing but submicrometric depth to promote fibroblast alignment and discourage bacterial adhesion. Surface topography and roughness of laser-textured surfaces were characterized using confocal microscopy, contact profiler, and Scanning Electron Microscopy. Zeta potential titration curves and contact angle measurements were used for the investigation of surface charge and wettability, while X-Ray Diffraction was employed for crystallographic characterization. Finally, the biological response (fibroblast adhesion and alignment and bacterial adhesion) was assessed. Similar results were obtained on commercially pure Ti and Ti6Al4V. Grooves with the designed features were obtained (about 15 μm spaced and 0.2μ deep) and the treated surfaces had a complex micro- and nano-scale morphology which reduced wettability. No evident chemical modification occurred. The treated surfaces were biocompatible and grooves had a contact guidance effect on human fibroblasts. The obtained topography had anti-adhesive action on bacteria (Staphylococcus aureus).

The efficacy and safety of low- versus high-fluence fractional picosecond Nd:YAG 1064-nm laser in the treatment of acne scars: A randomized split-face comparison study.

Differences in clinical efficacy based on the fluence of fractional picosecond laser treatment for acne scars are unknown. To compare the efficacy and safety of low-fluence versus high-fluence fractional picosecond Nd:YAG 1064-nm laser treatment in acne scar patients. In this 12-week, investigator-blinded, randomized, split-face study, 25 patients with moderate-to-severe acne scars received three sessions of high-fluence laser treatment (1.0 J/cm2 ) on one side of their face and low-fluence (0.3 J/cm2 ) on the other side every 4 weeks. Patients were assessed using acne scar counts, the scar global assessment (SGA), and the ECCA scar grading scale every 4 weeks. The histological analysis compared the acne scars obtained before and 4 weeks after treatment. At their last visit, 88.00% and 92.00% of the subjects achieved >30% reduction in scar counts on the low- and high-fluence sides, respectively, without a significant difference between the two sides. On both sides, the scar counts, SGA, and ECCA score significantly improved 4 weeks after the last treatment. Although the high-fluence side showed a greater reduction in scar counts (-66.73%) than the low-fluence side (-62.13%), the two sides had no significant difference in the grading scores. The high-fluence side showed significantly more severe pain and higher side-effect scores immediately and 4 weeks after treatment. Histological analysis revealed a significantly increased collagen, elastin, and vimentin expression after treatment on the low-fluence side. The low-fluence setting demonstrated comparable efficacy and superior safety in treating acne scars compared with the high-fluence setting.

Diffractive micro-lens array (DLA) for uniform and selective picosecond laser treatment.

Picosecond Nd:YAG lasers using diffractive optical elements (DOE) and micro-lens arrays (MLA) have widely been used in dermatology for the treatment of pigmented lesions and skin rejuvenation. This study designed and developed a new optical element of diffractive micro-lens array (DLA) by combing the features of DOE and MLA in order to achieve uniform and selective laser treatment. Both optical simulation and beam profile measurement demonstrated that DLA created a square macro-beam consisting of multiple micro-beams in a uniform distribution. Histological analysis confirmed that the DLA-assisted laser treatment generated micro-injuries at various skin depths from the epidermal layer to the deep dermal layer (up to 1200 µm) by adjusting the focal depths while DOE showed shallow penetration depths and MLA created non-uniform micro-injury zones. The DLA-assisted picosecond Nd:YAG laser irradiation can provide a potential benefit for pigment removal and skin rejuvenation via uniform and selective laser treatment.

Light nurtures plants: The picosecond laser-induced lithops-like microstructures on titanium alloy surface with broad-band ultra-low reflectivity

Micro-nanostructures on metal surfaces have received significant attention due to their widespread applications. Although ultrafast laser processing was a feasible method to fabricate micro-nanostructures, some issues involving the formation and application of novel micro-nanostructures still exist. Here, we proposed the unique lithops-like microstructures on titanium alloy (Ti-6Al-4V) by ultraviolet picosecond (UV-ps) laser treatment. These structures were either separate tomb-like bumps or bump clusters consisting of several interconnected bumps, which were similar in appearance to lithops. Due to nanoparticle deposition, these bumps were also covered with nanostructures. Titanium alloy was oxidized to form Ti2O3 and TiO2 during treatment. The formation of lithops-like microstructures involved the laser-induced physical/chemical processes of melting, flowing, vaporization, oxidation, solidification, and deposition of material. As laser energy increased, the smooth surface gradually evolved into lithops-like microstructures under the synergistic effects of electromagnetic interference, the Marangoni effect, preferential valley ablation, and thermal effects. By combining geometric light trapping within microstructures with surface plasmon resonance (SPR) absorption within nanostructures, these structures exhibited ultra-low reflectivity (0.02%∼2.31%) in the ultraviolet–visible-near-infrared band (200 ∼ 2500 nm). They also showed ultra-low reflectance (<3%) over a wide range of incidence angles (5°∼70°). The anti-reflection properties of lithops-like microstructures were superior to those of some typical micro-nanostructures.

Prospective comparison study of a 550 picosecond 755 nm laser vs a 50 ns 755 nm laser in the treatment of nevus of Ota

Since the introduction of selective photothermolysis, Q-switched nanosecond lasers have been used for the treatment of dermal pigmented lesions. Over the past several years, picosecond lasers have been introduced to the cosmetic community. We recently performed a study comparing a 550 picosecond 755nm laser versus a 50ns 755nm laser, with the purpose of evaluating the clinical efficacy and complications of each laser when treating nevus of Ota. Ten Asian patients with nevus of Ota were enrolled in the study. Each lesion was split into 2 parts, and patients were treated with a 755nm picosecond laser (PSL) and a 755nm nanosecond laser (NSL). The clinical endpoint for fluence choice was immediate whitening (PSL: 2.33 ~ 3.36J/cm2, NSL: 5.5 ~ 7J/cm2) of the treated area. The pulse duration was fixed at 550 picoseconds (PSL) and 50ns (NSL). The spot size of each laser was 2.5-3mm. Laser treatments were performed until excellent clinical improvement was observed. Patients were examined 1week after the first treatment, at each follow-up visit, and 6months after the last laser treatment. The average number of treatment sessions to achieve excellent clinical improvement was 4.2 treatments using PSL and 5.4 treatments using NSL. One case of hyperpigmentation and one case of hypopigmentation were observed in the NSL treatment group. There were no complications in the PSL treatment group. The 755nm 550 picosecond laser is significantly more effective than the 755nm 50ns laser in the treatment of nevus of Ota. The PSL treatment group also had minimum side effects.

Structural and Functional Picosecond Laser Modification of the Nimonic 263 Superalloy in Different Environmental Conditions and Optimization of the Irradiation Process.

In this experimental study, picosecond laser treatment was performed on a nickel-based superalloy Nimonic 263, aiming to investigate the surface effects induced by irradiation in different atmospheric conditions and, concerning changes in surface composition, regarding the possibility for improvement of its functionality. Besides the varying laser parameters, such as a number of pulses and pulse energy, environmental conditions are also varied. All surface modifications were carried out in standard laboratory conditions and a nitrogen- and argon-rich atmosphere. The resulting topography effects depend on the specific laser treatment and could be categorized as increased roughness, crater formation, and formation of the laser-induced periodic surface structures (LIPSS). Changes in the chemical surface composition are distinguished as the potential formation of the protective oxides/nitrides on the sample surface. Numerous characterization techniques analyse the resulting effects on the topography and surface parameters. The multi-response parametric optimization of the picosecond laser process was performed using an advanced statistical method based on Taguchi's robust parameter design. Finally, the optimal parameter conditions for Nimonic 263 modification are suggested.

Effectiveness of 730 nm Picosecond Laser for the Treatment of Freckles and Solar Lentigines: A Retrospective Analysis

Background. Freckles and solar lentigines are epidermal pigmentation disorders that affect the face and impact the quality of life of affected individuals. Aims. We aimed to observe and evaluate the clinical effectiveness of a 730 nm picosecond laser for the treatment of freckles and solar lentigines. Methods. We retrospectively collected patient information on freckles and solar lentigines and observed and evaluated the clinical outcome of a 730 nm picosecond laser. These included lesion clearance and recurrence rates, adverse reactions, and patient satisfaction. Results. Fifty cases of freckles and solar lentigines reported between January 1, 2022, and July 1, 2022, were included. All patients received two 730 nm picosecond laser treatments. The lesion clearance rates after one and two treatments were 53.1% and 78.4%, respectively, and the rates after one and six months of treatment were 78.7% and 78.4%, respectively. 90% of the patients reported ≥95% clearance of lesions after six months via a questionnaire survey. Among the patients, 86.0% were satisfied with their treatment. Postinflammatory hyperpigmentation occurred in two patients, both of whom had Fitzpatrick skin type IV. There was no recurrence of lesions. Conclusions. The 730 nm picosecond laser treatment for freckles and solar lentigines has the advantages of a high clearance rate, low recurrence rate, and high patient satisfaction. This trial is registered with ChiCTR2200058573.

Fixed drug eruption.

A 31-year-old woman presented to the dermatology department with an asymptomatic erythematous patch on the dorsum of her right foot ([Figure 1A][1]). She had taken 1 dose of doxycycline (100 mg) the previous day as empirical treatment after picosecond laser treatment for acne scars. She had had a

Long-Term Follow-up for 1,064-nm Nanosecond and Picosecond Laser Treatment of Acquired Bilateral Nevus of Ota-Like Macules.

Long-Term Follow-up for 1,064-nm Nanosecond and Picosecond Laser Treatment of Acquired Bilateral Nevus of Ota-Like Macules.

Favorable effect after single treatment session of 755-nm-picosecond laser with a diffractive optic lens on facial wrinkles and pore size in Asians.

Laser therapy has become one of the mainstay treatments for improvingsigns of aging including wrinkles, large pores, and skin pigmentation. However, in patients with pigmented skin, an increase in complicationsincludingpost-inflammatory hyperpigmentation (PIH) has been noted. The purpose ofthisstudy is to investigate not only the safety profile of 755-nmpicosecond laser withdiffractive lens array (DLA)at approximately 2250pulseson the facein people with darker skin, but also to evaluateitsefficacyin treating wrinkles and pore sizesafter one treatment sessionamong different age groups. This single-center, retrospective study enrolled patients between age 22 and 65 with both facial wrinkles and enlarged pore sizes. A total of 46 patients (7male, 39 female, mean age 43) with Fitzpatrick skin types III and IV were enrolled. Two independent data-blinded dermatologists assessed and scored the improvements of patients' wrinkles and pore sizes using photographs. After onetreatmentsession, statistically significant improvements were observed in lateral canthal wrinkles (p<0.001) and facial wrinkles (p=0.014).In addition, greater percentage of the patients from the aged group (50-65years) showed clinically significant improvement as compared with the younger group. For patients withtype III and IV skin,one session of DLApicosecond lasertreatment at around 2250 pulses to the face is safe and effective for clinically meaningful improvement of the wrinkles and pore sizes, especially forthe patients from 50- to 65-years of age.

Picosecond laser treated aluminium surface for photothermal seawater desalination

Interfacial solar steam generation has been proposed as an eco-friendly way for water desalination. However, the current interfacial evaporator still suffers from a complex process, high preparation cost, and poor stability. Here, by means of picosecond laser treatment of the aluminium surface, we developed a superhydrophilic, anti-gravity wicking, and efficient solar desalination evaporator. The picosecond laser treated aluminium (PLAL) surface has an open capillary structure, which contributes to the rapid transfer and evaporation of seawater. Moreover, larger size water clusters are formed on the surface, hence lowering its enthalpy of water evaporation dramatically to 541.25 ± 0.07 kJ/kg, which can effectively increase the evaporation rate to 1.24 kg·m−2·h−1 under one sun irradiation (1 Kw·m−2) even with only 67% energy efficiency, and is 0.3 kg·m−2·h−1 higher than that treated by high-cost femtosecond laser. Even under weaker natural sunlight, the evaporation rate remains 0.7–0.9 kg·m−2·h−1. Additional experiments were carried out at low laser power (30%) to evaluate the effect of PLAL surface structure on anti-gravity wicking. Additionally, during 25-day continuous desalination, the evaporation performance of PLAL surface remains stable, in contrast to that placed in ambient air, which changes to hydrophobic 20 days after laser treatment. Furthermore, low temperature annealing can restore the PLAL surface, which has been converted to hydrophobic, to superhydrophilic. The reason for transition may attribute to the increase in the carbon content of the surface causing an increase in the relative content of the CC bond of the surface. The PLAL surface fabricated here is easy to fabricate and scale-up and exhibits the potential to efficient desalinate seawater and purify wastewater, etc.

A single‐blinded, randomized, controlled trial comparing efficacy between low‐fluence alexandrite 755‐nm picosecond laser and low‐fluence neodymium‐doped yttrium aluminum garnet (Nd:YAG) 1064‐nm picosecond laser for the treatment of ultraviolet B‐induced hyperpigmentation

Hyperpigmentation is a common concern of patients in dermatology clinics. Although there are many treatment options, lasers are considered a promising therapy for various hyperpigmentary conditions. This study aims to evaluate the efficacy of alexandrite 755-nm picosecond and neodymium-doped yttrium aluminum garnet (Nd:YAG) 1064-nm picosecond lasers for the treatment of ultraviolet B (UVB)-induced hyperpigmentation in Asians. A randomized, single-blinded study was conducted. UVB-induced hyperpigmentation was performed in three spots by narrowband UVB. After 2weeks, these three spots were allocated into 755-treated, 1064-treated, and control sites. Patients received weekly laser treatments for five sessions. Follow-ups were scheduled at 1 and 2months after the last session. Twenty patients attended the study. Overall, 755-nm and 1064-nm picosecond lasers showed a significant improvement in the mean lightness index (L*) compared to the control site, which started at Day49 and Day77, respectively. The mean L* of the 755-nm-treated site was also higher than that of the 1064-nm-treated site at Day105 (p≤0.001). Initially, the mean L*, physician's visual analog scale (VAS), and patient satisfaction with the 1064-nm picosecond laser were better than those with the 755-nm picosecond laser. Nevertheless, an inversion of the mean L* and VAS was noted at Day49, whereas the mean patient satisfaction was noted at Day77. In the subgroup analysis, a 755-nm picosecond laser effectively treated Fitzpatrick skin types (FPTs) III and IV. However, the mean L* of the 1064-nm picosecond laser was not significantly different from that of the control for FPT4. The alexandrite 755-nm picosecond and Nd:YAG 1064-nm picosecond lasers appear to be effective and safe modalities for treating UVB-induced hyperpigmentation. With the setting employed in this study, the outcome after the 755-nm picosecond laser treatment seemed superior to that of the 1064-nm picosecond laser treatment, especially for FPT4.

Evaluation of Picosecond 755-nm Alexandrite Laser With a Diffractive Lens Array on Pore Size Reduction.

Medications, lasers and light therapy have all been shown to transiently minimize pore size. Current research of the 755-nm Alexandrite picosecond laser (Cynosure, MA) on pore size shows differing results regarding the efficacy, with one study of Asian volunteers (Fitzpatrick skin type IV) reporting &ldquo;marked&rdquo; improvement of pores, yet another study reporting no significant improvement in pore size in Chinese patients (Fitzpatrick skin type III&ndash;IV), causing some contention. This study aims to rectify the discordant results through the examination of the 755-nm Alexandrite picosecond laser on pore size reduction in a sample consisting of Fitzpatrick skin type I&ndash;III. Patients who received 755-nm Alexandrite picosecond laser treatment for photorejuvenation, (6 mm lens array) with a fluence of 0.71 J/cm2 of the face or head, with at least two treatments over four-week intervals were included in the study. A precision subject imaging system (Canfield VISIA&reg; Complexion Analysis Generation 7, NJ) was used to assess three parameters of pore size (feature count, score, percentile rank) at each time period at right lateral, left lateral and frontal views. A Wilcoxin signed rank test was performed to compare differences between time periods and a mixed model ANOVA was utilized to account for patients who received less than three treatments. Significance level set to P=&lt;0.05. 32 participants met criteria and underwent at least two picosecond laser treatments for photorejuvenation. There was an overall reduction in pore count in approximately 57% of participant data points from times 1 to 2 and 50% reduction from times 2 to 3. There was a 100% pore count reduction observed from baseline compared with the follow-up visit four weeks after the third treatment, at time 4. Further, there was a significant improvement of pores demonstrated by score from times 1 to 3 (Z= -2.197, P=0.028) as well as percentile rank between times 1 and 2 (Z= -2.070, P=0.038) and times 1 and 3 (Z= -2.201, P=0.028). Future studies should investigate the longterm effect of 755-nm Alexandrite picosecond laser on pore size reduction as continued patient recruitment and data collection is necessary to effectively discern the 755-nm Alexandrite picosecond laser debate. Thus, prolonged follow up post treatment should be evaluated in order to determine if results are maintained. Nonetheless, the 755-nm Alexandrite picosecond laser shows promising results for the improvement of skin pores thus far. J Drugs Dermatol. 2021;20(12):1302-1306. doi:10.36849/JDD.6199.

Treatment of nevus of Ota with 1064 nm picosecond Nd:YAG laser: A retrospective study.

Nevus of Ota has been successfully treated by lasers. Currently, 1064 nm picosecond Nd:YAG lasers have become available for the treatment of pigmented disorders. However, there are few studies concerning the application of 1064 nm picosecond Nd:YAG laser in nevus of Ota. This study aimed to evaluate the efficacy and safety of a 1064 nm picosecond Nd:YAG laser for the treatment of nevus of Ota. We conducted a retrospective analysis of Chinese patients with nevus of Ota who had been treated with a 1064 nm picosecond Nd:YAG laser. Those who had any other laser treatment during the period of picosecond laser treatment were excluded. Via a visual analog scale for percentage of pigmentary clearance in standard photographs, the treatment efficacy was assessed by three blinded physician evaluators. A total of 16 subjects were included in this retrospective study. The average age at the beginning of treatment was 16.87 years old (range of 4months to 59 years), and all patients were of Fitzpatrick skin type IV. Total treatment ranged from 1 to 5 sessions. A 1064 nm picosecond Nd:YAG laser with a mean fluence of 1.8-4.3J/cm2 was used at 3-12 month intervals. The mean efficacy score for all 16 patients was 2.56 after one session, and the mean efficacy score of 13 patients who completed two sessions and nine patients who completed three sessions were 3.15 and 3.51, respectively. Postinflammatory hyperpigmentation after treatment was only observed in 1 (1/16, 6.25%) patient. The 1064 nm picosecond Nd:YAG laser is an effective and safe approach for treating nevus of Ota.

Laser Assisted Size Reduction of Gold (Au) Particles onto a Titanium (Ti) Substrate Surface

This paper aims to perform laser assisted size reduction to nanoparticles of gold (Au) sputtered layer on titanium (Ti) base material using an innovative method that could potentially be applied in novel blood contact and thromboresistive devices in the living body, such as ventricular assist devices (VADs). The enrichment of the surface layer of titanium with gold nanoparticles, due to its bioproperties, may contribute to the reduction of inflammatory reactions and infections occurring mainly in the first postoperative period causing implant failure. The possibility of obtaining superficial size reduction and/or bonding of nano gold particles with Ti micromachining by picosecond laser treatment was evaluated. The quantitative assessment of the particles has been made using SEM and are depicted on the histograms, whereby the appropriate number of particles determine the antibacterial properties and health safety. The initial analysis of micromachining process of the prepared material was focused on power-depth dependence by confocal microscopy. The evaluation of gold particles was conducted using scanning electron microscopy (SEM) using SE and QBSD detectors with energy dispersive spectroscopy (EDS) analysis. Attempts to reduce the deposited gold coating to the size of Au nanoparticles and to melt them into titanium matrix using a laser beam have been successfully completed. There seems to be no strict relationship between particle size distribution of gold onto Ti, probably due to too low energy to excite titanium enough, resulting from difference in Ti and Au melting point temperatures. However, the obtained results allow continuation of pilot studies for augmented research and material properties analysis in the future.

The Picosecond Laser Effects on Tattoo Removal and Metabolic Pathways.

ObjectiveWe 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 MethodsWe 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.ResultsBased 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.ConclusionThe picosecond laser had perfect tattoo removal effects, which could be utilized as a reference for clinical tattoo removal.