Histological analysis of tattoo removal by water cavitation bubbles and jet formation using Nd: YAG and nanosecond laser pulses

Background: For efficient laser tattoo removal, photodisruption of tissue can ensure a very powerful means to shutter ink granules. At very high laser intensity level, photodisruption dominates and selective photothermolysis will have secondary effect in clearing the tattoo ink. Lower laser fluence is all what to trigger non-linear photons absorption and the generation of exploding cavitation bubbles that can tremendously hammer the ink granules. Subjects, materials, and methods: Three domestic white rabbits; each received simultaneous injections of a color pigment tattoo under general anesthesia, followed by a single session of (1064) Q.S Nd: YAG nanosecond laser pulses for tattoo removal. Results and Discussion: Spectroscopic properties of black, dark brown and red tattoo inks were studied. Near threshold laser fluence was selected to select the optimum conditions for obtaining scar-free treatment. Histological images of the biopsies, taken after thirty days of laser treatment of black, dark brown and red tattoos showed a marked reduction in pigment granules size with no appearance of hyperplasia or inflammatory cells. Coexistence of macrophages was suggested to be responsible for actively phagocytizing the laser-dispersed tattoo fragments. Conclusion: skin biopsies have demonstrated ink granules local redistribution. Photodisruption at 1064nm laser effectively targeted black and dark brown tattoo pigments by the generation of cavitation bubbles. The weaker laser light absorption of red pigments at 1064nm only showed tattoo clearance when using 532nm wavelength.

Personalized high-intensity laser therapy for patients with abnormal skin scars

Background. Scars are an inevitable consequence and the final outcome of the restoration of the skin, after injuries, thermal effects on the skin, and are also formed as a result of the resolution of rash elements in various infectious skin diseases, with adverse wound healing after plastic surgery and cosmetic procedures. According to WHO data for 2020, scar complications affect about 10% of the world's population, which is approximately 600 million people. High-intensity laser therapy technologies are considered by experts to be the "gold" standard in the correction of pathological scars, but a significant number of them are updated by the personalized approach developed in the last decade, aimed at individualizing treatment, searching for predictors of the effectiveness of various methods, taking into account a number of basic mechanisms of pathogenesis. Aims: Scientific substantiation of the concept of personalized high-intensity laser therapy for patients with pathological skin scars. Materials and methods. We studied 306 patients with atrophic (n=115), hypertrophic (n=100) and keloid (n=91) scars, which were divided into subgroups with emerging (formation period up to 1.5 years) and mature scars. Genetic, phenotypic, clinical, instrumental, laboratory, and medical-sociological methods were used to study the patient's condition and scar tissue. Laser therapy combinations were used: fractional ablative photothermolysis, homogeneous photothermolysis, planar ablative photodestruction, selective angiophotothermolysis, and fractional selective photothermolysis. Results. It was found that various combinations of high-intensity laser therapy in patients with pathological skin scars cause a significant regression of clinical signs, restore the microrelief of tissues, improve the functional properties of scars (elasticity, elasticity, moisture, vascularization, etc.), which is accompanied by an improvement in the quality of life of patients. The complex of laser technologies forms a pronounced refibromodeling therapeutic effect in patients with pathological skin scars. Conclusion. The concept of personalized (variant) high-intensity laser therapy in patients with atrophic, hypertrophic and keloid scars, which determines the dependence of the effectiveness of various options for laser correction of pathological scars on the genetic, phenotypic, clinical, morphofunctional and medical-sociological characteristics of patients, is scientifically substantiated. The determinants of the effectiveness of laser technologies have been identified, taking into account which allows the productive use of high-intensity laser radiation in patients with atrophic, hypertrophic and keloid skin scars.

Laser therapy in the treatment of post-burn scars in children

Burns are one of the most common injuries in the paediatric population. Despite improved medical care, many burn patients develop permanent scars, which are a serious cosmetic, functional and psychological burden. We present the possible use of a pulsed dye laser (PDL) and an ablative fractional CO2 laser (AFCL) in the treatment of post-burn scars, with particular emphasis on the paediatric population. PDL is intended to reduce scar redness through selective photothermolysis of blood vessels to reduce local hypervascularity. This type of laser can be also used to reduce pruritus, most likely by modifying local cytochemical reactions. Ablative fractional carbon dioxide laser therapy (AFCL) may be optionally used to improve scar texture and reduce its thickness. AFCL can also restore normal function of the scarred area. It causes vaporisation of scar tissue fragments, thereby stimulating collagen reconstruction. The fact that PDL and AFCL can be safely combined during the same procedure is an important advantage of using laser therapy in the treatment of hypertrophic scars. Combined therapy allows to reduce the overall number of sessions. The use of two lasers during one session also allows to reduce the amount of anaesthesia. The combined use of PDL and AFCL is safe. No serious complications were reported during combined therapy. Doctors treating patients with burn scars should consider the use of laser therapy as a modern standard for the treatment of hypertrophic scars. Scars that cause contractures and significantly impair motor functions may require multi-stage surgical treatment, supported by laser therapy, rehabilitation and conservative treatment.

Minimally Invasive Technologies for Treatment of HTS and Keloids: Pulsed-Dye Laser

We present another minimally invasive technology for the treatment of hypertrophic scars and keloids: the pulsed-dye laser. Being first introduced by two groups around Schaefer (Germany) and Sorokin & Lankard (USA) in 1966, the pulsed dye laser is a rather new technology. The first clinical use of pulsed-dye lasers was reported in 1983 for the treatment of naevus flammeus, and was the first laser used for the treatment of keloids in the mid-1990s.Its efficacy is based on the principle of selective photothermolysis, enabling a selective destruction of defined structures absorbing the respective wavelength used, as compared to other lasers working based on thermal coagulation or ablative tissue interaction. The preferred wavelengths being used are 585 or 595 nm, which makes small cutaneous vessels the main targets. Their destruction leads to a diminished blood supply of the irradiated area, thus reducing symptoms of hypertrophic scars like itching, vascularity, and redness, and secondary – probably by the induced hypoxemia – a reduction in scar height and pliability. This therapeutic approach also implies the use of pulsed-dye laser in the prevention of pathologic scars. While significant side effects are usually rare, slight signs of use like edema or scab formation can pertain for several days. Since the sensory impact of laser pulses are comparable to needle pricks, some form of analgesia during the application is highly recommended. The elusive data and still existing scarcity of high-quality studies on the use of pulsed-dye laser, however, make it hard to develop clear recommendations.

Selective photothermolysis of spider veins and reticular varices with the long-pulsed Nd:YAG laser

The therapy of spider veins, telangiectasia and reticular veins of lower extremities can be successfully performed with sclerotherapy or by using the long pulsed (LP) Nd:YAG laser. A matter of discussion, however, is how should laser parameters – such as wavelength, fluence, pulse duration, number of pulses – be utilized for effective and selective photothermolysis treatment without any side effects. The selective photothermolysis was introduced in 1983 by Anderson and Parrish 1 as a concept in laser treatment, meaning the selective thermal destruction of the target tissue (the chromophores – the light-absorption molecule is here the blood vessel) using a specific laser light wavelength, with minimal injury to surrounding tissue (the skin). The effectiveness of the selective photothermolysis process using an LP Nd:YAG laser at 1064 nm for the treatment of leg veins telangiectasias up to 2 mm in diameter, is the result of 30-years clinical experience sustained by patient satisfaction and photo documentation. The use of double and triple pulses seems to be the key of success in treating even larger vessels and has demonstrated superior safety and efficacy. Even bigger telangiectasias, reticular veins or other dilated veins on neckline, upper abdomen or in the face can be successfully treated with the LP Nd:YAG laser.

Diode Laser and Fractional Laser Innovations

Laser technology continues to increase in popularity and expand treatment options for patients with common but challenging skin conditions including facial telangiectasias, facial aging, striae distensae, and acne scars. Facial telangiectasias have been estimated to occur in tens of millions of people worldwide. The 585-nm laser was the first to follow the principle of selective photothermolysis for the treatment of cutaneous vascular lesions, but it caused significant postoperative purpura. Newer diode lasers target superficial and deep telangiectasias without the side effects of the 585-nm laser. Ablative resurfacing was introduced in the 1990s with the carbon dioxide laser to address facial rhytids and photoaging. While effective, the risks and downtime were significant. The newest fractionated nonablative lasers are demonstrating impressive results, with decreased risks and downtime. This new generation of lasers is being used extensively and in unique combinations for facial aging, striae, and acne scars.

Numerical Modeling and Clinical Evaluation of Pulsed Dye Laser and Copper Vapor Laser in Skin Vascular Lesions Treatment

Introduction: Different yellow lasers have been successfully used for the treatment of vascular lesions. This study is aimed to ascertain the role and efficiency of copper vapor lasers (CVLs) and pulsed dye lasers (PDLs) for the treatment of vascular lesions using numerical modeling and to compare results with our clinical experience. In this study we aimed to develop criteria for the choice of more efficient laser exposure mode, investigate more relevant modes of laser irradiation to ensure selective photothermolysis of target vessels, and compare the CVL and PDL efficiency in the course of patients with skin vascular lesions (SVL) treatment. Methods: We performed numerical simulation of the processes of heating a vessel with CVL and PDL to temperatures at which its coagulation could occur. Calculated fluencies were compared with clinical results of laser therapy performed on 1242 patients with skin hemangiomas and vascular malformations (SHVM), including 635 patients treated with CVL and 607 patients treated with PDL. PDL and CVL provided excellent results in 40 and ten days after treatment. The treatment was not painful. Patients did not need anesthesia. Postoperative crusts were greater with PDL than with CVL. Results: Results of computer simulation of a selective vessel heating using PDL and CVL radiation are presented. By results obtained, depth of the location and sizes of vessels that could be selectively heated to more than 75°C are determined. Conclusion: Based on calculated and clinical data, the heating mode for dysplastic vessels using a series of CVL micropulses could be regarded to be safer and more efficient than the mode of a PDL short, powerful pulse.

THE RESULTS OF HISTOLOGICAL STUDY OF THE IMPACT OF LASER RADIATION IN THE SELECTIVE PHOTOTHERMOLYSIS MODE ON VASCULAR LESIONS IN EXPERIMENT

This article is dedicated to the increasing of the effectiveness of treatment of patients with vascular lesions of the skin using the radiation of KTP-Nd:YAG laser with a wavelength of532 nm. An experimental research was conducted to study the effect of laser radiation with an energy density of 4, 6, and 8 J/cm2 used on blood vessels ofauricles of experimental animals (rabbits) according to the histological study in dynamics. As a result of the experiment, it was found that laser radiation with a radiation density of up to 4 and 6 J/cm2 does not damage the epidermis of the skin, which indicates the selectivity of the effect on the blood vessels of the rabbit auricles. The histological pattern is distinctive for that ofselective photothermolysis. The processes ofneoangiogenesis, proliferation of fibroblasts, collagen production, fibrillogenesis end with the maturation andfibrous transformation ofthe granulation tissue without its cicatrical deformation. The use of KTP-Nd:YAG laser may increase the quality of treatment of patients with skin lesions.

THE EFFECTIVENESS OF A NEODYMIUM (1064 NM) LASER AND FRACTIONAL PHOTOTHERMOLYSIS FOR THE CORRECTION OF THE ATROPHIC SCARS

One of the challenging problems for modern cosmetology is the cosmetic correction of the cutaneous scars of the skin that arises in the first place from the high prevalence of this condition and the lack of reliable and safe methods for its treatment The application of laser technologies including selective laser therapy as the method of fractional photothermolysis and the use of a neodymium (1064 nm) laser is considered to be a promising approach to address this problem. The present study included 18 patients presenting with hormone-dependent atrophic scars. All the patients were assigned for the treatment by selective photothermolysis (at the rate of 2 sessions per each treatment course performed with a 4 week interval) and irradiation by the neodymium laser (at the rate of 6-8 sessions conducted after fractional photothermolysis). The use of combined laser therapy in patients with hormone-dependent atrophic scars produced a pronounced effect as evidenced by the improvement of the clinical picture and was accompanied by the 78.1% reduction of the symptom index according to the DISC symptom scale and the 76.5% improvement of the dermatology life quality index (DLQI). The use of the combined method for the correction of atrophic cutaneous scars helps to restore the epidermal-dermal and epidermal structures of the skin in the association with the 1.4-fold, 1.7-fold, and 1.6-fold increase in the thickness of the epidermis, dermis, and hypodermis respectively; simultaneously, the acoustic density of the tissues increased by 1.8 times which corresponded to the improvement of the ultrasound picture by almost 75% when estimated in accordance with the Vancouver scar scale.