Ultraviolet-laser ablation of skin

We report on the use of pulsed ultraviolet-laser irradiation at 193 nm from an argon-fluoride laser and at 248 nm from a krypton-fluoride laser to ablate skin. In vitro, both wavelengths performed comparably, removing tissue precisely and cleanly, and leaving minimal thermal damage to the surrounding tissue. In vivo, the 193-nm laser radiation failed to remove tissue after bleeding began. The 248-nm radiation, however, continued to remove tissue despite bleeding and left a clean incision with only minimal thermal damage. The krypton-fluoride excimer laser beam at 248 nm, which should be deliverable through a quartz optical fiber, has great potential as a surgical instrument.     

点阵激光在医学美容的研究进展

点阵激光作为一种新型激光治疗模式,可调控皮肤显微热损伤区的深度、宽度、密度,充分利用点阵微孔周围正常皮肤的快速平行修复功能,以保证对局部皮肤的高强度效应,在保证确切疗效的同时,又可获得最短的恢复时间和最小的治疗风险,目前已在医学美容领域广泛应用.     

LASER-tissue interactions

As new laser devices continue to emerge, it becomes increasingly important for the clinical dermatologist to understand the basic principles behind their operation. A fundamental understanding of how lasers interact with tissue will enable the physician to choose the most appropriate laser for a given clinical situation. Although the physical laws guiding laser design are vastly complex, the fundamental principles of laser-tissue interaction can be summarized as they are applicable to the clinician.     

Laser transmission through transparent membranes used in cutaneous laser treatment

BACKGROUND: Some clinicians perform cutaneous laser treatments through transparent membranes to protect themselves and the surroundings from contamination by ejected tissue particles. Transmissibility of these membranes influences the tissue irradiance. OBJECTIVE: We compared the optical transmissibility of 8 membranes. METHODS: In part 1, a Schwartz Electro-Optics Q-switched alexandrite laser (wavelength of 720-800 nm, beam diameter of 3 mm) was directed through 8 membranes. A Molectron JD 2000 Joulemeter Ratiometer obtained measurements of percent loss of laser energy (for calculation of percent transmission) through each. To evaluate other wavelengths used in skin treatment, an SLM Aminco UV-VIS model 2000 spectrophotometer measured variance of transmission over a spectral region from 350 to 900 nm in 4 of the membranes. RESULTS: The samples listed in order of increasing amounts of light energy lost across the membrane as compared with control (direct irradiation) were as follows: (1) Handi Wrap plastic wrap: 7% loss, 93% transmission; (2) glass slide: 8% loss; (3) Bioclusive transparent dressing: 11% loss; (4) Tegaderm transparent dressing: 26% loss; (5) Vigilon dressing without plastic backing: 34% loss; (6) Vigilon dressing with one layer of plastic backing: 37% loss; (7) Acuderm dressing: 41% loss; and (8) OpSite IV: 48% loss. CONCLUSIONS: Transmissibility of the interposed membranes must be considered when determining the dosimetry of light energy required by the target tissue.     

Ultraviolet excimer laser ablation: the effect of wavelength and repetition rate on in vivo guinea pig skin

Multiple dermatologic conditions that are currently treated with traditional cold-knife surgery are amenable to laser therapy. The ideal surgical treatment would be precise and total removal of abnormal tissue with maximal sparing of remaining structures. The ultraviolet (UV) excimer laser is capable of such precise tissue removal due to the penetration depth of 193 nm and 248 nm irradiation of 1 micron per pulse. This type of ablative tissue removal requires a high repetition rate for efficient lesional destruction. Excimer laser radiation at 193 nm is capable of high repetition rates, which are necessary while 248 nm radiation causes increasing nonspecific thermal injury as the laser repetition rate is increased.     

Care of the burn wound.

The initial therapy of thermal injuries is directed at removal of loose debris and necrotic epidermis, alleviation of pain, and prevention of infection. Following initial wound debridement, bacterial growth in the wound itself is controlled primarily through the use of tropical antibiotic agents and daily hydrotherapy to clean the wounds and remove any loose eschar. Effectiveness of topical therapy is monitored by quantitative burn wound biopsy cultures; growth of greater than 10(4) micro-organisms per gram of tissue indicates invasive burn wound sepsis. Such bacterial invasion may be further controlled through the adjunctive use of antibiotics administered into the sub-eschar space. Once eschar separation has exposed healthy granulation tissue, the burn wound must be covered with suitable biologic dressings prior to autografting. All open wounds may then be autografted with sheet grafts to the face, neck, and areas exposed to trauma or by expansion mesh grafts to cover large areas from limited donor sites. Upon completion of autografting, a vigorous physical therapy program is necessary to rehabilitate victims of massive thermal injury to a functional existence.     

Fractional photothermolysis: a review and update

Fractional resurfacing is a new laser treatment modality that creates numerous microscopic thermal injury zones of controlled width, depth, and density that are surrounded by a reservoir of spared epidermal and dermal tissue, allowing for rapid repair of laser-induced thermal injury. This unique modality, if implemented with proper laser-delivery systems, enables high-energy treatments while minimizing risks. In this article, we review the various fractional laser devices, including the new fractional ablative devices, as well as the results of studies on the clinical efficacy of fractional photothermolysis. This technology offers patients significant clinical improvement in photodamage, melasma, and scarring with modest treatment-related downtime and minimal risk of complications.     

Putative photoacoustic damage in skin induced by pulsed ArF excimer laser

Argon-fluoride excimer laser ablation of guinea pig stratum corneum causes deeper tissue damage than expected for thermal or photochemical mechanisms, suggesting that photoacoustic waves have a role in tissue damage. Laser irradiation (193 nm, 14-ns pulse) at two different radiant exposures, 62 and 156 mJ/cm2 per pulse, was used to ablate the 15-microns-thick stratum corneum of the skin. Light and electron microscopy of immediate biopsies demonstrated damage to fibroblasts as deep as 88 and 220 microns, respectively, below the ablation site. These depths are far in excess of the optical penetration depth of 193-nm light (1/e depth = 1.5 micron). The damage is unlikely to be due to a photochemical mechanism because (a) the photons will not penetrate to these depths, (b) it is a long distance for toxic photoproducts to diffuse, and (c) damage is proportional to laser pulse intensity and not the total dose that accumulates in the residual tissue; therefore, reciprocity does not hold. Damage due to a thermal mechanism is not expected because there is not sufficient energy deposited in the tissue to cause significant heating at such depths. The damage is most likely due to a photoacoustic mechanism because (a) photoacoustic waves can propagate deep into tissue, (b) the depth of damage increases with increasing laser pulse intensity rather than with increasing total residual energy, and (c) the effects are immediate. These effects should be considered in the evaluation of short pulse, high peak power laser-tissue interactions.     

Fractional Laser treatment for pigmentation and texture improvement

Fractional laser treatment with the 1,550 nm erbium fiber laser (Fraxel Laser, Reliant Technologies) has bridged the gap between the ablative and nonablative laser modalities used to treat the epidermal and dermal signs of skin aging. By targeting water as its chromophore, the laser induces a dense array of microscopic, columnar thermal zones of tissue injury that do not perforate or impair the function of the epidermis. The significant skin remodeling that ensues can be used to treat, with limited downtime, epidermal pigmentation, melasma, and rhytides, as well as textural abnormalities that include acne-related and surgical scars.     

What is nonablative photorejuvenation of human skin?

Nonablative photorejuvenation has become an integral procedure in the emerging discipline of laser dermatologic surgery. The objective is to confine selectively, without any epidermal damage, thermal injury to the papillary, and upper reticular dermis leading to fibroblast activation and synthesis of new collagen and extracellular matrix material. The procedure results in minimal patient morbidity, no interference with lifestyle, and a low risk of complications, while providing a satisfying degree of rhytides reduction. Multiple devices have been studied and marketed for nonablative photorejuvenation of human skin. However, currently, nonablative photorejuvenation should not be considered an alternative to laser skin resurfacing. The skin surface is not removed or modified. What really occurs may be more accurately referred to as dermal "remodeling" or "toning" as a wound healing response is initiated and collagen regenerated. The narrow "therapeutic window" of laser-induced dermal heating and epidermal cooling must still be optimized so that effective treatments can be obtained routinely. Clinical verification of effective treatment parameters (irradiation wavelength, pulse structure, radiant exposure, cooling time) will be obtained through further human studies. Most importantly, understanding the relationship between the degree of dermal thermal injury and synthesis of new collagen and extracellular matrix material will be fundamental to predicting the clinical efficacy and limitations of nonablative photorejuvenation.     

Spotsize effects on guinea pig skin following pulsed irradiation

Laser irradiation parameters such as wavelength, irradiance (W/cm2), and pulse duration have been clearly shown to influence the extent to which tissue is damaged. The careful choice of these parameters can result in confining laser injury to specific targets in tissue. Spotsize, a parameter not commonly appreciated in the application of lasers to medicine and surgery, has been shown, in this study, to contribute to the ultimate outcome of laser effects in tissue. A series of histological events occurring in the skin are demonstrated to be directly related to the effects of spotsize on tissue at a fixed exposure time and wavelength. Many of these changes could contribute to unwanted adverse effects, such as scarring, which occur following certain laser therapies.     

Fractional CO2 laser for the treatment of sclerodermatous cGVHD

ABSTRACT

Sclerodermatous graft versus host disease (sclGVHD) is a debilitating complication of hematopoietic stem cell transplant and is characterized by skin thickening and fibrosis that can result in severe contractures. While immunosuppressive therapy remains a mainstay of treatment, the disease course often progresses and, in severe cases, renders patients immobile and wheelchair-bound. Lasers that can target sclerotic lesions to improve tissue pliability and restore range of motion are a promising potential treatment for sclGVHD. Fractional CO2 lasers promote selective collagen remodeling by creating microcolumns of thermal injury that stimulate a wound healing response. Here, we present 2 patients with sclGVHD who underwent treatment with fractional ablative CO2 laser. In this pilot case series demonstrating the novel use of CO2 laser for severe, refractory sclGVHD, two patients were treated with fractional ablative CO2 laser to a focal area of sclerosis. One patient also received clobetasol ointment under occlusion in between treatments. Both patients reported marked subjective improvement in pain and mobility. Objective measurements were recorded for patient 2 who gained roughly 10 degrees of extension and 2 degrees of flexion, as well as a 10% reduction in skin thickness in the treated area. CO2 laser therapy with or without clobetasol ointment under occlusion is a promising treatment modality for sclGVHD.     

Evaluation of tissue thermal effects from 1064/1320-nm laser-assisted lipolysis and its clinical implications

Liposuction is a standard for removing fat. Recently developed, laser lipolysis can be used to simultaneously remove unwanted fat and tighten skin. Laser lipolysis is accomplished with single or multiple sequential wavelengths. Development of an optimal method requires detailed understanding of tissue heating for the wavelengths employed. This study systematically evaluates tissue heating for superficial and deep laser lipolysis using three approaches, and correlates temperature rise with histology changes, defining appropriate system parameters. Two individuals scheduled for abdominoplasty had laser testing on healthy abdominal skin scheduled for excision. Each treatment was applied to 3×3 cm squares with various laser parameters. Treatment was conducted in the fatty layer for lipolysis and subdermally for skin tightening. Individual squares were treated with SmartLipo (Cynosure, Inc. Westford, MA, USA) using 1064 nm, 1320 nm, or MultiPlex (1064 nm/1320 nm) with laser doses of 8.3 to 333 J/cm². Exposures were applied at 3–5 mm or ～20 mm depth below the skin surface. Skin temperatures at the surface and at depths of 5 mm to 37 mm were recorded immediately post-treatment for each exposure. Treated tissue was excised and evaluated for thermal injury using H&E and transmission polarization microscopy. Histology was correlated to tissue temperature to determine appropriate treatment limits. Superficial treatment with surface temperatures exceeding 47°C (50°C and 55°C at 5 mm depth) typically caused epidermal and dermal injury, with blistering above 58°C. Below this threshold, focal collagen change and dermal inflammatory response were found in many samples without epidermal injury. These acute thermal effects may link to skin tightening during the healing process. Deep treatments, at up to 133 J/cm², exhibited minimal temperature rise and induced thermal effects in vessels and ligaments. Higher laser doses were associated with a significant temperature increase. In conclusion, superficial subdermal heating (within approximately 5 mm of the surface) during laser lipolysis should limit skin surface temperature to 42°C. The laser dose per surface temperature rise in treatments are 4.5 J/cm²/°C for 1320 nm, 6 J/cm²/°C for MultiPlex and 7.5 J/cm²/°C for 1064 nm. Clinical studies should be performed to validate these results.     

Facticious disorders in dermatology

Facticious Disorders are self inflicted skin lesions and includes the creation of physical or psychiatric symptoms in oneself or other reference persons. In dermatology frequently, there are mechanical injuries by pressures, friction, occlusion, biting, cutting, stabbing, thermal burns or self‐inflicted infections with wound‐healing impairment, abscesses, mutilations or damages by acids and other toxic to the skin. The current classification differentiates between four groups: 1. Dermatitis artefacta syndrome in the narrower sense as unconscious/dissociated self‐injury, 2. Dermatitis paraartefacta syndrome: Disorders of impulse control, often as manipulation of an existing specific dermatosis (often semi‐conscious, admitted – self‐injury), 3. Malingering: consciously simulated injuries and diseases to obtain material gain, 4. special forms, such as the Gardner Diamond Syndrome, Münchhausen Syndrome and Münchhausen‐by‐Proxy Syndrome. This categorization is helpful in understanding the different pathogenic mechanisms and the psychodynamics involved, as well as in developing various therapeutic avenues and determining the prognosis.     

Basics of laser application to dermatology

Q-switched lasers, with a pulse of light sufficiently short (nanosecond-domain) is demonstrated to be useful for treatment of dermal melanocytosis, blue–black tattoos, melanocytic nevi, and solar lentigines, although transient postinflammatory hyperpigmentation usually developed in the irradiated area during the following 3–4 months. If the postinflammatory pigmentation does not disappear after 1 year, incontinentia pigmenti histologica is a possibility. However, the pigment in café-au-lait macules responds variably to treatment. Melasma shows no response to laser. Therefore, accurate diagnosis is the key to success in the laser treatment. Laser treatment of vascular lesions is based on selective absorption by blood with thermal injury to the vessel wall. Therefore, the pulse-width of the vascular-specific lasers must be longer (microsecond-domain) than that of pigment-specific lasers. Because the wavelength of the lasers for vascular lesions, however, cannot penetrate into the deep areas of the skin, not all vascular lesions can be treated. Laser or light-assisted hair removal offers an efficient way to permanently reduce excessive hair growth. Skin rejuvenation is possible by laser or pulsed light with millisecond-domain pulse-width. Because these light sources, however, cause severe damage to the skin surface, the exposure energy must be reduced and the treatment must be combined with cooling devices. Therefore, the clinical results of light-assisted skin rejuvenation are not prominent. In conclusion, the pulse-width and wavelength of the laser light are critical parameters for laser treatments. If we obtain information about these parameters for specific lasers, we can expect the results of the treatment to be positive.     

Operative Therapie von akral lokalisierten Hauttumoren

Special knowledge is required to treat acral skin tumors. These lesions are encountered relatively often by dermatologic surgeons. A tissue-sparing operative approach is essential. Especially when dealing with malignant tumors, complete excision must be strived for. One must also consider the methods of local spread of the different tumors. Highly-sensitive 3D histology allows one to combine complete removal and tissue sparing. This helps in preserving function. The operative approach is made simpler by automatic subcutaneous infusion anesthesia with epinephrine added to the local anesthetic; this can also be employed without concern in acral regions.     

Basics of laser application to dermatology

Q-switched lasers, with a pulse of light sufficiently short (nanosecond-domain) is demonstrated to be useful for treatment of dermal melanocytosis, blue-black tattoos, melanocytic nevi, and solar lentigines, although transient postinflammatory hyperpigmentation usually developed in the irradiated area during the following 3-4 months. If the postinflammatory pigmentation does not disappear after 1 year, incontinentia pigmenti histologica is a possibility. However, the pigment in café-au-lait macules responds variably to treatment. Melasma shows no response to laser. Therefore, accurate diagnosis is the key to success in the laser treatment. Laser treatment of vascular lesions is based on selective absorption by blood with thermal injury to the vessel wall. Therefore, the pulse-width of the vascular-specific lasers must be longer (microsecond-domain) than that of pigment-specific lasers. Because the wavelength of the lasers for vascular lesions, however, cannot penetrate into the deep areas of the skin, not all vascular lesions can be treated. Laser or light-assisted hair removal offers an efficient way to permanently reduce excessive hair growth. Skin rejuvenation is possible by laser or pulsed light with millisecond-domain pulse-width. Because these light sources, however, cause severe damage to the skin surface, the exposure energy must be reduced and the treatment must be combined with cooling devices. Therefore, the clinical results of light-assisted skin rejuvenation are not prominent. In conclusion, the pulse-width and wavelength of the laser light are critical parameters for laser treatments. If we obtain information about these parameters for specific lasers, we can expect the results of the treatment to be positive.     

Micro-island damage with a nonablative 1540-nm Er:Glass fractional laser device in human skin

Background and objectives  Fractional photothermolysis produces micro-islands of thermal injury to the skin while preserving areas among treated tissue sites in order to promote wound healing. Histological changes associated with single and multiple passes of the 1540-nm Er:Glass fractional laser were examined using in vivo human skin.
Methods and materials  Panni of five abdominoplasty patients were treated intraoperatively with a Fractional Lux1540 erbium glass laser system at various laser parameters, with single and multiple passes. Biopsies were removed and examined using standard histological stains.
Results  Deep coagulated columns of collagen separated by regions of unaffected tissue were observed at variable fluence parameters. A direct correlation between the depth of penetration of the coagulated microcolumns and increasing energies was observed. Micro-islands of coagulation were ∼250 μm in diameter and separated by ∼800 μm of unaffected tissue. With multiple passes, significantly more disruption of the dermal–epidermal junction (DEJ) occurred at higher fluences. In contrast to the controlled fractional columns observed with single-pass treatments, nonuniform coagulated columns were distributed randomly throughout the tissue when instituting multiple passes over the same treatment region.
Conclusion  Micro-islands of thermal damage were observed at variable energy parameters. Pathological changes within the skin were clearly dependent on amount of energy and number of passes of the laser treatment. Significantly more superficial damage, accompanied by disruption of the DEJ was observed with multiple passes when compared with single pass at similar fluences. However, with multiple passes, depth of thermal injury did not increase with increasing energies but did disrupt the micro-island array observed with single-pass fractional treatments.     

Visualizing the neutrophil response to sterile tissue injury in mouse dermis reveals a three-phase cascade of events

Neutrophil granulocytes traffic into sites of organ injury in which they may not only participate in tissue repair and pathogen clearance but may also contribute to collateral cell damage through the release of noxious mediators. The dynamics and mechanisms of neutrophil migration in the extravascular space toward loci of tissue damage are not well understood. Here, we have used intravital multi-photon microscopy to dissect the behavior of neutrophils in response to tissue injury in the dermis of mice. We found that, following confined physical injury, initially rare scouting neutrophils migrated in a directional manner toward the damage focus. This was followed by the attraction of waves of additional neutrophils, and finally stabilization of the neutrophil cluster around the injury. Although neutrophil migration in the steady state and during the scouting phase depended on pertussis toxin-sensitive signals, the amplification phase was sensitive to interference with the cyclic adenosine diphosphate ribose pathway. We finally demonstrated that neutrophil scouts also transit through the non-inflamed dermis, suggesting immunosurveillance function by these cells. Together, our data unravel a three-step cascade of events that mediates the specific accumulation of neutrophils at sites of sterile tissue injury in the interstitial space.     

Pediatric dermatology procedures and pearls: Multimodal revision of earlobe keloids

Keloid scars are benign proliferations of fibrous tissue and collagen that usually occur in response to cutaneous injury. Many treatment modalities have been described in the literature, with variable rates of recurrence and no clear consensus. Keloids remain a therapeutic challenge to patients and physicians alike. Herein we describe a novel technique for treating recurrent earlobe keloids in an outpatient setting with multimodal therapy including shave removal followed immediately by ablative fractional laser resurfacing (AFR) and laser‐assisted delivery (LAD) of corticosteroids.