Effects of skin temperature on lesion size in fractional photothermolysis

Comprehensive approach to correct involutional-dystrophic skin changes in women

Skin aging is one of the most urgent problems that is not being studied today. The study involved 107 women with signs of age-related changes in the skin of the face aged 25 to 60 years. They were treated according to our autor’s technology neofibrolifting - autologous fibroblasts transplantation into the pretreated with platelet-rich plasma skin and ablative fractional photothermolysis procedure. The developed neofibrolifting technology allows reconstructing authentic skin structure, improving its appearance and immunity.

Deep pulse fractional CO2 laser combined with a radiofrequency system: results of a case series

OBJECTIVE

The purpose of this study was evaluation of the safety and efficacy of this new combined technology that adds deep ablation to thermal stimulation.

BACKGROUND DATA

Minimally ablative or subablative lasers, such as fractional CO2 lasers, have been developed in an attempt to achieve the same clinical results observed with traditional ablative lasers, but with fewer side effects. Despite being an ablative laser, the system used in this study is able to produce a fractional supply of the beam of light. Fractional ablation of skin is performed through the development of microscopic vertical columns surrounded by spared areas of epidermis and dermis, ensuring rapid wound healing and minimum down time. Simultaneous synchronized delivery of a radiofrequency (RF) current to the deeper layers of the skin completes the therapeutic scenario, ensuring an effective skin tightening effect over the entire treated area.

METHODS

Nine adult patients were treated for wrinkles and acne scars using this new laser technology. An independent observer evaluated the improvement using a five point scale.

RESULTS

All patients had good results in terms of improvement of skin texture, with mild and transitory side effects.

CONCLUSIONS

This novel combined system produced improvement in wrinkles and acne scars, with progressive enhancement of skin tone and elasticity.

Effects of deviation from focal plane on lesion geometry for ablative fractional photothermolysis

BACKGROUND AND OBJECTIVE

Fractional Photothermolysis (FP) is a method of skin treatment that generates a thermal damage pattern consisting of multiple columns of thermal damage, also known as microscopic treatment zones (MTZs). They are very small in diameter and are generated by application of highly focused laser beams. In order to obtain the smallest spot size, the treatment should be performed in the focal plane. Any deviation from the focal plane (DFP) results in an increase of spot size. FP devices typically utilize distance holders in order to facilitate exposures at this specific location. In spite of the use of distance holders, DFP can occur. In particular, variations of contact pressure to the skin surface and anatomical treatment areas of high surface curvature may be prone to DFP during FP treatments. The impact of such distance variation on lesion geometry, such as depth and diameter of the thermal injury, has not previously been evaluated. The objective of this study was to investigate the relation between DFP and the resulting lesion geometry for a selected ablative fractional device.

MATERIAL AND METHODS

A handpiece of an ablative fractional laser (DeepFX, UltraPulse Encore, Lumenis, Yokneam, Israel) was mounted to a rigid stand. Full thickness human skin obtained from abdominoplasty was mounted to a separate stand perpendicular to the handpiece. The tissue stand allowed the distance between the handpiece and the tissue to be adjusted to produce a variation up to ±3 mm from the focal plane. A 1 × 1 cm(2) scanning area of 169 MTZs, 50 mJ energy per MTZ, 120 μm nominal spot size, was applied at -3, -2, -1, 0, +1, +2, and +3 mm deviated from the focal plane. Minus (-) and plus (+) signs indicate decreasing and increasing distance between the handpiece and the tissue, respectively. Depth and diameter of the laser induced tissue lesions were assessed and quantified.

RESULTS

DFPs produced a significant alteration of the lesion geometry. DFPs of -3, -2, -1, 0, +1, +2, +3 mm resulted in average lesion depths of 1,020 (-40%), 1,180 (-31%), 1,400 (-18%), 1,700 (0%), 1,620 (-5%), 780 (-55%), 680 (-60%) µm, and average lesion diameters of 314 (+26%), 311 (+25%), 273 (+10%), 248 (0%), 256 (+3%), 316 (+27%), 359 (+44%) µm, respectively. The underlined values represent the focal plane. The percentage changes relative to values at focal plane are in parentheses.

CONCLUSIONS

A relatively minor DFP has a marked impact on the thermal injury profile, including lesion depth and diameter, of the laser-exposed tissue. Such marked changes of the thermal injury profile might affect the wound healing, safety, and efficacy of ablative fractional resurfacing procedures. Clinicians should carefully maintain the focal plane during ablative fractional treatment for reproducible results. The presented data are device specific and the clinical impact of such alteration of thermal injury profile warrants further investigation. Lasers Surg. Med. 48:555-561, 2016. © 2016 Wiley Periodicals, Inc.

Fractional Erbium laser in the treatment of photoaging: randomized comparative, clinical and histopathological study of ablative (2940nm) vs. non-ablative (1540nm) methods after 3 months

BACKGROUND

Fractional non-ablative lasers keep the epidermis intact, while fractional ablative lasers remove it, making them theoretically more effective.

OBJECTIVES

To evaluate the clinical and histological alterations induced by fractional photothermolysis for treating photoaging, comparing the possible equivalence of multiple sessions of 1540nm Erbium, to one session of 2940nm Erbium.

METHODS

Eighteen patients (mean age 55.9) completed the treatment with three sessions of 1540nm fractional Erbium laser on one side of the face (50 mJ/mB, 15ms, 2 passes), and one session of 2940nm on the other side (5mJ/mB, 0.25ms, 2 passes). Biopsies were performed before and 3 months after treatment. Clinical, histological and morphometric evaluations were carried out.

RESULTS

All patients presented clinical improvement with no statistically significant difference (p> 0.05) between the treated sides. Histopathology revealed a new organization of collagen and elastic fibers, accompanied by edema, which was more evident with the 2940nm laser. This finding was confirmed by morphometry, which showed a decrease in collagen density for both treatments, with a statistical significance for the 2940nm laser (p > 0.001).

CONCLUSIONS

Three 1540nm sessions were clinically equivalent to one 2940nm session. The edema probably contributed to the positive results after three months, togheter with the new collagen and elastic fibers organization. The greater edema after the 2940nm session indicates that dermal remodeling takes longer than with 1540nm. It is possible that this histological superiority relates to a more prolonged effect, but a cohort longer than three months is needed to confirm that supposition.

Treatment of cosmetic tattoos with nonablative fractional laser in an animal model: a novel method with histopathologic evidence

BACKGROUND AND OBJECTIVE

Cosmetic tattoos are difficult to treat using Q-switched lasers. We introduce a novel method for the treatment of cosmetic tattoos using a nonablative fractional laser and investigate the underlying pathophysiological mechanisms in an animal model.

STUDY DESIGN/MATERIALS AND METHODS

Ten rats were tattooed on their backs with white and flesh-colored pigments. One-half of each tattoo was treated with a 1,550-nm, erbium:glass fractional laser system with energy settings of 17 mJ and 169 MTZ/cm(2)  × 2 passes for five sessions at 1-month intervals. The untreated half of each tattoo served as the control. An independent physician reviewed the photographs and scored the clinical response. Serial skin samples were obtained at baseline and at various times after laser treatment. These tissue sections were stained with hematoxylin and eosin, and immunostained for types I, III, and IV collagen; laminin; fibronectin; and α-smooth muscle actin.

RESULTS

White tattoos showed excellent responses in two rats and good responses in eight rats, whereas flesh-colored tattoos showed excellent responses in four rats and good responses in six rats (P = 0.001 in both cases compared with baseline). Both tattoos exhibited a similar clearance rate (P > 0.05) and histological reactions. Microscopic epidermal necrotic debris (MEND) containing tattoo pigments and collagen fibrils appeared on day 1, increased on day 2, and was exfoliated after 5 days. The dermal-epidermal junction lost integrity 30 minutes after treatment, but recovered completely on day 3. The expression of fibronectin and collagen-III, which play key roles in wound healing, increased around the microscopic treatment zone on days 1-5 and 4-7, respectively. A few myofibroblasts appeared on days 4-7.

CONCLUSION

Nonablative fractional lasers (NAFLs) successfully remove cosmetic tattoos by transepidermal elimination of tattoo pigments through the disrupted dermal-epidermal junction. This action is facilitated by the wound healing process.

A randomized, controlled trial of four ablative fractionated lasers for photoaging: a quadrant study

BACKGROUND

Fractionated technology has revolutionized laser therapy. With the success of initial devices, several fractionated lasers have appeared on the market. Claims of superiority have made device choice difficult for physicians and patients.

MATERIALS AND METHODS

Twelve subjects were treated with fractionated ablative lasers (10,600-nm carbon dioxide and 2790-nm yttrium scandium gallium garnet) in this institutional review board-approved trial. Each face was divided into four quadrants, and each quadrant was randomly treated using one of four lasers. Clinical experience was used to optimize settings. Two patients submitted biopsies from each quadrant immediately after treatment. Patients and blinded investigators assessed pain during treatment and post-treatment improvement in photoaging (measured by rhytides, lentigines, texture, and pore size) using a five-point scale.

RESULTS

All devices resulted in statistical improvement in photoaging in all patients, but no device was statistically significantly superior. No statistically significant difference was found in pain scores. All patients reported satisfaction 1 month after treatment. Three patients experienced adverse reactions. Histologically, there were no statistically significant differences between devices.

CONCLUSIONS

Fractionated ablative lasers reliably result in improvement in photoaging. Despite marketing claims, no statistically significant differences were found in outcomes, pain during treatment, or histologic findings. Even with experienced users, significant adverse reactions are possible.

Novel Device for Tissue Cooling during Endoscopic Laryngeal Laser Surgery: Thermal Damage Study in an Ex Vivo Calf Model

Objectives:

Minimizing collateral thermal damage during endoscopic laryngeal laser surgery remains a priority, and tissue cooling is one way to achieve this goal. Cooling systems utilizing compressed air have been shown to reduce the extent of thermal trauma on the vocal folds, but these units are not ideal for endoscopic applications because cooling is inefficient at the low airflows needed. We examined whether a novel vortex cooling device that generates cooled air at low flow rates would provide a cooling benefit beyond that which could be obtained by using room-temperature air for cooling tissue or by using no cooling during simulated laryngeal laser surgery.

Methods:

A continuous-wave thulium laser was used to incise glottic tissue in 12 calf vocal folds. Cooling was achieved with a prototype vortex cooler (9°C air output; flow rate, 3 L/min), and tissue temperature measurements were compared to those with room-air cooling and no cooling. Thermal damage was analyzed histologically by measuring the depth of lactate dehydrogenase inactivation surrounding the mucosal incision. The cooling conditions were tested during time-constant cuts (8 seconds) and depth-constant cuts (into the thyroarytenoid muscle).

Results:

During time-constant cuts, comparison between vortex cooling and room-air cooling revealed that vortex cooling resulted in a thermal damage zone that was 14% smaller (519 versus 603 μm; p < 0.05). During depth-constant cuts, vortex cooling created a thermal damage zone that was 32% smaller than that created with no cooling (p < 0.01) and 9% smaller than that created with room-air cooling (p < 0.01).

Conclusions:

Vortex cooling reduces thermal damage more effectively than room-air cooling or no cooling during both time-constant and depth-constant thulium laser cuts.

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 approximately 250 microm in diameter and separated by approximately 800 microm 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.

Immunohistochemical investigation of wound healing in response to fractional photothermolysis

Despite growing clinical evidence of ablative fractional photothermolysis (AFP), little is known about the spatiotemporal molecular changes within the targeted compartments. Six subjects received three different single AFP treatments using a scanned 250 mum CO(2)-laser beam. Spatiotemporal changes of skin regeneration were estimated by immunohistochemical investigation (HSP70, HSP72, HSP47, TGFbeta, procollagen III, CD3, CD20, and CD68) in skin samples 1 h, 3 days, and 14 days postintervention. The remodeling was uniformly started by regrowth of the epidermal compartment followed by partial to complete replacement of the microscopic ablation zones (MAZ) by newly synthesized condensed procollagen III. From day 3 to 14, the number of macrophages as well as giant cells surrounding the MAZ increased. TGFbeta expression was highest 1 h to 3 days following AFP. HSP70 and HSP72 expressions were highest 3-14 days postintervention in the spinocellular layer leading to an upregulation of HSP47. AFP performed by a scanned CO(2)-laser results in an early epidermal remodeling, which is followed by a dermal remodeling leading to a replacement of the MAZ with newly synthesized (pro)-collagen. During this, an inflammatory infiltrate with CD3(+) and CD20(+) cells surrounds the MAZ. The count of macrophages and giant cells involved in the replacement of the necrotic zones seems to be crucial for wound healing.

Fractionated mid-infrared resurfacing

Fractional resurfacing devices thermally alter microscopic treatment columns in the skin, leaving intervening areas between the columns untouched. Because only a fraction of the skin is being modified, untreated areas are able to rapidly repopulate the treatment columns to greatly reduce recovery time and adverse events. Mid-infrared fractional systems have shown improvement in treating photoaging, scars, rhytides, dyschromia, and textural disorders. An additional advantage is that they are safe and effective for the treatment of nonfacial areas such as the neck, chest, and extremities.

Thermal damage during thulium laser dissection of laryngeal soft tissue is reduced with air cooling: ex vivo calf model study

OBJECTIVES

The 2-microm-wavelength thulium laser has recently been shown to be an effective cutting instrument in endolaryngeal surgery, although there is increased thermal trauma as compared with the carbon dioxide laser. This study investigated temperature changes and thermal trauma during thulium laser dissection of laryngeal tissue, with and without air cooling, in an ex vivo model.

METHODS

A continuous-wave thulium laser (400-microm fiber, 4-W continuous power, 4-second duration) was used to incise 10 calf vocal folds. Paired cooled and uncooled cuts were made in each fold with a dermatologic cooling device. A thermistor inserted into the glottic subepithelium was used to measure tissue temperatures. Thermal damage was analyzed histologically by measuring the depth of the zone of lactate dehydrogenase inactivation surrounding the mucosal incision.

RESULTS

The initial vocal fold temperature averaged 24.3 degrees C without cooling and 4.4 degrees C with cooling. The peak temperature during cutting averaged 59.1 degrees C without cooling and 28.0 degrees C with cooling. The thermal damage zone surrounding the cooled incisions was approximately 27% less than that surrounding the uncooled incisions.

CONCLUSIONS

Air cooling can reduce the extent of thermal trauma associated with thulium laser surgery of the vocal folds, and the high-temperature plume generated during laser cutting is effectively cleared.

[From dermabrasion to laser. Development of operative-interventional methods in aesthetic dermatology]

Many operative-interventional methods are available for aesthetic dermatology. The established high-speed dermabrasion as developed by Schreus has been replaced in many indications by newer approaches. Laser ablation can be effectively used for resurfacing of sun-damaged or scarred skin, but is associated with extensive side effects. Newer developments such as fractionated laser treatment are designed to fill the gap between ablative and non-ablative skin resurfacing. The side effects are much less severe, but the effectiveness must be confirmed in larger studies. Photorejuvenation with intense pulsed light (IPL) offers a wide variety of treatment parameters for a broad spectrum of skin changes. Both superficial and deep structures can be treatment in one session using IPL.