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Average percentage of vessels containing perivascular collagen coagulation for each variable in group 1 (A), group 2 (B), and group 3 (C). Asterisks indicate those values statistically greater than 0 (α = .05; error bars represent SDs).
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Increasing radiant exposure offers a means to increase treatment efficacy during laser-mediated treatment of vascular lesions, such as port-wine stains; however, excessive radiant exposure decreases selective vascular injury due to increased heat generation within the epidermis and collateral damage to perivascular collagen.
To determine if cryogen...
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Context 1
... sought to identify variable sets that statistically resulted in greater than 0% of vessels containing peri- vascular collagen coagulation. The asterisks in Figure 5 indicate those values that are statistically greater than 0 (=.05) using a 1-way analysis of variance and Bonfer- roni multicomparison method to correct for experimen- tal errors. 20 Significant levels of perivascular collagen coagulation occurred at radiant exposures greater than 8 J/cm 2 without CSC; however, CSC reduced levels of perivascular collagen coagulation. ...Similar publications
Phakomatosis pigmentovascularis (PPV) is a rare disorder defined as the simultaneous occurrence of a widespread vascular nevus and an extensive pigmentary nevus [1]. PPV is subclassified into five types depending on the pigmentary lesion and vascular lesion [2]. However, this subclassification is controversial [1, 3]. A recent publication reported...
Citations
... Laser-based microvascular hemostasis was first demonstrated in 1981 under the principle of selective photothermolysis 1 . Subsequently, additional work [2][3][4][5][6][7] was carried out to provide laser dosimetry to optimize various parameters (e.g., wavelength, pulse duration, fluence) to achieve hemostasis. Port wine stains (PWSs) are vascular malformations 7-10 and were one of the first target applications of selective photothermolysis, where a vascular-specific wavelength irradiates blood and is differentially absorbed by hemoglobin in blood. ...
Photocoagulation of blood vessels offers unambiguous advantages to current radiofrequency approaches considering the high specificity of blood absorption at available laser wavelengths (e.g., 532 nm and 1.064 µm). Successful treatment of pediatric vascular lesions, such as port-wine stains requiring microvascular hemostasis, has been documented. Although laser treatments have been successful in smaller diameter blood vessels, photocoagulation of larger sized vessels is less effective. The hypothesis for this study is that a primary limitation in laser coagulation of large diameter blood vessels (500–1000 µm) originates from shear stress gradients associated with higher flow velocities along with temperature-dependent viscosity changes. Laser (1.07 µm) coagulation of blood vessels was tested in the chicken chorio-allantoic membrane (CAM). A finite element model is developed that includes hypothetical limitations in laser coagulation during irradiation. A protocol to specify laser dosimetry is derived from OCT imaging and angiography observations as well as finite element model results. Laser dosimetry is applied in the CAM model to test the experimental hypothesis that blood shear stress and flow velocity are important parameters for laser coagulation and hemostasis of large diameter blood vessels (500–1000 µm). Our experimental results suggest that shear stress and flow velocity are fundamental in the coagulation of large diameter blood vessels (500–1000 µm). Laser dosimetry is proposed and demonstrated for successful coagulation and hemostasis of large diameter CAM blood vessels.
... An Epoxy resin (50 mm  50 mm  5 mm) is chosen as the skin phantom due to the similarity of its thermal properties with those of human skin. It has been widely used in previous studies [27][28][29]. Table 3 shows the thermal properties of the epoxy resin and epidermis [10,30]. ...
... [3] Besides, cooling will diminish the amount of oedema, which often develops as a complication of laser procedure. [4] To be precise, the basic principle is to protect the superficial layers of the skin from collateral thermal damage. It can be achieved by cold air convection, contact cooling or cryogen spray (dynamic) cooling. ...
Cooling devices and methods are now integrated into most laser systems, with a view to protecting the epidermis, reducing pain and erythema and improving the efficacy of laser. On the basis of method employed, it can be divided into contact cooling and non-contact cooling. With respect to timing of irradiation of laser, the nomenclatures include pre-cooling, parallel cooling and post-cooling. The choice of the cooling device is dictated by the laser device, the physician′s personal choice with respect to user-friendliness, comfort of the patient, the price and maintenance costs of the device. We hereby briefly review the various techniques of cooling, employed in laser practice.
... The temperature measurement method is schematically shown in Fig. 2. A epoxy resin substrate (50 mm  50 mm  5 mm) is used as cooling substrate due to its similarity of thermal property with that of human skin [21][22][23][24]. The thermal properties of epoxy resin are shown in Table 1 and the thermal properties of epidermis are also given for reference [6,24]. ...
... The temperature measurement method is schematically shown in Fig. 2. A epoxy resin substrate (50 mm  50 mm  5 mm) is used as cooling substrate due to its similarity of thermal property with that of human skin [21][22][23][24]. The thermal properties of epoxy resin are shown in Table 1and the thermal properties of epidermis are also given for reference [6,24]. ...
... The thermal properties of epoxy resin are shown in Table 1and the thermal properties of epidermis are also given for reference [6,24]. In traditional methods, commercial thermocouples of round or plate-shaped joints with diameter or depth more than 5 Â 10 À2 mm were buried on the surface or within the skin phantom in the experiments [6][7][8][9][10][21][22][23][24]. The upper side of thermocouple was covered by the thin foil and its bottom side was pasted to the skin phantom through the Scotch tape. ...
... 10 Incomplete photocoagulation of PWS vasculature is associated with suboptimal to no clearance, which prevails in 20% to 46% and 14% to 40% of patients, respectively, for several reasons. [9][10][11][12] First, the efficacy of selective photothermolysis depends on the extent of epidermal pigmentation, [13][14][15][16] optical shielding by blood and superimposed vessels, 9,11,12,[17][18][19] and PWS vascular anatomy and morphology. 9,11,[18][19][20][21] Generally, factors resulting in decreased treatment efficacy include those that reduce light penetration, such as superimposed vasculature, high melanin content, and an increased PWS vascular density, diameter, or depth. ...
Port wine stains (PWS) are the most common vascular malformation of the skin, occurring in 0.3% to 0.5% of the population. Noninvasive laser irradiation with flashlamp-pumped pulsed dye lasers (selective photothermolysis) currently comprises the gold standard treatment of PWS; however, the majority of PWS fail to clear completely after selective photothermolysis. In this review, the clinically used PWS treatment modalities (pulsed dye lasers, alexandrite lasers, neodymium:yttrium-aluminum-garnet lasers, and intense pulsed light) and techniques (combination approaches, multiple passes, and epidermal cooling) are discussed. Retrospective analysis of clinical studies published between 1990 and 2011 was performed to determine therapeutic efficacies for each clinically used modality/technique. In addition, factors that have resulted in the high degree of therapeutic recalcitrance are identified, and emerging experimental treatment strategies are addressed, including the use of photodynamic therapy, immunomodulators, angiogenesis inhibitors, hypobaric pressure, and site-specific pharmaco-laser therapy.
... The efficacy of SP depends on a combination of inevitable intrinsic factors, including epidermal pigmentation,36,80,146,153 optical shielding by blood and superimposed vessels,47,48,72,92,117,137 and vascular anatomy and morphology.47,48,72,117,149,154 In general, treatment efficacy correlates negatively with increased melanin content, vascular density and superimposition, and vessel diameter and depth, given that the prominence of these factors is inversely proportional to the optical penetration depth. ...
During the last three decades, several laser systems, ancillary technologies, and treatment modalities have been developed for the treatment of port wine stains (PWSs). However, approximately half of the PWS patient population responds suboptimally to laser treatment. Consequently, novel treatment modalities and therapeutic techniques/strategies are required to improve PWS treatment efficacy. This overview therefore focuses on three distinct experimental approaches for the optimization of PWS laser treatment. The approaches are addressed from the perspective of mechanical engineering (the use of local hypobaric pressure to induce vasodilation in the laser-irradiated dermal microcirculation), optical engineering (laser-speckle imaging of post-treatment flow in laser-treated PWS skin), and biochemical engineering (light- and heat-activatable liposomal drug delivery systems to enhance the extent of post-irradiation vascular occlusion).
... Mid-infrared nonablative fractional resurfacing may have the potential to produce deeper microscopic tissue coagulation or thermal damage with significant clinical benefits while sparing adjacent tissue to reduce downtime. For the purpose of this report, we have defined the dimension of each MTZ (or lesion) as the zone of collagen denaturation as measured histologically by hematoxylin & eosin (H&E) staining [12] or the zone of non-viable cells as measured histologically by nitro blue tetrazolium chloride (NBTC)1314. Previous work has shown the former method to be essentially equivalent to measurement of the loss of birefringence by cross-polarization microscopy of laser-induced thermal coagulation [15]. ...
Background and Objectives
We examined the effects of pulse energy variations on the dimensions of microscopic thermal injury zones (MTZs) created on human skin ex vivo and in vivo using nonablative fractional resurfacing.Materials and MethodsA Fraxel® SR laser system emitting at 1,550 nm provided an array of microscopic spots at variable densities. Pulse energies ranging from 4.5 to 40mJ were tested on human abdominal skin ex vivo and in vivo. Tissue sections were stained with hematoxylin and eosin (H&E) or nitro blue tetrazolium chloride (NBTC) and MTZ dimensions were determined. Ex vivo and in vivo results were compared. Dosimetry analyses were made for the surface treatment coverage calculation as a function of pulse energy and collagen coagulation based on H&E stain or cell necrotic zone based on NBTC stain.ResultsEach MTZ was identified by histological detection of a distinct region of loss of tissue birefringence and hyalinization, representing collagen denaturation and cell necrosis within the irradiated field immediately, 1, 3, and 7days after treatment. At high pulse energies, the MTZ depth could exceed 1 mm and width approached 200 µm as assessed by H&E. NBTC staining revealed viable interlesional tissue. In general, no statistically significant difference was found between in vivo and ex vivo depth and width measurements.Conclusions
The Fraxel® SR laser system delivers pulses across a wide range of density and energy levels. We determined that increases in pulse energy led to increases in MTZ depth and width without compromising the structure or viability of interlesional tissue. Lasers Surg. Med. 39:157–163, 2007. © 2007 Wiley-Liss, Inc.
... In recent years, clinicians and engineers have sought to expand the boundaries of laser dermatologic surgery, using higher fluences to improve therapeutic outcomes in patients of all skin types. [10][11][12] Several commercially available devices have been designed to deliver multiple intermittent cryogen spurts (MCS) before, after, or alternated with laser exposure in a variety of patterns in an effort to augment epidermal cooling and permit the safe use of higher fluences. 13 RAFT tissue culture model studies, however, demonstrated that epidermal injury risk increased for MCS patterns compared to SCS of the same total cryogen delivery time when the total cooling time was less than 110 milliseconds. ...
Despite widespread clinical use of cryogen spray cooling (CSC) in conjunction with laser dermatologic surgery, in vivo cutaneous effects have not been systematically evaluated.
The authors characterize the in vivo cutaneous effects for Fitzpatrick skin types I through VI after CSC exposures of varying spurt durations and spurt delivery patterns (single vs. multiple spurts).
Twenty-seven normal human subjects were exposed to single cryogen spurts from 10 to 80 milliseconds, and multiple spurt patterns consisting of two 20-millisecond spurts, four 10-millisecond spurts, and eight 5-millisecond spurts. Subjects were evaluated by clinical observation and photography at 1 hour, 1 day, and 1, 4, 8, and 12 weeks after CSC exposure.
Acute erythema and urticaria (1-24 hours) were noted in 14 of 27 and 3 of 27 subjects, respectively. Transient hyperpigmentation occurred in 4 of 27 subjects (skin types III-VI) but resolved spontaneously without medical intervention in all subjects by 8 weeks. No permanent skin changes were noted in any subjects. Skin reactions were more common with longer single-spurt durations (50 milliseconds or greater) and multiple spurt patterns.
Acute erythema, urticaria, and, less commonly, transient hyperpigmentation were observed after CSC exposure. Permanent skin injury was not observed and is unlikely.
... 1͑a͔͒. 16,17 As expected, intact dermal collagen was stained blue-green, while coagulated dermal collagen stained red by Gomori trichrome 14 ͓Fig. 1͑b͔͒. ...
The wound healing process in skin is studied in human subjects treated with fractional photothermolysis. In-vivo histological evaluation of vacuoles formed over microthermal zones (MTZs) and their content is undertaken. A 30-W, 1550-nm single-mode fiber laser system delivers an array of 60 microm or 140 microm 1e2 incidence microbeam spot size at variable pulse energy and density. Treatments span from 6 to 20 mJ with skin excisions performed 1-day post-treatment. Staining with hematoxylin and eosin demonstrates an intact stratum corneum with vacuolar formation within the epidermis. The re-epithelialization process with repopulation of melanocytes and keratinocytes at the basal layer is apparent by 1-day post-treatment. The dermal-epidermal (DE) junction is weakened and separated just above zones of dermal coagulation. Complete loss of dermal cell viability is noted within the confines of the MTZs 1-day post-treatment, as assessed by lactate dehydrogenase. All cells falling outside the irradiation field remain viable. Content within the epidermal vacuoles stain positively with Gomori trichrome, suggesting a dermal origin. However, the positive staining could be due to loss of specificity after thermal alteration. Nevertheless, this dermal extrusion hypothesis is supported by very specific positive staining with an antihuman elastin antibody. Fractional photothermolysis creates microthermal lesions that allow transport and extrusion of dermal content through a compromised DE junction. Some dermal material is incorporated into the microepidermal necrotic debris and shuttled up the epidermis to eventually be exfoliated through the stratum corneum. This is the first report of a nonablative laser-induced transport mechanism by which dermal content can be predictably extruded biologically through the epidermis. Thus, treatment with the 1550-nm fiber laser may provide the first therapeutic option for clinical indications, including pigmentary disorders such as medically recalcitrant melasma, solar elastosis, as well as depositional diseases such as mucinosis and amyloidosis.
