High-Energy 595 nm Pulsed Dye Laser Improves Refractory Port-Wine Stains

BACKGROUND: Port-wine stains respond quite well to 585 nm pulsed dye laser treatment, but often clearance is not complete. We investigated a prototype, a high-energy 595 nm pulsed dye laser capable of delivering up to 9.5 J/cm2 using a 10 mm circular spot, with a 1.5 ms pulse duration. OBJECTIVE: This study was undertaken to determine if the high-energy, 595 nm, variable-pulse duration pulsed dye laser could improve port-wine stains that had become refractory to conventional treatment. METHODS: Twenty patients were entered into the study and treated with the high-energy, 595 nm, variable-pulse duration pulsed dye laser using fluences ranging from 7.5 to 9.5 J/cm2, a 1.5 ms pulse duration, and a 10 mm spot size. RESULTS: Average improvement was rated as 40% prior to the initiation of the study after an average of 8.8 treatments at an average energy of 7.9 J/cm2 with the 585 nm pulsed dye laser and 76% following an average of 3.1 treatments with the high-energy 595 nm pulsed dye laser using an average fluence of 7.9 J/cm2. Dermal spectrometer erythema measurements improved from 2.2-fold that of normal skin to 1.5-fold that of unaffected skin. CONCLUSIONS: The high-energy 595 nm pulsed dye laser improves port-wine stains that have become refractory to the conventional 585 nm pulsed dye laser.     

The frequency-doubled Nd-YAG laser with automatic scanning in the treatment of port-wine stains: A preliminary report

The authors report their experience with two recent improvements in the treatment of port-wine stains. Firstly, the frequency-doubled Nd-YAG laser producing a 532 nm wavelength. This wavelength corresponds to greater absorption by haemoglobin (15–20% more than with the argon laser beam) and so is more selectively absorbed by angiomatous tissue. This gives better clinical results and the classic side effects of the argon laser are eliminated (with the frequency-doubled Nd-YAG, there is no damage to hair or to healthy non-angiomatous skin). Treatment is thus made easier, as shownn in our series of 79 patients who received 92 treatment sessions over a period of 14 months. In addition, an automatic device makes it possible to use the beam on a continuous mode scanning contiguous sections (Multiscan). With this automatic apparatus, treatment becomes uniform because the variations inherent to the use of a hand piece are eliminated. Extensive port-wine stains can also be treated in a single session instead of the multiple sessions which were previously necessary. An interval of 5–6 months should elapse before treating the residual part of the portwine stain, situated deeper in the dermis, which should be considered as a new port-wine stain. The association of the 532 nm wavelength and the automatic, scanning device makes it possible to use fluences of only 8–15 J cm⁻². This is explained by the dynamic nature of this treatment and distinguishes it from static treatments requiring higher fluences. Treatment of port-wine stains is thus improved for the ultimate benefit of the patients suffering from this disfigurement.

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Resumé Les auteurs rapportent dans ce travail une expérience nouvelle en matière de traitement des angiomes plans au laser: d'une part l'utilisation d'une fréquence de 532 nm par doublage de fréquence d'un laser Nd-YAG (1060 nm) en lieu et place du classique laser argon, et d'autre part l'utilisation d'un système entièrement automatisé afin de balayer la surface de l'angiome plan dans son intégralité. Cette longueur d'onde à 532 nm correspond à la partie verte du spectre visible, et correspond également à un pic d'absorption spectrophotométrique de l'hémoglobine. De cette interaction résulte un effet plus spécifique au niveau vasculaire, avec moins d'effet thermique, et donc des dégats tissulaires au niveau du derme angiomateux moins importants. Les suites post-thérapeutiques sont donc plus simples avec notamment une cicatrisation plus rapide et, à terme, une décoloration plus importante. Le système automatisé dont disposent les auteurs permet, tout en supprimant les aléas d'un traitement normal (erreur de focalisation, déplacement trop rapide ou trop lent de la pièce à main, absence d'effet ou surdosage), d'effectuer le traitement en une seule séance de surfaces angiomateuses importantes (1, 2 ou 3 territoires trigéminés). Un balayage à bandes jointives est effectué, le laser étant en fonctionnement sur un mode continu. La douleur, occasionnée impose d'effectuer un balayage sous anésthésie générale ou loco-régionale. Une stricte immobilité est en effet nécessaire afin que les bandes restent bien jointives et que le résultat soit homogène. L'association de ces deux systèmes (532 nm et automate) permet de réaliser le traitement en sélectionnant des puissances élevées (9 W) et des vitesses de balayage rapides (28 cm s⁻¹), réalisant ainsi au niveau cutané des fluences de moins de 8–15 J cm⁻² (notion de traitement dynamique). Le traitement est donc bref (10 min pour tout un territoire trigéminé) ce d'autant que l'effet à suppretuer cutané à obtenir sous l'impact du faisceau doit se résumer à une discrète augmentation de la température locale (4°C) accompagnée de l'apparition d'un, érythème. Tout blanchiment doit être évité, signe d'un surdosage. L'évolution se fait en 4 mois environ: épidermisation obtenue en 10 jours, suivie d'une phase imflammatoire progressivement décroissante dans ce laps de temps. Une nouvelle séance de traitement de la coloration angiomateuse résiduelle pourra être envisagée 6 mois après la précédente.

     

High-power argon laser treatment for port-wine stains: Clinical and histological results

A high-power argon laser system (maximum 20 W on the skin) was used with a 2-mm-spot size for the treatment of port-wine stains (PWS). Five hundred and thirty test treatments were evaluated. With short pulse times (< 15ms), relatively specific damage to vessels could be demonstrated histologically, but sufficient clinical lightening of PWS was seen only in 30% of patients due to the resulting low energy fluence (∼=10 Jcm⁻²_. With higher energy fluences and longer pulse times, clinical lightening increased but vessel specificity was lost. Overall results showed that with a high-power argon laser comparable clinical blanching can be achieved as with conventional argon lasers, but the necessary energy fluences are lower (∼=15 Jcm⁻²) leading to less pain under treatment and a minimal incidence of side-effects.     

Wavelengths for laser treatment of port wine stains and telangiectasia

Background and Objective: This report presents analytical modelling of the influence of wavelength on the amount of volumetric rate of heat produced in dermal blood vessels by millisecond laser radiation. Study design/Materials and Methods: A new anatomical model is proposed that represents port wine stains as well as telangiectatic lesions. It consists of a target blood vessel, representing the deepest dermal blood vessel that requires irreversible injury, and a layer of whole blood, representing all other dermal blood vessels above the target vessel. The laser light that interacts with the blood vessels is assumed to be diffuse. Selective photothermolysis is the basis for the analysis. We consider wavelengths between 577 nm and 600 nm, the argon laser wavelengths at 488/515 nm, and the frequency doubled Nd:YAG laser wavelength at 532 nm. Results: The rate of volumetric heat production of absorbed laser light in the target blood vessel is expressed analytically as a function of blood absorption, the concentration of additional dermal blood, and the depth of the target vessel. Conclusion: The model explains why 585 nm is a good compromise for treating port wine stains that vary widely in number of dermal blood vessels. It predicts that wavelengths between 577 nm and 582 nm are excellent for the treatment of port wine stains in young children, and it suggests a possible explanation as to why the argon laser is sometimes said to be capable of treating dark mature port wine stains. The copper vapour laser wavelenght at 578 nm, and the frequency doubled Nd:YAG laser wavelength at 532 nm, are predicted to be suitable for the treatment of port wine stains that contain, respectively, a small to moderate and a moderate number of dermal blood vessels. When laser beam spotsize becomes smaller, the best wavelength for producing maximal rate of heat in the target vessel is predicted to shift to 577 nm. © 1995 Wiley-Liss, Inc.     

Dynamic epidermal cooling in conjunction with laser treatment of port-wine stains: Theoretical and preliminary clinical evaluations

The clinical objective in laser treatment of port-wine stains (PWS) is to induce selective photothermolysis of subsurface blood vessels without damaging the overlying epidermis. This paper investigates the effectiveness of dynamic cooling, where a cryogen is sprayed on the skin surface for an appropriately short period of time, to eliminate epidermal thermal injury during laser treatment of PWS. Comparative measurements of radiometric surface temperature from cooled and uncooled laser irradiated (585 nm) PWS sites, and theoretical predictions of temperature distributions within skin in response to dynamic cooling in conjunction with laser irradiation are presented. Rapid reduction of skin surface temperature and localization of cooling the epidermis are obtained when a cryogen is sprayed on skin prior to laser irradiation. Successful blanching of the PWS without thermal injury to the overlying epidermis is accomplished.     

Methemoglobin formation during laser induced photothermolysis of vascular skin lesions

BACKGROUND AND OBJECTIVE: Monitoring dynamic changes during laser induced photothermolysis of vascular skin lesions is essential for obtaining an optimal therapeutic result. Rapid photoinduced thermal damage occurs at a threshold temperature of about 70 degrees C. It is therefore, relevant to identify markers to indicate if this threshold temperature has been reached. Methemoglobin, which is formed by a photo-induced oxidation of hemoglobin, indicates that the temperature has reached this threshold value. This study presents a proof of concept of a method for monitoring the in vivo presence of methemoglobin immediately after laser exposure. STUDY DESIGN/MATERIALS AND METHODS: The present study was designed to investigate the in vivo temperature dependence of hemoglobin absorption in the 450-800 nm spectrum range. In vivo diffuse reflectance measurements of port-wine stain (PWS) and telangiectasia were performed prior to, and immediately after, laser treatment with a pulsed dye laser (PDL) at 585 nm wavelength. RESULTS: In vivo measurements following laser treatment of vascular skin lesions showed an immediate increase in the optical absorption of blood. This effect, caused by thermal stress, is a result of an increased dermal blood volume fraction and methemoglobin formation. The effect is light dose dependent, and reflectance spectra revealed methemoglobin formation in patients treated with fluences above 5 J/cm2 at 585 nm wavelength. CONCLUSIONS: It was proved that methemoglobin can be measured in vivo by reflectance spectroscopy. Measurements of the average methemoglobin concentrations immediately after laser exposure may be a valuable diagnostic tool to verify that the blood temperature has been sufficiently high to induce thermal damage to the vessel wall.     

Histologic comparison of the pulsed dye laser and copper vapor laser effects on pig skin

Albino pig skin was exposed to the copper vapor (CVL) and flash-lamp pulsed dye (PDL) lasers at 578 nm with a 3 mm diameter spotsize over a range of fluences until purpura and whitening were first established. The total irradiation time was the parameter that was varied in order for the CVL to reach the desired fluence. The lowest fluence producing each clinical endpoint was designated the threshold fluence: 34 J/cm2 was required to produce purpura using the CVL compared to 7.5 J/cm2 with the PDL laser. Histologically, skin exposed to purpura fluences from the CVL revealed the presence of constricted, disrupted papillary dermal blood vessels with trapped RBC's within them which were unlike those exposed to PDL where the irradiated vessels were dilated and packed with masses of intravascular agglutinated RBC's. The whitening threshold fluences for the CVL and PDL lasers were 67 J/cm2 and 29 J/cm2, respectively. Streaming of epidermal cells and dermal collagen denaturation were observed in CVL irradiated skin, compared to occasional dyskeratotic epidermal cells and focal dermal collagen denaturation following PDL exposure. The mechanisms responsible for the clinical and histologic changes produced by the two laser systems are discussed.     

Alteration of argon laser–induced scars by the pulsed dye laser

Ten patients with portwine stains (PWS) with test sites previously exposed to an argon laser were evaluated and subsequently treated with five pulsed dye (585 nm) laser treatments over a 10 month period. Clinical assessments, skin surface texture analyses using optical profilometry, and light microscopic histological evaluations were performed prior to commencement and at the end of the study in all ten patients. A change in the skin texture with return of skin markings approximating those of normal skin measured by optical profilometry was observed in the argon treated PWS skin following pulsed dye laser treatments. © 1993 Wiley-Liss, Inc.     

Clinical effects of dynamic cooling during pulsed laser treatment of port-wine stains

Pulsed dye lasers permit effective treatment of port-wine stains without a significant risk of complications. However, epidermal damage manifested by weeping or crusting of the treated area have been reported in 48—83% of patients, and transient hyperpigmentation after treatment is observed in 10–57%. Theoretically, the epidermis can be protected from thermal damage with the use of the concept of selective epidermal cooling. This study examined the clinical effects of rapid cooling of the epidermis with a liquid refrigerant R-134a (boiling point — 26.5 ‡C) during pulsed dye laser therapy. In 23 patients with port-wine stains, a 50-ms-long cooling pulse delivered immediately prior to laser irradiation with a fluence of 6.0 J cm^-2 significantly reduced the pain, and shortened the period with purpura without compromising the clinical blanching. Cooling periods longer than 60 ms, as well as additional cooling pulses immediately after laser exposure, reduced the blanching in areas irradiated with 6.0 J cm^-2. Post-treatment hyperpigmentation was not prevented with dynamic cooling.     

Comparison of 585 and 595 nm laser-induced vascular response of normal in vivo human skin

BACKGROUND AND OBJECTIVES: Two wavelengths, 585 and 595 nm, are currently common options for treating vascular malformations such as port-wine stains (PWS). Controversy exists as to which wavelength induces greater photothermal damage to the blood vessels and subsequent resolution of the malformations. STUDY DESIGN/MATERIALS AND METHODS: We irradiated normal, human skin in vivo at 585 and 595 nm wavelengths using fluences of 10-30 J/cm(2) with a 1.5 millisecond laser pulse. The level of purpura, total vascular damage, maximum coagulation depth (MCD), and perivascular damage were quantified by gross observation and histological analysis. RESULTS: Results demonstrated that 585 nm light caused greater purpura, vascular damage, maximum coagulation depth, and perivascular damage than 595 nm. Purpura showed a positive correlation with total vascular damage to a certain extent beyond which the total vascular damage did not change. For equivalent purpura, 585 and 595 nm produced no statistically significant difference in vascular damage. The difference in the laser-induced vascular damage between 585 and 595 nm, although statistically significant, was no more than 50%. CONCLUSIONS: The bathochromic (red) shift and formation of met-hemoglobin, which reduces the 585 nm light absorption and increases that of 595 nm compared to native oxy-hemoglobin, play a considerable role in creating more parity in vascular damage between the two wavelengths than would be expected based on their respective "native" absorption coefficients alone.     

Dye laser treatment of port-wine stains

The author treated 456 cases of port-wine stains using a tunable dye laser (577-nm wavelength, 1-microsecond pulse, 2-3-mm diameter spot), and followed up 22 cases for a year or more after the initial treatment. The treatment was regarded as effective in 80.5% of the abnormal lesions. The results were influenced by location: good results were achieved in the neck region and face, but results in the extremities were poor. The dye laser can achieve selective injury to abnormal vessels of port-wine stains while inflicting less damage to the overlying dermis than the argon laser. Therefore, dye laser treatment for port-wine stains is more effective than argon laser treatment.     

Laser treatment of congenital facial port-wine stains: long-term efficacy and complication in Chinese patients

BACKGROUND AND OBJECTIVE: Pulsed dye laser (585 nm, 450 micros) and variable pulse width frequency doubled Nd:YAG 532 nm laser have been proven to be effective in treating vascular lesions in Caucasians especially in facial port-wine stain. Their roles in dark-skinned Asian have not been determined. The objective of this study was to assess the long-term outcome and complication of laser treatment of congenital facial port-wine stain in Chinese patients retrospectively. Study Design/Materials and Methods: Files of all patients with port-wine stains who had received laser treatment in a major regional laser center in a 5-year period were reviewed. Chinese patients with congenital facial port-wine stains were recruited for the study. They were called back for questionnaire assessment of their degree of clearance and clinical examination for treatment complication. Detail demographics, result of questionnaire and clinical examination were entered into a database and statistical analyses were conducted where applicable. RESULTS: One hundred and seven patients with congenital facial port-wine stain were recruited for the study. Thirty-six patients had received PDL treatment, 40 patients had VP532 treatment and 31 patients had been treated by both laser systems. A total of 665 treatment sessions had been performed with an average of 6.1 +/- 2.8 sessions (range 3-12). They had been followed-up from 2 to 5 years with a mean period of 3.4 +/- 1.1 years. Over 60% of patients had more than 25% of clearing and the majority of patients (41.1%) had 25-50% of clearing. Less than one-quarter of patients (23%) experienced a clearing more than 50% and no patient had complete clearing. There was no significant difference in the subjective assessment of clearing between patients that had different forms of laser treatments. No patient had recurrence of pigmentation after treatment. Fourteen percent of patients experienced complications and the majority of them had pigmentary changes. Sex, age, number of treatment session, and type of laser machine used were not related to a higher complication rate using the multiple regression analysis. CONCLUSIONS: Chinese patients were less responsive to laser treatment with higher complication rate. In addition, more treatment sessions were required to achieve a maximum clearing. However, most of our patients were satisfied with laser treatment (Patient Satisfaction Score=7.25). Dark-skinned patients should not be excluded from laser therapy provided that treatment expectations and risks are fully discussed.     

Comparative study of the "point-by-point technique" and the "scanning technique" for laser treatment of port-wine stain

Photocoagulation using the argon laser has been proven to be an effective method for the treatment of port-wine stains (PWS). However, it is very difficult to reproduce the parameters of laser treatment. This leads to inaccurate energy dosages secondary to the difference in treatment patterns. The aim of this study was to compare the conventional point-by-point technique (PT) for PWS treatment against a new scanning technique (ST) using a device called "Hexascan" (PREIN & Partners, Ferney-Voltaire, France). A total of 249 patients (171 females and 78 males) using the argon laser have been studied in a retrospective study. Clinical results are presented. For each technique, blanching and hypertrophic scarring were examined. The results are classified into two groups: satisfactory and unsatisfactory. The clinical results show that the ST with the Hexascan is superior to the conventional PT. Scarring is drastically reduced because overdosage and overheating are avoided. Because of precisely controlled spot patterns, quality and homogeneity of blanching is improved. Treatment time can be reduced to 20% of that of the PT.     

Dye laser treatment of port-wine stains

The author treated 456 cases of port-wine stains using a tunable dye laser (577-nm wavelength, 1-s pulse, 2–3-mm diameter spot), and followed up 22 cases for a year or more after the initial treatment. The treatment was regarded as effective in 80.5% of the abnormal lesions. The results were anfluenced by location; good results were achieved in the neck region and face, but results in the extremities were poor. The dye laser can achieve selective injury to abnormal vessels of port-wine stains while inflicting less damage to the overlying dermis than the argon laser. Therefore, dye laser treatment for port-wine stains is more effective than argon laser treatment.     

Dynamic optical absorption characteristics of blood after slow and fast heating

Laser treatment is the most effective therapy in dermatology for vascular skin disorders, such as port-wine stains (PWS). Changes in heat-induced absorbance in blood must be determined for accurate numerical simulation and implementation of multi-pulse laser therapy for treatment of PWS. Thermally induced absorbance changes in hemoglobin in blood were compared in vitro between slow water bath heating and fast heating irradiated by using sub-millisecond Nd:YAG laser. Blood composition at different temperatures was calculated by comparing blood absorption spectra with those of pure HbO₂, Hb, and metHb at room temperature. Blood absorbance to heat energy were categorized into three stages distinguished by metHb and coagulation points, which are the validity and security thresholds of the optimized therapy, respectively. Rapid laser heating can distinctively enhance blood absorbance by photochemically induced strong instability compared with slow heating at a constant temperature. Slow heating facilitates metHb point at 70 °C and coagulation point at 75 °C as the temperature of the water bath increases. However, the temperature at which metHb or coagulation point shifts to higher than 10 °C when pulses and fluence in laser irradiation change. Laser fluence less than 20 J/cm² and more than 50 J/cm² is unsuitable for laser treatment because of its low probability to coagulate vascular hyperplasia and high probability to damage normal tissues adjacent to target lesions, respectively. Few bubbles formed after mediate fluence is beneficial to minimize adverse side-effects. Considering blood absorbance, temperature evolution, and bubble formation, we recommend 30–40 J/cm² and 2–4 Hz frequency as the optimal laser parameters in sub-millisecond Nd:YAG laser.     

Q开关Nd:YAG激光不同波长治疗面部毛细血管扩张疗效比较

目的：观察Q开关Nd：YAG激光不同波长治疗面部毛细血管扩张的疗效及副反应。方法：128例病人按治疗波长随机分为532nm组75例，585nm组53例，治疗光斑2．0mm，能量密度2．2-6．8J／cm。，脉宽10ns；术后3个月根据术前照片判定疗效，标准分为Ⅳ级。结果：治疗次数1-4次，间隔时间3-5个月，两组共治愈71例(55，47％)，疗效与治疗次数成正相关。其中532nm组治愈36例(48．00％)，平均治愈次数2．64次；585nm组治愈35例(66．04％，)，平均治愈次数2．40次，两组痊愈率及副反应差异无显性。结论：Q开关Nd:YAG激光倍频532／nm和585nm两种波长对密度较低、直径较细的面部毛细血管扩张均有可靠疗效，术后除色素沉着发生较高外，其他不良反应较少。     

Copper vapour laser treatment of port-wine stains and other vascular malformations

Over a 2-year period more than 1350 treatment sessions have been conducted with yellow 578 nm light from a copper vapour laser on a variety of vascular malformations. Of these sessions half were of port-wine stains, from 297 patients. The light is applied by scanning a 1 mm optical fibre approximately 2 mm above the lesion along the lines of Langer. We use a maximum scan rate of 3 s/cm2, which is the highest rate at which minimal blanching can be produced. Up to 6.5 watts of light has been used, and a typical energy fluence is 20 to 30 J/cm2. Topical melanin suppressing creams are used before and after treatment, in order to maximise the effectiveness of the treatment. Non-vasoconstricting anaesthetics are always used. Repeat treatments are 3 months apart. The scan rate we used was directly correlated with the light intensity. The degree to which the colour of the port-wine stains lightened after the first treatment was also well correlated with the scan rate (p less than 0.0005). The faster the scan rate, the greater the colour reduction. This provides some supporting evidence for the short illumination time that theoretical models have indicated as "ideal". The lightening was more marked for patients whose lesion colour was initially dark (p less than 0.0005). Those whose skin had a high melanin content (Maori, Polynesian and Asian) responded more slowly than others. Thirty-six patients have had a greater than 70% reduction in the size of their lesions after an average of four treatments. Ten patients have responded poorly after at least four treatments (10% of all those who have had four or more treatments). The occurrence of scarring, hyperpigmentation and hypopigmentation was low in comparison with that reported previously from the green light of argon ion lasers.     

Port wine stain treatment with a dual-wavelength Nd:Yag laser and cryogen spray cooling: a pilot study

BACKGROUND AND OBJECTIVES: We report on a pilot study of port wine stain (PWS) treatment with a prototype Nd:YAG/KTP laser system, emitting simultaneously at 1,064 and 532 nm, and equipped with a cryogen spray cooling (CSC) device. STUDY DESIGN/PATIENTS AND METHODS: On 10 patients (4-36 years old, mean: 16.2 years) with skin types II-III, therapeutic efficacy of the dual-wavelength laser (KTP+) was compared with a standard KTP laser (532 nm only) at the same pulse duration (25 millisecond), spot diameter (3 mm), and CSC parameters. The fluences were selected in order to obtain the same immediate response with both laser systems. Blanching of each test segment was assessed 8 weeks post treatment by an independent evaluator and by the subjects, and graded on a 1-4 scale. RESULTS: Significant blanching of PWS was noted 8 weeks after a single therapeutic session with the KTP+ laser (mean: 532 nm radiant exposure: 8.2 J/cm(2)), very similar to that observed with KTP at 12.4 J/cm(2). The evaluator noticed a slight brownish coloration in areas treated with the KTP+ laser. Isolated beam-sized atrophic scars were present in two patients where KTP+ (9 and 10 J/cm(2)) and KTP (14 J/cm(2)) lasers were used. CONCLUSIONS: The addition of 1,064 nm radiation allowed a significant reduction of 532 nm radiant exposure with no loss of efficacy in PWS treatment.     

Influence of laser wavelength on the damage of comb��s vasculature by photodynamic therapy��simulation and validation of mathematical models

Lasers of different wavelengths have been used as a photodynamic therapy (PDT) light source in the treatment of port-wine stains. This study attempts to investigate the influence of wavelength on depth of vascular damage using a cock comb model and mathematical modeling/simulation. Monte Carlo simulation was used to calculate the distribution of laser light in skin tissue. A series of equations including the diffusion equation for modeling the distribution of photosensitizers and oxygen, and the photobleaching equation were established to calculate the singlet oxygen generation in PDT. The singlet oxygen generation in comb tissue model with vasculature was simulated with 532- and 627.8-nm laser, respectively. In the animal experiment, the comb was treated using hematoporphyrin monomethyl ether (HMME) (10 mg/kg dose) as a photosensitizer and lasers of two different wavelengths (532 and 627.8 nm) at an identical power density (100 mW/cm(2), fluence 120 J/cm(2)). The simulation results showed that the 627.8-nm laser was more effective in generating singlet oxygen in blood vessels at deep dermis. The animal experiments showed that the average depth of thrombosis was 1,012.5 ± 647.06 μm with the 532-nm laser, and 2,204.2 ± 410.35 μm with the 627.8-nm laser. The results showed that the laser wavelength had a strong effect on the depth of thrombosis in PDT treatment for the comb model. The simulation results were consistent with the animal experimental results.     

Treatment of Port-Wine Stain Birthmarks Using the 1.5-msec Pulsed Dye Laser at High Fluences in Conjunction with Cryogen Spray Cooling

BACKGROUND: The majority of port-wine stain (PWS) patients treated with the pulsed dye laser (PDL) do not achieve complete blanching. Safe administration of higher fluences has been proposed as a means of improving treatment efficacy. OBJECTIVE: To determine the safety and efficacy of PWS treatment with the 1.5-msec PDL at high fluences in conjunction with cryogen spray cooling. METHODS: Twenty PWS patients were treated with the PDL in combination with cryogen spray cooling utilizing a 7 or 10 mm spot size and fluences ranging from 6 to 15 J/cm2. Before and after treatment photographs were compared on a blinded basis. RESULTS: No scarring or skin textural changes occurred. Blanching scores were as follows: 20% of patients achieved 75% or greater blanching after an average of 3.3 treatments, 30% achieved 50-74% blanching, 20% achieved 25-49% blanching, and 30% achieved less than 25% blanching. CONCLUSION: In conjunction with cryogen spray cooling, the PDL can be safely used at high fluences. At this time it is not clear that the use of higher fluences improves treatment efficacy; however, as other aspects of PWS laser treatment are optimized, safe administration of higher fluences is likely to be advantageous.