Pulsed Dye Laser Irradiation Research Articles

Carbon monoxide combined with artificial blood cells acts as an antioxidant for tissues thermally-damaged by dye laser irradiation

Artificial red blood cells [i.e., hemoglobin vesicles (HbVs)] can be used as photosensitizers in pulsed-dye laser (PDL) treatment for port wine stains in animal models. Small HbVs are distributed in the vicinity of the endothelial cells of the blood vessels. In our previous in vivo experiments, both HbVs and red blood cells absorbed photons of the laser and generated heat, contributing to removal of very small blood vessels and large deeper subcutaneous blood vessels with PDL irradiation. Herein, we tested carbon monoxide-bound HbVs (CO-HbVs) that would produce heat energy while releasing CO in vessels after dye laser irradiation in a rabbit auricle model. We conducted this experiment to confirm secondary progression of thermal injury being reduced with the antioxidative property of CO. We histopathologically evaluated the damages to the large vessels and surrounding dermal tissue following PDL irradiation alone or subsequent to the intravenous injection of the qualified HbVs. The soft tissue damages were graded on a five-point scale and compared statistically. Intravenous CO-HbVs significantly reduced damage to the surrounding tissue after subsequent PDL irradiation; however, the degree of damage to the larger vessel wall resulted in a variety of changes, including a slight increase in our histopathological grades. This beneficial effect in dye laser treatment for port wine stains may be the result of the antioxidative property of CO against free radicals in the zone of stasis that may still be theoretically viable in burns. This effect of CO protecting tissues from thermal damage is consistent with previous reports of CO as a reducing agent. If the reducing agent can be delivered directly to the affected area immediately after the burn injury, even in a small amount, the complex inflammatory cascade may be reduced and unnecessary inflammation after laser treatment that lowers the patient’s quality of life can be avoided.

Topical metformin suppresses angiogenesis pathways induced by pulsed dye laser irradiation in animal models.

Pulsed dye laser (PDL) is the first-line treatment for port-wine stain (PWS). However, only a small portion of the lesions could be completely cleared by PDL treatment, which might be related to the regeneration and revascularization of the vascular structures after laser irradiation. Recently, it is believed that the suppression of regeneration and revascularization of photocoagulated blood vessels can achieve a better therapeutic outcome. We use rabbit ear and SD rat as the animal models to investigate whether PDL-induced angiogenesis can be suppressed by topical metformin. Our results showed that topical application of metformin can effectively suppress the PDL-induced early stage of angiogenesis via inhibition of the AKT/mTOR/P70S6K pathway in animal models.

Artificial red blood cells increase large vessel wall damage and decrease surrounding dermal tissue damage in a rabbit auricle model after subsequent flashlamp-pumped pulsed-dye laser treatment.

Artificial red blood cells (i.e. hemoglobin [Hb] vesicles [Hb-Vs]) function effectively as photosensitizers in flashlamp-pumped pulsed-dye laser (PDL) treatment for port-wine stains in animal models. Hb-Vs deliver more Hb to the vicinity of the endothelial cells. Both Hb-Vs and red blood cells absorb the laser energy and generate heat, supporting the removal of very small blood vessels and deeper subcutaneous blood vessels with PDL irradiation in in vivo experiments. Here, we analyzed the photosensitizing effect of Hb-Vs in PDL irradiation on large blood vessels and surrounding soft tissues. We histopathologically analyzed markers of damage to the large vessels and surrounding dermal tissue in a rabbit auricle model following PDL irradiation alone or subsequent to the addition of intravenous Hb-V injection. Markers were graded on a five-point scale and statistically compared. The changes in laser light absorption and reflection in a human skin model caused by the administration of Hb-Vs were evaluated using Monte Carlo light-scattering programs. Histological markers of damage to blood vessels were significantly greater in Hb-V-injected arteries and veins measuring 1-3mm in diameter as compared with the controls. However, Hb-V injection significantly reduced PDL-induced necrosis and hemorrhage in the surrounding tissues. During computer simulation, photon absorption increased within the vessel layer and decreased around the layer. Intravenous Hb-Vs increase the extent of damage in larger vessel walls but significantly reduce damage to the surrounding skin after subsequent PDL irradiation. These beneficial effects are the result of improving vessel selectivity by Hb-Vs in vessels. Hb-V administration prior to PDL irradiation therapy could mechanically improve the outcomes and safety profiles of port-wine stain treatment protocols.

Photothermal treatment of port-wine stains using erythrocyte-derived particles doped with indocyanine green: a theoretical study.

.Pulsed dye laser irradiation in the wavelength range of 585 to 600 nm is currently the gold standard for treatment of port-wine stains (PWSs). However, this treatment method is often ineffective for deeply seated blood vessels and in individuals with moderate to heavy pigmentation. Use of optical particles doped with the FDA-approved near-infrared (NIR) absorber, indocyanine green (ICG), can potentially provide an effective method to overcome these limitations. Herein, we theoretically investigate the effectiveness of particles derived from erythrocytes, which contain ICG, in mediating photothermal destruction of PWS blood vessels. We refer to these particles as NIR erythrocyte-derived transducers (NETs). Our theoretical model consists of a Monte Carlo algorithm to estimate the volumetric energy deposition, a finite elements approach to solve the heat diffusion equation, and a damage integral based on an Arrhenius relationship to quantify tissue damage. The model geometries include simulated PWS blood vessels as well as actual human PWS blood vessels plexus obtained by the optical coherence tomography. Our simulation results indicate that blood vessels containing micron- or nano-sized NETs and irradiated at 755 nm have higher levels of photothermal damage as compared to blood vessels without NETs irradiated at 585 nm. Blood vessels containing micron-sized NETs also showed higher photothermal damage than blood vessels containing nano-sized NETs. The theoretical model presented can be used in guiding the fabrication of NETs with patient-specific optical properties to allow for personalized treatment based on the depth and size of blood vessels as well as the pigmentation of the individual’s skin.

The effect of 595 nm pulsed dye laser on connective tissue growth factor (CTGF) expression in cultured keloid fibroblasts.

To investigate the effect of pulsed dye laser (PDL 595 nm) on the proliferation and expression of connective tissue growth factor (CTGF) in cultured keloid fibroblasts. Cultured keloid fibroblasts were exposed to pulsed dye laser irradiation at fluences of 6, 8, and 10 J/cm(2) , with pulse durations of 1.5, 3, and 10 ms. The viability of keloid fibroblasts was measured with CCK-8 at 72, 24, and 12 hours prior to irradiation. Subsequently, viability was measured at 12, 24, and 72 hours post-irradiation. Additionally, the fibroblast cell cycle and apoptosis rate were measured by flow cytometry. Finally, keloid fibroblasts underwent real-time polymerase chain reaction (PCR) and Western blot to investigate the CTGF mRNA and protein expression after PDL irradiation. The untreated cultured keloid fibroblasts served as controls. The proliferation of keloid fibroblasts was significantly inhibited after PDL irradiation. Both CTGF mRNA and protein expression were significantly down-regulated in 1.5, 3, and 10 ms pulse duration groups, in a dose dependent manner (P < 0.05). However, there was no statistically significant difference between groups of different pulse duration in 6, 8, and 10 J/cm(2) fluence ranges (P > 0.05). Within certain fluence ranges, pulsed dye laser can effectively suppress the growth of keloids and significantly down-regulate CTGF mRNA and CTGF expression.

One Possible Mechanism of Pulsed Dye Laser Treatment on Infantile Hemangioma: Induction of Endothelial Apoptosis and Serum vascular endothelial growth factor (VEGF) Level Changes.

Pulsed dye laser (PDL) is an important treatment for superficial infantile hemangioma, but few studies report on its cellular mechanism. The aim of this study was to evaluate alterations of serum vascular endothelial growth factor (VEGF) level in infantile hemangioma (IH) patients after laser treatment and effects of PDL irradiation on human umbilical vein endothelial cells (HUVECs) in vitro, as well as to explore the biomolecular mechanisms and ultrastructure changes of the PDL effect. 74 children with infant hemangioma including 45 patients in proliferating phase, 18 patients in involuting phase, 11 patients in involuted phase and 10 healthy children were engaged in this study. The plasma VEGF levels of children were measured with the enzymelinked immunosorbent assay (ELISA). 24 hours after, HUVECs cultured in vitro were irradiated with PDL, cell apoptosis, mRNA levels of VEGF, and changes of ultrastructure were evaluated using flow cytometry, real-time reverse transcriptase polymerase chain reaction (RT-PCR), and transmission electron microscopy, respectively. The serum VEGF concentrations in children with proliferating hemangiomas were significantly higher than in patients with involuting / involved hemangiomas and healthy patients. After receiving 3 laser treatments, the plasma VEGF levels of IH patients in proliferating hemangiomas decreased significantly. PDL irradiation could down-regulate VEGF mRNA expression of HUVECs, and increase cell apoptosis rate. The present study demonstrates that PDL irradiation imparts apoptosis induction effects on HUVECs in vitro. Furthermore, our results suggest that vascular endothelial growth factor may be of particular importance in pathophysiology and PDL treatment of hemangiomas, also serum VEGF levels may be used as an aid in the follow up of IH. This provides valuable evidence of the PDL effect on infantile hemangioma.

Histological study on the treatment of vascular malformations resistant to pulsed dye laser

The pulsed dye laser (PDL) is recognized both as an effective treatment for vascular malformations and the as first treatment of choice for these lesions. However, PDL irradiation has poor efficacy in some patients, particularly the elderly. The present study histologically assessed such patients to try to elucidate the reason.A pulsed dye laser was used in 3 subjects in whom previous laser treatment was ineffective. Three-millimeter punch biopsies were obtained before laser treatment, 1 week and 3 months after the laser treatment. Each specimen was stained with toluidine blue and examined under light microscopy followed by electron microscopy with oolong tea extract (OTE) staining.Microscopy revealed an increase in the vasculature at baseline and an increased number of dermal fibroblasts. One week post-irradiation, inflammatory cell infiltration was observed together with extensive interstitial perivascular edema. At 1 week and 3 months after laser irradiation, normal structures were observed for both blood vessels and capillary endothelial cells. Mild changes were noted in other interstitial features, but findings obtained 3 months after irradiation were almost similar to those before irradiation.The lower efficacy of PDL treatment in the elderly was possibly due to the markedly low amount of red blood cells in our subjects' blood vessels, a major chromophore for the PDL, was markedly low. It is possible that age-related denaturation of dermal matrix collagen plays some role in maintaining the vasculature in the interstitium with edema, and inflammatory cell infiltration could lead to the cellular release of some cytokines which favor reconstruction of the vasculature.

Histological study on the treatment of vascular malformations resistant to pulsed dye laser.

The pulsed dye laser (PDL) is recognized both as an effective treatment for vascular malformations and the as first treatment of choice for these lesions. However, PDL irradiation has poor efficacy in some patients, particularly the elderly. The present study histologically assessed such patients to try to elucidate the reason. A pulsed dye laser was used in 3 subjects in whom previous laser treatment was ineffective. Three-millimeter punch biopsies were obtained before laser treatment, 1 week and 3 months after the laser treatment. Each specimen was stained with toluidine blue and examined under light microscopy followed by electron microscopy with oolong tea extract (OTE) staining. Microscopy revealed an increase in the vasculature at baseline and an increased number of dermal fibroblasts. One week post-irradiation, inflammatory cell infiltration was observed together with extensive interstitial perivascular edema. At 1 week and 3 months after laser irradiation, normal structures were observed for both blood vessels and capillary endothelial cells. Mild changes were noted in other interstitial features, but findings obtained 3 months after irradiation were almost similar to those before irradiation. The lower efficacy of PDL treatment in the elderly was possibly due to the markedly low amount of red blood cells in our subjects' blood vessels, a major chromophore for the PDL, was markedly low. It is possible that age-related denaturation of dermal matrix collagen plays some role in maintaining the vasculature in the interstitium with edema, and inflammatory cell infiltration could lead to the cellular release of some cytokines which favor reconstruction of the vasculature.

Topical application of 5-aminolevulinic acid followed by 595-nm pulsed dye laser irradiation for the treatment of recalcitrant port-wine stains: A primary study

Objective: To evaluate the effectiveness and safety of topical application of 5-aminolevulinic acid (ALA) followed by pulsed dye laser (PDL) irradiation for the treatment of recalcitrant port-wine stain (PWS). Methods: Thirty-five patients (19 females and 16 males) with recalcitrant PWS were treated with topical application of 20% ALA and then irradiated with a 595-nm PDL (energy density of 6.5–9.0 J/cm2 and pulse duration of 6 or 10 ms) at 6–8 weeks intervals. Clinical improvement of lesions was evaluated by comparing photographs of lesions at baseline and 2 months after the last treatment. Results: Topical ALA spreading followed by irradiation with a 595-nm PDL improved PWS in 21 out of 35 patients who were previously recalcitrant to PDL treatment alone. Side effects were limited to transient erythema, vesicle formation, edema and mild purpura with no obvious subsequent scarring or undesirable pigment changes. Conclusion: The topical application of ALA followed by irradiation with a 595-nm PDL is an effective and safe treatment for PWS recalcitrant to PDL therapy alone.

Pulsed dye laser‐induced inflammatory response and extracellular matrix turnover in rat vocal folds and vocal fold fibroblasts

Disruption of the vocal fold extracellular matrix (ECM) can induce a profound and refractory dysphonia. Pulsed dye laser (PDL) irradiation has shown early promise as a treatment modality for disordered ECM in patients with chronic vocal fold scar; however, there are limited data addressing the mechanism by which this laser energy might induce cellular and extracellular changes in vocal fold tissues. In this study, we examined the inflammatory and ECM modulating effects of PDL irradiation on normal vocal fold tissues and cultured vocal fold fibroblasts (VFFs). We evaluated the effects of 585 nm PDL irradiation on inflammatory cytokine and collagen/collagenase gene transcription in normal rat vocal folds in vivo (3-168 hours following delivery of approximately 39.46 J/cm(2) fluence) and VFFs in vitro (3-72 hours following delivery of 4.82 or 9.64 J/cm(2) fluence). We also examined morphological vocal fold tissue changes 3 hours, 1 week, and 1 month post-irradiation. PDL irradiation altered inflammatory cytokine and procollagen/collagenase expression at the transcript level, both in vitro and in vivo. Additionally, PDL irradiation induced an inflammatory repair process in vivo that was completed by 1 month with preservation of normal tissue morphology. PDL irradiation can modulate ECM turnover in phenotypically normal vocal folds. Additional work is required to determine if these findings extend to disordered ECM, such as is seen in vocal fold scar. Lasers Surg. Med. 41:585-594, 2009. (c) 2009 Wiley-Liss, Inc.

Prevention of Thyroidectomy Scar Using a New 1,550-nm Fractional Erbium–Glass Laser

Surgical scars are a common cosmetic problem that occurs in various surgical fields including dermatology. Diverse trials have been made to prevent this annoying scar formation. Recently, 585- and 595-nm pulsed dye laser irradiation presented satisfactory cosmetic outcome for the treatment of surgical scars. Other fractionated lasers or light devices were also applied for scar treatment. To determine the effectiveness and safety of a newly developed 1,550-nm fractional erbium-glass laser in the prevention of scar formation after total thyroidectomy. Twenty-seven ethnic South Korean patients with linear surgical suture lines after total thyroidectomy operation were treated with a 1,550-nm fractional erbium-glass laser. The same surgeon performed all of the operations using the same surgical techniques. Each patient was treated four times at 1-month intervals using the same parameters (5- x 10-mm spot size, 10 mJ, 1,500 spot/cm(2), static mode). Initiation of the first irradiation was made approximately 2 to 3 weeks after the thyroidectomy. The scar prevention effects were evaluated each month for 6 months after thyroidectomy. Two kinds of assessment methods were applied in this evaluation. First, the Vancouver Scar Scale (VSS) was used. Second, three independent physicians gave a global assessment valuation to the final cosmetic results: poor (1), fair (2), good (3), or excellent (4). These results were compared with the surgical scars of a control group (patients who denied laser treatments and had no other treatments during the 6 months after total thyroidectomy by the same surgeon). The average VSS score was lower in the laser treatment group. The global assessment also presented better cosmetic outcomes in the treatment group than in the controls. A new 1,550-nm fractional erbium-glass laser may efficiently repress the formation and hypertrophy of thyroidectomy scars on the neck, and it can be safely applied in relatively dark Asian skin without noticeable adverse effects.

Vascular effects of photodynamic and pulsed dye laser therapy protocols

Pulsed dye laser (PDL) treatment of cutaneous vascular lesions is associated with variable and unpredictable efficacy. Thus, alternative treatment modalities are needed. Previous in vitro and in vivo studies have demonstrated enhanced selective vascular destruction with benzoporphyrin derivative (BPD) monoacid ring A photodynamic therapy (PDT) followed immediately by PDL irradiation (PDT+PDL). Here, we evaluate PDT alone, PDL alone, and PDT+PDL protocols using an optimized in vivo rodent dorsal window chamber model. A dorsal window chamber was surgically installed on male Golden Syrian hamsters. BPD solution was administered intravenously via a jugular venous catheter. Evaluated interventions included: (1) Control (no BPD, no light); (2) Control (BPD, no light); (3) PDT alone (lambda = 576 nm; 25, 50, 75, or 96 J/cm2 radiant exposure; 15 minutes post-BPD injection); (4) PDL alone at 7 J/cm2 (585 nm, 1.5 milliseconds pulse duration, 7 mm spot); and (5) PDT (25 or 75 J/cm2)+PDL (7 J/cm2). Laser speckle imaging was used to monitor blood flow dynamics before, immediately after, and 1, 3, and 5 days post-intervention. Perfusion reduction on day 1 post-intervention was achieved with PDT>50 J/cm2, PDL alone, and PDT+PDL. However, by day 5 post-intervention, recovery of flow was observed with PDT alone at 50 J/cm2 (-15.1%) and PDL alone (+215%). PDT (75 J/cm2)+PDL resulted in the greatest prolonged reduction in vascular perfusion (-99.8%). Our in vivo data suggest that the PDT+PDL therapeutic protocol can result in enhanced and persistent vascular shutdown compared to PDT or PDL alone. The PDT+PDL approach has potential for considerable superficial vascular destruction and should be considered as a treatment modality for cutaneous vascular lesions. Monitoring of blood flow changes for as long as possible is crucial for accurate assessment of light-based vascular interventions.

Control of Photobleaching in Photodynamic Therapy Using the Photodecarbonylation Reaction of Ruthenium Phthalocyanine Complexes via Stepwise Two-Photon Excitation

In this study, we have investigated the photochemical properties and photodynamic effects of ruthenium phthalocyanine (RuPc(CO)(Py)) and naphthalocyanine (RuNc(CO)(Py)) complexes. When a nanosecond-pulsed laser is used, the photodecarbonylation of our Ru complexes efficiently proceeds via stepwise two-photon excitation, while the reaction yields are negligibly small when a continuous-wave (CW) laser is employed. The pulsed laser selective photodecarbonylation decreases the Q-band absorbance, which satisfies what the photodynamic therapy (PDT) requires of the photobleaching. For RuPc(CO)(Py), the photochemical reactions including both the photodecarbonylation and just photobleaching occur in HeLa cells in vitro. Toxicity and phototoxicity tests indicate that our RuPc(CO)(Py) and RuNc(CO)(Py) complexes in concentrations of 0.3-1 microM and 1-2 microM, respectively, are applicable as PDT agents. The phototoxicity is consistent with the photochemical properties of these complexes, namely, excited triplet lifetimes (10 and 4.8 micros for the Pc and Nc complexes, respectively) and singlet oxygen yields (0.48 and 0.35 for the Pc and Nc complexes, respectively). On the basis of these results, we propose a novel concept for achieving a greater depth of necrosis in PDT as follows: (1) PDT of upper cellular layers using CW-laser irradiation; (2) efficient photobleaching in upper cellular layers using pulsed dye-laser irradiation, which results in an increase in the therapeutic depth of red light; (3) PDT directed toward deeper tumor tissues using CW laser irradiation. In addition, these Ru complexes are promising as CO release agents for investigative biochemistry.

Effects of lower fluence pulsed dye laser irradiation on production of collagen and the mRNA expression of collagen relative gene in cultured fibroblasts in vitro

Lower fluence of 585-nm flashlamp-pumped pulsed dye laser has been successfully used as a nonablative technique in the treatment of wrinkles. The objective of this study was to evaluate the effect of the pulsed dye laser (585 nm) on the production of collagen and the mRNA expression of collagen related gene in fibroblasts in vitro. Cultured fibroblasts were treated with a 585-nm flashlamp-pumped pulsed dye laser (fluence 3 J/cm(2), 4 J/cm(2), spot size 7 mm, pulse duration 450 micros). The production of collagen and the mRNA expression of transforming growth factor (TGF)-beta1, SMAD2, SMAD3, SMAD4, SMAD7 and type I procollagen alpha1, alpha2 in fibroblasts were investigated by colorimetry or real time polymerase chain reaction. The production of collagen was significantly up-regulated after treatment with a 585-nm flashlamp-pumped pulsed dye laser with a fluence of 3 J/cm(2) (P < 0.001). The mRNA expression of TGF-beta1, SMAD2, SMAD3, SMAD4, SMAD7 and procollagen I was significantly up-regulated after treatment with a 585-nm flashlamp-pumped pulsed dye laser with a fluence of 3 J/cm(2) (P < 0.001). No significant difference of mRNA expression of SMAD2, SMAD3, SMAD4, SMAD7 and type I procollagen was found between controls and fibroblasts treated with pulsed dye laser with a fluence of 4 J/cm(2) (P > 0.05). Lower fluence (3 J/cm(2)) pulsed dye laser increased the collagen production in fibroblasts by up-regulating TGF-beta1, SMAD2, SMAD3, SMAD4, SMAD7 and type I procollagen mRNA expression. These may be the reason it can be effectively used in the treatment of wrinkles.

Microvascular blood flow dynamics associated with photodynamic therapy, pulsed dye laser irradiation and combined regimens

Previous in vitro studies demonstrated the potential utility of benzoporphyrin derivative monoacid ring A (BPD) photodynamic therapy (PDT) for vascular destruction. Moreover, the effects of PDT were enhanced when this intervention was followed immediately by pulsed dye laser (PDL) irradiation (PDT/PDL). We further evaluate vascular effects of PDT alone, PDL alone and PDT/PDL in an in vivo rodent dorsal skinfold model. A dorsal skinfold window chamber was installed surgically on female Sprague-Dawley rats. One milligram per kilogram of BPD solution was administered intravenously via a jugular venous catheter. Evaluated interventions were: control (no BPD, no light), PDT alone (576 nm, 16 minutes exposure time, 15 minutes post-BPD injection, 10 mm spot), PDL alone at 7 J/cm2 (585 nm, 1.5 ms pulse duration, 7 mm spot), PDL alone at 10 J/cm2, PDT/PDL (PDL at 7 J/cm2), and PDT/PDL (PDL at 10 J/cm2). To assess changes in microvascular blood flow, laser speckle imaging was performed before, immediately after, and 18 hours post-intervention. Epidermal irradiation was accomplished without blistering, scabbing or ulceration. A reduction in perfusion was achieved in all intervention groups. PDT/PDL at 7 J/cm2 resulted in the greatest reduction in vascular perfusion (56%). BPD PDT can achieve safe and selective vascular flow reduction. PDT/PDL can enhance diminution of microvascular blood flow. Our results suggest that PDT and PDT/PDL should be evaluated as alternative therapeutic options for treatment of hypervascular skin lesions including port wine stain birthmarks.

Comparative study of cryogen spray cooling with R-134a and R-404a: implications for laser treatment of dark human skin

Cutaneous laser treatment in dark skin patients is challenging due to significant light absorption by the melanin at the basal layer of epidermis, which can result in irreversible nonspecific thermal injury to the epidermis. Cryogen spray cooling (CSC) with R-134a (boiling point approximately -26.2 degrees C at 1 atm), which is currently used during cutaneous laser treatment, has shown poor efficacy in protecting dark human skin. We investigated the potential of CSC with R-404a (boiling point approximately -46.5 degrees C at 1 atm), which has a lower boiling point than R-134a, for improved therapeutic outcome in dark human skin at three levels: in vitro (epoxy resin skin phantom), ex vivo (normal dark human skin sample), and in vivo (skin of the rabbit external ear). The skin phantom was used to acquire the surface and internal temperature profiles in response to CSC with R-134a or R-404a at various spurt durations, based upon which CSC-induced heat removal from the skin phantom was estimated using an algorithm that solved a one-dimensional inverse heat conduction problem. CSC with R-404a increased the temperature reductions within the phantom and subsequently the amount of heat removal from the phantom in comparison to that with R-134a. Normal ex vivo Fitzpatrick types V-VI human skin samples were used to investigate the thermal response of dark human skin epidermis to CSC (R-134a or R-404a) at various spurt durations in conjunction with 595-nm pulsed dye laser irradiation at various radiant exposures. Cryogen R-404a increased the threshold radiant exposures for irreversible thermal injury to the epidermis in dark pigmentation skin. No obvious CSC-induced morphological changes to human skin was observed when sprayed with R404-a spurts using durations up to 300 ms. In vivo rabbit ear vasculature was used as a model of cutaneous anomalies to assess the influences of CSC (with R-134a or R-404a) on the photothermolysis of dermal blood vessels. CSC (R-134a or R-404a) with the spurt durations of 100 to 300 ms increased the most superficial depth of thermally damaged dermal blood vessel compared with the sites without CSC, implying possible nonspecific cooling of superficial dermal blood vessels by the cryogen spurts with the settings applied.

Selective Photothermolysis of Blood Vessels Following Flashlamp-Pumped Pulsed Dye Laser Irradiation: In Vivo Results and Mathematical Modelling Are in Agreement

Laser therapy using the pulsed dye laser is the standard treatment for port-wine stains (PWS). But the mechanism of action has not been elucidated completely, yet. The dorsal skin-fold chamber model in hamsters was used to investigate the effects of laser treatment (lambda(em)=585 nm; pulse duration: 0.45 ms; fluence: 6 J per cm2) on blood vessels. Vessels (n=3394) were marked with FITC dextran (MW 150 kDa) and diameters (2-186 microm) were measured using intravital fluorescence microscopy up to 24 h following irradiation. Histology (H&E, TUNEL, CD31) was taken 1 or 24 h after irradiation. The experimental results were compared with the predictions of a mathematical model based on the finite-element method. Following irradiation treatment the number of unperfused vessels decreases with decreasing vessel diameter in vivo. Histology indicated a restriction of tissue injury to the irradiated area after 1 h. Blood vessels contained aggregated red blood cells. After 24 h tissue damage occurred also outside the irradiated area and thrombus formation was visible. These results were in agreement with the mathematical calculations. In addition to initial physical effects after pulsed dye laser treatment delayed biological processes contribute significantly to the reduction of perfused blood vessels. Because of incomplete photocoagulation of smaller blood vessels (diameter 2-16 microm) a complete bleaching of PWS seems to be unlikely.

Laser-Assisted Low-Dose Retinoic Acid in Oral Cancer Chemoprevention

Systemic retinoic acid (RA) treatment for chemoprevention of squamous cell carcinoma of the head and neck (HNSCC) is limited by RA's toxic side effects at therapeutic doses. The pulsed-dye laser (PDL), through a mechanism of selective vascular targeting, may allow reduction of the RA dose to one that is better tolerated when these treatments are used in combination. This study tests our hypothesis that combination therapy of PDL irradiation and low-dose systemic RA is as effective as high-dose RA therapy alone in the chemoprevention of HNSCC. Randomized, prospective study in a hamster model. Dysplastic lesions were induced in the cheek pouches of 48 hamsters by painting with topical 9,10-dimethl-1,2-benzanthrancene (DMBA). The hamsters were randomly divided into four treatment groups: 1) control (no treatment); 2) PDL irradiation only; 3) 5.0 mg RA (all-trans retinoid, 5.0 mg/kg per day, intraperitoneally [IP]); and (4) PDL + 0.5 mg RA (0.5 mg/kg per day, IP). The PDL irradiation was conducted at day 0 and 15, whereas the RA treatment was continued for 27 days. Tumor burden was measured over time. The lesions in all of three treatment groups grow more slowly than the untreated controls. The combination treatment of PDL and RA had the greatest inhibitory effect on tumors. This study suggests that combination treatment of PDL and low-dose RA is more effective than high-dose RA alone in the chemoprevention of HNSCC in a hamster cheek-pouch model, so that it should allow greatly improved tolerance of this regimen.

Epidermal and vascular damage analysis of in vivo human skin in response to 595 nm pulsed laser irradiation

Laser irradiation is the current modality for treatment of cutaneous hypervascular malformations such as port wine stains and telangiectasia. Although cryogen spray cooling (CSC) is used to protect the epidermis from non-specific laser-induced thermal damage in moderately-pigmented skin types, individuals with high melanin content are still at risk for epidermal damage using the current laser irradiation and CSC parameters. The objective of this study was to investigate the influence of the spray Weber number (1,100 or 5,100) on epidermal protection and examine vascular coagulation in response to pulsed dye laser irradiation. Normal, in vivo human skin from eight subjects of Fitzpatrick skin types I-V were precooled with either low or high Weber number cryogen sprays and subsequently irradiated with a pulsed dye laser at 595 nm. Analysis of gross purpura, morphological vascular damage, and apoptosis of the vascular walls were performed. Results demonstrated a high Weber number spray of 5,100 decreased the level of epidermal damage in darker and moderate pigmented individuals compared to a Weber number spray of 1,100. This study also established a positive correlation between gross purpura and the level of vessel wall apoptosis. This study has demonstrated that CSC with a high Weber number spray can decrease nonspecific thermal damage to the epidermis in response to laser irradiation in vivo. We have also established a positive correlation between gross purpura and the level of vessel wall apoptosis. Lasers Surg. Med. (c) 2005 Wiley-Liss, Inc.

Treatment of Facial Scarring and Ulceration Resulting from Acne Excoriée with 585-nm Pulsed Dye Laser Irradiation and Cognitive Psychotherapy

BACKGROUND Self-inflicted skin ulcers and scars are often observed in patients with compulsive skin picking. The term “neurotic excoriation” has been used to describe this condition and may or may not coexist with other true skin pathologies, such as acne. The condition poses a diagnostic and treatment challenge because patients often also have an undiagnosed underlying psychologic disorder. CASE REPORTS Two patients with numerous linear and stellate facial ulcers and hypertrophic and erythematous scars were diagnosed with acne excoriée in the setting of an obsessive-compulsive disorder linked to emotional stress and anxiety. The scars were treated with a 585-nm flashlamp-pumped pulsed dye laser using a 7-mm spot size, 1.5-msec pulse duration, and fluence range of 4.5 to 6.0 J/cm2. The patients received concomitant cognitive psychodynamic therapy to halt the cycle of impulse-driven skin picking and ulcer/scar formation. Marked clinical improvement of the scars and successful treatment of the acne excoriée were achieved with this combination approach. Relapses occurred when psychodynamic intervention was interrupted. conclusion The 585-nm flashlamp-pumped pulsed dye laser improves the appearance of hypertrophic erythematous facial scars and ulcers in patients with severe acne excoriée. Proper diagnosis of underlying impulse-control disorders and ongoing psychodynamic therapy is necessary to maintain improvement.