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Background and Objectives Port-wine stains (PWSs) are capillary vascular malformations that are commonly resistant to treatment. Currently, the pulsed dye laser (PDL) is the treatment of choice. Multiple treatments are required and complete blanching after laser irradiation is rarely achieved. We review current therapeutic modalities for PWSs and recent developments for enhanced clearance. Study Design/Materials and Methods Relevant literature was reviewed including PDL modifications for improved efficacy, alternative laser devices for treatment-resistant PWSs, and the addition of agents to modulate the wound-healing response after laser irradiation. Results Although PDL is the treatment of choice for PWSs, increased understanding of interactions between PWSs and PDL has led to improvements in therapeutic outcome in terms of lesion blanching. Conclusions Preliminary evidence of combination therapy using antiangiogenic agents after laser irradiation appears promising and could lead to the development of a new standard of care for PWSs. [ABSTRACT FROM AUTHOR]

Recent advances in the understanding of the metastatic phenomenon in cancer have led to the description of a metastatic niche. This concept describes a site prepared for the tumor cells in areas frequently associated with metastasis for the individual tumor studied. This niche is a “soil” that allows for the tumor cell or “seed” to lodge and grow. Certain aspects of the biology of infantile hemangioma cells suggest a relationship to the placenta as a possible site of origin for the hemangioma precursor cells. In this article, a relationship between the placenta, with or without a chorangioma and the hemangioma sites of localization, is hypothesized. The placenta is suggested as the site of humoral factors that prepare a niche similar to the function of malignant tumor cells. If the hypothesis proves to be valid, clues for possible treatment are outlined. Mihm MC, Nelson JS. Hypothesis: the metastatic niche theory can elucidate infantile hemangioma development [ABSTRACT FROM AUTHOR]

Background. When a cryogen spurt is applied to the skin surface for an appropriately short period of time (on the order of tens of milliseconds), the cooling remains localized in the epidermis, while leaving the temperature of the deeper port-wine stain (PWS) blood vessels unchanged. Objective. The objective of this study was to compare the efficacy and safety of noncooled laser treatment (NC-LT), and cryogen spray cooled laser treatment (CSC-LT) of PWS birthmarks in a large series of patients. Methods. A retrospective review was conducted of 196 patients with head or neck PWS birthmarks treated with the pulsed dye laser (λ = 585 nm; τp = 450 μsec) over a 7-year period. Subjects' ages ranged between 2 months and 62 years; there were 109 females and 87 males, all of whom were Asian. Ninety-eight patients received NC-LT using light dosages of 5–7 J/cm2. Subsequently, 98 patients received CSC-LT using light dosages of 8–10 J/cm2. The primary efficacy measure was the quantitative assessment of the blanching response scores of NC-LT PWSs as compared, on a blinded basis, to CSC-LT PWSs. Results. Based on chi-squared analysis, there were clinical, and statistically significant, differences in the blanching response scores favoring PWS receiving CSC-LT as compared to the NC-LT group (P < .001). Permanent scarring was noted in 3.1% (n = 3) of the patients in the NC-LT group. Permanent scarring was not observed in the CSC-LT treatment group. Transient hyperpigmentation was noted in 57% (n = 56) and 48% (n = 47) of the patients in the NC-LT and CSC-LT groups, respectively. In both groups, the transient hyperpigmentation resolved in all patients within 1 year. Two patients in the NC-LT group developed delayed permanent hypopigmentation. Permanent hypopigmentation was not observed in the CSC-LT group. Conclusion. CSC permitted the use of higher incident light dosages leading to improved PWS clearance without... [ABSTRACT FROM AUTHOR]

The precise removal of stratum corneum from cadaveric swine skin by a mid-infrared erbium: yttrium scandium gallium garnet laser (λ = 2.79 μm; 250 μsec pulse width) was assessed by electrical resistance measurements and documented by histology. The effects of stratum corneum removal by laser ablation and by adhesive tape-stripping on the in vitro penetration of ³H-hydrocortisone and 125I-γ-interferon were determined. Excised swine skin was irradiated with laser (1 J/cm² 31 mJ/pulse; 1 Hz; 2 mm spot diameter). For skin penetration studies, laser pulses were delivered to discrete 2-mm areas to ablate up to 12.6% of the total 3-cm² stratum corneum diffusional area. Franz in vitro skin penetration chambers were used to measure the cumulative 48-h penetration of ³H-hydrocortisone and 125I-γ-interferon in laser-treated and tape-stripped skin. Electrical resistance measurements and histologic studies demonstrated that 10-14 laser pulses at the above energy density were required to abolish skin resistance and selectively ablate stratum corneum without damage to adjacent dermal structures. Laser ablation of 12.6% of the surface area of stratum corneum produced a 2.8 and 2.1-times increase in permeability constant (kp) for ³H-hydrocortisone and 125I-λ-interferon, respectively. These studies demonstrate that a pulsed mid-infrared laser can reliably and precisely remove the stratum corneum, facilitating penetration of large molecules such as 125I-λ-interferon that cannot penetrate intact skin. This new technique may be useful for basic and clinical investigation of skin barrier properties. [ABSTRACT FROM AUTHOR]

Background. The treatment of medium-sized (1.5–20 cm diameter) congenital melanocytic nevi (CMN) has been the concern of dermatologists for decades. Although many techniques have been described and utilized, no single treatment has emerged as applicable under all circumstances. Methods The Q-switched ruby laser (QSRL) at 694 nm, a wavelength well absorbed by melanin relative to other optically absorbing structures in skin, causes highly selective destruction of pigment-laden cells. In addition, the 20-nanosecond pulse duration produced by this laser approximates the thermal relaxation time for melanosomes, thereby confining the energy to the targeted cells. Results. In the present report, treatment using the QSRL resulted in complete clinical removal of a biopsy-documented medium-sized compound CMN with no recurrence after 5 years. In contrast to other therapeutic modalities, complications such has hypertrophic scarring, dyspigmentation, or atrophy were not observed. [ABSTRACT FROM AUTHOR]

This article presents a letter to the editor in response to the article "Redarkening of port-wine stains 10 years after pulsed-dye-laser treatment," by M. Huikeshoven and colleagues in the March 22, 2007 issue.

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. [ABSTRACT FROM AUTHOR]

We determine experimentally the accuracy of pulsed photothermal radiometric (PPTR) temperature depth profiling in water-based samples. We use custom tissue phantoms composed of agar gel layers separated by very thin absorbing layers. Two configurations of the acquisition system are compared, one using the customary spectral band of the InSb radiation detector (3.0–5.5 μm) and the other with a spectrally narrowed acquisition band (4.5–5.5 μm). The laser-induced temperature depth profiles are reconstructed from measured radiometric signals using a custom minimization algorithm. The results correlate very well with phantom geometry as determined by optical coherence tomography (OCT) and histology in all evaluated samples. Determination of the absorbing layer depth shows good repeatability with spatial resolution decreasing with depth. Spectral filtering improves the accuracy and resolution, especially for shallow absorption layers (∼120 μm) and more complex structures (e.g., with two absorbing layers). The average full width at half maximum (FWHM) of the temperature peaks equals 23% of the layer depth. [ABSTRACT FROM AUTHOR]

BACKGROUND A number of studies have been performed for accurate evaluation of chromophores in skin lesions. Qualitative methods are subjective and cause user-dependent error in evaluation. Quantitative methods have limitations for widely distributed skin lesions due to poor spatial resolution, potential skin blanching, and difficulty in relocating identical sites for subsequent measurements and analysis. OBJECTIVE The objective was to develop a new imaging modality that provides both qualitative and quantitative methods to evaluate widely distributed skin lesions. METHODS We have developed a prototype polarization color imaging system named “DermaVision,” which provides quantitative on-line image analysis of polarization color images. Herein, we describe the hardware and software of DermaVision in terms of its performance and usefulness for dermatologic applications. RESULTS Polarization color images were successfully acquired from patients with vascular or pigmented skin lesions. The erythema and melanin index images were successfully computed and quantitatively confirmed the degree of erythema and pigmentation in the skin lesions. CONCLUSION We believe that DermaVision can be a useful auxiliary tool in dermatology because it simultaneously provides both qualitative and quantitative images of skin lesions. [ABSTRACT FROM AUTHOR]

Vascular ectasia in port wine stain birthmarks (PWS) might result from reduced innervation with loss of autonomic stimulation. We investigated this theory and evaluated nerve and blood vessel density, and mean blood vessel size in untreated and treated PWS skin. Skin biopsy specimens were obtained from uninvolved skin, untreated PWS, PWS with a good response to laser treatment and PWS with a poor response to laser treatment. Confocal microscopy was performed to determine nerve and blood vessel density, and mean blood vessel size. Nerve density was significantly decreased in all PWS sites compared to uninvolved skin. Mean blood vessel diameter was larger in untreated compared to treated PWS. PWS with a good response to treatment had decreased nerve density but blood vessel density and mean diameter was relatively normal. PWS with a poor response to treatment had decreased nerve density but increased blood vessel density and mean blood vessel diameter compared to normal skin. Nerve density was decreased in all evaluated PWS sites and this may be a factor in lesion pathogenesis. PWS blood vessel size correlated with pulsed dye laser response and may prove to be a useful prognostic indicator of therapeutic outcome. MONA M. SELIM, MD, KRISTEN M. KELLY, MD, J. STUART NELSON, MD, PHD, GWEN WENDELSCHAFER-CRABB, MS, WILLIAM R. KENNEDY, MD, AND BRIAN D. ZELICKSON, MD HAVE INDICATED NO SIGNIFICANT INTEREST WITH COMMERCIAL SUPPORTERS. [ABSTRACT FROM AUTHOR]

The turbidity of most biologic tissues hinders the use of lasers for diagnostic and therapeutic purposes. Hyperosmotic agents such as glycerol have been used to alter the optical scattering properties of turbid tissues. The mechanism of this effect, “optical clearing”, however, remains incompletely understood. Multiphoton microscopy utilizing second harmonic generation can be used to monitor collagen structural changes in the presence of glycerol. This study suggests that the use of glycerol for tissue “optical clearing” screens noncovalent intermolecular interactions between low-order collagen structures, resulting in fiber disassembly. Dissociation of collagen fibers in native and engineered tissues in the presence of glycerol and reassociation with the application of saline are imaged dynamically. Collagen fiber reassembly is governed by the displacement of glycerol by saline in native and engineered skin. These results reveal the assembly process of high-order collagen structures and propose a molecular mechanism for the increase in tissue transparency observed after glycerol application. [ABSTRACT FROM AUTHOR]

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/cm[sup 2] . 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. [ABSTRACT FROM AUTHOR]

In pulsed photothermal profiling of human skin, subsurface blood vessels may be difficult to resolve due to nonselective absorption in the overlying epidermis. The dual-wavelength excitation (DWE) technique solves this problem by exploiting spectral differences between the epidermal melanin and blood hemoglobin. An improved approach to determination of DWE-specific parameter β for depth profiling of port wine stain birthmarks in vivo using the 585 and 600 nm wavelengths is discussed. [ABSTRACT FROM AUTHOR]

Presents a letter to the editor about research on pigmentary changes after alexandrite laser hair removal.

Abstract: Background: Presently the heart rate is monitored in the Neonatal Intensive Care Unit with contact sensors: electrocardiogram or pulse oximetry. These techniques can cause injuries and infections, particularly in very premature infants with fragile skin. Camera based plethysmography was recently demonstrated in adults as a contactless method to determine heart rate. Aim: To investigate the feasibility of this technique for NICU patients and identify challenging conditions. Study design and participants: Video recordings using only ambient light were made of 19 infants at two NICUs in California and The Netherlands. Heart rate can be derived from these recordings because each cardiovascular pulse wave induces minute pulsatile skin color changes, invisible to the eye but measurable with a camera. Results: In all infants the heart beat induced photoplethysmographic signal was strong enough to be measured. Low ambient light level and infant motion prevented successful measurement from time to time. Conclusions: Contactless heart rate monitoring by means of a camera using ambient light was demonstrated for the first time in the NICU population and appears feasible. Better hardware and improved algorithms are required to increase robustness. [Copyright &y& Elsevier]

Background/purpose: Conventional treatment methods for acne vulgaris have various side effects such as the development of bacterial resistance, phototoxicity, vertigo, gastro-intestinal problems, and drug eruptions. To minimize such side effects, light and thermal methods have been alternately suggested. This study characterized a new acne vulgaris treatment device (AVTD) that combines both light and thermal methods and evaluated its clinical efficacy. Methods: We characterized the thermal and light properties of the AVTD itself and evaluated its thermal characteristics in ex vivo porcine skin samples. The Arrhenius equation was used to calculate the skin thermal injury coefficient to confirm the skin safety of the AVTD. Finally, the clinical efficacy of the AVDT was evaluated by analyzing cross-polarization and erythema index images, which were obtained from 13 volunteers undergoing treatment with the AVTD. Results: The temperature of the AVTD itself was maintained at 49.1 °C on the tip and 39.7 °C in the porcine skin samples. The peak intensity of the light-emitting diode (LED) light was observed at 468 nm. The skin safety of the AVTD was confirmed and 84.2% of the volunteers presented positive treatment results. Conclusion: The treatment of acne using the AVTD resulted in a high treatment rate in a clinical study, minimizing side effects. On the basis of these results, we can be sure that the AVTD may be effectively used for the treatment of acne vulgaris. [ABSTRACT FROM AUTHOR]

Various physico-chemical tissue optical clearing (TOC) methods have been suggested to maximize photon density in tissue. In order to enhance photon density, a compression-controlled low-level laser probe (CCLLP) system was developed by utilizing the principle of mechanical tissue compression. Negative compression (NC) was applied to the laser probes built in various diameters and simultaneously the laser was irradiated into ex-vivo porcine skin samples. Laser photon density (LPD) was evaluated as a function of NC and probe diameter by analyzing 2D diffusion images of the laser exposures. The CCLLP system resulted in a concentrated laser beam profile, which means enhancement of the LPD. As indicators of LPD, the laser peak intensity increased and the full width at half maximum (FWHM) decreased as a function of NC. The peak intensity at –30 kPa increased 2.74, 3.22, and 3.64 fold at laser probe diameters of 20, 30, and 40 mm, respectively. In addition, sample temperature was measured with a thermal camera and increased 0.4 K at –30 kPa after 60 s of laser irradiation as a result of enhanced LPD. The CCLLP system effectively demonstrated enhancement of the LPD in tissue and potentially its clinical feasibility. [ABSTRACT FROM AUTHOR]

Port-wine stains (PWS) represent a group of vascular malformations that are usually accompanied by psychological distress for affected patients, often reflected in high treatment demand. Although the pulsed-dye laser (PDL) was established as standard therapy for PWS more than a decade ago, therapeutic outcome may be unsatisfactory. One of the main drawbacks to successful PDL therapy is PWS revascularization shortly after laser exposure. Therefore, inhibition of revascularization should improve therapeutic outcome of PDL therapy. In this study, we first evaluated the effects of various light energies on normal cutaneous vessels over a period of 14 days, particularly the proliferation and stem cell marker expression of dermal endothelial cells, which were found to be highest 8 days following laser exposure. We found that PDL exposure induced dose-dependent damage of dermal vessels up to energy densities of 6 J/cm2, above which no increase in PDL-induced effects were observed with the energies employed in this study. In dermal endothelial cells of PDL-exposed skin, we found strong expression of the proliferation marker Ki-67 as well as the stem cell marker nestin but not other stem cell markers such as CD133 and CD166. The influence of rapamycin (RPM), used as an adjuvant to PDL exposure, was also investigated. RPM administration reduced Ki-67 and nestin expression in dermal endothelial cells and increased PDL-induced destruction of dermal vessels, indicating that the use of RPM after PDL exposure may be an interesting new approach for prolonging and improving PWS laser therapeutic outcome. Loewe R, Oble DA, Valero T, Zukerberg L, Mihm MC Jr, Nelson JS. Stem cell marker upregulation in normal cutaneous vessels following pulsed-dye laser exposure and its abrogation by concurrent rapamycin administration: implications for treatment of port-wine stain birthmarks. [ABSTRACT FROM AUTHOR]

A simple, compact, and low cost tunable ring laser with a commercial semiconductor optical amplifier (SOA) was demonstrated. The tunable ring laser is based on an external wavelength filter cavity that is analogous with the Littman configuration with a diffraction grating, a mirror, and a simple slit. The unique structural advantage of this new system is that the slit is displaced to select a desired wavelength instead of tilting the mirror as in the Littman configuration. This allows easy control over the selected wavelength by the translating action of the slit. The full width half maximum (FWHM) wavelength turning range is 45 nm, and the wavelength resolution is about 2 pm. The demonstrated tunable ring laser has 2 mW output power. The side mode suppression ratios is 70–73 dB. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1317–1320, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23340 [ABSTRACT FROM AUTHOR]

Background/purpose: During laser therapy of port wine stain (PWS) birthmarks in human skin, measurement of the epidermal temperature rise (Δ Tepi) is important to determine the maximal permissible light dose. In order to measure Δ Tepi on a specific PWS skin site, we developed an AC-coupled hand-held pulsed photothermal radiometry (PPTR) system, which overcomes the in vivo measurement limitations of bench-top systems. Methods: The developed hand-held PPTR system consists of an infrared (IR) lens, AC-coupled thermoelectrically cooled IR detector, laser hand-piece holder, and positioning aperture. The raw AC-coupled signal was integrated to obtain a higher signal-to-noise ratio (SNR). The experimental temperature difference (Δ T) calibration was compared with theoretical computations. In vitro and in vivo measurements of Δ T were performed with a tissue phantom as a function of radiant exposure and human subject as a function of melanin concentration, respectively. Results: The integrated AC-coupled signal provided higher SNR as compared with the raw AC-coupled signal. The experimental Δ T calibration resulted in good agreements with the theoretical results. The in vitro and in vivo results also presented good agreements with theory. Conclusions: A fiber-free, hand-held AC-coupled PPTR system is capable of accurate epidermis temperature rise (Δ Tepi) measurements of human skin during pulsed laser exposure. [ABSTRACT FROM AUTHOR]

BACKGROUND Despite widespread clinical use of cryogen spray cooling (CSC) in conjunction with laser dermatologic surgery, in vivo cutaneous effects have not been systematically evaluated. OBJECTIVE 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). METHODS AND MATERIALS 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. RESULTS 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. CONCLUSION Acute erythema, urticaria, and, less commonly, transient hyperpigmentation were observed after CSC exposure. Permanent skin injury was not observed and is unlikely. [ABSTRACT FROM AUTHOR]

Many commercially available dermatologic lasers utilize cryogen spray cooling for epidermal protection. A previous tissue culture study demonstrated that single cryogen spurts (SCS) of 80 ms or less were unlikely to cause cryo-injury in light-skinned individuals. More recently, multiple cryogen spurts (MCS) have been incorporated into commercial devices, but the effects of MCS have not been evaluated. The aim was to study an in vitro tissue culture model and the epidermal and dermal effects of SCS vs patterns of shorter MCS with the same preset total cryogen delivery time (Deltat(c)) and provide an explanation for noted differences. Four different spurt patterns were evaluated: SCS: one 40-ms cryogen spurt; MCS2: two 20-ms cryogen spurts; MCS4: four 10-ms cryogen spurts; MCS8: eight 5-ms cryogen spurts. Actual Deltat(c) and total cooling time (Deltat(Total)) were measured for each spurt pattern. RAFT tissue culture specimens were exposed to cryogen spurt patterns and biopsies were taken immediately and at days 3 and 7. Actual Deltat(c) was increased while Deltat(Total) remained relatively constant as the preset Deltat(c) of 40 ms was delivered as shorter MCS. Progressively more epidermal damage was noted with exposure to the MCS patterns. No dermal injury was noted with either SCS or MCS. For a constant preset Deltat(c) of 40 ms, delivering cryogen in patterns of shorter MCS increased the actual Deltat(c) and consequently the observed epidermal cryo-injury as compared to an SCS. [ABSTRACT FROM AUTHOR]

We present a method to solve the inverse problem in pulsed photothermal radiometry (PPTR) that exploits advantages of truncated singular value decomposition (T-SVD) while imposing a non-negativity constraint to the solution. The presented method is a hybrid in the sense that it expresses the solution vector as a linear superposition of right singular vectors, but with a non-negative constraint applied to it. The weights for the superposition are determined using an optimization algorithm. In one-dimensional PPTR simulation examples, the best reconstruction results are of comparable quality to those of the conjugate gradient method. Furthermore, the hybrid method exhibits a sharper knee in the L-curve and small susceptibility to over-iteration in presence of experimental noise, thus facilitating the regularization process. As a result, the reconstructed temperature profiles are more likely to be closer to the original initial profiles. [ABSTRACT FROM AUTHOR]

Treatment of port wine stain (PWS) birthmarks in human skin by pulsed laser irradiation requires the knowledge of the maximum epidermal temperature rise and PWS depth for an attending physician to select the optimal light dosage, irradiation wavelength, and cryogen spray cooling spurt duration on an individual patient basis. Pulsed photothermal radiometry (PPTR) is a promising technique to provide such information. In this article, computer simulations are performed to evaluate the performance of PPTR depth profiling of the laser-induced temperature rise in PWS. An iterative, non-negatively constrained conjugate gradient algorithm is used to reconstruct the laser-induced temperature profile from simulated PPTR signals. Human skin is assumed to contain an epidermal melanin layer and a single homogeneous PWS layer in the dermis. The influence of structural, experimental, and algorithm parameters on the temperature profile reconstruction are discussed. Accuracy of the maximum epidermal temperature rise and PWS depth determined from the reconstructed profiles is statistically analyzed. The simulations show that when the melanin and PWS layers are physically discrete, a good reconstruction can be obtained and the maximum epidermal temperature rise and PWS depth can be determined with accuracy sufficient for the intended clinical application. Measurements and reconstructions from PWS patients are performed and the results are in agreement with the simulations. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Although epidermal melanin content has been quantified non-invasively using visible reflectance spectroscopy (VRS), there is currently no way to determine melanin distribution in the epidermis. We have developed a photoacoustic probe that uses a Q-switched, frequency-doubled Nd:YAG (neodymium, yttrium, aluminum, garnet) laser operating at 532 nm to generate acoustic pulses in skin in vivo. The probe contained a piezoelectric element that detected photoacoustic waves that were then analyzed for epidermal melanin content using a photoacoustic melanin index (PAMI). Melanin content was compared between results of photoacoustics and VRS. Spectra from human skin were fitted to a model based on diffusion theory that included parameters for epidermal thickness, melanin content, hair color and density, and dermal blood content. Ten human subjects with skin phototypes I–VI were tested using the photoacoustic probe and VRS. A plot of PAMI v. VRS showed a good linear fit with r2=0.85. Photoacoustic and VRS measurements are shown for a human subject with vitiligo, indicating that melanin was almost completely absent. We present preliminary modeling for photoacoustic probe design and analysis necessary for depth profiling of epidermal melanin. [ABSTRACT FROM AUTHOR]

Cryogenic sprays are used for cooling human skin during laser dermatologic surgery. In this paper, six straight-tube nozzles are characterized by photographs of cryogenic spray shapes, as well as measurements of average droplet diameter, velocity, and temperature. A single-droplet evaporation model to predict average spray droplet diameter and temperature is tested using the experimental data presented here. The results show two distinct spray patterns—sprays for 1.4-mm-diameter nozzles (wide nozzles) show significantly larger average droplet diameters and higher temperatures as a function of distance from the nozzle compared with those for 0.5-0.8-mm-diameter nozzles (narrow nozzles). These results complement and support previously reported studies, indicating that wide nozzles induce more efficient heat extraction than the narrow nozzles. [ABSTRACT FROM AUTHOR]

Presents a study which used contact cooling with a sapphire window (6-12 degrees Celsius) and spray cooling with a freon substitute cryogen to investigate the thermal response of in-vivo human skin. What can be provided by surface cooling; Details on what radiometric measurements dependent on; Methods used to conduct study; Results of study.

Individual blood vessels in the chick chorioallantoic membrane were selectively coagulated through photothermolysis, using pulsed laser irradiation at 585 nm. Pulse durations were chosen to be 0.45 ms and 10 ms, which correspond to the thermal relaxation times in blood vessels of 30 μm and 150 μm diameter, respectively. The short pulses, at a light fluence F = 3 Jcm-2, caused permanent occlusion of vessels of 40 μm diameter or less, whereas larger caliber vessels (60- 120 μm) required F = 4- 5Jcm-2. The long-duration pulses, at F = 7 Jcm-2, caused coagulation of the larger diameter vessels; the small-caliber vessels and capillaries showed resistance to photothermolysis and required multiple exposures to achieve coagulation. The fluence versus diameter (F versus d) relationship for coagulation was calculated for the two pulse durations. The energy deposited in a cylindrical absorber of diameter d by an optical field, incident perpendicular to the vessel, was expressed analytically and compared with the energy required to coagulate a blood vessel of the same lumen diameter. When thermal diffusion is incorporated into the model, our findings can be accounted for quantitatively. This information will be of use for improving the laser treatment of port wine stains and other vasculopathies. A surprising observation was that arterioles were damaged at lower incident energy densities than venules having the same lumen diameter, despite the fact that absorbance in oxygen-rich and oxygen-poor blood is the same at 585 nm. [ABSTRACT FROM AUTHOR]

BACKGROUND AND OBJECTIVE. The objective of this study was to determine the effectiveness of a dynamic cooling device (DCD), spraying the skin with a brief spurt of cryogen prior to the laser pulse, in reducing transient pain associated with 585-nm pulsed dye laser (PDL) treatment of port-wine stains (PWS), and reducing epidermal damage (hypo/hyperpigmentation) caused by this laser during PWS treatment.MATERIALS AND METHODS. Matched treatment sites were compared with and without the use of the cryogen spray in 47 patients at two investigational sites. Pain ratings, clearance of the PWS, and pigmentation changes were assessed. The results were analyzed by skin type and patient age. RESULTS. A statistically significant reduction in pain ratings was found in all patient groups using the DEC without changing the efficacy of PWS clearance. Pain reduction was most remarkable in patients with darker skin types. Dynamic cooling prevented the occurrence of epidermal damage or pigmentation change in moist cases. CONCLUSIONS. This study suggests that dynamic cooling can dramatically diminish pain during PWS treatment with the 585-nm PDL without reducing treatment efficacy. The absence of epidermal damage in most patients suggests that precooling with the DCD may allow the use of higher laser fluences to expedite clearance without inducing epidermal change. Dynamic cooling has potential use with other lasers and different lesions where discomfort and epidermal effects limit therapy. [ABSTRACT FROM AUTHOR]

BACKGROUND. Successful laser treatment of hemangiomas requires selective photothermal destruction of dilated cutaneous vessels without damaging the overlying epidermis. Delivering a short cryogen spurt, on the order of milliseconds, has been shown to result in localized cooling of the superficial skin structures during laser irradiation. OBJECTIVE.The purpose of this study was to examine the effectiveness of cryogen spray cooling (CSC) in protecting superficial tissue structures during continuous Nd:YAG laser irradiation of an in vivo model hemangioma. METHODS. The highly vascularized chicken comb was selected as the animal model for hemangioma. The ND:YAG laser irradiation ranged from 2.6 to 35.1 1/mm². A feedback system utilizing infrared rediometry monitored the comb surface temperature and controlled delivery time to the cryogen spurt. When comb surface temperature during laser irradiation reached 36-42°C, a 30-100 msec cryogen spurt was delivered. Animals were euthanized 1 hour to 21 days following each experiment. Gross and histologic analyses were performed. RESULTS. Nd:YAG laser irradiation resulted in deep (up to 6.1 mm) tissue photocoagulation, which CSC preserved the overlying epidermis and papillary dermis. CONCLUSION. The results demonstrate that CSC is effective in protecting the epidermis and papillary dermis and papillary dermis, while achieving deep tissue photocoagulation during ND:YAG laser irradiation. Further pilot studies in humans appear warranted. [ABSTRACT FROM AUTHOR]

Port wine stain (PWS) is a congenital vascular malformation involving human skin. Approximately 15–20% of children a facial PWS involving the ophthalmic (V1) trigeminal dermatome are at risk for Sturge Weber syndrome (SWS), a neurocutaneous disorder with vascular malformations in the cerebral cortex on the same side of the facial PWS lesions. Recently, evidence has surfaced that advanced our understanding of the pathogenesis of PWS/SWS, including discoveries of somatic genetic mutations (GNAQ, PI3K), MAPK and PI3K aberrant activations, and molecular phenotypes of PWS endothelial cells. In this review, we summarize current knowledge on the etiology and pathology of PWS/SWS based on evidence that the activation of MAPK and/or PI3K contributes to the malformations, as well as potential futuristic treatment approaches targeting these aberrantly dysregulated signaling pathways. Current data support that: (1) PWS is a multifactorial malformation involving the entire physiological structure of human skin; (2) PWS should be pathoanatomically re-defined as "a malformation resulting from differentiation-impaired endothelial cells with a progressive dilatation of immature venule-like vasculatures"; (3) dysregulation of vascular MAPK and/or PI3K signaling during human embryonic development plays a part in the pathogenesis and progression of PWS/SWS; and (4) sporadic low frequency somatic mutations, such as GNAQ, PI3K, work as team players but not as a lone wolf, contributing to the development of vascular phenotypes. We also address many crucial questions yet to be answered in the future research investigations. [ABSTRACT FROM AUTHOR]

Cryogen spray cooling (CSC) protects the epidermis from unintended heating during cutaneous laser surgery. The present work investigated the time-dependent flow characteristics of cryogen sprays and correspondent thermal dynamics at the surface of a human tissue phantom. First, a numerical analysis was carried out to evaluate an epoxy block substrate as a human tissue phantom. Next, the velocity and diameter of cryogen droplets were measured simultaneously and correlated with surface temperature of the human tissue phantom during CSC. Finally, velocity and diameter measurements were used to compute the spray number, mass, and kinetic energy fluxes, and temperature measurements were used to compute the surface heat flux. Numerical modeling showed that the thermal response of our phantom was qualitatively similar to that of human stratum corneum and epidermis; quantitatively, thermal responses differed. A simple transformation to map the temperature response of the phantom to that of tissue was derived. Despite the relatively short spurt durations (10 ms, 30 ms, and 50 ms), cryogen delivery is mostly a steady state process with initial and final fluid transients mainly due to the valve dynamics. Thermal transients (16 ms) are longer than fluid transients (4 ms) due to the low thermal diffusivity of human tissues; steady states are comparable in duration ([approximate]10 ms, 30 ms, and 50 ms) although there is an inherent thermal delay ([approximate]12 ms). Steady state temperatures are the lowest surface temperatures experienced by the substrate, independent of spurt duration; hence, longer spurt durations result in larger exposures of the tissue surface to the same lower, steady state temperature as in shorter spurts. Temperatures in human tissue during CSC for the spray system and parameters used herein are estimated to be [approximate]-19°C at the stratum corneum surface and >0°C across the epidermis. [ABSTRACT FROM AUTHOR]