Port-wine stain treatment is wavelength independent in the range 488–620 nm using 200-ms pulses (original) (raw)
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Therapeutic response during pulsed laser treatment of port-wine stains
Selective photothermolysis with pulsed lasers is presumably the most successful therapy for port-wine stain birthmarks (flammeus nevi). Selectivity is obtained by using an optical wavelength corresponding to high absorption in blood, together with small absorption in tissues. Further on, the pulse length is selected to be long enough to allow heat to diffuse into the vessel wall, but simultaneously short enough to prevent thermal damage to perivascular tissues. The optical wavelength and pulse length are therefore dependent on vessel diameter, vessel wall thickness and depth in dermis. The present work demonstrates that in the case of a 0.45 ms long pulse at 585 nm wavelength, vessels of 40~0 Fm require minimum optical fluence. Smaller vessels require higher fluence because the amount of heat needed to heat the wall becomes a substantial fraction of the absorbed optical energy. Larger vessels also require a higher dose because the attenuation of light in blood prevents the blood in the centre of the lumen from participating in the heating process. It is shown that the commonly used optical dose in the range of 6-7 J cm-2 is expected to inflict vessel rupture rather than thermolysis in superficially located vessels. The present analysis might serve to draw guidelines for a protocol where the optical energy, wavelength and pulse length are optimized with respect to vessel diameter and depth in dermis.
Wavelengths for laser treatment of port wine stains and telangiectasia
Lasers in Surgery and Medicine, 1995
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 designlMaterials 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 4881515 nm, and the frequency doubled NdYAG 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. Conelmion: 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 t0 577 nm. Q 1995 Wiley-Liss, Inc.
Lasers in Medical Science, 1995
Selective photothermolysis with pulsed lasers is presumably the most successful therapy for port-wine stain birthmarks (flammeus nevi). Selectivity is obtained by using an optical wavelength corresponding to high absorption in blood, together with small absorption in tissues. Further on, the pulse length is selected to be long enough to allow heat to diffuse into the vessel wall, but simultaneously short enough to prevent thermal damage to perivascular tissues. The optical wavelength and pulse length are therefore dependent on vessel diameter, vessel wall thickness and depth in dermis. The present work demonstrates that in the case of a 0.45 ms long pulse at 585 nm wavelength, vessels of 40~0 Fm require minimum optical fluence. Smaller vessels require higher fluence because the amount of heat needed to heat the wall becomes a substantial fraction of the absorbed optical energy. Larger vessels also require a higher dose because the attenuation of light in blood prevents the blood in the centre of the lumen from participating in the heating process. It is shown that the commonly used optical dose in the range of 6-7 J cm-2 is expected to inflict vessel rupture rather than thermolysis in superficially located vessels. The present analysis might serve to draw guidelines for a protocol where the optical energy, wavelength and pulse length are optimized with respect to vessel diameter and depth in dermis.
Photomedicine and Laser Surgery, 2009
Background and Objectives: Pulsed dye laser (PDL) is the current treatment of choice for port-wine stains (PWS), but 25-50% of treated lesions do not demonstrate a significant improvement. Hybrid lasers may improve treatment efficacy, especially those using the synergies between PDL and Nd:YAG 1064 nm laser. The objectives of this study were to assess vessel wall damage and epidermal sparing after a dual wavelength treatment with the two lasers, using different laser parameters. Material and Methods: Post-treatment biopsies, after using a laser platform that allows sequential pulses of PDL and Nd:YAG 1064 nm lasers, were performed in five patients with PWS resistant to PDL. The biopsies were stained with nitroblue-tetrazolium chloride (NBTC), using enzymatic activity that stops immediately after cell death and allows a better identification of viable cells. Results: Five patients with PWS and a median age of 33 years were enrolled in this study. Selectivity and efficacy was observed with this dual wavelength approach, with the best results observed with PDL pulses shorter than 10 ms, use of the 10 mm spot, and a second pass with PDL only. Conclusions: Histochemical studies with NBTC stain can help the laser surgeon establish the best treatment parameters and understand some of the unwanted side effects. The dual wavelength used in this study showed efficacy, but better assessment of treatment parameters, such as the delay between the two lasers, is needed to avoid side effects.
2003
In therapy of port wine stain (PWS) birthmarks using pulsed green or yellow lasers, non-specific absorption by epidermal melanin reduces the amount of incident radiation that reaches the target PWS blood vessels. The related epidermal heating can induce blistering, dyspigmentation, or scarring, which limits the applicable radiant exposure, thus adversely affecting the efficacy of treatment in many patients. Our objective was to assess temperature depth profiles induced in PWS skin by a novel Nd:YAG laser emitting simultaneously at 1064 and 532 nm. The results should help determine safe radiant exposures for use in future clinical trials. The underlying hypothesis is that the added 1064 nm radiation may lead to a higher temperature increase in PWS relative to the epidermis, in comparison with a customary KTP/Nd:YAG laser system for vascular treatments (emitting at 532 nm only). The laser induced temperature profiles were determined in vivo using pulsed photothermal radiometry. A PWS test site was irradiated with a sub-therapeutic laser pulse and the transient change of the infrared radiant emission was recorded by a fast infrared camera. The laser-induced temperature profiles were reconstructed by solving the thermal-radiative inverse problem using an iterative minimization algorithm.
British Journal of Dermatology, 1987
The argon laser was used to treat 220 patients with port-wine stains with moderate efficacy and few complications although perfect cosmetic results were rarely achieved. Primary failure ofthe argon laser to produce permanent blanching graded good or excellent was the most important factor limiting the final cosmetic results whilst severe scarring was rare (<2%). In order to improve the efficacy of this treatment, a randomized controlled study of different parameters of laser treatment was undertaken in test patches of port-wine stains in 50 patients. A treatment pattern with contiguous or overlapping laser spots was significantly superior to treatment with spots of I or 2 mm separation. Increasing the power level to twice the minimum blanching power did not improve efficacy or significantly increase scarring. A randomized study of selective absorption using a neodymium (Nd) YAG laser showed similar efficacy for the different wavelengths although scarring was greater with the Nd-YAG laser. This study has shown that laser treatment can offer a moderately effective treatment for port-wine stains. For best results spot separation needs to be carefully controlled, whilst wavelength and power level appear to be less important than previously reported.
High-Energy 595 nm Pulsed Dye Laser Improves Refractory Port-Wine Stains
Dermatologic Surgery, 2008
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/cm 2 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, variablepulse 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/cm 2 , 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/cm 2 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/cm 2. 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.
Physics in Medicine and Biology, 1997
The treatment of port wine stains (PWSs) using a flashlamp-pumped pulsed dye laser is often performed using virtually identical irradiation parameters. Although encouraging clinical results have been reported, we propose that lasers will only reach their full potential provided treatment parameters match individual PWS anatomy and physiology. The purpose of this paper is to review the progress made on the technical development and clinical implementation of (i) infrared tomography (IRT), optical reflectance spectroscopy (ORS) and optical lowcoherence reflectometry (OLCR) to obtain in vivo diagnostic data on individual PWS anatomy and physiology and (ii) models of light and heat propagation, predicting irreversible vascular injury in human skin, to select optimal laser wavelength, pulse duration, spot size and radiant exposure for complete PWS blanching in the fewest possible treatment sessions. Although non-invasive optical sensing techniques may provide significant diagnostic data, development of a realistic model will require a better understanding of relevant mechanisms for irreversible vascular injury.