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Laser therapy has been widely used to treat port-wine stains (PWS) and other cutaneous vascular lesions via selective photothermolysis. Animal models are a valuable tool for investigating thermal responses beneath the skin. However, in previous animal experiments, such as the dorsal skin chamber model, one side of the skin was removed, resulting in the loss of mechanical support for the target blood vessel. In this study, the optical clearing technique was applied to the dorsal skin, allowing direct observation of real thermal responses within the tissue without removing the covering skin. The target blood vessels were irradiated with a pulsed 1064 nm Nd: YAG laser. The corresponding thermal responses were recorded using a CCD camera. Additionally, variations in skin reflectance spectra were measured before and after laser irradiation. Due to the optical clearing and reflectance spectra measurement, vessel responses such as contraction, reperfusion, and full occlusion were correlated with specific variation patterns in reflectance spectral signals., (© 2024. The Author(s), under exclusive licence to Springer-Verlag London Ltd., part of Springer Nature.)

Pulsed dye laser (PDL) at the wavelength of 595 nm is the common choice for the treatment of port-wine stains (PWSs). In this study, the efficacy of 595-nm PDL in treatment of PWSs in Chinese patients was investigated. A follow-up visit was performed on 261 Fitzpatrick skin type II-III Chinese patients with PWS who received more than two treatments with 595-nm PDL. Based on cosmetic improvement, treatment response was graded as follows: complete, if color blanching was > 90%; significant, if color blanching was 60-90%; moderate, if color blanching was 30-60%; and poor, if color blanching was < 30%. The efficacy of laser treatment on patients of different treatment numbers, ages, lesion locations, lesion colors, extents of hypertrophy, and laser pulse durations was evaluated. All patients improved following an average of almost 4 to 5 laser treatments. The earlier the intervention, the better the efficacy was. Lesions on cheek, neck, and forehead were better than that those on oral, eye periorbital, and nose areas. The purple group had a more excellent clearance, i.e., complete and significant clearance rate (53.6%), than the red group (36.1%). Treatment effect became worse as the extent of lesion hypertrophy increased. PWS lesions treated with short pulse durations of 0.45, 1.5, and 3 ms had better clearance (complete and significant clearance) rate of 56.5% than those treated with pulse durations of 6 ms or longer (34.8%). Pulsed dye laser with 595-nm laser equipped with dynamic cooling device is an effective option for the treatment of PWS in Chinese patients. Younger patients with lateral face position, larger vessel size (deeper color), and lesser hypertrophy received better clinical effect than the others. Treatment with short pulse duration of less than 3 ms for 4 to 5 times was recommended to treat PWS.

In the originally published article, the title was incorrectly copied from another article. The correct title is "Glucose in Conjunction with Multiple Laser Pulses on Laser Treatment of Port-wine Stain: An in vivo Study", which is also shown above.

Port-wine stain (PWS) birthmark is a congenital microvascular malformation of the skin. A 1064-nm Nd:YAG laser can achieve a deeper treatment, but the weak absorption by blood limits its clinical application. Multiple laser pulses (MLPs) are a potential solution to enhance the curative effect of a Nd:YAG laser. To reduce the pulse number (p n ) required for the thermal destruction of the blood vessel, the effect of glucose in conjunction with MLP was investigated. In vivo experiments were performed on a dorsal skin chamber model. Different concentrations (20, 25, 30, and 40%) of glucose were applied to the sub-dermal side of the hamster skin before laser irradiation. Identical vessels with diameters of 200 ± 30 and 110 ± 20 μm were chosen as representatives of typical PWS vessels. Instant thermal responses of the blood vessel were recorded by a high-speed camera. The required p n for blood vessel damage was compared with that without glucose pretreatment. Results showed that the use of glucose with a concentration of 20% combined with MLP Nd:YAG laser to damage blood vessels is more appropriate because severe hemorrhage or carbonization easily appeared in blood vessels at higher glucose concentration of 25, 30, and 40%. When 20% glycerol is pretreated on the sub-dermal hamster skin, the required p n for blood vessel damage can be significantly decreased for different power densities. For example, p n can be reduced by 40% when the power density is 57 J/cm 2 . In addition, generation of cavitation and bubbles in blood vessels is difficult upon pretreatment with glucose. The combination of glucose with MLP Nd:YAG laser could be an effective protocol for reducing the p n required for blood vessel damage. Randomized controlled trial (RCT) and human trials will be conducted in the future.

Port wine stains (PWS) are congenital vascular malformations that progressively darken and thicken with age. To improve the effect of laser therapy in clinical practice, thermal response of blood vessel to a 1064 nm Nd:YAG laser with controlled energy doses and pulse durations was evaluated using the dorsal skin chamber model. A total of 137 vessels with 30-300 μm diameters were selected from the dorsal skin of the mouse to match those capillaries in port wine stains. Experimental results showed that the thermal response of blood vessels to 1064 nm laser irradiation can be classified as follows: vessel dilation, coagulation, constriction with decreased diameter, complete constriction, hemorrhage, and collagen damage with increasing laser radiant exposure. In most cases, that is, 83 of 137 blood vessels (60.6%), Nd:YAG laser irradiation was characterized by complete constriction (immediate blood vessel disappearance). To reveal the possible damage mechanisms and evaluate blood vessel photocoagulation patterns, theoretical investigation using bioheat transfer equation was conducted in mouse skin with a depth of 1000 μm. Complete constriction as the dominant thermal response as evidenced by uniform blood heating within the vessel lumen was noted in both experimental observation and theoretical investigation. To achieve the ideal clinical effect using the Nd:YAG laser treatment, the radiant exposure should not only be high enough to induce complete constriction of the blood vessels but also controlled carefully to avoid surrounding collagen damage. The short pulse duration of 1-3 ms is better than long pulse durations because hemorrhaging of small capillaries is occasionally observed postirradiation with pulse durations longer than 10 ms.