Multiple laser pulses in conjunction with an optical clearing agent to improve the curative effect of cutaneous vascular lesions

Port-wine stains (PWSs) usually respond poorly to pulsed dye laser treatment because of the shallow penetration and light absorption of melanin in the epidermis. Multiple laser pulses (MLPs) Nd:YAG laser in conjunction with an optical clearing agent can help to reduce the total laser energy required for blood coagulation. The quantitative optical clearing effect (OCE) of glycerol was investigated by using a tissue-like phantom. Thereafter, an in vitro capillary tube experimental system and an in vivo hamster dorsal skin chamber experiment for the laser treatment of PWSs were established to visually obtain the quantitative relationship between the OCE and the blood coagulation properties under the irradiation of 1064 nm MLPs. Diffuse reflection coefficient decreases by 36.69% and transmission coefficient increases by 38.73% at 1064 nm, after applying 0.5 mL anhydrous glycerol for 10 min on the surface of the tissue-like phantom. The number of laser pulses required for blood coagulation decreases by 25% after the application of 0.5 mL anhydrous glycerol for 4 min, thrombosis appears after 10 min, and the 0.0854 clotting area completely blocks the capillary tubes in 6 pulses. For 10 min, the incident energy can be reduced by 35.09 and 29.82%. When the 0.3-mm vessel's buried depths are 1 and 0.5 mm, the pulse number can be reduced from 11 to 8 and from 6 to 4, respectively. Adding anhydrous glycerol directly on the hamster dorsal skin is an effective way to reduce the number of laser pulses from 4 similar to 5 to 2 similar to 3 for similar capillary tube diameter. Therefore, the MLPs of 1064 nm Nd: YAG demonstrates a substantial curative effect for large capillary tubes. In conjunction with glycerol, this approach may treat deeply buried cutaneous capillary tubes and prevent the unwanted thermal damage of normal dermal tissue.