Cryogen spray cooling during Nd:YAG laser treatment of hemangiomas. A preliminary animal model study

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 hemangiomas. The Nd:YAG laser irradiation ranged from 2.6 to 35.1 J/mm2. A feedback system utilizing infrared radiometry monitored the comb surface temperature and controlled delivery time of the cryogen spurt. When comb surface temperature during laser irradiation reached 36-42 degrees 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, while CSC preserved the overlying epidermis and papillary dermis. CONCLUSION: The results demonstrate that CSC is effective in protecting the epidermis and papillary dermis, while achieving deep tissue photocoagulation during Nd:YAG laser irradiation. Further pilot studies in humans appear warranted.