ND-YAG LASER IRRADIATION IN CONJUNCTION WITH CRYOGEN SPRAY COOLING INDUCES DEEP AND SPATIALLY SELECTIVE PHOTOCOAGULATION IN ANIMAL-MODELS

Successful laser treatment of haemangiomas requires selective photocoa gulation of subsurface targeted blood vessels without thermal damage t o the overlying epidermis. We present an in vivo experimental procedur e, using a chicken comb animal model, and an infrared feedback system to deliver repetitive cryogen spurts (of the order of milliseconds) du ring continuous Nd:YAG laser irradiation. Gross and histologic observa tions show deep-tissue photocoagulation is achieved, while superficial structures are protected from thermal injury due to cryogen spray coo ling. Experimental observation of epidermis protection in chicken comb animal models suggests selective photocoagulation of subsurface targe ted blood vessels for successful treatment of haemangiomas can be achi eved by repetitive applications of a cryogen spurt during continuous N d:YAG laser irradiation.