BONE ABLATION WITH ER-YAG AND CO-2 LASER - STUDY OF THERMAL AND ACOUSTIC EFFECTS

A pulsed Er:YAG laser at 2.94-mu-m and a superpulsed CO2 laser at 10.6-mu-m are used to investigate bone ablation applications in otolaryngology. Quantitative measurements of mass removal and the ablation depth of cat skull bone and rat femur are presented with the Er:YAG laser at fluences of 9-117 J/cm2. Histological results show that the minimal thermal injury zone from the edge of the lesion is 5-10-mu-m. Comparison of the photoacoustic and thermal effects during the ablation process indicates that the temperature rise from the 10.6-mu-m light was higher than that from the 2.94-mu-m light but that the photoacoustic wave amplitude produced with the Er:YAG laser was higher than that with the CO2 laser. The fluence used for the efficient ablation of bone tissues produces a photoacoustic wave ranging from 100 to 120 dB. The ear can tolerate this level for a short time period. Results of this study suggest that the Er:YAG laser can be an important surgical tool in otolaryngology.